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  • 11
    Electronic Resource
    Electronic Resource
    Kinetics of high conversion polymerization of vinyl acetate. Effects of mixing and reactor type on polymer properties (1982)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 27 (1982), S. 2249-2267 
    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 the present article the kinetics of polymerization of vinyl acetate in suspension up to high conversion was studied. The molecular weight distribution and the side chain branching of polyvinyl acetate produced were examined with respect to micro and macro mixing as well as to reactor type. The following results were achieved: the time-activity curves of the polymerization can be described up to high conversions considering the exponential increase in viscosity of the polymerizing system and combining the viscosity with rate constants of the polymerization. The change of volume of the polymerizing system has no significant influence on kinetics. The narrowest molecular weight distribution of the poly(vinyl acetate) produced was achieved when polymerizing in the homogeneous continuous stirred tank reactor while the broadest molecular weight distribution was observed in the segregated continuous stirred tank reactor. The batch reactor and the flow tube reactor produce polymers with molecular weight distributions lying in between. Considering the side chain branching, another order was found. The batch reactor and the tube reactor show the lowest side chain branching, the homogeneous continuous stirred tank reactor shows a larger one and the segregated continuous stirred tank reactor shows the largest. Possible reasons for the different behavior of the different reactors are discussed. The degree of segregation was determined by experiments.
    Additional Material: 18 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1982.070270634
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  • 12
    Electronic Resource
    Electronic Resource
    The influence of reactor type and operating conditions on the molecular weight distribution in vinyl acetate polymerization (1985)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 30 (1985), S. 227-250 
    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: The vinyl acetate polymerization system was investigated with respect to the breadth of the molecular weight distribution (MWD) in batch, continuous segregated, and continuous micromixed reactors. Models were developed employing a complex kinetic scheme including polymer transfer and terminal double bond polymerization, without neglecting initiation and termination steps. Inclusion of a gel effect for terminal double bond polymerization gave better agreement with experimental molecular weight data in suspension polymerization. Simulation results showed the MWD order in the three reactor types is not fixed, but a function of reactant concentrations and the importance of chain branching. In some cases changing the initiator type and concentration will change the MWD order.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1985.070300119
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  • 13
    Electronic Resource
    Electronic Resource
    Zur Bildung und Konzentration der aktiven Spezies löslicher Ziegler-Natta-Katalysatoren (1970)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 12 (1970), S. 175-183 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: The rate of polymerisation of ethylene by the soluble ZIEGLER-NATTA-catalyst (C5H5)2Ti(C2H5)Cl/Al(C2H5)Cl2 was investigated in toluene as solvent. From the dependence of the initial rate of the polymerisation follows, that the primary complex, formed by the catalyst components, is not the active species of this system. The obtained dependences rather suggest, that the active species is to be viewed as an equilibrium product and the location of this equilibrium is determined by the ratio of the catalyst compounds in that manner, that only at high Al/Ti-ratios the charged Ti(IV)-compound is equal to the initial concentration of the active species. The existence of such an equilibrium is also suggested by the increase of the rate, occuring at lower Al/Ti-ratios, when polymer is falling out. The desactivation of propagating chains is of complex nature. Considerable desactivation of the active species by the aluminiumorganic compound is obtained.
    Notes: Es wurde die Geschwindigkeit der Polyreaktion von äthylen mit dem löslichen ZIEGLER-NATTA-Katalysator (C5H5)2Ti(C2H5)Cl/Al(C2H5)Cl2 in Toluol als Lösungsmittel untersucht. Aus der Abhängigkeit der Anfangsgeschwindigkeit der Polyreaktion von der Aluminiumalkylkonzentration ergibt sich, daß der aus den Katalysatorkomponenten sich bildende Primärkomplex nicht die aktive Spezies dieses Systems ist. Vielmehr sprechen die ermittelten Abhängigkeiten dafür, daß die aktive Spezies als Gleichgewichtsprodukt anzusehen ist und die Gleichgewichtslage vom Verhältnis der Katalysatorkomponenten bestimmt wird, derart, daß erst bei sehr hohen Verhältnissen Al/Ti die insgesamt eingesetzte Titan(IV)-Verbindung momemtan als aktive Spezies vorliegt. Für das Vorliegen eines solchen Gleichgewichtes spricht auch der für kleine Verhältnisse Al/Ti stets zu beobachtende Geschwindigkeitsanstieg nach dem Ausfallen des Polymeren. Die Desaktivierung der wachsenden Ketten ist komplexer Natur. Es zeigt sich, daß das Aluminiumorganyl in starkem Maße an der Desaktivierung der aktiven Spezies beteiligt ist.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1970.050120114
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  • 14
    Electronic Resource
    Electronic Resource
    Mechanismus der Olefinpolymerisation mit Übergangsmetall-katalysatoren (1981)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 94 (1981), S. 1-23 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: In this work the mechanism of olefine polymerization with Ziegler-Natta catalysts is presented. The first part is a discussion of the results obtained with soluble catalysts of the (C5H5)2-Ti(IV) type in combination with various aluminiumorganyls. Important analytical results, the characteristics of the yielded polymers and the kinetics of homogeneous and heterogeneous polymerization are discussed. The second part deals with heterogeneous titanium-catalysts, especially so-called carrier-fixed catalysts with Mg-compounds as carrier. The kinetics of ethylene polymerization and the reason for the elevated catalytic activity of such systems is discussed. Finally some mechanisms and their conformity with experimental results are given.
    Notes: In der vorliegenden Arbeit wird der Mechanismus der Olefinpolymerisation mit Ziegler-Natta-Katalysatoren erörtert. Im 1. Teil dieser Arbeit werden Ergebnisse diskutiert, die mit löslichen Katalysatorsystemen auf Basis (C5H5)2Ti(IV)-Verbindungen in Kombination mit verschiedenen Aluminiumorganylen erzielt wurden. Angesprochen werden wichtige analytische Befunde, charakteristische Eigenschaften der erzeugten Polymeren sowie die Kinetik der Polymerisation im homogenen und heterogenen Bereich. Im 2. Teil werden heterogene Katalysatorsysteme auf Titan-Basis behandelt, insbesondere sogenannte trägerfixierte Katalysatoren mit Magnesium-Verbindungen als Trägerkomponente. Hierbei wird insbesondere die Kinetik der Ethylenpolymerisation in den Vordergrund gestellt und die Frage nach dem Grund für die erhöhte Polymerisationsaktivität derartiger Katalysatorsyteme erörtert. Zum Abschluß werden einige Mechanismen im Hinblick auf ihre Übereinstimmung mit experimentellen Befunden diskutiert.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1981.050940101
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  • 15
    Electronic Resource
    Electronic Resource
    Diskontinuierliche Polymerisation von Vinylchlorid in suspension mit Temperaturprogramm (1975)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 44 (1975), S. 141-149 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: The batch polymerization of vinyl chloride in suspension can be conducted with constant rate of polymerization up to very high degrees of conversion by means of a temperature programme. The temperature programme was determined from some conversion-time-curves of the batch polymerization of vinyl chloride at different temperatures. The molecular weight and the molecular weight distribution of the poly (vinyl chloride) produced with the temperature programme are in agreement with the calculated respectively expected values.
    Notes: Es wird über ein Verfahren zur Durchführung der diskontinuierlichen Suspensionspolymerisation von Vinylchlorid mit konstanter Polymerisationsgeschwindigkeit berichtet. Es besteht darin, daß die normalerweise sehr instationär verlaufende Polymerisation des Vinylchlorids mit Hilfe eines Temperaturprogramms durchgeführt wird. Das Temperaturprogramm läßt sich in einfacher Weise an Hand von einigen wenigen experimentell zu bestimmeneden Zeit-Umsatz-Kurven ermitteln. Molekulargewicht und Molekularge-wichtsverteilung des mit Temperaturprogramm erzeugten Polymeren stehen im Einklang mit den zu erwartenden Werten.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1975.050440112
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  • 16
    Electronic Resource
    Electronic Resource
    Einfluß des stofftransportes bei der polymerisation von äthylen und 1-okten mit Ziegler-Katalysatoren (1977)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 57 (1977), S. 211-224 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: The polymerization of ethylene and 1-octene with supported Ziegler-catalysts was investigated with regard to the influence of mass transport of monomers on the kinetics, molecular weight and molecular weight distribution.In the case of the polymerization of ethylene, it was found that for certain conditions of reaction the mass transport of ethylene can influence the kinetics of polymerization respectively the catalyst efficiency strongly.The molecular weight and molecular weight distribution of the polyethylene formed are practically not affected by the conversion as well as particle size of catalyst and polymer. The molecular weight distribution however is affected by the concentration of the catalyst. The polymerization process of ethylene in suspension is distinguished by chemical and physical processes. A continuous chain initiation, for example, is based on the continuous reduction of the catalyst particles to small pieces during the course of polymerization. An apparent chain termination respectively catalyst deactivation can occur when catalyst particles are encapsulated within the growing polymer particles.The polymerization of 1 -octene for similar conditions of reaction gave polymers which were solved completely in the system used. The molecular weight distribution of the polymer formed nevertheless was very broad. This indicates that the mass transport of the monomers through the solid phase of polymer cannot be the main reason for the broad molecular weight distribution of the polymers which are produced by heterogeneous Ziegler-catalysts in suspension.
    Notes: Untersucht wurde die Polymerisation von Äthylen und Okten-1 mit Ziegler-Katalysatoren auf Basis von TiCl4/Mg(OC2H5)2/Aluminiumtrialkyl unter dem Gesichtspunkt des Stofftransportes und sein Einfluß auf Kinetik, Molekulargewicht und Molekulargewichtsverteilung.Es zeigt sich im Falle der Äthylenpolymerisation, daß der Stofftransport des Äthylens durch das dreiphasige System unter bestimmten Reaktionsbedingungen einen ausgeprägten Einfluß auf das kinetische Verhalten der Polymerisation bzw. auf den Katalysator-Nutzungsgrad ausüben kann.Molekulargewicht und Molekulargewichtsverteilung des Polyäthylens scheinen weitgeheß unabhängig zu sein von Umsatz, Katalysator- und Polymerpartikelgröße, jedoch zeigt sich eine eindeutige Abhängigkeit von der Katalysatorbeladung des Systems. Das Polymerisationsgeschehen des Äthylens ist gekennzeichnet durch chemische und physikalische Teilschritte. So beruht der fortgesetzte Kettenstart auf einer fortgesetzten Neubildung von Katalysatoroberfläche infolge einer fortgesetzten Zerkleinerung der Katalysatorpartikeln während der Polymerisation durch das sich bildende Polymere. Auch kann es zu einer ausgeprägten Einkapselung der Katalysatorpartikeln durch das Polymere kommen. was einem scheinbaren Kettenabbruch bzw. einer Katalysator-Desaktivierung entspricht.Die Polymerisation des Oktens führt zu Polymeren, welche im verwendeten Lösungsmittel vollständig löslich sind. Trotzdem weist das gebildete Polyokten eine relativ breite Molekulargewichtsverteilung auf und spricht somit ebenfalls dafür, daß der Stofftransport des Monomeren durch die Polymerphase nicht die hauptsächliche Ursache für die Einstellung der breiten Molekulargewichtsverteilung dieser Polymeren sein kann.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1977.050570117
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  • 17
    Electronic Resource
    Electronic Resource
    Zur kinetik der niederdruckpolymerisation von äthylen mit löslichen ZIEGLER-katalysatoren (1973)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 169 (1973), S. 163-176 
    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: This paper deals with the kinetics of the low pressure polymerization of ethylene catalysed by the soluble ZIEGLER-catalyst (C5H5)2Ti(C2H5)Cl/Al(C2H5)Cl2. By a special technique it was possible to study for the first time the kinetics of the initial homogeneous part of the polymerization. The following results were obtained: The active species of this catalyst system is formed extremely rapid and seems to be a very dynamic equilibrium product. Its concentration depends on the ratio Al/Ti. The propagation reaction therefore corresponds to an intermitting process. The propagation rate constant was estimated to 15 dm3 · mol-1 · s-1 for 10°C. An excess of the aluminum component (Al/Ti 〉 1) acts as deactivator. The polymerization of the heterogeneous system is probably diffusion controlled. Therefore, the rate decay of the polymerization cannot be described by simple kinetic laws. For small ratios Al/Ti the polymerization has the character of a “living” system.
    Notes: Es wird die Kinetik der Äthylenpolymerisation mit dem löslichen Katalysatorsystem (C5H5)2Ti(C2H5)Cl/Al(C2H5)Cl2 behandelt. Mit Hilfe einer speziellen Meßmethode konnte erstmals der homogene Anfangsbereich der Polymerisation kinetisch erfaßt werden. Anhand der erzielten Befunde lassen sich folgende Schlußfolgerungen ziehen: Die polymerisationsaktive Spezies wird unmeßbar rasch nach dem Mischen der Katalysatorkomponenten gebildet und ist als ein sehr dynamisches Gleichgewichtsprodukt anzusehen, dessen Konzentration vom Verhältnis der Katalysatorkomponenten abhängt. Kettenwachstum ist demnach ein intermittierender Vorgang. Die Geschwindigkeitskonstante der Wachstumsreaktion wurde zu etwa 15 dm3 · mol-1 · s-1 für 10°C bestimmt. Überschüssiges Aluminium-organyl (Al/Ti 〉 1) wirkt desaktivierend. Die Polymerisation in heterogener Phase ist sehr wahrscheinlich diffusionsbestimmt. Die Abnahme der Polymerisationsgeschwindigkeit mit der Zeit ist komplexer Natur und ist mit einfachen kinetischen Zeitgesetzen nicht zu beschreiben. Die zeitliche Zunahme des Polymerisationsgrades für Verhältnisse Al/Ti = 2 weist darauf hin, daß die Polymerisation den Charakter eines „lebenden“ Systems aufweist.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1973.021690116
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  • 18
    Electronic Resource
    Electronic Resource
    On computing the inverse of a sparse matrix (1983)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 19 (1983), S. 1513-1526 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The Gauss-Jordan inversion algorithm requires 0(n3) arithmetic operations. In some practical applications, like state estimation or short-circuit calculation in power systems, the given matrix is sparse and only part of the inverse is needed. Most frequently in the diagonal dominant case this is the diagonal. There are two ways to exploit sparsity to determine elements of the inverse: 1Columnwise inversion via the solution of sparse linear systems with columns of the unit matrix as right-hand sides.2Application of the algorithm of Takahashi et al6.The latter algorithm arises very naturally from multiplying the left- and right-hand factors of the Zollenkopf bifactorization in reverse order. We indicate how computing time can be gained in the important symmetric diagonal dominant case if only part of the diagonal is needed and compare computing times of the method of Takahasi et al.6 with several variants of columnwise inversion. Whereas most of the theory holds for general matrices, experiments are performed on the symmetric diagonal dominant case. For band matrices the operation count is 0(n) both for computing a column of the inverse by columnwise inversion and the diagonal by the algorithm of Takahashi et al6.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620191009
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  • 19
    Electronic Resource
    Electronic Resource
    Mikrogravimetrie  -  Eine neue Methode zur Datenerfassung von Gasphasenpolymerisationen (1997)
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 69 (1997), S. 1242-1242 
    Details
    ISSN: 0009-286X
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cite.330690940
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  • 20
    Electronic Resource
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    Anwendung von Monte-Carlo-Methoden zur Modellierung von Polyreaktionen (1997)
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 69 (1997), S. 1242-1243 
    Details
    ISSN: 0009-286X
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cite.330690941
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