Impact resistant polypropylene compsn. - contg. ethylene-propylene copolymer incorporated by in situ polymerisation

摘要

An impact resistant, chemically prepd. propylene polymer compsn. contg. 3-40 mole% polymerised ethylene is produced in 3 stages. Stage (1) comprises polymerising propylene contg. 0-1 mole% another olefin in presence of a catalyst comprising (a) a Ti cpd. catalyst or a support contg. at the surface at least Mg halogen and Ti, and (b) an organoaluminium cpd., to form a crystalline polypropylene with an isotactic index =90, representing 55-95 wt.% of the final polymer compsn. Stage (2) comprises copolymerising propylene and ethylene in presence of the reactn. prod. from (1) and the same catalyst while keeping the propylene content in the gaseous phase of the polymn. zone at 65-90 mole% to form a propylene/ethylene copolymer with a propylene content of 60 - 85 mole%, representing 1-10 wt.% of the final polymer compsn. Stage (3) comprises polymerising ethylene opt. with propylene, in presence of the reactn. prod. from (2) and the same catalyst while maintaining the propylene content in the gaseous phase in the polymerisation zone at 0-15 mole%, to form polyethylene or EP copolymer with a propylene content of up to 10 mole%, having an intrinsic viscosity of =2.6 and representing 1-35 wt. % of the final polymer compsn. The prod. meets the impact strength requirements of ASTM D.