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Thursday, March 25, 2010

Cleaning Solvents

Solvents such as acetone, methyl ethyl ketone and methanol are used in large quantities to clean equipment and tools. Of these, acetone is the most widely used. Many fabricators have begun to replace acetone with dibasic ester @BE). DBE is a mixture of the methyl esters of adipic, glutaric and succinic acids that is both less volatile and less flammable than acetone (Lucas 1988). Methylene chloride has been used widely for cleaning because it is an effective solvent for many cured resins, although its use has been declining due to health and safety concerns.

Solvents are used to remove uncured resins from spray equipment, rollers, brushes, tools, and finished surfaces. Typical solvents used include acetone, methanol, methyl ethyl ketone (MEK), toluene and xylene. Acetone and other similar solvents are used for general cleaning, as standard practice for most open-mold fabricators of fiberglass products. To clean the spray equipment, acetone is usually circulated through the lines after the spray operation is shut down for the day. A simple but effective method practiced by some fabricators to minimize wastes is placing the containers of solvent near the resin spray area to prevent spills and drippage for tool cleaning. Generally, the solvent is reused until the high concentration of resin contamination prevents effective cleaning. However, if the containers are left uncovered, solvent will evaporate, increasing air emissions as well as resin concentration. Methylene chloride is an effective solvent for cured resins, and has been used by plastics fabricators.

Although many other solvents have been tried, including multicomponent mixtures, these have had mixed results. The best way to minimize the need for this chemical is to clean equipment before the resin dries. Disposal of contaminated solvents represents a major hazardous waste management expense. In addition, fugitive air emissions during the curing and cleaning processes are also of concern.