| 摘要 |
PROBLEM TO BE SOLVED: To provide an unsaturated nitrile-conjugated diene-based rubber that has excellent processability and can produce a vulcanized rubber having excel lent balance between mechanical properties, resistance to oil and the like, a rubber composition including the unsaturated nitrile-conjugated diene-based rubber and methods of producing the rubber and rubber composition. SOLUTION: After starting with prescribed amounts of olefinically unsaturated nitrile monomers and conjugated diene monomers, the polymerization is continued as these monomers are fed continuously or stepwise at a specific weight ratio to produce the objective unsaturated nitrile-conjugated diene-based rubber that has (A) an olefinic unsaturated nitrile monomer unit, for example acrylonitrile, and (B) a conjugated diene monomer unit, for example, butadiene as the recurring units wherein the content of the component (A) is 55-80 mass %, particularly exceeds 60 mass %, when the total amount of (A) and (B) is calculated as 100 mass %, the glass transition point is -15 to 30 deg.C, particularly -10 to 20 deg.C and the glass transition extrapolation terminal temperature is <=70 deg.C, particularly <=50 deg.C.
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