| abstract |
The invention is directed to olefin polymerization processes using bridged hafnocene catalyst complexes that are surprisingly stable under high temperature olefin polymerization processes such that olefin copolymers can be prepared with high molecular weights and catalyst activities. More specifically, the invention is a polymerization process for ethylene copolymers having a melt index of about 0.850 to about 0.930 comprising contacting, under homogeneous polymerization conditions at a reaction temperature at or above 60 °C to 225 °C, ethylene and one or more comonomers capable of insertion polymerization with a bridged hafnocene catalyst complex derived from: A) a biscyclopentadienyl hafnium organometallic compound having: i) at least one unsubstituted cyclopentadienyl ligand or aromatic fused-ring substituted cyclopentadienyl ligand; ii) one aromatic fused-ring substituted cyclopentadienyl ligant; iii) and a covalent bridge connecting the two cyclopentadienyl ligands, said bridge comprising a single carbon or silicon atom with two aryl groups, each substituted with a C1-C20 hydrocarbyl or hydrocarbylsilyl group at least one of which is a linear C3 or greater substitutent; and B) an activating cocatalyst. |