The Influence of Polymer Properties on 'Touch-up' of Architectural Flat Paints

摘要

One of the key requirements of interior flat paints is to maintain uniform appearance and sheen between first and second coats, regardless of the method of application or the temperature. Good consistency of appearance between coats is referred to as good "touch-up". Commonly, touch-up becomes important when brush applying a second coat of paint to cover small areas of a spray-applied first coat that have been marked or scraped. If the paint does not touch-up, an entire wall may have to be repainted, which results in high labor and material cost. Therefore, to be successful in the architectural market, good touch-up is a necessary property. Among the various raw materials that affect touch-up, such as extenders, rheology modifiers, surfactants, etc., is the type of latex that is incorporated in a paint formulation. Vinyl Acetate-Ethylene (VAE) copolymers have traditionally exhibited excellent touch-up properties at ambient and low temperatures. The superior coalescence of VAE copolymers combined with their excellent binding efficiency enables paint formulators to develop touch-up properties in high PVC formulations, many of which use little or no coalescing solvents. In this work, the impact of polymer design parameters on low temperature touch-up is investigated. Attempt is made to correlate polymer properties such as Tg, molecular weight and particle size to ambient & low temperature touch-up in standard high PVC flat formulations. The property of touch-up is evaluated via airless spray and brush application method. Our use of optical measurements to quantify the typically subjective ratings of touch-up is also discussed.