COPOLYMER RUBBER CONTAINING NITRILE GROUP, CROSSLINKABLE RUBBER COMPOSITION, AND RUBBER CROSSLINKED PRODUCT

A nitrile group-containing copolymer rubber which has a hydroxyl group, carboxyl group, or carbon-carbon double bond at an end carbon atom or on a carbon atom which bonds with the end carbon atom is provided. The nitrile group-containing copolymer rubber of the present invention is preferably obtained by a metathesis reaction. According to the present invention, a nitrile group-containing copolymer rubber which is excellent in cross-linkability can be provided.