The effective tandem catalysis systems including the trimerization catalyst of CrCl3/SNS [SNS = bis-(2-pentylsulfanyl-ethyl)-amine] and the copolymerization catalyst of rac-ethylene bis(indenyl) zirconium (IV) dichloride have been introduced. The CrCl3/SNS catalyst was synthesized via reaction between CrCl3(THF)3 precursor and SNS as efficient ligand at room temperature. An ethylene trimerization reaction at 90 °C and 23 bar ethylene, using the CrCl3/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 CrCl3/SNS amount yielded a series of copolymer samples with decreased T m and X c. The butyl branches of produced polymer were identified by 13C 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.
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Mohamadnia, Z., Ahmadi, E., Haghighi, M.N. et al. Preparation of LLDPE through tandem ethylene polymerization using chromium and zirconium catalysts. Iran Polym J 24, 621–628 (2015). https://doi.org/10.1007/s13726-015-0345-0