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  • 1
    Electronic Resource
    Electronic Resource
    Magnesium chloride supported catalysts for olefin polymerization. XIX. Titanium oxidation states, catalyst deactivation, and active site structure (1989)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 27 (1989), S. 1499-1514 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A precise method for the determinations of Ti+2, Ti+3 and Ti+4 was developed. The CW-procatalyst before activation contains mostly Ti+4 ions with 6% Ti+3 and 4% Ti+2 ions. Activation with AlEt3 alone at room temperature reduced all the titaniums to lower valence states consisting of 71% Ti+3 and 29% Ti+2. Reduction is incomplete when methyl-p-toluate was present as external Lewis base during activation: at 25°C the distribution of Ti+4 : Ti+3 : Ti+2 is 36% : 25% : 38%; the distribution at 50°C is 37% : 22% : 40%. Aging of the activated catalyst caused little or no changes in the distribution of [Ti+n]; whereas the catalytic activity decays rapidly with aging. The aged catalysts have polymerization activity comparable to the decreased activity of the catalyst during a polymerization. The [Ti+n] was determined for the CW-catalyst during the course of a decene polymerization; they were found to be Ti+4 : Ti+3 : Ti+2 = 30% : 27% : 43%, which did not change with polymerization time. These results suggest that the reducibility of Ti+4 species by AlEt3 or 3AlEt3/MPT to different valence states is predicated by their structures. These species do not undergo further changes in their oxidation states during either aging or polymerization. Their decays probably involve nonreductive metathesis reactions like those known for zirconium alkyls. Possible structures for the stereospecific and nonspecific sites are proposed.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1989.080270504
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  • 2
    Electronic Resource
    Electronic Resource
    Superactive and stereospecific catalysts. III. Definitive identification of active sites by electron paramagnetic resonance (1989)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 27 (1989), S. 897-913 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Superactive Ziegler-Natta catalysts have been prepared from a soluble MgCl2·2-ethyl hexanol adduct in the presence of organic esters through reactions with TiCl4 and activated with AlEt3/phenyltriethoxy-silane. Electron paramagnetic spectra (EPR) were used to elucidate the nature and amount of those Ti+3 ions not bridged to another Ti+3 ion; the chlorine bridged Ti+3 ions are EPR silent. The EPR spectra were attributed to two rhombic Ti+3 sites with principal values for the g-tensors (1.967, 1.949, 1.915; and 1.979, 1.935, 1.887). The total amount of the EPR species, obtained by double integration of the EPR spectra, is in close agreement with the concentration of isospecific catalytic sites determined by radiotagging. This suggests that the nonspecific sites are EPR silent. When o-phthalic ester was present during the catalyst synthesis, there appears an EPR signal at the free electron g-value. This signal was attributed to a Ti+3 phthalate species with resonance stabilization and spin delocalization; it is absent in the catalysts made in the presence of monoesters such as ethyl benzoate. The effects of monomer, O2, H2O, and I2 on the EPR spectra were investigated. The changes in the EPR spectral intensity and the total Ti+3 ions, the latter determined by redox titrations during a polymerization or catalyst aging, are described. The results were extensively compared with those observed for supported Ziegler-Natta catalyst prepared with crystalline MgCl2.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1989.080270315
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  • 3
    Electronic Resource
    Electronic Resource
    Magnesium chloride supported high-mileage catalysts for olefin polymerization. XVII. Effect of lewis base on propylene polymerization (1987)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 25 (1987), S. 2847-2870 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A systematic study has been made on the functions of external Lewis base (Be, methyl-p-toluate, MPT) and internal Lewis base (Bi, ethyl benzoate, EB) for the CW-catalyst system MgCI2/EB/PC/AlEt3/TiCl4-AlEt3/MPT (PC, p-cresol). Bi is a nonstereoselective modifier. It increases the active site concentrations and rate constants of propagation, kp, of both the isospecific and nonspecific sites, and thus the productivities of the stereoregular and irregular polypropylenes by five- to tenfold. It seems that Bi complexes with the MgCl2 support to lower the electronegativity of the surface Mg atoms. It also acts to lower the rate constant of chain transfer to aluminum alkyl, kAtr, by two- to fourfold. The action of Be is highly stereospecific. The isotacticity index of polypropylene is ≫ 95% in the presence of Be but ≪ 68% without it. Addition of Be decreases nonspecific [Ti*]a by about (11 ± 2)-fold; there is only about a twofold reduction of the isospecific [Ti*]i. It decreases kp,a about three times but has no effect on kp,i, so that the latter is (21 ± 4) times the former. Be decreases kAtr,i for transfer with aluminum alkyl much more than it does to kAtr,a; but it does not affect the rates of chain transfer with monomer and by β-hydride elimination or the rate of catalyst deactivation. The number of active sites without Be is [Ti*]i = 15% and [Ti*]a = 55% for a total of 70%. In the presence of Be they are both about 6%. Optimum performance in propylene polymerizations requires both Bi and Be in the case of the CW-catalyst.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1987.080251020
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  • 4
    Electronic Resource
    Electronic Resource
    Magnesium chloride supported high-mileage catalysts for olefin polymerizations. XVIII. Effect of hydrogen and lewis bases (1987)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 25 (1987), S. 2881-2892 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Hydrogen has been found earlier to increase the initial rate of polymerization by MgCl2/EB/PC/AlEt3/TiCl4-AlEt3/MPT, CW-catalyst (+Bi, +Be) (EB, ethyl benzoate; PC, p-cresol; MPT, methyl-p-toluate), but decays more rapidly as compared to polymerizations in the absence of H2. In this study the effect of H2 was studied when either the internal Lewis base, EB Bi, or the external Lewis base, MPT Be, or both are deleted from the CW-catalyst. H2 does not affect the stereospecificity of all the catalysts, but causes a slight increase of polymer yield, whereas the yield is virtually unchanged by H2 for the catalysts activated with Be. Unlike the catalyst (+Bi, +Be) where H2 increases active site concentrations [Ti*] about threefold, it affects [Ti*] negligibly when Be is absent. The rate constants of propagation is about the same with or without H2 for the CW-catalyst (+Bi, -Be) or (-Bi, -Be); the same statement can be said about the rate constant of chain transfer with AlEt3 or with H2. Hydrogen increases the rate of catalyst site deactivation for the various catalysts in the order of(+Bi, +Be) 〉 (-Bi, -Be) 〉 (+Bi, -Be).
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1987.080251022
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  • 5
    Electronic Resource
    Electronic Resource
    Superactive and stereospecific catalysts. I. Structures and productivity (1988)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 26 (1988), S. 2003-2018 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Two series of catalysts were made, one from MgCl2-A solution containing MgCl2, EH (2-ethylhexanol), and EB (ethyl benzoate) dissolved in decane and another from MgCl2-B solution containing MgCl2, EH, and phthalic anhydride which reacted to form the corresponding phthalic ester. Reactions of these solutions with TiCl4 with or without another ester produced a family of eight catalysts. They form two groups, one having monoesters as modifiers, and the other containing diesters as modifiers. The surface area, pore volume, x-diffractions, polymerization activity, and catalytic stereospecificity of these catalysts have been compared. The diester catalysts differ from the monoester catalysts in every respect. By comparison the corresponding member of the diester catalysts have half as much Ti per Mg, more than 10 times the pore volume, more than a 100-fold the surface area, about 50% more productivity, and greatly increased steroespecificity.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1988.080260802
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  • 6
    Electronic Resource
    Electronic Resource
    Superactive and stereospecific catalysts. II. Kinetics of propylene polymerizations (1988)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 26 (1988), S. 2973-2989 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The kinetics of propylene polymerization by superactive CH-catalyst prepared from toluene solution of MgCl2 · EH/PA/TiCl4-TEA/PES was investigated. The results are compared with CW-catalyst prepared from crystalline MgCl2/EB/PC/TEA/TiCl4-TEA/MPT (abbreviations given in the text). The former is four times more active than the latter and produces more isotactic polypropylene. The CH-catalyst has 25% of the Ti as isospecific sites as compared to 6.7% for the CW-catalysts. These sites have the same rate constant of propagation so that the higher polymerization activity of the CH-catalyst is attributable simply to a greater number of active sites. Differences in the kinetics of deactivation and of chain transfer for the two catalysts are described.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1988.080261109
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  • 7
    Electronic Resource
    Electronic Resource
    Superactive and stereospecific catalysts. IV. Influence of structure of esters on MgCl2 supported olefin polymerization catalystsPart III of this series: J. C. W. Chien and Y. Hu, J. Polym. Sci. Polym. Chem. Ed., in press. (1990)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 28 (1990), S. 273-284 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: CH-type catalysts were prepared by reacting MgCl2 · ROH, where ROH is 2-ethyl hexanol (EH), (R)-2-octanol (R-20), and (S)-2-octanol (S-20), with TiCl4 in the presence of di-i-butyl phthalate (BP), di-i-butyl terephthalate (BT), (-)-dimenthyl phthalate (MP), or (-)-dimenthyl terephthalate (MT). The MT catalysts were found to incorporate 8.9 to 13% Ti whereas the BP catalysts contain only 1.9 to 2.6% Ti. Comparison of the CH(EH, BP) and CH(EH, MT) catalysts showed that they have about equal number of isospecific active sites per gram of catalyst and the same rate constants of propagation for their nonspecific sites, however, the isospecific sites in the latter are less active by comparison. Consequently, the CH(EH, BP) catalysts is five times more active than the CH(EH, MT) catalysts and produces polypropylene which is 97% isotactic (reflux n-heptane insoluble) as compared to 84.7% for the latter. The catalysts derived from 2-octanols are much less active than the corresponding catalysts prepared with 2-ethyl hexanol due to lack of reactivity with phthalic anhydride which permits excessive incorporation of TiCl4 to form nonstereospecific catalytic sites as well as inactive Ti species.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1990.080280204
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  • 8
    Electronic Resource
    Electronic Resource
    Terpolymerization of propene, ethylene and 1-dodecene with highly efficient supported catalyst (1995)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 196 (1995), S. 3369-3378 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The terpolymerization of propene, ethylene and 1-dodecene (PED) with a highly efficient supported Ziegler-Natta catalyst and the main physical and mechanical properties of PED terpolymers were investigated. It was found that, under equal polymerization conditions, the polymerization activities followed the order: PED terpolymerization 〉 PE, PD copolymerizations 〉 E, D homopolymerizations. The 13C NMR spectra of PED terpolymers indicated the existence of long propylene chain sequences. The content of ethylene and 1-dodecene in PED terpolymers increased with the enhancement of the mole ratio of ethylene in the gas feed, whereas the effect of the concentration of 1-dodecene in the reactor is much smaller. The intrinsic viscosity, density, melting temperature and crystallinity of the terpolymers decrease when the amount of comonomers in the feed increases. Compared with polypropene, the tensile and bending strenghts of PED terpolymers are reduced, but the elongation at break is over 700%, and the Izod impact is enhanced both at ambient and low temperatures.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1995.021961023
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