KR20220050917A - Absorbent articles and auxiliary sheets - Google Patents

Abstract

An absorbent absorbent material comprising an absorbent core, an auxiliary sheet for assisting absorption of liquid by the absorbent core, a liquid impermeable sheet and a liquid permeable sheet, wherein the liquid impermeable sheet, the auxiliary sheet, the absorbent core and the liquid permeable sheet are disposed in this order. An absorbent article is disclosed as an article, wherein the auxiliary sheet includes a resin layer containing water-absorbent resin particles, and the absorbent water-absorbing resin particles have a dry powder liquid absorption rate of 0.25 or more and 1.0 or less.

Description

Absorbent articles and auxiliary sheets

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

Generally, an absorbent body containing water-absorbing resin particles is used for absorbent articles for absorbing liquids containing water as a main component, such as urine. For example, in the water-absorbing sheet constitution disclosed in Patent Document 1 below, water-absorbing resin particles having a physiological saline water absorption rate within a predetermined range are used for the liquid absorption layer.

Japanese Patent Laid-Open No. 2012-183175

In an absorbent article having an ultra-thin absorbent core, such as the absorbent sheet described above, liquid leakage may occur in a relatively short time (liquid absorption initial stage) after the liquid to be absorbed is provided to the absorber, and the liquid absorption initial stage The development of a technology to improve the liquid leakage of the was required.

Accordingly, one aspect of the present invention aims to provide an absorbent article in which leakage of liquid in the initial stage of absorption is suppressed. Another aspect of the present invention aims 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 provides an absorbent core, an auxiliary sheet for assisting absorption of liquid by the absorbent core, a liquid impermeable sheet and a liquid permeable sheet, wherein the liquid impermeable sheet, the auxiliary sheet, the absorbent core and the liquid permeable sheet are It relates to an absorbent article, arranged in order. The said absorbent article WHEREIN: The auxiliary sheet is provided with the resin layer containing water-absorbent resin particles, and the following steps (1), (2), (3), (4) and (5) are included in this order. The dry powder liquid-permeable liquid absorption rate of the water-absorbent resin particles measured by the following method is 0.25 or more and 1.0 or less.

(1) 0.2 g of water-absorbing resin particles are uniformly spread over the entire bottom surface of a cylindrical container having an inner diameter of 60 mm having a mesh-like bottom, and the total mass Wb (g) of the container and the water-absorbing resin particles sprayed in the container ) is measured.

(2) 20 mL of artificial urine with a liquid temperature of 25°C is injected into the container in 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 into the water absorbent resin particles to form a swollen gel in the container.

(3) After 30 seconds from the start of injection, the total mass Wa (g) of the container and the swollen gel in the container is measured.

(4) Calculate the amount (g) of liquid passing through dry powder from Wa(g)-Wb(g).

(5) As the ratio of the dry powder absorbed liquid amount (g) to the artificial urine saturated liquid absorption amount (g) of 0.2 g of water-absorbent resin particles, the dry powder passaged liquid absorption rate (g/g) is obtained.

ADVANTAGE OF THE INVENTION According to this invention, the absorbent article in which the liquid leakage of the initial stage of liquid absorption was suppressed can be provided.

Moreover, according to this invention, the auxiliary sheet|seat which can suppress the liquid leakage of the liquid absorption initial stage in an absorbent article can be provided.

1 is a cross-sectional view showing an example of an auxiliary sheet.
It is sectional drawing which shows an example of an absorbent article.
3 is a plan view illustrating an example of an adhesive application pattern formed on a core wrap sheet.
4 is a cross-sectional view showing an example of a sheet-like absorbent core.
5 is a schematic diagram showing a method for measuring the absorption rate of liquid passing through dry powder.
It is a schematic diagram which shows the apparatus for evaluating the liquid leakage of an absorbent article.

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

In the present specification, "(meth)acryl" is expressed by combining "acryl" and "methacrylic". “Acrylate” and “methacrylate” are also referred to as “(meth)acrylate”. In the numerical range described step by step in this specification, the upper limit or lower limit of the numerical range of a certain step may be arbitrarily combined with the upper limit or lower limit of the numerical range of another step. In the numerical range described herein, the upper limit or lower limit of the numerical range may be substituted with the value shown in Examples. "A or B" may include any one of A and B, and may include both. "Water solubility" means showing solubility of 5 mass % or more in water in 25 degreeC. The material illustrated in this specification may be used independently and may be used in combination of 2 or more type. The content of each component in the composition means the total amount of the plurality of substances present in the composition unless otherwise specified, when a plurality of substances corresponding to each component exist in the composition.

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

The auxiliary sheet has a resin layer containing water-absorbing resin particles, and is measured by a method including the following steps (1), (2), (3), (4) and (5) in this order. , the water-absorbent resin particles have a liquid-permeable liquid absorption rate of 0.25 or more and 1.0 or less.

(1) 0.2 g of water-absorbing resin particles are uniformly spread over the entire bottom surface of a cylindrical container having an inner diameter of 60 mm having a mesh-like bottom, and the total mass Wb (g) of the container and the water-absorbing resin particles sprayed in the container ) is measured.

(2) 20 mL of artificial urine with a liquid temperature of 25°C is injected into the container in 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 into the water absorbent resin particles to form a swollen gel in the container.

(3) After 30 seconds from the start of injection, the total mass Wa (g) of the container and the swollen gel in the container is measured.

(4) Calculate the amount (g) of liquid passing through dry powder from Wa(g)-Wb(g).

(5) As the ratio of the dry powder absorbed liquid amount (g) to the artificial urine saturated liquid absorption amount (g) of 0.2 g of water-absorbent resin particles, the dry powder passaged liquid absorption rate (g/g) is obtained.

In the present specification, artificial urine is sodium chloride (NaCl) 100.0 g, calcium chloride dihydrate (CaCl _{2 ·} H ₂ O) 3.0 g, magnesium chloride hexahydrate (MgCl _{2 ·} 6H ₂ O) 6.0 g, Triton X- It is an aqueous solution prepared with 25.0 g of 100 (1%), 0.25 g of Food Blue No. 1, and 9865.75 g of water.

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

The lower limit of the dry powder liquid absorption rate is 0.25 or more. or more, 0.70 or more, 0.75 or more, 0.80 or more, or 0.85 or more may be sufficient. The upper limit of the liquid-permeable liquid absorption rate of dry powder is 1.0 or less, and may be 0.95 or less, or 0.90 or less. Since the artificial urine saturated liquid absorption of 0.2 g of the water absorbent resin particles represents the same saturated absorption amount of the water absorbent resin particles of 0.2 g as the amount used for measuring the dry powder liquid passing rate, it is usually measured using the same amount of the water absorbent resin particles. In this case, the amount of liquid passing through dry powder does not exceed the saturated amount of artificial urine. Therefore, the upper limit of the absorption rate of liquid passing through dry powder is usually 1.0 or less.

The amount of liquid passing through dry powder may be, 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, 15.0 g or less, 12.0 g or more. g or less, or 10.0 g or less may be sufficient. A specific method for measuring the amount of liquid passing through dry powder is as described in Examples to be described later.

The artificial urine saturated liquid absorption amount of 0.2 g of water absorbent resin particles is calculated by a method including the following steps (a), (b), (c), (d) and (e) in this order.

(a) Put 500g of artificial urine into a 500mL beaker.

(b) Into the beaker to which the artificial urine was put, 2.0 g of water-absorbing resin particles were put while stirring the artificial urine at 600 rpm using a magnetic stirrer bar (8 mmφ×30 mm, no ring).

(c) After injection of the water absorbent resin particles, artificial urine and water absorbent resin particles are stirred at 600 rpm for 60 minutes to form a swollen gel.

(d) The contents in the beaker are filtered through a standard sieve with an eye size of 75 μm, and the excess water is removed by standing for 1 minute.

(e) The total mass Wc of the swollen gel and the sieve is measured, and from the previously measured mass Wd of the sieve, 0.2 g of saturated artificial urine absorption amount (g) is obtained by the following formula.

Saturated absorption of artificial urine of 0.2 g (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, from the viewpoint of the absorption characteristics of the water absorbent resin particles, 7.0 or more, 8.0 or more, 9.0 or more, or 10.0 or more, 20.0 or less, 15.0 or less, 13.0 or less or less, or 11.0 or less. The specific measurement method of the artificial urine saturated liquid absorption amount of 0.2 g of water absorbent resin particles is as described in the Example mentioned later.

The shape of the water-absorbing resin particles may be, for example, substantially spherical, crushed, or granular, and particles in which primary particles having these shapes are aggregated may be formed. The median particle diameter of the water-absorbing 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 obtained by the manufacturing method described later, but may adjust the particle size distribution by performing operations such as particle size adjustment using classification by a sieve.

The water absorbent resin particles may include, for example, a crosslinked polymer formed by polymerization of a monomer including an ethylenically unsaturated monomer. The crosslinked polymer has a monomer unit derived from an ethylenically unsaturated monomer.

The water-absorbing 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 viewpoints of ensuring good absorption characteristics of the resulting water-absorbing resin particles and facilitating control of polymerization reaction, a reversed-phase suspension polymerization method or an aqueous solution polymerization method may be applied. Below, as a method of superposing|polymerizing an ethylenically unsaturated monomer, the reverse phase suspension polymerization method is mentioned and demonstrated as an example.

<Water absorbent resin particles>

The ethylenically unsaturated monomer may be water-soluble. Examples of the water-soluble ethylenically unsaturated monomer include (meth)acrylic acid and salts thereof, 2-(meth)acrylamide-2-methylpropanesulfonic acid and salts thereof, (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, diethylaminopropyl (meth)acrylamide, etc. are mentioned. When the ethylenically unsaturated monomer has an amino group, the amino group may be quaternized. An ethylenically unsaturated monomer may be used independently and may be used in combination of 2 or more type. Functional groups, such as a carboxyl group and an amino group of the above-mentioned monomer, can function as a functional group which can bridge|crosslink in the surface crosslinking process mentioned 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 its salts, acrylamide, methacrylamide, and N,N-dimethylacrylamide. The compound may be included. The ethylenically unsaturated monomer may contain the at least 1 sort(s) of compound chosen from the group which consists of (meth)acrylic acid and its salt, and acrylamide. From the viewpoint of further enhancing water absorption characteristics, 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 for a 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 mass % or more and the saturation concentration or less, 25 to 70 mass %, or 30 to 55 mass %. may be As water used in aqueous solution, tap water, distilled water, ion-exchange water, etc. are mentioned.

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

When an ethylenically unsaturated monomer has an acidic radical, after neutralizing the acidic radical with an alkaline neutralizing agent, you may use a monomer solution for a polymerization reaction. The degree of neutralization by the alkaline neutralizing agent in the ethylenically unsaturated monomer increases the osmotic pressure of the water-absorbing resin particles obtained, and from the viewpoint of further enhancing the absorption characteristics (water absorption, etc.), 10 to 100 moles of the acidic group in the ethylenically unsaturated monomer. %, 50 to 90 mol%, or 60 to 80 mol% may be sufficient. Examples of the alkaline neutralizing agent include alkali metal salts such as sodium hydroxide, sodium carbonate, sodium hydrogencarbonate, potassium hydroxide and potassium carbonate; Ammonia etc. are mentioned. An alkaline neutralizing agent may be used independently and may be used in combination of 2 or more type. The alkaline neutralizing agent may be used in the state of an aqueous solution in order to simplify the neutralization operation. Neutralization of the acid group of an ethylenically unsaturated monomer can be performed by dripping and mixing aqueous solutions, such as sodium hydroxide and potassium hydroxide, to the monomer aqueous solution mentioned above, for example.

In the reversed-phase suspension polymerization method, the monomer aqueous solution is disperse|distributed in a hydrocarbon dispersion medium in presence of surfactant, and superposition|polymerization of an ethylenically unsaturated monomer can be performed using a radical polymerization initiator etc. As the radical polymerization initiator, a water-soluble radical polymerization initiator can be used.

Nonionic surfactants, anionic surfactants, etc. are mentioned as surfactant. As the nonionic surfactant, sorbitan fatty acid ester, (poly)glycerin fatty acid ester ("(poly)" means both with and without the prefix "poly". The same applies 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 alkylphenyl ether, polyoxyethylene Castor oil, polyoxyethylene hydrogenated castor oil, alkylallylformaldehyde condensed polyoxyethylene ether, polyoxyethylene polyoxypropylene block copolymer, polyoxyethylene polyoxypropyl alkyl ether, polyethylene glycol fatty acid ester, etc. are mentioned. there is. Examples of the anionic surfactant include fatty acid salts, alkylbenzenesulfonates, alkylmethyltaurates, polyoxyethylenealkylphenylether sulfate ester salts, polyoxyethylenealkylethersulfonates, polyoxyethylenealkylether phosphate esters, and Phosphoric acid ester of polyoxyethylene alkyl allyl ether, etc. are mentioned. Surfactant may be used independently and may be used in combination of 2 or more type.

From the viewpoint of good W/O-type reverse-phase suspension, easy to obtain water-absorbing resin particles having a suitable particle size, and easy industrial availability, surfactants are sorbitan fatty acid ester, polyglycerol fatty acid ester, and sucrose You may also contain the at least 1 sort(s) of compound chosen from the group which consists of fatty acid ester. From the viewpoint of easily improving the absorption properties of the water-absorbing resin particles obtained, as the surfactant, a sorbitan fatty acid ester and/or a sucrose fatty acid ester (eg, sucrose stearic acid ester) can be used. These surfactants may be used independently and may be used in combination of 2 or more type.

0.05-10 mass parts, 0.08-5 mass parts, or 0.1-3 mass parts may be sufficient as the quantity of surfactant with respect to 100 mass parts of monomer aqueous solution.

In reversed-phase suspension polymerization, you may use together a polymer type dispersing agent together with the surfactant mentioned above. Examples of the polymeric dispersant include maleic anhydride-modified polyethylene, maleic anhydride-modified polypropylene, maleic anhydride-modified ethylene/propylene copolymer, maleic anhydride-modified EPDM (ethylene/propylene/diene/terpolymer), maleic anhydride-modified pol Reviewtadiene, maleic anhydride/ethylene copolymer, maleic anhydride/propylene copolymer, maleic anhydride/ethylene/propylene copolymer, maleic anhydride/butadiene copolymer, polyethylene, polypropylene, ethylene/propylene copolymer , oxidized polyethylene, oxidized polypropylene, oxidized ethylene/propylene copolymer, ethylene/acrylic acid copolymer, ethyl cellulose, ethyl hydroxyethyl cellulose, and the like. A polymer type dispersing agent may be used independently and may be used in combination of 2 or more type. From the viewpoint of excellent dispersion stability of the monomer, the polymeric dispersant is maleic anhydride-modified polyethylene, maleic anhydride-modified polypropylene, maleic anhydride-modified ethylene/propylene copolymer, maleic anhydride/ethylene copolymer, maleic anhydride/propylene At least one selected from the group consisting of copolymer, maleic anhydride/ethylene/propylene copolymer, polyethylene, polypropylene, ethylene/propylene copolymer, oxidized polyethylene, oxidized polypropylene, and oxidized ethylene/propylene copolymer okay

The quantity of a polymeric dispersing agent may be 0.05-10 mass parts, 0.08-5 mass parts, or 0.1-3 mass parts with respect to 100 mass parts of monomer aqueous solution.

The hydrocarbon dispersion medium may contain at least one compound selected from the group consisting of a chain aliphatic hydrocarbon having 6 to 8 carbon atoms and an alicyclic hydrocarbon having 6 to 8 carbon atoms. Examples of the hydrocarbon dispersion medium 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-dimethyl alicyclic hydrocarbons such as cyclopentane; Aromatic hydrocarbons, such as benzene, toluene, and xylene, etc. are mentioned. A hydrocarbon dispersion medium may be used independently and may be used in combination of 2 or more type.

From the viewpoint of industrial availability and stable quality, the hydrocarbon dispersion medium may contain at least one selected from the group consisting of n-heptane and cyclohexane. In addition, from the same viewpoint, as the mixture of the hydrocarbon dispersion medium described above, for example, commercially available Exolheptane (manufactured by Exxon Mobil: n-heptane and containing 75 to 85% of isomer hydrocarbons) may be used.

The amount of the hydrocarbon dispersion medium may be 30 to 1000 parts by mass, 40 to 500 parts by mass, or 50 to 300 parts by mass relative to 100 parts by mass of the aqueous monomer solution from the viewpoint of appropriately removing the heat of polymerization and controlling the polymerization temperature. When the amount of the hydrocarbon dispersion medium is 30 parts by mass or more, control of the polymerization temperature tends to be easy. When the amount of the hydrocarbon dispersion medium is 1000 parts by mass or less, the productivity of polymerization tends to improve, which is economical.

The radical polymerization initiator may be water-soluble. Examples of the water-soluble radical polymerization initiator include persulfates such as potassium persulfate, ammonium persulfate, and sodium persulfate; Methyl ethyl ketone peroxide, methyl isobutyl ketone peroxide, di-t-butyl peroxide, t-butylcumyl peroxide, t-butylperoxyacetate, t-butylperoxyisobutyrate, t-butylperoxypival peroxides such as lactate and 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] dihydrochloride, 2,2'-azobis{2 -[1-(2-hydroxyethyl)-2-imidazolin-2-yl]propane} dihydrochloride, 2,2'-azobis{2-methyl-N-[1,1-bis(hydride) Roxymethyl)-2-hydroxyethyl]propionamide}, 2,2'-azobis[2-methyl-N-(2-hydroxyethyl)-propionamide], 4,4'-azobis(4- and azo compounds such as cyanovaleric acid). A radical polymerization initiator may be used independently and may be used in combination of 2 or more type. The radical polymerization initiator is potassium persulfate, ammonium persulfate, sodium persulfate, 2,2'-azobis(2-amidinopropane) dihydrochloride, 2,2'-azobis[2-(2-imida) zolin-2-yl)propane] dihydrochloride, and as 2,2'-azobis{2-[1-(2-hydroxyethyl)-2-imidazolin-2-yl]propane} dihydrochloride At least 1 type selected from the group which consists of may be sufficient.

0.00005-0.01 mol may be sufficient as the quantity of a radical polymerization initiator with respect to 1 mol of ethylenically unsaturated monomers. If the usage-amount of a radical polymerization initiator is 0.00005 mol or more, a long time is not required for a polymerization reaction, but it 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 illustrated radical polymerization initiator may be used as a redox polymerization initiator in combination with a reducing agent such as sodium sulfite, sodium hydrogen sulfite, ferrous sulfate or L-ascorbic acid.

In the case of a polymerization reaction, the monomer aqueous solution may contain the chain transfer agent. As a chain transfer agent, hypophosphite, thiols, thiolic acids, secondary alcohols, amines, etc. are mentioned.

In order to control the particle diameter of water-absorbent resin particles, the aqueous monomer solution used for polymerization may contain a thickener. As the thickener, 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. When the stirring rate during polymerization is the same, the higher the viscosity of the aqueous monomer solution, the larger the median particle diameter of the obtained particles tends to be.

Although crosslinking by self-crosslinking may occur during polymerization, crosslinking may be further performed by using an internal crosslinking agent. When an internal crosslinking agent is used, it is easy to control the water absorption characteristics of the water absorbent resin particles. An internal crosslinking agent is usually added to the reaction liquid at the time of a polymerization reaction. As an internal crosslinking agent, For example, di or tri of polyols, such as ethylene glycol, propylene glycol, trimethylol propane, glycerol, polyoxyethylene glycol, polyoxypropylene glycol, and polyglycerol. (meth)acrylic acid esters; unsaturated polyesters obtained by reacting the above-mentioned polyols with unsaturated acids (maleic acid, fumaric acid, etc.); bis(meth)acrylamides such as N,N'-methylenebis(meth)acrylamide; di or tri (meth)acrylic acid esters obtained by reacting polyepoxide with (meth)acrylic acid; di(meth)acrylic acid carbamyl esters obtained by reacting polyisocyanate (tolylene diisocyanate, hexamethylene diisocyanate, etc.) with hydroxyethyl (meth)acrylate; compounds having two or more polymerizable unsaturated groups, such as allylated starch, allylated cellulose, diallyl phthalate, N,N',N''-triallylisocyanurate, and divinylbenzene; (poly) ethylene glycol diglycidyl ether, (poly) propylene glycol diglycidyl ether, (poly) glycerin diglycidyl ether, (poly) glycerin triglycidyl ether, (poly) polyglycidyl compounds such as propylene glycol polyglycidyl ether and polyglycerol polyglycidyl ether; haloepoxy compounds such as epichlorohydrin, epibromohydrin and α-methylepichlorohydrin; The compound which has two or more reactive functional groups, such as an isocyanate compound (2, 4- tolylene diisocyanate, hexamethylene diisocyanate, etc.), is mentioned. An internal crosslinking agent may be used independently and may be used in combination of 2 or more type. As an internal crosslinking agent, a polyglycidyl compound may be sufficient and a diglycidyl ether compound may be sufficient. The internal crosslinking agent is at least selected from the group consisting of (poly) ethylene glycol diglycidyl ether, (poly) propylene glycol diglycidyl ether, and (poly) glycerin diglycidyl ether. You may include 1 type.

The amount of the internal crosslinking agent is 0 mmol or more, 0.01 mmol or more, per 1 mol of the ethylenically unsaturated monomer, from the viewpoint that the water-soluble property is suppressed by appropriately crosslinking the polymer obtained by polymerization of the above-mentioned aqueous monomer solution and a sufficient amount of water absorption is easy to be obtained; 0.015 mmol or more or 0.020 mmol or more may be sufficient, and 0.1 mol or less may be sufficient.

An aqueous phase containing an ethylenically unsaturated monomer, a radical polymerization initiator, and, if necessary, an internal crosslinking agent, etc., and an oil phase containing a hydrocarbon-based dispersant and, if necessary, a surfactant, a polymer-based dispersant, etc. In a state, it can be heated under stirring to perform reverse-phase suspension polymerization in a water-in-oil system.

When performing reverse-phase suspension polymerization, the monomer aqueous solution containing an ethylenically unsaturated monomer is disperse|distributed in a hydrocarbon dispersion medium in presence of surfactant (and a polymer type dispersing agent further as needed). At this time, as long as it is before starting the polymerization reaction, the timing of addition of the surfactant, the polymeric dispersant, etc. may be either before or after the addition of the aqueous monomer solution.

From the viewpoint of easily reducing the amount of the hydrocarbon dispersion medium remaining in the resulting water absorbent resin, the monomer aqueous solution may be dispersed in the hydrocarbon dispersion medium in which the polymeric dispersing agent is dispersed, and then a surfactant may be further dispersed, followed by polymerization.

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

When performing reverse phase suspension polymerization in two or more stages, after performing reverse phase suspension polymerization in the first stage, an ethylenically unsaturated monomer is added to the reaction mixture obtained by the polymerization reaction in the first stage and mixed, and the second stage is performed in the same manner as in the first stage What is necessary is just to perform the subsequent reverse-phase suspension polymerization. In the reverse phase suspension polymerization in each stage after the second stage, in addition to the ethylenically unsaturated monomer, the above-mentioned radical polymerization initiator is added at the time of reverse phase suspension polymerization in each stage after the second stage The amount of the ethylenically unsaturated monomer As a reference, it may be added within the range of the molar ratio of each component with respect to the above-mentioned ethylenically unsaturated monomer to perform reverse-phase suspension polymerization. In the reversed-phase suspension polymerization in each stage after the 2nd stage|stage, you may use an internal crosslinking agent as needed. When using an internal crosslinking agent, based on the amount of the ethylenically unsaturated monomer provided to each stage, you may add within the range of the molar ratio of each component with respect to the above-mentioned ethylenically unsaturated monomer, You may carry out reverse phase suspension polymerization.

Although the temperature of the polymerization reaction varies depending on the radical polymerization initiator used, the polymerization proceeds rapidly and the polymerization time is shortened, thereby improving economic feasibility, and from the viewpoint of easily removing the heat of polymerization and performing the reaction smoothly. 20-150 degreeC or 40-120 degreeC may be sufficient. Reaction time is 0.5 to 4 hours normally. The completion of the polymerization reaction can be confirmed, for example, by stopping the temperature rise in the reaction system. Thereby, the polymer of an ethylenically unsaturated monomer is obtained in the state of a hydrous gel-like polymer normally.

After polymerization, a crosslinking agent may be added to the obtained hydrogel polymer and heated to perform crosslinking after polymerization. By crosslinking after polymerization, the degree of crosslinking of the hydrogel polymer can be increased, thereby further improving the absorption characteristics of the water absorbent resin particles.

As a crosslinking agent for crosslinking after polymerization, for example, ethylene glycol, propylene glycol, 1,4-butanediol, trimethylol propane, glycerin, polyoxyethylene glycol, polyoxy polyols such as propylene glycol and polyglycerol; compounds having two or more epoxy groups, such as (poly)ethylene glycol diglycidyl ether, (poly) propylene glycol diglycidyl ether, and (poly) glycerin diglycidyl ether; haloepoxy compounds such as epichlorohydrin, epibromohydrin, and α-methylepichlorohydrin; 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 ethylene carbonate; and hydroxyalkylamide compounds such as bis[N,N-di(β-hydroxyethyl)]adipamide. Crosslinking agents for crosslinking after polymerization are (poly)ethylene glycol diglycidyl ether, (poly)glycerin diglycidyl ether, (poly)glycerin triglycidyl ether, (poly)propylene glycol Polyglycidyl compounds, such as cold polyglycidyl ether and polyglycerol polyglycidyl ether, may be sufficient. These crosslinking agents may be used independently and may be used in combination of 2 or more type.

The amount of the crosslinking agent used for crosslinking after polymerization is 0 to 0.03 moles, 0 to 0.01 moles, or 0.00001 to 0.005 moles per mole of the water-soluble ethylenically unsaturated monomer from the viewpoint of ensuring that the water-soluble gel-like polymer obtained exhibits suitable absorption characteristics by being appropriately crosslinked. may be malleable

The crosslinking agent for crosslinking after polymerization is added to the reaction solution after the polymerization reaction of the ethylenically unsaturated monomer. In the case of multistage polymerization, a crosslinking agent for crosslinking after polymerization may be added after multistage polymerization. In consideration of heat generation during and after polymerization, retention due to process delay, system opening during addition of the crosslinking agent, and fluctuations in moisture due to addition of water according to the addition of the crosslinking agent, the crosslinking agent for crosslinking after polymerization has a moisture content (described later) From a viewpoint, you may add in the area|region of [moisture content +/-3 mass % immediately after polymerization].

Then, moisture is removed from the obtained hydrogel polymer. By drying to remove moisture, polymer particles containing a polymer of an ethylenically unsaturated monomer are obtained. As the drying method, for example, (a) a method of removing moisture by azeotropic distillation in a state in which the hydrogel polymer is dispersed in a hydrocarbon dispersion medium, (b) taking out the hydrous gel polymer by decantation, A method of drying under reduced pressure, (c) a method of separating the water-containing gel polymer by filtration through a filter and drying under reduced pressure, and the like.

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 coagulant to the system after the polymerization reaction or at the initial stage of drying. By adding a coagulant, the particle diameter of the water absorbent resin particle obtained can be enlarged. As the coagulant, an inorganic coagulant can be used. Examples of the inorganic coagulant (eg, powdery inorganic coagulant) include silica, zeolite, bentonite, aluminum oxide, talc, titanium dioxide, kaolin, clay, hydrotalcite, and the like. At least 1 type selected from the group which consists of silica, aluminum oxide, a talc, and kaolin may be sufficient as a viewpoint of being excellent in the aggregation effect.

In the reversed-phase suspension polymerization, the coagulant may be previously dispersed in a hydrocarbon dispersion medium or water of the same kind as that used in the polymerization, and then mixed in a hydrocarbon dispersion medium containing an aqueous gel polymer under stirring.

0.001-1 mass part, 0.005-0.5 mass part, or 0.01-0.2 mass part may be sufficient as the quantity of a coagulant with respect to 100 mass parts of ethylenically unsaturated monomers used for superposition|polymerization. When the amount of the coagulant is within these ranges, it is easy to obtain water-absorbing resin particles having a target particle size distribution.

Polymerization reaction can be performed using various stirrers which have stirring blades. As the stirring blade, a flat blade blade, a grid blade, a paddle blade, a propeller blade, an anchor blade, a turbine blade, a Powdler blade, a ribbon blade, a full zone blade, a MaxBlend blade, etc. can be used. The flat blade has a shaft (stirring shaft) and a flat plate portion (stirring portion) arranged around the shaft. The flat plate portion may further include a slit or the like.

In the production of the water-absorbent resin particles, crosslinking (surface crosslinking) of the surface portion of the hydrous gel-like polymer may be performed using a crosslinking agent in the drying step (water removal step) or any subsequent step. By performing surface crosslinking, it is easy to control the water absorption characteristics of water-absorbent resin particles. The water content of the hydrous gel-like polymer to be surface crosslinked may be 5 to 50 mass%, 10 to 40 mass%, or 15 to 35 mass%. The water content (mass %) of the hydrous gel-like polymer is calculated by the following formula.

Moisture content = [Ww/(Ww+Ws)]×100

Ww: Calculated by adding the amount of water used as necessary when mixing the coagulant, the surface crosslinking agent, etc. to the amount obtained by subtracting the amount of water discharged to the outside of the system by the drying process from the amount of water contained in the aqueous monomer solution before polymerization in the entire polymerization process Moisture content of the hydrous gel polymer.

Ws: A solid content calculated from the input amount of materials such as an ethylenically unsaturated monomer, a crosslinking agent, and an initiator constituting the hydrogel polymer.

As a crosslinking agent for surface crosslinking (surface crosslinking agent), the compound which has two or more reactive functional groups is mentioned, for example. Examples of the crosslinking agent include polyols such as ethylene glycol, propylene glycol, 1,4-butanediol, trimethylol propane, glycerin, polyoxyethylene glycol, polyoxypropylene glycol, and polyglycerin. Ryu; (poly) ethylene glycol diglycidyl ether, (poly) glycerin diglycidyl ether, (poly) glycerin triglycidyl ether, trimethylol propane triglycidyl ether, (poly) ) polyglycidyl compounds such as propylene glycol polyglycidyl ether and (poly)glycerol polyglycidyl ether; haloepoxy compounds such as epichlorohydrin, epibromohydrin and α-methylepichlorohydrin; isocyanate compounds such as 2,4-tolylene diisocyanate and hexamethylene diisocyanate; 3-methyl-3-oxetanemethanol, 3-ethyl-3-oxetanemethanol, 3-butyl-3-oxetanemethanol, 3-methyl-3-oxetaneethanol, 3-ethyl-3-oxetaneethanol; oxetane compounds such as 3-butyl-3-oxetaneethanol; oxazoline compounds such as 1,2-ethylenebisoxazoline; carbonate compounds such as ethylene carbonate; and hydroxyalkylamide compounds such as bis[N,N-di(β-hydroxyethyl)]adipamide. A surface crosslinking agent may be used independently and may be used in combination of 2 or more type. The surface crosslinking agent may be a polyglycidyl compound, (poly) ethylene glycol diglycidyl ether, (poly) glycerin diglycidyl ether, (poly) glycerin triglycidyl ether, (poly) ) You may contain at least 1 sort(s) chosen from the group which consists of propylene glycol polyglycidyl ether and polyglycerol polyglycidyl ether.

The quantity of a surface crosslinking agent may be 0.00001-0.02 mol, 0.00005-0.01 mol, or 0.0001-0.005 mol with respect to 1 mol of the ethylenically unsaturated monomer used for superposition|polymerization. When the amount of the surface crosslinking agent is 0.00001 mol or more, the crosslinking density in the surface portion of the water absorbent resin particles is sufficiently high, and the gel strength of the water absorbent resin particles is easily increased. When the amount of the surface crosslinking agent is 0.02 mol or less, it is easy to increase the amount of water absorbed by the water absorbent resin particles.

In the production of the water-absorbent resin particles, the surface portion of the water-containing gel polymer may be treated (surface modification) using a surface modifier in the drying step (water removal step) or any subsequent step. The surface modification may be performed, for example, before, during, or after the surface crosslinking step. Above all, surface modification may be performed after surface crosslinking. In particular, in the case of water-containing gel polymers obtained by reverse-phase suspension polymerization, aqueous solution polymerization, and other polymerization methods, when the water-containing gel polymer is treated with a surface modifier after surface crosslinking, the resulting water absorbent resin particles have a high dry matter content. It tends to be easy to form a resin layer which shows a liquid-permeable liquid absorption rate.

Surfactants, such as an anionic surfactant, a cationic surfactant, an amphoteric surfactant, and a nonionic surfactant, may be sufficient as a surface modifier, for example. For example, the HLB value of the nonionic surfactant used as a surface modifier may be 3-12 or 6-10, for example. As a nonionic surfactant, sorbitan fatty acid ester, such as sorbitan monolaurate, is mentioned, for example. In particular, when the surface modifier is a nonionic surfactant having an HLB value within the above range, the resulting water-absorbing resin particles tend to easily form a resin layer exhibiting a high dry powder permeation liquid absorption rate. The HLB value is measured by the Griffin method.

0.01-0.50 mass part, 0.02-0.40 mass part, or 0.04-0.30 mass part may be sufficient as the quantity of a surface modifier with respect to 100 mass parts of ethylenically unsaturated monomers used for superposition|polymerization.

If necessary, after surface crosslinking and/or surface modification is performed, the dried polymer particles can be obtained by distilling off water and a hydrocarbon dispersion medium from the hydrogel polymer or the like.

The water absorbent resin particles according to the present embodiment may be composed of only polymer particles, but may further contain various additional components selected from, for example, gel stabilizers, metal chelating agents, and fluidity improving agents (lubricating agents). can The additional component may be disposed inside the polymer particle, on the surface of the polymer particle, or both. The additional component may be a fluidity improving agent (lubricating agent). The fluidity improving agent may contain inorganic particles. Examples of the inorganic particles include silica particles such as amorphous silica.

The water absorbent resin particle may contain the some inorganic particle arrange|positioned on the surface of a polymer particle. For example, by mixing a polymer particle and an inorganic particle, an inorganic particle can be arrange|positioned on the surface of a polymer particle. Silica particles, such as amorphous silica, may be sufficient as this inorganic particle. When the water absorbent resin particles include inorganic particles disposed 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, 1.0% by mass or more, or 1.5 Mass % or more may be sufficient, 5.0 mass % or less, or 3.5 mass % or less may be sufficient. The inorganic particles here usually have a small size compared with the size of the polymer particles. For example, the average particle diameter of an inorganic particle may be 0.1-50 micrometers, 0.5-30 micrometers, or 1-20 micrometers. The average particle diameter here may be a value measured by a dynamic light scattering method or a laser diffraction/scattering method.

<Secondary sheet>

1 is a cross-sectional view showing an example of an absorbent 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 arrange|positioned inside the sheet|seat base materials 62a, 62b. The resin layer 61 is shape-retained by being pinched|interposed between the sheet|seat base materials 62a, 62b of 2 sheets. The sheet base materials 62a, 62b may be two sheets, a folded sheet, or a single bag body.

The auxiliary sheet 60 may further have an adhesive agent 63a interposed between the sheet base material 62a and the resin layer 61 , and an adhesive agent interposed between the sheet base material 62b and the resin layer 61 . (63b) may be further included. The adhesives 63a and 63b may be, for example, water-based adhesives, solvent-based adhesives, elastic adhesives, aerosol adhesives, hot-melt adhesives, 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 may be 0.1 mm or more, 0.3 mm or more, or 0.5 mm or more. The thickness can be measured, for example, using a dial thinness gauge J-B made by Ozaki Seisakusho (the measuring instrument is made of aluminum with a diameter of 50 mm).

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

The thickness of the resin layer 61 may be, in a dry state, 2.0 mm or less, 1.5 mm or less, 1.0 mm or less, or 0.8 mm or less, 0.1 mm or more, or 0.3 mm or more may be sufficient as it, for example. 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 ² or more, Or 25 g/m ² or more may be sufficient.

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

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

The sheet base materials 62a and 62b may be, for example, a nonwoven fabric or a tissue. The two sheet base materials 62a and 62b may be the same or different nonwoven fabrics. The nonwoven fabric may be a nonwoven fabric (short fiber nonwoven fabric) composed of short fibers (ie, staples), or may be a nonwoven fabric composed of long fibers (ie filaments) (long fiber nonwoven fabric). The staple may generally have a fiber length of several hundred mm or less.

The nonwoven fabric used as the sheet base material 62a, 62b is selected from a thermal bond nonwoven fabric, an air through nonwoven fabric, a resin bond nonwoven fabric, a spun bond nonwoven fabric, a melt blown nonwoven fabric, an air laid nonwoven fabric, a spun lace nonwoven fabric, a point bond nonwoven fabric, or these A laminate containing two or more types of nonwoven fabrics may be used.

The nonwoven fabric used as the sheet substrates 62a and 62b may be a nonwoven fabric formed by 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), and poly such as nylon and fibers comprising a synthetic resin selected from amide and rayon. Examples of natural fibers include fibers comprising cotton, silk, hemp, or pulp (cellulose). The fibers forming the nonwoven fabric may be polyolefin fibers, polyester fibers, or a combination thereof. The sheet base materials 62a and 62b may be tissues.

The tissue used as the sheet base materials 62a and 62b may be a natural fiber or a natural fiber mixed with a synthetic fiber. 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 a method in which the resin layer 61 is sandwiched between the sheet base materials 62a and 62b, and the formed structure is pressurized while heating if necessary. Adhesives 63a, 63b are arrange|positioned between the sheet|seat base materials 62a, 62b and the resin layer 61 as needed.

The auxiliary sheet 60 is used in order to manufacture various absorbent articles, for example. Examples of the absorbent article include diapers (eg, paper diapers), toilet training pants, incontinence pads, sanitary materials (sanitary napkins, tampons, etc.), sweat-absorbing pads, pet sheets, toilet members, and animal excreta disposal materials. can be heard

<Absorbent article>

2 : is sectional drawing which shows an example of an absorbent article. The absorbent article 100 shown in FIG. 2 includes an absorbent core 50 , an auxiliary sheet 60 , a liquid-permeable sheet 30 , and a liquid-impermeable sheet 40 . In other words, the absorbent core 50 and the auxiliary sheet 60 are sandwiched between the liquid-permeable sheet 30 and the liquid-impermeable sheet 40 .

The absorbent core 50 includes an absorbent layer 10 and two core wrap sheets 20a and 20b. The core wrap sheets 20a and 20b are disposed on both sides of the absorbent layer 10 . In other words, the absorbent layer 10 is disposed inside the core wrap sheets 20a and 20b, and is sandwiched between the two core wrap sheets to form a shape. The core wrap sheets 20a and 20b may be individual sheets, a single folded sheet, or a single bag body. However, the absorbent core 50 does not need to have one or both of the two core wrap sheets 20a and 20b. For example, the core wrap sheet 20a may not be disposed between the absorbent layer 10 and the auxiliary sheet 60 . When the core wrap sheet is not disposed between the absorbent layer 10 and the auxiliary sheet 60 , for example, the absorbent layer 10 includes one core wrap sheet 20b and the auxiliary sheet 60 . It is shaped by being sandwiched between the

The absorbent core 50 may further include an adhesive interposed between the core wrap sheet 20a and the absorbent layer 10 , or further include an adhesive interposed between the core wrap sheet 20b and the absorbent layer 10 , there may be An adhesive layer may be interposed between the core wrap sheets 20a and 20b on both sides and the absorbent layer 10 . 3 is a plan view illustrating an example of an adhesive application pattern formed on a core wrap sheet. The adhesive 21 shown in FIG. 3 forms an application pattern composed of a plurality of linear portions arranged at intervals on the core wrap sheet 20a. The application pattern of the adhesive 21 may be linear, curved, dotted, or a combination thereof. The adhesive may be, for example, a water-based adhesive, a solvent-based adhesive, or a hot-melt adhesive.

The absorbent layer 10 has water absorbent resin particles 10a and a fibrous layer 10b containing a fibrous material. The absorbent layer 10 does not need to include the fibrous layer 10b. The content of the water absorbent resin particles in the absorbent layer may be 70 to 100 mass%, 80 to 100 mass%, or 90 to 100 mass% based on the mass of the absorbent 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 its salts, 2-(meth)acrylamide-2-methylpropanesulfonic acid and its salts, (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 are mentioned. An ethylenically unsaturated monomer may be used independently and may be used in combination of 2 or more type. 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 crosslinking the polymer. The water-absorbing 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 polymerization of a monomer containing an ethylenically unsaturated monomer. The polymerization method of the monomer may 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 viewpoints of ensuring good absorption characteristics of the water-absorbing resin particles and easy control of the polymerization reaction, a reversed-phase suspension polymerization method or an aqueous solution polymerization method may be employed.

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, crosslinking by reaction with a crosslinking agent, or both. The water-absorbing resin particles may be surface crosslinked by crosslinking at least the polymer of the surface layer portion with a crosslinking agent.

The water absorbent resin particle 10a may contain various additional components in addition to the polymer of an ethylenically unsaturated monomer. Examples of additional ingredients include gel stabilizers, metal chelating agents, and flow improvers (glidants). The additional component may be disposed inside the polymer particle comprising the polymer, on the surface of the polymer particle, or both. The additional component may be a fluidity improving agent (lubricating agent). The fluidity improving agent 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 median particle diameter of the water-absorbing resin particles may be 250 to 850 µm, 300 to 700 µm, or 300 to 600 µm. Moreover, as an absorption characteristic of the water absorbent resin particle 10a, the absorption amount of physiological saline may be 20-80 g/g, 30-70 g/g, or 40-65 g/g, for example.

The thickness of the absorbent layer 10 in a dry state 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, 0.1 mm or more, or 0.3 mm or more. 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.

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

The absorbent layer 10 (or the fiber layer 10b) may further contain an inorganic powder (eg, amorphous silica), a deodorant, an antibacterial agent, a fragrance, and the like. When the water absorbent resin particles 10a contain inorganic particles, the absorbent layer 10 may contain inorganic powder separately from the inorganic particles in the water absorbent resin particles 10a.

The core wrap sheets 20a and 20b may be, for example, nonwoven fabric. The two core wrap sheets 20a and 20b may be the same or different nonwoven fabrics. The nonwoven fabric may be a nonwoven fabric (short fiber nonwoven fabric) composed of short fibers (ie, staples), or may be a nonwoven fabric composed of long fibers (ie filaments) (long fiber nonwoven fabric). The staple may generally have a fiber length of several hundred mm or less.

The core wrap sheets 20a and 20b include a thermal bond nonwoven fabric, an air through nonwoven fabric, a resin bond nonwoven fabric, a spun bond nonwoven fabric, a melt blown nonwoven fabric, an air laid nonwoven fabric, a spun lace nonwoven fabric, a point bond nonwoven fabric, or two or more selected from these. A laminate including a nonwoven fabric may be used.

The nonwoven fabric used as the core wrap sheets 20a and 20b may be a nonwoven fabric formed by synthetic fibers, natural fibers, or a combination thereof. Examples of synthetic fibers include polyolefins such as polyethylene (PE) and polypropylene (PP), polyester such as polyethylene terephthalate (PET), polytrimethylene terephthalate (PTT) and polyethylene naphthalate (PEN), and poly such as nylon and fibers comprising a synthetic resin selected from amide and rayon. Examples of natural fibers include fibers comprising cotton, silk, hemp, or pulp (cellulose). The fibers forming the nonwoven fabric may be polyolefin fibers, polyester fibers, or a combination thereof. The core wrap sheets 20a and 20b may be tissues.

The absorbent core 50 is formed by sandwiching, for example, the water absorbent resin particles 10a or a mixture containing the water absorbent resin particles 10a and the fibrous material between the core wrap sheets 20a and 20b, the formed structure is formed. It can be obtained by the method of pressurizing, heating as needed. If necessary, an adhesive is disposed between the core wrap sheets 20a and 20b and the water absorbent resin particles 10a, or a mixture containing the same.

The absorbent core includes a core wrap sheet 20a, an absorbent layer 10 composed of absorbent resin particles 10a and a fibrous layer 10b, and an absorbent core in which the core wrap sheet 20b is disposed in this order, and the entire absorbent core is made of a fiber layer. The sheet form which does not contain substantially may be sufficient. 4 is a cross-sectional view of an absorbent core formed in a sheet shape, showing another example of the absorbent core. The absorbent core 50 shown in FIG. 4 includes a core wrap sheet 25a, an adhesive 26a, an absorbent layer 10A made of absorbent resin particles, a core wrap sheet 25b, and an absorbent layer 10B made of absorbent resin particles; The adhesive 26b and the corewrap sheet 25c are arranged in this order. The water-absorbing resin particles contained in the absorbent layers 10A and 10B may be of the same type or of different types. The mass and thickness per unit area of each of the absorption layers 10A and 10B may be the same or different.

The liquid-permeable sheet 30 is disposed at the position of the outermost layer on the side where the liquid to be absorbed enters. The liquid-permeable sheet 30 is disposed on the outside of the core wrap sheet 20b in a state in contact with the core wrap sheet 20b. The liquid-impermeable sheet 40 is disposed 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 disposed on the outside of the core wrap sheet 20a in a state in contact with the core wrap sheet 20a. The liquid-permeable sheet 30 and the liquid-impermeable sheet 40 have a main surface wider than the main surface of the absorbent core 50 , and the liquid-permeable sheet 30 and the liquid-impervious sheet 40 have outer edges The portion extends around the absorbent layer 10 and the core wrap sheets 20a and 20b. However, the magnitude relationship between the absorbent layer 10, the core wrap sheets 20a and 20b, the auxiliary sheet 60, the liquid-permeable sheet 30, and the liquid-impermeable sheet 40 is appropriately adjusted according to the purpose of the absorbent article, etc. do.

The liquid-permeable sheet 30 may be a nonwoven fabric. The nonwoven 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 that point of view, the liquid-permeable sheet 30 is a paper pulp test method No. 1 by the Paper Pulp Technology Association. 68 (2000) may be a nonwoven fabric having a hydrophilicity of 5 to 200 measured according to the measurement method. The hydrophilicity of the nonwoven fabric may be 10-150. Paper Pulp Test Method No. For details of 68, reference can be made, for example to WO2011/086843.

The nonwoven fabric having hydrophilicity may be formed of fibers exhibiting appropriate hydrophilicity, such as rayon fibers, or those formed by fibers obtained by hydrophilizing hydrophobic chemical fibers such as polyolefin fibers and polyester fibers. okay As a method of obtaining a nonwoven fabric containing hydrophobic chemical fibers treated with hydrophilicity, for example, a method of obtaining a nonwoven fabric by a spun bonding method using a mixture of a hydrophobic chemical fiber with a hydrophilizing agent, a spunbonding nonwoven fabric using a hydrophobic chemical fiber A method of entraining a hydrophilicizing agent when producing a spun-bonded nonwoven fabric obtained by using a hydrophobic chemical fiber may be impregnated with a hydrophilicizing agent. Examples of the hydrophilizing agent include anionic surfactants such as aliphatic sulfonates and higher alcohol sulfate ester salts, cationic surfactants such as quaternary ammonium salts, polyethylene glycol fatty acid esters, polyglycerol fatty acid esters, sorbitan fatty acid esters, etc. Silicone surfactants, such as an ionic surfactant and polyoxyalkylene modified silicone, and the stain release agent etc. which consist of polyester-type, polyamide-type, acryl-type, and urethane-type resin are used.

The weight per unit area (mass per unit area) of the nonwoven fabric used as the liquid-permeable sheet 30 is, from the viewpoint of imparting good liquid permeability, flexibility, strength and cushioning properties to the absorbent article, and speeding up the liquid permeation rate of the absorbent article. From the viewpoint of doing, 5-200 g/m ² , 8-150 g/m ² , or 10-100 g/m ² may be sufficient. 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 in the absorbent layer 10 or the resin layer 61 from leaking out from the liquid-impermeable sheet 40 side. The liquid-impermeable sheet 40 may be a resin sheet or a nonwoven fabric. The resin sheet may be a sheet made of a synthetic resin such as polyethylene, polypropylene, or polyvinyl chloride. The nonwoven fabric may be a spunbonded/meltblown/spunbonded (SMS) nonwoven fabric in which a water-resistant meltblown nonwoven fabric is sandwiched by a high-strength spunbonded nonwoven fabric. Further, the liquid-impermeable sheet 40 may be a composite sheet of a resin sheet and a nonwoven fabric (eg, spunbond nonwoven fabric or spunlace nonwoven fabric). The liquid-impermeable sheet 40 may have air permeability from the viewpoint of reducing moisture during wearing and reducing discomfort to the wearer. As the liquid-impermeable sheet 40 having air permeability, for example, a sheet of low-density polyethylene (LDPE) resin can be used.

The weight per unit area (mass per unit area) of the liquid-impermeable sheet 40 may be 5 to 100 g/m ² , or 10 to 50 g/m ² , from the viewpoint of ensuring flexibility so as not to impair the wearing comfort of the absorbent article.

The absorbent article 100 is manufactured, for example, by a method comprising disposing an absorbent core 50 and an auxiliary sheet 60 between the liquid permeable sheet 30 and the liquid impermeable sheet 40 . can do. A laminate in which the liquid impermeable sheet 40, the auxiliary sheet 60, the absorbent core 50 and the liquid permeable sheet 30 are laminated in this order is pressed as necessary. Alternatively, the liquid-permeable sheet 30, the core wrap sheet 20b, the water absorbent resin particles 10a, or a mixture containing the water absorbent resin particles 10a and a fibrous material, the core wrap sheet 20a, and an auxiliary material The absorbent article 100 can also be obtained by a method in which the sheet 60 and the liquid-impermeable sheet 40 are arranged in this order, and the formed structure is pressurized while heating if necessary. Moreover, you may couple|bond together between each structural unit with an adhesive agent.

Example

Hereinafter, the present invention will be described in more detail by way of Examples. However, the present invention is not limited to these Examples.

[Production of water absorbent resin particles]

Preparation Example 1

<Polymerization reaction in the first stage>

As a reflux condenser, a dropping funnel, a nitrogen gas introduction tube, and a stirrer, a round-bottomed cylindrical separable flask having an inner diameter of 11 cm and a capacity of 2 L equipped with a stirring blade having two stages of four inclined paddle blades with a blade diameter of 5 cm was prepared. To this flask, 293 g of n-heptane as a hydrocarbon dispersion medium, 0.736 g of maleic anhydride-modified ethylene/propylene copolymer (Mitsui Chemical Co., Ltd., High Wax 1105A) as a polymeric dispersant was added, and the temperature was raised to 80° C. while stirring. After dissolving the dispersant, it was cooled to 50°C.

To a 300 mL beaker, take 92.0 g (1.03 mol) of an 80.5 mass % aqueous acrylic acid solution as a water-soluble ethylenically unsaturated monomer, and while cooling from the outside, 147.7 g of a 20.9 mass % aqueous sodium hydroxide solution is added dropwise to neutralize 75 mol% After hydroxyethyl cellulose 0.092 g (Sumitomo Seika Co., Ltd., HECAW-15F) as a thickener, potassium persulfate 0.0736 g (0.272 mmol) as a water-soluble radical polymerization initiator, ethylene glycol diglycidyl ether as an internal crosslinking agent 0.010 g (0.057 mmol) was added and dissolved to prepare an aqueous monomer solution in the first stage.

Then, the first stage monomer aqueous solution prepared above was added to a separable flask, stirred for 10 minutes, and then sucrose stearic acid ester of HLB 3 (Mitsubishi Chemical Foods Co., Ltd., Lyoto) as a surfactant in 6.62 g of n-heptane. Sugar Ester S-370) 0.736 g of a surfactant solution was added by heating, and the temperature was raised by immersing the flask in a water bath at 70 ° C. and polymerization was carried out for 60 minutes to obtain a polymerization slurry liquid in the first stage.

<Second stage polymerization reaction>

128.8 g (1.44 mol) of an 80.5 mass % aqueous acrylic acid solution as a water-soluble ethylenically unsaturated monomer was taken into a 500 mL beaker, and while cooling from the outside, 159.0 g of a 27 mass % aqueous sodium hydroxide solution was added dropwise to neutralize 75 mol%. After that, 0.090 g (0.333 mmol) of potassium persulfate as a water-soluble radical polymerization initiator and 0.0116 g (0.067 mmol) of ethylene glycol diglycidyl ether as an internal crosslinking agent were added and dissolved to prepare an aqueous monomer solution in the second stage. did.

After cooling the inside of the separable flask system to 31 ° C. while stirring with the rotation speed of the stirrer set to 1000 rpm, the entire amount of the aqueous monomer solution in the second stage is added to the polymerization slurry liquid in the first stage, was replaced with nitrogen for 30 minutes, the flask was again immersed in a water bath at 70° C. to raise the temperature, and polymerization was performed for 60 minutes to obtain a hydrous gel polymer.

After polymerization, 0.589 g of a 45% by mass aqueous solution of diethylenetriamine pentasodium pentasodium was added to the obtained hydrogel polymer under stirring. Thereafter, the flask was immersed in an oil bath set at 125°C, and 275.8 g of water was taken out of the system while refluxing n-heptane by azeotropic distillation of n-heptane and water. Then, 4.42 g (0.507 mmol) of a 2 mass % ethylene glycol diglycidyl ether aqueous solution was added to the flask as a surface crosslinking agent, and it hold|maintained at 83 degreeC 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 Corporation) as a surfactant was dissolved in 6.62 g of n-heptane was added to the flask.

Thereafter, n-heptane and water were heated in an oil bath at 125°C, evaporated and dried to obtain a dried product of polymer particles. This polymer particle was passed through a sieve having an eye size of 850 μm, and 0.2 mass % of amorphous silica (Oriental Silicas Corporation, Tokusil NP-S) with respect to the mass of the polymer particle was mixed with the polymer particles to absorb amorphous silica containing 233.0 g of resin particles A were obtained. The median particle diameter of the water absorbent resin particle A was 128 micrometers.

Preparation 2

In the production of the hydrous gel polymer in the second stage, the temperature in the separable flask was changed to 25 °C instead of 31 °C, and in the hydrous gel polymer after polymerization in the second stage, 256.8 g of water was added by azeotropic distillation. 230.2 g of water-absorbent resin particles B were obtained in the same manner as in Production Example 1 except that the amount of the amorphous silica to be taken out of the system and mixed with the polymer particles was changed to 0.5 mass % with respect to the mass of the polymer particles. The median particle diameter of the water absorbent resin particle B was 358 µm.

Preparation 3

<Polymerization reaction in the first stage>

As a reflux condenser, a dropping funnel, a nitrogen gas introduction tube, and a stirrer, a round-bottomed cylindrical separable flask having an inner diameter of 11 cm and a capacity of 2 L equipped with a stirring blade having two stages of four inclined paddle blades with a blade diameter of 5 cm was prepared. To this flask, 293 g of n-heptane as a hydrocarbon dispersion medium, 0.736 g of maleic anhydride-modified ethylene-propylene copolymer (Mitsui Chemical Co., Ltd., High Wax 1105A) as a polymeric dispersant was added, and the temperature was raised to 80° C. while stirring. After dissolving the dispersant, it was cooled to 50°C.

To a 300 mL beaker, take 92.0 g (1.03 mol) of an 80.5 mass % aqueous acrylic acid solution as a water-soluble ethylenically unsaturated monomer, and while cooling from the outside, 147.7 g of a 20.9 mass % aqueous sodium hydroxide solution is added dropwise to neutralize 75 mol% , hydroxyethyl cellulose 0.092 g (Sumitomo Seika Co., Ltd., HECAW-15F) as a thickener, and 2,2'-azobis (2-amidinopropane) dihydrochloride as a water-soluble radical polymerization initiator 0.092 g (0.339 mmol) and 0.018 g (0.067 mmol) of potassium persulfate and 0.0046 g (0.026 mmol) of ethylene glycol diglycidyl ether as an internal crosslinking agent were added and dissolved to prepare an aqueous monomer solution in the first stage.

Then, the first-stage aqueous monomer solution prepared above was added to a separable flask, stirred for 10 minutes, and then sucrose stearic acid ester of HLB 3 (Mitsubishi Chemical Foods Co., Ltd., Lyoto) as a surfactant in 6.62 g of n-heptane. Sugar Ester S-370) 0.736 g of a surfactant solution was added by heating, and the temperature was raised by immersing the flask in a water bath at 70 ° C. and polymerization was carried out for 60 minutes to obtain a polymerization slurry liquid in the first stage.

<Second stage polymerization reaction>

128.8 g (1.44 mol) of an 80.5 mass % aqueous acrylic acid solution as a water-soluble ethylenically unsaturated monomer was taken into a 500 mL beaker, and while cooling from the outside, 159.0 g of a 27 mass % aqueous sodium hydroxide solution was added dropwise to neutralize 75 mol%. After carrying out, 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 ethylene glycol as an internal crosslinking agent 0.0116 g (0.067 mmol) of diglycidyl ether was added and dissolved to prepare an aqueous monomer solution in the second stage.

After cooling the inside of the separable flask system to 25° C. while stirring the rotation speed of the stirrer at 1000 rpm, the entire amount of the aqueous monomer solution in the second stage is added to the polymerization slurry liquid in the first stage, After replacing with nitrogen for 30 minutes, the flask was again immersed in a water bath at 70°C to raise the temperature, and polymerization reaction was performed for 60 minutes. Thus, a hydrous gel-like polymer was obtained.

After polymerization, 0.589 g of a 45% by mass aqueous solution of diethylenetriamine pentasodium pentasodium was added to the hydrogel polymer under stirring. Thereafter, the reaction solution was heated with an oil bath at 125°C, and 232.0 g of water was taken out of the system while refluxing n-heptane by azeotropic distillation of n-heptane and water. Then, 4.42 g (0.507 mmol) of a 2 mass % ethylene glycol diglycidyl ether aqueous solution was added to the flask as a surface crosslinking agent, and it hold|maintained at 83 degreeC 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 Corporation) as a surfactant was dissolved in 6.62 g of n-heptane was added to the flask.

Thereafter, n-heptane and water were heated in an oil bath at 125°C, evaporated and dried to obtain a dried product of polymer particles. This polymer particle was passed through a sieve having an eye size of 850 µm, and 0.2 mass% of amorphous silica (Oriental Silicas Corporation, Tokusil NP-S) was mixed with respect to the mass of the polymer particle to obtain 228.5 g of water absorbent resin particles C. The median particle diameter of the water absorbent resin particle C was 354 micrometers.

Preparation 4

229.0 g of water-absorbing resin particles D were obtained in the same manner as in Production Example 3 except that 216.7 g of water was taken out of the system by azeotropic distillation. The median particle diameter of the water absorbent resin particle D was 348 µm.

Preparation 5

A water-absorbent resin particle E 227.6 g was obtained in the same manner as in Production Example 3 except that 201.4 g of water was taken out of the system by azeotropic distillation. The median particle diameter of the water absorbent resin particle E was 356 m.

Preparation 6

A reflux condenser, a dropping funnel, a nitrogen gas introduction tube, and a stirrer (agitating blade having two stages of four inclined paddle blades (surface-treated with fluororesin) with a blade diameter of 5 cm) with an inner diameter of 11 cm and an internal volume of 2 L; Four round-bottom cylindrical separable flasks with sidewall baffles (baffle length: 10 cm, baffle width: 7 mm) were 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 Nichiyu Corporation) as a surfactant was added to obtain a mixture. . The mixture was heated up to 50°C while stirring at a rotation speed of 300 rpm of a stirrer to dissolve sorbitan monolaurate in n-heptane, and then the mixture was cooled to 40°C.

Next, 92.0 g (acrylic acid: 1.03 mol) of 80.5 mass % acrylic acid aqueous solution was put into the Erlenmeyer flask with an internal volume of 500 mL. Then, an aqueous solution of partially neutralized acrylic acid was obtained by neutralizing acrylic acid by dropping 147.7 g of a 20.9 mass % aqueous sodium hydroxide solution dropwise while cooling from the outside. Next, an aqueous monomer solution was prepared by dissolving 0.1012 g (0.374 mmol) of potassium persulfate as a water-soluble radical polymerization initiator in an aqueous solution of partially neutralized acrylic acid.

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

Then, while stirring at 1000 rpm of rotation speed of the stirrer, amorphous silica (Oriental Silicas Corporation, Tokusil NP-S) as a powdery inorganic coagulant in the resulting polymerization solution containing the hydrous gel-like polymer, n-heptane and surfactant The dispersion obtained by dispersing 0.092 g in 100 g of n-heptane in advance was added, followed by mixing for 10 minutes. Thereafter, the flask containing the reaction solution was immersed in an oil bath at 125°C, and 98.0 g of water was taken out of the system while refluxing n-heptane by azeotropic distillation of n-heptane and water. Then, after adding 4.14 g (ethylene glycol diglycidyl ether: 0.475 mmol) of a 2 mass % aqueous solution of ethylene glycol diglycidyl ether as a surface crosslinking agent, 2 at an internal temperature of 83±2 degreeC time kept

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

Thereafter, water and n-heptane were heated in an oil bath at 125°C to evaporate, and dried until the evaporated material from the system hardly flows out, thereby obtaining a dried product of polymer particles. By passing this polymer particle through a sieve having an eye size of 850 µm, 90.1 g of water-absorbing resin particles F were obtained. The median particle size of the water absorbent resin particles F was 352 µm.

Preparation 7

90.6 g of water-absorbing resin particles G were obtained in the same manner as in Production Example 6 except that no powdery inorganic coagulant was added to the hydrogel polymer. The median particle diameter of the water absorbent resin particle G was 156 micrometers.

Preparation 8

104.0 g of water was taken out of the system by azeotropic distillation, and as a surface crosslinking agent, 8.28 g of a 2% by mass aqueous solution of ethylene glycol diglycidyl ether (ethylene glycol diglycidyl ether: 0.951 mmol) was used. Except having changed, it carried out similarly to manufacture example 6, and obtained 90.3g of water-absorbent resin particles H. The median particle size of the water absorbent resin particles H was 420 µm.

Preparation 9

In the production of the hydrous gel polymer in the second stage, the temperature in the separable flask was changed to 25 °C instead of 31 °C, and in the hydrous gel polymer after polymerization in the second stage, 256.5 g of water was added by azeotropic distillation. 228.2 g of water-absorbent resin particles J were obtained in the same manner as in Production Example 1 except that the amount of the amorphous silica to be taken out of the system and mixed with the polymer particles was changed to 0.25 mass % with respect to the mass of the polymer particles. The median particle diameter of the water absorbent resin particle J was 360 micrometers.

Preparation 10

The stirring speed of the first stage was changed from 550 rpm to 500 rpm, and in the preparation of the hydrous gel-like polymer in the second stage, the temperature in the separable flask was changed to 25° C. instead of 31° C., and the hydrous after polymerization in the second stage In the gel polymer, 231.2 g of water absorbent resin particles K were obtained in the same manner as in Production Example 1 except that 257.2 g of water was taken out of the system by azeotropic distillation and that no surfactant was added after the surface crosslinking step. The median particle diameter of the water absorbent resin particle K was 359 µm.

Preparation 11

In the production of the water-containing gel polymer in the second stage, the temperature in the separable flask was changed to 28°C instead of 31°C, 234.7 g of water was taken out of the system by azeotropic distillation, and the surfactant was added after the surface crosslinking step. Except not adding, it carried out similarly to manufacture example 3, and obtained 230.1g of water-absorbent resin particles L. The median particle size of the water absorbent resin particles L was 308 µm.

Preparation 12

In the production of the hydrous gel polymer in the second stage, the temperature in the separable flask was changed to 25 °C instead of 31 °C, and in the hydrous gel polymer after polymerization in the second stage, 256.5 g of water was added by azeotropic distillation. 227.2 g of water-absorbent resin particles M were obtained in the same manner as in Production Example 1, except that the substance was taken out of the system, the surfactant was not added after the surface crosslinking step, and the amorphous silica was not mixed. The median particle size of the water absorbent resin particles M was 351 µm.

Preparation 13

In the production of the hydrous gel polymer in the second stage, the temperature in the separable flask was changed to 25 °C instead of 31 °C, and in the hydrous gel polymer after polymerization in the second stage, 256.5 g of water was added by azeotropic distillation. Except for having taken out of the system, having no surfactant added after the surface crosslinking step, and mixing the polymer particles with 0.5 mass % of amorphous silica (manufactured by Tosoh Silica Co., Ltd., Nipsil SS-30P) based on the mass of the polymer particles, In the same manner as in Production Example 1, 229.2 g of water-absorbing resin particles N were obtained. The median particle diameter of the water absorbent resin particles N was 359 m.

Preparation 14

As a reflux condenser, a dropping funnel, a nitrogen gas introduction tube, and a stirrer, a round-bottomed cylindrical separable flask having an inner diameter of 11 cm and a capacity of 2 L equipped with a stirring blade having two stages of four inclined paddle blades with a blade diameter of 5 cm was prepared. To this flask, 293 g of n-heptane as a hydrocarbon dispersion medium, 0.736 g of maleic anhydride-modified ethylene-propylene copolymer (Mitsui Chemical Co., Ltd., High Wax 1105A) as a polymeric dispersant was added, and the temperature was raised to 80° C. while stirring. After dissolving the dispersant, it was cooled to 50°C.

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

Then, the aqueous monomer solution prepared above was added to the separable flask, stirred for 10 minutes, and then sucrose stearic acid ester of HLB 3 (Mitsubishi Chemical Foods Co., Ltd., Lyoto Sugar Ester S-) as a surfactant in 6.62 g of n-heptane. 370) A surfactant solution obtained by dissolving 0.736 g by heating is further added, the rotation speed of the stirrer is set to 400 rpm, and the inside of the system is sufficiently substituted with nitrogen while stirring, and then the flask is immersed in a water bath at 70 ° C. By carrying out for 60 minutes, the polymerization slurry liquid of a 1st stage|stage was obtained.

Thereafter, the flask was immersed in an oil bath set at 125°C, and 116 g of water was taken out of the system while refluxing n-heptane by azeotropic distillation of n-heptane and water. Then, 1.84 g (0.211 mmol) of 2 mass % ethylene glycol diglycidyl ether aqueous solution was added to the flask as a surface crosslinking agent, and it hold|maintained at 83 degreeC for 2 hours.

Thereafter, n-heptane and water were evaporated to dryness at 125°C to obtain a dried product of polymer particles. This polymer particle was passed through a sieve having an eye size of 850 μm, and 0.2 mass % of amorphous silica (Oriental Silicas Corporation, Tokusil NP-S) with respect to the mass of the polymer particle was mixed with the polymer particles to absorb amorphous silica containing 90.9 g of resin particles P were obtained. The median particle diameter of the water absorbent resin particle P was 422 micrometers.

[Measurement of median particle diameter]

The median particle diameter of the particles was measured according to the following procedure. That is, the JIS standard sieve is taken from above, with an eye size 600 μm sieve, an eye size 500 μm sieve, an eye size 425 μm sieve, an eye size 300 μm sieve, an eye size 250 μm sieve, a 180 μm eye sieve, an eye size 150 μm sieve. , and the saucer were combined in the order. 50 g of particles were put into the combined uppermost sieve, and it classified according to JIS Z 8815 (1994) using a low-tap shaker (manufactured by Iida Seisakusho Co., Ltd.). The particle size distribution was calculated|required by calculating the mass of the particle|grains remaining on each sieve after classification as a mass percentage with respect to the whole quantity. Regarding this particle size distribution, by integrating the top of the sieve in order from the larger particle size, the relationship between the size of the sieve and the integrated value of the mass percentage of the particles remaining on the sieve was plotted on the logarithmic probability paper. By connecting the plots on the probability paper with a straight line, the particle diameter corresponding to 50 mass % of integrated mass percentage was obtained as a median particle diameter.

[Absorbed amount of physiological saline (g/g)]

The absorption amount of physiological saline solution of the water-absorbing resin particles was measured by the following method. In a 500 mL beaker, 500 g of physiological saline was weighed, and while stirring at 600 rpm (r/min) with a magnetic stirrer bar (8 mmφ × 30 mm, no ring), 2.0 g of water-absorbent resin particles were dispersed so as not to cause agglomeration. . It was left to stand for 60 minutes in a stirred state, and the water-absorbent resin particles were sufficiently swollen. Thereafter, the mass We (g) of a standard sieve with an eye size of 75 μm is measured in advance, and the contents of the beaker are filtered using this, and the sieve is tilted so as to have an inclination angle of about 30 degrees with respect to the horizontal, for 30 minutes. By leaving it to stand, the excess water|moisture content was separated by filtration. The mass Wf (g) of the sieve containing the swelling gel was measured, and the absorption amount of the physiological saline was calculated by the following formula.

Absorption of physiological saline = (Wf-We)/2.0

[Production of absorbent core]

Preparation 15

An air-laid non-woven fabric (Chinasilk (Shanghai) New Material Technology Co., Ltd. MB0401-T1) having a weight per unit area of 38 g/m ² was cut into two pieces to a size of 14 cm×42 cm, and the air-laid non-woven fabrics 1 and 2 were obtained. An air-through nonwoven fabric (manufactured by Hualong (Nanjing)) having a weight of 45 g/m ² per unit area cut to a size of 14 cm x 42 cm was placed on the air laid non-woven fabric-1, and an air flow mixing device (manufactured by AUTEC Co., Ltd., pad former) was installed. Using this, 6.0 g of water-absorbent resin particles (Aqua Keep SA60S manufactured by Sumitomo Seika Co., Ltd., absorption amount of physiological saline solution of 60 g/g, median particle diameter of 342 µm) were uniformly sprayed over a range of 10 cm × 40 cm in the center of the nonwoven fabric.

Air-laid non-woven fabric-2 with a hot melt coating machine (Hariz Co., Ltd., pump: Marshal150, table: XA-DT, tank set temperature: 150 ° C, hose set temperature: 165 ° C, gunhead set temperature: 170 ° C), all quantity 0.2 g of hot-melt adhesive (Henkel Japan Co., Ltd., ME-765E) was applied in 12 straight lines at intervals of 10 mm. The adhesive application pattern was a spiral stripe. The hot-melt side of the air-laid nonwoven fabric-2 was aligned at both ends with the side of the air-through nonwoven fabric sprayed with water-absorbent resin particles, sandwiched with a release paper, and inverted vertically. Thereafter, the release paper and the air-laid nonwoven fabric-1 were removed.

Among the air-through nonwoven fabric, 3.0 g of water absorbent resin particles (manufactured by Sumitomo Seika Co., Ltd.) in a range of 10 cm × 40 cm in the center of the nonwoven fabric using an airflow mixing device for the side opposite to the side on which the water absorbent resin particles were sprayed. Aqua Keep SA60S, an absorption amount of 60 g/g of physiological saline, a median particle diameter of 342 µm) was uniformly sprayed. 0.2 g of hot melt was applied to the removed air-laid nonwoven fabric-1 by the same operation as above. From the top of the air-through non-woven fabric, the air-laid non-woven fabric-1 is aligned so that the adhesive application side is on the bottom side, and sandwiched with release paper, and a laminating machine (Hashima Co., Ltd., Straight Linear Fussing Press, type HP-600LFS) is applied at 110°C. , was pressed and bonded under the conditions of 0.1 MPa, and only 10 cm x 40 cm in which the water absorbent resin particles were spread was cut out to produce an absorbent core. This was referred to as the absorbent core A. The absorbent core A has the same configuration as the absorbent core shown in FIG. 4 .

Preparation 16

12.0 g of water-absorbing resin particles (Aqua Keep SA60S manufactured by Sumitomo Seika Co., Ltd., absorption amount of physiological saline 60 g/g, median particle diameter 342 μm) and 3.0 g of ground pulp were blown into air using an airflow mixing device (made by AUTEC Co., Ltd., pad former) A sheet-like absorbent layer having a size of 40 cm x 10 cm was produced by uniformly mixing with sheeting. Next, an absorbent core was prepared by pressing while applying a load of 196 kPa to the entire absorbent layer for 30 seconds while holding the upper and lower sides of the absorbent layer with two tissues having the same size as the sheet-like absorbent layer and having a weight per unit area of 16 g/m ² . This was referred to as the absorbent core B. The produced absorbent core B has an absorbent layer composed of absorbent resin particles and pulverized pulp disposed between two tissues.

[Production of absorbent articles for testing]

Example 1

(Production of auxiliary sheet)

A tissue having a weight per unit area of 16 g/m ² was cut into two pieces to a size of 14 cm x 42 cm, and an upper sheet base material and a lower sheet base material were used as auxiliary sheets. After uniformly applying 0.3 g of adhesive (3M Japan Co., Ltd., 3M Spray Paste 77) to the inner surface of the roll of the lower sheet substrate, quickly use an airflow mixing device (manufactured by AUTEC Co., Ltd., pad former) to 1.5 g of the water-absorbent resin particles A prepared in Production Example 1 were uniformly sprayed over the central portion of the sheet base material having a size of 10 cm x 40 cm. 0.3 g of an adhesive (manufactured by 3M Japan Co., Ltd., 3M Spray Paste 77) was uniformly applied to the upper sheet substrate. Align the both ends of the upper sheet substrate with the adhesive-coated side to the side on which the water absorbent resin is sprayed of the lower sheet substrate, and align the overlapping surfaces, and adhere the entire surface to determine the area where the water absorbent resin is sprayed (10 cm × 40 cm) It was cut out and the auxiliary sheet was obtained.

(Production of absorbent articles for testing)

The absorbent core A produced 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 auxiliary sheets 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 auxiliary sheets 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 auxiliary sheets 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 auxiliary sheets 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 auxiliary sheets 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 auxiliary sheets 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 auxiliary sheets 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 auxiliary sheets were changed to the water absorbent resin particles J produced in Production Example 9.

Example 10

For the auxiliary sheet, the upper sheet substrate and the lower sheet substrate of the auxiliary sheet were changed to a spunbond nonwoven fabric having a weight per unit area of 17 g/m ² (manufactured by Toray Polytech (Nantong) Co., Ltd., trade name: LIVSEN), and for auxiliary sheets An absorbent article was obtained in the same manner as in Example 1 except that the water absorbent resin particles were changed to the water absorbent resin particles F produced in Production Example 6.

Example 11

In Production Example 6, the upper sheet substrate and the lower sheet substrate of the auxiliary sheet were changed to an air-through nonwoven fabric manufactured by Rengo Non Woven Products Co., Ltd. having a weight per unit area of 21 g/m ² , and water absorbent resin particles for the auxiliary sheet in Production Example 6 Except having changed into the produced water absorbent resin particle F, it carried out similarly to Example 1, and obtained the water absorbent article.

Example 12

The sheet base material for the upper part of the auxiliary sheet was changed to an air-through nonwoven fabric manufactured by Hualong (Nanjing) having a weight per unit area of 45 g/m ² , and the water absorbent resin particles for the auxiliary sheet were changed to the water absorbent resin particles F produced in Preparation Example 6 Except having carried out, it carried out similarly to Example 1, and obtained the absorbent article.

Example 13

(Production of auxiliary sheet)

Using an airflow mixing device (manufactured by AUTEC Co., Ltd., Pad Former), 1.5 g of the water absorbent resin particles F of Preparation Example 6 and 1.5 g of the pulverized pulp were uniformly mixed by air blowing to form a sheet having a size of 40 cm × 10 cm stratum was created. Next, by applying a load of 196 kPa to the whole for 30 seconds in a state where the upper and lower sides of the resin layer are clamped with two tissues having a weight per unit area of 16 g/m ² having the same size as the sheet-like resin layer, water-absorbent resin particles and An auxiliary sheet was obtained in which a resin layer made of pulverized pulp was disposed between two tissues.

(Production of absorbent articles for testing)

The absorbent core A produced in Production Example 15 was placed on the obtained auxiliary sheet to obtain an absorbent article.

Example 14

An absorbent article was obtained in the same manner as in Example 1 except that the water absorbent resin particles for auxiliary sheets 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.

Example 15

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

Example 16

An absorbent article was obtained in the same manner as in Example 1 except that the water absorbent resin particles for auxiliary sheets 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.

Comparative Example 1

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

Comparative Example 2

An absorbent core was obtained in the same manner as in Production Example 15 except that the amount of the water absorbent resin particles to be sprayed between the air-laid nonwoven fabric-2 of Production Example 15 and the air-through nonwoven fabric was changed from 6.0 g to 5.0 g. Only the absorbent core obtained without using an 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 no water absorbent resin particles were 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 auxiliary sheets 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 auxiliary sheets 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 auxiliary sheets 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 auxiliary sheets 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 auxiliary sheets were changed to the water absorbent resin particles P produced in Production Example 14.

Comparative Example 9

Only the absorbent core produced 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: 9865.75g

·NaCl: 100.0g

·CaCl _{2 ·} H ₂ O: 3.0 g

·MgCl _{2 ·} 6H ₂ O: 6.0 g

・Triton X-100 (1%): 25.0 g

・Edible Blue No. 1 (for coloring): 0.25 g

[Measurement of absorption rate of liquid passing through dry powder]

The dry powder permeation absorption rate is calculated by the formula: dry powder permeation liquid absorption rate = dry powder liquid passage absorption amount (g)/0.2 g of artificial urine saturated liquid absorption amount (g) of the absorbent resin. The dry powder flow-through liquid absorption amount and the 0.2 g artificial urine saturated liquid absorption amount were measured and calculated by the method shown below.

[Measurement of the amount of liquid absorbed through dry powder]

5 is a schematic diagram showing a method for measuring the absorption rate of liquid passing through dry powder. In an acrylic resin cylindrical container 52 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 (eye size 50 μm) was adhered as a mesh-like bottom portion, 0.2 g of water absorbent resin particles 61a ) was uniformly spread, and the total mass Wb of the container and the water absorbent resin particles 61a spread in the container was measured.

A plastic beaker having an opening diameter of 60 mm and a height of 70 mm was used as the receiving unit 53 , and the cylindrical container 52 was placed on the receiving unit 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. . The stopwatch was started while injecting artificial urine (45) (20 mL) adjusted to the liquid temperature of 25 degreeC at a constant rate of 8 mL/sec. 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 is absorbed by the water absorbent resin particles 61a. In the cylindrical container 52 , the water-absorbing resin particles 61a absorb the artificial urine 45 to form a swollen gel.

30 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 (g) of liquid passing through dry powder was determined by Wa-Wb.

[Measurement of Saturated Artificial Urine Absorption Volume of Absorbent Resin Particles]

In a 500 mL beaker, weigh 500 g of artificial urine, and stir at 600 rpm (r/min) using a magnetic stirrer bar (8 mm φ × 30 mm, no ring). dispersed so as not to Stirring was continued for 60 minutes, and the water-absorbent resin particles were sufficiently swollen. The mass Wc (g) of a standard sieve with an eye size of 75 µm was previously measured, and using this, the contents of the beaker were filtered, and the excess water was separated by filtration by allowing it to stand for 1 minute. The mass Wd (g) of the sieve containing the swelling gel was measured, and the artificial urine saturated liquid absorption amount was calculated|required 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 × artificial urine saturated liquid absorption amount (g/g)

[Evaluation of the thickness of the auxiliary sheet]

The thickness of the auxiliary sheet was measured using a precision thickness gauge (manufactured by Ozaki Seisakusho, Dial Thinness Gauge J-B, and a measurer: φ50 mm made of aluminum). The measurement was performed at a position in contact with the center portion of the auxiliary sheet, and the average of the values measured three times was defined as the thickness (mm) of the auxiliary sheet.

[Evaluation of liquid leakage in the initial stage of absorption]

6 : is a schematic diagram which shows the apparatus which evaluates the liquid leakage of an absorbent article. Using the apparatus shown in FIG. 6, the following procedures (i), (ii), (iii) and (iv) evaluated the liquid leakage property of the absorbent article 100 for a test in the initial stage of liquid absorption. Table 1 shows the results. Resin in the table represents water-absorbing resin particles, and gsm represents g/m ² .

(i) A mechanical fastener (3M mechanical fastener hook) is cut to the size of an acrylic resin plate 1 having a rectangular main surface of 45 cm in length and 62 cm in width, and the main surface (S ₁ ) of the acrylic resin plate 1 is applied to the entire adhered. On the main surface S ₁ of the acrylic resin plate 1, very fine irregularities were generated by the mechanical fasteners, but there was no retention and absorption of the liquid on the main surface S ₁ of the acrylic resin plate 1 .

(ii) The acrylic resin plate ₁ was fixed with the main surface S1 to which the mechanical fastener was adhere|attached upward, using the mount 41 for laboratory equipment commercially available. At this time, the long side of the acrylic resin plate 1 is parallel to the horizontal plane, and the main surface and the horizontal plane S ₀ of the acrylic resin plate 1 are fixed to form 45±2 degrees. The absorbent article 100 for a test is placed on the main surface S ₁ of the fixed acrylic resin plate 1 in a direction whose long side is perpendicular to the long side of the acrylic resin plate 1, the absorbent article 100 for a test ) was affixed so that the lower end of the acrylic resin plate 1 was in the same position as the lower end. The absorbent article 100 for testing, which consists of an absorbent core and an auxiliary sheet, was affixed on the acrylic resin board 1 so that an absorbent core might become the front side. For fall prevention, the upper end of the absorbent article 100 for a test was fixed to the acrylic resin board 1 with the adhesive tape.

(iii) 8 cm above the center of the absorbent core in the absorbent article 100 for testing as an input point, and from a position 1 cm vertically upward from the input point, a dropping funnel 42 (a dropping funnel made by Cosmos Bead Co., Ltd. 300 mL capacity, tip portion (with an inner diameter of 8 mm x 6 mm), the artificial urine 45 of a predetermined amount adjusted to the liquid temperature of 25 degreeC at the speed|rate of 8 mL/sec was inject|poured. When the absorbent core A provided with the absorbent layer made of water absorbent resin particles is used, the injection amount of the artificial urine 45 is 80 mL, and artificial urine 45 is used when the absorbent core B provided with the absorbent layer made of water absorbent resin particles and ground pulp is used. The injection amount of urine 45 was 120 mL (in Table 1, the Example or Comparative Example marked with *).

(iv) The artificial urine leaked from the absorbent article 100 for a test was previously installed below the absorbent article 100, and was collect|recovered in the metal tray 44 arrange|positioned on the balance. The recovered artificial urine was measured, and the ratio (%) of the amount (g) of the leaked artificial urine with respect to the input amount (g) of the artificial urine was calculated.

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

10, 10A, 10B… absorbent layer
10a… absorbent resin particles
10b… fiber layer
20a, 20b... core wrap sheet
21… glue
25a, 25b, 25c... core wrap sheet
26a, 26b... glue
30… liquid permeable sheet
40… liquid impermeable sheet
50… absorbent core
51… Mesh (bottom on mesh)
52... cylindrical container
60… auxiliary seat
61... resin layer
61a… absorbent resin particles
61b... fiber layer
62a, 62b... sheet material
63a, 63b... glue
100… absorbent article

Claims (3)

an absorbent core, an auxiliary sheet for assisting liquid absorption by the absorbent core, a liquid impermeable sheet and a liquid permeable sheet, wherein the liquid impermeable sheet, the auxiliary sheet, the absorbent core and the liquid permeable sheet are disposed in this order As an absorbent article,
The auxiliary sheet includes a resin layer containing water-absorbing resin particles,
A dry powder liquid absorption rate of the water-absorbing resin particles measured by a method including the following steps (1), (2), (3), (4) and (5) in this order is 0.25 or more and 1.0 or less; absorbent article.
(1) 0.2 g of water-absorbent resin particles are uniformly spread over the entire bottom surface of a cylindrical container having an inner diameter of 60 mm having a mesh-like bottom, and the total mass Wb of the water-absorbing resin particles dispersed in the container and the container (g) is measured.
(2) 20 mL of artificial urine with a liquid temperature of 25° C. is injected into the container in which the water absorbent resin particles are sprayed at a constant rate of 8 mL/sec, at least a part of the artificial urine is absorbed into the water absorbent resin particles, and the swelling gel in the container to form
(3) After 30 seconds from the start of injection, the total mass Wa (g) of the container and the swelling gel in the container is measured.
(4) Calculate the amount (g) of liquid passing through dry powder from Wa(g)-Wb(g).
(5) As the ratio of the dry powder absorbed liquid amount (g) to the artificial urine saturated liquid absorption amount (g) of 0.2 g of water-absorbent resin particles, the dry powder passaged liquid absorption rate (g/g) is obtained. The method according to claim 1,
An absorbent article that is a diaper. An absorbent article having an absorbent core, comprising: an auxiliary sheet used to assist absorption of liquid by the absorbent core;
A resin layer comprising water-absorbing resin particles is provided,
A dry powder liquid absorption rate of the water-absorbing resin particles measured by a method including the following steps (1), (2), (3), (4) and (5) in this order is 0.25 or more and 1.0 or less; auxiliary sheet.
(1) 0.2 g of water-absorbent resin particles are uniformly spread over the entire bottom surface of a cylindrical container having an inner diameter of 60 mm having a mesh-like bottom, and the total mass Wb of the water-absorbing resin particles dispersed in the container and the container (g) is measured.
(2) 20 mL of artificial urine with a liquid temperature of 25° C. is injected into the container in which the water absorbent resin particles are sprayed at a constant rate of 8 mL/sec, at least a part of the artificial urine is absorbed into the water absorbent resin particles, and the swelling gel in the container to form
(3) After 30 seconds from the start of injection, the total mass Wa (g) of the container and the swollen gel in the container is measured.
(4) Calculate the amount (g) of liquid passing through dry powder from Wa(g)-Wb(g).
(5) As the ratio of the dry powder absorbed liquid amount (g) to the artificial urine saturated liquid absorption amount (g) of 0.2 g of water-absorbent resin particles, the dry powder passaged liquid absorption rate (g/g) is obtained.

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