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Chlorinated solvents are organic compounds with at least one chlorine atom bonded in a covalent bond. They have various industrial applications, including as solvents for cleaning and degreasing, propellants, intermediate chemicals for plastics and resins, and heat transfer gases. Vinyl chloride is the most commonly produced chlorinated solvent and is used to make polyvinyl chloride (PVC). Other major chlorinated solvents include methylene chloride and perchlorethylene, which are used in food and pharmaceutical manufacturing, paint stripping, and dry cleaning. Some chlorinated solvents, such as dioxins, are highly toxic and carcinogenic.
A chlorinated solvent is an organic compound to which at least one chlorine atom or chlorine group is bonded in a covalent bond, where electrons are shared between atoms. Other common names for a chlorinated solvent chemical include a chlorinated hydrocarbon or an organochloride. They have a wide range of industrial applications and, in some forms, are controversial. Dioxins are a form of chlorinated solvent that has been shown to be the most toxic and carcinogenic substance ever created by man. Some dioxin compounds, however, can also be generated as a result of natural processes, such as forest fires.
Because chlorinated solvent compounds are miscible in water and have no normal flash points at which they can catch fire, they have a wide range of practical industrial uses. They also possess a structure that can be easily modified to produce a wide range of chemical properties. This makes them useful in four major areas. They are a class of solvents useful for degreasing and cleaning applications and are propellants for fire extinguishers or foam. Furthermore, the compounds are also intermediate chemicals for the production of plastics and resins and serve as an efficient heat transfer gas in environmental systems.
The most commonly produced chlorinated solvent is vinyl chloride gas, C2H3Cl, and 95% of global production of the chemical goes to the production of polyvinyl chloride (PVC), a plastic widely used in plumbing pipes and other industrial applications. Vinyl chloride was also once a chemical coolant and propellant used extensively in cosmetic and pesticide aerosols. Because it is toxic to humans by all routes of exposure including inhalation and skin contact, these uses of the compound have been banned in most nations.
Organochlorine compounds such as vinyl chloride are also used to make solvents, with approximately 10,000 tons per year of 1,1,1-trichloroethane chloromethane derived from vinyl chloride. Trichloroethane and trichlorethylene are used to clean metals or as an ingredient in specialty adhesives. Annual global vinyl chloride production in 2005 was 32,624,000 metric tons, which is up from about 18,000,000 metric tons produced in 1985. Major domestic producers are the United States at nearly 9,000,000 metric tons, Western European nations at 6,650,000 tons combined and China and Japan, each producing over 3,000,000 tons annually.
Two other major chlorinated chemical solvents are methylene chloride, which is used in food and pharmaceutical manufacturing as well as paint stripping, and perchlorethylene, which is widely used in the dry cleaning industry. U.S. manufacturers sell chlorocarbons in forms that can be used for everything from hydrochlorofluorocarbons (HCFCs) designed as a short-term replacement for ozone-depleting chlorofluorocarbons (CFCs) to degreasing chemicals and to create urethane foam. The chlorinated solvent of tetrafluoroethane is also used as an ingredient in the production of Teflon® for nonstick cooking surfaces.
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