Preparation of LLDPE through tandem ethylene polymerization using chromium and zirconium catalysts

The effective tandem catalysis systems including the trimerization catalyst of CrCl 3 /SNS [SNS = bis-(2-pentylsulfanyl-ethyl)-amine] and the copolymerization catalyst of rac -ethylene bis(indenyl) zirconium (IV) dichloride have been introduced. The CrCl 3 /SNS catalyst was synthesized via reaction between CrCl 3 (THF) 3 precursor and SNS as efficient ligand at room temperature. An ethylene trimerization reaction at 90 °C and 23 bar ethylene, using the CrCl 3 /SNS complex activated by 700 equivalents of methylaluminoxane, afforded 99.9 % 1-C6. Only 0.10 % PE was produced. Effect of different parameters such as ethylene pressure and Cr/Zr ratio was investigated during tandem polymerization. Successive increases in the CrCl 3 /SNS amount yielded a series of copolymer samples with decreased T m and X c . The butyl branches of produced polymer were identified by 13 C NMR analysis. Data from dynamic mechanical thermal analysis indicated formation of various polymeric materials with the branches, which their stiffness varied according to the Cr/Zr ratio used in the polymerization reaction.