Wall-paint comparison: in an alkaline resistance test, the test piece on the left, coated with paint that contains VINNAPAS® EP 3560, exhibited no efflorescence. The test piece on the right, which was treated with conventional paint, showed significant efflorescence in the lower section. (Photo: Wacker Chemie AG)
No organic solvents whatsoever are used in WACKER’s VAE technology due to the chemical structure: VAE copolymers are hydrophilic (water-loving). Instead of organic solvents, water suffices as coalescing agent or film-forming aid. As a coat of paint dries, it contracts in volume, drawing the pigments, fillers and polymer coils closer to one another. The particles have less room to maneuver, the polymer chains straighten out and the tangled structure reorganizes itself into a coherent polymer film. This process is subject to a threshold temperature. Thus, the film-forming temperature of VAE binders from WACKER for use in paints is in and around the freezing point. Paints formulated with other polymers would not form a film at these temperatures. They need the additional help of organic solvents, which evaporate as the paint dries and are responsible for the bulk of the VOCs.
Despite their advantages, paints formulated with VAE binders are not entirely free from VOC emissions, as the free-radical polymerization process requires further substances, for example for starting and stopping the chemical reaction. The experts at WACKER worked intensively on the polymerization and composition of the binder, coming up trumps with VINNAPAS® EP 3560, a high-quality, lower-odor and lower-emission product for matt to semi-gloss paints. They also succeeded in optimizing the dispersibility, which is responsible for better color development and color consistency. A further bonus is that the binder confers greater alkaline hydrolysis resistance on wall paints. As a result, paints based on VAE are better equipped to counteract efflorescence and so are ideal for primers applied to alkaline substrates such as concrete. The paints are breathable, too. This is a key criterion for preventing mold formation. Like VINNAPAS® EP 3360, the new product features high wet-scrub resistance and makes for excellent processing even at low temperatures. The minimum film-forming temperature of VINNAPAS® EP 3560 is approx. two degrees Celsius.