In-Mold Multi-Layer Coating for Strong Interlayer Adhesion

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Solution Overview

Problem

Existing in-mold coating methods for forming multi-layer coating films require additional spray coating steps, increasing environmental burden and compromising interlayer adhesion, especially when using fiber-reinforced plastic materials.

Innovation Solution

A method involving the formation of an uncured first in-mold coating film, followed by curing, separation of the mold, creating a gap, and injecting a second in-mold coating composition with reactive functional groups to form a multi-layer coating film, utilizing polymerizable unsaturated group-containing compounds and reactive functional groups for strong interlayer bonding.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If an upper layer of colored coating film is formed by spray coating after in-mold coating, then the in-mold coating film has excellent adhesion to fiber-reinforced plastic material, but the burden on the environment is increased

Engineering Contradiction:
Improveadhesion to fiber-reinforced plastic materialVSAvoidenvironmental burden
Core Design Contradiction:
ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent combines multiple coating layers into a single in-mold coating process. The multi-layer coating film includes a first layer with polymerizable unsaturated groups and a second layer with reactive functional groups, both applied through in-mold coating rather than separate in-mold and spray coating processes. This merging eliminates the environmental burden of spray coating while maintaining adhesion to fiber-reinforced plastic materials.

Inventive Principle:
Principle #5Merging (Combining)

Solution Approach 2:

The patent uses composite coating compositions with specific functional groups. The first coating composition contains polymerizable unsaturated groups that bond to the fiber-reinforced plastic matrix, while the second coating composition contains reactive functional groups that bond to the first layer. This composite approach ensures excellent adhesion to fiber-reinforced plastic material while avoiding environmentally harmful spray coating processes.

Inventive Principle:
Principle #40Composite materials

2Adaptability or versatility

If a multi-layer coating film is formed with additional spray coating steps, then coating functionality is achieved, but the number of steps is increased and environmental burden is increased

Engineering Contradiction:
Improvecoating functionalityVSAvoidnumber of steps
Core Design Contradiction:
Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent merges multiple coating functions into a single in-mold coating process. Both the first coating composition (with polymerizable unsaturated groups for matrix bonding) and the second coating composition (with reactive functional groups for interlayer bonding) are applied through in-mold coating, eliminating the need for separate spray coating steps and reducing process complexity while maintaining full coating functionality.

Inventive Principle:
Principle #5Merging (Combining)

Solution Approach 2:

The in-mold coating process is made multi-functional by applying different coating compositions with different functions in sequence within the same mold. The first composition provides matrix adhesion, the second provides interlayer adhesion, and both can be applied through the same in-mold coating equipment, making the process universal and eliminating the need for additional spray coating equipment and steps.

Inventive Principle:
Principle #6Universality (Multi-functionality)

3Adaptability or versatility

If a multi-layer coating film is formed with additional spray coating steps, then coating functionality is achieved, but the burden on the environment is increased

Engineering Contradiction:
Improvecoating functionalityVSAvoidenvironmental burden
Core Design Contradiction:
Adaptability or versatilityVSObject-affected harmful factors

Solution Approach 1:

The patent combines all coating functions into environmentally friendly in-mold coating processes. The first coating composition provides matrix adhesion and the second provides interlayer adhesion, both applied through in-mold coating without requiring spray coating equipment or processes, thus eliminating environmental burden while achieving complete coating functionality.

Inventive Principle:
Principle #5Merging (Combining)

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 achieves excellent interlayer adhesion between the first and second in-mold coating films with reduced environmental impact by eliminating the need for additional spray coating steps.

Implementation Method 1

a polymerizable unsaturated group-containing compound (x1) containing a polymerizable unsaturated group

Methodology Applied
Scientific EffectPolymerization: Photopolymerisation

Implementation Method 2

a compound (y1) containing a second reactive functional group capable of reacting with the first reactive functional group

Methodology Applied
Scientific EffectChemical reaction: Chemical Bonding

Implementation Method 3

heating the uncured first in-mold coating film to thereby cure the uncured first in-mold coating film

Methodology Applied
Scientific EffectThermal energy: Heating

Data Source

PatentUS12485593B2Method for forming in-mold coating multi-layer coating film
Publication Date: 2025.12.02 KANSAI PAINT CO LTD

AI summary

A method for forming an in-mold coating multi-layer coating film includes: forming an uncured first in-mold coating film by injecting a specific first in-mold coating material composition (X) between a molded base material and an inner wall of a first film coating mold; heating and curing the uncured first in-mold coating film; separating the first film coating mold from a surface of the cured first in-mold coating film; providing a gap between the surface of the cured first in-mold coating film and a second film coating mold; forming an uncured second in-mold coating film by injecting a specific second in-mold coating material composition (Y) between the surface of the cured first in-mold coating film and an inner wall of the second film coating mold; and heating and curing the uncured second in-mold coating film.