Influence of Ziegler−Natta Catalyst Regioselectivity on Polypropylene Molecular Weight Distribution and Rheological and Crystallization Behavior

2004 ◽  
Vol 37 (26) ◽  
pp. 9722-9727 ◽  
Author(s):  
John C. Chadwick ◽  
Frank P. T. J. van der Burgt ◽  
Sanjay Rastogi ◽  
Vincenzo Busico ◽  
Roberta Cipullo ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Molecular Weight Distribution ◽  
Weight Distribution ◽  
Crystallization Behavior ◽  
Natta Catalyst ◽  
Ziegler Natta Catalyst

Influences of silane/ether composite external donors on propylene polymerization with MgCl2-supported Ziegler-Natta catalyst in the presence of hydrogen

e-Polymers ◽  
2011 ◽  
Vol 11 (1) ◽  
Author(s):  
Song-tao Tu ◽  
Jun-qin Lou ◽  
Zhi-sheng Fu ◽  
Zhi-qiang Fan
Keyword(s):  
Molecular Weight ◽  
Catalytic Activity ◽  
High Activity ◽  
Molecular Weight Distribution ◽  
Weight Distribution ◽  
Catalyst System ◽  
Propylene Polymerization ◽  
External Donor ◽  
Natta Catalyst ◽  
Ziegler Natta Catalyst

AbstractIn this work, the effects of two silane type external donors, Ph2Si(OCH3)2 (DPDMS) and dicyclopentyldimethoxysilane (DCPDMS) on propylene slurry polymerization in the presence of hydrogen with a MgCl2/TiCl4/DIBP - Al(C2H5)3 catalyst system were investigated, and the tacticity distribution and molecular weight distribution (MWD) of polypropylene (PP) were further regulated by using silane/ether (ROCH3, R = n-Bu, i-C8H17) composite external donors. The tacticity distribution of PP, as revealed by successive self-nucleation and annealing (SSA) thermo analysis of the polymer, is markedly changed by the external donors. DCPDMS shows much stronger effects than DPDMS. Addition of the ether as an auxiliary external donor in MgCl2/TiCl4/DIBP-TEA/silane (DPDMS or DCPDMS) lead to further increase in catalytic activity and isotacticity of PP, and changes in tacticity distribution. By using the composite external donors, PP with both higher isotacticity index, lower molecular weight or narrower molecular weight distribution was prepared at high activity. Effects of the external donors on the active center distribution were discussed based on the results of deconvoluting the MWD curve with multiple Flory “most-probable” distributions, and possible mechanism of the external donor effects was proposed.

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