JPH03232709A - Polysilazane for silicon nitride fiber and production thereof - Google Patents

Abstract

PURPOSE:To obtain a perhydropolysilazane suitable for producing silicon nitride fiber by reacting dichlorosilane with a Lewis base and subsequently reacting the resultant complex with ammonia at specific temperature under specified pressure. CONSTITUTION:Dichlorosilane is reacted with a Lewis base at -5 to 20 deg.C under the atmospheric pressure to 10kg/cm<2>G to produce a complex. The complex is reacted with ammonia in a molar ratio of 1:>=3 at -5 to 50 deg.C under a pressure of the atmospheric pressure to 10kg/cm<2>G to provide the objective perhydropolysilazane. The perhydropolysilazane solution is, if necessary, further modified in an inert gas atmosphere or in an atmosphere having an ammonia mol fraction of <=0.85 at -5 to 120 deg.C under the atmospheric pressure to 15kg/ cm<2>G. The perhydropolysilazane has a skeleton composed of structural units of the formula, a number-average mol.wt. of 1400-4000 converted into that of polystyrene, a Mw/Mn ratio of <=7.0 between the weight-average mol.wt. Mw and the number-average mol.wt. Mn and a Si/N molar ratio of 0.75-1.25.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to perhydropolysilazane for silicon nitride fibers and a method for producing the same.

[Conventional technology]

The present applicant has disclosed a perhydropolysilazane that can be used as a precursor for producing silicon nitride and a method for synthesizing the same (Japanese Patent Publication No. 16325/1983). This perhydropolysilazane has a high ceramic yield because its side chains are all hydrogen and does not contain organic groups, and it also has excellent electrical insulation properties because it does not contain carbon. Even if it is solid, it is soluble in solvents, so it is easy to mold, especially to spin, and is therefore useful as a precursor for silicon nitride fibers.

In addition, in order to reduce the Si/N composition ratio of this perhydropolysilazane and increase its molecular weight, it also discloses a method of modifying with annimore and heating polymerization (Japanese Patent Application No. 1-138107, 1138108).

[Problem to be solved by the invention]

The perhydropolysilazane obtained by the above method has a broad molecular weight distribution, and the high molecular weight component tends to cause gelation, so there are the following problems especially in fiber applications where strict property control is required. That is, in the polymer concentration or spinning process, loss occurs due to gelation and the yield of fibers decreases.

In addition, gel is formed during the spinning process, resulting in thread breakage.

Therefore, in view of the above problems, an object of the present invention is to provide a perhydropolysilazane suitable for use in manufacturing silicon nitride fibers and a method for manufacturing the same.

[Means to solve the problem]

In order to achieve the above object, the present invention provides a perhydropolysilazane having a skeleton represented by the following general formula, which has a polystyrene equivalent number average molecular weight of 1400 to 40.
00, ratio M of weight average molecular weight Mw to number average molecular weight Mn
Provided is a perhydropolysilazane for silicon nitride fiber, characterized in that w/Mn is 7°0 or less and the molar composition ratio of Si to N is 0.75 to 1.25.

The perhydropolysilazane of the present invention is a reaction product of dichlorosilane and ammonia, or a product modified by annimore or thermal polymerization, as disclosed at the beginning of the prior art section and as described later. Therefore, it has a skeleton represented by the general formula +5HJH+, and has a structure in which an NH- unit based on ammonia is added to this skeleton.

The molecular weight of the perhydropolysilazane for silicon nitride fibers of the present invention (hereinafter also simply referred to as "polysilazane") is 1400 to 4000 (in terms of polystyrene).
It is. If the molecular weight is less than 1,400, it cannot be shaped into fibers due to insufficient coagulability, and if the molecular weight is less than 4,000,
This is because if it exceeds 100%, gelation tends to occur due to the high molecular weight.

In addition, the molecular weight distribution of polysilazane is the weight average molecular weight M-
and the number average molecular weight Mn (Mw/Mn) is 7.0 or less. This is because when Mw/Mn exceeds 7.0, the thermal stability of polysilazane deteriorates and gelation occurs.

Furthermore, the Si/N molar composition ratio of polysilazane is 0.7.
It should be within the range of 5 to 1.25. This is because if Si 2 /N exceeds 1.25, the mechanical strength of the silicon nitride fiber will drop significantly and the firing conditions for the precursor fiber will become severe. On the other hand, polysilazane with Si/N smaller than 0.75 tends to gel due to its crosslinked structure, making it difficult to handle.

According to the present invention, similarly, as a method for producing polysilazane as described above, dichlorosilane and a Lewis base are reacted at a temperature of -5°C to 20°C and a pressure of atmospheric pressure to 10 kg/cm2G to form a complex. The R form is reacted with 3 mol or more of ammonia per 1 mol of the complex at a temperature of -5°C to 50°C and a pressure of atmospheric pressure to 10 kg/cj G, and if necessary, the perhydrogen A solution of polysilazane is prepared in an inert gas atmosphere or with an annimol mole fraction of 0.85 or less, at a temperature of -5°C to 120°C, and at an atmospheric pressure of up to 15 kg.
Provided is a method characterized in that the reforming is carried out under a pressure of /dG.

Dichlorosilane is used as a starting material. Although it is possible to produce perhydrosilazane using other halosilanes, dichlorosilane is used in the present invention because it is preferred from the viewpoint of handling and economy.

First, a Lewis base is added to this dichlorosilane to form a complex.

The base used is a Lewis base that does not react with the halosilane other than to form an adduct. Examples of such bases include tertiary amines (trialkylamines such as trimethylamine, dimethylethylamine, diethylmethylamine, and triethylamine, pyridine, picoline dimethylaniline, and derivatives thereof), secondary bases having sterically hindered groups, etc. Amines, phosphine, stipine,
Examples include arsine and derivatives thereof (eg, trimethylphosphine, dimethylethylphosphine, methyldiethylphosphine, triethylphosphine, trimethylarsine, trimethylstibine, trimethylamine, triethylamine, etc.). Among these, bases with a low boiling point and less basicity than ammonia (for example, pyridine, picoline, trimethylphosphine, dimethylethylphosphine, methyldiethylphosphine, triethylphosphine) are preferable, and pyridine and picoline are particularly preferred from the viewpoint of handling and economy. The preferred amount of Lewis base to dichlorosilane is 0 in molar ratio.
．． 5 or more, preferably 1.0 or more, more preferably 1.
It is better to set it to 5 or more.

As a reaction medium for forming a complex by adding a Lewis base to dichlorosilane, it is preferable to use a Lewis base alone or a mixture of a non-reactive solvent and a Lewis base. 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, and aliphatic hydrocarbons. Ethers such as cyclic ethers can be used.

Preferred solvents are methylene chloride, chloroform, carbon tetrachloride, bromoform, ethylene chloride, ethylidene chloride,
Halogenated hydrocarbons such as trichloroethane and tetrachloroethane, ethyl ether, isopropyl ether,
Ethers such as ethyl butyl ether, butyl ether, 1,2-dioxyethane, dioxane, dimethyldioxane, tetrahydrofuran, tetrahydropyran, pentane, hexane, isohexane, methylpentane, heptane, isohebtan, octane, isooctane, cyclopenkune, methylcyclopentane, cyclohexane,
Hydrocarbons such as methylcyclohexane, benzene, toluene, xylene, and ethylbenzene. Among these solvents, dichloromethane and pyridine are particularly preferred from the viewpoint of safety.

The concentration of dichlorosilane in the solvent can be set arbitrarily, but it is preferably in the range of 1 to 15% by weight (hereinafter abbreviated as %).

In the present invention, this complex formation is carried out in an inert gas atmosphere.
It is preferable to carry out the reaction at a temperature of 5° C. to 20° C. and a pressure of atmospheric pressure −10 kg/all G. At temperatures above 20"C, pyridine does not react and scatters together with the inert gas, causing blockage of the outlet line and reduction in yield.Furthermore, 5iHzCfz causes disproportionation.

At temperatures below -5°C, a low-temperature refrigerant is required, resulting in high costs. Although there is no particular limitation on the pressure, atmospheric pressure -10 kg/ctAG is desirable for economical reasons.

Since the reaction is extremely fast, the reaction time can be set arbitrarily.

Next, the complex thus produced is reacted with dry ammonia to effect ammonolysis.

The ammonia used at this time may be either gas or liquid. Ammonia is preferably dried by, for example, passing it through solid sodium hydroxide and then passing it through metallic sodium. The amount of ammonia added is 3.0 or more in molar ratio, preferably 4 to 15 to the total amount of dichlorosilane.
It is better to double it. The reaction solvent, reaction pressure, and time may be the same as those used for complex formation. However, in a closed system, ammonia is pressurized. In addition, the amount of water in the reaction system is, for example, 500
It is desirable to set it to less than ppm.

Annimore or an inert gas atmosphere is used as the reaction atmosphere.

The reaction temperature is -5°C to 50°C. Conventionally, ammonolysis was carried out under the same conditions as when forming the complex, but increasing the temperature during the ammonolysis reaction increases the molecular weight of the product, which can be used to control the molecular weight.

After the reaction is completed, ammonium chloride can be removed using conventional means such as filtration to obtain polysilazane. If necessary, add a solvent to dilute and wash the polysilazane before removing ammonium chloride.

The obtained polysilazane can be a polysilazane having the desired characteristic values of the present invention depending on the production conditions, but it is easier to obtain the desired properties by controlling the conditions in combination with the following modification reaction. It is possible to produce polysilazane with characteristic values.

In the modification reaction, the polysilazane solution after removing ammonium chloride is heated at 5°C to 120°C in an ammonia or inert gas atmosphere.
Ammonia is added at a temperature of .degree. C. and a pressure of from atmospheric pressure to 15 kg/cmlG, and the porinrazan crosslinking reaction is carried out for about 0.5 to 30 hours.

At this time, the ammonia mole fraction in the polysilazane solution is set to 0.85 or less. If the ammonia fraction is 0.85 or more, the reforming reaction rate is too fast, making it difficult to control the molecular weight and S i /N ratio. In this modification reaction, especially Si/N
The molecular weight can be adjusted with the ratio. The molecular weight and Si/N ratio can be controlled by changing the amount of NH3 dissolved in pyridine, reaction temperature, and time.

Molecular weight can be controlled by varying the heating time and temperature. If the temperature is low, the reaction rate is slow, requiring a long heating time; if the temperature is high, the reaction rate is too fast, making control difficult. The Si/N ratio can be controlled by changing the reaction time and the ammonia mole fraction in the polysilazane solution. Increasing the ammonia mole fraction lowers the Si/N ratio of the reaction product. In addition, if the reaction time is long, Si
/N ratio decreases. If the temperature is increased while the pressure is constant, the ammonia mole fraction decreases, so the reaction temperature, pressure, and time are adjusted to match the number average molecular weight and Si/N ratio of the final product.

As described above, in the present invention, by controlling (1) complex formation of dichlorosilane, (2) ammonolysis reaction, (3) modification reaction, especially reactions (2) and (3), and modification conditions, Perhydropolysilazane for silicon nitride fibers having the desired characteristic values aimed at by the present invention can be produced.

〔Example〕

The Ko-311 reactor is shown in Figure 1. In Figure 1, 1 is a dichlorosilane storage tank, 2 is a solvent storage tank, 3 is a reactor, 4 is a nitrogen gas pipe,
5 is an ammonia gas pipe, 6 is a constant temperature oven, 7 is a motor, 8
1 is a heater linked to a thermometer 9, and 10 is an exhaust gas pipe. The following reactions were carried out using this apparatus.

After purging the inside of the reactor installed in a constant temperature bath with a temperature of 0°C with dry nitrogen, 900 m of dry pyridine was added and the temperature was maintained until the temperature became constant. Dichlorosilane (
101.0 g of Si82C12) was added to obtain a white solid adduct. The reaction mixture was cooled to OOC and 72 g of dry ammonia was bubbled in while stirring.

After the reaction was completed, dry nitrogen was blown in to remove unreacted ammonia, and the filtrate was filtered under pressure under a nitrogen atmosphere.
I got m. Dry this filtrate. 1,000 m of -xylene was added, and the solvent was removed under reduced pressure until it became about 900 -. Furthermore, 1,000 d of dry O-xylene was added and distilled under reduced pressure again to obtain 700 d of solvent. A portion of the solution was separated and the solvent was removed under reduced pressure to obtain a colorless viscous liquid.

When the molecular weight of this viscous liquid was measured by GPC, the number average molecular weight (Mn) was 528, and the weight average molecular weight (Mw
) was 996, and the ratio of weight average molecular weight to number average molecular weight (Mn/Mw) was 1.88.

In addition, as a result of analysis of its IR spectrum (solvent: 0-xylene), the wave number (C1-') was 3350 and 1175.
Absorption based on N-H of 2170; Absorption i based on Si-H of 1020-820 5i-H and 5i-N
-3i-based absorption was confirmed. moreover,
'H-NMR (proton nuclear magnetic resonance) of this polymer
Spectacle (60MHz, solvent; CDCj23
/Reference material TMS) was analyzed and it was 64.8 (br
, 5iHz or 5in) δ4.4 (br, Si
Absorption of H:+), 61.4 (br, NH) was confirmed. Furthermore, the elemental composition (wt%) of the polymer is Si
:64.3 N :26.8. O: 1.9
, C: 2.6.

f1■Eη The following reaction was carried out using the same apparatus as in Reference Example 1.

After replacing the inside of the reactor installed in a constant temperature bath with a temperature of 0°C with dry nitrogen, add 9ooIIdl of dry pyridine and maintain it until the temperature becomes constant, then add 101.0 g of dichlorosilane (SiH2C12) while stirring. In addition, a white solid adduct was obtained. The reaction mixture was then set at 30''C and 72 g of dry ammonia was bubbled in while stirring.

After the reaction was completed, dry nitrogen was blown in to remove unreacted ammonia, and the filtrate was filtered under pressure under a nitrogen atmosphere.
I got -. Dry this filtrate. - 1000m of xylene was added, and the solvent was removed under reduced pressure until it reached about 900d, and dried O-xylene 1000m was added and distilled under reduced pressure again to obtain a 700m solvent. ? A portion of the 8 liquid was separated and the solvent was removed under reduced pressure to obtain a white solid inorganic silazane.

When the molecular weight was measured by GPC, the number average molecular weight (M
n) is 1280, the weight average molecular weight (Mw) is 3359, and the ratio of weight average molecular weight to number average molecular weight (Mw/M
n) was 2.62. According to elemental analysis, the composition ratio of silicon to nitrogen was 1.20.

Husband-masu The following reaction was carried out using the same apparatus as in Reference Example 1.

After replacing the inside of the reactor installed in a constant temperature bath with a temperature of O''C with dry nitrogen, 900 m of dry pyridine was added and the temperature was maintained until the temperature became constant, and dichlorosilane (
101.0 g of SiH2C12) was added to obtain a white solid adduct. The reaction mixture was then heated to 50°C,
While stirring, 72 g of dry ammonia was blown into the solution.

After the reaction was completed, dry nitrogen was blown in to remove unreacted ammonia, followed by pressure filtration in a nitrogen atmosphere to obtain a filtrate 85 (
I got ld. Dry this filtrate. -Xylene 1000- was added, and the solvent was removed under reduced pressure until it became about 900-, and then dried 0-xylene 1000- was added and distilled under reduced pressure again to obtain a solution of 700-. A portion of the solution was separated and the solvent was removed under reduced pressure to obtain a white solid inorganic silazane.

When the molecular weight was measured by GPC, the number average molecular weight (M
n) is 1620, the weight average molecular weight (M-) is 5022, and the ratio of weight average molecular weight to number average molecular weight (Mw/Mn
) was 3.10. According to elemental analysis, the composition ratio of silicon to nitrogen was 1.25.

Furthermore, the solvent was removed under reduced pressure using a rotary evaporator. Vacuum removal was discontinued when the solution became sufficiently stringy. This solution was transferred to a defoaming container of a dry spinning device to obtain a spinning solution. After standing at 60°C for about 2 hours to degas, it was discharged at 30°C from a nozzle with a diameter of 0.1 rm into a spinning tower in a dry air atmosphere at 130°C, and wound at a speed of 300 m/min. Fiber diameter 7. n fibers were obtained.

Next, while applying a tension of 1 kg/now to the spun fibers, from room temperature to 1200° C. in a nitrogen atmosphere,
The temperature was raised at 180° C./hour to obtain silicon nitride fibers.

The tensile strength of this silicon nitride fiber is 200 to 290 kg.
/ tumor 2 (average 230 kg/m2), elastic modulus 16-26
ton/I! lll1” (average 21 tons/■
It was ri. Elemental analysis of this silicon nitride fiber revealed that
Nitrogen was 33.2% by weight and oxygen was 3.3% by weight.

Comparison example 1. When the solvent of the obtained inorganic silazane was removed under reduced pressure using a rotary evaporator, the viscosity was insufficient even after the solvent was completely removed, and the product could not be spun because it did not exhibit spinnability.

About Ml η Reference example 2. The solvent of the obtained inorganic silazane was removed under reduced pressure using a rotary evaporator. Vacuum removal was discontinued when the solution became sufficiently stringy. This solution was easily degassed and transferred to a dry spinning device to obtain a spinning solution. After standing at 60"C for about 2 hours to defoam, the diameter is 0.1 at 30℃.
The fibers were discharged from a nozzle of 130° C. into a spinning tower in a dry air atmosphere at 130° C., and wound up at a speed of 300 m/min to obtain fibers with an average fiber diameter of 10.1 μl.

The spun fibers were then spun from room temperature to 1200″ under a nitrogen atmosphere while applying a tension of 1 kg/me2.
The temperature was raised to C at 180"C/hour, but when the fired silicon nitride fibers were observed with a scanning electron microscope, some of them were fused to the surrounding fibers. The tensile strength of the unfused portions was・When the elastic modulus was measured, the tensile strength was 100 to 190 kg/m+++” (average 150 kg/f
f11112), elastic modulus is 12-20ton/ltm
2 (average 15 tons, /n112).

Fig. 2 shows the Fussen Spotted Stem Reaction Apparatus. In Fig. 2, 1 is an inorganic silazane storage tank, 2 is a reactor, 3 is a nitrogen gas pipe, 4 is an ammonia gas pipe, 5 is a thermostat, 6 is a motor 7, a heater linked to a thermometer 8, and 9 is a pressure gauge. The linked control valve 11 is an exhaust gas pipe.

After replacing the inside of the reactor installed in a constant temperature bath with a temperature of 60°C with dry nitrogen, Reference Example 1. A pyridine solution of the inorganic silazane obtained in step E600- was added and the temperature was maintained until the temperature became constant, and then ammonia gas was injected.

Excess gas is released from the control valve to reduce the reactor pressure to 5 k.
g/cdr G and maintained for 14 hours.

Gas chromatography analysis of the gas released during the process revealed that it contained a large amount of hydrogen.

After the reaction is completed, 700ad! After adding dry O-xylene and blowing dry nitrogen to remove unreacted ammonia,
The solvent was removed under reduced pressure until it reached about 100 d, and 700 Id of dry O-xylene was added and distilled under reduced pressure again to give 50 d.
A solution of 0 m was obtained. A portion of the solution was separated and the solvent was removed under reduced pressure to obtain a white solid silazane.

When the molecular weight was measured by GPC, the number average molecular weight (M
n) is 1927, the weight average molecular weight (Mw) is 7309, and the ratio of weight average molecular weight to number average molecular weight (Mw/Mn
) was 3.79. According to elemental analysis, the composition ratio of silicon to nitrogen was 1.05.

The solvent was removed under reduced pressure using a rotary evaporator. Vacuum removal was discontinued when the solution became sufficiently stringy. This solution was transferred to a defoaming container of a dry spinning device to obtain a spinning solution. After standing at 60"C for about 2 hours to degas the mixture, it was discharged from a nozzle with a diameter of 0.1 m at 30°C into a spinning tower in a dry air atmosphere at 130°C, and wound up at a speed of 300 m/min. Fibers with an average fiber diameter of 7 pa were obtained.

Next, while applying a tension of 1 kg/nm to the spun fibers, the spun fibers were heated from room temperature to 1200° C. for 1 hour under a nitrogen atmosphere.
The temperature was raised at 80° C./hour to obtain silicon nitride fibers.

The tensile strength of this silicon nitride fiber is 220 to 360 kg.
/■t (average 290 kg/m2), elastic modulus is 19
~30 ton/m" (average 24 ton/m). Elemental analysis of this silicon nitride fiber revealed that nitrogen was 35
．． 3% by weight, and oxygen was 2.1% by weight.

Example 2. The reaction was carried out using the same equipment.

After replacing the inside of the reactor installed in a constant temperature bath with a temperature of 30°C with dry nitrogen, Reference Example 1. A pyridine solution of the inorganic silazane obtained in step 600 was added and the temperature was maintained until the temperature became constant, and then ammonia gas was injected.

Excess gas is released from the control valve and the pressure in the reactor is 4 kg.
/cm2G and maintained for 10 hours.

On the way, the gas released was analyzed using a Gas Chromad Goo 7F, and it was found to contain a large amount of hydrogen.

After the reaction was completed, 700 d of dry O-xylene was added and dry nitrogen was blown in to remove unreacted ammonia.
00 ad! The solvent was distilled off under reduced pressure until the residue was dissolved, and this operation was repeated two more times. A portion of the solution was taken and the solvent was removed under reduced pressure to obtain silazane as a white solid.

When the molecular weight was measured by GPC, the number average molecular weight (M
n) is 2201, weight average molecular weight (M- is 8692, ratio of weight average molecular weight to number average molecular weight (M wr/M
n) was 3.95. According to elemental analysis, the composition ratio of silicon to nitrogen was 0.95.

Furthermore, the solvent was removed under reduced pressure using a rotary evaporator. Vacuum removal was discontinued when the solution became sufficiently stringy. This solution was transferred to a defoaming container of a dry spinning device to obtain a spinning solution. After standing at 60°C for about 2 hours to degas the mixture, it was discharged at 30°C from a nozzle with a diameter of 0.1 mm into a spinning tower in a dry air atmosphere at 130°C, and wound at a speed of 300 m/min. Fibers with a fiber diameter of 7 μm were obtained.

Next, while applying a tension of 1 kg/m2 to the spun fibers, the spun fibers were heated for 1 hour from room temperature to 1200''C in a nitrogen atmosphere.
The temperature was raised at 80° C./hour to obtain silicon nitride fibers.

The tensile strength of this silicon nitride fiber is 280 to 380 kg.
/=2 (average 320 kg/am”), elastic modulus is 2
1~30ton/ttm” (average 25ton/ma
+”).

Huarashi opening example 2. The following reaction was carried out using the same apparatus as .

After replacing the inside of the reactor installed in a constant temperature bath with a temperature of 80°C with dry nitrogen, Reference Example 1. 600 d of the pyridine solution of the inorganic silazane obtained in step 1 was added and kept in a closed system for 20 hours while pressurized with nitrogen. During this time, a large amount of gas was generated and the pressure rose, but analysis by gas chromatography revealed that the gas generated was hydrogen. After the reaction is completed, 100 d
Dry ethyl hanzene was added thereto, and the solvent was distilled off under reduced pressure at a temperature of 60°C to obtain a white solid inorganic silazane.

When the molecular weight was measured by GPC, the number average molecular weight (M
n) is 2312, weight average molecular weight (M- is 10599, ratio of weight average molecular weight to number average molecular weight (Mh/Mn)
) was 4.59. According to elemental analysis, the composition ratio of silicon to nitrogen was 1.20.

Toluene was added to this white powder to gradually dissolve it, and when the solution became sufficiently stringable, the addition of toluene was stopped. This solution was transferred to the degassing container of the dry spinning device and left to stand at 60°C for about 2 hours to defoam, and then heated to 40°C with a diameter of 0.0.
It was discharged from an 8m+ nozzle into a spinning tower under a dry air atmosphere at 130°C and wound up at a speed of 500m/min to obtain fibers with an average fiber diameter of 10#11.

Next, while applying a tension of 1 kg/■2 to the spun fibers, the spun fibers were heated from room temperature to 1200° C. for 18 hours in a nitrogen atmosphere.
The temperature was raised at 0° C./hour to obtain silicon nitride fibers.

The tensile strength of this silicon nitride fiber is 220 to 310 kg.
/IIIm'' (average 260 kg/mI), elastic modulus was 13-23 ton/mt (average 19 ton/m).

Husband±l Example 2. The reaction was carried out using the same equipment as.

After replacing the inside of the reactor installed in a constant temperature bath with a temperature of 120°C with dry nitrogen, Reference Example 1. 600 ml of the pyridine solution of the inorganic silazane obtained in step 1 was added and kept in a closed system for 12 hours while pressurized with nitrogen. During this time, a large amount of gas was generated and the pressure rose, but analysis by gas chromatography revealed that the gas generated was hydrogen. After the reaction, 700
- Dry ethylbenzene was added and the solvent was distilled off under reduced pressure at a temperature of 60°C to obtain a white solid inorganic silazane.

When the molecular weight was measured by GPC, the number average molecular weight (M
n) is 3290, weight average molecular weight (M-) is 19730
and the ratio of weight average molecular weight to number average molecular weight (M w/
Mn) was 6.00. According to elemental analysis, the composition ratio of silicon to nitrogen was 1822.

This white powder was used in Example 3. Spinning and firing were performed in the same manner as above to obtain silicon nitride fibers. The tensile strength of this silicon nitride fiber is 160 to 280 kg/m'' (average 220 kg/-
2) The elastic modulus was 15 to 30 tons/1111'' (average 21 tons/-).

Pig 11 reference Example 2. The reaction was carried out using the same equipment.

After purging the inside of the reactor installed in a constant temperature bath with a temperature of 60°C with dry nitrogen, 600 m of the pyridine solution of the inorganic silazane obtained in Reference Example 2 was added, and the temperature was maintained until the temperature became constant, and then ammonia gas was added. was injected.

Excess gas is released from the control valve and the pressure in the reactor is 5 kg.
/CdG and held for 14 hours.

Gas chromatography analysis of the gas released during the process revealed that it contained a large amount of hydrogen.

After the reaction was completed, 700 jd of dry O-xylene was added and dry nitrogen was blown into the flask to remove unreacted ammonia, and then the solvent was distilled off under reduced pressure until it became about 700 jle, and this operation was repeated two more times. A portion of the solution was separated and the solvent was removed under reduced pressure to obtain a white solid inorganic silazane.

When the molecular weight was measured by GPC, the number average molecular weight (M
n) is 2950, weight average molecular weight (M-) is 13730
and the ratio of weight average molecular weight to number average molecular weight (M w/
Mn) was 4.65. According to elemental analysis, the composition ratio of silicon to nitrogen was 1.02.

Finally, the solvent was removed under reduced pressure using a rotary evaporator. Vacuum removal was discontinued when the solution became sufficiently stringy. This solution was transferred to a defoaming container of a dry spinning device to obtain a spinning solution. After standing at 60°C for approximately 2 hours to defoam, the product was discharged at 30°C from a nozzle with a diameter of 0.1 mm into a spinning tower in a dry air atmosphere at 130°C, and wound at a speed of 300 m/min. , average fiber diameter 7. n fibers were obtained.

Next, while applying a tension of 1 kg/mi+'' to the spun fibers, the temperature was increased from room temperature to 1200°C under a nitrogen atmosphere.
The temperature was raised at 180° C./hour to obtain silicon nitride fibers.

The tensile strength of this silicon nitride fiber is 220 to 350 kg.
/B2 (average 300 kg/mm2), elastic modulus is 20-3
2ton/l1II112 (average 25ton/■2)
Met.

Note that among the above examples, the polysilazane obtained in Reference Example 1.2 and Comparative Example 1 could not be spun.

The main results of the above are shown in the table below.

Example 2. The reaction was carried out using the same equipment.

After replacing the inside of the reactor installed in a constant temperature bath with a temperature of 0° C. with dry nitrogen, Reference Example 1. A pyridine solution of the inorganic silazane obtained in step 600 was added and the temperature was maintained until the temperature became constant, and then ammonia gas was injected.

Excess gas is released from the control valve to reduce the reactor pressure to 2.5
kg/cm2G and maintained for 1 hour.

Gas chromatography analysis of the gas released during the process revealed that it contained a large amount of hydrogen.

After the reaction was completed, 700 d of dry O-xylene was added and dry nitrogen was blown in to remove unreacted ammonia.
The solvent was distilled off under reduced pressure until it reached 00d, and this operation was repeated two more times. A portion of the solution was separated and the solvent was removed under reduced pressure to obtain a white solid inorganic silazane.

When the molecular weight was measured by C, PC, the number average molecular weight (
Mn) is 1421, weight average molecular weight (M-) is 5826
and the ratio of weight average molecular weight to number average molecular weight (Mw/
M n ) was 4.10. From elemental analysis, the composition ratio of silicon to nitrogen was 0.86.

Furthermore, the solvent was removed under reduced pressure using a rotary evaporator. Vacuum removal was discontinued when the solution became sufficiently stringy. This solution was transferred to a degassing container of a dry spinning device, left to stand at 60°C for about 2 hours, and then passed through a nozzle with a diameter of 0.1 mm at 30°C to a spinning tower in a dry air atmosphere at 130°C. The fibers were discharged into a tube and wound at a speed of 300 m/min to obtain fibers with an average fiber diameter of 7.

Next, while applying a tension of 1 kg/m'' to the spun fibers, the spun fibers were heated for 1 hour from room temperature to 1200'C under a nitrogen atmosphere.
The temperature was raised at 80° C./hour to obtain silicon nitride fibers.

The tensile strength of this silicon nitride fiber is 240 to 380 kg.
/ Cabinet 2 (average 330 kg/■, elastic modulus 25-35
ton/m" (average 28 ton/a+m").

[Effects of the Invention] According to the present invention, perhydropolysilazane suitable as a precursor for producing silicon nitride fibers can be obtained, facilitating spinning and improving the yield of fibers.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of a synthesis apparatus of an example. 1... Dichlorosilane tank, 2... Solvent tank, 3...
Reactor, 4... Nitrogen gas pipe, 5... Ammonia pipe, 6... Constant temperature bath.

Claims (1)

[Claims] 1. A perhydropolysilazane having a skeleton represented by the general formula ▲ Numerical formulas, chemical formulas, tables, etc. ▼, which has a polystyrene equivalent number average molecular weight of 1400 to 40
00, the ratio Mw/Mn of weight average molecular weight Mw to number average molecular weight Mn is 7.0 or less, and the molar composition ratio of Si and N is 0.75 to 1.25. Perhydropolysilazane for textiles. 2. React dichlorosilane and Lewis base at a temperature of -5°C to 20°C and a pressure of atmospheric pressure to 10 kg/cm^2G to form a complex, and add 3 moles or more of ammonia per 1 mole of the complex to the complex. -5℃~50℃ temperature, atmospheric pressure~10k
The method for producing perhydropolysilazane for nitrided fibers according to claim 1, characterized in that the reaction is carried out under a pressure of g/cm^2G. 3. The perhydropolysilazane obtained by the method according to claim 2 is further heated at -5°C to - A method for producing perhydropolysilazane for silicon nitride fibers, which is modified at a temperature of 120°C and a pressure of atmospheric pressure to 15 kg/cm^2G.