Kinetic studies on the syndiotactic propylene polymerization catalyzed over iPr(Cp)(Flu)ZrCl2

Abstract

Kinetic studies on the syndiospecific polymerizations of propylene with iPr(Cp)(Flu)ZrCl2/methylaluminoxane (MAO) were performed at 20, 40 and 70 degreesC and at 5 atm with various Al/Zr molar ratios. The average polymerization activity for 60 min decreased, and the time to reach a maximum activity (t(max)) decreased as Al/Zr molar ratio increased. However, at Al/Zr molar ratio of 10,000, catalytic activity decreased rapidly and became the smallest among any other Al/Zr molar ratios after 20 min of polymerization. At higher Al/Zr molar ratio, methylation and cationization progress rapidly, but its polymerization rate decayed quickly due to strong interaction between MAO and metallocene, resulting in less active species. Regardless of change in polymerization temperature, t(max) was maintained around 15 min. Stereoregularity was strongly dependent on the polymerization temperature, and active site isomerization was dominant source for stereoirregularity, and it was strongly influenced by polymerization temperature. (C) 2003 Elsevier Ltd. All rights reserved.