Low density polyethylene by tandem catalysis with single site Ti(IV)/Co(II) catalysts |
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Authors: | M Frediani C Bianchini W Kaminsky |
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Institution: | (1) Department of Organic Chemistry, University of Florence, Polo Scientifico, via della Lastruccia 13, 50019 Sesto Fiorentino, Italy;(2) ICCOM-CNR, Area della Ricerca CNR di Firenze, via Madonna del Piano 10, 50019 Sesto Fiorentino, Italy;(3) Institute of Technical and Macromolecular Chemistry, University of Hamburg, Bundesstrasse 45, 20146 Hamburg, Germany |
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Abstract: | A variety of branched polyethylenes (PE), ranging from semicrystalline linear low density polyethylene to completely amorphous
low density polyethylene and rubbery PE, can be produced from ethylene alone by tandem catalysis using as oligomerization
catalysts the (imino)pyridyl Co(II) complexes NBTCoCl2 (1) ({6-(benzob]thiophen-2-yl)-2-(imine)pyridyl)}CoCl2), NETCoCl2 (2) ({6-(4-ethylthiophen-2-yl)-2-(imine)pyridyl)}CoCl2), or NPhCoCl2 (3) ({6-(phenyl)-2-(imine)pyridyl)}CoCl2) and as a copolymerization catalyst η5-C5Me4)SiMe2(t-BuN)]TiCl2 (4). The catalytic activity of the systems 1/4/MAO, 2/4/MAO, and 3/4/MAO has been evaluated under comparable experimental conditions (T = 30°C, ethylene] = 0.35 mol/l), varying the molar fraction of the cobalt precursors. A positive comonomer effect was observed
for all the systems investigated. The maximum productivity (4570 kg PE (mol Ti)−1 h−1) was obtained for the benzothiophenyl-substituted cobalt complex. An effective control of the branching in the polymer backbone
was achieved by varying either the oligomerization catalyst or its molar fraction. Completely amorphous materials with T
g as low as-60°C could be obtained.
The text was submitted by the authors in English. |
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