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  • 1
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 215 (1994), S. 35-46 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Das homogene Katalysatorsystem Zirconocendichlorid/Methylalumoxan/Trimethylaluminium (Cp2ZrCl2/MAO/TMA) wurde bezüglich des Einflusses der Variation des Almao/Zr-Verhäaltnisses, der absoluten Zr-Konzentration und der Addition von TMA auf die Polymerisationsaktivitäat von Ethylen und die Polymereigenschaften untersucht. Die Polymerisationsprofile bei kleinen Almao/Zr-Verhäaltnissen und die äAnderungen mit der Zr-Konzentration werden mit einem Komplexierungsgleichgewicht für den aktiven homogenen Katalysator und mit einem Wechsel zu einem heterogenen Katalysator aufgrund der Polymerabscheidung wäahrend der Polymerisation erkläart. Gute Polymerproduktivitäaten werden mit AlMAO/Zr 〈 1000 bei Zr-Konzentrationen zwischen 10-4und 10-5 mol/I und Zugabe von TMA (AlMAO/AlTMA ≈ 1.4) erreicht.
    Notes: A quantitative study was carried out on the homogeneous zirconocene dichloride/methylalumoxane/trimethylaluminum (Cp2ZrCl2/MAO/TMA) catalyst system in ethylene polymerization. The effects of variation of the AlMAO/Zr ratio, absolute Zr concentration, and addition of TMA on ethylene polymerization activity and polymer properties were investigated. The polymerization profiles for small AlMAO/Zr ratios and the changes with the Zr concentration are explained with a complexation equilibrium for the active homogeneous complex and with the change to a heterogeneous catalyst upon polymer precipitation. Good polymer productivities can be achieved at AlMAO/Zr 〈 1000 when working at Zr concentrations between 10-4 and 10-5 mol/l with addition of TMA (AlMAO/AlTMA≈ 1.4).
    Additional Material: 4 Ill.
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  • 2
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Das Katalysatorsystem Zirkonocendichlorid/Methylalumoxan wurde auf Siliciumdioxid aufgebracht, um Katalysatoren fur die Suspensions- order Gasphasenpolymerisation von Ethylen herzustellen. Die häochste Aktivitäat wurde für eine sandwichartige, dreilagige Verankerung von Zirkonzentren auf der Träageroberfläache gefunden. Dieneuen Katalysatorsysteme besitzen eine im Vergleich zu den entsprechenden homogenen Katalysatoren geringere Aktivitäat. Die Immobilisierung der aktiven Katalysatorzentren führt zu einer deutlichen Erhäohung der Polymermolmassen. Dabei bleibt die enge Molekulargewichtsverteilung der Polymerprodukte nahezu erhalten. Solche auf Träager aufgebrachte Metallocen-Katalysatoren käonnten für die Herstellung von Polyethylenen mit kontrollierter Rheologie Anwendung finden.
    Notes: The system zirconocene dichloride/methylalumoxane was supported on silica in order to provide ethylene polymerization catalysts for suspension or gas phase processes. Highest activity was found for a sandwich-like, three layer anchoring of the zirconium centers on the support surface. The new catalyst systems show a decrease of activity compared to polymerization experiments in homogeneous phase. However, the molecular weights are increased and the weight distributions remain narrow by immobilization of the active catalyst sites. Those supported metallocene catalysts could find application for the synthesis of polyethylene materials with controlled rheology.
    Additional Material: 3 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 31 (1993), S. 2959-2968 
    ISSN: 0887-624X
    Keywords: aluminoxanes ; metallocene catalysts, supported ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reaction of methylaluminoxane (MAO) with 1,6-hexanediol or 1,10-decanediol leads to white powdery materials which were studied by 13C and 27Al MAS NMR, scanning electron microscopy (SEM), and whose surface area and porosity was determined according to the BET method. The hydrolysis of trimethylaluminum with hydrogel was carried out and the product was investigated by SEM. © 1993 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
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  • 4
    ISSN: 1022-1336
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A series of tert-butyl substituted zirconocene/methylaluminoxane catalysts illustrates the potential for the tailoring of olefin oligomers with extremely narrow molar mass distributions, which are explained on the basis of a chain-length dependent propagation rate. Comparative oligomerization experiments provide a means to estimate the relative rates for chain propagation versus chain transfer as well as a correlation with the metallocene structure.
    Additional Material: 2 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Macromolecular Rapid Communications 15 (1994), S. 655-658 
    ISSN: 1022-1336
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
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