Multilayer Coating Film Low-Temperature Curing Method
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Solution Overview
Problem
Existing methods for forming multilayer coating films on automobile outer panels struggle with low temperature curing while maintaining performance, particularly in integrating metal and plastic members, and ensuring water resistance and finished appearance.
Innovation Solution
A method involving the application of an aqueous 2-package type first colored paint, followed by an aqueous 1-package type second colored paint, and a solvent-based 2-package type clear paint, with specific resin and polyisocyanate ratios, and subsequent heating to 75-100°C to cure the films simultaneously.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by stationary object
If the baking temperature is lowered to save energy, then energy consumption is reduced, but the performance of the coating film such as finished appearance and water resistance becomes difficult to ensure
Solution Approach 1:
The patent changes the chemical composition parameters of the coating materials, specifically using an aqueous base coating paint containing 10-60% by mass of solid content of an acrylic resin emulsion obtained by emulsion polymerization of a monomer mixture having 0.2-20% by mass of a crosslinking monomer, 5-40% by mass of solid content of a water-soluble acrylic resin, and 20-40% by mass of solid content of a melamine resin. This parameter change enables the coating to cure properly at lower temperatures while maintaining performance
Solution Approach 2:
The patent uses a composite coating system comprising multiple layers with specific material compositions: aqueous intermediate paint, aqueous base coating paint with specific resin content ratios, and clear paint. The composite structure allows each layer to contribute different properties, enabling low-temperature curing while maintaining water resistance and finished appearance
2Use of energy by stationary object
If a 3-coat 1-bake system is used to omit bake curing after intermediate paint application, then energy consumption is reduced, but the coating film performance may be compromised
Solution Approach 1:
The patent modifies the composition parameters of the aqueous base coating paint to include specific ratios of acrylic resin emulsion (10-60%), water-soluble acrylic resin (5-40%), and melamine resin (20-40%). This parameter change enables the coating to achieve proper curing and performance without requiring additional bake curing after intermediate paint application, thus maintaining energy efficiency
3Device complexity
If integrative painting of metal and plastic members is implemented, then manufacturing complexity is reduced, but coating uniformity and adhesion become difficult to control
Solution Approach 1:
The patent applies different primer treatments to metal and plastic members before applying the aqueous base coating paint. The metal member receives a conductive primer while the plastic member receives a different primer, allowing each substrate to receive appropriate surface preparation. This local quality approach ensures proper adhesion and uniform coating performance across different material types while maintaining integrated painting
Solution Approach 2:
The patent uses an aqueous base coating paint with specifically controlled composition parameters including 10-60% by mass of solid content of acrylic resin emulsion, 5-40% by mass of solid content of water-soluble acrylic resin, and 20-40% by mass of solid content of melamine resin. This parameter control enables uniform coating formation and proper curing on both metal and plastic members simultaneously
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
This method achieves a multilayer coating film with excellent low temperature curing properties and finished appearance on both metal and plastic members, enhancing water resistance and recoat adhesion.
Implementation Method 1
the solvent-based 2-package type clear paint (Z) contains a hydroxyl group-containing acrylic resin (Z1) and a polyisocyanate compound (Z2) in a ratio of 1.5 to 2.0 equivalents of isocyanate groups in the polyisocyanate compound (Z2) relative to 1 equivalent of hydroxyl groups in the hydroxyl group-containing acrylic resin (Z1)
Implementation Method 2
a step (4) of heating the uncured first colored coating film, the uncured second colored coating film and the uncured clear coating film formed in steps (1) to (3) to 75 to 100° C. so as to simultaneously cure these coating films
Data Source
AI summary
A method includes a step of applying an aqueous 2-package type first colored paint to form an uncured first colored coating film; a step of applying an aqueous 1-package type second colored paint to form an uncured second colored coating film; a step of applying a solvent-based 2-package type clear paint to form an uncured clear coating film; and a step of heating the uncured first colored coating film, the uncured second colored coating film and the uncured clear coating film to 75 to 100° C. to simultaneously cure these films. The solvent-based 2-package type clear paint contains a hydroxyl group-containing acrylic resin and a polyisocyanate compound in a ratio of 1.5 to 2.0 equivalents of isocyanate groups in the polyisocyanate compound relative to 1 equivalent of hydroxyl groups in the hydroxyl group-containing acrylic resin.