JPH0312081B

A highly effective photoinitiator for cationic polymerization of monomer formulations is prepared by reacting bis-[4-(diphenylsulfonio)phenyl] sulfide bis-halide wherein halide is chloride or bromide in an aqueous solution with a compound having the formula T.MF6 wherein M is one of phosphorus, antimony or arsenic and T is hydrogen or a metal whose halide salt is water soluble. The two compounds react in the aqueous medium to produce a precipitate which includes at least about 50 percent by weight bis-[4-(diphenylsulfonio) phenyl] sulfide bis-MF6, and this precipitate may be recovered and dried for utilization without further purification if so desired. Purification may be effected by dissolving the dried product in an organic solvent, cooling the solvent to precipitate the impurities, and thereafter recovering relatively pure bis-[4-(diphenylsulfonio) phenyl] sulfide bis-MF6 by chilling the solvent solution to form a precipitate, and then separating and drying the precipitate. The preferred compounds are those wherein the substituent M is phosphorus so that the product comprises bis-[4-(diphenylsulfonio) phenyl] sulfide bis-hexafluorophosphate. The cationic polymerization processes utilize the photoinitiator in an amount equal to about 0.5-6.0 percent by weight of the monomer therein.