| 摘要 |
A copolymer of etkylene and propylene having an average propylene content of 8 to 15 mole per cent, and an RSV of at least 1.5, and in which at least 90% of the copolymer has a propylene content within 5% of the average propylene content, is used either alone, or in admixture with fillers as an insulator for electrical conductors. The copolymer may be cross-linked. The fillers may be selected from carbon black, furnace black, silica e.g. aerogel, alkyl-surface-esterifie silica, alkyl chlorosilane-treated silica, calcium silicate, hydrated aluminium oxide, alumina, alpha-alumina and gamma-alumina. The cross-linking may be effected with peroxides and optionally sulphur. The copolymers are made by copolymerizing the monomers, in an inert liquid organic solvent, in the presence of a catalyst consisting of an organoaluminium halide and a vanadium compound of the formula VOY 3-nXn where Y is an alkoxide or acetylacetonate group, X is halogen, and n is 0-2 when Y is an alkoxide group, and n is 0 when Y is an acetylacetonate group. The catalyst may be preformed or formed in situ. Exemplified catalyst is diethylaluminium and tri -tbutyl orthovanadate. The polymerization reaction is stopped with n-butanol, and the product washed with small amounts of gluconic acid and 4,41-thio-bis(6-tert.-butyl-m-cresol), and aqueous sodium hydroxide. The copolymers may be stabilized. |
