Vulcanized rubber composition and production method thereof

A method for producing a vulcanized rubber composition, comprising:

• a first kneading step of obtaining a kneaded mixture comprising:
• a rubber component comprising at least one selected from the group consisting of natural rubbers and synthetic rubbers, a filler comprising an inorganic filler, and a sulfur-containing silane coupling agent;
• a second kneading step of adding sulfur and a vulcanization accelerator to the kneaded mixture, followed by kneading, to thereby obtain an unvulcanized rubber composition;
• and
• a vulcanization step of vulcanizing the unvulcanized rubber composition to thereby obtain a vulcanized rubber composition having a glass transition temperature of −30° C. or more and 0° C. or less, wherein
• at least one selected from the group consisting of compounds represented by formulae (1), (2), and (3) below is added, followed by kneading, in the first kneading step:
• wherein X is an acid that forms a salt together with a guanidine moiety;
• wherein X is an acid that forms a salt together with a guanidine moiety, R1 and R2 are each independently any one selected from the group consisting of a hydrogen atom and an alkyl group, a cycloalkyl group, an aryl group, an alkyl aryl group, and an alkenyl group which have 1 to 18 carbon atoms, these groups each optionally having one or more substituents containing at least one selected from the group consisting of a sulfur atom, a nitrogen atom, and an oxygen atom;
• and
• wherein X is an acid that forms a salt together with a guanidine moiety.