Multilayer Coating Film Low-Temperature Curing Layer Mixing
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Solution Overview
Problem
The 3C1B multilayer coating film formation method often results in layer mixing between the intercoat and base coating films, leading to reduced smoothness, chipping resistance, and water resistance due to changes in curing balance and migration of curing agents.
Innovation Solution
A method involving the sequential application of an aqueous two-component first pigmented coating material, a one-component second pigmented coating material, and a two-component clear coating material, where the second pigmented coating material contains a hydroxyl group-containing acrylic resin and a blocked polyisocyanate compound, and the first pigmented coating material includes a hydroxyl group-containing resin and a polyisocyanate compound, followed by simultaneous curing at a low temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a 3C1B system is used to eliminate bake curing after intercoat material application for energy savings, then energy consumption is reduced, but layer mixing occurs between intercoat and base coating films resulting in reduced smoothness, sharpness, chipping resistance, and water resistance
Solution Approach 1:
The patent changes the chemical parameters of the coating materials by specifying functional group contents (isocyanate groups 1.05-2.10 equivalents, hydroxyl groups 0.95-1.90 equivalents) and using specific resin combinations to enable low-temperature curing that prevents layer mixing while maintaining coating quality
Solution Approach 2:
The patent uses composite material formulations combining polyester resins, acrylic resins, and polyisocyanate compounds with specific functional group ratios to create a coating system that cures effectively at low temperatures without layer mixing, achieving both energy savings and coating precision
2Loss of energy
If a 3C1B system is used to eliminate bake curing after intercoat material application for energy savings, then energy consumption is reduced, but layer mixing occurs resulting in reduced chipping resistance and water resistance
Solution Approach 1:
The patent adjusts the equivalence ratios of isocyanate and hydroxyl groups to ensure complete curing at low temperatures, preventing the layer mixing that would otherwise compromise chipping resistance and water resistance while maintaining energy efficiency
Solution Approach 2:
The patent applies different resin compositions to different coating layers (intercoat, base coat, clear coat) with each layer having optimized functional group contents to ensure proper curing and prevent migration that would affect reliability
3Ease of manufacture
If conventional coating materials are used in a 3C1B system, then the process is simple, but low-temperature curing properties are insufficient resulting in poor hardness and finished outer appearance
Solution Approach 1:
The patent modifies the chemical composition parameters by specifying exact ranges for isocyanate equivalents (1.05-2.10) and hydroxyl equivalents (0.95-1.90) to enable effective low-temperature curing that produces excellent hardness and appearance while maintaining process simplicity
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 enables the formation of a multilayer coating film with excellent low-temperature curability, hardness, and outer appearance, while maintaining smoothness, sharpness, and water resistance.
Implementation Method 1
the aqueous one-component type second pigmented coating material (Y) contains a hydroxyl group-containing acrylic resin (Y1), a hydroxyl group-containing polyester resin (Y2) and a blocked polyisocyanate compound and/or melamine resin (Y3)... the aqueous two-component type first pigmented coating material (X) contains a hydroxyl group-containing resin (X1) and a polyisocyanate compound (X2)... heating the uncured first pigmented coating film, the uncured second pigmented coating film and the uncured clear coating film formed in steps (1) to (3) to simultaneously cure the coated films
Data Source
AI summary
Provided is a method for forming a multilayer coating film, which is capable of forming a multilayer coating film that exhibits excellent curability at low temperatures, while having excellent hardness and excellent finish appearance. A method for forming a multilayer coating film, which sequentially performs: (1) a step for forming an uncured first color coating film by applying a two-package type aqueous first color coating material (X) onto an object to be coated; (2) a step for forming an uncured second color coating film by applying a one-package type aqueous second color coating material (Y) onto the uncured first color coating film obtained in the step (1); (3) a step for forming an uncured clear coating film by applying a two-package type clear coating material (Z) onto the uncured second color coating film obtained in the step (2); and (4) a step for curing the uncured first color coating film, the uncured second color coating film and the uncured clear coating film, which are formed in the steps (1)-(3), at the same time by heating these coating films. This method for forming a multilayer coating film is configured such that the one-package type aqueous second color coating material (Y) contains a specific hydroxyl group-containing acrylic resin (Y1), a specific hydroxyl group-containing polyester resin (Y2), and a blocked polyisocyanate compound and/or a melamine resin (Y3).