JPH02141432A - Production of glass - Google Patents

Abstract

PURPOSE:To produce a glass body having a large area in spite of a large thickness by adding a specified amt. of ethylene glycol to sol when bulky glass is produced by a sol-gel process. CONSTITUTION:When glass is produced by a sol-gel process with at least alkyl silicate and fine silica powder as starting materials, 0.1-5 times (mol) as much ethylene glycol as the alkyl silicate is added to sol. The added ethylene glycol forms a chelate, makes a reaction moderate and reduces strain in gel. Accordingly, stress as the cause of cracking is reduced, the gel is hardly cracked and a thick large-sized quartz glass block is obtd.

Description

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

[Conventional technology]

Many methods have been reported for producing glass using the sol-gel method, but among them, Seiko Epson's Toki Their method is the best. Regarding the method of Toki et al.
No. 1833 describes this in detail. That is, silica particles are added to an acidic hydrolysis sol of ethyl silicate, and after being dispersed, the pH value of the sol is adjusted to 4 to 6 with aqueous ammonia, and after gelation, drying is performed to form a dry gel, and sintering is performed to obtain silica glass. It's a method.

[Problem to be solved by the invention]

However, the above-mentioned conventional technology has the following problems. With the conventional technology, if the plate glass is thin, a large quartz glass plate with a large area of about 50 cm square can be obtained, but when the thickness is increased, only a block with a small area can be obtained. Specifically, if the thickness is thinner than 1 cm, it is possible to obtain a quartz glass plate of 50 cm square or more, but if the thickness exceeds 3 cm, only a silica glass plate with a zero area of about 10 cm square can be obtained. This is because the stress due to the gel body's own weight increases as the thickness increases, and the density changes between the inside and the surrounding area of the gel body, reducing the homogeneity of the gel. These causes cause cracks to appear during drying and sintering.

The present invention is intended to solve these problems, and its purpose is to provide a method for obtaining a large-area glass body even if it is thick.

[Means to solve the problem]

The method for producing glass of the present invention is a method for producing glass by a sol-gel method using at least alkyl silicate and fine silica powder as raw materials, in which ethylene glycol is added to the sol solution by 0.1 to 5 times the mole of alkyl silicate. It is characterized by

[Effect]

The reason why adding ethylene glycol to the sol is effective in producing thick glass blocks and the effects of ethylene glycol will be described.

Ethylene glycol is C2H4(OH)2, OH
It is a bifunctional compound with two groups. It is thought that two OH groups are coordinated to a polymer produced by hydrolysis of ethyl silicate in the sol, and two OH groups are coordinated to SiH molecules to form a cyclic compound. This coordinated chelate is stable;
It is thought that the reactivity is lower than in the state where no chelate is formed. Therefore, if no chelate is present in the gel,
The polycondensation reaction occurs to a high degree and causes distortion, but when chelate is present in the gel, the reaction proceeds slowly and the induced distortion is thought to be small. Therefore, the addition of ethylene glycol has the effect of forming a chelate, slowing down the reaction, and reducing distortion in the gel. If the strain in the gel is small, the stress that causes cracking will be small, and it is naturally expected that the gel body will be less likely to crack. These phenomena led to the present invention.

〔Example〕

The present invention will be explained in more detail with reference to Examples below.

(Example 1) 1 mole of ethyl silicate, 0.07 mole of ammonia, 4.5 moles of water, and 6 moles of nitinol were mixed and allowed to stand at room temperature. The next day, the solution was condensed to bring the silica temperature to 35 wt%. Now the average particle size is 0.3
Colloidal silica containing μm silica particles was created.

On the other hand, 0.5 mol of ethyl silicate and 0°0008 of hydrochloric acid
mol and 2.3 mol of water were mixed and stirred vigorously for hydrolysis.

2N hydrochloric acid was added to the above colloidal silica to adjust the pH value to 2, and the mixture was added to the above hydrolyzed sol.

0.15 mol of ethylene glycol was added to this sol. After stirring thoroughly to make the mixture uniform, the pH value of the sol was adjusted to 4.5 by adding 0.2N aqueous ammonia.

Next, the sol created in this way is 400mm'xlO
A polypropylene container with an inner dimension of 0mm' and a height of 60mm.
I added it until it was.

After 1 hour, the gel was formed, and a wet gel measuring 400 mmφ×60 mmt was obtained. The wet gel was aged at 30"C for 5 days in a closed container, then transferred to a polypropylene container with suitable holes in the lid and dried at 70"C for 10 days. A dry gel measuring 290 mmφ×43.5 mm' was thus obtained. Dry gel in air up to 1000'C,
Next, it was heat treated in vacuum to 1400°C and then sintered to form quartz glass.

The quartz glass block was 200 mm 1' x 30 mm'. Such a large quartz glass block cannot be obtained by normal methods, and it can be seen that ethylene glycol has a great effect.

(Example 2) A sol was prepared in the same manner as in Example 1, but the amount of ethylene glycol was changed to 1 mole. This sol is 500mmφ
A quartz glass block was prepared by adding the mixture to a container with an inner dimension of 100 mm', gelling it, drying it, and sintering it.

The size was 225 mmφ x 27 mm'.

(Example 3) Colloidal silica of Example 1 was created as follows. That is, Aerosil 0X-50 (Deggu
60 g of fumed silica (SSA) was dispersed in water to obtain colloidal silica with a silica concentration of 35 wt%. The same treatment as in Example 1 was carried out thereafter. That is, the above colloidal silica was added to a sol prepared by hydrolyzing 0.5 mole of ethyl silicate with hydrochloric acid, and after dispersion, ethylene glycol 7
mol followed by the addition of 0.2N aqueous ammonia,
The pH value was adjusted to 5.0. This sol is sealed for 600m
, was added to a container with internal dimensions of m' x 150 mm' so that the height was 90 mm, and gelatinized. It was dried to form a dry gel and then sintered to form a quartz block. The size is
It was 210 mmφ×30 mm1. Such a large quartz glass block cannot be obtained by the conventional sol-gel method, and has the effect that the magnitude of the effect of ethylene glycol becomes clear. Also,
It is believed that the large-sized quartz glass blocks obtained in this manner will be used as optical materials for ultraviolet light and excimer laser materials, and will greatly contribute to lowering the cost of quartz glass plates.

that's all Applicant: Seiko Epson Corporation Agent: Patent attorney Kisanbe Suzuki and one other person.

〔Effect of the invention〕

Claims (1)

[Claims] In a method for producing glass by a sol-gel method using at least alkyl silicate and silica fine powder as raw materials,
A method for producing glass, characterized in that ethylene glycol is added to a sol solution in a molar amount of 0.1 to 5 times the amount of alkyl silicate.