JPS6296325A - Production of glass by sol gel method - Google Patents

Abstract

PURPOSE:In producing glass by sol-gel method, to readily eliminate bubbles occurring in hydrolysis without increasing an amount of an alcohol used and to make it possible to produce high-quality glass free from bubbles in a short time, by hydrolyzing a sol solution under reduced pressure. CONSTITUTION:One or more of metallic alcoholates such as Si(OCH3)4, Si(OC2 H5)4, Ti(CO4H9)4, Zr(OC2H5)4, etc. are dissolved in water and an alcohol such as methanol, ethanol, etc., to give a solution of the metallic alcoholate (sol solution). The solution is incorporated with an acid or alkali as a catalyst, hydrolyzed in a vacuum device such as a vacuum desiccator, vacuum furnace, etc., at room temperature - 80 deg.C while stirring and gelatinized. Since the operations are carried out under reduced pressure, high-quality glass hardly containing bubbles occurring upto gelatinization can be produced in an extremely short time even if the amount of the alcohol used is not increased.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application 1] The present invention relates to an improvement in a method for producing glass by a sol-gel method.

[Prior Art] When producing glass by the sol-gel method, an acid catalyst or an alkali catalyst is added to a sol solution obtained by dissolving one or more types of total dioptric alcohols 1- in water and alcohol. In addition, a method is generally employed in which the sol solution is hydrolyzed at a temperature of room temperature to 80° C. with stirring to form a gel, and the gel is dried (Q, calcination).

In this sol-gel method, the hydration of total alcoholate 5
) Bubbles are generated during melting, and these bubbles are known to adversely affect the quality of the glass product.

The generation of air bubbles can be a problem, especially when the amount of alcohol used is small, but if these bubbles occur during the initial stage of gelation, use a wrench, etc., or transfer the sol solution to another container. A method of removing it using means such as moving is used.

5 Problems to be Solved] However, adopting the above method at a stage when gelation has progressed and the viscosity of the liquid has increased will impair the uniformity of the liquid.
Bubbles generated in the latter half of the gelation process cannot be completely removed.

However, the generation of bubbles can be reduced to some extent by increasing the amount of alcohol used.
In this case, there is an inconvenience that it takes a long time of one week or more to complete the gelation.

Means for Solving Problem 1 1 The purpose of the present invention is to provide a means for easily removing air bubbles generated during hydrolysis without using alcohol. lυ and 4,
Specifically, by hydrolyzing a metal alcoholate solution (sol solution) under reduced pressure, air bubbles can be eliminated at both the early and late stages of the gelation process without impairing the homogeneity of the solution. The purpose is to remove the glass to produce high-quality glass using WIJ.

That is, the present invention is characterized in that, in a method for producing glass by a sol-gel method, at least a part of the hydrolysis of the metal alcoholate sol FFIa is carried out under reduced pressure.

In the present invention, as the metal alcoholate, S t
(OCH3) 4.8 t (QC,,H5>4
゜AI (i-QCH) Ti (QC4H9) 4
゜373'' 7r(OC2H5)4, etc., can be used alone or in combination.Also, as the alcohol, any alcohol commonly used in the sol-gel method, such as methanol or ethanol, can be used. Any acid or alkali commonly used in the art may be used.

According to the present invention, one or more metal alcohols
A sol solution prepared by dissolving 1- in water and alcohol and adding an acid or alkali thereto is subjected to hydrolysis under reduced pressure. In this case, the reduced pressure conditions do not necessarily need to be maintained for the entire period of hydrolysis. For example, a vacuum desiccator, a vacuum furnace, a vaporator, etc. can be used as a device for hydrolyzing a sol solution under reduced pressure.As a means for reducing the pressure in these devices, an aspirator, a vacuum pump, etc. can be used. can be used.

The degree of vacuum of the device for hydrolyzing the sol solution is approximately 10 to 7 Q a+ when the sol solution is not contained.
When the Sol FFJ liquid is contained, the degree of vacuum decreases as the alcohol evaporates, but it is preferably in the range of 150 to 750 n+ff111 g.
The effect of defoaming cannot be expected much, and 15 Q an + I1g
This is because components other than the by-product alcohol will be exposed in the following manner.

[Function] Taking tetramethoxysilane Si (OCH3) 4 as an example of a metal alcoholate in the sol-gel method, the hydrolysis reaction is shown by the reaction formula: s* (oc+ > + 1-+ 20 →
(OCI-131 (CI-130) -3i -OH+
It becomes CM 301-1 (OCH3). As is clear from this reaction formula, tetramethoxysilane produces methanol as a by-product through a hydrolysis reaction, and this methanol causes bubbles generated during the gelation process. In the present invention, since the water splitting reaction is carried out under reduced pressure, methanol bubbles generated in the sol solution are successively removed from the solution and do not remain in the solution for practical purposes. Since the n1 raw alcohol is removed from the system, the 81 questions required for gelation can also be shortened.

Example f911] Example 1 Tetramethoxysilanol 1a. I! ! A solution was prepared by mixing 0.01o acid. On the other hand, the vacuum desiccator was depressurized with an aspirator to bring the pressure inside the system to 25 mm/1 g, and the above solution was placed in it and stirred for 30 minutes while operating the aspirator. After the elapsed time, the agitation was stopped and gelation was continued for 5 hours at room temperature to form a wet gel without air bubbles.

This wet gel was heated to 60°C for 24rI! After heating for T, the gel was taken out of the container and heated at 40°C, 60°C, 80°C,
The mixture was heated at 100° C. and 120° C. for 12 hours, and then allowed to cool naturally to form a dry gel. Next, this Draigle was heated to 1100°C at a heating rate of 10°C/■5, and then heated to 311 L/ml at this temperature.
Hold for 1 hour to make clear glass without bubbles or cracks (
It was.

For comparison, when the above solution was stirred at room temperature under atmospheric pressure, it took 10 hours to complete gelation, and the resulting wet gel contained many air bubbles. Furthermore, when the operation of the aspirator was continued without stopping after 30 minutes, gelation could be completed in one hour.

Example 2 Tetramethoxysilane 20g, water 25Q1 ethanol 5
By mixing g, hydrochloric acid o, and oia and performing the same operation as in Example 1, a transparent glass without bubbles or cracks could be obtained.

Example 3 Tetramethoxysilane 20g, water 20Q, meta/-/
L, 10 Q, 1! A Te solution was prepared by mixing 1 g of wJO00. Also, aluminum isopropoxylide 29, zirconium tetraethyl-1-20° titanium tetrabutoxide 2Q, water 2g, methanol 10a
were mixed and stirred for 3 hours to prepare solution 8. Mix the above solution A and solution B and add 24111 without adding the solution.
The above mixed solution was put into an evaporator adjusted to have a volume of 11Q, and stirred for 20 minutes under reduced pressure.

Next, the above solution was placed in a petri dish and left to stand for 5 hours to form a wet gel without bubbles.This cologne was dried and baked under the same conditions as in Example 1 to eliminate bubbles and cracks. I was able to get clear glass without.

[Effect of the invention] As demonstrated in Example 1 above, when metal alcoholate is gelled by the usual method, numerous bubbles are generated in the wet gel, which are then dried and fired into glass. Although there are many bubbles in the glass, according to the method of the present invention, the bubbles are removed before gelation occurs, so by drying and firing the bubbles, a glass that contains almost no bubbles can be obtained. be able to.

Furthermore, although conventional methods require a long time of 10 hours or more to complete gelation, according to the method of the present invention, the time required for gelation can be shortened to about 1 hour.

Claims (1)

[Claims] 1. A method for producing glass by a sol-gel method, characterized in that at least a part of the hydrolysis of the metal alcoholate sol solution is carried out under reduced pressure.