Water-borne Coating Sagging Control via Polyisocyanate-Amine Reaction
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Solution Overview
Problem
Current water-borne automotive coatings face challenges in achieving proper rheological properties, particularly in preventing sagging without increasing organic solvent content, which is a requirement for both solvent-borne and water-borne coatings.
Innovation Solution
A water-borne coating composition is developed, comprising a water-soluble or water-dispersable binder and a sagging control agent (SCA) obtained by reacting aliphatic polyisocyanate with specific amines in the presence of the binder, enhancing the coating's rheological properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If commonly used sagging control agents are added to water-borne coatings, then sagging prevention is improved, but organic solvent content increases
Solution Approach 1:
The invention changes the chemical structure parameters of the sagging control agent by using aliphatic polyisocyanates with specific NCO functionality (2.0-5.0) and controlling the isocyanate to amine molar ratio (0.7-1.5), creating a water-borne compatible SCA that prevents sagging without requiring organic solvents
Solution Approach 2:
The invention creates a composite sagging control agent by reacting polyisocyanate with specific amines (C1-C10-alkoxy-C1-C10-alkylamine, di-C1-C10-alkoxy-C1-C10-alkylamine, C4-C10-alkyl substituted aniline, or di-C4-C10-alkyl substituted aniline) in the presence of the water-soluble or water-dispersable binder, forming a multifunctional component that provides both sagging control and water-borne compatibility
2Ease of operation
If viscosity is kept low during application for smooth coating, then spreading is improved, but dripping occurs on vertical surfaces
Solution Approach 1:
The invention creates a dynamic rheological system where the coating exhibits shear-thinning behavior during application (low viscosity for easy spreading) and then transitions to high viscosity at rest (preventing dripping), achieved through the unique molecular structure of the polyisocyanate-amine reaction product in water-borne medium
Solution Approach 2:
The invention utilizes time-dependent viscosity changes parameter, where the coating viscosity is low during the application phase for good spreading and then increases automatically after application to prevent sagging and dripping, controlled by the specific composition and concentration of the water-borne SCA
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 composition exhibits significantly improved rheological properties, effectively preventing sagging while maintaining low organic solvent content, suitable for both automotive finishing and refinishing applications.
Implementation Method 1
Component b) is obtained by reaction of b1) at least one aliphatic polyisocyanate, and b2) at least one amine selected from a group consisting of C1-C10-alkoxy-C1-C10-alkylamine, di-C1-C10-alkoxy-C1-C10-alkylamine, C4-C10-alkyl substituted aniline and di-C4-C10-alkyl substituted aniline in the presence of Component a)
Data Source
AI summary
Disclosed herein is a water-borne coating composition including a) at least one water-soluble or water-dispersable binder, and b) at least one sagging control agent (SCA) that is obtained by reaction of b1) at least one aliphatic polyisocyanate and b2) at least one amine selected from a group consisting of C1-C10-alkoxy-C1-C10-alkylamine, di-C1-C10-alkoxy-C1-C10-alkylamine, C4-C10-alkyl substituted aniline and di-C4-C10-alkyl substituted aniline in the presence of Component a). Further disclosed herein is a method of preparing the coating composition.