Latent Catalyst Coatings for Extended Pot Life and Rapid Curing
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Solution Overview
Problem
Water-based two-component coating compositions with polyisocyanate cross-linking agents and active hydrogen-containing binders face challenges in achieving a balance between long pot life and short drying time, especially at moderate temperatures, while avoiding surface defects like popping marks and reaction bubbles.
Innovation Solution
Incorporating a latent catalyst compound comprising cyclodextrin and a catalyst, such as amines or metal compounds, that forms a host-guest complex, allowing for extended pot life and rapid curing without premature reaction, even at elevated temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If catalysts are used to reduce drying time, then drying time is reduced, but pot life is reduced
Solution Approach 1:
The harmful effect of premature catalyst action is extracted and removed by using a latent catalyst that is separated from its activating agent (water). The catalyst is present in the composition but kept inactive until the moment of application, allowing long pot life while enabling rapid curing when needed.
Solution Approach 2:
The catalyst is prepared and incorporated into the coating composition in advance in a latent, inactive form. This preliminary preparation allows the composition to be stored and handled with extended pot life, while the curing action can be rapidly initiated when the composition is applied and exposed to moisture.
2Object-affected harmful factors
If water-based coating compositions are used, then VOC emissions are reduced, but reaction bubbles and popping marks occur
Solution Approach 1:
The harmful reaction between isocyanate and water that produces bubbles is converted into a beneficial process. By using a latent catalyst system that controls the timing of the reaction, the water-isocyanate reaction is harnessed to provide crosslinking and curing without premature bubble formation, transforming a defect into a functional advantage.
3Productivity
If latent catalysts activated by moisture are used, then curing is accelerated, but curing depends on environmental humidity
Solution Approach 1:
The activation mechanism is changed from direct moisture activation to activation by controlled water exposure during application. The latent catalyst system responds to the water present in the coating composition itself rather than environmental humidity, making the curing process independent of environmental conditions while maintaining rapid curing speed.
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 coating compositions achieve a pot life of 60 minutes to 20 hours with short drying times, preventing surface defects and enabling high-gloss, defect-free coatings up to 60-70 µm thickness without reaction bubbles, with improved early hardness and appearance.
Implementation Method 1
a catalyst compound, said catalyst compound comprising at least one catalyst for the curing reaction between the at least one functional group containing active hydrogen of component A and the at least one free isocyanate group of component B, and at least one cyclodextrine
Implementation Method 2
at least one catalyst for the curing reaction between the at least one functional group containing active hydrogen of component A and the at least one free isocyanate group of component B
Implementation Method 3
reaction bubbles caused by the reaction of isocyanate with water
Data Source
AI summary
The invention relates to a water-based coating composition comprising: A) at least one cross-linkable compound having at least one functional group containing active hydrogen, B) at least one polyisocyanate cross-linking agent with free isocyanate groups, C) at least one catalyst compound, said catalyst compound comprising at least one catalyst for the curing reaction between the functional groups containing active hydrogen of component A and the isocyanate groups of component B, and at least one cyclodextrine.