The effects of a new aminosilane external donor on propylene polymerization with MgCl2-supported Ziegler-Natta catalyst.

A new aminosilane external donor named piperidine methyl dimethoxysilane (Donor-PMe) was firstly synthesized, and then was used as external donor on propylene polymerization with MgCl₂-supported Ziegler-Natta catalyst. The effects of Donor-PMe on the catalytic activity, isotacticity, molecular weight distribution, isotactic sequence length, isotactic sequence distribution of polypropylene were studied by differential scanning calorimetry (DSC), gel permeation chromatography (GPC), and self-nucleation and annealing (SSA), respectively. It was found that it was conducive to improving the activity and stereoregularity of catalyst when the new aminosilane Donor-PMe was used as external donor with MgCl₂-supported Ziegler-Natta catalyst. The catalytic activity of the Ziegler-Natta catalyst and the isotacticity of PP prepared by Donor-PMe increased with the increase of Si/Ti ratio on propylene polymerization.The GPC results showed that the molecular weight distribution of polypropylene was about 6.7, which was broader than that of industrial homo-polypropylene about 3.0. The SSA results showed that the relative contents of the highest isotactic component and the lamellar thickness in the PP chain gradually increased with the increase of Si/Ti of Donor-PMe, indicating the isotactic sequence length of polypropylene got longer with the increase of Si/Ti ratio of Donor-PMe. Meanwhile, the lamellar thickness distribution of polypropylene became broader, revealing the isotactic sequence length distribution of polypropylene got broader, indicating there were more higher isotactic sequence length in PP chain. [ABSTRACT FROM AUTHOR]