Sag-Resistant Coating Composition for High Transfer Efficiency Application
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Solution Overview
Problem
Conventional spray application methods face challenges in achieving overspray-free, high transfer efficiency with sag-resistant coatings due to significant solvent evaporation and the inability to use certain rheology control agents, which hinder flow and leveling required for good appearance.
Innovation Solution
The development of sag-resistant coating compositions for high transfer efficiency applicators, which involve a partial polymerization process using radiation-polymerizable binders, minimizing volatile loss, and incorporating thermal and radiation-polymerizable components to achieve the necessary viscosity for sag control and flow, with a method that includes applying the coating composition, performing partial polymerization via radiation, and subsequent thermal curing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional spray application is used to achieve high transfer efficiency, then solvent evaporation increases viscosity and sag resistance, but overspray occurs and volatile loss is significant
Solution Approach 1:
The coating composition is formulated with specific binder combinations (polyester resin with epoxy groups, polyisocyanate crosslinker) that enable controlled curing behavior. The segmentation of curing mechanisms (initial adhesion through isocyanate-hydroxyl reaction, followed by crosslinking) allows the coating to maintain workability while minimizing volatile loss and preventing overspray-related defects.
Solution Approach 2:
The invention changes the chemical parameters of the coating system by using a polyester resin with epoxy groups instead of conventional hydroxyl-containing resins. This parameter change enables a different curing mechanism that reduces volatile loss and improves transfer efficiency while maintaining sag resistance through controlled crosslinking behavior.
2Stability of the object's composition
If rheology control agents are incorporated to resist sag, then sag resistance improves, but flow and leveling are impeded and jetting reliability degrades
Solution Approach 1:
The coating composition exhibits dynamic rheological behavior through the interaction between polyester resin with epoxy groups and polyisocyanate crosslinker. The system transitions from a fluid state suitable for jetting and leveling to a crosslinked network that provides sag resistance, without requiring conventional rheology control agents that would permanently impede flow.
Solution Approach 2:
The coating is applied in a uncrosslinked state that allows excellent flow and leveling, then crosslinking occurs subsequently to provide sag resistance. This preliminary action of applying before crosslinking enables the coating to achieve both good appearance and sag resistance without using rheology control agents.
3Ease of operation
If extra solvent and low-viscosity solution are used for reliable jetting, then jetting reliability improves, but sag control becomes more difficult
Solution Approach 1:
The coating composition uses a dynamic curing system where the polyester resin with epoxy groups and polyisocyanate crosslinker react after application. This allows the coating to be jetted in a low-viscosity state for reliable application, then dynamically transforms to a high-viscosity crosslinked network for sag control, eliminating the need to choose between jetting reliability and sag control.
Solution Approach 2:
The coating is formulated to allow preliminary jetting and application in a uncrosslinked, low-viscosity state that ensures reliable jetting performance. The crosslinking reaction is triggered after application, providing sag control without requiring the coating to be formulated with high initial viscosity that would compromise jetting reliability.
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 solution enables efficient, overspray-free application with improved sag resistance and appearance by maintaining low volatile loss and achieving the required viscosity for flow and leveling, ensuring effective coating performance on substrates.
Implementation Method 1
performing a partial polymerization via radiation of the applied layer
Implementation Method 2
thermally curing and drying the applied layer
Implementation Method 3
a loss of volatiles after application through the high transfer efficiency applicator is less than about 1 weight percent
Data Source
AI summary
Coating compositions for application to a substrate utilizing an applicator are provided. An exemplary coating composition provided for application to a substrate utilizing an applicator with an application efficiency greater than 80% has a loss of volatiles after application through the applicator of less than about 1 weight percent based on a total weight of the coating composition. The coating composition includes a radiation-polymerizable binder; wherein the coating composition has a pre-application viscosity at a shear rate of 1000 s−1 of less than about 100 centipoise (cP); and wherein the coating composition has a post-radiation-exposure viscosity at a shear rate of 0.1 s−1 of from about 500 cP to about 150,000 cP.