Halogenated butyl rubbers manufacture

Before the introduction of tubeless tires butyl rubber was used for inner tubes because it is impervious to air. Subsequently halogenated butyl rubbers were developed (halobutyls), which could be cured at higher temperature and vulcanized with other rubbers. Both chlorobutyls and bro-mobutyls are manufactured. These types of rubber are used in tubeless tires bonded to... 

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],... 

The chloride is used to manufacture silicones, tetramethyl lead and triptane (2,2,3 trimethylbutane). Lesser uses include the manufacture of butyl rubber, higher halogenated methanes, methyl cellulose, quaternary ammonium compounds, methyl mercaptan, methionine, fungicides and pesticides (primarily the Me-arsenate herbicides). Recently the chlorinated fluorocarbons have replaced CH3CI as high volume refrigerants and propellants (ref. 32) Tables 12 and 13 list the chemical and physical properties and potential numbers of workers exposed to the monohalomethanes. 

Butyl and Halobutyl Rubber. Butyl rubber is made by the copolymerization of isobutylene with 1-3% isoprene (eq. 5), which is added to provide sites for curing. It is designated HR because of these monomers. Halogenation of butyl rubber with bromine or chlorine increases the reaction rate for vulcanization (eq. 6). It is estimated that of the 200,000 kt of butyl (HR) and halobutyl (HIIR) rubber manufactured in North America, over 90% is used in tire applications. The halogenated polymer is used in the innerhner of tubeless tires. 

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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