Natural rubber hydrochlorination

Chlorination and hydrochlorination of natural rubber are industrial processes carried out on solutions of uncrosslinked rubber in chlorinated solvents [Allen, 1972 Ceresa, 1978 ... 

Synthetic polyisoprene rubbers were found by Harries during 1910 [19], to be successfully hydrochlorinated. These synthetic polyisoprenes resemble natural rubber, which is also a polymer of isoprene which occurs naturally and therefore hydrogen chloride is rapidly added when the rubber is exposed to it thus forming a protective film of chlorinated rubber or hydrogen chloride. Polybutadiene, and butadiene acrylonitrile rubbers do not add hydrogen chloride from hydrochloric acid. 

Hydrochlorination of natural rubber is often accompanied by cyclization ... 

Examples include the polyamides synthesized from fatty adds obtained via ozoanization of vegetable oils, chlorinated or hydrochlorinated natural rubber to obtain plastic materials, and the various modifications of cellulose or chitin. 

Natural rubber was chlorinated by G.A. Englehard and H.H. Day in 1859, hydrochlorinated in 1881 and isomerized by Leonhardi in 1881 (12). However, these rubber derivatives were not commercialized until the early part of the twentieth century. Likewise, polyvinyl chloride was described by Regnault in 1838, by Meyer in 1866 and by Baumann in 1872 (13,14) but was not commercialized until the 1930 s. It is of interest to note that Baumann considered the solid polymer to be an isomer of vinyl chloride. 

The hydrochlorination of natural rubber is a straightforward addition reaction which proceeds according to Markownikoff s rule ... 

Hydrochlorination of natural rubber usually yields a polymer with slightly less than the theoretical chlorine content for complete reaction (e.g. 33 5 cf. 33-9%). NMR studies (Golub and Heller, 1964) have established that some cyclization occurs during hydrohalogenation and this can account for the discrepancy. 

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