JP4422509B2 - Water-absorbent resin composition, use thereof and production method thereof - Google Patents

Description

The present invention relates to a water-absorbent resin composition used for sanitary materials such as disposable diapers and sanitary napkins, so-called incontinence pads , its use, and its production method.

For sanitary materials such as disposable diapers, sanitary napkins, and incontinence pads, absorbents comprising hydrophilic fibers such as pulp and water-absorbing resin are widely used for the purpose of absorbing body fluids.
In recent years, these sanitary materials have become highly functional and thin, and the amount of water-absorbing resin used per sanitary material and the ratio of water-absorbing resin to the entire absorbent body composed of water-absorbing resin and hydrophilic fibers have increased. Tend to. In other words, by reducing the number of hydrophilic fibers with a small bulk specific gravity, and using many water absorbent resins with excellent water absorption and a large bulk specific gravity, the ratio of the water absorbent resin in the absorbent body can be increased and the amount of water absorbed can be reduced. The sanitary material is made thinner.

However, a hygienic material having a low ratio of hydrophilic fibers and a high ratio of water-absorbing resin is preferable from the viewpoint of simply storing the liquid, but the liquid used in the actual use situation as a diaper or the like is preferable. When distribution and diffusion are considered, problems arise rather. For example, a large amount of water-absorbing resin becomes a soft gel by absorbing water, causing a phenomenon of gel blocking and dramatically reducing the diffusibility of the liquid in the sanitary material. In order to avoid such problems and maintain the absorption characteristics of the absorbent body, the ratio between the hydrophilic fiber and the water-absorbent resin is naturally limited, and the sanitary material is also made thinner.
As a means for obtaining a water-absorbing resin that suppresses gel blocking and has excellent liquid permeability and diffusibility, the following techniques for adding metal compounds (metal salts, metal cations, etc.) to the water-absorbing resin are known. Yes.

There is known a water-insoluble water-absorbent resin composition obtained by adding water containing a polyvalent metal salt and / or hydroxide to a water-absorbent resin (Patent Document 1).
A method for producing a water-absorbent resin is known in which a water-absorbent resin is treated with an aluminum compound capable of reacting with it in the presence of a polyhydric alcohol and water (Patent Document 2).
Known is a method for producing a water-absorbent resin in which a water-absorbent resin is treated with a cross-linking agent having two or more functional groups capable of reacting with the water-absorbent resin in the presence of a polyhydric alcohol and water. (Patent Document 3).
Water and / or an inorganic hydroxide in which an inorganic salt having a concentration of 5 to 50% by weight with respect to water after heat crosslinking is dissolved in the water absorbent resin particles in which the vicinity of the surface of the water absorbent resin is heat-crosslinked. There is known a method for producing water-absorbent resin particles having a modified particle brittleness by adding dissolved water to adjust the water content to 3 to 9% (Patent Document 4).

A polymer product obtained by treating a water-absorbent resin with a polyol and a cation in an aqueous solution and surface-crosslinking at 150 to 300 ° C. is known (Patent Document 5).
A polymer product is known in which a water-absorbent resin is treated with an organic surface secondary cross-linking agent (excluding polyol) and an aqueous cation to cross-link the surface (Patent Document 6).
A composition comprising aqueous fluid-absorbing polymer particles heat treated for more than 10 minutes at a temperature above 170 ° C., the composition being free of organic solvent or water insoluble and non-swellable powder after heat treatment A composition that is re-humidified with an aqueous additive solution and comprises 1 to 10 weight percent water, based on the total weight of the composition, and has an absorption capacity of greater than 20 g / g at 0.3 psi for 60 minutes Is known (Patent Document 7).

These (patent documents 1 to 7) are techniques for adding a metal compound (metal salt, metal cation, etc.) in an aqueous solution state. Since these techniques add a metal compound (metal salt, metal cation, etc.) in an aqueous solution state, the metal component penetrates into the water absorbent resin. For this reason, the effect of improving the liquid permeability and diffusibility corresponding to the added amount is not sufficient. In addition, since the metal component penetrates into the water-absorbent resin, the absorption capacity under no pressure and the absorption capacity under pressure have been reduced.
There has been known a modified water-insoluble water-absorbent resin composition obtained by imparting water to a mixture of a water-absorbent resin and a polyvalent metal salt and / or hydroxide (Patent Document 8).

A method is known in which a water-absorbent resin and a polyvalent metal salt are mixed, and then the mixture is brought into intimate contact with a binder in the absence of volatile alcohol (Patent Document 9).
In these techniques (Patent Documents 8 to 9), intermetallic bonds are generated by the dissolved metal salt, so that strong aggregates are easily generated, and the aggregates are caused by physical damage during actual production or actual use. When crushed, there was a problem that the absorption capacity under pressure was reduced. In addition, there is a problem that the dissolved metal salt penetrates into the particles of the water-absorbent resin, and the penetration when the particles of the polyvalent metal salt having a small particle diameter are used is remarkable. Due to this permeation, the same problem as described above, that is, the effect of improving the liquid permeability / diffusibility to meet the addition amount is not sufficient, or the metal component penetrates into the water absorbent resin. Decreases in absorption capacity and absorption capacity under pressure have occurred. In addition, for polyvalent metal salt particles having a relatively large particle size, sufficient binding force between particles cannot be obtained with a binder, and peeling or desorption occurs, resulting in a metal compound (metal salt, etc.). Also caused problems such as segregation.

In addition to these methods, for example, in the method of dry blending a water-absorbent resin and a metal compound (metal salt, etc.), segregation occurs because the particles are mixed with each other, and the performance of the water-absorbent resin is not stable. There is a risk of problems.
In addition to these, several techniques as described below are known as means for obtaining a water-absorbing resin that suppresses gel blocking and is excellent in liquid permeability and diffusibility.
For example, a method using two types of water-absorbing resins having different water absorption performance (Patent Document 10), a method using a composition containing a cationic ion-exchange hydrogel-forming polymer and an anionic ion-exchange hydrogel-forming polymer (Patent Document 11) A method using a water-absorbent resin having a high surface crosslinking density (Patent Document 12) has been proposed, but the absorption characteristics as an absorber having a high water-absorbent resin concentration are unsatisfactory or the price is high. Had a problem.

In addition, water-absorbing resin containing a lot of fine powder due to wear in the water-absorbing resin manufacturing process is likely to cause gel blocking, so that the water-absorbing resin contains 3% or more of water to improve brittleness. Although a method (Patent Document 13) has been proposed, there are problems such as a decrease in absorption capacity or swelling when water is added to produce particles having a too large particle diameter. It has also been proposed to use a special stirring device in order to reduce the generation of fine powder in the water absorbent resin production process (Patent Document 14).
Also, a method for improving blood absorption by mixing powders of organic and inorganic water-soluble salts (specific salts such as thiourea, saccharides, carboxylates, etc.) with a water-absorbent resin (Patent Document 15), water-absorbent resin And a permeability retention agent (silica, alumina, titania, clay, emulsion polymer, precipitation polymer, etc.) mixed with a vortex mixer, and then subjected to mechanical stress with an osterizer blender (Patent Document 16), water-insoluble water swelling A hydrophilic hydrogel with a three-dimensional or electrostatic spacer (Patent Document 17), a method using a water absorbent resin crosslinked with a specific metal ion (Patent Document 18, Patent Document 19), a highly water absorbent resin and High water absorption containing fine powder composed of an aggregate of hydrous oxides containing two kinds of metals M1 and M2 having at least a part of -M1-O-M2-bond A resin composition (Patent Document 20) are known.

  In these known methods (Patent Documents 15 to 20), gel blocking can be prevented, but the liquid diffusion performance in the diaper, in particular, the sustainability of saline flow conductivity (hereinafter abbreviated as SFC). Performance due to mechanical shock and friction when manufacturing water-absorbent resin or manufacturing absorbent articles using water-absorbent resin, even if the problem is low The deterioration was not taken into consideration, and sufficient performance could not be maintained in actual production. For example, even if an improvement effect is recognized in the laboratory, the effect may not be observed or may be reduced when the production machine includes a process in which physical energy is applied to powder such as stirring and pneumatic transportation.

A water-absorbing agent comprising 100 parts by weight of water-absorbent resin particles and 1 to 30 parts by weight of heat-fusible resin powder having a melting point of 50 to 160 ° C. is known (Patent Document 21).
Looking at this technique (Patent Document 21), after mixing the water-absorbent resin particles and the heat-fusible resin powder having a melting point of 50 to 160 ° C. A method of fixing to particles is disclosed. Such a heat-fusible resin powder is used in order to increase the adhesion to fibers such as pulp. That is, it is used as a binder between fibers and water-absorbent resin particles. However, although such heat-fusible resin powder improves the adhesion of the water-absorbent resin particles to the fiber, there is no interaction with the carboxyl group, so the effect of improving the liquid permeability / diffusibility of the water-absorbent resin is not It was not obtained. In addition, when the heat-sealable resin powder has strong hydrophobicity, it may cause a decrease in capillary suction of the water-absorbent resin composition, which is not necessarily a water-absorbent resin composition having sufficient performance. It was.
JP-A-62-2745 Japanese Unexamined Patent Publication No. 63-270741 JP-A-1-56707 JP-A-9-124879 Special Table 2002-539281 Special table 2002-538275 gazette JP-T-2001-523287 JP-A-61-257235 JP-T-2001-523289 JP 2001-252307 A International Publication No. 98/037149 Pamphlet Japanese Patent Laid-Open No. 06-057010 WO 01/25290 pamphlet International Publication No. 97/24394 Pamphlet US Pat. No. 4,693,713 International Publication No. 01/66056 Pamphlet US Publication No. 2002/0128618 Japanese translation of PCT publication No. 2002-513043 JP 2002-513059 gazette JP-A-10-147724 JP-A-6-248187

The problem to be solved by the present invention is less likely to cause gel blocking, excellent in liquid permeability and liquid diffusibility, and also has high absorption performance such as absorption capacity under no pressure, absorption capacity under pressure, capillary absorption capacity, An object of the present invention is to provide a water-absorbent resin composition that is resistant to physical damage during actual production or actual use , its use, and its production method.

  The present inventor has intensively studied to solve the above problems. As a result, a water absorbent resin composition comprising water absorbent resin particles obtained by polymerizing a monomer containing acrylic acid and / or a salt thereof and water soluble polyvalent metal salt particles, If the water-absorbent resin composition is crosslinked and has a mass average particle diameter of 100 to 600 μm, gel blocking is hardly caused, liquid permeability and liquid diffusibility are excellent, absorption capacity under no pressure, It has been found that the absorption performance such as the rolling absorption capacity and the capillary absorption capacity is high, and further, it is strong against physical damage during actual production or actual use, and the above problems can be solved brilliantly. Such a water-absorbent resin composition has a high physiological saline flow inductivity (SFC), a physiological saline flow inductive (SFC) retention rate after a paint shaker test, and a physiological saline flow induction after long-term liquid absorption. The water-absorbent resin composition having excellent property (SFC) retention was also found at the same time.

  In addition, when manufacturing a water absorbent resin composition in which a polyvalent metal is fixed on the surface of the water absorbent resin particles, a binder such as water is added to the water absorbent resin particles in advance to bind to the surface of the water absorbent resin particles. If water-soluble polyvalent metal salt particles are mixed in a state where the agent has permeated, the penetration of the polyvalent metal into the water-absorbent resin particles can be effectively suppressed, and the polyvalent metal is uniformly distributed over the entire surface of the water-absorbent resin particles. And it is fixed moderately (it is not completely fixed but not movable enough), and as a result, gel blocking is sufficiently suppressed, excellent liquid permeability and liquid diffusibility can be expressed, and excellent absorption performance It has also been found that the above problems can be solved brilliantly because it is also strong against physical damage during actual production and actual use.

That is, the water-absorbent resin composition according to the present invention comprises a water-absorbent resin comprising surface-crosslinked water-absorbent resin particles obtained by polymerizing a monomer containing acrylic acid and / or a salt thereof and water-soluble polyvalent metal salt particles. The water-soluble polyvalent metal salt particles are polyvalent metal salt particles that can be dissolved in pure water at room temperature at a concentration of 5% by mass or more, and the water-absorbent resin particles and the water-soluble resin composition. The polyvalent metal salt particles are mixed with each other by adding a binder to the water-absorbent resin particles and mixing the water-soluble polyvalent metal salt particles , and the mass average particle diameter of the composition is 100 to 100. It is 600 micrometers.
The water-absorbing resin composition according to the present invention also includes a water-absorbing resin comprising surface-crosslinked water-absorbing resin particles obtained by polymerizing a monomer containing acrylic acid and / or a salt thereof and water-soluble polyvalent metal salt particles. The water-soluble polyvalent metal salt particles are polyvalent metal salt particles that can be dissolved in pure water at room temperature at a concentration of 5% by mass or more, and the composition has a mass average Saline flow induction having a particle diameter of 100 to 600 μm and a saline flow conductivity (SFC) of at least 50 (× 10 ⁻⁷ · cm ³ · s · g ⁻¹ ), defined by the following formula: The property (SFC) retention is 60% or more.
SFC retention rate (%) = [SFC (2 hr) / SFC (1 hr)] × 100
The water-absorbent resin composition according to the present invention is preferably an aluminum salt in which water-soluble polyvalent metal salt particles have crystal water.

The water absorbent resin composition according to the present invention is preferably such that the water absorbent resin particles are surface-crosslinked with a polyhydric alcohol.
In the water absorbent resin composition according to the present invention, at least a part of the water absorbent resin particles is preferably a granulated body.
The water-absorbent resin composition according to the present invention preferably has an absorption capacity without load (CRC) of 20 g / g or more and an absorption capacity under pressure at 0.7 psi of 22 g / g or more.
The water absorbent resin composition according to the present invention preferably has a dust generation degree of 0.25 mg / m ³ .
The water absorbent resin composition according to the present invention preferably has a contact angle of 45 ° or less.
The water-absorbent resin composition according to the present invention preferably contains 20% by weight or more of particles having a mass average particle diameter of 400 μm or less and 150 μm or less of water-soluble polyvalent metal salt particles.
The water-absorbent resin composition according to the present invention is such that the use ratio of the water-absorbent resin particles and the water-soluble polyvalent metal salt particles is such that the water-soluble polyvalent metal is 100 parts by mass of the solid content of the water-absorbent resin particles. It is preferable to use the salt particles in the range of 0.1 to 2 parts by mass.
The water-absorbent resin composition according to the present invention has a saline flow conductivity (SFC) retention after a paint shaker (PS, soaked for 30 minutes at 800 cycles / min) test of the water-absorbent resin composition defined by the following formula: The rate is preferably 70% or more.
Retention rate after PS (%) = [SFC (after PS) / SFC (before PS)] × 100
A sanitary material for absorbing feces, urine, or blood according to the present invention includes the water-absorbent resin composition.

The method for producing a water-absorbent resin composition according to the present invention comprises adding a binder to water-absorbent resin particles obtained by polymerizing a monomer containing acrylic acid and / or a salt thereof, It is characterized by mixing metal salt particles.
In the method for producing a water absorbent resin composition according to the present invention, it is preferable that the water absorbent resin particles are surface-crosslinked.
In the method for producing a water-absorbent resin composition according to the present invention, the binder preferably contains a surface crosslinking agent.
In the method for producing a water absorbent resin composition according to the present invention, the binder preferably contains water and / or a polyhydric alcohol.

  In the method for producing a water absorbent resin composition according to the present invention, the temperature of the water absorbent resin particles when adding a binder to the water absorbent resin particles is preferably in the range of 40 to 100 ° C.

According to the present invention, it is difficult to cause gel blocking, and has excellent liquid permeability and liquid diffusibility, and also has high absorption performance such as absorption capacity under no pressure, absorption capacity under pressure, capillary absorption capacity, etc. It is possible to provide a water-absorbent resin composition that is resistant to physical damage during actual use , its use, and its production method.

Hereinafter, the present invention will be described in detail. The water absorbent resin composition of the present invention is a composition mainly composed of a water absorbent resin (water absorbent resin particles), and the water absorbent resin is preferably 80 to 100% by mass, more preferably 90 to 100% by mass. %, And is suitably used for sanitary materials such as disposable diapers, sanitary napkins, incontinence pads, and medical pads. In the present invention, “mass” has the same meaning as “weight”.

[Water-absorbent resin particles]
The water-absorbing resin particles used in the present invention are particles of a water-insoluble water-swellable hydrogel-forming polymer (hereinafter also referred to as a water-absorbing resin) that can be obtained by polymerizing a hydrophilic monomer, and at least physiological It has a spherical or irregular particle shape with an absorption rate of 10 times or more for saline. In the present invention, the water absorbent resin particles may be simply referred to as a water absorbent resin.

  Specific examples of the water-insoluble water-swellable hydrogel-forming polymer include partially neutralized crosslinked polyacrylic acid polymers (US Pat. No. 462501, US Pat. No. 4,654,039, US Pat. No. 5,250,640, US Pat. No. 5,275,773, EP 456136), cross-linked partially neutralized starch-acrylic acid graft polymer (US Pat. No. 4,076,663), isobutylene-maleic acid copolymer (US Pat. No. 4,389,513), vinyl acetate-acrylic Acid copolymer saponified product (US Pat. No. 4,124,748), acrylamide (co) polymer hydrolyzate (US Pat. No. 3,959,569), acrylonitrile polymer hydrolyzate (US Pat. No. 3,935,099) and the like. However, the water absorbent resin used in the present invention is acrylic acid and / or a salt thereof. It is preferably a water absorbing resin comprising polyacrylic acid (salt) -based cross-linked polymer obtained by polymerizing a monomer containing. In the present invention, the polyacrylic acid (salt) -based crosslinked polymer is a polymer of a monomer containing acrylic acid and / or a salt thereof in an amount of 50 mol% or more, preferably 70 mol% or more, more preferably 90 mol% or more. Is a cross-linked polymer obtained. Further, the acid group in the polymer is preferably neutralized by 50 to 90 mol%, more preferably 60 to 80 mol%, and the salt includes sodium, potassium and lithium. Examples thereof include alkali metal salts such as ammonium salts, amine salts, and the like. Neutralization of the water-absorbing resin for forming the salt may be performed in the monomer state before the polymerization, or may be performed in the polymer state during or after the polymerization, Also good.

  The polyacrylic acid (salt) -based cross-linked polymer that is a water-absorbing resin preferably used in the present invention is used in combination with a monomer (acrylic acid and / or a salt thereof) used as a main component and, if necessary, other It may be a copolymer of monomers. Specific examples of other monomers include methacrylic acid, maleic acid, vinyl sulfonic acid, styrene sulfonic acid, 2- (meth) acrylamido-2-methylpropane sulfonic acid, 2- (meth) acryloylethane sulfonic acid, Anionic unsaturated monomers such as 2- (meth) acryloylpropanesulfonic acid and salts thereof; acrylamide, methacrylamide, N-ethyl (meth) acrylamide, Nn-propyl (meth) acrylamide, N-isopropyl (meta ) Acrylamide, N, N-dimethyl (meth) acrylamide, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, methoxy polyethylene glycol (meth) acrylate, polyethylene glycol mono (meth) acrylate, vinyl pyrid Nonionic hydrophilic group-containing unsaturated monomers such as N-vinylpyrrolidone, N-acryloylpiperidine, N-acryloylpyrrolidine and N-vinylacetamide; N, N-dimethylaminoethyl (meth) acrylate, N, N- And cationic unsaturated monomers such as diethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylamide and quaternary salts thereof. it can. As for the usage-amount of monomers other than these acrylic acid and / or its salt, 0-30 mol% is preferable in all the monomers, More preferably, it is 0-10 mol%.

The water absorbent resin used in the present invention is a crosslinked polymer having an internal crosslinked structure.
As a method of introducing an internal cross-linked structure into the water-absorbent resin used in the present invention, a method of introducing by internal crosslinking without using a cross-linking agent, two or more polymerizable unsaturated groups and / or two or more in one molecule Examples thereof include a method of introducing an internal crosslinking agent having a reactive group by copolymerization or reaction. Preferably, the internal cross-linking agent is introduced by copolymerization or reaction.
Specific examples of these internal crosslinking agents include, for example, N, N'-methylenebis (meth) acrylamide, (poly) ethylene glycol di (meth) acrylate, (poly) propylene glycol di (meth) acrylate, trimethylolpropane tri (Meth) acrylate, trimethylolpropane di (meth) acrylate, glycerin tri (meth) acrylate, glycerin acrylate methacrylate, ethylene oxide modified trimethylolpropane tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, di Pentaerythritol hexa (meth) acrylate, triallyl cyanurate, triallyl isocyanurate, triallyl phosphate, triallylamine, poly (meth) allyloxyalkane, (poly) ethyl Glycol diglycidyl ether, glycerol diglycidyl ether, ethylene glycol, polyethylene glycol, propylene glycol, glycerol, pentaerythritol, ethylenediamine, polyethyleneimine, and glycidyl (meth) acrylate can be mentioned. These internal crosslinking agents may be used alone or in combination of two or more. Among them, it is preferable to use a compound having two or more polymerizable unsaturated groups as an internal cross-linking agent from the viewpoint of water absorption characteristics of the water-absorbing resin obtained. 0.005 to 3 mol% is preferable, and 0.01 to 1.5 mol% is more preferable.

In the polymerization, hydrophilic polymers such as starch-cellulose, starch-cellulose derivatives, polyvinyl alcohol, polyacrylic acid (salt), crosslinked polyacrylic acid (salt), hypophosphorous acid, etc. You may add chain transfer agents, such as (salt).
When polymerizing the monomer mainly composed of acrylic acid and / or a salt thereof to obtain the water-absorbent resin used in the present invention, bulk polymerization, reverse phase suspension polymerization, and precipitation polymerization may be performed. Although possible, it is preferable to perform aqueous solution polymerization using the monomer as an aqueous solution from the viewpoint of performance and ease of polymerization control. Such polymerization methods are described, for example, in US Pat. No. 462501, US Pat. No. 4,769,427, US Pat. No. 4,873,299, US Pat. No. 4,093,763, US Pat. No. 4,367,323, US Pat. U.S. Pat. No. 4,446,261, U.S. Pat. No. 4,683,274, U.S. Pat.No. 4,690,996, U.S. Pat. No. 4,721,647, U.S. Pat. No. 4,738,867, U.S. Pat. It is described in the description.

In performing the polymerization, radical polymerization initiators such as potassium persulfate, ammonium persulfate, sodium persulfate, t-butyl hydroperoxide, hydrogen peroxide, 2,2'-azobis (2-amidinopropane) dihydrochloride, ultraviolet rays And active energy rays such as electron beam can be used. Moreover, when using a radical polymerization initiator, it is good also as redox polymerization combining reducing agents, such as sodium sulfite, sodium hydrogensulfite, ferrous sulfate, and L-ascorbic acid. The amount of these polymerization initiators used is preferably 0.001 to 2 mol%, more preferably 0.01 to 0.5 mol%, based on all monomers.
The shape of the water-absorbing resin obtained by the above polymerization is generally an irregularly crushed shape, a spherical shape, a fiber shape, a rod shape, a substantially spherical shape, a flat shape, etc., but the water-absorbing resin used in the present invention is in the form of particles. It is desirable to use an irregularly pulverized product obtained by pulverization after drying because the effect of the present invention is further increased.

The water-absorbent resin used in the present invention is preferably one in which the vicinity of the surface is further crosslinked with a surface crosslinking agent.
Examples of the surface cross-linking agent that can be used for the surface cross-linking treatment include an organic surface cross-linking agent and a polyvalent metal compound having two or more functional groups that can react with a carboxyl group, in particular, a functional group that can react with a carboxyl group. For example, ethylene glycol, diethylene glycol, propylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, 1,3-propanediol, dipropylene glycol, 2,2,4-trimethyl-1,3-pentanediol, polypropylene glycol, Glycerin, polyglycerol, 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 copolymer, pentaerythritol, sorbitol Polyhydric alcohol compounds such as ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerol polyglycidyl ether, diglycerol polyglycidyl ether, polyglycerol polyglycidyl ether, propylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, glycidol, etc. Epoxy compounds; polyvalent amine compounds such as ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, polyethyleneimine, and inorganic or organic salts thereof (for example, azetidinium salts); 2,4-tri Polyisocyanate compounds such as range isocyanate and hexamethylene diisocyanate; 1,2-ethyl Polyvalent oxazoline compounds such as bis-oxazoline; carbonic acid derivatives such as urea, thiourea, guanidine, dicyandiamide, 2-oxazolidinone; 1,3-dioxolan-2-one, 4-methyl-1,3-dioxolan-2-one 4,5-dimethyl-1,3-dioxolan-2-one, 4,4-dimethyl-1,3-dioxolan-2-one, 4-ethyl-1,3-dioxolan-2-one, 4-hydroxy Methyl-1,3-dioxolan-2-one, 1,3-dioxan-2-one, 4-methyl-1,3-dioxan-2-one, 4,6-dimethyl-1,3-dioxane-2- Alkylene carbonate compounds such as ON, 1,3-dioxopan-2-one; haloepoxides such as epichlorohydrin, epibromohydrin, α-methylepichlorohydrin, etc. Si compounds and polyvalent amine adducts thereof (for example, Hercules Kaimen: registered trademark); silane coupling agents such as γ-glycidoxypropyltrimethoxysilane, γ-aminopropyltriethoxysilane; 3-methyl-3 -Oxetane methanol, 3-ethyl-3-oxetane methanol, 3-butyl-3-oxetane methanol, 3-methyl-3-oxetane ethanol, 3-ethyl-3-oxetane ethanol, 3-butyl-3-oxetane ethanol, 3 -Oxetane compounds such as chloromethyl-3-methyloxetane, 3-chloromethyl-3-ethyloxetane, and polyvalent oxetane compounds; hydroxides such as zinc, calcium, magnesium, aluminum, iron, and zirconium; And valent metal compounds. These surface cross-linking agents may be used alone or in combination of two or more. Of these, polyhydric alcohols are preferred because they are highly safe and can improve the hydrophilicity of the surface of the water-absorbent resin particles. In addition, the use of polyhydric alcohol improves the familiarity with the polyvalent metal particles on the surface of the water-absorbent resin particles. It becomes possible to make a valence metal particle exist more uniformly.

As for the usage-amount of a surface crosslinking agent, 0.001-5 mass parts is preferable with respect to 100 mass parts of solid content of a water absorbing resin.
Water may be used when mixing the surface cross-linking agent and the water-absorbent resin. The amount of water used is more than 0.5, preferably 10 parts by mass or less, and more preferably in the range of 1 part by mass to 5 parts by mass with respect to 100 parts by mass of the solid content of the water absorbent resin.
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.
In the case of using a hydrophilic organic solvent, for example, lower alcohols such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, t-butyl alcohol; ketones such as acetone; Ethers such as dioxane, tetrahydrofuran, methoxy (poly) ethylene glycol; amides such as ε-caprolactam and N, N-dimethylformamide; sulfoxides such as dimethyl sulfoxide; ethylene glycol, diethylene glycol, propylene glycol, triethylene glycol, tetra Ethylene glycol, polyethylene glycol, 1,3-propanediol, dipropylene glycol, 2,2,4-trimethyl-1,3-pentanediol, polypropylene Glycol, glycerin, polyglycerin, 2-butene-1,4-diol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,2-cyclohexane Examples include dimethanol, 1,2-cyclohexanol, trimethylolpropane, diethanolamine, triethanolamine, polyoxypropylene, oxyethylene-oxypropylene block copolymers, polyhydric alcohols such as pentaerythritol, sorbitol, and the like. The amount of the hydrophilic organic solvent used depends on the type, particle size, water content, etc. of the water absorbent resin, but is preferably 10 parts by mass or less, based on 100 parts by mass of the solid content of the water absorbent resin. Within the range of 5 parts by mass to 5 parts by mass is more preferable. In addition, inorganic acids, organic acids, polyamino acids and the like disclosed in European Patent No. 0668080 may be present as the third substance. These mixing aids may act as a surface cross-linking agent, but those that do not deteriorate the water absorption performance of the water-absorbent resin after surface cross-linking are preferred. In particular, volatile alcohols having a boiling point of less than 150 ° C. are volatilized during the surface cross-linking treatment, and therefore it is desirable that no residue remains.

Non-crosslinkable water-soluble inorganic bases (preferably alkali metal salts, ammonium salts, alkali metal hydroxides, and ammonia or hydroxides thereof) in order to mix the water absorbent resin and the surface cross-linking agent more uniformly. ) Or a non-reducing alkali metal salt pH buffer (preferably bicarbonate, dihydrogen phosphate, hydrogen phosphate, etc.) may be coexistent when the water absorbent resin and the surface cross-linking agent are mixed. good. Although these usage-amounts are based also on the kind of water-absorbing resin, a particle size, etc., the inside of the range of 0.005-10 mass parts is preferable with respect to 100 mass parts of solid content of a water-absorbing resin, 0.05-5 More preferably within the range of parts by mass.
The mixing method for mixing the water-absorbing resin and the surface cross-linking agent is not particularly limited. For example, surface cross-linking in which the water-absorbing resin is immersed in a hydrophilic organic solvent and dissolved in water and / or the hydrophilic organic solvent as necessary. Examples thereof include a method of mixing an agent, and a method of spraying or dropping a surface cross-linking agent dissolved in water and / or a hydrophilic organic solvent directly into a water absorbent resin.

After mixing the water-absorbent resin and the surface cross-linking agent, usually a heat treatment is performed to carry out the cross-linking reaction. Although the said heat processing temperature is based also on the surface crosslinking agent to be used, 40 to 250 degreeC is preferable and 150 to 250 degreeC is more preferable. When the treatment temperature is lower than 40 ° C., the absorption characteristics such as the absorption capacity under pressure may not be sufficiently improved. When the treatment temperature exceeds 250 ° C., the water-absorbent resin is deteriorated, and the performance may be lowered. The heat treatment time is preferably 1 minute to 2 hours, more preferably 5 minutes to 1 hour.
There is no particular limitation on the particle size or particle size distribution of the water-absorbent resin used in the present invention. The water absorption performance is significantly improved, which is preferable.

  The water-absorbent resin used in the present invention preferably has a mass average particle size of 500 μm or less, and more preferably 400 μm or less in order to improve performance such as water absorption rate and capillary absorption capacity. In the water absorbent resin, the ratio of particles having a particle size of less than 300 μm is preferably 10% by mass or more, more preferably 30% by mass or more, and 50% by mass with respect to the water absorbent resin. % Or more is more preferable. The water-absorbent resin having such a particle size can be preferably obtained by pulverizing the water-absorbent resin obtained by aqueous solution polymerization, or by adjusting the particle size by sieving them. In addition, a water-absorbent resin fine powder having a particle size of 300 μm or less may be granulated and adjusted in particle size, and a granulated product of fine powder may be added to irregularly shaped primary particles obtained by pulverization. A partially mixed water-absorbing resin may be used. When a part of the granulated product of the water-absorbent resin is mixed, the water-absorbent resin composition of the present invention having further excellent absorption characteristics such as water absorption rate and capillary absorption capacity can be obtained. The mixing amount of the granulated fine powder is preferably 5% by mass or more, more preferably 10% by mass or more, and further preferably 15% by mass or more.

  As a method for producing a fine granulated product, a known technique for regenerating fine powder can be used. For example, a method in which warm water and fine powder of a water absorbent resin are mixed and dried (US Pat. No. 6,228,930), a method in which a fine powder of water absorbent resin is mixed with a monomer aqueous solution and polymerized (US Pat. No. 5,264,495), water absorbency A method of adding water to a fine resin powder and granulating it at a specific surface pressure or higher (European Patent No. 844270), a method of sufficiently wetting the fine powder of a water-absorbent resin to form an amorphous gel, and drying and grinding (US) Patent No. 4950692), a method of mixing fine powder of water-absorbing resin and polymer gel (US Pat. No. 5,478,879) can be used, but preferably the above-mentioned hot water and fine powder of water-absorbing resin are mixed and dried. Is used. The particle diameter is indicated by the sieve diameter to be classified.

[Water-soluble polyvalent metal salt particles]
Although it is already well known that certain inorganic compound particles prevent gel blocking and impart high partitioning and diffusing capacity to the water-absorbent resin, the present inventor usually includes the water-absorbent resin manufacturing process as described above. A water-absorbent resin composition exhibiting high performance even when the water-absorbent resin is damaged due to air transportation or the like was investigated. Surprisingly, when water-soluble polyvalent metal salt particles are used as inorganic compound particles, the effect of improving the flow rate under pressure is remarkable, and the water-soluble polyvalent metal salt is added to the water-absorbent resin in an aqueous solution state. Rather than water absorption resin particles, only when a water-soluble polyvalent metal salt is added in the form of particles, the water absorption is excellent both in maintaining the flow rate under pressure for a long time and in physical damage resistance. It has been found that a resin composition can be obtained. It has also been found that the effect is particularly remarkable when the water-soluble polyvalent metal salt particles are hydrated crystals. The reason why the water-absorbent resin composition obtained by dry mixing exhibits such an effect is that a water-soluble polyvalent metal salt is added as an aqueous solution to the water-absorbent resin, or the water-absorbent resin particles and the water-soluble polyvalent metal are added. The effect of the present invention is remarkably reduced in a composition in which water-soluble polyvalent metal salt particles are dissolved and lost in a particulate form by adding water to a dry mixture of salt particles. Because the salt is in the form of particles and mixed with the water-absorbent resin particles, water-soluble polyvalent metal salt particles absorb the impact energy when physical damage such as impact force is applied to the water-absorbent resin composition. It is estimated that this is because the damage to the resin is reduced. At that time, it is considered that the impact energy is consumed for homogenization by pulverization of water-soluble polyvalent metal salt particles and rearrangement of the particles. Therefore, it is considered that the water-soluble polyvalent metal salt particles are preferably in a dry mixture state in which they can move with a certain degree of freedom, rather than being completely immobilized on the surface of the water-absorbent resin.

  In addition to this, the water-soluble polyvalent metal salt has the effect of making the surface of the water-absorbent resin particles hydrophilic, and when the water-absorbent resin composition absorbs an aqueous liquid, There is an effect of improving the flow rate under pressure by the action of dissolving and ion-crosslinking the surface of the water-absorbent resin, or the action of maintaining a wide gap between the water-absorbent resins. In that case, the effect is more remarkable when the polyvalent metal is not present inside the water-absorbent resin particles but is present in the vicinity or the vicinity of the surface. A water-absorbing resin composition prepared by adding a water-soluble polyvalent metal salt as an aqueous solution to a water-absorbing resin or adding water to a dry mixture of water-absorbing resin particles and water-soluble polyvalent metal salt particles. Since most of the salt has already penetrated into the water-absorbent resin, the effect of the polyvalent metal salt on the surface of the water-absorbent resin is reduced when absorbing an aqueous liquid such as urine. As a result, the performance of the water-absorbent resin composition, in particular, the liquid passing speed under pressure is lowered, and the water-absorbent resin composition has poor durability. And since the permeating polyvalent metal salt reacts with the carboxyl group to form a crosslinked structure, the liquid permeability is lowered due to process damage. In comparison, since the water-soluble polyvalent metal salt that can be used in the present invention is in the form of particles and mixed with the water-absorbent resin particles, the water-absorbent resin composition is not water-soluble for the first time when the water-absorbent resin composition absorbs urine or an aqueous liquid. The soluble polyvalent metal salt dissolves and acts on the surface of the water absorbent resin. By this action, the effect of the polyvalent metal salt can be more efficiently sustained for a long time on the surface of the water absorbent resin. And the water-absorbing resin composition of the present invention in which the water-soluble polyvalent metal salt particles are present on the surface of the water-absorbing resin particles has the water-soluble polyvalent metal salt particles on the surface of the water-absorbing resin particles even after being damaged by the process. Because it exists, it has excellent liquid permeability even after process damage. That is, it can be said that the water absorbent resin composition of the present invention has a structure that effectively exhibits the effect of the polyvalent metal without deteriorating the liquid absorption performance of the water absorbent resin itself.

The water-soluble polyvalent metal salt particles that can be used in the present invention are metal salts having a valence of 2 or more and are in a powder form. Considering that the water-absorbent resin composition of the present invention is used as an absorbent material for sanitary materials such as diapers, it is preferable to select a water-absorbent resin composition that does not color the water-absorbent resin composition and has low toxicity to the human body.
In order to maintain the effect of the polyvalent metal salt more efficiently for a long time during liquid absorption, a polyvalent metal salt that can be dissolved in pure water at room temperature at a concentration of 5% by mass or more is selected . Good Mashiku 10 mass% or more, more preferably selected and used that can dissolve more than 20 wt%.
Water-soluble polyvalent metal salt particles that can be used in the present invention include aluminum chloride, polyaluminum chloride, aluminum sulfate, aluminum nitrate, potassium bissulfate aluminum, sodium bissulfate aluminum, calcium chloride, calcium nitrate, magnesium chloride, Examples thereof include magnesium sulfate, magnesium nitrate, zinc chloride, zinc sulfate, zinc nitrate, zirconium chloride, zirconium sulfate, and zirconium nitrate. Moreover, it is preferable to use the salt which has these crystal waters also from the point of solubility with absorption liquids, such as urine. Particularly preferred are aluminum compounds, among which aluminum sulfate is preferred, and powders of hydrous crystals such as aluminum sulfate 18 hydrate and aluminum sulfate 14-18 hydrate can be most suitably used.

The particle diameter of the water-soluble polyvalent metal salt particles that can be used in the present invention is preferably smaller than the particle diameter of the water-absorbent resin from the viewpoint of mixing properties. The mass average particle diameter is preferably 500 μm or less, and more preferably 400 μm or less. From the viewpoint of performance, it is more preferably a particle containing 20% by mass or more, and most preferably a particle containing 30% by mass or more with respect to the water-soluble polyvalent metal salt particles.
As the properties of the water-soluble polyvalent metal salt particles that can be used in the present invention, a granulated body or the like is preferable from the viewpoint of mitigating damage, and the bulk specific gravity is preferably 0.5 g / cm ³ or more. 7 g / cm ³ or more is more preferable.

[Water-absorbing resin composition]
A water-absorbent resin composition according to the present invention is a water-absorbent resin composition comprising water-absorbent resin particles obtained by polymerizing a monomer containing acrylic acid and / or a salt thereof, and the mass average of the composition The particle diameter is 100 to 600 μm, and includes water-soluble polyvalent metal salt particles and surface-crosslinked water-absorbing resin particles.
The water-absorbing resin composition according to the present invention also includes a water-absorbing resin particle obtained by polymerizing a monomer containing acrylic acid and / or a salt thereof, and a water-absorbing polyvalent metal salt particle. The saline flow conductivity (SFC) is at least 50 (× 10 ⁻⁷ · cm ³ · s · g ⁻¹ ), and the saline flow conductivity (SFC) retention rate is 60 % or more. is there.

The water-absorbent resin composition of the present invention is mainly composed of water-absorbent resin particles and contains water-soluble polyvalent metal salt particles. It is suitably used as an absorbent material for sanitary materials.
Since the water-soluble polyvalent metal salt particles in the water-absorbent resin composition of the present invention are only mixed in the form of particles with the water-absorbent resin particles, the water-soluble polyvalent metal salt particles are particles on the surface of the water-absorbent resin particles. The water-soluble multivalent metal salt particles are present while maintaining the shape, or the water-soluble polyvalent metal salt particles are present while maintaining the particle shape in peripheral portions such as between the particles of the water-absorbent resin particles. A preferred form is a state in which the water-soluble polyvalent metal salt particles are substantially uniformly present with the water-absorbent resin particles. In order to form such a state, the water-soluble polyvalent metal salt particles may be weakly bonded to the water-absorbent resin particles using a binder or the like as long as the particle shape can be maintained. Although these states can be observed with a photograph such as an electron microscope, the water-absorbent resin particles and the water-soluble polyvalent metal are dispersed by a specific gravity difference after the water-absorbent resin composition is dispersed and stirred in an appropriate organic solvent or gas. This can be confirmed by separating the salt particles.

  The water-absorbent resin composition of the present invention preferably comprises water-absorbent resin particles and water-soluble polyvalent metal salt particles, and at least a part of the water-soluble polyvalent metal salt particles is water-absorbent resin particles by a binder. It is weakly bonded to the surface. For this reason, the penetration of the polyvalent metal into the water-absorbent resin particles is effectively suppressed, and the polyvalent metal is uniform and moderate on the entire surface of the water-absorbent resin particles. However, gel blocking is sufficiently suppressed, excellent liquid permeability and liquid diffusibility can be exhibited, and excellent absorption performance can be exhibited. Furthermore, during actual production and use It will be strong against physical damage. These states can also be observed with photographs such as an electron microscope.

The water absorbent resin particles contained in the water absorbent resin composition of the present invention are preferably subjected to surface crosslinking treatment.
The water-absorbent resin composition of the present invention preferably has a mass average particle diameter of 100 to 600 μm, and more preferably has a mass average particle diameter of 200 to 500 μm. When the mass average particle diameter is less than 100 μm, it is difficult to obtain the effects of the present invention even if water-soluble polyvalent metal salt particles are added. May segregate and the uniform mixing property may deteriorate. Further, in the water absorbent resin composition, the ratio of particles having a particle size of less than 300 μm is preferably 10% by mass or more, more preferably 30% by mass or more with respect to the water absorbent resin composition. Preferably, it is 50 mass% or more.

The water-absorbent resin composition of the present invention has an absorption capacity without load (CRC) of preferably 20 (g / g) or more, more preferably 22 (g / g) or more, and further preferably 24 (g / g). g) or more, more preferably 25 (g / g) or more, particularly preferably 27 (g / g) or more. If the absorption capacity without load (CRC) is lower than 20 (g / g), the absorption efficiency when used for sanitary materials such as diapers is deteriorated.
Water-absorbing resin composition of the present invention, the absorbency against pressure (AAP) is, under pressure of 0.7psi, 2 2 (g / g ) or more, good Mashiku is 24 (g / g) or more. When the absorption capacity under pressure (AAP) is lower than 22 (g / g), the absorption efficiency when used for sanitary materials such as diapers is deteriorated.

The water-absorbent resin composition of the present invention has a physiological saline flow conductivity (SFC) of preferably 50 (× 10 ⁻⁷ · cm ³ · s · g ⁻¹ ) or more, more preferably 100 (× 10 10). ⁻⁷ · cm ³ · s · g ⁻¹ ) or more, more preferably 120 (× 10 ⁻⁷ · cm ³ · s · g ⁻¹ ) or more, particularly preferably 150 (× 10 ⁻⁷ · cm ³ · s · ¹ ). g ⁻¹ ) or more. Although the saline flow conductivity (SFC) depends on the content of the water-absorbent resin composition in the sanitary material, the higher the content, the higher the saline flow conductivity (SFC) is required. .
In the water absorbent resin composition of the present invention, the absorption capacity under pressure (AAP) is compared with the absorption capacity under pressure (AAP) (under the same pressure) of the water absorbent resin particles before adding the water-soluble polyvalent metal salt particles. Therefore, it is desirable that the decrease is small, and it is preferable that the water absorption resin particles maintain an absorption ratio under pressure (AAP) of 0.85 times or more, more preferably 0.90 times or more, Preferably it is 0.95 times or more.

The water-absorbent resin composition of the present invention exhibits the effect that the absorption performance is hardly lowered even when subjected to various physical energy (damage) during production or actual use. That is, the water-absorbent resin composition of the present invention is a water-absorbent resin composition having the following absorption performance after physical energy is applied.
The water-absorbent resin composition of the present invention has a non-pressure absorption capacity (CRC after PS) after a paint shaker test (800 cycles / minute, 30 minutes of shaking), preferably 20 (g / g) or more, More preferably, it is 22 (g / g) or more, More preferably, it is 24 (g / g) or more, More preferably, it is 25 (g / g) or more, Most preferably, it is 27 (g / g) or more. If the absorption capacity without pressure (CRC after PS) after the paint shaker test is lower than 20 (g / g), the absorption efficiency when used for sanitary materials such as diapers is deteriorated.

The water-absorbent resin composition of the present invention has a physiological saline flow inductivity (SFC after PS) after the paint shaker test, preferably 50 (× 10 ⁻⁷ · cm ³ · s · g ⁻¹ ) or more. , More preferably 100 (× 10 ⁻⁷ · cm ³ · s · g ⁻¹ ) or more, further preferably 120 (× 10 ⁻⁷ · cm ³ · s · g ⁻¹ ) or more, particularly preferably 150 (× 10 ⁻⁷ · cm ³ · s · g ⁻¹ ) or more. Saline flow inductivity after paint shaker test (SFC after PS) depends on the content of the water-absorbent resin composition in the sanitary material, but the higher the content, the higher the saline flow induction. (SFC) is required.
The water-absorbent resin composition of the present invention has a ratio of SFC after PS to saline flow conductivity (SFC) before the paint shaker test, that is, saline flow conductivity retention (PS) after the paint shaker test. The subsequent SFC retention) is preferably 70% or more, more preferably 80% or more, still more preferably 90% or more, and particularly preferably 100% or more.

The water-absorbent resin composition of the present invention can maintain a high physiological saline flow conductivity (SFC) even when used for a long time in a sanitary material.
The water-absorbent resin composition of the present invention has a ratio of the saline flow conductivity (SFC) after the swelling time of 120 minutes to the saline flow conductivity (SFC) after the swelling time of 60 minutes, that is, the saline flow. The inductive retention rate (SFC retention rate) is preferably 40% or more, more preferably 50% or more, and still more preferably 60% or more. Conventional water-absorbing resin (or water-absorbing resin composition) to which metal particles have been added rapidly increases the flow rate when the swelling time exceeds 60 minutes in a physiological saline flow conductivity (SFC) test. Decrease is observed.

The water-absorbent resin composition of the present invention also has a feature that it is difficult to generate dust. The water absorbent resin composition of the present invention has a dust generation degree of preferably 0.25 (mg / m ³ ) or less, more preferably 0.23 (mg / m ³ ) or less, and further preferably 0.20 (mg / M ³ ) or less, more preferably 0.17 (mg / m ³ ) or less, and particularly preferably 0.15 (mg / m ³ ) or less.
The water-absorbent resin composition of the present invention has excellent wettability with respect to aqueous liquids, and among them, those using water-absorbent resin particles surface-crosslinked with a polyhydric alcohol are particularly excellent in wettability and contribute to improvement of absorption performance. ing. The wettability of the water absorbent resin composition with respect to the aqueous liquid can be evaluated by measuring the contact angle. Although it is not easy to accurately measure the contact angle of a liquid to a liquid-absorbing powder such as a water-absorbent resin composition, the apparent contact angle can be measured by a method described later. The water-absorbent resin composition of the present invention preferably has an apparent contact angle of 45 degrees or less, more preferably 30 degrees or less, and particularly preferably 20 degrees or less.

  The water-absorbent resin composition of the present invention comprises, in addition to water-absorbent resin particles and water-soluble polyvalent metal salt particles, silicon dioxide, titanium dioxide, aluminum oxide, magnesium oxide, zinc oxide, talc, calcium phosphate, barium phosphate, silicic acid. Or its salts, clay, diatomaceous earth, zeolite, bentonite, kaolin, hydrotalcite, water-insoluble fine particulate inorganic powders such as active white salts; cationic polymer compounds such as deodorants, perfumes, antibacterial agents, polyamines, It may contain additives such as foaming agents, pigments, dyes, fertilizers, oxidizing agents, reducing agents, etc., and may have been given or enhanced functions. The use ratio of these additives is less than 10% by mass, preferably less than 5% by mass, more preferably less than 1% by mass with respect to the total amount of the water-absorbent resin particles and the water-soluble polyvalent metal salt particles.

[Method for producing water-absorbing resin composition]
A preferred method for producing the composition of the present invention is the dry mixing method. The dry mixing method is a method in which water-absorbing resin particles (preferably, surface-crosslinked) and water-soluble polyvalent metal salt particles are mixed while the water-soluble polyvalent metal salt particles are substantially kept dry. It is a method to do. At that time, the water-soluble polyvalent metal salt particles are mixed under the condition that they can exist as independent particles.
In the production and storage of the water-absorbent resin composition of the present invention, it is necessary to avoid adding or mixing water in such an amount that the water-soluble polyvalent metal salt particles are dissolved, or placing it under high humidity. When the water-soluble polyvalent metal salt particles are in contact with the water-absorbent resin in a state dissolved in water or the like, the water-soluble polyvalent metal salt is applied to the surface of the water-absorbent resin particles or infiltrated into the interior, It does not exist as particles, and the effects of the present invention are not fully exhibited. For example, JP-T-2001-523289 (WO 98/48857) discloses a method for preparing a superabsorbent polymer, characterized in that the superabsorbent polymer is mixed with a polyvalent metal salt and then the mixture is brought into intimate contact with a binder. In the present invention, the water-absorbing resin particles and the water-soluble polyvalent metal salt particles are mixed in the production of the water-absorbing resin composition. Thereafter, it is completely different from the conventional method in that it is not necessary to add an aqueous liquid such as water or a water-soluble liquid. Therefore, the water-soluble polyvalent metal salt particles contained in the water-absorbent resin composition of the present invention are liquid. And are present together with the water-absorbent resin as substantially dry particles. The presence of water-soluble polyvalent metal salt particles in a dry particle state is an important technique of the present invention, and thereby a water-absorbing resin composition having excellent water-absorbing performance such as liquid permeability after damage can be obtained. It is.

The specific mixing method is not particularly limited as long as it is a dry mixing method, and for example, a known powder addition / mixing method may be used, and it may be added all at once, divided or continuously. The addition / mixing of the water-soluble polyvalent metal salt particles may be performed while stirring the water-absorbent resin particles, or the stirring operation may be performed after adding the water-soluble polyvalent metal salt particles. As a stirring device or a mixing device, a paddle blender, a ribbon mixer, a rotary blender, a jar tumbler, a plow jar mixer, a cylindrical mixer, a V-shaped mixer, a ribbon mixer, a screw mixer, a double-arm mixer A pulverizing type kneader, a groove type mixer, a vertical type mixer or the like can be used.
The water-absorbing resin particles and water-soluble polyvalent metal salt particles are used in a range of 0.01 to 5 parts by mass of water-soluble polyvalent metal salt particles with respect to 100 parts by mass of the water-absorbing resin particles. The range of 0.1 to 2 parts by mass is more preferable. If too much water-soluble polyvalent metal salt particles are added, the performance of the water-absorbent resin will be lowered, and if too small, the effect of water-soluble polyvalent metal salt particles will not appear.

Among the dry mixing methods, which are a preferred method for producing the composition of the present invention, a more preferred mode is binding to water-absorbent resin particles obtained by polymerizing a monomer containing acrylic acid and / or a salt thereof. In this form, water-soluble polyvalent metal salt particles are mixed with an agent added. The water-absorbent resin particles are preliminarily added with a binder, and the water-soluble polyvalent metal salt particles are mixed in a state where the binder penetrates the surface of the water-absorbent resin particles.
As described in the background art, JP-T-2001-523287, JP-A-9-124879, JP-A-63-270741, JP-T-2002-538275, an aqueous solution after absorbing the metal salt as an aqueous solution. In the form added to the resin, the metal penetrates even inside the water-absorbent resin particles, the absorption capacity is lowered under no pressure due to the influence of the metal inside the water-absorbent resin, and there is enough metal on the surface of the water-absorbent resin There are problems such as a decrease in absorption capacity under pressure due to not being performed, gel blocking, a decrease in liquid permeability and liquid diffusibility.

Further, as reported in JP-A-61-257235 and JP-T-2001-523289 described above as the background art, in a form in which water is added after dry blending a metal salt with a water-absorbent resin, it was dissolved. Bonding between particles is generated by metal salt, so that strong agglomerates are easily generated, and the absorption capacity under pressure is reduced when the agglomerates are crushed due to physical damage during actual production or actual use. There was a problem. There is also a problem that the dissolved metal salt penetrates into the water-absorbent resin particles.
On the other hand, according to the more preferable embodiment, the water-soluble polyvalent metal salt particles are mixed with the water-absorbent resin particles in a powder state in a state where the binder has penetrated the surface of the water-absorbent resin particles. Can be effectively suppressed, and the polyvalent metal is fixed uniformly and moderately on the entire surface of the water-absorbent resin particles (in a state where it is not completely fixed but not movable enough). As a result, gel blocking is sufficiently suppressed, excellent liquid permeability and liquid diffusibility can be exhibited, and excellent absorption performance can be exhibited.In addition, physical damage during actual production and use It will be in a strong state.

The binder that can be used in the present invention has a role as a binder for fixing the polyvalent metal to the surface of the water-absorbent resin particles, and the water-soluble polyvalent metal salt particles are mixed with the water-absorbent resin particles. Before adding, it is added to the water-absorbent resin particles in advance.
The binder that can be used in the present invention is not particularly limited as long as it includes those capable of expressing the above-mentioned role. For example, water, polyhydric alcohol, water-soluble polymer, thermoplastic resin, pressure-sensitive adhesive, adhesive, and the like can be used. Including, preferably, water and / or polyhydric alcohol.
The binder that can be used in the present invention may contain the aforementioned surface cross-linking agent. In particular, as will be described later, when using water-absorbent resin particles that are not surface-crosslinked, if the surface-crosslinking agent is included in the binder, the surface-crosslinking treatment in the process of producing the water-absorbent resin composition. Can be performed.

The amount of the binder that can be used in the present invention is preferably 0.1 to 10% by mass, more preferably 0.1 to 5% by mass, and still more preferably 0 to the solid content of the water-absorbent resin particles. .2-3 mass%. When the amount is less than 0.1% by mass, there is a possibility that proper fixing of the polyvalent metal cannot be realized. If it is more than 10% by mass, various properties of the resulting water-absorbent resin composition may be deteriorated.
The method for adding the binder to the water-absorbent resin particles is not particularly limited, but a method in which the binder can be uniformly added to the water-absorbent resin particles and mixed is preferable. A method of dropping and mixing can be exemplified. As an apparatus for mixing, for example, a cylindrical mixer, a V-shaped mixer, a ribbon mixer, a screw mixer, a double-arm mixer, a pulverizing kneader, a groove mixer, and a vertical mixer Etc.

When adding a binder to the water-absorbent resin particles, it is preferable to adjust the temperature of the water-absorbent resin particles in the range of 40 to 100 ° C. More preferably, it is 50-90 degreeC, More preferably, it is 60-80 degreeC. When the temperature is out of the above temperature range, it is difficult to uniformly add and mix the binder to the water-absorbent resin particles.
In the more preferable embodiment, the water-absorbent resin particles may be those that have been surface-crosslinked or those that are not surface-crosslinked. When using water-absorbent resin particles that are not surface-crosslinked, if the surface-crosslinking agent is included in the binder, it becomes possible to perform surface-crosslinking treatment in the process of producing the water-absorbent resin composition. .

In the above preferred embodiment, water-soluble polyvalent metal salt particles are mixed with water-absorbent resin particles to which a binder has been added.
The method for mixing the water-soluble polyvalent metal salt particles with the water-absorbent resin particles is the same as described above.
In the method for producing a water-absorbent resin composition in the present invention, a stirring operation when adding water-soluble polyvalent metal salt particles to the water-absorbent resin particles is not necessarily required. After adding the particles, mixing may be performed using a process to which physical energy such as impact, which is usually included in the water absorbent resin manufacturing process, is applied in a non-uniform mixed state.

A preferred embodiment of the present invention is a method of utilizing energy applied to the water absorbent resin when pneumatically transporting the water absorbent resin particles (powder) often employed in the water absorbent resin production process. In other words, if water-soluble polyvalent metal salt particles are added in the step prior to the step of pneumatically transporting the water-absorbent resin powder, and then pneumatically transported, there is no need for any special mixing or pulverizing process. In addition, it is possible to obtain a water absorbent resin composition having excellent absorption performance and the like.
The pneumatic transportation of the water absorbent resin particles (powder) in the water absorbent resin production process is usually a transport distance of 10 to 200 m and a transport speed of 0.1 to 15 m / second. The water-absorbing resin particles and the water-soluble polyvalent metal salt particles are crushed and mixed by passing through an air transportation process, by contacting or colliding with each other, or by colliding with the walls of the transportation path, The water absorbent resin composition of the present invention can be obtained.

  The energy received by the water-absorbent resin particles and water-soluble polyvalent metal salt particles during pneumatic transportation is equivalent to the energy received when the water-absorbent resin particles and water-soluble polyvalent metal salt particles are placed in a container with glass beads and shaken with a paint shaker. Therefore, the energy to be actually applied can be reproduced in the laboratory using a paint shaker (paint shaker test: hereinafter abbreviated as PS). The paint shaker test (PS) is a paint shaker (manufactured by Toyo Seiki Seisakusho, product No. 488) in which a glass bead having a diameter of 6 cm and a height of 11 cm is charged with 10 g of glass beads having a diameter of 6 mm and a water absorbent resin composition 30 g. And is shaken at 800 cycle / min (CPM) for 30 minutes, and details of the apparatus are disclosed in Japanese Patent Laid-Open No. 9-235378. The energy added to the water-absorbent resin particles and the water-soluble polyvalent metal salt particles is the energy corresponding to the range of 5 to 60 minutes, more preferably in the range of 5 to 30 minutes. Energy substantially equal to the energy required during pneumatic transportation. By changing the shaking time of PS within the above range, the optimum point of the performance of the water absorbent resin composition can be found, and the pneumatic transportation process such as pneumatic transportation distance and pneumatic transportation speed can be designed. It is also possible to determine the selection and use amount of water-soluble polyvalent metal salt particles by conducting a mixing test of water-absorbing resin particles and water-soluble polyvalent metal salt particles with a shaking time of PS corresponding to the energy of the pneumatic transportation process. When such a force is applied, some of the water-soluble polyvalent metal salt particles used in the present invention become extremely fine particles and are uniformly attached to the surface of the water-absorbent resin particles.

That is, in a preferable production method of the water-absorbent resin composition of the present invention, the water-absorbent resin particles are themselves powders of brittle crystals that are pulverized by the above physical energy, or aggregates and granulations of fine particles. It is preferable to use water-soluble polyvalent metal salt particles, and fine particles of water-soluble polyvalent metal salt particles uniformly adhere to water-absorbent resin particles (powder) without using a special pulverizer. A mixture can be obtained.

[Water absorber]
The water-absorbent resin composition of the present invention can be used as, for example, a water absorbent suitable as an absorbent layer for sanitary materials by combining with an appropriate material. Hereinafter, the water absorbing body in the present invention will be described.

  The water-absorbing body in the present invention is a molded article composed of a water-absorbing resin composition and other materials used for sanitary materials such as disposable diapers, sanitary napkins, incontinence pads, and medical pads that absorb blood, body fluids, urine and the like. An example of a material used is a cellulose fiber. Specific examples of cellulose fibers include wood pulp fibers such as mechanical pulp, chemical pulp, semi-chemical pulp, and dissolved pulp from wood, and artificial cellulose fibers such as rayon and acetate. A preferred cellulose fiber is wood pulp fiber. These cellulose fibers may partially contain synthetic fibers such as nylon and polyester. When the water absorbent resin composition of the present invention is used as a part of the water absorbent, the mass of the water absorbent resin composition of the present invention contained in the water absorbent is preferably in the range of 20% by mass or more. When the mass of the water absorbent resin composition of the present invention contained in the water absorbent is less than 20% by mass, a sufficient effect may not be obtained.

  In order to obtain a water absorbent from the water absorbent resin composition of the present invention and cellulose fibers, for example, a method of spraying the water absorbent resin composition on paper or mat made of cellulose fibers and sandwiching them with these as necessary, cellulose fibers and water absorbent Well-known means for obtaining a water-absorbing body, such as a method of uniformly blending the functional resin composition, can be appropriately selected. Preferably, the water-absorbing resin composition and the cellulose fiber are mixed in a dry manner and then compressed. By this method, it is possible to remarkably suppress the dropping of the water absorbent resin composition from the cellulose fiber. The compression is preferably performed under heating, and the temperature range is, for example, 50 to 200 ° C. In order to obtain a water-absorbing body, methods described in JP-T-9-509591 and JP-A-9-290000 are also preferably used.

The water-absorbent resin composition of the present invention is excellent in various physical properties when used in a water-absorbing body, so that the liquid can be taken in quickly and the remaining amount of liquid on the surface of the water-absorbing body is small. can get.
Since the water-absorbent resin composition of the present invention has excellent water absorption characteristics, it can be used as a water-absorbing water retaining agent for various applications. For example, water absorbent water absorbents for absorbent articles such as paper diapers, sanitary napkins, incontinence pads, medical pads; Anti-condensation agent for materials, water retention agent for construction such as cement additive; release control agent, cold insulation agent, disposable body warmer, sludge coagulant, food freshness preservation agent, ion exchange column material, sludge or oil dehydrating agent, desiccant Can be used as a humidity control material. The water-absorbent resin composition of the present invention is particularly preferably used for sanitary materials for absorbing feces, urine or blood, such as paper diapers and sanitary napkins.

When the water absorbent body in the present invention is used for sanitary materials such as disposable diapers, sanitary napkins, incontinence pads, medical pads, etc., (a) a liquid permeable top sheet disposed adjacent to the wearer's body, ( b) a liquid-impermeable backsheet disposed far from the wearer's body and adjacent to the wearer's clothing; and (c) a water absorbent disposed between the topsheet and the backsheet. It is preferable to be used in a configuration comprising Two or more water absorbent bodies may be used, or a water absorbent body may be used together with a pulp layer.

Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples, but the present invention is not limited to these. Hereinafter, for convenience, “part by mass” may be simply referred to as “part”, and “liter” may be simply referred to as “L”. Further, “mass%” may be described as “wt%”.
Measurement methods and evaluation methods in Examples and Comparative Examples are shown below.
Unless otherwise specified, the following measurements were performed under conditions of room temperature (25 ° C.) and humidity of 50 RH%.
In the case of a water-absorbent resin composition used as a final product such as sanitary material, the water-absorbent resin composition absorbs moisture. It may be measured later (for example, 1 mmHg or less, 12 hours at 60 ° C.). Moreover, the water content of the water-absorbent resin compositions used in the examples and comparative examples of the present invention was all 6% by mass or less.

<Absorption capacity without pressure (CRC)>
A 0.20 g water-absorbing resin or water-absorbing resin composition is accurately measured to a level of 0.0001 g, and is a non-woven fabric (made by Nankoku Pulp Co., Ltd., trade name: Heaton paper, model: GSP-22). (85 mm × 60 mm or 60 mm × 60 mm) was uniformly placed and sealed.
1 L of a 0.90 mass% sodium chloride aqueous solution (physiological saline) was charged into a 1 L container, and one evaluation sample was immersed in each container for 1 hour. Since the present invention focuses on the effect of ion migration, a plurality of samples must not be immersed in one container.

After 1 hour, the bag was pulled up, drained for 3 minutes at a centrifugal force of 250 G using a centrifuge (manufactured by Kokusan Co., Ltd., centrifuge: model H-122), and the mass W1 (g) of the bag was then determined. It was measured. Further, the same operation was performed without using the water absorbent resin or the water absorbent resin composition, and the mass W0 (g) at that time was measured. And from these W1 and W0, the absorption capacity (g / g) under no pressure was computed according to the following formula.
CRC (g / g) = [(W1 (g) -W0 (g)) / mass of water absorbent resin or water absorbent resin composition (g)]-1
<Absorption capacity under pressure (AAP)>
AAP was measured using the following method A or B. AAP may be measured using any of these methods, and the measured value is hardly affected by the measurement method.

As AAPs in the following Reference Examples, Examples and Comparative Examples, the AAPs listed in Table 1 are AAPs measured using the A method, and the other AAPs are AAPs measured using the B method.
(Method A)
Using the apparatus of FIG. 1, the absorption capacity (AAP) under pressure was measured.
A load 21 adjusted to a pressure of 4.83 kPa (0.7 psi) was prepared. A water-absorbent resin composition or about 0.90 g (Wp2) of a water-absorbing resin composition is sprayed on a metal mesh of a plastic cylinder 19 having a diameter of 60 mm and having a 400-mesh (mesh size 38 μm) metal mesh 18 attached to the bottom. A liquid absorbing device having a load of 21 (at 0.7 psi) is placed on the filter paper 17 on the glass filter 13 of FIG. 1, and after 60 minutes, the water absorbent resin composition or physiological saline absorbed by the water absorbent resin The value (Wc) of water (0.90 mass% NaCl aqueous solution) was measured. Absorption capacity under pressure was determined using the following equation.

AAP (g / g) = Wc / Wp2
(Method B)
It measured using the apparatus shown in FIG.
A stainless steel 400 mesh wire mesh (mesh size 38 μm) 101 is fused to the bottom of a plastic support cylinder 100 having an inner diameter of 60 mm and placed on the wire mesh under conditions of room temperature (20 to 25 ° C.) and humidity of 50 RH%. 0.90 g of water-absorbent resin or water-absorbent resin composition (102) is uniformly dispersed, and a load of 4.83 kPa (0.7 psi) is uniformly applied to the water-absorbent resin or water-absorbent resin composition. The piston 103 and the load 104, which are adjusted so that the outer diameter is slightly smaller than 60 mm and no gap is formed between the inner wall surface of the support cylinder and the vertical movement is not hindered, are mounted in this order. The mass Wa (g) of this set of measuring devices was measured.

A glass filter 106 having a diameter of 90 mm (manufactured by Mutual Riken Glass Co., Ltd., pore diameter: 100 to 120 μm) is placed inside a petri dish 105 having a diameter of 150 mm, and a 0.90 mass% sodium chloride aqueous solution (saline) 108 is placed. (20-25 ° C.) was added so as to be at the same level as the upper surface of the glass filter. On top of that, one sheet of filter paper (107) with a diameter of 90 mm (ADVANTEC Toyo Co., Ltd., product name: (JIS P 3801, No. 2), thickness 0.26 mm, reserved particle diameter 5 μm) is placed so that the entire surface becomes wet. And excess liquid was removed.
A set of measuring devices was placed on the wet filter paper, and the liquid was absorbed under load for a predetermined time. This absorption time was calculated from the start of measurement and was 1 hour later. Specifically, after 1 hour, the measuring device set was lifted and its mass Wb (g) was measured. This mass measurement must be performed as quickly as possible and without vibrations. And the absorption capacity | capacitance under pressure (AAP) (g / g) was computed from Wa and Wb by following Formula.

AAP (g / g) = [Wb (g) -Wa (g)] / mass of water absorbent resin or water absorbent resin composition (g)
<Saline flow conductivity (SFC)>
It carried out according to the physiological saline flow inductivity (SFC) test of Tokuheihei 9-509591.
Using the apparatus shown in FIG. 3, the water-absorbent resin or water-absorbent resin composition (0.900 g) uniformly placed in the container 40 was added to the artificial urine (1) under a pressure of 0.3 psi (2.07 kPa) under the pressure of 60 Swell for 1 minute (120 minutes for saline flow conductivity (SFC) retention measurements), record the gel layer height of gel 44, and then under pressure of 0.3 psi (2.07 kPa), A gel layer swollen from the tank 31 was passed through a 0.69 mass% sodium chloride aqueous solution 33 at a constant hydrostatic pressure. The SFC test was performed at room temperature (20-25 ° C.). Using a computer and a balance, the amount of liquid passing through the gel layer at 20 second intervals as a function of time was recorded for 10 minutes. The flow rate F _s (t) through the swollen gel 44 (mainly between the particles) was determined in units of g / s by dividing the increased mass (g) by the increased time (s). The time when the constant hydrostatic pressure and a stable flow rate had been obtained was set as t _s, using only data obtained in the course of t _s and 10 minutes flow rate calculation, the flow rate obtained in the course of t _s and 10 minutes Used to calculate the value of F _s (t = 0), ie the initial flow rate through the gel layer. F _s (t = 0) was calculated by extrapolating the result of the least square method of F _s (t) versus time to t = 0.

SFC
= (F _s (t = 0) × L _o ) / (ρ × A × ΔP)
= (F _s (t = 0) × L _o ) / 139506
here,
F _s (t = 0): flow rate L _o expressed in g / s: initial thickness of gel layer expressed in cm ρ: density of NaC1 solution (1.003 g / cm ³ )
A: Area above the gel layer in the cell 41 (28.27 cm ² )
ΔP: Hydrostatic pressure applied to the gel layer (4920 dyne / cm ² )
The unit of SFC is (× 10 ⁻⁷ · cm ³ · s · g ⁻¹ ).

  As an apparatus shown in FIG. 3, a glass tube 32 is inserted into the tank 31, and the lower end of the glass tube 32 is a 0.69 mass% sodium chloride aqueous solution 33 from the bottom of the swelling gel 44 in the cell 41. It was arranged so that it could be maintained at a height of 5 cm. The 0.69 mass% sodium chloride aqueous solution 33 in the tank 31 was supplied to the cell 41 through the L-shaped tube 34 with a cock. Under the cell 41, a container 48 for collecting the passed liquid is disposed, and the collection container 48 is installed on an upper pan balance 49. The inner diameter of the cell 41 is 6 cm. A 400 stainless steel wire mesh (aperture 38 μm) 42 was installed. The bottom of the piston 46 has a hole 47 sufficient for the liquid to pass through, and the bottom has a glass with good permeability so that the water absorbent resin or the water absorbent resin composition or their swelling gel does not enter the hole 47. A filter 45 was attached. The cell 41 was placed on a table on which the cell was placed, and the surface of the table in contact with the cell was placed on a stainless steel wire mesh 43 that did not prevent liquid permeation.

Artificial urine (1) consists of 0.25 g of calcium chloride dihydrate, 2.0 g of potassium chloride, 0.50 g of magnesium chloride hexahydrate, 2.0 g of sodium sulfate, 0.85 g of ammonium dihydrogen phosphate, A mixture of 0.15 g of diammonium hydrogen phosphate and 994.25 g of pure water was used.
<Saline flow conductivity after paint shaker test (SFC after PS)>
The following measurement was performed based on the apparatus described in JP-A-9-235378.
A glass bottle with a lid having a diameter of 6 cm and a height of 11 cm was charged with 30 g of a water-absorbent resin or a water-absorbent resin composition and about 10 g of glass beads (diameter 6 mm), and attached to a TOYOSEIKIPAINTSHAKER (for 100 V, 60 Hz) and agitated for 30 minutes. The glass beads and the water-absorbent resin or water-absorbent resin composition were decorated with a wire mesh of about 2 mm mesh to obtain a water-absorbent resin or water-absorbent resin composition after the paint shaker test.

The physiological saline flow inductivity of the obtained water-absorbent resin or water-absorbent resin composition was measured by the method described above.
In addition, CRC and AAP after PS can be measured similarly.
<Mass average particle diameter (D50) and logarithmic standard deviation of particle size distribution (σζ)>
The water-absorbing resin or water-soluble polyvalent metal salt particles or the water-absorbing resin composition is sieved with a JIS standard sieve having openings of 850 μm, 710 μm, 600 μm, 500 μm, 425 μm, 300 μm, 212 μm, 150 μm, 45 μm, etc. R was plotted on log probability paper. Thereby, the particle diameter corresponding to R = 50 mass% was read as the mass average particle diameter (D50). Further, the logarithmic standard deviation (σζ) of the particle size distribution is expressed by the following equation, and the smaller the value of σζ, the narrower the particle size distribution.

σζ = 0.5 × ln (X2 / X1)
(X1 is the particle size when R = 84.1% by mass, and X2 is the particle size when R = 15.9% by mass.)
The classification method for measuring the mass average particle diameter (D50) and the logarithmic standard deviation (σζ) of the particle size distribution is as follows. 20-25 ° C.) and humidity of 50 RH%, charged into a JIS standard sieve (THEIIDATESTINGSIEVE: diameter 8 cm) with openings of 850 μm, 710 μm, 600 μm, 500 μm, 425 μm, 300 μm, 212 μm, 150 μm, 45 μm, and vibration classifier ( IIDASIEVESHAKER, TYPE: ES-65 type, SER No. 0501), classification was performed for 5 minutes.

<Dust generation>
A water absorbent resin or a water absorbent resin composition was placed in a PE bag (No. 13) previously coated with an antistatic agent. After the bag was shaken 30 times, the bag was opened and measured with a DIGITAL DUST INDICATOR P-5L (manufactured by SHIBATA) for 1 minute. This measurement was performed 10 times, and the average value was obtained.
<Capillary absorption rate (CSF)>
CSF is an index representing the capillary suction force of a water absorbent resin or a water absorbent resin composition.
Capillary absorption capacity is determined by measuring the liquid absorption capacity of the absorber within a predetermined time in a negative pressure gradient of 20 cm of water under a 0.06 psi load.

With reference to FIG. 4, an apparatus and method for measuring these capillary absorption capacities will be described.
A glass filter 2 having a diameter of 60 mm and having a liquid absorption surface of a porous glass plate 1 (glass filter particle number # 3; Buchner type filter TOP 17G-3 (code no. 1175-03) manufactured by Mutual Science Glass Co., Ltd.) The conduit 3 was connected to the lower part, and this conduit 3 was connected to the mouth provided at the lower part of the reservoir 4 having a diameter of 10 cm. The porous glass plate of the glass filter has an average pore diameter of 20 to 30 μm, and even in a state where the liquid level height is 60 cm due to the capillary force, the porous glass plate resists the negative pressure of the water column. Water can be retained, and no air can be introduced. A support ring 5 for raising and lowering the height of the glass filter 2 is fitted, and the system is filled with 0.90% by mass physiological saline (0.90% by mass NaCl aqueous solution) (0.90% NaCl solution) 6 to collect the liquid. The container was placed on a balance 7. After confirming that there is no air in the conduit and at the bottom of the porous glass plate of the glass filter, the liquid surface level and the porosity of the upper part of the physiological saline (0.90 mass% NaCl aqueous solution) 6 in the liquid reservoir 4 The glass filter was fixed to the stand 8 by adjusting the height difference of the upper surface of the glass plate 1 to 20 cm.

0.44 g of the measurement sample 9 (water absorbent resin composition) is uniformly and quickly spread on the glass filter in the funnel on the porous glass plate 1, and a load 10 (0.06 psi) having a diameter of 59 mm is further placed thereon. After 30 minutes, the value (W20) of 0.90 mass% physiological saline (0.90 mass% NaCl aqueous solution) absorbed in the measurement sample 9 was measured.
Capillary absorption capacity is obtained by the following equation.
Capillary absorption rate (CSF) (g / g) = Amount absorbed (W20) (g) /0.44 (g)
<Saline flow conductivity (SFC) retention rate (SFC retention rate)>
In the measurement method of physiological saline flow inductivity (SFC), the swelling for 60 minutes under a pressure of 0.3 psi (2.07 kPa) was caused to swell for 120 minutes instead, and the same measurement was performed thereafter. Saline flow conductivity (SFC) measured after swelling for 60 minutes is denoted as SFC (1 hr), and saline flow conductivity (SFC) measured after swelling for 120 minutes is denoted as SFC (2 hr). The SFC retention rate is expressed by the following formula.

SFC retention rate (%) = [SFC (2 hr) / SFC (1 hr)] × 100
<Saline flow conductivity (SFC) retention after paint shaker test (PS retention)>
The following measurement was performed based on the apparatus described in JP-A-9-235378.
A glass bottle with a lid having a diameter of 6 cm and a height of about 11 cm was charged with 30 g of the water-absorbent resin composition and about 10 g of glass beads (diameter 6 mm), and attached to a TOYOSEIKI PAINT SHAKER (for 100 V 60 Hz) and shaken for 30 minutes. The water absorbent resin composition after the paint shaker test was obtained by sieving the glass beads and the water absorbent resin composition with a wire mesh of about 2 mm mesh. The liquid passing rate under pressure of the obtained water-absorbent resin composition was measured by the method described above. SPS (after PS) is the flow rate under pressure of the water-absorbent resin composition after the paint shaker test, and SPS (before PS) is maintained after PS when the flow rate under pressure of the water-absorbent resin composition before the paint shaker test is SFC (before PS) The rate is expressed by the following formula.

Retention rate after PS (%) = [SFC (after PS) / SFC (before PS)] × 100
<Contact angle>
A double-sided adhesive tape is affixed on a SUS plate, and a water-absorbing resin or a water-absorbing resin composition is spread on the SUS plate so that the water-absorbing resin or water-absorbing resin composition is dense and uniform. A sample plate whose surface was covered with a water absorbent resin or a water absorbent resin composition was prepared. A contact angle meter (Kyowa Interface Science Co., Ltd., FACE CA-X type) was used under the conditions of 20 ° C. and 60% RH when the physiological saline (0.90 mass%) was brought into contact with the sample plate. ) Using a droplet method. The contact angle 1 second after dropping the physiological saline droplet on the sample plate was measured five times for each sample, and the average value was obtained as the contact angle of the water absorbent resin or water absorbent resin composition.

<Amount of soluble component (water-soluble component)>
Weigh out 184.3 g of 0.90 mass% physiological saline in a plastic container with a cap of 250 ml capacity, add 1.00 g of water-absorbing resin particles or water-absorbing resin composition to the aqueous solution, and stir for 16 hours in the resin. The soluble component was extracted. Filtration of this extract using one sheet of filter paper (ADVANTEC Toyo Co., Ltd., product name: (JIS P 3801, No. 2), thickness 0.26 mm, retained particle diameter 5 μm) gave 50. 0 g was measured and used as a measurement solution.
First, only 0.90% by mass physiological saline is titrated with 0.1N NaOH aqueous solution to pH 10, and then titrated with 0.1N HCl aqueous solution to pH 2.7 to perform empty titration ([bNaOH] ml, [bHCl] ml).

The titration ([NaOH] ml, [HCl] ml) was determined by performing the same titration operation on the measurement solution.
For example, in the case of a water-absorbing resin or water-absorbing resin particle or water-absorbing resin composition comprising a known amount of acrylic acid and its sodium salt, the water absorbing property is determined based on the average molecular weight of the monomer and the titration amount obtained by the above operation. The soluble content in the resin can be calculated by the following formula. In the case of an unknown amount, the average molecular weight of the monomer is calculated using the neutralization rate obtained by titration.
Soluble content (mass%) = 0.1 × (average molecular weight) × 184.3 × 100 × ([HCl] − [bHCl]) / 1000 / 1.0 / 50.0
Neutralization rate (mol%) = (1 − ([NaOH] − [bNaOH]) / ([HCl] − [bHCl])) × 100
[Reference Example 1]
5438 g of an aqueous solution of sodium acrylate having a neutralization rate of 71.3 mol% in a reactor formed by attaching a jacket to a stainless steel double-armed kneader with a volume of 10 liters having two sigma-shaped blades ( 11.7 g (0.10 mol%) of polyethylene glycol diacrylate was dissolved in a monomer concentration of 39% by mass to obtain a reaction solution. Next, this reaction solution was degassed for 30 minutes in a nitrogen gas atmosphere. Subsequently, 29.34 g of a 10% by mass sodium persulfate aqueous solution and 24.45 g of a 0.1% by mass L-ascorbic acid aqueous solution were added to the reaction solution with stirring. Polymerization started after about 1 minute. Then, polymerization was performed at 20 to 95 ° C. while pulverizing the generated gel, and a hydrogel crosslinked polymer was taken out 30 minutes after the polymerization started. The obtained hydrogel crosslinked polymer was subdivided to have a diameter of about 5 mm or less. This finely divided hydrogel crosslinked polymer was spread on a 50 mesh (mesh opening 300 μm) wire net and dried in hot air at 180 ° C. for 50 minutes. In this way, a water-absorbing resin (1) in an irregular shape and easily pulverized in the form of particles, powder, or agglomerated particulate matter was obtained.

The obtained water absorbent resin (1) was pulverized using a roll mill, and further classified with a 850 μm JIS standard sieve. Next, the water-absorbing resin (1aF) that passed through the JIS standard sieve having an opening of 150 μm was removed by classifying the particles that passed through 850 μm by the above-described operation with a JIS standard sieve having an opening of 150 μm. In this way, a particulate water-absorbing resin (1a) was obtained.
The obtained water absorbent resin (1aF) was granulated according to the method of Granulation Example 1 described in US Pat. No. 6,228,930. This granulated product was pulverized and classified in the same procedure as described above. Thus, the water-absorbing resin (1aA) granulated was obtained.
90 parts by mass of the water absorbent resin (1a) thus obtained and 10 parts by mass of the water absorbent resin (1aA) were uniformly mixed to obtain a water absorbent resin (A).

Further, the water absorbent resin (1) obtained in the same manner was pulverized using a roll mill, and further classified with a 710 μm JIS standard sieve. Next, the water-absorbent resin particles (1bF) that passed through the JIS standard sieve having an opening of 150 μm were removed by classifying the particles that passed through 710 μm by the above-described operation with a JIS standard sieve having an opening of 150 μm. In this way, a particulate water-absorbing resin (1b) was obtained.
The obtained water absorbent resin (1bF) was granulated according to the method of Granulation Example 1 described in US Pat. No. 6,228,930. This granulated product was pulverized and classified in the same procedure as described above. Thus, the water-absorbing resin (1bA) granulated was obtained.

85 parts by mass of the water absorbent resin (1b) thus obtained and 15 parts by mass of the water absorbent resin (1bA) were uniformly mixed to obtain a water absorbent resin (B).
Further, similarly obtained water absorbent resin (1) was pulverized using a roll mill, and further classified with a JIS standard sieve having an opening of 600 μm. Next, the water-absorbent resin particles (1 cF) that passed through the JIS standard sieve having an opening of 150 μm were removed by classifying the particles that passed through 600 μm by the above-described operation with a JIS standard sieve having an opening of 150 μm. In this way, a particulate water-absorbing resin (1c) was obtained.
The obtained water absorbent resin (1cF) was granulated according to the method of Granulation Example 1 described in US Pat. No. 6,228,930. This granulated product was pulverized and classified in the same procedure as described above. A granulated water-absorbing resin (1cA) was thus obtained.

80 parts by mass of the water absorbent resin (1c) thus obtained and 20 parts by mass of the water absorbent resin (1cA) were uniformly mixed to obtain a water absorbent resin (C).
[Reference Example 2]
After mixing the surface treatment agent consisting of a mixed solution of 0.5 g of 1,4-butanediol, 1.0 g of propylene glycol and 3.0 g of pure water into 100 g of the water absorbent resin (C) obtained in Reference Example 1. The mixture was heat treated at 210 ° C. for 30 minutes. Further, the particles were pulverized until passing through a JIS standard sieve having an opening of 600 μm to obtain a water-absorbing resin (C1) whose surface was crosslinked.

Table 1 shows the results obtained by measuring various physical properties of the water absorbent resin (C1).
[Reference Example 3]
A surface treatment agent comprising a mixture of 0.1 g of 2-ethyloxetane, 3.0 g of pure water and 0.3 g of a 24% by weight sodium hydroxide aqueous solution on 100 g of the water absorbent resin (A) obtained in Reference Example 1. After mixing, the mixture was heat-treated at 200 ° C. for 30 minutes. Furthermore, the particles were pulverized until they passed through a JIS standard sieve having an opening of 850 μm, to obtain a water-absorbent resin (A1) whose surface was crosslinked.
Table 1 shows the results obtained by measuring various physical properties of the water absorbent resin (A1).

[Reference Example 4]
A surface treatment agent composed of a mixed solution of 0.5 g of 2-oxazolidinone, 1.0 g of propylene glycol, and 4.0 g of pure water was mixed with 100 g of the water absorbent resin (B) obtained in Reference Example 1, and then the mixture was mixed. Heat treatment was performed at 190 ° C. for 30 minutes. Further, the particles were pulverized until passing through a JIS standard sieve having a mesh size of 710 μm to obtain a water-absorbent resin (B1) having a crosslinked surface.
Table 1 shows the results obtained by measuring various physical properties of the water absorbent resin (B1).
[Reference Example 5]
A surface treatment agent composed of a mixed solution of 0.5 g of ethylene carbonate, 1.0 g of propylene glycol, and 4.0 g of pure water was mixed with 100 g of the water absorbent resin (C) obtained in Reference Example 1, and then the mixture was mixed with 195. Heat treatment was carried out at 30 ° C. for 30 minutes. Further, the particles were pulverized until passing through a JIS standard sieve having an opening of 600 μm to obtain a water-absorbent resin (C2) whose surface was crosslinked.

Table 1 shows the results obtained by measuring various physical properties of the water absorbent resin (C2).
[Reference Example 6]
100 g of the water-absorbent resin (A) obtained in Reference Example 1 above, a mixed solution of 0.5 g of ethylene carbonate, 6.0 g of pure water, and 14-18 hydrate of aluminum sulfate (obtained from Kanto Chemical Co., Ltd.) After mixing the surface treatment agent consisting of, the mixture was heat-treated at 195 ° C. for 30 minutes. Further, the particles were pulverized until passing through a JIS standard sieve having an opening of 850 μm to obtain a water-absorbing resin (A2) whose surface was crosslinked.
Table 1 shows the results obtained by measuring various physical properties of the water absorbent resin (A2).

[Reference Example 7]
Aluminum sulfate 14-18 is obtained by classifying aluminum sulfate 14-18 hydrate (obtained from Kanto Chemical Co., Ltd.) with a JIS standard sieve having an opening of 600 μm, an opening of 300 μm, and an opening of 150 μm. Water salt (1), aluminum sulfate 14-18 hydrate (2) having a particle size of substantially 300 to 150 μm, and aluminum sulfate 14-18 hydrate (3) having a particle size of substantially 600 to 300 μm were obtained. The weight average particle diameter of aluminum sulfate 14-18 hydrate (1) is 95 μm, the weight average particle diameter of aluminum sulfate 14-18 hydrate (2) is 203 μm, and the weight average particle of aluminum sulfate 14-18 hydrate (3) The diameter was 401 μm.

[Example 1]
To 100 parts by mass of the water-absorbent resin (C1) obtained in Reference Example 2, aluminum sulfate hydrate (13-14 hydrate, obtained from Sumitomo Chemical Co., Ltd., mass average particle size 165 μm, bulk specific gravity 0.86 g / Cm ³ , solubility in pure water at 0 ° C. 46.4% by mass) was uniformly mixed to obtain a water absorbent resin composition (1).
Table 1 shows the results obtained by measuring various physical properties of the water absorbent resin composition (1). Further, Table 4 shows the results of measuring CSF.
[Example 2]
To 100 parts by mass of the water-absorbent resin (C1) obtained in Reference Example 2, aluminum sulfate 14-18 hydrate (obtained from Kanto Chemical Co., Inc., mass average particle size 182 μm, bulk specific gravity 0.60 g / cm ³ ) 0 parts by mass were uniformly mixed to obtain a water absorbent resin composition (2).

Table 1 shows the results of measurements of various physical properties of the water absorbent resin composition (2) obtained. Further, the results of measuring the saline flow conductivity (SFC) retention rate are shown in Table 2, and the results of measuring CSF are shown in Table 4.
Example 3
To 100 parts by mass of the water-absorbent resin (A1) obtained in Reference Example 3, aluminum sulfate hydrate (13-14 hydrate, obtained from Sumitomo Chemical Co., Ltd., mass average particle size 165 μm, bulk specific gravity 0.86 g / Cm ³ ) 1.0 part by mass was mixed uniformly to obtain a water absorbent resin composition (3).
Table 1 shows the results obtained by measuring various physical properties of the water absorbent resin composition (3).

Example 4
To 100 parts by mass of the water-absorbent resin (B1) obtained in Reference Example 4, aluminum sulfate hydrate (13-14 hydrate, obtained from Sumitomo Chemical Co., Ltd., mass average particle diameter 165 μm, bulk specific gravity 0.86 g / Cm ³ ) 0.1 part by mass was uniformly mixed to obtain a water absorbent resin composition (4).
Table 1 shows the results obtained by measuring various physical properties of the water absorbent resin composition (4).
Example 5
To 100 parts by mass of the water-absorbent resin (C2) obtained in Reference Example 5, aluminum sulfate hydrate (13-14 hydrate, obtained from Sumitomo Chemical Co., Ltd., mass average particle size 165 μm, bulk specific gravity 0.86 g / Cm ³ ) 0.5 part by mass was uniformly mixed to obtain a water absorbent resin composition (5).

Table 1 shows the results obtained by measuring various physical properties of the water absorbent resin composition (5).
Example 6
To 100 parts by mass of the water-absorbent resin (C1) obtained in Reference Example 2, 0.5 part by mass of the aluminum sulfate 14-18 hydrate (1) obtained in Reference Example 7 is uniformly mixed to obtain a water-absorbent resin composition. A product (6) was obtained.
Table 1 shows the results obtained by measuring various physical properties of the water absorbent resin composition (6).
Example 7
100 parts by weight of the water absorbent resin (C1) obtained in Reference Example 2 and 0.5 part by weight of the aluminum sulfate 14-18 hydrate (2) obtained in Reference Example 7 are uniformly mixed to obtain a water absorbent resin composition. A product (7) was obtained.

Table 1 shows the results obtained by measuring various physical properties of the water absorbent resin composition (7) obtained.
Example 8
100 parts by mass of the water absorbent resin (C1) obtained in Reference Example 2 and 0.5 part by mass of the aluminum sulfate 14-18 hydrate (3) obtained in Reference Example 7 are uniformly mixed to obtain a water absorbent resin composition. Product (8) was obtained.
Table 1 shows the results obtained by measuring various physical properties of the water absorbent resin composition (8).
Example 9
The wettability of the water absorbent resin composition to physiological saline was evaluated by the contact angle.

Similar to Example 1 using the water-absorbent resin composition (1) obtained in Example 1 (aluminum sulfate additive) (before PS) and Aerosil R-972 (manufactured by Nippon Aerosil) instead of aluminum sulfate. The contact angle of physiological saline of the water-absorbent resin composition obtained by the above operation was measured by the method described above.
Table 3 shows the measurement results of the contact angle.
[Comparative Example 1]
The water absorbent resin (C1) obtained in Reference Example 2 was used as a comparative water absorbent resin (1).
Table 1 shows the results of measuring various physical properties of the comparative water absorbent resin (1).

[Comparative Example 2]
To 100 parts by mass of the water absorbent resin (A) obtained in Reference Example 1, aluminum sulfate 14-18 hydrate (obtained from Kanto Chemical Co., Inc., mass average particle size 182 μm, bulk specific gravity 0.60 g / cm ³ ). 5 parts by mass were mixed uniformly to obtain a comparative water absorbent resin composition (2).
Table 1 shows the results obtained by measuring various physical properties of the comparative water absorbent resin composition (2). Further, Table 4 shows the results of measuring CSF.
[Comparative Example 3]
To 100 parts by mass of the water-absorbent resin (A) obtained in Reference Example 1, aluminum sulfate 14-18 hydrate (obtained from Kanto Chemical Co., Ltd., mass average particle size 182 μm, bulk specific gravity 0.60 g / cm ³ , 23 ° C. A water-absorbing resin composition (3) was obtained by uniformly mixing 5 mass parts of a 10 mass% aqueous solution having a solubility in pure water of 37.5 mass%.

Table 1 shows the results obtained by measuring various physical properties of the obtained comparative water-absorbent resin composition (3). Further, Table 4 shows the results of measuring CSF.
[Comparative Example 4]
To 100 parts by mass of the water-absorbent resin (C1) obtained in Reference Example 2, aluminum sulfate 14-18 hydrate (obtained from Kanto Chemical Co., Ltd., mass average particle diameter 182 μm, bulk specific gravity 0.60 g / cm ³ ) 10 mass 5 parts by mass of a 5% aqueous solution was uniformly mixed to obtain a comparative water absorbent resin composition (4).
Table 1 shows a result obtained by measuring properties of the comparative water absorbent resin composition (4). Further, the results of measuring the saline flow conductivity (SFC) retention rate are shown in Table 2.

[Comparative Example 5]
The water absorbent resin (A2) obtained in Reference Example 6 was used as the comparative water absorbent resin (5).
Table 1 shows the results of measuring various physical properties of the comparative water absorbent resin (5). Further, Table 4 shows the results of measuring CSF.
[Comparative Example 6]
100 parts by mass of the water-absorbent resin (C2) obtained in Reference Example 5, aluminum sulfate hydrate (13-14 hydrate, obtained from Sumitomo Chemical Co., Ltd., mass average particle size 165 μm, bulk specific gravity 0.86 g / cm ³ ) 0.5 part by mass was uniformly mixed, and further 5 parts by mass of pure water was added to obtain a comparative water absorbent resin composition (6).

Table 1 shows a result obtained by measuring properties of the comparative water absorbent resin composition (6) obtained.
Example 10
The water absorbent resin composition (2) obtained in Example 2, the comparative water absorbent resin composition (4) obtained in Comparative Example 4, and the comparative water absorbent resin composition (6) obtained in Comparative Example 6 were used. The state of aluminum sulfate was examined using an electron micrograph.
The aluminum sulfate of the water absorbent resin composition (2) was present in the form of particles, but part or all of the aluminum sulfate of the comparative water absorbent resin composition (4) and the comparative water absorbent resin composition (6) was dissolved. It was not present in particulate form. The presence of aluminum sulfate was confirmed by EPMA analysis of aluminum.

[Reference Example 8]
5438 g of an aqueous solution of sodium acrylate having a neutralization rate of 71.3 mol% in a reactor formed by attaching a jacket to a stainless steel double-armed kneader with a volume of 10 liters having two sigma-shaped blades ( 11.7 g (0.10 mol%) of polyethylene glycol diacrylate was dissolved in a monomer concentration of 39% by mass to obtain a reaction solution. Next, this reaction solution was degassed for 30 minutes in a nitrogen gas atmosphere. Subsequently, 29.34 g of a 10% by mass sodium persulfate aqueous solution and 24.45 g of a 0.1% by mass L-ascorbic acid aqueous solution were added to the reaction solution with stirring. Polymerization started after about 1 minute. Then, polymerization was performed at 20 to 95 ° C. while pulverizing the generated gel, and a hydrogel crosslinked polymer was taken out 30 minutes after the polymerization started. The obtained hydrogel crosslinked polymer was subdivided to have a diameter of about 5 mm or less. This finely divided hydrogel crosslinked polymer was spread on a 50 mesh (mesh opening 300 μm) wire net and dried in hot air at 180 ° C. for 50 minutes. In this way, an amorphous water-absorbing resin (1) having an agglomerated particulate dry matter aggregate that was easily pulverized was obtained.

The obtained water absorbent resin (1) was pulverized using a roll mill, and further classified with a 850 μm JIS standard sieve. Next, the particles having passed through 850 μm in the above operation are classified with a JIS standard decoration having an opening of 150 μm to remove the water-absorbing resin (1aF) having passed through the JIS standard sieve having an opening of 150 μm. Resin (1a) was obtained.
The removed water absorbent resin (1aF) was granulated in accordance with the method of Granulation Example 1 described in US Pat. No. 6,228,930. This granulated product was pulverized and classified in the same procedure as described above. Thus, the water-absorbing resin (1aA) granulated was obtained.
80 parts by mass of the water absorbent resin (1a) thus obtained and 20 parts by mass of the water absorbent resin (1aA) were uniformly mixed to obtain a water absorbent resin (1C).

Next, after mixing 500 g of the water-absorbent resin (1C) and a surface treatment agent composed of a mixed solution of 2.5 g of 1,4-butanediol, 5.0 g of propylene glycol, and 15.0 g of pure water, the mixture was mixed with 210 g. Heat treatment was carried out at 30 ° C. for 30 minutes. The heat-treated water-absorbent resin was crushed until it passed through a JIS standard sieve having an opening of 600 μm to obtain a surface-crosslinked water-absorbent resin (1D).
Table 5 shows various physical properties of the surface-crosslinked water-absorbing resin (1D).
Table 6 shows the degree of dust generation of the surface-crosslinked water-absorbent resin (1D).
Example 11
After 300 g of the surface-crosslinked water-absorbing resin (1D) obtained in Reference Example 8 was heated in advance to 60 ° C., 1.5 g of water was spray-mixed with stirring in a Redige mixer. Subsequently, 3 g of aluminum sulfate 14-18 hydrate was added and mixed with stirring in a Redige mixer, and allowed to stand at room temperature for 30 minutes. The obtained mixture was pulverized until it passed through a JIS standard sieve having an opening of 600 μm to obtain a water absorbent resin composition (11).

Various physical properties of the water absorbent resin composition (11) are shown in Table 5.
Table 6 shows the degree of dust generation of the water absorbent resin composition (11).
[Examples 12 to 14]
In Example 11, water-absorbing resin compositions (12) to (14) were obtained in the same manner as in Example 11 except that the amount of water used was 3 g, 4.5 g, and 6 g, respectively.
Table 5 shows various physical properties of the water absorbent resin compositions (12) to (14).
Table 6 shows the degree of dust generation of the water absorbent resin compositions (12) to (14).
Example 15
In Example 11, water-absorbing resin composition (15) was obtained in the same manner as in Example 11 except that 6 g of water / glycerin = 50/50 (wt / wt) aqueous solution was used instead of 1.5 g of water. It was.

Various physical properties of the water absorbent resin composition (15) are shown in Table 5.
Example 16
In Example 11, a water absorbent resin composition (16) was prepared in the same manner as in Example 11 except that 6 g of water / propylene glycol = 50/50 (wt / wt) aqueous solution was used instead of 1.5 g of water. Obtained.
Various physical properties of the water absorbent resin composition (16) are shown in Table 5.
Example 17
In Example 11, a water-absorbent resin composition was used in the same manner as in Example 11 except that 6 g of water / polyethylene glycol (average molecular weight 600) = 50/50 (wt / wt) aqueous solution was used instead of 1.5 g of water. A product (17) was obtained.

Table 5 shows properties of the water absorbent resin composition (17).
[Comparative Example 7]
300 g of the surface-crosslinked water-absorbing resin (1D) obtained in Reference Example 8 and 3 g of aluminum sulfate 14-18 hydrate were mixed (dry blended) with stirring using a Redige mixer, and a comparative water-absorbing resin composition was prepared. A product (7) was obtained.
Table 5 shows properties of the comparative water absorbent resin composition (7).
Example 18
500 g of the non-surface-crosslinked water-absorbing resin (1C) obtained in Reference Example 8 was preheated to 50 ° C., and then 2.5 g of 1,4-butanediol, 5.0 g of propylene glycol, and 15.0 g of pure water. A surface treatment agent comprising the above mixture was mixed with a Readyge mixer, and subsequently 3 g of aluminum sulfate 14-18 hydrate was added and mixed with stirring with a Readyge mixer. The mixture was heat-treated at 210 ° C. for 30 minutes, and then crushed until it passed through a JIS standard sieve having an opening of 600 μm to obtain a water absorbent resin composition (18).

Various physical properties of the water absorbent resin composition (18) are shown in Table 5.
[Comparative Example 8]
500 g of the non-surface-crosslinked water-absorbing resin (1C) obtained in Reference Example 8, 2.5 g of 1,4-butanediol, 5.0 g of propylene glycol, 3 g of aluminum sulfate 14-18 hydrate, and pure water 15 A surface treatment agent composed of 0.0 g of a mixed solution was mixed with a Redige mixer. This mixture was heat-treated at 210 ° C. for 30 minutes and then crushed until it passed through a JIS standard sieve having an opening of 600 μm to obtain a comparative water absorbent resin composition (8).
Table 5 shows properties of the comparative water absorbent resin composition (8).

[Comparative Example 9]
To 500 g of the surface-crosslinked water-absorbing resin (1D) obtained in Reference Example 8, 50 g of a 12% by mass aqueous solution of aluminum sulfate 14-18 hydrate was spray-mixed with stirring using a Redige mixer, and then 80 ° C. For 30 minutes. The dried product was pulverized until it passed through a JIS standard sieve having an opening of 600 μm to obtain a comparative water absorbent resin composition (9).
Table 5 shows properties of the comparative water absorbent resin composition (9).
[Comparative Example 10]
To 500 g of the comparative water-absorbent resin composition (7) obtained in Comparative Example 7, 10 g of water was sprayed and mixed with a Redige mixer, and then allowed to stand at room temperature for 30 minutes. The obtained mixture was pulverized until it passed through a JIS standard sieve having an opening of 600 μm to obtain a comparative water absorbent resin composition (10).

Various physical properties of the comparative water absorbent resin composition (10) are shown in Table 5.
Example 19
In Example 13, a water-absorbent resin composition (19) was obtained in the same manner as in Example 13 except that aluminum sulfate 14-18 hydrate passed through a JIS standard sieve having an aperture of 105 μm was used.
Table 5 shows properties of the water absorbent resin composition (19).
[Reference Example 9]
In Reference Example 8, except that 7.6 g of polyethylene glycol diacrylate was used, the same procedure as in Reference Example 8 was carried out. First, the water-absorbent resin (2) of the particulate dried product aggregate that was easily pulverized in an irregular shape was obtained. Obtained.

  That is, an aqueous solution of sodium acrylate having a neutralization rate of 71.3 mol% in a reactor formed by attaching a lid to a stainless steel double-arm kneader with a 10 liter inner volume and having two sigma type blades In 5438 g (monomer concentration: 39% by mass), 7.6 g (0.065 mol%) of polyethylene glycol diacrylate was dissolved to obtain a reaction solution. Next, this reaction solution was degassed for 30 minutes in a nitrogen gas atmosphere. Subsequently, 29.34 g of a 10% by mass aqueous sodium persulfate solution and 24.45 g of a 0.1% by mass L-ascorbic acid aqueous solution were added to the reaction solution with stirring, and polymerization started about 1 minute later. Then, polymerization was performed at 20 to 95 ° C. while pulverizing the generated gel, and a hydrogel crosslinked polymer was taken out 30 minutes after the polymerization started. The obtained hydrogel crosslinked polymer was subdivided to have a diameter of about 5 mm or less. This finely divided hydrogel crosslinked polymer was spread on a 50 mesh (mesh opening 300 μm) wire net and dried with hot air at 180 ° C. for 50 minutes. In this way, a water-absorbing resin (2) of an agglomerated particulate dry matter aggregate which is irregular and easily pulverized was obtained.

The obtained water absorbent resin (2) was pulverized using a roll mill, and further classified with a 850 μm JIS standard sieve. Next, the particles having passed through 850 μm in the above operation are classified with a JIS standard decoration having an opening of 150 μm, so that the water absorbent resin (2aF) having passed through the JIS standard sieve having an opening of 150 μm is removed. Resin (2a) was obtained.
The removed water absorbent resin (2aF) was granulated in accordance with the method of Granulation Example 1 described in US Pat. No. 6,228,930. This granulated product was pulverized and classified in the same procedure as described above. Thus, the water-absorbing resin (2aA) granulated was obtained.
90 parts by mass of the water absorbent resin (2a) thus obtained and 10 parts by mass of the water absorbent resin (2aA) were uniformly mixed to obtain a water absorbent resin (2C).

Next, after mixing 500 g of the water-absorbing resin (2C) with a surface treatment agent composed of a mixture of 2.5 g of 1,4-butanediol, 5.0 g of propylene glycol, and 15.0 g of pure water, the mixture was mixed with 210 g. Heat treatment was performed at 0 ° C. for 30 minutes. The heat-treated water-absorbent resin was crushed until it passed through a JIS standard sieve having an opening of 850 μm to obtain a surface-crosslinked water-absorbent resin (2D).
Various physical properties of the surface-crosslinked water-absorbing resin (2D) are shown in Table 5.
Example 20
In Example 13, instead of the surface-crosslinked water-absorbing resin (1D), water-absorbing water was obtained in the same manner as in Example 13 except that the surface-crosslinked water-absorbing resin (2D) obtained in Reference Example 9 was used. Resin composition (20) was obtained.

Various physical properties of the water absorbent resin composition (20) are shown in Table 5.
Example 21
The distribution for each particle size of aluminum sulfate contained in the water absorbent resin compositions (11) to (17) obtained in Examples 11 to 17 and the comparative water absorbent resin composition (7) obtained in Comparative Example 7 is as follows. Obtained by the method of The results are shown in Table 7.
(I) The water-absorbent resin composition was sieved with JIS standard sieves having openings of 600 μm, 425 μm, and 300 μm, and particle size distributions of 600/425 μm, 425/300 μm, and 300 μm pass were obtained.

(Ii) 1 g of the water absorbent resin composition of each particle size classified in (i) above was accurately weighed.
(Iii) Place a 35 mm Teflon (registered trademark) rotor in a 260 ml polypropylene beaker, add 1 g of the water-absorbent resin composition weighed in (ii) above, 190 g of a 0.9 mass% sodium chloride aqueous solution, and 10 g of 2N hydrochloric acid. The mixture was stirred for 5 minutes using a magnetic stirrer.
(Iv) After stirring, the supernatant was sucked with a polypropylene syringe and filtered with a chromatodisc (GL chromatodisc 25A, manufactured by GL Sciences Inc.).
(V) The filtrate was analyzed by ICP (plasma emission spectroscopy), and the amount (%) of aluminum sulfate for each particle size contained in the classified water-absorbent resin composition of each particle size was determined.

(Vi) The distribution for each particle size of aluminum sulfate was determined according to the following formula.
Distribution of aluminum sulfate by particle size (%)
= [Aluminum sulfate amount (%) per particle size x particle size distribution (%)] x 100 / Σ [Aluminum sulfate amount (%) per particle size x particle size distribution (%)]
For example, 600/425 μm particle size distribution is 13%, 600/425 μm aluminum sulfate amount is 0.20%, 425/300 μm particle size distribution is 45%, 425/300 μm aluminum sulfate amount is 0.17%, 300 μm pass. When the particle size distribution of 42% and the amount of aluminum sulfate in the 300 μm pass is 0.89%, the distribution of aluminum sulfate 600/425 μm is
600/425 μm distribution of aluminum sulfate (%)
= (0.20 × 0.13) × 100 / (0.20 × 0.13 + 0.17 × 0.45 + 0.89 × 0.42) = 5 (%).

  Since the water-absorbent resin composition of the present invention has excellent water absorption characteristics, it can be used as a water-absorbing water retaining agent for various applications. For example, water absorbent water absorbents for absorbent articles such as disposable diapers, sanitary napkins, incontinence pads, and medical pads; moss substitutes, soil modification improvers, water retention agents, water retention agents for agricultural and horticultural use such as agrochemical potency retention agents; interior walls Anti-condensation agent for materials, water retention agent for construction such as cement additive; release control agent, cold insulation agent, disposable body warmer, sludge coagulant, food freshness preservation agent, ion exchange column material, sludge or oil dehydrating agent, desiccant Can be used as a humidity control material. The water-absorbent resin composition of the present invention is particularly preferably used for sanitary materials for absorbing feces, urine or blood, such as paper diapers and sanitary napkins.

It is general | schematic sectional drawing of the measuring apparatus used for the measurement of AAP (A method). It is general | schematic sectional drawing of the measuring apparatus used for the measurement of AAP (B method). It is general | schematic sectional drawing of the measuring apparatus used for a measurement of SFC. It is general | schematic sectional drawing of the measuring apparatus used for the measurement of CSF.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Porous glass plate 2 Glass filter 3 Conduit 4 Reservoir container 5 Support ring 6 0.90 mass% physiological saline 7 Balance 8 Stand 9 Measurement sample (water-absorbing resin particle, water-absorbing resin composition, etc.)
10 Load (0.41 kPa (0.06 psi))
11 Outside air intake pipe 12 Conduit 13 Glass filter 14 0.90 mass% physiological saline 15 Liquid storage container 16 Balance 17 Filter paper 18 Wire mesh 19 Plastic cylinder 20 Load (2.07 kPa (0.3 psi))
21 load (4.83 kPa (0.7 psi))
31 Tank 32 Glass tube 33 0.69 mass% sodium chloride aqueous solution 34 L-shaped tube with cock 35 Cock 40 Container 41 Cell 42 Stainless steel wire mesh 43 Stainless steel wire mesh 44 Swelling gel 45 Glass filter 46 Piston 47 Hole 48 in the piston Container 49 Upper pan balance 100 Plastic support cylinder 101 Stainless steel 400 mesh wire mesh 102 Swelling gel 103 Piston 104 Load (weight)
105 Petri dish 106 Glass filter 107 Filter paper 108 0.90 mass% physiological saline

Claims (17)

A water-absorbent resin composition comprising surface-crosslinked water-absorbent resin particles obtained by polymerizing a monomer containing acrylic acid and / or a salt thereof and water-soluble polyvalent metal salt particles,
The water-soluble polyvalent metal salt particles are polyvalent metal salt particles that can be dissolved in pure water at room temperature at a concentration of 5% by mass or more, and
The water-absorbing resin particles and the water-soluble polyvalent metal salt particles are mixed with each other by adding a binder to the water-absorbing resin particles and mixing the water-soluble polyvalent metal salt particles ,
The mass average particle size of the composition is 100 to 600 μm.
A water-absorbent resin composition characterized by that. A water-absorbent resin composition comprising surface-crosslinked water-absorbent resin particles obtained by polymerizing a monomer containing acrylic acid and / or a salt thereof and water-soluble polyvalent metal salt particles,
The water-soluble polyvalent metal salt particles are polyvalent metal salt particles that can be dissolved in pure water at room temperature at a concentration of 5% by mass or more, and
The composition has a mass average particle diameter of 100 to 600 μm and a physiological saline flow conductivity (SFC) of at least 50 (× 10 ⁻⁷ · cm ³ · s · g ⁻¹ ), and is defined by the following formula: Saline flow conductivity (SFC) retention is 60% or more,
A water-absorbent resin composition characterized by that.
SFC retention rate (%) = [SFC (2 hr) / SFC (1 hr)] × 100   The water-absorbent resin composition according to claim 1 or 2, wherein the water-soluble polyvalent metal salt particles are an aluminum salt having crystal water.   The water-absorbent resin composition according to any one of claims 1 to 3, wherein the surface-crosslinked water-absorbent resin particles are surface-crosslinked with a polyhydric alcohol.   The water absorbent resin composition according to any one of claims 1 to 4, wherein at least a part of the water absorbent resin particles is a granulated body.   6. The water absorbent resin composition according to claim 1, wherein the composition has an absorption capacity without load (CRC) of 20 g / g or more and an absorption capacity under pressure at 0.7 psi of 22 g / g or more. object. The water-absorbent resin composition according to any one of claims 1 to 6, wherein the dust generation degree of the composition is 0.25 mg / m ³ .   The water absorbent resin composition according to any one of claims 1 to 7, wherein the contact angle of the composition is 45 ° or less.   The water-absorbing resin composition according to any one of claims 1 to 8, wherein the water-soluble polyvalent metal salt particles have a mass average particle diameter of 400 µm or less and contain 20 wt% or more of particles having a size of 150 µm or less. object.   The use ratio of the water-absorbent resin particles and water-soluble polyvalent metal salt particles is 0.1 to 2 parts by mass of the water-soluble polyvalent metal salt particles with respect to 100 parts by mass of the solid content of the water-absorbent resin particles. The water absorbent resin composition according to any one of claims 1 to 9, which is used in a range. The saline flow conductivity (SFC) retention rate after a paint shaker (PS, soaked for 30 minutes at 800 Cycle / min) test of the water absorbent resin composition defined by the following formula is 70% or more. The water absorbent resin composition according to any one of 1 to 10.
Retention rate after PS (%) = [SFC (after PS) / SFC (before PS)] × 100   A sanitary material for absorbing feces, urine or blood, comprising the water-absorbent resin composition according to any one of claims 1 to 11.   A water-absorbent resin characterized by adding a binder to water-absorbent resin particles obtained by polymerizing a monomer containing acrylic acid and / or a salt thereof and mixing water-soluble polyvalent metal salt particles. A method for producing the composition.   The method for producing a water absorbent resin composition according to claim 13, wherein the water absorbent resin particles are surface-crosslinked.   The manufacturing method of the water absorbing resin composition of Claim 13 or 14 in which the said binder contains a surface crosslinking agent.   The method for producing a water absorbent resin composition according to any one of claims 13 to 15, wherein the binder contains water and / or a polyhydric alcohol.   The method for producing a water absorbent resin composition according to any one of claims 13 to 16, wherein a temperature of the water absorbent resin particles when adding a binder to the water absorbent resin particles is in a range of 40 to 100 ° C. .

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