SEDL / STP / STP1146-EB / STP20185S

N-Alkyl Pyrrolidone Requirement for Stable Water-Based Microemulsions

Narayanan, KS
Senior Research Scientist, International Specialty Products, Inc., ISP Management Company, Inc., Wayne, NJ

Chaudhuri, RK
Manager, Research and Development, International Specialty Products, Inc., ISP Management Company, Inc., Wayne, NJ

Pages: 20    Published: Jan 1993

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Abstract

Stable, efficacious microemulsions of carbaryl and a number of pyrethroids (D-Allethrin, Permethrin and tetramethrin), alone or as complex mixtures, both with and without piperonyl butoxide as a synergist, have been developed (patents pending). These active ingredients were microemulsified in a system comprised of: (A) an optimized solvent system in which certain C-1 to C-8 alkyl pyrrolidones were necessary components; (B) an optimized anionic and/or nonionic surfactant system; and (C) water @ ⩾ 85%(W/W). The system is uniquely thermodynamically stable, has low toxicity and is biodegradable, and may have universal applicability with minor modifications of the ratio of its components. The complex microemulsion system of pyrethroids has very low turbidity (⩽20 NTU at 10–25°C), and is thermally stable (45°C, 6 months). Turbidity increased with temperature (900 NTU at 45°C), but became clear when cooled to ambient temperature. A model is proposed that explains the role of the N-alkyl pyrrolidones in achieving stable microemulsion formulations.