The effect of the comonomer on the copolymerization of ethylene with long chain α-olefins using Ziegler-Natta catalysts supported on MgCl2(THF)2

The effect of the type of the comonomer (1-pentene, 1-hexene, 1-octene, 1-decene and 1-dodecene) on the copolymerization of ethylene with alpha-olefin over vanadium (VOCl3 and VCl4) and titanium (TiCl4) catalysts supported on MgCl2(THF)(2) and activated by Et2AlCl was studied. The results show that the introduction of a longer alpha-olefin in the ethylene polymerization feed depresses the catalytic activity of all investigated catalysts. The catalyst activity does not depend on the type of the comonomer applied but changes with the comonomer concentration in the feed. The incorporation of alpha-olefin in the polymer chain was found to be dependent on the type and concentration of the comonomer in the feed as well as the type of catalyst. The incorporation of alpha-olefin increases with the increase of the comonomer concentration in the polymerization feed and the comonomer reactivity decreases with the increase of the size of the alpha-olefin chain, especially in the case of comonomers longer than octene. It should be stressed, however, that both vanadium catalysts clearly demonstrate higher activity in the copolymerization process than their titanium counterpart and also produce copolymers with higher comonomer content. The density, crystallinity and melting temperature of the copolymers decrease with increase of the amount of the comonomer incorporated, but the type of the comonomer does not have a strong influence on these properties. (C) 2000 Elsevier Science Ltd. All rights reserved.