Copolymer rubber composition, rubber foamed product, and automotive sealant

Abstract

The copolymer rubber composition comprises 60 to 75% by weight of a copolymer rubber (1) and 40 to 25% by weight of a copolymer rubber (2), and [iodine value of the copolymer rubber (1)—iodine value of the copolymer rubber (2)] is 5 to 30. The copolymer rubber (1) is an ethylene-α-olefin-nonconjugated polyene copolymer rubber having an ethylene unit of 50 mol % to 70 mol %, an α-olefin unit of 50 mol % to 30 mol %, and an iodine value of 15 to 45, and the copolymer rubber (2) is an ethylene-α-olefinic copolymer rubber having an ethylene unit of more than 70 mol % and 95 mol % or less, an α-olefin unit of less than 30 mol % and 5 mol % or more, and an iodine value of 10 to 30.

1 . A copolymer rubber composition comprising:
 a copolymer rubber (1); and   a copolymer rubber (2), as a rubber component,   wherein the content of the copolymer rubber (1) is 60% by weight or more and 75% by weight or less, and the content of the copolymer rubber (2) is 40% by weight or less and 25% by weight or more, based on 100% by weight of the total of the copolymer rubber (1) and the copolymer rubber (2); and [iodine value of the copolymer rubber (1)—iodine value of the copolymer rubber (2)] is 5 or more and 30 or less, and   wherein,   the copolymer rubber (1) is an ethylene-α-olefin-nonconjugated polyene copolymer rubber wherein the content of a monomer unit based on ethylene is 50 mol % or more and 70 mol % or less; the content of a monomer unit based on α-olefin is 50 mol % or less and 30 mol % or more (provided that the total of the monomer unit based on ethylene and the monomer unit based on α-olefin is 100 mol %); and the iodine value is 15 or more and 45 or less, and   the copolymer rubber (2) is an ethylene-α-olefin-nonconjugated polyene copolymer rubber wherein the content of a monomer unit based on ethylene is more than 70 mol % and 95 mol % or less; the content of a monomer unit based on α-olefin is less than 30 mol % and 5 mol % or more (provided that the total of the monomer unit based on ethylene and the monomer unit based on α-olefin is 100 mol %); and the iodine value is 10 or more and 30 or less.   
     
     
         2 . The copolymer rubber composition according to  claim 1 , wherein the α-olefin is a propylene, and the nonconjugated polyene is at least one compound selected from the nonconjugated polyene group consisting of 5-ethylidene-2-norbornene, dicyclopentadiene and 5-vinyl-2-norbornene. 
     
     
         3 . The copolymer rubber composition according to  claim 1 , wherein the molecular weight distribution of a rubber component comprising the copolymer rubber (1) and the copolymer rubber (2) is 3 or more and 7 or less. 
     
     
         4 . The copolymer rubber composition according to  claim 1 , the rubber component comprising the copolymer rubber (1) and the copolymer rubber (2) being a rubber component obtained by a method using two tanks coupled in series involving manufacturing one of the copolymer rubber (1) and the copolymer rubber (2) in a first reaction tank, feeding the one copolymer rubber manufactured in the first reaction tank to a second reaction tank, and manufacturing the other copolymer rubber in the second reaction tank. 
     
     
         5 . A rubber foamed product, obtained by vulcanizing and foaming a copolymer rubber composition according to  claim 1  to a density of 0.3 kg/L or higher and 0.6 kg/L or lower. 
     
     
         6 . An automotive sealant, comprising the rubber foamed product according to  claim 5  as a sponge member.