The role of a dispersant in a millbase for any ink or coating formulation is very important as it contributes to the dispersion development, particle size reduction and stabilization of the particles, while optimizing the performance of the pigment or particle being dispersed. Choosing the right dispersant can help reduce the overall cost of a formulation.
The use of an optimal dispersant can improve many properties of the particle being dispersed, such as rheology and tinting strength (for pigments), which can result in the need for less pigment to achieve the same standard (STD) color. Reducing pigment will consequently reduce the overall formulation cost, as the pigment is often a major contributor in the total formula cost. An effective dispersant will be adsorbed onto the pigment surface, consequently reducing the Van der Waals attraction forces, which results in better rheology and a lower viscosity. Choosing the right dispersant can lead to less dispersant requirement to achieve the optimum Agent On Weight of Pigment (AOWP). The image below shows how viscosity is at the lowest when the correct amount of dispersant is used to minimize flocculation of the millbase.
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The diagram below illustrates several properties from the pigment, such as tinting strength, transparency, opacity, gloss, haze and flocculation, will be improved due to a more homogeneous particle size distribution and dispersion stability. When the millbase viscosity is minimized are when those properties are maximized. All those effects contribute to improve the final ink or coating properties.
This effect also allows the formulator to increase the pigment concentration in the millbase, which will improve efficiency and productivity. An optimized dispersion can deliver a formula cost reduction and the results can be very surprising! In the following example, increasing the concentration of an organic pigment (PB15:3) from the initial STD 13% up to 25% achieved a 92% pigment concentration increase in the same 100% formula.
| STD | SUG PB15:3 | |
| Add in order and under stirring. Mix at low speed for 15 minutes |
||
| Solvent | 41.15 | 56.00 |
| Laropal A81 Resin Solution | 40.00 | 10.00 |
| STD Dispersant | 5.85 | |
| Solsperse™ M388 (50% Actives) | 8.00 | |
| Solsperse™ 5000S (100% Actives) | 1.00 | |
| Add under stirring. Mix at low speed for 60 minutes | ||
| PB 15:3 | 13.00 | 25.00 |
| Milling | ||
| Total | 100.00 | 100.00 |
After milling and adjusting the pigment content to the same 13%, the results obtained were:
| STD | SUG PB15:3 | |
| Millbase Viscosity (KU) | 96 | 52 |
| Fineness (Hegman) | 7.0 | > 7.5 |
| Flocculation (1=Bad, 5=Excellent) Microscopy (400X Magnification) | 3 | 5 |
| Tinting Strength | 100.00 | 141.12 |
| DL | 0.00 | -3.53 |
| Da | 0.00 | -0.03 |
| Db | 0.00 | -2.30 |
The tinting strength was developed in more than 41%, as well as the color is much more saturated in the Blue axl (Db<0), which delivers a much cleaner color.
When making a cost simulation and comparing the formulas, after adjusting the pigment percentage (25% down to 13%) and the tinting strength gain (+41%) with resin and solvent, the overall result was a 16% cost reduction in the optimized formulation. This comparison is not considering the evident savings in the customer´s production, through better utilization of their equipment and increase in productivity.
With a robust portfolio of Solsperse™ Hyperdispersants designed for specific applications and formulations needs, Lubrizol can collaborate with formulators to integrate an effective dispersant that can optimize performance and reduce total formulation costs.
Contact us to discuss your next formulation challenge or visit our Dispersant Technology eBook to learn more about how Lubrizol dispersants can bring value to your formulations.
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