Multilayer Coating Film Metallic Luster via Segmented Curing
Solution Overview
Problem
Existing methods for forming multilayer coating films fail to achieve excellent metallic luster, particularly in automotive and home appliance applications, due to unsatisfactory performance of coating films formed with aqueous base paint compositions containing metal flakes and cellulose derivatives.
Innovation Solution
A method involving a multistep process: applying a base paint with a polyurethane resin, an alcohol, and an organic solvent to form a base coating film, followed by an effect pigment dispersion with cellulose nanofibers, and then a two-component clear paint to create a clear coating film, all of which are simultaneously cured to achieve a multilayer coating film with enhanced metallic luster.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If an aqueous base paint composition containing metal flakes and cellulose derivative is used, then the coating process is simplified, but the metallic luster is insufficient
Solution Approach 1:
The patent divides the coating process into three separate layers: base coat, effect coat, and clear coat. Each layer has specific functions - the base coat provides adhesion and coverage, the effect coat contains metal flakes for metallic luster, and the clear coat provides protection and enhances shine. This segmentation allows optimization of metallic luster in the effect coat without compromising the simplicity of the overall coating process.
Solution Approach 2:
The patent uses a composite paint composition combining organic solvents, water, cellulose derivatives, and metal flakes in specific proportions. The effect coat contains 60-80 mass% metal flakes to maximize metallic luster while maintaining processability. This composite approach achieves excellent metallic luster while keeping the manufacturing process relatively simple.
2Illumination intensity
If the effect pigment content is increased to enhance metallic luster, then the metallic luster improves, but the coating film becomes rough and loses smoothness
Solution Approach 1:
By separating the metal flakes into a dedicated effect coat layer, the patent achieves high metal flake content (60-80 mass%) for excellent metallic luster without disrupting the smoothness of the base coat and clear coat layers. The effect coat acts as an intermediate layer that concentrates the reflective particles away from the surface where smoothness is critical.
Solution Approach 2:
The patent applies different properties to different layers: the base coat and clear coat maintain low viscosity and smooth flow characteristics for surface smoothness, while the effect coat is specifically designed with high metal flake content for metallic luster. Each layer has optimized composition tailored to its specific function.
3Illumination intensity
If a multilayer coating system is implemented to improve metallic luster, then the metallic luster is enhanced, but the manufacturing complexity increases
Solution Approach 1:
The patent combines multiple functions into the effect coat layer: it provides the metallic luster through metal flakes, acts as a transition layer between base and clear coats, and contributes to the overall film build. This merging reduces the need for additional intermediate layers, simplifying the manufacturing process while maintaining excellent metallic luster.
Solution Approach 2:
The patent optimizes specific parameters for each layer to balance performance and manufacturability: base coat solids content of 30-62 mass%, effect coat solids content of 0.1-10 mass%, and clear coat solids content of 50-65 mass%. These parameter optimizations ensure proper layer formation and curing while maintaining a relatively simple three-layer process.
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 method produces a multilayer coating film with superior metallic luster, improving appearance and performance by optimizing the composition and curing process of the coating films.
Implementation Method 1
a two-component clear paint (Z) containing a hydroxy-containing resin and a polyisocyanate compound
Implementation Method 2
applying a base paint (X) having a solids content ratio of 30 to 62 mass % to a substrate to form a base coating film
Implementation Method 3
the effect pigment dispersion (Y) contains water, a flake-effect pigment (P), a resin emulsion (Q), and cellulose nanofibers (R)
Implementation Method 4
heating the uncured base coating film, the uncured effect coating film, and the uncured clear coating film formed in steps (1) to (3) to simultaneously cure these coating films
Data Source
AI summary
This invention provides a method for forming a multilayer coating film, comprising applying a base paint (X) having a solids content ratio of 30 to 62 mass % to a substrate to form a base coating film having a cured film thickness of 6 to 45 μm; applying an effect pigment dispersion (Y) having a solids content ratio of 0.1 to 10 mass % to the base coating film to form an effect coating film having a cured film thickness of 0.1 to 5.0 μm; applying a two-component clear paint (Z) containing a hydroxy-containing resin and a polyisocyanate compound to the effect coating film to form a clear coating film; and heating the base coating film, the effect coating film, and the clear coating film to simultaneously cure these coating films; wherein the base paint (X) contains a polyurethane resin (A), an alcohol (B) containing 6 to 12 carbon atoms, and an organic solvent (C) having an HLB of 7 to 9, and the effect pigment dispersion (Y) contains water, a flake-effect pigment (P), a resin emulsion (Q), and cellulose nanofibers (R).