Copolymerization of ethene with 1-hexene or 1-hexadecene over ethylene, dimethylsilylene and 1,4-butanediylsilylene bridged bis(indenyl) and bis(tetrahydroindenyl)zirconium dichlorides

Ethene was copolymerized with 1-hexene and 1-hexadecene over five different homogeneous methylaluminoxane (MAO) activated racemic ansa-metallocene catalysts in order to study both the influence of the ligand (indenyl and tetrahydroindenyl) and the influence of the interannular bridge (ethylene, dimethylsilylene and 1,4-butanediylsilylene) on the copolymerization behaviour. Hydrogenation of the indenyl ligands was found to decrease comonomer content and molar mass of the copolymers. A similar tendency was observed for the ethylene bridge compared to the silylene bridges. The reasons for this behaviour are discussed and related to structural differences of the catalyst precursors. In addition a segregation fractionation technique was applied to study the chemical composition distribution (CCD) of the produced copolymers. Batchwise feed of comonomer resulted in a broad CCD. More homogeneous copolymers could be produced using partly continuous feed of comonomer.