Epoxy Methacrylate Dual-Curing Composition for Shadow-Area Coatings
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Solution Overview
Problem
Existing photocurable compositions based on (meth)acrylate functional compounds face challenges in achieving complete curing in regions not illuminated by actinic radiation, leading to uncured areas due to the difficulty in exposing conformal coatings on highly contoured surfaces.
Innovation Solution
A dual curing composition comprising epoxy methacrylate monomers and thiol-functional compounds, which can be cured using both actinic radiation and heat, with a molar ratio of thiol groups to (meth)acrylate groups ranging from 0.5:1 to 1:1, and free of free-radical photoinitiators and thermal initiators, ensuring effective curing under both conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If photocurable compositions are used for conformal coatings on highly contoured surfaces, then fast curing is achieved through actinic radiation exposure, but complete curing cannot be attained in shadow areas
Solution Approach 1:
The patent combines two different curing mechanisms (photo-curing and thermal curing) into a single dual-curing composition. The composition contains both photoinitiators for UV/visible light curing and thermal initiators for heat-activated polymerization, allowing the coating to be cured by either method or both methods together, thereby ensuring complete curing throughout the coating thickness including shadow areas
Solution Approach 2:
The dual-curing composition is designed to perform multiple curing functions: it can be cured by actinic radiation (UV/visible light) through photoinitiators, or by heat through thermal initiators, or by a combination of both. This multi-functionality allows the same composition to adapt to different curing conditions and ensure complete polymerization regardless of light penetration limitations
2Productivity
If photoinitiators are used to enable photo-curing, then curing efficiency is improved, but residue compounds are produced in the final cured product
Solution Approach 1:
The patent changes the chemical parameters of the curing system by incorporating thermal initiators that decompose at elevated temperatures to generate free radicals for polymerization. This alternative curing pathway avoids the formation of photoinitiator residues while maintaining curing efficiency, as the thermal initiators decompose completely without leaving detectable residue compounds in the final cured product
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The composition achieves complete curing of coatings on complex surfaces by combining photo and thermal curing, eliminating residues from photoinitiators and enhancing curing efficiency in shadow areas.
Implementation Method 1
compositions which are curable by actinic radiation can conventionally be cured relatively quickly by exposure to a radiation source
Implementation Method 2
compositions which, in addition to being curable under exposure to actinic radiation, can also be cured upon exposure to heat
Data Source
AI summary
The present application is directed to dual curing composition which is both heat- and photo-curable, said composition comprising, based on the weight of the composition: from 20 to 90 wt. % of a) at least one epoxy methacrylate compound having at least two methacrylate groups; and, from 10 to 80 wt. % of b) at least one polythiol compound, wherein the composition is characterized in that the molar ratio of thiol(—SH) groups to (meth)acrylate groups is in the range from 0.5:1 to 1:1.