Hydrosilyl-modified polycarbosilane precursors for silicon carbide

Claim 2

A branched hydrosilyl-modified polycarbosilane comprising units of the formula ##STR7## wherein R is a lower alkyl, a is 0 or 1, b is 0-3, c is 0-4, d is 0-4, and a+b+c+d totals 4, with the provisos that, in different units, a, b, c, d, and R may differ, but that, in at least one unit, a+d must total 1 or more and units of the formula ##STR8## wherein R is defined as above, d is 1-2, e is 0-2, f is 1-3, and d+e+f totals 4.

Claim 3

A process for producing branched polycarbosilanes containing hydrosilyl groups which comprises reacting, with an active metal in an inert solvent or mixture of inert solvents at an elevated temperature, a compound system comprising one or more monomers of the formula (I) (CH.sub.2 ═CH).sub.a R.sub.b SiX.sub.c (CH.sub.2 X).sub.d (I) wherein R is lower alkyl, X is halo, a is 0 or 1, b is 0-3, c is 0-4, d is 0-4, a+b+c+d totals 4, and a+c+d totals at least 1, and one or more monomers of the formula (II) H.sub.d R.sub.e SiX.sub.f (II) wherein R and X are defined as above, d is 1 or 2, e is 0-2, f is 1-3, and d+e+f totals 4, said compound system being selected such that its average molar functionality is at lest 2.3 and the formation of silicon carbon bonds is favored.

Claim 4

A process for producing branched polycarbosilanes containing hydrosilyl groups which comprises reacting, with an active metal in an inert solvent or mixture of inert solvents at an elevated temperature, a compound system comprising one or more monomers of the formula (I) (CH.sub.2 ═CH).sub.a R.sub.b SiX.sub.c (CH.sub.2 X).sub.d (I) wherein R is lower alkyl, X is halo, a is 0 or 1, b is 0-3, c is 0-4, d is 0-4, a+b+c+d totals 4, and a+c+d totals at least 1, and one or more monomers of the formula (II) H.sub.d R.sub.e SiX.sub.f (II) wherein R and X are defined as above, d is 1 or 2, e is 0-2, f is 1-3, and d+e+f totals 4, said compound system being selected such that its average molar functionality is at lest 2.3 and the formation of silicon carbon bonds is favored.

Claim 5

The process as in claim 2 wherein said active metal is potassium.

Claim 6

The process as in claim 2 wherein the solvent is tetrahydrofuran, which has an atmospheric pressure reflux temperature above the melting point of potassium metal.

Claim 7

The process as in claim 2 wherein said monomer system contains at least two different monomers of formula (I), at least one of which is characterized by an a+c+d totals of 1 or 2, and one monomer of formula (II).

Claim 8

The process as in claim 2 wherein said monomer system contains at least one monomer of formula (I), having an a+c+d total of 3 or 4, and one monomer of formula (II).

Claim 9

The process as in claim 2 wherein R is methyl and X is chloro.

Claim 10

The branched, hydrosilyl-modified polycarbosilane of claim 1 wherein R is methyl and X is chloro.

Claim 11

The process as in claim 2 where the elevated temperature is the reflux temperature of the solvent of claim 4.

Claim 12

The branched, hydrosilyl-modified polycarbosilane as claimed in claim 1 which is thermoplastic and, at room temperature, is soluble in non-protic organic solvents.

Claim 13

The branched, hydrosilyl-modified polycarbosilane prepared according to the process of claim 2 wherein the compound system comprises a 1/1 molar ratio of MeSiHCl 2 and CH 2 ═CHSiMe 3 .

Claim 14

The branched, hydrosilyl-modified polycarbosilane prepared according to the process of claim 2 wherein the compound system comprises a molar ratio of MeSiHCl 2 and CH 2 ═CHSiMe

Claim 15

The branched, hydrosilyl-modified polycarbosilane prepared according to the process of claim 2 wherein the compound system comprises MeSiHCl 2 and ClCH 2 SiMe 2 Cl.

Claim 16

The branched, hydrosilyl-modified polycarbosilane prepared according to the process of claim 2 wherein the compound system comprises a 1/1 molar ratio of MeSiHCl 2 and CH 2 ═CHSiMe 2 Cl.

Claim 17

The branched hydrosilyl-modified polycarbosilane prepared according to the process of claim 2 wherein the compound system comprises the monomers Me 3 SiCl/MeSiHCl 2 /CH 2 ═CHSiMeCl 2 in the respective ratios of 0.85/0.3/1.0 or 3/1/3.

Claim 18

The branched hydrosilyl-modified polycarbosilane according to the process of claim 2 wherein the compound system comprises the monomers Me 3 SiCl/Me 2 SiCl 2 /MeSiHCl 2 /CH 2 ═CHSiMeCl 2 in the respective ratios of 0.85/0.3/0.3/1.0, 0.85/0.2/0.2/1.0, or 0.85/0.3/0.1/1.0.