Historically, the physical form of a dispersant wasn’t much of a concern because it would be dissolved in a solvent, whether a chemical solvent or water. Once dissolved in a solvent, the dispersant becomes easier for formulators to handle.

However, to meet regulatory requirements and sustainability goals, there has been a drive to reduce VOCs and move away from non-aqueous solvents to more water-borne solutions. Adding water reduces the viscosity of the dispersant, but it also means a biocide has to be used to prevent microbial growth and contamination, which presents its own challenges as permitted levels of biocides continue to decrease.

An alternative solution is to move to a 100% active dispersant which removes the need for any kind of solvent/diluent, eliminating environmental and regulatory concerns while improving manufacturing, shipping and storage efficiency.

Overcoming Handleability Challenges

The challenge then becomes the fact that many common dispersants which are 100% active have poor physical form and handleability at room temperature. Dispersants that are solid are often waxy and therefore cannot form powders while those that are liquid are often highly viscous (very sticky).

These physical forms are due to the molecular structures and components required to deliver the key performance attributes of dispersants, which can be split into two major components: asteric stabilization chain and an anchor. The steric stabilization chain must be soluble in the coating medium and be of a sufficient size to provide steric stabilization. Unfortunately, common materials that provide these features often negatively impact handleability. The anchor component needs to be designed for good binding to pigments, and must therefore be highly functional and highly interactive, which leads to the formation of intermolecular interactions. Unfortunately, it also tends to bind to anything else. While one part is often dominant in the composition, both parts play a role in the physical form and therefore both must be designed carefully to produce easier handleability.

Dispersants intrinsically come with challenges in terms of their physical form because if they're going to bind to a pigment (intermolecular interactions), they'll stick to other things as well. If the dispersant is waxy, it won’t easily flow from its storage container into the formulation. Heat would likely be needed to melt the dispersant, which comes with added energy costs and not all formulators have the equipment to do so. Highly viscous dispersants also won’t flow easily.

There is a balancing act between the “stickiness” of intermolecular interactions and performance attributes to overcome these physical and handleability challenges. At a high level, there are three methods to achieve this balancing act:

Careful selection of the raw materials to deliver a flowable dispersant.
Optimizing the size of the polymer. Larger particles tend to provide higher levels of performance but are more difficult to handle. The goal is to find the optimum spot between larger and smaller particles to deliver performance and handleability.
Using anchor technology to control the intermolecular interactions. By controlling exactly what those interactions are, how many of them there are, and how they’re acting, the physical form of the dispersant can also be controlled.

100% Active, Flowable Dispersant

Lubrizol utilized all three methods in developing Solsperse™ W150 Hyperdispersant, which is a 100% active dispersant that is flowable at room temperature. It is a multi-anchored dispersant that balances polymer size with flow properties and is designed for high performance water-based coatings and colorants. It is suitable for use across a wide range of organic pigments, inorganic pigments/ particles and fillers in both resin-containing and resin-free dispersions.

Because it is flowable, Solsperse™ W150 is easy to handle. Because it is 100% active, it eliminates the need for diluents and the hazards that can come with solvents or the need for water. Without water and the potential for microbial growth and contamination, there is no need for biocides, which provides regulatory and shelf-life benefits.

Being 100% active also delivers manufacturing and logistical efficiencies because less dispersant is needed. A typical dispersant might be 40% active. Therefore, shipping 100 tons of typical dilute product equates to 40 tons of active dispersant, whereas shipping 100 tons of 100% active product equals 100 tons of active dispersant, which results in savings in both shipping and storage costs.

Contact us to learn more about the value of 100% active, flowable dispersants. A webinar recording is also available for additional details.

The Value of 100% Active, Flowable Dispersants