Application of Electrosterically Stabilized Latex in Waterborne Coatings

Abstract

The stability/aggregation behavior of carboxylated latex particles used in water-borne coatings has been investigated. Three forces - van der Waal's attraction, electrostatic repulsion, and steric repulsion - are the principal factors affecting latex stability. The electrosteric repulsion is a combination of electrostatic and steric potentials - which result from ionization of carboxylic acid on the surface of the latex. These effects make the latex particles more resilient in high ionic strength and high shear environment. An experimental investigation has been conducted using colloidal latex solution as a carrier layer in a three-layer coating to simulate photographic coating operation. The results demonstrate that the coating defects associated with formation of aggregates of carboxylated-latex correlate well with the swelling characteristic of these latex particles as a function of pH. Latex particles that do not swell, when pH adjusted from original 4.8 to final 7.2, show a tendency to form coating streaks and develop build up of latex aggregates on the surface of the coating applicator.