Rubber composition adhesive to metal surface, laminated body of rubber composition and metal, vulcanized rubber product, and method of producing vulcanized rubber product

1. A rubber composition adhesive to a metal surface, the rubber composition being capable of adhering to a metal surface, the rubber composition comprising:

a diene polymer selected from the group consisting of styrene-butadiene rubber (SBR), nitrile-butadiene rubber (NBR), and ethylene-propylene-diene rubber (EPDM),

from 1.0 part by mass to 15 parts by mass of water, per 100 parts by mass of the diene polymer that can be sulfur-vulcanized, and

from 3.0 parts by mass to 6.0 parts by mass of a poly(acrylic acid) partial sodium salt crosslinked product as a water absorbing resin, per 100 parts by mass of diene polymer that can be sulfur-vulcanized.

2. The rubber composition adhesive to a metal surface according to claim 1 , the rubber composition further comprising a vulcanizing agent.

3. A laminated body of a rubber composition and a metal, in which a rubber layer containing the rubber composition adhesive to a metal surface and a reinforcing layer having a metal surface are laminated,

wherein the rubber composition comprises:

a diene polymer selected from the group consisting of styrene-butadiene rubber (SBR), nitrile-butadiene rubber (NBR), and ethylene-propylene-diene rubber (EPDM);

a poly(acrylic acid) partial sodium salt crosslinked product as an water absorbing resin; and

water,

wherein an amount of the water absorbing resin is 3.0 parts by mass to 6.0 parts by mass, and an amount of the water is 1.0 part by mass to 15 parts by mass, per 100 parts by mass of the diene polymer that can be sulfur-vulcanized.

4. The laminated body of a rubber composition and a metal according to claim 3 , wherein the metal surface is a brass-plated metal surface.

5. The laminated body of a rubber composition and a metal according to claim 4 , wherein the reinforcing layer has a braided structure in which wires have been braided, or a spiral structure.

6. A vulcanized rubber product, in which the rubber layer of the laminated body of a rubber composition and a metal described in claim 3 is vulcanized in the presence of a sulfur-containing vulcanizing agent and adhered to the reinforcing layer.

7. The vulcanized rubber product according to claim 6 , wherein the vulcanized rubber product is a hydraulic hose or a high pressure hose.

8. The vulcanized rubber product according to claim 7 , wherein the hydraulic hose or the high pressure hose is vulcanized by passing through an oven vulcanization device.

9. A method of producing a vulcanized rubber product, the method comprising:

a laminating step for producing a laminated body by laminating a reinforcing layer in which a surface is plated with brass and at least one rubber layer; and

a vulcanization adhering step of vulcanizing the rubber layer by passing the laminated body through an oven vulcanization device and adhering the brass-plated reinforcing layer;

the rubber layer being a rubber composition containing:

a diene polymer selected from the group consisting of styrene-butadiene rubber (SBR), nitrile-butadiene rubber (NBR), and ethylene-propylene-diene rubber (EPDM);

from 1.0 part by mass to 15 parts by mass of water, per 100 parts by mass of the diene polymer that can be sulfur-vulcanized, and

from 3.0 parts by mass to 6.0 parts by mass of a poly(acrylic acid) partial sodium salt crosslinked product as a water absorbing resin, per 100 parts by mass of diene polymer that can be sulfur-vulcanized; and

the vulcanized rubber product further comprising a sulfur-containing vulcanizing agent.

10. The laminated body according to claim 3 , wherein an adhesive strength of the rubber composition adhesive is with the range of 3.0 kN/m to 4.5 kN/m based on an adhesion test selected from steam vulcanization adhesion between newly kneaded rubber and brass-plated wires or oven vulcanization adhesion between newly kneaded rubber and brass-plated wires.