Spray-Dried Dye Compositions in Silica Matrix
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Solution Overview
Problem
Existing dye compositions encapsulated in silicon dioxide matrices suffer from high bleeding rates and instability under pH changes and ascorbic acid, which affects their coloring performance and longevity in applications like food and cosmetics.
Innovation Solution
Water-soluble dyes are encapsulated in a SiOx sol using a spray-drying process without additives, followed by secondary drying and temperature treatment to enhance matrix stability and reduce bleeding, resulting in a finely particulate pigment powder with low bleeding and stability to pH and ascorbic acid.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If dyes are adsorbed on the matrix surface, then the encapsulation process is simple, but the concentration of dyes inside the matrix is very limited and bleeding is relatively high
Solution Approach 1:
The patent changes the encapsulation mechanism from surface adsorption to internal incorporation by modifying the matrix formation process. The sol is formed in the presence of the dye, allowing the dye to be trapped within the matrix structure during gelation, rather than merely adsorbed on the surface. This parameter change in the encapsulation mechanism enables higher dye concentration and reduced bleeding.
Solution Approach 2:
The dye is incorporated into the sol before the matrix gelation occurs. By performing the dye incorporation action preliminarily, during the sol formation stage rather than after matrix formation, the dye becomes entrapped within the developing matrix structure, achieving better retention and concentration.
2Reliability
If pigment particles are coated with a dye-free matrix envelope, then bleeding is significantly reduced, but the coloring effect is adversely affected by additional reflection and scattering of light
Solution Approach 1:
The patent eliminates the need for separate coating layers by incorporating the dye within a single integrated matrix structure. The matrix itself serves as both the encapsulation medium and the protective envelope, removing the need for additional coating steps that would cause light scattering and reduce coloring effect.
Solution Approach 2:
The encapsulation function and the coloring function are merged into a single homogeneous structure. The dye-containing sol forms a unified matrix where the dye is distributed throughout, eliminating the separate coating layer that would otherwise be needed for protection, thus avoiding light reflection and scattering issues.
3Illumination intensity
If the particle size is reduced to improve coloring effect, then the coloring performance increases, but the particle stability and handling become more difficult
Solution Approach 1:
The sol-gel phase transition is utilized to form stable, finely divided particles. The controlled gelation of the silicate sol creates a rigid, stable matrix structure that maintains particle integrity even at small sizes. This phase transition provides a mechanism to produce particles with both small size for good coloring and sufficient structural stability for handling.
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 dye compositions with a bleeding rate of ≤0.5% and improved stability, ensuring effective coloration and resistance to chemical influences, maintaining color integrity across various pH values and ascorbic acid exposure.
Implementation Method 1
water-soluble dyes are in an insoluble form, encapsulated in a silicon dioxide matrix, thereby protecting the dyes from bleeding and from the influence of substrate components
Implementation Method 2
The dyed sol is subjected to a spray-drying process for gelling. Any solvent residues possibly present are removed by secondary drying.
Implementation Method 3
Surprisingly, the optionally subsequent temperature treatment can effect a definitely decrease of the dye release (bleeding) from the composition, wherein the temperature treatment is carried out during a time period of at least 2 hours at a temperature of above 50° C.
Data Source
AI summary
The invention relates to spray-dried, washfast dye compositions, preferably in the form of pigment powders, having a bleeding rate of ≤0.5% and consisting of water-soluble functional dyes, preferably food dyes, which are firmly incorporated in a silica matrix. Apart from low bleeding of dye, these compositions are remarkable for their high stability to pH changes and/or ascorbic acid. The invention is also directed to the production of the dye compositions and the use thereof. The dye compositions are preferably employed in coloring foods, cosmetics, pharmaceutical products, but also in other uses.