JP7339253B2 - Water absorbent resin particles, absorbent body and absorbent article containing the same - Google Patents

Description

TECHNICAL FIELD The present invention relates to water absorbent resin particles, absorbent bodies and absorbent articles containing the same.

2. Description of the Related Art In sanitary materials such as paper diapers, sanitary napkins, and incontinence pads, water-absorbing resins mainly composed of hydrophilic fibers such as pulp and acrylic acid (salt) are widely used as absorbents. Consumers in recent years tend to seek more comfort, and the demand is shifting to more dry and thinner products, and along with this, the amount of dryness and hydrophilic fibers used. Reduction has come to be desired. Therefore, the role of high initial absorption rate and liquid diffusion, which has hitherto been played by hydrophilic fibers, has come to be demanded of the water absorbent resin itself.

As means for improving the absorption rate of the water absorbent resin particles, a method of physically increasing the surface area of the water absorbent resin is generally used. For example, there is a method of increasing the drying speed of the water absorbent resin to lower the apparent density (Patent Document 1) and a method of improving the absorption speed by reducing the particle size of the water absorbent resin particles in the sieving process (Patent Document 2). Are known. However, in the absorbent body in which these water-absorbing resin particles are applied to absorbent articles (paper diapers, etc.), there is no problem when the content of hydrophilic fibers is greater than the content of water-absorbing resin particles, but the hydrophilic fibers If the content of is small or not included, the absorption rate of the water-absorbing resin will be uneven depending on the part of the absorbent, and the absorbent article cannot be effectively used, and in the part where the liquid to be absorbed remains Problems such as rashes are likely to occur.
As a method for solving the above problems, water-absorbing resin particles (Patent Document 3) are known in which the absorption speed (hereinafter referred to as absorption speed pattern) over time after contact with the liquid to be absorbed is controlled. When the water-absorbing resin particles are applied to absorbent articles, there is a problem that the absorption liquid is slowed down from the surface nonwoven fabric used in the absorbent article, and the dryness deteriorates.
Therefore, even in an absorbent body with a small amount of hydrophilic fibers, it exhibits a high initial absorption rate and liquid diffusibility, is excellent in dryness, and is free from problems such as rashes. There is a strong demand for flexible resin particles.

JP 2013-132434 A JP-A-2006-143972 Japanese Patent No. 5448699

An object of the present invention is to provide water-absorbing resin particles that exhibit high absorption rate and liquid diffusibility in the initial stage of contact with a liquid to be absorbed, are excellent in dryness, and have no problems such as rashes, an absorbent body containing the same, and an absorbent It is to provide goods.

The present invention provides a water-soluble vinyl monomer (a1) and/or a vinyl monomer (a2) which becomes a water-soluble vinyl monomer (a1) by hydrolysis (in other words, a water-soluble vinyl monomer (a1) and a water-soluble vinyl monomer by hydrolysis). At least one vinyl monomer selected from the group consisting of vinyl monomers (a2) serving as monomers (a1)) and a crosslinked polymer (A1) having a crosslinking agent (b) as an essential structural unit. The water-absorbent resin particles, which are resin particles, have a weight average particle diameter (μm) of 200 to 400, a span value (SPAN) represented by the following formula 1 of 1.0 or less, and (A1) The water absorbent resin particles have an absorption amount (M1) of 10 to 15 ml/g after 1 minute and an absorption amount (M2) of 45 to 55 ml/g after 5 minutes according to the DW (Demand Wetability) method.
SPAN = [D (90%) - D (10%)] / D (50%) ≤ 1.0 (Equation 1)
In the above formula 1, D (10%) is a particle with a cumulative weight fraction of 10% by weight from particles with the smallest particle diameter, with the total weight of the water-absorbing resin particles classified using a standard sieve being 100% by weight. D (50%) is the particle diameter at which the cumulative weight fraction is 50% by weight, and D (90%) is the particle diameter at which the cumulative weight fraction is 90% by weight.

The absorbent body of the present invention contains the water absorbent resin particles and the fibrous material.

The absorbent article of the present invention comprises the absorbent body described above.

The water absorbent resin particles of the present invention have a specific particle size distribution and absorption rate pattern. Therefore, when the water-absorbent resin particles of the present invention are applied to absorbent articles (disposable diapers, sanitary napkins, etc.), when they come into contact with the liquid to be absorbed, they exhibit a high initial absorption rate and liquid diffusibility, and dryness. is excellent, and there is no problem such as fogging. That is, the absorbent article using the water-absorbing resin particles having a DW absorption pattern of the present invention exhibits excellent liquid diffusibility because it has a moderately delayed absorption pattern in the initial stage, and the dryness of the entire absorbent body. Excellent for In addition, by setting the weight average particle size and span value within the range of the present invention, the liquid drawing property (absorbing and absorbing liquid; the same shall apply hereinafter) from the surface nonwoven fabric is improved, so that even better dryness is exhibited. do.

It is a figure showing typically the apparatus for measuring the absorption amount by DW method.

The water-soluble vinyl monomer (a1) is not particularly limited and is known {for example, Japanese Patent No. 3648553, Japanese Unexamined Patent Publication No. 2003-165883, Japanese Unexamined Patent Publication No. 2005-75982, Japanese Unexamined Patent Publication No. 2005-95759}. etc. can be used.

A vinyl monomer (hereinafter also referred to as a hydrolyzable vinyl monomer) (a2) that becomes a water-soluble vinyl monomer (a1) by hydrolysis is not particularly limited and is known {e.g., Japanese Patent No. 3648553, Japanese Patent Application Laid-Open No. 2003-165883. The vinyl monomers disclosed in JP-A-2005-75982 and JP-A-2005-95759 can be used. The water-soluble vinyl monomer means a vinyl monomer having a property of dissolving at least 100 g in 100 g of water at 25°C. Moreover, the term "hydrolyzable" means the property of being hydrolyzed by the action of water at 50° C. and, if necessary, a catalyst (acid, base, etc.) to become water-soluble. The hydrolysis of the hydrolyzable vinyl monomer may be performed during polymerization, after polymerization, or both, but preferably after polymerization from the viewpoint of the molecular weight of the resulting water-absorbing resin particles.

Among these, water-soluble vinyl monomers (a1) are preferred from the viewpoint of absorption properties, etc., more preferably anionic vinyl monomers, and then preferably carboxy (salt) groups, sulfo (salt) groups, amino groups, and carbamoyl groups. , a vinyl monomer having an ammonio group or a mono-, di- or tri-alkylammonio group, then preferably a vinyl monomer having a carboxy (salt) group or a carbamoyl group, particularly preferably (meth)acrylic acid (salt) and (Meth)acrylamide, then particularly preferably (meth)acrylic acid (salt), most preferably acrylic acid (salt).

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

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

In addition to the water-soluble vinyl monomer (a1) and the hydrolyzable vinyl monomer (a2), other vinyl monomers (a3) copolymerizable therewith can be used as structural units of the water-absorbing resin particles. .

Other copolymerizable vinyl monomers (a3) are not particularly limited and are known {for example, Japanese Patent No. 3648553, Japanese Unexamined Patent Publication No. 2003-165883, Japanese Unexamined Patent Publication No. 2005-75982, Japanese Unexamined Patent Publication No. 2005-95759. } can be used, and 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, and halogen-substituted styrene such as vinylnaphthalene and dichlorostyrene.
(ii) C2-C20 Aliphatic Ethylene Monomer Alkenes [ethylene, propylene, butene, isobutylene, pentene, heptene, diisobutylene, octene, dodecene, octadecene, etc.]; and alkadienes [butadiene, isoprene, etc.] and the like.
(iii) Alicyclic ethylene monomers having 5 to 15 carbon atoms, monoethylenically unsaturated monomers [pinene, limonene, indene, etc.];

When the other vinyl monomer (a3) is used as a structural unit, the content (mol%) of the other vinyl monomer (a3) unit is the water-soluble vinyl monomer (a1) unit and the hydrolyzable vinyl monomer (a2) unit. Based on the number of moles, it is preferably from 0.01 to 5, more preferably from 0.05 to 3, then preferably from 0.08 to 2, particularly preferably from 0.1 to 1.5. From the viewpoint of absorption properties, etc., it is most preferable that the content of other vinyl monomer (a3) units is 0 mol %.

The cross-linking agent (b) is not particularly limited and known {for example, Japanese Patent No. 3648553, Japanese Unexamined Patent Publication No. 2003-165883, Japanese Unexamined Patent Publication No. 2005-75982, Japanese Unexamined Patent Publication No. 2005-95759} and the like. Available. Among these, cross-linking agents having two or more ethylenically unsaturated groups are preferred from the viewpoint of absorption properties, more preferably poly(meth)allyl ethers of polyols having 2 to 10 carbon atoms, and particularly preferably triallyl sia. Nurate, triallyl isocyanurate, tetraallyloxyethane and pentaerythritol triallyl ether, most preferably pentaerythritol triallyl ether.

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

The crosslinked polymer (A1) may be one kind or a mixture of two or more kinds.

The crosslinked polymer (A1) can be prepared by known aqueous solution polymerization {adiabatic polymerization, thin film polymerization, spray polymerization, etc.; Japanese Patent Laid-Open Nos. 56-26909, 1-5808, etc.}. Of 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 without the need to use an organic solvent or the like.

Water-containing gel obtained by polymerization {consisting of a crosslinked polymer and water. } can be shredded as needed. The size (maximum diameter) of the gel after shredding is preferably 50 μm to 10 cm, more preferably 100 μm to 2 cm, particularly preferably 1 mm to 1 cm. Within this range, the drying property in the drying process is further improved.

Shredding can be performed by a known method, and can be shredded using a known shredding device {e.g., Vex mill, rubber chopper, farmer mill, mincing machine, impact pulverizer, and roll pulverizer}. .

When a solvent (organic solvent, water, etc.) is used for polymerization, it is preferable to distill off the solvent after 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, based on the weight of the water-absorbent resin particles. ~3, most preferably 0-1. Within this range, the absorption performance (especially water retention capacity) of the water-absorbing resin particles is further improved.

When the solvent contains water, the water content (% by weight) after distillation is preferably 0 to 20, more preferably 1 to 10, particularly preferably 2 to 9, most preferably 2 to 9, based on the weight of the crosslinked polymer. 3-8. Within this range, the absorption performance and the breakability of the water-absorbing resin particles after drying are further improved.

The content and water content of the organic solvent were measured using an infrared moisture meter {JE400 manufactured by KETT Co., Ltd., etc.: 120 ± 5 ° C., 30 minutes, atmospheric humidity before heating 50 ± 10% RH, lamp specifications 100 V, 40 W } from the weight loss of the measurement sample before and after heating when heated by

As a method for distilling off the solvent (including water), a method of distilling (drying) with hot air at a temperature of 80 to 230 ° C., a thin film drying method using a drum dryer or the like heated to 100 to 230 ° C., (heating ) Vacuum drying, freeze-drying, infrared drying, decantation, filtration, etc. can be applied.

The crosslinked polymer (A1) can be pulverized after drying. The method of pulverization is not particularly limited, and known pulverizers {eg, hammer pulverizers, impact pulverizers, roll pulverizers and jet jet pulverizers} can be used. The pulverized crosslinked polymer can be adjusted in particle size by sieving or the like, if necessary.

The weight average particle size (μm) of the crosslinked polymer (A1) when sieved if necessary is preferably 200-400, particularly preferably 210-390, and most preferably 230-380. Within this range, the absorption performance is further improved.

In addition, the weight average particle size was measured using a low-tap test sieve shaker and standard sieve (JIS Z8801-1: 2006), Perry's Chemical Engineers Handbook 6th Edition (McGraw Hill Book Company, 1984). , page 21). That is, JIS standard sieves 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 a saucer are combined in this order from the top. About 50 g of the particles to be measured are placed in the top sieve and shaken for 5 minutes with a Rotap test sieve shaker. The weight of the particles to be measured on each sieve and the tray is weighed, the total is 100% by weight, and the weight fraction of the particles on each sieve is obtained. ), the vertical axis is the weight fraction}, draw a line connecting each point, determine the particle diameter corresponding to a weight fraction of 50% by weight [D (50%)], which is the weight average particle diameter and

As described below, the particle diameter corresponding to the weight fraction of 10% by weight is D (10%), and the particle diameter corresponding to the weight fraction of 90% by weight is D (90%). .

In addition, since the smaller the content of fine particles, the better the absorption performance, the content of fine particles of 106 μm or less (preferably 150 μm or less) in all particles is preferably 3% by weight or less, more preferably 1% by weight or less. is. The content of fine particles can be determined using the plot created when determining the weight-average particle size.

The span value of the crosslinked polymer (A1) is preferably 1.0 or less, particularly preferably 0.9 or less, most preferably 0.8 or less. Within this range, the initial absorption rate is further improved, and the dryness is improved.

SPAN (span value) is a parameter representing the particle size distribution. The span value can be determined by measuring the particle size distribution of the water absorbent resin particles. In Equation 1, D (10%), D (50%) and D (90%) are all particle diameters expressed in "μm" and can be measured by a sieving particle size measurement method using a standard sieve. D (10%) has the smallest particle diameter when the water absorbent resin particles are classified in order of particle diameter after classifying the water absorbent resin particles with a standard sieve, with the total weight of the classified particles being 100% by weight. It means the particle diameter at which the cumulative weight fraction from the particles is 10% by weight. Similarly, D (50%) means a particle diameter with a cumulative weight fraction of 50% by weight, and D (90%) means a particle diameter with a cumulative weight fraction of 90% by weight.

The particle size distribution may be adjusted after classifying the crosslinked polymer (A1), or may be adjusted after classifying with water-absorbing resin particles.
The method for adjusting the particle size distribution is not particularly limited, and can be adjusted by, for example, mixing the particles on each sieve at a predetermined ratio.

The apparent density (g/ml) of the crosslinked polymer (A1) is preferably 0.55 to 0.65, more preferably 0.56 to 0.64, particularly preferably 0.57 to 0.63. Within this range, the absorption performance is further improved.
In addition, an apparent density is measured at 25 degreeC based on JISK7365:1999.

The shape of the crosslinked polymer (A1) is not particularly limited, and examples thereof include irregular crushed shape, scaly shape, pearl shape, rice grain shape and the like. Of these, irregularly crushed forms are preferred from the viewpoints of good entanglement with fibrous materials for use in paper diapers and the like, and no fear of falling off from fibrous materials.

The crosslinked polymer (A) preferably contains a hydrophobic substance (C) from the viewpoint of liquid diffusibility. The hydrophobic substance (C) includes a hydrophobic substance (C1) containing a hydrocarbon group, a hydrophobic substance (C2) having a polysiloxane structure, and the like.

Hydrophobic substances (C1) containing hydrocarbon groups include polyolefin resins, polyolefin resin derivatives, polystyrene resins, polystyrene resin derivatives, waxes, long-chain fatty acid esters, long-chain fatty acids and their salts, long-chain aliphatic alcohols, long-chain Chain fatty acid 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 1,000 to 1,000,000 {eg, polyethylene, polypropylene, polyisobutylene, poly(ethylene-isobutylene), isoprene, etc.} can be mentioned.

Polyolefin resin derivatives include polymers with a weight average molecular weight of 1,000 to 1,000,000 obtained by introducing a carboxy group (-COOH) or 1,3-oxo-2-oxapropylene (-COOCO-) into a polyolefin resin {for example, polyethylene heat Degraded product, polypropylene heat degraded product, maleic acid-modified polyethylene, chlorinated polyethylene, maleic acid-modified polypropylene, ethylene-acrylic acid copolymer, ethylene-maleic anhydride copolymer, isobutylene-maleic anhydride copolymer, maleated polybutadiene, ethylene-vinyl acetate copolymer, maleated ethylene-vinyl acetate copolymer, etc.}.

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

As the polystyrene resin derivative, a polymer having a weight average molecular weight of 1,000 to 1,000,000 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) {for example, styrene- maleic anhydride copolymer, styrene-butadiene copolymer, styrene-isobutylene copolymer, etc.}.

Waxes include waxes having a melting point of 50 to 200° C. {eg, paraffin wax, beeswax, carnauba wax, beef tallow, etc.}.

Examples of long-chain fatty acid esters include esters of fatty acids containing alkyl groups having 8 to 25 carbon atoms and alcohols having 1 to 12 carbon atoms {for example, methyl laurate, ethyl laurate, methyl stearate, ethyl stearate, oleic acid, Methyl, ethyl oleate, glycerin laurate monoester, glycerin stearate monoester, glycerin oleate monoester, pentaerythrityl laurate monoester, pentaerythrityl monostearate, pentaerythrityl oleate monoester, sorbitol laurin acid monoester, sorbitol monostearate, sorbitol monooleate, sucrose palmitate (sucrose palmitate monoester, sucrose palmitate diester, sucrose palmitate triester, etc.), sucrose stearate ( sucrose stearate monoester, sucrose stearate diester, sucrose stearate triester, etc.), sucrose erucate, beef tallow, etc.}. Among these, sucrose stearate (sucrose stearate monoester, sucrose stearate diester, sucrose stearate triester, etc.), sucrose palmitate ( sucrose palmitate monoester, sucrose palmitate diester, sucrose palmitate triester, etc.), sucrose erucate, and more preferably sucrose stearate (sucrose stearate monoester, sucrose stearate diester, sucrose stearate triester, etc.) and sucrose erucate.

Long-chain fatty acids and salts thereof include fatty acids containing alkyl groups of 8 to 25 carbon atoms {eg, lauric acid, palmitic acid, stearic acid, oleic acid, dimer acid, behenic acid, etc.}. Salts include salts with calcium, magnesium or aluminum (hereinafter abbreviated as Ca, Mg, Al) {eg, Ca palmitate, Al palmitate, Ca stearate, Mg stearate, Al stearate, etc.}. Ca stearate, Mg stearate, and Al stearate are preferable, and Mg stearate is more preferable, from the viewpoint of the liquid diffusibility of the absorbent article.

Long-chain fatty alcohols include fatty alcohols containing alkyl groups of 8 to 25 carbon atoms {eg, lauryl alcohol, palmityl alcohol, stearyl alcohol, oleyl alcohol, etc.}. Palmityl alcohol, stearyl alcohol, and oleyl alcohol are preferable, and stearyl alcohol is more preferable, from the viewpoint of the liquid diffusibility of the absorbent article.

Examples of long-chain fatty acid amides include fatty acid amides containing an alkyl group having 8 to 25 carbon atoms (eg, lauric acid amide, palmitic acid amide, stearic acid amide, oleic acid amide, erucic acid amide, etc.), and C8 to 25 Fatty acid bisamide {ethylene bislauric acid amide, ethylene bis stearic acid amide, hexamethylene bis stearic acid amide, N,N'-distearyladipic acid amide, ethylene bis oleic acid amide, ethylene bis erucic acid amide, etc.} be done. Ethylene bis-stearic acid amide is preferred from the viewpoint of the liquid diffusibility of the absorbent article.

Mixtures of two or more of these include mixtures of long-chain fatty acid esters and long-chain fatty alcohols {for example, mixtures of sucrose stearate and stearyl alcohol, etc.}, long-chain fatty acid esters and long-chain fatty acids, and their Mixtures of salts {for example, a mixture of sucrose stearate and Mg stearate} can be mentioned.

Hydrophobic substances (C2) having a polysiloxane structure include polydimethylsiloxane, polyether-modified polysiloxane {polyoxyethylene-modified polysiloxane and poly(oxyethylene/oxypropylene)-modified polysiloxane, etc.}, carboxy-modified polysiloxane, Included are organopolysiloxanes such as epoxy-modified polysiloxanes, amino-modified polysiloxanes, alkoxy-modified polysiloxanes, and the like, and mixtures thereof.

The position of the organic group (modifying group) of modified silicone {polyether-modified polysiloxane, carboxy-modified polysiloxane, epoxy-modified polysiloxane, amino-modified polysiloxane, etc.} is not particularly limited, but the side chain of polysiloxane, polysiloxane , one end of polysiloxane, and both side chains and both ends of polysiloxane. Among these, from the viewpoint of absorption properties, etc., both the side chain of polysiloxane and the side chain and both terminals of polysiloxane are preferable, and both the side chain and both terminals of polysiloxane are more preferable.

The organic group (modified group) of the polyether-modified polysiloxane includes a group containing a polyoxyethylene group or a poly(oxyethylene-oxypropylene) group. The content (number) of oxyethylene groups and/or oxypropylene groups contained in the polyether-modified polysiloxane is preferably 2 to 40, more preferably 5 to 30, particularly preferably 5 to 30 per molecule of polyether-modified polysiloxane. 7-20, most preferably 10-15. Within this range, the absorption characteristics are further improved. Further, when oxyethylene groups and oxypropylene groups are included, the content (% by weight) of oxyethylene groups is preferably 1 to 30, more preferably 3 to 25, and particularly preferably 5, based on the weight of the polysiloxane. ~20. Within this range, the absorption characteristics are further improved.

Polyether-modified polysiloxanes are readily available on the market, and the following products {modification position, type of oxyalkylene} are preferably exemplified.
· Shin-Etsu Chemical Co., Ltd. KF-945 {side chain, oxyethylene and oxypropylene}, KF-6020 {side chain, oxyethylene and oxypropylene}, X-22-6191 {side chain, oxyethylene and oxypropylene} , X-22-4952 {side chain, oxyethylene and oxypropylene}, X-22-4272 {side chain, oxyethylene and oxypropylene}, X-22-6266 {side chain, oxyethylene and oxypropylene}

・ Dow Corning Toray Co., Ltd. FZ-2110 {both ends, oxyethylene and oxypropylene}, FZ-2122 {both ends, oxyethylene and oxypropylene}, FZ-7006 {both ends, oxyethylene and oxypropylene}, FZ-2166 {both ends, oxyethylene and oxypropylene}, FZ-2164 {both ends, oxyethylene and oxypropylene}, FZ-2154 {both ends, oxyethylene and oxypropylene}, FZ-2203 {both ends, oxy ethylene and oxypropylene} and FZ-2207 {both ends, oxyethylene and oxypropylene}

The organic groups (modifying groups) of carboxy-modified polysiloxane include groups containing carboxy groups, etc. The organic groups (modifying groups) of epoxy-modified polysiloxane include groups containing epoxy groups, etc., and amino-modified polysiloxanes. Organic groups (modifying groups) of polysiloxane include groups containing amino groups (primary, secondary and tertiary amino groups). The organic group (modifying group) content (g/mol) of these modified silicones is preferably 200 to 11,000, more preferably 600 to 8,000, and particularly preferably 1,000 to 4,000 in terms of carboxy equivalent, epoxy equivalent, or amino equivalent. is. Within this range, the absorption characteristics are further improved. The carboxy equivalent is measured according to JIS C2101:1999 "16. Total acid value test". Moreover, an epoxy equivalent is calculated|required based on JISK7236:2001. In addition, the amino equivalent is measured according to JIS K2501:2003 "8. Potentiometric titration method (base number/hydrochloric acid method)".

Carboxy-modified polysiloxanes are readily available on the market, and the following products {modification position, carboxy equivalent (g/mol)} can be preferably exemplified.
· Shin-Etsu Chemical Co., Ltd. X-22-3701E {side chain, 4000}, X-22-162C {both ends, 2300}, X-22-3710 {one end, 1450}

· Dow Corning Toray Co., Ltd. BY 16-880 {side chain, 3500}, BY 16-750 {both ends, 750}, BY 16-840 {side chain, 3500}, SF8418 {side chain, 3500}

Epoxy-modified polysiloxanes are readily available on the market, and the following products {modification position, epoxy equivalent} can be preferably exemplified.
・ Shin-Etsu Chemical Co., Ltd. X-22-343 {side chain, 525}, KF-101 {side chain, 350}, KF-1001 {side chain, 3500}, X-22-2000 {side chain, 620} , X-22-2046 {side chain, 600}, KF-102 {side chain, 3600}, X-22-4741 {side chain, 2500}, KF-1002 {side chain, 4300}, X-22-3000T {side chain, 250}, X-22-163 {both ends, 200}, KF-105 {both ends, 490}, X-22-163A {both ends, 1000}, X-22-163B {both ends, 1750}, X-22-163C {both ends, 2700}, X-22-169AS {both ends, 500}, X-22-169B {both ends, 1700}, X-22-173DX {one end, 4500} , X-22-9002 {side chain/both ends, 5000}

・ Dow Corning Toray Co., Ltd. FZ-3720 {side chain, 1200}, BY 16-839 {side chain, 3700}, SF 8411 {side chain, 3200}, SF 8413 {side chain, 3800}, SF 8421 { side chain, 11000}, BY 16-876 {side chain, 2800}, FZ-3736 {side chain, 5000}, BY 16-855D {side chain, 180}, BY 16-8 {side chain, 3700}

Amino-modified silicones are readily available on the market, and the following products {modified position, amino equivalent} can be preferably exemplified.
・ Shin-Etsu Chemical Co., Ltd. KF-865 {side chain, 5000}, KF-864 {side chain, 3800}, KF-859 {side chain, 6000}, KF-393 {side chain, 350}, KF-860 {side chain, 7600}, KF-880 {side chain, 1800}, KF-8004 {side chain, 1500}, KF-8002 {side chain, 1700}, KF-8005 {side chain, 11000}, KF-867 {side chain, 1700}, X-22-3820W {side chain, 55000}, KF-869 {side chain, 8800}, KF-861 {side chain, 2000}, X-22-3939A {side chain, 1500} , KF-877 {side chain, 5200}, PAM-E {both ends, 130}, KF-8010 {both ends, 430}, X-22-161A {both ends, 800}, X-22-161B {both ends ends, 1500}, KF-8012 {both ends, 2200}, KF-8008 {both ends, 5700}, X-22-1660B-3 {both ends, 2200}, KF-857 {side chain, 2200}, KF -8001 {side chain, 1900}, KF-862 {side chain, 1900}, X-22-9192 {side chain, 6500}

・ Dow Corning Toray Co., Ltd. FZ-3707 {side chain, 1500}, FZ-3504 {side chain, 1000}, BY 16-205 {side chain, 4000}, FZ-3760 {side chain, 1500}, FZ -3705 {side chain, 4000}, BY 16-209 {side chain, 1800}, FZ-3710 {side chain, 1800}, SF 8417 {side chain, 1800}, BY 16-849 {side chain, 600}, BY 16-850 {side chain, 3300}, BY 16-879B {side chain, 8000}, BY 16-892 {side chain, 2000}, FZ-3501 {side chain, 3000}, FZ-3785 {side chain, 6000}, BY 16-872 {side chain, 1800}, BY 16-213 {side chain, 2700}, BY 16-203 {side chain, 1900}, BY 16-898 {side chain, 2900}, BY 16- 890 {side chain, 1900}, BY 16-893 {side chain, 4000}, FZ-3789 {side chain, 1900}, BY 16-871 {both ends, 130}, BY 16-853C {both ends, 360} , BY 16-853U {both ends, 450}

These mixtures include mixtures of polydimethylsiloxane and carboxyl-modified polysiloxane, and mixtures of polyether-modified polysiloxane and amino-modified polysiloxane.

The viscosity (mPa·s, 25° C.) of the hydrophobic substance having a polysiloxane structure is preferably 10-5000, more preferably 15-3000, particularly preferably 20-1500. Within this range, the absorption characteristics are further improved. In addition, the viscosity is JIS Z8803-1991 "viscosity of liquid" 9. Measured according to the viscosity measurement method using a cone and cone-plate rotary viscometer {for example, an E-type viscometer temperature-controlled to 25.0 ± 0.5 ° C. (RE80L manufactured by Toki Sangyo Co., Ltd., radius 7 mm , a conical cone with an angle of 5.24×10 ⁻² rad). }

By including the hydrophobic substance (C) in the water-absorbent resin particles, the absorption rate pattern of the water-absorbent resin particles (absorption amount after 1 minute and 5 minutes by DW method) can be easily controlled. , the water absorbent resin of the present invention preferably contains a hydrophobic substance (C). The absorption rate pattern of the water-absorbent resin particles can be arbitrarily adjusted by the strength of hydrophobicity and the amount added of the hydrophobic substance (C). The strength of hydrophobicity can be determined by a known technique such as the hydrophilic/hydrophobic balance (HLB value).
The HLB value means a hydrophilic-hydrophobic balance (HLB) value, and is determined by the Oda method (Introduction to Surfactants, p. 212, Takehiko Fujimoto, published by Sanyo Chemical Industry Co., Ltd., published in 2007).

Among these hydrophobic substances (C), long-chain fatty acid esters, long-chain fatty acids and salts thereof, and long-chain fatty acid amides are preferred, and sucrose stearate is more preferred, from the viewpoint of liquid diffusibility of absorbent articles. , Mg stearate, and ethylene bis stearamide. Since long-chain fatty acids generally have a carbon number distribution, stearic acid means a modified long-chain fatty acid containing stearic acid as a main component.

The content (% by weight) of the hydrophobic substance (C) is preferably 0.001 to 5.0, more preferably 0.08 to 1.0, particularly preferably 0.08 to 1.0, based on the weight of the crosslinked polymer (A1). is between 0.08 and 0.50. Within this range, both the liquid diffusing property of the absorbent article and the liquid drawing property from the nonwoven fabric are easily compatible, and the rash resistance is excellent, which is preferable.

Furthermore, the water absorbent resin particles of the present invention preferably contain a hydrophobic substance (C) and a penetrating agent (D). When the water-absorbing resin particles contain the hydrophobic substance (C) and the penetrating agent (D), it is preferable to use the hydrophobic substance (C) and the penetrating agent (D) at the same time. By using the penetrant (D) together with the hydrophobic substance (C), it becomes easier to achieve both the absorption amount by the DW method and the absorption rate by the lockup method. Penetrants (D) include nonionic surfactants (D1) and anionic surfactants (D2). It preferably has a long chain alkyl structure.

Specific examples of the nonionic surfactant (D1) include, for example, aliphatic alcohol (alkyl group having 8 to 18 carbon atoms) alkylene oxide (AO) (having 2 to 8 carbon atoms) adduct (degree of polymerization = 1 to 100) [Lauryl alcohol ethylene oxide adduct, cetyl alcohol ethylene oxide adduct, etc.], polyoxyalkylene (carbon number 2-8, degree of polymerization = 1-100) higher fatty acid (alkyl group carbon number 8-24) ester [ polyethylene glycol monolaurate, polyethylene glycol monopalmitate, polyethylene glycol dilaurate, etc.], and the like.

Among the nonionic surfactants (D1), preferred from the viewpoint of absorption rate control are aliphatic alcohols (alkyl group having 8 to 18 carbon atoms) alkylene oxide (AO) (having 2 to 8 carbon atoms) adducts ( Degree of polymerization = 1 to 100).

Examples of the anionic surfactant (D2) include hydrocarbon-based ether carboxylic acids having alkyl groups of 8 to 18 carbon atoms or salts thereof, [polyoxyethylene (degree of polymerization = 1 to 100) sodium lauryl ether acetate, polyoxyethylene ( degree of polymerization = 1 to 100) disodium lauryl sulfosuccinate, etc.], hydrocarbon sulfate salts having 8 to 18 carbon atoms [sodium lauryl sulfate, polyoxyethylene (degree of polymerization = 1 to 100) sodium lauryl sulfate, polyoxyethylene (degree of polymerization = 1 to 100) triethanolamine lauryl sulfate], hydrocarbon sulfonates having alkyl groups of 8 to 18 carbon atoms [sodium dodecylbenzenesulfonate, etc.], and hydrocarbon phosphate esters of 8 to 18 carbon atoms Salts [sodium lauryl phosphate, polyoxyethylene (degree of polymerization = 1 to 100) sodium lauryl ether phosphate, etc.], fatty acid salts [sodium laurate, triethanolamine laurate, etc.] and the like.

The content (% by weight) of the penetrating agent (D) is preferably 0.001 to 5.0, more preferably 0.08 to 1.0, particularly preferably 0.08 to 1.0, based on the weight of the crosslinked polymer (A1). 0.08 to 0.50. Within this range, the absorption rate can be appropriately adjusted.

As a method for mixing the crosslinked polymer (A1) and the hydrophobic substance (C), the hydrophobic substance (C) is present inside the water absorbent resin particles {that is, for example, the crosslinked polymer (A1) and There is no limitation as long as it is mixed with the hydrophobic substance (C) so as to form a sandwich structure. However, the hydrophobic substance (C) is preferably mixed with the hydrous gel of (A1) or the polymerization liquid of (A1) rather than the dried product of the crosslinked polymer (A1), more preferably (A1). It is to be mixed with hydrous gel. In addition, it is preferable that the mixture is uniformly mixed so as to be kneaded. When the crosslinked polymer (A1) is obtained by the aqueous solution polymerization method, the timing of mixing and kneading the hydrophobic substance (C) and (A1) is not particularly limited. Examples include during crushing (mincing) and during drying of hydrous gel. Among these, from the viewpoint of the anti-leakage property of the absorbent article, it is preferably immediately after the polymerization step and during the water-containing gel crushing (mincing) step, and more preferably during the water-containing gel crushing (mincing) step.

When the crosslinked polymer (A1) is obtained by reversed-phase suspension polymerization or emulsion polymerization, the timing of mixing the hydrophobic substance (C) and (A1) is not particularly limited, but during the polymerization step {(C) (A1) in the presence of}, immediately after the polymerization step, during the dehydration step (during the step of dehydrating to about 10% by weight of water), immediately after the dehydration step, during the step of separating and distilling off the organic solvent used in the polymerization , during drying of hydrous gel, and the like. Among these, from the viewpoint of the anti-leak property of the absorbent article, preferably during the polymerization step, immediately after the polymerization step, during the dehydration step, immediately after the dehydration step, and during the step of separating and distilling off the organic solvent used in the polymerization, and more preferably. is during the polymerization step and immediately after the polymerization step.

When the hydrous gel is mixed during drying, known apparatuses such as Vex mill, rubber chopper, farmer mill, mincing machine, impact pulverizer and roll pulverizer can be used as the mixing apparatus. When mixing in the polymerization liquid, a device with relatively high stirring power such as a homomixer and a biomixer can be used. Further, when the hydrous gel is mixed during drying, a kneading device such as an SV mixer can be used.

The mixing temperature (° C.) is preferably 20-100, more preferably 40-90, particularly preferably 50-80. Within this range, uniform mixing is facilitated, and absorption characteristics are further improved.

Further, in the method for producing the crosslinked polymer (A1) in the presence of the hydrophobic substance (C), the hydrophobic substance (C) is dissolved or emulsified (dispersed) in the polymerization liquid of the crosslinked polymer (A1). It is also possible to deposit (C) with the progress of polymerization of (A1) while forming the connection portion. The polymerization method is the same as for the crosslinked polymer (A1), except that the polymerization is carried out in the presence of the hydrophobic substance (C). The linking portion means a sandwich structure consisting of (A1)-(C)-(A1) formed by contact between the hydrophobic substance (C) and the crosslinked polymer (A1). In this case, the crosslinked polymer (A1) present inside the absorbent resin particles is linked to another crosslinked polymer (A1) via the hydrophobic substance (C) present on the surface thereof. structure.

When the hydrophobic substance (C) is used in combination with the penetrant (D), the penetrant (D) can be used at the same time as the hydrophobic substance (C) is mixed. The penetrant (D) may be mixed with the hydrophobic substance (C) in advance before use, or may be added separately at the same time.

A hydrogel containing a hydrophobic substance (C) and optionally a penetrant (D) can be cut into small pieces, if necessary. The size (longest diameter) of the water-containing gel particles after shredding is preferably 50 μm to 10 cm, more preferably 100 μm to 2 cm, particularly preferably 1 mm to 1 cm. Within this range, the drying property in the drying process is further improved. As the method for shredding, the same method as in the case of the crosslinked polymer (A1) can be employed.

When a solvent (including an organic solvent and/or water) is used in the production of water absorbent resin particles, the solvent can be distilled off after 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, based on the weight of the water-absorbent resin particles. ~3, most preferably 0-1. is. Within this range, the absorption performance (especially water retention capacity) of the water-absorbing resin particles is further improved.

Further, when the solvent contains water, 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 water-absorbing resin particles. Most preferably 3-8. Within this range, the absorption performance (particularly, the water retention capacity) and the breakability of the water-absorbing resin particles after drying are further improved. The method for measuring the content and water content of the organic solvent and the method for distilling off the solvent are the same as in the case of the crosslinked polymer (A1).

The crosslinked polymer (A1) can be surface-crosslinked with a surface-crosslinking agent, if necessary. As the surface cross-linking agent, known {JP-A-59-189103, JP-A-58-180233, JP-A-61-16903, JP-A-61-211305, JP-A-61-252212 JP, JP-A-51-136588, JP-A-61-257235, etc.} surface cross-linking agents {polyhydric glycidyl, polyhydric alcohol, polyamine, polyaziridine, polyhydric isocyanate, silane coupling agents and polyvalent metals} and the like can be used. Among these surface cross-linking agents, polyhydric glycidyls, polyhydric alcohols and polyhydric amines are preferred from the viewpoint of economy and absorption properties, more preferably polyhydric glycidyls and polyhydric alcohols, particularly preferably polyhydric glycidyls, and most preferably polyhydric glycidyls. Ethylene glycol diglycidyl ether is preferred.

In the case of surface cross-linking treatment, the amount (% by weight) of the surface cross-linking agent used is not particularly limited because it can be varied depending on the type of surface cross-linking agent, cross-linking conditions, target performance, etc., but absorption characteristics From the viewpoint of, etc., the water-soluble vinyl monomer (a1), the hydrolyzable vinyl monomer (a2), and when another vinyl monomer (a3) is also used, the sum of (a1) to (a3), and the cross-linking agent (b) is preferably 0.001 to 3, more preferably 0.005 to 2, and particularly preferably 0.01 to 1, based on the weight of

In the case of surface cross-linking treatment, the method of surface cross-linking treatment is known {for example, Japanese Patent No. 3648553, Japanese Unexamined Patent Publication No. 2003-165883, Japanese Unexamined Patent Publication No. 2005-75982, Japanese Unexamined Patent Publication No. 2005-95759}. is applicable.

The weight average particle size (μm) of the water-absorbent resin particles is 200-400, preferably 270-390, more preferably 290-380, and particularly preferably 320-370. The water absorbent resin particles can be pulverized. When the water-absorbing resin particles contain a solvent, it is preferable to distill off (dry) the solvent before pulverizing. When pulverized, the weight average particle diameter (μm) after pulverization is also preferably 200-400, more preferably 270-390, still more preferably 290-380, and particularly preferably 290-370. Within this range, the handling property (powder fluidity of the water-absorbent resin particles, etc.) after pulverization and the absorption rate of the water-absorbent resin particles become appropriate, so that the dryness of the absorbent article becomes even better. The weight average particle diameter can be measured in the same manner as in the case of the crosslinked polymer (A1).

The smaller the content of fine particles, the better the absorption performance. The content of fine particles of 106 μm or less in all particles is preferably 3% by weight or less, and more preferably the content of fine particles of 150 μm or less in all particles is 3% by weight. It is below. The content of fine particles can be determined using the plot created when determining the weight-average particle size. For pulverization and particle size adjustment, the same methods as in the case of the crosslinked polymer (A1) can be employed.

When pulverized, the span value after pulverization is preferably 1.0 or less, particularly preferably 0.9 or less, and most preferably 0.8 or less. Within this range, the particle size distribution of the water-absorbent resin particles is narrowed, so that spot absorption is less likely to occur or non-absorbing particles are less likely to occur, resulting in improved liquid drawing from the surface of the nonwoven fabric. The span value can be measured in the same manner as in the case of the crosslinked polymer (A1).

The apparent density (g/ml) of the water absorbent resin particles of the present invention is preferably 0.55 to 0.65, more preferably 0.56 to 0.64, and particularly preferably 0.57 to 0.63. . Within this range, the rash resistance of the absorbent article is further improved. The apparent density can be measured in the same manner as in the case of the crosslinked polymer (A1). The apparent density can be appropriately adjusted according to production conditions such as a gel pulverization method and drying conditions.

The shape of the water-absorbent resin particles is not particularly limited, and examples thereof include irregularly pulverized shape, scaly shape, pearl shape, rice grain shape, and the like. Of these, irregularly crushed forms are preferred from the viewpoints of good entanglement with fibrous materials for use in paper diapers and the like, and no fear of falling off from fibrous materials.

The absorption amount (M) (ml/g) by the DW method of the water-absorbing resin particles of the present invention is preferably 10 to 15 after 1 minute, from the viewpoint of the dryness of the absorbent article. is 11-14, more preferably 12-13. The absorption after 5 minutes (M2) is 45-55, preferably 46-54, more preferably 47-53. Within this range, the dryness of the absorbent article is further improved. The absorption amount by the DW method is obtained by adjusting the SPAN, the apparent density of the water-absorbing resin particles, the weight average particle diameter of the water-absorbing resin particles, the hydrophobic substance, the surfactant, etc. to the above preferable ranges. can be adjusted within a preferred range. Specifically, when the weight average particle size is large, the apparent density is high, the content or hydrophobicity of the hydrophobic substance is high, and the use of the penetrating agent used in combination with the hydrophobic substance is reduced, the effects of each are almost independent. It has the effect of lowering the absorption amount (M1) after 1 minute, and can be adjusted as appropriate. The amount absorbed after 5 minutes (M2) tends to increase as the amount of water retained increases, in addition to the operating factor of the amount absorbed after 1 minute (M1). When the absorption amount (M1) after 1 minute is less than 10, the initial absorption amount is insufficient and the dryness is deteriorated. biased, and dryness deteriorates. When the absorption amount after 5 minutes is less than 45, the absorption amount is insufficient and the dryness is deteriorated.

The DW (Demand Wetability) method is a method of measurement performed in a room at 25±2° C. and a humidity of 50±10% using the apparatus shown in FIG. The measuring apparatus shown in FIG. 1 consists of a burette (2) {scale volume 50 ml, length 86 cm, inner diameter 1.05 cm}, a conduit {inner diameter 7 mm}, and a measuring table (6). The burette part (2) has a rubber plug (1) at the top, an intake pipe (9) (tip inner diameter 3 mm) and a cock (7) at the bottom, and the top of the intake pipe (9) is There is a cock (8). A conduit is attached from the burette part (2) to the measuring platform (6). A hole with a diameter of 3 mm is drilled in the central part of the measuring table (6) as a physiological saline supply part, and a conduit is connected.

Using the measuring device of this configuration, first close the cock (7) of the burette part (2) and the cock (8) of the air introduction tube (9), and a predetermined amount of physiological saline (salt) adjusted to 25 ° C. concentration 0.9% by weight) was introduced from the upper part of the burette part (2), and after plugging the upper part of the burette part with the rubber stopper (1), the cock (7) of the burette part (2) and the cock of the air introduction tube (9) Open (8). Next, after wiping off the physiological saline overflowing onto the measuring table (6), the upper surface of the measuring table (6) and the water surface of the physiological saline coming out of the conduit opening in the center of the measuring table (6) are separated. Adjust the height of the measuring table (6) so that the height is the same. While wiping off the saline solution from the saline supply part, adjust the level of the saline solution in the burette part (2) to the top (0 ml line) of the scale of the burette part (2).

Subsequently, the cock (7) of the burette part (2) and the cock (8) of the air introduction tube (9) are closed, and a plain weave nylon mesh ( 5) (Opening 63 μm, 5 cm × 5 cm) is placed, and 0.50 g is placed on the plain weave nylon mesh (5) in a range of 2.7 cm in diameter centering on the physiological saline supply part of the measuring table (6). of the water absorbent resin particles (4) are evenly dispersed. After that, the cock (7) of the burette (2) and the cock (8) of the air introduction tube (9) are opened.

When the water-absorbent resin particles (4) begin to absorb water and the first bubbles introduced from the air introduction pipe (9) reach the surface of the physiological saline in the burette (2) (the burette (2) The time when the water level of the physiological saline solution inside the burette part (2) has fallen) is set as the measurement start time, and the amount of decrease in the physiological saline solution (3) in the burette part (2) (the amount of physiological saline water absorbed by the water-absorbing resin particles (4)) is continuously measured. Read the saline volume) M (ml). The absorption amount of the water-absorbent resin particles (4) after a predetermined time has elapsed from the start of water absorption is obtained by the following formula.

Absorption amount (ml/g) by DW method = M/0.50

The water retention capacity (g/g) of the water absorbent resin particles of the present invention is preferably 35 to 40, more preferably 36 to 39, from the viewpoint of dryness of the absorbent article. The water retention capacity of the water absorbent resin particles is measured by the following method.

<Method for measuring the amount of water retained by the water-absorbing resin particles>
Put 1.00 g of the measurement sample in a tea bag (20 cm long, 10 cm wide) made of nylon mesh with an opening of 63 μm (JIS Z8801-1: 2006), and add 1,000 ml of physiological saline (salt concentration 0.9% by weight). After being immersed therein for 1 hour without stirring, the water was drained by hanging for 15 minutes. After that, put the whole tea bag into a centrifuge, dehydrate by centrifugation at 150 G for 90 seconds to remove excess physiological saline, measure the weight (h1) including the tea bag, and calculate the water retention amount from the following formula. The physiological saline used and the temperature of the measurement atmosphere are set at 25°C ± 2°C. The weight of the tea bag after centrifugal dehydration is measured in the same manner as described above except that the measurement sample is not used (h2).

Water retention amount (g/g) = (h1) - (h2)

The absorption speed measured by the lockup method of the water-absorbing resin particles of the present invention is preferably 25 seconds or less, more preferably 24 seconds or less, and particularly preferably 23 seconds or less, from the viewpoint of liquid drawing from the nonwoven fabric surface. . In addition. The absorption rate of the water absorbent resin particles by the lockup method is measured by the following method.

<Absorption speed by lockup method of water absorbent resin>
1.000 g of a measurement sample is placed in a 100 ml tall beaker with a flat bottom defined in JIS R 3503. At this time, the upper surface of the water-absorbing resin placed in the beaker is made horizontal. Next, 50 g of deionized water adjusted to 23° C.±2° C. is weighed into a 100 ml glass beaker, and carefully and quickly poured into the 100 ml beaker containing the water absorbent resin. Timing is started as soon as the poured deionized water comes into contact with the water absorbent resin. Then, when the beaker into which the deionized water is poured is turned sideways at an angle of about 90°, the end point is the point where the fluid no longer seeps out from the surface of the water absorbent resin, and this time (unit: seconds) is measured by the lockup method. Absorption rate measured at

The water absorbent resin particles of the present invention can be used as an absorbent together with nonwoven fabric.

The nonwoven fabric used in the present invention is not particularly limited as long as it is a known nonwoven fabric, but from the viewpoint of liquid permeability, flexibility and strength when used as an absorbent, polyolefins such as polyethylene (PE) and polypropylene (PP) are used. Fibers, polyester fibers such as polyethylene terephthalate (PET), polytrimethylene terephthalate (PTT), polyethylene naphthalate (PEN), polyamide fibers such as nylon, rayon fibers, non-woven fabrics made of other synthetic fibers, cotton, silk, Examples include nonwoven fabrics produced by mixing hemp, pulp (cellulose) fibers, and the like. Among these nonwoven fabrics, nonwoven fabrics made of synthetic fibers are preferred from the viewpoint of enhancing the strength of the absorbent, and nonwoven fabrics made of rayon fibers, polyolefin fibers, and polyester fibers are more preferred. These non-woven fabrics may be non-woven fabrics of the above-mentioned fibers alone, or may be non-woven fabrics in which two or more types of fibers are combined.

The nonwoven fabric used in the present invention is moderately bulky and has a large basis weight from the viewpoint of imparting good liquid permeability, flexibility, strength and cushioning properties to the absorbent body and increasing the liquid permeation rate of the absorbent body. is preferred. The basis weight is preferably 5 to 300 g/m ² , more preferably 8 to 200 g/m ² , even more preferably 10 to 100 g/m ² , still more preferably 11 to 50 g/m ² . is. Moreover, the thickness of the nonwoven fabric is preferably in the range of 20 to 800 μm, more preferably in the range of 50 to 600 μm, and even more preferably in the range of 80 to 450 μm.

In the absorbent body of the present invention, the absorbent layer contains a water absorbent resin, a nonwoven fabric and, if necessary, an adhesive, and if desired, further contains hydrophilic fibers such as fluff pulp. After uniformly dispersing the water-absorbent resin on the non-woven fabric, if necessary, the non-woven fabric coated with an adhesive is further piled up, and if necessary, the non-woven fabric is heated under pressure. It can also be formed by uniformly dispersing a mixed powder of a water-absorbent resin and an adhesive on a nonwoven fabric, further overlapping the nonwoven fabrics, and heating near the melting temperature of the adhesive, if necessary, heating under pressure. be. The fluff pulp can be uniformly dispersed between the nonwoven fabric and the water absorbent resin particles.
In the absorbent body of the present invention, the absorbent layers can be stacked to form two or more layers.

Examples of adhesives used in the present invention include rubber-based adhesives such as natural rubber, butyl rubber, and polyisoprene; styrene-isoprene block copolymer (SIS), styrene-butadiene block copolymer (SBS), Styrene-based elastomer adhesives such as styrene-isobutylene block copolymer (SIBS) and styrene-ethylene-butylene-styrene block copolymer (SEBS); ethylene-vinyl acetate copolymer (EVA) adhesive; ethylene-acrylic acid Ethylene-acrylic acid derivative copolymer adhesives such as ethyl copolymer (EEA) and ethylene-butyl acrylate copolymer (EBA); ethylene-acrylic acid copolymer (EAA) adhesive; copolymer nylon, dimer Polyamide-based adhesives such as acid-based polyamide; Polyolefin-based adhesives such as polyethylene, polypropylene, atactic polypropylene, and copolymerized polyolefin; Polyester-based adhesives such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and copolymerized polyester etc., and acrylic adhesives. In the present invention, ethylene-vinyl acetate copolymer adhesives, styrene-based elastomer adhesives, and polyolefin adhesives are used from the viewpoint that they have strong adhesion and can prevent peeling of the nonwoven fabric in the water-absorbent sheet structure and dissipation of the water-absorbent resin. adhesives and polyester adhesives are preferred. These adhesives may be used alone or in combination of two or more.

When using a hot-melt adhesive, the melting temperature (softening temperature) of the adhesive is 60 to 180° C. from the viewpoint of sufficiently fixing the water-absorbent resin to the nonwoven fabric and preventing thermal deterioration and deformation of the nonwoven fabric. is preferred, 70 to 150°C is more preferred, and 75 to 125°C is even more preferred.

The content of the adhesive in the absorbent body is preferably in the range of 0.05 to 2.0 times the content (by mass) of the water absorbent resin, more preferably in the range of 0.08 to 1.5 times. A range of 1 to 1.0 times is more preferable. From the viewpoint of preventing detachment of the nonwoven fabric and dissipation of the water-absorbent resin by sufficient adhesion and enhancing the shape retention of the absorbent, the content ratio of the adhesive is preferably 0.05 times or more, and the adhesion becomes too strong. From the viewpoint of avoiding inhibition of swelling of the water-absorbing resin due to this, and improving the permeation speed and liquid leakage of the water-absorbing sheet structure, the content ratio of the adhesive is preferably 2.0 times or less.

The weight percentage of the water-absorbent resin particles based on the weight of the water-absorbent resin particles of the present invention and the above nonwoven fabric {weight of absorbent resin particles/(weight of water-absorbent resin particles + weight of nonwoven fabric)} is 40% by weight or more. is preferred, more preferably 60% by weight or more, and particularly preferably 80% by weight.

Moreover, it is preferable that the above-mentioned absorber constitutes an absorbent article {disposable diaper, sanitary napkin, etc.}. The manufacturing method of the absorbent article is a known one {JP-A-2003-225565, JP-A-2006-131767, JP-A-2005-097569, etc.} except for changing the above absorbent. is similar.

EXAMPLES The present invention will be further described below with reference to Examples , Reference Examples and Comparative Examples, but the present invention is not limited to these. In addition, unless otherwise specified, parts indicate parts by weight and % indicates weight %. The absorption amount by the DW method, the water retention amount of the water absorbent resin particles, and the absorption rate by the lockup method of the water absorbent resin particles were measured by the methods described above. In the following paragraphs, Production Example 1 to Production Example B6 shall be read as Reference Production Example 1 to Reference Production Example B6, respectively. Further, in the following paragraphs, Examples 1 to 11 shall be read as Reference Examples 1 to 11, respectively.

<Production Example 1>
Water-soluble vinyl monomer (a1-1) {acrylic acid, manufactured by Mitsubishi Chemical Corporation, purity 100%} 155 parts (2.15 mol parts), cross-linking agent (b1) {pentaerythritol triallyl ether, manufactured by Daiso Co., Ltd. } 0.6225 parts (0.0024 mole parts) and 340.27 parts of deionized water were kept at 3°C while stirring and mixing. After nitrogen was introduced into this mixture to make the dissolved oxygen content 1 ppm or less, 0.62 parts of a 1% aqueous hydrogen peroxide solution, 1.1625 parts of a 2% ascorbic acid aqueous solution and 2% 2,2'-azobis [ 2-Methyl-N-(2-hydroxyethyl)-propionamide] aqueous solution (2.325 parts) was added and mixed to initiate polymerization. After the temperature of the mixture reached 90° C., the mixture was polymerized at 90±2° C. for about 5 hours to obtain hydrous gel (1).

Next, 128.42 parts of a 48.5% sodium hydroxide aqueous solution was added and mixed while chopping 502.27 parts of this hydrous gel (1) with a mincing machine (12VR-400K manufactured by ROYAL), followed by hydrophobic Substance (C-1) {Mg stearate} 0.19 parts was added and mixed, shredded four times, and then dried with a through-air dryer {150°C, wind speed 2m/sec} to obtain a dry body. . After pulverizing the dried matter with a juicer mixer (Osterizer Blender manufactured by Oster), it was sieved, and the dried matter on each sieve was separately collected, and the weight average particle diameter was 350 μm, and the SPAN was 0.8. Crosslinked polymer particles (A1-1) were obtained by mixing the dried material on the sieve.

<Production Example 2>
"Hydrophobic substance (C-1) 0.19 parts" was not used and "weight average particle size 350 µm, SPAN 0.8" was changed to "weight average particle size 370 µm, SPAN 0.6" Crosslinked polymer particles (A1-2) were obtained in the same manner as in Production Example 1, except that the

<Production Example 3>
"Hydrophobic substance (C-1) 0.19 parts" is changed to "Hydrophobic substance (C-1) 0.29 parts", "Weight average particle size is 350 µm, SPAN is 0.8" Crosslinked polymer particles (A1-3) were obtained in the same manner as in Production Example 1, except that the average particle size was changed to 270 μm and the SPAN was changed to 0.9″.

<Production Example 4>
"Hydrophobic substance (C-1) 0.19 parts" was changed to "Hydrophobic substance (C-1) 0.38 parts", and "weight average particle diameter of 350 µm, SPAN was 0.8" was changed to "weight Crosslinked polymer particles (A1-4) were obtained in the same manner as in Production Example 1, except that the average particle size was changed to 200 μm and the SPAN was changed to 0.9″.

<Production Example 5>
Not using "hydrophobic substance (C-1) 0.19 parts" and "weight average particle size of 350 µm, SPAN of 0.8" to "weight average particle size of 315 µm, SPAN of 0.8" Crosslinked polymer particles (A1-5) were obtained in the same manner as in Production Example 1, except that the

<Production Example 6>
Crosslinked polymer particles (A1-6) in the same manner as in Production Example 1, except that "weight average particle size of 350 µm, SPAN of 0.8" was changed to "weight average particle size of 350 µm, SPAN of 1.2". got

<Production Example 7>
"Hydrophobic substance (C-1) 0.19 parts" was not used and "weight average particle size 350 µm, SPAN 0.8" was changed to "weight average particle size 420 µm, SPAN 0.8" Crosslinked polymer particles (A1-7) were obtained in the same manner as in Production Example 1, except that the

<Production Example 8>
Not using "hydrophobic substance (C-1) 0.19 parts" and "weight average particle size of 350 µm, SPAN of 0.8" to "weight average particle size of 160 µm, SPAN of 1.0" Crosslinked polymer particles (A1-8) were obtained in the same manner as in Production Example 1, except that the

<Production Example 9>
Not using "hydrophobic substance (C-1) 0.19 parts" and "weight average particle size of 350 µm, SPAN of 0.8" to "weight average particle size of 330 µm, SPAN of 0.8" Crosslinked polymer particles (A1-9) were obtained in the same manner as in Production Example 1, except that the

<Production Example 10>
Not using "hydrophobic substance (C-1) 0.19 parts" and "weight average particle size of 350 µm, SPAN of 0.8" to "weight average particle size of 290 µm, SPAN of 0.9" Crosslinked polymer particles (A1-10) were obtained in the same manner as in Production Example 1, except that the

<Production Example 11>
"Hydrophobic substance (C-1) 0.19 parts" is changed to "Hydrophobic substance (C-1) 0.29 parts", "Weight average particle size is 350 µm, SPAN is 0.8" Crosslinked polymer particles (A1-11) were obtained in the same manner as in Production Example 1, except that the average particle size was changed to 450 μm and the SPAN was changed to 0.7″.

<Production Example 12>
Crosslinked polymer particles (A1-12) in the same manner as in Production Example 1, except that "weight average particle size of 350 µm, SPAN of 0.8" was changed to "weight average particle size of 370 µm, SPAN of 1.2". got

<Production Example 13>
"Hydrophobic substance (C-1) 0.19 parts" was not used and "weight average particle size 350 µm, SPAN 0.8" was changed to "weight average particle size 240 µm, SPAN 1.5" Crosslinked polymer particles (A1-13) were obtained in the same manner as in Production Example 1, except that the

<Production Example B1>
"Hydrophobic substance (C-1) 0.19 parts" was changed to "Hydrophobic substance (C-2) {sucrose erucate, Mitsubishi Chemical Foods Co., Ltd. Ryoto (registered trademark; hereinafter abbreviated) sugar ester ER −290} 0.10 parts”, and “weight average particle size 350 μm, SPAN 0.8” was changed to “weight average particle size 355 μm, SPAN 0.7”. Crosslinked polymer particles (A1-B1) were obtained in the same manner as above.

<Production example B2>
"Hydrophobic substance (C-1) 0.19 parts" to "Hydrophobic substance (C-2) {sucrose erucate, Mitsubishi Chemical Foods Ryoto Sugar Ester ER-290} 0.30 parts" Crosslinked polymer particles ( A1-B2) were obtained.

<Production Example B3>
"Hydrophobic substance (C-1) 0.19 parts" to "hydrophobic substance (C-3) {sucrose stearate, Mitsubishi Chemical Foods Ryoto Sugar Ester S-370} 0.10 parts" Crosslinked polymer particles ( A1-B3) were obtained.

<Production Example B4>
"Hydrophobic substance (C-1) 0.19 parts" to "hydrophobic substance (C-3) {sucrose stearate, Mitsubishi Chemical Foods Ryoto Sugar Ester S-370} 0.30 parts" Crosslinked polymer particles ( A1-B4) were obtained.

<Production example B5>
Change "hydrophobic substance (C-1) 0.19 parts" to "hydrophobic substance (C-4) {ethylene bis distearic acid amide, Slipax (registered trademark) E manufactured by Mitsubishi Chemical Corporation} 0.20 parts" , and “Weight average particle size of 350 μm, SPAN of 0.8” was changed to “Weight average particle size of 355 μm, SPAN of 0.7” to obtain crosslinked polymer particles (A1- B5) was obtained.

<Production Example B6>
Change "hydrophobic substance (C-1) 0.19 parts" to "hydrophobic substance (C-5) {sorbitan oleic acid monoester, Sanyo Kasei Ionet S-80} 0.20 parts", and Crosslinked polymer particles (A1-B6) in the same manner as in Production Example 1, except that "weight average particle size of 340 µm, SPAN of 0.8" was changed to "weight average particle size of 355 µm, SPAN of 0.7". got

<Production example B7>
"Hydrophobic substance (C-1) 0.19 parts" was changed to "hydrophobic substance (C-1) 0.30 parts and penetrant (D-1) {polyoxyethylene alkyl ether, manufactured by Sanyo Chemical Co., Ltd. Naroacty CL -20} 0.20 parts”, and “weight average particle size of 340 μm, SPAN of 0.8” was changed to “weight average particle size of 321 μm, SPAN of 0.8”, Production Example 1 Crosslinked polymer particles (A1-B7) were obtained in the same manner as above.

<Production Example B8>
"Hydrophobic substance (C-1) 0.19 parts" was changed to "hydrophobic substance (C-2) 0.30 parts and penetrating agent (D-1) {polyoxyethylene alkyl ether, manufactured by Sanyo Chemical Co., Ltd. Naroacty CL -20} 0.20 parts”, and “weight average particle size of 340 μm, SPAN of 0.8” was changed to “weight average particle size of 321 μm, SPAN of 0.8”, Production Example 1 Crosslinked polymer particles (A1-B8) were obtained in the same manner as above.

<Production example B9>
"Hydrophobic substance (C-1) 0.19 parts" was changed to "hydrophobic substance (C-3) 0.30 parts and penetrant (D-1) {polyoxyethylene alkyl ether, manufactured by Sanyo Chemical Co., Ltd. Naloacty-CL -20} 0.20 parts”, and “weight average particle size of 340 μm, SPAN of 0.8” was changed to “weight average particle size of 321 μm, SPAN of 0.8”, Production Example 1 Crosslinked polymer particles (A1-B9) were obtained in the same manner as above.

<Production Example B10>
"Hydrophobic substance (C-1) 0.19 parts" was changed to "hydrophobic substance (C-4) 0.30 parts and penetrating agent (D-1) {polyoxyethylene alkyl ether, manufactured by Sanyo Chemical Co., Ltd. Naloacty CL -20} 0.20 parts”, and “weight average particle size of 340 μm, SPAN of 0.8” was changed to “weight average particle size of 321 μm, SPAN of 0.8”, Production Example 1 Crosslinked polymer particles (A1-B10) were obtained in the same manner as above.

<Production Example B11>
"Hydrophobic substance (C-1) 0.19 parts" was changed to "hydrophobic substance (C-5) 0.30 parts and penetrant (D-1) {polyoxyethylene alkyl ether, manufactured by Sanyo Chemical Co., Ltd. Naroacty CL -20} 0.20 parts”, and “weight average particle size of 340 μm, SPAN of 0.8” was changed to “weight average particle size of 321 μm, SPAN of 0.8”, Production Example 1 Crosslinked polymer particles (A1-B11) were obtained in the same manner as above.

<Example 1>
While 100 parts by weight of the crosslinked polymer particles (A1-1) obtained in Production Example 1 were stirred at high speed (high-speed stirring turbulizer manufactured by Hosokawa Micron; number of rotations: 2000 rpm), ethylene glycol di- amide was added thereto as a surface cross-linking agent. A mixed solution obtained by mixing 0.04 parts by weight of glycidyl ether and 3.0 parts by weight of a 50% propylene glycol aqueous solution as a solvent is added, mixed uniformly, and dried by standing at 130 ° C. for 30 minutes. By sieving the dried product, a water absorbent resin (P-1) of the present invention having a weight average particle size of 366 μm and a SPAN of 0.8 was obtained.

<Example 2>
"Crosslinked polymer particles (A1-1) 100 parts by weight" was changed to "Crosslinked polymer particles (A1-2) 100 parts by weight", and "ethylene glycol diglycidyl ether 0.04 parts by weight" was changed to "ethylene glycol di A water-absorbent resin (P-2) of the present invention having a weight average particle size of 384 μm and a SPAN of 0.6 was obtained in the same manner as in Example 1, except that the glycidyl ether was changed to 0.03 parts by weight.

<Example 3>
In the same manner as in Example 1, except that "crosslinked polymer particles (A1-1) 100 parts by weight" were changed to "crosslinked polymer particles (A1-3) 100 parts by weight", the weight average particle diameter was 299 µm, SPAN0 A water-absorbing resin (P-3) of the present invention having a weight of 0.9 was obtained.

<Example 4>
"Crosslinked polymer particles (A1-1) 100 parts by weight" was changed to "Crosslinked polymer particles (A1-4) 100 parts by weight", and "ethylene glycol diglycidyl ether 0.04 parts by weight" was changed to "ethylene glycol di A water-absorbent resin (P-4) of the present invention having a weight average particle diameter of 210 μm and a SPAN of 0.9 was obtained in the same manner as in Example 1, except that the glycidyl ether was changed to 0.03 parts by weight.

<Example 5>
"Crosslinked polymer particles (A1-1) 100 parts by weight" was changed to "Crosslinked polymer particles (A1-5) 100 parts by weight", and "ethylene glycol diglycidyl ether 0.04 parts by weight" was changed to "ethylene glycol di A water-absorbing resin (P-5) of the present invention having a weight average particle diameter of 323 μm and a SPAN of 0.8 was obtained in the same manner as in Example 1, except that the glycidyl ether was changed to 0.02 parts by weight.

<Example 6>
In the same manner as in Example 1, except that "100 parts by weight of crosslinked polymer particles (A1-1)" was changed to "100 parts by weight of crosslinked polymer particles (A1-B1)", the weight average particle diameter was 367 µm, SPAN0 A water-absorbing resin (P-6) of the present invention having a weight of 0.8 was obtained.

<Example 7>
In the same manner as in Example 1, except that "100 parts by weight of crosslinked polymer particles (A1-1)" was changed to "100 parts by weight of crosslinked polymer particles (A1-B2)", the weight average particle diameter was 333 µm, SPAN0 A water-absorbing resin (P-7) of the present invention having a weight of 0.8 was obtained.

<Example 8>
In the same manner as in Example 1, except that "100 parts by weight of crosslinked polymer particles (A1-1)" was changed to "100 parts by weight of crosslinked polymer particles (A1-B3)", the weight average particle diameter was 359 µm, SPAN0 A water-absorbing resin (P-8) of the present invention having a weight of 0.7 was obtained.

<Example 9>
In the same manner as in Example 1, except that "100 parts by weight of crosslinked polymer particles (A1-1)" was changed to "100 parts by weight of crosslinked polymer particles (A1-B4)", the weight average particle diameter was 331 µm, SPAN0 A water-absorbing resin (P-9) of the present invention having a weight of 0.7 was obtained.

<Example 10>
In the same manner as in Example 1, except that "100 parts by weight of crosslinked polymer particles (A1-1)" was changed to "100 parts by weight of crosslinked polymer particles (A1-B5)", the weight average particle diameter was 372 µm, SPAN0 A water-absorbing resin (P-10) of the present invention having a weight of 0.7 was obtained.

<Example 11>
In the same manner as in Example 1, except that "crosslinked polymer particles (A1-1) 100 parts by weight" were changed to "crosslinked polymer particles (A1-B6) 100 parts by weight", the weight average particle diameter was 362 µm, SPAN0 A water-absorbing resin (P-11) of the present invention having a weight of 0.8 was obtained.

<Example 12>
In the same manner as in Example 1, except that "100 parts by weight of crosslinked polymer particles (A1-1)" was changed to "100 parts by weight of crosslinked polymer particles (A1-B7)", the weight average particle diameter was 332 µm, SPAN0 A water-absorbing resin (P-12) of the present invention having a weight of 0.8 was obtained.

<Example 13>
In the same manner as in Example 1, except that "100 parts by weight of crosslinked polymer particles (A1-1)" was changed to "100 parts by weight of crosslinked polymer particles (A1-B8)", the weight average particle diameter was 335 µm, SPAN0 A water-absorbing resin (P-13) of the present invention having a weight of 0.8 was obtained.

<Example 14>
In the same manner as in Example 1, except that "100 parts by weight of crosslinked polymer particles (A1-1)" was changed to "100 parts by weight of crosslinked polymer particles (A1-B9)", the weight average particle diameter was 334 µm, SPAN0 A water-absorbing resin (P-14) of the present invention having a weight of 0.8 was obtained.

<Example 15>
In the same manner as in Example 1, except that "crosslinked polymer particles (A1-1) 100 parts by weight" were changed to "crosslinked polymer particles (A1-B10) 100 parts by weight", weight average particle diameter 330 µm, SPAN0 A water-absorbing resin (P-15) of the present invention having a weight of 0.8 was obtained.

<Example 16>
In the same manner as in Example 1, except that "crosslinked polymer particles (A1-1) 100 parts by weight" were changed to "crosslinked polymer particles (A1-B11) 100 parts by weight", weight average particle diameter 332 µm, SPAN0 A water-absorbing resin (P-16) of the present invention having a weight of 0.8 was obtained.

<Comparative Example 1>
In the same manner as in Example 1, except that "crosslinked polymer particles (A1-1) 100 parts by weight" were changed to "crosslinked polymer particles (A1-6) 100 parts by weight", weight average particle diameter 365 µm, SPAN1 A comparative water-absorbent resin (R-1) having a weight of 0.2 was obtained.

<Comparative Example 2>
"Crosslinked polymer particles (A1-1) 100 parts by weight" was changed to "Crosslinked polymer particles (A1-7) 100 parts by weight", and "ethylene glycol diglycidyl ether 0.04 parts by weight" was changed to "ethylene glycol di A water absorbent resin (R-2) for comparison having a weight average particle diameter of 428 μm and a SPAN of 0.8 was obtained in the same manner as in Example 1, except that the glycidyl ether was changed to 0.03 parts by weight.

<Comparative Example 3>
In the same manner as in Example 1, except that "100 parts by weight of crosslinked polymer particles (A1-1)" was changed to "100 parts by weight of crosslinked polymer particles (A1-8)", a weight average particle diameter of 180 µm, SPAN1 A comparative water-absorbent resin (R-3) with 0.0 was obtained.

<Comparative Example 4>
"Crosslinked polymer particles (A1-1) 100 parts by weight" was changed to "Crosslinked polymer particles (A1-9) 100 parts by weight", and "carboxy-modified polysiloxane (Shin-Etsu Chemical Co., Ltd.) was added to the mixed solution of the surface cross-linking agent. A comparative water-absorbing resin (R-4 ).

<Comparative Example 5>
"Crosslinked polymer particles (A1-1) 100 parts by weight" was changed to "Crosslinked polymer particles (A1-10) 100 parts by weight", and "ethylene glycol diglycidyl ether 0.04 parts by weight" was changed to "ethylene glycol di A water absorbent resin (R-5) for comparison having a weight average particle diameter of 305 μm and a SPAN of 0.9 was obtained in the same manner as in Example 1, except that the glycidyl ether was changed to 0.03 parts by weight.

<Comparative Example 6>
In the same manner as in Example 1, except that "crosslinked polymer particles (A1-1) 100 parts by weight" were changed to "crosslinked polymer particles (A1-11) 100 parts by weight", weight average particle diameter 458 µm, SPAN0 A comparative water absorbent resin (R-6) having a weight of 0.7 was obtained.

<Comparative Example 7>
In the same manner as in Example 1, except that "crosslinked polymer particles (A1-1) 100 parts by weight" were changed to "crosslinked polymer particles (A1-12) 100 parts by weight", weight average particle diameter 382 µm, SPAN1 A comparative water-absorbing resin (R-7) having a weight of 0.2 was obtained.

<Comparative Example 8>
In the same manner as in Example 1, except that "100 parts by weight of crosslinked polymer particles (A1-1)" was changed to "100 parts by weight of crosslinked polymer particles (A1-13)", a weight average particle diameter of 261 µm, SPAN1 A comparative water-absorbing resin (R-8) with a weight of 0.5 was obtained.

Regarding the water absorbent resins obtained in Examples 1 to 16 and Comparative Examples 1 to 8, measured physical properties {weight average particle size, SPAN} and performance evaluation results {absorbed amount by DW method, water retention amount, by lockup method absorption rate} is shown in Table 1. In Table 1, M1 and M2 indicate the absorption amount after 1 minute and 5 minutes by the DW method, respectively, and % is based on the weight of the crosslinked polymer (A1), content (% by weight) indicate.

As can be seen from Table 1, the water-absorbing resin particles of the present invention (Examples 1 to 16) have a small SPAN (narrow particle size distribution), and have appropriate weight-average particle diameters and absorption rate patterns. Specifically, although no hydrophobic substance was used in Examples 2 and 5, appropriate absorption rate patterns were obtained by appropriately setting the weight-average particle size and SPAN. It can be seen that in Examples 1, 3 and 4, the change in the absorption rate pattern due to the difference in the weight average particle size can be controlled within a specific range by adjusting the content of the hydrophobic substance. Further, Examples 6 to 11 illustrate examples using other suitable hydrophobic substances. Furthermore, in Examples 12 to 16, it can be seen that the combination of the hydrophobic substance (C) and the penetrating agent (D) further improved the absorption speed by the lockup method. On the other hand, Comparative Examples 1 and 7 tend to have a wider particle size distribution due to a higher SPAN than Example 1, and a lower M2 and a slower absorption rate by the lockup method. Comparative Example 2 has a low SPAN, but a large weight-average particle size and a slow absorption rate by the lockup method. Comparative Example 4 uses a highly hydrophobic "carboxy-modified polysiloxane (manufactured by Shin-Etsu Chemical Co., Ltd.: X-22-3701E)" for surface cross-linking, which reduces M2 and slows down the absorption rate by the lock-up method. there is In Comparative Example 5, the weight average particle size was lowered without using a hydrophobic substance, and M1 was excessively high. In Comparative Example 6, the weight-average particle size is large, a hydrophobic substance is also used, M1 is low, and the absorption rate by the lockup method is low. In Comparative Examples 3 and 8, the weight average particle size is small and the SPAN is high, so M1 is excessively high.

Subsequently, a low SPAN and an appropriate absorption rate pattern were evaluated as to what kind of absorption characteristics they exhibit when applied to an absorbent article. Using the water absorbent resin particles obtained in Examples 1 to 16 and Comparative Examples 1 to 8, absorbent articles (disposable diapers) were prepared in the following manner, and the dryness and SDME method by liquid drawing from the surface nonwoven fabric were measured. The results are shown in Table 2.

<Preparation of absorber>
A styrene-butadiene-styrene copolymer (SBS; softening point: 85°C) was applied as an adhesive to a non-woven fabric A (basis weight: 40 g/m ² , thickness: 0.5 mm, made of polypropylene) cut into rectangular pieces of 10 cm × 40 cm. It is applied evenly with a hot-melt applicator (AD41, manufactured by Nordson) so that the basis weight is 2.85 g/m ² . 10.6 g of the evaluation sample {water-absorbing resin particles} (basis weight: 265 g/m ² ) was evenly spread on the adhesive-applied surface, and then nonwoven fabric B (basis weight: 45 g/ m ² , thickness 7.0 mm, polypropylene) were stacked. The nonwoven fabric A-water absorbent resin-nonwoven fabric B sheet was sandwiched between acrylic plates (thickness 4 mm) and pressed at a pressure of 5 kg/cm ² for 30 seconds. After pressing, remove the acrylic plate on the nonwoven fabric A side, laminate the adhesive, the water-absorbent resin and the nonwoven fabric B in the same manner as above, sandwiched between the acrylic plates again, and press at a pressure of 5 kg / cm ² for 30 seconds, An absorbent was prepared.

<Preparation of absorbent article>
An absorbent article by placing a polyethylene sheet (polyethylene film UB-1 manufactured by Tamapoly Co., Ltd.) on one side of the absorbent body and a non-woven fabric (basis weight: 20 g/m ² , Eltas Guard manufactured by Asahi Kasei Corporation) on the opposite side. was prepared.

<Dryness test by liquid drawing from surface nonwoven fabric>
The absorber prepared above was placed in a box (made of stainless steel) measuring 11 cm wide×41 cm long×4 cm high and having an open top (11 cm×41 cm surface). 500 ml of deionized water adjusted to 32±2° C. was prepared and poured into the box containing the absorber at once. Timing began as soon as the deionized water contacted the absorbent. The deionized water retained on the surface nonwoven fabric was absorbed by the water-absorbing resin, and the time (whitening time) until the area of the surface nonwoven fabric that looked white became half of the nonwoven fabric was recorded.

<Surface dryness value by SDME method>
A paper diaper in which the detector of an SDME (Surface Dryness Measurement Equipment) tester (manufactured by WK system) is sufficiently moistened {artificial urine (potassium chloride 0.03% by weight, magnesium sulfate 0.08% by weight, sodium chloride 0.8% by weight % and deionized water 99.09% by weight) and left for 60 minutes. }, set the 0% dryness value, and then set the detector of the SDME tester to a dry paper diaper {Paper diaper was prepared by heating and drying at 80° C. for 2 hours. } and set 100% dryness to calibrate the SDME tester. Next, set a metal ring (inner diameter 70 mm, length 50 mm) in the center of the disposable diaper to be measured, inject 80 ml of artificial urine, and when the artificial urine has completely absorbed {when the luster due to artificial urine cannot be confirmed}, immediately The metal ring was removed, and three SDME detectors were placed in the center of the paper diaper and on its left and right (three locations at equal intervals of 10 cm from the edge of the 40 cm paper diaper) to start measuring the surface dryness value. Five minutes after the start of measurement. of the three SDME detectors, the dryness value of the center detector is the surface dryness value (1-1) {middle}, and the dryness value of the remaining two SDME detectors is the surface dryness value (1-2) {left}, surface dryness value (1-3) {right}. The artificial urine, measurement atmosphere, and storage atmosphere were 25±5° C. and 65±10% RH.

As can be seen from Table 2, the absorbent body and absorbent article using the water-absorbing resin particles of the present invention are whitening time and surface dryness value compared to the absorbent body and absorbent article using the water-absorbing resin particles for comparison. (1-1), (1-2), and (1-3) are even and excellent in dryness. On the other hand, Comparative Examples 1, 7, and 8 have a high SPAN, Comparative Examples 2 and 6 have a large weight average particle size, and Comparative Example 4 has a low absorption amount (M2) after 5 minutes. Poor liquid drawing from the surface. In Comparative Examples 3, 5 and 8, since M1 was excessively high, the liquid diffusibility was poor and spot absorption was caused, resulting in deviation of the surface dryness value and poor dryness. In Comparative Examples 1, 2, 4, and 6 to 8, the absorption rate by the lock-up method is also slow, and it can be seen that the whitening time tends to decrease. That is, when the water-absorbing resin particles of the present invention are applied to absorbent bodies and absorbent articles, it is easily predicted that they have excellent liquid drawing properties from nonwoven fabrics and surface drying properties, and that there is no fear of rashes or the like.

The water-absorbent resin particles of the present invention can be applied to absorbent bodies containing water-absorbent resin particles and fibrous materials, and absorbent articles comprising the absorbent body {disposable diapers, sanitary napkins, and blood-retaining medical products. agent etc.}. In addition, pet urine absorbents, urine gelling agents for portable toilets, freshness-preserving agents for fruits and vegetables, drip absorbents for meat and seafood, cooling agents, disposable body warmers, gelling agents for batteries, water-retaining agents for plants and soil, dew condensation It can also be used in a variety of applications such as inhibitors, waterproofing agents, packing agents and artificial snow.

1 rubber plug 2 burette part 3 physiological saline 4 water-absorbing resin particles 5 plain-woven nylon mesh 6 measuring table 7 cock 8 cock 9 air introduction pipe

Claims (6)

It comprises a water-soluble vinyl monomer (a1) and/or a vinyl monomer (a2) that becomes water-soluble vinyl monomer (a1) by hydrolysis, and a crosslinked polymer (A1) having a crosslinking agent (b) as an essential structural unit. The water absorbent resin particles have a weight average particle diameter (μm) of 200 to 400, a span value (SPAN) represented by the following formula 1 is 1.0 or less, and water absorbent Water absorbent resin particles having an absorption amount (M1) of 10 to 15 ml/g after 1 minute and an absorption amount (M2) of 45 to 55 ml/g after 5 minutes according to the DW (Demand Wetability) method of the resin particles . The absorption rate of the water-absorbent resin particles by the lockup method of ion-exchanged water is 25 seconds or less, the water-absorbent resin particles contain a hydrophobic substance (C) and a penetrant (D), and are hydrophobic The substance (C) is a long-chain fatty acid ester, a long-chain fatty acid, a salt of a long-chain fatty acid, a long-chain fatty acid amide, or a mixture of two or more thereof, and the penetrant (D) is a nonionic surfactant (D1) and the content of the hydrophobic substance (C) is 0.08 to 1.0% by weight based on the weight of the crosslinked polymer (A1) .
SPAN = [D (90%) - D (10%)] / D (50%) ≤ 1.0 (Equation 1)
(In Formula 1, D (10%) is the total weight of the water-absorbent resin particles classified using a standard sieve as 100% by weight, and the particles with the smallest particle size have a cumulative weight fraction of 10% by weight. is the diameter, D (50%) is the particle diameter at which the cumulative weight fraction is 50% by weight, and D (90%) is the particle diameter at which the cumulative weight fraction is 90% by weight.) The nonionic surfactant (D1) is an aliphatic alcohol (wherein the alkyl group has 8 to 18 carbon atoms.) alkylene oxide (wherein it has 2 to 8 carbon atoms.) Adduct (wherein the degree of polymerization is 1 ~100) . 3. The water absorbent resin particles according to claim 1 , wherein the content of the hydrophobic substance (C) is 0.08 to 0.3% by weight based on the weight of the crosslinked polymer (A1). 4. The water absorbent resin particles according to any one of claims 1 to 3, wherein the water absorbent resin particles have a water retention capacity of 35 to 40 g/g in physiological saline. An absorbent body comprising the water absorbent resin particles according to any one of claims 1 to 4 and a nonwoven fabric. An absorbent article comprising the absorbent body according to claim 5 .

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