JP3026099B2 - Method and apparatus for producing amorphous spherical silica fine powder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method and an apparatus for producing amorphous spherical silica fine powder by a CVD method (chemical vapor deposition) using an organic silicon compound as a raw material. About.

[Conventional technology]

Amorphous spherical silica fine powder is used as a high-density filler such as a synthetic resin, a raw material for synthetic quartz glass, and the like. Generally, a flame melting method of melting a natural silica raw material in an oxyhydrogen flame, a metal alkoxide, It is manufactured by a method such as a sol-gel method for hydrolyzing

However, in the flame melting method, impurities are easily mixed during the melting step, and the energy cost required for melt spheroidization is high. The sol-gel method has a lower energy cost than the flame melting method, but almost all metal alkoxides are very expensive, so that the overall cost is high and is not industrially sufficient.

Conventionally, in order to solve such a problem, there has been known a method for producing an amorphous spherical silica fine powder by a CVD method using an organic silicon compound as a raw material.

In this production method, a raw material gas is introduced into a vertical reaction tube from the upper or lower part together with a carrier gas, and the raw material gas is heated to cause a gas phase reaction, which is a so-called CVD (chemical vapor deposition) method. This is to produce spherical silica fine particles.

The method of producing amorphous spherical silica fine powder by the CVD method is that the raw material is easy to purify, that the obtained product is of high purity, that the generated fine powder particles have less aggregation and that the particle size distribution is narrow, Attention has been paid to the fact that the particle size distribution can be relatively easily controlled by the reaction conditions (temperature and concentration), and the control of the atmosphere in the reaction system is relatively easy.

The vapor phase deposition of amorphous spherical silica fine particles by the CVD method is simple in principle, but the process of forming the fine particles is complicated. In order to generate fine particles, it is necessary to make the reaction rate extremely high so that a large amount of nuclei appear at once, and it is necessary to rapidly cool to suppress the growth of the generated fine particles.

[Problems to be solved by the invention]

However, in the above-mentioned conventional method for producing an amorphous spherical silica fine powder, since the reaction tube is a vertical type, a mixing phenomenon of an introduced gas introduced from an upper portion or a lower portion thereof and generated fine particles occurs, and a desired product is produced. Is mixed with by-products and recovered, which is not preferable.

In addition, since the generated fine particles stay for a required time or more due to turbulence of the gas flow in the reaction tube or the like, there is a problem that the growth of some particles is promoted and the particle size varies.

Accordingly, an object of the present invention is to provide a method for producing an amorphous spherical silica fine powder capable of reliably separating and recovering a target product and having a narrow flow distribution, and an apparatus therefor.

[Means for solving the problem]

In order to solve the above-mentioned problems, a method for producing an amorphous spherical silica fine powder according to the first invention includes the steps of: producing an amorphous spherical silica fine powder by a CVD method using an organic silicon compound as a raw material; The raw material gas and pure water are introduced horizontally from one end together with the carrier gas, and while these are heated and reacted from the outer periphery of the horizontal reaction tube, the amorphous spherical silica fine particles produced by the reaction are removed horizontally. In this method, by-products and unreacted gas are introduced from the other end of the horizontal reaction tube to the lower side while being deposited on the other end of the reaction tube, and separated and recovered.

Further, an apparatus for producing amorphous spherical silica fine powder according to the second invention is an apparatus for producing amorphous spherical silica fine powder by a CVD method using an organic silicon compound as a raw material. A source gas introduction nozzle and a pure water introduction nozzle for horizontally introducing a reaction gas and pure water together with a carrier gas at one end of the tube, and fine particles for depositing amorphous spherical silica fine particles at the other end of the horizontal reaction tube. A collection vessel is provided, and a separation and recovery unit for separating and recovering by-products and unreacted gas is provided at the other end of the horizontal reaction tube and connected continuously at a lower position.

[Action]

In the above means, the flow of the raw material gas, the steam generated from the pure water and the flow of the carrier gas are horizontal parallel flows (laminar flows)
Then, the raw material gas reacts with the water vapor, and the generated amorphous spherical silica fine particles cause a reduction in the gas velocity, and are deposited on the fine particle collecting container by collision between the particles or collision with the inner wall of the reaction tube.

On the other hand, by-products generated during the reaction are sent to the separation and recovery unit together with the unreacted gas, and separated and recovered from the unreacted gas.

As an organic silicon compound, solid or liquid at normal temperature,
What can be vaporized by heating, for example, tetrachlorosilane (SiCl ₄ ), hexamethylcyclotrisilazane (Si (C
H ₃ ) ₂ NH), tetraethoxysilane (Si (OC ₂ H ₅ ) ₄ ),
Tetramethoxysilane (Si (OCH ₃ ) ₄ ) or the like is used.

As carrier gas, nitrogen gas, argon gas,
An inert gas such as helium gas is used.

The reaction temperature is generally 800-1200 ° C., preferably 1000
~ 1100 ° C.

〔Example〕

 Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic configuration diagram of an apparatus for producing amorphous spherical silica fine powder according to the present invention.

In the figure, reference numeral 1 denotes a cylindrical horizontal reaction tube made of quartz glass or alumina.
An external heating furnace 2 for heating at a temperature of ~ 1200 ° C is provided.
A raw material gas vaporized by an evaporator (not shown) and pure water produced by a pure water production device (not shown) are respectively supplied to a carrier gas at one end (right end in the figure) of the horizontal reaction tube 1. The raw material gas introduction nozzle 3 and the pure water introduction nozzle 4 which are introduced horizontally are provided, while the other end (the left end in the figure) which is not heated by the external heating furnace 2 in the horizontal reaction tube 1 has a non- A fine particle collection container 5 for depositing crystalline spherical silica fine particles is accommodated therein. Both the nozzles 3 and 4 and the particle collecting container 5 are made of quartz glass or the like, like the horizontal reaction tube 1. The tips of the nozzles 3 and 4 are at least 1/3 or less of the inner diameter of the middle part thereof. Inside diameter,
Alternatively, the fine particle collection container 5 is a half-cylindrical shape smaller than the inner diameter of the horizontal reaction tube 1, and is provided so that the outer peripheral surface is in contact with the inner peripheral surface of the horizontal reaction tube 1.

Further, below the other end of the horizontal reaction tube 1, a separation and recovery unit 6 for separating and recovering by-products and unreacted gas is provided. The other end is communicated through a conduit 7 having the same diameter as the other end. The separation / recovery unit 6 and the conduit 7 are made of quartz glass or the like as in the case of the horizontal reaction tube 1, and the separation / recovery unit 6 has a cylindrical shape having a diameter of at least twice, preferably three times or more the diameter of the horizontal reaction tube 1. It is composed of an upper part and a funnel-shaped lower part connected to the upper part. In the upper part of the separation and recovery unit 6, a conduit 7 is connected with a structure projecting from the lower end, while a gas recovery pipe 8 for recovering unreacted gas is provided in the upper part of the separation and recovery unit 6. Further, a cock 9 for collecting by-products and the like are provided below the separation and collection unit 6.

In the manufacturing apparatus having the above configuration, the raw material gas gasified by the evaporator is horizontally introduced into the horizontal reaction tube 1 from the raw material gas introducing nozzle 3 together with the carrier gas, while the pure water produced by the pure water manufacturing apparatus is produced. Is horizontally introduced into the horizontal reaction tube 1 from the pure water introduction nozzle 4 together with the carrier gas to become steam, and flows in parallel with the raw material gas to form a parallel flow.
The raw material gas reacts with water vapor by heating by the external heating furnace 2, and the generated amorphous spherical silica fine powder particles decrease in gas velocity, and due to impact between the particles or collision with the inner wall of the reaction tube. The particles are deposited on the particle collection container 5.

On the other hand, by-products generated during the reaction reach the separation / recovery unit 6 via the conduit 7 from the other end of the horizontal reaction tube 1 together with the unreacted gas, are separated from the unreacted gas, and are deposited thereunder. The unreacted gas is recovered by opening the cock 9 and the unreacted gas is recovered from the gas recovery pipe 8.

Here, a horizontal reaction tube 1 made of quartz glass having an inner diameter of 50 mm and a length of 1000 mm is heated to 800 ° C. by an electric furnace 2 of an outer periphery heating type.
About 2 g / min of tetrachlorosilane and about 1 g / min of pure water,
When the carrier gas was introduced horizontally into the horizontal reaction tube 1 from each of the introduction nozzles 3 and 4 together with nitrogen gas at about 2 / min, amorphous spherical silica fine particles were immediately generated in the horizontal reaction tube 1 and the generated fine particles were formed. Was deposited on the fine particle collection container 5.

One hour after the reaction, the collection and collection efficiency for all the generated fine powder was 70 to 80%, and the remainder remained in the horizontal reaction tube 1 or was scattered to the separation circuit unit 6.

No impurities, by-products, etc. were mixed in the fine powder produced by the fine particle collector 5 at all, and the silicon yield of the recovered fine powder with respect to the feed was 50 to 60%. Also, as a result of observing the shape of the fine particles with a scanning electron microscope and measuring the particle size distribution with a microtrack, more than 85% of the particles were truly spherical,
The spherical particles had a narrow particle size distribution and an average particle size of about 0.1 to 1.0 μm.

〔The invention's effect〕

As described above, according to the present invention, the flow of the raw material gas, the steam generated from pure water and the flow of the carrier gas become horizontal parallel flows, so that the residence time of the generated fine particles in the reaction tube is irregular as in the related art. And the particle size distribution of the produced fine particles can be narrowed.

In addition, the raw material gas reacts with water vapor, and the generated amorphous spherical silica fine particles decrease in gas velocity, and are deposited on the fine particle collection container by collision of the particles or collision with the inner wall of the reaction tube, while the reaction proceeds. The by-products generated along with the unreacted gas are sent to the separation / recovery unit and separated and recovered from the unreacted gas, so the target product can be more reliably separated and recovered than before. Can be.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing one embodiment of an apparatus for producing fine amorphous spherical silica powder according to the present invention. DESCRIPTION OF SYMBOLS 1 ... Horizontal reaction tube 2 ... External heating furnace 3 ... Material gas introduction nozzle 4 ... Pure water introduction nozzle 5 ... Fine particle collection container 6 ... Separation and recovery unit 7 ... Conduit 8 ... Gas Collection pipe, 9 ... cock

Continuation of front page (58) Field surveyed (Int.Cl. ⁷ , DB name) C01B 33/12-33/193

Claims (2)

(57) [Claims] In producing an amorphous spherical silica fine powder by a CVD method using an organic silicon compound as a raw material, a raw material gas and pure water are horizontally introduced together with a carrier gas from one end thereof into a horizontal reaction tube. While heating and reacting these from the outer peripheral portion of the horizontal reaction tube, while depositing amorphous spherical silica fine particles generated by the reaction at the other end in the horizontal reaction tube, by-products and unreacted gas are removed. A method for producing an amorphous spherical silica fine powder, wherein the fine powder is guided from the other end of a horizontal reaction tube to a lower portion thereof for separation and recovery. 2. An apparatus for producing amorphous spherical silica fine powder by a CVD method using an organosilicon compound as a raw material, wherein a reaction gas and pure water are respectively supplied to one end of a horizontal reaction tube of an outer peripheral heating system by a carrier gas. A raw material gas introduction nozzle and a pure water introduction nozzle are also provided, and a fine particle collection container for depositing amorphous spherical silica fine particles is provided at the other end of the horizontal reaction tube, and a sub-particle collection container is provided at the other end of the horizontal reaction tube. An apparatus for producing fine amorphous spherical silica powder, characterized in that a separation and recovery unit for separating and recovering a product and an unreacted gas is located below and connected continuously.