The effect of temperature on the polymerization of propene with dimethylsilylbis(1-indenyl)zirconium dichloride/methylaluminoxane and dimethylsilylbis(2-methyl-1-indenyl)zirconium dichloride/methylaluminoxane. Modeling of kinetics

Wester, Thale Sofie; Johnsen, Heidi; Kittilsen, Pål; Rytter, Erling

doi:10.1002/(sici)1521-3935(19980901)199:9<1989::aid-macp1989>3.0.co;2-5

Cited by 48 publications

(8 citation statements)

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“…[24] Consequently, there is no evidence for different pathways of propagation, or termination, prevailing at different monomer conversions under the reaction conditions chosen in this study, as assumed by Britovsek et al in the case of iron-catalyzed ethylene polymerization. [18] Reaction Order in Catalyst Concentration [25] The reaction order of the polymerization reaction with respect to the zirconocene, in 1-hexene polymerization with Cp 2 ZrCl 2 /MAO, is investigated by determination of the polymer yield after a fixed polymerization time, at varying catalyst concentrations. Two different polymerization times t p = 120 h and t p = 48 h ( Figure 6) are chosen in order to extend the investigation to lower/higher zirconocene concentration at comparably moderate monomer conversion.…”

Section: Monomer Conversion Molecular Weight and Mwdsupporting

confidence: 53%

Deviation from Single-Site Behavior in Zirconocene/MAO Catalyst Systems, 1. Influence of Monomer, Catalyst, and Cocatalyst Concentration

Frauenrath¹,

Keul²,

Höcker³

2001

Macromol. Chem. Phys.

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The polymerization of 1‐hexene with the catalyst systems Cp2ZrCl2/MAO and Me2SiInd2ZrCl2/MAO is investigated in order to elucidate the nature of the active species in zirconocene/MAO catalyzed polymerizations. Varying monomer concentration and monomer conversion does not result in any unexpected behavior. However, changing catalyst and cocatalyst concentration leads to broadened, or even bimodal, molecular weight distributions under certain reaction conditions. These results may be interpreted in terms of a coexistence of two active species with different rates of propagation and of termination.

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Section: Monomer Conversion Molecular Weight and Mwdsupporting

confidence: 53%

Deviation from Single-Site Behavior in Zirconocene/MAO Catalyst Systems, 1. Influence of Monomer, Catalyst, and Cocatalyst Concentration

Frauenrath¹,

Keul²,

Höcker³

2001

Macromol. Chem. Phys.

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“…The first article by Kaminsky et al on propylene polymerization with the bridged metallocene complex C 2 H 4 (Ind) 2 ZrCl 2 showed that as the temperature increases the IR isotacticity of the polymer noticeably decreases. [31] More recently, Rytter et al [32] studied propylene polymerization with the Me 2 Si(Ind) 2 ZrCl 2 -MAO system at a high [Al]:[Zr] ratio of 5 000, a prerequisite for single-center catalysis. [2] This catalyst produces predominantly isotactic polymers but, as the temperature increases from 40 to 90 8C (the same range as in our experiments), the [mmmm] value progressively decreases from 92 to 49%.…”

Section: Discussionmentioning

confidence: 99%

“…This trend is paralleled by a drastic decrease of the melting point of the polymers, from 142.5 to 83.0 8C. Similar temperature effects on NMR isotacticity and melting points were observed in the case of Me 2 Si(2-Me-Ind) 2 ZrCl 2 , [32] C 2 H 3 Ph(9-Flu) 2 ZrCl 2 , [33] Me 2 Si(2-Me-Benz[e]Ind) 2 -ZrCl 2 , [34] and other bridged metallocene complexes. [35] The degree of stereo-control in the case of syndiospecific Ph 2 C(Cp)(9-Flu)ZrCl 2 -based catalysts also noticeably deteriorates with temperature.…”

Section: Discussionmentioning

confidence: 99%

Propylene Polymerization with Titanium‐Based Ziegler‐Natta Catalysts: Effects of Temperature and Modifiers on Molecular Weight, Molecular Weight Distribution and Stereospecificity

Kissin

Ohnishi

Konakazawa

2004

Macro Chemistry & Physics

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Summary: The article discusses two subjects: (a) temperature effects on the molecular weight, molecular weight distribution and stereoregularity of crystalline fractions of propylene polymers prepared with a supported TiCl4/dibutyl phthalate/MgCl2 – Al(i‐Bu)3 catalyst system, and (b) effects of different modifiers (components of cocatalyst mixtures that either greatly increase or decrease the content of the crystalline material) on the structures of the crystalline and the amorphous fraction. The principal approach of the research is the combination of GPC data for a series of polypropylene samples prepared under different conditions, the data on the distributional stereoregularity of the polymers (from analytical temperature‐rising elution fractionation (Tref) and DSC), and the 13C NMR analysis in order to produce a coherent picture of functioning of active centers. The combination of the experimental results shows that the crystalline fractions of polypropylene are produced by several families of active centers. The centers significantly differ in the average molecular weights of the polymer components they produce and in stereospecificity. The steric control exerted by the active centers of the highest isospecificity slightly decreases with temperature. In contrast, average isotacticity parameters of the crystalline fractions (estimated by NMR) increase with temperature. The latter effect is mainly the outcome of the variation in the relative contents of polymer components of low isotacticity in the crystalline fractions prepared at different temperatures. When a silane is used as a part of a cocatalyst, it not only poisons aspecific centers but poisons the centers of reduced isospecificity as well. This effect results in the increase of the average molecular weight of the crystalline fraction, narrowing of its molecular weight distribution and the increase of its average isotacticity.Resolution of GPC curves of crystalline fractions into Flory components at 50 °C.imageResolution of GPC curves of crystalline fractions into Flory components at 50 °C.

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“…It is particularly advantageous to conduct the polymerization process at temperatures high enough to prevent precipitation of the polymer formed, with a low concentration of monomer and short catalyst residence times . However, both the molecular weight and stereoselectivity of a catalyst drop with an increase in the polymerization temperature. , In addition to that, the activity increases with the temperature until the catalyst begins to degrade; as a result, in the activity vs temperature profile a maximum at 60–90 °C is usually observed ,, for “common” ansa -metallocenes. The described set of requirements and peculiarities of the polymerization behavior makes the development of a single-site catalyst for production of highly isotactic and high-molecular-weight PP in a solution process extremely challenging, though it is still desirable…”

Section: Introductionmentioning

confidence: 99%

ansa-Metallocenes Bearing 4-(N-Azolyl)-2-methylindenyl and Related Ligands: Development of Highly Isoselective Catalysts for Propene Polymerization at Higher Temperatures

et al. 2019

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A series of Me 2 Si-bridged bis(2-Me-indenyl) ansa-zirconocenes containing N-pyrrolyl, N-indolyl, N-carbazolyl, and P-dibenzophospholyl substituents in position 4 of the indenyl moieties has been synthesized. Pd-catalyzed arylation of the azoles with 4-Br-2-Me-indene was used to synthesize the respective 4-(N-azolyl)indenes. 4-(P-Dibenzophospholyl)indene was obtained in high yield by reaction of 5-Cl-dibenzophosphole with (2-Me-inden-4-yl)MgBr. Some of the synthesized zirconocenes were characterized by X-ray crystallography. The raczirconocenes were tested in propylene polymerization in the presence of MAO or perfluoroarylborate activators. At 100 °C, the zirconocene rac-Me 2 Si[2-Me-4-(N-carbazolyl)indenyl] 2 ZrCl 2 /MAO afforded highly crystalline isotactic polypropylene with reasonable molecular weight (318 kDa) and a T m value of 157 °C determined by a remarkably low total number of stereo-and regioerrors, which makes it one of the most isoselective catalysts for high-temperature propylene polymerization.

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The effect of temperature on the polymerization of propene with dimethylsilylbis(1-indenyl)zirconium dichloride/methylaluminoxane and dimethylsilylbis(2-methyl-1-indenyl)zirconium dichloride/methylaluminoxane. Modeling of kinetics

Cited by 48 publications

References 0 publications

Deviation from Single-Site Behavior in Zirconocene/MAO Catalyst Systems, 1. Influence of Monomer, Catalyst, and Cocatalyst Concentration

Deviation from Single-Site Behavior in Zirconocene/MAO Catalyst Systems, 1. Influence of Monomer, Catalyst, and Cocatalyst Concentration

Propylene Polymerization with Titanium‐Based Ziegler‐Natta Catalysts: Effects of Temperature and Modifiers on Molecular Weight, Molecular Weight Distribution and Stereospecificity

ansa-Metallocenes Bearing 4-(N-Azolyl)-2-methylindenyl and Related Ligands: Development of Highly Isoselective Catalysts for Propene Polymerization at Higher Temperatures

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