Prepn. of block copolymers of ethylene and propylene - by vapour phase polymerisation, gives increased impact strength

摘要

Propylene-ethylene block copolymer (1) has a melt-flow range of 0.1-10 g/10 min., ratio of Mw/Mn above 6.5/1, polym. ethylene content above 1.0 wt.%, Ti content 3ppm, Mg content 40ppm, Cl content 100ppm and total ash content 400 ppm. Prepn. of (1) comprises (A) preformed propylene polymer prod. in presence of catalyst compsn. containing (a) (aluminium trialkyl)partially complexed with electron donor empd. and (b) Ti tri- or tetrahalide supported on Mg dihalide or complex of Ti Tri-or tetrahalide with electron donor supported on Mg dihalide; (B) introducing (A) into a continuously agitated reactor; (C) introducing ethylene, (E) and propylene(p)monomers in molar ratio E to P 0.15:1 to 0.3:1 and (D) polymerising E and P in the vapour phase onto (A). Propylene-ethylene block copolymers produced are used in applications where desired improvement in impact strength is required.