JPH0977821A - Polymer porous body - Google Patents

Abstract

(57) Abstract: [PROBLEMS] To provide a polymer porous body which has a good feel, flexibility and elasticity when wet, and quickly becomes wet and soft even after once dried. It is a thing. A polymer porous body obtained by reacting a modified polyvinyl alcohol (A) having a hydroxyalkyl group having 2 to 20 carbon atoms in its side chain with an aldehyde (B) and an acid (C).

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a polymer porous body.

[0002]

2. Description of the Related Art Conventionally, polyvinyl alcohol (hereinafter referred to as PV
Abbreviated as A), a pore forming aid such as starch is added to
The polyvinyl acetal-based porous body obtained by reacting an aldehyde and an acid has continuous pores and a high porosity,
Since it has OH groups in the molecule, it has a large water absorbency, a large mechanical strength, and has various characteristics such as excellent chemical resistance. Therefore, various filters, sponges for water-based cosmetics, sponge grindstones, water-absorbing rollers, Dewatering roller,
It is often used in kitchen sponges and bath sponges. However, a porous body obtained by using a usual polyvinyl alcohol has a good feel, flexibility and elasticity when wet, but has a bad feel when dry and becomes rigid. Further, once dried, it takes a considerable amount of time and effort to become wet and soft. In order to overcome these drawbacks, (1) other than polyvinyl alcohol, for example pulp powder, cotton linter, vinylon fiber, sponge powder and the like added to produce, to improve water absorption and feel, (2 ) Water absorption is imparted by post-treating the obtained porous body with an aqueous solution of a water-absorbing substance such as a surfactant, glycerin, or polyethylene glycol. (3) A water-absorbing resin is added during production to absorb water. Attempts have been made to increase the speed, (4) increase the water absorption speed by using a modified polyvinyl alcohol copolymerized with a hydrophilic monomer. However, the method of (1) deteriorates the physical properties of the obtained porous body, and the method of (2) can only obtain a temporary effect because the water-absorbing substance gradually falls off. The method of 4) improves the performance to some extent, but it still has a problem that it is not sufficient.

[0003]

DISCLOSURE OF THE INVENTION The present invention overcomes the above-mentioned drawbacks of conventional porous materials, has a good feel when wet, flexibility and elasticity, and quickly after being dried. An object of the present invention is to provide a polymeric porous body that is softened by wetting.

[0004]

Means for Solving the Problems As a result of intensive studies for solving the above-mentioned problems, the present inventors have found that modified polyvinyl alcohol (A) having a hydroxyalkyl group having 2 to 20 carbon atoms in its side chain is added to aldehyde (B). ) And an acid (C) to obtain a polymer porous body, and have completed the present invention.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The modified PVA (A) of the present invention is required to have a vinyl alcohol unit in the molecule and has a hydroxyalkyl group having 2 to 20 carbon atoms in the side chain. The side chain is modified PVA.
Must be directly attached to the main chain of. The modified P
The hydroxyalkyl group of VA has 2 to 20 carbon atoms, preferably 2 to 15 and more preferably 3 to 10. The hydroxyalkyl group is an alkyl group having at least one hydroxyl group (hydroxyl group), and a ω-hydroxylalkyl group is more preferable in terms of thermal stability and water solubility. As the alkyl group of the hydroxyalkyl group, its hydrogen atom may be substituted with a linear or branched alkyl group having 1 to 9 carbon atoms.

The hydroxyalkyl group having 2 to 20 carbon atoms is preferably present in the form of an olefin unit containing a hydroxyalkyl group. Among the olefin units containing a hydroxyalkyl group, modified PVA
3-butene-1 from the viewpoint of ease of controlling the degree of polymerization of
-Ol, 4-penten-1-ol, 5-hexene-
1-ol, 7-octen-1-ol, 9-decene-
Monomer units derived from 1-ol, 11-dodecen-1-ol, 3-methyl-3-buten-1-ol and the like are preferable. In addition to these monomer units, it may be a monomer unit containing an ester group capable of generating a hydroxyl group during the saponification reaction of the polyvinyl ester polymer, which is a raw material of the modified PVA.

The content of the hydroxyalkyl group having 2 to 20 carbon atoms in the modified PVA is preferably 0.1 to 20 mol%, more preferably 0.5 to 15 mol%, 1
It is more preferably from 10 mol%. The saponification degree of the modified PVA is not particularly limited, but is preferably 50 mol% or more,
70 mol% or more is more preferable. The viscosity average degree of polymerization of the modified PVA (hereinafter abbreviated as the degree of polymerization) is 100 to
20000 is preferable, 200-8000 is more preferable, 300-3000 is more preferable.

As a method for producing a modified PVA, a polyvinyl ester polymer obtained by copolymerizing a vinyl ester and an olefin having a hydroxyalkyl group having 2 to 20 carbon atoms is saponified in an alcohol or dimethylsulfoxide solution. A known method such as a method of Examples of the vinyl ester include vinyl formate, vinyl acetate, vinyl propionate, vinyl pivalate, and the like, with vinyl acetate being preferred.

Further, in the copolymerization of the above-mentioned hydroxyalkyl group-containing olefin and vinyl ester, a monomer copolymerizable therewith may be copolymerized within a range not impairing the effects of the present invention. These monomers include ethylene, propylene, isobutene and other α-
Olefin, acrylic acid, methacrylic acid, crotonic acid,
Maleic acid, itaconic acid, maleic anhydride or salts or alkyl esters thereof, acrylonitrile, methacrylonitrile, acrylamide, methacrylamide, N, N-dimethylacrylamide, alkyl vinyl ethers, N-vinylpyrrolidone, vinyl chloride, vinylidene chloride, Examples thereof include vinyl versatate.

The polymer porous material of the present invention is usually obtained by reacting the modified PVA (A) with the aldehyde (B) and the acid (C) in the presence of a pore forming aid. As the pore forming aid, the aldehyde (B) and the acid (C), those conventionally used for producing a porous body can be used.
Examples of the pore-forming aid include raw starch, various processed starches, dextrin, surfactants, pulp powder, inorganic foaming agents, organic foaming agents and the like. Examples of the aldehyde (B) include formaldehyde, acetaldehyde, butyraldehyde, aliphatic aldehyde such as 3-ethylhexyl aldehyde, and aromatic aldehyde such as benzaldehyde. Examples of the acid (C) include hydrochloric acid, sulfuric acid, acetic acid and the like.

As a method for producing the porous body, a conventional method can be used. The amount of aldehyde used is preferably about 80 to 300 mol% based on the modified PVA, and the amount of acid used is preferably about 50 to 200 mol% based on the aldehyde.
The reaction is usually performed by adding an aqueous solution of aldehyde and an acid or an aqueous dispersion to a modified PVA aqueous solution in the presence of a pore-forming aid, and heating at a temperature of 30 to 80 ° C. for 5 to 50 hours. After the completion of the acetalization reaction, the reaction product is washed with water or hot water to remove the pore forming aid, unreacted aldehyde, acid and the like, whereby a polymer porous body is obtained. The degree of acetalization of the porous body is an important factor that affects the physical properties of the porous body and varies depending on the type and amount of modified PVA, but is preferably 50 to 85 mol%.
5-80 mol% is more preferable.

In the present invention, other substances may be added and mixed within a range not impairing the object of the present invention. Examples of these substances include ordinary polyvinyl alcohol, various modified polyvinyl alcohols, hydroxyethyl cellulose and the like. Further, pulp powder, cotton linter, vinylon fiber, sponge powder, etc. may be added and used.

[0013]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited thereto. In the following, "parts" and "%" are respectively "parts by weight" and "% by weight" unless otherwise specified.
Means

Example 1 1680 g of vinyl acetate and 7-octen-1-ol were placed in a 3 liter polymerization tank equipped with a reflux condenser, a stirrer, a thermometer, a nitrogen inlet and a charging port for a post-addition liquid and a pump. 350 g,
420 g of methanol was charged. While stirring the polymerization solution, the system was replaced with nitrogen and heated, and when the temperature reached a constant temperature of 60 ° C., 2,2′-azobisisobutyronitrile (hereinafter referred to as “AIB
Abbreviated as "N") was added to initiate polymerization. From the start of the polymerization, the polymerization was carried out while analyzing the solid concentration in the system. After 4 hours, the polymerization was stopped by cooling the polymerization tank. The polymerization rate when the polymerization was stopped was 59%. The obtained polymerized paste was dropped into n-hexane to precipitate a polymer. Next, after dissolving the polymer in acetone and performing reprecipitation-purification operation in which it is precipitated in n-hexane three times, it is again dissolved in acetone, added dropwise to distilled water, and purified by boiling.
By drying at 60 ° C., purified polyvinyl vinyl acetate (hereinafter abbreviated as “PVAc”) was obtained. next,
Prepare a 30% methanol solution of purified PVAc to prepare 40
While stirring at 0 ° C., a 10% sodium hydroxide concentration in methanol was added to carry out a saponification reaction for 60 minutes.
After crushing the obtained gel-like material, washing with methanol, 50 ° C
The modified PVA as a white powder was obtained by drying at 18 ° C. for 18 hours. The modified PVA thus obtained had a 7-octen-1-ol unit content of 4.5 mol%, a polymerization degree of 590, and a vinyl acetate unit saponification degree of 80 mol%. Modified PVA above
500 parts of an aqueous solution containing 40 parts and 20 parts of PVA-217 (manufactured by Kuraray, unmodified PVA, average degree of polymerization 1700, degree of saponification 88.1 mol%) was prepared. By adding 30 parts of potato starch to 200 parts by dispersing it in water and adding to the above aqueous solution, and maintaining at 70 ° C. for 10 minutes while stirring,
The starch has gelatinized. This is cooled to 50 ° C. and the concentration is 37
% Formalin aqueous solution 100 parts and 50% concentration sulfuric acid aqueous solution 100 parts are mixed, and water is added to make 1000 parts, and the mixture is kept at 45 ° C. and sufficiently mixed, and then cast in a glass container to 70 parts. The reaction was performed at 12 ° C for 12 hours. A porous material was obtained by washing the reaction product with warm water. Table 1 shows the properties of the obtained porous body.

Example 2 The following polymerization was carried out in the same manner as in Example 1 using a 5 liter polymerization tank. 2800 g of vinyl acetate, 300 g of 7-octen-1-ol and 700 g of methanol were charged. While stirring the polymerization solution, the system was replaced with nitrogen and heated, and when the temperature reached a constant temperature of 60 ° C, 33 g of AIBN was added to start the polymerization, and the polymerization rate became 63% after 4.5 hours. At that point the polymerization was stopped. Purified PVA in the same manner as in Example 1.
c is obtained, followed by saponification and purification,
A modified PVA was obtained. The content of 7-octen-1-ol unit in the obtained modified PVA was 8.4 mol% and the degree of polymerization was 51.
0, the degree of saponification of vinyl acetate units was 88 mol%. A porous material was obtained in the same manner as in Example 1 except that 60 parts of the above-mentioned modified PVA (without using the unmodified PVA together) was used as the raw material. Table 1 shows the properties of the obtained porous body.

Example 3 Vinyl acetate 2800 g, 7-octen-1-ol 60 g, AI
Polymerization, saponification and purification were carried out in the same manner as in Example 1 except that the polymerization conditions were changed to BN 2.8 g, polymerization time 4.5 hours, and polymerization rate 40% to obtain a modified PVA.
The modified PVA thus obtained had a 7-octen-1-ol unit content of 1.6 mol%, a polymerization degree of 1740 and a vinyl acetate unit saponification degree of 98.5%. A porous material was obtained in the same manner as in Example 1 except that 60 parts of the above-mentioned modified PVA (without using the unmodified PVA together) was used as the raw material. Table 1 shows the properties of the obtained porous body.

Comparative Example 1 A porous material was obtained in the same manner as in Example 1 except that 60 parts of PVA-217 (unmodified PVA) was used as a raw material. Table 1 shows the properties of the obtained porous body.

[0018]

[Table 1]

(Note 1) Water absorption rate (second): Vertical 10 cm,
Dry sample (80 ℃
Dried for 24 hours) in water at 20 ℃
The time required for the water to reach a height of 3 cm above the water surface in the sample when held vertically so as to be submerged. (Note 2) Wetting rate (second): Vertical 10 cm, horizontal 10 c
A dry sample (dried at 80 ° C. for 24 hours) cut into m and 2 cm in thickness was gently floated on the water surface at 20 ° C., and the time required for the sample to submerge below the water surface was expressed. (Note 3) Water retention (%): Weight (wet weight) after water is kept twice as much as the absolute dry weight of the sample and then left in a thermo-hygrostat at 30 ° C and 50% RH for 7 hours. It was calculated from the following formula. Water retention (%) = (wet weight-excess dry weight) / absolute dry weight x 1
00

[0020]

EFFECT OF THE INVENTION The polymer porous material of the present invention has an extremely high water absorption rate of (1) a porous material, as compared with a porous material obtained by using a conventional ordinary polyvinyl alcohol,
Good water retention, (2) great flexibility when hydrated, smooth feel, (3) good acid resistance and alkali resistance, so while using the porous body It has features such as no deterioration in performance. The polymer porous body of the present invention has excellent water absorbency, particularly good water wettability, good elasticity, flexibility, touch, etc., so that it is a water-soluble cosmetic buff, bath sponge, synthetic It is preferably used for chamois, sponge chief, car wash sponge, water absorbing roller, kitchen sponge, various filters, sponge grindstone, and the like.

Claims (1)

[Claims] 1. A polymer porous body obtained by allowing an aldehyde (B) and an acid (C) to act on a modified polyvinyl alcohol (A) having a side chain of a hydroxyalkyl group having 2 to 20 carbon atoms.