JPWO2020017483A1 - Water-absorbent resin particles, absorbers containing them, and absorbent articles - Google Patents

Abstract

Provided are water-absorbent resin particles that exhibit a high initial absorption rate and liquid diffusivity in contact with a liquid to be absorbed, have excellent dryness, and do not have problems such as fogging. The present invention comprises a water-soluble vinyl monomer and / or a hydrolyzable vinyl monomer and a cross-linked polymer (A1) containing a cross-linking agent as an essential constituent unit, and has a weight average particle size (μm) of 200 to 400, and is described below. The SPAN value represented by the formula is 1.0 or less, the absorption amount after 1 minute by the DW method of (A1) is 10 to 15 ml / g, and the absorption amount after 5 minutes is 45 to 55 ml / g. Some water-absorbent resin particles. SPAN = [D (90%) -D (10%)] / D (50%) ≤ 1.0 (D (10%) is a particle size with a cumulative weight fraction of 10% by weight, D (50%). ) Is a particle size of 50% by weight, and D (90%) is a particle size of 90% by weight.)

Description

The present invention relates to water-absorbent resin particles, an absorber containing the same, and an absorbent article.

For sanitary materials such as disposable diapers, sanitary napkins, and incontinence pads, water-absorbent resins containing hydrophilic fibers such as pulp and acrylic acid (salt) as main raw materials are widely used as absorbers. In recent years, consumers have tended to seek more comfort, and the demand has shifted to those that are drier and thinner, which is accompanied by higher dryness and the amount of hydrophilic fibers used. Reduction has come to be desired. Therefore, the water-absorbent resin itself is required to play the role of the initial high absorption rate and liquid diffusivity that the hydrophilic fiber has played so far.

As a 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 common. For example, a method of increasing the drying rate of the water-absorbent resin to reduce the apparent density (Patent Document 1) and a method of improving the absorption rate by reducing the particle size of the water-absorbent resin particles in the sieving step (Patent Document 2). Are known. However, in an absorber in which these water-absorbent resin particles are applied to an absorbent article (paper diaper, etc.), there is no problem when the content of the hydrophilic fibers is larger than the content of the water-absorbent resin particles, but the hydrophilic fibers When the content of the absorbent is low or not, the absorption rate of the water-absorbent resin is biased depending on the part of the absorber, and the absorbent article cannot be effectively used. Problems such as fog are likely to occur.
As a method for solving the above problems, water-absorbent resin particles (Patent Document 3) in which the absorption rate (hereinafter, absorption rate pattern) with respect to the passage of time after contact with the liquid to be absorbed is controlled are known. When the water-absorbent resin particles are applied to the absorbent article, there is a problem that the liquid to be absorbed from the surface non-woven fabric used in the absorbent article is slowly drained and the dryness is deteriorated.
Therefore, even in an absorbent body in which the amount of hydrophilic fibers used is small, an absorbent article that exhibits a high initial absorption rate and liquid diffusivity, has excellent dryness, and does not have problems such as fogging, and water absorption that can be used for this. Sexual resin particles are strongly desired.

Japanese Unexamined Patent Publication No. 2013-132434 Japanese Unexamined Patent Publication No. 2006-143972 Japanese Patent No. 5448699

An object of the present invention is a water-absorbent resin particle that exhibits a high initial absorption rate and liquid diffusivity in contact with a liquid to be absorbed, has excellent dryness, and does not have problems such as fogging, an absorber containing the same, and absorbency. To provide goods.

The present invention relates to a water-soluble vinyl monomer (a1) and / or a vinyl monomer (a2) that becomes a water-soluble vinyl monomer (a1) by hydrolysis (in other words, a water-soluble vinyl monomer (a1) and a water-soluble vinyl by hydrolysis. Water absorption including at least one vinyl monomer selected from the group consisting of a vinyl monomer (a2) serving as a monomer (a1) and a crosslinked polymer (A1) containing a crosslinking agent (b) as an essential constituent unit. Among the resin particles, the weight average particle diameter (μm) of the water-absorbent resin particles is 200 to 400, the span value (SPAN) represented by the following formula 1 is 1.0 or less, and (A1). These are water-absorbent resin particles having an absorption amount (M1) after 1 minute and 45 to 55 ml / g after 5 minutes according to the DW (Polymer Wetability) method.
SPAN = [D (90%) -D (10%)] / D (50%) ≤ 1.0 (Formula 1)
In the above formula 1, D (10%) is a particle having a cumulative weight component of 10% by weight from the particle having the smallest particle size, where the total weight of the water-absorbent resin particles classified using a standard sieve is 100% by weight. In terms of diameter, D (50%) is a particle size having a cumulative weight component of 50% by weight, and D (90%) is a particle size having a cumulative weight component of 90% by weight.

The absorber of the present invention contains the above-mentioned water-absorbent resin particles and a fibrous substance.

The absorbent article of the present invention comprises the above absorber.

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 an absorbent article (paper diaper, sanitary napkin, etc.), they exhibit high initial absorption rate and liquid diffusivity when they come into contact with the liquid to be absorbed, and are dry. Is excellent, and there are no problems such as fogging. That is, the absorbent article using the water-absorbent resin particles having the DW absorption pattern of the present invention exhibits excellent liquid diffusivity because it has an absorption pattern that is appropriately delayed at the initial stage, and the dryness of the entire absorber is dry. Excellent for. Further, by setting the weight average particle size and the span value within the range of the present invention, the liquid drainability from the surface non-woven fabric (suction / absorption of the liquid; the same applies hereinafter) is improved, so that even better dryness is exhibited. do.

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

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

The vinyl monomer (hereinafter, also referred to as a hydrolyzable vinyl monomer) (a2) which becomes a water-soluble vinyl monomer (a1) by hydrolysis is known without particular limitation {for example, Japanese Patent Application Laid-Open No. 36485553, Japanese Patent Application Laid-Open No. 2003-165883. Japanese Patent Laying-Open No. 2005-75982, Japanese Unexamined Patent Publication No. 2005-59559} vinyl monomers and the like 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. Further, the hydrolyzable property means a 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 hydrolyzable vinyl monomer may be hydrolyzed during polymerization, after polymerization, or both, but it is preferable after polymerization from the viewpoint of the molecular weight of the obtained water-absorbent resin particles.

Of these, a water-soluble vinyl monomer (a1) is preferable, an anionic vinyl monomer is more preferable, and then a carboxy (salt) group, a sulfo (salt) group, an amino group, and a carbamoyl group are preferable from the viewpoint of absorption characteristics and the like. , Ammonio group or vinyl monomer having mono-, di- or tri-alkylammonio group, then preferably vinyl monomer having carboxy (salt) group or carbamoyl group, especially preferably (meth) acrylic acid (salt) and (Meta) acrylamide, then particularly preferably (meth) acrylic acid (salt), most preferably acrylic acid (salt).

The "carboxy (salt) group" means a "carboxy group" or a "carboxylate group", and the "sulfo (salt) group" means a "sulfo group" or a "sulfonate group". Further, (meth) acrylic acid (salt) means acrylic acid, acrylate, methacrylic acid or methacrylic acid, and (meth) acrylamide means acrylamide or methacrylamide. The salt includes an alkali metal (lithium, sodium, potassium, etc.) salt, an alkaline earth metal (magnesium, calcium, etc.) salt, an ammonium (NH ₄ ) salt, and the like. Among these salts, an alkali metal salt and an ammonium salt are preferable, and an alkali metal salt is particularly preferable, and a sodium salt is particularly preferable, from the viewpoint of absorption characteristics and the like.

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

As a constituent unit of the water-absorbent resin particles, in addition to the water-soluble vinyl monomer (a1) and the hydrolyzable vinyl monomer (a2), another vinyl monomer (a3) copolymerizable with these can be used as the constituent unit. ..

The other copolymerizable vinyl monomer (a3) is not particularly limited and is known {for example, Japanese Patent Application Laid-Open No. 36485553, JP-A-2003-165883, JP-A-2005-75982, JP-A-2005-595759. } Hydrophobic vinyl monomer and the like 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, halogen-substituted styrene such as vinylnaphthalene and dichlorostyrene and the like.
(Ii) Alkenes of aliphatic ethylene monomers having 2 to 20 carbon atoms [ethylene, propylene, butene, isobutylene, pentene, heptene, diisobutylene, octene, dodecene, octadecene, etc.]; and alkaziene [butadiene and isoprene, etc.] and the like.
(Iii) Alicyclic ethylene monomer having 5 to 15 carbon atoms Monoethylene unsaturated monomer [pinene, limonene, inden, etc.]; and polyethylene vinyl polymerizable monomer [cyclopentadiene, bicyclopentadiene, ethilidene norbornene, etc.] and the like.

When the other vinyl monomer (a3) is used as a constituent 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 0.01 to 5, more preferably 0.05 to 3, then preferably 0.08 to 2, and particularly preferably 0.1 to 1.5. From the viewpoint of absorption characteristics and the like, the content of the other vinyl monomer (a3) unit is most preferably 0 mol%.

The cross-linking agent (b) is not particularly limited, and known cross-linking agents (for example, Japanese Patent No. 3648553, Japanese Patent Application Laid-Open No. 2003-165883, Japanese Patent Application Laid-Open No. 2005-75982, Japanese Patent Application Laid-Open No. 2005-95759} can be used. Can be used. Of these, a cross-linking agent having two or more ethylenically unsaturated groups is preferable from the viewpoint of absorption characteristics and the like, more preferably a poly (meth) allyl ether of a polyol having 2 to 10 carbon atoms, and particularly preferably triallyl shear. Nurate, triallyl isocyanurate, tetraallyloxyetane and pentaerythritol triallyl ethers, most preferably pentaerythritol triallyl ethers.

The content (mol%) of the cross-linking agent (b) unit is based on the number of moles of the water-soluble vinyl monomer (a1) unit and the hydrolyzable vinyl monomer (a2) unit, and other vinyl monomers (a3) are also used. In the case, 0.001 to 5, more preferably 0.005 to 3, and particularly preferably 0.01 to 1, based on the total number of moles of the 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 a known aqueous solution polymerization {adiabatic polymerization, thin film polymerization, spray polymerization, etc .; JP-A-55-133413, etc.} or a known reverse phase suspension polymerization {Japanese Patent Publication No. 54-30710. It can be produced in the same manner as in Japanese Patent Application Laid-Open No. 56-26909, Japanese Patent Application Laid-Open No. 1-5808, etc.}. Of the polymerization methods, a solution polymerization method is preferable, and an aqueous solution polymerization method is particularly preferable because it is not necessary to use an organic solvent or the like and is advantageous in terms of production cost.

Hydrous gel obtained by polymerization {Consists of crosslinked polymer and water. } Can be shredded as needed. The size (longest diameter) of the gel after shredding is preferably 50 μm to 10 cm, more preferably 100 μm to 2 cm, and particularly preferably 1 mm to 1 cm. Within this range, the drying property in the drying step is further improved.

Shredding can be performed by a known method and can be shredded using a known shredding device {for example, a Beck's mill, a rubber chopper, a pharma mill, a minced machine, an impact crusher and a roll crusher}. ..

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

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

The content and moisture of the organic solvent are determined by an infrared moisture measuring instrument {JE400 manufactured by KETT Co., Ltd .: 120 ± 5 ° C., 30 minutes, atmospheric humidity 50 ± 10% RH before heating, lamp specification 100V, 40W. } To obtain the weight loss of the measurement sample before and after heating.

As a method for distilling off the solvent (including water), a method of distilling off (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 method, freeze drying method, infrared drying method, decantation, filtration, etc. can be applied.

The crosslinked polymer (A1) can be pulverized after drying. The crushing method is not particularly limited, and a known crushing device {for example, a hammer type crusher, an impact type crusher, a roll type crusher, a shet airflow type crusher} or the like can be used. The particle size of the pulverized crosslinked polymer can be adjusted by sieving or the like, if necessary.

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

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

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

Further, since the absorption performance is better when the content of the fine particles is small, the content of the fine particles of 106 μm or less (preferably 150 μm or less) in the total particles is preferably 3% by weight or less, more preferably 1% by weight or less. Is. The content of the fine particles can be determined using the plot prepared when determining the weight average particle size described above.

The span value of the crosslinked polymer (A1) is preferably 1.0 or less, particularly preferably 0.9 or less, and 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 the above formula 1, D (10%), D (50%) and D (90%) are all particle diameters represented by "μm" and can be measured by a sieving particle size measuring method using a standard sieve. D (10%) has the smallest particle size when the water-absorbent resin particles are classified by a standard sieve and then the water-absorbent resin particles are arranged in the order of particle size, with the total weight of the classified particles being 100% by weight. It means a particle size in which the cumulative weight fraction from the particles is 10% by weight. Similarly, D (50%) means a particle size having a cumulative weight fraction of 50% by weight, and D (90%) means a particle size having 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 further classifying with water-absorbent resin particles.
The method for adjusting the particle size distribution is not particularly limited, and the particle size distribution can be adjusted by a method of mixing the particles on each sieve at a predetermined ratio or the like.

The apparent density (g / ml) of the crosslinked polymer (A1) 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 absorption performance is further improved.
The apparent density is measured at 25 ° C. in accordance with JIS K7365: 1999.

The shape of the crosslinked polymer (A1) is not particularly limited, and examples thereof include amorphous crushed form, phosphorus flaky form, pearl form, and rice granule. Of these, the amorphous crushed form is preferable from the viewpoint that it is easily entangled with the fibrous material for use in disposable diapers and the like and there is no concern that it will fall off from the fibrous material.

The crosslinked polymer (A) 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.

Hydrocarbon-containing hydrophobic substances (C1) include polyolefin resins, polyolefin resin derivatives, polystyrene resins, polystyrene resin derivatives, waxes, long-chain fatty acid esters, long-chain fatty acids and salts thereof, long-chain aliphatic alcohols, and long chains. 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 10 to 1,000,000 {for example, polyethylene, polypropylene, polyisoprene, poly (ethylene-isoprene), isoprene, etc.} can be mentioned.

As the polyolefin resin derivative, a polymer having a weight average molecular weight of 10 to 1,000,000 in which a carboxy group (-COOH) or 1,3-oxo-2-oxapropylene (-COOCO-) is introduced into a polyolefin resin {for example, polyethylene heat Attenuated product, heat-attenuated polypropylene, maleic acid-modified polyethylene, chlorinated polyethylene, maleic acid-modified polypropylene, ethylene-acrylic acid copolymer, ethylene-maleic anhydride copolymer, isobutylene-maleic anhydride copolymer, maleic acid Polybutadiene, ethylene-vinyl acetate copolymer, and maleic acid of ethylene-vinyl acetate copolymer, etc.} can be mentioned.

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

As the polystyrene resin derivative, a polymer having a weight average molecular weight of 10 to 1,000,000 in which styrene is an essential constituent monomer (the content of styrene is at least 50% by weight based on the weight of the polystyrene derivative) {for example, styrene- Maleic anhydride copolymers, styrene-butadiene copolymers, styrene-isobutylene copolymers, etc.} can be mentioned.

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

Examples of long-chain fatty acid esters include esters of fatty acids containing an alkyl group 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 lauric acid monoester, glycerin stearate monoester, glycerin oleic acid monoester, pentaerythlit lauric acid monoester, pentaerythlit stearate monoester, pentaerythlit oleic acid monoester, sorbit laurin Acid monoester, sorbit stearic acid monoester, sorbit oleic acid monoester, sucrose palmitate (sucrose palmitate monoester, sucrose palmitate diester, sucrose palmitate triester, etc.), sucrose palmitate (sucrose stearate) Sucrose stearic acid monoester, sucrose stearic acid diester, sucrose stearic acid triester, etc.), sucrose erucic acid ester, beef fat, etc.}. Of these, sucrose stearic acid esters (sucrose stearic acid monoesters, sucrose stearic acid diesters, sucrose stearic acid triesters, etc.) and sucrose palmitate (sucrose palmitate) (from the viewpoint of liquid diffusivity of absorbable articles, etc.) Sucrose palmitic acid monoester, sucrose palmitic acid diester, sucrose palmitic acid triester, etc.), sucrose erucic acid ester are preferable, and sucrose stearic acid ester (sucrose stearic acid monoester, sucrose stearic acid) is more preferable. Diester, sucrose stearic acid triester, etc.) and sucrose erucic acid ester.

Examples of long-chain fatty acids and salts thereof include fatty acids containing an alkyl group having 8 to 25 carbon atoms {for example, lauric acid, palmitic acid, stearic acid, oleic acid, dimer acid, behenic acid, etc.}. Examples of the salt include salts with calcium, magnesium or aluminum (hereinafter abbreviated as Ca, Mg, Al) {for example, Ca palmitate, Al palmitate, Ca stearate, Mg stearate, Al stearate, etc.}. From the viewpoint of liquid diffusivity of the absorbent article, Ca stearate, Mg stearate, and Al stearate are preferable, and Mg stearate is more preferable.

Examples of the long-chain fatty alcohol include aliphatic alcohols containing an alkyl group having 8 to 25 carbon atoms {for example, lauryl alcohol, palmityl alcohol, stearyl alcohol, oleyl alcohol, etc.}. From the viewpoint of liquid diffusivity of the absorbent article, palmityl alcohol, stearyl alcohol, and oleyl alcohol are preferable, and stearyl alcohol is more preferable.

Examples of long-chain fatty acid amides include fatty acid amides containing an alkyl group having 8 to 25 carbon atoms {for example, lauric acid amide, palmitic acid amide, stearic acid amide, oleic acid amide, erucic acid amide, etc.} and 8 to 25 carbon atoms. Fatty acid bisamides {ethylene bislauric acid amides, ethylene bisstearic acid amides, hexamethylene bisstearic acid amides, N, N'-distearyl adipate amides, ethylene bisoleic acid amides, ethylene biserucic acid amides, etc.} Be done. Ethylene bisstearic acid amide is preferable from the viewpoint of liquid diffusivity of the absorbent article.

As a mixture of two or more of these, a mixture of a long-chain fatty acid ester and a long-chain fatty acid {for example, a mixture of a sucrose stearic acid ester and a stearyl alcohol}, a long-chain fatty acid ester and a long-chain fatty acid, and the like thereof. Examples include a mixture of salts {for example, a mixture of sucrose stearic acid ester and Mg stearyl acid}.

Examples of the hydrophobic substance (C2) having a polysiloxane structure include polydimethylsiloxane, polyether-modified polysiloxane {polyoxyethylene-modified polysiloxane and poly (oxyethylene / oxypropylene) -modified polysiloxane, etc.}, carboxy-modified polysiloxane, and the like. Includes organic polysiloxanes such as epoxy-modified polysiloxanes, amino-modified polysiloxanes, alkoxy-modified polysiloxanes and mixtures thereof.

The position of the organic group (modifying group) of the modified silicone {polyether-modified polysiloxane, carboxy-modified polysiloxane, epoxy-modified polysiloxane, amino-modified polysiloxane, etc.} is not particularly limited, but is a side chain of polysiloxane, polysiloxane. It may be either both ends of, one end of polysiloxane, or both side chains and both ends of polysiloxane. Of these, from the viewpoint of absorption characteristics and the like, both the side chain of polysiloxane and the side chain of polysiloxane and both ends are preferable, and more preferably both the side chain of polysiloxane and both ends.

Examples of the organic group (modifying group) of the polyether-modified polysiloxane include a polyoxyethylene group, a group containing a poly (oxyethylene / oxypropylene) group, and the like. The content (pieces) of the oxyethylene group and / or the oxypropylene group contained in the polyether-modified polysiloxane is preferably 2 to 40, more preferably 5 to 30, and particularly preferably 5 to 30 per molecule of the polyether-modified polysiloxane. 7 to 20, most preferably 10 to 15. Within this range, the absorption characteristics are further improved. When an oxyethylene group and an oxypropylene group are contained, the content (% by weight) of the oxyethylene group 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.

The polyether-modified polysiloxane is easily available on the market, and for example, the following products {modified position, type of oxyalkylene} can be preferably exemplified.
-KF-945 {side chain, oxyethylene and oxypropylene}, KF-6020 {side chain, oxyethylene and oxypropylene}, X-22-6191 {side chain, oxyethylene and oxypropylene} manufactured by Shin-Etsu Chemical Industry Co., Ltd. , X-22-4952 {side chain, oxyethylene and oxypropylene}, X-22-4272 {side chain, oxyethylene and oxypropylene}, X-22-6266 {side chain, oxyethylene and oxypropylene}

FZ-2110 {both ends, oxyethylene and oxypropylene}, FZ-2122 {both ends, oxyethylene and oxypropylene}, FZ-7006 {both ends, oxyethylene and oxypropylene}, manufactured by Toray Dow Corning Co., Ltd. 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 group (modifying group) of the carboxy-modified polysiloxane includes a group containing a carboxy group, and the organic group (modifying group) of the epoxy-modified polysiloxane includes a group containing an epoxy group and is amino-modified. Examples of the organic group (modifying group) of the polysiloxane include a group containing an amino group (1, 2, 3rd-order amino group) and the like. The organic group (modifying group) content (g / mol) of these modified silicones is preferably 200 to 11000, more preferably 600 to 8000, and particularly preferably 1000 to 4000, as a carboxy equivalent, an epoxy equivalent or an amino equivalent. Is. Within this range, the absorption characteristics are further improved. The carboxy equivalent is measured according to "16. Total Acid Value Test" of JIS C2101: 1999. The epoxy equivalent is determined in accordance with JIS K7236: 2001. The amino equivalent is measured in accordance with JIS K2501: 2003 "8. Potentiometric titration method (base value / hydrochloric acid method)".

The carboxy-modified polysiloxane is easily available on the market, and for example, the following products {modified 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}

-Toray Dow Corning 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 for example, the following products {modified position, epoxy equivalent} can be preferably exemplified.
-Shinetsu Chemical Industry 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}

FZ-3720 {side chain 1200}, BY 16-839 {side chain 3700}, SF 8411 {side chain 3200}, SF 8413 {side chain 3800}, SF 8421 {manufactured by Toray Dow Corning Co., Ltd. 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 for example, the following products {modified position, amino equivalent} can be preferably exemplified.
-KF-865 {side chain 5000}, KF-864 {side chain 3800}, KF-859 {side chain, 6000}, KF-393 {side chain, 350}, KF-860 manufactured by Shin-Etsu Chemical Industry Co., Ltd. {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 1500}, KF-8012 {both ends 2200}, KF-8008 {both ends 5700}, X-22-1660B-3 {both ends 2200}, KF-857 {side chains, 2200}, KF −8001 {side chain, 1900}, KF-862 {side chain, 1900}, X-22-9192 {side chain, 6500}

-Toray Dow Corning 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}

Examples of these mixtures include a mixture of polydimethylsiloxane and carboxyl-modified polysiloxane, a mixture of polyether-modified polysiloxane and amino-modified polysiloxane, and the like.

The viscosity (mPa · s, 25 ° C.) of the hydrophobic substance having a polysiloxane structure is preferably 10 to 5000, more preferably 15 to 3000, and particularly preferably 20 to 1500. Within this range, the absorption characteristics are further improved. The viscosity is defined in JIS Z8803-1991 “Liquid Viscosity” 9. Conical and Conical-Measured according to the viscosity measurement method using a flat plate type rotational viscometer {For example, an E-type viscometer whose temperature is adjusted to 25.0 ± 0.5 ° C (RE80L manufactured by Toki Sangyo Co., Ltd., radius 7 mm) It is measured using a conical cone) angle 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 the DW method) can be easily controlled. , It is preferable that the water-absorbent resin of the present invention contains a hydrophobic substance (C). The absorption rate pattern of the water-absorbent resin particles can be arbitrarily adjusted according to the hydrophobic strength of the hydrophobic substance (C) and the amount of addition. The strength of hydrophobicity can be determined by a known method such as a hydrophilic balance (HLB value).
The HLB value means a hydrophilic-lipophilic balance (HLB) value, and is obtained by the Oda method (Introduction to Surfactants, p. 212, Takehiko Fujimoto, published by Sanyo Chemical Industries, 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 preferable, and sucrose stearic acid ester is more preferable, from the viewpoint of liquid diffusivity of the absorbent article. , Mg stearate, ethylene bisstearic acid amide. Since long-chain fatty acids generally have a carbon number distribution, when expressed as stearic acid, it means that they are modified long-chain fatty acids 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, and particularly preferably 0.08 to 1.0, based on the weight of the crosslinked polymer (A1). Is 0.08 to 0.50. Within this range, the liquid diffusivity of the absorbent article and the liquid drainability from the non-woven fabric are likely to be compatible, and the anti-fog resistance is excellent, which is preferable.

Further, the water-absorbent resin particles of the present invention preferably contain a hydrophobic substance (C) and a penetrant (D). When the water-absorbent resin particles contain the hydrophobic substance (C) and the penetrant (D), it is preferable to use the hydrophobic substance (C) and the penetrant (D) at the same time. By using the penetrant (D) in combination with the hydrophobic substance (C), it becomes easy to achieve both the absorption amount by the DW method and the absorption rate by the lockup method. Examples of the penetrant (D) include a nonionic surfactant (D1) and an anionic surfactant (D2), which have a structure of a surfactant having excellent permeability, that is, an appropriate number of carbon atoms (8 to 18). It preferably has a long-chain alkyl structure.

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

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

Examples of the anionic surfactant (D2) include hydrocarbon-based ether carboxylic acids having 8 to 18 alkyl group carbon atoms or salts thereof, [polyoxyethylene (polymerization degree = 1 to 100) sodium lauryl ether acetate, and polyoxyethylene (polyoxyethylene). Degree of polymerization = 1-100) Sodium lauryl sulfosuccinate, etc.], Hydrocarbon sulfates with 8 to 18 carbon atoms [Sodium lauryl sulfate, polyoxyethylene (degree of polymerization = 1-100) Sodium lauryl sulfate, polyoxyethylene (Degree of polymerization = 1-100) Sodium lauryl sulfate triethanolamine], hydrocarbon sulfonates with alkyl group carbon number 8-18 [sodium dodecylbenzene sulfonate, etc.] and hydrocarbon phosphate esters with carbon number 8-18 Examples thereof include salts [sodium lauryl phosphate, polyoxyethylene (polymerization degree = 1 to 100) sodium lauryl ether phosphate, etc.], fatty acid salts [sodium lauryl sulfate, triethanolamine laurate, etc.] and the like.

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

As a method of 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, with the crosslinked polymer (A1). There is no limitation as long as it is mixed so that the hydrophobic substance (C) has a sandwich structure}. However, the hydrophobic substance (C) is preferably mixed with the hydrogel of (A1) or the polymer solution of (A1), not the dried product of the crosslinked polymer (A1), and more preferably of (A1). It is to be mixed with a hydrogel. 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, but during the polymerization step, immediately after the polymerization step, and the hydrogel. Examples thereof include during crushing (minced) and during drying of a hydrogel. Of these, from the viewpoint of leakage resistance of the absorbent article, it is preferable immediately after the polymerization step and during the crushing (mincing) step of the hydrogel, and more preferably during the crushing (mincing) step of the hydrogel.

When the crosslinked polymer (A1) is obtained by the reverse phase suspension polymerization method or emulsion polymerization, the timing of mixing the hydrophobic substances (C) and (A1) is not particularly limited, but during the polymerization step {(C) In the presence of (A1)}, 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 for the polymerization , Drying of hydrogel, etc. Of these, from the viewpoint of leakage resistance of the absorbent article, it is preferable, more 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 for the polymerization. Is during the polymerization step and immediately after the polymerization step.

When mixing during drying of the hydrogel, known devices such as a Beck's mill, a rubber chopper, a pharma mill, a minced machine, an impact crusher and a roll crusher can be used as the mixing device. When mixing in a polymer solution, a device having a relatively high stirring power such as a homomixer or a biomixer can be used. Further, when mixing while drying the hydrogel, a kneading device such as an SV mixer can also be used.

The mixing temperature (° C.) is preferably 20 to 100, more preferably 40 to 90, and particularly preferably 50 to 80. Within this range, uniform mixing becomes easier, and the absorption characteristics become even better.

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 polymer solution of the crosslinked polymer (A1). It is also possible to form a connecting portion while precipitating (C) as the polymerization of (A1) progresses. The polymerization method is the same as that of the crosslinked polymer (A1) except that the polymerization is carried out in the presence of the hydrophobic substance (C). The connecting portion means a sandwich structure composed of (A1)-(C)-(A1) formed by contacting the hydrophobic substance (C) and the crosslinked polymer (A1). In this case, the crosslinked polymer (A1) existing inside the absorbent resin particles is linked to another crosslinked polymer (A1) via the hydrophobic substance (C) existing on the surface thereof. It becomes a structure.

When the penetrant (D) is used in combination with the hydrophobic substance (C), the penetrant (D) can be used at the same time as the timing of mixing the hydrophobic substance (C) described above. The penetrant (D) may be used after being mixed with the hydrophobic substance (C) in advance, or may be added and used separately at the same time.

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

When a solvent (including an organic solvent and / or water) is used for producing the water-absorbent resin particles, the solvent can be distilled off after the polymerization. When the solvent contains an organic solvent, the content (% by weight) of the organic solvent after distillation is preferably 0 to 10, more preferably 0 to 5, and particularly preferably 0, based on the weight of the water-absorbent resin particles. ~ 3, most preferably 0 to 1. Is. Within this range, the absorption performance (particularly the amount of water retention) of the water-absorbent resin particles is further improved.

When water is contained in the solvent, the water content (% by weight) after distillation is preferably 0 to 20, more preferably 1 to 10, and particularly preferably 2 to 9, based on the weight of the water-absorbent resin particles. Most preferably, it is 3 to 8. Within this range, the absorption performance (particularly the amount of water retained) and the breakability of the water-absorbent 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. Known examples of the surface cross-linking agent include JP-A-59-189103, JP-A-58-180233, JP-A-61-16903, JP-A-61-21305, and JP-A-61-252212. No., JP-A-51-136588, JP-A-61-257235, etc.} Surface cross-linking agents {multivalent glycidyl, polyhydric alcohol, polyvalent amine, polyvalent aziridine, polyvalent isocyanate, silane coupling Agents and polyvalent metals, etc.} can be used. Of these surface cross-linking agents, polyhydric glycidyl, polyhydric alcohols and polyhydric amines are preferable, and polyhydric glycidyl and polyhydric alcohols are particularly preferable, and polyhydric glycidyl is most preferable, from the viewpoint of economic efficiency and absorption characteristics. Ethylene glycol diglycidyl ether is preferred.

When the surface cross-linking treatment is performed, the amount (% by weight) of the surface cross-linking agent used can be variously changed depending on the type of the surface cross-linking agent, the conditions for cross-linking, the target performance, etc. When water-soluble vinyl monomer (a1), hydrolyzable vinyl monomer (a2), and other vinyl monomers (a3) are also used, the total of (a1) to (a3) and the cross-linking agent (b) It is preferably 0.001 to 3, more preferably 0.005 to 2, and particularly preferably 0.01 to 1, based on the weight of the above.

When the surface cross-linking treatment is performed, the method of the surface cross-linking treatment is a known method {for example, Japanese Patent No. 3648553, Japanese Patent Application Laid-Open No. 2003-165883, Japanese Patent Application Laid-Open No. 2005-75982, Japanese Patent Application Laid-Open No. 2005-95759}. Can be applied.

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

The smaller the content of the fine particles, the better the absorption performance, and the content of the fine particles of 106 μm or less in the total particles is preferably 3% by weight or less, and more preferably the content of the fine particles of 150 μm or less in the total particles is 3% by weight. It is as follows. The content of the fine particles can be determined using the plot prepared when determining the weight average particle size described above. For pulverization and particle size adjustment, the same method as for the crosslinked polymer (A1) can be adopted.

In the case of pulverization, 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 distribution of the particle size of the water-absorbent resin particles is narrowed, so that spot absorption is less likely to occur and particles that are not absorbed are less likely to be formed, so that the liquidability from the surface of the non-woven fabric is improved. 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 anti-fog resistance of the absorbent article becomes even better. 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 depending on the production conditions such as the gel crushing method and the drying conditions.

The shape of the water-absorbent resin particles is not particularly limited, and examples thereof include amorphous crushed particles, phosphorus flakes, pearl particles, and rice granules. Of these, the amorphous crushed form is preferable from the viewpoint that it is easily entangled with the fibrous material for use in disposable diapers and the like and there is no concern that it will fall off from the fibrous material.

The absorption amount (M) (ml / g) of the water-absorbent resin particles of the present invention by the DW method is preferably 10 to 15 after 1 minute from the viewpoint of the dryness of the absorbent article. Is 11 to 14, more preferably 12 to 13. The amount of absorption (M2) after 5 minutes is 45 to 55, preferably 46 to 54, and more preferably 47 to 53. Within this range, the dryness of the absorbent article becomes even better. The amount absorbed by the DW method can be determined by adjusting the SPAN, the apparent density of the water-absorbent resin particles, the weight average particle size of the water-absorbent resin particles, the hydrophobic substance, the surfactant, etc. within the above-mentioned preferable ranges. Can be adjusted to a preferable range. Specifically, if 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 penetrant used in combination with the hydrophobic substance is reduced, the respective actions become almost independent. It has the effect of lowering the absorption amount (M1) after 1 minute, and can be adjusted as appropriate. The absorption amount (M2) after 5 minutes tends to increase as the water retention amount increases, in addition to the operating factor of the absorption amount (M1) after 1 minute. If the absorption amount (M1) after 1 minute is less than 10, the initial absorption amount is insufficient and the dryness deteriorates, and if it is higher than 15, the initial absorption amount is too high and is absorbed when it is used as an absorber. Is biased and the dryness deteriorates. If the amount of absorption after 5 minutes is less than 45, the dryness is deteriorated because the amount of absorption is insufficient, and if it is higher than 55, the amount of absorption in the absorber is biased and the dryness is deteriorated.

The DW (Demand Wetting) method is a measurement method performed in a room at 25 ± 2 ° C. and a humidity of 50 ± 10% using the apparatus shown in FIG. The measuring device shown in FIG. 1 includes a burette portion (2) {scale capacity 50 ml, length 86 cm, inner diameter 1.05 cm,}, a conduit {inner diameter 7 mm}, and a measuring table (6). The burette portion (2) has a rubber stopper (1) at the upper part, an intake introduction pipe (9) {tip inner diameter 3 mm} and a cock (7) at the lower part, and further, the upper part of the intake introduction pipe (9) is connected. There is a cook (8). A duct is attached from the burette portion (2) to the measuring table (6). In the central part of the measuring table (6), there is a hole with a diameter of 3 mm as a physiological saline supply part, and a conduit is connected to the hole.

Using the measuring device having this configuration, first, the cock (7) of the burette portion (2) and the cock (8) of the air introduction pipe (9) are closed, and a predetermined amount of physiological saline (salt) adjusted to 25 ° C. (Concentration 0.9% by weight) is inserted from the upper part of the burette part (2), the upper part of the burette is plugged with the rubber stopper (1), and then the cock (7) of the burette part (2) and the cock of the air introduction pipe (9). Open (8). Next, after wiping off the physiological saline overflowing on the measuring table (6), the upper surface of the measuring table (6) and the water surface of the physiological saline coming out from the conduit port in the center of the measuring table (6) are contacted. Adjust the height of the measuring table (6) so that the height is the same. While wiping the saline solution from the saline supply section, adjust the water level of the saline solution in the burette section (2) to the top of the burette section (2) scale (0 ml line).

Subsequently, the cock (7) of the burette part (2) and the cock (8) of the air introduction pipe (9) are closed, and a plain weave nylon mesh (on the measuring table (6) so that the physiological saline supply part is at the center) 5) Place (opening 63 μm, 5 cm × 5 cm) on this plain weave nylon mesh (5), and 0.50 g in a range of 2.7 cm in diameter centered on the physiological saline supply part of the measuring table (6). The water-absorbent resin particles (4) of No. 1 are uniformly sprayed. After that, the cock (7) of the burette portion (2) and the cock (8) of the air introduction pipe (9) are opened.

When the water-absorbent resin particles (4) start to absorb water and the first bubble introduced from the air introduction pipe (9) reaches the water surface of the physiological saline in the burette portion (2) (burette portion (2)). The measurement start time is set as the measurement start time (when the water level of the physiological saline solution in the burette is lowered), and the amount of decrease in the physiological saline solution (3) in the burette portion (2) (the physiology of the water-absorbing resin particles (4) absorbing water) is continuously set. (Saline amount) M (ml) is read. The amount of water-absorbent resin particles (4) absorbed after a lapse of a predetermined time from the start of water absorption is calculated by the following formula.

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

The water retention amount (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 amount of the water-absorbent resin particles is measured by the following method.

<Measurement method of water retention of water-absorbent resin particles>
Put 1.00 g of the measurement sample in a tea bag (length 20 cm, width 10 cm) made of a nylon net with an opening of 63 μm (JIS Z8801-1: 2006), and put 1,000 ml of physiological saline (salt concentration 0.9% by weight). After immersing the sample in it for 1 hour without stirring, it was hung for 15 minutes to drain water. Then, the tea bag is placed in a centrifuge and centrifuged at 150 G for 90 seconds to remove excess physiological saline, the weight (h1) including the tea bag is measured, and the amount of water retained is calculated from the following formula. The temperature of the physiological saline used and the measurement atmosphere shall be 25 ° C ± 2 ° C. The weight of the tea bag after centrifugal dehydration is measured in the same manner as above except that the measurement sample is not used (h2).

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

The absorption rate measured by the lock-up method of the water-absorbent 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 liquidation from the surface of the non-woven fabric. .. note that. The absorption rate of the water-absorbent resin particles by the lock-up method is measured by the following method.

<Absorption rate by lock-up method of water-absorbent resin>
Place 1.000 g of the measurement sample in a 100 ml tall beaker with a flat bottom specified in JIS R 3503. At this time, the upper surface of the water-absorbent resin placed in the beaker should be horizontal. Next, 50 g of deionized water whose temperature has been adjusted to 23 ° C. ± 2 ° C. is weighed in a 100 ml glass beaker, and carefully and quickly poured into a 100 ml beaker containing a water-absorbent resin. The time measurement is started at the same time when 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 does not seep out from the surface of the water-absorbent resin, and this time (unit: seconds) is used as the lock-up method. Let it be the absorption rate measured in.

The water-absorbent resin particles of the present invention can be used as an absorber together with the non-woven fabric.

The non-woven fabric used in the present invention is not particularly limited as long as it is a known non-woven fabric, but from the viewpoint of liquid permeability, flexibility and strength when used as an absorber, 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, etc. Examples thereof include non-woven fabrics produced by mixing hemp, pulp (polyethylene) fibers and the like. Among these non-woven fabrics, synthetic fiber non-woven fabrics are preferable, and more preferably rayon fibers, polyolefin fibers, and polyester fibers, from the viewpoint of increasing the strength of the absorber. These non-woven fabrics may be a non-woven fabric of the fibers alone or a non-woven fabric in which two or more kinds of fibers are combined.

The non-woven fabric used in the present invention is a non-woven fabric that is moderately bulky and has a large amount of grain from the viewpoint of imparting good liquid permeability, flexibility, strength and cushioning property to the absorber and accelerating the liquid permeation rate of the absorber. Is preferable. The basis weight is preferably 5 to 300 g / m ² , more preferably 8 to 200 g / m ² , still more preferably 10 to 100 g / m ² , and even more preferably 11 to 50 g / m ^2. Is. The thickness of the non-woven 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 non-woven fabric and, if necessary, an adhesive, and if desired, further contains hydrophilic fibers such as fluff pulp. For example, an adhesive is applied. After uniformly spraying the water-absorbent resin on the non-woven fabric, the non-woven fabric coated with the adhesive is further layered if necessary, and if necessary, it is formed by heating under pressure. It is also formed by uniformly spraying a mixed powder of a water-absorbent resin and an adhesive on a non-woven fabric, stacking the non-woven fabrics, and heating the non-woven fabric near the melting temperature of the adhesive, if necessary, under pressure. NS. Fluff pulp can be uniformly sprayed between the non-woven fabric and the water-absorbent resin particles.
In the absorber of the present invention, the absorption layers may be stacked to form two or more layers.

Examples of the adhesive used in the present invention include rubber-based adhesives such as natural rubber-based, butyl rubber-based, and polyisoprene; styrene-isoprene block copolymer (SIS), styrene-butadiene block copolymer (SBS), and the like. Styrene-based elastomer adhesives such as styrene-isobutylene block copolymer (SIBS), 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) adhesives; copolymerized nylon, dimer Polyamide-based adhesives such as acid-based polyamides; polyolefin-based adhesives such as polyethylene, polypropylene, atactic polypropylene, and copolymerized polyolefins; polyester-based adhesives such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and copolymerized polyesters. Etc., and acrylic adhesives. In the present invention, an ethylene-vinyl acetate copolymer adhesive, a styrene-based elastomer adhesive, and a polyolefin can be obtained from the viewpoint that the adhesive strength is strong and the peeling of the non-woven fabric and the dissipation of the water-absorbent resin in the water-absorbent sheet structure can be prevented. Based adhesives and polyester adhesives are preferable. These adhesives may be used alone or in combination of two or more.

When a heat-melt type adhesive is used, 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 non-woven fabric and preventing thermal deterioration and deformation of the non-woven fabric. Is preferable, 70 to 150 ° C. is more preferable, and 75 to 125 ° C. is even more preferable.

The content ratio of the adhesive in the absorber is preferably in the range of 0.05 to 2.0 times, more preferably 0.08 to 1.5 times the content of the water-absorbent resin (mass basis), and is 0. The range of 1 to 1.0 times is more preferable. From the viewpoint of preventing peeling of the non-woven fabric and dissipation of the water-absorbent resin by sufficient adhesion and enhancing the morphological retention of the absorber, the content ratio of the adhesive is preferably 0.05 times or more, and the adhesion becomes too strong. From the viewpoint of avoiding the inhibition of swelling of the water-absorbent resin and improving the permeation rate and liquid leakage of the water-absorbent sheet structure, the content ratio of the adhesive is preferably 2.0 times or less.

Weight% of water-absorbent resin particles based on the weight of the water-absorbent resin particles of the present invention and the above-mentioned non-woven fabric {weight of absorbent resin particles / (weight of water-absorbent resin particles + weight of non-woven fabric)} is 40% by weight or more. Is more preferable, and more preferably 60% by weight or more, and particularly preferably 80% by weight.

Further, it is preferable that the above-mentioned absorber constitutes an absorbent article {paper diaper, sanitary napkin, etc.}. As for the method for producing the absorbent article, the absorbers of known ones {Japanese Patent Laid-Open No. 2003-225565, JP-A-2006-131767, JP-A-2005-097569, etc.} are changed from the above-mentioned absorbers. Is similar.

Hereinafter, the present invention will be further described with reference to Examples and Comparative Examples, but the present invention is not limited thereto. Unless otherwise specified, parts indicate parts by weight and% indicates% by weight. The absorption amount by the DW method, the water retention amount of the water-absorbent resin particles, and the absorption rate by the lock-up method of the water-absorbent resin particles were measured by the above-mentioned methods.

<Manufacturing example 1>
Water-soluble vinyl monomer (a1-1) {acrylic acid, manufactured by Mitsubishi Chemical Co., Ltd., 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 mol parts) and 340.27 parts of deionized water were kept at 3 ° C. while stirring and mixing. After influxing nitrogen into this mixture to reduce the amount of dissolved oxygen to 1 ppm or less, 0.62 parts of a 1% aqueous hydrogen peroxide solution and 1.1625 parts of a 2% ascorbic acid aqueous solution and 2% of 2,2'-azobis [ 2.325 parts of an aqueous solution of 2-methyl-N- (2-hydroxyethyl) -propionamide] was added and mixed to initiate polymerization. After the temperature of the mixture reached 90 ° C., a hydrogel (1) was obtained by polymerizing at 90 ± 2 ° C. for about 5 hours.

Next, 502.27 parts of this hydrogel (1) was shredded with a mincing machine (12VR-400K manufactured by ROYAL), and 128.42 parts of a 48.5% sodium hydroxide aqueous solution was added and mixed, followed by hydrophobicity. 0.19 parts of the substance (C-1) {Mg stearate} was added and mixed, shredded four times, and then dried in a ventilation type dryer {150 ° C., wind speed 2 m / sec} to obtain a dried product. .. After crushing the dried product with a juicer mixer (OSTERIZER BLENDER manufactured by Oster), the dried product is sieved and the dried product on each sieve is collected separately so that the weight average particle size is 350 μm and the SPAN is 0.8. Crosslinked polymer particles (A1-1) were obtained by mixing the dried product on the sieve.

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

<Manufacturing example 3>
"0.19 parts of hydrophobic substance (C-1)" was changed to "0.29 parts of hydrophobic substance (C-1)", and "weight average particle size was 350 μm, SPAN was 0.8" was changed to "weight". 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 ”.

<Manufacturing example 4>
"0.19 parts of hydrophobic substance (C-1)" was changed to "0.38 parts of hydrophobic substance (C-1)", and "weight average particle size was 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 ”.

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

<Manufacturing example 6>
Crosslinked polymer particles (A1-6) in the same manner as in Production Example 1 except that "weight average particle size is 350 μm and SPAN is 0.8" is changed to "weight average particle size is 350 μm and SPAN is 1.2". Got

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

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

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

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

<Manufacturing example 11>
"0.19 parts of hydrophobic substance (C-1)" was changed to "0.29 parts of hydrophobic substance (C-1)", and "weight average particle size was 350 μm, SPAN was 0.8" was changed to "weight". 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 ”.

<Manufacturing example 12>
Crosslinked polymer particles (A1-12) in the same manner as in Production Example 1 except that "weight average particle size is 350 μm and SPAN is 0.8" is changed to "weight average particle size is 370 μm and SPAN is 1.2". Got

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

<Manufacturing example B1>
"Hydrophobic substance (C-1) 0.19 part" is changed to "Hydrophobic substance (C-2) {sucrose erucic acid ester, Ryoto (registered trademark. Hereinafter, notation omitted) sugar ester ER manufactured by Mitsubishi Chemical Foods Co., Ltd.) Production Example 1 except that "-290} 0.10 part" was changed and "weight average particle size was changed to 350 μm and SPAN was 0.8" to "weight average particle size was changed to 355 μm and SPAN was 0.7". Crosslinked polymer particles (A1-B1) were obtained in the same manner as above.

<Manufacturing example B2>
"Hydrophobic substance (C-1) 0.19 parts" changed to "Hydrophoic substance (C-2) {sucrose erucic acid ester, Ryoto sugar ester ER-290} 0.30 parts manufactured by Mitsubishi Chemical Foods Co., Ltd." The crosslinked polymer particles (weight average particle size: 350 μm, SPAN: 0.8” were changed to “weight average particle size: 321 μm, SPAN: 0.8” in the same manner as in Production Example 1. A1-B2) was obtained.

<Manufacturing example B3>
"0.19 part of hydrophobic substance (C-1)" to "0.10 part of hydrophobic substance (C-3) {sucrose stearic acid ester, Ryoto sugar ester S-370} manufactured by Mitsubishi Chemical Foods Co., Ltd." The crosslinked polymer particles (weight average particle size: 350 μm, SPAN: 0.8” were changed to “weight average particle size: 355 μm, SPAN: 0.7” in the same manner as in Production Example 1. A1-B3) was obtained.

<Manufacturing example B4>
"Hydrophobic substance (C-1) 0.19 parts" changed to "Hydrophoic substance (C-3) {sucrose stearic acid ester, Ryoto sugar ester S-370} 0.30 parts manufactured by Mitsubishi Chemical Foods Co., Ltd." Crosslinked polymer particles (weight average particle size: 350 μm, SPAN: 0.8” changed to “weight average particle size: 321 μm, SPAN: 0.8” in the same manner as in Production Example 1. A1-B4) was obtained.

<Manufacturing example B5>
Changed "0.29 parts of hydrophobic substance (C-1)" to "0.20 parts of hydrophobic substance (C-4) {ethylene bisdistearate amide, Slipax (registered trademark) E} manufactured by Mitsubishi Chemical Co., Ltd." , And "Weight average particle size 350 μm, SPAN 0.8" was changed to "Weight average particle size 355 μm, SPAN 0.7", but the crosslinked polymer particles (A1- B5) was obtained.

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

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

<Manufacturing example B8>
"Hydrophobic substance (C-1) 0.19 parts" to "Hydrophobic substance (C-2) 0.30 parts and penetrant (D-1) {polyoxyethylene alkyl ether, Sanyo Kasei Co., Ltd. Naroacty CL Production Example 1 except that "-20} 0.20 parts" was changed and "weight average particle size was changed to 340 μm and SPAN was 0.8" to "weight average particle size was changed to 321 μm and SPAN was 0.8". Crosslinked polymer particles (A1-B8) were obtained in the same manner as above.

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

<Manufacturing example B10>
"Hydrophobic substance (C-1) 0.19 parts" to "Hydrophobic substance (C-4) 0.30 parts and penetrant (D-1) {polyoxyethylene alkyl ether, Sanyo Kasei Co., Ltd. Naroacty CL Production Example 1 except that "-20} 0.20 parts" was changed and "weight average particle size was changed to 340 μm and SPAN was 0.8" to "weight average particle size was changed to 321 μm and SPAN was 0.8". Crosslinked polymer particles (A1-B10) were obtained in the same manner as above.

<Manufacturing example B11>
"Hydrophobic substance (C-1) 0.19 parts" to "Hydrophobic substance (C-5) 0.30 parts and penetrant (D-1) {polyoxyethylene alkyl ether, Sanyo Kasei Co., Ltd. Naroacty CL Production Example 1 except that "-20} 0.20 parts" was changed and "weight average particle size was changed to 340 μm and SPAN was 0.8" to "weight average particle size was changed to 321 μm and SPAN was 0.8". 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 solvent manufactured by Hosokawa Micron: rotation speed 2000 rpm), ethylene glycol di as a surface crosslinking agent was added to the crosslinked polymer particles (A1-1). A mixed solution prepared by mixing 0.04 part by weight of glycidyl ether and 3.0 parts by weight of a 50% propylene glycol aqueous solution as a solvent was added, and after uniform mixing, the mixture was dried by allowing it to stand at 130 ° C. for 30 minutes to dry it. By sieving the dried material, the water-absorbent resin (P-1) of the present invention having a weight average particle diameter of 366 μm and a SPAN of 0.8 was obtained.

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

<Example 3>
Similar to Example 1, the weight average particle diameter is 299 μm and SPAN0, except that “100 parts by weight of the crosslinked polymer particles (A1-1)” is changed to “100 parts by weight of the crosslinked polymer particles (A1-3)”. The water-absorbent resin (P-3) of the present invention, which is 9.9, was obtained.

<Example 4>
"100 parts by weight of crosslinked polymer particles (A1-1)" was changed to "100 parts by weight of crosslinked polymer particles (A1-4)", and "0.04 parts by weight of ethylene glycol diglycidyl ether" 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 it was changed to “0.03 parts by weight of glycidyl ether”.

<Example 5>
"100 parts by weight of crosslinked polymer particles (A1-1)" was changed to "100 parts by weight of crosslinked polymer particles (A1-5)", and "0.04 parts by weight of ethylene glycol diglycidyl ether" was changed to "ethylene glycol di." A water-absorbent 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 mixture was changed to "0.02 parts by weight of glycidyl ether".

<Example 6>
Similar to Example 1, the weight average particle diameter is 367 μm, SPAN0, except that “100 parts by weight of the crosslinked polymer particles (A1-1)” is changed to “100 parts by weight of the crosslinked polymer particles (A1-B1)”. The water-absorbent resin (P-6) of the present invention (0.8) was obtained.

<Example 7>
Similar to Example 1, the weight average particle diameter is 333 μm, SPAN0, except that “100 parts by weight of the crosslinked polymer particles (A1-1)” is changed to “100 parts by weight of the crosslinked polymer particles (A1-B2)”. A water-absorbent resin (P-7) of the present invention (0.8) was obtained.

<Example 8>
Similar to Example 1, the weight average particle diameter is 359 μm and SPAN0, except that “100 parts by weight of the crosslinked polymer particles (A1-1)” is changed to “100 parts by weight of the crosslinked polymer particles (A1-B3)”. The water-absorbent resin (P-8) of the present invention, which is 0.7, was obtained.

<Example 9>
Similar to Example 1, the weight average particle diameter is 331 μm and SPAN0, except that “100 parts by weight of the crosslinked polymer particles (A1-1)” is changed to “100 parts by weight of the crosslinked polymer particles (A1-B4)”. The water-absorbent resin (P-9) of the present invention, which is 0.7, was obtained.

<Example 10>
Similar to Example 1, the weight average particle diameter is 372 μm and SPAN0, except that “100 parts by weight of the crosslinked polymer particles (A1-1)” is changed to “100 parts by weight of the crosslinked polymer particles (A1-B5)”. The water-absorbent resin (P-10) of the present invention, which is 0.7, was obtained.

<Example 11>
Similar to Example 1, the weight average particle diameter is 362 μm and SPAN0, except that “100 parts by weight of the crosslinked polymer particles (A1-1)” is changed to “100 parts by weight of the crosslinked polymer particles (A1-B6)”. A water-absorbent resin (P-11) of the present invention (0.8) was obtained.

<Example 12>
Similar to Example 1, the weight average particle diameter is 332 μm and SPAN0, except that “100 parts by weight of the crosslinked polymer particles (A1-1)” is changed to “100 parts by weight of the crosslinked polymer particles (A1-B7)”. A water-absorbent resin (P-12) of the present invention (0.8) was obtained.

<Example 13>
Similar to Example 1, the weight average particle diameter is 335 μm and SPAN0, except that “100 parts by weight of the crosslinked polymer particles (A1-1)” is changed to “100 parts by weight of the crosslinked polymer particles (A1-B8)”. A water-absorbent resin (P-13) of the present invention (0.8) was obtained.

<Example 14>
Similar to Example 1, the weight average particle diameter is 334 μm and SPAN0, except that “100 parts by weight of the crosslinked polymer particles (A1-1)” is changed to “100 parts by weight of the crosslinked polymer particles (A1-B9)”. A water-absorbent resin (P-14) of the present invention (0.8) was obtained.

<Example 15>
Similar to Example 1, the weight average particle diameter is 330 μm, SPAN0, except that “100 parts by weight of the crosslinked polymer particles (A1-1)” is changed to “100 parts by weight of the crosslinked polymer particles (A1-B10)”. A water-absorbent resin (P-15) of the present invention (0.8) was obtained.

<Example 16>
Similar to Example 1, the weight average particle diameter is 332 μm and SPAN0, except that “100 parts by weight of the crosslinked polymer particles (A1-1)” is changed to “100 parts by weight of the crosslinked polymer particles (A1-B11)”. A water-absorbent resin (P-16) of the present invention (0.8) was obtained.

<Comparative example 1>
Similar to Example 1, the weight average particle diameter is 365 μm, SPAN1 except that “100 parts by weight of the crosslinked polymer particles (A1-1)” is changed to “100 parts by weight of the crosslinked polymer particles (A1-6)”. A comparative water-absorbent resin (R-1) of .2 was obtained.

<Comparative example 2>
"100 parts by weight of crosslinked polymer particles (A1-1)" was changed to "100 parts by weight of crosslinked polymer particles (A1-7)", and "0.04 parts by weight of ethylene glycol diglycidyl ether" was changed to "ethylene glycol di." A comparative water-absorbent resin (R-2) 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 it was changed to "0.03 parts by weight of glycidyl ether".

<Comparative example 3>
Similar to Example 1, the weight average particle diameter is 180 μm, SPAN1 except that “100 parts by weight of the crosslinked polymer particles (A1-1)” is changed to “100 parts by weight of the crosslinked polymer particles (A1-8)”. A water-absorbent resin (R-3) for comparison, which was 0.0, was obtained.

<Comparative example 4>
"100 parts by weight of crosslinked polymer particles (A1-1)" was changed to "100 parts by weight of crosslinked polymer particles (A1-9)", and "carboxy-modified polysiloxane (Shinetsu Chemical Industry Co., Ltd.) was added to the mixed solution of the surface crosslinking agent. A comparative water-absorbent resin (R-4) having a weight average particle diameter of 346 μm and a SPAN of 0.8, in the same manner as in Example 1, except that "Company: X-22-3701E) 0.01 parts by weight" was added. ) Was obtained.

<Comparative example 5>
"100 parts by weight of crosslinked polymer particles (A1-1)" was changed to "100 parts by weight of crosslinked polymer particles (A1-10)", and "0.04 parts by weight of ethylene glycol diglycidyl ether" was changed to "ethylene glycol di." A comparative water-absorbent resin (R-5) 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 it was changed to "0.03 parts by weight of glycidyl ether".

<Comparative Example 6>
Similar to Example 1, the weight average particle diameter is 458 μm, SPAN0, except that “100 parts by weight of the crosslinked polymer particles (A1-1)” is changed to “100 parts by weight of the crosslinked polymer particles (A1-11)”. A comparative water-absorbent resin (R-6) of 0.7 was obtained.

<Comparative Example 7>
Similar to Example 1, the weight average particle diameter is 382 μm, SPAN1 except that “100 parts by weight of the crosslinked polymer particles (A1-1)” is changed to “100 parts by weight of the crosslinked polymer particles (A1-12)”. A comparative water-absorbent resin (R-7) of .2 was obtained.

<Comparative Example 8>
Similar to Example 1, the weight average particle diameter is 261 μm, SPAN1 except that “100 parts by weight of the crosslinked polymer particles (A1-1)” is changed to “100 parts by weight of the crosslinked polymer particles (A1-13)”. A comparative water-absorbent resin (R-8) of .5 was obtained.

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

As can be seen from Table 1, the water-absorbent resin particles of the present invention (Examples 1 to 16) have a small SPAN (narrow particle size distribution), and the weight average particle size and absorption rate pattern are appropriate. Specifically, although hydrophobic substances are not used in Examples 2 and 5, an appropriate absorption rate pattern can be obtained by appropriately setting the weight average particle size and SPAN. In Examples 1, 3 and 4, it can be seen that 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. In addition, Examples 6 to 11 exemplify examples using other suitable hydrophobic substances. Further, in Examples 12 to 16, it can be seen that the absorption rate by the lockup method can be further improved by using the hydrophobic substance (C) and the penetrant (D) in combination. On the other hand, in Comparative Examples 1 and 7, since the SPAN is high, the particle size distribution is wide, the M2 is low, and the absorption rate by the lockup method tends to be slow. In Comparative Example 2, although the SPAN is low, the weight average particle size is large and the absorption rate by the lockup method is slow. In Comparative Example 4, "carboxy-modified polysiloxane (manufactured by Shin-Etsu Chemical Co., Ltd .: X-22-3701E)" having strong hydrophobicity is used for surface cross-linking, M2 is lowered, and the absorption rate by the lockup method is slowed down. There is. In Comparative Example 5, the weight average particle size is lowered without using a hydrophobic substance, and M1 is excessively high. In Comparative Example 6, the weight average particle size is high and a hydrophobic substance is also used, M1 is low, and the absorption rate by the lockup method is lowered. In Comparative Examples 3 and 8, M1 is excessively high because the weight average particle size is small and the SPAN is high.

Subsequently, it was evaluated what kind of absorption characteristics were exhibited when applied to an absorbent article when the SPAN was low and the absorption rate pattern was appropriate. Using the water-absorbent resin particles obtained in Examples 1 to 16 and Comparative Examples 1 to 8, an absorbent article (paper diaper) was prepared as follows, and the dryness and SDME method by liquidation from the surface non-woven fabric were performed. The surface dryness value was evaluated by Table 2, and the results are shown in Table 2.

<Preparation of absorber>
Styrene-butadiene-styrene copolymer (SBS; softening point 85 ° C.) was applied as an adhesive to non-woven fabric A (grain size 40 g / m ^{2, thickness 0.5 mm, made of polypropylene) shredded into a rectangle of 10 cm x 40 cm.} Apply evenly with a hot melt coating machine (AD41, manufactured by Nordson) so that the grain size is 2.85 g / m ² . ^{After uniformly spraying 10.6 g (grain amount 265 g / m 2} ) of the evaluation sample {water-absorbent resin particles} on the surface coated with the adhesive, the non-woven fabric B (grain size 45 g / m 2) shredded into a rectangle of 10 cm × 40 cm. m ² , thickness 7.0 mm, made of polypropylene) were stacked. The sheet of the non-woven fabric A-water-absorbent resin-nonwoven fabric B was sandwiched between acrylic plates (thickness 4 mm) and pressed at a pressure of ^{5 kg / cm 2 for 30 seconds.} After pressing, the acrylic plate on the non-woven fabric A side is removed, the adhesive, the water-absorbent resin and the non-woven fabric B are laminated in the same manner as above, sandwiched between the acrylic plates again, and pressed at a pressure of ^{5 kg / cm 2 for 30 seconds.} An absorber was prepared.

<Preparation of absorbent articles>
Absorbent article by arranging a polyethylene sheet (polyethylene film UB-1 manufactured by Tamapoli) on one side of the absorber and a non-woven fabric (basis weight 20 g / m ² , Eltas guard manufactured by Asahi Kasei) on the other side. Was prepared.

<Dryness test by dripping from surface non-woven fabric>
The absorber prepared above was placed in a box (stainless steel) measuring 11 cm in width × 41 cm in length × 4 cm in height and having an empty upper part (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. Time measurement was started as soon as the deionized water came into contact with the absorber. The time (whitening time) until the deionized water held on the surface non-woven fabric was absorbed by the water-absorbent resin and the range in which the surface non-woven fabric appeared white became half that of the non-woven fabric was recorded.

<Surface dryness value by SDME method>
A disposable diaper in which the detector of the 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 99.09% by weight of deionized water) soaked the disposable diaper and left it for 60 minutes to prepare. } To set a 0% dryness value, then the detector of the SDME tester was prepared by drying a dry disposable diaper {a disposable diaper at 80 ° C. for 2 hours. } Was placed on top of it to set 100% dryness, and the SDME tester was calibrated. 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 been absorbed {when the gloss due to the artificial urine cannot be confirmed}, immediately Remove the metal ring, place three SDME detectors on the center of the disposable diaper and on the left and right {three locations at equal intervals of 10 cm from the edge of the disposable diaper}, start measuring the surface dryness value, and 5 minutes after the start of measurement. Of the three SDME detectors, the dryness value of the central detector is the surface dryness value (1-1) {center}, 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, the measurement atmosphere, and the neglected atmosphere were performed at 25 ± 5 ° C. and 65 ± 10% RH.

As can be seen from Table 2, the absorbent body and the absorbent article using the water-absorbent resin particles of the present invention have a whitening time and a surface dryness value as compared with the absorbent body and the absorbent article using the water-absorbent resin particles for comparison. (1-1), (1-2), and (1-3) are not biased and have excellent dryness. On the other hand, since 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, so that the whitening time, that is, the non-woven fabric Poor liquid drainage from the surface. In Comparative Examples 3, 5 and 8, since M1 is excessively high, the liquid diffusivity is poor and spot absorption occurs, so that the surface dryness value is biased and the dryness is deteriorated. In Comparative Examples 1, 2, 4 and 6 to 8, it can be seen that the whitening time tends to decrease because the absorption rate by the lockup method is also slow. That is, when the water-absorbent resin particles of the present invention are applied to an absorber and an absorbent article, it is easily predicted that the water-absorbent resin particles are excellent in liquidability from the non-woven fabric and surface dryness, and there is no concern about fogging or the like.

The water-absorbent resin particles of the present invention can be applied to an absorbent body containing the water-absorbent resin particles and a fibrous substance, and the absorbent article provided with the absorbent body {paper diaper, sanitary napkin and medical blood retention It is useful for agents, etc.}. In addition, pet urine absorbent, urine gelling agent for portable toilets, freshness preserving agent for fruits and vegetables, drip absorbent for meat and seafood, cold insulation agent, disposable body warmer, gelling agent for batteries, water retention agent for plants and soil, dew condensation. It can also be used for various purposes such as preventive agents, water blocking agents, packing agents and artificial snow.

1 Rubber stopper 2 Burette part 3 Saline 4 Water-absorbent resin particles 5 Plain woven nylon mesh 6 Measuring table 7 Cock 8 Cock 9 Air introduction tube

Claims (6)

It contains a water-soluble vinyl monomer (a1) and / or a vinyl monomer (a2) that becomes a water-soluble vinyl monomer (a1) by hydrolysis, and a cross-linked polymer (A1) containing a cross-linking agent (b) as an essential constituent 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 of 1.0 or less, and water absorption. Water-absorbent resin particles having an absorption amount (M1) of the resin particles after 1 minute by the DW (Polymer Wetability) method of 10 to 15 ml / g and an absorption amount (M2) of the resin particles after 5 minutes of 45 to 55 ml / g.
SPAN = [D (90%) -D (10%)] / D (50%) ≤ 1.0 (Formula 1)
(In Equation 1, D (10%) is a particle having a cumulative weight component of 10% by weight from the particle having the smallest particle size, where the total weight of the water-absorbent resin particles classified using a standard sieve is 100% by weight. In terms of diameter, D (50%) is a particle size having a cumulative weight component of 50% by weight, and D (90%) is a particle size having a cumulative weight component of 90% by weight.) The water-absorbent resin particles according to claim 1, wherein the water-absorbent resin particles contain a hydrophobic substance (C). The water-absorbent resin particles according to claim 1 or 2, wherein the absorption rate of the water-absorbent resin particles by the lock-up method of ion-exchanged water is 25 seconds or less. The water-absorbent resin particles according to any one of claims 1 to 3, wherein the water-retaining amount of the physiological saline of the water-absorbent resin particles is 35 to 40 g / g. An absorber comprising the water-absorbent resin particles according to any one of claims 1 to 4 and a non-woven fabric. An absorbent article comprising the absorber according to claim 5.

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