An acrylic rubber containing 100 parts by mass of an alkyl acrylate and 30 parts by mass or more of an alkyl methacrylate, as monomer units.

An acrylic rubber containing 100 parts by mass of an alkyl acrylate and 30 parts by mass or more of an alkyl methacrylate, as monomer units.

A nitrile-group-containing copolymer rubber, including 15% by weight or more and less than 28% by weight of α,β-ethylenically unsaturated nitrile monomer units (a), 10 to 50% by weight of α,β-ethylenically unsaturated monocarboxylic acid ester monomer units (b), 22 to 74% by weight of conjugated diene monomer units (c), and 1 to 10% by weight of carboxyl group-containing monomer units (d) and having an iodine value of 120 or less, wherein the conjugated diene monomer units (c) are at least partially hydrogenated, and the proportion of isoprene units in the conjugated diene monomer units (c) is 5% by weight or more and less than 33% by weight.

A nitrile-group-containing copolymer rubber, including 15% by weight or more and less than 28% by weight of α,β-ethylenically unsaturated nitrile monomer units (a), 10 to 50% by weight of α,β-ethylenically unsaturated monocarboxylic acid ester monomer units (b), 22 to 74% by weight of conjugated diene monomer units (c), and 1 to 10% by weight of carboxyl group-containing monomer units (d) and having an iodine value of 120 or less, wherein the conjugated diene monomer units (c) are at least partially hydrogenated, and the proportion of isoprene units in the conjugated diene monomer units (c) is 5% by weight or more and less than 33% by weight.

An acrylic rubber including: a polymer composition of: 70 to 99.9% by weight of a bonding unit derived from at least one (meth) acrylic acid ester selected from (meth) acrylic acid alkyl ester and (meth) acrylic acid alkoxyalkyl ester; 0.1 to 10% by weight of a bonding unit derived from a monomer containing a reactive group; and 0 to 20% by weight of a bonding unit derived from other monomer, wherein ash content is 0.15% by weight or less, total amount of sodium and sulfur in the ash is 60% by weight or more, a ratio of sodium to sulfur by weight ratio is in the range of 0.5 to 2.5, ratio of Z-average molecular weight to weight average molecular weight is 1.3 or more, and weight average molecular weight is in the range of 1,000,000 to 5,000,000.

An acrylic rubber including: a polymer composition of: 70 to 99.9% by weight of a bonding unit derived from at least one (meth) acrylic acid ester selected from (meth) acrylic acid alkyl ester and (meth) acrylic acid alkoxyalkyl ester; 0.1 to 10% by weight of a bonding unit derived from a monomer containing a reactive group; and 0 to 20% by weight of a bonding unit derived from other monomer, wherein ash content is 0.15% by weight or less, total amount of sodium and sulfur in the ash is 60% by weight or more, a ratio of sodium to sulfur by weight ratio is in the range of 0.5 to 2.5, ratio of Z-average molecular weight to weight average molecular weight is 1.3 or more, and weight average molecular weight is in the range of 1,000,000 to 5,000,000.

An acrylic rubber includes 20 to 35% by weight of ethyl methacrylate units (a), 0 to 20% by weight of ethyl acrylate units (b), 50 to 75% by weight of n-butyl acrylate units (c), and 0.5 to 4% by weight of carboxyl group-containing monomer units (d).

An acrylic rubber includes 20 to 35% by weight of ethyl methacrylate units (a), 0 to 20% by weight of ethyl acrylate units (b), 50 to 75% by weight of n-butyl acrylate units (c), and 0.5 to 4% by weight of carboxyl group-containing monomer units (d).

An aspect of the present invention is an acrylic rubber containing an alkyl acrylate, an alkyl methacrylate and ethylene as monomer units, wherein a content of a polyvinyl alcohol in the acrylic rubber is 0.5 to 2% by mass.

An aspect of the present invention is an acrylic rubber containing an alkyl acrylate, an alkyl methacrylate and ethylene as monomer units, wherein a content of a polyvinyl alcohol in the acrylic rubber is 0.5 to 2% by mass.