JPH05320356A - Polyborisilazane and its production - Google Patents

Abstract

PURPOSE:To obtain a polyborosilazane having excellent mechanical strength, heat-resistance, corrosion resistance and oxidation resistance, easily convertible to ceramic and useful for fiber, etc., by reacting a specific dihalosilane and a trihaloborane with a Lewis base and reacting the obtained complex mixture with ammonia. CONSTITUTION:The polyborosilazane containing randomly distributed units of formula II and formula III and having a number-average molecular weight of 100-50,000 is produced by reacting (A) a dihalosilane of formula I (R is H, alkyl, alkenyl, aryl, cycloalkyl, aralkyl, alkylamino or alkylsilyl; X is halogen) (e.g. dichlorosilane) and (B) a trihaloborane (e.g. trichloroborane) with a Lewis base (e.g. trimethylamine) and reacting the obtained complex mixture with ammonia. The molar ratio of A/B is preferably 1/99 to 99/1.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a novel polyborosilazane and a method for producing the same.

[0002]

Polyorgano (hydro) silazanes made by reacting organodichlorosilanes such as methyldichlorosilane with dry ammonia in a non-reactive solvent are known. The composition of the polyorgano (hydro) silazane produced by this method has the general formula-(RSiHNH)
n- [wherein R represents an organo group such as an alkyl group or an aryl group, and n represents a degree of polymerization], and the degree of polymerization n is low, and is mainly a mixture of cyclic compounds of n = 3 to 5 Consists of.

Using such a low degree of polymerization cyclic material as a raw material,
It has been proposed that this is heated to 100 to 300 ° C. in the presence of a clay-like solid catalyst to open a ring and polymerize to produce a high molecular weight polysilazane (JP-A-54-54).
No. 93100). Similarly, using the above low degree of polymerization cyclic material as a raw material, mixing with bis (trimethylsilyl) amine, and heating to 110 ° C. in the presence of a ruthenium catalyst
It has also been proposed to open a ring and polymerize it to produce a high molecular weight polysilazane. Also, after reacting dichlorosilanes with dry ammonia, a low degree of polymerization cyclic silazane obtained by separating and removing ammonium chloride, further high molecular weight ladder polysilazane produced using a catalyst such as KH, NaH Are known. (D. Seyferth et al., Commu
nication of the American Ceramic Society, C-132 (6),
1984).

Further, a method of reacting dihalosilane with a Lewis base in a non-reactive solvent to form a complex and then reacting with ammonia to produce polysilazane (Japanese Patent Publication No. 63-16325, JP-A No. 61-89230). No. 2) and a method for producing polyborosilazane in which a polysilazane obtained by this method is reacted with a boron compound to introduce a boron atom in the form of a cross-link (JP-A-2-84437).

As described above, various substances and methods have been proposed for the polysilazane-based polymer and the method for producing the same, but polyborosilazane having a structure in which a boron atom is introduced into the main chain of polysilazane has not been reported yet. Absent.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a polyborosilazane having a structure in which a boron atom is introduced into the main chain of polysilazane and a method for producing the same.

[0007]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have found that when an inorganic or organic dihalosilane and trihaloborane are reacted with a Lewis base, a boron atom in the main chain is reacted. It was found that the polyborosilazane having the following formula can be obtained in good yield, and the degree of branching of this polyborosilazane can be easily adjusted by its boron content, and as a result, the physical properties of the polyborosilazane are independent of the molecular weight. The inventors have found that they can be controlled by means of the above, and have completed the present invention.

That is, according to the present invention, the general formula RHSiX
A polyborosilazane synthesized by reacting a complex mixture obtained by reacting a dihalosilane represented by ₂ with a trihaloborane with a Lewis base, and reacting the complex mixture with ammonia. (In the above formula, R is a hydrogen atom, an alkyl group, an alkenyl group, a cycloalkyl group, an aryl group, an aralkyl group,
Provided is a polyborosilazane having a number average molecular weight in the range of 100 to 50,000, which randomly has a unit represented by an alkylamino group or an alkylsilyl group, and X represents halogen. According to the present invention, the general formula RHSiX ₂ (wherein R represents a hydrogen atom, an alkyl group, an alkenyl group, a cycloalkyl group, an aryl group, an aralkyl group, an alkylamino group or an alkylsilyl group, and X is There is provided a method for producing polyborosilazane, which comprises reacting a complex mixture obtained by reacting a dihalosilane represented by (showing a halogen atom) and trihaloborane with a Lewis base and ammonia.

The polyborosilazane of the present invention is characterized by using a mixture of dihalosilane and trihaloborane as a raw material. Since the halogen atom of dihalosilane reacts with ammonia to form a bond, the number of silicon bonds is two and only a linear or cyclic polymer is produced only from dihalosilane, but trihaloborane When it exists, the number of boron bonds is three, so it becomes possible to form a three-dimensional bond. Therefore, in the polyborosilazane of the present invention, its molecular structure, in particular, the degree of branching can be changed depending on the proportion of the trihaloborane used.

In the present invention, a unit obtained by reacting dihalosilane with ammonia through an adduct has a unit represented by the general formula A: The unit obtained by reacting trihaloborane with ammonia via an adduct is a unit represented by the general formula B: Is a unit represented by. The free bond of each unit is directly bonded to the free bond of another unit, or is bonded to the free bond of another unit via —NH— based on the ammonia that has been excessively reacted. However, the molecule as a whole has a three-dimensional molecular structure in which the proportion of linear portions or cyclic portions or the density of branching changes depending on the ratio of trihaloborane to dihalosilane used.

Since the polyborosilazane of the present invention is produced in a basic solvent, it is a polymer having a high molecular weight and excellent solvent solubility. When a polysilazane is reacted with a boron compound and a boron atom is introduced into the molecule in the form of a cross-link, the molecular weight of the polymer rapidly increases as the amount of boron increases, and a gel is formed. Therefore, the introduction amount of boron is limited in the polyborosilazane in which a boron atom is introduced in the form of a cross-link, but in the present invention, polyborosilazane is obtained by reacting ammonia with a complex mixture of dihalosilane and trihaloborane. Therefore, compared to cross-linked polymers,
Since the boron content in the polymer can be increased and the degree of branching also increases, the viscosity decreases when compared with the same molecular weight. Therefore, the present invention has an advantage that the polyborosilazane concentration in the polyborosilazane solution can be increased and the condition setting for removing the solvent at the time of forming the ceramic can be facilitated. Further, since the content of boron can be increased, it is possible to control the characteristics such as conductivity and hardness of the ceramic obtained by firing.

The polyborosilazane of the present invention generally has a number average molecular weight in the range of 100 to 50,000. The high molecular weight polyborosilazane can be obtained by heating the once generated polyborosilazane, if necessary, but when the molecular weight exceeds the above range, it gels. Polyborosilazane, which has a small heating loss and is useful as a ceramics precursor, preferably has a high molecular weight, and more preferably has a number average molecular weight of 500 or more, particularly 1000 or more.

The polyborosilazane of the present invention is characterized by having a molecular structure mainly composed of the above-mentioned two types of units, and the ratio of trihaloborane to dihalosilane used is not particularly limited and is generally 1:99 to 99: It can be appropriately selected and used within the range of 1 (molar ratio).

The base used is a Lewis base that does not react with dihalosilanes and trihaloboranes except to form adducts. Such bases include, for example, 3
Secondary amines (for example, trialkylamines such as trimethylamine, dimethylethylamine, diethylmethylamine, and triethylamine, pyridine, picoline, dimethylaniline and their derivatives), secondary amines having a sterically hindering group, phosphine, stibine , Arsine and derivatives thereof (eg, trimethylphosphine, dimethylethylphosphine, methyldiethylphosphine, triethylphosphine, trimethylarsine, trimethylstibin, trimethylamine, triethylamine, etc.). Among them, a base having a low boiling point and a basicity lower than that of ammonia (e.g., pyridine, picoline, trimethylphosphine, dimethylethylphosphine, methyldimethylphosphine, triethylphosphine) is preferable, and pyridine and picoline are particularly advantageous in handling and economical Is preferred.

The trihaloborane used in the present invention has the formula BX
A compound represented by ₃ (X is a halogen atom), BCl ₃ , BB
r ₃ , BF _3, etc.

The dihalosilane used in the present invention has the following general formula: (In the formula, R represents a hydrogen atom, an alkyl group, an alkenyl group, a cycloalkyl group, an aryl group, an aralkyl group, an alkylamino group or an alkylsilyl group, and X represents a halogen). Of these, R is usually a carbon number of 1 to 7, preferably 1 to 5, more preferably 1 to 2 alkyl group, 2 to 7 alkenyl group, 5 to 7 cycloalkyl group, generally aryl. And X is usually fluorine, chlorine, bromine and iodine, preferably chlorine. As the aryl group, phenyl, tolyl,
Xylyl, medityl, cumenyl, benzyl, phenethyl, α-methylbenzyl, benzhydryl, trityl,
Styryl, cinnamyl, biphenylyl, naphthyl and the like can be used. As the alkylsilyl group (mono-, di-, tri-substituted product), one having 1 to 7 carbon atoms is usually used.

The Lewis base used in the present invention is cheaper than the conventional method of potassium hydride or methyl iodide and can be reused, so that there is an advantage that the manufacturing cost is reduced. The amount of Lewis base with respect to the total amount of dihalosilane and trihaloborane is 0.5 or more, preferably 1.0 or more, and more preferably 1.5 or more in molar ratio.

In the present invention, a Lewis base is added to the above-mentioned trihaloborane and dihalosilane to form a complex. At this time, the reaction solvent is a Lewis base alone or a mixture of a non-reactive solvent and a Lewis base. Good to use. Examples of non-reactive solvents include aliphatic hydrocarbons, alicyclic hydrocarbons, aromatic hydrocarbon hydrocarbon solvents, halogenated methane, halogenated ethane, halogenated hydrocarbons such as halogenated benzene, aliphatic ethers, and aliphatic hydrocarbons. Ethers such as cyclic ethers can be used.

Preferred solvents are halogenated hydrocarbons such as methylene chloride, chloroform, carbon tetrachloride, bromoform, ethylene chloride, ethylidene chloride, trichloroethane and tetrachloroethane, ethyl ether, isopropyl ether, ethyl butyl ether, butyl ether, 1,2-.
Ethers such as dioxyethane, dioxane, dimethyldioxane, tetrahydrofuran, tetrahydropyran, pentane, hexane, isohexane, methylpentane, heptane, isoheptane, octane, isooctane, cyclopentane, methylcyclopentane, cyclohexane, methylcyclohexane, benzene, toluene,
Hydrocarbons such as xylene and ethylbenzene.

The concentrations of trihaloborane and dihalosilane in the solvent may be arbitrary, but are preferably in the range of 1 to 15% by weight (hereinafter abbreviated as%). Further, as the conditions for forming the complex, the temperature may be any as long as the reaction system becomes a liquid, but is preferably -10 ° C to room temperature,
The pressure is preferably atmospheric pressure to 5 kg / cm ² . Since the reaction is extremely fast, the reaction time can be set arbitrarily.

Next, the complex thus prepared is reacted with dry ammonia to cause decomposition (ammonolysis). The ammonia used at this time may be gas or liquid. Drying of ammonia is preferably carried out, for example, by passing it through solid sodium hydroxide and then passing through metallic sodium. The addition amount of ammonia is 3.0 to 2 in molar ratio with respect to the total amount of trihaloborane and dihalosilane.
It is preferably 0 times, preferably 4 to 15 times, more preferably 5 to 10 times. The reaction solvent, reaction temperature, reaction pressure, and time may be the same as the conditions for complex formation. However, in a closed system, ammonia pressure is applied. The amount of water in the reaction system is, for example, 50
It is desirable to set it to 0 ppm or less. After completion of the reaction, ammonium chloride is removed by a conventional means such as filtration to obtain polyborosilazane.

[0022]

The present invention will be described in more detail with reference to the following examples.

Example 1 A synthesis apparatus is shown in FIG. In the figure, 1 is a reactor, 2 is a constant temperature bath,
3 is a trihaloborane storage tank, 4 is a dihalosilane storage tank, 5 is a pyridine storage tank, 6 is a nitrogen gas, 7 is an ammonia gas, 8 is a heater, 9 is a temperature monitor linked with the heater 8, 10 is a stirrer, 11 is exhaust. It is gas. After replacing the inside of the reactor installed in a thermostat with a temperature of 0 ° C with dry nitrogen, dry pyridine 90
After adding ₃ ml of trichloroborane (BCl ₃ ) and dichlorosilane (Si
H ₂ Cl ₂ ) 67.4 g respectively to form a complex mixture,
A white solid adduct was obtained. The reaction mixture was cooled to 0 ° C. and 65 g of dry ammonia was bubbled into it with stirring. After the reaction was completed, dry nitrogen was blown in to remove unreacted ammonia, followed by pressure filtration under a nitrogen atmosphere,
800 ml of filtrate was obtained. When 1 l of dry o-xylene was added to this filtrate and the solvent was removed under reduced pressure, 39.3 g of a yellow powder was obtained. This powder was soluble in toluene, chloroform and other organic solvents. The number average molecular weight of the polymer powder was 1370 in terms of polystyrene when measured by GPC. In addition, as a result of analysis of its IR spectrum, absorption based on NH of wave numbers (1 / cm) 3350 and 1175: 2170
SiH-based absorption; 1020-820 SiNSi-based absorption; 1400
It was confirmed that the BN-based absorption was exhibited. Further, the elemental analysis result of the polymer is Si: 50.7%, N: 26.8% by weight.
%, C: 6.8%, O: 2.9%, B: 8.6%, H: 4.2%.

Example 2 Similar to Example 1, the synthetic reaction was carried out using the synthesizer shown in FIG. After replacing the inside of the reactor installed in a constant temperature bath at a temperature of 0 ° C. with dry nitrogen, 900 ml of dry pyridine was added and maintained until the temperature became constant, and then 23.4 g of trichloroborane (BCl ₃ ) while stirring. , 80.8 g of dichlorosilane (SiH ₂ Cl ₂ ) were respectively added to form a complex mixture, and a white solid adduct was obtained. The reaction mixture was cooled to 0 ° C. and 72 g of dry ammonia was bubbled into it with stirring. After completion of the reaction, dry nitrogen was blown in to remove unreacted ammonia, and then pressure filtration was performed under a nitrogen atmosphere to obtain 850 ml of a filtrate. When 1 ml of dry o-xylene was added to this filtrate and the solvent was removed under reduced pressure, 39.7 g of a viscous liquid was obtained. The number average molecular weight of this substance was 940 in terms of polystyrene when measured by GPC.

Example 3 Similar to Example 1, a synthetic reaction was carried out using the synthesizer shown in FIG. After replacing the inside of the reactor installed in a constant temperature bath at a temperature of 0 ° C. with dry nitrogen, dry γ-picoline 104 was added.
After adding 0 ml and keeping the temperature constant, 23.0 g of trichloroborane (BCl ₃ ) was added while stirring.
Methyldichlorosilane (CH ₃ SiHCl ₂ ) 70.2 g
To form a complex mixture, and a white solid adduct was obtained. The reaction mixture was cooled to 0 ° C. and 78 g of dry ammonia was bubbled into it with stirring.
After the reaction was completed, dry nitrogen was blown in to remove unreacted ammonia, and then pressure filtration was performed under a nitrogen atmosphere.
0 ml was obtained. 1000 m of dry o-xylene was added to this filtrate.
When 1 was added and the solvent was removed under reduced pressure, 32.1 g of a viscous liquid was obtained. The number average molecular weight of this substance is GP
When measured by C, it was 620 in terms of polystyrene.

Example 4 The borosilazane obtained in Example 1 was treated with 10% ammonia.
By heating to 00 ° C. at a temperature rising rate of 3 ° C./min and thermally decomposing, a white solid ceramic was obtained in a yield of 84.0% by weight. When powder X-ray diffraction measurement was performed on the obtained ceramics, it was confirmed to be amorphous. The elemental analysis results of this solid are Si: 56.2% and N: 2 by weight.
9.2%, C: 1.3%, O: 4.5%, B: 8.8%
Met. Next, the solid is further added to nitrogen at 1700 ° C.
It was heated and calcined at a heating rate of 10 ° C./min to obtain a gray solid. From the powder X-ray diffraction results of this substance, it was confirmed that the substance remained in an amorphous state.

[0027]

EFFECTS OF THE INVENTION (1) The polyborosilazane of the present invention is soluble in an organic solvent, and can be converted into Si—N—B type ceramics by firing, so that it should be used as a raw material for high-performance ceramic compacts. You can That is, continuous fibers, films and coatings having high mechanical strength at high temperature and excellent heat resistance, corrosion resistance, oxidation resistance and thermal shock resistance can be easily obtained from the polyborosilazane of the present invention. Further, since the yield of ceramization is high, it can be used as a binder for sintering, an impregnating agent, or the like. (2) The polyborosilazane of the present invention does not have impurities of a residual catalyst that promotes decomposition in the polymer, so that stability is improved and handling is easy, and the purity of ceramics baked at high temperature is high. Is improved. (3) Since no catalyst remains in polyborosilazane,
The stability is improved, and long-term storage is possible even after removing the solvent. (4) The branching degree of polyborosilazane can be controlled by the amount of trihaloborane added. Therefore, it is possible to easily synthesize polyborosilazane having an arbitrary degree of branching. By increasing the degree of branching, the viscosity of polyborosilazane can be lowered independently of the molecular weight, so dry spinning using a solution with a higher concentration is possible compared to polysilazane synthesized from dihalosilane alone. Moreover, the strength of the obtained polyborosilazane fiber is improved, and the film thickness of the coating can be controlled by controlling the viscosity. (5) Low cost and safe because no expensive and dangerous catalyst is used. (6) In the ceramic obtained by firing polyborosilazane, since boron coexists in the ceramic, the hardness of the ceramic can be improved. (7) Since the composition of ceramics can be controlled, the conductivity of ceramics can be selected from a wide range.

[Brief description of drawings]

FIG. 1 is a schematic diagram of an apparatus for synthesizing polyborosilazane.

[Explanation of symbols]

 1 Reactor 2 Constant Temperature Tank 3 Trihaloborane Storage Tank 4 Dihalosilane Storage Tank 5 Pyridine Storage Tank 6 Nitrogen Gas 7 Ammonia Gas

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Toru Funayama Tohru Funayama 1-3-1 Nishitsurugaoka, Oi-cho, Iruma-gun, Saitama Prefecture Tonen Corporation Research Laboratory (72) Inventor Takeshi Isoda 1 Nishitsurugaoka, Oi-cho, Iruma-gun, Saitama 3-3-1 Tonen Co., Ltd. Research Institute

Claims (4)

[Claims] 1. A polyborosilazane synthesized by reacting a complex mixture obtained by reacting a dihalosilane represented by the general formula RHSiX ₂ and a trihaloborane with a Lewis base, with ammonia. (In the above formula, R is a hydrogen atom, an alkyl group, an alkenyl group, a cycloalkyl group, an aryl group, an aralkyl group,
A polyborosilazane having a number average molecular weight in the range of 100 to 50,000, which randomly has a unit represented by an alkylamino group or an alkylsilyl group and X represents halogen. 2. The polyborosilazane of claim 1, wherein the molar ratio of dihalosilane to trihaloborane is in the range of 1:99 to 99: 1. 3. A compound represented by the general formula RHSiX ₂ (wherein R represents a hydrogen atom, an alkyl group, an alkenyl group, a cycloalkyl group, an aryl group, an aralkyl group, an alkylamino group or an alkylsilyl group, and X represents a halogen atom). A), a complex mixture obtained by reacting a dihalosilane represented by the formula (1) and trihaloborane with a Lewis base is reacted with ammonia, and a method for producing polyborosilazane. 4. The method of claim 3 wherein the molar ratio of dihalosilane to trihaloborane is within the range of 1:99 to 99: 1.