Dark-Color Multi-Layer Coating with Low NIR Absorption

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Solution Overview

Problem

Dark-color coatings containing carbon black pigments absorb near-infrared radiation, causing substrates to heat up, which is undesirable, especially in applications like motor vehicles, where it increases air-conditioning fuel consumption.

Innovation Solution

A wet-on-wet-on-wet coating process using waterborne pigmented coating compositions with aqueous microgel and sheet silicate, where the first layer contains <90% aluminum flake pigments for low NIR absorption, and the second layer consists of 50-100% black pigments with low NIR absorption, preventing intermixing and achieving a dark-color shade with minimal heat development.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If carbon black pigments are used to achieve dark-color coating, then the coating exhibits desired dark color shade, but the substrate heats up significantly in sunlight due to NIR absorption

Engineering Contradiction:

Improvesubstrate temperatureVSAvoidcolor shade achievement

Core Design Contradiction:

TemperatureVSEase of manufacture

Solution Approach 1:

The patent changes the chemical composition parameters of the pigment layer by using specific black pigments with low NIR absorption characteristics instead of conventional carbon black pigments. This parameter change allows the coating to maintain dark color appearance while reducing NIR absorption and substrate heating

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent creates a composite pigment layer combining multiple black pigments (at least two different black pigments) to achieve both dark color shade and low NIR absorption. This composite approach allows optimization of both aesthetic and thermal properties simultaneously

Inventive Principle:

Principle #40Composite materials

2Productivity

If wet-on-wet-on-wet coating process is used to apply multiple layers quickly, then productivity increases, but coating layers may intermix and lose structural integrity

Engineering Contradiction:

Improvecoating application speedVSAvoidcoating layer structure

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent applies a preliminary action by incorporating specific additives and resin systems in the coating compositions that promote rapid solvent evaporation and initial film formation. This preliminary structuring of the coating layers during application prevents intermixing even when layers are applied in quick succession without intermediate drying

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent uses intermediary substances (specific additives and resin systems) that act as mediators between the applied coating layers. These intermediaries facilitate rapid solvent removal and initial film formation, creating a stable structure that prevents intermixing of subsequent layers during the wet-on-wet-on-wet application process

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 process produces dark-color multi-layer coatings that heat up minimally in sunlight, maintaining the desired color shade even in industrial mass production settings with short time intervals between coating steps, reducing fuel consumption for air-conditioning in vehicles.

Implementation Method 1

both coating compositions A and B comprise aqueous microgel and sheet silicate. It has been found that the combination of aqueous microgel and sheet silicate in each of the coating compositions A and B prevents intermixing of the coating compositions once applied to a substrate

Methodology Applied

Scientific EffectPhysical barrier formation:

Implementation Method 2

Dark-color coatings often contain carbon black pigments which absorb radiation in the near-infrared wavelength range and transform it into heat

Methodology Applied

Scientific EffectNear-infrared absorption: Absorption (EM radiation)

Implementation Method 3

carbon black pigments which absorb radiation in the near-infrared wavelength range and transform it into heat

Methodology Applied

Scientific EffectPhotothermal transformation:

Implementation Method 4

this occurs via heat conduction, i.e., heat is directly transferred to the substrate from the coating layer containing carbon black pigments and heated by solar radiation

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Data Source

PatentUS8784941B2Process for the production of a dark-color multi-layer coating

Publication Date: 2014.07.22 AXALTA COATING SYSTEMS IP CO LLC

AI summary

A process for the production of a dark-color multi-layer coating, comprising the successive steps:(1) applying an NIR-opaque coating layer A′ from a waterborne pigmented coating composition A to a substrate,(2) applying a coating layer B′ from a waterborne pigmented coating composition B onto the substrate provided with coating layer A′,(3) subjecting the coated substrate obtained in step (2) to a drying step,(4) applying a clear coat layer, and(5) curing the coating layers simultaneously;wherein both coating compositions A and B comprise aqueous microgel and sheet silicate,wherein the pigment content of coating composition A comprises <90 wt. % of aluminum flake pigments and has such a composition that coating layer A′ exhibits low NIR absorption,wherein the pigment content of coating composition B consists 50 to 100 wt. % of black pigment with low NIR absorption and 0 to 50 wt. % of further pigment.