JPH0577366A - Water-absorbable composite and production thereof - Google Patents

Abstract

PURPOSE:To produce a water-absorbable composite convenient to use by suppressing the exposure or detachment of a water-absorbable polymer and making a resin film for improving dimensional stability hard to release. CONSTITUTION:A resin film non-tacky at room temp. is formed to at least the single surface of a water-absorbable sheet formed by polymerizing a water- soluble ethylenic unsaturated monomer convertible to a water-absorbable polymer to directly fix the formed polymer to a fiber sheet by coating processing. When a tackifier layer is provided on the resin film, the formed water- absorbable composite can be easily adapted to a place easy to generate water or steam.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water absorbent composite and a method for producing the same. More specifically, the present invention relates to a water-absorbent composite which is less likely to fall off of the water-absorbent polymer and has a free shape, and a simple method for producing the same.

[0002]

2. Description of the Related Art In recent years, a water-absorbing polymer has been immobilized on a substrate by adhering a monomer to a fibrous substrate by a method such as spraying or coating and then polymerizing it to prevent the polymer from falling off or moving during absorption of water. Many sex sheets are known. Although these water-absorbent sheets are designed to prevent the polymer from falling off to a considerable extent and improve the shape retention of the sheet, if they are used as they are, the water-absorbent polymer is exposed on the surface. The surface is slippery, the polymer directly touches the object during water absorption, or the polymer easily peels from the substrate when it touches, or the dimensional stability of the water absorbent sheet deteriorates during water absorption. It was difficult to use.

Recently, in order to solve such problems,
A water-absorbent composite in which a water-absorbent sheet is bonded to another substrate via a hydrogel, or an adhesive is used has been proposed (see JP-A-63-28639). ..

[0004]

However, in such a water-absorbent composite, when the water-absorbent composite and the adhesive are weakened when water is absorbed, the water-absorbent sheet and other base material are easily peeled off from each other. It is not possible to prevent exposure of the water-absorbent polymer and removal from the base material. In addition, once the water absorbent sheet and other base material are peeled off, reuse is difficult. The use of the adhesive is not always an industrially advantageous method because the elution of the adhesive and the swelling of the water-absorbent polymer due to the adhesive are likely to occur and the manufacturing process is complicated.

The present invention solves the above problems. Therefore, the object of the present invention is to have good dimensional stability,
It is an object of the present invention to provide a water-absorbent composite which is convenient for use while suppressing exposure and loss of the water-absorbent polymer, and a method for producing the same.

[0006]

In order to solve the above-mentioned problems, the present invention comprises a water-absorbing polymer directly fixed to a fiber sheet by a reaction of a water-absorbing polymer-forming material which can be converted into a water-absorbing polymer by a reaction. Provided is a water-absorbent composite in which a non-adhesive resin film is formed at room temperature on at least one surface of a water-absorbent sheet by coating.

The present invention is also non-adhesive at room temperature to at least one surface of a water-absorbent sheet obtained by directly adhering a water-absorbent polymer to a fiber sheet by a reaction of a water-absorbent polymer-forming material which can be converted into a water-absorbent polymer by a reaction. Provided is a method for producing a water-absorbent composite, which comprises applying and processing a resin material capable of forming a water-resistant film (hereinafter sometimes simply referred to as "resin material").

The substrate to which the water-absorbent polymer is directly adhered, which is used in the present invention, is a fibrous substrate made of various fibers, particularly a sheet-like fibrous substrate, that is, a fibrous sheet, which is woven cloth, non-woven cloth, Examples include paper and knitted fabric,
Nonwoven fabrics made from various fibrous webs are preferably used. In the present invention, the fibers may be hydrophilic fibers or hydrophobic fibers. As the hydrophilic fiber used,
Wood pulp, cotton, wool, rayon, acetate, vinylon and the like can be mentioned. As the hydrophobic fiber, polyester,
Acrylic, nylon, polyethylene, polypropylene,
In addition to polyvinyl chloride and the like, mixed fiber of these is exemplified. The fibrous sheet includes, for example, a tape-shaped fibrous sheet, and the thickness thereof is not particularly limited.
-100 mm is used. A long product can be used as the fiber sheet, and the production method of the present invention can be applied while continuously supplying the product. In this way, the water-absorbent composite of the present invention can be obtained with good productivity. .. Various printings can be performed on these fiber sheets in advance depending on the application. Further, after the water-absorbent composite is obtained, various printing can be performed on the water-absorbent sheet.

In the present invention, when the resin film which is non-adhesive at room temperature is made of a thermoplastic resin, it is preferable that at least a part of the fiber sheet is made of thermoplastic fibers. This is because the resin material can be applied more easily. When the resin film is made of a thermoplastic resin, it becomes easier to form a composite with another base material. The water-absorbent sheet used in the present invention needs to have a water-absorbent polymer directly fixed to the fiber sheet,
For example, it can be obtained by attaching a water-absorbing polymer-forming material that can be converted into a water-absorbing polymer by a reaction such as polymerization or crosslinking, to a fiber sheet, and then performing a reaction such as polymerization or crosslinking. The water-absorbent polymer-forming material is a water-soluble ethylenically unsaturated monomer that can be converted into a water-absorbent polymer by polymerization, a water-soluble polymer that can be converted into a water-absorbent polymer by crosslinking, such as polyacrylate. From the viewpoint of economic performance and the performance and durability of the resulting water-absorbent composite, the water-absorbent sheet obtained by polymerizing after adhering the water-soluble ethylenically unsaturated monomer to the fiber sheet is preferably used. It

The water-absorbing polymer-forming material is wholly or partially attached to the fibrous sheet and is converted into the water-absorbing polymer by reaction. The water-absorbent sheet is formed by directly or entirely fixing the water-absorbent polymer to the fiber sheet. Here, "partial" includes the case where only one side of the fiber sheet is present. The water-soluble ethylenically unsaturated monomer used in the present invention is not particularly limited as long as it can be polymerized and converted into a water-absorbing polymer, and examples thereof include acrylic acid, methacrylic acid and 2-
(Meth) acryloylethanesulfonic acid, 2- (meth)
Acryloyl propane sulfonic acid, 2- (meth) acrylamido-2-methyl propane sulfonic acid, vinyl sulfonic acid, (meth) allyl sulfonic acid, and their alkali metal salts and ammonium salts; (meth) acrylamide, N, N ' -Dimethylaminoethyl (meth) acrylate and quaternary compounds thereof; hydroxyalkyl (meth) acrylate; and polyalkylene glycol (meth) acrylate, and the like, and one or more of these can be used. .. Acrylic acid or its salt is preferred. A water-soluble polyfunctional ethylenically unsaturated monomer represented by methylenebisacrylamide and polyethylene glycol diacrylate may be added to the monomer. The method for adhering the aqueous monomer solution to the fiber sheet is not particularly limited, but, for example, printing, spraying, impregnation, and a method of squeezing after impregnation are adopted. The aqueous monomer solution thus attached to the fiber sheet is polymerized by a known means to obtain a water absorbent sheet. As the polymerization method, for example, heat,
It can be polymerized by a method using light, electron beam, ultraviolet ray, or the like.
If necessary, a water-soluble radical polymerization initiator and other additives may be added to the aqueous monomer solution. The content of the water absorbent polymer in the water absorbent sheet is preferably in the range of 10 to 90% by weight based on the weight of the solid content of the water absorbent sheet.

The resin film formed by coating on at least one surface of the water absorbent sheet must be non-adhesive at room temperature. The resin film having non-tackiness at room temperature is, for example, a resin film that can be easily separated without contact with any other solid or film.
If the resin film has tackiness at room temperature, for example, there is a problem that the composites will stick to each other when the water-absorbent composite is wound up. Examples of the resin film used in the present invention include polyethylene, polypropylene, polyvinyl chloride, polyvinylidene chloride, ethylene-vinyl acetate copolymer, polystyrene, polyamide, ethylene-α-
Thermoplastic resins selected from olefin copolymers, ethylene-α, β-unsaturated carboxylic acid ester copolymers, thermoplastic elastomers, or single-layer or multi-layer products such as polyurethane, polyester, amino resin, and phenol resin. be able to. When the fibrous sheet contains thermoplastic fibers, it is preferable to provide a resin film of the same kind of thermoplastic resin because the adhesion between the water absorbent sheet and the resin film can be further enhanced. The resin film is preferably made of polyolefin such as polyethylene or polypropylene from the viewpoints of being inexpensive, having high water resistance and durability (mechanical strength), and not impairing the flexibility of the water absorbent sheet. When the water-absorbent polymer is adhered only to one surface side of the water-absorbent sheet, the resin film is preferably formed on the surface of the sheet on which the water-absorbent polymer is adhered.
With such a structure, it is possible to prevent the water-absorbing polymer from being exposed on the surface, so that the texture of the composite surface is improved, or it is possible to prevent the polymer from directly touching hands or foods, Further, when the condensed water is absorbed, the surface is kept in a dry state, the texture becomes good, and dirt and dust are less likely to adhere.

The present invention is characterized in that the resin film is coated on at least one side of the water-absorbent sheet, but in the case of double-sided coating, at least one of them must be perforated. If both sides are non-porous, the function of the water-absorbent composite is deteriorated, which is not preferable. The perforated resin film can be achieved by a known technique, for example, by irradiating the resin film with an electron beam, or by coating the resin film in a slit shape, a dot shape, or a lattice shape to form fine holes and slits. .. Depending on the pore size, a moisture-impermeable and water-impermeable resin film may be used. The thickness of the resin film is usually preferably in the range of 1 to 100 μm. It is also possible to provide resin coatings of the same thickness and type on both sides.

Various kinds of printing can be applied to the resin film surface depending on the application. Specific examples of the coating processing method in the present invention include (1) solvent method, (2) heat dissolution method,
Known methods such as (3) calendar method, (4) emulsion method, (5) extrusion method can be mentioned, but in the present invention, extrusion coating method is adopted from the viewpoint of uniformity of film and economical efficiency. preferable.

(1) The solvent method is a method in which a resin material capable of forming a non-adhesive film at room temperature is dissolved in an appropriate solvent and the solution is applied and processed. (2) The heat melting method is a method in which a liquid material obtained by heating and melting a resin material is applied and processed, and then cooled to form a coating film. (3) The calendering method is a method in which the raw materials including the resin material are premixed and then the liquid material is applied while being passed between a plurality of rolls.

(4) The emulsion method is a method in which an emulsion containing a resin material is applied and processed and then dried to form a film. (5) The extrusion method is preferably a melt extrusion method, and is a method of forming a film by extruding the resin material in a melted state into a thin film, coating the water absorbent sheet, cooling and solidifying. The temperature of the resin material is not particularly limited as long as it is a temperature in a molten state, and is appropriately set within the same temperature range as in a normal extrusion method. According to the extrusion method, the step of removing the solvent and the dispersion medium is unnecessary, and the process can be simplified as compared with the methods (1) and (4).
High productivity. Moreover, since the molten liquid of the resin material does not excessively penetrate into the water-absorbent sheet as compared with the resin solution or the emulsion, there is less risk of covering the water-absorbent polymer, and the water-absorbent property and the flexibility are not impaired.

In the present invention, a pressure-sensitive adhesive layer can be further provided wholly or partially on the resin film of the water-absorbent composite obtained as described above. By providing the pressure-sensitive adhesive layer, the water-absorbent composite can be easily applied to a place where water or water vapor is likely to be generated. As the pressure-sensitive adhesive used in the present invention, conventionally known pressure-sensitive adhesives can be used, and various pressure-sensitive adhesives can be selected and used according to the place, conditions and use of the water-absorbent composite. Specific examples thereof include acrylic adhesives containing butyl acrylate or 2-ethylhexyl acrylate as a main component, rubber adhesives containing natural rubber or various synthetic rubbers as a main component, and silicone adhesives. One kind or two or more kinds of them may be used as they are, or in a form in which a crosslinking agent, a plasticizer, a tackifier, an antioxidant and other additives are added as necessary. Among these adhesives, acrylic adhesives are preferably used in terms of performance such as weather resistance and durability, and acrylic solvent-based adhesives are particularly preferable in terms of water resistance.

As the method for providing the pressure-sensitive adhesive layer on the resin film surface of the water-absorbent composite, for example, the pressure-sensitive adhesive is directly applied to the resin film surface and then dried, or the pressure-sensitive adhesive is applied and transferred from the dried release paper. Examples include a method of laminating a double-sided tape impregnated with an adhesive on a release paper, and further laminating a resin film surface of the water-absorbent composite. Further, when the water-absorbent composite is used, it can be applied to a desired place by using a commercially available double-sided pressure-sensitive adhesive tape. The pressure-sensitive adhesive layer can be provided on the entire surface of the resin film or partially, and is appropriately set depending on the use conditions of the water-absorbent composite.

In the present invention, in order to improve the adhesive force between the pressure-sensitive adhesive layer and the resin film, it is preferable to previously subject the resin film to corona discharge treatment. By applying the corona discharge treatment, the wettability of the resin film is improved and the adhesive force with the pressure-sensitive adhesive is improved. The conditions of the corona discharge treatment can be appropriately set depending on the type and thickness of the resin film to be provided.

When the water-absorbent composite of the present invention has a pressure-sensitive adhesive layer, a release-treated surface of a release sheet such as release paper having at least one release-treated release layer is applied to the exposed surface of the pressure-sensitive adhesive layer. It is preferable to handle and store the water-absorbent composite. When the release sheet is applied in this manner, the water-absorbent composite has a resin film (preferably a film thickness of 1 to 1).
100 μm), the tunneling phenomenon is unlikely to occur.

In the present invention, functional materials such as an antifungal agent, an antibacterial agent, a deodorant, and a flame retardant can be added within a range that does not deteriorate the performance of the resulting water-absorbent composite. These functional materials may be added to any part of the water absorbent sheet, the resin film and the adhesive layer. The water-absorbent composite of the present invention thus obtained has all of the following characteristics (a) to (d) and, in some cases, also has the following characteristics (e) to (g). is there.

(A) Since the resin film is integrally provided on at least one surface of the water absorbent sheet, for example, when the resin film is made of a thermoplastic resin, it can be easily combined with another substrate by heat fusion. it can. Further, only the water-absorbent composite of the present invention can be packaged. For example, the water-absorbent composite of the present invention is bent or overlapped so that the resin film is on the inside or the outside, and heat-fused at a portion where the resin film is overlapped to form a tubular or bag-like material. Can be made.

(B) Since the resin film can be formed in-line, the thickness of the resin film can be arbitrarily changed and the production speed can be increased. Therefore, the manufacturing cost can be significantly reduced. The water-absorbent composite can be wound up without controlling humidity. The resin film can be made thin. Therefore, manufacturing costs and distribution costs can be significantly reduced.

(C) Since no adhesive is used to form a resin film on one side or both sides of the water absorbent sheet, the swelling of the water absorbent polymer is not suppressed and the adhesive is not eluted. Since the water-absorbent polymer is directly adhered to the fiber sheet and no binder is used, the surface of the water-absorbent polymer is not covered with the binder, so that the moisture absorption / desorption efficiency and the response speed do not decrease.
If a polymer is used to prevent the polymer from falling off, the water absorption rate will decrease, but the water absorption rate will not decrease due to the water-absorbing polymer directly adhering to the fiber sheet.

(D) There is no peeling of the resin film from the water absorbent sheet after absorbing water. Therefore, repeated use of water absorption and drying is possible. (E) When a resin film having pores is provided on the surface of the water-absorbent sheet, water can be absorbed without exposing the water-absorbing polymer and without falling off of the water-absorbing polymer. It can be used in fields that have been difficult to use such as drip absorbers.

(F) If the water-absorbent sheet has a resin film on only one side, it can be used as a material having both hydrophilicity and hydrophobicity. (G) By providing a pressure-sensitive adhesive layer on the resin film of the water-absorbent composite, the following advantages (1) to (4) are produced. The water-absorbent composite can be freely applied according to the purpose.

Since the water-absorbent composite has extremely high dimensional stability, it is possible to prevent a so-called tunneling phenomenon, which is a peeling phenomenon that causes a gap between the release paper and the pressure-sensitive adhesive layer when stored for a long period of time. Since the strength of the water-absorbent composite is maintained by the resin film, removability is improved.

Therefore, the water-absorbent composite of the present invention is, for example, a disposable diaper, sanitary cotton, onesheets, medical sheets, foot wipe mats, drip absorbents, food freshness-retaining materials, food trays, coasters, anti-condensation sheets, It can be suitably used for applications such as waterproofing materials for cables, cold insulation materials, water retention materials for agriculture and horticulture, cement curing sheets, sludge coagulation materials, and artificial anus.

In particular, the water-absorbent composite of the present invention is preferable because the water-absorbent sheet is subjected to a softening treatment before or after the resin film is formed, because the water-absorbent sheet is easily deformed and has a soft texture. The softening process is, for example,
The water-absorbent polymer of the water-absorbent sheet has a saturated water absorption of 25
It is carried out by absorbing water to a weight percentage or more and drying. If water absorption is performed within the above range when water absorption and drying are repeated, the softening treatment is automatically performed.

[0029]

[Function] Since the non-adhesive resin film is formed on at least one surface of the water-absorbent sheet at room temperature, the water-absorbent polymer is prevented from being exposed, and the polymer and the object are in direct contact during water absorption, Can be prevented from peeling off from the fiber sheet. In addition, the water-absorbent polymer is directly fixed to the fiber sheet by the reaction of the water-absorbent polymer-forming material such as a water-soluble ethylenically unsaturated monomer that forms a water-absorbent polymer by the reaction, and a resin film is formed on one side or both sides of the sheet. Since the sheet is formed, the shape retention and dimensional stability of the sheet are high, and it is possible to prevent the dimensional stability of the water absorbent sheet from deteriorating when absorbing water. Moreover, since the water-absorbent polymer is directly adhered to the fiber sheet, it does not easily fall off and the water absorption does not decrease.

Since the resin film is formed by applying and processing the resin material in a liquid state, the water-absorbent sheet is more likely to soak into the water-absorbent sheet and peeled from the water-absorbent sheet as compared with the case of laminating the resin film. It becomes difficult, and the water absorbent composite becomes easy to handle. When the resin film is made of a thermoplastic resin and at least a part of the fiber sheet is composed of thermoplastic fibers, the adhesion between the fiber sheet and the resin film is improved, and it is easy to form a composite with another substrate. Become.

By further providing a pressure-sensitive adhesive layer on the resin film, the water-absorbent composite can be arbitrarily applied to a desired place. When the pressure-sensitive adhesive layer is provided, if the resin film is subjected to corona discharge treatment in advance, the adhesion between the resin film and the pressure-sensitive adhesive layer is improved, and the durability becomes excellent.

[0032]

The present invention will be further described below with reference to examples, but the present invention is not limited thereto. (Synthesis Example 1 of water-absorbent sheet) Methylenebisacrylamide 0.5 mol% (vs. sodium acrylate monomer) and sodium persulfate 1.0 g / mol (vs. sodium acrylate monomer) dissolved in acryl adjusted to pH 5.6 A basis weight of 30 g / in a 43 wt% aqueous solution of sodium acid
A m ² ES (ES: polyethylene-polypropylene composite fiber) non-woven fabric is immersed and impregnated with the aqueous solution, and the amount of the aqueous monomer solution adhering to the substrate is set to 200% by weight to perform radical polymerization to perform water-absorbing sheet ( 1) was obtained.
This product had a water absorption of 40 g / g and a thickness of 900 μm.

(Synthesis example 2 of water-absorbent sheet) 0.5 mol% of methylenebisacrylamide (to sodium acrylate monomer) and 1.0 g / mol of sodium persulfate (to sodium acrylate monomer) were dissolved to have a pH of 5.6.
A polypropylene non-woven fabric having a basis weight of 25 g / m ² was dipped in a 43 wt% aqueous solution of sodium acrylate adjusted to 1, and the aqueous solution was impregnated into the non-woven fabric, and the amount of the monomer aqueous solution adhering to the substrate was heated to 180 wt% to perform radical polymerization. Then, a water absorbent sheet (2) was obtained. The water absorption of this product is 20g
/ G, the thickness was 500 μm.

(Example 1) On one surface of a long water absorbent sheet (1) having a width of 1 m, polyethylene was melted and applied at a line speed of 200 m / min by an extrusion coating method to form a water absorbent sheet ( There was obtained a water-absorbent composite (1) of the present invention in which a polyethylene layer having a thickness of 30 μm was laminated on one surface of (1).

(Example 2) In the same manner as in Example 1, a water absorbent sheet (2) was used instead of the water absorbent sheet (1) to obtain a water absorbent composite (2) of the present invention. (Comparative Example 1) A water-absorbent sheet (1) and a polyethylene film having a thickness of 30 µm were bonded together with a polyurethane adhesive to obtain a comparative water-absorbent composite (1).

(Examples 3 and 4 and Comparative Example 2) 10 cm
The water-absorbent composite (1) of the present invention, which is cut to a size of 20 cm.
(2) and the comparative water-absorbent composite (1) were immersed in tap water for 10 minutes to determine the amount of water absorption. At this time, the adhesion of the polyethylene layer to the water absorbent sheet was visually compared. Drying the water-absorbent composite and the comparative water-absorbent composite after absorbing water,
The water absorption test was performed again, and the water absorption test was repeated. The results are shown in Table 1.

[0037]

[Table 1] Water-absorbing composite (1) Water-absorbing composite (2) Comparative water-absorbing composite (1) First-time water absorption 13 g / g 6 g / g 4 g / g First-time adhesion Good / no peeling Good・ No peeling Partial peeling Water absorption at 2nd time 13g / g 6g / g --- Adhesion at 2nd time Good ・ No peeling Good ・ No peeling Complete peeling Water absorption at 3rd time 13g / g 6g / g --- 3rd time Adhesiveness Good / No peeling Good / No peeling Complete peeling As is clear from the results shown in Table 1, the water-absorbent composite of the present invention has good adhesiveness to the resin film, and even after repeated water absorption / dehydration. No deterioration in quality was observed.

Example 5 Acrylic acid prepared by dissolving 0.3 mol% of methylenebisacrylamide (to sodium acrylate monomer) and 1.0 g / mol of sodium persulfate (to sodium acrylate monomer) and adjusting the pH to 5.6. 43% by weight aqueous solution of sodium, basis weight 30 g /
A water-absorbent sheet (3) having a water-absorbent polymer fixed on one side of a nonwoven fabric is obtained by applying it to one side of a m ² ES non-woven fabric and heating the amount of the monomer aqueous solution adhered to the base material to 150% by weight for radical polymerization. Obtained. Subsequently, a polyethylene layer was provided on the water-absorbent polymer layer side by an extrusion coating method in a state where polyethylene was melted to obtain a water-absorbent composite (3) of the present invention. The water absorption of this product was 10 g / g. This product was suitable for a drip absorbent sheet because the water-absorbent polymer was not exposed or dropped even after absorbing water.

(Example 6) 0.01 mol% of methylenebisacrylamide (based on sodium acrylate monomer),
Sodium persulfate 1.0 g / mol (vs. sodium acrylate monomer), and hydroxyethyl cellulose 2
A non-woven fabric of polyethylene-polyester composite fiber having a basis weight of 30 g / m ² is dipped in a 43 wt% aqueous solution of sodium acrylate adjusted to have a pH of 5.6 in which wt% (versus sodium acrylate monomer) is dissolved. Impregnated with 200 times the amount of the monomer aqueous solution attached to the substrate
A water absorbent sheet (4) was obtained by heating at a weight percentage and radical polymerization. Subsequently, a polyethylene layer having a thickness of 30 μm was provided on one surface of the water-absorbent sheet (4) by an extrusion coating method with polyethylene melted to obtain a water-absorbent composite (4) of the present invention.

(Example 7 and Comparative Example 2) 10 cm in length and width
The water-absorbent composite (4) and the water-absorbent sheet (4) of the present invention, which were cut to a size of 20 cm, were immersed in tap water for 10 minutes to determine the water absorption. At this time, the vertical and horizontal sizes were measured. The results are shown in Table 2.

[0041]

[Table 2] Water-absorbent composite (4) Water-absorbent sheet (4) Water absorption amount 75 g / g 100 g / g Good adhesion, no peeling-Size (length x width) 10 cm x 20 cm 9 cm x 34 cm Polymer loss 1% 2% As is clear from the results shown in Table 2, the water-absorbent composite of the present invention has good adhesion of the resin film, excellent polymer shape retention, and excellent dimensional stability as a sheet, and dimensional stability. The sex is also very good.

(Comparative Example 3) 0.01 mol% of methylenebisacrylamide (relative to sodium acrylate monomer),
P dissolving 1.0 g / mol of sodium persulfate (to sodium acrylate monomer) and 2% by weight of hydroxyethyl cellulose (to sodium acrylate monomer)
43% by weight of sodium acrylate adjusted to H5.6
After degassing the aqueous solution with nitrogen, it was dropped onto a stainless steel belt heated to 120 ° C. under a nitrogen atmosphere to carry out thin film polymerization. The polymer after polymerization is scraped from the surface of the belt, dried and then pulverized to obtain a powdery water-absorbent polymer (1).
Got The water absorption capacity of this product in tap water is 110 g /
It was g.

Subsequently, the nonwoven fabric used in Example 6 was dipped in a water-absorbing polymer suspension solution consisting of 10 parts by weight of butyl rubber, 90 parts by weight of water-absorbing polymer (1) and 100 parts by weight of toluene, and the suspension was added thereto. Was impregnated, and the amount of the suspension attached to the substrate was adjusted to 200% by weight, and the suspension was dried. Subsequently, in the same manner as in Example 6, a comparative water-absorbent composite (2) having a polyethylene layer laminated on one side with a thickness of 30 μm was obtained.

This comparative water absorbent composite (2) was treated with 10 cm ×
It was cut into 20 cm and immersed in tap water for 10 minutes to determine the water absorption. At this time, the adhesiveness of the polyethylene layer to the water absorbent sheet and the state of the polymer falling off were visually observed.
The results are shown in Table 3.

[0045]

[Table 3] As is clear from the results shown in Table 3, since the water-absorbent polymer was fixed to the fiber base material with the binder, the water-absorbent polymer almost fell off during water absorption, resulting in poor sheet shape retention. Further, the resin film was also peeled off from the water absorbent sheet due to the falling of the polymer, and the adhesiveness with the sheet was poor.

Example 8 A mixture of a commercially available acrylic solvent-based pressure-sensitive adhesive having an isocyanate crosslinkable solid content of 45% by weight and a predetermined amount of a trifunctional isocyanate crosslinker was added so that the thickness after drying was 30 μm. The pressure-sensitive adhesive layer was formed on the release paper by coating on the release paper and drying to evaporate the solvent.

The polyethylene resin film surface of the water absorbent composite (1) obtained in Example 1 was subjected to corona discharge treatment. The pressure-sensitive adhesive layer formed on the release paper was transferred to the polyethylene resin film surface of the water-absorbent composite (1) that had been subjected to this corona discharge treatment, and the water-absorbent composite (5) of the present invention provided with the release paper. Got The water absorption of this product was 11 g / g. When this product was stored indoors for a long period of time, the tunneling phenomenon between the release paper and the adhesive layer did not occur. This product was useful as a dew condensation preventing wall material when attached to a wall and had good removability.

(Comparative Example 4) Synthesis of water-absorbent sheet The pressure-sensitive adhesive layer formed on the release paper used in Example 8 was transferred to one surface of the water-absorbent sheet (1) synthesized in Example 1 and released. A comparative water-absorbent composite (3) having a pattern was obtained. When this product was stored indoors for a long period of time, a tunneling phenomenon occurred between the release paper and the adhesive layer.

Example 9 Synthesis example 1 except that a commercially available antifungal agent (trade name PL-600 manufactured by Tokyo Fine Chemical Co., Ltd.) was added in 1% by weight (to acrylic acid monomer) in Synthesis example 1 of water-absorbent sheet. A water-absorbent sheet (5) was obtained in the same manner as in. This product had a water absorption of 40 g / g and a thickness of 900 μm, and had good antifungal properties against blue mold, black mold, psychrophilic mold, etc. and good antibacterial properties against bacilli. A polyethylene resin film was provided on one surface of this sheet in the same manner as in Example 6, and then an adhesive layer was provided on this polyethylene resin film in the same manner as in Example 8 to give the water-absorbent composite (6) of the present invention. Got This product was useful as a dew condensation preventing wall material and had good removability.

(Example 10) The water-absorbing composite (1) obtained in Example 1 was subjected to extrusion coating in a molten state of polyethylene on the side not provided with the polyethylene resin film, to form a parallel film having a width of 2 mm. Striped polyethylene layer (thickness 20μ
m) was laminated (the interval between the streaks in the polyethylene layer was 1 mm) to obtain a water absorbent composite (7). The water absorption of this product was 10 g / g. In this product, the water-absorbing polymer was not exposed on the surface, and the polyethylene resin film was laminated in a streak shape, so that water and water could be absorbed and desorbed between them. In addition, when the water was absorbed, the polyethylene layer was laminated on the entire surface and the water was not leaked to the side where the polyethylene layer was laminated. This product was suitable for a food freshness-preserving sheet because the water-absorbent polymer was not exposed and dropped off after absorbing water, and the polymer did not come into direct contact with food or the like.

(Example 11) Methylenebisacrylamide 2 mol% (to sodium acrylate monomer), sodium persulfate 1.0 g / mol (to sodium acrylate monomer) and hydroxyethyl cellulose 2% by weight.
Dissolve (to sodium acrylate monomer), pH
A 37 wt% aqueous solution of sodium acrylate adjusted to 5.6 was prepared. A polypropylene non-woven fabric having a floral pattern printed on one side was dipped in this monomer aqueous solution at a basis weight of 55 g / m ² , and after impregnating the aqueous solution, the excess monomer aqueous solution was squeezed to remove the amount of the monomer aqueous solution attached to the substrate. It was set to 250% by weight. The impregnated material was heated to carry out radical polymerization to obtain a water absorbent sheet (6). There was no difference in the hue of the printed floral pattern before and after the water-absorbent polymer was fixed. Subsequently, a polypropylene layer having a thickness of 20 μm is formed by extrusion coating in a state where polypropylene is melted on one surface of the water absorbent sheet (6) on which the floral pattern is not printed, and the water absorbent composite of the present invention ( 8) was obtained. The water absorption of this product was 10 g / g. This one was useful as a coaster.

Example 12 A mixture of a commercially available acrylic solvent-based pressure-sensitive adhesive having an isocyanate crosslinkable solid content of 45% by weight and a predetermined amount of a trifunctional isocyanate crosslinker was added so that the thickness after drying was 50 μm. The pressure-sensitive adhesive layer was formed on the release paper by coating on the release paper and drying to evaporate the solvent.

Water-absorbent composite (8) obtained in Example 11
The polypropylene resin film surface of was subjected to corona discharge treatment. The pressure-sensitive adhesive layer formed on the release paper is transferred to the polypropylene resin film surface of the water-absorbent composite (8) that has been subjected to the corona discharge treatment, and the water-absorbent composite (9) of the present invention with the release paper attached. ) Got. The water absorption of this product was 8 g / g. When this product was stored for a long period of time, the shrinkage of the water-absorbent composite did not occur, and the tunneling phenomenon between the release paper and the pressure-sensitive adhesive layer did not occur. This product was useful as a dew condensation preventing wall material when attached to a wall, and had good removability. In addition, even when used for a long period of time, the water-absorbent composite did not expand or contract, and the pattern of the water-absorbent composites (9) stuck side by side did not shift.

(Comparative Example 5) Example 1 was applied to the surface of the water absorbent sheet (6) obtained in Example 11 on the non-printed side.
The pressure-sensitive adhesive layer formed on the release paper used in 2 was transferred to obtain a comparative water-absorbent composite (4) with release paper. When this product was stored for a long time, the comparative water-absorbing composite shrank,
A tunneling phenomenon occurred between the release paper and the adhesive layer.

The water-absorbent composites obtained in the above examples and the water-absorbent sheets used were examined for dimensional stability during water absorption. The water-absorbent composite and the water-absorbent sheet, which were cut into a size of 10 cm × 20 cm, were immersed in tap water for 10 minutes and then pulled up to measure the length and width. The results are shown in Table 4.

[0056]

[Table 4] As is clear from the results in Table 4, the water-absorbent composite of the present invention is provided with the resin film, and thus the dimensional stability upon water absorption is significantly improved as compared with the corresponding water-absorbent sheet.

The water-absorbent composites (7) and (9) and the comparative water-absorbent composites (3) and (4) were cut into a size of 10 cm × 20 cm and left in the room, and the space between the pressure-sensitive adhesive layer and the release paper was cut. The presence or absence of peeling (tunneling phenomenon) was observed. In addition, the size of the composite after standing was measured. The results are shown in Table 5.

[0058]

[Table 5] Tunneling size after standing (length / cm) x (width / cm) Water-absorbing complex (7) No 10x20 Water-absorbing complex (9) No 10x20 Comparative water-absorbing complex (3) ) Yes 9.6 × 19.6 Comparative water-absorbing composite (4) Yes 9.4 × 19.4

[0059]

EFFECTS OF THE INVENTION The water-absorbent composite of the present invention has a resin film formed on at least one surface of a water-absorbent sheet that is difficult to peel off, so that the water-absorbent polymer can be prevented from being exposed or dropped off, and the dimensional stability is good, so that it can be used. It is convenient. According to the method for producing a water absorbent composite of the present invention, such an excellent water absorbent composite can be easily obtained.

Claims (9)

[Claims] 1. A non-adhesive at room temperature by applying a coating process to at least one surface of a water-absorbent sheet obtained by directly adhering a water-absorbent polymer to a fiber sheet by a reaction of a water-absorbent polymer-forming material that can be converted into a water-absorbent polymer by a reaction. Of a water-absorbent composite having a water-soluble resin film formed thereon. 2. The water-absorbing polymer-forming material is a water-soluble ethylenically unsaturated monomer that can be converted into a water-absorbing polymer by polymerization, and the water-absorbing sheet polymerizes the monomer after attaching the monomer to the fiber sheet. The water-absorbent composite according to claim 1, which is obtained by 3. The water absorbent composite according to claim 1 or 2, wherein the resin film is made of a thermoplastic resin, and at least a part of the fiber sheet is made of thermoplastic fibers. 4. The water absorbent composite according to claim 1, wherein an adhesive layer is provided on at least a part of the resin film. 5. A non-adhesive film at room temperature is formed on at least one surface of a water-absorbent sheet obtained by directly adhering a water-absorbent polymer to a fiber sheet by the reaction of a water-absorbent polymer-forming material that can be converted into a water-absorbent polymer by a reaction. A method for producing a water-absorbent composite, which comprises applying and processing a liquid material of a resin material that can be formed. 6. The water-absorbing polymer-forming material is a water-soluble ethylenically unsaturated monomer that can be converted into a water-absorbing polymer by polymerization, and the water-absorbing sheet polymerizes the monomer after attaching the monomer to the fiber sheet. The method for producing a water absorbent composite according to claim 5, which is obtained by 7. The method for producing a water absorbent composite according to claim 5, wherein the coating process of the resin material is extrusion coating in a molten state of the resin material. 8. The method according to claim 5, wherein a resin material is applied and processed to form a non-adhesive resin film at room temperature, and then an adhesive layer is provided on at least a part of the resin film. A method for producing the water-absorbing composite as described. 9. The method for producing a water-absorbent composite according to claim 8, wherein the pressure-sensitive adhesive layer is provided after the corona discharge treatment is performed on the non-adhesive resin film at room temperature.