Ethylene/propylene and ethylene/propylene/5-ethylidene-2-norbornene copolymerizations on metallocene/(2,6-tBu2PhO-)AliBu2 catalyst systems

Abstract

This work explores new catalytic systems for the synthesis of ethylene-propylene (EPM) and ethylene-propylene-diene (EPDM) copolymers. We present the results on ethylene/propylene copolymerization and terpolymerization of ethylene/propylene/5-ethylidene-2-norbornene with different metallocenes activated by (2,6-tBu2PhO-)AliBu2. Metallocenes employed are EtInd2TiMe2, rac-EtInd2ZrMe2, rac-EtInd2HfMe2, rac-Et(2-MeInd)2ZrMe2, rac-Me2Si(2-MeInd)2ZrMe2. The data encompasses catalytic performance of the systems and copolymers properties: composition, molecular weight, thermo-physical, and mechanical characteristics. The highest copolymerization activities were observed for zirconocenes, the lowest — for rac-EtInd2HfMe2. On the other hand, rac-EtInd2HfMe2 shows the best incorporation of both propylene and 5-ethylidene-2-norbornene, yielding polymers with high molecular weights, low crystallinities and melting points. This catalyst system demonstrated the possibility of producing terpolymers with propylene content up to 39 wt % and 5-ethylidene-2-norbornene up to 18 wt %. Copolymers of ethylene with propylene with the highest tensile strength and elongation at break are obtained on rac-Me2Si(2-MeInd)2ZrMe2, while terpolymer with good elastic properties is formed on rac-EtInd2ZrMe2 and rac-EtInd2HfMe2. Copolymers with the best relaxation properties were synthesized on rac-EtInd2HfMe2.