Stabilizers for organic materials

A composition comprising an organic material liable to thermal, oxidative and/or actinic degradation and at least one compound of formula (I) ##STR43## wherein Q is a radical ##STR44## wherein n is 1 or 2 and k is 0, 1 or 2,

• or Q together with R.sub.5 forms a group ##STR45## and n is 1, R is hydrogen, has the same possible meanings as R.sub.3 O or, when R.sub.3 is hydrogen and n is 1, together with R.sub.1 or with R.sub.2 forms a group ##STR46## R.sub.1 is hydrogen, C.sub.1 -C.sub.18 alkyl or C.sub.5 -C.sub.12 cycloalkyl,
• R.sub.3 is hydrogen, C.sub.1 -C.sub.18 alkyl or C.sub.5 -C.sub.12 cycloalkyl,
• R.sub.4 and R.sub.5 are each independently of the other hydrogen, C.sub.1 -C.sub.12 alkyl or C.sub.5 -C.sub.12 cycloalkyl,
• R.sub.6 is --NO.sub.2, --C.tbd.N, --COOR.sub.13, --S--R.sub.14, --SOR.sub.14, --SO.sub.2 --R.sub.14, --NR.sub.7 R.sub.7a, Cl, Br, F, --OR.sub.15 or --COR.sub.16, or two radicals R.sub.6 together form a fused-on benzo ring,
• R.sub.7 and R.sub.7a are each independently of the other hydrogen or C.sub.1 -C.sub.12 alkyl,
• R.sub.13 is hydrogen or C.sub.1 -C.sub.18 alkyl,
• R.sub.14 is C.sub.1 -C.sub.8 alkyl or phenyl,
• R.sub.15 is hydrogen, C.sub.1 -C.sub.18 alkyl, or C.sub.5 -C.sub.12 cycloalkyl, and
• R.sub.16 is C.sub.1 -C.sub.18 alkyl, or C.sub.5 -C.sub.6 cycloalkyl.