Photocurable Composition with Dual-Stage Curing for Adhesive Applications
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Solution Overview
Problem
Photocurable compositions using radical or cationic species as initiators face issues such as oxygen inhibition, corrosion, and yellowing, while those using anionic species have slow second-stage reactions, making them impractical for immediate use as adhesives.
Innovation Solution
A photocurable composition comprising an acrylic ester compound with acryloyl groups, an acrylic ester compound with acryloyl and epoxy groups, a thiol compound, a photoradical generator, and a photobase generator, with specific mass ratios and reaction conditions to control the timing of the second-stage reaction, allowing for delayed curing and improved adhesive properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If radical species are used as reaction initiators, then the polymerization reaction can proceed, but the radical species are captured by oxygen causing polymerization inhibition and curing failure
Solution Approach 1:
The patent divides the curing process into two distinct stages: first-stage radical polymerization and second-stage anionic polymerization. This segmentation allows each stage to use initiators optimized for their specific reaction type, with the anionic stage serving to complete curing and overcome oxygen inhibition that affects the radical stage.
Solution Approach 2:
The patent employs a composite photoinitiation system containing both photoradical generators and photobase generators, along with both radically polymerizable compounds (acrylates) and anionically polymerizable compounds (epoxies). This composite approach enables dual-mechanism curing that overcomes the limitations of single-initiator systems.
2Reliability
If cationic species are used as reaction initiators, then polymerization is not inhibited by oxygen, but strong acid causes corrosion or yellowing of cured product and peripheral members
Solution Approach 1:
The patent separates the polymerization process into radical and anionic stages, avoiding the use of strong acid-generating cationic initiators entirely. The anionic stage uses base-generated species that achieve polymerization without the harmful side effects of cationic systems.
Solution Approach 2:
The patent changes the chemical nature of the initiator from acidic (cationic) to basic (anionic), thereby achieving polymerization capability while eliminating the corrosion and yellowing problems associated with strong acid generation.
3Reliability
If anionic species are used as reaction initiators, then contraction is small and polymerization is not inhibited by oxygen or moisture, but the second-stage reaction is significantly slower making it impractical for immediate use as adhesive
Solution Approach 1:
The patent performs the fast radical polymerization first to establish initial curing and provide structural foundation, then follows with the anionic polymerization to complete the curing process. This preliminary action sequence optimizes both speed and reliability.
Solution Approach 2:
The patent ensures continuous useful action by designing the two-stage system where the first-stage radical polymerization and second-stage anionic polymerization are sequential and complementary, with each stage contributing to the overall curing process without interruption, thereby achieving both rapid initial set and complete final cure.
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 enables controlled timing of the second-stage reaction, ensuring sufficient working time before curing, enhancing its usability as a delayed curing adhesive with improved storage stability and adhesive strength.
Implementation Method 1
a component (D) which is a photoradical generator
Implementation Method 2
a component (E) which is a photobase generator
Implementation Method 3
the polymerization reaction may be inhibited by the radical species being captured by oxygen
Data Source
AI summary
Provided is a photocurable composition includinga component (A) which is an acrylic ester compound containing one or more acryloyl groups in one molecule;a component (B) which is an acrylic ester compound containing one or more acryloyl groups and one or more epoxy groups in one molecule;a component (C) which is a compound containing two or more thiol groups in one molecule;a component (D) which is a photoradical generator; anda component (E) which is a photobase generator,in which a ratio between a total mass of the component (A) and the component (B) and a mass of the component (C) is in a range of 67.8:32.2 to 88.0:12.0, inclusive.