Ethylene Polymerization Using Novel Titanium Catalytic Precursors Bearing N,N-Dialkylcrbamato Ligands

Polymerization catalysts based on N,N-dialkylcarbamato complexes of titanium(IV) appear particularly interesting, because these novel catalytic precursors are rather cheap and easy to synthesize and handle. This contribution reports ethylene polymerization behavior of titanium(IV) complexes of general formula Ti(O2CNR2)(4) R = Me (I) and Et (II) and TiCl2(O2CNMe2)(2) (III). These precursors in conjunction with methylaluminoxane resulted active catalysts for the polymerization of ethylene, affording high-density polyethylene with limited branch content. The influence of the polymerization parameters was studied with particular reference to the type of catalyst components, solvent, temperature, monomer concentration, and Al/Ti ratio. The nature of the solvent appears crucial for catalytic performances: when toluene was replaced by chlorobenzene, a significant increase of the productivity was ascertained. The obtained polymers were characterized by DSC, size exclusion chromatography, FTIR, and NMR techniques.