Azo free radical initiators containing ultraviolet light stabilizing groups

A free radical initiator containing ultraviolet light stabilizing groups and having the formula:

• R--N = N--R'
• wherein
• R' is selected from the group consisting of alkyl of 1-20 carbons cycloalkyl of 3-10 carbons, aralkyl of 7-20 carbons and ##EQU20## wherein Y is selected from the group consisting of NC--, N.sub.3 -- , ##EQU21## ##EQU22## wherein R.sub.1 and R.sub.2 are selected from the group consisting of alkyl of 1-20 carbons, cycloalkyl of 3-6 carbons, and alkylene of 2-30 carbons when R.sub.1 and R.sub.2 are joined together;
• and wherein one but not both of R.sub.1 and R.sub.2 may in addition be phenyl, tolyl, xylyl, benzyl, or phenethyl;
• R.sub.3 is t-alkyl of 4-8 carbons, t-cycloalkyl of 4-8 carbons or t-aralkyl of 9-15 carbons;
• R.sub.4 and R'.sub.4 are alkyl of 1-6 carbons, cycloalkyl of 3-6 carbons or aryl of 6-12 carbons
• R is any of the foregoing radicals for R', and in addition, may be selected from the group consisting of aryl of 6-14 carbons, acyl of 2-20 carbons, aroyl of 7-20 carbons, carbamoyl, alkylcarbamoyl of 2-7 carbons, cycloalkylcarbamoyl of 4-11 carbons, --CO.sub.2 Na, --CO.sub.2 K, alkoxycarbonyl of 2-7 carbons, cycloalkoxycarbonyl of 4-11 carbons, and aryloxycarbonyl of 7-13 carbons, with the proviso that when R is carbamoyl, R' can be, in addition, alkoxycarbonyl of 2-7 carbons, cycloalkoxycarbonyl of 4-11 carbons, or aryloxycarbonyl of 4-11 carbons and
• at least one of R and R' contains an ultraviolet light stabilizing radical of a compound selected from the group consisting of ##SPC22##
• where R.sub.6 is alkyl of 1-6 carbons.