Sulfur-vulcanized rubber compositions comprising substituted succinimide compounds

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, wherein said process is carried out in the presence of 0.1 to 10 parts by weight of a coagent of the formula I:

• ##STR4## wherein R.sub.1 and R.sub.2 represent each independently hydrogen or a leaving group suitable to form an endocyclic or exocyclic double bond;
• R.sub.3 and R.sub.4 are independently selected from hydrogen, OH, CH.sub.2 OH, CH.sub.2 Cl, CH.sub.2 Br, CH.sub.2 NH.sub.2, CH.sub.2 CN, CH.sub.2 I, CHF.sub.2, CHClBr, CHI.sub.2, CH.sub.2 R.sub.1, CH.sub.2 R, CH.sub.2 OR, SO.sub.2 R, CHCl.sub.2, CCl.sub.3, CHBr.sub.2, CBr.sub.3, CH.sub.2 F and CF.sub.3, wherein R is hydrogen, C.sub.1-10 alkyl, C.sub.6-18 aryl, C.sub.7-20 alkaryl or C.sub.7-20 aralkyl, the aryl groups being optionally substituted;
• provided that R.sub.1 and R.sub.3, and R.sub.2 and R.sub.4, are not both hydrogen;
• R.sub.5 and R.sub.6 are independently selected from the same substituents as for R.sub.3 and may also be halogen;
• B.sub.1, B.sub.2, B.sub.3, and B.sub.4 are independently selected from oxygen and sulfur;
• n is an integer from 1 to 10;
• and D is an (n+1) polyvalent radical;
• to compensate for from 10 to 200 percent of the reversion of said rubber composition.

A method for improving the physical properties of rubber which comprises vulcanizing said rubber in the presence of a coagent of the formula I:

• ##STR5## wherein R.sub.1 and R.sub.2 represent each independently hydrogen or a leaving group suitable to form an endocyclic or exocyclic double bond;
• R.sub.3 and R.sub.4 are independently selected from hydrogen, OH, CH.sub.2 OH, CH.sub.2 Cl CH.sub.2 Br, CH.sub.2 HN.sub.2, CH.sub.2 CN, CH.sub.2 I, CHF.sub.2, CHClBr, CHI.sub.2, CH.sub.2 R.sub.1, CH.sub.2 R, CH.sub.2 OR, SO.sub.2 R, CHCl.sub.2, CCl.sub.3, CHBr.sub.2, CBr.sub.3, CH.sub.2 F and CF.sub.3, wherein R is hydrogen, C.sub.1-10, alkyl, C.sub.6-18 aryl, C.sub.7-20 alkaryl or C.sub.7-20 aralkyl, the aryl groups being optionally substituted;
• provided that R.sub.1 and R.sub.3, and R.sub.2 and R.sub.4, are not both hydrogen;
• R.sub.5 and R.sub.6 are independently selected from the same substituents as for R.sub.3 and may also be halogen;
• B.sub.1, B.sub.2, B.sub.3, and B.sub.4 are independently selected from oxygen and sulfur;
• n is an integer from 1 to 10;
• and D is an (n+l) polyvalent radical;
• in an amount effective to compensate for from 10 to 200 percent of the reversion of said rubber composition.