Polyolefin production

A process for preparing a metallocene catalyst for the production of a short sequence syndiotactic/isotactic block polyolefin comprising activating a Cl symmetric metallocene compound and of general formula R″(CpRn)(Cp′R′m)MQp for use as a catalyst component in the production of short sequence syndiotactic/isotactic block polyolefins, wherein Cp is a substituted cyclopentadienyl;

• each R is independently aryl or hydrocarbyl having 1 to 20 carbon atoms, at least position 3 of Cp is substituted with aryl, at least one other position of Cp is substituted with a non-bulky substituent, and n is an integer in the range from 2 to 4;
• Cp′ is substituted or unsubstituted fluorenyl;
• each R′ is independently hydrocarbyl having 1 to 20 carbon atoms and m is O or an integer in the range from 1 to 8;
• R″ is a structural bridge to impart stereorigidity between Cp and Cp′;
• M is a metal from Group IIIB, IVB, VB or VIB;
• Q is a hydrocarbyl radical having 1 to 20 carbon atoms or a halogen;
• and p is the valence of M minus 2, with a cocatalyst.

A catalyst system for use in preparing short sequence syndiotactic/isotactic block polyolefms, which comprises (a) a metallocene compound of general formula R″(CpRn) (Cp′R′m)MQp for use as a catalyst component in the production of short sequence syndiotactic/isotactic block polyolefins, wherein Cp is a substituted cyclopentadienyl;

• each R is independently aryl or hydrocarbyl having 1 to 20 carbon atoms, at least position 3 of Cp is substituted with aryl, at least one other position of Cp is substituted with a non-bulky substituent, and n is an integer in the range from 2 to 4;
• Cp′ is substituted or unsubstituted fluorenyl;
• each R′ is independently hydrocarbyl having 1 to 20 carbon atoms and m is O or an integer in the range from 1 to 8;
• R″ is a structural bridge to impart stereorigidity between Cp and Cp′;
• M is a metal from Group IIIB, IVB, VB or VIB;
• Q is a hydrocarbyl radical having 1 to 20 carbon atoms or a halogen;
• and p is the valence of M minus 2;
• and (b) a cocatalyst capable of activating the metallocene compound.

A process for preparing a short sequence syndiotactic/isotactic block polyolefin, which comprises contacting a catalyst system, which comprises (a) a metallocene compound of general formula R″(CpRn)(Cp′R′m)MQp for use as a catalyst component in the production of short sequence syndiotactic/isotactic block polyolefins, wherein Cp is a substituted cyclopentadienyl;

• each R is independently aryl or hydrocarbyl having 1 to 20 carbon atoms, at least position 3 of Cp is substituted with aryl, at least one other position of Cp is substituted with a non-bulky substituent, and n is an integer in the range from 2 to 4;
• Cp′ is substituted or unsubstituted fluorenyl;
• each R′ is independently hydrocarbyl having 1 to 20 carbon atoms and m is O or an integer in the range from 1 to 8;
• R″ is a structural bridge to impart stereorigidity between Cp and Cp′;
• M is a metal from Group IIIB, IVB, VB or VIB;
• Q is a hydrocarbyl radical having 1 to 20 carbon atoms or a halogen;
• and p is the valence of M minus 2;
• and (b) a cocatalyst capable of activating the metallocene compound, with at least one olefin in a reaction zone under polymerization conditions.