Solvent-Free Curable PSA Formulations
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Solution Overview
Problem
Current pressure-sensitive adhesive (PSA) systems face challenges in achieving high tack, peel, and shear properties simultaneously, while also being environmentally safe and having fast curing times.
Innovation Solution
The development of curable PSA systems comprising a combination of urethane (meth)acrylate oligomers, mono (meth)acrylate functional monomers, and tackifying resins, with optional additives such as photo-initiators and multifunctional monomers, which are curable without solvents or water, allowing for the formation of films with improved adhesive properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If solvent-based PSA systems are used, then ease of coating and processing is improved, but environmental safety deteriorates due to volatile organic compounds
Solution Approach 1:
The patent removes solvents and water from the PSA composition entirely, creating a solvent-free and water-free system. This extraction of harmful volatile organic compounds and water eliminates environmental concerns while maintaining processability through the specific formulation of reactive oligomers and monomers that can be applied and cured without solvent evaporation.
Solution Approach 2:
The patent changes the fundamental parameters of the adhesive system by using curable reactive compositions with specific functional groups (isocyanate, hydroxyl, carboxyl, amine) that undergo chemical transformation. This parameter change from stable adhesive to curable system allows solvent-free application while achieving desired performance through curing reactions.
2Ease of operation
If hot-melt type adhesive systems are used, then ease of application is improved, but shear and peel properties deteriorate at high temperature
Solution Approach 1:
The patent incorporates reactive functional groups (isocyanate, hydroxyl, carboxyl, amine) into the adhesive composition before application. These groups are prepared in advance to undergo curing reactions that will subsequently enhance the adhesive's thermal resistance and mechanical properties, transforming the adhesive from a simple hot-melt system to a crosslinked network structure.
Solution Approach 2:
The patent creates a composite chemical system combining multiple reactive components (oligomers with isocyanate groups, compounds with hydroxyl groups, compounds with carboxyl groups, and compounds with amine groups). This composite formulation enables the adhesive to develop enhanced shear and peel properties through intermolecular reactions while maintaining ease of application in a curable state.
3Device complexity
If conventional PSA systems are used, then processing simplicity is improved, but curing time increases
Solution Approach 1:
The patent replaces thermal curing mechanisms with photo-initiated or chemically-triggered curing systems. By incorporating photo-initiators or relying on ambient moisture/temperature to activate the reactive groups, the system achieves rapid curing without complex heating equipment or extended processing times, substituting mechanical/thermal processes with chemical/photochemical reactions.
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
These systems achieve enhanced peel strength, tack, and shear resistance without the need for heat, making them suitable for various applications including adhesive tapes, sheets, and sprays, while being environmentally friendly.
Implementation Method 1
UV-curable pressure sensitive adhesives are generally based on acrylic, styrenic block copolymers or urethane chemistry
Data Source
AI summary
Pressure sensitive adhesive (PSA) compositions that include at least one urethane (meth)acrylate oligomer having a molecular weight between about 2,000 g/mol and about 50,000 g/mol and an OH number of from 0.01 mg KOH/g to 100 mg KOH/g, at least one mono (meth)acrylate functional monomer and at least one tackifying resin. The PSA systems may also optionally include other additives, such as at least one initiator system that includes at least one photo-initiator or free radical initiator. The PSA systems are liquid at a temperature of 25°C ± 2°C with a viscosity of 15,000 cPs or less and are adapted to form smooth, uniform coatings or films upon curing without the application of heat, whereby the resulting films have advantageous properties with respect to peel strength, tack and shear resistance. In embodiments, the PSA systems include less than 1 wt% of solvent and less than 1 wt% of water or are free of solvent and are free of water.