Catalyst systems for improved stereoselectivity and broader molecular weight distribution in polymerization of olefins

A catalyst system for the polymerization and copolymerization of olefins comprising:

• (a) a conventional Ziegler-Natta catalyst component comprising a solid catalyst component obtained by (i) suspending a dialkoxy magnesium in an aromatic hydrocarbon that is liquid at normal temperatures, (ii) contacting the dialkoxy magnesium with a titanium halide and further (iii) contacting the resulting composition a second time with the titanium halide, and contacting the dialkoxy magnesium with a diester of an aromatic dicarboxylic acid at some point during the treatment with the titanium halide in (ii);
• (b) a mixture of two electron donors wherein one electron donor is diisopropyldimethoxysilane and the other electron donor is cyclohexylmethyldimethoxysilane in a molar ratio of from about 1:3 to about 3:1 of the second to the first;
• and
• (c) triethylaluminum as a co-catalyst, wherein the Si/Ti molar ratio is about 2.

A catalyst for polymerization of propylene, comprising:

• (a) a conventional Ziegler-Natta catalyst component which comprises a transition metal compound of the general formula MR.sup.+.sub.x where M is titanium, R.sup.+ is a halogen or a hydrocarboxyl and x is the valence of titanium;
• (b) an organoaluminum compound;
• (c) a mixture of at least two electron donors, the first described by the formula:
• ##STR7## wherein R.sub.1 and R.sub.4 are both an alkyl or cycloalkyl group containing a secondary or tertiary carbon atom attached to the silicon atom, R.sub.1 and R.sub.4 being the same, R.sub.2 and R.sub.3 are alkyl or aryl groups, R.sub.2 and R.sub.3 being the same or different,
• and the second is cyclohexylmethyldimethoxysilane,
• wherein the two electron donors are in a molar ratio of from about 1:3 to about 1:1 of the second to the first, and
• wherein silicon and titanium are in a molar ratio (Si/Ti molar ratio) within the range from about 0.5 to about 10.

A catalyst for the polymerization of propylene, comprising:

• (a) a conventional Ziegler-Natta catalyst component which comprises a transition metal compound of the general formula MR.sup.+.sub.x where M is titanium, R.sup.+ is a halogen or a hydrocarboxyl and x is the valence of titanium;
• (b) an organoaluminum compound;
• (c) a mixture of at least two electron donors, the first described by the formula:
• ##STR8## wherein R.sub.1 and R.sub.4 are both an alkyl or cycloalkyl group containing a secondary or tertiary carbon atom attached to the silicon atom, R.sub.1 and R.sub.4 being the same, R.sub.2 and R.sub.3 are alkyl or aryl groups, R.sub.2 and R.sub.3 being the same or different,
• and the second is cyclohexylmethyldimethoxysilane,
• wherein the two electron donors are in a molar ratio of from about 1:3 to about 3:1 of the second to the first, and
• wherein silicon and titanium are in a molar ratio (Si/Ti molar ratio) within the range from about 0.5 to about 10.

A catalyst for the polymerization of propylene, comprising:

• (a) a conventional Ziegler-Natta catalyst wherein the conventional Ziegler-Natta catalyst comprising a solid catalyst component obtained by (i) suspending a dialkoxy magnesium in an aromatic hydrocarbon that is liquid at normal temperatures, (ii) contacting the dialkoxy magnesium with a titanium halide and further (iii) contacting the resulting composition a second time with the titanium halide, and contacting the dialkoxy magnesium with a diester of an aromatic dicarboxylic acid at some point during the treatment with the titanium halide in (ii);
• (b) an organoaluminum compound;
• (c) a mixture of at least two electron donors, the first described by the formula:
• ##STR9## wherein R.sub.1 and R.sub.4 are both an alkyl or cycloalkyl group containing a secondary or tertiary carbon atom attached to the silicon atom, R.sub.1 and R.sub.4 being the same, R.sub.2 and R.sub.3 are alkyl or aryl groups, R.sub.2 and R.sub.3 being the same or different,
• and the second is cyclohexylmethyldimethoxysilane
• wherein the two electron donors are in a molar ratio of from about 1:3 to about 1:1 of the second to the first, and
• wherein the Si/Ti molar ratio is within the range from about 0.5 to about 10.

A catalyst for the polymerization of propylene, comprising:

• (a) a conventional Ziegler-Natta catalyst component wherein the conventional Ziegler-Natta catalyst comprising a solid catalyst component obtained by (i) suspending a dialkoxy magnesium in an aromatic hydrocarbon that is liquid at normal temperatures, (ii) contacting the dialkoxy magnesium with a titanium halide and further (iii) contacting the resulting composition a second time with the titanium halide, and contacting the dialkoxy magnesium with a diester of an aromatic dicarboxylic acid at some point during the treatment with the titanium halide in (ii);
• (b) an organoaluminum compound;
• (c) a mixture of at least two electron donors, the first described by the formula:
• ##STR10## wherein R.sub.1 and R.sub.4 are both an alkyl or cycloalkyl group containing a secondary or tertiary carbon atom attached to the silicon atom, R.sub.1 and R.sub.4 being the same, R.sub.2 and R.sub.3 are alkyl or aryl groups, R.sub.2 and R.sub.3 being the same or different,
• and the second is cyclohexylmethyldimethoxysilane
• wherein the two electron donors are in a molar ratio of from about 1:3 to about 3:1 of the second to the first, and
• wherein the Si/Ti molar ratio is within the range from about 0.5 to about 10.