Abstract: The present invention is an additive for rubber comprising a compound represented by the following chemical formula (1): wherein each of R1 and R2 is an aliphatic hydrocarbon group with 1 or more and 33 or less carbons; a total number of carbons in R1 and R2 is 2 or more and 34 or less; X is a single bond or an aliphatic hydrocarbon group with 1 or more and 5 or less carbons; A represents —O—CH2—CH(OH)—CH2OH, —O—CH (—CH2—OH)2 or —N (R3) (R4); R3 is a hydrogen atom, a methyl group or a hydroxyalkyl group with 2 or more and 4 or less carbons; and R4 represents a hydroxyalkyl group with 2 or more and 4 or less carbons.

Abstract: Modified cellulose fibers comprising cellulose fibers bound to one or more substituents, via an ether bonding, selected from substituents represented by the following general formula (1) and substituents represented by the following general formula (2) and one or more substituents selected from substituents represented by the following general formula (3) and substituents represented by the following general formula (4): —CH2—CH(OH)—R1 (1); —CH2—CH(OH)—CH2—(OA)n—O—R1 (2); —CH2—CH(OH)—R2 (3); —CH2—CH(OH)—CH2—(OA)n—O—R2 (4), wherein the modified cellulose fibers have cellulose I crystal structure.

Abstract: A method for producing an additive for a rubber composition, including the step of preparing modified cellulose fibers including introducing one or more compounds selected from unsaturated group-containing alkylene oxide compounds and unsaturated group-containing glycidyl ether compounds to cellulose-based raw materials in the presence of a base, via an ether bonding, and thereafter carrying out a finely fibrillating treatment, wherein the modified cellulose fibers are cellulose fibers bound to one or more substituents, via an ether bonding, selected from substituents represented by the following general formula (1) and substituents represented by the following general formula (2): —CH2—CH(OH)—R1 (1); and —CH2—CH(OH)—CH2—(OA)n—O—R1 (2), wherein the modified cellulose fibers have cellulose I crystal structure.