EFFECTS OF LATEX PARTICLE STABILIZATION PACKAGE ON RHEOLOGICAL RESPONSES OF WATERBORNE COATINGS CONTAINING ASSOCIATIVE THICKENERS

摘要

Associative thickeners have enabled the formulators to optimize rheology of waterborne latex coatings in ways that had not been possible before their introduction. However, unlike traditional thickeners such as cellulose derivatives, this class of thickeners is quite sensitive to variations in formulation ingredients. This sensitivity is due to the fact that associative thickeners are hydrophobically-modified, water-soluble polymers that thicken formulations via complex interactions with other ingredients as well as via self-associations. Understanding these mechanisms has been the focus of many research groups. Our initial work has focused on how associative thickeners interact with vinyl acetate/ethylene copolymer latices that are traditionally used in flat and satin formulations, but are gaining acceptance in semi-gloss formulations because of their inherent advantages such as scrub resistance, and low odor. This work has led us to more recent, fundamental work on aqueous associative thickener/latex blends. Latex variables studied include particle size and stabilization package (acid monomer, surfactant level and type, and hydroxyethyl cellulose protective colloid). These variables were shown to cause dramatic differences in the way associative thickeners respond. This report describes results related to hydrophobically-modified, ethoxilated urethanes (HEUR), and conventional HEC thickeners. The relative importance of above latex variables on various thickening mechanisms is presented.