Kinetic and thermal study of ethylene-propylene copolymerization catalyzed by ansa-zirconocene activated with Alkylaluminium / borate : Effects of linear and branched alkylaluminium compounds as cocatalyst

摘要: Ethylene-propylene (EP) copolymerizations was carried out with two ansa-metallocene: rac-Me2Si(2-Me-4-Ph-Ind)2ZrCl2 (Mt-I) and rac-Et(Ind)2ZrCl2 (Mt-II) combined borates activators like ([Me2NPh][B(C6F5)4] (Borate-I), [Ph3C][B(C6F5)4] (Borate-II). Different structures of alkylaluminum( triethylaluminium (TEA), triisobutylaluminium (TIBA) TEA/TIBA mixture 25/75, 50/50, 75/25 mol ratios were used as cocatalysts. The choice ligand structure and, more importantly, the nature cocatalyst significantly impact these systems' activity polymeric materials' properties. Borate-II has been shown giving higher activities than Borate-I both ansa-metallocene, attending 5.6 × 106 g/mol Zr*h. Mt-I gives molecular weight but produced copolymers low ethylene content, melting points, crystallinity Mt-II. very close to each other 100% TIBA. Still, became active Mt-II when TEA 25% in system. effects alkylaluminiums catalysts on EP copolymer (Mw) distribution (MWD) much complicated. MWD curve changed from broad narrow TIBA replaced by a different mole ratio ratio. technique for assessment centers [C*]/[Zr] fraction ansa-metallocene catalyst quenched label using 2-thiophenecarbonyl chloride (TPCC) determine propagation rate constants (kP) copolymers. value Mt-I/Borate-I/TIBA is lower those Mt-I/Borate-I/TEA Mt-I/Borate-I/TEA/TIBA main differences appear between containing pure TEA, possibly due faster chain transfer Al—Et bulky Al—iBu. Adding metallocene/borate/alkylaluminiums can be applied an effective method regulate high degree