Macromolecules, Vol.37, No.17, 6275-6282, 2004
Supporting a metallocene on functional polypropylene granules for slurry ethylene polymerization
We report on the exploration of functional polypropylene as supporting material for homogeneous metallocene catalyst. The copolymerization of propylene and 5-hexenyl-9-BBN by a spherical MgCl2-supported TiCl4 catalyst containing diisobutyl phthalate internal electron donor combined with AlEt3 activator and dimethoxydiphenylsilane external donor afforded isotactic polypropylene granules bearing reactive alkyl-9-BBN groups, which, upon being treated with H2O2/NaOH, resulted in polypropylene granules containing hydroxy functionality. Immobilization of Cp2ZrCl2/MAO was then conducted in toluene solution at an elevated temperature following the procedure of treating the hydroxyl-containing polymers sequentially with MAO and Cp2ZrCl2. Elemental analysis of the Zr contents of the supported catalysts reveals that they are proportional to the concentrations of hydroxy group on the support. In turn, the efficiency of the supported catalysts in slurry ethylene polymerization also exhibits a significant dependency on the hydroxy group concentration: the higher the concentration, the higher the polymerization efficiency. The polymers produced by the functional polypropylene-supported catalysts possess improved apparent morphology as compared with those by the homogeneous catalyst as well as by the hydroxyl-free, net polypropylene-supported one.