Patent ID: 8222358

Claim:
A process for adjusting the molecular weight of a propylene-ethylene copolymer, said process comprising: contacting in a homogeneous solution process propylene and ethylene with a catalyst system comprising: (a) dimethylsilylbisindenyl hafnium dimethyl; and (b) an activator comprising a fluoroarylborate anion represented by the formula: Ct + [B(Ar) x (R) n ] − where Ct + is a cation capable of extracting an alkyl group from, or breaking a carbon-metal bond of, the organometallic compound; Ar is a fluorophenyl group; R is a fluoronaphthyl group and each of x and n is 0, 1, 2, or 3, with the proviso that the sum of x+n=4, and wherein said propylene-ethylene copolymer contains units derived from propylene in an amount greater than or equal to 65 weight percent and units derived from ethylene in an amount of from 5 to 35 weight percent; and adjusting the molecular weight of the propylene-ethylene copolymer from about 140,000 g/mole to about 550,000 g/mole by changing the n of the activator between 0, 1, 2, and 3, as when the lowest molecular weight propylene copolymer is desired, n=0 and the activator having n=0 is contacted with the metallocene, and when the highest molecular weight is desired, n=3 and the activator having n=3 is contacted with the metallocene.