| abstract |
(57) [Summary] [Purpose] By compounding a specific compound into rubber, Improves adhesion and rubber hardness in vulcanization adhesion with a reinforcing material. [Structure] Per 100 parts by weight of a rubber component (A) such as natural rubber, (B) 2,4,4-trimethyl-2 ', 0.5-10 parts by weight of 4 ', 7-trihydroxyflavan, and (C) formula (X) [In the formula, k is 0, 1 or 2, and the group enclosed by () 2-k is 2-position or 6-position of 1,3-benzenediol. Bound to the position] and 7,7'-dihydroxy-4,4,4 ', 4'-tetramethyl-2, A rubber composition is obtained by blending 0.005 to 1 part by weight of a chroman compound selected from 2'-spirobichroman. The rubber composition is vulcanized under contact with the reinforcing material to bond the two. Further, an additive for rubber containing the compound (B) and the chroman compound (C) as active ingredients, and a chroman compound of the formula (X) are also provided. |