JPH07112129A - Absorbing article - Google Patents

Abstract

PURPOSE:To obtain a compact thin absorbing article having satisfactory absorbing characteristics, not causing the transfer of a water absorbing polymer, ensuring softness even when a large amt. of the water absorbing polymer is contained and excellent in profitableness. CONSTITUTION:Hydrous gelatinous crosslinked polymer particles of 10-1,000mum average size obtd. by polymn. are disposed as an absorbent without drying to <=20wt.% water content after polymn. to obtain the objective absorbing article.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an absorbent article containing a water-absorbing polymer. More specifically, absorption amount, absorption speed,
Hygienic and medical products such as sanitary napkins, disposable diapers, etc. that are highly safe and extremely energy-saving, keep freshness of vegetables and meat, or agricultural and forestry fields such as drip absorption sheets. In addition, the present invention relates to an absorbent article that can be suitably used in a field requiring water retention.

[0002]

2. Description of the Related Art Conventionally, water-absorbent polymers have been widely used as absorbent materials for absorbent articles such as sanitary napkins or disposable diapers. As the water-absorbent polymer, for example,
Polyacrylic acid (salt) crosslinked polymer, saponified product of acrylic ester-vinyl acetate copolymer, crosslinked polyvinyl alcohol modified product, crosslinked isobutylene-maleic anhydride copolymer, starch-hydrolyzate of acrylonitrile graft polymer, Starch-acrylic acid (salt) graft polymers and the like are known. These are usually used in the form of dry particles having a particle size of 1000 to 10 microns. Therefore, application of water-absorbing polymers to these absorbent articles often involves
There was a problem that a special granulating device was required because it was used as a sandwich with paper or mixed with pulp, and that the working environment was deteriorated due to the scattering of fine powder during granulation.

As an absorbent article using water-absorbing polymer particles as an absorbent material, various application of water-absorbing polymer particles is known. For example, Japanese Patent Publication No. 57-56561 discloses an absorbent material containing dried water-absorbing polymer particles. In Japanese Patent Laid-Open No. 59-204956, 1
An absorbent structure is disclosed which comprises a compressed mixture of dried water-absorbing polymer particles having a water content of up to 0% by weight and ground pulp. JP-A-57-73051 discloses an immobilized absorbent composition comprising liquid polyhydroxy compound and dry water-absorbing polymer particles. JP-A-5
6-131683 and JP-A-58-131133 disclose absorbent articles obtained by softening dry water-absorbing polymer particles with water, applying the particles to a substrate and then drying. Japanese Unexamined Patent Publication No. 1-230671 discloses a water-absorbing substance comprising a mixture of dry water-absorbing polymer particles and an aqueous liquid. Furthermore, JP-A-4-236203
Japanese Patent Publication discloses an absorbent article containing a sheet-like hydrogel obtained by polymerization.

[0004]

However, the absorbent articles known so far have some problems. For example, when focusing on the dried water-absorbing polymer that constitutes the main component of the absorbent material of these absorbent articles, the water-absorbing cross-linked polymer obtained by polymerizing an aqueous liquid of a monomer that can be converted into a water-absorbing polymer by polymerization. A step of drying the combined hydrous material to 20% or less, which is a water content range that can be handled as a powder, and a crushing or crushing step for forming powder particles are indispensable, and a large amount of energy is required for that. The water-absorbing polymer obtained is not only costly, but also has a water content of 20.
In some cases, the deterioration of the polymer inevitably occurs in the drying step of reducing the content to less than 100%, and the amount of soluble components in the polymer increases, which is not preferable in terms of various absorption characteristics.

On the other hand, when an absorbent article containing a dried water-absorbent polymer is focused on, it is difficult to insert the dried water-absorbent polymer into the intended absorbent article, which is unfavorable in working environment. It is necessary to have a process and an apparatus for handling the water-soluble polymer particles, and to fix the dried water-absorbing polymer particles as an absorbent in the absorbent article, a process such as softening / drying with water or compression is required. Further, the complexity of the process of obtaining the absorbent article and the device due to the necessity has not been solved. Japanese Unexamined Patent Publication (Kokai) No. 4-236203 suggests, as a method for solving these problems, to directly insert a sheet-like water-containing gel-like water-absorbing crosslinked polymer obtained under specific polymerization conditions into an absorbent article. However, the sheet-like water-containing gel-like water-absorbing cross-linked polymer has a smaller surface area than the powder-like water-absorbing cross-linked polymers known so far, and therefore has a low absorption rate and a large surface area. Requires a molding operation into a film shape or the like. Liquid transfer space between water-absorbing polymers that have swollen even if they are film-formed,
Due to the lack of the swelling permissible space, the absorption amount and the absorption speed of the obtained absorbent article were insufficient, and it was not satisfactory in terms of flexibility. Therefore, it has good absorption characteristics, is compact and thin, and there is no migration of the water-absorbent polymer, even if a large amount of the water-absorbent polymer is contained in the absorbent material,
At present, there is a demand in the market for absorbent articles that are both flexible and economical.

[0006]

Means and Actions for Solving the Problems The present inventors have
As a result of intensive studies to solve the above problems, it was found that an absorbent article in which hydrous cross-linked polymer particles having a specific average size are directly arranged is extremely superior to conventional ones in terms of various absorption characteristics and economy. The present invention has been reached. That is, the present invention relates to an absorbent article containing a water-absorbent polymer as at least one absorbent material, wherein the water-absorbent polymer has a water content of 10 to 1000 microns on average and is obtained by polymerization of a water-soluble ethylenically unsaturated monomer. The absorbent article is characterized in that the gelled crosslinked polymer particles are directly arranged after the polymerization so as to have a water content of 20% by weight or less without drying treatment. The present invention further relates to an absorbent article comprising a water-absorbent polymer layer as at least one absorbent material, wherein the water-absorbent polymer has an average size of 10 to 1000 microns obtained by polymerization of a water-soluble ethylenically unsaturated monomer. The present invention also provides an absorbent article characterized in that the hydrous gel-like crosslinked polymer particles are directly arranged after being coagulated and molded to have a water content of 20% by weight or less after polymerization. .

The present invention will be described in detail below.

The water-absorbent polymer constituting the absorbent material of the absorbent article of the present invention is composed of hydrous gel-like cross-linked polymer particles obtained by polymerizing a water-soluble ethylenically unsaturated monomer. The particles in the present invention mean that the hydrogel crosslinked polymers obtained by the polymerization exist in the form of independent units. The preferred shape is irregular or spherical. The hydrogel crosslinked polymer particles in the present invention are required to have an average size in a specific range, and the range is 10 to 1000 microns.
If the size of the particles is larger than this range, the flexibility and absorption speed of the resulting absorbent article will be reduced. On the other hand, if the particle size is smaller than this range, the absorption amount and absorption speed of the resulting absorbent article are reduced, which is not preferable. The preferred average size is in the range 100-800 microns.

Further, an agglomerate molded article obtained by agglomerating and molding the water-containing gel-like crosslinked polymer particles originally existing in the state of particles to a water content of 20% by weight or less without drying treatment is originally obtained. Without losing the absorption properties the particles had
Since the hydrous gel-like cross-linked polymer particles can be handled as a molded body that is easier to handle, the present invention can provide a more preferable absorbent article.

In the absorbent article of the present invention, the water-containing gel-like cross-linked polymer particles obtained by polymerization have a water content of 2 after polymerization.
It is characterized in that it is directly arranged as a water-absorbing cross-linked polymer that constitutes an absorbent material, without being subjected to a drying treatment to 0% by weight or less. That is, the absorbent article of the present invention is a particulate material obtained in the polymerization step without passing through the drying step, which has heretofore been considered to be an essential step for synthesizing the water-absorbing polymer, and the crushing or crushing step after drying. The water-containing gel-like cross-linked polymer of, without undergoing an intentional drying step for pulverizing or pulverizing the dried product,
The present invention provides an absorbent article directly applied as a constituent material of an absorbent material.

In the present invention, the term "hydrogel-like" means a state in which a crosslinked hydrophilic polymer absorbs an aqueous liquid and swells. Usually, the water-absorbent polymer has a water content of about 20 to 30 relative to the total weight of the water-containing gel-like polymer containing water.
It becomes gel-like in a region higher than around the weight%.
When the water content is 20% by weight or less, the water-absorbent polymer becomes brittle or hard, so that it is necessary to reinforce its strength and flexibility in order to use it as an absorbent in an absorbent article.
In addition, the amount of soluble components in the water-absorbent polymer may increase by performing the drying treatment to a water content of 20% by weight or less. Further, in this case, much energy and time are required as compared with drying up to a water content of 20% by weight. Therefore, in the present invention, the hydrogel-like crosslinked polymer particles obtained by the polymerization must be placed in the absorbent article after the polymerization without being dried to reduce the water content to 20% by weight or less. The preferred water content is in the range of 30 to 70% by weight.

The hydrogel-like crosslinked polymer particles of the present invention are irradiated with active energy rays before being directly placed in an absorbent article, thereby dramatically improving the polymerization rate in the hydrogel-like crosslinked polymer. In addition to being able to do so, the amount of soluble components in the hydrogel crosslinked polymer can be reduced, so that a more preferable absorbent article can be provided in terms of safety.

Further, the water-containing gel-like crosslinked polymer particles of the present invention are subjected to coagulation molding and then irradiated with active energy, so that in addition to the effect of irradiation in the above-mentioned particle state, they are flexible and have shape retention before and after liquid absorption. It is possible to provide a water-absorbing polymer having excellent properties in an absorbent article. That is, the molded body that has been subjected to coagulation molding and then irradiated with active energy rays can be given a property of expanding into a substantially similar shape to the shape before absorbing when swelling with liquid absorption. This makes it possible to fix the water-absorbent polymer constituting the absorbent material in the absorbent article at a desired position even after absorbing the liquid. Therefore, it is possible to provide an absorbent article in which the water-absorbent polymer is provided in the absorbent material at an unprecedentedly high concentration.

Examples of the water-soluble ethylenically unsaturated monomer that can be used in the present invention include (meth) acrylic acid, (anhydrous) maleic acid, fumaric acid, crotonic acid, itaconic acid,
Anionic unsaturated monomer such as 2- (meth) acryloylethanesulfonic acid, 2- (meth) acryloylpropanesulfonic acid, 2- (meth) acrylamido-2-methylpropanesulfonic acid, vinylsulfonic acid, styrenesulfonic acid Body and its salts; (meth) acrylamide, N-substituted (meth) acrylamide, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, methoxypolyethylene glycol (meth)
Nonionic hydrophilic group-containing unsaturated monomers such as acrylate and polyethylene glycol (meth) acrylate;
N, N-dimethylaminoethyl (meth) acrylate,
N, N-dimethylaminopropyl (meth) acrylate
Specific examples thereof include amino group-containing unsaturated monomers such as ginseng, N, N-dimethylaminopropyl (meth) acrylamide, and their quaternized products. The amount of the hydrogel-like crosslinked polymer to be obtained does not extremely hinder the hydrophilicity, for example, methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate and the like. Hydrophobic monomers such as acrylic acid esters, vinyl acetate and vinyl propionate may be used. As the water-soluble ethylenically unsaturated monomer component, one kind or two or more kinds can be selected from these and used. Considering various water absorption characteristics of the water-absorbing crosslinked polymer obtained by the polymerization, (Meth) acrylic acid (salt), 2- (meth) acryloylethanesulfonic acid (salt), 2- (meth) acrylamido-2-methylpropanesulfonic acid (salt), (meth)
1 selected from acrylamide, methoxypolyethylene glycol (meth) acrylate, N, N-dimethylaminoethyl (meth) acrylate or a quaternary compound thereof.
One or more kinds are preferable, and one containing acrylic acid or an acrylic acid salt as a main component is more preferable. More preferably, 30 to 90 mol% of acrylic acid is a monomer neutralized with a basic substance.

The water-containing gel-like crosslinked polymer of the present invention can be treated as particles if the various properties of the water-absorbent cross-linked polymer to be obtained can meet desired criteria. If possible, it may be a self-crosslinking type obtained without using a crosslinking agent or a self-crosslinking type obtained using a crosslinking agent. When the hydrogel-like crosslinked polymer obtained by the polymerization does not have a crosslinked structure, it is difficult to apply it to the absorbent article of the present invention as particles, which is beyond the scope of the present invention. When a crosslinking agent is used, its amount is usually 0.001 to 5 mol% based on the monomer components,
It is preferably in the range of 0.01 to 1 mol%.

Examples of the cross-linking agent usable in the present invention include N, N'-methylenebis (meth) acrylamide,
(Poly) ethylene glycol di (meth) acrylate,
Glycerin tri (meth) acrylate, trimethylolpropane tri (meth) acrylate, triallylamine, triallyl cyanurate, triallyl isocyanurate, tetraallyloxyethane, pentaerythritol tetraacrylate, etc. Compounds having at least two unsaturated groups; Glycidyl (meth) acrylate, N-methylol (meth) acrylamide, etc., having at least one polymerizable unsaturated group, and a monomeric functional group A compound having at least one group capable of reacting with a group; polyvalent alcohol
, Diethanolamine, epichlorohydrin, ethylenediamine, polyethyleneimine, aluminum sulfate,
Specific examples thereof include compounds having at least two groups capable of reacting with functional groups of the same monomer, and among these, one or more kinds can be used in consideration of reactivity.

In obtaining the hydrogel crosslinked polymer particles, the above monomer components are polymerized in the presence of a hydrophilic polymer such as starch, cellulose, polyvinyl alcohol, polyoxyethylene, etc., if necessary. Can be made.
The amount of these hydrophilic polymers is usually 0 to 20%, preferably 0 to 10% based on the weight of the water-soluble ethylenically unsaturated monomer.
% Range.

In the present invention, the water-soluble ethylenically unsaturated monomer is specifically, so that the water content of the water-containing gel-like cross-linked polymer obtained by the polymerization is greater than 20% by weight for the above-mentioned reason. Polymerization is carried out in an aqueous liquid state in which the solid content concentration of the monomer is less than 80% by weight. The preferred polymerization concentration is in the range of 30 to 50% by weight. Examples of the method of initiating the polymerization include a method using a radical polymerization catalyst, a method of irradiating with radiation, ultraviolet rays, an electron beam and the like.
A method using a radical polymerization catalyst is simple and preferable. Examples of the radical polymerization catalyst used include peroxides, persulfates, hydroperoxides and azo compounds. Above all, a method of using a water-soluble radical polymerization initiator such as hydrogen peroxide, a persulfate or a water-soluble azo compound is preferable. These polymerization initiators can be used as a mixture of two or more kinds, and further, sulfite, ascorbic acid and the like can be added and used as a redox polymerization initiator. A known amount of the radical polymerization catalyst is used, but it is usually 0.00001 to the monomer component.
It is in the range of 5 mol%.

The polymerization method for obtaining the hydrogel-like crosslinked polymer in the present invention is not particularly limited, and a conventionally known method can be adopted. Therefore, in the present invention, for example, an aqueous solution polymerization method,
A method such as a reverse phase suspension polymerization method can be adopted. More specifically, JP-A-55-133413 and JP-A-57-3
4101, JP-A-60-55002, JP-A-59-38962, JP-A-57-34101, JP-A-56-131608, JP-A-53-53.
46389, JP-A-57-158209, etc., a method of aqueous solution polymerization in a mold, a method of aqueous solution polymerization while subdividing a hydrous gel polymer produced by the polymerization, an aqueous monomer solution. A polymerization method such as a method of suspending in a hydrophobic organic solvent in the presence of a dispersant to perform polymerization can be exemplified.
A preferred polymerization method is a method of polymerizing while subdividing the hydrogel crosslinked polymer by shearing force. As the polymerization method, either a batch method or a continuous method can be adopted.

The hydrogel-like cross-linked polymer obtained by the aqueous solution polymerization method may be in the form of lumps, and in order to obtain a particle size suitable for the present invention, a step of making fine particles after the polymerization may be necessary. . A conventionally known method can be adopted as a method for forming the hydrogel crosslinked polymer obtained by the polymerization into particles having a desired average size. For example, a method of applying a shearing force to the hydrogel cross-linked polymer to form it into particles can be mentioned. Specifically, the gel particle size control method utilizing a shearing force, which is disclosed in JP-A-5-11265 and JP-A-5-70597, can be adopted. Shearing force is applied to the water-containing gel-like cross-linked polymer, and as a specific device for forming into particles, screw type extruders such as meat chopper, pressure kneader, internal mixer,
A kneader such as a Banbury mixer can be exemplified.

After the polymerization, the water-containing gelled crosslinked polymer particles obtained by the polymerization may be adjusted for water content within a range in which the water content can be kept at 20% by weight or more. In this case, it is preferable that the water content is adjusted to be as uniform as possible. Therefore, preferable methods for adjusting the water content include, for example, microwave drying and hot air drying using relatively low temperature hot air having a high dew point. In this case, the water-containing gel-like cross-linked polymer particles are physically contacted with each other to form a desired shape, and the water content is adjusted by the above method without substantially applying an external force such as a shearing force. The crosslinked polymer particles can also be agglomerated into various shapes without losing their particle properties.

The coagulation molding in the present invention refers to a state in which a large number of originally independent particle-shaped hydrogel crosslinked polymers are physically brought into contact with each other to form an agglomerate. That is, instead of being in an agglomerated state via a third substance such as an adhesive or a fibrous base material, the hydrous gel-like crosslinked polymer particles are in direct contact with each other to form a continuous agglomerate. It is in the state of being formed. And since the coagulated molded article in the present invention is formed from a hydrogel crosslinked polymer having a specific average particle size, it has continuous pores through which liquid can pass between particles, and an integrally molded sheet. It is distinguished from the water-containing gel-like crosslinked polymer.

The method of agglomerating the hydrogel-like crosslinked polymer particles of the present invention is not particularly limited. For example, embossing,
Usual methods such as extrusion and rolling may be mentioned. Alternatively, a method of filling the water-containing gel polymer into a container, mold, bag or the like having a desired shape may be used. The fresh hydrous gel-like polymer obtained by polymerization usually has a temperature of about 40 to 90 ° C. due to the heat of polymerization, and aggregates can also be obtained by allowing these to cool in a stacked state. The shape of agglomeration molding can be arbitrarily selected according to the purpose of use of the resulting absorbent article. For example, a sheet shape, a tape shape, a mat shape, a rod shape, a string shape, a plate shape, a column shape, a spherical shape, an amorphous shape, or the like can be appropriately selected depending on the application and purpose. Also size, length,
There is no particular limitation on the width. In addition, it is also possible to use after being once coagulated and molded, cut into an arbitrary shape.

When the coagulated molded product is in the form of a sheet or a mat, which is the more preferred form of the present invention, for example, a support having a low adhesiveness to the hydrogel crosslinked polymer is selected. , Spraying hydrogel-like crosslinked polymer particles on a support that is transported in a certain direction, and spreading this while evenly spreading the particles, while the particles are in close contact with each other, the hydrogel-like crosslinked polymer particles on the support are Method of heating and drying with hot air, steam, heater, etc., method of dehydrating the hydrous gel-like polymer on the same support by immersing in a hydrophilic organic solvent, hydrous gel-like cross-linked polymer on the same support A high-frequency electric field to
The desired aggregated molded product can be obtained by a method such as dielectric heating and drying. At this time, if the adhesiveness between the support and the hydrogel crosslinked polymer is large, when the hydrogel crosslinked polymer loses water and contracts, a strain occurs in the hydrogel polymer in the surface state, and the hydrogel In some cases, the cohesion of the polymer particles becomes insufficient, and the strength of the resulting water-absorbent material may be reduced. Examples of the support having low adhesiveness to the hydrogel crosslinked polymer include a support whose surface is covered with a non-adhesive material such as a fluororesin.

A more preferable specific size of the coagulated molded article in the present invention is a sheet having at least a part of continuous cohesive surface, and preferably 5 cm ² on one side (front surface or back surface). Or more, more preferably 1
It has an area of 0 cm ² or more, and more preferably 15 cm ² or more. In this case, for example, the aggregation surface may be a surface having one or a plurality of through holes of any shape. It may be waved or pleated. Further, it may have a strip shape, a string shape, or a strip shape.

In the present invention, more preferably, the hydrogel-like crosslinked polymer particles are molded into a planar shape with the thickness regulated to about 0.3 to 20 mm. If the thickness is less than about 0.3 mm, the strength of the resulting water-absorbent material will be low and the handleability will be poor. On the other hand, when the thickness exceeds 20 mm, the resulting water-absorbent polymer becomes thick, which may be unfavorable as a water-absorbent polymer for providing a compact and thin absorbent article for the purpose of the present invention.

The thus obtained coagulated molded article composed of the hydrogel-like cross-linked polymer particles has flexibility by itself because it is in the hydrogel state. A plasticizer may be added in order to further increase the temperature. Examples of suitable plasticizers include polyhydric alcohols such as glycerin, ethylene glycol, polyethylene glycol and polyvinyl alcohol. The plasticizer is in a solution state, for example, with respect to the hydrogel crosslinked polymer particles,
It can be added by various methods such as spraying, coating and dipping before and after the coagulation molding step. The amount of the plasticizer used is preferably in the range of 0.01 to 100 parts by weight with respect to 100 parts by weight of the water-absorbing crosslinked polymer.

Various surfactants and inorganic or organic fine particles may be added to the hydrogel crosslinked polymer particles for the purpose of improving the absorption characteristics. These auxiliary components may act to increase the water absorption rate of the resulting absorbent article, or may act to facilitate the molding of the hydrogel polymer. For example, as the surfactant, polyoxyethylene alkyl ether, polyoxyethylene alkylphenol ether, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene acyl ester, oxyethyleneoxypropylene block copolymer, sucrose fatty acid ester Etc. can be mentioned. The water-insoluble inorganic fine particles include mica, pyrophyllite, kaolinite, halcite, and other similar clay minerals and Aerosil 200 (manufactured by Nippon Aerosil Co., Ltd.) mainly composed of silicon dioxide particles having an average particle size of 50 μm or less. ) And Carplex # 80 (manufactured by Shionogi Co., Ltd.). Examples of the water-insoluble organic fine particles include carbon black, activated carbon and pulp powder. Among them, fine particle silica is preferable because it has a large effect of increasing the water absorption rate. The amount of these auxiliary components used is 0.1 to 10 parts by weight, preferably 0.5 to 5 parts by weight, based on 100 parts by weight of the hydrous gel-like crosslinked polymer particles.

In the present invention, the active energy rays with which the hydrogel crosslinked polymer particles are irradiated are ultraviolet rays, electron beams,
It has high energy such as radiation. Among them, those having high permeability are preferable, and electron beams and gamma rays are preferable. In the present invention, the absorbed dose of the active energy ray irradiated to the water-containing gel-like crosslinked polymer particles varies depending on the water content of the water-containing gel-like crosslinked polymer, the type of the polymer, or the irradiation atmosphere, but generally 1 to 1000kG
The range is y, preferably 10 to 500 kGy. If the absorbed dose exceeds 1000 kGy, the absorption amount of the obtained absorbent article may become too small, and 1 kG
If the absorbed dose is less than y, the absorption rate of the resulting absorbent article and the shape retention of the water-absorbent polymer after liquid absorption may not be improved. The absorbent article of the present invention comprises the above-mentioned hydrogel crosslinked polymer in the form of particles or in the form of an aggregated molded article,
The water-absorbent polymer constituting at least a part of the absorbent is directly placed after polymerization, but in this case, it may be arranged in combination with another absorbent known as an absorbent. Other absorbent materials include, for example, wood pulp, cotton,
Examples include natural or semi-synthetic and synthetic fibers such as wool, rayon, vinylon, acetate, polyethylene, polypropylene; webs, woven fabrics and nonwoven fabrics using these fibers; crepe paper, tissues and the like. As a combination method, a method conventionally known for combination with powdery water-absorbent polymer particles, that is, a method such as mixing or sandwiching can be adopted.

At least one of the absorbent materials obtained by the above method or structure is covered with a liquid-permeable sheet to obtain the absorbent article of the present invention. As a liquid permeable sheet,
For example, synthetic resin films, non-woven fabrics, papers and the like having pores may be used, and knitted fabrics, woven fabrics, nets and the like made of natural fibers or synthetic resins may also be used. Examples of the liquid impermeable sheet include polyethylene film, polypropylene film, polyester film, nylon film, and the like, and examples of the material of the nonwoven fabric include rayon, polyethylene, polypropylene, polyester, and the like.

As an example of the production of an absorbent article, an absorbent material is sandwiched between a liquid-permeable sheet and a liquid-permeable sheet, or a liquid-permeable sheet and a liquid-impermeable sheet, and the periphery thereof is bonded with an adhesive. They may be bonded, or each material may be selected and bonded by a known method such as heat sealing or ultrasonic bonding.

The absorbent article of the present invention thus obtained is thinner and more compact than the conventional absorbent article containing the powdery water-absorbing polymer, but exhibits an absorption performance equal to or higher than the conventional one. Is.

In the absorbent article of the present invention, since the water-absorbing crosslinked polymer is in the form of a hydrogel and is directly placed after the polymerization, it has a good water-absorbing property (water-absorption rate and water-absorption amount). It can be immobilized at a desired position in an absorbent article, and at a relatively low concentration in a fibrous matrix, like a water absorbent article using conventional water absorbent polymer particles to prevent gel blocking. The hydrogel-like crosslinked polymer particles can be incorporated into the absorbent article at a relatively high concentration without the need for incorporation. The absorbent article of the present invention makes it possible to make a water absorbent article in which about 40 to 100% by weight of the water absorbent polymer is arranged based on the total weight of the absorbent material in the absorbent article. The preferred amount of water-absorbing polymer in the absorbent is about 5
The water absorbing polymer content is 0 to 100% by weight, more preferably about 60 to 100% by weight. Even when an absorbent article having such a high polymer concentration is prepared, the absorbent article of the present invention can be used in the absorbent article manufacturing process, the packaging step and the transportation step, so that the water-absorbent polymer migrates and the water-absorbent weight in the absorbent article. There is no coalescence spill. In addition, there is no dust.

The obtained absorbent article of the present invention is suitable for absorbing many fluids such as body fluids such as urine and menstrual blood, meat, fish or juice of foods such as fruits and vegetables, and diapers, Incontinence products, products such as bed pads, sanitary napkins, sanitary products such as tampons and towels, bandages,
It can be applied to products such as food freshness keeping sheets.

[0035]

The absorbent article of the present invention has large flexibility,
It has good water absorption (water absorption rate and water absorption amount), is excellent in fixing the water-absorbent polymer before and after liquid absorption, and has little residual monomer and soluble components in the water-absorbent polymer. Therefore, it can be used for various purposes for absorbing or absorbing water. Examples thereof include sanitary materials, dew-condensation absorbent sheets, water retaining sheets for agriculture, waterproofing agents for civil engineering, medical sheets, freshness-retaining agents for foods, drip absorbents for foods, and water-absorbing agents for miscellaneous goods. In addition, during the production of the absorbent article and when used for these purposes, dust is not generated and the environment is not polluted. It is thin and compact while having the same or better absorption characteristics than conventional absorbent articles. In addition, it has characteristics that it is highly flexible, fits well to the object of use, and is easy to use.

[0036]

EXAMPLES The structure and manufacturing method of the absorbent article of the present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto. Parts and% in the examples and comparative examples are parts by weight.

The average size of the water-containing gelled crosslinked polymer particles, the water content, and the absorption amount of the absorbent article in the present invention,
The absorption rate and the flexibility were measured by the following methods.

[1]: Average size of hydrogel-like crosslinked polymer particles Sampled hydrogel-like crosslinked polymer particles (solid content α
Wt%) 25 g, 20 wt% sodium chloride aqueous solution 1
Put in 200g, stirrer chip 300rpm
Rotate and stir for 60 minutes. After stirring, sieve (opening 2000 micron, 850 micron, 60 micron, 30 micron, 150 micron, 75 micron,
And 45 μm), the dispersion was charged, and 6000 g of a 20 wt% sodium chloride aqueous solution was slowly poured from the top of the sieve to classify the hydrous gel-like crosslinked polymer particles. The classified hydrogel-like crosslinked polymer particles on each sieve were thoroughly drained and then weighed. The sieve opening is the sieve opening R corresponding to the solid content α% by weight of the hydrogel-like crosslinked polymer particles according to the following formula 1.
Converted to (α). The particle size distribution of the hydrous gel-like crosslinked polymer particles corresponding to the solid content α% by weight was plotted on a logarithmic probability paper.
From the obtained graph, the sieve opening was read so that the proportion on the sieve was 50% by weight, and this was taken as the average size of the sample.

[0039]

[Equation 1]

R (α): Screen size of the sieve (micron) when converted to water-containing gelled crosslinked polymer particles having a solid content of α% by weight w: Total weight of water-containing gelled polymer after classification and draining
(G) γ: mesh size of sieve obtained by classifying hydrogel-like crosslinked polymer particles swollen in 20% sodium chloride aqueous solution (micron) [2]: water content of hydrogel-like crosslinked polymer particles sampled hydrogel-like 5 g of the crosslinked polymer was spread on a petri dish and dried at 180 ° C. for 120 minutes. The water content of the hydrogel-like crosslinked polymer particles was determined according to the following mathematical formula 2.

[0041]

[Equation 2]

B1: Weight of the hydrogel crosslinked polymer after drying (g) (Example 1) Internal volume 75 liters, hydraulic pressure cover,
An aqueous solution of a monomer consisting of 70 mol% sodium acrylate and 30 mol% acrylic acid was added to a stainless steel mechanical pressure kneader (made by Kurimoto Steel Works) equipped with two Z-shaped blades, a jacket and a thermometer. 30 kg (monomer concentration 34% by weight) and 12.6 g of N, N'-methylenebisacrylamide (0.1% by mole of monomer) as a cross-linking agent were charged, and nitrogen gas was blown into the reaction system. Was replaced with nitrogen. Warm the jacket with warm water at 30 ° C
14 g of sodium persulfate and 0.6 g of L-ascorbic acid were added as a polymerization initiator while rotating and stirring at rpm. After 1 minute from the addition of the polymerization initiator, the polymerization starts,
After 2 minutes, the polymerization peak temperature of 82 ° C. was reached, and a particulate hydrogel polymer was obtained. The warm water temperature of the jacket is 7
The temperature was raised to 0 ° C., the hydraulic device was operated, and the pressure cover was lowered onto the hydrous gel polymer. The hydraulic pressure was adjusted so that a surface pressure of about 0.4 kg / cm ² was applied to the hydrogel polymer, and rotary stirring with a Z-type blade was continued for 20 minutes under the load. After the reaction was completed, hydrogel-like crosslinked polymer particles (1) were obtained. The obtained water-containing gelled crosslinked polymer particles (1) had an average size of 460 microns and a water content of 65% by weight.
Then, on a flat plate of polytetrafluoroethylene,
25 g of the hydrous gel-like cross-linked polymer particles (1) were spread out and coagulated and molded to a thickness of about 4 mm and a size of 100 × 100 mm. This was placed in a household microwave oven and partially dried for 5 minutes to obtain a sheet-shaped water-absorbing polymer (1A) in which hydrogel-like crosslinked polymer particles were aggregated. The water-absorbent polymer (1A) was sealed in a polyethylene bag and treated with a gamma irradiation device at an absorbed dose of 25 kGy. The water content of the obtained water-absorbent polymer (1B) after gamma-ray irradiation was 34% by weight, and it could be handled as an integrated sheet even when pulled by hand. Furthermore, the flexibility was large and the polymer did not fall off. The amount of soluble components of this product was as small as 0.6%, and the amount of unpolymerized monomer was 30%.
It was as low as ppm (versus water-absorbent polymer). Commercially available disposable diaper ping pong pants L size (Shiseido Co., Ltd.) waterproof material sheet made of polyethylene film is cut in the longitudinal direction to obtain an absorbent material made of powdery water-absorbent polymer, cotton-like pulp and water-absorbent paper. I removed it. The sheet-shaped water-absorbent polymer (1B) was incorporated into the chassis of the disposable diaper thus obtained, and the cut of the waterproof material sheet was closed with an adhesive tape to give an absorbent article (1) of the present invention. The obtained absorbent article (1) of the present invention was thin, supple and had a good feel. The obtained absorbent article (1) is
It is attached to a baby model equipped with a urinary tract based on an infant with a weight of 10 kg, and physiological saline is 60 ml / 10 sec.
Was discharged at a rate of. The same urination operation was performed every 30 minutes, and when the physiological saline absorbed until the physiological saline leaked from the absorbent article (1) was measured, the absorbent article (1) of the present invention showed 320 ml of physiological saline. Absorbed. Further, a sheet-shaped water-absorbing polymer (1B) inserted as an absorbent material
Absorbed physiological saline and expanded into a shape similar to the original shape, and maintained the sheet state even after absorbing the liquid.

Comparative Example 1 The hydrogel crosslinked polymer particles (1) obtained in Example 1 were dried in a hot air dryer at 150 ° C. until the water content became 5% by weight. Then, this was crushed and passed through a 20-mesh sieve to obtain a powdery dry water-absorbing polymer (soluble component amount 6%, unpolymerized monomer amount 400 ppm). This dry water-absorbent polymer particle 1
In the same manner as in Example 1, 7 g was inserted into a diaper to obtain a comparative absorbent article (1). When this was mounted on a baby model in the same manner as in the example and the amount of physiological saline absorbed was measured, the comparative absorbent article (1) absorbed only 200 ml of physiological saline and leaked.

Example 2 To 472 g of an aqueous solution of a monomer consisting of 25 mol% of acrylic acid and 75 mol% of sodium acrylate (concentration of monomer: 30% by weight) was added polyethylene glycol diacrylate (polyethylene) as a crosslinking agent. 0.39 g of the average degree of polymerization of glycol part 8) (0.2 mol% based on the monomer) and 0.19 g of sodium persulfate as a polymerization initiator were added, and the mixture was stirred and dissolved at room temperature. 20 with a reflux condenser whose system was previously replaced with nitrogen
A 00 ml flask was charged with 1000 ml of cyclohexane and 4 g of sorbitan monostearate, and the surfactant was dissolved at 40 to 45 ° C while stirring at 220 rpm.
Then, the above-mentioned aqueous monomer solution containing a polymerization initiator was added dropwise and suspended. When the bath temperature was raised and kept at 55 ° C., polymerization started, and after 10 minutes, the polymerization peak temperature of 72 ° C. was reached. Raise the bath temperature and keep the internal temperature at 70 ° C for 10
The reaction was carried out for 0 minutes. The suspension of the obtained polymer was filtered to obtain gelled crosslinked polymer particles (2). The average size of the resulting hydrogel-like crosslinked polymer particles (2) was 120 μm.
And the water content was 70% by weight. The amount of soluble components was 2%, and the residual amount of unpolymerized monomer was 300 ppm. 100 parts of the hydrogel-like crosslinked polymer particles (2) was mixed with 70 parts of crushed pulp in a kneader to obtain 20 g of the mixture.
The absorbent article (2) of the present invention was obtained by sandwiching between a polyethylene film having a size width of 10 cm and a length of 20 cm and a polypropylene nonwoven fabric, and heat-sealing the periphery. This was useful as a pet sheet.

Example 3 The hydrous gel-like cross-linked polymer particles (2) obtained in Example 2 were air-dried to a water content of 55% by weight, and then a gamma irradiation apparatus was used to obtain an absorbed dose of 100 kGy. Processed. The water-soluble polymer (2) obtained had an amount of soluble components of 0.3% and the amount of unpolymerized monomer remained was 60 ppm.
Met. The water-absorbent polymer (2) was sandwiched and integrated with a tissue paper and further enclosed in a bag made of polyethylene nonwoven fabric to obtain an absorbent article (3) of the present invention. When this was used as a meat drip absorbent, it showed a good drip absorbing capacity.

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Claims (5)

[Claims] 1. An absorbent article comprising a water-absorbent polymer as at least one absorbent material, wherein the water-absorbent polymer is a water-containing ethylenically unsaturated monomer obtained by polymerization of a water-soluble ethylenically unsaturated monomer and having an average size of 10 to 1000 μm. An absorbent article, characterized in that the gel-like crosslinked polymer particles are directly arranged after the polymerization so as to have a water content of 20% by weight or less without being dried. 2. The hydrogel crosslinked polymer particles are obtained by polymerizing an aqueous solution of a water-soluble ethylenically unsaturated monomer containing acrylic acid or an acrylate as a main component. Absorbent article. 3. The water-containing gel-like crosslinked polymer particles, after polymerization,
The absorbent article according to claim 1 or 2, which has been irradiated with active energy rays. 4. An absorbent article containing a water-absorbent polymer as at least one absorbent material, wherein the water-absorbent polymer is a water-containing polymer having an average size of 10 to 1000 microns obtained by polymerization of a water-soluble ethylenically unsaturated monomer. An absorbent article, characterized in that the gel-like cross-linked polymer particles are directly arranged after coagulation molding after the polymerization to a water content of 20% by weight or less without drying treatment. 5. The absorbent article according to claim 4, wherein the water-absorbent polymer is obtained by agglomerating hydrogel-like cross-linked polymer particles, further irradiating them with active energy rays, and directly arranging them.