Copolymerization of propene with low amounts of ethene in propene bulk phase

Propene homopolymers and propene–ethene copolymers with small amount of ethene were synthesized using three catalyst systems [p-CH3OPh2C(2,7-di-tertBuFlu)(Cp)]ZrCl2/Me2HNPh][B(C6F5)4] (Cat I), [p-CH3OPh2C(2,7-di-tertBuFlu)(Cp)]ZrCl2/[Ph3C][B(C6F5)4] (Cat II) and [p-CH3OPh2C(2,7-di-tertBuFlu)(Cp)]ZrCl2/MAO (Cat III) in propene bulk phase. The activity of the catalyst was dependent on the formed ion pair: Cat I showed the highest activity, up to 96,000 kgpol/molZr h, at the used polymerization conditions. The produced homo- and copolymers have high molecular weights, between 400 and 600 kg/mol. The ethene incorporation rate was nearly the same with the different catalyst systems; the amount of ethene in the copolymer was increasing linearly with the amount of ethene in feed. The syndiotacticity of the homopolymer was highest, [rrrr]>90%, with Cat I when it was 81.4 with Cat II and 80.8 with Cat III. The small amount of ethene in the copolymer allows the control of the melting and crystallization behavior. Also the crystallization temperatures of the copolymers were found to depend on the used catalyst system.