Titanium Dioxide Coating Without Drying
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Solution Overview
Problem
Conventional titanium dioxide pigment production processes are energy-intensive and costly due to the need for drying steps, which can cause particle aggregation and require subsequent micronizing to achieve the desired particle size distribution, leading to inefficiencies and increased costs.
Innovation Solution
A method involving the preparation of a titanium dioxide product by maintaining colloidal stability during coating with inorganic oxides or hydrous oxides, allowing for concentration without drying, thus avoiding the need for energy-intensive micronizing and reducing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a drying step is applied to titanium dioxide dispersion, then the coating is sufficiently condensed onto the particles, but energy consumption increases and particles aggregate
Solution Approach 1:
The patent changes the physical-chemical parameters of the dispersion system by controlling pH and adding electrolytes to achieve coating condensation without drying. The coating process is performed at controlled pH levels (typically 2-3 units below the isoelectric point) with specific electrolyte concentrations to enable particle aggregation and coating deposition in the wet state, eliminating the need for energy-intensive drying steps.
Solution Approach 2:
The patent replaces the thermal drying process with a chemical/co胶idal control mechanism. Instead of using heat to evaporate water and condense coating, the invention uses pH adjustment and electrolyte addition to control the zeta potential and induce controlled aggregation, allowing coating to deposit effectively in the wet dispersion state.
2Reliability
If particles are aggregated by drying, then coating condensation is achieved, but particle size distribution deteriorates and micronizing is required
Solution Approach 1:
The patent controls the degree of aggregation through precise parameter adjustment - specifically controlling pH to be 2-3 units below the isoelectric point and adjusting electrolyte concentration to achieve optimal zeta potential. This controlled aggregation provides sufficient coating condensation while maintaining particle size distribution within acceptable ranges, eliminating the need for subsequent micronizing operations.
3Manufacturing precision
If conventional drying and micronizing steps are applied, then desired particle size distribution is achieved, but production cost increases
Solution Approach 1:
The patent eliminates costly drying and micronizing steps by adjusting dispersion parameters during the coating process. By controlling pH and electrolyte concentration to achieve optimal colloidal stability and controlled aggregation, the process achieves both adequate coating condensation and acceptable particle size distribution in a single integrated step, significantly reducing production costs.
4Stability of the object's composition
If pH is adjusted away from isoelectric point, then colloidal stability is maintained, but coating efficiency decreases
Solution Approach 1:
The patent optimizes the balance between colloidal stability and coating efficiency by controlling pH to be specifically 2-3 units below the isoelectric point. At this pH range, the zeta potential is sufficiently negative to maintain reasonable colloidal stability preventing excessive aggregation, while still allowing adequate coating material deposition on particle surfaces. Electrolyte concentration is simultaneously adjusted to fine-tune the aggregation behavior and coating efficiency.
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 a titanium dioxide pigment concentrate with reduced photocatalytic activity, suitable for use in paints and inks, offering good durability without the need for drying or micronizing, resulting in a more energy and cost-efficient process.
Implementation Method 1
The surface treatment step generally includes precipitating alumina, silica, zirconia, and/or other metal oxides, on the surface of the titanium dioxide
Implementation Method 2
concentrating the dispersion, by subjecting the dispersion to the effects of cross-flow filtration
Implementation Method 3
The drying step after the surface treatment is believed to ensure that the coating is sufficiently condensed onto the particles
Data Source
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AI summary
The invention provides a method for preparing a titanium dioxide product, comprising the steps of: -providing a dispersion comprising titanium dioxide particles, wherein the dispersion contains from 50g/l to 600g/l TiO2; and then, in any order, -applying an inorganic coating to the titanium dioxide particles, whilst maintaining colloidal stability before and/or during the coating step; -concentrating the dispersion, by subjecting the dispersion to the effects of cross-flow filtration and continuing the cross-flow filtration process until the dispersion is in a concentrated form that contains 800g/l or more TiO2; so as to provide a titanium dioxide product in the form of a concentrated dispersion of coated particles. The concentrated dispersion of coated particles may optionally be dispersed within a vehicle to obtain a pigment product.