Title of article :
Polyethylenes produced with zirconocene immobilized on MAO-modified silicas
Author/Authors :
Bianchini، نويسنده , , Daniela and Bichinho، نويسنده , , Kلtia Messias and dos Santos، نويسنده , , Joمo Henrique Zimnoch and Moncada، نويسنده ,
Issue Information :
دوهفته نامه با شماره پیاپی سال 2002
Pages :
7
From page :
2937
To page :
2943
Abstract :
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/SiO2. Commercial MAO-modified silica (Witco) containing 24.4 wt% Al/SiO2 was used for comparative reasons. The resulting modified-silicas were employed as supports for grafting (nBuCp)2ZrCl2. 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/SiO2 range. According to DSC analysis, one Tm peak was detected for polymer obtained with catalyst prepared with 0.5 wt% Al/SiO2 (135 °C), but two Tm peaks were observed for polymers obtained with catalysts prepared with 10.0 wt% Al/SiO2 (136 and 141 °C) and 20.0 wt% Al/SiO2 (133 and 141 °C).
Keywords :
Ethylene polymerization , zirconocene , Silica-supported metallocenes
Journal title :
Polymer
Serial Year :
2002
Journal title :
Polymer
Record number :
1717192
Link To Document :
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