Ethers of Ethylene Glycol and Derivatives

Abstract

There are currently seven U.S. manufacturers of ethers and other derivatives of ethylene glycol (EG), diethylene glycol (DEG), and higher glycols. Five of them are members of the American Chemistry Council (ACC) Glycol Ethers' Panel. The glycol ethers most commonly encountered industrially are colorless liquids that have mild ethereal odors. Alkyl glycol ethers are manufactured in a closed, continuous process by reacting ethylene oxide with an anhydrous alcohol in the presence of a suitable catalyst. Depending on the molar ratios of the reactants and other process parameters, the product mixtures obtained contain varying amounts of the monoethylene-, diethylene-, triethylene-, and higher glycol ethers. Typically, the products in these mixtures are separated and purified by fractional distillation. The miscibility of most of these ethers with water and with a large number of organic solvents makes them especially useful as solvents in oil–water compositions. Their relatively slow rate of evaporation also makes them useful as solvents and coalescing agents in paints. Other uses include inks, cleaners, chemical intermediates, process solvents, brake fluids, and deicers. The ethers of the higher glycols are used as hydraulic fluids. An estimate of the U.S. production and use of representative ethylene glycol ethers is presented. Production of ethylene glycol ethers (total) in Western Europe amounted to 245 thousand metric tons in 1995. Occupational exposure to glycol ethers occurs dermally and by inhalation. Ingestion is not a concern in industrial exposure, although some cases of intentional ingestion of consumer products containing ethylene glycol ethers have been reported. A number of analytical methods have been published that are suitable for detecting glycol ethers in environmental air samples. Glycol ethers generally have low acute, single-dose toxicity, and LD50 values generally range from 1.0 to 4.0 g/kg of body weight. In animals and humans, high-dose administrations (>350 mg/kg) result in central nervous system depression, although the results from many studies show no specific damage to neural tissues. Other toxicological effects attributable to glycol ethers are associated with metabolism to the corresponding alkoxyacetic acids. In the case of EGME, EGEE, and certain other glycol ether derivatives, significant reproductive, developmental, hematologic, and immunologic effects have been associated with the formation of either methoxyacetic (MAA) or ethoxyacetic acids (EAA). For other glycol ether derivatives substituted with propyl, butyl, or higher homologues, developmental effects secondary to maternal toxicity (without teratogenic effects), as well as hematologic effects, are observed. Ethylene glycol ethers and acetates may enter the environment from manufacturing effluents and emissions and as a result of their use in commercial products. Keywords: Ethylene glycol ethers; Analytical methods; Elimination; Structure-activity relationship; Hematologic effects; Ethylene glycol acetates; Vapors