Polypropylene catalyst

Disk holder material Polypropylene Catalyst specific surface area 3.6 0.4 m g ... 

Obviously, the polymerization of ethylene does not involve isotactic steric control, since no isomers are possible in the linear polyethylene polymer. However, as the simpliest member of the vinyl monomer series, ethylene should be considered along with the substituted ethylenes. Where does the Ziegler catalyst, which produces polyethylene, lie in relation to the polypropylene catalysts ... 

It should be pointed out that these polypropylene catalysts require a second Lewis base together with the Al-alkyl during the polymerization phase. 

As an additional example, benzoate or phthalate esters are used to modify the solid support and are incorporated into the solid-phase structure. Here, they become effective as internal bases [14], which are critical components in high-stereospecific polypropylene catalysts. As the range of suitable internal bases for stereoregulation increases, these compounds also find their way into reaction schemes involving Grignard reagents. 

B. L. Goodall, "Polypropylene Catalysts and Polymerization Aspects" in this work. Chapter 1, pp. 1-125 in S. van der Ven, Polypropylene and Other Polyolefins Polymerization and Characterization, Elsevier Science Publishers, New York, 1990. H.H. Brintzinger, D. Fischer, R. Miilhaupt, B. Rieger and R.M. Waymouth, Angew. Chem. Int. Ed. Engl. 34 (1995) 1143. M. Bochmann,/. Chem. Soc. Dalton Trans., 1996,255. 

Ewen, J.A. Jones, R.L. Elder, M.J. Rheingold, A.L. Liable-Sands, L.M. Sommer, R.D. Chiral flns fl-metallocenes with Cp ring-fused to thiophenes and pyrroles syntheses, crystal structures, and isotactic polypropylene catalysts. J. Am. Chem. Soc. 2001, 123, 4763. 

Goodall, B.L. Polypropylene catalysts and polymerization aspects. In Polypropylene and other Polyolefins. Polymerization and Characterization Van der Ven, S., Ed. Elsevier Amsterdam, 1990 1-133. 

Bernard, A. Fiasse, P. New Solvay SB 12 TiCls polypropylene catalyst. In Catalytic Olefin Polymerization Keii, T., Soga, K., Eds. Elsevier Amsterdam, 1990 405-423. 

Plastics, polyethylene, polystyrene polypropylene catalysts for polymerisation ... 

Proprietary catalyst and donor systems The Dow Chemical Co. manufactures and provides a family of polypropylene catalysts (SHAC catalyst) and a family of external electron donors (SHAC ADT) for use in the UNIPOL PP process. SHAC catalyst offers high catalyst activity (up to 35 kg/g-hr using conventional external donor and up to 60 kg/g-hr using a SHAC ADT) and competitive polymer properties. SHAC ADT performs three functions ... 

Table 4. Bridged Bis(indenyl) Zirconocenes as Polypropylene Catalysts Ligand Effects ...

Table 5. Comparison of Bridged Cp-Fluorenyl Metallocenes as Syndiotactic Polypropylene Catalysts...

A number of groups have contributed to the development of computational models of ansa-metallocene-based isotactic polypropylene catalysts. Their work will be briefly reviewed here. 

Bormann-Rochotte, L. M. Molecular Modeling Applied to an Isotactic Polypropylene Catalyst. Ph. D. Thesis, Colorado State University, Fort Collins Colorado, 1998. Diss. Abstr. Int. B. 1998, 59, 2228 Chem. Abstr. 1998,129, 260917. 

In the polypropylene catalyst shown in Figure 14, an isotactic-atactic block copolymer can be formed by rotation of one ring relative to the Zr-centroid axis. (For descriptions of polymer stereochemistry, see Fig. 9.) The isospecific rac rotomer of the catalyst gives rise to the isotactic block, while the aspecific meso form gives rise to the atactic block (Fig. 14). Using UFF (4) and RFF (85,86) (as weU as ab initio methods and DFT), the workers were able to confirm experimental evidence (89,90) that the indenyl substituent, R in Figure 14, could influence the equilibrium between the rac and meso rotomers. Using RFF the workers were able to successfully predict the relative amount of isotactic and atactic blocks in the polymer and to correlate that with R. 

With polypropylene, catalyst selectivity for the isotactic isomer is so high that removal of the small quantity of atactic polymer formed is not needed. 

Although polypropylene was only produced on a small scale from 1957, and despite the relatively greater importance of high-density polyethylene, woik on improving polypropylene catalysts led to a better overall understanding of both catalysts and process operation. 

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