Removal of mononuclear alkylaluminum species in aluminoxane using a crosslinked polymer bearing bulky phenoxy groups

In olefin polymerization using methylaluminoxane (MAO) as a cocatalyst, the remaining trialkylaluminum (R3Al) in MAO sometimes leads to negative effects, such as a decrease in activity and molecular weight of the obtained polymer. Thus, in this study, the amount of R3Al in modified MAO (MMAO) was reduced by using a crosslinked terpolymer bearing bulky phenoxy groups as a solid support for R3Al. The R3Al removal efficiency of the terpolymer at a certain hydroxy group content was found to be much higher than that of SiO2, which has been previously reported to be an efficient R3Al remover. This is probably because of the steric bulkiness around the hydroxy groups and because some R3Al is physically adsorbed into the terpolymer. The chain transfer reaction derived from residual R3Al in propylene polymerization is mostly suppressed after the treatment of MMAO with the terpolymer. Selective adsorption of trialkylaluminums (R3Al) in modified methylaluminoxane (MMAO) onto crosslinked terpolymer bearing bulky phenoxy groups was performed. The phenoxy groups on the terpolymer can more selectivity react with R3Al than the hydroxy groups on SiO2, and some R3Al was physically adsorbed into the terpolymer. As a result, more efficient removal of R3Al from MMAO solution was achieved. The propylene polymerization using terpolymer-treated MMAO as a cocatalyst was free from chain transfer reaction, which is generally derived from the residual R3Al.