Rubber hydrochloride

Reaction of the natural rubber hydrocarbon with hydrochloric acid yields rubber hydrochloride. The hydrogen chloride adds on according to Markownikoff s rule (that the halogen atom attaches itself to the carbon atom with the least number of hydrogen atoms). 

The hydrohalide is liable to dehydrochlorination, particularly when moist acid is used in its preparation, so that hydrochloric acid acceptors such as lead carbonate are useful stabilisers. Dibutyl phthalate and tritolyl phosphate are effective plasticisers. Rubber hydrochloride is used as a packaging film (Pliofilm) and as a rubber-to-metal bonding agent (e.g. Typly). 

Many chemical derivatives of mbber, produced in the course of attempts to elucidate the structure of mbber, became of practical commercial value but have been superseded by the diversity of synthetic polymers. See Cyclised Rubber, Chlorinated Rubber, Rubber Hydrochloride, Rubbone. 

Subramaniam, 1988]. Hydrochlorination, usually carried out at about 10°C, proceeds by electrophilic addition to give the Markownikoff product with chlorine on the tertiary carbon (Eq. 9-33) [Golub and Heller, 1964 Tran and Prud homme, 1977]. Some cyclization of the intermediate carbocation (XXVI) also takes place (Sec. 9-7). The product, referred to as rubber hydrochloride, has low permeability to water vapor and is resistant to many aqueous solutions (hut not bases or oxidizing acids). Applications include packaging film laminates with metal foils, paper, and cellulose films, although it has been largely replaced by cheaper packaging materials such as polyethylene. 

Fig. 199. Rubber hydrochloride. Molecular configuration suggested by the repeat distance and the principle of staggered bonds. (Hydrogen atoms omitted.)...

Fig. 200. Rubber hydrochloride. Projection along a. Consideration of arrangement with ti glide plane parallel to the paper.

The principal interest of the rubber hydrochloride structure (apart from its bearing on the theory of the relation between the physical properties and the molecular structure of polymers) is that it formed the first test of validity and usefulness of the principle of staggered bonds. Abnormal structures f In all the structures considered so far two... 

Hydrochloric acid forms a layer of rubber hydrochloride film when in contact with ebonite and this film prevents further reaction with the acid, thus protecting against corrosion. Similarly, wet chlorine forms a layer of chlorinated rubber film when in contact with ebonite, and this prevents further reaction with chlorine thereby giving protection against corrosion. 

These same types of compounds are also more resistant to many acids at high temperatures than natural rubber can handle. Neoprene should not be used in parts which are bonded to metal for hydrochloric acid service because acid migration can cause failures. For hydrochloric acid service ebonite lined mild steel equipment is the correct selection. Ebonites form rubber hydrochloride film in contact with natural rubber and this film is the protective layer against corrosion. 

Fig. 15. Temperature dependence on the dielectric constant of various polymers at 75cps. (O) Polyhexamethyl-ene-adipamide 0.005 in ( ) Silicone-bonded samica 0.004 in (O) Cellulose 0.005 in ( ) Polyimide 0.0048 in ( ) Polyethylene 0.005 in ( ) Rubber hydrochloride 0.002 in (A) Polyethylene terephthalate (Melinex) 0.005 in (A) Polyethylene terephthalate (Mylar) 0.002 in (V) Polypropylene 0.010 in (A) Polytetrafluoroethylene 0.0075 in (X) Polystyrene 0.005 in (+) Aromatic polyamide 0.0027 in (1 in = 2.54 cm)...

A cohort of 748 white male workers occupationally exposed to benzene for varying time periods between 1940 and 1949 in 2 manufacturing facilities producing rubber hydrochloride (Pliofilm ) has been studied (Infante 1978 Infante et al. 1977). The initial report (Infante et al. 1977) included evaluation of mortality statistics up to 1975, and the follow-up study (Infante 1978) included evaluation up to 1977. A summary of the overall results is presented here. Included for the study were all white males assigned to Pliofilm production who were hourly employees at any time between January 1, 1940 and December 31, 1949. 

Utterback DF, Rinsky RA. 1995. Benzene exposure assessment in rubber hydrochloride workers a critical evaluation of previous estimates. Am J Ind Med May 1995 27(5) 661-676. 

The association between benzene exposure and leukemia has been made since the late nineteenth century however, the dose-response relationship and mechanistic explanation have been quite contentious. The most reliable evidence associating chronic benzene exposure with AML was presented in a retrospective NIOSH study of rubber hydrochloride workers in Akron, OH, from 1940 to 1949. Unfortunately, the mechanism of how benzene exposure leads to the development of AML is not known. The two most frequently discussed potential mechanisms of toxicity involve either a point mutation or a chromosomal deletion. The latter is considered more likely since neither benzene nor its metabolites are mutagenic or teratogenic. 

Use Ingredient of polishes, special lubricants, and coatings lubricants for metals and in textile and molding industries in wax polishes as dye solvent plasticizer for laminated fiber products rubber hydrochloride chlorinated rubber and cable lacquers carbon paper and inks emolhent in cosmetic and pharmaceutical products lipsticks damp proofer for concrete flavoring. 

Use Production of vinyl chloride from acetylene and alkyl chlorides from olefins, hydrochlorination (see rubber hydrochloride), polymerization, isomerization, alkylation, and nitration reactions. 

---