Rapid curing of epoxy resin coating compositions by combination of photoinitiation and controlled heat application

Claim 1

In a method for coating substrates with an epoxy coating material to develop a tack-free surface condition in relatively short periods of time, the steps comprising: A. applying to a substrate a fluid coating of a polymerizable composition comprising at least one epoxidic prepolymer material polymerizable to a higher molecular weight at which it is tack-free and up to 5 percent by weight of said polymerizable composition of a radiation-sensitive catalyst precursor which decomposes upon exposure to electromagnetic radiation to provide a Lewis acid effective to initiate polymerization of said epoxidic prepolymer material, said catalyst precursor being ineffective to cure said epoxidic prepolymer material to a tack-free surface condition at ambient temperatures in a period of two minutes following exposure to radiation to effect decomposition thereof, said epoxidic prepolymer material containing less than about 15 percent by weight thereof of epoxidic prepolymer material having two epoxycycloalkyl groups per molecule; B. exposing said coating to said electromagnetic radiation to effect decomposition of said catalyst precursor and thereby generate a Lewis acid; and C. maintaining said coating at a temperature of about 50°-90° C. for a period of at least about 0.5 second and less than about 2 minutes following initiation of said exposure to radiation to effect polymerization to a substantially tack-free surface condition in a period of less than 30 seconds following the combination of said steps of radiation exposure and temperature maintenance.