COPOLYMERIZATION OF ETHYLENE AND PROPYLENE CATALYZED BY MAGNESIUM CHLORIDE SUPPORTED VANADIUM/TITANIUM BIMETALLIC ZIEGLER-NATTA CATALYSTS

Magnesium chloride supported vanadium/titanium bimetallic Ziegler-Natta catalysts with di-i-butyl phthalate as internal donor for copolymerization of ethylene and propylene were prepared. The effects of reaction temperature, ethylene/propylene molar ratio, aluminium/vanadium （Al/V） molar ratio and titanium/vanadium molar ratio on the catalytic activity were investigated. The molecular weight, molecular weight distribution, sequence composition and crystallinity of the products were measured by gel permeation chromatography, ^13C-NMR and differential scanning calorimetry analysis, respectively. In comparison to the vanadium and titanium catalysts, the bimetallic catalyst showed higher catalytic activity and better copolymerization performance. The obtained ethylene/propylene copolymers have high molecular weight （105）, broad molecular weight distribution, high propylene content with random or short blocked sequence structures （rErp = 1.919）, low melting temperatures and low crystallinities （Xc 〈 20%）.