Y. Soc. Cosmetic Chemists, 20, 199-213 (March 4, 1969) Solubilization Experiments on a Three-component System of Liquid Paraffin-Water-Nonionic Suroeactant TAKEO MITSUI, B.S., and YASUHIKO MACHIDA, B.S? Presented May 16, 1968, Filth IFSCC Congress, Tokyo, Japan Synopsis A triangular diagram with oil, water, and surfactant represented at left, right, and top corners of the triangle, respectively, was used to study the effects of factors such as the surfactant type, number of ethylene oxide (EO) molecules in the surfactant, aging, and aging temperatnre on the appearance of the solubilization region. The results indicate that the homogeneous solubilization region (the S region) becomes the widest when a surfactant with the optimum EO molecule number is used. The S region is shifted towards the left side when a surfactant with a smaller nnmber of EO units than the optimum number is used, and towards the right side when a surfactant with a larger number is used. The S region consists mainly of the W/O type solubilization systems in the former, and mainly of the O/W type in the latter. The S region using surfactant with the optimum EO molecule number consists of a mixture of W/O and O/W type. In addition, the relation between the structure of the surfactant molecule and the solubilizing power and the comparison of the optimum HLB for solubilizati(m with that for emulsification are discussed. INTRODUCTION In a three-component system of oil-watcr-surfactant, a solubilization or an emulsion appears depending upon the ratio of the three components. In the present study, liquid paraffin was mainly used as the oil and special attention was paid to the solubilization system. Liquid paraffin was chosen as the oil because it is one of the principal raw materials in the manufacture • Shiseido Laboratory, 1050, Nippa-Cho, Kohoku-Ku, Japan. 199 Yokohama-Shi, Kanagawa-Ken,

200 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS of cosmetics and a correlation of the present study with that on emulsification of liquid paraffin carried out earlier by the same authors ( 1 ) is intended. 2-Octyl dodecanol and squalane were used in addition to liquid paraffin in the experiments designed for a study on a correlation between the optimum HLB in the emulsion system and that in the solubilization system. With a triangular diagram and oil, water, and surfactant represented at each corner of the triangle, the effects of factors such as the surfactant type, number of ethylene oxide molecules in the surfactant, aging, and aging temperature on the appearance of the solubilization region were studied. The term "solubilization system" here means the system in which oil is homogeneously and transparently dispersed in water or vice versa. EXPERIMENTAL METHOD Oils and Surfactants Used Liquid paraffin (Saybolt viscosity of 70 at 100øF) was mainly used as the oil. Twenty-seven surfactants were chosen from seven types which are regarded as having a relatively strong solubilizing power according to the experiences of the authors (Table I). All oils and surfactants used were commercial brands and were not specially refined for the present experiments, because the experimental results were to be used in actually preparing cosmetics where correlation of results would be necessary. Table I Surfactants Used 1. POE • alkyl ether type POE olcyl ether POE lauryl ether 2. POE alkylaryl ether type POE octylphenyl ether POE nonylphenyl ether POE dinonylphenyl ether 3. POE fatty acid diester type POE dioleate 4. POE sorbitan monoester type POE sorbitan monooleate N o =5, 10, 20 mols N=3, 5, 10, 20 N=3, 5, 10, 20 N=3, 4, 5, 7, 10, 20 N=5, 10, 20 N=9, 18, 36 N =3, 5, 10, 20 •POE, polyoxyethylene. ON, munber of ethylene oxide (EO) molecules.