Stabilized polyisoprene composition

A stabilized polyisoprene composition comprising 100 parts by weight of polyisoprene and 0.15-3.0 parts by weight of a binary system antioxidant consisting of a phosphite type antioxidant represented by the formula:

• ##STR7## wherein R.sub.1, R.sub.2 and R.sub.3, which may be the same or different, represent aryl or alkaryl groups having 6 to 33 carbon atoms, and
• a triazine derivative type antioxidant represented by the formula ##STR8## wherein X.sub.1, X.sub.2 and X.sub.3, which may be the same or different, are selected from the group consisting of --NH--, --O--, and --S--, and R', R", and R"', which may be the same or different, represent alkyl groups having 2 to 15 carbon atoms, or alkyl-substituted or unsubstituted hydroxyphenyl groups having 1 to 10 carbon atoms in the alkyl group,
• or 2,4,6-tris (3',5'-di-t-butyl-4'-hydroxyphenylethoxy)-1,3,5-trizaine,
• wherein the weight ratio of the phosphite type antioxidant to the triazine derivative type antioxidant is 70/10-95/5.