Patent ID: 7923518

Claim:
A nitrile rubber which contains repeating units of at least one α,β-unsaturated nitrile and, at least one conjugated diene and (i) has a calcium content of 150 ppm to 1290 ppm, based on the nitrile rubber, and a chlorine content of at least 40 ppm, based on the nitrile rubber, and (ii) contains 2,2,4,6,6-pentamethylheptane-4-thio, 2,4,4,6,6-pentamethylheptane-2-thio, 2,3,4,6,6-pentamethylheptane-2-thio and 2,3,4,6,6-pentamethylheptane-3-thio end groups, wherein the nitrile rubber has a storage stability of not more than 3 Mooney units, said storage stability calculated by the formula (I), storage stability = MV 2 −MV 1 (I) where MV1 is the Mooney viscosity of the nitrile rubber and MV2 is the Mooney viscosity of the same nitrile rubber after storage at 100 ° C. for 48 hours.