Activation of Bridged Metallocenes by Solid Acid Supports

1 Activation of Bridged Metallocenes by Solid Acid Supports 

In an important follow-up study to the activation of the non-bridged metallocene compounds by solid add supports discussed above, scientists at Chevron-Phillips Chemical Company reported [7] the activation of bridged metallocenes, designated as ansa-metallocenes, using the same solid acid supports investigated above [5]. 

The activation of certain ansa-metallocenes to solid acid supports produces polyethylene with relatively low levels of long-chain branching, which is sufficient to moderately increase the molecular weight distribution of the polyethylene, and improve the polymer processability, but not be detrimental to the properties of the finished fabricated product. Consequently, low levels of LCB improve the shear-thinning behavior of the molten polyethylene, which resolves the processing disadvantage of polyethylene with a polydispersity index of 2. 

The catalyst prepared with this particular bridged metallocene provided an ethylene/1 -hexene copolymer at 80 C with an of283,000 and a polydispersity index value (MyMj of 3.1 utilizing commercial polymerization conditions. 

Polyethylene products produced with the Phillips loop process using catalysts prepared with metallocene compounds activated with solid acid supports are available commercially. 

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