SYNTHESIS AND PROPERTIES OF HOMOPOLYMER AND COPOLYMERS OBTAINED FROM 1-OCTADECENE WITH ZIRCONOCENE CATALYSTS

摘要

Studies related to the behavior of different metallocene catalysts for the homopolymerization of 1-octadecene andits copolymerization with ethylene will be presented. The metallocenes: rac-Et（Ind）2ZrCl2, rac-Me2Si（Ind）2ZrCl2 andPh2C（Flu）（Cp）ZrCl2 were chosen for the homopolymerization study. They show important differences in catalytic activity athigh temperatures （≥70℃）, with rac-Et（Ind）2ZrCl2 showing the highest activity. At lower temperatures （≤30℃） thedifferences are negligible. For the copolymerization of ethylene with 1-octadecene only the catalysts rac-Et（Ind）2ZrCl2 andrac-Me2Si（Ind）2ZrCl2 were studied. The results show that their catalytic activity is just like that for the homopolymerizationof 1-octadecene, with higher activity for the metallocene with the Et-bridged catalyst. 13C-NMR analysis shows that thecomposition of the copolymerization products depends on the catalytic systems. Copolymers obtained with rac-Me2Si（Ind）2ZrCl2 have greater comonomer incorporation. Thermal analysis shows that poly-1-octadecene synthesized withthe catalyst rac-Et（Ind）2ZrCl2 is very dependent on the polymerization temperature. The homopolymer obtained at 70℃presents two endothermal peaks at 41℃ and 53℃, as compared with the one obtained at 30℃ which presents one wider peakwith a maximum at 67℃. For the catalyst rac-Me2Si（Ind）2ZrCl2 this trend is not observed. The type of metallocene and thereaction time do not significantly change the intrinsic viscosity, but the polymerization temperature changes it drastically,giving higher values at lower temperature. Viscosity measurements on the copolymers show that an increase of comonomerconcentration in the feed reduces the molecular weight of the copolymer, and it was also found that for homopolymer, themolecular weight is independent of the catalytic systems.