CN111094441B

CN111094441B - Water-absorbent resin composition and method for producing same

Info

Publication number: CN111094441B
Application number: CN201880060747.2A
Authority: CN
Inventors: 宫岛徹; 松原佑介; 王艳雯
Original assignee: SDP Global Co Ltd
Current assignee: SDP Global Co Ltd
Priority date: 2017-09-22
Filing date: 2018-09-10
Publication date: 2022-02-01
Anticipated expiration: 2038-09-10
Also published as: JP2023029421A; CN111094441A; WO2019059019A1; JPWO2019059019A1

Abstract

A water-absorbent resin which is excellent in blocking resistance at the initial swelling, and which is excellent in liquid permeability between swollen gels and water absorption performance under load. The present invention is a water-absorbent resin composition comprising a crosslinked polymer (A), water-insoluble alumina-containing fine particles (c), and a water-soluble aluminum salt (d), wherein the crosslinked polymer (A) comprises a water-soluble vinyl monomer (a1) and/or a vinyl monomer (a2) which is hydrolyzed to a water-soluble vinyl monomer (a1), and a crosslinking agent (b) as essential constituent units, and the surface aluminum coverage of the crosslinked polymer (A) is 60 to 100%.

Description

Water-absorbent resin composition and method for producing same

Technical Field

The present invention relates to a water-absorbent resin composition and a method for producing the same.

Background

In sanitary materials such as disposable diapers, sanitary napkins, and incontinence pads, water-absorbent resins mainly composed of hydrophilic fibers such as pulp and acrylic acid (salt) have been widely used as absorbents. In recent years, from the viewpoint Of improvement Of QOL (Quality Of Life), demands for these sanitary materials are shifting to lighter and thinner materials, and accordingly, it is desired to reduce the amount Of hydrophilic fibers used. Therefore, the water-absorbent resin itself is required to function as the liquid diffusibility and initial absorption in the absorbent body which have been conventionally carried out by the hydrophilic fibers, and a water-absorbent resin having high liquid absorption under load and high liquid permeability between swollen gels is required.

As a method for improving the liquid permeability between swollen gels, the following methods are known: crosslinking the surface of the water-absorbent resin increases the crosslinking density of the surface of the water-absorbent resin, suppresses deformation of the swollen gel surface, and effectively forms gel gaps (see, for example, patent document 1). However, the liquid permeability between swollen gels cannot be sufficiently satisfied by only surface crosslinking.

As a method for improving the liquid permeability between swollen gels, there are known: (1) a method of adding inorganic compounds such as silica and talc to form a physical space; (2) a method of forming a gel space by performing surface treatment using a hydrophobic polymer having a small surface free energy such as modified silicone to suppress adhesion of swollen gels to each other; and (3) a method of adding aluminum sulfate, aluminum lactate, or the like (see, for example, patent document 2, patent document 3, and patent document 4). However, these methods have a problem that the blocking resistance at the initial swelling is insufficient, and therefore, when hydrophilic fibers such as pulp are reduced, a site with insufficient liquid diffusibility is generated in the absorbent body, and the absorption performance is unstable. Therefore, the water-absorbent resin is required to further improve the liquid permeability between gels.

Documents of the prior art

Patent document

Patent document 1: international publication No. 00/053664 pamphlet

Patent document 2: japanese laid-open patent publication No. 2012-161788

Patent document 3: japanese patent laid-open publication No. 2013-133399

Patent document 4: japanese patent laid-open publication No. 2014-512440

Disclosure of Invention

Problems to be solved by the invention

The purpose of the present invention is to provide a water-absorbent resin which has excellent blocking resistance at the initial swelling, and which has excellent liquid permeability between swollen gels and excellent water absorption performance under load.

Means for solving the problems

The present invention relates to a water-absorbent resin composition comprising a crosslinked polymer (A), water-insoluble alumina-containing fine particles (c), and a water-soluble aluminum salt (d), wherein the crosslinked polymer (A) comprises a water-soluble vinyl monomer (a1) and/or a vinyl monomer (a2) which is hydrolyzed to a water-soluble vinyl monomer (a1), and a crosslinking agent (b) as essential constituent units, and the surface aluminum coverage of the crosslinked polymer (A) is 60 to 100%; and

a method for producing a water-absorbent resin composition having a surface aluminum coverage of 60 to 100% by a crosslinked polymer (A), characterized by adding an aqueous colloidal fluid containing 0.01 to 1% by weight of water-insoluble alumina-containing fine particles (c) based on the weight of the crosslinked polymer (A) and an aqueous solution containing 0.05 to 5% by weight of a water-soluble aluminum salt (d) based on the weight of the crosslinked polymer (A) to the crosslinked polymer (A), and then crosslinking the surface of the crosslinked polymer (A).

ADVANTAGEOUS EFFECTS OF INVENTION

The water-absorbent resin composition of the present invention and the water-absorbent resin composition obtained by the production method of the present invention have at least a part of the surface thereof coated with the water-insoluble alumina-containing fine particles and the water-soluble aluminum salt, and therefore, the water-absorbent resin composition has high blocking resistance at the initial swelling and very excellent liquid permeability between swollen gels. Therefore, excellent absorption performance (for example, liquid diffusibility, absorption rate, absorption amount, and the like) is stably exhibited in each use case.

Drawings

FIG. 1 is a sectional view schematically showing a filtration cylinder tube for measuring the flow rate of a gel.

FIG. 2 is a perspective view schematically showing a pressurizing shaft and a weight for measuring the liquid passing speed of the gel.

Detailed Description

The water-absorbent resin composition of the present invention comprises a crosslinked polymer (A) containing a water-soluble vinyl monomer (a1) and/or a vinyl monomer (a2) which is hydrolyzed to a water-soluble vinyl monomer (a1), and a crosslinking agent (b) as essential constituent units, a water-insoluble alumina-containing fine particle (c), and a water-soluble aluminum salt (d).

The water-soluble vinyl monomer (a1) in the present invention is not particularly limited, and known monomers can be used, for example, vinyl monomers having at least 1 water-soluble substituent and an ethylenically unsaturated group (for example, anionic vinyl monomers, nonionic vinyl monomers and cationic vinyl monomers) disclosed in paragraphs 0007 to 0023 of Japanese patent application laid-open No. 3648553, anionic vinyl monomers, nonionic vinyl monomers and cationic vinyl monomers disclosed in paragraphs 0009 to 0024 of Japanese patent application laid-open No. 2003-165883, and vinyl monomers having at least one selected from the group consisting of a carboxyl group, a sulfo group, a phosphono group, a hydroxyl group, a carbamoyl group, an amino group and an ammonium group disclosed in paragraphs 0041 to 0051 of Japanese patent application laid-open No. 2005-75982.

The vinyl monomer (a2) [ hereinafter also referred to as "hydrolyzable vinyl monomer (a2) ] which is hydrolyzed to water-soluble vinyl monomer (a1) is not particularly limited, and known vinyl monomers and the like { for example, a vinyl monomer having at least 1 hydrolyzable substituent which is hydrolyzed to become a water-soluble substituent as disclosed in paragraphs 0024 to 0025 of Japanese patent No. 3648553, and a vinyl monomer having at least 1 hydrolyzable substituent [1, 3-oxo-2-oxapropylene (-CO-O-CO-) group, acyl group, cyano group and the like ] as disclosed in paragraphs 0052 to 0055 of Japanese patent application laid-open No. 2005-75982 } can be used }. The water-soluble vinyl monomer means a vinyl monomer in which at least 100g of water is dissolved in 100g of water at 25 ℃. The hydrolyzability of the hydrolyzable vinyl monomer (a2) means that it is hydrolyzed by water and a catalyst (acid, alkali, or the like) used as needed to be water-soluble. The hydrolysis of the hydrolyzable vinyl monomer (a2) may be carried out during, after, or both the polymerization, and is preferably carried out after the polymerization in view of the absorption performance of the resulting water-absorbent resin composition.

Among these, from the viewpoint of absorption performance and the like, the water-soluble vinyl monomer (a1) is preferable, the anionic vinyl monomer, the vinyl monomer having a carboxylate group, a sulfonate group, an amino group, a carbamoyl group, an ammonium group or a monoalkylammonium group, a dialkylammonium group or a trialkylammonium group is more preferable, the vinyl monomer having a carboxylate group or a carbamoyl group is further preferable, the (meth) acrylic acid (salt) and the (meth) acrylamide are particularly preferable, the (meth) acrylic acid (salt) is particularly preferable, and the acrylic acid (salt) is most preferable.

The "carboxylate group" means "carboxyl group" or "carboxylate group", and the "sulfonate group" means "sulfo group" or "sulfonate group". The term (meth) acrylic acid (salt) means acrylic acid, acrylic acid salt, methacrylic acid or methacrylic acid salt, and the term (meth) acrylamide means acrylamide or methacrylamide. Examples of the salt include alkali metal (lithium, sodium, potassium, and the like), alkaline earth metal (magnesium, calcium, and the like), and ammonium (NH)₄) Salts and the like. Among these salts, alkali metal salts and ammonium salts are preferable, alkali metal salts are more preferable, and sodium salts are particularly preferable, from the viewpoint of absorption performance and the like.

When any of the water-soluble vinyl monomer (a1) and the hydrolyzable vinyl monomer (a2) is used as a structural unit, 1 species may be used alone, or 2 or more species may be used as a structural unit as required. The same applies to the case where the water-soluble vinyl monomer (a1) and the hydrolyzable vinyl monomer (a2) are used as the constituent units. When the water-soluble vinyl monomer (a1) and the hydrolyzable vinyl monomer (a2) are used as the constituent units, the molar ratio [ (a1)/(a2) ] is preferably 75/25 to 99/1, more preferably 85/15 to 95/5, particularly preferably 90/10 to 93/7, and most preferably 91/9 to 92/8. When the amount is within this range, the absorption performance becomes better.

As the structural unit of the crosslinked polymer (a), other vinyl monomer (a3) copolymerizable with the water-soluble vinyl monomer (a1) and the hydrolyzable vinyl monomer (a2) may be used as the structural unit. One kind of the other vinyl monomer (a3) may be used alone, or two or more kinds may be used in combination.

The other copolymerizable vinyl monomer (a3) is not particularly limited, and known hydrophobic vinyl monomers and the like (for example, hydrophobic vinyl monomers disclosed in paragraphs 0028 to 0029 of Japanese patent No. 3648553, vinyl monomers disclosed in paragraphs 0025 of Japanese patent application laid-open No. 2003-165883, and vinyl monomers disclosed in paragraphs 0058 of Japanese patent application laid-open No. 2005-75982) can be used, and specifically, the following vinyl monomers (i) to (iii) and the like can be used.

(i) An aromatic ethylenic monomer having 8 to 30 carbon atoms

And halogen-substituted compounds of styrene such as styrene, α -methylstyrene, vinyltoluene and hydroxystyrene, and styrene such as vinylnaphthalene and dichlorostyrene.

(ii) Aliphatic ethylenic monomer having 2 to 20 carbon atoms

Olefins (ethylene, propylene, butene, isobutylene, pentene, heptene, diisobutylene, octene, dodecene, octadecene, etc.); and dienes (butadiene, isoprene, etc.), and the like.

(iii) Alicyclic ethylenic monomer having 5 to 15 carbon atoms

Monoethylenically unsaturated monomers (pinene, limonene, indene, and the like); and multiethylenic vinyl monomers [ cyclopentadiene, dicyclopentadiene, ethylidene norbornene, etc. ], and the like.

The content (mol%) of the units of the other vinyl monomer (a3) is preferably 0 to 5, more preferably 0 to 3, particularly preferably 0 to 2, and particularly preferably 0 to 1.5 based on the total mol number of the units of the water-soluble vinyl monomer (a1) and the hydrolyzable vinyl monomer (a2) from the viewpoint of absorption performance and the like, and the content of the units of the other vinyl monomer (a3) is most preferably 0 mol% from the viewpoint of absorption performance and the like.

The crosslinking agent (b) is not particularly limited, and a known crosslinking agent or the like can be used (for example, a crosslinking agent having 2 or more ethylenically unsaturated groups disclosed in paragraphs 0031 to 0034 of Japanese patent No. 3648553, a crosslinking agent having at least 1 functional group capable of reacting with a water-soluble substituent and having at least 1 ethylenically unsaturated group, and a crosslinking agent having at least 2 functional groups capable of reacting with a water-soluble substituent, a crosslinking agent having 2 or more ethylenically unsaturated groups disclosed in paragraphs 0028 to 0031 of Japanese patent laid-open No. 2003-165883, a crosslinking agent having an ethylenically unsaturated group and a reactive functional group, and a crosslinking agent having 2 or more reactive substituents, a crosslinkable vinyl monomer disclosed in paragraph 0059 of Japanese patent laid-open No. 2005-75982, and a crosslinkable vinyl monomer disclosed in paragraphs 0015 to 0016 of Japanese patent laid-open No. 2005-95759). Among these, from the viewpoint of absorption performance and the like, a crosslinking agent having 2 or more ethylenically unsaturated groups is preferable, poly (meth) allyl ether of a polyhydric alcohol having 2 to 40 carbon atoms, a (meth) acrylate of a polyhydric alcohol having 2 to 40 carbon atoms, and a (meth) acrylamide of a polyhydric alcohol having 2 to 40 carbon atoms are more preferable, polyallyl ether of a polyhydric alcohol having 2 to 40 carbon atoms is particularly preferable, and pentaerythritol triallyl ether is most preferable. The crosslinking agent (b) may be used alone or in combination of two or more.

The content (mol%) of the unit of the crosslinking agent (b) is preferably 0.001 to 5, more preferably 0.005 to 3, and particularly preferably 0.01 to 1 based on the total mol number of the units of the water-soluble vinyl monomer (a1) and the hydrolyzable vinyl monomer (a2) (when another vinyl monomer (a3) is used, based on the total mol number of the units of (a1) to (a 3). When within this range, the absorption performance becomes better.

As the method for producing the crosslinked polymer (A), a hydrogel polymer (comprising a crosslinked polymer and water) obtained by a known solution polymerization (adiabatic polymerization, film polymerization, spray polymerization, etc.; Japanese patent application laid-open No. 55-133413, etc.), a known suspension polymerization, or a known reversed-phase suspension polymerization (Japanese patent application laid-open No. 54-30710, Japanese patent application laid-open No. 56-26909, Japanese patent application laid-open No. 1-5808, etc.) can be obtained by heating, drying, and pulverizing, as required. The crosslinked polymer (a) may be a single polymer or a mixture of two or more polymers.

Among the polymerization methods, the solution polymerization method is preferred, and the aqueous solution polymerization method is particularly preferred because it is advantageous in terms of production cost because it is not necessary to use an organic solvent or the like, and the aqueous solution adiabatic polymerization method is most preferred because a water-absorbent resin composition having a large water retention amount and a small amount of water-soluble components can be obtained and temperature control during polymerization is not necessary.

In the case of aqueous solution polymerization, a mixed solvent comprising water and an organic solvent may be used, and examples of the organic solvent include methanol, ethanol, acetone, methyl ethyl ketone, N-dimethylformamide, dimethyl sulfoxide, and a mixture of 2 or more thereof.

In the case of aqueous solution polymerization, the amount (wt%) of the organic solvent is preferably 40 or less, more preferably 30 or less, based on the weight of water.

When a catalyst is used for the polymerization, a conventionally known radical polymerization catalyst can be used, examples thereof include azo compounds [ azobisisobutyronitrile, azobiscyanovaleric acid, 2' -azobis (2-amidinopropane) hydrochloride, etc. ], inorganic peroxides (hydrogen peroxide, ammonium persulfate, potassium persulfate, sodium persulfate, etc.), organic peroxides [ benzoyl peroxide, di-t-butyl peroxide, cumene hydroperoxide, succinic acid peroxide, di (2-ethoxyethyl) peroxydicarbonate, etc. ], and redox catalysts (catalysts comprising a combination of a reducing agent such as alkali metal sulfite or bisulfite, ammonium sulfite, ammonium bisulfite, and ascorbic acid, and an oxidizing agent such as alkali metal persulfate, ammonium persulfate, hydrogen peroxide, and organic peroxide, etc.). These catalysts may be used alone, or two or more of them may be used in combination.

The amount (% by weight) of the radical polymerization catalyst to be used is preferably 0.0005 to 5, more preferably 0.001 to 2, based on the total weight of the water-soluble vinyl monomer (a1) and the hydrolyzable vinyl monomer (a2) (based on the total weight of (a1) to (a3) in the case where another vinyl monomer (a3) is used).

In the polymerization, a polymerization control agent such as a chain transfer agent may be used in combination as necessary, and specific examples thereof include sodium hypophosphite, sodium phosphite, alkyl mercaptan, alkyl halide, thiocarbonyl compound, and the like. These polymerization control agents may be used alone, or two or more of them may be used in combination.

The amount (% by weight) of the polymerization control agent to be used is preferably 0.0005 to 5, more preferably 0.001 to 2, based on the total weight of the water-soluble vinyl monomer (a1) and the hydrolyzable vinyl monomer (a2) (based on the total weight of (a1) to (a3) in the case where another vinyl monomer (a3) is used).

When the suspension polymerization method or the reversed-phase suspension polymerization method is employed as the polymerization method, the polymerization may be carried out in the presence of a conventionally known dispersant or surfactant as needed. In the case of the reversed-phase suspension polymerization method, the polymerization can be carried out using a conventionally known hydrocarbon solvent such as xylene, n-hexane, and n-heptane.

The polymerization initiation temperature may be appropriately adjusted depending on the kind of the catalyst used, and is preferably 0 to 100 ℃, and more preferably 2 to 80 ℃.

When a solvent (an organic solvent, water, or the like) is used in the polymerization, it is preferable to remove the solvent by distillation after the polymerization. When the solvent contains an organic solvent, the content (% by weight) of the organic solvent after the distillation is preferably 0 to 10, more preferably 0 to 5, particularly preferably 0 to 3, and most preferably 0 to 1 based on the weight of the crosslinked polymer (a). When the amount is within this range, the absorption performance of the water-absorbent resin composition becomes better.

When the solvent contains water, the water content (wt%) after the distillation is preferably 0 to 20, more preferably 1 to 10, particularly preferably 2 to 9, and most preferably 3 to 8 based on the weight of the crosslinked polymer (a). When within this range, the absorption performance becomes better.

The crosslinked polymer (A) can be obtained by the above-mentioned polymerization method, and can be obtained by obtaining a hydrous gel-like material (hereinafter referred to as hydrous gel) containing water of the crosslinked polymer (A) and further drying the hydrous gel.

When an acid group-containing monomer such as acrylic acid or methacrylic acid is used as the water-soluble vinyl monomer (a1), the aqueous gel may be neutralized with a base. The neutralization degree of the acid group is preferably 50 to 80 mol%. When the neutralization degree is less than 50 mol%, the tackiness of the resulting hydrogel polymer increases, and workability during production and use may deteriorate. Further, the water-retention capacity of the resulting water-absorbent resin composition may be lowered. On the other hand, when the neutralization degree exceeds 80%, the pH of the resulting resin is increased, and there is a concern about safety to human skin.

The neutralization may be carried out at any stage after the polymerization of the crosslinked polymer (A) in the production of the water-absorbent resin composition, and a preferable example thereof is a method of neutralizing in a state of a hydrogel, for example.

As the base to be neutralized, alkali metal hydroxides such as sodium hydroxide and potassium hydroxide; alkali metal carbonates such as sodium carbonate, sodium hydrogen carbonate, and potassium carbonate.

The aqueous gel obtained by the polymerization may be chopped as necessary. The size (longest diameter) of the gel after cutting is preferably 50 μm to 10cm, more preferably 100 μm to 2cm, and particularly preferably 1mm to 1 cm. When the amount is within this range, the drying property in the drying step becomes better.

The chopping can be carried out by a known method, and can be carried out by a chopping device (e.g., a conical mill (Bexmill), a rubber cutter (rubber chopper), a pharmaceutical mill (Pharmamill), a chopper, an impact mill, a drum mill), or the like.

The content and moisture of the organic solvent are measured by an infrared moisture meter [ for example, JE400 manufactured by KETT corporation: 120. + -. 5 ℃ for 30 minutes, ambient humidity before heating of 50. + -. 10% RH, lamp specification of 100V, 40W ] was measured.

As a method for removing the solvent (including water) in the aqueous gel by distillation, the following method can be applied: a method of removing (drying) by distillation with hot air at 80 to 230 ℃, a thin film drying method with a drum dryer or the like heated to 100 to 230 ℃, (heating) a reduced pressure drying method, a freeze drying method, a drying method with infrared rays, decantation, filtration, and the like.

After the aqueous gel is dried to obtain the crosslinked polymer (A), further pulverization may be carried out. The pulverization method is not particularly limited, and pulverization devices (e.g., hammer mills, impact mills, drum mills, and jet mills) and the like can be used. The particle size of the crosslinked polymer after pulverization can be adjusted by sieving or the like as necessary.

The weight average particle diameter (μm) of the crosslinked polymer (A) which is optionally sieved is preferably 100 to 800, more preferably 200 to 700, still more preferably 250 to 600, particularly preferably 300 to 500, and most preferably 350 to 450. When within this range, the absorption performance becomes better.

The weight average particle size is measured by a method described in the Peltier's Chemical Engineers' Handbook 6 th edition (Mgelow-Hill book, 1984, pages 21) using an Ro-Tap type sieve shaker (ロータップ reaction test sieve shaker とう) and a standard sieve (JIS Z8801-1: 2006). That is, the JIS standard sieves were combined in the order of 1000. mu.m, 850. mu.m, 710. mu.m, 500. mu.m, 425. mu.m, 355. mu.m, 250. mu.m, 150. mu.m, 125. mu.m, 75. mu.m, and 45 μm from above and trays. About 50g of the test particles were put on the uppermost sieve and vibrated for 5 minutes by a Ro-Tap type test sieve shaker. The weight of the particles measured on each sieve and tray was weighed, and the total weight was taken as 100% by weight, the weight fraction of the particles on each sieve was obtained, and the value was plotted on a logarithmic probability paper (the horizontal axis represents the mesh (particle diameter) of the sieve, and the vertical axis represents the weight fraction), and then the points were connected to each other to obtain a particle diameter corresponding to a weight fraction of 50% by weight, and this was taken as a weight-average particle diameter.

Further, since the absorption performance is better as the content of the fine particles contained in the crosslinked polymer (a) is smaller, the content (% by weight) of the fine particles having a particle size of 106 μm or less (preferably 150 μm or less) in the total weight of the crosslinked polymer (a) is preferably 3 or less, and more preferably 1 or less. The content of the fine particles can be determined using a map prepared when the weight average particle diameter is determined.

The shape of the crosslinked polymer (A) is not particularly limited, and examples thereof include an amorphous crushed shape, a flake shape, a pearl shape, a rice grain shape and the like. Among these, the amorphous crushed form is preferable because the fiber is well entangled with the fibrous material in the use of a disposable diaper and the like, and there is no fear of falling off from the fibrous material.

The crosslinked polymer (a) may contain a small amount of other components such as a residual solvent and a residual crosslinking component within a range not impairing the performance thereof.

The water-absorbent resin composition of the present invention preferably has a structure in which the surface of the crosslinked polymer (A) is crosslinked by the organic surface-crosslinking agent (e). By crosslinking the surface of the crosslinked polymer (a), the gel strength of the water-absorbent resin composition can be improved, and the water-absorbent resin composition can further satisfy the desired water retention capacity and absorption capacity under load. As the organic surface-crosslinking agent (e), known organic surface-crosslinking agents and the like can be used (e.g., polyglycidyl compounds (poly value グリシジル compounds) described in Japanese patent application laid-open No. 59-189103, polyamines, polyazepine compounds, and polyisocyanate compounds, polyols described in Japanese patent application laid-open Nos. 58-180233 and 61-169903, silane coupling agents described in Japanese patent application laid-open Nos. 61-211305 and 61-252212, alkylene carbonates described in Japanese patent application laid-open No. 5-508425, and polyvalent oxazoline compounds described in Japanese patent application laid-open No. 11-240959). Among these surface crosslinking agents, from the viewpoint of economy and absorption characteristics, polyglycidyl compounds, polyols and polyamines are preferred, polyglycidyl compounds and polyols are more preferred, polyglycidyl compounds are particularly preferred, and ethylene glycol diglycidyl ether is most preferred. The organic surface cross-linking agent (e) may be used alone or in combination of two or more.

In the case of surface crosslinking, the amount (% by weight) of the organic surface crosslinking agent (e) used is not particularly limited since it varies depending on the kind of the surface crosslinking agent, the condition for crosslinking, the target performance, and the like, but is preferably 0.001 to 3, more preferably 0.005 to 2, and particularly preferably 0.01 to 1.5 based on the weight of the water-absorbent resin composition from the viewpoint of absorption characteristics and the like.

The surface crosslinking of the crosslinked polymer (a) can be carried out by mixing and heating the crosslinked polymer (a) with the organic surface crosslinking agent (e). Examples of the method for mixing the crosslinked polymer (A) and the organic surface crosslinking agent (e) include a method of uniformly mixing the crosslinked polymer (A) and the organic surface crosslinking agent (e) using a mixing apparatus such as a cylindrical mixer, a screw type extruder, a high-speed paddle mixer (Turbulizer), a nauta type mixer, a double arm type kneader, a flow type mixer, a V type mixer, a chopper mixer, a ribbon type mixer, a jet type mixer, a rotary disk type mixer, a conical mixer, or a drum mixer. In this case, the organic surface cross-linking agent (e) may be diluted with water and/or an arbitrary solvent and used.

The temperature at the time of mixing the crosslinked polymer (A) and the organic surface crosslinking agent (e) is not particularly limited, but is preferably 10 to 150 ℃, more preferably 20 to 100 ℃, and particularly preferably 25 to 80 ℃.

The crosslinked polymer (a) and the organic surface crosslinking agent (e) are mixed and then usually subjected to heat treatment. The heating temperature is preferably 100 to 180 ℃, more preferably 110 to 175 ℃, and particularly preferably 120 to 170 ℃ from the viewpoint of the fracture resistance of the resin particles. When the heating temperature is 180 ℃ or lower, indirect heating by steam is possible, which is advantageous in terms of facilities; at a heating temperature of less than 100 ℃, the absorption properties may be deteriorated. The heating time may be set as appropriate depending on the heating temperature, and is preferably 5 to 60 minutes, and more preferably 10 to 40 minutes from the viewpoint of absorption performance. The water-absorbent resin obtained by surface crosslinking may be further surface-crosslinked by using an organic surface-crosslinking agent of the same type as or different from the organic surface-crosslinking agent used initially.

The particle size is adjusted by crosslinking the surface of the crosslinked polymer (a) with the organic surface crosslinking agent (e) and then screening the crosslinked polymer (a) as needed. The average particle diameter of the obtained particles is preferably 100 to 600 μm, and more preferably 200 to 500 μm. The content of the fine particles is preferably small, and the content of the particles having a particle size of 100 μm or less is preferably 3% by weight or less, and more preferably the content of the particles having a particle size of 150 μm or less is 3% by weight or less.

The water-absorbent resin composition of the present invention contains water-insoluble alumina-containing fine particles (c). Examples of the water-insoluble alumina-containing fine particles (c) include alumina (alumina) fine particles, alumina-modified silica fine particles, boehmite fine particles, aluminum hydroxide fine particles, aluminum phosphate fine particles, aluminosilicate fine particles such as zeolite and montmorillonite, and the like, and from the viewpoint of obtaining easiness, handling easiness, and absorption performance, alumina fine particles and alumina-modified silica fine particles are preferable, and alumina-modified silica fine particles are more preferable. (c) One kind may be used alone, or two or more kinds may be used in combination. Here, the alumina-modified silica refers to a fine particle generally having a structure in which at least a part of the surface of a silica fine particle is coated with alumina.

The water-insoluble alumina-containing fine particles (c) in the present invention are preferably spherical or amorphous particles having an average primary particle diameter of 1 to 100 nm. In the case of spherical or amorphous particles, the powder flowability of the water-absorbent resin composition becomes good. The average primary particle diameter of the water-insoluble alumina-containing fine particles (c) is preferably 2 to 80nm, more preferably 3 to 60nm, particularly preferably 5 to 50nm, and most preferably 5 to 20 nm. When the average primary particle diameter is less than 1nm, the absorption characteristics of the water-absorbent resin composition under load may be deteriorated. When the particle diameter is larger than 100nm, the liquid permeability of the water-absorbent resin composition may be deteriorated.

The measurement of the average primary particle size of the water-insoluble alumina-containing fine particles (c) may be carried out by a conventionally known method, and examples thereof include the following methods: a method of obtaining an average value of the longest diameter and the shortest diameter of each of 100 or more particles from a 5 ten thousand-fold image by a transmission electron microscope; a method using a scattering-type particle size distribution measuring apparatus using a dynamic light scattering method or a laser diffraction method; in the case of spherical particles, the specific surface area is calculated by the BET method. When a commercially available product is used, the catalog value thereof may be used instead. When there is a significant difference in the measurement method in the determination by measurement, the above-described method using a transmission electron microscope is used. In the method, the number of particles is calculated to obtain the number-based average particle size.

The water-absorbent resin composition of the present invention can be obtained by mixing the crosslinked polymer (a) with the water-insoluble alumina-containing fine particles (c). Examples of the mixing method include a method of uniformly mixing the components using a known mixing apparatus such as a cylinder type mixer, a screw type extruder, a high speed paddle type mixer (Turbulizer), a nauta type mixer, a double arm type kneader, a flow type mixer, a V type mixer, a chopper mixer, a ribbon type mixer, an air flow type mixer, a rotary disk type mixer, a conical mixer, and a drum type mixer.

Mixing of the crosslinked polymer (A) with the water-insoluble alumina-containing fine particles (c) are preferably added to the crosslinked polymer (A) under stirring. The added water-insoluble alumina-containing fine particles (c) may be added simultaneously with water and/or a solvent. When the water-insoluble alumina-containing fine particles (c) are added together with water and/or a solvent, a dispersion obtained by dispersing the water-insoluble alumina-containing fine particles (c) in water and/or a solvent may be added, and from the viewpoint of workability, the addition of the dispersion is preferable, and the addition of the water dispersion is more preferable. When the dispersion liquid is added, it is preferably added by spraying or dropwise addition.

When the dispersion liquid containing the water-insoluble alumina-containing fine particles (c) is used, the content of the water-insoluble alumina-containing fine particles (c) in the dispersion liquid is preferably 5 to 70% by weight, more preferably 10 to 60% by weight, based on the total weight of the dispersion liquid.

The dispersion of the water-insoluble alumina-containing fine particles (c) may be a dispersion obtained by directly granulating a raw material by a conventionally known method by reacting the raw material in water and/or a solvent, or a dispersion obtained by mechanically dispersing fine particles in water and/or a solvent.

From the viewpoint of stability of the dispersion, it is preferable to use a dispersion obtained by directly granulating a raw material by reacting the raw material in water and/or a solvent. The dispersion of the water-insoluble alumina-containing fine particles (c) can be obtained as an aqueous colloidal solution (sol) on the market.

The dispersion liquid may contain an optional additive such as a stabilizer, if necessary. Examples of the stabilizer include commercially available surfactants and dispersants, and commercially available acid compounds [ phosphoric acid (salt), boric acid (salt), alkali metal (salt), alkaline earth metal (salt), hydroxycarboxylic acid (salt), fatty acid (salt), and the like ].

From the viewpoint of absorption performance, the temperature at the time of mixing the crosslinked polymer (a) and the water-insoluble alumina-containing fine particles (c) is preferably 10 to 150 ℃, more preferably 20 to 100 ℃, and particularly preferably 25 to 80 ℃.

After the crosslinked polymer (a) is mixed with the water-insoluble alumina-containing fine particles (c), a heat treatment may be further performed. The heating temperature is preferably 25 to 180 ℃, more preferably 30 to 175 ℃, and particularly preferably 35 to 170 ℃ from the viewpoint of the fracture resistance of the resin particles. When heating is performed at 180 ℃ or lower, indirect heating by steam is possible, which is advantageous in terms of facilities. In addition, when heating is not performed, the water and the solvent used in combination may remain in an excessive amount in the water-absorbent resin, and the absorption performance may be deteriorated. The amount of water or solvent remaining in the water-absorbent resin is preferably 1 to 10 parts by weight per 100 parts by weight of the water-absorbent resin. The amounts of water and solvent remaining in the water-absorbent resin can be obtained by a heat reduction method in accordance with JIS K0067 1992 (chemical reduction and residue test method).

When the crosslinked polymer (a) and the water-insoluble alumina-containing fine particles (c) are mixed and then heated, the heating time may be set as appropriate depending on the heating temperature, and is preferably 5 to 60 minutes, and more preferably 10 to 40 minutes from the viewpoint of absorption performance. The water-absorbent resin obtained by mixing the crosslinked polymer (A) and the water-insoluble alumina-containing fine particles (c) may be further subjected to a surface treatment using the same or different water-insoluble alumina-containing fine particles as the water-insoluble alumina-containing fine particles used at first.

The water-absorbent resin composition of the present invention can be used by mixing the crosslinked polymer (a) with the water-insoluble alumina-containing fine particles (c), and then screening the mixture to adjust the particle size. The average particle diameter of the particles obtained by the particle size adjustment is preferably 100 to 600 μm, and more preferably 200 to 500 μm. The content of the fine particles is preferably small, and the content of the particles having a particle size of 100 μm or less is preferably 3% by weight or less, and more preferably the content of the particles having a particle size of 150 μm or less is 3% by weight or less.

The content of the water-insoluble alumina-containing fine particles (c) in the water-absorbent resin composition of the present invention can be adjusted depending on the use of the water-absorbent resin composition, and is preferably 0.01 to 1% by weight, more preferably 0.02 to 0.8% by weight, and particularly preferably 0.05 to 0.5% by weight, based on the weight of the crosslinked polymer (A). When the amount is within this range, the water-absorbent resin composition has good liquid permeability, and is more preferable.

The water-absorbent resin composition of the present invention contains a water-soluble aluminum salt (d). Examples of the water-soluble aluminum salt (d) include aluminates [ sodium aluminate, potassium aluminate, hydrates thereof, and the like ], aluminum sulfates and double salts thereof [ aluminum sulfate, potassium aluminum sulfate, sodium aluminum sulfate, hydrates thereof, and the like ], aluminum chlorides [ aluminum chloride, polyaluminum chloride, hydrates thereof, and the like ], and organic acid salts of aluminum [ aluminum lactate, aluminum acetate, hydrates thereof, and the like ]. (d) One kind may be used alone, or two or more kinds may be used in combination.

The water-soluble aluminum salt (d) in the present invention preferably has a pH of 10g/100gH at 20 ℃₂A crystalline salt having a water solubility of O or more.

The water-solubility of the water-soluble aluminum salt (d) is more preferably 20g/100gH₂O or more, more preferably 25g/100gH₂O or more. The water solubility is less than 10g/100gH₂When O is used, it is difficult to uniformly mix the crosslinked polymer (A), and the liquid permeability of the water-absorbent resin composition is deteriorated.

(d) When the amorphous state is obtained, the aluminum water-soluble salt is likely to be eluted during swelling of the water-absorbent resin, and the absorption performance is deteriorated, so that (d) is preferably crystalline. When (d) is a crystalline salt having high water solubility, the surface of the water-absorbent resin is easily coated with fine crystals of the water-soluble aluminum salt, and the liquid permeability is particularly excellent.

Among the water-soluble aluminum salts (d), from the viewpoint of crystallinity, high water solubility, and easy availability, aluminum sulfate and double salts thereof are preferable, and aluminum sulfate tetradecahadecanoic hydrate and aluminum sodium sulfate dodecahydrate are more preferable.

The water-absorbent resin composition of the present invention can be obtained by mixing the crosslinked polymer (A) with the water-soluble aluminum salt (d). Examples of the mixing method include a method of uniformly mixing the components using a known mixing apparatus such as a cylinder mixer, a screw extruder, a high-speed paddle mixer (Turbulizer), a nauta mixer, a double arm kneader, a flow mixer, a V-type mixer, a chopper mixer, a ribbon mixer, an air flow mixer, a rotary disk mixer, a conical mixer, and a drum mixer.

Mixing of the crosslinked polymer (A) with the water-soluble aluminum salt (d) it is preferable to add the water-soluble aluminum salt (d) to the crosslinked polymer (A) under stirring. The added water-soluble aluminum salt (d) may be added simultaneously with water and/or a solvent. When the water-soluble aluminum salt (d) is added together with water and/or a solvent, a solution obtained by dissolving the water-soluble aluminum salt (d) in water and/or a solvent may be added, and an aqueous solution obtained by dissolving the water-soluble aluminum salt (d) in a water-containing solvent is more preferably added, from the viewpoints of workability, liquid permeability, and the like. In the case of adding the solution, it is preferably added by spraying or dropwise addition.

When the solution of the water-soluble aluminum salt (d) is used, the content of the water-soluble aluminum salt (d) in the solution is preferably 5 to 70% by weight, more preferably 10 to 60% by weight, based on the total weight of the solution.

The temperature at the time of mixing the crosslinked polymer (A) and the water-soluble aluminum salt (d) is not particularly limited, but is preferably 10 to 150 ℃, more preferably 20 to 100 ℃, and particularly preferably 25 to 80 ℃.

After the crosslinked polymer (A) is mixed with the water-soluble aluminum salt (d), a heat treatment may be further performed. The heating temperature is preferably 25 to 180 ℃, more preferably 30 to 175 ℃, and particularly preferably 35 to 170 ℃ from the viewpoint of the fracture resistance of the resin particles. When heating is performed at 180 ℃ or lower, indirect heating by steam is possible, which is advantageous in terms of facilities. In addition, when heating is not performed, the water and the solvent used in combination may remain in an excessive amount in the water-absorbent resin, and the absorption performance may be deteriorated. The amount of water or solvent remaining in the water-absorbent resin is preferably 1 to 10 parts by weight per 100 parts by weight of the water-absorbent resin. The amounts of water and solvent remaining in the water-absorbent resin can be obtained by a heat reduction method in accordance with JIS K0067 1992 (chemical reduction and residue test method).

When the crosslinked polymer (a) and the water-soluble aluminum salt (d) are mixed and then heated, the heating time may be set as appropriate depending on the heating temperature, and is preferably 5 to 60 minutes, more preferably 10 to 40 minutes, from the viewpoint of absorption performance. The water-absorbent resin obtained by mixing the crosslinked polymer (A) and the water-soluble aluminum salt (d) may be further surface-treated with the same or different water-soluble aluminum salt as the water-soluble aluminum salt used first.

The water-absorbent resin composition of the present invention can be used by mixing the crosslinked polymer (A) with the water-soluble aluminum salt (d), and then screening the mixture to adjust the particle size. The average particle diameter of the particles obtained by the particle size adjustment is preferably 100 to 600 μm, and more preferably 200 to 500 μm. The content of the fine particles is preferably small, and the content of the particles having a particle size of 100 μm or less is preferably 3% by weight or less, and more preferably the content of the particles having a particle size of 150 μm or less is 3% by weight or less.

The content of the water-soluble aluminum salt (d) in the water-absorbent resin composition of the present invention can be adjusted depending on the use of the water-absorbent resin composition, and is preferably 0.05 to 5% by weight, more preferably 0.1 to 4% by weight, and particularly preferably 0.2 to 3% by weight, based on the weight of the crosslinked polymer (A). When the amount is within this range, the water-absorbent resin composition has good liquid permeability, and is more preferable. Here, when the water-soluble aluminum salt (d) is a hydrate, the mass excluding the water of hydration is taken as a reference.

The water-absorbent resin composition of the present invention can be obtained by mixing the crosslinked polymer (A) with the water-insoluble alumina-containing fine particles (c) and the water-soluble aluminum salt (d), and the water-insoluble alumina-containing fine particles (c) and the water-soluble aluminum salt (d) may be added to the crosslinked polymer (A) at the same time or may be added separately. From the viewpoint of coating uniformity and liquid permeability, it is preferable to add them at the same time. The simultaneous addition means that the simultaneous addition is carried out in the respective steps of drying, pulverization, surface crosslinking, etc. described above at once or separately.

When the surface of the crosslinked polymer (A) has a structure crosslinked by the organic surface crosslinking agent (e), the water-insoluble alumina-containing fine particles (c) and the water-soluble aluminum salt (d) may be added at any stage of before and after the surface crosslinking with the organic surface crosslinking agent (e), and from the viewpoint of absorption performance under pressure of the water-absorbent resin composition, it is preferable that at least one of the water-insoluble alumina-containing fine particles (c) and the water-soluble aluminum salt (d) is added simultaneously with or before the addition of the organic surface crosslinking agent (e), and it is more preferable that at least one of the water-insoluble alumina-containing fine particles (c) and the water-soluble aluminum salt (d) is added simultaneously with the addition of the organic surface crosslinking agent (e), it is particularly preferable to add the water-insoluble alumina-containing fine particles (c), the water-soluble aluminum salt (d) and the organic surface cross-linking agent (e) at the same time. By adding these three components before the surface crosslinking, particularly simultaneously, it has been surprisingly found that the blocking resistance, liquid permeability and gel strength in the initial swelling can be further improved by forming a composite coating of the water-insoluble alumina-containing fine particles (c) and the water-soluble aluminum salt (d) in the surface crosslinked layer.

In the water-absorbent resin composition of the present invention, the surface aluminum coverage of the crosslinked polymer (A) is 60 to 100%. The surface aluminum coating ratio is preferably 65 to 100%, more preferably 70 to 100%, and particularly preferably 75 to 100% from the viewpoints of blocking resistance, liquid permeability, and gel strength in the initial swelling. The surface aluminum coverage can be adjusted to 60 to 100% by adjusting the amounts of the water-insoluble alumina-containing fine particles (c) and the water-soluble aluminum salt (d) to the above ranges. The surface aluminum coverage is an index indicating a state of coating with the water-insoluble alumina-containing fine particles (c) and the water-soluble aluminum salt (d), and can be measured by aluminum element mapping using energy dispersive X-ray analysis described later.

The water-absorbent resin composition of the present invention may further contain a polyhydric alcohol (f) having 4 or less carbon atoms. Examples of the polyhydric alcohol (f) having 4 or less carbon atoms include ethylene glycol, propylene glycol, 1, 3-propanediol, glycerin, 1, 4-butanediol, and the like. Among these, propylene glycol and glycerin are preferable, and propylene glycol is more preferable, from the viewpoint of safety and availability. (f) One kind may be used alone, or two or more kinds may be used in combination.

The amount (% by weight) of the polyol (f) having 4 or less carbon atoms is preferably 0.05 to 5, more preferably 0.1 to 3, and particularly preferably 0.2 to 2 based on the weight of the crosslinked polymer (A) in view of absorption performance and liquid permeability.

In the case where the polyhydric alcohol (f) having 4 or less carbon atoms is contained, it may be added in an arbitrary step, and from the viewpoint of liquid permeability, it is more preferable to add the polyhydric alcohol (f) together with the water-soluble aluminum salt (d), and it is particularly preferable to add the water-insoluble alumina-containing fine particles (c), the water-soluble aluminum salt (d) and the organic surface-crosslinking agent (e) together. By using (f), the deposition rate of the water-soluble aluminum salt (d) on the surface of the water-absorbent resin can be controlled, and the coating rate and liquid permeability can be improved.

The water-absorbent resin composition of the present invention may further contain a hydrophobic substance (g). As the hydrophobic substance (g), there are included: a hydrophobic substance containing a hydrocarbon group (g1), a hydrophobic substance containing a hydrocarbon group having a fluorine atom (g2), a hydrophobic substance having a polysiloxane structure (g3), and the like.

Examples of the hydrophobic substance (g1) containing a hydrocarbon group include polyolefin resins, polyolefin resin derivatives, polystyrene resins, polystyrene resin derivatives, waxes, long-chain fatty acid esters, long-chain fatty acids and salts thereof, long-chain fatty alcohols, long-chain fatty amides, and mixtures of 2 or more thereof.

Examples of the polyolefin resin include polymers { for example, polyethylene, polypropylene, polyisobutylene, poly (ethylene-isobutylene), isoprene and the like } having a weight average molecular weight of 1000 to 100 ten thousand and containing an olefin having 2 to 4 carbon atoms { for example, ethylene, propylene, isobutylene, isoprene and the like } as an essential constituent monomer (the content of the olefin is at least 50% by weight based on the weight of the polyolefin resin).

Examples of the polyolefin resin derivative include polymers having a weight-average molecular weight of 1000 to 100 ten thousand obtained by introducing a carboxyl group (-COOH), a1, 3-oxo-2-oxapropylene (-COOCO-) and the like into a polyolefin resin { for example, polyethylene thermal degradation products, polypropylene thermal degradation products, maleic acid-modified polyethylene, chlorinated polyethylene, maleic acid-modified polypropylene, ethylene-acrylic acid copolymers, ethylene-maleic anhydride copolymers, isobutylene-maleic anhydride copolymers, maleated polybutadiene, ethylene-vinyl acetate copolymers, and maleic acid products of ethylene-vinyl acetate copolymers }.

The polystyrene resin may be a polymer having a weight average molecular weight of 1000 to 100 ten thousand.

Examples of the polystyrene resin derivative include polymers { for example, a styrene-maleic anhydride copolymer, a styrene-butadiene copolymer, a styrene-isobutylene copolymer, and the like } having a weight average molecular weight of 1000 to 100 ten thousand and containing styrene as an essential constituent monomer (the content of styrene is at least 50% by weight based on the weight of the polystyrene derivative).

Examples of the wax include waxes having a melting point of 50 to 200 ℃ (for example, paraffin wax, beeswax, carnauba wax, and tallow).

Examples of the long-chain fatty acid ester include esters of fatty acids having 8 to 30 carbon atoms and alcohols having 1 to 12 carbon atoms { for example, methyl laurate, ethyl laurate, methyl stearate, ethyl stearate, methyl oleate, ethyl oleate, monolaurin, pentaerythritol monostearate, pentaerythritol oleate, monolaurin, sorbitol monostearate, sorbitol stearate monoester, sorbitol oleate monoester, sucrose palmitate, sucrose stearate monoester, sucrose stearate triester, tallow, etc. }.

Examples of the long-chain fatty acid and a salt thereof include fatty acids having 8 to 30 carbon atoms { for example, lauric acid, palmitic acid, stearic acid, oleic acid, dimer acid, behenic acid, and the like }, and examples of a salt thereof include a salt with zinc, calcium, magnesium, or aluminum (hereinafter, each may be abbreviated as Zn, Ca, Mg, and Al) { for example, Ca palmitate, Al palmitate, Ca stearate, Mg stearate, and Al stearate }.

Examples of the long-chain aliphatic alcohol include aliphatic alcohols having 8 to 30 carbon atoms { for example, lauryl alcohol, palmityl alcohol, stearyl alcohol, oleyl alcohol, and the like }. From the viewpoint of leakage resistance of the absorbent article, etc., palmitic alcohol, stearyl alcohol, and oleyl alcohol are preferable, and stearyl alcohol is more preferable.

Examples of the long-chain aliphatic amide include an amidation product of a long-chain aliphatic primary amine having 8 to 30 carbon atoms and a carboxylic acid having a hydrocarbon group having 1 to 30 carbon atoms, an amidation product of ammonia or a primary amine having 1 to 7 carbon atoms and a long-chain fatty acid having 8 to 30 carbon atoms, an amidation product of a long-chain aliphatic secondary amine having at least one aliphatic chain having 8 to 30 carbon atoms and a carboxylic acid having 1 to 30 carbon atoms, and an amidation product of a secondary amine having two aliphatic hydrocarbon groups having 1 to 7 carbon atoms and a long-chain fatty acid having 8 to 30 carbon atoms.

The amidation product of a long-chain aliphatic primary amine having 8 to 30 carbon atoms and a carboxylic acid having a hydrocarbon group having 1 to 30 carbon atoms is classified into a product obtained by reacting a primary amine with a carboxylic acid in a 1:1 ratio and a product obtained by reacting a primary amine with a carboxylic acid in a 1:2 ratio. Examples of the 1:1 reaction product include N-octylamide acetate, N-hexacosanylamide acetate, N-octylamide heptacosanoic acid, and N-hexacosanylamide heptacosanoic acid. Examples of the 1:2 reaction product include diacetic acid N-octylamide, diacetic acid N-hexacosanylamide, di (heptacosanoic acid) N-octylamide, and di (heptacosanoic acid) N-hexacosanylamide. In the case of a product obtained by reacting a primary amine with a carboxylic acid in a 1:2 ratio, the carboxylic acids used may be the same or different.

The amidation products of long-chain fatty acids having 8 to 30 carbon atoms and ammonia or primary amines having 1 to 7 carbon atoms are classified into those obtained by reacting ammonia or primary amines with carboxylic acids at a ratio of 1:1 and those obtained by reacting ammonia or primary amines with carboxylic acids at a ratio of 1: 2. Examples of the 1:1 reaction product include nonanoic acid amide, nonanoic acid methylamide, nonanoic acid N-heptyl amide, heptacosanoic acid N-methyl amide, heptacosanoic acid N-heptyl amide, and heptacosanoic acid N-hexacosanyl amide. Examples of the substance obtained by the 1:2 reaction include dinonylic acid amide, dinonylic acid N-methylamide, dinonylic acid N-heptylamide, dioctadecylic acid amide, dioctadecylic acid N-ethylamide, dioctadecylic acid N-heptylamide, heptacosanoic acid amide, heptacosanoic acid N-methylamide, heptacosanoic acid N-heptylamide, and heptacosanoic acid N-hexacosanylamide. The carboxylic acids used in the reaction of ammonia or a primary amine with a carboxylic acid in a 1:2 ratio may be the same or different.

Examples of the amidation product of a long-chain aliphatic secondary amine having at least one aliphatic chain having 8 to 30 carbon atoms and a carboxylic acid having 1 to 30 carbon atoms include N-methyloctylamide acetate, N-methylhexacosanylamide acetate, N-octylhexacosanylamide acetate, N-dicosanylamide acetate, N-methyloctylamide heptacosanoic acid, N-methylhexacosanylamide heptacosanoic acid, N-octylhexacosanylamide heptacosanoic acid, and N-dicosanylamide heptacosanoic acid.

Examples of amidation products of secondary amines having two aliphatic hydrocarbon groups of 1 to 7 carbon atoms and long-chain fatty acids of 8 to 30 carbon atoms include nonanoic acid N-dimethylamide, nonanoic acid N-methylheptylamide, nonanoic acid N-diheptylamide, heptacosanoic acid N-dimethylamide, heptacosanoic acid N-methylheptylamide, and heptacosanoic acid N-diheptylamide.

Examples of the hydrophobic substance (g2) containing a hydrocarbon group having a fluorine atom include perfluoroalkanes, perfluoroolefins, perfluoroaromatics, perfluoroalkyl ethers, perfluoroalkyl carboxylic acids, perfluoroalkyl alcohols, and mixtures of 2 or more of these.

Examples of the hydrophobic substance having a polysiloxane structure (g3) include polydimethylsiloxane, polyether-modified polysiloxane { polyoxyethylene-modified polysiloxane, poly (oxyethylene-oxypropylene) -modified polysiloxane, etc }, carboxyl-modified polysiloxane, epoxy-modified polysiloxane, amino-modified polysiloxane, alkoxy-modified polysiloxane, and mixtures thereof.

The HLB value of the hydrophobic substance (g) is preferably 1 to 10, more preferably 2 to 8, and particularly preferably 3 to 7. When the amount is within this range, the blocking resistance at the initial swelling becomes better. The HLB value is a hydrophilic-hydrophobic balance (HLB) value, and is obtained by the microtia method (new surfactant entry, 197, lian wu, sanyang chemical industry co., published 1981).

Among the hydrophobic substances (g), from the viewpoint of blocking resistance at the time of initial swelling, the hydrophobic substance (g1) containing a hydrocarbon group is preferable, the long-chain fatty acid ester, the long-chain fatty acid and a salt thereof, the long-chain fatty alcohol, and the long-chain fatty amide are more preferable, the sorbitan stearate, the sucrose stearate, stearic acid, Mg stearate, Ca stearate, Zn stearate, and Al stearate are further preferable, the sucrose stearate and Mg stearate are particularly preferable, and the sucrose stearate is most preferable.

The amount (% by weight) of the hydrophobic substance (g) is preferably 0.001 to 1, more preferably 0.005 to 0.5, and particularly preferably 0.01 to 0.3 based on the weight of the crosslinked polymer (A) from the viewpoints of absorption performance and blocking resistance at the time of initial swelling.

In the case where the hydrophobic substance (g) is contained, it may be added in an arbitrary step, and from the viewpoint of absorption performance, it is preferable to add the hydrophobic substance (g) before adding the water-insoluble alumina-containing fine particles (c) and the water-soluble aluminum salt (d), and in the case where the surface of the crosslinked polymer (a) has a structure crosslinked by the organic surface crosslinking agent (e), it is more preferable to add the hydrophobic substance (g) before the surface crosslinking by the organic surface crosslinking agent (e).

The water-absorbent resin composition of the present invention may contain additives (for example, preservatives, antifungal agents, antibacterial agents, antioxidants, ultraviolet absorbers, coloring agents, fragrances, deodorizing agents, liquid permeability enhancers, organic fibers, and the like which are known (for example, as described in Japanese unexamined patent publication No. 2003-225565 and Japanese unexamined patent publication No. 2006-131767). When these additives are contained, the content (% by weight) of the additive is preferably 0.001 to 10, more preferably 0.01 to 5, particularly preferably 0.05 to 1, and most preferably 0.1 to 0.5 based on the weight of the crosslinked polymer (A).

The production process of the present invention comprises subjecting the crosslinked polymer (A) to surface treatment using an aqueous colloidal solution of water-insoluble alumina-containing fine particles (c) and an aqueous solution of a water-soluble aluminum salt (d), and then subjecting the resulting product to surface crosslinking. Specific examples of the aqueous colloidal solution of the water-insoluble alumina-containing fine particles (c) and the water-soluble aluminum salt (d) are as described above. As described above, the amounts and the methods of adding these are also preferably such that, from the viewpoint of liquid permeability, the crosslinked polymer (a) is simultaneously added with the aqueous colloidal solution of the insoluble alumina-containing fine particles (c), the aqueous solution of the water-soluble aluminum salt (d), the organic surface crosslinking agent (e), and the polyhydric alcohol having 4 or less carbon atoms, and then subjected to heat treatment.

The water retention capacity (g/g) of the water-absorbent resin composition of the present invention and the water-absorbent resin composition obtained by the production method of the present invention (hereinafter, these are referred to as the water-absorbent resin composition of the present invention without distinguishing) can be measured by the method described below, and is preferably 28 or more, more preferably 33 or more, and still more preferably 35 or more in view of the absorption capacity of the diaper. In addition, the upper limit value is preferably 60 or less, more preferably 55 or less, and even more preferably 50 or less, from the viewpoint of the absorption amount under load. The water retention can be appropriately adjusted by the amounts (wt%) of the crosslinking agent (b) and the organic surface crosslinking agent (e).

The gel permeation rate (ml/min) of the water-absorbent resin composition of the present invention can be measured by the method described later, and is preferably 5 to 300, more preferably 10 to 280, and particularly preferably 15 to 250 in view of the absorption rate of a diaper. It is empirically known that the gel permeation rate is opposite to the water retention amount, and that there are cases where a high water retention amount is required and cases where a high gel permeation rate is required depending on the diaper configuration.

The water-absorbent resin composition of the present invention has an apparent density (g/ml) of preferably 0.50 to 0.80, more preferably 0.52 to 0.75, and particularly preferably 0.54 to 0.70. When the amount is within this range, the absorbent article can have better skin irritation resistance. The apparent density of the water-absorbent resin composition was measured at 25 ℃ in accordance with JIS K7365: 1999.

The water-absorbent resin composition of the present invention has a blocking ratio at the initial swelling of preferably 0 to 50%, more preferably 0 to 40%, and particularly preferably 0 to 30%. When the amount is within this range, the liquid diffusibility in the absorbent body can be sufficiently ensured, and the absorption performance is stable.

Gel Strength (kN/m) of Water-absorbent resin composition of the present invention²) Preferably 2.5 or more, and more preferably 2.7 or more. Within this range, the liquid permeability under load can be sufficiently ensured, and the absorption performance is stable.

An absorbent body can be obtained using the water-absorbent resin composition of the present invention. The absorbent material may be a water-absorbent resin composition alone or may be an absorbent material prepared by using the water-absorbent resin composition together with other materials.

As other materials, fibrous materials and the like can be cited. The structure and production method of the absorber when used together with a fibrous material are the same as those of known absorbers (e.g., japanese patent laid-open nos. 2003-225565, 2006-131767, and 2005-097569).

The fibrous material is preferably cellulose fibers, organic synthetic fibers, or a mixture of cellulose fibers and organic synthetic fibers.

Examples of the cellulose-based fibers include natural fibers such as fluff pulp, and cellulose-based chemical fibers such as viscose rayon, acetate rayon, and cuprammonium rayon. The raw material (coniferous tree, hardwood tree, etc.), the production method (chemical pulp, semi-chemical pulp, mechanical pulp, CTMP, etc.), the bleaching method, and the like of the cellulose-based natural fiber are not particularly limited.

Examples of the organic synthetic fibers include polypropylene-based fibers, polyethylene-based fibers, polyamide-based fibers, polyacrylonitrile-based fibers, polyester-based fibers, polyvinyl alcohol-based fibers, polyurethane-based fibers, and thermal fusion-bondable composite fibers (fibers in which at least 2 of the above fibers having different melting points are combined into a sheath-core type, an offset-core type, a side-by-side type, or the like, fibers in which at least 2 of the above fibers are mixed, and fibers in which the surface layer of the above fibers is modified).

Among these fibrous materials, cellulosic natural fibers, polypropylene fibers, polyethylene fibers, polyester fibers, heat-fusible composite fibers, and mixed fibers thereof are preferable, and fluff pulp, heat-fusible composite fibers, and mixed fibers thereof are more preferable from the viewpoint that the obtained water absorbing agent is excellent in shape retention after water absorption.

The length and thickness of the fibrous material are not particularly limited, and can be suitably used in the range of 1 to 200mm in length and 0.1 to 100 denier in thickness. The shape is not particularly limited as long as it is fibrous, and examples thereof include a thin cylindrical shape, a split thread shape, a short fiber shape, a filament shape, and a mesh shape.

When the water-absorbent resin composition is used together with a fibrous material to form an absorbent body, the weight ratio of the water-absorbent resin composition to the fibers (weight of the water-absorbent resin composition/weight of the fibers) is preferably 40/60 to 90/10, and more preferably 70/30 to 80/20.

An absorbent article can be obtained using the water-absorbent resin of the present invention. Specifically, the absorber described above is used. As the absorbent article, the absorbent article can be suitably used not only as a sanitary product such as a disposable diaper and a sanitary napkin, but also as an article used in various applications such as an absorbent or a retaining agent for various aqueous liquids and a gelling agent, which will be described later. The method for producing the absorbent article and the like are the same as known methods (methods described in japanese patent laid-open nos. 2003-225565, 2006-131767, 2005-097569 and the like).

Examples

The present invention will be further illustrated by the following examples and comparative examples, but the present invention is not limited thereto. Hereinafter, unless otherwise specified, parts means parts by weight and% means% by weight. The water retention capacity of the water-absorbent resin composition with respect to physiological saline, the absorption capacity under load, the gel permeation rate, the surface aluminum coating ratio, the blocking ratio at the initial swelling, and the gel strength were measured by the following methods.

< method for measuring Water holding amount >

A measurement sample (1.00 g) was added to a tea bag (length: 20cm, width: 10cm) made of a nylon net having a mesh opening of 63 μm (JIS Z8801-1:2006), and the bag was immersed in 1,000ml of physiological saline (salt concentration: 0.9%) without stirring for 1 hour, then pulled up, suspended for 15 minutes, and dehydrated. Thereafter, the tea bag was put into a centrifugal separator together with the tea bag, and the centrifugal separator was centrifuged at 150G for 90 seconds to remove the remaining physiological saline, and the weight including the tea bag was measured (h1), and the water retention was determined by the following equation. The temperature of the physiological saline used and the temperature of the measurement atmosphere were 25 ℃. + -. 2 ℃.

Water retention (g/g) ═ h1 (h2)

Note that (h2) represents the weight of the tea bag measured by the same procedure as described above in the case where no measurement sample is present.

< method for measuring absorption under load >

A measurement sample obtained by sieving a nylon net having a mesh size of 63 μm (JIS Z8801-1:2006) with a 30-mesh sieve and a 60-mesh sieve in the range of 250 to 500 μm was weighed in a cylindrical plastic tube (inner diameter: 25mm, height: 34mm) having a bottom surface to which a nylon net was attached, the cylindrical plastic tube was set to be vertical, the thickness of the measurement sample was adjusted so as to be approximately uniform on the nylon net, and a weight (weight: 210.6g, outer diameter: 24.5mm) was placed on the measurement sample. The weight of the entire cylindrical plastic tube was measured (M1), and the cylindrical plastic tube containing the measurement sample and the weight was vertically placed in a dish (diameter: 12cm) containing 60ml of physiological saline (salt concentration: 0.9%), and the nylon net side was immersed in the lower surface of the cylindrical plastic tube, followed by standing for 60 minutes. After 60 minutes, the cylindrical plastic tube was lifted from the plate and tilted, and water adhering to the bottom was collected at one point and dropped as water droplets to remove excess water, and then the weight of the entire cylindrical plastic tube containing the measurement sample and the weight was measured (M2), and the amount absorbed under load was determined from the following equation. The temperature of the physiological saline used and the temperature of the measurement atmosphere were 25 ℃. + -. 2 ℃.

Absorption capacity under load (g/g) { (M2) - (M1) }/0.16

< method for measuring gel permeation Rate >

The measurement was performed by the following procedure using the instrument shown in fig. 1 and 2.

The measurement sample (0.32 g) was immersed in 150ml of physiological saline 1 (common salt concentration: 0.9%) for 30 minutes to prepare swollen gel particles (2). Then, a filtration cylinder tube having a metal mesh 6 (mesh 106 μm, JIS Z8801-1:2006) and a freely openable/closable cock 7 (inner diameter of liquid passing portion 5mm) at the bottom of a vertically standing cylinder 3{ diameter (inner diameter) 25.4mm, length 40cm, and scale marks 4 and 5 provided at positions 60ml and 40ml from the bottom part, respectively }, the prepared swollen gel particles 2 were transferred into the filter cylinder tube together with physiological saline with the cock 7 closed, and then a pressing shaft 9 (weight 22g, length 47cm) vertically bonded to the metal mesh surface of a circular metal mesh 8 (mesh 150 μm, diameter 25mm) was placed on the swollen gel particles 2 so that the metal mesh and the swollen gel particles were in contact with each other, and a weight 10(88.5g) was further placed on the pressing shaft 9 and allowed to stand for 1 minute. Then, the cock 7 was opened, and the time (T1; sec) required for the liquid level in the filter cylinder tube to reach from 60ml mark 4 to 40ml mark 5 was measured, and the gel permeation rate (ml/min) was determined by the following equation.

Gel infusion speed (ml/min) ═ 20ml × 60/(T1-T2)

The temperature of the physiological saline used and the temperature of the measurement atmosphere were measured at 25 ℃. + -. 2 ℃, and T2 was the time measured by the same procedure as described above in the case where no measurement sample was present.

< method for measuring surface aluminum coating >

10 or more measurement samples screened to a range of 250 to 500 μm using a 30-mesh screen and a 60-mesh screen were fixed on a sample stage to which a carbon tape was attached so that the particles did not overlap each other, and the measurement samples were set in a field emission scanning electron microscope "JSM-7000" manufactured by JEOL corporation equipped with an energy dispersive X-ray analysis (EDS analysis) apparatus manufactured by Oxford corporation. The magnification was 150 times, and 1 particle was displayed on the screen, and EDS analysis was performed in the element mapping mode. The surface aluminum coverage was determined by the following equation, where the detection area of aluminum as the target element was S1, and the detection area of the characteristic element of the water-absorbent resin composition (sodium when the main component of the water-absorbent resin composition was a sodium polyacrylate) was S0.

Surface aluminum coverage (%) (S1/S0) × 100

For each measurement sample, 5 particles were randomly measured, and the arithmetic average value was defined as the coverage of the measurement sample. Note that, as the detection areas S0 and S1, values obtained by outputting frequency distributions of the respective detection intensities in a histogram are used.

< blocking Rate (%) at initial swelling >

In the water-absorbent resin, particles passed through a metal sieve having a mesh of 4.0mm and a diameter of 8cm by tapping five times were used as a measurement sample. This measurement sample (1.5 g) was uniformly charged into a disposable cup made of PP (polypropylene) having a diameter of 5cm and a height of 7cm, 0.14g of physiological saline was uniformly added by spraying, and the cup was left to stand for 1 minute. The weight (OW) of the measurement sample remaining on the metal sieve was measured by tapping five times using a 4.0mm metal sieve, the Total Weight (TW) of the measurement sample remaining on the metal sieve and the measurement sample passing through the sieve was measured, and the initial swelling blocking ratio (%) was calculated from the following equation.

(blocking ratio (%) at initial swelling ═ OW). times.100/(TW)

The measurement was performed 3 times for each measurement sample, and the arithmetic average value was taken as the blocking ratio of the measurement sample.

< method for measuring gel Strength >

In a 100ml beaker (inner diameter: 5cm), 60.0g of artificial urine [ 200 parts by weight of urea, 80 parts by weight of sodium chloride, 8 parts by weight of magnesium sulfate heptahydrate, 3 parts by weight of calcium chloride dihydrate, 2 parts by weight of iron (III) sulfate heptahydrate, and 9704 parts by weight of ion-exchanged water ] was weighed out, and 2.0g of a measurement sample was accurately weighed and put into the beaker in the same manner as in the procedure described in JIS K7224-1996 to prepare a 30-fold swollen gel. In order to prevent the swelling gel from drying, a beaker containing 30 times the swelling gel was covered with a wrap film, the beaker was allowed to stand at 40. + -. 2 ℃ for 3 hours and further at 25. + -. 2 ℃ for 0.5 hours, and then the wrap film was removed, and the gel strength of the swelling gel was measured at 30 times by a curometer (for example, Curd-Meter MAX ME-500 manufactured by Itec technology Engineering Co., Ltd.). The curd meter conditions were as follows.

Pressure-sensitive shaft: 8mm

A spring: 100g with

Load: 100g

Rising speed: 1 inch/7 seconds

Test properties: fracture of

Measurement time: 6 seconds

Measurement of atmospheric temperature: 25 +/-2 DEG C

< example 1>

Acrylic acid (a1-1) { Mitsubishi chemical corporation, purity 100% }131 parts, crosslinking agent (b-1) { pentaerythritol triallyl ether, Daiso corporation, 0.44 parts, and deionized water 362 parts were mixed with stirring and maintained at 3 ℃. After nitrogen was flowed into the mixture to reduce the dissolved oxygen amount to 1ppm or less, 0.5 part of a 1% hydrogen peroxide solution, 1 part of a 2% ascorbic acid aqueous solution, and 1 part of a 2% 2, 2' -azobisamidinopropane dihydrochloride aqueous solution were mixed to initiate polymerization. After the temperature of the mixture reached 80 ℃, polymerization was carried out at 80. + -. 2 ℃ for about 5 hours, whereby an aqueous gel was obtained.

Subsequently, the aqueous gel was minced by a chopper (12 VR-400K manufactured by ROYAL Co., Ltd.), and 108 parts of a 48.5% aqueous sodium hydroxide solution was added thereto and mixed and neutralized to obtain a neutralized gel (neutralization degree: 72%). The neutralized hydrogel was further dried by means of a vented dryer {200 ℃ C., air speed 2 m/sec }, to obtain a dried product. The dried product was pulverized with a juicer mixer (Oster corporation, Osterizer BLENDER), and sieved to adjust the particle size to 710 to 150 μm, thereby obtaining a crosslinked polymer (A-1).

Then, while stirring 100 parts of the resulting crosslinked polymer (A-1) at a high speed (high-speed paddle mixer manufactured by Hosokawa Micron: 2000rpm), a mixed solution obtained by mixing 1.0 part of LUDOX CL (manufactured by SIGMA-ALDRICH Japan K.K.) as a water-insoluble alumina-containing fine particle (c), 0.1 part of ethylene glycol diglycidyl ether as an organic surface crosslinking agent (e), 1.0 part of propylene glycol as a polyhydric alcohol (f) having 4 or less carbon atoms, and 1.6 parts of water, and a mixed solution obtained by mixing 0.6 part of sodium aluminum sulfate dodecahydrate as a water-soluble aluminum salt (d), 0.5 part of propylene glycol as a polyhydric alcohol (f) having 4 or less carbon atoms, and 1.4 parts of water were added simultaneously and mixed uniformly, the resultant was heated at 130 ℃ for 30 minutes to obtain a water-absorbent resin composition (P-1) of the present invention.

< trait of LUDOX CL >

Aqueous dispersion colloidal fluid of alumina-modified silica

The solid content concentration was 30%

Number-based average primary particle diameter of 12nm

< example 2>

While 100 parts of the crosslinked polymer (A-1) obtained in the same manner as in example 1 was stirred at a high speed (high-speed paddle mixer manufactured by Hosokawa Micron: rotation speed 2000rpm), a mixed solution obtained by mixing 4.0 parts of "Bairaru Al-L7" (manufactured by Polywood chemical Co., Ltd.) as the water-insoluble alumina-containing fine particles (c), 0.1 part of ethylene glycol diglycidyl ether as the organic surface crosslinking agent (e), 0.5 part of propylene glycol as the polyhydric alcohol (f) having 4 or less carbon atoms and 1.1 part of water, and 0.6 part of sodium aluminum sulfate dodecahydrate as the water-soluble aluminum salt (d), 0.5 part of propylene glycol as the polyhydric alcohol (f) having 4 or less carbon atoms and 1.4 parts of water were simultaneously added thereto and uniformly mixed, the resultant was heated at 130 ℃ for 30 minutes to obtain a water-absorbent resin composition (P-2) of the present invention.

< trait of Bairaru Al-L7 >

Aqueous dispersion colloidal body fluid of alumina

The solid content concentration was 7%

Number-based average primary particle diameter of 5 to 10nm

< example 3>

100 parts of the crosslinked polymer (A-1) obtained in the same manner as in example 1 was stirred at a high speed (high-speed paddle mixer manufactured by Hosokawa Micron: rotational speed 2000rpm), 1.5 parts of "Bairau Al-C20" (manufactured by Polywood chemical Co., Ltd.) as the water-insoluble alumina-containing fine particles (C), 0.1 part of ethylene glycol diglycidyl ether as the organic surface crosslinking agent (e), 0.8 part of propylene glycol as the polyhydric alcohol (f) having 4 or less carbon atoms, and 1.3 parts of water were simultaneously added thereto, and a mixed solution obtained by mixing 0.6 part of sodium aluminum sulfate dodecahydrate as the water-soluble aluminum salt (d), 0.5 part of propylene glycol as the polyhydric alcohol (f) having 4 or less carbon atoms, and 1.4 parts of water was uniformly mixed, the resultant was heated at 130 ℃ for 30 minutes to obtain a water-absorbent resin composition (P-3) of the present invention.

< trait of Bairaru Al-C20 >

Aqueous dispersion colloidal body fluid of alumina

The solid content concentration was 20%

The number-based average primary particle diameter is in the range of 15-20nm

< example 4>

While 100 parts of the crosslinked polymer (A-1) obtained in the same manner AS in example 1 was stirred at a high speed (high-speed paddle mixer manufactured by Hosokawa Micron: rotational speed 2000rpm), a mixed solution obtained by mixing 3.0 parts of "Bairaru AS-L10" (manufactured by Polywood chemical Co., Ltd.) AS the water-insoluble alumina-containing fine particles (c), 0.1 part of ethylene glycol diglycidyl ether AS the organic surface crosslinking agent (e), 0.5 part of propylene glycol AS the polyhydric alcohol (f) having 4 or less carbon atoms and 1.1 part of water, 0.6 part of sodium aluminum sulfate dodecahydrate AS the water-soluble aluminum salt (d), 0.5 part of propylene glycol AS the polyhydric alcohol (f) having 4 or less carbon atoms and 1.4 parts of water was simultaneously added thereto and uniformly mixed, the resultant was heated at 130 ℃ for 30 minutes to obtain a water-absorbent resin composition (P-4) of the present invention.

< trait of Bairaru AS-L10 >

Aqueous dispersion colloidal body fluid of mullite

The solid content concentration was 10%

Number-based average primary particle diameter of 5-50nm

< example 5>

While 100 parts of the crosslinked polymer (A-1) obtained in the same manner as in example 1 was stirred at a high speed (high-speed paddle mixer manufactured by Hosokawa Micron: 2000rpm), 1.0 part of LUDOX CL (manufactured by SIGMA-ALDRICH Japan K.K.) as a water-insoluble alumina-containing fine particle (c), 0.1 part of ethylene glycol diglycidyl ether as an organic surface crosslinking agent (e), 1.0 part of propylene glycol as a polyhydric alcohol (f) having 4 or less carbon atoms, and 1.6 parts of water were added thereto, and after uniform mixing, the mixture was heated at 130 ℃ for 30 minutes and cooled to room temperature, and then a mixture of 0.6 parts of sodium sulfate aluminum dodecahydrate as a water-soluble aluminum salt (d), 0.5 parts of propylene glycol as a polyhydric alcohol (f) having 4 or less carbon atoms, and 1.4 parts of water was simultaneously added thereto while stirring at a high speed (high-speed paddle mixer manufactured by Hosokawa Micron: 2000rpm), after the uniform mixing, the mixture was heated at 130 ℃ for 30 minutes to obtain a water-absorbent resin composition (P-5) of the present invention.

< example 6>

100 parts of the crosslinked polymer (A-1) obtained in the same manner as in example 1 was stirred at a high speed (high-speed paddle mixer manufactured by Hosokawa Micron: rotation speed 2000rpm), and a mixed solution obtained by mixing 0.75 parts of LUDOX CL-P (manufactured by Grace) as the water-insoluble alumina-containing fine particles (c), 0.1 parts of ethylene glycol diglycidyl ether as the organic surface crosslinking agent (e), 1.0 parts of propylene glycol as the polyhydric alcohol (f) having 4 or less carbon atoms, and 1.6 parts of water, and a mixed solution obtained by mixing 0.6 parts of sodium aluminum sulfate dodecahydrate as the water-soluble aluminum salt (d), 0.5 parts of propylene glycol as the polyhydric alcohol (f) having 4 or less carbon atoms, and 1.4 parts of water were simultaneously added thereto and uniformly mixed, the resultant was heated at 130 ℃ for 30 minutes to obtain a water-absorbent resin composition (P-6) of the present invention.

< trait of LUDOX CL-P >

Aqueous dispersion colloidal fluid of alumina-modified silica

The solid content concentration was 40%

Number-based average primary particle diameter of 22nm

< comparative example 1>

A mixed solution prepared by mixing 1.2 parts of sodium aluminum sulfate dodecahydrate as a water-soluble aluminum salt (d), 0.1 part of ethylene glycol diglycidyl ether as an organic surface crosslinking agent (e), 0.5 part of propylene glycol as a polyhydric alcohol (f) having 4 or less carbon atoms, and 1.1 parts of water was added thereto while stirring 100 parts of the crosslinked polymer (A-1) obtained in the same manner as in example 1 at a high speed (high-speed stirring paddle mixer manufactured by Hosokawa Micron: 2000rpm), followed by uniform mixing, and then heating at 130 ℃ for 30 minutes to obtain a water-absorbent resin composition (R-1) for comparison.

< comparative example 2>

100 parts of the crosslinked polymer (A-1) obtained in the same manner as in example 1 was stirred at a high speed (high-speed paddle mixer manufactured by Hosokawa Micron: rotational speed 2000rpm), 1.0 part of LUDOX CL (manufactured by SIGMA-ALDRICH Japan K.K.) as the water-insoluble alumina-containing fine particles (c), 0.1 part of ethylene glycol diglycidyl ether as the organic surface crosslinking agent (e), 1.0 part of propylene glycol as the polyhydric alcohol (f) having 4 or less carbon atoms, and 1.6 parts of water were added thereto and mixed uniformly, and then the mixture was heated at 130 ℃ for 30 minutes to obtain a water-absorbent resin composition (R-2) for comparison.

< comparative example 3>

A water-absorbent resin composition (R-3) for comparison was obtained in the same manner as in example 1, except that 1.0 part of LUDOX CL (manufactured by SIGMA-ALDRICH Japan K.K.) as the water-insoluble alumina-containing fine particles (c) was changed to 1.0 part of LUDOX HS-30 (manufactured by SIGMA-ALDRICH Japan K.K.).

< trait of LUDOX HS-30 >

Aqueous colloidal dispersion of silica

The solid content concentration was 30%

Number-based average primary particle diameter of 12nm

The evaluation results of the performances (water retention amount, absorption amount under load and gel permeation rate), surface aluminum coverage, blocking rate at initial swelling and gel strength of the water-absorbent resin compositions (P-1) to (P-6) of examples 1 to 6 and the water-absorbent resin compositions (R-1) to (R-3) of comparative examples 1 to 3 are shown in Table 1.

[ Table 1]

As is clear from the results in table 1, the examples and comparative examples have good water retention, and no significant difference is observed, but the examples have good absorption under load and good gel liquid permeability. In addition, in the examples, the surface aluminum coverage was high, and the blocking rate at the initial swelling was significantly low. In addition, the gel strength is particularly good in the examples. On the other hand, in the comparative examples of the embodiment in which the water-insoluble alumina-containing fine particles (c) and the water-soluble aluminum salt (d) are not combined, the blocking ratio at the initial swelling is remarkably high. Even if the surface aluminum coverage was high (comparative example 1), both the absorption amount under load and the gel liquid permeability were low.

Industrial applicability

The water-absorbent resin composition of the present invention has high blocking resistance, liquid permeability and gel strength in initial swelling, and therefore, can be applied to various absorbers to produce absorbent articles having a large absorption amount and excellent rewet and surface dryness, and is therefore suitably used for sanitary goods such as disposable diapers (e.g., child diapers and adult diapers), sanitary napkins (e.g., sanitary napkins for menstrual use), paper towels, liners (e.g., incontinence pads and surgical pads), and pet diapers (e.g., pet diapers), and particularly, is most suitably used for disposable diapers. The water-absorbent resin composition of the present invention is useful not only for sanitary products but also for various applications such as a pet urine absorbent, a urine gelling agent for portable toilets, a freshness keeping agent for vegetables and fruits, a drip absorbent for meat and aquatic products, a cold retaining agent, a disposable chest warmer, a gelling agent for batteries, a water retaining agent for plants and soil, a dew condensation preventing agent, a water stopping material, a sealing material, and artificial snow.

Description of the symbols

1 physiological saline

2 aqueous gel particles

3 cylinders

4 graduation mark at the position 60ml from the bottom

5 Scale lines at a position 40ml from the bottom

6 Metal mesh

7 cock

8 round metal net

9 pressurized shaft

10 weight

Claims

1. A water-absorbent resin composition comprising a crosslinked polymer (A) having a water-soluble vinyl monomer (a1) and/or a vinyl monomer (a2) that is hydrolyzed to a water-soluble vinyl monomer (a1), and a crosslinking agent (b) as essential constituent units, wherein the crosslinked polymer (A) has a surface aluminum coverage of 60 to 100%, wherein the surface of the crosslinked polymer (A) has a structure crosslinked by an organic surface crosslinking agent (e) that is ethylene glycol diglycidyl ether, and the water retention of the water-absorbent resin composition is 35g/g or more.

2. The water-absorbent resin composition according to claim 1, wherein the water-insoluble alumina-containing fine particles (c) are spherical or amorphous particles having an average primary particle diameter of 1 to 100 nm.

3. The water-absorbent resin composition according to claim 1 or 2, wherein the water-insoluble alumina-containing fine particles (c) are alumina-modified silica.

4. The water-absorbent resin composition according to claim 1 or 2 wherein the water-soluble aluminum salt (d) has a pH of 10g/100gH at 20 ℃₂A crystalline salt having a water solubility of O or more.

5. The water-absorbent resin composition according to claim 1 or 2 wherein the water-soluble aluminum salt (d) has a sulfate ion.

6. The water-absorbent resin composition according to claim 1 or 2, wherein the content of the water-insoluble alumina-containing fine particles (c) is 0.01 to 1% by weight and the content of the water-soluble aluminum salt (d) is 0.05 to 5% by weight, based on the weight of the crosslinked polymer (A).

7. The water-absorbent resin composition according to claim 1 or 2, wherein the water-absorbent resin composition further contains a polyhydric alcohol (f) having 4 or less carbon atoms.

8. The water-absorbent resin composition according to claim 1 or 2, wherein the water-absorbent resin composition further comprises a hydrophobic substance (g).

9. A process for producing a water-absorbent resin composition having a surface aluminum coverage of a crosslinked polymer (A) of 60 to 100% and surface-crosslinked with ethylene glycol diglycidyl ether as an organic surface-crosslinking agent (e), wherein the water retention of the water-absorbent resin composition is 35g/g or more, characterized by adding an aqueous colloidal fluid containing water-insoluble alumina-containing fine particles (c) in an amount of 0.01 to 1% by weight based on the weight of the crosslinked polymer (A) and an aqueous solution containing water-soluble aluminum salt (d) in an amount of 0.05 to 5% by weight based on the weight of the crosslinked polymer (A) to the crosslinked polymer (A), and then surface-crosslinking the crosslinked polymer (A); wherein the crosslinked polymer (A) has a water-soluble vinyl monomer (a1) and/or a vinyl monomer (a2) which becomes a water-soluble vinyl monomer (a1) by hydrolysis, and a crosslinking agent (b) as essential structural units.

10. The production process according to claim 9, wherein the crosslinked polymer (A) is surface-crosslinked after adding simultaneously water-insoluble alumina-containing fine particles (c) in an aqueous colloidal solution, a water-soluble aluminum salt (d) and ethylene glycol diglycidyl ether as the organic surface-crosslinking agent (e).

11. The production process according to claim 9 or 10, wherein the crosslinked polymer (A) is surface-crosslinked after adding simultaneously an aqueous colloidal solution of insoluble alumina-containing fine particles (c), an aqueous solution of a water-soluble aluminum salt (d), ethylene glycol diglycidyl ether as the organic surface-crosslinking agent (e), and a polyhydric alcohol (f) having 4 or less carbon atoms.