Patent ID: 7696287

Claim:
A method for the polymerization of an olefin in a double loop reactor system having first and second interconnected loop reactors comprising: a) introducing an olefin monomer, and a diluent carrier liquid into a first loop reactor of said reactor system; b) supplying to said first loop reactor a polymerization catalyst system comprising a first supported Ziegler-Natta catalyst component having a particle size distribution d50 within the range of greater than 5 μm to less than 20 μm; c) circulating said diluent liquid and olefin monomer through said first loop reactor while polymerizing said olefin monomer in the presence of said first 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particles in said diluent carrier liquid; d) withdrawing said slurry from said first loop reactor and supplying said withdrawn slurry to said second loop reactor; e) introducing an olefin monomer and a diluent carrier liquid into said second loop reactor; f) introducing into said second loop reactor a second Ziegler-Natta catalyst system comprising a supported second Ziegler-Natta catalyst component having a particle size distribution d50 within the range of greater than 5 μm to less than 20 μm separately from the introduction of the first polymerization catalyst system to said first loop reactor in subparagraph b); g) circulating said diluent liquid and olefin monomer through said second loop reactor while polymerizing said olefin monomer in the presence of said second catalyst system to produce a slurry of olefin polymer particles in said diluent liquid in said second reactor; and h) recovering said olefin polymer from said second loop reactor.