JP2002045395A - Absorber and absorptive goods using the same, and water absorptive resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an absorber that has enough air permeability even in a humid condition and enough absorption magnification under pressure, absorptive goods the comfortable property of which is further enhanced by using the same absorber, and an absorptive resin which is adequately used for the goods. SOLUTION: The absorber relating to this invention is made up of such absorptive resin in which at least more than two conditions such as air permeability resistance, absorption magnification under non-pressure and/or absorption magnification under pressure, weight average particle diameter and the content of a water soluble component are limited. Its absorption magnification under pressure of 2.0 kPa is more than 24 g/g, and its air permeability under pressure of 4.9 kPa in a humid condition is less that 50 kPa.sec/m. Meanwhile, the absorptive goods relating to this invention is made up by using the above absorber. Therefore, air permeability of the goods is raised when it is attachably used, and since return amount of a water soluble-liquid is small, comfortable feeling when attaching this absorptive goods can further be enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an absorbent body for absorbing body fluids and the like, and absorbent articles such as disposable diapers, incontinence pads and sanitary napkins using the absorbent body.
In addition, the present invention relates to a water-absorbent resin suitably used for these absorbers and absorbent articles.

[0002]

2. Description of the Related Art Conventionally, absorbent articles such as disposable disposable diapers, incontinence pads, sanitary napkins and the like have a basic structure including a top sheet, a back sheet, and an absorber sandwiched between these sheets. . The top sheet is a liquid permeable sheet, which comes into contact with the body side when worn, allows body fluids to permeate and reach the absorber. The back sheet is a liquid-impermeable sheet, which is located outside when attached, to prevent leakage of bodily fluid (aqueous liquid) absorbed by the absorber.

[0003] Here, since the back sheet has liquid impermeability, the gas permeability of the back sheet is very low in most cases. Therefore, the vapor emitted from the body and the vapor obtained by evaporating the absorbed body fluid due to the body temperature are not dissipated, but are accumulated between the absorbent article and the body.
As a result, when the absorbent article is worn, a high humidity environment will be formed at the site where the absorbent article is worn, causing discomfort such as stuffiness and stickiness at the time of wearing, and when worn for a long time, It may also cause rash.

[0004] Therefore, conventionally, it has been attempted to improve the comfort by preventing the occurrence of the above-mentioned discomfort when the absorbent article is worn, and the following three techniques are mainly used as techniques for that purpose. ing.

First, as a first technique, there is an improvement in a back sheet. In this method, by maintaining the liquid impermeability of the back sheet while providing air permeability,
Avoids the formation of high humidity environments.

Specifically, a technique using a liquid-impermeable moisture-proof sheet formed by kneading and stretching a polyolefin, a filler, and the like, forming a film, and further forming fine pores as the above-mentioned back sheet (particularly, Japanese Patent Application Laid-Open No. 58-149303) and a technique using a moisture-permeable film formed by stretching and opening a resin composition containing fine filler particles and blending a cellulosic powder as the back sheet (Japanese Patent Laid-Open No. Hei. JP-A-11-106536), as the back sheet, a resin composition containing fine particles of filler, which is melted at a molding temperature and blended with a non-flowable polyolefin particle, is formed by stretching and pore-forming. A technique using a film (Japanese Patent Application Laid-Open No. 11-106537) is exemplified.

Next, as a second method, there is provided a moisture absorbing material. In this method, the formation of a high-humidity environment is avoided by removing generated steam with a hygroscopic material. Specifically, there is a technique (Japanese Patent Application Laid-Open No. 6-218007) in which an absorbent article is provided with a hygroscopic material such as a water-absorbing resin to suppress vaporization of body fluid.

[0008] A third technique is to improve the structure of the absorbent article itself. In this method, by improving the structure and the like of the absorbent article, the generation of steam is suppressed or the dissipation of steam is promoted to avoid the formation of a high humidity environment. Specifically, a technique is disclosed in which the area of the absorber that comes into contact with the body is made as small as possible, and at the time of wearing, a breathable gap is formed between the body and the body by a covering member that covers the absorber (Japanese Patent Laid-Open No. 11-99165) Gazette).

[0009]

However, any of the above techniques has a problem that the comfort when the absorbent article is worn cannot be sufficiently improved.
That is, in order to increase the comfort at the time of wearing the absorbent article, at least the problem of reducing the return amount of the absorbed bodily fluid by increasing the absorption capacity under pressure (to avoid the feeling of stickiness), and It is necessary to simultaneously achieve the two problems of increasing the air permeability of the absorber itself (avoid stuffiness), but these technologies have not sufficiently achieved these two problems.

[0010] In particular, since the absorbent article absorbs bodily fluids in contact with the body, the area of the absorber is inevitably increased. Therefore, not only the back sheet but also the absorber itself that has absorbed the bodily fluid serves as an airtight partition, which impedes the emission of vapor accumulated between the absorbent article and the body.

For this reason, in the technique which cannot avoid the formation of an airtight partition of the absorber itself that has absorbed body fluids or the like as in the first to third techniques, the above-described problem (avoidance of stuffiness) is sufficiently solved. As a result, comfort at the time of wearing the absorbent article cannot be sufficiently improved.

[0012]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies in view of the above problems, and as a result, have noticed that the absorber becomes an airtight partition when in a wet state absorbing body fluids and the like.
It is possible to further improve the comfort when wearing the absorbent article by ensuring the air permeability of the absorbent in a wet state and also ensuring the state in which the amount of the absorbed body fluid returned is reduced. And completed the present invention.

That is, in order to solve the above-mentioned problems, the absorbent according to the present invention has an absorption capacity under pressure at 2.0 kPa of 24 g / g or more when physiological saline is absorbed, and It is characterized in that the ventilation resistance under a pressure of 4.9 kPa in a wet state is 50 kPa · sec / m or less. The absorber preferably contains a water-absorbing resin so that the ratio becomes 40% by weight or more, and the maximum basis weight is preferably 700 g / m ² or less.

Further, the absorbent article according to the present invention comprises an absorbent layer containing the above-mentioned absorbent, a liquid-permeable sheet,
Ventilation resistance is 1 kPa · sec / m or more and 50 kPa · sec /
m and a liquid-impermeable sheet in the range of m or less, wherein the absorbing layer is disposed between the two sheets.

In conventional absorbers and absorbent articles, no consideration is given to the air permeability of the absorber itself in a wet state. Therefore, in a wet state, usually 100 kP
It exhibited a high airflow resistance of at least a · sec / m, and was in a state of substantially no air permeability. In addition, although there are absorbers that ensure air permeability in a wet state, it cannot be said that the amount of the aqueous liquid held under pressure and the amount of the absorbed aqueous liquid returned are not sufficiently reduced.

On the other hand, according to the present invention, by having the above-described structure, a very high air permeability can be ensured even when the absorbent or the absorbent article is in a wet state, and the amount of the absorbed aqueous liquid returned. Can be avoided. Therefore, it is possible to avoid the formation of an airtight partition wall of the absorber, to prevent a high humidity environment from being formed between the body and the absorber or the absorbent article, and to sufficiently retain the aqueous liquid once absorbed under pressure. can do. As a result, it is possible to simultaneously prevent both stuffiness and stickiness, and it is possible to further improve comfort when the absorbent article is worn.

Further, as an example of the water-absorbing resin suitably used in the absorbent body and the absorbent article according to the present invention, the water-absorbing resin has a gas flow resistance of 250 kPa · sec / at a pressure of 4.9 kPa in a wet state. m or less, the absorption capacity under no pressure when absorbing physiological saline is 32 g /
g or more and when physiological saline is absorbed.
Absorption under pressure at 0 kPa is not less than 32 g / g, and a weight average particle diameter is 430 μm or more.

Further, as an example of the water-absorbing resin suitably used in the absorbent body and the absorbent article according to the present invention, the water-absorbing resin has a gas flow resistance under a pressure of 4.9 kPa in a wet state of 250 kPa · sec /. m or less,
When the physiological saline is absorbed, the absorption capacity under no pressure is 34.
g / g or more and a water-soluble component amount of 18% by weight or less.

Further, as an example of the water-absorbing resin suitably used in the absorbent body and the absorbent article according to the present invention, the water-absorbing resin has a ventilation resistance of 250 kPa · sec / at 4.9 kPa in a wet state under pressure. m, the absorption capacity under pressure at 2.0 kPa when absorbing physiological saline is 34 g / g or more, and the amount of water-soluble component is 1
And 8% by weight or less.

In other words, the water-absorbent resin according to the present invention has a basic condition that the ventilation resistance under a pressure of 4.9 kPa in a wet state is 250 kPa · sec / m or less. The absorption capacity under no pressure when absorbed is 32 g / g or more, and the absorption capacity under pressure at 2.0 kPa when absorbing physiological saline is 32 g.
/ G or more, and the weight-average particle diameter has a particle shape of 430 μm or more, or the absorption capacity under no pressure when absorbing physiological saline is 34 g / g or more, And the second condition group in which the amount of the water-soluble component is 18% by weight or less, or 2.0 when the physiological saline is absorbed.
It is characterized by satisfying any of the third condition group in which the absorption capacity under pressure at kPa is 34 g / g or more and the amount of water-soluble component is 18% by weight or less.

That is, by using a water-absorbing resin that satisfies at least the above parameters, the absorption resistance in a wet state of the absorber is 50 kPa · sec / m or less.
And the absorption capacity of the absorber under pressure at 2.0 kPa is 24 g.
/ G or more. In addition, it has been found that the absorbent article obtained by using the above absorbent body has no stuffiness or stickiness even in a monitor test, and can be a low-humidity state when worn. Therefore, the above-mentioned water-absorbent resin can be suitably used for the absorbent body and the absorbent article according to the present invention.

In particular, as described above, the absorber according to the present invention preferably contains the water-absorbing resin in an amount of 40% by weight or more. As a result, it is possible to reliably prevent the absorbent body from becoming airtight partitions, so that it is possible to simultaneously prevent both stuffiness and stickiness, and to further improve comfort when the absorbent article is mounted. .

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below. Note that the present invention is not limited to this.

The absorbent according to the present invention has at least sufficient air permeability even in a wet state in which an aqueous liquid has been absorbed, and can sufficiently retain the aqueous liquid once absorbed under pressure. I have.

The term "absorber" used in the present embodiment refers to a portion that absorbs water (such as urine absorption or blood absorption) in an absorbent article such as a disposable diaper or a sanitary napkin. The shape is usually a sheet having a thickness of 0.1 mm or more and 30 mm or less, preferably 1 mm or more and 10 mm or less, or a substantially cylindrical shape such as a tampon, but is not particularly limited.

Although the specific structure of the absorber is not particularly limited, it contains a water-absorbent resin as a main component for water absorption, and in addition to the water-absorbent resin, fibers such as hydrophilic fibers More preferably, it contains a material.

Specifically, the structure of the absorber is as follows.
For example, a structure in which a water-absorbent resin and a fiber material are uniformly mixed; a structure in which the water-absorbent resin and the fiber material are uniformly mixed to form a layer, and a layered fiber material is laminated thereon. Structure: a structure in which a water-absorbent resin and a fiber material are uniformly mixed to form a layer, and a water-absorbent resin is sandwiched between the layer and the fiber material formed in a layer; A configuration in which a water-absorbing resin is sandwiched; Above all, a configuration in which a water-absorbing resin and a fiber material are uniformly mixed is preferable because the absorption and air permeability in the present invention can be sufficiently exhibited.

Examples of the above fiber material include natural cellulose fibers such as mechanical pulp, chemical pulp, semi-chemical pulp, and dissolved pulp obtained from wood; artificial cellulose fibers such as rayon and acetate;
Hydrophilic fibers such as are preferably used. Among them, natural cellulose fibers are more preferable. The hydrophilic fibers may include synthetic fibers such as polyamide, polyester, and polyolefin, and may include other materials. Further, the fiber material used for the absorber according to the present invention is not limited to the fibers exemplified above.

The absorber according to the present invention may contain other materials in addition to the water-absorbing resin and the fiber material. For example, when the ratio of the fiber material in the absorber is relatively small, an adhesive binder may be included for bonding the fiber materials to each other. By adhering the fiber materials to each other with this adhesive binder, the strength and shape retention of the absorber before and during use can be increased.

Examples of the adhesive binder include thermally fusible fibers and adhesive emulsions, such as polyolefin fibers such as polyethylene, polypropylene, ethylene-propylene copolymer and 1-butene-ethylene copolymer. . These adhesive binders may be used alone or as a mixture of two or more. The weight ratio of the hydrophilic fiber to the adhesive binder is preferably in the range of 50/50 or more and 99/1 or less, more preferably in the range of 70/30 or more and 95/5 or less, and more preferably 80/20 or more and 95/5 or less. Is more preferable.

In addition, for the above-mentioned absorber and water-absorbent resin, for example, depending on the intended use of the absorber, deodorants, antibacterial agents, fragrances, various inorganic powders, foaming agents, chelating agents, pigments , Dyes, hydrophilic short fibers, fertilizers, oxidizing agents, water, salts and the like. By adding these materials, various functions can be imparted to the absorber and the absorbent article provided with the absorber.

Further, the absorber according to the present invention may have a structure in which the water-absorbent resin is formed into a sheet by mixing a specific amount of water with the water-absorbent resin. Needless to say, this configuration may include other various materials.

The airflow resistance under pressure of 4.9 kPa in the wet state of the absorber according to the present invention is 50 kPa · sec / m or less as described above, and is preferably 4 kPa · sec / m.
0 kPa · sec / m or less, more preferably 30 kPa
・ Second / m or less. Airflow resistance in wet condition is 5
If it exceeds 0 kPa · sec / m, the absorber becomes an airtight partition, and particularly when the absorber is used for an absorbent article such as a disposable diaper, a high-humidity environment is formed between itself and the body to provide comfort when worn. This greatly impairs the performance.

In the present invention, the above-mentioned airflow resistance of the absorber is measured by the method described in the section “Airflow resistance under pressure in a wet state of the absorber” in Examples described later. The range of the airflow resistance is a value measured by this method.

The absorption capacity under pressure of 2.0 kPa of the absorber according to the present invention is 2 when absorbed with physiological saline.
It is at least 4 g / g, preferably at least 26 g / g, more preferably at least 28 g / g. If the absorption capacity under pressure is less than 24 g / g, the absorbed liquid is not sufficiently retained by the absorber and oozes out by pressurization (weighting by weight), so that when used for absorbent articles such as disposable diapers. In this case, the wearer feels stickiness or the like, and causes rash when worn for a long period of time, which greatly impairs the comfort during wearing. The absorption capacity under pressure corresponds to the amount of aqueous liquid retained per gram of the absorbent body when the absorbent body is pressurized under predetermined conditions, and correlates with the result of the monitor test as shown in the examples described later. Was found. The measurement conditions of the absorption capacity under pressure and the composition of artificial urine will be described in detail in Examples described later.

In other words, in the absorber according to the present invention, the amount of liquid once absorbed by the absorber that oozes out again under the pressurized condition, that is, the return amount (wet back) of the absorber is as small as possible. Desirably small. The preferred range of the return amount is not particularly limited, and the preferred range differs depending on the purpose of use of the absorber, that is, the type and shape of the absorbent article.

As described above, the absorber according to the present invention contains a water-absorbing resin as a main component. That is, the ratio (weight ratio) of the water-absorbing resin contained in the absorbent according to the present invention is preferably 40% by weight or more, more preferably 50% by weight or more, still more preferably 60% by weight or more. % By weight or more is particularly preferred. Further, the upper limit of the ratio of the water-absorbing resin contained in the absorber according to the present invention is preferably 100% by weight or less, and 9% by weight or less.
It is more preferably at most 7% by weight, further preferably at most 95% by weight. The ratio of water absorbent resin is 4
When the content is less than 0% by weight, the ratio of the fiber material and the like increases,
In some cases, the absorption capacity under pressure or the like may be reduced, and the comfort at the time of wearing the absorbent article may be reduced.

The maximum basis weight of the absorber (the basis weight of the thickest part in one absorber) is preferably 700 g / m ² or less, more preferably 600 g / m ² or less. More preferably, it is 500 g / m ² or less. The maximum basis weight of the absorber is 700 g / m
^{If it is} larger than ² , the thickness and weight of the absorber may be increased more than necessary, and the comfort at the time of wearing the absorbent article may decrease.

In order to enhance the comfort when the absorbent article is worn, which is the object of the present invention, at least the problem of reducing the amount of return by increasing the absorption capacity under pressure (avoid the feeling of stickiness). It is necessary to simultaneously achieve the two problems of improving the air permeability of the absorber itself (avoiding a feeling of stuffiness).

Here, when the absorbent contains a water-absorbent resin and a fiber material as main components, in order to achieve the object, the ratio of the water-absorbent resin in the absorber is increased. If the ratio of the resin is too large, the air permeability of the absorber decreases. Conversely, in order to achieve the above problem, the ratio of the fiber material in the absorber must be increased. However, if the ratio of the fiber material is too large, the absorption capacity under pressure decreases and the return amount increases.

Therefore, the water-absorbing resin according to the present invention, which is preferably used for the absorbent, has a ventilation resistance under a pressure of 4.9 kPa in a wet state of the water-absorbing resin of 250.
kPa · sec / m or less, preferably 200 kPa · sec
/ M or less, more preferably 150 kPa · sec / m or less, still more preferably 100 kPa · sec / m or less, and particularly preferably 50 kPa · sec / m or less. When physiological saline is absorbed, it is absorbed under no pressure. Magnification and 2.
The absorption capacity under load at 0 kPa is 32 g / g or more, preferably 34 g / g or more, more preferably 36 g / g or more, and the weight average particle diameter is 400 μm or more, preferably 430 μm or more, more preferably 450 μm or more. Having a particle shape of
It is very particularly preferred that the amount of particles smaller than 6 μm is below 5% by weight, preferably below 3% by weight, more preferably below 1%. In addition, the water-soluble component amount of the water-absorbent resin,
It is very particularly preferred that it is no more than 18% by weight, preferably no more than 14% by weight, more preferably no more than 10% by weight.

Further, in the above water-absorbing resin,
The absorption capacity under a high pressure of 9 kPa is preferably 24 g / g or more, more preferably 2 g / g or more with respect to physiological saline.
The value is at least 6 g / g, particularly preferably at least 28 g / g. The absorption capacity under high pressure of 4.9 kPa is preferably 30 g / g or more, more preferably 32 g / g or more, and particularly preferably 34 g, with respect to artificial urine.
/ G or more. The bulk specific gravity and solid content of the water-absorbent resin are in the range of the precursor described below.

When the water-absorbing resin has a high value of airflow resistance in a wet state, when it is used as an absorber, particularly in an absorber having a high ratio of the water-absorbing resin, sufficient air permeability can be obtained during its actual use. And cannot achieve the task. On the other hand, if the absorption capacity under no pressure and the absorption capacity under pressure are low, a sufficient amount of the aqueous liquid cannot be absorbed, and the absorbed liquid is not sufficiently held by the absorber even under pressure, so that the subject cannot be achieved. When the weight average particle diameter of the water-absorbent resin is small and the amount of fine powder of less than 106 μm is large, when the aqueous liquid is absorbed and gelled, there is no gap between the particulate gels and sufficient air permeability is obtained. Can no longer be obtained, and the task of can not be achieved.

As another method for achieving the above object, there is a method of increasing the strength of the gel. However, if the gel strength is increased, the absorption capacity under no pressure usually decreases, which is not preferable. On the other hand, if the absorption capacity under no pressure is too high, the strength of the gel becomes low, and a gap between the gels cannot be secured, and the problem described above cannot be achieved. Furthermore, even when the water-soluble component of the water-absorbent resin is large, when the aqueous liquid is absorbed and gelled, the space between the particulate gels is blocked by the water-soluble component eluted by the gel, resulting in sufficient air permeability. Can no longer be obtained,
Can not be achieved.

That is, the present inventors have proposed an absorption capacity under no pressure, an absorption capacity under pressure, and the like as a water-absorbing resin suitably used for an absorbent having a water-absorbing resin ratio of 40% by weight or more.
It has been found that the balance between the weight average particle size, the amount of fine powder having a particle size of less than 106 μm, and the amount of the water-soluble component is very important.

Therefore, by using the water-absorbing resin according to the present invention, it is possible to obtain an absorbent body that can sufficiently absorb an aqueous liquid, has a small amount of return even under pressure, and can secure air permeability. Therefore, it is possible to reliably obtain an absorbent body that simultaneously achieves the above-mentioned problems, and it is possible to further improve the comfort at the time of mounting when the absorbent article is used.

The conditions for measuring the absorption capacity under no pressure, the absorption capacity under pressure, the air flow resistance of the water-absorbent resin, the amount of water-soluble components, and the weight average particle diameter are described in detail in the examples described later. I do.

The water-absorbent resin precursor has a bulk specific gravity of 0.55 g / ml or more and 0.85 g / ml or less, preferably 0, measured by a bulk specific gravity measuring device (manufactured by Kuramochi Kaikiki Seisakusho Co., Ltd.). 0.60g / ml or more and 0.80g / ml
Within the following range, more preferably within the range of 0.65 g / ml or more and 0.75 g / ml or less, and the absorption capacity under no pressure when absorbing physiological saline is 35 g / g or more and 50 or more.
g / g or less, preferably 37 g / g or more and 48 g
/ G or less. Further, the water-absorbent resin precursor has a water-soluble component amount of 18% by weight or less, preferably 5% by weight or more and 18% by weight or less, and a solid content of 90% by weight or more and 100% by weight or less. % By weight, preferably in the range of 91% by weight to 99% by weight, more preferably in the range of 92% by weight to 98% by weight.

When the bulk specific gravity is lower than 0.55 g / ml, the physical properties may be reduced due to the difficulty in mixing the surface crosslinking agent described below, and the transport cost may be increased due to the weight reduction per unit volume. Absent. If the bulk specific gravity is higher than 0.85 g / ml, it may be difficult to secure a ventilation space between the gels.

When the water absorbing resin precursor has an absorption capacity under no load of 35 g / g or less when absorbing physiological saline, the absorption capacity under no pressure after surface cross-linking described below also becomes low, It is not preferable because the return amount of the absorber increases. Further, when the absorption capacity under no pressure is 50 g / g or more, when the aqueous liquid is absorbed and gelled, the degree of deformation of the gel due to pressure may increase, and the space between the particulate gels is eluted from the gel. It is not preferable because sufficient water permeability cannot be obtained because the water-soluble component is blocked.

Further, when the amount of the water-soluble component of the water-absorbing resin precursor is large, when the aqueous liquid is absorbed and gelled, the space between the particulate gels is blocked by the water-soluble component eluted from the gel, It is not preferable because sufficient air permeability cannot be obtained.

When the solid content is less than 90% by weight,
Aggregation is likely to occur at the time of surface cross-linking, whereby the mixing property between the water-absorbing resin precursor and the surface cross-linking agent is deteriorated, and it is difficult to obtain physical properties caused by surface cross-linking as expected, which is not preferable.

The conditions for measuring the bulk specific gravity and the solid content will be described in detail in Examples described later.

The above water-absorbent resin according to the present invention is generally obtained by a production method in which the surface of a water-absorbent resin precursor is subjected to a crosslinking treatment. The water-absorbent resin precursor has a weight average particle diameter of 400 μm or more, preferably 430 μm or more, and a ratio (ratio) of particles having a particle diameter of less than 106 μm is 5%.
It is a resin having a carboxyl group that is not more than 1% by weight, preferably not more than 1% by weight, and forms a hydrogel by absorbing a large amount of water.

The above water-absorbing resin precursor is synthesized, for example, by aqueous solution polymerization or reverse phase suspension polymerization, preferably by aqueous solution polymerization. Specific examples of the water-absorbent resin precursor include a crosslinked product of a partially neutralized polyacrylic acid, a hydrolyzate of a starch-acrylonitrile graft polymer, a neutralized product of a starch-acrylic acid graft polymer, and acetic acid. Saponified vinyl-acrylate copolymer, hydrolyzate of acrylonitrile copolymer or acrylamide copolymer or cross-linked product thereof, carboxyl group-containing cross-linked polyvinyl alcohol modified product, cross-linked isobutylene-maleic anhydride copolymer, etc. Is mentioned.

The above-mentioned water-absorbing resin precursor may be, for example, an unsaturated carboxylic acid such as (meth) acrylic acid, maleic acid, maleic anhydride, fumaric acid, crotonic acid, itaconic acid, β-acryloyloxypropionic acid, or the like. After polymerizing or copolymerizing one or more types of monomers selected from neutralized products of the above, operations such as pulverization and classification are performed on the polymer as necessary to adjust the weight average particle size. can get. Among the above monomers, (meth) acrylic acid and neutralized products thereof are more preferable.

Further, the water absorbent resin precursor may be a copolymer of the above monomer and another monomer copolymerizable with the monomer. Specific examples of the other monomer include vinyl sulfonic acid, styrene sulfonic acid, 2- (meth) acrylamido-2-methylpropane sulfonic acid, 2- (meth) acryloyl ethane sulfonic acid, and 2- (meth) acryloylethanesulfonic acid. Anionic unsaturated monomers such as (meth) acryloylpropanesulfonic acid and salts thereof; acrylamide, methacrylamide, N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide, Nn-
Propyl (meth) acrylamide, N-isopropyl (meth) acrylamide, N, N-dimethyl (meth) acrylamide, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate,
Nonionic hydrophilic group-containing unsaturated monomers such as methoxypolyethylene glycol (meth) acrylate, polyethylene glycol mono (meth) acrylate, vinylpyridine, N-vinylpyrrolidone, N-acryloylpiperidine, N-acryloylpyrrolidine; Dimethylaminoethyl (meth) acrylate, N, N-diethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylamide, quaternary salts thereof and the like And the like.

The content of the carboxyl group in the water-absorbing resin precursor is not particularly limited, but it is preferable that the carboxyl group is present in an amount of 0.01 equivalent or more per 100 g of the water-absorbing resin precursor. When the water-absorbent resin precursor is, for example, a partially neutralized crosslinked polyacrylic acid, the proportion of the unneutralized polyacrylic acid in the crosslinked product is in the range of 1 mol% to 60 mol%. Is more preferably in the range of 10 mol% or more and 50 mol% or less, and particularly preferably in the range of 20 mol% or more and 40 mol% or less. This neutralization may be carried out with a monomer, a polymer, or a combination thereof. The neutralization of the carboxyl group is performed with an alkali metal salt and / or an ammonium salt, preferably with an alkali metal salt, and more preferably with a sodium salt, a potassium salt, and a lithium salt among the alkali metal salts. .

The water absorbing resin precursor is internally crosslinked by reacting or copolymerizing with a crosslinking agent having a plurality of polymerizable unsaturated groups or a plurality of reactive groups (internal crosslinking agent). Is preferred. Further, the water-absorbing resin precursor may be a self-crosslinking type that does not require a crosslinking agent.

As the crosslinking agent, specifically, for example, N, N'-methylenebis (meth) acrylamide,
(Poly) ethylene glycol di (meth) acrylate,
(Poly) propylene glycol di (meth) acrylate, trimethylolpropane di (meth) acrylate,
Trimethylolpropane tri (meth) acrylate, glycerin tri (meth) acrylate, glycerin acrylate methacrylate, ethylene oxide-modified trimethylolpropane tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate, triary Lucyanurate, triallyl isocyanurate, triallyl phosphate, triallylamine, poly (meth) allyloxyalkane, (poly) ethylene glycol diglycidyl ether, glycerol diglycidyl ether, ethylene glycol, polyethylene glycol, propylene glycol, glycerin, penta Erythritol, ethylenediamine, polyethyleneimine, glycidyl (meth) acrylate Etc., and the like.

These crosslinking agents may be used alone or in combination of two or more. In the present invention,
Among the compounds exemplified above, it is more preferable to use a compound having a plurality of polymerizable unsaturated groups as a crosslinking agent.

The amount of the crosslinking agent to be used is preferably in the range of 0.005 to 2 mol%, and more preferably in the range of 0.05 to 1 mol%, based on the total amount of the monomers. Is more preferred. When the use amount of the crosslinking agent is less than 0.005 mol%, the expanded gel of the water-absorbent resin has
It is not preferable because stability to body fluids such as urine may decrease.

In addition to the above-mentioned monomers and crosslinking agents, if necessary, hydrophilic polymers (starch, polyvinyl alcohol, polyacrylic acid (salt) and / or cross-linked products thereof), foaming agents, chain transfer The polymerization may be carried out by adding an agent, a surfactant, a chelating agent and the like.

At the start of the polymerization in the above polymerization reaction, for example, potassium persulfate, ammonium persulfate,
Radical polymerization initiators such as sodium persulfate, t-butyl hydroperoxide, hydrogen peroxide, 2,2′-azobis (2-amidinopropane) dihydrochloride, or active energy rays such as ultraviolet rays and electron beams. Can be used. When an oxidizing radical polymerization initiator is used, redox polymerization may be performed using a reducing agent such as sodium sulfite, sodium hydrogen sulfite, ferrous sulfate, or L-ascorbic acid. The amount of these polymerization initiators used is preferably in the range of 0.001 mol% to 2 mol%, more preferably 0.01 mol% to 0.5 mol%, based on the total amount of the above monomers. Is more preferred.

The above polymerization is usually carried out as an aqueous solution,
The solid content of the monomer is in the range of 10% to 80% by weight, preferably in the range of 20% to 70% by weight, and more preferably in the range of 30% to 65% by weight. Polymerized.

When the polymer obtained after the above polymerization is a hydrogel, it is further dried, and if necessary, ground and classified to obtain a water-absorbent resin precursor.

The drying is carried out up to the solid content in the range of 80 ° C. to 250 ° C., preferably in the range of 150 ° C. to 200 ° C. Although a specific method is not particularly limited, for example, azeotropic dehydration, fluidized drying, standing hot air drying and the like are preferably used, and still standing hot air drying is more preferably used.

The above water-absorbent resin precursor generally has an absorption capacity under pressure within the preferred range of the present invention (32 g / g).
Above). For this reason, it is necessary to use a specific surface cross-linking agent to make the cross-linking density near the surface of the water-absorbent resin precursor higher than that inside. That is, by crosslinking the vicinity of the surface of the water-absorbent resin precursor using the specific surface cross-linking agent, the water-absorbent resin according to the present invention can be obtained.

That is, the water-absorbent resin according to the present invention is, for example, a water-absorbent resin precursor obtained by aqueous solution polymerization or reverse phase suspension polymerization, preferably obtained by the above-described aqueous solution polymerization, that is, having a weight average particle diameter of 400 μm or more and 850 μm.
m, and more preferably the weight average particle size is 43
0 μm or more and 850 μm or less, particularly preferably 4 μm or less.
Within a range of 50 μm or more and 850 μm or less, a particle size of 106
It is obtained by performing an operation such as classification so that the ratio of particles having a particle diameter of less than μm is 5% by weight or less, and then performing a heat treatment in the presence of a surface crosslinking agent. The resulting water-absorbent resin has an absorption capacity under no pressure when absorbing physiological saline and an absorption capacity under pressure at 2.0 kPa of 32 g /.
g or more, and the weight average particle diameter is 400 μm or more, preferably 430 μm or more, more preferably 450 μm or more.
That is all.

The water-absorbent resin precursor may be granulated in a predetermined shape, or may be in various shapes such as a sphere, a scale, an irregular crushed shape, and a granule. further,
The water-absorbing resin precursor may be primary particles,
It may be a granulated product of the secondary particles or a mixture. When the weight average particle size is smaller than 400 μm or when the ratio of particles having a particle size smaller than 106 μm exceeds 5% by weight, the water-absorbent resin or absorber according to the present invention satisfying the above-mentioned parameters can be obtained. May not be.

As the surface crosslinking agent, various known crosslinking agents can be used, and there is no particular limitation. However, it is preferable to use two kinds of crosslinking agents (first surface crosslinking agent and second surface crosslinking agent) having different solubility parameters (SP values) in combination. This is because the infiltration of the cross-linking agent into the surface of the water-absorbent resin and the thickness of the cross-linking can be easily selected arbitrarily, and in particular, a water-absorbent resin having excellent absorption capacity under pressure can be easily obtained. This is because the water-absorbent resin having excellent air permeability according to the present invention can be easily obtained.

The solubility parameter is a value generally used as a factor indicating the polarity of a compound. In the present invention, the above-mentioned solubility parameter is compared with the polymer handbook, 3rd edition (WILEY INTERSCIENCE
Solvent solubility parameter δ (J / m ³ ) ^1/2 described on pages 527 to 539 (ie, (cal /
cm ³ ) ^1/2 ). Further, regarding the solubility parameter of the solvent not described in the above-mentioned page, the Hom described in page 525 of the polymer handbook with respect to the Small's formula described in page 524 of the polymer handbook.
The value derived by substituting the cohesive energy constant of y is applied.

The first surface cross-linking agent is capable of reacting with a carboxyl group and has a solubility parameter of 0.0256 (J /
m ³ ) ^1/2 (ie 12.5 (cal / cm ³ ) ^1/2 )
The above compounds are preferable, and 0.0266 (J / m ³ )
Compounds of ^1/2 (that is, 13.0 (cal / cm ³ ) ^1/2 ) or more are more preferable. As the first surface crosslinking agent,
Specifically, for example, ethylene glycol, propylene glycol, glycerin, pentaerythritol, sorbitol, ethylene carbonate (1,3-dioxolan-2-one), propylene carbonate (4-methyl-1,3-dioxolan-2-one) And the like, but are not particularly limited to these compounds. These first surface cross-linking agents may be used alone or in combination of two or more.

The second surface crosslinking agent has a carboxyl group and
The reactable solubility parameter is 0.0256 (J /
m^Three)^1/2(That is, 12.5 (cal / cm^Three)^1/2)
Less than 0.0202 (J / m^Three)
^1/20.0246 (J / m ^Three)^1/2Within the following range
(Ie, 9.5 (cal / cm^Three)^1/2~ 12.0 (ca
l / cm^Three)^1/2Are more preferable.
As the second surface cross-linking agent, specifically, for example,
For example, diethylene glycol, triethylene glycol,
Tetraethylene glycol, dipropylene glycol,
Tripropylene glycol, 1,3-propanediol
1,4-butanediol, 1,5-pentanedio
, 2,4-pentanediol, 1,6-hexanediol
, 2,5-hexanediol, trimethylolpro
Bread, diethanolamine, triethanolamine, d
Tylene glycol diglycidyl ether, polyethylene
Glycol diglycidyl ether, glycerol polyg
Lysidyl ether, diglycerol polyglycidyl ether
Ter, polyglycerol polyglycidyl ether, pro
Pyrene glycol diglycidyl ether, polypropylene
Glycol diglycidyl ether, ethylene diamine
, Diethylenetriamine, triethylenetetramine,
2,4-tolylene diisocyanate, hexamethylene di
Isocyanate, 4,5-dimethyl-1,3-dioxo
Run-2-one, epichlorohydrin, epibromohydr
Phosphorus and the like, but are not particularly limited to these compounds.
Not something. These second surface cross-linking agents are used alone
Or a mixture of two or more types.

The amount of the above-mentioned surface cross-linking agent depends on the compound to be used and the combination thereof, but the amount of the first surface cross-linking agent is preferably 0.1 to 100 parts by weight of the solid content of the water-absorbing resin precursor. The amount of the second surface cross-linking agent is preferably in the range of 0.001 to 1 part by weight, and the amount of the first surface cross-linking agent is preferably 0.1 to 2 parts by weight. Parts by weight or less, the amount of the second surface crosslinking agent used is 0.00
The content is more preferably in the range of 5 parts by weight or more and 0.5 parts by weight or less.

By using the above-mentioned surface cross-linking agent,
The water-absorbing resin precursor, that is, the cross-linking density in the vicinity of the surface of the water-absorbing resin can be made higher than the inside, and as a result, the absorption capacity under pressure required for the water-absorbing resin according to the present invention is set to a sufficiently high value. be able to. The amount of surface cross-linking agent used is 10
When the amount exceeds the weight part, not only is it uneconomical, but also because the amount of the surface cross-linking agent becomes excessive in forming the optimum cross-linked structure in the water-absorbing resin, the absorption capacity under no pressure is preferably reduced. Absent. Further, the amount of the surface cross-linking agent used is 0.
If the amount is less than 001 parts by weight, it is difficult to obtain the effect of improving the absorption capacity under pressure of the water-absorbent resin, so that it is not preferable.

When mixing the above water-absorbing resin precursor and the surface crosslinking agent, it is preferable to use water as a solvent.
The amount of water used depends on the type and particle size of the water-absorbing resin precursor, but is preferably more than 0 and 20 parts by weight or less based on 100 parts by weight of the solid content of the water-absorbing resin precursor. It is more preferably in the range of 5 parts by weight or more and 10 parts by weight or less.

In the present invention, a polyhydric alcohol, more preferably propylene glycol, is preferably used as the surface crosslinking agent. By using the polyhydric alcohol, the physical properties can be further improved, and when the absorber is produced, the shape retention and moldability of the absorber are also improved.

When mixing the water-absorbing resin precursor and the surface crosslinking agent, a hydrophilic organic solvent may be used as a solvent, if necessary. Examples of such a hydrophilic organic solvent include lower alcohols such as methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol and t-butanol (2-methyl-2-propanol); Ketones such as acetone; ethers such as dioxane and tetrahydrofuran; amides such as N, N-dimethylformamide; and sulfoxides such as dimethyl sulfoxide. The amount of the hydrophilic organic solvent used depends on the type and particle size of the water-absorbing resin precursor, but is preferably 20 parts by weight or less based on 10 parts by weight of the solid content of the water-absorbing resin precursor, and 0.1% by weight or less.
The range is more preferably from 10 parts by weight to 10 parts by weight.

When mixing the above-mentioned water-absorbing resin precursor and the surface cross-linking agent, for example, after dispersing the water-absorbing resin precursor in the above-mentioned hydrophilic organic solvent, the surface cross-linking agent may be mixed. Although good, the mixing method itself is not particularly limited. Among various mixing methods, water and / or
Alternatively, a method of directly spraying or dripping the water-absorbent resin precursor and mixing it is preferable.

In particular, it is preferable to use a method of spraying a surface cross-linking agent on the water-absorbing resin precursor which is stirred at a high speed, since the physical properties can be further improved. The stirring at this time is 300 rpm or more, more preferably 1000 rpm.
The rotation is performed at a rotation speed of 3000 rpm or less. Also,
Spraying at this time is performed so as to form a mist within a range of 100 μm or more and 500 μm or less, more preferably 200 μm or more and 400 μm or less.

In the mixing, it is preferable that the mixing temperature, that is, at least one of the temperature of the water-absorbing resin precursor before mixing and the temperature of the surface cross-linking agent is within a specific range. This makes it easier to control the thickness of the surface cross-linked layer formed by the surface cross-linking agent, and to easily bring out the performance of the water absorbent resin according to the present invention. The temperature of the water-absorbent resin precursor before the mixing is generally 0
In the range of not less than 100 ° C. and preferably not more than 60 ° C.
In the range of not less than 80 ° C and more preferably not more than 60 ° C.
In the range of not less than 75 ° C and more preferably not more than 60 ° C.
It is in the range of not less than 70 ° C and not less than 70 ° C.

If the temperature of the water-absorbing resin precursor before the addition of the aqueous solution is high, the mixing of the surface cross-linking agent becomes non-uniform, and if it is low, the aggregation of the powder (ie, the water-absorbing resin precursor) is observed. Absent. The temperature of the surface crosslinking agent is 5 ° C.
In the range of not less than 45 ° C and preferably not more than 10 ° C and not more than 40 ° C
It is in the following range, more preferably in the range of 15 ° C or more and 35 ° C or more. Since the above surface cross-linking agent may contain a component having high volatility (low flash point),
A high temperature of the surface cross-linking agent may not be preferable for safety.

When the water-absorbent resin precursor and the surface cross-linking agent are mixed using water, fine particles insoluble in water or a surfactant may be used together.

The mixing device used for mixing the water absorbent resin precursor and the surface cross-linking agent preferably has a large mixing force in order to uniformly and surely mix the two. Examples of the mixing device include a cylindrical mixer, a double-walled conical mixer, a V-shaped mixer, a ribbon-type mixer, a screw-type mixer, a fluidized-type rotary desk-type mixer, and a gas-flow-type mixer. , Double-armed kneader, internal mixer,
A pulverizing kneader, a rotary mixer, a screw type extruder and the like are suitable.

After mixing the water-absorbing resin precursor and the surface cross-linking agent, a heat treatment is performed to crosslink the vicinity of the surface of the water-absorbing resin precursor. The treatment temperature of the above-mentioned heat treatment (defined by the temperature of the heat source for heating or the temperature of the precursor during heating, preferably the temperature of the heat source) depends on the type of the surface cross-linking agent to be used.
The range is preferably from 0 ° C to 250 ° C, more preferably from 120 ° C to 250 ° C, and particularly preferably from 160 ° C to 250 ° C. Processing temperature is 10
When the temperature is lower than 0 ° C., a uniform crosslinked structure is not formed, and therefore, a water-absorbing resin having excellent properties such as diffusion absorption capacity cannot be obtained, which is not preferable. Processing temperature is 2
If the temperature exceeds 50 ° C., the water-absorbent resin precursor is deteriorated, and the performance of the water-absorbent resin is deteriorated.

The above heat treatment can be carried out using a usual dryer or heating furnace. Examples of the dryer include a groove-type mixing dryer, a rotary dryer, a desk dryer, a fluidized-bed dryer, a gas-flow dryer, and an infrared dryer.

The thus obtained water-absorbent resin of the present invention may further contain, if necessary, a deodorant,
Fragrances, various inorganic powders, foaming agents, pigments, dyes, antibacterial agents,
A hydrophilic short fiber, a plasticizer, a pressure-sensitive adhesive, a surfactant, a fertilizer, an oxidizing agent, a reducing agent, a chelating agent, water, salts and the like may be added during or after the production. Thereby, various functions can be imparted to the water-absorbing resin.

The inorganic powder is not particularly limited as long as it is a substance which is inactive against an aqueous liquid or the like.
For example, fine particles of various inorganic compounds, fine particles of clay minerals, and the like can be given. In particular, the inorganic powder preferably has a suitable affinity for water and is insoluble or hardly soluble in water. Specific examples include metal oxides such as silicon dioxide and titanium oxide, silicic acids (salts) such as natural zeolites and synthetic zeolites, kaolin, talc, clay, bentonite and the like. Among them, silicon dioxide and silicic acid (salt) are more preferable, and the average particle diameter measured by the Coulter counter method is 200 μm.
m or less of silicon dioxide and silicic acid (salt) are particularly preferred.

The amount of the inorganic powder used in the water-absorbent resin according to the present invention depends on the combination of the water-absorbent resin and the inorganic powder, but is usually 0.001 part by weight per 100 parts by weight of the water-absorbent resin. The range is not less than 10 parts by weight and more preferably not more than 0.01 part by weight and not more than 5 parts by weight. The method of mixing the water-absorbent resin and the inorganic powder is not particularly limited, and for example, a dry blending method, a wet mixing method, or the like can be adopted, and among them, the dry blending method is preferable.

As described above, the water absorbent resin according to the present invention is generally obtained by a production method in which the surface of the water absorbent resin precursor is subjected to a crosslinking treatment. The water absorbent resin precursor has a bulk specific gravity of 0.55 g / ml or more and 0.85 g / ml.
Within the following range, the solid content is within the range of 90% by weight or more and 100% by weight or less, and the absorption capacity under no pressure when absorbing physiological saline is within the range of 35g / g or more and 50g / g or less. And the amount of the water-soluble component is 18% by weight or less,
And the ratio (ratio) of particles having a weight average particle size of 400 μm or more and a weight average particle size of less than 106 μm is 5% by weight
It is as follows. In addition, a surface crosslinking agent in the range of 5 ° C to 45 ° C is spray-added to the water absorbent resin precursor in the range of 0 ° C to 100 ° C, preferably 60 ° C to 75 ° C. Then, the water-absorbing resin according to the present invention can be obtained by performing the surface crosslinking treatment by the heat treatment. Preferably, the surface crosslinking agent is a polyhydric alcohol,
More preferably, propylene glycol is included.

The absorbent article according to the present invention comprises the above-described water-absorbent resin, and includes an absorbent layer including the absorbent having the above-described structure, between the top sheet (top sheet) and the back sheet (back sheet). It is something that is pinched. Specific examples of such absorbent articles include, but are not particularly limited to, various sanitary materials such as disposable diapers (disposable diapers), sanitary napkins, and so-called incontinence pads. Since the absorbent article has excellent water absorption properties, for example, when the absorbent article is a paper diaper, it is possible to prevent leakage of urine,
A so-called dry feeling (described later) can be imparted.

As the top sheet, a sheet having a property of permeating an aqueous liquid (liquid permeability) (hereinafter referred to as a liquid permeable sheet) is used. The material used as the liquid permeable sheet is not particularly limited as long as it is a material that can transmit an aqueous liquid.
For example, a nonwoven fabric, a woven fabric, a porous synthetic resin film made of polyethylene, polypropylene, polyester, polyamide or the like can be used.

As the back sheet, a sheet having a property of not permeating an aqueous liquid and having excellent air permeability as described later (hereinafter referred to as a liquid impermeable sheet) is used. The material used as the liquid-impermeable sheet is not particularly limited, but may be, for example, a synthetic resin film made of polyethylene, polypropylene, ethylene vinyl acetate, polyvinyl chloride, or the like; Film made of a material; a film made of a composite material of the above synthetic resin and woven fabric;

[0095] Each of the above-mentioned films is subjected to various processes for ensuring air permeability. The processing method for ensuring the air permeability is not particularly limited, and for example, a method of forming micropores after stretching in at least one direction is preferably used.

The air-permeation resistance of the liquid impermeable sheet is 1 k
It is preferably in a range from Pa · sec / m to 50 kPa · sec / m, and is preferably from 1 kPa · sec / m to 40 k.
Pa / sec / m or less, more preferably 1 kPa · sec / m or more and 30 kPa · sec or more.
/ M or less. If the gas flow resistance is less than 1 kPa · sec / m, the gas permeability is too high and the liquid-impermeable back sheet cannot function sufficiently. On the other hand, the airflow resistance is 50 kPa
If it exceeds sec / m, the air permeability is too low, and there is no point in improving the air permeability of the absorber. The airflow resistance of the liquid-impermeable sheet is measured in a substantially dry state, and the range of the airflow resistance is a value measured under these conditions.

The structure of the absorbing layer is not particularly limited, and it is sufficient that the absorbing layer includes the absorbing material. That is, the above-mentioned absorbent layer appropriately contains other members other than the absorbent according to the type and intended use of the absorbent article. Also, the method for producing the absorbing layer is not particularly limited. further,
The diffusion layer may be disposed on the upper surface of the absorption layer, the back surface of the back sheet, or the upper surface of the top sheet. This diffusion layer is intended to more efficiently and quickly absorb the liquid by the absorber by helping the diffusion of the liquid absorbed by the absorption layer. The material of the diffusion layer is not particularly limited as long as it can assist liquid diffusion, and examples thereof include a layer mainly composed of nonwoven fabric, cellulose, crosslinked cellulose, or the like.

The method for sandwiching the absorbent layer between the top sheet and the back sheet, that is, the method for producing an absorbent article is not particularly limited. That is,
If the absorbent article is a disposable diaper, a conventional method for producing a disposable diaper can be preferably used, and if the absorbent article is a sanitary napkin, a conventional method for producing a sanitary napkin can be suitably used. Can be.

When the absorbent article according to the present invention is a sanitary material that absorbs bodily fluids, the user does not feel any discomfort when worn, such as stuffiness due to high humidity or stickiness due to the amount of aqueous liquid returned under pressure. A state, that is, a feeling close to a dry state (this is referred to as a dry feeling) can be realized. The criteria for this dry feeling vary depending on the user, but basically, the humidity between the body and the absorbent article at the time of wearing (humidity in the wearing) is low. Hereinafter, it is preferably 65% or less (that is, the feeling of stuffiness is small), and the return amount described above is small (that is, the feeling of stickiness is small).

The preferred ranges of the in-wear humidity and the return amount are appropriately set depending on the type and shape of the absorbent article, and are not particularly limited.

[0101]

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples and FIGS. 1 to 4, but the present invention is not limited to these. In addition, the absorption capacity under no pressure of the water-absorbent resin or the water-absorbent resin precursor, the absorption capacity under pressure, the amount of water-soluble component, the bulk specific gravity, the solid content, and the weight average particle size, the weight of the absorber under pressure in a wet state Ventilation resistance, ventilation resistance under pressure in the wet state of the water-absorbent resin,
The absorption capacity under pressure of the absorber at 2.0 kPa, the return amount (wet back), the humidity inside the disposable diaper, and the monitor evaluation were measured or evaluated by the following methods.

[Absorptive Capacity of Water Absorbent Resin Under No Pressure] 0.2 g of a water absorbent resin or a water absorbent resin precursor is uniformly placed in a nonwoven fabric bag (60 mm × 60 mm), and physiological saline at 23 ° C. (composition: An aqueous solution of 0.9% by weight of sodium chloride) or artificial urine (composition: 0.2% by weight of sodium sulfate, 0.2% by weight of potassium chloride, and 0.1% of magnesium chloride hexahydrate).
(Aqueous solution of 0.05% by weight, 0.025% by weight of calcium chloride dihydrate, 0.085% by weight of ammonium dihydrogen phosphate, and 0.015% by weight of diammonium hydrogen phosphate). After 60 minutes, the bag is pulled up and drained at 250 G for 3 minutes using a centrifuge.
₁ (g) was measured. Further, the same operation was performed without using the water-absorbing resin, and the weight W ₀ (g) at that time was measured. Then, from these weights W ₁ · W ₀ , the absorption capacity under no pressure (g / g) = ｛(weight W ₁ (g) −weight W ₀ (g)) / water-absorbent resin (or water-absorbent resin precursor) Of the water-absorbent resin (or the water-absorbent resin precursor) was calculated according to the weight (g)｝-1 of the body).

[Absorption Capacity Under Pressure of Water Absorbent Resin] First, a measuring apparatus used for measuring the absorption capacity under pressure of a water absorbent resin will be briefly described below with reference to FIG.

As shown in FIG. 1, the measuring device is a balance 1
And a container 2 having a predetermined capacity mounted on the balance 1, an outside air suction pipe 3, a conduit 4, a glass filter 6, and a measuring unit 5 mounted on the glass filter 6. I have. The container 2 has an opening 2a at the top and an opening 2b at the side, and the outside air suction pipe 3 is fitted into the opening 2a, while the opening 2b
Is fitted with a conduit 4.

The container 2 contains a predetermined amount of physiological saline 1
2 or artificial urine (for the respective compositions, see [Absorptive power of water-absorbent resin under no pressure]), and the lower end of the outside air suction pipe 3 is filled with this physiological saline 12 or artificial urine (25 ° C.). Submerged inside. The above glass filter 6
Is formed to have a diameter of 70 mm, and the container 2 and the glass filter 6 are connected to each other by a conduit 4. The upper part of the glass filter 6 is fixed at a position slightly higher than the lower end of the outside air suction pipe 3.

The measuring section 5 includes a filter paper 7 and a support cylinder 8.
And a wire mesh 9 attached to the bottom of the support cylinder 8, and a weight 10. Then, the measuring unit 5 places the filter paper 7 and the support cylinder 8 (that is, the wire mesh 9) on the glass filter 6 in this order, and places the weight 10 inside the support cylinder 8, that is, on the wire mesh 9. Has become. Support cylinder 8
Has an inner diameter of 60 mm. The wire mesh 9 is made of stainless steel and is formed in a 400 mesh (mesh size 38 μm). A predetermined amount of water-absorbent resin 1
1 are evenly distributed. The weight 10
4.9 kP for the wire mesh 9, that is, the water absorbent resin 11.
The weight is adjusted so that a and a load of 2.0 kPa can be applied uniformly.

The water absorbing resin 1 was measured using the measuring device having the above-described structure.
The absorption capacity under load of 1 was measured. The measuring method will be described below.

First, a predetermined preparation operation such as putting a predetermined amount of physiological saline 12 or artificial urine into the container 2 and fitting an outside air suction pipe 3 into the container 2 was performed. 7 was placed. On the other hand, in parallel with these mounting operations, 0.9 g of the water-absorbent resin 11 is evenly dispersed inside the support cylinder 8, that is, on the wire mesh 9.
The weight 10 was placed on 1.

Next, the weight W ₂ (g) of the physiological saline 12 or the artificial urine absorbed by the water-absorbent resin 11 for 60 minutes from the time when the support cylinder 8 was placed on the filter paper 7 was measured using the balance 1. It was measured.

Then, the absorption under pressure 60 minutes after the start of absorption is calculated from the above weight W _{2 according} to the following equation: absorption capacity under pressure (g / g) = weight W ₂ (g) / weight of water-absorbent resin (g). Magnification (g
/ G) was calculated.

[Water-Soluble Component Content of Water Absorbent Resin] 0.500 g of the water absorbent resin or the water absorbent resin precursor was dispersed in 1000 ml of deionized water, stirred at 23 ° C. for 16 hours, and filtered with a filter paper. Next, 50 g of the obtained filtrate was added to 1
In a 00 ml beaker, 1 ml of a 0.1 mol / l aqueous sodium hydroxide solution was added to the filtrate, and N / 200-
10.00 ml of an aqueous solution of methyl glycol chitosan and 4 drops of a 0.1% by weight aqueous solution of toluidine blue were added.
Next, the solution in the above beaker was subjected to colloidal titration using an aqueous solution of N / 400-potassium polyvinyl sulfate, and the titration end point was determined as the end point of the titration when the color of the solution changed from blue to magenta. Further, the same operation was performed using 50 g of deionized water instead of 50 g of the filtrate, and the titration amount Bml was determined as a blank titration.

The titration amounts Aml and Bml
And the neutralization ratio C of acrylic acid used for the production of the water absorbent resin
mol%, the following formula: Water-soluble component amount (% by weight) = (BA) × 0.01 × (72 ×
The water-soluble component amount (% by weight) of the water-absorbent resin (or water-absorbent resin precursor) was calculated according to (100−C) + 94 × C) / 100.

[Bulk specific gravity of water-absorbent resin] JIS K 3362 was measured using a bulk specific gravity measuring instrument (manufactured by Kuramochi Kaikiki Seisakusho Co., Ltd.).
It measured according to. Specifically, in a room at a temperature of 25 ± 2 ° C. and a relative humidity of 30% or more and 50% or less, 120 g of the water-absorbent resin or the water-absorbent resin precursor is put into a funnel with the damper closed, and then the damper is quickly opened. Transfer the sample to a receiver (100
ml). After the sample raised from this receiver is ground with a glass rod, the weight (g) of the receiver containing the sample is accurately measured to 0.1 g, and the bulk specific gravity (g / g) is measured.
ml).

[Solid Content of Water Absorbent Resin] 1.000 g of the obtained water absorbent resin or water absorbent resin precursor is placed in an aluminum cup (inner diameter 53 mm × height 23 mm) and dried again in a windless oven at 180 ° C. for 3 hours. The solid content (% by weight) of the water-absorbent resin (or water-absorbent resin precursor) was calculated from the loss on drying (g).

[Weight Average Particle Size of Water Absorbent Resin] A water absorbent resin powder was sieved with a JIS standard sieve (850 μm, 600 μm, 300
μm, 150 μm, 106 μm), and the particle size of each sieve (850 μm on product / 850-600 μm / 60)
0-300 μm / 300-150 μm / 150 μm-1
(06 μm / 106 μm pass product). If necessary, a JIS standard sieve was added, and the obtained particle size distribution was plotted on logarithmic probability paper to determine the weight average particle size (D50).

[Ventilation Resistance Under Pressure in Wet State of Absorbent Body] A measuring device used for measuring the ventilation resistance of the absorbent body is a permeability tester (KES-F8-AP1, manufactured by Kato Tech Co., Ltd., Location: Japan) Minami-ku, Kyoto). The cell section for setting the measurement absorber will be briefly described below with reference to FIG.

As shown in FIG. 2, the cell section 22 in which the absorber 13 is set includes a cell set 23 in which the absorber 13 to be measured is placed, a weight 29 above the cell, and a weight 29.
Wire mesh 28 (with 9 mm opening) for mounting
Consists of The cell set 23 includes a cylindrical outer cell 24 (inner diameter 89.5 mm) and an inner cell 25 (outer diameter 89. mm).
2 mm), and two wire meshes 26 and 27 (having an opening of 7 mm) are fixed to the lower surfaces of the outer cell 24 and the inner cell 25, respectively. The outer cell 24 and the inner cell 25 are accessories (manufactured by Kato Tech Co., Ltd.) of the air permeability tester 21.

The weight of the weight 29 was adjusted so that a load of 4.9 kPa could be uniformly applied to the metal mesh 27 on the lower surface of the inner cell 25, that is, the absorber 13.

Using the measuring device having the above configuration, 4.9 kP
The air permeability under pressure at a is determined by the airflow resistance R (unit: kPa · se).
c / m). The gas flow resistance R is a value indicating whether the gas permeability of the sample is good or bad. If the gas permeability of the absorber is good, the gas flow resistance R is small, and if the gas permeability is bad, the gas flow resistance R is large. The method for measuring the ventilation resistance R will be described below.

In this embodiment, the measurement of the ventilation resistance R is as follows.
The test was performed in a constant temperature and humidity room at a temperature of 23 ° C. and a humidity of 65% RH.

To measure the ventilation resistance R, first, the diameter 8
The upper and lower sides of the absorber 13 cut to 9.4 mm have a diameter of 89.
A nonwoven fabric 30 (Heatron paper: GS-22, manufactured by Nankoku Pulp & Paper Co., Ltd.) cut into a size of 4 mm was inserted into the outer cell 24, and then the inner cell 25 was inserted into the outer cell 24. Further, a wire mesh 2 is placed on the upper part of the inner cell 25.
8. Next, the weight 29 was placed.

Thereafter, 40 g of a previously prepared physiological saline solution at 23 ° C. was poured into the absorbent 13 under the above-mentioned pressurized state, and allowed to stand for 30 minutes.
1 and the airflow resistance R was measured. The piston speed of the cylinder in the air permeability tester 21 at the time of measurement was 2 cm /
set to sec.

The airflow resistance R is measured using a mechanism that sends a constant flow of air to the sample by the piston movement of a cylinder built in the air permeability tester 21 (arrow in the figure), and discharges and sucks the sample into the atmosphere. Is what is done. In this mechanism, the pressure loss due to the sample is measured using a semiconductor differential pressure gauge within 10 seconds per cycle, and as a result,
The ventilation resistance R of the sample can be read directly by a digital panel meter.

When the basis weight of the absorber in one diaper varies depending on the site (location), the diameter is 89.4 mm including the portion having the largest basis weight, that is, the portion having the maximum basis weight.
After the absorber was cut into a substantially circular shape, the airflow resistance was measured. However, the top sheet and back sheet have been removed.

The air-permeation resistance of the liquid-impermeable sheet was measured in the same manner as the air-permeation resistance of the absorber except that the liquid-impermeable sheet of the diaper was cut to a diameter of 89.4 mm in a dry state. Measured by the method.

[Air Permeation Resistance Under Pressure in Wet State of Water Absorbent Resin] The measuring device used for measuring the air permeation resistance of the water absorbent resin is the air permeability tester (KES -F8-AP1, Kato Tech Co., Ltd.
Manufactured). Therefore, in the following description, the description will be made with reference to FIG. 2 only when the measurement differs from the measurement of [airflow resistance under pressure in a wet state of the absorber].

First, in the wet state of the water-absorbing resin.
In order to measure the ventilation resistance under pressure at 9 kPa, first, 2 g of the water-absorbing resin was added to 30 g of physiological saline (23 ° C.) for 30 minutes.
Allowed to swell for minutes. Thereafter, a nylon mesh (having an opening of 305 μm) cut to a diameter of 89.4 mm was put into the outer cell 24 of the air permeability tester shown in FIG. 2, and the swollen water-absorbent resin was evenly sprayed thereon. 8 diameter on it
After placing the nylon mesh cut to 9.4 mm, the inner cell 25 was inserted into the outer cell 24. Further, a wire net 28 and then a weight 29 were placed on the upper part of the inner cell 25. After placing the weight 29, the cell portion 22 was allowed to stand still for 3 minutes, and the cell portion 22 was attached to the gas permeability tester 21, and the gas flow resistance R was measured. The piston speed of the cylinder in the air permeability tester 21 at the time of measurement was set to 2 cm / sec.

[Absorbency under Pressure of 2.0 kPa of Absorber] First, a measuring apparatus used for measuring the absorbency under pressure of the absorber will be briefly described with reference to FIGS. 3 and 4.

As shown in FIG. 3, the measuring device is a balance 1
, Container 2, outside air suction pipe 3, conduit 4, diameter 2
A glass filter 36 having a thickness of 0 mm and a measuring unit 35 mounted on the glass filter 36 are provided. The configuration of the container 2 is the same as that described in the section of [Absorbency under pressure of water-absorbent resin], and thus detailed description is omitted. In addition, the physiological saline 12 (23
° C).

As shown in FIG. 4, the measuring section 35 has a filter paper 37, a supporting square tube 38, and a weight 39.
On the glass filter 36, a filter paper 37, a support square tube 38
Are placed in this order, and a weight 39 is placed inside the support square tube 38. The support square tube 38 is
The inner size is formed to be 100 mm × 100 mm. The absorber 13 having a predetermined size is placed inside the support square tube 38 and directly below the weight 39.

The absorption capacity under pressure of the absorber 13 was measured using the measuring apparatus having the above-mentioned configuration. The measuring method will be described below.

First, the absorber 13 is 100 mm × 100 m
m. Further, the same preparatory operation was performed as in the case described in the section of “Absorbency under pressure of water-absorbent resin”. Next, the filter paper 37 was placed on the glass filter 36, and then the supporting square tube 38 was placed so that the center portion thereof was aligned with the center portion of the glass filter 36. Thereafter, the absorber 13 having the predetermined size is provided inside the support square tube 38.
And a weight 39 was placed on the absorber 13. The weight of the weight 39 is adjusted so that a load of 2.0 kPa can be uniformly applied to the absorber 13. The operation of placing the absorber 13 and the weight 39 was performed quickly.

Then, the weight W ₃ (g) of the physiological saline absorbed by the absorber 13 was measured using the balance 1 for 60 minutes from the time when the absorber 13 was placed on the filter paper 37. From this weight W ₃ , the following formula: Absorption capacity under pressure of the absorber (g / g) = weight W ₃ (g) /
According to the weight (g) of the absorber, the absorption capacity under pressure (g / g) of the absorber 13 after 60 minutes from the start of water absorption was calculated.

If the basis weight of the absorber in one diaper varies depending on the site (location), the portion having the largest basis weight, that is, 100 mm × 10 including the portion having the maximum basis weight is included.
After the absorber was cut into a substantially square shape of 0 mm, the absorption capacity under pressure was measured. However, the top sheet and back sheet have been removed.

[Return amount of the absorber (wet back)] First, 120 g of physiological saline (23 ° C.) was poured into the absorber cut to 100 mm × 100 mm and left for 60 minutes. A weight W ₄ (g) of a half-folded fifteen stack of NEPIA (registered trademark) kitchen towel (manufactured by Oji Paper Co., Ltd.) was measured, placed on the upper part of the absorber, and further weighed 10 kg. The weight was placed for one minute. Then, the weight W ₅ (g) of the kitchen towel removed from the upper part of the absorber
Was measured. Then, the return amount (g) was calculated from the weights W ₄ and W _{5 according} to the following equation: return amount (g) = weight W ₅ (g) −weight W ₄ (g).

[Ambient Humidity in Absorbent Article] First, a disposable diaper (absorbent article) to be measured was prepared by the following method.

The water-absorbent resin and the ground wood pulp were dry-mixed using a mixer. Then the resulting mixture is
A web was formed on a wire screen formed into a 400 mesh (mesh size: 38 μm) by using a batch-type air-making apparatus. Further, the web was pressed at a pressure of 2 kg / cm ² (196 kPa) for 5 seconds to obtain an absorber.

Subsequently, a back sheet (liquid-impermeable sheet) made of liquid-impermeable polypropylene and having a so-called leg gather, the above-mentioned absorber, and a top sheet (liquid-permeable sheet) made of liquid-permeable polypropylene Were adhered to each other in this order using a double-sided tape, and two so-called tape fasteners were attached to the adhered product to obtain a disposable diaper (that is, an absorbent article).

The air-permeation resistance of the liquid impermeable sheet used for the disposable diaper was 24 kPa · sec / m.

The above-mentioned disposable diaper is 55 cm long and weighs 5 k.
g plastic doll. The doll has a humidity sensor (ThermoHygrosensor: mode) between the crotch and the buttocks.
l THP-14) is fixed, and a change in humidity over time can be measured.

After the doll with the disposable diaper is placed in a prone position, a tube is inserted between the disposable diaper and the doll, and 50 ml of physiological saline (23 ° C.) is injected into a position corresponding to a position where urination is performed in the human body. After leaving for 30 minutes, the humidity inside the disposable diaper was measured.

For the value of the humidity in the mounting, the value displayed on the Data stocker (THR-DM2: manufactured by SHINYEI) connected to the humidity sensor was read.

[Absorbent article monitor evaluation] The monitor evaluation was performed by an adult adult using an adult paper diaper (absorbent article). The disposable diaper used for the evaluation was produced by the following method.

First, the absorbent resin and the ground wood pulp were dry-mixed using a mixer. Next, the obtained mixture was air-formed on a wire screen formed into 400 mesh (having an opening of 38 μm) using a batch-type air-paper-making apparatus to obtain 200 mm × 700 m.
m was formed into a web. Further, the web was pressed at a pressure of 2 kg / cm ² (196 kPa) for 5 seconds to obtain an absorber.

Subsequently, a back sheet (liquid-impermeable sheet) made of liquid-impermeable polypropylene and having a so-called leg gather, the above-described absorber, and a top sheet (liquid-permeable sheet) made of liquid-permeable polypropylene ) Were adhered to each other in this order using a double-sided tape, and two so-called tape fasteners were attached to the adhered product to obtain a disposable diaper (that is, an absorbent article).

The obtained disposable diapers were evaluated for comfort during use during use. The evaluation was performed on 10 monitors. Evaluation by a monitor was performed to examine the presence or absence of stuffiness and stickiness in the wearing after one urination.

Example 1 A polyethylene glycol diacrylate (average number of moles of ethylene oxide added: 8) was added to 5,500 g (monomer concentration: 35% by weight) of an aqueous solution of sodium acrylate having a neutralization ratio of 75 mol%. .03
5 mol% was dissolved to obtain a reaction solution. Next, the reaction solution was degassed for 30 minutes under a nitrogen gas atmosphere.

Next, the reaction solution was supplied to a reactor formed by attaching a lid to a jacketed stainless steel double-arm kneader having two sigma-type blades and having a capacity of 10 liters, and
The system was purged with nitrogen gas while maintaining the reaction solution at 20 ° C. Subsequently, while stirring the reaction solution, 3.5% sodium persulfate was added.
g and L-ascorbic acid 0.02 g were added, and polymerization started about 1 minute later. And 20 ° C ~
Polymerization was carried out at 90 ° C., and a hydrogel polymer was taken out 60 minutes after the initiation of the polymerization.

The obtained hydrogel polymer was finely divided into a diameter of about 5 mm. The finely divided hydrogel polymer was spread on a 50-mesh (mesh size: 300 μm) wire mesh and dried with hot air at 170 ° C. for 60 minutes. Then, the dried product was pulverized using a vibrating mill, and was crushed to a mesh size of 20 (85 mesh).
(0 μm). Furthermore, a classification operation was performed so that the amount of the pulverized product having a particle size of less than 106 μm was 5% by weight or less, whereby an amorphous crushed water-absorbent resin precursor (a) was obtained.
The bulk specific gravity of the water absorbent resin precursor (a) is 0.68 g / m
1, the solid content is 98% by weight, the absorption capacity under no pressure when physiological saline is absorbed is 40 g / g, and the amount of water-soluble component is 13
% By weight.

To 100 parts by weight (70 ° C.) of the obtained water-absorbent resin precursor (a), 1 part by weight of 1,4-butanediol and 0.05 part of ethylene glycol diglycidyl ether were added.
A surface cross-linking agent (30 ° C.) consisting of 1 part by weight of water, 2 parts by weight of water and 1 part by weight of ethanol was mixed. Add the above mixture to 19
By performing a heat treatment at 5 ° C. for 50 minutes, a water absorbent resin (1) was obtained. The weight average particle diameter of the obtained water-absorbent resin (1) was 450 μm. The amount of the water-absorbent resin having a particle size of less than 106 μm was 2% by weight or less. Table 1 shows the results of the absorption capacity under no pressure, the absorption capacity under pressure, the amount of water-soluble components, the weight average particle size, and the airflow resistance of the water absorbent resin (1).

Example 2 0.03 mol% of N, N'-methylenebisacrylamide was dissolved in 5,500 g (monomer concentration: 35% by weight) of an aqueous solution of sodium acrylate having a neutralization ratio of 75 mol%. Then, polymerization was carried out in the same manner as in Example 1 except that the reaction solution was used, and a hydrogel polymer was taken out. Further, the obtained hydrogel polymer was used in Example 1
In the same manner as in the above, pulverization and classification were performed to obtain an irregularly crushed water-absorbent resin precursor (b). The bulk specific gravity of the water-absorbent resin precursor (b) is 0.68 g / ml, the solid content is 97% by weight, and the absorption capacity without pressure when absorbing physiological saline is 48 g / g.
The water-soluble component amount was 16% by weight.

To 100 parts by weight (75 ° C.) of the obtained water-absorbing resin precursor (b), 1 part by weight of propylene glycol was added.
A surface cross-linking agent (28 ° C.) composed of 0.05 parts by weight of ethylene glycol diglycidyl ether, 2 parts by weight of water, and 1 part by weight of ethanol was mixed. The above mixture at 200 ° C
By heating for 40 minutes in water-absorbent resin (2)
I got The weight average particle size of the obtained water absorbent resin (2) is 5
It was 00 μm. The amount of the water-absorbing resin having a particle size of less than 106 μm was 1% by weight or less. Table 1 shows the absorption capacity under no pressure, the absorption capacity under pressure, the amount of water-soluble components, the weight average particle diameter, and the airflow resistance of the water absorbent resin (2).

[Comparative Example 1] A dried product of the hydrogel polymer obtained in the same manner as in Example 1 was pulverized using a vibrating mill and further classified using a 20-mesh (850 μm mesh) wire mesh. As a result, an amorphous crushed water-absorbent resin precursor (c) was obtained. The bulk specific gravity of the water-absorbent resin precursor (c) is 0.71 g / ml, the solid content is 98% by weight, the absorbency under no pressure when absorbing physiological saline is 39 g / g, and the amount of water-soluble components. Was 13% by weight.

To 100 parts by weight (65 ° C.) of the obtained water-absorbent resin precursor (c), 1 part by weight of propylene glycol, 0.03 part by weight of ethylene glycol diglycidyl ether, 3 parts by weight of water, and 1 part by weight of ethanol Of a surface cross-linking agent (35 ° C.). The mixture was heat-treated at 210 ° C. for 60 minutes to obtain a water-absorbent resin (3). The weight average particle size of the obtained water absorbent resin (3) is 31.
It was 0 μm. The amount of the water-absorbent resin having a particle size of less than 106 μm was 6% by weight. Table 1 shows the absorption capacity under no pressure, the absorption capacity under pressure, the amount of water-soluble components, the weight average particle diameter, and the airflow resistance of the water absorbent resin (3).

[Comparative Example 2]
Polymerization was carried out in the same manner as in Example 1 except that 5,500 g (monomer concentration: 39% by weight) of an aqueous solution of sodium acrylate having a neutralization ratio of 1.3 mol% was used, and a hydrogel polymer was obtained. Was taken out. Then, hot air drying was performed at 170 ° C for 7 minutes.
The hydrogel polymer was dried and classified in the same manner as in Example 1 except that the operation was carried out for 0 minute, to obtain an amorphous crushed water-absorbent resin precursor (d). The bulk specific gravity of the water-absorbent resin precursor (d) is 0.67 g / ml, the solid content is 98% by weight, the absorption capacity under no pressure when absorbing physiological saline is 31 g / g, and the amount of water-soluble components. Was 7% by weight.

To 100 parts by weight (78 ° C.) of the obtained water-absorbent resin precursor (d), 0.5 parts by weight of propylene glycol, 0.5 parts by weight of 1,4-butanediol, and 3 parts by weight of water And a surface cross-linking agent (20 ° C.) composed of 0.5 parts by weight of isopropyl alcohol. 210 of the above mixture
By heating at 30 ° C. for 30 minutes, a water absorbent resin (4) was obtained. The weight average particle size of the obtained water absorbent resin is 430 μm
Met. The amount of the water-absorbent resin having a particle size of less than 106 μm was 3% by weight. Table 1 shows the results of the absorption capacity under no pressure, the absorption capacity under pressure, the amount of water-soluble components, the weight average particle diameter, and the airflow resistance of the water absorbent resin (4).

[Comparative Example 3] A dried product of the hydrogel obtained in the same manner as in Example 2 was pulverized using a vibrating mill, and classified with a 20-mesh wire net to obtain irregularly crushed water absorption. The reactive resin precursor (e) was obtained. The bulk specific gravity of the water absorbent resin precursor (e) is 0.68 g / ml, and the solid content is 9
The absorption capacity under no pressure when absorbing physiological saline was 48 g / g, and the amount of water-soluble component was 16% by weight.

A surface cross-linking agent (25 ° C.) comprising 0.5 parts by weight of glycerin, 1 part by weight of water and 1 part by weight of ethanol based on 100 parts by weight (80 ° C.) of the obtained water-absorbent resin precursor (e).
Was mixed. The mixture was heat-treated at 195 ° C. for 30 minutes to obtain a water-absorbent resin (5). The weight average particle size of the obtained water-absorbent resin (5) was 480 μm.
The amount of the water-absorbent resin having a particle size of less than 106 μm is 2% by weight.
Met. Absorption capacity of this water-absorbent resin (5) under no pressure,
Table 1 shows the results of the absorption capacity under pressure, the amount of water-soluble components, the weight average particle size, and the airflow resistance.

[Example 3] Polyethylene glycol diacrylate (average number of moles of ethylene oxide added: 9) of 0.07 was added to 5,500 g (monomer concentration: 38% by weight) of an aqueous solution of sodium acrylate having a neutralization ratio of 75 mol%. Polymerization was carried out in the same manner as in Example 1 except that the reaction solution was dissolved by mol%, and a hydrogel polymer was taken out. Further, the obtained hydrogel polymer was pulverized and treated in the same manner as in Example 1.
After classification, an irregularly crushed water-absorbent resin precursor (f) was obtained. The bulk specific gravity of the water absorbent resin precursor (f) is 0.67 g.
/ Ml, the solid content was 97% by weight, the absorption capacity under no pressure when absorbing physiological saline was 38 g / g, and the amount of water-soluble components was 14% by weight.

To 100 parts by weight (70 ° C.) of the obtained water-absorbent resin precursor (f), 0.5 part by weight of 1,4-butanediol, 0.5 part by weight of propylene glycol and 4.0 parts by weight of water were added. (35 ° C.) was mixed. The mixture was heat-treated at 199 ° C. for 30 minutes to obtain a water-absorbent resin (6). The weight average particle size of the obtained water absorbent resin (6) was 550 μm. In addition, the particle size
The amount of water-absorbent resin less than m was 1% by weight. Table 1 shows the results of the absorption capacity under no pressure, the absorption capacity under pressure, the amount of water-soluble components, the weight average particle size, and the airflow resistance of the water absorbent resin (6).

Example 4 A water-absorbent resin (7) was obtained by mixing 0.01 part by weight of silicon dioxide with 100 parts by weight of the water-absorbent resin (1) obtained in Example 1. Absorption capacity under no pressure, absorption capacity under pressure,
Table 1 shows the results of the water-soluble component amount, the weight average particle size, and the airflow resistance.

[0162]

[Table 1]

Example 5 75 parts by weight of the absorbent resin (1) obtained in Example 1 and 25 parts by weight of ground wood pulp were dry-mixed using a mixer. Next, the obtained mixture was air-formed on a wire screen formed into 400 mesh (having an opening of 38 μm) using a batch-type air-paper-making apparatus to obtain 120 mm × 350 mm.
It was formed into a web having a size of mm. Further, the web was pressed at a pressure of 2 kg / cm ² (196 kPa) for 5 seconds to obtain an absorbent (1) having a basis weight of about 500 g / cm ² . Further, an absorbent article (1) (paper diaper) was prepared using the absorbent (1) as described above. The weight of the absorbent article (1) was 44 g.

Tables 2 and 3 show the measurement results of the airflow resistance, absorption capacity under pressure, and return amount of the absorbent (1), the humidity inside the absorbent article (1), and the humidity inside the absorbent article. Table 2 shows the evaluation results of the comfort.

Example 6 The procedure of Example 5 was repeated, except that the water absorbent resin (2) obtained in Example 2 was used instead of the water absorbent resin (1). Body (2) was obtained, and subsequently an absorbent article (2) was prepared in the same manner. The weight of the absorbent article (2) was 44 g.

In the same manner as in Example 5, the measurement of the ventilation resistance, absorption capacity under load, and return amount of the absorbent (2), humidity in the mounting of the absorbent article (2), and comfort in the mounting by the monitor were performed in the same manner as in Example 5. Was evaluated, and the results are shown in Table 2.

Comparative Example 4 The procedure of Example 5 was repeated, except that the water-absorbent resin (3) obtained in Comparative Example 1 was used instead of the water-absorbent resin (1). Body (3) was obtained, and subsequently an absorbent article (3) was prepared in the same manner. The weight of the absorbent article (3) was 44 g.

The same operation as in Example 5 was carried out to measure the airflow resistance, absorption capacity under pressure, return amount of the absorbent (3), the humidity in the mounting of the absorbent article (3), and the comfort in the mounting by the monitor. Was evaluated, and the results are shown in Table 2.

Comparative Example 5 The procedure of Example 5 was repeated, except that the water-absorbent resin (4) obtained in Comparative Example 2 was used instead of the water-absorbent resin (1). The body (4) was obtained, and subsequently, an absorbent article (4) was similarly prepared. The weight of this absorbent article (4) was 44 g.

In the same manner as in Example 5, the measurement of the ventilation resistance, absorption capacity under load, return amount of the absorbent (4), the humidity in the mounting of the absorbent article (4), and the comfort in the mounting by the monitor were performed in the same manner as in Example 5. Was evaluated, and the results are shown in Table 2.

Comparative Example 6 The procedure of Example 5 was repeated, except that the water-absorbent resin (5) obtained in Comparative Example 3 was used instead of the water-absorbent resin (1). The body (5) was obtained, and subsequently, an absorbent article (5) was similarly prepared. The weight of the absorbent article (5) was 44 g.

In the same manner as in Example 5, measurement of the ventilation resistance, absorption capacity under load, and return amount of the absorbent (5), humidity in the mounting of the absorbent article (5), and comfort in the mounting by the monitor were performed. Was evaluated, and the results are shown in Table 2.

Example 7 The procedure of Example 5 was repeated, except that the water-absorbent resin (6) obtained in Example 3 was used instead of the water-absorbent resin (1). The body (6) was obtained, and subsequently, an absorbent article (6) was similarly prepared. The weight of this absorbent article (6) was 44 g.

In the same manner as in Example 5, the measurement of the ventilation resistance, absorption capacity under pressure, and the amount of return of the absorbent (6), humidity in the mounting of the absorbent article (6), and comfort in the mounting by the monitor were performed in the same manner as in Example 5. Was evaluated, and the results are shown in Table 2.

Example 8 The procedure of Example 5 was repeated, except that the water-absorbent resin (7) obtained in Example 4 was used instead of the water-absorbent resin (1). The body (7) was obtained, and subsequently, an absorbent article (7) was prepared in the same manner. The weight of the absorbent article (7) was 44 g.

In the same manner as in Example 5, the measurement of the ventilation resistance, absorption capacity under pressure, and the amount of return of the absorbent (7), the humidity in the mounting of the absorbent article (7), and the comfort in the mounting by the monitor were carried out. Was evaluated, and the results are shown in Table 2.

[0177]

[Table 2]

[Comparative Water Absorbent Resin and Comparative Absorbent] 10
Absorbents were taken out of various types of commercially available absorbent articles (paper diapers), and used as comparative absorbents in Comparative Examples 17 to 26 described later. Further, the water-absorbing resins used in these absorbers were separated from each other, and used as comparative water-absorbing resins in Comparative Examples 7 to 16 described below. For each comparative water-absorbent resin and comparative absorbent, Table 3 shows the brand name of the commercially available absorbent article from which the article was derived, the manufacturer and the nationality of the absorbent article, and the date of acquisition of the absorbent article. .

[0179]

[Table 3]

[Comparative Examples 7 to 16] Except that the above ten kinds of comparative water absorbent resins were used, the same operation as in Example 1 was carried out, and the absorbency under no pressure and the absorbency under pressure of each comparative water absorbent resin were used. , The amount of water-soluble components, the weight average particle size, and the airflow resistance were measured. The results are shown in Table 4.

[0181]

[Table 4]

[Comparative Examples 17 to 26] The measurement of the air flow resistance, the absorption capacity under pressure, and the return amount of each of the above-mentioned absorbers was performed in the same manner as in Example 5 except that the above-mentioned ten types of comparative absorbers were used. went. Further, a comparative absorbent article was prepared again from each comparative absorbent in the same manner as in Example 5, and the humidity in the mounting of each comparative absorbent article and the comfort in the mounting were evaluated by a monitor. Table 5 shows the results. Table 5 also shows the airflow resistance of the liquid impermeable sheet (backsheet) provided in each of the commercially available absorbent articles.

[0183]

[Table 5]

As shown in the above tables, in the case of the water-absorbent resin, the absorbent and the absorbent article deviating from the parameters specified in the present invention, the absorption capacity under pressure is increased to reduce the amount of return (stickiness). A sense of avoidance)
Although it is not possible to simultaneously achieve both the problem of increasing the air permeability of the absorber itself (avoiding the feeling of stuffiness), the absorbent, the absorbent article, and the water-absorbent resin according to the present invention have the above-mentioned problems.
Both problems can be realized at the same time. As a result, the comfort at the time of wearing in the absorbent article can be further improved.

[0185]

As described above, the absorber according to the present invention has a structure having at least sufficient air permeability even in a wet state and an absorbency against pressure. Further, the absorbent article according to the present invention uses the absorbent having the above-described configuration. Furthermore, the water-absorbent resin according to the present invention has low airflow resistance, has sufficient absorption capacity under no pressure and absorption capacity under pressure, and has a weight-average particle size of not less than a predetermined value or an amount of a water-soluble component. It is below a predetermined amount.

Therefore, according to the structure of the present invention, even if the absorbent absorbs an aqueous liquid such as a body fluid, the absorbent can secure sufficient air permeability, and the absorbed aqueous liquid can be removed under pressure. It can be secured enough. Therefore, it is possible to prevent the absorber from being airtight, to prevent a high humidity environment from being formed between the body and the absorber or the absorbent article, and to avoid an increase in the amount of return.

As a result, for example, when the absorbent article is a disposable diaper, for example, the user does not feel any discomfort such as stuffiness or stickiness, and can maintain a dry feeling. The effect that the comfort at the time of wearing can be further improved.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view showing a configuration of a measuring device used for an absorption capacity under pressure, which is one of the properties exhibited by a water absorbent resin and an absorbent according to the present invention.

FIG. 2 is a schematic cross-sectional view showing the configuration of a measuring device used for measuring airflow resistance, which is one of the properties exhibited by the absorbent and the water absorbent resin according to the present invention.

FIG. 3 is a schematic sectional view showing a configuration of a measuring device used for measuring an absorption capacity under pressure, which is one of the performances of the absorbent article according to the present invention.

FIG. 4 is a schematic cross-sectional view showing a configuration of a measuring unit in the measuring device shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Balance 2 Container 3 External air suction pipe 4 Pipe 5 Measurement part 11 Water-absorbing resin 12 Physiological saline 13 Absorber 21 Air permeability tester 22 Cell part 23 Cell set 35 Measurement part

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) A61L 15/60 (72) Inventor Ishi ▲ Saki ▼ Kunihiko 992 Nishioki, Akihama-ku, Aboshi-ku, Himeji-shi, Hyogo 1 Co., Ltd. F term in Nippon Shokubai (reference) 3B029 BA04 BA15 BA17 4C003 AA23 CA06 GA02 4C098 AA09 CC02 CC10 DD01 DD24 DD25 DD26 DD27 DD28 DD30

Claims (5)

[Claims] (1) 2.0 KP when physiological saline is absorbed
the absorption capacity under pressure at a is 24 g / g or more, and
An absorbent body, wherein a ventilation resistance under a pressure of 4.9 kPa in a wet state is 50 kPa · sec / m or less. 2. An absorbent layer comprising the absorbent according to claim 1, a liquid permeable sheet, and a gas flow resistance of 1 kPa · sec /.
a liquid-impervious sheet in a range of not less than m and not more than 50 kPa · sec / m, wherein the absorbent layer is disposed between the two sheets. 3. The air flow resistance under pressure at 4.9 kPa in a wet state is 250 kPa · sec / m or less, and the absorption capacity under no pressure when absorbing physiological saline is 32 g / m 2.
g or more and when physiological saline is absorbed.
A water-absorbent resin having an absorption capacity under pressure at 0 kPa of 32 g / g or more and having a particle shape with a weight average particle size of 430 μm or more. 4. An air-flow resistance under a pressure of 4.9 kPa in a wet state is 250 kPa · sec / m or less, and an absorption capacity under a non-pressure when absorbing physiological saline is 34 g / cm 2.
g, and the amount of water-soluble component is 18% by weight or less. 5. An airflow resistance under a pressure of 4.9 kPa in a wet state is not more than 250 kPa · sec / m, and an absorption capacity under a pressure of 2.0 kPa when a physiological saline solution is absorbed is 34 g / g. And the amount of water-soluble components is 18
A water-absorbing resin, which is not more than weight%.