A RARE-EARTH CATALYST FOR DIENE POLYMERIZATION BASED ON BUTYL LITHIUM

Butyl lithium can be used in place of aluminium alkyls in catalysts of the AlR3/neodymium complex/Al alkyl halide type. With catalysts consisting of Al alkyl halide/neodymium complex/BuLi, both order of addition and, in particular, the ratio of catalyst components are critical. Polymer with a high cis content can be made from butadiene and isoprene but conversions are lower and more variable than with standard aluminium alkyl-based catalysts, even when high catalyst concentrations are used. The catalyst can be used as a premix or added to mixed feed as separate components. In both cases the catalyst mixture is somewhat heterogeneous and polymerization rates are improved by shaking or stirring during polymerization.