Anti-fatigue coagents for rubber vulcanization

A process for the vulcanization, at a temperature of from 110.degree. to 220.degree. C. for up to 24 hours, of a vulcanizable composition comprising at least one natural or synthetic rubber in the presence of 0.1 to 25 parts by weight of sulfur or a sufficient amount of a sulfur donor to provide the equivalent of 0.1 to 25 parts by weight of sulfur, characterized in that said process is carried out in the presence of an effective amount of an anti-fatigue coagent represented by the formulas I and II:

• ##STR5## wherein R.sub.1, R.sub.2 and R.sub.3 are independently selected from hydrogen, C.sub.1 -C.sub.18 alkyl groups, C.sub.3 -C.sub.18 cycloalkyl groups, C.sub.6 -C.sub.18 aryl groups, C.sub.7 -C.sub.30 aralkyl groups and C.sub.7 -C.sub.30 alkaryl groups and R.sub.2 and R.sub.3 may combine to form a ring when R.sub.1 is hydrogen;
• R.sub.4 is selected from divalent, trivalent or tetravalent linear or branched radical chosen from a C.sub.1 -C.sub.18 alkyl, C.sub.2 -C.sub.18 alkenyl, C.sub.2 -C.sub.18 alkynyl, C.sub.3 -C.sub.18 cycloalkyl, C.sub.3 -C.sub.18 polycycloalkyl, C.sub.6 -C.sub.18 aryl, C.sub.6 -C.sub.30 polyaryl, C.sub.7 -C.sub.30 aralkyl, C.sub.7 -C.sub.30 alkaryl, oligomers of one or more of these radicals, and which radicals may optionally contain one or more of oxygen, nitrogen, silicon, phosphorus, sulfur, sulphone, sulfoxy and boron;
• B and B.sup.1 are independently selected from the following hetero atoms:
• oxygen and sulfur, X is a metal selected from Mg, Ti, Zn, Cd, Sr, Ba, Fe, V, Sn, Te, Mo, Mn, Pb and Al, m is an integer from 1-3 and n is an integer of from 2-4.