JPS6126521A - Production of quartz glass - Google Patents

Abstract

PURPOSE:To produce completely homogeneous quartz glass of high quality usable in an optical system, by filtering a sol through a porous filter, and gelatinizing the filtered sol. CONSTITUTION:In production of quartz glass from at least an alkyl silicate and an ultrafine powdery silica as raw materials by the sol-gel method, sol is passed through a fine filter having <50mu pore diamter once or more, and gelatinized. Thus, completely homogeneous quartz glass of high quality can be produced, and the resultant quartz glass can be used in an optical system and applied to quartz substrates for photomasking, quartz glass fibers for ptical communication, various optical cells, etc. The sol has a high viscosity, and is gelatinized by drying to make the filtering operation difficult. Therefore, a method for continuously filtering the sol with a liquid supply pump under pressure is very effective. The use of a coarser filter to a finer filter one after another is preferred since clogging is not easily caused.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a method for producing quartz glass using the Sol-Q-gel method.

[Prior art]

Quartz glass came to be used for crucibles, boards, diffusion furnaces, etc. during the production of industrial carbon, and its usefulness was recognized, and furnaces with fewer hydroxyl groups and those with good optical uniformity were developed. As a result, silica glass fibers have come to be widely used in various optical applications, and quartz glass fibers for optical communications have recently attracted attention.

As described above, quartz glass is used in various fields, and the scope of its use is expanding. However, the manufacturing cost of quartz glass is high, and the high price is a problem. The sol-O-gel method has been hailed as a method for producing high-quality quartz glass at low cost.

As a method for obtaining large-sized quartz glass with good yield using the sol-gel method, ultrafine powdered silica is added to a sol prepared by hydrolyzing alkyl silicate, and the KPH is adjusted to 3 to 6, followed by 50 to 90. There is a method of drying at ℃ and sintering. This solves the problem of bending during dry gel production and the problems of splitting and cracking during sintering at the same time (1. Song.

Methods for manufacturing high-quality quartz glass that does not contain crystals, bubbles, or impurities include a method of effectively dispersing ultrafine silica powder using ultrasonic vibration, and a method of dispersing the remaining lumps due to insufficient dispersion by centrifugation. We have been able to suggest ways to remove it, and it has been very effective. (Irregularly shaped foreign objects (number,
50 μm), and it has not been possible to produce completely homogeneous quartz glass.

Irregularly shaped foreign substances include dust mixed in the manufacturing process and commercially available ultrafine powdered silica (e.g. Cσ, b-θ-5il).
(manufactured by Cabot), Aerosil (Deguri+,
manufactured by SSA), yransil (yransil a)
:JIM), D, c, 5ilica (Da, w
The cause is thought to be coarse particles (which do not pass through a 45 μm filter) contained in CoTning (manufactured by CoTning). Unless these foreign substances already present in the sol are separated and a homogeneous sol is prepared, high-quality quartz glass cannot be manufactured. As it currently stands, it cannot be used in optical systems, and its range of application is therefore limited. [Purpose] The present invention is intended to solve these problems, and to create a completely homogeneous material. [Summary] The method for producing quartz glass of the present invention is a sol-gel method using at least alkyl silicate and ultrafine powder silica as raw materials. In the method for manufacturing quartz glass according to
It is characterized by gelling the ridge that has leaked at least once using a filter finer than tam.

The sol has a high viscosity (several tens of ops) and turns into a gel when dried, making it difficult to concentrate. Continuous pressurized concentration using a liquid pump or the like is very effective and increases processing capacity.

In addition, Kl- in the sol contains large particles (several tens of micrometers), and if it suddenly passes through a fine filter, it tends to become clogged. Therefore, it is effective to pass through a mesh filter and then use successively finer filters to concentrate. The finer the filter is used, the better the quality of the quartz glass becomes.Even with the same size filter, the quality can be improved by passing it through several times. 1 will be explained in detail based on an example.

Example 1 44 tons of ethyl silicate and 6.6 tons of 005N hydrochloric acid aqueous solution
The mixture was stirred vigorously to obtain a colorless and transparent homogeneous solution. There is ultrafine powdered silica (Aerosil ox-5o) 1
, 5 Kp were gradually added and stirred thoroughly. 2 sol
When irradiated with 213 KH2 ultrasound for 2 hours at 0°C, the viscosity decreased from 50 cp (25°C) to 25 cg, and the average particle size decreased from 0.22 μm to 0.16 μm.

A centrifugal force of 1500 G was further applied for 10 minutes to precipitate the poorly dispersed giant particles.A highly homogeneous sol (hereinafter referred to as sol A) was produced using a γ-pump to reduce the pore size. It was sent to a 50 μm filter (polypropylene cartridge type filter (manufactured by Toyo Kagaku Sangyo Co., Ltd.)) and heated at 3K? Concentration was carried out at a pressure of 1 liter/Cl. 8 tons of sol could be processed in 2 minutes.

After collecting and adjusting the pH of the sol to 4.1, an amount of the sol to a depth of 1 cm was transferred to a polypropylene container (width 20 cm x 20 cm x height 10 a) and dried at 60°C for 7 days. . A dry gel with a diameter of 14 mm and a thickness of 0.7 Q was obtained, and when heated to 1300 °C at a heating rate of 180 °C/hr, quartz glass with a diameter of j0 cm and a thickness of 0.5 cm was produced.

Although the quartz glass contained some irregularly shaped foreign matter of several tens of micrometers, it was superior in quality to the quartz glass produced by directly gelling Sol A.

Example 2 Sol A was passed through a filter with a pore size of 50 μm, and then passed through a filter with a pore size of 10 μm. I was able to process 8 tons of sol in 3 minutes by applying a pressure of -2 to 3.

When the recovered sol was made into quartz glass by the same operation as in Example 1, only a few irregularly shaped foreign particles of 10 to 20 μm were present in 1-, and the homogeneity threshold was quite high.

Example 3 Sol A was stretched through a filter with a pore size of 50 μm and then passed through a filter with a pore size of 10 μm three times.

When the recovered sol was made into quartz glass by the same operation as in Example 1, there was no irregularly shaped foreign matter of 10 μm or more, and the quality was extremely high.

Example 4 Sol A was passed through filters with pore diameters of 50 μm and 10 μm, and then further passed through a filter with pore diameter of 5 μm.

Applying a pressure of 5 Kp/cm2, 81 sols could be processed in 3 minutes.

When the recovered sol was made into quartz glass by the same operation as in Example 1, there was no irregularly shaped foreign matter of 10 μm or more, and the quality was extremely high.

Example 5 Solhachi was passed through filters with a pore size of 50 μm and 10 μm, and then passed through a filter with a pore size of 1 μm through UL.
8 tons of sol was processed in 5 minutes by applying a pressure of 17 cm 2 K. When the recovered sol was made into quartz glass by the same operation as in Example 1, it was completely homogeneous and of extremely high quality.

When Comparative Example Sol A was made into quartz glass by the same operation as in Example 1 without using a filter, irregularly shaped foreign matter of several tens of micrometers was scattered, and it was thought that it had been mixed in from the outside. things were also observed.

〔effect〕

As described above, according to the present invention, in the method for producing quartz glass by the sol-gel method using at least alkyl silicate and ultrafine powder silica as raw materials, the sol is
Completely homogeneous, high-quality quartz glass can be produced by concentrating in one pass using a filter finer than μm and then gelling it. As a result, it became possible to use the manufactured quartz glass in optical systems, opening the way to limitless applications such as quartz substrates for photo yasks, quartz glass fibers for optical communications, and each other. , t h

Claims (1)

[Claims] 1) In a method for producing quartz glass by a sol-gel method using at least an alkyl silicate and ultrafine powdered silica as raw materials, the sol is passed through a filter finer than 50 μm one or more times and then gelled. A method for manufacturing quartz glass characterized by: 2) The method for producing quartz glass according to claim 1, characterized in that pressurized leakage is performed continuously using a liquid feeding pump or the like. 3) The method for producing quartz glass according to claim 1 or 2, wherein the quartz glass is first passed through a coarse filter and then sequentially passed through finer filters.