Influence of “TMA-depleted” MAO and alkylaluminiums on propylene polymerization at high temperature with TiCl4/MgCl2 catalysts

Abstract A study of the effect of “trimethylaluminium (TMA)-depleted” methylaluminoxane (MMAO) and alkylaluminiums on propylene polymerization at high temperature in the use of a TiCl 4 /MgCl 2 /aromaticdiester-alkoxysilane catalyst has shown that, MMAO was not the actual cocatalyst. However, at low Et 3 Al/Ti mole ratio addition of MMAO to catalyst improved the catalyst activity and stereospecificity and the catalyst showed a high proportions of isotactic polypropylene (95%) and high activity with the mixture of MMAO and Et 3 Al at 100 °C. Addition of MMAO reduced the molecular weights of isotactic polypropylene (iPP) but had no effect on the crystallinity of the iPPs. The appearance of β modification in the iPP obtained with Et 3 Al crystallization process implied that the microstructure of iPP obtained with Et 3 Al was different from that of iPP obtained with i -Bu 3 Al and Hex 3 Al at 100 °C.