JPS6319545B2 - - Google Patents

Description

[Detailed description of the invention]

(Field of Industrial Application) The present invention relates to a method and a paint for imparting water absorbency to the surface of polyolefin resin, which is inherently hydrophobic. The purpose of the present invention is to provide a paint that imparts only water absorption performance without changing other physical properties. (Prior Art) Conventionally, there are products that require a relatively high water supply capacity, such as sanitary products, diapers, disposable cloths, 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. At the same time, it is required to have water absorption ability, shape stability when water is absorbed, and stability against mold, bacteria, etc. Conventionally, methods to meet these demands have been to create materials that utilize the physical water absorption properties of porous materials such as pulp, cloth, or sponge, or to partially cross-link water-soluble resins called water-absorbent resins, which have large water absorption and water retention capabilities. The present inventors have also developed a mixed coating solution of a non-aqueous binder and a highly water-absorbing polymer powder, including a "water-absorbent/water-retaining sheet" (Japanese Patent Application Laid-Open No. 103838/1983). We are proposing a method of imparting water absorbency by coating and applying it to the base material. Polyolefin resins, represented by polyethylene and polypropylene, are widely used in many industrial fields due to their chemical stability, water resistance, ease of processing, physical properties, and good cost balance. It is widely used in water-related fields as a material that has a waterproof function, and it is known that its physical properties do not deteriorate even when used underwater or in high humidity conditions for a long time, and that mold and bacteria do not grow. ing. (Problem to be Solved by the Invention) However, polyolefin is originally a material that is difficult for paint to adhere to, and simply applying it to such a material will adhere sufficiently to the polyolefin without causing blocking, and moreover, Neither a paint that retains water absorption ability nor a method for applying it was known. In consideration of the above circumstances, the present inventors have developed the method of applying superabsorbent polymers that has been proposed in the past, while maintaining the useful physical properties of polyolefin resins, which are inherently inert and hydrophobic. The present invention was completed as a result of intensive study on imparting only a water absorbing function to the product. (Means for Solving the Problems) That is, the present invention provides a non-aqueous paint containing 200 parts by weight or more and 1000 parts by weight or less of a water-insoluble water-absorbing resin powder based on 100 parts by weight of a resin binder. The binder is chlorinated ethylene-vinyl acetate resin (hereinafter abbreviated as "chlorinated EVA")
and chlorinated polypropylene resin (hereinafter referred to as “chlorinated PP”)
chlorination in the resin binder.
To provide a water-absorbing paint characterized by having an EVA ratio of 50% by weight or more and 80% by weight or less. (Explanation of Examples) The water-insoluble/water-absorbent resin used in the present invention is a starch-sodium acrylate graft polymer, a starch-acrylonitrile graft polymer hydrolyzate, a partially crosslinked starch-poly(meth) ) Starch-graft polymers such as acrylic acid polymers, partially cross-linked starch-polymethyl methacrylate hydrolysates, and salts of the above substances, or partially cross-linked polyacrylates, polyisobutylene- Examples include cross-linked synthetic resins such as maleic anhydride copolymer and hydrolyzate of methyl methacrylate-vinyl acetate copolymer, but basically they are made by partially cross-linking water-soluble polymers. , insolubilized, and when it comes into contact with water or an aqueous solution such as a salt, it can quickly absorb water or an aqueous solution, swell, and retain moisture, and there are no particular limitations. It is not something that will be done. Although some of these water-absorbing resins are obtained in the form of fibers, they are used in the form of fine powder in the present invention. Its powder particle size is preferably less than 35Mesh
It is better to have a mesh size of 100 mesh or less and a diameter of 5 μ or more, and a shape close to a spherical shape is better. Particle size is 35Mesh
In the above case, there are problems with the stability, fluidity, and coating workability of the paint, and there are also problems with the smoothness and uniformity of the coated surface, making it easy to fall off from the polyolefin resin surface and making it difficult to handle. In addition, if it is less than 5μ, the water absorption capacity of the resin itself decreases, and the gel strength when absorbing water decreases, making it difficult to handle and collecting floating particles.
The disadvantage is that the powder particles become embedded in the binder film after application, making it difficult to obtain the desired high water absorption. As a resin binder for mixing and dispersing these insoluble/water-absorbing resins, it is basically insoluble in water,
It must also have good adhesion to treated and untreated polyolefins, be able to hold and bind at least twice as much water-absorbing resin as itself, and must be uncrosslinked so as not to suppress the swelling of the water-absorbing resin. Furthermore, since it is necessary to obtain a paint containing a large amount of water-absorbing resin, it is necessary to be able to apply it as a hydrocarbon solvent solution that does not dissolve or swell the water-absorbing resin.
Considering the above points, the following resin binders are optimal. In other words, chlorinated EVA is used as the resin binder.
A non-aqueous solvent solution is used which is a mixture of EVA and chlorinated PP, and in which the proportion of chlorinated EVA is 50% by weight or more and 80% by weight or less. Chlorinated EVA alone has good retention of water-absorbing resins and adhesion to various polyolefin resins, but has problems with heat resistance, such as blocking of coated surfaces together at high temperatures in the summer. In addition, with chlorinated PP alone, the fluidity and application workability of the paint are good, but it lacks adhesion to PE other than PP resin, and the solvents that can be used are limited to toluene etc., causing problems with the drying properties of the paint film. remains. resin binder
The resin binder is chlorinated in order to retain more than 200 parts by weight of water-absorbing resin per 100 parts by weight and to be able to adhere to treated and untreated polyolefins.
EVA needs to be at least 50% by weight or more, and chlorinated PP needs to be at least 20% by weight in order to obtain fluidity of the paint and non-blocking properties of the coating film.
Toluene is used as the solvent for the resin binder, but within this composition range, toluene/MEK/ethyl acetate = 1/1/1 has better solvent removal properties.
It is also possible to use a solvent base. Water-absorbing resin is per 100 parts by weight of resin binder
Mix in a range of 200 parts by weight or more and 1000 parts by weight or less. Even if the amount is less than 200 parts by weight, water absorption capacity is proportional to the amount of water-absorbing resin added, but it takes time for the coating film to actually start swelling after it comes into contact with water, resulting in poor absorption speed. Although it depends on the shape of the resin binder, by setting the volume fraction to approximately 65%, that is, 200 parts by weight or more, which is a range that does not completely cover the surface of the water-absorbing resin, the water-absorbing resin's original water absorption ability can be demonstrated. I can do it. If the amount exceeds 1,000 parts by weight, even if the particle size distribution of the water-absorbing resin powder shifts to a finer one, there will be insufficient resin binder to hold it as a film and make it adhere to the polyolefin resin, resulting in a loss of practicality. It is difficult to mix the water-absorbing resin and the resin binder by ordinary stirring alone even if the amount of solvent is increased, and it is preferable to use a mixing method with higher energy such as an attritor or a ball mill. The paint actually obtained is a dispersion in which a large amount of water-absorbing resin powder is dispersed in a large amount of solvent in which a small amount of binder resin is dissolved.
In order to improve viscosity, fluidity, and coating workability, additives such as nonaqueous dispersants, viscosity modifiers, and colorants are added to the paint in an amount of 2% by weight or less based on the total solid content. The coating of the present invention can be applied using coating methods normally used for solvent-based coating agents, but since the coating is a dispersion containing a large amount of highly drying solvent, it can be applied using gravure coating, roll coating, flow coating, etc. method, dipping method, etc. are preferable. The spray method can be applied by modifying the nozzle shape. The applicable polyolefin resins are:
LDPE, MDPE, HDPE, PP, polybutene-1
and copolymers thereof, and their forms include films, sheets, yarns, nonwoven fabrics, and molded products. (Effects of the Invention) As described above in detail, various effects can be obtained by applying the present invention. For example, commercially available water-absorbing resins such as starch-graft polymerization and crosslinked synthetic resins can absorb 200 to 1000 times their own weight of pure water, but the one to which the present invention is applied can absorb a small amount of pure water with a low coating amount. It can provide a high water absorption capacity of 10 to several 100 times that is impossible with physical water absorption such as pulp, and since the polyolefin resin that serves as the base material is completely water resistant, it has excellent shape retention and strength. , it can be easily applied to various forms of polyolefin resin without the need for special equipment, and has many effects and advantages, such as the ability to obtain surface-absorbing polyolefin resins with various textures and shapes depending on the application. . Furthermore, for example, by processing the polypropylene yarn obtained in the present invention into a filter shape, a mat capable of removing water contained in oil can be obtained. Alternatively, by using it as a film or sheet as a backing material for plywood, wallpaper, etc., it can be used as a building material that blocks moisture and prevents condensation, and has great industrial value. The present invention will be explained below with reference to Examples, but the present invention is not limited thereto. <Example 1> The composition shown below was mixed and adjusted using an attritor to make a paint, and the untreated surface of an untreated high-density polyethylene film (80μ) and a biaxially stretched polypropylene film (40μ) was coated using a gravure method. Application amount
A one-sided water-absorbing polyolefin film was obtained by applying 5.0 g/m ² and drying. [・ Cross-linked starch graft polymerization water absorbent resin fine powder (Sunwet IM-300MPS, manufactured by Sanyo Chemical Industries, Ltd.) 2100 parts by weight ・ Chlorinated EVA 20% toluene solution (Super Chron B, manufactured by Sanyo Kokusaku Pulp Co., Ltd.) 800 〃 ・ Chlorinated PP 20% toluene solution (Super Chron 803MW, manufactured by Sanyo Kokusaku Pulp Co., Ltd.) 400 parts by weight ・ Fine silica powder (Syroid 244, manufactured by Fuji Davison Co., Ltd.) 23.4 〃 ・ Solvent (Toluene / MEK / Ethylene Vinegar) =1/1/
1) 1500〃〃〕 * Solid content (TNV) 49% * Resin binder: Water-absorbing resin = 100:875
(Weight ratio) * Resin binder ~ Chlorinated EVA: Chlorinated PP
= 67:33 (weight ratio) <Comparative example> Example 1 was prepared by mixing and adjusting the coating liquid with the composition of ~ shown below using an attritor.
Same as untreated HDPE film (80μ) OPP
(40μ) using gravure method, coating amount 5.0g/m ²
After coating and drying, a single-sided water-absorbing polyolefin film was obtained. Sunwet IM-300 MPS Super Chron B Super Chron 803MW Thyroid 244 Solvent (Toluene/MEK/FA=1:1:1) 240 400 800 4.8 0TNV=34% Resin binder: Water absorbent resin = 100:100 Sunwet IM-300 MPS Sparkron B Superchron 803MW Thyroid 244 Solvent (Toluene/MEK/FA=1:1:1) 2500 400 800 27.4 2000TNV=48% Resin binder: Water-absorbing resin=100:1042 Sunwet IM-300 MPS Sparklon B Thyroid 244 Solvent (Toluene/MEK/EA=1:1:1) 2100 1200 23.4 1500TNV=49% Resin binder: Water-absorbing resin=100:875 Chlorinated EVA 100% Sunwet IM-300 MPS Sparkron 803MW Thyroid 244 Solvent (Toluene 100% ) 2100 1200 23.4 1500TNV = 4.9% Resin binder: Water-absorbing resin = 100: 875 Chlorinated PP100% Sunwet IM-300 MPS Byron #200 Cyroid 244 Solvent (EA100%) 2100 240 23.4 2460TNU = 49% Resin binder: Water-absorbing resin =100:875 100% polyester * Byron #200 ~ linear polyester resin,
Manufactured by Toyobo The following performance evaluation results are shown in Table 1 for Examples and Comparative Examples.

【table】

[Table] As is clear from Table 1, Example 1 according to the present invention shows good results in all aspects, but the comparative example has a low initial water absorption capacity, lacks water absorption speed, and the comparative example has poor coating suitability. It has poor adhesion, poor adhesion, and lacks film strength. The comparative example has blocking properties, the comparative example lacks adhesion to HDPE, and if dried too slowly, it blocks due to the influence of residual toluene, and the comparative example lacks adhesion to both PE and PP. I understand. Furthermore, if a resin binder containing 80% or more of Superchron B and less than 20% of Superchron 803MW is used, the resulting paint will have comparatively the same drawbacks, with less than 50% of Superchron B and less than 20% of Superchron 803MW. When 803MW used more than 50% resin binder, it had the same drawbacks as the comparative example.

Claims (1)

[Claims] 1. A non-aqueous paint containing 200 parts by weight or more and 1000 parts by weight or less of water-insoluble water-absorbing resin powder based on 100 parts by weight of the resin binder, wherein the resin binder is
A mixture of chlorinated ethylene-vinyl acetate resin (hereinafter abbreviated as chlorinated EVA) and chlorinated polypropylene resin (hereinafter abbreviated as chlorinated PP), where the ratio of chlorinated EVA in the resin binder is 50% by weight or more and 80% by weight or less A water-absorbing paint characterized by: