Multilayer Coating System with Tertiary Amine Catalyst
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Solution Overview
Problem
Existing multilayer coating systems have slow curing speeds in shadow areas and require irradiation with visible or ultraviolet light for fast curing, which is undesirable, and may cause strike-in effects on underlying base coat layers.
Innovation Solution
A multilayer coating system comprising a layer with isocyanate-functional and thiol-functional compounds, along with a photolatent base, and an aqueous coating composition containing a tertiary amine catalyst, which allows rapid curing even in the absence of light and minimizes strike-in effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a photoactivatable coating composition is used to achieve fast curing, then curing speed is improved under light irradiation, but curing speed in shadow areas becomes slow and requires additional UV/visible light equipment
Solution Approach 1:
The patent changes the chemical parameters of the coating composition by incorporating specific catalysts (tertiary amines like triethanolamine) and isocyanate-functional compounds that enable rapid ambient temperature curing without requiring photoinitiators or light irradiation. This chemical parameter modification allows the coating to cure rapidly in both light and shadow areas, eliminating the need for complex UV/visible light curing equipment while maintaining fast curing speeds.
2Speed
If a catalyst is added to accelerate curing, then curing speed is improved, but pot life of the composition is decreased
Solution Approach 1:
The patent employs a dynamic catalyst system where the tertiary amine catalyst remains dormant or less active during storage and application, then becomes highly active upon coating application. The catalyst concentration and type are specifically selected (e.g., triethanolamine at controlled levels) to provide rapid curing when needed while maintaining adequate pot life during storage and application. This dynamic behavior allows the system to adapt between storage, application, and curing phases.
3Strength
If a clear coat composition is applied over a base coat, then a protective top layer is formed, but strike-in effect occurs on the underlying base coat layer
Solution Approach 1:
The patent employs a water-based clear coat composition that uses water as the primary solvent instead of organic solvents. This water-based formulation dries rapidly through water evaporation, minimizing the time the clear coat remains wet and potentially migratory. The rapid drying prevents strike-in effects on the underlying base coat while still forming a protective layer. The composition is designed to be environmentally friendly and compatible with modern low-VOC regulations.
4Speed
If UV/visible light irradiation is used to cure the coating, then curing speed is improved, but additional equipment and energy consumption are required
Solution Approach 1:
The patent employs a self-curing mechanism where the coating composition contains all necessary components (isocyanate-functional compounds, thiol-functional compounds, and tertiary amine catalysts) to cure rapidly at ambient temperature without external energy input from UV or visible light sources. The chemical reaction is self-sustaining once applied, utilizing the ambient environment and the inherent reactivity of the components. This eliminates the need for additional curing equipment and reduces energy consumption significantly.
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 system achieves rapid curing in shadow areas without irradiation while maintaining a long pot life and preventing strike-in effects on the underlying base coat, resulting in improved drying times and performance characteristics.
Implementation Method 1
coating composition b) comprises at least 17 mmol/kg, calculated on the weight of coating composition b), of a catalyst for the addition reaction of the at least one thiol-functional compound and the at least one isocyanate-functional compound, and wherein said catalyst is a tertiary amine
Implementation Method 2
The photoactivatable coating composition can be a clear coat composition which is to be applied on top of a base coat composition. The photoactivatable coating composition has a long pot life and exhibits fast curing upon irradiation with ultraviolet and visible light.
Data Source
AI summary
The invention relates to a multi-layer coating system comprising at least one layer a) comprising a coating composition a) comprising at - least one isocyanate-functional compound and at least one thiol-functional compound, and - at least one layer b) comprising an aqueous coating composition b), wherein at least one layer a) and at least one layer b) have at least one common layer boundary, and wherein coating composition b) comprises at least 17 mmol/kg, calculated on the weight of coating composition b), of a catalyst for the addition reaction of the at least one thiol-functional compound and the at least one isocyanate-functional compound.