Titanium Oxide Composite Particles UV Stability
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Solution Overview
Problem
Existing coatings containing titanium oxide for fluororesin films and outdoor articles suffer from discoloration, decomposition, and photocatalysis due to ultraviolet rays, leading to changes in visible light reflectance and mechanical strength deterioration, with insufficient durability against hydrogen fluoride.
Innovation Solution
Composite particles with a three-layer structure, comprising a titanium oxide core, a silicon oxide intermediate layer, and a cerium oxide outer layer, are used to form a coating layer, which reduces photocatalysis and enhances durability against hydrogen fluoride, maintaining the inherent color and mechanical strength of the coating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a coating layer containing titanium oxide pigment is formed on fluororesin film to reflect visible light, then visible light transmittance is suppressed, but titanium oxide undergoes discoloration and decomposition by ultraviolet rays causing the coating layer to change color and lose mechanical strength
Solution Approach 1:
The invention uses a composite particle structure consisting of a titanium oxide core surrounded by a silica shell. This composite structure combines the high reflectance property of titanium oxide with the UV resistance and chemical stability of silica, allowing the coating to maintain both visible light reflection and long-term durability under outdoor exposure.
Solution Approach 2:
The silica layer acts as an intermediary protective barrier between the titanium oxide pigment and the harmful ultraviolet rays. This intermediate layer absorbs or scatters UV radiation before it can reach the titanium oxide core, preventing photocatalytic degradation while allowing the titanium oxide to maintain its light-reflecting function.
2Illumination intensity
If titanium oxide is used as white pigment in coating layer, then visible light reflectance is improved, but photocatalysis by ultraviolet rays causes discoloration and mechanical strength deterioration of fluororesin film
Solution Approach 1:
The composite particle structure of titanium oxide core with silica shell creates a material that combines the beneficial optical properties of titanium oxide with the protective properties of silica, eliminating the harmful photocatalytic effects on the fluororesin substrate.
Solution Approach 2:
The silica layer serves as a protective intermediary that blocks ultraviolet rays from reaching the fluororesin film, thereby preventing photocatalytic degradation of the substrate while allowing the titanium oxide core to provide visible light reflection.
3Illumination intensity
If titanium oxide undergoes photocatalysis by ultraviolet rays, then hydrogen fluoride is formed which causes color fading of pigments in coating layer
Solution Approach 1:
The silica layer acts as a protective barrier that prevents the formation of hydrogen fluoride by blocking UV-induced photocatalysis of titanium oxide. This intermediate protection layer preserves the color stability of all pigments in the coating by eliminating the source of HF that would otherwise cause color fading.
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 composite particles effectively prevent discoloration, decomposition, and photocatalysis of titanium oxide, ensuring stable visible light reflectance and mechanical strength over a long period, even under outdoor exposure, while maintaining the coating's inherent color and adhesion.
Implementation Method 1
a method of reflecting the visible light, a method of absorbing the visible light, etc. may be mentioned
Implementation Method 2
a pigment having cerium oxide and dense amorphous silica precipitated on the surface of rutile-type titanium oxide
Implementation Method 3
By photocatalysis of titanium oxide by ultraviolet rays, the fluororesin film and the coating layer are likely to undergo discoloration
Data Source
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AI summary
Composite particles capable of constantly and highly preventing discoloration, decomposition and photocatalysis by ultraviolet rays despite containing titanium oxide; and a composition for forming a coating layer to be used as a coating material composition, particularly as a printing ink, and a coated article, employing such composite particles. Composite particles characterized in that each of them comprises, in order from the inside, a particle containing titanium oxide, a first covering layer containing silicon oxide, a second covering layer containing cerium oxide and a third covering layer containing silicon oxide, and their average particle size is from 0.15 to 3 µm. A composition for forming a coating layer and a coated article, employing the composite particles.