Why does titanium dioxide stratify and settle in water-based color pastes? What are some good solutions?
Core Reason: Titanium dioxide has a high density (approximately 4.2 g/cm³). If the dispersant in the color paste is
insufficiently adsorbed, the system viscosity is too low, or the thixotropy is poor, the particles are prone to
agglomeration and sedimentation due to gravity.
Solutions:
1. Select a suitable dispersant: Prioritize using titanium dioxide-specific dispersants (such as polycarboxylate dispersants),
and control the addition amount (usually 3%-8% of the titanium dioxide mass) to ensure the formation of a stable
adsorption layer on the particle surface.
2. Optimize the grinding process: Grind the titanium dioxide to a stable particle size of 2-5 μm to reduce the probability
of agglomeration and improve dispersion uniformity.
3. Adjust the system viscosity: Add an appropriate amount of thickener (such as hydroxyethyl cellulose or bentonite) to
increase the viscosity of the color paste (controlled at 500-2000 mPa·s at 25℃), enhancing thixotropy and hindering
sedimentation.
4. Control pH value: Maintain the pH of the aqueous system at 8-9 to avoid surface charge imbalance of titanium
dioxide leading to agglomeration.
Do you need me to recommend specific brands of dispersants/thickeners, or provide specific parameters for
adjusting the color paste formula?
I. Dispersant + Thickener Combination Schemes (3 Highly Compatible Combinations)
1. General Purpose (Cost-Effective): Dispersant: Polycarboxylate (e.g., RK-4017E, 4%-5% addition) + Thickener:
Hydroxyethyl cellulose (HEC, 0.3%-0.5% addition). Compatible with most water-based construction/industrial color
pastes, with a sedimentation inhibition rate of 90%+.
2. Highly Stable (Long-Lasting Storage): Dispersant: Phosphate ester (e.g., RK-4026, 5%-6% addition) + Thickener:
Organobentonite (1%-1.5% addition). Strong thixotropic, no significant sedimentation after 3 months of storage at
low temperature (0-5℃).
3. Low-odor, environmentally friendly (food/toy grade): Dispersant: Polyether-based (e.g., RK-4044, 3%-4% addition)
+ Thickener: Xanthan gum (0.2%-0.4% addition). Odorless, meets environmental standards, and exhibits excellent
dispersion stability.
II. Key Parameters for Pigment Formulation Adjustment (Directly Apply)
- Titanium Dioxide Content: Controlled at 25%-35% (too high leads to overload and sedimentation; too low
results in cost waste);
- Grinding Endpoint: Particle size D90≤3μm (detected using a laser particle size analyzer);
- System pH: 8.5±0.3 (calibrated with a pH meter, can be adjusted with AMP-95);
- Final Viscosity: 800-1200 mPa·s at 25℃ (tested with a rotational viscometer at 60 rpm).
Do you need me to refine the formulation for a specific application scenario (e.g., coatings, inks, plastics),
or provide specific operating procedures for sedimentation testing? I. Highly Compatible Dispersant +
Thickener Combinations (3 Practical Combinations)
1. General Purpose (Cost-Effective First Choice)
- Dispersant: Polycarboxylate (e.g., RK-4017E, RK-4044), addition amount 4%-6% (based on titanium dioxide mass)
- Thickener: Hydroxyethyl cellulose (HEC, e.g., Natrosol 250HBR) + Bentonite (e.g., Bentonite LT), HEC addition
amount 0.3%-0.8%, bentonite 0.5%-1%, system viscosity controlled at 800-1200 mPa·s
2. Anti-Settling Enhanced Type (High Titanium Dioxide Content Scenarios)
- Dispersant: Phosphate ester dispersant (e.g., RK-4026) + Synergistic dispersant (e.g., RK-4008Y), total addition
amount 6%-8%
- Thickener: Polyurethane thickener + Fumed silica, PU thickener 0.5%-1.2%, fumed silica 0.3%-0.6%, viscosity
1200-1800 mPa·s
3. Low-odor, environmentally friendly type (for coatings/inks)
- Dispersant: Environmentally friendly polyether dispersant (e.g., RK-4044), addition 3%-5%
- Thickener: Associative alkali-swelling thickener, addition 0.4%-1.0%, viscosity 600-1000 mPa·s
II. Key parameters for adjusting pigment paste formulation (directly apply)
- Titanium dioxide content: Recommended to be controlled at 40%-60% (too high and it will easily settle; too low
and the cost-effectiveness is low)
- pH value: Strictly maintain 8.2-8.8, adjusted with AMP-95 (2-amino-2-methyl-1-propanol)
- Grinding endpoint: Particle size D90≤3μm (detected with a laser particle size analyzer)
- Storage conditions: Avoid high temperatures (<40℃) and drastic temperature differences. Stir thoroughly
before standing. Check sedimentation weekly.
