Time Dependence of Molecular Weight in Propylene Bulk Polymerization with MgCb-SupportecS Ziegler-Natta Catalyst

摘要

In the chemistry of Ziegler-Natta catalyst, little has been known about the influence of time on molecular weight. We explored this influence and found that Mw value for the resultant polypropylene (PP) decreased with time even when H2 concentrations were kept constant, For the explanation of this phenomenon, a three-site model was proposed. In this paper, the formation of stereo-block polypropylene is reported. This experimental fact would be a good proof of the existence of a fluctuating site, which is one of the key points of the proposed three-site model.