Rapid curing of epoxy resin coating compositions by combination of photoinitiation and controlled heat application
First 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.
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Abstract
A method for the high speed coating of various substrates utilizes an epoxy composition containing a radiation-sensitive catalyst precursor which will decompose upon exposure to electromagnetic radiation to provide a Lewis acid effective to induce cationic polymerization of the epoxy composition. The formulation does not require any special epoxy monomeric materials or accelerators and is stable until so exposed. Subsequent to applying the formulation to the substrate, the coating is exposed to electromagnetic radiation and a controlled temperature of 50°-90° C. is maintained in the coating for a limited period of time to effect polymerization of the formulation to a tack free surface condition within a period of less than 30 seconds. Maintenance at the elevated temperature following initiation of irradiation may be for a period of as little as 0.5 second.
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Citations
14 Claims
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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:
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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. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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Specification