Ziegler-Natta catalysts development

In contrast to early generations of multi-site Ziegler-Natta catalysts, developed on the basis of trial-and-error research, modern metallocene catalysts contain... 

Before the development of the Ziegler-Natta catalyst systems (Section 6 21) polymer ization of propene was not a reaction of much value The reason for this has a stereo chemical basis Consider a section of polypropylene... 

Mamzen Oil Co. has developed various Ziegler-Natta catalysts that can produce poly(butadiene-i //-prop5iene) (PBR) (78). PBR shows tack (self-adhesion) and green (unvulcanized) dynamic properties superior to those of BR and EPDM. Carbon black-loaded vulcanizates can be compounded to give high strength and elongation at break (79,80). PBR can also be covulcanized with SBR, BR, and EPDM. 

The revolutionary development of stereospecific polymerization by the Ziegler-Natta catalysts also resulted ia the accomplishment ia the 1950s of a 100-year-old goal, the synthesis of i7j -l,4-polyisoprene (natural mbber). This actually led to the immediate termination of the U.S. Government Synthetic Rubber Program ia 1956 because the technical problem of dupHcating the molecular stmcture of natural mbber was thereby solved, and also because the mbber plantations of the Far East were again available. 

Polybutadiene was first prepared in the early years of the 20th century by such methods as sodium-catalysed polymerisation of butadiene. However, the polymers produced by these methods and also by the later free-radical emulsion polymerisation techniques did not possess the properties which made them desirable rubbers. With the development of the Ziegler-Natta catalyst systems in the 1950s, it was possible to produce polymers with a controlled stereo regularity, some of which had useful properties as elastomers. 

The development of rubbers with a more closely controlled molecular structure. Such materials are made using anionic or Ziegler-Natta catalysts and are polymerised in solution (solution SBRs). 

Heterogeneous Ziegler-Natta catalysts used to polymerize olefins exhibit phenomena characteristic of active site heterogeneity (1- 5). Complex kinetic models which account for this likelihood have been developed and used only in simulation studies (6-7). 

Alphabutol Also called IFP-SABIC. A process for dimerizing ethylene to 1-butene. It operates under pressure at 80°C, using a complex Ziegler-Natta catalyst, a titanium alkoxide. Developed by the Institut Frangais du Petrole. First operated in Thailand in 1987. Seven plants had been licensed by 1993, of which three were operating. 

ATOL [Atochem polymerization] A gas-phase process for making polyethylene. Developed by Atochem and first commercialized in 1991. It uses a Ziegler-Natta catalyst containing titanium and magnesium halides. First commercialized at Gonfreville, France, in 1991. 

Catalloy A gas-phase process for making olefin co-polymers, using Ziegler-Natta catalysts. It uses a series of three gas-phase reactors to which monomer is progressively added. The properties of the product can be varied according to the monomer grades used. Developed by Himont and first commercialized in 1990. Now operated by a joint venture of Montell Polyolefins and Japan Polyolefins. See also Hivalloy. 

Hivalloy A process for grafting styrenic polymers on to polyolefines, using a Ziegler-Natta catalyst. The products combine the physical properties of both polymer types. Developed by Montell and commercialized in the United States in 1997. See also Catalloy. Oxley, D. F., Chem. Ind. (London), 1998, (8), 307. 

Idemitsu A process for making C6-C18 a-olefins from ethylene, catalyzed by a modified homogeneous Ziegler-Natta catalyst containing a zirconium chloride. Developed by the Idemitsu Petroleum Company in 1988. 

Spherilene [Spherical polyethylene] A process for making polyethylene in the form of granules. The catalyst combines a Ziegler-Natta catalyst with a silane. Developed by Montecatini, Italy. The first plant was due for startup by Himont, in Lake Charles, LA, in 1993. 

Natta catalyst. A stereospecific catalyst made from metal alkyls and titanium chloride developed by the chemist Giulio Natta. See also Ziegler-Natta catalyst. 

Ziegler-Natta catalyst. Gi ulio Natta developed a catalyst based on his work with Karl Ziegler for polymerizing vinyl monomers to give stereoregular, tailored, three-dimensional chains. The catalyst is based on aluminum alkyls and TiCU or other transition metal halides. 

G. Natta of Imperia and Karl Ziegler of Germany were awarded the Nobel Prize for Chemistry in 1963for the development of Ziegler-Natta catalyst... 

New and improved polymerization catalysts are continuously being developed to produce polymer with higher rates and with improved properties. Early Ziegler Natta catalysts were supported on porous alumina or sihca catalyst supports. These catalysts had low activity, and large amounts of catalysts had to be used that had to be separated from the molten polymer because otherwise the catalyst would color the polymer. With high-activity catalysts, the catalyst can be left in the polymer, thus saving considerable cost in separation. 

One recent development in Ziegler Natta catalysts was in producing catalyst particles that expanded as the polymerization reaction occurred. In this polymer the catalyst remains dispersed throughout the polymer, retaining its activity. This led to the development of fluidized bed processes to make polyethylene and polypropylene in which a sphere of polymer formed around each initial catalyst particle, and the polymer remained sohd as the reaction proceeded, rather than requiring a liquid solution. A major class of these catalysts and fluidized bed reactor was developed by Union Carbide and by Shell Oil and called the Unipol process. In this process a very active solid catalyst is introduced into the reactor, and reaction occurs on the catalyst particles, which expand to maintain active sites on the growing polymer sphere. 

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