Ethylene/1-hexene copolymerization with MgCl 2-supported Ziegler–Natta catalysts containing aryloxy ligands. Part I: Catalysts prepared by immobilizing TiCl 3(OAr) onto MgCl 2 in batch reaction

Abstract

Novel aryloxy-containing MgCl 2-supported Ziegler–Natta catalysts were prepared by treating TiCl 3(OAr) (Ar = C 6H 5-, 2,6-Me 2C 6H 3-, 2,6- i-Pr 2C 6H 3-, 2,6- t-Bu 2C 6H 3-) with MgCl 2 in batch reaction. The influences of aryloxy group on the titanium content and aryloxy/Ti molar ratio in the catalysts was investigated. Because of ligand exchanges between the immobilized titanium species and TiCl 3(OAr) in the solution, the aryloxy/Ti molar ratio in these catalysts were less than 1. Using triethylaluminum (TEA) or triisobutylaluminum (TIBA) as cocatalyst, these catalysts showed different catalytic behaviors in ethylene-1-hexene copolymerization. Using TIBA as cocatalyst, the aryloxy-containing catalysts showed higher activity than a TiCl 4/MgCl 2 blank catalyst. Although the total 1-hexene incorporation of the copolymers prepared by the novel catalysts were lower than that of the blank system, the difference in 1-hexene content between the boiling n-heptane soluble part and the insoluble part was markedly lower, and the blockiness of comonomer sequence distribution was evidently higher. The TIBA activated aryloxy-containing catalysts were found to produce poly(ethylene- co-1-hexene) with more uniform chemical composition distribution.