JPH0234529A - Production of glass product - Google Patents

Abstract

PURPOSE:To effectively inhibit the generation of bubbles during sintering by substituting alkoxyl groups for hydroxyl groups in a specified dried gel body, drying and sintering the gel body. CONSTITUTION:A soln. of starting materials including an organometallic compd. is hydrolyzed, condensed and converted into a gel body. This gel body is dried and immersed in a soln. contg. >=80vol.%. alcohol at room temp. for 1-24hr to substitute alkoxyl groups for hydroxyl groups in the gel body. The gel body is then dried and sintered.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for manufacturing glass products, and in particular, after gelling a solution by hydrolysis and condensation of an organometallic compound raw material, The present invention relates to a method for manufacturing glass products, commonly called the sol-gel method, in which a gel body is dried and fired to form a glass body.

[Prior Art] In the production of glass products by the sol-gel method using organometallic compounds, in the final step, a porous gel body is
It is necessary to make it non-porous (vitrified) by heat treatment. A problem at this time is foaming of the gel body containing a large amount of hydroxyl groups.

This ifI phenomenon occurs because the pores of the gel disappear before the water generated by the dehydration condensation reaction of the silanol groups is sufficiently removed from the gel.

This dehydration condensation reaction starts at a relatively low temperature, 1000
Zero-foaming glass, which is said to occur up to about 0.9°C, becomes so-called foam glass, has no transparency at all, and cannot be used for ordinary glass purposes.

In recent years, several measures have been proposed to solve this problem. Typical methods include: ■ A method in which the temperature is raised very slowly during firing to provide sufficient time for water molecules to exit the gel (for example, Kamiya et al., Journal of the Ceramic Industry Association, 1978).
(2013, Vol. 86, p. 552), ■Calcination in a vacuum to force water molecules out of the gel (for example, G.
J., Garvey et al., J.

de Physique, 43, 271 (19
82)), ■ Calcination is performed in a chlorine or helium atmosphere,
Methods of replacing gas in pores (for example, Matsuya
ma et al., 8u11. Am,CeraIl,soc, ,
63 1408 (1984)).

[Problem H to be solved by the invention] However, in the above-mentioned prior art, the method (2) of slowing the temperature rise requires a long time for baking, and furthermore, the gel essentially contains a large amount of water. Therefore, there is a risk of foaming unless the temperature is controlled very precisely. Also,
The method of firing in a vacuum (2) requires a large investment in equipment and has poor productivity because it uses a vacuum firing furnace. The problem was that the price of the product had to be expensive due to the notification of the recovery method and the price of helium gas.

The present invention provides a method for effectively suppressing l@ bubbles during firing and obtaining high quality glass by overcoming the above-mentioned prior art.

[Means for Solving the Problems] The present invention has been made in order to solve the above-mentioned problems, and includes producing a gel body by gelling a starting material solution containing an organometallic compound, and producing a gel body. A method of drying and then sintering to produce a glass product, which is characterized by replacing the hydroxyl groups in the gel after drying with flucoxyl groups, then drying the gel again, and sintering it. This is a manufacturing method for glass products.

The present invention relates to a method in which, for example, a starting material solution containing an organometallic compound is gelled to produce a gel body, the gel body is dried, and then sintered to produce a glass product. This can be carried out by bringing the gel body into contact with a solution containing it, then redrying the gel body, and sintering it.

The type of alcohol that can be used in the present invention is preferably one in which the above-mentioned substitution reaction easily occurs. Specifically, either methanol or ethanol, or a mixture of these two alcohols is preferable. Higher alcohols higher than propatool are not preferred because the rate of the reaction is low and the molecules are large, making it difficult to diffuse into the gel.

There are no particular limitations on the replacement treatment conditions in the present invention, but if the alcohol treatment is performed excessively, the reaction progresses as follows: Si -0-St + ROH → 5i-OR + 5i-OH, and the siloxane bonds in the gel are broken. At temperatures around room temperature, which is undesirable since the strength of the gel itself decreases, contact with the alcohol solution for 1 to 24 hours is sufficient.

In order to efficiently advance the above reaction to the right side, it is best to use a solution with as high an alcohol content as possible, specifically a solution with an alcohol content lower than 80 volume percent, preferably 80 volume percent or more. If used, foaming during firing cannot be sufficiently suppressed.

As components other than alcohol in a solution containing 80% by volume or more of alcohol, any component that does not adversely affect the gel body and is difficult to separate from alcohol can be used. Examples include water and organic solvents such as acetone.

The composition of the gel body that can be used in the present invention is not particularly limited, and any gel body obtained by hydrolysis/dehydration condensation reaction of an organometallic compound can be effective. .

Normally, when a dried gel body is immersed in a certain solution,
Cracks may occur due to capillary force generated when this solution enters the pores of the gel. At that time, whether or not cracks occur is determined by the bulk specific gravity of the dry gel and the surface tension of the solution, and dry gels with large bulk specific gravity are less likely to generate cracks. In the case of an alcohol solution, if the bulk specific gravity of the dry gel is less than 0.65, cracks are likely to occur when immersed in the alcohol solution. Therefore, the bulk specific gravity is preferably 0.65 or more. Although there is no particular upper limit to the bulk specific gravity of the dry gel that can be used, if the bulk specific gravity is too large, the diffusion of the alcohol solution into the gel body will be slow. Undesirable.

[Function] Generally, alkoxyl groups and hydroxyl groups coexist in the gel body after drying. The remaining alkoxyl groups are almost completely oxidized and removed by heating at about 400°C in the air, but most of the hydroxyl groups in the gel are
It is removed only by a dehydration condensation reaction between hydroxyl groups.

The temperature range in which this reaction occurs is continuous from a low temperature to a high temperature of about 1000° C., but as the temperature of the gel body increases, the viscous flow of the gel body becomes active and non-porosity occurs. If the gel becomes non-porous due to this viscous flow at an earlier stage than the dehydration condensation reaction, water molecules cannot sufficiently exit the gel body, resulting in a state where foaming is likely to occur.

As a result of investigating the cause of foaming that occurs during conventional gel sintering, the present inventors found that in order to suppress foaming during the sintering process, it is necessary to make as many functional groups as possible in the dried gel into alkoxyl groups. I discovered something good.

The simplest and most effective method is to bring the gel body into contact with a solution containing alcohol as a natural enemy (for example, by immersing the gel body in this solution).

Through this operation, the hydroxyl groups remaining in the gel are converted into It-conversion to alkoxyl groups according to the following reaction.

5i-OH+ R-OH → 5i-OR+ H2O (R: alkyl group) According to the present invention, the functional group on the pore surface of the gel body is substituted from a hydroxyl group to an alkoxyl group, which usually makes the gel body non-porous. Since dehydration condensation between hydroxyl groups that occurs in the temperature range that occurs is reduced, foaming during firing is significantly suppressed.

Hereinafter, the present invention will be explained in more detail based on Examples.

Example 1 Commercially available methyl orthosilicate, ethanol, and water were mixed at a volume ratio of 1:1:1.30 to obtain a solution.

Continue stirring, and after about 30 minutes, 200ml of this liquid is -
The mixture was placed in a Teflon-coated stainless steel container with sides of 15 cm and sealed, and gelatinized and cured at 60° C. for 24 hours. Next, this wet gel was immersed in 200 ml of pure water and treated at 60° C. for 24 hours. Thereafter, this gel body was placed in a dryer and dried at <80°C. A dry gel was obtained after 2 days.

This dry gel has a bulk specific gravity of 0.8 and a size of approximately 8c.
It was m.

This gel body was immersed in commercially available special grade methanol 2001 and left at room temperature for 4 hours. Thereafter, the gel body was taken out from the methanol solution and re-dried at room temperature. During this methanol treatment and re-drying, no cracks were generated at all, and their size did not change.

The heat treatment was performed in the air using an electric furnace. Heating rate 5
When the temperature was raised to 1000°C at a rate of 0°C/h and held there for 4 hours, a glass with very good transparency was obtained.

In addition, the solution used for the operation of substituting a hydroxyl group with an alkoxyl group was mixed with 80 volume percent methyl alcohol and 20
Even when changing to a mixed solution of volume percent water, a glass with similar good transparency was obtained.

Example 2 The dried gel obtained in Example 1 was treated under the same conditions using commercially available special grade ethanol instead of methanol, and redrying and sintering resulted in the same results as in Example 1. Similarly, a transparent glass was obtained.

Comparative Example-1 A dried gel obtained in the same manner as in Example-1 was sintered under the same conditions as in Example-1 without being treated with methanol. Most of the resulting glass was foamed.

Example 3 A dried gel obtained in the same manner as in Example 1 above was treated under the same conditions using commercially available special grade isopropanol instead of methanol, and re-dried and sintered. Although foaming was observed in the obtained glass, the area was reduced to about half.

Examples 4 to 6 T i (O
C4H9) 4 (Example 4) Z r (OC4H
9) 4 (Example 5) AI (OC3H7) 3
A mixed solution of the commercially available organometallic compound of Example 6 was prepared so that 5 wt % of each oxide was contained after firing, and a wet gel was obtained. Each gel body was dried in the same manner as in Example-1 to obtain a dry gel. The bulk specific gravity of each dry gel is 0.83. 0.80. 0°8
It was 5.

These dried gels were subjected to methanol substitution treatment and redrying under the same conditions as in Example-1. When this re-dried gel body was sintered, a clean glass with good transparency could be obtained at 1050 to 1150°C.

Example 7 In the above example, a wet gel obtained by gelling an organometallic compound solution is immersed in pure water to increase the strength of the gel body, but this operation is substantially different from the present invention. There is no such relationship, and as shown below, a gel body obtained by drying a wet gel as it is may be used.

The wet gel obtained in the same manner as in Example 1 above was placed in a Teflon container, closed with a lid having 5 0.5 mm pinholes, heated to 80°C, and dried in that state. I did it. After 14 days, the gel body was completely dried, and its bulk specific gravity was 1. It was 2.

This dried gel was subjected to methanol substitution treatment and redrying under the same conditions as in Example-1. When this re-dried gel body was sintered, a clean glass with good transparency could be obtained.

Further, the operation for increasing the strength as performed in Examples 1 to 6 is not limited to the above-mentioned examples, and any method having the same effect can be used.

Furthermore, the operation of substituting a hydroxyl group with an alkoxyl group is not limited to the above-mentioned operation using an alcohol, but similar effects can be expected by using a compound having a group (for example, a carboxylic acid such as acetic acid) that substitutes for a hydroxyl group.

[Effects of the Invention] As is clear from the above examples, the present invention alleviates the tendency of foaming during the firing process, making it possible to easily obtain high-quality glass.

Claims (2)

[Claims] (1) In a method in which a starting material solution containing an organometallic compound is gelled to produce a gel body, the gel body is dried, and then sintered to produce a glass product, the hydroxyl groups in the gel body after drying are A method for producing a glass product, which comprises substituting an alkoxyl group, then drying the gel body again, and sintering the gel body. (2) The method for producing glass products according to claim 1, wherein the means for replacing the hydroxyl groups in the gel body after drying with alkoxyl groups is a method of bringing the gel body after drying into contact with a solution containing alcohol.