Dark-Color Multi-Layer Coating with NIR Reflection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Dark-color coatings absorb near-infrared radiation, causing substrates to heat up, which is undesirable, especially in applications like motor vehicles, where it increases the need for air-conditioning fuel consumption.
Innovation Solution
A wet-on-wet-on-wet multi-layer coating process using solventborne pigmented coating compositions with specific components like melamine-formaldehyde resin crosslinker, cellulose ester binder, sheet silicate, fumed silica, urea SCA, and polyolefine wax, applied in successive steps with simultaneous thermal curing, to achieve a dark-color shade with low NIR absorption and reduced heat development.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If dark-color pigments (carbon black) are used in coating, then the coating provides desired dark color shade, but the substrate heats up significantly in sunlight due to NIR absorption
Solution Approach 1:
The coating is divided into multiple layers with different functions: a first layer containing IR-reflective pigments (aluminum flake, titanium dioxide) to reflect near-infrared radiation, and a second layer containing dark-color pigments (carbon black, iron oxide) to provide the desired dark color shade. This segmentation allows each layer to perform its specific function without interfering with the other, resolving the contradiction between heat reflection and color appearance.
Solution Approach 2:
The invention uses composite coating compositions combining different types of pigments and binders. The first coating composition includes IR-reflective pigments (aluminum flake pigment, titanium dioxide) combined with specific binders (cellulose ester, NAD binder) to create a layer that reflects NIR radiation. The second coating composition includes dark-color pigments (carbon black, iron oxide) to provide the dark color shade. This composite approach allows the coating to simultaneously achieve heat reflection and desired color appearance.
2Temperature
If multi-layer coating structure is used to reduce heat absorption, then thermal impact is reduced, but the coating process becomes more complex
Solution Approach 1:
The invention combines multiple coating compositions (first and second coating compositions with different pigment systems) into a single multi-layer coating structure applied in sequence. The first coating layer with IR-reflective pigments is applied first, followed by the second coating layer with dark-color pigments. This merging of functional layers into a unified coating system achieves heat reduction while maintaining a manageable coating process through systematic layer application.
3Temperature
If specific binder compositions (cellulose ester, NAD binder) are used to achieve low NIR absorption, then heat development is reduced, but formulation complexity increases
Solution Approach 1:
The invention specifies precise parameter ranges for binder composition (cellulose ester content, NAD binder content, resin solids content) and pigment content in both coating compositions. By controlling these parameters within defined ranges, the coating achieves optimal NIR reflection properties and low heat development. The first coating composition requires 5-20 wt% cellulose ester binder and 10-100 wt% NAD binder with 15-30 wt% resin solids, while the second coating composition requires similar binder ratios with 20-40 wt% resin solids. These parameter specifications ensure low NIR absorption while maintaining formulation manageability through clear numerical guidelines.
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 effectively produces dark-color multi-layer coatings that minimize heat absorption in sunlight, maintaining a desired color shade while reducing thermal impact on substrates, suitable for industrial mass production.
Implementation Method 1
both coating compositions A and B comprise resin solids consisting of binder solids plus crosslinker solids comprising melamine-formaldehyde resin crosslinker
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
Implementation Method 3
carbon black pigments which absorb radiation in the near-infrared wavelength range and transform it into heat
Implementation Method 4
thermally curing the coating layers applied in steps (1), (2), and (4) simultaneously
Implementation Method 5
applying a coating layer B from a solventborne pigmented coating composition B onto the substrate provided with coating layer A
Data Source
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 solventborne coating composition A to a substrate,(2) applying a coating layer B′ from a solventborne 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 binders and crosslinkers comprising melamine-formaldehyde resin crosslinker,wherein both coating compositions A and B comprise certain proportions of cellulose ester binder and NAD binder and/or sheet silicate and/or fumed silica and/or urea SCA and/or polyolefine wax,wherein the pigment content of coating composition A comprises <90 wt. % of aluminum flake pigments and is composed in such a way that NIR-opaque 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.