Toward the bimodality of polyethylene, initiated with a mixture of a Ziegler–Natta and a metallocene/MAO catalyst system

Abstract

Polymerization of ethylene catalyzed by a mixture of a Ziegler–Natta (Z–N) and a metallocene system cocatalyzed with methylaluminoxane (MAO) were carried out in a single reactor. The Z–N catalyst can be activated in the presence of MAO, without any addition of a conventional Z–N activator. The activities of the mixture Z–N with Cp 2MCl 2 (M=Ti,Zr,Hf) ( 1, 2, 3) or CpZrCl 3 ( 4) were lower than the obtained with the mixture Z–N and en(Ind) 2ZrCl 2 ( 5) . The weight-average molecular weight (Mw) of the polyethylene (PE) obtained with the mixture Z–N with Cp 2MCl 2 (M=Ti,Zr,Hf) or en(Ind) 2ZrCl 2 was lower than the PE obtained with Z–N and CpZrCl 3. For the binary mixture of Z–N with CpZrCl 3 ( 4), the PE obtained showed a bimodal molecular weight distribution (MWD) for an appropriate composition of the mixed catalyst in the absence of hydrogen in the reaction medium.