Role of Mildewcide in Yellow Discoloration of Latex Paints

By Lakshmi Sadasivan, Roger C. Montemayor, Judith N. Varner

Paint formulators must take into account many factors including, but not limited to, ease of application, durability, scrub resistance, fading, and discoloration when formulating a new paint. Although discoloration can be caused by many factors including tannin-related stain bleeding, mildew-related sap staining, fading due to sunlight, yellowing due to alkyd modification, and interactions between colorants and pigments, clay, and other filler pigments, this article specifically explores the effect of mildewcides on yellowing.

The effect of mildewcides on yellowing in latex paints has been an ongoing concern for paint manufacturers. Mildewcides and their interactions with various paint ingredients including certain in-can preservatives, binders, pigments, and clay are a known phenomenon.5 Through experience, paint companies have developed formulations to optimize the efficacy of mildewcides and minimize their adverse effects in paints.

Recently, formulators have been facing a new challenge to produce low- or zero-VOC paints. 10 These lower- or zero-VOC paint requirements came about due to legislation such as the South California Air Quality Management District law (SCAQMD) as well as the public’s increasing concerns for the environment. Lowering VOC content can affect application characteristics, and presents the new challenge to minimize changes in the performance properties of the coatings including yellowing in low- or zero-VOC formulations.