Stepwise polymerization of propylene and ethylene with Cr(acetylacetonate)_3/MgCl_2 ethylbenzoate/diethylaluminium chloride catalyst system

摘要

During propylene polymerization with the Cr(acetylacetonate)_3/MgCl_2-Et_2AlCl-ethylbenzoate catalyst system which shows high isospecificity for propylene polymerization, it was found that the chain transfer and termination reactions can be neglected. Based on this result,some stepwise polymerizations of propylene and ethylene were carried out with the same catalyst system varying polymerization conditions. The resulting copolymers were separated by temperature rising elution fractionation (TREF) and afforded two fractions which were eluted at different temperatures. From the ~(13)C NMR, DSC and GPS analyses of each fraction, it was considered that the corresponding block copolymer existed in the fraction eluted at higher temperature.