JPH04209606A - Crosslinking of hydroxylated polymer - Google Patents

Abstract

PURPOSE:To crosslink a hydroxylated polymer at low temperatures to give a product of an improved environmental resistance by adding a metal alkoxide to a solution of the polymer and effecting a sol-gel reaction of the hydroxyl groups with the metal alkoxide. CONSTITUTION:A metal alkoxide (e.g. dimethyldiethoxysilane) is added to a solution of a hydroxylated polymer (e.g. PVA or cellulose), and a sol-gel reaction of the hydroxyl groups with the metal alkoxide is effected to crosslink the polymer through the metal of the alkoxide. As compared with a conventional crosslinking process, this process can be performed at lower temperatures and the environmental resistance can be improved. The crosslinking density can be controlled by changing the amount of the crosslinking agent used, and even a polymer of a different degree of saponification and a different degree of polymerization can be crosslinked by selecting the metal alkoxide.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to polymers having hydroxyl groups, and particularly to a crosslinking method for improving environmental resistance.

(Prior Art) When using a polymer having hydroxyl groups, such as polyvinyl alcohol or cellulose, as a coating film, it is generally necessary to crosslink the polymer in order to improve environmental resistance such as heat resistance, moisture resistance, and durability. Are known.

(Problem to be Solved by the Invention) By the way, as a method for crosslinking, a crosslinking agent such as a methyl vinyl/maleic anhydride copolymer is added to a solution of the polymer, and crosslinking is performed by heating. Is there a method of crosslinking by irradiating light, such as ultraviolet light, in addition to heating? Both methods are complicated, as the state of crosslinking varies depending on the conditions of the heating and light irradiation.

In addition, so-called capsule-type liquid crystal display elements in which liquid crystal is dispersed and held in the polymer, for example, Japanese Patent Publication No. 58-50163
In Publication No. 1 and Japanese Unexamined Patent Publication No. 60-252687,
When external factors such as heating and light irradiation are applied, there may be problems such as destruction of the capsule structure or other deterioration of the liquid crystal display element.

(Means for Solving the Problems) The present invention adds a metal alkoxide to a solution of a polymer having hydroxyl groups, and bridges the metal of the metal alkoxide by a sol-gel reaction between the hydroxyl groups in the solution and the metal alkoxide. Its role is to crosslink the solution.

(Function) Polymers having hydroxyl groups can be crosslinked without requiring external factors.

(Example) Next, examples of the present invention will be described.

Tetraethoxysilane (Si(O
CJs) 4) A homogeneous solution was prepared by adding 10 parts by weight to 20 parts by weight of dimethyl sulfoxide prepared as a solvent to increase compatibility and 5 parts by weight of ethyl alcohol, and this homogeneous solution was prepared as a polymer having a hydroxyl group. 20wt
% polyvinyl alcohol (manufactured by Kuraray: P VA20
3) In addition to 140 parts by weight, add 0.1 parts by weight of acetic acid prepared as a catalyst, mix and stir using a homogenizer, coat this solution on an aluminum substrate using a doctor blade, and heat at 25°C in a 50% RH atmosphere. After drying at 60° C. for 6 hours, the film was further dried at 60° C. for 1 hour to form membrane body A of Example.

Further, as a comparative example, a film body B of a comparative example was formed by coating and drying the same PVA203 on an aluminum substrate under the same conditions as in the above example.

The DSC (differential scanning calorimetry) curves of the membranes A and B are shown in FIG.
In contrast to film B, which had a melting peak near C, the softening temperature of film A rose to 70.6°C, and the melting peak disappeared.

Further, when membrane bodies A and B were each immersed in water and left for 24 hours at 25°C, membrane body B completely dissolved in water, but membrane body A did not dissolve.

From the above, it was found that in film body A, polyvinyl alcohol was crosslinked by the sol-gel reaction with tetraethoxysilane, and the environmental resistance was improved.

Note that the present invention is not limited to the above embodiments, and various modifications can be made within the scope of the gist of the present invention. For example, examples of polymers having hydroxyl groups include cellulose, examples of metal alkoxides include dimethyljethoxysilane ((CH3)Sl(OC2H6)), etc.
Furthermore, a solvent that increases compatibility is not necessarily required when the amount of metal alkoxide is small, and the catalyst may be omitted.

(Effects of the Invention) The present invention adds a metal alkoxide to a solution of a polymer having a hydroxyl group, and by a sol-gel reaction between the hydroxyl group of the solution and the metal alkoxide, the metal of the metal alkoxide is used as a bridge to dissolve the solution. By crosslinking,
It enables crosslinking at lower temperatures than conventional methods and improves environmental resistance.

Moreover, the crosslinking density can be controlled by the amount of crosslinking agent added, and
It has the advantage that polymers having different degrees of saponification and polymerization can be crosslinked by selecting the metal alkoxide.

[Brief explanation of the drawing]

Figure 1 shows DSC of a film body of an example of the present invention and a film body of a comparative example.
It is a curve graph.・ −−= Te soil Fu ni ni 3; Figure 1

Claims (1)

[Claims] (1) A metal alkoxide is added to a solution of a polymer having hydroxyl groups, and the solution is crosslinked by a sol-gel reaction between the hydroxyl groups of the solution and the metal alkoxide, using the metal of the metal alkoxide as a bridge. A method for crosslinking polymers with characteristic hydroxyl groups.