JPS5879006A - Preparation of water-containing gel - Google Patents

Abstract

PURPOSE:To obtain a water-containing elastic gel having excellent water-retainability, by the crosslinking reaction of an aqueous solution of a polymer consisting of a mixture of acrylic acid and a copolymerizable monomer and having neutralized carboxyl groups, with an epoxy group-containing polymerizable unsaturated monomer. CONSTITUTION:An aqueous solution of a polymer composed of acrylic acid or a mixture of acrylic acid and a minor amount of copolymerizable monomer (e.g. acrylamide) wherein at least a part of the carboxyl group of the polymer is neutralized, (preferably an aqueous solution of the salt of polyacrylic acid, etc. having a concentration of 1-30wt%, especially 5-20wt%), is crosslinked by adding and dissolving a crosslinking agent comprising an epoxy group-containing polymerizable unsaturated monomer (e.g. glycidyl methacrylate) and if necessary, a water-retaining agent, a poultice base, etc. to the solution to obtain the objective water-containing gel. The amount of the crosslinking agent is >=0.1% of the aqueous solution. USE:Material for keeping the cool or hot state, a fragrance-retaining agent, material for medical use, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a water-containing glue starting from an aqueous solution of a polymer. The constituent unit is a mixture of monomers, and at least a portion of the carboxyl group is neutralized. -Regarding the method of three-dimensionally cross-linking and producing a hydrogel It is. Especially in recent years,
As a water-insoluble and hydrophilic polymer material for medical use, it is expected to be used in a wide variety of industries.

Water-containing gels made from natural materials such as agar and gelatin were known, but in recent years, gels made from synthetic polymer materials have been attracting attention due to their high resistance to 7. It has become.

Polyacrylate is known as a water-soluble polymer that is safe for the gland, as evidenced by the fact that its Na salt is used as a food additive. Suggestions have been made. One method is to provide a hydrogel by aqueous solution polymerization of acrylate and acrylic acid in the presence of a polyfunctional monomer. This method starts from an aqueous solution of monomers and polymerizes and cross-links them at the same time, so it is only one method. However, in this case, unpolymerized residual acrylic acid heptamine is present in the hydrogel, and its use for medical purposes has a major disadvantage in that it poses a problem of toxicity. exists.

On the other hand, as a method to overcome this drawback, a method has been proposed in which a water-containing gel is produced by ionic crosslinking of an aqueous solution of polyacrylate and polyacrylic acid using a polyvalent metal salt such as magnesium chloride or calcium chloride. However, with this method, the gelation rate was too fast, making it difficult to mold it into any desired shape, and the water retention ability and stability over time were poor, so it was still far from practical.

The present inventors have completed the present invention as a result of intensive studies on a new method for producing hydrogel that can solve the drawbacks of the prior art. A polymerizable unsaturated product containing acrylic acid as a main component and a monomer mixture copolymerizable with it as a constituent unit, with at least 4 parts of the carboxyl groups being neutralized and containing an epoxy group as a crosslinking agent in an aqueous solution of the mourning polymer. This is a method for producing a hydrogel, characterized by dissolving monomers and crosslinking the polymer by a crosslinking reaction.

The polymer in the present invention has a constituent unit composed of acrylic acid alone or a monomer mixture mainly composed of acrylic acid and copolymerizable with the same, and has at least a portion of its carboxyl groups neutralized.

Monomers that can be copolymerized with acrylic acid may be monomers that do not impair the water solubility of the monomer obtained from the monomer mixture, such as acrylic acid, methyl acrylate, methyl methacrylate, and acetic acid. Examples include beer.

Neutralized polyacrylic acid is less prone to crosslinking and has the desired water content.

Can't get gel. The degree of neutralization of the polymer is
In order to obtain a desired hydrated group by crosslinking reaction, the molecular weight is preferably 10 or more, and more preferably 30qIb or more. The alkali used for neutralization can be arbitrarily selected from hydroxides of alkali metals such as sodium and potassium, ammonia, and various amines depending on the purpose.

The molecular weight of the polymer used is preferably 10,000 to 1,000,000. If it is less than 10,000, the gel strength is too weak and it tends to be difficult to maintain a constant shape. If it exceeds 1,000,000, the viscosity becomes high and the crosslinking agent, It is not suitable because it tends to be difficult to mix the polymerization catalyst and the like, and the resulting hydrous gel tends to become hard.

The polymer used in the present invention, whose constituent units are acrylic acid alone or a monomer mixture mainly composed of acrylic acid and copolymerizable with it (hereinafter referred to as polyacrylic acids), can be produced by a conventional method. The neutralization method may include neutralizing a predetermined amount of polyacrylic acids with an alkali, or a mixture of polyacrylic acids and neutralized salts of polyacrylic acids may be used. The water solubility of the polymer in the present invention, that is, the salt of nine polyacrylic acids that is at least partially neutralized, is 1 to 30 w.
More preferably, the t-power I L <, 5 to 20 wt1G. If the immersion resistance is less than 1, the crosslinking density will be low and it will be difficult to obtain a water-containing glue that maintains a constant shape.If it exceeds 30Is, the crosslinking will proceed too much and a syneresis phenomenon will easily occur, which is not preferable.

Next, an epoxy group-containing polymerizable unsaturated monomer is added and dissolved in an aqueous solution of a salt of at least partially neutralized polyacrylic acids such as -, and a hydrogel is obtained by crosslinking. .

The polymerizable unsaturated monomer containing an epoxy group used as a crosslinking agent in the present invention is often a monomer containing an epoxy group and further having a vinyl group, an allyl group, etc., such as glycidyl. Examples include methacrylate, glycidyl acrylate, allyl glycidyl ether, methallyl glycidyl ether, and 2,3-epoxybutyl acrylate. The amount of this monomer added to the aqueous solution is 0.1 wt'! OG, preferably 4 or more, 1
vt9! If it is less than 9, it is difficult for the crosslinking reaction to occur satisfactorily. The upper limit varies depending on the solubility of the monomer in the polymer aqueous solution, but is approximately 59G1! degree. A hydrogel can be produced by crosslinking the thus prepared polymer in the aqueous monomer solution containing the polymer with a polymerizable unsaturated phosphor containing an epoxy group.

It is presumed that the crosslinking reaction of the polymer in the present invention is carried out by a combined reaction of a reaction between a carboxyl group and an epoxy group and a polymerization reaction between vinyl groups.

The polymerization reaction between vinyl groups can be carried out by a polymerization method commonly used in the polymerization of vinyl group-containing monomers. Although photopolymerization and radiation polymerization can also be employed, it is generally preferable to use a radical polymerization catalyst. Water-soluble peroxides such as ammonium persulfate, hydrogen peroxide, sodium bromate, or these together with ferrous sulfate,
The redox catalyst used in combination with a water-soluble reducing agent such as sodium sulfite, or a water-soluble azo compound such as 2,2'-azobis(2-amidinopropane) hydrochloride can be used.

When producing the hydrogel of the present invention, other substances such as water retention agents such as alcohol, glycerin, and polyethylene glycol, poultice components such as menthol, and coloring agents are dissolved in the aqueous solution depending on the purpose of use of the hydrogel. Alternatively, it is of course possible to disperse them.

According to the present invention, the paper has excellent water retention ability, that is, there is no phenomenon of water separation over time, and even after water has been evaporated by forced heating, the paper can be restored by contacting it with water again. There is no softening phenomenon that would destroy the crosslinked structure even at high temperatures, and it is possible to easily produce an elastic hydrogel.

Next, the present invention will be explained in more detail with reference to Examples.

Example 1 A 151 aqueous solution of polyacrylic acid sodium salt having a neutralization degree of 60% was prepared by mixing the solution and water.

100g of this aqueous solution, 5
Add g and dissolve uniformly. Furthermore, 1 ml of 11 aqueous solution of 2,2'-azobis(2-amidinopropane) hydrochloride was added to this.
After adding Tl and mixing well, it was poured into a polyethylene mold to a thickness of 1 mm, sealed, and then heated at 60°C.
When the mixture was heated in a constant temperature bath for 2 hours to cause a crosslinking reaction, a transparent and elastic hydrogel was obtained.

This was placed in a polyethylene/aluminum composite film bag, sealed, and then left in a thermostat at 50° C. for 5 days. After that, it was taken out and examined. No softening phenomenon was observed, and almost no syneresis was observed.

Example 2 Example! Sodium polyacrylate A (7m/
A-2OL) 2) Add 1.0 g of 7lyl glycidyl ether and 1 mA of 1-aqueous solution of 2.29-azobis(2-amidinopropane) hydrochloride to 100 g of 101 aqueous solution, mix well, and add Kll as in Example 1. The mixture was poured onto the body and heated at 60°C for 2 hours to cause a crosslinking reaction, resulting in a transparent and elastic hydrogel.

Example 3 A 20% aqueous solution of polyacrylic acid partially neutralized to a sodium salt by mixing polyacrylic acid, polyacrylic acid, and water used in Example 1.
00g is a friend. Add 1.0g of glycidyl acrylate to this
was added and mixed well. Additionally, 1 tl of ammonium persulfate
After adding 1 mt each of I aqueous solution and sodium sulfite in aqueous solution, they were poured into a mold in the same manner as in Example 1, and left at room temperature for 24 hours to carry out a crosslinking reaction.
A transparent and elastic water-containing glue was produced.

Example 4 Polyacrylic acid used in Example 1 (Aron A-10
H) was neutralized with ethanolamine to obtain 100 g of a 15% aqueous solution of polyacrylic acid ethanolamine salt. To this, 0.5 g of glycidyl methacrylate and 2.2'-
After adding 1 mA of a 1-aqueous solution of azobis(2-amidinopropane) hydrochloride, pour it into a mold and seal it.
G'C was heated for 12 hours to carry out a crosslinking reaction, and as a result, a water-containing gel of brown color and excellent flexibility was obtained.

patent applicant Toagosei Chemical Industry Co., Ltd. 32-

Claims (1)

[Claims] 1. Acrylic acid alone or a monomer mixture copolymerizable with acrylic acid as the main component is the constituent site, and at least a part of the carboxyl group is neutralized to form an aqueous solution of nine-bosunmer,
A method for producing a hydrogel, which comprises dissolving a polymerizable unsaturated monomer containing an epoxy group as a crosslinking agent, and crosslinking the polymer through a crosslinking reaction.