Polypropylene production route

The fundamental reaction mechanism for the free-radical oxidation of hydrocarbons has been used to relate the consumption of oxygen to the formation of oxidation products in polypropylene. A kinetic interpretation is based on the steady-state approximation equating the rates of the initiation and termination reactions. With this approach it is possible to derive mathematical equations describing the consumption of oxygen or the formation of specific oxidation products. To solve the equations it is necessary to determine the most likely route for initiation of oxidation. The initiation mechanism chosen is the bimolecular reaction of hydroperoxides, reaction (1 ) of Scheme 1.55, with a rate coefficient k. ... 

Another Bristol-Meyers Squibb process represents an enzymatic route for the production of side-chain precursors of Paclitaxel (33, Scheme 10) [69]. Racemic czs-azetidinone acetate (rac-31) is subjected to the hydrolytic treatment of Pseudomonas cepacia lipase (PCL), which is used in its immobilized form on polypropylene beads. Thus, (3R,4S)-acetate 31 can be obtained in high ee as well as the remaining alcohol 32. The process takes place in 150 1 reactors where 1.2 kg mc-31/batch can be resolved with a hydrolysis rate of 0.12 g/lh. Lowering the reaction temperature to 5 °C after full conversion causes (3R,4S)-31 subsequently to crystallize. Due to the immobilization, the enzyme can be reused for at least ten cycles without any loss of activity, productivity, or optical purity of the product. Paclitaxel is finally accessible by further chemical steps. 

Polyolefins, especially polyethylene and polypropylene, are used in a wide range of applications, since they incorporate an excellent combination of mechanical, chemical and electronic properties and processibility. Nevertheless, deficiencies, such as the lack of reactive groups in the polymer structure, have limited some of their end uses, particularly those in which adhesion, dyeability, paintability, printability or compatibility with other functional polymers is paramount. Accordingly, the chemical modification of polyolefins has been an area of increasing interest as a route to higher value products and various methods of functionalization (1-3) have been employed to alter their chemical and physical properties. 

Like the denizens of the plant and animal kingdoms, plastics fall into distinguishable genera. The main subdivisions are thermoplastics and duroplastics. Thermoplastics are those that soften when heated, and so can be formed into the desired shapes, to harden again when cooled. They make up the greater part of the products of the plastics industry, and include predominantly polyethylene, polypropylene, polystyrene, and polyvinyl chloride (PVC). They are not cross-linked (or only very sparsely so), and they are all synthesized by the same type of chemical reaction, for all are made from monomers with carbon-carbon double bonds, which open up to create a chain. (This is not a universal rule, though some of the less familiar thermoplastics are made by different routes.)... 

F. Gugumus [21] provides an alternative view of the thermal oxidation reactions in polymers. Various possibilities arising from inter- and intramolecular reactions between hydroperoxide groups, peroxy radicals, and alkoxy radicals are postulated. The author underlines the plausible over-estimation of degradation attributed to -scissions in polypropylene (PP) and offers alternative (non (3-scission) routes that result in formation of 1,2-dioxetane which can account for auto-oxidation, chain scissions and enhanced chemiluminescence of PP oxidation products. An illustration of this proposed scheme is provided in Scheme 6.4. 

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