JPS61270225A - Production of high-silica glass - Google Patents

Abstract

PURPOSE:To prevent the generation of cracking and cracking during the drying of a gel, by hydrolyzing a raw material containing a specific amount of a metal alkoxide polymer, and gelatinizing, drying and sintering the obtained hydrosol. CONSTITUTION:A raw material containing a metal alkoxide polymer is hydrolyzed under a condition to give a high-silica glass containing >=1wt% SiO2 originated from said metal alkoxide polymer. The obtained hydrosol is gelatinized, dried and sintered. The initial polymerization reaction in the state of sol and gel can be accelerated by the use of the above raw material, and a gel having high polymerization degree can be produced to prevent the cracking and crazing during the drying stage. The metal alkoxide polymer used as a raw material is e.g. polymer of silicon methoxide Si(OCH3)4, i.e. SiXOX-1(OCH3)2X+2.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for producing high silica glass used for optical purposes and the like.

(Conventional technology) High silica glass has excellent optical properties and heat resistance.

Among various manufacturing methods, the so-called sol-gel method, in which hydrosol is gelled, dried and sintered, has recently been recognized as having chemical resistance and is useful in the semiconductor industry.
The method of depositing glass using an oxyhydrogen flame using Cla, SiH4, etc. as a raw material is also energy saving and low cost since it can be obtained at low temperatures, and it is easy to purify and has high purity because the raw material is a liquid. is obtained. AI for mixing in liquid phase! zOs.

It has the advantage that doping with Cab, YzOs, etc. can be done uniformly and a homogeneous high silica glass can be obtained.
It has been receiving particular attention recently.

(Problems to be Solved by the Invention) However, there are still unresolved problems in the production of high silica glass using sol-gel, and it has not been put into practical use.

In particular, the biggest problem was that the gel would crack or crack during the drying process.

An object of the present invention is to provide a method for producing high silica glass that does not cause the above-mentioned problems during the drying process.

(Means for Solving the Problems) The inventors discovered that Si, which is produced by decomposition in the obtained glass,
By using a metal alkoxide polymer as a raw material so that the O2 content is 1% by weight or more, the initial polymerization reaction in the state of sol and gel (...0-8i-0-8i
The present inventors have completed the present invention by discovering that a gel with a high degree of polymerization can be obtained by accelerating the bonding reaction of .

The present invention involves hydrolyzing a raw material containing the metal alkoxide polymer so that 5 iOa in the metal alkoxide polymer is contained in the obtained high silica glass at 1% by weight or more, and gelling the obtained hydrosol. This invention relates to a method for producing high silica glass by drying and sintering.

Examples of metal alkoxide polymers include 9, for example, silicon methoxide S i (OCH3) 4 polymer S ix 0
x−1(0CH3)2X+2t”, but is not limited thereto.

The metal alkoxide polymer used as a raw material in the present invention may be used alone or as 5i(OCHs)4. Si(0C
Metal alkoxides such as 2H8)4, Ca1)ot's Cab-0-Bit), Degussa's A
erosil! Mix with finely powdered silica, silica gel, etc., make it into a liquid (add a solvent such as alcohol as necessary), mix with water (adjust the pH with acid or alkali as necessary), and hydrolyze. , is considered a hydrosol.

High silica glass is obtained by transferring the hydrosol to a container, allowing it to gel, and then drying it to remove water, alcohol, etc. to form a dry gel, and then sintering it.

The reason why SiO2 in one combination of metal alkoxide is contained in the high silica glass is 1111 or more.
As mentioned above, the purpose is to promote the initial polymerization reaction in the sol and gel state to prevent cracking in the crank during the process of drying the gel, and if it is less than 1 weight, it has no effect. It is preferably used in an amount of 10-weight or more.

(Example) Next, an example will be explained.

Example 1 The raw material is silicon methoxide pentamer 5isO4 (OCH
x) A polymer with 1* in the center (referred to as raw material A) alone, 4 moles of methanol is added to 1 mole of raw material A in terms of SiO*, and the solution is stirred until the pH becomes 10.6. 15 mol of ammonia water prepared as above was added and thoroughly mixed to obtain a uniform silica sol.

90■ This silica sol is coated with Teflon.
IOn in a petri dish of φ! Fill it to the thickness of I, cover it with aluminum foil using double-sided tape, leave it at room temperature for about 2 hours to gel, and leave it at room temperature for 1 day, then make 2 pinholes in the lid. The gel was opened and dried for 7 days in a constant temperature bath at 50°C, and then transferred to a constant temperature bath at 120°C and dried all day and night to obtain a dry gel.

The bulk density of the obtained dry gel is 0.80 g/cm
”, the specific surface area was approximately 850 cm x 9, and there were no cracks or cracks at all. This dry gel was heated and sintered at a heating rate of 1° C./min to 1050° C., and a crack with a diameter of 45 M1 and a thickness of 5 WI was formed. A transparent high silica glass without any silica was obtained.As a result of analysis, this high silica glass had the same characteristics as commercially available quartz glass, such as the coefficient of thermal expansion.

Example 2 Raw materials At-8i in Example 1 (0.5 mol in terms of h, 0.5 mol of silicon methoxide, and 4.5 mol of methanol)
To the mixed and stirred solution were added 4 moles of ammonia water whose pH was adjusted to 10.6, and the mixture was sufficiently mixed to obtain a uniform silica sol. This silica sol was placed in a petri dish in the same manner as in Example 1, covered with aluminum foil, and allowed to stand at room temperature, where it gelled in about 40 minutes. This gel was aged and dried in the same manner as in Example 1 to obtain a dry gel. The volume of this dried gel shrank to approximately 30% of that immediately after gelation.

The bulk density was 0.706/am'' and there were no cracks or cracks.The dried gel was heated at a rate of 1°C per minute.
As a result of heating and sintering to 150''c, a crack-free, transparent high silica glass with a diameter of 40 mm and a thickness of 4.5 mm was obtained, and its properties matched those of commercially available quartz glass.

Comparative example Silicon methoxide monomer S i (0CHs)4
1 mol of methanol, 4.5 mol of methanol and aqueous ammonia (p
4 moles of H10,6) were thoroughly mixed and a dried gel was prepared in the same manner as in Example 1, but the gel developed cracks and cracks during drying.

(Effects of the Invention) According to the present invention, it is possible to prevent the occurrence of cracks and cracks during the gel drying process, so that high silica glass can be manufactured at a lower cost than in the past. Furthermore, the method of the present invention can be applied not only to quartz glass but also to other glass fields.

Claims (1)

[Claims] 1. Hydrolyze the raw material containing the metal alkoxide polymer so that SiO_2 in the metal alkoxide polymer is contained at 1% by weight or more in the obtained high silica glass,
A method for producing high silica glass, which comprises gelling, drying and sintering the resulting hydrosol.