Photostabilizing activity of tertiary hindered amines

The influence of the N‐alkyl group of tertiary hindered amines on the photostabilization of polymers was studied. The photostabilizing effects of the tertiary amine derivatives of 4‐benzoyloxy‐2,2,6,6‐tetramethylpiperidine (1a) in polypropylene were compared. All tertiary amine derivatives having α‐H to hindered N showed higher effectiveness than 1a. Model liquid phase photoxidations were carried out by irradiating (UV‐lamp) the solutions of tertiary hindered amines containing tert‐butyl hydroperoxide as a photoinitiator. The tertiary hindered amines were oxidized more easily than corresponding parent hindered amine and converted to the parent amine, which was identified as its salt, resulting from the carboxylic acid produced from the N‐alkyl group by oxidation. The thermal reaction of the tertiary hindered amines with tert‐butyl hydroperoxide was also studied in the liquid phase. The tertiary hindered amines decomposed tert‐butyl hydroperoxide more rapidly than the parent secondary hindered amine, and generated the parent amine. It was also found that the photostabilizing effects of tertiary hindered amines for polyolefins were higher than that of the parent secondary hindered amine.