Ethylene-propylene-diene rubber, elastomer composition and vulcanized rubber thereof

A vulcanized rubber obtained by vulcanizing a vulcanizable elastomer composition comprising an unvulcanized vulcanizable rubber mixture which mixture consists essentially of

• (A) 90 to 40% by weight of a high-molecular-weight ethylene-propylene-diene rubber having an ethylene content of 60 to 82 mol %, an intrinsic viscosity ( ) of 3.0 to 5.0 dl/g as measured at 135.degree. C. in decalin and an iodine value of 8 to 35,
• (B) 10 to 60% by weight of a low-molecular-weight ethylene-propylene-diene rubber having an ethylene content of 60 to 82 mol %, an intrinsic viscosity ( ) of 0.15 to 0.8 dl/g as measured at 135.degree. C. in decalin and an iodine value of 8 to 35, and
• (C) sulfur, in an amount of 0.1 to 3 parts by weight based on 100 parts by weight of said ethylene-propylene-diene rubber, wherein the sulfur is uniformly dispersed therein at a temperature of 90.degree. to 160.degree. C., prior to the addition of a vulcanization accelerator, and
• (D) a vulcanization accelerator, wherein the ethylene-propylene-diene rubber has a Mooney viscosity of ML.sub.1+4 (100.degree. C.) of 60 to 120.

A process for preparing a vulcanized rubber which comprises the successive steps of:

• (a) uniformly dispersing sulfur at a temperature of 90.degree.-160.degree. C. in an ethylene-propylene-diene rubber, in an amount of 0.1 to 5.0 parts by weight of sulfur based on 100 parts by weight of the rubber, which is a mixture of
• (A) 90-40% by weight of a high-molecular-weight ethylene-propylene-diene rubber having an ethylene content of 60 to 80 mol %, an intrinsic viscosity (.eta.) of 3.0 to 5.0 dl/g as measured at 135.degree. C. in decalin and an iodine value of 8 to 35, and
• (B) 10 to 60% by weight of a low-molecular-weight ethylene-propylene-diene rubber having an ethylene content of 60 to 82 mol %, an intrinsic viscosity (.eta.) of 0.15 to 0.8 dl/g as measured at 135.degree. C. in decalin and an iodine value of 8 to 35, wherein the sulfur is dispersed prior to the addition of an accelerator, to obtain an unvulcanized vulcanizable rubber having a Mooney viscosity ML.sub.1+4 (100.degree. C.) of 60 to 120,
• (b) adding an accelerator to the sulfur dispersed mixture to produce a vulcanizable elastomer composition, and
• (c) vulcanizing the vulcanizable elastomer composition to obtain vulcanized rubber.

A vulcanized rubber obtained by vulcanizing a vulcanizable elastomer composition comprising an ethylene-propylene-diene rubber mixture which consists essentially of

• (A) 90 to 40% by weight of a high-molecular weight ethylene-propylene-diene rubber having an ethylene content of 60 to 82 mol %, an intrinsic viscosity ( ) of 3.0 to 5.0 dl/g as measured at 135.degree. C. in decalin and an iodine value of 8 to 35,
• (B) 10 to 60% by weight of a low-molecular-weight ethylene-propylene-diene rubber having an ethylene content of 60 to 82 mol %, an intrinsic viscosity ( ) of 0.15 to 0.8 dl/g as measured at 135.degree. C. in decalin and an iodine value of 8 to 35, and
• (C) sulfur, in an amount of 0.1 to 3 parts by weight based on 100 parts by weight of said ethylene-propylene-diene rubber, wherein the sulfur is uniformly dispersed therein by mixing a solution of sulfur with a solution of ethylene-propylene-diene rubber, followed by removing the solvent, prior to the addition of a vulcanization accelerator, and
• (D) a vulcanization accelerator, wherein the ethylene-propylene-diene rubber has a Mooney viscosity ML.sub.1+4 (100.degree. C.) of 60 to 120.

A process for preparing a vulcanized rubber which comprises the successive steps of:

• (a) uniformly dispersing sulfur in an ethylene-propylene-diene rubber by mixing a solution of the sulfur with a solution of the ethylene-propylene-diene rubber at a temperature of 90.degree. to 160.degree. C., in an amount of 0.1 to 3.0 parts by weight of sulfur based on 100 parts by weight of the rubber, prior to the addition of a vulcanization accelerator to obtain a vulcanizable elastomer composition,
• (b) removing the solvent,
• (c) adding a vulcanization accelerator, and
• (d) vulcanizing the vulcanizable elastomer composition to obtain the vulcanized rubber, wherein said ethylene-propylene-diene rubber is a mixture of
• (A) 90 to 40% by weight of a high-molecular-weight ethylene-propylene-diene rubber having an ethylene content of 60 to 82 mol %, an intrinsic viscosity (.eta.) of 3.0 to 5.0 dl/g as measured at 135.degree. C. in decalin and an iodine value of 8 to 35,
• (B) 10 to 60% by weight of a low-molecular-weight ethylene-propylene-diene rubber having an ethylene content of 60 to 82 mol %, an intrinsic viscosity (.eta.) of 0.15 to 0.8 dl/g as measured at 135.degree. C. in decalin and an iodine value of 8 to 35, wherein the ethylene-propylene-diene rubber has a Mooney viscosity ML.sub.1+4 (100.degree. C.) of 60 to 120.