Development of a New High Orientation Paint System to Achieve Outstanding Real Metallic Designs 2020-01-0899
High metallic silver colors using thin, smooth aluminum flake pigments are typically adopted for the luxury grades by each car manufacturer. Regarding the paint formulation for these types of colors, low non-volatile(N.V.) content and high aluminum flake pigment content are generally known to be necessary to achieve high metallic appearance designs. However, poor distribution of the aluminum flake pigments can cause mottling. In addition, a high concentration of aluminum flake pigments can result in a weak coating. Therefore, current paint systems are limited in the degree of high metallic appearance design that is possible.
As a countermeasure to those problems, we investigated whether cellulose nanofiber (CNF) dispersion liquid can function as both the coating binder and rheology control agent in a new type of waterborne paint system.
CNF is an effective rheology control agent because it forms strong hydrogen bonds with other fiber surfaces when it is dispersed for waterborne paint. For example, viscosity versus shear rate testing of an aqueous solution of 0.4wt% CNF and less than N.V. 5wt% showed a response curve similar to conventional waterborne paint.
Furthermore, CNF's surface bonds with isocyanate resin which penetrates from the clearcoat layer, and a strong fiber-reinforced layer is constructed. Our evaluation confirms that this new paint system achieved our target coating performance level.
We made a concept silver color using the new CNF low N.V. waterborne paint system with vapor deposition aluminum pigments. The resulting color's Flip Flop (FF) exceeded even the highest FF silver in the Lexus color palette while maintaining its Lexus performance quality.