Patent ID: 7220806
Filing Date: 2007-05-22
Classification: C08F

Abstract:
1. A process for preparing random copolymers comprising polymerizing a mixure of monomers comprising propylene and ethylene monomer in a loop reactor to form a random copolymer, in the presence of a catalyst system comprising a metallocene catalyst having the general structure: wherein Cp is a cyclopentadienyl ring; Flu is a fluorenyl ring; X is a structural bridge imparting stereorigidity; R 1 is a substituent on the cyclopentadienyl ring which is distal to the bridge, and which distal substituent comprises a bulky group of the formula R 4 R 5 3 in which R 4 is chosen from Group IVA, and each R 5 is the same or different and is a hydrogen or a hydrocarbyl of from 1 to 20 carbon atoms; R 2 is a substituent on the cyclopentadienyl ring which is proximal to the bridge and positioned non-vicinal to the distal substituent and is of the formula R 6 R 7 3 in which R 6 is chosen from group IVA, and each R 7 is the same or different and chosen from hydrogen or hydrocarbyl of 1 to 7 carbon atoms; each R 3 is the same or different and is a hydrogen or a hydrocarbyl having from 1 to 20 carbon atoms with one R 3 being substituted at a position selected from 2, 3 or 4 on the fluorenyl group and the other R 3 being substituted at a position selected from 5, 6 or 7 on the fluorenyl group; M is a Group IVB transition metal or vanadium; and each Q is and hydrogen or a hydrocarbyl having 1 to 20 carbon atoms or a halogen, wherein the process exhibits a ratio of ethylene incorporation to ethylene feed concentration of from about 4:1 to about 15:1.