Patent ID: 7745551

Claim:
A method for the polymerization of ethylene in a double loop reactor system comprising first and second interconnected loop reactors comprising: a) introducing an ethylene monomer, and a diluent carrier liquid into a first loop reactor of said reactor system; b) supplying a polymerization catalyst system comprising a supported chromium-based catalyst component to said first loop reactor; c) circulating said diluent liquid and ethylene monomer through said first loop reactor while polymerizing said ethylene monomer in the presence of said catalyst system to produce a slurry of polymer fluff particles in said diluent carrier liquid; d) withdrawing said slurry from said first loop reactor and supplying said withdrawn slurry to said second loop reactor; e) introducing an ethylene monomer and a diluent carrier liquid into said second loop reactor; f) circulating said diluent liquid and ethylene monomer through said second loop reactor while polymerizing said ethylene monomer in the presence of said catalyst system to produce a slurry of polymer particles in said diluent in said second reactor; g) controlling the polymerization conditions in said first and second reactors to produce a final ethylene polymer at a productivity of less than 3500 grams of polymer per gram of catalyst component and wherein said first and second reactors are operated under conditions such to produce a polymer having a mono modal polydispersity, such conditions comprising operating the first and second reactors at substantially the same temperature; h) recovering said ethylene polymer from said second loop reactor.