Bisazo free radical initiators containing ultraviolet light stabilizing groups

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

• (R--N=N--).sub.2 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, 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, aryloxycarbonyl of 7-13 carbons, and ##STR37## wherein Y is selected from the group consisting of NC--, N.sub.3 --, ##STR38## 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 can 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 selected from the groups consisting of di-t-alkylene of 6-20 carbons, di-t-cycloalkylene of 6-20 carbons, di-t-aralkylene of 12-20 carbons, ##STR39## wherein R.sub.5 is alkylene of 1-10 carbons, cycloalkylene of 3-10 carbons, alkyleneoxyalkylene of 2-20 carbons, and ##STR40## when R is alkyl, cycloalkyl, aralkyl or ##STR41## R' can be, in addition, diacyl of 3-10 carbons, diaroyl of 8-14 carbons, arylene of 6-12 carbons, or ##STR42## and at least one of R and R' contains an ultraviolet light stabilizing radical or diradical of a compound selected from the group consisting of ##STR43## where R.sub.6 is alkyl of 1-6 carbons.