Sulfide Semiconductor Coatings Preventing Binder Chalking
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Solution Overview
Problem
Photocatalytic coatings face issues with chalking and reduced photocatalytic activity due to the degradation of organic binders by OH radicals and the limitations of using titanium dioxide, particularly in breaking down non-polar hydrocarbons like methane.
Innovation Solution
A coating material comprising an organic binder, a sulfidic photocatalytically active semiconductor such as zinc sulfide, and a filler/pigment, with minimal or no titanium dioxide, which reduces OH radical formation and enhances photocatalytic activity for air pollutant degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If titanium dioxide is used as photocatalyst in coating materials, then photocatalytic activity is improved, but chalking occurs due to degradation of organic binders by OH radicals
Solution Approach 1:
The patent changes the photocatalyst material parameter from titanium dioxide to zinc sulfide, which fundamentally alters the photocatalytic mechanism. Zinc sulfide generates fewer OH radicals compared to titanium dioxide, thereby reducing the degradation of organic binders and preventing chalking while maintaining photocatalytic activity for pollutant degradation.
Solution Approach 2:
The patent creates a composite coating material system combining zinc sulfide photocatalyst with organic binders and fillers/pigments. This composite approach allows the zinc sulfide to provide photocatalytic functionality while the organic binder matrix provides coating stability and adhesion, resolving the contradiction between photocatalytic activity and coating durability.
2Ease of manufacture
If organic binders are used in photocatalytic coatings, then ease of manufacture and coating flexibility are improved, but binder degradation by photocatalytic effects leads to chalking
Solution Approach 1:
The patent changes the photocatalyst type to zinc sulfide, which has different photocatalytic properties compared to titanium dioxide. Zinc sulfide generates fewer highly reactive OH radicals, thereby reducing the harmful photocatalytic degradation of organic binders and preventing chalking while allowing continued use of organic binder systems for ease of manufacture.
3Productivity
If titanium dioxide is used to achieve high photocatalytic activity, then degradation of pollutants is improved, but the coating becomes prone to yellowing reactions
Solution Approach 1:
The patent substitutes zinc sulfide for titanium dioxide as the photocatalyst. This material parameter change alters the photocatalytic pathway, reducing the formation of OH radicals that cause yellowing of organic binders, while zinc sulfide maintains effective photocatalytic degradation of atmospheric pollutants.
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 effectively prevents chalking and maintains high photocatalytic activity for breaking down harmful gases like methane and nitrogen oxides, while being durable and suitable for both indoor and outdoor use.
Implementation Method 1
a sulfide photocatalytically active semiconductor
Implementation Method 2
the desired photocatalytic reactions
Implementation Method 3
degradation of pollutants contained in the atmosphere and/or ambient air
Data Source
Figure 1
AI summary
The present invention relates to photocatalytic coating materials. In particular, the present invention relates to a coating material comprising at least one organic binder, at least one sulfide photocatalytically active semiconductor, and at least one filler and/or pigment, wherein the coating material is essentially free of titanium dioxide. The invention also relates to the use of such coating materials for the degradation of pollutants contained in atmospheric air, such as methane in particular.