Solvents Used in Cold Cleaning

Abstract

Solvents encountered in cold cleaning applications include: methylene chloride, chloroform, carbon tetrachloride, ethylene dichloride, 1,1,1-trichloroethane, trichloroethylene, perchloroethylene, propylene dichloride, o-dichlorobenzene, monochlorobenzene, trichlorofluoromethane, trichlorotrifluoroethane, and blends of one or more of the halogenated solvents with other chemical solvents, such as petroleum fractions, alcohols, ketones, esters, and ethers. Some of the more important properties of these materials are outlined below: (a) Carbon tetrachloride (tetrachloromethane)—A dense, water-white, nonflammable and nonexplosive liquid having good solvent power for most organic compounds. It has been largely replaced by less toxic halogenated solvents for cold cleaning applications. (b) Chloroform (trichloromethane)—A heavy, colorless, volatile liquid. Although a powerful solvent for oils, greases, tars, and other organics, its industrial applications are limited by its toxic properties. (c) Ethylene dichloride (1,2-dichloroethane, ethylene chloride)—A colorless, volatile liquid. Although it burns with difficulty, it definitely exhibits a flash and fire point. It is an excellent solvent for greases, oils, fats and waxes, but it is seldom used alone in cold cleaning. (d) Fluorotrichloromethane (trichlorofluoromethane)—A dense, colorless liquid, highly volatile, nonflammable, and miscible with most organic compounds. It is used in mixtures where a fast evaporation rate is desired and in closed-loop flushing operations. (e) Methylene chloride (dichloromethane, methylene dichloride)—A colorless, heavy, nonflammable, highly volatile, low boiling liquid possessing excellent solvent power for greases, oils, waxes, and many other organic compounds. Its low boiling point makes it especially suitable in applications where a fast evaporation rate is required. (f) Monochlorobenzene (chlorobenzene)—A flammable, colorless liquid. Miscible with most organic solvents, it is usually blended in most cold cleaning compounds for removal of tar, paint, grease, etc. (g) O-Dichlorobenzene (1,2-dichlorobenzene)—A stable, heavy, colorless liquid with an aromatic odor. Although it is of low flammability, it will burn when ignited. It finds use in cold cleaning formulations where good solvency and a slow evaporation rate are desired. (h) Perchloroethylene (tetrachloroethylene)—A dense, colorless liquid, nonflammable and miscible with most organic liquids. Its solvency power is comparable to carbon tetrachloride, and it is used in cold cleaning applications where slower evaporation rates are desired. (i) Propylene dichloride (1,2-dichloropropane, propylene chloride)— A colorless, volatile, flammable liquid. Although a good solvent for greases and oils, its use is usually restricted to blends because of its flammability. (j) 1,1,1-Trichloroethane (methyl chloroform)—A dense, water-white, nonflammable liquid of good solvent power. The inhibited grade has found use in cold cleaning applications, either alone or blended. (k) Trichloroethylene (1,1,2-trichlorethylene)—A heavy, volatile, nonflammable liquid. It dissolves fats, greases, tars, waxes, and many other organic compounds. It finds widespread use in cold cleaning formulations. (l) Trichlorotrifluoroethane (1,1,2-trichloro-1, 2,2-trifluoroethane)— A nonflammable, colorless liquid of high volatility. It is often used in cold cleaning formulations either alone or blended, and its lower solvency for synthetics makes it especially suited to the degreasing of electrical insulation and many plastics and elastomers.