JP7239276B2 - Water-absorbing resin particles and method for producing the same - Google Patents

Description

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

In sanitary materials such as paper diapers, sanitary napkins, and incontinence pads, a water-absorbing resin (also referred to as a Super Absorbent Polymer: SAP) mainly composed of hydrophilic fibers such as pulp and acrylic acid (salt) is used in the absorber. Widely used. In recent years, from the viewpoint of improving QOL (quality of life), the demand for these sanitary materials has shifted to lighter and thinner ones, and along with this, it has become desirable to reduce the amount of hydrophilic fibers used. . Therefore, there is a demand for SAP to play the role that hydrophilic fibers have hitherto played in the absorbent body. For example, an important function of diapers is leakage reduction due to rapid absorption of urine. Conventional absorbents have a high rate of urine absorption due to the physical space existing between bulky hydrophilic fibers, but in absorbents with a high SAP ratio in which the amount of hydrophilic fibers used is reduced, the SAP particles have a filling structure. There is a problem that the physical space is small and the rate of urine absorption is slow.

In addition, conventional absorbers have high urine diffusibility due to capillary action caused by hydrophilic fibers, and urine can be diffused throughout the absorber. In addition to being low, the swelling gel inhibits the diffusion of urine, so that the diffusion of urine in the absorber is remarkably reduced. This reduction in diffusivity, coupled with the aforementioned reduction in absorption rate, is a serious cause of diaper leakage.

As a method for preventing a decrease in diffusibility, the surface of SAP is crosslinked with an aqueous solution containing a specific organic cross-linking agent compound and a specific cation to suppress deformation of the swollen gel surface, thereby efficiently forming gel gaps. is known (see, for example, Patent Document 1).

However, in the method described in Patent Document 1, the liquid permeability between the swollen gels of the absorbent body, that is, the gel bed permeability at 0 psi swelling pressure (hereinafter abbreviated as GBP) is improved, but the SAP absorption speed itself is improved. No improvements have been made, and sufficient performance against diaper leaks and rashes has not yet been demonstrated.

As a method of improving the SAP absorption speed itself, a method of physically increasing the surface area of SAP is generally used. For example, a method of reducing the apparent density by internal foaming in the SAP drying process (Patent Document 2) and a method of reducing the particle size of SAP in the sieving process are also known (Patent Document 3).

Also known is a method of controlling the absorption rate by allowing a surfactant to exist on the SAP surface (for example, Patent Documents 4 and 5).

WO 00/53664 pamphlet Japanese Patent Publication No. 2015-508836 JP-A-2006-143972 JP 2013-203842 A JP 2012-007062 A

However, in the conventional method, the apparent density is greatly reduced, which increases the brittleness of SAP, and the fine powder increases in the diaper manufacturing process. There was a problem of having to increase the basis weight of SAP when manufacturing diapers. Also, when a surfactant is present on the surface of the SAP, the surfactant adhering to the surface dissolves in the urine and lowers the surface tension of the urine. There was also the problem of causing diaper rash.

Therefore, the present invention has a high absorption rate of SAP without reducing the particle size or lowering the apparent density, and even with an absorbent having a high SAP ratio, the diffusibility of the liquid to be absorbed is high, and a surfactant is not used. It is an object of the present invention to provide water-absorbent resin particles that do not dissolve in a liquid to be absorbed even when contained therein and that realize an absorbent body with high diaper performance and the like.

The present invention provides a crosslinked polymer (A) comprising a water-soluble vinyl monomer (a1) and/or a vinyl monomer (a2) that becomes a water-soluble vinyl monomer (a1) by hydrolysis and an internal cross-linking agent (b) as essential structural units. is a water-absorbing resin particle having a structure in which the surface of the resin particles (B) containing containing 0.01 to 0.4% by weight of surfactant (C), the absorption rate measured by the vortex absorption rate measurement method by the whole grain method and the absorption rate measured by the vortex absorption rate measurement method by the sieving method Water-absorbing resin particles whose velocity (second) ratio satisfies formula 1:
0.6<Vt(150-600)/Vt(500-600)<1 (Formula 1)
(In Formula 1, Vt(150-600): Vortex absorption time (whole grain method), Vt(500-600): Vortex absorption time (sieving method).
Further, the present invention provides a monomer composition comprising a water-soluble vinyl monomer (a1) and/or a vinyl monomer (a2) that becomes a water-soluble vinyl monomer (a1) by hydrolysis and an internal cross-linking agent (b) as essential structural units. a polymerization step of polymerizing a substance to obtain a hydrous gel of the crosslinked polymer (A); and adding the surfactant (C) in a step prior to the surface cross-linking step.

The water-absorbing resin particles of the present invention and the water-absorbing resin particles obtained by the production method of the present invention solve the above-described problems and have excellent properties described in detail below. Among them, the absorbent body using the water-absorbing resin particles of the present invention has a high absorption rate and exhibits stable and excellent absorption performance (for example, liquid diffusibility, absorption rate, and absorption amount) in any state. Diaper rash is less likely to occur.

The water-soluble vinyl monomer (a1) is not particularly limited and is known (for example, a vinyl monomers (e.g., anionic vinyl monomers, nonionic vinyl monomers, cationic vinyl monomers), anionic vinyl monomers disclosed in paragraphs 0009 to 0024 of JP-A-2003-165883, nonionic vinyl monomers, cations at least one selected from the group consisting of a carboxylic vinyl monomer, a carboxy group, a sulfo group, a phosphono group, a hydroxyl group, a carbamoyl group, an amino group and an ammonio group disclosed in paragraphs 0041 to 0051 of JP-A-2005-75982. A vinyl monomer such as a vinyl monomer having a vinyl monomer can be used.

The vinyl monomer (a2) that becomes the water-soluble vinyl monomer (a2) by hydrolysis (hereinafter also referred to as hydrolyzable vinyl monomer (a2)) is not particularly limited and is known (for example, 0024 to 0025 of Japanese Patent No. 3648553). A vinyl monomer having at least one hydrolyzable substituent that becomes a water-soluble substituent by hydrolysis disclosed in paragraph, and at least one hydrolyzate disclosed in paragraphs 0052 to 0055 of JP-A-2005-75982. A vinyl monomer such as a vinyl monomer having a decomposable substituent (a 1,3-oxo-2-oxapropylene (--CO--O--CO--) group, an acyl group, a cyano group, etc.) can be used. The water-soluble vinyl monomer means a vinyl monomer having a property of dissolving at least 100 g in 100 g of water at 25°C. Moreover, hydrolyzability means the property of being hydrolyzed by the action of water at 50° C. and, if necessary, a catalyst (acid, base, etc.) to become water-soluble. The hydrolysis of the hydrolyzable vinyl monomer may be performed during polymerization, after polymerization, or both, but preferably after polymerization from the viewpoint of the molecular weight of the resulting water-absorbing resin particles.

Among these, the water-soluble vinyl monomer (a1) is preferable from the viewpoint of absorption properties. The water-soluble vinyl monomer (a1) is preferably an anionic vinyl monomer, more preferably a carboxy (salt) group, a sulfo (salt) group, an amino group, a carbamoyl group, an ammonio group or a mono-, di- or tri-alkyl It is a vinyl monomer having an ammonio group. Among these, more preferably a vinyl monomer having a carboxy (salt) group or a carbamoyl group, more preferably (meth)acrylic acid (salt) and (meth)acrylamide, particularly preferably (meth)acrylic acid (salt), Acrylic acid (salt) is most preferred.

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

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

In addition to the water-soluble vinyl monomer (a1) and the hydrolyzable vinyl monomer (a2), other vinyl monomers (a3) copolymerizable therewith are used as structural units of the crosslinked polymer (A). can be done.

Other copolymerizable vinyl monomers (a3) are not particularly limited and are known (for example, hydrophobic vinyl monomers disclosed in paragraphs 0028 to 0029 of Japanese Patent No. 3648553; Paragraph, vinyl monomers disclosed in JP-A-2005-75982, paragraph 0058) can be used, and the following vinyl monomers (i) to (iii) can be used.
(i) Aromatic ethylenic monomer having 8 to 30 carbon atoms Styrene such as styrene, α-methylstyrene, vinyltoluene and hydroxystyrene, and halogen-substituted styrene such as vinylnaphthalene and dichlorostyrene.
(ii) C2-C20 Aliphatic Ethylene Monomer Alkenes [ethylene, propylene, butene, isobutylene, pentene, heptene, diisobutylene, octene, dodecene, octadecene, etc.]; and alkadienes [butadiene, isoprene, etc.] and the like.
(iii) Alicyclic ethylene monomers having 5 to 15 carbon atoms, monoethylenically unsaturated monomers [pinene, limonene, indene, etc.];

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

The internal cross-linking agent (b) is not particularly limited and is known (for example, a cross-linking agent having two or more ethylenically unsaturated groups disclosed in paragraphs 0031 to 0034 of Japanese Patent No. 3648553; A cross-linking agent having at least one functional group capable of reacting with a water-soluble substituent and having at least one ethylenically unsaturated group, a cross-linking agent having at least two functional groups capable of reacting with a water-soluble substituent, JP-A-2003-165883 A cross-linking agent having two or more ethylenically unsaturated groups, a cross-linking agent having an ethylenically unsaturated group and a reactive functional group, and a cross-linking having two or more reactive substituents disclosed in paragraphs 0028 to 0031 of the publication crosslinkable vinyl monomers disclosed in paragraph 0059 of JP-A-2005-75982, and crosslinkable vinyl monomers disclosed in paragraphs 0015-0016 of JP-A-2005-95759). can. Among these, cross-linking agents having two or more ethylenically unsaturated groups are preferred from the viewpoint of absorption properties, more preferably poly(meth)allyl ethers of polyols having 2 to 10 carbon atoms, and particularly preferably triallyl sia. Nurate, triallyl isocyanurate, tetraallyloxyethane, trimethylolpropane diallyl ether and pentaerythritol triallyl ether, most preferably pentaerythritol triallyl ether.

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

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

Examples of the method for producing the crosslinked polymer (A) include known aqueous solution polymerization (adiabatic polymerization, thin film polymerization, spray polymerization, etc.; JP-A-55-133413, etc.) and known reverse-phase suspension polymerization 54-30710, JP-A-56-26909, JP-A-1-5808, etc.). Of the polymerization methods, the solution polymerization method is preferred, and the aqueous solution polymerization method is particularly preferred because it is advantageous in terms of production cost without the need to use an organic solvent or the like.

During the polymerization, if necessary, a polymerization control agent represented by a chain transfer agent may be used in combination. A carbonyl compound etc. are mentioned. These polymerization control agents may be used alone, or two or more of them may be used in combination. The amount (% by weight) of the polymerization control agent used is the water-soluble vinyl monomer (a1) and the hydrolyzable vinyl monomer (a2), or (a1) to (a3) when the other vinyl monomer (a3) is also used. , preferably 0.0005 to 5, more preferably 0.001 to 2, based on the total weight.

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

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

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

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

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, atmospheric humidity before heating 50 ± 10% RH, lamp specifications 100 V, 40 W ) is obtained from the weight loss of the measurement sample before and after heating when heated by ).

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

In the present invention, surfactants (C) include nonionic surfactants (C1), anionic surfactants (C2), cationic surfactants (C3), and amphoteric surfactants (C4). .

Specific examples of nonionic surfactants (C1) include, for example, aliphatic alcohols (8 to 24 carbon atoms) alkylene oxide (AO) (2 to 8 carbon atoms) adducts (degree of polymerization = 1 to 100) [ Lauryl alcohol ethylene oxide adduct (polymerization degree = 20), oleyl alcohol ethylene oxide adduct (polymerization degree = 10), Macco alcohol ethylene oxide adduct (polymerization degree = 35), etc.], polyoxyalkylene (carbon number 2-8 , degree of polymerization = 1 to 100) higher fatty acid (carbon number 8 to 24) ester [polyethylene glycol monostearate (degree of polymerization = 20), polyethylene glycol distearate (degree of polymerization = 30), etc.], polyvalent (bivalent to 10-valent or more) alcohol fatty acid (C8-24) ester [glyceryl monostearate, ethylene glycol monostearate, sorbitan laurate (mono/di) ester, sorbitan palmitate (mono/di) ester, sorbitan stearin acid (mono/di) ester, sorbitan oleic acid (mono/di) ester, sorbitan coconut oil (mono/di) ester, etc.], polyoxyalkylene (carbon number 2-8, degree of polymerization = 1-100) polyvalent ( Divalent to decavalent or higher) alcohol higher fatty acid (C8-24) ester [polyoxyethylene (degree of polymerization = 10) sorbitan lauric acid (mono/di) ester, polyoxyethylene (degree of polymerization = 20) sorbitan Palmitic acid (mono/di) ester, polyoxyethylene (degree of polymerization = 15) sorbitan stearic acid (mono/di) ester, polyoxyethylene (degree of polymerization = 10) sorbitan oleic acid (mono/di) ester, polyoxyethylene (degree of polymerization = 25) lauric acid (mono/di) ester, polyoxyethylene (degree of polymerization = 50) stearic acid (mono/di) ester, polyoxyethylene (degree of polymerization = 18) oleic acid (mono/di) ester , polyoxyethylene (degree of polymerization = 50) methyl dioleate glucoside, etc.], fatty acid alkanolamide [1:1 type coconut oil fatty acid diethanolamide, 1:1 type lauric acid diethanolamide, etc.], polyoxyalkylene (having 2 to 8, degree of polymerization = 1 to 100) alkyl (carbon number 1 to 22) phenyl ether (polyoxyethylene (degree of polymerization = 20) nonylphenyl ether, etc.), polyoxyalkylene (carbon number 2 to 8, degree of polymerization = 1 to 100) Alkyl (C8-C24) amino ethers and alkyl (8-24 carbon atoms) dialkyl (1-6 carbon atoms) amine oxide [lauryldimethylamine oxide, etc.], polydimethylsiloxane polyoxyethylene adduct, polyoxyethylene/polyoxypropylene block polymer (weight average molecular weight = 150 ~ 10000) and the like.

Of the nonionic surfactants (C1), preferred from the viewpoint of suppressing the reversion of urine to the diaper surface are aliphatic alcohols (8 to 24 carbon atoms) alkylene oxide (AO) (2 to 8 carbon atoms) addition (degree of polymerization = 1 to 100), and compounds represented by the following general formula (I) are more preferred.
R ¹ —O—(AO) _k —H (I)
In general formula (I), R ¹ represents an alkyl or alkenyl group having 8 to 24 carbon atoms, AO represents an oxyalkylene group having 2 to 4 carbon atoms, k represents the average number of added moles, and 2 to 35 represents the number of

In general formula (I), R ¹ is preferably an alkyl or alkenyl group having 8 to 24 carbon atoms. Examples of alkyl groups having 8 to 24 carbon atoms include linear or branched alkyl groups and cycloalkyl groups. Specifically, n- or isooctyl group, 2-ethylhexyl group, n- or isononyl group, n- or isodecyl group, n- or isoundecyl group, n- or isododecyl group, n- or isotridecyl group, n- or isotetra decyl group, n- or isohexadecyl group, n- or isooctadecyl group, n- or isononadecyl group, n- or isoeicosyl group and n- or isotetracosyl group.
Examples of alkenyl groups having 8 to 24 carbon atoms include linear or branched alkenyl groups. Specifically, n- or isooctenyl group, n- or isononenyl group, n- or isodecenyl group, n- or isoundecenyl group, n- or isododecenyl group, n- or isotetradecenyl group, n- or isohexadecenyl group senyl group, n- or isooctadecenyl group, n- or isogadoleyl group, and the like.

Of R ¹ , from the viewpoint of suppressing the reversion of urine to the diaper surface, alkyl and alkenyl groups having 10 to 20 carbon atoms are more preferred, and alkyl and alkenyl groups having 12 to 18 carbon atoms are particularly preferred. .

Specific examples of AO in general formula (I) include an oxyethylene group (hereinafter abbreviated as EO), an oxypropylene group (hereinafter abbreviated as PO), an oxybutylene group, and the like. PO may be linear or branched. As AO, an oxyalkylene group having 2 or 3 carbon atoms is preferable from the viewpoint of suppressing the reversion of urine to the diaper surface. Specific examples include EO and PO.

k in the general formula (I) represents the average number of added moles of the oxyalkylene group, and is a number of 2-35. It is preferably 2 to 30, particularly preferably 2 to 20, from the viewpoint of preventing urine from flowing back to the surface of the diaper. Note that k is not always an integer.

(AO) _k in general formula (I) may contain two or more oxyalkylene groups, and may be random addition or block addition.

The content of EO in (AO) _k is preferably 50 to 100% by weight, more preferably 55 to 100% by weight, based on the total weight of EO and PO, from the viewpoint of suppressing the reversion of urine to the diaper surface. and particularly preferably 60 to 100% by weight.

Examples of the anionic surfactant (C2) include hydrocarbon ether carboxylic acids having 8 to 24 carbon atoms or salts thereof, [polyoxyethylene (degree of polymerization = 1 to 100) sodium lauryl ether acetate, polyoxyethylene (degree of polymerization = 1 to 100) disodium lauryl sulfosuccinate, etc.], hydrocarbon sulfuric ester salts having 8 to 24 carbon atoms [sodium lauryl sulfate, polyoxyethylene (degree of polymerization = 1 to 100) sodium lauryl sulfate, polyoxyethylene (polymerization degree = 1 to 100) triethanolamine lauryl sulfate, polyoxyethylene (degree of polymerization = 1 to 100) coconut oil fatty acid monoethanolamide sodium sulfate,], hydrocarbon sulfonate having 8 to 24 carbon atoms [dodecylbenzene sulfone sodium acid, etc.] and hydrocarbon phosphate salts having 8 to 24 carbon atoms [sodium lauryl phosphate, polyoxyethylene (degree of polymerization = 1 to 100) sodium lauryl ether phosphate, etc.], fatty acid salts [sodium laurate, triethanolamine laurate, etc.], acylated amino acid salts [sodium cocoate methyltaurate, sodium cocoate sarcosine, cocoate sarcosine triethanolamine, N-cocoate acyl-L-glutamic acid triethanolamine, N- sodium coconut oil fatty acid acyl-L-glutamate, sodium lauroylmethyl-β-alanine, etc.], and others [polyoxyethylene sulfosuccinate (degree of polymerization = 1 to 100) disodium lauroylethanolamide, etc.].

Examples of the cationic surfactant (C3) include quaternary ammonium salt type [stearyltrimethylammonium chloride, behenyltrimethylammonium chloride, distearyldimethylammonium chloride, ethyl sulfate lanolin fatty acid aminopropylethyldimethylammonium, etc.], amine salt type [ stearic acid diethylaminoethylamide lactate, dilaurylamine hydrochloride, oleylamine lactate, etc.] and the like.

Examples of amphoteric surfactants (C4) include betaine-type amphoteric surfactants [coconut fatty acid amidopropyldimethylaminoacetate betaine, lauryldimethylaminoacetate betaine, 2-alkyl-N-carboxymethyl-N-hydroxyethylimidazolinium betaine , lauryl hydroxysulfobetaine, lauroylamidoethyl hydroxyethyl carboxymethyl betaine sodium hydroxypropyl phosphate, etc.], amino acid type amphoteric surfactants [sodium .beta.-laurylaminopropionate, etc.].

One or more of these surfactants can be used. Among these, nonionic surfactants (C1) and anionic surfactants (C2) are preferred. Nonionic surfactant (C1) is more preferred. Nonionic surfactants represented by general formula (I) are particularly preferred. By using a surfactant in combination, the effects of the present invention can be exhibited more remarkably.

The amount of the surfactant (C) added is the water-soluble vinyl monomer (a1), the hydrolyzable vinyl monomer (a2), (a1) to (a3) when another vinyl monomer (a3) is also used, and the internal It is 0.01 to 0.4% by weight based on the total weight of the cross-linking agent (b) (in other words, the weight of the cross-linked polymer (A)). If it is less than 0.01% by weight, the effect on the vortex absorption rate is small, and if it exceeds 0.4% by weight, the surfactant kneaded inside bleeds out to the surface to lower the surface tension of urine. It is preferably 0.05 to 0.3% by weight, more preferably 0.1 to 0.2% by weight.

As the water absorbent resin particles of the present invention, the water absorbent resin particles having a structure in which the surface of the resin particles (B) containing the crosslinked polymer (A) is crosslinked with the surface crosslinking agent (d) is a surfactant (C ), but from the viewpoint of absorption properties, it is preferable that the surfactant (C) is present without being unevenly distributed inside the crosslinked polymer (A).

A preferred method for obtaining water-absorbent resin particles containing a surfactant (C) is (i) a water-soluble vinyl monomer (a1) and/or a hydrolyzable vinyl monomer (a2) and an internal cross-linking agent (b). A method of polymerizing a monomer composition as an essential component in the presence of a surfactant (C) (hereinafter also referred to as a polymerization method), (ii) a hydrous gel containing the crosslinked polymer (A) a method of mixing with a surfactant (C) (hereinafter also referred to as a mixing method); (hereinafter also referred to as a surface cross-linking method). The water-absorbing resin particles obtained by the polymerization method (i) and the mixing method (ii) have the surfactant (C) present without being unevenly distributed inside the crosslinked polymer (A), so from the viewpoint of absorption characteristics preferred from

The polymerization method (i) can be carried out by allowing the surfactant (C) to coexist with the monomer composition and polymerizing by the method described above. Among them, a method of performing aqueous polymerization in the presence of a surfactant (C) is preferred.

The mixing method (ii) can be performed by mixing the surfactant (C) with the hydrogel obtained by aqueous polymerization of the monomer composition. The hydrogel and the surfactant (C) can be mixed by mixing the hydrogel and the surfactant (C) with a known stirring and mixing device (Henschel mixer, planetary mixer, universal mixing device, etc.). can. Alternatively, when the hydrous gel is cut by a cutting device, the hydrous gel and the surfactant (C) can be put into the cutting device at the same time. When the surfactant (C) is mixed with the hydrous gel, (C) may be added neat (neat), but (C) is an aqueous solution or a dispersion solution, which is a crosslinked polymer It is preferable because it can be uniformly added to the inside of (A). When (C) is an aqueous solution or dispersion solution, the appropriate concentration is 0.01 to 50% by weight. More preferably, it is 0.1 to 30% by weight. When the solution concentration is 0.01% by weight or more, the amount of water in the hydrogel does not increase and the drying efficiency does not deteriorate when the amount of the (C) solution added to the hydrogel increases. When the amount is 50% by weight or less, the viscosity of the aqueous solution or dispersion solution of (C) does not increase, the handling is easy, the addition to the hydrous gel becomes uniform, and the effect of improving the vortex absorption speed is exhibited.

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

The product (hydrous gel) obtained by polymerization method (i) or mixing method (ii) can be pulverized after drying. The method of pulverization is not particularly limited, and a pulverizer (for example, a hammer type pulverizer, an impact type pulverizer, a roll type pulverizer, and a jet pulverizer) or the like can be used. The pulverized crosslinked polymer can be adjusted in particle size by sieving or the like, if necessary.

The water-absorbing resin particles of the present invention have a structure in which the surfaces of the resin particles (B) containing the crosslinked polymer (A) are surface-crosslinked with the surface-crosslinking agent (d).

As the surface cross-linking agent (d), known ones (polyhydric glycidyl compounds, polyhydric amines, polyhydric aziridines, polyhydric isocyanates, etc. described in JP-A-59-189103) can be used. Among these surface cross-linking agents (d), polyhydric glycidyl compounds are preferred, and ethylene glycol diglycidyl ether is most preferred, from the viewpoint of economy and absorption properties.

The amount (% by weight) of the surface cross-linking agent (d) used is not particularly limited because it can be varied depending on the type of the surface cross-linking agent (d), cross-linking conditions, target performance, etc. From the point of view, when other vinyl monomers (a3) of the water-soluble vinyl monomer (a1), the hydrolyzable vinyl monomer (a2), and the internal cross-linking agent (b) used in the crosslinked polymer (A) are also used, Based on the total weight of (a1) to (a3), it is preferably 0.03 to 0.5, more preferably 0.05 to 0.3, and particularly preferably 0.08 to 0.2.

The surface cross-linking with the surface cross-linking agent (d) is preferably carried out, for example, by surface-cross-linking the resin particles (B) containing the cross-linked polymer (A) and the surfactant (C) with the surface cross-linking agent (d). It can be done in the process. On the other hand, if the surfactant (C) is added at the time of surface cross-linking, absorption characteristics such as liquid permeability may be deteriorated, which may not be preferable.

The surface cross-linking step can be performed by mixing the resin particles (B) and the surface cross-linking agent (d) and further heating, and is known (for example, Japanese Patent No. 3648553, Japanese Patent Application Laid-Open No. 2003-165883). , surface cross-linking treatment methods described in JP-A-2005-75982 and JP-A-2005-95759).

As a preferred method for the step of surface cross-linking, while stirring the resin particles (B), an aqueous solution of the surface cross-linking agent (d) is sprayed onto the surfaces of the resin particles (B), and then the resin particles (B) are stirred or allowed to stand still. A method of heating to 100 to 200° C. (preferably 120 to 160° C.) can be mentioned.
When an aqueous solution of the surface cross-linking agent (d) is sprayed onto the surfaces of the resin particles (B), the concentration of the surface cross-linking agent (d) contained in the aqueous solution to be sprayed can be adjusted according to the type of the surface cross-linking agent (d). However, from the viewpoint of absorption characteristics, etc., it is preferably 0.1 to 10% by weight.
The amount of the aqueous solution to be sprayed is preferably 0.5 to 15% by weight based on the weight of the resin particles (B) from the viewpoint of uniformity of surface cross-linking.
Among the steps of surface cross-linking, spraying an aqueous solution of the surface-cross-linking agent (d) onto the resin particles (B) under stirring can be carried out using a known fluidized humidifying mixing granulator [Flexomix (manufactured by Hosokawa Micron Corporation) and Shugi Flexomix (manufactured by Powrex Co., Ltd., etc.)] and known powder mixers [V-type mixer, Henschel mixer and turbulizer (manufactured by Hosokawa Micron Corporation), etc.], and mixing devices equipped with known spray devices, etc. can be done using

Among the steps of surface cross-linking, heating to 100 to 200 ° C. in a stirred state is performed by subjecting the resin particles (B) sprayed with a surface cross-linking agent to a known stirring device equipped with a heating device (dual-arm kneader, etc.). It can be carried out by stirring while heating using.
In the step of surface cross-linking, heating to 100 to 200° C. in a stationary state can be performed using a known heat drying device (air circulation dryer, etc.).
The heating time for heating to 100 to 200° C. is 3 to 60 minutes, preferably 10 to 40 minutes.

As a method for mixing the resin particles (B) and the surface cross-linking agent (d), in addition to the method of spraying the aqueous solution of the surface cross-linking agent (d), the resin particles (B) are mixed with the surface cross-linking agent (d). A method of immersion in an aqueous solution can also be used. When the resin particles (B) are immersed in an aqueous solution of the surface cross-linking agent (d), surface cross-linking can be performed by heating while stirring.

After performing the step of surface cross-linking, the particle size may be adjusted by further sieving.

When the particle size is adjusted by sieving, the weight average particle diameter (μm) of the water-absorbent resin particles obtained after sieving is preferably 100 to 800, more preferably 200 to 700, and next preferably 250. ~600, particularly preferably 300-500, most preferably 350-450. Within this range, the absorption performance is further improved.

In addition, the weight average particle size was measured using a low-tap test sieve shaker and standard sieve (JIS Z8801-1: 2006), Perry's Chemical Engineers Handbook 6th Edition (McGrow Hill Book Company, 1984). , page 21). That is, JIS standard sieves of 1000 μm, 850 μm, 710 μm, 500 μm, 425 μm, 355 μm, 250 μm, 150 μm, 125 μm, 75 m, and 45 μm and a saucer are combined in this order from the top. About 50 g of the particles to be measured are placed in the top sieve and shaken for 5 minutes with a Rotap test sieve shaker. The weight of the particles to be measured on each sieve and the tray is weighed, the total is 100% by weight, and the weight fraction of the particles on each sieve is obtained. ) and weight fraction on the vertical axis), draw a line connecting each point, determine the particle diameter corresponding to a weight fraction of 50% by weight, and take this as the weight average particle diameter.

In addition, from the viewpoint of absorption performance, the content of fine particles of 106 μm or less (preferably 150 μm or less) contained in the water absorbent resin particles is added to the total weight of the water absorbent resin particles. 3% by weight or less, more preferably 1% by weight or less. The content of fine particles can be determined using the plot created when determining the weight-average particle size.

The apparent density (unit: g/ml; hereinafter the same) of the water absorbent resin particles is preferably 0.54 to 0.70, more preferably 0.56 to 0.68, particularly preferably 0.58 to 0.58. is 66. Within this range, the absorption performance is further improved. In addition, an apparent density is measured at 25 degreeC based on JISK7365:1999.

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

The water absorbent resin particles of the present invention can be preferably produced by the production method of the present invention. In the production method of the present invention, a monomer having a water-soluble vinyl monomer (a1) and/or a vinyl monomer (a2) that becomes a water-soluble vinyl monomer (a1) by hydrolysis and an internal cross-linking agent (b) as essential structural units A polymerization step of polymerizing the composition to obtain a hydrous gel of the crosslinked polymer (A), and a step of surface-crosslinking the surface of the resin particles (B) containing the crosslinked polymer (A) with the surface-crosslinking agent (d). and adding the surfactant (C) in a step prior to the surface cross-linking step. In the production method of the present invention, the water-soluble vinyl monomer (a1) is preferably (meth)acrylic acid. The above-described methods can be used for the polymerization step and the surface-crosslinking step, respectively. Further, the step of adding the surfactant (C) in a step prior to the step of surface-crosslinking is also performed, for example, before the step of surface-crosslinking with the surface-crosslinking agent (d), the cross-linked polymer (A) and the surfactant It can be carried out by preparing resin particles (B) containing (C).

The water-absorbent resin particles of the present invention can further contain inorganic powder (E) on the particle surface, and for this reason, the production method of the present invention may further include a step of mixing with inorganic powder (E). The inorganic powder (E) includes hydrophilic inorganic particles (e1) and hydrophobic inorganic particles (e2). Examples of hydrophilic inorganic particles (e1) include particles of glass, silica gel, silica and clay. Examples of the hydrophobic inorganic particles (e2) include particles of carbon fiber, kaolin, talc, mica, bentonite, sericite, asbestos and shirasu. Among these, hydrophilic inorganic particles (e1) are preferred, and silica is most preferred.

The shape of the hydrophilic inorganic particles (e1) and the hydrophobic inorganic particles (e2) may be amorphous (crushed), spherical, film-like, rod-like, or fibrous. Alternatively, it is preferably spherical, more preferably spherical.

The content (% by weight) of the inorganic powder (E) {amount present on the surface of the particles} is preferably 0.01 to 3.0, more preferably 0.05 to 0.05, based on the weight of the crosslinked polymer (A). 1.0, then preferably 0.1 to 0.8, particularly preferably 0.2 to 0.7 and most preferably 0.3 to 0.6. Within this range, the rash resistance of the absorbent article is further improved.

The water absorbent resin particles of the present invention may further contain a polyvalent metal salt (f), and for this reason, the production method of the present invention may further include a step of mixing with the polyvalent metal salt (f). good. By containing the polyvalent metal salt (f), the blocking resistance and liquid permeability of the water absorbent resin particles are improved. Examples of the polyvalent metal salt (f) include salts of at least one metal selected from the group consisting of magnesium, calcium, zirconium, aluminum and titanium and the aforementioned inorganic or organic acids. As the polyvalent metal salt (f), from the viewpoint of availability and solubility, inorganic acid salts of aluminum and inorganic acid salts of titanium are preferable, and aluminum sulfate, aluminum chloride, potassium aluminum sulfate and sulfuric acid are more preferable. Sodium aluminum, particularly preferred are aluminum sulphate and sodium aluminum sulphate, most preferred is sodium aluminum sulphate. These may be used individually by 1 type, and may use 2 or more types together.

The amount (% by weight) of the polyvalent metal salt (f) used is preferably 0.05 to 5, more preferably 0.1 to 100 parts by weight of the water-absorbing resin, from the viewpoint of absorption performance and blocking resistance. 3, particularly preferably 0.2 to 2.

When the production method of the present invention includes the step of mixing with the polyvalent metal salt (f), the step of mixing with the polyvalent metal salt (f) is performed before the surface cross-linking step, after the surface cross-linking step, and at the same time as the step of surface cross-linking.

Mixing methods for the polyvalent metal salt (f) include a cylindrical mixer, a screw mixer, a screw extruder, a turbulizer, a Nauta mixer, a double-arm kneader, a fluid mixer, and a V-type mixer. a mixing machine, a mincing mixer, a ribbon type mixer, an air flow type mixer, a rotating disc type mixer, a conical blender, a roll mixer, and the like, and a method of uniform mixing using such known mixing devices.
When mixing before or after the step of surface cross-linking, the temperature during mixing is not particularly limited, but is preferably 10 to 150°C, more preferably 20 to 100°C, and particularly preferably 25 to 80°C.
When mixing at the same time as the step of surface cross-linking, the temperature at the time of mixing is not particularly limited, but it can be carried out under the same conditions as in the step of surface cross-linking with the surface cross-linking agent (d).
In the production method of the present invention, the particle size may be further adjusted after the step of mixing with the polyvalent metal salt (f).

The water-absorbent resin particles of the present invention may contain other additives {for example, known antiseptic agents (Japanese Unexamined Patent Publication No. 2003-225565, Japanese Unexamined Patent Publication No. 2006-131767, etc.), antifungal agents, antibacterial agents, antioxidants, ultraviolet Absorbents, coloring agents, fragrances, deodorants, organic fibrous materials, etc.} may also be included. When these additives are contained, the content (% by weight) of the additives is preferably 0.001 to 10, more preferably 0.01 to 5, especially 0.01 to 5, based on the weight of the crosslinked polymer (A). It is preferably between 0.05 and 1, most preferably between 0.1 and 0.5.

The water-absorbent resin particles of the present invention have a ratio (formula 1) of the absorption rate (sec) measured by the vortex absorption rate measurement method by the whole grain method and the absorption rate (second) measured by the vortex absorption rate measurement method by the sieving method. greater than 0.6 and less than 1.
0.6<Vt(150-600)/Vt(500-600)<1 (Formula 1)

The absorption rate measured by the vortex absorption rate measurement method by the whole grain method (hereinafter also referred to as the vortex absorption rate measurement method (whole grain method)) is the measurement sample (b1) containing particles with a small particle size. vortex absorption rate (seconds) and is denoted as Vt (150-600). In addition, the absorption rate measured by the vortex absorption rate measurement method by the sieving method (hereinafter also referred to as the vortex absorption rate measurement method (sieving method)) is the measurement sample (b2) excluding the small particle size. vortex absorption rate (seconds) and is denoted as Vt (500-600).

The ratio [Vt (150-600)/Vt (500-600)] of the vortex absorption speed (seconds) measured by the whole grain method and the vortex absorption speed (seconds) measured by the sieving method is 0.6. greater than and less than one. If it is 0.6 or less, the absorption rate of the water-absorbent resin particles is too fast, causing spot absorption of urine, which is not practical for diaper use. On the other hand, if it is 1 or more, it is necessary to have a small particle size and a low apparent density in order to improve the absorption speed, and as a result, the absorption characteristics are adversely affected. It is known that the absorption rate depends on the particle size and surface area, and that the smaller the particle size, the higher the absorption rate. The water-absorbing resin particles of the present invention have a low dependence of the absorption rate on the particle diameter, and by optimizing the absorption rate ratio, exhibit excellent absorption properties even at a high absorption rate. From the viewpoint of absorption performance, it is preferably 0.70 to 1, more preferably 0.80 to 0.92.

The absorption time measured by the vortex absorption rate measurement method is measured in a room at 25±2° C. and a humidity of 50±10% by the following method. The temperature of the physiological saline solution to be used is adjusted in advance to 25°C ± 2°C.

<Absorption rate measured by vortex absorption rate measurement method>
2.000 g of water-absorbent resin particles were required to absorb 50 g of physiological saline stirred at 600 revolutions per minute in a 100 ml tall beaker with a flat bottom defined in JIS R 3503. The time (unit: seconds) is measured in accordance with JIS K7224-1996, and taken as the absorption rate measured by the vortex test. The whole grain method and the sieving method described herein perform vortex absorption rate measurements according to the following method.

<Whole grain method>
Using a low-tap test sieve shaker and standard sieves (JIS Z8801-1:2006), JIS standard sieves are combined in the order of 600 μm, 500 μm, 300 μm, 150 μm and a saucer from the top. About 100 g of the surface-crosslinked resin particles (B) are placed in the uppermost sieve and shaken for 5 minutes with a Rotap test sieve shaker. The resin particles (B) on each sieve (500 μm, 300 μm, 150 μm) are collected, and 35% by weight from the 500 μm sieve, 55% by weight from the 300 μm sieve, and 10% by weight from the 150 μm sieve are mixed and mixed. (B1) is obtained. Standard sieves of 600 μm, 300 μm, and a tray are combined in this order, resin particles (B1) are put from above, shaken for 5 minutes with a low-tap test sieve shaker, and the sample on the 300 μm sieve is vortexed to measure the absorption rate. This is sample (b1). The vortex absorption rate measured using the measurement sample (b1) is defined as Vt (150-600).

<Sieving method>
Standard sieves of 600 μm, 500 μm and a tray are combined in this order, the resin particles (B1) are put in from above, shaken with a low-tap test sieve shaker for 5 minutes, and the sample on the 500 μm sieve is subjected to vortex absorption speed measurement. is a measurement sample (b2). The vortex absorption rate measured using the measurement sample (b2) is defined as Vt (500-600).

Moreover, the water absorbent resin particles of the present invention preferably satisfy the following formula 2.
0.6≦Vt(Surfactant)/Vt(Blank)≦0.9 (Formula 2)
In Formula 2, Vt (Surfactant) represents the vortex absorption rate of the water-absorbent resin particles containing the surfactant (C), and Vt (Blank) represents the vortex absorption rate of the absorbent resin particles not containing the surfactant (C). Absorption rate (absorption rate measured by vortex absorption kinetics) is expressed. The ratio of the absorption speed (seconds) of the water-absorbing resin particles containing the surfactant (C) measured by the vortex absorption speed measurement method to the absorption speed (seconds) without the surfactant (C) was 0.5. It is preferably 6 or more and 0.9 or less. If it is less than 0.6, the absorption speed of the water-absorbing resin particles is too fast, and spot absorption of urine may occur. On the other hand, if it is larger than 0.9, it is necessary to have a small particle size and a low apparent density in order to improve the absorption speed, and as a result, the absorption characteristics may be adversely affected.

The water-absorbing resin particles of the present invention are obtained by adding 1 g of water-absorbing resin particles to 200 ml of physiological saline (25° C.) and extracting the eluted components by the method described below. It is preferably 60 to 73 dyn/cm, more preferably 67 to 73 dyn, from the viewpoint of urine reversion. The surface tension of the extract is measured in a room at 25±2° C. and 50±10% humidity by the following methods. The temperature of the physiological saline solution to be used is adjusted in advance to 25°C ± 2°C.

<Surface tension of water absorbent resin particle extract>
The surface tension (T) of the extract was measured by putting 200 ml of 0.9 wt% sodium chloride aqueous solution (physiological saline) and a stirrer piece (total length of 37 mm) in a 250 ml glass beaker and stirring the stirrer piece at 600 ± 5 rpm. 1.000 ± 0.005 g of the sample water-absorbing resin particles was added to the physiological saline solution while stirring, and the stirring was continued for 3 minutes, and then allowed to stand for 15 minutes. Then, the surface tension of the supernatant liquid is measured with a Denuy surface tensiometer (for example, a Denuy surface tensiometer manufactured by Shimadzu Corporation). This operation is repeated three times, and the arithmetic mean value of these is taken as the surface tension of the extract.

<Surfactant Content in Water Absorbent Resin Particles>
The content of the surfactant (C) in the water absorbent resin particles is determined by adding deionized water or a mixed solvent of deionized water and a hydrophilic organic solvent (e.g., acetone, methanol, ethanol, diethylene glycol, etc.) to the water absorbent resin. After (C) in the particles is extracted (method below), it can be quantified using high-performance liquid chromatography (eg, column: SCR-101H, temperature: 40° C., eluent: water/methanol, etc.). Extraction is performed by pulverizing 1 g of the water-absorbent resin with a roll mill, dispersing it in 249 g of physiological saline, and stirring at 25° C.±2° C. for 3 hours. This solution is filtered and the filtrate is analyzed by liquid chromatography according to known methods. The amount of surfactant in the water-absorbing resin particles is obtained by converting the measured surfactant content in the filtrate per 1 g of resin.

<Centrifugal Retention Volume (CRC) of Physiological Saline>
Measured according to the CRC test method described in Japanese Patent No. 5236668, 0.200 g of the water-absorbent resin particles were placed in physiological saline (0.9% by mass sodium chloride aqueous solution) for 30 minutes under no pressure. After swelling, the water is drained by a centrifuge, and the amount of physiological saline retained by the water-absorbing resin particles after draining (unit: [g/g]) is measured. In addition, the higher the CRC, the higher the water absorption performance of the water-absorbing resin particles, and from the viewpoint of the relationship with the water absorption property and other physical properties, it is preferably 25 or more, more preferably 27 or more, and even more preferably 29 or more. . Moreover, 40 or less are preferable and, as for an upper limit, 38 or less are more preferable.

<Gel bed permeability test (GBP) at swelling pressure at 0 psi>
It is measured according to the GBP test method at 0 psi swelling pressure described in Japanese Patent No. 5236668 (unit: [darcies]). In addition, the higher the GBP, the more excellent the absorption rate of the water-absorbent resin particles and the liquid permeability between the swollen gels. Preferably, 40 or more is even more preferable.

The water-absorbing resin particles obtained by the method for producing the water-absorbing resin particles of the present invention or the water-absorbing resin particles of the present invention (hereinafter also simply referred to as the water-absorbing resin particles or the water-absorbing resin particles of the present invention without distinguishing between the two) ) may be used alone as an absorber, or may be used together with other materials to form an absorber. Other materials preferably include fibrous materials. The structure and manufacturing method of the absorbent when used with fibrous materials are the same as those of known ones (Japanese Patent Laid-Open Nos. 2003-225565, 2006-131767 and 2005-097569). be.

Cellulose fibers, organic synthetic fibers, and mixtures of cellulosic fibers and organic synthetic fibers are preferable as the fibrous material.

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

Examples of organic synthetic fibers include polypropylene fibers, polyethylene fibers, polyamide fibers, polyacrylonitrile fibers, polyester fibers, polyvinyl alcohol fibers, polyurethane fibers, and heat-fusible composite fibers (the above fibers having different melting points). (sheath-and-core type, eccentric type, side-by-side type, etc.), fibers obtained by blending at least two of the above fibers, and fibers obtained by modifying the surface layer of the above fibers.

Among these fibrous materials, cellulosic natural fibers, polypropylene fibers, polyethylene fibers, polyester fibers, heat-fusible conjugate fibers and mixed fibers thereof are preferred, and more preferred are fluff pulp, heat-fusible conjugate fibers and mixed fibers thereof in that they are excellent in shape retention after water absorption by the water absorbing agent.

The length and thickness of the above-mentioned fibrous material are not particularly limited, and a length of 1 to 200 mm and a thickness of 0.1 to 100 denier can be suitably used. The shape is not particularly limited as long as it is fibrous, and examples include a thin cylindrical shape, a split yarn shape, a staple shape, a filament shape, a web shape, and the like.

In the case of the absorbent containing the water absorbent resin particles and the fibrous material, the weight ratio of the water absorbent resin particles to the fibrous material (weight of the water absorbent resin particles/weight of the fibrous material) is 40/60. ~90/10 is preferred, more preferably 70/30 to 80/20.

The absorbent body of the present invention contains the water absorbent resin particles. The absorbent body of the present invention may be an absorbent body containing water-absorbing resin particles alone, or may be an absorbent body containing water-absorbing resin particles and fibrous materials. The absorbent body of the present invention can be used as an absorbent article. Absorbent articles include not only sanitary products such as paper diapers and sanitary napkins, but also various applications such as absorption and retention of various aqueous liquids, gelling agent applications (e.g., pet urine absorbent, urine gel for portable toilets, etc.) freshness-preserving agents for fruits and vegetables, drip absorbents for meat and seafood, refrigerants, disposable body warmers, gelling agents for batteries, water-retaining agents for plants and soil, anti-condensation agents, waterproofing materials, packing materials, artificial snow etc.). The manufacturing method of the absorbent article and the like are the same as those known (described in JP-A-2003-225565, JP-A-2006-131767, JP-A-2005-097569, etc.).

EXAMPLES The present invention will be further described with reference to Examples and Comparative Examples below, but the present invention is not limited to these.

< Reference example 1>
Acrylic acid (manufactured by Mitsubishi Chemical Co., Ltd., purity 100%, the same applies hereinafter) 135 parts, pentaerythritol triallyl ether (manufactured by Daiso Co., Ltd., the same applies hereinafter) 0.4 parts and Beaulight LCA-30 (Sanyo 0.068 parts of Kasei Kogyo Co., Ltd.) and 363 parts of deionized water were kept at 3° C. while stirring and mixing. After nitrogen was introduced into this mixture to reduce the dissolved oxygen content to 1 ppm or less, 0.5 part of a 1% aqueous hydrogen peroxide solution, 1 part of a 2% ascorbic acid aqueous solution and 2% 2,2'-azobisamidinopropane were added. 0.3 part of an aqueous dihydrochloride solution was added and mixed to initiate polymerization. After the temperature of the mixture reached 80° C., the mixture was polymerized at 80±2° C. for about 5 hours to obtain hydrous gel (1).

Next, while shredding the entire amount of the obtained hydrous gel (1) with a mincing machine (12VR-400K manufactured by ROYAL), 180 parts of a 30% aqueous sodium hydroxide solution is added and mixed and neutralized to obtain a shredded gel. got Further, the shredded gel was dried with a ventilation band dryer (140° C., wind speed 2 m/sec) to obtain a dry body. After pulverizing the dried product with a juicer mixer (Osterizer Blender manufactured by Oster), it is sieved and adjusted to a particle size range of 600 to 150 μm with an opening (400 μm as a weight average particle size), and the moisture content is 6%. Resin particles (B1) were obtained.

2% aqueous solution of ethylene glycol diglycidyl ether (Denacol EX-810, manufactured by Nagase Kasei Kogyo Co., Ltd.) while stirring 100 parts of the obtained resin particles (B1) at high speed (high-speed stirring turbulizer manufactured by Hosokawa Micron: 2000 rpm). 4 parts are added and mixed while spraying, and the mixture is allowed to stand at 140° C. for 30 minutes in a circulating air dryer (manufactured by Tabai Espec Co., Ltd.) to perform surface cross-linking, and the water absorbent resin particles (1) of the present invention are obtained. Obtained.

< Reference example 2>
The present invention to obtain water absorbent resin particles (2).

<Example 3>
135 parts of acrylic acid (manufactured by Mitsubishi Chemical Corporation, purity 100%, the same applies hereinafter), 0.4 parts of pentaerythritol triallyl ether (manufactured by Daiso Co., Ltd., the same applies hereinafter), and 363 parts of deionized water are stirred. • Maintained at 3°C while mixing. After nitrogen was introduced into this mixture to reduce the dissolved oxygen content to 1 ppm or less, 0.5 part of a 1% aqueous hydrogen peroxide solution, 1 part of a 2% ascorbic acid aqueous solution and 2% 2,2'-azobisamidinopropane were added. 0.3 part of an aqueous dihydrochloride solution was added and mixed to initiate polymerization. After the temperature of the mixture reached 80° C., the mixture was polymerized at 80±2° C. for about 5 hours to obtain hydrous gel (2).

Next, while shredding the entire amount of the obtained hydrous gel (2) with a mincing machine (12VR-400K manufactured by ROYAL), 180 parts of a 30% aqueous sodium hydroxide solution is added and mixed and neutralized to obtain a shredded gel. got Further, 0.204 parts of Naloacty CL-20 (manufactured by Sanyo Chemical Industries, hereinafter the same) was added to the shredded gel and kneaded with the above mincing machine. After that, it was dried with a ventilation type band dryer (140° C., wind speed 2 m/sec) to obtain a dried product. The dried product was pulverized with a juicer mixer (Osterizer Blender manufactured by Oster), sieved, and adjusted to a particle size range of 600 to 150 μm (weight average particle size: 400 μm) to obtain resin particles.

4 parts of a 2% aqueous solution of ethylene glycol diglycidyl ether (Denacol EX-810, manufactured by Nagase Kasei Kogyo Co., Ltd.) was added to 100 parts of the resulting resin particles while stirring at high speed (high-speed stirring turbulizer manufactured by Hosokawa Micron: 2000 rpm). They were added and mixed while being sprayed, and allowed to stand at 140° C. for 30 minutes in a circulating dryer (manufactured by Tabai Espec Co., Ltd.) for surface cross-linking to obtain the water absorbent resin particles (3) of the present invention.

< Reference example 4>
In the same manner as in Example 3, except that "Naroacty CL-20 (manufactured by Sanyo Chemical Industries) 0.204 parts" was changed to "Lebon LD-36 (manufactured by Sanyo Chemical Industries) 0.408 parts", Water absorbent resin particles (4) were obtained.

< Reference example 5>
"Pentaerythritol triallyl ether (manufactured by Daiso Co., Ltd., the same applies hereinafter) 0.4 parts" was changed to "Pentaerythritol triallyl ether (manufactured by Daiso Co., Ltd., the same applies hereinafter) 0.68 parts". Water absorbent resin particles (5) of the present invention were obtained in the same manner as in Reference Example 4 except for the above.

< Reference example 6>
"Pentaerythritol triallyl ether (manufactured by Daiso Co., Ltd., the same applies hereinafter) 0.4 parts" was changed to "Pentaerythritol triallyl ether (manufactured by Daiso Co., Ltd., the same applies hereinafter) 0.80 parts". Water absorbent resin particles (6) of the present invention were obtained in the same manner as in Reference Example 4 except for the above.

<Example 7>
135 parts of acrylic acid (manufactured by Mitsubishi Chemical Corporation, purity 100%, the same applies hereinafter), 0.068 parts of pentaerythritol triallyl ether (manufactured by Daiso Co., Ltd., the same applies hereinafter), and 363 parts of deionized water are stirred. • Maintained at 3°C while mixing. After nitrogen was introduced into this mixture to reduce the dissolved oxygen content to 1 ppm or less, 0.5 part of a 1% aqueous hydrogen peroxide solution, 1 part of a 2% ascorbic acid aqueous solution and 2% 2,2'-azobisamidinopropane were added. 0.3 part of an aqueous dihydrochloride solution was added and mixed to initiate polymerization. After the temperature of the mixture reached 80° C., the mixture was polymerized at 80±2° C. for about 5 hours to obtain hydrous gel (7).

Next, while shredding the entire amount of the obtained hydrous gel (7) with a mincing machine (12VR-400K manufactured by ROYAL), 180 parts of a 30% aqueous sodium hydroxide solution is added and mixed and neutralized to obtain a shredded gel. Obtained. Further, 0.014 part of Naloacty CL-20 (manufactured by Sanyo Chemical Industries) was added to the shredded gel and kneaded with the above mincing machine. After that, it was dried with a ventilation type band dryer (140° C., wind speed 2 m/sec) to obtain a dried product. The dried product was pulverized with a juicer mixer (Osterizer Blender manufactured by Oster), sieved, and adjusted to a particle size range of 600 to 150 μm with openings to obtain resin particles.

1 part of a 2% aqueous solution of ethylene glycol diglycidyl ether (Denacol EX-810, manufactured by Nagase Kasei Kogyo Co., Ltd.) was added to 100 parts of the obtained resin particles while stirring at high speed (high-speed stirring turbulizer manufactured by Hosokawa Micron; number of rotations: 2000 rpm). They were added and mixed while being sprayed, and allowed to stand at 140° C. for 30 minutes in a circulating air dryer (manufactured by Tabai Espec Co., Ltd.) for surface cross-linking to obtain the water absorbent resin particles (7) of the present invention.

<Example 8>
135 parts of acrylic acid (manufactured by Mitsubishi Chemical Corporation, purity 100%, the same applies hereinafter), 0.169 parts of pentaerythritol triallyl ether (manufactured by Daiso Co., Ltd., the same applies hereinafter), and 363 parts of deionized water are stirred. • Maintained at 3°C while mixing. After nitrogen was introduced into this mixture to reduce the dissolved oxygen content to 1 ppm or less, 0.5 part of a 1% aqueous hydrogen peroxide solution, 1 part of a 2% ascorbic acid aqueous solution and 2% 2,2'-azobisamidinopropane were added. 0.3 part of an aqueous dihydrochloride solution was added and mixed to initiate polymerization. After the temperature of the mixture reached 80° C., polymerization was carried out at 80±2° C. for about 5 hours to obtain hydrous gel (8).

Next, while shredding the entire amount of the obtained hydrous gel (8) with a mincing machine (12VR-400K manufactured by ROYAL), 180 parts of a 30% aqueous sodium hydroxide solution is added and mixed and neutralized to obtain a shredded gel. Obtained. Further, 0.068 part of Sannonic SS-30 (manufactured by Sanyo Chemical Industries) was added to the shredded gel and kneaded with the above mincing machine. After that, it was dried with a ventilation type band dryer (140° C., wind speed 2 m/sec) to obtain a dried product. The dried product was pulverized with a juicer mixer (Osterizer Blender manufactured by Oster), sieved, and adjusted to a particle size range of 600 to 150 μm with openings to obtain resin particles.

2 parts of a 2% aqueous solution of ethylene glycol diglycidyl ether (Denacol EX-810, manufactured by Nagase Kasei Kogyo Co., Ltd.) was added to 100 parts of the obtained resin particles while stirring at high speed (high-speed stirring turbulizer manufactured by Hosokawa Micron: 2000 rpm). They were added and mixed while being sprayed, and allowed to stand at 140° C. for 30 minutes in a circulating air dryer (manufactured by Tabai Espec Co., Ltd.) for surface cross-linking to obtain the water absorbent resin particles (8) of the present invention.

< Reference example 9>
135 parts of acrylic acid (manufactured by Mitsubishi Chemical Corporation, purity 100%, the same applies hereinafter), 0.371 parts of pentaerythritol triallyl ether (manufactured by Daiso Co., Ltd., the same applies hereinafter), and 363 parts of deionized water are stirred. • Maintained at 3°C while mixing. After nitrogen was introduced into this mixture to reduce the dissolved oxygen content to 1 ppm or less, 0.5 part of a 1% aqueous hydrogen peroxide solution, 1 part of a 2% ascorbic acid aqueous solution and 2% 2,2'-azobisamidinopropane were added. 0.3 part of an aqueous dihydrochloride solution was added and mixed to initiate polymerization. After the temperature of the mixture reached 80° C., polymerization was carried out at 80±2° C. for about 5 hours to obtain hydrous gel (9).

Next, while shredding the entire amount of the obtained hydrous gel (9) with a mincing machine (12VR-400K manufactured by ROYAL), 180 parts of a 30% aqueous sodium hydroxide solution is added and mixed and neutralized to obtain a shredded gel. Obtained. Further, 0.135 part of Newpol PE-61 (manufactured by Sanyo Chemical Industries) was added to the shredded gel and kneaded with the mincing machine. After that, it was dried with a ventilation type band dryer (140° C., wind speed 2 m/sec) to obtain a dried body. The dried product was pulverized with a juicer mixer (Osterizer Blender manufactured by Oster), sieved, and adjusted to a particle size range of 600 to 150 μm with openings to obtain resin particles.

4 parts of a 2% aqueous solution of ethylene glycol diglycidyl ether (Denacol EX-810, manufactured by Nagase Kasei Kogyo Co., Ltd.) was added to 100 parts of the resulting resin particles while stirring at high speed (high-speed stirring turbulizer manufactured by Hosokawa Micron: 2000 rpm). They were added and mixed while being sprayed, and allowed to stand at 140° C. for 30 minutes in a circulating air dryer (manufactured by Tabai Espec Co., Ltd.) for surface cross-linking to obtain the water absorbent resin particles (9) of the present invention.

< Reference Example 10>
135 parts of acrylic acid (manufactured by Mitsubishi Chemical Corporation, purity 100%, the same applies hereinafter), 0.81 parts of pentaerythritol triallyl ether (manufactured by Daiso Co., Ltd., the same applies hereinafter), and 363 parts of deionized water are stirred. • Maintained at 3°C while mixing. After nitrogen was introduced into this mixture to reduce the dissolved oxygen content to 1 ppm or less, 0.5 part of a 1% aqueous hydrogen peroxide solution, 1 part of a 2% ascorbic acid aqueous solution and 2% 2,2'-azobisamidinopropane were added. 0.3 part of an aqueous dihydrochloride solution was added and mixed to initiate polymerization. After the temperature of the mixture reached 80° C., the mixture was polymerized at 80±2° C. for about 5 hours to obtain hydrous gel (10).

Next, while shredding the entire amount of the obtained hydrous gel (10) with a mincing machine (12VR-400K manufactured by ROYAL), 180 parts of a 30% aqueous sodium hydroxide solution is added and mixed and neutralized to obtain a shredded gel. Obtained. Further, 0.27 part of Beaurite LCA-30D (manufactured by Sanyo Chemical Industries) was added to the shredded gel and kneaded with the above mincing machine. After that, it was dried with a ventilation type band dryer (140° C., wind speed 2 m/sec) to obtain a dried product. The dried product was pulverized with a juicer mixer (Osterizer Blender manufactured by Oster), sieved, and adjusted to a particle size range of 600 to 150 μm with openings to obtain resin particles.

100 parts of a 2% aqueous solution of ethylene glycol diglycidyl ether (Denacol EX-810, manufactured by Nagase Kasei Kogyo Co., Ltd.) was added to 100 parts of a 2% aqueous solution of ethylene glycol diglycidyl ether (manufactured by Nagase Kasei Kogyo Co., Ltd., Denacol EX-810) while stirring at high speed (high-speed stirring turbulizer manufactured by Hosokawa Micron Co., Ltd.; number of rotations: 2000 rpm). They were added and mixed while being sprayed, and allowed to stand at 140° C. for 30 minutes in a circulating dryer (manufactured by Tabai Espec Co., Ltd.) for surface cross-linking to obtain the water absorbent resin particles (10) of the present invention.

<Example 11>
135 parts of acrylic acid (manufactured by Mitsubishi Chemical Corporation, purity 100%, the same applies hereinafter), 0.574 parts of pentaerythritol triallyl ether (manufactured by Daiso Co., Ltd., the same applies hereinafter), and 363 parts of deionized water are stirred. • Maintained at 3°C while mixing. After nitrogen was introduced into this mixture to reduce the dissolved oxygen content to 1 ppm or less, 0.5 part of a 1% aqueous hydrogen peroxide solution, 1 part of a 2% ascorbic acid aqueous solution and 2% 2,2'-azobisamidinopropane were added. 0.3 part of an aqueous dihydrochloride solution was added and mixed to initiate polymerization. After the temperature of the mixture reached 80° C., polymerization was carried out at 80±2° C. for about 5 hours to obtain hydrous gel (11).

Next, while shredding the entire amount of the obtained hydrous gel (11) with a mincing machine (12VR-400K manufactured by ROYAL), 180 parts of a 30% aqueous sodium hydroxide solution is added and mixed and neutralized to obtain a shredded gel. Obtained. Further, 0.203 part of Sannonic SS-50 (manufactured by Sanyo Chemical Industries) was added to the shredded gel and kneaded with the mincing machine. After that, it was dried with a ventilation type band dryer (140° C., wind speed 2 m/sec) to obtain a dried body. The dried product was pulverized with a juicer mixer (Osterizer Blender manufactured by Oster), sieved, and adjusted to a particle size range of 600 to 150 μm with openings to obtain resin particles.

8 parts of a 2% aqueous solution of ethylene glycol diglycidyl ether (Denacol EX-810, manufactured by Nagase Kasei Kogyo Co., Ltd.) was added to 100 parts of the obtained resin particles while stirring at high speed (high-speed stirring turbulizer manufactured by Hosokawa Micron: 2000 rpm). They were added and mixed while being sprayed, and allowed to stand at 140° C. for 30 minutes in a circulating dryer (manufactured by Tabai Espec Co., Ltd.) for surface cross-linking to obtain the water absorbent resin particles (11) of the present invention.

<Example 12>
135 parts of acrylic acid (manufactured by Mitsubishi Chemical Corporation, purity 100%, the same applies hereinafter), 0.439 parts of pentaerythritol triallyl ether (manufactured by Daiso Co., Ltd., the same applies hereinafter), and 363 parts of deionized water are stirred. • Maintained at 3°C while mixing. After nitrogen was introduced into this mixture to reduce the dissolved oxygen content to 1 ppm or less, 0.5 part of a 1% aqueous hydrogen peroxide solution, 1 part of a 2% ascorbic acid aqueous solution and 2% 2,2'-azobisamidinopropane were added. 0.3 part of an aqueous dihydrochloride solution was added and mixed to initiate polymerization. After the temperature of the mixture reached 80° C., the mixture was polymerized at 80±2° C. for about 5 hours to obtain hydrous gel (12).

Next, while shredding the entire amount of the obtained hydrous gel (12) with a mincing machine (12VR-400K manufactured by ROYAL), 180 parts of a 30% aqueous sodium hydroxide solution is added and mixed and neutralized to obtain a shredded gel. Obtained. Further, 0.405 part of Naloacty CL-50 (manufactured by Sanyo Chemical Industries) was added to the shredded gel and kneaded with the above mincing machine. After that, it was dried with a ventilation type band dryer (140° C., wind speed 2 m/sec) to obtain a dried body. The dried product was pulverized with a juicer mixer (Osterizer Blender manufactured by Oster), sieved, and adjusted to a particle size range of 600 to 150 μm with openings to obtain resin particles.

While 100 parts of the resulting resin particles were stirred at high speed (high-speed stirring turbulizer manufactured by Hosokawa Micron: 2000 rpm), 6 parts of a 2% aqueous solution of ethylene glycol diglycidyl ether (Denacol EX-810 manufactured by Nagase Kasei Kogyo Co., Ltd.) was added. They were added and mixed while being sprayed, and allowed to stand at 140° C. for 30 minutes in a circulating air dryer (manufactured by Tabai Espec Co., Ltd.) for surface cross-linking to obtain the water absorbent resin particles (12) of the present invention.

<Reference Example 13>
135 parts of acrylic acid (manufactured by Mitsubishi Chemical Corporation, purity 100%, the same applies hereinafter), 0.095 parts of pentaerythritol triallyl ether (manufactured by Daiso Co., Ltd., the same applies hereinafter), and 363 parts of deionized water are stirred. • Maintained at 3°C while mixing. After nitrogen was introduced into this mixture to reduce the dissolved oxygen content to 1 ppm or less, 0.5 part of a 1% aqueous hydrogen peroxide solution, 1 part of a 2% ascorbic acid aqueous solution and 2% 2,2'-azobisamidinopropane were added. 0.3 part of an aqueous dihydrochloride solution was added and mixed to initiate polymerization. After the temperature of the mixture reached 80° C., the mixture was polymerized at 80±2° C. for about 5 hours to obtain hydrous gel (13).

Next, while shredding the entire amount of the obtained hydrous gel (13) with a mincing machine (12VR-400K manufactured by ROYAL), 180 parts of a 30% aqueous sodium hydroxide solution is added and mixed and neutralized to obtain a shredded gel. Obtained. Further, 0.041 part of cationic DDC-80 (manufactured by Sanyo Chemical Industries) was added to the shredded gel and kneaded with the above mincing machine. After that, it was dried with a ventilation type band dryer (140° C., wind speed 2 m/sec) to obtain a dried body. The dried product was pulverized with a juicer mixer (Osterizer Blender manufactured by Oster), sieved, and adjusted to a particle size range of 600 to 150 μm with openings to obtain resin particles.

3 parts of a 2% aqueous solution of ethylene glycol diglycidyl ether (Denacol EX-810, manufactured by Nagase Kasei Kogyo Co., Ltd.) was added to 100 parts of the obtained resin particles while stirring at high speed (high-speed stirring turbulizer manufactured by Hosokawa Micron: 2000 rpm). They were added and mixed while being sprayed, and allowed to stand at 140° C. for 30 minutes in a circulating dryer (manufactured by Tabai Espec Co., Ltd.) for surface cross-linking to obtain the water absorbent resin particles (13) of the present invention.

<Example 14>
135 parts of acrylic acid (manufactured by Mitsubishi Chemical Corporation, purity 100%, the same applies hereinafter), 0.203 parts of pentaerythritol triallyl ether (manufactured by Daiso Co., Ltd., the same applies hereinafter), and 363 parts of deionized water are stirred. • Maintained at 3°C while mixing. After nitrogen was introduced into this mixture to reduce the dissolved oxygen content to 1 ppm or less, 0.5 part of a 1% aqueous hydrogen peroxide solution, 1 part of a 2% ascorbic acid aqueous solution and 2% 2,2'-azobisamidinopropane were added. 0.3 part of an aqueous dihydrochloride solution was added and mixed to initiate polymerization. After the temperature of the mixture reached 80° C., polymerization was carried out at 80±2° C. for about 5 hours to obtain hydrous gel (14).

Next, while shredding the entire amount of the obtained hydrous gel (14) with a mincing machine (12VR-400K manufactured by ROYAL), 180 parts of a 30% aqueous sodium hydroxide solution is added and mixed and neutralized to obtain a shredded gel. Obtained. Further, 0.101 part of Emalmin NL-80 (manufactured by Sanyo Chemical Industries) was added to the shredded gel and kneaded with the above mincing machine. After that, it was dried with a ventilation type band dryer (140° C., wind speed 2 m/sec) to obtain a dried product. The dried product was pulverized with a juicer mixer (Osterizer Blender manufactured by Oster), sieved, and adjusted to a particle size range of 600 to 150 μm with openings to obtain resin particles.

5 parts of a 2% aqueous solution of ethylene glycol diglycidyl ether (Denacol EX-810, manufactured by Nagase Kasei Kogyo Co., Ltd.) was added to 100 parts of the resulting resin particles while stirring at high speed (high-speed stirring turbulizer manufactured by Hosokawa Micron; number of rotations: 2000 rpm). They were added and mixed while being sprayed, and allowed to stand at 140° C. for 30 minutes in a circulating dryer (manufactured by Tabai Espec Co., Ltd.) for surface cross-linking to obtain the water absorbent resin particles (14) of the present invention.

< Reference Example 15>
135 parts of acrylic acid (manufactured by Mitsubishi Chemical Corporation, purity 100%, the same applies hereinafter), 0.338 parts of pentaerythritol triallyl ether (manufactured by Daiso Co., Ltd., the same applies hereinafter), and 363 parts of deionized water are stirred. • Maintained at 3°C while mixing. After nitrogen was introduced into this mixture to reduce the dissolved oxygen content to 1 ppm or less, 0.5 part of a 1% aqueous hydrogen peroxide solution, 1 part of a 2% ascorbic acid aqueous solution and 2% 2,2'-azobisamidinopropane were added. 0.3 part of an aqueous dihydrochloride solution was added and mixed to initiate polymerization. After the temperature of the mixture reached 80° C., the mixture was polymerized at 80±2° C. for about 5 hours to obtain hydrous gel (15).

Next, while shredding the entire amount of the obtained hydrous gel (15) with a mincing machine (12VR-400K manufactured by ROYAL), 180 parts of a 30% aqueous sodium hydroxide solution is added and mixed and neutralized to obtain a shredded gel. Obtained. Further, 0.162 part of Naloacty ID-70 (manufactured by Sanyo Chemical Industries) was added to the shredded gel and kneaded with the above mincing machine. After that, it was dried with a ventilation type band dryer (140° C., wind speed 2 m/sec) to obtain a dried body. The dried product was pulverized with a juicer mixer (Osterizer Blender manufactured by Oster), sieved, and adjusted to a particle size range of 600 to 150 μm with openings to obtain resin particles.

While 100 parts of the obtained resin particles were stirred at high speed (high-speed stirring turbulizer manufactured by Hosokawa Micron: 2000 rpm), 1.5 parts of 2% aqueous solution of ethylene glycol diglycidyl ether (Denacol EX-810 manufactured by Nagase Kasei Kogyo Co., Ltd.) was added. are added and mixed while spraying, and allowed to stand at 140 ° C. for 30 minutes in a circulating dryer (manufactured by Tabai Espec Co., Ltd.) to perform surface cross-linking to obtain the water absorbent resin particles (15) of the present invention. rice field.

< Reference Example 16>
135 parts of acrylic acid (manufactured by Mitsubishi Chemical Corporation, purity 100%, the same applies hereinafter), 0.743 parts of pentaerythritol triallyl ether (manufactured by Daiso Co., Ltd., the same applies hereinafter), and 363 parts of deionized water are stirred. • Maintained at 3°C while mixing. After nitrogen was introduced into this mixture to reduce the dissolved oxygen content to 1 ppm or less, 0.5 part of a 1% aqueous hydrogen peroxide solution, 1 part of a 2% ascorbic acid aqueous solution and 2% 2,2'-azobisamidinopropane were added. 0.3 part of an aqueous dihydrochloride solution was added and mixed to initiate polymerization. After the temperature of the mixture reached 80° C., the mixture was polymerized at 80±2° C. for about 5 hours to obtain hydrous gel (16).

Next, while shredding the entire amount of the obtained hydrous gel (16) with a mincing machine (12VR-400K manufactured by ROYAL), 180 parts of a 30% aqueous sodium hydroxide solution is added and mixed and neutralized to obtain a shredded gel. Obtained. Further, 0.203 parts of Lebon LD-36 (manufactured by Sanyo Chemical Industries) was added to the shredded gel and kneaded with the above mincing machine. After that, it was dried with a ventilation type band dryer (140° C., wind speed 2 m/sec) to obtain a dried body. The dried product was pulverized with a juicer mixer (Osterizer Blender manufactured by Oster), sieved, and adjusted to a particle size range of 600 to 150 μm with openings to obtain resin particles.

While 100 parts of the obtained resin particles were stirred at high speed (high-speed stirring turbulizer manufactured by Hosokawa Micron: 2000 rpm), a 2% aqueous solution of ethylene glycol diglycidyl ether (Denacol EX-810 manufactured by Nagase Kasei Kogyo Co., Ltd.) was added at 5.5%. are added and mixed while spraying, and allowed to stand at 140 ° C. for 30 minutes in a circulating air dryer (manufactured by Tabai Espec Co., Ltd.) to perform surface cross-linking to obtain the water absorbent resin particles (16) of the present invention. rice field.

<Example 17>
135 parts of acrylic acid (manufactured by Mitsubishi Chemical Corporation, purity 100%, the same applies hereinafter), 0.608 parts of pentaerythritol triallyl ether (manufactured by Daiso Co., Ltd., the same applies hereinafter), and 363 parts of deionized water are stirred. • Maintained at 3°C while mixing. After nitrogen was introduced into this mixture to reduce the dissolved oxygen content to 1 ppm or less, 0.5 part of a 1% aqueous hydrogen peroxide solution, 1 part of a 2% ascorbic acid aqueous solution and 2% 2,2'-azobisamidinopropane were added. 0.3 part of an aqueous dihydrochloride solution was added and mixed to initiate polymerization. After the temperature of the mixture reached 80° C., the mixture was polymerized at 80±2° C. for about 5 hours to obtain hydrous gel (17).

Next, while shredding the entire amount of the obtained hydrous gel (17) with a mincing machine (12VR-400K manufactured by ROYAL), 180 parts of a 30% aqueous sodium hydroxide solution is added and mixed and neutralized to obtain a shredded gel. Obtained. Further, 0.338 part of Naloacty CL-70 (manufactured by Sanyo Chemical Industries) was added to the shredded gel and kneaded with the above mincing machine. After that, it was dried with a ventilation type band dryer (140° C., wind speed 2 m/sec) to obtain a dried body. The dried product was pulverized with a juicer mixer (Osterizer Blender manufactured by Oster), sieved, and adjusted to a particle size range of 600 to 150 μm with openings to obtain resin particles.

9 parts of a 2% aqueous solution of ethylene glycol diglycidyl ether (Denacol EX-810, manufactured by Nagase Kasei Kogyo Co., Ltd.) was added to 100 parts of the resulting resin particles while stirring at high speed (high-speed stirring turbulizer manufactured by Hosokawa Micron: 2000 rpm). They were added and mixed while being sprayed, and allowed to stand at 140° C. for 30 minutes in a circulating dryer (manufactured by Tabai Espec Co., Ltd.) for surface cross-linking to obtain the water absorbent resin particles (17) of the present invention.

<Example 18>
135 parts of acrylic acid (manufactured by Mitsubishi Chemical Corporation, purity 100%, the same applies hereinafter), 0.371 parts of pentaerythritol triallyl ether (manufactured by Daiso Co., Ltd., the same applies hereinafter), and 363 parts of deionized water are stirred. • Maintained at 3°C while mixing. After nitrogen was introduced into this mixture to reduce the dissolved oxygen content to 1 ppm or less, 0.5 part of a 1% aqueous hydrogen peroxide solution, 1 part of a 2% ascorbic acid aqueous solution and 2% 2,2'-azobisamidinopropane were added. 0.3 part of an aqueous dihydrochloride solution was added and mixed to initiate polymerization. After the temperature of the mixture reached 80° C., polymerization was carried out at 80±2° C. for about 5 hours to obtain hydrous gel (18).

Next, while shredding the entire amount of the obtained hydrous gel (18) with a mincing machine (12VR-400K manufactured by ROYAL), 180 parts of a 30% aqueous sodium hydroxide solution is added and mixed and neutralized to obtain a shredded gel. Obtained. Further, 0.236 part of Sannonic SS-70 (manufactured by Sanyo Chemical Industries) was added to the shredded gel and kneaded with the above mincing machine. After that, it was dried with a ventilation type band dryer (140° C., wind speed 2 m/sec) to obtain a dried body. The dried product was pulverized with a juicer mixer (Osterizer Blender manufactured by Oster), sieved, and adjusted to a particle size range of 600 to 150 μm with openings to obtain resin particles.

While 100 parts of the obtained resin particles were stirred at high speed (high-speed stirring turbulizer manufactured by Hosokawa Micron: 2000 rpm), 7 parts of 2% aqueous solution of ethylene glycol diglycidyl ether (Denacol EX-810 manufactured by Nagase Kasei Kogyo Co., Ltd.) was added. They were added and mixed while being sprayed, and allowed to stand at 140° C. for 30 minutes in a circulating air dryer (manufactured by Tabai Espec Co., Ltd.) for surface cross-linking to obtain the water absorbent resin particles (18) of the present invention.

< Reference Example 19>
135 parts of acrylic acid (manufactured by Mitsubishi Chemical Corporation, purity 100%, the same applies hereinafter), 0.135 parts of pentaerythritol triallyl ether (manufactured by Daiso Co., Ltd., the same applies hereinafter), and 363 parts of deionized water are stirred. • Maintained at 3°C while mixing. After nitrogen was introduced into this mixture to reduce the dissolved oxygen content to 1 ppm or less, 0.5 part of a 1% aqueous hydrogen peroxide solution, 1 part of a 2% ascorbic acid aqueous solution and 2% 2,2'-azobisamidinopropane were added. 0.3 part of an aqueous dihydrochloride solution was added and mixed to initiate polymerization. After the temperature of the mixture reached 80° C., the mixture was polymerized at 80±2° C. for about 5 hours to obtain hydrous gel (19).

Next, while shredding the entire amount of the obtained hydrous gel (19) with a mincing machine (12VR-400K manufactured by ROYAL), 180 parts of a 30% aqueous sodium hydroxide solution is added and mixed and neutralized to obtain a shredded gel. Obtained. Further, 0.135 part of Sedran SNP-112 (manufactured by Sanyo Chemical Industries) was added to the shredded gel and kneaded with the above mincing machine. After that, it was dried with a ventilation type band dryer (140° C., wind speed 2 m/sec) to obtain a dried product. The dried product was pulverized with a juicer mixer (Osterizer Blender manufactured by Oster), sieved, and adjusted to a particle size range of 600 to 150 μm with openings to obtain resin particles.

While 100 parts of the obtained resin particles were stirred at high speed (high-speed stirring turbulizer manufactured by Hosokawa Micron: 2000 rpm), 2% aqueous solution of ethylene glycol diglycidyl ether (Denacol EX-810 manufactured by Nagase Kasei Kogyo Co., Ltd.) was added to 3.5%. are added and mixed while spraying, and allowed to stand at 140 ° C. for 30 minutes in a circulation dryer (manufactured by Tabai Espec Co., Ltd.) to perform surface cross-linking to obtain the water absorbent resin particles (19) of the present invention. rice field.

<Example 20>
135 parts of acrylic acid (manufactured by Mitsubishi Chemical Corporation, purity 100%, the same applies hereinafter), 0.236 parts of pentaerythritol triallyl ether (manufactured by Daiso Co., Ltd., the same applies hereinafter), and 363 parts of deionized water are stirred. • Maintained at 3°C while mixing. After nitrogen was introduced into this mixture to reduce the dissolved oxygen content to 1 ppm or less, 0.5 part of a 1% aqueous hydrogen peroxide solution, 1 part of a 2% ascorbic acid aqueous solution and 2% 2,2'-azobisamidinopropane were added. 0.3 part of an aqueous dihydrochloride solution was added and mixed to initiate polymerization. After the temperature of the mixture reached 80° C., polymerization was carried out at 80±2° C. for about 5 hours to obtain a hydrous gel (20).

Next, while shredding the entire amount of the obtained hydrous gel (20) with a mincing machine (12VR-400K manufactured by ROYAL), 180 parts of a 30% aqueous sodium hydroxide solution is added and mixed and neutralized to obtain a shredded gel. Obtained. Further, 0.061 part of Naloacty CL-95 (manufactured by Sanyo Chemical Industries) was added to the shredded gel and kneaded with the above mincing machine. After that, it was dried with a ventilation type band dryer (140° C., wind speed 2 m/sec) to obtain a dried body. The dried product was pulverized with a juicer mixer (Osterizer Blender manufactured by Oster), sieved, and adjusted to a particle size range of 600 to 150 μm with openings to obtain resin particles.

4 parts of a 2% aqueous solution of ethylene glycol diglycidyl ether (Denacol EX-810, manufactured by Nagase Kasei Kogyo Co., Ltd.) was added to 100 parts of the resulting resin particles while stirring at high speed (high-speed stirring turbulizer manufactured by Hosokawa Micron: 2000 rpm). They were added and mixed while being sprayed, and allowed to stand at 140° C. for 30 minutes in a circulating air dryer (manufactured by Tabai Espec Co., Ltd.) for surface cross-linking to obtain the water absorbent resin particles (20) of the present invention.

<Example 21>
135 parts of acrylic acid (manufactured by Mitsubishi Chemical Corporation, purity 100%, the same applies hereinafter), 0.439 parts of pentaerythritol triallyl ether (manufactured by Daiso Co., Ltd., the same applies hereinafter), and 363 parts of deionized water are stirred. • Maintained at 3°C while mixing. After nitrogen was introduced into this mixture to reduce the dissolved oxygen content to 1 ppm or less, 0.5 part of a 1% aqueous hydrogen peroxide solution, 1 part of a 2% ascorbic acid aqueous solution and 2% 2,2'-azobisamidinopropane were added. 0.3 part of an aqueous dihydrochloride solution was added and mixed to initiate polymerization. After the temperature of the mixture reached 80° C., polymerization was carried out at 80±2° C. for about 5 hours to obtain hydrous gel (21).

Next, while shredding the entire amount of the obtained hydrous gel (21) with a mincing machine (12VR-400K manufactured by ROYAL), 180 parts of a 30% aqueous sodium hydroxide solution is added and mixed and neutralized to obtain a shredded gel. Obtained. Further, 0.108 part of Sannonic SS-90 (manufactured by Sanyo Chemical Industries) was added to the shredded gel and kneaded with the above mincing machine. After that, it was dried with a ventilation type band dryer (140° C., wind speed 2 m/sec) to obtain a dried product. The dried product was pulverized with a juicer mixer (Osterizer Blender manufactured by Oster), sieved, and adjusted to a particle size range of 600 to 150 μm with openings to obtain resin particles.

While 100 parts of the obtained resin particles were stirred at high speed (high-speed stirring turbulizer manufactured by Hosokawa Micron: 2000 rpm), 1.25 of a 2% aqueous solution of ethylene glycol diglycidyl ether (Denacol EX-810 manufactured by Nagase Kasei Kogyo Co., Ltd.) was added. are added and mixed while spraying, and allowed to stand at 140 ° C. for 30 minutes in a circulating air dryer (manufactured by Tabai Espec Co., Ltd.) to perform surface cross-linking to obtain the water absorbent resin particles (21) of the present invention. rice field.

<Example 22>
135 parts of acrylic acid (manufactured by Mitsubishi Chemical Corporation, purity 100%, the same applies hereinafter), 0.878 parts of pentaerythritol triallyl ether (manufactured by Daiso Co., Ltd., the same applies hereinafter), and 363 parts of deionized water are stirred. • Maintained at 3°C while mixing. After nitrogen was introduced into this mixture to reduce the dissolved oxygen content to 1 ppm or less, 0.5 part of a 1% aqueous hydrogen peroxide solution, 1 part of a 2% ascorbic acid aqueous solution and 2% 2,2'-azobisamidinopropane were added. 0.3 part of an aqueous dihydrochloride solution was added and mixed to initiate polymerization. After the temperature of the mixture reached 80° C., polymerization was carried out at 80±2° C. for about 5 hours to obtain a hydrous gel (22).

Next, while shredding the entire amount of the obtained hydrous gel (22) with a mincing machine (12VR-400K manufactured by ROYAL), 180 parts of a 30% aqueous sodium hydroxide solution is added and mixed and neutralized to obtain a shredded gel. Obtained. Further, 0.216 part of Naloacty CL-120 (manufactured by Sanyo Chemical Industries) was added to the shredded gel and kneaded with the above mincing machine. After that, it was dried with a ventilation type band dryer (140° C., wind speed 2 m/sec) to obtain a dried body. The dried product was pulverized with a juicer mixer (Osterizer Blender manufactured by Oster), sieved, and adjusted to a particle size range of 600 to 150 μm with openings to obtain resin particles.

While 100 parts of the resulting resin particles were stirred at high speed (high-speed stirring turbulizer manufactured by Hosokawa Micron: 2000 rpm), 6 parts of a 2% aqueous solution of ethylene glycol diglycidyl ether (Denacol EX-810 manufactured by Nagase Kasei Kogyo Co., Ltd.) was added. They were added and mixed while being sprayed, and allowed to stand at 140° C. for 30 minutes in a circulating air dryer (manufactured by Tabai Espec Co., Ltd.) for surface cross-linking to obtain the water absorbent resin particles (22) of the present invention.

<Example 23>
135 parts of acrylic acid (manufactured by Mitsubishi Chemical Corporation, purity 100%, the same applies hereinafter), 0.574 parts of pentaerythritol triallyl ether (manufactured by Daiso Co., Ltd., the same applies hereinafter), and 363 parts of deionized water are stirred. • Maintained at 3°C while mixing. After nitrogen was introduced into this mixture to reduce the dissolved oxygen content to 1 ppm or less, 0.5 part of a 1% aqueous hydrogen peroxide solution, 1 part of a 2% ascorbic acid aqueous solution and 2% 2,2'-azobisamidinopropane were added. 0.3 part of an aqueous dihydrochloride solution was added and mixed to initiate polymerization. After the temperature of the mixture reached 80° C., the mixture was polymerized at 80±2° C. for about 5 hours to obtain hydrous gel (23).

Next, while shredding the entire amount of the obtained hydrous gel (23) with a mincing machine (12VR-400K manufactured by ROYAL), 180 parts of a 30% aqueous sodium hydroxide solution is added and mixed and neutralized to obtain a shredded gel. Obtained. Further, 0.162 part of Sannonic SS-120 (manufactured by Sanyo Chemical Industries) was added to the shredded gel and kneaded with the above mincing machine. After that, it was dried with a ventilation type band dryer (140° C., wind speed 2 m/sec) to obtain a dried body. The dried product was pulverized with a juicer mixer (Osterizer Blender manufactured by Oster), sieved, and adjusted to a particle size range of 600 to 150 μm with openings to obtain resin particles.

While 100 parts of the obtained resin particles were stirred at high speed (high-speed stirring turbulizer manufactured by Hosokawa Micron: 2000 rpm), 11 parts of a 2% aqueous solution of ethylene glycol diglycidyl ether (Denacol EX-810 manufactured by Nagase Kasei Kogyo Co., Ltd.) was added. They were added and mixed while being sprayed, and allowed to stand at 140° C. for 30 minutes in a circulating air dryer (manufactured by Tabai Espec Co., Ltd.) for surface cross-linking to obtain the water absorbent resin particles (23) of the present invention.

< Reference example 24>
135 parts of acrylic acid (manufactured by Mitsubishi Chemical Corporation, purity 100%, the same applies hereinafter), 0.506 parts of pentaerythritol triallyl ether (manufactured by Daiso Co., Ltd., the same applies hereinafter), and 363 parts of deionized water are stirred. • Maintained at 3°C while mixing. After nitrogen was introduced into this mixture to reduce the dissolved oxygen content to 1 ppm or less, 0.5 part of a 1% aqueous hydrogen peroxide solution, 1 part of a 2% ascorbic acid aqueous solution and 2% 2,2'-azobisamidinopropane were added. 0.3 part of an aqueous dihydrochloride solution was added and mixed to initiate polymerization. After the temperature of the mixture reached 80° C., the mixture was polymerized at 80±2° C. for about 5 hours to obtain hydrous gel (24).

Next, while shredding the entire amount of the obtained hydrous gel (24) with a mincing machine (12VR-400K manufactured by ROYAL), 180 parts of a 30% aqueous sodium hydroxide solution is added and mixed and neutralized to obtain a shredded gel. Obtained. Furthermore, 0.54 part of Nonipol 40 (manufactured by Sanyo Chemical Industries) was added to the shredded gel and kneaded with the mincing machine. After that, it was dried with a ventilation type band dryer (140° C., wind speed 2 m/sec) to obtain a dried body. The dried product was pulverized with a juicer mixer (Osterizer Blender manufactured by Oster), sieved, and adjusted to a particle size range of 600 to 150 μm with openings to obtain resin particles.

While 100 parts of the obtained resin particles were stirred at high speed (high-speed stirring turbulizer manufactured by Hosokawa Micron: 2000 rpm), a 2% aqueous solution of ethylene glycol diglycidyl ether (Denacol EX-810 manufactured by Nagase Kasei Kogyo Co., Ltd.) was added at 6.5%. are added and mixed while spraying, and allowed to stand at 140 ° C. for 30 minutes in a circulating air dryer (manufactured by Tabai Espec Co., Ltd.) to perform surface cross-linking to obtain the water absorbent resin particles (24) of the present invention. rice field.

<Comparative Example 1>
Water-absorbing resin particles (1) for comparison were obtained in the same manner as in Example 1, except that 0.068 parts of "Viewlite LCA-30 (manufactured by Sanyo Chemical Industries)" was not added.

<Comparative Example 2>
Water absorbent resin particles (2) for comparison were obtained in the same manner as in Example 3, except that "0.204 parts of NaroActy CL-20" was changed to "0.027 parts of NaroActy CL-20". .

<Comparative Example 3>
Water absorbent resin particles (3) for comparison were obtained in the same manner as in Example 3, except that "0.204 parts of NaroActy CL-20" was changed to "0.68 parts of NaroActy CL-20". .

<Comparative Example 4>
135 parts of acrylic acid (manufactured by Mitsubishi Chemical Corporation, purity 100%, the same applies hereinafter), 0.4 parts of pentaerythritol triallyl ether (manufactured by Daiso Co., Ltd., the same applies hereinafter), and 363 parts of deionized water are stirred. • Maintained at 3°C while mixing. After nitrogen was introduced into this mixture to reduce the dissolved oxygen content to 1 ppm or less, 0.5 part of a 1% aqueous hydrogen peroxide solution, 1 part of a 2% ascorbic acid aqueous solution and 2% 2,2'-azobisamidinopropane were added. 0.3 part of an aqueous dihydrochloride solution was added and mixed to initiate polymerization. After the temperature of the mixture reached 80° C., the mixture was polymerized at 80±2° C. for about 5 hours to obtain hydrous gel (2).

Next, while shredding the entire amount of the obtained hydrous gel (2) with a mincing machine (12VR-400K manufactured by ROYAL), 180 parts of a 30% aqueous sodium hydroxide solution is added and mixed and neutralized to obtain a shredded gel. got After that, it was dried with a ventilation type band dryer (140° C., wind speed 2 m/sec) to obtain a dried body. The dried product was pulverized with a juicer mixer (Osterizer Blender manufactured by Oster), sieved, and adjusted to a particle size range of 600 to 150 μm (weight average particle size: 400 μm) to obtain resin particles.

100 parts of the resulting resin particles were added to 4 parts of a 2% aqueous solution of ethylene glycol diglycidyl ether (Denacol EX-810, manufactured by Nagase Kasei Kogyo Co., Ltd.) while stirring at high speed (high-speed stirring turbulizer manufactured by Hosokawa Micron; number of rotations: 2000 rpm). A surface cross-linking solution to which 0.204 parts of Naloacty CL-20 was added was added while spraying and mixed, and the mixture was allowed to stand at 140°C for 30 minutes in a circulating air dryer (manufactured by Tabai Espec Co., Ltd.) to perform surface cross-linking. , to obtain water absorbent resin particles (4) for comparison.

<Comparative Example 5>
Water-absorbing resin particles (5) for comparison were obtained in the same manner as in Example 5, except that "0.408 parts of Lebon LD-36 (manufactured by Sanyo Chemical Industries)" was not added.

<Comparative Example 6>
Water absorption for comparison in the same manner as in Example 6 except that "Lebon LD-36 (manufactured by Sanyo Chemical Industries) 0.408 parts" was changed to "Naroacty CL-20 (Sanyo Chemical Industries) 0.68 parts" A flexible resin particle (6) was obtained.

<Comparative Example 7>
Water-absorbing resin particles were prepared in the same manner as in Example 1, except that 0.068 parts of "Viewlite LCA-30 (manufactured by Sanyo Chemical Industries, Ltd.)" was not added. Combine JIS standard sieves of 425 μm, 300 μm and a tray in that order from the top, put the water-absorbent resin particles from above, shake with a low-tap test sieve shaker for 5 minutes, and sample on the 300 μm sieve ( 320 μm as a weight average particle diameter) was used as water absorbent resin particles (7) for comparison.

<Comparative Example 8>
JIS standard sieves of 425 μm, 300 μm, and a tray are combined in this order, and the water-absorbent resin particles (5) obtained in Comparative Example 5 are put in from above, and shaken for 5 minutes with a low-tap test sieve shaker, The sample on the 300 μm sieve (320 μm in terms of weight average particle size) was used as water absorbent resin particles (8) for comparison.

Examples 3, 7-8, 11-12, 14, 17-18, 20-23, Reference Examples 1, 2, 4-6, 9-10, 13, 15-16, 19, 24 and Comparative Examples 1- Vortex absorption rate Vt (150-600), Vt (500-600), and Vt (150-600)/Vt measured by the method described in paragraphs 0080 and 0081 for each water-absorbing resin particle obtained in 8. (500-600), Vt (Surfactant), Vt (Blank), Vt (Surfactant)/Vt (Blank), and the surface tension, CRC and GBP of the water absorbent resin particle extract are summarized in Tables 1 and 2. In addition, in Examples and the like, resin particles prepared without using a surfactant were separately prepared and measured in order to measure Vt (Blank).

Tables 1 and 2 show that the water-absorbent resin particles of the present invention are less affected by the particle size than the resin particles of the comparative examples in terms of the absorption rate measured by the vortex test method, and that depending on the amount of surfactant added, It can be seen that the influence on the vortex is large. According to Examples 7 and 8, Reference Example 13, and Example 20, since the amount of surfactant added was low, the vortex Vt (blank) of the resin to which no activator was added and the vortex Vt of the resin to which the activator was added (Surfactant) shows no significant difference. In addition, according to Examples 12 and 17 and Reference Example 24, Vt ((Surfactant)/Vt (Blank)) does not decrease even if the amount of the active agent added exceeds 2000 ppm. , it can be seen that Vt (Surfactant) does not depend on the amount of surfactant added. Further, according to Reference Example 24 and Comparative Examples 3 and 6 in which the amount of surfactant is outside the scope of the present invention, when the amount of surfactant exceeds 4000 ppm, the surface tension of the water-absorbing resin particle extract is extremely increased. It can be easily imagined that the rewet performance deteriorates. In addition, according to Comparative Example 4, it can be seen that surfactant treatment in the surface cross-linking step has almost no effect on vortexing (obviously compared with Reference Example 1). The resin particles of the comparative example are greatly affected by the particle size. Further, according to Comparative Examples 7 and 8, it is considered that the vortex is improved by lowering the weight average particle diameter, but the CRC and GBP performance are significantly lowered. In Comparative Examples 7 and 8, since particles of 300 μm or less and 425 μm or more were cut according to the above-described operation procedure, Vt (150-600) and Vt (500-600) data are not shown. Moreover, Vt of Comparative Examples 2 and 4 is outside the scope of the present invention. From the above, it can be seen that distribution of an appropriate amount of surfactant inside the water-absorbing resin particles is good for vortexing and diaper performance.

The water absorbent resin composition of the present invention has an effect on the vortex absorption speed without reducing the particle size by adjusting the particle size or reducing the apparent density to improve the surface area. can be applied to various absorbents, it can be used for absorbent articles having a high absorption rate, excellent reversion property and surface dryness, and is suitable for sanitary products.

Claims (8)

A resin containing a water-soluble vinyl monomer (a1) and/or a vinyl monomer (a2) that becomes a water-soluble vinyl monomer (a1) by hydrolysis and a crosslinked polymer (A) having an internal cross-linking agent (b) as essential structural units Water-absorbing resin particles having a structure in which the surfaces of the particles (B) are surface-crosslinked with a surface-crosslinking agent (d), and the resin particles (B) are 0.05% based on the weight of the crosslinked polymer (A). Absorption rate (seconds) measured by vortex absorption rate measurement by whole grain method and vortex absorption rate measurement by sieving method, containing ~0.3% by weight of surfactant (C) ratio satisfies formula 1, wherein the surfactant (C) is a nonionic surfactant represented by the following general formula (I).
0.6<Vt(150-600)/Vt(500-600)<1 (Formula 1)
(However, in formula 1, Vt (150-600): Vortex absorption time (whole grain method), Vt (500-600): Vortex absorption time (sieving method).)
R ¹ —O—(AO) _k —H (I)
In general formula (I), R ¹ represents an alkyl or alkenyl group having 12 to 18 carbon atoms, AO represents an oxyalkylene group having 2 or 3 carbon atoms, k represents the average number of added moles, and 2 to 30 represents the number of 2. The water-absorbent resin particles according to claim 1 , wherein 1 g of the water-absorbent resin particles is added to 200 ml of physiological saline (25° C.) and the eluted components are extracted, and the resulting extract has a surface tension of 60 to 73 dyn/cm. 3. The water absorbent resin particles according to claim 1 or 2, having an apparent density of 0.54 to 0.70 g/ml. The water absorbent resin particles according to any one of claims 1 to 3 , having a weight average particle diameter of 350 to 450 µm. Polymerizing and cross-linking a monomer composition containing a water-soluble vinyl monomer (a1) and/or a vinyl monomer (a2) that becomes a water-soluble vinyl monomer (a1) by hydrolysis and an internal cross-linking agent (b) as essential structural units and a step of surface-crosslinking the surfaces of resin particles (B) containing the crosslinked polymer (A) with a surface-crosslinking agent (d). 0.05 to 0.3% by weight of a nonionic surfactant (C) represented by the following general formula (I) based on the weight of (A) is added in a step prior to the surface cross-linking step. , a method for producing water-absorbing resin particles.
R ¹ —O—(AO) _k —H (I)
In general formula (I), R ¹ represents an alkyl or alkenyl group having 12 to 18 carbon atoms, AO represents an oxyalkylene group having 2 or 3 carbon atoms, k represents the average number of added moles, and 2 to 30 represents the number of 6. The method for producing water absorbent resin particles according to claim 5 , wherein the water-soluble vinyl monomer (a1) is (meth)acrylic acid. An absorbent body comprising the water-absorbing resin particles according to any one of claims 1 to 4 and a fibrous material. An absorbent article using the absorbent body according to claim 7 .