Acid-Epoxy Crosslinked Pressure-Sensitive Adhesive
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Solution Overview
Problem
High-performance pressure-sensitive adhesives (PSAs) require improved crosslinking agents that do not generate corrosive or toxic by-products, are compatible with various polymer systems, and maintain tack and adhesion properties at elevated temperatures, while avoiding undesirable color formation and oxygen sensitivity.
Innovation Solution
A (meth)acrylic solute copolymer comprising alkyl(meth)acrylate, epoxy-functional monomers, and acid-functional ethylenically unsaturated monomers, which can crosslink in the absence of ionic photoacid generators, using epoxy resins with multiple polymerizable epoxy groups and low levels of photoacid generators, allowing for efficient crosslinking without chlorinated triazine crosslinking agents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If traditional crosslinking agents (polyfunctional acrylates, acetophenones, benzophenones, triazines) are used to improve shear holding capability, then crosslinking efficiency is enhanced, but corrosive or toxic by-products are generated and undesirable color formation occurs
Solution Approach 1:
The patent changes the chemical parameters of the crosslinking system by using acid-functional monomers (acrylic acid, methacrylic acid, itaconic acid, fumaric acid) combined with epoxy resins instead of traditional crosslinking agents. This parameter change eliminates the generation of corrosive by-products and undesirable color while maintaining crosslinking efficiency and shear holding capability.
Solution Approach 2:
The patent creates a composite crosslinking system combining acid-functional polymers with epoxy resins. This composite approach provides synergistic effects where the acid groups catalyze epoxy ring-opening reactions, forming a crosslinked network that achieves high shear holding power without the harmful effects of traditional crosslinking agents.
2Strength
If UV crosslinkers (copolymerizable benzophenones or post-added photocrosslinkers) are used to achieve crosslinking, then shear holding power is improved, but high sensitivity to oxygen and requirement of separate photoactive compounds are introduced
Solution Approach 1:
The patent merges the crosslinking functionality and photoactive functionality into a single integrated system. The acid-functional monomers serve dual purposes: they provide crosslinking sites and act as photoactive components when combined with epoxy resins, eliminating the need for separate photoactive compounds and reducing oxygen sensitivity.
Solution Approach 2:
The acid-functional groups in the polymer system self-catalyze the crosslinking reaction with epoxy resins without requiring external photoactive compounds. The system serves itself by using its own functional groups to initiate and drive the crosslinking process, particularly under UV irradiation conditions.
3Temperature
If crosslinking is increased to maintain tack and adhesion at elevated temperatures, then thermal performance is improved, but tack and adhesion properties may be compromised
Solution Approach 1:
The patent applies local quality by creating a crosslinked network structure that provides thermal stability while maintaining a tacky matrix phase for adhesion. The crosslinked regions provide heat resistance and structural integrity, while the unreacted or lightly crosslinked polymer regions maintain tack and adhesion properties, achieving both requirements simultaneously.
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 solution provides PSAs with balanced tack, peel adhesion, and shear holding power, meeting Dahlquist criteria, and is suitable for applications at elevated temperatures without the drawbacks of traditional crosslinking agents, such as corrosive by-product generation or color issues.
Implementation Method 1
the acid groups of the solute copolymer and epoxy groups of the epoxy resin can crosslink in the absence of an ionic photoacid generator
Implementation Method 2
an epoxy resin having on average greater than 1 polymerizable epoxy groups per molecule
Data Source
AI summary
A pre-adhesive composition is described comprising an acid-functional (meth)acryloyl copolymer and epoxy resin, which when crosslinked with or without using an ionic photoacid generator (PAG) provides a (e.g. pressure-sensitive) adhesive.