Copolymer rubber composition, molded 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 exhibits a difference in iodine value of 5 to 30 between the copolymer rubber (1) and the copolymer rubber (2). 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 10 to 30, 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 0 to 8.

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 the difference in iodine value between the copolymer rubber (1) and 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 10 or more and 30 or less, and   the copolymer rubber (2) is an ethylene-α-olefinic 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 0 or more and 8 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 , a 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 molded product, obtained by vulcanizing a copolymer rubber composition according to  claim 1 . 
     
     
         6 . The molded product according to  claim 5 , wherein the molded product has a density of 0.7 kg/L or more and 1.1 kg/L or less, and a hardness of 30 to 100. 
     
     
         7 . An automotive sealant, comprising the molded product according to  claim 5  as a solid member.