Olefin polymerization polypropylenes

Polymerization Reactions. Polymerization addition reactions are commercially the most important class of reactions for the propylene molecule and are covered in detail elsewhere (see Olefin polymers, polypropylene). Many types of gas- or liquid-phase catalysts are used for this purpose. Most recently, metallocene catalysts have been commercially employed. These latter catalysts requite higher levels of propylene purity. 

Polymerization. Supported catalysts are used extensively in olefin polymerization, primarily to manufacture polyethylene and polypropylene. Because propylene can polymerize in a stereoregular manner to produce an isotactic, or crystalline, polymer as well as an atactic, or amorphous, polymer and ethylene caimot, there are large differences in the catalysts used to manufacture polyethylene and polypropylene (see Olefin polymers). 

The next major commodity plastic worth discussing is polypropylene. Polypropylene is a thermoplastic, crystalline resin. Its production technology is based on Ziegler s discovery in 1953 of metal alkyl-transition metal halide olefin polymerization catalysts. These are heterogeneous coordination systems that produce resin by stereo specific polymerization of propylene. Stereoregular polymers characteristically have monomeric units arranged in orderly periodic steric configuration. 

Gas phase olefin polymerizations are becoming important as manufacturing processes for high density polyethylene (HOPE) and polypropylene (PP). An understanding of the kinetics of these gas-powder polymerization reactions using a highly active TiCi s catalyst is vital to the careful operation of these processes. Well-proven models for both the hexane slurry process and the bulk process have been published. This article describes an extension of these models to gas phase polymerization in semibatch and continuous backmix reactors. 

Finally, in the fourth section the fundamentals of the modelling concerning two basic olefin polymerization processes are examined heterogeneous slurry polymerization and gas-phase polymerization. The SPERIPOL process for making High Impact PolyPropylene (HIPP) is then described as an illustrative example for combining fundamentals and elements of product and technology development. 

Bis(phenoxy-imine) catalysts in olefin polymerization, 4, 1096 for syndiotactic polypropylene polymerization, 4, 1115 Bis(phenoxy) imine-donor complexes, with Zr(IV) and Hf(IV), 4, 814... 

Hafnium complexes with bis(cyclopentadienyl)s, 4, 731 in carbometallations, overview, 10, 255 in C-C bond formation, 10, 424 in ethylene polymerization, 4, 1139 for isotactic polypropylene, 4, 1126 metal-metal bonds, 4, 755 mixed-valence compounds, 4, 755 with pyridyl amines, for olefin polymerization, 4, 1094 in Ru-Os heterodinuclear compounds, 6, 1046 with silicon, 3, 515... 

The traditional catalysts for olefin polymerization were invented by Hogan et al. (their catalyst is the Phillips catalyst) (13-15) in 1952 and Ziegler et al. (16, 17) and Natta and Corradini (18, 19) in 1953. Commercialization of olefin polymerization with these catalysts provided the first linear polyethylene and the first isotactic polypropylene. Before these innovations,... 

Danusso s conclusion that the monomer is only weakly polarized in the complex must certainly be true for the stereospecific coordinated anionic catalysts, such as AlR3/TiCl3, which are used for a-olefin polymerization. If it were not so, then rapid termination would take place through hydride abstraction by the strongly polarized monomer. This appears to be the case when strongly acidic alkyl metal chlorides are used in catalysts. For example, low molecular weight polypropylene oils are obtained with RAlCl2/TiCla catalyst (308) and polyethylene oils are obtained with RjA Cla/TiC catalysts in reactive alkyl halide solvents (309). 

Giulio Natta (1903-1979) one of the early supporters of the oxo reaction [9, 81], discovered in 1956 the isotacticity and syndiotacticity of olefin polymerization (e. g., propylene Section 2.3.1.1) using Ziegler s Me-tallorganische Mischkatalysatoren (see above). The industrial production of isotactic polypropylene started at Montecatini in Italy in 1956. Natta was a professor at the universities of Turin and Milan. He received the Nobel prize for chemistry together with Karl Ziegler in 1963. 

Antberg, M. Dolle, V. Klein, R. Rohrmann, J. Spaleck, W. Winter, A. Propylene Polymerization by Stereorigid Metallocene Catalysts Some New Aspects of the Metallocene Stmcture/polypropylene Microstructure Correlation. In Catalytic Olefin Polymerization, Studies in Surface Science and Catalysis-, Keii, T., Soga, K., Eds. Kodansha-Elsevier Tokyo, 1990 p 501. 

Work in the application of metallocene-based catalysis to olefin polymers has become a research topic of growing interest in recent years. A great number of symmetrie and chiral zirconocenes have been synthesized to give totally different structures of isotactic, syndiotactic, atactic or block polymers. The isotactic sequence length of polypropylene is influenced by the nature of the ligands of the metallocene. New ring or bridge substituted metallocene/methylalumoxane catalysts for the olefin polymerization are described. 

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. 

---