Aspartate Coating Color Stability via Chain Extension

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Solution Overview

Problem

Aspartate-based coating compositions tend to discolor and yellow during storage, leading to color instability, which is not effectively addressed by existing solutions, affecting the final color and mechanical/optical properties of the coating.

Innovation Solution

A coating composition comprising a chain-extended aspartate prepolymer free of isocyanate groups, combined with a curing agent having free isocyanate groups and a UV absorber such as oxanilide or benzotriazole, which maintains color stability for at least 12 months while preserving mechanical and optical properties.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If aspartate-based coating compositions are combined with UV absorber, then UV protection is improved, but the component containing the curable aspartate remarkably discolours during storage

Engineering Contradiction:

ImproveUV protectionVSAvoidcolor stability during storage

Core Design Contradiction:

Object-affected harmful factorsVSStability of the object's composition

Solution Approach 1:

The invention changes the chemical structure of the aspartate prepolymer by ensuring it is free of isocyanate groups and has a specific NH equivalent weight range (250-1,000 g), which fundamentally alters its stability parameters and prevents discoloration during storage while maintaining UV protection capabilities

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention creates a composite coating system combining chain-extended aspartate prepolymer with specific curing agents (polyisocyanates with NCO index 5-150) and UV absorbers, where the synergistic interaction of components provides both UV protection and color stability without the discoloration issues of conventional aspartate formulations

Inventive Principle:

Principle #40Composite materials

2Reliability

If conventional aspartate based coating compositions are used, then coating performance is achieved, but the final colour of the obtained coating does not match the desired or targeted colour due to discoloration during storage

Engineering Contradiction:

Improvecoating performanceVSAvoidcolor accuracy

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The invention performs preliminary stabilization by formulating the aspartate prepolymer with specific structural characteristics (free of isocyanate groups, controlled NH equivalent weight) that prevent discoloration before storage, ensuring color accuracy is maintained from production through application without matching issues

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The invention introduces a specific curing agent component (polyisocyanate with controlled NCO index) that acts as an intermediary between the aspartate prepolymer and the final coating, mediating the crosslinking reaction to achieve both performance and color stability without discoloration

Inventive Principle:

Principle #24Intermediary (Mediator)

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 solution significantly reduces discoloration and yellowing of the coating during storage at room and elevated temperatures, maintaining high adhesion, interlayer adhesion, abrasion, and corrosion resistance.

Implementation Method 1

at least one UV absorber consisting of oxanilide or a derivative thereof and/or benzotriazole or a derivative thereof

Methodology Applied

Scientific EffectUV absorption: Absorption (EM radiation)

Data Source

PatentEP3110867B1Coating compositions comprising diisocyanate chain extended bisaspartates

Publication Date: 2021.10.06 AXALTA COATING SYST GMBH

AI summary

This invention relates to a coating composition, a method for coating of a metallic substrate as well as the use of the coating in a two-component coating composition.