Modification of a Ziegler‐Natta catalyst with a metallocene catalyst and its olefin polymerization behavior

A Ziegler‐Natta catalyst was modified with a metallocene catalyst and its polymerization behavior was examined. In the modification of the TiCl 4 catalyst supported on MgCl 2 (MgCl 2 ‐Ti) with a rac ‐ethylenebis(indenyl)zirconium dichloride ( rac ‐Et(Ind) 2 ZrCl 2 , EIZ) catalyst, the obtained catalyst showed relatively low activity but produced high isotactic polypropylene. These results suggest that the EIZ catalyst might block a non‐isospecific site and modify a Ti‐active site to form highly isospecific sites. To combine two catalysts in olefin polymerization by catalyst transitioning methods, the sequential addition of catalysts and a co‐catalyst was tried. It was found that an alkylaluminum like triethylaluminum (TEA) can act as a deactivation agent for a metallocene catalyst. In ethylene polymerization, catalyst transitioning was accomplished with the sequential addition of bis(cyclopentadienyl)zirconium dichloride (Cp 2 ZrCl 2 )/methylaluminoxane (MAO), TEA, and a titanium tetrachloride/vanadium oxytrichloride (TiCl 4 /VOCl 3 , Ti‐V) catalyst. Using this method, it was possible to control the molecular weight distribution (MWD) of polyethylene in a bimodal pattern. In the presence of hydrogen, polyethylene with a very broad MWD was obtained due to a different hydrogen effect on the Cp 2 ZrCl 2 and Ti‐V catalyst. The obtained polyethylene with a broader MWD exhibited more apparent shear thinning.