WO2020017483A1

WO2020017483A1 - Water absorbing resin particles, and absorbent body and absorbent article containing same

Info

Publication number: WO2020017483A1
Application number: PCT/JP2019/027845
Authority: WO
Inventors: 武南里
Original assignee: Ｓｄｐグローバル株式会社
Priority date: 2018-07-19
Filing date: 2019-07-16
Publication date: 2020-01-23
Also published as: CN112334517B; CN112334517A; JPWO2020017483A1; JP7339253B2

Abstract

Provided are water absorbing resin particles that exhibit a high initial absorption speed and liquid diffusion properties when brought into contact with a liquid to be absorbed, have excellent dry properties and cause no problem such as skin rash. The water absorbing resin particles according to the present invention comprise a crosslinked polymer (A1) which has an essential constituting unit comprising a water-soluble vinyl monomer and/or a hydrolyzable vinyl monomer and a crosslinking agent, wherein: the weight-average particle diameter (μm) is 200-400; the SPAN value represented by the formula SPAN=[D(90%)-D(10%)]/D(50%) [wherein D(10%), D(50%) and D(90%) stand for the particle diameters at which the cumulative weight fraction attains 10 wt%, 50 wt% and 90 wt% respectively] is not more than 1.0; and, when measured by the DW method, (A1) shows water absorption amounts of 10-15 ml/g and 45-55 ml/g after 1 minute and after 5 minutes respectively.

Description

Water-absorbing resin particles, absorber containing the same, and absorbent article

{Circle over (1)} The present invention relates to a water-absorbent resin particle, an absorbent containing the same, and an absorbent article.

衛生 As sanitary materials such as disposable diapers, sanitary napkins, incontinence pads, etc., water-absorbent resins mainly composed of hydrophilic fibers such as pulp and acrylic acid (salt) are widely used as absorbers. In recent years, consumers have been demanding more comfort, and the demand has shifted to more dry and thinner ones. Reduction has become desired. Therefore, the role of the water-absorbent resin itself has been required to have the role of the high absorption rate and liquid diffusivity in the early stage that the hydrophilic fiber has played so far.

As a means for improving the absorption speed of the water-absorbent resin particles, a method of physically increasing the surface area of the water-absorbent resin is generally used. 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 increasing the absorption rate by reducing the particle size of the water-absorbent resin particles in the sieving step (Patent Document 2) Are known. However, there is no problem in the case where the content of the hydrophilic fiber is larger than the content of the water-absorbent resin particles in the absorbent in which these water-absorbent resin particles are applied to an absorbent article (paper diaper or the like). If the content of is small or does not contain, the absorption rate of the water-absorbent resin is biased depending on the location of the absorber, it is not possible to effectively use the absorbent article, and in the portion where the liquid to be absorbed remains Problems such as rash are likely to occur.
As a method for solving the above-mentioned problem, a water-absorbent resin particle (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 is known. When the water-absorbent resin particles are applied to the absorbent article, there is a problem in that the liquid to be absorbed from the surface nonwoven fabric used in the absorbent article is slowly drained, and dryness is deteriorated.
Therefore, even in an absorber using a small amount of hydrophilic fiber, it exhibits an initial high absorption rate and liquid diffusivity, is excellent in dryness, and further has no problem such as fogging. Resin particles are strongly desired.

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

An object of the present invention is to exhibit a high absorption rate and liquid diffusivity in the initial stage in contact with the liquid to be absorbed, to have excellent dryness, and to further eliminate problems such as rash, an absorbent body containing the water-absorbent resin particles, and an absorbent. To provide goods.

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

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

吸収 The absorbent article of the present invention is provided with the above-mentioned absorber.

水性 The water-absorbent resin particles of the present invention have a specific particle size distribution and absorption rate pattern. Therefore, when the water-absorbent resin particles of the present invention are applied to absorbent articles (such as disposable diapers and sanitary napkins), they exhibit an initial high absorption rate and liquid diffusivity when they come in contact with the liquid to be absorbed, and exhibit dryness. And no problems such as rash. That is, the absorbent article using the water-absorbent resin particles having a DW absorption pattern of the present invention exhibits excellent liquid diffusivity because of having an absorption pattern that is appropriately delayed at the initial stage, and exhibits dryness over the entire absorber. Excellent. In addition, by setting the weight average particle size and the span value within the ranges of the present invention, the liquid drainage property from the surface nonwoven fabric (to absorb and absorb the liquid; the same applies hereinafter) is improved, and therefore, a more excellent dry property is exhibited. I do.

It is the 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, vinyl monomers disclosed in Japanese Patent Nos. 3648553, 2003-165883, 2005-75982, and 2005-95759). Etc. can be used.

The vinyl monomer (a2) which becomes a water-soluble vinyl monomer (a1) by hydrolysis (hereinafter also referred to as a hydrolyzable vinyl monomer) (a2) is not particularly limited and is known. For example, Japanese Patent No. 3648553, Japanese Patent Application Laid-Open No. 2003-165883. JP-A-2005-75982, JP-A-2005-95759, and the like. 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. The term "hydrolyzable" means the property of being hydrolyzed by the action of water at 50 ° C. and, if necessary, a catalyst (acid or base, etc.). The hydrolysis of the hydrolyzable vinyl monomer may be carried out during the polymerization, after the polymerization, or both of them, but is preferably performed after the polymerization from the viewpoint of the molecular weight of the obtained water-absorbent resin particles.

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

The “carboxy (salt) group” means “carboxy group” or “carboxylate group”, and the “sulfo (salt) group” means “sulfo group” or “sulfonate group”. Also, (meth) acrylic acid (salt) means acrylic acid, acrylate, methacrylic acid or methacrylic acid, and (meth) acrylamide means acrylamide or methacrylamide. Examples of the salt include an alkali metal (such as lithium, sodium, and potassium) salt, an alkaline earth metal (such as magnesium and calcium) salt, and an ammonium (NH ₄ ) salt. Among these salts, alkali metal salts and ammonium salts are preferred from the viewpoint of absorption characteristics and the like, more preferably alkali metal salts, and particularly preferably sodium salts.

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

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 therewith can be used as a constituent unit. .

The other copolymerizable vinyl monomer (a3) is not particularly limited and is known. For example, JP-A-3648553, JP-A-2003-165883, JP-A-2005-75982, and JP-A-2005-95759.疎水 hydrophobic vinyl monomers 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, and halogen-substituted styrene such as vinylnaphthalene and dichlorostyrene.
(Ii) C2-C20 aliphatic ethylene monomers alkenes [ethylene, propylene, butene, isobutylene, pentene, heptene, diisobutylene, octene, dodecene, octadecene, etc.]; and alkadienes [butadiene, isoprene, etc.] and the like.
(Iii) alicyclic ethylene monomers having 5 to 15 carbon atoms, monoethylenically unsaturated monomers such as pinene, limonene and indene; and polyethylene-based vinyl polymerizable monomers such as cyclopentadiene, bicyclopentadiene and ethylidene norbornene.

When the other vinyl monomer (a3) is a constituent unit, the content (mol%) of the other vinyl monomer (a3) unit is determined based on the water-soluble vinyl monomer (a1) unit and the hydrolyzable vinyl monomer (a2) unit. Based on the number of moles, it is preferably from 0.01 to 5, more preferably from 0.05 to 3, then preferably from 0.08 to 2, particularly preferably from 0.1 to 1.5. From the viewpoint of absorption characteristics and the like, the content of the other vinyl monomer (a3) unit is most preferably 0 mol%.

The crosslinking agent (b) is not particularly limited and is known in the art (for example, crosslinking agents disclosed in Japanese Patent Nos. 3648553, 2003-165883, 2005-75982, and 2005-95759). Can be used. Among these, a crosslinking 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 sialic acid. Nurate, triallyl isocyanurate, tetraallyloxyethane and pentaerythritol triallyl ether, most preferably pentaerythritol triallyl ether.

The content (mol%) of the crosslinking 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 this case, it is preferably 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 (a1) to (a3) units. Within this range, the absorption characteristics are further improved.

The crosslinked polymer (A1) may be a single type or a mixture of two or more types.

The crosslinked polymer (A1) can be prepared by a known aqueous polymerization method (adiabatic polymerization, thin film polymerization, spray polymerization method, etc .; JP-A-55-133413, etc.) or a known reversed-phase suspension polymerization (Japanese Patent Publication No. 54-30710). And JP-A-56-26909 and JP-A-1-5808. Among the polymerization methods, a solution polymerization method is preferable, and an aqueous solution polymerization method is particularly preferable because there is no need to use an organic solvent or the like and the production cost is advantageous.

<< Hydrogel obtained by polymerization >> Consists of a 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, Vex Mill, Rubber Chopper, Pharma Mill, Minch Machine, Impact Grinding Machine and Roll Grinding Machine} or the like. .

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

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 20, based on the weight of the crosslinked polymer. 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 water content of the organic solvent were measured using an infrared moisture meter @ JE400 manufactured by KETT Co., Ltd .: 120 ± 5 ° C., 30 minutes, atmosphere humidity before heating 50 ± 10% RH, lamp specification 100V, 40W It is determined from the weight loss of the measurement sample before and after heating when heating according to｝.

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

The crosslinked polymer (A1) can be pulverized after drying. The pulverizing method is not particularly limited, and a known pulverizing apparatus (for example, a hammer pulverizer, an impact pulverizer, a roll pulverizer, a shed air pulverizer) and the like can be used. The particle size of the pulverized crosslinked polymer can be adjusted by sieving or the like, if necessary.

架橋 The weight average particle diameter (μm) of the crosslinked polymer (A1) when sieved as required 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 diameter was measured using a low tap test sieve shaker and a standard sieve (JIS Z8801-1: 2006), 6th edition of Perry's Chemical Engineers Handbook (Mac Glow Hill Book Company, 1984). , Page 21). That is, JIS standard sieves are combined from the top 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 pan in the order from the top. About 50 g of the particles to be measured is put into the uppermost sieve and shaken with a low tap test sieve shaker for 5 minutes. The weights of the particles measured on each sieve and the pan are weighed, and the weight fraction of the particles on each sieve is determined by taking the total as 100% by weight. The logarithmic probability paper ｛the horizontal axis indicates the sieve aperture (particle size) ), The vertical axis is plotted as the weight fraction 、, and a line connecting the points is drawn to obtain a particle diameter [D (50%)] corresponding to the weight fraction of 50% by weight, and this is calculated as the weight average particle diameter. And

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

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

(4) 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 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 measurement method using a standard sieve. D (10%) is such that when the water-absorbent resin particles are classified by a standard sieve and the water-absorbent resin particles are arranged in order of particle diameter, the total weight of the classified particles is 100% by weight, and the particle diameter is the smallest. It means the particle diameter at which the cumulative weight fraction from the particles becomes 10% by weight. Similarly, D (50%) means a particle diameter at which the cumulative weight fraction becomes 50% by weight, and further, a particle diameter at which the D (90%) cumulative weight fraction becomes 90% by weight.

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

The apparent density (g / ml) of the crosslinked polymer (A1) is preferably 0.55 to 0.65, more preferably 0.56 to 0.64, 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.

形状 The shape of the crosslinked polymer (A1) is not particularly limited, and examples thereof include irregularly crushed, scaly, pearl, and rice grain shapes. Of these, the irregularly crushed shape is preferred from the viewpoint that it is well entangled with fibrous materials for use in disposable diapers, and there is no fear of falling off from the fibrous materials.

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

Examples of the hydrocarbon group-containing hydrophobic substance (C1) include polyolefin resin, polyolefin resin derivative, polystyrene resin, polystyrene resin derivative, wax, long-chain fatty acid ester, long-chain fatty acid and its salt, long-chain aliphatic alcohol, and long-chain aliphatic alcohol. Chain fatty acid amides and mixtures of two or more of these.

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

As the polyolefin resin derivative, a polymer having a weight average molecular weight of 1,000 to 1,000,000 obtained by introducing a carboxy group (—COOH) or 1,3-oxo-2-oxapropylene (—COOCO—) into a polyolefin resin {for example, polyethylene Degradation products, polypropylene thermal degradation products, maleic acid-modified polyethylene, chlorinated polyethylene, maleic acid-modified polypropylene, ethylene-acrylic acid copolymer, ethylene-maleic anhydride copolymer, isobutylene-maleic anhydride copolymer, maleated Polybutadiene, ethylene-vinyl acetate copolymer, maleic product of ethylene-vinyl acetate copolymer, and the like.

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

As the polystyrene resin derivative, a polymer having a weight-average molecular weight of 10 to 1,000,000 containing styrene as an essential constituent monomer (the content of styrene is at least 50% by weight based on the weight of the polystyrene derivative) {for example, styrene- Maleic anhydride copolymer, styrene-butadiene copolymer, styrene-isobutylene copolymer, and the like.

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

Examples of the long-chain fatty acid ester include an ester of a fatty acid containing an alkyl group having 8 to 25 carbon atoms and an alcohol having 1 to 12 carbon atoms such as methyl laurate, ethyl laurate, methyl stearate, ethyl stearate, oleic acid Methyl, ethyl oleate, glycerin lauric acid monoester, glycerin stearic acid monoester, glycerin oleic acid monoester, pentaerythritol laurate monoester, pentaerythritol stearic acid monoester, pentaerythritol oleic acid monoester, sorbitol lauric acid Acid monoester, sorbitol stearic acid monoester, sorbit oleic acid monoester, sucrose palmitate (sucrose palmitate monoester, sucrose palmitate diester, sucrose palmitate) Michin acid triester, etc.), sucrose stearate (sucrose stearic acid monoester, sucrose stearic acid diester, sucrose stearic acid triester, etc.), sucrose erucic acid ester, and beef tallow} and the like. Among them, sucrose stearic acid esters (sucrose stearic acid monoester, sucrose stearic acid diester, sucrose stearic acid triester, etc.), sucrose palmitate ( Sucrose palmitic acid monoester, sucrose palmitic acid diester, sucrose palmitic acid triester, etc.) and 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 and the like) 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, such as lauric acid, palmitic acid, stearic acid, oleic acid, dimer acid, and behenic acid. Examples of the salt include salts with calcium, magnesium, or aluminum (hereinafter abbreviated as Ca, Mg, Al), such as Ca palmitate, Al palmitate, Ca stearate, Mg stearate, Al stearate, and the like. From the viewpoint of the liquid diffusibility of the absorbent article, Ca stearate, Mg stearate, and Al stearate are preferred, and Mg stearate is more preferred.

{Examples of long-chain aliphatic alcohols include aliphatic alcohols containing an alkyl group having 8 to 25 carbon atoms, such as lauryl alcohol, palmityl alcohol, stearyl alcohol, and oleyl alcohol. From the viewpoint of the liquid diffusibility of the absorbent article, palmityl alcohol, stearyl alcohol, and oleyl alcohol are preferred, and stearyl alcohol is more preferred.

Examples of the long-chain fatty acid amide include fatty acid amides containing an alkyl group having 8 to 25 carbon atoms such as lauric amide, palmitic amide, stearic amide, oleic amide, erucamide, etc. Fatty acid bisamides such as ethylenebislauric acid amide, ethylenebisstearic acid amide, hexamethylenebisstearic acid amide, N, N'-distearyladipamide, ethylenebisoleic acid amide, ethylenebiserucic acid amide, etc. Can be Ethylenebisstearic acid amide is preferred from the viewpoint of the liquid diffusibility of the absorbent article.

Examples of the mixture of two or more of these include a mixture of a long-chain fatty acid ester and a long-chain aliphatic alcohol (for example, a mixture of sucrose stearic acid ester and stearyl alcohol), a long-chain fatty acid ester and a long-chain fatty acid, and a mixture thereof. A mixture of salts {for example, a mixture of sucrose stearic acid ester and Mg stearylate} may be mentioned.

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

The position of the organic group (modified group) of the modified silicone (polyether-modified polysiloxane, carboxy-modified polysiloxane, epoxy-modified polysiloxane, amino-modified polysiloxane, etc.) is not particularly limited, but the side chain of polysiloxane, polysiloxane , One end of polysiloxane, or both the side chain and both ends of polysiloxane. Of these, from the viewpoint of absorption characteristics and the like, both the side chain of polysiloxane and both the side chain and both ends of the polysiloxane are preferable, and more preferably both the side chain and both ends of the polysiloxane.

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

The polyether-modified polysiloxane can be easily obtained from the market. 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 Co., Ltd. , X-22-4954 {side chain, oxyethylene and oxypropylene}, X-22-4272 {side chain, oxyethylene and oxypropylene}, X-22-6266 {side chain, oxyethylene and oxypropylene}

-Toray Dow Corning Co., Ltd. FZ-2110 {both terminals, oxyethylene and oxypropylene}, FZ-2122 {both terminals, oxyethylene and oxypropylene}, FZ-7006 {both terminals, oxyethylene and oxypropylene}, FZ-2166 {terminals, oxyethylene and oxypropylene}, FZ-2164 {terminals, oxyethylene and oxypropylene}, FZ-2154 {terminals, oxyethylene and oxypropylene}, FZ-2203 {terminals, oxy Ethylene and oxypropylene {and FZ-2207 {both terminals, 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. Examples of the organic group (modifying group) of the polysiloxane include a group containing an amino group (a primary, secondary, or tertiary amino group). The content (g / mol) of the organic group (modified group) of these modified silicones is preferably 200 to 11000, more preferably 600 to 8000, particularly preferably 1000 to 4000 as carboxy equivalent, epoxy equivalent or amino equivalent. It is. Within this range, the absorption characteristics are further improved. The carboxy equivalent is measured in accordance with JIS C2101: 1999 “16. Total acid value test”. The epoxy equivalent is determined in accordance with JIS K7236: 2001. The amino equivalent is measured according to JIS K2501: 2003, “8. Potentiometric titration method (base number / hydrochloric acid method)”.

The carboxy-modified polysiloxane can be easily obtained from the market. 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 terminals, 2300}, X-22-3710 {one terminal, 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 polysiloxane can be easily obtained from the market. For example, the following products {modified position, epoxy equivalent} can be preferably exemplified.
・ Shin-Etsu Chemical Co., Ltd. X-22-343 ｛side chain, 525｝, KF-101 ｛side chain, 350｝, KF-1001 ｛side chain, 3500｝, X-22-2000 ｛side chain, 620｝ , X-22-2046 ｛side chain, 600｝, KF-102 ｛side chain, 3600｝, X-22-4741 ｛side chain, 2500｝, KF-1002 ｛side chain, 4300｝, X-22-3000T {Side chain, 250}, both ends of X-22-163}, 200}, both ends of KF-105 {490}, both ends of X-22-163A, both ends of 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｝

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

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

・ 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 ｛ End, 360 °, BY 16-853U {both ends, 450 °

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

The viscosity (mPa · s, 25 ° C.) of the hydrophobic substance having a polysiloxane structure is preferably from 10 to 5,000, more preferably from 15 to 3,000, and particularly preferably from 20 to 1500. Within this range, the absorption characteristics are further improved. The viscosity is measured in accordance with JIS Z8803-1991 “Viscosity of liquid”. Cone and cone-measured in accordance with a viscosity measurement method using a flat plate type viscometer. For example, an E-type viscometer temperature-controlled to 25.0 ± 0.5 ° C. (RE80L, radius 7 mm, manufactured by Toki Sangyo Co., Ltd.) , An angle of 5.24 × 10 ⁻² rad). ｝

By including the hydrophobic substance (C) in the water-absorbent resin particles, it is possible to easily control the absorption rate pattern of the water-absorbent resin particles (the amount of absorption after 1 minute and 5 minutes by the DW method). Preferably, 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 depending on the hydrophobicity and the amount of the hydrophobic substance (C). The hydrophobicity can be determined by a known method such as a hydrophilic-hydrophobic balance (HLB value).
The HLB value means a hydrophilic-hydrophobic balance (HLB) value, and is determined by the Oda method (introduction to surfactants, page 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 preferred from the viewpoint of the liquid diffusibility of the absorbent article, and more preferably sucrose stearate. , Mg stearate and ethylene bisstearic acid amide. Since long-chain fatty acids generally have a carbon number distribution, stearic acid means a modified long-chain fatty acid containing stearic acid as a main component.

The content (% by weight) of the hydrophobic substance (C) is preferably 0.001 to 5.0, more preferably 0.08 to 1.0, 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 diffusibility of the absorbent article and the liquid drainage property from the nonwoven fabric are easily compatible, and the antifogging property is excellent.

Furthermore, 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. When the penetrant (D) is used in combination with the hydrophobic substance (C), the amount of absorption by the DW method and the absorption rate by the lock-up method can be easily compatible. Examples of the penetrant (D) include a nonionic surfactant (D1) and an anionic surfactant (D2). The structure of the surfactant having excellent permeability, that is, a surfactant having 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, for example, an aliphatic alcohol (alkyl group having 8 to 18 carbon atoms) alkylene oxide (AO) (2 to 8 carbon atoms) adduct (polymerization degree = 1 to 1) 100) [lauryl alcohol ethylene oxide adduct, cetyl alcohol ethylene oxide adduct, etc.], polyoxyalkylene (2-8 carbon atoms, polymerization degree = 1-100) higher fatty acid (alkyl group having 8-24 carbon atoms) ester [ Polyethylene glycol monolaurate, polyethylene glycol monopalmitate, polyethylene glycol dilaurate, etc.].

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

Examples of the anionic surfactant (D2) include a hydrocarbon ether carboxylic acid having an alkyl group having 8 to 18 carbon atoms or a salt thereof, [polyoxyethylene (degree of polymerization = 1 to 100) sodium lauryl ether acetate, polyoxyethylene ( Degree of polymerization = 1 to 100) disodium lauryl sulfosuccinate], hydrocarbon sulfate having 8 to 18 carbon atoms [sodium lauryl sulfate, polyoxyethylene (degree of polymerization = 1 to 100) sodium lauryl sulfate, polyoxyethylene (Degree of polymerization = 1 to 100) triethanolamine lauryl sulfate], a hydrocarbon sulfonate having 8 to 18 carbon atoms [sodium dodecylbenzenesulfonate] and a hydrocarbon phosphate having 8 to 18 carbon atoms Salt [sodium lauryl phosphate, polyoxyethylene (degree of polymerization = 1 to 1) 0) lauryl ether sodium phosphate, etc.], sodium fatty acid salts [laurate, 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). 0.08 to 0.50. Within this range, the absorption rate can be adjusted appropriately.

The method of mixing the crosslinked polymer (A1) with the hydrophobic substance (C) is such that the hydrophobic substance (C) is present inside the water-absorbent resin particles. There is no limitation as long as it is mixed with the hydrophobic substance (C) so as to form a sandwich structure. However, it is preferable that the hydrophobic substance (C) is not a dried product of the crosslinked polymer (A1), but is mixed with the hydrogel of (A1) or the polymerization solution of (A1), and more preferably of (A1). It is to be mixed with a hydrogel. In addition, it is preferable to mix uniformly so that it may be kneaded. When the crosslinked polymer (A1) is obtained by the aqueous solution polymerization method, there is no particular limitation on the timing of mixing and kneading the hydrophobic substances (C) and (A1). During crushing (mincing) and during drying of the hydrogel. Among these, from the viewpoint of the moisture resistance and the like of the absorbent article, it is preferable immediately after the polymerization step and during the crushing (mincing) step of the hydrogel, 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. (A1) is produced in the presence of｝. Immediately after the polymerization step, during the dehydration step (during the step of dehydrating to about 10% by weight of water), immediately after the dehydration step, during the step of separating and distilling off the organic solvent used for the polymerization. And during the drying of the hydrogel. Among these, from the viewpoint of the moisture resistance of the absorbent article, during the polymerization step, immediately after the polymerization step, during the dehydration step, immediately after the dehydration step, preferably during the step of separating and distilling off the organic solvent used for the polymerization, more preferably Is immediately after the polymerization step during the polymerization step.

混合 In the case of mixing during the drying of the hydrogel, as the mixing device, a known device such as a Vex mill, a rubber chopper, a pharma mill, a mincing machine, an impact mill or a roll mill can be used. When mixing in the polymerization solution, a device having relatively high stirring power such as a homomixer or a biomixer can be used. When mixing during the drying of the hydrogel, a kneading device such as an SV mixer can 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 are further improved.

Further, in the method for producing the crosslinked polymer (A1) in the presence of the hydrophobic substance (C), the hydrophobic substance (C) is dissolved or emulsified (dispersed) in a polymerization solution of the crosslinked polymer (A1). Alternatively, the connecting portion can be formed while depositing (C) with the progress of the polymerization of (A1). The polymerization method is the same as in the case of the crosslinked polymer (A1), except that the polymerization is performed 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. Structure.

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

水 The hydrogel containing the hydrophobic substance (C) and, if necessary, the penetrant (D) can be cut into pieces as needed. 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.

溶媒 When a solvent (including an organic solvent and / or water) is used for the production of 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 to 5, based on the weight of the water-absorbent resin particles. -3, most preferably 0-1. It is. Within this range, the water-absorbing resin particles will have better absorption performance (particularly, water retention).

When the solvent contains water, the water content (% by weight) after the distillation is preferably 0 to 20, more preferably 1 to 10, 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 water retention amount) 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 those for the crosslinked polymer (A1).

The crosslinked polymer (A1) can be subjected to a surface crosslinking treatment with a surface crosslinking agent, if necessary. Examples of the surface cross-linking agent include those disclosed in JP-A-59-189103, JP-A-58-180233, JP-A-61-16903, JP-A-61-211305, and JP-A-61-252212. Nos. 1, JP-A-51-136588 and JP-A-61-257235, etc. {Surface crosslinking agents} Polyhydric glycidyl, polyhydric alcohols, polyamines, polyaziridines, polyisocyanates, silane coupling Agents and polyvalent metals can be used. Among these surface cross-linking agents, polyhydric glycidyl, polyhydric alcohol and polyhydric amine are preferable from the viewpoint of economy and absorption properties, more preferably polyhydric glycidyl and polyhydric alcohol, particularly preferably polyhydric glycidyl, Preferred is ethylene glycol diglycidyl ether.

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

In the case of performing the surface cross-linking treatment, the method of the surface cross-linking treatment is known, for example, the method described in Japanese Patent No. 3648553, JP-A-2003-165883, JP-A-2005-75982, and JP-A-2005-95759. Can be applied.

(4) 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 that the solvent is distilled off (dried) before pulverization. In the case of pulverization, the weight average particle size (μm) after pulverization is also preferably 200 to 400, more preferably 270 to 390, further preferably 290 to 380, and particularly preferably 290 to 370. Within this range, the handling properties (powder fluidity of the water-absorbent resin particles) after pulverization and the absorption rate of the water-absorbent resin particles become appropriate, so that the dryness of the absorbent article is 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. The content of the fine particles of 106 μm or less in the total particles is preferably 3% by weight or less, 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 a plot created when the above-mentioned weight average particle size is determined. The same method as in the case of the crosslinked polymer (A1) can be employed for pulverization and particle size adjustment.

In the case of pulverization, the span value after the pulverization is preferably 1.0 or less, particularly preferably 0.9 or less, and most preferably 0.8 or less. Within this range, the particle size distribution of the water-absorbent resin particles becomes narrow, so that it becomes difficult for spot absorption to occur or particles that do not absorb are difficult to be produced, so that the liquid drainage property from the surface of the nonwoven 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 antifogging property of the absorbent article is further improved. The apparent density can be measured in the same manner as in the case of the crosslinked polymer (A1). The apparent density can be appropriately adjusted by gel pulverizing method, production conditions such as drying conditions.

形状 The shape of the water-absorbent resin particles is not particularly limited, and examples thereof include irregular crushed shapes, scaly shapes, pearl shapes, and rice grain shapes. Of these, the irregularly crushed shape is preferred from the viewpoint that it is well entangled with fibrous materials for use in disposable diapers, and there is no fear of falling off from the fibrous materials.

The absorption amount (M) (ml / g) of the water-absorbent resin particles of the present invention by the DW method is preferably from 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 absorption amount (M2) after 5 minutes is from 45 to 55, preferably from 46 to 54, more preferably from 47 to 53. Within this range, the dryness of the absorbent article is further improved. The absorption amount by the DW method is adjusted by adjusting the SPAN, the apparent density of the water-absorbent resin particles, the weight average particle diameter of the water-absorbent resin particles, the hydrophobic substance, the surfactant, and the like to the preferable ranges described above. Can be adjusted to a preferable range. Specifically, when the weight average particle size is large, the apparent density is high, the content or hydrophobicity of the hydrophobic substance is high, and the use of the penetrant used in combination with the hydrophobic substance is reduced, the actions of each are almost independent. It has the effect of reducing the amount of absorption (M1) after one minute, and can be adjusted as appropriate. The absorption amount after 5 minutes (M2) tends to increase as the water retention amount increases, in addition to the operation factor of the absorption amount after 1 minute (M1). When the absorption amount (M1) after 1 minute is less than 10, the initial absorption amount is insufficient and the dryness is deteriorated. When the absorption amount is higher than 15, the initial absorption amount is too high and the absorption when the absorbent is used. And the dryness deteriorates. When the absorption amount after 5 minutes is less than 45, the dryness deteriorates because the absorption amount is insufficient, and when it is higher than 55, the absorption amount in the absorber is biased, and the dryness deteriorates.

The DW (Demand Wetability) method is a measurement method performed using a device shown in FIG. 1 in a room at 25 ± 2 ° C. and 50 ± 10% humidity. The measuring device shown in FIG. 1 comprises a burette part (2) {scale volume 50 ml, length 86 cm, inner diameter 1.05 cm,}, conduit {inner diameter 7 mm}, measuring table (6). The buret part (2) is connected with a rubber stopper (1) at the upper part, a suction inlet pipe (9) {tip inner diameter 3 mm} and a cock (7) at the lower part, and furthermore, an upper part of the suction inlet pipe (9). There is a cook (8). A conduit is attached from the burette section (2) to the measuring table (6). At the center of the measuring table (6), a hole having a diameter of 3 mm is provided as a physiological saline supply part, and a conduit is connected thereto.

Using the measuring device having this configuration, the cock (7) of the burette part (2) and the cock (8) of the air introduction pipe (9) are first closed, and a predetermined amount of physiological saline (salt) adjusted to 25 ° C. (Concentration: 0.9% by weight) from the upper part of the burette part (2), plug the upper part of the burette with a rubber stopper (1), and then stop the cock (7) of the burette part (2) and the cock of the air inlet pipe (9). Open (8). Next, after spilling the physiological saline which overflowed into the measuring table (6), the upper surface of the measuring table (6) and the surface of the physiological saline coming out from the conduit port in the center of the measuring table (6) were moved. The height of the measuring table (6) is adjusted so as to have the same height. While wiping the physiological saline from the physiological saline supply unit, the surface of the physiological saline in the burette unit (2) is adjusted to the top (0 ml line) of the buret unit (2) scale.

Subsequently, the cock (7) of the burette section (2) and the cock (8) of the air introduction pipe (9) are closed, and a plain woven nylon mesh (5) is placed on the measuring table (6) so that the physiological saline supply section becomes the center. 5) Place (opening 63 μm, 5 cm × 5 cm), and further, on this plain-woven nylon mesh (5), 0.50 g in a range of 2.7 cm in diameter centering on the physiological saline supply part of the measuring table (6). The water-absorbent resin particles (4) are uniformly dispersed. Thereafter, the cock (7) of the burette part (2) and the cock (8) of the air introduction pipe (9) are opened.

When the water-absorbent resin particles (4) begin to absorb water and the first foam introduced from the air introduction pipe (9) reaches the surface of the physiological saline in the burette part (2) (the burette part (2) The time when the level of the physiological saline in the sample falls) is defined as the measurement start time, and the amount of decrease in the physiological saline (3) in the burette portion (2) (physiological conditions in which the water-absorbing resin particles (4) absorb water) is continuously measured. Read M (ml of saline). The absorption amount of the water-absorbent resin particles (4) after a predetermined time has elapsed from the start of water absorption is determined by the following equation.

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

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

<Method for measuring water retention of water-absorbent resin particles>
1.00 g of a measurement sample is placed in a tea bag (length 20 cm, width 10 cm) made of nylon mesh having a mesh size of 63 μm (JIS Z8801-1: 2006), and 1,000 ml of physiological saline (salt concentration: 0.9% by weight) is added. After being immersed in the solution for 1 hour without stirring, it was suspended for 15 minutes and drained. Then, the whole tea bag is put in a centrifuge, centrifuged at 150 G for 90 seconds to remove excess physiological saline, the weight (h1) including the tea bag is measured, and the water retention amount is calculated from the following equation. In addition, the temperature of the physiological saline used and the measurement atmosphere is set to 25 ° C. ± 2 ° C. The weight of the tea bag after centrifugal dehydration is measured in the same manner as described above except that the measurement sample is not used, and is defined as (h2).

水 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 liquid drainage from the nonwoven fabric surface. . In addition. The absorption rate of the water-absorbent resin particles by the lock-up method is measured by the following method.

<Absorption rate of water-absorbent resin by lock-up method>
1.000 g of a measurement sample is put into a 100 ml tall beaker having a flat bottom surface specified in JIS R 3503. At this time, the upper surface of the water-absorbent resin placed in the beaker is horizontal. Next, 50 g of deionized water adjusted to 23 ° C. ± 2 ° C. is weighed into a 100 ml glass beaker, and carefully poured quickly 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. When the beaker into which deionized water is poured is turned sideways at an angle of about 90 °, the point at which the fluid does not leach from the surface of the water-absorbent resin is determined as the end point, and this time (unit: seconds) is determined by the lock-up method. It is the absorption rate measured in.

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

The nonwoven fabric used in the present invention is not particularly limited as long as it is a known nonwoven fabric, but from the viewpoint of liquid permeability, flexibility and strength when used as an absorbent, polyolefins such as polyethylene (PE) and polypropylene (PP) Non-woven fabrics made of fibers, polyester fibers such as polyethylene terephthalate (PET), polytrimethylene terephthalate (PTT), polyethylene naphthalate (PEN), polyamide fibers such as nylon, rayon fiber, other synthetic fibers, cotton, silk, Nonwoven fabrics produced by mixing hemp, pulp (cellulose) fibers and the like are included. Among these nonwoven fabrics, from the viewpoint of increasing the strength of the absorber, a nonwoven fabric made of synthetic fibers is preferable, and a nonwoven fabric made of rayon fiber, polyolefin fiber, and polyester fiber is more preferable. These nonwoven fabrics may be a single nonwoven fabric of the above fibers or a nonwoven fabric combining two or more fibers.

The nonwoven fabric used in the present invention is suitably bulky and has a large basis weight from the viewpoint of imparting good liquid permeability, flexibility, strength and cushioning property to the absorber and increasing the liquid penetration rate of the absorber. Is preferred. The basis weight is preferably from 5 to 300 g / m ² , more preferably from 8 to 200 g / m ² , still more preferably from 10 to 100 g / m ² , and still more preferably from 11 to 50 g / m ^2. It is. Further, the thickness of the nonwoven fabric is preferably in the range of 20 to 800 μm, more preferably in the range of 50 to 600 μm, and still more preferably in the range of 80 to 450 μm.

In the absorbent body of the present invention, the absorbent layer contains a water-absorbent resin, a nonwoven fabric, and an adhesive if necessary, and optionally further contains a hydrophilic fiber such as fluff pulp. After uniformly dispersing the water-absorbing resin on the nonwoven fabric thus obtained, the nonwoven fabric to which the adhesive is applied is further laminated if necessary, and if necessary, the nonwoven fabric is formed by heating under pressure. It is also formed by uniformly spreading a mixed powder of a water-absorbent resin and an adhesive on a non-woven fabric, further laminating the non-woven fabric, and heating at a temperature around the melting temperature of the adhesive, and if necessary, heating under pressure. You. The fluff pulp can be uniformly dispersed between the nonwoven fabric and the water-absorbent resin particles.
In the absorber of the present invention, two or more absorption layers can be stacked.

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

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

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

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

It is preferable that the above-mentioned absorber constitutes an absorbent article {paper diaper, sanitary napkin, etc.}. The method of manufacturing an absorbent article is the same as that described in JP-A-2003-225565, JP-A-2006-131767, and JP-A-2005-097569, except that the above-mentioned absorber is changed. 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, “part” indicates “part 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 of the water-absorbent resin particles by the lock-up method were measured by the methods described above.

<Production Example 1>
Water-soluble vinyl monomer (a1-1) ｛acrylic acid, manufactured by Mitsubishi Chemical Corporation, purity 100%｝ 155 parts (2.15 mol part), crosslinking agent (b1) ｛pentaerythritol triallyl ether, manufactured by Daiso Corporation 0.6225 parts (0.0024 mole part) and 350.27 parts of deionized water were maintained at 3 ° C. with stirring and mixing. After introducing nitrogen into the mixture to reduce the dissolved oxygen content to 1 ppm or less, 0.62 parts of a 1% aqueous hydrogen peroxide solution, 1.1625 parts of a 2% aqueous ascorbic acid solution, and 2% 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., polymerization was carried out at 90 ± 2 ° C. for about 5 hours to obtain a hydrogel (1).

Next, while shredding 502.27 parts of this hydrogel (1) with a mincing machine (12VR-400K manufactured by ROYAL), 128.42 parts of a 48.5% aqueous sodium hydroxide solution was added and mixed. The substance (C-1) {Mg stearate} 0.19 parts was added and mixed. After chopping four times, the resultant was dried with a ventilation dryer {150 ° C, wind speed 2m / sec} to obtain a dried product. . After the dried product is pulverized with a juicer mixer (OSTERIZER @ BLENDER manufactured by Oster), the dried product is sieved, and the dried product on each sieve is separately collected so that the weight average particle diameter is 350 μm and the SPAN is 0.8. The dried polymer on the sieve was mixed to obtain crosslinked polymer particles (A1-1).

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

<Production Example 3>
Change "0.19 parts of hydrophobic substance (C-1)" to "0.29 parts of hydrophobic substance (C-1)", and change "weight average particle diameter 350 μm, SPAN 0.8" to "weight Crosslinked polymer particles (A1-3) were obtained in the same manner as in Production Example 1, except that the average particle diameter was changed to 270 μm and the SPAN to 0.9 ”.

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

<Production Example 5>
"The hydrophobic substance (C-1) 0.19 parts" was not used, and "the weight average particle diameter was 350 μm and SPAN was 0.8" was changed to "the weight average particle diameter was 315 μm and SPAN was 0.8" In the same manner as in Production Example 1, except that the above conditions were changed, crosslinked polymer particles (A1-5) were obtained.

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

<Production Example 7>
"The hydrophobic substance (C-1) 0.19 parts" was not used, and "the weight average particle diameter was 350 μm and SPAN was 0.8" was changed to "the weight average particle diameter was 420 μm and SPAN was 0.8" In the same manner as in Production Example 1, except that the above conditions were changed, crosslinked polymer particles (A1-7) were obtained.

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

<Production Example 9>
"The hydrophobic substance (C-1) 0.19 part" was not used, and "the weight average particle diameter was 350 μm and SPAN was 0.8" was changed to "the weight average particle diameter was 330 μm and SPAN was 0.8" In the same manner as in Production Example 1, except that the above conditions were changed, crosslinked polymer particles (A1-9) were obtained.

<Production Example 10>
"The hydrophobic substance (C-1) 0.19 part" was not used, and "the weight average particle diameter was 350 μm and SPAN was 0.8" was changed to "the weight average particle diameter was 290 μm and SPAN was 0.9" In the same manner as in Production Example 1, except that the above conditions were changed, crosslinked polymer particles (A1-10) were obtained.

<Production Example 11>
Change "0.19 parts of hydrophobic substance (C-1)" to "0.29 parts of hydrophobic substance (C-1)", and change "weight average particle diameter 350 μm, SPAN 0.8" to "weight Crosslinked polymer particles (A1-11) were obtained in the same manner as in Production Example 1, except that the average particle diameter was changed to 450 μm and the SPAN to 0.7 ”.

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

<Production Example 13>
"The hydrophobic substance (C-1) 0.19 part" was not used, and "the weight average particle diameter was 350 μm and SPAN was 0.8" was changed to "the weight average particle diameter was 240 μm and SPAN was 1.5" In the same manner as in Production Example 1, except that the above conditions were changed, crosslinked polymer particles (A1-13) were obtained.

<Production Example B1>
0.19 parts of "hydrophobic substance (C-1)" was replaced with "hydrophobic substance (C-2) @sucrose erucic acid ester, Ryoto (registered trademark) manufactured by Mitsubishi Chemical Foods Co., Ltd. Sugar ester ER Production Example 1 except that "-290 粒子 0.10 parts" was changed, and "weight average particle diameter was 350 μm, SPAN was 0.8" and "weight average particle diameter was 355 μm, SPAN was 0.7". In the same manner as in the above, crosslinked polymer particles (A1-B1) were obtained.

<Production Example B2>
"Hydrophobic substance (C-1) 0.19 parts" is changed to "Hydrophobic substance (C-2) @ sucrose erucate ester, Ryoto Sugar Ester ER-290 @ 0.30 parts manufactured by Mitsubishi Chemical Foods, Inc." In the same manner as in Production Example 1, except that the weight-average particle diameter was 350 μm and SPAN was 0.8, and the weight-average particle diameter was 321 μm and SPAN was 0.8. A1-B2) was obtained.

<Production Example B3>
"Hydrophobic substance (C-1) 0.19 parts" is changed to "Hydrophobic substance (C-3) @ sucrose stearic acid ester, Ryoto Sugar Ester S-370 @ 0.10 parts by Mitsubishi Chemical Foods, Inc." In the same manner as in Production Example 1, except that the weight-average particle diameter was 350 μm and SPAN was 0.8, and the weight-average particle diameter was 355 μm and SPAN was 0.7. A1-B3) was obtained.

<Production Example B4>
"Hydrophobic substance (C-1) 0.19 parts" is changed to "Hydrophobic substance (C-3) @ sucrose stearic acid ester, Ryoto Sugar Ester S-370 @ 0.30 parts manufactured by Mitsubishi Chemical Foods, Inc." In the same manner as in Production Example 1, except that the weight-average particle diameter was 350 μm and SPAN was 0.8, and the weight-average particle diameter was 321 μm and SPAN was 0.8. A1-B4) was obtained.

<Production Example B5>
Changed "hydrophobic substance (C-1) 0.19 parts" to "hydrophobic substance (C-4) @ ethylene bis distearic acid amide, Slipax (registered trademark) E @ 0.20 parts by Mitsubishi Chemical Corporation" And the weight-average particle diameter was changed to 350 μm and SPAN was changed to “355 μm and the SPAN was changed to 0.7”, and the crosslinked polymer particles (A1- B5) was obtained.

<Production Example B6>
"Hydrophobic substance (C-1) 0.19 parts" was changed to "hydrophobic substance (C-5) @ sorbitan oleic acid monoester, IONET S-80 @ Sanyo Chemical Co., Ltd. 0.20 parts", and Crosslinked polymer particles (A1-B6) in the same manner as in Production Example 1, except that "the weight average particle diameter was 340 μm and SPAN was 0.8" was changed to "the weight average particle diameter was 355 μm and SPAN was 0.7". I got

<Production Example B7>
"0.19 parts of hydrophobic substance (C-1)" is replaced with "0.30 parts of hydrophobic substance (C-1) and penetrant (D-1) @polyoxyethylene alkyl ether, NAROACTY CL manufactured by Sanyo Chemical Co., Ltd. Production Example 1 except that “−20｝ 0.20 parts” was changed and “weight average particle diameter was 340 μm, SPAN was 0.8” was changed to “weight average particle diameter was 321 μm, SPAN was 0.8”. In the same manner as in the above, crosslinked polymer particles (A1-B7) were obtained.

<Production Example B8>
"0.19 part of hydrophobic substance (C-1)" is replaced with "0.30 part of hydrophobic substance (C-2) and penetrant (D-1) @polyoxyethylene alkyl ether, NAROACTY CL manufactured by Sanyo Chemical Co., Ltd." Production Example 1 except that “−20｝ 0.20 parts” was changed and “weight average particle diameter was 340 μm, SPAN was 0.8” was changed to “weight average particle diameter was 321 μm, SPAN was 0.8”. In the same manner as in the above, crosslinked polymer particles (A1-B8) were obtained.

<Production Example B9>
"0.19 parts of hydrophobic substance (C-1)" is replaced with "0.30 parts of hydrophobic substance (C-3) and penetrant (D-1) @polyoxyethylene alkyl ether, NAROACTY-CL manufactured by Sanyo Chemical Co., Ltd. Production Example 1 except that “−20｝ 0.20 parts” was changed and “weight average particle diameter was 340 μm, SPAN was 0.8” was changed to “weight average particle diameter was 321 μm, SPAN was 0.8”. In the same manner as in the above, crosslinked polymer particles (A1-B9) were obtained.

<Production Example B10>
"0.19 parts of hydrophobic substance (C-1)" is replaced with "0.30 parts of hydrophobic substance (C-4) and penetrant (D-1) @polyoxyethylene alkyl ether, NAROACTY CL manufactured by Sanyo Chemical Co., Ltd." Production Example 1 except that “−20｝ 0.20 parts” was changed and “weight average particle diameter was 340 μm, SPAN was 0.8” was changed to “weight average particle diameter was 321 μm, SPAN was 0.8”. In the same manner as in the above, crosslinked polymer particles (A1-B10) were obtained.

<Production Example B11>
"0.19 part of hydrophobic substance (C-1)" is replaced with "0.30 part of hydrophobic substance (C-5) and penetrant (D-1) @polyoxyethylene alkyl ether, NAROACTY CL manufactured by Sanyo Chemical Co., Ltd." Production Example 1 except that “−20｝ 0.20 parts” was changed and “weight average particle diameter was 340 μm, SPAN was 0.8” was changed to “weight average particle diameter was 321 μm, SPAN was 0.8”. In the same manner as in the above, crosslinked polymer particles (A1-B11) were obtained.

<Example 1>
While 100 parts by weight of the crosslinked polymer particles (A1-1) obtained in Production Example 1 were stirred at high speed (high-speed stirring turbulizer manufactured by Hosokawa Micron: 2,000 rpm), ethylene glycol distilling agent as a surface crosslinking agent was added thereto. A mixed solution obtained by mixing 0.04 parts by weight of glycidyl ether and 3.0 parts by weight of a 50% aqueous propylene glycol solution as a solvent was added, and after uniform mixing, the mixture was dried by standing at 130 ° C. for 30 minutes. The dried product was sieved to obtain a water-absorbent resin (P-1) of the present invention having a weight average particle size of 366 μm and a SPAN of 0.8.

<Example 2>
“100 parts by weight of crosslinked polymer particles (A1-1)” is changed to “100 parts by weight of crosslinked polymer particles (A1-2)”, and “0.04 parts by weight of ethylene glycol diglycidyl ether” is changed to “ethylene glycol diglycidyl ether”. 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 the glycidyl ether was changed to 0.03 parts by weight.

<Example 3>
Except that “100 parts by weight of crosslinked polymer particles (A1-1)” was changed to “100 parts by weight of crosslinked polymer particles (A1-3)”, the weight average particle diameter was 299 μm and SPAN0 was the same as in Example 1. 2.9 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 diglycidyl ether”. A water-absorbent resin (P-4) of the present invention having a weight average particle diameter of 210 μm and a SPAN of 0.9 was obtained in the same manner as in Example 1, except that the glycidyl ether was changed to 0.03 parts by weight.

<Example 5>
“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 diglycidyl ether”. 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 glycidyl ether was changed to 0.02 parts by weight.

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

<Example 7>
Except that “100 parts by weight of crosslinked polymer particles (A1-1)” was changed to “100 parts by weight of crosslinked polymer particles (A1-B2)”, a weight average particle diameter of 333 μm, SPAN0 was obtained in the same manner as in Example 1. Water-absorbent resin (P-7) of the present invention having a pH of 0.8 was obtained.

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

<Example 9>
Except that “100 parts by weight of crosslinked polymer particles (A1-1)” was changed to “100 parts by weight of crosslinked polymer particles (A1-B4)”, the weight average particle diameter was 331 μm and SPAN0 was the same as in Example 1. The water-absorbent resin (P-9) of the present invention having a pH of 0.7 was obtained.

<Example 10>
Except that “100 parts by weight of crosslinked polymer particles (A1-1)” was changed to “100 parts by weight of crosslinked polymer particles (A1-B5)”, a weight average particle diameter of 372 μm, SPAN0 was obtained in the same manner as in Example 1. Water-absorbent resin (P-10) of the present invention having a pH of 0.7.

<Example 11>
Except that “100 parts by weight of crosslinked polymer particles (A1-1)” was changed to “100 parts by weight of crosslinked polymer particles (A1-B6)”, a weight average particle diameter of 362 μm, SPAN0 was obtained in the same manner as in Example 1. Water-absorbent resin (P-11) of the present invention having a pH of 0.8 was obtained.

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

<Example 13>
Except that “100 parts by weight of crosslinked polymer particles (A1-1)” was changed to “100 parts by weight of crosslinked polymer particles (A1-B8)”, a weight average particle diameter of 335 μm, SPAN0 was obtained in the same manner as in Example 1. 0.8 was obtained.

<Example 14>
Except that “100 parts by weight of crosslinked polymer particles (A1-1)” was changed to “100 parts by weight of crosslinked polymer particles (A1-B9)”, a weight average particle diameter of 334 μm, SPAN0 was obtained in the same manner as in Example 1. Water-absorbent resin (P-14) of the present invention having a pH of 0.8.

<Example 15>
Except that “100 parts by weight of crosslinked polymer particles (A1-1)” was changed to “100 parts by weight of crosslinked polymer particles (A1-B10)”, the weight average particle diameter was 330 μm and SPAN0 was the same as in Example 1. 0.8 was obtained.

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

<Comparative Example 1>
Except that “100 parts by weight of crosslinked polymer particles (A1-1)” was changed to “100 parts by weight of crosslinked polymer particles (A1-6)”, a weight average particle diameter of 365 μm was obtained in the same manner as in Example 1. 2 was obtained as a comparative water-absorbent resin (R-1).

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

<Comparative Example 3>
Except that “100 parts by weight of crosslinked polymer particles (A1-1)” was changed to “100 parts by weight of crosslinked polymer particles (A1-8)”, a weight average particle diameter of 180 μm and SPAN1 were obtained in the same manner as in Example 1. Water absorbent resin (R-3) for comparison 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 (Shin-Etsu Chemical Co., Ltd.) Company: X-22-3701E) in the same manner as in Example 1 except that 0.01 part by weight) was added, and a comparative water-absorbent resin (R-4) having a weight average particle size of 346 μm and a SPAN of 0.8 was used. ) Got.

<Comparative Example 5>
“100 parts by weight of crosslinked polymer particles (A1-1)” is changed to “100 parts by weight of crosslinked polymer particles (A1-10)”, and “0.04 parts by weight of ethylene glycol diglycidyl ether” is changed to “ethylene glycol diglycidyl ether”. 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 the glycidyl ether was changed to 0.03 parts by weight.

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

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

<Comparative Example 8>
Except that “100 parts by weight of crosslinked polymer particles (A1-1)” was changed to “100 parts by weight of crosslinked polymer particles (A1-13)”, a weight average particle diameter of 261 μm and SPAN1 were obtained in the same manner as in Example 1. Thus, a comparative water-absorbent resin (R-8) was obtained.

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

判 As can be seen from Table 1, the water-absorbing resin particles of the present invention (Examples 1 to 16) have a small SPAN (narrow particle size distribution) and an appropriate weight average particle size and absorption rate pattern. Specifically, in Examples 2 and 5, no hydrophobic substance was used, but an appropriate absorption rate pattern was obtained by appropriately setting the weight average particle diameter and SPAN. In Examples 1, 3, and 4, it can be seen that the absorption rate pattern due to the difference in the weight average particle diameter can be controlled to a specific range by adjusting the content of the hydrophobic substance. Examples 6 to 11 illustrate examples using other suitable hydrophobic substances. Furthermore, in Examples 12 to 16, it can be seen that the combined use of the hydrophobic substance (C) and the penetrant (D) further improved the absorption rate by the lock-up method. On the other hand, Comparative Examples 1 and 7 tend to have a higher SPAN and therefore a broader particle size distribution, a lower M2 and a lower absorption rate by the lock-up method than Example 1. In Comparative Example 2, although the SPAN was low, the weight average particle diameter was large, and the absorption rate by the lock-up method was low. Comparative Example 4 uses a highly hydrophobic “carboxy-modified polysiloxane (X-22-3701E, manufactured by Shin-Etsu Chemical Co., Ltd.)” for surface cross-linking, decreases M2, and decreases the absorption rate by the lock-up method. I have. In Comparative Example 5, the weight average particle diameter was reduced without using a hydrophobic substance, and M1 was excessively high. Comparative Example 6 has a high weight average particle diameter and also uses a hydrophobic substance, has a low M1, and has a low absorption rate by the lock-up method. In Comparative Examples 3 and 8, M1 is excessively high because the weight average particle diameter is small and SPAN is high.

Subsequently, when the SPAN was low and the absorption rate pattern was appropriate, what kind of absorption characteristics when applied to an absorbent article was evaluated. 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 the SDME method by liquid drainage from a surface nonwoven fabric were performed. The surface dryness value was evaluated, and the results are shown in Table 2.

<Preparation of absorber>
A styrene-butadiene-styrene copolymer (SBS; softening point: 85 ° C.) was used as an adhesive on a nonwoven fabric A (basis weight: 40 g / m ² , thickness: 0.5 mm, made of polypropylene) cut into rectangular pieces of 10 cm × 40 cm. A hot melt coater (AD41, manufactured by Nordson) is used to uniformly apply to a basis weight of 2.85 g / m ² . An evaluation sample {water-absorbent resin particles} 10.6 g (basis weight 265 g / m ² ) was evenly spread on the surface to which the adhesive was applied, and then nonwoven fabric B (basis weight 45 g / m ² , thickness 7.0 mm, made of polypropylene). Its nonwoven A- absorbent resin - sandwiching sheets became nonwoven B in the acrylic plate (thickness 4 mm), and pressed for 30 seconds at a pressure of 5 kg / cm ^2. After pressing, the acrylic plate on the nonwoven fabric A side is removed, the adhesive, the water-absorbent resin, and the nonwoven fabric B are laminated in the same manner as described above, sandwiched again with the acrylic plate, and pressed at a pressure of 5 kg / cm ² for 30 seconds. An absorber was prepared.

<Preparation of absorbent article>
An absorbent article is provided by disposing a polyethylene sheet (polyethylene film UB-1 manufactured by Tamapoli) on one surface of the absorber and a nonwoven fabric (20 g / m ² basis weight, Eltas Guard manufactured by Asahi Kasei Corporation) on the other surface. Was prepared.

<Dry test by liquid drainage from surface nonwoven fabric>
The absorber prepared above was placed in a box (made of stainless steel) having a width of 11 cm × a length of 41 cm × a height of 4 cm and an open upper portion (11 cm × 41 cm). 500 ml of deionized water adjusted to 32 ± 2 ° C. was prepared and poured into the box containing the absorber at a stretch. Time measurement was started as soon as the deionized water came in contact with the absorber. The time (whitening time) until the deionized water retained on the surface nonwoven fabric was absorbed by the water-absorbent resin and the area where the surface nonwoven fabric appeared white became half of the nonwoven fabric was recorded.

<Surface dryness value by SDME method>
A disposable diaper in which the detector of an SDME (Surface Dryness Measurement Equipment) tester (manufactured by WK system) is sufficiently moistened. Artificial urine (0.03% by weight of potassium chloride, 0.08% by weight of magnesium sulfate, 0.8% by weight of sodium chloride) % And 99.09% by weight of deionized water) to prepare a paper diaper. ＳＤ, and a 0% dryness value was set. Then, the detector of the SDME tester was prepared by drying and drying the paper diaper at 80 ° C. for 2 hours. The sample was placed on the｝, 100% dryness was set, 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 absorption of the artificial urine is completed {if the gloss due to the artificial urine cannot be confirmed}, immediately Remove the metal ring, place three SDME detectors at the center of the disposable diaper and on the left and right sides (3 places at equal intervals of 10 cm from the end 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 values of the remaining two SDME detectors are the surface dryness values (1-2). {Left}, surface dryness value (1-3) {right}. The measurement was performed at 25 ± 5 ° C. and 65 ± 10% RH in artificial urine, measurement atmosphere and standing atmosphere.

As can be seen from Table 2, the absorbent 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 and the absorbent article using the comparative water-absorbent resin particles. (1-1), (1-2) and (1-3) have no bias and are excellent in dryness. On the other hand, Comparative Examples 1, 7, and 8 had a high SPAN, Comparative Examples 2 and 6 had a large weight average particle diameter, and Comparative Example 4 had a low absorption amount (M2) after 5 minutes, and thus had a whitening time, that is, a nonwoven fabric. Poor liquid drainage from the surface. In Comparative Examples 3, 5 and 8, since M1 was excessively high, the liquid diffusibility was poor, and spot absorption was caused, so that the surface dryness value was biased and the dryness was poor. In Comparative Examples 1, 2, 4, and 6 to 8, the absorption speed by the lock-up method is also slow, which indicates that the whitening time tends to decrease. That is, when the water-absorbent resin particles of the present invention are applied to an absorbent body and an absorbent article, it is easily predicted that the non-woven fabric is excellent in liquid drainage and surface dryness, and there is no fear of rash and the like.

The water-absorbent resin particles of the present invention can be applied to an absorber containing the water-absorbent resin particles and a fibrous material, and an absorbent article provided with the absorber, a disposable diaper, a sanitary napkin, and a medical blood retention. It is useful for agents and the like. In addition, pet urine absorbent, urine gelling agent for portable toilets, freshness preserving agent for fruits and vegetables, drip absorbing agent for meat and seafood, cooling agent, disposable body warmer, gelling agent for batteries, water retaining agent for plants and soil, dew condensation It can also be used for various applications such as inhibitors, waterproofing agents, packing agents and artificial snow.

DESCRIPTION OF SYMBOLS 1 Rubber stopper 2 Bullet part 3 Physiological saline 4 Water-absorbing resin particles 5 Plain-woven nylon mesh 6 Measurement table 7 Cock 8 Cock 9 Air introduction pipe

Claims

It comprises a water-soluble vinyl monomer (a1) and / or a vinyl monomer (a2) which becomes a water-soluble vinyl monomer (a1) by hydrolysis, and a crosslinked polymer (A1) having a crosslinker (b) as an essential constituent unit. Water-absorbent resin particles, the weight-average particle size (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, Water-absorbent resin particles having an absorption (M1) of 1 to 15 ml / g after 1 minute and an absorption (M2) of 45 to 55 ml / g after 5 minutes according to a DW (Demand Wetability) method.
SPAN = [D (90%)-D (10%)] / D (50%) ≦ 1.0 (Equation 1)
(In Formula 1, D (10%) is a particle having a cumulative weight fraction of 10% by weight from the particle having the smallest particle size, with the total weight of the water-absorbent resin particles classified using a standard sieve being 100% by weight. D (50%) is the particle size at which the cumulative weight fraction is 50% by weight, and D (90%) is the particle size at which the cumulative weight fraction is 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 water-absorbent resin particles have an absorption rate of 25 seconds or less by a lock-up method of ion-exchanged water.
(4) The water-absorbent resin particles according to any one of (1) to (3), wherein the water-absorbent resin particles have a water retention capacity of physiological saline of 35 to 40 g / g.
An absorbent body comprising the water-absorbent resin particles according to any one of claims 1 to 4 and a nonwoven fabric.
An absorbent article comprising the absorber according to claim 5.