WO2021039714A1

WO2021039714A1 - Absorbent article and auxiliary sheet

Info

Publication number: WO2021039714A1
Application number: PCT/JP2020/031838
Authority: WO
Inventors: 海紗生谷口
Original assignee: 住友精化株式会社
Priority date: 2019-08-26
Filing date: 2020-08-24
Publication date: 2021-03-04
Also published as: JP7457718B2; CN114269310A; CN114269310B; KR20220050917A; JPWO2021039714A1

Abstract

Disclosed is an absorbent article comprising: a water-absorbing core; an auxiliary sheet that supplements liquid absorption by the water-absorbing core; a liquid-impermeable sheet; and a liquid-permeable sheet, the liquid-impermeable sheet, auxiliary sheet, water-absorbing core, and liquid-permeable sheet being arranged in this order. The auxiliary sheet is provided with a resin layer containing water-absorbent resin particles, and the dry powder liquid absorption rate of the water-absorbent resin particles is 0.25-1.0.

Description

Absorbent articles and auxiliary sheets

The present invention relates to an absorbent article and an auxiliary sheet.

Absorbents containing water-absorbent resin particles are generally used as absorbent articles for absorbing water-based liquids such as urine. For example, in the water-absorbent sheet structure disclosed in Patent Document 1 below, water-absorbent resin particles having a physiological saline water absorption rate within a predetermined range are used in the liquid-absorbent layer.

Japanese Unexamined Patent Publication No. 2012-183175

In an absorbent article having an ultra-thin water-absorbing core such as the above-mentioned water-absorbing sheet, when the liquid to be absorbed occurs in a relatively short time (initial stage of liquid absorption) after the liquid to be absorbed is provided to the absorber. Therefore, there was a need to develop a technology to improve liquid leakage in the initial stage of water absorption.

Therefore, one aspect of the present invention is to provide an absorbent article in which liquid leakage at the initial stage of liquid absorption is suppressed. Another aspect of the present invention is to provide an auxiliary sheet capable of suppressing liquid leakage in the initial stage of liquid absorption in an absorbent article.

One aspect of the present invention includes a water absorbing core, an auxiliary sheet for assisting liquid absorption by the water absorbing core, a liquid impermeable sheet and a liquid permeable sheet, and includes a liquid impermeable sheet, an auxiliary sheet, a water absorbing core and a liquid permeable sheet. With respect to absorbent articles in which the sheets are arranged in this order. In the absorbent article, the auxiliary sheet includes a resin layer containing water-absorbent resin particles, and the following steps (1), (2), (3), (4) and (5) are included in this order. The measured dry powder passing liquid absorption rate of the water-absorbent resin particles is 0.25 or more and 1.0 or less.
(1) 0.2 g of water-absorbent resin particles are uniformly sprayed over the entire bottom surface of a cylindrical container having an inner diameter of 60 mm having a mesh-like bottom, and the total amount of the container and the water-absorbent resin particles sprayed in the container. The mass Wb (g) is measured.
(2) 20 mL of artificial urine having a liquid temperature of 25 ° C. is injected into the container on which the water-absorbent resin particles are sprayed at a constant rate of 8 mL / sec, and at least a part of the artificial urine is absorbed by the water-absorbent resin particles to make the container. A swelling gel is formed within.
(3) 30 seconds after the start of injection, the total mass Wa (g) of the container and the swollen gel in the container is measured.
(4) The dry powder passing liquid absorption amount (g) is determined from Wa (g) -Wb (g).
(5) The dry powder passage liquid absorption rate (g / g) is obtained as the ratio of the dry powder passage liquid absorption amount (g) to the artificial urine saturated liquid absorption amount (g) of 0.2 g of the water-absorbent resin particles.

According to the present invention, it is possible to provide an absorbent article in which liquid leakage at the initial stage of liquid absorption is suppressed.

Further, according to the present invention, it is possible to provide an auxiliary sheet capable of suppressing liquid leakage in the initial stage of liquid absorption in an absorbent article.

It is sectional drawing which shows an example of the auxiliary sheet. It is sectional drawing which shows an example of an absorbent article. It is a top view which shows an example of the application pattern of the adhesive formed on the core wrap sheet. It is sectional drawing which shows an example of a sheet-shaped water absorption core. It is a schematic diagram which shows the measuring method of the dry powder passing liquid absorption rate. It is a schematic diagram which shows the apparatus which evaluates the liquid leakage of an absorbent article.

Hereinafter, some embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments.

In this specification, "acrylic" and "methacryl" are collectively referred to as "(meth) acrylic". Similarly, "acrylate" and "methacrylate" are also referred to as "(meth) acrylate". In the numerical range described stepwise in the present specification, the upper limit value or the lower limit value of the numerical range of one step can be arbitrarily combined with the upper limit value or the lower limit value of the numerical range of another step. In the numerical range described in the present specification, the upper limit value or the lower limit value of the numerical range may be replaced with the value shown in the examples. “A or B” may include either A or B, or both. "Water-soluble" means that it exhibits a solubility in water of 5% by mass or more at 25 ° C. The materials exemplified in the present specification may be used alone or in combination of two or more. The content of each component in the composition means the total amount of the plurality of substances present in the composition when a plurality of substances corresponding to each component are present in the composition, unless otherwise specified.

The absorbent article according to the embodiment includes a water absorbing core, an auxiliary sheet for assisting liquid absorption by the water absorbing core, a liquid impermeable sheet, and a liquid permeable sheet. In the absorbent article, the liquid impermeable sheet, the auxiliary sheet, the water absorbing core and the liquid permeable sheet are arranged in this order. That is, the auxiliary sheet is arranged so as to be in contact with the surface of the absorbent core provided with the water absorbing core, which is opposite to the side on which the liquid to be absorbed is invaded. The auxiliary sheet is used in an absorbent article provided with a water absorbing core to assist the liquid absorption of the water absorbing core.

The auxiliary sheet includes a resin layer containing water-absorbent resin particles, and is measured by a method including the following steps (1), (2), (3), (4) and (5) in this order. The dry powder water absorption rate of the resin particles is 0.25 or more and 1.0 or less.
(1) 0.2 g of water-absorbent resin particles are uniformly sprayed over the entire bottom surface of a cylindrical container having an inner diameter of 60 mm having a mesh-like bottom, and the total amount of the container and the water-absorbent resin particles sprayed in the container. The mass Wb (g) is measured.
(2) 20 mL of artificial urine having a liquid temperature of 25 ° C. is injected into the container on which the water-absorbent resin particles are sprayed at a constant rate of 8 mL / sec, and at least a part of the artificial urine is absorbed by the water-absorbent resin particles to make the container. A swelling gel is formed within.
(3) 30 seconds after the start of injection, the total mass Wa (g) of the container and the swollen gel in the container is measured.
(4) The dry powder passing liquid absorption amount (g) is determined from Wa (g) -Wb (g).
(5) The dry powder passage liquid absorption rate (g / g) is obtained as the ratio of the dry powder passage liquid absorption amount (g) to the artificial urine saturated liquid absorption amount (g) of 0.2 g of the water-absorbent resin particles.

In this specification, the artificial urine, sodium chloride (NaCl) 100.0 g, calcium chloride dihydrate _{_{(CaCl 2 · H 2 O)}} 3.0g, magnesium chloride hexahydrate _(MgCl 2 · _6H 2 O) It is an aqueous solution prepared from 6.0 g, 25.0 g of Triton X-100 (1%), 0.25 g of Edible Blue No. 1, and 9865.75 g of water.

The artificial urine saturated liquid absorption amount is an index showing the saturated liquid absorption amount of artificial urine in a predetermined amount of water-absorbent resin particles, and the dry powder passing liquid absorption amount is a short time after contact between the water-absorbent resin particles and artificial urine. It is an index that reflects the amount of liquid absorbed during (initial). The high dry powder passage liquid absorption rate, which is the ratio of the dry powder passage liquid absorption amount to the artificial urine saturated liquid absorption amount, means that the liquid permeability of the water-absorbent resin particles in a short time (initial) after contact with artificial urine is high. It is thought to mean high. The auxiliary sheet provided with the resin layer containing the water-absorbent resin particles having high liquid permeability at the initial stage instantly absorbs the liquid that could not be absorbed by the water-absorbing core, so that the liquid at the initial stage of liquid absorption in the absorbent article It is presumed that leakage will be suppressed.

The lower limit of the liquid absorption rate of dry powder is 0.25 or more, and from the viewpoint of further excellent effect of suppressing liquid leakage in the initial stage of liquid absorption, 0.30 or more, 0.35 or more, 0.40 or more, 0. It may be 45 or more, 0.50 or more, 0.55 or more, 0.60 or more, 0.65 or more, 0.70 or more, 0.75 or more, 0.80 or more, or 0.85 or more. The upper limit of the dry powder passing liquid absorption rate is 1.0 or less, and may be 0.95 or less, or 0.90 or less. The artificial urine saturated liquid absorption amount of 0.2 g of the water-absorbent resin particles shows the same amount of saturated absorption of 0.2 g of the water-absorbent resin particles as the amount used for measuring the dry powder passage liquid absorption rate, and therefore is usually the same amount. When measured using water-absorbent resin particles, the amount of dry powder flowing through the liquid does not exceed the amount of artificial urine saturated liquid absorbed. Therefore, the upper limit of the dry powder liquid absorption rate is usually 1.0 or less.

The amount of dry powder flowing through is, for example, 2.7 g or more, 3.0 g or more, 4.0 g or more, 5.0 g or more, 6.0 g or more, 7.0 g or more, 8.0 g or more, or 9.0 g or more. It may be 15.0 g or less, 12.0 g or less, or 10.0 g or less. A specific method for measuring the amount of dry powder flowing through the liquid is as described in Examples described later.

The artificial urine saturated liquid absorption amount of 0.2 g of the water-absorbent resin particles is calculated by a method including the following steps (a), (b), (c), (d) and (e) in this order.
(A) Put 500 g of artificial urine into a 500 mL beaker.
(B) 2.0 g of water-absorbent resin particles are charged into the beaker into which the artificial urine is charged while stirring the artificial urine at 600 rpm using a magnetic stirrer bar (8 mmφ × 30 mm, without ring).
(C) The artificial urine and the water-absorbent resin particles are stirred at 600 rpm for 60 minutes after the water-absorbent resin particles are added to form a swollen gel.
(D) The contents in the beaker are filtered through a 75 μm standard sieve with an opening, and allowed to stand for 1 minute to remove excess water.
(E) The total mass Wc of the swollen gel and the sieve is measured, and 0.2 g of the artificial urine saturated liquid absorption amount (g) is obtained from the previously measured mass Wd of the sieve by the following formula.
0.2 g artificial urine saturated liquid absorption amount (g) = 0.2 × (Wc-Wd) /2.0

The artificial urine saturated liquid absorption amount of 0.2 g of the water-absorbent resin particles is, for example, 7.0 or more, 8.0 or more, 9.0 or more, or 10.0 from the viewpoint of the water absorption characteristics of the water-absorbent resin particles. It may be 20.0 or less, 15.0 or less, 13.0 or less, or 11.0 or less. A specific method for measuring the artificial urine saturated liquid absorption amount of 0.2 g of the water-absorbent resin particles is as described in Examples described later.

The shape of the water-absorbent resin particles may be, for example, substantially spherical, crushed or granular, and particles having agglomerated primary particles having these shapes may be formed. The medium particle size of the water-absorbent resin particles may be 45 to 850 μm, 75 to 700 μm, 100 to 600 μm, or 200 to 600 μm. The water-absorbent resin particles may have a desired particle size distribution at the time of being obtained by the production method described later, but the particle size distribution may be adjusted by performing an operation such as particle size adjustment using classification with a sieve. Good.

The water-absorbent resin particles can include, for example, a crosslinked polymer formed by polymerizing a monomer containing an ethylenically unsaturated monomer. The crosslinked polymer has a monomer unit derived from an ethylenically unsaturated monomer.

The water-absorbent resin particles can be produced by a method including a step of polymerizing a monomer containing an ethylenically unsaturated monomer. Examples of the polymerization method include a reverse phase suspension polymerization method, an aqueous solution polymerization method, a bulk polymerization method, and a precipitation polymerization method. From the viewpoint of ensuring good water absorption characteristics of the obtained water-absorbent resin particles and facilitating control of the polymerization reaction, a reverse phase suspension polymerization method or an aqueous solution polymerization method may be applied. In the following, a reverse phase suspension polymerization method will be described as an example as a method for polymerizing an ethylenically unsaturated monomer.

<Water-absorbent resin particles>
The ethylenically unsaturated monomer may be water-soluble. Examples of water-soluble ethylenically unsaturated monomers include (meth) acrylic acid and its salts, 2- (meth) acrylamide-2-methylpropanesulfonic acid and its salts, (meth) acrylamide, N, N-dimethyl. (Meta) acrylamide, 2-hydroxyethyl (meth) acrylate, N-methylol (meth) acrylamide, polyethylene glycol mono (meth) acrylate, N, N-diethylaminoethyl (meth) acrylate, N, N-diethylaminopropyl (meth) Examples thereof include acrylate and diethylaminopropyl (meth) acrylamide. When the ethylenically unsaturated monomer has an amino group, the amino group may be quaternized. The ethylenically unsaturated monomer may be used alone or in combination of two or more. Functional groups such as the carboxyl group and amino group of the above-mentioned monomers can function as functional groups capable of cross-linking in the surface cross-linking step described later.

From the viewpoint of industrial availability, the ethylenically unsaturated monomer is at least one selected from the group consisting of (meth) acrylic acid and salts thereof, acrylamide, methacrylamide, and N, N-dimethylacrylamide. It may contain a compound of the species. The ethylenically unsaturated monomer may contain (meth) acrylic acid and a salt thereof, and at least one compound selected from the group consisting of acrylamide. From the viewpoint of further enhancing the water absorption property, the ethylenically unsaturated monomer may contain at least one compound selected from the group consisting of (meth) acrylic acid and salts thereof.

The ethylenically unsaturated monomer can be used in the polymerization reaction as an aqueous solution. The concentration of the ethylenically unsaturated monomer in the aqueous solution containing the ethylenically unsaturated monomer (hereinafter, simply referred to as "monomer aqueous solution") is 20% by mass or more and the saturation concentration or less, 25 to 70% by mass, or 30. It may be up to 55% by mass. Examples of the water used in the aqueous solution include tap water, distilled water, ion-exchanged water and the like.

As the monomer for obtaining the water-absorbent resin particles, a monomer other than the above-mentioned ethylenically unsaturated monomer may be used. Such a monomer can be used, for example, by being mixed with an aqueous solution containing the above-mentioned ethylenically unsaturated monomer. The amount of the ethylenically unsaturated monomer used may be 70 to 100 mol% with respect to the total amount of the monomers. The ratio of (meth) acrylic acid and a salt thereof may be 70 to 100 mol% with respect to the total amount of the monomer.

When the ethylenically unsaturated monomer has an acid group, the acid group may be neutralized with an alkaline neutralizer and then the monomer solution may be used in the polymerization reaction. The degree of neutralization of an ethylenically unsaturated monomer by an alkaline neutralizing agent increases the osmotic pressure of the obtained water-absorbent resin particles and further enhances the water absorption characteristics (water absorption amount, etc.). It may be 10-100 mol%, 50-90 mol%, or 60-80 mol% of the acidic group in the body. Examples of the alkaline neutralizer include alkali metal salts such as sodium hydroxide, sodium carbonate, sodium hydrogen carbonate, potassium hydroxide and potassium carbonate; ammonia and the like. The alkaline neutralizer may be used alone or in combination of two or more. The alkaline neutralizer may be used in the form of an aqueous solution to simplify the neutralization operation. Neutralization of the acid group of the ethylenically unsaturated monomer can be performed, for example, by adding an aqueous solution of sodium hydroxide, potassium hydroxide or the like to the above-mentioned monomer aqueous solution and mixing them.

In the reverse phase suspension polymerization method, the monomer aqueous solution is dispersed in a hydrocarbon dispersion medium in the presence of a surfactant, and the ethylenically unsaturated monomer is polymerized using a radical polymerization initiator or the like. Can be done. As the radical polymerization initiator, a water-soluble radical polymerization initiator can be used.

Examples of the surfactant include nonionic surfactants and anionic surfactants. As the nonionic surfactant, sorbitan fatty acid ester and (poly) glycerin fatty acid ester (“(poly)” means both with and without the prefix of “poly”. The same shall apply hereinafter. ), Sucrose fatty acid ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene glycerin fatty acid ester, sorbitol fatty acid ester, polyoxyethylene sorbitol fatty acid ester, polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene himashi Examples thereof include oil, polyoxyethylene cured castor oil, alkylallyl formaldehyde condensed polyoxyethylene ether, polyoxyethylene polyoxypropylene block copolymer, polyoxyethylene polyoxypropyl alkyl ether, polyethylene glycol fatty acid ester and the like. Examples of anionic surfactants include fatty acid salts, alkylbenzene sulfonates, alkylmethyl taurates, polyoxyethylene alkylphenyl ether sulfates, polyoxyethylene alkyl ether sulfonates, and phosphoric acid esters of polyoxyethylene alkyl ethers. , And the phosphate ester of polyoxyethylene alkyl allyl ether and the like. The surfactant may be used alone or in combination of two or more.

From the viewpoint that the W / O type reverse phase suspension is in a good state, water-absorbent resin particles having a suitable particle size can be easily obtained, and industrially available, the surfactant is a sorbitan fatty acid ester. It may contain at least one compound selected from the group consisting of polyglycerin fatty acid ester and sucrose fatty acid ester. From the viewpoint of easily improving the water absorption characteristics of the obtained water-absorbent resin particles, a sorbitan fatty acid ester and / or a sucrose fatty acid ester (for example, sucrose stearic acid ester) can be used as the surfactant. These surfactants may be used alone or in combination of two or more.

The amount of the surfactant may be 0.05 to 10 parts by mass, 0.08 to 5 parts by mass, or 0.1 to 3 parts by mass with respect to 100 parts by mass of the monomer aqueous solution.

In reverse phase suspension polymerization, a polymer-based dispersant may be used in combination with the above-mentioned surfactant. Examples of the polymer dispersant include maleic anhydride-modified polyethylene, maleic anhydride-modified polypropylene, maleic anhydride-modified ethylene / propylene copolymer, maleic anhydride-modified EPDM (ethylene / propylene / diene / terpolymer), and maleic anhydride. Modified polybutadiene, maleic anhydride / ethylene copolymer, maleic anhydride / propylene copolymer, maleic anhydride / ethylene / propylene copolymer, maleic anhydride / butadiene copolymer, polyethylene, polypropylene, ethylene / propylene copolymer Examples thereof include coalescence, oxidized polyethylene, oxidized polypropylene, oxidized ethylene / propylene copolymer, ethylene / acrylic acid copolymer, ethyl cellulose, ethyl hydroxyethyl cellulose and the like. The polymer-based dispersant may be used alone or in combination of two or more. From the viewpoint of excellent monomer dispersion stability, the polymer-based dispersant includes maleic anhydride-modified polyethylene, maleic anhydride-modified polypropylene, maleic anhydride-modified ethylene / propylene copolymer, and maleic anhydride / ethylene copolymer. , Maleic anhydride / propylene copolymer, maleic anhydride / ethylene / propylene copolymer, polyethylene, polypropylene, ethylene / propylene copolymer, oxidized polyethylene, oxidized polypropylene, and oxidized ethylene / propylene copolymer It may be at least one selected from the group consisting of.

The amount of the polymer-based dispersant may be 0.05 to 10 parts by mass, 0.08 to 5 parts by mass, or 0.1 to 3 parts by mass with respect to 100 parts by mass of the monomer aqueous solution.

The hydrocarbon dispersion medium may contain at least one compound selected from the group consisting of chain aliphatic hydrocarbons having 6 to 8 carbon atoms and alicyclic hydrocarbons having 6 to 8 carbon atoms. Hydrocarbon dispersion media include chain aliphatic hydrocarbons such as n-hexane, n-heptane, 2-methylhexane, 3-methylhexane, 2,3-dimethylpentane, 3-ethylpentane, and n-octane; cyclohexane. , Methylcyclohexane, cyclopentane, methylcyclopentane, trans-1,2-dimethylcyclopentane, cis-1,3-dimethylcyclopentane, trans-1,3-dimethylcyclopentane and other alicyclic hydrocarbons; benzene, Examples include aromatic hydrocarbons such as toluene and xylene. The hydrocarbon dispersion medium may be used alone or in combination of two or more.

From the viewpoint of being industrially easily available and having stable quality, the hydrocarbon dispersion medium may contain at least one selected from the group consisting of n-heptane and cyclohexane. From the same viewpoint, as the mixture of the above-mentioned hydrocarbon dispersion medium, for example, commercially available ExxonHeptane (manufactured by ExxonMobil: containing 75 to 85% of n-heptane and isomeric hydrocarbons) is used. You may.

The amount of the hydrocarbon dispersion medium is 30 to 1000 parts by mass, 40 to 500 parts by mass, or 50 parts by mass with respect to 100 parts by mass of the monomer aqueous solution from the viewpoint of appropriately removing the heat of polymerization and easily controlling the polymerization temperature. It may be up to 300 parts by mass. When the amount of the hydrocarbon dispersion medium is 30 parts by mass or more, the polymerization temperature tends to be easily controlled. When the amount of the hydrocarbon dispersion medium is 1000 parts by mass or less, the productivity of polymerization tends to be improved, which is economical.

The radical polymerization initiator may be water-soluble. Examples of water-soluble radical polymerization initiators are persulfates such as potassium persulfate, ammonium persulfate, and sodium persulfate; methyl ethyl ketone peroxide, methyl isobutyl ketone peroxide, di-t-butyl peroxide, and t-butyl cumylper. Peroxides such as oxides, t-butylperoxyacetate, t-butylperoxyisobutyrate, t-butylperoxypivalate, hydrogen peroxide; 2,2'-azobis (2-amidinopropane) dihydrochloride , 2,2'-azobis [2- (N-phenylamidino) propane] dihydrochloride, 2,2'-azobis [2- (N-allylamidino) propane] dihydrochloride, 2,2'-azobis [ 2- (2-Imidazolin-2-yl) propane] 2 hydrochloride, 2,2'-azobis {2- [1- (2-hydroxyethyl) -2-imidazolin-2-yl] propane} 2 hydrochloride, 2,2'-azobis {2-methyl-N- [1,1-bis (hydroxymethyl) -2-hydroxyethyl] propionamide}, 2,2'-azobis [2-methyl-N- (2-hydroxy) Ethyl) -propionamide], azo compounds such as 4,4'-azobis (4-cyanovaleric acid) can be mentioned. The radical polymerization initiator may be used alone or in combination of two or more. The radical polymerization initiators are potassium persulfate, ammonium persulfate, sodium persulfate, 2,2'-azobis (2-amidinopropane) dihydrochloride, 2,2'-azobis [2- (2-imidazolin-2-yl). ) Propane] 2 hydrochloride and 2,2'-azobis {2- [1- (2-hydroxyethyl) -2-imidazolin-2-yl] propane} 2 hydrochloride at least selected from the group. There may be.

The amount of the radical polymerization initiator may be 0.00005 to 0.01 mol per 1 mol of the ethylenically unsaturated monomer. When the amount of the radical polymerization initiator used is 0.00005 mol or more, the polymerization reaction does not require a long time and is efficient. When the amount of the radical polymerization initiator is 0.01 mol or less, it is easy to suppress the occurrence of a rapid polymerization reaction.

The exemplified radical polymerization initiator can also be used as a redox polymerization initiator in combination with a reducing agent such as sodium sulfite, sodium hydrogen sulfite, ferrous sulfate, and L-ascorbic acid.

At the time of the polymerization reaction, the aqueous monomer solution may contain a chain transfer agent. Examples of the chain transfer agent include hypophosphates, thiols, thiolic acids, secondary alcohols, amines and the like.

In order to control the particle size of the water-absorbent resin particles, the monomer aqueous solution used for the polymerization may contain a thickener. Examples of the thickener include hydroxyethyl cellulose, hydroxypropyl cellulose, methyl cellulose, carboxymethyl cellulose, polyacrylic acid, polyethylene glycol, polyacrylamide, polyethyleneimine, dextrin, sodium alginate, polyvinyl alcohol, polyvinylpyrrolidone, polyethylene oxide and the like. If the stirring speed at the time of polymerization is the same, the higher the viscosity of the aqueous monomer solution, the larger the medium particle size of the obtained particles tends to be.

Cross-linking by self-cross-linking may occur during polymerization, but cross-linking may be further performed by using an internal cross-linking agent. When an internal cross-linking agent is used, it is easy to control the water absorption characteristics of the water-absorbent resin particles. The internal cross-linking agent is usually added to the reaction solution during the polymerization reaction. Examples of the internal cross-linking agent include di or tri (meth) acrylic acid esters of polyols such as ethylene glycol, propylene glycol, trimethylpropane, glycerin, polyoxyethylene glycol, polyoxypropylene glycol, and polyglycerin; Unsaturated polyesters obtained by reacting polyols with unsaturated acids (maleic acid, fumaric acid, etc.); bis (meth) acrylamides such as N, N'-methylenebis (meth) acrylamide; polyepoxides and (meth) Di or tri (meth) acrylic acid esters obtained by reacting with acrylic acid; di (meth) obtained by reacting polyisocyanate (tolylene diisocyanate, hexamethylene diisocyanate, etc.) with hydroxyethyl (meth) acrylate. ) Acrylic acid carbamil esters; compounds having two or more polymerizable unsaturated groups, such as allylated starch, allylated cellulose, diallyl phthalate, N, N', N "-triallyl isocyanurate, divinylbenzene; Poly such as (poly) ethylene glycol diglycidyl ether, (poly) propylene glycol diglycidyl ether, (poly) glycerin diglycidyl ether, (poly) glycerin triglycidyl ether, (poly) propylene glycol polyglycidyl ether, polyglycerol polyglycidyl ether, etc. Glyceridyl compound; haloepoxy compound such as epichlorohydrin, epibromhydrin, α-methylepichlorohydrin; 2 reactive functional groups such as isocyanate compound (2,4-tolylene diisocyanate, hexamethylene diisocyanate, etc.) Examples thereof include compounds having more than one. The internal cross-linking agent may be used alone or in combination of two or more. The internal cross-linking agent may be a polyglycidyl compound or diglycidyl. It may be an ether compound. The internal cross-linking agent comprises at least one selected from the group consisting of (poly) ethylene glycol diglycidyl ether, (poly) propylene glycol diglycidyl ether, and (poly) glycerin diglycidyl ether. It may be.

The amount of the internal cross-linking agent is not ethylenious from the viewpoint that the water-soluble property is suppressed by appropriately cross-linking the polymer obtained by the polymerization of the above-mentioned monomer aqueous solution, and a sufficient water absorption amount can be easily obtained. It may be 0 mmol or more, 0.01 mmol or more, 0.015 mmol or more, 0.020 mmol or more, or 0.1 mol or less, per 1 mol of saturated monomer.

An aqueous phase containing an ethylenically unsaturated monomer, a radical polymerization initiator, an internal cross-linking agent, etc., if necessary, and an oil containing a hydrocarbon-based dispersant and, if necessary, a surfactant, a polymer-based dispersant, etc. Reverse-phase suspension polymerization can be carried out in an aqueous system in oil by heating with stirring in a state where the phases are mixed.

When performing reverse phase suspension polymerization, a monomer aqueous solution containing an ethylenically unsaturated monomer is used as a hydrocarbon dispersion medium in the presence of a surfactant (and, if necessary, a polymer-based dispersant). Disperse in. At this time, before the start of the polymerization reaction, the timing of adding the surfactant, the polymer-based dispersant, etc. may be either before or after the addition of the monomer aqueous solution.

From the viewpoint of easily reducing the amount of the hydrocarbon dispersion medium remaining in the obtained water-absorbent resin, the monomer aqueous solution is dispersed in the hydrocarbon dispersion medium in which the polymer-based dispersant is dispersed, and then the surfactant is further dispersed. It may be allowed to carry out polymerization.

Reverse phase suspension polymerization can be carried out in one stage or in multiple stages of two or more stages. Reversed phase suspension polymerization may be carried out in two or three stages from the viewpoint of increasing productivity.

When reverse phase suspension polymerization is carried out in two or more stages, an ethylenically unsaturated monomer is added to the reaction mixture obtained in the first step polymerization reaction after the first step reverse phase suspension polymerization is carried out. It may be added and mixed, and the reverse phase suspension polymerization of the second and subsequent steps may be carried out in the same manner as in the first step. In the reverse phase suspension polymerization in each stage of the second and subsequent stages, in addition to the ethylenically unsaturated monomer, the above-mentioned radical polymerization initiator is used in the reverse phase suspension polymerization in each stage of the second and subsequent stages. Based on the amount of the ethylenically unsaturated monomer to be added, it may be added within the range of the molar ratio of each component to the above-mentioned ethylenically unsaturated monomer to carry out reverse phase suspension polymerization. In the reverse phase suspension polymerization in each stage after the second stage, an internal cross-linking agent may be used if necessary. When an internal cross-linking agent is used, it is added within the range of the molar ratio of each component to the above-mentioned ethylenically unsaturated monomer based on the amount of the ethylenically unsaturated monomer provided in each stage, and the suspension is reversed. Muddy polymerization may be carried out.

The temperature of the polymerization reaction varies depending on the radical polymerization initiator used, but by advancing the polymerization rapidly and shortening the polymerization time, the efficiency is improved and the heat of polymerization is easily removed to carry out the reaction smoothly. From the viewpoint, it may be 20 to 150 ° C. or 40 to 120 ° C. The reaction time is usually 0.5-4 hours. The completion of the polymerization reaction can be confirmed, for example, by stopping the temperature rise in the reaction system. As a result, the polymer of the ethylenically unsaturated monomer is usually obtained in the state of a hydrogel-like polymer.

After polymerization, cross-linking may be performed after polymerization by adding a cross-linking agent to the obtained hydrogel polymer and heating it. By performing cross-linking after polymerization, the degree of cross-linking of the hydrogel polymer can be increased, whereby the water-absorbing characteristics of the water-absorbent resin particles can be further improved.

Examples of the cross-linking agent for performing post-polymerization cross-linking include polyols such as ethylene glycol, propylene glycol, 1,4-butanediol, trimethylolpropane, glycerin, polyoxyethylene glycol, polyoxypropylene glycol, and polyglycerin; Compounds having two or more epoxy groups such as (poly) ethylene glycol diglycidyl ether, (poly) propylene glycol diglycidyl ether, and (poly) glycerin diglycidyl ether; epichlorohydrin, epibromhydrin, α-methylepicrolhydrin, etc. Haloepoxide compounds; compounds having two or more isocyanate groups such as 2,4-tolylene diisocyanate and hexamethylene diisocyanate; oxazoline compounds such as 1,2-ethylenebisoxazoline; carbonate compounds such as ethylenecarbonate; bis [N , N-di (β-hydroxyethyl)] hydroxyalkylamide compounds such as adipamide can be mentioned. Cross-linking agents for post-polymerization cross-linking are (poly) ethylene glycol diglycidyl ether, (poly) glycerin diglycidyl ether, (poly) glycerin triglycidyl ether, (poly) propylene glycol polyglycidyl ether, and polyglycerol polyglycidyl ether. It may be a polyglycidyl compound such as. These cross-linking agents may be used alone or in combination of two or more.

The amount of the cross-linking agent used for post-polymerization cross-linking is 1 mol of the water-soluble ethylenically unsaturated monomer from the viewpoint of appropriately cross-linking the obtained hydrogel-like polymer to exhibit suitable water absorption characteristics. It may be 0 to 0.03 mol, 0 to 0.01 mol, or 0.00001 to 0.005 mol.

The cross-linking agent for post-polymerization cross-linking is added to the reaction solution after the polymerization reaction of the ethylenically unsaturated monomer. In the case of multi-stage polymerization, a cross-linking agent for post-polymerization cross-linking may be added after the multi-stage polymerization. Considering the fluctuation of water content due to heat generation during and after polymerization, retention due to process delay, opening of the system when adding a cross-linking agent, and addition of water due to addition of a cross-linking agent, the cross-linking agent for post-polymerization cross-linking is , From the viewpoint of water content (described later), it may be added in the region of [water content immediately after polymerization ± 3% by mass].

Subsequently, water is removed from the obtained hydrogel polymer. Drying to remove water gives polymer particles containing a polymer of ethylenically unsaturated monomers. Examples of the drying method include (a) a method of removing water by azeotropic distillation in a state where the hydrogel polymer is dispersed in a hydrocarbon dispersion medium, and (b) a method of taking out the hydrogel polymer by decantation and reducing the pressure. Examples thereof include a method of drying, (c) a method of filtering the hydrogel polymer by a filter and drying under reduced pressure.

The particle size of the water-absorbent resin particles can be adjusted by adjusting the rotation speed of the stirrer during the polymerization reaction, or by adding a flocculant into the system after the polymerization reaction or in the early stage of drying. By adding a flocculant, the particle size of the obtained water-absorbent resin particles can be increased. As the flocculant, an inorganic flocculant can be used. Examples of the inorganic flocculant (for example, powdered inorganic flocculant) include silica, zeolite, bentonite, aluminum oxide, talc, titanium dioxide, kaolin, clay, hydrotalcite and the like. From the viewpoint of excellent aggregating effect, the aggregating agent may be at least one selected from the group consisting of silica, aluminum oxide, talc and kaolin.

In reverse phase suspension polymerization, a coagulant is previously dispersed in a hydrocarbon dispersion medium of the same type as that used in the polymerization or water, and then this is placed in a hydrocarbon dispersion medium containing a hydrogel polymer under stirring. May be mixed with.

The amount of the flocculant is 0.001 to 1 part by mass, 0.005 to 0.5 part by mass, or 0.01 to 0.2 with respect to 100 parts by mass of the ethylenically unsaturated monomer used for the polymerization. It may be a mass part. When the amount of the flocculant is within these ranges, it is easy to obtain water-absorbent resin particles having a desired particle size distribution.

The polymerization reaction can be carried out using various stirrers having stirring blades. As the stirring blade, a flat plate blade, a lattice blade, a paddle blade, a propeller blade, an anchor blade, a turbine blade, a Faudler blade, a ribbon blade, a full zone blade, a max blend blade and the like can be used. The flat plate blade has a shaft (stirring shaft) and a flat plate portion (stirring portion) arranged around the shaft. Further, the flat plate portion may have a slit or the like.

In the production of the water-absorbent resin particles, even if the surface portion of the hydrogel polymer is crosslinked (surface crosslink) using a cross-linking agent in any of the drying step (moisture removing step) and subsequent steps. Good. By performing surface cross-linking, it is easy to control the water absorption characteristics of the water-absorbent resin particles. The water content of the surface-crosslinked hydrogel polymer may be 5 to 50% by mass, 10 to 40% by mass, or 15 to 35% by mass. The water content (mass%) of the water-containing gel polymer is calculated by the following formula.
Moisture content = [Ww / (Ww + Ws)] x 100
Ww: When the flocculant, surface cross-linking agent, etc. are mixed in the amount obtained by subtracting the amount of water discharged to the outside of the system by the drying step or the like from the amount of water contained in the monomer aqueous solution before polymerization in the total polymerization step. The amount of water in the hydrogel polymer calculated by adding the amount of water used as needed.

Ws: The amount of solids calculated from the amount of materials such as ethylenically unsaturated monomers, cross-linking agents, and initiators that make up the hydrogel polymer.

Examples of the cross-linking agent (surface cross-linking agent) for performing surface cross-linking include compounds having two or more reactive functional groups. Examples of cross-linking agents include polyols such as ethylene glycol, propylene glycol, 1,4-butanediol, trimethylolpropane, glycerin, polyoxyethylene glycol, polyoxypropylene glycol, and polyglycerin; (poly) ethylene glycol diglycidyl. Polyglycidyl compounds such as ether, (poly) glycerin diglycidyl ether, (poly) glycerin triglycidyl ether, trimethylpropan triglycidyl ether (poly) propylene glycol polyglycidyl ether, (poly) glycerol polyglycidyl ether; epichlorohydrin , Epibrom hydrin, α-methyl epichlorohydrin and other haloepoxy compounds; 2,4-tolylene diisocyanate, hexamethylene diisocyanate and other isocyanate compounds; 3-methyl-3-oxetane methanol, 3-ethyl-3-oxetane Oxetane compounds such as methanol, 3-butyl-3-oxetane methanol, 3-methyl-3-oxetane ethanol, 3-ethyl-3-oxetane ethanol, 3-butyl-3-oxetane ethanol; 1,2-ethylenebisoxazoline and the like. Oxetane compounds; carbonate compounds such as ethylene carbonate; hydroxyalkylamide compounds such as bis [N, N-di (β-hydroxyethyl)] adipamide can be mentioned. The surface cross-linking agent may be used alone or in combination of two or more. The surface cross-linking agent may be a polyglycidyl compound, and may be (poly) ethylene glycol diglycidyl ether, (poly) glycerin diglycidyl ether, (poly) glycerin triglycidyl ether, (poly) propylene glycol polyglycidyl ether, and It may contain at least one selected from the group consisting of polyglycerol polyglycidyl ether.

The amount of the surface cross-linking agent is 0.00001 to 0.02 mol, 0.00005 to 0.01 mol, or 0.0001 to 0.005 per 1 mol of the ethylenically unsaturated monomer used for the polymerization. It may be a molar. When the amount of the surface cross-linking agent is 0.00001 mol or more, the cross-linking density on the surface portion of the water-absorbent resin particles is sufficiently increased, and the gel strength of the water-absorbent resin particles can be easily increased. When the amount of the surface cross-linking agent is 0.02 mol or less, it is easy to increase the water absorption amount of the water-absorbent resin particles.

In the production of water-absorbent resin particles, the surface portion of the hydrogel polymer is treated (surface modification) with a surface modifier in either the drying step (moisture removal step) or a subsequent step. May be good. The surface modification may be carried out, for example, before, during or after the surface cross-linking step. Surface modification may be carried out after surface cross-linking. In particular, in a hydrogel polymer obtained by a reverse phase suspension polymerization method, an aqueous solution polymerization method, or another polymerization method, when the hydrogel polymer is treated with a surface modifier after surface cross-linking, The obtained water-absorbent resin particles tend to easily form a resin layer showing a high dry powder passing liquid absorption rate.

The surface modifier may be, for example, a surfactant such as an anionic surfactant, a cationic surfactant, an amphoteric surfactant, or a nonionic surfactant. For example, the HLB value of the nonionic surfactant used as the surface modifier may be, for example, 3 to 12, or 6 to 10. Examples of the nonionic surfactant include sorbitan fatty acid esters such as sorbitan monolaurate. In particular, when the surface modifier is a nonionic surfactant having an HLB value within the above range, the obtained water-absorbent resin particles tend to easily form a resin layer showing a high dry powder flow-through liquid absorption rate. The HLB value is measured by the Griffin method.

The amount of the surface modifier is 0.01 to 0.50 parts by mass, 0.02 to 0.40 parts by mass, or 0.04 with respect to 100 parts by mass of the ethylenically unsaturated monomer used for the polymerization. It may be ~ 0.30 parts by mass.

If necessary, after surface cross-linking and / or surface modification, water and a hydrocarbon dispersion medium can be distilled off from the hydrogel polymer to obtain polymer particles which are dry products. it can.

The water-absorbent resin particles according to the present embodiment may be composed of only polymer particles, but various additional particles selected from, for example, a gel stabilizer, a metal chelating agent, a fluidity improver (lubricant), and the like. Ingredients can be further included. Additional components may be placed inside the polymer particles, on the surface of the polymer particles, or both. The additional component may be a fluidity improver (lubricant). The fluidity improver may contain inorganic particles. Examples of the inorganic particles include silica particles such as amorphous silica.

The water-absorbent resin particles may contain a plurality of inorganic particles arranged on the surface of the polymer particles. For example, by mixing the polymer particles and the inorganic particles, the inorganic particles can be arranged on the surface of the polymer particles. The inorganic particles may be silica particles such as amorphous silica. When the water-absorbent resin particles include inorganic particles arranged on the surface of the polymer particles, the ratio of the amount of the inorganic particles to the mass of the polymer particles is 0.2% by mass or more, 0.5% by mass or more, 1 It may be 0.0% by mass or more, 1.5% by mass or more, 5.0% by mass or less, or 3.5% by mass or less. The inorganic particles here usually have a minute size as compared with the size of the polymer particles. For example, the average particle size of the inorganic particles may be 0.1 to 50 μm, 0.5 to 30 μm, or 1 to 20 μm. The average particle size here can be a value measured by a dynamic light scattering method or a laser diffraction / scattering method.

<Auxiliary sheet>
FIG. 1 is a cross-sectional view showing an example of an auxiliary sheet. The auxiliary sheet 60 shown in FIG. 1 has a resin layer 61 and two

sheet base materials

62a and 62b. The

sheet base materials

62a and 62b are arranged on both sides of the resin layer 61. In other words, the resin layer 61 is arranged inside the

sheet base materials

62a and 62b. The resin layer 61 is held in shape by being sandwiched between the two

sheet base materials

62a and 62b. The

sheet base materials

62a and 62b may be two sheets, one folded sheet, or one bag.

The auxiliary sheet 60 may further have an adhesive 63a interposed between the sheet base material 62a and the resin layer 61, and further has an adhesive 63b interposed between the sheet base material 62b and the resin layer 61. You may have. The

adhesives

63a and 63b may be, for example, a water-based adhesive, a solvent-based adhesive, an elastic adhesive, an aerosol adhesive, a hot melt adhesive, or the like.

The thickness of the auxiliary sheet 60 may be, for example, 3.0 mm or less, 2.5 mm or less, 2.0 mm or less, or 1.8 mm or less, and 0.1 mm or more, 0.3 mm or more, or 0.5 mm or more. It may be. The thickness can be measured using, for example, a dial thickness gauge JB manufactured by Ozaki Seisakusho Co., Ltd. (the stylus is made of aluminum having a diameter of 50 mm).

The resin layer 61 has the water-absorbent resin particles 61a according to the above-described embodiment and the fiber layer 61b containing a fibrous material. The resin layer 61 does not have to have the fiber layer 61b. The content of the water-absorbent resin particles in the resin layer may be 70 to 100% by mass, 80 to 100% by mass, or 90 to 100% by mass based on the mass of the resin layer 61.

The thickness of the resin layer 61 may be, for example, 2.0 mm or less, 1.5 mm or less, 1.0 mm or less, or 0.8 mm or less in a dry state, and is 0.1 mm or more, or 0.3 mm or more. You may. The mass per unit area of the resin layer 61 may be 100 g / m ² or less, 80 g / m ² or less, 60 g / m ² or less, or 40 g / m ² or less, 10 g / m ² or more, 20 g / m. ^It ^{may be 2} or more, or 25 g / m 2 or more.

The fibrous material constituting the fiber layer 61b can be, for example, a cellulosic fiber, a synthetic fiber, or a combination thereof. Examples of cellulosic fibers include crushed wood pulp, cotton, cotton linters, rayon and cellulosic acetate. Examples of synthetic fibers include polyamide fibers, polyester fibers, and polyolefin fibers. The fibrous material may be hydrophilic fibers (for example, pulp).

The resin layer 61 may further contain inorganic particles (for example, amorphous silica), a deodorant, an antibacterial agent, a fragrance, and the like.

The

sheet base materials

62a and 62b may be, for example, non-woven fabric, tissue, or the like. The two

sheet base materials

62a and 62b can be the same or different non-woven fabrics. The non-woven fabric may be a non-woven fabric composed of short fibers (that is, staples) (short-fiber non-woven fabric) or a non-woven fabric composed of long fibers (that is, filaments) (long-fiber non-woven fabric). The staples may generally have a fiber length of several hundred mm or less.

The non-woven fabrics used as the

sheet base materials

62a and 62b are thermal-bonded non-woven fabrics, air-through non-woven fabrics, resin-bonded non-woven fabrics, spunbonded non-woven fabrics, melt-blown non-woven fabrics, air-laid non-woven fabrics, spunlaced non-woven fabrics, point-bonded non-woven fabrics, or two or more kinds selected from these. It may be a laminate containing a non-woven fabric.

The non-woven fabric used as the

sheet base materials

62a and 62b can be a non-woven fabric formed of synthetic fibers, natural fibers, or a combination thereof. Examples of synthetic fibers include polyolefins such as polyethylene (PE) and polypropylene (PP), polyesters such as polyethylene terephthalate (PET), polytrimethylene terephthalate (PTT) and polyethylene naphthalate (PEN), polyamides such as nylon, and Examples thereof include fibers containing a synthetic resin selected from rayon. Examples of natural fibers include fibers containing cotton, silk, hemp, or pulp (cellulose). The fibers forming the non-woven fabric may be polyolefin fibers, polyester fibers or a combination thereof. The

sheet base materials

62a and 62b may be tissues.

The tissues used as the

sheet base materials

62a and 62b may be natural fibers or natural fibers mixed with synthetic fibers. The mass per unit area of the tissue may be ^{16 ± 2 g / m 2.} The thickness of the tissue may be 0.12 ± 0.02 mm.

The auxiliary sheet 60 can be obtained, for example, by sandwiching the resin layer 61 between the

sheet base materials

62a and 62b and pressurizing the formed structure while heating it as necessary. If necessary, the

adhesives

63a and 63b are arranged between the

sheet base materials

62a and 62b and the resin layer 61.

The auxiliary sheet 60 is used, for example, for producing various absorbent articles. Examples of absorbent articles include diapers (eg paper diapers), toilet training pants, incontinence pads, sanitary materials (sanitary napkins, tampons, etc.), sweat pads, pet sheets, toilet components, and animal waste treatment materials. Can be mentioned.

<Absorbable article>
FIG. 2 is a cross-sectional view showing an example of an absorbent article. The absorbent article 100 shown in FIG. 2 includes a water absorbing core 50, an auxiliary sheet 60, a liquid permeable sheet 30, and a liquid impermeable sheet 40. In other words, the water absorption core 50 and the auxiliary sheet 60 are sandwiched between the liquid permeable sheet 30 and the liquid impermeable sheet 40.

The water absorption core 50 has an absorption layer 10 and two

core wrap sheets

20a and 20b. The

core wrap sheets

20a and 20b are arranged on both sides of the absorption layer 10. In other words, the absorbent layer 10 is arranged inside the

core wrap sheets

20a and 20b, and is held in shape by being sandwiched between the two core wrap sheets. The

core wrap sheets

20a and 20b may be separate sheets, one folded sheet, or one bag body. However, the water absorption core 50 does not have to have one or both of the two

core wrap sheets

20a and 20b. For example, the core wrap sheet 20a may not be arranged between the absorption layer 10 and the auxiliary sheet 60. When the core wrap sheet is not arranged between the absorption layer 10 and the auxiliary sheet 60, for example, the absorption layer 10 is sandwiched between one core wrap sheet 20b and the auxiliary sheet 60. It is kept in shape.

The water absorption core 50 may further have an adhesive interposed between the core wrap sheet 20a and the absorption layer 10, and further has an adhesive interposed between the core wrap sheet 20b and the absorption layer 10. May be. An adhesive layer may be interposed between the

core wrap sheets

20a and 20b on both sides and the absorption layer 10. FIG. 3 is a plan view showing an example of an adhesive application pattern formed on the core wrap sheet. The adhesive 21 shown in FIG. 3 forms a coating pattern composed of a plurality of linear portions arranged at intervals on the core wrap sheet 20a. The coating pattern of the adhesive 21 may be linear, curved, dot-shaped, or a combination thereof. The adhesive may be, for example, a water-based adhesive, a solvent-based adhesive, or a hot melt adhesive.

The absorption layer 10 has water-absorbent resin particles 10a and a fiber layer 10b containing a fibrous material. The absorption layer 10 does not have to have the fiber layer 10b. The content of the water-absorbent resin particles in the absorption layer may be 70 to 100% by mass, 80 to 100% by mass, or 90 to 100% by mass based on the mass of the absorption layer 10.

The water-absorbent resin particles 10a may be particles containing a polymer containing an ethylenically unsaturated monomer as a monomer unit. The ethylenically unsaturated monomer may be a water-soluble monomer, and examples thereof include (meth) acrylic acid and salts thereof, 2- (meth) acrylamide-2-methylpropanesulfonic acid and its salts. Salt, (meth) acrylamide, N, N-dimethyl (meth) acrylamide, 2-hydroxyethyl (meth) acrylate, N-methylol (meth) acrylamide, polyethylene glycol mono (meth) acrylate, N, N-diethylaminoethyl (meth) ) Acrylate, N, N-diethylaminopropyl (meth) acrylate, and diethylaminopropyl (meth) acrylamide. The ethylenically unsaturated monomer may be used alone or in combination of two or more. When the ethylenically unsaturated monomer has a functional group such as a carboxyl group or an amino group, they can function as a functional group for cross-linking the polymer. The water-absorbent resin particles may be particles containing a polymer containing at least one of (meth) acrylic acid or a salt of (meth) acrylic acid as a monomer unit.

The water-absorbent resin particles 10a can be produced, for example, by a method including polymerizing a monomer containing an ethylenically unsaturated monomer. The monomer polymerization method can be selected from, for example, a reverse phase suspension polymerization method, an aqueous solution polymerization method, a bulk polymerization method, and a precipitation polymerization method. From the viewpoint of ensuring good water absorption characteristics of the water-absorbent resin particles and easily controlling the polymerization reaction, a reverse phase suspension polymerization method or an aqueous solution polymerization method may be adopted.

The polymer constituting the water-absorbent resin particles 10a may be a crosslinked polymer. In this case, the polymer may be crosslinked by self-crosslinking, cross-linking by reaction with a cross-linking agent, or both. The water-absorbent resin particles may be surface-crosslinked by cross-linking at least the polymer of the surface layer portion with a cross-linking agent.

The water-absorbent resin particles 10a may contain various additional components in addition to the polymer of the ethylenically unsaturated monomer. Examples of additional ingredients include gel stabilizers, metal chelating agents, and fluidity improvers (lubricants). Additional components may be placed inside the polymer particles, including the polymer, on the surface of the polymer particles, or both. The additional component may be a fluidity improver (lubricant). The fluidity improver may contain inorganic particles. Examples of the inorganic particles include silica particles such as amorphous silica.

The shape of the water-absorbent resin particles 10a may be, for example, substantially spherical, crushed or granular, and particles in which primary particles having these shapes are aggregated may be formed. The medium particle size of the water-absorbent resin particles may be 250 to 850 μm, 300 to 700 μm, or 300 to 600 μm. As for the water absorption characteristics of the water-absorbent resin particles 10a, for example, the water absorption amount of the physiological saline may be 20 to 80 g / g, 30 to 70 g / g, or 40 to 65 g / g.

The thickness of the absorption layer 10 may be, for example, 20 mm or less, 15 mm or less, 10 mm or less, 5 mm or less, 4 mm or less, or 3 mm or less in a dry state, and may be 0.1 mm or more or 0.3 mm or more. Good. The mass per unit area of the absorption layer 10 may be 1000 g / m ² or less, 800 g / m ² or less, or 600 g / m ² or less, 100 g / m ² or more, or 200 g / m ² or more. May be good.

The fibrous material constituting the fiber layer 10b can be, for example, a cellulosic fiber, a synthetic fiber, or a combination thereof. Examples of cellulosic fibers include crushed wood pulp, cotton, cotton linters, rayon and cellulosic acetate. Examples of synthetic fibers include polyamide fibers, polyester fibers, and polyolefin fibers. The fibrous material may be hydrophilic fibers (for example, pulp).

The absorption layer 10 (or fiber layer 10b) may further contain an inorganic powder (for example, amorphous silica), a deodorant, an antibacterial agent, a fragrance, and the like. When the water-absorbent resin particles 10a contain inorganic particles, the absorption layer 10 may contain inorganic powder in addition to the inorganic particles in the water-absorbent resin particles 10a.

The

core wrap sheets

20a and 20b may be, for example, a non-woven fabric. The two

core wrap sheets

20a and 20b can be the same or different non-woven fabrics. The non-woven fabric may be a non-woven fabric composed of short fibers (that is, staples) (short-fiber non-woven fabric) or a non-woven fabric composed of long fibers (that is, filaments) (long-fiber non-woven fabric). The staples may generally have a fiber length of several hundred mm or less.

The

core wrap sheets

20a and 20b are laminated including a thermal bond non-woven fabric, an air-through non-woven fabric, a resin bond non-woven fabric, a spunbond non-woven fabric, a melt blow non-woven fabric, an air-laid non-woven fabric, a spunlace non-woven fabric, a point bond non-woven fabric, or two or more kinds of non-woven fabrics selected from these. It can be a body.

The non-woven fabric used as the

core wrap sheets

20a and 20b can be a non-woven fabric formed of synthetic fibers, natural fibers, or a combination thereof. Examples of synthetic fibers include polyolefins such as polyethylene (PE) and polypropylene (PP), polyesters such as polyethylene terephthalate (PET), polytrimethylene terephthalate (PTT) and polyethylene naphthalate (PEN), polyamides such as nylon, and Examples thereof include fibers containing a synthetic resin selected from rayon. Examples of natural fibers include fibers containing cotton, silk, hemp, or pulp (cellulose). The fibers forming the non-woven fabric may be polyolefin fibers, polyester fibers or a combination thereof. The

core wrap sheets

20a and 20b may be tissues.

The water-absorbing core 50 is sandwiched between, for example, the water-absorbent resin particles 10a or a mixture containing the water-absorbent resin particles 10a and the fibrous material and the

core wrap sheets

20a and 20b, and the formed structure is heated as necessary. It can be obtained by the method of pressurizing. If necessary, an adhesive is placed between the

core wrap sheets

20a and 20b and the water-absorbent resin particles 10a or a mixture containing the same.

The water-absorbing core substantially includes a fiber layer as a whole, in addition to the water-absorbing core in which the core wrap sheet 20a, the water-absorbent resin particles 10a, the absorption layer 10 composed of the fiber layer 10b, and the core wrap sheet 20b are arranged in this order. It may be in the form of no sheet. FIG. 4 is a cross-sectional view of the water absorption core formed in a sheet shape, showing another example of the water absorption core. The water-absorbent core 50 shown in FIG. 4 includes a core wrap sheet 25a, an adhesive 26a, an absorption layer 10A made of water-absorbent resin particles, a core wrap sheet 25b, an absorption layer 10B made of water-absorbent resin particles, an adhesive 26b, and a core wrap. The sheets 25c are arranged in this order. The water-absorbent resin particles contained in the

absorption layers

10A and 10B may be of the same type or different types. The mass and thickness of each of the

absorption layers

10A and 10B per unit area may be the same or different.

The liquid permeable sheet 30 is arranged at the position of the outermost layer on the side where the liquid to be absorbed enters. The liquid permeable sheet 30 is arranged on the outside of the core wrap sheet 20b in contact with the core wrap sheet 20b. The liquid permeable sheet 40 is arranged at the position of the outermost layer on the side opposite to the liquid permeable sheet 30 in the absorbent article 100. The liquid impermeable sheet 40 is arranged on the outside of the core wrap sheet 20a in contact with the core wrap sheet 20a. The liquid permeable sheet 30 and the liquid permeable sheet 40 have a main surface wider than the main surface of the water absorbing core 50, and the outer edges of the liquid permeable sheet 30 and the liquid permeable sheet 40 are an absorbing layer. It extends around 10 and the

core wrap sheets

20a and 20b. However, the magnitude relationship of the absorbent layer 10, the

core wrap sheets

20a and 20b, the auxiliary sheet 60, the liquid permeable sheet 30, and the liquid permeable sheet 40 is appropriately adjusted according to the use of the absorbent article and the like.

The liquid permeable sheet 30 may be a non-woven fabric. The non-woven fabric used as the liquid permeable sheet 30 may have appropriate hydrophilicity from the viewpoint of the liquid absorption performance of the absorbent article. From this point of view, the liquid permeable sheet 30 is a pulp and paper test method No. 1 by the Paper and Pulp Technology Association. A non-woven fabric having a hydrophilicity of 5 to 200 measured according to the measuring method of 68 (2000) may be used. The hydrophilicity of the non-woven fabric may be 10 to 150. Pulp and paper test method No. For details of 68, for example, WO2011 / 086843 can be referred to.

The non-woven fabric having hydrophilicity may be formed of fibers showing appropriate hydrophilicity such as rayon fiber, or obtained by hydrophilizing a hydrophobic chemical fiber such as polyolefin fiber or polyester fiber. It may be formed of rayon fibers. As a method for obtaining a non-woven fabric containing hydrophobic chemical fibers that have been hydrophobized, for example, a method for obtaining a non-woven fabric by a spunbond method using a mixture of hydrophobic chemical fibers and a hydrophilic agent, hydrophobic chemistry. Examples thereof include a method of accommodating a hydrophilic agent when producing a spunbonded nonwoven fabric from fibers, and a method of impregnating a spunbonded nonwoven fabric obtained by using a hydrophobic chemical fiber with a hydrophilic agent. Examples of the hydrophilizing agent include anionic surfactants such as aliphatic sulfonates and higher alcohol sulfates, cationic surfactants such as quaternary ammonium salts, polyethylene glycol fatty acid esters, polyglycerin fatty acid esters, and sorbitan fatty acids. Nonionic surfactants such as esters, silicone-based surfactants such as polyoxyalkylene-modified silicones, and stain-releasing agents made of polyester-based, polyamide-based, acrylic-based, and urethane-based resins are used.

The amount of texture (mass per unit area) of the non-woven fabric used as the liquid permeable sheet 30 is from the viewpoint of imparting good liquid permeability, flexibility, strength and cushioning property to the absorbent article, and the liquid of the absorbent article. From the viewpoint of increasing the permeation rate, it may be 5 to 200 g / m ² , 8 to 150 g / m ² , or 10 to 100 g / m ² . The thickness of the liquid permeable sheet 30 may be 20 to 1400 μm, 50 to 1200 μm, or 80 to 1000 μm.

The liquid impermeable sheet 40 prevents the liquid absorbed by the absorption layer 10 or the resin layer 61 from leaking to the outside from the liquid impermeable sheet 40 side. The liquid impermeable sheet 40 may be a resin sheet or a non-woven fabric. The resin sheet may be a sheet made of a synthetic resin such as polyethylene, polypropylene, or polyvinyl chloride. The non-woven fabric may be a spunbond / melt blow / spunbond (SMS) non-woven fabric in which a water resistant melt blow non-woven fabric is sandwiched between high-strength spunbond non-woven fabrics. Further, the liquid permeable sheet 40 may be a composite sheet of a resin sheet and a non-woven fabric (for example, a spunbonded non-woven fabric or a spunlaced non-woven fabric). The liquid impermeable sheet 40 may have breathability from the viewpoint that stuffiness at the time of wearing is reduced and discomfort given to the wearer can be reduced. As the liquid impermeable sheet 40 having breathability, for example, a sheet of low density polyethylene (LDPE) resin can be used.

From the viewpoint of ensuring flexibility so as not to impair the wearing feeling of the absorbent article, the basis weight (mass per unit area) of the liquid impermeable sheet 40 is 5 to 100 g / m ² or 10 to 50 g / m ^2. It may be.

The absorbent article 100 can be manufactured, for example, by a method including arranging the water absorbing core 50 and the auxiliary sheet 60 between the liquid permeable sheet 30 and the liquid impermeable sheet 40. A laminate in which the liquid impermeable sheet 40, the auxiliary sheet 60, the water absorption core 50, and the liquid permeable sheet 30 are laminated in this order is pressurized as necessary. Alternatively, the liquid permeable sheet 30, the core wrap sheet 20b, the water-absorbent resin particles 10a, or the mixture containing the water-absorbent resin particles 10a and the fibrous material, the core wrap sheet 20a, the auxiliary sheet 60, and the liquid non-liquid. The absorbent article 100 can also be obtained by arranging the permeable sheets 40 in this order and pressurizing the formed structure while heating if necessary. In addition, each structural unit may be bonded with an adhesive.

Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to these examples.

[Preparation of water-absorbent resin particles]
Manufacturing example 1
<First stage polymerization reaction>
A round-bottomed cylindrical separable flask with an inner diameter of 11 cm and a volume of 2 L equipped with a reflux condenser, a dropping funnel, a nitrogen gas introduction pipe, and a stirring blade having four inclined paddle blades with a blade diameter of 5 cm in two stages as a stirrer. Got ready. To this flask, take 293 g of n-heptane as a hydrocarbon dispersion medium, add 0.736 g of a maleic anhydride-modified ethylene-propylene copolymer (Mitsui Chemicals Co., Ltd., High Wax 1105A) as a polymer-based dispersant, and stir. The temperature was raised to 80 ° C. to dissolve the dispersant, and then cooled to 50 ° C.

In a beaker with an internal volume of 300 mL, take 92.0 g (1.03 mol) of an 80.5 mass% aqueous acrylic acid solution as a water-soluble ethylenically unsaturated monomer, and cool it from the outside to 20.9 mass%. After adding 147.7 g of an aqueous sodium hydroxide solution to neutralize 75 mol%, 0.092 g of hydroxylethyl cellulose (Sumitomo Seika Co., Ltd., HECAW-15F) as a thickener, as a water-soluble radical polymerization initiator. 0.0736 g (0.272 mmol) of potassium persulfate and 0.010 g (0.057 mmol) of ethylene glycol diglycidyl ether as an internal cross-linking agent were added and dissolved to prepare a first-stage monomer aqueous solution.

Then, the first-stage monomer aqueous solution prepared above was added to the separable flask, and after stirring for 10 minutes, 6.62 g of n-heptane was added as a surfactant to the sucrose stearic acid ester of HLB3. Mitsubishi Chemical Foods Co., Ltd., Ryoto Sugar Ester S-370) 0.736 g of a surfactant solution dissolved by heating is further added, and the inside of the system is sufficiently filled with nitrogen while stirring at a stirring speed of 550 rpm. After the replacement, the flask was immersed in a water bath at 70 ° C. to raise the temperature, and polymerization was carried out for 60 minutes to obtain a first-stage polymerization slurry solution.

<Second stage polymerization reaction>
Take 128.8 g (1.44 mol) of an 80.5 mass% acrylic acid aqueous solution as a water-soluble ethylenically unsaturated monomer in a beaker having an internal volume of 500 mL, and while cooling from the outside, 27 mass% sodium hydroxide. After 159.0 g of the aqueous solution was added dropwise to neutralize 75 mol%, 0.090 g (0.333 mmol) of potassium persulfate was used as the water-soluble radical polymerization initiator, and ethylene glycol diglycidyl ether was used as the internal cross-linking agent. 0116 g (0.067 mmol) was added and dissolved to prepare a second-stage monomer aqueous solution.

After cooling the inside of the separable flask system to 31 ° C. while stirring at a stirring speed of 1000 rpm, the entire amount of the monomer aqueous solution in the second stage is added to the polymerized slurry liquid in the first stage. After adding and replacing the inside of the system with nitrogen for 30 minutes, the flask was again immersed in a water bath at 70 ° C. to raise the temperature, and the polymerization reaction was carried out for 60 minutes to obtain a hydrogel polymer.

After the polymerization, 0.589 g of a 45% by mass diethylenetriamine-5 sodium acetate aqueous solution was added to the obtained hydrogel polymer under stirring. Then, the flask was immersed in an oil bath set at 125 ° C., and 275.8 g of water was extracted from the system while refluxing n-heptane by azeotropic distillation of n-heptane and water. Then, 4.42 g (0.507 mmol) of a 2% by mass ethylene glycol diglycidyl ether aqueous solution was added to the flask as a surface cross-linking agent, and the flask was kept at 83 ° C. for 2 hours.

Next, a surfactant solution in which 0.074 g of sorbitan monolaurate (trade name: Nonion LP-20R, HLB value 8.6, manufactured by Nichiyu Co., Ltd.), which is a surfactant, was dissolved in 6.62 g of n-heptane was added. Added in the flask.

Then, n-heptane and water were heated in an oil bath at 125 ° C. to evaporate and dry to obtain a dried product of polymer particles. The polymer particles are passed through a sieve having an opening of 850 μm, and 0.2% by mass of amorphous silica (Oriental Silicas Corporation, Toxile NP-S) with respect to the mass of the polymer particles is mixed with the polymer particles. , 233.0 g of water-absorbent resin particles A containing amorphous silica were obtained. The medium particle size of the water-absorbent resin particles A was 128 μm.

Manufacturing example 2
In the preparation of the hydrogel polymer in the second stage, the temperature in the separable flask was changed to 25 ° C instead of 31 ° C, and in the hydrogel polymer after the polymerization in the second stage, co-boiling was performed. Production Example 1 except that 256.8 g of water was extracted from the system by distillation and the amount of amorphous silica mixed with the polymer particles was changed to 0.5% by mass with respect to the mass of the polymer particles. In the same manner as above, 230.2 g of water-absorbent resin particles B were obtained. The medium particle size of the water-absorbent resin particles B was 358 μm.

Manufacturing example 3
<First stage polymerization reaction>
A round-bottomed cylindrical separable flask with an inner diameter of 11 cm and a volume of 2 L equipped with a reflux condenser, a dropping funnel, a nitrogen gas introduction pipe, and a stirring blade having four inclined paddle blades with a blade diameter of 5 cm in two stages as a stirrer. Got ready. To this flask, take 293 g of n-heptane as a hydrocarbon dispersion medium, add 0.736 g of a maleic anhydride-modified ethylene-propylene copolymer (Mitsui Chemicals Co., Ltd., High Wax 1105A) as a polymer-based dispersant, and stir. The temperature was raised to 80 ° C. to dissolve the dispersant, and then cooled to 50 ° C.

In a beaker having an internal volume of 300 mL, 92.0 g (1.03 mol) of an 80.5 mass% acrylic acid aqueous solution as a water-soluble ethylenically unsaturated monomer was placed, and while being cooled from the outside, 20.9 mass%. After adding 147.7 g of an aqueous sodium hydroxide solution to neutralize 75 mol%, 0.092 g of hydroxylethyl cellulose (Sumitomo Seika Co., Ltd., HECAW-15F) as a thickener, as a water-soluble radical polymerization initiator. 0.092 g (0.339 mmol) of 2,2'-azobis (2-amidinopropane) dihydrochloride, 0.018 g (0.067 mmol) of potassium persulfate, and ethylene glycol diglycidyl ether as an internal cross-linking agent. 0046 g (0.026 mmol) was added and dissolved to prepare a first-stage monomer aqueous solution.

<Second stage polymerization reaction>
Take 128.8 g (1.44 mol) of an 80.5 mass% acrylic acid aqueous solution as a water-soluble ethylenically unsaturated monomer in a beaker having an internal volume of 500 mL, and while cooling from the outside, 27 mass% sodium hydroxide. After 159.0 g of the aqueous solution was added dropwise to neutralize 75 mol%, 0.129 g (0.476 mmol) of 2,2'-azobis (2-amidinopropane) dihydrochloride as a water-soluble radical polymerization initiator. , 0.026 g (0.096 mmol) of potassium persulfate, and 0.0116 g (0.067 mmol) of ethylene glycol diglycidyl ether as an internal cross-linking agent are added and dissolved to prepare a second-stage monomer aqueous solution. did.

After cooling the inside of the separable flask system to 25 ° C. while stirring at a stirring speed of 1000 rpm, the entire amount of the monomer aqueous solution in the second stage is added to the polymerized slurry liquid in the first stage. After the addition, the inside of the system was replaced with nitrogen for 30 minutes, and then the flask was again immersed in a water bath at 70 ° C. to raise the temperature, and the polymerization reaction was carried out for 60 minutes. As a result, a hydrogel polymer was obtained.

After the polymerization, 0.589 g of a 45% by mass diethylenetriamine-5 sodium acetate aqueous solution was added to the hydrogel polymer under stirring. Then, the temperature of the reaction solution was raised in an oil bath at 125 ° C., and 232.0 g of water was extracted from the system while refluxing n-heptane by azeotropic distillation of n-heptane and water. Then, 4.42 g (0.507 mmol) of a 2% by mass ethylene glycol diglycidyl ether aqueous solution was added to the flask as a surface cross-linking agent, and the flask was kept at 83 ° C. for 2 hours.

Then, n-heptane and water were heated in an oil bath at 125 ° C. to evaporate and dry to obtain a dried product of polymer particles. The polymer particles are passed through a sieve having an opening of 850 μm, 0.2% by mass of amorphous silica (Oriental Silicas Corporation, Toxile NP-S) is mixed with respect to the mass of the polymer particles, and a water-absorbent resin is mixed. 228.5 g of particle C was obtained. The medium particle size of the water-absorbent resin particles C was 354 μm.

Manufacturing example 4
229.0 g of water-absorbent resin particles D were obtained in the same manner as in Production Example 3 except that 216.7 g of water was extracted from the system by azeotropic distillation. The medium particle size of the water-absorbent resin particles D was 348 μm.

Production example 5
Water-absorbent resin particles E227.6 g were obtained in the same manner as in Production Example 3 except that 201.4 g of water was extracted from the system by azeotropic distillation. The medium particle size of the water-absorbent resin particles E was 356 μm.

Production example 6
Inner diameter 11 cm, contents equipped with a reflux condenser, a dropping funnel, a nitrogen gas introduction pipe, and a stirrer (a stirrer blade having two stages of four inclined paddle blades (surface treated with fluororesin) with a blade diameter of 5 cm). A round-bottomed cylindrical separable flask with a stack of 2 L and four side wall baffles (baffle length: 10 cm, baffle width: 7 mm) was prepared. To this flask, 451.4 g of n-heptane as a hydrocarbon dispersion medium was added, and 1.288 g of sorbitan monolaurate (Nonion LP-20R, HLB value: 8.6, manufactured by NOF CORPORATION) was added as a surfactant. The mixture was obtained by addition. The sorbitan monolaurate was dissolved in n-heptane by heating the mixture to 50 ° C. while stirring at a stirring speed of 300 rpm, and then the mixture was cooled to 40 ° C.

Next, 92.0 g (acrylic acid: 1.03 mol) of an 80.5 mass% acrylic acid aqueous solution was placed in an Erlenmeyer flask having an internal volume of 500 mL. Subsequently, 147.7 g of a 20.9 mass% sodium hydroxide aqueous solution was added dropwise from the outside while cooling with ice to neutralize the acrylic acid, thereby obtaining an aqueous solution of a partially neutralized acrylic acid. Next, a monomer aqueous solution was prepared by adding 0.1012 g (0.374 mmol) of potassium persulfate as a water-soluble radical polymerization initiator to the acrylic acid partially neutralized aqueous solution and then dissolving the mixture.

After adding the above-mentioned aqueous monomer solution to the above-mentioned separable flask, the inside of the system was sufficiently replaced with nitrogen. Then, the flask was immersed in a water bath at 70 ° C. while stirring at a rotation speed of 700 rpm of the stirrer, and then held for 60 minutes to complete the polymerization, thereby obtaining a hydrogel polymer.

After that, while stirring at a stirring speed of 1000 rpm, amorphous silica (Oriental Silicas Corporation, oriental silicas corporation, etc.) was added to the polymer solution containing the produced hydrogel polymer, n-heptane and a surfactant as a powdery inorganic flocculant. A dispersion obtained by previously dispersing 0.092 g of Toxile NP-S) in 100 g of n-heptane was added and then mixed for 10 minutes. Then, the flask containing the reaction solution was immersed in an oil bath at 125 ° C., and 98.0 g of water was extracted from the system while refluxing n-heptane by azeotropic distillation of n-heptane and water. Then, 4.14 g (ethylene glycol diglycidyl ether: 0.475 mmol) of 2% by mass of an ethylene glycol diglycidyl ether aqueous solution was added as a surface cross-linking agent, and the mixture was maintained at an internal temperature of 83 ± 2 ° C. for 2 hours.

Then, water and n-heptane were heated in an oil bath at 125 ° C. to evaporate, and dried until almost no evaporation from the system was distilled off to obtain a dried product of polymer particles. The polymer particles were passed through a sieve having an opening of 850 μm to obtain 90.1 g of water-absorbent resin particles F. The medium particle size of the water-absorbent resin particles F was 352 μm.

Production example 7
90.6 g of water-absorbent resin particles G were obtained in the same manner as in Production Example 6 except that the powdery inorganic flocculant was not added to the hydrogel polymer. The medium particle size of the water-absorbent resin particles G was 156 μm.

Production Example 8
104.0 g of water was extracted from the system by azeotropic distillation, and the surface cross-linking agent was changed to 8.28 g of an ethylene glycol diglycidyl ether aqueous solution (ethylene glycol diglycidyl ether: 0.951 mmol). Except for the above, 90.3 g of water-absorbent resin particles H were obtained in the same manner as in Production Example 6. The medium particle size of the water-absorbent resin particles H was 420 μm.

Manufacturing example 9
In the preparation of the hydrogel polymer in the second stage, the temperature in the separable flask was changed to 25 ° C instead of 31 ° C, and in the hydrogel polymer after the polymerization in the second stage, co-boiling was performed. Production example except that 256.5 g of water was extracted from the system by distillation and the amount of amorphous silica mixed with the polymer particles was changed to 0.25% by mass with respect to the mass of the polymer particles. In the same manner as in 1, 228.2 g of water-absorbent resin particles J was obtained. The medium particle size of the water-absorbent resin particles J was 360 μm.

Production Example 10
The stirring speed of the first stage was changed from 550 rpm to 500 rpm, and in the preparation of the hydrogel polymer of the second stage, the temperature inside the separable flask was changed to 25 ° C instead of 31 ° C. In the hydrogel polymer after the stage polymerization, 257.2 g of water was extracted from the system by co-boiling distillation, and no surfactant was added after the surface cross-linking step. Similarly, 231.2 g of water-absorbent resin particles K were obtained. The medium particle size of the water-absorbent resin particles K was 359 μm.

Production Example 11
In the preparation of the water-containing gel polymer in the second stage, the temperature inside the separable flask was changed to 28 ° C instead of 31 ° C, and 234.7 g of water was extracted from the system by azeotropic distillation. 230.1 g of water-absorbent resin particles L were obtained in the same manner as in Production Example 3 except that no surfactant was added after the surface cross-linking step. The medium particle size of the water-absorbent resin particles L was 308 μm.

Production Example 12
In the preparation of the water-containing gel polymer in the second stage, the temperature in the separable flask was changed to 25 ° C instead of 31 ° C, and in the water-containing gel polymer after the polymerization in the second stage, co-boiling was performed. Similar to Production Example 1, except that 256.5 g of water was extracted from the system by distillation, no surfactant was added after the surface cross-linking step, and amorphous silica was not mixed. 227.2 g of water-absorbent resin particles M were obtained. The medium particle size of the water-absorbent resin particles M was 351 μm.

Production Example 13
In the preparation of the hydrogel polymer in the second stage, the temperature in the separable flask was changed to 25 ° C instead of 31 ° C, and in the hydrogel polymer after the polymerization in the second stage, co-boiling 256.5 g of water was extracted from the system by distillation, no surfactant was added after the surface cross-linking step, and 0.5% by mass of amorphous silica with respect to the mass of the polymer particles (Tosoh. 229.2 g of water-absorbent resin particles N were obtained in the same manner as in Production Example 1 except that Nipsil SS-30P manufactured by Silica Co., Ltd. was mixed with the polymer particles. The medium particle size of the water-absorbent resin particles N was 359 μm.

Production example 14
A round-bottomed cylindrical separable flask with an inner diameter of 11 cm and a volume of 2 L equipped with a reflux condenser, a dropping funnel, a nitrogen gas introduction pipe, and a stirring blade having four inclined paddle blades with a blade diameter of 5 cm in two stages as a stirrer. Got ready. To this flask, take 293 g of n-heptane as a hydrocarbon dispersion medium, add 0.736 g of a maleic anhydride-modified ethylene-propylene copolymer (Mitsui Chemicals Co., Ltd., High Wax 1105A) as a polymer-based dispersant, and stir. The temperature was raised to 80 ° C. to dissolve the dispersant, and then cooled to 50 ° C.

In a beaker with an internal volume of 300 mL, take 92.0 g (1.03 mol) of an 80.5 mass% aqueous acrylic acid solution as a water-soluble ethylenically unsaturated monomer, and cool it from the outside to 20.9 mass%. After 147.7 g of an aqueous sodium hydroxide solution was added dropwise to neutralize 75 mol%, 1.38 g of hydroxylethyl cellulose (Sumitomo Seika Co., Ltd., HECAW-15F) was used as a thickener, and as a water-soluble radical polymerization initiator. 0.0736 g (0.272 mmol) of potassium persulfate and 0.010 g (0.057 mmol) of ethylene glycol diglycidyl ether as an internal cross-linking agent were added and dissolved to prepare a first-stage monomer aqueous solution.

Then, the monomer aqueous solution prepared above was added to the separable flask, and after stirring for 10 minutes, sucrose stearic acid ester of HLB3 as a surfactant in 6.62 g of n-heptane (Mitsubishi Chemical Foods Co., Ltd.) , Ryoto Sugar Ester S-370) 0.736 g of a surfactant solution is further added, and the inside of the system is sufficiently replaced with nitrogen while stirring at a stirring speed of 400 rpm, and then the flask. Was immersed in a water bath at 70 ° C. to raise the temperature, and polymerization was carried out for 60 minutes to obtain a first-stage polymerization slurry solution.

After that, the flask was immersed in an oil bath set at 125 ° C., and 116 g of water was extracted from the system while refluxing n-heptane by azeotropic distillation of n-heptane and water. Then, 1.84 g (0.211 mmol) of a 2% by mass ethylene glycol diglycidyl ether aqueous solution was added to the flask as a surface cross-linking agent, and the flask was kept at 83 ° C. for 2 hours.

Then, n-heptane and water were evaporated at 125 ° C. and dried to obtain a dried product of polymer particles. The polymer particles are passed through a sieve having an opening of 850 μm, and 0.2% by mass of amorphous silica (Oriental Silicas Corporation, Toxile NP-S) with respect to the mass of the polymer particles is mixed with the polymer particles. , 90.9 g of water-absorbent resin particles P containing amorphous silica were obtained. The medium particle size of the water-absorbent resin particles P was 422 μm.

[Measurement of medium particle size]
The medium particle size of the particles was measured by the following procedure. That is, from the top, the JIS standard sieve has a mesh size of 600 μm, a mesh size of 500 μm, a mesh size of 425 μm, a mesh size of 300 μm, a mesh size of 250 μm, a mesh size of 180 μm, and a mesh size of 150 μm. , And the saucer in that order. 50 g of particles were placed in the best combined sieve and classified according to JIS Z 8815 (1994) using a low-tap shaker (manufactured by Iida Seisakusho Co., Ltd.). After classification, the mass of the particles remaining on each sieve was calculated as a mass percentage with respect to the total amount, and the particle size distribution was obtained. The relationship between the mesh size of the sieve and the integrated value of the mass percentage of the particles remaining on the sieve was plotted on a logarithmic probability paper by integrating the particle size distribution on the sieve in order from the largest particle size. By connecting the plots on the probability paper with a straight line, the particle size corresponding to the cumulative mass percentage of 50% by mass was obtained as the medium particle size.

[Water absorption of saline (g / g)]
The amount of physiological saline absorbed by the water-absorbent resin particles was measured by the following method. Weigh 500 g of physiological saline in a 500 mL beaker and stir with a magnetic stirrer bar (8 mmφ x 30 mm, no ring) at 600 rpm (r / min) to generate 2.0 g of water-absorbent resin particles. Dispersed so as not to. The water-absorbent resin particles were sufficiently swollen by being left to stand for 60 minutes in a stirred state. After that, the mass We (g) of a standard sieve having an opening of 75 μm is measured in advance, and the contents of the beaker are filtered using this so that the sieve has an inclination angle of about 30 degrees with respect to the horizontal. Excess water was filtered off by leaving it in an inclined state for 30 minutes. The mass Wf (g) of the sieve containing the swelling gel was measured, and the amount of water absorbed by the physiological saline was determined by the following formula.
Water absorption of saline = (Wf-We) /2.0

[Manufacturing of water absorption core]
Production example 15
^Two air-laid non-woven fabrics (Chinasilk (Shanghai) New Material Technology Co., Ltd. MB0401-T1) having a basis weight of 38 g / m 2 were cut into two pieces having a size of 14 cm × 42 cm to obtain air-laid non-woven fabrics-1 and 2. ^{An air-through non-woven fabric (manufactured by Hualong (Nanjining)) with a grain size of 45 g / m 2} cut into a size of 14 cm x 42 cm is placed on the air-laid non-woven fabric-1 and an air flow type mixer (manufactured by Otec Co., Ltd., pad former) is installed. 6.0 g of water-absorbent resin particles (Aquakeep SA60S manufactured by Sumitomo Seika Chemical Co., Ltd., water absorption of physiological saline 60 g / g, medium particle diameter 342 μm) for a range of 10 cm × 40 cm in the center of the non-woven fabric. Was evenly sprayed.

Air-laid non-woven fabric-2 with hot melt coating machine (Henkel Co., Ltd., pump: Marshal150, table: XA-DT, tank set temperature: 150 ° C, hose set temperature: 165 ° C, gun head set temperature: 170 ° C) 0.2 g of hot melt adhesive (Henkel Japan Ltd., ME-765E) was applied in 12 linear lines at 10 mm intervals. The adhesive application pattern was a spiral stripe. The surface of the air-laid non-woven fabric-2 to which the hot melt was attached was aligned with the surface on which the water-absorbent resin particles of the air-through non-woven fabric were sprayed, and sandwiched between release papers and turned upside down. Then, the release paper and the air-laid non-woven fabric-1 were removed.

Of the air-through non-woven fabric, 3.0 g of water-absorbent resin particles (Sumitomo) was used on the surface opposite to the surface on which the water-absorbent resin particles were sprayed, using an air-flow type mixer to cover a range of 10 cm x 40 cm in the center of the non-woven fabric. Aquakeep SA60S manufactured by Seika Co., Ltd., water absorption of physiological saline 60 g / g, medium particle size 342 μm) were uniformly sprayed. 0.2 g of hot melt was applied to the removed air-laid nonwoven fabric-1 by the same operation as described above. Align both ends of the air-laid non-woven fabric-1 from the top of the air-through non-woven fabric so that the adhesive coating surface is on the lower side, sandwich it with release paper, and use a laminating machine (Hashima Co., Ltd., Straight Liner Fusion Press, model HP-600LFS) 110 It was pressed and bonded under the conditions of ° C. and 0.1 MPa, and only 10 cm × 40 cm on which the water-absorbent resin particles were sprayed was cut out to prepare a water-absorbent core. This was designated as the water absorption core A. The water absorption core A has the same configuration as the water absorption core shown in FIG.

Production example 16
Water-absorbent resin particles (Aquakeep SA60S manufactured by Sumitomo Seika Chemical Co., Ltd., water absorption of physiological saline 60 g / g, medium particle diameter 342 μm) using an air flow type mixer (Padformer manufactured by Otec Co., Ltd.) A sheet-shaped absorbent layer having a size of 40 cm × 10 cm was prepared by uniformly mixing 12.0 g and 3.0 g of pulverized pulp by air papermaking. Next, water absorption is performed by applying a load of 196 kPa to the entire surface for 30 seconds with the upper and lower sides of the absorbent layer sandwiched between two sheets of tissue having the same size as the sheet-shaped absorbent layer and having a basis weight of 16 g / m ^2. The core was made. This was designated as the water absorption core B. The produced water-absorbing core B has an absorbing layer made of water-absorbing resin particles and crushed pulp arranged between two sheets of tissue.

[Preparation of absorbent articles for testing]
Example 1
(Preparation of auxiliary sheet)
Two pieces of tissue having a basis weight of 16 g / m ² were cut into a size of 14 cm × 42 cm to obtain an upper sheet base material and a lower sheet base material of the auxiliary sheet. After uniformly applying 0.3 g of adhesive (3M Spray Glue 77 manufactured by 3M Japan Ltd.) to the inner surface of the roll of the lower sheet base material, promptly airflow type mixing device (manufactured by Otec Co., Ltd., pad former) ) Was used to uniformly spray 1.5 g of the water-absorbent resin particles A prepared in Production Example 1 over a range of 10 cm × 40 cm in the center of the lower sheet base material. 0.3 g of an adhesive (3M spray glue 77 manufactured by 3M Japan Ltd.) was uniformly applied to the upper sheet base material. The surface coated with the adhesive of the upper sheet base material is overlapped with the surface on which the water-absorbent resin of the lower sheet base material is sprayed, with both ends aligned, and the entire surface is adhered to the area where the water-absorbent resin is sprayed. (10 cm × 40 cm) was cut out to obtain an auxiliary sheet.

(Preparation of absorbent articles for testing)
The water-absorbing core A prepared in Production Example 15 was placed on the upper sheet base material of the obtained auxiliary sheet to obtain an absorbent article.

Example 2
An absorbent article was obtained in the same manner as in Example 1 except that the water-absorbent resin particles for the auxiliary sheet were changed to the water-absorbent resin particles B produced in Production Example 2.

Example 3
An absorbent article was obtained in the same manner as in Example 1 except that the water-absorbent resin particles for the auxiliary sheet were changed to the water-absorbent resin particles C produced in Production Example 3.

Example 4
An absorbent article was obtained in the same manner as in Example 1 except that the water-absorbent resin particles for the auxiliary sheet were changed to the water-absorbent resin particles D produced in Production Example 4.

Example 5
An absorbent article was obtained in the same manner as in Example 1 except that the water-absorbent resin particles for the auxiliary sheet were changed to the water-absorbent resin particles E produced in Production Example 5.

Example 6
An absorbent article was obtained in the same manner as in Example 1 except that the water-absorbent resin particles for the auxiliary sheet were changed to the water-absorbent resin particles F produced in Production Example 6.

Example 7
An absorbent article was obtained in the same manner as in Example 1 except that the water-absorbent resin particles for the auxiliary sheet were changed to the water-absorbent resin particles G produced in Production Example 7.

Example 8
An absorbent article was obtained in the same manner as in Example 1 except that the water-absorbent resin particles for the auxiliary sheet were changed to the water-absorbent resin particles H produced in Production Example 8.

Example 9
An absorbent article was obtained in the same manner as in Example 1 except that the water-absorbent resin particles for the auxiliary sheet were changed to the water-absorbent resin particles J produced in Production Example 9.

Example 10
The upper sheet base material and the lower sheet base material of the auxiliary sheet were changed to spunbonded non-woven fabric (manufactured by Toray Polytech (Nantong) Co., Ltd., trade name: LIVESEN) ^{having a basis weight of 17 g / m 2.} An absorbent article was obtained in the same manner as in Example 1 except that the water-absorbent resin particles for the sheet were changed to the water-absorbent resin particles F produced in Production Example 6.

Example 11
The upper sheet base material and the lower sheet base material of the auxiliary sheet were changed to air-through non-woven fabric manufactured by Rengo Nonwoven Products Co., Ltd. with a grain ^{size of 21 g / m 2, and water-absorbent resin particles for the auxiliary sheet were produced.} An absorbent article was obtained in the same manner as in Example 1 except that the particles were changed to the water-absorbent resin particles F produced in 1.

Example 12
The upper sheet base material of the auxiliary sheet was changed to an air-through non-woven fabric manufactured by Hualong (Nanjining) with a grain ^{size of 45 g / m 2, and the water-absorbent resin particles for the auxiliary sheet were prepared in Production Example 6.} An absorbent article was obtained in the same manner as in Example 1 except that it was changed to F.

Example 13
(Preparation of auxiliary sheet)
By using an air flow type mixer (Padformer manufactured by Otec Co., Ltd.) to uniformly mix 1.5 g of the water-absorbent resin particles F and 1.5 g of crushed pulp of Production Example 6 by air papermaking, the size is 40 cm × 10 cm. A sheet-shaped resin layer having a size was prepared. Next, a load of 196 kPa is applied to the entire surface for 30 seconds while the resin layer is sandwiched between two sheets of tissue having the same size as the sheet-shaped resin layer and having a ^{grain size of 16 g / m 2, and pressed.} An auxiliary sheet was obtained in which a resin layer composed of water-absorbent resin particles and crushed pulp was arranged between two sheets of tissue.

(Preparation of absorbent articles for testing)
The water-absorbing core A prepared in Production Example 15 was placed on the obtained auxiliary sheet to obtain an absorbent article.

Example 14
The same as in Example 1 except that the water-absorbent resin particles for the auxiliary sheet were changed to the water-absorbent resin particles F produced in Production Example 6 and the amount of the water-absorbent resin particles used was changed to 1.0 g. An absorbent article was obtained.

Example 15
An auxiliary sheet was obtained in the same manner as in Example 1 except that the water-absorbent resin particles for the auxiliary sheet were changed to the water-absorbent resin particles F produced in Production Example 6. The water-absorbing core B produced in Production Example 16 was placed on the obtained auxiliary sheet to obtain an absorbent article.

Example 16
The same as in Example 1 except that the water-absorbent resin particles for the auxiliary sheet were changed to the water-absorbent resin particles F produced in Production Example 6 and the amount of the water-absorbent resin particles used was changed to 0.4 g. An absorbent article was obtained.

Comparative Example 1
Only the water-absorbing core A produced in Production Example 15 without using the auxiliary sheet was used as the absorbent article for the test.

Comparative Example 2
The water-absorbing core was prepared in the same manner as in Production Example 15 except that the amount of the water-absorbent resin particles sprayed between the air-laid non-woven fabric-2 and the air-through non-woven fabric of Production Example 15 was changed from 6.0 g to 5.0 g. Obtained. Only the above-mentioned water-absorbing core obtained without using the auxiliary sheet was used as an absorbent article for testing.

Comparative Example 3
An absorbent article was obtained in the same manner as in Example 1 except that the water-absorbent resin particles were not used.

Comparative Example 4
An absorbent article was obtained in the same manner as in Example 1 except that the water-absorbent resin particles for the auxiliary sheet were changed to the water-absorbent resin particles K produced in Production Example 10.

Comparative Example 5
An absorbent article was obtained in the same manner as in Example 1 except that the water-absorbent resin particles for the auxiliary sheet were changed to the water-absorbent resin particles L produced in Production Example 11.

Comparative Example 6
An absorbent article was obtained in the same manner as in Example 1 except that the water-absorbent resin particles for the auxiliary sheet were changed to the water-absorbent resin particles M produced in Production Example 12.

Comparative Example 7
An absorbent article was obtained in the same manner as in Example 1 except that the water-absorbent resin particles for the auxiliary sheet were changed to the water-absorbent resin particles N produced in Production Example 13.

Comparative Example 8
An absorbent article was obtained in the same manner as in Example 1 except that the water-absorbent resin particles for the auxiliary sheet were changed to the water-absorbent resin particles P produced in Production Example 14.

Comparative Example 9
Only the absorbent core prepared in Production Example 16 without using the auxiliary sheet was used as the absorbent article for the test.

[Preparation of artificial urine]
Artificial urine was prepared using the following materials.
-Ion-exchanged water: 9865.75 g
-NaCl: 100.0 g
・ CaCl ₂・ H ₂ O: 3.0 g
_{_{· MgCl 2 · 6H 2 O:}} 6.0g
-Triton X-100 (1%): 25.0 g
・ Edible blue No. 1 (for coloring): 0.25g

[Measurement of dry powder flow absorption rate]
The dry powder passing liquid absorption rate is calculated by the formula: dry powder passing liquid absorbing rate = dry powder passing liquid absorbing amount (g) / 0.2 g artificial urine saturated liquid absorbing amount (g) of the water-absorbent resin. The dry powder passing liquid absorption amount and the artificial urine saturated liquid absorption amount of 0.2 g were measured and calculated by the methods shown below.

[Measurement of dry powder flow absorption amount]
FIG. 5 is a schematic view showing a method for measuring the liquid absorption rate of dry powder. 0.2 g of water-absorbent resin particles in a cylindrical container 52 made of acrylic resin having an inner diameter of 60 mm, an outer diameter of 69 mm, and a height of 60 mm to which a stainless steel mesh 51 (opening 50 μm) is adhered as a mesh-like bottom. 61a was uniformly sprayed, and the total mass Wb of the container and the water-absorbent resin particles 61a sprayed in the container was measured.

A plastic beaker with an opening diameter of 60 mm and a height of 70 mm was used as the receiver 53, and the cylindrical container 52 was placed on the receiver 53.

The dropping funnel 54 was installed so that the distance H between the tip 54a and the upper surface of the mesh 51 was 13 mm and the tip 54a was located above the center of the bottom surface of the cylindrical container 52. Artificial urine 45 (20 mL) adjusted to a liquid temperature of 25 ° C. was injected at a constant rate of 8 mL / sec, and the stopwatch was started at the same time. The artificial urine diffuses over the entire bottom surface of the cylindrical container 52, passes through the mesh 51 and falls into the receiver 53, but a part of the artificial urine is absorbed by the water-absorbent resin particles 61a. In the cylindrical container 52, the water-absorbent resin particles 61a absorb the artificial urine 45 to form a swollen gel.

Thirty seconds after the liquid injection, the total mass Wa of the cylindrical container 52 and the swollen gel in the cylindrical container 52 was measured. The amount of dry powder flowing through the liquid (g) was determined by Wa-Wb.

[Measurement of artificial urine saturated liquid absorption amount of water-absorbent resin particles]
Weigh 500 g of artificial urine into a 500 mL beaker, and stir at 600 rpm (r / min) using a magnetic stirrer bar (8 mmφ x 30 mm, without ring) to add 2.0 g of water-absorbent resin particles to Mamako. Was dispersed so that Stirring was continued for 60 minutes to sufficiently swell the water-absorbent resin particles. The mass Wc (g) of a standard sieve having a mesh size of 75 μm was measured in advance, and the contents of the beaker were filtered using this and allowed to stand for 1 minute to filter out excess water. The mass Wd (g) of the sieve containing the swelling gel was measured, and the artificial urine saturated liquid absorption amount was determined by the following formula.
-Artificial urine saturated liquid absorption (g / g) = (Wd-Wc) /2.0
-0.2 g of artificial urine saturated liquid absorption (g) = 0.2 x artificial urine saturated liquid absorption (g / g)

[Auxiliary sheet thickness evaluation]
The thickness of the auxiliary sheet was measured using a precision thickness measuring instrument (manufactured by Ozaki Seisakusho, dial thickness gauge JB, stylus: aluminum φ50 mm). The measurement was performed at a position where the stylus was in contact with the central portion of the auxiliary sheet, and the average of the values measured three times was taken as the thickness (mm) of the auxiliary sheet.

[Evaluation of liquid leakage in the initial stage of liquid absorption]
FIG. 6 is a schematic view showing an apparatus for evaluating liquid leakage of an absorbent article. Using the apparatus shown in FIG. 6, the liquid leakage property at the initial stage of liquid absorption of the absorbent article 100 for testing was evaluated by the following procedures (i), (ii), (iii) and (iv). .. The results are shown in Table 1. The resin in the table represents water-absorbent resin particles, and gsm represents g / m ² .

(I) is a mechanical fastener (3M mechanical fastener hook), vertical 45cm, was cut to the size of the acrylic resin plate 1 having a rectangular main surface of the lateral 62cm, was adhered to the entire main surface _{S 1} of the acrylic resin plate 1. On the main surface S ₁ of the acrylic resin plate 1 is extremely fine irregularities are caused by mechanical fasteners, no retention and absorption of liquids on the main surface S ₁ of the acrylic resin plate 1.
The (ii) an acrylic resin plate 1, and the main surface S ₁ in which a mechanical fastener is adhered upwardly, and fixed with the frame 41 of a commercially available laboratory equipment. At this time, the long side of the acrylic resin plate 1 was parallel to the horizontal plane, and the main surface of the acrylic resin plate 1 and the horizontal plane S ₀ were fixed so as to form 45 ± 2 degrees. A fixed main surface S ₁ of the acrylic resin plate 1, the absorbent article 100 for testing, in a direction that long sides are perpendicular to the long side of the acrylic resin plate 1, an absorbent article for testing 100 The lower end of the acrylic resin plate 1 was attached so as to be at the same position as the lower end of the acrylic resin plate 1. The test absorbent article 100 composed of the water absorption core and the auxiliary sheet was attached on the acrylic resin plate 1 so that the water absorption core was on the front side. The upper end of the absorbent article 100 for testing was fixed to the acrylic resin plate 1 with an adhesive tape to prevent it from falling.
(Iii) The loading point is 8 cm above the center of the absorption core in the absorbent article 100 for testing, and from a position 1 cm vertically above the loading point, the dropping funnel 42 (300 mL of dropping funnel manufactured by Cosmos Bead Co., Ltd., tip) An inner diameter of 8 mm × 6 mm) was used to inject a predetermined amount of artificial urine 45 adjusted to a liquid temperature of 25 ° C. at a rate of 8 mL / sec. The injection amount of artificial urine 45 when using the water-absorbing core A having an absorption layer made of water-absorbent resin particles is 80 mL, and when using the water-absorbing core B having an absorption layer made of water-absorbent resin particles and crushed pulp. The injection amount of artificial urine 45 was 120 mL (Examples or comparative examples marked with * in Table 1).
(Iv) The artificial urine leaked from the absorbent article 100 for testing was collected in a metal tray 44 previously placed below the absorbent article 100 and placed on the balance. The collected artificial urine was weighed, and the ratio (%) of the amount of leaked artificial urine (g) to the input amount (g) of artificial urine was calculated.

Table 1 shows the evaluation results. It has been shown that an absorbent article having an auxiliary sheet prepared by using water-absorbent resin particles having a dry powder passing liquid absorption rate of a specific numerical value improves liquid leakage in the initial stage of liquid absorption.

10, 10A, 10B ... Absorbent layer, 10a ... Water-absorbent resin particles, 10b ... Fiber layer, 20a, 20b ... Core wrap sheet, 21 ... Adhesive, 25a, 25b, 25c ... Core wrap sheet, 26a, 26b ... Adhesive , 30 ... Liquid permeable sheet, 40 ... Liquid permeable sheet, 50 ... Water absorption core, 51 ... Mesh (mesh-like bottom), 52 ... Cylindrical container, 60 ... Auxiliary sheet, 61 ... Resin layer, 61a ... Water absorption Sex resin particles, 61b ... fiber layer, 62a, 62b ... sheet base material, 63a, 63b ... adhesive, 100 ... absorbent article.

Claims

A water absorption core, an auxiliary sheet assisting liquid absorption by the water absorption core, a liquid impermeable sheet and a liquid permeable sheet are provided, and the liquid impermeable sheet, the auxiliary sheet, the water absorption core and the liquid permeable sheet are the same. Absorbent articles arranged in order,
The auxiliary sheet includes a resin layer containing water-absorbent resin particles.
The dry powder passing liquid absorption rate of the water-absorbent resin particles measured by a method including the following steps (1), (2), (3), (4) and (5) in this order is 0.25 or more. Absorbent article, 1.0 or less.
(1) 0.2 g of water-absorbent resin particles are uniformly sprayed over the entire bottom surface of a cylindrical container having an inner diameter of 60 mm having a mesh-like bottom, and the container and the water-absorbent resin particles sprayed in the container. The total mass Wb (g) of the above is measured.
(2) 20 mL of artificial urine having a liquid temperature of 25 ° C. is injected into the container on which the water-absorbent resin particles are sprayed at a constant rate of 8 mL / sec, and at least a part of the artificial urine is absorbed by the water-absorbent resin particles. Let it liquid to form a swollen gel in the container.
(3) 30 seconds after the start of injection, the total mass Wa (g) of the container and the swollen gel in the container is measured.
(4) The dry powder passing liquid absorption amount (g) is determined from Wa (g) -Wb (g).
(5) The dry powder passage liquid absorption rate (g / g) is obtained as the ratio of the dry powder passage liquid absorption amount (g) to the artificial urine saturated liquid absorption amount (g) of 0.2 g of the water-absorbent resin particles.
The absorbent article according to claim 1, which is a diaper.
An auxiliary sheet used to assist the absorption of liquid in the water absorption core in an absorbent article including the water absorption core.
With a resin layer containing water-absorbent resin particles,
The dry powder passing liquid absorption rate of the water-absorbent resin particles measured by a method including the following steps (1), (2), (3), (4) and (5) in this order is 0.25 or more. Auxiliary sheet that is 1.0 or less.
(1) 0.2 g of water-absorbent resin particles are uniformly sprayed over the entire bottom surface of a cylindrical container having an inner diameter of 60 mm having a mesh-like bottom, and the container and the water-absorbent resin particles sprayed in the container. The total mass Wb (g) of the above is measured.
(2) 20 mL of artificial urine having a liquid temperature of 25 ° C. is injected into the container on which the water-absorbent resin particles are sprayed at a constant rate of 8 mL / sec, and at least a part of the artificial urine is absorbed by the water-absorbent resin particles. Let it liquid to form a swollen gel in the container.
(3) 30 seconds after the start of injection, the total mass Wa (g) of the container and the swollen gel in the container is measured.
(4) The dry powder passing liquid absorption amount (g) is determined from Wa (g) -Wb (g).
(5) The dry powder passage liquid absorption rate (g / g) is obtained as the ratio of the dry powder passage liquid absorption amount (g) to the artificial urine saturated liquid absorption amount (g) of 0.2 g of the water-absorbent resin particles.