Polymerization of ethylene with the (C5H5)2TiCl2-(C2H5)2AlCl catalytic system under the conditions of classical metallocene catalysis

The effects of the concentration of the components of the (C 5 H 5 ) 2 TiCl 2 -(C 2 H 5 ) 2 AlCl catalytic system, Al: Ti molar ratio, the solvent nature, as well as temperature, on the rate of ethylene polymerization and the yield and molecular mass of the resulting polymer were studied. When polymerization was carried out in ethyl chloride at low concentrations of the catalyst, the activity and specific productivity of the (C 5 H 5 ) 2 TiCl 2 -(C 2 H 5 ) 2 AlCl catalytic system increased sharply. At [(C 5 H 5 ) 2 TiCl 2 ] > 10 -6 mol/l and the Al: Ti molar ratios 1000-2000, the specific productivity of the given catalytic system approached the productivity of the classical metallocene catalysts. It was established that the enhanced activity of this system in ethyl chloride at 20-40°C is associated with an increase in the rate constant of chain propagation from 3-10 l/(mol s) (toluene) to 360-550 l/(mol s) (ethyl chloride). It was inferred that the high activity of the metallocene catalyst under investigation, which exceeds 30 PE macromoles/mol (C 5 H 5 ) 2 TiCl 2 , is related to a chain transfer to (C 2 H 5 ) 2 AlCl. It was found that, in the temperature range 20-40°C, the rate constant of this reaction varies from 0.7 to 6.0 mol/(1 s).