Titanium Dioxide Photostability via pH-Controlled Aluminum Oxide
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Solution Overview
Problem
Titanium dioxide particles produced via the chloride process exhibit poor photochemical stability and UV-greying resistance, leading to chalking and discoloration in paints and laminates, and the use of nitrate to suppress UV-greying is environmentally undesirable.
Innovation Solution
A method involving a mixture of titanium tetrahalide, an oxygen-containing gas, and an aluminum compound is used to form titanium dioxide particles with increased aluminum oxide on their surface, processed in a reaction zone at controlled temperatures and pH levels between 4.0 and 9.5, preferably 5.0 and 6.0, to enhance stability and resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If titanium dioxide is produced via the chloride process, then manufacturing efficiency and cost-effectiveness are improved, but photochemical stability and UV-greying resistance deteriorate
Solution Approach 1:
The patent changes the pH parameter of the aqueous suspension from the conventional highly acidic range (below 3.5) to a neutral or slightly alkaline range (pH 4.0-9.0, preferably 6.5-8.5). This parameter change fundamentally alters the surface chemistry of the titanium dioxide particles, enabling the formation of a protective aluminum oxide layer that improves photochemical stability while maintaining the benefits of the chloride process
Solution Approach 2:
The patent creates a composite structure by forming aluminum oxide on the surface of the titanium dioxide particles. This composite material combines the high refractive index and pigmentary properties of titanium dioxide with the photochemical stability and UV resistance of aluminum oxide, thereby resolving the contradiction between manufacturing efficiency and photochemical stability
2Reliability
If aluminum oxide is increased on the titanium dioxide surface, then photochemical stability improves, but manufacturing complexity increases
Solution Approach 1:
The patent merges the pigment production step with the surface treatment step into a single integrated process. By adjusting the pH of the aqueous suspension after chloride process production, the formation of aluminum oxide on the titanium dioxide surface occurs automatically during the same manufacturing sequence, eliminating the need for separate surface treatment equipment and processes
Solution Approach 2:
The patent employs a self-service mechanism where the aluminum compounds already present in the system (from the chloride process) automatically form aluminum oxide on the titanium dioxide surface when the pH is adjusted to 4.0-9.0. This self-organizing process requires no additional reagents, energy input, or complex control systems, thereby improving photochemical stability without increasing manufacturing complexity
3Reliability
If nitrate is used to suppress UV-greying, then UV-greying resistance improves, but environmental friendliness deteriorates
Solution Approach 1:
The patent extracts and eliminates the harmful nitrate substance from the system by replacing it with an environmentally benign approach. By adjusting the pH to 4.0-9.0 and utilizing aluminum compounds, the patent achieves UV-greying resistance without incorporating nitrate, thereby removing the environmental pollution problem while maintaining the protective function
Solution Approach 2:
The patent replaces the persistent environmental pollutant (nitrate) with a harmless, naturally occurring system based on pH adjustment and aluminum oxide formation. This substitution uses environmentally friendly materials that do not accumulate or cause pollution, thereby achieving UV protection without compromising environmental friendliness
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 method produces titanium dioxide particles with improved photochemical stability and reduced UV-greying resistance, allowing for the potential reduction or elimination of nitrate use, while maintaining environmental friendliness.
Implementation Method 1
reacting the titanium tetrahalide, the oxygen-containing gas and the aluminum compound in a reaction zone to form a titanium dioxide particle and aluminum oxide on the surface of said particle
Implementation Method 2
reacting the titanium tetrahalide, the oxygen-containing gas and the aluminum compound in a reaction zone to form a titanium dioxide particle
Data Source
AI summary
The invention relates to a method for obtaining a titanium dioxide particle according to the chloride process which exhibit improved photostability and UV-greying resistance, said particle obtained by this method and the use of the obtained titanium dioxide particle in various applications. Also, the invention pertains to the use of a pH value of 4.0 to 9.0 to obtain a photostable titanium dioxide particle.