JP5839534B2 - Absorber and absorbent article - Google Patents

Description

  The present invention relates to an absorbent body and an absorbent article used for sanitary napkins and the like.

  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 people, whose main areas of residence are Indonesia, Malaysia, etc., have a habit of washing used sanitary napkins with water and washing off absorbed menstrual blood etc. 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 that do not contain a water-absorbing polymer. 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 and absorbent article which have practically sufficient absorption performance and peeling strength, and are easy to wash with water.

  The present invention comprises a water-absorbing polymer having a centrifugal retention amount of 20 g / g or less and a fiber sheet according to JIS K 7223, and the water-absorbing polymer and the fiber sheet are an anionic or nonionic binder. The above-mentioned problems are solved by providing an absorbent body that is bonded to each other through a gap.

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

  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 of the fiber sheet constituting the absorbent body is practically sufficient, it is possible to prevent inconvenience caused by peeling of the fiber sheet that may occur during product processing or use. it can. 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 cross-sectional view schematically showing a cross section of another embodiment of the absorbent body of the present invention. FIG. 3 is a schematic view showing a manufacturing process of the absorbent body shown in FIG. FIG. 4 is a perspective view of a sanitary napkin that is an embodiment of the absorbent article of the present invention. FIG. 5 is a cross-sectional view schematically showing a cross section taken along line XX of FIG. 6 is a view corresponding to FIG. 5 of the sanitary napkin of Example 6. FIG.

  Hereinafter, first, the absorber of the present invention will be described in detail. The absorbent body of the present invention comprises a water absorbent polymer having a centrifugal retention amount of 20 g / g or less and a fiber sheet in accordance with JIS K 7223, and the water absorbent polymer and the fiber sheet are anionic or nonionic. Are bonded to each other through a binder.

  The centrifugal retention amount based on JIS K 7223 of the water-absorbing polymer used in the present invention 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 (255 mesh) is cut into a rectangle 10cm wide and 40cm long, folded in half in the center in the longitudinal direction, and heat sealed at both ends to make a nylon bag 10cm wide (inner size 9cm), 20cm long Is made. 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 after centrifugal dehydration and the nylon bag, b is before water absorption of the nylon bag (when dried) The mass (g) and c of the sample represent 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.

  A water-absorbing polymer having a centrifugal retention amount of 20 g / g or less based on JIS K 7223 can be obtained, for example, by performing an operation that moderately increases the degree of crosslinking of a conventional water-absorbing polymer. More specifically, for example, using a known polyacrylic acid-based water-absorbing polymer production method such as a reverse phase suspension polymerization method or an aqueous solution polymerization method described later, It is possible to obtain a water-absorbing polymer having a centrifugal retention of 20 g / g or less by obtaining a water-absorbing polymer (or hydrogel) having a carboxylate group and subjecting the water-absorbing polymer to a crosslinking treatment. it can.

  In this way, by performing the crosslinking treatment again on the crosslinked water-absorbing polymer, the degree of crosslinking of the water-absorbing polymer is efficiently increased as compared with the case where the crosslinking treatment is not performed twice. As a result, the network of molecular chains becomes finer, and hemoglobin, which is the main cause of blood redness, is prevented from penetrating into the deep part of the water-absorbing polymer, and the centrifugal retention amount of the water-absorbing polymer is reduced. The two cross-linking treatments can be performed by the same method and conditions.

  As an example of the material of the water-absorbing polymer used in the present invention, the following polycarboxylic acids subjected to crosslinking treatment or salts thereof (lithium, sodium, potassium, cesium) may be mentioned. Poly (meth) acrylic acid, (acrylic acid-vinyl alcohol) copolymer, (starch-acrylic acid) graft polymer, (isobutylene-maleic anhydride) copolymer and saponified product thereof, polyglutamic acid, and the like. These 1 type can be used individually or in mixture of 2 or more types.

  A water-absorbing polymer having a centrifugal retention amount of 20 g / g or less in accordance with JIS K 7223 is, for example, 1) polymerizing a monomer containing (meth) acrylic acid and / or an alkali metal salt thereof, Or a polymer obtained by crosslinking a polymer 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) includes two or more polymerizable unsaturated groups in the molecule, or a reactive group capable of reacting with two or more carboxy groups and / or carboxylate groups in the molecule. And a compound having two or more hydroxyl groups in the molecule, a compound having two or more polymerizable double bonds, a compound having two or more epoxy groups, and the like.

  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, pentaerythridine. 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.

  As the shape of the water-absorbing polymer used in the present invention, in addition to a spherical shape (particulate), a block shape such as a rectangular parallelepiped shape, a shape in which a plurality of spherical particles are combined, a shape in which a plurality of block particles are combined, a spherical shape The shape may be a combination of particles and block particles, 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. When the water-absorbing polymer used in the present invention has a spherical or nearly spherical particle shape, the average particle size of the water-absorbing polymer is preferably 50 to 800 μm, more preferably 100 to 600 μm, and even more preferably 150 to 500 μm. It is.

  The absorber of the present invention may contain a water-absorbing polymer other than the water-absorbing polymer having a centrifugal retention amount of 20 g / g or less. From the viewpoint of more surely exerting the effect of the water-absorbing polymer having a centrifugal retention amount of 20 g / g or less, the content of the water-absorbing polymer having a centrifugal retention amount of 20 g / g or less is the absorption of the present invention. It is preferable that it is 80 mass% or more with respect to the total mass of all the water-absorbing polymers contained in the body, in particular 90 mass% or more, especially 100 mass%. All the water-absorbing polymers contained in the absorbent body of the present invention are ideal in terms of action and effect when the centrifugal retention amount is 20 g / g or less.

  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.

In addition, the distribution amount (spraying basis weight) of the water-absorbing polymer (all the water-absorbing polymers in the absorber including the water-absorbing polymer having a centrifugal retention amount of 20 g / g or less) in the absorbent body of the present invention is preferably 10 to 200 g / m ^2, more preferably 20 to 150 g / m ^2, deliberately preferably 30 to 120 g / m ^2.

As the fiber sheet constituting the absorbent body of the present invention, a sheet-like material comprising fibers is used. In particular, the water-absorbing polymer having a centrifugal retention amount of 20 g / g or less is passed through a binder described later. And those having an appropriate liquid absorption ability are preferable. As the fiber sheet, for example, paper, woven fabric, non-woven fabric, knitted fabric, parchment, papyrus, pulp piled fiber and the like can be used. 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 fiber sheet may be a sheet having a single layer structure or a sheet having a multilayer structure. The basis weight of the fiber sheet, the fiber sheet is paper, woven fabric, in the case of non-woven fabric is preferably 10 to 80 g / m ^2, more preferably from 15 to 50 g / m ^2, also fiber sheet pulp product in the case of繊体is preferably 50 to 1000 g / m ^2, more preferably 100 to 600 / m ^2, more preferably from 150~500g / m ^2.

  In the absorbent body of the present invention, the number of fiber sheets is not particularly limited, and the number of fiber sheets may be one. When the number of fiber sheets is one, the fiber stack is preferably a single fiber sheet. That is, the absorbent body of the present invention may be one in which a water-absorbing polymer and one piece of pulp piled body are bonded to each other via a binder described later. In addition, the absorbent body of the present invention may be configured to include a water-absorbing polymer and a single fiber sheet, and the layer made of the water-absorbing polymer may be wrapped with the single fiber sheet. In this case, the one fiber sheet is preferably paper. When two or more fiber sheets are used, the plurality of fiber sheets may have the same composition and / or dimensions, or may be different from each other.

  FIG. 1 schematically shows a cross section of an embodiment of the absorbent body of the present invention. The absorbent body 10 shown in FIG. 1 has a configuration in which a water-absorbing polymer 11 having a centrifugal retention amount of 20 g / g or less is sandwiched between two fiber sheets 12 and 13 having the same composition and / or dimensions. The water-absorbing polymer 11 and the fiber sheets 12 and 13 are bonded to each other through a binder (not shown) described later. As the fiber sheets 12 and 13, for example, paper or a pulp pile is preferably used.

FIG. 2 schematically shows a cross section of another embodiment of the absorbent body of the present invention. The absorbent body 30 shown in FIG. 2 includes the water-absorbing polymer 11 having a centrifugal retention amount of 20 g / g or less and the fiber sheets 31 and 32, and the water-absorbing polymer 11 and the fiber sheets 31 and 32 are described later. Are bonded to each other via a binder (not shown). The absorbent body 30 includes a fiber sheet 31 made of a relatively thick pulp pile fiber body and a fiber sheet 32 made of paper having a relatively small thickness. It has a covered configuration, and a large number of water-absorbing polymers 11 are interposed between the fiber sheets 31 and 32. The two fiber sheets 31 and 32 may be different from each other only in the dimension including the thickness, may be different only in the composition, or may be different in dimension and composition. Like the absorbent body 30, an absorbent body using two fiber sheets, one of which is a pulp-stacked fiber body and the other of which is a paper sheet, has a simple absorption process and a manufacturing process of the absorbent body. From this point, it is preferable. Here, the paper is a fiber sheet that can be produced by a known wet papermaking method and has a thickness of 1 mm (basis weight 30 g / m ² ) or less, and examples thereof include tissue paper. The pulp pile is a fiber aggregate obtained by fiber accumulation in air according to a known dry method, and has a thickness of 2 mm (basis weight 150 g / m ² ) or more.

  In the absorbent body of the present invention, the water-absorbing polymer having a centrifugal retention amount of 20 g / g or less and the fiber sheet are bonded to each other through an anionic or nonionic binder. Since the water-absorbing polymer having a centrifugal retention amount of 20 g / g or less has less water-soluble content than the water-absorbing polymer having a centrifugal retention amount of more than 20 g / g, the polymer itself has poor adhesiveness. If the water-absorbing polymer is simply sandwiched between two fiber sheets, the peel strength between the fiber sheets is low, so that the fiber sheets are displaced during product processing or use, and the absorber may be destroyed. In the present invention, an anionic or nonionic binder is used as an adhesive between the water-absorbing polymer and the fiber sheet, because of the disadvantage of using such a water-absorbing polymer having a low centrifugal retention amount (low tackiness). By avoiding that.

  In addition, “the water-absorbing polymer and the fiber sheet are bonded to each other via a binder” means a state in which the water-absorbing polymer is not detached from the fiber sheet by the binder, specifically, a) The water-absorbing polymer is fixed to the fiber sheet through the binder so as not to move and cannot be moved from the fixing position. b) The water-absorbing polymer can be moved to the fiber sheet through the binder. Including the state fixed to. As an example of the state of b), for example, the binder that bonds the water-absorbing polymer and the fiber sheet has some fluidity and can be deformed at room temperature. A state in which the water-absorbing polymer integrated with the binder is movable within a relatively narrow range can be mentioned.

  The anionic or nonionic binder used in the present invention is preferably a water-soluble binder. If a water-insoluble binder (for example, a hot melt pressure-sensitive adhesive) is used as an adhesive between the water-absorbing polymer and the fiber sheet, the absorption performance of the water-absorbing polymer is hindered, leading to inconveniences such as a decrease in liquid absorption rate and liquid return Although there is a possibility, when a water-soluble binder is used as the adhesive, there is very little possibility of causing such inconvenience.

  In addition, by using a water-soluble binder for bonding the water-absorbing polymer and the fiber sheet in the absorbent body in this way, it becomes easy to wash away the blood absorbed by the absorbent body with water. The reason is not clear, but water-soluble binders tend to sterically and / or electrostatically prevent red blood cells (or hemoglobin, which is the main cause of redness of blood) from entering the water-absorbing polymer. It is also presumed that red blood cells (or hemoglobin which is the main cause of redness of blood) are easily washed away together with the water-soluble binder when the absorbent body or the absorbent article containing the absorbent body is washed with water. .

  Examples of the anionic water-soluble binder used in the present invention include carboxymethyl cellulose salt, poly (meth) acrylic acid, poly (meth) acrylate (including partially neutralized product), and acrylamide-acrylate (in the part). (Including Japanese) copolymer, maleic acid-acrylate (including partially neutralized) copolymer, polyamino acid salt (including partially neutralized), etc. Or 2 or more types can be mixed and used. As far as the present inventors have studied, the anionic water-soluble binder includes an anionic polymer obtained by polymerizing an acid group-containing unsaturated monomer, that is, an acid group-containing unsaturated monomer as a repeating unit. Polymers are preferable, and among them, acrylamide-acrylate copolymer, polyacrylic acid, polyacrylate, and maleic acid-acrylate copolymer are preferable. The acrylamide-acrylate copolymer, polyacrylic acid, polyacrylate, and maleic acid-acrylate copolymer are all polymers containing a carboxyl group-containing monomer as a repeating unit.

  The anionic binder (water-soluble binder) used in the present invention has a carboxyl group, and the neutralization degree of the carboxyl group is preferably 0 mol% or more, particularly 50 mol% or more, and particularly preferably 80 mol% or more. . What was illustrated previously as an anionic water-soluble binder is a binder which has a carboxyl group. When the neutralization degree of the carboxyl group in the anionic binder is 80 mol% or more, even if the water-absorbing polymer is reddish due to adhesion / absorption of menstrual blood etc., it is easy to remove the reddish by subsequent washing with water. The effect that it is. Adjustment of the neutralization degree of the anionic binder is, for example, water-soluble hydroxide such as lithium hydroxide, sodium hydroxide, potassium hydroxide, water glass, sodium hydrogen carbonate, sodium carbonate, potassium hydrogen carbonate, potassium carbonate, etc. The water-soluble carbonate compound can be used. The degree of neutralization of the binder is measured as follows.

<Measurement method of neutralization degree of binder>
First, a neutralization titration curve of the main chain polymer of the binder is prepared. For example, a case where the binder is sodium polyacrylate will be described as an example. A sodium hydroxide solution was appropriately added dropwise to an ion exchange aqueous solution of polyacrylic acid (Wako Pure Chemical Industries, average molecular weight 250,000), and the pH of the solution was measured using a pH meter. At this time, the degree of neutralization was calculated from the molecular weight of polyacrylic acid and the number of moles of added sodium hydroxide, and the neutralization degree was plotted on the horizontal axis and the pH was plotted on the vertical axis to draw a neutralization titration curve. The degree of neutralization was in the range of 50 to 100%. As the pH meter, Horiba pH ion meter D53 and electrode type 6583 were used. Next, 0.1 g of binder is put into 20 ml of ion-exchanged water, and after stirring for 10 minutes, the pH of the stirred solvent is measured. From the obtained pH value, the neutralization titration curve is used for the purpose. The degree of neutralization was calculated.

  Regarding the measurement of the degree of neutralization of the binder, instead of the above method, the amount of sodium in the binder was quantified by elemental analysis, and the following theoretical structural formula (1) (theoretical structural formula applied to acrylic acid polymers) ) May be used to calculate the target neutralization degree. Moreover, it may replace with the said method and may calculate the target neutralization degree from the value measured by the method based on JISK0113-1997. A method based on JIS K0113-1997 is a method in which a 0.1 N potassium hydroxide aqueous solution is used as a titrant to perform potentiometric titration, and an end point is determined by an inflection point method. Moreover, when neutralizing acrylic acid and then polymerizing to obtain sodium polyacrylate, or when neutralizing polyacrylic acid to obtain sodium polyacrylate, the degree of neutralization of the acrylic acid unit (the neutralized carboxyl The number of moles of sodium acid divided by the number of moles of carboxylic acid before neutralization).

  Note that polyacrylic acid or a salt thereof preferably used as an anionic water-soluble binder in the present invention is non-swelling unlike polyacrylic acid used as a material for a water-absorbing polymer. Specifically, in the case of a water-absorbing polymer, polyacrylic acid or a salt thereof is networked by a crosslinking agent, and swells according to the state of the network when water is absorbed. On the other hand, polyacrylic acid or a salt thereof preferably used as a water-soluble binder is basically non-crosslinked (does not construct a network) and is therefore non-swellable (cannot hold or hardly hold liquid).

  Examples of the nonionic water-soluble binder used in the present invention include polyvinyl alcohol, polyacrylamide, starch, polyethylene glycol, gum, methylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, hydroxypropylmethylcellulose, and polyvinylpyrrolidone. These 1 type can be used individually or in mixture of 2 or more types. In the range examined by the present inventors, the nonionic water-soluble binder is a nonionic polymer having a cyclic group, in particular, a nonionic polymer containing a monomer having a cyclic group as a repeating unit. Of these, polyvinylpyrrolidone is preferred.

  The weight average molecular weight (Mw) of the binder (anionic or nonionic binder) used in the present invention is not less than 5,000, particularly not less than 10,000 (10,000 to 3,000) from the viewpoint of compatibility between adhesiveness and processability. In particular, it is preferably 30,000 or more (30,000 to 25 million). The weight average molecular weight can be measured using a general gel permeation chromatography (for example, HLC-8020 manufactured by Tosoh Corporation). In addition, the column used in the measurement is properly used in consideration of the expected weight average molecular weight and ionicity.

  In the absorbent body of the present invention, the mass ratio of the binder to the water-absorbing polymer (binder / water-absorbing polymer) is 0.002 to 0.3, particularly preferably from the viewpoint of achieving both adhesiveness and processability. It is preferable that it is 005-0.2, especially 0.01-0.1.

  Further, the content of the binder in the absorbent body of the present invention is preferably 0.001 to 0.1% by mass, more preferably 0.002 to 0.08% by mass, and still more preferably 0.005 to 0.05% by mass. %.

  There is no restriction | limiting in particular in the method of including the said binder in an absorber, 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 binder is added in advance to the stock (fiber dispersion) when a fiber sheet is produced by a wet papermaking method. As an external addition method, for example, in the case of using two fiber sheets like the above-described absorbers 10 and 30, after forming each of the two fiber sheets, a water absorbent polymer is applied to one of the fiber sheets. There is a method of spraying, applying a binder to the spraying surface (surface on which the other sheet is superposed) by an application means such as spray, and superimposing the other fiber sheet thereon. Moreover, a binder may be apply | coated to one fiber sheet, and a water absorbing polymer may be spread | dispersed on the application surface (surface on which the other sheet | seat is overlaid) of the binder. Moreover, you may spray a water absorbing polymer and a binder simultaneously on one surface of one fiber sheet. When spraying the water-absorbing polymer and the binder at the same time, the water-absorbing polymer and the binder may be mixed in advance and the mixture may be sprayed, or the water-absorbing polymer and the binder aqueous solution may be mixed in advance and the mixture The binder may be adhered to the surface of the water-absorbing polymer by drying the water-absorbing polymer, and the water-absorbing polymer to which the binder has adhered may be sprayed. When the internal addition method is used, the binder is present substantially uniformly over substantially the entire area of the absorbent body (fiber sheet). When the external addition method is used, the overlapping surface of each of the two fiber sheets and It is localized in the vicinity. When the external addition method is used, the existing amount of the binder usually decreases as the distance from the overlapping surface increases in the sheet thickness direction.

  From the viewpoint of ensuring the effect of improving the peel strength by the binder, it is preferable to include a water-soluble binder in the absorbent body by the external addition method. For example, the absorbent body 10 (see FIG. 1) described above 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 sprinkled on one surface, and a separate body thereon. Those obtained by superimposing these sheets and integrating both sheets are preferred. A method for manufacturing the absorber 10 will be described later.

  Further, as another example of the external addition method, the above-described absorber 30 (see FIG. 2) is obtained by using another fiber having a relatively large thickness on one surface of the paper as the fiber sheet 32 having a relatively small thickness. After placing the pulp pile as the sheet 31 and spraying the water-absorbing polymer 11 and the binder simultaneously on the pulp pile, the fiber sheet 32 having a relatively small thickness is spread on the spreading surface. Those obtained by superimposing papers of the above are preferred. Thus, by simultaneously spraying the water-absorbing polymer and the binder, the binder can be disposed close to the water-absorbing polymer, so that the effect of improving the peel strength of the absorber can be enhanced. In particular, a method in which a binder is attached to the surface of the water-absorbing polymer and the water-absorbing polymer to which the binder is attached is more effective for improving the peel strength of the absorber. The manufacturing method of such an absorber 30 will be described later.

  When the absorbent body of the present invention is configured to include two fiber sheets like the absorbent bodies 10 and 30 described above, the peel strength of the absorbent body is preferably 3 cN / 40 mm or more, Preferably it is 5-200cN / 40mm, More preferably, it is 8-200cN / 40mm. The peel strength is measured by the following measurement method.

<Measurement method of peel strength>
An absorbent body to be measured (absorber having a structure in which two sheets are overlapped) is taken out from the absorbent article, and 40 mm in the same direction as the longitudinal direction of the absorbent article is perpendicular to the longitudinal direction from the absorbent body. A rectangular shape of 30 mm or more is cut out in the same direction as the width direction, and this is used as a test piece, and two sheets constituting the absorber are peeled in an area extending about 1 cm from one end in the width direction of the test piece. In this way, the test piece from which a part was peeled was attached to a push-pull gauge (CPU gauge MODEL-9500 made by Aiko Engineering) with one end in the width direction so that the width direction became the tensile direction, The other end is about 300 mm / min. Then, the sheet is pulled at a pulling speed of T and peeled off from one sheet to the other sheet, and the peak value of stress at this time is measured. The measurement is performed 5 times, and the average value of the measured values is taken as the peel strength of the absorber.

  In the above <Method for measuring peel strength>, when the absorbent body to be measured has the same configuration as the absorbent body 30 shown in FIG. 2, that is, “the whole fiber sheet made of pulp pile fiber body” Is coated with a fiber sheet made of paper having a thickness smaller than that of the pulp pile, and has a configuration in which two fiber sheets made of the paper are overlapped, A test piece is prepared as follows, and the test piece is measured according to the above <Method of measuring peel strength>. First, an absorbent body to be measured is taken out from the absorbent article, the absorbent body is cut so that the length in the same direction as the longitudinal direction of the absorbent article is 40 mm, and then the absorbent body is configured. A portion of the paper (fiber sheet) that covers both side edges (both side faces) along the longitudinal direction of the pulp piled body (fiber sheet) (that is, both side edges along the longitudinal direction of the paper) Are cut off to form cut end portions along the longitudinal direction of the paper. And one of the two sheets of paper constituting the overlapping portion (two sheets of the paper covering the dispersion surface side of the water absorbent polymer of the pulp stack fiber) is replaced with the cut end portion. As a starting point, a T-shape is peeled off from the pulp piled fiber, and the peel strength is measured. Next, the other of the two sheets constituting the overlapping portion is peeled off from the pulp pile by using a cut end located on the side opposite to the cut end as a starting point. Measure strength. The peeling of the paper and the measurement of the peeling strength are performed according to the above <Method for measuring peel strength>. In the measurement of peel strength, the peel strength of each of the two sheets of paper is treated as a single measured value. When the peeling length of one of the two sheets to be peeled is less than 10 mm, the measurement is performed using only the other paper.

  In the absorbent body of the present invention, it is preferable that the number of water-absorbing polymers dropped out by the following measuring method is 100 or less, particularly 50 or less, particularly 20 or less. It can be considered that the peeling strength of the fiber sheet which comprises an absorber is so strong that there are few drop-off numbers of this water absorbing polymer, and it becomes high evaluation.

<Method for measuring the number of water-absorbing polymers falling off>
An absorbent article in which an absorbent body to be measured is incorporated is enclosed in a plastic bag having a size that can accommodate the absorbent article, and the plastic bag is handshaked 50 times with a vertical movement width of about 20 cm. . Here, the handshake is the same as the operation performed when, for example, various kinds of powders are put in a plastic bag and mixed. Specifically, the handshake is a plastic bag in which an absorbent article is enclosed. It is an operation to hold and shake quickly in the vertical direction. After the handshake, the plastic bag is opened, the contents are visually observed, the number of water-absorbing polymers that have fallen off from the absorbent article is counted, and this is the number of water-absorbing polymers that have dropped out.

The absorber of the present invention can be thinned by having the above-described configuration. The thickness of the absorber of the present invention is 0.1 to 5 mm, preferably 0.1 to 2 mm, and more preferably 0.2 to 1.5 mm. The thickness of the absorber here means the thickness under a load of 7 g / cm ² . The 7 g / cm ² load assumes body pressure that the absorbent body receives when the absorbent article is worn when the absorbent body is used in an absorbent article such as a sanitary napkin.

  Hereinafter, the fiber sheet used in the present invention will be further described. It is preferable that the fiber sheet contains 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.

  Content of the said hydrophilic fiber becomes like this. Preferably it is 20 mass% or more with respect to the total mass of a fiber sheet, More preferably, it is 35-90 mass%.

  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 and immobilization of the water-absorbing polymer are further improved, but also when paper is used as the fiber sheet, wet paper drainage is performed during the wet papermaking. Can be controlled more easily. 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 fiber sheet.

  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) from Federal Paper Board Co. and “INDORAYON” (trade name) from 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 bulky cellulose fiber, there is a crosslinked cellulose fiber obtained by crosslinking cellulose molecules within and / or between molecules. Such a crosslinked cellulose fiber has a feature that 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 a polycarboxylic acid or a 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 bulky cellulose fibers described above, 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 cross-linked 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 between the molecule | numerators by the above-mentioned method is also preferable.

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

  More preferable bulky cellulose fibers are those 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 method described above.

  Particularly preferred bulky cellulose fibers are pulps 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 above-described method.

  The fiber sheet used in the present invention may be configured to include the above-described crosslinked cellulose fiber, but the adhesive effect between the water-absorbing polymer and the fiber sheet is more reliably expressed by the anionic or nonionic binder described above. In particular, when the same configuration as that of the absorbent body 30 shown in FIG. 2 is adopted, the fiber sheet 32 is a fiber that has not been subjected to the above-described crosslinking treatment, in particular, has been subjected to crosslinking treatment. Those mainly composed of non-pulp fibers are preferred. The content of the pulp fiber not subjected to the crosslinking treatment in the fiber sheet 32 is preferably 60% by mass or more, and more preferably 70% by mass or more with respect to the total mass of the fiber sheet 32. On the other hand, when the same configuration as that of the absorbent body 10 shown in FIG. 1 is adopted, the fiber sheets 12 and 13 are preferably mainly composed of pulp fibers that have been subjected to a crosslinking treatment.

  The fiber sheet used in the present invention can contain a hot-melt adhesive fiber or a paper strength reinforcing agent from the viewpoint of imparting practically sufficient wet strength.

  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 hot-melt adhesive fiber, the fiber sheet used in the present invention includes 30 to 99 parts by weight of the hydrophilic fiber and 1 to 50 parts by weight of the hot-melt adhesive fiber based on 100 parts by weight of the fiber sheet. It is preferable that it consists of. 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 the fiber 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 a fiber sheet used in the present invention, 0.2 to 10% by mass (preferably 1 to 5% by mass) of polyvinyl alcohol fiber (hot melt adhesive fiber) and 0.1% of sponge (paper strength reinforcing agent) are used. What contains 1-1 mass% (preferably 0.2-0.8 mass%) is mentioned.

  Next, the manufacturing method of the absorbent body of the present invention will be described with reference to the drawings, taking as an example the manufacturing method (hereinafter also referred to as the first manufacturing method) of the absorbent body 10 (see FIG. 1) of the embodiment. 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. 3 is a schematic diagram showing a manufacturing process of the absorbent body 10 shown in FIG.

  In the first manufacturing method, as shown in FIG. 3, the water-absorbing polymer 11 is sprayed on the one surface 12a of the wet fiber sheet 12, and the binder 14 is applied to the spraying surface of the water-absorbing polymer 11, and then the top. It includes the steps of stacking separate fiber sheets 13 and drying and integrating them.

  The fiber sheet 12 can be manufactured according to the manufacturing method of the sheet | seat containing this kind of fiber, There is no restriction | limiting in particular in the manufacturing method, A wet method or a dry method may be sufficient. When the fiber sheet 12 is manufactured by the wet papermaking method, a wet fiber sheet is always obtained, so that the labor of making the dry fiber sheet wet in a separate process can be saved. In this embodiment, the fiber 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 fiber sheet 12 is produced by a wet papermaking method, the fibers forming the fiber sheets 12 and 13 and other components other than the binder are dispersed in water to a predetermined concentration to form a slurry. The slurry is introduced into a wet paper machine, and is made to flow and thinly flat on a wet paper machine according to a conventional method to form a wet fiber sheet 12.

  Next, excess water is dehydrated from the wet fiber 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 moisture content of the fiber sheet 12 (sheet immediately before the water-absorbing polymer is sprayed) after the dehydration step 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 fiber sheet 12. The water-absorbing polymer 11 may be uniformly distributed over the entire surface 12a of the wet fiber sheet 12, or may be partially distributed in the form of a streak at a predetermined interval in the longitudinal direction of the wet sheet 12. Alternatively, it may be intermittently sprayed in the form of shots in the longitudinal direction of the wet sheet 12.

Next, the binder 14 is applied to the spray surface of the water absorbent polymer 11. In this embodiment, the binder is dissolved or dispersed in an appropriate solvent such as water to obtain a binder liquid, and this binder liquid is sprayed by spraying. It is preferable that the binder liquid is uniformly applied to the entire surface of the fiber sheet 12 on which the water-absorbing polymer 11 is spread on the one surface 12a. The application amount of the 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 fiber sheet 13 is superposed on the dispersion surface (one surface 12 a) of the water absorbent polymer 11 in the fiber sheet 12 to form a laminate of both sheets 12 and 13. In this laminated body, the water-absorbing polymer 11 is further buried in the fiber sheets 12 and 13 and the constituent fibers of the fiber sheets 12 and 13 are entangled with each other. The fiber sheet 13 can be manufactured by the same method as the fiber 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.

  Subsequently, the laminated body of the fiber sheets 12 and 13 is dried and integrated by the drying means 71. By drying the laminate, the constituent fibers of the fiber sheets 12 and 13 are entangled with each other, and further, when hydrogen bonding or the heat-fusible adhesive fiber is used, a heat-sealing action is also added. , 13 are integrated, and the adhesive force of the binder is expressed, and the water-absorbing polymer 11 adheres to the fiber sheets 12 and 13 (component fibers of the sheet) by the adhesive force. At this time, the water-absorbing polymer 11 enters the fiber sheet 12, 13, that is, the space formed by the constituent fibers of the sheet 12, 13, and stresses the fiber sheet 12, 13 from the outside. Even if is added, the water-absorbing polymer 11 is hardly moved or dropped off. The adhesive strength of the binder is considered to contribute to the integration of the fiber sheets 12 and 13.

  Although the drying temperature at the time of drying the laminated body of the fiber sheets 12 and 13 is based also on a composition etc. of a fiber sheet, 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.

  Moreover, the absorber of this invention, especially the absorber 30 mentioned above (refer FIG. 2) can also be manufactured as follows. A manufacturing method of the absorbent body 30 (hereinafter also referred to as a second manufacturing method) is a method in which a pulp product fiber 31 as another fiber sheet 31 is disposed on one surface of a paper 32 as a fiber sheet 32, and a pulp product After water and the mixture of the water-absorbing polymer 11 and the binder are sprayed in this order or in the reverse order, the fiber sheet is applied to the spray surface of the mixture in the pulp stack 31. The process of superimposing the paper 32 as is included. In this step, the water-absorbing polymer and the binder are simultaneously sprayed by mixing and spraying the water-absorbing polymer and the binder.

  In the second manufacturing method, the paper 32 has a size larger than that of the pulp pile 31 and can cover the whole pulp pile 31. The mixture dispersed on the pulp pile 31 is obtained by mixing a water-absorbing polymer and a binder. For example, a binder liquid is prepared by dissolving or dispersing the binder in a solvent such as water. It is obtained by mixing the binder liquid and the water-absorbing polymer. The order of spreading on the pulp pile 31 may be the order of water and the mixture, or the order of the mixture and water. The amount of water sprayed is such that the water content of the pulp pile 31 after spraying water and the mixture is 0.5 to 10% by weight, particularly 1 to 8% by weight, and further 1.5 to 5% by weight. It is preferable to adjust to. The spray location of the water and the said mixture in the pulp pile fiber body 31 shall be the same, and the spray pattern of the said mixture can be made the same as the spray pattern of the water absorbing polymer 11 in a said 1st manufacturing method.

  In the second production method, after spraying water and the mixture on the pulp pile 31, the extending portion from the pulp pile 31 in the paper 32 is rolled up along the side surface of the pulp pile 31, Furthermore, the upper surface (spreading surface of the mixture) of the pulp stack 31 is covered with the extending portion. Thus, after covering the whole pulp pile fiber 31 with the paper 32, the pulp pile fiber 31 and the whole paper 32 are compressed by press work as needed. The absorber 30 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. 4 is a perspective view of the sanitary napkin of the present embodiment, and FIG. 5 is a cross-sectional view schematically showing a cross section taken along line XX of FIG. The napkin 20 according to the present embodiment includes the absorbent body 10 (see FIG. 1).

  The napkin 20 has a shape that is long in one direction as shown in FIG. 4, and includes a top 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. 5, 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 of the absorbent article or a component thereof that faces the wearer's skin when the absorbent article is worn, and the non-skin contact surface is the absorbent article. Or it is a surface which is turned to the opposite side to a wearer's skin side at the time of wear of an absorptive article in the constituent member. 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.

  In addition, the napkin 20 may be provided with the absorber 30 (refer FIG. 2) instead of the absorber 10 as an absorber. In that case, the absorbent body 30 has a non-skin contact of the napkin 20 on the side where the water-absorbing polymer 11 is spread on the fiber sheet 31 (pulp pile) (the side where the water-absorbing polymer is relatively present). It is preferably arranged so as to face the surface side (back surface sheet 22 side).

  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 extending 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.

  Moreover, the absorber 10 (refer FIG. 1) has one laminated body of the two fiber sheets 12 and 13 which pinches | interposes the water absorbing polymer whose amount of centrifugal retention based on JISK7223 is 20 g / g or less. However, the absorbent body of the present invention includes a form having a plurality of laminates of such two sheets.

  Further, the absorbent body 30 (see FIG. 2) has a configuration in which the entire fiber sheet 31 made of a pulp pile is covered with a fiber sheet 32 made of a single sheet of paper. Instead, the configuration may be such that the upper and lower surfaces of the fiber sheet 31 made of pulp piled body are covered with another fiber sheet 32 made of paper. In this case, the absorbent body 30 includes two fiber sheets 32. Yes.

  In the first production method, the water-absorbing polymer 11 is sprayed on the one surface 12a of the wet sheet 12, and the water-soluble binder 14 is applied to the spraying surface of the water-absorbing polymer 11. In the production method of the absorber, the order of application of the water-absorbing polymer and the binder to the sheet is not particularly limited, and may be applied in the order of the binder and the water-absorbing polymer, or the water-absorbing polymer and the binder may be applied simultaneously. good. When both are applied simultaneously, as described above, the water-absorbing polymer and the binder may be mixed in advance, and the mixture may be applied as it is or after drying.

  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. Unless otherwise specified, “%” means “mass%”.

  Hereinafter, a method for synthesizing the water-absorbing polymer used in this example will be described. The synthesis method includes a step of polymerizing a water-absorbing polymer (polymerization step), a step of subjecting the obtained water-absorbing polymer to a crosslinking treatment (crosslinking step), and a step of neutralizing the crosslinked water-absorbing polymer (medium). Sum process).

[Synthesis Example 1 (Production of water-absorbing polymer I)]
I-1. Polymerization process Polyoxyalkylene ether phosphate 0.1% (as opposed to acrylic) as a dispersant in a SUS304 5L reaction vessel (using anchor blades) equipped with a stirrer, reflux condenser, monomer dropping port, nitrogen gas inlet tube and thermometer Acid mass, amount of active ingredients) and 1500 ml of normal heptane was added. The temperature was raised to an internal temperature of 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%) 1050 g of sodium (72% neutralized product, concentration about 47%) was obtained. To this monomer aqueous solution, 0.25 g of N-acylated sodium glutamate (Ajinomoto, trade name Amisoft PS-11) dissolved in 4.4 g of ion-exchanged water was added, and then 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 an aqueous solution of ammonium iron (III) (manufactured by Kanto Kagaku) and 10 g of ion-exchanged water were mixed and dissolved to prepare an initiator (A) solution. Moreover, 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. Furthermore, a titanium citrate aqueous solution (50% citric acid and titanyl sulfate aqueous solution were 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.

  The monomer A, monomer B, and 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 the order of 60 minutes for polymerization. After completion of monomer dropping, azeotropic dehydration is 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- as a crosslinking agent) 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 Brite ADPA-60A, manufactured by Rhodia) was added. After cooling, normal heptane was removed and dried to obtain a water-absorbing polymer.

I-2. Crosslinking step Into the same reaction vessel (using anchor blades) as used in the polymerization step, 500 g of the water-absorbing polymer obtained in the polymerization step is charged, and sucrose fatty acid ester (trade name, manufactured by Mitsubishi Chemical Foods) is used as a dispersant. 2% of Ryoto Sugar Ester S-770 (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 g of ion-exchanged water was dropped from the dropping port using a dropping funnel, and then 15 g of ethylene glycol diglycidyl ether (trade name Denacol EX-810, manufactured by Nagase ChemteX) as a crosslinking agent was added to 10 g of ion-exchanged water. Was added and the mixture was refluxed for 1.5 hours.

I-3. Neutralization Step Subsequently, a solution obtained by dissolving 30 g of commercially available sodium hydroxide in 500 g of ion-exchanged water was added dropwise over 1 hour. After dehydrating 600 g over 2 hours, the mixture was cooled to remove cyclohexane and dried to obtain a water-absorbing polymer I.

[Synthesis Example 2 (Production of water-absorbing polymer II)]
In Synthesis Example 1, a water-absorbing polymer II was obtained in the same manner as in Synthesis Example 1 except that the amount of the crosslinking agent used in the crosslinking step was changed from 15 g to 0.25 g.

[Synthesis Example 3 (Production of water-absorbing polymer III)]
III-1. Polymerization process Kao Co., Ltd. Emar 20C [Polyoxyethylene (EO average) as a dispersant in a SUS304 5L reaction vessel (using anchor blades) equipped with a stirrer, reflux condenser, monomer dropping port, nitrogen gas inlet tube, thermometer Number of moles added 3) Alkyl (C12) ether sulfate Na] 0.15% (based on acrylic acid mass) was charged, and 1600 ml of a polymerization solvent cyclohexane was added. The temperature was raised to an internal temperature of 76 ° 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%) 1100 g of sodium (76% neutralized product, concentration about 48%) was obtained. To this aqueous monomer solution, 0.175 g of N-acylated glutamic acid sodium (Ajinomoto Healthy Supply Co., Ltd., trade name Amisoft GS-11F) dissolved in 3.15 g of ion-exchanged water was added and stirred for a while. It was divided into 275 g (hereinafter referred to as monomer aqueous solution D), 275 g (hereinafter referred to as monomer aqueous solution E), and 550 g (hereinafter referred to as monomer aqueous solution F).

  Next, 0.20 g of 2,2′-azobis (2-amidinopropane) dihydrochloride (manufactured by Wako Pure Chemical Industries, trade name V-50), 0.20 g of polyethylene glycol (manufactured by Kao, PEG 6000), iron iron citrate ( III) 4 g of aqueous solution (manufactured by Kanto Chemical) and 10 g of ion-exchanged water were mixed and dissolved to prepare an initiator (C) solution. Further, 0.49 g of sodium persulfate (manufactured by Wako Pure Chemical Industries, Ltd.) was dissolved in 10 g of ion-exchanged water to prepare an initiator (D) solution. Furthermore, a titanium citrate aqueous solution (50% citric acid and titanyl sulfate aqueous solution were mixed at a mass ratio of 20/27) was prepared.

  To monomer aqueous solution D, 7.2 g of initiator (C) solution was added to prepare monomer D, and to monomer aqueous solution E, 7.2 g of initiator (C) solution and 1.5 g of the above titanium citrate aqueous solution were added to form monomer. E was prepared, and monomer F was prepared by adding 10.5 g of the initiator (D) solution and 3 g of the titanium citrate aqueous solution to the monomer aqueous solution F.

  After confirming that the internal temperature of the 5 L reaction vessel was 77 ° C., the monomer D was dropped from the monomer dropping port using a microtube pump over 15 minutes for polymerization. Subsequently, monomer E was added dropwise over 15 minutes for polymerization. Subsequently, monomer F was dropped and polymerized over 30 minutes. After completion of the polymerization, azeotropic dehydration is 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) as a crosslinking agent. ) A solution of 0.25 g dissolved in 10 g of ion exchange water was added. Thereafter, azeotropic dehydration was further performed, and after cooling, cyclohexane was removed and dried to obtain a water-absorbing polymer.

III-2. Crosslinking process A 1 L kneader with two sigma-type stirring blades is charged with 500 g of the water-absorbing polymer obtained in the polymerization process, and sucrose fatty acid ester (trade name Ryoto Sugar Ester S, manufactured by Mitsubishi Chemical Foods) as a dispersant. -770) 0.1% (with respect to the mass of the water-absorbing polymer, the amount of active ingredients) was charged, and the temperature was raised to 80 ° C. with stirring in a nitrogen atmosphere. Subsequently, a solution obtained by dissolving 12.5 g of ethylene glycol diglycidyl ether (manufactured by Nagase ChemteX, trade name Denacol EX-810) as a crosslinking agent was added to 250 g of ion-exchanged water, and the mixture was stirred for 2 hours. Then, it dried and obtained the water absorbing polymer III.

[Synthesis Example 4 (Production of water-absorbing polymer IV)]
An anionic water-soluble binder was adhered to the surface of the water-absorbing polymer III. That is, 400 g of the water-absorbing polymer III was charged into a jacketed 1 L kneader having two sigma-type stirring blades and stirred in a nitrogen atmosphere. Subsequently, 400 g of a 5% by mass aqueous solution of polyacrylate (A190 made by MT Aquapolymer, polymerization average molecular weight 7 million, neutralization degree of carboxyl group is unknown) as an anionic water-soluble binder was dropped over 1 hour. . Thus, the water-absorbing polymer III treated with the binder was dried to obtain a water-absorbing polymer IV.

[Synthesis Example 5 (Production of water-absorbing polymer V)]
V-1. Polymerization process Polyoxyalkylene ether phosphate 0.1% (as opposed to acrylic) as a dispersant in a SUS304 5L reaction vessel (using anchor blades) equipped with a stirrer, reflux condenser, monomer dropping port, nitrogen gas inlet tube and thermometer Acid mass, amount of active ingredients) 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, concentration about 47%) was obtained. To this monomer aqueous solution, 0.25 g of N-acylated glutamic acid soda (trade name: Amisoft PS-11) dissolved in 4.4 g of ion-exchanged water was added, and then 500 g (hereinafter referred to as monomer aqueous solution G). ), 500 g (hereinafter referred to as monomer aqueous solution H).

  The monomer G is prepared by adding the initiator (A) solution used in the production of the water-absorbing polymer I to the monomer aqueous solution G, and the initiator (B) used in the production of the water-absorbing polymer I in the monomer aqueous solution H. Monomer H was prepared by adding the solution.

  The monomer G and monomer H, 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 over 60 minutes for polymerization. After completion of monomer dropping, azeotropic dehydration is performed using a dehydrating tube to adjust the water content of the water-absorbing polymer (hydrogel) to 70%, and then ethylene glycol diglycidyl ether (manufactured by Nagase ChemteX, product name) as a crosslinking agent. Denacol EX-810) having 1000 mg / kg (mass acrylic acid) dissolved in 10 g of ion-exchanged water was added, and water was removed to a water content of about 10% to obtain a water-absorbing polymer.

V-2. Crosslinking step In a nitrogen atmosphere, 100 parts by mass (in terms of solid content) of the above-mentioned water-absorbing polymer and 200 parts by mass of normal heptane are kept at 80 to 90 ° C. with stirring, and then 60 parts by mass of ion-exchanged water are mixed with ethylene as a crosslinking agent. A solution prepared by dissolving 3 parts by mass of glycol diglycidyl ether (manufactured by Nagase ChemteX, trade name Denacol EX-810) was added dropwise and refluxed for 2 hours.

V-3. Neutralization Step Subsequently, 6 parts by mass of sodium hydroxide dissolved in 100 parts by mass of ion-exchanged water was dropped. Thereafter, the water content of the water-absorbing polymer (hydrogel) was adjusted to 35 ± 5% by azeotropic dehydration.

V-4. Binder treatment step Subsequently, 5 mass of sodium salt of maleic acid-acrylate copolymer as an anionic water-soluble binder (Socaran CP5 manufactured by BASF, weight average molecular weight 70,000, neutralization degree of carboxyl group is unknown) 100 parts by mass of a% aqueous solution was added dropwise. After dehydration to a water content of 35 ± 5%, normal heptane was removed and dried to obtain a water-absorbing polymer V.

[Synthesis Example 6 (Production of water-absorbing polymer VI)]
In Synthesis Example 5, as an anionic water-soluble binder, a polyacrylic acid sodium salt A (weight average molecular weight 250,000, carboxyl group neutralization degree 100 mol%) prepared by the following synthesis method 100 mass% of 5 mass% aqueous solution A water-absorbing polymer VI was obtained in the same manner as in Synthesis Example 5 except that the part was used.

  Synthesis method of sodium salt A of polyacrylic acid: Polyacrylic acid (manufactured by Wako Pure Chemical Industries, Ltd., weight average molecular weight 250,000) was added to ion-exchanged water being stirred to prepare an aqueous suspension. A 5N aqueous sodium hydroxide solution was added dropwise so that the degree of neutralization of the carboxyl groups in the polyacrylic acid was 100 mol%, to obtain a 5 mass% aqueous solution of sodium salt A of polyacrylic acid.

[Synthesis Example 7 (Production of water-absorbing polymer VII)]
In Synthesis Example 5, 15 mass% aqueous solution 100 mass of polyacrylic acid sodium salt B (weight average molecular weight 10,000, carboxyl group neutralization degree 96 mol%) prepared by the following synthesis method as an anionic water-soluble binder A water-absorbing polymer VII was obtained in the same manner as in Synthesis Example 5 except that the part was used.

  Synthesis method of sodium salt B of polyacrylic acid: 225 g of ion-exchanged water was charged into a 2 L 4-neck separable flask, heated in a 70 ° C. bath, heated to 450 g of 80% acrylic acid aqueous solution and 12 g of sodium persulfate An aqueous sodium persulfate solution dissolved in 90 g of exchange water and an aqueous sodium hydrogen sulfite solution prepared by dissolving 26 g of sodium hydrogen sulfite in 78 g of ion exchange water were respectively added dropwise for 4 hours for polymerization. The reaction solution was cooled at room temperature and then neutralized with 395 g of a 48% aqueous sodium hydroxide solution. Subsequently, after adding 22 g of 35% hydrogen peroxide solution and mixing for 3 hours, sodium hydrogen sulfite having a molar equivalent of 1.05 times the amount of hydrogen peroxide remaining in the reaction solution was added, and a sodium polyacrylate aqueous solution was added. Further, 1% by mass (2.4 parts by mass of the reducing agent with respect to 100 parts by mass of the polymer) of sodium hydrogen sulfite was added to the sodium polyacrylate aqueous solution so as to exist. Then, it prepared so that solid content concentration might be 40%. The weight average molecular weight of the 96 mol% neutralized polyacrylic acid sodium salt B thus obtained was 10,000.

[Evaluation of water-absorbing polymer]
Various characteristics (centrifugal retention amount, degree of neutralization) were evaluated for the water-absorbing polymers I to VII obtained in the respective synthesis examples. The results are shown in Table 1 below. The measurement of the centrifugal retention amount of the water-absorbing polymer was in accordance with the above method, and the neutralization degree of the water-absorbing polymer was in accordance with the following method. In addition, what classified the produced water-absorbing polymer was used for the characteristic evaluation of a water-absorbing polymer.

<Measurement method of neutralization degree of water-absorbing polymer>
First, a neutralization titration curve of the main chain polymer of the water-absorbing polymer is prepared. For example, when the water absorbent polymer is an acrylic acid crosslinked polymer, the main chain polymer of the water absorbent polymer is polyacrylic acid. The case where the water-absorbing polymer is an acrylic acid crosslinked polymer will be described below as an example. A sodium hydroxide solution was appropriately added dropwise to an ion exchange aqueous solution of polyacrylic acid (Wako Pure Chemical Industries, average molecular weight 250,000), and the pH of the solution was measured using a pH meter. At this time, the degree of neutralization was calculated from the molecular weight of polyacrylic acid and the number of moles of added sodium hydroxide, and the neutralization degree was plotted on the horizontal axis and the pH was plotted on the vertical axis to draw a neutralization titration curve. The degree of neutralization was in the range of 50 to 100%. As the pH meter, Horiba pH ion meter D53 and electrode type 6583 were used. Next, 0.1 g of the water-absorbing polymer was put into 20 ml of ion-exchanged water, and after stirring for 10 minutes, the pH of the stirred solvent was measured. From the obtained pH value, the neutralization titration curve was used for the purpose. The degree of neutralization was calculated.

  In addition, regarding the measurement of the neutralization degree of the water-absorbing polymer, instead of the above-mentioned method, the amount of sodium in the water-absorbing polymer is quantified by elemental analysis, and the theoretical structural formula used in the measurement of the neutralization degree of the binder described above ( 1) The target degree of neutralization may be calculated based on (theoretical structural formula applied to an acrylic acid polymer). Moreover, it may replace with the said method and may calculate the target neutralization degree from the value measured by the method based on JISK0113-1997. A method based on JIS K0113-1997 is a method in which a 0.1 N potassium hydroxide aqueous solution is used as a titrant to perform potentiometric titration, and an end point is determined by an inflection point method. In addition, when acrylic acid is neutralized and then polymerized to obtain a water-absorbing polymer, it can be determined from the degree of neutralization of acrylic acid (number of moles of acrylate after neutralization ÷ number of moles of acrylic acid before neutralization). .

[Example 1]
According to the second manufacturing method, an absorber having the same configuration as the absorber 30 shown in FIG. 2 was manufactured. That is, pulp pile fiber (basis weight 200 g / m) as a fiber sheet, separately manufactured by a known dry method on paper (tissue paper, width 17 cm, length 30 cm) having a basis weight of 16 g / m ² as a fiber sheet. ² , width 7 cm, length 30 cm). This tissue paper is made of pulp fibers which are larger in size than the fiber web and which have not been cross-linked. Next, 0.1 g of ion-exchanged water is sprayed on a part (range of 19 cm in the longitudinal direction and 5.5 cm in the width direction) on the pulp-stacked fiber, and then the ion-exchanged water in the pulp-stacked fiber is sprayed. The mixture of the water-absorbing polymer I of Synthesis Example 1 and the binder was uniformly sprayed on the portions. This mixture contains 0.5 g of the water-absorbing polymer I of Synthesis Example 1 and an acrylamide-acrylate copolymer (MT Aqua Polymer A150, weight average molecular weight of 15 million, carboxyl group) as an anionic water-soluble binder. It was prepared by mixing 0.5 g of a 5% by weight aqueous solution of which the degree of neutralization is unknown) and drying the mixture, and an anionic water-soluble binder is adhered to the surface of the water-absorbing polymer I. . Subsequently, after covering the whole pulp laminated fiber with the tissue paper, press working was performed so that the thickness became 2 mm. Further, both ends in the longitudinal direction of the pulp pile fiber body were cut into a curved shape to obtain an absorbent body having a length of 19 cm in the longitudinal direction.

  An adhesive is applied to the non-skin contact surface side of the obtained absorbent body (spreading surface side of the water-absorbing polymer in the fiber sheet 31), and the back surface on the non-skin contact surface of the absorbent body through the adhesive The sheet was fixed. Next, the entire surface of the skin contact surface of the absorbent is covered with a surface sheet, and the skin contact surface side of the surface sheet is embossed according to a conventional method to form a leak-proof groove, and a napkin precursor Got. 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 Laurie Softcare manufactured by Kao Corporation) was used as the top sheet, and a polyethylene film having a thickness of 25 μm was used as the back sheet. The napkin generally has the structure shown in FIG. The napkin thus obtained was used as a sample of Example 1.

[Example 2]
In Example 1, polyacrylic acid salt as an anionic water-soluble binder was used instead of 0.5 g of 5% by weight aqueous solution of acrylamide-acrylic acid copolymer in the preparation of the mixture of water-absorbing polymer I and binder. A napkin was produced in the same manner as in Example 1 except that 0.5 g of a 5% by mass aqueous solution (A190 made of MT Aquapolymer, weight average molecular weight 7 million, neutralization degree of carboxyl group is unknown) was used. Samples of

Example 3
In Example 1, in the preparation of the mixture of the water-absorbing polymer I and the binder, instead of 0.5 g of a 5% by mass aqueous solution of acrylamide-acrylate copolymer, polyvinylpyrrolidone as a nonionic water-soluble binder (Japan) A napkin was produced in the same manner as in Example 1 except that 0.5 g of a 5% by weight aqueous solution of K90 (catalyst, weight average molecular weight 1,200,000) was used, and a sample of Example 3 was obtained.

Example 4
In Example 1, in preparation of the mixture of the water-absorbing polymer I and the binder, instead of 0.5 g of the 5 mass% aqueous solution of the acrylamide-acrylate copolymer, 3 mass% of the acrylamide-acrylate copolymer was used. A napkin was produced in the same manner as in Example 1 except that 0.5 g of the aqueous solution was used, and a sample of Example 4 was obtained.

Example 5
In Example 1, the water absorbent polymer IV of Synthesis Example 4 was used in place of the mixture of the water absorbent polymer I and the binder. Otherwise, a napkin was produced in the same manner as in Example 1 to obtain a sample of Example 5.

Example 6
In Example 1, the napkin was prepared in the same manner as in Example 1 except that the absorber was replaced with the following, and the thickness of the napkin (thickness under a load of 7 g / cm ² ) was 3.5 mm. A sample of Example 6 was obtained.

(Absorber of Example 6)
A hot melt adhesive (P-618B manufactured by Toyo Petrolite) was applied separately at a coating amount of 5 g / m ² , and prepared separately on the adhesive coating surface of a tissue paper (upper fiber sheet) having a basis weight of 16 g / m ^2. A pulp fiber fiber web (basis weight 200 g / m ² , width 7 cm, length 17 cm) was placed. This tissue paper has larger dimensions than the fiber web. Next, a small amount of ion-exchanged water was sprayed uniformly over the fiber web, and then 0.5 g of the water-absorbing polymer V of Synthesis Example 5 was sprayed uniformly over the entire fiber web. Further, a tissue paper (lower fiber sheet) having a basis weight of 16 g / m ² on which the adhesive is not applied is stacked on the surface of the fiber web where the water-absorbing polymer is applied, and the upper fiber sheet extends from the fiber web. Was wound on the upper surface of the lower fiber sheet, and the fiber web was turned upside down to obtain a rectangular absorbent body in a plan view in which substantially the entire absorbent body was covered with tissue paper (fiber sheet). . A schematic cross-sectional view (corresponding to FIG. 5) of the napkin of Example 6 is shown in FIG. In FIG. 6, reference numeral 20A is a sanitary napkin, reference numeral 21 is a top sheet, reference numeral 22 is a back sheet, reference numeral 25 is a leak-proof groove, reference numeral 30A is an absorbent, reference numeral 11 is a water-absorbing polymer, reference numeral 31 is a fiber web (relative The reference numeral 32a is an upper fiber sheet (fiber sheet having a relatively small thickness), and the reference numeral 32b is a lower fiber sheet (fiber sheet having a relatively small thickness).

Example 7
In Example 6, instead of the water-absorbing polymer V, the water-absorbing polymer VI of Synthesis Example 6 was used. Otherwise, a napkin was produced in the same manner as in Example 6 to obtain a sample of Example 7.

Example 8
In Example 6, instead of the water-absorbing polymer V, the water-absorbing polymer VII of Synthesis Example 7 was used. Otherwise, a napkin was produced in the same manner as in Example 6 to obtain a sample of Example 8.

[Comparative Example 1]
A napkin was produced in the same manner as in Example 1 except that no binder was used in the production of the absorber, and a sample of Comparative Example 1 was obtained.

[Comparative Example 2]
A napkin was produced in the same manner as in Example 1 except that the water-absorbing polymer II of Synthesis Example 2 (centrifugal holding amount 26 g / g) was used.

[Comparative Example 3]
A napkin was produced in the same manner as in Comparative Example 2 except that no binder was used in the production of the absorber, and a sample of Comparative Example 3 was obtained.

[Comparative Example 4]
In Example 1, the water-absorbing polymer III of Synthesis Example 3 was used instead of the mixture of the water-absorbing polymer I and the binder. Otherwise, a napkin was produced in the same manner as in Example 1 to obtain a sample of Comparative Example 4.

[Evaluation of absorbent articles (napkins)]
About each sample (sanitary napkin) of an Example and a comparative example, the peeling strength of the absorber and the number of drops of the water-absorbing polymer were measured by the above methods. In addition, as an evaluation of the absorption performance of each sample, the absorption time and the liquid return amount are measured by the following methods, and also the evaluation of detergency (in this specification, the ease of removing redness derived from blood by washing with water). The red degree a ^* value was measured by the following method. These results are shown in Tables 2 and 3 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 cleaning performance of the napkin. The smaller the a ^* value, the lower the red part of the red part, and the blood is washed with water. It means that it is washed away cleanly.

Procedure 1: Inject 12 g of blood into the sanitary napkin from the surface layer side of the sanitary napkin, leave it for 30 minutes in an environment of 25 ° C., 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, Indonesian water for daily use, which is one of the countries that have a habit of washing used sanitary napkins, has different hardness 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”. Therefore, the amount of water used for washing the napkin for 3 minutes in the procedure 1 is approximately 100 g as described above because the amount of water used in one water application operation is approximately 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 clear from the results in Table 2, all of the napkins of Examples 1 to 8 have good absorption performance, can easily remove blood redness by washing with water, and the water-absorbing polymer is removed. The number is small and the peel strength of the absorber is high. Therefore, the napkin of the embodiment is less likely to shift the fiber sheet constituting the absorbent body during product processing or use, and can be stably manufactured and used.

  On the other hand, as is apparent from the results in Table 3, the napkins of Comparative Examples 1 and 4 have the same absorption performance as that of the Example, and the napkin of Comparative Example 1 has the same cleanability as that of the Example. Since the binder that mainly promotes adhesion between the water-absorbing polymer and the fiber sheet is not used, the number of water-absorbing polymer drops off is large, and the peel strength of the absorber is low. Therefore, the napkins of Comparative Examples 1 and 4 may cause inconvenience during product processing or use. Moreover, since the napkin of Comparative Examples 2 and 3 uses a water-absorbing polymer whose centrifugal retention amount exceeds 20 g / g mainly in accordance with JIS K 7223, it has poor detergency, and the redness of blood is removed by washing with water. Is not easy.

10, 30, 30A Absorbent body 11 Absorbent polymer 12, 13, 31, 32, 32a, 32b Fiber sheet 20, 20A Sanitary napkin (absorbent article)
21 Top sheet 22 Back sheet 25 Leak-proof groove

Claims (8)

It is composed of a water-absorbing polymer having a centrifugal retention amount of 20 g / g or less and a fiber sheet according to JIS K 7223, and the water-absorbing polymer and the fiber sheet are bonded to each other through an anionic water-soluble binder. And the binder is an anionic polymer obtained by polymerizing an acid group-containing unsaturated monomer .   The absorber according to claim 1, wherein the binder has a weight average molecular weight of 10,000 or more. The binder over the polyacrylic acid non-crosslinked or claim 1 or 2 absorber according a salt thereof. Before fang Indah is acrylamide - absorber according to claim 1 or 2 wherein the acrylic acid salt copolymer. Absorber defined before Kiba Indah has a carboxyl group, any one of claims 1-4 neutralization degree of the carboxyl groups is 80 mol% or more. The absorbent mass according to any one of claims 1 to 5 , wherein a content ratio of the binder to the water-absorbing polymer (binder / water-absorbing polymer) is 0.002 to 0.3. The fiber sheet includes a relatively thick pulp product and a relatively thin paper, and the entire pulp product has a configuration in which the paper is covered with the paper. Item 7. The absorbent body according to any one of Items 1 to 6 . An absorptive article containing the absorber according to any one of claims 1 to 7 .

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