nPB is effective in dissolving fats/oils, waxes and resins. As a degreasing agent, nPB is used in operations such as:
• metal finishing and metal working;
• precision cleaning;
• auto parts cleaning;
• dry cleaning; and
• removing solder flux residue in electronic parts manufacturing.
nPB is also used as a chemical processing intermediate in the synthesis of pharmaceuticals, insecticides, quaternary ammonium compounds, flavors and fragrances, and as a solvent for extracting tar from asphalt.
Some facilities using nPB as a drop-in substitute had problems with equipment corrosion. Similar to other halogenated solvents, nPB must be stabilized to prevent the build up of acid breakdown products, and to inhibit reaction with metals. If not properly stabilized, nPB breaks down into hydrobromic acid, which can corrode equipment and potentially emit very toxic hydrogen bromide gas. Chemicals used as stabilizers are often claimed trade secret by manufacturers, but may include 1,3-dioxolane and 1,2- butylene oxide.
EPA’s Significant New Alternatives Policy (SNAP) program, which evaluates and regulates substitutes for ozone depleting chemicals, considers nPB an acceptable substitute for chlorofluorocarbon -113 and for methyl chloroform when used as a solvent in industrial cleaning equipment for metals, electronics, and precision cleaning. However, EPA issued a proposed rule in 2007 finding nPB unacceptable as an aerosol solvent or as an adhesive carrier under SNAP.
Health concerns and increased regulation of TCE (for degreasing and metal cleaning) and perc (for garment cleaning) have resulted in increasing use of nPB as a relatively inexpensive and unregulated drop-in substitute for these two chlorinated solvents. However, as reviewed earlier, scientific evidence indicates that nPB is not a safe substitute for TCE or perc, or for other solvents such as methylene chloride. Workers may unknowingly be exposed to hazardous levels as nPB has been marketed as a “green” product. One recent study of multiple dry cleaning establishments found that nPB levels in the breathing zone of dry cleaning operators were routinely high — over twice to 10 times the exposure limit of 5 ppm (TWA) set by the California Occupational Safety and Health Standards Board.