Synthesis of reactor blend of linear and branched polyethylene using metallocene/Ni-diimine binary catalyst system in a single reactor

This work reports the synthesis of a series of reactor blends of linear and branched polyethylene materials using a combination of [1,4-bis(2,6-diisopropylphenyl) acenaphthene diimine nickel(II) dibromide] (1)/MMAO, known as an active catalyst for the production of branched polyethylene, and [rac-ethylenebis(indenyl) zirconium dichloride] (2)/MMAO, which is active for the production of linear polyethylene. The polymerization runs were performed at various levels of temperature, pressure, and catalyst 2 molar fractions. At 5 degrees C, there was very low influence of catalyst 2 molar fraction on the overall catalyst activity. However, at 30 degrees C and 50 degrees C, the overall catalyst activity increased linearly with catalyst 2 molar fraction. The same linear dependency was also found for the polymerization reactions carried out at 60 degrees C and 100 degrees C. At various levels of temperature and ethylene pressure, higher melting temperature and crystallinity were observed with an increase in catalyst 2 molar fraction. At 60 degrees C and 100 psig, the DSC thermograms of the polymers produced with 1/2/MMAO exhibited two distinct peaks with melting temperatures closely corresponding to the melting temperatures of the polymers produced with the individual catalysts, 1/MMAO and 2/MMAO. The GPCV analysis of ail polyethylene samples showed monomodal molecular weight distributions with low polydispersities. (c) 2005 Wiley Periodicals, Inc.