JPH0794162B2 - Water absorbent sheet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a water absorbent sheet. More specifically, it relates to a novel water-absorbent sheet which can be easily attached to a place where a large amount of water or water vapor is likely to be generated and can absorb a large amount of water or water vapor, which is useful as, for example, a dew condensation preventing material.

[Conventional technology]

In recent years, anti-condensation paints using a water-absorbent polymer for the purpose of absorbing water or absorbing moisture such as dew condensation prevention have been known (Japanese Patent Laid-Open No. Sho 60-96).
57-27176). However, since such a dew condensation preventing coating is wet, it takes a lot of work to construct, and when a water-based coating is used, the water-absorbent polymer swells and is difficult to handle. In order to solve such a problem, a water-absorbent sheet has been proposed in which a dew condensation preventing coating is attached to a breathable sheet-shaped substrate and further provided with a back layer (Japanese Patent Publication No. 61-43193, JP-A No. 62-43193). 21140 gazette), these are made by a method of impregnating a fiber web with a coating in which fine powder of a water-absorbent polymer is dispersed or dissolved, so that the polymer easily falls off from the fiber web and has sufficient durability as a dew condensation preventing material. It wasn't. Although such a defect can be improved to some extent by using a binder or the like, when the water-absorbent polymer is covered with the binder or the like, the original performance of the water-absorbent polymer cannot be exhibited and the dew condensation preventing effect is lowered.
Further, when it swells due to water absorption or moisture absorption, the water-absorbent polymer is likely to drop off or move due to contact with other objects, and the fibrous web to which the water-absorbent polymer adheres easily separates from the back layer, which is not preferable.

On the other hand, a water-absorbent sheet formed by fixing a water-absorbent polymer to a fibrous web by polymerization of a water-soluble ethylenically unsaturated monomer forming the polymer and paper are laminated with a water-resistant resin barrier layer interposed therebetween to prevent dew condensation. A wall material has been proposed (JP-A-1-198943). This anti-condensation wall material prevents water from moving from the water-absorbent sheet to the paper by the water-resistant resin barrier layer so that it will not peel off from the wall, but when used in a high humidity atmosphere for a long time, it absorbs water. There is a problem in terms of durability such that the sheet swells and is easily peeled off from the water resistant resin barrier layer, which is also not preferable.

[Problems to be Solved by the Invention]

Therefore, an object of the present invention is a water-absorbent sheet that can be easily attached to a place where a large amount of water or water vapor is likely to be generated, and can absorb a large amount of water or water vapor. It is difficult to peel off afterwards, and there is no drop-off / movement / peeling of the water-absorbent polymer that forms the water-absorbent sheet after water absorption / moisture absorption. Therefore, for example, when used as a dew-prevention material, the anti-condensation effect lasts for a long time. It is to provide a water-absorbent sheet having excellent durability.

[Means for Solving the Problems]

The present inventors have conducted intensive studies to solve the above problems, and as a result, have found that the above problems can be solved by providing a specific pressure-sensitive adhesive layer on a fibrous web to which a water-absorbing polymer is attached, and the present invention has been completed. Came to do.

That is, the present invention provides a water-absorbent polymer on which a fibrous web is provided with a pressure-sensitive adhesive layer, wherein the pressure-sensitive adhesive layer contains a water-absorbent polymer and a crosslinking agent capable of reacting with the pressure-sensitive adhesive. Provide the seat.

The present invention will be described in detail below.

The water absorbent sheet of the present invention can be obtained, for example, by the following steps. However, the water absorbent sheet of the present invention,
It is not limited to those manufactured by such a process.

A water-soluble ethylenically unsaturated monomer that forms a water-absorbing polymer by polymerization (hereinafter, such monomer is referred to as monomer (a)) is attached to at least one side of the fibrous web.

The monomer (a) attached to the fibrous web is converted into a water-absorbing polymer by a known polymerization method to obtain a fibrous web on which the water-absorbing polymer is fixed.

Then, a pressure-sensitive adhesive layer containing a water-absorbing polymer and a cross-linking agent capable of reacting with the pressure-sensitive adhesive is formed on the surface of the fibrous web to which the water-absorbing polymer is attached to obtain the water-absorbing sheet of the present invention.

The fibrous web used in the present invention is not particularly limited as long as it is a breathable web, and a place where a water absorbent sheet is used.
It can be appropriately selected and used according to the conditions and purposes, and examples thereof include fiber webs such as papers, non-woven fabrics and woven fabrics made of fibers such as nylon, polyester, polyorphin, rayon, pulp and cellulose. The thickness of the fibrous web is not particularly limited, but is, for example, about 0.1 to 50 mm when the fibrous web is left standing on a flat surface with the upper surface open.

Examples of the monomer (a) include water-soluble ethylenically unsaturated monomers having a hydrophilic group such as a carboxyl group, a sulfonic acid group, an amide group, a hydroxyl group, a polyoxyalkylene group, and an amino group, and specifically, Acrylic acid,
Methacrylic acid, 2- (meth) acryloylethanesulfonic acid, 2- (meth) acryloylpropanesulfonic acid,
2- (meth) acrylamido-2-methylpropanesulfonic acid, vinylsulfonic acid, (meth) allylsulfonic acid, and their alkali metal salts or ammonium salts such as lithium, sodium and potassium, (meth) acrylamide, hydroxyethyl (Meth) acrylate,
Hydroxypropyl (meth) acrylate, polyethylene glycol mono (meth) acrylate, polypropylene glycol mono (meth) acrylate, methoxypolyethylene glycol mono (meth) acrylate, methoxypolypropylene glycol mono (meth) acrylate and the like can be mentioned. One kind or two or more kinds can be used. Among them, (meth) acrylic acid and its salt, 2- (meth) acryloylethanesulfonic acid and its salt, and 2- (meth) acrylamide-2 are preferable.
-At least one monomer selected from the group consisting of methylpropanesulfonic acid and its salts, and (meth) acrylamide. From the viewpoint of water absorption properties of the resulting water-absorbent sheet, acrylic acid and its alkali metal salt are particularly preferable, and acrylic acid and its alkali metal salt are preferably contained in an amount of 50 mol% or more.

In the present invention, a crosslinking agent can be used when the monomer (a) is applied to the fiber web and polymerized (hereinafter, such a crosslinking agent is referred to as a crosslinking agent (A)). The use of the cross-linking agent (A) is preferable from the viewpoint of adjusting the water absorption capacity of the water-absorbent polymer and enhancing the durability of the water-absorbent polymer. Examples of the cross-linking agent (A) used include ethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, N, N'-methylenebis (meth) acrylamide, trimethylolpropane tri (meth) acrylate and the like. Functional ethylenically unsaturated monomers, ethylene glycol, polyethylene glycol, glycerin,
Examples thereof include compounds having two or more functional groups that react with a carboxyl group or a sulfonic acid group, such as ethylene glycol diglycidyl ether and polyethylene glycol diglycidyl ether.

The proportion of the monomer (a) and the cross-linking agent (A) used is, for example, 0.0
05 to 5 parts by weight. If it is out of this range, the water absorbing property of the resulting water absorbent sheet may deteriorate.

The monomer (a) and the crosslinking agent (A) are preferably used in the form of an aqueous solution. Generally, the solid content concentration of this aqueous solution is, for example, 30% by weight to a saturated concentration. If it is out of this range, the polymerizability of the monomer may be lowered, or the water absorption / moisture absorption properties of the resulting water absorbent sheet may be lowered.

As a method of applying the aqueous solution containing the monomer (a) and the cross-linking agent (A) to the fiber web, a known printing and printing method can be used. For example, a bar coater / kiss coater / gravure coater / squeeze coater / dip coater.・ Spray, brush coating, etc. can be mentioned.

The monomer (a) can be attached to the entire surface or a part of both surfaces or one surface of the fibrous web, or to the entire fibrous web. By coating the monomer (a) on only one surface of the fibrous web, it is possible to avoid direct contact of a person or thing with the water-absorbent polymer when the resulting water-absorbent sheet is attached to a wall or the like.

As one preferred embodiment of the present invention, a cross-linking agent capable of reacting with the water-absorbent polymer and the pressure-sensitive adhesive is attached to the polymer-adhered surface of the fibrous web having the water-absorbent polymer adhered on one side (hereinafter, such a cross-linking agent is referred to as a cross-linking agent (B The water-absorbent sheet provided with a pressure-sensitive adhesive layer containing)).

The amount of the aqueous monomer solution attached to the fibrous web is not particularly limited, but considering the water absorption properties and the hygroscopic properties of the resulting water absorbent sheet, 0.1 to 10 parts by weight of the water absorbent polymer after polymerization adheres to 1 part by weight of the fibrous web. It is preferable to attach the aqueous monomer solution so that When the amount of polymer is less than 0.1 parts by weight, the amount of water absorption or moisture absorption is small, and even when the amount of polymer exceeds 10 parts by weight, the amount of water absorption or moisture absorption does not increase so much, and the water absorption rate or moisture absorption rate decreases on the contrary. It is not preferable because there is.

As a method for polymerizing the monomer (a) attached to the fibrous web, a conventionally known method can be used. For example, a method of polymerizing a monomer by irradiating a fiber web to which a monomer is attached with an electron beam; a water-soluble solution such as persulfate, hydrogen peroxide, or 2,2'-azobis (2-amidinopropane) dihydrochloride. A method of sandwiching between polymerization-inert surfaces by the action of a radical polymerization initiator or performing thermal polymerization in an oven under a polymerization-inert atmosphere such as nitrogen gas or water vapor; between an oxidizing initiator and a reducing agent A method of polymerizing by action; a method of photopolymerizing by irradiation of ultraviolet rays by the action of a photopolymerization initiator; and the like.

Examples of the pressure-sensitive adhesive used in the present invention include acrylic pressure-sensitive adhesives. The pressure-sensitive adhesive may be either a water-soluble emulsion type or a solvent type, but the solvent type is preferable in terms of durability.

The acrylic solvent-based pressure-sensitive adhesive that can be used in the present invention is, for example, one or more (meth) acrylic acid alkyl ester having an alkyl group having 1 to 14 carbon atoms (this is the main component); An ethylenically unsaturated monomer having a functional group capable of reacting with the cross-linking agent (B) (hereinafter, such a monomer is referred to as a monomer (b)); and, if necessary, another ethylenically unsaturated monomer (hereinafter, referred to as a monomer). , A copolymer having a glass transition temperature of −20 ° C. or lower obtained by copolymerizing a monomer mixture containing such a monomer (which is referred to as a monomer (c)), and an organic solvent capable of dissolving or dispersing the copolymer. Solution or dispersion, any of which can be used in the present invention.

Examples of the (meth) acrylic acid alkyl ester having an alkyl group having 1 to 14 carbon atoms include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, and isopropyl (meth) acrylate. ,
Butyl (meth) acrylate, isobutyl (meth) acrylate, sec-butyl (meth) acrylate, tert-butyl (meth) acrylate, amyl (meth) acrylate, isoamyl (meth) acrylate, (meth) acrylic Hexyl acid, cyclohexyl (meth) acrylate, heptyl (meth) acrylate, octyl (meth) acrylate, isooctyl (meth) acrylate, 2- (meth) acrylic acid
Ethylhexyl, nonyl (meth) acrylate, (meth)
Isononyl acrylate, decyl (meth) acrylate,
Dodecyl (meth) acrylate and the like can be used alone or in combination of two or more.

As the functional group that the monomer (b) may have, any conventionally known functional group may be used as long as it is a functional group capable of reacting with the cross-linking agent (B), and among them, a preferable functional group is Examples thereof include a carboxyl group and a hydroxyl group. Examples of the ethylenically unsaturated monomer having such a functional group, that is, the monomer (b) include, for example, (meth) acrylic acid, itaconic acid, monoalkyl esters of itaconic acid, maleic acid, maleic anhydride, and maleic acid monoesters. Carboxyl group-containing ethylenically unsaturated monomers such as alkyl esters, fumaric acid, fumaric acid monoalkyl esters, acryloxypropionic acid, citraconic acid, citraconic acid monoalkyl esters, crotonic acid; hydroxyethyl (meth) acrylate, hydroxypropyl (Meth) acrylate, hydroxy (meth) acrylate modified with caprolactone, mono (meth) polyester diol obtained from fumaric acid and propylene glycol
Acrylate, mono (meth) acrylate of polyester diol obtained from phthalic acid and ethylene glycol, mono (meth) acrylate of polyester diol obtained from succinic acid and propylene glycol, of polyester diol obtained from succinic acid and ethylene glycol Examples thereof include hydroxyl group-containing ethylenically unsaturated monomers such as mono (meth) acrylate. Of these, one or more selected from (meth) acrylic acid, hydroxyethyl (meth) acrylate, and caprolactone-modified hydroxy (meth) acrylate are preferable.

Examples of the monomer (c) include aliphatic unsaturated hydrocarbons such as ethylene and butadiene; halogen-substituted aliphatic unsaturated hydrocarbons such as vinyl chloride; styrene and α-
Aromatic unsaturated hydrocarbons such as methylstyrene; Vinyl esters such as vinyl acetate; Vinyl ethers; Esters of allyl alcohol with various organic acids and esters with various alcohols; Unsaturated cyanide compounds such as acrylonitrile; Unsaturated amide compounds such as acrylamide; (meth) acrylic acid butoxyethyl ester, (meth) acrylic acid ethyl carbitol ester, (meth) acrylic acid methyl triglycol ester, (meth) acrylic acid dipropylene glycol methyl ether ester, (meth ) Acrylic acid aryl esters, various esters of unsaturated monobasic carboxylic acids such as methacrylic acid and crotonic acid, and various diesters of unsaturated dibasic carboxylic acids such as maleic acid and fumaric acid. One or two selected from It is possible to use the above.

The (meth) acrylic acid alkyl ester in which the alkyl group has 1 to 14 carbon atoms, the monomer (b), and the monomer (c) are not particularly limited in the proportion to be used. To the department
Monomer (b) 0.01 to 20 parts by weight, Monomer (c) 0 to 30
It is considered to be part by weight. If it is out of these ranges, it may be difficult to exert sufficient performance as an adhesive.

As the organic solvent used for the pressure-sensitive adhesive, any conventionally known one can be used as long as it can dissolve or disperse the copolymer, and the one used for the polymerization reaction may be used as it is. From the viewpoint of ease of production and storage stability of the acrylic solvent-based pressure-sensitive adhesive, it is preferable to use a solvent that dissolves the copolymer to prepare a solution. Examples of the organic solvent for obtaining such a solution include toluene and ethyl acetate. The ratio of the copolymer to the organic solvent is, for example, 50 to 300 parts by weight of the organic solvent with respect to 100 parts by weight of the copolymer, but is not limited thereto.

The acrylic solvent-based pressure-sensitive adhesive used in the present invention comprises a (meth) acrylic acid alkyl ester having an alkyl group having 1 to 14 carbon atoms, a monomer (b), and a monomer (c) which are organic according to a conventionally known method. It is preferable to carry out the solution polymerization in the presence of a solvent, but after isolating the copolymer obtained by other methods such as emulsion polymerization, suspension polymerization and bulk polymerization,
It can also be dissolved in an organic solvent.

As the crosslinking agent (B), a compound having two or more isocyanate groups, a compound having two or more epoxy groups,
Examples thereof include melamine compounds, guanamine compounds, oxazoline compounds, polyvalent metals and the like. As the compound having two or more isocyanate groups, tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, 1,5-naphthalene diisocyanate, hydrogenated tolylene diisocyanate, hydrogenated xylylene diisocyanate, isophorone A diisocyanate compound such as diisocyanate; a general formula (I) such as Sumijour N (Sumijour is a registered trademark) (manufactured by Sumitomo Bayer Urethane Co.) [Wherein R ¹ , R ² and R ³ represent the same or different divalent organic groups]; Desmodur IL, HL (Desmodur is a registered trademark) (Bayer A.G. (Made by AG), Coronate EH (coronate is a registered trademark) (made by Nippon Polyurethane Industry Co., Ltd.)
A polyisocyanate compound having an isocyanurate ring such as Sumijour L (Sumijour is a registered trademark)
(Sumitomo Bayer Urethane Co., Ltd.), Coronate L (Coronate is a registered trademark) (Nippon Polyurethane Industry Co., Ltd.),
Chemical formulas (II), (III) such as Coronate HH (Coronate is a registered trademark) (manufactured by Nippon Polyurethane Industry Co., Ltd.) And an adduct polyisocyanate compound represented by. The number of isocyanate groups contained in the molecule of the above-mentioned isocyanate compound is 2 or more, but those having more than 4 are usually difficult to obtain as commercial products. Those having are preferred. Examples of the compound having two or more epoxy groups include polyglycidyl compounds such as trimethylolpropane triglycidyl ether and diglycidyl amine, and bisphenol A / epichlorohydrin type epoxy resin. Specific examples of melamine-based compounds include precondensates of melamine-formaldehyde resins and alkyl ethers thereof; specific examples of guanamine-based compounds include precondensates of benzoguanamine, cyclohexanecarboguanamine, norbornanecarboguanamine, and alkyl ethers thereof. Compounds; isopropenyl oxazoline polymers and copolymers as oxazoline compounds; and aluminum trisacetylacetonate and zinc oxide as polyvalent metal compounds.

These cross-linking agents (B) can be used alone or in combination of two or more.

The amount of the cross-linking agent (B) used can be arbitrarily set depending on the kind of the cross-linking agent (B), the composition of the pressure-sensitive adhesive, the kind of the water-absorbing polymer, etc., but generally 0.01 to 1 per 100 parts by weight of the copolymer.
The range of 0 parts by weight is preferable, and the range of 0.1 to 5 parts by weight is more preferable. If the amount of the cross-linking agent (B) is less than 0.01 parts by weight, the pressure-sensitive adhesive layer may creep to deteriorate the water absorption / moisture absorption properties of the water absorbent sheet, or prevent the cohesive failure of the pressure-sensitive adhesive layer. If it is more than 10 parts by weight, the adhesiveness between the pressure-sensitive adhesive layer and the adherend may deteriorate.

In the present invention, a tackifier (rosin ester resin, phenol resin, xylene resin, xylene phenol resin, terpene phenol resin, petroleum resin, coumarone resin, low molecular weight styrene resin, terpene resin, etc.) is optionally added to the adhesive layer. , Thickeners (polyvinyl alcohol, sodium polyacrylate, carboxymethyl cellulose, methyl cellulose, etc.), pH adjusters (ammonia, amine, sodium hydroxide, potassium hydroxide, acetic acid, boric acid, phosphoric acid, etc.), colorants (pigments, dyes) Etc.), a plasticizer, a softening agent, an antioxidant, a filler, a viscosity modifier, and the like, can be contained in appropriate amounts.

As a method of providing the pressure-sensitive adhesive layer on the polymer-adhered surface of the fiber web to which the water-absorbing polymer is adhered, a method of directly coating the polymer-adhered surface of the fiber web with a pressure-sensitive adhesive containing a crosslinking agent (B) and removing the solvent, A method in which a pressure-sensitive adhesive containing a cross-linking agent (B) is applied to release paper to remove the solvent and then transferred to the polymer-bonded surface of the fibrous web, a double-sided tape impregnated with the adhesive is laminated on the release paper, Further, a method of laminating a fibrous web to which a water-absorbent polymer is attached by polymerization may be mentioned. In this case, the pressure-sensitive adhesive layer may be provided on the entire surface of the fibrous web to which the water-absorbing polymer is attached,
Further, if necessary, they may be discontinuously provided in various patterns such as a striped pattern, a polka dot pattern, and a grid pattern. When the pressure-sensitive adhesive layer is provided, it is preferably provided so as not to substantially impair the water absorption / moisture absorption properties of the water absorbent polymer. For example, the pressure-sensitive adhesive layer does not excessively penetrate into the fibrous web to which the water-absorbent polymer is attached so as not to impair the water-absorbing / moisture-absorbing properties of the water-absorbing polymer.

The pressure-sensitive adhesive layer has a thickness of, for example, 1 to 200 μm, preferably 10 to 100 μm. If the thickness is less than 1 μm, the adhesiveness will be poor. If it is thicker than 200 μm, the water-absorbent sheet may be inferior in water absorption / moisture absorption characteristics.

The pressure-sensitive adhesive layer before aging has fluidity, a part of the water-absorbent polymer and the fiber web is embedded when the pressure-sensitive adhesive layer is applied to the polymer-attached surface of the fiber web to which the water-absorbent polymer is attached, It is firmly bonded. Since the pressure-sensitive adhesive layer contains the cross-linking agent (B), the fluidity of the pressure-sensitive adhesive layer is lost with the passage of time (heating may be performed if necessary). Adhesion between the agent layer and the fibrous web becomes stronger, and peeling from the adhering surface of the water absorbent sheet does not occur. Further, since the adhesive does not creep, the coating of the water-absorbent polymer by the creep does not occur. Therefore, the water absorption / moisture absorption characteristics of the water absorbent sheet can be maintained for a long period of time. In this invention, the pressure-sensitive adhesive layer contains a water-absorbing polymer and a crosslinking agent capable of reacting with the pressure-sensitive adhesive, so that when the water-absorbing polymer swells due to water absorption / moisture absorption, The effect that peeling does not occur between them is exhibited. Further, the water absorption / moisture absorption characteristics of the water absorbent polymer are not deteriorated by the adhesive layer.

In the present invention, an antifungal agent can be used if necessary. Examples of the fungicide include benzimidazole compounds, phenol compounds, thiazole compounds, and the like. One or more of these fungicides can be used. These fungicides can be added to any part of the fibrous web, the water-absorbent polymer and the pressure-sensitive adhesive layer.

It is also possible to prevent mold from occurring by copolymerizing a (meth) acrylic acid alkyl ester having a quaternary ammonium group or an N-substituted (meth) acrylamide with a water-absorbing polymer or a monomer forming an adhesive.

〔Example〕

Hereinafter, the present invention will be described based on examples, but the present invention is not limited to the following examples.

-Reference Example 1-To a flask of 3 equipped with a thermometer, a cooling conditioner, a nitrogen introducing tube and a stirrer, 1500 parts by weight of toluene, 450 parts by weight of butyl acrylate, and 10 parts of hydroxyethyl acrylate were added.
Parts by weight, 450 parts by weight of 2-ethylhexyl acrylate, 40 parts by weight of acrylic acid, and 50 parts by weight of vinyl acetate were charged, and the temperature was raised to 80 ° C. with stirring under a nitrogen stream. Next, 2 parts by weight of benzoyl peroxide was added as a polymerization disclosing agent, and the mixture was stirred at the same temperature for 2 hours, then 1 part by weight of benzoyl peroxide was added and further stirred for 2 hours to obtain a mixture of a nonvolatile content of 40% by weight. A polymer solution was obtained.

Next, to 100 parts by weight of the obtained copolymer solution, 8 parts by weight of pentaline C (manufactured by Rika Hercules Co., Ltd., pentaerythritol ester of polymerized rosin, softening point 126 ° C.) as a tackifier was added and dissolved. Further, 1 part by weight of Coronate L-55E (Coronate is a registered trademark) (a trifunctional isocyanate cross-linking agent manufactured by Nippon Polyurethane Industry Co., Ltd.) is added as a cross-linking agent to obtain a non-volatile content of 44.5% by weight (composition). ) Got.

-Example 1-Into 100 parts by weight of a partially neutralized acrylic acid aqueous solution (monomer concentration 37% by weight) in which 75% was neutralized with sodium hydroxide
1.3 parts by weight of N, N′-methylenebisacrylamide, 0.2 parts by weight of sodium persulfate, 0.7 of hydroxyethyl cellulose
Part by weight was dissolved, and then dissolved oxygen was removed from the aqueous monomer solution with nitrogen gas.

After impregnating the entire surface of a polypropylene nonwoven fabric having a basis weight of 22 g / m ² with this monomer aqueous solution, the amount of the squeezed monomer aqueous solution was set to 100 g / m ² .

Next, the nonwoven fabric on which the aqueous solution of the monomer was attached to the entire surface was held at 120 ° C. for 5 minutes in a nitrogen atmosphere to polymerize the monomer, thereby obtaining a fibrous web on which the water absorbing polymer was attached to the entire surface.

The pressure-sensitive adhesive obtained in Reference Example 1 was applied to release paper on a fibrous web on which the water-absorbing polymer was evenly attached, and the thickness after drying was 30%.
The water-absorbent sheet (1) of the present invention is provided with a pressure-sensitive adhesive layer which is applied to have a thickness of μm, is dried, and is solvent-removed before being laminated.
Got

-Example 2-The procedure of Example 1 was repeated, except that one side of the rayon-polyester blended nonwoven fabric having a basis weight of 95 g / m ² was kiss coated with the aqueous monomer solution used in Example 1 so as not to be exposed on the opposite side of the nonwoven fabric. In the same manner as in Example 1, a fibrous web having a water absorbing polymer attached to one side was obtained.

A pressure-sensitive adhesive layer was provided on the surface of the fibrous web on which the water-absorbent polymer was adhered in the same manner as in Example 1 to obtain a water-absorbent sheet (2) of the present invention.

-Example 3-A water absorbent sheet (3) according to the present invention in the same manner as in Example 2 except that the fibrous web used in Example 2 was paper having a basis weight of 40 g / m ^2.
Got

-Example 4-A water absorbent sheet (4) of the present invention was obtained in the same manner as in Example 2 except that a polypropylene spunbonded nonwoven fabric having a basis weight of 60 g / m ² was used for the fibrous web.

-Example 5-In Example 1, the amount of N, N'-methylenebisacrylamide used was 0.06 parts by weight, and the fiber web had a basis weight of 100 g.
A water absorbent sheet (5) of the present invention was obtained in the same manner as in Example 1 except that a polyester non-woven fabric of / m ² was used.

-Example 6-1.8 parts by weight of N, N'-methylenebisacrylamide and 0.3 parts of sodium persulfate were added to 100 parts by weight of a partially neutralized acrylic acid aqueous solution (monomer concentration: 60% by weight) in which 75 mol% was neutralized with potassium hydroxide. Parts by weight, hydroxyethyl cellulose
0.6 part by weight was dissolved, and then dissolved oxygen was removed from the aqueous monomer solution with nitrogen gas.

This monomer aqueous solution was kiss-coated on one side of a nylon spunbonded nonwoven fabric having a basis weight of 60 g / m ^{2 so} that the monomer aqueous solution was not exposed on the opposite side, and the amount of the monomer aqueous solution attached was 90 g / m ² .

The nonwoven fabric to which the aqueous monomer solution was attached was held at 90 ° C. for 10 minutes to polymerize the monomer in a nitrogen atmosphere. Continue
It was dried in a hot air dryer at 110 ° C. for 20 minutes to obtain a fibrous web having a water-absorbent polymer attached on one side.

A pressure-sensitive adhesive layer was provided on the surface of the fibrous web on which the water-absorbent polymer was adhered in the same manner as in Example 1 to obtain a water-absorbent sheet (6) of the present invention.

-Comparative Examples 1 to 6- As a pressure-sensitive adhesive in Reference Example 1, a crosslinking agent Coronate L-55
Comparative water absorbent sheets (1) to (6) were obtained in the same manner as in Examples 1 to 6 except that the pressure-sensitive adhesive to which E (Coronate is a registered trademark) was not used.

-Example 7- When the water absorbent sheets (1) to (6) obtained in Examples 1 to 6 were attached to an acrylic plate and immersed in pure water, the water absorbent sheets (1) to (6) were water absorbent. Even after the swelling of the polymer, it did not peel at the interface between the fibrous web and the pressure-sensitive adhesive layer, and did not peel even when pressed with a finger. There was no shedding of the water-absorbent polymer from the fibrous web.

-Comparative Example 7-For comparison, when comparative water absorbent sheets (1) to (6) were similarly attached to an acrylic plate and immersed in pure water, the comparative water absorbent sheets (1) to (6) were made of a water absorbent polymer. After swelling, it was peeled off at the interface between the fibrous web and the pressure-sensitive adhesive layer by simply pressing it with a finger. There was no shedding of the water absorbent polymer from the fibrous web.

The water-absorbent sheets (1) to (6) and the comparative water-absorbent sheets (1) to (6) immersed in pure water were pulled up, drained sufficiently, and then weighed to determine the water absorption amount by the following formula. .

Water absorption (g / m ² ) [(weight of water-absorbent sheet after immersion)-
(Weight of water absorbent sheet before immersion)] / (Area of water absorbent sheet) The following results are summarized in Table 1.

-Example 8-The water-absorbent sheets (1) to (6) obtained in Examples 1 to 6 were attached around a glass beaker, and the temperature was 25 ° C and the relative humidity was 60%. When ice water was added, dew condensation did not occur at all, and the water-absorbent sheet was not peeled off from the beaker at all.

The surfaces of the water absorbent sheets (2), (3), (4) and (6) remained dry, and the surfaces of the water absorbent sheets (1) and (5) were slightly moist.

-Comparative Example 8-Comparative water-absorbent sheets (1) to (6) were likewise attached to a glass beaker, and although no dew condensation occurred at all, when left for a while, they adhered to the fibrous web at the edge portion of the comparative water-absorbent sheet. The agent layer was beginning to peel off.

-Comparative Example 9- When nothing was attached around the beaker, water droplets immediately formed on the surface of the beaker and dew condensation occurred.

-Example 9- When the water-absorbent sheet (2) obtained in Example 2 was attached to the inner wall of a Styrofoam container and frozen crab and a commercially available cold-preserving agent were added, no leakage occurred inside and it remained dry. The water absorbent sheet (2) was also not peeled off from the inner wall.

-Comparative Example 10- When the comparative water absorbent sheet (2) was used in the same manner, the fibrous web was almost peeled off from the pressure-sensitive adhesive layer, although it did not leak inside and remained dry.

-Comparative Example 11- Further, when the water absorbent sheet was not used, a large amount of water was accumulated at the bottom of the container.

〔The invention's effect〕

The water absorbent sheet of the present invention has the following effects.

It can be easily applied to places where water or water vapor is likely to be generated by the adhesive.

In the present invention, by containing a water-absorbing polymer and a crosslinking agent capable of reacting with the pressure-sensitive adhesive in the pressure-sensitive adhesive layer, when the water-absorbing polymer swells by absorbing water / moisture, the pressure-sensitive adhesive layer and the water-absorbing polymer are The effect that peeling does not occur between them is exhibited. Further, the water absorption / moisture absorption characteristics of the water absorbent polymer are not deteriorated by the adhesive layer.

In this invention, if the water-absorbent polymer is attached to the fibrous web by polymerization of the monomer forming the polymer, the following effects are also exhibited.

Polymer does not fall off or migrate from the fibrous web when absorbing large amounts of water or water vapor.

Further, in the present invention, by providing the pressure-sensitive adhesive layer on the polymer-adhered surface of the fibrous web having the water-absorbent polymer adhered on one surface, the following effects (1) to (3) are also exhibited.

Since the water-absorbent polymer is not exposed on the surface, people and things do not come into direct contact with the water-absorbent polymer, and the texture of the surface becomes good.

Since the water-absorbent polymer is not exposed on the surface, the dry feeling of the surface is maintained even when absorbing a large amount of aqueous liquid or water vapor, and the texture becomes good.

Since the water-absorbent polymer is not exposed on the surface, it is possible to easily print a design or the like.

Therefore, since the water-absorbent sheet of the present invention has the above-mentioned advantages, it can be used inside walls, ceilings, floors and closets of rooms, basements and warehouses, inside walls of containers, inside Styrofoam containers used for freezing and courier service, inside cardboard boxes, etc. , The inside of a plastic bag, the entrance, the entrance of a bathroom, the bottom of a window, etc. are directly applied to a place where dew condensation or liquid leakage is likely to occur, and it is excellent in preventing dew condensation or liquid leakage. In addition, when applied to containers such as Styrofoam and cardboard, it can be preferably used for keeping freshness of fresh foods in these containers and absorbing drip. However, the use of the water absorbent sheet of the present invention is not limited to those listed here.

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Claims (6)

[Claims] 1. A water-absorbent sheet comprising a pressure-sensitive adhesive layer provided on a fibrous web having a water-absorbent polymer adhered thereto, wherein the pressure-sensitive adhesive layer contains a water-absorbent polymer and a crosslinking agent capable of reacting with the pressure-sensitive adhesive. . 2. The water absorbent sheet according to claim 1, wherein the water absorbent polymer is obtained by polymerizing a water-soluble ethylenically unsaturated monomer applied to a fibrous web. 3. The water absorbent sheet according to claim 1 or 2, wherein the water absorbent polymer is attached to one surface of the fibrous web, and the pressure-sensitive adhesive layer is provided on the side to which the water absorbent polymer is attached. 4. The water absorbent sheet according to any one of claims 1 to 3, wherein the water absorbent polymer has a carboxyl group. 5. The water absorbent sheet according to claim 1, wherein the pressure sensitive adhesive is an acrylic solvent type pressure sensitive adhesive. 6. The water absorbent sheet according to claim 1, wherein the crosslinking agent is a compound having at least two functional groups selected from an isocyanate group and an epoxy group.