Catalysis Ziegler

An important group of polymers used as moulding resins and in extruded forms (e.g. film). Can be electroplated. Useful polymerization is by Ziegler catalysis and gives an isotactic material. U.S. production 1983 1 -7 megatonnes. 

In the early days of Ziegler catalysis (the 1960s) there was considerable effort expended, and a flurry of patents and papers on the copolymerization of ethylene with countless polar monomers. It is generally accepted that none of these attempts was successful, and at least some of the erroneous claims must be attributed to lack of sophisticated analytical methods in those pioneering days. For interested parties this work is best surveyed in the book of John Boor [14],... 

The recent study by Overberger and Jarovitzky (37) shows clearly the cationic nature of the propagation step in the polymerization of alpha-D-styrene by Ziegler catalysis. 

Ziegler catalysis involves rapid polymerization of ethylene and a-ole-fins with the aid of catalysts based on transition-element compounds, normally formed by reaction of a transition-element halide or alkoxide or alkyl or aryl derivative with a main-group element alkyl or alkyl halide (1,2). Catalysts of this type operate at low pressures (up to 30 atm), but often at 8-10 atm, and, in special cases, even under reduced pressure, and at temperatures up to 120°C, but often as low as 20-50°C. Approximately 2,200,000 tons of polyethylene and 2,900,000 tons of polypropylene are produced per year with the aid of such catalysts. The polyeth-... 

The next most prominent transition metal in Ziegler catalysis is vanadium. In typical fashion, a stable high-oxidation state vanadium compound, such as vanadium oxytrichloride, is reacted with a metal alkyl derivative to generate a reduced form of the... 

H. Sinn, Symposium 40 Years Ziegler Catalysis, 1-3 Sept. 1993, Freiburg. 

Elsewhere (66) it was mentioned that these criteria would encompass not only the two types of reaction discussed but also metathesis and Ziegler catalysis as is briefly illustrated in Table VIII, which is self-explanatory. 

The addition of small amounts of metal alkyls to the reactor can significantly enhance the activity of Phillips catalysts, and modify the polymers they produce as well. This behavior was discovered during the 1950s and has been used commercially ever since, at least for some polymer grades. When used in this way, metal alkyls are usually called "cocatalysts", with the term borrowed from Ziegler catalysis. But in contrast to Ziegler catalysts, Phillips catalysts do not require cocatalysts. They are, at most, used to enhance the activity, not develop it. 

Second, in some cases they can perhaps even alkylate the chromium to initiate the first chain, and this action is similar to the role of the cocatalyst in Ziegler catalysis. 

Monomer Substituent Free radicals Initiation by Ziegler catalysis... 

In a sequence of gas phase reactors, (see the chapter on Ziegler catalysis) for the Novolen process of BASF AG [21], EPM rubber can be incorporated into PP during the second stage. This reactor blend can be tailored to improve low-temperature impact resistance of PP. Typical PP-based reactor blends contain high rubber contents and exploit the benefits of modern supported catalysts. In comparison to PP extruder... 

G. Fink, R. Mulhaupt, and H. H. Brintzinger, Ziegler Catalysis Recent Scientific Innovations and Technological Improvements, Springer-Verlag, New York, 1995. 

Alkyl lithium polyisoprene ceased to be manufactured in the U.S. in the early 1970 s in favor of polyisoprene polymerized by Ziegler catalysis and because of the greatly improved domestic reserve of natural rubber,Nevertheless, the work that was carried out on the copolymer end-block tire rubbers is a worthwhile addition to our knowledge. Although the idea and the work with this polymer occurred over a decade ago, new insight into the nature of ordered and disordered states and their transition makes this subject relevant in todays world. 

E. Drent, J. A. M. van Broekhoven, M. J. Doyle, and P. K. Wong, in Ziegler Catalysis, G. Fink, R. Muelhaupt, and H. H. Brintzinger, Eds., Springer, Berlin, 1995, 481-496. Palladium Catalyzed Copolymerization of Carbon Monoxide with Olefins to Alternating Polyketones and Polyspiroketals. 

General discussions on the preparation and properties of PVC will be found in such references as 1, 4, 5, and 22-24. The manufacture, processing, stabilization, and applications of PVC are also discussed in references 4 and 25-32. A review of the history of ionic and Ziegler catalysis polymerization of vinyl chloride is found in Feldman [33] and Yamazaki [34]... 

In a classic paper in the field of Ziegler catalysis, experimental evidence into the insertion of an rmsaturated monomer into a titanium-methyl bond associated with a titanium cation was first reported by Eisch et al. [33]. 

The study of polymerization in a tubular reactor involves simultaneous consideration of the velocity profile, heat release and conduction, as well as the kinetics of the polymerization. This work was undertaken to determine the effect of this type of reactor upon the molecular weight distribution of the polymer produced. The system studied was the copolymerization of an elastomer from ethylene, propylene, and 1,4-hexadlene In solution using Ziegler catalysis. Laminar flow polymerization similar to previously described work involving polymerization of sytrene in tubular reactors (1, 2, was analyzed, but the numerical... 

As applied to copolymerization with Ziegler catalysis, tubular reactors are limited in conversion for two principal reasons. The reaction is highly exothermic and high temperatures are detrimental to the catalyst. In addition, since the monomers have differing reactivity, polymer of varying composition is obtained as the monomers are depleted. Useful EPDM elastomers have a restricted compositional range. The material produced in these studies have compositions of 55 to 70% ethylene, 30 to 45% propylene and about 3% hexadlene by weight. 

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