High-Pigment Titanium Dioxide Slurry via Non-Milling Dispersion
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Solution Overview
Problem
Current titanium dioxide slurries for automotive coatings face challenges such as high binder content, low pigment content, and high viscosity, which limit their use and require a milling step, making them energy-intensive, costly, and incompatible with various binder systems, while also suffering from storage stability issues.
Innovation Solution
A method for producing an aqueous titanium dioxide slurry with a high pigment content (65-85 wt.%) and low viscosity, using a non-milling mixing process with a dispersion medium containing water, organic solvents, defoamers, and dispersing agents, allowing for easy redispersement and universal employability in different coating compositions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a two-step milling process is used to produce titanium dioxide slurry, then particle size distribution and storage stability are improved, but pigment content is limited to not more than 50 wt.-% and binder content becomes relatively high
Solution Approach 1:
The invention changes the key parameter of viscosity by using a high-boiling-point organic solvent (boiling point >100°C) in the dispersion medium. This allows the slurry to maintain low viscosity (below 2000 mPa·s at 20°C) even with high pigment content (65-85 wt.-%), eliminating the need for a second milling step while achieving both high pigment content and good storage stability
Solution Approach 2:
The invention extracts the milling step from the traditional two-step process by using a specially formulated dispersion medium that enables direct dispersion of titanium dioxide pigment at high concentrations without requiring mechanical milling. This removes the limiting factor of milling viscosity that previously constrained pigment content to below 50 wt.-%
2Manufacturing precision
If milling is performed to achieve desired particle size distribution, then fineness is improved, but energy consumption and process complexity increase
Solution Approach 1:
The invention extracts and eliminates the milling step from the traditional two-step process. By using a high-boiling-point organic solvent in the dispersion medium, the pigment can be directly dispersed to the desired fineness (Hegman scale <15 μm) without mechanical milling, thereby reducing process complexity and energy consumption while maintaining manufacturing precision
Solution Approach 2:
The invention replaces the mechanical milling system with a chemical/physical dispersion approach. The high-boiling-point organic solvent creates a dispersion medium that enables direct dispersion of pigment particles to the required fineness through mixing alone, substituting mechanical grinding with a solvent-based dispersion mechanism
3Reliability
If high binder content is used to maintain storage stability, then stability against pigment settlement is improved, but compatibility with various binder systems is reduced
Solution Approach 1:
The invention changes the composition parameters of the dispersion medium by incorporating a high-boiling-point organic solvent (10-30 wt.-%) along with water and dispersing agents. This parameter change enables the system to achieve storage stability through controlled dispersion rather than high binder content, resulting in low binder content (1-10 wt.-%) and broad compatibility with various binder systems in the final coating composition
4Ease of operation
If low viscosity is achieved by increasing liquid carrier medium, then pumpability is improved, but pigment content decreases
Solution Approach 1:
The invention changes the viscosity parameter by introducing a high-boiling-point organic solvent into the dispersion medium. This solvent modification allows the slurry to maintain low viscosity (below 2000 mPa·s at 20°C) while simultaneously achieving high pigment content (65-85 wt.-%), thus improving pumpability without sacrificing pigment concentration
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 results in a stable, easily pumpable titanium dioxide slurry with excellent storage stability, suitable for various coating compositions, eliminating the need for milling and ensuring good gloss, brightness, and levelling in coatings without increasing operational costs or complexity.
Implementation Method 1
1.0 wt.-% to 5.0 wt.-% of at least one dispersing agent being selected from the group consisting of polymers containing polyalkyleneoxide groups
Implementation Method 2
providing an aqueous dispersion medium, containing, based on the total weight of the dispersion medium, a. at least 50 wt.-% of water; b. 10 wt.-% to 28 wt.-% of at least one water-soluble and/or water-miscible organic solvent
Data Source
AI summary
Disclosed herein is a method for producing an aqueous titanium dioxide slurry. The method includes (a) providing an aqueous dispersion medium, and (b) dispersing titanium dioxide into the aqueous dispersion medium provided in step (a) to obtain a titanium dioxide slurry containing at least 65 wt.-% up to 85 wt.-% of titanium dioxide, based on the total weight of the thus obtained slurry, where step (b) is carried out by sole use of a non-milling mixing device and at least until the Hegman fineness of the titanium dioxide particles is below 8 μm. Further disclosed herein are a slurry obtained from the disclosed method, a coating composition containing the same, and a method for producing a coating and a thus coated substrate.