Synthesis of polypropylene using bis(2-alkylindenyl)zirconium dichloride/MAO systems

Yoon, Jin‐San; Lee, Yoo-Su; Park, Eun-Soo; Lee, Ik-Mo; Park, Duck-Kyung; Jung, Sung‐Ouk

doi:10.1016/s0014-3057(99)00165-2

Cited by 11 publications

(5 citation statements)

References 18 publications

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“…Polypropylene elastomers were first reported by Natta, who was the first to propose that the elastomeric properties of these materials were a consequence of a stereoblock structure consisting of alternating runs of crystalline isotactic and amorphous atactic diastereosequences. − After Natta's work, there have been a number of efforts to improve the selectivity of catalyst systems for the production of elastomeric polypropylenes with notable advances by Collette and co-workers at Dupont 11-16 and Job at Shell . More recently, several classes of metallocene catalysts have been developed for the production of elastomeric polypropylenes, − notably those developed by Chien, − Collins, − Rieger, , Pellon, and our group. ,− As for the polyethylene-derived polyolefin elastomers, − potential advantages of metallocene catalysts are the ability to tailor the structures and properties of the propylene elastomers by suitable modifications of the coordination catalyst precursors.…”

Section: Introductionmentioning

confidence: 99%

Heterogeneous Composition and Microstructure of Elastomeric Polypropylene from a Sterically Hindered 2-Arylindenylhafnium Catalyst

et al. 2004

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The metallocene catalyst bis(2-(3,5-di-tert-butylphenyl)indenyl)hafnium dichloride yields elastomeric polypropylene in the presence of a MAO cocatalyst at 50 °C in liquid propylene. The polymer synthesized has M w ) 201 000 and narrow polydispersity (Mw/Mn ) 2.3) with an average isotacticity [mmmm] ) 34%. Several methods of fractionations were carried out to investigate the heterogeneity of the elastomeric polypropylene: thermal fractionation by DSC, boiling-solvent extraction, supercritical fluid fractionation employing increasing pressure profiling (IPP), and critical isobaric temperature rising elution fractionation (CITREF). Thermal fractionation reveals a distribution of crystallizable fractions with several melting points between 40 and 100 °C and a large melting endotherm at 150 °C which is attributed to the presence of long crystallizable segments. Fractionation by boiling-solvent extraction separates the elastomeric polypropylene into three fractions where the molecular weight, tacticity, and crystallinity increase in the following order: ether-soluble < heptane-soluble < heptane-insoluble fractions. Supercritical fluid fractionations by either molecular weight (IPP) or crystallinity (CITREF) show that the tacticities, melting points, and heats of fusion increase gradually with increasing molecular weight.

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Section: Introductionmentioning

confidence: 99%

Heterogeneous Composition and Microstructure of Elastomeric Polypropylene from a Sterically Hindered 2-Arylindenylhafnium Catalyst

et al. 2004

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“…Recent advances in catalyst technology have made available a variety of low-density polypropylenes that exhibit elastomeric properties. The potential commercial applications of elastomeric polypropylenes (ePP) have driven a number of studies in the past few years. − Our group has shown that metallocene catalysts derived from 2-arylindene ligands produced elastomeric polypropylenes. − Polypropylenes produced with this class of catalysts have narrow molecular weight distributions and low levels of crystallinity. Despite its low crystallinity, morphological studies have revealed crystalline structures reminiscent of classical semicrystalline polymers, showing lamellae organizing into hedrites and spherulites .…”

Section: Introductionmentioning

confidence: 99%

Dynamic Response of Stereoblock Elastomeric Polypropylene Studied by Rheooptics and X-ray Scattering. 2. Orthogonally Oriented Crystalline Chains

et al. 2002

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A combination of tensile stress, rheooptical birefringence, and wide-angle X-ray scattering (WAXS) was used to probe the dynamic response of the low-tacticity ether-soluble (ES) fraction of elastomeric polypropylene (ePP) derived from metallocene 2-arylindene hafnium catalyst. The ES fraction has isotactic pentad distribution [mmmm] ) 21% and a very low amount of crystallinity (e2% by differential scanning calorimetry and WAXS). In tensile stretching and step-strain shearing, ES exhibits unusual deformation behavior of crystalline chains preferentially oriented orthogonal relative to the deformation axis. Under deformation, WAXS shows arcing along the meridian axis at a scattering angle 2θ ) 16.0°(d ) 0.551 ( 0.002 nm) which coincides with one of the characteristic reflections of the β-form, but the higher order reflection for the β-form at 2θ ) 21.3°is not observed. The meridional arcing, which signifies crystallization of the low-tacticity fraction of ePP, is also observed when ES is blended with higher-tacticity fractions of ePP. The meridional arcing, however, is observed at 2θ ) 14.0°, corresponding to (110) reflection of the R-form, instead of at 2θ ) 16.0°for the neat ES. The crystallization in the R-form offers evidence of cocrystallization of the ES fraction with the higher-tacticity components in the same crystalline form as the host matrix. We believe that the cocrystallization occurs through an epitaxial growth in the ac-faces of the R-form.

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“…Previous investigations of the mechanism of propylene polymerization by unbridged bis(2-arylindenyl)zirconium dichloride ((2-ArInd) 2 ZrCl 2 ) activated with methylaluminoxane (MAO) have led to the proposal of a kinetic model (Figure ) where the rate of monomer enchainment is competitive with isomerization of the catalyst between two states which exhibit different stereoselectivities. − The differences in catalyst productivity and molecular weight (MW) and the microstructure of the polypropylenes (PPs) formed by (2-ArInd) 2 ZrCl 2 with variations in ligand structure, ,,,, metal, and polymerization conditions 19,22 have been investigated but are difficult to predict in the absence of a more complete kinetic model. An understanding of the kinetic behavior of the parent system bis(2-phenylindenyl)zirconium dichloride ((2-PhInd) 2 ZrCl 2 ) would assist in the interpretation of past work and aid in designing new catalysts.…”

Section: Introductionmentioning

confidence: 99%

Kinetics of Propylene Polymerization Using Bis(2-phenylindenyl)zirconium Dichloride/Methylaluminoxane

et al. 2000

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The kinetics of propylene polymerization in toluene solution by bis(2-phenylindenyl)zirconium dichloride/methylaluminoxane at 20 °C were investigated. As the structure and properties of elastomeric polypropylenes produced by these catalysts depend sensitively on the reaction conditions, a detailed study of the kinetics was carried out to evaluate the influence of these parameters on the polymerization behavior. Studies of the solubilities and mass-transfer rates reveal that dissolved atactic polypropylene has little effect on propylene solubility but influences the mass-transfer rate of propylene into solution. The rates of propylene polymerization reach a maximum after 10−20 min and then decrease. The decrease in rate over time is faster at higher monomer concentrations. Catalyst activity was negligible at [Al]/[Zr] = 1000 but constant from [Al]/[Zr] = 2500 to [Al]/[Zr] = 10 000. Analysis of molecular weights as a function of monomer concentration reveal β-hydride elimination to be the primary chain-transfer mechanism. Narrow molecular weight distributions (M w/M n = 2.0−2.6) were obtained. The increase of the isotactic dyads and pentads ([m] and [mmmm]) with increasing monomer concentration reveals an additional kinetic event which competes with the stereodifferentiating olefin insertion step. Modeling studies are more consistent with a mechanism involving interconversion of the catalyst between isospecific and aspecific states than a mechanism involving epimerization of the stereogenic centers of the growing polymer chain.

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Synthesis of polypropylene using bis(2-alkylindenyl)zirconium dichloride/MAO systems

Cited by 11 publications

References 18 publications

Heterogeneous Composition and Microstructure of Elastomeric Polypropylene from a Sterically Hindered 2-Arylindenylhafnium Catalyst

Heterogeneous Composition and Microstructure of Elastomeric Polypropylene from a Sterically Hindered 2-Arylindenylhafnium Catalyst

Dynamic Response of Stereoblock Elastomeric Polypropylene Studied by Rheooptics and X-ray Scattering. 2. Orthogonally Oriented Crystalline Chains

Kinetics of Propylene Polymerization Using Bis(2-phenylindenyl)zirconium Dichloride/Methylaluminoxane

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