JPS61232232A - Silica glass manufacturing method - Google Patents

Abstract

PURPOSE:To alleviate the clogging of final filter and prolong the life of the filter in sol-gel process, by using a filter having larger mesh size than the final filter in the process for the preparation and filtration of sol. CONSTITUTION:Sol solution composed mainly of an alkyl silicate and ultrafine silica powder is passed twice or more through a filter having mesh of >=10mum which is larger than the mesh size of the final filter. The coarse particles, etc., are separated by the filter to alleviate the clogging of the final filter.

Description

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

[Summary of the invention]

The present invention provides a method for producing quartz glass using the sol-gel method, by using a filter with a considerably larger pore size (10 μm or more) than the final desired filter during the sol-preparation process. Reduces clogging, extends filter life, and
This enables smooth sol filtration.

[Conventional technology]

In the production of quartz glass by the sol-gel method using conventional alkyl silica) and ultrafine silica as the main raw materials, the purpose is to remove foreign substances such as coarse particles of fine powder silica and dust that are present in the prepared sol. The filter used in the filtration process had a pore size of 10 μm or less.

[Problems and Objectives to be Solved by the Invention] However, in the prior art described above, the maximum pore diameter of the filter used during the filtration process is 10 μm or less, so the filter becomes clogged and the life of the filter is shortened. It is short and expensive, and due to clogging, the sol input pressure increases, the variation in filtration accuracy becomes large, and large-scale processing is difficult.

Therefore, the present invention is intended to solve these problems, and its purpose is to use the sol-gel method, which makes it possible to simplify the filtration process and reduce costs by adding a pretreatment step to the conventional technology. The purpose of the present invention is to provide a method for manufacturing quartz glass.

[Means for solving problems]

The method of the present invention is characterized in that it includes a pretreatment step in addition to the conventional technology during the sol preparation filtration process in the production of quartz glass by the sol-gel method using alkyl silicate and ultrafine silica as main raw materials.

[Effect]

According to the present invention, insufficiently dispersed and agglomerated particularly coarse particles in the prepared sol, as well as particularly large solids that gel and cause filter clogging, can be separated prior to the conventional filtration process. It is possible to extend the life of the filter by alleviating clogging of the filter, and improve filtration accuracy by alleviating the increase in input pressure.

〔Example〕

(1) Commercially available ethyl silicate 28 (Si(OE
t)4) 152t, 1g I NHOt 108L
and ultrafine silica (product name: Aerosil oxso
(Degussa)) 451'y was mixed at the same time and stirred for 4 hours using a disilver (stirring and dispersing device) to prepare a sol in which ethyl silicate was hydrolyzed and ultrafine silica was dispersed to some extent. Ultrasonic irradiation (combined with stirring) was applied to the dispersion solution for 55 minutes to improve dispersibility.
I did it for an hour. At this time, in order to prevent the sol temperature from increasing due to ultrasonic irradiation, the sol temperature was kept constant using a cooling device.

As the next step, the sol is centrifuged (3000 rpm) to remove semi-gelled jelly-like substances, coarse particles containing impurities, and dirt in the sol.

50-) was added.

The subsequent filtration process was performed with the following configuration.

First, the sol was passed through a filter with a pore size of 20 to 50 μm, and then subjected to conventional filtration in which the sol was passed through filters with pore sizes of 10 μm, 5 μm, and 1 μm. In this case, in the case of conventional filtration, five or more filters of each pore size are required to treat all of the sol, and the input pressure becomes more than 2.5 oA due to clogging. However, 10μm
Two tubes were used, one each for 5 μm and 1 μm, and the entire amount could be processed, and the input pressure was less than α5 groups/cd.

The sol after filtration is then subjected to pH adjustment (pH=
5-6), subjected to treatments such as recentrifugation and redefiltration, and placed in 400 pieces of 600g each into polypropylene containers of size 36 x 24 x 12 (wound) to gel in a sealed state, and then shrink. When drying starts, change the lid of the container to one with holes of a specified porosity to adjust the drying speed, put it in a dryer, and heat it from room temperature to 60~8℃ at a heating rate of 5℃/n''r.
The gel was heated to 0°C and maintained at this temperature for 10 to 15 days to obtain a dried gel with a size of 25.3 x 15.8 A transparent glass body was obtained by heating and sintering at 1300 to 1450°C using a heating method. The thickness of this glass was 1 a8X.
The dimensions were 11.5 x 135 (m:) and the weight was around 180 g. When the glass obtained as described above was observed using an optical microscope and a condensing lamp, there was almost no difference in the foreign matter in the glass depending on the glass.
There are almost no more than that, and there are only a few things less than that, so there is much less variation than before. Furthermore, the results of various physical property analyzes regarding this glass were consistent with those of fused silica glass, including Vickers hardness, specific gravity, coefficient of thermal expansion, infrared absorption spectrum, near-infrared absorption spectrum, and refractive index.

(2) Centrifugation treatment of the sol prepared in the same manner as in Example 1 (
3000rpm, 30sim), and before the conventional one-pass process, it was first passed through a filter with a pore size of 20 to 50μm, and the Shin filter was circulated for about 200 minutes at a flow rate of 5t7.After this, it was passed through a conventional filter. As a result, there was no clogging at all, and the entire amount could be processed with one tube of each type. The subsequent treatment of the sol was exactly the same as in Example 1, and the variation in quality among the obtained glasses was further reduced.

〔Effect of the invention〕

On the other hand, since the quartz glass manufactured according to the present invention uses the above-mentioned f-filtering process, the variation in quality between products is extremely small, the amount of filters used is drastically reduced, and the cost is low. In addition, the quality is also high because there is no timely increase in input pressure, and coarse particles and dust that cause foreign matter in the glass after sintering are almost completely removed from the prepared sol. , which is at a high level.

In this way, in addition to having the advantage of being lower cost than the fusion method, it is also possible to easily mass-produce extremely high-quality quartz glass. Of course, photomask substrate for engineering C,
We believe that its application will expand to various fields such as base materials for optical fibers.

that's all

Claims (1)

[Claims] (1) A method for producing quartz glass by a sol-gel method using alkyl silicate and ultrafine silica as main raw materials, which includes the following treatment method during the sol preparation filtration process. a) Pore size significantly larger than the final desired filter pore size (
b) pass through the filter described in a) two or more times, or circulate for a predetermined period of time.