Sag & leveling
Paint has good leveling when the support, once covered, features an even surface, with no application marks from the brush or the roller.
Flow and leveling are therefore relevant to the quality of the final film. Insufficient flow and leveling will lead to surface defects such as brush or roller marks thus impacting optical properties of the dry coating film, particularly in the case of low PVC formulations based coatings (satin, gloss paints, varnish and lacquers).
The use of preferentially newtonian rheology modifiers helps improve flow and leveling properties, unlike conventional HEC thickeners.
Coatex newtonian to balanced polyurethane thickeners like Coapur™ 830W (for medium PVC) and Coapur™ 2025 (for low PVC) offer the optimized flow and leveling you need.
With Coapur™ 2025
Compared to conventional cellulosic thickeners, these rheology modifiers ensure an improved leveling and as well provide a better film build thanks to accurate control of the application viscosity.
Water & weather resistance
The main interest for the paint producer is to provide low VOC to VOC free coatings with a high level of water proof qualities.
Exterior coatings should be resistant to hard weathering conditions such as rain, while interior coatings should generally be resistant to wet scrub.
Binders are usually present in major component of low PVC waterborne coatings such as eggshell, semi-gloss or glossy paints, and contribute to improve the hydrophobicity of the film surface, in that water repellency is less considered as a real concern.
In coatings formulation with medium and low PVC, hydrophobic characteristics of polyurethane type thickeners (HEUR) improve the water resistance. In the graph below water barrier properties are improved by using Coapur™ 830 W (for medium PVC) and Coapur™ 3025 (for low PVC) comparatively to that of cellulosics
Figure 1: PU provides better wet scrub resistance compared to that of cellulosics, while reaching similar rheology
In very high PVC systems, the quantity of available binder is not sufficient to ensure thorough coating of the mineral particles within the film.
A hydrophobic dispersant is therefore used to help partly offset this shortcoming, delay the ingress of water and detergent during the wet scrub test, and therefore increase the water resistance of such formulations.
Wet scrub resistance of matt paint containing a hydrophobic dispersant PVC= 77% with Coadis™ 123K
Optical efficiency is achieved thanks to good pigment dispersion, if not the light scattering on aggregates will not be high enough leading to low scattering effect and low opacity.
The more the particles are stabilized and dispersed the better are the opacity and light scattering.
Product recommendation per performance and formulation type:
- High loading in TiO2 + fillers: Ecodis™ P 30
- TiO2 dispersion for Semi gloss/Gloss: Coadis™ 123 K
- TiO2 dispersion for Gloss: Coadis™ BR 85