Ethylene polymerization or ethylene and at least one other alpha - copolymerization of olefins, a method for starting in the presence of vapor phase catalysts based on chromium oxide

摘要

The present invention relates to a process for the start of polymerization of ethylene or copolymerization of ethylene and of at least one other alpha - olefin by contact, under conditions of polymerization or copolymerization in the fluidized bed and or stirred mechanically, of the ethylene and optionally at least one other alpha - olefin with a powder charge, in the presence of a catalyst comprising a chromium oxide, and the associated with a granular support and activated by heat treatment, this catalyst being used in the form of a prepolymer, characterizes in that the powder charge used is beforehand subjected to a treatment by contacting said powder of the load, with an organoaluminium comprises, in such a way that the polymerization or copolymerization started immediately of the contact of the ethylene and optionally at least one other alpha - olefin with a powder of the prepolymer in the presence of the prepolymer.