JP2010220903A - Absorber, method for manufacturing the same, and absorbing article - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an absorber having practically sufficient absorbability and peeling strength and easily washable by water, a method for manufacturing the same, and an absorbing article. <P>SOLUTION: The absorber 10 includes a constitution in which an absorptive polymer 11 with centrifugal holding strength of 20 g/g or less according to JIS K 7223 is sandwiched with two sheets 12, 13 and the absorptive polymer 11 is bonded to the sheet 12, 13 via a water soluble binder. The absorber 10 can be obtained by applying the absorptive polymer 11 and the water soluble binder onto one surface of the sheet 12 in a wet condition, by superposing the other sheet 13 on the same, by drying the same, and by integrating the same. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an absorbent body used for sanitary napkins and the like, a method for producing the same, and an absorbent article.

  2. Description of the Related Art As absorbent bodies used for absorbent articles such as sanitary napkins and disposable diapers, those having a configuration in which a water-absorbing polymer is sandwiched between two sheets are known. For example, in Patent Document 1, after applying a pressure-sensitive adhesive such as a hot-melt pressure-sensitive adhesive on a sheet-like absorbent material having an appropriate liquid absorption capacity in a dot-like, linear or curved shape at an appropriate density, There is described an absorbent sheet obtained by spraying a water-absorbing polymer on top and further compressing and integrating separate sheet-like absorbent materials. Patent Document 2 discloses an absorptivity obtained by spraying a water-absorbing polymer on a wet fiber web obtained by a wet papermaking method, superimposing a fiber assembly thereon, and drying and integrating them. A sheet is described.

  By the way, some people represented by the Malay ethnic group whose main residence area is Indonesia, Malaysia, etc. have a habit of washing used sanitary napkins with water, washing away absorbed menstrual blood, etc., and then discarding them. is there. Traditionally, sanitary napkins that have been mainly used in Malay ethnic areas are composed of absorbent napkins made of cloth and pulp fibers, and do not contain water-absorbing polymers. The absorbed menstrual blood and the like can be washed away with water.

  However, such a sanitary napkin has poor menstrual blood absorption / retention performance, and may cause so-called liquid return in which, for example, body fluid absorbed on the surface of the absorbent material oozes out. Therefore, in a conventional sanitary napkin that can be washed with water and does not contain a water-absorbing polymer, the use of a large amount of pulp fibers compensates for the lack of absorption performance. However, such sanitary napkins become thick due to the bulkiness of the pulp fibers, are particularly bulky when folded and packaged, are inconvenient to carry, and have a poor fit.

  At present, the present applicant has not found any prior art documents that have raised the above-mentioned problems relating to water washing of napkins. However, people who have a habit of cleaning napkins are thought to exist in areas other than the above-mentioned residential areas, and sanitary napkins that contain a water-absorbing polymer and are easy to wash are widely used in women's lifestyles. It is considered that it has the potential to greatly affect

JP-A-5-38350 JP-A-8-246395

  As a result of various investigations on an absorbent body that has practically sufficient absorption performance by containing a water-absorbing polymer and can remove redness caused by absorbed menstrual blood etc. by washing with water, The knowledge that the thing containing the water-absorbing polymer whose quantity exists in a specific range was effective was acquired. However, an absorbent body having a structure in which such a specific water-absorbing polymer is sandwiched between two sheets has a low peel strength between the two stacked sheets, and therefore the sheets are stacked during product processing or use. There was a possibility that a shift occurred in the alignment position and the absorber was destroyed.

  Therefore, the subject of this invention is providing the absorber which has practically sufficient absorption performance and peeling strength, and is easy to wash with water, its manufacturing method, and an absorbent article.

  The present invention has a structure in which a water-absorbing polymer having a centrifugal retention amount of 20 g / g or less according to JIS K 7223 is sandwiched between two sheets, and the water-absorbing polymer is attached to the sheet via a water-soluble binder. The problem is solved by providing a fixed absorbent body.

  Moreover, this invention solves the said subject by providing the absorbent article containing the said absorber.

  Further, the present invention is a method for producing the absorbent body, wherein a water-absorbing polymer and a water-soluble binder are provided on one surface of a wet sheet, and a separate sheet is overlaid thereon, and these are dried. The problem is solved by providing a manufacturing method of an absorbent body including a step of integrating.

  According to the present invention, there are provided an absorbent body and an absorbent article which have practically sufficient absorption performance and peel strength and can be easily washed with water. In particular, the absorbent body and absorbent article of the present invention can remove redness due to absorbed menstrual blood and the like by washing with water, so it is suitable for people who have a habit of washing the absorbent article after use with water and then discarding it. In addition, since the peel strength between the sheets constituting the absorber is practically sufficient, it is possible to prevent inconvenience due to the peeling of the sheet that may occur during product processing or use. . Moreover, since the absorbent body and absorbent article of the present invention contain a water-absorbing polymer, the liquid return can be effectively suppressed, for example, the absorption performance is good, and the thickness can be designed to be thin. It is not bulky and can be excellent in portability and wearing feeling.

FIG. 1 is a cross-sectional view schematically showing a cross section of an embodiment of the absorbent body of the present invention. FIG. 2 is a schematic view showing a manufacturing process of the absorbent body shown in FIG. FIG. 3 is a perspective view of a sanitary napkin that is an embodiment of the absorbent article of the present invention. 4 is a cross-sectional view schematically showing a cross section taken along line XX of FIG.

  Hereinafter, first, the absorber of the present invention will be described based on a preferred embodiment thereof with reference to the drawings. The schematic diagram which shows the cross section of the absorber of this embodiment is shown by FIG. The absorbent body 10 of the present embodiment has a configuration in which a water-absorbing polymer 11 having a centrifugal retention amount of 20 g / g or less according to JIS K 7223 is sandwiched between two sheets 12 and 13, and the water-absorbing polymer 11 is It adheres to the sheets 12 and 13 via a water-soluble binder (not shown).

  The centrifugal retention amount of the water-absorbing polymer 11 according to JIS K 7223 is preferably 5 to 20 g / g, more preferably 8 to 15 g / g. Even if the water-absorbing polymer having a centrifugal retention amount of 20 g / g or less is reddish due to adhesion / absorption of menstrual blood or the like, it is possible to remove the reddish by subsequent washing with water. An easy absorber or absorbent article can be obtained. The water-absorbing polymer having a centrifugal retention amount exceeding 20 g / g has a strong redness caused by absorbed blood, and it is difficult to remove such redness by washing with water. The centrifugal retention amount is measured by the following measurement method.

<Measuring method of centrifugal retention>
The saturated water absorption is measured according to JIS K 7223 (1996). Nylon woven fabric (mesh opening 255, sold by Sanriku Manufacturing Co., Ltd., product name: nylon net, standard: 250 x mesh width x 30 m) is cut into a rectangle with a width of 10 cm and a length of 40 cm and folded in half at the center in the longitudinal direction. Both ends are heat-sealed to produce a nylon bag having a width of 10 cm (inner dimension: 9 cm) and a length of 20 cm. 1.00 g of the water-absorbing polymer as a measurement sample is precisely weighed and placed uniformly at the bottom of the produced nylon bag. The nylon bag containing the sample is immersed in physiological saline (0.9 mass% sodium chloride water) adjusted to 25 ° C. After 30 minutes from the start of immersion, the nylon bag is taken out from the physiological saline, suspended in a vertical state for 1 hour and drained, and then dehydrated using a centrifugal dehydrator (Kokusan Co., Ltd., model H-130C special model). The dehydration condition is 143 G (800 rpm) for 10 minutes. After dehydration, the mass of the sample is measured, and the target centrifugal retention amount is calculated according to the following formula. Centrifugal retention amount (g / g) = (a′−b−c) / c; where a ′ is the total mass (g) of the sample and the nylon bag after centrifugal dehydration, and b is before the water absorption of the nylon bag (dried) Mass) (g), c represents the mass (g) of the sample before water absorption (during drying). 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.

  The water-absorbing polymer 11 having a centrifugal retention amount of 20 g / g or less in accordance with JIS K 7223 can be obtained, for example, by subjecting a conventional water-absorbing polymer to a treatment that moderately increases the degree of surface cross-linking. More specifically, for example, using a known method for producing a polyacrylic acid-based water-absorbing polymer such as a reverse phase suspension polymerization method or an aqueous solution polymerization method described later, The water-absorbing polymer 11 can be obtained by obtaining a water-absorbing polymer having a group and / or a carboxylate group and subjecting the water-absorbing polymer to a surface crosslinking treatment.

  In this way, by subjecting the water-absorbing polymer that has been subjected to surface cross-linking treatment to a surface cross-linking treatment, cross-linking in the vicinity of the surface of the water-absorbing polymer as compared with the case where such surface cross-linking treatment is not performed twice. By increasing the degree, the network of molecular chains becomes finer, preventing hemoglobin, which is the main cause of blood redness, from penetrating into the deep part of the water-absorbing polymer, and reducing the centrifugal retention amount of the water-absorbing polymer. The two surface cross-linking treatments can be performed by the same method and conditions.

  Materials for the water-absorbing polymer 11 include polyacrylic acid soda, (acrylic acid-vinyl alcohol) copolymer, polyacrylic acid soda cross-linked product, (starch-acrylic acid) graft polymer, (isobutylene-maleic anhydride) co Examples thereof include polymers and saponified products thereof, potassium polyacrylate, cesium polyacrylate, and the like, and these can be used alone or in admixture of two or more.

  For example, the water-absorbing polymer 11 having a centrifugal retention amount of 20 g / g or less in accordance with JIS K 7223 is obtained by polymerizing a monomer containing 1) (meth) acrylic acid and / or an alkali metal salt thereof. Can be obtained by a method of crosslinking with a crosslinking agent, or 2) a method of polymerizing a monomer containing (meth) acrylic acid and / or an alkali metal salt thereof in the presence of a crosslinking agent.

  The methods 1) and 2) can be performed using a known method for producing a polyacrylic acid-based water-absorbing polymer. As this known production method, for example, (i) a reverse phase suspension polymerization method using an anionic surfactant described in Japanese Patent No. 2721658 as a dispersant, and (ii) Japanese Patent Laid-Open No. 2003-235889 And the aqueous solution polymerization method described in 1. In the above methods 1) and 2), a polymer obtained by polymerizing a monomer containing (meth) acrylic acid and / or an alkali metal salt thereof in the presence of a crosslinking agent is further subjected to a crosslinking treatment with a crosslinking agent. You may do it.

  The polymer of the monomer containing (meth) acrylic acid and / or an alkali metal salt thereof prepared by the method 1) described above is (meth) acrylic acid from the viewpoints of blood absorbability control, safety, production cost and the like. A homopolymer, a copolymer thereof, or a cross-linked product thereof. Examples of the homopolymer of (meth) acrylic acid include polyacrylic acid and polymethacrylic acid. Examples of the copolymer of (meth) acrylic acid include acrylic acid or methacrylic acid, maleic acid, itaconic acid, acrylamide, Copolymers obtained by copolymerizing co-monomers such as 2-acrylamido-2-methylpropanesulfonic acid, 2- (meth) acryloylethanesulfonic acid, 2-hydroxyethyl (meth) acrylate, or styrenesulfonic acid, starch-acrylic acid Examples thereof include a graft copolymer. The amount of the comonomer of the copolymer is preferably in a range that does not deteriorate blood absorption performance. Moreover, as an alkali metal salt of (meth) acrylic acid, sodium salts, such as polyacrylic acid and polymethacrylic acid, are preferable.

  Among these, (meth) acrylic acid or an alkali metal salt homopolymer or copolymer cross-linked product thereof, starch-acrylic acid graft copolymer cross-linked product is preferable, and acrylic acid or alkali metal acrylate single salt A cross-linked polymer is more preferred. These polymers usually contain 50 mol% or more of acrylic acid monomer units, preferably 60 mol% or more, more preferably 70 mol% or more, still more preferably 80 mol% or more, and are substantially insoluble in water. Although it is a polymer having a high degree of swelling.

  The crosslinking agent used in the methods 1) and 2) is a reaction capable of reacting with two or more polymerizable unsaturated groups in the molecule, or two or more carboxy groups and / or carboxylate groups in the molecule. Any compound having a functional group may be used, and examples thereof include a compound having two or more hydroxyl groups in the molecule, a compound having two or more polymerizable double bonds, and a compound having two or more epoxy groups.

  Examples of the compound having two or more hydroxyl groups in the molecule include ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, glycerin, polyglycerin, propylene glycol, diethanolamine, polyoxypropylene, sorbitan fatty acid ester, trimethylolpropane, and pentaerythritol. Trit, 1,3-propanediol, sorbitol and the like can be mentioned.

Examples of the compound having two or more polymerizable double bonds in the molecule include bis (meth) acrylamide, allyl (meth) acrylamide, di- or polyester of (meth) acrylic acid by polyol (for example, diethylene glycol diacrylate, trimethylol). Propane triacrylate, polyethylene glycol diacrylate, etc.), unsaturated mono-or polyols derived from the reaction of C ₁ -C ₁₀ polyhydric alcohols with 2 to 8 C ₂ -C ₄ alkylene oxides per hydroxyl group or Examples thereof include polycarboxylic acid di- or polyester (for example, ethoxylated trimethylolpropane triacrylate and the like).

  Compounds having two or more epoxy groups in the molecule include ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, glycerin triglycidyl ether, glycerol polyglycidyl ether, polyglycerol polyglycidyl ether, trimethylol. Examples thereof include polyglycidyl ethers such as propane polyglycidyl ether, sorbitol polyglycidyl ether, pentaerythritol polyglycidyl ether, resorcinol diglycidyl ether, neopentyl glycol diglycidyl ether, hydrogenated bisphenol A type diglycidyl ether.

  Among these crosslinking agents, a compound having two or more polymerizable double bonds and a compound having two or more epoxy groups in the molecule are preferable, and a compound having two or more epoxy groups in the molecule is more preferable. Specifically, ethylene glycol diglycidyl ether and trimethylolpropane polyglycidyl ether are particularly preferable.

  In the methods 1) and 2), the crosslinking agent is used in an amount of 0.15 / 100 to the mass ratio of [crosslinking agent / monomer] from the viewpoint of blood absorption performance and removal of redness caused by absorbed blood. 40/100, preferably 0.2 / 100 to 30/100, and more preferably 0.3 / 100 to 20/100.

  The shape of the water-absorbing polymer 11 is not limited to a spherical shape (particulate shape) as shown in FIG. 1, but a block shape such as a rectangular parallelepiped shape, a shape in which a plurality of spherical particles are combined, or a plurality of block-shaped particles are combined. It may be a shape, a shape in which spherical particles and block-shaped particles are combined, a fiber shape, a plate shape, or the like. The particulate water-absorbing polymer includes an amorphous type, a block type, a bowl type, a spherical agglomeration type, a spherical type, and the like due to the difference in shape, and any type can be used in the present invention. The average particle diameter of the water-absorbing polymer 11 having a spherical or nearly spherical particle shape is preferably 50 to 800 μm, more preferably 100 to 600 μm.

  The absorbent body 10 may contain a water-absorbing polymer other than the water-absorbing polymer 11 having a centrifugal retention amount of 20 g / g or less. From the viewpoint of more surely exhibiting the effects of the water-absorbing polymer 11 described above, the content of the water-absorbing polymer 11 is based on the total mass of all the water-absorbing polymers contained in the absorbent body 10. It is preferably 80% by mass or more, particularly 90% by mass or more, and particularly preferably 100% by mass. If all of the water-absorbing polymer contained in the absorbent body 10 is the water-absorbing polymer 11, it is ideal in terms of action and effect.

  In the present specification, “mass” means “mass at the time of drying” unless otherwise specified. The “mass at the time of drying” of the constituent member of the absorbent body or absorbent article is measured as follows. Measuring method of mass at the time of drying: The object to be measured is left for 24 hours in an environment of constant temperature and high humidity at a temperature of 23 ° C. and a humidity of 50%, then the mass is measured in the environment, and the measured value is measured. This is the “mass when dried” of the object.

Moreover, the distribution amount (dispersion basis weight) of the water-absorbing polymer (all water-absorbing polymers in the absorber 10 including the water-absorbing polymer 11) in the absorbent body 10 is preferably 10 to 100 g / m ² , and more preferably 20 ˜80 g / m ² .

  As the two sheets 12 and 13, a sheet-like material including fibers is used, and a material that can sandwich the water-absorbing polymer 11 and has an appropriate liquid absorbing power is preferable. As the sheets 12 and 13, for example, paper, woven fabric, non-woven fabric, knitted fabric, parchment, papyrus, pulp piled fiber, and the like can be used. Among these, paper is particularly preferable. Examples of the nonwoven fabric include a chemical bond nonwoven fabric, a thermal bond nonwoven fabric, an airlaid nonwoven fabric, a spunlace nonwoven fabric, a spunbond nonwoven fabric, a melt blown nonwoven fabric, a needle punch nonwoven fabric, and a stitch bond nonwoven fabric. The two sheets 12 and 13 may have the same composition and / or dimensions, or may be different from each other. Further, the sheets 12 and 13 may have a single layer structure or a multilayer structure. Moreover, the sheet | seats 12 and 13 may be comprised with one sheet | seat, and the form which wraps the layer which consists of the water absorbing polymer 11 with this one sheet | seat may be sufficient. Details of the sheets 12 and 13 will be described later.

The basis weights of the sheets 12 and 13 are preferably 10 to 80 g / m ² and more preferably 15 to 50 g / m ² , respectively.

  In the present embodiment, the water-absorbing polymer 11 having a centrifugal retention amount of 20 g / g or less based on JIS K 7223 is fixed to the sheets 12 and 13 via a water-soluble binder. The water-absorbing polymer 11 having a centrifugal retention amount of 20 g / g or less has a harder surface than the water-absorbing polymer having a centrifugal retention amount of more than 20 g / g, and lacks the adhesiveness of the polymer itself. If the water-absorbing polymer 11 is simply sandwiched between the sheets 12 and 13, the peel strength between the sheets 12 and 13 is low, so that the sheet may be displaced during product processing or use, and the absorber may be destroyed. In the present embodiment, the disadvantage of using the water-absorbing polymer 11 having such a low centrifugal retention amount (low adhesion) is obtained by using a water-soluble binder as a fixing agent for the sheets 12 and 13 of the water-absorbing polymer 11. By avoiding that. If a water-insoluble binder (for example, a hot melt adhesive) is used as a fixing agent for the water-absorbing polymer sheet, the absorption performance of the water-absorbing polymer is hindered, resulting in problems such as a decrease in liquid absorption rate and liquid return. Although there is a possibility of incurring, since the water-soluble binder is used in the present embodiment, there is very little possibility of causing such inconvenience.

  As the water-soluble binder, a cationic binder is preferably used. Examples of the cationic binder include cationized starch, cationized sodium carboxymethylcellulose, and cationized polyvinyl alcohol. These can be used alone or in combination of two or more. In the range examined by the present inventors, the cationic binder described above was more effective in improving the peel strength than the anionic binder such as carboxymethylcellulose (CMC).

  The content of the water-soluble binder is preferably 0.01 to 10% by mass, more preferably 0.05 to 1% by mass with respect to the total mass of the absorbent body 10.

  There is no restriction | limiting in particular in the method of including the said water-soluble binder in the absorber 10, An internal addition method may be sufficient and an external addition method may be sufficient. Examples of the internal addition method include a method in which a water-soluble binder is added in advance to the stock (fiber dispersion) when the two sheets 12 and 13 are produced by a wet papermaking method. As an external addition method, for example, as will be described later, after forming two sheets 12 and 13, an application means such as spray is applied to the spray surface (superimposed surface of the sheets) of the water absorbent polymer 11 in one sheet 12. The method of apply | coating a water-soluble binder and superimposing the other sheet | seat 13 on it is mentioned. Further, the water-absorbing polymer 11 may be dispersed on the application surface of the water-soluble binder (sheet overlapping surface) on one sheet 12. Furthermore, an absorbent polymer and a water-soluble binder may be simultaneously applied to one surface of one sheet 12. In the external addition method, the water-soluble binder is usually dissolved or dispersed in a suitable solvent such as water, and the solution or dispersion is applied to the sheet. When the internal addition method is used, the water-soluble binder is present substantially uniformly over substantially the entire area of the absorber 10 (sheets 12 and 13). When the external addition method is used, the two sheets 12 are used. , 13 are localized on each overlapping surface and its vicinity. When the external addition method is used, the abundance of the water-soluble binder usually decreases as the distance from the overlapping surface in the sheet thickness direction increases.

  From the viewpoint of ensuring the effect of improving the peel strength by the water-soluble binder, it is preferable that the absorbent body 10 contains a water-soluble binder by the external addition method. Especially, the absorber 10 of this embodiment provides a water-soluble binder on the one surface (water-absorbing polymer-spreading surface) of the sheet on which the water-absorbing polymer 11 is spread on one surface, and a separate sheet thereon. Are preferably obtained by superimposing and integrating both sheets. A method for manufacturing the absorber 10 will be described later.

  The peel strength of the absorbent body 10 of the present embodiment is preferably 20 cN / 25 mm or more, more preferably 25 to 100 cN / 25 mm or more. The peel strength is measured by the following measurement method.

<Measurement method of peel strength>
From the absorber to be measured (absorber having a configuration in which two sheets are superposed) to MD (conveying direction at the time of manufacturing the sheet constituting the absorber) 150 mm, CD (direction perpendicular to MD) 25 mm It cuts out and makes this a test piece, The two sheets which comprise this absorber in the area | region covering about 3 cm from one end of MD (longitudinal direction) of this test piece are peeled. After the test piece thus partially peeled was mounted on a chuck (distance between chucks: 25 mm) of a tensile tester (manufactured by Shimadzu Autograph AG-1kN) so that MD was in the tensile direction, 300 mm / min. The sheet is pulled at a pulling speed of 110 mm until the distance between the chucks becomes 110 mm, and the sheet is separated from one sheet and the other sheet, and the peel strength at this time is measured. The measurement area of the peel strength is set to a distance between chucks of 10 to 110 mm, and the average peel strength is calculated. The measurement is performed 5 times, and the average of these values is taken as the peel strength of the absorber.

The absorber 10 of the present embodiment can be thinned by having the above-described configuration. The thickness of the absorber 10 is preferably 0.1 to 2 mm, more preferably 0.2 to 1.5 mm. The thickness of the absorber 10 here means the thickness under a load of 7 g / cm ² .

  Hereinafter, the two sheets 12 and 13 constituting the absorber 10 will be further described. It is preferable that the sheets 12 and 13 contain hydrophilic fibers. The hydrophilic fiber can be used without particular limitation as long as it is a fiber having a hydrophilic surface and can form a sheet in which the fibers have a high degree of freedom in the wet state. Examples of such hydrophilic fibers include natural cellulose fibers such as wood pulp such as softwood kraft pulp and hardwood kraft pulp and non-wood pulp such as cotton pulp and straw pulp; regenerated cellulose fibers such as rayon and cupra; polyvinyl alcohol fiber , Hydrophilic synthetic fibers such as polyacrylonitrile fibers; synthetic fibers such as polyethylene terephthalate (PET) fibers, polyethylene (PE) fibers, polypropylene (PP) fibers, and polyester fibers that have been hydrophilized with a surfactant. These 1 type can be used individually or in mixture of 2 or more types.

  The content of the hydrophilic fiber is preferably 20% by mass or more, more preferably 35 to 90% by mass with respect to the total mass of the sheet 12 or 13.

  Among the hydrophilic fibers, preferred are cellulose fibers. Cellulose fibers are preferred because they have a stable hydrophilic surface and maintain hydrophilicity even after wetting. In particular, bulky cellulose fibers such as natural cellulose fibers and regenerated cellulose fibers are preferred. From the viewpoint of cost, it is preferable to use wood pulp, and conifer kraft pulp is particularly preferable. In addition, fibers obtained by hydrophilizing synthetic fibers such as PET, PE, and PP are also preferably used in the present invention as bulky hydrophilic fibers. In this specification, “bulky fiber” means that the fiber shape has a three-dimensional structure such as a twisted structure, a crimped structure, a bent and / or branched structure, or the fiber cross section is extremely thick (for example, the fiber roughness is high). 0.3 mg / m or more).

  By using the bulky cellulose fiber, not only the dispersibility of the water-absorbing polymer and the degree of immobilization are further improved, but when paper is used as the sheets 12 and 13, wet paper is used during wet papermaking. It is possible to more easily control the drainage performance. Furthermore, since the bulky cellulose fiber can form a bulky and high-porosity sheet, the water-absorbing polymer is easily embedded, dispersed and fixed three-dimensionally in the sheet, and the gel-absorbing of the water-absorbing polymer is also likely to occur. Can be suppressed. Although there is no restriction | limiting in particular in the average fiber length of the said bulky cellulose fiber, As a general range, it is preferable that it is 1-20 mm.

  The content of the bulky cellulose fiber is preferably 5% by mass or more, more preferably 10 to 65% by mass with respect to the total mass of the sheet 12 or 13.

  Preferred examples of the bulky cellulose fiber include cellulose fibers having a fiber roughness of 0.3 mg / m or more, particularly 0.3 to 2 mg / m, especially 0.32 to 1 mg / m. Cellulose fibers having a fiber roughness of 0.3 mg / m or more are preferred because the cellulose fibers accumulate in a bulky state, so that a bulky network structure is easily formed in the sheet. Further, it is preferable because the liquid movement resistance is small and the liquid passage speed is high. The “fiber roughness” is used as a scale representing the thickness of a fiber having a non-uniform fiber thickness such as wood pulp. For example, a fiber roughness meter (FS−) 200, manufactured by KAJANNI ELECTRONICS LTD.). Examples of cellulose fibers with a fiber roughness of 0.3 mg / m or more include softwood kraft pulp (“ALBACEL” (trade name) manufactured by Federal Paper Board Co. and “INDORAYON” (trade name) manufactured by PT Inti Indorayon Utama. )] And the like.

  Other preferable examples of the bulky cellulose fibers include cellulose fibers having a fiber cross-section roundness of 0.5 to 1, particularly preferably 0.55 to 1. Cellulose fibers having a fiber cross-section with a roundness of 0.5 to 1 are preferred because they have low liquid movement resistance and high liquid permeation speed. The roundness of the fiber cross section can be measured as follows.

<Measurement of roundness of fiber cross section>
The fiber to be measured is sliced in a cross-sectional direction orthogonal to the length direction. When slicing, be careful not to change the cross-sectional area of the fiber as much as possible. The cross section of the fiber obtained by slicing is imaged using an electron microscope, and the cross-sectional photograph is analyzed with an image analyzer (“Avio EXCEL” (trade name) manufactured by Nippon Avionics Co., Ltd.). The roundness of the target fiber cross section was obtained. In addition, 100 degrees of arbitrary fiber cross sections measured this roundness, and it was set as the average value. (Roundness of fiber cross section) = 4 × π × (cross section area of measurement fiber) / (perimeter of cross section area of measurement fiber) ²

  As described above, it is preferable to use wood pulp as the cellulose fiber, but in general, the cross section of the wood pulp is flattened by delignification treatment, and most of its roundness is less than 0.5. In order to make the roundness of such wood pulp 0.5 or more, for example, such wood pulp may be mercerized to swell the cross section of the wood pulp.

  Thus, as the bulky cellulose fiber, mercerized pulp having a roundness of 0.5 to 1 obtained by mercerizing wood pulp is also preferable. Examples of commercially available mercerized pulp that can be used in the present invention include “FILTRANIER” (trade name) manufactured by ITT Rayonier Inc. and “POROSANIER” (trade name) manufactured by the same company.

  Moreover, when a cellulose fiber having a fiber roughness of 0.3 mg / m or more and a roundness of the fiber cross section of 0.5 to 1 is used, a bulky network structure is more easily formed, and the liquid passage speed is increased. Is also preferable because it becomes larger.

  As another example of the preferred bulky cellulose fiber, there is a crosslinked cellulose fiber obtained by crosslinking the intramolecular and / or intermolecular molecules of the cellulose fiber. Such a crosslinked cellulose fiber is preferable because it can maintain a bulky structure even in a wet state.

  Although there is no restriction | limiting in particular in the method for bridge | crosslinking a cellulose fiber, For example, the crosslinking method using a crosslinking agent is mentioned. Examples of such crosslinking agents include N-methylol compounds such as dimethylolethyleneurea and dimethyloldihydroxyethyleneurea; polycarboxylic acids such as citric acid, tricarballylic acid and butanetetracarboxylic acid; polyols such as dimethylhydroxyethyleneurea A cross-linking agent for polyglycidyl ether compounds. In particular, a crosslinking agent of polycarboxylic acid or polyglycidyl ether compound that does not generate formalin or the like harmful to the human body during crosslinking is preferable.

  The amount of the crosslinking agent used is preferably 0.2 to 20 parts by mass with respect to 100 parts by mass of the cellulose fiber. If the amount used is less than 0.2 parts by mass, the crosslink density of the cellulose fibers is low, so the elastic modulus may be greatly reduced when wet. If the amount used exceeds 20 parts by mass, the cellulose fibers become rigid. Since the cellulose fiber may become brittle when excessively stressed, the above range is preferable.

  In order to cross-link cellulose fibers using the cross-linking agent, for example, a cellulose fiber is impregnated into an aqueous solution of a cross-linking agent, if necessary, so that the aqueous solution of the cross-linking agent becomes a design adhesion amount. The cellulose fibers are dehydrated and then heated to a crosslinking temperature, or an aqueous solution of a crosslinking agent is sprayed on the cellulose fibers so as to have a designed adhesion amount by spraying or the like, and then heated to the crosslinking temperature to cause a crosslinking reaction.

  Examples of commercially available crosslinked cellulose fibers include “High Bulk Additive” manufactured by Weyerhaeuser Paper Co.

  In addition to the above-described bulky cellulose fibers, bulky cellulose fibers in which the intramolecular and / or intermolecular molecules of cellulose fibers such as pulp having a fiber roughness of 0.3 mg / m or more are crosslinked by the above-described method are also preferable. .

  Moreover, the bulky cellulose fiber which bridge | crosslinked the molecule | numerator of the pulp whose fiber cross-section roundness is 0.5-1 and / or the molecule | numerator by the above-mentioned method is also preferable.

  Moreover, the bulky cellulose fiber which bridge | crosslinked the molecule | numerator and / or molecule | numerator of the mercerized pulp whose fiber cross section is 0.5-1 by the above-mentioned method is also preferable.

  The more preferred bulky cellulose fiber is obtained by crosslinking a pulp having a fiber roughness of 0.3 mg / m or more and a roundness of the fiber cross section of 0.5 to 1 by the above-described method.

  Particularly preferred bulky cellulose fibers are those having a fiber roughness of 0.3 mg / m or more and mercerized to roundness of 0.5 to 1 and then crosslinked by the method described above.

  From the viewpoint of imparting practically sufficient wet strength, the sheets 12 and 13 can contain hot-melt adhesive fibers or paper strength reinforcing agents.

  As the hot-melt adhesive fibers, fibers that are melted by heating and bonded to each other can be used. Specifically, for example, polyolefin fibers such as polyethylene, polypropylene, and polyvinyl alcohol, polyester fibers, and polyethylene-polypropylene. Examples thereof include a composite fiber, a polyethylene-polyester composite fiber, a low melting point polyester-polyester composite fiber, a polyvinyl alcohol-polypropylene composite fiber having a hydrophilic fiber surface, and a polyvinyl alcohol-polyester composite fiber. When using a composite fiber, any of a core-sheath type composite fiber and a side-by-side type composite fiber can be used. These hot-melt adhesive fibers can be used alone or in combination of two or more. Examples of the hot-melt adhesive fibers preferably used in the present invention include polyvinyl alcohol fibers that are dissolved in hot water, and core-sheath type polyester fibers. In general, the heat-meltable adhesive fiber preferably has a fiber length of 2 to 60 mm, and a fiber diameter of 0.1 to 3 denier (particularly 0.5 to 3 denier).

  When using the said hot melt adhesive fiber, the sheets 12 and 13 comprise 30-99 mass parts of the said hydrophilic fiber and 1-50 mass parts of the said hot melt adhesive fiber based on 100 mass parts of each sheet | seat. It is preferable. More preferably, it comprises 50 to 97 parts by mass of the hydrophilic fiber and 3 to 30 parts by mass of the hot-melt adhesive fiber based on 100 parts by mass of each sheet.

  Examples of the paper strength reinforcing agent include polyamine / epichlorohydrin resin, dialdehyde starch, sponge and carboxymethylcellulose. These paper strength reinforcing agents can be added in an amount of 0.01 to 30 parts by mass, preferably 0.01 to 20 parts by mass based on 100 parts by mass of each sheet (12 or 13).

  As an example of what is preferable as the sheets 12, 13, 0.2 to 10% by mass (preferably 1 to 5% by mass) of polyvinyl alcohol fiber (hot-melt adhesive fiber) and 0.1 to 0.1% of sponge (paper strength reinforcing agent) are used. What contains 1 mass% (preferably 0.2-0.8 mass%) is mentioned.

  Next, the manufacturing method of the absorber of the present invention will be described with reference to the drawings, taking the manufacturing method of the absorber 10 of the embodiment as an example. In the description of the manufacturing method of the present invention, which will be described later, the same components as those in the above embodiment are given the same reference numerals, and the description thereof is omitted. The description of the above embodiment is applied as appropriate to components that are not particularly described. FIG. 2 is a schematic view showing a manufacturing process of the absorbent body 10 shown in FIG.

  As shown in FIG. 2, the manufacturing method of the absorbent body according to this embodiment scatters the water-absorbing polymer 11 on the one surface 12 a of the wet sheet 12, and gives the water-soluble binder 14 to the diffusing surface of the water-absorbing polymer 11. In addition, a process of superimposing a separate sheet 13 thereon, drying them and integrating them is included.

  The sheet 12 can be manufactured according to a manufacturing method of a sheet containing this type of fiber, and the manufacturing method is not particularly limited, and may be a wet method or a dry method. When the sheet 12 is manufactured by the wet papermaking method, a wet sheet is always obtained, so that it is possible to save the trouble of making the dry sheet wet in a separate process. In this embodiment, the sheet 12 is manufactured by a wet papermaking method. Examples of the wet paper machine used in the wet paper machine include a short paper machine, a long paper machine, a twin wire paper machine, an on-top paper machine, a hybrid paper machine, and a round paper machine.

  When the sheet 12 is produced by a wet papermaking method, a slurry is formed by dispersing the fibers forming the sheets 12 and 13 and other components excluding the water-soluble binder in water to a predetermined concentration. The slurry is introduced into a wet paper machine, and is flowed onto a wet paper machine net according to a conventional method to make it thin and flat, thereby forming a wet sheet 12.

  Next, excess water is dehydrated from the wet sheet 12 by the dehydrating means 70. The dehydrating means 70 includes a suction device that sucks water from the wet sheet, a pressurizing device that compresses the wet sheet from above and below to squeeze out water, and the like. The water content of the sheet 12 that has undergone the dehydration step (the sheet immediately before the water-absorbing polymer is sprayed) is preferably 20 to 500% by mass, and more preferably 50 to 300% by mass.

  Next, the water-absorbing polymer 11 is sprayed on the one surface 12 a of the wet sheet 12. The water-absorbing polymer 11 may be uniformly distributed over the entire surface 12a of the wet sheet 12, or may be partially distributed in a streak form at a predetermined interval in the longitudinal direction of the wet sheet 12, Alternatively, it may be intermittently sprayed in shots in the longitudinal direction of the wet sheet 12.

Next, a water-soluble binder 14 is applied to the spray surface of the water-absorbing polymer 11. In this embodiment, the water-soluble binder such as cationized starch is dissolved or dispersed in a suitable solvent such as water to obtain a binder liquid, and this binder liquid is sprayed by spraying. The binder liquid is preferably uniformly applied to the entire surface of the sheet 12 on which the water-absorbing polymer 11 is spread on the one surface 12a. The application amount of the water-soluble binder (binder liquid) is appropriately set in consideration of the spraying amount of the water-absorbing polymer 11, and is preferably 0.5 to 20 g / m ² , more preferably 1 to 10 g / m ² . .

  Next, a separate sheet 13 is superposed on the spray surface (one surface 12 a) of the water absorbent polymer 11 in the sheet 12 to form a laminate of both sheets 12 and 13. In this laminate, the water-absorbing polymer 11 is further buried in the sheets 12 and 13, and the constituent fibers of the sheets 12 and 13 are entangled with each other. The sheet 13 can be manufactured by the same method as the sheet 12. In the present embodiment, a wet sheet 13 obtained by a wet papermaking method and having excess water dehydrated by a dehydrating means (not shown), the water-absorbing polymer 11 in the traveling sheet 12 is placed on the spreading surface. By supplying, the laminated body of both the sheets 12 and 13 is formed.

  Next, the laminated body of the sheets 12 and 13 is dried and integrated by the drying means 71. By drying the laminate, the constituent fibers of the sheets 12 and 13 are entangled with each other. Furthermore, when hydrogen bonding or the heat-melting adhesive fiber is used, an action of heat-sealing is also added. 13 is integrated, and an adhesive force of the water-soluble binder is expressed, and the water-absorbing polymer 11 is fixed to the sheets 12 and 13 (component fibers of the sheet) by the adhesive force. At this time, the water-absorbing polymer 11 enters the space carried by the sheets 12 and 13, that is, the space formed by the constituent fibers of the sheets 12 and 13, and stress is applied to the sheets 12 and 13 from the outside. Even in this case, the water-absorbing polymer 11 is not easily moved or dropped. The adhesive strength of the water-soluble binder is considered to contribute to the integration of the sheets 12 and 13.

  Although the drying temperature at the time of drying the laminated body of the sheets 12 and 13 is based also on a composition of a sheet | seat etc., Preferably it is 100-180 degreeC, More preferably, it is 120-160 degreeC. There is no restriction | limiting in particular as the drying means 71, For example, a Yankee dryer, an air through dryer, etc. can be used. The absorber 10 is obtained as described above.

  Next, the absorbent article of this invention is demonstrated with reference to drawings based on the sanitary napkin which is one preferable embodiment. In the description of the absorbent article according to the present invention, which will be described later, the same components as those of the above-described embodiment are denoted by the same reference numerals and description thereof is omitted. The description of the above embodiment is applied as appropriate to components that are not particularly described. FIG. 3 is a perspective view of the sanitary napkin of the present embodiment, and FIG. 4 is a cross-sectional view schematically showing a cross section taken along line XX of FIG. The napkin 20 of the present embodiment is configured to include the absorbent body 10.

  The napkin 20 has a shape that is long in one direction as shown in FIG. 3, and includes a surface sheet 21 as a liquid-permeable surface layer, a back sheet 22 as a liquid-impermeable back layer, and both sheets 21, The liquid-retaining absorbent 10 is interposed between the two. The absorbent body 10 has a shape that is long in one direction, and the longitudinal direction of the absorbent body 10 coincides with the longitudinal direction of the napkin 20 and is arranged at the center in the napkin width direction.

  The absorber 10 may be substantially entirely covered with a covering sheet (not shown). When substantially the entire absorber is covered with a covering sheet, it is particularly effective for improving the shape stability of the absorber and preventing the water-absorbing polymer from falling off. Examples of the covering sheet include hydrophilic fiber sheets and perforated films. Examples of the hydrophilic fiber sheets include paper such as tissue paper and various non-woven fabrics (spunbond non-woven fabric, spunbond-meltblown-spunbond). Nonwoven fabric, spunbond-meltblown-meltblown-spunbond nonwoven fabric, spunlace nonwoven fabric containing hydrophilic fibers such as acrylic and rayon, and the like can be used.

  As shown in FIG. 4, the top sheet 21 covers the entire skin contact surface (upper surface) of the absorber 10, and the back sheet 22 covers the entire non-skin contact surface of the absorber 10. . End seals are applied to the top sheet 21 and the back sheet 22 at portions extending outward from the peripheral edge of the absorbent body 10, and end seal portions 26 are formed. An adhesive is applied on the non-skin contact surface of the back sheet 22 to form a fixing portion (not shown) for fixing the napkin 1 to shorts or the like. The top sheet 21 can be made of the same material as that conventionally known. For example, a hydrophilic nonwoven fabric or a perforated film is used. The back sheet 22 is composed of, for example, a liquid-impermeable film sheet, and the liquid-impermeable film sheet may have water vapor permeability.

  In the present specification, the skin contact surface is a surface directed toward the wearer's skin when the absorbent article is worn, and the non-skin contact surface is the wearer's skin side when the absorbent article is worn. Is the side facing the other side. Moreover, a longitudinal direction is a direction along the long side direction of an absorbent article or its structural member, and a width direction is a direction orthogonal to this longitudinal direction.

  On the skin contact surface side (surface sheet 21 side) of the napkin 20, leakage preventing grooves 25, 25 extending in the longitudinal direction of the napkin 20 are formed on both left and right sides in the longitudinal direction. Each leakage prevention groove 25 is formed by compacting and integrating the topsheet 21 and the absorber 10 from the topsheet 21 side by pressing means such as embossing. Each leak-proof groove 25 has a substantially symmetrical shape with a virtual straight line (not shown) that bisects the napkin 20 in the width direction. The leakage prevention grooves 25 have their front and rear ends connected to each other, thereby forming a closed shape as a whole. By forming the leak-proof grooves 25, 25, body fluid and the like flowing outward in the napkin width direction are blocked, and leakage (lateral leakage) from the side of the napkin 20 is effectively prevented and cleaning is performed. Since the decomposition of the napkin 20 at the time can be suppressed, the washing operation can be easily performed, and the blood can be easily washed away. Further, the fact that the leak-proof grooves 25 and 25 reach the vicinity of the lower part of the absorbent body 10 is to prevent water from flowing through the entire absorbent body during cleaning and to prevent blood from remaining due to the absorbent body being biased. preferable.

  An end seal portion 26 is formed on the periphery of the napkin 20 at a position spaced outward from the absorbent body 10. The end seal portion 26 in the present embodiment is formed by integrating the top sheet 21 and the back sheet 22. More specifically, in the present embodiment, the top sheet 21 and the back sheet 22 extend from the peripheral edge portion of the absorbent body 10, and are joined to each other by a heat embossing process at the extended portions. Is formed. The end seal portion 26 has an effect of preventing the water absorbent material constituting the absorbent body 10 from flowing out when the napkin 1 is washed (when wet). It is preferable that the end seal portion 26 is not provided with a material that causes swelling or the like due to water used for the absorbent body 10 from the viewpoint of not separating each sheet material that is a constituent material of the end seal portion during cleaning. Further, the end seal portion 26 is formed by heat embossing with an adhesive such as hot melt disposed at a predetermined portion of the sheet material, thereby improving and stabilizing the flexibility of the seal portion and the seal strength when wet. From the viewpoint of making it more preferable.

  The napkin 20 of the present embodiment is used by being attached to an undergarment in the same manner as a normal sanitary napkin of this type. Since the napkin 20 includes the absorbent body 10, the napkin 20 can be easily washed with water while having practically sufficient absorption performance, and the attached blood can be easily washed away with water. For this reason, it can be suitably used for people who have a habit of discarding the used napkin after washing with water. Further, the napkin 20 can be designed to have a small thickness, is not bulky, and can be excellent in portability and wearing feeling. Further, since the napkin 20 has a practically sufficient peel strength between the sheets 12 and 13 constituting the absorbent body 10, the sheet 12 and 13 may be displaced during the processing of the product or used, and the absorbent body resulting therefrom. Inconvenience such as destruction of 10 can be prevented in advance.

  As mentioned above, although this invention was demonstrated based on the preferable embodiment, this invention is not restrict | limited to the said embodiment. For example, the absorbent article of the present invention may not include the leak-proof groove 25, the adhesive portion (not shown), the wing portion, the rear flap portion, and the like included in the embodiment. Each of the wing part and the rear flap part is a part that extends outward from the both side edges in the longitudinal direction of the absorbent body 10, and the wing part is normally opposed to the excretion part that is disposed to face the excretion part of the napkin wearer. The rear flap part is located behind the wing part in the napkin longitudinal direction.

  Further, the absorbent body 10 of the above embodiment has one laminated body of two sheets 12 and 13 holding a water-absorbing polymer having a centrifugal retention amount of 20 g / g or less according to JIS K 7223. However, the absorbent body of the present invention includes a form having a plurality of such laminates of two sheets as in Example 1 below, for example.

  In addition to the above-described embodiment, the absorbent body of the present invention may have a form in which an absorbent material containing a pulp pile fiber and / or a water-absorbing polymer is wrapped with paper such as tissue paper. In this case, the water-soluble binder may be contained in the absorbent material, or may be dispersed between the absorbent material and the tissue paper.

  Moreover, in the manufacturing method of the absorber of the said embodiment, although the water-absorbing polymer 11 was sprayed on the one surface 12a of the wet sheet 12, the water-soluble binder 14 was provided to the spraying surface of the water-absorbing polymer 11. In the method for producing the absorbent body of the present invention, the order of application of the water-absorbing polymer and the water-soluble binder to the sheet is not particularly limited, and the water-soluble binder and the water-absorbing polymer may be applied in this order, or the water-absorbing polymer. And a water-soluble binder may be added simultaneously.

  Further, the absorbent article to which the absorbent body of the present invention can be applied, or the absorbent article of the present invention is not limited to sanitary napkins, but is used for disposable diapers, incontinence pads, urine-absorbing pads, pet diapers, pet sheets, etc. Is also applicable. The technique of the present invention can also be applied to a water-absorbing polymer with low adhesiveness, and in that case, the effect of the present invention can be obtained regardless of the amount of centrifugal retention of the water-absorbing polymer.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to such examples.

  Hereinafter, a method for synthesizing the water-absorbing polymer used in this example will be described. The synthesis method includes a step of synthesizing a water-absorbing polymer and a step of subjecting the obtained water-absorbing polymer to a crosslinking treatment.

(Synthesis of water-absorbing polymer)
Polyoxyalkylene ether phosphate 0.1% (as opposed to acrylic acid mass) as a dispersant in SUS304 5L reaction vessel (using anchor blade) equipped with stirrer, reflux condenser, monomer dropping port, nitrogen gas inlet tube, thermometer , Active ingredient amount), and 1500 ml of normal heptane was added. The temperature was raised to 90 ° C. while stirring in an atmosphere of nitrogen gas. On the other hand, in a 2 L three-necked flask, acrylic acid as a monomer aqueous solution from 80% acrylic acid (manufactured by Toagosei Co., Ltd., act. 80.6%), ion-exchanged water, 48% sodium hydroxide aqueous solution (manufactured by Asahi Glass Co., Ltd., act. 49.7%) 1000 g of sodium (72% neutralized product) was obtained. After adding 0.25 g of N-acylated glutamic acid soda (trade name: Amisoft PS-11) dissolved in ion-exchanged water 4.41 g to this monomer aqueous solution, 550 g (hereinafter referred to as monomer aqueous solution A). ), 250 g (hereinafter referred to as monomer aqueous solution B), and 250 g (hereinafter referred to as monomer aqueous solution C).

Next, 2,2′-azobis (2-amidinopropane) dihydrochloride (Wako Pure Chemical Industries, trade name V-50) 0.05 g, polyethylene glycol (Kao, K-PEG6000 LA) 0.5 g, citric acid 4 g of ammonium iron (III) (manufactured by Kanto Chemical) and 10 g of ion-exchanged water were mixed and dissolved to prepare an initiator (A) solution. Further, 0.6 g of sodium persulfate (manufactured by Wako Pure Chemical Industries, Ltd.) was dissolved in 10 g of ion-exchanged water to prepare an initiator (B) solution. Further, a titanium citrate aqueous solution (50% citric acid and 7.6% (TiO ₂ ) titanyl sulfate aqueous solution mixed at a mass ratio of 20/27) was prepared.

  To monomer aqueous solution A, 12 g of initiator (A) solution is added to prepare monomer A. To monomer aqueous solution B, 5 g of initiator (B) solution is added to prepare monomer B. To monomer aqueous solution C, initiator ( B) Monomer C was prepared by adding 5 g of the solution and 2 g of the aqueous titanium citrate solution.

  A monomer A, a monomer B, and a monomer C, which were allowed to stand for 5 minutes or more, were dropped into the 5 L reaction vessel from the monomer dropping port using a microtube pump in this order for polymerization. After completion of monomer dropping, azeotropic dehydration was performed using a dehydrating tube to adjust the water content of the water-absorbing polymer (hydrogel), and then ethylene glycol diglycidyl ether (manufactured by Nagase ChemteX, trade name Denacol EX- 810) A solution prepared by dissolving 0.4 g in 10 g of ion-exchanged water was added. Thereafter, 1.6 g of a 60% 1-hydroxyethylidene-1,1′-diphosphonic acid aqueous solution (trade name Bryce ADPA-60A, manufactured by Rhodia) was added. After cooling, normal heptane was removed and dried to obtain a water-absorbing polymer.

[Crosslinking treatment of water-absorbing polymer]
Into the same reaction vessel (using anchor blades) as used in [Synthesis of water-absorbing polymer], 500 parts by mass of the water-absorbing polymer obtained in [Synthesis of water-absorbing polymer] was charged, and sucrose was used as a dispersant. 2% of fatty acid ester (trade name Ryoto Sugar Ester S-770, manufactured by Mitsubishi Chemical Foods Co., Ltd.) (weight of water-absorbing polymer, amount of active ingredient) was charged, and 1600 ml of cyclohexane was added. While stirring in a nitrogen atmosphere, the temperature was raised to 75 ° C. Thereafter, 300 ml of ion-exchanged water was dropped from the dropping port using a dropping funnel, and then ethylene glycol diglycidyl ether (trade name Denacol EX-810, manufactured by Nagase ChemteX) was added as a crosslinking agent to 10 g of ion-exchanged water. The dissolved one was added. After refluxing for 1.5 hours, cyclohexane was removed and dried to obtain a crosslinked water-absorbing polymer.

[Synthesis Examples 1 and 2]
In Synthesis Examples 1 and 2 according to [Synthesis of water-absorbing polymer] and [Crosslinking treatment of water-absorbing polymer], two kinds of crosslinked water-absorbing polymers were obtained. Synthesis Example 1 and Synthesis Example 2 differ only in the amount of the crosslinking agent used in [Crosslinking of water-absorbing polymer]. In Synthesis Example 1, 15 g of the crosslinking agent, and in Synthesis Example 2, 0.25 g of the crosslinking agent. Using. The centrifugal retention amount of the water-absorbing polymer obtained in Synthesis Example 1 in accordance with JIS K 7223 was 11 g / g, and the centrifugal retention amount of the water-absorbing polymer obtained in Synthesis Example 2 was 26 g / g.

[Example 1]
70 parts by mass of a crosslinked pulp (“High Bulk Additive HBA-S” manufactured by Weyerhauser Paper) having a fiber roughness of 0.32 mg / m and a fiber cross-section of 0.30, and a fiber roughness of 0.18 and a fiber cross-section 30 parts by weight of softwood kraft pulp (Skeena Cellulose Co. “SKEENA PRIME”) having a roundness of 0.32 is dispersed and mixed in water, and further, a paper strength reinforcing agent (polyamide) is added to 100 parts by dry weight of the mixed pulp. Epichlorohydrin resin (manufactured by Nippon PMC Co., Ltd., Kaimen WS-570) is dispersed and mixed in water with 1 part by weight of resin component to obtain a predetermined concentration, and then this dispersed mixture is dried in the forming part of a wet paper machine. The fiber web was formed so that the basis weight of the resin was 20 g / m ² . Next, the fiber web was dehydrated with a suction box until the water content became 100 parts by mass based on 100 parts by mass of the dry fiber web. Next, immediately before the press part, the water-absorbing polymer of Synthesis Example 1 (the centrifugal retention amount 11 g / g) was spread almost uniformly at a spreading basis weight of 30 g / m ² on the wet fiber web after dehydration, Further, a 5% by mass aqueous solution of a water-soluble binder (cationized starch, manufactured by Matsutani Chemical Industry Co., Ltd.) separately prepared was sprayed on the entire spray surface of the water-absorbing polymer. Next, a sheet made in advance (paper basis weight of 30 g / m ² ) having the same composition as that of the fiber web is superimposed on the surface of the fiber web to which the water-absorbing polymer is dispersed to obtain a laminate. The laminate was introduced into a dryer, dried at a temperature of 130 ° C., and integrated to obtain an absorbent body having a structure in which a water-absorbing polymer was sandwiched between two sheets. Content of the water-soluble binder (cationized starch) in the obtained absorber was 0.5 mass% with respect to the total mass of this absorber.

  From the thus obtained long absorbent body (a laminate of two sheets), two rectangles each having two sizes of 185 mm × 75 mm rectangle (large rectangle) and 90 mm × 35 mm rectangle (small rectangle) were obtained. Each sheet was cut so that its long side was in the MD (traveling direction of the fiber web in the wet paper machine) direction, and stacked so that the centers matched in the order of large rectangle, small rectangle, small rectangle, and large rectangle. This was used as a napkin absorber. An adhesive was applied to one side of the absorbent body, and the back sheet was fixed via the adhesive. Next, the entire other surface side of the absorbent body was covered with a surface sheet, and the outer surface of the surface sheet was embossed according to a conventional method to form a leak-proof groove, whereby a napkin precursor was obtained. An adhesive is applied to a predetermined portion of the non-skin contact surface (outer surface of the back sheet) of the napkin precursor obtained in this manner to form an adhesive part, and further, the extension from the peripheral part of the absorber in each of the front and back sheets. The end portion was subjected to end sealing according to a conventional method to obtain a napkin. In this napkin, an air-through nonwoven fabric (a perforated sheet used for a Kao Co., Ltd. Laurier Super Slim Guard) was used as the top sheet, and a polyethylene film having a thickness of 25 μm was used as the back sheet. The napkin has a structure generally shown in FIGS. 3 and 4 except for the laminated structure of the absorber described above. The napkin thus obtained was used as a sample of Example 1.

[Example 2]
A napkin was prepared in the same manner as in Example 1 except that the spraying basis weight of the water-absorbing polymer was 50 g / m ^2, and this was used as the sample of Example 2.

Example 3
A napkin was prepared in the same manner as in Example 1 except that the concentration of the aqueous solution of the water-soluble binder (cationized starch) sprayed on the sheet was 2.5% by mass, and this was used as the sample of Example 3. The content of the water-soluble binder (cationized starch) in the absorber in the sample of Example 3 was 0.125% by mass with respect to the total mass of the absorber.

[Comparative Example 1]
A napkin was prepared in the same manner as in Example 1 except that the water-soluble binder was not applied, and this was used as a sample of Comparative Example 1.

[Comparative Example 2]
A napkin was prepared in the same manner as in Example 2 except that the water-soluble binder was not added, and this was used as a sample of Comparative Example 2.

[Comparative Example 3]
A napkin was prepared in the same manner as in Example 1 except that the water-absorbing polymer of the synthesis example (the centrifugal retention amount 26 g / g) was used, and this was used as a sample of Comparative Example 3.

[Reference Example 1]
A napkin was prepared in the same manner as in Example 3 except that carboxymethylcellulose (Daiichi Kogyo Seiyaku Co., Ltd.) was used instead of cationized starch as the water-soluble binder, and this was used as a sample of Reference Example 1. The content of the water-soluble binder (carboxymethylcellulose) in the absorber in the sample of Reference Example 1 was 0.25% by mass with respect to the total mass of the absorber.

[Reference Example 2]
A napkin was prepared in the same manner as in Reference Example 1 except that the spraying basis weight of the water-absorbing polymer was 50 g / m ^2, and this was used as a sample of Reference Example 2.

[Evaluation]
For each sample (sanitary napkin) of Examples, Comparative Examples and Reference Examples, the peel strength of the absorbent was measured according to the measurement method. In addition, as an evaluation of the absorption performance of each sample, the absorption time and liquid return amount are measured by the following method, and as an evaluation of the ability to wash with water (ease of removing redness derived from blood by washing with water), the following method is used. The red degree a ^* value was measured. These results are shown in Table 1 below.

<Measurement method of absorption time>
With the sanitary napkin to be measured spread in a plane and fixed on a horizontal surface with the top sheet facing up, an acrylic plate with a cylindrical injection part is placed on the top sheet in the center of the absorber. Further, a weight is placed on the acrylic plate, and a load of 5 g / cm ² is applied to the center of the absorber. The injection part provided on the acrylic plate has a cylindrical shape with an inner diameter of 10 mm, and the central axis of the cylindrical injection part coincides with the central axis in the longitudinal direction and the width direction of the acrylic plate, and the cylindrical injection part A through-hole having an inner diameter of 10 mm is formed so as to communicate between the inside and the surface sheet facing surface of the acrylic plate. Next, an acrylic plate is arranged so that the central axis of the cylindrical injection portion coincides with the central portion of the absorber in plan view, and 6 g of blood is injected from the cylindrical injection portion and absorbed by the sanitary napkin. The time (seconds) from when the blood reached the surface of the napkin until the total amount of 6 g was absorbed by the napkin was measured, and this was taken as the absorption time. The smaller the value of this absorption time, the faster the absorption speed and the higher the evaluation.

<Measurement method of liquid return amount>
In the above <Method for measuring absorption time>, 3 minutes after blood injection, the acrylic plate and the weight are removed, and on the skin contact surface of the napkin (on the top sheet), the basis weight is 30 g / m ² at 7 cm × 15 cm. Ten sheets of absorbent paper (commercial tissue paper) were placed on top of each other, and a load of 68 g / cm ² was applied for 1 minute from the top of the absorbent paper. After the loading, 10 sheets of absorbent paper were removed, and the weight of the 10 sheets of absorbent paper was measured. From this measured value and the measured value of the weight of 10 sheets of absorbent paper before the load obtained in advance, the mass (g) of blood absorbed in 10 sheets of absorbent paper is determined, and this mass is taken as the liquid return amount. did. The smaller the liquid return amount, the higher the napkin absorption performance and the higher the evaluation.

<Measurement method of red degree a ^* value>
After the blood is injected and washed according to the following procedures 1 to 3, the red degree a ^* value of the red part stained with red blood on the napkin is measured. The a ^* value obtained according to the following procedures 1 to 3 is a scale for evaluating the superiority or inferiority of the napkin's ability to wash water. The smaller the a ^* value, the lower the redness of the red part, and the blood is washed with water. Means that it has been washed away.

Procedure 1: Inject 12 g of blood into the sanitary napkin from the surface layer side of the sanitary napkin, leave it in an environment of 25 ° C. for 30 minutes, and then remove the sanitary napkin with water having a water temperature of 25 ° C. and a hardness of 5 ° DH. The sanitary napkin is squeezed by hand, and the water contained in the napkin is squeezed out as much as possible.
Procedure 2: On the surface layer side of the wet sanitary napkin obtained in the procedure 1, the red degree a ^* using a spectrocolorimeter for the five most reddish spots of the red part stained with blood ^. Measure the value.
Procedure 3: The average of the three measured values obtained by removing the maximum value and the minimum value from the five measured values obtained in the procedure 2 is defined as the red degree a ^* value of the sanitary napkin.

  In the procedures 1 to 3, horse blood is used as blood to be injected into the napkin. More specifically, equine defibrinated blood manufactured by Japan Biotest Laboratory Co., Ltd. is used. The viscosity of this horse defibrinated blood is less than 15 mPa · S as measured with a (B type) viscometer TVB-10M (measurement temperature 25 ° C., rotor L adapter) manufactured by Toki Sangyo Co., Ltd.

  In steps 1 to 3, the water used for washing the napkin is water prepared by dissolving calcium chloride and magnesium chloride in ion exchange water having an electric conductivity of 1 μS / cm or less. The water content ratio (calcium ion: magnesium ion) is 7: 3, and the German hardness is 5 ° DH. In addition, the water for domestic use in Indonesia, which is one of the countries that have a custom of washing used sanitary napkins, varies depending on the region, but water with a German hardness of 5 ° DH used in the above steps 1 to 3 It is almost the same as domestic water used in at least part of Indonesia.

  In the procedure 1, the environment in which the napkin into which blood has been injected is allowed to stand for 30 minutes before washing is an air temperature of 25 ° C. and a humidity of 60%. The napkin is washed by hand, and “the operation of putting about 100 g of water on the napkin with one hand and squeezing the napkin with the other hand” is repeated three times in 10 seconds. That is, the operation performed for 10 seconds is “sprinkle water → squeeze the napkin → spread water → squeeze the napkin → spread water → squeeze the napkin”. Accordingly, the amount of water used for washing the napkin for 3 minutes in the procedure 1 is about 100 g as described above because the amount of water used in one water application operation is about 100 g as described above. 3 =) 5400 g. In the above formula, 100 × 3 corresponds to the amount of water used for 10 seconds, and 100 × 3 × 6 corresponds to the amount of water used for 1 minute. When watering the napkin, use a beaker or the like, and do not squeeze the napkin while watering. In the procedure 1, the pressure when the napkin is squeezed by hand after washing the napkin for 3 minutes, that is, the grip strength of the hand is usually about 10 to 15 kg.

When measuring the red degree a ^* value of the red part, the measurement sample and the spectral color difference meter are brought into close contact with each other so that external light does not enter. As the spectral color difference meter, a simple spectral color difference meter “NF333” (pen type detector) manufactured by JASCO Corporation can be used.

  As is apparent from the results in Table 1, all of the napkins of Examples 1 to 3 have good absorption performance, can easily remove redness of blood by washing with water, and peel strength of the absorber. Is expensive. Therefore, the napkin of the embodiment is less likely to shift the sheet constituting the absorber during product processing or use, and can be stably manufactured and used. In particular, the napkins of Examples 1 and 2 mainly have a large amount of the water-soluble binder, and therefore the peel strength of the absorbent body is higher than others.

  On the other hand, the napkins of Comparative Examples 1 and 2 have the same absorption performance and water washability as the Examples, but mainly do not use the water-soluble binder that promotes the fixing of the water-absorbing polymer to the sheet. The peel strength of the body is low, which may cause inconvenience during product processing or use. Moreover, since the napkin of Comparative Example 3 uses a water-absorbing polymer having a centrifugal retention amount exceeding 20 g / g mainly in accordance with JIS K 7223, it is poor in ability to be washed with water, and it is possible to remove redness of blood by washing with water. It's not easy.

  In addition, since the napkin of Reference Examples 1 and 2 mainly uses carboxymethyl cellulose (CMC) which is an anionic binder as the water-soluble binder, it is compared with the embodiment using cationized starch as the water-soluble binder. Thus, the peel strength of the absorber is low.

10 Absorber 11 Water-absorbing polymer 12, 13 Sheet 20 Sanitary napkin (absorbent article)
21 Top sheet 22 Back sheet

Claims (5)

  It has a configuration in which a water-absorbing polymer having a centrifugal retention amount of 20 g / g or less according to JIS K 7223 is sandwiched between two sheets, and the water-absorbing polymer is fixed to the sheet via a water-soluble binder. Absorber.   The absorber according to claim 1, wherein the water-soluble binder is a cationic binder.   The water-absorbing polymer is spread on one surface of the wet sheet, the water-soluble binder is applied to the surface of the water-absorbing polymer, the separate sheets are stacked on top of each other, and they are dried. The absorbent body according to claim 1 or 2, wherein the absorbent body is produced by integrating.   The absorbent article containing the absorber in any one of Claims 1-3.   The method for producing an absorbent body according to claim 1 or 2, wherein a water-absorbing polymer and a water-soluble binder are provided on one surface of a wet sheet, a separate sheet is overlaid thereon, and these are dried. The manufacturing method of the absorber including the process to integrate.

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