Process for treating catalytic components on porous metaloxide supports for gasphase polymerization of defins and use of the catalyst so obtained in polymerization of olefins

摘要

Treatment process making it possible to maintain the morphology of a catalyst component for the gas-phase polymerisation or copolymerisation of ethylene or of ethylene and of at least one alpha olefin containing from 3 to 12 carbon atoms, the said component containing at least titanium, magnesium, chlorine and optionally an electron-donor, the process consisting, after impregnation of a porous metal oxide support with titanium, magnesium and chlorine compounds and optionally with the electron-donor, in involving this catalyst component in the presence of an alkylaluminium-based cocatalyst in a prepolymerisation, at least partially in suspension, of ethylene or of ethylene and of an alpha-olefin characterised in that the prepolymerisation is conducted, in the presence of a cocatalyst consisting of an alkylaluminium complexed with an electron-donor to a degree of prepolymerisation appropriate to the gas-phase polymerisation process in which the resulting active prepolymer will subsequently be used.