2K Water-Borne Coating Composition for Low-VOC Moderate-Bake Curing
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Solution Overview
Problem
Existing water-borne coating compositions for automotive refinishing face challenges in achieving proper crosslinking and curing under moderate or low baking conditions, often requiring stringent drying processes and incorporating volatile organic co-solvents to mitigate drying issues, which may not comply with stringent VOC regulations.
Innovation Solution
A two-part water-borne coating composition comprising a binder part with hydroxyl-functional (meth)acrylate copolymers and non-aromatic polyesters, and a crosslinker part with polyisocyanate compounds, optimized for a molar ratio of active hydrogen atoms to NCO groups, allowing for effective crosslinking under moderate baking conditions without volatile organic compounds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If water-borne coating compositions are used to reduce VOC emissions, then environmental compliance is improved, but crosslinking and curing require stringent baking conditions with controlled air movement and humidity
Solution Approach 1:
The patent changes the chemical parameters of the coating composition by using water-dilutable hydroxyl-functional (meth)acrylate copolymers and non-aromatic polyesters with specific hydroxyl values and functionalities. These parameter changes allow the composition to achieve proper crosslinking under moderate baking conditions without requiring stringent control of air movement and humidity, thus resolving the contradiction between VOC reduction and process complexity
Solution Approach 2:
The patent creates a composite water-borne coating system combining hydroxyl-functional (meth)acrylate copolymers, non-aromatic polyesters with active hydrogen groups, and polyisocyanate crosslinkers. This composite material formulation enables effective crosslinking under moderate baking conditions while maintaining water-borne status for VOC compliance, thereby resolving the technical contradiction
2Productivity
If volatile organic co-solvents are incorporated to improve drying properties, then drying performance is improved, but VOC content increases reducing regulatory compliance
Solution Approach 1:
The patent extracts and eliminates volatile organic co-solvents from the coating formulation by using a water-borne system with hydroxyl-functional (meth)acrylate copolymers and non-aromatic polyesters. The composition achieves adequate drying and curing through water evaporation and subsequent crosslinking reactions, removing the need for VOC-containing accelerators while maintaining productivity
Solution Approach 2:
The patent changes the solvent system parameters from organic volatile co-solvents to water as the primary diluent. The binder composition parameters (hydroxyl values, molecular weights, functionalities) are specifically selected to enable proper film formation and crosslinking in a water-borne system, thus achieving drying performance without VOC content
3Use of energy by moving object
If water removal is achieved through flash drying, then energy consumption is reduced, but proper crosslinking cannot be achieved due to water's high boiling point
Solution Approach 1:
The patent changes the chemical composition parameters to include hydroxyl-functional (meth)acrylate copolymers and non-aromatic polyesters with high hydroxyl values (100-600 mg KOH/g) and functionalities (2-8). These parameter changes enable effective crosslinking reactions to proceed at moderate temperatures after water evaporation, ensuring crosslinking effectiveness without requiring high-energy flash drying processes
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 achieves good leveling and optical properties, facilitating use in automotive finishing and refinishing applications with reduced energetic burden and compliance with VOC regulations.
Implementation Method 1
a crosslinker part with polyisocyanate compounds, optimized for a molar ratio of active hydrogen atoms to NCO groups, allowing for effective crosslinking under moderate baking conditions
Data Source
AI summary
A two-part (2K) water-borne coating composition includes a) a binder part comprising (a1) at least one hydroxyl-functional (meth)acrylate copolymer; and (a2) at least one non-aromatic polyester having active hydrogen groups; and b) a crosslinker part comprising at least one polyisocyanate compound having pendant —NCO groups, wherein the non-aromatic polyester of constituent (a2) has a number average molecular weight (Mn) of from 500 to 5000 Daltons, an acid value from about 0 to about 30 mg KOH/g, a calculated hydroxyl value of from about 100 to about 600 mg KOH/g and, a calculated hydroxyl functionality of from about 2 to about 8; and, wherein the molar ratio of active hydrogen atoms to —NCO groups in the composition is from 5:1 to 1:5.