TICL4/MGH2-SUPPORTED ZIEGLER-TYPE CATALYST SYSTEM .3. NEW FINDINGS ON THE CONCENTRATION OF ACTIVE-SITES IN ETHYLENE/1-HEXENE COPOLYMERIZATION

The effect of 1-hexene on the rate constant of ethylene polymerization and on the number of active centres in the copolymerization of ethylene with 1-hexene is reported. Using three TiCl4/MgH2-Al(C2H5)3 Catalysts, of different Ti contents and surface area in the polymerization reveals that the addition of small amounts of the comonomer 1-hexene results in a two- to three-fold increase in the rate of ethylene consumption when a low-Ti-content catalyst is used. In contrast, no fundamental change in the catalytic activity was observed when a high-Ti-content catalyst is employed. The determination of the concentration of active centres C* by means of the (CO)-C-14 radio-labelling technique, shows that C* in ethylene/1-hexene copolymerization is more or less the same as in ethylene homopolymerization.