Ethylene polymerization with hafnocene adamantolate/MAO system

Summary

A new alcoholate of cyclopentadienyl metallocene with voluminous group as ligand substituting chlorine atoms and formula Cp₂Hf(OMAd)₂ (where Cp = cyclopentadienyl and OMAd = derived of 2-methyl-2-adamantol) was synthesized and employed as catalyst for olefin polymerization. The compound was evaluated in ethylene polymerization activated by methylaluminoxane (MAO) using several experimental conditions. These conditions were determined by a statistic method, and a model for dependent variables like catalyst activity and average molecular weight of polymers were developed. The hafnocene alcoholate produced polyethylenes with molecular weights in the same range of the corresponding metallocene dichloride. The new catalyst system showed high stability under temperature of 100°C. In the presence of H₂ as molecular weight controlling agent, the catalyst showed a maximum of activity in the concentration range used.