Production of polyethylene having a bimodal molecular weight distribution

Abstract

A process for producing high density polyethylene, the process comprising polymerising ethylene, or copolymerising ethylene and an alpha-olefinic comonomer comprising from 3 to 10 carbon atoms, in the presence of a catalyst system comprising first and second chromium-based catalysts, the first chromium-based catalyst having been reduced and reoxidised and the second chromium-based catalysts having been activated, fluoridised before or during the activation step, and reduced, the first and second chromium-based catalysts having a pore volume difference of at least 0.8 cc/g. There is further provided a catalyst system for the production of high density polyethylene by polymerising ethylene or copolymerising ethylene and an alpha-olefinic comonomer comprising from 3 to 10 carbon atoms, the catalyst system comprising first and second chromium-based catalysts, the first chromium-based catalyst having been reduced and reoxidised and the second chromium-based catalyst been activated, fluoridised before or after the activation step, and reduced, and the first and second chromium-based catalysts having a pore volume difference of at least 0.8 cc/g. There is further provided the use of the catalyst system for increasing the biomodality of the molecular weight distribution of a high density polyethylene.

Dependencies are inferred from the claim text.