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Ethylene Polymerization using Combined Ni and Ti Catalysts Supported in situ on MAO‐Modified Silica
Author(s) -
Junges Fernando,
de Souza Roberto F.,
dos Santos João H. Zimnoch,
Casagrande Osvaldo L.
Publication year - 2005
Publication title -
macromolecular materials and engineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.913
H-Index - 96
eISSN - 1439-2054
pISSN - 1438-7492
DOI - 10.1002/mame.200400371
Subject(s) - polyethylene , methylaluminoxane , materials science , polymerization , catalysis , linear low density polyethylene , scanning electron microscope , polymer chemistry , polymer , nuclear chemistry , chemical engineering , metallocene , organic chemistry , composite material , chemistry , engineering
Summary: Branched polyethylene/linear polyethylene blends (BPE/LPE) were prepared using the combined Ni( α ‐diimine)Cl 2 ( 1 ) ( α ‐diimine = 1,4‐bis(2,6‐diisopropylphenyl)acenaphthenediimine) and {Tp Ms* }TiCl 3 ( 2 ) (Tp Ms* = hydridobis(3‐mesitylpyrazol‐1‐yl)(5‐mesitylpyrazol‐1‐yl)) catalysts supported in situ on methylaluminoxane (MAO)‐modified silica (4.0 wt.‐% Al/SiO 2 ). The polymerization reactions were performed in toluene at two different polymerization temperatures (0 and 30 °C) and several nickel molar fractions ( x Ni ), using MAO as external cocatalyst. At all temperatures, the activities show an approximate linear correlation with x Ni , indicating a non‐synergistic effect between the nickel and the titanium species. Higher activities were found at 0 °C. The melting temperatures for the polyethylene blends produced at 0 °C decrease as x Ni increases in the medium, indicating good compatibility between the polyethylene phases made by both catalysts. The melting temperature ( T m ) of the polyethylene blends was shown to depend on the order in which the catalysts were immobilized on the MAO‐modified silica support. The initial immobilization of 1 on the support ( 2 / 1 /SMAO‐4) affords polymers with a lower T m than those produced with 1 / 2 /SMAO‐4. In addition, scanning electron microscopy (SEM) studies revealed that the spherical morphology of the supported catalyst is replicated in the polyethylene particles.Influence of polymerization temperature on the activity of 1 / 2 /SMAO‐4 with varying x Ni .