Waterborne Electrodepositable Coating for Heat-Sensitive Substrates
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Solution Overview
Problem
Existing coating compositions for electrodeposition and radiation curing face challenges with poor solubility in water, leading to dispersibility issues and inadequate adhesion on heat-sensitive materials, particularly metalized plastics, and require tedious selection of photo initiators for effective curing.
Innovation Solution
A radiation curable electrodepositable coating composition comprising an aqueous dispersion of a partially neutralized (meth)acrylic modified amine epoxy adduct and an ethylenically unsaturated compound, with optional photo initiators, which improves dispersibility and reduces dependence on initiators for curing, allowing for low temperature application on heat-sensitive materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If coating compositions with radiation curable oligomers and monomers are used for UV curing, then curing speed is improved and low temperature application is enabled, but adhesion to base material deteriorates and film becomes fragile
Solution Approach 1:
The invention uses a composite coating composition containing both radiation curable components (oligomers and monomers for UV curing) and thermosetting components (polyisocyanates or amino resins for high temperature curing). This composite formulation enables the coating to achieve both fast initial curing at low temperature and strong adhesion through subsequent high temperature crosslinking, resolving the contradiction between curing speed and adhesion strength.
2Adaptability or versatility
If energy curable components are added to achieve both electrodepositability and radiation curability, then versatility is improved, but solubility in water deteriorates and dispersibility becomes problematic
Solution Approach 1:
The invention changes the parameter of pH by using partially neutralized polyepoxy resins with carboxylic acid groups. This partial neutralization creates an amphoteric resin that can disperse in water while maintaining compatibility with both electrodepositability and radiation curability requirements, thus achieving dual functionality without sacrificing water dispersibility.
3Stability of the object's composition
If carefully selected species of photo initiators are used to prevent poor solubility, then dispersibility is improved, but manufacturing complexity increases due to tedious selection process
Solution Approach 1:
The invention extracts the photo initiator from the essential components list by demonstrating that the coating composition can achieve effective curing without relying on carefully selected photo initiators. The partially neutralized polyepoxy resin system enables curing through its inherent chemical reactivity, eliminating the need for complex photo initiator selection and simplifying the manufacturing process.
4Strength
If thermosetting coating compositions are used for electrodeposition, then adhesion is improved, but application to heat-sensitive materials is limited due to high curing temperature
Solution Approach 1:
The invention applies a preliminary low temperature radiation curing step that forms an initial coating layer with adequate adhesion, followed by an optional high temperature thermosetting step that enhances crosslinking. This two-stage approach allows heat-sensitive materials to receive the benefits of thermosetting curing without being exposed to high temperatures that would damage them.
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 high reactivity, low tackiness, excellent adhesion, and high gloss, with improved corrosion resistance and compatibility, enabling effective coating of heat-sensitive materials like plastics without the need for critical photo initiator selection.
Implementation Method 1
the reactive monomer is used for diluting other components in place of an organic solvent and thus becomes part of the cross-linked polymer network after radical polymerization
Implementation Method 2
cured coating film produced from this type of coating material... after radical polymerization
Data Source
AI summary
The present invention relates to waterborne curing compositions for electrodeposition and radiation curing and processes to obtain such compositions. The compositions are characterized in that an ethylenically unsaturated compound (b), is dispersed in an aqueous solution by an at least partially neutralized (meth)acrylic modified amine epoxy adduct. The compositions of the invention are particularly suitable for coating metallic materials and temperature sensitive materials such as electrically conductive plastic materials.