Preparation of polysilazane polymers and the polymers therefrom
AssigneeDow Corning Corporation
InventorJohn H. Gaul
Life of this patent
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Abstract
What is disclosed is a process for preparing polysilazane polymers by contacting and reacting chlorine-containing disilanes with ammonia. The polysilazane polymers are useful as chemical intermediates to produce silicon-containing chemical compounds. They are also useful in the formation of silicon carbide-containing ceramic materials.
Claims31
A process of preparing a polysilazane polymer which consists of contacting and reacting in an inert, essentially anhydrous, atmosphere, at a temperature in the range of 25.degree. C. to 370.degree. C.
- (A) ammonia and
- (B) chlorine-containing disilanes selected from the group consisting of
- (i) a chlorine-containing disilane having the general formula
- [Cl.sub.a R.sub.b Si].sub.2
- and
- (ii) a mixture of chlorine-containing disilanes having the general formula
- [Cl.sub.c R.sub.d Si].sub.2
- wherein
- a has a value of 1.5-2.0;
- b has a value of 1.0-1.5;
- the ratio of c to d is in the range of 1:1 to 2:1,
- the sum of a+b is equal to three;
- the sum of c+d is equal to three;
- and
- R in each case is selected from the group consisting of the vinyl group, alkyl radicals of 1-3 carbon atoms and the phenyl group.
A method of preparing a silicon carbide ceramic material which consists of heating a polysilazane polymer in an inert atmosphere or in a vacuum to at least a temperature of 750.degree. C. until the polysilazane polymer is converted to silicon carbide ceramic material, which polysilazane polymer is obtained by a process which consists of contacting and reacting in an inert, essentially anhydrous, atmosphere, at a temperature in the range of 25.degree. C. to 370.degree. C.
- (A) ammonia and
- (B) chlorine-containing disilanes selected from the group consisting of
- (i) a chlorine-containing disilane having the general formula
- [Cl.sub.a R.sub.b Si].sub.2
- and
- (ii) a mixture of chlorine-containing disilanes having the general formula
- [Cl.sub.c R.sub.d Si].sub.2
- wherein
- a has a value of 1.5-2.0;
- b has a value of 1.0-1.5;
- the ratio of c to d is in the range of 1:1 to 2:1,
- the sum of a+b is equal to three;
- the sum of c+d is equal to three;
- and
- R in each case is selected from the group consisting of the vinyl group, alkyl radicals of 1-3 carbon atoms and the phenyl group.
A method of preparing a silicon carbide containing ceramic article which consists of (A) forming an article of the desired shape from a polysilazane polymer;
- (B) heating the article formed in (A) in an inert atmosphere or in a vacuum to an elevated temperature of at least 750.degree. C. until the polysilazane polymer is converted to silicon carbide containing ceramic, which polysilazane polymer is obtained by a process which consists of contacting and reacting in an inert, essentially anhydrous, atmosphere, at a temperature in the range of 25.degree. C. to 370.degree. C.
- (A) ammonia and
- (B) chlorine-containing disilanes selected from the group consisting of
- (i) a chlorine-containing disilane having the general formula
- [Cl.sub.a R.sub.b Si].sub.2
- and
- (ii) a mixture of chlorine-containing disilanes having the general formula
- [Cl.sub.c R.sub.d Si].sub.2
- wherein
- a has a value of 1.5-2.0;
- b has a value of 1.0-1.5;
- the ratio of c to d is in the range of 1:1 to 2:1,
- the sum of a+b is equal to three;
- the sum of c+d is equal to three;
- and
- R in each case is selected from the group consisting of the vinyl group, alkyl radicals of 1-3 carbon atoms and the phenyl group.
A method for preparing a substrate coated with a silicon carbide containing ceramic which consists of
- (A) coating a substrate with polysilazane polymer which polysilazane polymer is obtained by a process which consists of contacting and reacting in an inert, essentially anhydrous, atmosphere at a temperature in the range of 25.degree. C. to 370.degree. C.,
- (a) ammonia and
- (b) chlorine-containing disilanes selected from the group consisting of
- (i) a chlorine-containing disilane having the general formula
- [Cl.sub.a R.sub.b Si].sub.2
- and
- (ii) a mixture of chlorine-containing disilanes having the general formula
- [Cl.sub.c R.sub.d Si].sub.2
- wherein
- a has a value of 1.5-2.0;
- b has a value of 1.0-1.5;
- the ratio of c to d is in the range of 1:1 to 2:1,
- (B) heating the coated substrate in an inert atmosphere or in a vacuum to an elevated temperature of at least 750.degree. C. until the coating is converted to a silicon carbide ceramic material, whereby a silicon carbide-containing ceramic coated substrate is obtained
- the sum of a+b is equal to three;
- the sum of c+d is equal to three;
- and
- R in each case is selected from the group consisting of the vinyl group, alkyl radicals of 1-3 carbon atoms and the phenyl group.
A process for preparing a polysilazane polymer which consists of contacting and reacting in an inert, essentially anhydrous atmosphere at a temperature in the range of 25.degree. C. to 370.degree. C.,
- (A) ammonia and
- (B) a mixture of chlorine-containing disilanes and monosilanes selected from the group consisting essentially of
- (i) a mixture of a chlorine-containing disilane and a monosilane,
- (ii) a mixture of a chlorine-containing disilane and a mixture of monosilanes and
- (iii) a mixture of chlorine-containing disilanes mixed with a mixture of monosilanes, wherein
- the chlorine-containing disilanes have the general formula
- (Cl.sub.a R.sub.b Si).sub.2
- and wherein the monosilanes in each case have the general formula
- R'.sub.n SiCl.sub.4-n,
- wherein R is a vinyl group, an alkyl radical of 1-3 carbon atoms or the phenyl group;
- R' is vinyl, hydrogen, an alkyl group of 1-3 carbon atoms or the phenyl group;
- a has a value of 1.5-2.0;
- b has a value of 1.0-1.5;
- the sum of a+b is equal to three and n has a value of 0, 1, or 3.
Dependencies are inferred from the claim text.