NEW MATERIAL:A diphenylamine derivative of formula I: (R is aromatic residue, 1W12C hydrocarbon group; R1 and R2 are H, chlorine, bromine, or 1W12C hydrocarbon group; n is 2 or 3).

EXAMPLE: N,N'-Di-4-anilinophenylmalein-amide.

USE: Deterioration inhibitors for rubber capable of giving products having improved heat, ozone, and oil resistance and weatherability, in an amount of preferably 0.1W5 parts by wt. per 100 parts by wt. of rubber-like polymers.

PROCESS: An amine of formula II: (R1 and R2 are H, chlorine, bromine, or 1W12C alkyl groups) is reacted with an aliphatic or aromatic di-or tricarboxylic acid chloride, e.g. oxalyl chloride or terephthaloyl chloride, to give the desired derivative.