Controling Crystal Morphology or Additive Design in Paint Formation

The prediction of crystal habit, the analysis of surface structure, and the design of additives is leading to pigments which show greatly improved performance expressed by a higher color strength, improved color shades, and a better color saturation.

BASF researchers successfully applied molecular modeling techniques to design high-performance additives which act as synergists in the formulation of paint [1]. The rheological properties of paints, the stability of pigment dispersions, and the optical properties of the resulting coatings are closely related to colloidal stabilization of the pigment particles.

In a first step the crystal habit of the industrially relevant C.I. Pigment Red 179 was successfully predicted by the attachment energy method available in the Morphology module (Figure 1). The [011] crystal face was identified as a dominant crystal face and analyzed in detail. To estimate the activity of possible additives, relative intermolecular enthalpies gained by embedding several molecules in the (011) face (Figure 2) were calculated and compared to each other. These calculations indicated that perylene-3,4-dicarboxylic acid imides (PDCls) are promising additive candidates. Adsorption and crystallization experiments provided excellent proof of this hypothesis.

This computational study demonstrated how the prediction of the crystal habit, the analysis of the surface structure and the design of additives is leading to pigments which show greatly improved performance expressed by a higher color strength, a more yellowish color shade and a better color saturation.

References

1. P. Erk, J. Hetzenegger, A. Böhm, European Coating Journal, 906 (1997)