JPS6050884B2 - Method for producing silicon carbide fiber mainly composed of SiC - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing silicon carbide fibers mainly made of SiC.

The present inventors previously applied for a patent in 1986-265.
No. 27, Special Publication No. 58-38534, Special Publication No. 57-53
No. 892, JP-A-51-149925, JP-A-51-
No. 149926, Japanese Patent Publication No. 57-53893, Japanese Patent Publication No. 1977
As described in Japanese Patent Publication No. 1-147624, Japanese Patent Publication No. 57-56566, Japanese Patent Publication No. 58-38535, and Japanese Patent Publication No. 57-53894, organic silicon polymer compounds having silicon and carbon as main skeleton components are spun. After heating the spun fiber at a low temperature in an oxidizing atmosphere, the spun fiber is heated in a vacuum or at least one kind selected from inert gas, CO gas, hydrogen gas, hydrocarbon gas, organosilicon compound gas, and ammonia gas. After preheating in an atmosphere, silicon carbide fibers are obtained by firing at a high temperature in a temperature range of 1000 to 2000°C in a vacuum or at least one atmosphere selected from inert gas, CO gas, and hydrogen gas. Invented something that can be done.

The present invention relates to an improvement of the invention of the present inventors,
The purpose of this invention is to produce silicon carbide fibers mainly made of SlC at low cost and in large quantities, which have high strength and excellent oxidation resistance at high temperatures. Invented it and applied for a patent in 1986-34.
Silicon carbide fibers mainly made of SiC are made using an organosilicon polymer compound mainly made of carbon and silicon containing at least one of the different elements other than silicon, carbon, hydrogen, and oxygen described in 01 Trowel. By obtaining this, you can achieve your goal.

The present invention provides a new method for producing an organosilicon polymer compound mainly composed of carbon and silicon containing at least one element selected from Ti, MO, Cr, or Pr in its structure at low cost and in large quantities. This is what I discovered and came up with the invention.

The present invention relates to a combined application of the following first invention and second invention. First invention (1) Compound containing only Si-C bonds.

(2) Compounds containing Si-H bonds in addition to Si-C bonds.

(3) A compound having a Si-Hal bond.

(4) A compound having a Si-0R (R=alkyl, aryl) bond.

(5) Compound having S1-0H bond.

(6) Compounds containing Si-Si bonds.

(7) Compound containing Sj-0-Si bond.

(8) Organosilicon compound esters. (9) Organosilicon compound peroxide.

at least one compound selected from the organosilicon compounds of (1) to (9) above, and Ti, MO, Cr.
or Pr, using as a starting material a mixture with an organometallic compound containing at least one metal element selected from Pr, and produced by a polycondensation reaction by at least one of adding a polycondensation catalyst, irradiation, and heating. a first step of producing an organosilicon polymer compound whose main skeleton components are silicon and carbon containing at least one metal element selected from Ti, MO, Cr, or Pr; A second step of obtaining an organosilicon polymer compound with a low content of low molecular weight compounds from a polymer compound, a third step of preparing a spinning stock solution of the organosilicon polymer compound and spinning it, and performing the spinning in an oxidizing atmosphere. A fourth step of heating at a low temperature under the action of tension or no tension, and heating the spun yarn heated at a low temperature in a vacuum or in a small amount of one or more selected from air, oxygen, ozone, and steam. , in a vacuum, in a mixed atmosphere of one or more selected from inert gas, CO gas, hydrogen gas, hydrocarbon gas, organosilicon compound gas, and ammonia gas under tension or no tension. A fifth step of preheating at a temperature of ~1300'C, and treating the preheated spun yarn with a strong acid, molten salt or phosphoric acid to remove S contained in the spun yarn.
A 6th step of removing by-product impurities such as graphite, free carbon, and silica other than 1C, and a 7th step of heating at a high temperature of 800 to 2000°C in a vacuum or non-oxidizing gas atmosphere. A method for producing silicon carbide fiber mainly made of SiC.

Second invention (1) Compounds containing only Si-C bonds.

(2) Compounds containing Sj-H bonds in addition to Si-C bonds.

(3) Compound having S]-Hal bond.

(4) A compound having a Si-0R (R=alkyl, aryl) bond.

(5) Compound having S1-0H bond.

(6) Compounds containing Si-Sj bonds.

(7) Compounds containing Si-0-Si bonds.

(8) Organosilicon compound esters. (9) Organosilicon compound peroxide.

at least one compound selected from the organosilicon compounds of (1) to (9) above, and Ti, MO, Cr.
Or Ti, MO produced by a polycondensation reaction using a mixture with an organometallic compound containing Pr as a starting material and at least one of adding a polycondensation catalyst, irradiation, and heating.
, Cr, or Pr, a first step of producing an organosilicon polymer compound whose main skeleton components are silicon and carbon, the structure of which contains at least one metal element selected from Cr, or Pr; A second step of obtaining an organosilicon polymer compound with a low content of low molecular weight compounds from the compound, a third step of preparing and spinning a spinning dope of the organosilicon polymer compound, and spinning the spinning material under tension or under an oxidizing atmosphere. A fourth step of heating at a low temperature under the action of no tension, and heating the spun yarn heated at a low temperature in a vacuum or in a small amount of air, oxygen, ozone, or steam.
species or more, in vacuum, inert gas, CO gas, hydrogen gas,
800 to 1300°C under tension or no tension in a mixed atmosphere consisting of one or more selected from hydrocarbon gas, organosilicon compound gas, and ammonia gas.
a fifth step of preheating at a temperature of 6 step, and a 7th step of heating at a high temperature of 800 to 2000 ° C. in vacuum or in an atmosphere of non-oxidizing gas, and in an atmosphere of at least one of oxygen gas, air, ozone, and water vapor. 800~1600'C
and an eighth step of removing free carbon during spinning by treatment at a temperature of .

Next, the present invention will be explained in detail.

In the present invention, at least one or more of the organosilicon compounds (1) to (9) described below and Ti, MO,
A mixture of Cr or Pr with at least one organometallic compound can be used as a starting material.

(However, R in the formula represents an alkyl group or an allyl group 7.) (
1) Compound containing only Si-C bonds R4S called silane hydrocarbon (SilahydrOcarbOn)
This includes R3Si(R″SiR)NR″SjR2 and its carbon monofunctional derivatives.

Example (CH3)4Si, (CH2=CH)
4Si,(CH3)3S1C=CSi(CH3)3,(
CH2)5S1 (CH2)4, (C2H5)3S1CH
2CH2C1, (C6H5)3S1C02H, (2)S
Compounds containing Si-H bonds in addition to j-C bonds: mono-, di-, and triorganosilanes belong to this category.

Example (C2H5)2SiH2, (CH2)5SiH
2, (CH3)3S1CH2Si(CH3)2H,C1
CH2SiSiH3, (3) Compound having Si-Hal bond Organohalogensilane excluding monosilane.

Example CH2=CHSiF3, C2H5SiHCI2, (C
H3)2(CICH2)SlSi(CH3)2C1(C
6H5)3SiBr, (4)Si-0R1 organoalkoxy (or alloxy) silane.

Example (CH3)2S1(0C2H5)2,C2H5S
1C12(0C2H5), P-ClC6HlOSi(C
H3) 3, (5) Compounds having Si-0H bond Examples of organosilanols (C2H5)3S10H, (C
H3)2Si(0H)2,C6H5Si(0H)3,(
HO)(CH3)2SiCH2Si(CH3)2(0H
), (6) Examples of compounds containing Si-Si bonds (CH3)3SiSi(CH3)2C1, (CH
3) 3SiSi(CH3)3, (C6H5)3SiSi
(C6H5)2Si(C6H5)2C1, (7)Si-
It is a compound containing an 0-Si bond, orkanosiloxane.

Example (CH3)3Sj0Si(CH3)3,H0(CH3
)2Si0Si(CH3)20H,C12(CH3)S
iOSi(CH3)CIOSi(CH3)Cl2, [(
C6H5)2Si0]4, CH2=C(CH3)CO2
CH2Si● (CH3)2CH202C(CH3)=
CH2, (8) Organosilicon compound ester; an ester thought to be formed from silanol and acid;
3) 2Si(0C0CH3)2, etc. belong to this category.

(9) Organosilicon compound peroxide: (CH3)3Sj
00C(CH3)3;(CH3)3Si00Si(CH
3) 3 etc. (10) Organometallic compound (coordination-containing compound) containing Ti, MO, Cr or Pr. TiC, Cr3C
2, MO2C, Cr2O3, TiB2, COB, MOB
The ratio of mixing the organometallic compound to the organosilicon compound is such that the metal element contained in the produced polymer is from 0.01 to
A range of 20% is good; if the amount of the metal element is 0.01% or less, the effect of adding the metal element is not significant, and if the amount of the metal element is 20% or more, the organosilicon polymer compound containing the metal element is not produced, a range of 0.01 to 20% is suitable.

The mixture raw material is heated in a temperature range of 200 to 1500°C in vacuum or inert gas, hydrogen gas, CO gas, CO2
Under any atmosphere selected from gas, hydrocarbon gas, and organosilicon compound gas, and if necessary under pressure,
An organosilicon polymer compound containing a metal element can be synthesized by polycondensation. In the synthesis reaction, 2
At temperatures lower than 00°C, the synthesis reaction does not proceed sufficiently, and at temperatures higher than 1500°C, the reaction proceeds too much, resulting in an inorganic compound mainly composed of SiC.
A temperature range of 1500'C is advantageous and 30
Best results are obtained in a temperature range of 0 to 1200°C.

In the synthesis reaction, a radical initiator may be added to the starting materials in an amount of 10% or less, if necessary.

As the radical initiator, benzoyl peroxide, di-tert-butyl peroxyoxalate, di-tert-butyl peroxide, azoisobutyronitrile, etc. can be used. Although these radical initiators are not necessarily required in the synthesis reaction, their use can lower the reaction initiation temperature by subsequent heating or increase the average molecular weight of the heated product. . In the above synthetic reaction, if oxygen is present during the heating reaction, the radical polycondensation reaction will not occur due to oxygen, or even if it occurs, it will stop midway, so inert gas, hydrogen gas, CO gas, CO2 gas, carbonization Selected from hydrogen gas and organosilicon compounds. It is necessary to heat the material under at least one type of atmosphere or under vacuum. During the pyrolysis polycondensation reaction in the synthesis reaction, pressure is applied, so pressurization is not necessarily necessary, but if pressurized, the inert gas, hydrogen gas,
Pressurization can be performed using an atmosphere of one or more selected from CO gas, CO2 gas, hydrocarbon gas, and organosilicon compounds.

An example of a device for carrying out the synthesis reaction is a stationary autoclave. In this case, the heating temperature is 300-50
A temperature range of 0°C is preferred. Furthermore, as another example of carrying out the above-mentioned synthesis reaction, there is a flow type apparatus shown in the figure.
In the figure, raw materials are charged into heating device 2 through valve 1, and
Temperature range from 00 to 1500'C, preferably from 500 to 12
The organosilicon polymer compound containing the organometallic compound of the present invention in the reaction product is sent to the separation column 4 via valve 3 and separated by distillation, and the gas is passed through valve 5 to the system. B is discharged outside, and the high molecular weight polymer is taken out of the system via valve 7. Note that the low molecular weight compounds separated in the separation column 4 are circulated through the valve 6 to the heating device 2 again. The presence of metal elements in the organosilicon polymer compound containing metal elements obtained by the production method of the present invention can be confirmed by infrared absorption spectra and nuclear magnetic resonance absorption spectra, and the presence of metal elements can be confirmed by elemental analysis. The amount can be quantified.

In addition, as a result of measuring the average molecular weight using a molecular weight measuring device, the average molecular weight varies depending on the starting materials, heating temperature, and heating time, and is distributed between 300 and 50,000. Even if the amount of the radical initiator used in the present invention exceeds 10%, the effect does not particularly increase, and it is not economical, so it must be kept at 10% or less, and 0.01
The best effect is obtained in the range of ~1%. Depending on the starting materials or reaction conditions, the organosilicon polymer compound produced by the various reactions may contain low molecular weight compounds that are soluble in alcohols such as methyl alcohol and ethyl alcohol, or acetone, and the content may vary. The softening temperature may be about 50° C. or higher or about 50° C. or lower depending on the process, but as described later, this softening temperature needs to be 50° C. or higher in order to form a spinning dope. Therefore, when the organosilicon polymer compound having a softening temperature of about 50'C or more is used as a starting material, the second method of the present invention
The process can be omitted.

In the production method of the present invention, the organosilicon polymer compound is extracted with an alcohol such as methyl alcohol or ethyl alcohol, or a solvent such as acetone to obtain a high molecular weight polymer having a softening temperature of about 50° C. or higher. When using the high molecular weight polymer as a spinning dope, in order to improve its softening temperature and viscosity, the extracted low molecular weight compound is
The high molecular weight polymer remaining without being extracted has a softening temperature of 5.
It can be added as long as the temperature does not drop below 0°C.

Alternatively, an organosilicon polymer compound containing silicon and carbon as main skeleton components containing the organometallic compound is prepared in vacuum, or in air, oxygen, inert gas, CO gas, ammonia gas, CO2 gas, hydrocarbon gas, The low molecular weight compound in the organosilicon polymer compound is fully aged in a temperature range of 50 to 700°C under any atmosphere selected from organosilicon compound gases, optionally under pressure. is polymerized to form a high molecular weight polymer with a softening temperature of about 50'C or higher.

The atmosphere for this aging is vacuum, air,
A gas atmosphere selected from oxygen, inert gas, hydrogen gas, CO gas, ammonia gas, CO2 gas, hydrocarbon gas, and organosilicon compound gas can be used, and aging can be performed under pressure if necessary. . Of these, air
When using either oxygen or ammonia gas, oxygen or nitrogen atoms can be advantageously used because they have a crosslinking effect that polymerizes low molecular weight compounds. Note that the various gas atmospheres are not necessarily limited to one type of gas, and may be a mixed atmosphere of two or more types of gases, but in this case, it is preferable that the mixed gases do not react with each other. The aging can be carried out under vacuum, normal pressure, or pressurization. Vacuum has the effect of accelerating the evaporation of low-molecular compounds, and under pressure, low-molecular-weight compounds with a molecular weight of 1000 or less contained in the organosilicon polymer compound can be aged. Product yield is improved because the compound is polymerized to form a high molecular weight polymer without volatilization. In the present invention, if the temperature at which the organosilicon polymer compound is aged is lower than 50°C, the polymerization reaction is extremely uneconomical, and if it exceeds 700'C, the decomposition of the compound becomes severe. It is necessary to keep the temperature within the range of 700'C, and the preferred temperature range for the ripening temperature varies depending on the type of atmosphere, type of raw material, average molecular weight of the raw material, etc., but it is generally 80'C in an air, oxygen, or ammonia gas atmosphere. Good results were obtained in the range of ~300'C, and generally in the range of 120~300'C in inert gas, hydrogen gas, CO gas, CO2 gas, hydrocarbon gas, organosilicon compound gas atmosphere.
Good results are obtained in the range of 450°C.

The holding time for aging is related to the aging temperature; the higher the temperature, the shorter the holding time may be, but decomposition and more crosslinking reactions than necessary occur at high temperatures, so when heating at high temperatures, It is advantageous to shorten the heating time.

However, when heating at low temperatures, it is advantageous to lengthen the heating time. If anything, better results can be obtained by taking a longer time at a lower temperature, and it is generally preferable to hold for 30 minutes to 1 (4) hours at the above-mentioned preferred temperature. The aging process has the effect of changing the molecular weight distribution of the organosilicon polymer compound, making spinning easier, and increasing the strength of the spun fibers.

It is advantageous to use the aforementioned methods to reduce the amount of low molecular weight compounds so that the softening temperature of the organosilicon polymer is at least 50°C.

If an organosilicon polymer compound with a softening temperature of 50'C or less is spun into fibers, the spinning process may be carried out in an oxidizing atmosphere at
The softening temperature of the organosilicon polymer must be 50°C or higher because the fiber loses its shape during the process of infusible spinning by heating at a low temperature in the temperature range of 400°C. Examples of organosilicon polymer compounds with a low content of low molecular weight compounds include benzene, toluene, xylene, ethylbenzene, styrene, cumene, pentane, hexane, octane, cyclopentadiene, cyclohexane, cyclohexene, methylene chloride, chloroform, carbon tetrachloride, 1,1-dichloroethane, 1,2-dichloroethane, methylchloroform, 1,1,2-trichloroethane
(dissolved in a solvent that can dissolve organic silicon polymer compounds such as hexachloroethane, chlorobenzene, dichlorobenzene, ethyl ether, dioxane, tetrahydrofuran, methyl acetate, ethyl acetate, acetonitrile, carbon disulfide, and other organosilicon polymer compounds), and the spinning stock solution is After this is filtered to remove macrogels, impurities, and other harmful substances during spinning, the spinning stock solution is spun using a dry spinning method using a commonly used synthetic fiber spinning device, and the draft is increased to obtain the desired thin fiber. You can get it. At this time, the atmosphere in the spinning tube of the spinning device is a mixed atmosphere of a saturated vapor atmosphere of at least one of the solvents and at least one gas selected from air and an inert gas, or Alternatively, an atmosphere of air, inert gas, hot air, hot inert gas, steam, ammonia gas, hydrocarbon gas, or organosilicon compound gas may be used.
This is advantageous in that the solidification of the spun yarn in the spinning tube can be controlled.

In addition to the method of creating a spinning stock solution using the above-mentioned solvent, the above-mentioned organosilicon polymer compound with a softening temperature of 50°C or higher is heated and melted to create a spinning stock solution, and this is filtered to remove microgels, impurities, etc. that are harmful during spinning. It is also possible to remove the material and spin it using the spinning device.

The temperature of the spinning dope during spinning varies depending on the softening temperature of the organosilicon polymer compound used as the raw material, but a temperature range of 50 to 400°C is advantageous. In the spinning device, a spinning tube is attached as necessary, and the atmosphere inside the spinning tube is changed to air,
Fibers with a narrow diameter can be obtained by increasing the draft in an atmosphere of one or more selected from inert gas, hot air, hot inert gas, steam, and ammonia gas. The spinning speed in the melt spinning varies depending on the average molecular weight, molecular weight distribution, and polymer molecular structure of the organosilicon polymer compound that is the raw material, but is 50 to 50.
Good results are obtained in the range of 0.007 TL/min. Next, the spun yarn is heated at a low temperature in the temperature range of 50 to 400°C for several minutes to 5 hours under tension or no tension in an oxidizing atmosphere to infusible the spun yarn. do.

At this time, if heated at a low temperature without tension, the spun yarn will take on a wavy shape due to shrinkage, but this can sometimes be corrected by preheating in the post-process, and tension is not necessarily required, but it is possible to apply tension. In this case, the tension may be large enough to at least prevent the spun yarn from becoming wavy even if it shrinks during the low-temperature heating. The purpose of the low-temperature heating is to create a thin oxidation on the spinning surface! This is to form a film and protect the spun yarn from melting with the oxide film during the preheating step described later.

The oxide film formed by the low-temperature heating may be very thin and will not affect the strength, other mechanical properties, and chemical composition of the final silicon carbide fiber. Because of the oxide film, the spun fibers do not melt during preheating in the post-process, and even if they come into contact with adjacent spun fibers, they do not adhere. The oxidizing atmosphere for the low-temperature heating is preferably an oxidizing gas atmosphere of one or more selected from air, ozone, oxygen, chlorine gas, and bromine gas, and the low-temperature heating in the gas atmosphere is preferably performed for 50' Even if spinning is carried out below C, an oxide film cannot be formed on the spinning material.
At temperatures above 400°C, the oxidation of spinning progresses too much, so good results can be obtained at temperatures in the range of 50 to 400°C.

The low temperature heating time is related to the temperature and ranges from several minutes to 5 minutes.
The time range is appropriate. KMnO4, K2Cr2O7 in addition to the oxidizing gas atmosphere as the low-temperature heating atmosphere.
, H2O2 and other inorganic peroxides may also be used, in which case the temperature is preferably in the range from room temperature to 90 DEG C., and the time is preferably in the range from 0.5 to 5 hours.
As mentioned above, the tension to be applied during the low-temperature heating is sufficient to prevent the spun fibers from shrinking and forming a wavy shape, so a slight tension may be sufficient, but for practical purposes, tension should not be applied to the spun fibers. For low temperature heating, 0.001 to 5
Good results were obtained by applying a tension in the range of k9/TrliL, 0.001 kg/Tr! I. Even if the following tension is applied, it is possible to apply a tension that does not cause the spinning yarn to sag.If a tension of 5 kg/d or more is applied, the tension is too large and the spinning yarn may break, so the tension is A range of 0.001 to 5k9/d is preferable.

Next, the low-temperature heated spinning is carried out in a vacuum or with a small amount of air.
One selected from oxygen, ozoso, and steam
In a mixed atmosphere consisting of a species or two or more species and one or two or more species selected from vacuum, inert gas, CO gas, hydrogen gas, hydrocarbon gas, organosilicon compound gas, and ammonia gas, Preheating is carried out under tension or no tension in the temperature range of ~1300°C.

In this preheating, the organosilicon polymer compound forming the spun fiber releases easily volatile components through a thermal polycondensation reaction and a thermal decomposition reaction. The spun yarn therefore shrinks and bends, and the application of tension during preheating is particularly advantageous in preventing this bending. At this time, the tension may be set to a value that can at least prevent the spun yarn from forming a wavy shape even if it shrinks during the preheating, but practically, it is 0.001 to 20k9/ Good results were obtained by applying a tension in the range of d, 0.001 kg
Even if a tension of less than /d is applied to the spinning yarn, it is not possible to apply a tension that will not cause the spinning yarn to sag, and the tension of 20kg/Tru
If a tension of more than i is applied, the tension may be too large and the spinning fibers may break. Therefore, the tension applied to the spinning fibers during preheating is preferably in the range of 0.001 to 20k9/i. The preheating is performed in a vacuum or with a small amount of one or more selected from air, oxygen, ozone, and steam, using an inert gas, CO gas, hydrogen gas, hydrocarbon gas, or an organosilicon compound. It is advantageous to carry out the process in a mixed atmosphere consisting of one or more selected from gas and ammonia gas in order to increase the strength of the silicon carbide fibers finally obtained. For example, the degree of vacuum in the vacuum atmosphere used in the preheating step is 1 to 10-4T! RInHg may be used, and the presence of a small amount of gas such as air, oxygen, ozone, or steam does not hinder the execution of this process and is particularly advantageous in terms of production. Further, firing in an atmosphere containing a small amount of gas such as air, oxygen, ozone, or steam in an inert gas is no problem, as is the case in a vacuum. In this case, air, oxygen, ozone,
The partial pressure where steam etc. exists is approximately 10? Hg or less is better. The partial pressure of air, oxygen, ozone, steam, etc. is 10 theoretical Hg.
If the temperature is higher, the oxidation of the fibers heated at low temperature becomes significant during the firing process, and the strength of the silicon carbide fibers obtained by high-temperature firing may decrease. The temperature range for the pre-calcination is set to 800 to 1300°C because it is necessary for the organosilicon polymer compound to release easily volatile components through thermal polycondensation reaction and thermal decomposition reaction in this step. This is because. The purpose of this preheating is that the small amount of low molecular weight compounds remaining during spinning, as well as the low molecular weight compounds produced as a result of the polycondensation reaction and decomposition reaction due to heating, act as a solvent to dissolve the spinning yarn. If high-temperature firing (described later) is performed with these still present, the spun fibers will melt and the fiber shape will not be maintained, so preheating is performed to evaporate them.

Furthermore, when polycarbosilane spun filaments are heated at high temperatures, some of the low molecular weight compounds contained in the filaments are volatilized and deposited on the furnace wall while the spun filaments are heated, but other parts are It carbonizes and remains in the filament.

Therefore, if the low molecular weight compounds in the filament are not sufficiently removed, a large amount of free carbon will be contained in the fired SiC fiber. Note that the low molecular weight compounds deposited on the furnace wall when heated to a high temperature are evaporated onto the filament surface and become carbon. When a SlC fiber containing a large amount of free carbon is heated to a high temperature of 600°C or higher, especially in an oxidizing atmosphere, voids and notches are formed on the fiber surface due to decarburization, stress is concentrated in this area, and The strength of the fibers is significantly reduced. After preheating to sufficiently remove low molecular weight compounds, the filament is fired to become dense.

For the preheated spinning, graphite, free carbon, silica or Si-C-0, Si-C-0-N. ．． Si-C-
Since it contains a non-stoichiometric compound consisting of 0-H, etc., when the spun yarn is fired at a higher temperature, graphite, free carbon, and/or silica remain as impurities in the SiC fiber, which causes a decrease in the tensile strength and variation of the fiber. becomes.

Therefore, the pre-calcined fibers are treated with sulfuric acid, nitric acid, a mixed acid of sulfuric acid and nitric acid, hydrochloric acid, a mixed acid of nitric acid and hydrochloric acid, a sulfuric acid acidic solution of potassium dichromate, a sulfuric acid acidic solution of potassium permanganate, and hydrofluoric acid. Impurities contained in the pre-fired fibers are eluted by immersion in a mixed acid of hydrofluoric acid and sulfuric acid, a mixed acid of hydrofluoric acid and sulfuric acid, or the like.

In addition, as other methods, borax, Na2cO
3, K2CO3, K2cO3/Na2cO3, Na2s
O4, KNO2, NaClIKClO3, Na2O. ,
Molten salt such as K2CO3/KNO3 or NaOH can be used to elute the silica in the impurity, and there is no problem in using it.Also, phosphoric acid can be used to elute the free carbon in the impurity. Therefore, it is advantageous to use molten salt or phosphoric acid in the cleaning process to remove impurities that are to be avoided depending on the use of the fiber of the present invention.In order to achieve the purpose of this process, a hydrofluoric acid solution , for example I+', HF/HNO3, 8/H2SO4
The use of SiO, etc. is chemically inert to SlC, which is the main component of this fiber, and has no effect on SiO.
It is most excellent in that only 2 can be eluted. The time required to remove the SiO2 is when the fiber diameter is 10 to 20PT1. In this case, it depends on the temperature of the hydrofluoric acid solution, but a range of 1 to 5 degrees is good. For example, when using a 1:1 solution of 50% HF and concentrated sulfuric acid at a liquid temperature of 90°C, 3
The hour is fine. In addition, high-temperature heating is carried out in a temperature range of 800 to 2000°C under tension or no tension, and the atmosphere is one selected from vacuum, inert gas, CO gas, hydrogen gas, and hydrocarbon gas. or more than one type can be used.

Next, the silicon carbide fibers obtained in this way may contain free carbon that normally remains when converted to organosilicon polymer compound GLC, and this free carbon acts as an impurity and reduces the strength of the silicon carbide fibers. This may lead to a decrease in the temperature. This free carbon is preferably 800 to 1600 in an oxidizing atmosphere of at least one selected from oxygen gas, air, oxygen, ozone, and water vapor.
It can be removed by heating the silicon carbide fibers in the temperature range of 0C. The firing time is 800
Free carbon cannot be removed sufficiently even if carried out at a temperature below 1600'C, and since the reaction between SiC and the atmospheric gas becomes significant when the temperature exceeds 1600'C, it is not preferable to remove free carbon above this temperature. The firing time in the above atmosphere varies depending on the firing temperature and the structure of the firing furnace.If the firing temperature is low, the firing time will be short, but if the firing temperature is high, the firing time may be short. On the other hand, better results can be obtained by firing at a lower temperature for a relatively long time because the amount of reaction products produced between SiC and the atmospheric gas is smaller. This is preferable for obtaining high-strength silicon carbide fibers. Although it is not necessarily necessary to apply tension in the high temperature firing, the tension may be 0.001 to 100 kg/Tl7i. High-strength silicon carbide fibers with reduced bending are produced by firing at high temperatures while applying tension in the range of . Even if a tension of 0.001k9/Mlt or less is applied, there is no effect, and even if a tension of 100kg/TrIiL or more is applied, there is no change in the effect, so the tension to be applied is 0.
A range of 001 to 100 kg/i is preferable. To explain in detail the process of manufacturing the silicon carbide fiber according to the present invention, the main skeleton components are silicon and carbon containing at least one metal element selected from Tj, MO, Cr, or Pr. The organosilicon polymer compound thermally decomposed during the heat treatment process, excess carbon and hydrogen are volatilized as volatile components, and the remaining carbon and silicon combine to form SiC.
becomes. This process takes a long enough time to build up and heat up, gradually combining to form SiC.
It plays a role in supporting the self-sintering properties of SlC, which has slow self-diffusion. In addition, when converted to SiC, SjC microcrystals are formed, and the crystal grain size is usually 30 to 70A, which is significantly smaller than that of conventionally known SlC sintered bodies. The surface area becomes significantly larger, and the apparent Sl
The self-diffusion coefficient of C is thought to be very large, which increases the self-sintering properties of the silicon carbide fibers targeted by the present invention, resulting in high strength and good oxidation resistance. The reason why these ultra-fine silicon carbide particles are produced is that during the process of thermal decomposition of an organosilicon polymer compound whose main skeleton components are silicon and carbon that contain metal elements in its structure, This is thought to be because oxides, borides, or carbides of various microcrystalline metals are uniformly and finely dispersed, and at the same time, silicon carbide microcrystals, which are mainly produced, are suppressed from becoming coarse and densified. Suppressing the coarsening of SiC microcrystals does not cause a decrease in strength even if the SiC fiber is kept at a high temperature such as 1500'C for a long time, and therefore the SiC fiber of the present invention has stable strength at high temperatures. expensive.

In this way, metal oxides, carbides, or borides are thought to play an important role in obtaining the various effects described above.

It is further advantageous to use metals that have relatively high melting points and form chemically stable metal oxides, carbides, and borides as shown in Tables 1-3. The silicon carbide fibers obtained by the method of the present invention have a tensile strength of 30
0 to 400 k9/d can be easily obtained, and has a specific gravity of about 3.0 and a specific strength of about 4.1 x 107 cm1 and an elastic modulus of 42500.
k9/MlL, a specific elastic modulus of approximately 1.20×1σCm was obtained, and the elastic modulus exceeded that of carbon fiber and was approximately 6
It has doubled.

It also has excellent acid resistance and oxidation resistance, and has a heat resistance of 1300'C.
It can withstand up to 2000'C, has better wetting with metals and alloys than carbon fiber, and has poor reactivity with metals and alloys, so fiber reinforced metals, plastic and rubber fiber materials, Electric heating fibers, fireproof fabrics, acid-resistant diaphragms, nuclear reactor materials, aircraft structural materials, bridges, building materials, fusion reactor materials, rocket materials, luminous bodies, polishing cloths, wire lobes, ocean development materials, golf shaft materials, skis stock materials, tennis racket materials, fishing rods,
It can be used as a shoe sole material, etc. In addition, for the purpose of obtaining high strength properties, firing up to about 1500'C is sufficient, but when even higher temperature resistance is required, firing up to 1500'C is sufficient.
High-purity crystalline silicon carbide fibers can be obtained by firing at high temperatures of from 2000°C to 2000°C.

Next, the present invention will be explained with reference to examples.

Example 1 200q of tetramethylsilane and 24y of titanium oxyacetylacetate were placed in a 1F autoclave, and
The reaction was carried out at 40'C for an extended period of time.

After the reaction was completed, the n-hexane solution was removed from the autoclave, filtered, and concentrated under vacuum to 150°C.
Organosilicon polymer compound containing titanium element 84
I got y. The softening temperature of the polymer compound is 180°C, and this is melted and filtered to obtain a spinning stock solution, and the spinning temperature is 2.
15℃, spinneret diameter 250 μm 1 spinning speed 800T
Melt-spun at rL/min to a diameter of 2? m fibers.

A tension of 200y/70771 was applied to the spinning yarn, and the temperature was slowly raised to 180°C in air over 1.5 hours.
The powder is kept at 80°C and heated at a low temperature, and then preheated by raising the temperature from room temperature to 1200'C over 3 hours while applying a tension of 400y/Wi in nitrogen gas containing a trace amount of oxygen. did. Add this to aqua regia with a liquid temperature of 90℃ for 12 minutes.
After being immersed in I-Terama and washed with water, the temperature was raised from room temperature to 1000°C at a rate of 1000°C/hour in argon gas, and then fired at a high temperature of 200°C/hour to 1300°C in the presence of a trace amount of ozone gas. Made of carbide fiber. 1
The tensile strength of 300'C treated fiber is fiber diameter 22P, 7T1
．． It was 360k9/d for the one.

Example 2 A mixture of 10 kg of dimethyldichlorosilane, 500 g of chromium acetate, and 500 q of hexacarbonyl molybdenum was used as a raw material in the apparatus shown in the figure, and the temperature of the heating device was 68.
A thermal polycondensation reaction was carried out at 0°C. That is, the raw material mixture preheated to 120° C. is heated to 680° C. at a flow rate of 2 e/hour through a valve 1 with a heating device 2 (vibe heater with a total length of 1.5 Tr.1. We synthesized molecular compounds. This organosilicon polymer compound contained 0.4% chromium and 0.9% molybdenum. By the dry spinning method, the diameter of the spinneret was 250 pn1. was used to introduce air with a partial pressure of benzene of 0.01 into the spinning cylinder, and the spinning speed was set to 1507TL. /
55 pm in diameter was spun at a spinning temperature of 25°C. The spinning was carried out at 200°C in air containing ozone at a rate of 50q/
One powder was heated at a low temperature while applying a tension of 100 mA, and then 100 m
Preheating was carried out by increasing the temperature from room temperature to 1000'C over 4 hours while applying a tension of g/d. This material was immersed in a 1:3 mixed acid of concentrated nitric acid and concentrated hydrochloric acid at a liquid temperature of 70°C for 2 hours to remove impurities, washed with water, heated to 1000'C in an argon atmosphere for 5 hours, and further This material was heated to 1400'C in air for 8 hours to obtain silicon carbide fibers. Is the tensile strength of this thing fiber diameter 1? The weight was 400k9/d, and the bulk specific gravity was 2.98. It was found that the amount of free carbon contained in this material was extremely small. In this way, the silicon carbide fibers immersed in the mixed acid are first heated to about 1000°C in a non-oxidizing atmosphere, and then heated in a temperature range of 800 to 1700°C in an oxidizing atmosphere to increase the density of the SiC fibers. The chemical treatment and the decarbonization treatment can be performed simultaneously. - Example 3 2.51 g of anhydrous xylene and 383 g of sodium were placed in a 3-Lof flask (5e), and dimethyldichlorosilane 1e was added dropwise little by little under a stream of alkone gas.

After the dropwise addition was completed, the mixture was similarly heated under reflux in an argon stream for 8 hours to form a precipitate. This precipitate was filtered and washed first with methanol and then with water to obtain polydimethylsilane 415y as a white powder. 100 g of the polydimethylsilane thus obtained and tris(2,2,6,6-tetramethyl-3,5-heptanedionato) Pr(■) 1
The mixture with y was heated to 470°C under normal pressure and refluxed,
After carrying out a time polycondensation reaction, an organosilicon polymer compound 32y was obtained. After filtration, the mixture was heated and concentrated in vacuo to 150° C. to obtain an organosilicon polymer compound containing praseodium. This product was dissolved in 50ml of hexane, and 400cc of acetone was further added to obtain 25y of acetone-insoluble precipitate. 2 parts of the acetone-insoluble precipitate and 1 part of the acetone-soluble part were mixed, heated and melted, and filtered to prepare a spinning stock solution, which was then heated to 270°C and a spinning speed of 4007TL. A fiber with a diameter of 20PrrL was obtained by spinning from a nozzle with a diameter of 300P7n. The spun yarn was heated in air under a tension of 20 g/Mit, heated from room temperature to 180°C over 1 hour, held at 180°C for 3 minutes, heated at a low temperature, and then heated with nitrogen gas containing oxygen. Inside 10
Under the action of tension of 0y/Wllt, from room temperature to 1100℃
After preheating by raising the temperature to 1300 sulfuric acid C over 3 hours, it was immersed in 50% sulfuric acid at a liquid temperature of 80°C for 5 hours, and after washing with water, it was fired at a temperature increasing rate of 1000 C/hour to 1300 sulfur C in an argon stream. Silicon carbide fibers were obtained. The tensile strength of this material was 300k9/d with a fiber diameter of 18P7T1, and the bulk specific gravity was 2.90. Example 4 100y of octaphenylcyclotetrasilane was added with 1y of benzoyl peroxide and further titanocene [(C5ll5)
A mixture to which 8 g of 2TiC12] was added was placed in an autoclave, the autoclave was purged with argon gas, and then heated at 410° C. under about 35 atmospheres for 2 hours.

The average molecular weight of this product was about 1,800. This polymer compound. Dissolve the substance in 200mL of hexane and add 1000
mL of acetone to obtain an acetone-insoluble precipitate of 53f. This material was melted by heating and filtered to obtain a spinning stock solution, which had a diameter of 250 prr1. Using a spinneret, the spinning temperature was 260°C and the spinning speed was 450rrI. /min diameter 10
pm(7) fiber. Spun into yarn. This spinning is carried out in the air for 220 min.
The three powders were heated at a low temperature while applying a tension of 50 y/d at ℃, and then 200 y/TI7:! under an argon atmosphere. i
4 from room temperature to 1000'C while applying a tension of
Preheating was performed by raising the temperature over time. The strength of this amorphous silicon carbide fiber treated at 1000℃ is 350k9
It was /i. The preheated fibers are then treated with an acidic solution of potassium permanganate in sulfuric acid, washed with water, and then fired at a high temperature of 1350'C in a graphite crucible under an argon atmosphere.
did. The strength of this silicon carbide fiber is 380 kg.
It was /i. If this is further fired at a high temperature of 1800'C, the strength will be 120kg/rl! Although the weight of the silicon carbide fibers was less than 1 ton, it was confirmed that highly pure crystalline silicon carbide fibers were produced. Therefore, for the purpose of obtaining high-strength fibers, firing up to about 15,000 C is sufficient, but in order to obtain SiC with even higher heat resistance, high-temperature firing up to 2,000° C. is necessary. As described above, according to the present invention, an organosilicon polymer compound mainly composed of carbon and silicon containing at least one metal element selected from Ti, MO, Cr, or Pr can be produced inexpensively and in large quantities. , it is possible to obtain dense silicon carbide fibers with good oxidation resistance and high strength.

[Brief explanation of drawings]

The figure is a system diagram showing an example of a fluidized heating reactor used in the production method of the present invention. 1, 3, 5, 6, 7... Valve, 2... Heating device,
4... Separation tower.

Claims (1)

[Claims] 1(1) A compound containing only Si-C bonds. (2) Compounds containing Si-H bonds in addition to Si-C bonds. (3) A compound having a Si-Hal bond. (4) A compound having a Si-OR (R=alkyl, aryl) bond. (5) A compound having a Si-OH bond. (6) Compounds containing Si-Si bonds. (7) Compounds containing Si-O-Si bonds. (8) Organosilicon compound esters. (9) Organosilicon compound peroxide. at least one compound selected from the organosilicon compounds of (1) to (9) above, and Ti, Mo, Cr.
or Pr, using as a starting material a mixture with an organometallic compound containing at least one metal element selected from Pr, and produced by a polycondensation reaction by at least one of adding a polycondensation catalyst, irradiation, and heating. a first step of producing an organosilicon polymer compound whose main skeleton components are silicon and carbon containing at least one metal element selected from Ti, Mo, Cr or Pr; a second step of obtaining an organosilicon polymer compound with a low content of low molecular weight compounds from a silicon polymer compound; a third step of preparing and spinning a spinning dope of the organosilicon polymer compound; a fourth step of heating at a low temperature under the action of tension or no tension; and spinning the spun fibers heated at a low temperature in a vacuum or in a small amount of air, oxygen, ozone, or steam. and,
800 to 1300 under tension or without tension in a vacuum, in a mixed atmosphere consisting of one or more selected from inert gas, CO gas, hydrogen gas, hydrocarbon gas, organosilicon compound gas, and ammonia gas. A fifth step of preheating at a temperature of °C, and treating the preheated spun yarn with strong acid, molten salt, or phosphoric acid to remove by-product impurities other than SiC contained in the spinning, such as graphite, free carbon, and silicon. A method for producing silicon carbide fibers mainly made of SiC, comprising a sixth step and a seventh step of heating at a high temperature of 800 to 2000° C. in a vacuum or in a non-oxidizing gas atmosphere. 2(1) Compounds containing only Si-C bonds. (2) Compounds containing Si-H bonds in addition to Si-C bonds. (3) A compound having a Si-Hal bond. (4) A compound having a Si-OR (R=alkyl, aryl) bond. (5) A compound having a Si-OH bond. (6) Compounds containing Si-Si bonds. (7) Compounds containing Si-O-Si bonds. (8) Organosilicon compound esters. (9) Organosilicon compound peroxide. at least one compound selected from the organosilicon compounds of (1) to (9) above, and Ti, Mo, Cr.
or Pr, using as a starting material a mixture with an organometallic compound containing at least one metal element selected from Pr, and produced by a polycondensation reaction by at least one of adding a polycondensation catalyst, irradiation, and heating. a first step of producing an organosilicon polymer compound whose main skeleton components are silicon and carbon containing at least one metal element selected from Ti, Mo, Cr or Pr; A second step of obtaining an organosilicon polymer compound with a low content of low molecular weight compounds from a polymer compound, a third step of preparing a spinning stock solution of the organosilicon polymer compound and spinning it, and performing the spinning in an oxidizing atmosphere. A fourth step of heating at a low temperature under the action of tension or no tension, and heating the spun yarn heated at a low temperature in a vacuum or in a small amount of one or more selected from air, oxygen, ozone, and steam. , in a vacuum, in a mixed atmosphere of one or more selected from inert gas, CO gas, hydrogen gas, hydrocarbon gas, organosilicon compound gas, and ammonia gas under tension or no tension. A fifth step of preheating at a temperature of ~1300°C, and treating the preheated spun yarn with a strong acid, molten salt, or phosphoric acid to remove Si contained in the spun yarn.
A sixth step of removing graphite, free carbon, and silica as by-product impurities other than C, and a seventh step of further heating at a high temperature of 800 to 2000°C in a vacuum or a non-oxidizing gas atmosphere.
and an eighth step of removing free carbon during spinning by treating at a temperature of 800 to 1600°C in an atmosphere of at least one of oxygen gas, air, ozone, and water vapor, A method for producing silicon carbide fiber mainly made of SiC.