This invention relates to dicycloalkyl-p-phenylene-diamines and to their use in vulcanized or vulcanizable rubber as a preservative or antidegradant.
N,N'-substituted p-phenylenediamine compounds have found extensive use in rubber compounds as antidegradants. Especially in protection against ozone attack these compounds have been shown to be very effective. When incorporated into vulcanizable rubber at a level of from 0.1 to 5 percent by weight, based on the weight of the rubber, their use is effective in preventing surface cracking of rubber articles, even in such extreme service conditions as are encountered in pneumatic tire sidewalls. There, the continual flexing action renders other protection methods (such as incorporation of wax in the rubber compound) relatively ineffective. While wax offers protection against ozone in static use, the presence of wax in a rubber compound can actually have a negative effect on dynamic ozone resistance.
Many N,N'-substituted p-phenylenediamine compounds have been suggested for this use, and a number have found widespread acceptance in the rubber industry. Some of these compounds, however, are relatively expensive or difficult to prepare, exhibit skin-sensitizing behavior, or are in a form so as to be difficult to handle in the rubber mixing operations.