Hydroxyaryl hydantoins and their use as stabilizers

A compound of the formula ##STR31## wherein m is an integer from 1 to 2 and R.sub.1 denotes an alkyl group with 1 to 8 carbon atoms, a cycloalkyl group with 6 to 8 carbon atoms or an aralkyl group with 7 to 9 carbon atoms, R.sub.2 denotes hydrogen, an alkyl group with 1 to 8 carbon atoms, cycloalkyl group with 6 to 8 carbon atoms or an aralkyl group with 7 to 9 carbon atoms, R.sub.3 denotes hydrogen or a methyl group, R.sub.4 denotes hydrogen or a ##STR32## group, R.sub.5, if m is 1 or 2, is an alkyl group with 1 to 17 carbon atoms, a cyclohexyl group, a phenyl group or phenyl substituted by halogen, hydroxyl groups, alkyl groups with 1 to 4 carbon atoms or alkoxy groups with 1 to 18 carbon atoms or an aralkyl group which can be substituted by alkyl and/or hydroxyl groups in the aromatic radical, and, if m is 1, is a group ##STR33## X is selected from the group consisting of hydantoin, 5,5-dimethylhydantoin, and alkylene-bis-hydantoin, said hydantoin being bonded to the rest of the molecules via the nitrogen in position 3, and n denotes an integer from 2 to 8.