COPOLYMERIZATION OF ETHYLENE WITH 1-HEXENE AND 1-OCTENE - CORRELATIONBETWEEN TYPE OF CATALYST AND COMONOMER INCORPORATED

The behaviour of catalytic systems based on zirconium compounds for th e copolymerization of ethylene with 1-hexene and 1-octene is reported. The metallocenes (2CH(3))(2)SiCp(2)ZrCl(2), Cp(2)ZrCl(2) (Cp = eta(5) -cyclopentadienyl), (C2H4[Ind]2ZrCl2 and [Ind]2ZrCl2 (Ind = eta(5)-ind enyl) were chosen for this study. The bridged catalysts, (CH3)(2)SiCp( 2)ZrCl(2) and C2H4[Ind]2ZrCl2, and the metallocene Cp(2)ZrCl(2) showed similar catalytic activities for homo- and copolymerization of ethyle ne with 1-hexene. C-13 NMR analysis showed that the composition of cop olymerization products depends on the catalytic system, in other words , on the ligand structure of the transition metal. Copolymers obtained using the bridged catalysts have greater incorporation of comonomer. Thermal analysis and viscosity measurements demonstrated that an incre ase of the comonomer concentration reduces the melting point, the crys tallinity and the molecular weight of the copolymer. Results from infr ared spectroscopy showed that beta-elimination is one of the possible termination reactions. The monomer reactivity ratios r were determined for all catalytic systems using Fineman-Ross and C-13 NMR methods. Th e values of r(1) (M(1) = ethylene) and r(2) (M(2) = alpha-olefin) show ed an effect of the type of metallocene and of alpha-olefin on the str ucture of the copolymer obtained.