NL8202219A - METHOD FOR MANUFACTURING SHAPED SILICONITRIDE PREPARATIONS AND THUS FORMING PREPARATIONS. - Google Patents

Description

* ί * VO 3 ^ 09 / /

A method for manufacturing molded articles of silicon nitride and articles thus formed.

The invention relates to novel compounds of the silicon nitride type in the form of articles of manufacture and a process for their manufacture.

Silicon nitride is excellent in its heat and oxidation resistance and is particularly favorable in its low thermal expansion, high heat impact strength and high resistance to molten metal erosion. Since silicon nitride has such good and unique properties, it has so far been widely used as an electrically insulating material at high temperatures, a material for electronic parts, a refractory material in the metal industry, as a material for high temperature parts must pass, sintering binders, coating material, abrasion resistant material, material for use in the preparation of alloys and the like.

Silicon nitride has hitherto been prepared by heating powdered silicon at 1200-1300 ° C in the presence of nitrogen or ammonia or by heating a silicon-containing inorganic or organic monomer in the presence of nitrogen or ammonia. Thus, the hitherto conventional silicon nitride was usually obtained in the form of a powder.

The reaction between silicon and nitrogen is accompanied by heat development. Thus, when powdered silicon is reacted with nitrogen, a silicon nitride film is formed on the surface of the powdered silicon, making it difficult to carry out the nitriding reaction also inside the silicon powder, with the result that it is difficult. very pure nitride.

If such a silicon nitride powder is manufactured into an article of a predetermined shape for the various boyen-mentioned purposes, the articles will have the drawback of a low strength. More specifically, a binder such as magnesium oxide is required to process a conventional silicon nitride into the desired shape because the conventional nitride is usually obtained in a powder form so that the articles obtained have the drawback that they are of a reduced quality. heat resistance and mechanical strength.

Furthermore, in the production of conventional silicon nitride articles from silicon nitride or silicon powder, care must be taken with regard to temperature increase and the like. It is thus particularly difficult to obtain molded articles with very good heat resistance and mechanical properties.

The present invention now contemplates shaped silicon nitride articles which are free from the aforementioned drawbacks and it has now been found that the resin compound having an .sub.1 silazan group and a vinyl or glyceride group must be synthesized as an intermediate for silicon nitride; when the compound thus obtained is subsequently further treated, e.g. formed or by melt spinning, to obtain the desired product and the shaped product is finally heated in an ammonia or nitrogen atmosphere to form a silicon nitride of the desired form (o the silazan group-containing resin compound is processed or impregnated in a base material, such as carbon fibers, a carbon material, a carbon fiber reinforced carbon material, silicon carbide, silicon nitride, a metal oxide such as alumina, a ceramic material or a ceramic fiber reinforced material and then heated in an ammonia or nitrogen atmosphere Nitride in the base material obtained, which has improved heat resistance and oxidation resistance, The invention is based on this finding.

The core of the invention is based on the fact that a compound with a silazan group copolymerized with a polymerizable group, a compound with a polyalcohol and a silazan group, a mixture of these compounds or a base material impregnated therewith is heated to form in a predetermined shape and then heated in a nitrogen or ammonia atmosphere, thus obtaining a compound of the silicon nitride type having the predetermined shape.

It is thus also possible to obtain a compound of the silicon nitride type in the fiber form by heating such a silazan group-containing polycondensate to melting and then extruding the polycondensate thus melted via nozzles.

A compound with a silazan group copolymerized with a polymerizable group can be converted to silicon nitride by heating it in a nitrogen or ammonia atmosphere. More in particular, such a silicon nitride can be obtained by adding in an organic solvent an organohalogen silane with a polymerizable group 5 such as a vinyl group with a monomer copolymerizable with this polymerizable group or a number of polymerizable groups containing monomer in the presence of ammonia gas. or converting an ammonia producing compound.

The polymerizable monomers include styrene, divinylbenzene, vinyl chloride, vinylidene chloride, acrylonitrile, vinyl acetate, acrylic acid, methyl acrylate, ethyl acrylate, other acrylic acid esters, methyl methacrylate, ethyl methacrylate, and 2-ethylhexyl methyl acrylate.

The organic solvent includes methanol, ethanol, propanol, other aliphatic alcohols, polyvalent alcohols, xylene, n-hexane and other organic solvents.

The above-mentioned silazan group-containing compound is obtained by reacting in an solvent an organohalogen silane with a polymerizable group with a copolymerizable monomer or a monomer with a number of polymerizable groups as well as with ammonia gas or an ammonia-producing compound. The reaction temperature varies depending on the nature of the starting materials and is usually between room temperature and 9 ° C, most preferably between 30 ° and 80 ° C.

The organohalosilane to be reacted with the monomer with at least one polymerisable group is represented by the following general formula E (urSl-, where X is a halogen atom, n a number of U-3 and B is a hydrogen-35 atom, alkyl group, alkylene group, allyl group, vinyl group or aryl group 82 02 2 1 9. - ------------ ----------------- - k - proposals.

The compound with a silazan group which is reacted with a polyvalent alcohol is obtained by reacting the organohalo silane, the polyvalent alcohol and ammonia gas or an ammonia producing compound. Glycerol and glycols can be mentioned as polyvalent alcohols.

Molded articles consisting of the silazan-containing compound or a material impregnated therewith are heated at 1000-1800 ° C, preferably 1500-1600 ° C in an ammonia or nitrogen atmosphere, converting them into silicon nitride articles.

In this case, if the formed products of the silane group-containing compound, ie a polycondensate, were abruptly heated to a high temperature, they would be subjected to a heat shock, causing an abrupt decomposition reaction causing their original shape can be damaged. They are preferably heated for this purpose at a heating rate of 5-10 ° C per hour until a temperature of 600-700 ° C is reached, after which they can be heated at a higher heating rate.

The silazan group-containing compound can be heated to a temperature above its melting point whereby it is liquid or semi-melted and then deformed into fibers, films, sheets, plates and other desired shapes using a conventional method. This compound can be mixed with carbon fibers, graphite powder, metal oxide powders or alumina powder or ceramic powders such as silicon nitride powder or silicon carbide powder and then processed into an article of a silicon nitride type compound. In addition, the silazan-containing compound in carbon fibers, a carbon fiber reinforced composite material, a ceramic material or a ceramic fiber reinforced material can be impregnated and subsequently molded into a molded product of the silicon nitride type. These molded articles of silicon nitride are obtained without the aid of a binder, which differs from the usual molded silicon nitride articles, but because of this they are particularly strong, mechanically sturdy, heat-resistant and oxidation-resistant.

8202 2 1 - - --------------------- -, r - »- 5 -

Furthermore, a fibrous silicon nitride can be used to reinforce plastics and rubbers, such as polyesters, epoxies, phenol polyimide and rubbers, as well as to reinforce a metal matrix, such as aluminum, copper, titanium or a magnesium matrix, and further to reinforce carbon. , glass, silicon nitride or other materials.

The invention is further illustrated by the following non-limiting examples.

Yoorbeeld I

100 g of vinyl methyl dichlorosilane as organochlorosilane, 100 g of glycerol and 5 g of methyl acrylate monomer containing 0.05 g of benzoyl peroxide as a polymerization initiator were mixed. The resulting mixture was processed in small amounts at 30 ° C with ammonium carbamate as an ammonium producing compound to copolymerize the organochlorosilane with the methyl acrylate monomer to form a copolymer which is converted with ammonia into a polymer with a silazan group. The reaction was carried out for 1 hour at 30-50 ° C and then 3 hours at 60-70 ° C. The reaction product consisted of two 3 days, an upper layer of a white colored liquid material with ammonium chloride as a by-product and a lower layer. consisting of a white colored resinous solid. The reaction product was heated to 80 ° C to dissolve the ammonium chloride by-product in glycerol to separate the white colored resinous solid from the ammonium chloride. The viscous material thus obtained was heated and extruded into fibers through nozzles.

These fibers were heated at 100 ° C per hour in an ammonia gas or stream in a tubular electric oven at 100 ° C and then left at 1500 ° C for 10 minutes in another electric oven with yellow- green-black colored fibers were obtained.

These fibers were subjected to an X-ray diffraction, which was found to consist predominantly of silicon nitride.

• o

They prayed a tensile strength of 150 kg / mm.

Image II

Example I was re-cured with this difference. that in place of 100 g of vinyl methyl dichlorosilane 115 g thereof was used, whereby 8202 21 9 -6 was also obtained a fibrous silicon nitride. This fibrous silicon nitride was also examined with an X-ray diffraction and it was found that this material also consisted mainly of oc-silicon nitride.

Example III

100 µg of vinyl methyl dichlorosilane as an organohalogen silane with a polymerisable group, 200 g of glycerol and 15 g of divinylbenzene containing 1% by weight of benzoyl chloride were mixed and processed in small amounts at 30 ° C with 10 g of ammonium carbamate. The resulting mixture was heated at 65 ° C for hours until the reaction was complete.

In this case, as the reaction proceeds, the ammonium carbamate is pyrolyzed to release ammonia, resulting in the formation of a white colored resinous material.

The white colored resinous material thus obtained was separated from the glycerol as a solvent and the ammonium chloride as a by-product. The resinous material was then heated to 90 ° C to form a viscous liquid which was formed into a film. This movie was shot in. brought a porcelain foam, further placed in a cylindrical electric oven, then at a heating rate of 50 ° C per hour at 1000 ° C (placed in an ammonia atmosphere and further heated at 1500 ° C in a nitrogen atmosphere, creating a yellow-green-black colored film.

The film thus obtained was examined by X-rays to show that it mainly consisted of ος-type silicon nitride while the remainder consisted of a very small amount of 3-silicon nitride. ·

The film was further heated to 1300 ° C at a rate of 10 ° C per hour and held at this temperature for 2 hours in an air stream using a differential calorimeter (from Eigaku Electric Co., Ltd.} resulting in a weight increase of the film from 2.1 mg / cm 2.

Example IV

100 g of vinyl methyl dichlorosilane was mixed with 20 g of methyl acrylate containing 1% behzoyl peroxide to give a mixture of yer-35 which was reacted with 15 g of ammonium carbamate in xylene. The reac- 8202 2 1 9 -................

The process proceeded at 65 ° C for k hours, then the xylene removed from the reaction mixture and a vit colored rubber elastic resin obtained. The resin thus obtained is mixed with 35 mm short fibers of silicon carbide in an amount of 35 parts. % 5 of the resin and then formed into a sheet-like body of 30 mm x 50 mm x 5 mm. The sheet-like body thus obtained is heated at a speed of 3 ° C per hour in an ammonia gas atmosphere at 1000 ° C and further heated in nitrogen gas at 1500 ° C for some time. The product obtained had a flexural strength of k60 kg / cm2. If this product was heated in an air stream at 700 ° C for 1 hour, the result would be that the change in composition of the product would be negligible.

Yoorbeeld V

100 g of silicon tetrachloride are mixed with 100 g of glycerol, then this mixture is diluted with 20 g of ammonium carbamate. The whole was initially stirred at room temperature before a polycondensation occurred and then the temperature was raised to 65 ° C, and the temperature was maintained for 3 hours. The resulting reaction mixture is liberated from glycerol and ammonium chloride as a by-product, after which a vit-colored viscous resin is obtained.

A separately prepared 10mm thick 100mm diameter carbon fiber reinforced carbon matrix composite material impregnated with this viscous resin under reduced pressure, heat treated in an ammonia atmosphere at 1000 ° C and then further in a nitrogen atmosphere 1500 ° C treated. These impregnation and heat treatments at 1500 ° C were repeated three times. The composite material thus treated had a flexural strength of 650 kg / cm which is a strength increase of about 20%.

Image VI

50 g of methylthrechlorosilane diluted with 100 µg of glycerol are dyed into a mixture which is dyed in small portions with 7.5 g of ammonium carbamate and reacted for 1+ hours at 30 ° C. The reaction was carried out under rigid foams to obtain a vit colored resinous material. The reaction mixture thus obtained, freed from the oveimate glycerol, is then freed to obtain a vit colored viscous resin which is useful for impregnating a carbon or ceramic material. 82 02 2 1 9 ------------ - - - - 8 - material.

If, in the above procedure, the glycerol was replaced with 150 g of xylene, the result was that the silazan worming could be confirmed by infrared analysis, but a white colored solid sediment was formed which was not resinous.

Thus, for resin formation, it was necessary to use glycerol if such functional groups were present.

Example 711 100 g of dimethyldichlorosilane was mixed with 100 g of glycerol 10, after which this mixture was processed with 15 g of ammonium carbamate at 30 ° C.

This reaction was continued at 60 DEG C. for a white colored jelly-like resin.

This resin was processed with powdered alumina in a weight amount of 2.5 times the amount of the resin, mixed well, housed in a metal mold of 10 mm thickness, 50 mm width and 80 mm length, and then below. heating formed under pressure. The thus-voided article was heated in nitrogen gas at 1300 ° C to obtain a solid elongated article with a flexural strength of 380 kg / cm 2.

Example VIII

The compounds of Table A were reacted with one another under the conditions set forth in Table A to obtain silazane group-containing compounds. These silazane group containing compounds were processed into the shapes shown in Table A and heat treated under the conditions of Table A to yield molded silicon nitride type products having the properties shown in Table A.

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Claims (5)

1. A process for the production of silicon nitride-shaped articles, characterized in that a silicon halide and a polymerisable group-containing organohalosilane of the formula wherein X is a halogen atom, n is a number of U-i and E is a hydrogen atom, alkyl group, alkylene group, allyl group, vinyl group or aryl group, converts a monomer copolymerizable with the polymerisable group or a monomer with some of these polymerisable groups, glycerol or a glycol as well as converts ammonia gas or an ammonia producing compound into a compound with a silazan group copolymerized with the polymerizable group, Compounds thus obtained: with a silazan group, compounds with a silazan group together with a polyvalent alcohol, mixtures of both the aforementioned compounds or mixtures of the three aforementioned materials with a base material into a molded article of a predetermined shape, and d then the shaped article thus obtained is heated in an atmosphere of nitrogen gas or ammonia to a shaped article of the silicon nitrite type. Method according to claim 1, characterized in that the basic material used is carbon fiber, graphite powder, alumina powder, silicon nitride powder or silicon carbide powder. Method according to claim 1, characterized in that the thermoforming is carried out by heating the material to be melted to melt and then extruding this melted material through fibers to form nozzles. b. The method according to claim 1, characterized in that the thermoforming is carried out by melting the material to melt and then impregnating the molten material into the base material by impregnating the base material as a molded yoort material. Obtained method according to claim b, characterized in that as basic material 82 0 2 2T9 -ϊ * * - 12 - carbon fibers, a carbon fiber reinforced carbon composite material, a ceramic material or a ceramic fiber reinforced material is used. 6. Process according to claims 1, 3 or 1+, characterized in that the monomer comprises a vinyl compound, styrene, divinyl benzene, vinyl chloride, vinylidene chloride, acrylonitrile, vinyl acetate, aerosol, methyl acrylate, ethyl acrylate, methyl methacrylate, ethyl methacrylate, or is 2-ethylbexyl methacrylate. 7. Process according to claim 1, 3 or 1+, characterized in that the silazan group-containing compound is converted into silicon nitride at 1500-1600 ° C. Fiber-shaped material obtained according to claim-3. ✓ ---------- 8202 2 1 9 ----------------------------------- ---------- -