PROPERTIES OF ETHYLENE-PROPYLENE COPOLYMERS SYNTHESIZED BY A SUPPORTED ZIEGLER-NATTA CATALYST BASED ON TICL4 MGCL2/PCL3/

Enthylene-propylene copolymers were synthesized through Ziegler-Natta catalysts based on TiCl4, MgCl2 and PCl3. The catalyst system TiCl4/Mg Cl2/PCl3 was prepared by impregnating the support, obtained by ball mi lling of MgCl2 with varied amounts of PCl3, with TiCl4. The addition o f PCl3 has, remarkably, increased MgCl2 surface area and, according to plasma spectrometry data, promoted the PCl3 incorporation in the cata lyst. The effect of PCl3 on the ethylene homopolymerization, ethylene- propylene copolymerization and on the copolymer properties was studied . The employed catalyst system produced propylene-ethylene copolymers up to 75% (w/w) of propylene. The reduction on the copolymer molecular weight distribution suggested the PCl3 acted as an internal donor, po isoning some catalytic active sites. The effect of Al/Ti ratio on the copolymer structures was investigated. Low ratio caused increase of pr opylene incorporation in the copolymer and high Al/Ti ratio promoted o verreduction of titanium as shown by EEE triad content. The reactivity ratio data indicated the ethylene-propylene copolymerization present a tendency to produce block copolymers. (C) 1997 Elsevier Science Ltd.