Organoclay rheological additives: Past,present and future

Rheological or flow properties have important implications in many and diverse applications. Often, an additive is used to impart the desired flow behavior. Among these, organoclay products, formed by the reaction of organic cations with smectite clays, are the most widely used additives for solvent-based coatings. The cation— usually a quaternary ammonium salt—used will influence the performance of the resultant organoclay. Criteria to consider in the choice of a cation are molecular size, compatibility with the fluid in which the organoclay is to be used, stability and reactivity. To form a stable organoclay product, the organic cation must contain at least one long-chain alkyl group. Othr groups attached to the cation may be divided into two categories: “filler” groups serve to complete the tetrahedron around the nitrogen, whereas “active” groups contribute beneficially to the performance of the organoclay. Our study of the structure/property relationships has led to the development of new additives described here. These are superior, particularly in terms of use, while providing the same excellent rheological control offered by earlier additives.