2-Butoxyethanol

Miscibility with water Miscibility of 2-butoxyethanol with water depends on temperature. Depending on the composition of the mixture, the two liquids are partially miscible. This mixture shows both a lower and an upper critical solution temperature: below around 49 °C (lower critical solution temperature), the liquids are completely miscible. The same is true for temperatures above around 130 °C (upper critical solution temperature). Between these temperatures, however, the liquids do not mix in all proportions and two phases might appear, each of which is formed by various ratios of the two liquids. ==Production==

2-Butoxyethanol is commonly obtained through two processes; the ethoxylation reaction of butanol and ethylene oxide in the presence of a catalyst: or the etherification of butanol with 2-chloroethanol. 2-Butoxyethanol can be obtained in the laboratory by performing a ring opening of 2-propyl-1,3-dioxolane with boron trichloride. It is often produced industrially by combining ethylene glycol and butyraldehyde in a Parr reactor with palladium on carbon. In 2006, the European production of butyl glycol ethers amounted to 181 kilotons, of which approximately 50% (90 kt/a) was 2-butoxyethanol. World production is estimated to be 200 to 500 kt/a, of which 75% is for paints and coatings In the US, it is considered a high production volume chemical because more than 100 million pounds of this chemical are produced per year. ==Uses==

2-Butoxyethanol is a glycol ether with modest surfactant properties, which can also be used as a mutual solvent (soluble in both water and oil). Commercial uses 2-Butoxyethanol is a solvent for paints and surface coatings, as well as cleaning products and inks. Products that contain 2-butoxyethanol include acrylic resin formulations, asphalt release agents, firefighting foam, leather protectors, oil spill dispersants, degreaser applications, photographic strip solutions, whiteboard and glass cleaners, liquid soaps, cosmetics, dry cleaning solutions, lacquers, varnishes, herbicides, latex paints, enamels, printing paste, varnish removers, and silicone caulk. Products containing this compound are commonly found at construction sites, automobile repair shops, print shops, and facilities that produce sterilizing and cleaning products. It is the main ingredient of many home, commercial and industrial cleaning solutions. Since the molecule has both polar and non-polar ends, 2-butoxyethanol is useful for removing both polar and non-polar substances, like grease and oils. It is also approved by the U.S. FDA to be used as direct and indirect food additives, which include antimicrobial agents, defoamers, stabilizers, and adhesives. In the petroleum industry 2-Butoxyethanol is commonly produced for the oil industry because of its surfactant properties. In the petroleum industry, 2-butoxyethanol is a component of fracturing fluids, drilling stabilizers, and oil slick dispersants for both water-based and oil-based hydraulic fracturing. The compound is also used to facilitate the release of the gas by preventing congealing. which was widely used in the aftermath of the 2010 Deepwater Horizon oil spill. ==Safety==

2-Butoxyethanol has a low acute toxicity, with of 2.5 g/kg in rats. Laboratory tests by the U.S. National Toxicology Program have shown that only sustained exposure to high concentrations (100–500 ppm) of 2-butoxyethanol can cause adrenal tumors in animals. American Conference of Governmental Industrial Hygienists (ACGIH) reports that 2-butoxyethanol is carcinogenic in rodents. These rodent tests may not directly translate to carcinogenicity in humans, as the observed mechanism of cancer involves the rodents' forestomach, which humans lack. OSHA does not regulate 2-butoxyethanol as a carcinogen. 2-Butoxyethanol has not been shown to penetrate shale rock in a study conducted by Manz. Disposal and degradation 2-Butoxyethanol can be disposed of by incineration. It was shown that disposal occurs faster in the presence of semiconductor particles. It has not been identified as a major environmental contaminant, nor is it known to bio-accumulate. 2-Butoxyethanol biodegrades in soils and water, with a half life of 1–4 weeks in aquatic environments. 2-Butoxyethanol and its metabolites fall to undetectable levels in urine after about 30 hours in men. 2-Butoxyethanol is metabolized in mammals by the enzyme alcohol dehydrogenase. Neurological effects have also been observed in animals exposed to 2-butoxyethanol. Fischer 344 rats exposed to 2-butoxyethanol at concentrations of 523 ppm and 867 ppm experienced decreased coordination. Male rabbits showed a loss of coordination and equilibrium after exposure to 400 ppm of 2-butoxyethanol for two days. When exposed to 2-butoxyethanol in drinking water, both F344/N rats and B63F1 mice showed negative effects. The range of exposure for the two species was between 70 mg/kg body weight per day to 1300 mg/kg body weight per day. Decreased body weight and water consumption were seen for both species. Rats had reduced red blood cell counts and thymus weights, as well as lesions in the liver, spleen, and bone marrow. Under these regulations, products containing 2-butoxyethanol are to be diluted below a certain concentration. Only those in which the user performs the required dilution are required to include it on labelling information. Regulation in the US 2-Butoxyethanol is listed in California as a hazardous substance and the state sets an 8 hour average airborne concentration exposure limit at 25 ppm, and in California employers are required to inform employees when they are working with it. 2-Butoxyethanol is prohibited from use as a chemical additive in hydraulic fracturing fluids (Rule 437, Table 437-1) in Colorado where all chemicals used in downhole operations are required to be disclosed (§34-60-132 C.R.S.) to the Energy and Carbon Management Commission. It is approved by the Food and Drug Administration as "an indirect and direct food additive for use as an antimicrobial agent, defoamer, stabilizer and component of adhesives", After its deletion from a UN list of substances requiring special toxicity labeling in 1994, and a subsequent petition by the American Chemistry Council, 2-butoxyethanol was removed from the U.S. Environmental Protection Agency's list of hazardous air pollutants in 2004. The safety of products containing 2-butoxyethanol as normally used is defended by the industry trade groups the American Chemistry Council and the Soap and Detergent Association. ==References==