JP2014073448A - Particulate water absorbent and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a particulate water absorbent excellent in handleability as a powder and the particulate water absorbent having high absorption performance in a wide range of salt concentrations and suitable for various applications.SOLUTION: A particulate water absorbent contains a polyacrylic acid (salt)-based water absorbing resin containing surfactant as a main constituent, and the surfactant is a reactive surfactant containing functional groups other than hydroxyl groups, which may react with a carboxyl group and a surface tension of the absorbent is 55 to 73 mN/m and a 20 mass% saline vertical absorption index is 1.5 to 10.0 [g/g].

Description

  The present invention is not limited to sanitary materials, and is preferably used for various applications such as a civil engineering / architectural waterproofing material, a water retention material for warmers, a waterproofing material for cables, etc., particularly for sheet-like or tape-like applications. The present invention relates to a particulate water absorbing agent and a method for producing the same.

  Conventionally, water-absorbing resin has been used for materials such as paper diapers, sanitary napkins, incontinence pads, and other materials intended to prevent water leakage from the ground in tunnel construction and to prevent seawater from entering the sheath due to deterioration of the sheath of the submarine cable. It is widely used as a water-absorbing agent for materials that absorb body fluid such as blood.

  In these fields, water-absorbing resins have been proposed to be used in many forms such as powder, gel, sheet, film, and fiber. Powdered water-absorbing resins are often used as particulate water-absorbing agents. Has been. The particulate water-absorbing agent is used in various forms such as a greening water retaining material, a waste liquid solidifying material, a cement water reducing material, an aromatic gel, an interior gel, a hygroscopic material, and a sandbag as it is. On the other hand, sanitary materials such as paper diapers and sanitary napkins, water-stopping tapes, disposable warmers, etc., are combined with other base materials (for example, pulp and non-woven fabric) or fixed to form a tape, It is used after being processed into a sheet or the like.

  In recent years, with the increase in the amount of water-absorbing resin used, the rate at which the water-absorbing resin is processed into a tape or sheet (production per unit time) tends to increase dramatically. In addition to the water absorption performance (for example, water absorption capacity under no pressure, water absorption capacity under pressure, water absorption speed, liquid permeability, etc.) required for absorbent resins, it relates to the handleability of powder in the process of manufacturing absorbent articles. Improvement in performance (powder fluidity during drying and moisture absorption) is also very important.

Therefore, techniques for adding water-insoluble inorganic compounds such as amorphous silicon dioxide and kaolin to the water-absorbent resin in order to improve the powder fluidity of the water-absorbent resin are disclosed (Patent Documents 1 to 4). . However, these techniques have a problem of reducing the water absorption performance of the water-absorbing agent under pressure (for example, absorption at a load of 20 to 50 [g / cm ² ] in 0.9% by mass saline). Moreover, in order to improve powder flowability (Anti-Caking performance), the technique (patent documents 5-19) which coat | covers polysiloxane, a metal soap, specific surfactant, etc. on the water-absorbent resin surface is also proposed, In particular, the metal soap described in Patent Document 9 is in the form of particles that maintain powder flowability and water absorption performance under pressure (for example, absorption at a load of 20 to 50 [g / cm ² ] in 0.9% by mass saline). It is known that water-absorbing agents can be provided. In addition to Patent Documents 5, 16, and 17, techniques for adding polysiloxane and silicone-based surfactants to water-absorbing resins are also known in Patent Documents 18 and 19.

  Conventionally, as a basic performance of a water-absorbent resin, it is desired that the water absorption capacity under pressure is high, and many parameter patents that define the water absorption capacity under pressure have been proposed. In measuring the water absorption capacity under pressure, the main use of the water-absorbent resin was paper diapers, and physiological saline (for example, about 0.9 mass% saline) and artificial urine of various compositions were used as the liquid to be absorbed. It is used. And the water absorption magnification is mainly evaluated, and the basis weight (the amount of water-absorbing resin per unit area at the time of measurement) is also mainly evaluated by the basis weight of about a paper diaper. The measuring method of these water-absorbing resins is also defined by JIS (Japanese Industrial Standards) and EDANA (to be described later) (Non-Patent Documents 1 to 5), and the evaluation with physiological saline is also central.

  Furthermore, many parameters whose absorption behavior is defined by artificial urine or physiological saline are also known. For example, Patent Document 20 is excellent in water absorption capacity under pressure, residual monomer, water-soluble component, and pore diameter of foaming. A water absorbent resin is disclosed.

  Patent Document 21 discloses an excellent water-absorbent resin having an absorption index under pressure (PAI) and a water-soluble content of 16% by mass or less. Patent Document 22 discloses a water-absorbing resin having a water-soluble component of 1% by mass or less per minute and having a high water absorption ratio under pressure and a high absorption efficiency of the upper and lower gel layers. Patent Document 23 discloses a water-absorbing resin that is excellent in water absorption capacity and vertical absorption capacity under pressure and has a soluble content of 4% by mass or less. Patent Document 24 discloses a water-absorbing resin excellent in water absorption capacity without pressure, water absorption capacity under pressure, swelling pressure after 20 minutes, water-soluble content (3.5 to 10% by mass), and maximum rewet amount. ing.

  In Patent Document 25, a diffusion absorption index indicating a maximum absorption amount per unit time is obtained by measuring the mass of physiological saline absorbed by the absorbent composition over 60 minutes with time. The absorbent composition which is 5 [g / g / min] or more is disclosed. Patent Document 26 discloses a water-absorbing agent having a diffusion absorption capacity of 25 [g / g] or more after 60 minutes from the start of absorption, and having a water-soluble content of more than 0 and 7% by mass or less. . Patent Document 27 discloses a water-absorbing resin excellent in three of absorption capacity, gel strength, water-soluble content, and water absorption speed. Patent Document 28 discloses a water-absorbent resin having a low water-soluble content having a water absorption capacity of 20 [g / g] or more under pressure, which is obtained by polymerizing unneutralized acrylic acid and then neutralizing. .

Patent Document 29 discloses a water-absorbent resin having a transport value (TW) of at least 15000 cm ³ s or the like. Patent Document 30 discloses a water-absorbent resin that defines vertical absorption of at least 12 [g / g]. Patent Document 31 discloses a water absorbent resin having a CAUL (Column Absorbency Under Load) of about 10 [g / g] or more.

  In Patent Document 11, a ratio between a time (t1) until the swelling volume reaches 5 ml and a time (t2) until the swelling volume reaches 40 ml by mixing a hydrophobic substance into the monomer or gel ( An absorptive resin in which t2 / t1) is 5 to 20 is disclosed.

  However, although these non-patent documents 1 to 5 and patent documents 11, 20 to 31, etc., a lot of water absorption performance is defined by parameters, in particular, although the water absorption capacity under pressure in physiological saline or artificial urine has been proposed. However, a water-absorbent resin that is a particulate water-absorbing agent that is excellent in powder flowability and processed into a tape-like or sheet-like shape does not exhibit sufficient physical properties in actual use.

  Furthermore, the present inventors have found the importance of the 20 mass% saline vertical absorption index and the moisture absorption blocking rate as an application of a new idea as an unpublished prior application at the time of filing this application, and Patent Document 32 (PCT / JP2012 / 058515). Filed. At present, further improvements are demanded in these patent documents 1-31 and unpublished prior patent document 32.

JP 59-80459 A JP 2000-093792 A JP 2001-137704 A International Publication No. 2000/010619 Pamphlet International Publication No. 95/033558 Pamphlet Japanese Patent Laid-Open No. 2003-082250 International Publication No. 2002/034384 Pamphlet WO97 / 37695 pamphlet European Patent Publication No. 1592750 JP-A-61-58658 International Publication No. 2010/073658 Pamphlet JP 2010-0665107 A JP-A-6-220227 JP-A-8-027278 International Publication No. 2005/077500 Pamphlet JP-A-9-136966 JP 2004-99803 A US Pat. No. 6,395,830 JP 2004-966803 A US Pat. No. 5,985,944 US Pat. No. 5,601,542 US Pat. No. 6,127,454 US Pat. No. 6,602,950 US Pat. No. 6,060,557 US Pat. No. 5,797,893 US Patent No. 5760080 US Pat. No. 4,666,975 US Pat. No. 6,187,872 US Pat. No. 7,759,422 US Pat. No. 6,297,335 U.S. Pat. No. 7,838,721 PCT / JP2012 / 058515

Japanese Industrial Standard (JIS) K7223-1996 Japanese Industrial Standard (JIS) K7224-1996 ERT441.2-02 (2002) ERT442.2-02 (2002) ERT470.2-02 (2002)

  The problem to be solved by the present invention is to provide a particulate water-absorbing agent that is excellent in handling with powder, and has high absorption performance in a wide range of salt concentrations, and can be used for many purposes. And providing a particulate water-absorbing agent. Furthermore, it is to further improve the unpublished prior patent document 32 (PCT / JP2012 / 058515).

The inventors of the present invention who have studied such problems are particulate water-absorbing agents excellent in powder flowability, and as a result of examining to obtain a particulate water-absorbing agent excellent in actual use in the form of a sheet or tape, The metal soap described in Patent Document 9 provides a particulate water-absorbing agent that maintains fluidity and water absorption performance under pressure (for example, absorption at a load of 20 to 50 [g / cm ² ] in 0.9% by mass saline). Despite being able to do so, these technologies have also found the problem of reducing the water absorption performance, especially the absorption performance at the high salt concentration required for civil engineering / building waterproofing materials, cable waterproofing materials, etc. .

And in the said nonpatent literatures 1-5, the said patent documents 1-32, etc., the water absorption resin conventionally evaluated by 0.9 mass% salt solution or artificial urine, and the water absorption capacity | capacitance under pressure are according to paper diapers. With respect to the water absorbent resin that has been evaluated by the basis weight (the amount of the water absorbent resin per unit area), Patent Documents 5 to 15 improve the powder fluidity and maintain the water absorption performance, in particular, the metal soap described in Patent Document 9 A particulate water-absorbing agent that maintains fluidity and water-absorbing performance under pressure (for example, absorption at a load of 20 to 50 [g / cm ² ] in 0.9% by mass saline solution) has been proposed.

  However, in the related art including Patent Documents 1 to 32, the water absorption ratio in ultra-high-concentration salt water (particularly 20% by mass saline solution) that has not been noticed at all is extremely low, and ultra-high basis weight ( The fact that the water absorption capacity under pressure at a basis weight of about 6.2 times the basis weight (to be described later), etc., was also found to be extremely reduced. And in addition to powder flowability, the absorption capacity under pressure in ultra-high concentration salt water (especially 20% by mass saline) and ultra high basis weight, which has not been noticed in the past, is actually in the form of a sheet or tape. I found it important to use.

  Moreover, although it is also known from Patent Documents 1 to 4 and Patent Document 9 that the anti-moisture blocking rate (anti-caking performance) is important, the present inventors have a low hygroscopic blocking rate (high Anti-blocking rate after production). It has been found that even with a water-absorbing resin having a -Caking performance, the moisture absorption blocking rate increases during actual use. And in the evaluation of the conventional moisture absorption blocking rate, it does not show a sufficient effect at the time of actual use, and the cause thereof is peeling of various Anti-Caking agents by transporting the water absorbent resin powder (for example, various transport machines such as pneumatic transport). And the moisture absorption blocking rate was found to increase. And it replaced with the conventional evaluation of the moisture absorption blocking rate, and discovered that the moisture absorption blocking rate after the impact test (modeled on conveyance) was important for actual use. Further, the use of an anti-caking agent such as silica has the problem of lowering the water absorption characteristics (particularly the water absorption capacity under pressure) of the water absorbent resin in addition to the problem of cost and dust.

  Furthermore, there are those that reduce the surface tension of the water-absorbing agent in the prior art, including the use of various surfactants such as Patent Document 8 and other unpublished prior application Patent Document 32 (PCT / JP2012 / 058515). As an adverse effect, it was found that the amount of reversion in the absorbent article was increased.

  In order to solve the above-mentioned problems, attention has been paid to surface tension in unpublished prior patent application 32 (PCT / JP2012 / 058515), etc., and as a result of intensive studies by the present inventors, the “particulate water absorbing agent” in the present invention According to the first embodiment, the particulate water-absorbing agent includes a reactive surfactant containing a functional group other than a hydroxyl group capable of reacting with a carboxyl group, and has a specific surface tension and 20% by mass normal saline absorption. It has been found that by controlling the index within a specific range, it becomes a water-absorbing agent excellent in actual use in the form of a sheet or tape, and the above-mentioned problems can be solved. And the said subject was solved by using the reactive surfactant of a specific structure further for specific water absorbing resin.

  That is, the particulate water-absorbing agent of the present invention is a particulate water-absorbing agent mainly comprising a polyacrylic acid (salt) -based water-absorbing resin containing a surfactant, and the surfactant can react with a carboxyl group. A reactive surfactant containing a functional group other than the above, the surface tension of the water-absorbing agent is 55 to 73 mN / m, and the 20% by mass saline vertical absorption index is 1.5 to 10.0 [g / g]. Provide a water-absorbing agent. However, the surface tension is defined by the surface tension of the water-absorbing agent dispersion in physiological saline. The vertical absorption index is an absorption ratio with respect to 20% by mass of 1.0 g of a water absorbing agent having an inner diameter of 25.4 mm under pressure of 2.06 kPa.

  Such a water-absorbing agent of the present invention can be obtained by taking the following production methods (first method to third method) as an example.

  That is, the manufacturing method (first manufacturing method) of the particulate water-absorbing agent mainly composed of the polyacrylic acid (salt) -based water-absorbing resin of the present invention is based on the water-absorbing resin at the time of surface crosslinking or after surface crosslinking. The present invention also provides a method for producing a particulate water-absorbing agent, comprising a step of adding a reactive surfactant containing a functional group other than a hydroxyl group capable of reacting with a carboxyl group. The preferred HLB of the reactive surfactant is 7-12.

  That is, the manufacturing method (second manufacturing method) of the particulate water-absorbing agent mainly composed of the polyacrylic acid (salt) -based water-absorbing resin of the present invention has a water absorption capacity of 20 (g / g) or higher in absorption capacity under pressure. A method for producing a particulate water-absorbing agent, comprising a step of adding a reactive surfactant having 7 to 12 HLB containing a functional group other than a hydroxyl group capable of reacting with a carboxyl group with respect to a reactive resin. provide.

  Moreover, the manufacturing method (3rd method) of the particulate water-absorbing agent which has a polyacrylic acid (salt) type water-absorbing resin as a main component has 7-12 HLB containing functional groups other than the hydroxyl group which can react with a carboxyl group. A step of adding a reactive surfactant, a surface cross-linking step until the absorption capacity under pressure is 20 (g / g) or more at the same time as or before or after the addition step. A method for producing a water-absorbing agent is provided.

  (1) In order to maintain the surface tension of the water-absorbing agent at 55 to 73 mN / m, the reactive surfactant is preferably a compound having an amino group and / or an epoxy group as a functional group. A compound having one or more functional groups is preferred, and the reactive surfactant is more preferably a polymer compound.

  More preferably, the reactive surfactant contains an amino group as a functional group, and the neutralization rate of the water absorbent resin is 69 mol% or less.

  The content of the reactive surfactant is preferably 0.0001 to 2.0% by mass, more preferably 0.001 to 0.2% by mass with respect to the polyacrylic acid (salt) water-absorbing resin. is there. And it is more preferable to heat-process after mixing the said reactive surfactant and polyacrylic acid (salt) type water absorbing resin.

(2) In order to control the saline vertical absorption index to be high, a reactive surfactant having an HLB of 7 to 12 is suitable. As the structure of the reactive surfactant,
Preferably, it has polyoxyalkylene units,
More preferably, it further has a polysiloxane structure,
More preferably, it further has a functional group other than a hydroxyl group capable of reacting with a carboxyl group and a hydrophilic or hydrophobic functional group other than a functional group other than a hydroxyl group capable of reacting with the carboxyl group.

Moreover, the viscosity of the reactive surfactant is preferably 10 to 20000 mm ² / s (25 ° C.).

(3) In order to control the saline vertical absorption index to be high,
Preferably, it is surface cross-linked
More preferably, the surface cross-linking is made with a cross-linking agent or monomer other than the reactive surfactant,
More preferably, the surface cross-linking agent is a polyhydric alcohol or a derivative thereof (alkylene carbonate, oxazolidinone), and the obtained water-absorbing agent further contains a polyhydric alcohol in addition to the reactive surfactant.

  Further, the water absorption capacity (AAP) under pressure of 4.83 kPa is preferably 20 g / g or more and / or the water absorption capacity (AAP) under pressure of 2.06 kPa is preferably 25 g / g or more.

  The mass average particle diameter (D50) of the water absorbent resin or water absorbent is 250 to 450 μm, the content of particles having a particle diameter of less than 150 μm is 0 to 5 mass%, and the logarithmic standard deviation (σζ) is 0 to 0.45. Is preferable.

(4) For high urine resistance and coloring prevention,
Preferably, the water absorbing agent further contains a chelating agent in addition to the reactive surfactant,
More preferably, the content of the chelating agent is 0.001 to 5.0 mass% with respect to the polyacrylic acid (salt) water-absorbing resin,
More preferably, the chelating agent is a water-soluble organic compound having a nitrogen atom and / or a phosphorus atom and / or an α-hydroxycarboxylic acid (salt).

(5) Physical properties of water-absorbing agent for actual use in diapers
Preferably, the amount of increase in degradation soluble content in the degradation acceleration test is 0 to 15% by mass,
More preferably, the water content is 1 to 20% by mass,
More preferably, the powdering rate in the impact test is 1.0% by mass or less.

  According to the particulate water-absorbing agent and its production method defined in the present invention, the vertical absorption index and the absorption capacity under pressure are high, and powder flowability (Anti-) is an important factor when processing into an absorbent article. Since the particulate water-absorbing agent excellent in (Caking performance) can be provided, trouble during processing is reduced, and as a result, the productivity of the absorbent article can be improved. Furthermore, it is possible to produce and provide an absorbent article that is versatile and excellent in absorption performance. Not only has high anti-caking performance and absorption capacity under pressure, but also has an advantage that the return amount (Re-Wet) in the diaper is small due to high surface tension.

  That is, an extremely excellent particulate water-absorbing agent capable of simultaneously improving the conflicting performances of “powder handling (powder fluidity during drying and moisture absorption)” and “absorption performance” and a method for producing the same. Can be provided.

  By using the particulate water-absorbing agent obtained in the present invention for an absorbent article, it is possible to provide an absorbent article that is versatile and excellent in absorbent performance while maintaining high productivity.

FIG. 1 is a side view schematically showing an apparatus for measuring water absorption under pressure and a 20 mass% saline vertical absorption index.

  Hereinafter, the particulate water-absorbing agent and the production method thereof according to the present invention will be described in detail. However, the scope of the present invention is not limited to these descriptions, and other than the following examples, the scope of the present invention can be changed and implemented as appropriate without departing from the spirit of the present invention.

  Specifically, the present invention is not limited to the following embodiments, and various modifications can be made within the scope shown in the claims, and obtained by appropriately combining technical means disclosed in different embodiments. Embodiments to be made are also included in the technical scope of the present invention.

[1] Definition of terms (1-1) "Water absorbent resin"
The “water-absorbing resin” in the present invention means a water-swellable water-insoluble polymer gelling agent. “Water swellability” means that the CRC (water absorption capacity under no pressure) specified by ERT442.2-02 is 5 [g / g] or more, and “water insolubility” means ERT470.2. Extr. (Water-soluble component) is 0 to 50% by mass.

  The water-absorbent resin can be appropriately designed according to its use and is not particularly limited, but may be a hydrophilic cross-linked polymer obtained by cross-linking an unsaturated monomer having a carboxyl group. preferable. The total amount (100% by mass) is not limited to a form of a polymer, and may be a composition containing a surface-crosslinked polymer, an additive and the like within a range in which the above performance is maintained. In the present invention, the hydrophilic cross-linked polymer is a water-absorbent resin that is pulverized into a powder form. The water-absorbent resin before surface treatment or surface cross-linking is referred to as “water-absorbent resin powder” or “water-absorbent resin precursor”. The water-absorbent resin after surface treatment or surface cross-linking is referred to as “water-absorbent resin particles”. Furthermore, in the present invention, even if the water-absorbent resin is different in shape obtained in each step (for example, a sheet shape, a fiber shape, a film shape, a gel shape, etc.), the water absorption containing additives Even a water-soluble resin composition is collectively referred to as a “water-absorbing resin”.

(1-2) “Particulate water-absorbing agent”
The “particulate water-absorbing agent” in the present invention refers to an aqueous liquid gelling agent mainly composed of a water-absorbing resin (particularly polyacrylic acid (salt) -based water-absorbing resin). In particular, in the present invention, in addition to the water-absorbent resin, a reactive surfactant (or a surfactant having an amino group) described later and optionally water (1 to 20% by mass, more preferably described in (3-4) Range).

  In addition, the content of the water-absorbing resin contained in the particulate water-absorbing agent according to the present invention is preferably 60 to 99% by mass, more preferably 75 to 99% by mass with respect to the whole particulate water-absorbing agent. More preferably, it is 80-99 mass%. The aqueous liquid is not limited to water, but may be urine, blood, feces, waste liquid, moisture or steam, ice, a mixture of water and organic solvent and / or inorganic solvent, rain water, ground water, sea water, salt water, etc. The water is not particularly limited.

(1-3) “Particles”
The “particle” in the present invention refers to a powder having fluidity, preferably a powder in a state where PSD (particle size distribution by sieving classification) defined by ERT420.2-02 can be measured (preferably The range of the particle size will be described later in (3-3)). Therefore, the “water-absorbent resin powder” and the like described in (1-1) above are “particles” in light of this definition, but in the present invention, different expressions are adopted to distinguish the presence or absence of surface crosslinking.

(1-4) “Polyacrylic acid (salt)”
The “polyacrylic acid (salt)” in the present invention optionally includes a graft component, and a repeating unit of acrylic acid and / or a salt thereof (hereinafter referred to as acrylic acid (salt)) as a main component. Means a polymer.

  Specifically, among the total monomers (excluding the internal crosslinking agent) used for polymerization, acrylic acid (salt) is essentially 50 to 100 mol%, preferably 70 to 100 mol%, more preferably 90 to 90 mol%. A polymer containing 100 mol%, particularly preferably substantially 100 mol%. Alternatively, polyacrylic acid (salt) may be obtained from a saponified product such as polyacrylonitrile or polyacrylamide. Moreover, when using a polyacrylate as a polymer, a water-soluble salt is essential, a monovalent salt is preferable as a main component of the neutralized salt, an alkali metal salt or an ammonium salt is more preferable, and an alkali metal salt is further included. Sodium salts are preferred, especially.

(1-5) “EDANA” and “ERT”
“EDANA” is an abbreviation for European Disposables and Nonwovens Associations, and “ERT” is an abbreviation for a method for measuring water-absorbent resin (EDANA Recommended Test Methods), which is a European standard (substantially world standard). is there. In the present invention, unless otherwise specified, the measurement is performed according to the ERT original (known document: revised in 2002).

(A) "CRC" (ERT441.2-02)
“CRC” is an abbreviation for Centrifugation Retention Capacity (centrifuge retention capacity) and means water absorption capacity without pressure (hereinafter also referred to as “water absorption capacity”). Specifically, 0.200 g of the water-absorbent resin in the non-woven bag was freely swollen in a large excess of 0.9 mass% sodium chloride aqueous solution for 30 minutes and then drained with a centrifuge. Magnification (unit: [g / g]).

(B) “AAP” (ERT442.2-02)
“AAP” is an abbreviation for Absorption Against Pressure, which means water absorption capacity under pressure. Specifically, 0.900 g of the water-absorbent resin was swollen under a load of 2.06 kPa (0.3 psi, 21 [g / cm ² ]) for 1 hour with respect to a 0.9 mass% sodium chloride aqueous solution. It is the water absorption magnification (unit; [g / g]). In ERT442.2-02, it is written as Absorption Under Pressure, but it has substantially the same content.

(C) “PSD” (ERT420.2-02)
“PSD” is an abbreviation for Particle Size Distribution, and means a particle size distribution measured by sieving classification. The mass average particle size (D50) and the particle size distribution width are measured by the same method as “(1) Average Particle Diameter and Distribution of Particle Diameter” described in European Patent No. 1594556.

(1-6) “Surface treatment” and “surface crosslinking”
“Surface treatment” in the present invention is a superordinate concept including surface cross-linking, and is a treatment for adding / mixing additives to the surface of water-absorbent resin powder (water-absorbent resin precursor, base polymer), coating treatment, and unsaturated. The process which forms a core-shell structure by superposing | polymerizing a monomer etc. and the process which bridge | crosslinks the surface of a water absorbing resin powder with a surface crosslinking agent are said.

  For example, an additive such as inorganic fine particles or a surfactant is added to and mixed with the water-absorbent resin powder, and the surface is subjected to a process of adsorbing the additive (physical bonding) or a coating, That is, radical crosslinking by a polymerization initiator when polymerizing an unsaturated monomer on the surface of the water absorbent resin powder, or physical crosslinking of the surface of the water absorbent resin by polymerization of the unsaturated monomer on the surface (polymer chains ), And performing covalent bond crosslinking or ionic bond crosslinking with a surface crosslinking agent is referred to as “surface treatment”.

  In the present invention, “surface crosslinking” refers to the surface treatment of the water-absorbent resin powder by the covalent crosslinking or ionic bonding crosslinking by the surface crosslinking agent, the irradiation of active energy rays, the radical polymerization initiator, etc. Is a cross-linking of polymer chains constituting the.

(1-7) Others In this specification, “X to Y” indicating a range means “X or more and Y or less”. Further, “t (ton)” as a unit of mass means “Metric ton”, and unless otherwise noted, “ppm” means “mass ppm” or “mass ppm”. "Means. In the present specification, “mass” and “weight”, “mass%” and “wt%”, and “part by mass” and “part by weight” are synonymous, and there is no particular limitation on the measurement of physical properties and the like. When there is not, it measures at room temperature (20-25 degreeC) / relative humidity 40-50%. Further, “˜acid (salt)” means “˜acid and / or salt thereof”, and “(meth) acryl” means “acryl and / or methacryl”.

[2] Manufacturing method of particulate water-absorbing agent The manufacturing method of the particulate water-absorbing agent of the present invention is a manufacturing method of a water-absorbing agent mainly composed of a polyacrylic acid (salt) -based water-absorbing resin, which is used during surface crosslinking or Provided is a method for producing a particulate water-absorbing agent, comprising a step of adding a reactive surfactant containing a functional group other than a hydroxyl group capable of reacting with a carboxyl group to a water-absorbing agent after surface crosslinking. .

  Although the manufacturing method of unpublished prior application Patent Document 32 (PCT / JP2012 / 058515) is cited as necessary, the description cited in Patent Document 32 is used as it is.

  Hereinafter, (2-1) a step of polymerizing an aqueous monomer solution containing acrylic acid (salt) as a main component and (2-2) a step of adding a surfactant will be described in order.

(2-1) Step of polymerizing monomer aqueous solution mainly composed of acrylic acid (salt) (2-1-1) Polymerization step (Unsaturated monomer)
In the present invention, one or more of polyacrylic acid (salt) -based crosslinked polymers (mixture) is used as a water-absorbing resin in order to solve the problems (objective physical properties), and acrylic acid (salt) is used as a monomer. ) Is preferably used as a main component, but monomers such as acrylamide and acrylonitrile that generate polyacrylic acid by hydrolysis after polymerization may be used, and monomers other than acrylic acid (salt) (hereinafter, (Referred to as “other monomers”) may be used as a copolymerization component. In addition, the polyacrylic acid (salt) water-absorbing resin may be a single product, or a plurality of water-absorbing resins having different neutralization rates, particle sizes, and crosslinking densities may be mixed, and if necessary, polyacrylic acid (salt) water-absorbing resin A water-absorbing resin other than the resin, for example, a polyamine cross-linked water-absorbing resin may be used in combination.

  The polyacrylic acid (salt) -based crosslinked polymer optionally contains a graft component, and may preferably contain 0 to 50% by mass, more preferably 0 to 40% by mass. Even if it is a coalescence, it is generically called a polyacrylic acid (salt) -based crosslinked polymer (polyacrylic acid (salt) -based water-absorbing resin).

  Although it does not specifically limit as said other monomer, For example, the water-soluble or hydrophobic unsaturated monomer of prior application patent document 32 can be mentioned.

  Moreover, the usage-amount of said other monomer is 0-50 mol% with respect to the total number of moles of the whole unsaturated monomer similarly to patent document 32, and 0-30 mol% is more preferable. 0 to 10 mol% is more preferable, and 0 to 5 mol% is particularly preferable. In other words, the usage amount of acrylic acid (salt) as the main component is preferably 50 to 100 mol%, more preferably 70 to 100 mol%, based on the total number of moles of the unsaturated monomers. ~ 100 mol% is more preferable, and 95-100 mol% is most preferable, but from the viewpoint of the water absorption performance (CRC, AAP, etc.) of the obtained water-absorbent resin and particulate water-absorbing agent, 100 mol% is substantially most preferable. .

  In addition, when using a monomer having an acid group as an unsaturated monomer (including the above-mentioned other monomers), as a salt of the unsaturated monomer, an alkali metal salt, an alkaline earth metal salt, An ammonium salt may be used. Among these salts, monovalent salts are preferable from the viewpoint of the water-absorbing performance (CRC, AAP, etc.) of the water-absorbing resin and particulate water-absorbing agent obtained, industrial availability of unsaturated monomer salts, safety, etc. In particular, it is preferable to use monovalent metal salts, especially sodium salts or potassium salts.

  Moreover, when using acrylic acid (salt) as an unsaturated monomer, the ratio of acrylic acid and acrylate is 0-50 mol% of acrylic acid and 100-50 mol% of acrylate (however, the total of both) Is preferably 100 mol% or less), more preferably 10 to 40 mol% of acrylic acid and 90 to 60 mol% of acrylate. That is, the “neutralization rate”, which is the molar ratio of acrylate to the total amount of acrylic acid and acrylate, is preferably 50 to 100 mol%, and more preferably 60 to 90 mol%. Furthermore, it is the range of 50-80 mol% and 55-69 mol%.

  To form the acrylate, neutralize acrylic acid in the monomer state before polymerization, neutralize in the polymer state during or after polymerization, or use these operations in combination. Is mentioned. Moreover, you may form acrylic acid (salt) by mixing acrylic acid and acrylate.

(Internal crosslinking agent)
If the water-absorbent resin in the present invention has “water swellability” and “water insolubility” defined in the above (1-1), a crosslinked structure (surface crosslinking (secondary crosslinking) described later) is provided therein. Is considered to have internal cross-linking. Therefore, although it can be obtained by self-crosslinking of an unsaturated monomer, a water absorbent resin obtained by copolymerization or reaction of an unsaturated monomer and an internal crosslinking agent is preferable. Examples of the internal cross-linking agent include compounds having two or more polymerizable unsaturated groups or two or more reactive groups in one molecule.

  Although it does not specifically limit as said internal crosslinking agent, For example, N, N'-methylenebis (meth) acrylamide, (poly) ethylene glycol di (meth) acrylate, (poly) propylene glycol di (meth) acrylate, trimethylolpropane Tri (meth) acrylate, glycerin tri (meth) acrylate, glycerin acrylate methacrylate, ethylene oxide modified trimethylolpropane tri (meth) acrylate, pentaerythritol hexa (meth) acrylate, triallyl cyanurate, triallyl isocyanurate, triallyl phosphate , Triallylamine, poly (meth) allyloxyalkane, (poly) ethylene glycol diglycidyl ether, glycerol diglycidyl ether, ethylene glycol Polyethylene glycol, propylene glycol, glycerol, pentaerythritol, ethylenediamine, ethylene carbonate, propylene carbonate, polyethylenimine, and glycidyl (meth) acrylate. These internal crosslinking agents may be used alone or in combination of two or more. In consideration of the water absorption performance of the water-absorbing resin and particulate water-absorbing agent obtained, it is preferable to use an internal cross-linking agent having two or more polymerizable unsaturated groups during the polymerization. The internal cross-linking agent may be added all at once to the reaction system, or may be added separately. Moreover, what is necessary is just to add to the reaction system before superposition | polymerization of an unsaturated monomer, after superposition | polymerization, after superposition | polymerization, or after neutralization.

  The amount of the internal cross-linking agent used is appropriately determined according to the desired 1-hour soluble content, water absorption capacity (CRC), etc., but the monomer excluding the internal cross-linking agent (unsaturated monomer as a whole) Is preferably 0.001 to 2 mol%, more preferably 0.005 to 0.5 mol%, still more preferably 0.01 to 0.2 mol%, and 0.03 to 0.15 mol%. Particularly preferred. When the amount used is less than 0.001 mol% or exceeds 2 mol%, the water absorbing performance of the water-absorbing resin and particulate water-absorbing agent obtained cannot be sufficiently obtained, which is not preferable.

(Polymerization initiator)
The polymerization initiator used in the polymerization step of the present invention is appropriately selected depending on the polymerization form and is not particularly limited, and examples thereof include a photodegradable polymerization initiator, a thermal decomposition polymerization initiator, and a redox polymerization initiator. It is done.

  Examples of the photodegradable polymerization initiator include benzoin derivatives, benzyl derivatives, acetophenone derivatives, benzophenone derivatives, azo compounds, and the like. Examples of the thermal decomposition polymerization initiator include persulfates such as sodium persulfate, potassium persulfate, and ammonium 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, and the like. Furthermore, examples of the redox polymerization initiator 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. Moreover, combined use with the said photodegradable polymerization initiator and a thermal decomposition type polymerization initiator is also mentioned as a preferable form.

  The amount of these polymerization initiators used is preferably 0.001 to 2 mol% and more preferably 0.01 to 0.1 mol% with respect to the monomer. When the amount used exceeds 2 mol%, it is difficult to control the polymerization, and when the amount used is less than 0.001 mol%, the amount of residual monomer increases, which is not preferable.

(Polymerization method)
The polymerization method of the unsaturated monomer in the present invention is not particularly limited, and can be carried out by bulk polymerization or precipitation polymerization which is substantially solvent-free, but the obtained water-absorbing resin and particulate water-absorbing agent can be used. From the viewpoint of water absorption performance, further water absorption performance of the hydrogel crosslinked polymer, other ease of polymerization control, etc., a polymerization method in which an unsaturated monomer is used as an aqueous solution, particularly spray polymerization, droplet polymerization, aqueous solution Polymerization and reverse phase suspension polymerization are preferably employed. In addition, the unsaturated monomer mentioned above shall contain another monomer and an internal crosslinking agent.

  When the unsaturated monomer is an aqueous solution, the monomer concentration in the aqueous solution is appropriately determined depending on the temperature of the aqueous solution and the type of monomer, and is not particularly limited, but is preferably 10 to 70% by mass, and 20 to 60% by mass. % Is more preferable.

  The polymerization of the unsaturated monomer is initiated by addition of the polymerization initiator, irradiation with active energy rays such as ultraviolet rays, electron beams and γ rays, or a combination thereof. The polymerization temperature may be appropriately selected according to the type of polymerization initiator and active energy ray to be used, and is not particularly limited, but is preferably 15 to 130 ° C. from the reaction start temperature to the reaction peak temperature, and 20 to 120. ° C is more preferred. If the reaction temperature is outside the above range), the amount of residual monomer in the resulting water-absorbent resin is increased, and the self-crosslinking reaction proceeds excessively, so that the water-absorbing performance of the water-absorbent resin and the particulate water-absorbing agent is decreased. Absent.

  The reverse phase suspension polymerization is a method in which an aqueous monomer solution is suspended in a hydrophobic organic solvent for polymerization. For example, U.S. Pat. Nos. 4,093,776, 4,367,323, 4,446,261, Nos. 4,683,274 and 5,244,735.

  The aqueous solution polymerization is a method of polymerizing an aqueous monomer solution without using a dispersion solvent. For example, U.S. Pat. Nos. 4,462,001, 4,873,299, 4,286,682, 4,973,632, and 4,985,518. No. 5,124,416, No. 5,250,640, No. 5,264,495, No. 5,145,906, No. 5,380808, etc., and European Patent Nos. 081636, 09555086, 0922717, etc. . It should be noted that a solvent other than water may be used in combination as necessary, and the type thereof is not particularly limited. Therefore, the water-absorbent resin of the present invention can be obtained by applying the unsaturated monomer, the polymerization initiator, and the like to the polymerization methods disclosed in the above patent documents.

(2-1-2) Fine-graining step The gel during or after polymerization is finely divided with a kneader, meat chopper, or the like as necessary for heat removal during polymerization or drying efficiency. The mass average particle diameter (D50) of the hydrogel is preferably 0.5 to 4 mm, more preferably 0.3 to 3 mm, and even more preferably 0.5 to 2 mm. The mass average particle diameter can be measured using the wet classification method described in paragraph [0091] of JP-A No. 2000-63527.

(2-1-3) Drying step The drying method in the present invention is not particularly limited as long as the desired moisture content can be obtained, and various methods can be employed. Specific examples include heat drying, hot air drying, vacuum drying, infrared drying, microwave drying, azeotropic dehydration drying with a hydrophobic organic solvent, and high humidity drying using high-temperature steam.

  As drying temperature, 60-250 degreeC is preferable, 100-220 degreeC is more preferable, 120-200 degreeC is further more preferable. The drying time may be appropriately selected within the range of 1 minute to 5 hours, preferably 10 minutes to 2 hours.

  The moisture content (% by mass) of the dried polymer after drying is determined from loss on drying (1 g of powder or particles is dried at 180 ° C. for 3 hours). Moreover, 80 mass% or more is preferable, as for resin solid content (100%-moisture content) after drying, 85-99 mass% is more preferable, and 90-98 mass% is further more preferable.

  The “moisture content” in the present invention refers to the amount of water contained in the particulate water-absorbing agent, and the weight loss when 1 g of the particulate water-absorbing agent is dried at 180 ° C. for 3 hours is based on the mass before drying. The numerical value expressed by the ratio (mass%).

(2-1-4) Grinding step, classification step When the polymerization step is reverse phase suspension polymerization, the particle size is controlled at the time of polymerization, so the pulverization step is optional. The aggregate may be crushed (operation for loosening the aggregate). Moreover, when the said polymerization process is aqueous solution polymerization, although the grinding | pulverization process after drying can also be abbreviate | omitted at the time of superposition | polymerization or the degree of gel crushing after superposition | polymerization, Preferably grinding | pulverization and classification are performed further.

  That is, the dry polymer obtained in the drying step can be used as a water absorbent resin powder as it is, but in order to obtain the particulate water absorbing agent of the present invention, it is preferable to control to a specific particle size by pulverization and classification. . The particle size control is not limited to pulverization and classification, and can be appropriately performed in each step such as fine powder collection and granulation in addition to polymerization. Hereinafter, the particle size is defined by a standard sieve (JIS Z8801-1 (2000)).

  A preferable particle size is omitted because it will be described later in (3-3), but also for improving the 20 mass% saline vertical absorption index, moisture absorption blocking rate and other physical properties described later in (3-1) and later. The mass average particle diameter (D50) of the water-absorbent resin before surface crosslinking is 250 μm to 450 μm, the content of particles having a particle diameter of less than 150 μm is 0 to 5% by mass, and the logarithmic standard deviation (σζ) is 0 to 0.45. Furthermore, it is preferable that the particle size described later in (3-3) is controlled before surface crosslinking. The classification step is preferably provided before the surface cross-linking, and if necessary, a classification step (second classification step) is preferably further provided after the surface cross-linking to control the particle size.

(2-1-5) Surface cross-linking step In the present invention, in order to control the saline vertical absorption index of the resulting water-absorbing agent to be high,
Preferably, it is surface cross-linked
More preferably, the surface crosslinking is performed with a crosslinking agent or monomer other than the reactive surfactant,
More preferably, the surface cross-linking agent is a polyhydric alcohol or a derivative thereof (preferably alkylene carbonate or oxazolidione), and the obtained water-absorbing agent further contains a polyhydric alcohol in addition to the reactive surfactant.

  Further, the water absorption capacity (AAP) under pressure of 4.83 kPa of the water-absorbing agent is preferably 12 g / g or more and / or the water absorption capacity (AAP) under pressure of 2.06 kPa is preferably 20 g / g or more.

  The mass average particle diameter (D50) of the water-absorbing resin or “water-absorbing agent” is 250 to 450 μm, the content of particles having a particle diameter of less than 150 μm is 0 to 5 mass%, and the logarithmic standard deviation (σζ) is 0 to 0.00. It is preferable that it is 45.

  The saline vertical absorption index is preferably controlled by using the above or below surface cross-linking and a reactive surfactant described later in combination.

  That is, the water-absorbent resin powder is obtained through each of the above steps, and then the surface of the water-absorbent resin powder is further subjected to crosslinking (secondary crosslinking with respect to the internal crosslinking which is primary crosslinking) to absorb water. By increasing the crosslink density near the resin surface, various physical properties of the water-absorbent resin particles and the particulate water-absorbing agent, especially the water absorption capacity under pressure (AAP) and the 20% by mass saline normal absorption index are improved. Is done. That is, the present invention preferably includes a step of further surface cross-linking the dried water-absorbent resin. The water absorbent resin in the water absorbent is preferably surface-crosslinked. A known method can be used for surface cross-linking, and it may be carried out with a cross-linking agent that reacts with a carboxyl group, and the surface is radicalized with a polymerization initiator such as persulfate that generates radicals by heat, radiation (UV) or a reducing agent. The surface may be cross-linked, or the surface may be highly cross-linked by surface polymerization by adding a polymerizable monomer or a polymerizable cross-linking agent to the surface.

  When surface crosslinking is performed in the present invention, it may be performed before or after the step of adding a reactive surfactant (preferably a surfactant having an amino group) or at the same time. A step of adding a step of adding a surfactant (preferably a surfactant having an amino group) is sequentially included.

(Surface cross-linking agent)
The surface cross-linking agent used in the present invention is not particularly limited as long as it is a surface cross-linking agent that improves the physical properties of the water-absorbing resin particles and particulate water-absorbing agent obtained, and a carboxyl group that is a functional group of the water-absorbing resin and Covalent bonds or ionic bonds, particularly surface cross-linking agents (also known as organic surface cross-linking agents) that are covalently bonded are preferable. For example, polyhydric alcohol compounds, epoxy compounds, polyvalent amine compounds, condensates of polyvalent amine compounds and haloepoxy compounds. Oxazoline compounds, monooxazolidinone compounds, dioxazolidinone compounds, polyoxazolidinone compounds, polyvalent metal salts, alkylene carbonate compounds, and the like. These surface cross-linking agents may be used alone or in combination of two or more. The surface cross-linking agent may be the same compound as the reactive surfactant or may be another compound, but preferably the reactive surfactant and another surface cross-linking agent are used simultaneously or separately. Examples of the surface cross-linking agent of the present invention for reactive surfactants, compounds having substantially no surface activity, non-polymeric compounds, compounds having functional groups other than amino groups, and non-silicone compounds .

  More specifically, organic surface crosslinking agents disclosed in US Pat. Nos. 6,228,930, 6071976, 6254990 and the like can be mentioned. That is, monoethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, monopropylene glycol, 1,3-propanediol, dipropylene glycol, 2,3,4-trimethyl-1,3-pentanediol, polypropylene Glycol, glycerin, polyglycerin, 2-butene-1,4-diol, 1,4-butanediol, 1,3-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,2-cyclohexane Polyhydric alcohol compounds such as dimethanol; Epoxy compounds such as ethylene glycol diglycidyl ether and glycidol; Ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentae Polyvalent amine compounds such as lenhexamine, polyethyleneimine and polyamide polyamine; haloepoxy compounds such as epichlorohydrin, epibromohydrin and α-methylepichlorohydrin; condensates of the polyvalent amine compounds and the haloepoxy compounds An oxazolidinone compound such as 2-oxazolidinone; an alkylene carbonate compound such as ethylene carbonate;

(Ion-binding surface cross-linking agent)
In addition to the organic surface cross-linking agent (covalent surface cross-linking agent), a polyvalent metal salt, polyamine polymer, or the like can be used as the ion-bonding surface cross-linking agent. Furthermore, liquid permeability etc. can also be improved by using an inorganic surface crosslinking agent other than the said organic surface crosslinking agent. In this case, the inorganic surface cross-linking agent to be used is preferably a divalent or higher, more preferably a trivalent or tetravalent polyvalent metal salt (organic salt or inorganic salt) or a hydroxide. Examples of the salt include International Publication Nos. 2007/121037, 2008/09843, 2008/09842, U.S. Pat. Nos. 7,157,141, 6,605,673, and 6620889, and U.S. Patent Application Publication No. 2005/0288182. No., 2005/0070671, 2007/0106013, 2006/0073969, and the like. More specifically, examples include aluminum and zirconium, and examples include aluminum lactate and aluminum sulfate. The inorganic surface cross-linking agent is used simultaneously with or separately from the organic surface cross-linking agent.

  Moreover, a liquid permeability etc. can also be improved by using a polyamine polymer, especially a polyamine polymer with a mass average molecular weight of about 5000 to 1 million simultaneously or separately with the organic surface crosslinking agent. In this case, the polyamine polymer used is, for example, US Pat. No. 7098284, International Publication Nos. 2006/082188, 2006/082189, 2006/082197, 2006/111402, and 2006. / 111403, 2006/111404, and the like.

(Amount of surface cross-linking agent used)
Among the various surface cross-linking agents described above, in order to improve the physical properties of the water-absorbent resin particles as much as possible, it is preferable to use a covalently-bonded surface cross-linking agent, and further prevent a decrease in water content during the surface treatment. Therefore, an epoxy compound, a haloepoxy compound, and an oxazolidinone compound that react at a low temperature are more preferable, and at least an epoxy compound and a haloepoxy compound are more preferable. Particularly preferably, an alkylene carbonate or a polyhydric alcohol is used in combination.

  In addition, when using a dehydration-reactive surface cross-linking agent selected from alkylene carbonate, oxazolidinone, and polyhydric alcohol, since the surface cross-linking at high temperature, particularly dehydration esterification reaction with polyacrylic acid, the water content is more significantly reduced. Become. Therefore, water is appropriately added after the surface crosslinking to adjust the water content to be described later.

  When a dehydration-reactive surface cross-linking agent is used, preferably a non-polymer compound, more preferably a water-soluble non-polymer, more preferably a non-silicone compound is used, and has 2 to 10 carbon atoms, preferably 3 carbon atoms. A cyclic or acyclic surface crosslinking agent of 8 to 8 is used, and it may be a heterocyclic structure having oxygen, nitrogen or the like in addition to a functional group such as alkylene carbonate and oxazolidinone. For example, when a polyhydric alcohol is used, a polyhydric alcohol having 2 to 10 carbon atoms is preferred, a polyhydric alcohol having 3 to 8 is more preferred, and a diol is particularly preferred.

  The amount of the surface cross-linking agent used depends on the type of surface cross-linking agent used, the combination of the water-absorbing resin powder and the surface cross-linking agent, etc. 0.001 to 10 parts by mass, and more preferably 0.01 to 5 parts by mass.

(Water and solvent and the amount used)
In the surface cross-linking treatment, it is preferable to use water together with the surface cross-linking agent. The amount of water used at this time depends on the water content of the water absorbent resin powder, but is usually preferably 0.5 to 20 parts by mass with respect to 100 parts by mass of the water absorbent resin powder. 10 parts by mass is more preferable. When mixing the surface cross-linking agent or its aqueous solution, a hydrophilic organic solvent or a third substance may be used as a mixing aid.

  Examples of the hydrophilic organic solvent (particularly water-soluble organic solvent) include lower alcohols such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, and t-butyl alcohol; Ketones such as acetone; Ethers such as dioxane, tetrahydrofuran and methoxy (poly) ethylene glycol; Amides such as ε-caprolactam and N, N-dimethylformamide; Sulphoxides such as dimethyl sulfoxide; Ethylene glycol, diethylene glycol and propylene glycol , Triethylene glycol, tetraethylene glycol, polyethylene glycol, 1,3-propanediol, dipropylene glycol, 2,2,4-trimethyl-1,3-pentanedi , Polypropylene glycol, glycerin, polyglycerin, 2-butene-1,4-diol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1 , 2-cyclohexanedimethanol, 1,2-cyclohexanol, trimethylolpropane, diethanolamine, triethanolamine, polyoxypropylene, oxyethylene-oxypropylene block copolymers, polyhydric alcohols such as pentaerythritol, sorbitol, etc. It is done.

  The polyhydric alcohol is classified as a surface crosslinking agent when it reacts with the water-absorbent resin, and is classified as a hydrophilic organic solvent when it does not react. The presence or absence of the reaction can be easily discriminated by the residual amount of polyhydric alcohol or the increased amount of ester (IR analysis or the like).

  The amount of the hydrophilic organic solvent used is preferably 10 parts by mass or less with respect to 100 parts by mass of the solid content of the water-absorbent resin powder, although it depends on the type, particle size, water content and the like of the water-absorbent resin powder. .1 to 5 parts by mass is more preferable.

(Other auxiliaries)
As other auxiliaries (third substances), inorganic acids, organic acids, polyamino acids and the like described in EP 0668080 and surfactants described later may be present.

  In order to mix the water-absorbent resin powder and the surface cross-linking agent more uniformly, non-cross-linkable water-soluble inorganic bases (preferably alkali metal salts, ammonium salts, alkali metal hydroxides, and ammonia or hydroxide thereof) Product) and non-reducing alkali metal salt pH buffer (preferably hydrogen carbonate, dihydrogen phosphate, hydrogen phosphate, etc.) are allowed to coexist when the water absorbent resin powder and the surface cross-linking agent are mixed. May be.

  Although these usage-amounts are based also on the kind of water-absorbent resin powder, a particle size, etc., 0.005-10 mass parts is preferable with respect to 100 mass parts of solid content of a water-absorbent resin powder, 0.05-5 Part by mass is more preferable.

(Physical properties after surface crosslinking)
The surface cross-linking is preferably controlled within the range of AAP, which will be described later, but when adding a reactive surfactant, the water absorption capacity under pressure (AAP) under a load of 2.06 kPa depends on the surface cross-linking step before or after the addition. 20 [g / g] or more, further 25 [g / g] or more, and / or the absorption capacity under load (AAP) under a load of 4.83 kPa is 12 [g / g] or more, Surface crosslinking is performed to [g / g] or more, and further to 20 [g / g] or more. More preferably, the absorption capacity under pressure after surface crosslinking is in the following range.

  The preferred non-pressurized water absorption capacity (CRC) after surface crosslinking is the range described later in (3-9), and the preferred pressurized water absorption capacity (AAP) after surface crosslinking is described later in (3-10). The reaction time, reaction temperature, type of surface cross-linking agent, amount of use thereof, and the like may be appropriately adjusted to such a range.

  Further, the particle size distribution before and after the surface crosslinking is preferably such that the mass average particle size (D50) is 250 to 450 μm, the content of particles having a particle size of less than 150 μm is 0 to 5% by mass, and the logarithmic standard deviation (σζ). Is 0 to 0.45, and further within the above range.

  In the present invention, in order to control the absorption index under vertical pressure, a reactive surfactant containing a functional group other than a hydroxyl group capable of reacting with a carboxyl group is added to the water-absorbent resin during surface crosslinking or after surface crosslinking. In addition, it is preferable that the absorption ratio under pressure and the particle size distribution after the surface cross-linking are also controlled as described above. A suitable surface cross-linking agent for controlling the absorption index under vertical pressure is also in the above range.

(Method for adding surface cross-linking agent)
The surface cross-linking agent can be added by various techniques. For example, when the water-absorbent resin powder is obtained by aqueous solution polymerization, the water-absorbent resin powder during or after the drying step, particularly the water-absorbent resin powder whose particle size is controlled through the above (2-1-4). On the other hand, a method of premixing the surface cross-linking agent with water and / or a hydrophilic organic solvent as needed and dropping and mixing it with the water-absorbent resin powder is preferable, and a spraying method is more preferable. The size of the droplets to be sprayed is preferably 0.1 to 300 μm, more preferably 1 to 200 μm, as a volume average droplet diameter.

  As a mixing device used when mixing the water-absorbent resin powder, the surface cross-linking agent, water or a hydrophilic organic solvent, a mixing device having a large mixing force in order to uniformly and reliably mix these compounds. An apparatus is preferred. Examples of such a mixing apparatus include a cylindrical mixer, a double wall conical mixer, a high-speed stirring mixer, a V-shaped mixer, a ribbon mixer, a screw mixer, a double-arm kneader, Pulverization type kneaders, rotary mixers, airflow type mixers, turbulizers, batch-type Redige mixers, continuous-type Redige mixers, and the like are preferably used.

(Heat treatment)
After the surface cross-linking agent (preferably an aqueous solution thereof) and the water absorbent resin powder are mixed, heat treatment is preferably performed. Conditions for performing the heat treatment are appropriately set according to the crosslinking agent. For example, in the case of an epoxy crosslinking agent such as a glycidyl ether compound or an ion-reactive crosslinking agent, the temperature of the water-absorbent resin powder or the heat used for the heat treatment. The temperature of the medium is preferably 60 to 250 ° C, more preferably 60 to 150 ° C, still more preferably 80 to 120 ° C. The heating time for the heat treatment is preferably 1 minute to 2 hours. Preferable examples of the combination of the heating temperature and the heating time include 0.1 to 1.5 hours at 180 ° C. and 0.1 to 1 hour at 100 ° C.

  In addition, when using dehydration reactive surface crosslinking agents, such as an oxazolidinone, an alkylene carbonate, a polyhydric alcohol, as a surface crosslinking agent, the temperature of the water absorbing resin powder or the temperature of the heat medium used for heat processing becomes like this. Preferably it is 100-250. ° C, more preferably 150 to 250 ° C, and still more preferably 170 to 210 ° C. When alkylene carbonate or polyhydric alcohol is used as the surface cross-linking agent and heating is performed in the temperature range, from the viewpoint of the powdering rate described later in (3-5) after surface cross-linking, preferably (3- In 4), the water content of the particulate water-absorbing agent described later is adjusted.

  Further, when the water-absorbent resin powder is obtained by reverse phase suspension polymerization, during the azeotropic dehydration after the completion of polymerization and / or after the completion of the azeotropic dehydration, for example, the water content of the hydrogel is 50% by mass or less, When the amount is preferably 40% by mass or less, more preferably 30% by mass or less (the lower limit is preferably 5% by mass or more, more preferably 10% by mass or more, and particularly preferably 15% by mass or more). The surface-crosslinked water-absorbent resin particles can be obtained by dispersing the surface cross-linking agent, preferably a glycidyl ether compound, in the hydrophobic organic solvent used in (1).

(Moisture content after surface crosslinking)
In the above-described surface cross-linking, particularly dehydration-reactive surface cross-linking agent (dehydration-reactive cross-linking agent) or high-temperature surface cross-linking (eg, 150 to 250 ° C.), the water-absorbing resin obtained has high physical properties (particularly high AAP). Most of the water in the water-absorbing resin existing after the drying step and the water added to the water-absorbing resin as a solvent for the crosslinking agent are removed. For this reason, the water content of the water-absorbent resin after the surface cross-linking reaction is usually as low as 0 to 5% by mass, further 0 to 3% by mass, and further 0 to 1% by mass. Therefore, generally high water absorption and high water content are not compatible. Therefore, in the prior art, a technique of adding water after high-temperature surface cross-linking has also been proposed. However, when water is added, adhesion between water-absorbing resin particles is expressed, and it can be stably produced in the production process. Have difficulty.

  That is, the water-absorbing resin having such a low water content has a problem of impact resistance stability (powdering after impact (increase in fine powder) and a decrease in water-absorbing performance such as AAP). A technique for adding water (also known as rehumidification) has been proposed. However, since an adhesive force is generated between the particles when water is added, if the amount of water to be added increases, the load on the mixer increases and the mixing device frequently stops, and mixing aids (eg, inorganic) With the addition of (salt), the physical properties of the water-absorbent resin (for example, the water absorption capacity under pressure) are reduced.

  In order to solve such a problem, in the production method of the present invention, a surfactant is an essential component, and preferably, water is added simultaneously with or after the addition of the compound, so that the water-absorbing resin or the particulate water-absorbing agent is added. The moisture content can be adjusted to a predetermined range (1 to 20%, more preferably 5 to 20% by mass) described later. Therefore, in the present invention, a predetermined amount of water to the surface-crosslinked water-absorbent resin having a low water content (preferably 0 to 5% by mass, more preferably 0 to 3% by mass, and still more preferably 0 to 1% by mass). Addition (rehumidification) is preferable because uniform water mixing can be performed, and the deterioration of physical properties after surface cross-linking (derived from rehumidification) is substantially small. The addition of water at the same time as the addition of the compound refers to the addition of the compound powder and water to the water-absorbent resin at the same time as well as addition in the form of an aqueous dispersion or an aqueous solution.

(2-2) Reactive surfactant addition step (2-2-1) Water-absorbing agent of the present invention and production method thereof In the production method of the present invention, for the water-absorbent resin simultaneously with surface crosslinking or after surface crosslinking. And a step of adding a reactive surfactant. That is, the manufacturing method of the water absorbing agent of the present invention provides the following three methods (1) to (3).

A method for producing a particulate water-absorbing agent comprising a polyacrylic acid (salt) water-absorbing resin as a main component,
(1) A reactive surfactant containing a functional group other than a hydroxyl group capable of reacting with a carboxyl group is added to a water-absorbent resin (preferably a water-absorbent resin powder having a specific particle size) during or after surface crosslinking. It is a manufacturing method of a particulate water-absorbing agent characterized by including a process, and it is preferable that this reactive surfactant is 7-12 of HLB of a reactive surfactant.
(2) An HLB containing a functional group other than a hydroxyl group capable of reacting with a carboxyl group is 7 with respect to a water absorbent resin (preferably a water absorbent resin powder having a specific particle size) having an absorption capacity of 20 (g / g) or more under pressure. A method for producing a particulate water-absorbing agent, comprising a step of adding ˜12 reactive surfactants.
(3) A step of adding a reactive surfactant having a HLB of 7 to 12 containing a functional group other than a hydroxyl group capable of reacting with a carboxyl group to a water absorbent resin (preferably a water absorbent resin powder having a specific particle size), the addition step A method for producing a particulate water-absorbing agent, comprising a surface cross-linking step until the absorption capacity under pressure becomes 20 (g / g) or more simultaneously with or before and after the step.

The present invention is a particulate water-absorbing agent composed mainly of a polyacrylic acid (salt) -based water-absorbing resin containing a surfactant, taking the production methods (1) to (3) as an example. It is a reactive surfactant containing a functional group other than a hydroxyl group capable of reacting with a carboxyl group, the surface tension of the water-absorbing agent is 55 to 73 mN / m, and the 20 mass% saline vertical absorption index is 1.5 to 10.0. A water-absorbing agent that is [g / g] is provided. However, the surface tension is defined by the surface tension of the water-absorbing agent dispersion in physiological saline.
(2-2-2) Reactive surfactant suitable for obtaining In order to maintain the surface tension of the water-absorbing agent of the present invention at 55 to 73 mN / m, the reactive surfactant is preferably an amino group and a functional group. It has an epoxy group, more preferably 2 or more functional groups in the molecule, and still more preferably a polymer compound.

  Moreover, it is preferable that the reactive surfactant contains an amino group as a functional group and the neutralization rate of the water absorbent resin is 69 mol% or less.

  Moreover, the preferable addition amount of the said reactive surfactant is 0.0001-2.0 mass% with respect to polyacrylic acid (salt) type water absorbing resin, Furthermore, 0.001-0.2 mass%. .

  Preferably, the reactive surfactant and the polyacrylic acid (salt) water-absorbing resin are mixed and heat-treated.

  When the above-mentioned preferable reactive surfactants and their use conditions (heating) are deviated, the surface tension of the resulting water-absorbing agent is lowered, and as a result, the return amount may increase during actual use such as diapers. .

Further, in order to control the saline vertical absorption index high, a reactive surfactant having an HLB of 7 to 12 is suitable, and the structure of the reactive surfactant is as follows:
Preferably, it has polyoxyalkylene units,
More preferably, it has a polysiloxane structure,
More preferably, it has a functional group other than a hydroxyl group capable of reacting with a carboxyl group and a hydrophilic or hydrophobic functional group other than a hydroxyl group capable of reacting with the carboxyl group.

Moreover, it is preferable in the viscosity of this reactive surfactant being 10-20000 mm < ² > / s (25 degreeC).

  In the case of other than the above-mentioned preferable reactive surfactant, the normal water absorption index of the resulting water-absorbing agent is reduced to less than 1.5, and as a result, the return amount may increase during actual use such as diapers. There is. Hereinafter, the water-absorbing agent of the present invention and the production method thereof will be further described.

(2-2-3) Structure of Reactive Surfactant In order to solve the problems of the present invention, the reactive functional group of the reactive surfactant is unsaturated of polyacrylic acid (salt) water-absorbing resin. A functional group that reacts with a group (double bond) may be used, but a functional group that reacts with a carboxyl group of the water-absorbing resin is preferable, and a functional group other than a hydroxyl group having low reactivity is more preferable. The reaction may be an ionic bond, a covalent bond, or may coexist. Examples of the reactive functional group include known functional groups that react with a carboxy group, such as an epoxy group, an amino group, an aziridine group, an oxazolidine group, an alkylene carbonate group, an oxazoline group, and preferably an epoxy group or an amino group And further an amino group.

  The reactive surfactant preferably has 2 or more, more preferably 3 or more and 4 or more reactive functional groups in the molecule. The amino group may be a primary, secondary, tertiary, or quaternary amino group, particularly a primary or secondary amino group or a tertiary amino group. 100 mol%, 30-100 mol%, 50-100 mol%, 70-100 mol% is preferable.

  Specific examples of the compound include an organic polysiloxane compound and a long-chain alkyl compound. Particularly, the compound has an amino group, an epoxy group, or an amino group, and has oxyalkylene or polysiloxane in the side chain or main chain. Examples of polysiloxane include (A) amine / polyoxyalkyl modified silicone, (B) epoxy / polyoxyalkyl modified silicone, and (C) carboxyl / polyoxyalkyl modified silicone, and (D) amino as long chain alkyl compound.・ Polyoxyalkylene alkyl ether, (E) epoxy polyoxyalkylene alkyl ether, (F) amino sorbitan fatty acid ester, (G) epoxy sorbitan fatty acid ester, (H) amino polyoxyalkyl sorbitan fatty acid ester, etc. Preferably, the following reactive surfactants can be preferably used.

(HLB)
In order to further solve the problems of the present invention, the HLB of the reactive surfactant is preferably 5 to 14, more preferably 6 to 12, and most preferably 7 to 11. The balance between the hydrophobic group and the hydrophilic group can be adjusted as appropriate to adjust the HLB range. If the HLB range deviates from the above, the intended Anti-Caking performance and 20% by mass saline vertical absorption index cannot be obtained, which is not preferable.

  In order to further solve the problem of the present invention, the reactive surfactant is not a non-polymer or a polymer, but is preferably a polymer-reactive surfactant. By using a polymer surfactant, the HLB can be controlled in a more suitable range, and it becomes a water-absorbing agent excellent in 20% by mass saline normal absorption index and anti-caking performance.

(Melting point)
20-350 degreeC is preferable, as for melting | fusing point (or Tg of an organic polymer compound) of the reactive surfactant which concerns on this invention, 40-350 degreeC is more preferable, 50-350 degreeC is more preferable, 60-350 degreeC is preferable. Even more preferred is 70-350 ° C, most preferred 80-350 ° C. The organic polysiloxane may be solid at room temperature, but a compound that is liquid at room temperature is preferably used.

(Neutralization rate of water absorbent resin)
The water absorbent resin is preferably partially neutralized, and a neutralization rate of 90 mol% or less is more preferable because of high reactivity with the reactive surfactant and high surface tension of the obtained water absorbent. A rate of 80 mol% or less is more preferred, and a neutralization rate of 75 mol% or less is most preferred. Moreover, when the neutralization rate is 69 mol% or less, the water-absorbing agent according to the second aspect of the present invention can be provided by using a surfactant having an amino group.

(Suitable polymer repeat structure)
In order to further solve the problem of the present invention, the reactive surfactant has a polyoxyalkylene unit, and the polyoxyalkylene is a block or random copolymer of oxyethylene, oxypropylene, oxyethylene / oxypropylene.

  In order to further solve the problem of the present invention, the reactive surfactant has a polysiloxane structure in the main skeleton, and the functional group of the side chain includes alkyl, phenylalkyl, etc., preferably an alkyl group, The alkyl group preferably has 1 to 5 carbon atoms, more preferably has 1 to 2 carbon atoms, and particularly preferably has 1 carbon atom (methyl group) of 50 mol% or more and less than 100 mol% of the side chain group. .

  In order to further solve the problem of the present invention, in addition to a functional group other than a hydroxyl group capable of reacting with a carboxyl group, the reactive surfactant is hydrophilic or hydrophobic other than a functional group other than a hydroxyl group capable of reacting with the carboxyl group. It is preferable to have a functional group of Thereby, HLB can be controlled to a suitable range.

(Structural formula of polysiloxane-based reactive surfactant)
As typical structures, polysiloxysans represented by the following chemical formulas 1 and 2 and epoxy group or amino group-containing polysiloxane reactive surfactants can be preferably used.

In order to further solve the problems of the present invention, the reactive surfactant preferably has a viscosity (measured in accordance with JIS Z-8803) of 10 to 20000 mm ² / s. When deviating from this range, the uniform dispersion of the surfactant on the particle surface is impaired, resulting in poor anti-caking performance. The polyoxyethylene group in the structural formula may be a random copolymer or block copolymer of an oxyethylene group and an oxypropylene group, but the ratio of the oxyethylene group to the oxypropylene group is usually (100 -50): (0-50), preferably (100-60): (0-40).

  The number of reactive functional groups of the organic polysiloxane having reactivity may be usually one or more in one molecule of silicone oil. However, it is preferable to have two or more reactive functional groups for the purpose of crosslinking the vicinity of the surface of the resin particles. From the viewpoint of efficient crosslinking, the functional group equivalent (molecular weight per functional group) is in the range of 100 to 100,000, more preferably 200 to 10,000, and 300 to 8,000. Moreover, the number of the more preferable reactive functional group is 2-200, Furthermore, 2-20. Moreover, as a position of a reactive functional group, any of the terminal of a silicone polymer molecule, a side chain, or both of a terminal and a side chain may be sufficient.

  The organic polysiloxane may be liquid at normal temperature, and the molecular weight is not particularly limited, but is preferably 1000 or more, more preferably 3000 or more. The upper limit of the molecular weight of the organic polysiloxane is not particularly limited, but is usually about 1 million, more preferably about 100,000, and further preferably about 20,000. It is preferable to use an organic polysiloxane having a molecular weight of 1000 or more because there is no possibility that the moisture absorption blocking rate and the dustiness will deteriorate over time. If the molecular weight or degree of polymerization is low, it may have to be used in large quantities, while if the molecular weight or degree of polymerization is too high, the viscosity and melting point may become too high, making uniform processing difficult. is there.

(Specific reactive surfactant)
The reactive surfactants of the present invention preferably include the above (A) to (H), and specifically, the following reactive surfactants can be preferably used.
Examples of (A) amine / polyoxyalkyl-modified silicone include side-chain aminopropyl polyoxyethylene ether-modified polydimethylsiloxane, terminal aminopropyl polyoxyethylene ether-modified polydimethylsiloxane, and both terminal aminopropyl polyoxyethylene ether-modified poly Dimethylsiloxane, side-chain aminopropyl / side-chain polyoxyethylene-modified polydimethylsiloxane, side-chain aminopropyl / terminal polyoxyethylene-modified polydimethylsiloxane, terminal aminopropyl / side-chain polyoxyethylene-modified polydimethylsiloxane, terminal aminopropyl / Terminal polyoxyethylene modified polydimethylsiloxane, side chain aminopropyl, both ends polyoxyethylene modified polydimethylsiloxane, both ends aminopropyl, side chain polio Xylethylene-modified polydimethylsiloxane, side chain 3- (2-aminoethylamino) propyl-polyoxyethylene ether-modified polydimethylsiloxane, terminal 3- (2-aminoethylamino) propyl-polyoxyethylene ether-modified polydimethylsiloxane, both Terminal 3- (2-aminoethylamino) propyl-polyoxyethylene ether-modified polydimethylsiloxane, side chain 3- (2-aminoethylamino) propyl / side-chain polyoxyethylene ether-modified polydimethylsiloxane, side chain 3- ( 2-aminoethylamino) propyl-terminated polyoxyethylene ether-modified polydimethylsiloxane, terminal 3- (2-aminoethylamino) propyl-side-chain polyoxyethylene ether-modified polydimethylsiloxane, terminal 3- (2-aminoethyl) Amino) propyl terminal polyoxyethylene ether modified polydimethylsiloxane, side chain 3- (2-aminoethylamino) propyl both ends polyoxyethylene ether modified polydimethylsiloxane, both ends 3- (2-aminoethylamino) propyl -Side chain polyoxyethylene ether modified polydimethylsiloxane, side chain aminopropyl polyoxyethylene / oxypropylene ether modified polydimethylsiloxane, and the like.
(B) Examples of the epoxy-polyoxyalkyl-modified silicone include, for example, side-chain polyoxyethylene glycidyl ether-modified polydimethylsiloxane, terminal polyoxyethylene glycidyl ether-modified polydimethylsiloxane, both terminal polyoxyethylene glycidyl ether-modified polydimethylsiloxane, Side chain polyoxyethylene glycol / side chain propyl glycidyl ether modified polydimethylsiloxane, side chain polyoxyethylene glycol / terminal propyl glycidyl ether modified polydimethylsiloxane, terminal polyoxyethylene glycol / side chain propyl glycidyl ether modified polydimethylsiloxane, terminal Polyoxyethylene glycol, terminal propyl glycidyl ether modified polydimethylsiloxane, side chain polyoxyethylene glycol Both ends propyl glycidyl ether-modified polydimethylsiloxane, both ends of polyoxyethylene glycol side chain propyl glycidyl ether-modified polydimethylsiloxane.

  Examples of the (C) carboxyl / polyoxyalkyl-modified silicone include side-chain polyoxyethylene / terminal propionic acid-modified polydimethylsiloxane, side-chain polyoxyethylene / side-chain propionic acid-modified polydimethylsiloxane, and terminal polyoxyethylene / terminal. Examples include propionic acid-modified polydimethylsiloxane.

  Examples of (D) amino / polyoxyalkylene alkyl ethers include aminopropyl polyoxyethylene lauryl ether, 3- (2-aminoethylamino) propyl polyoxyethylene lauryl ether, aminopropyl polyoxyethylene cetyl ether, 3- ( 2-aminoethylamino) propyl polyoxyethylene cetyl ether, aminopropyl polyoxyethylene stearyl ether, 3- (2-aminoethylamino) propyl polyoxyethylene stearyl ether, aminopropyl polyoxyethylene oleyl ether, 3- (2- Aminoethylamino) propyl polyoxyethylene oleyl ether, aminopropyl polyoxyethylene octyldodecyl ether, 3- (2-aminoethylamino) propyl polio Shi ethylene octyldodecyl ether, and the like.

  (E) Examples of the epoxy-polyoxyalkylene alkyl ether include glycidyl ether polyoxyethylene lauryl ether, glycidyl ether polyoxyethylene cetyl ether, glycidyl ether polyoxyethylene stearyl ether, glycidyl ether polyoxyethylene oleyl ether, glycidyl ether poly Examples thereof include oxyethylene octyl decyl ether.

  Examples of (F) amino sorbitan fatty acid esters include aminopropyl sorbitan monolaurate.

  Examples of (G) epoxy sorbitan fatty acid ester include glycidyl ether sorbitan monolaurate.

  Examples of (H) amino / polyoxyalkyl sorbitan fatty acid esters include aminopropyl polyoxyethylene sorbitan monolaurate, 3- (2-aminoethylamino) propyl polyoxyethylene sorbitan monolaurate, and aminopropyl polyoxyethylene. Sorbitan monopalmitate, 3- (2-aminoethylamino) propyl polyoxyethylene sorbitan monopalmitate, aminopropyl polyoxyethylene sorbitan monostearate, 3- (2-aminoethylamino) propyl polyoxyethylene sorbitan monostearate , Aminopropyl polyoxyethylene sorbitan tristearate, 3- (2-aminoethylamino) propyl polyoxyethylene sorbitan tristearate, aminopropyl poly Xylethylene sorbitan monooleate, 3- (2-aminoethylamino) propyl polyoxyethylene sorbitan monooleate, aminopropyl polyoxyethylene sorbitan triisostearate, 3- (2-aminoethylamino) propyl polyoxyethylene sorbitan Examples thereof include triisostearate, aminopropyltetraoleic acid polyoxyethylene sorbitol, and 3- (2-aminoethylamino) propyltetraoleic acid polyoxyethylene sorbitol.

  Examples of (H) epoxy-polyoxyalkyl sorbitan fatty acid esters include glycidyl ether polyoxyethylene sorbitan monolaurate, glycidyl ether polyoxyethylene sorbitan monopalmitate, glycidyl ether polyoxyethylene sorbitan monostearate, glycidyl ether poly Examples thereof include oxyethylene sorbitan tristearate, glycidyl ether polyoxyethylene sorbitan monooleate, glycidyl ether polyoxyethylene sorbitan triisostearate, and glycidyl ether tetraoleate polyoxyethylene sorbite.

  Among these reactive surfactants, (A) amine / polyoxyalkyl-modified silicone, (D) amino / polyoxyalkylene alkyl ether, (E) epoxy / polyoxyalkylene alkyl ether, (F) amino A reactive surfactant containing an amino group selected from sorbitan fatty acid ester, (H) amino polyoxyalkyl sorbitan fatty acid ester, side chain aminopropyl polyoxyethylene ether modified polydimethylsiloxane, side chain 3 -(2-aminoethylamino) propyl-polyoxyethylene ether modified polydimethylsiloxane, side chain 3- (2-aminoethylamino) propyl / side chain polyoxyethylene ether modified polydimethylsiloxane, aminopropyl polyoxyethylene lauric Reactivity selected from ether, 3- (2-aminoethylamino) propyl polyoxyethylene lauryl ether, aminopropyl polyoxyethylene sorbitan monolaurate, 3- (2-aminoethylamino) propyl polyoxyethylene sorbitan monolaurate A surfactant is preferably used.

  The surface tension is not particularly limited, but is preferably 20 or more [mN / m], more preferably 30 or more [mN / m]. The viscosity is not particularly limited as long as it is liquid at normal temperature, but it is preferably 10 to 20000 centistokes [cst] at normal temperature (25 ° C.), and particularly preferably, it is not necessary to dilute with solvents and absorbs water. 30 to 1000 [cst] in that mixing with a functional resin is easy.

  Organopolysiloxanes also use linear dimethylpolysiloxanes as the base polymer, and their end groups can be blocked in different ways ("Chemieund Technology des Kalthaertenden Siliconcoattchurks" ["Chemistry and Technoltechnology"). 48-64, SILICONE-Chemieund Technology [SILICONES-Chemistry and technology], [Symposium, April 28, 1989], Vulcan Publishing, Essen).

  Depending on the type and addition amount of the surfactant, the surface tension of the resulting particulate water-absorbing agent is excessively lowered, and the amount of liquid returned from the absorbent article (especially paper diapers) (Re-Wet “Rewet”). May be increased). Therefore, more preferably, the surface tension of the particulate water-absorbing agent (defined in US Pat. No. 7,473,739 and defined by the surface tension of the water-absorbing agent dispersion in physiological saline) is 55 (mN / m) or more, The type and amount of the surfactant added so that it is in the range of 60 (mN / m) or more, further 65 (mN / m) or more, 68 (N / m) or more, and further 70 (N / m) or more. Should be selected. The upper limit is about 73 (mN / m).

(2-2-4) Amount of Reactive Surfactant Added The content of the reactive surfactant contained in the particulate water-absorbing agent according to the present invention and / or the amount added to the water-absorbing resin is polyacrylic. 0.0001-2 mass% is preferable with respect to acid (salt) type | system | group water absorbing resin, 0.0005-1.0 mass% is more preferable, 0.001-0.5 mass% is further more preferable, 0.001 -0.2 mass% is especially preferable.

  When deviating from the above, the intended Anti-Caking performance, surface tension, and 20% by mass saline normal absorption index cannot be obtained.

  When the surfactant is added as a (water) solution, water or a mixed solution of water and an organic solvent is used as a solvent. In this case, the amount of added water or a mixed solvent of water and an organic solvent is preferably 3 to 25% by mass, more preferably 3 to 20% by mass, and 5 to 10% by mass with respect to the water absorbent resin. Further preferred. The solvent may be removed by drying if necessary.

  Thus, by adding a surfactant, water, or a surfactant (water) solution within the above range, and further controlling the water content to be described later, the impact resistance stability of the particulate water-absorbing agent is improved. Property and powdering rate are dramatically improved.

(2-2-5) Addition timing The addition timing of the reactive surfactant can be added at any step during surface crosslinking or after surface crosslinking.

  In the method for producing a particulate water-absorbing agent according to the present invention, the polymerization step, the drying step, and the surface cross-linking step are essential steps. In addition to these steps, a degassing step, a granulating step, and other modifiers are added. There may be other processes such as processes.

(2-2-6) Addition method The reactive surfactant can be added to the water-absorbent resin by a method in which the reactive surfactant is dissolved in water or an organic solvent and added as a solution. In the case of liquid state at room temperature or in a heated state, a method of adding directly to the water-absorbing resin can also be employed.

  The surfactant uniformly dispersed in water using a dispersion stabilizer has fluidity, and examples of the form include slurry, suspension, and emulsified liquid. The upper limit of the viscosity is about 10,000 cps (25 ° C.). However, even if the viscosity is low, there is no problem and the viscosity may be substantially the same as that of water.

  Furthermore, when the surfactant is produced in the state of an aqueous dispersion, it can be used as it is without being dried, or in a state of being appropriately concentrated or diluted.

(Mixing device)
In the present invention, the apparatus for mixing the water-absorbing resin and the surfactant (or a solution or dispersion thereof) is not particularly limited. For example, a cylindrical mixer, a screw mixer, a screw extruder Machine, turbulizer, nauter type mixer, V type mixer, ribbon type mixer, double-arm kneader, fluid type mixer, airflow type mixer, rotating disk type mixer, roll mixer, rolling mixer And Redige mixer. Moreover, as a mixing form, although a continuous type, a batch type, or these combined use is employable, a continuous type mixing is more preferable from a viewpoint of production efficiency.

  As the mixing device, a rotary mixer is generally used, and the number of rotations is not particularly limited as long as the water-absorbent resin is not damaged, and is preferably 5 to 3000 rpm, preferably 10 to 500 rpm. Is more preferable, and 15-300 rpm is still more preferable. When the said rotation speed exceeds 3000 rpm, since the dust of a water absorbing resin generate | occur | produces and water absorption performance falls, it is unpreferable. On the other hand, when the rotational speed is less than 5 rpm, the mixing property is insufficient and the intended effect of improving the hygroscopic fluidity cannot be obtained.

  Moreover, especially the powder temperature of the water absorbing resin at the time of mixing is although it does not restrict | limit, Room temperature-120 degreeC is preferable, 50-100 degreeC is more preferable, 50-80 degreeC is further more preferable. When the said powder temperature exceeds 120 degreeC, since the added water evaporates and in order to obtain the target moisture content, a lot of water is needed, and also the load of a mixing apparatus increases, which is not preferable.

  The mixing time is not particularly limited, but is preferably 1 second to 20 minutes, more preferably 10 seconds to 10 minutes, and further preferably 20 seconds to 5 minutes. When the mixing time exceeds 20 minutes, it is not possible to obtain an effect commensurate with it, and conversely promote the powdering of the water-absorbent resin, and the amount of fine powder (fine particles passing through a sieve having an opening of 150 μm) and Since the amount of dust increases, it is not preferable.

(2-2-7) “Curing” and “Curing process” after addition
In the above addition, when a surfactant, a chelating agent or the like is added to the water absorbent resin as an aqueous solution or aqueous dispersion, the surface of the water absorbent resin becomes wet due to the action of water, but then the water is absorbed inside. As a result, the surface becomes dry. Here, the term “curing” or “curing step” is sometimes referred to as abbreviated as the particle surface is dried by standing or heating for a predetermined time and the particles are lightly aggregated. Further, the aggregated particles may be referred to as “cured product”. Therefore, when water is used for the addition of a surfactant, a chelating agent, etc., it is preferably heated at a predetermined temperature (for example, 40 to 150 ° C.), or left for a predetermined time at room temperature or in a heated state (for example, 1 minute to 3 hours). ) May be performed through a curing step. It is preferable because the water-absorbent resin fine powder can be reduced by agglomeration (also known as granulation) in the curing step.

The fluidity of the dried (Dry) water-absorbent resin powder after curing can be defined by the Flow-Rate specified by ERT450.2-02, and the lightly agglomerated water-absorbent resin powder is crushed and classified as necessary. Thus, for example, it is preferable that the water absorbent resin powder (particulate water absorbing agent) is 30 [g / s] or less, further 20 [g / s] or less, and further 15 [g / s] or less. The wet water-absorbent resin powder after the addition of the aqueous dispersion may be left standing or heated (or dried by heating) for a predetermined time until it falls within the Flow-Rate range, and further crushed and classified as necessary. (2-3) Chelating agent addition step (optional)
For actual use in diapers, the amount of increase in degradation soluble content (specified by the difference between degradation soluble content (%) and soluble content (%)) in the degradation acceleration test is 0 to 15% by mass. Degradable solubles are controlled by increasing the amount of crosslinking agent during polymerization, using a chain transfer agent, using an inorganic reducing agent, using a chelating agent, etc., according to the method described in the pamphlet of International Publication No. 2005/092956 Although it can be controlled, it can preferably be controlled with a chelate. That is, in the water-absorbing agent of the present invention and the method for producing the same, the water-absorbing agent preferably further contains a chelating agent in addition to the reactive surfactant from the viewpoint of urine resistance and coloration prevention.

  Preferably, the content of the chelating agent is 0.001 to 5.0% by mass with respect to the polyacrylic acid (salt) water-absorbing resin, and more preferably the chelating agent contains nitrogen atoms and / or It is a water-soluble organic compound having a phosphorus atom and / or an α-hydroxycarboxylic acid (salt).

  In the particulate water-absorbing agent and the method for producing the same according to the present invention, a chelating agent is preferably used. Preferably, the production method further includes a step of adding a chelating agent.

  The chelating agent is not particularly limited as long as the effects on the colorability with time and the increase rate of the deteriorated soluble content of the present invention are exhibited, but a water-soluble organic chelating agent is preferable from the viewpoint of availability and handling properties. From the viewpoint of cost-effectiveness, a water-soluble organic chelating agent having a nitrogen atom and / or a phosphorus atom or a water-soluble organic chelating agent having an α-hydroxycarboxylic acid structure is more preferable, and an amino polyvalent carboxylic acid (salt), organic More preferred are water-soluble organic chelating agents selected from polyvalent phosphoric acid (salt), aminopolyvalent phosphoric acid (salt), and α-hydroxycarboxylic acid (salt). Organic polyvalent phosphoric acid (salt), aminopolyvalent phosphorous A water-soluble organic chelating agent selected from acids (salts) and α-hydroxycarboxylic acids (salts) is particularly preferred.

  “Chelating agent” refers to a compound that captures metal ions such as transition metal ions. In the present invention, the mass average molecular weight is preferably 100 from the viewpoint of the effect on polymerization and the physical properties of the resulting particulate water-absorbing agent. An organic chelating agent that is a water-soluble non-polymeric compound of ˜5000, more preferably 100˜2000, even more preferably 100˜1000, particularly preferably 100˜500 is used. If the mass average molecular weight exceeds 5,000, for example, the viscosity of the unsaturated monomer aqueous solution may increase depending on the timing of addition of the chelating agent.

  The solubility of the chelating agent that can be used in the present invention in deionized water is preferably 1 g or more, more preferably 5 g or more, and even more preferably 10 g or more with respect to 100 g of deionized water at 20 ± 1 ° C. 20 g or more is particularly preferable.

(Preferred chelating agent)
As described above, amino polyvalent carboxylic acid (salt), organic polyvalent phosphoric acid (salt), and amino polyvalent phosphoric acid (salt) are preferable examples of the chelating agent of the present invention. Or an amino polyvalent carboxylic acid (salt) having 2 or more, preferably 3 or more, more preferably 3 to 100, still more preferably 3 to 20, and particularly preferably 3 to 10 phosphate groups in the molecule. ), Organic polyvalent phosphoric acid (salt) or amino polyvalent phosphoric acid (salt).

  The amino polyvalent carboxylic acid (salt) in the present invention is not particularly limited. For example, iminodiacetic acid, hydroxyethyliminodiacetic acid, nitrilotriacetic acid, nitrilotripropionic acid, ethylenediaminetetraacetic acid, hydroxyethylenediaminetriacetic acid, hexa Methylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid, triethylenetetraminehexaacetic acid, trans-1,2-diaminocyclohexanetetraacetic acid, bis (2-hydroxyethyl) glycine, diaminopropanoltetraacetic acid, ethylenediamine-2-propionic acid, glycol ether diamine Tetraacetic acid, bis (2-hydroxybenzyl) ethylenediaminediacetic acid, ethylenediaminedisuccinic acid, L-glutamic acid diacetic acid, 3-hydroxy-2,2'-iminodisuccinic acid, glycol ether Tetraacetic acid, and methyl glycine diacetic acid and the like salts thereof.

  Although it does not specifically limit as organic polyvalent phosphoric acid (salt) or amino polyvalent phosphoric acid (salt) in this invention, For example, hydroxyethylene diphosphoric acid, ethylenediamine-N, N'- di (methylene phosphinic acid), Ethylenediaminetetra (methylphosphinic acid), nitriloacetic acid-di (methylenephosphinic acid), nitriloacetic acid- (methylenephosphinic acid), nitriloacetic acid-6-propionic acid-methylenephosphonic acid, nitrilotris (methylenephosphonic acid), cyclohexanediaminetetra (Methylenephosphonic acid), ethylenediamine-N, N′-diacetic acid-N, N′-di (methylenephosphonic acid), ethylenediamine-N, N′-di (methylenephosphonic acid), ethylenediaminetetra (methylenephosphonic acid), Polymethylenediaminetetra (methylenephos Phosphate), diethylene triamine penta (methylene phosphonic acid), 1-hydroxyethylidene-diphosphonic acid and salts thereof. One or two or more of these can be used. Further, from the viewpoint of water solubility, preferable examples of the salt include alkali metal salts such as sodium salt and potassium salt, ammonium salt, and amine salt.

  Among the above-described chelating agents, amino polyvalent phosphoric acid (salt) having an aminophosphonic acid group is most preferable from the viewpoint of water absorption characteristics (water absorption capacity, increase rate of deteriorated soluble matter, coloration with time, etc.).

(Α-hydroxycarboxylic acid (salt))
As the water-soluble organic chelating agent of the present invention, α-hydroxycarboxylic acid can also be mentioned as a preferred example. Hydroxycarboxylic acid refers to a carboxylic acid having a hydroxyl group in the molecule. In the present invention, α-hydroxycarboxylic acid having a hydroxyl group bonded to carbon at the α-position is preferably used. Among these, α-hydroxycarboxylic acids such as non-polymeric α-hydroxycarboxylic acids are preferable, and aliphatic α-hydroxycarboxylic acids having no cyclic structure or unsaturated group are more preferable. Use of an aromatic α-hydroxycarboxylic acid or an aliphatic α-hydroxycarboxylic acid having a cyclic structure or an unsaturated group is not preferred because these themselves are colored by an oxidation reaction or the like.

  The α-hydroxycarboxylic acid (salt) in the present invention is not particularly limited. For example, lactic acid (salt), citric acid (salt), malic acid (salt), isocitric acid (salt), glyceric acid (salt), Examples thereof include tartaric acid (salt) and D-form, L-form, meso-form and the like thereof. Among these, α-hydroxymonocarboxylic acid such as lactic acid or the like, or preferably 2 or more, more preferably 2 to 10, more preferably 2 to 6, more preferably 2 or more carboxyl groups in the molecule. Is an α-hydroxy polyvalent carboxylic acid having 2-4. As the α-hydroxy polyvalent carboxylic acid, malic acid (salt), citric acid (salt), isocitric acid (salt), and tartaric acid (salt) are particularly preferably used from the viewpoint of water absorption characteristics and coloring improvement.

  When α-hydroxycarboxylate is used, monovalent salts are preferable from the viewpoint of solubility in water, and alkali metal salts such as lithium, potassium and sodium, ammonium salts, monovalent amine salts and the like are more preferable. . Further, when α-hydroxy polyvalent carboxylic acid is used as a salt, all the carboxyl groups may be used as a salt, or only a part may be used as a salt.

(Method of adding chelating agent)
As the method for adding a chelating agent in the present invention, the method for adding a chelating agent described in Patent Document 32 can be applied as it is.

  The addition method described in the above (2-2-6) and the mixing device thereof can be used as appropriate. Specifically, the above-described (1) a method of dissolving in hot water or an organic solvent and adding as a solution, (2 A method of dry blending as a powder, and (3) a method of adding a suspension as a water dispersion of fine powder. Among these, the method of adding in the form of a solution or an aqueous dispersion is preferable from the viewpoint of fixing to a particulate water-absorbing agent.

  Moreover, as long as the effect of the present invention is manifested, the chelating agent can be added at any stage in the production process of the water-absorbent resin or the particulate water-absorbing agent, and added in any one or a plurality of steps. can do.

(Amount of chelating agent added)
The content of the chelating agent contained in the particulate water-absorbing agent according to the present invention and / or the addition amount of the chelating agent added to the water-absorbing resin is an effect on the coloration with time and the increase rate of the deteriorated soluble component of the present invention. However, 0.001 to 5 mass% is preferable with respect to the polyacrylic acid (salt) water-absorbing resin, 0.0025 to 5 mass% is more preferable, and 0.005 to 3 is preferable. More preferred is mass%.

  However, since the amount required to obtain the effect of the present invention differs depending on the type of chelating agent, specifically, in the case of organic polyvalent phosphoric acid (salt) and amino polyvalent phosphoric acid (salt), even a small amount In order to exert the effect, 0.001 to 0.5% by mass is preferable with respect to the polyacrylic acid (salt) -based water absorbent resin, more preferably 0.001 to 0.1% by mass, Preferably 0.005-0.1% by mass is sufficient. In the case of α-hydroxycarboxylic acid (salt) and amino polyvalent carboxylic acid (salt), 0.01 to 5% by mass is preferable with respect to the polyacrylic acid (salt) -based water absorbent resin. 05-5 mass% is more preferable, 0.1-3 mass% is further more preferable, and 0.2-3 mass% is especially preferable.

(2-4) Water addition step (optional) and method for adjusting water content For actual use in diapers and the like, the water content is preferably 1 to 20% by mass. Preferably, the pulverization rate in the impact test (the amount of increase in 150 μm passing matter (%) before and after the impact test described later) is 0 to 1.0% by mass or less, and further within the following range.

  The water content of the particulate water-absorbing agent according to the present invention (specified by loss on drying at 180 ° C. for 3 hours) is preferably 1 to 20% by mass, more preferably 5 to 20% by mass, and preferably 5 to 18% by mass. More preferably, it is 6-18 mass%, More preferably, it is 7-15 mass%, Most preferably, it is 8-13 mass%.

  By adjusting the moisture content of the particulate water-absorbing agent within the above range, the powdering rate, moisture-absorbing fluidity, water-absorbing performance (AAP), which will be described later, are improved, and impact resistance (abrasion resistance) is excellent. A particulate water-absorbing agent can be obtained. Furthermore, it becomes possible to suppress charging of the particulate water-absorbing agent, and the handleability of the powder is remarkably improved. In addition, when the water content is less than 1% by mass, sufficient impact resistance stability cannot be obtained, and when the water content exceeds 20% by mass, water absorption performance (CRC, AAP, etc.) and moisture absorption fluidity can be obtained. Since it causes a decrease, it is not preferable.

  The method for adjusting the moisture content is not particularly limited. For example, when the reactive surfactant or the chelating agent is added as an aqueous dispersion or (water) solution, the moisture content of the water absorbent resin to be used is adjusted. Accordingly, the addition amount may be appropriately adjusted, and water may be further added to the particulate water-absorbing agent after adding the aqueous dispersion of fatty acid (salt) or chelating agent or (water) solution. Furthermore, as another adjustment method, after adding water, a reactive surfactant, and a chelating agent within the above ranges to the water-absorbent resin, it can be adjusted by drying by heating or drying under reduced pressure. When the moisture content is adjusted by heat drying or the like, the penetration of water into the water-absorbent resin is promoted, and the surface can be dried and rapidly formed into particles.

  In the method for producing a particulate water-absorbing agent according to the present invention, the surface of the water-absorbent resin immediately after adding an aqueous dispersion or (water) solution of a reactive surfactant or a chelating agent or only water is water. Since it wets or gelates, the fluidity is poor. However, since water existing on the surface of the water-absorbent resin is absorbed and diffused inside the water-absorbent resin after a certain period of time, the particles again have fluidity. Therefore, in the present invention, the wet water-absorbent resin may be allowed to stand for a certain period of time in order to promote the diffusion of water into the interior, or may be heated or partially dried while maintaining the moisture content. .

  When the moisture content is adjusted by the heat drying, the heating temperature is preferably 200 ° C. or less, preferably 30 to 100 ° C., more preferably 50 to 90 ° C., and further preferably 60 to 80 ° C. The heating time is preferably 1 second to 3 hours, more preferably 1 minute to 1 hour, and is appropriately determined within the above range.

  In addition, the water-absorbing agent that has been particulated by heat drying can be used as it is, but operations such as crushing and classification may be performed as necessary. In particular, the water-absorbent resin powder that has become wet by the addition of water may have a dry surface and agglomerate particles slightly due to the diffusion or drying of water from the resin surface to the inside. In this case, although it depends on the degree of aggregation, it may be classified by crushing (operation for mechanically loosening the aggregation) as necessary. These crushing and classifying operations are optional and are performed as necessary. Examples of the crushing apparatus and classifying apparatus that can be used are exemplified in the granulation method described in US Pat. Nos. 4,734,478 and 5,369,148. Has been.

(2-5) Particle size adjustment step (granulation step, granulation step, fine powder recovery step) (optional)
In the method for producing a particulate water-absorbing agent of the present invention, in order to adjust the particulate water-absorbing agent to a particle size described later in (3-3), a granulation step, a sizing step, a fine powder collection step, etc., as necessary. You may perform a particle size adjustment process suitably. In addition, as a particle size adjustment process, the process currently disclosed by US Patent Application Publication No. 2004/181031, 2004/242761, 2006/247351 etc. is employable, for example.

(2-6) Step of adding insoluble inorganic fine particles, polyvalent metal salt, inorganic reducing agent, etc. (optional)
In addition, an addition step of adding insoluble inorganic fine particles, polyvalent metal salt, inorganic reducing agent and the like, which will be described later in (3-12), may be included. Among them, the addition of an inorganic reducing agent can suppress the coloration of the particulate water-absorbing agent over time and deterioration due to urine at a higher level, and reduce the residual monomer amount.

(2-7) Prior Art Patent Document 5 (WO95 / 033558), Patent Document 16 (Japanese Patent Laid-Open No. 9-136966), and Patent Document 17 (Japanese Patent Laid-Open No. 2004-99803) are for anti-caking during moisture absorption. Discloses the use of silicone surfactants or reactive silicone compounds. Patent Document 18 (US Pat. No. 6,395,830) also discloses the use of an amino-modified silicone compound in order to suppress the water absorption rate. Patent Document 19 (Japanese Patent Application Laid-Open No. 2004-966803) also discloses the use of water-soluble silicone for gel grinding.

  However, these patent documents do not disclose the HLB of the water absorbing agent, the absorption index under vertical pressure (1.5 to 10 g / g), the reactive surfactant having a specific structure, and the water content.

[3] Particulate water-absorbing agent The particulate water-absorbing agent of the present invention obtained by taking the above production method as an example is a particulate water-absorbing agent containing a polyacrylic acid (salt) water-absorbing resin as a main component, and the surface of the water-absorbing agent The tension is 55 mN / m or more, and the 20 mass% saline vertical absorption index is 1.5 to 10.0 [g / g]. The preferred surface tension and normal saline absorption index are in the above ranges, and more preferably, the moisture absorption blocking rate is 0 to 40% (more preferably 0 to 30%).

  That is, a water-absorbing resin that has been conventionally evaluated with 0.9% by mass saline solution or artificial urine, or a basis weight (amount of water-absorbing resin per unit area, for example, (5 -2), with respect to the water-absorbing resin evaluated in AAP (spreading 0.9 g of water-absorbing resin in a range of 60 mm in diameter)), Patent Documents 5 to 15 further improve powder fluidity and water absorption performance. The water-absorbing resin, particularly, in Patent Document 9, by adding metal soap, powder flowability and water-absorbing performance under pressure (for example, a load of 0.96 to 4.83 wt. There has been proposed a water-absorbent resin in which [absorption at [kPa]) is maintained.

  However, in such a conventional technique, the water absorption ratio in ultra-high-concentration salt water (especially 20% by mass saline solution) that has not been noticed at all is extremely reduced. Water absorption capacity under pressure (20% by mass saline vertical absorption index) at a high basis weight (spraying 10 g of water-absorbing resin in a range of 25.4 mm in diameter. Basis weight about 6.2 times that of AAP) is extremely reduced. I found the facts. And in addition to powder fluidity, the addition of ultra-high-concentration salt water (especially 20% by mass saline) and ultra-high basis weight (basis weight about 6.2 times that of AAP), which has not been noticed in the past. It has been found that the reduced water absorption is important during actual use in the form of a sheet or tape.

  Moreover, although it is also known in the above-mentioned patent documents that the moisture absorption blocking rate (anti-caking performance) is important, the present inventors have a low water absorption blocking rate (high anti-caking performance) after production. It has been found that even with a resin, the moisture absorption blocking rate increases during actual use. And in the evaluation of the conventional moisture absorption blocking rate, it does not show a sufficient effect at the time of actual use, and the cause thereof is peeling of various Anti-Caking agents by transporting the water absorbent resin powder (for example, various transport machines such as pneumatic transport). And the moisture absorption blocking rate was found to increase. And it replaced with the conventional evaluation of the moisture absorption blocking rate, discovered that the moisture absorption blocking rate after an impact test (modeling conveyance) was important for actual use, and completed this invention. Furthermore, some of the prior arts reduce the surface tension of the water-absorbing agent, and it has been found that the adverse effect is to increase the amount of reversion in the final product. Hereinafter, preferable 20 mass% saline vertical absorption index, moisture absorption blocking ratio after impact test, surface tension and the like will be further described.

(3-1) 20 mass% saline vertical absorption index As a means for achieving the above production method, a reactive surfactant having a specific structure (preferably a surfactant having an amino group) is further added to a specific water absorbent resin. Thus, the 20 mass% saline vertical absorption index of the particulate water-absorbing agent according to the present invention is 1.5 [g / g] or more.

  The surface crosslinking is preferably controlled within the range of AAP, which will be described later, but the water absorption capacity under pressure (AAP) under a load of 2.06 kPa by the surface crosslinking step is 20 [g / g] or more, and further 25 [g / g g] or more, and / or absorption capacity under load (AAP) under a load of 4.83 kPa is 12 [g / g] or more, further 15 [g / g] or more, and even more preferably 20 [g / g g] is cross-linked to the surface. More preferably, the absorption capacity and particle size under pressure after surface crosslinking are in the following ranges. The measurement method will be described later in (5-3), but compared to the conventional water absorption capacity under pressure (AAP), which has been evaluated with the basis weight of paper diapers, 0.9% by mass saline and artificial urine, The 20 mass% saline vertical absorption index of the present invention is that the salt concentration of the absorbing solution is about 22 times, and the basis weight of the water absorbing agent at the time of measurement (the amount of water absorbing agent per unit area) is about 6.2 times. The idea is fundamentally different from conventional measurement methods.

  The 20% by mass saline vertical absorption index in the present invention is preferably 1.5 [g / g] or more, more preferably 2.0 [g / g] or more, and further preferably 3.0 [g / g] or more. 4.0 [g / g] or more is even more preferable, 5.0 [g / g] or more is particularly preferable, and 6.0 [g / g] or more is most preferable. The upper limit is preferably higher, but 15 [g / g] or less, more preferably 10 [g / g] or less is sufficient from the balance with other physical properties and costs.

  When the 20 mass% saline vertical absorption index is less than 1.5 [g / g], the conventional well-known physical properties, for example, 0.9 mass% saline solution or artificial urine, It has been found that even when the water absorption capacity under pressure (AAP) is about the same, when the particulate water-absorbing agent is used in the form of a sheet or tape, it is inferior in water absorption characteristics during actual use.

  The 20% by mass saline vertical absorption index is affected by the structure (or HLB) of the reactive surfactant, the amount added, and the dispersion state on the surface of the water absorbent resin particles (mixing property of the reactive surfactant). It can be set to 1.5-5.0 by controlling to the above-mentioned preferable range.

  The surface tension of the particulate water-absorbing agent of the present invention is 55 (mN / m) or more, further 60 (mN / m) or more, and further 65 (mNN) as defined by the surface tension of the water-absorbing agent dispersion in physiological saline. / M) or more, 68 (N / m) or more, and 70 (N / m) or more, the type and amount of the surfactant may be selected. The upper limit is about 73 (mN / m).

  In addition to the above water-absorbing agent, the water-absorbing agent (second water-absorbing agent) of the present invention is a particulate water-absorbing agent mainly composed of a polyacrylic acid (salt) water-absorbing resin containing a reactive surfactant. The reactive surfactant is a reactive surfactant having 7 to 12 HLB containing a function other than a hydroxyl group capable of reacting with a carboxyl group, and the absorption capacity of the water-absorbent resin under pressure at 2.06 kPa Is a water-absorbing agent (second water-absorbing agent / preferably also applied to the first water-absorbing agent) of 20 g / g or more.

  Furthermore, in addition to the above water-absorbing agent, the water-absorbing agent (third water-absorbing agent) of the present invention is a particulate water-absorbing agent mainly comprising a polyacrylic acid (salt) -based water-absorbing resin containing a reactive surfactant. The reactive surfactant contains an amino group as a functional group, and the neutralization rate of the water-absorbent resin is 69 mol% or less (the third water-absorbing agent / preferably also applied to the first water-absorbing agent). ).

(3-2) Moisture absorption fluidity after impact test (moisture absorption blocking rate)
The moisture absorption blocking rate (after the impact test) of the particulate water-absorbing agent according to the present invention is preferably 0 to 40% by mass, more preferably 0 to 30% by mass, further preferably 0 to 20% by mass, and 0 to 5% by mass. % Is particularly preferable, and 0 to 2% by mass is most preferable. Although the measurement method will be described later in (5-9), it is fundamentally different from the conventional measurement method because it is an evaluation after the impact test compared to the conventional moisture absorption blocking rate.

  If the moisture absorption blocking rate after the impact test exceeds 20% by mass, even if the moisture absorption blocking rate after the production of the water absorbing agent is excellent, the anti-caking agent may be detached due to transportation of the particulate water absorbing agent, etc. Poor handling of particulate water-absorbing agent in the environment. Therefore, in a manufacturing apparatus such as a thin absorbent body for sanitary materials, aggregation or clogging of the particulate water absorbing agent occurs in the transfer pipe or the like, or the hydrophilic fiber and the particulate water absorbing agent are mixed uniformly. This may cause a problem that it cannot be performed.

  This can be achieved by using a reactive surfactant while controlling the particle size of the water-absorbent resin.

(3-3) Particle size Among the particulate water-absorbing agent according to the present invention, the proportion of the particulate water-absorbing agent having a particle diameter (specified by a standard sieve) of 150 μm or more and less than 850 μm is 95-100. % By mass is preferable, 97 to 100% by mass is more preferable, 98 to 100% by mass is further preferable, and 99 to 100% by mass is particularly preferable. In particular, from the viewpoint of liquid permeability and the like, the amount of the particulate water-absorbing agent according to the present invention is preferably 0 to 5% by mass, more preferably 0 to 3% by mass of a 150 μm passing material (corresponding to particles having a particle diameter of less than 150 μm). %, More preferably 0 to 2% by mass, particularly preferably 0 to 1% by mass.

  Furthermore, the mass average particle diameter (D50) of the particulate water-absorbing agent is preferably 250 to 450 μm, more preferably 300 to 450 μm, and further preferably 325 to 425 μm. Moreover, regarding the particle size distribution of the particulate water-absorbing agent, the logarithmic standard deviation (σζ) serving as an index of uniformity is preferably 0 to 0.45, more preferably 0 to 0.425, and most preferably 0 to 0.40. .

  When the proportion of the particulate water-absorbing agent having a particle diameter of 850 μm or more exceeds 5% by mass with respect to all the particles, a foreign material sensation may be produced or the touch may be deteriorated when sanitary materials such as paper diapers are produced. It is not preferable because it gives the user an unpleasant feeling. Further, when the ratio of the particulate water-absorbing agent having a particle diameter of less than 150 μm exceeds 5% by mass with respect to all particles, or when the logarithmic standard deviation (σζ) exceeds 0.45, the water absorption capacity under pressure Many problems occur, such as drastic decrease in moisture and fluidity of moisture absorption, deterioration of working environment due to dust generated during the manufacture of sanitary materials such as paper diapers, and increased segregation due to wide particle size distribution. It is not preferable.

  The particle size of the particulate water-absorbing agent can be defined by the method described later in (5-4), and may be controlled by the water-absorbing resin production process or by the particulate water-absorbing agent production process. The particle size is preferably controlled in advance before surface crosslinking. The control method can be appropriately performed by pulverization, classification, granulation, preparation of the particle size after classification, and the like. Such particle size control is preferably performed in a classification step before the surface crosslinking (first classification step) or the like, and further performed in a classification step after the surface crosslinking (second classification step) to control the particle size. Specific particle size control can be performed by the steps described in U.S. Patent Application Publication Nos. 2004/181031, 2004/242761, 2006/247351, and the like.

(3-4) Moisture content The moisture content of the particulate water-absorbing agent is 1 to 20% by mass, more preferably 5 to 20% by mass, preferably 5 to 18% by mass, more preferably 6 to 18% by mass, Preferably it is 7-15 mass%, Most preferably, it is 8-13 mass%. The water content of the particulate water-absorbing agent can be defined by the method described later in (5-5) (loss on drying at 180 ° C. for 3 hours).

  By adjusting the moisture content of the particulate water-absorbing agent within the above range, the moisture absorption fluidity described in (3-2) above, the 20% by mass saline vertical absorption index described in (3-1), and Moreover, it leads also to the improvement of the powdering rate described in the following (3-5), and the particulate water-absorbing agent excellent in impact resistance (abrasion resistance) can be obtained. Furthermore, it becomes possible to suppress charging of the particulate water-absorbing agent, and the handleability of the powder is remarkably improved. When the moisture content is less than 1% by mass, sufficient impact resistance stability cannot be obtained. When the moisture content exceeds 20% by mass, the water absorption performance (CRC, AAP, etc.) This is not preferable because it causes a decrease in the property.

  The method for adjusting the water content is not particularly limited. For example, when a reactive surfactant or a chelating agent is added in an aqueous dispersion or (water) solution, depending on the water content of the water-absorbing resin to be used, The addition amount may be appropriately adjusted, and water may be further added to the particulate water-absorbing agent after the aqueous dispersion or (water) solution is added. Furthermore, as another adjustment method, after adding water, a reactive surfactant, and a chelating agent within the above ranges to the water-absorbent resin, it can be adjusted by drying by heating or drying under reduced pressure. When the moisture content is adjusted by heat drying or the like, the penetration of water into the water-absorbent resin is promoted, and the surface can be dried and rapidly formed into particles.

(3-5) Powdering rate The powdering rate of the particulate water-absorbing agent according to the present invention (increase in 150 μm passing material after impact test) is preferably 0 to 1.0% by mass, and 0 to 0.8% by mass. % Is more preferable, and 0 to 0.6% by mass is more preferable. When the above-mentioned pulverization rate exceeds 1.0% by mass, liquid permeability may be reduced due to dust generated during transportation or use of the particulate water-absorbing agent (for example, during processing into sanitary materials) This is not preferable because it may cause deterioration. The water content of the particulate water-absorbing agent can be defined by the method described later in (5-5).

  The control of the pulverization rate can be performed by the control of the moisture content or the like, and can be performed by setting the moisture content to a predetermined value or more, particularly within the range described in (3-4) above.

(3-6) Surface cross-linking In order to improve the 20 mass% saline vertical absorption index, etc., in the present invention, preferably, the above-described method in the particulate water-absorbing agent is performed by the method described in (2-1-5) above. Surface cross-linking is applied to the polyacrylic acid (salt) water-absorbing resin.

(3-7) Chelating agent The particulate water-absorbing agent preferably further contains a chelating agent in order to suppress the increase amount and the rate of increase of the deteriorated soluble component described in the following (3-8) and to prevent coloring. Content of a chelating agent is 0.001-5.0 mass% with respect to polyacrylic acid (salt) type water absorbing resin, and also is the range as described in said (2-4). A preferable chelating agent is the compound described in the above (2-4), and the chelating agent is a water-soluble organic chelating agent having a nitrogen atom and / or a phosphorus atom, or the chelating agent is an α-hydroxycarboxylic acid. (Salt).

  By using such a chelating agent, the amount of increase in the degradation soluble content in the degradation acceleration test can be set to 0 to 15% by mass, and further within the following range (3-8).

(3-8) Increase amount and increase rate of deteriorated soluble component and adjustment method thereof The particulate water-absorbing agent according to the present invention is characterized by an increase amount and an increase rate of deteriorated soluble component in the deterioration acceleration test. In addition, the specific measuring method regarding the increase amount and increase rate of a deterioration acceleration test and a deterioration soluble part is later mentioned in (5-7).

  0-15 mass% is preferable, 0-15 mass% is more preferable, 0-13 mass% is more preferable, 0-11 mass% is further more preferable, and the increase amount in the deterioration accelerated test of the particulate water absorbing agent of this invention is 0-10. Mass% is particularly preferred.

  Moreover, the increase rate (times) of the deterioration soluble part in the deterioration acceleration test of the particulate water-absorbing agent of the present invention is 1.0 to 4.0, preferably 1.0 to 3.5, 1.0 to 3.0 is more preferable, 1.0 to 2.5 is more preferable, and 1.0 to 2.0 is particularly preferable.

  By setting the amount of increase (%) and rate of increase (times) within the above range, the water-absorbing performance as designed can be maintained even in an environment where the particulate water-absorbing agent can be deteriorated. For example, even when the particulate water-absorbing agent is used as a paper diaper for a long time, the absorption performance of the paper diaper is not lowered, and troubles such as urine leakage and rough skin can be reduced. On the other hand, when the increase amount and the rate of increase of the deteriorated soluble component are out of the above ranges, the water absorption performance deteriorates over time in an environment where the particulate water absorbent may be deteriorated. When used for a long time, the absorption performance of paper diapers is lowered, and troubles such as urine leakage and rough skin are increased.

  The method for adjusting the amount of increase (%) and the rate of increase (times) of the above-described soluble component is adjusted by appropriately setting the one-hour soluble component or the amount of use (addition amount) of the internal crosslinking agent and / or chelating agent. can do. If the amount of the internal cross-linking agent is large, the amount of the chelating agent needs to be decreased. Conversely, if the amount of the internal cross-linking agent is small, the amount of the chelating agent needs to be increased. Similarly, it is necessary to reduce the amount of chelating agent when the amount of soluble component for one hour is large, and conversely, when the amount of soluble component for one hour is small, the amount of chelating agent must be increased.

(3-9) Absorption capacity without pressure (CRC)
The water absorption capacity without load (CRC) of the particulate water-absorbing agent according to the present invention is preferably 10 [g / g] or more, more preferably 15 [g / g] or more, and further preferably 25 [g / g] or more. 28 [g / g] or more is even more preferable, 30 [g / g] or more is particularly preferable, and 33 [g / g] or more is most preferable. The upper limit is not particularly limited, but is preferably 60 [g / g] or less, more preferably 55 [g / g] or less, further preferably 50 [g / g] or less, and 45 [g / g] or less. Is particularly preferred. CRC can be defined by the method described later in (5-1), and can be appropriately adjusted by the amount of the crosslinking agent and the ratio of surface crosslinking during the polymerization described in (2-1).

  The upper and lower limits of the CRC can be appropriately selected within this range. For example, 10 to 60 [g / g], further 15 to 50 [g / g], particularly 25 (28, 30, 33) to 45 [g / g]. ] Is controlled within the range. When the CRC is less than 10 [g / g], the amount of water absorption is small when used in the absorbent body, and it is not suitable for the use of sanitary materials such as paper diapers. On the other hand, when the CRC exceeds 60 [g / g], there is a possibility that a particulate water-absorbing agent having an excellent liquid uptake rate into the absorber cannot be obtained.

(3-10) Absorption capacity under pressure (AAP)
In the particulate water-absorbing agent according to the present invention, a significant reduction in physical properties (due to damage, re-humidification, etc.) is suppressed by the addition of a long-chain alkyl compound or an organic polysiloxane, so that a high water absorption capacity under pressure is obtained.

  The water absorption capacity (AAP) under pressure of the particulate water-absorbing agent according to the present invention is preferably 12 [g / g] or more, more preferably 15 [g / g] or more under a pressure (under load) of 2.06 kPa. 20 [g / g] or more is more preferable, 25 [g / g] or more is particularly preferable, and 28 [g / g] or more is most preferable. The upper limit is not particularly limited, but is preferably 50 [g / g] or less, and more preferably 40 [g / g] or less from the viewpoint of ease of production and balance with other physical properties. When the AAP is less than 12 [g / g], when a particulate water-absorbing agent is used for the absorber, the return amount of the liquid when the pressure is applied to the absorber (referred to as Re-Wet) is small. Absorber may not be obtained.

  AAP can be defined by the method described later in (5-2), and can be appropriately adjusted by the ratio of surface cross-linking described in (2-1-5) above.

(3-11) Soluble content The 1 hour soluble content of the particulate water-absorbing agent according to the present invention is preferably 25% by mass or less, more preferably 23% by mass or less, still more preferably 20% by mass or less, and 18% by mass. The following is particularly preferable, and 15% by mass or less is most preferable. The lower limit is 0% by mass. If the 1-hour soluble component exceeds 25% by mass, the liquid take-up rate will be slow or the water absorption rate will be reduced when used in an absorber. It is not preferable. The soluble component can be defined by the method described later in (5-6), and can be appropriately adjusted by the amount of the crosslinking agent and the ratio of surface crosslinking during the polymerization described in (2-1).

(3-12) Other components contained in particulate water-absorbing agent The particulate water-absorbing agent of the present invention comprises the above-described components (water-absorbing resin, long-chain alkyl compound or organic polysiloxane, surfactant, preferably further a chelating agent. In addition to water and water), insoluble inorganic fine particles, polyvalent metal salts, inorganic reducing agents, and the like may be included to impart various performances. Among these, addition of an inorganic reducing agent can suppress the coloring and deterioration of the particulate water-absorbing agent over time at a higher level.

  The inorganic reducing agent refers to a compound having a reducing inorganic element. Specifically, it is a compound having a reducing sulfur atom or phosphorus atom, and the compound corresponds to an inorganic compound or an organic compound. The inorganic reducing agent may be acid type or salt type, but is preferably salt type, more preferably monovalent or polyvalent metal salt, and more preferably monovalent salt. Among these inorganic reducing agents, an oxygen-containing reducing inorganic compound, that is, an inorganic reducing agent in which sulfur or phosphorus is combined with oxygen is preferable, and an oxygen-containing reducing inorganic salt is more preferable.

  The addition amount of the insoluble inorganic fine particles, the polyvalent metal salt, or the inorganic reducing agent depends on the combination with various components contained in the particulate water-absorbing agent, but is 0 to 6 mass with respect to 100 parts by mass of the water-absorbing resin. Part may be sufficient, 0.001-5 mass parts is more preferable, 0.01-3 mass parts is especially preferable, and 0.01-1 mass part is the most preferable. When the addition amount is out of the above range, it is difficult to prevent a decrease in water absorption performance when receiving damage, which is not preferable.

  The mixing operation of the water absorbent resin and the insoluble inorganic fine particles, the polyvalent metal salt, or the inorganic reducing agent is not particularly limited, and may be performed simultaneously with the addition or separately as described above. Moreover, about the addition method, what is called wet mixing method etc. which suspend and add in water etc. may be employ | adopted, and the dry blend method of mixing powders may be employ | adopted.

[4] Absorber, Absorbent Article The particulate water-absorbing agent of the present invention is used for various purposes for the purpose of water absorption, and particularly used for processing into a sheet or tape. Processing of the particulate water-absorbing agent is performed by means of compression, suction, adhesion, etc., using another base material or adhesive as necessary. Specifically, the particulate water-absorbing agent is preferably processed to have a thickness (Z-axis direction) of 5 mm or less, and further about 0.1 to 4 mm and 0.3 to 3 mm. The direction and the planar shape are appropriately selected according to the purpose. For example, the area is 10 cm ^{2 to} 100 m ² and the length is about 1 cm to 1000 m. Furthermore, after processing into a sheet form and a tape form, you may cut | judge at the time of use. The absorbent body of the present invention processed into a sheet form or a tape form can be used as an absorbent article (final consumer goods) such as water-stopping rubber, water-stopping tape, kitchen sheet, pet sheet, hemostatic sheet, paper diaper and napkin. Can be used. Further, since the particulate water-absorbing agent of the present invention is excellent in impact resistance and hygroscopic fluidity, when used in an absorbent body or absorbent article, trouble reduction in the manufacturing process of the absorbent article and improvement of the working environment can be achieved. In addition, the reduction in water absorption performance due to damage can be suppressed, and the original performance of the particulate water absorbing agent can be sufficiently exhibited in an absorbent article or the like.

  In addition, the particulate water-absorbing agent of the present invention has high water absorption performance (CRC, AAP, etc.), excellent color tone with time, and excellent urine resistance as evaluated by the rate of increase in degraded soluble content. Therefore, since coloring with time and deterioration of water absorption performance of absorbent articles and the like can be suppressed, problems such as liquid (urine) leakage and rough skin do not occur even after processing into a sheet or tape.

  The absorbent body and absorbent article of the present invention comprise the particulate water-absorbing agent of the present invention, and the “absorber” referred to here is an absorption molded mainly with the particulate water-absorbing agent and hydrophilic fibers. Say the material.

  The present invention provides an absorbent body, particularly a sheet-like absorbent body, which is molded to contain 20 to 100% by weight of a particulate water-absorbing agent and 80 to 0% by weight of hydrophilic fibers. The absorber means a structure substantially consisting of a hydrophilic or water-absorbing material capable of absorbing liquid (particularly 90 to 100% by mass), and the content of the particulate water-absorbing agent in the absorber. (Core concentration; content with respect to the total mass of the particulate water-absorbing agent and the hydrophilic fiber) is preferably 20 to 100% by mass, more preferably 25 to 90% by mass, further preferably 30 to 80% by mass, and 40 to 80%. Mass% is most preferred. The higher the content, the more easily the water absorption performance of the absorbent body or absorbent article is affected by the water absorption performance of the particulate water absorbing agent.

  Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. The technical contents shown in each embodiment can be used in appropriate combination with the technical contents shown in another embodiment.

  All electric devices used in the examples and comparative examples are used under the conditions of 100 V and 60 Hz. Unless otherwise specified, each of the electric devices is used under the conditions of room temperature (25 ° C. ± 2 ° C.) and relative humidity of 50% RH. Physical properties were measured.

  In addition, each physical property of the particulate water-absorbing agent of the present invention is defined by each evaluation method shown below. For convenience, “mass%” may be described as “wt%” and “liter” as “L”. Furthermore, in this specification, “0.90 mass% sodium chloride aqueous solution” may be referred to as “physiological saline”, but both are treated as the same. Furthermore, in the following (5-1) to (5-11), for convenience, it is described as “particulate water absorbent”, but when measuring about “water absorbent resin powder” or “water absorbent resin particles” or the like, “Particulate water-absorbing agent” is read as “water-absorbing resin powder” or “water-absorbing resin particles”.

(5-1) Absorption capacity without pressure (CRC)
The measurement of water absorption capacity without load (CRC) of the particulate water-absorbing agent according to the present invention was performed according to ERT441.2-02.

  Specifically, 0.200 g (weight W0 [g]) of the particulate water-absorbing agent was uniformly put in a non-woven bag (85 mm × 60 mm) and heat-sealed, and then the temperature was adjusted to 25 ± 3 ° C., and the temperature was excessively large (usually 500 ml). Was immersed in an aqueous 0.9 mass% sodium chloride solution. After 30 minutes, the bag was pulled up and drained using a centrifuge (Centrifuge manufactured by Kokusan Co., Ltd .: Model H-122) under conditions of 250 G for 3 minutes. Then, the mass (W1 [g]) of the bag was measured.

  The same operation was performed without adding the particulate water-absorbing agent, and the mass (W2 [g]) of the bag at that time was measured. From the obtained W0 [g], W1 [g] and W2 [g], the water absorption capacity (CRC) under no pressure was calculated according to the following formula 1.

(Formula 1) CRC [g / g] = {(W1-W2) / W0} -1
(5-2) Absorption capacity under pressure (AAP)
The water absorption capacity under load (AAP) of the particulate water-absorbing agent according to the present invention was measured according to ERT442.2-02.

  That is, 0.9 g (mass W3 [g]) of the particulate water-absorbing agent was put into a measuring device (see FIG. 2), and the mass (W4 [g]) of the measuring device set was measured. Next, a 0.90 mass% sodium chloride aqueous solution was absorbed into the particulate water-absorbing agent under a pressure of 2.06 kPa to 4.83 kPa. After 1 hour, the mass (W5 [g]) of the measuring device set was measured. From the obtained W3 [g], W4 [g] and W5 [g], the absorption capacity under load (AAP) was calculated according to the following formula 2.

(Formula 2) AAP [g / g] = (W5-W4) / W3
In the measuring apparatus shown in FIG. 2, a glass filter 106 (manufactured by Mutsura Chemical Glass Co., Ltd., pore diameter 100 to 120 μm) 106, filter paper 107, and plastic support cylinder 100 having an inner diameter of 60 mm are placed in this order in a Petri dish 105. A stainless steel 400 mesh wire net 101, a piston 103, and a weight 104 for applying a load are inserted into the support cylinder 100. Then, a particulate water-absorbing agent is put on the wire net 101, and after placing the piston 103 and the weight 104 on the particulate water-absorbing agent, 0.90% by mass (or 20% by mass) sodium chloride is placed on the Petri dish 105. The measurement is started by putting the aqueous solution 108 so that the filter paper 107 is not immersed. That is, the measurement is continued for one hour after the 0.90 mass% (or 20 mass%) sodium chloride aqueous solution 108 sucked up by the glass filter 106 wets the filter paper 107. During the measurement, the particulate water-absorbing agent absorbs 0.90% by mass (or 20% by mass) of the sodium chloride aqueous solution 108 to become the swollen gel 102, and pushes up the piston 103 and the weight 104. Therefore, during the measurement, the swelling gel 102 (particulate water absorbing agent) is always loaded with the piston 103 and the weight 104, and 0.90% by mass (or 20%) under a pressure of 2.06 kPa to 4.83 kPa. Mass%) sodium chloride aqueous solution 108 is absorbed.

(5-3) 20% by mass saline vertical absorption index The measurement of the 20% by mass saline vertical absorption index of the particulate water-absorbing agent according to the present invention is under the load of 2.06 kPa described in (5-2) above. The measurement was performed by partially changing the water absorption ratio (AAP) measurement conditions.

  That is, the amount of the particulate water-absorbing agent used is 0.9 g to 1.0 g, the inner diameter of the support cylinder 100 of the measuring device is 60 mm to 25.4 mm, and the concentration of the sodium chloride aqueous solution is 0.9 mass% to 20 mass. %, The absorption time (AAP) under a load of 2.06 kPa was measured by changing the absorption time from 1 hour to 30 minutes. In addition, by changing the inner diameter of the support cylinder 100 to 25.4 mm, the basis weight (amount of water absorbing agent per unit area) was increased by about 6.2 times.

(5-4) Mass average particle diameter (D50) and logarithmic standard deviation of particle size distribution (σζ)
The measurement of the mass average particle diameter (D50) and the logarithmic standard deviation (σζ) of the particle size distribution of the particulate water-absorbing agent according to the present invention was performed according to the measurement method disclosed in European Patent 0349240.

  That is, using a sieve corresponding to a JIS standard sieve (JIS Z8801-1 (2000)) having an opening of 850 μm, 710 μm, 600 μm, 500 μm, 420 μm, 300 μm, 212 μm, 150 μm, 106 μm, 45 μm, or JIS standard sieve, 10 g of the particulate water-absorbing agent was classified. After classification, the mass of each sieve was measured, and the residual percentage R of each particle size was plotted on logarithmic probability paper. And the particle diameter corresponding to R = 50 mass% was read as a mass average particle diameter (D50). The logarithmic standard deviation (σζ) of the particle size distribution was calculated according to the following formula 3.

(Expression 3) σζ = 0.5 × ln (X2 / X1)
Here, X1 indicates a particle diameter corresponding to R = 84.1% by mass, and X2 indicates a particle diameter corresponding to R = 15.9% by mass. Note that the smaller the value of σζ, the narrower the particle size distribution.

(5-5) Moisture content The moisture content of the particulate water-absorbing agent according to the present invention was measured according to ERT430.2-02 (however, only the sample mass and the drying temperature were changed).

  That is, after measuring 1.000 g (mass W6 [g]) of the particulate water-absorbing agent in an aluminum cup (mass W7 [g]) having a bottom diameter of 5 cm, it is left standing in a windless dryer at 180 ° C. Dried. After 3 hours, the total mass (W8 [g]) of the sample was measured, and the water content was calculated according to the following formula 4.

(Formula 4) Moisture content [mass%] = [{W6- (W8-W7)} / W6] × 100
(5-6) 1-hour soluble component The “1-hour soluble component” in the present invention is an Ext (water soluble component) measurement method defined in ERT470.2-02, and the extraction time is changed to 1 hour. It refers to the water-soluble matter obtained as described above.

  That is, 200.0 g of 0.90 mass% sodium chloride aqueous solution was weighed out into a plastic container with an inner lid and an outer lid having a capacity of 250 ml containing a 35 mm-long rotor, and then 1.00 g of the particulate water-absorbing agent was added to the above. It was added to the aqueous solution and sealed with an inner lid and an outer lid. Then, it stirred at room temperature for 1 hour using the stirrer (rotation speed about 500 rpm). By the above operation, the water-soluble component of the particulate water-absorbing agent was extracted.

  After stirring, the extract, which is the above aqueous solution, was filtered using a filter paper (manufactured by ADVANTEC Toyo Co., Ltd .; product name: JIS P 3801 No.2 / thickness 0.26 mm, reserved particle diameter 5 μm), and obtained. The filtrate 50.0 g was used as a measurement liquid. Subsequently, after titrating the said measuring liquid with 0.1N-NaOH aqueous solution until it became pH10, it titrated with 0.1N-HCl aqueous solution until it became pH2.7. The titer at this time was determined as [NaOH] ml and [HCl] ml.

  Further, the same operation was performed using only 200.0 g of a 0.90 mass% sodium chloride aqueous solution without adding a particulate water-absorbing agent, and the empty titration amounts ([b1NaOH] ml and [b1HCl] ml) were obtained.

  From the above titration amount and monomer average molecular weight, the soluble component for 1 hour was calculated according to the following formula 5.

(Formula 5) 1 hour soluble content [% by mass] = 0.1 × (monomer average molecular weight) × 200 × 100 × ([HCl] − [b1HCl]) / 1000 / 1.0 / 50.0
In addition, when the monomer average molecular weight was unknown, the monomer average molecular weight was calculated using the neutralization rate calculated according to the following formula 6.

(Formula 6) Neutralization rate [mol%] = {1-([NaOH]-[b1NaOH]) / ([HCl]-[b1HCl])} × 100
(5-7) Degradable soluble matter (degradation acceleration test, increase amount of degradable soluble component, rate of increase of degradable soluble component)
The “degradable soluble component” in the present invention is an Ext (water soluble component) measuring method defined by ERT470.2-02, and a 0.90 mass% sodium chloride aqueous solution is replaced with a 0.90 mass% sodium chloride aqueous solution. It is changed to an aqueous solution (deterioration test solution) in which L-ascorbic acid is mixed, and the water-soluble component when stirred for 1 hour after standing at 60 ° C. for 2 hours. This test is called “degradation acceleration test”, and the difference between the obtained degradation soluble component and the one-hour soluble component calculated in (5-6) above is defined as “increase amount of degradation soluble component”. The ratio between the soluble content and the 1-hour soluble content calculated in (5-6) above is referred to as “increase rate of the deteriorated soluble content”.

  That is, an aqueous solution (deterioration test solution) containing 0.05% by mass of L-ascorbic acid and 0.90% by mass of sodium chloride in a plastic container with an inner lid and an outer lid with a capacity of 250 ml containing a 35 mm long rotor. / L-ascorbic acid 0.10 g and a 0.90 mass% sodium chloride aqueous solution 199.90 g) 200.0 g was weighed, and then particulate water-absorbing agent 1.00 g was added to the above aqueous solution. The cap was sealed with an outer lid. Then, it left still for 2 hours to the thermostat adjusted to 60 +/- 2 degreeC. After the elapse of 2 hours, the container was taken out from the thermostat and stirred at room temperature for 1 hour using a stirrer (rotation speed: about 500 rpm). By the above operation, the water-soluble component of the particulate water-absorbing agent was extracted.

  After stirring, the extract, which is the above aqueous solution, was filtered using a filter paper (manufactured by ADVANTEC Toyo Co., Ltd .; product name: JIS P 3801 No.2 / thickness 0.26 mm, reserved particle diameter 5 μm), and obtained. The filtrate 50.0 g was used as a measurement liquid. Subsequently, after titrating the said measuring liquid with 0.1N-NaOH aqueous solution until it became pH10, it titrated with 0.1N-HCl aqueous solution until it became pH2.7. The titer at this time was determined as [NaOH] ml and [HCl] ml.

  Further, the same operation was carried out using only 200.0 g of the deterioration test solution without adding the particulate water-absorbing agent, and empty droplet quantification ([b2NaOH] ml and [b2HCl] ml) was determined.

  From the above titration amount and monomer average molecular weight, the degradation soluble component was calculated according to the following formula 7.

(Formula 7) Degradable soluble content [% by mass] = 0.1 × monomer average molecular weight × 200 × 100 × ([HCl]-[b2HCl]) / 1000 / 1.0 / 50.0
In addition, when the monomer average molecular weight was unknown, the monomer average molecular weight was calculated using the neutralization rate calculated in the above (5-6).

  Further, the increase amount of the deteriorated soluble component was calculated according to the following equation 8, and the increase rate of the deteriorated soluble component was calculated according to the following equation 9.

(Formula 8) Increase amount of deterioration soluble part [mass%] = (deterioration soluble part)-(one hour soluble part)
(Formula 9) Increase rate of deteriorated soluble component [-] = (degradable soluble component) / (1 hour soluble component)
(5-8) Dusting rate
The “powdering rate” in the present invention refers to a physical property value for evaluating the amount of fine powder generated when a particulate water-absorbing agent is used, and can be determined by the following method.

  That is, the particle size distribution of the particulate water-absorbing agent was measured according to the method described in (5-4) above, and the content of particles having a particle size of less than 150 μm was determined according to the following formula 10.

(Formula 10) Particle content of less than 150 μm particle size [mass%] = (mass of particles less than 150 μm particle size) / (mass of water-absorbing resin or particulate water-absorbing agent)
Separately from this, in the P / S test (impact test) specified in (5-10) below, the same operation was performed except that the shaking time was changed from 30 minutes to 60 minutes, causing damage. A particulate water-absorbing agent was obtained. And about the obtained particulate water-absorbing agent, the particle size distribution was measured according to the method as described in said (5-4), and the particle content rate with a particle size of less than 150 micrometers was calculated | required according to the said formula. Subsequently, according to the following Formula 11, the powdering rate of the particulate water-absorbing agent was determined.

(Formula 11) Pulverization rate [% by mass] = (Particle content less than 150 μm particle size after P / S test) − (Particle content less than 150 μm particle size before P / S test)
The lower the value of the powdering rate, the better the particulate water-absorbing agent is in impact resistance stability.

(5-9) Hygroscopic fluidity after impact test (Hygroscopic blocking rate / 60 minutes value)
“Hygroscopic fluidity” in the present invention is an abbreviation for “powder fluidity after moisture absorption” after the impact test. After the impact test (shaking for 10 minutes), the particulate water-absorbing agent is heated to a temperature of 25 ° C. and a relative humidity. The physical property value evaluated for fluidity as blocking, caking, or powder when left under the condition of 90% RH, and judged by “moisture absorption blocking rate”.

  In the present invention, assuming a process damage when processed into an absorbent article, in the P / S test (impact test) defined in the following (5-10), the shaking time is from 30 minutes. Except for changing to 10 minutes, the same operation was performed, and the moisture absorption blocking rate was measured by the following procedure for the particulate water-absorbing agent damaged by the P / S test (shaking for 10 minutes).

  That is, about 2 g of a particulate water-absorbing agent is uniformly sprayed on an aluminum cup having a diameter of 52 mm, and then a thermo-hygrostat (manufactured by Tabay Espec Co., Ltd .; PLATINOUS LUCIFER PL) adjusted to a temperature of 25 ° C. and a relative humidity of 90 ± 5% RH. -2G) for 1 hour (60 minutes).

  Thereafter, the particulate water-absorbing agent in the aluminum cup was gently transferred onto a JIS standard sieve (The IIDA TESTING SIEVE / inner diameter 80 mm) having an opening of 2000 μm (8.6 mesh), and a low-tap type sieve shaker (Iida Co., Ltd.). Using an ES-65 type sieve shaker / rotational speed of 230 rpm and impact number of 130 rpm, classification was performed for 5 seconds under conditions of a temperature of 20 to 25 ° C. and a relative humidity of 50% RH.

  Next, the mass of the particulate water-absorbing agent (mass W9 [g]) remaining on the JIS standard sieve and the particulate water-absorbing agent (mass W10 [g]) that passed through the JIS standard sieve was measured. Hygroscopic fluidity (moisture absorption blocking rate) was calculated.

(Formula 12) Moisture absorption blocking rate [mass%] = {W9 / (W9 + W10)} × 100
The moisture absorption blocking rate indicates that the lower the value (closer to 0%), the better the particulate water-absorbing agent is in the moisture absorption fluidity.

(5-10) Paint shaker test (P / S test (shaking for 30 minutes))
The “paint shaker test (P / S test)” in the present invention refers to a test in which the particulate water-absorbing agent is subjected to process damage equivalent to actual equipment (corresponding to process damage received in an actual manufacturing plant). This is a test that reproduces the energy equivalent to the energy actually received by the particulate water-absorbing agent by pneumatic transportation at the laboratory scale.

  That is, a glass container having a diameter of 6 cm, a height of 11 cm, and an internal volume of 225 ml (preferably, a mayonnaise bottle manufactured by Yamamura Glass Co., Ltd., trade name: A-29 or equivalent), 30 g of a particulate water-absorbing agent and a glass having a diameter of 6 mm. 10 g of beads (soda-lime glass beads for precision fraction filling) are put in, and after the resinous inner lid (material: polyethylene) and outer lid (material: polypropylene) for the container, paint shaker (Toyo Seisakusho) Product No. 488) and shaken at 800 [cycle / min] (CPM) for 30 minutes. Thereafter, the glass beads were removed with a JIS standard sieve having an opening of 2 mm to obtain a damaged particulate water-absorbing agent. For the paint shaker device (P / S tester), glass container, and other conditions, reference can be made to JP-A-9-235378 (specifications and FIGS. 12 to 15).

(5-11) Surface Tension 50 ml of physiological saline adjusted to 23 to 25 ° C. is put in a 100 ml beaker that has been thoroughly washed. First, the surface tension of the physiological saline is measured with a surface tension meter (K11 automatic surface Tensiometer, KR USS). In this measurement, the surface tension value must be in the range of 71 to 75 mN / m 2. Next, a well-washed 25 mm long fluororesin rotor and 0.5 g of a water-absorbing agent were put into a beaker containing physiological saline after surface tension measurement adjusted to 23 to 25 ° C., and 500 r. p. m. The mixture was stirred for 4 minutes under the following conditions. After 4 minutes, the stirring was stopped and the water-absorbing water-containing agent settled, and then the surface tension of the supernatant was measured again by the same operation. In the present invention, a plate method using a platinum plate was adopted, and the plate was thoroughly washed before each measurement and heated and washed with a burner.

(5-12) Evaluation test with water-absorbing sheet Using the particulate water-absorbing agent 8.4 [g] and the wood pulverized pulp 12.6 [g] obtained in this example, 12 cm × 38 cm, thickness of about 5 mm An absorbent sheet (core concentration: 40% by mass) was prepared. Next, the absorbent sheet was spread on a flat surface, and a resin cylinder (inner diameter 25 mm, internal volume 60.3 [g / cm ² ]) was placed in the center of the sheet. Subsequently, 60 ml of a 0.9% by mass aqueous sodium chloride solution was quickly poured into the cylinder, and the time [second] from when the liquid was poured into the cylinder until the liquid in the cylinder was absorbed and disappeared was measured. Then, 60 ml of 0.9 mass% sodium chloride aqueous solution was injected three times in total, and each absorption amount (absorption amount per minute) was calculated according to the following formula 13.

(Equation 13) Absorption amount [g] = {60 [g] / (Time until the liquid in the cylinder disappears) [second]} × 60 [second]
[Production example]
Polyethylene glycol diacrylate (molecular weight 523) 2.28 g (0.02 mol%: monomer) was dissolved in 5500 g (monomer concentration 35 mass%) of an aqueous sodium acrylate solution having a neutralization rate of 75 mol%. After obtaining the monomer aqueous solution (a), it was deaerated under a nitrogen gas atmosphere for 30 minutes.

  Next, the monomer aqueous solution (a) is charged into a reactor formed by attaching a lid to a double-arm jacketed stainless steel kneader having two sigma type blades with an internal volume of 10 L, and the liquid temperature is set to 30. Nitrogen gas was blown into the reactor while maintaining the temperature, and nitrogen gas substitution was performed so that dissolved oxygen in the system (monomer aqueous solution (a)) became 1 ppm or less.

  Subsequently, 24.6 g of a 10% by mass sodium persulfate aqueous solution and 21.8 g of a 0.2% by mass L-ascorbic acid aqueous solution were added separately while stirring the monomer aqueous solution (a). Polymerization started about 1 minute after the addition was completed. Then, the resulting hydrogel crosslinked polymer (a) was polymerized at 30 to 90 ° C. while pulverizing, and the hydrogel crosslinked polymer (a) was taken out from the reactor after 60 minutes from the start of polymerization. The obtained hydrogel crosslinked polymer (a) had a diameter of about 5 mm.

  The finely divided hydrogel crosslinked polymer (a) is spread on a wire mesh having an opening of 300 μm (50 mesh), dried with hot air at 180 ° C. for 45 minutes, pulverized with a roll mill, and further opened. Classification was carried out with 850 μm and 150 μm JIS standard sieves. By this series of operations, a water absorbent resin powder (a) having a particle size of 150 μm or more and less than 850 μm was obtained. The CRC of the water absorbent resin powder (a) (absorption capacity under no pressure) was 53.0 [g / g].

  Next, the surface treatment agent comprising 0.02 parts by mass of ethylene glycol diglycidyl ether, 1.5 parts by mass of propylene glycol and 3.0 parts by mass of water is uniformly applied to 100 parts by mass of the water absorbent resin powder (a). And heated at 100 ° C. for 45 minutes. Thereafter, a paint shaker test (shaking for 30 minutes) was performed, and the particles were sized as a passing product of a JIS standard sieve having an opening of 850 μm, thereby obtaining water-absorbent resin particles (A) having a crosslinked surface.

[Example 1]
_{CH 3 -Si (CH 3) 2} -O- [Si _{(CH 3)} 2 -O] _m - _{[Si (CH 3) (R)} -O- ] _n -Si _{(CH 3)} 3
_{R = (C 2 H 4 O} ) a (C3H6O) b -NH 2
(HLB = 10, viscosity = 4000 mm2 / s)
A reactive surfactant (X) consisting of

  0.5 parts by mass of a mixed solution of 0.05 part by mass of reactive surfactant (X) and 0.45 part by mass of 2-propanol with respect to 100 parts by mass of water-absorbing resin particles (A) obtained from the above production example Then, an aqueous solution of 0.04 parts by mass of ethylenediaminetetra (methylenephosphonic acid) pentasodium (hereinafter abbreviated as “EDTMP · 5Na”) and 6.66 parts by mass of water was stirred. And added for 1 minute. After that, the product was transferred to a bag with a zipper, manufactured by Nihon-Pakku Co., Ltd. (Unipack (registered trademark)), sealed, cured at 80 ° C. for 1 hour, and then cured until it passed through a JIS standard sieve having an opening of 850 μm. Was crushed to obtain a particulate water-absorbing agent (1). Table 1 shows various performances of the obtained particulate water-absorbing agent (1).

[Comparative Example 1]
The following comparative particulate water-absorbing agent was prepared according to Example 1 of unpublished prior patent application 28 (PCT / JP2012 / 058515).
That is, zinc stearate aqueous dispersion (manufactured by ADEKA Chemical Supply Co., Ltd .; trade name EFCODISPER ZD (registered trademark) / solid content 42.5% by mass, including surfactant) 0.706 parts by mass and water 6.254 After mixing parts by mass, a dispersion (1) was prepared by adding 0.04 parts by mass of EDTMP · 5Na.

  Next, 7 parts by mass of the dispersion (1) (substantial addition amount: 0.3 parts by mass of zinc stearate, EDTMP · 5Na0) with respect to 100 parts by mass of the water-absorbent resin particles (A) obtained in the production example. 0.04 parts by mass and 6.66 parts by mass of water) were added with stirring and mixed for 1 minute. Then, after transferring to a bag with a chuck, sealing, and curing at 80 ° C. for 1 hour, the cured product was crushed until it passed through a JIS standard sieve having an opening of 850 μm to obtain water absorbent resin particles (B1). .

  Further, a surfactant aqueous solution (1) comprising 0.1 part by mass of polyoxyethylene alkyl ether (manufactured by Nippon Shokubai Co., Ltd .; Softanol 90 (registered trademark) / solid content of 100% by mass) and 2.0 parts by mass of water was prepared. did. Then, 2.1 parts by mass of the surfactant aqueous solution (1) was added to 100 parts by mass of the water-absorbent resin particles (B1) with stirring, and mixed for 1 minute. After that, it was transferred to a bag with a chuck (produced by Nihon Co., Ltd .; Unipack (registered trademark)), sealed, cured at 80 ° C. for 1 hour, and then cured until it passed through a JIS standard sieve having an opening of 850 μm. The product was crushed (sized) to obtain a comparative particulate water-absorbing agent (1). Table 1 shows various performances of the obtained comparative particulate water-absorbing agent (1).

[Comparative Example 2]
A method corresponding to Comparative Example 2 of the unpublished prior application Patent Document 28 (PCT / JP2012 / 0585515) is shown below.

  That is, except that the surfactant aqueous solution was not added to Comparative Example 1, the same operation as in Comparative Example 1 was performed to obtain a comparative particulate water-absorbing agent (2). Table 1 shows various performances of the obtained comparative particulate water-absorbing agent (2).

[Comparative Example 3]
A method corresponding to Example 1 described in Japanese Patent No. 3169133 is shown below. That is, a mixed solution (3) of 0.5 parts by mass of amino-modified silicone (manufactured by Shin-Etsu Chemical Co., Ltd .; KF-888) and 4.5 parts by mass of methanol was prepared. Next, 5.0 parts by mass of the above mixed solution (3) is added to 100 parts by mass of the water-absorbent resin particles (A) obtained from the above production example with stirring, and then mixed for 1 minute. For 20 minutes. Thereafter, the mixture was pulverized until it passed through a JIS standard sieve having an opening of 850 μm to obtain a particulate water-absorbing agent (3). Table 1 shows various performances of the obtained particulate water-absorbing agent (3).

[Example 2]
Using the particulate water-absorbing agent (1) obtained in Example 1, the evaluation test using the water-absorbing sheet described in the above (5-12) was performed. The results are shown in Table 2.

[Comparative Example 4]
Using the comparative particulate water-absorbing agent (1) obtained in Comparative Example 1, the evaluation test using the water-absorbing sheet described in the above (5-12) was performed. The results are shown in Table 2.

(Summary) Tables 1 and 2
As shown in Table 1, the comparative particulate water-absorbing agent (1) of Comparative Example 1 corresponding to Example 1 of the unpublished prior patent application 28 (PCT / JP2012 / 0585515) is excellent in hygroscopic fluidity. Although the mass% saline vertical absorption index is high, the surface tension is significantly reduced.

  On the other hand, as shown in Table 1, the particulate water-absorbing agent (1) according to Example 1 (addition of modified silicone) of the present invention (1) excellent in hygroscopic fluidity and high 20% by mass saline vertical absorption index. In addition, it can be seen that the decrease in surface tension is slight. That is, it can be seen that an excellent particulate absorbent can be obtained by the production method of the present invention.

  Moreover, from Table 2, the particulate water-absorbing agent of the present invention (Example 1) has a further excellent performance in the water-absorbing sheet because the surface tension is slightly lower than that of the comparative particulate water-absorbing agent (1). I found out.

  The method for producing a particulate water-absorbing agent according to the present invention is suitable for producing a particulate water-absorbing agent mainly composed of a water-absorbing resin having high physical properties. The particulate water-absorbing agent according to the present invention is not limited to sanitary materials, but is used for various applications such as civil engineering / architectural water-stopping materials, warmers for cairo, and water-stopping materials for cables. The particulate water-absorbing agent according to the present invention is particularly preferably used for sheet-like or tape-like applications, and can be widely used in various industries.

DESCRIPTION OF SYMBOLS 100 Support cylinder 101 Wire net 102 Swelling gel 103 Piston 104 Weight 105 Petri dish 106 Glass filter 107 Filter paper 108 0.90 mass% (or 20 mass%) Sodium chloride aqueous solution

Claims (47)

Reactive surfactant comprising a particulate water-absorbing agent composed mainly of a polyacrylic acid (salt) water-absorbing resin containing a surfactant, wherein the surfactant activator has a function other than a hydroxyl group capable of reacting with a carboxyl group A water-absorbing agent, wherein the surface tension of the water-absorbing agent is 55 to 73 mN / m and the 20 mass% saline vertical absorption index is 1.5 to 10.0 [g / g].
However, the surface tension is defined by the surface tension of the water-absorbing agent dispersion in physiological saline. The vertical absorption index is an absorptivity with respect to 20% by mass of 1.0 g of a water-absorbing agent having an inner diameter of 25.4 mm under pressure of 2.06 kPa.   The water absorbing agent according to claim 1, wherein the reactive surfactant has an HLB of 7-12.   A particulate water-absorbing agent mainly comprising a polyacrylic acid (salt) -based water-absorbing resin containing a surfactant, wherein the surfactant activator contains a functional group other than a hydroxyl group capable of reacting with a carboxyl group = 7 to A water-absorbing agent which is a reactive surfactant of No. 12 and has an absorption capacity of 20 g / g or more under pressure of the water-absorbent resin.   The water-absorbing agent according to any one of claims 1 to 3, wherein the reactive surfactant has an amino group and / or an epoxy group as a functional group.   The water absorbing agent according to any one of claims 1 to 4, wherein the reactive surfactant has two or more functional groups in the molecule.   The water absorbing agent according to any one of claims 1 to 5, wherein the reactive surfactant is a polymer.   A particulate water-absorbing agent mainly comprising a polyacrylic acid (salt) -based water-absorbing resin containing a surfactant, wherein the surfactant contains an amino group as a functional group, and the neutralization rate of the water-absorbing resin is 69 mol% or less Is a water-absorbing agent.   The water absorbing agent according to any one of claims 1 to 7, wherein the reactive surfactant has a polyoxyalkylene unit.   The water absorbing agent according to any one of claims 1 to 8, wherein the reactive surfactant has a polysiloxane structure.   The water-absorbing agent according to any one of claims 1 to 9, wherein the reactive surfactant has another hydrophilic or hydrophobic functional group in addition to a functional group other than a hydroxyl group capable of reacting with a carboxyl group. The water absorbing agent according to claim 1, wherein the reactive surfactant has a viscosity of 10 to 20000 mm ² / s (25 ° C.).   The water absorbing agent according to any one of claims 1 to 11, wherein the reactive surfactant is 0.0001 to 2.0 mass% with respect to the polyacrylic acid (salt) water-absorbing resin.   The water absorbing agent according to claim 12, wherein the reactive surfactant is 0.001 to 0.2 mass%.   The water-absorbing agent according to any one of claims 1 to 13, wherein the water-absorbing resin is surface-crosslinked.   The water-absorbing agent according to claim 14, wherein the surface crosslinking is performed with a crosslinking agent or a monomer other than the reactive compound.   The water absorption capacity of the water-absorbing agent under pressure of 4.83 kPa (AAP) is 12 g / g or more and / or the water absorption capacity under pressure of 2.06 kPa (AAP) is 20 g / g or more. Water-absorbing agent according to item.   The water-absorbing agent according to any one of claims 1 to 16, further comprising a chelating agent in addition to the reactive surfactant.   The water-absorbing agent according to claim 17, wherein the content of the chelating agent is 0.001 to 5.0 mass% with respect to the polyacrylic acid (salt) -based water-absorbing resin.   The water-absorbing agent according to claim 17 or 18, wherein the chelating agent is a water-soluble organic compound having a nitrogen atom and / or a phosphorus atom.   The particulate water-absorbing agent according to claim 17 or 18, wherein the chelating agent is α-hydroxycarboxylic acid (salt).   The particulate water-absorbing agent according to any one of claims 1 to 20, further comprising a polyhydric alcohol in addition to the reactive surfactant.   The particulate water-absorbing agent according to any one of claims 1 to 21, wherein an increase in deterioration-soluble component in the deterioration acceleration test is 0 to 15% by mass.   The particulate water-absorbing agent according to any one of claims 1 to 22, wherein the water content is 1 to 20% by mass.   The particulate water-absorbing agent according to any one of claims 1 to 23, wherein a powdering rate in an impact test is 1.0 mass% or less.   The mass average particle diameter (D50) is 250 to 450 μm, the content of particles having a particle diameter of less than 150 μm is 0 to 5 mass%, and the logarithmic standard deviation (σζ) is 0 to 0.45. The water-absorbing agent according to any one of the above.   An absorbent body comprising 20 to 80% by mass of the particulate water-absorbing agent according to any one of claims 1 to 25 and 80 to 20% by mass of a hydrophilic fiber. A method for producing a particulate water-absorbing agent comprising a polyacrylic acid (salt) water-absorbing resin as a main component,
A particulate water-absorbing agent comprising a step of adding a reactive surfactant containing a functional group other than a hydroxyl group capable of reacting with a carboxyl group to a water-absorbing resin during or after surface crosslinking Production method.   The manufacturing method of Claim 27 whose HLB of a reactive surfactant is 7-12.   A method for producing a particulate water-absorbing agent comprising a polyacrylic acid (salt) -based water-absorbing resin as a main component, wherein the water-absorbing resin has an absorption capacity of 20 (g / g) or more under pressure of 2.06 kPa. A method for producing a particulate water-absorbing agent, comprising a step of adding a reactive surfactant having an HLB containing 7 to 12 containing a functional group other than a hydroxyl group capable of reacting with a group.   A method for producing a particulate water-absorbing agent comprising a polyacrylic acid (salt) -based water-absorbing resin as a main component, and a reactive surfactant having 7 to 12 HLB containing a functional group other than a hydroxyl group capable of reacting with a carboxyl group A method for producing a particulate water-absorbing agent, comprising a step of adding a surface, a surface cross-linking step until the absorption capacity under pressure is 20 (g / g) or more simultaneously with or before and after the adding step.   The production method according to any one of claims 27 to 31, wherein the reactive surfactant is a polymer.   The production method according to any one of claims 27 to 31, wherein the reactive surfactant has an amino group and / or an epoxy group as a functional group.   The production method according to any one of claims 27 to 32, wherein the reactive surfactant has two or more functional groups in the molecule.   The production method according to any one of claims 27 to 33, wherein the reactive surfactant has a polyoxyalkylene unit.   The production method according to any one of claims 27 to 34, wherein the reactive surfactant has a polysiloxane structure.   The production method according to any one of claims 27 to 35, wherein the reactive surfactant has another hydrophilic or hydrophobic functional group in addition to a functional group other than a hydroxyl group capable of reacting with a carboxyl group. The viscosity of the water-insoluble or sparingly water-soluble compound is ^{10~20000mm 2 / s (25 ℃)} , The method according to any one of claims 27 to 36.   The manufacturing method of any one of Claims 27-37 whose reactive surfactant is 0.0001-2.0 mass% with respect to polyacrylic acid (salt) type water absorbing resin.   28. Surface cross-linking of a water absorbing agent or a water absorbent resin to a water absorption capacity (AAP) under pressure of 4.83 kPa of 12 g / g or more and / or a water absorption capacity (AAP) of 2.06 kPa under pressure to 20 g / g or more. The manufacturing method of any one of -38.   The production method according to any one of claims 27 to 39, wherein a chelating agent is further mixed with the water-absorbent resin or its monomer in addition to the reactive surfactant.   The production method according to claim 40, wherein the content of the chelating agent is 0.001 to 5.0 mass% with respect to the polyacrylic acid (salt) -based water absorbent resin.   The production method according to claim 40 or 41, wherein the chelating agent is a water-soluble organic compound having a nitrogen atom and / or a phosphorus atom.   The production method according to claim 40 or 41, wherein the chelating agent is α-hydroxycarboxylic acid (salt).   44. The production method according to any one of claims 27 to 43, wherein in addition to the reactive surfactant, a polyhydric alcohol or a polyhydric alcohol derivative that becomes polyhydric alcohol by heating is further mixed.   The manufacturing method of any one of Claims 27-44 which mixes water so that it may become 1-20 mass% in addition to a reactive surfactant.   The manufacturing method of any one of Claims 27-45 which is further heat-processed after mixing a reactive surfactant.   The mass average particle diameter (D50) is 250 to 450 µm, the content of particles having a particle diameter of less than 150 µm is 0 to 5 mass%, and the logarithmic standard deviation (σζ) is 0 to 0.45. The manufacturing method of any one of Claims 1.

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