PURPOSE: To provide a polymer material containing bis-(polyalkylpiperidinylamino)-1,3,5-triazines as stabilizers, which has excellent stability against oxidative or light-induced degradation and is useful for preparing films, fibers, tapes or the like.

CONSTITUTION: The objective polyolefin is obtained by incorporating 0.05 parts of pentaerythritol-tetrakis-[β-(3,5-di-tert. butyl-4-hydroxyphenyl)]-propionate, 0.05 parts of tris-(2,4-di-tert. butylphenyl)phosphite and 0.05 parts of a light stabilizer of bis-(polyalkylpiperidinylamino)-1,3,5-triazine of formula I [X is a group of formula II (R3, R4 are each a 1-18C alkyl, 5-12C cycloalkyl, 2-4C hydroxyalkyl or the like), OR5 (R5 is a 1-18C alkyl, 3-12C alkenyl or the like), SR5; R1 is a 1-18C alkyl, 5-12C cycloalkyl or the like; R2 is H, a 1-4C alkyl, benzyl or the like] into 1000 parts of polypropylene powder, then mixing them and granulating the mixture at a temp. of 180-220°C using an extruder.