HK1213167B - Absorbent article - Google Patents

Description

absorbent articles

Technical Field

The present invention relates to an absorbent article, and more particularly to preventing rashes on the user's skin and preventing odor of the absorbent article after absorbing body fluids.

Background Art

Absorbent articles such as disposable diapers, sanitary napkins, and incontinence pads are typically worn with their topsheets in direct contact with the wearer's skin. Therefore, if the topsheet becomes alkaline due to bodily fluids such as urination and menstrual blood, it creates an environment where sebum, proteins, and amino acids in the wearer's skin membranes can be easily lost, leading to skin rashes.

Absorbent articles for preventing such rashes have been proposed in the past. For example, Patent Document 1 discloses a disposable absorbent article for preventing or reducing diaper rash while absorbing excreted body fluids, characterized by comprising: (A) a liquid-impermeable backing sheet; (B) a relatively hydrophobic, liquid-permeable top sheet, wherein one or more pH adjusters are preferably incorporated therein or thereon, the pH adjusters being used to maintain the skin pH within a range of approximately 3.0 to 5.5 in the presence of urea; and (C) a plastic absorbent core located between the backing sheet and the top sheet (the plastic absorbent core being composed of an essentially hydrophilic fiber material and particles of a substantially water-insoluble, highly neutralized hydrogel material, wherein at least 50% of the acidic functional groups of the hydrogel material are neutralized by salt-forming cations.) (See Patent Document 1 (Claim 7)).

Prior art literature

Patent Literature

Patent Document 1: Japanese Patent Application Laid-Open No. 62-28402

Summary of the Invention

Problems to be solved by the invention

In the above-mentioned patent document 1, organic acids such as citric acid, adipic acid, and fumaric acid are listed as pH regulators (Patent Document 1, page 9, lower left column, line 18 to lower right column, line 3). However, since water-soluble compounds such as citric acid are easily dissolved and diffused in body fluids, they cannot be retained in the body fluid discharge site (urination site, menstrual blood discharge site). Therefore, the body fluid discharge site that contacts the user cannot be kept in a weakly acidic state, thereby failing to exert the effect of preventing rashes. In addition, in the above-mentioned patent document 1, a water-insoluble pH regulator such as fumaric acid is not actually used, nor is the carrying capacity of such a water-insoluble compound explored.

Furthermore, since putrefactive bacteria easily multiply in body fluids, used absorbent articles may emit a foul odor over time. However, there are no adequate countermeasures against the foul odor caused by putrefactive bacteria.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an absorbent article that can prevent rashes on the wearer's skin and suppress the generation of bad odor after absorbing body fluids.

Solutions to the Problem

The absorbent article of the present invention is characterized in that it comprises an absorbent body and a fumaric acid carrier sheet disposed on the skin surface side of the absorbent body, wherein the fumaric acid carrier sheet is a sheet carrying fumaric acid particles having an average particle size of 30 μm or less and/or a sheet having at least a portion of its constituent fibers coated with fumaric acid. Fumaric acid, which is poorly water-soluble, does not dissolve immediately even when it comes into contact with body fluids, but rather slowly dissolves into the body fluids. Therefore, the provision of a fumaric acid carrier sheet can prevent the surrounding area from becoming alkaline due to body fluids for a long time. If the average particle size of the fumaric acid particles in the fumaric acid carrier sheet is 30 μm or less, it is easy to carry on a supporting member (e.g., a sheet) and is not easily detached from the supporting member. Furthermore, if the constituent fibers are coated with fumaric acid, the fumaric acid is not easily detached from the constituent fibers. Therefore, if the fumaric acid carrier sheet is disposed in an area of the absorbent article that may come into contact with body fluids, rashes can be suppressed for a long time. Fumaric acid also has the effect of inhibiting the growth of putrefactive bacteria. Therefore, if a fumaric acid-supporting sheet is arranged at a portion of an absorbent article that may come into contact with body fluids (eg, around the water-absorbent resin powder), it is possible to prevent the absorbent article from generating bad odor after absorbing body fluids.

Preferably, at least a portion of the surface of the fumaric acid particles is coated with a dispersant. The fumaric acid loading of the fumaric acid-supporting sheet is preferably 0.01 g/m ² to 10 g/m ² . The dispersant is preferably at least one selected from the group consisting of anionic polymer dispersants, anionic surfactant dispersants, and nonionic surfactant dispersants.

Preferred embodiments of the absorbent article include, for example, a top sheet disposed on the skin-facing side of the absorbent body and a back sheet disposed on the outer surface of the absorbent body, wherein the top sheet is the fumaric acid-carrying sheet; or an embodiment wherein the top sheet is disposed on the skin-facing side of the absorbent body and the back sheet is disposed on the outer surface of the absorbent body, with the fumaric acid-carrying sheet disposed as an intermediate sheet between the absorbent body and the top sheet. The fumaric acid-carrying sheet is preferably a sheet in which the fumaric acid is carried by contacting a fumaric acid-containing liquid containing fumaric acid and a solvent with a sheet substrate and then removing the solvent. The fumaric acid-containing liquid preferably contains a dispersant.

Effects of the Invention

The absorbent article of the present invention can prevent rashes on the wearer's skin and suppress the generation of bad odor after absorbing body fluids.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic cross-sectional view of a fumaric acid-supported sheet.

FIG2 is a schematic cross-sectional view of another example of a fumaric acid-supported sheet.

FIG3 is a plan view of an example of the absorbent article of the present invention.

FIG4 is a schematic cross-sectional view along line V-V in FIG3 .

FIG5 is a schematic cross-sectional view of another example of the absorbent article of the present invention.

FIG6 is a schematic cross-sectional view of another example of the absorbent article of the present invention.

DETAILED DESCRIPTION

The absorbent article of the present invention is characterized in that it comprises an absorbent body and a fumaric acid-carrying sheet disposed on the skin-facing side of the absorbent body. The fumaric acid-carrying sheet is a sheet carrying fumaric acid particles having an average particle size of 30 μm or less and/or a sheet in which at least a portion of its constituent fibers are coated with fumaric acid. Fumaric acid has a water solubility of 0.63 g/100 g (at 25°C), making it poorly water-soluble. Even upon contact with body fluids, such fumaric acid does not dissolve immediately but dissolves slowly. Furthermore, fumaric acid has two carboxyl groups within its molecule, making it acidic in liquids. Therefore, placing the fumaric acid-carrying sheet in areas of the absorbent article that may come into contact with body fluids can prevent the surrounding area from becoming alkaline due to body fluids for a long period of time. If the average particle size of the fumaric acid particles in the fumaric acid-carrying sheet is 30 μm or less, the fumaric acid particles can be easily carried on a carrier member (e.g., a sheet such as a nonwoven fabric) and can also be prevented from falling off the carrier member. Furthermore, if the constituent fibers are coated with fumaric acid, the fumaric acid is less likely to fall off the constituent fibers. Therefore, by placing a fumaric acid carrier sheet on an absorbent article, the user's skin rashes can be suppressed for a long time. Furthermore, fumaric acid inhibits the growth of putrefactive bacteria. Therefore, placing a fumaric acid carrier sheet around absorbent resin powder that retains body fluids can prevent the absorbent article from generating foul odors after absorbing body fluids. The fumaric acid carrier sheet can be placed anywhere it can come into contact with the body fluids absorbed by the absorbent article, but is preferably placed on the side closer to the skin surface than the absorbent body, as described later.

Examples of the fumaric acid-supporting sheet used in the present invention include sheets supporting fumaric acid particles having an average particle size of 30 μm or less, and sheets in which at least a portion of the constituent fibers are coated with fumaric acid. Examples of the sheet substrate of the fumaric acid-supporting sheet include liquid-permeable sheet materials, such as nonwoven fabrics. Examples of such nonwoven fabrics include point-bonded nonwoven fabrics, air-through nonwoven fabrics, spunlace nonwoven fabrics, and spunbond nonwoven fabrics. Examples of the fibers forming these nonwoven fabrics include hydrophilic fibers such as cellulose, rayon, and cotton; hydrophobic fibers such as polypropylene, polyethylene, polyester, polyamide, and nylon; and hydrophobic fibers whose surfaces have been hydrophilized with a surfactant.

Examples of the sheet carrying the fumaric acid particles include a nonwoven fabric having fibers carrying fumaric acid particles. The average particle size of the fumaric acid particles used in the sheet carrying the fumaric acid particles is 30 μm or less, preferably 25 μm or less, and more preferably 20 μm or less. An average particle size of 30 μm or less facilitates carrying the fumaric acid particles on a sheet such as a nonwoven fabric and also prevents them from falling off the sheet. The lower limit of the average particle size of the fumaric acid particles is not particularly limited, but is preferably 0.05 μm. In the present invention, the average particle size of the fumaric acid particles can be measured using a laser diffraction/scattering particle size analyzer before being supported on the sheet substrate. Furthermore, in the case where the fumaric acid particles are supported by contacting the sheet substrate with a fumaric acid particle dispersion, as described later, the average particle size of the fumaric acid particles in the fumaric acid particle dispersion is considered to be the average particle size of the fumaric acid particles supported on the fumaric acid-supporting sheet. The average particle size of the fumaric acid particles in the fumaric acid particle dispersion can be measured using a laser diffraction/scattering particle size analyzer. In the present invention, the average particle size of the fumaric acid particles is a volume-based average particle size.

Preferably, at least a portion of the particle surface of the fumaric acid particles is coated with a dispersant. By coating with the dispersant, the dispersant acts as a binder between the fumaric acid particles and the sheet substrate. Therefore, the retention of the fumaric acid particles on the supporting member can be further improved, thereby further reducing the fumaric acid particles from falling off the sheet substrate. In addition, in the case of supporting the fumaric acid particles by coating a fumaric acid particle dispersion on the sheet substrate as described later, the fumaric acid particles can be more evenly dispersed by adding a dispersant to the dispersion. In addition, coating the fumaric acid particles with a dispersant can be carried out by mixing the fumaric acid particles, the dispersant, and the solvent and then removing the solvent.

The dispersant is not particularly limited as long as it has an effect of improving the dispersibility of the fumaric acid particles in the dispersion, and for example, a polymeric dispersant or a surfactant-type dispersant can be used. The polymeric dispersant and the surfactant-type dispersant include anionic, nonionic, and cationic dispersants, respectively, with anionic or nonionic dispersants being preferred.

The polymeric dispersant has a repulsive effect due to the steric hindrance of the dispersant molecules, thereby providing excellent long-term dispersion stability. Furthermore, the polymeric dispersant functions well as a binder for bonding the fumaric acid particles to the support member. The weight-average molecular weight of the polymeric dispersant is preferably greater than 1,000, preferably less than 200,000, and more preferably less than 100,000.

As anionic polymer dispersants, polycarboxylic acid (salt) type dispersants, polysulfonic acid type dispersants, etc. can be cited. As the polycarboxylic acid (salt) type dispersants, unsaturated carboxylic acid (co) polymers (such as polyacrylic acid, isobutylene-maleic acid copolymer, diisobutylene-maleic acid copolymer, styrene-maleic acid copolymer, styrene-maleic acid-(methyl) acrylate copolymer, (methyl) acrylic acid-(methyl) acrylate copolymer, etc.), carboxylated polysaccharides (such as carboxymethyl cellulose, etc.) and salts of these substances (such as organic amine salts, alkali metal salts, alkaline earth metal salts). As the polysulfonic acid type dispersants, naphthalenesulfonic acid formalin condensates, polystyrene sulfonic acid, and salts of these substances (such as organic amine salts, alkali metal salts, alkaline earth metal salts) can be cited. As nonionic polymer dispersants, polyvinyl alcohol, polyethylene glycol, etc. can be cited. Examples of cationic polymer dispersants include inorganic acid (hydrochloric acid, phosphoric acid, etc.) or organic acid (formic acid, acetic acid, lactic acid, etc.) salts of N,N-dialkylaminoalkyl (meth)acrylate (co)polymers. In N,N-dialkylaminoalkyl (meth)acrylate (co)polymers, the alkyl group bonded to the nitrogen atom preferably has 1 to 3 carbon atoms, and the alkenyl group preferably has 2 or 3 carbon atoms.

The surfactant-type dispersant is adsorbed on the surface of the fumaric acid particles to improve the wettability of the fumaric acid particles to the solvent. The weight average molecular weight of the surfactant-type dispersant is preferably greater than 100 and preferably less than 10,000.

Examples of anionic surfactant-type dispersants include carboxylic acid (salt) dispersants, sulfonic acid (salt) dispersants, and sulfate ester salts. Examples of carboxylic acid (salt) dispersants include salts of fatty acids having 6 to 15 carbon atoms (e.g., organic amine salts, alkali metal salts, and alkaline earth metal salts). Examples of sulfonic acid (salt) dispersants include dialkyl sulfosuccinates (e.g., organic amine salts, alkali metal salts, and alkaline earth metal salts). In dialkyl sulfosuccinates, the alkyl group preferably has 6 to 15 carbon atoms. Examples of sulfate ester salts include polyoxyalkylene alkyl ether sulfates (e.g., organic amine salts, alkali metal salts, and alkaline earth metal salts) and polyoxyalkylene alkylphenyl ether sulfates (e.g., organic amine salts, alkali metal salts, and alkaline earth metal salts). In polyoxyalkylene alkyl ether sulfates and polyoxyalkylene alkylphenyl ether sulfates, the alkenyl group preferably has 2 to 4 carbon atoms, and the alkyl group preferably has 1 to 20 carbon atoms. Examples of nonionic surfactant-type dispersants include polyoxyalkylene dispersants and polyol dispersants. Examples of polyoxyalkylene dispersants include polyoxyalkylene alkyl ethers, polyoxyalkylene fatty acid esters, polyoxyalkylene polyol fatty acid esters, polyoxyalkylene alkylphenyl ethers, polyoxyalkylene alkylamino ethers, and polyoxyethylene/propylene block polymers. Examples of polyol-type dispersants include polyol fatty acid esters, polyol alkyl ester ethers, and fatty acid dialkanolamides. Examples of cationic surfactant-type dispersants include quaternary ammonium salt-type dispersants.

Among these, as the dispersant, anionic polymer dispersants, anionic surfactant dispersants, and nonionic surfactant dispersants are preferred, anionic polymer dispersants are more preferred, and polycarboxylate (salt) dispersants are particularly preferred.

If a polycarboxylate dispersant is used, aggregates of fumaric acid particles can be more easily separated and ground by mechanical manipulation in a fumaric acid particle dispersion. Furthermore, the polycarboxylate adsorbed on the particle surface dissociates to form an electrical double layer, which inhibits the reaggregation of fumaric acid particles through electrical repulsion. Consequently, the fumaric acid particles in the fumaric acid particle dispersion have improved dispersion stability.

Specific examples of polycarboxylate (salt) type dispersants include “Charibon (registered trademark) B”, “Charibon L-400”, “Charibon AR-33”, “Sunspread (registered trademark) PS-8”, and “Grann App (registered trademark) PC-121” sold by Sanyo Chemical Industries, Ltd., “UTC-124” sold by Takemoto Oil & Fats Co., Ltd., “Shallol (registered trademark) AN-103P” and “Shallol AN-144P” sold by Dai-ichi Kogyo Seiyaku Co., Ltd., and “Sharknare A-818” sold by San Nopco.

Relative to 100 mass parts of fumaric acid particles, the consumption of described dispersant is preferably more than 1 mass part, more preferably more than 2 mass parts, further preferably more than 5 mass parts, preferably below 50 mass parts, more preferably below 45 mass parts, further preferably below 40 mass parts.If the consumption of dispersant is within the above scope, then the dispersion stability of fumaric acid particles improves. On the other hand, even if the consumption of dispersant surpasses 50 mass parts, also can not see the raising of dispersion stability, poor economy, and dispersion liquid viscosity increases, and operability may decline.

As the sheet in which at least a portion of the constituent fibers is coated with fumaric acid, a non-woven fabric in which at least a portion of the constituent fibers is coated with fumaric acid can be cited. In the case where the constituent fibers are coated with fumaric acid, there is no particular limitation on the fibers used, but fibers having polar groups (hydroxyl groups, ester groups, ether groups, etc.) are preferred. If fibers having polar groups are used as fibers, it is believed that it is easier to coat them through hydrogen bonds. In addition, if the method described later is to coat the fibers with fumaric acid by contacting the sheet substrate with a fumaric acid solution, even hydrophobic fibers can be easily coated. In the case where the constituent fibers are coated with fumaric acid, the thickness of the fumaric acid coating the fibers is preferably 0.1 μm or less.

The fumaric acid loading of the fumaric acid-supporting sheet is preferably 0.01 g/ ^m² or greater, more preferably 0.02 g/ ^m² or greater, even more preferably 0.03 g/m² or ^greater , preferably 10 g/m² or ^less , more preferably 5.0 g/m² or ^less , even more preferably 4.5 g/ ^m² or less, and particularly preferably 4.0 g/ ^m² or less. Within this range, the effects of suppressing skin irritation and odor are further enhanced. The fumaric acid loading can be determined by Soxhlet extraction of a fumaric acid-supporting sheet cut into a certain size (e.g., 1 ^cm² ) with a large amount of ethanol (e.g., 2 L), dissolving all the supported fumaric acid, and measuring the mass of the fumaric acid in the solution. Alternatively, when a fumaric acid-containing liquid is sprayed onto the sheet substrate as described below, the fumaric acid concentration can also be determined based on the fumaric acid concentration of the fumaric acid-containing liquid and the amount of liquid sprayed.

Furthermore, the ratio of the amount of fumaric acid supported on the fumaric acid-supported sheet to the mass per unit area of the water-absorbent resin powder in the absorbent article described below (fumaric acid supported amount/mass per unit area of the water-absorbent resin powder) is preferably 0.001 or more, more preferably 0.002 or more, and even more preferably 0.003 or more, and is preferably 20 or less, more preferably 18 or less, and even more preferably 16 or less. When the ratio is within the above range, the effects of suppressing skin irritation and odor are further enhanced.

The fumaric acid-carrying sheet can be obtained by carrying fumaric acid particles on a sheet substrate or coating the fibers constituting the sheet substrate with fumaric acid. There are no particular limitations on the method for preparing the fumaric acid-carrying sheet, and examples include: a method of sprinkling fumaric acid particle powder on a carrier member; a method of contacting a fumaric acid-containing liquid containing fumaric acid and a solvent with the sheet substrate and then removing the solvent; and the like. Examples of embodiments for carrying fumaric acid particles on a sheet substrate include: a method of spraying a dispersion containing fumaric acid particles on a carrier member and then removing the solvent; and a method of immersing a carrier member in a dispersion containing fumaric acid particles and then removing the solvent. Examples of embodiments for coating the fibers constituting the sheet substrate with fumaric acid include: a method of spraying a fumaric acid solution containing fumaric acid on a carrier member and then removing the solvent; and a method of immersing a carrier member in a fumaric acid solution containing fumaric acid and then removing the solvent. Furthermore, when preparing an absorbent article, a fumaric acid-carrying sheet can be prepared in advance and used as a top sheet, a middle sheet, or the like. Furthermore, when producing an absorbent article, a sheet substrate that does not carry fumaric acid may be disposed as a top sheet, an intermediate sheet, or the like, and then the fumaric acid-containing liquid may be sprayed onto the sheet substrate.

The fumaric acid content in the fumaric acid-containing liquid is preferably 0.05% by mass or greater, more preferably 0.10% by mass or greater, and even more preferably 0.15% by mass or greater, and is preferably 50% by mass or less, more preferably 47% by mass or less, and even more preferably 45% by mass or less. When the fumaric acid content is within this range, the supportability on the support member is further improved.

In addition, the fumaric acid-containing liquid preferably contains the above-mentioned dispersant. The content of the dispersant in the fumaric acid-containing liquid is preferably 1 part by mass or more, more preferably 2 parts by mass or more, further preferably 5 parts by mass or more, preferably 50 parts by mass or less, more preferably 45 parts by mass or less, and further preferably 40 parts by mass or less, relative to 100 parts by mass of fumaric acid. If the content of the dispersant is within the above-mentioned range, the dispersion stability of the fumaric acid particles is improved. On the other hand, even if the amount of the dispersant used exceeds 50 parts by mass, no improvement in dispersion stability is seen, resulting in poor economic efficiency, and the dispersion liquid may increase in viscosity, which may reduce workability.

As the solvent of the fumaric acid-containing liquid, water, a mixed solution of water and a hydrophilic organic solvent, etc. can be used. Examples of the hydrophilic organic solvent include methanol, ethanol, acetone, glycerol, ethylene glycol, propylene glycol, etc. As a method for removing the solvent, a method of bringing the dispersion into contact with a support member and then volatilizing the solvent can be mentioned.

The absorbent article of the present invention has an absorbent body that can absorb body fluids. The absorbent body is composed of at least one absorbent layer. The absorbent layer preferably contains the absorbent resin powder as the absorbent material. The absorbent layer may further contain absorbent fibers as the absorbent material. Examples of the absorbent fibers include pulp fibers, cellulose fibers, and rayon. In addition to the absorbent resin powder, the absorbent layer may also contain a fiber base material. Examples of the fiber base material include thermal bonding fibers. Thermal bonding fibers are used to improve shape retention. Specific examples of thermal bonding fibers include polyolefin fibers such as polyethylene and polypropylene, polyester fibers, and composite fibers. An absorbent layer containing only absorbent resin powder as the absorbent material can be made thinner, while an absorbent layer containing a fiber base material has excellent body fluid dispersion.

The absorbent layer can be obtained, for example, by mixing granular water-absorbent resin powder with an aggregate layer of hydrophilic fibers such as crushed pulp fibers or cellulose fibers, fixing the mixture on a paper sheet such as tissue paper or a liquid-permeable nonwoven fabric sheet, or wrapping the mixture with a liquid-permeable nonwoven fabric sheet, and molding the mixture into a predetermined shape such as a rectangle, an hourglass, a gourd, or a badminton bat.

The water-absorbent resin powder used in the present invention is not particularly limited, but preferably uses a cross-linked polymer (A) composed primarily of acrylic acid, at least some of whose carboxyl groups are neutralized. The content of the acrylic acid component constituting the cross-linked polymer (A) is preferably 90% by mass or greater, more preferably 95% by mass or greater, and preferably 99% by mass or less, more preferably 97% by mass or less. When the acrylic acid content is within the above range, the resulting water-absorbent resin powder readily exhibits desired absorption performance.

The cations that neutralize at least a portion of the carboxyl groups of the crosslinked polymer (A) are not particularly limited; examples include alkali metal ions such as lithium, sodium, and potassium; and alkaline earth metal ions such as magnesium and calcium. The degree of neutralization of the carboxyl groups of the crosslinked polymer is preferably 60 mol% or greater, more preferably 65 mol% or greater. This is because if the neutralization degree is too low, the absorption performance of the resulting water-absorbent resin powder may be reduced. There is no particular upper limit on the degree of neutralization; all carboxyl groups may be neutralized. The degree of neutralization is calculated according to the following formula.

Neutralization degree (mol %) = 100 × [number of moles of neutralized carboxyl groups in the cross-linked polymer] / [total number of moles of carboxyl groups in the cross-linked polymer (including neutralized and unneutralized carboxyl groups)]

The cross-linked polymer is preferably obtained by polymerizing an unsaturated monomer composition containing (a1) a water-soluble ethylenically unsaturated monomer and/or (a2) a hydrolyzable monomer that generates the (a1) water-soluble ethylenically unsaturated monomer by hydrolysis, and (b) an internal cross-linking agent.

As the water-soluble ethylenically unsaturated monomer (a1), for example, a monomer having at least one water-soluble substituent and an ethylenically unsaturated group can be used. A water-soluble monomer is a monomer that dissolves at least 100 g in 100 g of water at 25°C. Furthermore, the hydrolyzable monomer (a2) is hydrolyzed in 50°C water under the action of a catalyst (such as an acid or base) as needed to produce the water-soluble ethylenically unsaturated monomer (a1). The hydrolysis of the hydrolyzable monomer (a2) can be performed during polymerization of the cross-linked polymer, after polymerization, or both. However, from the perspective of the molecular weight of the resulting water-absorbent resin powder, it is preferably performed after polymerization.

Examples of water-soluble substituents include carboxyl groups, sulfo groups, sulfonyloxy groups, phosphoryl groups, hydroxyl groups, carbamoyl groups, amine groups, or salts thereof and ammonium salts. Preferred are carboxyl salts (carboxylates), sulfo salts (sulfonates), and ammonium salts. Examples of salts include alkali metal salts such as lithium, sodium, and potassium; and alkaline earth metal salts such as magnesium and calcium. Ammonium salts may be salts of primary or tertiary amines or quaternary ammonium salts. Among these salts, alkali metal salts and ammonium salts are preferred from the perspective of absorption properties, alkali metal salts are more preferred, and sodium salts are even more preferred.

As the water-soluble ethylenically unsaturated monomer having a carboxyl group and/or its salt, an unsaturated carboxylic acid having 3 to 30 carbon atoms and/or its salt is preferred. Specific examples of the water-soluble ethylenically unsaturated monomer having a carboxyl group and/or its salt include: unsaturated monocarboxylic acids and/or their salts such as (meth)acrylic acid and (meth)acrylates; unsaturated dicarboxylic acids and/or their salts such as maleic acid and maleate; monoalkyl esters of unsaturated dicarboxylic acids and/or their salts such as monobutyl maleate. In addition, in the description of the present invention, "(meth)propylene" means "propylene" and/or "methpropylene". As the water-soluble ethylenically unsaturated monomer having a sulfonic group and/or its salt, vinyl sulfonic acid, styrene sulfonic acid, etc. can be cited.

The (a2) hydrolyzable monomer is not particularly limited, but preferably is an ethylenically unsaturated monomer having at least one hydrolyzable substituent that forms a water-soluble substituent by hydrolysis. Examples of the hydrolyzable substituent include acid anhydride groups, ester bond groups, and cyano groups. Examples of ethylenically unsaturated monomers having an acid anhydride group include unsaturated dicarboxylic acid anhydrides having 4 to 20 carbon atoms. Examples of ethylenically unsaturated monomers having an ester bond group include lower alkyl esters of ethylenically unsaturated carboxylic acids and esters of ethylenically unsaturated alcohols. Examples of ethylenically unsaturated monomers having a cyano group include vinyl-containing nitrile compounds such as (meth)acrylonitrile.

The water-soluble ethylenically unsaturated monomer (a1) and the hydrolyzable monomer (a2) may be used alone or as a mixture of two or more thereof. The same applies when the water-soluble ethylenically unsaturated monomer (a1) and the hydrolyzable monomer (a2) are used in combination.

As monomers constituting the crosslinked polymer (A), in addition to the water-soluble ethylenically unsaturated monomer (a1) and the hydrolyzable monomer (a2), other vinyl monomers (a3) copolymerizable with these monomers may be used. As the other vinyl monomers (a3), hydrophobic vinyl monomers may be used, but are not limited thereto. In addition, from the viewpoint of absorption properties, the content of the other vinyl monomers (a3) is preferably 0 mol%.

Examples of the (b) internal crosslinking agent include: (b1) an internal crosslinking agent having two or more ethylenically unsaturated groups; (b2) an internal crosslinking agent having at least one functional group that can react with the water-soluble substituent of the (a1) water-soluble ethylenically unsaturated monomer and/or the water-soluble substituent generated by hydrolysis of the (a2) hydrolyzable monomer and having at least one ethylenically unsaturated group; and (b3) an internal crosslinking agent having at least two functional groups that can react with the water-soluble substituent of the (a1) water-soluble ethylenically unsaturated monomer and/or the water-soluble substituent generated by hydrolysis of the (a2) hydrolyzable monomer.

Examples of the internal crosslinking agent (b1) include bis(meth)acrylamide having 8 to 12 carbon atoms, poly(meth)acrylates of polyols having 2 to 10 carbon atoms, polyallylamine having 2 to 10 carbon atoms, and poly(meth)allyl ethers of polyols having 2 to 10 carbon atoms. Specific examples thereof include N,N'-methylenebis(meth)acrylamide, ethylene glycol di(meth)acrylate, poly(polymerization degree 2 to 5) ethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, glycerol (di or tri)acrylate, trimethylolpropane triacrylate, diallylamine, triallylamine, triallyl cyanurate, triallyl isocyanurate, tetraallyloxyethane, pentaerythritol diallyl ether, pentaerythritol triallyl ether, pentaerythritol tetraallyl ether, and diglycerol di(meth)acrylate.

Examples of the internal bridging agent (b2) include ethylenically unsaturated compounds having 6 to 8 carbon atoms and having an epoxy group, ethylenically unsaturated compounds having 4 to 8 carbon atoms and having a hydroxyl group, and ethylenically unsaturated compounds having 4 to 8 carbon atoms and having an isocyanate group.

Examples of the internal bridging agent (b3) include polyols, polyglycidols, polyamines, polyaziridines, and polyisocyanates.

As the polymerization method of the cross-linked polymer (A), known methods can be used, such as solution polymerization, emulsion polymerization, suspension polymerization, and reversed suspension polymerization. In addition, the polymer liquid form during polymerization can be thin film-like and mist-like. As the method for controlling polymerization, adiabatic polymerization, temperature-controlled polymerization, and isothermal polymerization can be used. When suspension polymerization or reversed suspension polymerization is used as the polymerization method, known dispersants and protective colloids can be used as needed. In addition, during reversed suspension polymerization, solvents such as hexane can be used for polymerization. As the polymerization method, solution polymerization is preferred, and aqueous solution polymerization is more preferred because it is not necessary to use an organic solvent and is advantageous in terms of production cost.

The hydrogel (composed of a cross-linked polymer and water) obtained by polymerization can be minced as needed. The size (maximum diameter) of the minced gel is preferably 50 μm to 10 cm. Within this range, drying efficiency during the drying process is improved. Mincing can be performed using known methods, for example, using known mincing devices such as a Bexmill, a rubber cutter, a pharmaceutical mill, a mincer, an impact mill, and a roller mill.

When a solvent (organic solvent, water, etc.) is used during polymerization, it is preferably removed by distillation after polymerization. If the solvent contains an organic solvent, the organic solvent content (mass %) after distillation is preferably 0% to 10% by mass relative to the mass of the cross-linked polymer (100% by mass). Within this range, the absorbent resin powder exhibits improved absorption performance (particularly water retention).

As methods for distilling off the solvent (including water), there can be used: a method of distilling off (drying) using hot air at a temperature of 80°C to 230°C, a thin film drying method using a drum dryer heated to 100°C to 230°C, a (heating) reduced pressure drying method, a freeze drying method, a drying method using infrared rays, decantation and filtration, etc.

The cross-linked polymer (A) can be pulverized after drying. There are no particular restrictions on the pulverization method. For example, a conventional pulverizing device such as a hammer mill, an impact mill, a roller mill, and a jet mill can be used. The particle size of the pulverized cross-linked polymer (A) can be adjusted by sieving or the like as needed. The weight average particle size (μm) of the cross-linked polymer (A) is preferably 100 μm to 800 μm. If the weight average particle size (μm) of the cross-linked polymer (A) is within the above range, the absorption performance is better. In addition, the weight average particle size is measured using a ro-tap test sieve shaker and a standard sieve (JIS Z8801-1: 2006) according to the method described in Perry's Chemical Engineer's Handbook, 6th edition (McGraw-Hill Companies, 1984, page 21).

The cross-linked polymer (A) may be surface cross-linked as needed. The same cross-linking agent as used for the internal cross-linking agent (b) can be used as the cross-linking agent for surface cross-linking. From the perspective of the absorbent properties of the water-absorbent resin powder, the surface cross-linking agent is preferably the cross-linking agent (b3), more preferably polyglycidol, further preferably ethylene glycol diglycidyl ether and glycerol diglycidyl ether, and most preferably ethylene glycol diglycidyl ether.

The cross-linked polymer (A) may be a single species or a mixture of two or more species. The cross-linked polymer (A) may be further treated with a surface modifier (B). Examples of the surface modifier (B) include polyvalent metal compounds such as aluminum sulfate, potassium alum, ammonium alum, sodium alum, (poly)aluminum chloride, and hydrates thereof; polycationic compounds such as polyethyleneimine, polyvinylamine, and polyallylamine; inorganic microparticles; (B1) surface modifiers containing hydrocarbon groups; (B2) surface modifiers containing hydrocarbon groups with fluorine atoms; and (B3) surface modifiers having a polysiloxane structure.

Examples of the inorganic fine particles include oxides such as silicon oxide (silica), aluminum oxide (alumina), iron oxide, titanium oxide, magnesium oxide, and zirconium oxide; carbides such as silicon carbide and aluminum carbide; nitrides such as titanium nitride; and composites thereof (e.g., zeolite and talc). Among these, oxides are preferred, and silicon oxide is more preferred. The volume average particle size of the inorganic fine particles is not particularly limited, but is preferably 1 nm to 500 nm. The specific surface area of the inorganic fine particles is preferably 20 m ² /g to 4000 ^{m 2} /g. When the specific surface area is within this range, the absorption performance is better. The specific surface area is measured in accordance with JIS Z8830:2001 (nitrogen, volumetric method, multipoint method).

The method for treating the cross-linked polymer (A) with the surface modifier (B) is not particularly limited as long as the surface modifier (B) is present on the surface of the cross-linked polymer (A). However, from the perspective of controlling the amount of the surface modifier (B) on the surface, it is preferred that the surface modifier (B) be mixed with the dried product of the cross-linked polymer (A) rather than with the aqueous gel of the cross-linked polymer (A) or the polymerization solution before polymerization of the cross-linked polymer (A). Furthermore, uniform mixing is preferred.

The shape of the water-absorbent resin powder is not particularly limited, and examples thereof include amorphous crushed shapes, flaky shapes, pearly shapes, and rice grain shapes. Of these, amorphous crushed shapes are preferred from the perspective of being well entangled with fibrous materials in applications such as disposable diapers, without the risk of them falling off the fibrous materials.

The absorption rate of the water-absorbent resin powder, as measured by the vortex method, is preferably 5 seconds or longer, more preferably 7 seconds or longer, and preferably 55 seconds or shorter, more preferably 53 seconds or shorter. If the absorption rate exceeds 55 seconds, the body fluid may not be fully absorbed when the body fluid is excreted rapidly and a large amount of body fluid is excreted at once. This can lead to fluid leakage. While a lower absorption rate is preferred, if it is less than 5 seconds, the stability of the water-absorbent resin powder to urine, particularly its stability under load, may decrease. The absorption rate measured by the vortex method is evaluated by measuring the time (in seconds) required to absorb body fluid. Therefore, the shorter the measurement time (in seconds), the faster the water-absorbent resin powder absorbs body fluid.

The absorbency of the water-absorbent resin powder is preferably 50 g/g or greater and 70 g/g or less. It is more preferably 52 g/g or greater, particularly preferably 54 g/g or greater, more preferably 68 g/g or less, and particularly preferably 64 g/g or less. The absorbency is a measure of how much water the water-absorbent resin powder can absorb. An absorbency of 50 g/g or greater allows the absorption capacity to be maintained at a predetermined level with a small amount of water-absorbent resin powder, making it easy to manufacture a thin absorbent body. From the perspective of preventing liquid leakage, a higher absorbency is preferred, but it is preferably 70 g/g or less. This is because an absorbency of 70 g/g or less improves the stability of the water-absorbent resin powder to urine.

The water retention capacity of the water-absorbent resin powder is preferably 20 g/g or greater and 65 g/g or less. It is more preferably 22 g/g or greater, particularly preferably 24 g/g or greater, more preferably 63 g/g or less, and particularly preferably 61 g/g or less. Water retention is a measure of how much absorbed liquid a water-absorbent resin powder can hold. A water retention capacity of 20 g/g or greater allows for maintaining a desired level of bodily fluid retention with a small amount of water-absorbent resin powder, making it easier to manufacture thin absorbents. From the perspective of preventing liquid leakage, a higher water retention capacity is preferred, but preferably 65 g/g or less. This is because a water retention capacity of 65 g/g or less improves the stability of the water-absorbent resin powder to urine.

The absorption rate, absorption ratio, and water retention capacity of the water-absorbent resin powder can be adjusted by appropriately selecting the composition of the cross-linked polymer (A), the type of the surface modifier, the particle size of the water-absorbent resin powder, and the drying conditions.

The water-absorbent resin powder may contain additives such as preservatives, antifungal agents, antibacterial agents, antioxidants, ultraviolet absorbers, colorants, fragrances, deodorants, inorganic powders, and organic fibers. Examples of additives include those listed in Japanese Patent Application Laid-Open Nos. 2003-225565 and 2006-131767. When these additives are present, the content (mass %) of the additive relative to the cross-linked polymer (A) (100 mass %) is preferably 0.001 to 10 mass %, more preferably 0.01 to 5 mass %, even more preferably 0.05 to 1 mass %, and most preferably 0.1 to 0.5 mass %.

The mass per unit area of the water-absorbent resin powder in the absorbent article is preferably 50 g/ ^m² or greater, more preferably 75 g/ ^m² or ^greater , and even more preferably 100 g/m² or greater, and preferably 800 g/ ^m² or less, more preferably 700 g/ ^m² or less, and even more preferably 600 g/ ^m² or less. A mass per unit area of 50 g/m² or ^greater further improves the strength of the absorbent. A mass per unit area of 600 g/m² or ^less improves the feel of the absorbent.

Next, the structure of the absorbent article of the present invention will be described. Examples of the absorbent article structure of the present invention include: (1) an absorbent article comprising an absorbent body, a top sheet disposed on the skin surface side of the absorbent body, and a back sheet disposed on the outer surface side of the absorbent body, wherein the top sheet is an embodiment of the fumaric acid carrier sheet; (2) an absorbent article comprising an absorbent body, a top sheet disposed on the skin surface side of the absorbent body, and a back sheet disposed on the outer surface side of the absorbent body, wherein an intermediate sheet is disposed between the absorbent body and the top sheet, wherein the intermediate sheet is an embodiment of the fumaric acid carrier sheet; and (3) an absorbent article comprising an absorbent body, a top sheet disposed on the skin surface side of the absorbent body, and a back sheet disposed on the outer surface side of the absorbent body, wherein the absorbent body is wrapped with the fumaric acid carrier sheet.

Specific application examples of the absorbent article of the present invention are described below. Examples of the absorbent article of the present invention include absorbent articles for absorbing body fluids discharged from the human body, such as incontinence pads, disposable diapers, and sanitary napkins.

When the absorbent article is an incontinence pad or sanitary napkin, for example, an absorbent body and, if necessary, an intermediate sheet can be arranged between a liquid-permeable top sheet and a liquid-impermeable back sheet. The top sheet and/or the intermediate sheet can be a fumaric acid carrier sheet. Examples of the shape of the incontinence pad or sanitary napkin include a roughly rectangular, hourglass-shaped, gourd-shaped, and the like. In addition, as needed, liquid-impermeable side sheets can be provided on both sides of the liquid-permeable top sheet in the width direction. The side sheets are connected to the upper surface of both sides of the top sheet in the width direction, and the side sheets on the inner side of the connection point in the width direction form a pair of upright wings along the two side edges of the absorbent body.

The liquid-permeable top sheet and the intermediate sheet are liquid-permeable sheet materials, for example, nonwoven fabrics formed by hydrophilic fibers, which rapidly capture the wearer's body fluids and transfer them to the absorbent. The nonwoven fabric used as the top sheet can be, for example, point-bonded nonwoven fabrics, hot air nonwoven fabrics, spunlace nonwoven fabrics, or spunbonded nonwoven fabrics. As the hydrophilic fibers forming these nonwoven fabrics, cellulose, rayon, cotton, etc. can be used usually. In addition, as the top sheet, the liquid-permeable nonwoven fabric formed by the hydrophobic fibers (for example, polypropylene, polyethylene, polyester, polyamide, nylon) that have been hydrophilized by surface surfactants can also be used.

As the liquid-impermeable sheet for back sheet, side sheet, for example, can utilize the waterproofness formed by hydrophobic fiber (for example polypropylene, polyethylene, polyester, polyamide, nylon) or liquid-impermeable nonwoven fabric (for example spunbond nonwoven fabric, meltblown nonwoven fabric, SMS (spunbond meltblown spunbond) nonwoven fabric) and waterproofness or liquid-impermeable plastic film etc., be used to prevent the body fluid that arrives at liquid-impermeable sheet from seeping into the absorbent article outside.When plastic film is used in liquid-impermeable sheet, from the viewpoint of preventing damp feeling to improve wearer's comfort, preferably use plastic film with moisture permeability (breathability).In addition, in order to further give diffusivity and shape stability, also can configure paper sheet between plastic film and absorbent.

When the absorbent article is a disposable diaper, examples of the disposable diaper include: an unfolded disposable diaper having a pair of fastening members on the left and right sides of the back or front abdomen, which are formed into a shorts shape by the fastening members when worn; and a shorts-type disposable diaper having a waist opening and a pair of leg openings formed by connecting the front abdomen and the back.

When absorbent article is disposable diaper, in disposable diaper, for example, the laminated body that can be made of inner sheet and outer sheet forms the diaper main body that is made of front abdomen, back and the crotch portion positioned therebetween, and the described water-absorbing layer is configured in the described crotch portion.In addition, disposable diaper for example also can be made of the laminated body that has been configured with absorbent body between top sheet and back sheet, and this laminated body has front abdomen, back and the crotch portion positioned therebetween.In addition, front abdomen, back and crotch portion refer to that, when wearing disposable diaper, the position that connects with the wearer's ventral side is called front abdomen, the position that connects with the wearer's hip side is called back, and the position that is positioned between front abdomen and back and connects with the wearer's crotch portion is called crotch portion. The preferred hydrophilicity or waterproofness of described inner sheet, the preferred waterproofness of described outer sheet.

Preferably, the absorbent article has raised wings along the side edges of the absorbent body. These raised wings can be positioned, for example, on the widthwise edges of the upper surface of the absorbent body, or on the widthwise outer sides of the absorbent body. The raised wings can prevent side leakage of bodily fluids. The raised wings can also be formed by rising from the inner sides of side panels positioned on both sides of the top sheet in the widthwise direction. The raised wings and side panels are preferably waterproof.

Hereinafter, the absorbent article of the present invention will be described with reference to the drawings, but the present invention is not limited to the embodiments shown in the drawings.

Figures 1 and 2 are schematic cross-sectional views illustrating embodiments of a fumaric acid-supporting sheet. In Figures 1 and 2, the upper side in the C direction of the paper is the skin surface side, and the lower side is the outer surface side. In the fumaric acid-supporting sheet 1 shown in Figure 1, particles of fumaric acid 2 having an average particle size of 30 μm or less are supported on fibers 3 constituting a substrate sheet. In the fumaric acid-supporting sheet 1 shown in Figure 1, the particles of fumaric acid 2 may also be coated with a dispersant (not shown). In the fumaric acid-supporting sheet 1 shown in Figure 2, at least a portion of the fibers 3 constituting the substrate sheet is coated with fumaric acid 2.

FIG3 illustrates an incontinence pad as an example of an absorbent article according to the present invention. FIG3 is a plan view of the incontinence pad. FIG4 is a cross-sectional view of the incontinence pad of FIG3 taken along line V-V. In the figure, arrow B defines the width direction, and arrow A defines the length direction. Furthermore, the direction on the plane formed by arrows A and B is defined as the planar direction.

The incontinence pad 11 comprises a liquid-permeable top sheet 12, a liquid-impermeable back sheet 13, and an absorbent body 20 disposed therebetween. The absorbent body 20 is formed by fixing a water-absorbent resin powder 21 and a fiber base material 22 to a tissue 14. The top sheet 12 is composed of a fumaric acid carrier sheet 1.

The top sheet 12 is positioned toward the wearer's crotch and is designed to permeate the wearer's body fluids. The body fluids that permeate the top sheet 12 enter the absorbent core 20 and are absorbed by the absorbent resin powder 21. Since fumaric acid 2 (not shown) is poorly water-soluble, it dissolves gradually rather than immediately in body fluids. Therefore, the absorbent resin powder 21 prevents the top sheet 12 from becoming alkaline for a long time, even after absorbing body fluids.

Side panels 15 extending along the longitudinal direction A of the incontinence pad 11 are attached to both side edges of the top sheet 12 in the width direction B. The side panels 15 are made of a liquid-impermeable plastic film or a waterproof nonwoven fabric. Elastic members 16 are provided on the inner ends of the side panels 15 in the width direction of the incontinence pad 11. When the incontinence pad 11 is in use, the inner ends of the side panels 15 are lifted toward the wearer's skin by the contractile force of the elastic members 16, thereby preventing side leakage of bodily fluids.

FIG5 is a schematic cross-sectional view of another example of an absorbent article according to the present invention. The incontinence pad depicted in FIG5 includes a fumaric acid-carrying sheet 1 as an intermediate sheet disposed between a liquid-permeable top sheet 12 and an absorbent body 20. FIG5 illustrates an embodiment in which the intermediate sheet is the fumaric acid-carrying sheet 1, but both the intermediate sheet and the top sheet 12 may be configured as the fumaric acid-carrying sheet 1. Furthermore, in FIG4 and FIG5 , the absorbent body 20 is formed by attaching a water-absorbent resin powder 21 and a fiber substrate 22 to a tissue 14. However, the water-absorbent resin powder 21 and the fiber substrate 22 may also be wrapped with the tissue 14.

FIG6 is a schematic cross-sectional view of another example of an absorbent article according to the present invention. In the incontinence pad shown in FIG6 , an absorbent body 20 composed of a water-absorbent resin powder 21 and a fiber base material 22 is wrapped with a fumaric acid carrier sheet 1. FIG6 illustrates an embodiment in which the liquid-permeable sheet wrapping the absorbent body 20 serves as the fumaric acid carrier sheet 1. However, the top sheet 12 may also serve as the fumaric acid carrier sheet 1, and the fumaric acid carrier sheet 1 may further serve as the intermediate sheet. Furthermore, FIG4 to FIG6 illustrate an embodiment in which the absorbent body 20 has a single absorbent layer, but the absorbent body 20 may also have multiple absorbent layers. Furthermore, FIG4 to FIG6 illustrate an embodiment in which the absorbent article 11 has a single absorbent body 20, but two or more absorbent bodies 20 may also be provided. The same reference numerals in FIG5 and FIG6 for the same components as in FIG4 are omitted from their description.

Specific examples of the absorbent article of the present invention include absorbent articles for absorbing body fluids discharged from the human body, such as disposable diapers, sanitary napkins, and incontinence pads.

Example

The present invention will be described in detail below by way of examples. However, the present invention is not limited to the following examples, and any changes and embodiments that do not depart from the spirit and scope of the present invention are included within the scope of the present invention.

[Evaluation method]

(Method for measuring water absorption rate by vortex method)

A 100 mL glass beaker was filled with 50 mL of physiological saline (0.9% by mass sodium chloride aqueous solution) and a magnetic stirrer (8 mm diameter at the center, 7 mm diameter at both ends, 30 mm long, and coated with fluororesin). The beaker was then placed on a magnetic stirrer ("HPS-100" manufactured by AS ONE). The magnetic stirrer was adjusted to 600 ± 60 rpm to stir the physiological saline. 2.0 g of sample was added to the stirring physiological saline at the center of the vortex. The water absorption rate (seconds) of the water-absorbent resin powder was measured according to JIS K 7224 (1996). Specifically, a stopwatch was started when the water-absorbent resin powder was completely added to the beaker. The stopwatch was stopped when the stirrer was covered by the test liquid (the vortex disappeared and the liquid surface flattened). The time (seconds) was recorded as the water absorption rate. Five measurements (n = 5) were performed, and the maximum and minimum values were discarded. The average of the remaining three values was used as the measured value. These measurements were performed at 23±2°C and a relative humidity of 50±5%, and the samples were stored in the same environment for at least 24 hours before measurement.

(Measurement method of absorbance)

The absorption rate is measured according to JIS K 7223 (1996). A nylon sieve with a mesh size of 63 μm (JIS Z8801-1: 2000) is cut into a rectangle with a width of 10 cm and a length of 40 cm, folded in half at the center of the length direction, and heat-sealed at both ends to make a nylon bag with a width of 10 cm (inner dimension 9 cm) and a length of 20 cm. Accurately weigh 1.00 g of the test sample and place it evenly at the bottom of the prepared nylon bag. Soak the nylon bag containing the sample in physiological saline. 60 minutes after the start of immersion, remove the nylon bag from the physiological saline, hang it in a vertical state for 1 hour to control the moisture, and then measure the sample mass F1 (g). In addition, the same operation is performed without using a sample, and the mass F0 (g) at this time is measured. From these masses F1, F0 and the sample mass, the target absorption rate is calculated according to the following formula.

Absorption rate (g/g) = (F1-F0)/sample mass

(Measurement method of water retention)

The water retention capacity is measured according to JIS K 7223 (1996). A nylon sieve with a mesh size of 63 μm (JIS Z8801-1: 2000) is cut into a rectangle with a width of 10 cm and a length of 40 cm. The nylon sieve is folded in half at the center of the length direction and heat-sealed at both ends to make a nylon bag with a width of 10 cm (inner dimension 9 cm) and a length of 20 cm. 1.00 g of the test sample is accurately weighed and evenly placed at the bottom of the prepared nylon bag. The nylon bag containing the sample is immersed in physiological saline. 60 minutes after the start of immersion, the nylon bag is removed from the physiological saline, hung vertically for 1 hour to drain the water, and then dehydrated using a centrifugal dehydrator (manufactured by Cocuson, model H-130C special). The dehydration conditions are 143 G (800 rpm) for 2 minutes. The mass R1 (g) after dehydration is measured. In addition, the same operation is performed without using a sample, and the mass R0 (g) at this time is measured. From these masses R1, R0 and the sample mass, the target water retention amount is calculated according to the following formula.

Water retention (g/g) = (R1-R0-sample mass)/sample mass

(Skin irritation, odor intensity)

An absorbent article, 5 cm wide and 5 cm long, was used to absorb 5 mL of urine in three separate passes. The urine-soaked absorbent article was placed on the inner thigh of the subject, with the top sheet (a liquid-permeable nonwoven fabric) in contact with the skin, and left in place for 16 hours. After 16 hours, the absorbent article was removed, and the skin condition at the contact area was visually observed and evaluated on a 5-point scale. Furthermore, the odor intensity of the removed absorbent article was evaluated on a 6-point scale. Each evaluation was performed by 20 subjects, and the average of the 20 evaluations was used as the evaluation value for the absorbent article.

<Evaluation Criteria for Skin Irritation>

5: No change

4: Basically no change

3: A little redness

2: Redness

1: The skin is in a rash state

<Evaluation Criteria for Odor Intensity>

0: Odorless

1: I feel like there is something bad.

2: There is a slight odor, but it is weak.

3: Easily feel bad smell

4: Strong odor

5: Strong odor

[Preparation of Laminated Body]

A synthetic rubber hot-melt adhesive was applied to a liquid-impermeable sheet, and a tissue paper was laminated on top. After applying the synthetic rubber hot-melt adhesive to the tissue paper, pulp and a water-absorbent resin powder ("Aquapal (registered trademark) DS560, manufactured by Sanada Polymer Co., Ltd.) were mixed and sprinkled (water-absorbent resin powder mass per unit area: 100 g/ ^m² ) to form a water-absorbent layer. A synthetic rubber hot-melt adhesive was applied to this water-absorbent layer, and the tissue paper was laminated on top. A synthetic rubber hot-melt adhesive was further applied to the tissue paper, and a liquid-permeable nonwoven fabric was laminated to form a laminate. The physical properties of the water-absorbent resin powder were as follows: water absorption rate 60 g/g, water retention capacity 42 g/g, and water absorption rate measured by vortex method 38 seconds.

[Preparation of absorbent articles]

Absorbent articles1

A mixed solution containing 47.5 g of room temperature distilled water and 12.5 g of Karibon (registered trademark) B (polycarboxylate (salt) type dispersant, solid content concentration 40% by mass, manufactured by Sanyo Chemical Industries, Ltd.) as a dispersant is prepared. 40 g of fumaric acid is added thereto, and a homogenizer (manufactured by Nippon Seiki Manufacturing Co., Ltd., BioMikisa BM-2) is used to crush and disperse the fumaric acid particles to a volume average particle size of 2 μm. Distilled water is further added to adjust the fumaric acid concentration to 0.1% by mass to obtain a fumaric acid dispersion. The content of the dispersant is 12.5 parts by mass relative to 100 parts by mass of fumaric acid. The volume average particle size of the fumaric acid in the dispersion is measured using a laser diffraction/scattering particle size analyzer (manufactured by Nippon Seiki Manufacturing Co., Ltd., MT3000II). The fumaric acid dispersion was sprayed onto the liquid-permeable nonwoven fabric (top sheet) of the above-mentioned laminate and dried to produce an absorbent article 1. The amount of fumaric acid dispersion applied was adjusted so that the fumaric acid loading on the liquid-permeable nonwoven fabric of the absorbent article 1 was 1.0 g/ ^m² . This absorbent article 1 had a top sheet loaded with fumaric acid particles having an average particle size of 30 μm or less.

Absorbent articles 2-12

Absorbent articles 2 to 12 were prepared in the same manner as absorbent article 1 except that the type and volume average particle size of the acidic compound were changed as described in Table 1.

Absorbent articles13

An absorbent article 13 was prepared in the same manner as the absorbent article 1 except that fumaric acid was not used.

The absorbent articles 1 to 13 were evaluated for skin irritation and odor intensity. The results are shown in Table 1.

[Table 1]

As shown in Table 1, in absorbent articles 1 to 3, where the average particle size of the supported fumaric acid is 30 μm or less, the fumaric acid maintains a weakly acidic topsheet, reducing skin irritation. Furthermore, in these absorbent articles 1 to 3, the growth of putrefactive bacteria is suppressed, and the odor intensity is also reduced.

In contrast, absorbent article 9, in which the average particle size of the loaded fumaric acid exceeded 30 μm, experienced increased skin irritation and odor intensity, failing to fully demonstrate the effect of loaded fumaric acid. Furthermore, when adipic acid, succinic acid, itaconic acid, benzoic acid, and silicon oxide were used, as in absorbent articles 4 to 8, even when the average particle size was adjusted to 30 μm or less, the effects of suppressing skin irritation and odor intensity were minimal. Furthermore, when lactic acid or citric acid was used, as in absorbent articles 11 and 12, the acidic compounds dissolved in urine and were not retained on the top sheet. Consequently, the skin irritation evaluation was comparable to that of absorbent article 13, which did not use an acidic compound.

Absorbent articles14

A mixed solution containing 47.5 g of room temperature distilled water and 12.5 g of Calibon (registered trademark) B (a polycarboxylate-type dispersant, solids concentration 40% by mass, manufactured by Sanyo Chemical Industries, Ltd.) as a dispersant was prepared. 40 g of fumaric acid was added to this solution, and the fumaric acid particles were pulverized to a volume average particle size of 8 μm using a homogenizer (Biomic BM-2 manufactured by Nippon Seiki Co., Ltd.). Water was removed from the dispersion to obtain a fumaric acid particle powder having a volume average particle size of 8 μm. The fumaric acid particles were sprinkled on the liquid-permeable nonwoven fabric (top sheet) of the above-mentioned laminate to prepare an absorbent article 14. The amount of fumaric acid particles sprinkled was adjusted so that the fumaric acid loading on the liquid-permeable nonwoven fabric of the absorbent article 14 was 1.0 g/ ^m² . This absorbent article 14 is a sheet in which fumaric acid particles having an average particle size of 30 μm or less are supported on a top sheet.

Absorbent article 14 was evaluated for skin irritation and odor intensity, and the results are shown in Table 2. For comparison, the evaluation results for absorbent article 2 are also shown. Furthermore, to compare the fumaric acid particle loading performance, absorbent articles 2 and 14 were also evaluated for skin irritation and odor intensity after being subjected to vibration treatment. The vibration treatment was performed as follows: the absorbent article was placed with the top sheet facing downward on a physiological shaker (SF-300, manufactured by Sansho Industry Co., Ltd.) and vibrated for 1 minute.

[Table 2]

*Amount relative to 100 parts by mass of fumaric acid particles

Absorbent article 2 is a sheet in which fumaric acid particles are supported by coating a fumaric acid dispersion on a liquid-permeable nonwoven fabric. Absorbent article 14 is a sheet in which fumaric acid particles are supported by scattering fumaric acid particle powder on a liquid-permeable nonwoven fabric. The evaluation results of skin irritation and odor intensity of these absorbent articles 2 and 14 before vibration treatment were basically the same. Therefore, it can be seen that the effect of fumaric acid on skin irritation and odor intensity is not affected by the supporting method. However, while the evaluation of skin irritation and odor intensity of absorbent article 2 before and after vibration treatment did not change, the evaluation of skin irritation and odor intensity of absorbent article 14 after vibration treatment became worse. This is believed to be because the fumaric acid particles fell off due to the vibration treatment. Therefore, it can be seen that the supporting strength of fumaric acid particles supported by coating a fumaric acid dispersion on the supporting component is high. Absorbent article 15

1.0 g of fumaric acid was added to 200 g of warm water adjusted to 50°C, and stirred with a magnetic ultrasonic stirrer USS-2 (manufactured by Nippon Seiki Seisakusho) to completely dissolve the fumaric acid, thereby preparing a fumaric acid solution 1. This fumaric acid solution 1 was sprayed onto the liquid-permeable nonwoven fabric (top sheet) of the aforementioned laminate and dried to produce an absorbent article 15. The amount of fumaric acid solution 1 applied was adjusted so that the fumaric acid loading on the liquid-permeable nonwoven fabric of the absorbent article 15 was 1.0 g/ ^m² . This absorbent article 15 was a sheet in which at least a portion of the fibers constituting the top sheet were coated with fumaric acid.

Absorbent articles16

1.0 g of fumaric acid was added to 200 g of ethanol (95% purity or higher) adjusted to a temperature of 30°C. The mixture was stirred with a magnetic ultrasonic stirrer USS-2 (manufactured by Nippon Seiki Seisakusho) to completely dissolve the fumaric acid, thereby preparing a fumaric acid solution 2. This fumaric acid solution 2 was then applied to the liquid-permeable nonwoven fabric (top sheet) of the aforementioned laminate using a sprayer and dried to produce an absorbent article 16. The amount of fumaric acid solution 2 applied was adjusted so that the fumaric acid loading on the liquid-permeable nonwoven fabric of the absorbent article 16 was 1.0 g/ ^m² . This absorbent article 16 was a sheet in which at least a portion of the fibers constituting the top sheet were coated with fumaric acid.

The absorbent articles 15 and 16 were evaluated for skin irritation and odor intensity, and the results are shown in Table 3. In addition, the evaluation results of the absorbent article 1 are also shown for comparison.

[Table 3]

Absorbent articles 15 and 16 are made by contacting a fumaric acid-containing liquid containing dissolved fumaric acid with a sheet substrate, then removing the solvent to coat at least a portion of the fibers constituting the sheet substrate with fumaric acid. Evaluations of skin irritation and odor intensity for absorbent articles 15 and 16 yielded results essentially similar to those for absorbent article 1. These results demonstrate that the solvent for the fumaric acid-containing liquid can also be warm water or a hydrophilic organic solvent in which fumaric acid is soluble.

Possibility of industrial application

The present invention is suitable for use as, for example, an absorbent article for absorbing body fluids discharged from the human body, and is particularly suitable for use as an absorbent article such as an incontinence pad, a disposable diaper, and a sanitary napkin.

Explanation of symbols

1: Fumaric acid carrier sheet, 2: Fumaric acid, 3: Fiber, 11: Incontinence pad (absorbent article), 12: Top sheet, 13: Back sheet, 14: Tissue, 15: Side sheets, 16: Elastic member for raising, 20: Absorbent body, 21: Water-absorbent resin powder, 22: Fiber base material.

Claims (8)

1. An absorbent article, characterized in that the absorbent article has an absorbent body and a fumaric acid support sheet disposed on the skin surface side of the absorbent body, the fumaric acid support sheet being a sheet loaded with fumaric acid particles with an average particle size of less than 30 μm, wherein at least a portion of the fumaric acid particles are coated with a dispersant. 2. The absorbent article according to claim 1, wherein the dispersant is a polycarboxylate dispersant or a polycarboxylate salt dispersant. 3. The absorbent article according to claim 1, wherein the fumaric acid loading of the fumaric acid-supported tablet is 0.01 g/ ^m² to 10 g/ ^m² . 4. The absorbent article according to claim 1, wherein the dispersant is selected from at least one of the group consisting of anionic polymeric dispersants, anionic surfactant dispersants, and nonionic surfactant dispersants. 5. The absorbent article according to claim 1, wherein the absorbent article has a top sheet disposed on the skin surface side of the absorbent and a back sheet disposed on the outer surface side of the absorbent, the top sheet being the fumaric acid-supported sheet. 6. The absorbent article according to claim 1, wherein the absorbent article has a top sheet disposed on the skin surface side of the absorbent and a back sheet disposed on the outer surface side of the absorbent, and the fumaric acid-supported sheet as an intermediate sheet is disposed between the absorbent and the top sheet. 7. The absorbent article according to any one of claims 1, 3 to 6, wherein the fumaric acid supported sheet is a sheet in which fumaric acid particles are supported by contacting a fumaric acid particle dispersion containing fumaric acid particles, a solvent and a dispersant with a sheet substrate, and then removing the solvent. 8. The absorbent article according to claim 7, wherein the dispersant is a polycarboxylate dispersant or a polycarboxylate salt dispersant.