Bianchini, Daniela; Bichinho, Kátia Messias; dos Santos, João Henrique Zimnoch
Polyethylenes produced with zirconocene immobilized on MAO-modified silicas
Teil von
  • Polymer (Guilford), 2002, Vol.43 (10), p.2937-2943
Ort / Verlag
OXFORD: Elsevier Ltd
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The effect of Al content on MAO-modified silicas was evaluated on catalyst activity, on polymer properties and on residual metal content in the resulting polyethylenes. MAO-modified silicas were prepared by impregnating MAO toluene solutions in concentration range between 0.5 and 20.0 wt% Al/SiO 2. Commercial MAO-modified silica (Witco) containing 24.4 wt% Al/SiO 2 was used for comparative reasons. The resulting modified-silicas were employed as supports for grafting ( nBuCp) 2ZrCl 2. Using external MAO as cocatalyst (Al/Zr=2000) no difference in catalyst activity was observed. Nevertheless, for Al/Zr=500, catalyst activities were shown to be higher for supported zirconocene systems containing 0.0–2.0 wt% Al/SiO 2 range. According to DSC analysis, one T m peak was detected for polymer obtained with catalyst prepared with 0.5 wt% Al/SiO 2 (135 °C), but two T m peaks were observed for polymers obtained with catalysts prepared with 10.0 wt% Al/SiO 2 (136 and 141 °C) and 20.0 wt% Al/SiO 2 (133 and 141 °C).

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