Title of Invention	A PROCESS FOR THE SYNTHESIS OF CROSSLINKED POLYSILAHYDROCARBON
Abstract	This invention relates trJ a process for the synthesis of crosslinked polysilahydrocarbon which comprises reacting atleast one organodichlorosilane with styrene in the pesence of an alkali metal. One of the organodichlorosilanes in the mixture must. be alkyl vinyldichlorosilane. The crosslinked po1.ysilahydrocarbon is recovered from the reaction mixture by precipitate washirlg and drying.

Full Text

This invention relates to a process for the synthesis of cross linked polysilahydrocarbons. Polysilahydrooarbons are polymers that oontaln sllyl linkages which are separated by two oor more hydrocarbon units. Major drawback associated with polsilahydrocarbons is thier poor thermal stability. Lack of branching or cross linking and the presence of disilyl linkage are found to be responsible for the poor thernal stability of these compounds. Thermal stability of polysilahydrocarbons has been improved by subjecting the polymers to heat treating in an inert atmosphere. However, the yield of thermally stable polymer obtained by this method is poor and is only in the range of 20-30%. Highly branched/crosslinked and thermally stable polysilahydrocarbons find use In the preparation of funotionalized polymers and non-oxide ceramic powders. The object of this invention is to develop a simple synthetic method for producing cross linked thermaly stable polysilahydrocarbons. Alkylvinyldichlorosilane or a mixture of alkylvinyldiohlorosllane and organic substituted dich1orosilanes is treated with styrene in the presence of an alkali metal or an alloy of alkali metals. Dechlorination of the substituted silanes take place initially to result in the formation of disilyl Intermediates which react with styrene to form a copolymer or a terpolymer. During the above dechlorination unsaturated substituted groups such as vinyl groups attached to Bilicon open up and take part in the cross linking step of the reaction. In otherwords, simultaneous polymerization and cross linking takes place resulting in the production of cross linked polysilahydrocarbons. This method not only eleminates several process steps but also results in high yield of 75% to 95%. The raw materials used are also easily and cheaply available. The crosslinked polysilahydrocarbons were synthesized by the Wurtz type reaction of alkylvinyldichlorosilane with styrene or a mixture of alkylvinyldichlorosilane and dialtlkyldichlorosilane/alkylaryldichlorosilane and styrene in presence of alkali metal in an inert solvent. The alkylvinyldichlorosilane monomer can be methylvlnyldiohlorosilane, ethylvlnyldichlorosilane or a combination of these monomers in any proportion. the dialkyldlohlorosilane can be dimethyldlchlorosilane, dlethyldichloresilane, ethylmethyldiohlorosilane or a combintion of two or more of these monomers in any proportion and the alkylaryldichlorosilane can be methylphenyldlchlorosllane |or methyltolyldichlorosilane or a combination of these monomers ;in any proportion. The alkali metal used for the synthesis can be sodium, potassium or an alloy of these two metals. the polymerization is preferably done in a hydrocarbon solvent selected among benzene, toluene or xylene or a mixture of two for more of these solvents taken in any proportion. The monomer to solvent ratio (by weight) can vary from 1:4 to 1:6. The diortfanodlohlorosilane to styrene ratio can vary from 4:1 to 1:7. The polymerization is performed in the temperature range 100 to 135oC. The reaction time can vary from 1 to 5 hr. vinyl The polymerization occurs primarily through, the reaction of disilyl intermediates with the double bonas of styrene resulting in the formation of Si-C bonds. The 'above polymerization reaction is followed by crosslinking involving the disilyl intermediates or growing polymeric chains and the groups attached to silicon. This invention relates to a process for the synthesis of crosslinked polysilahydrocarbons which comprises reacting at least one organodichlorosilane with styrene, one of said organodichlorosilane in the reaction mixture being alkylvinyl dichlorosilane, said organo group being an alkyl, alkenyl and aryl, the alkyl and alkenyl group having 1 to 8 carbon atoms and the aryl group being benzyl or alkyl substituted benzyl groups under known dechlorination conditions in the presence of atleast one alkali metal and recovering the resultant crosslinked polysilahydrocarbon therefrom by known methods. r The reaction scheme shown herein below explains the simultaneous polymerization and crosslinking reaction. The following non-limitive examples illustrate the invention: Bxaaple 1: Synthesis of crosslinked polysilahydrocarbons from Bethylvlnyldlohlorosllane and styrene (1:0.25 sole ratio) A four necked round bottomed flask fitted w1th a stirrer mantle, condenser, inlet and outlet for inert gas and n calcium chloride guard tube is charged with 7.5 g(0.327 mol) of freshly cut sodium in 90 ml of toulene. Sodium is melted under reflux conditions of toluene with stirring. To the finely divided sodium, monomer mixture containing 21.15 g (0.15 mol:) of methylvinyldlchlorosilane and 3.9 g (0.375 mol) of styrenei is added using a pressure equalizing funnel over a period of 10 min. The reactuion mixture is allowed to reflux gently for a period of 2 hr. The; unreacted sodium is neutralized with methenol/toluene mixture and the reaction mixture is poured into excess of methanol. The precipitate obtained is collected and washed several times with methanol/water mixture to remove Rodium chloride and finally with methanol and then dried in a vacuum oven at 100oC for 10 hr. After drying, the polymer is soaked in 100ml of toluene and kept overnight. It is filtered to remove the soluble fraction. The soluble fraction is obtained in negligible yield. The insoluble polymer obtained is dried in a vacuum oven at 100oC for 1 hr. The yield of the final product is about 79%. Example 2, Synthesis of crosslinked polysilahydrocarbon from nethylvinyldichlorosilane and styrene (1:0.5 mole ratio) Following the experimental procedure described above, a orosslinked copolymer is synthesized by reaotinrt a mixture of 21.15g (0.15 mol) methylvinyldichlorosilane and 7.8 g (0.07.H mol) I of styrene in 90 ml of toluene at 110˚C. The soluble polymer is obtained in 2% yield and the insoluble polymer is obtained '\x\ 93% yield. Bxample 3, SyntheslB of polyBllahydrocarbon from methylvlnyldlnhloroailane, dinethyldlchloroBllane and styrene (1:1:0,9 mole ratio) Following the procedure,described above, a crosslinked terpolymer is synthesized in 79% yield by reacting a monomer mixture containing 7.26 g (0.0515 mol) methylvinyldichlorosilane, 6.7 g (0,0519 mol) of dimethyldichlorosilane and 5.02 g (0.048 mol) of styrene in 100 ml of toluene with 5.52 g (0.24 mol) of sodium. This polymer is stable up to 400˚C in nitrogen atmosphere and undergoes degradation above this temperature giving a ceramic residue of 40% at 900^0. Though the invention is described hereinabove with specific embodiments, obvious equivalents known to persons skilled in the art are within its scope and that of the appended claims. WE CLAIM: 1. A process for the synthesis or crosslinked polysilahydrooarbons comprising reacting atleast one organodiohlorosilane with styrene, one of said organodlohlorosilane in the reaction mixture being alkyl vinyldichlorosilane, said organo group being alkyl, alkenyl and aryl, the alkyl and alkenyl group having 1-8 carbon atoms and the aryl group being benzyl or alkyl substituted benzyl groups, under known dechlorination condition in the presence of at least one to alkali metal or an alkali metal alloy and recovering the resultant crosslinked polysilahydrocarbon there from by known methods. 2. The process as claimed in claim 1, wherein the reaction is carried out in the presence of an organic solvent. 3. The process as claimed in claim 2, wherein said organic solvent is a hydrocarbon solvent selected from benzene, toluene or xylene or a mixture thereof. 4. The process as claimed in claims 13. wherein ; the I ! monomer solvent ratio is from 1:4 to 1:6 by weight. 5. The process as claimed in any of the preceding claims ii wherein the organodichlorosilane to styrene ratio is from 4 1 to 1:7 by weight. 6. The process as claimed in any of the preoeedinrt claims wherein the reaction is carried out at a temperature range of 100 to 135˚C. 7. The process as claimed in any of the preceding claims. wherein the alkali metal is sodium, potassium or an alley thereof. 8. The process as claimed in any of the preced ing olaims, wherein the reaction mixture is refluxed for a period of 30hts hours and the unreacted alkali metal is neutralised thereafter. 9. The process as claimed in claim 8 wherein the reaction \ ill mixture is poured into excess alcohol to precipitate said polymer which is subsequently washed and dried. 10. A process for the synthesis of cross 1 inked polysllahydrocarbons substantially as herein described with particular reference to the Examples.

Documents:

1164-mas-1999-abstract.pdf

1164-mas-1999-claims duplicate.pdf

1164-mas-1999-claims original.pdf

1164-mas-1999-correspondance others.pdf

1164-mas-1999-correspondance po.pdf

1164-mas-1999-description complete duplicate.pdf

1164-mas-1999-description complete original.pdf

1164-mas-1999-form 1.pdf

1164-mas-1999-form 19.pdf

1164-mas-1999-form 26.pdf

1164-mas-1999-form 3.pdf