Over the past several years, there has been a murmur in the coatings industry with regards to the concentration and levels of crystalline silica within various paint formulations, particularly architectural coatings. While there are countless architectural coating formulations, commonly the largest component on a volume basis is calcium carbonate. The combination of the regulatory focus on crystalline silica, in conjunction with the impact calcium carbonate can have on a formulation’s crystalline silica levels, inspired Imerys to both re-evaluate and optimize the processing of calcium carbonate to support paint formulators to continue to drive down the crystalline silica levels in their products.
Before a deep dive into the optimization process, it is important to understand the differences between crystalline silica and “respirable” crystalline silica, as well as the dangers posed to both employees and consumers from respirable crystalline silica. Crystalline silica (Figure 1) is a basic component of sand, soil and other minerals, and comes in three forms - cristobalite, tridymite and quartz - with quartz being the most common. The primary EHS concern with crystalline silica arises when small particles (typically less than 10 micron) are strewn into the air and become inhaled by either production workers or consumers. Some activities that can cause crystalline silica to become respirable include manufacturing of paints, pouring/handling powders, abrasive blasting, sanding of joint compound, sanding paints, manufacturing brinks and hydraulic fracturing.