Narrowing Titanium Dioxide Particle Size via Cascade Milling
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Solution Overview
Problem
Titanium dioxide pigments produced by the sulfate process typically have a broader particle size distribution, which affects their suitability for use in coatings and printing inks, as they can compromise opacity and gloss.
Innovation Solution
A multi-passage milling process in a cascade of at least three agitator ball mills is used, where the grinding media in the first mill have a larger diameter and higher density than in subsequent mills, optimizing energy input and minimizing the production of fine fractions, with adjustments made based on the decreasing viscosity of the suspension.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If sulfate process is used to produce titanium dioxide pigment, then production cost and feasibility are improved, but particle size distribution becomes broader
Solution Approach 1:
The grinding process is divided into multiple sequential passages through a cascade of at least three agitator ball mills. Each mill performs a specific stage of size reduction, with the first mill handling coarse grinding and subsequent mills performing finer grinding. This segmentation allows progressive control over particle size distribution, transforming the broad distribution from sulfate process into a narrow distribution suitable for high-quality coatings and printing inks.
2Loss of time
If single-pass wet milling is performed, then processing time is reduced, but particle size distribution remains broad
Solution Approach 1:
The grinding operation is segmented into multiple passages through a cascade of three or more agitator ball mills arranged in series. The suspension progresses sequentially through each mill, with each mill contributing to progressive size reduction. This multi-pass approach achieves narrow particle size distribution without requiring excessive residence time in any single mill, balancing processing efficiency with product quality.
3Use of energy by moving object
If grinding media with smaller diameter are used, then energy input is reduced, but particle size distribution broadens
Solution Approach 1:
The cascade configuration segments the grinding function across three or more mills, allowing each mill to operate with optimally sized grinding media for its specific stage. The first mill can use larger media for efficient coarse grinding, while subsequent mills use progressively smaller media for finer size reduction. This segmentation enables energy-efficient operation at each stage while achieving the cumulative effect of narrow particle size distribution.
4Manufacturing precision
If circuit grinding or multi-batch grinding is performed, then particle size distribution narrows, but device complexity and processing time increase
Solution Approach 1:
The invention implements segmentation in a linear cascade configuration rather than requiring complex circuit loops or multiple batches. The suspension flows sequentially through three or more mills in series, with each mill performing a defined portion of the size reduction task. This linear segmented approach achieves narrow particle size distribution with simpler process flow and reduced operational complexity compared to circuit grinding systems that require recirculation and control mechanisms.
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
This process achieves a narrower particle size distribution, enhancing the pigment's suitability for coatings and printing inks by optimizing particle size and reducing excess grinding, thereby improving optical properties such as opacity and gloss.
Implementation Method 1
the wet milling is conducted as a passage milling in a cascade of at least three agitator ball mills and that the grinding media of the first agitator ball mill have a larger diameter and a higher density
Implementation Method 2
the titanium dioxide particles obtained by the sulfate process are ground in an aqueous suspension
Data Source
AI summary
The invention relates to a process for producing a titanium dioxide pigment obtainable by the sulfate process with a narrow particle size distribution, the pigment itself, and the use of said pigments in coatings and printing inks.