Alkylbenzenesulfonates based on toluene, xylene, as well as cumene, and alkylnaphthalenesulfonates, act as hydrotropes in surfactant systems. A novel sodium diisopropylnaphthalene sulfonate (SDIPNS) has been developed that contains about 92% diisopropylnaphthalene sulfonate, compared to other diisopropylnaphthalene sulfonate preparations that contain less than 50% diisopropylnaphthalene sulfonate. This material is both a hydrotrope and a surfactant. The color of a 35% solution is light yellow, Gardner 3, significantly lighter than comparable materials. Draves wetting time for a 0.5% solution is about 30 s. The Ross-Miles foam test (1% solution) indicates a significant level of initial foam, but the foam is unstable. The solubilities of toluene and limonene in SDIPNS are much higher than in other hydrotropes tested. Hydrotropes raise the cloud point of nonionic surfactants; SDIPNS is the most efficient hydrotrope found for this application. Another measure of hydrotropicity is the amount of hydrotrope required to clear a cloudy detergent formulation; this hydrotrope is quite effective. Another measure is the modification of surfactant formulation viscosity; SDIPNS is quite effective. Additionally, SDIPNS changes the solubility of nonionic surfactants in water. SDIPNS is a surfactant as well as a hydrotrope, demonstrating a critical micelle concentration at about 1%.
