JPH03197364A - Production of silicon carbide nitride-based molded article - Google Patents

Abstract

PURPOSE:To obtain the subject molded article having a low content of oxygen and excellent strength, etc., by adsorbing and/or affecting a specific amount of halogen to a molded article of a nitrogen-containing organic silicon polymer, affecting a basic substance in a non-oxidative atmosphere, making to infusible and calcining. CONSTITUTION:A nitrogen-containing organic silicon polymer (e.g. polycarbosilazane copolymer) is formed to a shape of fiber, tape, film, sheet or thin film, etc. Next, halogen (e.g. iodine) in an amount of 0.01-150wt.% of resultant molded article is adsorbed in and/or affects on the molded article. Then, a resultant article is affected by a basic substance (e.g. ammonia) in a non-oxidative atmosphere at a temperature of <=200 deg.C to at least partially made to infusible. Thus, the infusibility is accelerated by further heat-treating in an inert gas atmosphere, as necessary, and the calcining is further performed in an inert gas atmosphere to afford the objective silicon carbide nitride-based molded article.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention provides silicon carbide nitride molded products (fibers, tapes, films, This invention relates to a method for efficiently manufacturing sheets, thin films, etc.).

[Prior Art] Conventionally, as a method for manufacturing silicon carbide nitride ceramics, US Pat. No. 3,853,567
After molding the carbosilazane resin into a molded article such as a fiber or film as described in Japanese Patent Publication No. 55-46995, the resin is heat-treated in an oxidizing atmosphere such as air, oxygen, or ozone to make it invincible. It is known to produce silicon carbide nitride molded products by firing in an inert gas atmosphere. In addition, a method is known in which the material is treated with steam or a mixture of steam and oxygen to make it infusible and then fired (Japanese Patent Laid-Open No. 295273/1983).

All of these involve the step of heating a molded product made of a precursor polymer to about 100 to 200°C in the air to thermally oxidize it and make it invulnerable, so the resulting silicon carbide nitride molded product is Contains a significant amount of oxygen
As a result, the physical properties of the molded product become insufficient.

As a result of research to solve the above-mentioned problems in silicon carbide molded products, the present inventors first applied halogen and a basic substance to sequentially act on the precursor polymer molded product. proposed a method for obtaining silicon carbide-based molded products with low oxygen content and improved physical properties by making them infusible in a completely oxygen-free atmosphere and then firing them (Japanese Patent Application No. 63-200133).
issue).

[Object of the Invention] The object of the present invention is to use a novel infusible method previously proposed by the present inventors in a method for producing a silicon carbide nitride molded product from a nitrogen-containing organosilicon polymer. Silicon carbide nitride with low oxygen content and good physical properties is produced by applying a method for manufacturing silicon carbide molded products obtained by sequentially applying halogen and basic substances to polymer molded products. The object of the present invention is to provide a method for producing a molded product based on the above-mentioned system.

[Structure of the Invention] The object of the present invention as described above is to form a nitrogen-containing organosilicon polymer into the shape of a fiber, tape, film, sheet, thin film, etc., and then perform the following steps on the molded product. achieved by the method.

(A+ Step of adsorbing and/or acting on a nitrogen-containing organosilicon polymer molding with halogen in an amount of 0.01 to 150% (by weight) based on the weight of the molding; (B) Molding with halogen adsorbed and/or acting on the molded product; (C1) If necessary, the molded product treated with a basic substance is heat-treated at a temperature of 200°C or less in an inert gas atmosphere to complete infusibility; (D) A process of firing in an active gas atmosphere.

Hereinafter, each component of the present invention will be explained in detail.

In the method of the present invention, the nitrogen-containing organosilicon polymer used as a raw material is a nitrogen-containing organosilicon polymer that is a precursor of a silicon carbide nitride molded product, and is synthesized, for example, as follows.

That is, the nitrogen-containing organosilicon polymer used in the present invention is a polycarbosilazane copolymer whose main skeleton components are a silicon-carbon bond, a silicon-nitrogen bond, and a silicon-silicon bond. Polyphenylalkylsilanes such as polysilastyrene (U.S. Pat. No. 4.324.9)
01) and Cycook silazane by a co-thermal decomposition polymerization method.

Polyphenylalkylsilane is usually produced by dehalogenation condensation of phenylalkyldichlorosilane and dimethyldichlorosilane using a sodium metal dispersed catalyst, but polyphenylalkylsilane may be produced by other methods.

(However, R1 represents hydrogen or a methyl group, the position represents a methyl group or a phenyl group, and X and y are X/y = 2/
Positive integer from 8 to 7/3, number is 5 or more, preferably 1
It is an integer from 0 to 1000. ) Of this polysilastyrene, R1 and river are methyl groups, x/y = 3/7 to 6/4
, those having an average molecular weight of 100 to 50,000 are particularly preferred.

On the other hand, suitable silazane includes cyclic silazane, hexamethyldisilazane, and the like. Cyclic silazane is easily produced by the reaction of dichlorodimethylsilane and ammonia, and is usually produced from 3-41 as shown below.
It is the body.

Hexamethyldisilazane has the following molecular structure and is easily produced by reaction of trimethylchlorosilane and ammonia.

Moreover, polysilazane can also be used as the silazane.

Preferred nitrogen-containing organosilicon polymers in the method of the present invention are:
It is produced by co-thermal decomposition polycondensation reaction of polysilastyrene as described above and silazane such as cyclic silazane.

In order to carry out the co-thermal decomposition polycondensation reaction, a method is adopted in which both of the above components are charged in a predetermined ratio into a reaction vessel such as an autoclave and heated under vacuum (deoxygenation) or under an inert gas atmosphere such as nitrogen. .

The blending ratio of polysilastyrene and silazane needs to be in the range of 9/1 to 1/9 in terms of weight ratio of polysilastyrene/silazane, and is preferably in the range of 9/1 to 2/1. If the blending ratio is outside this range, the effect of the method of the present invention will be poor and it will be difficult to achieve the objective.

Heating temperature is 300-600℃, preferably 350-55℃
The temperature range is 0℃, and the heating time is 2 minutes or more depending on the temperature.
The time period is appropriately selected within the range of 20 hours. For example, 350℃
When the reaction is carried out by heating, 10 to 20 hours are required. Further, when performing a thermal reaction at 550°C, 5 to 60 minutes is sufficient.

In this way, by carrying out a co-thermal decomposition polycondensation reaction, silicon-carbon bonds (-8i-C-), silicon-silicon bonds (-8i-Si-), and silicon-nitrogen bonds are formed in the polymer main chain. (-Si-N-) is formed. The degree of polymerization of the polymer can be adjusted depending on the degree of polymerization of the raw materials by selecting the conditions for the colysis polycondensation reaction (temperature, 9 hours, 1 set acid ratio).

When producing a precursor polymer for producing silicon carbide nitride fibers, it is preferable to adjust the softening point of the produced polymer to 150 to 300°C.

In the method of the present invention, fibers, tapes, and films of nitrogen-containing organosilicon polymers prepared as described above are used.

The method for forming sheets, thin sheets, etc. may be either a melting method or a dry method (solution method). Generally, when forming fibers, melt spinning is preferred, and when forming films and sheets, solution casting or casting is preferred.

After forming a molded product such as a fiber or film in this way, in order to make the molded product infusible, halogen is first adsorbed and/or acted upon (Step A).

Examples of the halogen used in Step A include chlorine, bromine, and iodine, and among these, iodine is most preferred.

The amount of halogen to be adsorbed/acted on is selected within the range of 0.01 to 150% (by weight) based on the weight of the molded product (for example, fibers immediately after spinning), and particularly 0.1 to 50% (by weight). )% is preferred. Any method of adsorption/action can be used, such as placing an organosilicon polymer molding in a halogen gas or immersing an organosilicon polymer molding in a solution in which a halogen is dissolved. Industrially, a method in which the molded product is placed in a halogen gas is preferably used. The atmosphere in which the halogen is adsorbed/acted on is preferably an atmosphere that does not substantially contain oxygen, such as an inert gas atmosphere or a vacuum atmosphere.

In the method of the present invention, the temperature at which halogen is adsorbed/acted on the molded product is usually 50°C or higher and a temperature at which no fusion occurs, preferably 100°C or higher, in order to increase processing efficiency.
Temperatures from 0.degree. C. to (polymer melting point -10.degree. C.) are employed.

Next, a basic substance is made to act on the nitrogen-containing organosilicon polymer molded article on which the halogen has been adsorbed/acted on in a non-oxidizing atmosphere (Step B).

Examples of the basic substance used in step 13 include ammonia methylamine, ethylene diamine, and the like, with ammonia being the most preferred.

The specific method of making these basic substances act is as follows:
Although there are various methods, it is usually preferable to make the basic substance into a gaseous state and to make it work in the presence/absence of an inert gas. In either case, it is necessary to carry out the process under conditions substantially free of oxygen. In this step B, the amount of the basic substance applied varies depending on the amount of halogen adsorbed/acted on the molded article in the previous step, but it is preferable to apply the basic substance in sufficient excess to the amount of halogen. Generally, a range of equivalents to 400 equivalents to the acting halogen is preferably employed. The temperature at which the basic substance is applied is room temperature to 200℃.
up to ℃. If this temperature is too high, fusion of the molded products will occur, which is not preferable.

In this way, the molded article treated with a halogen and then with a basic substance has already become considerably invulnerable, and is usually heat-treated in an inert gas to more completely make it infusible (Step C).

The heat treatment for this is 200-700℃, preferably 2
A method of processing in an inert gas (nitrogen, etc.) atmosphere at a temperature of 00 to 600° C. for 1 minute to 3 hours is preferably used from the viewpoint of operability. This heat treatment in an inert atmosphere (
Step C) is not necessarily essential, and basic substance treatment (B
Depending on the infusible state after step), it may be immediately subjected to step E described below.

The organosilicon polymer molded product, which has been rendered invulnerable in a non-oxygen atmosphere by further carrying out Step B and Step C if desired, is then heated for 80 minutes in an inert gas (nitrogen, argon gas, etc.) atmosphere.
Firing is carried out at a temperature of 0 to 1400° C. for about 1 minute to 2 hours to form the desired silicon carbide nitride molded product.

[Effects of the Invention] The silicon carbide nitride molded product thus obtained contains only a small amount of oxygen, and therefore has significantly improved heat resistance and mechanical properties in air. Therefore, the method of the present invention is extremely useful as a method for industrially producing high quality silicon carbide nitride fibers, tapes, films, etc. The silicon carbide nitride molded product thus obtained is suitable as a reinforcing material for heat-resistant fiber materials, plastics, metals, ceramics, and the like.

[Examples] Next, Examples and Comparative Examples of the present invention will be described in more detail, but the present invention is not limited thereto.

Example 1 (Manufacture of polysilastyrene) Using a 0.45:0.55 molar equivalent mixture of dichlorodimethylsilane and dichlorophenylmethylsilane, 2.1 molar equivalent relative to the raw material silane was prepared in a toluene solvent. A polymerization reaction was carried out at 100 to 110°C using a sodium-dispersed catalyst. After the reaction was completed, the reaction mixture was cooled to room temperature, methanol was added to decompose the unreacted sodium catalyst, and the mixture was washed with water several times to dissolve and remove methanol and Nael to obtain a cloudy mixture. This mixture was filtered to remove the precipitate, and then applied to an ultracentrifuge to obtain a clear toluene solution. Toluene was distilled off from this toluene solution, and polysilastyrene (PP) with a softening point of 96 to 104°C was
S) was obtained.

(Obtaining cyclic silazane) Commercially available Toshiba Silicon ■, product No. TSL-881
0 was obtained and used.

(Hachi depolycondensation reaction) The above polysilastyrene (PSS) and cyclic silazane (TSL-88101) were charged into an autoclave at a weight ratio of 3/1, heated at 420°C for 3 hours in a nitrogen atmosphere, and then heated at 300°C for 3 hours in a nitrogen atmosphere. ℃, 1 under reduced pressure of 3-10 mmHg
By treating for 0 minutes, the bee dethermal polycondensation reaction is not performed.

The softening point of the obtained polycarbosilazane copolymer was 230
The polymerization yield was 45% at ℃.

(Manufacture of fibers) The polycarbosilazane above is melt-spun at 250°C, and the obtained polycarbosilazane copolymer fiber is continuously fed to an iodine treatment device having a gaseous iodine supply port maintained in a nitrogen atmosphere. Shina. The inside of the iodine gas treatment apparatus was maintained at 120° C., and iodine was continuously supplied in an amount equivalent to 25 wt % to the supplied fibers.

The iodine treatment device that is continuously taken out from the device is then led to a basic substance treatment device that is kept at room temperature and is continuously supplied with ammonia gas in an amount equivalent to three times the amount of iodine. It has been processed. The ammonia-treated fibers continuously taken out from the apparatus were then heated to 400° C. in a nitrogen atmosphere to obtain infusible fibers. The invulnerable fiber was then fired at 1200° C. in a nitrogen atmosphere to obtain a silicon carbide nitride fiber. The oxygen content of this fiber is 3.8 wt%, and the C/Si atomic ratio is 1.
It was 2. Also, the tensile strength of this fiber is 330 kg
/+am2, showing excellent strength.

When the heat resistance of this fiber was evaluated by heating it at 1200° C. for 60 minutes, very good results were obtained.

Claims (6)

[Claims] (1) After molding the nitrogen-containing organosilicon polymer into a shape such as a fiber, tape, film, sheet, thin film, etc., the nitrogen-containing organosilicon polymer molded product (A) 0.01 to 150 (per weight of the molded product) weight)%
(B) Then, in a non-oxidizing atmosphere, a basic substance is applied at a temperature of 200°C or less to make it at least partially infusible, and (C) as necessary. , further heat-treated in an inert gas atmosphere to promote infusibility, and (D) followed by firing in an inert gas atmosphere. . (2) The production method according to claim (1), wherein the nitrogen-containing organosilicon polymer is a polycarbo-silazane copolymer whose main skeleton components are silicon-carbon bonds, silicon-nitrogen bonds, and silicon-silicon bonds. . (3) The manufacturing method according to claim (1) or (2), wherein the halogen used in the step (A) is iodine. (4) Claims (1) to (3) in which halogen is adsorbed and/or acted on the organosilicon polymer molded article in an inert atmosphere.
The manufacturing method described in any of the above. (5) The manufacturing method according to any one of claims (1) to (4), wherein the basic substance used in the step (B) is ammonia. (6) Halogen is adsorbed and/or acted on the nitrogen-containing organosilicon polymer molded product at a temperature of 50°C or higher and at a temperature that does not cause fusion, and then a basic substance is added to the molded product at 200°C or lower in a non-oxidizing atmosphere. Silicon Carbide Nitride The manufacturing method according to any one of claims (1) to (5), wherein the method is converted into.