Multilayer Coating Film Process for Metallic Luster Without Sagging
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for forming multilayer coating films on plastic molded articles fail to achieve a high-quality finish with sufficient metallic luster and are prone to sagging, especially when using effect pigment dispersions with low solids content, and require baking at different temperatures for various components.
Innovation Solution
A method involving sequential application of an aqueous primer paint, base paint, effect pigment dispersion, and clear paint, followed by preheating and simultaneous curing at 110 to 130°C, using specific resin particles and additives to achieve a film thickness of 0.5 to 1.5 μm.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If effect pigment dispersion with low solids content is used, then the coating process is easier and film formation is improved, but sagging occurs and metallic luster is insufficient
Solution Approach 1:
The patent changes the solids content parameter of the effect pigment dispersion to a specific range (5-15 mass%) to balance flowability and sag resistance. It also specifies precise aluminum pigment particle parameters (D50: 13-40 μm, thickness: 0.4-2.5 μm) to achieve both uniform distribution and metallic luster without sagging
Solution Approach 2:
The patent creates a composite coating system combining effect pigment dispersion with specific aluminum pigments having controlled particle morphology and size distribution. This composite approach allows the low solids content dispersion to flow properly while the aluminum pigment structure prevents sagging and provides metallic luster
2Ease of operation
If effect pigment dispersion with low solids content is used, then the coating process is easier, but metallic luster is insufficient
Solution Approach 1:
The patent optimizes the aluminum pigment parameters (particle size D50: 13-40 μm, thickness: 0.4-2.5 μm, aspect ratio: 5-100) to maximize light reflection and metallic luster. The specific thickness control ensures sufficient luster even at low solids content
Solution Approach 2:
The patent combines effect pigment dispersion with specifically engineered aluminum flake pigments to create a composite system where the aluminum pigment structure compensates for the low solids content, maintaining metallic luster while enabling easier coating application
3Manufacturing precision
If multiple coating films are applied sequentially, then design quality and luster are improved, but baking process complexity increases
Solution Approach 1:
The patent merges multiple coating applications (base paint, effect pigment dispersion, clear paint) into a single wet-on-wet process that is cured in one baking step at 100-150°C. This combines multiple operations while maintaining film quality and reducing process complexity
4Illumination intensity
If aluminum pigment with larger particle size is used, then metallic luster is improved, but uniform distribution is reduced
Solution Approach 1:
The patent specifies a controlled particle size distribution for aluminum pigments (D50: 13-40 μm) rather than using uniformly large particles. This size control ensures sufficient metallic luster while preventing aggregation and maintaining uniform distribution in the low solids content dispersion
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 results in a multilayer coating film with excellent finished appearance and luster on plastic molded articles, addressing sagging issues and ensuring uniform film thickness.
Implementation Method 1
the uncured effect coating film formed in step (4)
Implementation Method 2
heating the preheated primer coating film, the preheated base coating film, the preheated effect coating film, and the uncured clear coating film at a temperature in the range of 110 to 130° C. to simultaneously cure the coating films
Data Source
AI summary
An object of the present invention is to provide a method for forming a multilayer coating film, the method being capable of providing a multilayer coating film with excellent finished appearance and luster. The aqueous base paint (X) comprises: a hydroxy-containing acrylic resin particle (X1) having a core-shell structure wherein the shell has an acid value of 90 to 100 mg KOH/g; and a hydroxy-containing acrylic resin particle (X2) having a core-shell structure wherein the shell has an acid value of 110 to 120 mg KOH/g; and an associative thickener (X3), wherein the proportions of the hydroxy-containing acrylic resin particle (X1) and the hydroxy-containing acrylic resin particle (X2) contained in the aqueous base paint (X) are such that the ratio by mass of the hydroxy-containing acrylic resin particle (X1) to the hydroxy-containing acrylic resin particle (X2) (X1/X2) is in the range of 70/30 to 30/70. The effect pigment dispersion (Y) contains a flake-aluminum pigment (Y1), a cellulose-based rheology control agent (Y2), a surface-adjusting agent (Y3), and water, and has a solids content within the range of 2 to 6 mass %. The effect coating film formed using the effect pigment dispersion (Y) has a cured film thickness of 0.5 to 1.5 μm.