JP2005334616A - Absorber and absorptive article using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an absorber and an absorptive article using the absorber having a sufficient absorption quantity of aqueous liquid even if reducing the content of hydrophilic fiber in the absorber, and having excellent absorbability of aqueous liquid even under pressure. <P>SOLUTION: The absorber comprising water absorptive resin and hydrophilic fiber is characterized in that the basis weight of the water absorptive resin is 270 g/m<SP>2</SP>or less, that the basis weight of the hydrophilic fiber is 180 g/m<SP>2</SP>or less, that the physiological saline water capacity A of the water absorptive resin is 45-60 g/g and that a physiological saline water absorption quantity B1 under the pressure of 2,069 Pa is 25 g/g or more. The absorptive article is formed by holding the absorber between a liquid permeable sheet and a liquid impermeable sheet. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an absorbent body and an absorbent article in which the absorbent body is used. More specifically, the present invention relates to a sanitary material such as a paper diaper, an incontinence pad, and a sanitary napkin, in particular, an absorbent body suitably used for a paper diaper and an absorbent article using the same.

  Absorbent articles such as disposable diapers, sanitary napkins, incontinence pads, etc. are composed of a liquid permeable sheet disposed on the side in contact with the body, and a liquid impermeable sheet disposed on the side opposite to the side in contact with the body. Between, the absorber is held. The absorbent body absorbs and retains an aqueous liquid such as urine and blood excreted from the body, and is composed of a water-absorbent resin and hydrophilic fibers for absorbing and retaining the aqueous liquid. ing.

  Hydrophilic fibers have a feature of low water absorption per unit weight and easy release of absorbed aqueous liquid when pressure is applied, but very fast water absorption speed and good liquid diffusibility. Therefore, the hydrophilic fiber plays a role of holding and diffusing the aqueous liquid until the water absorbent resin absorbs the aqueous liquid. Further, the hydrophilic fibers can prevent so-called gel blocking, in which the swollen water-absorbing resin is deformed by pressurization to close the gaps between the water-absorbing resins and prevent the flow of the aqueous liquid through the gaps. Furthermore, the hydrophilic fiber also plays a role of preventing the movement of the water absorbent resin in the absorbent body and imparting flexibility to the absorbent body.

  On the other hand, the water-absorbent resin has a property that it has a large amount of water absorption per unit weight and does not easily release an aqueous liquid even when a certain amount of pressure is applied. Therefore, the water absorbent resin has a role of absorbing and holding the aqueous liquid held and diffused by the hydrophilic fiber.

  Therefore, in the absorbent body, the ratio between the hydrophilic fiber and the water absorbent resin is a factor that greatly affects the performance of the absorbent body. That is, when the ratio of the hydrophilic fiber in the absorbent body is large, the diffusibility of the aqueous liquid is improved, but the amount of reversal of the aqueous liquid increases when pressure is applied. In addition, if the proportion of the water-absorbent resin in the absorbent body is large, gel blocking occurs, the diffusibility of the aqueous liquid deteriorates, and the aqueous liquid is absorbed only in a small region of the absorbent body, and the original performance of the absorbent body is exhibited. Therefore, the amount of return of the aqueous liquid increases.

  In recent years, the thickness of absorbent articles has been reduced, and in the absorbent body, the amount of water-absorbing resin having a large amount of water absorption and a low bulk has been increased in order to prevent the water absorption amount from being reduced even when the thickness is reduced. There is a tendency to reduce the amount of hydrophilic fiber which is small and bulky. As such an absorbent body and an absorbent article in which the absorbent body is used, for example, an absorbent body using a water-absorbing resin focusing on a specific property and an absorbent article in which the absorbent body is used are known (for example, Patent Documents 1, 2, 3 and 4).

  However, if the content of the hydrophilic fiber in the absorbent body is reduced to reduce the thickness of the absorbent article, gel blocking occurs, and the water absorbent resin in the absorbent body cannot be used effectively. As a result, the total amount of the aqueous liquid that can be absorbed by the absorber is reduced, and there is a problem that the aqueous liquid cannot be completely absorbed and leaks from the absorber or the amount of reversion increases.

  Therefore, in recent years, an absorption having a sufficient absorption capacity of an aqueous liquid even when the content of hydrophilic fibers in the absorbent body is reduced and having an excellent absorption capacity of an aqueous liquid even when pressure is applied. Body development is desired.

US Pat. No. 5,147,343 JP-A-5-200068 JP-A-6-254118 Japanese National Publication No. 9-510889

  INDUSTRIAL APPLICABILITY The present invention has an absorbent body that has a sufficient amount of absorption of an aqueous liquid even if the content of hydrophilic fibers in the absorbent body is reduced, and that is excellent in absorbability of an aqueous liquid even under pressure, and the same. It is an object to provide an absorbent article.

That is, the present invention
(1) An absorbent body composed of a water absorbent resin and hydrophilic fibers, wherein the basis weight of the water absorbent resin is 270 g / m ² or less, the basis weight of the hydrophilic fibers is 180 g / m ² or less, and the water absorbency. (2) the absorbent body, wherein the physiological saline water retention amount (A) of the resin is 45 to 60 g / g, and the physiological saline water absorption amount (B1) under a pressure of 2069 Pa is 25 g / g or more; It is related with the absorbent article formed by hold | maintaining the absorber as described in (1) between a liquid-permeable sheet and a liquid-impermeable sheet.

  According to the present invention, there is provided an absorbent body having a sufficient amount of absorption of an aqueous liquid even when the content of hydrophilic fibers in the absorbent body is reduced, and having excellent aqueous liquid absorbency even under pressure, and The absorbent article used is provided. Therefore, the absorbent body of the present invention and the absorbent article in which the absorbent body is used can reduce the content of hydrophilic fibers in the absorbent body, and thus can be reduced in thickness, such as disposable diapers, incontinence pads, It can be suitably used for disposable sanitary materials such as sanitary napkins and breast milk pads, especially disposable diapers.

  The absorbent body of the present invention and the absorbent article using the same will be described below. Examples of the absorbent article include disposable sanitary materials such as disposable diapers, incontinence pads, sanitary napkins, and breast milk pads, but the present invention is not limited to such examples.

  The absorbent article of the present invention has a liquid permeable sheet (top sheet) through which an aqueous liquid can pass and a liquid impermeable sheet (back) through which the aqueous liquid cannot pass. Sheet). The liquid permeable sheet is disposed on the side in contact with the body, and the liquid impermeable sheet is disposed on the side opposite to the side in contact with the body.

  Examples of the liquid permeable sheet include a nonwoven fabric made of a synthetic resin such as polyethylene, polypropylene, polyester, and polyamide, and a porous synthetic resin sheet. However, the present invention is not limited to such examples. .

  Examples of the liquid-impermeable sheet include films made of synthetic resins such as polyethylene, polypropylene, and polyvinyl chloride, and sheets made of composite materials of these synthetic resins and nonwoven fabrics. It is not limited to only.

  Since the sizes of the liquid permeable sheet and the liquid impermeable sheet vary depending on the use of the absorbent article, etc., they cannot be determined in general. Therefore, it is preferable to appropriately adjust the size according to the application.

Since the basis weight of the liquid permeable sheet and the liquid impermeable sheet varies depending on the use of the absorbent article, etc., it cannot be determined unconditionally. For example, if the absorbent article is a disposable diaper, these basis weight, respectively, usually it is preferably ^{10~300g / m 2, 15~200g / m} 2 is more preferable.

  The absorbent body of the present invention is composed of a water absorbent resin and hydrophilic fibers. Examples of the structure of the absorber include a mixing structure in which a water-absorbing resin and hydrophilic fibers are uniformly blended, a sandwich structure in which a water-absorbing resin is held between layered hydrophilic fibers, and a water-absorbing resin and hydrophilic fibers. Although the structure etc. which were wrapped with water-permeable papers, such as tissue paper, are mentioned, this invention is not limited only to this illustration. The absorbent body of the present invention may contain synthetic fibers as a reinforcing material.

The basis weight of the water-absorbent resin in the absorbent body, the water-absorbing resin from the viewpoint of suppressing the movement, preferably 270 g / m ² or less in reducing or absorbing member of flexible absorber, 130~270g / m ² Is more preferable. On the other hand, the basis weight of the hydrophilic fibers in the absorbent body, from the viewpoint of thinning of the absorber is preferably 180 g / m ² or less, 80~180g / m ² is more preferable.

  Examples of the hydrophilic fiber include cellulose fibers such as cotton-like pulp, mechanical pulp, chemical pulp, and semi-chemical pulp obtained from wood, and artificial cellulose fibers such as rayon and acetate. It is not limited to only. . In addition, as long as the objective of this invention is in the range which is not inhibited, the hydrophilic fiber may contain synthetic fibers, such as polyamide, polyester, polyolefin, for example.

  The physiological saline water retention amount (A) of the water absorbent resin used in the present invention is preferably 45 to 60 g / g, more preferably 45 to 55 g / g. When the physiological saline water retention amount is less than the lower limit in the above numerical range, the amount of reversal of the obtained absorbent tends to increase, and when the amount exceeds the upper limit, the amount of water absorption under pressure of the absorber tends to decrease. There is.

  In addition, the physiological saline water retention amount (A) of the water-absorbent resin is a value when measured according to the measurement method described in “(1) physiological saline water retention amount” described later.

  The physiological saline water absorption (B1) under pressure of 2069 Pa of the water absorbent resin used in the present invention is 25 g / g or more, preferably 25 to 50 g / g, more preferably 29 to 45 g / g.

  Moreover, the physiological saline water absorption amount (B2) under pressure of 4137 Pa of the water-absorbent resin is 12 g / g or more, preferably 12 to 40 g / g, and more preferably 13 to 35 g / g.

  Furthermore, the physiological saline water absorption amount (B3) of the water absorbent resin under a pressure of 6206 Pa is 8 g / g or more, preferably 8 to 30 g / g, more preferably 9 to 25 g / g.

  Note that the pressure under 2069 Pa, 4137 Pa or 6206 Pa is set here because the absorbent article is exposed to various pressures when the wearer of the absorbent article takes a posture such as sitting or standing. This is based on the reason that the water-absorbent resin has the ability to absorb more liquid even in the wet state.

  In addition, the physiological saline water absorption amount of the water-absorbing resin under the pressure of 2069 Pa, 4137 Pa or 6206 Pa is set to be equal to or higher than the lower limit value, which is deformed when the swollen water-absorbing resin is pressurized. In addition, it suppresses the occurrence of gel blocking that blocks the gap between the water-absorbent resins and prevents the flow of the aqueous liquid through the gap, and the pressure is normally applied to the water-absorbent resin when the absorbent article is used. Therefore, even under pressure, the physiological saline water absorption amount of the water absorbent resin is satisfied.

  The physiological saline water absorption amount (B1) to (B3) under pressure of the water-absorbent resin is described in “(2) physiological saline water absorption amount under pressure (2069 Pa)” to “(4) under pressure. It is a value when measured according to the measurement method described in “Water absorption amount of physiological saline (6206 Pa)”.

  The water absorption rate (C) of the water absorbent resin is 25 to 100 seconds, preferably 30 to 90 seconds, and more preferably 35 to 80 seconds. When the water absorption rate of the water absorbent resin is less than the lower limit in the above numerical range, the aqueous liquid is absorbed by the water absorbent resin without sufficiently diffusing in the absorber, and as a result, the amount of reversion from the absorber increases. There is a tendency, and when the upper limit is exceeded, the aqueous liquid tends to leak from the absorber.

  The water absorption rate (C) of the water absorbent resin is a value when measured according to the measurement method described in “(5) Water absorption rate” described later.

  The water-absorbent resin used in the present invention is desirably water-absorbent resin particles having a weight average particle diameter (D) of 200 to 500 μm, preferably 250 to 400 μm. When the weight average particle diameter of the water-absorbent resin is less than the lower limit in the above numerical range, it becomes difficult to handle due to powdering and the like, and gel blocking tends to occur in the absorbent body, and exceeds the upper limit. In this case, there is a tendency that the diffusibility of the aqueous liquid is deteriorated, the user feels a foreign body feeling, and the absorbent article cannot be used comfortably.

  In addition, the weight average particle diameter (D) of the water absorbent resin is a value when measured according to the measurement method described in “(6) Weight average particle diameter” described later.

  Examples of the water-absorbing resin include crosslinked acrylate polymers, crosslinked vinyl alcohol / acrylate copolymers, crosslinked maleic anhydride grafted polyvinyl alcohol, crosslinked isobutylene / maleic anhydride copolymers, carboxymethyl cellulose. And a hydrolyzate of starch / acrylonitrile graft copolymer. In these, an acrylate polymer crosslinked material is preferable.

  The water-absorbing resin is usually obtained by polymerizing a hydrophilic unsaturated monomer and then crosslinking. The hydrophilic unsaturated monomer is not particularly limited as long as it is usually used for polymerization.

  The hydrophilic unsaturated monomer is, for example, selected from the group consisting of (meth) acrylic acid, maleic acid, maleic anhydride, fumaric acid and other α, β-unsaturated carboxylic acids and partially neutralized products thereof. And monomers containing at least one kind. Of these, (meth) acrylic acid is preferred. In the present specification, “(meth) acryl” means “acryl” and / or “methacryl”.

  If necessary, the hydrophilic unsaturated monomer may be copolymerized with other monomers. Examples of other monomers include (meth) acrylamide, N-substituted (meth) acrylamide, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, methoxypolyethylene glycol (meth) acrylate, and polyethylene. Nonionic hydrophilic group-containing monomers such as glycol (meth) acrylate; N, N-dimethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylate, N, N-dimethylaminopropyl (meta) ) Amino group-containing unsaturated monomers such as acrylamide; vinyl sulfonic acid, styrene sulfonic acid, 2- (meth) acrylamido-2-methylpropane sulfonic acid, 2- (meth) acryloylethanesulfonic acid and their salts And sulfonic acid monomers These may be used alone or in admixture of two or more thereof.

  The hydrophilic unsaturated monomer is usually used as an aqueous solution. The concentration of the hydrophilic unsaturated monomer in the hydrophilic unsaturated monomer aqueous solution is preferably 25% by weight to a saturated concentration.

  The degree of neutralization of the water absorbent resin is 20 to 100 mol%, preferably 30 to 90 mol% of the total amount of acid groups of the water absorbent resin. The neutralization of the water-absorbing resin may be performed on the monomer that is the raw material, or may be performed during or after the polymerization.

  Examples of the salt used when neutralizing the water absorbent resin include alkali metal salts, alkaline earth metal salts, ammonium salts, and the like. In these, alkali metal salts, such as sodium and potassium, are preferable.

  The polymerization method of the hydrophilic unsaturated monomer is not particularly limited, and examples thereof include a reverse phase suspension polymerization method, an aqueous solution polymerization method, a bulk polymerization method, and a precipitation polymerization method. Among these polymerization methods, from the viewpoint of water absorption and ease of control of polymerization, the reverse phase suspension polymerization method and the aqueous solution polymerization method are preferable, and the multistage polymerization method in which the reverse phase suspension polymerization is performed in two or more stages. Is more preferable.

  Hereinafter, a reverse phase suspension polymerization method will be described as an example of a method for polymerizing a hydrophilic unsaturated monomer, but the present invention is not limited to such a polymerization method.

  In the reverse phase suspension polymerization method, a hydrophilic unsaturated monomer aqueous solution is dispersed in an organic solvent in the presence of at least one of a surfactant and a polymer protective colloid, for example, a water-soluble radical. By using a polymerization initiator or the like, the hydrophilic unsaturated monomer is polymerized.

  Examples of the organic solvent include aliphatic hydrocarbon solvents such as n-pentane, n-hexane, n-heptane, and ligroin; alicyclic hydrocarbon solvents such as cyclopentane, methylcyclopentane, cyclohexane, and methylcyclohexane; benzene, And aromatic hydrocarbon solvents such as toluene and xylene. Of these organic solvents, n-heptane and cyclohexane are preferred.

  The surfactant and the polymer protective colloid may be used alone or in combination of two or more.

  Examples of the surfactant include sorbitan fatty acid ester, mono fatty acid glycerin, polyglycerin fatty acid ester, sucrose fatty acid ester, polyoxyethylene hydrogenated castor oil, polyoxyethylene hydrogenated castor oil laurate, and polyoxyethylene (tri) isostearate. Nonionic surfactants such as hydrogenated castor oil, polyoxyethylene alkylphenyl ether, polyoxyethylene lauryl ether, polyoxyethylene hexyl decyl ether; fatty acid salt, alkylbenzene sulfonate, alkylmethyl taurate, polyoxyethylene alkyl And anionic surfactants such as phenyl ether sulfate ester salt and polyoxyethylene alkyl ether sulfonate salt.

  Examples of the polymer protective colloid include ethyl cellulose, ethyl hydroxyethyl cellulose, polyethylene oxide, anhydrous maleated polyethylene, anhydrous maleated polybutadiene, and anhydrous maleated ethylene propylene diene terpolymer.

  The amount of the surfactant and the polymer protective colloid used is preferably 0.1 to 5 parts by weight, more preferably 0.2 to 3 parts by weight with respect to 100 parts by weight of the aqueous solution of the hydrophilic unsaturated monomer. is there. When the amount of the surfactant and the polymer protective colloid used is less than the lower limit in the above numerical range, the dispersion of the hydrophilic unsaturated monomer aqueous solution tends to be insufficient, and when the upper limit is exceeded, There is a tendency that the effect corresponding to the amount of use is not seen, and it becomes less economical.

When initiating the polymerization of the hydrophilic unsaturated monomer, a water-soluble radical polymerization initiator can be used. Examples of the water-soluble radical polymerization initiator include persulfates such as potassium persulfate, ammonium persulfate, and sodium persulfate; peroxides such as hydrogen peroxide; 2,2′-azobis (2-amidinopropane) 2 hydrochloric acid Examples thereof include azo compounds such as salts. Suitable water-soluble radical polymerization initiators include potassium persulfate, ammonium persulfate, sodium persulfate, 2,2′-azobis (2-amidinopropane) dihydrochloride, and the like. Or two or more of them may be used in combination.
The water-soluble radical polymerization initiator may be used as a redox polymerization initiator by using it together with sulfite or the like.

  It is preferable that the usage-amount of a water-soluble radical polymerization initiator is 0.00005-0.01 mol with respect to 1 mol of hydrophilic unsaturated monomers. When the amount of the water-soluble radical polymerization initiator used relative to 1 mol of the hydrophilic unsaturated monomer is less than 0.00005 mol, the polymerization time tends to be long. The polymerization reaction tends to be difficult to control.

  The polymerization temperature for carrying out the polymerization reaction varies depending on the type of hydrophilic unsaturated monomer and water-soluble radical polymerization initiator used, the concentration of the aqueous monomer solution, etc. From the viewpoint of easily removing the polymerization heat and performing a smooth polymerization reaction, the temperature is preferably 20 to 110 ° C, more preferably 40 to 80 ° C.

  In addition, from the viewpoint of increasing the water retention amount and the water absorption amount under pressure of the obtained water absorbent resin, an internal crosslinking agent having two or more polymerizable unsaturated groups or two or more reactive groups is used. It is preferable to internally cross-link the resin.

  Examples of the internal cross-linking agent include (poly) ethylene glycol, (poly) propylene glycol, 1,4-butanediol, trimethylolpropane, polyoxyethylene glycol, polyoxypropylene glycol, diols such as (poly) glycerin, and triols. Or polyols; unsaturated polyesters obtained by reacting the diols, triols or polyols with unsaturated acids such as (meth) acrylic acid, maleic acid, fumaric acid; N, N′-methylenebisacrylamide, etc. Bisacrylamides; diols, triols or polyols obtained by reacting polyepoxides with (meth) acrylic acid; polyisocyanates such as tolylene diisocyanate, hexamethylene diisocyanate and hydroxy methacrylates (meth) acrylic acid Di (meth) acrylic acid carbamyl esters obtained by reaction with ruthenium; polymerizable non-polymerization such as allylated starch, allylated cellulose, diallyl phthalate, N, N ′, N ″ -triallyl isocyanate, and divinylbenzene Compounds having two or more saturated groups; diglycidyl ether compounds such as (poly) ethylene glycol diglycidyl ether, (poly) propylene glycol diglycidyl ether, (poly) glycerin diglycidyl ether; epichlorohydrin, epibromohydrin, α- Epihalohydrin compounds such as methyl epichlorohydrin; compounds having two or more reactive functional groups such as isocyanate compounds such as 2,4-tolylene diisocyanate and hexamethylene diisocyanate; 3-methyl-3-oxetanemethanol, 3-ethyl-3 Examples include oxetane compounds such as -oxetanemethanol, 3-butyl-3-oxetanemethanol, 3-methyl-3-oxetaneethanol, 3-ethyl-3-oxetaneethanol, and 3-butyl-3-oxetaneethanol. These may be used alone or in combination of two or more.

  The amount of the internal cross-linking agent used is such that the obtained polymer exhibits sufficient water absorption by suppressing water solubility by appropriate cross-linking, with respect to 1 mol of the hydrophilic unsaturated monomer. , 0.000001 to 0.001 mol is preferable.

  Furthermore, it is preferable to polymerize a hydrophilic unsaturated monomer in the presence of a phosphorus compound from the viewpoint of increasing the water retention amount of the water-absorbing resin obtained and the water absorption amount under pressure. When reverse phase suspension polymerization is performed in two or more stages, it is preferable to add a phosphorus compound in at least one stage after the second stage.

  Examples of phosphorus compounds include phosphorous acid; orthophosphoric acid salts such as disodium phosphite, dipotassium phosphite, diammonium phosphite, sodium hydrogen phosphite, potassium hydrogen phosphite, Phosphorous acid compounds such as acid salts of phosphorous acid such as ammonium hydrogen phosphate; phosphoric acid; normal salts of phosphoric acid such as sodium phosphate, potassium phosphate, ammonium phosphate, sodium dihydrogen phosphate, diphosphoric acid phosphate Phosphoric acid compounds such as potassium hydrogen, ammonium dihydrogen phosphate, disodium hydrogen phosphate, dipotassium hydrogen phosphate, diammonium hydrogen phosphate, etc .; phosphorous acid; hypophosphorous acid; sodium hypophosphite, Hypophosphite compounds such as hypophosphites such as potassium hypophosphite and ammonium hypophosphite; pyrophosphoric acid, tripolyphosphoric acid, polyphosphoric acid and salts thereof; trime phosphate Le, include nitrilotriacetic such as methylene tri phosphonic acid. These can be used alone or in admixture of two or more. Moreover, you may use the hydrate as a phosphorus compound. Among the phosphorus compounds, phosphite compounds, phosphate compounds and hypophosphite compounds are preferable, and disodium phosphite, sodium dihydrogen phosphate and sodium hypophosphite are more preferable.

  The amount of the phosphorus compound used is preferably 0.00001 to 0.05 mol, more preferably 0.00005 to 0.02 mol, still more preferably 0.0001 to 1 mol per 1 mol of the hydrophilic unsaturated monomer. 0.01 mole. When the amount of the phosphorus compound used is less than the lower limit in the above numerical range, the effect due to the use of the phosphorus compound tends not to be sufficiently expressed, and when it exceeds the upper limit, the polymerization rate tends to be slow. is there.

  After radical polymerization of the hydrophilic unsaturated monomer, a post-crosslinking agent containing two or more functional groups having reactivity with a carboxyl group is allowed to act on the obtained water-absorbing resin to perform post-crosslinking. Preferably it is done.

  As the post-crosslinking agent, one that can react with the carboxyl group of the water-absorbent resin is used. Specific examples of the post-crosslinking agent include (poly) ethylene glycol, (poly) propylene glycol, 1,4-butanediol, trimethylolpropane, polyoxyethylene glycol, polyoxypropylene glycol, diols such as (poly) glycerin, Triols or polyols; diglycidyl ether compounds such as (poly) ethylene glycol diglycidyl ether, (poly) propylene glycol diglycidyl ether, (poly) glycerin diglycidyl ether; epichlorohydrin, epibromhydrin, α-methylepichlorohydrin, etc. Epihalohydrin compounds; compounds having two or more reactive functional groups such as isocyanate compounds such as tolylene diisocyanate and hexamethylene diisocyanate. These may be used alone or in combination of two or more.

  The amount of the post-crosslinking agent varies depending on the type of the post-crosslinking agent, and thus cannot be determined unconditionally, but is usually preferably 0.00001 to 0.01 with respect to 1 mol of the hydrophilic unsaturated monomer. Mol, more preferably 0.00005 to 0.005 mol, and still more preferably 0.0001 to 0.002 mol. When the amount of the post-crosslinking agent used is less than the lower limit in the above numerical range, the crosslinking density of the water absorbent resin cannot be sufficiently increased, and the water absorption amount under pressure tends to decrease, When the upper limit is exceeded, the amount of the cross-linking agent becomes excessive, so that an unreacted cross-linking agent tends to remain.

  The method for adding the post-crosslinking agent is not particularly limited, but in order to add the post-crosslinking agent while uniformly dispersing the water-absorbent resin, the post-crosslinking agent is dissolved in a hydrophilic solvent such as water and added. It is preferable. Further, the post-crosslinking agent may be added in one or two or more divided portions.

  The water absorbent resin can be dried by removing moisture and organic solvent from the water absorbent resin thus obtained. In addition, you may classify the obtained water absorbing resin with a sieve etc. as needed.

  For the purpose of imparting other functions, additives such as a lubricant, an oxidizing agent, a reducing agent, a deodorant, and an antibacterial agent may be added to the obtained water absorbent resin.

  Next, the present invention will be described in more detail based on examples, but the present invention is not limited to such examples.

Production Example 1
In a 1000 mL five-necked cylindrical round bottom flask equipped with a stirrer, reflux condenser, dropping funnel, thermometer and nitrogen gas inlet tube, 340 g of n-heptane and sucrose fatty acid ester [Mitsubishi Chemical Foods Co., Ltd. Manufactured, trade name: S-370] 0.92 g was added and dispersed, heated to 80 ° C. and dissolved, and then cooled to 55 ° C.

  Separately, 92 g (1.02 mol) of an 80 wt% aqueous acrylic acid solution was added to a 500 mL Erlenmeyer flask. While cooling from the outside so that the internal temperature becomes about 5 ° C., 102.2 g (0.76 mol) of a 30 wt% aqueous sodium hydroxide solution was dropped into this Erlenmeyer flask, and 75 mol% of acrylic acid was added in the middle. It was summed up. Further, 50.2 g of water, 0.11 g (0.41 mmol) of potassium persulfate and 8.3 mg (0.047 mmol) of ethylene glycol diglycidyl ether were added to prepare a monomer aqueous solution for the first stage polymerization. did.

  In the five-necked cylindrical round bottom flask, the entire amount of the monomer aqueous solution for the first stage polymerization is added and dispersed under stirring, and the system is sufficiently replaced with nitrogen gas, and then heated to a bath. After maintaining the temperature at 70 ° C. and carrying out the polymerization reaction for 1 hour, the polymerization slurry was cooled to room temperature.

  In another 500 mL Erlenmeyer flask, 119.1 g (1.32 mol) of 80 wt% aqueous acrylic acid solution was added and cooled to about 5 ° C., while 132.2 g (0.99 wt) of 30 wt% aqueous sodium hydroxide solution was cooled. Mol) was added dropwise to neutralize 75 mol% of acrylic acid, and further 27.4 g of water, 0.14 g (0.52 mmol) of potassium persulfate and 0.72 g of disodium phosphite pentahydrate ( 3.3 mmol) was added to prepare an aqueous monomer solution for the second stage polymerization and cooled in an ice-water bath.

  After adding the total amount of the monomer aqueous solution for the second stage polymerization to the polymerization slurry liquid, the system was again sufficiently replaced with nitrogen gas, and then the temperature was raised and the bath temperature was kept at 70 ° C. The second stage polymerization reaction was carried out for 2 hours. After completion of the polymerization, the mixture was heated in an oil bath at 120 ° C., and only water was removed from the system by azeotropic distillation to obtain a gel-like product.

  Next, 15.8 g (1.8 mmol) of a 2 wt% aqueous solution of ethylene glycol diglycidyl ether is added to the obtained gel, mixed and post-crosslinked, and water and n-heptane are distilled. And dried to obtain 213.5 g of a water absorbent resin having a weight average particle diameter of 360 μm.

Production Example 2
In Production Example 1, the amount of disodium phosphite pentahydrate used in the second-stage polymerization monomer aqueous solution was changed from 0.72 g (3.3 mmol) to 0.53 g (2.4 mmol). Example 1 except that the amount of the 2 wt% ethylene glycol diglycidyl ether aqueous solution used as the post-crosslinking agent was changed from 15.8 g (1.8 mmol) to 7.8 g (0.90 mmol). 1 was used to obtain a water absorbent resin 214.5 having a weight average particle diameter of 398 μm.

Production Example 3
In a 1000 mL five-necked cylindrical round bottom flask equipped with a stirrer, reflux condenser, dropping funnel, thermometer and nitrogen gas inlet tube, 340 g of n-heptane and sucrose fatty acid ester [Mitsubishi Chemical Co., Ltd. , Trade name: S-370] 0.92 g was added and dispersed, heated to 80 ° C. to dissolve, and then cooled to 55 ° C.

  Separately, 92 g (1.02 mol) of an 80 wt% aqueous acrylic acid solution was added to a 500 mL Erlenmeyer flask. While cooling from the outside so that the internal temperature becomes about 5 ° C., 102.2 g (0.76 mol) of a 30 wt% aqueous sodium hydroxide solution was dropped into this Erlenmeyer flask, and 75 mol% of acrylic acid was added in the middle. It was summed up. Further, 50.2 g of water, 0.11 g (0.41 mmol) of potassium persulfate and 11.0 mg (0.062 mmol) of ethylene glycol diglycidyl ether were added to prepare a monomer aqueous solution for the first stage polymerization. did.

  In the five-necked cylindrical round bottom flask, the entire amount of the monomer aqueous solution for the first stage polymerization is added and dispersed under stirring, and the system is sufficiently replaced with nitrogen gas, and then heated to a bath. After maintaining the temperature at 70 ° C. and carrying out the polymerization reaction for 1 hour, the polymerization slurry was cooled to room temperature.

  In another 500 mL Erlenmeyer flask, 119.1 g (1.32 mol) of 80 wt% aqueous acrylic acid solution was added and cooled to about 5 ° C., while 132.2 g (0.99 wt) of 30 wt% aqueous sodium hydroxide solution was cooled. Mol) was added dropwise to neutralize 75 mol% of the acrylic acid, and further 27.4 g of water, 0.14 g (0.52 mmol) of potassium persulfate and 11.9 mg (0.067 mmol) of ethylene glycol diglycidyl ether. Was added to prepare an aqueous monomer solution for the second stage polymerization and cooled in an ice-water bath.

  After adding the total amount of the monomer aqueous solution for the second stage polymerization to the polymerization slurry liquid, the system was again sufficiently replaced with nitrogen gas, and then the temperature was raised and the bath temperature was kept at 70 ° C. The second stage polymerization reaction was carried out for 2 hours. After completion of the polymerization, the mixture was heated in an oil bath at 120 ° C., and only water was removed from the system by azeotropic distillation to obtain a gel-like product.

  Next, 7.4 g (0.85 mmol) of a 2% by weight ethylene glycol diglycidyl ether aqueous solution was added to the obtained gel and mixed, followed by post-crosslinking treatment, and further water and n-heptane were distilled. And dried to obtain 216.5 g of a water absorbent resin having a weight average particle diameter of 390 μm.

Production Example 4
In Production Example 3, the amount of ethylene glycol diglycidyl ether used in the monomer aqueous solution for the first stage polymerization was changed from 11.0 mg (0.062 mmol) to 8.3 mg (0.047 mmol), The amount of ethylene glycol diglycidyl ether used in the monomer aqueous solution for the second stage polymerization was changed from 11.9 mg (0.067 mmol) to 10.7 mg (0.061 mmol), and 2 wt% ethylene glycol Except for changing the amount of diglycidyl ether aqueous solution used from 7.4 g (0.85 mmol) to 7.8 g (0.90 mmol), water absorption with a weight average particle size of 385 μm was carried out in the same manner as in Production Example 3. 215.9 g of functional resin was obtained.

  Next, the obtained water absorbent resin was evaluated according to the following methods. The results are shown in Table 1.

(1) Amount of physiological saline retained water 2.0 g of the water-absorbing resin was weighed into a cotton bag (Membroad No. 60, width 100 mm × length 200 mm) and placed in a 500 mL beaker. Into a cotton bag, 500 g of physiological saline was poured at a time, and the saline was dispersed so as not to generate water-absorbent resin. The upper part of the cotton bag was bound with a rubber band and left for 1 hour to fully swell the water-absorbent resin. The weight of the cotton bag containing the swollen gel after dehydration by dehydrating the cotton bag for 1 minute using a dehydrator (manufactured by Kokusan Centrifuge Co., Ltd., product number: H-122) set so that the centrifugal force is 167G Wa (g) was measured. The same operation was performed without adding the water-absorbent resin, and after measuring the wet hourly space weight Wb (g) of the cotton bag, the physiological saline water retention amount was expressed by the formula:
Physiological saline water retention amount (g / g) = [Wa-Wb] (g) / weight of water-absorbent resin (g)
Calculated by

(2) Absorption amount of physiological saline under pressure (2069 Pa)
The water absorption amount of the physiological saline under pressure of 2069 Pa of the water absorbent resin was measured using the measuring device X shown in FIG.

  The measuring device X shown in FIG. 1 is placed on a balance 1, a bottle 2 placed on the balance 1, an air suction pipe 3, a conduit 4, a glass filter 5, and the glass filter 5. It consists of a measurement unit 6.

  The balance 1 is connected to a computer 7 and can record the weight change in seconds or minutes. The bottle 2 holds physiological saline therein, and an air suction pipe 3 is placed in the opening at the top thereof, while a conduit 4 is attached to the trunk portion. The lower end of the air suction pipe 3 is immersed in the physiological saline 8. The diameter of the glass filter 5 is 25 mm. As the glass filter 5, glass filter No. 1 (pore diameter 100-160 μm) was used.

  The bottle 2 and the glass filter 5 are communicated with each other by a conduit 4. The glass filter 5 is fixed at a slightly higher position with respect to the lower end of the air suction pipe 3. The measurement unit 6 includes a cylinder 10, a nylon mesh 11 attached to the bottom of the cylinder 10, and a weight 12 having a diameter of 19 mm and a weight of 59.80 g. The inner diameter of the cylinder 10 is 20 mm. The nylon mesh 11 is formed to 200 mesh (a sieve opening: 75 μm). A predetermined amount of water-absorbing resin 9 is uniformly distributed on the nylon mesh 11. The weight 12 is placed on the water absorbent resin 9 so that a pressure of 2069 Pa can be applied to the water absorbent resin 9.

  In the measuring apparatus X having such a configuration, first, a predetermined amount of physiological saline and the air suction pipe 3 are placed in the bottle 2 to prepare for measurement. Next, 0.1 g of the water absorbent resin 9 is uniformly spread on the nylon mesh 11 of the cylinder 10, and the weight 12 is placed on the water absorbent resin 9. The measurement unit 6 is placed on the glass filter 5 so that the center thereof coincides with the center of the glass filter 5.

  On the other hand, the computer 7 connected to the electronic balance 1 is started and the weight of the physiological saline in the bottle 2 is continuously reduced from the time when the water absorption starts (the weight of the physiological saline absorbed by the water absorbent resin 9) Wj. Based on the value obtained from the balance 1, (g) is recorded in the computer 7 in minutes, preferably in seconds. The amount of physiological saline absorbed under pressure of the water absorbent resin 9 after 60 minutes from the start of water absorption is obtained by dividing the weight Wc (g) after 60 minutes by the weight of the water absorbent resin 9 (0.1 g). Calculated by

(3) Water absorption amount of physiological saline under pressure (4137Pa)
The water absorption amount of the physiological saline under pressure of 4137 Pa of the water-absorbent resin is the same as (2) except that the weight 12 is changed from 59.80 g to 119.63 g in the measurement method of (2). Measurement was performed and the amount of physiological saline absorbed under pressure of 4137 Pa was determined.

(4) Absorption amount of physiological saline under pressure (6206 Pa)
The water absorption amount of physiological saline under pressure of 6206 Pa of the water-absorbent resin is the same as (2) above except that the weight 12 is changed from 59.80 g to 179.46 g in the measurement method of (2). Measurement was performed to determine the amount of water absorbed by physiological saline under pressure of 6206 Pa.

(5) Water absorption rate In a 100 mL beaker, weigh 50 ± 0.01 g of physiological saline at a temperature of 25 ± 0.2 ° C., and put a magnetic stirrer bar (without 8 mmφ × 30 mm ring). It was placed on a stirrer (product number: HS-30D, manufactured by Iuchi). Subsequently, the magnetic stirrer bar was adjusted to rotate at 600 ppm, and the bottom of the vortex generated by the rotation of the magnetic stirrer bar was adjusted to be close to the top of the magnetic stirrer bar.

  Next, the water-absorbent resin was classified with two kinds of standard sieves corresponding to JIS-Z8801 (1982) (screen opening: 500 μm or 300 μm), and the particle size was adjusted (500 μm or less, 300 μm or more) 1.0 ± 0 0.002 g was quickly poured between the center of the vortex in the beaker and the side surface of the beaker, and the time (seconds) from the time when the vortex was converged until the time when the vortex converged was measured with a stopwatch to obtain the water absorption speed.

(6) Weight average particle diameter 100 g of the water-absorbent resin was weighed, and eight standard sieves corresponding to JIS-Z8801 (1982) (screen openings: 850 μm, 500 μm, 355 μm, 300 μm, 250 μm, 180 μm, 106 μm, Put in the top sieve (stacked in the order of the bottom container), vibrate for 10 minutes using a low-tap type sieve vibrator, weigh each sieve, weigh 50% based on the result The particle size to be the formula:
[Weight average particle diameter] = [(50−a) / (da)] × (c−b) + b
(In the formula, a is the cumulative value (g) when the weight is sequentially accumulated from the coarser particle size distribution, and the cumulative value at the point closest to 50% by weight is less than 50% by weight. ), B is the sieve opening (μm) when the integrated value is obtained, d is the cumulative weight sequentially from the coarser particle size distribution, and the integrated weight is 50% by weight or more and 50% by weight. The integrated value (g) when the integrated value of the nearest point is obtained, and c is the sieve opening (μm) when the integrated value is obtained)
Calculated by

Example 1
10 g of the water-absorbent resin obtained in Production Example 1 and 6 g of pulverized pulp were dry-mixed using a mixer and sprayed onto tissue paper having a size of 40 cm × 12 cm and a weight of 0.6 g, and then the same size. The tissue paper having a thickness and a weight was overlapped to form a sheet, and a weight of 196 kPa was applied to the whole for 30 seconds and pressed to obtain an absorbent body.

The obtained absorbent body is a polyethylene air-through porous liquid permeable sheet having a size of 40 cm × 12 cm and a basis weight of 22 g / m ^{2, and} a polyethylene liquid impervious having the same size and a basis weight of 40 g / m ² . by sandwiching between the sheets, basis weight of the water-absorbent resin is 208g / m ^2, the basis weight of the hydrophilic fibers to obtain an absorbent article of 125 g / m ^2.

Example 2
In Example 1, an absorbent article was obtained in the same manner as in Example 1 except that the water absorbent resin obtained in Production Example 2 was used.

Example 3
A mixture of 12 g of the water-absorbent resin obtained in Production Example 1 and 8 g of pulverized pulp using a mixer was sprayed onto a tissue having a size of 40 cm × 12 cm and a weight of 0.6 g, and then the same size. And the tissue paper of a weight was piled up, it was made into a sheet form, the weight of 196kPa was added to the whole for 30 seconds, and the absorber was obtained.

The obtained absorbent body is a polyethylene air-through porous liquid permeable sheet having a size of 40 cm × 12 cm and a basis weight of 22 g / m ^{2, and} a polyethylene liquid impervious having the same size and a basis weight of 40 g / m ² . by sandwiching between the sheets, basis weight of the water-absorbent resin is 250 g / m ^2, the basis weight of the hydrophilic fibers to obtain an absorbent article of 167 g / m ^2.

Example 4
In Example 3, an absorbent article was obtained in the same manner as in Example 3 except that the water absorbent resin obtained in Production Example 2 was used.

Comparative Example 1
In Example 1, an absorbent article was obtained in the same manner as in Example 1 except that the water absorbent resin obtained in Production Example 3 was used.

Comparative Example 2
In Example 1, an absorbent article was obtained in the same manner as in Example 1 except that the water absorbent resin obtained in Production Example 4 was used.

Comparative Example 3
In Example 3, an absorbent article was obtained in the same manner as in Example 3 except that the water absorbent resin obtained in Production Example 3 was used.

Comparative Example 4
In Example 3, an absorbent article was obtained in the same manner as in Example 3 except that the water absorbent resin obtained in Production Example 4 was used.

  Next, the absorbent articles obtained in each Example and each Comparative Example were evaluated according to the following methods. The results are shown in Table 2.

(A) Preparation of artificial urine In a 10 L container, 60 g of sodium chloride, 1.8 g of calcium chloride dihydrate, 3.6 g of magnesium chloride hexahydrate and an appropriate amount of distilled water were completely dissolved.

  Next, 0.02 g of polyoxyethylene nonylphenyl ether was added to the resulting solution, and distilled water was added to adjust the total weight of the aqueous solution to 6000 g. Furthermore, it colored with a small amount of blue No. 1 to obtain artificial urine.

(B) Penetration time under pressure A 4.5 kg weight (bottom: 10 cm × 10 cm square, height: 6.8 cm) with a 3 cm diameter cylindrical through hole in the vicinity of the center of the absorbent article. Place 50 mL of artificial urine that has been kept at 25 ± 0.2 ° C. in a constant temperature water tank into the cylindrical through-hole, and at the same time, start the stopwatch and completely absorb the artificial urine. The time until penetration into the article was measured (first penetration time under pressure).

  Next, 30 minutes after the start of the first artificial urine injection, 50 mL of artificial urine was poured again, and at the same time, the stopwatch was started, and the time required for the artificial urine to completely penetrate into the absorbent article was measured. (Second penetration time under pressure). Furthermore, the penetration time under the third pressurization was measured by the same method.

(C) Reversal amount Filter paper (Toyo filter paper No. 2) cut in advance to 10 cm × 10 cm was overlaid so that its weight was about 80 g, and its dry weight (g) was measured.

  After 60 minutes have elapsed from the end of the measurement of the penetration time under pressure, a filter paper is placed in the center of the absorbent article from which the weight has been removed, and a 5 kg weight (bottom: 10 cm × 10 cm square) is placed thereon for 5 minutes. After the weighting, the weight (g) of the filter paper that removed the weight and absorbed the return liquid was measured. The amount of reversal was calculated by subtracting the dry weight (g) from the weight (g) of the filter paper that absorbed the reversal solution.

  From the results shown in Table 2, each of the absorbent articles obtained in each Example has a small amount of reversion, a sufficient amount of absorption, and a short permeation time under pressure, It can be seen that the absorbency under pressure is also excellent.

FIG. 1 is a schematic explanatory diagram of a measuring device X used when measuring the water absorption of physiological saline under pressure.

Explanation of symbols

X measuring device 1 balance 2 bottle 3 air suction pipe 4 conduit 5 glass filter 6 measuring section 7 computer 8 physiological saline 9 water absorbent resin 10 cylinder 11 nylon mesh 12 weight

Claims (6)

An absorbent body comprising a water absorbent resin and hydrophilic fibers, wherein the basis weight of the water absorbent resin is 270 g / m ² or less, the basis weight of the hydrophilic fibers is 180 g / m ² or less, and the physiology of the water absorbent resin. An absorbent, wherein the saline water retention amount (A) is 45 to 60 g / g, and the physiological saline water absorption amount (B1) under a pressure of 2069 Pa is 25 g / g or more.   The absorbent according to claim 1, wherein the water absorption amount (B2) of physiological saline under pressure of 4137 Pa of the water absorbent resin is 12 g / g or more.   The absorbent according to claim 1 or 2, wherein the water-absorbent resin has a physiological saline water absorption (B3) of 8 g / g or more under a pressure of 6206 Pa.   The absorbent body according to any one of claims 1 to 3, wherein the water absorption rate (C) of the water absorbent resin is 25 to 100 seconds.   The absorbent according to any one of claims 1 to 4, wherein the water absorbent resin is a water absorbent resin particle having a weight average particle diameter (D) of 200 to 500 µm.   An absorbent article comprising the absorbent body according to any one of claims 1 to 5 held between a liquid-permeable sheet and a liquid-impermeable sheet.

Images