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1985 | Buch

Isospecific Polymerization of Olefins

With Heterogeneous Ziegler-Natta Catalysts

verfasst von: Y. V. Kissin

Verlag: Springer New York

Buchreihe : Polymers

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Über dieses Buch

The discoveries of organometallic catalysts for olefin polymerization by Karl Ziegler and that of stereoregular olefin polymers by Giulio Natta are probably the two most important achievements in the areas of catalysis and polymer chemistry in the second half of this century. They led to the development of a new branch of chemical industry, and to a large volume production of high-density and linear low-density polyethylene, isotactic polypropylene, ethylene-propylene rubbers, isotactic poly­ I-butene, and poly-4-methyl-l-pentene. These discoveries merited the Nobel prize, which was awarded to K. Ziegler and G. Natta in 1963. The initial works of Ziegler and Natta were followed by an "explosion" of scientific papers and patents covering all aspects of polymerization chemistry, catalyst synthesis, and polymerization kinetics as well as the structural, chemical, physical, and technological characteristics of stereo regular polyolefins, polydienes, and olefin copolymers. It is sufficient to say that in the twenty-five years after the first publications more than 15,000 papers and patents appeared on subjects related to the area. . The development brought about the establishment of several prominent groups of scientists occupied with the study of olefin polymerization. The most important of these were scientific schools in Italy, Germany, England, the United States, Japan, the Soviet Union, Czechoslovakia, and Venezuela. In addition, many major chemical and petrochemical corporations throughout the world established labora­ tories devoted to the development of the technology of catalyst synthesis and olefin polymerization.

Inhaltsverzeichnis

Frontmatter
I. Kinetics of Olefin Polymerization with Heterogeneous Ziegler-Natta Catalysts
Abstract
The kinetics of any catalytic polymerization process, including olefin polymerization with heterogeneous Ziegler-Natta catalysts, is essentially the overlap of three simultaneous events: the time-dependent change of catalyst activity (sometimes influenced by the monomer presence), kinetics of the polymerization process itself, and the time-dependent diffusion processes.
Y. V. Kissin
II. Heterogeneous Ziegler-Natta Catalysts: Chemistry and Kinetics of the Formation and Functioning of Active Centers
Abstract
In the previous discussion no particular description of active centers has been given and the only quantitative parameter used for their characterization was C 0 , the total amount of active centers in the system. This amount was assumed constant in the case of stable heterogeneous catalysts (with the exception of the initial acceleration period, see Section I-2-b) whereas in the case of unstable catalysts this value consisted of two parts: stable centers (C 0, 1 ) and undunstable centers (C0, 2 = C 0 - C 0, 1 ).
Y. V. Kissin
III. Stereospecificity of Heterogeneous Ziegler-Natta Catalysts
Abstract
The most prominent feature of heterogeneous Ziegler-Natta catalysts is their ability to produce isotactic olefin polymers exhibiting a combination of outstanding mechanical characteristics. This ability adds a new dimension to the description of the catalysts and the polymerization processes: the study of catalyst and polymerization parameters influencing polyolefin stereoregularity. Such studies usually pursue two goals: improvement of catalyst isospecificity and understanding of the mechanism of isotactic polymer formation. It is the second topic that constitutes the main subject of this chapter.
Y. V. Kissin
IV. Inhonogeneity of Active Centers of Heterogeneous Ziegler-Natta Catalysts
Abstract
Active center inhomogeneity with respect to kinetic characteristics is a well-known attribute of any heterogeneous catalyst. In the case of usual catalytic processes, where both reagents and products are low molecular compounds, the inhomogeneity of the centers is frequently masked by overlapping adsorption and desorption phenomena: under a given set of conditions, the most active centers are blocked by adsorbed products, the least active centers weakly adsorb reagents, and only the centers of medium activity “function.” In the case of heterogeneous Ziegler-Natta catalysts these masking phenomena have no great significance. The mean olefin adsorption capacity of their active centers is low (see Section II-8) and the reaction products, polyolefin molecules, are not adsorbed on the active centers at all. For this reason, these catalysts can be regarded as good subjects for the study of active center inhomogeneity.
Y. V. Kissin
V. Mechanism of Isospecific Olefin Polymerization
Y. V. Kissin
Backmatter
Metadaten
Titel
Isospecific Polymerization of Olefins
verfasst von
Y. V. Kissin
Copyright-Jahr
1985
Verlag
Springer New York
Electronic ISBN
978-1-4612-5084-5
Print ISBN
978-1-4612-9556-3
DOI
https://doi.org/10.1007/978-1-4612-5084-5