JP6300498B2 - Absorber and absorbent article having the same - Google Patents

Description

  The present invention relates to an absorbent body having a water-absorbent resin powder, and more particularly to a technique for improving the absorption amount of the absorbent body.

  Absorbent articles are provided in absorbent articles such as disposable diapers, sanitary napkins, and incontinence pads. The absorbent body has a water-absorbing resin powder, and the water-absorbing resin powder absorbs and holds body fluids such as urine and menstrual blood discharged from the body. In such an absorber, in order to prevent scattering and unevenness of the water-absorbing resin powder, one in which the water-absorbing resin powder is fixed to a base material is known.

  For example, in Patent Document 1, a water absorbent resin powder is bonded to one surface of a first nonwoven fabric by a hot melt adhesive so that a water absorbent resin powder existing region and a water absorbent resin powder non-existing region exist. It is an ultra-thin absorbent sheet body, the water-absorbing resin powder non-existing region is present in the ultra-thin absorbent sheet body width direction ultra-ends, and at least one place between these both ends, The water absorbent resin powder includes a first hot melt adhesive layer formed on the upper side of the first nonwoven fabric and on the lower side of the water absorbent resin powder, and on the upper side of the water absorbent resin powder existing region and the water absorbent resin powder non-existing region. And a second hot melt adhesive layer formed so as to cover the first nonwoven fabric, both of the first and second hot melt adhesive layers being linear hot melt adhesives Ultra-thin that is an aggregate of Absorbent sheet has been proposed (see Patent Document 1 (claim 1)).

  As described in Patent Document 1, a material having rubber elasticity such as an elastomer or rubber is used for the adhesive for fixing the water-absorbing resin powder (Patent Document 1 (No. 15). Page 13-13))).

International Publication No. 01/088943

  Since the water-absorbing resin takes in the body fluid into the gaps between the polymer chains, it swells when the body fluid is absorbed. In other words, the water absorbent resin needs to swell in order to absorb body fluid. Here, as in Patent Document 1, when the water-absorbing resin powder is fixed with an adhesive having rubber elasticity, the swelling of the water-absorbing resin powder is inhibited by the adhesive. In this case, the water-absorbent resin powder cannot sufficiently exhibit the original absorption performance, and the absorption performance of the absorber is lowered. This invention is made | formed in view of the said situation, and it aims at providing the absorber excellent in the absorption amount in the absorber formed by adhering a water-absorbent resin powder to a base material.

  The absorbent body of the present invention has a base material and a water-absorbing resin powder fixed to the base material with a fixing agent, and the fixing agent has a penetration (JIS K 2235) of 10 or less. And A sticking agent having a penetration of 10 or less has substantially no rubber elasticity. When the water-absorbing resin powder is fixed using such a fixing agent, the fixing agent that covers the water-absorbing resin powder easily breaks due to swelling of the water-absorbing resin powder. Therefore, the swelling of the water absorbent resin powder is not hindered by the fixing agent, and the water absorbent resin powder can sufficiently exhibit its absorption performance.

The absorption capacity under pressure of 2 kPa of the water absorbent resin powder is preferably 10 g / g to 35 g / g, and the water absorption rate by vortex method is preferably 10 seconds to 75 seconds. Basis weight of the water-absorbent resin powder ^is preferably ^{20g / m 2 ~500g / m 2} . The amount of the sticking agent used is preferably 0.3 parts by mass to 5 parts by mass with respect to 100 parts by mass of the water absorbent resin powder. The fixing agent is preferably a compound having in the molecule at least one selected from the group consisting of an ether group, an ester group, a carboxyl group, a hydroxyl group and an amide group. The melting temperature of the fixing agent is preferably 50 ° C to 160 ° C.

  The substrate is preferably a thermal bond nonwoven fabric. The base material is an eccentric core-sheath type spontaneously crimped fiber composed of a core portion made of the first component and a sheath portion made of the second component, or a parallel type made of the first component and the second component. It is preferable to contain the spontaneous crimped fiber. The base material preferably contains at least one selected from the group consisting of polyethylene, polypropylene, and polyethylene terephthalate as a constituent material.

  The absorbent body of the present invention is preferably prepared by heat-treating the water-absorbent resin particles coated with the fixing agent on a substrate. The present invention also includes a water-absorbent resin powder used in the absorber, wherein the water-absorbent resin particles constituting the water-absorbent resin powder are coated with the fixing agent. Moreover, the absorbent article provided with the said absorber is also contained in this invention.

  ADVANTAGE OF THE INVENTION According to this invention, it is an absorber which fixed the water absorbent resin powder to the base material, Comprising: The absorber which was excellent in the absorbed amount is obtained.

The top view of an example of the absorbent article of this invention. The typical sectional view of the II line of Drawing 1. FIG. 2 is a schematic cross-sectional view taken along line II-II in FIG. 1.

  The absorber of the present invention has a base material and a water-absorbing resin powder fixed to the base material with a fixing agent. The sticking agent has a penetration (JIS K 2235) of 10 or less. A sticking agent having a penetration of 10 or less has substantially no rubber elasticity. Such an adhesive breaks easily when stretched. When the water absorbent resin powder is fixed using such an adhesive, when the water absorbent resin powder swells, the adhesive that covers the water absorbent resin powder is easily broken by this swelling force. Therefore, the swelling of the water absorbent resin powder is not hindered by the fixing agent, and the water absorbent resin powder can sufficiently exhibit its absorption performance.

Fixing agent The penetration of the fixing agent is 10 or less, preferably 8 or less, more preferably 5 or less. When the penetration is more than 10, the fixing agent is easily elastically deformed due to swelling of the water absorbent resin powder, and the fixing agent does not break and inhibits swelling of the water absorbent resin powder. The penetration of the fixing agent is preferably 0.1 or more, more preferably 0.3 or more.

  The melting temperature of the fixing agent is preferably 50 ° C. or higher, more preferably 55 ° C. or higher, further preferably 60 ° C. or higher, preferably 160 ° C. or lower, more preferably 155 ° C. or lower, more preferably 150 ° C. or lower. is there. If the melting temperature is 50 ° C. or higher, the fixing agent can be prevented from melting even when the absorber is exposed to a high temperature, and if it is 160 ° C. or lower, it can be fixed at a relatively low temperature. Deterioration of the substrate can be suppressed when fixing.

  The sticking agent is not particularly limited as long as the penetration is 10 or less. Examples of the fixing agent include natural wax and synthetic wax. Natural waxes include plant-derived waxes such as carnauba wax, candelilla wax, and rice wax; waxes derived from petroleum such as paraffin wax, microstalline wax, and petrolatum; waxes derived from minerals such as montan wax and ozokerite; beeswax, whale Animal derived waxes such as waxes; and derivatives thereof. Examples of the synthetic wax include olefin wax, ester wax, amide wax, modified olefin wax, and acrylic olefin.

  The fixing agent is preferably a compound having at least one selected from the group consisting of an ether group, an ester group, a carboxyl group, a hydroxyl group and an amide group in the molecule. By having said functional group in a molecule | numerator, a hydrogen bond can be formed between water absorbent resin powders, and the adhering force of a water absorbent resin powder improves.

  The viscosity average molecular weight of the fixing agent is preferably 500 or more, more preferably 600 or more, still more preferably 700 or more, preferably 80000 or less, more preferably 70000 or less, and further preferably 60000 or less. If the viscosity average molecular weight is 500 or more, the fixing property becomes better. If the viscosity average molecular weight is 80000 or less, the mechanical strength of the fixing agent does not become too high, and it is easily broken by the expansion force of the water absorbent resin powder. Inhibiting the absorbability of the resin powder can be further reduced.

Next, the water absorbent resin powder used in the present invention will be described. The water-absorbent resin powder used in the present invention is not particularly limited, but is a (A) cross-linked polymer containing acrylic acid as a main constituent, wherein at least a part of the carboxyl group is neutralized. It is preferable to do. 90 mass% or more is preferable, as for the content rate of the acrylic acid component which comprises the said (A) crosslinked polymer, 95 mass% or more is more preferable, 99 mass% or less is preferable, and 97 mass% or less is more preferable. If the content rate of an acrylic acid component exists in the said range, the water-absorbing-resin powder obtained will become easy to express desired absorption performance.

  (A) The cation that neutralizes at least a part of the carboxy group of the crosslinked polymer is not particularly limited. For example, alkali metal ions such as lithium, sodium, and potassium; alkaline earth metal ions such as magnesium and calcium And so on. Among these, it is preferable that at least a part of the carboxy group of the crosslinked polymer is neutralized with sodium ions. In addition, neutralization of the carboxy group of the crosslinked polymer may be performed by neutralizing the carboxy group of the crosslinked polymer obtained by polymerization, or the crosslinked polymer using a previously neutralized monomer. May be formed.

The degree of neutralization of the carboxy group of the crosslinked polymer is preferably 60 mol% or more, and more preferably 65 mol% or more. This is because if the degree of neutralization is too low, the absorption performance of the resulting water-absorbent resin powder may deteriorate. Moreover, the upper limit of the neutralization degree is not particularly limited, and all of the carboxy groups may be neutralized. In addition, a neutralization degree is calculated | required by a following formula.
Degree of neutralization (mol%) = 100 × “number of moles of carboxy group neutralized in crosslinked polymer” / “total number of moles of carboxy group in crosslinked polymer (including neutralized and unneutralized)”

  The crosslinked polymer comprises (a1) a water-soluble ethylenically unsaturated monomer and / or (a1) a water-soluble ethylenically unsaturated monomer by hydrolysis, (a2) a hydrolyzable monomer, and (b) an internal crosslinking agent. And those obtained by polymerizing an unsaturated monomer composition containing

  As the (a1) water-soluble ethylenically unsaturated monomer, for example, a monomer having at least one water-soluble substituent and an ethylenically unsaturated group can be used. The water-soluble monomer means a monomer having a property of dissolving at least 100 g in 100 g of water at 25 ° C. The (a2) hydrolyzable monomer is hydrolyzed by the action of 50 ° C. water and, if necessary, a catalyst (acid or base) to produce (a1) a water-soluble ethylenically unsaturated monomer. (A2) Hydrolysis of the hydrolyzable monomer may be performed either during the polymerization of the cross-linked polymer, after the polymerization, or both of these, but from the viewpoint of the molecular weight of the resulting water-absorbent resin powder, and the like.

  Examples of the water-soluble substituent include a carboxyl group, a sulfo group, a sulfooxy group, a phosphono group, a hydroxyl group, a carbamoyl group, an amino group, or a salt thereof, and an ammonium salt. A salt of a carboxyl group (carboxylate) ), A salt of a sulfo group (sulfonate), and an ammonium salt. Examples of the salt include alkali metal salts such as lithium, sodium and potassium, and alkaline earth metal salts such as magnesium and calcium. The ammonium salt may be either a primary to tertiary amine salt or a quaternary ammonium salt. Of these salts, alkali metal salts and ammonium salts are preferable, alkali metal salts are more preferable, and sodium salts are more preferable from the viewpoint of absorption characteristics.

  The water-soluble ethylenically unsaturated monomer having a carboxy group and / or a salt thereof is preferably an unsaturated carboxylic acid having 3 to 30 carbon atoms and / or a salt thereof. Specific examples of the water-soluble ethylenically unsaturated monomer having a carboxy group and / or a salt thereof include unsaturated monocarboxylic acids such as (meth) acrylic acid, (meth) acrylic acid salt, crotonic acid and cinnamic acid and / or Or a salt thereof; unsaturated dicarboxylic acid such as maleic acid, maleate, fumaric acid, citraconic acid and itaconic acid and / or a salt thereof; maleic acid monobutyl ester, fumaric acid monobutyl ester, ethyl carbitol mono of maleic acid Examples thereof include monoalkyl (carbon number 1 to 8) esters and / or salts of unsaturated dicarboxylic acids such as esters, ethyl carbitol monoester of fumaric acid, citraconic acid monobutyl ester, and itaconic acid glycol monoester. In the description of the present invention, “(meth) acryl” means “acryl” and / or “methacryl”.

  The water-soluble ethylenically unsaturated monomer having a sulfo group and / or a salt thereof is preferably a sulfonic acid having 2 to 30 carbon atoms and / or a salt thereof. Specific examples of the water-soluble ethylenically unsaturated monomer having a sulfo group and / or a salt thereof include aliphatic groups such as vinyl sulfonic acid, (meth) allyl sulfonic acid, styrene sulfonic acid, and α-methyl styrene sulfonic acid, or Aromatic vinyl sulfonic acid; (meth) acryloxypropyl sulfonic acid, 2-hydroxy-3- (meth) acryloxypropyl sulfonic acid, 2- (meth) acryloylamino-2,2-dimethylethanesulfonic acid, 3- ( (Meth) acryloyl-containing alkylsulfonic acids such as (meth) acryloxyethanesulfonic acid, 2- (meth) acrylamide-2-methylpropanesulfonic acid, and 3- (meth) acrylamide-2-hydroxypropanesulfonic acid; and alkyl (Meth) allylsulfosuccinate It is.

  Examples of the water-soluble ethylenically unsaturated monomer having a sulfooxy group and / or a salt thereof include hydroxyalkyl (meth) acrylate sulfate ester; polyoxyalkylene mono (meth) acrylate sulfate ester and the like.

  Water-soluble ethylenically unsaturated monomers having a phosphono group and / or a salt thereof include phosphoric acid monoester of hydroxyalkyl (meth) acrylate, phosphoric diester of hydroxyalkyl (meth) acrylate, and (meth) acrylic Examples thereof include alkylphosphonic acid.

  Examples of the water-soluble ethylenically unsaturated monomer having a hydroxyl group include (meth) allyl alcohol and monoethylenically unsaturated alcohol having 3 to 15 carbon atoms such as (meth) propenyl alcohol; alkylene glycol having 2 to 20 carbon atoms, Monoethylenically unsaturated carboxylic acid ester or monoethylenic unsaturated ester of 2-6 valent polyol such as glycerin, sorbitan, diglycerin, pentaerythritol, polyalkylene (2 to 4 carbon atoms) glycol (weight average molecular weight 100 to 2000) Saturated ether and the like are included. Specific examples thereof include hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, triethylene glycol (meth) acrylate, poly-oxyethylene-oxypropylene mono (meth) allyl ether, and the like.

  Examples of water-soluble ethylenically unsaturated monomers having a carbamoyl group include (meth) acrylamide; N-alkyl (1 to 8 carbon atoms) (meth) acrylamide such as N-methylacrylamide; N, N-dimethylacrylamide, N, N N-N-dialkyl (alkyl having 1 to 8 carbon atoms) acrylamide such as di-n- or i-propyl acrylamide; N-hydroxyalkyl such as N-methylol (meth) acrylamide and N-hydroxyethyl (meth) acrylamide (C1-C8) (meth) acrylamide; N, N-dihydroxyalkyl (C1-C8) (meth) acrylamide, such as N, N-dihydroxyethyl (meth) acrylamide, is mentioned. In addition to these, as the unsaturated monomer having a group consisting of amide, a vinyl lactam having 5 to 10 carbon atoms (such as N-vinylpyrrolidone) can also be used.

Examples of the water-soluble ethylenically unsaturated monomer having an amino group include an amino group-containing ester of monoethylenically unsaturated mono- or di-carboxylic acid and an amino group-containing amide of monoethylenically unsaturated mono- or di-carboxylic acid. Is mentioned. As the amino group-containing ester of monoethylenically unsaturated mono- or di-carboxylic acid, dialkylaminoalkyl (meth) acrylate, di (hydroxyalkyl) aminoalkyl ester and morpholinoalkyl ester can be used, and dimethylaminoethyl (meta ) Acrylate, diethylamino (meth) acrylate, morpholinoethyl (meth) acrylate,
Examples thereof include dimethylaminoethyl fumarate and dimethylaminoethyl malate. The amino group-containing amide of monoethylenically unsaturated mono- or di-carboxylic acid is preferably monoalkyl (meth) acrylamide, and examples thereof include dimethylaminoethyl (meth) acrylamide and diethylaminoethyl (meth) acrylamide. As the water-soluble ethylenically unsaturated monomer having an amino group, vinyl pyridine such as 4-vinyl pyridine and 2-vinyl pyridine can also be used.

  Hydrolysis (a1) Generates a water-soluble ethylenically unsaturated monomer (a2) The hydrolyzable monomer is not particularly limited, but has at least one hydrolyzable substituent that becomes a water-soluble substituent by hydrolysis. Ethylenically unsaturated monomers are preferred. Examples of the hydrolyzable substituent include a group containing an acid anhydride, a group containing an ester bond, and a cyano group.

  Examples of the ethylenically unsaturated monomer having a group containing an acid anhydride include unsaturated dicarboxylic acid anhydrides having 4 to 20 carbon atoms such as maleic anhydride, itaconic anhydride, and citraconic anhydride. Examples of the ethylenically unsaturated monomer having a group containing an ester bond include lower alkyl esters of monoethylenically unsaturated carboxylic acids such as methyl (meth) acrylate and ethyl (meth) acrylate; and vinyl acetate, acetic acid And esters of monoethylenically unsaturated alcohols such as (meth) allyl. Examples of the ethylenically unsaturated monomer having a cyano group include (meth) acrylonitrile and nitrile compounds containing a vinyl group having 3 to 6 carbon atoms such as 5-hexenenitrile.

  As (a1) water-soluble ethylenically unsaturated monomer and (a2) hydrolyzable monomer, further, Japanese Patent No. 3648553, Japanese Patent Application Laid-Open No. 2003-165883, Japanese Patent Application Laid-Open No. 2005-75982, and Japanese Patent Application Laid-Open No. 2005-2005. The thing of -95759 gazette can be used. (A1) The water-soluble ethylenically unsaturated monomer and (a2) hydrolyzable monomer may be used alone or as a mixture of two or more.

  In addition to (a1) the water-soluble ethylenically unsaturated monomer and (a2) the hydrolyzable monomer, (a3) other vinyl monomers copolymerizable with these can be used for the unsaturated monomer composition. As the copolymerizable (a3) other vinyl monomer, a hydrophobic vinyl monomer or the like can be used, but is not limited thereto. (A3) As other vinyl monomers, the following vinyl monomers (i) to (iii) are used.

(I) an aromatic ethylenic monomer having 8 to 30 carbon atoms;
Styrene such as styrene, α-methylstyrene, vinyltoluene and hydroxystyrene, and halogen substituted products of styrene such as vinylnaphthalene and dichlorostyrene.
(Ii) an aliphatic ethylene monomer having 2 to 20 carbon atoms;
Alkenes such as ethylene, propylene, butene, isobutylene, pentene, heptene, diisobutylene, octene, dodecene and octadecene; and alkadienes such as butadiene and isoprene.
(Iii) an alicyclic ethylene monomer having 5 to 15 carbon atoms;
Monoethylenically unsaturated monomers such as pinene, limonene and indene; and polyethylene vinyl polymerizable monomers such as cyclopentadiene, bicyclopentadiene and ethylidene norbornene.

  (A3) As other vinyl monomers, those described in Japanese Patent No. 3648553, Japanese Patent Application Laid-Open No. 2003-165883, Japanese Patent Application Laid-Open No. 2005-75982, and Japanese Patent Application Laid-Open No. 2005-95759 should be used. Can do.

  In the present invention, from the viewpoint of obtaining a crosslinked polymer containing acrylic acid as a main component, (a1) a water-soluble ethylenically unsaturated monomer and / or (a1) a water-soluble ethylenically unsaturated monomer is produced by hydrolysis. As (a2) hydrolyzable monomer, it is preferable to use (a1) acrylic acid or acrylate, or (a2) hydrolyzable monomer that generates acrylic acid or acrylate by hydrolysis. (A) (a1) Acrylic acid or acrylate in the unsaturated monomer composition forming the crosslinked polymer, or (a2) Hydrolyzable monomer 90 mass% or more is preferable, as for content rate, 95 mass% or more is more preferable, 99 mass% or less is preferable, and 97 mass% or less is more preferable.

  (B) As an internal crosslinking agent, (b1) an internal crosslinking agent having two or more ethylenically unsaturated groups, (b2) (a1) a water-soluble substituent of a water-soluble ethylenically unsaturated monomer and / or (a2) An internal cross-linking agent having at least one functional group capable of reacting with a water-soluble substituent generated by hydrolysis of a hydrolyzable monomer and having at least one ethylenically unsaturated group, and (b3) ( a1) a water-soluble substituent of a water-soluble ethylenically unsaturated monomer and / or (a2) an internal crosslinking agent having at least two functional groups capable of reacting with a water-soluble substituent generated by hydrolysis of a hydrolyzable monomer Can be mentioned.

  (B1) As an internal crosslinking agent having two or more ethylenically unsaturated groups, bis (meth) acrylamide having 8 to 12 carbon atoms, poly (meth) acrylate of a polyol having 2 to 10 carbon atoms, or 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 (degree of polymerization 2 to 5) ethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, Glycerin (di or tri) acrylate, trimethylolpropane triacrylate, diallylamine, triallylamine, triallyl cyanurate, triallyl isocyanurate, tetraallyloxyethane, pentaerythritol diallyl ether, pentaerythritol triallyl ether, pentaerythritol tetraallyl ether And diglycerin di (meth) acrylate and the like.

  (B2) (a1) having at least one functional group capable of reacting with a water-soluble substituent of a water-soluble ethylenically unsaturated monomer and / or (a2) a water-soluble substituent generated by hydrolysis of a hydrolyzable monomer As the internal crosslinking agent having at least one ethylenically unsaturated group, an ethylenically unsaturated compound having an epoxy group having 6 to 8 carbon atoms, an ethylenically unsaturated compound having a hydroxyl group having 4 to 8 carbon atoms And ethylenically unsaturated compounds having an isocyanato group having 4 to 8 carbon atoms. Specific examples thereof include glycidyl (meth) acrylate, N-methylol (meth) acrylamide, hydroxyethyl (meth) acrylate and isocyanatoethyl (meth) acrylate.

  (B3) (a1) having at least two functional groups capable of reacting with a water-soluble substituent of a water-soluble ethylenically unsaturated monomer and / or (a2) a water-soluble substituent generated by hydrolysis of a hydrolyzable monomer Examples of the internal crosslinking agent include polyhydric alcohols, polyhydric glycidyl, polyhydric amines, polyhydric aziridines and polyhydric isocyanates. Examples of the polyvalent glycidyl compound include ethylene glycol diglycidyl ether and glycerin diglycidyl ether. Examples of the polyvalent amine compound include ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, and polyethyleneimine. Examples of the polyvalent aziridine compound include Chemitite (registered trademark) PZ-33 {2,2-bishydroxymethylbutanol-tris (3- (1-aziridinyl) propinate)} manufactured by Nippon Shokubai Chemical Industry Co., Ltd., Chemite HZ-22 { 1,6-hexamethylenediethylene urea} and chemite DZ-22 {diphenylmethane-bis-4, 4′-N, N′-diethylene urea} and the like. Examples of the polyvalent isocyanate compound include 2,4-tolylene diisocyanate and hexamethylene diisocyanate. These internal crosslinking agents may be used alone or in combination of two or more.

  (B) The internal cross-linking agent is preferably an internal cross-linking agent having 2 or more ethylenically unsaturated groups from the viewpoint of absorption performance (particularly absorption amount and absorption rate), and has 2 to 10 carbon atoms. Poly (meth) allyl ether of polyol is more preferred, triallyl cyanurate, triallyl isocyanurate, tetraallyloxyethane or pentaerythritol triallyl ether is more preferred, and pentaerythritol triallyl ether is most preferred.

  (B) As the internal crosslinking agent, those described in Japanese Patent No. 3648553, Japanese Patent Application Laid-Open No. 2003-165883, Japanese Patent Application Laid-Open No. 2005-75982, and Japanese Patent Application Laid-Open No. 2005-95759 may be further used. it can.

  (A) As a polymerization form of a crosslinked polymer, a conventionally known method can be used, and a solution polymerization method, an emulsion polymerization method, a suspension polymerization method, and a reverse phase suspension polymerization method can be applied. Further, the shape of the polymerization solution at the time of polymerization may be a thin film shape, a spray shape, or the like. As a polymerization control method, an adiabatic polymerization method, a temperature control polymerization method, an isothermal polymerization method, or the like can be applied. As the polymerization method, a solution polymerization method is preferable, and an aqueous solution polymerization method is more preferable because it is not necessary to use an organic solvent or the like and is advantageous in terms of production cost.

  The hydrogel {consisting of a crosslinked polymer and water} obtained by polymerization can be chopped as necessary. The size (longest diameter) of the gel after shredding is preferably 50 μm to 10 cm, more preferably 100 μm to 2 cm, and even more preferably 1 mm to 1 cm. Within this range, the drying property in the drying process is further improved.

  Shredding can be performed by a known method. For example, the shredding can be performed using a conventional shredding device such as a bex mill, rubber chopper, pharma mill, mincing machine, impact pulverizer, and roll pulverizer.

  When using a solvent (organic solvent, water, etc.) for the polymerization, it is preferable to distill off the solvent after the polymerization. When water is contained in the solvent, the water content (% by mass) after distillation is preferably 0% by mass to 20% by mass, and more preferably 1% by mass to 10% by mass with respect to the mass (100% by mass) of the crosslinked polymer. % By mass, more preferably 2% by mass to 9% by mass, and most preferably 3% by mass to 8% by mass. When the water content (% by mass) is within the above range, the absorption performance and the breakability of the water absorbent resin powder after drying are further improved.

  In addition, the content rate and moisture of the organic solvent are an infrared moisture meter {JE400 manufactured by KETT Co., Ltd .: 120 ± 5 ° C., 30 minutes, atmospheric humidity before heating 50 ± 10% RH, lamp specification 100V, 40W } Is obtained from the weight loss of the measurement sample before and after heating.

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

  (A) The crosslinked polymer can be pulverized after drying. The pulverization method is not particularly limited, and for example, a normal pulverizer such as a hammer pulverizer, an impact pulverizer, a roll pulverizer, and a shet airflow pulverizer can be used. The pulverized (A) crosslinked polymer can be adjusted in particle size by sieving or the like, if necessary.

  The weight average particle diameter (μm) of the (A) crosslinked polymer when screened if necessary is preferably 300 μm or more, more preferably 350 μm or more, further preferably 400 μm or more, preferably 500 μm or less, more preferably 480 μm. Hereinafter, it is more preferably 450 μm or less. (A) If the weight average particle diameter (μm) of the crosslinked polymer is within the above range, the absorption performance is further improved.

  In addition, the weight average particle diameter was measured using a low-tap test sieve shaker and a standard sieve (JIS Z8801-1: 2006), Perry's Chemical Engineers Handbook, 6th edition (McGlow Hill Book Company, 1984). , Page 21). That is, JIS standard sieves are combined in the order of 1000 μm, 850 μm, 710 μm, 500 μm, 425 μm, 355 μm, 250 μm, 150 μm, 125 μm, 75 μm and 45 μm, and a tray from the top. About 50 g of the measured particles are put in the uppermost screen and shaken for 5 minutes with a low-tap test sieve shaker. The mass of the measured particles on each sieve and the pan is weighed, and the total is 100% by mass to obtain the mass fraction of the particles on each sieve. This value is logarithmic probability paper {the horizontal axis is the sieve aperture (particle size ), After the vertical axis is plotted in mass fraction}, a line connecting the points is drawn to obtain a particle diameter corresponding to a mass fraction of 50 mass%, which is defined as a weight average particle diameter.

  In addition, the smaller the content of fine particles, the better the absorption performance. Therefore, the content of fine particles of 106 μm or less (preferably 150 μm or less) in all particles is preferably 5% by mass or less, more preferably 3% by mass or less. is there. The content of the fine particles can be obtained by using a plot created when obtaining the above-described mass average particle diameter.

  (A) The crosslinked polymer may be further treated with (B) a surface modifier. (B) As surface modifiers, polyvalent metal compounds such as aluminum sulfate, potassium alum, ammonium alum, sodium alum, (poly) aluminum chloride, hydrates thereof; polyethyleneimine, polyvinylamine, polyallylamine, etc. Polycation compounds; inorganic fine particles; (B1) surface modifiers containing hydrocarbon groups having fluorine atoms; and (B2) surface modifiers having a polysiloxane structure.

  Examples of the inorganic fine particles include silicon oxide, aluminum oxide, iron oxide, titanium oxide, magnesium oxide, oxides such as zirconium oxide, carbides such as silicon carbide and aluminum carbide, nitrides such as titanium nitride, and these. (For example, zeolite and talc). Of these, oxides are preferable, and silicon oxide is more preferable. The volume average particle diameter of the inorganic fine particles is preferably 10 nm to 5000 nm, more preferably 30 nm to 1000 nm, still more preferably 50 nm to 750 nm, and most preferably 90 nm to 500 nm. The volume average particle diameter is measured in a solvent by a dynamic light scattering method. Specifically, it is measured at a temperature of 25 ° C. in a solvent cyclohexane using a nanotrack particle size distribution analyzer UPA-EX150 (light source: He—Ne laser) manufactured by Nikkiso Co., Ltd.

  (B1) As the surface modifier containing a hydrocarbon group having a fluorine atom, perfluoroalkane, perfluoroalkene, perfluoroaryl, perfluoroalkyl ether, perfluoroalkyl carboxylic acid or a salt thereof, perfluoroalkyl alcohol , And a mixture of two or more of these.

  (B2) As the surface modifier having a polysiloxane structure, polydimethylsiloxane; polyether-modified polysiloxane such as polyoxyethylene-modified polysiloxane and poly (oxyethylene oxypropylene) -modified polysiloxane; carboxy-modified polysiloxane; Examples thereof include epoxy-modified polysiloxanes; amino-modified polysiloxanes; alkoxy-modified polysiloxanes, and mixtures thereof.

  (B) As the surface modifier, from the viewpoint of absorption characteristics, (B2) a surface modifier having a polysiloxane structure and inorganic fine particles are preferable, and amino-modified polysiloxane, carboxy-modified polysiloxane, and silica are preferable. More preferred.

  (A) As a method of treating the crosslinked polymer with (B) the surface modifier, if (B) the surface modifier is treated so that it exists on the surface of the (A) crosslinked polymer, in particular It is not limited. However, (B) the surface modifier is mixed with (A) the dried polymer of the cross-linked polymer, not (A) the hydrogel of the cross-linked polymer or (A) the polymer solution before polymerizing the cross-linked polymer. It is preferable from the viewpoint of controlling the amount of the surface modifier (B) on the surface. The mixing is preferably performed uniformly.

  The shape of the water-absorbent resin powder is not particularly limited, and examples thereof include an irregularly crushed shape, a flake shape, a pearl shape, and a rice grain shape. Among these, from the viewpoint of good entanglement with the fibrous material in the use of paper diapers and the like and no fear of dropping off from the fibrous material, an irregular crushed shape is preferable.

  The cross-linked polymer can be further subjected to surface cross-linking as necessary. As the crosslinking agent (surface crosslinking agent) for performing the surface crosslinking, the same as the (b) internal crosslinking agent can be used. As the surface cross-linking agent, from the viewpoint of absorption performance of the water-absorbent resin powder, (b3) (a1) water-soluble substituent of water-soluble ethylenically unsaturated monomer and / or (a2) hydrolysis of hydrolyzable monomer A cross-linking agent having at least two functional groups capable of reacting with the generated water-soluble substituent is preferred, more preferably polyvalent glycidyl, more preferably ethylene glycol diglycidyl ether and glycerin diglycidyl ether, most preferably ethylene glycol di- Glycidyl ether.

  In the case of surface crosslinking, the content (% by mass) of the surface crosslinking agent is (a1) a water-soluble ethylenically unsaturated monomer and / or (a2) a hydrolyzable monomer, (b) an internal crosslinking agent, and if necessary. (A3) 0.001% by mass to 7% by mass is preferable with respect to the total mass (100% by mass) of other vinyl monomers, more preferably 0.002% by mass to 5% by mass, and still more preferably 0.003%. It is mass%-4 mass%. That is, in this case, the upper limit of the content (mass%) of the surface cross-linking agent is preferably 7 mass% based on the total mass of (a1) and / or (a2), (b) and (a3). Preferably it is 5 mass%, More preferably, it is 4 mass%, Similarly, a minimum is 0.001 mass%, More preferably, it is 0.002 mass%, More preferably, it is 0.003 mass%. When the content of the surface cross-linking agent is within the above range, the absorption performance is further improved. Surface cross-linking can be achieved by a method of spraying or impregnating a water-absorbent resin powder with an aqueous solution containing a surface cross-linking agent, followed by heat treatment (100 to 200 ° C.).

  The water-absorbent resin powder contains additives such as preservatives, fungicides, antibacterial agents, antioxidants, ultraviolet absorbers, colorants, fragrances, deodorants, inorganic powders and organic fibrous materials. Can do. Examples of the additive include those exemplified in JP2003-225565A, JP2006-131767A, and the like. When these additives are contained, the content (% by mass) of the additive is preferably 0.001% by mass to 10% by mass, more preferably based on (A) the crosslinked polymer (100% by mass). It is 0.01 mass%-5 mass%, More preferably, it is 0.05 mass%-1 mass%, Most preferably, it is 0.1 mass%-0.5 mass%.

  The water absorbent resin powder has an absorption capacity of preferably 40 g / g or more, more preferably 42 g / g or more, still more preferably 45 g / g or more, and preferably 80 g / g or less. The absorption ratio is a scale indicating how much water absorbent resin powder can absorb water. When the absorption ratio is 40 g / g or more, a desired absorption capacity can be realized with a small amount of water-absorbent resin powder, so that an efficient absorber design can be achieved. If the said absorption capacity is 80 g / g or less, the stability with respect to urine of a water absorbent resin powder can be maintained.

The water-absorbent resin powder preferably has an absorption capacity under pressure of 10 g / g or more, more preferably 12 g / g or more, still more preferably 15 g / g or more, preferably 35 g / g or less, more preferably 33 g / g. Hereinafter, it is more preferably 30 g / g or less. The absorption capacity under pressure is a scale indicating how much the water-absorbent resin powder can absorb water under a pressure of ² kPa (20 gf / cm ² ). If the absorption capacity under pressure is 10 g / g or more, a desired absorption capacity can be realized with a small amount of water-absorbent resin powder, so that an efficient absorber design can be achieved. If the absorption capacity under pressure is 35 g / g or less, the stability of the water-absorbent resin powder to urine can be maintained.

  The water-absorbent resin powder has an absorption rate by a vortex method of preferably 10 seconds or more, more preferably 12 seconds or more, still more preferably 15 seconds or more, preferably 75 seconds or less, more preferably 73 seconds or less, Preferably it is 70 seconds or less. The absorption speed by the vortex method is evaluated by measuring the time (seconds) to absorb the body fluid. Therefore, the shorter the measurement time (seconds), the greater the rate at which the water absorbent resin powder absorbs body fluid. If the absorption rate by the vortex method is 10 seconds or more, the stability of the water-absorbent resin powder to urine, particularly the stability under pressure, becomes better. If the absorption rate by the vortex method is 75 seconds or less, the bodily fluid excretion rate is high, and even when a large amount of bodily fluid is excreted at a time, the bodily fluid can be sufficiently absorbed.

  The bulk density of the water absorbent resin powder is preferably 0.40 g / ml or more, more preferably 0.42 g / ml or more, still more preferably 0.45 g / ml or more, and preferably 0.85 g / ml or less. More preferably, it is 0.83 g / ml or less, More preferably, it is 0.80 g / ml or less. The bulk density is an index of the shape of the water absorbent resin powder. If the bulk density is within the above range, a void as a body fluid passage is easily formed between the water-absorbent resin powders. As a result, the absorption rate and the repeated absorption rate are improved.

  The absorption capacity, absorption rate, and bulk density of the water-absorbent resin powder are adjusted by appropriately selecting the composition of the (A) crosslinked polymer, the type of surface modifier, the particle size of the water-absorbent resin powder, and the drying conditions. Can do.

Base material The base material used for this invention is not specifically limited, Either a liquid-permeable sheet and a liquid-impermeable sheet can be used. Examples of the liquid permeable sheet include a nonwoven fabric formed from hydrophilic fibers and a nonwoven fabric formed from hydrophobic fibers that have been hydrophilically treated. Examples of the nonwoven fabric include point bond nonwoven fabric, thermal bond nonwoven fabric, spunlace nonwoven fabric, and spunbond nonwoven fabric. As the material for the hydrophilic fiber, cellulose, rayon, cotton, or the like is used. Examples of the material of the hydrophobic fiber include polyolefins such as polypropylene and polyethylene; polyesters such as polyethylene terephthalate and polyamides. Examples of the liquid-impervious sheet include a water-repellent or liquid-impervious nonwoven fabric (for example, a spunbond nonwoven fabric, a meltblown nonwoven fabric, an SMS (spunbond / meltblown / spunbond) nonwoven fabric) formed of hydrophobic fibers, And a water-repellent or liquid-impervious plastic film. When a plastic film is used as the liquid-impermeable sheet, a plastic film having moisture permeability (breathability) is preferably used from the viewpoint of preventing stuffiness and improving wearer's comfort. Among these, as a base material, a moisture-permeable sheet is preferable and a thermal bond nonwoven fabric is more preferable.

  When a nonwoven fabric is used as the substrate, the fibers constituting the nonwoven fabric are preferably crimped fibers, and more preferably spontaneously crimped fibers. By using the crimped fiber, the water-absorbent resin powder is easily entangled with the fiber, and the fixing property of the water-absorbent resin powder is improved. As the spontaneous crimped fiber, an eccentric core-sheath type spontaneously crimped fiber composed of a core part composed of a first component and a sheath part composed of a second component; a parallel type composed of a first component and a second component Self-crimped fibers; and the like. In these spontaneously crimped fibers, the first component and the second component have different heat shrinkage, and crimping occurs due to the heat shrinkage difference when heat treatment is performed. Examples of the combination of the first component and the second component include polyethylene / polyethylene terephthalate, polyamide / polyurethane, and polyethylene / polypropylene.

The basis weight of the substrate is preferably 5 g / m ² or more, more preferably 10 g / m ² or more, still more preferably 13 g / m ² or more, and preferably 70 g / m ² or less, more preferably 60 g / m ^2. Hereinafter, it is more preferably 50 g / m ² or less. If the basis weight is 5 g / m ² or more, the strength of the sheet is improved and the sheet is hardly broken, and if it is 70 g / m ² or less, the flexibility of the absorbent body is improved.

Absorbent body The absorbent body of the present invention has a base material and a water-absorbent resin powder fixed to the base material with a fixing agent. The basis weight of the water-absorbent resin powder in the absorber is preferably 20 g / m ² or more, more preferably 60 g / m ² or more, still more preferably 100 g / m ² or more, and preferably 500 g / m ² or less. Is 400 g / m ² or less, more preferably 300 g / m ² or less. When the basis weight is 20 g / m ² or more, the absorption amount of the absorber is further improved. If the basis weight is 500 g / m ² or less, the texture of the absorber becomes better.

  The content of the fixing agent in the absorbent body is preferably 0.3 parts by mass or more, more preferably 0.4 parts by mass or more, further preferably 0.5 parts by mass or more with respect to 100 parts by mass of the water absorbent resin powder. It is preferably 5.0 parts by mass or less, more preferably 4.5 parts by mass or less, and still more preferably 4.0 parts by mass or less. If the content of the sticking agent is 0.3 parts by mass or more, the sticking property of the water absorbent resin powder to the substrate is improved, and if it is 5.0 parts by weight or less, the absorption performance of the water absorbent resin powder is not impaired.

  The water absorbent may include a water absorbent material such as a water absorbent fiber in addition to the water absorbent resin powder. Examples of the water absorbent fiber include pulp fiber, cellulose fiber, rayon, and acetate fiber.

  As the structure of the absorbent body, for example, an embodiment comprising one sheet-like base material and a water-absorbent resin powder fixed to one surface of the base material; two sheet-like base materials, and these And the like composed of water-absorbent resin powder fixed between the substrates. The water-absorbing resin powder to be fixed to the base material may be fixed uniformly over the entire surface of the base material, or may be fixed in the form of multiple rows of streaks extending continuously (or intermittently) in one direction. The shape of the absorbent body in plan view is not particularly limited, and examples thereof include a rectangular shape, an hourglass shape, a gourd shape, and a battledore shape.

  The method for producing the absorbent body is not particularly limited. For example, a method in which a sticking agent is applied on a base material, a water-absorbing resin powder is sprayed thereon, and then heat-treated; coating the water-absorbing resin particles with the sticking agent Then, a method of spraying the water-absorbent resin particles coated with the fixing agent on the base material and heat-treating it can be mentioned. The temperature of the heat treatment is preferably from the melting temperature of the fixing agent to 160 ° C.

  The method for coating the water absorbent resin particles with the fixing agent is not particularly limited, and the water absorbent resin powder and the fixing agent may be mixed, heated, and kneaded. The heating temperature is preferably from the melting temperature of the fixing agent to 160 ° C. The mixture after kneading may be formed into a sheet shape or pulverized after cooling. The water-absorbent resin particles coated with the sticking agent need only have at least a part of the particle surface covered with the sticking agent. In the powder composed of water-absorbing resin particles coated with the fixing agent, the amount of the fixing agent used is preferably 0.3 parts by mass or more, more preferably 0.4 parts by mass with respect to 100 parts by mass of the water-absorbing resin powder. As mentioned above, More preferably, it is 0.5 mass part or more, 5.0 mass part or less is preferable, More preferably, it is 4.5 mass part or less, More preferably, it is 4.0 mass part or less.

Next, a specific application example of the absorbent body of the present invention will be described. As an absorbent article which can use the absorber of this invention, the absorbent article used in order to absorb the bodily fluid discharged | emitted from a human body, such as an incontinence pad, a disposable diaper, and a sanitary napkin, is mentioned, for example.

  When the absorbent article is an incontinence pad or a sanitary napkin, for example, an absorbent body is disposed between a liquid-permeable top sheet and a liquid-impermeable back sheet. Examples of the shape of the incontinence pad and sanitary napkin include a substantially rectangular shape, an hourglass shape, and a gourd shape. Further, if necessary, liquid-impervious side sheets may be provided on both sides in the width direction of the liquid-permeable top sheet. The side sheets are bonded to the upper surfaces on both sides in the width direction of the top sheet, and the side sheets inward in the width direction from the bonding points form a pair of rising flaps along both side edges of the absorber.

  When the absorbent article is a disposable diaper, as the disposable diaper, for example, a pair of fastening members are provided on the left and right of the back part or the front part of the abdomen, and the deployable disposable that is formed into a pants shape when worn by the fastening member Diapers; pants-type disposable diapers in which a waist opening and a pair of leg openings are formed by joining the front part and the back part;

  When the absorbent article is a disposable diaper, the disposable diaper forms, for example, a diaper main body in which a laminate composed of an inner sheet and an outer sheet is composed of a front abdomen, a back part, and a crotch part positioned therebetween. The water absorber may be disposed in the crotch portion. The disposable diaper is composed of, for example, a laminated body in which an absorbent body is disposed between a top sheet and a back sheet, and this laminated body has a front part, a back part, and a crotch part located between them. You may do it. The front part, the back part, and the crotch part are referred to as the front part of the wearer's abdomen when wearing disposable diapers and the back part of the part as it applies to the buttocks side of the wearer. A portion that is located between the abdomen and the back portion and is placed between the wearer's crotch is referred to as a crotch portion. The inner sheet is preferably hydrophilic or water repellent, and the outer sheet is preferably water repellent.

  The absorbent article is preferably provided with rising flaps along both side edges of the absorbent body. For example, the rising flaps may be provided on both side edges in the width direction of the upper surface of the absorber, or may be provided on both outer sides in the width direction of the absorber. By providing the rising flap, it is possible to prevent side leakage of body fluid. The rising flaps may be formed by raising the inner ends of the side sheets provided on both sides of the top sheet in the width direction. The rising flap and the side sheet are preferably water-repellent.

  Hereinafter, although the absorbent article of this invention is demonstrated referring drawings, this invention is not limited to the aspect shown by drawing.

  1 is a plan view (development view) of an example of the absorbent article of the present invention, FIG. 2 is a schematic cross-sectional view taken along line II in FIG. 1, and FIG. 3 is a schematic cross-sectional view taken along line II-II in FIG. It is. 1-3, arrow A shows the length direction of an absorbent article, arrow B shows the width direction of an absorbent article, the upper side of the C direction of a paper surface is a skin surface side, and the lower side is an outer surface side.

  In FIG. 1, an example of the underpants type disposable diaper (absorbent article) of this invention was shown (development figure). The pants-type disposable diaper 1 has a front part 2 and a back part 3 in the length direction A, and has a crotch part 4 between the front part 2 and the back part 3. The front abdomen 2 is in contact with the wearer's abdomen, and the back part 3 is in contact with the wearer's buttocks. The crotch part 4 is provided with a notch 5 along the circumference of the wearer's leg. In the pants-type disposable diaper 1 of FIG. 1, the side edge 2a of the front part 2 and the side edge 3a of the back part 3 are joined, and it becomes the pants-type disposable diaper 1 which has a waist opening part and a pair of leg opening part.

  The pants-type disposable diaper 1 has an absorbent main body 20 attached to the skin surface side of the exterior sheet material 6. The absorbent main body 20 extends along the length direction A from the center of the crotch portion 4.

  A front waist elastic member 8 and a rear waist elastic member 9 are attached to the pants-type disposable diaper 1 along the edge 7 of the exterior sheet material 6 in a state of being stretched in the width direction B. Further, along the notch 5, the front leg elastic member 10 and the rear leg elastic member 11 are attached in an extended state. A state where the front waistline elastic member 12 and the back waistline elastic member 13 are extended in the width direction B between the waist elastic member and the leg elastic member in each of the front abdominal part 2 and the back back part 3. It is attached with. The pants-type disposable diaper 1 fits the wearer by contraction of each elastic member.

  FIG. 2 is a diagram schematically illustrating a cross section taken along line II of the pant-type disposable diaper of FIG. With reference to FIG. 2, the structure of the underpants type disposable diaper 1 is demonstrated. The exterior sheet material 6 includes an outer sheet 6a and an inner sheet 6b, and elastic members 8 and 9 for the waist, elastic members 10 and 11 for the legs, and elastic members 12 and 13 for the waistline are stretched between the two sheets. It is attached with. The outer sheet 6a is longer in the length direction than the inner sheet 6b, and is folded back to the inner surface side (skin surface side) at the end edge 7 to form a folded portion 14.

  An absorbent main body 20 is attached to the skin surface side of the exterior sheet material 6. The absorbent main body 20 includes an absorbent body 21, a top sheet 22 made of a nonwoven material disposed on the skin surface side of the absorbent body 21, and a liquid-impermeable back sheet 23 provided on the outer surface side of the absorbent body 21. Have. The absorber 21 includes a water absorbent resin powder 24, a fixing agent 25 for covering the water absorbent resin powder 24, and base materials 26 and 27 to which the water absorbent resin powder is fixed. In the pants-type disposable diaper 1, a front end press sheet 15 and a rear end press sheet 16 are provided so as to cover the lengthwise ends of the absorbent main body 20 at the front abdomen 2 and the back part 3 of the inner surface of the inner sheet 6 b. ing.

  FIG. 3 is a diagram schematically illustrating a cross section taken along line II-II of the pants-type disposable diaper of FIG. As shown in FIG. 3, a side sheet 17 made of a non-woven material is joined to the top of both side edges in the width direction of the top sheet 22 made of a non-woven material. The side seat 17 forms a rising flap that stands up toward the wearer's skin by the contraction force of the elastic member 18 attached in a stretched state in the length direction, and serves as a barrier that prevents lateral leakage of urine and the like. .

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

  Hereinafter, the present invention will be described in detail by way of examples. However, the present invention is not limited to the following examples, and all modifications and embodiments without departing from the gist of the present invention are not limited thereto. Included in range.

[Evaluation method]
The penetration of the sticking agent The penetration of the sticking agent was measured based on JIS K 2235 (1991). Specifically, the fixing agent was put into a container (inner diameter 55 mm, height 35 mm), and heated so as not to be higher than 90 ° C. above the softening point of the fixing agent, thereby melting the fixing agent. The melted fixing agent was left at room temperature (25 ° C.) for 1.5 hours. Next, the cooled sticking agent was placed in a thermostatic bath set at 25 ° C. and left for 1.5 hours, which was used as a measurement sample. For the measurement, an automatic needle penetration measuring device (Daiichi Science Co., Ltd., EX-210ED) is used. Needle (made of stainless steel, 2.5 g), needle holder (47.5 g), weight (50 g), The test time was 5 seconds.

Fixing agent melting temperature The melting temperature was measured using a differential scanning calorimeter (DSC).

Bulk density The bulk density is measured according to JIS K 6219-2 (2005). A water-absorbent resin powder as a sample is poured into a central part of a cylindrical container (a stainless steel container having a diameter of 100 mm, a capacity of 1000 ml) having a known mass and capacity from a height of 50 mm or less from the upper end of the container. At this time, a sufficient amount of sample is poured into the cylindrical container so that the poured sample forms a triangular pyramid above the upper end of the cylindrical container. Then, use a spatula to wipe off the excess sample above the upper end of the cylindrical container, measure the mass of the container in this state, and subtract the mass of the container from the measured value to obtain the mass of the sample. Then, this is divided by the capacity of the container to calculate the target bulk density. The measurement was performed 5 times (n = 5), the values at each of the upper and lower points were deleted, and the average value of the remaining three points was taken as the measured value. These measurements are performed at 23 ± 2 ° C. and a relative humidity of 50 ± 5%, and are measured after the sample is stored in the same environment for 24 hours or more before the measurement.

Absorption magnification The absorption magnification is measured according to JIS K 7223 (1996). Nylon mesh (JIS Z8801-1: 2000) with a mesh size of 63 μm is cut into a rectangle with a width of 10 cm and a length of 40 cm, folded in half at the center in the longitudinal direction, and both ends are heat sealed to a width of 10 cm (inner dimension: 9 cm), long A 20 cm long nylon bag is prepared. 1.00 g of a measurement sample is precisely weighed and placed uniformly in the bottom of the produced nylon bag. The nylon bag containing the sample is immersed in physiological saline. After 60 minutes from the start of immersion, the nylon bag is taken out from the physiological saline, suspended in the vertical state for 1 hour and drained, and then the mass F1 (g) of the sample is measured. Further, the same operation is performed without using a sample, and the mass F0 (g) at that time is measured. Then, from the masses F1 and F0 and the mass of the sample, a target absorption magnification is calculated according to the following formula.
Absorption capacity (g / g) = (F1-F0) / mass of sample

Absorption capacity under pressure (absorption under pressure of 2 kPa)
The absorption capacity under pressure is measured as follows in an environment of 25 ± 2 ° C. and a relative humidity of 50% ± 5%. That is, 0.10 g of a sample was weighed in a cylindrical plastic tube (inner diameter: 30 mm, height: 60 mm) in which a nylon mesh (JIS Z 8801-1: 2000) having an opening of 63 μm was attached to the bottom surface. Adjust the cylindrical plastic tube vertically so that the sample has a uniform thickness on the nylon mesh, and apply a weight of 29.5mm outer diameter x 22mm thickness in the cylindrical plastic tube so that the pressure of 2kPa is applied to the sample. Inserted. The weight of the cylindrical plastic tube and the weight is measured in advance. Next, a cylindrical plastic tube containing a sample and a weight in a petri dish (diameter: 120 mm) containing 60 ml of physiological saline is vertically immersed with the nylon mesh side as the bottom surface. At this time, the cylindrical plastic tube is immersed to the depth of the bottom of the petri dish. After 60 minutes, the cylindrical plastic tube containing the sample and the weight is pulled up from the water, the mass is weighed, the weight of the cylindrical plastic tube and the weight previously measured is subtracted, and the weight of the physiological saline absorbed by the sample is calculated. . A value obtained by multiplying the weight of the absorbed physiological saline by 10 was defined as an absorption amount under pressure (g / g).

Water absorption rate by vortex method In a 100 mL glass beaker, 50 mL of physiological saline (0.9 mass% sodium chloride water) and a magnetic stirrer chip (center diameter 8 mm, both ends diameter 7 mm, length 30 mm, surface is fluororesin And the beaker is placed on a magnetic stirrer (manufactured by ASONE, “HPS-100”). The rotational speed of the magnetic stirrer is adjusted to 600 ± 60 rpm, and the physiological saline is stirred. 2.0 g of the sample is put into the liquid at the center of the vortex of the saline solution being stirred, and the water absorption rate (seconds) of the water absorbent resin powder is measured according to JIS K 7224 (1996). Specifically, the stopwatch was started when the sample water-absorbent resin powder was completely charged into the beaker, and when the stirrer chip was covered with the test liquid (the vortex disappeared and the liquid surface became flat Stop the stopwatch at the time) and record the time (in seconds) as the water absorption rate. The measurement was performed 5 times (n = 5), the values at each of the upper and lower points were deleted, and the average value of the remaining three points was taken as the measured value. These measurements are performed at 23 ± 2 ° C. and a relative humidity of 50 ± 5%, and are measured after the sample is stored in the same environment for 24 hours or more before the measurement.

Absorption amount The absorbent was put into 0.9% by mass physiological saline and allowed to stand for a predetermined time, and then the absorbent was taken out of the physiological saline and placed on a net for 10 minutes. After leaving for 10 minutes, the mass of the absorber was measured. The amount of absorption was calculated from the mass of the absorbent before and after absorption of physiological saline. The standing time in physiological saline was 10 minutes, 30 minutes, and 60 minutes. As a comparative test, the amount of water absorption resin 2g in a nylon net bag was measured in the same manner.

[Preparation of adhesive]
The following sticking agents 1 to 5 were prepared as sticking agents.
Fixing agent 1: Low molecular weight polyolefin wax (manufactured by Mitsui Chemicals, high wax 1160H, having an aromatic group in the molecule)
Fixing agent 2: Low molecular weight polyolefin wax (manufactured by Mitsui Chemicals, high wax 4202E, having a carboxyl group in the molecule)
Fixing agent 3: Low molecular weight polyolefin wax (Mitsui Chemicals, Excellex (registered trademark) 15341PA, having a carboxyl group in the molecule)
Fixing agent 4: Low molecular weight polyolefin wax (manufactured by Mitsui Chemicals, high wax 110P, having no functional group in the molecule)
Adhesive 5: Synthetic rubber hot melt adhesive (MORESCO, Morescommelt TN-260Z, having an aromatic group in the molecule)

[Synthesis of water-absorbing resin powder]
<Synthesis Example 1>
Water-soluble ethylenically unsaturated monomer (a1-1) {acrylic acid, manufactured by Mitsubishi Chemical Corporation, purity 100%} 155 parts by mass (2.15 mol part), internal cross-linking agent (b1) {pentaerythritol triallyl ether, Made by Daiso Co., Ltd.} 0.6225 parts by mass (0.0024 mol part) and 340.27 parts by mass of deionized water were kept at 1 ° C. while stirring and mixing. After flowing nitrogen into this mixture to reduce the dissolved oxygen amount to 0.1 ppm or less, 0.31 part by mass of a 1% by mass hydrogen peroxide aqueous solution, 1.1625 parts by mass of an aqueous 1% by mass ascorbic acid solution, and 0.5% by mass Polymerization was initiated by adding and mixing 2.325 parts by weight of a 2,2′-azobis [2-methyl-N- (2-hydroxyethyl) -propionamide] aqueous solution. After the temperature of the mixture reached 85 ° C., a water-containing gel was obtained by polymerization at 85 ± 2 ° C. for about 10 hours.

  Next, 128.42 parts by mass of 48.5 mass% sodium hydroxide aqueous solution was added and mixed while chopping 502.27 parts by mass of this hydrogel with a mincing machine (ROYAL, “12VR-400K”). Further, 3 parts by mass of a 1% by mass aqueous solution of ethylene glycol diglycidyl ether was added and mixed to obtain a chopped gel (2). Further, the chopped gel (2) was dried with a ventilation band dryer {200 ° C., wind speed 5 m / sec} to obtain a dried product. The dried product was pulverized with a juicer mixer (manufactured by Oster, “OSTERIZER BLENDER”), and then adjusted to a particle size of 150 μm to 710 μm using a sieve having openings of 150 μm and 710 μm to obtain dried particles.

  While stirring 100 parts by mass of the dry particles (high-speed stirring turbulizer: 2,000 rpm, manufactured by Hosokawa Micron Co., Ltd.), a 2% water / methanol mixed solution of ethylene glycol diglycidyl ether (mass ratio of water / methanol = 70/30) 5 parts by mass was added by spraying and mixed, and the mixture was allowed to stand at 150 ° C. for 30 minutes for surface crosslinking to obtain (A) a crosslinked polymer. With respect to 100 parts by mass of this (A) cross-linked polymer, (B) 0.5 part by mass of silica (manufactured by Toshin Kasei Co., Ltd., “Aerosil 380”) and carboxy-modified polysiloxane (Shin-Etsu Chemical) 0.02 parts by mass of “X-22-3701E” manufactured by Kogyo Co., Ltd. was added and stirred at 85 ° C. for 60 minutes. The weight average particle diameter of the obtained resin powder was adjusted to 400 μm to obtain a water absorbent resin powder. The resulting water-absorbent resin powder had a bulk density of 0.72 g / ml, a water absorption ratio of 60 g / g, a water absorption capacity under pressure of 2 kPa of 35 g / g, and a water absorption speed by vortex method of 45 seconds.

[Production of absorber]
Absorber 1
A beaker was charged with 20 g of water-absorbent resin powder and 0.5 g of fixing agent 1 and kneaded while heating to 130 ° C. Thereafter, the mixture was cooled to 80 ° C. to obtain a water-absorbent resin powder coated with the fixing agent 1. On the first substrate (68 mm × 150 mm), 2 g of the water absorbent resin coated with the fixing agent 1 was sprayed. The water-absorbing resin was sprayed in a plurality of streaks (7 mm) so as to be parallel to the longitudinal direction of the first base material, and the streak spacing was 7 mm. A second base material (68 mm × 150 mm) was stacked on the first base material so as to sandwich the water-absorbent resin, and thermocompression bonded at 150 ° C. to prepare the absorbent body 1. Note that air-through nonwoven fabric (component fiber: polyethylene / polyethylene terephthalate fiber) was used for the first base material and the second base material.

Absorber 2, 3
Absorbers 2 and 3 were produced in the same manner as the absorber 1 except that the adhesive 1 was changed to the adhesives 2 and 3.

Absorber 4
On the first base material (68 mm × 150 mm), the fixing agent 4 was applied so as to have a basis weight of 10 g / m ^2, and ² g of water-absorbing resin powder was sprayed on the fixing agent 4. The water-absorbing resin was sprayed in a plurality of streaks (7 mm) so as to be parallel to the longitudinal direction of the first base material, and the streak spacing was 7 mm. On the second substrate (68 mm × 150 mm), the fixing agent 4 was applied so as to have a basis weight of 10 g / m ² . On the first base material, the second base material was overlapped with the side to which the fixing agent 4 was applied inward so as to sandwich the water-absorbent resin, and thermocompression bonded at 140 ° C. to prepare the absorbent body 4. Note that air-through nonwoven fabric (component fiber: polyethylene / polyethylene terephthalate fiber) was used for the first base material and the second base material.

Absorber 5
Absorber 5 was produced in the same manner as absorber 4 except that adhesive 4 was changed to adhesive 5.

  Table 1 shows the results of evaluation of the absorption amount of the absorber and the physical properties of the fixing agent.

  As shown in Table 1, in the absorbent bodies 1 to 3 using the sticking agent having a penetration of 10 or less, the absorption amount was smaller than that of the comparative test (water absorbent resin powder only) for 10 minutes. For the absorption time of 30 minutes and 60 minutes, the absorption amount was the same as in the comparative test. From this result, it can be seen that the fixing agent having a penetration of 10 or less does not inhibit the swelling of the water-absorbent resin powder and can maximize the absorbability of the water-absorbent resin powder.

  On the other hand, in the absorbent bodies 4 and 5 using the sticking agent having a penetration of 25 and 60, the absorption amount was smaller than that of the comparative test at any of the absorption times of 10, 30, and 60 minutes. This is presumably because the swelling of the water-absorbent resin powder was inhibited by the fixing agent, and the absorbability of the water-absorbent resin powder could not be sufficiently exhibited.

  The absorbent body of the present invention can be suitably used for, for example, an absorbent article used to absorb bodily fluids discharged from the human body, and particularly suitably used as an absorbent article such as an incontinence pad, a disposable diaper, and a sanitary napkin. it can.

1: disposable diaper (absorbent article), 2: front abdomen, 3: back of the back, 4: crotch, 5: notch, 6: exterior sheet material, 7: edge, 8: elastic member for front waist, 9 : Elastic member for rear waist, 10: elastic member for front leg, 11: elastic member for rear leg, 12: elastic member for front waist, 13: elastic member for rear waist, 15: front end press sheet , 16: rear end pressing sheet, 17: side sheet, 18: elastic member, 20: water-absorbing main body, 21: absorbent body, 22: liquid-permeable top sheet, 23: liquid-impermeable back sheet, 24: water-absorbing sheet Resin powder, 25: fixing agent, 26, 27: substrate

Claims (13)

Having a base material and a water-absorbing resin powder fixed to the base material by a fixing agent;
The fixing agent is a penetration (JIS K 2235) of 0.1 or more state, and are 10 or less,
The fixing agent has a melting temperature of 50C to 160C;
The absorbent body, wherein the amount of the sticking agent used is 0.3 part by mass to 5 parts by mass with respect to 100 parts by mass of the water absorbent resin powder .   The absorbent according to claim 1, wherein the water-absorbent resin powder has an absorption capacity under pressure of 2 kPa of 10 g / g to 35 g / g.   The absorbent according to claim 1 or 2, wherein the water absorption rate of the water absorbent resin powder by a vortex method is 10 seconds to 75 seconds. The absorber according to any one of claims 1 to 3 , wherein the fixing agent is natural wax or synthetic wax .   The said fixing agent is a compound which has at least 1 sort (s) selected from the group which consists of an ether group, ester group, a carboxyl group, a hydroxyl group, and an amide group in a molecule | numerator. Absorber. The water-absorbent resin powder is a crosslinked polymer having an acrylic acid component content of 90% by mass or more, and at least a part of the carboxyl groups is neutralized . The absorber according to one item. The basis weight of the water-absorbent resin ^powder, the absorbent body according to any one of claims 1 to 6 is a ^{20g / m 2 ~500g / m 2} .   The absorber according to any one of claims 1 to 7, wherein the base material contains at least one selected from the group consisting of polyethylene, polypropylene, and polyethylene terephthalate as a constituent material.   The said base material is a thermal bond nonwoven fabric, The absorber as described in any one of Claims 1-8.   The base material is an eccentric core-sheath type spontaneously crimped fiber composed of a core part composed of a first component and a sheath part composed of a second component, or a parallel type composed of a first component and a second component. The absorbent body according to any one of claims 1 to 9, comprising a spontaneous crimped fiber.   The absorbent body according to any one of claims 1 to 10, wherein the absorbent body is produced by heat-treating the water-absorbent resin particles coated with the fixing agent on a substrate. A water-absorbent resin powder used for the absorber according to claim 11,
A water absorbent resin powder, wherein water absorbent resin particles constituting the water absorbent resin powder are coated with the fixing agent.   An absorbent article comprising the absorbent body according to any one of claims 1 to 11.

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