EFFECTS OF HYDROGEN ON THE POLYMERIZATION OF PROPYLENE WITH A MAGNESIUM-CHLORIDE SUPPORTED ZIEGLER-NATTA CATALYST

The addition of hydrogen produced no change in the number of active sites and the propagation rate constant in a polymerization system approximating actual conditions in which propylene was polymerized with a magnesium chloride-supported catalyst. A plausible explanation for reversible hydrogen activation is that, on addition of hydrogen to the polymerization system, a rapid ligand exchange occurs favorably between propylene and a terminal unsaturated bond of the polymer, formed by a beta-hydrogen elimination from a titanium-polymer bond. On the basis of analyses of FD-MS and H-1-NMR spectra of low molecular weight polymers, it is considered that the beta-hydrogen elimination is suppressed to some extent in the presence of hydrogen.