Patent ID: 8076419

Claim:
A method of producing a propylene impact copolymer comprising an unbalanced polypropylene matrix, comprising: (a) contacting a catalyst composition with propylene, a first amount of a chain terminating agent and optionally ethylene or C4 to C12 α-olefins in a first reactor to form a first polypropylene having a melt flow rate, MFR 1 , comprising no more than 5 wt %, by weight of the first polypropylene, of ethylene or α-olefin derived units; (b) contacting a catalyst composition and first polypropylene with propylene, a second amount of a chain terminating agent, and optionally ethylene or C4 to C12 α-olefins in a second reactor to form a second polypropylene having a melt flow rate, MFR 2 , comprising no more than 5 wt %, by weight of the second polypropylene, of ethylene or α-olefin derived units, wherein the second amount of chain terminating agent is greater than the first amount of chain terminating agent and is sufficient to control the ratio MFR 2 /MFR 1 to be greater than 1.5; and (c) contacting a catalyst composition, first polypropylene and second polypropylene in a third reactor with propylene and ethylene to form ethylene-propylene copolymer elastomer, comprising sufficient ethylene-derived units such that the overall ethylene content of the impact copolymer is within the range from 35 to 70 wt, and the MFR of the impact copolymer, MFR ICP , is from 6 to 18 dg/min.