Control of molecular weight distribution in propylene polymerization with Ziegler–Natta/metallocene catalyst mixtures

Propylene polymerization was investigated with a sequential addition of Ziegler–Natta and metallocene catalysts. From the fact that the molecular weights of polypropylene (PP) produced with Ziegler–Natta and with metallocene catalysts differ, it was possible to control the molecular weight distribution (MWD) of PP with a sequential addition of methylaluminoxane and rac-ethylenebis(indenyl)zirconium dichloride followed by triethylaluminum and magnesium dichloride-supported titanium tetrachloride catalyst. The obtained PP exhibited a wide MWD curve with shoulder peak. The position and height of each peak was controlled with the variation of polymerization time for each catalyst as well as the amount of each catalyst. The MWD of PP prepared with sequential addition of catalysts was much wider than that of PP obtained from each catalyst. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:2213–2222, 1998