Cyclic diphenylacetonitriles as stabilizers

A composition comprising

• a) an organic material subjected to oxidative, thermal or light-induced degradation and
• b) an effective stabilizing amount of at least one compound of the formula I ##STR96## in which R.sub.1, R.sub.2, R.sub.3, R.sub.4, R.sub.5, R.sub.6, R.sub.7 and R.sub.8 independendy of one another are hydrogen, haloge or C.sub.2 -C.sub.25 salkyl which is interrupted by oxygen, sulfur or ##STR97## C.sub.5 C.sub.8 cloalkyl which is unsubstituted or substituted by C.sub.1 C.sub.4 alkyl;
• phenyl which is unsubstituted or substituted by C.sub.1 -C.sub.4 alkyl;
• C.sub.7 -C.sub.9 phenylalkyl, hydroxyl, C.sub.1 C.sub.18 alkoxy or C.sub.3 C.sub.18 alkoxy which is interrupted by oxygen, sulfur or ##STR98## mercapto, C.sub.1 -C.sub.18 alkylthio or C.sub.3 C.sub.18 alkylthio which is interrupted by oxygen, sulfur or ##STR99## C.sub.1 C.sub.25 alkanoyloxy or C.sub.3 C.sub.25 alkanoyloxy which is interrupted by oxygen, sulfur or ##STR100## C.sub.3 -C.sub.25 alkenoyloxy, benzoyloxy or benzoyloxy which is substituted by C.sub.1 C.sub.12 alkyl;
• nitro, cyano, --(CH.sub.2).sub.m COR.sub.11 or ##STR101## and furthermore the radicals R.sub.1 and R.sub.2, R.sub.2 and R.sub.3, R.sub.3 and R.sub.4, R.sub.5 and R.sub.6, R.sub.6 and R.sub.7 or R.sub.7 and R.sub.8, together with the carbon atoms to which they are bonded, form a benzo ring, or the same pairs of radicals together are --O(CH.sub.2).sub.n O--, with the condition that at least one of the radicals R.sub.1, R.sub.2, R.sub.3 or R.sub.4 and at least one of the radicals R.sub.5, R.sub.6, R.sub.7 or R.sub.8 is hydrogen, R is additionally a radical of the formula II, R.sub.2 is additionally a radical of the formula III, R.sub.3 is additionally a radical of the formula IV and R.sub.4 is additionally a radical of the formula V, and at the same time only one radical of the formula II, III, IV or V occurs in the compound of the formula I, ##STR102## R.sub.9 is hydrogen or a radical of the formula VI ##STR103## in which R.sub.1, R.sub.2, R.sub.3 and R.sub.4 are not a radical of the formula II, III, IV or V,
• R.sub.10 is hydrogen or C.sub.1 -C.sub.8 alkyl,
• R.sub.11 is hydroxyl, C.sub.1 C.sub.18 alkoxy or ##STR104## R.sub.12 and R.sub.13 independendy of one another are hydrogen or C.sub.1 -C.sub.18 alkyl,
• R.sub.14 is a direct bond, C.sub.1 C.sub.18 alkylene or C.sub.2 -C.sub.18 alkylene which is interrupted by oxygen, sulfur or ##STR105## R.sub.15 and R.sub.16 independenfiy of one another are hydrogen, CF.sub.3, C.sub.1 -C.sub.12 alkyl or phenyl, or R.sub.15 and R.sub.16, together with the C atom to which they are bonded, form a C.sub.5 C.sub.8 cycloalkylidene ring which is unsubstimted or substituted by 1 to 3 C.sub.1 -C.sub.4 alkyl groups,
• R.sub.17 is a direct bond, C.sub.1 C.sub.18 alkylene or C.sub.2 -C.sub.18 alkylene which is interrupted by oxygen, sulfur or ##STR106## C.sub.2 -C.sub.18 alkenylene, C.sub.2 -C.sub.20 alkylidene, C.sub.7 C.sub.20 phenylalkylidene, C.sub.5 -C.sub.8 cycloalkylene, C.sub.7 C.sub.8 bicycoalcne, phcnyenc which is unsuhsdtuted or substituted by C.sub.1 C.sub.4 alkyl, ##STR107## m is 0,1 or 2 and n is 1 or 2.