Tired of doing things the hard way

Fumed silicas for rheology control are popular with formulators - if it weren't for the time-consuming grinding processes. Evonik has developed a solution for this problem: With an innovative manufacturing process, we have expanded our AEROSIL® family with a new easy-to-disperse (E2D) product group that is significantly easier to disperse. The new product group consisting of AEROSIL® E 805, AEROSIL® E 812, AEROSIL® E 972 and AEROSIL® E 9200 is such that formulators can omit the time-consuming and costly grinding step, for example with a bead mill, when incorporating them into paints or coatings.

Increasing customer focus to improve process efficiency has driven raw material innovation to reduce the complexity of the dispersion process. Using a bead mill to create the perfect dispersion is the most technically challenging and time-consuming processing step in manufacturing paints and coatings. To overcome this, raw materials manufacturers offer dispersions, preparations, and pastes in which the dispersion of insoluble solids (silica, pigments, fillers, etc.) has been optimized. Dispersions such as these, however, may also contain undefined quantities of solvents, water, binders, or additives. While formulators have no control over this, the effects of these components can have a significant influence to finished coating system.

It would be far simpler if manufacturers could use typical high-speed dispersion to process the solid raw materials for the coating. Unfortunately, the particle sizes that can be achieved by dispersing materials under typical dissolver type dispersion conditions are routinely significantly above the maximum particle size accepted for use in paint and coating products.

Thanks to an innovation in the production process of fumed silica by Evonik, standard fumed silica technology routinely used by the coatings industry can now undergo wetting and dispersion processes in a single high-speed dispersion step, when previously it had to be carried out in two separate steps (bead mill, dissolver) (Figure 1).

Figure 1: Milling processes for incorporation of fumed silica with high shear milling (left) and innovative dissolver milling (right)

The specialty chemicals group's four new easy-to-disperse (E2D) products are suitable for rheology control in both pigmented and clear coating formulations. The main applications are wood, plastic, automotive, and general industrial coatings. Powder coatings and can coatings are typical application fields alike. AEROSIL® E 972 is more universally applicable, while the other silicas are intended for specific applications - for example, AEROSIL® E 812 and AEROSIL® E 805 are suitable for automotive OEM clear coats, and AEROSIL® E 9200 is used primarily for durability improvement, e.g. scratch resistance.

Figure 2: AEROSIL® E2D offer advantages for every type of coating formulation

The 1:1 replacement to standard fumed silica enables the use of new AEROSIL® E2D grades very easily.

Figure 3 displays the comparison of both milling processes and highlights the advantage of low-shear milling step via dissolver. The advantages become noticeable in significant time savings, along with major energy - and thus, monetary - savings.

Evonik Coating Additives business line has developed an AEROSIL® E2D calculator for individual calculation of mentioned savings aspects. Each customer can independently calculate their own savings by using AEROSIL® Easy-to-Disperse with low shear dissolver milling.

In summary, paints and coatings manufacturers have been looking for ways of making dispersion processes less complex. Pertaining to fumed silica technology, this innovation has met this demand in two ways. First, by reducing the number of production steps needed for processing. Second, the required batch cycle time has decreased to achieve the optimum degree of dispersion. These combined efficiencies ultimately reduce production costs and energy, while maintaining performance.