WO2022209441A1

WO2022209441A1 - Absorber

Info

Publication number: WO2022209441A1
Application number: PCT/JP2022/007363
Authority: WO
Inventors: 知穗大仁田; 嘉津義 ▲高▼松
Original assignee: 住友精化株式会社
Priority date: 2021-03-30
Filing date: 2022-02-22
Publication date: 2022-10-06
Also published as: JPWO2022209441A1; CN117083043A

Abstract

This absorber has a longitudinal direction and a width direction perpendicular to the longitudinal direction, and has a region A containing water-absorbing resin particles a having a 5-minute value of non-pressurization DW of 10 ml/g or less and water-absorbing resin particles b having a 5-minute value of non-pressurization DW of more than 10 ml/g, and a region B containing the water-absorbing resin particles b having the 5-minute value of non-pressurization DW of more than 10 ml/g. The amount of the water-absorbing resin particles a contained in the region A is 15-55% by mass of the total amount of the water-absorbing resin particles contained in the region A, and the amount of the water-absorbing resin particles a contained in the region B is 0% by mass or more and less than 15% by mass of the total amount of the water-absorbing resin particles contained in the region B. The region B is at least partially located at or near both ends in the longitudinal direction of the absorber.

Description

Absorber

The present disclosure relates to absorbent bodies.

Conventionally, absorbent articles containing water-absorbent resin particles have been used in absorbent articles for absorbing liquids, such as urine, whose main component is water. For example, Patent Literature 1 describes a method for producing water-absorbing resin particles having a particle size suitable for use in absorbent articles such as diapers.

JP-A-6-345819

The absorber is required that the liquid once absorbed in the absorber does not easily release to the outside even when pressurized, that is, the amount of regurgitation is small. The present inventors have found that the amount of backflow can be reduced by using water-absorbent resin particles exhibiting a 5-minute value of no-pressure DW of 10 ml/g or less for the absorbent body. However, it has been found that when such water-absorbent resin particles are used over the entire surface of the absorbent, leakage in the longitudinal direction of the absorbent, particularly from the back side during wearing, may not be prevented.

One aspect of the present disclosure relates to providing an absorbent body capable of suppressing backflow after liquid absorption and reducing leakage in the longitudinal direction of the absorbent body.

An absorbent body according to one aspect of the present disclosure is an absorbent body having a longitudinal direction and a width direction orthogonal to the longitudinal direction, wherein the water absorbent resin particles a exhibit a 5-minute value of unpressurized DW of 10 ml/g or less, and a region A containing water-absorbing resin particles b exhibiting a 5-minute value of no-pressure DW exceeding 10 ml / g, and a region comprising water-absorbing resin particles b exhibiting a 5-minute value of no-pressure DW exceeding 10 ml / g B, the amount of the water absorbent resin particles a contained in the region A is 15 to 55% by mass with respect to the total amount of the water absorbent resin particles contained in the region A, and the water absorbent resin particles contained in the region B The amount of a is 0% by mass or more and less than 15% by mass with respect to the total amount of the water-absorbing resin particles contained in the region B, and at least a part of the region B is located at or near both ends in the longitudinal direction of the absorbent body. .

In the above absorber, the regions B may be positioned at both ends of the absorber in the longitudinal direction and formed along the shapes of both ends of the absorber.

In the absorbent body, at least part of the region B may be formed at a position where the distance from the longitudinal end of the absorbent body is 0 to 40% of the length of the absorbent body in the longitudinal direction.

In the above absorber, the total area of region B may be 20 to 80% of the total absorber.

It is preferable that the physiological saline water absorption speed of the water-absorbing resin particles a is 60 seconds or longer.

It is preferable that the water-absorbent resin particles a have a physiological saline water retention capacity of 16 to 55 g/g.

The water-absorbent resin particles a are preferably coated resin particles having a crosslinked polymer particle and a water-insoluble coating layer covering at least part of the surface of the crosslinked polymer particle.

According to one aspect of the present disclosure, it is possible to provide an absorbent body capable of suppressing backflow after liquid absorption and reducing leakage in the longitudinal direction of the absorbent body.

1 is a schematic plan view showing an embodiment of an absorbent body; FIG. (a) and (b) are schematic plan views showing other embodiments of the absorbent body. (a) and (b) are schematic plan views showing other embodiments of the absorbent body. 1 is a schematic cross-sectional view showing an embodiment of an absorbent article; FIG. FIG. 2 is a schematic diagram showing a method for measuring the amount of water absorbed under load of water absorbent resin particles. FIG. 3 is a schematic diagram showing a method for measuring the non-pressure DW of water absorbent resin particles. It is a schematic diagram which shows the method to evaluate the leakiness of an absorbent article.

Several embodiments of the present disclosure will be described in detail below. However, the present disclosure is not limited to the following embodiments.

In this specification, "acrylic" and "methacrylic" are collectively referred to as "(meth)acrylic". "Acrylate" and "methacrylate" are similarly written as "(meth)acrylate". "(poly)" shall mean both with and without the "poly" prefix. In the numerical ranges described stepwise in this specification, the upper limit value or lower limit value of the numerical range in one step can be arbitrarily combined with the upper limit value or lower limit of the numerical range in another step. In the numerical ranges described herein, the upper or lower limits of the numerical ranges may be replaced with the values shown in the examples. The materials exemplified in this specification may be used alone or in combination of two or more. The content of each component in the composition means the total amount of the plurality of substances present in the composition unless otherwise specified when there are multiple substances corresponding to each component in the composition. The term "layer" includes not only a shape structure formed over the entire surface but also a shape structure formed partially when observed as a plan view. Unless otherwise specified, the area, length and shape of the absorber refer to those in plan view. A planar view of the absorbent body means that the main surface of the absorbent body (the surface that does not constitute the thickness) is placed on a horizontal plane and viewed from above in the vertical direction in the thickness direction of the absorbent body.

The absorbent body according to this embodiment has a longitudinal direction and a width direction orthogonal to the longitudinal direction, and has regions A and B. Region A includes water absorbent resin particles a exhibiting a 5-minute value of no-pressure DW of 10 ml/g or less, and water-absorbent resin particles b exhibiting a 5-minute value of no-pressure DW exceeding 10 ml/g. Region B contains water-absorbent resin particles b that exhibit a 5-minute value of unpressurized DW greater than 10 ml/g. The amount of the water absorbent resin particles a contained in the region A is 15 to 55% by mass with respect to the total amount of the water absorbent resin particles contained in the region A, and the amount of the water absorbent resin particles a contained in the region B is It is 0% by mass or more and less than 15% by mass with respect to the total amount of the water-absorbent resin particles contained in B. At least part of the region B is located at or near both ends in the longitudinal direction of the absorbent body.

By having the absorber having the above structure, it is possible to suppress the backflow amount of the absorber after liquid absorption and reduce leakage in the longitudinal direction of the absorber. Specifically, by arranging the region A containing a sufficient amount of the water-absorbent resin particles a with a sufficiently low 5-minute value of the non-pressurized DW, the amount of water absorption is saved and the initial diffusibility of the liquid is increased. , the backflow amount after liquid absorption is reduced. In addition, since a region B containing a sufficient amount of water-absorbing resin particles b having a 5-minute value of non-pressurized DW higher than a certain value is arranged at or near both ends of the absorbent body, it is not absorbed in the region A. It is possible to quickly absorb the collected liquid in the region B and reduce leakage in the longitudinal direction of the absorbent body.

Region A includes water-absorbing resin particles a exhibiting a 5-minute value of no-pressure DW of 10 ml/g or less, and water-absorbing resin particles b exhibiting a 5-minute value of no-pressure DW exceeding 10 ml/g. The amount of the water absorbent resin particles a contained in the region A is 15 to 55% by mass with respect to the total amount of the water absorbent resin particles contained in the region A.

The amount of the water-absorbent resin particles a contained in the region A is 18% by mass or more, 19% by mass or more, 20% by mass or more, 25% by mass or more, or 30% by mass with respect to the total amount of the water-absorbent resin particles contained in the region A. % or more, 35% by mass or more, 40% by mass or more, 45% by mass or more, or 50% by mass or more, 53% by mass or less, 50% by mass or less, 45% by mass or less, 40% by mass or less, 35% by mass % or less, 30 mass % or less, 25 mass % or less, or 22 mass % or less. The amount of the water absorbent resin particles a contained in the region A may be 18 to 53 mass % or 20 to 50 mass % with respect to the total amount of the water absorbent resin particles contained in the region A.

The amount of water-absorbing resin particles b contained in region A is 45% by mass or more, 50% by mass or more, 55% by mass or more, 60% by mass or more, relative to the total amount of water-absorbing resin particles contained in region A. It may be 65% by mass or more, 70% by mass or more, 75% by mass or more, 80% by mass or more, 81% by mass or more, or 82% by mass or more. The amount of the water absorbent resin particles b contained in the region A is 85% by mass or less, 82% by mass or less, 81% by mass or less, 80% by mass or less with respect to the total amount of the water absorbent resin particles contained in the region A, It may be 75% by mass or less, 70% by mass or less, 65% by mass or less, 60% by mass or less, 55% by mass or less, or 52% by mass or less. The amount of the water absorbent resin particles b contained in the region A may be 45 to 85 mass % or 50 to 80 mass % with respect to the total amount of the water absorbent resin particles contained in the region A. The water-absorbing resin particles a contained in the region A from the viewpoint of improving the absorption speed and reducing the amount of backflow after absorbing the liquid by increasing the initial diffusibility of the liquid and suppressing the occurrence of the gel blocking phenomenon. and the amount of the water absorbent resin particles b is preferably within the above range.

Region B contains water-absorbent resin particles b that exhibit a 5-minute value of non-pressurized DW of more than 10 ml/g. The amount of the water absorbent resin particles b contained in the region B is more than 85% by mass with respect to the total amount of the water absorbent resin particles contained in the region B.

The amount of the water absorbent resin particles b contained in the region B is 88% by mass or more, 90% by mass or more, 92% by mass or more, 95% by mass or more, 98% by mass of the total amount of the water absorbent resin particles contained in the region B. Above, it may be 99% by mass or more, 99.5% by mass or more, or 100% by mass. The amount of water-absorbing resin particles b contained in region B is 100% by mass or less, 99.5% by mass or less, 99% by mass or less, or 98% by mass or less with respect to the total amount of water-absorbing resin particles contained in region B. It's okay. The amount of the water absorbent resin particles b contained in the region B may be 88 to 100% by mass, or 90 to 100% by weight with respect to the total amount of the water absorbent resin particles contained in the region B.

Region B may or may not contain water-absorbent resin particles a. The amount of the water absorbent resin particles a contained in the region B is 0 mass % or more and less than 15 mass % with respect to the total amount of the water absorbent resin particles contained in the region B. The amount of the water absorbent resin particles a contained in the region B is 0.5% by mass or more, 1% by mass or more, 2% by mass or more, 5% by mass or more, 7 % by mass or more, 10% by mass or more, or 12% by mass or more, 12% by mass or less, 10% by mass or less, 7% by mass or less, 5% by mass or less, 2% by mass or less, 1% by mass or less, or It may be 0.5% by mass or less. From the viewpoint of reducing leakage in the longitudinal direction of the absorbent body, the amounts of the water absorbent resin particles a and the water absorbent resin particles b contained in the region B are preferably within the above range. The amount of the water absorbent resin particles a contained in the region B may be 0 to 12% by weight, or 0 to 10% by weight with respect to the total amount of the water absorbent resin particles contained in the region B.

The water-absorbent resin particles a contained in region A and the water-absorbent resin particles a contained in region B may be of the same type, or may be of different types, for example, obtained under different manufacturing conditions. The water-absorbent resin particles b contained in the region A and the water-absorbent resin particles b contained in the region B may be of the same type, or may be of different types, for example, obtained under different production conditions.

Hereinafter, embodiments of the absorbent body of the present disclosure will be described in detail with reference to the drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and overlapping descriptions are omitted. Also, for convenience of drawing, the dimensional ratios in the drawings do not necessarily match those in the description.

FIG. 1 is a schematic plan view of the absorbent body according to the present embodiment, and is viewed from the side with which the liquid contacts first when the absorbent body is used. The absorber 10 is sheet-like, rectangular in plan view, and has a longitudinal direction X and a width direction Y orthogonal to the longitudinal direction. The length in the longitudinal direction X is longer than the length in the width direction Y. A ratio X/Y of the length in the longitudinal direction X to the length in the width direction Y may be 1.0 to 5.0. The ratio X/Y may be 1.5 or greater, 2.0 or greater, 2.5 or greater, or 3.0 or greater, and 4.5 or less, 4.0 or less, 3.5 or less, or 3.0 or less. can be The absorbent body 10 has two regions B at both ends in the longitudinal direction. Region B is rectangular and formed to extend along the shape of both ends of absorbent body 10 . In FIG. 1, the region B is in contact with the entire lengthwise end 1 of the absorbent body 10, and connects portions of the two opposite short lengthwise ends 3 to each other. A region A occupies a portion of the absorbent body 10 other than the region B, including the vicinity of the central portion of the absorbent body. By arranging the region A near the center of the absorbent body, the amount of water absorption in the vicinity of the central part of the absorbent body, which the liquid first comes into contact with in the early stage of water absorption, is saved, and the initial diffusibility of the liquid is further increased. can be reduced more efficiently.

In FIG. 1, the longitudinal length d1 of the absorbent body 10 in one region B is 10 to 40% of the longitudinal length (maximum length) of the absorbent body 10. The longitudinal length d1 of the absorbent body 10 in region B is 12% or more, 15% or more, 18% or more, 20% or more, 25% or more, 30% or more, or 35% of the longitudinal length of the absorbent body 10. % or more, and may be 35% or less, 30% or less, 25% or less, 20% or less, 15% or less, or 12% or less. Note that the length d1 is the maximum length of the region B in the longitudinal direction of the absorbent body 10, and in the embodiment shown in FIG. 1, the length d1 is constant over the entire width direction of the absorbent body.

FIGS. 2(a) and 2(b) are schematic plan views showing modifications of the absorbent body 10. FIG. In FIG. 2( a ), regions B are formed in the vicinity of both longitudinal ends of the absorbent body 10 . Specifically, the region B is formed to extend near the longitudinal end 1 and is not in contact with the longitudinal end 1 and the lateral end 3 of the absorbent body 10 .

At least a portion of region B (e.g., 50% or more, 60% or more, 70% or more, 80% or more, 90% or more, 95% or more, 98% or more, or 100% of the total area of region B) absorbs It is formed at a position where the distance d2 from the longitudinal end 1 of the body 10 is 0 to 40% of the length (maximum length) of the absorbent body 10 in the longitudinal direction. The formation position of the region B is such that the distance d2 from the longitudinal end 1 of the absorbent body 10 is 0% or more, 3% or more, 5% or more, 8% or more, or 10% of the longitudinal length of the absorbent body 10. 15% or more, or 20% or more, and may be 40% or less, 35% or less, 30% or less, 25% or less, or 20% or less. At least part of the region B is formed at a position where the distance d2 from the longitudinal end 1 of the absorbent body 10 is 3 to 35% or 5 to 30% of the longitudinal length of the absorbent body 10. may Region B may be formed in a position other than the above in addition to the above range of absorbent body 10 . The entire region B (100% of the total area of the region B) is formed at a position where the distance d2 from the longitudinal end 1 of the absorbent body 10 is 0 to 40% of the length of the absorbent body 10 in the longitudinal direction. preferably. Note that the portion of the end 1 that serves as a reference for the distance d2 is the portion of the end 1 that extends farthest to the outside of the absorbent body. In the embodiment shown in FIG. 2(a), since the edge 1 is parallel to the width direction over the entire length, any part of the edge 1 may be used as the reference for the distance d2 of the edge 1. FIG.

In FIG. 2(b), the regions B are divided into 6 regions, and 3 regions are formed near the two ends 1 of the absorbent body 10 in the longitudinal direction. Thus, the region B formed at one end side in the longitudinal direction of the absorbent body 10 may be one, or may be divided into a plurality of regions. In FIGS. 2A and 2B, each region B is drawn as a rectangle, but it may have any shape such as a circle, an ellipse, a polygon, and an irregular shape.

FIGS. 3(a) and 3(b) are schematic plan views showing modifications of the absorbent body 10. FIG. In FIG. 3( a ), the region B is formed in an annular shape over the entire circumference of the absorbent body 10 . A region A is formed in the vicinity of the central portion of the absorbent body 10 . The regions B formed around the entire circumference of the absorbent body 10 may all be connected to one (may be an endless ring), and even if there are one or more locations divided by the region A good. The regions B need only be formed at least at the longitudinal ends of the absorbent body 10 or in the vicinity thereof, and may or may not be formed at the lateral ends 3 of the absorbent body 10 or in the vicinity thereof. good.

The longitudinal end 1 and the lateral end 3 of the absorber 10 may be straight or curved. The shape of the absorbent body 10 is typically rectangular, but the shape is not particularly limited as long as it has a longitudinal direction X and a width direction Y shorter than this. In FIG. 3(b), the absorber 10 has a longitudinal end 1 that curves outwardly, and a transverse end 3 that curves outwardly. In FIG. 3B, regions B are formed along the shape of both ends of the absorbent body 10 in the longitudinal direction. The ends 3 in the width direction may be curved lines convex outward from the absorbent body, or may be straight lines. The ends 1 in the longitudinal direction may be curved lines convex toward the inner side of the absorbent body, or may be straight lines.

In FIG. 3(b), the region B is formed at a position where the distance d2 from the end 1 in the longitudinal direction of the absorbent body 10 is 0 to 40% of the length d in the longitudinal direction of the absorbent body 10. As shown in FIG. When the absorbent body 10 has a shape other than a rectangle as shown in FIG. The distance d2 from the direction edge 1 refers to the longitudinal distance from the position of the longitudinal edge 1 that protrudes most outward in the longitudinal direction.

The total area of region A may be 20 to 80% of the area of absorbent body 10 . The area of the region A is 20% or more, 25% or more, 30% or more, 35% or more, 40% or more, 45% or more, 50% or more, 55% or more, 60% or more of the area of the absorbent body 10, 65% or more, 70% or more, 75% or more, 80% or less, 75% or less, 70% or less, 65% or less, 60% or less, 55% or less, 50% or less, 45% or less, 40% 35% or less, 30% or less, or 25% or less.

The total area of region B may be 20 to 80% of the area of absorbent body 10 . The area of the region B is 20% or more, 25% or more, 30% or more, 35% or more, 40% or more, 45% or more, 50% or more, 55% or more, 60% or more of the area of the absorbent body 10, 65% or more, 70% or more, 75% or more, 80% or less, 75% or less, 70% or less, 65% or less, 60% or less, 55% or less, 50% or less, 45% or less, 40% 35% or less, 30% or less, or 25% or less.

The absorbent body 10 may be line-symmetrical or asymmetrical with respect to an axis passing through the central part of the absorbent body and parallel to the longitudinal direction of the absorbent body. The absorbent body may be line-symmetrical or asymmetrical with respect to an axis passing through the central portion of the absorbent body and parallel to the lateral direction of the absorbent body.

[Water absorbent resin particles a]
The water absorbent resin particles a show a 5-minute value of no-pressure DW of 10 ml/g or less. The 5-minute value of no-pressure DW is the water absorption rate represented by the amount of physiological saline absorbed by the water-absorbing resin particles in 5 minutes after contact with the physiological saline under no pressure. The non-pressurized DW is represented by the absorbed amount [mL] per 1 g of the water-absorbing resin particles before absorption of physiological saline.

The 5-minute value of the non-pressurized DW of the water absorbent resin particles a is less than 10 ml/g, 9 ml/g or less, 8 ml/g or less, 7 ml/g or less, 6 ml/g or less, 5 ml/g or less, 4 ml/g or less. , or 3 ml/g or less. The 5-minute value of the non-pressurized DW of the water absorbent resin particles a is 0.1 ml/g or more, 1 ml/g or more, 2 ml/g or more, 3 ml/g or more, 4 ml/g or more, 5 ml/g or more, 6 ml/g or more. g or more, 7 ml/g or more, or 8 ml/g or more. The 5-minute value of the non-pressurized DW of the water absorbent resin particles a may be 0.1 ml/g or more and less than 10 ml/g, or 1 ml/g or more and 9 ml/g or less. The 5-minute value of no-pressure DW is measured by the method described in Examples below.

The physiological saline water retention capacity of the water-absorbing resin particles a is 16 g/g or more, 20 g/g or more, 25 g/g or more, 30 g/g or more, from the viewpoint of making it easier to achieve both prevention of liquid leakage and excellent regurgitation amount. may be 32 g/g or greater, 34 g/g or greater, 36 g/g or greater, or 38 g/g or greater; 55 g/g or less; 53 g/g or less; 51 g/g or less; It may be 45 g/g or less, 43 g/g or less, 41 g/g or less, or 39 g/g or less. The physiological saline water retention capacity of the water absorbent resin particles a may be 16 to 55 g/g, 25 to 51 g/g, or 32 to 47 g/g. The water retention capacity of physiological saline is measured by the method described in Examples below.

The water absorption rate of the water-absorbing resin particles a (physiological saline water absorption rate according to the Vortex method) is 60 seconds or longer, 61 seconds or longer, 70 seconds or longer, 75 seconds or longer, 80 seconds or longer, 85 seconds or longer, 90 seconds or longer, and 95 seconds. 98 seconds or more, or 100 seconds or more, 240 seconds or less, 200 seconds or less, 180 seconds or less, 170 seconds or less, 160 seconds or less, 150 seconds or less, 140 seconds or less, 130 seconds or less, 120 seconds or less , 110 seconds or less, or 105 seconds or less. The water absorption speed of the water absorbent resin particles a may be 60 to 240 seconds, or 60 to 200 seconds. When the water absorption speed of the water-absorbent resin particles a is 60 seconds or more, the initial diffusibility of urine is increased, an excellent amount of regurgitation is more likely to be achieved, and the occurrence of gel blocking phenomenon is easily suppressed, which is preferable. It is preferable that the water-absorbent resin particles a have a remarkably lower water absorption speed according to the Vortex method than the water-absorbent resin particles b. The water absorption rate of the water absorbent resin particles Aa by the Vortex method may be 1.5 to 3 times the value of the water absorbent resin particles b. The water absorption rate by the Vortex method is measured in accordance with Japanese Industrial Standards JIS K 7224 (1996) as described in Examples below.

The water absorption under load of the water absorbent resin particles a may be, for example, 16 ml/g or more, 18 ml/g or more, 20 ml/g or more, 22 ml/g or more, or 24 ml/g or more, and may be 30 ml/g or less, 28 ml. /g or less, 26 ml/g or less, or 24 ml/g or less. The water absorption under load of the water absorbent resin particles a may be 16 to 30 ml/g, or 18 to 28 ml/g. The water absorption under load is measured by the method described in Examples below.

The water-absorbing resin particles a may be, for example, crosslinked polymer particles and coated resin particles having a water-insoluble coating layer covering at least part of the surface of the crosslinked polymer particles.

The crosslinked polymer particles that make up the coated resin particles contain a water-absorbing resin, and may contain, for example, a crosslinked polymer formed by polymerization of a monomer containing an ethylenically unsaturated monomer. The crosslinked polymer can have monomeric units derived from ethylenically unsaturated monomers. Crosslinked polymer particles can be produced, for example, by a method including a step of polymerizing a monomer containing an ethylenically unsaturated monomer. Examples of the polymerization method include a reverse phase suspension polymerization method, an aqueous solution polymerization method, a bulk polymerization method, a precipitation polymerization method, and the like.

The ethylenically unsaturated monomer may be a water-soluble ethylenically unsaturated monomer (an ethylenically unsaturated monomer whose solubility in 100 g of water is 1 g or more at 98°C). Examples of water-soluble ethylenically unsaturated monomers include (meth)acrylic acid and its salts, 2-(meth)acrylamido-2-methylpropanesulfonic acid and its salts, (meth)acrylamide, N,N-dimethyl (Meth)acrylamide, 2-hydroxyethyl (meth)acrylate, N-methylol (meth)acrylamide, polyethylene glycol mono (meth)acrylate, N,N-diethylaminoethyl (meth)acrylate, N,N-diethylaminopropyl (meth) Acrylate, diethylaminopropyl (meth)acrylamide and the like. When the ethylenically unsaturated monomer has an amino group, the amino group may be quaternized. Ethylenically unsaturated monomers may be used alone or in combination of two or more.

When the ethylenically unsaturated monomer has an acid group, the acid group may be neutralized with an alkaline neutralizer before use in the polymerization reaction. The neutralization degree of the ethylenically unsaturated monomer with an alkaline neutralizing agent is, for example, 10 to 100 mol%, 50 to 90 mol%, or 60 to 80 mol of the acidic groups in the ethylenically unsaturated monomer. %.

From the viewpoint of industrial availability, the ethylenically unsaturated monomer is at least one selected from the group consisting of (meth)acrylic acid and its salts, acrylamide, methacrylamide, and N,N-dimethylacrylamide. It may contain a compound of the species. The ethylenically unsaturated monomer may contain at least one compound selected from the group consisting of (meth)acrylic acid and its salts, and acrylamide.

As a monomer for obtaining crosslinked polymer particles, a monomer other than the ethylenically unsaturated monomers described above may be used. Such monomers can be used, for example, by mixing with an aqueous solution containing the ethylenically unsaturated monomers described above. The amount of ethylenically unsaturated monomer used may be 70 to 100 mol % of the total amount of monomers. The ratio of (meth)acrylic acid and its salt may be 70 to 100 mol % with respect to the total amount of monomers.

Cross-linking may occur due to self-crosslinking during polymerization, but cross-linking may be promoted by using an internal cross-linking agent. The use of an internal cross-linking agent facilitates control of the water absorption properties (water retention capacity, etc.) of the crosslinked polymer particles. An internal cross-linking agent is usually added to the reaction solution during the polymerization reaction.

The crosslinked polymer particles may be crosslinked in the vicinity of the surface (surface crosslinked). In addition, the crosslinked polymer particles may be composed only of polymer particles (crosslinked polymer). Additional ingredients may also be included. The additional component can be located inside the polymer particles, on the surface of the polymer particles, or both. An additional ingredient may be a flow improver (lubricant). The fluidity improver may contain inorganic particles. Examples of inorganic particles include silica particles such as amorphous silica.

The shape of the coated resin particles is not particularly limited, and may be, for example, substantially spherical, crushed, or granular, or may be an aggregate of primary particles having these shapes.

The median particle size of the coated resin particles may be 100-800 μm, 150-700 μm, 200-600 μm, or 250-500 μm. The median particle size can be measured by the following method.

[Method for measuring median particle size]
JIS standard sieves from the top, 600 μm sieve, 500 μm sieve, 425 μm 425 μm sieve, 300 μm sieve, 250 μm sieve, 180 μm sieve, 150 μm sieve, and , in the order of the saucer. 50 g of the water-absorbing resin particles are placed in the combined uppermost sieve, and classified according to JIS Z 8815 (1994) using a low-tap shaker (manufactured by Iida Seisakusho Co., Ltd.). After classification, the mass of the particles remaining on each sieve is calculated as a mass percentage of the total amount to determine the particle size distribution. For this particle size distribution, the sieve top is accumulated in descending order of particle size, and the relationship between the sieve opening and the integrated value of the mass percentage of the particles remaining on the sieve is plotted on logarithmic probability paper. By connecting the plots on the probability paper with a straight line, the particle size corresponding to the cumulative mass percentage of 50% by mass is obtained as the median particle size.

The water-insoluble coating layer that constitutes the coated resin particles is a layer that contains a water-insoluble component. In the present specification, the water-insoluble component may include not only completely water-insoluble substances but also substances slightly soluble in water (poorly water-soluble substances). The solubility of the water-insoluble component in 100 g of water at 25° C. is, for example, less than 10 g, preferably less than 5 g, more preferably less than 3 g, and even more preferably less than 1 g.

The coating layer may be a layer containing at least one water-insoluble component selected from water-insoluble organic compounds and water-insoluble inorganic compounds.

Examples of water-insoluble organic compounds include acid-modified polymers containing substituted or unsubstituted alkene as structural units, and polymers containing substituted or unsubstituted alkene as structural units and polymers containing alkylene oxide as structural units. Mixed compositions include polyurethanes, polyesters, polyamides, polystyrenes, polycarbonates, polyacrylates, and polyacetals.

Among these, acid-modified polymers containing substituted or unsubstituted alkenes as structural units, and mixed compositions of polymers containing substituted or unsubstituted alkenes as structural units and polymers containing alkylene oxides as structural units Preferably, it contains at least one selected from the group consisting of an acid-modified copolymer containing unsubstituted alkene as a structural unit, and a copolymer containing unsubstituted alkene as a structural unit and a polymer containing alkylene oxide as a structural unit. It is more preferable to contain at least one selected from the group consisting of a mixed composition of

The acid-modified copolymer containing unsubstituted alkenes as structural units may be acid-modified copolymers containing only two or more unsubstituted alkenes as structural units, and one or more unsubstituted alkenes and Acid-modified copolymers containing monomer components other than unsubstituted alkenes as structural units may also be used. Preferred are acid-modified copolymers containing only two or more unsubstituted alkenes as structural units, more preferably acid-modified copolymers containing only two unsubstituted alkenes as structural units. Unsubstituted alkenes used in such copolymers include, for example, ethylene, propylene, and butenes, preferably ethylene and propylene are used.

In addition, the acid modification of the copolymer may be realized with at least one acid anhydride selected from the group consisting of maleic anhydride, succinic anhydride, and phthalic anhydride, preferably maleic anhydride and/or It is realized by succinic anhydride, more preferably by maleic anhydride.

In summary, the acid-modified copolymer containing an unsubstituted alkene as a structural unit is preferably an acid-modified ethylene/propylene copolymer, and is a maleic anhydride-modified ethylene/propylene copolymer. is more preferable.

The copolymer containing unsubstituted alkenes contained in the mixed composition as structural units may be a copolymer containing only two or more unsubstituted alkenes as structural units, and may be a copolymer containing only one or two or more unsubstituted alkenes and unsubstituted It may be a copolymer containing monomer components other than alkenes as structural units. Preferably, it is a copolymer containing one type of unsubstituted alkene and a monomer component other than the unsubstituted alkene as structural units.

Examples of unsubstituted alkenes used in the copolymer include ethylene, propylene, and butene, preferably ethylene and/or propylene, more preferably ethylene. As a monomer component other than the unsubstituted alkene used in the copolymer, a water-soluble ethylenically unsaturated monomer is preferably used. As the water-soluble ethylenically unsaturated monomer, the compounds listed above can be used, but (meth)acrylic acid and/or salts thereof are preferably used.

Summarizing these, the copolymer containing alkene as a structural unit is preferably a copolymer containing ethylene and a water-soluble ethylenically unsaturated monomer as a structural unit, and ethylene and (meth) acrylic acid and / or a salt thereof as a structural unit. is more preferred, a copolymer containing ethylene and an acrylate as structural units is more preferred, and a copolymer containing ethylene and sodium acrylate as structural units (ethylene/sodium acrylate copolymer) is particularly preferred.

The polymer containing the alkylene oxide contained in the mixed composition as a structural unit may be a polyalkylene oxide (homopolymer) containing only one alkylene oxide as a structural unit, or two or more alkylene oxides as structural units. It may be a polyalkylene oxide (copolymer) containing one or more alkylene oxides and may be a copolymer containing monomer components other than alkylene oxide as structural units, but preferably only one type of alkylene oxide is used as a constituent unit.

Alkylene oxide includes, for example, ethylene oxide or propylene oxide, preferably ethylene oxide.

In summary, the polymer containing alkylene oxide as a structural unit is selected from the group consisting of a homopolymer (polyethylene glycol) containing ethylene oxide as a structural unit and an ethylene-propylene copolymer containing ethylene oxide and propylene oxide as structural units. At least one is preferable, and polyethylene glycol is more preferable.

Examples of water-insoluble inorganic compounds include light anhydrous silicic acid, calcium silicate, silicon dioxide (silica), talc, silicon oxide, and synthetic hydrotalcite. These inorganic compounds may be used individually by 1 type, and may be used in combination of multiple types. Preferably, at least one of silicon dioxide and talc is used, and silicon dioxide is more preferably used because it can exhibit relatively high water permeability when the coating layer is formed. Silicon dioxide may be hydrophilic or hydrophobic. Silicon dioxide is preferably hydrophobic because it facilitates adjustment of the water absorption rate of the water-absorbent resin particles and the 5-minute value of the no-pressure DW within an appropriate range.

When forming a coating layer on the crosslinked polymer particles, the crosslinked polymer particles and a coating material may be mixed to form a coating layer on at least part of the surface of the crosslinked polymer particles. The coating material is, for example, a component capable of forming the coating layer described above or a material forming the component. For example, when the coating layer contains polyurethane, the coating material may contain polyurethane itself, or may contain polyol and polyisocyanate, which are the forming materials of the polyurethane.

The method of forming the coating layer is not particularly limited. For example, after dispersing the crosslinked polymer particles, a coating material can be brought into contact with the dispersed crosslinked polymer particles to form a coating layer. Specifically, when the coating material is dissolved in the dispersion medium in which the polymer particles are dispersed, the crosslinked polymer particles and the coating material are added to the dispersion medium to form a coating layer on the surface of the crosslinked polymer particles. good too. Further, when a polyol and a polyisocyanate are used as the coating material, an aqueous solution of the polyol is mixed with the dispersion liquid of the crosslinked polymer particles so that the crosslinked polymer particles and the polyol are brought into contact with each other, and then the liquid containing the polyisocyanate is applied. Upon mixing, the polyol and polyisocyanate may be polymerized to form a coating layer containing polyurethane on the surface of the crosslinked polymer particles.

The dispersion medium may contain a hydrocarbon solvent. Examples of hydrocarbon solvents include chain aliphatic hydrocarbons such as n-hexane, n-heptane, 2-methylhexane, 3-methylhexane, 2,3-dimethylpentane, 3-ethylpentane and n-octane. alicyclic hydrocarbons such as cyclohexane, methylcyclohexane, cyclopentane, methylcyclopentane, trans-1,2-dimethylcyclopentane, cis-1,3-dimethylcyclopentane, trans-1,3-dimethylcyclopentane; Aromatic hydrocarbons such as benzene, toluene and xylene can be mentioned.

When a solid inorganic compound is used as the coating material, a coating layer can be formed by pressing the coating material onto the surface of the crosslinked polymer particles using a particle compounding device. Specifically, a predetermined amount of crosslinked polymer particles and a solid inorganic compound are charged into a particle compounding device. After that, the crosslinked polymer particles and the inorganic compound are subjected to stress (compressive stress and shear stress) by rotation of the stirring blades provided in the device, and the stress causes the inorganic compound to be pressure-bonded to the surface of the crosslinked polymer particles for coating. A resin particle is produced.

[Water absorbent resin particles b]
The 5-minute value of the non-pressurized DW of the water absorbent resin particles b is more than 10 ml/g. The 5-minute value of the non-pressurized DW of the water absorbent resin particles b is 11 ml/g or more, 13 ml/g or more, 15 ml/g or more, 20 ml/g or more, 25 ml/g or more, 30 ml/g or more, 35 ml/g or more. , 40 ml/g or more, 45 ml/g or more, 50 ml/g or more, or 55 ml/g or more. The 5-minute value of the non-pressurized DW of the water absorbent resin particles b is 70 ml/g or less, 65 ml/g or less, 60 ml/g or less, 55 ml/g or less, 50 ml/g or less, 45 ml/g or less, 40 ml/g or less. , 35 ml/g or less, 30 ml/g or less, or 25 ml/g or less. The 5-minute value of the non-pressurized DW of the water absorbent resin particles b may be more than 10 ml/g and 70 ml/g or less, or 15 ml/g or more and 60 ml/g or less.

The physiological saline water retention capacity of the water-absorbent resin particles b is 16 g/g or more, 20 g/g or more, 25 g/g or more, 30 g/g or more, from the viewpoint of making it easier to achieve both prevention of liquid leakage and excellent regurgitation amount. may be 32 g/g or greater, 34 g/g or greater, 36 g/g or greater, or 38 g/g or greater; 55 g/g or less; 53 g/g or less; 51 g/g or less; It may be 45 g/g or less, 43 g/g or less, 41 g/g or less, or 39 g/g or less. The water-absorbent resin particles b may have a physiological saline water retention capacity of 16 to 55 g/g, 25 to 51 g/g, or 32 to 47 g/g.

The water absorption speed (water absorption speed according to the Vortex method) of the water-absorbing resin particles b is 2 seconds or more, 5 seconds or more, 10 seconds or more, 15 seconds or more, 20 seconds or more, 25 seconds or more, 30 seconds or more, 32 seconds or more, 35 seconds or more. Seconds or more, or 38 seconds or more, and may be 55 seconds or less, 50 seconds or less, 45 seconds or less, 43 seconds or less, 40 seconds or less, or 38 seconds or less. When the water absorption speed of the water absorbent resin particles b is 55 seconds or less, leakage in the longitudinal direction of the absorbent body can be more easily prevented, which is preferable. The water absorption speed of the water absorbent resin particles b may be 2 to 55 seconds, 5 to 50 seconds, or 10 to 45 seconds.

The water absorption under load of the water absorbent resin particles b may be, for example, 16 ml/g or more, 18 ml/g or more, 20 ml/g or more, 22 ml/g or more, or 24 ml/g or more, and may be 30 ml/g or less, 28 ml. /g or less, 26 ml/g or less, or 24 ml/g or less. The water absorption under load of the water absorbent resin particles b may be 16 to 30 ml/g, or 18 to 28 ml/g.

The water absorbent resin particles b may contain, for example, crosslinked polymer particles formed by polymerization of monomers containing ethylenically unsaturated monomers. The crosslinked polymer particles can have monomer units derived from ethylenically unsaturated monomers. The water absorbent resin particles can be produced, for example, by a method including a step of polymerizing a monomer containing an ethylenically unsaturated monomer. Examples of the polymerization method include a reverse phase suspension polymerization method, an aqueous solution polymerization method, a bulk polymerization method, a precipitation polymerization method, and the like.

For the crosslinked polymer particles constituting the water absorbent resin particles b, for example, the same aspect as the crosslinked polymer particles constituting the above-described coated resin particles can be applied. The water absorbent resin particles b may not be coated with a resin.

The water-absorbent resin particles b may be crosslinked near the surface (surface crosslinked). The water-absorbent resin particles b may be composed only of polymer particles (crosslinked polymer). may further comprise additional components of The additional component can be located inside the polymer particles, on the surface of the polymer particles, or both. An additional ingredient may be a flow improver (lubricant). The fluidity improver may contain inorganic particles. Examples of inorganic particles include silica particles such as amorphous silica.

The shape of the water-absorbing resin particles b is not particularly limited.

The median particle size of the water-absorbing resin particles b may be 100-800 μm, 150-700 μm, 200-600 μm, or 250-500 μm.

[Absorber]
In the absorbent body, the regions A and B may each contain a fibrous material in addition to the water absorbent resin particles. Region A and region B may be a mixture containing water absorbent resin particles and fibrous materials. The structure of the absorbent body may be, for example, a structure in which water-absorbing resin particles and fibrous substances are uniformly mixed.

The total content of the water-absorbing resin particles in the entire absorbent body is 10% by mass or more, 20% by mass or more, 30% by mass or more, 40% by mass or more, or 50% by mass with respect to the total of the water-absorbing resin particles and fibrous materials. % or more, 60% by mass or more, 80% by mass or more, 90% by mass or more, 95% by mass or more, or 100% by mass, 100% by mass or less, 98% by mass or less, 96% by mass or less, 95% by mass or less , 90% by mass or less, 85% by mass or less, 80% by mass or less, 75% by mass or less, 70% by mass or less, or 65% by mass or less. The total content of the water absorbent resin particles in the entire absorbent body is 10 to 100% by mass, 30 to 100% by mass, or 50 to 100% by mass with respect to the total of the water absorbent resin particles and the fibrous material. good.

The total content of the water-absorbent resin particles in region A is 10% by mass or more, 20% by mass or more, 30% by mass or more, 40% by mass or more, based on the total content of the water-absorbent resin particles and fibrous materials in region A. 50% by mass or more, 60% by mass or more, 80% by mass or more, 90% by mass or more, or 95% by mass or more, 100% by mass, 100% by mass or less, 98% by mass or less, 96% by mass or less, 95 % by mass or less, 90% by mass or less, 85% by mass or less, 80% by mass or less, 75% by mass or less, 70% by mass or less, or 65% by mass or less. The total content of water absorbent resin particles in region A is 10 to 100% by mass, 30 to 100% by mass, or 50 to 100% by mass with respect to the total content of water absorbent resin particles and fibrous materials in region A. may

The total content of the water-absorbent resin particles in region B is 10% by mass or more, 20% by mass or more, 30% by mass or more, 40% by mass or more with respect to the total of the water-absorbent resin particles and fibrous materials in region B, 50% by mass or more, 60% by mass or more, 80% by mass or more, 90% by mass or more, or 95% by mass or more, 100% by mass, 100% by mass or less, 98% by mass or less, 96% by mass or less, 95 % by mass or less, 90% by mass or less, 85% by mass or less, 80% by mass or less, 75% by mass or less, 70% by mass or less, or 65% by mass or less. The total content of water absorbent resin particles in region B is 10 to 100% by mass, 30 to 100% by mass, or 50 to 100% by mass with respect to the total content of water absorbent resin particles and fibrous materials in region B. may

The total content of the water-absorbent resin particles a in the entire absorber is 3% by mass or more, 5% by mass or more, 10% by mass or more, 12% by mass or more with respect to the total content of the water-absorbent resin particles in the entire absorber. , 15% by mass or more, 18% by mass or more, 20% by mass or more, 22% by mass or more, 25% by mass or more, 30% by mass or more, 35% by mass or more, or 40% by mass or more, and 50% by mass or less , 45% by mass or less, 40% by mass or less, 35% by mass or less, 30% by mass or less, or 25% by mass or less. The total content of the water absorbent resin particles a in the entire absorbent body is 3 to 50% by mass, 5 to 40% by mass, or 10 to 25% by mass with respect to the total content of the water absorbent resin particles in the entire absorbent body. There may be.

The total content of the water absorbent resin particles b in the entire absorbent body is 50% by mass or more, 55% by mass or more, 60% by mass or more, 65% by mass or more with respect to the total content of the water absorbent resin particles in the entire absorbent body. , 70% by mass or more, 75% by mass or more, 80% by mass or more, 85% by mass or more, 90% by mass or more, or 95% by mass or more, and 97% by mass or less, 95% by mass or less, 90% by mass or less , 85% by mass or less, 80% by mass or less, 75% by mass or less, 70% by mass or less, 65% by mass or less, 60% by mass or less, or 55% by mass or less. The total content of the water absorbent resin particles b in the entire absorbent body is 50 to 97% by mass, 60 to 95% by mass, or 75 to 90% by mass with respect to the total content of the water absorbent resin particles in the entire absorbent body. There may be.

The total content of water-absorbing resin particles in the entire absorbent body is 100 g or more, 200 g or more, 300 g or more, 400 g or more, 500 g or more, 600 g or more, 700 g or more, 800 g or more, or 900 g or more per 1 m ² of the absorbent body. Well, it may be 1000g or less, 900g or less, 800g or less, 700g or less, 600g or less, 500g or less, 400g or less, or 300g or less. The total content of water absorbent resin particles in the entire absorbent body may be 100 to 1000 g per 1 m ² of the absorbent body.

The total content of the water-absorbing resin particles in region A may be 100 g or more, 200 g or more, 300 g or more, 400 g or more, 500 g or more, 600 g or more, 700 g or more, 800 g or more, or 900 g or ^more per square meter of region A. , 1000 g or less, 900 g or less, 800 g or less, 700 g or less, 600 g or less, 500 g or less, 400 g or less, or 300 g or less. The total content of water absorbent resin particles in the region A may be 100 to 1000 g per 1 m ² of the region A.

The total content of the water-absorbing resin particles in region B is 100 g or more, 200 g or more, 300 g or more, 400 g or more, 500 g or more, 600 g or more, 700 g or more, 800 g or more, or 900 g or more per 1 m ² of region B. Well, it may be 1000g or less, 900g or less, 800g or less, 700g or less, 600g or less, 500g or less, 400g or less, or 300g or less. The total content of water-absorbing resin particles in region B may be 100 to 1000 g per 1 m ² of region B.

The content of the fibrous material in the absorbent body may be 10 g or more, 50 g or more, or 100 g or more, and may be 800 g or less, 600 g or less, 500 g or less, 300 g or less, or 200 g or less per 1 m ² of the absorbent body. . The content of fibrous material in the absorbent may be 10-800 g, 10-500 g, or 10-300 g per ^square meter of absorbent.

The content of the fibrous material in region A may be 10 g or more, 50 g or more, or 100 g or more, and 800 g or less, 600 g or less, 500 g or less, 300 g or less, or 200 g or less per 1 m ² of region A. good. The fibrous content in region A may be from 10 to 800 g, from 10 to 500 g, or from 10 to 300 g per ^square meter of region A.

The content of the fibrous material in region B may be 10 g or more, 50 g or more, or 100 g or more, and 800 g or less, 600 g or less, 500 g or less, 300 g or less, or 200 g or less per 1 m ² of region B. good. The fibrous content in region B may be from 10 to 800 g, from 10 to 500 g, or from 10 to 300 g per ^square meter of region B.

Examples of fibrous materials include pulverized wood pulp; cotton; cotton linter; rayon; cellulosic fibers such as cellulose acetate; synthetic fibers such as polyamide, polyester and polyolefin; The fibrous material may be used alone or in combination of two or more. Hydrophilic fibers can be used as fibrous materials. As hydrophilic fibers, cellulosic fibers such as wood pulp, cotton, cotton linter, rayon, and cellulose acetate are preferred.

In order to enhance the shape retention of the absorbent material before and during use, the fibers may be adhered to each other by adding an adhesive binder to the fibrous material. Examples of adhesive binders include heat-fusible synthetic fibers, hot-melt adhesives, adhesive emulsions, and the like. An adhesive binder may be used independently and may be used in combination of 2 or more type.

Heat-fusible synthetic fibers include, for example, all-melting binders such as polyethylene, polypropylene and ethylene-propylene copolymer; Only the polyethylene portion can be heat-sealed in the above-mentioned non-total melting type binder.

Hot melt adhesives include, for example, ethylene-vinyl acetate copolymer, styrene-isoprene-styrene block copolymer, styrene-butadiene-styrene block copolymer, styrene-ethylene-butylene-styrene block copolymer, styrene-ethylene-propylene-styrene block copolymer. , amorphous polypropylene, and other base polymers with tackifiers, plasticizers, antioxidants, and the like.

Examples of adhesive emulsions include polymers of at least one monomer selected from the group consisting of methyl methacrylate, styrene, acrylonitrile, 2-ethylhexyl acrylate, butyl acrylate, butadiene, ethylene, and vinyl acetate.

The absorber according to this embodiment may contain inorganic powder (for example, amorphous silica), deodorant, antibacterial agent, pigment, dye, fragrance, adhesive, and the like. These additives can impart various functions to the absorbent. When the water absorbent resin particles contain inorganic particles, the absorber may contain inorganic powder separately from the inorganic particles in the water absorbent resin particles. Examples of inorganic powders include silicon dioxide, zeolite, kaolin, and clay-based powders.

The shape of the absorber according to this embodiment may be, for example, a sheet shape. The thickness of the absorber (for example, the thickness of a sheet-like absorber) may be 0.1-20 mm or 0.3-15 mm.

A liquid flow path may be provided in the absorber. The liquid channels may be provided, for example, by embossing the absorbent body.

In the absorbent body having the regions A and B, for example, the absorbent body forming the region A and the absorbent body forming the region B are manufactured in a sheet form, respectively, and then cut into a predetermined shape to form the region A and the region B. can be manufactured by joining the Further, for the absorbent body having the regions A and B, after manufacturing the region containing only the water-absorbing resin particles a in the entire absorber, the region containing only the water-absorbing resin particles b is manufactured, and two layers are laminated. It may be manufactured by combining. Also, the absorbent body having the regions A and B may be manufactured by using a duct for rapidly switching the type of absorbent resin particles to be dispersed when manufacturing one sheet-like absorbent body.

[Absorbent article]
The absorber according to this embodiment is suitable as a structure of an absorbent article. That is, the absorbent article may include the absorbent body according to this embodiment. Other constituent members of the absorbent article include a core wrap that retains the shape of the absorbent body and prevents the constituent members of the absorbent body from falling off and flowing; liquid-impermeable sheet; a liquid-impermeable sheet disposed on the outermost side opposite to the side into which the liquid to be absorbed is permeated. Absorbent articles include diapers (e.g., paper diapers), toilet training pants, incontinence pads, sanitary materials (sanitary napkins, tampons, etc.), perspiration pads, pet sheets, simple toilet members, animal excrement disposal materials, and the like. . The absorbent article may be disposable.

FIG. 4 is a cross-sectional view showing an example of an absorbent article. The absorbent article 100 shown in FIG. 4 includes an absorbent body 10,

core wrap sheets

20a and 20b, a liquid permeable sheet 30, and a liquid impermeable sheet 40. As shown in FIG. In the absorbent article 100, the liquid impermeable sheet 40, the core wrap sheet 20b, the absorbent body 10, the core wrap sheet 20a, and the liquid permeable sheet 30 are laminated in this order. In FIG. 4, there is a part where there is a gap between the members, but the members may be in close contact with each other without the gap.

The absorbent body 10 has water absorbent resin particles 10a and a fiber layer 10b containing fibrous materials. The water absorbent resin particles 10a are dispersed in the fiber layer 10b. The water absorbent resin particles 10a are water absorbent resin particles a, water absorbent resin particles b, or a mixture thereof.

The core wrap sheet 20a is arranged on one side of the absorbent body 10 (upper side of the absorbent body 10 in FIG. 4) while being in contact with the absorbent body 10. As shown in FIG. The core wrap sheet 20b is arranged on the other side of the absorbent body 10 (lower side of the absorbent body 10 in FIG. 4) while being in contact with the absorbent body 10. As shown in FIG. The absorbent body 10 is arranged between the core wrap sheet 20a and the core wrap sheet 20b. Examples of the

core wrap sheets

20a and 20b include tissues, nonwoven fabrics, woven fabrics, synthetic resin films having liquid permeable holes, net-like sheets having meshes, and the like. The core wrap sheet 20a and the core wrap sheet 20b have, for example, main surfaces of the same size as the absorber 10. As shown in FIG.

The liquid-permeable sheet 30 is arranged on the outermost side on the side into which the liquid to be absorbed enters. The liquid-permeable sheet 30 is arranged on the core wrap sheet 20a while being in contact with the core wrap sheet 20a. The liquid-permeable sheet 30 may be a sheet made of resin or fiber commonly used in the technical field. The liquid-permeable sheet 30 is made of, for example, polyolefins such as polyethylene (PE) and polypropylene (PP), polyethylene terephthalate (PET), and polytrimethylene from the viewpoint of liquid permeability, flexibility, and strength when used in absorbent articles. Polyester such as terephthalate (PTT) and polyethylene naphthalate (PEN), polyamide such as nylon, synthetic resin such as rayon, or synthetic fibers containing these synthetic resins, cotton, silk, hemp, or pulp It may be a natural fiber containing (cellulose). From the viewpoint of increasing the strength of the liquid permeable sheet 30, the liquid permeable sheet 30 may contain synthetic fibers. Synthetic fibers may in particular be polyolefin fibers, polyester fibers or combinations thereof. These materials may be used alone, or two or more materials may be used in combination.

The liquid-permeable sheet 30 may be a nonwoven fabric, a porous sheet, or a combination thereof. A nonwoven is a sheet in which fibers are intertwined without being woven. The nonwoven fabric may be a nonwoven fabric (short fiber nonwoven fabric) composed of short fibers (ie, staple) or a nonwoven fabric (long fiber nonwoven fabric) composed of long fibers (ie, filaments). The staple may generally have a fiber length of several hundred mm or less, although not limited thereto.

The liquid-permeable sheet 30 is a thermal-bonded nonwoven fabric, an air-through nonwoven fabric, a resin-bonded nonwoven fabric, a spunbonded nonwoven fabric, a melt-blown nonwoven fabric, an air-laid nonwoven fabric, a spunlaced nonwoven fabric, a point-bonded nonwoven fabric, or a laminate of two or more types of nonwoven fabrics selected from these. It's okay. These non-woven fabrics may be formed, for example, from the synthetic or natural fibers mentioned above. The laminate of two or more types of nonwoven fabrics may be, for example, a spunbond/meltblown/spunbond nonwoven fabric, which is a composite nonwoven fabric in which a spunbond nonwoven fabric, a meltblown nonwoven fabric, and a spunbond nonwoven fabric are laminated in this order. The liquid-permeable sheet 30 may be a thermal-bond nonwoven fabric, an air-through nonwoven fabric, a spunbond nonwoven fabric, or a spunbond/meltblown/spunbond nonwoven fabric from the viewpoint of liquid leakage suppression.

The nonwoven fabric used as the liquid permeable sheet 30 preferably has moderate hydrophilicity in order to improve the liquid absorption performance of the absorbent article. From the viewpoint of having moderate hydrophilicity, the liquid-permeable sheet 30 is tested according to Paper Pulp Test Method No. 2 by the Japan Pulp and Paper Technical Association. 68 (2000), a hydrophilicity of 5 to 200. The hydrophilicity of the nonwoven fabric may be 10-150. Paper pulp test method no. 68 can be referred to, for example, WO2011/086843.

The non-woven fabric having hydrophilicity as described above may be formed of fibers showing moderate hydrophilicity such as rayon fibers, for example, and hydrophobic chemical fibers such as polyolefin fibers and polyester fibers are hydrophilized. It may be formed from fibers obtained by Methods for obtaining a nonwoven fabric containing hydrophobic chemical fibers that have been hydrophilized include, for example, a method of obtaining a nonwoven fabric by a spunbond method using a mixture of hydrophobic chemical fibers and a hydrophilizing agent; Examples include a method of entraining a hydrophilizing agent when producing a spunbond nonwoven fabric from fibers, and a method of impregnating a spunbond nonwoven fabric obtained using hydrophobic chemical fibers with a hydrophilizing agent. Examples of hydrophilizing agents include anionic surfactants such as aliphatic sulfonates and higher alcohol sulfates, cationic surfactants such as quaternary ammonium salts, polyethylene glycol fatty acid esters, polyglycerin fatty acid esters, and sorbitan fatty acids. Nonionic surfactants such as esters, silicone surfactants such as polyoxyalkylene-modified silicones, and stain release agents made of polyester, polyamide, acrylic or urethane resins are used.

The liquid-permeable sheet 30 is moderately bulky from the viewpoint of imparting good liquid permeability, flexibility, strength and cushioning properties to the absorbent article, and from the viewpoint of increasing the liquid permeation speed of the absorbent article. It may be a nonwoven fabric with a large The nonwoven fabric used for the liquid-permeable sheet 30 may have a basis weight of 5 to 200 g/m ² , 8 to 150 g/m ² , or 10 to 100 g/m ² . The thickness of the nonwoven fabric used for the liquid-permeable sheet 30 may be 20-1400 μm, 50-1200 μm, or 80-1000 μm.

In addition, the surface of the liquid permeable sheet 30 may be embossed or perforated in order to improve the diffusibility of the liquid. Embossing or perforating can be carried out by a known method. In order to reduce irritation to the skin, the liquid-permeable sheet 30 may contain a skin lotion, a moisturizing agent, an antioxidant, an anti-inflammatory agent, a pH adjuster, and the like. The shape of the liquid-permeable sheet 30 depends on the shapes of the absorbent body and absorbent article, but may be a shape that covers the absorbent body 10 so as to prevent liquid leakage.

The size relationship of the absorbent body 10, the

core wrap sheets

20a and 20b, the liquid permeable sheet 30, and the liquid impermeable sheet 40 is not particularly limited, and is appropriately adjusted according to the use of the absorbent article. In addition, the method for retaining the shape of the absorbent body 10 using the

core wrap sheets

20a and 20b is not particularly limited, and as shown in FIG. You may wrap an absorber with a sheet.

The absorbent article 100 is manufactured, for example, by a method including placing the absorbent body 10 in the

core wrap sheets

20a and 20b and placing them between the liquid permeable sheet 30 and the liquid impermeable sheet 40. can do. A laminate in which the liquid impermeable sheet 40, the core wrap sheet 20b, the absorber 10, the core wrap sheet 20a, and the liquid permeable sheet 30 are laminated in this order is pressurized as necessary.

The shape of the absorbent article 100 is appropriately determined according to its use. For example, when the absorbent article is a urine pad or a sanitary napkin, it may be approximately rectangular, oval, hourglass, battledore, or the like.

In addition to the liquid-permeable sheet, absorber, liquid-impermeable sheet, and core wrap described above, the absorbent article may also include members as appropriate according to the application and function. Examples thereof include a liquid acquisition diffusion sheet, which will be described later.

(liquid acquisition diffusion sheet)
Although not shown in FIG. 1, the absorbent article may include a liquid acquisition diffusion sheet. A liquid acquisition and diffusion sheet may be placed, for example, on the bottom surface of the liquid permeable sheet 30 . As a result, the liquid that has permeated the liquid permeable sheet 30 can be quickly moved to the absorbent body 10 side, or the backflow can be further reduced. Adhesion between the liquid acquisition diffusion sheet and the liquid permeable sheet 30 may use a hot melt adhesive, heat embossing, or ultrasonic welding. As the liquid acquisition/diffusion sheet, a non-woven fabric or a resin film having a large number of through-holes can be used. As the nonwoven fabric, materials similar to those described in the section of the liquid permeable sheet 30 can be used. It is preferable because it has excellent liquid transfer characteristics.

The liquid acquisition and diffusion sheet is normally arranged in the central portion with a width shorter than that of the absorbent body 10, but may be arranged over the entire width. The length of the liquid acquisition and diffusion sheet in the front-rear direction may be substantially the same as the total length of the absorbent article, may be substantially the same as the total length of the absorbent body 10, or may be within a range of lengths assuming the portion into which the liquid is introduced. good.

(Outer cover non-woven fabric)
Also, the outer cover nonwoven fabric may be arranged outside the liquid impermeable sheet 40 . The outer cover nonwoven fabric can be adhered to the liquid impermeable sheet 40 using an adhesive, for example. The outer cover nonwoven fabric may be formed of one or more layers and may be a soft material. The outer cover non-woven fabric may be given a soft touch, may have a pattern printed on it, may have a plurality of joints, embossed parts, etc. so as to appeal to consumers' willingness to purchase or for other reasons. It may be machined or formed into a three-dimensional form.

(leg gather)
The absorbent article according to the present embodiment includes legs having stretchable elastic members arranged outside both widthwise end portions of the absorbent body 10 and substantially parallel to the longitudinal direction of the absorbent body 10. May have gathers. The length of the leg gathers is set to be around the wearer's leg or longer. The elongation rate of the leg gathers is appropriately set from the viewpoint of preventing the leakage of discharged liquid and reducing the feeling of oppression when worn for a long time.

(front/back gather)
The absorbent article according to the present embodiment may have front/back gathers that are arranged in the vicinity of both ends in the longitudinal direction of the absorbent article and that include elastic members that expand and contract in the width direction.

The absorbent article has front/back gathers that can stand up above the side edges in the width direction of the absorbent body 10 . That is, on both sides of the absorbent article in the longitudinal direction, a front/back gather sheet member having a gather elastic member is arranged to constitute a front/back gather.

The member for the front/back gathers is usually made of a liquid-impermeable or water-repellent material, preferably a moisture-permeable material. Examples thereof include a liquid-impermeable or water-repellent porous sheet, a liquid-impermeable or water-repellent nonwoven fabric, and a laminate of the porous sheet and the nonwoven fabric. Nonwoven fabrics include, for example, thermal bonded nonwoven fabrics, spunbond nonwoven fabrics, meltblown nonwoven fabrics, spunlaced nonwoven fabrics, spunbond/meltblown/spunbond nonwoven fabrics, and the like. The basis weight of the member may be 5 to 100 g/m ² , 8 to 70 g/m ² , or 10 to 40 g/m ² .

Hereinafter, the present disclosure will be described more specifically with examples. However, the present disclosure is not limited to these examples.

<Production of particles>
[Production Example 1]
A round-bottom cylindrical separable flask with an inner diameter of 11 cm and an internal volume of 2 L was prepared, equipped with a reflux condenser, a dropping funnel, a nitrogen gas inlet tube, and a stirrer. As a stirrer, a stirring blade having two stages of four inclined paddle blades with a blade diameter of 5 cm was used. 293 g of n-heptane and 0.736 g of a maleic anhydride-modified ethylene-propylene copolymer (Hi-Wax 1105A, Mitsui Chemicals, Inc.) as a dispersant were added to the flask and mixed. The dispersant was dissolved in n-heptane by raising the temperature to 80° C. while stirring the mixture in the flask at 300 rpm. The formed solution was cooled to 50°C.

In a beaker with an internal volume of 300 mL, 92.0 g (1.03 mol) of an aqueous acrylic acid solution of 80.5% by mass as a water-soluble ethylenically unsaturated monomer is added, and while cooling from the outside, 20.9% by mass of Neutralization of 75 mol % was carried out by dropping 147.7 g of an aqueous sodium hydroxide solution into the beaker. After that, 0.092 g (Sumitomo Seika Co., Ltd., HEC AW-15F) of hydroxyl ethyl cellulose as a thickener, 0.0736 g (0.272 mmol) of potassium persulfate as a radical polymerization initiator, and ethylene glycol diethylene as an internal cross-linking agent. A first stage aqueous solution was prepared by adding and dissolving 0.010 g (0.057 mmol) of glycidyl ether.

The first-stage aqueous solution was added to the n-heptane solution containing the dispersant in the flask, and the formed reaction solution was stirred for 10 minutes. Separately, a surfactant solution was prepared by dissolving 0.736 g of sucrose stearate (Mitsubishi Kagaku Foods Co., Ltd., Ryoto Sugar Ester S-370, HLB: 3) as a surfactant in 6.62 g of n-heptane. prepared. The surfactant solution was added to the flask, and the system was sufficiently purged with nitrogen while stirring the reaction solution with a stirrer at 550 rpm. Thereafter, the flask was immersed in a water bath at 70° C. to raise the temperature of the reaction solution, and the polymerization reaction was allowed to proceed for 60 minutes to obtain a first-stage polymerization slurry.

128.8 g (1.44 mol) of an 80.5% by mass acrylic acid aqueous solution was placed in another beaker having an internal volume of 500 mL, and 159.0 g of a 27% by mass aqueous sodium hydroxide solution was added dropwise while cooling from the outside. to neutralize 75 mole percent of the acrylic acid. 0.103 g (0.381 mmol) of potassium persulfate as a radical polymerization initiator and 0.0116 g (0.067 mmol) of ethylene glycol diglycidyl ether as an internal cross-linking agent were placed in a beaker containing the neutralized acrylic acid aqueous solution. were added and dissolved to prepare a second-stage aqueous solution.

While stirring the stirrer at a rotation speed of 1000 rpm, the first-stage polymerization slurry liquid in the flask was cooled to 25°C, and the whole amount of the second-stage aqueous solution was added thereto. After purging the inside of the flask with nitrogen for 30 minutes, the flask was again immersed in a water bath at 70°C to raise the temperature of the reaction solution, and the second-stage polymerization reaction was performed for 60 minutes to obtain a water-containing gel-like polymer. .

After that, the flask was immersed in an oil bath set at 125°C, and 257.7 g of water was extracted from the system by azeotropic distillation of n-heptane and water. Then, 4.42 g (0.507 mmol) of 2% by mass ethylene glycol diglycidyl ether aqueous solution was added as a surface cross-linking agent to the flask, and the mixture was kept at 83° C. for 2 hours.

Furthermore, polymer particles were obtained by removing n-heptane by drying at 125°C. The polymer particles were passed through a 850 μm JIS standard sieve to obtain 228 g of water absorbent resin particles (1).

[Production Example 2]
As coating materials, ethylene-sodium acrylate copolymer (Sumitomo Seika Co., Ltd., Zaixen N) and polyethylene glycol (Tokyo Chemical Industry Co., Ltd., PEG6000) were prepared. A coating liquid was prepared by mixing 345 g of distilled water, 200 g of a 25% by mass aqueous emulsion of ethylene-sodium acrylate copolymer, and 5 g of polyethylene glycol.

　500 g of water-absorbing resin particles (1) were put into a container of a fluidized bed granulator, and hot air at 50°C was blown from the bottom of the container. 550 g of the coating liquid was sprayed while being dried onto the water absorbent resin particles (1) that were being blown up by air. After the coating liquid was sprayed for about 92 minutes (spray rate 6 g/min), it was dried at 50° C. for 30 minutes to obtain a precursor of coated resin particles.

A Teflon (registered trademark) coating vat with a bottom size of 250 x 185 (mm) was added with 100 g of the precursor of the coated resin particles, covered with aluminum foil and covered with a lid. The aluminum foil was perforated and heated at 80° C. for 1 hour with a hot air dryer (ADVANTEC, FV-320). This precursor was passed through a JIS standard sieve with an opening of 850 μm to obtain 95 g of coated resin particles (1).

[Production Example 3]
A round-bottom cylindrical separable flask with an inner diameter of 11 cm and an internal volume of 2 L was prepared, equipped with a reflux condenser, a dropping funnel, a nitrogen gas inlet tube, and a stirrer. As a stirrer, a stirring blade having two stages of four inclined paddle blades with a blade diameter of 5 cm was used. 250 g of n-heptane, 100 g of the water-absorbent resin particles (1) obtained in Production Example 1, and 20 g of maleic anhydride-modified ethylene/propylene copolymer (Hi-Wax 1105A, Mitsui Chemicals, Inc.) were added to the flask. Then, while stirring at 1000 rpm, the temperature was raised to 85° C. and the mixture was stirred for 10 minutes. As a result, a coating liquid in which the maleic anhydride-modified ethylene/propylene copolymer was dissolved in n-heptane was adhered to the surface of the water absorbent resin particles.

Then, n-heptane was removed by drying in an oil bath at 125°C to obtain a coated resin particle precursor having a coating layer containing a maleic anhydride-modified ethylene/propylene copolymer. This precursor was passed through a JIS standard sieve with an opening of 850 μm to obtain coated resin particles (2).

[Production Example 4]
An absorbent mixture composed of water-absorbing resin particles and pulp was taken out from a child's diaper (Unicharm Co., Ltd., product names: Moonyman, Super Big, Pants Type) commercially available in Japan. Next, the pulp was removed from the absorbent mixture to obtain about 40 g of water-absorbing resin sample (1).

<Particle evaluation>
[Physiological saline water retention]
The measurement was performed in an environment of 25° C. and 50% humidity. 2.00 g of water-absorbent resin particles were dispersed in 500 g of 0.9% physiological saline in a 500 ml beaker, and stirred at 600 rpm for 30 minutes to swell. Pour the swollen gel into a cotton bag (Membrane No. 60, width 100 mm x length 200 mm), tie the top of the cotton bag with a rubber band, and set the centrifugal force to 167 G. 122) for 1 minute. The mass Wa (g) of the cotton bag containing the swollen gel after dehydration was measured. The same operation was performed without adding the water-absorbent resin particles, and the empty weight Wb (g) of the wet cotton bag was measured, and the physiological saline water retention capacity was calculated from the following formula. Table 1 shows the results.
Physiological saline water retention amount (g / g) = [Wa - Wb] / amount of water absorbent resin particles

[Water absorption rate]
50.0 g of 0.9% sodium chloride aqueous solution and a magnetic stirrer bar (8 mmφ×30 mm, without ring) were added to a 100 ml beaker and placed in a constant temperature water bath adjusted to 25°C. Next, 2.00 g of the water-absorbing resin particles were precisely weighed and added into a beaker adjusted to 600 rpm, and at the same time, measurement with a stopwatch was started. After that, when the vortex disappeared and the liquid level became horizontal, the stopwatch was stopped and the water absorption speed was recorded. Table 1 shows the results.

[Measurement of AUL (normal saline water absorption under 4.14 kPa load)]
Physiological saline water absorption under a load of 4.14 kPa (water absorption under load) was measured using a measuring apparatus outlined in FIG. The measuring device comprises a burette part 11 , a clamp 12 , a conduit 13 , a pedestal 14 , a measuring table 15 and a measuring part 16 placed on the measuring table 15 . The burette part 11 includes a burette tube 21 with a scale, a rubber stopper 23 for sealing the upper opening of the burette tube 21, a cock 22 connected to the tip of the lower part of the burette tube 21, and the lower part of the burette tube 21. It has an air introduction pipe 25 and a cock 24 connected to the . The burette part 11 is fixed with a clamp 12 . A flat measuring table 15 has a through-hole 15a with a diameter of 2 mm formed in its central portion, and is supported by a pedestal 14 whose height is variable. Through hole 15 a of measurement table 15 and cock 22 of burette portion 11 are connected by conduit 13 . The inner diameter of conduit 13 is 6 mm.

The measurement unit 16 has a Plexiglas cylinder 31 , a polyamide mesh 32 adhered to one opening of the cylinder 31 , and a weight 33 vertically movable within the cylinder 31 . Cylinder 31 is placed on measuring table 15 via polyamide mesh 32 . The inner diameter of the cylinder 31 is 20 mm. The opening of the polyamide mesh 32 is 75 μm (200 meshes). The weight 33 has a diameter of 19 mm and a mass of 119.6 g, and can apply a load of 4.14 kPa (0.6 psi) to the water absorbent resin particles 10a uniformly arranged on the polyamide mesh 32 as described later. can.

The measurement of the physiological saline water absorption under a load of 4.14 kPa with the measuring device shown in Fig. 5 was performed indoors at 25°C. First, the

cocks

22 and 24 of the burette part 11 were closed, and 0.9% by mass physiological saline adjusted to 25° C. was introduced into the burette tube 21 through the upper opening of the burette tube 21 . Next, after sealing the upper opening of the burette tube 21 with a rubber stopper 23, the

cocks

22 and 24 were opened. The inside of the conduit 13 was filled with 0.9% by mass saline 50 so as not to introduce air bubbles. The height of the measuring table 15 was adjusted so that the height of the water surface of the 0.9 mass % saline solution reaching the inside of the through-hole 15 a was the same as the height of the upper surface of the measuring table 15 . After the adjustment, the height of the water surface of the physiological saline solution 50 in the burette tube 21 was read from the scale of the burette tube 21, and the position was taken as the zero point (read value at 0 seconds).

In the measurement unit 16, 0.10 g of the water-absorbent resin particles 10a are uniformly arranged on the polyamide mesh 32 in the cylinder 31, a weight 33 is arranged on the water-absorbent resin particles 10a, and the cylinder 31 is moved so that the center of the cylinder 31 is It was installed so as to match the conduit opening at the center of the measuring table 15 . Decreased amount of physiological saline in burette tube 21 60 minutes after water-absorbent resin particles 10a began to absorb physiological saline from conduit 13 (that is, the amount of physiological saline absorbed by water-absorbent resin particles 10a) Wc (ml) was read, and the physiological saline water absorption amount of the water absorbent resin particles 10a under a load of 4.14 kPa was calculated according to the following formula. Table 1 shows the results.
Physiological saline water absorption amount (ml/g) under a load of 4.14 kPa = Wc (ml)/mass of water absorbent resin particles (g)

[No pressure DW]
The non-pressurized DW of the water absorbent resin particles was measured using the measuring device shown in FIG. The measuring device has a burette part 11 , a conduit 13 , a measuring table 15 , a nylon mesh sheet 17 , a pedestal 14 and a clamp 12 . The burette part 11 includes a burette tube 21 with a scale, a rubber stopper 23 for sealing the upper opening of the burette tube 21, a cock 22 connected to the tip of the lower part of the burette tube 21, and the lower part of the burette tube 21. It has an air introduction pipe 25 and a cock 24 connected to the . The burette part 11 is fixed with a clamp 12 . A flat measuring table 15 has a through-hole 15a with a diameter of 2 mm formed in its central portion, and is supported by a pedestal 14 whose height is variable. Through hole 15 a of measurement table 15 and cock 22 of burette portion 11 are connected by conduit 13 . The inner diameter of conduit 13 is 6 mm.

The measurement was performed in an environment with a temperature of 25°C and a humidity of 60±10%. First, the

cocks

22 and 24 of the burette part 11 were closed, and a 0.9% by mass saline solution 50 adjusted to 25° C. was introduced into the burette tube 21 through the upper opening of the burette tube 21 . The salt solution concentration of 0.9% by mass is the concentration based on the mass of the salt solution. After sealing the opening of the burette tube 21 with a rubber stopper 23, the

cocks

22 and 24 were opened. The inside of the conduit 13 was filled with 0.9% by mass saline 50 so as not to introduce air bubbles. The height of the measuring table 15 was adjusted so that the height of the water surface of the 0.9 mass % saline solution reaching the inside of the through-hole 15 a was the same as the height of the upper surface of the measuring table 15 . After the adjustment, the height of the water surface of the 0.9% by mass saline solution 50 in the burette tube 21 was read from the scale of the burette tube 21, and the position was taken as the zero point (read value at 0 seconds).

A nylon mesh sheet 17 (100 mm x 100 mm, 250 mesh, thickness of about 50 µm) was laid near the through hole 15a on the measurement table 15, and a cylinder with an inner diameter of 30 mm and a height of 20 mm was placed in the center. 1.00 g of water-absorbent resin particles 10a were evenly dispersed in this cylinder. After that, the cylinder was carefully removed to obtain a sample in which the water-absorbing resin particles 10a were circularly dispersed in the center of the nylon mesh sheet 17 . Next, the nylon mesh sheet 17 on which the water-absorbing resin particles 10a are placed is moved quickly enough to prevent the water-absorbing resin particles 10a from scattering so that the center of the nylon mesh sheet 17 is positioned at the through-hole 15a, and the measurement is started. . The time when air bubbles were first introduced into the burette tube 21 from the air introduction tube 25 was defined as the start of water absorption (0 second).

The amount of decrease in the 0.9% by mass saline solution 50 in the burette tube 21 (that is, the amount of 0.9% by mass saline solution absorbed by the water absorbent resin particles 10a) is sequentially read in units of 0.1 mL, and the water absorbent resin particles Five minutes after the start of water absorption of 10a, the weight loss Wd (g) of the 0.9% by mass saline solution 50 was read. From Wd, the 5-minute value of no-pressure DW was determined by the following formula. The non-pressurized DW is the water absorption amount per 1.00 g of the water absorbent resin particles 10a. Table 1 shows the results.
5-minute value of unpressurized DW (mL/g) = Wd/1.00

<Preparation of absorber>
[Production Example A]
12.0 g of water-absorbing resin particles and 8.0 g of crushed pulp (Rayfloc manufactured by Leonia) were uniformly mixed by air papermaking to prepare an absorbent core with a size of 40 cm×12 cm. Next, the upper and lower sides of the absorbent core were sandwiched between two tissue papers of the same size as the absorbent core and having a basis weight of 16 g/m ² , and a load of 141 kPa was applied to the whole for 30 seconds to absorb water. An absorbent body having a 60% by mass organic resin content was produced.

Furthermore, an air-through type porous liquid-permeable polyethylene sheet having the same size as the absorber and having a basis weight of 22 g/m 2 is placed on the upper surface of the absorber, and an air-through type porous liquid-permeable sheet made of polyethylene having the same size as the absorber and having a basis weight of 22 g/m ² is placed on the lower surface. An absorbent article was obtained by arranging the polyethylene liquid-impermeable sheets No. ² and sandwiching the absorbent body.

[Production Example B]
An absorbent article was produced in the same manner as in Production Example A, except that instead of 12.0 g of the water-absorbing resin particles, a total of 12.0 g of the water-absorbing resin particles and the coated resin particles previously mixed in a predetermined ratio was used. made.

[Production Example C]
A total of 12.0 g of water-absorbent resin particles and coated resin particles pre-mixed at a predetermined ratio and 8.0 g of crushed pulp (Layfloc manufactured by Leonia) are uniformly mixed by air papermaking to obtain a 40 cm An absorbent core with a size of ×12 cm was produced. Separately, using 12.0 g of water-absorbing resin particles and 8.0 g of crushed pulp, an absorbent core was produced in the same manner. Each absorbent core was cut into a target size with a cutter and arranged side by side to prepare an absorbent core with a size of 40 cm x 12 cm. Thereafter, an absorbent article was produced in the same manner as in Production Example A.

[Production Example D]
12.0 g of water-absorbing resin particles and 8.0 g of crushed pulp (Rayfloc manufactured by Leonia) were uniformly mixed by air papermaking to prepare an absorbent core with a size of 40 cm×12 cm. Subsequently, a cutter was used to cut the absorbent core into a size of 30 cm×9 cm.

[Production Example E]
An absorbent article was produced in the same manner as in Production Example D, except that a total of 12.0 g of water absorbent resin particles and coated resin particles previously mixed at a predetermined ratio was used instead of 12.0 g of water absorbent resin particles. did.

[Production Example F]
A total of 12.0 g of water-absorbent resin particles and coated resin particles premixed at a predetermined ratio and 8.0 g of crushed pulp (Layfloc manufactured by Leonia) were uniformly mixed by air papermaking to obtain a 40 cm × An absorbent core with a size of 12 cm was produced. Separately, using 12.0 g of water-absorbing resin particles and 8.0 g of crushed pulp, an absorbent core was produced in the same manner. Each absorbent core was cut into a desired size with a cutter and joined together to produce an absorbent core with a size of 30 cm×9 cm. Thereafter, an absorbent article was produced in the same manner as in Production Example A.

[Comparative Example 1]
Using 12 g of the water absorbent resin particles (1) obtained in Production Example 1, an absorbent article was produced as in Production Example A and evaluated.

[Comparative Example 2]
Using 9.6 g of the water absorbent resin particles (1) obtained in Production Example 1 and 2.4 g of the coated resin particles (1) obtained in Production Example 2, an absorbent article was produced as in Production Example B, made an evaluation.

[Example 1]
An absorbent article was produced as in Production Example C and evaluated. Details are shown below. Using 9.6 g of the water absorbent resin particles (1) obtained in Production Example 1 and 2.4 g of the coated resin particles (1) obtained in Production Example 2, an absorbent core having a size of 40 cm×12 cm was produced. Then, an absorbent core (region A) measuring 30 cm×12 cm was cut out using a cutter.

Using only 12 g of the water absorbent resin particles (1) obtained in Production Example 1, an absorbent core with a size of 40 cm × 12 cm was produced, and then a cutter was used to prepare an absorbent core with a size of 5 cm × 12 cm ( Two pieces of region B) were cut out. The absorbent cores of the region B were connected to both outsides of the region A to prepare an absorbent core having a size of 40 cm×12 cm, and an absorbent article was prepared and evaluated.

[Example 2]
An absorbent article was produced as in Production Example C and evaluated. Details are shown below. Using 9.6 g of the water absorbent resin particles (1) obtained in Production Example 1 and 2.4 g of the coated resin particles (1) obtained in Production Example 2, an absorbent core having a size of 40 cm×12 cm was produced. Then, an absorbent core (region A) measuring 20 cm×12 cm was cut out using a cutter.

Using 10.8 g of the water absorbent resin particles (1) obtained in Production Example 1 and 1.2 g of the coated resin particles (1) obtained in Production Example 2, an absorbent core having a size of 40 cm×12 cm was produced. Then, using a cutter, two absorbent cores (region B) with a size of 10 cm×12 cm were cut out. The absorbent cores of the region B were connected to both outsides of the region A to prepare an absorbent core having a size of 40 cm×12 cm, and an absorbent article was prepared and evaluated.

[Comparative Example 3]
Using 8.4 g of the water absorbent resin particles (1) obtained in Production Example 1 and 3.6 g of the coated resin particles (1) obtained in Production Example 2, an absorbent article was produced as in Production Example B, made an evaluation.

[Example 3]
An absorbent article was produced as in Production Example C and evaluated. Details are shown below. Using 8.4 g of the water absorbent resin particles (1) obtained in Production Example 1 and 3.6 g of the coated resin particles (1) obtained in Production Example 2, an absorbent core having a size of 40 cm×12 cm was produced. Then, a cutter was used to cut out an absorbent core (area A) measuring 24 cm×12 cm.

Using only 12 g of the water-absorbent resin particles (1) obtained in Production Example 1, an absorbent core with a size of 40 cm × 12 cm was produced, and then a cutter was used to prepare an absorbent core with a size of 8 cm × 12 cm ( Two pieces of region B) were cut out. The absorbent cores of the region B were connected to both outsides of the region A to prepare an absorbent core having a size of 40 cm×12 cm, and an absorbent article was prepared and evaluated.

[Comparative Example 4]
Using 7.2 g of the water absorbent resin particles (1) obtained in Production Example 1 and 4.8 g of the coated resin particles (1) obtained in Production Example 2, an absorbent article was produced as in Production Example B, made an evaluation.

[Example 4]
An absorbent article was produced as in Production Example C and evaluated. Details are shown below. Using 7.2 g of the water absorbent resin particles (1) obtained in Production Example 1 and 4.8 g of the coated resin particles (1) obtained in Production Example 2, an absorbent core having a size of 40 cm×12 cm was produced. Then, an absorbent core (region A) measuring 20 cm×12 cm was cut out using a cutter.

Using only 12 g of the water-absorbent resin particles (1) obtained in Production Example 1, an absorbent core with a size of 40 cm × 12 cm was produced, and then a cutter was used to prepare an absorbent core with a size of 10 cm × 12 cm ( Two pieces of region B) were cut out. The absorbent cores of the region B were connected to both outsides of the region A to prepare an absorbent core having a size of 40 cm×12 cm, and an absorbent article was prepared and evaluated.

[Comparative Example 5]
Using 6 g of the water absorbent resin particles (1) obtained in Production Example 1 and 6 g of the coated resin particles (1) obtained in Production Example 2, an absorbent article was produced and evaluated as in Production Example B. .

[Example 5]
An absorbent article was produced as in Production Example C and evaluated. Details are shown below. Using 6 g of the water absorbent resin particles (1) obtained in Production Example 1 and 6 g of the coated resin particles (1) obtained in Production Example 2, an absorbent core having a size of 40 cm × 12 cm was produced, followed by a cutter. was used to cut out an absorbent core (region A) measuring 20 cm x 12 cm.

[Example 6]
An absorbent article was produced as in Production Example C and evaluated. Details are shown below. Using 6 g of the water absorbent resin particles (1) obtained in Production Example 1 and 6 g of the coated resin particles (1) obtained in Production Example 2, an absorbent core having a size of 40 cm × 12 cm was produced, followed by a cutter. was used to cut out an absorbent core (region A) measuring 10 cm×12 cm.

Using only 12 g of the water-absorbing resin particles (1) obtained in Production Example 1, an absorbent core having a size of 40 cm × 12 cm was produced, and then a cutter was used to prepare an absorbent core having a size of 15 cm × 12 cm ( Two pieces of region B) were cut out. The absorbent cores of the region B were connected to both outsides of the region A to prepare an absorbent core having a size of 40 cm×12 cm, and an absorbent article was prepared and evaluated.

[Comparative Example 6]
An absorbent article was produced as in Production Example C and evaluated. Details are shown below. Using 3.6 g of the water absorbent resin particles (1) obtained in Production Example 1 and 8.4 g of the coated resin particles (1) obtained in Production Example 2, an absorbent core having a size of 40 cm×12 cm was produced. Then, a cutter was used to cut out an absorbent core (region A) measuring 10 cm×12 cm.

[Comparative Example 7]
Using 9.6 g of the water absorbent resin particles (1) obtained in Production Example 1 and 2.4 g of the coated resin particles (2) obtained in Production Example 3, an absorbent article was produced as in Production Example B, made an evaluation.

[Example 7]
An absorbent article was produced as in Production Example C and evaluated. Details are shown below. Using 9.6 g of the water absorbent resin particles (1) obtained in Production Example 1 and 2.4 g of the coated resin particles (2) obtained in Production Example 3, an absorbent core having a size of 40 cm×12 cm was produced. Then, an absorbent core (region A) measuring 30 cm×12 cm was cut out using a cutter.

[Comparative Example 8]
Using 12 g of the water absorbent resin sample (1) obtained in Production Example 4, an absorbent article was produced as in Production Example A and evaluated.

[Comparative Example 9]
Using 8.4 g of the collected water-absorbent resin product (1) obtained in Production Example 4 and 3.6 g of the coated resin particles (1) obtained in Production Example 2, an absorbent article was produced as in Production Example B. , made an evaluation.

[Example 8]
An absorbent article was produced as in Production Example C and evaluated. Details are shown below. Using 8.4 g of the collected water-absorbing resin product (1) obtained in Production Example 4 and 3.6 g of the coated resin particles (1) obtained in Production Example 2, an absorbent core having a size of 40 cm x 12 cm was produced. Then, a cutter was used to cut out an absorbent core (area A) measuring 20 cm×12 cm.

[Comparative Example 10]
Using 12 g of the water absorbent resin particles (1) obtained in Production Example 1, an absorbent article was produced as in Production Example D and evaluated.

[Comparative Example 11]
Using 9.6 g of the water absorbent resin particles (1) obtained in Production Example 1 and 2.4 g of the coated resin particles (1) obtained in Production Example 2, an absorbent article was produced as in Production Example E, made an evaluation.

[Example 9]
An absorbent article was produced as in Production Example F and evaluated. Details are shown below. Using 9.6 g of the water absorbent resin particles (1) obtained in Production Example 1 and 2.4 g of the coated resin particles (1) obtained in Production Example 2, an absorbent core having a size of 40 cm×12 cm was produced. Then, a cutter was used to cut out an absorbent core (area A) measuring 22.5 cm×9 cm.

Using only 12 g of the water absorbent resin particles (1) obtained in Production Example 1, an absorbent core with a size of 40 cm × 12 cm was produced, and then an absorbent core with a size of 3.75 cm × 9 cm was produced using a cutter. Two cores (region B) were cut out. The absorbent cores of the region B were connected to both outsides of the region A to prepare an absorbent core having a size of 30 cm×9 cm, and an absorbent article was prepared and evaluated.

<Evaluation of absorber>
[Preparation of test solution]
In a 10 L container, 100.0 g of sodium chloride, 3.0 g of calcium chloride dihydrate, 6.0 g of magnesium chloride hexahydrate, 1% triton (polyoxyethylene [10] octalphenyl ether X-100) .0 g and 99.0 g of distilled water) and 9866.0 g of distilled water were added and dissolved completely. The solution was colored with a small amount of Blue No. 1 to prepare a test solution.

[Performance evaluation of absorber]
(30° leak test)
FIG. 7 is a schematic diagram showing a method for evaluating the leakiness of absorbent articles. A support plate 19 (an acrylic resin plate in this case) having _a length of 45 cm and a thickness of 0.3 cm and having a flat inclined surface S1 was fixed by a mount 41 while being inclined at 30 _± 2° with respect to the horizontal surface S0. . The dropping funnel had a capacity of 300 mL, an inner diameter of about 8 mmφ at the tip, and was equipped with a two-way cock. A balance 43 on which a metal tray 44 is placed is installed at the bottom of the support plate 19, and receives all the test liquid that leaks from the end of the absorbent article and records its mass with an accuracy of 0.1 g. . A leak test using such a device was performed according to the following procedure.

In a room at a temperature of 25±2° C., the test absorbent article 100 was attached onto the inclined surface S ₁ of the fixed support plate 19 with its longitudinal direction along the longitudinal direction of the support plate 19 . The bottom edge of the absorbent article was not stuck on the acrylic plate so as not to artificially stop leakage. Next, the test liquid 50 (artificial urine) adjusted to 25±1° C. was dropped from the dropping funnel 42 arranged vertically above the absorbent article 100 toward the center of the absorbent body in the absorbent article 100 . The distance between the tip of the dropping funnel 42 and the absorbent article was 10±2 mm. 150 mL of the test solution was added at once for evaluation of the absorbent core with a size of 40 cm×12 cm, and 70 mL of the test solution was added at once for evaluation of the absorbent core with a size of 30 cm×9 cm. The surface of the support plate 19 was smooth and no liquid was retained or absorbed by the plate. When the test liquid that was not absorbed by the absorbent article 100 leaked from the lower part of the support plate 19 , the leaked test liquid was collected in the metal tray 44 arranged below the support plate 19 . The weight (g) of the collected test liquid was measured by the balance 43, and the value was recorded as the amount of leakage.

(Absorption speed of absorbent article)
First, an absorbent article was placed on a horizontal table. A liquid charging cylinder having an opening with an inner diameter of 3 cm is placed in the center of the absorbent article, and 150 mL in the evaluation of the absorbent core with a size of 40 cm × 12 cm, and 150 mL in the evaluation of the absorbent core with a size of 30 cm × 9 cm. 70 mL of the test solution was introduced into the cylinder at once. The absorption speed (seconds) was measured as the time from when the test liquid was introduced until the test liquid was completely absorbed by the absorbent article. Table 3 shows the results.

(Absorption rate improvement)
The absorption rate in the absorbent article of the obtained example or comparative example is divided by the absorption rate in the absorbent article in Production Example A or D using only the corresponding water-absorbing resin particles, and the degree of improvement in the absorption rate is calculated. did. Table 3 shows the results. A value of less than 1 indicates an improvement.

(Reverse amount)
The cylinder used for measuring the absorption speed of the absorbent article was removed, and the absorbent article was stored as it was. After 5 minutes from the end of adding the test solution, place a 10 cm square filter paper whose mass (about 75 g) was measured in advance near the position on the absorbent article where the test solution was added, and further place the filter paper on each side with a bottom surface of 10 cm × 10 cm. was loaded with a mass of 5.0 kg (about 0.7 psi). After the load was applied for 5 minutes, the mass of the filter paper was measured, and the increased mass was defined as the amount of reversion (g). Table 3 shows the results.

(Return amount improvement)
The degree of improvement in the amount of backflow is calculated by dividing the amount of backflow in the obtained absorbent articles of Examples or Comparative Examples by the amount of backflow in the corresponding absorbent articles in Production Example A or D using only water-absorbing resin particles. did. A value of less than 1 indicates an improvement. Table 3 shows the results.

It was shown that the absorbent articles obtained in Examples had a reduced amount of leakage in the longitudinal direction and an improved amount of reversion.

REFERENCE SIGNS LIST 1 longitudinal end 3 lateral end 10 absorbent 10a water absorbent resin particles

10b fiber layer

20a, 20b core wrap sheet 30 liquid permeable sheet 40 liquid Impermeable sheet, 50... Test solution, 100... Absorbent article.

Claims

An absorbent body having a longitudinal direction and a width direction orthogonal to the longitudinal direction,
a region A containing water-absorbing resin particles a exhibiting a 5-minute value of no-pressure DW of 10 ml/g or less and water-absorbing resin particles b exhibiting a 5-minute value of no-pressure DW exceeding 10 ml/g;
and a region B containing water-absorbing resin particles b exhibiting a 5-minute value of non-pressurized DW exceeding 10 ml / g,
The amount of the water absorbent resin particles a contained in the region A is 15 to 55% by mass with respect to the total amount of the water absorbent resin particles contained in the region A,
The amount of the water absorbent resin particles a contained in the region B is 0% by mass or more and less than 15% by mass with respect to the total amount of the water absorbent resin particles contained in the region B,
At least part of the region B is an absorbent body located at or near both ends in the longitudinal direction of the absorbent body.
The absorbent body according to claim 1, wherein the regions B are located at both ends of the absorbent body in the longitudinal direction and are formed along the shapes of both ends of the absorbent body.
1 or 2, wherein at least part of said region B is formed at a position where the distance from said longitudinal end of said absorbent is 0 to 40% of said longitudinal length of said absorbent. 2. The absorbent body according to 2.
The absorbent body according to any one of claims 1 to 3, wherein the total area of said region B is 20 to 80% of the entire absorbent body.
The absorber according to any one of claims 1 to 4, wherein the water-absorbent resin particles a have a physiological saline water absorption speed of 60 seconds or more.
The absorbent body according to any one of claims 1 to 5, wherein the water-absorbent resin particles a have a physiological saline water retention capacity of 16 to 55 g/g.
7. The water-absorbent resin particles a are coated resin particles having a crosslinked polymer particle and a water-insoluble coating layer covering at least part of the surface of the crosslinked polymer particle. 10. Absorber according to item.