JPS6325083B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing high-strength inorganic fibers from an organosilicon polymer compound obtained by subjecting an organosilicon compound to thermal decomposition polycondensation.

Conventional inorganic fibers containing silicon include polycarbosilane with silicon and carbon as the main skeleton components, polytitanocarbosilane with silicon and carbon as well as titanium as the main skeleton components, or silicon and carbon with zirconium as the main skeleton. Using polyzirconocarbosilane as a starting material, spinning, infusibility,
A method has been proposed in which the material is then fired at a high temperature. (For example, JP-A-51-13024, JP-A-51-139929,
(Refer to Japanese Patent Application Laid-open No. 56-128315 and Japanese Patent Application Laid-open No. 57-106718).

That is, due to the thermal decomposition polycondensation reaction of polydimethylsilane, cleavage of silicon-silicon bonds, accompanying hydrogen abstraction, and rearrangement to methylene groups occur.
A polycarbosilane whose main skeleton components are silicon and carbon is produced. Polytitanocarbosilane and polyzirconocarbosilane are also produced in substantially the same manner.

Next, an organosilicon polymer compound with a low content of low molecular weight organosilicon compounds is obtained from these organosilicon polymer compounds, and the organosilicon polymer compound is made into fibers by melt spinning or wet spinning. The fibers are heated in an oxidizing atmosphere such as air, oxygen, or ozone to make them infusible, and then fired at a high temperature in an inert gas to produce inorganic fibers containing silicon carbide as a main component. Even if the low molecular weight organosilicon compound is removed from the organosilicon polymer compound produced by thermal decomposition polycondensation of the organosilicon compound as described above and used for spinning, the Since it is a relatively low molecular weight polymer with a number average molecular weight of 800 to 10,000, by performing high temperature firing after the fiber is infusible, the low molecular weight organosilicon compound present in the fiber and the organosilicon polymer by heating are removed. Pyrolysis of some of the compounds occurs to produce low molecular weight organosilicon compounds, which are released from the fibers in gaseous form. Therefore, pores remain in the preheated fiber due to the release of these gases, which become mineralized by high-temperature firing.
Even if the fibers shrink, these pores cannot be filled sufficiently and remain, causing a decrease in the strength of the inorganic fibers, resulting in the disadvantage that high-strength fibers cannot be obtained.

The present invention solves these drawbacks and provides high-strength inorganic fibers, particularly inorganic fibers containing silicon carbide as a main component, such as silicon carbide fibers, and inorganic fibers containing silicon carbide as a main component and titanium carbide or zirconium carbide. This is what you get.

That is, the present invention includes a first step of producing an organosilicon polymer compound by thermal decomposition polycondensation reaction of an organosilicon compound, and an organosilicon polymer compound having a low content of low molecular weight organosilicon compounds from the organosilicon polymer compound. a third step of preparing and spinning a spinning dope of the organosilicon polymer compound; and a third step of preparing a spinning stock solution of the organosilicon polymer compound and spinning the fiber, and spinning the spun fiber in an oxidizing atmosphere under a pressure of at least 0.1 kg/cm ² (gauge) at a rate of 50 to 300 kg/cm 2 (gauge).
A fourth step of heating the fiber at a low temperature at a temperature of ℃, and heating the fiber heated at a low temperature under tension by heating one or more types selected from nitrogen, argon, hydrogen, hydrocarbon gas, organosilicon compound gas, and carbon monoxide. The fifth step is preheated at 300-600°C under a pressure of at least 0.1 Kg/cm ² (gauge) in an inert gas atmosphere of
The preheated fibers are fired under tension at a high temperature of 800 to 1500°C in an atmosphere of one or more inert gases selected from nitrogen, argon, hydrogen, ammonia gas, and carbon monoxide. The present invention relates to a method for producing high-strength inorganic fibers, characterized by comprising a sixth step of forming inorganic fibers containing silicon carbide as a main component.

That is, the reason why the fourth and fifth steps are carried out under pressure in the present invention is that thermal decomposition occurs in the low molecular weight organosilicon compound contained in the fibers and in a part of the organosilicon polymer compound due to heating. This is to prevent the formation of silicon compounds and the release of these low molecular weight organosilicon compounds in gaseous form from the fibers. The effects of applying pressure are thought to be due to the following reasons. By performing the infusibility treatment under pressure, the low molecular weight organosilicon compound does not diffuse and forms a network structure by crosslinking with oxygen, so the low molecular weight organosilicon compound is used as an effective substance in the fiber. can be left in. Furthermore, preheating under pressure prevents the generation of low-molecular organosilicon compounds caused by thermal decomposition, and the organosilicon compounds in the fibers undergo intramolecular or intermolecular thermal condensation, making them effective substances. It is thought that this allows silicon atoms to remain and that high-strength inorganic fibers can be obtained by high-temperature firing.

Next, each step of the present invention will be specifically explained.

The raw organosilicon compound that can be used in the production of the high-strength inorganic fiber of the present invention is selected from polydimethylsilane or polysilane in which a part of the methyl group is substituted with a phenyl group, an alkyl group, an aryl group, or hydrogen. An organosilicon polymer compound such as polycarbosilane, polytitanocarbosilane or polyzirconosilane is produced by a known method. (First step): Next, an organosilicon polymer compound containing a low content of low molecular weight organosilicon compounds is obtained from the organosilicon polymer compound by a concentration method or a solvent fractionation method. The number average molecular weight of this organosilicon polymer compound is 800 to 10,000. (Second step); The organosilicon polymer compound was melted by heating or dissolved in a solvent to prepare a spinning dope, and this was spun using a spinning device to obtain fibers with a fiber diameter of 15 to 18 μm. (Third step); The fibers are heated at a low temperature under pressure in an oxidizing atmosphere to make them infusible. The pressure is applied to prevent the low molecular weight organosilicon compound from evaporating, and the pressure is 0.1
The effect will be seen if the pressure is more than Kg/cm ² (gauge), but preferably 0.5Kg/cm ² (gauge)
That's all. However, applying a pressure of 10 kg/cm ² (gauge) or more does not change the effect, and the equipment is expensive, so it is not economical, so a pressure of 10 kg/cm ² (gauge) or less is sufficient.

As the atmosphere, one or more gases selected from air, ozone, oxygen, and nitrogen dioxide are used. It is also possible to use these oxidizing gases in combination with an inert gas such as nitrogen or argon. The low temperature heating is preferably carried out in the range of 50 to 300°C. Even if low-temperature heating is performed at temperatures below 50°C, crosslinking cannot occur due to the low molecular weight organosilicon compound oxygen in the fibers, and at temperatures above 300°C crosslinking due to oxygen in the fibers increases, i.e. oxidation progresses too much. Undesirable.

The time for low-temperature heating is related to the above-mentioned temperature and atmospheric gas, and is suitably in the range of several minutes to 10 hours.
A slight tension may be applied during this low-temperature heating to prevent the fibers from shrinking into a wavy shape. In order to practically apply tension to the fibers and heat them at a low temperature, it is necessary to use 0.001 to 10 kg/
It is sufficient to apply a tension in the range of mm ² . (Fourth step); Next, the low-temperature heated fibers are treated with nitrogen, argon,
Preheating is performed under pressure and tension in an atmosphere of one or more inert gases selected from hydrogen, hydrocarbon gas, organosilicon compound gas, and carbon monoxide. During this preheating, the organosilicon polymer compound that forms the fiber undergoes a thermal polymerization condensation reaction and a thermal decomposition reaction, which causes the vaporization of the lower molecular weight organosilicon compound from within the fiber, which mainly occurs between 300 and 600°C. . At higher temperatures, lower hydrocarbons, hydrogen,
Carbon monoxide and carbon dioxide are mainly generated. The reason for applying pressure is to prevent the formation of low molecular weight organosilicon compounds due to thermal decomposition reactions, and the pressure is 0.1Kg/cm ²
(gauge) or more, the effect will appear, but preferably 0.5Kg/cm ² (gauge)
That's all. However, the effect does not change even if the pressure exceeds 10Kg/cm ² (gauge), so the pressure should be 0.1 to 10Kg/cm ²
(gauge) range is appropriate.

In order to prevent the fibers from shrinking and forming a wavy shape during preheating, good results can be obtained by applying a tension in the range of 0.01 to 10 Kg/mm ² . Even if a tension of 0.001Kg/ ^mm2 or less is applied to the fibers, it is not possible to apply tension that will not cause the fibers to sag, and 10Kg/mm2 or less cannot be applied to the fibers.
If a tension of mm ² or more is applied, the tension is too large and the fibers may break, so a range of 0.001 to 10 Kg/mm ² is appropriate. (Fifth step); To make the preheated fibers into inorganic fibers containing silicon carbide as a main component by firing the preheated fibers at a high temperature, a gas selected from nitrogen, argon, hydrogen, ammonia gas, and carbon monoxide is used. 800 to 1500℃ in an inert gas atmosphere consisting of a species or two or more species
High temperature firing under tension in the temperature range.

By performing the high temperature firing while applying tension in the range of 0.01 to 100 Kg/mm ² , high strength inorganic fibers without bending can be obtained. A tension of less than 0.01Kg/ ^mm2 has no effect, and even if a tension of 100Kg/ ^{mm2 or} more is applied, the effect remains the same. (Sixth step); It was found that by carrying out the method of the present invention, high-strength inorganic fibers could be obtained and the residual weight of the inorganic fibers after high-temperature firing was improved.

Example 1 Polydimethylsilane synthesized from dimethyldichlorosilane was charged into a four-necked flask equipped with a thermometer, a stirrer, a volatile gas delivery pipe, and an inert gas introduction pipe and gradually heated. 360
Thermal decomposition polymerization started at 450°C, so the reaction was continued at 450°C while distilling off the volatile components produced, and polycarbosilane was obtained.

30 g of this polycarbosilane was dissolved in 30 ml of toluene, and this solution was added to 300 ml of acetone, and the insoluble matter was about 70%. This insoluble matter was spun at 240° C. and 200 m/min by a melt spinning method to obtain fibers with a diameter of 15 μm. While applying a tension of 2 kg/mm ² to this fiber in air pressurized to 2 kg/cm ² (gauge),
Infusibility treatment was carried out by increasing the temperature to 200°C at a rate of 5°C/hour. Next, 1 infusible polycarbosilane fiber
600 at a heating rate of 100℃/hour while applying a tension of 3Kg/ ^mm2 in nitrogen pressurized to Kg/ ^cm2 (gauge).
After preheating to 1200° C., pressurization was stopped and firing was continued at a high temperature of 1200° C. under a nitrogen atmosphere to obtain a black, glossy silicon carbide fiber with a tensile strength of 350 Kg/mm ² .

Note that the residual weight after firing was 75%.

Example 2 Polytitanocarbosilane was obtained by adding 8 g of titanium tetrabutoxide to 30 g of the polycarbosilane obtained in Example 1 without removing the low molecular weight organosilicon and reacting at 350°C for 3 hours. .

The resulting polytitanocarbosilane was heated under reduced pressure to remove volatile components, and its molecular weight was determined to be 1,800.

Next, this polymer was heated to 270℃ and melted to 300℃.
The fiber was spun at m/min to obtain a fiber with a diameter of 17μ.

This fiber is heated to 220℃ while applying a tension of 0.5Kg/mm ² in air pressurized to 5Kg/cm ² (gauge).
Infusibility treatment was performed by increasing the temperature at 10°C/hour. Next, 3 kg/cm ² of infusible polytitanocarbosilane fiber was added.
500℃ at a heating rate of 200℃/hour while applying a tension of 4Kg/mm ² in argon pressurized to (gauge)
After preheating to 1,350 degrees Celsius, pressurization was stopped and firing was continued at a high temperature of 1,350 degrees Celsius under an argon atmosphere to produce a black glossy inorganic material containing silicon carbide as the main component and titanium carbide, with a tensile strength of 410 kg/mm ² . Obtained fiber. The residual weight after firing was 79%.

Example 3 10 g of zirconium tetrabutoxy was added to 30 g of the polycarbosilane obtained in Example 1 without removing the low molecular weight organosilicon, and the mixture was reacted at 300° C. for 3 hours to obtain polyzirconocarbosilane.

The resulting polyzirconocarbosilane was heated under reduced pressure to remove volatile components, and its molecular weight was determined to be 1,700.

Next, this polymer was heated to 260°C and dissolved to 150°C.
The fiber was spun at m/min to obtain a fiber with a diameter of 16μ.

This fiber was heated to 170° C. at a rate of 5° C./hour to perform an infusibility treatment while applying a tension of 0.1 kg/mm ² in air heated to 8 kg/cm ² (gauge). Next, add 0.5 kg of infusible polyzirconosilane fiber to
400℃ at a heating rate of 100℃/hour while applying a tension of 0.5Kg/mm ² in nitrogen pressurized to cm ² (gauge).
After preheating to 1,250° C., the pressurization was stopped and high-temperature firing was continued at 1,250° C. under a nitrogen atmosphere to obtain an inorganic fiber mainly composed of silicon carbide and containing zirconium carbide and having a tensile strength of 380 Kg/mm ² . The weight remaining after firing was 73%.

Comparative Example Polycarbosilane with a low content of low molecular weight organosilicon compounds obtained in Example 1 was heated at 240°C for 200°C.
Spun fibers with a diameter of 15 μm at a speed of 2 kg/min in air.
Infusibility treatment was performed by increasing the temperature to 200°C at 5°C while applying a tension of mm ² . Next, the infusible polycarbosilane fibers were heated to 1200°C under a nitrogen atmosphere at a heating rate of 100°C/hour while applying a tension of 3 kg/mm ² .
When fired at high temperatures, black and glossy silicon carbide fibers were obtained. The tensile strength was 260Kg/ ^mm2 .

The weight remaining after firing was 65%.

Claims (1)

[Scope of Claims] 1. A first step of producing an organosilicon polymer compound by a thermal decomposition polycondensation reaction of an organosilicon compound, and an organosilicon polymer with a low content of low molecular weight organosilicon compounds from the organosilicon polymer compound a second step of obtaining a molecular compound; a third step of preparing and spinning a spinning stock solution of the organosilicon polymer compound; and a step of spinning the spun fiber in an oxidizing atmosphere of at least 0.1
The fourth step is low-temperature heating at 50 to 300°C under pressure of Kg/cm ² (gauge), and the low-temperature heated fibers are heated under tension with nitrogen, argon, hydrogen, hydrocarbon gas, organosilicon compound gas and nitrogen. Under a pressure of at least 0.1 Kg/cm ² (gauge) in an atmosphere of one or more inert gases selected from carbon oxides.
A fifth step of preheating at 300 to 600°C, and heating the preheated fibers under tension in an atmosphere of one or more inert gases selected from nitrogen, argon, hydrogen, ammonia gas, and carbon monoxide. To,
A method for producing high-strength inorganic fibers, comprising a sixth step of baking at a high temperature of 800 to 1500°C to form inorganic fibers containing silicon carbide as a main component. 2. A patent claim characterized in that the organosilicon polymer compound produced by the polycondensation reaction of thermal decomposition of an organosilicon compound in the first step is polycarbosilane, polytitanocarbosilane, or polyzirconocarbosilane. A method for producing a high-strength inorganic fiber according to Item 1.