An Expanding Array of Solvent Systems is Helping Produce New Converts — And New Concerns
Choice in solvents has expanded exponentially in the last 20 years due to the regulatory pressure on the use of perchloroethylene in drycleaning. Ongoing research and development is a testament to the industry’s ingenuity, flexibility and importance, but the industry is still far from having a new “solvent of choice.”
“Drycleaning is a trade, but it’s also an art,” says Fred Schwarzmann Jr., president of A.L. Wilson Chemical Co. “Every garment is a unique challenge. Solvent marketers are giving people a lot of choice in how best to meet that challenge.”
In order for a solvent to be viable, the industry agrees, it must accomplish the task at hand — cleaning clothes — while satisfying current and projected concerns about health, safety and the environment.
“I don’t know that you’re going to find a perfect solvent, but whatever solvent you use should effectively remove a wide range of soils from garments,” says Robert Blacker, director of technical services and solvent operations for Naperville, Ill.-based distributor R.R. Street & Co. “People didn’t go into business to manage hazardous wastes; they went into business to clean clothes.”
How do the options stack up? First, longtime industry standard perc offers exceptional cleaning, and improved machinery and management practices are helping it continue to be a cost-effective option. And although it is still a target for regulators, the only deadline for a phaseout is California’s.
“If your equipment is in good shape and your procedures are up-to-snuff, there’s no reason you can’t use perc,” Schwarzmann says. “In some places, there’s no end date; in others, if you have an old machine, you could be out of business tomorrow.”
High-flashpoint (isoparaffin) hydrocarbons are the second-most-popular solvents in use today. They are VOCs, but Exxon DF-2000 and Chevron-Phillips EcoSolv are manufactured to be safer to use than low-flashpoint ancestors such as Stoddard solvent. “The benzene, the toluene and the xylene have been removed, lowering toxicity,” Blacker says. “Mineral spirits has about 20% aromatics; DF-2000 has .02%.”
High-flashpoint hydrocarbons also have only about half the ozone-depleting reactivity rating of Stoddard, and in new machines, produce 1/25 the emissions. They biodegrade in a matter of days.
Perhaps more important, state-of-the-art machinery is making isoparaffins easy to use. “Equipment technology has caught up with them,” Blacker says. “You don’t have the moisture or distillation issues anymore.”
Users of GreenEarth’s D5 silicone solvent report it is gentle and effective, but it can require high drying temperatures. GreenEarth is not an ozone producer, and the California Air Resources Board (ARB) calls it “an acceptable alternative to perc,” saying it poses no risk to operators or the public.
Beyond the plant, exposures may be an issue. Canada moved to limit D5 in waste streams last year, citing concerns about bioaccumulation. California’s Office of Environmental Health Hazard Assessment (OEHHA) recently named it to a “Priority” list of chemicals for human biomonitoring.
Next, n-Propyl Bromide (nPB) solvents are touted as an “envirofriendly” drop-in replacement for perc. They are not considered hazardous air pollutants (HAPs) by the EPA. While nPB is an extremely effective degreaser, users have reported difficulty containing it, since it can easily produce corrosive acids under certain operating conditions. And like perc, the solvent must be handled carefully to avoid exposures.
Used in textile care since 1999, liquid CO2 is a favorite of regulators for its minimal environmental impact. The process was slow to gain acceptance, however, due to its high cost and low aggressiveness. No equipment supplier serves the few remaining liquid-CO2 users, leaving them to find or forge their own replacement parts.
The latest system to hit the market is making converts of those who can afford to adopt it early. Using a propylene glycol ether surfactant and a liquid CO2 “dry” cycle, Solvair is by most accounts easy to use, effective, and of extremely low potential impact to health and the environment. Solvair is not subject to RCRA regulations, and recently won approval over other solvent drycleaning systems from the Sierra Club.
Last, wetcleaning is an important supplement to any technology, but rarely is seen as a stand-alone process. “As much as they want to push all-wetcleaning, it is just not sustainable,” Blacker says. “It’s a great adjunct, but solvent cleaning is here to stay.”
Whatever solvent you choose, look for one that handles your customers’ clothing, has excellent support from suppliers, offers good operational capabilities, and meets or beats environmental concerns. “Start with the premise that you’re going to perform the drycleaning function,” Schwarzmann says, “and work backward from there.”