JPS6143193B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a water-absorbing or hygroscopic sheet material, and particularly aims to provide a water-absorbing or hygroscopic sheet material useful as a dew condensation prevention material for houses and other places where moisture is likely to occur. In recent years, housing has tended to become clustered and high-rise, and many non-hygroscopic materials such as concrete, steel frames, and glass are used as building materials.
In addition, as a result of the use of sashes, doors, etc., which made homes hermetically sealed, and the spread of various types of heating, condensation frequently occurred on indoor walls, floors, and ceilings.
Damages such as peeling of wall materials, growth of mold, damage to tatami mats, and contamination of furniture have become frequent. As methods for preventing dew condensation as described above, there are known methods such as heat insulation methods using heat insulating materials, ventilation/dehumidification methods, and breathable dew condensation prevention coating methods, but the heat insulation methods require a very thick insulation layer. , it was not possible to obtain sufficient effects in terms of cost, space, and construction methods.
Ventilation is the best method, but it is actually impossible because it conflicts with the heating effect, and dehumidifiers are not suitable for general households. In addition, in the method using anti-condensation paint, the amount of moisture absorbed by the formed coating film is low, and when it absorbs moisture, its surface becomes swollen.
It is difficult to apply various types of interior decoration on it, and when interior decoration is applied, the interior material often peels off. As a result of intensive research to solve the above-mentioned drawbacks of the conventional technology, the inventor of the present invention found ^that
It can absorb a large amount of moisture (approximately 100 to 3000 g per unit), and its surface remains dry even when it absorbs moisture, and when the atmosphere is dry, it gradually releases the absorbed moisture, so-called breathable water absorption.・We developed a hygroscopic sheet and were able to solve the above-mentioned drawbacks of the conventional technology. That is, the present invention involves applying a liquid composition containing a water-absorbing material to one side of a sheet-like base material having air permeability, and impregnating the water-absorbing material into the base material while leaving a surface layer of the base material. This is a method for producing a water-absorbent/hygroscopic sheet material, which comprises forming a back layer substantially free of water-absorbing material on the coated surface. The invention will now be described in detail with reference to the accompanying drawings, which illustrate embodiments of the invention. FIG. 1 shows a typical and preferred example of the water-absorbent/hygroscopic sheet material of the present invention, where 1 indicates the water-absorbent/hygroscopic sheet material of the present invention, and 2 may be provided as necessary. Adhesive layer 3 is a heat insulating material or release paper that may be provided as necessary, 4 is a back layer substantially free of water-absorbing material, and 5 is a water-absorbing/hygroscopic layer made of a water-absorbing material. 6 is a breathable surface layer substantially free of water-absorbing material. In this embodiment, the base material of the sheet material indicated by 1 is a nonwoven fabric made of synthetic fibers with a thickness of about 0.1 to 5 mm, and one surface of this nonwoven fabric 1 is coated with fine powder of a water-absorbing material. Alternatively, a liquid material (paint) dispersed or dissolved in water or an organic medium is applied together with an arbitrary binder, and impregnated so as to leave part 6 of the other surface of the nonwoven fabric, thereby forming a water-absorbing/hygroscopic layer 5. Then, a non-porous plastic sheet, a non-woven or other breathable sheet is attached to the surface coated with the above paint, or a synthetic resin paint or a polyurethane paint that can form a breathable layer is applied. A back layer 4 substantially free of water-absorbing material is formed. This back layer 4 may also serve as the adhesive layer 2. Furthermore, a heat insulating material or release paper 3 may be provided as necessary. In this embodiment, it is important to leave the breathable layer 6 on the surface of the nonwoven fabric 1 without impregnating the entire surface of the nonwoven fabric 1 with a paint made of a water-absorbing material. Such a structure can be easily achieved by adjusting the viscosity of the paint made of water-absorbing material, the concentration of the water-absorbing material, etc. according to the properties of the nonwoven fabric used, and controlling the impregnation rate of the water-absorbing material. can do. Alternatively, the portion where the breathable surface 6 is to be formed is filled with a solvent-soluble substance in advance, the nonwoven fabric is sufficiently impregnated with a paint made of a water-absorbing material, and after drying, the filling substance is eluted and removed. Even if it is formed, the air permeable surface layer 6 can be formed. If the water-absorbing material is present even in the air-permeable surface layer 6, it will be difficult to keep the surface of the sheet material 1 dry at all times, and therefore it will be difficult to perform various treatments on the surface of the sheet material 1. Furthermore, if a substantial amount of water-absorbing material is present in the back layer, it will be difficult to perform various decorative treatments as with the front layer, and it will also be difficult to adhere to walls and the like. FIG. 2 shows another embodiment of the water-absorbent/hygroscopic sheet material of the present invention. This sheet material
In No. 1 , a water-absorbent/hygroscopic layer 5 is prepared separately, and then both surfaces thereof are processed. That is, a base material 5 such as a nonwoven fabric is entirely impregnated with a paint made of a water-absorbing material, and then a breathable layer is formed on both sides using wet polyurethane or acrylic resin paint, and one side is covered with a surface layer 6. The other layer is used as the back layer 4. Alternatively, the back layer 4 may be formed by applying a plastic sheet, film, synthetic resin paint, etc. to one side of the water/hygroscopic layer 5, and then a breathable material such as non-woven fabric may be laminated to the other side, or The water absorbent/hygroscopic sheet 1 of the present invention is formed by forming the same breathable layer 6 as described above. Also,
The surface layer 6 and the back layer 4 may be formed by laminating breathable materials such as non-woven fabrics on both sides. In this case, it is important that the adhesive interface between the surface layer 6 and the water-absorbent/hygroscopic layer 5 be ventilated. This can be easily achieved by conventionally known means such as spot bonding with adhesive or suturing with thread. Although typical embodiments of the present invention have been illustrated above, the present invention is not limited to these examples, and various modifications and modified embodiments are possible, and such embodiments are also included. be. In addition to nonwoven fabrics, base materials used in the present invention include
Paper, woven fabric, synthetic resin foam, felt, cotton, web, sponge, glass cloth, and other breathable materials can all be used, with a preferred thickness of approx.
It is about 0.1 to 15 mm. The water-absorbing material used in the present invention includes (1) a hydrophobic polymer or copolymer having a hydrophilic group, as disclosed in JP-A-54-47796, 83091, 83989, 87791 and others; (2) starch-sodium polyacrylate grafted product, saponified starch-polyacrylonitrile grafted product, cellulose-sodium polyacrylate Water-soluble resins such as grafted products, vinyl alcohol-sodium acrylate copolymers, vinyl alcohol-sodium methacrylate copolymers, sodium polyacrylate, carboxymethyl cellulose soda salt, polyethylene oxide, etc. water-absorbing polymers, water-absorbing resins, water-swellable polymers, such as those made water-absorbent by crosslinking with
Any water-swellable resin etc. can be used.
Various other solid desiccants can also be used, but preferred ones are water-absorbing agents that do not dissolve even if they absorb a large amount of moisture (for example, tens to hundreds of times their own weight). polymeric material [mentioned above]
(1) and (2)] are preferred. Such water-absorbing materials can be used in the present invention in various organic solvents such as toluene, xylene, cyclohexane, methyl ethyl ketone, ethyl acetate, dioxane, tetrahydrofuran, dimethylformamide, methanol, ethanol, butanol, or mixtures thereof. Finely dispersed in a proportion of 50% by weight, preferably further containing chloroprene rubber,
Acrylic rubber, urethane rubber, butyral resin,
Water-absorbing materials such as ethylene-vinyl acetate copolymer, styrene-butadiene copolymer, butadiene synthetic rubber, nitrile rubber, isobrene rubber, polystyrene-polybutadiene-polystyrene block copolymer, polystyrene-polyisoprene-polystyrene block copolymer, etc.
Preferably, it is present in a proportion of about 5 to 60 parts by weight and used as a liquid composition having a viscosity of about 10 to 10,000 centipoise. Furthermore, if necessary, plasticizers, fungicides, flame retardants, fragrances, ultraviolet absorbers, colorants, deodorizers, etc. may be added. Such a liquid composition can be applied or impregnated onto a substrate such as a nonwoven fabric by conventionally known means such as a brush, spatula, bar coater, hand roller, spray, roll coater, flow coater, dip coater, or the like. The amount to be applied or impregnated depends on the type and thickness of the substrate used, its purpose,
Although it cannot be definitively determined as it varies depending on the type of water-absorbent material, water absorption rate, and other conditions, if the application is a sheet for preventing condensation, the water absorption amount of the resulting water-absorbent sheet material is approximately 100 to 1,500 g of water. / ^m2 . When using the water-absorbing material described in JP-A-54-47796, approximately ¹⁰ ~
Preferably, 100 g of water-absorbing material is included in the water-absorbent layer. Further, it is preferable to impregnate the surface layer so that the thickness of the surface layer, which is substantially free of the water-absorbing material, is about 1 to 100 microns. The materials used to form the back layer substantially free of water-absorbing material in the present invention vary depending on the method of formation, but when forming by applying a paint-type composition, in addition to the binder component described above, A polymeric material such as a vinyl chloride-vinyl acetate copolymer, an acrylic copolymer, a urethane resin for wet urethane, a polyester resin, or a vinyl acetate resin is dissolved in any organic solvent as mentioned above, and this is applied by any coating method. It can be formed by applying the film and drying it to form an air permeable or non-air permeable film of about 1 micron or more. Alternatively, a back layer can be formed by applying a solvent-free hot melt adhesive or a heat-sensitive adhesive, and then laminated with release paper or a relatively thin heat insulating material. The water-absorbing/hygroscopic sheet material of the present invention obtained as described above has a structure consisting of an air-permeable surface layer, a water-absorbing/hygroscopic layer, and a back layer, and the air-permeable surface layer and back layer are substantially Contains no water-absorbing materials. Therefore, such sheet materials can absorb and retain a large amount of moisture that should normally condense in a high humidity atmosphere (for example, on the north wall of a closet in a heated room in winter or on the back side of a tatami mat). Since the surface layer and back surface are kept dry even when the surface is exposed, wallpaper and other interior materials provided on the surface will not peel off or become contaminated. Furthermore, since the back layer of the water-absorbent/hygroscopic sheet of the present invention is always in a dry state, absorbed moisture will not impair the adhesion between the sheet and the wall surface. As described above, the water-absorbing sheet of the present invention is very useful as a dew condensation prevention material for houses, as well as for use as an underlay for pets, insoles for shoes, for removing moisture from the ground surface and underground, and for water retention and moisture release in plant pots. It is useful for applications that require hygroscopicity or water absorption, such as humidity control. Next, the present invention will be specifically explained with reference to Examples. Note that parts and percentages in the text are based on weight. Example 1 An equivalent amount of thioglycolic acid was added to polybutadiene of a telechelic type block copolymer represented by (polystyrene)-(polybutadiene=polystyrene) (polystyrene content 30%), and then a water-absorbing polymer (water absorption
60) A paint is obtained by mixing a dispersion obtained by decomposing 16 parts into 62 parts of methyl ethyl ketone and 20 parts of a 20% chloroprene rubber toluene solution. This paint was applied at a rate of 200 g/m ² to one side of a polyester nonwoven fabric having a basis weight of 100 g/m ² and a thickness of 0.4 mm using a bar coater. The paint permeated through the nonwoven fabric to a thickness of approximately 0.3 mm, but did not reach the back side. Then 80℃
and dried for 20 minutes. Then, apply 20% chloroprene rubber toluene solution to the same side of the above impregnated nonwoven fabric.
Coated with a bar coater at a rate of 125g/ ^m2 ,
It was dried at ℃ for 20 minutes to form a back layer, thereby obtaining a water-absorbing and hygroscopic sheet material of the present invention. The surface layer of this sheet material is approximately 0.12 mm thick, the water-absorbent layer is approximately 0.25 mm thick, and the back layer is approximately 0.12 mm thick.
It was 30 microns thick. When this water-absorbing/hygroscopic sheet material was left in an atmosphere with a relative humidity of 100% and a temperature difference of about 60°C for 4 hours, it absorbed about 700 g/m ² of moisture, and was then placed indoors at a relative humidity of 50% (20°C). When it was left to stand, the entire amount was released in about 6 hours. Even after repeating this operation 10 times, no change was observed in the amount of moisture absorbed. Further, no change was observed in the surface condition of the sheet. Furthermore, when the bedding was placed on the floor of a closet in a high-rise house where bedding gets wet due to condensation during the winter, the bedding no longer gets wet at all. Example 2 A 4 mm thick closed-cell polyethylene insulation sheet was adhered to the back layer of the water-absorbing/hygroscopic sheet material of Example 1 with an adhesive to obtain another water-absorbing/hygroscopic sheet of the present invention. . The moisture absorption amount of this sheet under the same conditions as Example 1 was 500 g/m ² (after 4 hours),
It showed 700 g/m ² after 6 hours, demonstrating the heat insulating effect of the foam. Regarding this sheet, moisture absorption and moisture release are
Even after repeating the test 10 times, no decrease in the adhesive strength between the sheet and the heat insulating material was observed. Example 3 Dispersion of water-absorbing polymer used in Example 1 50
200 g/m ² of the above paint was mixed on one side of a nylon nonwoven fabric with a basis weight of 120 g/m ² and a thickness of 0.5 mm. Impregnate in proportion. The impregnation in this case was 50% of the thickness of the nonwoven. After drying, a 15% acrylic rubber toluene-ethyl acetate solution was applied to the impregnated surface at a rate of 134 g/m ² and dried in the same manner as in Example 1 to obtain a water-absorbent/hygroscopic sheet material of the present invention. . The thickness of the surface layer of this sheet was about 0.23 mm, the thickness of the water-absorbing/hygroscopic layer was about 0.25 mm, and the thickness of the back layer was about 20 microns.
When this water-absorbing/hygroscopic sheet is placed in an atmosphere with a relative humidity of 100% and a temperature difference of 60°C, it will absorb approximately 200 g/m ² in approximately 4 hours.
When it was left in a room with a relative humidity of 50% (20°C), the entire amount of moisture was released in about 2 hours. After a decorative paper was attached to the surface layer of this sheet material, the decorative paper did not peel off even when it was left in an atmosphere with a relative humidity of 100% and a temperature difference of 60° C. for 2 hours. Example 5 The two sheets of the water-absorbing/hygroscopic sheet material obtained in Example 1 were bonded together on their backs by thermocompression, and the maximum water absorption amount reached 1500 g/ ^m2 , and the moisture released when drying was also rapid. Ta. When I cut this sheet to make insoles for rubber boots and used it, it showed very good moisture absorption, and my feet hardly felt stuffy. It was possible. Example 6 In Example 1, before applying the water-absorbing polymer and the back layer to the nonwoven fabric, a methanol solution of polyvinyl acetate (about 1000 poise) was applied to one side of the nonwoven fabric at a rate of about 4 g/m ² (solid content). After coating and drying, the operation of Example 1 was repeated on the other side, and finally it was immersed in methanol for one day to dissolve and remove the polyvinyl acetate and regenerate the breathable surface layer. A hygroscopic sheet material was obtained. The properties of this sheet material were similar to those of Example 1. Examples 7 to 10 A water-absorbing polymer (water absorbency 80) made by reacting a telechelic type block copolymer of (polystyrene, polybutadiene, polystyrene) (polystyrene content: 40%) with acetylsulfonic acid to form a sodium salt (water absorption: 80), A water-absorbing polymer based on sodium polyacrylate (water absorption 100) (Example 8), a water-absorbing polymer obtained by saponifying a crosslinked methyl acrylate-vinyl acetate copolymer (water absorption 120) (Example 9), and starch with acrylic The performance of the water-absorbing/hygroscopic sheet material of the present invention obtained using a water-absorbing polymer grafted with sodium chloride (water absorbency 150) (Example 10) and in the same manner as in Example 1 is shown in Table 1 below. It was hot on the street. In addition, "water absorption" in the above examples is
It represents the amount of water (g) that 1 g of water-absorbing polymer can absorb and retain.

[Table] Comparative Example 1 A water-absorbent/hygroscopic sheet material obtained by the same procedure as in Example 1, except that the entire nonwoven fabric was uniformly impregnated with a water-absorbing polymer using the method of Example 1. The amount of water absorbed was about 500 g/m ² , but the water-absorbing polymer present in the surface layer swelled with water and became an uneven surface, and the water-absorbing polymer on the surface fell off due to friction. In addition, when a decorative paper was attached to the surface before moisture absorption, the decorative paper peeled off. Comparative Example 2 A water-absorbing/hygroscopic sheet material obtained by performing the same procedure as in Example 1 except that the back layer was not formed had a water absorption amount of about 500 g/m ^{2 .} As shown, the sheet material was easily peeled off from the wall surface when it was allowed to absorb moisture after being attached to the wall surface. Example 11 A polyester nonwoven fabric having a thickness of 0.1 mm was sewn onto the surface of the water absorbent/hygroscopic sheet obtained in Comparative Example 1 to obtain a water absorbent/hygroscopic sheet material of the present invention. The performance of this sheet material was similar to that of Example 1. Example 12 After applying the same water-absorbing material liquid as in Example 1 to a nonwoven fabric in the same manner as in Example 1, a wet urethane resin solution (Rezamin CV-520) (solvent dimethylformamide) was applied to the coated surface of the water-absorbing material. It was coated with a bar coater, then immersed in water to form a film, dehydrated with isopropyl alcohol, and dried to obtain a water-absorbent/hygroscopic sheet material of the present invention. This product was useful as a dew-proof sheet and a humidity control sheet.

[Brief explanation of the drawing]

1 and 2 show embodiments of the present invention. DESCRIPTION OF SYMBOLS 1... Water-absorbent/hygroscopic sheet material, 2... Adhesive layer, 3... Heat insulating material, 4... Back layer, 5... Water-absorbent/hygroscopic layer, 6... Surface layer.

Claims (1)

[Claims] 1. Apply a liquid composition containing a water absorbent material to one side of a breathable sheet-like base material, leave a surface layer of the base material and impregnate the water absorbent material into the base material, and then apply the water absorbent material to one side of the base material. 1. A method for producing a water-absorbing/hygroscopic sheet material, which comprises forming a back layer substantially free of water-absorbing material.