JP2002068727A - Method for manufacturing high purity silica - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a high purity silica capable of producing a high purity silica particle at a low cost and a silica having the desired size and shape. SOLUTION: A pure silica is produced by severally vaporizing a high purity alkoxysilane and water, feeding the generated vapor into a reactor vessel, and making it hydrolyzed in a vapor phase.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for producing high-purity silica, and more particularly to a method for producing high-purity silica by hydrolyzing alkoxysilane in a gas phase to form silica.

[0002]

2. Description of the Related Art In recent years, high-purity silica particles have been used in various fields, such as artificial quartz for optical fibers, IC encapsulants in the semiconductor industry, silica fine particles for liquid crystal spacers in the field of photomask substrates and liquid crystal displays, or high-purity silica glass for substrates. The needs are expanding.

[0003] In any field, those having high purity and uniform shape and size are desired.
More advanced fields, such as the semiconductor industry, require very strict specifications and control over their quality.

For example, as a method for producing high-purity quartz glass, (1) a method of purifying and producing natural quartz. (2) A method of melting fumed silica produced by burning a silicon compound such as silicon tetrachloride with an oxyhydrogen flame. (3) A method of melting powder obtained by firing silica gel obtained by liquid phase hydrolysis of silicon alkoxide and sol-gel reaction. And the like.

[0005]

However, in the method (1), there is a limit in reducing the concentration of impurities, and in the method (2), the production cost is high, and when silicon tetrachloride is used. Is generated in a large amount of hydrochloric acid at high temperature,
Corrosion countermeasures such as the use of expensive materials with high corrosion resistance are required for manufacturing equipment, and environmental measures are also required.Therefore, manufacturing equipment and environmental measures also increase costs. Was.

The method (3) is carried out in a liquid phase. Silica gel having properties different from those of the method (2) can be produced. However, impurities present in the liquid phase produce silica.
Since it adheres during the growth process, there is a limit in reducing the concentration of impurities, and there is a problem that the operation of solid-liquid separation of fine particles is considerably troublesome.

[0007] The silica particles produced by the method (2) are widely used as dry silica, but have problems such as formation of OH groups on the surface of the silica and adsorption of hydrogen chloride or chlorine on the silica. There was a point.

Accordingly, an object of the present invention is to provide a method for producing high-purity silica which can produce high-purity silica particles at low cost and produce silica having a desired size and shape. .

[0009]

According to the method of the present invention for producing high-purity silica, alkoxysilane and water are allowed to undergo a gas phase reaction to carry out hydrolysis to produce silica.

In this configuration, since silica particles are formed by using a gas phase reaction without passing through chlorides, high-purity silica particles can be produced at low cost.

Further, in the gas phase method, since the amount of water present in the reaction field can be easily suppressed, the concentration of OH groups and silanol groups formed on the surface of the generated silica can be reduced. By minimizing the amount of supplied water, silica having a small number of OH groups can be produced.

Here, by using hydrogen or oxygen or water and hydrogen or oxygen instead of water, it is possible to reduce the concentration of OH groups on the generated silica surface.

Further, by growing and collecting the silica particles using a filter or a plate, the generated silica can be recovered in a form as it is generated.

Further, silica is grown using the seed particles,
By collecting, high-purity silica can be formed on the surface of the seed particles.

Further, by performing a gas phase reaction in a fluidized bed or a moving bed, silica particles can be continuously produced, and high-purity silica can be produced efficiently.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the structure of a method for producing high-purity silica of the present invention is shown in FIG. 1 using a block diagram.

In the present invention, high-purity alkoxysilane and water are separately vaporized (10, 11), the generated vapor is led to a reactor, and subjected to a hydrolysis reaction (20) in the gas phase, thereby producing high-purity silica. (SiO ₂ ) is produced, and collection (30) is performed.

Here, as the alkoxysilane, trimethoxysilane, tetramethoxysilane, triethoxysilane, tetraethoxysilane and the like can be used.

At this time, for example, when using trimethoxysilane, the reaction formula is as follows: The reaction formula when using triethoxysilane is as follows: The reaction formula when using tetramethoxysilane is: The reaction formula when using tetraethoxysilane is: Becomes

It is to be noted that hydrogen or oxygen, or a mixture of water, hydrogen and oxygen can be used in place of water as a reaction raw material.

At this time, for example, when trimethoxysilane and hydrogen are used, the reaction formula is as follows: The reaction formula when using triethoxysilane and hydrogen is as follows: The reaction formula when using tetramethoxysilane and hydrogen is: The reaction formula when using tetraethoxysilane and hydrogen is as follows: The reaction formula when using trimethoxysilane, hydrogen and oxygen is as follows: The reaction formula when using triethoxysilane, hydrogen and oxygen is as follows: The reaction formula when using tetramethoxysilane and hydrogen or oxygen is as follows: The reaction formula when using tetraethoxysilane, hydrogen, and oxygen is Becomes

The gas phase reaction is carried out at a reaction temperature of 150 ° C. to 1
300 ° C., preferably 400 ° C. to 1200 ° C., and the supply gas flow rate is 100 to 10,000 in gas hourly space velocity (GHSV).
01 / h, preferably 400 to 10000 / h.

Further, in the hydrolysis reaction, by adjusting the reaction temperature, the reaction pressure, the temperature of the particle collecting section, the flow rate of the reactant, the residence time of the reactant in the reactor, and the like, the production rate and shape of the silica particles are adjusted. , Size, particle size distribution, specific surface area, purity, OH group concentration on silica surface, etc. can be controlled.

As a reaction vessel for the hydrolysis, silica particles can be continuously produced and recovered by using a fluidized bed reactor, and an empty column type or a suitable silica collector and a filler can be used. A reactor installed inside the empty tower can be used.

Although various filters can be used as the silica collector, a fibrous filter having good gas permeability is preferably used.

Further, by using a configuration in which a plurality of reactors are connected in series, it is possible to improve the conversion ratio of alkoxysilane from introduction into the reactor to recovery, or to recover silica having different properties. it can.

By installing a silica collector for collecting and collecting particles inside or downstream of the reactor, it is possible to grow silica on the surface of the seed particles.

Here, particles composed of substantially the same components as silica produced as seed particles are basically used, but different particles different from silica, such as titania fine particles, can also be used as seed particles.

The properties (particle size, shape, etc.) of the produced particles can be controlled by adding a suitable solvent such as alcohol to the starting alkoxysilane.

Further, binary or ternary metal oxide particles are formed by using a material obtained by adding a metal alkoxide other than silicon (for example, an alkoxide of titanium or zirconium) to alkoxysilane as a raw material. be able to.

Hereinafter, the method for producing high-purity silica according to the present invention will be described in detail with reference to examples.

[0032]

Example 1 In this example, tetramethoxysilane and pure water were introduced as vapor into the reactor at predetermined flow rates through respective evaporators.

[0033] The flow rate of each gas here, tetramethoxysilane 500 cm ³ / min, steam 330 cm ³ /
min and argon were set at 500 cm ³ / min.

The reactor used had an inner diameter of 8 mm and a length of 50
A 0 mm SUS304 tube was used.

The analysis of the gas generated by the reaction is performed by Gas
kuropack54 is a SUS column (4 mm x 3 mm
× 2 mL) and performed using a TCD detector with a heating program.

The analysis of silica, which is a product, is performed by reacting with a sample deposited on a particle collection plate (here, a SEM sample table is diverted) installed inside a particle collection quartz glass fiber filter in the reactor. SEM observation and XRD analysis were performed on two types of samples collected on a cylindrical quartz glass fiber filter installed near the center of the vessel.

The shapes and sizes of the produced silica particles are shown in FIGS. 3 to 6 using SEM photographs.

The reaction conditions in each figure are as follows. Figure 2: Silica glass filter for particle collection before silica particle generation Figure 3: Silica particles collected on the particle collection plate in Example 1 (reaction temperature 850 ° C) Figure 4: Quartz glass fiber in Example 1 Silica particles collected by the filter (reaction temperature: 850 ° C.) FIG. 5: Silica particles collected by the quartz glass fiber filter in Example 1 (reaction temperature: 850 ° C., sample at a different point from FIG. 4) FIG. Silica particles collected on the particle collection plate in Example 1 (reaction temperature: 875 ° C.) Further, in the XRD analysis, the peak of the collected particles coincides with the peak of silica, and it is determined that the generated particles are silica. Was done.

[0039]

Example 2 Each storage tank of tetramethoxysilane and pure water was placed in a temperature-controlled oil bath, argon was passed through each storage tank as a carrier gas, and vapors of tetramethoxysilane and water were converted to argon gas. And introduced into the reactor.

At this time, the concentration of tetramethoxysilane in the raw material gas is 1 to 2%, the concentration of water is 2.6%, and the temperature of the oil bath and the flow rate of argon gas as a carrier gas are changed to form tetramethoxysilane and tetramethoxysilane. The gas generated by the same method as in Example 1 was analyzed while changing the flow rate of water.

The silica particles produced at a reaction temperature of 800 ° C. are collected by a cylindrical quartz glass fiber filter and observed by SEM. The shape and size of the produced silica particles are shown in FIG. 7 using SEM photographs.

As shown in this photograph, when the reaction is carried out under conditions such as a relatively small amount of raw material supplied, a relatively low temperature and a long gas residence time (low flow rate), large particles with high sphericity are grown. In this example, as shown in FIG. 7, silica particles having a diameter of about 500 microns were obtained.

The product was identified by XRD analysis. As a result, it was found that the product completely matched the sample silica and that silica particles were formed.

Since the silica particles shown in FIG. 6 have a very small particle size, the properties of the particles are not clear in the SEM photograph. Thus, FIG. 8 shows the result of observation of the same sample particles as in FIG. 6 by TEM (100,000 times magnification).

According to this, the particle size is 5 to 10 nm.
It can be seen that fine particles having a relatively spherical shape and a uniform particle size and low cohesiveness were generated.

The particles seen in such SEM and TEM photographs are relatively similar to fine particle silica produced and marketed by silicon oxychloride as a raw material by an oxyhydrogen flame method, and are expected as a new particle production method. Is big.

[0047]

Example 3 In Example 3, reaction conditions were the same as in Example 1 except that hydrogen was used instead of water as a reactant.
The reaction temperature was changed in the range of 100 ° C. to 800 ° C. to produce silica particles, and the obtained particles were subjected to XRD analysis.

As a result, the XRD spectrum of the produced particles matched the XRD spectrum of the standard quartz sample, and the formation of silica particles was confirmed. The properties of the obtained particles were almost similar to those in FIG. 4 or FIG. Yes, the same results as in Example 1 were obtained.

[0049]

Example 4 The reactants water and air were mixed at a volume ratio of 9: 1.
Water and oxygen (water: oxygen = 20:
Silica was produced under the same reaction conditions as in Example 1 except that the mixture of 1) was used in place of water.

As a result, silica particles having the same properties as in Example 1 were obtained, and the rate of silica formation was accelerated by about 10 to 20% as compared with the case where the reactant was water alone.

[0051]

Example 5 Water and hydrogen as reactants were mixed at a volume ratio of 4: 1, and the mixture was replaced with water under the same reaction conditions as in Example 1 except that water was used instead of water. Generated.

As a result, silica particles having the same properties as in Example 1 were obtained, and the silica production rate was increased by about 20 to 30% as compared with the case where the reactant was water alone.

[0053]

According to the present invention, since silica is produced without passing through chlorides, the cost is greatly reduced as compared with the conventional method, which is expensive due to the generation of chlorine and hydrogen chloride. Can be expected.

Further, in the present invention, since silica is formed using a gas phase method, OH groups formed on the silica surface can be reduced as compared with a method for forming silica using a liquid phase method, which is troublesome. The merit is great, for example, there is no need for a solid-liquid separation operation of fine particles.

Further, since a continuous operation in which the reaction proceeds using a fluidized bed is possible, the productivity of silica can be greatly improved as compared with the conventional liquid phase method.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration in a method for producing high-purity silica of the present invention.

FIG. 2 SEM photograph of a quartz glass filter

FIG. 3 is an SEM photograph of silica particles collected on a particle collection plate.

FIG. 4 is an SEM photograph of silica particles collected on a quartz glass fiber filter.

FIG. 5 is an SEM photograph of silica particles collected on a quartz glass fiber filter.

FIG. 6 is an SEM photograph of silica particles collected on a particle collection plate.

FIG. 7 is an SEM photograph of silica particles collected by a quartz glass fiber filter.

FIG. 8 is a TEM photograph of silica particles collected on a particle collection plate.

[Explanation of symbols]

 10, 11: vaporization step 20: reaction step 30: recovery step

Claims (5)

[Claims] 1. A method for producing high-purity silica, comprising subjecting alkoxysilane and water to a hydrolysis reaction in a gas phase to produce silica. 2. A process for producing high-purity silica, comprising subjecting at least one of hydrogen or water and hydrogen or water and oxygen to a hydrolysis reaction with an alkoxysilane to produce silica. 3. The method for producing high-purity silica according to claim 1, wherein the silica particles are collected using a filter or a plate. 4. Growing the silica using seed particles,
The method for producing high-purity silica according to claim 1 or 2, wherein the silica is collected. 5. The method for producing high-purity silica according to claim 1, wherein the gas phase reaction is performed in a fluidized bed.