High-Resolution13C NMR Configurational Analysis of Polypropylene Made with MgCl2-Supported Ziegler−Natta Catalysts. 1. The “Model” System MgCl2/TiCl4−2,6-Dimethylpyridine/Al(C2H5)3

Busico, Vincenzo; Cipullo, Roberta; Monaco, Guglielmo; Talarico, Giovanni; Vacatello, Michele; Chadwick, John C.; Segre, Anna Laura; Sudmeijer, Olof

doi:10.1021/ma981941n

Cited by 204 publications

(219 citation statements)

References 36 publications

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“…Below 0.1 wt-%, the mmmm value became constant at around 37 mol%, indicating that the interaction between TiCl 3 molecules disappears and each molecule becomes isolated. Above 0.1 wt-%, the mmmm value monotonously increased from 37 to 50 mol%, which corresponds to the formation of TiCl 3 multinuclear species [8,9]. The other properties, such as the polymerization activity and MWD, follow the same dependences on the Ti content.…”

Section: Introductionmentioning

confidence: 85%

Precise Active Site Analysis for TiCl3/MgCl2 Ziegler-Natta Model Catalyst Based on Fractionation and Statistical Methods

Takahashi¹,

Wada²,

Taniike³

et al. 2013

Catalysts

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Abstract:In heterogeneous Ziegler-Natta catalysts for olefin polymerization, isolation of a single type of active sites is a kind of ambition, which would solve long-standing questions on the relationship between active site and polymer structures. In this paper, polypropylene produced by TiCl 3 /MgCl 2 model catalysts with minimum Ti heterogeneity was analyzed by combined solvent fractionation and the two-site statistical model. We found that the active sites of the model catalysts were classified into only three types, whose proportions were dependent on the Ti dispersion state. The addition of external donors not only newly formed highly isospecific sites, but also altered the stereochemical nature of the other active sites.

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Section: Introductionmentioning

confidence: 85%

Precise Active Site Analysis for TiCl3/MgCl2 Ziegler-Natta Model Catalyst Based on Fractionation and Statistical Methods

Takahashi¹,

Wada²,

Taniike³

et al. 2013

Catalysts

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“…2 [33 -35]. As reported [13,33], Ti-species a, b could produce PPs with low isotacticity, while c, d with high isotacticity. The polymers synthesized by the equilibriums between a and c (or b and d) were of stereoblock structures.…”

Section: Possible Structures Of Catalytic Active Centersmentioning

confidence: 81%

Study on the microstructures of polypropylene synthesized by a novel MgCl2-supported and low Ti-loading Ziegler–Natta catalyst

Zhao

Wang

et al. 2007

Designed Monomers and Polymers

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Abstract-A novel MgCl 2 -supported and low Ti-loading Ziegler-Natta (Z-N) catalyst was prepared by one-pot ball milling. Polypropylenes (PPs) with special microstructures were synthesized by using this catalyst. Complex gel-permeation chromatography (GPC) data of the resultant PPs were analyzed by fitting the molecular weight distribution (MWD) curves with multiple Flory-Schulz functions. 13 C-NMR spectra of the PPs were also analyzed. A multi-site active center model and the probable structures of the active centers were proposed. Simulation of the pentad intensities of the PPs showed that the modeling results could satisfactorily account for the experimental data, which indicated that the multi-site active center model was plausible and reasonable.

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“…It is clear that adding external donor lead to improvement in isotacticity of all the PP chains in the n-heptane-insoluble fraction. This kind of donor effect can be 6 explained by a mechanistic model proposed by Busico V. et al [14]. In this model, the silane coordinates at catalyst surface in vicinity to the active site and increase its isospecificity.…”

Section: Tabmentioning

confidence: 99%

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

Lou

et al. 2011

E-Polymers

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Abstract:In this work, the effects of two silane type external donors, Ph 2 Si(OCH 3 ) 2 (DPDMS) and dicyclopentyldimethoxysilane (DCPDMS) on propylene slurry polymerization in the presence of hydrogen with a MgCl 2 /TiCl 4 /DIBP -Al(C 2 H 5 ) 3 catalyst system were investigated, and the tacticity distribution and molecular weight distribution (MWD) of polypropylene (PP) were further regulated by using silane/ether (ROCH 3 , R = n-Bu, i-C 8 H 17 ) 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 MgCl 2 /TiCl 4 /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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High-Resolution¹³C NMR Configurational Analysis of Polypropylene Made with MgCl₂-Supported Ziegler−Natta Catalysts. 1. The “Model” System MgCl₂/TiCl₄−2,6-Dimethylpyridine/Al(C₂H₅)₃

Cited by 204 publications

References 36 publications

Precise Active Site Analysis for TiCl3/MgCl2 Ziegler-Natta Model Catalyst Based on Fractionation and Statistical Methods

Precise Active Site Analysis for TiCl3/MgCl2 Ziegler-Natta Model Catalyst Based on Fractionation and Statistical Methods

Study on the microstructures of polypropylene synthesized by a novel MgCl2-supported and low Ti-loading Ziegler–Natta catalyst

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

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