NEW SILICONES FOR THE COSMETIC INDUSTRY* By C. C. Cu•.I•I and R. C. GERGLE Dow Corning Product Engineering Laboratories, Mid/an, Mich. SILICONES ARE both unique and singularly versatile materials. A silicone fluid, for example, may be used to release resin bonded sand shells in a foundry as a dielectric fluid in transformers, and even to relieve bloat in cows. Silicone resins may be used to make masonry and brick walls water repellent as insulation for electric motors and to protect industrial smokestacks against the ravages of heat and moisture. Because of this versatility and the widespread use of silicones, it is difficult to keep abreast of all the latest developments in every industry where silicones are used. While we have learned quite a bit about the requirements of your industry, we are far from being experts in the formula- tion of cosmetics. We do feel, however, that through our familiarity with the chemistry and applications of silicones, we may be able to help with problems you face in the development of improved cosmetic formulations. Much of the work of our research laboratories is directed toward the synthesis of new, silicon-containing chemicals. Literally hundreds of new silicones have been synthesized. The problem of selecting the silicones that are most likely to interest you is fortunately simplified by establishing certain criteria. First, the silicones should be relatively inexpensive. Second, the sili- cones must exhibit characteristics different from those of the products commonly used in the cosmetic industry. They must be unique either in their chemical structure or in some property such as compatibility or physical form. With these considerations in mind, our laboratories have developed three new types of silicones: 1. Salicyloxymethyl dimethylsilyl end-blocked fluids 2. Fatty alcohol esters of dimethylpolysiloxane 3. Ethylene or polyethylene glycol esters of dimethylpolysiloxane SALICYLOXYMETHYL DIMETHYLSILYL END-BLOCKED FLUIDS The first type of silicone we shall' discuss is a salicylate end-blocked * Presented at the December 15, 1955, Meeting, New York City. 234

NEW SILICONES FOR THE COSMETIC INDUSTRY 235 fluid represented by the structural formula: o o [1 Me Me Me II COCH2 Si--O(Si•)• SiCH2OC n 5- 0 OH Me Me Me •OH The simplest structure in this series is the disiloxane, where n is equal to zero. As n is increased the resulting fluid behaves more and more like a dimethylpolysiloxane and the effect of the salicylate radical on physical properties is diminished. For example, when n is equal to zero, the vis- cosity of the polymer is 33.2 cs. at 25øC. When n equals 4 the viscosity drops to a low value of 18 cs. Then, as n increases the viscosity follows an upward trend similar to other silicone polymers. If n were infinitely great, we would expect that the resulting fluid would be indistinguishable from its analogue, Me Me3SiO(SiO).SiMe3 n --• •o Me The effect of the salicylate group is still evident, however, in a polymer containing 12 dimethylsiloxane units. A fluid of this length is compared with a dimethylpolysiloxane fluid in Table 1. Note that the salicylate TABLE 1--TYPICAL PROPERTIES OF SALICYLATE END-BLOCKED FLUIDS COMPARED TO DIMETHYL POL¾SILOXANE FLUID Specific Surface Viscosity, Freezing Refractive Gravity, Tenelan, Fluid C•olor cs of :75 C• Point Index, :75 C• 25 C•/25 C• dyne/cm Sollcylate end- water 27.2 --75 C 1.4348 1.025 23.5 blocked white Dimethyl poly- water 20 --60 C 1.4000 0.955 20.5 siloxone white radical is responsible for a higher density, refractive index and surface tension. The lower freezing point is probably caused by an interruption of the symmetry of the molecule due to the bulky ring at each end of the chain. Because of these facts any salicylate end-blocked dimethylsiloxane is likely to be a compromise,between a fluid predominantly organic in nature and one which exhibits the characteristics expected from dimethylpoly- siloxane fluids. These fluids, like the dimethylpolysiloxane fluids of comparable viscosity, are water-white liquids possessing rather low surface tensions. Due to this low surface tension, the fluids spread easily and deposit a non-oily film on the skin.