Ethylene/propylene copolymerization with half-titanocene/mao catalyst I. synthesis of ethylene/propylene copolymer

A novel half-titanocene compound, (η⁵-pentamethylcyclopentadienyl) titanium triallyloxide (Cp*Ti(OCH₂-CH=CH₂)₃), and modified methylalumiloxane (mMAO) were synthesized and employed in the study on ethylene-propylene copolymerization. The influences of the amount of residual TMA in MAO,ethylene-propylene feeding molar ratio,polymerization temperature and the concentrations of catalyst and mMAO on activity of ethylene-propylene copolymerization,molecular weight of copolymer have been discussed in detail. It was found that the catalytic activity increased with the decreasing of the amount of residual TMA in MAO, such as from 22.3% to 14.8% TMA content in MAO, resulting in the Ti(IV) species content from 40.8% up to 88. 8 % , which indicated that the Ti (IV) species is favorable for the ethylene-propylene copolymerization. The activity also increased with the decreasing of ethylene molar ratio in feeding comonomer,it perhaps related to the chain structure and physical state of copolymer. The catalytic activity was affected obviously by the polymeric temperature,but it was not as sensitive in higher ethylenepropylene feeding molar ratio (E/P = 70 : 30) as that in lower E/P feeding ratio (E/P = 10 : 90), this performance suggested that higher temperature was more suitable for ethylene polymerization than for propylene polymerization. The varying ranges of Al/Ti = 140-230mol/mol and [Ti] = 1.0 × 10^-3∼1.2 × 10^-3mol/L were the optimum conditions for ethylene-propylene copolymerization. Subsequently, high molecular weight random ethylene-propylene copolymer elastomers, most of those can be soluble in hexane, were obtained by the catalyst.