Polyethylene glycol ethers of stearic acid make up the Steareth ingredients (Steareth-2, Steareth-4, Steareth-6, Steareth-7, Steareth-10, Steareth-11, Steareth-13, Steareth-15, and Steareth-20). Steareth-20 primarily functions as a surfactant and emulsifier in cosmetic products and is generally available as a waxy, solid material. It can be used in the creation of personal hygiene products, deodorants, fragrances, skin, eye, and hair products.
Origin
Alkaline catalysis is by far the most common method of manufacture of alkyl PEG ethers, although acid catalysis is known. The initiation of the alkaline catalyzed synthesis of alkyl PEG ethers consists of the addition of ethylene oxide to a dry solution of the appropriate alcohol (e.g., stearyl alcohol is used to synthesize steareths) with an alkali earth metal (e.g., potassium hydroxide) or alkoxide (e.g., sodium methoxide). The reaction continues to propagate (i.e., continues to add additional units of ethylene glycol to the alcohol) until the available ethylene oxide is consumed and/or the reaction is terminated by the addition of an acid (e.g., hydrochloric acid). Dioxane (1,4-diethylene dioxide; 1,4-dioxane) is commonly formed as a byproduct. Finally, a finishing step is commonly employed via the addition of one or more oxidizing agents (e.g., hydrogen peroxide) or antioxidants/stabilizers (e.g., butylated hydroxytoluene (BHT) or α-tocopherol (vitamin E).