Dual-Cure Pressure Sensitive Adhesive Composition
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Solution Overview
Problem
There is a need for curable compositions that combine the ease of use of traditional pressure sensitive adhesives (PSAs) with the ease of curing of UV-PSAs, while overcoming the issue of insufficient adhesive or cohesive strength.
Innovation Solution
The curable compositions comprise a free radical polymerizable resin, a cationically polymerizable resin, a free radical photoinitiator, a photoacid generator, and a polyol, with a specific weight ratio of the free radical polymerizable resin to the cationically polymerizable resin ranging from 32:1 to 2:1.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If actinically-curable PSAs are used to improve curing efficiency and reduce environmental footprint, then curing time and energy consumption are reduced, but adhesive strength is insufficient
Solution Approach 1:
The patent combines two different polymerizable resin systems (free radical and cationic) with two different photoinitiator types to create a composite curable composition. This dual-mechanism approach allows the composition to achieve both efficient curing and high adhesive strength, as the cationic polymerization component provides enhanced crosslinking and strength while the free radical component ensures rapid initial curing.
Solution Approach 2:
The patent modifies the chemical composition parameters by introducing specific ratios of free radical polymerizable resin to cationically polymerizable resin (from 32:1 to 2:1), and by selecting appropriate photoinitiators and photoacid generators. These parameter changes enable the composition to achieve optimal balance between curing efficiency and adhesive strength.
2Ease of operation
If solvent-based PSAs are used to achieve ease of handling and application, then processing is simplified, but energy consumption and environmental pollution increase
Solution Approach 1:
The patent removes the solvent component from the PSA composition entirely, creating a 100% solid actinically-curable formulation. By eliminating the solvent, the composition avoids VOC emissions and the energy-intensive drying process, while the composition remains processable through its liquid state before curing and transitions to a flexible solid after curing.
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
This composition achieves enhanced adhesive strength, as evidenced by increased 180-degree peel strength and static shear resistance, making it suitable for applications requiring strong and durable pressure sensitive adhesives.
Implementation Method 1
a free radical photoinitiator operable to initiate polymerization of the free radical polymerizable resin upon exposure to actinic radiation within a first wavelength range
Implementation Method 2
a photoacid generator operable to initiate polymerization of the cationically polymerizable resin upon exposure to actinic radiation within a second wavelength range
Data Source
AI summary
A curable composition comprises a free radical polymerizable resin comprising at least one (meth)acrylate monomer, at least one (meth)acrylate oligomer, or both; B) a cationically polymerizable resin; C) a free radical photoinitiator; D) a photoacid generator; and E) a polyol; wherein a weight ratio of A:B is from 32:1 to 2:1. Methods of using the curable composition include using it as a dually curable pressure sensitive adhesive having good peel and cohesive strength.