JPS60166212A - Production of silicon carbide - Google Patents

Abstract

PURPOSE:To obtain easily a powdery silicon carbide of high purity, hydrolyzing a disilane compound expressed by a specific general formula in the presence of carbon powder, and reducing the hydrolysis product at a given temperature in a monoxidizing atmosphere. CONSTITUTION:A disilane compound expressed by the formula (R is H or the same or different monofunctional hydrocarbon group; X is halogen atom; n is an integer 1-5) is hydrolyzed in the presence of carbon powder to give a fine powdery silica obtained by hydrolysis of the disilane compound as a mixture thereof with the carbon powder. The resultant mixture is then reduced at 1,600- 2,100 deg.C in a monoixidizing atmosphere to give easily powdery silicon arbide. The above-mentioned disilane compound as a starting material can be easily purified highly by distillation, etc. at a low cost, and the aimed silicon carbide can be obtained economically in high purity.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing silicon carbide, and particularly to a method for producing high purity silicon carbide using a disilane compound as a starting material.

Silicon carbide has long been produced in large quantities by heating and reacting silica stone and carbon powder in an Acheson electric furnace, and is widely used as an abrasive and heat-resistant structural material. In recent years, from the viewpoint of resource and energy conservation, applications have been developed for engineering ceramics and electro-X related sectors by taking advantage of its excellent physical properties. However, the purity of silicon carbide produced using silica as a starting material varies because silica is a natural mineral and contains a large amount of various impurities (and because the product obtained from an electric furnace is made into lumps). The disadvantage was that it had to be crushed.

The present invention relates to a method for producing silicon carbide which solves these disadvantages, and which has the general formula RX Si2,
A disilane compound represented by R is a hydrogen atom, an atom or group selected from the same or different types of monovalent hydrocarbon groups, or a halogen atom, n is an integer from 1 to 5) is added to the carbon powder. 1.600 to 2,100 in a non-oxidizing atmosphere after hydrolysis in the presence of
It is characterized by carrying out a reduction reaction at ℃.

Namely, the present inventors made silicon carbide with high purity.

Moreover, as a result of various studies on how to easily obtain it in powder form, we found that when a disilane compound represented by the general formula RX Si1l-nz as described above is hydrolyzed in the presence of carbon powder, a fine powder obtained by hydrolysis of a disilane compound can be obtained. It was discovered that silica in the form of a mixture with carbon powder can be obtained as a mixture with carbon powder, and silicon carbide can be easily obtained in powder form by subjecting it to a reduction reaction. Moreover, since this can be easily made impure by distillation, etc., we have confirmed that the desired carbonized silicon can be obtained economically and with high purity, and have developed the present invention. Completed.

The disilane compound used as a starting material in the method of the present invention is represented by the general formula RXSi, where 6-n2R is an aqueous atom, a methyl group, an ethyl group, or a propyl group.

X is the same or different atoms or groups selected from alkyl groups such as butyl groups, alkenyl groups such as vinyl groups and allyl groups, aryl groups such as phenyl groups and tolyl groups, and Schifftetraalkyl groups such as cyclohexyl groups; Halogen atoms such as chlorine, bromine, and fluorine, and n7b''-1 to 5 integers.

Although this product is produced as a by-product in the direct synthesis method of organochlorosilanes in the silicone industry, it is economically advantageous because it can be used as a by-product that is currently discarded because there is no way to utilize it effectively. Moreover, since it can be easily purified by distillation, it is considered to be advantageous as a raw material for producing highly pure silicon carbide. As the disilane compound, trichlorotrimethyldisilane, tetrachlorodimethyldisilane, or a mixture thereof, which is available in large quantities from a practical standpoint, is suitable, but dichlorodimethylsilane, trichloromethylsilane, methyl Monosilane compounds such as trivinylsilane, trifluorosilane, silicon tetrachloride, trichlorophenylsilane, and dichlorodiphenylsilane may be mixed.

In the method of the present invention, the above-mentioned disilane compound is hydrolyzed in the presence of carbon powder, and according to this method, fine silica produced by hydrolysis is obtained as a homogeneous mixture with carbon powder. It can be used as is as a raw material for the reduction reaction in the next step to produce silicon carbide.

In order to create a homogeneous mixture with the silica powder, this carbon powder should be made as fine as possible, for example, with an average particle size of 20 to 50 mμ, but this is also as fine as possible. Since it is preferable to use a highly pure carbon black, carbon black such as 7 Arnes black or acetylene black is preferable.

In addition, for this dispersion, the disilane compound is homogeneously dispersed in water in advance using a hydrocarbon solvent such as acetone or various dispersants such as a surfactant, etc., prior to hydrolysis of the disilane compound. That's good. Hydrolysis of the disilane compound progresses in a curved manner by adding the disilane compound to water in which carbon powder is dispersed, but the silica produced by this hydrolysis is converted into carbon powder by washing with water and drying after hydrolysis. obtained as a homogeneous mixture of

The mixture of silica powder and carbon powder obtained by pressing in this way is used as a raw material for the reduction reaction in the next step, but if the mixing ratio of silica and carbon is less than 0.6, silica reduction will occur. The reaction does not proceed sufficiently, and the purity of the carbonized purple color that is produced is also low.

If the carbon excess is increased to 1.0 or more, the amount of carbon remaining in the water increases per charcoal produced, so this becomes 0.
It is recommended that the temperature be within the range of 6 to 1.0 (1°) This mixture of silica powder and carbon powder is converted into silicon carbide by heat treatment in a non-oxidizing atmosphere. If this heating is below 6oQ°C, the desired reaction will not substantially proceed, and if it is above 2,100°C, the resulting silicon carbide will have a large particle size, which is also economically disadvantageous. , this is 1,600-2,100℃
It is recommended that the range be within the range of . In addition, the atmosphere for this reaction must be non-oxidizing, and this may be nitrogen gas, argon gas, helium gas, or a mixed gas atmosphere of these, but if necessary, hydrogen gas may be mixed in. It may be.

The silicon carbide obtained in this way is a purified disilane compound as a starting material, and the carbon powder is also said to be highly pure, so it is extremely pure compared to that obtained by conventional methods. .

Furthermore, since it is obtained in powder form, it has the advantage of being able to be used as is for various purposes;
The carbon remaining therein may be oxidized and removed by heat treatment at 00° C., thereby making it possible to obtain a carbide with higher purity.

Next, examples of the method of the present invention will be given.

Example: 36g of carbon black with an average particle size of about 30mμ was charged into a 3t separable 72 Scooter equipped with a stirrer, and about 10 (1+l) of acetone was added to it to moisten it.
t was added to uniformly disperse the carbon black in the water.

Next, trichlorotrinotyldisila 711 was weighed so that the flask was a/s 1o, s.
0g was added using a dropping funnel for sufficient hydrolysis, and the resulting hydrolyzate was washed with water and dried.
95 g of a uniformly mixed composition with a ratio of 0.6 was obtained, which was pulverized into a fine powder with an average particle size of 0.5.

Next, this composition was placed in a silicon carbide tray, subjected to a reduction reaction at 2,000°C for 1 hour in a nitrogen gas atmosphere in a carbon furnace, and then taken out after cooling, and further heated to 700°C in a Matsufuru furnace. When heated to remove excess carbon by oxidation, greenish-gray powder 35P was obtained, which was subjected to X-ray diffraction and chemical analysis, and was found to be β-type silicon carbide containing a small amount of α-type silicon carbide. It was confirmed to be silicon carbide powder.

In addition, in the above method, this trichlorotrimethyldisilane is used as another disilane compound, and the reduction reaction temperature,
The O/810 ratio is shown in Table 1! When silicon carbide was produced in the same manner as above except that the temperature was changed to 5, the same results as listed in the first paragraph were obtained.
Silicon carbide was produced in the same manner when the temperature was 550 DEG C. to 2,200 DEG C. and when silica stone was used as the starter, and the same results as described in Chapter 1 were obtained.

(Note) ≠ 1... n = a mixture of 2 and 3 in equal amounts.

Also contains a small amount of monosilane and disilane ■2... Indicates the total amount of impurities such as Fe - Al and Oa ≠3... Silica powder (commercially available 325 mesh pass product) and the same carbon as in Example 1 Mixture with black patent applicant Shin-Etsu Chemical Co., Ltd.

Claims (1)

[Claims] 1. In the general formula RX81, R is an n s-H2 hydrogen atom, an atom or group selected from the same or different monovalent hydrocarbon groups, and X is a halogen atom. Carbonization characterized by hydrolyzing a disilane compound (n is an integer of 1 to 5) in the presence of carbon powder and then subjecting it to a reduction reaction at 1,600 to 2,100°C in a non-oxidizing atmosphere. Method of manufacturing silicon. 2. The method for producing silicon carbide according to claim 1, wherein the disilane compound is trichlorotrimethyldisilane and/or nato-2chlorodimethyldisilane.