Ethylene as catalyst reactivator in the propene-styrene copolymerization

An experiment was conducted to show the presence of ethylene as catalyst reactivator in the propene-styrene copolymerization. The copolymerizations have been performed by bubbling the gaseous monomers at atmospheric pressure into a flask containing a styrene solution of the prototypical ansa-zirconocene complex rac-(ethylene)bis(1-indenyl)zirconium dichloride activated by methylalumoxane. In structure A one tertiary carbon atom bearing the phenyl ring is surrounded in both sides by sequences of two methylene groups while in structure B the junction is characterized by the presence of two tertiary carbon atoms bearing the phenyl ring separated by three methylene groups. By reducing the styrene content in the comonomer feed composition ([E]/[P]/[S] ) 1/135/65 in the liquid phase) a copolymer with a 6% styrene units is obtained. The results reported show that it is possible to introduce some styrene units in an isotactic polypropylene sequence by using a small amount of ethylene to reactivate the catalyst after the styrene insertion.