In automotive coatings, color is king. From snow white to metallic blue to jet black and everything in between, color is one of the most important features in the automotive marketplace. And dispersants in the base coat have always been critical to delivering depth of color and multiple other key properties.

Because color quality and consistency are so key to automotive coatings, polymeric dispersants are often necessary to achieve color design targets. Dispersants are designed to interact strongly with pigment surfaces, delivering a permanent attachment of the dispersant to the surface of the pigment. The stabilizing chain keeps those particles from flocculating and recombining, which is how dispersants enhance stabilization and color development.

Dispersants aid in color consistency because they enable faster development of color and particles, and more consistent development of particles. A more consistent particle size reduces the chances for having large aggregates that can cause defects in the film. Dispersants also play a role in obtaining good color consistency within the color base going into the paint.

However, as the automotive coatings industry continues to transition to water-based coatings, there are a couple of significant challenges that are not as prevalent in solvent-borne coating systems.

Water Resistance, the hydrophilicity of water-borne dispersants can allow water to permeate the film which can impact humidity resistance, adhesion, durability, and corrosion resistance. Lubrizol combats this by increasing the hydrophobicity of the dispersant without killing its solubility, thereby improving water resistance in the cured film.
Compatibility with Resins – water-borne coatings typically use latexes which are stabilized by surfactants. Special care must be given to not destabilize the latex particles while in the liquid form.

Solsperse™ Hyperdispersants for Water-Based Systems

Lubrizol has extensive experience in developing high-performance solvent-based dispersants for use in the automotive industry. More recently, that experience, knowledge of pigments and R&D efforts have been put to use in developing high-performance water-based dispersants for high-end applications like automotive that address both the hydrophilicity and compatibility challenges.

Lubrizol offers a wide range of Solsperse™ Hyperdispersants that can enable formulators to develop high quality dispersions of a diverse range of pigments, fillers and other active particles. There are many materials that formulators might want to disperse into water, and choosing the right dispersant is critical to achieving an optimal dispersion.

The correct choice of dispersant will properly stabilize the particles and increase milling and dispersion efficiency, resulting in formulations that offer particle size and viscosity stability under the most challenging of conditions. When it comes to pigments, Lubrizol dispersants enable the user to achieve exceptional color development. Colors appear stronger, cleaner and brighter. Transparency or opacity are enhanced and the jetness of carbon blacks is maximized.

In addition to Solsperse Hyperdispersants, Lubrizol offers multiple other polymers and additives for use in automotive coatings, including Solthix™ Rheology Modifiers, Aptalon™ Polyamide Polyurethanes, and Carboset® Acrylic Resins.

Improved Color Strength

Typically, with automotive coatings, pigments are the most expensive material in the paint. Dispersants are used to reduce the particle size and stabilize the pigment to improve color strength, which reduces the amount of pigment needed to achieve a certain color and in turn reduces costs. Additionally, dispersants can allow for higher pigment loadings which can help achieve hiding in certain color spaces, which can be difficult with thin film targets and can improve the jetness, vibrance, or transparency to achieve unique and difficult color targets.

There are also some pigments that are unique to the automotive industry that create their own challenges, such as polycyclic aromatic pigments like perylenes. These pigments are intended to be highly transparent and need to achieve a fine particle size to maintain that transparency, which is key in metallic finishes to deliver a clean, highly chromatic color. These types of pigments are difficult to disperse and difficult to disperse to a particle size where they’re transparent.

Carbon black presents another challenging task when it comes to achieving optimum dispersion of pigments. In black automotive coatings, jetness refers to how black the finish is (where the darkest black with blueish undertones are ideal). Jetness values depend on stabilized primary particles.

Both carbon blacks and polycyclic aromatic pigments have high surface areas, which typically correlate to challenges with stabilization. They have a high demand for polymer absorption to the surface of those particles, with dispersants providing the permanent attachment for stability.

The molecular weight and overall design of the dispersant can also be fine-tuned to reduce particle size faster for reduced milling time, which allows for reductions in capacity to reduce costs – that’s especially important as many automotive plants are constrained with how much dispersion they can make in a set amount of time as they work to quickly fulfill color matched, made-to-order parts. Cutting cycle time with a dispersant enables faster turnaround.

The Importance of Dispersants in Water-Based Automotive Coatings