Polyolefin-supported homogeneous titanium based Ziegler catalyst for the production of polyethene with narrow molecular weight distribution

摘要

A novel EPDM (ethene-propene-diene monomer)-supported homogeneous Ziegler catalyst was developed for the production of polyethene with narrow molecular weight distribution. Ethene polymerization was investigated in terms of the stability of the active sites on the catalyst and of the variation of the molecular weight distribution arising from a change in co-catalyst. The activity of the catalyst remained constant without deactivation at 60 degrees C for 25 h, regardless of the kind of co-catalyst and the polyolefin support. The molecular weight distribution of polyethene was found to be affected by the co-catalyst. High molecular weight polyethene with (M) over bar(w)/(M) over bar(n) = 2.2, was obtained with triethylaluminium as a co-catalyst at appropriate conditions. The extraction experiment of the resulting polymer was performed to elucidate whether the chain growth occurs via ethene insertion into (1) a Ti-carbon bond formed by alkylation of the titanium species during the activation reaction with the co-catalyst, or (2) a bond between the Ti species and the polymer support produced during the catalyst preparation. Route 1 was confirmed by fractionation. [References: 12]