There are provided a modified liquid diene rubber that can be used for a curable resin composition and a resin composition containing the modified liquid diene rubber. The curable resin composition containing the modified liquid diene rubber has a much higher curing rate than that in the related art, and the resulting cured product has excellent mechanical properties, transparency, and heat resistance. Produced are a modified liquid diene rubber and a resin composition containing the modified liquid diene rubber. The modified liquid diene rubber includes a modifying group (p) partly containing a (meth)acryloyl group therein and a monomer unit (a1) derived from a conjugated diene compound. A carbon-carbon double bond derived from the conjugated diene compound has a hydrogenation rate of 30 to 95 mol %, and the modifying group (p) has a functional group equivalent weight of 700 to 20,000 g/eq.

There are provided a modified liquid diene rubber that can be used for a curable resin composition and a resin composition containing the modified liquid diene rubber. The curable resin composition containing the modified liquid diene rubber has a much higher curing rate than that in the related art, and the resulting cured product has excellent mechanical properties, transparency, and heat resistance. Produced are a modified liquid diene rubber and a resin composition containing the modified liquid diene rubber. The modified liquid diene rubber includes a modifying group (p) partly containing a (meth)acryloyl group therein and a monomer unit (a1) derived from a conjugated diene compound. A carbon-carbon double bond derived from the conjugated diene compound has a hydrogenation rate of 30 to 95 mol %, and the modifying group (p) has a functional group equivalent weight of 700 to 20,000 g/eq.

A modified liquid diene-based rubber (A) including, in a molecule, a modified group (a) containing a (meth)acryloyl group as a part thereof and at least one modified group (b) selected from a dicarboxylic acid monoester and a dicarboxylic acid monoamide, with the proviso that the modified group (b) comprises no (meth)acryloyl group as a part thereof, wherein the functional group equivalent weights of the modified group (a) and the modified group (b) are each in the range of 700 to 40,000 g/eq. Also provided is a curable resin composition containing the modified liquid diene-based rubber.

A cross-linkable rubber composition for a seal material which is used at an oilfield or gas well comprising a nitrile group-containing copolymer rubber which contains ,-ethylenically unsaturated nitrile monomer units 10 to 60 wt % and has an iodine value of 120 or less, an ,-ethylenically unsaturated carboxylic acid metal salt (B), and an organic peroxide cross-linking agent (C) is provided. According to the present invention, it is possible to provide a rubber composition which is excellent in shapeability, is high in durability against hydrogen sulfide and other corrosive gases, and is suitable for application as a seal material which is used at an oilfield or gas well.