HYBRID POWDERS FOR BODY MALODORS 199 Figure I. Scanning electron micrograph of spherical polyethylene powder. pulverizing aluminum chlorohydrate (Hoechst, maximum particle size 50 gm) by means of a jet mill (single-track jet mill STJ-200, Seishin Enterprise Co., Ltd). A microscopic profile of fine-particle aluminum chlorohydrate is shown in Figure 3. Fine-particle zinc oxide and spherical polyethylene powder were added and mixed in various weight ratios inside a Henschel mixer (Mitsui Miike Machinery Co., Ltd., Model 10B) for five minutes. The mixture was placed inside a centrifugal ball mill (Retsch, Type S2) charged with alumina balls where it was mixed and compressed ii 0840 !$K !Suu Figure 2. Scanning electron micrograph of fine-particle zinc oxide.

200 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Figure 3. Scanning electron micrograph of fine-particle aluminum chlorohydrate (ACH). mechanochemically to produce HPZ. HPA was produced by treating fine-particle alu- minum chlorohydrate and spherical polyethylene powder in the same manner. TEXTURE EVALUATION OF HYBRID POWDERS The texture of fine-particle zinc oxide, HPZ, fine-particle aluminum chlorohydrate, and HPA was evaluated by directly applying the powders to human skin (direct evalua- tion method) and by measuring their coefficients of kinetic friction by instrumental means (instrumental evaluation method). Direct evaluation method. Double-blind trials for evaluating fine-particle zinc oxide and HPZ directly on human skin were performed. A panel of 20 subjects (8 men and 12 women) from our Research Center, who had not been specially trained for evaluating the compounds of interest, was chosen. Each subject was given two figured bottles, one containing fine-particle zinc oxide, and the other, HPZ. The identity of each bottle was only distinguishable by the supervisor who collected the final results. The subjects applied each powder ad libitum on the back of their hands, and by rubbing them were asked to compare the texture of the two powders as cited below: A B: A is by far preferred to B A B: A is preferred to B A = B: A is more or less equal to B A B: B is preferred to A A 4 B: B is by far preferred to A The same experiment was carried out on fine-particle aluminum chlorohydrate and HPA as well. Instrumental evaluation method. To measure the coefficients of kinetic friction, a friction analyzer (7) that we have developed to evaluate the texture of various powders was