Dry cleaning has long been a prime target on every environmentalist’s hit list. Its main cleaning agent-perchlorethylene-is a volatile organic solvent whose toxic emissions cause headaches, dizziness, and nausea after short-term exposure and liver and kidney damage over the long term. In fact, all dry cleaners are required by law to protect employees from exposure to the chemicals.
The main approach so far toward meeting the regulations has been to install costly vapor-recovery systems and seal up the dry-cleaning machines to reduce perchlorethylene leaks. Now, however, Joseph DiSimone, a professor of chemical engineering at North Carolina State University, has developed a novel dry cleaning technology that completely eliminates perchlorethylene with one of the most common and innocuous substances on earth: carbon dioxide.
Normally, the benign nature of CO2 that makes it such an environmentally friendly medium would limit its usefulness as a cleaning agent, since contaminants would not dissolve well in it. But DiSimone discovered a unique surfactant, or detergent, whose molecules have an affinity for oils and dirt on one end and for CO2 on the other. When mixed in liquid CO2, the surfactant organizes into clusters, called micelles, that capture dirt and grease as garments are immersed in the solution. Unlike conventional dry cleaning, which creates toxic waste, all that is left over from DiSimone’s technique is liquid CO2 and dirty surfactant, both of which are harmless and recyclable.
DiSimone discovered the substance several years ago while working on a process to use CO2 as a solvent in making acrylic polymers. He has since started Micell Technologies, Inc. in Raleigh, N.C., to commercialize the process. The company joined with American Dryer Corp. of Fall River, Mass., to build a 100-gallon dry cleaning machine that it hopes to unveil early next year in North Carolina.
The technology has already won raves from the federal government. Last June, the U.S. Environmental Protection Agency, which has funded much of DiSimone’s work, awarded the researcher its 1997 Green Chemistry Award for his surfactants. “Virtually all approaches to reducing risk to human health so far have been to reduce exposure” to toxic chemicals and solvents such as perchlorethylene, says Paul Anastas of the EPA’s Office of Pollution Prevention. But in so-called “green chemistry” programs like this, he says, the aim is to reduce or eliminate the intrinsic hazard by finding replacements for polluting technologies.
Lienhart says Micell hopes to sell machines to dry cleaners along with regular shipments of surfactants. The process produces so little waste, he says, that Micell will have store owners ship back the dirty surfactants for recycling.
Lienhart figures that a process enabling operators to clean a broader variety of fabrics with less labor and no environmental headaches will provide enough of an incentive for business owners to accept the higher cost of the machines-$125,000, about twice the cost of perchlorethylene machines.
Several other cost-saving considerations also weigh in favor of CO2 cleaning. Because the units must operate at high pressure-about 900 pounds per square inch to keep the CO2 liquefied-cleaning can be done at roughly room temperature, eliminating the likelihood of heat damage to garments. Dry cleaners will also be able to use the machines to add coatings that require high-pressure application, such as stain resistance or water repellents, eliminating the cost of separate coating machines.
Beyond the cleaning industry, Micell has been researching the possibility of using a carbon-dioxide process to dye fabrics. Tremendous amounts of water and heat are now used to set dyes in fabrics, Lienhart says. A deeply penetrating CO2 process performed at room temperature could accomplish huge savings.
The company has also been talking with institutional dry cleaners, and even the Navy, which Lienhart notes is “interested in getting perchlorethylene off their ships.” The company is also eyeing other niches in the huge industry of organic solvents, including the cleaning of precision machine parts.
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