Hematite Pigment Color Saturation via Goethite Oxidation
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Solution Overview
Problem
Current methods for producing hematite pigments result in red pigments with low color saturation, primarily used in the building industry, and existing improvements do not adequately address color appearance issues, particularly with high b* values causing an orange cast.
Innovation Solution
A process involving suspending a goethite-containing pigment and alkali metal phosphate in water, followed by oxygen treatment at 750-1000°C, to produce hematite pigments with specific CIELAB values and low water content, achieving improved color properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional methods (nitrate process, precipitation, hydrolysis) are used to produce hematite pigments, then the production process is established and widely used, but the color saturation is low and the b* value is high causing orange cast
Solution Approach 1:
The patent changes key parameters including using goethite as starting material instead of iron salts, controlling particle size to 10-100 nm, adjusting aspect ratio to 1.05-1.3, and optimizing CIELAB values (a*≥28.5, b*≤71% of a*). These parameter changes transform the pigment properties to achieve high color saturation while maintaining manufacturability through a systematic process.
Solution Approach 2:
The invention uses composite structures with goethite particles having specific morphology (aspect ratio 1.05-1.3) and size distribution (10-100 nm), creating a composite pigment system that achieves superior color properties. The composite nature of the goethite structure itself (with controlled internal architecture) enables the desired optical properties.
2Manufacturing precision
If hematite pigments are produced with high color saturation and improved a* and b* values, then color appearance is enhanced, but the production process becomes more complex and requires precise control
Solution Approach 1:
The patent applies preliminary action by using goethite as a pre-formed starting material with controlled morphology and size distribution before the final hematite formation. This preliminary structuring of the iron oxide particles ensures that when converted to hematite, the desired aspect ratio (1.05-1.3) and particle size (10-100 nm) are already in place, reducing the need for complex post-processing control.
Solution Approach 2:
The invention replaces conventional mechanical mixing and thermal processing with a chemical transformation approach using goethite as starting material. This substitution allows for more precise control of particle morphology and size distribution through chemical means rather than mechanical means, achieving the target CIELAB values with less process complexity.
3Adaptability or versatility
If conventional hematite production methods are used, then the process is simple and well-established, but the pigments are primarily limited to building industry applications
Solution Approach 1:
The patent creates universal hematite pigments with superior color properties (a*≥28.5, b*≤71% of a*) that can serve multiple industrial applications beyond just the building industry. The controlled particle size (10-100 nm), aspect ratio (1.05-1.3), and color values make the pigment suitable for paints, coatings, plastics, and other applications requiring high color saturation, thereby achieving multi-functionality.
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 yields hematite pigments with enhanced color saturation and appearance, specifically a* and b* values, suitable for broader industrial applications beyond the building sector.
Implementation Method 1
treating the isolated solids of step b) in the presence of oxygen at a temperature of 750 to 1000°C
Implementation Method 2
treating the isolated solids of step b) in the presence of oxygen at a temperature of 750 to 1000°C
Data Source
AI summary
A hematite pigment having i) an aspect ratio AR of lower than 1.5, preferably lower than 1.3, most preferably lower than 1.2,5 ii) a CIELAB a* value of ≥ 28.5, in particular from 29 to 33, iii) a CIELAB b*-value of ≤ 71% of the CIELAB a* value, preferably ≤ 70% of the CIELAB a* value iv) a CIELAB L* value of ≥ 39, in particular from 40 to 43, preferably 40 to 41.10