Patent ID: 8633280

Claim:
A method of depolymerizing a nitrile butadiene rubber (NBR) or styrene-butadiene rubber, comprising contacting a nitrile butadiene rubber (NBR) or styrene-butadiene rubber at 30-100° C. in the presence of at least one transition metal catalyst represented by the formula Ia or Ib: wherein: m=0 or 1, n=0 or 1; when n=0, p=0 or 1; when n=1, p=0; when m=0, n=1 or n=0 and p=1; when m=1, n=0 or 1 and p=0 or 1, wherein when n=1, p=0; M is a transition metal selected from the group consisting of ruthenium (Ru), molybdenum (Mo) and tungsten (W); L 1 and L 2 are the same or different and each are selected from the group consisting of halide anion, carboxylate and aryloxide anion; L is an electron-donating ligand; “Y X” is either single bond or double bond; when m=1, X is oxygen, nitrogen, sulfur, CH, CH 2 or carbonyl and Y is nitrogen, oxygen, CH, CH 2 or imino; when m=0, Y is oxygen, nitrogen, carbonyl or imino; when n=0 and p=1, L 3 is an electron-donating ligand; when n=1 and p=0, X 1 and Y 1 each is oxygen, nitrogen, sulfur, carbonyl, imino, CH or CH 2 ; R 1 is H, alkyl, alkenyl, aryl, arylenyl, alkoxy, alkylthio, arylthio, aryloxy, heteroaryl or heterocyclic group; R 2 is H, halogen, alkyl, aryl, alkylcarbonyl, arylcarbonyl, alkyoxycarbonyl, aryloxycarbonyl, aminocarbonyl, heteroaryl or heterocyclic group; and E, E 1 , E 2 , E 3 , E 4 , E 5 , E 6 and E 7 are each independently selected from the group consisting of H, halogen atom, nitro, amino, cyano, formyl, sulfinyl, sulfonyl, alkyl, alkoxy, alkylthio, alkenyloxy, silanyl, alkylsilyloxy, aryl, aryloxy, alkylcarbonyl, arylcarbonyl, alkoxycarbonyl, aryloxycarbonyl, alkylaminocarbonyl, arylaminocarbonyl, alkylamido, arylamido, alkylaminosulfonyl, arylaminosulfonyl, sulfonylamido, heteroaryl and heterocyclic group; each optionally substituted with an alkyl, alkoxy, alkylthio, aryl, aryloxy, halogen atom and heterocyclic group.