Some aspects of propylene and ethylene copolymerization over titanium - magnesium and metallocene catalysts

Propylene/ethylene copolymers were prepared over two complex catalyst systems: (i) an AlEt3-activated MgCl2-supported titanium catalyst TiCl4/MgCl2 with dibutyl phthalate and propyltrimethoxysilane used as respectively internal and external donors and (ii) two methylaluminoxane (MAO)-activated, unsupported zirconocene catalyst systems differing in indenyl ligand structure, viz., Me2SiInd2ZrCl2 and [Me2Si(4-Ph-2-Et-Ind)2]ZrCl2 (rac:meso = 1:2). The olefins were copolymerized (Table 1) in liquid propylene at 50 - 60°C at constant ethylene overpressures (above C3 pressure) varying over 0.3 to 3 atm corresponding to ethylene concentrations of 0.07 to 0.69 mol/L in the liquid phase. The copolymers contained 1.6-18% of C2 mers. Catalyst activity (Fig. 1) and kinetics of copolymerization (Fig. 1) were studied and the microstructure, molecular weight characteristics (Table 2) and mechanical properties (Tables 3, 5) of the resulting copolymers were determined. IR spectra (recorded, not included) are discussed. The comonomer reactivity coefficients were evaluated for the copolymerizations run over the three catalytic systems.