Patent ID: 7276564
Filing Date: 2007-10-02
Classification: C08F,Y10S

Abstract:
1. Process for the polymerisation or copolymerisation in the gas phase of ethylene by bringing the said ethylene into contact, under polymerization or copolymerisation conditions in a reactor in which the start-up bed is fluidised and/or agitated with mechanical stirring, with a catalyst system, which process comprises a pre start-up operation wherein, prior to the introduction of the catalytic system in the reactor, said process comprises the following steps 1. determining the density d and melt index Ml of all the polyethylene powders (grade slate) to be produced during the campaign from start-up to shut down, 2. heating the reactor by controlling the temperature inside the reactor such that the temperature is maintained at a value equal to or higher than the highest temperature corresponding to a RTSE value of 4.4 for all the polyethylene powders to be produced during the campaign, wherein all the polymer grades to be produced during the campaign require a heating temperature of at least 95° C.