JP7094281B2 - Water-absorbent resin particles and their manufacturing method - Google Patents

Description

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

For sanitary materials such as disposable diapers, menstrual napkins, and incontinence pads, water-absorbent resin particles mainly made of hydrophilic fibers such as pulp and acrylic acid (salt) are widely used as absorbers. From the viewpoint of improving QOL (quality of life) in recent years, the demand for these sanitary materials is shifting to lighter and thinner ones, and along with this, it is desired to reduce the amount of hydrophilic fibers used. .. Therefore, it has become necessary for the water-absorbent resin particles themselves to play the role of liquid diffusivity and initial absorption in the absorber, which has been played by hydrophilic fibers, and the liquid permeability between the swollen gels is increased. High water absorbent resin particles are required.

As a method for improving the liquid permeability between swollen gels, (1) a method of forming a physical space by adding an inorganic compound such as silica to the surface of water-absorbent resin particles, and (2) a surface of modified silicone or the like. Known methods include a method of suppressing coalescence of swollen gels to form gel gaps by surface treatment with a hydrophobic polymer having a small free energy, and (3) a method of adding aluminum sulfate, aluminum lactate, or the like. (See, for example, Patent Document 1, Patent Document 2, and Patent Document 3). However, with these methods, the liquid permeability between the swollen gels, especially the liquid permeability in the antigravity direction, was not sufficiently satisfactory.

Japanese Unexamined Patent Publication No. 2012-161788 Japanese Unexamined Patent Publication No. 2013-133399 Japanese Unexamined Patent Publication No. 2014-512440

An object of the present invention is to provide water-absorbent resin particles having a sufficient amount of water retention and excellent initial liquid diffusivity and liquid permeability in the antigravity direction between swollen gels.

The present invention comprises a water-soluble vinyl monomer (a1) and / or a vinyl monomer (a2) that becomes a water-soluble vinyl monomer (a1) by hydrolysis, and a cross-linking polymer (A) containing a cross-linking agent (b) as an essential constituent unit. The water-absorbent resin particles contain 1 to 20% by weight of aluminum oxide and 0.1 to 10% by weight of the talc (c) based on the weight of the crosslinked polymer (A). A method for producing water-absorbent resin particles, which comprises a step of mixing the crosslinked polymer (A) and the talc (c) contained therein.

The water-absorbent resin particles of the present invention and the water-absorbent resin particles obtained by the production method of the present invention have a sufficient amount of water retention, and are excellent in initial liquid diffusivity and liquid permeability in the antigravity direction between swollen gels. Therefore, it exhibits stable and excellent absorption performance even in various usage conditions. Since the absorbent resin particles of the present invention do not inhibit the swelling of the gel, the absorption performance is improved, and the initial liquid diffusivity and the liquid permeability between the swelled gels, particularly the liquid passage in the antigravity direction. Excellent in sex.

The water-absorbent resin particles of the present invention include a crosslinked polymer (A) containing a water-soluble vinyl monomer (a1) and / or a vinyl monomer (a2) which becomes a water-soluble vinyl monomer (a1) by hydrolysis as an essential constituent unit. It is a water-absorbent resin particle containing talc (c) containing 1 to 20% by weight of aluminum oxide.

The water-soluble vinyl monomer (a1) in the present invention is not particularly limited, and is a known monomer, for example, at least one water-soluble substituent disclosed in paragraphs 0007 to 0023 of Japanese Patent No. 36485553 and ethylenia-free. Vinyl monomers having a saturated group (for example, anionic vinyl monomers, nonionic vinyl monomers and cationic vinyl monomers), anionic vinyl monomers and nonionic vinyl monomers disclosed in paragraphs 0009 to 0024 of JP-A-2003-165883. Select from the group consisting of a sex vinyl monomer, a cationic vinyl monomer, and a carboxy group, a sulfo group, a phosphono group, a hydroxyl group, a carbamoyl group, an amino group and an ammonio group disclosed in paragraphs 0041 to 0051 of JP-A-2005-75982. A vinyl monomer having at least one of these can be used.

A vinyl monomer (a2) that becomes a water-soluble vinyl monomer (a1) by hydrolysis {hereinafter, also referred to as a hydrolyzable vinyl monomer (a2). } Is not particularly limited, and is known [for example, a vinyl monomer having at least one hydrolyzable substituent which becomes a water-soluble substituent by hydrolysis disclosed in paragraphs 0024 to 0025 of Japanese Patent No. 3648553, Japanese Patent Application Laid-Open No. At least one hydrolyzable substituent {1,3-oxo-2-oxapropylene (-CO-O-CO-) group, acyl group and cyano disclosed in paragraphs 0052 to 0055 of JP-A-2005-75982. A vinyl monomer having a group} or the like] can be used. The water-soluble vinyl monomer is a concept well known to those skilled in the art, but when expressed using a quantity, it means, for example, a vinyl monomer that dissolves at least 100 g in 100 g of water at 25 ° C. Further, the hydrolyzable property of the hydrolyzable vinyl monomer (a2) means, for example, the property of being hydrolyzed by the action of water and, if necessary, a catalyst (acid, base, etc.) to become water-soluble. The hydrolyzable vinyl monomer (a2) may be hydrolyzed during or after the polymerization, or both of them, but it is preferable after the polymerization from the viewpoint of the absorption performance of the obtained water-absorbent resin particles.

Of these, the water-soluble vinyl monomer (a1) is preferable from the viewpoint of absorption performance, and the above-mentioned anionic vinyl monomer, carboxy (salt) group, sulfo (salt) group, amino group, and carbamoyl group are more preferable. Vinyl monomers having an ammonio group or a mono-, di- or tri-alkyl ammonio group, more preferably a vinyl monomer having a carboxy (salt) group or a carbamoyl group, particularly preferably (meth) acrylic acid (salt) and (Meta) acrylamide, particularly preferred is (meth) acrylic acid (salt), most preferred is acrylic acid (salt).

In addition, "carboxy (salt) group" means "carboxy group" or "carboxylate group", and "sulfo (salt) group" means "sulfo group" or "sulfonate group". Further, (meth) acrylic acid (salt) means acrylic acid, acrylate, methacrylic acid or methacrylamide, and (meth) acrylamide means acrylamide or methacrylamide. Examples of the salt include alkali metal (lithium, sodium, potassium, etc.) salt, alkaline earth metal (magnesium, calcium, etc.) salt, ammonium (NH ₄ ) salt, and the like. Of these salts, alkali metal salts and ammonium salts are preferable, and alkali metal salts are more preferable, and sodium salts are particularly preferable, from the viewpoint of absorption performance and the like.

When either the water-soluble vinyl monomer (a1) or the hydrolyzable vinyl monomer (a2) is used as a constituent unit, one of each may be used alone as a constituent unit, or two or more thereof may be used as a constituent unit, if necessary. good. The same applies to the case where the water-soluble vinyl monomer (a1) and the hydrolyzable vinyl monomer (a2) are used as constituent units. When the water-soluble vinyl monomer (a1) and the hydrolyzable vinyl monomer (a2) are used as constituent units, the molar ratio {(a1) / (a2)} thereof is preferably 75/25 to 99/1. It is more preferably 85/15 to 95/5, particularly preferably 90/10 to 93/7, and most preferably 91/9 to 92/8. Within this range, the absorption performance is further improved.

As a constituent unit of the crosslinked polymer (A), in addition to the water-soluble vinyl monomer (a1) and the hydrolyzable vinyl monomer (a2), another vinyl monomer (a3) copolymerizable with these shall be a constituent unit. Can be done. As the other vinyl monomer (a3), one type may be used alone, or two or more types may be used in combination.

The other vinyl monomer (a3) is not particularly limited, and is known (for example, the hydrophobic vinyl monomer disclosed in paragraphs 0028 to 0029 of Japanese Patent No. 3648553, paragraph 0025 and Japanese Patent Application Laid-Open No. 2003-165883. Hydrophobic vinyl monomers (such as the vinyl monomers disclosed in paragraph 0058 of JP-A-2005-75982) can be used, and specifically, for example, the following vinyl monomers (i) to (iii) can be used.
(I) Aromatic ethylenic monomer having 8 to 30 carbon atoms Styrene such as styrene, α-methylstyrene, vinyltoluene and hydroxystyrene, halogen substituted styrene such as vinylnaphthalene and dichlorostyrene and the like.
(Ii) Alkene (ethylene, propylene, butene, isobutylene, pentene, heptene, diisobutylene, octene, dodecene, octadecene, etc.); and alkaziene (butadiene and isoprene, etc.) having 2 to 20 carbon atoms.
(Iii) Alicyclic ethylenic monomer having 5 to 15 carbon atoms Monoethylene unsaturated monomer (pinene, limonene, inden, etc.); Polyethylene vinyl monomer (cyclopentadiene, bicyclopentadiene, etylidene norbornene, etc.) and the like.

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

The cross-linking agent (b) is not particularly limited and reacts with a cross-linking agent having two or more ethylenically unsaturated groups and a water-soluble substituent disclosed in paragraphs 0031 to 0034 of Japanese Patent No. 3648553 (for example). JP-A-2003-165883, a cross-linking agent having at least one functional group to be obtained and having at least one ethylenically unsaturated group and a cross-linking agent having at least two functional groups capable of reacting with a water-soluble substituent. A cross-linking agent having two or more ethylenically unsaturated groups, a cross-linking agent having an ethylenically unsaturated group and a reactive functional group, and a cross-linking agent having two or more reactive substituents disclosed in paragraphs 0028 to 0031. , A cross-linking agent of the cross-linking vinyl monomer disclosed in paragraph 0059 of JP-A-2005-75982 and the cross-linking vinyl monomer disclosed in paragraphs 0015 to 0016 of JP-A-2005-59559) can be used. .. Of these, a cross-linking agent having two or more ethylenically unsaturated groups is preferable from the viewpoint of absorption performance and the like, and more preferable is a poly (triallyl cyanurate, triallyl isocyanurate and a polyol having 2 to 40 carbon atoms). Meta) Allyl ethers, particularly preferred are triallyl cyanurate, triallyl isocyanurate, tetraallyloxyetane, polyethylene glycol diallyl ether and pentaerythritol triallyl ether, most preferably pentaerythritol triallyl ether. The cross-linking agent (b) may be used alone or in combination of two or more.

The content (mol%) of the cross-linking agent (b) unit is the water-soluble vinyl monomer (a1) unit and the hydrolyzable vinyl monomer (a2) unit, and when other vinyl monomers (a3) are also used (a1). Based on the total number of moles of (a3), 0.001 to 5, more preferably 0.005 to 3, and particularly preferably 0.01 to 1. Within this range, the absorption performance is further improved.

Examples of the polymerization method of the crosslinked polymer (A) include known solution polymerization (adiabatic polymerization, thin film polymerization, spray polymerization, etc .; JP-A No. 55-133413, etc.) and known reverse phase suspension polymerization (Tokusho). 54-30710, JP-A-56-26909, JP-A No. 1-5808, etc.).

The crosslinked polymer (A) can be obtained by polymerizing a monomer composition containing a water-soluble vinyl monomer (a1) and / or a hydrolyzable vinyl monomer (a2) and a crosslinking agent (b) as essential constituents. However, the solution polymerization method is preferable as the polymerization method, and since it is not necessary to use an organic solvent and is advantageous in terms of production cost, the aqueous solution polymerization method is particularly preferable because it has a large amount of water retention and has a large water retention capacity. The aqueous solution adiabatic polymerization method is most preferable because water-absorbent resin particles having a small amount of water-soluble components can be obtained and temperature control during polymerization is not required.

When performing aqueous solution polymerization, a mixed solvent containing water and an organic solvent can be used, and the organic solvent includes methanol, ethanol, n-propyl alcohol, isopropyl alcohol, n-butanol, isobutyl alcohol, and t-butyl alcohol. , Isopentyl alcohol, acetone, methyl ethyl ketone, N, N-dimethylformamide, dimethylsulfoxide and mixtures of two or more thereof. In the case of aqueous solution polymerization, the amount (% by weight) of the organic solvent used is preferably 40 or less, more preferably 30 or less, based on the weight of water.

When an initiator is used for polymerization, an initiator for radical polymerization can be used, for example, azo compounds {azobisisobutyronitrile, azobiscyanovaleric acid and 2,2'-azobis (2-amidinopropane) hydrogen peroxide, etc. }, Inorganic peroxides (hydrogen peroxide, ammonium persulfate, potassium persulfate, sodium persulfate, etc.), organic peroxides {benzoyl peroxide, di-t-butyl peroxide, cumene hydroperoxide, succinate peroxide And di (2-ethoxyethyl) peroxydicarbonate, etc.} and redox catalysts (alkali metal sulfites or bicarbonates, reducing agents such as ammonium sulfite, ammonium bicarbonate and ascorbic acid, and alkali metal persulfates, hydrogen peroxide, etc. (Combined with oxidizing agents such as ammonium sulfate, hydrogen peroxide and organic peroxide) and the like. These catalysts may be used alone or in combination of two or more of them. The amount (% by weight) of the radical polymerization initiator used is (a1) to (a3) when other vinyl monomers (a3) of the water-soluble vinyl monomer (a1) and the hydrolyzable vinyl monomer (a2) are also used. Based on the total weight of the above, 0.0005 to 5 is preferable, and 0.001 to 2 is more preferable.

At the time of polymerization, a polymerization control agent typified by a chain transfer agent may be used in combination, and specific examples thereof include sodium hypophosphite, sodium phosphite, alkyl mercaptans, and alkyl halides. , Thiocarbonyl compounds and the like. These polymerization control agents may be used alone or in combination of two or more of them. The amount (% by weight) of the polymerization control agent used is that of the water-soluble vinyl monomer (a1) and the hydrolyzable vinyl monomer (a2), and when other vinyl monomers (a3) are also used, the amounts thereof are (a1) to (a3). , 0.0005 to 5, more preferably 0.001 to 2, based on the total weight.

When a suspension polymerization method or a reverse phase suspension polymerization method is used as the polymerization method, the polymerization may be carried out in the presence of a dispersant or a surfactant, if necessary. Further, in the case of the reverse phase suspension polymerization method, the polymerization can be carried out using a hydrocarbon solvent such as xylene, normal hexane and normal heptane.

The polymerization start temperature can be appropriately adjusted depending on the type of catalyst used, but is preferably 0 to 100 ° C, more preferably 2 to 80 ° C.

When a solvent (organic solvent, water, etc.) is used for the polymerization, it is preferable to distill off the solvent after the polymerization. When the solvent contains an organic solvent, the content (% by weight) of the organic solvent after distillation is preferably 0 to 10, more preferably 0 to 5, and particularly preferably 0 to 5, based on the weight of the crosslinked polymer (A). Is 0 to 3, most preferably 0 to 1. Within this range, the absorption performance of the water-absorbent resin particles is further improved.

When water is contained in the solvent, the water content (% by weight) after distillation is preferably 0 to 20, more preferably 1 to 10, particularly preferably 2 to 9, based on the weight of the crosslinked polymer (A). Most preferably, it is 3 to 8. Within this range, the absorption performance is further improved.

A water-containing gel-like product in which the cross-linked polymer (A) contains water by the above-mentioned polymerization method {that is, a cross-linked polymer (A) which is a water-containing gel-like product. Hereinafter, it is abbreviated as a water-containing gel}, and further, the dried crosslinked polymer (A) can be obtained by drying the water-containing gel. When an acid group-containing monomer such as acrylic acid or methacrylic acid is used as the water-soluble vinyl monomer (a1), the water-containing gel may be neutralized with a base. The degree of neutralization of the acid group is preferably 50 to 80 mol%. When the degree of neutralization is less than 50 mol%, the adhesiveness of the obtained hydrogel polymer may be high, and the workability during production and use may be deteriorated. Further, the amount of water retention of the obtained water-absorbent resin particles may decrease. On the other hand, when the degree of neutralization exceeds 80%, the pH of the obtained resin becomes high, and there may be a concern about the safety of the human body on the skin. The neutralization may be performed at any stage after the polymerization of the crosslinked polymer (A) in the production of the water-absorbent resin particles, and for example, a method of neutralizing in the state of a hydrogel is preferable. Illustrated. As the base to be neutralized, alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, and alkali metal carbonates such as sodium carbonate, sodium hydrogencarbonate and potassium carbonate can be usually used.

The hydrogel obtained by polymerization can be shredded as needed before drying. The size (longest diameter) of the gel after shredding is preferably 50 μm to 10 cm, more preferably 100 μm to 2 cm, and particularly preferably 1 mm to 1 cm. Within this range, the drying property in the drying step is further improved.

Shredding can be performed by a known method, and can be shredded using a shredding device (for example, a Beck's mill, a rubber chopper, a pharma mill, a minced machine, an impact type crusher, a roll type crusher) or the like.

The content and moisture of the organic solvent were heated by an infrared moisture measuring instrument (JE400 manufactured by KETT Co., Ltd., 120 ± 5 ° C., 30 minutes, atmospheric humidity 50 ± 10% RH before heating, lamp specification 100 V, 40 W). It is obtained from the weight loss of the measurement sample at the time.

As a method for distilling off the solvent (including water) of the hydrogel and drying it, a method of distilling off (drying) with hot air at a temperature of 80 to 230 ° C., a drum dryer heated to 100 to 230 ° C., or the like is used. Thin film drying method, (heating) vacuum drying method, freeze drying method, infrared drying method, decantation, filtration and the like can be applied.

After the hydrous gel is dried, it can be further pulverized. The crushing method is not particularly limited, and a crushing device (for example, a hammer type crusher, an impact type crusher, a roll type crusher, a shet airflow type crusher) or the like can be used. The particle size of the pulverized crosslinked polymer can be adjusted by sieving or the like, if necessary.

The weight average particle size (μm) of the crosslinked polymer (A) when sieved as necessary is preferably 100 to 800, more preferably 200 to 700, then preferably 250 to 600, and particularly preferably 300 to 500. , Most preferably 350-450. Within this range, the absorption performance is further improved.

The weight average particle size is determined by using a low-tap test sieve shaker and a standard sieve (JIS Z8801-1: 2006), Perry's Chemical Engineers Handbook 6th Edition (McGlow Hill Book Canvas, 1984, 21). Page)). That is, the JIS standard sieves are combined in the order of 1000 μm, 850 μm, 710 μm, 500 μm, 425 μm, 355 μm, 250 μm, 150 μm, 125 μm, 75 μm and 45 μm, and the saucer from the top. Place about 50 g of the measurement particles in the uppermost sieve and shake with a low-tap test sieve shaker for 5 minutes. Weigh the measured particles on each sieve and saucer, and set the total to 100% by weight to obtain the weight fraction of the particles on each sieve. ), The vertical axis is the weight fraction}, then a line connecting each point is drawn to obtain the particle diameter corresponding to the weight fraction of 50% by weight, and this is used as the weight average particle diameter.

When pulverized, the smaller the content of fine particles contained in the crosslinked polymer (A) after pulverization, the better the absorption performance. Therefore, the total weight of the crosslinked polymer (A) is 106 μm or less (preferably 150 μm or less). The content (% by weight) of the fine particles of the above is preferably 3 or less, more preferably 1 or less. The content of the fine particles can be determined by using the graph created when determining the weight average particle diameter described above.

When pulverized, the shape of the crosslinked polymer (A) after pulverization is not particularly limited, and examples thereof include amorphous crushed form, phosphorus fragment form, pearl form, and rice granules. Of these, the amorphous crushed form is preferable from the viewpoint that it is easily entangled with the fibrous material for use in disposable diapers and the like and there is no concern that it will fall off from the fibrous material.

The crosslinked polymer (A) may contain some other components such as a residual solvent and a residual crosslinked component as long as the performance is not impaired.

The water-absorbent resin particles of the present invention contain talc (c) containing aluminum oxide, and are preferably contained on the surface of the resin particles. The content of aluminum oxide in talc (c) is 1 to 20% by weight. If it is out of this range, the initial wettability is poor. It is preferably 4 to 18% by weight, more preferably 5 to 15% by weight. The volume average particle size of talc (c) is preferably 2.0 to 20 μm, and more preferably 5 to 15 μm from the viewpoint of water absorption characteristics. The content of aluminum oxide in talc containing aluminum oxide varies depending on the place of origin of the ore, and talc produced from ore containing impurities such as chlorite is used. As the talc (c), for example, products such as Simgon, SSS, N-70 (all trade names, manufactured by Nippon Talc Co., Ltd.) can be used. By having the talc (c), the water-absorbent resin particles of the present invention can impart initial liquid diffusivity in the absorber and liquid permeability in the antigravity direction between the swollen gels. This is because the aluminum oxide contained in talc (c) gives the surface of the water-absorbent resin particles initial wettability, and gaps derived from the talc shape are generated between the swollen gels, causing capillarity and antigravity. It is presumed that this is to impart liquid permeability in the direction.

The content of talc (c) is 0.1 to 10% by weight, preferably 0.5 to 5.0% by weight, more preferably 0.5% by weight, based on the weight of the water-absorbent resin particles, from the viewpoint of absorption characteristics. , 1.0 to 3.0% by weight. When the content of talc (c) is less than 0.1% by weight, the liquid permeability between the swollen gels is low. On the other hand, if it exceeds 10% by weight, the water retention amount may decrease. Further, even when the talc (c) is present on the surface of the resin particles, the talc (c) present on the surface of the resin particles is preferably in the above-mentioned quantity range. Here, the surface of the resin particles refers to the surface or the vicinity of the surface, and means a surface layer portion having a thickness of several tens of μm or less or a surface layer portion having a thickness of 1/10 or less of the total thickness.

In the water-absorbent resin particles of the present invention, the crosslinked polymer (A) preferably further contains a hydrophobic substance (d).

Examples of the hydrophobic substance (d) include a hydrophobic substance (d1) containing a hydrocarbon group, a hydrophobic substance (d2) containing a hydrocarbon group having a fluorine atom, and a hydrophobic substance (d3) having a polysiloxane structure. Etc. are included.

Examples of the hydrophobic substance (d1) containing a hydrocarbon group include a polyolefin resin, a polyolefin resin derivative, a polystyrene resin, a polystyrene resin derivative, a wax, a long-chain fatty acid ester, a long-chain fatty acid and a salt thereof, a long-chain aliphatic alcohol, and a long chain. Chain aliphatic amides and mixtures of two or more of these are included.

As the polyolefin resin, the weight of an olefin having 2 to 4 carbon atoms (ethylene, propylene, isobutylene, isoprene, etc.) as an essential constituent monomer (the content of the olefin is at least 50% by weight based on the weight of the polyolefin resin). Polymers having an average molecular weight of 10 to 1,000,000 {for example, polyethylene, polypropylene, polyisoprene, poly (ethylene-isoprene), isoprene, etc.} can be mentioned.

As the polyolefin resin derivative, a polymer having a weight average molecular weight of 10 to 1,000,000 (for example, polyethylene heat) in which a carboxy group (-COOH), 1,3-oxo-2-oxapropylene (-COOCO-) or the like is introduced into the polyolefin resin is used. Amenity, Polypropylene heat-attenuated, Maleic acid-modified polyethylene, Chlorinated polyethylene, Maleic acid-modified polypropylene, Ethylene-acrylic acid copolymer, Ethylene-maleic anhydride copolymer, Isobutylene-maleic anhydride copolymer, Maleinized Examples thereof include polypropylene, ethylene-vinyl acetate copolymer and maleinized product of ethylene-vinyl acetate copolymer).

As the polystyrene resin, a polymer having a weight average molecular weight of 10 to 1,000,000 can be used.

As the polystyrene resin derivative, a polymer having a weight average molecular weight of 10 to 1,000,000 (for example, styrene-) in which styrene is an essential constituent monomer (the content of styrene is at least 50% by weight based on the weight of the polystyrene derivative). Examples thereof include maleic anhydride copolymers, styrene-butadiene copolymers and styrene-isobutylene copolymers).

Examples of the wax include waxes having a melting point of 50 to 200 ° C. (for example, paraffin wax, beeswax, carnauba wax (or carnauba wax), beef tallow, etc.).

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, and oleic acid). Ethyl, glycerin lauric acid monoester, glycerin stearate monoester, glycerin oleic acid monoester, pentaerythlit lauric acid monoester, pentaerythlit lauric acid monoester, pentaerythlit oleic acid monoester, sorbit lauric acid monoester, Solbit stearate monoester, sorbit oleic acid monoester, sucrose palmitic acid monoester, sucrose palmitate diester, sucrose palmitate triester, sucrose stearate monoester, sucrose stearate diester, sucrose stearate tri. Esters, beef fat, etc.).

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

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

The long-chain aliphatic amide is an amidate 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, ammonia or a primary amine having 1 to 7 carbon atoms. And amidates of long-chain fatty acids having 8 to 30 carbon atoms, amidates of long-chain aliphatic secondary amines having at least one aliphatic chain having 8 to 30 carbon atoms and carboxylic acids having 1 to 30 carbon atoms, and Examples thereof include amidates 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.

As an amidate 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, a product obtained by reacting a primary amine with a carboxylic acid in a ratio of 1: 1 and 1 : Divided into those that reacted in 2. Examples of the 1: 1 reaction include acetic acid N-octylamide, acetate N-hexacosylamide, heptacosane acid N-octylamide, and heptacosane acid N-hexacosylamide. Examples of the 1: 2 reaction include diacetic acid N-octylamide, diacetic acid N-hexacosylamide, diheptacosanoic acid N-octylamide and diheptacosanoic acid N-hexacosylamide. When the primary amine and the carboxylic acid are reacted in a ratio of 1: 2, the carboxylic acid used may be the same or different.

The amidate of ammonia or a primary amine having 1 to 7 carbon atoms and a long-chain fatty acid having 8 to 30 carbon atoms is 1: 2 with a 1: 1 reaction of ammonia or a primary amine with a carboxylic acid. It is divided into those that have reacted. The 1: 1 reaction products include nonanoic acid amide, nonanoic acid methylamide, nonanoic acid N-heptylamide, heptacosanoic acid amide, heptacosanoic acid N-methylamide, heptacosanoic acid N-heptylamide and heptacosanoic acid N-hexacosylamide. And so on. The 1: 2 reaction was dinonanoic acid amide, dinonanoic acid N-methylamide, dinonanoic acid N-heptylamide, dioctadecanoic acid amide, dioctadecanic acid N-ethylamide, dioctadecanic acid N-heptylamide, diheptacosanoic acid amide. , Diheptacosanoic acid N-methylamide, diheptacosanoic acid N-heptylamide, diheptacosanoic acid N-hexacosylamide and the like. As for the product obtained by reacting ammonia or a primary amine with a carboxylic acid in a ratio of 1: 2, the carboxylic acid used may be the same or different.

Examples of the amidate 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 and N-methylhexakoshi acetate. Luamide, N-octylhexacosylamide acetate, N-dihexacosylamide acetate, N-methyloctylamide heptacosanoic acid, N-methylhexacosylamide heptacosanoic acid, N-octylhexacosylamide heptacosanoate and heptacosane Acid N-dihexacosylamide and the like can be mentioned.

Examples of the amidate of the secondary amine having two aliphatic hydrocarbon groups having 1 to 7 carbon atoms and the long chain fatty acid having 8 to 30 carbon atoms include nonanoic acid N-dimethylamide and nonanoic acid N-methylheptylamide. Examples thereof include nonanoic acid N-diheptylamide, heptacosanoic acid N-dimethylamide, heptacosanoic acid N-methylheptylamide and heptacosanoic acid N-diheptylamide.

Examples of the hydrophobic substance (d2) containing a hydrocarbon group having a fluorine atom include perfluoroalkane, perfluoroalkene, perfluoroaryl, perfluoroalkyl ether, perfluoroalkylcarboxylic acid, perfluoroalkyl alcohol and 2 thereof. A mixture of seeds or more is included.

Examples of the hydrophobic substance (d3) having a polysiloxane structure include polydimethylsiloxane, polyether-modified polysiloxane {polyoxyethylene-modified polysiloxane and poly (oxyethylene / oxypropylene) -modified polysiloxane}, carboxy-modified polysiloxane, and the like. Includes epoxy-modified polysiloxanes, amino-modified polysiloxanes, alkoxy-modified polysiloxanes and the like, and mixtures thereof.

The HLB value of the hydrophobic substance (d) is preferably 1 to 10, more preferably 2 to 8, and particularly preferably 3 to 7. Within this range, the leak resistance of the absorbent article becomes even better. The HLB value means a hydrophilic-hydrophobic balance (HLB) value, and is obtained by the Oda method (Introduction to New Surfactants, p. 197, Takehiko Fujimoto, published by Sanyo Chemical Industries, Ltd., 1981). ..

Among the hydrophobic substances (d), the hydrophobic substance (d1) containing a hydrocarbon group is preferable, and more preferably a long-chain fatty acid ester, a long-chain fatty acid and a salt thereof, from the viewpoint of leakage resistance of the absorbent article. Long-chain aliphatic alcohols and long-chain aliphatic amides, more preferably sorbit stearic acid ester, sucrose stearic acid ester, stearic acid, Mg stearate, Ca stearate, Zn stearate and Al stearate, particularly preferably. Sucrose stearic acid ester and stearic acid Mg, most preferably sucrose stearic acid monoester.

The water-absorbent resin particles of the present invention preferably have a structure in which the surface of the crosslinked polymer (A) is crosslinked by the surface crosslinking agent (e). By cross-linking the surface of the crosslinked polymer (A), the gel strength of the water-absorbent resin particles can be improved, and the desirable water-retaining amount of the water-absorbent resin particles and the absorption amount under load can be satisfied. Examples of the surface cross-linking agent (e) include polyvalent glycidyl compounds, polyvalent amines, polyvalent aziridine compounds and polyhydric isocyanate compounds described in JP-A-59-189103, and JP-A-58-180233. And the polyhydric alcohol of JP-A-61-16903, the silane coupling agent described in JP-A-61-221305 and JP-A-61-252212, and described in JP-A-5-508425. Uses alkylene carbonates, polyvalent oxazoline compounds described in JP-A-11-240959, and surface cross-linking agents of JP-A-51-136588 and JP-A-61-257235 (multi-valent metals, etc.). can. Among these surface cross-linking agents, polyhydric glycidyl compounds, polyhydric alcohols and polyhydric amines are preferable, and polyhydric glycidyl compounds and polyhydric alcohols are more preferable, and polyhydric alcohols are particularly preferable, from the viewpoint of economy and absorption characteristics. Valuable glycidyl compounds, most preferably ethylene glycol diglycidyl ethers. One type of surface cross-linking agent may be used alone, or two or more types may be used in combination.

In the case of surface cross-linking, the amount (part by weight) of the surface cross-linking agent (e) used is not particularly limited because it can be variously changed depending on the type of the surface cross-linking agent, the conditions for cross-linking, the target performance, and the like. From the viewpoint of absorption characteristics and the like, it is preferably 0.001 to 3, more preferably 0.005 to 2, and particularly preferably 0.01 to 1.5 with respect to 100 parts by weight of the crosslinked polymer (A).

The surface cross-linking of the cross-linked polymer (A) can be carried out by mixing the cross-linked polymer (A) and the surface cross-linking agent (e) and heating as necessary. As a method of mixing the crosslinked polymer (A) and the surface crosslinking agent (e), a cylindrical mixer, a screw type mixer, a screw type extruder, a turbulizer, a Nauter type mixer, a double arm type kneader, and a flow Cross-linking polymer (A) and surface cross-linking using a mixer such as a type mixer, V-type mixer, minced mixer, ribbon type mixer, air flow type mixer, rotary disk type mixer, conical blender and roll mixer. Examples thereof include a method of uniformly mixing the agent (e). At this time, the surface cross-linking agent (e) may be diluted with water and / or any solvent before use.

The temperature at which the crosslinked polymer (A) and the surface crosslinking agent (e) are mixed is not particularly limited, but is preferably 10 to 150 ° C, more preferably 20 to 100 ° C, and particularly preferably 25 to 80 ° C. ..

After mixing the crosslinked polymer (A) and the surface crosslinking agent (e), heat treatment is performed. The heating temperature is preferably 100 to 180 ° C., more preferably 110 to 175 ° C., and particularly preferably 120 to 170 ° C. from the viewpoint of breakage resistance of the resin particles. Indirect heating using steam is possible if the heating is 180 ° C or lower, which is advantageous in terms of equipment, and if the heating temperature is lower than 100 ° C, the absorption performance may deteriorate. The heating time can be appropriately set depending on the heating temperature, but is preferably 5 to 60 minutes, more preferably 10 to 40 minutes from the viewpoint of absorption performance. It is also possible to further surface-crosslink the water-absorbent resin obtained by surface-crosslinking with a surface-crosslinking agent of the same type or different from the surface-crosslinking agent used first.

After the surface of the crosslinked polymer (A) is crosslinked with the surface crosslinking agent (e), the particle size is adjusted by sieving if necessary. The average grain diameter of the obtained particles is preferably 100 to 600 μm, more preferably 200 to 500 μm. The content of the fine particles is preferably small, the content of the particles of 100 μm or less is preferably 3% by weight or less, and the content of the particles of 150 μm or less is more preferably 3% by weight or less.

The water-absorbent resin particles of the present invention may further contain water-insoluble inorganic particles (f). By including the water-insoluble inorganic particles (f), the surface of the particles contained in the water-absorbent resin particles is surface-treated with the water-insoluble inorganic particles (f), so that the blocking resistance and liquid permeability of the water-absorbent resin particles are improved. improves.

Examples of the water-insoluble inorganic particles (f) include colloidal silica, fumed silica, clay, and the like, and colloidal silica and fumed silica are preferable and more preferable from the viewpoint of availability, ease of handling, and absorption performance. Is colloidal silica. One kind of water-insoluble inorganic particles (f) may be used alone, or two or more kinds may be used in combination.

The amount (parts by weight) of the water-insoluble inorganic particles (f) used is preferably 0.01 to 5, more preferably 0.05 to 1, and particularly preferably 0.05 to 1 part by weight with respect to 100 parts by weight of the water-absorbent resin from the viewpoint of absorption performance. Is 0.1 to 0.5.

When the water-insoluble inorganic particles (f) are contained, it is preferable to mix the water-absorbent resin particles and the water-insoluble inorganic particles (f), and the mixing may be carried out in the same manner as the mixing of talc (c) described later. Yes, the conditions are the same.

The water-absorbent resin particles after mixing the water-insoluble inorganic particles (f) may be used after adjusting the particle size, and the particle size adjustment can be performed in the same manner as the particle size adjustment performed after crosslinking with the surface cross-linking agent (e). The same applies to the particle size after adjusting the particle size.

The water-absorbent resin particles of the present invention are, if necessary, an additive {for example, known (for example, JP-A-2003-225565 and JP-A-2006-131767) preservatives, fungicides, antibacterial agents, and oxidations. It can also contain inhibitors, UV absorbers, colorants, fragrances, deodorants, liquid permeability improvers (eg, sodium aluminum sulfate dodecahydrate, etc.), organic fibrous materials, etc.}. When these additives are contained, the content (% by weight) of the additives is preferably 0.001 to 10, more preferably 0.01 to 5, and particularly preferably 0.01 to 5, based on the weight of the polymer (A). Is 0.05 to 1, most preferably 0.1 to 0.5.

The production method of the present invention includes a step of mixing the crosslinked polymer (A) and talc (c). The production method of the present invention is suitable for obtaining the water-absorbent resin particles of the present invention. As a mixing method of the crosslinked polymer (A) and the talc (c), a cylindrical mixer, a screw type mixer, a screw type extruder, a turbulizer, a Nauter type mixer, a double arm type kneader, and a fluid mixing type are mixed. Examples thereof include a method of uniformly mixing using a known mixing device such as a machine, a V-type mixer, a minced mixer, a ribbon-type mixer, an air-flow type mixer, a rotary disk-type mixer, a conical blender, and a roll mixer.

For mixing the crosslinked polymer (A) and talc (c), it is preferable to add talc (c) under stirring of the polymer (A). The added talc (c) may be added at the same time as water and / or a solvent. When talc (c) is added at the same time as water and / or a solvent, a dispersion in which talc (c) is dispersed in water and / or a solvent can be added, and it is preferable to add a solution dispersed in water. When the dispersion is added, it is preferable to add it by spraying or dropping.

When a dispersion liquid in which talc (c) is dispersed in water is used, the content of talc (c) contained in the dispersion liquid is preferably 0.5 to 30% by weight, more preferably 0.5% by weight, based on the total weight of the dispersion liquid. It is 1.0 to 15% by weight. If the concentration is lower than the above range, the amount of water added increases and the resin particles tend to block each other, and if the concentration is high, the resin particles become non-uniform, which is not preferable.

The type of solvent is not particularly limited, but polyhydric alcohols (ethylene glycol, propylene glycol, 1,4-butanediol, etc.) are preferably used, and the solvent may be used alone or in combination of two or more. Is also good.

The temperature at which the crosslinked polymer (A) and talc (c) are mixed is preferably 30 to 150 ° C, more preferably 50 to 100 ° C. Within this range, uniform mixing becomes easier and the absorption characteristics become even better.

After cross-linking the surface of the cross-linked polymer (A) with the surface cross-linking agent (e), it is preferable to mix the dispersion liquid of talc (c).

When heating after mixing the polymer (A) and talc (c), the heating time can be appropriately set depending on the heating temperature, but from the viewpoint of absorption performance, it is preferably 5 to 60 minutes, more preferably 10 to 10 to. 40 minutes. It is also possible to further surface-treat the water-absorbent resin obtained by mixing the polymer (A) and talc (c).

The water-absorbent resin particles of the present invention may be used after being mixed with the crosslinked polymer (A) and talc (c) and then sieved to adjust the particle size. The particle size adjustment can be performed in the same manner as the particle size adjustment performed after crosslinking with the surface cross-linking agent (e), and the particle size adjustment after the particle size adjustment is also the same.

The water content of the water-absorbent resin of the present invention is preferably controlled to 1 to 10% by weight, more preferably 2 to 9% by weight, and particularly preferably 3 to 8% by weight from the viewpoint of breakage resistance. The apparent density (g / ml) of the water-absorbent resin particles of the present invention is preferably 0.52 to 0.70, more preferably 0.54 to 0.68, and particularly preferably 0.56 to 0.66. .. Within this range, the function of immobilizing the water-absorbent resin (gel) swollen due to urination of the absorbent article becomes even better. The apparent density of the water-absorbent resin particles is measured at 25 ° C. in accordance with JIS K7365: 1999. The moisture content can be appropriately adjusted by air-drying using a dryer.

The water retention amount (g / g) of the water-absorbent resin particles of the present invention can be measured by a method described later, and from the viewpoint of water absorption performance, 33 or more is preferable, 35 or more is more preferable, and 37 or more is further preferable. .. Further, the upper limit value is preferably 49 or less, more preferably 47 or less, still more preferably 45 or less, from the viewpoint of the amount of absorption under load. The amount of water retention can be appropriately adjusted by the amount (% by weight) of the surface cross-linking agent (e) used.

The initial wetting time (seconds) based on the Drop test method for the water-absorbent resin particles of the present invention can be measured by the method described later, and is preferably less than 7 and less than 5 from the viewpoint of suppressing leakage of the absorbent article. More preferred. If it exceeds 7, the initial absorption rate is slow, and leakage is likely to occur due to insufficient absorption rate, which is not preferable. The initial wetting time (seconds) can be appropriately adjusted by the amount of talc (c) used (% by weight).

The diffusion length (cm) after 5 minutes based on the Wicking test method of the water-absorbent resin particles of the present invention can be measured by the method described later, and is preferably 9 or more, preferably 11 or more, from the viewpoint of liquid permeability. More preferred. If it is less than 9, leakage is likely to occur due to poor liquid diffusivity after repeated use, which is not preferable. After 5 minutes, the diffusion length (cm) can be appropriately adjusted by the amount (% by weight) of talc (c) used.

The water-absorbent resin particles of the present invention constitute an absorbent body used for sanitary materials such as disposable diapers, menstrual napkins, incontinence pads, medical pads, etc., and are suitably used for absorbent articles including absorbent bodies. Be done. The water-absorbent body using the water-absorbent resin particles of the present invention has an excellent absorption amount, an excellent liquid uptake speed, and an excellent dry touch property under pressure after absorption.

The absorber using the water-absorbent resin particles of the present invention may be composed of the absorbent resin particles alone or may be composed of the water-absorbent resin particles and the hydrophilic fibers. Specific examples of the hydrophilic fiber include mechanical pulp from wood, chemical pulp, semi-chemical pulp, wood pulp fiber such as dissolving pulp, artificial cellulose fiber such as rayon and acetate, and the like. The preferred hydrophilic fiber is wood pulp fiber. These hydrophilic fibers may partially contain synthetic fibers such as nylon and polyester.

As the structure of the absorber, the water-absorbent resin particles are sandwiched between the mixed dispersion obtained by mixing the water-absorbent resin particles and the hydrophilic fibers so as to have a uniform composition, and the layered hydrophilic fibers. Examples thereof include a sandwich structure, a structure in which water-absorbent resin particles and hydrophilic fibers are wrapped in a tissue, and the like. The absorber may contain other components, for example, an adhesive binder such as a heat-fusing synthetic fiber, a hot melt adhesive, or an adhesive emulsion for enhancing the shape retention of the absorber. ..

Further, the absorber using the water-absorbent resin particles is held between the liquid permeable sheet (top sheet) through which the liquid can pass and the liquid permeable sheet (back sheet) through which the liquid cannot pass. It can also be an absorbent article. The liquid permeable sheet is placed on the side that comes into contact with the body, and the liquid permeable sheet is placed on the opposite side that comes into contact with the body.

Examples of the liquid permeable sheet include non-woven fabrics such as air-through type, spunbond type, chemical bond type and needle punch type, and porous synthetic resin sheets made of fibers such as polyethylene, polypropylene and polyester. Examples of the liquid impermeable sheet include a synthetic resin film made of a resin such as polyethylene, polypropylene, and polyvinyl chloride.

Hereinafter, the present invention will be further described with reference to Examples and Comparative Examples, but the present invention is not limited thereto. Hereinafter, unless otherwise specified, parts indicate parts by weight and% indicates weight%. The amount of water retained in the physiological saline of the water-absorbent resin, the initial wetting time, and the diffusion length after 5 minutes were measured by the following methods.

<Measurement method of water retention>
Put 1.00 g of the measurement sample in a tea bag (length 20 cm, width 10 cm) made of a nylon net with an opening of 63 μm (JIS Z8801-1: 2006), and put it in 1,000 ml of physiological saline (salt concentration 0.9%). After soaking for 1 hour without stirring, the sample was pulled up and hung for 15 minutes to drain water. Then, each tea bag was placed in a centrifuge, dehydrated by centrifugation at 150 G for 90 seconds to remove excess physiological saline, the weight (h1) including the tea bag was measured, and the amount of water retained was determined from the following formula. The temperature of the physiological saline used and the measurement atmosphere was 25 ° C ± 2 ° C. (H2) is the weight of the tea bag measured by the same operation as above when there is no measurement sample.
Water retention (g / g) = (h1)-(h2)

<Measurement method of initial wetting time (Drop test method)>
Using a JIS standard sieve (JIS Z8801-1: 2006), about 10 g of absorbent resin particles were classified into 300 to 500 μm. A polyethylene film having a thickness of 100 μm or more was cut into 3 × 4 cm pieces, and double-sided tape {Nice Duck NM-40 (manufactured by Nichiban Co., Ltd.)} was attached to one side. Then, the classified absorbent resin particles were sprayed on the upper part of the adhesive surface of the film until the adhesive surface of the film was completely hidden. After spraying, the film was turned over to remove the non-adhesive absorbent resin particles. Subsequently, an appropriate amount of Blue No. 1 was added to physiological saline (salt concentration 0.9% by weight) to prepare a stained physiological saline. Using a 200 μl volume micropipette {PIPETMAN Model P-200 (manufactured by Gilson)} and a 200 μl volume microchip, 40 μl of the stained saline solution was sucked out and dropped onto a film to which the absorbent resin particles were adhered. The time was measured with the time point of dropping as 0 seconds, and the time (seconds) obtained with the time point when the liquid on the absorbent resin particles disappeared as the end point was recorded. The temperature of the stained physiological saline used and the measurement atmosphere was 25 ° C ± 2 ° C. This measurement was repeated 5 times and the average value (seconds) was taken as the initial wetting time.

<Measurement method of diffusion length after 5 minutes (Wicking test method)>
The diffusion length after 5 minutes was measured using the suction index measuring device described in JP-A-5-200068 (EP532002). The trough sheet was made of SUS304 with a stainless steel grade 2B finish.

1.0 g of water-absorbent resin particles were evenly sprayed on the trough groove of the trough sheet installed at an angle of 30 ° so as to have a distance of 30 cm. Subsequently, an appropriate amount of Blue No. 1 is added to physiological saline (salt concentration 0.9% by weight) to prepare a stained physiological saline, which is injected into a liquid storage tank. After adjusting the liquid level in the liquid storage tank to be 0.5 cm above the lowest position of the trough, the time was measured with 0 seconds as the time when the screen mesh of stainless steel came into contact with the liquid, and 5 minutes later, The distance (cm) to the swollen water-absorbent resin particles was recorded. The temperature of the stained physiological saline used and the measurement atmosphere was 25 ° C ± 2 ° C.

<Manufacturing example 1>
Acrylic acid (a1-1) {Mitsubishi Chemical Corporation, 100% purity} 270 parts, cross-linking agent (b-1) {Daiso-pentaerythritol triallyl ether} 0.98 parts and ion-exchanged water 712 parts Was kept at 3 ° C. while stirring and mixing. After inflowing nitrogen into this mixture to reduce the amount of dissolved oxygen to 1 ppm or less, 1.1 parts of a 1% hydrogen peroxide solution and 2.0 parts of a 2% ascorbic acid solution and 2% of 2,2'-azobis 13.5 parts of an aqueous solution of amidinopropane dihydrochloride was added and mixed to initiate polymerization. After the temperature of the mixture reached 80 ° C., it was aged at 80 ± 2 ° C. for about 5 hours to obtain a hydrogel.

Next, while shredding this hydrogel with a mincing machine (12VR-400K manufactured by ROYAL), 220 parts of a 49% sodium hydroxide aqueous solution was added and mixed, and then sucrose stearic acid as a hydrophobic substance (d) was added. 0.62 parts of an ester (Ryoto Sugar Ester S-770, HLB: 7 manufactured by Mitsubishi Chemical Foods Co., Ltd.) was added and mixed to obtain a neutralized gel. Further, the neutralized water-containing gel was aerated and dried using an aeration type dryer (manufactured by Inoue Metal Industry Co., Ltd.) under the conditions of a supply temperature of 150 ° C. and a wind speed of 1.5 m / sec until the water content became 4%. A dry body was obtained. The dried product is pulverized with a juicer mixer (OSTERIZER BLENDER manufactured by Oster), sieved, adjusted to a particle size range of 710 to 150 μm opening, and resin particles (A-1) containing a crosslinked polymer are obtained. Obtained.

Then, while stirring 100 parts of the obtained resin particles (A-1) at high speed (high-speed stirring turbulizer manufactured by Hosokawa Micron Co., Ltd., rotation speed 2000 rpm), ethylene glycol diglycidyl ether as a surface cross-linking agent (e) was added to this. A mixed solution containing 0.12 parts, 1.0 part of propylene glycol, 1.0 part of Klebosol 30cal25 (coloidal silica manufactured by AZ Material Co., Ltd.) as water-insoluble inorganic fine particles (f), and 1.7 parts of ion-exchanged water is passed through. A mixed solution of 0.6 parts of sodium aluminum sulfate dodecahydrate, 0.6 parts of propylene glycol and 1.5 parts of ion-exchanged water as a liquid property improving agent was added at the same time, uniformly mixed, and then at 135 ° C. The mixture was heated for 30 minutes to obtain surface-crosslinked resin particles (A-2).

<Manufacturing example 2>
Production Example 1 except that the surface cross-linking agent (e) used for 100 parts of the obtained resin particles (A-1) was changed to 0.16 part of ethylene glycol diglycidyl ether and 1.4 parts of propylene glycol. The surface-crosslinked resin particles (A-3) were obtained in the same manner as above.

<Manufacturing example 3>
Production Example 1 except that the surface cross-linking agent (e) used for 100 parts of the obtained resin particles (A-1) was changed to 0.08 part of ethylene glycol diglycidyl ether and 0.5 part of propylene glycol. The surface-crosslinked resin particles (A-4) were obtained in the same manner as above.

<Example 1>
Simgon as talc (c) while stirring 100 parts of the surface-crosslinked resin particles (A-2) obtained in Production Example 1 at high speed (high-speed stirring turbulizer manufactured by Hosokawa Micron Co., Ltd., rotation speed 2000 rpm). 3.0 parts of aluminum oxide, volume average particle diameter 10 μm) manufactured by Nippon Tarku Co., Ltd. and 3.0 parts of ion-exchanged water were uniformly mixed. Then, it was heated at 80 ° C. for 30 minutes to obtain the water-absorbent resin particles (P-1) of the present invention.

<Example 2>
While 100 parts of the surface-crosslinked resin particles (A-2) obtained in Production Example 1 were stirred at high speed (high-speed stirring turbulizer manufactured by Hosokawa Micron Co., Ltd., rotation speed 2000 rpm), SSS (Nippon Tarku) was used as talc (c). Made by Co., Ltd., containing 13% of aluminum oxide, volume average particle diameter (12 μm), 3.0 parts, and ion-exchanged water (3.0 parts) were uniformly mixed. Then, it was heated at 80 ° C. for 30 minutes to obtain the water-absorbent resin particles (P-2) of the present invention.

<Example 3>
In Example 2, the same operation as in Example 2 was performed except that the surface-crosslinked resin particles (A-2) were changed to the surface-crosslinked resin particles (A-3), and the water-absorbent resin of the present invention was carried out. Particles (P-3) were obtained.

<Example 4>
In Example 2, the same operation as in Example 2 was performed except that the surface-crosslinked resin particles (A-2) were changed to the surface-crosslinked resin particles (A-4), and the water-absorbent resin of the present invention was carried out. Particles (P-4) were obtained.

<Comparative Example 1>
The surface-crosslinked resin particles (A-2) obtained in Production Example 1 were used as they were as water-absorbent resin particles (R-1) for comparison.

<Comparative Example 2>
While 100 parts of the surface-crosslinked resin particles (A-2) obtained in Production Example 1 were stirred at high speed (high-speed stirring turbulizer manufactured by Hosokawa Micron Co., Ltd., rotation speed 2000 rpm), SSS (Nippon Tarku) was used as talc (c). 20.0 parts of (manufactured by Co., Ltd.) and 5.0 parts of ion-exchanged water were uniformly mixed. Then, it was heated at 80 ° C. for 30 minutes to obtain water-absorbent resin particles (R-2) for comparison.

<Comparative Example 3>
While 100 parts of the surface-crosslinked resin particles (A-4) obtained in Production Example 3 were stirred at high speed (high-speed stirring turbulizer manufactured by Hosokawa Micron Co., Ltd., rotation speed 2000 rpm), D-1000 (c) was used as talc (c). 3.0 parts of aluminum oxide, manufactured by Nippon Tarku Co., Ltd., containing 0.1% of aluminum oxide, volume average particle diameter of 1 μm), and 3.0 parts of ion-exchanged water were uniformly mixed. Then, it was heated at 80 ° C. for 30 minutes to obtain water-absorbent resin particles (R-3) for comparison.

<Comparative Example 4>
While 100 parts of the surface-crosslinked resin particles (A-4) obtained in Production Example 3 were stirred at high speed (high-speed stirring turbulizer manufactured by Hosokawa Micron Co., Ltd., rotation speed 2000 rpm), P-3 (c) was used as talc (c). 3.0 parts of aluminum oxide, manufactured by Nippon Tarku Co., Ltd., containing 0.1% of aluminum oxide, volume average particle diameter of 5 μm), and 3.0 parts of ion-exchanged water were uniformly mixed. Then, it was heated at 80 ° C. for 30 minutes to obtain water-absorbent resin particles (R-4) for comparison.

Performance evaluation results (maintenance) of the water-absorbent resin particles (P-1) to (P-4) of Examples 1 to 4 and the water-absorbent resin particles (R-1) to (R-4) of Comparative Examples 1 to 4. The amount of water, the initial wetting time, and the diffusion length after 5 minutes) were measured. The results are shown in Table 1.

From the comparison between the water-absorbent resin particles P-1 and R-1, the inclusion of talc (c) improves the initial wetting time and the diffusion length after 5 minutes. From R-2, it can be seen that if the content of talc (c) is not appropriate, the water absorption performance such as the water retention amount and the diffusion length is inferior. Further, it can be seen that the water-absorbent resin particles R-3 and R-4 using talc having a low aluminum oxide content are inferior in the initial wetting time. Since the absorbent resin particles of the present invention do not inhibit the swelling of the gel, the absorption performance is improved, and the initial liquid diffusivity and the liquid permeability between the swelled gels, particularly the liquid passage in the antigravity direction. It turns out that it is excellent in sex.

Claims (6)

A vinyl monomer (a2) that becomes a water-soluble vinyl monomer (a1) and / or a water-soluble vinyl monomer (a1) by hydrolysis, a cross-linked polymer (A) containing a cross-linking agent (b) as an essential constituent unit, and aluminum oxide. It is a water-absorbent resin particle containing 4 to 20% by weight of a talc (c), and contains 0.1 to 10% by weight of the talc (c) based on the weight of the polymer (A). Resin particles.
The water-absorbent resin particle according to claim 1, wherein the talc (c) has a volume average particle diameter of 2.0 to 20 μm. The water-absorbent resin particle according to claim 1 or 2, further containing a hydrophobic substance (d). The water-absorbent resin particle according to any one of claims 1 to 3, wherein the content of aluminum oxide in the talc (c) is 5 to 15% by weight. A vinyl monomer (a2) that becomes a water-soluble vinyl monomer (a1) and / or a water-soluble vinyl monomer (a1) by hydrolysis, a cross-linked polymer (A) containing a cross-linking agent (b) as an essential constituent unit, and aluminum oxide. A method for producing water-absorbent resin particles, which comprises a step of mixing with a talc (c) containing 4 to 20% by weight of.
The method for producing water-absorbent resin particles according to claim 5, wherein the talc (c) has a volume average particle diameter of 2.0 to 20 μm.