JPS61168538A - Mass-production of quartz glass - Google Patents

Abstract

PURPOSE:To enable the mass-production of quartz glass with a low-cost apparatus in high efficiency, by producing a dry gel from a metal alkoxide or ultrafine silica powder, and passing the gel through a belt furnace having a temperature gradient varying continuously from room temperature to the required temperature. CONSTITUTION:A raw material at least composed of a metal alkoxide or ultrafine silica powder is hydrolyzed, pH-controlled, and subjected to a sol-gel process to produce a gel, which is dried to a dry gel. A refractory plate 3 is placed on a refractory belt 4 in a belt furnace 1, and the above dry gel 2 is supplied continuously on the refractory plate. The belt furnace 1 is provided with temperature gradient varying continuously from room temperature to a specific temperature and extending from one end to the other end. The dry sol 2 is sintered in the course of being transferred from one end to the other end of the belt furnace 1, and is delivered continuously from the furnace as a completely sintered transparent quartz glass.

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, and more particularly to a method for mass production of sintered dry gel.

[Conventional technology]

In the method of manufacturing quartz glass by the sol-gel method using metal alkoxide or fine powder silica as raw materials, the conventional dry gel sintering method involves putting the dry gel into a sintering furnace and raising the temperature of the furnace appropriately from room temperature. It was a batch process that involved heating and sintering according to a program.

[Problem that the invention seeks to solve]

However, the above-mentioned conventional technology has the following drawbacks.

In other words, in conventional batch processing, the amount of quartz glass produced is determined by the amount of dry gel that can be fed into the sintering furnace at one time and the cycle time of the sintering process.
Unless you have a very large sintering furnace, efficient mass production is not possible. Furthermore, since a large sintering furnace requires a large amount of electric power, the cost of electrical wiring work becomes large.

Therefore, the present invention aims to solve these problems.
The purpose is to provide a manufacturing method for sintering that has low cost for electrical work and has good mass productivity.

[Means for solving problems]

The method for mass producing quartz glass of the present invention is as follows. That is, a metal alkoxide or finely powdered silica is used as a raw material, and after hydrolysis with a suitable catalyst such as an alkali or an acid, the pH value is adjusted to 3 to 6 if necessary, and the sol is gelled.

This gel is shrink-dried under appropriate drying conditions to obtain a dry gel. A heat-resistant plate is placed on the heat-resistant belt of the belt furnace shown in FIG. 1, and the dry gel is continuously poured onto the heat-resistant plate. Sintering of the dry gel progresses while it is moving from one end of the belt furnace to the other, and when it leaves the other end, the sintering is completed and becomes transparent quartz glass.Transparent quartz glass can be continuously obtained.

@1 In Figure 1, 1 is a belt furnace, 2 is a dry gel, 3 is a heat-resistant plate, 4 is a heat-resistant belt, 5 is a cart, and 6 is a quartz glass in which the dry gel has been sintered. Moreover, FIG. 2 shows the temperature distribution from one end of the belt furnace to the other end.

The temperature at the inlet of the dry gel is room temperature, and the temperature at the outlet is at the sintering temperature.The sintering mass production method described above enables continuous production of quartz glass and is excellent in mass productivity.

〔Example〕

Hereinafter, the present invention will be explained in detail with reference to Examples.

Example 1 0.01N hydrochloric acid 2800+tA was added to purified commercially available silicon ethoxide 20BOf (10 mol)! was added and hydrolyzed by vigorous stirring. Ultrafine powdered silica (Aerosil 0X50 with a surface area of 50 m"/f) was added to this solution.
900F (15 mol) was added with stirring and ultrasonic vibration was applied. Further, clumps were removed by centrifugation. Add 0.1N ammonia water dropwise to this sol and P
The H value was adjusted to 4.0. Next, this sol box-shaped container made entirely of polypropylene CW30
H10) 10 pieces were prepared so that the height was 1 cIrL. The mixture was sealed tightly and allowed to stand at 20°C to form a gel, and was then stored overnight.

Next, the lid of the container was changed to one with an open area ratio of 0.8%, the temperature was raised from room temperature to 60°C, and the lid was dried at this temperature for 10 days.
0 pieces were obtained.

The temperature distribution of the belt furnace shown in FIG. 1 was set as shown in FIG. 2, and the dry gels were introduced one by one from one end, and 10 pieces were continuously introduced. The dry gel that was first introduced during the 24-hour period was sintered and came out as transparent quartz glass. After that, 10 pieces of sintered quartz glass arrived.
It has been found that dry gels can be sintered continuously.

As shown in the examples above, using the manufacturing method of the present invention allows dry gel to be sintered continuously, so silica glass can be manufactured with good mass productivity.

Further, the method of the present invention is not limited to the sol-gel method using silicon ethoxide and finely powdered silica as raw materials as shown in this example. In addition, various types of belt furnace structure, internal temperature distribution, and temperature can be considered other than this example, but it is clear that the scope of application of the present invention is not limited to this example.

〔Effect of the invention〕

As described above, according to the present invention, mass production of dry gel sintering by the sol-gel method can be carried out efficiently and easily, which greatly contributes to the mass production of quartz glass manufacturing.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of a belt furnace for sintering dry gel according to the present invention. Further, FIG. 2 is a diagram showing the temperature distribution inside the belt furnace of FIG. 1. that's all

Claims (1)

[Claims] In the low-temperature synthesis method in which silica glass is produced by the sol-gel method using at least metal alkoxide or ultrafine powdered silica as raw materials, the process of sintering dry gel to form transparent quartz glass is performed continuously at room temperature from one end to the other. The dry gel is continuously introduced from one end of the belt furnace at room temperature, which has a temperature gradient from , a method for mass production of quartz glass.