Nitrile rubber composition and rubber cross-linked product

1. A nitrile rubber composition, comprising:

a carboxyl group-containing nitrile rubber having an iodine value of 120 or less and containing 5 to 30% by weight of an α,β-ethylenically unsaturated nitrile monomer unit, 0.1 to 10% by weight of a carboxyl group-containing monomer unit, 15 to 60% by weight of an α,β-ethylenically unsaturated monocarboxylic acid ester monomer unit, and 20 to 64.9% by weight of a conjugated diene monomer unit;

a reactive silicone oil; and

silica, wherein

the reactive silicone oil has a content ratio of 0.1 to 2 parts by weight with respect to 100 parts by weight of the carboxyl group-containing nitrile rubber,

wherein the silica has a content ratio of 20 to 80 parts by weight with respect to 100 parts by weights of the carboxyl group-containing nitrile rubber; and

wherein the reactive silicone oil is a compound represented by the following general formula (1):

wherein, in the above formula (1), R 1 is a hydrocarbon group having 1 to 30 carbon atoms that may have a heteroatom in a main chain and/or a side chain; X 1 is a reactive group having an amino group; “m” is an integer of 1 to 10,000; and “n” is an integer of 1 to 10,000.

2. The nitrile rubber composition according to claim 1 , wherein the reactive silicone oil has a content ratio of 1 to 2 parts by weight with respect to 100 parts by weight of the carboxyl group-containing nitrile rubber.

3. The nitrile rubber composition according claim 1 , further comprising a polyamine cross-linking agent.

4. A cross-linked rubber obtained by cross-linking the nitrile rubber composition according to claim 1 .

5. The cross-linked rubber according to claim 4 which is a seal material, a belt, a hose, or a gasket.

6. The nitrile rubber composition according to claim 1 , wherein the carboxyl group-containing nitrile rubber has an iodine value of 60 or less and contains 8 to 27% by weight of the α,β-ethylenically unsaturated nitrile monomer unit, 1 to 9% by weight of the carboxyl group-containing monomer unit, 18 to 55% by weight of the α,β-ethylenically unsaturated monocarboxylic acid ester monomer unit, and 25 to 60% by weight of the conjugated diene monomer unit.

7. The nitrile rubber composition according to claim 1 , wherein the carboxyl group-containing nitrile rubber has an iodine value of 40 or less and contains 10 to 25% by weight of the α,β-ethylenically unsaturated nitrile monomer unit, 2 to 8% by weight of the carboxyl group-containing monomer unit, 20 to 50% by weight of the α,β-ethylenically unsaturated monocarboxylic acid ester monomer unit, and 30 to 50% by weight of the conjugated diene monomer unit.

8. The nitrile rubber composition according to claim 1 , wherein the carboxyl group-containing nitrile rubber has an iodine value of 30 or less and contains 15 to 24.5% by weight of the α,β-ethylenically unsaturated nitrile monomer unit, 3 to 7% by weight of the carboxyl group-containing monomer unit, 20 to 50% by weight of the α,β-ethylenically unsaturated monocarboxylic acid ester monomer unit, and 30 to 50% by weight of the conjugated diene monomer unit.

9. The nitrile rubber composition according to claim 1 , wherein the carboxyl group-containing nitrile rubber has an iodine value of 15 or less and contains 15 to 24.5% by weight of the α,β-ethylenically unsaturated nitrile monomer unit, 3 to 7% by weight of the carboxyl group-containing monomer unit, 20 to 50% by weight of the α,β-ethylenically unsaturated monocarboxylic acid ester monomer unit, and 30 to 50% by weight of the conjugated diene monomer unit.