Multilayer Coating Film Formation for Stable Metallic Pigment Orientation
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Solution Overview
Problem
Multilayer coating films formed using water-based paints exhibit metallic unevenness and decreased brightness due to disordering of effect pigments, particularly in low-humidity environments, and the 3C1B method exacerbates these issues.
Innovation Solution
A method involving the application of a first water-based paint with a compound containing a hydroxyl and acid group, followed by a second water-based paint with a binder component and effect pigment, and a clear coat, all cured simultaneously to form a multilayer coating film with improved metallic unevenness resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If water-based paints are used for multilayer coating to reduce environmental burden, then environmental friendliness is improved, but the volatilization rate of water is slow and is greatly impacted by application environment conditions, causing effect pigment orientation to become disordered and brightness to decrease
Solution Approach 1:
The patent applies parameter changes by precisely controlling the paint solid content within 5-20 mass% and the effect pigment content within 1-50 mass%, and by optimizing the compound (A) with specific acid value (50-150 mg KOH/g) and hydroxyl value (100-300 mg KOH/g) ranges. These parameter optimizations ensure proper paint film formation and effect pigment orientation while using water-based paints, thereby maintaining brightness and reducing environmental burden simultaneously
Solution Approach 2:
The patent uses composite materials by combining compound (A) containing both hydroxyl and acid groups with film-forming resin (B) and crosslinking agent (C) to create a multifunctional paint system. This composite approach provides both the environmental benefits of water-based paints and the performance reliability needed to prevent effect pigment disordering through enhanced film formation control
2Productivity
If effect pigment-containing base paint and clear paint are applied in wet-on-wet manner to form multilayer coating film, then manufacturing efficiency is improved, but the orientation of effect pigment becomes disordered, resulting in decrease in brightness
Solution Approach 1:
The patent applies preliminary action by pre-optimizing the paint solid content and compound (A) characteristics before applying the effect pigment-containing paint. This preliminary preparation ensures that the underlying paint film has optimal properties to support and stabilize effect pigment orientation during subsequent wet-on-wet application, preventing disordering while maintaining manufacturing efficiency
Solution Approach 2:
The patent controls the paint solid content within 5-20 mass% and effect pigment content within 1-50 mass% to achieve proper paint film viscosity and flow characteristics. These parameter settings allow the effect pigment to orient correctly during wet-on-wet application without becoming disordered, thereby maintaining brightness while preserving the productivity benefits of the 3C1B method
3Productivity
If the paint solid content is increased to improve coating efficiency, then productivity is improved, but the orientation of effect pigment becomes more easily disordered, causing metallic unevenness to occur
Solution Approach 1:
The patent optimizes the paint solid content within the specific range of 5-20 mass% and compound (A) with acid value of 50-150 mg KOH/g and hydroxyl value of 100-300 mg KOH/g. These parameter settings balance coating efficiency with effect pigment orientation stability, preventing metallic unevenness while maintaining productive coating operations
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 forms a multilayer coating film with enhanced metallic unevenness resistance and brightness, even in low-humidity conditions, by controlling the paint solid content and using specific compounds to stabilize the effect pigment orientation.
Implementation Method 1
the first water-based paint (P1) contains a compound (A) containing a hydroxyl group and an acid group... to form a multilayer coating film with improved metallic unevenness resistance
Implementation Method 2
curing a multilayer coating film including the first coating film, the second coloring coating film, and the clear coat coating film formed in the steps (1) to (3) at one time by heating the multilayer coating film
Data Source
AI summary
The purpose of the present invention is to provide a method for forming a multilayer coating film which makes it possible to form a multilayer coating film having excellent metallic mottling resistance. The method for forming a multilayer coating film comprises: (1) a step for applying a first aqueous coating material (P1) on an object to be coated to form a first coating film; (2) a step for applying a second aqueous colored coating material (P2) on the first coating film to form a second colored coating film that contains a binder component (AP2) and lustrous pigment (BP2); (3) a step for applying a clear-coat coating material (P3) on the second colored coating film to form a clear-coat coating film; and (4) a step for heating a multilayer coating film that includes the first coating film, the second colored coating film, and the clear-coat coating film so as to cure the multilayer coating film all at once. The first aqueous coating material (P1) contains a compound (A) containing a hydroxyl group and an acid group and that has an acid value of from 50 to 150 mg KOH/g, a hydroxyl value of from 100 to 300 mg KOH/g, and a weight-average molecular weight of from 500 to 8000, a film-forming resin (B), and a crosslinking agent (C).