328 JOURNAL OF COSMETIC SCIENCE CERAMIC MICROSPHERES Madeline P. Shinbach 3M Company, 3M Center, St. Paul, MN 55144-1000 INTRODUCTION: A new class of cosmetic raw materials has been engineered using ceramic technology. Ceramic spheres of high purity and excellent color are manufactured in a controlled narrow particle size range, representing a new generation of filler pigments suitable for use in a wide range of decorative cosmetics and other personal care products. The manufacture of the ceramic spheres involves a proprietary high temperature technique. The process is capable of transforming amorphous shaped inorganic particles into spheroidal forms. As do all spherical particles, the ceramic microspheres possess excellent skin feel due to the "ball bearing" effect as they are rubbed out. The microspheres are unusual in their low oil absorption and relatively high bulk density which pernfits incorporation into dispersed systems at significant levels without either initial or long term viscosity increase. The particles function as an "invisible" filler useful in formulating deep shades in which the chalky whitening effect of many ingredients is a disadvantage. The inorganic microspheres offer a cost effective alternative to polymeric microparticles and are completely compatible with the full range of aqueous and non- aqueous formulations. MATERIAL, PROCESS AND PROPERTIES OF CERAMIC MICROSPHERES: A. Process: Particles are passed through a natural gas/air flame of approximate stoichiometric proportions with the particles reaching temperatures up to 1350øC. As the mineral particles melt, spheroidal formation occurs. The flame-formed product is cooled by mixing with ambient temperature air and then separated from the resulting gas stream with a cyclone device. B. Materials: Materials with chemical compositions substantially consisting of the following categories - clay, talc, and hydrated silicates such as mica will be topics of discussion. The high temperature process converts the morphology from crystalline to amorphous resulting in a ceramic or-glass composition. This ceramic composition of the microspheres provides its extreme chemical inertness, stability, and insolubility. C. Properties: The transformation from an amorphous or platy shaped particle to a sphere can be expected to yield a number of interesting changes in material properties. The significant reduction in surface area achieved can be demonstrated in Fig. 1. A result of the minimized surface area can then be shown in Fig. 2 by the corresponding reduction in oil absorption by these nonporous spheres. The reduced surface area also enables increased ease of dispersibility of the microspheres as well as higher pigment loading potential due to lower viscosity buildup. The microspheres allow for an efficient packing factor leading to increased bulk densities as compared to the unspheroidized material. The spherical nature, as shown in Fig. 3, provides lower coefficient of friction values as would be expected with a "ball bearing" as opposed to a platy structure leading to an enhanced texture or "feel". COSMETIC APPLICATIONS: A. Pressed Powder: The performance of spheroidal magnesium silicate was evaluated in a pressed powder formulation versus a talc control. The spherical filler improved slip and imparted the perception of increased softness and creaminess. In a pressed powder eyeshadow formulation, 20% spheroidal magnesium silicate was found to yield equal or better slip and skin feel when compared to 10% boron nitride or polymethylmethacrylate (PMMA). Even at these levels, the spherical ceramic product offers an economical alternative to other texture enhancers. The nonporous nature and inermess of the spheroidal magnesium silicate are advantageous in that the texture of the formulated product remains constant over time,

2000 ANNUAL SCIENTIFIC SEMINAR 329 B. Lipstick: In lipsticks, ceramic microspheres offer a means to incorporate significant levels of inert filler to improve adhesion to the lips as well as to reduce creeping and feathering in moisturizing formulations. Because the atmospheric and chemical water have been removed, the ceramic microspheres are more suitable for use in anhydrous, hot pour systems than native or natural (raw) minerals. 8-11% levels of spheroidal magnesium silicate were added to a transparent gloss lipstick. The result was a creamy emo!!ient product which adhered well to the lips. Without the added filler, the texture of gloss lipsticks tends to be greasy, yet hard, due to the higher wax levels used to achieve high temperature stability. Polymeric fillers have the disadvantage of porosity which can cause the texture to become drier over time or vary according to processing conditions. C. Powder Cream Formulation: The objective in the development of a powder cream product is to achieve the highest pigment load possible while maintaining pourability in the melted state. Ceramic microspheres, with or without surface treatment, can be used to raise the solids percentage due to their properties of low surface area, nonporosity, and low oil absorption. Other spherical materials commonly used to achieve a smooth, dry feel have the disadvantage of high oil absorption which reduces pourability of the hot melt. Fig. 1 Reduction in Surface Area Due to Spheroidization Fig. 2 Reduction in Oil Absorption Due to Spheroidization 10 . 5- 0 • ', -89% ß ld•oestum • Alumltmm • PoP.slum • • S/•e •te•e •e •,,n Aluminum 1.2- 1.1 - 1.0- 0.8- 0ø7- 0•8- 0.4- o.3- xx -45% \ \ \\ •7% \ \ Aluminum Alumthorn Fig. 3 Scanning Electron Micrograph of Spheroidized Potassium Aluminum Silicate