Chlorobutyl rubber chlorination

Chlorobutyl rubber is prepared by chlorination of butyl rubber (chlorine content is about 1 wt%). This is a substitution reaction produced at the allylic position, so little carbon-carbon double unsaturation is lost. Therefore, chlorobutyl rubber has enhanced reactivity of the carbon-carbon double bonds and supplies additional reactive sites for cross-linking. Furthermore, enhanced adhesion is obtained to polar substrates and it can be blended with other, more unsaturated elastomers. 

Fig. 33. Vulcanization kinetics and tensile properties of chlorinated HTI (CHTI, ) and comparison with chlorobutyl rubber (CIIR, ). Recipe as in Fig. 23 except, MBT = 1 T = 160 °C...

Grafting from, exploits the active sites, which exist or can easily be generated on a polymer. Halogenated polymers are most frequently used for this purpose poly(vinyl) chloride), polychloroprene, chlorinated EPDM, chlorobutyl rubber, bromobutyl rubber, chlorinated polybutadiene, chlorinated butadiene-styrene copolymers etc.145). 

Gas-liquid mixture outgoing from reactor was inputted to separation after which rubber solution was purified by water, and then by 10% solution of NaOH. Chlorobutyl rubber solution purified from salts was degassed by direct steam. Estimation of chlorine content values dispersion in chlorobutyl rubber was held on three samples taken every 30 minutes. 

Numerical value of chemical reaction characteristic time is of fundamental importance in respect to possibility of realization of novel continuous process of chlorobutyl rubber synthesis. According with [27] in temperature interval 290-325 K time of chlorination reaction is less than 60 sec, and in concrete case of chlorination of 15-16% butyl rubber solution in methylchloride (328 K, dosage of molecular chlorine - 3-3,5 mass %) is equal to 7,5 2,5 sec [176]. 

Novel process on the base of compact tubular reactors is principally fitted for production of bromobutyl rubber and also others chlorinated elastomers. Process is accepted at OAO "Nizhne-kamskneftekhim". In 2001-2002 pilot plant worked at which chlorobutyl rubber of required quality was received without any problems. Technical schedule was made. At present experimental-industrial plant is projected. 

Chlorobutyl rubber is chlorinated isobutylene-isoprene. It has the same general properties as butyl rubber but with slightly higher allowable operating temperatures. 

A series of interesting graft copolymers have been synthesized using this principle. The key choice is the macromolecular coinitiator. Chlorobutyl rubber is an excellent coinitiator because it contains allylic chlorine atoms in its main chain... 

The mechanism proposed by Kennedy requires that allylic or tertiary chlorines be attached to the first polymer chain. Chlorobutyl rubber, PVC, and other chlorine-containing polymers usually have 1-2% of mers with chlorines in the required reactive positions. The halogen-containing polymer is dissolved in an inert but polar solvent in the presence of an organoaluminum catalyst and a cationically polymerizable monomer, such as styrene, and polymerization is effected, usually at about — 50 C. The major point is that the second component chains can be initiated only at an active chlorine site on the first polymer. 

Synonyms Butyl rubber, chlorinated Chlorinated butyl rubber Chlorinated isobutylene/isoprene copolymer Chlorobutyl rubber CNR... 

Chlorinated BR macromolecules predominantly contain exomethylene groups [structure (2)], up to 90%. The content of endomethylene groups [structure (1)] is about 9%. Macromolecules may also include saturated groups [structure (4)], up to 1%, which are generally formed at low temperatures. The relative content of structures (2) to (1) defines the performance characteristics of chlorobutyl rubber particularly, the thermal load stability and processing stability. Before introducing one chlorine atom per one isoprene unit, in the case of chlorinating BR, an increase of the chlorine content in the polymer (linear relationship) is observed. BR contains up to 50 mol% of the added chlorine. 

Close characteristic times of a chemical reaction also resulted from the experiments on producing chlorobutyl rubber by the reaction of BR with chlorine in a commercial Nefras solvent within turbulent flows. Calculations of BR chlorination reactor geometry were performed according to the relationships of turbulent mixing in a self-similar mode of a highly viscous mixture flow. At a 0.21 m /h rate of feeding of the BR solution in a commercial Nefras solvent, and a 2.1 m /h rate of feeding the... 

Chlorobutyl Rubber and Bromobutyl Rubbers (CIIR and BUR). The addition of chlorine or bromine to HR in an inert solvent (e.g., hexane) gives the facile attachment of one halogen atom per isoprene unit in the allylic position. Compared with HR, the halogenated butyl rubbers have certain advantages. The cure reactivity is increased to give faster vulcanization rates, greater extents of vulcanization, and reduced reversion. Also, the halo-genation improves the compatibility of the isoprene polymer with other types of rubber (e.g., NR) to make useful rubber-blend compositions possible. 

CIIR Chlorinated isobutylene-isoprene rubber (chlorobutyl rubber)... 

Oxygen flask combustion methods have been used to determine traces of chlorine in PVC [15] and in polyolefins and chlorobutyl rubber [16]. 

Butyl rubber (HR) contains isobutylene as the parent material to which small proportions of butadiene or isoprene are added. Commercial butyl rubber may contain 5% butadiene as a copolymer. Chlorobutyl rubber (CIIR) is chlorinated isobutylene-isoprene. Both rubbers have the same general properties except that chlorobutyl rubber has a slightly higher allowable operating temperature. 

Polychloroprene (CR) has much more chlorine than the chlorobutyl rubber examined by Lawson and good adhesion to untreated CR wonld be expected provided there was no weak layer was on the surface. If such layers exist a suitable solvent treatment or abrasion should result in good adhesion. Cyclisation has been recommended as a pre-treatment [50, 51]. Lawson noted a large uptake of chlorine, nitrogen and oxygen on treatment of polychloroprene with TCICA, indicating addition across the carbon-carbon donble bond. 

In commercial halogenated butyl rubbers the extent of halogenation is small. One typical chlorobutyl rubber contains 1-1-1-3 wt% chlorine and a typical bromobutyl rubber 1-8-2-4% bromine. Brominated butyl rubber generally cures at a faster rate than chlorinated butyl. 

Exxon butyl rubber and its chlorinated analog, chlorobutyl rubber are isobutylene-isoprene copolymers. They are basically inert, nonpolar, stable elastomers which exhibit outstanding resistance to attack by a great many different chemicals. 

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