GB1412628A - Crosslinking process - Google Patents

Abstract

1412628 Cross-linking chlorinated polyethylene DOW CORNING Ltd 29 May 1973 [7 June 1972] 26463/72 Addition to 1286460 Heading C3P Chlorinated polyethylene is cross-linked by a process which comprises (A) reacting chlorinated polyethylene with a silane of formula where R is an olefinically unsaturated radical composed of hydrogen, carbon and optionally oxygen and bonded to silicon through a C-Si bond, Y is a hydrolysable organic radical selected from alkoxy, alkoxyalkoxy and acyloxy radicals of less than 6 carbon atoms and oximo radicals of less than 14 carbon atoms, and R<SP>1</SP> is a monovalent hydrocarbon radical free from aliphatic unsaturation, R or Y; in the presence of a free radical generating compound having a half-life at the reaction temperature, which is above 140‹ C., of less than 6 minutes; and (B) exposing the product to water in the presence of a silanol condensation catalyst. A stabilizer for chlorinated polymers and/or non-chlorinated polyethylene may be present during step (A). The condensation catalyst may be provided in a separate component of chlorinated or non- chlorinated polyethylene which is mixed with the product of step (A) before cross-linking. Preferred silanes are vinyl triethoxy-silane and vinyl trimethoxysilane. Many suitable peroxy and azo compound free radical generating compounds are specified. The catalyst may be formed in situ by hydrolysis or thermal decomposition of an acyloxy silane, or may be an organic metal compound, e.g. of tin, lead, zinc, iron, cobalt or titanium, an organic base or a mineral of fatty acid. Examples describe the cross-linking of products obtained from chlorinated polyethylene, triphenyl phosphite, calcium stearate, dicumyl peroxide and vinyl trimethoxysilane together with (1) cadmium/ barium stabilizer and epoxidized soya bean oil and (2 and 4) epoxidized soya bean oil by exposing to an aqueous emulsion of dibutyl tin dilaurate; and (3) the cross-linking of blends of low density polyethylene compounded with dibutyl tin dilaurate and products obtained from chlorinated polyethylene, barium/cadmium stabilizer, triphenyl phosphite, calcium stearate, dicumyl peroxide and vinyl trimethoxysilane by exposing to water.