In the past, nitrile rubber (acrylonitrile-butadiene copolymer rubber), taking advantage of its oil resistance, mechanical characteristics, chemical resistance, etc., has been used as a material for hoses, tubes, and other rubber parts for automobiles. Further, hydrogenated nitrile rubber (hydrogenated acrylonitrile-butadiene copolymer rubber) which is obtained by hydrogenating the carbon-carbon double bonds in the polymer main chain of nitrile rubber is further excellent in heat resistance, so is used for seals, belts, hoses, diaphrams, and other rubber parts.
In such a nitrile rubber, for example, in Patent Document 1, to suppress the rise in Mooney viscosity at the time of hydrogenation, the method is proposed of metathesis decomposition of the nitrile rubber in the presence of a catalyst and phosphane or diphosphane.