JPS6340665B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a water-absorbing/water-retaining sheet, and more specifically, the present invention relates to a water-absorbing/water-retaining sheet, and more specifically, a coating liquid consisting of a blend of a non-aqueous binder and a super water-absorbing polymer fine powder is applied to a base material with relatively low water absorption, and a hydrophilic/water-permeable material is By laminating it into a sandwich sandwich, a sheet with high water absorption and water retention properties is provided. The water-absorbing/water-retaining sheet referred to here is a sheet that has the property of quickly absorbing water or an aqueous solution when it comes into contact with water or an aqueous solution such as salt, swelling, and retaining water so that it does not move. It means the sheet that is. Conventionally, there are products that require a relatively high water absorption capacity, such as sanitary products, diapers, disposable rags, paper towels, and medical gauze. In addition, architectural interior materials such as wall and ceiling materials and agricultural soil retention sheets are required to have high water absorption and water retention performance from the viewpoint of preventing dew condensation and water retention. To meet these demands, there have been sheets that utilize the physical absorbency of pulp or papers that contain water-soluble resins such as carboxymethylcellulose (CMC), but in order to achieve high water absorption, it is necessary to Quality stability may be affected, such as when it is necessary to increase the amount and thickness of the paper, or during the manufacturing process, the water-soluble resin is temporarily insolubilized and then neutralized with acid or alkali to make it water-soluble again after papermaking. There's a problem. Furthermore, in recent years, in order to satisfy the demand for high water absorption and water retention ability, cross-linked polyethylene oxide, cross-linked Popal, starch-polyacrylonitrile graft polymer hydrolyzate, partially cross-linked starch
Water-insoluble and highly water-absorbing substances such as poly(meth)acrylic acid copolymers have been proposed, but most of these are powders with low adhesion or highly viscous liquids. Difficult to apply to base materials. Furthermore, as a method of application to these base materials, these super absorbent substances can be directly mixed and dispersed in pulp etc. to form a sheet, or the powder of these super absorbent polymers can be mixed with a water-soluble binder such as polyvinyl alcohol or CMC. At the same time, methods have been proposed in which the base material is coated and impregnated as a dispersion with 500 to 1000 times the weight of the powder in water.
Currently, there are many problems such as the manufacturing method is not versatile, requires a huge amount of energy to evaporate a large amount of water, and furthermore, the resin that absorbs water and swells falls off from the base material. It is. Taking the above circumstances into consideration, the present inventors have repeatedly investigated various ways to obtain a sheet with high water absorption and water retention properties, and have applied a mixed coating liquid of a non-aqueous binder and super water absorbent polymer fine powder to a base material. In addition, by laminating this base material and a hydrophilic water-permeable material and forming a water-absorbing resin-containing layer into a sandwich layer, a sheet having high water-absorbing capacity without shedding of the super-absorbent polymer can be obtained. By discovering this and combining this with printing, coating, and laminating techniques, he proposed a water-absorbing and water-retaining sheet as shown in Japanese Patent Application No. 180127-1983. Special application 1984-
The invention described in No. 180127 mixes a water-insoluble and water-absorbing polymer fine powder in a solid content ratio of 20 parts by weight or more per 100 parts by weight of the resin binder with a non-aqueous solvent or solvent-free resin binder, If necessary, a coating liquid made by further mixing inorganic powder is partially applied to an arbitrary base material to form a film, and an adhesive is applied to the non-applied parts of the base material to form a film smaller than the fine polymer powder. It is a water-absorbing/water-retaining sheet made by partially adhering a hydrophilic/water-permeable material with an opening diameter, and the portion coated with a superabsorbent polymer is not bonded. By the way, as a result of repeated research,
By forming the intermediate layer with a mixture of super absorbent polymer fine powder and binder resin in a larger amount, even higher water absorbency can be obtained, and at the same time, the intermediate layer becomes porous, making it possible to improve the coating method. If this intermediate layer is devised and applied to the substrate in the form of a film with pores or openings that lead to the substrate, and then a suitable adhesive is applied, this adhesive will penetrate into the intermediate layer and adhere to the substrate. The present invention was completed after discovering the facts.
According to the present invention, it is not affected by the powder shape or particle size distribution of the superabsorbent polymer used, and there is no need to use special or complicated equipment for registering the superabsorbent polymer application area and adhesive. In addition, it can be easily created using the normal full-surface coating method and dry lamination method, has a fast water absorption rate, can provide large water absorption and water retention properties with a small coating layer, and has hydrophilicity and water permeability with the base material. A stable sheet with strong adhesion to the material can be obtained. That is, the present invention provides a non-aqueous solvent or a solvent-free resin binder and a water-insoluble superabsorbent polymer fine powder in a solid content ratio of 100 parts by weight or more based on 100 parts by weight of the resin binder, on the base material 1. an intermediate layer 2 having pores or openings 21 in the coated portion reaching from the surface of the layer to the substrate 1; A hydrophilic adhesive layer 3 having a communicating hole with an opening diameter smaller than the diameter of the super-absorbent polymer fine powder used in the intermediate layer 2 is inserted through a water-resistant cured cross-linkable adhesive layer 3 partially provided so as to cover the intermediate layer 2. This is a water-absorbent/water-retentive sheet made by laminating water-permeable materials 4. As shown in FIG. 1 of the drawings, in the sheet of the present invention, a water-absorbing/water-retaining intermediate layer 2 consisting of a super-absorbent polymer fine powder and a non-aqueous binder is attached to a base material 1.
It is sandwiched between a hydrophilic and water-permeable material 4, and is composited and held by an adhesive layer 3 that penetrates through the intermediate layer 2. The water-insoluble superabsorbent polymers used in the present invention include starch-sodium acrylate graft polymers, starch-acrylonitrile graft polymer hydrolysates, and partially crosslinked starch-poly(meth)acrylic acid copolymers. Starch-graft polymers such as coalesced and partially crosslinked starch-polymethyl methacrylate hydrolysates, and salts of the above substances, or methyl methacrylate-
Examples include cross-linked synthetic resins such as vinyl acetate copolymer hydrolysates, but basically any water-soluble polymer that has been cross-linked at a low density to make it water-insoluble will suffice, and there are no particular restrictions. It is not something that will be done. Some of these superabsorbent polymers are obtained in the form of fibers, but in the present invention, those in the form of fine powder are used. Its powder particle size is less than 35Mesh,
Preferably it is 100 mesh or less and 5μ or more. If the powder particle size is 35 mesh or more, there are problems with the stability, fluidity, and coating workability of the coating solution. In addition, if the particle size is less than 5μ, it is difficult to handle and collect the floating particles, and the powder particles are buried in the intermediate layer 2.
It has the disadvantage that it is difficult to obtain the high water absorbency that is the objective of the present invention. Examples of resin binders for mixing and dispersing these water-insoluble super absorbent polymer fine powders include alcohols such as methanol and ethanol, ethyl acetate,
Solutions, departions, and non-aqueous emulsions based on acetic esters such as butyl acetate, ketones such as acetone, methyl ethyl ketone, and methyl isobutyl ketone, and non-aqueous solvents such as hydrocarbon solvents such as n-hexane and toluene. , a curable solvent-free resin solution made of urethane oligomers, or a melted thermoplastic resin. Specific resins used for the resin binder include polyamide resins, linear thermoplastic polyester resins, vinyl chloride-vinyl acetate copolymers, cyclized rubber, chlorinated rubber, chlorinated polypropylene, and chlorinated ethylene-vinyl acetate copolymers. Combined, urethane, etc. 1
seeds or mixtures thereof. Furthermore, porous inorganic fine powder such as calcium carbonate, calcium silicate, silicon oxide, etc. is added to these resin binders in an amount not exceeding 20 parts by weight per 100 parts by weight of the resin binder, thereby dispersing it in the intermediate layer 2. At the same time, the viscosity of the mixed coating liquid is adjusted to prevent sedimentation of the superabsorbent polymer fine powder over time, thereby increasing the coating liquid. This has the effect of increasing the stability of If the addition ratio exceeds 20 parts by weight, the fluidity of the coating solution will drop significantly, causing problems in coating workability. Super absorbent polymer fine powder is resin binder 100
It is necessary to mix at least 100 parts by weight or more, preferably 200 parts by weight or more, based on the weight part,
If the amount is less than 100 parts by weight, most of the super absorbent polymer fine powder will be buried in the intermediate layer 2, making it impossible to obtain the high water absorbency that is the objective of the present invention. The upper limit of the amount of super absorbent polymer fine powder added can be increased as long as the fluidity of the coating liquid, coating workability, and adhesion retention to the substrate 1 are maintained, and there is no particular restriction. There isn't. Mixing of super absorbent polymer fine powder and resin binder is possible by normal stirring operation, but by kneading while crushing super absorbent polymer fine powder using a ball mill, attritor, etc., the super absorbent polymer fine powder particles can be mixed. By making the diameter uniform, it is possible to further improve the stability, fluidity, and coating workability of the coating solution, and by adding additives such as non-aqueous dispersants and viscosity modifiers, the coating solution can be made into a coating solution. Ru. When the mixed coating solution prepared as described above is applied on the substrate 1 as the intermediate layer 2, the adhesive directly adheres to the surface of the substrate 1 and forms a bond between the substrate 1 and the hydrophilic/water permeable material 4.
In order to firmly adhere the material, the application shape is as shown in FIG. 2, so that the final application area is provided so as to form pores or openings 21 communicating from the surface of the intermediate layer 2 to the base material 1, and the application is applied to the entire surface. do. The most suitable coating method is to use a gravure method without using a smoother. There is no particular restriction on the amount of coating as long as the super absorbent polymer fine powder protrudes above the intermediate layer 2 after drying. After coating, the coating solution is dried, cured, or cooled to form a film, and the surface thereof is basically non-adhesive. Further, on the intermediate layer 2 made of a mixture of super water-absorbing polymer fine powder and resin binder, which is coated on the entire surface of the intermediate layer 2 so as to form pores or openings 21 leading from the surface of the intermediate layer 2 to the base material, a water-resistant hardening layer is applied. After partially applying a cross-linking adhesive to form an adhesive layer 3, a hydrophilic/water-permeable material 4 having communicating holes with an opening diameter smaller than that of the fine super-absorbent polymer powder is laminated and bonded by pressure. The agent is cured and crosslinked to form an integral composite. In this case, the adhesive penetrates the intermediate layer 2 through the pores or openings 21 of the intermediate layer 2 due to the pressure at the time of crimping, reaches the surface of the base material 1, and hardens, thereby causing the adhesive to penetrate into the intermediate layer 2 at the adhesive-applied portion. The super water absorbent polymer fine powder becomes non-swellable with water, and the base material 1 and the hydrophilic/water permeable material 4 are firmly adhered to each other. It is possible to withstand the swelling pressure when the fine polymer powder absorbs water and swells, and to provide sufficient adhesive force to prevent the base material 1 and the hydrophilic/water permeable material 4 from peeling off. A sheet with high water retention can be obtained without the water-absorbing polymer fine powder moving or falling off. Furthermore, according to the method of the present invention, there is no need to use a special device for registering the adhesive and the area to which the mixture of super absorbent polymer fine powder and resin binder is applied, and it is possible to use the conventional full-surface coating method and dry lamination. It also has the advantage in terms of the manufacturing process that the desired water-absorbing/water-retaining sheet can be easily produced by the Shion method. The base material 1 used in the present invention is, for example, paper,
There are no particular limitations as long as the material is in sheet form, such as non-woven fabric, cotton fabric, wood, plastic, metal, glass, or asbestos. The hydrophilic/water permeable material 4 to be laminated is one that has communicating pores with an opening diameter smaller than that of the super absorbent polymer fine powder, the diameter of which is preferably 5μ or less, and is flexible and stretchable. is particularly preferred. For example, paper, nonwoven fabric, or cloth having a low Steckigt sizing degree may be used, but water permeable microporous films or nonwoven fabrics such as polyethylene or polypropylene that have been subjected to hydrophilic treatment may also be used. It is obvious and within the scope of the present invention that by using the hydrophilic/water-permeable material 4 for the base material 1 itself, a water-absorbing/water-retaining sheet having water-absorbing properties on both sides can be obtained. As described above in detail, various effects can be obtained by applying the present invention. For example, commercially available water-absorbing polymers such as starch-graft polymers and crosslinked synthetic resins can absorb and retain 3 to 400 times, or even 1000 times as much pure water as their own weight. The base material and laminated material are both made of plastic film, and are completely water resistant and have high water absorption and water retention performance, making it possible to obtain a highly water absorbing sheet that is several times to several tens of times the weight of the sheet, which is impossible with physical water absorption such as pulp. It can be easily produced using ordinary printing, coating, and laminating machines without the need for special equipment.You can freely select the base material and laminated material, and it can be used in a variety of ways depending on the application. It has many effects and advantages, such as being able to obtain a good texture and shape. Furthermore, the water-absorbing/water-retaining sheet obtained by the present invention can be applied as a release control base material for water-soluble functional chemicals such as preservatives, bactericides, antifungal agents, fragrances, and deodorizers. The water absorbency obtained with
The water-retaining sheet can be used to absorb excess water from marine products, fruits and vegetables, or to prevent them from wilting, and the water-absorbing and water-retaining sheet obtained by the present invention can be further used as wallpaper to be laminated to a plywood board. It also has great industrial utility value, such as the ability to produce wall and ceiling materials that do not cause condensation. The present invention will be explained below with reference to Examples, but the present invention is not limited thereto. Example 1 Starch-acrylic acid graft copolymer (water-absorbing polymer) fine powder (Sunwet
IM300MPS, manufactured by Sanyo Chemical Industries) 20 parts ●Chlorinated polypropylene resin binder solution (solid content concentration 20%) (Super Chron 803MW,
Sanyo Kokusaku Pulp) 11.5 parts ●Toluene 5 parts ●Methyl ethyl ketone 5 parts ●Ethyl acetate 5 parts Mix and stir the above materials to prepare a coating liquid. This coating liquid has a solid composition of 100 parts of resin binder and 870 parts of super absorbent polymer fine powder.
This coating solution is coated on the entire surface of a 20μ biaxially stretched polypropylene film (Torefane BO-2535, manufactured by Toray Industries) using a 100/in-60μ depth beta gravure plate, and is dried to allow it to pass through the base polypropylene film. Form an intermediate layer having openings, and further layer
50/in-120μ depth, grid width 2mm, grid pitch 15
A two-component curing urethane adhesive (AD305/AD355,
(manufactured by Toyo Morton) in a grid pattern, dried and after removing the solvent (ethyl acetate), unsized processed base paper 60g/
m ² (manufactured by Nagoya Pulp) were stacked and dry laminated to obtain a water-absorbing/water-retaining sheet according to the present invention, which was water-absorbing on one side. However, the amount of coating liquid applied is 7.2
g/m ² , of which the amount of super absorbent polymer fine powder was 6.5 g/m ² . Also, as a blank, 2
A sheet (comparative example) was prepared by dry laminating a 20 μm axially stretched polypropylene film and 60 g/m ² of unsized processed base paper using the above plate and adhesive. Table 1 shows the results of comparing the water absorbency of the sheet of the example of the present invention and the blank sheet of the comparative example. As described above, the water-absorbing/water-retaining sheet of the present invention absorbed approximately 11 times the basis weight of the sheet, that is, 154 times the weight of the superabsorbent polymer itself, and exhibited good water absorbency. In addition, even after water absorption, the adhesion between the base polypropylene film and the non-sized processed base paper is good, and the two do not separate, and the super absorbent polymer fine powder that swells with water and is present in the intermediate layer moves. It also did not fall off the seat. Example 2 The single-sided water-absorbing sheet prepared in Example 1 was mixed with 1 part by weight of a plant vitalizer containing divalent iron ions (trade name: Menedel, manufactured by Menedel Chemical Research Institute) and 100 parts by weight of water.
parts by weight of the mixed solution for 30 minutes. The amount of liquid absorbed at this time was 720 g/m ² . The inner diameter of the absorbent sheet is adjusted so that the non-sized processing base paper side is the inner surface.
I wrapped it around the inside of a 15cm x 20cm high flowerpot, then filled the pot with dry soil and planted a flowering chrysanthemum. For comparison, a blank flower pot without the absorbent sheet was similarly filled with dry soil and a flowering ``chrysanthemum'' plant was planted.
Table 2 shows the results of comparing the freshness of flowers, leaves, etc. of both plants. In this way, when the water-absorbing/water-retaining sheet of the present invention is used, the water and plant vitality agent contained in the liquid-absorbing and swollen super-absorbent polymer fine powder are gradually released into the soil through the unsized processed base paper. By being dispersed and absorbed through the chrysanthemum roots, both the flowers and leaves remain fresh. As described above in Example 1 and Example 2, according to the present invention, it is possible to create a sheet with extremely high water absorption by a simple method, and as an example of how to use the sheet of the present invention, Application to horticultural cultivation is also effective.

【table】

【table】

【table】 [Brief explanation of the drawing]

The drawings all show embodiments of the present invention; Fig. 1 is a partially cutaway perspective view of a water-absorbing/water-retaining sheet, and Fig. 2 is a cross-sectional view showing the application shape of the coating liquid and adhesive. be. 1...Base material, 2...Intermediate layer, 3...Adhesive layer,
4... Hydrophilic/water permeable material, 21... Pores or openings.

Claims (1)

[Claims] 1 A mixture of a non-aqueous solvent or solvent-free resin binder and a water-insoluble super absorbent polymer fine powder in a solid content ratio of 100 parts by weight or more per 100 parts by weight of the resin binder is placed on the base material 1. , an intermediate layer 2 having pores or openings 21 made of a coated portion reaching from the surface of the layer to the substrate 1 is provided, and a portion is provided on the intermediate layer 2 so as to cover at least a part of the pores or openings 21. A hydrophilic/water-permeable material 4 having a communicating hole having an opening diameter smaller than the diameter of the super-absorbent polymer fine powder used in the intermediate layer 2 is inserted through the water-resistant cured cross-linkable adhesive layer 3 provided in the intermediate layer 2. A water-absorbing and water-retaining sheet that is laminated.