JPH0121175B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a formal sponge with improved water retention, water return properties, and texture. Formal sponges made from polyvinyl alcohol are widely used, but they tend to be extremely hard when dried, do not always return smoothly when brought into contact with water, and have some problems with the texture when soaked with water. There are problems such as a lack of smoothness. In order to improve this point, it has been proposed to incorporate polyhydric alcohol into the formal sponge, but the effect of this is temporary and not sustainable. Japanese Patent Publication No. 38-9428 also discloses an attempt to formalize using modified polyvinyl alcohol into which acid groups or acid ester groups have been introduced as a raw material, but the improvement effect cannot be said to be sufficient. However, as a result of extensive research, the present inventor has found that when formalizing modified polyvinyl alcohol modified with an unsaturated sulfonic acid compound (or a mixture of this and polyvinyl alcohol) in the presence of a strong acid, water retention, The inventors have discovered that a formal sponge with outstanding water return properties and texture can be obtained, leading to the completion of the present invention. Comparing the sponge obtained by formalizing the above-mentioned modified polyvinyl alcohol in the presence of a strong acid with the conventional product, (1) The volume of the sponge of the present invention when immersed in water is approximately 2 to 8 when the conventional product is 1. It will also happen. (2) When a dry sponge is put into water, the sponge of the present invention returns water faster than the conventional sponge. (3) The sponge of the present invention is much more flexible when returned to water (when soaked with water).
Excellent texture. That is, when it touches the skin, it does not have a rough feel and gives an extremely smooth feeling. There are differences in effectiveness, such as: As the modified polyvinyl alcohol as a raw material in the present invention, polyvinyl alcohol modified with an unsaturated sulfonic acid compound is used. Such modified polyvinyl alcohol can be produced by any method. Next, some examples are: ○I Olefin sulfonic acid or its salt such as ethylnsulfonic acid, allylsulfonic acid, metaallylsulfonic acid, etc. and vinyl ester such as vinyl acetate are mixed in alcohol or an alcohol/water mixed solvent. A method of saponifying the copolymer obtained by polymerization. ○B General formula

[Formula] or

[Formula] [R ₁ is an alkyl group, R ₂ is an alkylene group, M is hydrogen or an alkali metal,
A method of saponifying a copolymer obtained by copolymerizing a sulfoalkyl maleate represented by ammonium ion] and a vinyl ester such as vinyl acetate. Examples of the above-mentioned sulfoalkyl malates include sodium sulfopropyl 2-ethylhexyl maleate, sodium sulfopropyl tridecyl maleate, and sodium sulfopropyleicosyl maleate. ○C General formula

[Formula] A copolymer obtained by copolymerizing a sulfoalkyl (meth)acrylate represented by [R ₁ is hydrogen or a methyl group, R ₂ is an alkylene group, and M is the same as in ○ and B] and a vinyl ester such as vinyl acetate. How to saponify union. ○D General formula

[Formula] or

[Formula] [R ₁ is hydrogen or methyl group, R ₂ is alkylene group,
A method of saponifying a copolymer obtained by copolymerizing a sulfoalkyl (meth)acrylamide represented by R ₃ is hydrogen or an alkyl group, and M is the same as in ○ and a vinyl ester such as vinyl acetate. 2-acrylamido-2-methylpropanesulfonic acid (sodium salt) included in the range of ○2 among the above The degree of polymerization of modified polyvinyl alcohol obtained by saponifying a copolymer of polyvinyl alcohol and vinyl acetate does not decrease even when highly modified, and the sulfonic acid compound does not decompose during the saponification reaction. It is particularly excellent in terms of strength, water retention, texture, etc., and is therefore preferably used. In the above production, vinyl acetate is advantageously used as the vinyl ester, but any vinyl ester such as vinyl propionate, vinyl butyrate, isopropenyl acetate, etc. can also be used, and two or more of these may also be used in combination. do not have. Furthermore, in producing each of the above-mentioned modified polyvinyl alcohols, a small amount of a monomer that can be copolymerized with the unsaturated sulfonic acid compound and the vinyl ester may also be allowed to copolymerize with the unsaturated sulfonic acid compound and the vinyl ester. Such copolymerizable monomers include olefins such as ethylene, propylene, isobutylene, α-octene, α-dodecene, and α-octadecene, acrylic acid, methacrylic acid, crotonic acid, maleic acid,
Unsaturated acids such as maleic anhydride and itaconic acid or their salts or mono- or dialkyl esters, nitriles such as acrylonitrile and methacrylonitrile, amides such as acrylamide and methacrylamide, alkyl vinyl ethers, vinyl ketones, N-vinylpyrrolidone , vinyl chloride,
Examples include vinylidene chloride. However, it is not necessarily limited to these. Copolymerization ratio of unsaturated sulfonic acid compound is 0.01 to 20
It is appropriate to set the content to 0.1 to 10 mol%, in particular, if the content is too small, the improvement effect will be lacking, while if it is too large, the elastic recovery power will be lacking and a good sponge will not be obtained. Although the degree of saponification of the vinyl ester component can vary widely, it is appropriate to set it to 70 mol% or more; if it is less than 70 mol%, it tends to lack elasticity and become too flexible. The above-mentioned modified polyvinyl alcohol can be used alone or mixed with ordinary polyvinyl alcohol for formalization. When polyvinyl alcohol is used in combination, the weight ratio of modified polyvinyl alcohol/polyvinyl alcohol is 0.1 or more, preferably 0.2.
or more, and the ratio of the unsaturated sulfonic acid compound to the total amount of both is 0.01 to 20 mol%,
In particular, it should be between 0.1 and 10 mol%. Formalization is carried out by reacting formaldehyde, polyoxymethylene, hexamethylenetetramine, etc. in an aqueous solution using a strong acid as a catalyst according to a known method. Other aldehydes can also be used in small amounts. As the strong acid catalyst, hydrochloric acid, phosphoric acid, nitric acid, sulfuric acid, trichloroacetic acid, organic sulfonic acid, etc. are used. Foaming methods include mechanical stirring and foaming, using soluble substances, mixing fibers and other binding substances, using substances that give high viscosity, using pressurized gas, and foaming. Any known method, such as a method using a chemical agent, can be employed. For example, a soluble substance such as starch is added to the aqueous solution of modified polyvinyl alcohol, formalin and a strong acid are added to carry out a formalization reaction, and the resulting solid is thoroughly washed with water to remove the soluble substance. Just remove it. In the present invention, the sponge may have any shape including a thin film shape. Alternatively, the sponge may be formed on a base material such as a woven fabric, a non-woven fabric, or a mesh body, and the sponge may be laminated with these base materials. The sponge thus obtained can be used for household use (cosmetic,
It can be used for a wide range of purposes, including baths, kitchens), industrial uses, interior decoration, personal items, and agricultural and horticultural uses. Next, the method of the present invention will be further explained with reference to Examples. Hereinafter, "parts" and "%" are expressed on a weight basis unless otherwise specified. Example 1 Sodium 2-acrylamido-2-methylpropanesulfonate was obtained by saponifying 98 mol% of the vinyl acetate component of a sodium 2-acrylamido-2-methylpropanesulfonate/vinyl acetate copolymer with a content of 1.5 mol%. A 10% aqueous solution was prepared by dissolving 90 parts of modified polyvinyl alcohol in 810 parts of water, and 45 parts of horse starch, 124.2 parts of 37% formalin, and 180 parts of 50% sulfuric acid were added to this aqueous solution, and further water was added to dissolve the entire solution. 1500 copies were published. This mixed aqueous solution was allowed to react in a mold at a temperature of 50° C. for 24 hours, and then the solid matter was taken out and thoroughly washed in water to obtain a sponge. In addition, as a control example, the degree of polymerization was 1400 and the degree of saponification was 98 mol%.
A sponge was obtained in the same manner as in Example 1, except that polyvinyl alcohol was used as the raw material. The above results are shown in Table 1.

[Table] Examples 2 to 3 Sponges were produced in the same manner as in Example 1, except that the following modified polyvinyl alcohols were used. Example 2 Sodium allylsulfonate content 1.5
Modified polyvinyl alcohol obtained by saponifying 98 mol% of the vinyl acetate component of sodium allylsulfonate/vinyl acetate copolymer with mol% Example 3 Sodium sulfopropyl with 1.5 mol% sodium sulfopropyl 2-ethylhexyl maleate content 2-ethylhexyl maleate/
Modified polyvinyl alcohol obtained by saponifying 98 mol% of the vinyl acetate component of a vinyl acetate copolymer. The results are shown in Table 2.

[Table] Examples 4 to 5 98 mol% of the vinyl acetate component of a sodium 2-acrylamido-2-methylpropanesulfonate/vinyl acetate copolymer with a sodium 2-acrylamido-2-methylpropanesulfonate content of 3.0 mol% 25 parts of modified polyvinyl alcohol obtained by saponification and 50 parts of polyvinyl alcohol with a degree of polymerization of 1400 and a degree of saponification of 98 mol% are dissolved in water to prepare a 10% aqueous solution, and 40 parts of horse starch is added to this aqueous solution.
Add 105 parts of 37% formalin and 180 parts of 50% sulfuric acid,
Further water was added to bring the total volume to 1500 parts. This mixed aqueous solution was allowed to react in a mold at a temperature of 65° C. for 8 hours, and then the solid matter was taken out and thoroughly washed in water to obtain a sponge. (Example 4) Also, the content of sodium allylsulfonate as a raw material
25 parts of modified polyvinyl alcohol obtained by saponifying 98 mol% of the vinyl acetate component of a 3.0 mol% sodium allylsulfonate/vinyl acetate copolymer and 50 parts of polyvinyl alcohol with a degree of polymerization of 1400 and a degree of saponification of 98 mol%. A sponge was manufactured in the same manner as above, except that . (Example 5) The above results are shown in Table 3.

【table】

Claims (1)

[Claims] 1. An improved method for producing a formal sponge, which comprises formalizing modified polyvinyl alcohol modified with an unsaturated sulfonic acid compound or a mixture of this and polyvinyl alcohol in the presence of a strong acid. 2. The manufacturing method according to claim 1, wherein the unsaturated sulfonic acid compound is sodium 2-acrylamido-2-methylpropanesulfonate.