Bimodal Ultrahigh Molecular Weight Polyethylenes Produced from Supported Catalysts: The Challenge of Using a Combined Catalyst System

Molecular precatalysts complexes (nBuCp)2ZrCl2 (Zr) and (η1:η5‐Me2NCH2CH2C5Me4)CrCl2 (Cr) have been successfully supported on silica nanoparticles, via a single support (SS) or a double support (DS) strategy. These catalyst systems have been successfully used to produce bimodal polyethylenes with an...

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Bibliographic Details
Published in:Macromolecular chemistry and physics 2017-03, Vol.218 (5), p.np-n/a
Main Authors: Liu, Hao, Bastiaansen, Cees W. M., Goossens, Johannes G. P., Schenning, Albertus P. H. J., Severn, John R.
Format: Article
Language:English
Subjects:
bimodal distribution
Catalysis
Catalysts
Molecular weight
Molecular weight distribution
Nanoparticles
Polyethylene
Polyethylenes
Polymerization
silica nanoparticle
single‐site catalyst
Strategy
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Summary:Molecular precatalysts complexes (nBuCp)2ZrCl2 (Zr) and (η1:η5‐Me2NCH2CH2C5Me4)CrCl2 (Cr) have been successfully supported on silica nanoparticles, via a single support (SS) or a double support (DS) strategy. These catalyst systems have been successfully used to produce bimodal polyethylenes with an ultrahigh molecular weight polyethylene content in a single reactor. The SS and DS catalyst systems have been fully evaluated under an identical polymerization condition to assess the challenges in tailoring the molecular weight distribution. The results show that a detrimental interaction exists between Zr and Cr catalysts, part of the Cr catalyst species is deactivated during polymerization in the both DS and SS systems. The detrimental interaction in the DS system is reduced because the catalysts are supported on separate nanoparticles. But, surprisingly the two catalysts in the DS system are still able to “communicate” to each other via cocatalyst‐induced catalyst leaching or other potential reasons. Bimodal polyethylenes with ultrahigh molecular weight polyethylene content are produced utilizing a combination of molecular catalysts, via two separate supportation strategies (single support and double support). The polymerization results show that predictive tailoring molecular weight and molecular weight distributions in a single reactor is challenging due to a combination of antagonistic interaction, varying reactivity ratios and kinetic profiles.
ISSN:1022-1352
1521-3935
DOI:10.1002/macp.201600490