Patent ID: 9475892
Filing Date: 2016-10-25
CPC Classification: C08F

Claim Text:
1. Process for the transition T1 between an ethylene or a propylene polymerization process carried out in a polymerization reactor in the presence of a catalyst a1, ethylene or propylene and optionally an olefin co-monomer A1 to produce an ethylene polymer or a propylene polymer P1 into an ethylene or a propylene polymerization process carried out in the same polymerization reactor in the presence of a catalyst a2, ethylene or propylene and optionally an olefin co-monomer A2 to produce an ethylene polymer or a propylene polymer P2, wherein: the reactor is a gas phase fluidized bed reactor; and further wherein the mass of the polymer present in the reactor during the transition is at least 75% of the mass of the polymer just before the start of the transition; and the transition includes an additional polymerization control step which takes place at the beginning of or towards the end of the transition T1 and which takes into account the intrinsic behavior of the respective polymerization catalyst a1 and a2 and which includes at least one action chosen amongst a decrease/increase of the main monomer partial pressure, a decrease/increase of the main monomer feed rate, a decrease/increase of the ratio of comonomer to main monomer, a decrease/increase of the rate of introduction of the co-catalyst, a decrease/increase of the rate of introduction of a catalyst activity improver, a decrease/increase of the partial pressure of hydrogen.