Stabilizer systems of triarylphosphites and phenols

A stabilized composition consisting essentially of

• (a) a polymer which is polybutadiene, polyisoprene, polystyrene, a styrene copolymer, a styrene graft polymer, a halogen-containing vinyl polymer or copolymer, a polymer derived from an alpha,.beta.-unsaturated acid, a polyacrylate, a polymethacrylate, a polyacrylic amide, polyacrylonitrile, a polymer derived from an unsaturated alcohol or its acyl or acetyl derivatives, a polyacetal, a polyurethane, a polycarbonate, a polyamide or a polyester, and
• (b) from 0.005 to 5% by weight of component (a) of a mixture of
• (1) a triaryl phosphite of the formula ##STR4## wherein R.sub.1 represents tert-butyl or 1,1-dimethylpropyl,
• R.sub.2 represents methyl, tert-butyl or 1,1-dimethylpropyl, and
• (2) a hindered phenolic antioxidant selected from the group consisting of 2,6-di-tert-butyl-4-methylphenol, 1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl) isocyanurate, n-octadecyl 3,5-di-tert-butyl-4-hydroxyhydrocinnamate, 1,3,5-tris-(3,5-di-tert-butyl-4-hydroxybenzyl)-2,4,6-trimethylbenzene, hexamethylene bis(3,5-di-tert-butyl-4-hydroxyhydrocinnamate), pentaerythrityl tetrakis(3,5-di-tert-butyl-4-hydroxyhydrocinnamate), 2,2'-methylene-bis(4-methyl-6-tert-butylphenol) and N,N'-hexamethylene-bis(3,5-di-tert-butyl-4-hydroxyhydrocinnamamide), with the ratio of the phosphite to antioxidant being 10:1 to 1:5.