Patent ID: 8445607

Claim:
Process for the preparation of a particulate bimodal polyethylene product in a serially connected double loop reactor, comprising the steps of: (a) feeding ethylene monomer, a liquid hydrocarbon diluent, at least one polymerization catalyst, optionally hydrogen, and optionally one or more olefin co-monomers to a first loop reactor; (b) polymerizing said ethylene and said optionally one or more olefin co-monomers in said first loop reactor to produce a first polyethylene product; (c) transferring said first polyethylene product to a second loop reactor; (d) feeding ethylene monomer, a diluent, optionally hydrogen, and optionally one or more olefin co-monomers to said second loop reactor; (e) polymerizing said ethylene and said optionally one or more olefin co-monomers in said second loop reactor in the presence of said first polyethylene product to produce a bimodal polyethylene product; (f) recovering from said second loop reactor said bimodal polyethylene product having a median particle diameter of less than 300 μm; wherein said polymerization catalyst comprises a particulate metallocene-alumoxane catalyst immobilized on a porous silica support, and wherein said polymerization catalyst has a median particle diameter of less than 50 μm, and whereby the ratio of the median particle diameter of said bimodal polyethylene product to the median particle diameter of said polymerization catalyst is less than 30.