Two-phase ethylene-propylene block copolymerization process

Claim 1

A continuous sequential vapor phase block copolymerization process for the production of impact resistant ethylene-propylene polymers at high productivity rates, which comprises: (A) preparing a propylene prepolymer in finely divided form and containing active catalyst residues by polymerizing propylene at a pressure sufficient to maintain propylene in liquid phase and at a temperature ranging between about 145° F. and about 160° F. in the presence of a catalyst composition containing the components: (a) a first at least partial complex of an alkyl aluminum compound with an electron donor compound wherein the alkyl aluminum is selected from aluminum trialkyl or a mixture of aluminum trialkyl and a dialkyl aluminum halide and wherein the mole ratio of alkyl aluminum to electron donor is maintained between about 2 and about 5, and, (b) a complex of an electron donor compound with a titanium tri- or tetrahalide supported on magnesium dihalide, where the components (a) and (b) are being provided in a molar ratio of Al/Ti between about 40:1 and about 150:1, and, separating the propylene prepolymer from volatile constituents; (B) introducing the propylene prepolymer, ethylene and propylene into at least one continuously agitated vapor phase reaction zone; (C) introducing to said vapor phase reaction zone: (i) a quantity of a second at least partial complex of an alkyl aluminum compound with an electron donor compound, wherein the alkyl aluminum is selected from trialkyl aluminum or mixtures of trialkyl aluminum and dialkyl aluminum halide and wherein the mole ratio of alkyl aluminum to electron donor compound is maintained in a range from about 8:1 to about 15:1 and the quantity of aluminum alkyl compound is between about 15 to about 50% of the aluminum alkyl compound of component (a), and, (ii) an additional quantity of component (b) sufficient to provide a molar ratio of Al/Ti of components (i) and (ii) between about 75:1 and about 125:1, (D) polymerizing said ethylene and propylene onto the propylene prepolymer in said vapor phase reaction zone at the temperature of from about 140° F. to about 170° F.