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  • 1
    Electronic Resource
    Electronic Resource
    Propylene polymerization in a semibatch slurry reactor over supported TiCl4/MgCl2/ethyl benzoate/triethyl aluminum catalyst. I. Catalytic behavior (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 37 (1989), S. 1605-1623 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: High activity TiCl4/MgCl2/ethyl benzoate (EB)/triethyl aluminum (TEA) catalysts for the polymerization of propylene were synthesized and characterized for particle size distribution and crystallinity. Polymerization was carried out in a semibatch, constant pressure slurry reactor. A correction for interfacial mass transfer was found to be necessary to relate the monomer feed rate to the instantaneous rate of polymerization. Without such a correction serious misinterpretation of rate data could result. Optimum productivity was observed with respect to the Al/Ti ratio. Similar behavior was observed with polymerization temperature. Isotacticity increased with polymerization tamperature and decreased with Al/Ti ratio. The addition of a small amount of 2,2,6,6-tetramethylpiperidine increased the percentage of isotactic polypropylene to 98% without significantly affecting productivity.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1989.070370615
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  • 2
    Electronic Resource
    Electronic Resource
    Propylene polymerization in a semibatch slurry reactor over supported TiCl4/MgCl2/ethyl benzoate/triethyl aluminum catalyst. II. A kinetic study based on a multisite model (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 37 (1989), S. 1625-1644 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: In propylene polymerization over TiCl4/MgCl2/ethyl benzoate (EB)/triethyl aluminum (TEA) catalysts, experimental evidence strongly suggests that active sites have differing propagation and termination rate constants. Although the chemical structure of these sites may be quite similar, their location on the support may affect their polymerization activity, and this results in a distribution of the propagation and deactivation rate constants. To model this type of system, we developed a kinetic model accounting for multiple active sites. The model was fitted to simulated polymerization data to investigate the validity of mathematical approximations used in the derivation of the model equation. Using experimental data, the adequacy of the model was tested, and the statistical inference of parameter estimation was also discussed. The effects of experimental operating variables and additives on the kinetic model parameters revealed an important insight into the fundamentals of this system. The optimum productivity commonly observed has been shown to be the result of differing rates of increase of both propagation and termination rates with Al/Ti ratio and temperature. Kinetic evidence also suggests that the additive selectively poisons atactic-specific sites.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1989.070370616
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  • 3
    Electronic Resource
    Electronic Resource
    Preparation and polymerization of racemic and optically active tert-butyl thiiraneDedicated to Professor Dr. CH. SADRON on the occasion of his 70th birthday (1972)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 156 (1972), S. 55-64 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die Darstellung und die Polymerisation von tert-Butyl-äthylensulfid werden beschrieben. Das racemische Monomere wurde durch Umsetzung von tert-Butyl-äthylenoxid mit Kaliumrhodanid in wäßriger Lösung erhalten. Das linksdrehende Enantiomere wurde aus R(-)-3.3-Dimethyl-butandiol-(1.2) über das cyclische Carbonat als Zwischenprodukt synthetisiert. Die Polymerisation des racemischen Monomeren mit Koordinationskatalysatoren ergibt kristalline, lösliche Produkte hohen Molekulargewichts und von hohem Schmelzpunkt (nahe bei 205°C). Kristalline, lösliche Polymere mit hohem Molekulargewicht, jedoch mit tieferen Schmelzpunkten (nahe bei 160°C) konnten auch mit dem linksdrehenden Enantiomeren entweder durch koordinierte oder durch anionische Initiierung erhalten werden. Diese Polymeren besitzen hohe optische Drehungszahlen, welche in allen verwendeten Lösungsmitteln positives Vorzeichen besitzen. NMR-Messungen zeigen, daß racemische und optisch aktive kristalline Polymere die gleiche isotaktische Struktur haben. Wie die Röntgendiagramme zeigen, sind die Unterschiede in den Schmelzpunkten auf die Existenz verschiedener kristalliner Modifikationen zurückzuführen. Diese Resultate zeigen einen starken Unterschied zu den bei der Polymerisation von Methyläthylensulfid gewonnenen Ergebnissen.
    Notes: Preparation and polymerization of tert-butyl thiirane are described. The racemic monomer was obtained by reaction in aqueous solution of tert-butyl oxirane and potassium thiocyanate. The levorotatory enantiomer was synthesized from R(-) 3.3-dimethyl 1.2-butane diol passing through the intermediate of the cyclic carbonate. Polymerization of the racemic monomer with coordinate type initiators give crystalline, soluble products of high molecular weights and high melting points (close to 205°C). Crystalline, soluble, high molecular weight polymers but of lower melting points (close to 160°C) could also be obtained with the levorotatory enantiomer, either by coordiante or purely anionic initiation. These polymers have high optical activities of positive sign in all the solvents used. NMR measurements show that racemic and optically active crystalline polymers have the same isotactic structure. The differences in melting point and X-ray diagrams show the existence of several crystalline modifications. These results indicate a strong difference in the behaviour of tert-butyl thiirane as compared to methyl thiirane.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1972.021560106
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  • 4
    Electronic Resource
    Electronic Resource
    Polymérisation et copolymérisation du sulfure de propylène amorcées par des systèmes dérivés du triéthylaluminiumDédié à Monsieur le Professeur CH. SADRON à l'occasion de son 70e anniversaire (1972)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 156 (1972), S. 65-79 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Bei der Polymerisation von Propylensulfid mit dem binären Initiatorsystem Al(C2H5)3/H2O entstehen normalerweise amorphe Produkte von niedrigem Molekulargewicht. Unter speziellen Bedingungen ist es jedoch möglich, ein hochschmelzendes cyclisches Tetrameres zu erhalten. Es wird angenommen, daß dieses durch einen kationischen Mechanismus gebildet wird. Dafür spricht die Tatsache, daß ein Zusatz von Tetrahydrothiophen die Bildung des Tetrameren vollkommen unterdrückt.Ternäre Initiatorsysteme vom Typ Al(C2H5)3/H2O/ROH führen zu hochmolekularen, kristallinen Polymeren, wie sie ähnlich schon früher mit Zn(C2H5)2/H2O erhalten wurden.Copolymerisationsversuche von Propylensulfid und Isobutylensulfid mit den Systemen Al(C2H5)3/H2O (1 : 1) oder BF3/(C2H5)2O zeigten, daß das Propylensulfid das reaktivere Monomere ist.
    Notes: La polymérisation du sulfure de propylène amorcée par les systèmes binaires AIEt3/H2O conduit principalement à la formation de polymères amorphes de bas poids moléculaires. Dans certaines conditions, on peut obtenir également une petite fraction d'un tétramère cyclique cristallin de haut point de fusion. L'addition de tétrahydrothiophène au système AIEt3/H2O inhibe la formation du tétramère cyclique, pour laquelle l'intervention d'un mécanisme cationique a été proposé. Les amorceurs ternaires AIEt3/H2O/ROH permettent par contre d'obtenir des polymères de hauts poids moléculaires partiellement cristallins, analogues à ceux obtenus par amorçage avec le système ZnEt2/H2O.Dans les copolymérisations du sulfure de propylène et du sulfure d'isobutène amorcées par les systèmes AIEt3/H2O (1:1) et BF3/Et2O, le sulfure de propylène est le monomère le plus réactif.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1972.021560107
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  • 5
    Electronic Resource
    Electronic Resource
    Temperature effect on the stereoelective polymerization of methylthiirane in homogeneous phase (1981)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 182 (1981), S. 2225-2231 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Chiral cadmium thiolates of cysteine with cyclohexyl or (-)menthyl ester groups were prepared and compared with similar compounds (with isopropyl or methyl ester groups) as initiators for stereospecific polymerization of methylthiirane in homogeneous phase. The resulting polymers are highly isotactic and in all cases stereoelection can be reversed with a small change in polymerization temperature. This temperature effect permitted to differentiate two stages in the polymerization corresponding to the formation of a precursor and to that of a high polymer, respectively.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1981.021820812
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  • 6
    Electronic Resource
    Electronic Resource
    Stereospecific polymerization of methylthiirane in homogeneous phase, 2.Part 1: cf. ref.3. Mechanism of stereoregulation (1992)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 193 (1992), S. 1709-1721 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: In the living polymerization of methylthiirane initiated with bis(isopropyl-(S)-cysteinato)-cadmium, stereospecificity depends on temperature of propagation, on initiator concentration and also on the length of the growing polymer chain. The kinetics of stereospecific and non-stereospecific processes are described. In both cases, the order with respect to monomer is equal to zero and that with respect to initiator is one-half. The stereospecific propagation is proposed to involve cadmium thiolates associated as “dimeric species” and coordinated by both the monomer and by an oligomeric or polymeric chain.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1992.021930714
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  • 7
    Electronic Resource
    Electronic Resource
    Stereospecific polymerization of methylthiirane in homogeneous phase, 4. Solvent effect on stereospecificity and enantioasymmetry (1993)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 194 (1993), S. 1015-1025 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The living stereospecific polymerization of methylthiirane initiated by a chiral cadmium compound was run in different solvents. The general features of the mechanism of stereoregulation are the same as in bulk. In heptane and in heptane/propylene carbonate mixtures, the stereospecificity of the reaction does not depend on monomer concentration and on the dielectric constant ε of the medium. This independence of stereospecificity is in agreement with the absence of a variation of the complexation constant between a model cadmium derivative and the monomer with the variation of ε in a large range. The enantioasymmetric process depends on the molecular weight of the chain bearing the active sites. A change from diastereoisomeric to enantiomeric forms of active sites occurs for molecular weights around 50000. The enantioasymmetric constant depends on the nature of the medium and we observed a Born law for the dependence of the enantioasymmetric constant versus reciprocal dielectric constant: log kR ∝ 1/ε. This effect can be explained by a variation of the reactivities of the two types of active sites and occurs without a change in their relative amounts.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1993.021940324
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  • 8
    Electronic Resource
    Electronic Resource
    Stereospecific polymerization of methylthiirane in homogeneous phase, 3.Part 2: cf. ref. 6 Study of the enantioasymmetric process (1993)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 194 (1993), S. 1003-1014 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Enantioasymmetry was studied for polymerizations of methylthiirane initiated by bis(isopropyl-S-cysteinato)cadmium and run in bulk. The ratio of rates of consumption of the two antipodes is independent of their concentrations. The enantioasymmetric constant kR, measuring the preferential choice of the R-antipode, is depending on both the relative number of the two types of active sites and on their reactivities. An effect on enantioasymmetry of the molecular weight of the growing chains bearing the active sites, is occurring with two distinct stages: The first one is observed, with an enantioasymmetric constant kR = 1,5, from the appearance of stereospecificity up to molecular weights of 35000 (for the main chain) and the second one with kR = 1,07 for molecular weights higher than 35000. In the first stage, the cysteinato end group of the oligomer chain remains linked to cadmium (by cadmium-nitrogen complexation) and the two active sites are diastereoisomers having different reactivities. In the second stage, the macrocyclic oligomer becomes too large and cadmium-nitrogen interaction is suppressed. The active sites are now enantiomers having the same reactivity. In this case, enantioasymmetry depends only on the unbalance between the amounts of the two types of active sites. The maximum size the macrocyclic oligomer can reach depends on the initiator concentration.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1993.021940323
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  • 9
    Electronic Resource
    Electronic Resource
    Stereospecific polymerization of methylthiirane in homogeneous phase, 1. Oligomerization step and change in stereocontrol with molecular weight (1984)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 185 (1984), S. 1317-1326 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The polymerization of methylthiirane in homogeneous phase initiated by bis(isopropylcysteinato)cadmium is a living process. For low conversions, oligomers (essentially heptamers and octamers) are formed, apparently using one valency of cadmium, the main propagation taking place by using the other one. However, the size of the oligomers may still grow for higher conversions. The mechanism of the oligomer formation depends on the temperature. A “normal” insertion of the monomer is observed at -23°C, whereas at 20°C a disulfide bond is formed. The preferential choice of a different enantiomer in the main propagation reaction may depend on the presence of a particular type of oligomer, in the vicinity of cadmium, linked to the cysteine group. However, stereospecificity (stereoselection and stereoelection) appears only with molecular weights higher than 6000 and also depends on the temperature of propagation: with decreasing temperature, the stereoregularity increases and the stereoelection can be inverted (for a definite oligomer structure).
    Additional Material: 5 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1984.021850705
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  • 10
    Electronic Resource
    Electronic Resource
    Role of cocatalysts in polymerizations initiated with benzyl derivatives of transition metals, 1. Polymerization of ethylene (1983)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 184 (1983), S. 1389-1395 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Polymerization of ethylene initiated in naphta solution by Zr(CH2C6H5)4 at 200°C under high purity conditions showed a cocatalytic effect of water with a maximum rate for a mole ratio H2O/Zr close to 0,1. No activity was observed for the hypothetical compound (C6H5CH2)3ZrOZr(CH2C6H5)3. Ethylene polymerization was also initiated with supported catalysts obtained by reaction of Zr(CH2C6H5)4 with silicium oxide or pre-dried aluminium oxide with an increase of activity (by a factor of 5). The resulting polyethylenes were found to be virtually linear with 1,5 CH3 groups for 1000 C atoms and with melting points of 134 - 136,5°C. They have high molecular weights with very broad distribution. These results were interpreted by a mechanism involving Ziegler-like active centers.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1983.021840707
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