Wax-Based Rheological Additives

Optimization of Optical Properties of Metallic Coatings with Wax-Based Rheological Additives Metallic coatings provide unique effects when formulated onto metal, wood and other substrates. However, adjusting the desired properties in coatings to achieve this effect is generally difficult for the formulator. This situation particularly means adjusting the compatibility of metal-based effect pigments in coatings for subsequent coating requirements. A special rheological effect is required to achieve the most effective metallic finish. This flat-particle, metal-based pigment, like others, achieves its most effective orientation parallel to the coating surface. The focus here is on the viscosity and structural recovery behavior after the stress generated by the coating application alone. If structural recovery is very slow, pigment effects will collapse. If viscosity returns to its original state quickly, this will result in too little time for pigment orientation (alignment). Therefore, both effects will result in reduced optical quality of the resulting film (for example, a less effective flop effect). Diamide-based rheology modifiers THIXATROL P2100 and THIXATROL 5020W, respectively with EVA (Ethylene-Vinyl Acetate) wax and ideally compatible with standard rheological modifiers (for example polyacrylate-based), are suitable tools for aqueous metallic coatings to adjust the required optical effects. Both stages are already in use without the need for an additional activation step with temperature or high shear. In the case of THIXATROL® P 2100W, in suitable solvents (for example DPnB, DB or DPM), only the transferred paste-consistency diamide wax requires pre-dilution.

THIXATROL® 5020W already consists of a liquid ethylene vinyl acetate wax emulsion. It can be applied directly without requiring any processing.

THIXATROL® P 2100W and THIXATROL® 5020W are used separately. However, in combination with a thickener such as ASE (Alkali Swellable Emulsion), the system adjusts the standard viscosity. In pure acrylic metallic coating, THIXATROL® P 2100W and THIXATROL® 5020W, when compared to a sample equipped with a pure acrylic thickener set to equal low shear viscosity, provide significantly higher flop and gloss values.   Rheological data on this subject confirm these practical findings. Differences were shown in a viscosity recovery test using three separate measurement steps. In the first and second sections, viscosity was measured at low and high shear. This is analogous to the behavior of the samples before and during application. Finally, in the third section of the measurements, low shear was reapplied to demonstrate the material's post-application behavior. Thus, the sample with ASE thickener showed the fastest viscosity recovery, and therefore the strongest pseudoplastic behavior. Both samples formulated with either THIXATROL® P 2100W or THIXATROL® 5020W show slightly delayed viscosity recovery. Based on the practical findings shown initially, this means that both wax emulsions provide somewhat longer time for the metallic pigments in the final film to align. In addition, all tested samples show excellent storage stability. No gassing (poisoning) of the samples was detected in any case. Furthermore, THIXATROL® P 2100W and THIXATROL® 5020W showed excellent compatibility with various binder technologies, so both grades can be applied in a wide range of system technologies. [gallery ids="eyJ1cmwiOiJodHRwczpcL1wvd3d3LnR1cmtjaGVtLm5ldFwvd3AtY29udGVudFwvdXBsb2Fkc1wvMjAxOVwvMDlcL2ZpcmF0Xy5qcGciLCJ0aXRsZSI6ImZpcmF0XyIsImNhcHRpb24iOiJBdXRob3I6IEZcdTAxM2ZyYXQgUHx1MDEzMXJlbjxicj5QYWludCBQcm9kdWN0IG1hbmFnZXI8YnI+RnVjaHMgS2lteWEgQS5cdTAxNWUuIiwiYWx0IjoiIiwiZGVzY3JpcHRpb24iOiIifQ==,eyJ1cmwiOiJodHRwczpcL1wvd3d3LnR1cmtjaGVtLm5ldFwvd3AtY29udGVudFwvdXBsb2Fkc1wvMjAxOVwvMDlcL2ZyYW5rXy5qcGciLCJ0aXRsZSI6ImZyYW5rXyIsImNhcHRpb24iOiJDb250YWN0OiBGcmFuayBBYnNjaGxhZzxicj5UZWNobuljYWwgU2FsZXMgTWFuYWdlciA8YnI+UGFpbnRzIEVNRUEgRWxlbWVudGlzIiwiYWx0IjoiIiwiZGVzY3JpcHRpb24iOiIifQ==,eyJ1cmwiOiJodHRwczpcL1wvd3d3LnR1cmtjaGVtLm5ldFwvd3AtY29udGVudFwvdXBsb2Fkc1wvMjAxOVwvMDlcL3Vkb18uanBnIiwidGl0bGUiOiJ1ZG9fIiwiY2FwdGlvbiI6IkNvbnRhY3Q6IFVkbyBTY2hvbmhvZmY8YnI+VGVjaG5pY2FsIFNhbGVzIE1hbmFnZXI8YnI+UGFpbnRzIEVNRUEgRWxlbWVudGlzIiwiYWx0IjoiIiwiZGVzY3JpcHRpb24iOiIifQ=="]