Core/Shell Water-Based Coating for Multilayer Adhesion
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Solution Overview
Problem
In the 3C1B method for forming multilayer coating films, layer mixing occurs between the first and second coating films when preliminary heating is not carried out, resulting in poor appearance and adhesion issues without preheating.
Innovation Solution
A water-based coating composition with a core/shell type emulsion resin, where the core is an acrylic resin and the shell is a polyurethane resin containing specific proportions of dibasic acids and dihydric alcohols, is used to form a multilayer coating film without preliminary heating, ensuring excellent adhesion and appearance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If preliminary heating is not carried out after the first coating film is formed in the 3C1B method, then energy consumption is reduced and process time is shortened, but layer mixing occurs between the first and second coating films resulting in poor appearance and adhesion
Solution Approach 1:
The first coating film is formulated with predetermined properties (water-based composition, specific resin content, controlled drying rate) that enable it to form a stable, non-mixing layer without requiring preliminary heating. This preliminary design of the coating composition allows direct overlay of the second coating material while maintaining layer separation and appearance quality.
2Use of energy by stationary object
If preliminary heating is not carried out after the first coating film is formed, then energy consumption is reduced, but layer mixing occurs between the first and second coating films resulting in poor adhesion
Solution Approach 1:
The invention changes the chemical and physical parameters of the first coating film by using a water-based composition with specific resin content (5-50 mass%), hydroxyl group value (10-100 mg KOH/g), and acid value (0-50 mg KOH/g). These parameter adjustments create a film that maintains proper viscosity and surface properties at ambient temperature, preventing layer mixing and ensuring adhesion without preliminary heating.
3Object-generated harmful factors
If water-based intermediate coating composition is used to reduce VOCs, then environmental performance is improved, but water absorption and water elution of the intermediate coating film must be controlled to prevent layer mixing
Solution Approach 1:
The invention controls the water absorption and water elution properties by adjusting the resin composition parameters (hydroxyl group value of 10-100 mg KOH/g, acid value of 0-50 mg KOH/g, and specific resin content). These parameter controls ensure the water-based intermediate coating film maintains appropriate moisture content and viscosity, preventing layer mixing while achieving reduced VOC emissions.
Data Source
AI summary
Disclosed is a water-based coating composition having as a base resin, a core/shell type emulsion resin comprising an acrylic resin as the core portion and a polyurethane resin as the shell portion, wherein the mass ratio of the core portion and the shell portion in the aforementioned core/shell type emulsion resin is between 20/80 and 80/20, the aforementioned acrylic resin has a hydroxyl group value of 40 to 140 mg KOH/g and an acid value of 0 to 10 mg KOH/g, the aforementioned polyurethane resin has a hydroxyl group value of 20 to 80 mg KOH/g and an acid value of 10 to 60 mg KOH/g, and the total mass ratio of constituent units derived from dibasic acids and/or dihydric alcohols having 10 to 60 carbon atoms in the aforementioned polyurethane resin is 10 to 50 mass % relative to the solid resin content of the aforementioned polyurethane resin.