Photostabilizing activity of N‐acylated hindered amine

Abstract

The influence of the acyl groups of N‐acylated hindered amine on the photostabilization of polymers was discussed. The effects of the N‐acyl derivatives of 4‐benzoyloxy‐2,2,6,6‐tetramethylpiperidine (6) in the photostabilization of polypropylene were compared. Although the stabilizing effects of all the N‐acyl derivatives were lower than that of the N‐oxyl derivative (7), N‐acryloyl (4) and N‐benzoyl (5) derivatives showed higher effects than that of parent NH 6. To discuss the stabilizing mechanism of N‐acylated hindered amine, the reaction of N‐acylated hindered amine with model hydroperoxide (tert‐butyl hydroperoxide) was carried out at an elevated temperature (132°C). N‐Acylated hindered amine decomposed tert‐butyl hydroperoxide more rapidly than corresponding secondary hindered amine, and changed into the parent secondary amine.

Photostabilisation of Polymer Materials

“…In other studies the influence of N substitution on the effectivity of 4-benzoyloxy-2,2,6,6-tetramethylpiperidine was studied [116][117][118]. In this case the effectivity decreased in the order O > O-butyl > butyl > hydrogen > acetyl.…”

Conformational Studies of an N-Acylated Hindered Amine Light Stabilizer

“…As oxidation occurs at the nitrogen atom, substitution on this atom will certainly have an effect on the rate of this process. It has been suggested that oxidation of N -acylated HALS proceeds through the secondary amine. , As a result, their rate of entry into the HALS stabilization cycle is slowed, and this is manifested by their poorer performance (relative to secondary amines) as light stabilizers. − Moreover, it has also been suggested that the spirocyclic structure of 1 , in addition to its amidic proton in the hydantoin ring system, is responsible for the existence of an intramolecularly hydrogen bonded (trans-annular) form of the molecule. It has been further implied that this form is even less susceptible to oxidation than similar N -acylated HALS which cannot form a trans-annular hydrogen bond such as structures 2 and 3…”

“…It has been suggested that oxidation of N-acylated HALS proceeds through the secondary amine. 11,12 As a result, their rate of entry into the HALS stabilization cycle is slowed, and this is manifested by their poorer performance (relative to secondary amines) as light stabilizers. [13][14][15] Moreover, it has also been suggested that the spirocyclic structure of 1, in addition to its amidic proton in the hydantoin ring system, is responsible for the existence of an intramolecularly hydrogen bonded (trans-annular) form of the molecule.…”