Ziegler-Natta polymerization polyolefins

Cyclic Polyolefins (GPO) and Gycloolefin Copolymers (GOG). Japanese and European companies are developing amorphous cycHc polyolefins as substrate materials for optical data storage (213—217). The materials are based on dicyclopentadiene and/or tetracyclododecene (10), where R = H, alkyl, or COOCH. Products are formed by Ziegler-Natta polymerization with addition of ethylene or propylene (11) or so-called metathesis polymerization and hydrogenation (12), (101,216). These products may stiU contain about 10% of the dicycHc stmcture (216). 

V. Dufaud and J. M. Basset, Catalytic Hydrogenolysis at Low Temperature and Pressure of Polyethylene and Polypropylene to Diesels or Lower Alkanes by a Zirconium Hydride Supported on Silica-Alumina a Step Toward Polyolefin Degradation by the Microscopic Reverse of Ziegler-Natta Polymerization, Angew. Chem. Int. Ed., 37, 806-810 (1998). 

V. Dufaud and J.-M. Basset, Catalytic hydrogenolysis at low temperature and pressure of polyethylene and polypropylene to diesels or lower alkanes by silica-alumina a step toward polyolefin degradation by the microscopic reverse of Ziegler-Natta polymerization, Angew. Chem. Int.Ed., (1998) 37(6) 806-810. I. Nakamura and K. Fujimoto, Development of new disposable catalyst for waste plastics treatment for high quality transportation fuel. Catalysis Today, 27,175-179 (1996)... 

Control of Distribution in Polyolefins with Catalytic Systems Table 2. Kinetic scheme for Ziegler-Natta polymerization (ethylene)... 

Table 9. Main parameters of industrial Ziegler-Natta polymerization which could affect polyolefins MWD... 

Several interesting CTs have been studied in the past decades with the major objective of introducing functional (polar) groups at the polyolefin chain end. In the past, aluminum-alkyl and zinc-alkyl were reported to act as coinitiator and CT in heterogenous Ziegler-Natta polymerization.f Recently, two hydride CTs, i.e., silane and borane containing Si-H and B-H moieties, respectively, have been successfully applied... 

Ziegler-Natta polymerization of alkenes is an important industrial process for the manufacture of polyolefins. Although it originally involved the use of the triethylaluminum-TiCft complex as the catalysts, many other transition metal complexes and /-block compounds (lanthanides) also catalyze the polymerization of alkenes. Group IV metallocenes exhibit particularly outstanding properties. 

Since the discovery of olefin polymerization using the Ziegler-Natta eatalyst, polyolefin has become one of the most important polymers produeed industrially. In particular, polyethylene, polypropylene and ethylene-propylene copolymers have been widely used as commercial products. High resolution solution NMR has become the most powerful analytieal method used to investigate the microstructures of these polymers. It is well known that the tacticity and comonomer sequence distribution are important factors for determining the mechanical properties of these copolymers. Furthermore, information on polymer microstructures from the analysis of solution NMR has added to an understanding of the mechanism of polymerization. 

The property envelope of polyolefins has been expanded by the direct synthesis, in the reactor, of novel alloys and blends with a balance of properties not possible ftom conventional, third-generation catalyst polymerization. Such advances in Ziegler-Natta polymerization technology show that polyolefin-based resins can continue to provide the most cost-effective solutions for a wide and ever-increasing range of plications in the global plastics market. 

For example, see Zhang, Y. Keaton, R. J. Sita, L. R. Degenerative transfer living Ziegler-Natta polymerization Application to the synthesis of monomodal stereoblock polyolefins of narrow poly-dispersity and tunable block length. J. Am. Chem. Soc. 2003, 125, 9062-9069 and references therein. 

Koo, K. Marks, T. J. Silicon-modified Ziegler-Natta polymerization. Catalytic approaches to sUyl-capped and sUyl-finked polyolefins using single-site cationic Ziegler-Natta catalysts. J. Am. Chem. Soc. 1999,121, 8791-8802. 

The preparation of functional polyolefins by direct Ziegler-Natta polymerization has long been a goal of synthetic polymer chemists. A new method has been developed based on borane monomers and polymers. The value of this method rests with the "cleanliness" and versatility of its chemistry. Not only can the borane derivatives be quantitatively carried through the Ziegler-Natta process, but they can also be quantitatively converted to a host of other functionalities. 

Monomer concentrations and pressures are not very high in Ziegler-Natta polymerization (about 2-3 MPa), contrary to the free radical polymerization of ethylene which requires very high pressures. For obvious reasons, industrial producers of polyolefins focus their attention on the productivity of a catalytic system which corresponds to the mass of polymer produced (and not its rate of formation) per mass unit of transition metal, without mention of time. In Table 8.18 the typical components of a currently used Ziegler-Natta system for the industrial production of polypropylene are given. 

The annual production of various polymers can be measured only in billion tons of which polyolefins alone figure around 100 million tons per year. In addition to radical and ionic polymerization, a large part of this huge amount is manufactured by coordination polymerization technology. The most important Ziegler-Natta, chromium- and metallocene-based catalysts, however, contain early transition metals which are too oxophiUc to be used in aqueous media. Nevertheless, with the late transition metals there is some room for coordination polymerization in aqueous systems [1,2] and the number of studies published on this topic is steadily growing. 

High magnetic fields and in particular C-NMR spectroscopy allow the analysis of even longer configurational sequences (tetrads up to nonads). This proved to be important in particular for the analysis of polyolefins like polypropylene or cycloolefin copolymers (COC). These polymers are available via transition-metal mediated (Ziegler-Natta, metallocene) insertion polymerizations, and the configurational analysis provides deep insight into the respective polymerization mechanisms as well as into the structure-property relationships. 

Reith RL, Eaton FR, Coates WG. Polymerization of ureidopyrimidinone-functionalized olefins by using late-transition metal Ziegler-Natta catalysts synthesis of thermoplastic elastomeric polyolefins. Angew Chem Int Ed 2001 40 2153-2156. 

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