Process for devulcanization of cured rubbers

Abstract

This invention is based upon the unexpected discovery that cured rubber can be devulcanized by heating it to a temperature of at least about 150° C. under a pressure of at least about 3.4×106 Pascals in the presence of a solvent selected from the group consisting of alcohols and ketones having a critical temperature within the range of about 200° C. to about 350° C. The molecular weight of the rubber can be maintained at a relatively high level if the devulcanization is carried out at a temperature of no more than about 300° C. This devulcanization technique does not significantly change the microstructure of the rubber. In other words, the devulcanized rubber can be recompounded and recured into useful articles in substantially the same way as was the original rubber. This invention more specifically discloses a process for devulcanizing cured rubber into devulcanized rubber that is capable of being recompounded and recured into useful rubber products, said process comprising (1) heating the cured rubber to a temperature which is within the range of about 150° C. to about 300° C. under a pressure of at least about 3.4×106 Pascals in the presence of a solvent selected from the group consisting of alcohols and ketones, wherein said solvent has a critical temperature which is within the range of about 200° C. to about 350° C., to devulcanize the cured rubber into the devulcanized rubber thereby producing a slurry of the devulcanized rubber in the solvent; and (2) separating the devulcanized rubber from the solvent.

Dependencies are inferred from the claim text.