Cocatalytic activities of methylaluminoxane prepared by direct water addition method in ethylene polymerization over Cp2ZrCl2

The characterization of ethylene polymerization behaviors catalyzed over Cp2ZrCl2/MAO homogeneous system using methylaluminoxanes prepared by the direct hydrolysis of AlMe3 (Me=methy1) were reported. The MAO was prepared at the ratio of [H2O]/[A1]=1 and 0.5 and at three different temperatures, i.e., −40, −60 and −80 °C. The polymerization rate was not decreased with polymerization time when the MAO prepared at the ratio of [H2O]/[AlMe3]=l at −60 °C was used as a cocatalyst regardless of the ratio of Al/Zr and the polymerization temperature. The polymerization rate drastically decreased with polymerization time above 60 °C in case of using MAO prepared at the ratio of [H2O]/[AlMe3]=l at −80 °C. However, in case of the MAO prepared at the ratio of [H2O]/ [AlMe3]=0.5 at −80 °C, the rate continuously increased with polymerization time at the polymerization temperature of 70 °C and 80 °C. The amount of MAO needed to activate Cp2ZrC12 was larger than that of MAO prepared at the ratio of [H2O]/[A1]=1. The viscosity molecular weight of polyethylene (PE) cocatalyzed with MAO prepared at the ratio of [H2O]/[Al]=0.5 was lower than that of polyethylene obtained with MAO prepared at the ratio of [H2O]/[A1]=1.