JPH0829934B2 - Method for producing high-purity silica - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing silica powder having high purity and a uniform particle size.

<Prior Art and its Problems> In order to produce high-purity quartz glass or the like used as an electronic material, uniform silica powder having a particle diameter of 150 to 425 μm is required. As the raw material, conventionally, one obtained by pulverizing relatively high-purity natural quartz or artificially hydrolyzing SiCl ₄ with pure water, dehydrochlorination and dehydration is used.

However, in order to pulverize natural quartz, it is necessary to use a ball mill, a jaw crusher, or other pulverizer to produce powder with an appropriate particle size, and wear occurs due to the mechanism of these pulverizers. It is unavoidable that the purity decreases. Also, in the method of artificially producing high-purity silica by hydrolyzing SiCl ₄ with pure water, the particle size of conventionally-produced high-purity silica is relatively large, and it is necessary to pulverize it as in the case of natural quartz. Therefore, mixing of impurities from the crusher is unavoidable.

The present inventors have <knowledge relating to problem solving> is 2 selected from highly pure a and results were studied how to obtain a suitable particle size silica powder as a raw material of quartz glass for electronic materials SiCl _4, HSiCl ₃ and H ₂ SiCl ₂ It has been found that by hydrolyzing a mixture of at least one kind of silicon halide, silica particles having a desired particle size can be produced, and the particle size of silica particles can be adjusted by changing the mixing ratio.

<Structure of Invention> The present invention is a method for producing high-purity silica in which silicon halide is hydrolyzed with pure water, wherein a mixture of two or more kinds of silicon halide is hydrolyzed with pure water. The present invention provides a method for producing silica, and further provides a method for producing silica particles having different particle sizes in high yield by changing the mixing ratio of these silicon halides.

As the silicon halide of the present invention, a mixture of two or more selected from three kinds of SiCl ₄ , HSiCl ₃ and H ₂ SiCl ₂ is used. SiCl ₄ is obtained by distilling and refining the by-product of producing polycrystalline silicon from HSiCl ₃ and high-purity hydrogen, and HSiCl ₃ and H ₂ SiCl ₂ are synthesized by the reaction between metallic silicon powder and HCl. The obtained product is obtained by rectification separation.

The particle size of the silicon particles produced depends on the mixing ratio in the silicon halide mixture. For example, in a mixture of SiCl ₄ and HSiCl ₃ as shown in Examples below, HSiCl
_{As the} amount of ₃ increased, the particle size of silicon particles produced gradually became finer, and when the amount of HSicl ₃ was less than about 4% by weight,
About 90% by weight or more of the produced silica particles have a particle size of 425μ or more. Further, when the amount of HSiCl ₃ is in the range of about 8% by weight to about 20% by weight, about 83-40% by weight of the produced silica particles have a particle size of 150-425 μm. When the amount of HSiCl ₃ exceeds about 20% by weight, almost all of the produced silica particles are fine particles of 150 μm or less. Therefore, it is suitable as a quartz glass raw material for electronic materials.
HS to produce silica particles with a particle size of 0-425 μm
The amount of iCl ₃ is about 4 wt% to about 20 wt% (SiCl ₄ / HSiCl ₃ = 96/4
~ 80/20) will do.

The pure water used in the present invention is preferably deionized with an ion exchange resin and purified by reverse osmosis. Alternatively, HCl produced from a hydrolyzate of a silicon halide according to the present invention
Cooled condensed water after removing water (hereinafter referred to as "recovered water")
May be used.

To carry out the present invention, pure water or recovered water is charged into a reaction vessel in which hydrolysis is carried out, the inside of the vessel is made an inert gas atmosphere, and then a mixture of silicon halides having a predetermined composition is introduced into the reactor through a supply nozzle. The reaction vessel is preferably made of quartz or Teflon-coated metal. When the silicon halide is introduced, it may be stirred by a blade-type stirrer or non-contact stirring with an ultrasonic vibration wave in order to accelerate the hydrolysis reaction. The reaction is carried out at atmospheric pressure and the temperature is below the boiling point of the silicon halide, for example SiCl ₄ (boiling point 57
(° C) is the main, it is preferable to control the temperature to 57 ° C or lower. In the hydrolysis of silicon halide, HCl is generated, and this is dissolved and absorbed in pure water to generate heat, so the reaction vessel is equipped with a jacket type cooling device, for example, and is cooled with water to control the temperature. To do. The reaction is terminated when the reaction product gels. After the completion of the reaction, the gelled substance is dehydrated, dehydrochlorinated and dried to obtain a silica powder having a desired particle size of high purity and uniform, which does not require pulverization.

<Effect of the Invention> According to the method of the present invention, powdery high-purity silica can be easily produced in a high yield by the hydrolysis reaction of two or more kinds of silicon halides with pure water. Further, in the method of the present invention, the silica particles obtained can be adjusted by an appropriate mixing ratio of two or more kinds of silicon halides.

In particular, according to the method of the present invention, it is possible to produce silica particles having an optimum particle size as a raw material for quartz glass for electronic materials,
Quartz glass of extremely high purity can be obtained without crushing or granulating.

<Examples> Examples 1 to 8 A nozzle for supplying a silicon halide, a nozzle for supplying pure water, a nozzle for introducing an inert gas, a gas outlet, a thermometer pocket, a stirrer, and a jacket cooling device. A Teflon-coated iron reaction vessel was charged with 1,000 ml of pure water, and an inert gas was introduced to maintain the inside of the reaction vessel in an inert gas atmosphere. Then, a mixture of SiCl ₄ and HSiCl ₃ 16
Flow rate from a weighing tank pressurized from 2.2 g to 426.2 g with an inert gas.
It was fed to the reaction vessel with stirring at 20 ml / powder. HC generated as the hydrolysis reaction of a silicon halide mixture progresses
Since the temperature of the reaction solution rises due to the heat of absorption of 1 in pure water, the temperature inside the container was controlled to about 57 ° C or lower. The end of the hydrolysis reaction was at the time when the produced silica gelled, and the supply of silicon halide was stopped at this time. The gel-like material was heated, dehydrated and dried to obtain high-purity silica powder. The particle size and yield of the silica powder are shown in the following table. The results are shown in the same table when the ratio of SiCl ₄ / HSiCl ₃ was changed.

Claims (2)

[Claims] 1. A method for producing high-purity silica by hydrolyzing silicon halide with pure water, wherein a mixture of two or more kinds of silicon halide is hydrolyzed with pure water. . 2. A silicon halide is silicon tetrachloride (SiC
a mixture of l ₄ ) and trichlorosilane (HSiCl ₃ )
The method for producing high-purity silica according to claim 1, wherein the ratio of Cl ₄ / HSiCl ₃ is 96/4 to 80/20.