High-rigidity, high-melt-viscoelasticity polypropylene and process for producing the same

Claim 1

A process for producing a high-rigidity and high-melt-viscoelasticity polypropylene for sheets to be post-processed and for blow molding, obtained by subjecting propylene to a multi-stage polymerization in the presence of a catalyst prepared by reacting an organoaluminum compound (I) or a reaction product of an organoaluminum compound (I) with an electron donor (A), with TiCl 4 (C); reacting the resulting solid product (II) with an electron donor (A) and an electron acceptor (B); and combining the resulting solid product (III) with an organoaluminum compound (IV) and an aromatic carboxylic acid ester (V), so as to give a molar ratio (V/VIII) of the aromatic carboxylic acid ester to the solid product (III) of 0.1 to 10.0; in this polymerization, adjusting the amount of propylene polymerized at the first stage so as to constitute 35 to 65% by weight based on the total amount polymerized and that at the second stage et seq so as to constitute 65 to 35% by weight based thereon; and when the intrinsic viscosity of the polymer portion having a higher molecular weight is named [η] H and that having a lower molecular weight is named [η] L , between the polymer portion formed at the first stage and that formed at the second stage et seq, adjusting the intrinsic viscosity values of the respective polymer portions so as to satisfy a relationship 3.0≦[η].sub.H -[η].sub.L ≦6.5 (1).