Ethylene-propylene block copolymerization process and product

Claim 1

A continuous sequential vapor phase block copolymerization process for the production of impact resistant ethylenepropylene polymers at high productivity rates, which comprises: (A) providing a preformed propylene polymer in finely divided form, said preformed polymer containing active catalyst residues and having been prepared by polymerizing propylene in the presence of a catalyst composition containing the components (a) an aluminum trialkyl or an aluminum trialkyl at least partially complexed with an electron donor compound, and (b) titanium tri- or tetrahalide supported on magnesium dihalide, or a complex of a titanium tri- or tetrahalide with an electron donor compound supported on magnesium dihalide, the components (a) and (b) being provided in a molar ratio of Al/Ti between about 10 and about 200; (B) introducing said preformed polymer, ethylene and propylene into at least one continuously agitated reaction zone, (C) introducing an additional quantity of component (a) to said reaction zone, said quantity ranging from about 5 to about 50% of the quantity in the preparation of the prepolymer; and (D) polymerizing said ethylene and propylene monomers in the vapor phase in the reaction zone onto said preformed propylene prepolymer.