MULTISTEP PROCESS FOR PREPARING HETEROPHASIC PROPYLENE COPOLYMERS

摘要

A multistage process comprising the step of polymerizing propylene in the presence the presence of a catalysts system, comprising one or more metallocene compound of formula (I): wherein M is an atom of a transition metal; p is an integer from 0 to 3, X, same or different, is a hydrogen atom, a halogen atom, or a hydrocarbon group; L is a divalent bridging R<1> and R<2> , are C1 -C20-alkyl radicals; T, equal to or different from each other, is a moiety of formula (Ilb) or (Ila): wherein R<3>, R<4>, R<5>, R<6>, R<7>, R<3'>, R<4'>, R<5'>,R<6'> and R<7'>, are hydrogen atoms or hydrocarbon groups; with the proviso that at least one among R<3>, R<4>, R<5>, R<6>, R<7> is different from hydrogen; R<11> is a hydrogen atom or a hydrocarbon group; R<8>, R<9> and R<10>, are hydrogen atoms or hydrocarbon groups; and further comprising the step of contacting, under polymerization conditions, in a gas phase, ethylene and one or more comonomers. Where the amount of the polymer obtained in the first step ranges from 5% by weight and 90% by weight, of the polymer obtained in the whole process.