Performance of New Biodegradable Di-Sulfonate Surfactants as Hydrotropes in High-Temperature and Salinity Environments

Propyl alkyl ether sulfonate (PAES) surfactants, recently developed by The Dow Chemical Company, show excellent electrolyte, hard water and caustic solubility, with attractive ECOTOX profile and biodegradability. Due to their unique structure and properties, they are good candidates for use as hydrotropes in formulations containing nonionic surfactants. The goal of these studies was to evaluate hydrotropic efficiency of PAES materials via cloud point analysis. The effects of PAES alkyl tail length, concentration, and mono- and di-sulfonate components on the cloud point of TERGITOL™ 15-S-9 in solutions of varying electrolyte strength were investigated. In the presence of high electrolyte levels, PAES 12C had the highest hydrotropic efficiency of all materials tested, including commonly used commercial hydrotropes. Di-sulfonate components of the PAES materials were found to be more efficient hydrotropes than mono-sulfonate in high electrolyte environments for all tail lengths tested. The di/mono ratio and tail length were found to be critical parameters.