JPH0366347B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a novel water absorbing and water retaining material made by uniformly mixing a super absorbent polymer and a swellable urethane with a soft resin or rubber.
Soft resins or rubbers are hydrophobic materials, and there has been a demand for imparting water absorbing and water retaining properties to these base materials. Various methods have been proposed for this purpose. For example, a method of chemically treating the surface of a base material to increase its hydrophilicity, a method of coating or mixing a super absorbent polymer on the surface of a base material, and the like are known. Among these, the method using a superabsorbent polymer is relatively easy to implement, and the present inventors have developed a method for imparting water absorbency and water retention, which is characterized by mixing a superabsorbent polymer into a base material. , Japanese Patent Application Publication No. 1973-
9108, JP-A-56-33032 was proposed. On the other hand, caulking compositions in which swelling urethane is mixed with a base material such as urethane or rubber, such as JP-A-51-96848, JP-A-53-143653, JP-A-54-
7463, JP-A-54-7461, JP-A-54-20066, JP-A-57-23618, JP-A-57-23654, JP-A-57-
145170, JP-A-57-147570, etc. have been proposed. For example, when manufacturing a water-swellable caulking material based on natural rubber, if a super absorbent polymer is mixed as a water-absorbing substance, permanent deformation will not occur over a long period of time, and the restoring force will be reduced. is large, so
It can be said that its water-stopping ability is superior to other caulking materials. However, the drawback is that the initial swelling rate in water is slow. On the other hand, water-swellable caulking materials made by mixing natural rubber with swellable urethane have a high swelling rate in water, but have a low water absorption rate, and have the disadvantage that water retention capacity decreases due to hydrolysis for long-term use. It was hot. As a result of intensive research into water-absorbing and water-retaining materials that have improved the above-mentioned drawbacks, the present inventors have found that a finely powdered super-absorbent polymer with an average particle size of 100 μm or less (preferably 20 μm or less) and a swellable urethane are used to soften the material. By uniformly mixing it into a resin or rubber, we succeeded in achieving the water absorbing and water retaining properties aimed at by the present invention. The present invention requires the use of a soft resin or rubber, and the simultaneous use of finely powdered super absorbent molecules and swelling urethane. Although the mechanism by which the water absorption and water retention properties are significantly improved in the present invention is not clear, it is likely that
It is presumed that the initial water absorption begins due to the swellable urethane contained in the base material, and as the water absorption progresses into the interior of the base material, secondary swelling is induced by the superabsorbent polymer. It was completely unexpected that the swelling rate would be synergistically accelerated in the case of the present invention, compared to when they were individually mixed into the base material. As mentioned above, the greatest feature of the present invention is that, due to the synergistic effect of both, sufficient water absorbency and water retention can be provided even if the amount of each mixed in the base material is small. In addition, the mechanical properties (especially elongation and tear strength) of the base material are less likely to deteriorate due to the addition of the water-absorbing substance, and the economical effects are also large. The superabsorbent polymer used in the present invention has a weight of 50% of its own weight.
It is desirable that it absorbs more than twice as much pure water and is insoluble in water. If a super absorbent polymer with a water absorbency lower than 50 times is used, the performance as a water absorbing and water retaining material will be poor, which is not preferable. Further, it is desirable that the particle size is as small as possible, and the smaller the particle size, the better the material can be obtained in which the superabsorbent polymer does not fall off during water absorption. The superabsorbent polymer used in the present invention is one in which a polymer electrolyte is physically or chemically crosslinked, and in particular, a superabsorbent polymer that is a polymer electrolyte containing a carboxylic acid salt has a high water absorption capacity. It is desirable to use this because it also has excellent strength after water absorption. For example, starch/sodium acrylate graft copolymer, isobutylene/maleic anhydride copolymer salt, styrene/maleic anhydride copolymer salt, polysodium acrylate crosslinked product, polyvinyl alcohol/acrylate graft copolymer. Examples include saponified products of polymers, copolymers of vinyl ester/ethylenically unsaturated carboxylic acids or derivatives thereof, and the like. In particular, vinyl ester (X) and ethylenically unsaturated carboxylic acid or its derivative (Y) are the main components, and X:Y=20:80-80:
The saponified product of the copolymer and the crosslinked product of sodium polyacrylate composed of a molar ratio in the range of 20 have high strength after water absorption, and are useful in increasing the rigidity of the water-absorbing and water-retaining material of the present invention when water is absorbed. . The swellable urethane used in the present invention has the general formula [R(OR ₁ )nOH]p [where R is a polyhydric alcohol residue, (OR ₁ )n is an oxyethylene group and 3 carbon atoms]
A polyoxyalkylene chain consisting of an oxyalkylene group having ~4 alkylene groups, provided that the proportion of oxyalkylene groups accounts for 20 to 100% of the molecular weight, n is a number indicating the degree of polymerization of the oxyalkylene group, and is the hydroxyl equivalent The number corresponding to 200 to 2500,
Terminal NCO group content 1 to 12%, preferably 2 to 7, obtained by reacting one or a mixture of two or more polyether polyols represented by p is 2 to 8, preferably 2 to 4, with a polyisocyanate. %
isocyanate group-containing prepolymer. Note that the isocyanate group-containing play polymer may be moisture-cured (one-component type), or
It may also be cured with a polyamine or polyol curing agent such as MOCA (4,4'-methylenebis-1-chloroaniline). Furthermore, the term "swellable urethane" as used in the present invention refers to a urethane resin that exhibits a weight increase of 10% or more after being immersed in tap water at 25°C for 7 days. The soft resin used in the present invention includes ethylene-vinyl acetate copolymer, saponified ethylene-vinyl acetate copolymer, ethylene-isobutylene copolymer, ethylene-acrylic acid ester copolymer, and ethylene-acrylate copolymer. These include vinyl chloride polymers and vinyl chloride copolymers. Rubbers include natural rubber or synthetic rubber, and synthetic rubbers include butadiene rubber, styrene-butadiene rubber, acrylonitrile-butadiene rubber, butyl rubber, chloroprene rubber, fluorine rubber, ethylene propylene rubber, chlorosulfonated polyethylene, and silicone. Many known rubbers include rubber, urethane rubber, polysulfide rubber, and acrylic rubber. These soft resins and rubbers may be used alone or in combination of two or more. Further, these soft resins and rubbers can be appropriately selected from those having physical properties corresponding to the field of use in terms of water absorption and water retention. The water-retaining and water-absorbing material of the present invention is produced by mechanically or uniformly dispersing and mixing finely powdered superabsorbent polymer and swelling urethane in soft resin or rubber. Of course, the mixing ratio and amount of the water-absorbing substance to the base material can be appropriately selected depending on the field of use. For example, extruder mixers with roll kneading, Banbury kneading, Dalmage type screws, etc.
Mechanical dispersion mixing methods that can be applied to the present invention include kneading in a mulch machine and the like. The novel water-retaining and water-supplying materials obtained by the present invention can be used, for example, in water-stopping agents, anti-condensation wall materials, cleaning wipes, toys, water-absorbing and sweat-absorbing sheets, medical hygiene materials, sanitary products, and fragrance agents. It can be used as a carrier, concrete curing mat, etc. In the present invention, fillers, colorants, packaging agents, crosslinking agents, accelerators, curing agents, solvents,
Known substances such as stabilizers, anti-aging agents, fragrance agents, etc. may be used in combination. The present invention will be explained in more detail with reference to Examples below, but the present invention is not limited thereto.
Note that parts in the examples are based on weight. The water absorption rate and water retention rate in the Examples are based on the following definitions and test methods, respectively. Water absorption rate (g/g) = Weight of water-absorbed base material / Weight of dry base material Water retention rate (g/g) = The water-absorbed base material was wrapped in a 300 mesh wire mesh and centrifuged at 100G for 10 minutes. Remaining Water Absorption Example 1 0.7 mol of vinyl acetate, 0.5 mol of methyl acrylate, 0.03 mol of ethylene glycol diacrylate as a crosslinking agent, and 0.02 mol of benzoyl peroxide as a polymerization initiator were mixed, and this was partially quenched as a dispersion stabilizer. Dispersed in 300 ml of water containing 3 g of polyvinyl alcohol and 10 g of NaCl,
Suspension polymerization was carried out at 65°C for 6 hours. Next, 10 g of the above copolymer was dispersed in 200 ml of methanol, and 40%
40 ml of NaOH aqueous solution was added and saponified at 60°C for 5 hours. The degree of saponification was approximately 91 mol%. The superabsorbent polymer obtained is spherical with a diameter of 20 to 200μ,
It is insoluble in water and has a water absorption rate of 550 times. This was mechanically pulverized using a jet mill to obtain a fine powder with an average particle size of 20μ. On the other hand, a molecular weight of 3000 was obtained by randomly adding propylene oxide to glycerin, and 20 parts of a trifunctional polyether with an oxyethylene group content of 51%, and a molecular weight obtained by randomly adding propylene oxide and ethylene oxide to propylene glycol. 2000, oxyethylene group content 80
% bifunctional polyether, tolylene diisocyanate was added thereto, and the reaction was carried out at 90° C. for about 2 hours in a conventional manner to produce an isocyanate group-containing prepolymer with an NCO content of 3.08%. Next, the superabsorbent polymer and swellable urethane obtained above were mixed with the ethylene-vinyl acetate copolymer (Evatate R5011 manufactured by Sumitomo Chemical) at 60°C for about 10 minutes using roll mixing. did. Then, a test piece with a thickness of 2 mm was obtained by press molding at 100°C. (The formulation and measurement results are shown in Table 1) After immersing this test piece in water for 24 hours, the water absorption rate and water retention rate were determined.

【table】

[Table] The water-absorbing sheet obtained by the present invention swells uniformly and can be used for toys, water-stopping agents, etc. Example 2 The superabsorbent polymer and swellable urethane obtained in Example 1 were mixed with vinyl chloride resin and kneaded for 20 minutes in a mulch machine. The ingredients and proportions are shown in Table 2. The resulting paste sol was applied to a thickness of 300 μm on paper and heated at 120°C for 1 minute to semi-gelify it.
Then, the foamed paper was heat-treated at 200°C for 3 minutes to obtain foamed paper.
After the foamed paper thus obtained was immersed in water for 24 hours, the water absorption rate and water retention rate were determined and are shown in Table 2.

[Table] The foamed paper obtained according to the present invention can be used as a wall material to prevent condensation. Example 3 Swellable urethane obtained in Example 1 and sodium polyacrylate crosslinked product (Aqua Keep)
10SH crushed product, average particle size 20μ, manufactured by Seitetsu Kagaku Kogyo)
is added to natural rubber and the blend is rolled into a 6-inch roll.
The mixture was kneaded at 80°C for about 15 minutes to form an unvulcanized compound. (The formulation is shown in Table 3) This compound was heated at 170℃ in a steam press machine.
After vulcanization for 15 minutes, a test piece with a thickness of 2 mm was obtained. After immersing this test piece in water for 24 hours, the water absorption rate and water retention rate were determined.

[Table] The water-absorbing sheet obtained by the present invention swells uniformly and can be used as a water stopper, wiper, etc. Example 4 A superabsorbent polymer and swelling urethane were added to a polystyrene/polybutadiene thermoplastic elastomer (Califlex TR4113, manufactured by Zeon Corporation), and the mixture was kneaded with a 6-inch roll at 70°C for about 15 minutes. Then, by press molding at 80° C., a test piece with a thickness of 2 mm was obtained. This test piece
After being immersed in water for 24 hours, the water absorption rate and water retention rate were determined. The formulation and measurement results are shown in Table 4.

[Table] The water-absorbing sheet obtained by the present invention swells uniformly and can be used as a water-stopping agent.

Claims (1)

[Claims] 1. A finely powdered super water-absorbing polymer having an average particle size of 100 μm or less and being a polymer electrolyte containing a carboxylate, and having the general formula R[(OR ₁ )n OH]p [wherein , R is a polyhydric alcohol residue,
(OR ₁ ) n is a polyoxyalkylene chain consisting of an oxyethylene group and an oxyalkylene group having an alkylene group having 3 to 4 carbon atoms, provided that the oxyethylene group accounts for 20 to 100% of the molecular weight,
n is a number indicating the degree of polymerization of the oxyalkylene group and is a number corresponding to a hydroxyl group equivalent of 200 to 2500,
p is 2 to 8] A swollen isocyanate group-containing prepolymer with a terminal NCO group content of 1 to 12% obtained by reacting one or a mixture of two or more polyether polyols represented by the following with a polyisocyanate. A water-absorbing and water-retaining material characterized by being made by uniformly mixing polyurethane into a soft resin or rubber. 2 The super absorbent polymer is a starch/sodium acrylate graft copolymer, a salt of an isobutylene/maleic anhydride copolymer, a salt of a styrene/maleic anhydride copolymer, a polysodium acrylate crosslinked product, or a polyvinyl The water-absorbing and water-retaining material according to claim 1, which is selected from alcohol/acrylate graft copolymers and saponified copolymers of vinyl ester/ethylenically unsaturated carboxylic acids or derivatives thereof. 3 The super absorbent polymer is composed of vinyl ester (X) and ethylenically unsaturated carboxylic acid or its derivative (Y) in a molar ratio of X:Y = 20:80 to 80:20. The water-absorbing and water-retaining material according to claim 2, which is a saponified product of a copolymer. 4. The water absorbing and water retaining material according to claim 2, wherein the super absorbent polymer is a crosslinked polysodium acrylate. 5 Swellable polyurethane is obtained by reacting one type or a mixture of two or more polyether polyols in which p in the general formula is 2 to 4 with polyisocyanate, and has a terminal NCO group content of 2 to 7%.
The water-absorbing and water-retaining material according to claim 1, which is an isocyanate group-containing prepolymer. 6. The water-absorbing and water-retaining material according to claim 1, wherein the soft resin is selected from ethylene copolymers and vinyl chloride polymers. 7. The water-absorbing and water-retaining material according to claim 1, wherein the rubber is natural rubber or synthetic rubber.