Synthesis of branched polyethylene from ethylene by tandem action of iron and zirconium single site catalysts

The synthesis of low-density polyethylene from ethylene as the only monomer feed has been investigated as an alternative route to branched polyethylen e and to obtain new materials with different properties, avoiding the need to feed l-alkenes into l;he polymerization process. The details of the eval uation of two combination catalyst systems based on single site catalysts a re discussed. The { [(2-ArN=C(Me))(2)C5H3N]FeCl2} (Ar = 2-C6H4(Et)) compoun d, designated as catalyst 1, oligomerizes ethylene to produce linear alpha -olefins with high selectivity, and Me(2)SiInd(2)ZrCl(2) (2) or EtInd(2)ZrC l(2) (3) are used as catalysts that incorporate the alpha -olefins in the p olymer. For catalyst 1 in the presence of methylaluminoxane (MAO) and ethyl ene, a wide range of alpha -olefin products were found, both soluble and in soluble. Also, tandem catalyst combinations 1 and 2 or 1 and 3 in the prese nce of ethylene alone can readily produce branched polyethylene with levels of 1-4 branches per 100 units of ethylene. A change in activity was found for variations in the Fe/Zr ratio for both systems, with lower activity but higher frequency of branching in the polymer backbone for catalyst 2. The final product obtained by the 1/3/MAO systems, however, shows a more homoge neous structure as determined by DSC and GPC.