Effect of triethylaluminum/transition-metal ratio on the physical properties and chemical composition distributions of ethylene-hexene copolymers produced by a rac-Et(Ind)2ZrCl2/TiCl4/MAO/SMB catalyst

A silica-magnesium bisupport (SMB) was prepared by a sol-gel method for use as a support for a metallocene/Ziegler-Natta hybrid catalyst. The prepared rac-Et(Ind)(2)ZrC1(2)/TiCl4/MAO(methylaluminoxane)/SMB catalyst was applied to the copolymerization of ethylene with 1-hexene using a variable triethylaluminum (TEA)/transition-metal (Ti) ratio and fixed MAO/transition-metal (Zr) ratio. The effect of the A1(TEA)/Ti ratio on the physical properties and chemical composition distributions (CCDs) of the ethylene-hexene copolymers produced by the hybrid catalyst was investigated. In the ethylene-hexene copolymers, two melting temperatures attributed to the metallocene and Ziegler-Natta catalysts were clearly observed. The number of CCD peaks was increased from six to seven and the temperature region in which the peaks for the short chain branches of the ethylene-hexene copolymer were distributed became lower as the A1(TEA)/Ti ratio was increased from 300 to 400. Furthermore, the temperature regions corresponding to the lamellas in the copolymer became lower and those corresponding to the small lamellas in the copolymer became higher as the A1(TEA)/Ti ratio was increased from 300 to 400. In the copolymer produced with A1(TEA)/Ti = 500, however, only four CCD peaks were observed and the short chain branches were poorly distributed.