Continuous solution process

The first pubHshed information on the halogenation of butyl mbber was provided by B. F. Goodrich Co. (2). Brominating agents such as /V-bromosuccinimide were used the bromination occurred ia a bulk reaction. This technology was commercialized ia 1954, but withdrawn ia 1969 (3). Exxon Chemical researchers pursued the chlorination of butyl mbber ia hexane solution usiag elemental chlorine, and a continuous process was commercialized ia 1961 (4). Currentiy, both chlorination and bromination are carried out ia continuous-solution processes. 

At present all commercial polystyrene (with average molecular weights between 100,000 and 400,000) is manufactured by radical polymerization, which yields atactic polymers.476 Peroxides and azo compounds are commonly used initiators. The suspension process (usually as a batch process in water at 80-140°C) produces a product with relatively high residual monomer content.223 More important is the continuous solution process (usually in ethylbenzene solvent at 90-180°C), which yields high-purity product. Styrene can be copolymerized with numerous other monomers.477 One of these copolymers, the styrene-divinylbenzene copolymer produced by free-radical polymerization, has a crosslinked stucture and is used in... 

A continuous solution process [61] has been developed and is operated in the USSR (now CIS). Copolymerization is performed in 10-12 wt% comonomers solution in isopentane or other C5-C7 hydrocarbons, at temperatures between -90 and -50° C, initiated by an aluminum alkyl halide/water catalyst. The catalyst is eliminated by adding a low amount of methanol to the reactor effluent stream, and the polymer is extracted by contacting the solution with hot water and steam. Further operations are similar to those of slurry process. 

The alternative path of evolution was to the continuous solution process, first demonstrated with the tower process by I. G. Farben and implemented by Dow and others as either towers or tanks filled with heat transfer tubes. These... 

Because of the rate limitations of the tower and tube-tank processes that were primarily heat transfer constraints, further developments in the continuous solution process for crystal polystyrene (GP) were aimed at improving heat transfer. One obvious solution was to incorporate agitation of some type in the reactor. Although at Dow the incorporation of agitation in the reactors came about with the development of rubber-modified polystyrene [11], and this aspect will be discussed in a later section, agitation also significantly raises the heat transfer... 

Styrene is one of the oldest and most studied monomers. It spontaneously generates free radials upon heating above 100 °C and polymerizes yielding amorphous polystyrene (PS). Styrene can also be polymerized by other mechanisms (anionic, cationic, or Zeigler-Natta) with the aid of chemical initiators. Commercially, over twenty billion pounds of PS are produced annually worldwide. All of this polystyrene is produced via free radical (FR) chemistry, and mostly via continuous solution polymerization processes. The commercial preference for the continuous solution process is due mainly to economic factors. Non-solution polymerization processes (suspension and emulsion) have lower reactor efficiency (product/reactor volume) due to reactor volume occupied by the water which adds to the manufacturing cost. 

The continuous solution processes are usually carried out between 120-160 C at 400-500 Ib/in pressure. The diluents may be cyclohexane or isooctane. In one-zone reactors the solid catalyst is evenly dispersed throughout the reactor. In the two-zone reactors (specially constructed) the polymerizations are conducted with stirring in the lower zone where the catalysts are present in concentrations of 0.2-0.6% of the diluent. Purified ethylene is fed into the bottom portions of the reactors. The polymers that form are carried with small portions of the catalyst to the top and removed. To compensate for the loss, additional catalysts are added intermittently to the upper quiescent zones. 

What are the industrial conditions for preparations of high-density polyethylene Describe the continuous solution process, the slurry process, and the gas-phase process. 

Note that other key features of Dow s continuous solution process are the relatively high ethylene conversion rates and the relatively short catalyst... 

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