JPH05310404A - Boron nitride precursor and method for producing boron nitride - Google Patents

Abstract

PURPOSE:To produce boron nitride or boron nitride fibers simply without complicated process by no use of borazines or decaborane which are expensive and chemically unstable. CONSTITUTION:An adduct of a boron trihalide such as boron trichloride to a nitrile such as acetonitrile or benzonitrile and ammonium chloride or an amide hydrochloride are heated at about 125 deg.C in the presence of a boron trihalide to prepare the precursor of boron nitride. The resultant boron nitride precursor is heat-treated at about 1,500 deg.C in a non-oxidative atmosphere such as nitrogen gas to give boron nitride. Or, the boron nitride precursor is dissolved in a solvent such as N,N-dimethyl-formamide and the solution is extruded into fibers and the fibers are heat-treated at about 1,500 deg.C in a non-oxidative atmosphere such as nitrogen gas to give boron nitride fibers.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to boron nitride, boron nitride fiber and a method for producing a boron nitride precursor used therein.

[0002]

2. Description of the Related Art Boron nitride, especially boron nitride fiber, is excellent in chemical stability, heat resistance and wettability and is useful as a reinforcing material for ceramics and metals. In recent years, as a method for producing a boron nitride fiber, various methods have been studied in which a boron nitride precursor that is melted or soluble in a solvent is spun and then heat-treated. Known precursors used in the production of boron nitride fibers are borazine polymers obtained by polycondensing borazine or borazine derivatives (hereinafter also referred to as borazines), alkenylborazine polymers, and borane-amine addition polymers. ing.

Examples of using borazine multimers include:
The following methods are known. By heating B-triamino-N-triphenylborazine to 250 ° C. under a nitrogen atmosphere, condensation accompanied by elimination of aniline gives a softening point of 15
A polymer having a temperature of 0 to 250 ° C. is obtained.

[0004]

[Chemical 1]

The polymer directly bonded with the borazine ring is melt-spun and then heat-treated to obtain a boron nitride fiber (Japanese Patent Laid-Open No. 51-53000).

By heating B-tris (trimethylsilylamino) borazine to 250 to 260 ° C. in a nitrogen atmosphere, a multimer having 3 to 4 borazine rings condensed with elimination of methylsilylamine can be obtained. ..

[0007]

[Chemical 2]

A boron nitride fiber is obtained by melt spinning a multimer having a borazine ring bonded by the NH group and then heat treating it (US Pat. No. 4,707,556).
issue). Further, by heating borazine to 70 ° C. under reduced pressure to condense with desorption of hydrogen, a solvent-soluble borazine oligomer is obtained, and similarly, spinning and heat treatment give boron nitride fibers. (Chem.M
ater. , 2, 96-97 (1990)).

[0009]

[Chemical 3]

As an example of using a polymer of alkenylborazine, B-vinylborazine is synthesized by a reaction of borazine and acetylene using a catalyst, and a polymer having a borazine ring in a side chain is prepared by thermal polymerization at 120 ° C. Is obtained,
From this, it is known that a boron nitride fiber can be similarly obtained (J. Am. Ceram. Soc., 109, 5).
867 (1987)).

[0011]

[Chemical 4]

Further, as an example using an addition polymer of borane and amine, a solvent-soluble boron nitride precursor is obtained by polymerizing a complex polymer of decaborane and ethylenediamine, and boron nitride fiber is produced from this. (J. Am. Cer
am. Soc. , 71, C194 (1988)).

[0013]

Among the precursors capable of forming boron nitride fibers, in the method using a complex polymer of borane and amine, toxic and expensive borane must be used as a raw material.

On the other hand, when producing a polycondensate of borazines or a polymer of alkenylborazine, trichloroborazine is generally used as a raw material. Trichloroborazine is not only expensive, but in order to produce a boron nitride precursor, steps such as synthesis of a borazine derivative and polycondensation of a borazine derivative must be performed. Furthermore, since trichloroborazine and borazine derivatives are generally easily hydrolyzed by water in the air, the production method requiring multiple steps such as synthesis and polycondensation of borazine derivatives is complicated.

As described above, in the method for producing boron nitride or boron nitride fiber using the boron nitride precursor, the raw material of the boron nitride precursor and the complicated production process of the boron nitride precursor are industrialized. It is an obstacle to this. Therefore, it has been desired to establish an inexpensive and simple method for industrially useful boron nitride or a boron nitride precursor capable of producing a boron nitride fiber.

[0016]

The present inventors have found that the reaction product of an addition product of a boron trihalide and a nitrile compound and ammonium chloride or amine hydrochloride under a specific condition under a non-oxidizing atmosphere. It was found that the material was converted into boron nitride by heat treatment, and the present invention was completed and the present invention was proposed.

That is, the present invention is characterized by reacting an adduct of boron trihalide with a nitrile compound and ammonium chloride or amine hydrochloride in the presence of boron trihalide. A method for producing a precursor, another invention is a method for producing boron nitride, characterized in that the boron nitride precursor obtained by the method is heat-treated under a non-oxidizing atmosphere, Another invention is characterized in that the boron nitride precursor obtained by the above method is dissolved in a boron nitride precursor-soluble solvent, the solution is spun, and then heat-treated in a non-oxidizing atmosphere. This is a method for producing boron fiber.

The boron trihalide used in the present invention can be arbitrarily selected from boron trifluoride, boron trichloride, boron tribromide and boron triiodide.

Further, the nitrile compound which forms an adduct with the boron trihalide promotes the dehydrohalogenation reaction of the boron trihalide with ammonium chloride or amine hydrochloride, and the boron atom and the nitrogen atom are reacted with each other. After forming the bond, most of them are released. As the nitrile compound, a known compound having a nitrile group can be used without particular limitation. Specific examples include acetonitrile, propionitrile, capronitrile, acrylonitrile, crotonnitrile, tolunitrile, and benzonitrile.

Amine hydrochlorides generally have the formula RNH ₂ .HC
A compound represented by 1 and in which R is an alkyl group such as a methyl group, an ethyl group or a propyl group, or an aryl group such as a phenyl group, a tolyl group or a xylyl group is used without limitation. However, when the carbon number of R increases, the carbon contained in the boron nitride precursor increases and the elimination component at the time of boronitization by heat treatment increases, so that R is a methyl group or an ethyl group. It is more preferable to use amine hydrochloride.

In the reaction of the present invention, it is essential to use an adduct of boron trihalide and a nitrile compound as a reaction raw material, but the boron trihalide and the nitrile compound are easily reacted and added. Since they make things, they can be contacted immediately before the reaction. Without the nitrile compound, only the by-product trichloroborazine is produced.

The method of producing the adduct is not particularly limited, but for example, a method of dropping boron trihalide into a solution of the nitrile compound dissolved in the organic solvent at room temperature, a method of dissolving the nitrile compound in the organic solvent, Next, the adduct can be produced by a method of blowing boron trihalide or a method of dissolving boron trihalide in an organic solvent and then dropping a nitrile compound.

It is essential that boron trihalide be present during the reaction of the adduct with ammonium chloride or amine hydrochloride. When boron trihalide is not present during the reaction, the boron nitride precursor of the present invention is not produced in good yield, and the spinning solvent for spinning, for example, N, N-, described later is used.
A reaction byproduct insoluble in dimethylformamide (hereinafter also referred to as DMF) is generated.

The boron trihalide may be present at least during the reaction between the adduct and ammonium chloride or amine hydrochloride. Therefore, even if unreacted boron trihalide is contained in advance in the adduct by using excess boron trihalide when forming the adduct of the nitrile compound and boron trihalide. good. The amount of boron trihalide added to the nitrile compound can be arbitrarily selected from the range of 1.05 to 2.00 in terms of molar ratio (boron trihalide / nitrile compound). However, when the amount of boron trihalide added is small, DMF insoluble components are produced,
Further, when the amount of boron trihalide added is large, the amount of boron trihalide that does not contribute to the reaction increases, so the more preferable molar ratio of boron trihalide to the nitrile compound is 1.1 to 1.5. At this time, the boron trihalide and the nitrile compound form a 1: 1 adduct, so that the amount of boron trihalide present during the reaction is in a molar ratio (boron trihalide / addition 0.1)
It is in the range of 0.5.

The concentration of the nitrile compound in the reaction solvent is not particularly limited, but it is preferably in the range of 0.1 to 10 mol / l.

The amount of ammonium chloride or amine hydrochloride added is 0.6 in terms of molar ratio to the nitrile compound (ammonium chloride or amine hydrochloride / nitrile compound).
It is preferable to select from the range of 7 to 1.5. When the amount of ammonium chloride or amine hydrochloride is large, a DMF-insoluble component is produced, and when the amount of the adduct is large, the amount of unreacted adduct tends to increase. You just have to choose.

The solvent used in the reaction of the present invention is not particularly limited, but it is preferable that the reaction by-product trichloroborazine is easily dissolved and removed when the reaction product boron nitride precursor is separated. From this point of view, a non-polar organic solvent such as benzene, toluene, xylene, chlorobenzene is preferably selected.

The heating temperature for reacting the adduct with ammonium chloride or amine hydrochloride generally requires a long time for the reaction at a low temperature, and at a high temperature, components insoluble in DMF increase and the reaction yield decreases. Therefore, the heating temperature is 100 ℃ ~
It may be selected from the range of 160 ° C. The heating time may vary depending on the temperature, but may be selected within the range of 3 to 30 hours.

By performing the above heat treatment, a boron nitride precursor is formed as a precipitate, and a by-product of the general formula X ₃ B ₃ N ₃ H ₃ (X is an F, Cl, Br, I atom) is formed.
A trihalogenated borazine represented by Since this by-product is dissolved in the non-polar solvent, the boron nitride precursor can be separated by filtering the reaction solution.

The present invention can be implemented using known equipment. However, since both the adduct and the boron nitride precursor are hydrolyzed, the reaction system equipment should be thoroughly dried in advance with nitrogen gas, etc., and the water content in the air should not enter from outside the reaction system during the reaction. It is necessary to place a hygroscopic agent such as calcium chloride in the open area. The boron nitride precursor thus obtained is an orange to brown solid, and the following findings have been obtained.

The main constituent elements are boron, nitrogen, halogen. The content of hydrogen and carbon varies depending on the type of nitrile compound, ammonium chloride or amine hydrochloride used, but is 15.7 to 25.
7, 15.4-25.4, 10.1-20.1, 2.1
˜12.1, 31.8 to 41.8%.

Although this boron nitride precursor is hydrolyzed, it is more stable than trichloroborazine. But,
When water is added to the boron nitride precursor, it reacts with heat generation and dissolves in water. When this aqueous solution is evaporated to dryness, a white precipitate mainly composed of boric acid and ammonium halide is produced.

The boron nitride precursor is soluble in DMF, and its solubility depends on the type of boron trihalide, nitrile compound or ammonium chloride or amine hydrochloride used, but it is 5 per 100 parts by weight of DMF. ~ 30 parts by weight of boron nitride precursor dissolve. Further, tetrahydrofuran, pyridine, benzene, acetonitrile, dimethylacetamide, dimethyl sulfoxide, triethylamine, dioxane, acrylonitrile, chlorobenzene diethyl ether, ethyl acetate, carbon tetrachloride, chloroform, dichloromethane, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether and n.
Insoluble in pentane, these solvents do not give a homogeneous solution.

The boron nitride precursor was subjected to size exclusion chromatography (size exclusio), which was detected by absorption of ultraviolet light at 270 nm using DMF as a solvent.
nchromatography) shows a single peak. The weight average molecular weight of the boron nitride precursor calculated in terms of polystyrene is in the range of 3,000 to 7,000, and the polydispersity (weight average molecular weight / number average molecular weight) is in the range of 1.5 to 2.5.

The infrared absorption spectrum of this boron nitride precursor is 3500-2500 cm ^-1 , 1750-85.
Shows the each broad absorption in the 0 cm ^-1 and 850~400cm ^-1, shoulder is present in 1700~1600cm ^-1.

This boron nitride precursor is heated at 600 to 2200 ° C. in a non-oxidizing atmosphere such as an inert gas such as nitrogen or argon or an ammonia gas,
Decomposes without melting and produces hexagonal or turbostratic boron nitride. For example, the weight loss due to thermal decomposition in a nitrogen atmosphere is almost completed in the range of 600 to 900 ° C., and the amount of boron nitride produced relative to the boron nitride precursor is the same as that of the boron trihalide, nitrile compound or chloride used. Although depending on the ammonium or amine hydrochloride, it is in the range of 15 to 60% by weight based on the boron nitride precursor.

By dissolving the boron nitride precursor in a precursor-soluble solvent such as DMF, an orange or brown transparent spinning solution can be obtained. The preferred concentration range of the spinning solution depends on the spinning method, but is 0.01 to 1.0 g / ml, and the viscosity at that time is 10 to 5000 P.

When this spinning solution is left to stand in the air, it is gradually hydrolyzed by the water content in the air to produce a yellowish white precipitate, so that it is usually stored in a dry air atmosphere.

As a method for spinning the spinning solution, a widely known method can be used, and examples thereof include a method of extruding the spinning solution from a spinning nozzle by gas pressure or centrifugal force. The boron nitride fiber is obtained by heat-treating the fiber spun from the spinning solution. The heat treatment is performed in an atmosphere of an inert gas such as nitrogen gas or an ammonia gas at 60
It may be heated at a high temperature of 0 ° C. or higher, preferably 800 ° C. or higher to dissociate and separate carbon, hydrogen, halogen and the like.

[0040]

Industrial Applicability According to the present invention, boron nitride or boron nitride fiber can be produced without using expensive and chemically unstable borazines, decaborane, etc., and without further complicated production steps. be able to. This result demonstrates that the present invention can be highly evaluated as an industrial boron nitride precursor manufacturing technique.

[0041]

EXAMPLES The present invention will be described in detail with reference to the following examples, but the invention is not limited thereto. Example 1 A stirrer is provided in the middle tube of a 1-liter three-necked flask, and boron trichloride is provided in one of the side tubes. A Dewar cold finger with a cylinder containing was attached, and a ball cooling tube was attached to the remaining side tubes. A Dewar type cold finger was attached to the ball cooling tube, and a calcium chloride tube was attached to the outlet of the cold finger. 200 ml of nitrogen per minute to this device
After being circulated for 4 hours to dry the inside of the apparatus, 300 ml of chlorobenzene dried with anhydrous sodium sulfate overnight and 16.4 g of acetonitrile were added. Two cold fingers were filled with dry ice-acetone, and while stirring with a stirrer, 60 g of boron trichloride was dropped from the cold fingers directly attached to the three-neck flask over 2 hours. This produced a white boron trichloride acetonitrile adduct. After finishing the addition of boron trichloride,
Remove the cold fingers attached directly to the three-necked flask and dry overnight at 110 ° C with ammonium chloride.
1.5 g was added. When this suspension was heated to 125 ° C. for 8 hours, hydrogen chloride was hardly generated and a brown precipitate was formed. The precipitate formed is filtered off and chlorobenzene 1
Washed with 00 ml and dried under reduced pressure to produce boron nitride precursor 24
g (yield 83%) was obtained.

This boron nitride precursor has a Mw = 5000.
It was a single substance having a molecular weight and a molecular weight distribution such that Mw / Mn = 2.08 (in terms of polystyrene). As a result of elemental analysis, the atomic percentages of boron, nitrogen, chlorine, carbon and hydrogen were 20.8, 20.4, 15.
1, 7.1 and 36.8%.

Infrared absorption spectrum of this boron nitride precursor
The wave number is 3500 to 2500 cm ^-1, 1750-85
0 cm^-1And 850-400 cm^-1Each is broad
Shows absorption, 1700 to 1600 cm-¹On the shoulder
Existed.

10 g of this boron nitride precursor was added to DMF30.
After dissolving in 0 ml, 100 ml of DMF was distilled off to obtain a uniform viscous solution. A large number of fibers having a length of about 1 m were spun by immersing the tip of a glass rod in this solution and pulling it up while changing the pulling speed variously. When the obtained fiber was heated to 1500 ° C. at a temperature rising rate of 5 ° C./min under a nitrogen stream and held for 1 hour to be heat-treated, a fiber having a fiber diameter of 1 to 100 μm was obtained. As a result of powder X-ray diffraction and thermal analysis, it was confirmed to be hexagonal or turbostratic boron nitride.

Example 2 A stirrer was attached to the middle tube of a 1-liter three-necked flask, a dropping funnel containing 128 g of boron tribromide was placed in one of the side tubes, and a ball containing cooling tube was attached to the remaining side tubes. A calcium chloride tube was attached to the outlet of the ball containing cooling tube. Nitrogen is added to this device at 200 m / min
After being circulated at 1 for 4 hours to dry the inside of the apparatus, 300 ml of chlorobenzene dried overnight with anhydrous sodium sulfate and 16.4 g of acetonitrile were added. While stirring with a stirrer, boron tribromide was added dropwise from the dropping funnel over 2 hours. This produced a white boron tribromide acetonitrile adduct. After dropping the boron tribromide, remove the dropping funnel attached to the three-necked flask,
21.5 g of ammonium chloride dried at 110 ° C. overnight was added. The suspension was heated at 125 ° C. for 8 hours, filtered, washed with 100 ml of chlorobenzene, and dried under reduced pressure to obtain a brown precipitate (48 g, yield 80%).

After dissolving 15 g of this precipitate in 300 ml of DMF, 100 ml of DMF was distilled off to obtain a uniform viscous solution. Dip the tip of the glass rod into this solution,
A large number of fibers having a length of about 1 m were spun by pulling while changing the pulling speed variously.

The obtained fiber was heated at 5 ° C. under a nitrogen stream.
When the temperature was raised to 1500 ° C. at a temperature rise rate of min and held for 1 hour to perform heat treatment, fibers having a fiber diameter of 1 to 100 μm were obtained. As a result of powder X-ray diffraction and thermal analysis,
It was confirmed to be hexagonal or turbostratic boron nitride.

Example 3 A stirrer was attached to the middle tube of a 1-liter three-necked flask, a dropping funnel containing 16.4 g of acetonitrile was placed in one of the side tubes, and a ball containing cooling tube was attached to the remaining side tubes. A calcium chloride tube was attached to the outlet of the ball containing cooling tube. This equipment is filled with nitrogen 20
After flowing with 0 ml for 4 hours to dry the inside of the apparatus, 300 ml of chlorobenzene dried with anhydrous sodium sulfate overnight and 200 g of boron triiodide were added. While stirring with a stirrer, acetonitrile was added dropwise from the dropping funnel over 2 hours. This produced a white boron triiodide acetonitrile adduct. After the addition of boron triiodide was completed, the cold finger directly attached to the three-necked flask was removed, and 21.5 g of ammonium chloride dried at 110 ° C. overnight was added. This suspension is heated to 125 ° C for 8 hours.
After heating for an hour, it was filtered off, washed with 100 ml of chlorobenzene and dried under reduced pressure to give 65 g of brown precipitate (yield 79
%) Was obtained.

After dissolving 20 g of this precipitate in 300 ml of DMF, 100 ml of DMF was distilled off to obtain a uniform viscous solution. Dip the tip of the glass rod into this solution,
A large number of fibers having a length of about 1 m were spun by pulling while changing the pulling speed variously.

The obtained fiber was heated at 5 ° C. under a nitrogen stream.
When the temperature was raised to 1500 ° C. at a temperature rise rate of min and held for 1 hour to perform heat treatment, fibers having a fiber diameter of 1 to 100 μm were obtained. As a result of powder X-ray diffraction and thermal analysis,
It was confirmed to be hexagonal or turbostratic boron nitride.

Example 4 A stirrer was attached to the middle tube of a 1-liter three-necked flask, a Dewar type cold finger with a cylinder containing boron trichloride was attached to one of the side tubes, and a ball containing cooling tube was attached to the remaining side tubes. .. A Dewar type cold finger was attached to the ball cooling tube, and a calcium chloride tube was attached to the outlet of the cold finger. 200 ml of nitrogen per minute to this device
After being circulated for 4 hours to dry the inside of the apparatus, 300 ml of chlorobenzene dried with anhydrous sodium sulfate overnight and 16.4 g of acetonitrile were added. Two cold fingers were filled with dry ice-acetone, and while stirring with a stirrer, 60 g of boron trichloride was dropped from the cold fingers directly attached to the three-neck flask over 2 hours. This produced a white boron trichloride acetonitrile adduct. After finishing the addition of boron trichloride,
Remove the cold finger attached directly to the three-necked flask and dry it at 110 ° C overnight.
7.2 g was added. When this suspension was heated to 125 ° C. for 8 hours, hydrogen chloride was hardly generated and a brown precipitate was formed. The precipitate formed is filtered off and chlorobenzene 1
It was washed with 00 ml and then dried under reduced pressure to obtain 25 g (yield 80%) of a boron nitride precursor.

After dissolving 10 g of this precipitate in 300 ml of DMF, 100 ml of DMF was distilled off to obtain a uniform viscous solution. Dip the tip of the glass rod into this solution,
A large number of fibers having a length of about 1 m were spun by pulling while changing the pulling speed variously.

The obtained fiber was heated at 5 ° C. under a nitrogen stream.
When the temperature was raised to 1500 ° C. at a temperature rise rate of min and held for 1 hour to perform heat treatment, fibers having a fiber diameter of 1 to 100 μm were obtained. As a result of powder X-ray diffraction and thermal analysis,
It was confirmed to be hexagonal or turbostratic boron nitride.

Example 5 A stirrer was attached to the inner tube of a 1-liter three-necked flask, a Dewar cold finger with a cylinder containing boron trichloride was attached to one of the side tubes, and a ball containing cooling tube was attached to the remaining side tubes. .. A Dewar type cold finger was attached to the ball cooling tube, and a calcium chloride tube was attached to the outlet of the cold finger. 200 ml of nitrogen per minute to this device
After being circulated for 4 hours to dry the inside of the apparatus, 300 ml of chlorobenzene dried over anhydrous sodium sulfate overnight and 41.2 g of benzonitrile were added. Two cold fingers were filled with dry ice-acetone, and while stirring with a stirrer, 60 g of boron trichloride was dropped from the cold fingers directly attached to the three-neck flask over 2 hours. This produced a white boron trichloride benzonitrile adduct. After finishing the addition of boron trichloride,
Remove the cold fingers attached directly to the three-necked flask and dry overnight at 110 ° C with ammonium chloride.
1.5 g was added. When this suspension was heated to 125 ° C. for 8 hours, hydrogen chloride was hardly generated and a brown precipitate was formed. The precipitate formed is filtered off and chlorobenzene 1
It was washed with 00 ml and then dried under reduced pressure to obtain 27 g (yield 79%) of a boron nitride precursor.

After dissolving 10 g of this precipitate in 300 ml of DMF, 100 ml of DMF was distilled off to obtain a uniform viscous solution. A large number of fibers having a length of about 1 m were spun by immersing the tip of a glass rod in this solution and pulling it up while changing the pulling speed variously. The obtained fiber was subjected to 1 at a heating rate of 5 ° C./min under a nitrogen stream.
When the temperature was raised to 500 ° C. and heat treatment was performed for 1 hour, fibers having a fiber diameter of 1 to 100 μm were obtained. As a result of powder X-ray diffraction and thermal analysis, it was confirmed to be hexagonal or turbostratic boron nitride.

Example 6 A stirrer was attached to the middle tube of a 1-liter three-necked flask, a Dewar cold finger with a cylinder containing boron trichloride was attached to one of the side tubes, and a ball containing cooling tube was attached to the remaining side tubes. .. A Dewar type cold finger was attached to the ball cooling tube, and a calcium chloride tube was attached to the outlet of the cold finger. 200 ml of nitrogen per minute to this device
After being circulated for 4 hours to dry the inside of the apparatus, 300 ml of chlorobenzene dried over anhydrous sodium sulfate overnight and 41.2 g of acrylonitrile were added. Two cold fingers were filled with dry ice-acetone, and while stirring with a stirrer, 60 g of boron trichloride was dropped from the cold fingers directly attached to the three-neck flask over 2 hours. This produced a white boron trichloride acrylonitrile adduct. After the addition of boron trichloride was completed, the cold finger directly attached to the three-necked flask was removed, and 21.5 g of ammonium chloride dried overnight at 110 ° C. was added. When this suspension was heated to 125 ° C. for 8 hours, hydrogen chloride was hardly generated and a brown precipitate was formed. The formed precipitate was separated by filtration, washed with 100 ml of chlorobenzene, and then dried under reduced pressure to obtain 24 g (yield 77%) of a boron nitride precursor.

After dissolving 10 g of this precipitate in 300 ml of DMF, 100 ml of DMF was distilled off to obtain a uniform viscous solution. A large number of fibers having a length of about 1 m were spun by immersing the tip of a glass rod in this solution and pulling it up while changing the pulling speed variously. The obtained fiber was subjected to 1 at a heating rate of 5 ° C./min under a nitrogen stream.
When the temperature was raised to 500 ° C. and heat treatment was performed for 1 hour, fibers having a fiber diameter of 1 to 100 μm were obtained. As a result of powder X-ray diffraction and thermal analysis, it was confirmed to be hexagonal or turbostratic boron nitride.

Comparative Example 1 47 g of boron trichloride, 16.4 g of acetonitrile,
That is, the reaction was carried out in the same manner as in Example 1 except that the molar ratio of both was 1: 1 to obtain 6 g (yield 21%) of a DMF-soluble brown precipitate.

Claims (3)

[Claims] 1. A boron nitride precursor characterized by reacting an adduct of boron trihalide with a nitrile compound and ammonium chloride or amine hydrochloride in the presence of boron trihalide. Production method. 2. A boron nitride precursor obtained by reacting an adduct of boron trihalide with a nitrile compound and ammonium chloride or amine hydrochloride in the presence of boron trihalide is non-oxidized. A method for producing boron nitride, which comprises performing heat treatment in a neutral atmosphere. 3. A boron nitride precursor obtained by reacting an adduct of a boron trihalide with a nitrile compound and ammonium chloride or an amine hydrochloride in the presence of boron trihalide is a boron nitride precursor. 1. A method for producing a boron nitride fiber, which comprises dissolving the element precursor in a soluble solvent, spinning the solution, and then heat treating the solution in a non-oxidizing atmosphere.