Aqueous Polyurethane Coating Composition for Stable High-Solids Films
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Solution Overview
Problem
Existing coating compositions containing aqueous polyurethane dispersion face challenges such as difficulty in dispersion, gelation, increased viscosity, and reduced solid content, leading to thinner coatings with compromised performance, while also posing health risks due to organic solvents.
Innovation Solution
A coating composition comprising an aqueous polyurethane dispersion prepared with a polyurethane prepolymer derived from polyisocyanate, polyfunctional polyether polyol with a star-shaped structure, and cycloaliphatic polyisocyanate, along with a crosslinking agent and optional additives, to enhance hand-felt softness, anti-sticking, and washing resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If an aqueous polyurethane dispersion is used to eliminate organic solvents, then health safety is improved, but the dispersion stability and coating performance deteriorate due to gelation and high viscosity
Solution Approach 1:
The patent changes the chemical structure parameters of the polyurethane polymer by introducing specific side chain configurations and controlling the NCO index (1.05-3.5), which fundamentally alters the dispersion's gelation behavior and viscosity characteristics, enabling stable aqueous dispersion without organic solvents
Solution Approach 2:
The patent creates a composite aqueous polyurethane dispersion system combining polyurethane polymers with specific side chains, water, and optional co-solvents or additives, achieving synergistic effects that maintain both health safety and dispersion stability
2Ease of operation
If the solid content of aqueous polyurethane dispersion is reduced to lower viscosity, then ease of application is improved, but coating thickness and performance deteriorate
Solution Approach 1:
The patent changes the rheological parameters of the dispersion by modifying polymer side chain structure and molecular weight distribution, which decouples the relationship between solid content and viscosity, allowing high solid content (5-50%) with manageable viscosity for easy application
Solution Approach 2:
The patent introduces dynamic flow characteristics to the coating composition through shear-thinning behavior induced by side chain architecture, enabling the coating to flow easily during application then maintain thickness upon drying
3Adaptability or versatility
If polyurethane polymer with high hydrophilicity is used to improve water permeability, then moisture permeability is improved, but dispersion stability deteriorates due to gelation
Solution Approach 1:
The patent applies local quality by introducing hydrophilic side chains only in specific regions of the polyurethane polymer structure, creating localized hydrophilic zones that enable water permeability while the overall polymer backbone maintains dispersion stability
Solution Approach 2:
The patent precisely controls the NCO index (1.05-3.5) and side chain content (5-50 wt%) to optimize the balance between hydrophilicity for moisture permeability and structural integrity for dispersion stability
Data Source
AI summary
The present invention relates to a coating composition, a coating system comprising the coating composition, a coating method and application of the coating system, and a product coated with the coating system. The coating composition comprises: (A) at least one aqueous polyurethane dispersion and/or one aqueous polyacrylate dispersion, wherein the aqueous polyurethane dispersion comprises at least one polyurethane polymer (a), wherein the polyurethane polymer (a) is obtained by a reaction comprising at least one polyurethane prepolymer (a1) and at least one isocyanate-reactive component (a2), wherein the polyurethane prepolymer (a1) is obtained by a reaction comprising the following components: (a1-1) at least one polyisocyanate having an isocyanate functionality of no less than 2, and (a1-2) at least one polyfunctional polyether polyol having a hydroxyl functionality of no less than 3, wherein the polyfunctional polyether polyol has an amount of 1 wt% to 20 wt%, based on the amount of the components for preparing the polyurethane prepolymer being 100 wt%, and (B) at least one crosslinking agent.