JPS621296B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a water absorbing agent with excellent gel stability.
In recent years, there has been a demand for highly water-absorbent materials in the food, medical, and horticultural fields, and cross-linked polyethylene oxide and cross-linked poval have been developed as materials that have better water absorption and water retention than existing water-absorbing materials such as paper and pulp. A large number of polymer electrolytes have been proposed, including water-soluble crosslinked polymers such as, hydrolysates of starch-polyacrylonitrile graft polymers, starch-polyacrylic acid crosslinked grafts, and polyvinyl alcohol-polyacrylic acid copolymers. . However, they are still unsatisfactory in terms of water absorption performance, stability of quality, rot resistance, ease of disposal, etc. In particular, when these existing materials are left in a water-containing state for a long period of time, their water absorption properties are significantly reduced, and they tend to cause syneresis or gel collapse. Although some gels have good stability, they are hardly biodegradable and have to be incinerated for disposal. The present inventors have conducted extensive research on water-absorbing agents that have gel-like stability within a range that does not cause any practical problems and are biodegradable. The present invention was completed by discovering that a copolymer obtained by polymerizing functional monomers has unprecedented water absorption properties. An object of the present invention is to provide a polymeric material having excellent water absorption and water retention properties and high gel stability. Another object of the present invention is to provide a method for manufacturing the above-mentioned excellent water-absorbing material industrially easily and inexpensively. The above purpose is to prepare at least one polyfunctional monomer selected from the group of fibroin (A), di(meth)acrylates of polyhydric alcohols, di(meth)acrylamide compounds, diglycidyl ethers and glycidyl(meth)acrylates. A water-absorbing agent made of a polymer whose main components are the compound (B) and the acrylic acid compound (C) represented by the following formula. [However, R ₁ represents hydrogen or a methyl group, and R ₂ represents hydrogen, an alkali metal, or an ammonium ion. ] is achieved. (R ₁ and R ₂ are the same as above) The water-absorbing copolymer according to the present invention is composed of fibroin
(A), polyhydric alcohol di(meth)acrylate,
At least one polyfunctional monomer selected from the group of di(meth)acrylamide compounds, diglycidyl ethers, and diglycidyl(meth)acrylates
(B) (hereinafter abbreviated as crosslinkable monomer) and acrylic acid (C) as main components, preferably the above-mentioned fibroin (A), crosslinkable monomer (B) ) and acrylic acids (C) in a weight ratio of 1 to 40:
0.1-5:50-90, more preferably 1-25:0.2-
The reaction was carried out at a ratio of 3:70 to 95. At this time, as a third component, for example, a copolymerizable monofunctional monomer other than the main component, such as an ethylene derivative, a styrene derivative, or a (meth)acrylic acid derivative, is added within a range that does not impair the water absorption properties of the copolymer. They may be copolymerized. The fibroin solution used in the present invention is prepared by a known method.
Silk raw materials such as cocoons, raw silk scraps, kiki, bis, and boulette are scoured to remove sericin according to conventional methods, and then processed into copper-ethylenediamine aqueous solution, copper hydroxide-alkali-glycerin aqueous solution, copper hydroxide-ammonia aqueous solution, and halogenated It is prepared by dissolving an aqueous lithium solution, calcium, magnesium or zinc nitrate, hydrochloride, or thiocyanate in a solvent such as water, or by further desalting the thus obtained solvent solution of fibroin by dialysis. It goes without saying that when carrying out the method of the present invention, other known methods may be used. In addition, the crosslinkable monomer (B) has an ethylenically unsaturated group or a glycidyl group at the end, and the crosslinkable monomer (B)
and acrylic acids (C) to form three-dimensional crosslinks, such as polyhydric alcohols such as ethylene glycol dimethacrylate, polyethylene glycol diacrylate, and 1,6-hexanediol diacrylate. Glycidyl compounds such as meth)acrylates, glycidyl (meth)acrylate, glycidyl polyethylene (meth)acrylate, (poly)ethylene glycol diglycidyl ether, acrylamides such as N・N′-methylenebisacrylamide,
Examples include vinyls such as divinylbenzene. Furthermore, acrylic acids (C) are compounds represented by the above general formula, including (meth)acrylic acid, (meth)
Preferable examples include sodium acrylate, potassium (meth)acrylate, ammonium (meth)acrylate, and the like, and when sodium acrylate is used, the water absorption properties of the obtained polymer become even more excellent. Further, specific compounds of the third component include, for example, acrylamide, N-methylolated acrylamide, 2-hydroxyethyl methacrylate, N-vinylpyrrolidone, vinylsulfonic acid, P-styrenesulfonic acid, 2-acrylamide-2-methyl -propanesulfonic acid and the like. Particularly preferred acrylic acids are sodium or potassium salts of acrylic acid or methacrylic acid, and particularly preferred crosslinking monomers are di(meth)acrylic acid esters of polyhydric alcohols. If the content of acrylic acids exceeds 98% by weight, the water-absorbing gel tends to become weak, and if the content of fibroin exceeds 40% by weight or the content of crosslinking monomer exceeds 5% by weight, the amount of water absorbed tends to decrease. The form of the water absorbing agent of the present invention can be appropriately selected depending on the application, such as powder, film, fiber, or block form. The water-absorbing agent according to the present invention is prepared by mixing a fibroin (A) solution with an acrylic acid (C), a crosslinkable monomer (B), and if necessary the third component, and then irradiating it with radiation, electron beams, or ultraviolet rays or using a radical polymerization catalyst. It can be obtained by polymerization and neutralization if necessary. Acrylic acids (C)
For neutralization, for example, a hydroxide or carbonate of an alkali metal or ammonia may be used. In general, during the reaction, an aqueous solution of fibroin (A) is further mixed with acrylic acids (C), a crosslinkable monomer (B), and a third component if necessary, and reacted in an aqueous medium. A hydrophobic organic solvent such as benzene may be added and mixed to react in a dispersed system. Further, a hydrophilic organic solvent such as methyl alcohol, ethyl alcohol, or tetrahydrofuran may be added to the aqueous medium. Next, oxygen in the reaction system is preferably removed using an inert gas such as nitrogen gas, and radiation, electron beams, ultraviolet rays, etc. are irradiated, or a radical polymerization catalyst is added for polymerization. Radical polymerization catalysts include hydrogen peroxide, benzoyl peroxide, potassium persulfate,
It may be appropriately selected from commonly used materials such as ammonium persulfate, ceric salt, and azobisisobutyronitrile. Further, at the same time, sulfites, ferrous salts, and amines can be used in combination for polymerization in a redox system. However, it is preferable to use a persulfate as a polymerization catalyst because a product with a high degree of polymerization can be obtained and production is easy. Polymerization temperature is usually 10-110℃, preferably 20-80℃
℃ and the polymerization time is 20-600 minutes, preferably 30-600 minutes.
It is 300 minutes. Next, the reaction product can be used as it is or after being subjected to treatments such as neutralization, washing, drying, molding, and pulverization. Neutralization can be carried out using an aqueous solution of an alkali metal or ammonia hydroxide or carbonate, or a mixed system with a water-soluble solvent such as alcohol. After the reaction, washing is performed to remove unreacted monomers, etc. . For cleaning, water, alcohol, acetone, hexane, etc. are appropriately selected and used alone or in combination. After that, usually 20-100℃, preferably 30-80℃
Dry at normal pressure or under reduced pressure. The water-absorbing agent of the present invention obtained in this manner exhibits high water-absorbing performance, that is, a water absorption rate of 100 to 500 times its own weight, does not lose its water-retention ability even under pressure, and stably maintains a hydrogel state for a long period of time. There is. Furthermore, since it has fibroin in its structure, it exhibits biodegradability, but in practical terms it has stable water retention over a long period of time. In particular, if a preservative is used in combination, further long-term stability can be obtained. The water absorbing agent of the present invention is for medical, sanitary,
In the horticultural field, it can be used as a water absorbing agent, water retaining agent, dehydrating agent, gelling agent, thickening agent, etc. The present invention will be specifically explained below with reference to Examples. Example 1 1 kg of raw silk waste was mixed with 1% by weight Marcel soap aqueous solution
30 and treated at 98°C for 3 hours to substantially remove sericin and oil. 2 kg of 65% by weight aqueous calcium chloride solution and 0.5 kg of ethyl alcohol
Add 0.5 kg of the above-mentioned scouring silk and heat at 70 to 75℃ for 1 hour.
Stir and dissolve for hours. Next, the mixture was mixed and diluted with 2 kg of 70°C hot water, and after cooling, it was desalted using a hollow fiber dialyzer. This fibroin aqueous solution, acrylic acid, and polyethylene glycol diacrylate <CH ₂ =
CHCO ₂ ^- (CH ₂ CH ₂ O) ₁₄ ^- COCH=CH ₂ > was mixed in the proportions shown in Table 1, diluted to a total of 15% by weight, and ammonium persulfate was added to acrylic acid under a nitrogen stream. Add 0.5% by weight to 3% at 40℃
Allowed time to react. The resulting gel-like polymer was treated with sodium hydroxide, potassium hydroxide, and ammonia.
Neutralize in 50% by weight ethyl alcohol aqueous solution,
Then, after washing with a 50% by weight aqueous ethyl alcohol solution, it was dried under reduced pressure at 60°C for 24 hours. next
A fibroin-acrylate polymer was obtained by grinding into a powder of 100 to 300μ. 1 g of each powder was immersed in 1 water, and after 1 hour and 1 month at 25°C, after 1 week at 60°C, the free water was filtered through a 100 mesh wire mesh, and the water absorption was determined by the weight of the insoluble gel. was calculated.

[Table] The biodegradability of Experiment Nos. 1-1, 1-2, 1-5, and 1-10 was measured based on the test method published by the Ministry of International Trade and Industry.
It was 37.4%. From Table 1 and the above biodegradability results, it can be seen that the water absorbing agents of the present invention not only have high water absorption performance, but also have long-term stable water retention and biodegradability. . Example 2 Using the fibroin aqueous solution obtained in Example 1,
20 each of fibroin, acrylic acid, sodium acrylate, and the crosslinking monomer shown in Table 2,
They were mixed in amounts of 14.5, 65, and 0.5 parts, and concentrated or diluted to a concentration of 35% by weight. Next, potassium persulfate was added at 0.3% by weight based on the total monomers100
Dispersion polymerization was carried out at 45° C. for 3 hours using Span 60, which was 1.5 parts of hexane (250 parts per part). The obtained precipitate was washed with hexane and methanol and then dried. Next, performance was evaluated in the same manner as in Example 1.

【table】

[Table] As shown from the results in Table 2, it can be seen that all the water absorbing agents of the present invention maintain high water absorption rates for a long period of time. Example 3 Using the aqueous fibroin solution used in Example 1, fibroin, acrylic acid or methacrylic acid, 1,6-hexanediol diacrylate, and the addition polymerizable monomer shown in Table 3 were added to
After mixing to give a concentration of 74.5, 0.5, and 10 parts by weight to a concentration of 20% by weight, 0.3% by weight of potassium persulfate based on the total monomers was added and polymerized at 50°C for 3 hours. The obtained polymer was neutralized with sodium hydroxide in a 50% aqueous methanol solution, then washed and dried. Next, performance was measured in the same manner as in Example 1. In addition, as a control, a polymer containing no crosslinking monomer, that is, in the composition of the above example, 1.6-
Excluding hexanediol diacrylate, 15% each of fibroin, acrylic acid or methacrylic acid, and the addition polymerizable monomers shown in Table 3 below,
They were mixed in amounts of 74.5 and 10 parts by weight, and the same operations as in the above example were performed to obtain a polymer. Result 3-8
and 3-9 are also shown in Table 3.

[Table] As shown in Table 3, the water absorption rate of water absorbing agents 3-8 and 3-9, which correspond to comparative examples that do not contain crosslinking monomers, was halved in 3 weeks at 60°C. On the other hand, it can be seen that all of the water absorbing agents 3-1 to 3-7 according to the present invention have high water absorbing performance and stability. Example 4 Using the fibroin aqueous solution used in Example 1, 10 parts by weight of fibroin and 0.4 parts by weight of ethylene glycol dimethacrylate were mixed with acrylic acid and sodium acrylate in the proportions shown in Table 4 to make 100 parts by weight. After adjusting the concentration to 20% by weight, add hydrogen peroxide and sodium sulfite to the total monomer.
0.5 part by weight was added and polymerized at 50° C. for 4 hours. The resulting polymer was thoroughly washed with a 50% by weight aqueous methanol solution and then with methanol, and then dried.

[Table] Next, 1 g of the obtained water-absorbing agent was immersed in 1 part water or 1 wt% saline solution 1. After 1 hour at 25°C, the water-absorbing gel was separated using a 100-mesh wire mesh or 1 kg/cm ² was added from above. After applying a load and allowing water to separate for 30 minutes, the water absorption rate was calculated from the weight of the water-absorbing gel. After 3 weeks of being immersed in water at 60°C, the water-absorbing gel was separated and the water absorption rate was calculated. As shown in the results in Table 4, all the water absorbing agents according to the present invention maintain high water absorbing performance for a long period of time, exhibit little water separation even under pressure, and exhibit high water absorbing power even for salt aqueous solutions.

Claims (1)

[Scope of Claims] 1. At least one polyfunctional compound selected from the group of fibroin (A), di(meth)acrylate of polyhydric alcohol, di(meth)acrylamide compound, diglycidyl ether, and glycidyl(meth)acrylate. A water absorbing agent made of a polymer whose main components are a monomer (B) and an acrylic acid (C) represented by the following formula. [However, R ₁ represents hydrogen or a methyl group, and R ₂ represents hydrogen, an alkali metal, or an ammonium ion. 2. The water absorbing agent according to claim 1, wherein the di(meth)acrylate of polyhydric alcohol is ethylene glycol dimethacrylate, polyethylene glycol diacrylate, or 1,6-hexanediol diacrylate. 3 The di(meth)acrylamide compound is N.
The water absorbing agent according to claim 1 or 2, which is N'-methylenebisacrylamide. 4. The water absorbing agent according to any one of claims 1 to 3, wherein the acrylic acid (C) is sodium (meth)acrylate.