DE3220559A1 - SHAPED BODY OF THE SILICON NITRIDE TYPE AND METHOD FOR THE PRODUCTION THEREOF - Google Patents

Description

Silicon nitride type molded article and method for their manufacture

The invention relates to new compounds of the silicon nitride type in the form of shaped bodies and a method for their Manufacturing.

Silicon nitride is excellent in heat resistance and oxidation resistance, and because of its unique properties have the advantage that it has low thermal expansion, high thermal impact resistance and high erosion resistance to molten metals. Because silicon nitride is such excellent and novel Having properties, it has hitherto been used as a high-temperature electrical insulating material, as a material for electronic Parts, as a refractory (refractory) material for use in the metal industry, as a material for high-temperature parts of buildings (structures), as a binder for sintering, as a coating material, as an abrasion-resistant material, as a material for

TEUEFON (089) 233862

Used in the manufacture of alloys and the like.

Conventional silicon nitride has heretofore been produced by heating powdered silicon to 1200 to 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. IQ In this way, the conventional silicon nitride has been obtained powder is usually in the form.

The reaction between silicon and nitrogen generates heat. If now powdery silicon with stick- * 5 substance is converted, a silicon nitride film is formed on the surface of the powdery silicon, whereby It is difficult to achieve a nitration reaction inside the silicon powder, with the result that it difficult to obtain a nitride with a high purity

20 hold.

When such silicon nitride powder is used for the above specified various uses is molded into a molded article having a predetermined shape the moldings obtained have the disadvantage that their strength is low. In particular, a binder is such as magnesia, is required to shape conventional silicon nitride into the desired shape bring, since the conventional nitride is usually obtained in powder form, and accordingly have obtained Molded articles suffer from the disadvantage that various properties thereof, such as heat resistance, deteriorate and mechanical strength.

In the production of conventional silicon nitride moldings of silicon nitride powder or silicon powder must also the temperature increase operation and the like. a lot of attention is paid to it. So it is

extremely difficult to manufacture molded articles with excellent heat resistance and mechanical properties.
5

After extensive research with the aim of finding silicon nitride type compounds / those in the molded State are free of the aforementioned disadvantages, a method has now been found according to the invention in which a Resin compound containing a silazane group and a vinyl or contains glyceride group, as an intermediate for silicon nitride is synthesized, the synthesized compound is then treated, for example molded or is melted to produce the desired

Molded body made therefrom, and the molded body obtained thereby Finally, heating is carried out in an ammonia or nitrogen atmosphere to form silicon nitride in the desired state Shape, and in which the resin compound containing a silazane group is incorporated into a base material such as e.g.

Carbon fiber, a carbon material, one with carbon fibers reinforced carbon material, silicon carbide, SiIi-. cium nitride, a metal oxide such as alumina, a ceramic material or a fiber-reinforced ceramic material is incorporated or this base material is impregnated with it,

and then heated in an atmosphere of ammonia or nitrogen is formed with the formation of silicon nitride in the base material, with the result that the latter is improved in Regarding its heat resistance and its resistance to oxidation. The present invention is based on this.

The essence of the invention described in the present application is based on the fact that a compound having a Contains silazane group that is linked to a polymerizable

. Group is copolymerized, a compound that is a 85

Contains polysaccharide and silazane groups, a mixture These compounds or a base material impregnated therewith is heated to shape them into the specified To bring shape, and then in a nitrogen or

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■ (,

Ammonia atmosphere is heated to produce a compound of the silicon nitride type in the form of the specified

Molded body. 5

By heating such a silazane group-containing polycondensate until it melts and then Extruding the thus molten polycondensate through nozzles can also be a silicon nitride type compound can be obtained in the fiber form.

A compound that contains a silazane group linked to copolymerized with a polymerizable group

by heating in a nitrogen or ammonia atmosphere

re converted into silicon nitride. One such

In particular, silicon nitride can be obtained by reacting an organohalosilane which is a polymerizable Group such as vinyl group, in an organic solvent with one polymerizable with the Group of copolymerizable monomers or with a monomer, which contains a large number of polymerizable groups, in the presence of ammonia gas or an ammonia-forming compound.

Suitable polymerizable monomers include styrene, divinylbenzene, vinyl chloride, vinylidene chloride, acrylonitrile, Vinyl acetate, acrylic acid, methyl acrylate, ethyl acrylate, others Acrylic acid esters, methyl methacrylate, ethyl methacrylate and 2-ethylhexyl methacrylate.

Organic solvents that can be used according to the invention methyl alcohol, ethyl alcohol, propyl alcohol, other aliphatic alcohols, polyhydroxy alcohols, xylene, η-hexane and other organic solvents.

The above compound containing a silazane group is obtained by reacting in a solvent Organohalosilane, which has a polymerizable group

contains, a copolymer with the polymerizable group! - manageable monomer or a monomer that has a plurality

of polymerizable groups, and ammonia gas 5

or an ammonia-forming compound is reacted with one another.

The reaction temperature varies depending on the kinds of the starting materials, and it can be within the range from room temperature to 90 C, preferably from

30 to 30 ° C. 10

The organohalosilane that reacted with a monomer should be, the at least one polymerizable group contains is represented by the general formula

15 ^R (4-n) " ^Si - ^X n

where mean:

X is a halogen atom, η is an integer from 4 to 1 and

R is a hydrogen atom, an alkyl group, an alkylene group, an allyl group, a vinyl group or an aryl group.

The compound that contains a silazane group associated with a polyhydroxy alcohol has been reacted, is obtained by joint reaction of the organohalosilane, of the polyhydroxy alcohol and ammonia gas or an ammonia generating compound. Suitable polyhydroxy, Alcohols include glycerin and glycols.

³ ^ Shaped bodies, which consist of the compound containing silazane or a material impregnated therewith, are heated in an ammonia or nitrogen atmosphere to 1000 to 1800 ° C, preferably 1500 to 1600 ° C, in order to convert them into those made of silicon antiride. In this case, if the moldings made from the compound containing a silane group, ie from a polycondensate, were abruptly heated to a high temperature, they would suffer a thermal shock and an abrupt disintegration would occur.

Set in a settlement reaction with the risk of. Damage to their original shape. They are therefore ρ- preferably at a rate of temperature increase of 5 to 10 ° C / hour. heated until their temperature has reached 600 to 70O ⁰ C, and then they can be heated with a higher rate of temperature increase.

The silazane group-containing compound may be heated to a temperature higher than its own Melting point to liquefy it or to convert it into a semi-molten state, and it can then to Fibers, films, sheets, plates and other desired molded articles can be molded by using a conventional one Molding process. This connection can be made with carbon fibers, Graphite powder, metal oxide powder such as aluminum oxide powder, or ceramic powder such as silicon nitride

2Q powder or silicon carbide powder, mixed and then molded are used to produce a molded article from a compound of the silicon nitride type. In addition, carbon fibers, carbon composite material reinforced with carbon fibers, Ceramic material or a material reinforced with ceramic fibers with the compound containing silazane impregnated and then into a molded body made of a compound * silicon nitride type formation. These silicon nitride-type compound molded articles are without Use a binder as opposed to preserved

3Q conventional silicon nitride molded bodies and they exhibit hence excellent in purity, mechanical strength, heat resistance and oxidation resistance.

The fibrous silicon nitride can be used for gg Reinforcement of plastics and rubbers, e.g.

Polyesters, epoxy resins, phenolic polyimides and rubbers, it can also be used to reinforce a metal matrix / such as an aluminum, copper, titanium

or magnesium matrix and it can also be used to reinforce carbon (carbon) / glass, SiIi-. cium nitride or various other materials. 5

The invention is further illustrated by the following examples explained, but without being limited thereto.

Example 1 10

100 g vinylmethyldichlorosilane as organochlorosilane, 100 g Glycerine and 5 g of methyl acrylate monomer containing 0.05 g of benzoyl peroxide as a polymerization initiator, were mixed together. Ammonium carbamate was added in small portions at 30 ° C. to the mixture obtained in this way incorporated as an ammonia-forming compound to convert the organochlorosilane with the methyl acrylate monomers:. to copolymerize to obtain a copolymer which was then reacted with ammonia to form one Polymer containing a silazane group. The reaction was carried out at 30 to 50 ° C for 1 hour and then for 3 hours carried out at 60 to 70 ° C for a long time. The reaction product contained two layers, of which the upper layer consisted of a white colored liquid material containing ammonium chloride as a by-product and the lower one Layer consisted of a white colored resinous solid.

The reaction product was heated to 80 ° C to convert the by-product ammonium chloride contained therein into glycerin to dissolve, thereby separating the white colored resinous solid from the ammonium chloride. The received resinous solid was heated and injected through nozzles

extruded to obtain fibers composed therefrom. 35

The fibers obtained were in an ammonia gas or ammonia stream a tubular electric furnace at a rate of 5 ° C / hour. heated to 1000 ° C and then they became 10

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«W # te« VW * W * W W *

ΊΟ

In another electric furnace at 1500 C for minutes subjected to further heat treatment, whereby yellow-

greenish black colored fibers received. 5

The fibers obtained were subjected to X-ray diffraction, whereby it was confirmed that they were mainly composed of cA silicon nitride. Besides, they had one

2 tensile strength of 150 kg / mm.

Example 2

The procedure of Example 1 was repeated, wherein

this time 115 g vinylmethyldichlorosilane instead of 100 g 15th

were used, being fibrous silicon nitride received. The fibrous silicon nitride became one Subjected to X-ray diffraction, whereby it was confirmed that it was mainly composed of (^ -silicon nitride.

Example 3

100 g of vinylmethyldichlorosilane as one polymerizable Group containing organohalosilane, 200 g glycerine

and 15g divinylbenzene, which contains 1% by weight benzoyl peroxide

held were mixed together to make a

Mixture in which 10 g of ammonium carbamate were incorporated in small portions at 30 ° C. The obtained mixture was heated for 4 hours at 65 ° C for Completing: _or, concentrating the reaction. In this case, as the reaction proceeded, the ammonium carbonate was pyrolyzed with evolution of ammonia, with the result that a white colored resinous material was formed.

_o _ The white colored resinous material formed was do

separated from the glycerin as a solvent and the ammonium chloride as a by-product. The one separated in this way resinous material was heated to 90.degree. C. to obtain a viscous liquid which then closed

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was formed into a film. The molded film was turned into a Porcelain boats placed, introduced into a cylindrical electric furnace and then in an ammonia atmosphere with a speed of 50 ° C / hour. heated to 1OOO ° C and also heated to 15OO ° C in a nitrogen gas atmosphere, a yellow-greenish-black colored film was obtained.

The film obtained was subjected to an X-ray analysis, which confirmed that it consisted mainly of oC-type silicon nitride with the remainder a minute amount of silicon carbide was of the ß-type.

_O

In addition, the film was run at a speed of 10 C / Hours. Heated to 1300 ° C and 2 hours at this temperature kept in a stream of air using a differential calorimeter (manufactured by Rigaku Electric Co., Ltd.), with the result that the weight

20 2

Increase in film was 2.1 mg / cm.

■ Example 4

100 g of vinylmethyldichlorosilane were mixed with 20 g of methyl acrylate,

containing 1% benzoyl peroxide mixed for manufacture

a mixture which was reacted with 15 g of ammonium carbaraate in xylene. The reaction was carried out for 4 hours at 65 ° C carried out, then the xylene was removed from the reaction mixture, leaving a white rubber-30

term elastic resin received. The obtained resin was made with chopped silicon carbide fibers of 3 mm in length in an amount of 35% by weight of the resin and then mixed into a sheet-like body

Size of 30mm 50mm 5mm molded. The thus obtained 35

Shaped body was in an ammonia gas at a rate of 3 ° C / hour. heated to 1000 ⁰ C (burned) and in an N ₂ gas a further heat treatment at 1500 ° C

subjected. The product obtained had a flexural strength of 460 kg / cm. In addition, the product became a Heat-treated for one hour in a stream of air at 700 ° C, the change in the weight of the product was negligibly small.

Example 5

100 g of silicon tetrachloride was mixed with 100 g of glycerin to produce a mixture of 20 g of ammonium carbamate were incorporated. The whole was first stirred at room temperature, with the polycondensation progress, gradually the temperature was raised to 65 ° C and held at this temperature for 3 hours. The reaction mixture obtained was freed from the glycerol and the NH ^ Cl obtained as a by-product, with a viscous resin colored white was obtained.

A separately produced circular composite material with a carbon fiber reinforced carbon or carbon fiber. Carbon matrix with a size of 10 mm (thickness) χ 100 now (diameter) was impregnated with the viscous resin under reduced pressure in an ammonia atmosphere at 100 ° C heat-treated and then further heat-treated in a ^ atmosphere at 1500 ° C. Impregnation and heat treatment at 1500 ° C were repeated 3 times. The composite material treated in this way had a bending

O
strength of 650 kg / cm, which increases the strength

30 corresponded to about 20%. Example 6

50 g of methyltrichlorosilane (CH ₃ SiCl ₃ ) were incorporated into 100 g of glycerol, a mixture being obtained in which 7.5 g of ammonium carbamate was incorporated in small portions and which was then reacted at 30 ° C. for 4 hours. The reaction proceeded at the same time

strong foaming to give a white colored resinous material. The reaction mixture formed The excess glycerin was removed from g to give a white colored viscous resin suitable was for impregnating carbon or carbon material or ceramic material.

jQ The procedure described above was repeated, this time using 150g xylene instead of glycerine where a silazane was formed, which was confirmed by infrared analysis, but it turned white colored solid sediment formed which is not resinous.

was tig. It was therefore necessary to use glycerin for the conversion to a resin in the case where such functional groups were present.

Example 7

100 g of dimethyldichlorosilane ((CH3) ^. SiCl ₂ ) were mixed with 100 g of glycerol to produce a mixture into which 15 g of ammonium carbamate were incorporated at 30 ° C. for the reaction. Then the reaction lasted for 4.5 hours

received like resin.

continued at 60 ° C, whereby a white colored gel-

In the resin thus obtained, powdered alumina was incorporated in an amount by weight 2.5 times Corresponding to the amount of resin, both were mixed together thoroughly, into a 10 mm thick, 50 mm wide and 80 mm long metal mold and then molded under heat and pressure. The molded body obtained was burned in a nitrogen gas at 1300 ° C, whereby

a rigid rectangular shaped body with a flexural strength of 380 kg / cm ^{2 was} obtained.

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w ■ w W <**

Example 8

₅ The compounds given in the following table

were reacted with one another under the reaction conditions also given in the table below
Preparation of compounds containing a silazane group. The silazane group-containing compounds thus obtained were molded into the respective molded articles shown in the following table and heat-treated under the conditions also shown in the following table, silicon nitride type molded articles having those shown in the following table
, [- Properties received.

ω
cn

ω
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to

cn

cn

Tabel

Compounds, reaction conditions

Shape of the moldings

Bromotrimethylsilane, Divinylbenzene, Glycerin and Acrylonitrile
were at 60 C for 4 hours
implemented with each other while
Ammonia gas in excess against the
Reaction mixture was blown '

Dibromodiphenylsilane and glycol
were at 8CPc for 2 hours
implemented with each other while
Ammonia gas in excess against
the reaction mixture was blown

Iodotrimethylsilane, styrene, glycerin and vinyl acetate were made
Reacted with one another for 4 hours in the presence of ammonium carbamate at 80 ° C

Vinyltrichlorosilane and divinylbenzene were left at 70 ° C for 2 hours
implemented with each other while
Aimoniakgas in excess against the
Reaction mixture was blown

10 mm 20 mm 20 mm block-like

Heat treatment conditions

Ammonia cat

nDsphere,

1000 ⁰ C properties of the molded bodies of the silicon nitride type

Weight increase of 1.8 mg / cm after 2 hours of heat treatment at 1OCO ⁰ C in an air atmosphere

16C0 ° C

there were chopped carbon fibers 1 mm long in one Weight amount of 20% incorporated and then 1 mm thick films were made therefrom

it became powdery N ^ atmosphere

ges silicon nitride in

an amount of 45%

incorporated and then

were 50 ram 50 mm

100 mm blocks

formed therefrom g-atmosphere, weight increase of 1.2 mg / cm after treatment for 2 hours at 1COO ⁰ C in an air atmosphere

1500 ⁰ C

Fibers with a through-ammonia knife from 15jam sphere ,, (while spinning a few% polyethylene oxide were added) the strength was 1.7-anal so high like that of a silicon nitride sintered body made from conventional powdery cm Silicon nitride was obtained

Tensile strength 120 kg / mm

1800 ° C

cn cn to

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cn

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cn cn

Table - Continuation

Divinyldichlorosilane and
Methyl acrylate was 3 hours.
long at 8O ⁰ C in the presence
set together by Äinmoniuircarbaitiat

Fibers with a diameter of 15 pm

(A few% of polyethylene oxide were added during the spinning process) N ^ atmosphere, tensile strength 100 kg / mm 150O ⁰ C

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Although the invention has been preferred with reference to FIG Execution fonts explained in more detail, but it is for the

A person skilled in the art of course, that they are by no means 5

is limited, -but that this is limited in many ways can be changed and modified without departing from the scope of the present invention will.

Claims (8)

Claims Process for producing a molded body of the silicon nitride type, characterized by the following levels: Reacting (1) a member selected from the group consisting of the silicon halides and the one polymerizable group - ^ containing organohalosilanes. . the general formula % -n) ~ ^Si " ^X n where X is a halogen atom, η is an integer from 4 to 1 and R is a hydrogen atom, an alkyl group, an alkylene group, an allyl group, a vinyl group or an aryl group 15 mean, (2) a representative selected from the group of monomers copolymerizable with the polymerizable group, containing a plurality of polymerizable groups Monomers and glycerin or glycols and (3) a representative selected from the group consisting of ammonia gas and the Ammonia-forming compounds, together to produce a compound having a silazane group which is linked to the polymerizable group is copolymerized, thermal deformation of a representative selected from the 25th Group (^) of the obtained compounds containing the silazane group, Lq) of the compounds containing a silazane group, together with a polyhydroxy alcohol, (C) the mixtures of the compounds (a) and (b) and (D) the mixtures of each of the compounds (A) to (c) with a base material for producing a molded body with a predetermined shape and subsequent heating of the molded body obtained in a nitrogen gas or in an ammonia atmosphere for production of the silicon nitride type molded body. 2. The method according to claim 1, characterized in that carbon fibers, graphite powder, aluminum oxide powder, Silicon nitride powder or silicon carbide powder -V- is used. 3. The method according to claim 1 and / or 2, characterized in that the heat deformation is carried out by Heating the body to melt it and then extruding the molten body through nozzles to produce fibers therefrom as molded bodies. 4. The method according to claim 1 and / or 2, characterized in that that the heat deformation is carried out by Heating the body to melt it and then impregnating the base material with the molten one Body for the production of an impregnated bath sismaterials as molded bodies. 5. The method according to claim 4, characterized in that carbon fibers as the base material, one by carbon fibers reinforced carbon or carbon composite material Ceramic material or a fiber-reinforced ceramic material is used. 6. The method according to at least one of claims 1 to 5, characterized in that the monomer (2) is a vinyl compound, styrene, divinylbenzene, vinyl chloride, vinylidene chloride, Acrylonitrile, vinyl acetate, acrylic acid, methyl acrylate, ethyl acrylate, methyl methacrylate, ethyl methacrylate or 2-ethylhexyl methacrylate is used. 7. The method according to at least one of claims 1 to 6, characterized in that the compound containing a silazane group
is converted. at 1500 to 1600 ° C in silicon nitride. 8. Shaped body in fiber form, characterized in that it has been produced by the method of claim 3.