JPH0477324A - Production of quartz glass powder - Google Patents

Abstract

PURPOSE:To improve purity by mixing a specific volume of water with ester silicate and gelatinizing the mixture or further adding water to the mixture and subjecting the mixture to a heat treatment to gelatinize the mixture, then grinding the mixture in water and subjecting the powder to dry filtering, disintegrating, sieving and calcining. CONSTITUTION:The refined water is added at >=2mol to 1mol ester silicate, such as methyl silicate, and if necessary, a catalyst, such as nitric acid, is added thereto and the mixture is hydrolyzed and gelatinized at pH3 to10. Further, the water of 0.5 to 50 wt. times the weight of the liquid ester silicate/water mixture at need and the mixture is gelatinized by the heat treatment at 50 to 120 deg.C. This gel is charged to a hard glass or resin vessel and water is added thereto at 1 to 2l per 1mol raw material ester silicate. After the mixture is mechanically pulverized in the water, the excess water is removed by filtering and the mixture is dried at >=100 deg.C. The mixture is thereafter disintegrated with a ball mill made of a synthetic resin or the like and is sieved to form 75 to 300mu powder. Further, the powder is calcined at >=1000 deg.C, by which the quartz glass powder is obtd.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a method for producing quartz glass powder.

More specifically, by performing mechanical pulverization while the object to be pulverized is in a gel state, which conventionally could not avoid contamination with impurities, it is possible to produce products such as quartz glass products for the semiconductor industry, multi-component products for optical communications, etc. The present invention relates to a method for producing quartz glass powder that can efficiently obtain high-purity quartz glass powder that can be suitably used for various purposes such as glass raw materials through simple operations.

For example, demands for higher purity of quartz glass powder, which is a raw material for quartz glass products for the semiconductor industry, multi-component glass for optical communications, etc., are increasing.

For example, in recent years, as semiconductor devices have become more highly integrated, the demand for high-purity silicon single crystals has increased, and crucibles for producing the same have been required to have higher purity.

[Conventional technology]

In response to this demand for high purity, in recent years, high purity natural quartz or synthetic quartz has been used instead of fused and crushed natural silica stone with low purity. However, when natural quartz or synthetic quartz is mechanically pulverized under conventional dry conditions, powders with a particle size of 75 to 300 microns, which is the preferred raw material powder for forming quartz glass products for the semiconductor industry, especially quartz crucibles, are produced. There is a problem that only about 50% can be obtained and the remainder becomes fine powder of 75 microns or less.

Furthermore, in the case of melt-pulverized natural quartz or dry-pulverized conventional synthetic quartz, impurities such as aluminum originating from the alumina ball mill used in the pulverization process are unavoidable.

For example, crucibles for pulling silicon single crystals manufactured using these raw material powders usually contain about 10 ppm of A.
l, several ppm@f of FelTi%Zr.

Na, Ca%, and B and Cu at a few tenths of a ppm.

If a silicon single crystal containing impurities such as Ni is pulled using such a crucible, the impurities in the crucible will migrate into the single crystal, making it impossible to obtain a highly pure silicon single crystal.

Furthermore, high-purity transparent quartz glass is required for furnace core tubes and the like used in the heat treatment process of semiconductor wafers.

However, since conventional transparent quartz tubes are formed using natural quartz as a raw material that contains trace impurities such as aluminum and alkali, conventional transparent quartz glass tubes also contain these trace impurities.

Therefore, in conventional transparent glass quartz tubes, there is a problem in that thermal deformation and devitrification caused by impurities cannot be avoided.

In general, thermal deformation and devitrification in quartz glass materials are
It is known that this phenomenon is noticeable when an alkali metal is present as an impurity, and there is a demand for high purity of the raw material powder.

[Problem to be solved by the invention]

An object of the present invention is to provide a new technique for efficiently producing high-purity quartz glass powder in order to solve the problems of conventional products and meet industrial demands.

In order to solve the above-mentioned problems, the present inventors have made extensive studies and have developed a gel obtained by gelling a mixture of a silicate ester and a specific amount of water, or a gel obtained by adding a specific amount of water to the mixture. The gel obtained by addition and heat treatment is mechanically crushed in water, and the filtered gel becomes an aggregate that is easily powdered after drying.
The present invention was achieved by discovering that high-purity quartz glass powder with a particle size of from micron to 300 microns can be efficiently obtained.

[Means to solve the problem]

The structure of the present invention is a gel obtained by gelling a mixture of a silicate ester and 2 moles or more of water per 1 mole of the silicate ester, or a gel obtained by adding a specific amount of water to the mixture and subjecting it to heat treatment. This method for producing quartz glass powder is characterized by pulverizing the resulting gel in water, filtering it out, drying the gel, crushing it, separating it through a sieve, and then firing it.

The manufacturing method of the present invention will be explained in detail below.

In addition to methyl silicate, ethyl silicate, and propyl silicate, all silicic esters that can form a solution with water in the coexistence of an acid or an alkali can be used as the silicic ester used in the present invention. In particular, silicic acid esters in which the alkoxy group has 1 to 3 carbon atoms are suitable because hydrolysis proceeds rapidly.

In the present invention, the amount of water mixed with the silicate ester is 2 moles or more per 1 mole of the silicate ester. If the amount of water is less than 2 moles, the hydrolysis reaction of the silicate ester will not progress sufficiently, and when the resulting dry gel is fired, the remaining alkoxy groups may carbonize and the product may take on a black color. .

The water to be used is preferably one that has been sufficiently purified to remove impurities.

Further, in the method of the present invention, a catalyst can be used together with the water.

The catalyst that can be suitably used is not particularly limited as long as it can vary the pH of the mixed solution of the silicate ester and the water, and specifically, acids,
Examples of the alkali include nitric acid, oxalic acid, and acetic acid, and examples of the alkali include ammonia, triethylamine, and ethylenediamine.

When the catalyst is used, the pH of the mixed solution of the silicate ester and water is preferably K, usually in the range of 3 to 10, in order to rapidly progress the hydrolysis of the silicate ester.

In the present invention, a specific amount of water is added to a mixed solution of silicate ester and water in order to prevent foaming and blackening of the silica powder during the firing process, and to maintain constant properties of the gel to be subjected to the pulverization process. Then, heat treatment can be performed.

The amount of water used in the heat treatment can be arbitrarily added in an amount of 0.45 times to 5 times the weight of the mixed solution of silicate ester and water. Furthermore, it is preferable that the water used in the heat treatment be sufficiently purified to remove impurities.

The temperature of the heat treatment is in the range of 50°C to 120°C, preferably 70°C to 90°C. In addition, the heat treatment time is
Although it varies depending on the temperature, it is 4 hours to 24 hours, preferably 16 hours to 20 hours.

The heating device used in the heat treatment is preferably one that does not cause local heating, and is preferably heated by a well-stirred oil bath or an electric heater wound at regular intervals.

Gels obtained from a mixed solution of silicate ester and water, or gels obtained by adding a specific amount of water to the mixed solution and subjecting them to heat treatment, either change the shape of the container when gelatinized or the shape of the container due to progress of condensation. It has a slightly reduced shape, and if it dries as it is, it will become a large glass lump or fragment.

Even after pulverization, the fragmented gel has a particle size of 75 microns to 3 microns, which is a preferable particle size for quartz glass powder for the semiconductor industry.
Only about 50% of powder with a particle size of 0.00 microns can be obtained,
In addition, the dried gel should not be in a dense state, but the particle size is adjusted by mixing impurities from the pulverizer during pulverization, so that the gel can be easily powdered after drying. That is, in the present invention, the above-mentioned number is 1 to 21 per mole of the silicate ester as a raw material.

Specifically, the above-mentioned pulverization is carried out using a single-shaft or multi-shaft stirring blade, and there is no particular restriction on the shape or number of stirring blades, and propeller-type or turbine-type stirring blades can be used.

The shape of the container used for pulverization is not particularly limited, but it is preferably cylindrical and has sufficient depth for the gel and added water, and more preferably has two or more interference plates such as baffles inside. Things are good. The rotation speed of the stirring blade depends on the shape of the stirring blade and the shape of the container used.
It may be set arbitrarily between ~400 rotations.

In any case, it is important that mechanical shear force is effectively applied to the gel.

Further, as the material of the container used for the above-mentioned pulverization, in addition to hard glass, it is preferable to use a resin-made or resin-coated metal container in order to avoid contamination with metal impurities. In addition to Futomi resin, the resins include nylon resin, polyurethane resin, polypropylene resin,
Polyethylene resin or the like is preferably used.

Although it varies depending on the grinding time line in the grinding, the state of the gel to be ground, and the stirring conditions, it may take 15 minutes to 1 hour.
The time is preferably 20 minutes, and more preferably 30 minutes to 60 minutes.

By carrying out the pulverization, a mixture of paste-like silicic acid gel particles and water is obtained.

The mixture of the pasty silicic acid particles and water that has been crushed is filtered to remove excess water and then dried.

For drying, the filtered gel is transferred to a drying container, such as an eggplant-shaped flask, and heated and dried using a rotary dryer, such as a rotary evaporator.

The drying method may be either normal pressure drying or reduced pressure drying, and the drying temperature is usually 100°C or higher.

As the gel dries, the particles reagglomerate, resulting in a particle size suitable for use, i.e., from 75 microns to 300 microns.
The re-agglomerated quartz powder is crushed, as the yield of micron-sized powder is significantly reduced.

Although any shape or type of crusher can be used, a rotary ball mill is preferred.

In addition, in order to prevent metal impurities from being mixed in, the main body and balls of the crusher, such as a ball mill, are made of fluorine resin, nylon, polyurethane, polyester, polypropylene, etc., or metal coated with the above resin, such as stainless steel. A main body and a ball are preferably used.

Next, in order to take out quartz powder having a desired particle size from the crushed quartz powder, sieving is performed.

Sieving can be done by using a mesh with any mesh size.
It is possible to extract quartz powder of any desired particle size from the crushed quartz powder.

The sieving separation can be performed by manual sieving operation or sieving separation using mechanical vibration, ultrasonic waves, or low frequency vibration.

a sieve net and a sieve frame used for said sieve separation;
The material of the supply load, etc. is preferably made of resin or metal coated with resin, similarly to the crusher, in order to prevent metal impurities from being mixed in.

After the sieving is completed, firing is performed using quartz powder of the desired particle size. The firing temperature may be 1000°C or higher, similar to the firing temperature in the so-called sol-gel method.
The firing time is usually one hour or more.

The synthetic silica powder obtained as described above is in a crushed form and can be suitably used for quartz glass products for the semiconductor industry, particularly as raw materials for quartz crucibles. Furthermore, due to its high purity, it can also be used as a raw material for multi-component glasses for optical communications.

[Example] The present invention will be explained in more detail using Examples and Comparative Examples.

Example 1 8 moles of ion-exchanged water (144,9) were placed in a four-hole flask made of hard glass having an internal volume of 11, and the flask was set in a water bath adjusted to 20°C. While stirring the fluorine with a resin stirring blade, 1 mole of methyl orthosilicate (152,9>) weighed in a separate container was gradually added to the water over 4 hours. After the addition was completed, the mixture was stirred for 1 hour. Continue to mix thoroughly.

The resulting mixed solution was transferred to a polyethylene wide-mouth bottle with an internal volume of 1) and left at room temperature. After 3 hours, the mixture had gelled and became a uniform solid.

Add 2 to 3 c1 of the gel with a polypropylene spoon! The mixture was crushed into L-angle pieces and taken out into a container for underwater pulverization. Further, 100ON of water was added to the container and the container was covered with a lid. The container used is a cylindrical container with a total capacity of 51 cm, has four baffles, and is made of stainless steel coated with fluororesin. Further, a turbine type stirring blade having four blades was used. As with the container, the stirring blades were made of stainless steel coated with fluororesin.

After the gel and water were charged into the disintegration container, the stirrer was rotated at 400 revolutions per minute. Rotation was continued for 1 hour to completely crush the gel.

Next, the pulverized gel was filtered using a Kiryama funnel to separate the gel and excess water.

The filtered gel was placed in an eggplant-shaped flask and dried using a rotary evaporator. Drying was carried out by heating in an oil bath at a drying temperature of 150° C. for 4 hours at normal pressure, and then by reducing the pressure to −160 m×Hg using a vacuum pump for 4 hours, for a total of 8 hours. During drying, the gel temporarily became pasty, and as the drying progressed further, it became a bulky dry silica powder.

Next, the dry silica powder was crushed.

A nylon cylindrical mill with a capacity of 31 mm was used for crushing. In addition, the crushing ball is made of urethane with a diameter of 3
40 pieces of 0m were used.

Dry silica and balls were placed in the pot mill, the pot mill was covered, and the pot mill was placed on a two-roller type rotary table and rotated at 120 revolutions per minute for 30 minutes, and then the dry silica was taken out from inside.

Next, the pulverized silica was separated through a sieve, and particles having a particle size of more than 75 microns and less than 300 microns were taken out. Both the sieve net and frame were made of nylon.

Use a sieve with an opening of 300 microns for the upper screen and a 75 micron opening for the lower screen, and sieve the above dried silica over 0.300 microns, over 0.75 microns but below 300 microns, and ■75 microns below. divided.

At this time, the ratio of the sieved silica powder ■ to the weight of the entire dry silica powder subjected to sieving is 6
It was 3.5% by weight.

The sieved silica powder (1) was fired in an electric furnace at a firing temperature of 1100° C. for 4 hours to obtain white high-purity silica powder. The volatile content resulting from the calcination was 6% by weight based on the weight of the dry silica subjected to the calcination.

Example 2 A mixed solution of water and methyl orthosilicate was prepared using the same method as in Example 1.

Water 9009 which was further ion-exchanged to the obtained mixed liquid
was added, placed in a household electric heating pot with an internal volume of 2.2 mm, and electricity was applied to the pot to continue heating for 18 hours. This was followed by heat treatment at 95° C. for 18 hours. The contents of the pot were a gelatinous solid with excess water.

After heating, the gel-like solids and water were transferred from the pot to a container equipped with stirring blades for crushing, and further, 2000.9
water was added and the lid was closed. Thereafter, the same operation as in Example 1 was carried out, and the ratio of the silica powder (2) obtained after the sieving to the total dry silica was 76.9% by weight.

In addition, the flow of the manufacturing process of Example 1 and Example 2 is shown in FIG. 1 and FIG. 2.

Comparative Example 1 1 mole of methyl orthosilicate (15
2,9) was added over 4 hours with stirring.

The mixture was left to stand for several hours to obtain a gel-like solid. This gel-like solid was transferred to a 2-inch eggplant-shaped flask, dried with a rotary evaporator at a temperature of 150°C and normal pressure for 4 hours, and then reduced to -760 flHg for 4 hours with a vacuum pump. Drying was performed for 8 hours. The gel was white, opaque, and several U square pieces of dry silica powder.

The above dried silica powder was charged into a nylon pot mill having a capacity of 3J along with a grinding ball. The pot mill was rotated at 120 revolutions per minute for 30 minutes on a roller stand.

When the dry silica powder extracted from the bot mill was sieved, the ratio of silica powder with a particle size of more than 75 microns and 300 microns or less to the total dry silica was 52%. And compared to Example 2, the yield was poor.

Comparative Example 2 1 mole of methyl orthosilicate (15
19) was added over 4 hours with stirring, and the mixture was left to stand for several hours to obtain a shell-like solid. This gel-like city-shaped product was transferred to a box-shaped dryer, and kept at 200° C. and stirred for 10 hours while passing dry nitrogen gas.

The obtained dry silica powder was a transparent glass-like powder having a size of several microns to one square inch.

The dried silica powder was charged into a 31 capacity nylon pot mill along with grinding balls.

Rotate the above pot mill at 120 revolutions per minute for 30 minutes on a roller stand.
Rotated for a minute. When the silica powder extracted from the pot mill was separated by sieving, the particle size exceeded 75 microns.
The proportion of silica powder having a particle size of 0.00 microns or less based on the total dry silica was 52% by weight, and the yield was poor compared to Examples 1 and 2 in which pulverization was carried out in water.

〔Effect of the invention〕

According to the present invention, (1) By performing pulverization, which was conventionally done dry, in water and in a gel state, impurities can be prevented and high-purity quartz glass powder can be obtained with simple operations. .

(2) The silica powder obtained after drying is bulky and easy to crush, so it can be made into powder by simple crushing, and the resulting powder has the advantage of having a sharp particle size distribution. This is an industrially useful method for producing quartz glass powder.

[Brief explanation of drawings]

Figure 1 shows the basic manufacturing flow of the present invention. In addition to the flow shown in FIG. 1, FIG. 2 shows a manufacturing flow in which a specific amount of water is further added and heat treatment is performed after mixing of the raw materials is completed. that's all

Claims (1)

[Claims] (1) For 1 mole of silicate ester and the silicate ester,
A gel obtained by gelatinizing a mixture with 2 moles or more of water, or a gel obtained by adding a specific amount of water to the mixture and heating it, is mechanically crushed in water, filtered and dried, and then dissolved. A method for producing quartz glass powder, which comprises crushing, sieving, and then firing.