PROCESS FOR THE START UP OF POLYMERISATION OR COPOLYMERISATION IN THE GAS PHASE OF ALPHA-OLEFINS IN THE PRESENCE OF A ZIEGLER-NATTA CATALYST SYSTEM

摘要

The present invention relates to a process for the start up of polymerization or copolymerization in the gas phase by bringing the said alpha-olefins in contact under polymerization or copolymerization conditions in a fluidized bed and/or with mechanical stirring with a charge powder, in the presence of a catalyst system of the Ziegler-Natta type, this process being characterized in that the charge powder used is previously dehydrated and subjected to a treatment by bringing the said charge powder into contact with an organoaluminum compound for a period of at least five minutes, so that the polymerization or copolymerization starts up immediately after the contracting of the alpha-olefins with the charge powder in the presence of the catalyst system.