Aqueous Coating Composition Sag Resistance via Rapid Crosslinking
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Solution Overview
Problem
High transfer efficiency coating methods struggle with sagging issues on large or heavy objects with vertical surfaces, as conventional coating methods do not allow for adequate evaporation of solvents, leading to a less viscous coating and impractical use of masking or overspray containment.
Innovation Solution
The use of an aqueous coating composition applied with a high transfer efficiency applicator, comprising a film-forming resin with crosslinking-functional groups and a co-reactive material, which rapidly develops viscosity upon application, achieving a cured coating layer with 100 MEK double rubs and reduced sagging through dehydration and curing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If conventional coating methods are used to allow solvent evaporation, then the coating has adequate viscosity, but the coating process has low transfer efficiency and requires masking materials
Solution Approach 1:
The patent changes the chemical parameters of the coating composition by incorporating reactive functional groups (isocyanate, hydroxyl, carboxyl, or amino groups) that enable rapid crosslinking reactions. This allows the coating to quickly transition from a low-viscosity applied state to a high-viscosity cured state, resolving the contradiction between transfer efficiency and viscosity stability
Solution Approach 2:
The coating composition is pre-formulated with reactive components that will automatically react upon application. The crosslinking reaction is initiated beforehand in the composition design, so that once applied, the coating rapidly develops viscosity through the predetermined chemical reaction pathway, preventing sag before the coating can be applied
2Ease of operation
If high transfer efficiency applicators are used to reduce overspray, then masking materials are eliminated, but the coating sags on vertical surfaces
Solution Approach 1:
The coating composition contains pre-configured reactive groups that initiate crosslinking immediately upon application. This preliminary chemical preparation ensures that viscosity builds rapidly before the coating can sag, allowing high transfer efficiency application without masking while maintaining shape integrity on vertical surfaces
Solution Approach 2:
The patent modifies the chemical composition parameters by incorporating crosslinking agents and reactive functional groups that fundamentally change the viscosity-time profile of the coating. This allows the coating to maintain operability during application while rapidly achieving sag resistance through chemical crosslinking
3Manufacturing precision
If the coating composition remains less viscous after application, then the coating can be applied uniformly, but the coating cannot resist sagging
Solution Approach 1:
The patent implements a time-dependent parameter change in viscosity through chemical crosslinking. The coating starts with low viscosity for uniform application, then rapidly increases viscosity through crosslinking reactions, achieving both manufacturing precision and sag resistance at different stages of the coating process
Solution Approach 2:
The coating composition is designed to dynamically change its viscosity parameter over time. The crosslinking reaction creates a dynamic transition from a fluid state suitable for application to a rigid state that resists sag, allowing the coating to adapt its properties to different process requirements
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 method provides a coating layer with improved sag resistance and rapid dehydration, allowing for precise boundary formation and reduced drying time, suitable for vertical surfaces without the need for masking materials.
Implementation Method 1
a film-forming resin having at least one crosslinking-functional group and a co-reactive material having at least one functional group reactive with the crosslinking-functional group
Implementation Method 2
aqueous carrier, rapid dehydration
Data Source
AI summary
Methods and compositions for forming a coating layer on a substrate that include a) applying an aqueous coating composition to at least a portion of the substrate using a high transfer efficiency applicator that expels the coating composition; and b) curing the coating composition to form a cured coating layer. The aqueous coating composition includes an aqueous carrier, a film-forming resin having at least one crosslinking-functional group, and a co-reactive material having at least one functional group reactive with the crosslinking-functional group. The cured coating layer of the aqueous coating composition achieves 100 MEK double rubs as measured in accordance with ASTM D5402-19 (2019) after baking at 80° C. for 30 minutes at coating thickness of 35 gm.