STUDY OF HYDROGEN EFFECT IN PROPYLENE POLYMERIZATION ON (WITH) THE MGCL2-SUPPORTED ZIEGLER-NATTA CATALYST .2. EFFECT OF CS2 ON POLYMERIZATION CENTERS

The effect of CS2 on the catalytic system TiCl4/MgCl2/DBPH-AlEt(3)/TEPS in propylene polymerization in the presence and absence of hydrogen was studied. It was shown that CS2 poisons active centres in both cases by a similar way. The yield of polypropylene decreases with the CS2 effect, but the isotactic centres poison to the greatest degree. Results obtained by the study of polymerization kinetics, fractional composition and molecular mass distribution of polymers permit a conclusion that there is not any differentiation between initial and ''hydrogen'' centres, i.e. these centres have the same nature. An observed hydrogen activation effect is explained by the revival of ''dormant'' centres, resulting from 2-1 propylene insertion in the polymer chain in the chain transfer reaction with H-2. Seemingly the competition between the polymerization rate retarding by irregular monomer insertion and the activation by hydrogen takes place. It leads to non-stationary kinetics of propylene polymerization in the presence of hydrogen.