Study On A New Type Of Heterocyclic Transition Metal Catalysts And Their Catalytic Performance Of Ethylene Propylene Copolymerization

Eight heterocyclic transition metal complexes bearing two kinds of ligands with different electron effects were designed and synthesized. Elemental analysis(EA) and’H NMR analysis revealed the structure of complexes. Complexes/methylalumoxane(MAO) catalyst system catalyzed ethylene polymerization, ethylene-propylene copolymerization and ethylene-propylene-1-octene copolymerization.13C NMR, DSC, FT-IR, GPC were used to characterize the polymer. Researched the effects of structure of ligands, polymerization temperature, polymerization time, Al/M, monomer feed ratio and other factors on the polymerization activity and the sequence structure of polymer.Through the research in the ethylene homopolymerization and copolymerization suggested that the performance of the catalysts were effected by different electron effects. The early transition metal catalysts, with electron-donating effect group can effectively improve the catalytic performance, but in the late transition metal catalyst, with electron withdrawing effect group can improve the performance of the catalyst. The activity of early transition metal catalysts were higher than late transition metal catalysts. Cat.5 has high activity on ethylene homopolymerization,ethylene-propylene copolymerization and ethylene-propylene-1-octene copolymerization.When the molar ratio of Al/Ti is 400:1, polymerization time is 1 hour, polymerization temperature is 50℃, concentration of catalyst is 1.5×10-4mol/L,the activity of ethylene polymerization was up to 2.41 x 105 g PE/mol.M.h,.Even though the temperature rose to 80℃,the catalyst can still maintain a good activity. In copolymerization, it can get the ethylene-propylene copolymer with the propylene content of 11.5mol%.In ethylene-propylene-1-octene copolymer,the propylene content was up to 26.1mol%. Through the DSC analysis, the melting point of the polymer have been effectively reduced. Through the calculation of 13C-NMR spectra,found that the copolymer was random copolymer.