PURPOSE: A synthetic resin composition having improved light and heat resistance and oxidation stability, prepared by incorporating a cyclic amine and an alkyl- thioalkanoic amide of specific structures at stabilizers into a resin.
CONSTITUTION: (A) A synthetic resin is incorporated with (B) 0.01W3wt% of a sterically hindered cyclic amine of formula I: (X is 5W7 membered ring-forming organic group; R 1 , R 2 , R 3 and R 4 are lower alkyl groups or may form an alkylene group, etc.; n is 1 or 2; Y is H, alkyl group, etc. when n is 1, or alkylene, alkenylene group, etc. when n is 2), preferably a piperidine derivative, and (C) 0.01W 3wt% of am alkylthioalkanoic amide of formula II or III: (R is 4W50C alkyl group; R' is 1W3C alkylene group; Q is mono-to trifunctional amine residue; m is 1W3; R 5 is H, alkyl group, etc.; R 6 and R 7 are direct bonds, alkylene groups, etc.).