JPS61174108A - Production of silicon imide or polysilazane - Google Patents

Abstract

PURPOSE:To produce inexpensively high-purity silicon imide or polysilazane easily and efficiently by allowing mainly trichlorosilane to react with a base and incorporating a process forming an adduct thereby. CONSTITUTION:In a method for synthesizing silicon imide or polysilazane as a precursor for producing a sintered silicon nitride body, a process forming an adduct by allowing mainly trichlorosilane to react with a base is incorporated. The above-mentioned trichlorosilane can be easily produced by the reaction of silicon for a metalworking industry and hydrogen chloride and a small quantity of the other silane may be contained therein. As the base, tertiary Lewis base and tertiary amines are suitable and one or more kinds of trialkylamine, aromatic tertiary amine, trialkylphosphine and trialkylstibine are preferably used.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a method for producing silicon imide or polysilazane. More particularly, the present invention relates to a method for producing silicon imide or polysilazane as a precursor for producing silicon nitride.

(Prior art) Silicon nitride sintered bodies have excellent high-temperature strength, thermal shock resistance, and oxidation resistance, so they can be used as high-temperature structural materials for gas turbines, diesel engines, etc., or as cutting tools, etc., for energy and resource conservation. It is important as one of the high-performance materials that can make a large contribution.

Conventionally, as a method for producing high-purity α-type silicon nitride with good yield, an imide amide thermal decomposition method is used to heat silicon imide or silicon amide obtained by ammonolysis of silicon tetrachloride in a non-oxidizing atmosphere to obtain silicon nitride. It has been known. However, when this method is used, the tubes of the reactor are likely to become clogged when silicon imide or polysilazane is synthesized, and the reaction is difficult to control because it is a rapidly exothermic reaction. Improved methods for solving these drawbacks have been disclosed in recent years (for example, Japanese Patent Publication No. 56-44006, Japanese Patent Application Publication No. 58-88110, and Japanese Patent Application Publication No. 54-134098). Apart from methods for the improvement of adducts of halosilanes and bases, which are extremely easy to handle (details on this can be found, for example, in the Journal of the Chemical Society (J, Chem.

Soc, Vol. (A), p. 705, 1967) was proposed.

Additionally, a method has been proposed in which polysilazane obtained by thermally decomposing organic polysilazane is heated at 800 to 2000°C to sinter silicon nitride (Hajime Saito, Journal of the Japan Institute of Textile Technology v!2L)
LL 1111.65-72 [1982]), but this method had the disadvantage that silicon carbide and free carbon were produced at the same time as silicon nitride.9 On the other hand, inorganic polysilazane, which is soluble in solvents, It is known that it is useful as a silicon precursor, and a method for obtaining high-purity α-type silicon nitride from inorganic polysilazane has been developed (Japanese Patent Application No. 80109/1982). There is room for improvement.

The present inventors proposed a method of using halosilanes as a method to solve the conventional problems (Patent Application No. 1983-
No. 247240 and Japanese Patent Application No. 113984/1984).

(Problems to be solved by the invention) The above-mentioned Japanese Patent Application No. 58-247240 and Japanese Patent Application No. 59-1
The outline of No. 13984 is that if an adduct that is easily formed from an easily purified halosilane and a base is used and this adduct is quantitatively ammonolysed, there is no need to use catalysts such as iron or calcium. Since there is no residual base, there are very few impurities, and ammonium chloride can be easily removed, making it possible to produce extremely high purity silicon nitride powder.The present invention relates to these improvements. It is.

Therefore, a first object of the present invention is to provide a method for efficiently producing high purity silicon imide or polysilazane useful as a precursor of silicon nitride powder.

A second object of the present invention is to provide a method for easily producing high-purity silicon imide or polysilazane useful as a precursor for silicon nitride powder using commonly used and inexpensive raw materials.

(Means for Solving the Problems) The object of the present invention is to mainly react trichlorosilane with a base in a method for synthesizing silicon imide or polysilazane as a precursor for producing a silicon nitride sintered body. This has been achieved by a method for producing silicon imide or polysilazane, which is characterized by including the step of forming an adduct.

(Disclosure of the Invention) Trichlorosilane used in the present invention can be easily produced by reaction of metal industrial silicon and hydrogen chloride.

In the present invention, the silane that reacts with the base is mainly trichlorosilane, but also has the general formula SiHm
It is also possible to mix one or more types other than trichlorosilane represented by rn (X = F s Cj! SB r or I). Of the halosilanes that can be mixed, dichlorosilane is particularly preferred, but in order to efficiently produce the desired silicon nitride, it is preferred that the proportion of trichlorosilane be sufficiently large.

The base used in the present invention can be selected from a wide range of bases that can form adducts with halosilanes, but it is particularly preferable to use Lewis bases that do not react with halosilanes other than to form adducts. Examples of the base include tertiary amines (trialkylamines such as trimethylamine, dimethylethylamine, diethylmethylamine and triethylamine, pyridine, picoline,
dimethylaniline and derivatives thereof), secondary amines having sterically hindered groups, phosphine, stibine, arsine and derivatives thereof (e.g. trimethylphosphine, dimethylethylphosphine, methyldiethylphosphine, triethylphosphine, (trimethylarsine, trimethylstibine, trimethylamine, triethylamine, etc.). Among these, bases with low boiling points and less basicity than ammonia (e.g. pyridine, picoline, trimethylphosphine, dimethylethylphosphine, methyldiethylphosphine, triethylphosphine) are preferred, and pyridine and picoline are particularly preferred due to handling and economic considerations. preferred. The amount of base used does not need to be particularly strict; it is sufficient that the base, including the amine in the adduct, is present in excess of the stoichiometric amount relative to the silane.

In the present invention, a Lewis base and/or a non-reactive main solvent can be used as a reaction solvent.

Examples of non-reactive solvents include hydrocarbon solvents such as aliphatic hydrocarbons, alicyclic hydrocarbons, and aromatic hydrocarbons, halogenated hydrocarbons such as halogenated methane, halogenated ethane, and halogenated benzene, aliphatic ethers, Ethers such as alicyclic ethers can be used. Of these, especially °
Preferred solvents are methylene chloride, chloroform, carbon tetrachloride, bromoform, ethylene chloride, ethylidene chloride,
Halokenized hydrocarbons such as trichloroethane and tetrachloroethane, ethers such as ethyl ether, isopropyl ether, ethyl butyl ether, butyl ether, 1,2-dioxyethane, dioxane, dimethyldioxane, tetrahydrofuran, tetrahydropyran, pentane, hexane, isohexane, methylpentane , heptane, isohbutane, octane, isooctane, cyclopentane, methylcyclopentane, cyclohexane, methylcyclohexane, benzene, toluene, xylene,
Hydrocarbons such as ethylbenzene.

The halosilane adduct in the present invention can be easily formed from a halosilane and a base by a conventional method, but it is sufficient that the adduct is substantially produced as a reaction intermediate.
It may or may not actually be separated as an adduct of halosilane.

In the present invention, the adduct obtained as described above is further reacted with ammonia to synthesize silicon imide or polysilazane. In this case, gas phase ammonia may be used. The amount of ammonia to be used is not critical, and it is sufficient if it is in excess of the amount of silane.

The reaction conditions for the synthesis of silicon imide or polysilazane of the present invention are such that if the reaction temperature is from 178°C to 100°C, preferably from 140°C to 80°C, the reaction rate is high, so there is no need for reaction time or reaction pressure. If the reaction salinity, which is not particularly limited, is below 178°C, the reaction rate will decrease, and if the reaction temperature is above 100°C, the produced siliconimide or polysilazane will decompose again. Undesirable. The synthesis reaction of silicon imide or polysilazane is preferably carried out under an inert gas atmosphere, and nitrogen or argon is preferably used as the inert gas.

(Function) The superiority of the present invention can be easily understood from the following reaction, which compares one example of the reaction in the present invention which mainly uses trichlorosilane with the case where silicon tetrachloride is used.

5iHC13+ 4.5 NH3 5in(NH)1.5 + 3NH4Cj! 5iCI
14 + 6NH3 -→ 5i(NH)2 +4NH4C1 In other words, in the case of the present invention, not only the amount of ammonia used is small, but also the amount of ammonium chloride produced as a by-product is small, so it is possible to produce high-purity silicon nitride as cheaply as possible. The object of the present invention can be achieved.

In the present invention, siliconimide or polysilazane that can be obtained by the above-described synthesis method is heat-treated in the presence of nitrogen to obtain a product with high purity and a high α-type crystal structure ratio, that is, a high α-type crystal structure ratio. Silicon nitride of 70% or more can be easily manufactured.

In the present invention, the presence of nitrogen refers to the presence of ammonia alone, nitrogen alone, or a mixture of nitrogen and an inert gas, such as nitrogen and hydrogen, nitrogen and ammonia, nitrogen and argon, or nitrogen-containing decomposition gas, such as ammonia gas. meaning that it must contain nitrogen element. When using a mixed gas, the proportion thereof is not particularly limited, but it is desirable that it contains an excessive amount of nitrogen element.

Generally, silicon nitride as a raw material powder for a silicon nitride sintered body preferably has high purity and has an α-type crystal structure. This is because when α phase is used as a raw material, a transition from α phase to β phase occurs during the sintering process, resulting in improved sinterability and development of a fibrous structure, resulting in high-strength silicon nitride sintering. Because you will gain a body.

In order to obtain a high yield of silicon nitride powder that is 70% or more α-type and has extremely excellent sinterability using the silicon imide or polysilazane produced according to the present invention, the heat treatment temperature must be particularly adjusted to about 0.0000%. It must be within a limited range of 1400°C to about 1400°C.

If the heat treatment temperature is extremely low, such as 500°C or less, unreacted chlorine and hydrogen will be incompletely removed, and the resulting silicon nitride will contain chlorine and hydrogen.
Furthermore, if the processing temperature exceeds 1900'C, the produced silicon nitride will dissociate, which is not preferable. or,
Even if the processing temperature is not as above, the siliconimide or polysilazane obtained in the present invention may be heated from about 700°C to 1°C.
If treated at temperatures below 1,400°C, a mixed system of mainly amorphous silicon nitride and silicon can be obtained;
If the treatment is carried out at a temperature of 0° C. or lower, mainly β-type silicon nitride will be obtained, which is not preferable.

As for the heat treatment time, the time required for the production of by-product gases to stop due to heat generation is a rough guideline, but it is relatively short at high temperatures, relatively long at low temperatures, and relatively long to ripen the crystals. However, it is not particularly limited. Preferred heat treatment times are about 8 to about 20 hours, particularly preferably about 10 to about 16 hours.

Furthermore, in the present invention, when silicon imide or polysilazane is heat-treated in a heating furnace under a nitrogen atmosphere, non-oxide materials,
For example, it is desirable to use a furnace material made of silicon nitride, silicon carbide, tantalum, molybdenum, or the like.

Only under the above conditions can a highly purified silicon nitride powder with a nitrogen content of 39% or more and a chlorine content of 0.001% or less and with 70% or more of α-type crystal structure be obtained. If necessary, elements known to be effective in promoting sintering of silicon nitride, such as Mgs YSAnts Fe
, B, etc. can also be obtained.

(Effects of the Invention) In the present invention, in order to synthesize silicon imide or polysilazane using an adduct and ammonia that can be stably present in a reaction solvent in a solid state as substantial raw materials, the scattering of halosilane that occurs in the conventional method is It is possible to prevent inconveniences such as clogging of the reactor and clogging of the reactor. That is, (1) since there is no scattering of halosilane, the reaction temperature can be raised higher than before, and there is no danger from the viewpoint of toxicity or ignitability; (2)
The reaction rate of silicon imide or polysilazane synthesis can be controlled because the concentration of halosilane in the reactant can be substantially increased.

In addition, by allowing the adduct to pass through, not only does it prevent clogging of the reactor tubes, but gaseous ammonia can also be used, which not only improves work efficiency but also simplifies the reactor. I can do it. In particular, in the present invention, which mainly uses trichlorosilane, not only can the raw material cost be lowered, but also the amount of by-product ammonium chloride is small, so the equipment used in the silicon imide or polysilazane firing process can be made smaller.

EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited thereto.

(Example) Example 1 Synthesis of hydrochlorosilane-pyridine adduct A three-hole flask with an internal volume of 200 mJ was equipped with a mechanical stirrer, a condenser, and a dropping funnel, and after purging the reaction system with nitrogen, 50% of hydrochlorosilane was placed in the three-hole flask. m 11 and dry dichloromethane 80 m j! was added and kept at room temperature. Next, 15 ml of dry pyridine was added from the dropping funnel, producing a white complex slurry. After the reaction is complete, unreacted substances and solvent are removed under reduced pressure (
40° C., 5III Hg), a white powdery solid product was obtained quantitatively.

Table-1 Elj” Zu Enokimata Lord, 1lkL Hero Loro Scene E ° “1
-1 Dichlorosilane (S i H2Cj!2) 9
B, 6χ-+ oo sh"'n 5iHC7! 99
．． 22 The infrared absorption spectrum of the product is shown in Figures 1 and 2.
As shown in the figure, the literature [H.J. Champbell-Ferguson
The infrared absorption spectrum of the hydrochlorosilane-pyridine adduct described in J. Chem. Although the peak of 1485ca+-1 was not described in the literature, it was confirmed that it was an absorption of pyridinium salt. Thermal analysis of the biothermal material is shown in Figures 3 and 4.

Table-2 A η ・ , Nll surgery
・Day ℃ Example 2 Synthesis of silicon imide/ammonium chloride mixture via trichlorosilane-pyridine adduct Internal volume: 200 mj! A gas blowing tube, a mechanical stirrer, a dewar condenser, and a dropping funnel were installed in a four-row flask, and after purging the reaction system with nitrogen, 5 ml of trichlorosilane (0,049 m
o l) and 80 ml of dry dichloromethane were added and kept at room temperature. Next, 15 mff of dry pyridine was added through the dropping funnel, resulting in approximately 95 mj of white slurry!
was generated. 3.8 g of ammonia was mixed with nitrogen gas and bubbled in over a period of 0.8 to 1 hour while the reaction mixture was maintained at about 0 to about 5° C. and vigorously stirred. After the reaction, unreacted substances and solvent were removed under reduced pressure (100°C, 51mlH
g) 10.2 g of solid product were obtained.

This corresponds to a yield of 97.9% based on trichlorosilane. It was confirmed that no powder mist was generated during the entire reaction, and that the gas flow path and ammonia supply port were not clogged.

The infrared absorption spectrum of the product is shown in FIG. 5, and the infrared absorption spectrum of ammonium chloride is shown in FIG. 6 for comparison.

Example 3 Synthesis of silicon imide/ammonium chloride mixture via hydrochlorosilane-pyridine adduct A four-bottle flask with an internal volume of 209 mjl was equipped with a gas blowing tube, a mechanical stirrer, a dewar condenser, and a dropping funnel, and the reaction system was replaced with nitrogen. After that, 5 ml of hydrochlorosilane shown in Table 3 and 3 Q ml of dichloromethane were placed in a four-bottle flask, and the flask was kept at room temperature. Next, 15mj2 of dry pyridine was added through the dropping funnel, resulting in a white slurry of about 95mj! was generated. While maintaining the reaction mixture at a temperature of about 16 to about 25° C. and stirring vigorously, about 4.0 g of ammonia is mixed with nitrogen gas to give 0.0 g.
It took 8 to 1 hour to blow. After the reaction was completed, unreacted substances and the solvent were removed under reduced pressure (100° C., 5 mmHg) to obtain a solid product.

Comparative Example 1 Synthesis of silicon imide/ammonium chloride mixture by blowing ammonia gas into trichlorosilane solution Internal volume 20 Qmj! A three-hole flask was equipped with a gas blowing tube, a mechanical stirrer, and a dewar condenser, and the inside of the reaction system was replaced with nitrogen. Then, 5 ml of trichlorosilane and 95 ml of dry carbon tetrachloride were added to the three-hole flask.
1 was added and maintained at a predetermined temperature. Next, while stirring the mixture vigorously, about 4.0 g of dry ammonia was mixed with nitrogen gas and blown into the solution over a period of about 1.0 hours. When the reaction started, a powder box was generated and deposited in the gas flow path, which sometimes caused the ammonia supply port to become clogged, so it was opened by increasing the pressure of nitrogen gas. Moreover, the product was deposited and fixed on the inner wall of the reaction vessel. After the reaction was completed, unreacted substances and the solvent were removed under reduced pressure (50 to 100°C, 5 mmHg) to obtain a solid product. As shown in Table 4, the yield was lower than when using the method of the present invention.

Table-4 Bokusouji JJ Shikusha) [Kou 1 ゛ ℃ 工 ' 05
-1 0~10 88.1-
8-5'' 62.6 Comparative Example 2 Synthesis of silicon imide/ammonium chloride mixture by direct reaction of trichlorosilane and ammonia A reaction vessel with an internal volume of 100 mjt was cooled with dry ice/methanol cryogen, and 5 ml of trichlorosilane was added. While keeping the temperature below -34°C, about 4.0 g of dry ammonia was mixed with nitrogen gas and blown into it over a period of 1.0 hours.As the reaction started, fumes were generated in the gas phase, and the trichlorosilane liquid level increased. A solid product precipitated on top.Furthermore, a solid product stuck around the ammonia supply port.Even after the entire amount of ammonia was blown in, unreacted liquid bones remained.

After the reaction, unreacted substances were removed under reduced pressure (50°C, 5mmHg
) 4.27 g of solid product were obtained.

FIG. 7 shows the infrared absorption spectrum of the product, which is in good agreement with that of the product obtained in Example 2 herein. However, in this method, as in Comparative Example 1, a powder box is generated at the start of the reaction, discharged from the reaction vessel, and deposited in the gas flow path, and the yield is 41.0% based on silicon. It was confirmed that the yield was much lower than that of the invention.

Comparative Example 3 Synthesis of silicon imide/ammonium chloride mixture by direct reaction of trichlorosilane and ammonia (room temperature gas phase method) A pair of gas blowing tubes were installed at the upper end of a glass reaction tube with an inner diameter of 2 cx and a length of 100 c11, and an internal volume at the lower end. A 500 mn settling product collector was installed. The opening of the gas blowing tube was set at a position of 10 cm from the upper end of the reaction tube for trichlorosilane, and at the same position <3 cm from the upper end of the reaction tube for ammonia. Next, after purging the reaction system with nitrogen, ammonia was dried with solid caustic soda and metallic sodium and blown into the reaction tube. Also, 0-5℃
6.66 g of trichlorosilane was placed in a saturator maintained at 100 mL, and the trichlorosilane was saturated with a carrier gas and blown into the reaction tube. At the start of the reaction, the product flowed into the collector through the reaction tube in the form of a fume from the opening of the gas blowing tube. As the reaction progressed, products adhered and deposited on the opening of the gas blowing pipe, the inner wall of the reactor, and the gas flow path downstream of the collector. When 4.94 g of trichlorosilane in the saturator was vaporized, the gas blowing pipe was blocked, so the reaction was stopped. The powdery solid product in the collector was 1.86 g, which corresponded to only 24.1% based on silicon, which was confirmed to be a much lower yield than in the case of the present invention. The infrared absorption spectrum of the obtained product is as shown in Figure 8.
Good agreement with that of the product obtained in Example 2 herein.

Example 4 Calcination of silicon imide/ammonium chloride mixture via hydrochlorosilane-pyridine adduct 5 g of the products obtained in Examples 2 and 3 were placed in a boat made of silicon nitride sintered body, and placed in an alumina furnace with an inner diameter of 50 mm. It was placed in a tube furnace equipped with a core tube. 5℃ under ammonia atmosphere
The mixture was heated to 450° C. at a heating rate of 1/2 min and held for 1 hour. Thereafter, in a nitrogen atmosphere, at a heating rate of 10°C/min,
The mixture was heated to the temperature shown in No. 5 and held for about 2 hours to obtain a product. The crystallinity of the obtained product was evaluated by X-ray diffraction, and the results are shown in Table 5.

[Brief explanation of drawings]

FIG. 1 is an infrared absorption spectrum of the dichlorosilane-pyridine adduct obtained in Example 1. FIG. 2 is an infrared absorption spectrum of the trichlorosilane-pyridine adduct obtained in Example 1. FIG. 3 is a graph showing a DTA (differential thermal analysis) curve and a TG (thermogravimetry) curve of the dichlorosilane-pyridine adduct obtained in Example 1. FIG. 4 is a graph showing the DTA curve and 70 curve of the trichlorosilane-pyridine adduct obtained in Example 1. FIG. 5 is an infrared absorption spectrum of the mixture of silicon imide and ammonium chloride obtained in Example 2. FIG. 6 is an infrared absorption spectrum of commercially available ammonium chloride for comparison. FIG. 7 shows the infrared absorption vector of the mixture of silicon imide and ammonium chloride obtained in Comparative Example 2. FIG. 8 is an infrared absorption spectrum of the mixture of silicon imide and ammonium chloride obtained in Comparative Example 3.

Claims (3)

[Claims] (1) A method for synthesizing silicon imide or polysilazane as a precursor for producing a silicon nitride sintered body, which is characterized by including a step of mainly reacting trichlorosilane with a base to form an adduct. A method for producing imide or polysilazane. (2) The method for producing silicon imide or polysilazane according to claim 1, wherein the base is at least one base selected from tertiary Lewis bases and tertiary amines. (3) Claim 2, characterized in that the base is at least one selected from trialkylamines, aromatic tertiary amines, trialkylphosphines, trialkylarsines, and trialkylstibines. A method for producing silicon imide or polysilazane as described in .