Dynamic properties of valcanized rubber are improved, without accelerating scorching property remark­ably nor deteriorating flex-cracking resistance, by incorporating in a filler-containing natural or synthetic rubber composition, a dinitrodiamine derivative repre­sented by the general formula
wherein A represents a divalent aliphatic group, a divalent cycloaliphatic group, a divalent aromatic group or a group represented by the formula -CH₂-X-CH₂-, wherein X represents a cycloalkylene group or a phenylene group, provided that if A represents a cycloaliphatic group or an aromatic group, the two carbon atoms in A which are bonding to the nitrogen atom are not vicinal to each other; R and Rʹ independently represent hydrogen atom or an alkyl group having 1 - 12 carbon atoms and may conjointly form a ring; and Rʺ represents hydrogen atom, an aliphatic group, a cycloaliphatic group or an aromatic group. A process for producing the dinitrodiamine derivatives is also disclosed.