JP3059290B2 - Water-absorbing composite and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water-absorbing composite and a method for producing the same. More specifically, the present invention relates to a water-absorbing composite that can be formed into a free shape with little loss of a water-absorbing polymer and a simple method for producing the same.

[0002]

2. Description of the Related Art In recent years, a water-absorbing polymer is fixed to a fibrous base material by spraying or applying a monomer onto the fibrous base material and then polymerized, thereby preventing the polymer from falling off or moving during water absorption. Many sheets are known. Although these water-absorbent sheets prevent the polymer from dropping to a considerable extent and improve the shape retention of the sheet, the water-absorbent polymer is exposed on the surface when used as it is. The surface is slimy, the polymer directly contacts the object when absorbing water, or the polymer easily peels off from the base material when touched, or the dimensional stability of the water-absorbent sheet deteriorates when absorbing water It was difficult to use.

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

[0004]

However, in such a water-absorbent composite, the water-absorbent sheet and other base material are easily peeled off from the water-absorbent sheet when the water-absorbent composite or the adhesive is weakened due to the weakened adhesive force. It is impossible to completely prevent the water-absorbing polymer from being exposed or falling off from the substrate. Further, once the water-absorbent sheet and the other base material have been peeled off, it has been difficult to reuse them. In addition, the use of an adhesive is not always an industrially advantageous method because the elution of the adhesive and the poor swelling of the water-absorbing polymer due to the adhesive are likely to occur, and the production process is complicated.

The present invention solves the above-mentioned problems. Therefore, the object of the present invention is that the dimensional stability is good,
An object of the present invention is to provide a water-absorbing composite which is convenient for use while suppressing exposure and falling off of a water-absorbing polymer, and a method for producing the same.

[0006]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a water-absorbing polymer which is directly bonded 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-absorbing composite having a non-adhesive resin film formed at normal temperature on at least one surface of a water-absorbent sheet by coating.

The present invention also provides a water-absorbent polymer which can be converted to a water-absorbent polymer by a reaction. Provided is a method for producing a water-absorbing composite by applying and processing a resin material capable of forming a water-soluble film (hereinafter, may be simply referred to as “resin material”).

The substrate used in the present invention to which the water-absorbing polymer is directly fixed is a fibrous substrate made of various fibers, especially a sheet-like fibrous substrate, that is, a fibrous sheet. Paper, knitted fabric, etc.
Nonwoven fabrics made from various fiber webs are preferably used. In the present invention, the fibers can be either hydrophilic fibers or hydrophobic fibers. As the hydrophilic fibers used,
Wood pulp, cotton, wool, rayon, acetate, vinylon and the like, as the hydrophobic fiber, polyester,
Acrylic, nylon, polyethylene, polypropylene,
In addition to polyvinyl chloride, these blended fibers are exemplified. The fiber sheet includes, for example, a tape-like sheet, and its thickness is not particularly limited.
１００100 mm is used. A long object is used as a fiber sheet, and the production method of the present invention can be applied while continuously supplying the long sheet. In this case, the water-absorbent composite of the present invention can be obtained with good productivity. . Various printings can be applied to these fiber sheets in advance depending on the application. After obtaining the water-absorbing composite, the water-absorbing sheet can be subjected to various printings.

In the present invention, when the non-adhesive resin film 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 more easily applied. If the resin film is made of a thermoplastic resin, it can be easily combined with another base material. The water-absorbent sheet used in the present invention must be one in which the water-absorbent polymer is 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-absorbing polymer-forming material is a water-soluble ethylenically unsaturated monomer that can be converted to a water-absorbing polymer by polymerization, or a water-soluble polymer that can be converted to a water-absorbing polymer by crosslinking, such as a polyacrylate. From the economic viewpoint and the performance and durability of the resulting water-absorbent composite, a water-absorbent sheet obtained by polymerizing the water-soluble ethylenically unsaturated monomer after attaching it to the fiber sheet is preferably used. You.

[0010] The water-absorbing polymer-forming material is converted to a water-absorbing polymer by reacting it, in whole or in part, on the fiber sheet. The water-absorbent sheet is one in which the water-absorbent polymer is directly or entirely fixed to the fiber sheet. Here, the term “partial” includes a 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 to be converted into a water-absorbing polymer. For example, acrylic acid, methacrylic acid, 2-
(Meth) acryloylethanesulfonic acid, 2- (meth)
Acryloylpropanesulfonic acid, 2- (meth) acrylamide-2-methylpropanesulfonic acid, vinylsulfonic acid, (meth) allylsulfonic acid, and alkali metal salts and ammonium salts thereof; (meth) acrylamide, N, N ′ -Dimethylaminoethyl (meth) acrylate and its quaternary products; hydroxyalkyl (meth) acrylate; and polyalkylene glycol (meth) acrylate, and the like, and one or more of these can be used. . Preferred is acrylic acid or a salt thereof. A water-soluble polyfunctional ethylenically unsaturated monomer represented by methylenebisacrylamide or polyethylene glycol diacrylate may be added to the monomer. The method for attaching the aqueous monomer solution to the fiber sheet is not particularly limited, but for example, printing, spraying, impregnation, a method of squeezing after impregnation, or the like is employed. 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,
Polymerization can be performed by a method using light, an electron beam, ultraviolet light, 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-absorbing 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 on at least one side of the water-absorbent sheet by coating must be non-adhesive at room temperature. The non-adhesive resin film at room temperature is, for example, a resin film that can be easily separated without any resistance even when it comes into contact with another solid or film.
If the resin film has tackiness at room temperature, for example, there is a problem in that when the water-absorbing composite is wound up, the composites adhere to each other. As the resin film used in the present invention, for example, polyethylene, polypropylene, polyvinyl chloride, polyvinylidene chloride, ethylene-vinyl acetate copolymer, polystyrene, polyamide, ethylene-α-
A thermoplastic resin selected from olefin copolymers, ethylene-α, β-unsaturated carboxylic acid ester copolymers, and thermoplastic elastomers, or a single layer or multilayer such as polyurethane, polyester, amino resin, and phenol resin. be able to. In the case where the fiber sheet contains thermoplastic fibers, it is preferable to provide a resin film of the same type of thermoplastic resin because the adhesion between the water-absorbent sheet and the resin film can be further improved. The resin film is preferably made of a polyolefin such as polyethylene or polypropylene from the viewpoint that it is inexpensive, has high water resistance and durability (mechanical strength), and does not impair the flexibility of the water absorbent sheet. When the water-absorbing polymer is fixed only on one side of the water-absorbing sheet, the resin film is preferably formed on the surface of the sheet on the side where the water-absorbing polymer is fixed.
With this configuration, the surface of the composite can be improved because the water-absorbing polymer can be prevented from being exposed to the surface, or the polymer can be prevented from directly touching hands or foods, Further, when the dew water is absorbed, the surface is kept in a dry state, the texture is good, and dirt, dust and the like are hardly adhered.

The present invention is characterized in that the resin film is coated on at least one side of the water-absorbent sheet. In the case of double-sided coating, at least one of the two must be perforated. When both surfaces are nonporous, the function as a water-absorbing composite is reduced, which is not preferable. The perforated resin film is achieved by providing micropores / slits by a known technique, for example, by irradiating the resin film with an electron beam or applying the resin film in a slit shape, a dot shape, or a grid shape. . Depending on the pore size, a moisture-permeable and water-impermeable resin film can be used. The thickness of the resin film is usually preferably in the range of 1 to 100 μm. Resin films of the same thickness and type can be provided on both surfaces.

Various printings can be applied to the resin film surface depending on the application. Specific examples of the coating method in the present invention include (1) a solvent method, (2) a thermal melting method,
Known methods such as (3) a calender method, (4) an emulsion method, and (5) an extrusion method can be mentioned. In the present invention, an extrusion coating method is preferably used from the viewpoint of uniformity of film and economical viewpoint. 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. (2) The heat melting method is a method in which a liquid material obtained by heating and melting a resin material is applied and then cooled to form a coating film. (3) The calendering method is a method in which a raw material containing a resin material is preliminarily mixed, and then the liquid material is applied while being passed through a plurality of rolls.

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

In the present invention, a pressure-sensitive adhesive layer can be further entirely or partially provided on the resin film of the water-absorbing composite obtained as described above. By providing the pressure-sensitive adhesive layer, the water-absorbing composite can be easily applied to a place where water or water vapor is easily generated. As the pressure-sensitive adhesive used in the present invention, conventionally known pressure-sensitive adhesives can be used, and the pressure-sensitive adhesive can be selected from various pressure-sensitive adhesives depending on the place, conditions, and application in which the water-absorbing composite is used. Specific examples include acrylic pressure-sensitive adhesives mainly containing butyl acrylate or 2-ethylhexyl acrylate, rubber-based pressure-sensitive adhesives mainly containing natural rubber or various synthetic rubbers, silicone-based pressure-sensitive adhesives, and the like. One or two or more of these can be used as they are or in a form to which a crosslinking agent, a plasticizer, a tackifier, an antioxidant and other additives are added as required. Among these pressure-sensitive adhesives, acrylic pressure-sensitive adhesives are preferable in terms of performance such as weather resistance and durability, and acrylic solvent-type pressure-sensitive adhesives are particularly preferable in terms of water resistance and the like.

As a method for providing the pressure-sensitive adhesive layer on the resin film surface of the water-absorbent composite, for example, a method in which the pressure-sensitive adhesive is directly applied to the resin film surface and then dried, or a method in which the pressure-sensitive adhesive is applied and transferred from a release paper which is dried And a method of laminating a double-sided tape impregnated with a pressure-sensitive adhesive on release paper, and further laminating the resin film surface of the water-absorbing composite. In addition, when using the water-absorbing composite, it can be applied to a desired location using a commercially available double-sided pressure-sensitive adhesive tape. The pressure-sensitive adhesive layer can be provided on the entire surface or a part of the resin film, and is appropriately set according to the use conditions of the water-absorbing composite.

In the present invention, in order to improve the adhesive strength between the pressure-sensitive adhesive layer and the resin film, it is preferable that the resin film is previously subjected to a corona discharge treatment. By performing the corona discharge treatment, the wettability of the resin film is improved, and the adhesive strength with the adhesive is improved. The conditions of the corona discharge treatment can be appropriately set according to the type and thickness of the resin film to be provided.

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

In the present invention, functional materials such as a fungicide, an antibacterial agent, a deodorant, a flame retardant and the like can be added as long as the performance of the obtained water-absorbing composite is not deteriorated. These functional materials may be added to any part of the water-absorbing sheet, the resin film, and the pressure-sensitive adhesive layer. The water-absorbing 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 a 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 composited with another substrate by heat fusion. it can. In addition, it is possible to perform packaging processing of only the water-absorbing composite of the present invention. For example, the water-absorbent composite of the present invention may be bent or overlapped so that the resin film is on the inside or outside, and heat-fused at the 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. Winding of the water-absorbing composite is possible without humidity control. The resin film can be made thin. Therefore, manufacturing costs and distribution costs can be significantly reduced.

(C) Since no adhesive is used to provide a resin film on one or both surfaces of the water-absorbing sheet, swelling of the water-absorbing polymer is not suppressed, and no adhesive is eluted. Since the water-absorbing polymer is directly adhered to the fiber sheet and no binder is used, the surface of the water-absorbing polymer is not covered with the binder, so that the efficiency of absorbing and releasing moisture and the response speed do not decrease.
When the binder is used to prevent the polymer from falling off, the water absorption decreases, but the water absorption does not decrease because the water-absorbing polymer directly adheres to the fiber sheet.

(D) There is no peeling of the resin film from the water-absorbing sheet after water absorption. Therefore, repeated use of water absorption and drying is possible. (E) When a porous resin film is provided on the surface of the water-absorbent sheet, water can be absorbed without exposing the water-absorbent polymer and without falling off the water-absorbent 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 hydrophilic and hydrophobic properties. (G) By providing an adhesive layer on the resin film of the water-absorbing composite, the following advantages are obtained. The water-absorbing composite can be applied freely according to the purpose.

Since the dimensional stability of the water-absorbing composite is extremely high, a peeling phenomenon in which a gap is formed between the release paper and the pressure-sensitive adhesive layer when stored for a long time, that is, a so-called tunneling phenomenon can be prevented. Since the strength of the water-absorbing composite is maintained by the resin film, the removability is improved.

Thus, the water-absorbing composite of the present invention can be used, for example, in the form of disposable diapers, sanitary cotton, oneshed sheets, medical sheets, foot wiping mats, drip absorbents, food freshness holding materials, food trays, coasters, dew condensation preventing sheets, It can be suitably used for applications such as a water-blocking material for cables, a cold-retaining material, a water-retaining material for agriculture and horticulture, a cement-cured sheet, a sludge coagulant, and an artificial anus.

In particular, the water-absorbing composite of the present invention is preferably formed by subjecting the water-absorbing sheet to a softening treatment before or after forming the resin film, because the water-absorbing sheet is easily deformed and the texture becomes soft. The softening process, for example,
The water-absorbing polymer of the water-absorbing sheet is reduced to its saturated water absorption of 25
It is carried out by absorbing water to a weight percent or more and drying. If water absorption is performed within the above range when water absorption / drying is repeated, a softening process is automatically performed.

[0029]

[Function] Since a non-adhesive resin film is formed on at least one surface of the water-absorbing sheet at normal temperature, the exposure of the water-absorbing polymer is prevented, and the polymer and the object are directly in contact with each other at the time of water absorption. Is prevented from peeling off from the fiber sheet. In addition, the water-absorbing polymer is directly fixed to the fiber sheet by the reaction of a water-absorbing polymer-forming material such as a water-soluble ethylenically unsaturated monomer that forms a water-absorbing polymer by reaction, and a resin film is formed on one or both sides of the sheet. Since it is formed, the shape retention and dimensional stability of the sheet are high, and the dimensional stability of the water-absorbent sheet is prevented from being deteriorated when absorbing water. Further, since the water-absorbing polymer is directly fixed to the fiber sheet, it does not easily fall off and does not cause a decrease in water absorption.

Since the resin film is formed by applying and processing the resin material in a liquid state, penetration into the water-absorbent sheet is improved and peeling from the water-absorbent sheet as compared with the case where the resin film is laminated. And the water-absorbing 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 made of thermoplastic fiber, 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, a water-absorbing composite can be arbitrarily applied to a desired portion. By providing a corona discharge treatment to the resin film in advance when providing the pressure-sensitive adhesive layer, the adhesion between the resin film and the pressure-sensitive adhesive layer is improved, and the durability is excellent.

[0032]

The present invention will be further described below with reference to examples, but the present invention is not limited to these examples. (Synthesis Example 1 of Water Absorbent Sheet) Acrylic adjusted to pH 5.6 in which 0.5 mol% of methylenebisacrylamide (based on sodium acrylate monomer) and 1.0 g / mol of sodium persulfate (based on sodium acrylate monomer) are dissolved. The basis weight of 30 g /
m ² ES (ES: polyethylene-polypropylene composite fiber) non-woven fabric is immersed in the non-woven fabric, the aqueous solution is impregnated with the non-woven fabric, the amount of the monomer aqueous solution attached to the substrate is set to 200% by weight, and the mixture is heated to perform radical polymerization. 1) was obtained.
The water absorption was 40 g / g and the thickness was 900 μm.

(Synthesis example 2 of water-absorbent sheet) pH 5.6 in which 0.5 mol% of methylenebisacrylamide (based on sodium acrylate monomer) and 1.0 g / mol of sodium persulfate (based on sodium acrylate monomer) are dissolved.
A polypropylene nonwoven fabric having a basis weight of 25 g / m ² is immersed in a 43% by weight aqueous solution of sodium acrylate adjusted to the above, and the aqueous solution is impregnated with the aqueous solution. To obtain a water-absorbent sheet (2). The water absorption of this product is 20g
/ G, thickness was 500 μm.

Example 1 One side of a long water-absorbent sheet (1) having a width of 1 m was coated with polyethylene at a line speed of 200 m / min by extrusion coating in a state where polyethylene was melted. The water-absorbent composite (1) of the present invention in which the polyethylene layer was laminated on one surface of the layer (1) with a thickness of 30 μm was obtained.

Example 2 A water-absorbent composite (2) of the present invention was obtained in the same manner as in Example 1, except that the water-absorbent sheet (2) was used instead of the water-absorbent sheet (1). Comparative Example 1 A comparative water-absorbing composite (1) was obtained by laminating a water-absorbent sheet (1) and a 30-μm-thick polyethylene film with a polyurethane-based adhesive.

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

[0037]

[Table 1] Water-absorbing composite (1) Water-absorbing composite (2) Comparative water-absorbing composite (1) First water absorption 13 g / g 6 g / g 4 g / g First adhesion Good / No peeling Good・ No peeling Partial peeling Second water absorption 13g / g 6g / g --- Second adhesion good ・ No peeling Good ・ No peeling Complete peeling Third water absorption 13g / g 6g / g --3rd Good adhesion, no peeling Good, no peeling Complete peeling As is clear from the results shown in Table 1, the water-absorbing composite of the present invention has good adhesion to the resin film and can be repeatedly subjected to water absorption and dehydration. No deterioration in quality was observed.

Example 5 Acrylic acid adjusted to pH 5.6 in which 0.3 mol% of methylenebisacrylamide (based on sodium acrylate monomer) and 1.0 g / mole of sodium persulfate (based on sodium acrylate monomer) were dissolved. A 43% by weight aqueous solution of sodium was added to a basis weight of 30 g /
m ² is applied to one surface of the ES non-woven fabric, the amount of the monomer aqueous solution adhered to the substrate is set to 150% by weight, and the radical polymerization is performed by heating. Obtained. Subsequently, a polyethylene layer was provided on the water-absorbing polymer layer side by an extrusion coating method in a state in which polyethylene was melted to obtain a water-absorbing composite (3) of the present invention. Its water absorption was 10 g / g. This product was suitable for a drip absorbing sheet without exposing or falling off the water-absorbing polymer even after absorbing water.

Example 6 0.01 mol% of methylenebisacrylamide (based on sodium acrylate monomer),
1.0 g / mol of sodium persulfate (based on sodium acrylate monomer), and hydroxyethyl cellulose 2
A non-woven fabric having a basis weight of 30 g / m ² made of polyethylene-polyester composite fiber is immersed in a 43% by weight aqueous solution of sodium acrylate adjusted to pH 5.6 in which a weight% (based on sodium acrylate monomer) is dissolved. And the adhesion amount of the aqueous monomer solution to the substrate is 200
The resulting mixture was heated to a weight percentage to perform radical polymerization to obtain a water-absorbent sheet (4). 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 in a state where polyethylene was 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 cut into 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-absorbing composite (4) Water-absorbing sheet (4) Water absorption 75 g / g 100 g / g Good adhesion and no peeling-Size (length × width) 10 cm × 20 cm 9 cm × 34 cm Dropping of polymer 1% 2% As is evident from the results shown in Table 2, the water-absorbing composite of the present invention has good adhesiveness of the resin film, does not fall off the polymer, has excellent shape retention as a sheet, and has dimensional stability. The properties are also very good.

Comparative Example 3 0.01 mol% of methylenebisacrylamide (based on sodium acrylate monomer)
1.0 g / mol of sodium persulfate (based on sodium acrylate monomer) and 2% by weight of hydroxyethylcellulose (based on sodium acrylate monomer) dissolved p
43% by weight of sodium acrylate adjusted to H5.6
After the aqueous solution was degassed with nitrogen, it was dropped on a stainless steel belt heated to 120 ° C. in a nitrogen atmosphere to polymerize the thin film. The polymer after polymerization is scraped off from the belt surface, dried and pulverized to obtain a powdery water-absorbing polymer (1).
I got Its water absorption capacity in tap water is 110 g /
g.

Subsequently, the nonwoven fabric used in Example 6 was immersed in a suspension of a water-absorbing polymer comprising 10 parts by weight of butyl rubber, 90 parts by weight of the water-absorbing polymer (1), and 100 parts by weight of toluene. To 200 wt% of the suspension on the substrate, followed by drying. Subsequently, in the same manner as in Example 6, a comparative water-absorbing composite (2) in which a polyethylene layer was laminated on one surface to a thickness of 30 μm was obtained.

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

[0045]

[Table 3] As is evident from the results shown in Table 3, since the water-absorbing polymer was fixed to the fiber base material with the binder, the water-absorbing polymer almost dropped off when absorbing water, resulting in poor shape retention as a sheet. In addition, the resin film also peeled off from the water-absorbent sheet as the polymer fell off, and the adhesion to the sheet was poor.

Example 8 A mixture obtained by mixing a predetermined amount of a trifunctional isocyanate cross-linking agent with a commercially available acrylic solvent-type pressure-sensitive adhesive having a solid content of 45% by weight capable of isocyanate cross-linking so that the thickness after drying becomes 30 μm. The adhesive layer was formed on the release paper by applying it on release paper and evaporating the solvent by drying.

The surface of the polyethylene resin film of the water-absorbing composite (1) obtained in Example 1 was subjected to a corona discharge treatment. The pressure-sensitive adhesive layer formed on the release paper is transferred to the polyethylene resin film surface of the water-absorbent composite (1) that has been subjected to the corona discharge treatment, and the water-absorbent composite (5) of the present invention provided with release paper I got Its water absorption was 11 g / g. When this was stored in a room for a long time, no tunneling phenomenon occurred between the release paper and the pressure-sensitive adhesive layer. This material was useful as a dew-preventing wall material when attached to a wall, and had good removability.

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

Example 9 Synthesis Example 1 except that a commercially available fungicide (PL-600, trade name, manufactured by Tokyo Fine Chemical Co., Ltd.) was added in an amount of 1% by weight (based on acrylic acid monomer) in Synthesis Example 1 of the water-absorbent sheet. In the same manner as in the above, a water-absorbent sheet (5) was obtained. It had a water absorption of 40 g / g and a thickness of 900 μm, and exhibited good antifungal properties against blue mold, black mold, and dry-dry mold, and good antibacterial properties against bacilli. After a polyethylene resin film was provided on one surface of the sheet in the same manner as in Example 6, an adhesive layer was provided on the polyethylene resin film in the same manner as in Example 8, and the water-absorbing composite (6) of the present invention was obtained. I got This was useful as a dew-prevention wall material and had good removability.

Example 10 The water-absorbent composite (1) obtained in Example 1 was subjected to extrusion coating in a molten state of polyethylene on the side on which the polyethylene resin film was not provided, so as to have a width of 2 mm. A polyethylene layer (thickness 20μ)
m) were laminated (the interval between the streaks in the polyethylene layer was 1 mm) to obtain a water-absorbing composite (7). Its water absorption 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 absorption / absorption / desorption could be carried out from between. Further, when water was absorbed, water did not leak to the side on which the polyethylene layer was laminated on the entire surface, and the water remained dry. This product was suitable for a freshness preserving sheet of food without exposing or falling off the water-absorbing polymer after water absorption, and without causing the polymer to directly contact food or the like.

Example 11 2 mol% of methylene bisacrylamide (based on sodium acrylate monomer), 1.0 g / mol of sodium persulfate (based on sodium acrylate monomer) and 2% by weight of hydroxyethyl cellulose
(Sodium acrylate monomer)
A 37% by weight aqueous solution of sodium acrylate adjusted to 5.6 was prepared. A nonwoven fabric made of polypropylene having a floral pattern printed on one side at a basis weight of 55 g / m ² is immersed in this aqueous monomer solution, and after impregnating the aqueous solution, excess monomer aqueous solution is squeezed out with a roller to determine the amount of the monomer aqueous solution attached to the substrate. It was 250% by weight. The impregnated material was heated to perform radical polymerization to obtain a water-absorbent sheet (6). There was no difference in the color of the printed floral pattern before and after fixation of the water-absorbing polymer. Subsequently, a polypropylene layer is provided with a thickness of 20 μm by extrusion coating in a state where polypropylene is melted on one side 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. Its water absorption was 10 g / g. This was useful as a coaster.

Example 12 A mixture obtained by mixing a predetermined amount of a trifunctional isocyanate crosslinking agent with a commercially available acrylic solvent-type pressure-sensitive adhesive having a solid content of 45% by weight capable of isocyanate crosslinking so that the thickness after drying becomes 50 μm. The adhesive layer was formed on the release paper by applying it on release paper and evaporating the solvent by drying.

The water-absorbing composite (8) obtained in Example 11
Was subjected to a corona discharge treatment. The pressure-sensitive adhesive layer formed on the release paper is transferred to the surface of the polypropylene resin film of the water-absorbent composite (8) which has been subjected to the corona discharge treatment, and the water-absorbent composite (9 ) Got. Its water absorption was 8 g / g. When this product was stored for a long period of time, the water-absorbing composite did not shrink, and the tunneling phenomenon between the release paper and the pressure-sensitive adhesive layer did not occur. This material was useful as a dew-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-absorbing composite did not expand or contract, and there was no shift in the pattern between the water-absorbing composites (9) pasted together.

(Comparative Example 5) The surface of the water-absorbent sheet (6) obtained in Example 11 on the side on which no printing was performed was prepared according to Example 1.
The pressure-sensitive adhesive layer formed on release paper used in Step 2 was transferred to obtain a comparative water-absorbing composite (4) with release paper. When stored for a long period of time, the comparative water-absorbing composite shrinks,
Tunneling occurred between the release paper and the pressure-sensitive adhesive layer.

With respect to the water-absorbing composite obtained in the above example and the water-absorbing sheet used, the dimensional stability during water absorption was examined. The water-absorbent composite and the water-absorbent sheet cut to 10 cm × 20 cm in length and width 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 evident from the results in Table 4, the dimensional stability of the water-absorbent composite of the present invention at the time of water absorption is significantly improved by providing the resin film, as compared with the corresponding water-absorbent sheet.

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

[0058]

[Table 5] Tunneling Size after standing (vertical / cm) × (horizontal / cm) Absorbent composite (7) None 10 × 20 Absorbent composite (9) None 10 × 20 Comparative absorbent composite (3) ) Yes 9.6 × 19.6 Comparative water-absorbing complex (4) Yes 9.4 × 19.4

[0059]

According to the water-absorbing composite of the present invention, since the resin film formed on at least one surface of the water-absorbing sheet is not easily peeled off, the exposure and falling off of the water-absorbing polymer are suppressed, and the dimensional stability is good. It is convenient. According to the method for producing a water-absorbing composite of the present invention, such an excellent water-absorbing composite can be easily obtained.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-2-289197 (JP, A) JP-A-63-28639 (JP, A) JP-A-3-767 (JP, A) (58) Survey Field (Int.Cl. ⁷ , DB name) B32B 1/00-35/00 A41B 13/02 A61F 13/18

Claims (9)

(57) [Claims] 1. A water-absorbent polymer which can be converted into a water-absorbent polymer by a reaction. The water-absorbent polymer is directly adhered to a fiber sheet by a reaction. A water-absorbing composite formed with a water-soluble resin film. 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 a fiber sheet. The water-absorbing composite according to claim 1, which is obtained by: 3. The water-absorbent composite according to claim 1, wherein the resin film is made of a thermoplastic resin, and at least a part of the fiber sheet is made of a thermoplastic fiber. 4. The water-absorbing 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 coated on at least one surface of a water-absorbent sheet having a water-absorbent polymer directly fixed 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. A method for producing a water-absorbing composite, wherein a liquid material of a resin material that can be formed is applied and processed. 6. The water-absorbing polymer-forming material is a water-soluble ethylenically unsaturated monomer which can be converted into a water-absorbing polymer by polymerization, and the water-absorbing sheet is formed by polymerizing said monomer after attaching said monomer to a fiber sheet. The method for producing a water-absorbing composite according to claim 5, which is obtained by: 7. The method for producing a water-absorbing composite according to claim 5, wherein the application of the resin material is extrusion coating in a molten state of the resin material. 8. The method according to claim 5, wherein after applying a resin material to form a non-adhesive resin film at room temperature, an adhesive layer is provided on at least a part of the resin film. A method for producing the water-absorbing composite according to the above. 9. The method for producing a water-absorbing composite according to claim 8, wherein a pressure-sensitive adhesive layer is provided after performing a corona discharge treatment on the non-adhesive resin film at room temperature.