TiO2 Coating Agitator Energy Control for Uniform Particle Surfaces
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Solution Overview
Problem
Existing methods for coating inorganic particles in aqueous suspensions often result in uneven, non-uniform coatings due to local concentration, pH, viscosity, and temperature gradients, leading to excessive shear forces and detachment of coating substances, which negatively impact optical properties.
Innovation Solution
A method involving heating the suspension to 30-95°C, adding water-soluble precursors at controlled pH levels, and using an agitator with low energy input to circulate the suspension through a circuit, minimizing gradients and avoiding high shear forces, thereby ensuring a smooth and uniform coating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If intense stirring is applied to improve mixing during coating, then coating uniformity improves, but shear forces increase causing coating detachment and rough surfaces
Solution Approach 1:
The patent changes the physical parameters of the mixing process by reducing energy input from intense stirring to gentle agitation (0.5-2.0 kWh/m³), and by controlling temperature (30-95°C) and pH (3-10.5) to optimize coating formation while minimizing shear forces that would detach the coating
Solution Approach 2:
The patent applies dynamic control by adjusting mixing energy input within a specific range (0.5-2.0 kWh/m³) to achieve sufficient mixing without excessive shear forces, and by controlling the addition rate of precursor compounds to maintain uniform concentration without causing local precipitation
2Ease of manufacture
If batch process with large stirred vessel is used, then coating can be applied, but local concentration and pH gradients occur causing uneven coating
Solution Approach 1:
The patent transitions from static batch processing to a dynamic continuous process where the suspension flows through the coating zone, ensuring continuous mixing and uniform distribution of precursor compounds, eliminating local concentration and pH gradients that occur in batch processes
Solution Approach 2:
The patent applies preliminary action by pre-dissolving precursor compounds and pre-adjusting pH before entering the coating zone, ensuring uniform distribution before coating formation begins, which prevents local gradients during the coating process
3Productivity
If rotor-stator mixer is used to improve mixing, then mixing efficiency improves, but high shear forces damage the coating
Solution Approach 1:
The patent replaces the high-shear mechanical rotor-stator mixing system with a gentle agitation system that provides sufficient mixing (0.5-2.0 kWh/m³ energy input) without creating high shear forces, substituting intense mechanical action with controlled, low-energy mixing
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 achieves a uniform and continuous surface coating with improved optical properties, reduced sulfuric acid solubility, and enhanced flowability of coated particles, while avoiding shearing of post-treatment shells.
Implementation Method 1
the aqueous suspension passes during coating step b), preferably coating steps b) and c), at least one agitator, wherein the at least one agitator provides an energy input of 1.6 kWh/m³
Implementation Method 2
a) heating the aqueous suspension of inorganic particles to a temperature in the range of from 30 to 95°C, preferably of from 70 to 95°C
Implementation Method 3
The pH of the suspension is then adjusted with alkaline or acidic substances so that the precursor compounds precipitate as oxides, hydroxides, etc.
Data Source
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AI summary
The present invention relates to a method for coating inorganic particles in an aqueous suspension with at least one coating substance, comprising the steps of a) heating the aqueous suspension of inorganic particles to a temperature in the range of from 30 to 95°C; b) adding a first watersoluble precursor of a coating substance to the aqueous suspension and curing the aqueous suspension in a temperature range of from 30 to 95°C at a pH in the range of from 3 to 10.5; d) wherein the temperature of the aqueous suspension during the overall coating process is set in the range of from 30 to 95°C and the pH of the aqueous suspension during the overall coating process is in the range of from 3.0 to 10.5; e) wherein the aqueous suspension passes during coating step b) at least one agitator wherein the at least one agitator provides an energy input of 1.6 kWh/m3 or less and has a rotational speed of 5900 rpm or less; and f) wherein the aqueous suspension is circulated at least during step b) by the at least one agitator in a circuit, wherein the circuit contains the at least one agitator and at least one vessel.