JPS6312994Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a sheet-like water-absorbing material in which super-absorbent resin powder is laminated with a woven fabric made of water-soluble polyvinyl alcohol filament.

A water-absorbing resin that can absorb several hundred times its own weight of water within a few minutes is also commonly known as a hydrogel (hereinafter referred to as hydrogel), and is conventionally known.

Such hydrogels can be used in sanitary products such as sanitary napkins, disposable diapers, disposable cloths, water retention agents for agriculture and horticulture,
Applications have been found in a wide range of fields involving water, such as oil-water separation agents, solid-liquid separation agents for sludge, and water-absorbing materials for ceilings, walls, etc.

Hydrogels are obtained by moderately physically or chemically crosslinking water-soluble resins made of various polymer electrolytes.Due to their composition and resin properties, hydrogels do not exhibit thermoplasticity, and can be formed into films or fibers by themselves. It is difficult to prepare a powder, and it is usually supplied in powder form.

Considering the inherent property of hydrogels to absorb water, it is rather preferable that the hydrogel is in powder form, since the area of contact with water is large and the rate of water absorption can be increased. However, since the hydrogel is in the form of a powder, the hydrogel powder that has swollen after absorbing water exhibits stickiness and tends to adhere to various substrates, which often causes disadvantages in practical terms.

For example, when painting the walls or floors of a building that are wet with water, hydrogel powder may be sprinkled on the walls or floors to remove adhering moisture. It is difficult to spray efficiently and uniformly, and at the same time, it is difficult to recover the sticky hydrogel that has swollen due to the absorption of adhering water, which not only requires a great deal of effort to clean the wall surface, but also causes the residual hydrogel to smear. This leads to disadvantages such as poor adhesion of the film.

Therefore, in order to effectively use powdered hydrogel, it is necessary to (1) sandwich the hydrogel between two tissues, (2) place it on top of the tissue, as seen in sanitary napkins, disposable diapers, etc. (3) Pulp and hydrogel are mixed and then sandwiched between two tissue sheets; (4) Hydrogel is spread on a water-permeable resin membrane made of a hydrophilic polymer. The handling properties of hydrogels have been improved by (5) products made by mixing hydrogels with various synthetic resins and molding them into sheets, pellets, sponges, etc.

However, in the cases of (1) to (3) mentioned above, the hydrogel can swell relatively freely in the horizontal direction due to water absorption, so it has excellent water absorption in the horizontal direction, but it has excellent water absorption in the vertical direction. Water absorption is restricted by the tissue, which limits the free space, so swelling is limited, and the water absorption capacity of the hydrogel body cannot be fully demonstrated.Water absorption also reduces the strength of the tissue itself, so it cannot be applied to a large area. It is difficult to apply. (4) When the material is sandwiched between water permeable resin films, the water absorption rate is significantly reduced due to the water permeation resistance of the resin film. Furthermore, those used in combination with various synthetic resins (5) are inhibited from changing volume due to water absorption and swelling, resulting in a significant decrease in water absorption capacity. It has various problems such as.

As a result of various studies to solve these problems, the inventor of the present invention found that it is easy to install and remove when removing water existing on the surface of various shapes without reducing the water absorption speed and ability of the hydrogel. Therefore, we discovered a sheet-shaped water-absorbing material that has many advantages, such as being able to be dried and reused, and arrived at the present invention.

That is, the present invention consists of a laminate of a woven fabric A made of water-soluble polyvinyl alcohol fibers, a hydrogel layer B, and a spacer C having a mesh with an opening of at least 840 μm, and the laminate includes A, B, The present invention provides a sheet-like water absorbing material having a structure in which C, B, and A are laminated in this order.

Hereinafter, the present invention will be explained in detail based on the drawings.

The drawing is a cross-sectional view of the sheet-like water-absorbing material of the present invention, and shows a structure in which the woven fabric A, hydrogel layer B, and spacer C are laminated in the order of A, B, C, B, and A. It is something that

The woven fabric A used in the present invention is a support for forming a layer of hydrogel, and the woven fabric (support) does not impede the permeation of water into the hydrogel layer, and at the same time, the woven fabric A is a support for forming a layer of hydrogel. It is necessary that the material does not adversely affect the water absorption rate, does not shrink or change its shape before and after use, has excellent affinity with the hydrogel that forms the layer, and does not allow the hydrogel to separate when bent, etc. Not being recognized is also an important characteristic that is required.

Woven fabrics that satisfy these required characteristics include water-soluble polyvinyl alcohol fibers, such as fibers produced by the method described in Japanese Patent Publication No. 43-8992 (polyvinyl alcohol having a saponification degree of 95 to 99 mol%). Woven fabrics made from dry-spun polyurethane are preferred and are commonly used as base fabrics for chemical laces.

The water-soluble polyvinyl alcohol fiber has a melting temperature ranging from 20°C to 95°C depending on its manufacturing method.
There are various grades, including those that are soluble in hot water above 60°C, but those that are soluble in hot water below 60°C show 40 to 45% shrinkage in 25°C water under no tension, making them difficult to use. There is a possibility that the shape may change from front to back. For this reason
It is preferable to use fibers manufactured to be soluble in hot water of 70°C or higher.

There are no special restrictions on how to make Woven Fabric A, but depending on the manufacturing method, hydrogels may contain very fine particles, so the finer the opening of the woven fabric, the finer the particles. It is possible to prevent loss, and for this reason, the opening is about 200 μm.
It is preferable to set it as approximately. A woven fabric with an opening of approximately 200 μm can be obtained by weaving fibers having a thickness of 28 denier, for example, so that the number of warp and weft yarns is approximately 90 per square inch.

The hydrogel used to form hydrogel layer B is made of water that is several tens to hundreds of times its own weight for several seconds.
Those that have the ability to absorb within minutes can be used. For example, saponified starch-acrylonitrile graft polymers, starch (or cellulose)-sodium acrylate graft polymers, partially saponified polyacrylic acid crosslinked polymers by heat treatment, sodium (meth)acrylate and Copolymers with crosslinking agents, saponified self-crosslinking polymers that utilize the self-crosslinking properties of acrylic acid during polymerization reactions, ionic complex polymers of polyacrylic acid with polyvalent metal ions, and polyvinyl alcohol copolymers. A graft polymer of sodium polyacrylate that takes advantage of its crystallinity, a polymer that introduces cross-linking by esterifying polyvinyl alcohol with a dibasic acid, and a polymer that is basic by copolymerizing vinyl ester and (meth)acrylate ester. It is a powder of a polymer obtained by saponifying a polymer saponified with a substance, a copolymer of hydroxyethyl (meth)acrylate and an acrylic ester, and these are examples and are not limited to these. isn't it. Furthermore, there is no particular limitation on the particle size of the hydrogel powder, and particles with a particle size of 70 to 2000 μm can be suitably used.

Spacer C is to secure the free space necessary for water absorption and swelling of the hydrogel, and is made of natural fibers such as cotton and silk linen, and synthetic fibers such as nylon, polyester polyacrylic, and polyvinyl alcohol.
It is preferable to use a sheet that is knitted or formed into a net shape so that its opening size is at least 840 μm. If the opening size of the spacer is smaller than 840 μm, it is difficult to obtain the free space necessary for the water absorption and swelling of the hydrogel, and the water absorption ability of the hydrogel cannot be fully exhibited.

As the material used for the spacer C, it is preferable to use a net or net-like material made of polyvinyl alcohol fibers in consideration of durability, cost, and affinity with water.

There are no particular limitations on the method for laminating the woven fabric A, hydrogel layer B, and spacer C.
An example of this is as follows.

That is, one side of woven fabric A is sprayed with hydrogel powder and then an aqueous solution of acetone or lower alcohol, or a hydrogel dispersed in acetone or lower alcohol aqueous solution is sprayed to make the hydrogel sticky. The hydrogel powder layer B is applied to one side of the woven fabric A. After drying the hydrogel layer B, or without drying, a spacer C is superimposed on the layer B, and then a woven fabric A with the hydrogel layer B obtained by the above method is placed on top of the spacer C so that the hydrogel-attached side is the spacer C side. The sheet-like water-absorbing material of the present invention can be obtained by laminating the water-absorbing material so as to be in contact with the water-absorbing material.

The solvent used when dispersing the hydrogel powder is preferably acetone and/or a mixed solvent of lower alcohol and water, which is soluble in water without being absorbed by the hydrogel, and the amount of water used is less than that of acetone and/or water. It is preferred to use 10 parts or less based on the lower alcohol. This is to increase the adhesion of the hydrogel to the polyvinyl alcohol fibers, and if more than 10 parts is used, the fibers of Woven Fabric A may shrink when dried.

When the hydrogel layer B formed by dispersing the hydrogel powder is dried, when the fibers of the woven fabric A are placed in a high temperature atmosphere, the crystal structure changes and the water solubility decreases. For this reason, it is preferable to dry with warm air at 80°C or lower.

Since the sheet-like water absorbing material of the present invention obtained as described above uses a hydrophilic porous woven fabric as a support for the hydrogel layer, the water absorption rate of the hydrogel is not inhibited. Since free space is maintained by the spacer, the water absorption capacity of the hydrogel is not reduced, and therefore the amount of hydrogel used can be reduced. Since the durability and mechanical strength of the hydrogel support are fully utilized, it can be applied over a wide area and reused. It has many characteristics such as

The present invention will be explained in detail by the following examples.

Example 1 As a support for the hydrogel layer, a woven fabric made of water-soluble vinylon fibers (Solblon manufactured by Nichibi Co., Ltd.) was used as a support for the hydrogel layer.
GH400, 28 denier thread, 100 warps x 96 wefts
Two pieces of cloth cut into 5 x 4 cm pieces were prepared (a woven fabric woven in a length of 1/2 inch), spread on a wire mesh so as not to wrinkle, and fixed on all four sides. Hydrogel powder (Sunwet IM-300 manufactured by Sanyo Chemical Co., Ltd., pure water absorption capacity, 470 ml/g) was ground in a mortar, and 100 g of the powder that passed through a 40-mesh sieve was dispersed in an alcoholic solution containing 10 g of water and 190 g of methanol, and stirred. The mixture was sprayed onto each of the two woven fabrics so that the amount of hydrogel after drying was 10 g/m ² , and dried overnight at room temperature to produce a woven fabric with a hydrogel layer formed thereon.

Next, it consisted of Solblon MH manufactured by Nichibi.
A 50 denier thread is knitted into a net shape with 30 warp threads and 30 weft threads per inch and cut into 5 x 4 cm pieces as a spacer, and the two previously prepared hydrogel layers are inserted through the spacer. After stacking the formed woven fabrics so that the hydrogel layers faced each other, the four sides were bonded and fixed using a commercially available epoxy adhesive to make a sheet-like water-absorbing material so that there would be no misalignment between the woven fabrics.

The sheet-like water-absorbing material made as above was 28
When the sheet was floated in a 22 x 3 cm stainless steel container filled with 1500 ml of tap water, it was observed that the sheet absorbed water more rapidly than the surface that came into contact with the water, and after 5 minutes the sheet was completely soaked. When the sheet was taken out after 1 hour and the amount of water absorbed was measured, it was found that 14 g of water was absorbed, which was 74.5% of the water absorption capacity of the hydrogel itself. Further, when the sheet after water absorption was left at room temperature, the amount of residual moisture after 15 days was 1.4 g, and no deformation of the sheet was observed. Furthermore, when the water-absorbing sheet was made to absorb water again in the same manner as described above, it absorbed 13g of water, and this value was comparable to the initial water absorption, indicating that it is a water-absorbing material that can withstand repeated use. It was hot.

Example 2 A woven fabric made of water-soluble vinylon fibers (Solblon GL400, 28 manufactured by Nichibi Co., Ltd.) was used as a support for the hydrogel.
A sheet-like water-absorbing material was made in the same manner as in Example 1, except that a woven fabric woven with denier yarn (100 warps x 106 wefts/inch) was used, and the water-absorbing ability was tested in the same manner. . As a result, the water absorption amount was 13 g, which was about 69% of the water absorption capacity of the hydrogel itself.

Example 3 As a hydrogel powder, Sumikagel S-50 (manufactured by Sumitomo Chemical Co., Ltd., pure water absorption capacity 500 g/g) was crushed and
A sheet-like water-absorbing material was prepared in the same manner as in Example 1, except that mesh-passing powder was used, and the test was conducted in the same manner as in Example 1. The water absorption weight was 13 g, which was 65% of the water-absorbing capacity of the hydrogel itself. It was shown to be effective. After repeated use three times, the amount of water absorbed was 12.5 g, showing almost no decrease in water absorption capacity, indicating that the material was highly recyclable.

Example 4 As a support for the hydrogel layer, a woven fabric made of vinylon fibers soluble in hot water at 60°C (manufactured by Nichibi Co., Ltd., Solblon SX5788, 56 denier yarn with 50 warps) was used.
An attempt was made to create a sheet-like water-absorbing material in the same manner as in Example 1 using a woven fabric woven with 60 wefts/inch, but a water-methanol mixed solvent Shrinkage occurred, which was thought to be due to the water inside, and it was difficult to obtain a sheet-like water absorbent material with excellent smoothness.

Comparative Example 1 As a support for the hydrogel layer, a commercially available shirt fabric whose fibers are 80% polyester and 20% cotton as indicated on the label was washed with water and acetone three times, dried, and then cut into 5 x 4 cm pieces. A sheet-like water absorbing material was produced in the same manner as in Example 1 except for the above. The average value of the aperture measured using a microscope was approximately 88 μm. When the same water absorption test as in Example 1 was conducted, this water absorbing material remained floating on the water surface and no rapid water absorption was observed, so when it was forcibly immersed in water, it seems that cotton was used as the support. Swelling of the hydrogel was observed only in the areas where the water was absorbed, indicating that the material had a significantly low water absorption capacity.

Comparative Example 2 As a spacer, Solblon GH400 (woven fabric used as a support for the hydrogel layer in Example 1)
A sheet-like water-absorbing material was prepared in the same manner as in Example 1, except that the following was used. The obtained water absorbing material was tested in the same manner as in Example 1, and the water absorption amount was
It is extremely small at 0.235g, which is lower than the water absorption capacity of hydrogel.
It reached only 1.25%. This was because a woven fabric with a very small opening was used as a spacer, so the free space necessary for the hydrogel to absorb water and swell was not secured.

[Brief explanation of the drawing]

The drawing is a cross-sectional view showing the laminated structure of the sheet-like water-absorbing material of the present invention. A...Woven fabric, B...Water absorbent resin layer, C...Spacer.

Claims (1)

[Scope of utility model registration request] It consists of a laminate of a woven fabric A made of water-soluble polyvinyl alcohol fibers, a water-absorbing resin layer B, and a spacer C having a mesh with an opening of at least 840 μm, and the laminate includes A, B, C, B. ，
A sheet-like water absorbing material having a structure in which layers are laminated in the order of A.