Polymerizable compositions containing iodonium photoinitiators and photosensitizers therefor

#Photosensitizers and photoinitiators, used for the photoinduced free radical polymerization of monomers, are important in radiation curable coatings, bulk polymerization, and the graphic arts. Polymeric photosensitizers are also known in the art. Advantages of polymeric photosensitizers and photoinitiators over low molecular weight materials are: greater processability, lower likelihood of loss of photosensitizer from photosensitive coatings through sublimation or leaching, and generally lower toxicity. Any improved efficiency in the utilization of incident light to photoinitiate polymerization allows for shorter exposure times or lower light intensities in the photocuring process, whether on a web, in solution or in graphic arts applications.

#Use of polymeric photoinitiators to allow polymerization was described by Flamigni et al. [Eur. Polym. J., 20, 171 (1984)], and other examples can be found in U.S. Pat. Nos. 3,429,852 and 3,622,848.

#Carbonyl containing polymeric quaternary ammonium salts as photoinitiators of polymerization have been reported by Shibanov and Protsyuk [Russian Pat. No. USSR 787,416, see Chemical Abstracts, 94, 122299r, 1981)]. Photoinitiated polymerization of methyl methacrylate with poly(methylisopropenyl ketone) was taught by Naito et al. [Kobunshi Ronbunshu 36, 777 (1979)]. Carlini et al. [Polymer, 24, 599 (1983)] cured acrylic compositions with benzophenone/dimethylaniline-substituted polymers.

#In the following examples, parts are reported as parts by weight unless indicated otherwise, and polymer structures were confirmed spectroscopically.

#The following example is typical for the preparation of polymer of general structure I, where R.sup.1 =R.sup.2 =R.sup.3 =H, R.sup.4 --R.sup.6 =CH.sub.2 --CH.sub.2 --, R.sup.5 =--CH.sub.2 --CH.sub.2 --, a=x=1 and Ar=C.sub.6 H.sub.5.

#To a mixture of 19.4 parts of piperazine hexahydrate in 20 parts methanol was added slowly 12 parts of glacial acetic acid. After addition was complete, the precipitated salt was redissolved when 16.2 parts of 37% aqueous formalin was added. The clear solution was allowed to stir on an ice bath for an hour and then at room temperature overnight.