Table 1. Typical composition of a De-icer 50.0% Methanol 41.0% Deionized Water 5.0% Ethylene Glycol 0.2% Morpholine – Purified (Low odor) 0.2% Monocor BE – Mixed orgasnic borates 3.0% Carbon Dioxide these products are almost always used in open air conditions, so that any hazardous ingredient vapors would be very quickly diluted and removed. The protection of young children could still be an issue if an uncapped can was available to them. Other aerosols that contain methanol are used to improve car tire traction on snow and ice, to formulate certain adhesives and even a few outside grill cleaners. Lastly, methanol can be readily dehydrated to produce dimethyl ether (DME) propellant. Ethanol Ethanol is by far the most commercially important alcohol. It is used mostly as an aerosol solvent and diluent. Ethanol is still made by the fermentation of starches such as corn, rice and molasses, using various yeast instigators. However, the more important process involves synthesis by the catalyzed hydrolysis of ethylene (CH2=CH2), using an excess of extremely pure water under heat and high pressure conditions. The fermentation process uniquely produces a major and important by-product, known as fusel oil in about 3–5% amounts. It is a valuable source for several higher alcohols and other compounds. In contrast, the direct hydration process produces a very high grade of ethanol. The few impurities, such as DME, higher alcohols (including unsaturated ones), propane, iso-butane, “heavy oils” and so forth are easily removed by fractional distillation (Editors note: the propane and butane created from this process, however, are not used as propellants). The resulting ethanol is isolated as the azeotropic composition of 95.57 weight-% ethanol and 4.43 weight-% water. When desired, the water can be removed by ternary distillation, using diethyl ether (DEE) or sometimes other added compounds. The result is anhydrous (200 proof) ethanol. Since there is no extra charge, aerosol fillers usually purchase only the anhydrous grade. If they need the 190 proof ethanol product they can simply add 4.43 weight-% of water. In this way, they can use only one bulk tank for anhydrous ethanol storage. From 1948 to 1980, aerosol fillers could purchase anhydrous ethanol in tank-cars or tank-trucks where the moisture content was a mere 25 to about 60ppm. Later, for various commercial reasons, the water specification became 1,000ppm and moisture levels increased. This slight change had no deleterious effects on formulations and failed to cause any can corrosion. Fillers utilized a manual, then automatic, Karl Fisher Method (KFM) analysis to determine the moisture of incoming ethanol shipments and final aerosol products, such as hair sprays. They quickly found that anhydrous ethanol was very hygroscopic and often absorbed humidity from the air during the sampling process unless special precautions were taken. The initial furor regarding the traces of moisture in anhydrous ethanol has now dissipated. The use of ethanol is complicated by a regulatory burden. Of the 50 or so Specially Denatured Alcohols (SDA), four Proprietary Solvents, six Special Industrial Solvents and one Completely Denatured Solvent—all authorized for particular uses by the Bureau of Alcohol, Tobacco, Firearms & Explosives within the U.S. Justice Dept.—the aerosol industry utilizes only about three. SDA 23A (denatured with 7.43% acetone if anhydrous) is authorized for deodorants, body sprays, antiseptics and other uses. SDA 40, the most popular, has five compositions, of which SDA 40B is now the most widely used. The anhydrous product contains 0.16% tert.butanol and 0.0006% Denatonium Benzoate, N.F. (Bitrex) as denaturants. It is used in hair care, disinfectants/deodorants and many other products. Finally, there is SDA 39C (denatured with 1.39% diethyl phthalate if anhydrous), often used in colognes and perfumes. Fillers must keep careful records of SDA alcohol receipts and uses, with emphasis on yield accounting. A manufacturing shrink of 1% is permitted. If the loss is more than that and unexplained, the full beverage tax is applied to the excess. Occasionally, fillers may purchase tax-paid ethanol for food formulations, oral products and certain pharmaceuticals. The product is often delivered in 55 U.S. gallon steel drums. They must be stored in dedicated “lock-up” areas to avoid any possibility of thefts for beverage use. The hygroscopic nature of anhydrous ethanol has posed problems when it is stored in large bulk tanks. If the top of such tanks contains a simple “gooseneck” breathing pipe, humid air will enter during cool nights and dehydrated air (plus some ethanol fumes) will exit during the relative warmth of daylight hours. This can be partly counteracted by adding a conservation fitting to the breathing pipe, allowing the tank to become very slightly pressurized before it opens. A better approach is to also add a 5–10 U.S. gallon container to the pipe. The container is then 80% filled with anhydrous calcium chloride (CaCl2) and doped with a small amount of anhydrous cobalt (II) chloride (CoCl2). When the CaCl2 becomes saturated with moisture, forming the hexahydrate (CaCl2.6H20), the cobalt chloride will start to pick up moisture, changing in color from light blue to dark red as it forms CoCl2.6H20. This signals the need for content replacement. Anhydrous ethanols have a flash point of 54.8°F (12.6°C) and the “95 vol.% or 190 Proof” ethanols flash at 60.1°F (15.6°C). Ethanol, due to its widespread use and flammability, is the cause of most laboratory fires. Heating of ethanolic concentrates must be done in the absence of flames or sparks. It has a lower explosive limit (LEL) of 3.28 vol.% in air. Anhydrous ethanol dissolves many inorganic salts, but less effectively than methanol. It March 2017 Spray 39
Spray March 2017
To see the actual publication please follow the link above