JPH0711001A - Boron-containing organosilazane polymer and its production - Google Patents

Abstract

PURPOSE:To obtain a boron-containing organosilazane polymer suitable as a ceramic precursor for getting an Si-B-C-N ceramic capable of keeping amor phous structure even at a high temperature and to provide a production process therefor. CONSTITUTION:This boron-containing organosilazane polymer has a skeleton part mainly composed of Si-N bond and B-N bond, contains Si and B randomly bonded with each other through Si-N-B bond and is soluble in organic solvents. The polymer is produced by mixing a mixture of an organohalogenosilane and boron trichloride in an organic solvent at (R)0 deg.C and subjecting the product to coammonolysis with ammonia gas.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a boron-containing organosilazane polymer suitable as a precursor of a ceramic composed of Si-B-C-N and a method for producing the same.

[0002]

2. Description of the Related Art Ceramics have been attracting attention as materials excellent in heat resistance, abrasion resistance, high temperature strength, etc. However, it is extremely difficult to process ceramics because they are hard and brittle. Therefore, when manufacturing a ceramic product, a method in which fine powder of ceramics is formed into a desired shape in advance by a method such as processing and then sintered, or an organometallic polymer as a ceramic precursor is melted or dissolved in a solvent A precursor method in which this is processed into a desired shape and then calcined to be inorganic is used. The most important feature of the precursor method is that a ceramic product having a shape that cannot be obtained by a sintering method using fine powder can be obtained, and is particularly suitable for the production of fibers and thin films and the impregnation operation.

[0003]

Among the ceramics, SiC and Si ₃ N ₄ have excellent characteristics at high temperature, such as SiC having excellent heat resistance and high temperature strength, and Si ₃ N ₄ having excellent thermal shock resistance. It has been attracting widespread attention for its possession, and various precursors have been actively researched. Ceramic fiber produced by the precursor method has been actively researched as a reinforcing material for fiber-reinforced composite materials by combining it with plastics, metals or ceramics by taking advantage of its characteristics of light weight, heat resistance and high strength. There is.
In addition, a method of using a precursor as a matrix for a composite material has also attracted attention.

However, the ceramics synthesized by the precursor method are inevitably crystallized through the amorphous state because they are produced by the thermal decomposition of the precursor polymer, and when this crystallization occurs, the strength of the ceramics decreases. To do. It has been difficult to keep the structure of ceramics synthesized by the precursor method in an amorphous state up to a high temperature.

The present invention has been made in view of the above circumstances.
An object of the present invention is to provide a boron-containing organosilazane polymer suitable as a ceramic precursor for obtaining a Si-B-C-N ceramics having an amorphous structure even at a high temperature, and a method for producing the same.

[0006]

According to the present invention, a novel boron is characterized in that a mixture of an organohalogensilane and boron trichloride is mixed in an organic solvent at a temperature of 0 ° C. or lower and co-ammonolysis is carried out with ammonia gas. The method for producing the contained organosilazane polymer and the skeleton obtained by the production method are mainly composed of Si—N bonds and B—N bonds, and silicon and boron are randomly bonded through Si—N—B bonds, and Boron-containing organosilazane polymers that are soluble in organic solvents are provided.

The present invention will be described in more detail below.

One of the starting materials used in the process of the invention is preferably of the general formula

[0009]

[Chemical 2]

It is an organohalogensilane having the following structure. This organohalogensilane may have a cyclic or branched structure. Although n ≧ 2, it needs to be in the range of being soluble in an organic solvent. The organohalogensilane has at least two halogen groups in one molecule, and R ₁ , R ₂ , R ₃ and R ₄ other than halogen are each hydrogen, an alkyl group or an aryl group, and chlorine is preferable as the halogen. Is. In addition, an organohalogensilane having one halogen group in one molecule can be introduced at the end of a boron-containing organosilazane polymer to be used when controlling the molecular weight. These polysilanes are synthesized by any known method.

Boron trichloride, which is another starting material used in the method of the present invention, has a high vapor pressure at room temperature (boiling point near 12.5 ° C.) and is used in a liquid state after cooling.

In the method of the present invention, the boron trichloride is added to at least one of the organohalogensilanes, and the ratio of boron atoms to silicon atoms is 0.01.
The mixture is mixed in an organic solvent at a temperature of 0 [deg.] C. or lower so as to be ~ 2, and co-ammonolysis is performed with ammonia gas in an atmosphere inert to the reaction.

The most preferred embodiment of the method of the present invention is a method for co-ammonolysis of a mixture, in which ammonia gas is bubbled while stirring in a cooled organic solvent to carry out the reaction.

That is, in the method of the present invention, the organohalogensilane and the boron trichloride are mixed in advance in a desired amount ratio to carry out co-ammonolysis.
-B bond is rapidly generated, and a polymer having a uniform composition is obtained. It is difficult to control the amount of boron by the method using boron trichloride in a gas, and when the product obtained by ammonolysis of organohalogensilane and boron trichloride have to react with each other, the boron is uniformly bonded at the atomic level. The polymer obtained cannot be obtained.

In the method of the present invention, it is necessary to carry out the coammonolysis in an organic solvent inert to the reaction.
As these organic solvents, for example, toluene, xylene, tetrahydrofuran, diethyl ether and the like are suitable.

In the method of the present invention, it is necessary to carry out the co-ammonolysis in an atmosphere inert to the reaction. As the inert atmosphere, for example, nitrogen, argon or the like is suitable, while mixing with ammonia gas. It is preferably introduced into the reaction vessel.

The reaction temperature in the method of the present invention is 0 ° C. or lower. Above 0 ° C., it becomes difficult to control the composition of the polymer due to evaporation of the raw material, especially boron trichloride. In addition, it is not preferable to set the reaction temperature below the freezing point of the solvent because the reaction does not proceed uniformly. However, since the boiling point of the raw material rises as the reaction progresses, the reaction may be performed while gradually raising the temperature to room temperature.

Further, the reaction time in the method of the present invention is usually such that the amount of ammonia gas is at most twice as much as the amount of ammonia gas required for converting all of the organohalogensilane and chlorine of boron trichloride into ammonium halide into the reaction system. However, it is usually preferable to continue the reaction in an inert atmosphere for 1 to 24 hours after that so that halogen does not remain in the product.

If necessary, a step of heating the reaction mixture at a temperature not higher than the boiling point of the solvent can be added after the completion of the co-ammonolysis. By this step, excess ammonia dissolved in the reaction mixture can be removed, the reaction of the unstable functional group in the reaction product can be promoted, and a stable boron-containing organosilazane polymer can be obtained. The heating time is not particularly limited, but 0.5 to 10 hours is usually suitable.

The polymer obtained by the above co-ammonolysis can be produced by removing the ammonium halide produced by filtration and then removing the solvent by distillation under atmospheric pressure or reduced pressure.

The important and novel characteristic of the thus obtained boron-containing organosilazane polymer of the present invention is that the skeleton portion is mainly composed of Si-N bond and BN bond, and silicon and boron are bonded via Si-N-B bond. That is, the polymer is soluble in an organic solvent that is randomly bonded.
Further, as described above, the polymer that is a precursor of ceramics such as SiC and Si ₃ N ₄ has a defect that it is crystallized at a high temperature, but the polymer of the present invention covers the defect and has a new function. Expected to appear.

Boron trichloride, which is one of the starting materials of the present invention, has a low boiling point as described above and is a gas at room temperature.
The amount of evaporation from the mixture with another starting material, organohalogensilane, is large, and the composition of the mixture cannot be kept uniform. When this mixture is co-ammonolysed,
Due to the large amount of ammonium halide produced, the reaction system cannot be stirred and a uniform reaction does not proceed. In addition, the reaction between the products is too fast and gelation occurs, resulting in a low polymer yield. In order to solve these problems, the present invention has found that a method of mixing raw materials in a solvent cooled to 0 ° C. or lower and introducing ammonia into the reaction system in a gaseous state is extremely useful. That is, the evaporation of the raw materials was suppressed by cooling to 0 ° C. or lower, the stirring was efficiently performed by using a solvent, and the reaction was successfully controlled by introducing ammonia in a gaseous state. The reaction mechanism is

[0023]

[Chemical 3]

Reactions such as
It is expected that a -N bond will be produced and a Si-NB bond will be produced.

In the present invention, for the purpose of synthesizing a polymer in which boron is evenly distributed, when the proportion of boron trichloride in the mixture increases, the amount of B—N—B bonds produced increases.
The ratio of boron atoms to silicon atoms is preferably 0.01-2.

Next, the structure of the polymer of the present invention will be described. The infrared absorption spectrum of the obtained polymer is 12
Si-N-B and B-N- at 00 to 1500 cm ^-1
The absorption attributed to the BN bond of the B bond is shown, and also 90
The absorption attributed to the Si—N bond is shown in the vicinity of 0 cm ^−1, which indicates that the organosilazane polymer containing boron is produced. The organohalogensilane used in the present invention may be a polysilane having two or more silicon atoms bonded, and at that time, the polymer contains a polysilane skeleton. The so-called polysilane skeleton in which silicon atoms are localized is decomposed at about 300 to 500 ° C. when the polymer is converted into ceramics by thermal decomposition, and rearrangement of atoms occurs, so that no problem occurs.

As described above, in the structure of the polymer obtained by the method of the present invention, the skeleton is mainly composed of Si--N bonds and B
It has a -N bond, and has a structure in which silicon and boron are randomly bonded through a Si-N-B bond. The number average molecular weight of the polymer of the present invention is usually 300 to 10,000.
Is. Furthermore, the polymers obtained by the process of the present invention have distinct features which differ from conventional precursor polymers in the following respects. First, the polymer of the present invention, in the presence of an organic solvent, that is, in a solution state, causes almost no increase in molecular weight even when heated at the boiling point of the solvent,
When the organic solvent is removed, intermolecular cross-linking occurs and it exhibits thermosetting properties. The temperature for heat curing depends on the composition and structure of the polymer and may be room temperature curable, but since intermolecular crosslinking hardly occurs in the presence of a solvent, it can be stored and used in a solution state. . In the case of room temperature curing, the polymer solution is concentrated by removing a part of the solvent by distillation, for example, by a dry spinning method to form fibers, or by forming a coating film and drying and removing the solvent to proceed with curing. be able to. Further, in the case of a polymer whose curing progresses at the boiling point of the solvent or higher, for example, it becomes possible to produce a composite material by a melt impregnation method, and further it is possible to increase the ceramic yield by heat curing.

Another feature of the polymer of the present invention is that when the polymer is calcined in a non-oxidizing atmosphere, Si-B
The point is that it is converted to —C—N ceramics, and this ceramic has an amorphous structure even at a high temperature of 1500 ° C. or higher. Generally, the organosilazane polymer is 1500 ° C.
Then, crystallization of SiC or Si ₃ N ₄ starts, which deteriorates the characteristics of ceramics. In the boron-containing organosilazane polymer of the present invention, the boron atoms form the polymer skeleton randomly and uniformly, so that the crystallization of SiC or Si ₃ N _{4 in} the thermal decomposition product is suppressed. It is highly promising to synthesize ceramics with new functions.

The present invention will be described below with reference to examples.
The present invention is not limited to the examples below.

Example 1 80.7 g of dichlorodiphenylsilane and 2 of boron trichloride
5 g were mixed in toluene cooled to 0 ° C., and 50 cm ³
A mixed gas of ammonia gas / min and nitrogen gas of 100 cm ³ / min was bubbled and reacted for 20 hours while stirring. After the reaction was completed, the reaction mixture was filtered under a nitrogen atmosphere, and then 2
The mixture was heated to 50 ° C. in a nitrogen atmosphere and the solvent was removed by distillation to obtain 57.8 g of a polymer. This polymer had a number average molecular weight of 570 and was cured when heated to 300 ° C.
From the results of elemental analysis, the composition of the polymer is SiB _0.7 C
_{It was 12.9} N _2.2 H _16.6 . When this polymer was pyrolyzed to 1580 ° C. in a nitrogen stream of 100 cm ³ / min, the ceramic yield was 52% and the structure of the ceramic was amorphous as a result of X-ray diffraction. The ceramic yield of the polymer before curing was 32%. Its composition is SiB
_{It was 0.8} C _2.8 N _0.3 .

Example 2 41.2 g of dichlorodimethylsilane and 2 of boron trichloride
Mix 5.0 g in toluene cooled to -20 ° C and mix 5
Bubble a mixed gas of 0 cm ³ / min of ammonia gas and 100 cm ³ / min of nitrogen gas, and stir for 20 minutes.
Reacted for hours. At the end of the reaction, the temperature of the reaction mixture had risen to room temperature. Then, filter under a nitrogen atmosphere,
Then, the mixture was heated to 150 ° C. in a nitrogen atmosphere and the solvent was removed by distillation to obtain 26.1 g of a polymer. The polymer had a number average molecular weight of 420 and was cured when heated at 320 ° C. From the results of elemental analysis, the composition of the polymer is SiB
_{It was 0.7} C _2.1 N _2.3 H _6.5 . When this polymer was pyrolyzed to 1580 ° C. in a nitrogen stream of 100 cm ³ / min, the ceramic yield was 68% and the structure of the ceramic was amorphous as a result of X-ray diffraction. Its composition is S
It was iB _0.8 C _1.5 N _0.4.

Example 3 41.2 g of dichlorodimethylsilane and 5 of boron trichloride
Mix 0.0g in toluene cooled to -50 ° C and mix 1
00cm ³ / min was bubbled ammonia gas and 100 cm ³ / min nitrogen gas mixed gas, stirring 2
The reaction was allowed for 0 hours. At the end of the reaction, the temperature of the reaction mixture had risen to room temperature. Then, the polymer was obtained by filtering under a nitrogen atmosphere, removing toluene from the toluene solution at room temperature under reduced pressure, and sampling the polymer to obtain a number average molecular weight of 7,800. Then, the mixture was heated to 150 ° C. in a nitrogen atmosphere and the solvent was removed by distillation to obtain 29.3 g of a polymer.
Obtained. The polymer cured upon removal of solvent. From the result of elemental analysis, the composition of the polymer is SiB _1.3 C
_{It was 2.1} N _3.2 H _6.7 . This polymer is 10
When pyrolyzed to 1580 ° C. in a nitrogen stream of 0 cm ³ / min, the ceramic yield was 68%, and the structure of the ceramic was amorphous as a result of X-ray diffraction. Its composition is SiB
_{It was 1.4} C _1.6 N _0.4 .

Example 4 41.2 g of organohalogensilane of Si ₂ (CH ₃ ) _2.6 Cl _3.4 and 25.0 g of boron trichloride were -50
The mixture was mixed in toluene cooled to 0 ° C., a mixed gas of 100 cm ³ / min of ammonia gas and 100 cm ³ / min of nitrogen gas was bubbled, and the mixture was reacted for 10 hours while stirring. At the end of the reaction, the temperature of the reaction mixture had risen to room temperature. Then, the polymer was filtered under a nitrogen atmosphere, and toluene was removed from the toluene solution at room temperature under reduced pressure to sample the polymer. The number average molecular weight of the polymer was 490 (the infrared absorption spectrum of the polymer is shown in FIG. 1). ). Thereafter, the toluene solution was heated at 120 ° C. for 4 hours, and then the number average molecular weight similarly measured was 500, and the number average molecular weight after leaving this solution at room temperature for 2 days was 535, which was almost unchanged. The solvent was removed by distillation by heating to 150 ° C. in a nitrogen atmosphere to obtain 25.3 g of a polymer. The polymer had a number average molecular weight of 730 and hardened when left at room temperature. From the result of elemental analysis, the composition of the polymer was SiB _0.6 C _1.4 N _1.8 H _3.1 . 1 of this polymer in a nitrogen stream of 100 cm ³ / min
The ceramic yields when pyrolyzed at 000, 1200, 1400, and 1600 ° C. are 64.5, 64.1,
At 64.3 and 65.2%, the structure of the ceramic was amorphous as a result of X-ray diffraction (FIG. 2). The composition of the obtained ceramic was approximately SiB _0.6 C _0.9 N _0.5 (infrared absorption spectrum is shown in FIG. 3). The thermal decomposition in an argon stream was almost the same.

Example 5 106.7 g of organohalogensilane consisting of Si ₂ (CH ₃ ) _2.6 Cl _3.4 and 64.7 g of boron trichloride-50
The mixture was mixed in toluene cooled to ° C, a mixed gas of 200 cm ³ / min of ammonia gas and 100 cm ³ / min of nitrogen gas was bubbled, and the reaction was carried out for 20 hours while stirring. At the end of the reaction, the temperature of the reaction mixture had risen to room temperature. Then, the mixture was refluxed at 70 ° C. under a nitrogen atmosphere for 5 hours, cooled to room temperature and filtered, and heated to 150 ° C. in a nitrogen atmosphere to remove the solvent by distillation to give a polymer of 68.
2 g was obtained. This polymer exhibited the same properties as in Example 4.

[Brief description of drawings]

FIG. 1 is an infrared absorption spectrum of the polymer obtained in Example 4.

2 is an X-ray diffraction pattern of the ceramic obtained in Example 4. FIG.

FIG. 3 is an infrared absorption spectrum of the ceramic obtained in Example 4.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Takeshi Kono, Takeshi Kono 8 Chidori-cho, Naka-ku, Yokohama-shi, Kanagawa, Japan Central Petroleum Research Institute (72) Inventor Yutaka Sanogawa Chidori-cho, Naka-ku, Yokohama-shi, Kanagawa Address: Central Research Laboratory, Nippon Sekiyu Co., Ltd. (72) Inventor Yoshio Hasegawa 2687-5 Isohama-cho, Oarai-cho, Higashi-Ibaraki-gun, Ibaraki Prefecture

Claims (7)

[Claims] 1. A skeleton part mainly contains Si—N bonds and B—
A boron-containing organosilazane polymer which is composed of an N bond, in which silicon and boron are randomly bonded via a Si—N—B bond and which is soluble in an organic solvent. 2. The boron-containing organosilazane polymer according to claim 1, which is room temperature curable or thermosetting in the absence of an organic solvent. 3. The boron according to claim 1, which is converted into Si—B—C—N ceramics by thermal decomposition in a non-oxidizing atmosphere, and the ceramics have an amorphous structure even at a high temperature of 1500 ° C. or higher. Containing organosilazane polymer. 4. A method for producing a boron-containing organosilazane polymer, which comprises mixing a mixture of an organohalogensilane and boron trichloride in an organic solvent at a temperature of 0 ° C. or lower and co-ammonolysis with ammonia gas. 5. An organohalogensilane is represented by the general formula: Which has at least two halogen groups in one molecule, R ₁ , R ₂ , R ₃ and R ₄ other than halogen are each hydrogen, an alkyl group or an aryl group, and n is 2 or more. The method for producing a boron-containing organosilazane polymer according to claim 4, which is a compound. 6. The ratio of boron trichloride to organohalogensilane and the ratio of boron atoms to silicon atoms is 0.0.
The method for producing a boron-containing organosilazane polymer according to claim 4, wherein the boron-containing organosilazane polymer is mixed so as to be 1 to 2. 7. The step of heating the reaction mixture at a temperature below the boiling point of the solvent after the co-ammonolysis.
A method for producing the described boron-containing organosilazane polymer.