Aqueous Coil Coating with Mixed Hydroxide for UV Resistance
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Solution Overview
Problem
Conventional coil coating processes for metal strips used in producing metallic components, such as automobile parts, face challenges in achieving effective corrosion protection and UV resistance without using organic solvents, which are ecologically harmful.
Innovation Solution
Aqueous coating composition containing a mixed hydroxide of the general formula [(M2+(1-x)(M3+(x))(OH)2][A(y-) (x/y)]·(H2O)n, where M2+ and M3+ are divalent and trivalent metallic cations, A(y-) are specific anions, and x and n are within specified ranges, is applied as a topcoat layer in the coil coating process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional liquid coating compositions containing organic solvents are used in the coil coating process, then sufficient UV resistance particularly to UV-A radiation can be achieved, but environmental harm increases due to the presence of semi-volatile organic solvents
Solution Approach 1:
The invention changes the fundamental parameter of the coating composition from organic solvent-based to water-based, eliminating semi-volatile organic solvents while maintaining UV resistance through the specific polymer composition and crosslinking mechanism described in the patent
Solution Approach 2:
The invention uses a composite coating system comprising a primer layer and a topcoat layer with specific polymer combinations (polyester polyurethane resin and acrylic resin) that work together to provide both environmental compatibility and UV resistance
2Object-affected harmful factors
If aqueous coating compositions are used to eliminate organic solvents, then environmental harm is reduced, but UV resistance particularly to UV-A radiation is insufficient
Solution Approach 1:
The invention modifies the chemical composition parameters of the aqueous coating by incorporating specific polymers with UV-resistant properties and crosslinking agents that form a durable network structure, enabling water-based coatings to achieve adequate UV resistance
Solution Approach 2:
The invention applies different properties to different layers: the primer layer provides corrosion protection and adhesion, while the topcoat layer specifically provides UV resistance and weatherability, with each layer optimized for its particular function
3Reliability
If topcoat layers are applied to provide mechanical resistance and weather resistance, then coating performance is improved, but the coating process becomes more complex with multiple layers
Solution Approach 1:
The coating system is segmented into functionally distinct primer and topcoat layers, where the primer provides corrosion protection and the topcoat provides UV and weather resistance, allowing each layer to be optimized independently for its specific function
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 solution provides a topcoat layer with excellent adhesion, UV resistance, particularly to UV-A radiation, and maintains high gloss retention, with gloss retention of at least 80% after 12 weeks of exposure, while being ecologically harmless due to the absence of organic solvents.
Implementation Method 1
at least partial coating of at least one metal surface of a substrate, which is at least partially coated with at least one primer layer, with an aqueous coating composition
Data Source
AI summary
The present invention relates to a method for at least single-sided application of a topcoat layer to a substrate, comprising, as step (a), at least partial coating of at least one metal surface of a substrate that has been at least partly coated with at least one primer layer with an aqueous coating composition comprising at least one polymer dissolved or dispersed therein, wherein the coating composition additionally contains at least one mixed hydroxide of the general formula (I) and the method is a coil-coating method, to a topcoat layer which has been applied to at least one side of the substrate and is obtainable by this method, to a substrate which has been coated at least partially and at least on one side with a topcoat layer by this method, and to use of this coating composition for at least partial coating of at least one metal surface of a substrate that has been at least partly coated with at least one primer layer with a topcoat layer in a coil-coating method.