Conventional Technology for Aqueous White Dispersions
- jessicawieland
- 13 minutes ago
- 4 min read
Written by: Dr. Cathy Cooper, Technical Manager
Introduction
Titanium dioxide is one of the most widely used pigments globally, with millions of tonnes consumed each year across a range of coatings applications. Its exceptional refractive index and ability to scatter light make it particularly effective at delivering the high levels of opacity and brightness required in modern coatings. As formulators increasingly prioritise water‑based technologies to meet tightening environmental standards, achieving consistent and stable TiO₂ dispersion in aqueous systems has become a critical technical challenge. Although pigment manufacturers apply a variety of surface treatments to improve pigment handling, these alone cannot alone ensure the degree of separation and long-term stability required for optimum performance. This places significant importance on the dispersant technology selected to control particle interactions and maintain the desired fine particle size distribution.
In response to these challenges, Lankem has continued to develop a broad portfolio of high‑performance dispersants based on conventional chemistry that deliver reliable and robust pigment stabilization. Among these are Lansperse SPA and Lansperse DS80; two established products designed to promote effective wetting, deflocculation, and long‑term stability of inorganic pigments in water‑based formulations. Lansperse SPA is a sodium polyacrylate‑based dispersant engineered to provide strong electrostatic stabilisation. Lansperse DS80 is a proprietary anionic dispersing agent, combining effective wetting with complementary steric and electrostatic stabilisation mechanisms to give effective protection against pigment flocculation.
This report presents findings from our latest laboratory studies in which Lansperse SPA and Lansperse DS80 were evaluated against a sodium polyacrylate market standard in controlled titanium dioxide dispersion tests. By examining parameters such as viscosity and particle size development, these trials aim to provide a clear and objective comparison of performance.
Figure 1: Structural representation and details of the dispersing agents tested
Experimental
Pre-mixes were made using a Silverson at 1000 rpm, adding ingredients as specified in Table 1 with all liquid components mixed first before addition of pigment over 10 minutes. Once all the pigment was added, further homogenisation was performed at 4000 rpm for 15 minutes.
Table 1: Aqueous formulations of titanium dioxide and a range of dispersants at a pigment loading of 65% w/w and a dispersant loading of 1% actives w/w relative to the pigment.
Component | Percentage (as supplied) | ||
Market Standard | 1.62 | --- | --- |
Lansperse DS80 | --- | 0.81 | --- |
Lansperse SPA | --- | --- | 1.55 |
Dfoam AR2 | 0.10 | 0.10 | 0.10 |
Biocide | 0.10 | 0.10 | 0.10 |
Kemectant EB3 | 2.00 | 2.00 | 2.00 |
Tioxide® TR92 | 65.00 | 65.00 | 65.00 |
Deionised Water | To 100% | To 100% | To 100% |
The viscosity of the resulting dispersions was measured with a Haake Roto-Visco 1 instrument at a shear rate range of 5-100 s-1. Particle size was measured with a Malvern Instruments Mastersizer, giving values for the Dx(10), Dx(50) and Dx(90) in µm. Storage stability was evaluated by placing the dispersions in an oven at 50 °C for 1 week and re-measuring viscosity and particle size after equilibration back to room temperature.
Results and Discussion
Figure 2 shows the initial viscosity of the three dispersions as a function of shear rate. Both sodium polyacrylate dispersants showed thixotropic behaviour, with a decrease in viscosity with shear rate. This was more subtle with Lansperse DS80, arising from the combination of the electrostatic and steric hinderance giving improved particle-particle separation and protecting against weak flocculation at low shear rates.
Initial particle size is displayed in Figure 3. Although Dx(10) and Dx(50) are broadly similar for the three samples, the differences in Dx(90) highlight dispersion quality. When the market standard sodium polyacrylate was used, the Dx(90) was 166 µm, indicating the presence of large undispersed aggregates still present within the sample. The Lankem variant of the same chemistry gave an improved performance, with a Dx(90) of 8.29 µm for Lansperse SPA. However, the proprietary anionic dispersant Lansperse DS80 had a significantly lower Dx(90) of 1.45 µm, indicative of a more uniform distribution of pigment particle sizes.
Figure 2: Initial millbase viscosity as a function of applied shear rate for aqueous titanium dioxide dispersions made with three synthetic dispersing agents
Figure 3: Initial particle size of the three titanium dioxide dispersions. Although Dx(50) is similar, the Dx(90) for the market standard product is significantly higher than the Lankem dispersions.
Storage stability data is displayed Figure 4. On the left, the initial viscosity at a shear rate of 10 s-1 is compared with the viscosity after storage at an elevated temperature of 50 °C. Lansperse DS80 gives the lowest storage viscosity and the least change from the initial value. The large drop for the market standard is indicative of the dense titanium dioxide pigment settling to the bottom of the sample under gravity.
This effect is also seen in the significant change of Dx(90) particle size. For the market standard dispersant, the initial particle size was high, but during storage the flocculated pigment has settled and in the measurement at 7 days the Dx(90) is comparable to the other dispersions. Lansperse DS80 gives the most stable dispersion, with no significant change in particle size between the initial and the storage measurements.
Figure 4: Storage performance of the dispersions; on the left is viscosity at shear rate 10 s-1 immediately after milling and upon storage at 50°C for 7 days. The graph on the right shows the change in Dx(90) particle size over time.
Conclusion
This study demonstrates that dispersant selection has a significant influence on both the initial dispersion quality and the storage stability of high‑solids aqueous titanium dioxide systems. While all three dispersants evaluated could produce workable dispersions under identical processing conditions, clear and measurable differences were observed in viscosity behaviour, particle size distribution, and resistance to pigment settling during elevated temperature storage.
Compared with a typical market‑standard sodium polyacrylate, Lansperse SPA provides a clear step forward in dispersion quality, delivering improved control of coarse particle populations while maintaining the familiar handling and formulation flexibility associated with polyacrylate‑based systems. For formulators seeking enhanced performance without moving away from established technology, this makes Lansperse SPA a reliable and practical option for aqueous titanium dioxide dispersions. Where maximum dispersion efficiency and stability are required, Lansperse DS80 offers the highest level of performance, combining strong wetting with complementary steric and electrostatic stabilisation to deliver fine particle size distributions, lower low‑shear viscosity, and excellent storage stability. Together, these results highlight how a tailored approach to dispersant selection allows formulators to balance performance, robustness, and formulation objectives in aqueous white systems.
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