Polymerization process

A method for polymerization of propylene with a Ziegler catalyst to provide a high melt flow index propylene polymer, the method comprising:

• providing a supported catalyst component comprising a titanium tetrahalide supported on a magnesium based support and an internal electron donor comprising a diester of an aromatic dicarboxylic acid, said catalyst component containing titanium in an amount of from 1.7 wt to 2.2 wt;
• providing a trialkyl aluminum co-catalyst component selected from the group consisting of trimethylaluminum and triethylaluminum;
• providing an organosilyl external electron donor component;
• combining said supported catalyst component, said organoaluminum co-catalyst component and said external electron donor component in relative amounts to provide an aluminum/silicon mol ratio within the range of 10–500 an aluminum/titanium molar ratio within the range of 50–500 and a silicon/titanium mol ratio within the range of 1–50;
• introducing said combined catalyst system into a polymerization reactor and into a contact with propylene;
• supplying hydrogen into said polymerization reactor;
• and
• within said polymerization reactor effecting polymerization of said propylene in the presence of said catalyst system to produce a polymer fluff having a melt flow rate of at least 300 grams/10 minutes and a xylene soluble content of no more than 4 wt %.

A method to produce a stereo regular propylene polymer, the method comprising:

• operating a polymerization reactor under temperature and pressure conditions effective for the reaction of propylene supplied to said reactor to produce a stereo regular propylene polymer fluff;
• supplying a monomer stream containing propylene to said reactor;
• incorporating into said monomer stream a titanium-based supported Ziegler-Natta Catalyst having an internal electron donor consisting essentially of a phthalate compound and a titanium content in amount of at least 1.7 wt. %;
• supplying to said propylene monomer stream a co-catalyst comprising a trialkylaluminum wherein the co-catalyst is present in an amount to provide an aluminum/titanium molar ratio within the range of 50–500;
• supplying to said propylene monomer stream a silicone-based external electron donor in an amount to provide an aluminum/silicon molar ratio within the range of 10–500;
• and
• recovering polymer fluff from said polymerization reactor having a melt flow rate of at least 200 grams/10 minutes and a xylene soluble content of no more than 4 wt. %.