Preparation of LLDPE by in situ copolymerization of ethylene with polymerization catalyst supported on montmorillonite

Linear low-density polyethylene (LLDPE) has been prepared by in situ copolymerization of ethylene with a dual functional catalyst, which was composed of rac-Et (Ind)₂ZrCl₂ supported on montmorillonite (MMT) and {[(2-ArN = C (Me))₂ C₅ H₃ N] FeCl ₂} (Ar = 2, 4-C₆ H₄ (Me)₂) oligomerization catalyst. A series of LLDPE with different branching degrees were obtained by adjusting the molar ratio of Fe and Zr (Fe/Zr), the molar ratio of Al and (Fe + Zr) (Al/(Fe + Zr)) as well. The kinetics curves of polymerization show that the two catalysts exhibit respective catalytic characterizations, and the activity of copolymerization catalyst is more smoothly after supported on MMT. As increasing the Fe/Zr ratio, the densities of polymers measured by density gradient method and the melting points of polymers obtained from DSC decrease. ¹³C-NMR shows that the polymers are LLDPE, and their branching degrees increase as the increasing of the Fe/Zr ratio. At the same time, there are some unreacted α-olefins in polymers, which were confirmed by ¹³C-NMR and GPC.The SEM shows that the polymerization catalyst supported on MMT may produce LLDPE with better morphology than that produced by the catalyst in homogeneous.