2001 ANNUAL SCIENTIFIC SEMINAR 415 a kinetic stabilization can be exploited to stabiliz.e sprayable emulsions. Below 1 •tm the random Brownian particle motion is faster than creaming or sedimentation. Thus all droplets of a sprayable emulsion should be smaller than 1 pro. In this case droplets need to be protected against fusion in case of the collision with another droplet. Apart from very low interfacial tensions to allow the formation of extremely small droplets the CERALUTION TM system forms a protective probably lameliar layer around the dispersed oil droplets. To give optimal results the gemini blends, CERALUTION TM H (0.5 wt %) and CERALUTION TM F (1.0 wt %) are complemented with a small amount of an isotrideceth-12 (0.5 wt %). This level of emulsifier can cope with l0 to 28 wt % of oil with varying polarities. To improve heat stability, i.e. stability against droplet fusion on collision, at least 0.1 wt % of a hydrocolloid, cellulose, starch, Xanthan Gum or combinations of them are added. The hydrocolloid will lead to a structural viscosity which helps to stabilize the emulsion against sedimentation or creaming but collapses easily when shear stress (pump action of a spray pump) is applied. Moreover the structural viscosity improves the spray application itself as the applied emulsion stays in. Variation of the hydrocolloid concentration (0.1 to 0.4 wt %) helps to adjust emulsion viscosity to the pump system. Although gel network formation and foaming are switched off when the CERALUTION TM building blocks are combined the high flexibility of the system can still be exploited. Contrary to PIT spray emulsions CERALUT[ON TM sprays can cope relatively easily with changes in oil polarities (e.g. variations in oil soluble UV filters or emollients) and electrolytes (e.g. water soluble UV filters). Looking at spray characteristics the gemini blends lead to a smaller surface tension of the whole spray formulation. As a large new surface is formed when the emulsion is sprayed the lowest possible surface tension is required to form small spray droplets and thus an even distribution of the sunscreen. A typical CERALUTION TM based sun spray shows a surface tension, ix, of 31 mN*m 4 whereas the best commercial system is found to have a surface tension of 33 nN*m 4 and for the majority of other nonionic systems surface tensions between 36 and 37 mN*m 4 are found. When preparing a CERALUTION TM based emulsion spray a three step procedure proved to give best results and to be quite economical as well. The combination of the complete oil and water phases (typical examples in table 1) will not lead to the shear forces needed to achieve the small oil droplets wanted. Therefore only one fifth to one sixth of the water but the complete amount of hydrocolloid glycerin and CERALUTION TM F is combined with the oil phase at 60 øC (instead of about 85 øC for PIT emulsions). The pre-emulsion has a viscosity that allows proper homogenization. As soon as the required droplet size (figure 1) is reached (i.e. all droplets smaller lam, median smaller 400 nm) the pre-emulsion is cooled to 35 øC and diluted with the rest of the water and other temperature sensitive compounds. This procedure requires only 40 % of the homogenization volume which is necessary for a PIT emulsion. If homogenization takes too long in a given equipment (total energy input required to achieve the small droplets depends on the individual set up of the homogenization device) a slight decrease in water phase (1 to 2 %) is sufficient. Figure 1: Droplet size distribution for sunspray: median: 370 rim, l•m: 99,4 % Area % 14 12 10 8 8 4 2 0

416 JOURNAL OF COSMETIC SCIENCE Table I: Formulation Examples CTFA/INCI Trade Name [wt %] 1. Model formulation Phase A Behenyl Alcohol, Glyceryl Stearate, Glyceryl Stearate CERALUTION H 0.50 Citrate, Sodium Dicocoylethylenediamine PEG-15 Sulfate lsotrideceth- 12 Marlipal O 13 / 120 0.50 Caprylic / capfie triglyceride Miglyol 812 25.00 Phase B Aqua 10.00 Sodium Lauroyl Lactylate, Sodium Dicocoyl- CERALUTION F 1.00 ethylenediamine PEG- 15 Sulfate Xanthan gum 0.10 Glycerin 6.00 Phase C Aqua 50.90 Alcohol [Ethanol] 6.00 2. Sunspray (SPF 20) Phase A Behenyl Alcohol, Glyceryl Stearate, Glyceryl Stearate CERALUTION H 0.50 Citrate, Sodium Dicocoylethylenediamine PEG- 15 Sulfate lsotrideceth-12 Marlipal O 13 / 120 0.50 Cyclomethicone 4.00 Triethyl titrate 4.00 C 12-C 15 AIkylbenzoate COSMACOL EBI 2.50 Caprylic / caprio triglyceride Miglyol 812 5.00 Octocrylene 5.00 Octyl methoxycinnamate 5.00 Butyl methoxydibenzoylmethane 1.00 Tocopherol acetate 0.50 Phase B Aqua 12.75 Sodium Lauroyl Lactylate, Sodium Dicocoyl- CERALUTION F 1.00 ethylenediarnine PEG-15 Sulfate . . Hydroxyethylce!lulose 0.20 Glycerin 5.00 Phase C Aqua ad 100 Alcohol [Ethanol] 5.00 Phenylbenzimidazole-5-sul fonic acid 4.50 Sodium hydroxide 6.00 Production: Heat phases A and B to 60 øC Add phase A to phase B, homogenize until droplet size is at about 400 nm or smaller Add phase C and homogenize for 2 min. Cool and de-aerate