US Patent 8058373 Polypropylene solution polymerization process

A process for polymerization of propylene, optionally ethylene, and further optionally one or more C4-30 α-olefins and/or one or more conjugated or nonconjugated dienes under continuous, solution polymerization conditions to prepare a high molecular weight polymer or interpolymer, said process comprising conducting the polymerization in the presence of a catalyst composition comprising a hafnium complex of a polyvalent aryloxyether.