Table-1 Formulation for testing water-based sunscreen gel containing P-ZnO. q. s.: quantum sufficit. J. Soc. Cosmet. Chem. Jpn. Vol. 42, No. 2 2008 103

Fig.-1 X-ray diffraction patterns of P-ZnO. Fig. -3 Spectral transmission factors of P-ZnO and a commercial SiO2-ZnO dispersed in water. Fig. -2 Infrared spectrum of P-ZnO in the range of 700-4000cm-1.

Fig. -4 Spectral transmission factors of P-ZnO dispersed in water after one week at room temperature. Fig. -7 Spectral transmission factors of P-ZnO dispersed in water-based gel after one week at room temperature. Fig. -5 Spectral transmission factors of the commercial SiO2-ZnO dispersed in water after one week at room temperature. Fig. -8 Spectral transmission factor of P-ZnO dispersed in water-based gel through a thin layer of the gel on a slide quartz-glass. Fig. -6 (a) (b) Dispersibility of each zinc oxide compound into water-based gel. (a) SiO2-ZnO, (b) P-ZnO. Fig. -9 UVB irradiated sites on the forearm of the volunteer. The skin of both sites showed normal appearance. (a) Our new gel-protected site, (b) The commercial W/O sunscreen-protected site. J. Soc. Cosmet. Chem. Jpn. Vol. 42, No. 2 2008 105

Fig. -12 Spectral transmission factor of the test samples through a thin layer. Fig. -10 The result of the sensory evaluation of our experimental gel-type sunscreen compared to W/O type sunscreen containing TiO2 and ZnO on a scale of +2 (much more), +1 (slightly more), 0 (no differences), -1 (less), -2 (much less). Fig. -13 Absorbance of the supernatant solution of each compound at 450nm. Fig. -11 The result of the sensory evaluation of our experimental gel-type sunscreen compared to sunscreen gel containing organic UV on a scale of +2 (much more), + 1 (slightly more), 0 (no differences), -1 (less), -2 (much less). Fig. -14 Transmission electron micrographs of P-ZnO. White circle indicates ZnO particle with 10nm in diameter.

Fig. -15 Cryo-scanning electron microscope micro graphs of P-ZnO dispersed in water. Fig. -17 Transmission electron micrographs of P-ZnO. Structural layer of non crystalline, amorphous sodium poly-acrylate was observed (black arrow) in the P-ZnO composite. Fig. -18 Spectral transmission factors of P-ZnO and a commercial SiO2-TiO2 dispersed in water. Fig. -16 Schematic reaction mechanism for P-ZnO composite formation. J. Soc. Cosmet. Chem. Jpn. Vol. 42, No. 2 2008 107

A Novel Water-Based Sunscreen Gel using a Polymer -Zinc Oxide Composite* Eiji Takahashi**, Tetsuya Oikawa**, Hirokazu Iyanagi**, Kunihiko Mohri**, Katsuhiko Nakamae*** R & D Department, POLA Chemical Industries, Inc.**, Japan Synchrotron Radiation Research Institute*** Conventional sunscreen products generally must strike a compromise between efficacy and product feel ; the hydrophobic ingredients that provide the sun protection generally impart an unpleasant, greasy feel and the greater the SPF rating, the worse the greasy feel. We tested an idea that a water-based sunscreen gel formulation containing inorganic UV absorbers would provide an effective way to address these problems. Our goal was to find a way to disperse inorganic sunscreen materials in water and to incorporate them into a water-based gel which would provide a more pleasant product feel. After extensive research we discovered a polymer zinc oxide composite (P-ZnO) with high UV protective effect and high dispersibility in water. In dried powdered form, P-ZnO can be easily dispersed in water. P-ZnO makes it possible to formulate a gel-type sunscreen, which is not possible using commercially available inorganic powders. The composite size of P-ZnO is about 500 nm and its structure consists of a dense aggregate of nano-zno having a size distribution in the 5-10 nm range and amorphous layers of poly acrylic acid coating zinc oxide to control the particle growth, block surface activity and prevent aggregation. The water-based P-ZnO sunscreen gel offers UV protection comparable to conventional products in a delivery vehicle that is much more pleasant to use. Key words: polymer, zinc oxide, composite, water-based gel, sunscreen, efficacy, product feel, inorganic, UV absorbers, nano J. Soc. Cosmet. Chem. Jpn. Vol. 42, No. 2 2008 109