Latent Catalyst Polyurethane Adhesive for Food Packaging
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Solution Overview
Problem
Solventless polyurethane adhesives used in laminating processes have a short pot-life and long curing time, and existing latent catalysts, especially tin-based ones, are not suitable for food packaging applications due to activation conditions that do not align with lamination processes.
Innovation Solution
A solvent-less polyurethane adhesive formulation using a latent catalyst formed from the reaction of amidine, guanidine, or amine compounds with carbon dioxide, water, an alcohol, or a thiol, which can be activated by heat, mechanical force, or radiation, ensuring compatibility with food packaging and improved reaction profiles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If solventless polyurethane adhesives are used for laminating, then the adhesive provides strong bonding and is suitable for food packaging, but the pot-life is short (20-40 minutes) and curing time is long (up to 10 days)
Solution Approach 1:
The patent applies preliminary action by pre-reacting the amidine or guanidine catalyst with carbon dioxide to form a blocked catalyst complex that is stable during storage and lamination. This blocking prevents premature catalysis, extending pot-life, while allowing rapid curing when activated by heat during the lamination process.
2Loss of time
If tin-based latent catalysts are used to extend pot-life, then the catalyst can be activated at controlled conditions, but the catalyst is not suitable for food packaging applications
Solution Approach 1:
The patent replaces expensive and harmful tin-based catalysts with inexpensive, food-safe amidine or guanidine compounds that serve as effective latent catalysts. These organic compounds achieve the same pot-life extension function without the toxicity concerns of tin-based alternatives, making them suitable for food packaging applications.
3Adaptability or versatility
If existing latent catalysts are used, then the catalyst activation can be controlled, but the activation conditions do not align with the lamination process
Solution Approach 1:
The patent applies parameter changes by designing a catalyst system where the blocked amidine or guanidine catalyst is specifically engineered to activate at the temperature range (80-150°C) typical of lamination processes. This temperature-dependent activation ensures that the catalyst remains dormant during adhesive application and lamination, then activates rapidly to complete curing after the lamination cycle, achieving perfect process alignment.
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 adhesive formulation provides a longer pot-life during lamination and high reactivity post-lamination, while being compatible with food packaging standards by using non-tin, amidine or guanidine-based latent catalysts that can be activated within the lamination process.
Implementation Method 1
which can be activated by heat, mechanical force, or radiation
Implementation Method 2
a latent catalyst which is the reaction product of i) an amidine-containing compound, a guanidine-containing compound, or an amine-containing compound
Data Source
Figure 1
AI summary
An adhesive formulation comprising a) a polyurethane composition; and b) a latent catalyst which is the reaction product of i) an amidine-containing compound, a guanidine-containing compound, or an amine-containing compound; ii) carbon dioxide; and iii) water, an alcohol, an amine, or a thiol, is disclosed.