A New Material: Anhydride Rubber. I

In earlier work on the action of various unsaturated compounds on rubber, Compagnon and the present author described briefly a new reaction of maleic anhydride. It should be added, as a matter of record, that the reaction of maleic anhydride and rubber had already been studied by Bacon and Farmer, who, in a very interesting work, described a process for obtaining addition products of rubber and maleic anhydride. It is well, therefore, first of all to describe the principle of their work and the results which were obtained. The first observation made by Bacon and Farmer was that when a toluene solution of milled crude rubber is heated for several hours at about 100° C with maleic anhydride in the presence of benzoyl peroxide, which acts as a catalyst, a definite reaction takes place. The reaction product can be precipitated by alcohol, and can then be recovered in the form of a white or pale yellow resin which does not have any of the elastic properties of rubber. In a more extensive investigation of the reaction, where the experimental conditions were varied, e.g., the proportions of benzoyl peroxide and of maleic anhydride, nature of the solvent, concentration of the solution, and time and temperature of heating, Bacon and Farmer succeeded in obtaining a true series of addition products, whose properties changed progressively with the proportion of chemically combined maleic anhydride. With increase in the proportion of maleic anhydride, there was a gradual transition from products which were still somewhat rubbery to fibrous products, and finally to hard brittle resins which contained more than one-third by weight of chemically combined maleic anhydride and which had none of the physical properties characteristic of rubber. As might be expected, the solubilities likewise changed progressively from products which were soluble in rubber solvents to those which were soluble in solvents for maleic anhydride; e.g., some of the derivatives were soluble in boiling ethyl alcohol.