Advanced rheology for waterborne paints, the key to good flow and application properties

摘要

Waterborne trim paints have been developed up to a level where they are essentially equal in performance to solvent based alkyd trim paints. As an additional benefit, they have fast drying and non-yellowing characteristics. Their durability is close or equal to that of super-durable alkyd paints. However, waterborne trim paints still lack the excellent application properties of solventbome alkyd paints, thus leading to a lack of flow, levelling and open time. Solutions to overcome these problems often lead to higher VOC or use of alkyd emulsion hybridization and as a consequence lead to yellowing, slower drying and softer films. The solution Nuplex developed is based on tailor made rheology control by a new class of acrylic-acrylic hybrid polymers improving flow and levelling during drying. Inferior flow, levelling and open time of waterborne trim paints with (very) low VOC is due to the adverse viscosity development during drying. In other words, the adverse rheology flow diagram with increasing solids content leads in a very early stage of drying to a steep increase of both low and high shear viscosity as a function of increasing solids content. The flow, levelling and open time can be improved substantially if this steep viscosity increase can be delayed during the drying process. In this paper this effect will be discussed from a theoretical perspective, supported by experimental results. Based on the fundamental theoretical insights obtained from these studies, a novel binder concept was developed that offers superior application properties combined with all the advantages that all-acrylic binders have to offer.