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WO2014162843A1 - Procédé de production d'un matériau absorbant l'eau, et matériau absorbant l'eau - Google Patents

Procédé de production d'un matériau absorbant l'eau, et matériau absorbant l'eau Download PDF

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Publication number
WO2014162843A1
WO2014162843A1 PCT/JP2014/056801 JP2014056801W WO2014162843A1 WO 2014162843 A1 WO2014162843 A1 WO 2014162843A1 JP 2014056801 W JP2014056801 W JP 2014056801W WO 2014162843 A1 WO2014162843 A1 WO 2014162843A1
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Prior art keywords
water
weight
agent
absorbing
absorbent resin
Prior art date
Application number
PCT/JP2014/056801
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English (en)
Japanese (ja)
Inventor
英訓 和田
幸恵 北畑
芳史 足立
井村　元洋
邦彦 石▲崎▼
Original Assignee
株式会社日本触媒
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Priority claimed from JP2013079697A external-priority patent/JP2016112475A/ja
Priority claimed from JP2013079558A external-priority patent/JP2016112474A/ja
Priority claimed from JP2013204229A external-priority patent/JP2016113465A/ja
Application filed by 株式会社日本触媒 filed Critical 株式会社日本触媒
Publication of WO2014162843A1 publication Critical patent/WO2014162843A1/fr

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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F265/00—Macromolecular compounds obtained by polymerising monomers on to polymers of unsaturated monocarboxylic acids or derivatives thereof as defined in group C08F20/00
    • C08F265/02—Macromolecular compounds obtained by polymerising monomers on to polymers of unsaturated monocarboxylic acids or derivatives thereof as defined in group C08F20/00 on to polymers of acids, salts or anhydrides
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61L—METHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES
    • A61L15/00—Chemical aspects of, or use of materials for, bandages, dressings or absorbent pads
    • A61L15/16—Bandages, dressings or absorbent pads for physiological fluids such as urine or blood, e.g. sanitary towels, tampons
    • A61L15/42—Use of materials characterised by their function or physical properties
    • A61L15/60—Liquid-swellable gel-forming materials, e.g. super-absorbents
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/22—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising organic material
    • B01J20/26—Synthetic macromolecular compounds
    • B01J20/265—Synthetic macromolecular compounds modified or post-treated polymers
    • B01J20/267—Cross-linked polymers
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J3/00—Processes of treating or compounding macromolecular substances
    • C08J3/24—Crosslinking, e.g. vulcanising, of macromolecules
    • C08J3/245—Differential crosslinking of one polymer with one crosslinking type, e.g. surface crosslinking
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2333/00—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides, or nitriles thereof; Derivatives of such polymers
    • C08J2333/02—Homopolymers or copolymers of acids; Metal or ammonium salts thereof

Definitions

  • the present invention relates to a method for producing a water-absorbing agent mainly composed of a poly (meth) acrylic acid (salt) -based water-absorbing resin, and a water-absorbing agent that can be produced by the production method. More specifically, in the present invention, the poly (meth) acrylic acid (salt) -based water-absorbing resin is mixed with a predetermined surface treatment liquid and then the reaction step is performed, so that the water absorption capacity under no pressure and the water absorption capacity under pressure.
  • the present invention relates to a technique for producing a water-absorbing agent having an excellent balance and improved safety.
  • a water-absorbing agent mainly composed of a water-absorbing resin has been used as one of the constituent materials of sanitary materials that absorb sanitary cotton, disposable diapers, or other body fluids.
  • the water-absorbing resin constituting such a water-absorbing agent include a hydrolyzate of starch-acrylonitrile graft polymer, a neutralized product of starch-acrylic acid graft polymer, and a Ken acetate of vinyl acetate-acrylic ester copolymer.
  • the properties desired for such a water-absorbent resin include a high water absorption ratio, a high water absorption speed, a high gel strength, an excellent suction force for sucking water from the base material, and a high liquid permeability.
  • Non-Patent Document 1 a cross-linking agent having a plurality of functional groups capable of reacting with a carboxyl group present in the water absorbent resin is used in the vicinity of the surface of the water absorbent resin.
  • a method of forming a cross-linked structure and increasing the surface cross-linking density of the water-absorbent resin (surface cross-linking) has been performed (Non-Patent Document 1).
  • Patent Document 1 alkylene carbonate (Patent Document 1), mono- or polyvalent oxazolidinone (Patent Document 2), polyol (Patent Document 3), oxetane, thiourea (Patent Document 4), and the like
  • Patent Document 5 a plurality of crosslinking agents (for example, glycerin and diepoxy compound) having different solvent parameters are mixed in a water-absorbent resin and heated at 160 ° C. or higher to effect surface crosslinking. It is exemplified that a water-absorbing agent having excellent diffusion absorption capacity is obtained (first surface crosslinking method).
  • Patent Document 6 a technique for improving water content by adding water after surface crosslinking in order to improve dust generation and mechanical damage due to low moisture content after surface crosslinking.
  • Patent Document 7 a technique for adding a cleaning agent or a reducing agent for the obtained water-absorbing agent has also been proposed (Patent Document 7), but the process is complicated. Had.
  • polyvalent metal salts for example, aluminum sulfate
  • polyglycidyl compounds for example, ethylene glycol diglycidyl ether
  • surface cross-linking agents that react at relatively low temperatures (for example, 150 ° C. or less, further 120 ° C. or less).
  • the polyvalent metal salt has a problem of physical properties
  • the polyglycidyl compound has a problem of safety of the remaining crosslinking agent.
  • a radically polymerizable monomer, an organic crosslinking agent, and a radical polymerization initiator are mixed in a water-absorbing resin, and the mixture is heated or irradiated with active energy rays such as ultraviolet rays to crosslink the surface.
  • active energy rays such as ultraviolet rays
  • Patent Documents 8 to 10 As a polymerization method after mixing these water-absorbing resin with a radical polymerizable monomer, an organic crosslinking agent, and a radical polymerization initiator, in Patent Documents 8 to 10, surface crosslinking is performed at a low temperature by heating at about 100 ° C. Things are illustrated. Patent Documents 11 to 14 exemplify surface crosslinking under conditions of about room temperature by irradiating ultraviolet rays. According to the disclosure in these patent documents, on the surface of the water-absorbent resin, radically polymerizable monomers and the like are polymerized, and the surface cross-linking density of the water-absorbent resin is increased, and various water absorption characteristics can be improved. Yes.
  • amide-based crosslinking agents such as N, N′-methylenebisacrylamide have problems such as mutagenicity and reproductive toxicity, and amide-based crosslinking agents are still 100% safe as raw materials for water-absorbing resins. It was not.
  • radical polymerization initiator may not reduce the residual monomer, It has been a problem to cause coloring (with time), generation of odor, change in absorption performance with time, and the like. Furthermore, since radical polymerization initiators are expensive and contain many dangerous compounds, the technique of adding a large amount of radical polymerization initiator from the viewpoint of cost and safety (skin sensitization, etc.) is not a preferable method. It was.
  • Patent Documents 15 and 16 have also been proposed.
  • a radical polymerization initiator is mixed with a water-absorbing resin and heated at 120 ° C. to 130 ° C. to perform surface crosslinking.
  • Patent Document 16 surface crosslinking is performed by mixing a water-absorbing resin and a water-soluble radical polymerization initiator, and irradiating the obtained mixture with active energy rays.
  • Patent Document 17 discloses a technique for granulating water-absorbent resin particles with water
  • Patent Document 6 also adds water to the water-absorbent resin.
  • a technique for imparting the damage resistance is disclosed.
  • Patent Documents 18 and 19 disclose a technique for reducing residual monomers
  • Patent Document 20 discloses a technique for improving colorability. Yes.
  • these techniques have never been used as a technique for solving the above-mentioned problems peculiar to the second surface crosslinking method and the third surface crosslinking method.
  • moisture content in a water absorbing resin by controlling the relative humidity and dew point of atmosphere at the time of the heat processing of the 1st surface crosslinking method surface crosslinking by the crosslinking agent which reacts with a carboxyl group
  • Patent Document 21, 22 a technology that prescribes the size of a device for cooling the water-absorbent resin after the heat treatment
  • Patent Document 24 a technology that adds an aqueous liquid during the heat treatment
  • Patent Document 25 and a technique for pretreating a humidified product by controlling the dew point before surface crosslinking are proposed.
  • Patent Document 27 a technique of adding water to the water-absorbent resin after surface cross-linking reaction and granulating
  • Patent Document 28 water absorption after heat treatment Technology for adding an aqueous liquid when cooling the water-soluble resin
  • Patent Document 29 a technique for improving the damage resistance by adding an aqueous liquid after heat treatment
  • Patent Document 30 the moisture content of the product Technology for improving damage resistance by adjusting
  • Patent Document 31 Technology for increasing moisture content of water-absorbent resin by re-humidification after heat treatment
  • Patent Document 34 Addition of polyvalent metal salt aqueous solution after surface crosslinking
  • the water-absorbent resin produced using the above-described surface cross-linking technology, etc. may be subjected to mechanical damage in the transportation process, filling process, and processing to absorbent articles such as paper diapers by the user, For this reason, generation
  • Patent Documents 21 to 28 when producing a water-absorbing resin having a high moisture content having damage resistance, the water-absorbing resin is applied to the inner wall of a mixer, a reactor, or a cooler. May stick to the surface, and stable continuous production may not be possible, leading to decreased productivity and physical properties.
  • an aqueous solution in which an inorganic compound, a polyvalent metal salt, or an alkanolamine is dissolved is used as an aqueous liquid for damage resistance (also known as impact resistance stability).
  • damage resistance also known as impact resistance stability
  • the object of the present invention is low cost (low temperature and short time), excellent balance and safety of water absorption capacity without pressure and water absorption capacity under pressure, and also has a small amount of residue such as a crosslinking agent and an initiator. It is to provide a method for producing a surface-crosslinked water-absorbing resin (water-absorbing agent).
  • the present inventors have found that among the first to third surface cross-linking methods, the second surface cross-linking method (monomer cross-linking method) described in Patent Documents 8 to 14 and the like.
  • the surface cross-linking by polymerization it has been found that the above-mentioned problems can be solved by using a specific cross-linking agent.
  • many proposals have been made as conventional crosslinking agents for polymerization of water-absorbent resins (for example, Patent Documents 35 to 50 described later), but the present invention has a molecular weight of 200 in surface crosslinking by monomer crosslinking polymerization. It was found that by using less specific crosslinking agent, the above problems were solved and the effects of the present invention (reduction of residual crosslinking agent, improvement of absorption capacity under pressure) were obtained.
  • the crosslinking agent is used. It was found that the molecular weight and functional group of the polymer greatly affected the remaining cross-linking agent and physical properties. When a specific cross-linking agent having a molecular weight of less than 200 was used, the residual cross-linking agent was very little, and safety was excellent. It was found that a surface-crosslinked water-absorbing resin (water-absorbing agent) excellent in the balance between the water absorption ratio under pressure and the water absorption capacity under pressure and cost performance can be produced.
  • the water-absorbing resin (base polymer) before surface cross-linking may be polymerized using such a specific cross-linking agent having a molecular weight of less than 200
  • the cross-linking agent is used for the production of the water-absorbing resin (base polymer). Even if it is used, the above effects (reduction of residual crosslinking agent, improvement of absorption capacity under pressure) are not particularly obtained, and the above effect is exhibited for the first time by using a specific crosslinking agent for surface crosslinking by monomer crosslinking polymerization. Is done.
  • a method for producing a water-absorbing agent (1) it is a method for producing a water-absorbing agent containing a poly (meth) acrylic acid (salt) -based water-absorbing resin as a main component, a) a mixing step in which a surface treatment liquid containing a radical polymerizable monomer and an organic crosslinking agent is mixed with a poly (meth) acrylic acid (salt) water absorbent resin to obtain a mixture; b) a reaction step of surface cross-linking polymerization of the mixture, The amount of the surface treatment liquid is 50 parts by weight or less with respect to 100 parts by weight of the water absorbent resin, The surface treatment liquid contains a mixing aid as necessary, An organic crosslinking agent having a plurality of functional groups selected from the group consisting of a functional group capable of reacting with a (meth) acrylate group and a functional group capable of reacting with a carboxyl group, and having a molecular weight of less than 200 Provided
  • the present inventors have conducted intensive research on the behavior of radical polymerization initiators.
  • the cause is the oxidation of the polymer by the radical polymerization initiator. This is because the reaction rate of the radical polymerization initiator added in the surface cross-linking step in the second and third surface cross-linking methods is extremely low compared to the polymerization step of the monomer aqueous solution, and a large amount remains unreacted. It was thought to be caused by this. That is, it was a phenomenon unique to the second and third surface crosslinking methods.
  • the reaction rate of the radical polymerization initiator can be significantly increased by adding a liquid containing water at a specific stage. It was.
  • a method for producing a water-absorbing agent (2) it is a method for producing a water-absorbing agent mainly composed of a poly (meth) acrylic acid (salt) -based water-absorbing resin, a) a mixing step of obtaining a mixture by mixing a surface treatment liquid containing a radical polymerization initiator with a poly (meth) acrylic acid (salt) water-absorbing resin having a water content of 30% by weight or less; b) a reaction step of subjecting the mixture to heat treatment or active energy ray irradiation treatment, There is provided a method for producing a water-absorbing agent, further comprising a water-containing liquid mixing step of mixing a liquid containing water with the mixture during and / or after the reaction step.
  • the present inventors have intensively studied various conditions for surface crosslinking when producing a surface-crosslinked water-absorbing resin (water-absorbing agent).
  • the physical properties of the water-absorbing resin such as damage resistance, moisture content, water absorption capacity under load, residual monomer, etc., depend on the internal dew point of the reactor used in the surface cross-linking reaction process and the powder temperature of the water-absorbing resin. It has been found that the internal atmosphere temperature and the inner wall surface temperature of the reaction apparatus affect the dependence and prevention of adhesion to the reaction apparatus and the like.
  • a method for producing a water-absorbing agent (3) it is a method for producing a water-absorbing agent containing a poly (meth) acrylic acid (salt) -based water-absorbing resin as a main component, a) a mixing step of mixing a surface treatment liquid containing a thermal decomposition type radical polymerization initiator with a poly (meth) acrylic acid (salt) water-absorbing resin to obtain a mixture; b) a reaction step of subjecting the mixture to a heat treatment,
  • the internal atmosphere dew point of the reaction apparatus used is 60 to 95 ° C.
  • the inner wall surface temperature of the reaction apparatus is not less than the atmospheric dew point and not more than 250 ° C.
  • the mixture is heated to treat the water absorbent resin.
  • a method for producing a water-absorbing agent is provided, characterized in that the temperature is 70 to 130 ° C.
  • the water absorbing agent which has a poly (meth) acrylic acid (salt) type water absorbing resin as a main component is shown.
  • the moisture content is 3 to 13% by weight
  • the moisture absorption capacity without pressure (CCRC) after correction of the moisture content is 33 (g / g) or more
  • the water absorption capacity under pressure after correction of the moisture content (CAAP 4.83 kPa) is 18 (g / g) or more
  • the residual monomer amount is 500 ppm or less
  • the total residual amount of the organic crosslinking agent having a molecular weight of less than 200 is 500 ppm or less
  • the residual amount of persulfate is 1 ppm or more and 1000 ppm or less
  • a water absorbing agent is provided in which the residual amount of the sulfur-based reducing agent is 1 ppm or more and 2500 ppm or less.
  • the fourth form (water-absorbing agent) can typically be obtained by the first form (water-absorbing agent production method (1)) to the third form (water-absorbing agent production method (3)), In particular, the production method is not limited.
  • any of the first form (the method for producing a water-absorbing agent (1)) to the third form (the method for producing a water-absorbing agent (3)) may be carried out singly or in combination. More specifically, it is preferable to combine the first and second modes, the first and third modes, the second and third combinations, and all the first to third modes.
  • a surface-crosslinked water-absorbing resin (water-absorbing agent) can be produced in a small amount.
  • the water-absorbing agent according to the present invention has high physical properties and a small amount of internal and surface residual cross-linking agent (particularly vinyl cross-linking agent), it is excellent in safety. Incontinence pads and sanitary napkins).
  • Water absorbing agent in the present invention means an aqueous liquid absorption gelling agent mainly composed of a surface-crosslinked water-absorbing resin.
  • the content of the water-absorbing resin in the water-absorbing agent is preferably 70 to 100% by weight, more preferably 75 to 97% by weight, still more preferably 80 to 95% by weight, and particularly preferably 85 to 95% by weight.
  • the other components (0 to 30% by weight, 3 to 25% by weight, 5 to 20% by weight, 5 to 15% by weight) preferably contain water as a main component, and further include inorganic fine particles and cationic polymers.
  • the aqueous liquid is not limited to water, but may contain water such as urine, waste water, blood, saline, waste liquid, deodorant, and fragrance. Further, the form of the aqueous liquid is not limited to liquid, but may be solid or gaseous (for example, water vapor or moisture).
  • the “water-absorbing resin” in the present invention means a water-swellable, water-insoluble polymer gelling agent and has the following physical properties. That is, as an indicator of “water swellability”, CRC (water absorption capacity under no pressure) defined by ERT441.2-02 (2002) is 5 (g / g) or more, and as an indicator of “water insolubility”, It means a polymer gelling agent having a physical property of Ext (water-soluble content) defined by ERT470.2-02 (2002) of 50% by weight or less.
  • the water-absorbent resin can be appropriately designed according to its use and is not particularly limited, but is preferably a hydrophilic cross-linked polymer obtained by cross-linking an unsaturated monomer having a carboxyl group.
  • the water-absorbing resin is not limited to a form in which the total amount (100% by weight) is a polymer, and is a water-absorbing resin composition containing additives and the like within a range satisfying the above physical properties (CRC, Ext). May be.
  • the content of the water-absorbent resin is preferably relative to the entire water absorbent resin composition. Is 70 to 99.9% by weight, more preferably 75 to 99% by weight, still more preferably 80 to 97% by weight, and particularly preferably 80 to 95% by weight.
  • water is preferable from the viewpoint of water absorption speed and impact resistance, and additives described later are included as necessary.
  • the water absorbent resin in the present invention is a term encompassing intermediates in the production process of the water absorbent resin. If there is a need for distinction separately, “hydrogel after polymerization”, “dry polymer after drying”, “water absorbent resin before surface crosslinking (base polymer)”, “water absorbent resin after surface crosslinking ( “Water-absorbing agent)” may be distinguished.
  • examples of the shape of the water-absorbing resin include a sheet shape, a fiber shape, a film shape, a particle shape, and a gel shape.
  • a particulate water-absorbing resin is preferable.
  • the “poly (meth) acrylic acid (salt) -based water-absorbing resin” in the present invention optionally includes a graft component, and (meth) acrylic acid and / or a salt thereof (hereinafter referred to as “(meth) acrylic”) It is a polymer mainly composed of “acid (salt)”.
  • the “main component” means that the content (use amount) of (meth) acrylic acid (salt) is usually from 50 to 100 mol based on the entire monomer (excluding the internal cross-linking agent) used in the polymerization. %, Preferably 70 to 100 mol%, more preferably 90 to 100 mol%, still more preferably substantially 100 mol%.
  • the poly (meth) acrylate as a polymer essentially contains a water-soluble salt, preferably a monovalent salt, more preferably an alkali metal salt or an ammonium salt.
  • CRC Centrifugation Retention Capacity
  • water absorption capacity means water absorption capacity without pressure (sometimes referred to as “water absorption capacity”.
  • 0.2 g of the water-absorbent resin in the nonwoven fabric was freely swollen for 30 minutes with respect to a large excess of 0.9 wt% sodium chloride aqueous solution, and then drained with a centrifuge (250 G). It is a water absorption magnification (unit; g / g).
  • the weight of 0.2 g of the water-absorbing resin is corrected by the water content (%), and the corrected water absorption ratio for the net water-absorbing resin excluding water is corrected. Is called CCRC (corrected CRC).
  • Ext is an abbreviation for Extractables and means a water-soluble component. Specifically, for 1.0 g of water-absorbing resin, a value obtained by measuring the amount of dissolved polymer after stirring for 16 hours at 500 rpm with respect to 200 ml of 0.9 wt% aqueous sodium chloride solution (unit: wt%) ).
  • “Moisture Content” (ERT430.2-02) “Moisture Content” means the water content of the water-absorbent resin. Specifically, it is a value (unit:% by weight) calculated from a loss on drying when 4.0 g of the water absorbent resin is dried at 105 ° C. for 3 hours. In the present invention, the measurement was performed by changing the water-absorbing resin to 1.0 g and the drying temperature to 180 ° C.
  • Residual Monomers means the amount of monomer (monomer) remaining in the water-absorbent resin (hereinafter referred to as “residual monomer” (RM)). Specifically, with respect to 1.0 g of the water-absorbing resin, the amount of residual monomer dissolved after stirring for 1 hour at 500 rpm with respect to 200 ml of 0.9 wt% sodium chloride aqueous solution was measured by high performance liquid chromatography (HPLC). Value (unit: ppm by weight). Note that the residual monomer after correction for the net water-absorbing resin excluding water is referred to as CRM (corrected RM) as in the CCRC of (a) above.
  • CRM corrected RM
  • PSD is an abbreviation for Particle Size Distribution and means a particle size distribution measured by sieve classification.
  • the weight average particle size (D50) and the particle size distribution width are described in US Pat. No. 7,638,570, columns 27 and 28, “(3) Mass-Average Particle Diameter (D50) and Logical Standard Deviation ( ⁇ )”. The measurement is performed in the same manner as the “of Particle Diameter Distribution”.
  • AAP is an abbreviation for Absorption Against Pressure, which means water absorption capacity under pressure. Specifically, 0.9 g of water-absorbing resin was swollen under a load of 2.06 kPa (21 g / cm 2, 0.3 psi) for 1 hour against a large excess of 0.9 wt% sodium chloride aqueous solution. Of water absorption (unit: g / g). In ERT442.2-02, “Absorption Under Pressure” is described, but it has substantially the same content as AAP.
  • the load condition may be changed to 4.83 kPa (0.7 psi, 50 [g / cm 2 ])
  • the measurement result under a load of 2.06 kPa is AAP 2.06 kPa. It describes and the result measured under the load of 4.83 kPa is described as AAP4.83 kPa.
  • CAAP corrected AAP
  • molecular weight means the third decimal place for each atom based on the atomic weight table (2012 edition) defined by the International Union of Pure and Applied Chemistry. Is a value calculated using the atomic weight obtained by rounding off. If the atomic weight of a typical atom is mentioned, it will be 1.01 of a hydrogen atom, 12.01 of a carbon atom, 14.01 of a nitrogen atom, and 16.00 of an oxygen atom.
  • FSC (ERT440.2-02): An abbreviation for Free Well Capacity, which means the free swelling ratio (unit: g / g) of the water-absorbent resin.
  • Flow Rate (ERT450.2-02): The flow rate of the water-absorbing resin.
  • Density (ERT460.2-02): means the bulk specific gravity of the water-absorbent resin.
  • X to Y indicating a range means “X or more and Y or less”.
  • t (ton) as a unit of weight means “Metric ton”
  • ppm means “weight ppm” or “mass ppm”.
  • weight and “mass”, “parts by weight” and “parts by mass”, “% by weight” and “% by mass” are treated as synonyms.
  • ⁇ acid (salt) means “ ⁇ acid and / or salt thereof”
  • (meth) acryl means “acryl and / or methacryl”.
  • liter may be described as “l” or “L”
  • wt% may be described as “wt%”.
  • N.sub. D. Non Detected
  • This step is a step of preparing an aqueous solution (monomer aqueous solution) containing (meth) acrylic acid (salt) as a main component.
  • the monomer aqueous solution may be in the form of an emulsion and / or slurry as long as it does not impair the water absorption performance of the resulting water-absorbing agent. Included as an aqueous solution.
  • the (meth) acrylic acid used as the monomer of the present invention is not limited in raw materials and production methods, and usually contains trace components such as a polymerization inhibitor and impurities.
  • a polymerization inhibitor phenols are preferable, methoxyphenols are more preferable, and the concentration of the polymerization inhibitor is preferably 1 to 200 ppm in consideration of the influence on the polymerizability of the monomer and the color of the resulting water-absorbing agent. More preferably, it is 10 to 160 ppm.
  • the impurities include compounds described in US Patent Publication No. 2008/0161512.
  • (Other monomers) in the present invention, other monomers may be used in combination with (meth) acrylic acid (salt), and examples of the other monomers include water-soluble or hydrophobic unsaturated monomers. Specific examples include monomers (excluding (meth) acrylic acid) described in paragraph [0035] of US Patent Application Publication No. 2005/215734.
  • the water-absorbing resin may contain the other monomer as a copolymerization component.
  • a monovalent salt such as an alkali metal salt, ammonium salt or alkanolamine salt, particularly an alkali metal salt, and further a sodium salt.
  • a polyvalent metal salt compound may be used in a very small amount (for example, about 0 to 5 mol% with respect to the monomer).
  • the neutralization rate of the monomer aqueous solution is preferably 10 to 90 mol%, more preferably 40 to 85 mol%, still more preferably 50 to 80 mol%, and particularly preferably 60 to 75 mol%.
  • the neutralization rate is represented by the amount of acid groups in the aqueous monomer solution, particularly the amount of basic compound added to the carboxylic acid group derived from the monomer.
  • the neutralization may be performed on the hydrogel after polymerization in addition to the monomer and / or the monomer aqueous solution before polymerization, or both may be used in combination. In addition, when performing several times, it is preferable to adjust to the range of the said neutralization rate in consideration of the addition amount of all the basic compounds.
  • the internal cross-linking agent used in the present invention is preferably a compound having two or more functional groups capable of reacting with (meth) acrylic acid, such as the cross-linking agents described in Patent Documents 35 to 54, for example, US Pat. No. 6,241,928. In the 14th column.
  • the crosslinking agent is a compound having two or more radical polymerizable functional groups, particularly two or more radical polymerizable compounds having a (poly) alkylene glycol structural unit.
  • a compound having a functional group preferably an allyl group, a (meth) acrylate group, particularly an acrylate group
  • Preferable examples of the alkylene glycol unit include polyethylene glycol having an n number of 1 to 100, and further 6 to 50. Of these, one or more are used.
  • the molecular weight of the internal cross-linking agent may be from 50,000 to 50,000, and is preferably larger than the cross-linking agent used for surface cross-linking described later (less than 200 molecular weight) in view of the physical properties of the resulting water-absorbing agent. Specifically, 200 to 40,000 is preferable, 300 to 30,000 is more preferable, and 400 to 10,000 is more preferable.
  • the amount of the internal crosslinking agent used is preferably 0.005 to 2 mol%, more preferably 0.01 to 1 mol%, and still more preferably 0.05 to 0.5 mol%, based on the monomer. is there. By setting the amount of the internal cross-linking agent used within the above range, desired water absorption characteristics can be obtained.
  • a method of adding an internal crosslinking agent after polymerization or post-crosslinking after polymerization a method of radical crosslinking with a radical polymerization initiator, an electron
  • a method of radiation cross-linking with a wire or the like a method in which a predetermined amount of an internal cross-linking agent is previously added to the monomer for polymerization and a cross-linking reaction at the same time as the polymerization is more preferable.
  • the polymerization initiator used in the polymerization step of the present invention is appropriately selected depending on the form of polymerization.
  • examples of such a polymerization initiator include a photodegradable radical polymerization initiator, a thermally decomposable radical polymerization initiator, and a redox polymerization initiator.
  • the amount of the polymerization initiator used is preferably from 0.0001 to 1 mol%, more preferably from 0.001 to 0.5 mol%, based on the monomer.
  • Examples of the photodegradable radical polymerization initiator include benzoin derivatives, benzyl derivatives, acetophenone derivatives, benzophenone derivatives, azo compounds, and the like.
  • Examples of the thermally decomposable radical polymerization initiator include persulfates such as sodium persulfate, ammonium persulfate and potassium persulfate; peroxides such as hydrogen peroxide, t-butyl peroxide and methyl ethyl ketone peroxide; 2 , 2′-azobis (2-amidinopropane) dihydrochloride, 2,2′-azobis [2-2 (-imidazolin-2-yl) propane] dihydrochloride, 2,2′-azobis (2-methylpro Examples thereof include azo compounds such as (pionitrile).
  • redox polymerization initiator examples include a system in which a reducing compound such as L-ascorbic acid or sodium bisulfite is used in combination with the persulfate or peroxide, and the both are combined. Moreover, it can also be mentioned as a preferable aspect to use together the said photodegradable radical polymerization initiator and a thermally decomposable radical polymerization initiator.
  • the water-soluble resin or water-absorbent resin is preferably added in an amount of 0 to 50% by weight, more preferably 0 to 20% by weight.
  • a foaming agent for example, carbonate, azo compound, bubbles, etc.
  • surfactant for example, chelating agent, chain transfer agent, etc.
  • I can do it.
  • water-soluble resin or water-absorbent resin gives a graft polymer or a water-absorbent resin composition (eg, starch- (meth) acrylic acid polymer, PVA- (meth) acrylic acid polymer, etc.).
  • a water-absorbent resin composition eg, starch- (meth) acrylic acid polymer, PVA- (meth) acrylic acid polymer, etc.
  • These polymers and water-absorbing resin compositions are also collectively referred to as poly (meth) acrylic acid (salt) -based water-absorbing resins in the present invention.
  • a monomer aqueous solution is prepared by mixing the above-described substances.
  • the concentration of the monomer component in the aqueous monomer solution is not particularly limited, but is preferably from the viewpoint of the physical properties of the water-absorbent resin. It is 10 to 80% by weight, more preferably 20 to 75% by weight, still more preferably 30 to 70% by weight.
  • spray droplet polymerization, aqueous solution polymerization, and reverse phase suspension polymerization are preferable from the viewpoint of water absorption characteristics and ease of polymerization control.
  • Aqueous solution polymerization and reverse phase suspension polymerization are more preferred, and aqueous solution polymerization is more preferred.
  • continuous aqueous solution polymerization is particularly preferable, and either continuous belt polymerization or continuous kneader polymerization may be used.
  • continuous belt polymerization is described in US Pat. Nos. 4,893,999 and 6,241,928, US Patent Application Publication No. 2005/215734, etc.
  • continuous kneader polymerization is described in US Pat. No. 6,987,151. , No. 6710141 specification, etc., respectively.
  • High temperature initiation polymerization means that the temperature of the monomer aqueous solution is preferably 30 ° C. or higher, more preferably 35 ° C. or higher, still more preferably 40 ° C. or higher, particularly preferably 50 ° C. or higher (the upper limit is the boiling point of the monomer).
  • the “high concentration polymerization” means that the monomer concentration is preferably 30% by weight or more, more preferably 35% by weight or more, still more preferably 40% by weight or more, particularly preferably.
  • Gel crushing step In aqueous solution polymerization, gel pulverization (formation of hydrous gel) is performed before or after polymerization, before drying. When the polymerization process is kneader polymerization, the polymerization process and the gel grinding process are performed simultaneously.
  • the gel pulverization method disclosed in International Publication WO2011 / 126079 is preferably applied.
  • This step is a step of obtaining a dry polymer by drying the particulate hydrogel obtained in the polymerization step and / or the gel grinding step to a desired resin solid content.
  • the resin solid content is determined from loss on drying (weight change when 1 g of water-absorbent resin is heated at 180 ° C. for 3 hours), and is usually 70% by weight or more, preferably 80% by weight or more, more preferably 85 to It is 99% by weight, more preferably 90 to 98% by weight, and particularly preferably 92 to 97% by weight (the remainder is mainly water).
  • the dried water-absorbent resin may contain water in the above range inside, but unless otherwise specified, the weight-based water-absorbent resin and water-absorbing agent including water are described below. (For example, in the weight ratio described later, 100 parts by weight of the water-absorbing resin refers to the weight including water contained in the resin).
  • drying step of the present invention although not particularly limited, for example, heat drying, hot air drying, vacuum drying, fluidized bed drying, infrared drying, microwave drying, drum dryer drying, drying by azeotropic dehydration with a hydrophobic organic solvent, Various drying methods such as high-humidity drying using high-temperature steam are applied.
  • hot air drying is preferable because of high efficiency, and band drying in which hot air drying is performed on a belt is particularly preferable.
  • the hot air temperature is preferably 100 to 250 ° C., more preferably 120 to 220 ° C. from the viewpoint of color tone and efficiency.
  • Examples of the equipment used in the pulverization process of the present invention include a high-speed rotary pulverizer such as a roll mill, a hammer mill, a screw mill, and a pin mill, a vibration mill, a knuckle type pulverizer, and a cylindrical mixer. Is done.
  • the particle size adjustment method in the classification step of the present invention is not particularly limited, and examples thereof include sieve classification using a JIS standard sieve (JIS Z8801-1 (2000)) and airflow classification.
  • the particle size adjustment of the water-absorbing resin is not limited to the above pulverization step and classification step, but is a polymerization step (especially reverse phase suspension polymerization or spray droplet polymerization) or other steps (for example, granulation step, fine powder recovery step). Therefore, it can be carried out as appropriate.
  • the weight average particle diameter (D50) is preferably 200 to 600 ⁇ m, more preferably 200 to 550 ⁇ m, still more preferably 250 to 500 ⁇ m, and particularly preferably 300 to 450 ⁇ m.
  • the ratio of particles having a particle diameter of less than 150 ⁇ m is preferably 0 to 10% by weight, more preferably 0 to 5% by weight, and still more preferably 0 to 1% by weight.
  • the ratio of particles having a particle diameter of 850 ⁇ m or more is preferably It is 0 to 5% by weight, more preferably 0 to 3% by weight, still more preferably 0 to 1% by weight.
  • the logarithmic standard deviation ( ⁇ ) of the particle size distribution is preferably 0.20 to 0.50, more preferably 0.25 to 0.40, and still more preferably 0.27 to 0.35. These particle sizes are measured using a standard sieve according to the measurement methods disclosed in US Pat. No. 7,638,570 and EDANA ERT420.2-02.
  • the above-mentioned particle size is applied not only to the water-absorbing resin before surface crosslinking but also to the water-absorbing resin after surface crosslinking and the water-absorbing agent as the final product. Therefore, it is preferable that the fluctuation of the particle diameter is small before and after the surface crosslinking step.
  • the ratio of the average particle diameter after surface crosslinking to that before surface crosslinking is preferably 0.8 to 1.5, more preferably 0.9 to 1.2.
  • This step is a step for obtaining a water-absorbing agent using a water-absorbing resin that is not surface-crosslinked, and a predetermined surface treatment liquid is mixed with a poly (meth) acrylic acid (salt) -based water-absorbing resin to obtain a mixture.
  • this surface cross-linking step it is possible to increase the cross-linking density of the surface layer of the water-absorbent resin (part of several ⁇ m to several tens ⁇ m from the surface of the water-absorbent resin).
  • a water absorbent resin obtained in accordance with the method for producing the poly (meth) acrylic acid (salt) water absorbent resin obtained in accordance with the method for producing the poly (meth) acrylic acid (salt) water absorbent resin.
  • the surface cross-linking step may be repeated not only once but also a plurality of times.
  • the surface cross-linking step is preferably performed on the water-absorbing resin before surface cross-linking, but the surface cross-linking is already performed on the water-absorbing resin surface-crosslinked by the methods described in Patent Documents 1 to 5.
  • the surface cross-linking may be further performed by the methods described in Patent Documents 1 to 5.
  • This step is a step of obtaining a water absorbent resin mixture (hereinafter referred to as “mixture”) by adding and mixing the surface treatment liquid to the water absorbent resin described above.
  • the surface treatment liquid essentially contains a radical polymerizable monomer and an organic crosslinking agent, in addition to a radical polymerization initiator (particularly a thermal decomposition type radical polymerization initiator), a solvent, A mixing aid or the like is optionally included.
  • the surface treatment liquid essentially contains a radical polymerization initiator (particularly a thermal decomposition type radical polymerization initiator), and in addition, a radical polymerizable monomer, an organic crosslinking agent, Solvents, mixing aids and the like are optionally included.
  • the surface treatment liquid essentially contains a pyrolytic radical polymerization initiator, and in addition, a radical polymerizable monomer, an organic crosslinking agent, a solvent, a mixing aid and the like. Optionally included.
  • the organic crosslinking agent has a plurality of functional groups selected from the group consisting of a functional group capable of reacting with a (meth) acrylate group and a functional group capable of reacting with a carboxyl group. And an organic compound having a molecular weight of less than 200.
  • the surface cross-linking agent by using the surface cross-linking agent, there is very little remaining of the cross-linking agent, the safety is excellent, and the balance between the water absorption magnification under no pressure and the water absorption magnification under pressure and the cost performance.
  • a surface-crosslinked water-absorbing resin (water-absorbing agent) excellent in the above can be obtained.
  • the total amount of the surface treatment liquid is preferably more than 0 and 50 parts by weight or less, more preferably 0.1 to 40 parts by weight with respect to 100 parts by weight of the water-absorbing resin (including moisture if necessary), More preferred is 1 to 30 parts by weight, particularly preferred is 3 to 20 parts by weight, and most preferred is 5 to 15 parts by weight.
  • the total amount of the surface treatment liquid is small, surface crosslinking may be insufficient, and if the total amount exceeds 50 parts by weight, adhesion or clogging of the water absorbent resin mixture, etc. This is not preferable because of the occurrence of this problem, the absorption capacity (CRC) of the water-absorbing agent without applying pressure, and the handleability of the mixture of the water-absorbent resin and the surface treatment liquid are lowered.
  • CRC absorption capacity
  • the radical polymerizable monomer means a compound that can be polymerized by radical polymerization, and specifically, a monomer having an (preferably terminal) unsaturated double bond, such as the poly (meta) described above.
  • (Meth) acrylic acid (salt) used in the production of acrylic acid (salt) -based water-absorbent resin and / or monomers used in combination may be preferably used.
  • the radical polymerizable monomer preferably contains an acid group and has a predetermined neutralization rate (mol% of neutralized acid groups in all acid groups).
  • a compound containing an acid group is very excellent in terms of water absorption characteristics.
  • the acid group include a carboxyl group, a sulfone group, and a phosphoric acid group.
  • the acid group-containing monofunctional radical polymerizable monomer is preferably a monomer containing an acid group.
  • (meth) acrylic acid, 2- (meth) acryloylethanesulfonic acid, 2- (meth) acryloylpropanesulfonic acid, 2- (meth) acrylamido-2-methylpropanesulfonic acid, vinylsulfonic acid, styrene Examples include sulfonic acids and / or their salts. Of these, (meth) acrylic acid and 2- (meth) acrylamido-2-methylpropanesulfonic acid are more preferable, and acrylic acid is particularly preferable in terms of water absorption characteristics.
  • the proportion of the total amount of acrylic acid (salt) in the radically polymerizable monomer containing all acid groups is preferably 50 to 100 mol%, more preferably 70 to 100 mol%, particularly preferably 90 to 100 mol%. is there.
  • the acid group-containing radical polymerizable monomer may be used alone or in a mixture of two or more.
  • the monomer is preferably a monovalent salt selected from alkali metal salts, ammonium salts, and amine salts.
  • an alkali metal salt is more preferable, and a salt selected from a sodium salt, a lithium salt, and a potassium salt is particularly preferable.
  • the neutralization rate of the acid group-containing radical polymerizable monomer is appropriately determined in the range of 0 to 100 mol%, and may be the same as or different from the neutralization rate of the water-absorbent resin as the base polymer. It may be.
  • the “total acid groups of the acid group-containing radical polymerizable monomer” and “neutralized acid group” are all acid groups when there are two or more acid group-containing radical polymerizable monomers.
  • the total of the acid group and the neutralized acid group in a containing radically polymerizable monomer is pointed out. For example, when acrylic acid and sodium acrylate are used in a molar ratio of 1: 1 as the acid group-containing radical polymerizable monomer, the neutralization rate of the acid group-containing radical polymerizable monomer is 50 mol. %.
  • the amount of the radical polymerizable monomer present in the crosslinking polymerization reaction system is preferably 100 parts by weight of the water absorbent resin.
  • the amount is 0.1 to 20 parts by weight, more preferably 1 to 15 parts by weight, still more preferably 2 to 10 parts by weight, and particularly preferably 3 to 7 parts by weight. If the amount of the monomer is less than 0.1 parts by weight or unused (0), the water absorption performance under pressure of the surface-crosslinked water-absorbing resin is not improved to a sufficient value, which is not preferable. On the other hand, when the amount of the radically polymerizable monomer exceeds 20 parts by weight, the water absorption capacity without load of the surface-crosslinked water-absorbing resin is remarkably lowered, which is not preferable.
  • radical polymerizable monomers used in the second and third forms are optional, but when used, the radical polymerizable monomer species and amount exemplified in the first embodiment are used. . Also in the second and third embodiments, it is preferable to include a radically polymerizable monomer in the surface crosslinking agent solution because the amount of the organic crosslinking agent and radical polymerization initiator described later can be reduced.
  • the organic crosslinking agent used in the surface crosslinking step of the present invention is one or more carboxyl groups, particularly from the viewpoint of the survivability of the crosslinking agent, the safety of the crosslinking agent alone, and the efficiency of surface crosslinking with respect to the amount of crosslinking agent used. It has two or more functional groups capable of reacting with (meth) acrylate groups and has a molecular weight of less than 200.
  • the organic cross-linking agent is an organic covalent cross-linking agent, and is a cross-linking agent that cross-links with a functional group of a monomer or a water absorbent resin through a covalent bond.
  • a crosslinking agent that forms a crosslink with an ionic bond such as aluminum acrylate (for example, a polyvalent metal salt of an unsaturated organic acid) is not included in the organic crosslinker in the present invention, and is an ionic crosslink only with a polyvalent metal salt.
  • the effect of the present invention is not exhibited in terms of improving the absorption capacity under pressure.
  • the molecular weight of the organic crosslinking agent is less than 200, preferably less than 190, more preferably less than 180.
  • the smaller molecular weight is preferable because the cross-linking efficiency is excellent.
  • the molecular weight is 200 or more, the crosslinking agent molecule becomes large and it is difficult to penetrate from the surface of the water-absorbent resin, so that the CRC is difficult to be lowered. This is not preferable because the residual crosslinking agent in the resin increases.
  • the lower limit of the molecular weight is usually preferably 50 or more, more preferably 80 or more, and 100 or more.
  • the molecular weight of the organic crosslinking agent is smaller than the molecular weight of the crosslinking agent (so-called internal crosslinking agent) used in the production of the water-absorbent resin, for example, the molecular weight ratio (molecular weight of surface crosslinking agent / molecular weight of internal crosslinking agent). ) Less than 1, particularly 0.05 to 0.9, 0.1 to 0.8, and 0.2 to 0.5.
  • examples of the functional group capable of reacting with a carboxyl group include a cyclic functional group, a hydroxy group, a primary amino group, a secondary amino group, and an isocyanate group.
  • examples of cyclic functional groups include an epoxy group, an aziridine group, an oxetane group, an ethylene carbonate group, an oxazoline group, and an oxazolidinone group.
  • the reaction between the functional group of the cross-linking agent and the carboxyl group of the water-absorbent resin may be performed at the time of mixing with the surface treatment liquid containing an organic cross-linking agent, or may be simply performed in the (3-1-2) cross-linking polymerization step described later.
  • the functional group of the cross-linking agent and the carboxyl group of the water-absorbing resin may be reacted.
  • the functional group of the cross-linking agent and the water-absorbing resin can be reacted.
  • a carboxyl group may be reacted.
  • organic crosslinking agent for example, an internal crosslinking agent used in the production of the poly (meth) acrylic acid (salt) -based water-absorbing resin, U.S. Pat. Nos. 6,228,930 and 6071976, You may select the organic type crosslinking agent which satisfy
  • a cross-linking agent having a molecular weight of less than 200 and having a plurality of (meth) acrylate groups a cross-linking agent having a functional group capable of reacting with a (meth) acrylate group and a functional group capable of reacting with a carboxyl group, and reacting with a carboxyl group
  • a cross-linking agent having two or more functional groups that can be used.
  • the crosslinking agent has an organic crosslinking agent having a molecular weight of less than 200, and has (a) a polyfunctional (meth) acrylate crosslinking agent, and (b) a functional group capable of reacting with a carboxyl group (A cross-linking agent selected from a (meth) acrylate-based cross-linking agent and (c) a cross-linking agent having a functional group capable of reacting with a plurality of carboxyl groups is used.
  • the (a) is a di (meth) acrylate-based crosslinking agent
  • the (b) is a (meth) acrylate group
  • other functional groups include a cyclic functional group, a hydroxy group, a primary amine
  • the (c) as the crosslinking agent having a functional group capable of reacting with a plurality of carboxyl groups particularly a polyol-based crosslinking Agents, polyamine crosslinking agents, polyisocyanate crosslinking agents, and crosslinking agents having one or more cyclic functional groups.
  • a cyclic functional group such as an epoxy group or an ethylene carbonate group
  • it can react with another carboxyl group after once generating a hydroxyl group or an amino group by a ring-opening reaction with the carboxyl group.
  • one cyclic functional group has two reactive sites, it is a crosslinking agent that can react with a plurality of carboxyl groups, and in the present invention, it has a plurality of functional groups that can react with carboxyl groups.
  • (meth) acrylate groups are preferable because they are excellent in copolymerizability with radical polymerizable monomers, and epoxy groups and ethylene carbonate groups are excellent in reactivity with carboxyl groups. .
  • (A) Multifunctional (meth) acrylate-based crosslinking agent As the organic crosslinking agent having a plurality of (meth) acrylate groups and a molecular weight of less than 200, that is, a multifunctional (meth) acrylate-based crosslinking agent, di ( A (meth) acrylate-based cross-linking agent is used, and these di (meth) acrylate-based cross-linking agents having a molecular weight of less than 200 have a plurality of functional groups that are easily copolymerizable with a radically polymerizable monomer, and therefore have a good cross-linking efficiency and are particularly good.
  • the polyfunctionality means that there are a plurality of acrylate groups and methacrylate groups in one molecule, and di (meth) acrylate is a general term for diacrylate, dimethacrylate, and acrylate methacrylate.
  • ethylene glycol diacrylate molecular weight 170.18
  • ethylene glycol acrylate methacrylate molecular weight 184.21
  • ethylene glycol dimethacrylate molecular weight 198.24
  • Propylene glycol diacrylate molecular weight 184.21
  • 1,3-propylene glycol diacrylate molecular weight 184.21
  • propylene glycol acrylate methacrylate molecular weight 198.24
  • 1,3-propylene glycol acrylate methacrylate molecular weight 198.24
  • 1,3-butanediol diacrylate molecular weight 198.24
  • 1,4-butanediol diacrylate molecular weight 198.24
  • (B) (meth) acrylate-based crosslinking agent having a functional group capable of reacting with a carboxyl group an organic crosslinking agent having a molecular weight of less than 200 having both a (meth) acrylate group and a functional group capable of reacting with a carboxyl group
  • the monofunctional (meth) acrylate crosslinking agent having a functional group capable of reacting with a carboxyl group has a functional group that is easily copolymerized with one or two radical polymerizable monomers, that is, a (meth) acrylate group.
  • it since it has a functional group excellent in reactivity with a carboxyl group contained in the water-absorbing resin and / or radically polymerizable monomer, it is more preferable because of its good crosslinking efficiency.
  • a cross-linking agent having an epoxy group converted to ethylene carbonate (glycerol carbonate acrylate, molecular weight 172.15), and a cross-linking agent having an epoxy group converted to ethylene carbonate group by reacting glycidyl methacrylate with carbon dioxide (glycerol carbonate methacrylate, molecular weight 186) .18), 2-isocyanate ethyl acrylate (molecular weight 141.14), 2-isocyanate ethyl methacrylate (molecular weight 155.17), glycerin monoacrylate (molecular weight 146.16), glycerin Monometallate (molecular weight 160.19), hydroxyethyl acrylate (molecular weight 116.13), hydroxyethyl methacrylate (molecular weight 130.16), aminoethyl acrylate (molecular weight 115.15), aminoethyl methacrylate (molecular weight 129.18) 1,3-propy
  • (meth) acrylates having cyclic functional groups (especially epoxy groups or ethylene carbonate groups) as functional groups in particular glycidyl (meth) acrylates and glycerol carbonate (meth) acrylates are (meth) acrylate-based crosslinking agents. Is more preferable.
  • a cross-linking agent having a plurality of functional groups capable of reacting with a carboxyl group is a water-absorbing resin and / or a radically polymerizable monomer. Since it has a plurality of functional groups excellent in reactivity with the carboxyl group contained in the monomer, crosslinking efficiency is good and preferable.
  • oxazolidinone molecular weight 87.09
  • oxetane molecular weight 58.09
  • ethylene urea molecular weight 86.11
  • ethylene carbonate molecular weight 88.07
  • propylene carbonate molecular weight 102.10
  • ethylene glycol A crosslinking agent having a cyclic functional group such as diglycidyl ether (molecular weight 174.22), propylene glycol diglycidyl ether (molecular weight 188.25), glycerin carbonate (molecular weight 118.10), glycidol (molecular weight 74.09), Ethylene glycol monoglycidyl ether (molecular weight 118.15), propylene glycol monoglycidyl ether (molecular weight 132.18), glycerin monoglycidyl ether (molecular weight 148.18), trimethylolpropane monoglycidyl este
  • crosslinking agents having a plurality of functional groups capable of reacting with a carboxyl group are preferably a crosslinking agent selected from hydroxyl groups and cyclic functional groups, and further a functional group selected from hydroxyl groups, carbonate groups and glycidyl groups.
  • a cross-linking agent is used.
  • the functional group of the organic crosslinking agent having a molecular weight of less than 200 is an amide group, specifically, N, N′-methylenebisacrylamide (molecular weight 154.19), N, N′-methylenebismethacrylamide (Molecular weight 182.25) and the like are not preferable in actual use because they have safety problems such as mutagenicity and reproductive toxicity.
  • the organic crosslinking agent has an allyl group or a vinyl group and another functional group is one compound, specifically, allyl acrylate (molecular weight 112.14), allyl methacrylate (molecular weight 126.17), vinyl In the case of acrylate (molecular weight 98.11), vinyl methacrylate (molecular weight 112.14), etc., the allyl group or vinyl group is inferior in copolymerizability with the radical polymerizable monomer. Is not preferable, because a water-absorbent resin having a low balance between water absorption capacity without pressure and water absorption capacity under pressure cannot be obtained.
  • the molecular weight of the organic crosslinking agent is 200 or more, the crosslinking agent molecule becomes large and it is difficult to penetrate from the surface of the water-absorbent resin, so that the CRC is difficult to be lowered.
  • the residual cross-linking agent in the water-absorbent resin increases, which is not preferable.
  • the scope of the present invention is not limited, as a reason why the specific crosslinking agent having a molecular weight of less than 200 exhibits the above-mentioned effect specifically in the surface crosslinking polymerization, the monomer aqueous solution containing the crosslinking agent is polymerized as it is. Unlike the polymerization of the water-absorbent resin, it is presumed to be the influence of the permeability to the water-absorbent resin due to the molecular weight.
  • the amount of the organic crosslinking agent having a molecular weight of less than 200 is 0.001 to 5 parts by weight with respect to 100 parts by weight of the water-absorbent resin, preferably 0.01 to 2 parts by weight, more preferably 0.05 to 1 part by weight. If the amount used is less than 0.001 part by weight, the water-absorbent resin is not easily cross-linked and the water absorption performance under pressure is not improved to a sufficient value, which is not preferable.
  • the amount used exceeds 5 parts by weight, not only is the water absorption capacity of the surface-crosslinked water-absorbent resin under no pressure significantly reduced, but it is also not preferable because it causes an increase in cost and an increase in the amount of the remaining crosslinking agent.
  • the organic crosslinking agent having a molecular weight of less than 200 one or two or more other crosslinking agents may be used in combination, if necessary.
  • the range is 0 to 100 parts by weight with respect to parts by weight.
  • the ratio of the monomer to the crosslinking agent can also be determined as appropriate.
  • the range is 001 parts by weight.
  • Organic crosslinking agent used in the second and third embodiments an organic crosslinking agent is arbitrarily used.
  • an organic crosslinking agent exemplified below is used.
  • organic crosslinking agent one or more can be arbitrarily selected from the internal crosslinking agent and the organic crosslinking agent used in the first embodiment.
  • the molecular weight of the organic crosslinking agent is preferably less than 5000, more preferably less than 500, and still more preferably less than 200 (the lower limit is usually 50).
  • the smaller molecular weight is preferable because the crosslinking efficiency is excellent, and when the molecular weight is too large, particularly when 5000 or more, the cross-linking agent molecule is too large, the permeability into the water-absorbent resin is lowered, and the CRC is hardly lowered. This is not preferable because the surface crosslinking efficiency is reduced, and the amount of the remaining crosslinking agent in the water-absorbent resin after the surface crosslinking is increased.
  • a crosslinking agent having a plurality of (meth) acrylate groups and (meth) acrylamide groups ethylene glycol diacrylate, ethylene glycol acrylate methacrylate, ethylene glycol dimethacrylate, propylene glycol diacrylate
  • examples include propylene glycol acrylate methacrylate, 1,3-butanediol diacrylate, 1,4-butanediol diacrylate, glycidyl acrylate, glycidyl methacrylate, N, N'-methylenebisacrylamide, N, N'-methylenebismethacrylamide Is done.
  • cross-linking agent having one or more functional groups capable of reacting with (meth) acrylate groups and carboxyl groups
  • glycidol, glycidyl (meth) acrylate, and glycidyl (meth) acrylate are reacted with carbon dioxide to convert the epoxy ring to an ethylene carbonate ring.
  • Examples of the crosslinking agent are as follows.
  • crosslinking agent having a plurality of functional groups covalently bonded to carboxyl groups alkylene carbonates such as ethylene carbonate and propylene carbonate, polyvalent glycidyl ethers such as ethylene glycol diglycidyl ether and propylene glycol diglycidyl ether, propanediol, propylene glycol and the like
  • alkylene carbonates such as ethylene carbonate and propylene carbonate
  • polyvalent glycidyl ethers such as ethylene glycol diglycidyl ether and propylene glycol diglycidyl ether
  • propanediol propylene glycol and the like
  • Oxazolidinones such as polyhydric alcohol, oxazolidinone, dioxazolidinone and the like
  • organic crosslinking agents include the organic crosslinking agents exemplified in the first embodiment.
  • the amount of the organic crosslinking agent exemplified in the first embodiment is used, and the organic crosslinking agent is included in the surface crosslinking agent solution. Is preferable because the amount of the radically polymerizable monomer and radical polymerization initiator used is small.
  • an inorganic crosslinking agent can be used, and it is more preferable to use it together with an organic crosslinking agent.
  • the inorganic crosslinking agent include polyvalent metal salts used in the art, more preferably water-soluble polyvalent metal salts, particularly aluminum salts such as aluminum sulfate and aluminum acetate.
  • the added amount of the inorganic crosslinking agent is preferably 0.01 to 5 parts by weight, more preferably 0.05 to 1 part by weight with respect to 100 parts by weight of the water absorbent resin powder.
  • the surface crosslinking reaction step of the water-absorbent resin is preferably performed in the presence of a radical polymerization initiator.
  • the surface treatment liquid essentially contains a radical polymerization initiator (preferably a thermal decomposition type radical polymerization initiator)
  • the reaction step is performed in the presence of the radical polymerization initiator. It is essential that
  • the surface treatment liquid essentially contains a thermal decomposition type radical polymerization initiator, so that the reaction step must be performed in the presence of the thermal decomposition type radical polymerization initiator. is there.
  • the radical polymerization initiator that can be used in the surface crosslinking reaction step is not particularly limited, and the polymerization initiators described in Patent Documents 8 to 14 (particularly, Patent Documents 9 to 14) can be applied, and the above poly (meth) acrylic acid can be used. What is necessary is just to use the thermal decomposition type radical polymerization initiator and photodecomposition type radical polymerization initiator which can be used at the time of manufacture of (salt) type
  • the thermal decomposition type radical polymerization initiator is a compound that generates radicals by heating, and preferably has a 10-hour half-life temperature of 0 ° C. or higher and 120 ° C. or lower, more preferably 20 ° C. or higher and 100 ° C. or lower, Considering the temperature conditions for irradiating the active energy ray, those of 40 ° C. or more and 80 ° C. or less are particularly preferable. If the 10-hour half-life temperature is less than 0 ° C. (lower limit), it is unstable during storage, and if it exceeds 120 ° C. (upper limit), it may be chemically too stable to lower the reactivity.
  • Specific thermal decomposition type radical polymerization initiators include persulfates such as sodium persulfate, ammonium persulfate and potassium persulfate; hydrogen peroxide; organic peroxides such as t-butyl hydroperoxide; 2,2 ′ -Azobis (2-amidinopropane) dihydrochloride, 2,2'-azobis [2-2 (-imidazolin-2-yl) propane] dihydrochloride, 2,2'-azobis (2-methylpropionitrile) And azo compounds such as Among them, persulfates such as sodium persulfate, ammonium persulfate, and potassium persulfate having a 10-hour half-life temperature of 40 to 80 ° C., and 2,2′-azobis (2-amidinopropane) dihydrochloride, 2, Azo compounds such as 2′-azobis [2-2 (-imidazolin-2-yl) propane] dihydrochloride and 2,2′-azobis (2-
  • a water-soluble pyrolytic radical polymerization initiator particularly a persulfate
  • a persulfate is preferable in that the absorption capacity under pressure, liquid permeability, and free swelling ratio are all excellent.
  • Persulfate can be used in combination of not only one type but also two or more types having different counter ions.
  • the photodegradable initiator is a compound that generates radicals upon irradiation with light (preferably active energy rays), and examples thereof include benzoin derivatives, benzyl derivatives, benzophenone derivatives, and acetophenone derivatives.
  • benzoin derivatives preferably benzoin derivatives
  • benzyl derivatives preferably benzophenone derivatives
  • acetophenone derivatives preferably benzoin derivatives
  • commercially available products include hydroxycyclohexyl-phenyl ketone (trade name Irgacure (registered trademark) 184 of Ciba Specialty Chemicals), 1- [4- (2-hydroxyethoxy) -phenyl] -2-hydroxy-2-methyl- 1-propan-1-one (Irgacure (registered trademark) 2959) or the like is more preferably used.
  • the amount of the radical polymerization initiator contained in the water absorbent resin in the surface crosslinking reaction step or mixed with the water absorbent resin before the reaction step is preferably 0.01 to 100 parts by weight with respect to 100 parts by weight of the water absorbent resin. 2 parts by weight, more preferably 0.05 to 1 part by weight, particularly preferably 0.1 to 0.5 part by weight. If the amount of the radical polymerization initiator is less than 0.01 parts by weight, the crosslinked structure is not effectively introduced on the surface of the water absorbent resin, which is not preferable. On the other hand, if the amount of the radical polymerization initiator exceeds 2 parts by weight, a large amount of the initiator remains or is colored, and the water absorption performance of the water absorbent resin after surface cross-linking is not preferable.
  • the radical polymerizable monomer, the organic cross-linking agent, and the radical polymerization initiator are present together with the water-absorbing resin in the form of the radical polymerizable monomer, the organic cross-linking agent, and the radical polymerization initiator. May be directly mixed with the water-absorbent resin as it is, but a form in which these are mixed with the water-absorbent resin in a state where they are dissolved in a solvent is preferably employed.
  • the solvent is not particularly limited as long as the solvent described in Patent Documents 8 to 14 (particularly Patent Documents 9 to 14) can be applied and can dissolve these solvents, but is not limited thereto.
  • Water is preferable as the solvent because the solubility of the radical polymerization initiator, the safety of the solvent, and the water-absorbing resin have water-absorbing properties.
  • the amount of water added to and mixed with the water absorbent resin is preferably 1 to 20 parts by weight, more preferably 2 to 10 parts by weight with respect to 100 parts by weight of the water absorbent resin. If the amount of water is less than 1 part by weight, the radically polymerizable monomer, the organic crosslinking agent, the radical polymerization initiator, etc. may not dissolve, and the surface treatment liquid will not easily penetrate into the water absorbent resin.
  • the aqueous solution for adding the radical polymerizable monomer, the organic crosslinking agent, and the radical polymerization initiator is not limited to the solubility / permeability of the surface treatment liquid, and other solvents and other components (for example, And a mixing aid described later).
  • the concentration of the crosslinking agent and the monomer (aqueous solution concentration) in the case of using a solvent is not particularly limited as long as it is a concentration that satisfies the above-mentioned usage amount, but is preferably 0.001 to 99% by mass, 01 to 90% by mass is more preferable, and 0.1 to 80% by mass is a more preferable range. If the concentration is less than 0.001%, the water-absorbent resin may not be sufficiently surface-crosslinked and the absorption capacity under pressure may not be improved. If the concentration is 99% or more, a large amount of the crosslinking agent and the monomer may remain. is there.
  • a radical polymerizable monomer, an organic crosslinking agent, a radical polymerization initiator, and water are present in the crosslinking polymerization reaction system together with the water-absorbing resin.
  • a mixing aid may be present in the reaction system.
  • the mixing aid is not particularly limited as long as it can suppress aggregation of the water-absorbing resin with water and can improve the mixing property of the surface treatment liquid and the water-absorbing resin.
  • Patent Documents 8 to 14 particularly Patent Document 9). To 14) can be applied.
  • the mixing aid By adding the mixing aid, the water-absorbing resin is prevented from aggregating with water, and the surface treatment liquid is more uniformly mixed with the water-absorbing resin. As a result, the entire surface of the water absorbent resin can be more uniformly cross-linked.
  • mixing aid examples include, for example, surfactants, water-soluble polymers, hydrophilic organic solvents, water-soluble inorganic compounds, inorganic acids (salts), and organic acids (salts).
  • mixing aids may be used alone or in the form of a mixture of two or more.
  • the amount of the mixing aid in the cross-linking polymerization reaction system is not particularly limited as long as it is a form that can suppress aggregation of the water-absorbing resin with water and improve the mixing property between the surface treatment liquid and the water-absorbing resin.
  • the amount is preferably from 0.0001 to 20 parts by weight, more preferably from 0.001 to 10 parts by weight, still more preferably from 0.005 to 5 parts by weight, particularly preferably from 0.01 to 100 parts by weight based on 100 parts by weight of the water absorbent resin. 1 part by weight.
  • the order of addition of the mixing aid in the case of using the mixing aid is also not particularly limited, and after adding the mixing aid to the water-absorbent resin in advance, a radical polymerizable monomer or an organic crosslinking agent (in some cases) Is a method in which a surface treatment liquid containing these is added and mixed, and a method in which a mixing aid is dissolved in the surface treatment liquid and mixed with a water-absorbent resin simultaneously with a radical polymerizable monomer or an organic crosslinking agent, etc. Can be used.
  • the total amount is the surface treatment liquid amount in the surface crosslinking step.
  • the surface treatment liquid preferably contains a polymerization inhibitor and / or oxygen (dissolved oxygen), and is preferably stored and prepared at a predetermined temperature or lower.
  • the polymerization inhibitor is preferably phenols, more preferably methoxyphenols.
  • the concentration thereof is preferably 1 to 200 ppm (vs. radically polymerizable monomer), more preferably 10 to 160 ppm, from the viewpoint of polymerizability and the color of the water-absorbent resin.
  • the amount of oxygen (dissolved oxygen) is 1 ppm to saturated concentration.
  • the temperature may be 50 ° C. or lower, preferably 40 ° C. or lower, more preferably 30 ° C. or lower, and may be a temperature that does not cause the surface treatment liquid to freeze or cause components to precipitate or separate. ° C or higher is preferable, and 5 ° C or higher is more preferable.
  • the method for adding and mixing the surface treatment liquid in the present invention is not particularly limited, but after preparing the liquid mixture as the surface treatment liquid in advance, it is preferably sprayed or dropped into the water absorbent resin (powder) and mixed. What is necessary is just to spray and mix.
  • the mixing device used for the mixing is not particularly limited, but a high-speed stirring type mixing device is preferable, a high-speed stirring type continuous mixing device is more preferable, and a horizontal or vertical type high-speed stirring type continuous mixing device is further provided. preferable.
  • Specific examples include Shugi mixers and turbulizers (both manufactured by Hosokawa Micron) and Redige mixers (manufactured by Redige).
  • the rotational speed of the mixing apparatus is preferably 100 to 10,000 rpm, more preferably 300 to 2000 rpm.
  • the residence time is preferably within 180 seconds, more preferably from 0.1 to 60 seconds, and even more preferably from 1 to 30 seconds.
  • the temperature of the water absorbent resin powder supplied to the mixing step is preferably 20 to 100 ° C., more preferably 30 to 80 ° C., and still more preferably 40 to 70 ° C. By setting it as the said temperature range, the physical-property fall of a water absorbing resin can be suppressed.
  • the surface treatment liquid may be added after being mixed in advance, may be added separately for each component, or may be added after mixing some of each component. Furthermore, the surface treatment solution may be added from one place or may be added in a plurality of places. In addition, when adding by dividing
  • the liquid temperature at the time of adding the surface treatment liquid containing the radical polymerization initiator is preferably lower than the half-life temperature of the thermally decomposable radical polymerization initiator to be used.
  • the thermally decomposable radical polymerization initiator specifically, 0 ° C. or higher and 99 ° C. or lower is preferable, 0 ° C. or higher and 70 ° C. or lower is more preferable, 0 ° C. or higher and 50 ° C. or lower is particularly preferable, and 0 ° C. or higher. Most preferred is 30 ° C. or lower.
  • the reaction proceeds in the vicinity of the surface of the water-absorbent resin particles contained in the mixture obtained in the mixing step, so that the surface layer of the water-absorbent resin (part of several tens of ⁇ m from the surface of the water-absorbent resin) Further, it is a step of forming a portion having a high crosslinking density.
  • Patent Documents 8 to 14 exemplify surface crosslinking by heating.
  • Patent Documents 11 to 13 exemplify performing surface crosslinking by irradiating ultraviolet rays.
  • the radically polymerizable monomer and the organic crosslinking agent mixed with the water-absorbent resin are heated and / or irradiated with active energy rays, and / or the surface of the water-absorbent resin.
  • Crosslink polymerization in the vicinity when performing both heating and irradiation of an active energy ray with respect to a water absorbing resin, you may carry out simultaneously and may carry out separately.
  • the weight loss after drying of the resin at 180 ° C. for 3 hours is preferably 1 to 30% by weight, more preferably 3 to 25% by weight, and still more preferably in the first and third embodiments of the present invention. 5 to 20% by weight.
  • it is essential that the water content of the water absorbing resin in a reaction process is 30 weight% or less, and its preferable range is the same as the above.
  • the component for forming a crosslink such as a radical polymerization initiator easily penetrates into the water-absorbent resin, and the reaction proceeds more rapidly, and the residual amount of the radical polymerization initiator is also reduced. Is done.
  • the component for forming a crosslink such as a radical polymerization initiator penetrates deeply into the water-absorbent resin. This is preferable because the relationship is improved and handling is also improved.
  • the water content of the water absorbent resin during the reaction step may be adjusted by adjusting the amount of water in the surface treatment liquid in the mixing step, or by adjusting the water content of the water absorbent resin before surface crosslinking. May be. Further, during surface crosslinking, a method of sealing the reaction vessel during surface crosslinking, increasing the atmospheric dew point of the reaction vessel during surface crosslinking, or adding water to the water absorbent resin during surface crosslinking, etc. Thus, the water content of the water-absorbing resin can be adjusted. One of these methods may be selected and performed, or a plurality of methods may be combined.
  • the cross-linking polymerization reaction system including each component described above may be heated, and preferably heated in a relatively high humidity atmosphere. There are no particular restrictions on the specific conditions of such an atmosphere and the specific conditions of the heat treatment.
  • the mixture is heated to 50 to 150 ° C., preferably 60 to 140 ° C., more preferably 70 to 130 ° C., and still more preferably 80 to 120 ° C.
  • the method for heating the mixture is not particularly limited, but heating by heating a heat transfer surface such as a jacket with steam, hot water, nighter, oil, etc., heating by applying hot air, and heating the atmosphere. The heating etc. by the thing is mentioned.
  • the surface cross-linking reaction may be insufficient.
  • the powder temperature exceeds 150 ° C., the amount of water evaporated from the water absorbent resin is large and the evaporation rate is fast, so that the surface treatment liquid does not easily penetrate into the water absorbent resin powder and surface crosslinking is not performed. Since a water-absorbing resin having a desired water content cannot be obtained, it is not preferable.
  • the temperature of the atmosphere is preferably 50 to 150 ° C., more preferably 70 to 130 ° C., and still more preferably 80 to 120 ° C.
  • the dew point of the atmosphere is usually 20 ° C. or higher and lower than 100 ° C., preferably 30 to 95 ° C., more preferably 40 to 90 ° C., still more preferably 50 to 90 ° C., particularly preferably 60 to 90 ° C., and most preferably 70 ⁇ 90 ° C.
  • the powder temperature of the above mixture means the maximum temperature in the reaction step.
  • the water absorbent resin particles immediately after completion of the reaction reaction after heat-treating the mixture of the water absorbent resin powder and the surface crosslinking agent solution. Evaluation).
  • the internal atmospheric dew point is less than 20 ° C.
  • the amount of water that evaporates from the water absorbent resin is large and the evaporation rate is fast, so that the surface treatment liquid does not easily penetrate into the water absorbent resin powder, and surface crosslinking is not desired. It is not possible to obtain a water-absorbing resin having a water content.
  • the internal atmosphere dew point exceeds 100 ° C., not only the water content of the water absorbent resin after surface crosslinking becomes excessively high, but also the surface treatment liquid penetrates into the water absorbent resin powder, and after surface crosslinking. This is not preferable because it leads to a decrease in water absorption performance under pressure of water-absorbent resin and the occurrence of lumps and adhesion.
  • the heating time for the heat treatment is not particularly limited, but is preferably 1 to 90 minutes, more preferably 3 to 60 minutes, still more preferably 5 to 45 minutes, and particularly preferably 10 to 30 minutes.
  • a heating time of 1 minute or less is not preferable because the introduction of a crosslinked structure on the surface of the water-absorbent resin becomes insufficient.
  • a heating time of 90 minutes or more is not preferable because productivity deteriorates and water absorption performance decreases.
  • a known dryer can be used.
  • a conduction heat transfer type, a radiant heat transfer type, a hot air heat transfer type, and a dielectric heating type dryer are preferably used.
  • a stationary type a belt type, a fluidized bed type, an air flow type, a paddle type, a rotation type Mold, kneading type, infrared type, electron beam type dryer and the like.
  • the time from the end of the addition of the surface treatment liquid to the end of the cross-linking polymerization step is 0.1 minutes or more, preferably 1 minute or more, more preferably 3 minutes or more, still more preferably It is necessary to adjust it to be 5 minutes or more, particularly preferably 10 minutes or more.
  • a reaction step is performed on a mixture obtained by mixing a surface treatment liquid containing a thermal decomposition type radical polymerization initiator with a water absorbent resin. It is characterized in that the internal atmosphere dew point and the inner wall surface temperature of the reactor are controlled, and the temperature of the water absorbent resin is also controlled by heat-treating the mixture.
  • the moisture content of the mixture can be maintained within the above range by sealing the reaction apparatus or increasing the internal atmosphere dew point.
  • the moisture content can be easily maintained by adjusting the heating conditions in this reaction step.
  • a storage process and a stirring process that do not involve a reaction are provided as necessary between the mixing process and the reaction process, and the surface treatment liquid penetrates or diffuses into the water absorbent resin (powder) before being used in the reaction process. You may let them.
  • reaction apparatus As a reaction apparatus used in this reaction step, an apparatus having the same form as that of the mixing apparatus used in the mixing step may be used, but an apparatus having another form is preferably used. Specifically, it is preferable to use an apparatus provided with a gas supply mechanism and / or a gas discharge mechanism (hereinafter sometimes referred to as “gas supply / discharge mechanism”) in a known dryer or heating furnace. Further, the reaction apparatus may be a continuous type or a batch type, but a continuous type reaction apparatus is more preferable from the viewpoint of productivity.
  • the reactor is a batch type, a method of heating the mixture substantially uniformly dispersed in one or a plurality of trays or perforated plates, or a single tank or a plurality of tanks equipped with stirring blades, etc. It is preferable that the surface cross-linking reaction is performed by a method in which the mixture is filled and heated while stirring, a method in which the mixture is heated while stirring in a fluidized bed, or the like.
  • the reaction apparatus when the reaction apparatus is a continuous type, the mixture is substantially uniformly dispersed on a belt or a perforated plate and heated while being transferred, and the mixture is stirred and transferred with a stirring blade or a screw. It is preferable that the surface cross-linking reaction is performed by a method of heating while heating, a method of heating while transferring the mixture using the inclination of the heating surface, or the like.
  • the heating method in the reactor is not particularly limited, and examples thereof include a conduction heat transfer type, a radiation conduction type, a hot air heat transfer type, and a dielectric heating type.
  • a conduction heat transfer type and / or a hot air heat transfer type are preferable, and a conduction heat transfer type is more preferable.
  • these heat sources For example, high pressure steam (pressurized steam), warm water, nighter (molten salt), oil etc. are mentioned.
  • a conductive heat transfer type reactor using high-pressure steam (pressurized steam) as a heat source is particularly preferable, although it may be appropriately selected according to the purpose.
  • the mechanism for stirring and / or flowing the mixture (hereinafter sometimes referred to as “stirring / flowing mechanism”) from the viewpoint of heating efficiency and uniform surface cross-linking reaction. It is preferable that the device is provided.
  • the agitation / fluid mechanism is not particularly limited, and examples thereof include a grooved agitation type, a screw type, a rotation type, a disk type, a kneading type, and a fluidized bed type.
  • a stirring type using a stirring blade (paddle) and a stirring type in which a heat transfer surface itself such as a rotary retort furnace is movable are preferable, and a paddle type reaction apparatus is particularly preferable.
  • the heat transfer area is not particularly limited as long as the powder temperature of the mixture can be controlled within the following temperature range.
  • the amount of the mixture to be treated is preferably 5 to 100 m 2 / (t / hr), more preferably 10 to 50 m 2 / (t / hr).
  • the reactor preferably has an inclination that allows the mixture to flow down naturally in the direction of the discharge port.
  • the following is preferable, and more than 0 ° and 10 ° or less are more preferable. If the inclination exceeds 20 °, the reaction time may be uneven and the physical properties of the water-absorbent resin may be deteriorated.
  • the reaction apparatus used in the present invention is equipped with the gas supply / discharge mechanism, and the gas supply / discharge mechanism controls the atmospheric dew point and the atmospheric temperature in the reaction apparatus. At this time, it is preferable to adjust not only the supply / exhaust port but also the amount and pressure of the gas flowing through the reactor using a blower or the like.
  • each of the air supply / exhaust ports is not limited to a single location, and a plurality of locations can be provided in consideration of the size of the reactor used, the atmospheric dew point, and the atmospheric temperature.
  • the heating method, the stirring method, the gas supply method and the discharge method in the reactor can be used as a plurality of reactors in which the same or different forms are combined.
  • the air flow in a certain direction so that the atmospheric dew point and the atmospheric temperature in the reactor are stably within the following ranges.
  • the “constant direction” does not mean the same direction in every place, but means that the direction of airflow does not change from a macro viewpoint. For example, a partial and / or temporary turbulent state or vortex state of the airflow caused by stirring or the like is out of the scope of the airflow control of the present invention.
  • the airflow state of the air supply from the air supply port and the airflow from the exhaust port changes to the airflow state of the air supply from the exhaust port and the exhaust from the air supply port during the surface cross-linking reaction, It ’s not the direction. ”
  • the internal atmosphere dew point and the internal atmosphere temperature in this reaction step mean the average dew point and average temperature of the gas existing in the upper space of the mixture in the reaction apparatus, and are heated by the heating unit in the reaction apparatus. It is preferable to measure vertically above the mixture.
  • the range described later may be exceeded immediately after the start of the surface cross-linking reaction, in a continuous system, immediately after the mixture is introduced into the heating unit, or immediately before the reaction product is discharged from the heating unit, the range described later may be exceeded.
  • the direction of the air flow is in the flow direction of the mixture charged into the reaction apparatus.
  • the vertical direction or the horizontal direction is preferable, the horizontal direction is more preferable, the counter flow and / or the parallel flow is further preferable, and the parallel flow is particularly preferable.
  • a countercurrent position and a parallel flow position may coexist in the reaction apparatus.
  • the flow rate of the air flow is not particularly limited as long as the internal atmospheric dew point and the internal atmospheric temperature of the reaction apparatus can be controlled to a desired range, but at least exceeds 0.1 (Nm 3 / hr) and 10000 (Nm 3 / hr)
  • the following is preferable, 5000 (Nm 3 / hr) or less is more preferable, and 3000 (Nm 3 / hr) or less is more preferable.
  • 3000 (Nm ⁇ 3 > / t) or less is preferable and 1000 (Nm ⁇ 3 > / t) or less is more preferable.
  • “Nm 3 ” means the volume of gas converted to the standard state (0 ° C., 1 atm), and does not mean the volume of gas existing under the conditions of 0 ° C., 1 atm.
  • the flow rate and ratio of the airflow are values defined by the total flow rate of the discharged gas and the supply rate of the water-absorbent resin powder introduced into the surface cross-linking step, but at the start of operation or operation stop If the steady state is not in continuous production, such as time, the ratio may be out of the range.
  • the gas introduced into the reactor is not particularly limited as long as the internal atmosphere dew point can be controlled within the following range, but is not limited to air, dry air, nitrogen, helium, argon and other inert gases, and these gases and water vapor. And a mixture thereof. These gases may be heated or cooled, and may be pressurized or depressurized. Usually, air at 0 to 150 ° C. may be supplied at a substantially normal pressure (preferably 1 atm (101.3 kPa) ⁇ 10%, more preferably 1 atm ⁇ 5%, further preferably 1 atm ⁇ 1%). .
  • the pressure in the reaction apparatus is slightly reduced pressure.
  • the differential pressure with respect to the atmospheric pressure is preferably ⁇ 10 to 0 kPa, more preferably ⁇ 5 to 0 kPa, and further preferably ⁇ 2 to 0 kPa.
  • the inner wall surface temperature of the reaction apparatus is essentially the atmospheric dew point to 250 ° C., preferably the atmospheric dew point + 5 ° C. to 230 ° C., more preferably 100 to 200 ° C., more preferably 110 to 150. Control at °C.
  • the inner wall surface temperature is lower than the atmospheric dew point, the water-absorbing resin adheres due to condensation generated on the inner wall surface of the reaction apparatus, which may cause a decrease in productivity and physical properties.
  • the temperature of the inner wall surface exceeds 250 ° C., partial overheating occurs, which may cause deterioration of physical properties, which is not preferable.
  • the inner wall surface temperature of the reaction apparatus can be controlled by the heat source and the heating method described above.
  • Control of the internal atmospheric dew point and internal atmospheric temperature is based on the amount of gas supplied and discharged in consideration of heat transfer from the inner wall surface of the reactor and the water-absorbent resin, and an increase in dew point due to water vapor generated from the water-absorbent resin.
  • the temperature, dew point, and the like may be appropriately controlled.
  • a method in which a measuring device is installed in the reaction apparatus and the above-mentioned gas is introduced and adjusted as necessary a method in which the measurement is adjusted by changing the gas discharge amount or pressure, and the like.
  • a plurality of control methods may be appropriately combined.
  • the internal atmospheric dew point and the internal atmospheric temperature change with the position of the heating site and the processing time, but it is more preferable to control the internal atmospheric dew point and the internal atmospheric temperature within a certain range in the reaction apparatus.
  • the “within a certain range” is preferably 50% or more, more preferably 70% or more, and still more preferably 80% or more, based on the total time of the heat treatment.
  • the range is preferably within 20 ° C, more preferably within 10 ° C, still more preferably within 5 ° C, and particularly preferably within 2 ° C.
  • the dew point and temperature at an appropriate measurement point in the gas discharge mechanism of the reaction apparatus may be set as the internal atmosphere dew point and the internal atmosphere temperature of the reaction apparatus defined in the present invention.
  • the moving time of the gas from the part to the measurement point is required to be within 1 second.
  • the active energy rays used include one or more of ultraviolet rays, electron beams, and gamma rays. .
  • ultraviolet rays and electron beams are preferable.
  • the irradiation conditions are preferably an irradiation intensity of 3 to 1000 mW / cm 2 and an irradiation amount of 100 to 10000 mJ / cm 2 .
  • Examples of the apparatus for irradiating ultraviolet rays include a high pressure mercury lamp, a low pressure mercury lamp, a metal halide lamp, a xenon lamp, and a halogen lamp.
  • the ultraviolet rays are irradiated, particularly as long as the ultraviolet rays in the wavelength range are irradiated, other radiations and wavelengths may be included, and the method is not particularly limited.
  • the acceleration voltage is preferably 50 to 800 kV and the absorbed dose is 0.1 to 100 Mrad.
  • the time for irradiating the active energy ray depends on the amount of the water-absorbing resin to be treated, but is preferably 0.1 minutes or more and less than 60 minutes, more preferably 0.5 minutes or more and less than 20 minutes, still more preferably 0.5. Min. To less than 5 minutes, particularly preferably from 1 minute to less than 3 minutes.
  • the surface when the surface is crosslinked by irradiating with active energy rays, it is not necessary to heat, but when the irradiation with active energy rays is performed under heating, the surface-crosslinked water-absorbing property is excellent in water absorption characteristics. Since resin is obtained, it is more preferable.
  • the heating temperature is preferably in the range of 0 to 150 ° C, more preferably 10 to 120 ° C, still more preferably room temperature to 100 ° C, and particularly preferably 50 to 100 ° C.
  • the active energy ray can be uniformly irradiated to the mixture of the water absorbent resin and the surface treatment liquid by stirring.
  • a well-known mixer is used. Specific examples include vibration type, vibration feeder type, ribbon type, conical ribbon type, screw extrusion type, airflow type, batch kneader, continuous kneader, paddle type, high-speed flow type, floating flow type mixer, etc. It is done.
  • the water-absorbent resin is subjected to a heat treatment step at a temperature higher than the reaction step in the range of 50 to 250 ° C., if necessary. Also good.
  • a heat treatment step a water absorbing agent having a desired water content can be obtained, the safety of the water absorbing agent can be increased, and the crosslinking efficiency of the water absorbing agent can be increased.
  • an apparatus similar to the apparatus described in the heat treatment of the reaction step is preferably used.
  • the functional group of the cross-linking agent is a hydroxyl group or a carbonate group
  • the reaction is heated to 100 to 240 ° C., more preferably 120 to 230 ° C., and 130 to 220 ° C. for 1 minute or more (more preferably about 5 to 300 minutes). By doing so, the crosslinking reaction can be promoted.
  • a crosslinking agent having a plurality of functional groups capable of reacting with a carboxyl group particularly a polyol-based crosslinking agent, specifically a polyol such as propylene glycol, is also used as a solvent or a mixing aid.
  • a polyol-based crosslinking agent specifically a polyol such as propylene glycol
  • the polyol when specifically contributing to the crosslinking reaction (or when heating at a temperature sufficient for crosslinking), the polyol is an organic crosslinking agent, otherwise it is classified as a solvent or a mixing aid.
  • the presence or absence of a crosslinking reaction can be confirmed by a decrease in water absorption ratio (particularly 1 g / g or more in CRC), and the heating temperature sufficient for crosslinking is in the above range in the case of, for example, a hydroxyl group or a carbonate group.
  • This cooling step is an optional step performed after the surface cross-linking reaction step for the purpose of stopping the above-mentioned surface cross-linking reaction step, transporting it to the next step, or the like.
  • the water-absorbent resin obtained in the reaction step is preferably subjected to a cooling step in a short time, and the time is preferably more than 0 seconds and within 3 minutes, more preferably more than 0 seconds. Within 2 minutes, more preferably over 0 seconds and within 1 minute, particularly preferably over 0 seconds and within 30 seconds.
  • the time can be controlled by the layout of both devices, such as direct connection between the heating device in the reaction step and the cooling device in the cooling step, or connection at a short distance (for example, within 10 m).
  • the cooling device used in the cooling step is not particularly limited, and examples thereof include a stirring device or a flow device having a cooling function by a transmission surface, an air flow, or the like.
  • a device of the same type as the paddle type heating device preferably used in the reaction step it can be used as a cooling device by changing the heat medium to a refrigerant.
  • the size of the apparatus may be appropriately set in consideration of cooling efficiency and the like, and is not necessarily the same size as the reaction apparatus.
  • the refrigerant of the cooling device is not particularly limited, and examples thereof include water, warm water, antifreeze and the like.
  • the cooling temperature (heat transfer surface temperature of the jacket or the like) is preferably 0 to 90 ° C, more preferably 20 to 85 ° C, and still more preferably 40 to 80 ° C.
  • This step is a step of adding an additive for the purpose of improving the physical properties of the water-absorbent resin, and is an optional step that is performed as necessary.
  • the addition step can be appropriately performed depending on the nature of the additive used.
  • the additive may react with the surface treatment liquid or when it may be affected by heating, after the reaction step or when the cooling step is installed, after the cooling step or the cooling step (Additives can be added simultaneously with cooling in the same apparatus).
  • the additive adding device is not particularly limited, but preferably a stirring device or a fluidizing device is mentioned, and the stirring device is a stirring mixer described in International Publication WO2008 / 141818. Can also be preferably used.
  • additive in order to impart various additional functions to the water-absorbing resin obtained, it is preferable to add the following various additives, which are added in an aqueous liquid state in which the additive is dissolved or dispersed.
  • additives which are added in an aqueous liquid state in which the additive is dissolved or dispersed.
  • those used in each of the first to third embodiments are not optional components but essential components).
  • a deodorizer for example, a deodorizer, an antibacterial agent, a coloring inhibitor, a chelating agent, an inorganic monovalent salt or polyvalent salt, an acidic compound, a reducing agent, an alkaline compound, surfactant, etc.
  • a water-soluble additive is preferable, and a water-soluble additive selected from a chelating agent, an inorganic reducing agent, a polyvalent metal salt, and a deodorant is more preferable. From these additives, one type or two or more types are selected according to the purpose.
  • the addition of a chelating agent is preferred from the viewpoint of preventing coloring and deterioration of the resulting water-absorbent resin (urine resistance).
  • a chelating agent for example, various chelating agents disclosed in “[2] chelating agent” of International Publication No. 2011/040530 and the amount of use thereof are also applied to the present invention.
  • water-soluble non-polymeric amino polyvalent carboxylic acids or amino polyvalent phosphoric acids and salts thereof (particularly monovalent salts) are preferable.
  • the second aspect of the present invention further includes a step of adding a metal chelating agent to the water absorbent resin.
  • the addition amount of the metal chelating agent is preferably 0.001 to 6% by weight with respect to 100% by weight of the water absorbent resin.
  • the addition process of this metal chelating agent may be performed before a water-containing liquid addition process (further heating process), may be performed simultaneously, and may be performed after that.
  • an inorganic reducing agent is preferably added from the viewpoint of preventing coloring and deterioration of the resulting water-absorbent resin and reducing the residual monomer.
  • the inorganic reducing agent for example, various inorganic reducing agents disclosed in “[3] Inorganic reducing agent” of International Publication No. 2011/040530 and the amount of use thereof are also applied to the present invention.
  • a water-soluble phosphorus-based reducing agent or a sulfur-based reducing agent is preferable, and a sulfite such as sodium bisulfite (SBS) is more preferable.
  • an inorganic salt particularly a polyvalent metal salt and / or a cationic polymer may be added.
  • a polyvalent metal salt and / or a cationic polymer include various polyvalent metal salts disclosed in “[7] Polyvalent metal salt and / or cationic polymer” of WO 2011/040530 pamphlet.
  • the cationic polymers and / or the amounts used are also applicable to the present invention.
  • an inorganic salt of aluminum is preferable.
  • the deodorant is not particularly limited, and a synthetic or natural deodorant can be mentioned.
  • a deodorant derived from a plant component disclosed in International Publication WO2003 / 104349 pamphlet is preferably used. More specifically, polyphenols such as tannin can be mentioned.
  • the total concentration is preferably 0.01 to 50% by weight, more preferably 0.1 to 40% by weight, and further preferably 1 to 30% by weight.
  • the amount added to the water-absorbent resin may be appropriately set depending on the purpose and is not particularly limited, but the total amount is preferably 1 ppm to 10% by weight, more preferably 10 ppm to 1% by weight, still more preferably. 20 ppm to 0.5% by weight.
  • Water-containing liquid mixing step (especially second mode)
  • the addition step in the form of the aqueous liquid described above is performed as an essential step called a water-containing liquid mixing step in the second embodiment of the present invention.
  • this step is a step of mixing a liquid containing water with the mixture obtained in the mixing step during and / or after the completion of the reaction step in the second mode of the present invention.
  • the reaction rate of the radical polymerization initiator added in the mixing step can be increased, the initiator remaining in the water-absorbing resin or the water-absorbing agent in an unreacted state is reduced, and the remaining radical polymerization initiator is In addition to solving problems such as coloration (with time) and changes in absorption performance over time, the amount of radical polymerization initiator used in the surface treatment liquid can be reduced. Further, when the surface treatment liquid contains a radical polymerizable monomer, there is an effect of reducing unreacted monomer (residual monomer).
  • the liquid containing water is water alone or an aqueous solution or dispersion containing water (liquid water) as a main component and optionally containing another organic solvent or additive, preferably an aqueous solution containing a reducing substance. .
  • the content of water in the water-containing liquid is preferably 50 to 100% by weight, more preferably 60 to 100% by weight, still more preferably 70 to 100% by weight, particularly preferably 80 to 100% by weight, and most preferably. Is 90 to 100% by weight.
  • a reducing agent is preferably contained, and in addition, a hydrophilic organic solvent, a surfactant, a deodorant, a chelating agent, an antibacterial agent, and the like may be contained.
  • a lower monovalent or polyhydric alcohol or the like can be preferably used as the organic solvent.
  • Surfactants that can be used are exemplified in US Pat. No. 7,473,739, preferably in a range in which the surface tension (specified by the method of US Pat. No. 7,473,739) of the resulting water-absorbing agent is not excessively reduced (particularly less than 55 N / m). Is used in an amount of 0 to 0.05 parts by weight, further 0 to 0.02 parts by weight, based on 100 parts by weight of the water absorbent resin.
  • the amount of the hydrophilic organic solvent used is preferably more than 0 parts by mass and 10 parts by mass or less, more preferably 0 parts by mass with respect to 100 parts by mass of the water absorbent resin powder. It is more than 5 parts by mass.
  • the hydrophilic organic solvent is preferably a primary alcohol having 1 to 4 carbon atoms, more preferably 2 to 3 carbon atoms, and other examples include lower ketones having 4 or less carbon atoms such as acetone.
  • an inorganic or organic reducing agent As the reducing substance used in the present invention, an inorganic or organic reducing agent can be exemplified, and furthermore, a phosphorus reducing agent and a sulfur reducing agent (particularly an oxygen-containing sulfur reducing agent) can be used as the inorganic reducing agent.
  • the reducing substance is a water-soluble reducing substance, preferably a water-soluble reducing substance having a solubility of 0.1 g / 100 g or more at 25 ° C., more preferably 1 g / 100 g or more and 10 g / 100 g or more.
  • hypophosphorous reducing agent As the phosphorous reducing agent that can be used in the present invention, hypophosphorous acid (salt) having an oxidation number of +1, phosphorous acid (salt) having an oxidation number of +3, pyrophosphorous acid (salt), hypophosphoric acid (salt) having an oxidation number of +4 ), Etc., phosphinic acid represented by the general formula R 2 PO 2 H and salts thereof, phosphorous acid represented by the general formula ROPO 2 H 2 , (RO) 2 POH, (RO) 3 P Organic phosphorus reducing agents such as esters are exemplified.
  • Sulfur-based reducing agents include inorganic compounds such as sulfoxylate having an oxidation number of +2, dithionic acid (salt) having an oxidation number of +3, sulfite having an oxidation number of +4, bisulfite, pyrosulfite, sulfamic acid, etc.
  • organic reducing agents such as sulfur reducing agents, formamidine sulfinic acid, sulfinic acid represented by 2-hydroxy-2-sulfinate acetic acid, and various thiols represented by cysteine.
  • inorganic sulfites such as sodium sulfite, potassium sulfite, calcium sulfite, zinc sulfite, and ammonium sulfite
  • bisulfites such as sodium bisulfite, potassium bisulfite, calcium bisulfite, and ammonium bisulfite
  • pyro Pyrosulfites such as sodium sulfite, potassium pyrosulfite and ammonium pyrosulfite
  • dithiones such as sodium dithionite, potassium dithionite, ammonium dithionite, calcium dithionite and zinc dithionite Acid salts
  • trithionates such as potassium trithionate and sodium trithionate
  • tetrathionates such as potassium tetrathionate and sodium tetrathionate
  • thiosulfates such as sodium thiosulfate, potassium thiosulfate and ammonium thiosulfate Etc.
  • Organic sulfur-based reducing agents are commercially available from Bruggemann Chemical (Heilbron, Germany) as BRUGGOLITE (R) FF6 and BRUGGOLITE (R) FF7 reducing agents.
  • the sulfur-based reducing agent of the present invention the sulfur-based reducing agent having an SO bond such as the above sulfite is generically referred to as an oxygen-containing sulfur-based reducing agent with respect to the thiol-based reducing agent having no SO bond.
  • the system reducing agent may have a sulfur odor, and therefore, an oxygen-containing sulfur-based reducing agent is preferably used in the present invention.
  • nitrite reducing agent examples include nitrites such as sodium nitrite, potassium nitrite, calcium nitrite, and zinc nitrite.
  • metal reducing agent examples include silver salts such as silver nitrate, ferrous salts such as ferrous chloride and ferrous sulfate; cuprous salts such as cuprous chloride and cuprous sulfate.
  • amine reducing agent examples include hydroxylamine or salt (for example, hydroxylamine hydrochloride), ammonia, monoethanolamine, polyethyleneimine, and the like.
  • organic reducing agents examples include ascorbic acid, erythorbic acid, and reducing sugars (such as glucose).
  • the organic reducing agent refers to a reducing substance derived from an OH group or CHO.
  • the reducing substance may be a salt, and for example, any salt of alkali metal including ammonium and alkaline earth metal is suitable. Particularly preferred are aqueous solutions containing at least one cation selected from lithium, sodium, potassium, ammonium, calcium, strontium, aluminum and magnesium, in particular alkali metal ions.
  • reducing agents preferably, a phosphorus-based reducing agent or a sulfur-based reducing agent, further an inorganic or organic oxygen-containing sulfur-based reducing agent, further an inorganic sulfur-based reducing agent, specifically, sulfite, sulfite.
  • Inorganic sulfur reducing agents selected from hydrogen salts, pyrosulfites and dithionites are preferred, and sulfites such as sodium sulfite and potassium sulfite, and bisulfites such as sodium bisulfite and potassium bisulfite are more preferred.
  • the amount of the reducing substance added is 0.01 to 5 parts by weight, preferably 0.02 to 3 parts by weight with respect to 100 parts by weight of the water-absorbing resin. If content of a reducing substance is less than 0.01 weight part, the effect which fully raises the reaction rate of a radical polymerization initiator will not be acquired. Further, if the content of the reducing substance exceeds 5 parts by weight, it is not preferable because deterioration of the water-absorbing resin such as an increase in water-soluble content is observed.
  • the concentration of the reducing substance in the liquid containing water ranges from 0% by weight to a saturated concentration, preferably from 0.1 to 30% by weight, and further from 0.1 to 25% by weight. Exceeding the above range is not preferable because an effect corresponding to the addition amount is not exhibited, and on the contrary, it is not economical.
  • the amount of the liquid containing water is preferably 0.1 to 15 parts by weight, particularly preferably 1 to 15 parts by weight, based on 100 parts by weight of the water absorbent resin. If the addition amount is less than 0.1 parts by weight, the effect of sufficiently advancing the reaction of the radical polymerization initiator cannot be obtained, which is not preferable. Moreover, when the addition amount exceeds 15 parts by weight, it is not preferable because the absorption performance of the resulting water-absorbing agent is lowered or the handleability is deteriorated.
  • the mixing of the liquid containing water is preferably performed during and / or after the completion of the reaction step described in (3-1-2) above.
  • the mixing method the method described in the mixing conditions of the mixing step described in (3-1-1) above can be used.
  • the liquid containing water needs to be added as a liquid, not a solid (ice) or gas (water vapor).
  • it may be at a temperature that can maintain the solubility of the substance and suppress decomposition, and is preferably 0 ° C. or higher and 99 ° C. or lower, more preferably 0 ° C. or higher and 70 ° C. or lower, and still more preferably Is from 0 ° C. to 50 ° C., particularly preferably from 0 ° C. to 30 ° C.
  • the reason why the liquid containing water is added in liquid form is that the reducing substance cannot be dissolved in the form of water vapor. Furthermore, in the form of water vapor, it is difficult to adjust the addition amount added to the water-absorbent resin, and it is preferable because it takes too much time to give a predetermined amount of water in addition to excessively adding moisture or conversely too little moisture. Absent. Further, the ice form is not preferable because the addition becomes uneven and the addition method becomes complicated.
  • the atmospheric dew point in this step is 5 ° C. or higher, 20 ° C. or higher, preferably 30 ° C. or higher, more preferably 40 ° C. or higher, still more preferably 50 ° C. or higher, particularly preferably 60 ° C. or higher.
  • the upper limit of the atmospheric dew point is not particularly limited, but generally may be less than 100 ° C, and more preferably 90 ° C or less.
  • the temperature of the water-absorbing agent (or water-absorbing resin) and the atmospheric temperature when adding a liquid containing water are higher than the atmospheric dew point. It is more preferable. Specifically, the temperature of the water-absorbing agent (or water-absorbing resin) and the atmosphere is preferably 20 ° C. to 150 ° C., further 40 to 150 ° C., more preferably 60 to 120 ° C. When the temperature is lower than the above range, the absorption rate of the liquid containing water is slow, and it becomes easy to generate lumps, which may make the operation difficult.
  • the atmospheric temperature and the water-absorbing agent (water-absorbing resin) temperature are preferably 1 to 80 ° C higher than the atmospheric dew point, more preferably 5 to 70 ° C higher, still more preferably 10 to 60 ° C higher, and 10 to 50 ° C higher. Most preferred. If it is below the above range, it is not preferable because condensation tends to occur in the apparatus. When the above range is exceeded, the added water is likely to evaporate, not only the effect of the present invention to add a liquid containing water is reduced, but also because the amount of fine powder generated during operation is large, the damage resistance is poor, It is not preferable.
  • Heating step is a step of performing a heat treatment after the addition of the liquid containing water.
  • a preferable heating time is 1 minute to 3 hours after addition of the liquid containing water, more preferably 5 minutes to 2 hours, and still more preferably 10 minutes to 1 hour.
  • the preferred heat treatment temperature is preferably 40 ° C. to 150 ° C., more preferably 50 ° C. to 150 ° C., and further preferably 60 to 120 ° C., and more preferably by heating while maintaining the water content.
  • the initiator can be reduced.
  • the heating process may be independent, or a range satisfying the above conditions in the reaction process or the cooling process may be substituted as the heating process.
  • the water content of the water-absorbent resin after the heating step is preferably 1 to 30% by weight, more preferably 3 to 25% by weight.
  • the liquid containing water may be added as long as the conditions such as the atmospheric dew point, the atmospheric temperature, and the temperature of the water absorbing agent (or water absorbing resin) satisfy the above ranges, and during and / or completion of the reaction step. Later, it may be performed by a mixing device provided in the same and / or separately as the device used in the reaction step, or a device used in a cooling step optionally performed after the reaction step.
  • addition of the liquid containing water may be performed at one location within the above range, or may be performed at a plurality of locations in the vertical or horizontal direction of the apparatus. Further, it can be added in both the reaction step and the cooling step.
  • a mixing device for mixing a liquid containing water using a separate mixing device is not particularly limited, but a device having the same form as the device used for mixing the surface cross-linking agent is preferable. Used (see above 3-1-1) mixing step). Specifically, a high-speed stirring type mixing device is preferable, a high-speed stirring type continuous mixing device is more preferable, and a horizontal or vertical high-speed stirring type continuous mixing device is further preferable. More specifically, Shugi mixer (manufactured by Paulek Co., Ltd.), turbulizer (manufactured by Hosokawa Micron Corporation), Redige mixer (manufactured by Redige Corporation) and the like can be mentioned.
  • the rotational speed is preferably 100 to 10,000 rpm, more preferably 300 to 2000 rpm, and the residence time is preferably within 180 seconds, more preferably 0.1 to 60 seconds, and still more preferably 1 to 1 second. 30 seconds.
  • liquidity is provided because a water
  • the adding apparatus to be used is not particularly limited, but preferably the liquid containing water can be uniformly dropped or sprayed in a narrow range (area).
  • An apparatus more preferably an apparatus capable of spraying, includes a one-fluid type or two-fluid type spray having a flat spray, hollow cone, or full cone spray pattern. More preferably, the narrow angle spray which can be sprayed to a narrow area
  • the liquid-containing liquid mixing step (further including heat treatment) is in a reduced pressure state. By making it a reduced pressure state, the mixing property is further improved, and aggregates accompanying the addition of a liquid containing water can also be reduced.
  • ⁇ ⁇ Depressurized state means a state where the atmospheric pressure is lower than the atmospheric pressure, and the pressure difference from the atmospheric pressure is called “decompression degree”.
  • compression degree the pressure difference from the atmospheric pressure
  • a positive (plus) value is used.
  • the degree of reduced pressure 10 kPa
  • the atmospheric pressure is 91.3 kPa.
  • the Flow Rate specified by ERT450.2-02 is preferably 3 (g / s) or more, more preferably 5 (g / s) or more, and further preferably 7 (g / s). s) or more.
  • a classification step and optionally a crushing step of aggregates may be provided.
  • a sizing step is provided, and more preferably, aggregates (coarse particles) or fine powder are removed in the classification step. Aggregates or fines (particularly particles having a size of less than 150 ⁇ m) removed in the classification step may be discarded, and the aggregates may be crushed (operation for loosening the aggregates) or recycled.
  • a step of adding an antibacterial agent, polymer polyamine, pulp, thermoplastic fiber, etc., preferably 0 to 3 parts by weight, more preferably 0 to 1 part by weight, with respect to 100 parts by weight of the water absorbent resin may be provided. .
  • a water-absorbing agent mainly comprising a poly (meth) acrylic acid (salt) -based water-absorbing resin, wherein the water content is 3 to 13% by weight, the water content Uncorrected water absorption ratio (CRC) after correction of 33 (g / g) or more, water absorption ratio after correction of water content (AAP 4.83 kPa) of 18 (g / g) or more, residual monomer after water content correction
  • CRC Uncorrected water absorption ratio
  • AAP 4.83 kPa water absorption ratio after correction of water content
  • the total residual amount of the organic crosslinking agent having an amount of 500 ppm or less and a molecular weight of less than 200 is 500 ppm or less, and the residual amount of persulfate is 1 ppm or more and 1000 ppm or less, or the residual amount of the sulfur-based reducing agent is 1 ppm.
  • a water-absorbing agent having a content of 2500 ppm or less is provided.
  • the residual amount of persulfate is 1 ppm or more and 1000 ppm or less, and no sulfur-based reducing agent remains, or no persulfate remains, and the residual amount of sulfur-based reducing agent is 1 ppm or more and 2500 ppm or less. It is a water-absorbing agent.
  • the total remaining amount of the organic crosslinking agent is 500 ppm or less, the remaining amount of the epoxy crosslinking agent is 1 ppm or less, and the organic crosslinking agent having a (meth) acrylate group and / or a (meth) acrylamide group.
  • the residual amount is 100 ppm or less, and the residual amount of the organic crosslinking agent having a hydroxy group is 500 ppm or less.
  • the initial L value is 88 or more
  • the change rate of the L value after coloring over time is 20% or less.
  • a water absorbing agent further containing a chelating agent is most preferable.
  • the water content, water absorption capacity without pressure (CRC), water absorption capacity under pressure (AAP 4.83 kPa), residual monomer, residual organic A water-absorbing agent in which the system crosslinking agent is controlled within the above range and the residual persulfate and / or the residual sulfur reducing agent is further controlled within the above range is obtained.
  • the water-absorbing agent is, in particular, among organic crosslinking agents, the residual amount of epoxy crosslinking agent is 1 ppm or less, the residual amount of organic crosslinking agent having a (meth) acrylate group and / or (meth) acrylamide group is 100 ppm or less, hydroxy
  • the water-absorbing agent is preferably used for sanitary articles, particularly paper diapers.
  • the physical properties to be controlled include, in addition to the following (4-1) to (4-9), FSC (free swelling ratio), pH, Flow Rate (flow rate), Density (bulk specific gravity), Respirable Particles (respiratory dust), Dust (dust), etc. are mentioned, but when the range shown below is not satisfied, the effect of the present invention is insufficient or the amount of water absorbent used per paper diaper is insufficient. In many high-concentration diapers, sufficient performance may not be exhibited.
  • the physical properties to be controlled and the measuring method thereof are appropriately determined, but the measuring method disclosed in EDANA can be applied to the production of the polyacrylic acid (salt) water-absorbing resin of the present invention.
  • the water-absorbing agent of the present invention is preferably 33 (g / g) or more, more preferably 34 (g / g) or more, and still more preferably 35 (g / g) as a water absorption ratio (CCRC) after correction of moisture content. )
  • CCRC water absorption ratio
  • the upper limit is not particularly limited, but is preferably 50 (g / g) or less, more preferably 45 (g / g) or less, and still more preferably 40 (g / g) or less from the balance with other physical properties. I just need it.
  • the water-absorbing agent of the present invention is preferably 20 (g / g) or more, more preferably 25 (g / g) or more, still more preferably 30 (g / g) as a water absorption capacity under pressure after correction of moisture content (CAAP 2.06 kPa).
  • g) or more particularly preferably 31 (g / g) or more, most preferably 32 (g / g) or more.
  • the upper limit value is not particularly limited, but is preferably 40 (g / g) or less in view of balance with other physical properties.
  • the water-absorbing agent of the present invention is preferably 18 (g / g) or more, more preferably 19 (g / g) or more, and still more preferably 20 (g / g) as the water absorption capacity under pressure after correction of moisture content (CAAP 4.83 kPa).
  • g / g) or more even more preferably 21 (g / g) or more, particularly preferably 22 (g / g) or more, and most preferably 23 (g / g) or more.
  • the upper limit value is not particularly limited, but is preferably 30 (g / g) or less from the balance with other physical properties.
  • AAP 4.83 kPa When the value of AAP 4.83 kPa is less than the lower limit, the amount of liquid returned when pressure is applied to the absorber (usually referred to as “Re-Wet”) increases, and sanitary conditions such as paper diapers. Not suitable as an absorbent material.
  • AAP2.06kPa and AAP4.83kPa can be controlled by a particle size, a composition and usage-amount of a surface crosslinking agent solution.
  • the water content of the water-absorbing agent of the present invention is preferably 3 to 13% by weight, more preferably 4 to 12% by weight, and still more preferably 6 to 10% by weight.
  • the water-absorbing agent of the present invention preferably has a water-soluble component (Ext) of 35% by weight or less, more preferably 25% by weight or less, still more preferably 15% by weight or less, and particularly preferably 10% by weight or less.
  • the water-soluble component (Ext) can be controlled by the above polymerization conditions (such as the amount of crosslinking agent) and drying conditions (drying temperature).
  • Residual monomer (RM) in the water-absorbing agent according to the present invention, the residual monomer amount determined by quantification by HPLC (high performance liquid chromatography) described later is 0 or more and 500 ppm or less, more preferably 0 or more and 300 ppm or less, and still more preferably 0 or more and 100 ppm or less.
  • the main component of the monomer used for the polymerization is acrylic acid and / or a salt thereof
  • the content of unreacted acrylic acid and / or a salt thereof is 500 ppm or less.
  • the residual monomer amount of the water-absorbing agent of the present invention exceeds 500 ppm, there is a possibility that a strange odor may be generated during swelling after absorption of human urine when actually used in an absorbent article such as a diaper. Considering the possibility of contact, there is a problem in terms of hygiene. Moreover, there is a concern that the powder scattering at the manufacturing site of the absorbent article may adversely affect the health of the worker.
  • the CRM is the amount of residual monomer corrected based on the water content described later in the examples.
  • Residual organic crosslinking agent (RX) Since the water-absorbing agent of the present invention is obtained by the second or third surface cross-linking, there are few residual organic cross-linking agents and a high water absorption capacity under pressure is exhibited.
  • the amount of the residual organic crosslinking agent of the present invention is preferably 500 ppm or less, more preferably 300 ppm or less, particularly preferably 100 ppm or less, and most preferably 50 ppm or less.
  • the remaining organic cross-linking agent surface cross-linking agent and its organic solvent, for example, polyol
  • the fluidity of the water-absorbing agent derived from the remaining organic crosslinking agent is also lowered, there is no such problem in the present invention.
  • the residual organic crosslinking agent is a surface crosslinking agent and a decomposition product thereof (for example, ethylene glycol which is a decomposition product of ethylene carbonate) or a solvent (for example, propanediol), and particularly the residual organic crosslinking agent is a polyol. .
  • the remaining amount of epoxy crosslinking agent is preferably 1 ppm or less, more preferably not detected (ND). .
  • ND preferably not detected
  • the residual amount of the organic crosslinking agent having a (meth) acrylate group and / or (meth) acrylamide group is from the viewpoint of skin sensitization and the like.
  • the residual amount of the organic crosslinking agent having a hydroxy group is preferably 500 ppm or less, more preferably 100 ppm, from the viewpoint of fluidity of the water absorbent resin.
  • it is more preferably 10 ppm or less, and most preferably not detected (ND).
  • the remaining initiator amount of the water-absorbing agent according to the present invention is preferably 0 to 200 ppm by weight, more preferably 0 to 100 ppm by weight, from the viewpoints of safety, prevention of coloring, and reduction of changes in absorption performance over time. ⁇ 50 ppm by weight and 0-10 ppm by weight are particularly preferred, and it is most preferred not to be detected (ND). When outside the above range, problems caused by the remaining initiator (aging), problems such as coloring, and safety concerns caused by the remaining crosslinking agent can be minimized.
  • the water-absorbing agent of the present invention is preferably 1 ppm to 1000 ppm, more preferably 1 ppm to 500 ppm, still more preferably from 1 ppm to 1000 ppm as the residual persulfate from the viewpoint of safety, prevention of coloring, and reduction in changes in water absorption performance over time.
  • the amount of residual sulfur-based reducing agent in the water-absorbing agent according to the present invention is preferably 1 ppm or more and 2500 ppm or less, more preferably 1 ppm or more and 1000 ppm or less, further preferably 1 ppm or more and 500 ppm or less, more preferably 1 ppm or more from the viewpoint of preventing an increase in water-soluble content. 100 ppm or less is particularly preferable. It is preferable that at least 1 ppm or more of the persulfate and the sulfur-based reducing agent remain at least 1 ppm from the viewpoint of reducing the monomers remaining in the water-absorbing agent and the organic crosslinking agent over time.
  • the initiator reaction rate of the water-absorbing agent of the present invention is preferably 80% or more, and more preferably 90%, from the viewpoints of safety, prevention of coloring, and reduction of changes in absorption performance over time. % Or more.
  • the initiator reaction rate is a ratio of the amount of the reacted initiator to the amount of the initiator used, expressed as a percentage. An index indicating that the higher the value, the higher the efficiency of the radical polymerization initiator reaction. It is.
  • the method for quantifying the residual amount of persulfate and hydrogen peroxide is exemplified in the examples described later as representative examples, but other azo initiators and photoinitiators are quantified by a conventionally known method. Then, the initiator reaction rate may be obtained.
  • Particle size distribution (PSD), weight average particle size (D50) and particle size distribution width ( ⁇ )) of the water-absorbing agent of the present invention may be classified, granulated or crushed after surface cross-linking as necessary. (Agglomeration of the agglomerates) is preferably controlled within the same range as the above-described water absorbent resin before surface crosslinking.
  • the initial color tone of the water-absorbing agent of the present invention is preferably 88 or more, more preferably 89 or more, and still more preferably 90 or more.
  • the upper limit is 100, but if it shows at least 88, there will be no problem with color tone.
  • the a value is preferably -3 to 3, more preferably -2 to 2, and still more preferably -1 to 1.
  • the b value is preferably 0 to 12, more preferably 0 to 10, and still more preferably 0 to 9. Outside the above range, when the water-absorbing agent is used for sanitary materials such as paper diapers and sanitary napkins, the color of those products deteriorates and the commercial value is lowered, which is not preferable.
  • the whiteness increases as the L value approaches 100, and the a value and the b value become substantially white with low coloration as the value approaches 0.
  • the measurement of initial coloring was performed by the method as described in the Example mentioned later.
  • the color tone with time of the water-absorbing agent of the present invention is preferably 72 or more, more preferably 75 or more, still more preferably 80 or more, and particularly preferably 83 or more in the Hunter Lab color system.
  • the upper limit is 100.
  • the a value is preferably -3 to 3, more preferably -2 to 2, and still more preferably -1 to 1.
  • the b value is preferably 0 to 15, more preferably 0 to 12, and still more preferably 0 to 10.
  • the whiteness increases as the L value approaches 100, and the a value and the b value become substantially white with low coloration as the value approaches 0.
  • the water-absorbing agent of the present invention is not particularly limited, but is preferably used as a sanitary material because it has a high water absorption ratio and a high water absorption capacity under high pressure, and is particularly used as a paper diaper, sanitary napkin, incontinence pad It is used as an absorber used for absorbent articles such as.
  • excellent performance is exhibited when used in an upper layer portion of an absorbent body in an absorbent article.
  • the absorbent body may contain an absorbent material such as pulp fiber as an optional component.
  • the content of the water absorbent resin is preferably 30 to 100% by weight, more preferably Is 40 to 100% by weight, more preferably 50 to 100% by weight, still more preferably 60 to 100% by weight, particularly preferably 70 to 100% by weight, and most preferably 75 to 95% by weight.
  • the water-absorbing agent of the present invention is excellent in coloration and fluidity with time, and can be stored for a long time at a humidity of 30% RH or more.
  • the humidity is preferably 30 to 100% RH, more preferably 40 to 90% RH, and still more preferably 50 to 80% RH.
  • the storage period is preferably 1 to 300 days, more preferably 10 to 100 days, and still more preferably 20 to 80 days.
  • the water-absorbing agent of the present invention is excellent in coloring with time and fluidity in a preferred embodiment, and therefore can be used for sanitary materials manufactured in an environment with a humidity of 30% RH or higher.
  • the humidity is preferably 30 to 100% RH, more preferably 40 to 90% RH, and still more preferably 50 to 80% RH. That is, there is no problem in the manufacture of disposable diapers including hygienic materials, especially mixing with pulp, even under high humidity.
  • electrical equipment used in Examples etc. uses a 200V or 100V power supply, and also has the conditions of room temperature (20-25 ° C) and relative humidity 50% RH.
  • the physical properties of the water absorbent resin were measured below.
  • “liter” may be described as “l” or “L”
  • “wt%” may be described as “wt%”.
  • the result of measurement under the condition that the sample amount was changed to 1.0 g and the drying temperature was changed to 180 ° C. was evaluated as “moisture content”.
  • CCRC water absorption ratio
  • the water absorption ratio (CCRC) after correction of the water content is 33.3 (g / g).
  • the measurement was also performed under the condition where the load condition was changed to 4.83 kPa.
  • values obtained by the above measurement divided by (1-water content [% by weight] / 100) are “water absorption under pressure after correction of water content (CAAP 2.06 kPa)” and “water content correction”, respectively. It was evaluated as “water absorption capacity under pressure (CAAP 4.83 kPa)”.
  • Residual monomer (RM) The residual monomer (RM) of the water-absorbing agent obtained by the production method according to the present invention is measured according to ERT410.2-02.
  • (D) Crosslinking agent having residual (meth) acrylate group and / or (meth) acrylamide group
  • Crosslinking having residual (meth) acrylate group and / or (meth) acrylamide group of the water-absorbing agent obtained by the production method according to the present invention.
  • the agent is measured according to the following method.
  • a glass beaker having a capacity of 250 ml was charged with 200 ml of a 0.9% by weight sodium chloride aqueous solution, and 1.0 g of a water absorbing agent was added thereto, followed by stirring at 500 rpm for 16 hours to extract the remaining crosslinking agent.
  • the obtained extract was filtered using one sheet of filter paper (product name: JIS P 3801, No. 2, thickness 0.26 mm, reserved particle diameter 5 ⁇ m / manufactured by ADVANTEC Toyo Co., Ltd.), and the obtained filtrate was filtered.
  • the amount of the remaining cross-linking agent was 0.95% by weight sodium chloride aqueous solution, 0.005 ppm (1 ppm in terms of water-absorbing agent), 0.025 ppm (5 ppm in terms of water-absorbing agent), 0.05 ppm (with respect to water-absorbing agent). 10 ppm), 0.25 ppm (50 ppm converted to water absorbent), 0.5 ppm (100 ppm converted to water absorbent), 2.5 ppm (500 ppm converted to water absorbent), 5 ppm (1000 ppm converted to water absorbent) Based on the calibration curve created from
  • Residual initiator amount (RI) and initiator reaction rate The residual initiator amount (RI) and initiator reaction rate of the water-absorbing agent obtained by the production method according to the present invention are measured according to the following method. In the following, a method for measuring the residual amounts of persulfate and hydrogen peroxide, which are representative radical polymerization initiators in the present invention, is described. When the radical polymerization initiator to be used is a peroxide (persulfate, hydrogen peroxide), the residual amount of initiator and the initiator reaction rate may be determined according to this measurement method.
  • the radical polymerization initiator to be used is a peroxide (persulfate, hydrogen peroxide)
  • the residual amount of initiator and the initiator reaction rate may be determined according to this measurement method.
  • a radical polymerization initiator other than peroxide for example, an ultraviolet polymerization initiator such as azo initiator or acetophenone
  • a conventionally known quantification method for example, HPLC (high performance liquid chromatography) The remaining amount may be quantified according to the analysis).
  • a beaker with a capacity of 200 mL was charged with 1 g of a water-absorbing agent and 100 g of a 5 wt% sodium chloride aqueous solution, and stirred at 500 rpm at room temperature using a Teflon (registered trademark) -coated 25 mm rotor. After 2 hours, filtration was performed, and the filtrate was passed through a filter (GL Science Disc, aqueous 25A, pore size 0.45 ⁇ m, manufactured by GL Sciences Inc.).
  • the measurement limit is appropriately determined depending on the polymer amount, sensitivity, etc.
  • it is usually 0.5 ppm by weight, and less than the detection limit (for example, 0.5 ppm by weight) is N.P.
  • D Non-Detactable
  • the initiator reaction rate [%] was calculated from the residual initiator amount (CRI [weight ppm]) corrected for water content and the initiator addition amount (AI [weight ppm]) according to the following formula.
  • Initiator reaction rate [%] ⁇ (AI ⁇ (CRI)) / AI ⁇ ⁇ 100 (F) Residual epoxy crosslinking agent
  • the residual epoxy crosslinking agent of the water absorbing agent obtained by the production method according to the present invention is measured according to the following method.
  • crosslinking agent having residual hydroxy group The crosslinking agent having a residual hydroxy group of the water-absorbing agent obtained by the production method according to the present invention is measured according to the following method.
  • the amount (ppm) of the system reducing agent can be determined.
  • the malachite green solution was prepared by adding 2 mmol / mL of eluent prepared from 500 mL of methanol 2000 mL, hexane 30 mL, 0.01 M 2-morpholine ethanesulfonic acid (pH adjusted to 6 with 0.1 N sodium hydroxide aqueous solution). Malachite green is dissolved so as to be L.
  • Particle size distribution (PSD), weight average particle size (D50), particle size distribution width ( ⁇ ) The particle size distribution and the weight average particle diameter (D50) of the water-absorbing agent obtained by the production method according to the present invention are measured according to the measurement method disclosed in US Pat. No. 7,638,570.
  • a sample container is filled with about 5 g of a water-absorbing agent, and the L-value (Lightness: lightness index) and a value of the surface of the water-absorbing agent are measured with a spectrophotometer in an atmosphere of room temperature (20 to 25 ° C.) and a relative humidity of 50 RH%. , B values were measured.
  • the color tone of the water-absorbing agent immediately after production, or the water-absorbing agent that has a storage period within one year after production in an atmosphere at a temperature of 30 ° C. or less and a relative humidity of 50 RH% or less is referred to as “initial color tone”
  • the L value measured at this time is called “lightness index before exposure”.
  • a “coloring promotion test” the following operation was performed, and “lightness index after exposure” was measured.
  • thermo-hygrostat Espec Co., Ltd. small environment tester; model SH-641
  • SH-641 thermo-hygrostat
  • the color tone of the water-absorbing agent after exposure is referred to as “temporal color tone”, and the L value measured at this time is referred to as “lightness index after exposure”.
  • the whiteness increases as the L value approaches 100, and as the a value and the b value approach 0 (zero), the color becomes low color and substantially white.
  • Examples 1-1 to 1-8 are examples of the first mode (further examples 1-8 are examples of the first and second modes), and conditions and results are shown in Tables 1 and 2.
  • Examples 2-1 to 2-9 are examples of the second mode, and conditions and results are shown in Tables 3 to 5.
  • Examples 3-1 to 3-20 are the examples of the third mode (further, except Examples 3-9, 10 and 17 to 19 are examples of the first and third modes.
  • -12 and 3-13 are examples of the first to third forms), and conditions and results are shown in Tables 6 and 7.
  • the polymerization reaction proceeded by expanding and foaming in all directions toward the upper side of the bat-type reactor while generating water vapor, and then contracted to a size slightly larger than the bottom surface of the reactor. This polymerization reaction (expansion / shrinkage) was completed in about 1 minute. After completion of the polymerization, it was kept in the reaction apparatus for 4 minutes and taken out as a hydrogel crosslinked polymer (1).
  • hydrogel A hydrogel crosslinked polymer (hereinafter referred to as “hydrogel”) (1) obtained by the above polymerization reaction was used as a meat chopper (manufactured by Iizuka Kogyo Co., Ltd .; MEAT-CHOPER TYPE 12VR-400KSOX / die pore diameter: 6.4 mm). And the number of holes: 38, die thickness: 8 mm), and gel pulverization gave a particulate hydrous gel (1).
  • the hydrogel was added at 250 (g / min), and water adjusted to 90 ° C. in parallel was added at 50 (g / min).
  • the obtained particulate hydrous gel (1) was spread on a stainless steel wire mesh having an opening of 850 ⁇ m, and then dried at 180 ° C. for 30 minutes using a hot air dryer. Subsequently, the obtained dried polymer (1) was pulverized using a roll mill (manufactured by Inoguchi Giken Co., Ltd .; WML type roll pulverizer), and then classified using a JIS standard sieve having openings of 850 ⁇ m and 150 ⁇ m.
  • a roll mill manufactured by Inoguchi Giken Co., Ltd .; WML type roll pulverizer
  • the weight average particle size (D50) is 350 ⁇ m
  • the content of particles having a particle size of 150 ⁇ m or more and less than 850 ⁇ m is 97% by weight
  • the 150 ⁇ m passing material is 3% by weight (of which 106 ⁇ m passing material is 1%)
  • a regularly crushed water-absorbing resin (1) was obtained.
  • the water-absorbing resin (1) thus obtained has a water absorption capacity (CRC) under no pressure of 51.1 (g / g), a water absorption capacity under pressure of AAP of 2.06 kPa is 7.1 (g / g), and an AAP of 4.83 kPa is 6 0.5 (g / g), the water content was 4.0% by weight.
  • the residual crosslinking agent polyethylene glycol diacrylate in the water absorbent resin (1) is N.I. D. (The detection limit was less than 10 ppm).
  • Example 1-1 (Mixing process) With respect to 100 parts by weight of the water-absorbent resin (1) obtained in Production Example 1, 4.0 parts by weight of acrylic acid as a radical polymerizable monomer and ethylene glycol diacrylate (EGDA) (molecular weight 170 as an organic crosslinking agent) .18, 2 acrylate groups) 0.2 parts by weight, water 7.0 parts by weight, 0.25 parts by weight of ammonium persulfate as a radical polymerization initiator, polyethylene glycol monomethyl ether (number average molecular weight about 2000) 0 as a mixing aid Then, 11.55 parts by weight of the surface treatment liquid previously mixed with 1 part by weight was dropped and mixed uniformly to obtain a mixture (1-1).
  • EGDA ethylene glycol diacrylate
  • Table 1 shows the conditions for surface crosslinking polymerization of the obtained water-absorbing agent (1-1), and Table 2 shows the performance of the water-absorbing agent.
  • Example 1-2 In Example 1-1, the same operation as in Example 1-1 was performed, except that 0.2 parts by weight of ethylene glycol dimethacrylate (molecular weight 198.24, two methacrylate groups) was used as the organic crosslinking agent. A water absorbing agent (1-2) was obtained.
  • ethylene glycol dimethacrylate molecular weight 198.24, two methacrylate groups
  • Example 1-3 In Example 1-1, except that 0.2 parts by weight of 1,4-butanediol diacrylate (molecular weight: 198.24, two acrylate groups) was used as the organic crosslinking agent, the same as Example 1-1 Operation was performed to obtain a water-absorbing agent (1-3).
  • 1,4-butanediol diacrylate molecular weight: 198.24, two acrylate groups
  • the conditions for surface cross-linking polymerization of the obtained water-absorbing agent (1-3) are shown in Table 1, and the performance of the water-absorbing agent is shown in Table 2.
  • Example 1-4 In Example 1-1, glycerol carbonate acrylate (a compound in which an epoxy group of glycidyl acrylate was reacted with carbon dioxide to form an ethylene carbonate group) as an organic crosslinking agent (molecular weight 172.15, one acrylate group + carbonate ring) 1) Except that 0.2 parts by weight was used, the same operation as in Example 1-1 (polymerization of acrylate groups in the reaction step) was performed, and then the water-absorbent resin after the reaction step was obtained. Before the granulation step, the water-absorbing agent (1-4) was obtained by heating the carbonate ring for 30 minutes as a heat treatment step at a higher temperature (140 ° C.) than the reaction step.
  • a higher temperature 140 ° C.
  • Table 1 shows the conditions for surface crosslinking polymerization of the obtained water-absorbing agent (1-4), and Table 2 shows the performance of the water-absorbing agent.
  • Example 1-5 The same operation as in Example 1-1 except that 0.05 part by weight of glycidyl methacrylate (molecular weight 142.17, 1 methacrylate group, 1 epoxy group) was used as the organic crosslinking agent in Example 1-1. To obtain a water absorbing agent (1-5).
  • Example 1-6 In Example 1, water absorption was carried out in the same manner as in Example 1-1, except that 0.05 part by weight of ethylene glycol diglycidyl ether (molecular weight 174.22, 2 epoxy groups) was used as the organic crosslinking agent. Agent (1-6) was obtained.
  • the conditions for surface crosslinking polymerization of the obtained water-absorbing agent (1-6) are shown in Table 1, and the performance of the water-absorbing agent is shown in Table 2.
  • Example 1-7 A water absorbing agent (1-7) was obtained in the same manner as in Example 1-2, except that in Example 1-2, the amount of acrylic acid used was changed to 8 parts by weight.
  • the conditions for the surface crosslinking polymerization of the obtained water-absorbing agent (1-7) are shown in Table 1, and the performance of the water-absorbing agent is shown in Table 2.
  • Example 1-8 To 100 parts by weight of the water-absorbing agent (1-7) obtained in Example 1-7, 2 parts by weight of a 2.5% by weight aqueous solution of sodium bisulfite (sodium bisulfite 500 ppm with respect to the water-absorbent resin) 30 g of the resulting mixture was placed in a polyethylene plastic bag with a chuck (Unipack C-4, manufactured by Nippon Shokubai Co., Ltd .: length 100 mm ⁇ width 70 mm ⁇ thickness 0.04 mm), and sealed. After heating at 0 ° C. for 30 minutes, the mixture was classified using a JIS standard sieve having an aperture of 850 ⁇ m to obtain a water absorbing agent (1-8). In addition, the ON product (impervious material) of the sieve was crushed until the entire amount passed 850 ⁇ m.
  • aqueous solution of sodium bisulfite sodium bisulfite 500 ppm with respect to the water-absorbent resin
  • a comparative water absorbing agent (1-1) was obtained in the same manner as in Example 1-1 except that it was used.
  • the conditions for surface cross-linking polymerization of the obtained comparative water-absorbing agent (1-1) are shown in Table 1, and the performance of the water-absorbing agent is shown in Table 2.
  • Example 1-1 the same operation as in Example 1-1 was performed, except that 0.2 parts by weight of diethylene glycol diacrylate (molecular weight 214.24, two acrylate groups) was used as the organic crosslinking agent. A water absorbing agent (1-2) was obtained.
  • diethylene glycol diacrylate molecular weight 214.24, two acrylate groups
  • Example 1-1 0.2 part by weight of glycerin acrylate methacrylate (Shin Nakamura Chemical Co., Ltd. NK ester 701A: molecular weight 214.24, one acrylate group + one methacrylate group) was used as an organic crosslinking agent.
  • a comparative water-absorbing agent (1-3) was obtained in the same manner as in Example 1-1 except for the above.
  • Table 1 shows the surface crosslinking polymerization conditions of the comparative water-absorbing agent (1-3) obtained, and Table 2 shows the performance of the water-absorbing agent.
  • Comparative Example 1-4 A comparative water absorbing agent (1-4) was obtained in the same manner as in Comparative Example 1-3, except that the amount of glycerin acrylate methacrylate used in Comparative Example 1-3 was changed to 0.05 parts by weight.
  • Example 1-5 In Example 1-1, except that 0.2 parts by weight of glycerin dimethacrylate (Shin Nakamura Chemical Co., Ltd., NK ester 701: molecular weight 228.27, two methacrylate groups) was used as the organic crosslinking agent. A comparative water-absorbing agent (1-5) was obtained in the same manner as in 1-1.
  • Example 1-1 the same operation as in Example 1-1 was performed, except that 0.2 part by weight of pentaerythritol triacrylate (molecular weight 298.32, 3 acrylate groups) was used as the organic crosslinking agent. A comparative water-absorbing agent (1-6) was obtained.
  • the conditions for surface cross-linking polymerization of the obtained comparative water-absorbing agent (1-6) are shown in Table 1, and the performance of the water-absorbing agent is shown in Table 2.
  • Example 1-7 The same operation as in Example 1-1 except that 0.2 parts by weight of allyl methacrylate (molecular weight 126.17, one acrylate group + one allyl group) was used as the organic crosslinking agent in Example 1-1. To obtain a comparative water-absorbing agent (1-7).
  • Example 1-8 The same operation as in Example 1-1 except that 0.2 parts by weight of vinyl methacrylate (molecular weight: 112.14, one acrylate group + one vinyl group) was used as the organic crosslinking agent in Example 1-1. To obtain a comparative water-absorbing agent (1-8).
  • Example 1-9 Comparative Example 1-9
  • Comparative Example 1-9 comparative water absorption was carried out in the same manner as in Example 1-1 except that 0.1 part by weight of ethylene glycol diacrylate and 0.1 part by weight of glycerin acrylate methacrylate were used in combination as the organic crosslinking agent.
  • Agent (1-9) was obtained.
  • the surface crosslinking conditions of the comparative water-absorbing agent (1-9) obtained are shown in Table 1, and the performance of the water-absorbing agent is shown in Table 2.
  • Comparative Example 1-10 50 g of the comparative water-absorbing agent (1-3) obtained in Comparative Example 1-3 was added to a polyethylene plastic bag with a chuck (Unipack D-4, manufactured by Nippon Shokubai Co., Ltd .: length 120 mm ⁇ width 85 mm ⁇ thickness 0.04 mm). ) And sealed at room temperature for 6 months to obtain a comparative water-absorbing agent (1-10).
  • EGDA ethylene glycol diacrylate
  • B ethylene glycol dimethacrylate
  • C 1,4-butanediol di
  • the heating conditions indicate that I: 100 ° C. for 30 minutes and II: 100 ° C. for 30 minutes and further 140 ° C. for 30 minutes.
  • Examples 1-1 to 1-8 AAP 2.06 was improved to 20 g / g or more, AAP 4.83 was improved to 12 g / g or more, and the remaining crosslinking agent was N.I. D. It can be seen that when the molecular weight is less than 200, the residual crosslinking agent amount is reduced.
  • Examples 1-1 to 1-3 and 1-7 are di (meth) acrylate-based crosslinking agents, and Examples 1-4 and 1-5 are examples of acrylate-based crosslinking agents having a cyclic functional group.
  • Example 1-6 is an example using a cross-linking agent having a plurality of cyclic functional groups, and Example 1-4 further includes a heat treatment step (reaction step of carbonate ring) after cross-linking polymerization. It can be seen that the agent also gives good results.
  • Comparative Example 1-4 in order to reduce the residual amount of the organic crosslinking agent in Comparative Example 1-3 (0.2 parts by weight of crosslinking agent and 671 ppm of remaining crosslinking agent), the amount of crosslinking agent was set to 0.05 parts by weight. Although the amount of the remaining crosslinking agent was reduced to 15 ppm, AAP4.83 was halved (from 16.8 g / g to 8.8 g / g), and a sufficient crosslinking effect was not obtained. I understand. Further, as in Comparative Example 1-9, it can be seen that the organic crosslinking agent having a molecular weight of 200 or more tends to remain even when the organic crosslinking agent is used in combination and the respective amounts used are reduced.
  • the polymerization reaction proceeded by expanding and foaming in all directions toward the upper side of the bat-type reactor while generating water vapor, and then contracted to a size slightly larger than the bottom surface of the reactor. This polymerization reaction (expansion / shrinkage) was completed in about 1 minute. After completion of the polymerization, it was kept in the reaction apparatus for 4 minutes and taken out as a hydrogel crosslinked polymer (2-1).
  • hydrogel A hydrogel crosslinked polymer (hereinafter referred to as “hydrogel”) (2-1) obtained by the above polymerization reaction was used as a meat chopper (manufactured by Iizuka Kogyo Co., Ltd .; MEAT-CHOPER TYPE 12VR-400KSOX / die pore diameter: 6). Gel pulverization was performed using 4 mm, the number of holes: 38, and the die thickness: 8 mm, to obtain a particulate hydrous gel (2-1).
  • the hydrogel was added at 250 (g / min), and water adjusted to 90 ° C. in parallel was added at 50 (g / min).
  • the obtained particulate hydrogel (2-1) was spread on a stainless steel wire mesh having an opening of 850 ⁇ m, and then dried at 180 ° C. for 30 minutes using a hot air dryer. Subsequently, the obtained dried polymer (2-1) was pulverized using a roll mill (manufactured by Inoguchi Giken Co., Ltd .; WML type roll pulverizer), and then classified using JIS standard sieves having openings of 850 ⁇ m and 150 ⁇ m. did.
  • a roll mill manufactured by Inoguchi Giken Co., Ltd .; WML type roll pulverizer
  • the weight average particle size (D50) is 350 ⁇ m
  • the content of particles having a particle size of 150 ⁇ m or more and less than 850 ⁇ m is 97% by weight
  • the 150 ⁇ m passing material is 3% by weight (of which 106 ⁇ m passing material is 1%)
  • a regularly crushed water-absorbing resin (2-1) was obtained.
  • the water absorption capacity (CRC) of the obtained water absorbent resin (2-1) under no pressure was 51 (g / g), and the water content was 4.0% by weight.
  • the remaining initiator amount of the water-absorbent resin (2-1) was N.P. D. (Below detection limit).
  • Comparative Example 2-1 In Comparative Example 2-1, the same operation as in Comparative Example 2-1 was performed, except that an aqueous solution (A2) in which ammonium persulfate in the surface treatment solution used in the surface crosslinking mixing step was changed to 1 part by weight was used. Thus, a surface-crosslinked water-absorbing resin (2-2) was obtained.
  • the production conditions of the surface-crosslinked water-absorbent resin (2-2) thus obtained are shown in Table 3, various physical properties are shown in Table 4, and the color tone is shown in Table 5.
  • Comparative Example 2-3 In Comparative Example 2-1, the surface-crosslinked water-absorbing resin (2-3) was obtained by performing the same operation as in Comparative Example 2-1, except that the heating time in the surface crosslinking reaction step was changed to 30 minutes. Obtained.
  • the production conditions of the surface-crosslinked water-absorbing resin (2-3) obtained are shown in Table 3, various physical properties are shown in Table 4, and the color tone is shown in Table 5.
  • Comparative Example 2-5 In Comparative Example 2-4, the same operation as in Comparative Example 2-4 was performed, except that an aqueous solution (A4) in which ammonium persulfate in the surface treatment liquid used in the surface crosslinking mixing step was changed to 1 part by weight was used. Thus, a surface-crosslinked water-absorbing resin (2-5) was obtained.
  • the production conditions of the surface-crosslinked water-absorbing resin (2-5) thus obtained are shown in Table 3, various physical properties are shown in Table 4, and the color tone is shown in Table 5.
  • UV- ultraviolet irradiation device
  • a metal halide lamp manufactured by USHIO INC., UVL-1500M2-N1.
  • 152 / 1MNSC3-AA06 was irradiated with ultraviolet rays at room temperature for 10 minutes at an irradiation intensity of 60 mW / cm 2 .
  • Example 2-1 With respect to 100 parts by weight of the surface-crosslinked water-absorbing resin (2-1) obtained in Comparative Example 2-1, 2.5 parts by weight of 10% by weight aqueous sodium hydrogen sulfite solution (B1) (based on the water-absorbing resin) And uniformly mixed as a sodium bisulfite (0.25% by weight), and 30 g of the resulting mixture is uniformly spread on a bat (manufactured by SUS304: length 158 mm ⁇ width 128 mm ⁇ depth 25 mm), and a polyethylene plastic bag with a chuck (Unipack H-4, manufactured by Nippon Shokubai Co., Ltd .: 240 mm long x 170 mm wide x 0.04 mm thick), sealed, heated at 100 ° C.
  • Example 2-2 In Example 2-1, the same operation as in Example 2-1 was performed, except that the amount of the aqueous solution (B1) added was changed to 5 parts by weight (sodium bisulfite 0.5% by weight with respect to the water absorbent resin). And a water absorbing agent (2-2) was obtained.
  • the production conditions of the water-absorbing agent (2-2) obtained are shown in Table 3, various physical properties are shown in Table 4, and the color tone is shown in Table 5.
  • Example 2-3 In Example 2-1, the same operation as in Example 2-1 was performed, except that the addition amount of the aqueous solution (B1) was changed to 10 parts by weight (1.0% by weight of sodium bisulfite with respect to the water absorbent resin). And a water absorbing agent (2-3) was obtained.
  • the production conditions of the water-absorbing agent (2-3) obtained are shown in Table 3, various physical properties are shown in Table 4, and the color tone is shown in Table 5.
  • Example 2-4 In Example 2-1, instead of the aqueous solution (B1), 5 parts by weight of a 5% strength by weight sodium hydrogen sulfite aqueous solution (B2) was added (0.25% by weight of sodium hydrogen sulfite with respect to the water absorbent resin).
  • the water absorbing agent (2-4) was obtained in the same manner as in Example 2-1.
  • the production conditions of the water-absorbing agent (2-4) obtained are shown in Table 3, various physical properties are shown in Table 4, and the color tone is shown in Table 5.
  • Example 2-5 In Example 2-1, instead of the aqueous solution (B1), 12.5 parts by weight of a sodium bisulfite aqueous solution (B3) having a concentration of 2% by weight (0.25% by weight of sodium bisulfite with respect to the water-absorbent resin) was added.
  • the following water-absorbing agent (2-5) was obtained in the same manner as in Example 2-1, except for the following.
  • the production conditions of the water-absorbing agent (2-5) obtained are shown in Table 3, various physical properties are shown in Table 4, and the color tone is shown in Table 5.
  • Example 2-6 To 100 parts by weight of the surface-crosslinked water-absorbing resin (2-4) obtained in Comparative Example 2-4, 5 parts by weight of water was uniformly dropped and mixed, and 30 g of the resulting mixture was added to a vat (made of SUS304). : 158mm x 128mm x depth 25mm) uniformly spread and put in a polyethylene plastic bag with a chuck (Unipack H-4, manufactured by Nippon Shokubai Co., Ltd .: length 240mm x width 170mm x thickness 0.04mm) After sealing and heating for 15 minutes at 100 ° C., the mixture was classified using a JIS standard sieve having an opening of 850 ⁇ m to obtain a water absorbing agent (2-6).
  • Example 2-7 The following water-absorbing agent (2-7) was obtained in the same manner as in Example 2-6 except that the heating time was changed to 60 minutes in Example 2-6.
  • the production conditions of the water-absorbing agent (2-7) obtained are shown in Table 3, various physical properties are shown in Table 4, and the color tone is shown in Table 5.
  • Example 2-8 For 100 parts by weight of the surface-crosslinked water-absorbing resin (2-6) obtained in Comparative Example 2-6, 2 parts by weight of a 12.5 wt% aqueous sodium hydrogen sulfite solution (B4) (based on the water-absorbing resin) Then, 30 g of the resulting mixture is mixed with a polyethylene plastic bag with a chuck (Unipack C-4, manufactured by Nippon Shokubai Co., Ltd .: length 100 mm ⁇ width 70 mm ⁇ thickness). 0.04 mm) and sealed, heated at 60 ° C. for 30 minutes, and then classified using a JIS standard sieve having an aperture of 850 ⁇ m to obtain a water absorbing agent (2-8).
  • a polyethylene plastic bag with a chuck Unipack C-4, manufactured by Nippon Shokubai Co., Ltd .: length 100 mm ⁇ width 70 mm ⁇ thickness). 0.04 mm
  • Example 2-9 In Example 2-8, except that the aqueous solution (B4) was replaced with 2 parts by weight of a sodium sulfite aqueous solution (B5) having a concentration of 12.5% by weight (0.25% by weight of sodium sulfite with respect to the water absorbent resin).
  • a water absorbing agent (2-9) was obtained.
  • the production conditions of the water-absorbing agent (2-9) obtained are shown in Table 3, various physical properties are shown in Table 4, and the color tone is shown in Table 5.
  • the water absorbing agents 2-1 to 2-9 have a residual initiator amount by mixing a liquid containing water during or after the reaction step. It can be seen that the amount of residual monomer can be reduced, and the problem of coloring is also suppressed.
  • Comparative Examples 2-1 and 2-4 since the reaction rate of the initiator is low, it is recognized that the amount of residual initiator is large, the amount of residual monomer is large, and the colorability is high.
  • the comparative water-absorbing agent 2-2 when the radical polymerization initiator is excessively used, the reaction with the radical polymerizable monomer does not proceed well, and conversely, an increase in residual monomer and a deterioration in colorability are observed.
  • Comparative Water Absorbing Agent 2-5 although the amount of residual monomer is suppressed by using a large amount of radical polymerization initiator, there is a problem of coloring.
  • the comparative water-absorbing agent 2-6 there is a problem of colorability by using a large amount of a radical polymerization initiator and irradiating with ultraviolet rays.
  • the amount of residual persulfate exceeds 1000 ppm
  • the colorability deteriorates.
  • the water-soluble content was 25.3% by weight in Example 2-1, 34.7% by weight in Example 2-2, and 48.4% by weight in Example 2-3, the remaining reduction It can be seen that when the amount exceeds 2500 ppm, the water-soluble component is greatly increased.
  • the reaction solution (3) was immediately poured into a stainless steel bat-type reactor (bottom surface: 340 ⁇ 340 mm, height: 25 mm, inner surface; Teflon (registered trademark) coating) in an open air system, and polymerization was performed after about 15 seconds.
  • the reaction started.
  • the stainless steel bat type reactor was preliminarily set to a surface temperature of 40 ° C. using a hot plate (NEO HOTPLATE HI-1000 / manufactured by Inoue Seieido Co., Ltd.).
  • the polymerization reaction proceeded by expanding and foaming in all directions toward the upper side of the bat-type reactor while generating water vapor, and then contracted to a size slightly larger than the bottom surface of the reactor.
  • the polymer obtained by this operation was designated as a hydrogel crosslinked polymer (hereinafter referred to as “hydrogel”) (3).
  • hydrogel (3) was held
  • the hydrogel (3) was subjected to gel pulverization using a meat chopper (MEAT-CHOPER TYPE 12VR-400KSOX; die hole diameter: 6.4 mm, hole number: 38, die thickness: 8 mm / manufactured by Iizuka Kogyo Co., Ltd.)
  • a particulate hydrous gel (3) was obtained.
  • pulverization was performed by throwing into a meat chopper separately the hydrogel (3) 250 (g / min) and the warm water 50 (g / min) adjusted to 90 degreeC, respectively.
  • the particulate hydrogel (3) obtained by the gel pulverization was dried using a hot air dryer to obtain a dried polymer (3).
  • the drying was performed by spreading and placing the particulate hydrous gel (3) on a stainless steel wire mesh having an opening of 850 ⁇ m and aerated with 180 ° C. hot air for 30 minutes.
  • the dried polymer (3) obtained by the above drying is pulverized using a roll mill (WML type roll pulverizer / manufactured by Inoguchi Giken Co., Ltd.), and then classified using a JIS standard sieve having openings of 850 ⁇ m and 150 ⁇ m. Thus, an irregularly shaped water-absorbing resin powder (3) was obtained.
  • the water absorbent resin powder (3) has a weight average particle size (D50) of 350 ⁇ m, a content of particles having a particle size of 150 ⁇ m or more and less than 850 ⁇ m of 97% by weight, and a content of particles having a particle size of less than 150 ⁇ m of 3% by weight (of which 106 ⁇ m Less than 1% by weight), water absorption capacity without pressure (CRC) is 51.1 (g / g), water absorption capacity under pressure (AAP2.06 kPa) is 7.1 (g / g), water absorption capacity under pressure (AAP4 0.83 kPa) was 6.5 (g / g), the water content was 4.0% by weight, and the residual monomer was 370 ppm.
  • D50 weight average particle size
  • Example 3-1 (Mixing process) For 100 parts by weight of the water-absorbent resin powder (3) obtained in Production Example 3, 5.0 parts by weight of acrylic acid as a radical polymerizable monomer and sodium persulfate (10 hours as a thermally decomposable radical polymerization initiator) Half-life temperature: 71 ° C.) 0.25 part by weight, ethylene glycol diacrylate (EGDA) 0.3 part by weight as organic crosslinking agent, polyethylene glycol monomethyl ether (PEGOMe ⁇ number average molecular weight; about 2000) 0 as a mixing aid 9.65 parts by weight of the surface treatment liquid (3-1) consisting of 0.1 part by weight and 4.0 parts by weight of ion-exchanged water were uniformly dropped and mixed to obtain a mixture (3-1).
  • EGDA ethylene glycol diacrylate
  • PEGOMe polyethylene glycol monomethyl ether
  • a stationary dryer having a capacity of 27 L was prepared as a reaction apparatus for performing the surface crosslinking reaction step.
  • the dryer (reactor) has a gas supply port at the top and a gas exhaust port at the bottom, and the internal atmosphere dew point and the internal atmosphere temperature of the dryer (reaction device) are constant temperature and dew point.
  • the inner wall surface temperature of the dryer (reaction apparatus) is controlled by the set temperature of the dryer, and is controlled.
  • Example 3-1 the set temperature (inner wall surface temperature) was set to 100 ° C., and the mixture (3-1 The bat containing) was placed for 15 minutes as the heating time, and the surface crosslinking reaction step was performed.
  • the internal atmosphere dew point of the dryer (reactor) is 80 ° C. (relative humidity 50% RH)
  • the internal atmosphere temperature is 100 ° C.
  • the inner wall surface temperature is 100 ° C. So that each was always controlled.
  • the surface cross-linking reaction step was classified using a JIS standard sieve having an aperture of 850 ⁇ m to obtain a water absorbing agent (3-1).
  • the ON product (impervious material) of the sieve was crushed until the entire amount passed 850 ⁇ m.
  • Table 6 shows conditions of the surface crosslinking reaction step
  • Table 7 shows properties of the water-absorbing agent (3-1).
  • Example 3-2 In Example 3-1, a water absorbing agent was obtained by performing the same operation as in Example 3-1, except that the internal atmosphere temperature of the dryer (reaction apparatus) was controlled to 120 ° C. (relative humidity 24% RH). (3-2) was obtained. Table 6 shows various conditions of the surface crosslinking reaction step, and Table 7 shows various physical properties of the water-absorbing agent (3-2) obtained.
  • Example 3-1 is the same as Example 3-1 except that the internal atmosphere temperature of the dryer (reactor) was controlled to 120 ° C. (relative humidity 24% RH) and the inner wall surface temperature to 120 ° C.
  • the water-absorbing agent (3-3) was obtained by the above operations.
  • Table 6 shows various conditions of the surface crosslinking reaction step, and Table 7 shows physical properties of the water-absorbing agent (3-3) obtained.
  • Example 3-1 was the same as Example 3-1 except that the internal atmosphere temperature of the dryer (reactor) was controlled to 180 ° C. (relative humidity 5% RH) and the inner wall surface temperature to 180 ° C. As a result, a comparative water-absorbing agent (3-1) was obtained. Table 6 shows conditions of the surface crosslinking reaction step, and Table 7 shows properties of the comparative water-absorbing agent (3-1).
  • Example 3-4 In Example 3-1, except that the internal atmosphere temperature of the dryer (reactor) was controlled to 80 ° C., the internal atmosphere dew point was 75 ° C. (relative humidity 85% RH), and the inner wall surface temperature was 80 ° C. The same operation as in Example 3-1 was performed to obtain a water absorbing agent (3-4). Table 6 shows conditions of the surface crosslinking reaction step, and Table 7 shows properties of the water-absorbing agent (3-4).
  • Example 3-5 In Example 3-1, the same operation as in Example 3-1 was performed, except that the internal atmosphere dew point of the dryer (reaction apparatus) was controlled to 90 ° C. (relative humidity 77% RH). (3-5) was obtained. Table 6 shows the various conditions of the surface crosslinking reaction step, and Table 7 shows the physical properties of the water-absorbing agent (3-5).
  • Example 3-1 a water oven (trade name: Hersio, model number: AX-HC3 / Sharp Co., Ltd.) was used as a reaction apparatus, and heated for 5 minutes in a steamed (strong) mode to carry out a reaction process for surface crosslinking.
  • a comparative water absorbing agent (3-2) was obtained in the same manner as in Example 3-1, except that this was done.
  • Table 6 shows the conditions for the surface crosslinking reaction step
  • Table 7 shows the physical properties of the comparative water-absorbing agent (3-2).
  • the treatment in the steamed (strong) mode is a mode in which heating is performed with saturated steam, and by setting the set temperature to 100 ° C., the internal atmosphere temperature, the internal atmospheric dew point, and the inner wall surface temperature of the oven are set to 100 respectively. It can be controlled to ° C. (relative humidity is 100% RH).
  • the water oven was pre-heated by operating in a steamed (strong) mode (set temperature: 100 ° C.) for 5 minutes before performing the above operation.
  • Comparative Example 3-3 A comparative water absorbing agent (3-3) was obtained in the same manner as in Comparative Example 3-2 except that the water oven cake mode (set temperature: 120 ° C.) was changed in Comparative Example 3-2.
  • Various conditions of the surface crosslinking reaction step are shown in Table 6, and various properties of the comparative water-absorbing agent (3-3) obtained are shown in Table 7.
  • the treatment in the water oven cake mode is a form in which heating is performed by superheated steam that is further heated after vaporization.
  • the set temperature By setting the set temperature to 120 ° C., the internal atmosphere temperature and the inner wall surface temperature of the oven are set.
  • the internal dew point can be controlled to 120 ° C. and 100 ° C., respectively (relative humidity is 51% RH).
  • the water oven was preheated by operating the water oven for 5 minutes in the water oven cake mode (set temperature 120 ° C.) before performing the above operation.
  • Example 3-6 In Example 3-1, the ion-exchanged water was changed to 5.0 parts by weight, the surface treatment liquid (3-6) was made 10.65 parts by weight, and the internal atmosphere dew point of the dryer (reaction apparatus) was 70. A water-absorbing agent (3-6) was obtained in the same manner as in Example 3-1, except that the temperature was controlled to be 0 ° C. (relative humidity 32% RH). Table 6 shows various conditions of the surface crosslinking reaction step, and Table 7 shows various physical properties of the obtained water-absorbing agent (6).
  • Example 3-4 Comparative Example 3-4
  • Comparative Example 3-4 comparative water absorption was performed by performing the same operation as in Example 3-6, except that the internal atmosphere dew point of the dryer (reaction apparatus) was controlled to 50 ° C. (relative humidity 12% RH). Agent (3-4) was obtained.
  • Table 6 shows various conditions of the surface cross-linking reaction step, and Table 7 shows various physical properties of the comparative water-absorbing agent (3-4).
  • Example 3-7 In Example 3-1, surface treatment was carried out by changing the acrylic acid to 10.0 parts by weight, ethylene glycol dimethacrylate (EGDM) as an organic crosslinking agent to 0.5 parts by weight, and ion-exchanged water to 5.0 parts by weight.
  • EGDM ethylene glycol dimethacrylate
  • a water absorbing agent (3-7) was obtained in the same manner as in Example 3-1, except that the liquid (3-7) was 15.85 parts by weight.
  • Table 6 shows the conditions for the surface crosslinking reaction step
  • Table 7 shows the physical properties of the water-absorbing agent (3-7).
  • Example 3-8 In Example 3-1, except that 0.1 parts by weight of the mixing aid (polyethylene glycol monomethyl ether (PEGOMe)) was not used, and 9.55 parts by weight was used as the surface treatment liquid (3-8). The same operation as in 3-1 was performed to obtain a water absorbing agent (3-8). Table 6 shows conditions of the surface crosslinking reaction step, and Table 7 shows properties of the water-absorbing agent (3-8).
  • the mixing aid polyethylene glycol monomethyl ether (PEGOMe)
  • Example 3-9 In Example 3-1, except that 0.3 part by weight of the organic crosslinking agent (ethylene glycol diacrylate (EGDA)) was not used and 9.35 parts by weight was used as the surface treatment liquid (3-9). The same operation as in Example 3-1 was performed to obtain a water absorbing agent (3-9). Table 6 shows conditions of the surface crosslinking reaction step, and Table 7 shows properties of the water-absorbent resin (3-9) obtained.
  • the organic crosslinking agent ethylene glycol diacrylate (EGDA)
  • Example 3-10 In Example 3-1, 5.0 parts by weight of acrylic acid and 0.3 parts by weight of an organic crosslinking agent (ethylene glycol diacrylate (EGDA)) were not used, and sodium persulfate was changed to 0.5 parts by weight.
  • a water absorbing agent (3-10) was obtained in the same manner as in Example 3-1, except that the surface treatment liquid (3-10) was changed to 4.60 parts by weight.
  • Table 6 shows the conditions for the surface crosslinking reaction step
  • Table 7 shows the physical properties of the water-absorbing agent (3-10).
  • Example 3-1 5.0 parts by weight of acrylic acid, 0.3 parts by weight of an organic crosslinking agent (ethylene glycol diacrylate (EGDA)) and 0.25 parts by weight of sodium persulfate were not used.
  • a comparative water-absorbing agent (3-5) was obtained in the same manner as in Example 3-1, except that the amount of the liquid (3-5) was 4.10 parts by weight.
  • Table 6 shows conditions of the surface crosslinking reaction step, and Table 7 shows properties of the comparative water-absorbing agent (3-5).
  • Example 3-11 In Example 3-1, the amount of ethylene glycol diacrylate used was changed to 1.0 part by weight, and the surface treatment liquid (3-11) was changed to 10.35 part by weight. To obtain a water-absorbing agent (3-11). Table 6 shows various conditions of the surface crosslinking reaction step, and Table 7 shows physical properties of the water-absorbing agent (3-11) thus obtained.
  • Example 3-12 To 100 parts by weight of the water-absorbing agent (3-11) obtained in Example 3-11, 2 parts by weight of a 2.5% strength by weight sodium hydrogen sulfite aqueous solution (500 ppm of sodium hydrogen sulfite relative to the water-absorbent resin) was homogeneous 30 g of the resulting mixture was placed in a polyethylene plastic bag with a chuck (Unipack C-4, manufactured by Nippon Shokubai Co., Ltd .: length 100 mm ⁇ width 70 mm ⁇ thickness 0.04 mm), and sealed. After heating at 0 ° C. for 30 minutes, the mixture was classified using a JIS standard sieve having an opening of 850 ⁇ m to obtain a water absorbing agent (3-12). In addition, the ON product (impervious material) of the sieve was crushed until the entire amount passed 850 ⁇ m.
  • Table 7 shows properties of the water-absorbing agent (3-12) so obtained.
  • Example 3-13 In Example 3-12, a water absorbing agent (3-13) was obtained in the same manner as in Example 3-12 except that sodium sulfite was used instead of sodium hydrogen sulfite.
  • Table 7 shows properties of the water-absorbing agent (3-13) so obtained.
  • Example 3-14 50 g of the water-absorbing agent (3-11) obtained in Example 3-11 was put into a vat of 158 mm in length, 128 mm in width, 25 mm in height and made of SUS304, so that the thickness of the powder layer became uniform. The mixture was heated at 180 ° C. for 30 minutes with standing, and then classified using a JIS standard sieve having an opening of 850 ⁇ m to obtain a water absorbing agent (3-14). In addition, the ON product (impervious material) of the sieve was crushed until the entire amount passed 850 ⁇ m.
  • Table 7 shows properties of the water-absorbing agent (3-14) so obtained.
  • Example 3-15 35 g of the water-absorbing agent (3-11) obtained in Example 3-11 and 10 g of glass beads were placed in a 225 ml mayonnaise bottle, and a paint shaker (manufactured by Toyo Seiki Seisakusho Co., Ltd., 100 V / 60 Hz, vibration speed: 750 c) .Pm vibration) for 30 minutes.
  • a paint shaker manufactured by Toyo Seiki Seisakusho Co., Ltd., 100 V / 60 Hz, vibration speed: 750 c) .Pm vibration
  • Table 7 shows properties of the water-absorbing agent (3-15) so obtained.
  • Example 3-16 The same operation as in Example 3-15 was performed, except that the water absorbing agent (3-14) obtained in Example 3-14 was used instead of the water absorbing agent (3-11). -16) was obtained.
  • Table 7 shows properties of the water-absorbing agent (3-16) so obtained.
  • Example 3-17 In Example 3-1, 3 parts by weight of 75% neutralized sodium acrylate as a radical polymerizable monomer, 0.1 part by weight of methylenebisacrylamide (MBAA) as an organic crosslinking agent, and 5. 5 of ion-exchanged water.
  • the water absorbing agent (3-17) was obtained in the same manner as in Example 3-1, except that the amount was changed to 0 part by weight and the surface treatment liquid (3-17) was changed to 8.45 parts by weight.
  • Table 6 shows the various conditions of the surface crosslinking reaction step
  • Table 7 shows the physical properties of the water-absorbing agent (3-17) obtained.
  • Example 3-18 In Example 3-7, the organic crosslinking agent was changed to 0.2 part by weight of glycerol acrylate methacrylate (701A), the surface treatment liquid (3-18) was changed to 15.55 parts by weight, and the heating time was extended to 30 minutes.
  • a water absorbent resin (3-18) was obtained in the same manner as in Example 3-7 except that Table 6 shows conditions of the surface crosslinking reaction step, and Table 7 shows properties of the water-absorbing agent (3-18).
  • a water-absorbing agent (3-19) Table 6 shows conditions for the surface crosslinking reaction step, and Table 7 shows properties of the water-absorbing agent (3-19) obtained.
  • Example 3-20 In Example 3-1, the same procedure as in Example 3-1 was performed, except that polyethylene glycol (PEG, number average molecular weight; about 2000) was changed to 0.1 part by weight as a mixing aid. ⁇ 20) was obtained.
  • Table 6 shows the conditions for the surface crosslinking reaction step
  • Table 7 shows the physical properties of the water-absorbing agent (3-20).
  • Example 3-6 From the results of Example 3-6 and Comparative Example 3-4, it was confirmed that when the internal atmosphere dew point of the reactor was less than 60 ° C., the water content of the water-absorbent resin tends to decrease.
  • Example 3-17 From the results of Example 3-17, it can be seen that a high-performance water-absorbing agent can be obtained even if the neutralization rate of the radical polymerizable monomer is high.

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Abstract

Le problème décrit par la présente invention est de pourvoir à un procédé de production, à bas coût (à basse température et en un court laps de temps), d'une résine absorbant l'eau réticulée en surface (matériau absorbant l'eau) qui présente un bon équilibre entre l'absorption de l'eau sous aucune pression et celle sous pression, fait preuve d'une excellente sécurité et dans laquelle la quantité de matière résiduelle telle qu'un agent de réticulation ou un amorceur est réduite au minimum. La solution selon l'invention porte sur un procédé de production d'un matériau absorbant l'eau qui comprend une résine absorbant l'eau à base d'acide poly(méth)acrylique (ou sel de celui-ci) à titre de composant principal, caractérisé en ce que : le procédé comprend (a) une étape de mélange consistant à mélanger une résine absorbant l'eau à base d'acide poly(méth)acrylique (ou sel de celui-ci) avec un fluide de traitement de surface qui contient à la fois un monomère polymérisable par voie radicalaire et un agent de réticulation organique, pour former ainsi un mélange, et (b) une étape de réaction consistant à soumettre le mélange à une polymérisation de réticulation superficielle. La quantité de fluide de traitement de surface est d'au plus 50 parties en poids pour 100 parties en poids de résine absorbant l'eau ; le fluide de traitement de surface contient un auxiliaire de mélange si nécessaire ; et l'agent de réticulation organique est un composé organique ayant de multiples groupes fonctionnels choisis parmi des groupes fonctionnels réagissant avec des groupes (méth)acrylate et des groupes fonctionnels réagissant avec des groupes carboxyle et ayant un poids moléculaire inférieur à 200.
PCT/JP2014/056801 2013-04-05 2014-03-13 Procédé de production d'un matériau absorbant l'eau, et matériau absorbant l'eau WO2014162843A1 (fr)

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JP2013-079558 2013-04-05
JP2013079558A JP2016112474A (ja) 2013-04-05 2013-04-05 吸水剤の製造方法
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Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2016104472A (ja) * 2014-12-01 2016-06-09 ユニ・チャーム株式会社 生分解性吸水剤
JP6006409B2 (ja) * 2013-05-10 2016-10-12 株式会社日本触媒 ポリアクリル酸（塩）系吸水性樹脂の製造方法
JP2016216713A (ja) * 2015-05-14 2016-12-22 株式会社日本触媒 吸水性樹脂の製造方法
EP3009474B1 (fr) 2014-10-16 2017-09-13 Evonik Degussa GmbH Procédé de fabrication pour polymères solubles dans l'eau
EP3424987A4 (fr) * 2016-12-19 2019-03-20 LG Chem, Ltd. Procédé de production de polymère superabsorbant
WO2019098244A1 (fr) * 2017-11-16 2019-05-23 株式会社日本触媒 Agent d'absorption et article absorbant
WO2021132026A1 (fr) * 2019-12-23 2021-07-01 住友精化株式会社 Procédé de production de particules de résine absorbant l'eau
CN115087691A (zh) * 2020-02-14 2022-09-20 株式会社日本触媒 吸水性树脂及其制造方法
CN115768555A (zh) * 2020-07-13 2023-03-07 株式会社日本触媒 吸水剂组合物及其制造方法

Citations (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS6036516A (ja) * 1983-08-10 1985-02-25 Kao Corp 高機能性吸水性樹脂の製造方法
JPS62230813A (ja) * 1986-02-04 1987-10-09 アライド・コロイド・リミテツド 水溶性または水膨潤性ポリマ−の製法
JPS6399211A (ja) * 1986-06-04 1988-04-30 Hayashikane Zosen Kk 改質吸水性樹脂の製造方法
JPH01126314A (ja) * 1987-11-12 1989-05-18 Nippon Shokubai Kagaku Kogyo Co Ltd 改良された吸水性樹脂の製造法
JPH04130113A (ja) * 1990-09-20 1992-05-01 Mitsubishi Petrochem Co Ltd 巨大ビーズ状吸水性樹脂の製造法
JPH05320270A (ja) * 1992-05-27 1993-12-03 Nippon Kayaku Co Ltd 吸水性ポリマーの製造法
JPH09124879A (ja) * 1995-10-31 1997-05-13 Sanyo Chem Ind Ltd 改質された吸水性樹脂粒子およびその製法
JP2002201290A (ja) * 2000-09-20 2002-07-19 Nippon Shokubai Co Ltd 吸水性樹脂およびその製造方法
WO2006068067A1 (fr) * 2004-12-24 2006-06-29 Sumitomo Seika Chemicals Co., Ltd. Procédé servant à produire des particules de résine absorbant l'eau
JP2006297373A (ja) * 2005-02-15 2006-11-02 Nippon Shokubai Co Ltd 吸水剤、吸収性物品及び吸水剤の製造方法
JP2007302856A (ja) * 2006-04-10 2007-11-22 Nippon Shokubai Co Ltd 吸水性樹脂の表面処理方法
JP2008523197A (ja) * 2004-12-10 2008-07-03 株式会社日本触媒 改質された吸水性樹脂の製造方法
WO2009125849A1 (fr) * 2008-04-11 2009-10-15 株式会社日本触媒 Procédé de traitement de surface d’une résine absorbant l’eau et procédé de fabrication d’une résine absorbant l’eau
JP2011500872A (ja) * 2007-10-09 2011-01-06 株式会社日本触媒 吸水性樹脂の表面処理方法

Patent Citations (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS6036516A (ja) * 1983-08-10 1985-02-25 Kao Corp 高機能性吸水性樹脂の製造方法
JPS62230813A (ja) * 1986-02-04 1987-10-09 アライド・コロイド・リミテツド 水溶性または水膨潤性ポリマ−の製法
JPS6399211A (ja) * 1986-06-04 1988-04-30 Hayashikane Zosen Kk 改質吸水性樹脂の製造方法
JPH01126314A (ja) * 1987-11-12 1989-05-18 Nippon Shokubai Kagaku Kogyo Co Ltd 改良された吸水性樹脂の製造法
JPH04130113A (ja) * 1990-09-20 1992-05-01 Mitsubishi Petrochem Co Ltd 巨大ビーズ状吸水性樹脂の製造法
JPH05320270A (ja) * 1992-05-27 1993-12-03 Nippon Kayaku Co Ltd 吸水性ポリマーの製造法
JPH09124879A (ja) * 1995-10-31 1997-05-13 Sanyo Chem Ind Ltd 改質された吸水性樹脂粒子およびその製法
JP2002201290A (ja) * 2000-09-20 2002-07-19 Nippon Shokubai Co Ltd 吸水性樹脂およびその製造方法
JP2008523197A (ja) * 2004-12-10 2008-07-03 株式会社日本触媒 改質された吸水性樹脂の製造方法
WO2006068067A1 (fr) * 2004-12-24 2006-06-29 Sumitomo Seika Chemicals Co., Ltd. Procédé servant à produire des particules de résine absorbant l'eau
JP2006297373A (ja) * 2005-02-15 2006-11-02 Nippon Shokubai Co Ltd 吸水剤、吸収性物品及び吸水剤の製造方法
JP2007302856A (ja) * 2006-04-10 2007-11-22 Nippon Shokubai Co Ltd 吸水性樹脂の表面処理方法
JP2011500872A (ja) * 2007-10-09 2011-01-06 株式会社日本触媒 吸水性樹脂の表面処理方法
WO2009125849A1 (fr) * 2008-04-11 2009-10-15 株式会社日本触媒 Procédé de traitement de surface d’une résine absorbant l’eau et procédé de fabrication d’une résine absorbant l’eau

Cited By (18)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US10662300B2 (en) 2013-05-10 2020-05-26 Nippon Shokubai Co., Ltd. Method for producing polyacrylic acid (salt)-based water-absorbent resin
JP6006409B2 (ja) * 2013-05-10 2016-10-12 株式会社日本触媒 ポリアクリル酸（塩）系吸水性樹脂の製造方法
EP2995639A4 (fr) * 2013-05-10 2016-12-07 Nippon Catalytic Chem Ind Procédé de production de résine hygroscopique à base d'acide (sel) polyacrylique
EP3009474B1 (fr) 2014-10-16 2017-09-13 Evonik Degussa GmbH Procédé de fabrication pour polymères solubles dans l'eau
JP2016104472A (ja) * 2014-12-01 2016-06-09 ユニ・チャーム株式会社 生分解性吸水剤
US10183094B2 (en) 2014-12-01 2019-01-22 Unicharm Corporation Biodegradable water absorbent
JP2016216713A (ja) * 2015-05-14 2016-12-22 株式会社日本触媒 吸水性樹脂の製造方法
EP3424987A4 (fr) * 2016-12-19 2019-03-20 LG Chem, Ltd. Procédé de production de polymère superabsorbant
US11225556B2 (en) 2016-12-19 2022-01-18 Lg Chem, Ltd. Method for producing super absorbent polymer
JPWO2019098244A1 (ja) * 2017-11-16 2020-12-10 株式会社日本触媒 吸水剤および吸収性物品
CN111356426A (zh) * 2017-11-16 2020-06-30 株式会社日本触媒 吸水剂及吸收性物品
WO2019098244A1 (fr) * 2017-11-16 2019-05-23 株式会社日本触媒 Agent d'absorption et article absorbant
US11607667B2 (en) 2017-11-16 2023-03-21 Nippon Shokubai Co., Ltd. Absorption agent and absorbent article
WO2021132026A1 (fr) * 2019-12-23 2021-07-01 住友精化株式会社 Procédé de production de particules de résine absorbant l'eau
CN115087691A (zh) * 2020-02-14 2022-09-20 株式会社日本触媒 吸水性树脂及其制造方法
EP4105242A4 (fr) * 2020-02-14 2024-07-10 Nippon Shokubai Co., Ltd. Résine hydroabsorbante et son procédé de fabrication
US12337295B2 (en) 2020-02-14 2025-06-24 Nippon Shokubai Co., Ltd. Water-absorbing resin and manufacturing method for same
CN115768555A (zh) * 2020-07-13 2023-03-07 株式会社日本触媒 吸水剂组合物及其制造方法

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