Multilayer Coating Film Scratch Resistance
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for forming multilayer coating films on automobile bodies, such as the three-coating-one-baking method, often result in suboptimal coating film appearance due to mixing or chemical changes during curing, and lack sufficient scratch resistance, especially for the clear coating film.
Innovation Solution
A method involving multiple aqueous base coating steps and a clear coating step, where the first aqueous base coating composition contains a carbodiimide compound, and the clear coating composition includes a hydroxyl group-containing acrylic resin, polyisocyanate, and polycarbonate diol, with specific ratios and components to achieve improved scratch resistance and appearance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple coating films are applied and cured simultaneously (three-coating-one-baking method), then productivity is improved and energy consumption is reduced, but coating film appearance deteriorates due to mixing or joining between layers and physical or chemical changes during curing
Solution Approach 1:
The patent divides the coating process into distinct stages: first applying and partially drying the base coating film, then applying the clear coating film separately. This segmentation prevents mixing between layers while maintaining the efficiency benefits of reduced baking cycles, resolving the contradiction between productivity and appearance quality.
Solution Approach 2:
The patent performs preliminary drying of the base coating film before applying the clear coating film. This preliminary action stabilizes the base layer, preventing subsequent mixing or chemical changes that would deteriorate appearance, while still allowing efficient simultaneous curing in the final baking stage.
2Loss of substance
If the clear coating film is made thinner to reduce material cost, then loss of substance is reduced, but scratch resistance deteriorates
Solution Approach 1:
The patent changes the chemical composition parameters of the clear coating film by incorporating specific polymers and crosslinking agents. This allows the film to achieve sufficient scratch resistance at reduced thickness through enhanced material properties rather than relying solely on increased thickness.
Solution Approach 2:
The patent creates a composite clear coating formulation combining multiple functional components (polymers, crosslinking agents, resins) that work synergistically to provide both protection and adhesion at optimal thickness levels, reducing material waste while maintaining scratch resistance.
3Strength
If the clear coating film is made thicker to improve scratch resistance, then strength is improved, but coating film appearance deteriorates due to increased visibility of defects and orange peel effect
Solution Approach 1:
The patent optimizes the thickness parameter of the clear coating film to a specific range that balances scratch resistance and appearance. Additionally, it changes the chemical composition to enhance film formation quality, reducing orange peel effect and defect visibility at the optimal thickness level.
Solution Approach 2:
The patent ensures uniform distribution of functional components throughout the clear coating film, creating consistent local properties that prevent defect formation and maintain smooth appearance across the entire coating surface while providing adequate scratch resistance.
4Object-affected harmful factors
If aqueous base coating compositions are used instead of solvent-based compositions, then environmental friendliness is improved and health safety is enhanced, but coating film appearance may deteriorate due to water-based formulation limitations
Solution Approach 1:
The patent adjusts key parameters of the aqueous base coating composition including pH value, solid content, and surfactant concentration to optimize film formation. These parameter changes enable water-based formulations to achieve smooth, defect-free coating films comparable to solvent-based systems while maintaining environmental benefits.
Solution Approach 2:
The patent introduces surfactants and co-solvents as intermediary substances that facilitate proper film formation in aqueous systems. These intermediaries bridge the gap between water-based formulation and quality coating film production, enabling good appearance while maintaining the environmental advantages of aqueous coatings.
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 excellent scratch resistance and appearance, suitable for automobile bodies, by ensuring proper curing and orientation of the clear coating film, while maintaining the smoothness and durability of the coating.
Implementation Method 1
the first aqueous base coating composition contains a carbodiimide compound
Implementation Method 2
the clear coating composition contains a hydroxyl group-containing acrylic resin (A), a polyisocyanate compound (B)
Implementation Method 3
a curing step of forming a multilayer coating film composed of a first base coating film, a second base coating film, and a clear coating film by simultaneously heat curing
Data Source
AI summary
A method for forming a multilayer coating film which includes forming an uncured coating film by applying a first aqueous base coating composition, forming an uncured coating film by applying a second aqueous base coating composition, forming an uncured coating film by applying a clear coating composition, and simultaneously heat curing the obtained coating films. The first aqueous base coating composition contains a carbodiimide compound, the clear coating composition contains a hydroxyl group-containing acrylic resin (A) having a hydroxyl value of 120 to 160 mgKOH/g and an acid value of 5 to 10 mgKOH/g, a polyisocyanate compound (B), and a polycarbonate diol compound (C). The component (A) has a hydroxyl group-containing alkyl moiety having 3 or less carbon atoms, and the ratio of the numbers of moles of the isocyanate functional groups of the component (B) and the hydroxyl group functional groups of the component (A) is 1.15 to 1.35.