Halogenated butyl rubbers producers

Halogenated Butyl Rubber. The halogenation is carried out in hydrocarbon solution using elemental chlorine or bromine in a 1 1 molar ratio with enchained isoprene. The reactions ate fast chlorination is faster. Both chlorinated and brominated butyl mbbers can be produced in the same plant in blocked operation. However, there are some differences in equipment and reaction conditions. A longer reaction time is requited for hromination. Separate faciUties are needed to store and meter individual halogens to the reactor. Additional faciUties are requited because of the complexity of stabilising brominated butyl mbber. 

Butyl rubber (HR) is an isobutylene-based rubber which includes copolymers of isobutylene and isoprene, halogenated butyl rubbers, and isobutylene/p-methylstyrene/bromo-p-methylstyrene terpoly-mers. HR can be slurry polymerized from isobutylene copolymerized with small amounts of isoprene in methyl chloride diluent at -130 to - 148°F (-90 to - 100°C). Halogenated butyl is produced by dissolving butyl rubber in a hydrocarbon solvent and introducing elemental halogen in gas or liquid state.Cross-linked terpolymers are formed with isobutylene + isoprene + divinylbenzene. 

In addition to the grades of halogenated butyl rubber shown in the table, both brominated and chlorinated butyl polymers are produced by Polysar Limited, e.g., Polysar Chlorobutyl 1240. 

Common solvent is used for polymerization and bromination in production of bro-mobutyl rubber. Solvent is aliphatic hydrocarbon. Liquid, solventless ethylene propylene diene rubber can be produced according to invention." It is possible to produce water and solvent-free synthetic rubber products such as non-halogenated and halogenated butyl rubber products. ... 

Forms of BR and polyisobutylene. The properties of butyl rubber and polyisobutylene depend on their moleeular weight, degree of unsaturation, nature of the stabilizer incorporated during manufacture and, in some cases, chemical modification. It is common to produce halogenated forms of butyl rubber to increase polarity and to provide a reactive site for alternate cure mechanisms [6],... 

Butyl rubber is produced at very low temperature (below — 90°C) to control the rapid exotherm, and to provide high molecular weight. The process consists of charging isobutylene along with isoprene (2-4%) with an inert diluent such as methyl chloride to a reactor to which a Friedel-Crafts catalyst is added. The polymerization is very rapid, and the polymer forms in a crumb or slurry in the diluent. Heat is removed via the reactor jacket. The slurry is steam-stripped to remove all volatiles. The catalyst is neutralized, and antioxidants are added to the slurry prior to drying.53 The halogenated derivatives are produced by the direct addition of the halogen to a solution of the isobutylene-isoprene polymer. 

In the presence of light, halogens attack both vulcanised and unvulcanised butyl rubber. Whether vulcanised or unvulcanised the effect of the reaction is to produce rapid deterioration in molecular weight. A strip of butyl vulcanisate suspended in bromine gas degrades rapidly. In a few minutes the specimen becomes fluid enough to drip to the bottom of the vessel. Chlorosulfonated polyethylene is resistant to ozone being better than Neoprene and butyl rubber compounds [18]. 

Isobutylene and isoprene are in a ratio of approximately 50 1. Chlorobutyl rubber and bromobutyl rubber are produced by the halogenation of butyl rubber. Butyl rubber and halobutyl rubber are highly impermeable to air and show very low water absorption, and good heat, oxygen and ozone resistance. As noted earlier, they therefore find extensive use in liners of radial tires, covers and insulation of high-voltage electric cables, and automobile engine and radiator hoses. 

The manufacture of halobutyl rubbers such as Bromobutyl, Chlorobutyl, and Exxpro [bromopoly(isobutylene-co-/j-methylstyrene)] requires a second chemical reaction the halogenation of the polymer backbone. This can be achieved in two ways, the finished polymer produced in the butyl plant can be dissolved in a hydrocarbon solvent such as hexane or pentane, or a solvent replacement process can be used to dissolve the polymer from the slurry leaving the reactor. A schematic flow diagram of the halogenation process is shown by Figure 2. 

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