Natural rubber hydrochloride

The possibility of tacticity is not, of course, restricted to vinyl polymers. Other types of polymer which contain asymmetric carbon atoms and which ha/e been obtained in tactic forms include poly(propylene oxide) and natural rubber hydrochloride ... 

On the commercial scale natural rubber hydrochloride is manufactured either by reaction in solution or in a positively charged latex. The polymer is polycrystalline and is a tough semi-elastic material. It is marketed as a packaging film (Pliofilm) and as a rubber-to-metal adhesive (Ty-Ply). 

As in the case of hydrohalogenation the bulk of the theoretical studies on the halogenation of diene polymers has been made on natural rubber with chlorine as the halogen. As with natural rubber hydrochloride the derivative has some commercial value. 

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). 

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. 

Natural rubber offers excellent resistance to most inorganic salt solutions, alkalies, and nonoxidizing acids. Hydrochloric acid will react with soft rubber to form rubber hydrochloride, and therefore, it is not recommended that natural rubber be used for items that will come into contact with that... 

Typically, rubber hydrochloride is prepared by treating a solution of masticated natural rubber in benzene with hydrogen chloride at 10°C for about 6 hours. Usually, the material is isolated in film form, in which case the solution is neutralized and a plasticizer (e.g., tritolyl phosphate or dibutyl phthalate) added. The mixture is then cast on to a belt which passes through a chamber at lOO C. The solvent evaporates to leave a continuous film. 

Over the years many chemical derivatives of rubbers have been introduced. These include chlorinated rubber, rubber hydrochloride and cyclized rubber. Whilst little work was done in this area in the period 1955-75 the renewed appreciation that natural rubber, unlike coal and oil, is a replaceable raw material has stimulated further study of the products to be derived from it. 

In 1900 Weber passed hydrogen chloride into a chloroform solution of natural rubber to produce what is commonly known as rubber hydrochloride . While natural rubber, the synthetic 1,4- and 3,4-polyisoprenes and poly-1,4-dimethyl butadiene add hydrochloric acid with ease (a, b, and c, respectively), 1,2-polyisoprene and the 1,2- and 1,4-polybutadienes (d, e and f, respectively) are relatively unreactive. 

This chapter has considered the application of several well-known reactions of alkenes to diene polymers. Whilst the basic reactions are generally predictable from a knowledge of alkene reactivity they are influenced by the fact that the double bond is part of a very long chain molecule consisting of double bond-containing repeat units. In particular the tendency to cyclize has been noted, for example in the case of chlorinated natural rubber and with rubber hydrochloride whilst in other cases degradation or cross-linking has occurred. It may be noted here that the ability to produce cyclized natural rubber is a direct consequence of the affinity of a carbonium ion for a double bond when activated in a polymeric environment. 

In ordinary vulcanized rubber used in tire industries, the material contains about 2-3% sulfur. If this sulfur content is increased to about 30%, the resultant material is a very hard nonrubbery material known as ebonite or hard rubber. The double bonds of natural rubber can easily imdergo addition reaction with hydrochloric acid, forming rubber hydrochloride ... 

Pyridine is a flammable, colorless, and relatively stable and unreactive liquid with a characteristic pungent, unpleasant odor. Anhydrous pyridine has a boiling point of 115 °C and a density of 0.9819 g/cm. Pyridine is miscible with water and virtually all organic solvents. It is weakly basic, and with hydrochloric acid it forms a crystalline hydrochloride salt, which melts at 145-147 °C. Pyridine was first isolated from bone pyrolysates. Its name was derived from the Greek for fire pyr and the suffix idine was used to designate aromatic bases. Pyridine is also used as a solvent, and its derivatives have been used as pharmaceuticals, vitamins, food flavorings, paints, dyes, rubber products, adhesives, insecticides, and herbicides, etc Pyridine can also be formed from the breakdown of many natural materials in the environment. 

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