Abstract
Generally speaking, it is said that fluoro-compound treated powder does not show good compatibility with oil binders in cosmetics. However, especially, in the case of tri-decafluoro octyltriethoxysilane (TDFOS), we have found a very good dispersing system with an oil binder. In this work we report the evaluation of this novel fluoro-compound treated ultra-fine zinc oxide (ZnO) dispersion compared with a methylhydrogen polysiloxane (MHPS) treated one. We prepared treated ultra-fine zinc oxides with TDFOS or MHPS. As a dispersant, we chose dimethicones modified with polyglycerin (PGSI) or polyether (PESI), and as a dispersed medium, polydimethyl siloxane (PDMS). As the result, the TDFOS-ZnO/PGSI dispersion systems showed good dispersibility and higher hydrophobicity in application. Furthermore, the best dispersion system was the dispersion containing 5 wt% of PGSI. In this system, although in the initial state the viscosity was relatively high, the viscosity became stable at a lower level after a certain period of time. In the formulations of these dispersions in sunscreen products, the dispersion which is TDFOS-ZnO/PGSI 5wt% gave the best performance, namely stable lower viscosity and higher hydrophobicity in application to skin. Moreover, the whitening effect in water in application to skin was much less with this system and the feeling during application became the smoothest.
