POLYOLEFIN-SUPPORTED HOMOGENEOUS TITANIUM-BASED ZIEGLER CATALYST FOR THE PRODUCTION OF POLYETHENE WITH NARROW MOLECULAR-WEIGHT DISTRIBUTION

A novel EPDM (ethene-propene-diene monomer)-supported homogeneous Zieg ler catalyst was developed for the production of polyethene with narro w molecular weight distribution. Ethene polymerization was investigate d in terms of the stability of the active sites on the catalyst and of the variation of the molecular weight distribution arising from a cha nge in co-catalyst. The activity of the catalyst remained constant wit hout deactivation at 60 degrees C for 25 h, regardless of the kind of co-catalyst and the polyolefin support. The molecular weight distribut ion of polyethene was found to be affected by the co-catalyst. High mo lecular weight polyethene with (M) over bar(w)/(M) over bar(n) = 2.2, was obtained with triethylaluminium as a co-catalyst at appropriate co nditions. The extraction experiment of the resulting polymer was perfo rmed to elucidate whether the chain growth occurs via ethene insertion into (1) a Ti-carbon bond formed by alkylation of the titanium specie s during the activation reaction with the co-catalyst, or (2) a bond b etween the Ti species and the polymer support produced during the cata lyst preparation. Route 1 was confirmed by fractionation.