Zetasperse® 3800 – Sometimes "Less" Is More

The manufacturing of pigmented systems is significantly affected by the dispersion process. Dispersion comprises three main stages: wetting of pigments, conversion into pigment dispersions, and provision of long-term stabilization. This entire process is critical for ensuring long-term storage stability of the system. The presence of different inputs in the system such as resin, pigment, and solvent makes this process more complex. This explains why dispersion is so important. To understand wetting and dispersion agents, it is first necessary to know the fundamental principles of the dispersion process. Dispersion agents stabilize deflocculated pigment particles. To achieve this stabilization of primary particles, the dispersion agent must overcome the Van der Waals and other attractive forces holding them together. All commercially used pigments have an agglomerate structure, meaning they exist as larger particles bound together. During grinding, the mechanical energy used breaks down agglomerates into physically smaller particles.

The dispersion of a pigment in a liquid medium consists of three main processes shown below:

Wetting: The first stage of good dispersion is the wetting of pigments. At this stage, all air and moisture within the pigment aggregates and agglomerates are replaced by resin solution or the liquid carrier being used. For successful wetting of pigment agglomerates and primary particles, the surface tension of the resin or carrier liquid must be lower than the surface tension of the pigment. This process is achieved with wetting agents. There is a fundamental difference in the wetting process between water-based and solvent-based systems. The wetting of pigments is easier in solvent-based systems than in water-based systems due to the low surface tension of solvents. Butyl Acetate: 25 mN/m Toluene: 28 mN/m Xylene: 30 mN/m White Spirit: 24 mN/m Alkyd: 30-40 mN/m Due to the high surface tension of water, effective wetting agents are needed to reduce surface tension and ensure pigment wetting. Water: 73 mN/m Dispersion Intermediate: 30-40 mN/m Reduction of surface tension becomes even more essential in water-based systems when hydrophobic pigments such as organic pigments and carbon blacks are to be dispersed.

Wetting agents provide the wetting process through three unique properties:

• Wetting of pigment particles through reduction of the surface tension of the "resin medium", • Reduction of micro-foaming and increased density during grinding, • Improvement of grinding efficiency. Grinding: After the wetting stage, it is necessary to prevent pigment agglomeration and accumulation. This stage represents the actual pigment grinding stage. This process is usually carried out through mechanical operations using high-efficiency grinding equipment. Mechanical energy breaks down agglomerates into smaller particles. Stabilization: Upon completion of grinding, agglomerates transform into primary pigment particles. These particles have a high tendency to re-form into agglomerates. To achieve a stable state, the system tends to shift from high energy to low energy state. For this reason, pigment dispersions must be brought to a stable state to prevent flocculation formation. This stabilization mechanism consists of three different principles: With complete understanding of the dispersion process, the remaining important step is selecting the best dispersion agent for each application. The most important functions of dispersion agents are providing viscosity reduction, shortening dispersion time, increasing color and hiding power, preventing settling and flocculation, and ensuring compatibility with binders. To achieve these, appropriate dispersion agents must be selected for the system. Therefore, before selecting a dispersion agent for an application, certain criteria must be considered: • Pigment and filler type, • System and polarity, • Final application.

Otherwise, formulation personnel may encounter side effects in the finished product such as high rub-out values, low gloss, settling, and phase separation.

Zetasperse® 3800 allows for viscosity reduction while demonstrating superior performance with all pigment types. Even when used in lower quantities, it provides successful results in pigment stabilization. It has positive effects on final product performance and cost. Zetasperse® 3800 is a polymeric dispersion and wetting additive developed for high-quality water-based formulations, containing 40% active matter, with a light anionic structure. Its negative effect on the properties of the dry paint film is negligible. Additionally, it contains no solvents or harmful substances. The main applications where Zetasperse® 3800 demonstrates high performance are pigment concentrates, automotive coatings, industrial coatings, construction coatings, and wood coatings. Below are results from different applications made with pigment concentrates.

Outstanding Features of ZETASPERSE® 3800 Compared to Other Dispersion Agents

In addition to many positive effects they provide, wetting and dispersion agents can have negative side effects such as foam retention tendency and reduction of dry film performance. ZETASPERSE® 3800 causes less foam formation during grinding. As shown in the image below, ZETASPERSE® 3800 produces less foam compared to a competitor agent, enabling faster dispersion process initiation and more effective grinding. During the work, ZETASPERSE® 3800 performance was tested on difficult pigments that often cause problems for formulation owners - yet must be used to achieve the desired color. The first pigment tested was titanium dioxide, the most widely used pigment in the paint industry. To determine the dispersion agent requirement, concentrates were prepared at different doses with the same additive. Results were evaluated in terms of viscosity reduction, color intensity, and long-term stabilization. In this test, while optimum results with the competitor product were obtained after 3% addition, the same results with Zetasperse® 3800 were achieved at much lower doses. When the same amount was tested with a lower dose of the competitor product, severe settling was encountered due to insufficient stabilization. A similar approach was also conducted with carbon black, another difficult pigment. Using the correct dose is extremely important in achieving optimum performance. In this case, the lowest viscosity and best stabilization with the competitor product were observed after 50% dispersion agent addition.

With Zetasperse® 3800 application, the same performance was achieved with much better stabilization at 35% addition.

Similarly, when color properties were considered, the dM value tracked by the increase in blue undertone in black pigments was obtained even when Zetasperse® 3800 was used at low doses. A similar approach was also conducted with carbon black, another difficult pigment. Using the correct dose is extremely important in achieving optimum performance. In this case, the lowest viscosity and best stabilization with the competitor product were observed after 50% dispersion agent addition. With Zetasperse® 3800 application, the same performance was achieved with much better stabilization at 35% addition. Similarly, when color properties were considered, the dM value tracked by the increase in blue undertone in black pigments was obtained even when Zetasperse® 3800 was used at low doses. To determine Zetasperse 3800's performance, difficult organic pigments PV 23, PR 48:2, PR 122 were examined comparatively with other competing dispersion agents in the market. Since optimum results could not be obtained with the same competitor product for all pigments, different competitor products were used as reference for each pigment. For PV 23 pigment, Comp. D, a competitor product developed only for organic pigments, was pitted against Zetasperse® 3800. Both products provided similar performance in terms of viscosity reduction. When color values and rub-out performances were compared, the highest color intensity was obtained with Zetasperse® 3800. Additionally, due to its high compatibility property, Zetasperse® 3800 provided very low rub-out values even when mixed with a base containing an unknown dispersion agent. For PV 23 pigment, Comp. D, a competitor product developed only for organic pigments, was pitted against Zetasperse® 3800. Both products provided similar performance in terms of viscosity reduction. When color values and rub-out performances were compared, the highest color intensity was obtained with Zetasperse® 3800. Additionally, due to its high compatibility property, Zetasperse® 3800 provided very low rub-out values even when mixed with a base containing an unknown dispersion agent. For the PR 48:2 study, Comp. E product was selected as reference due to gelling problems encountered with previously tested competitor dispersion agents. In this study, Zetasperse® 3800 provided very good viscosity reduction and, more importantly, very good color stability, enabling the preparation of very stable pigment concentrates with low rub-out values. In addition to the pigments mentioned above, performance tests were conducted on PG 7, PB 15:2, PR 101, PY 42 and PR 122 pigments, with similar positive results obtained in terms of very good viscosity reduction, high color intensity, low rub-out values and stability.

In summary, Zetasperse® 3800 emerges as a very attractive option for formulation owners requiring exceptional performance, providing the following properties:

• Universal dispersion agent providing optimum performance for all pigment types, • Minimum side effects on dry film properties (e.g. corrosion resistance), • Enabling achievement of durable dry films through lower dosage requirements.   Alptekin Akgümüş Senior Technical and Laboratory Director Evonik