Propylene polymerisations with novel heterogeneous combination metallocene catalyst systems

Propylene was polymerised with novel combination metallocene catalyst systems prepared by an emulsion-based heterogenisation method in liquid monomer conditions. The catalyst combinations investigated were rac-dimethylsilanylbis(2-methyl-4-phenyl-1-indenyl)zirconium dichloride/rac-[ethylenebis(2-(tert-butyldimethylsiloxy)indenyl)]zirconium dichloride/methylaluminoxane (MAO) (1+2) and rac-dimethylsilanylbis(2-methyl-4-phenyl-1-indenyl)zirconium dichloride/rac-dimethylsilanylbis(2-isopropyl-4-[3,5-dimethylphenyl]indenyl)zirconium dichloride/MAO (1+3). The effects of polymerisation temperature and hydrogen on catalyst performance and polymer properties, as well as copolymerisation with hexene and ethylene were investigated. Depending on the polymerisation conditions, Mw of polypropylene varied from 144 to 286kg/mol for 1+2 and from 200 to 390kg/mol for 1+3. Combination 1+2 produced broader molecular weight distribution (MWD) than 1+3, and a bimodal MWD with clearly separated low- and high-Mw polymer fractions was observed with 1+2. The two catalyst systems showed similar hydrogen and hexene responses. Each metallocene precursor showed individual response towards the polymerisation conditions, especially polymerisation temperature, suggesting that interaction between the catalyst active sites was negligible in the studied systems.