Process for producing high stiffness polypropylene

Abstract From the Canadian patent

A process for producing polypropylene having improved stiffness is disclosed, which comprises polymerizing propylene in multiple stages in the presence of a catalyst, which is prepared by reacting (i) an organoaluminum compound or (vi) a reaction product between the organoaluminum compound (i) and (a) an electron donor with (c) titanium tetrachloride to obtain (ii) a solid product, reacting the resulting solid product (ii) with (a) an electron donor and (b) an electron acceptor to obtain (iii) a solid product and, combining the resulting solid product (iii) with (iv) an organoaluminum compound and (v) an aromatic carboxylic acid ester at a molar ratio of the aromatic carboxylic acid ester …