ETHYLENE ALPHA-OLEFINS COOLIGOMERIZATION VERSUS COPOLYMERIZATION BY ZIRCONOCENE CATALYSTS/

Non-bridged zirconocene complexes activated with methylalumoxane can p olymerize monoalkenes to high polymers with very high activity. The ma in control of molecular weight in these systems is due to beta-H trans fer from the growing chain, the effect becoming very remarkable in the case of substituted ethylene monomers and with increasing temperature . This work is mainly devoted to test the real capacity of the subject catalyst to produce structurally controlled oligomers from ethylene o r ethylene/alpha-olefin mixtures in good yield by investigating the in fluence of different reaction parameters. On the basis of the relevant results obtained, conditions were identified favouring the cooligomer ization of ethylene with propylene and higher alpha-olefins versus the formation of high molecular weight macromolecules. The role of reacti on conditions (catalyst, cocatalysts, temperature, pressure, structure of comonomer and presence of hydrogen) on products structure and yiel d is discussed with reference to previously proposed chain propagation and chain transfer mechanisms. Copyright (C) 1996 Elsevier Science Lt d.