BUSINESS
N-METHYLPYRROLIDONE enabled environmentally friendlier products, but now it has toxicity problems ONCE TOUTED as benign, the
solvent N-methyl-2-pyrrolidone (NMP) is under scrutiny because of concerns over its potential health effects. Although manufacturers say NMP is safe to use when handled properly, these health concerns have opened opportunities for alternative solvents and processes that make do without NMP. Paint makers and other solvent users regarded NMP as something of a wonder chemical during the 1980s and ’90s, when they used it to create environmentally friendly line for several years.” In the polyurethane coatings, paint stripON THE LOOKOUT Paint makers polymer preparation process, pers, and agricultural chemical seek alternative Bayer is replacing NMP with formulations. solvents to acetone but removing the But NMP has increasingly attract- formulate acetone before it ships the ed attention as environmental regu- polyurethane coatings like the product to paint makers. Bayer lators, first in California and more one covering the makes just about all its polyrecently in the European Union, panel here. urethane coatings materials have sought to exercise control over in the U.S. and Germany with the solvent in markets where it poses the acetone process, Schmitt an inhalation hazard. The impact notes, and the same will soon be true at its on one group of users was evident at last facilities in China. month’s American Coatings Show in CharNMP is a desirable paint solvent because lotte, N.C., where polyurethane material it doesn’t contribute high levels of volatile suppliers were offering customers alternaorganic compounds, has a low level of toxtives to NMP-containing coatings. icity, and has low flammability, says Glenn “NMP is a great solvent for waterborne H. Petschke, urethanes technical manager polyurethanes,” says Peter Schmitt, aquefor Reichhold. But his firm has also adous technology platform leader at Bayer opted the acetone process and produces MaterialScience, a major urethanes manuNMP-free polyurethanes that either don’t facturer. It enables smooth handling in the require a solvent besides water or use an dispersion production process and remains alternative such as dipropylene glycol diin the polymer as it dries, thereby helping to methyl ether, made by both Dow Chemical form a crack-free film, he explains. and Clariant. Petschke would like to find a However, in 2001, California listed NMP simple drop-in replacement for NMP, but as a reproductive toxicant, and in 2003, he says one is not available. the state set workplace exposure limits, BASF, LyondellBasell Industries, and Schmitt notes. Also in 2003, the EuroInternational Specialty Products (ISP), pean Commission Working Group on the which together make up the Washington, Classification & Labeling of Dangerous D.C.-based N-Methylpyrrolidone ProducSubstances labeled NMP dangerous to chilers Group, are not eager to talk about their dren in utero. It has since recommended plans for NMP in the coatings industry. limits on worker exposure to NMP. BASF will only state that it sees no major In response, Schmitt says, “we’ve been impact on its NMP business because of regreformulating our polyurethane product WWW.C E N- ONLI NE .ORG
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SOLVENT USERS LOOK TO REPLACE NMP
ulatory concerns. LyondellBasell referred C&EN to the NMP Producers Group, but the group’s spokeswoman did not return C&EN’s calls. Carlos Restrepo, vice president of industrial chemicals for ISP, says that because “the polyurethane coatings and paintstripping markets represent only a small portion of the overall market, any potential impact is not significant to ISP.” He adds that the NMP Producers Group is trying to evaluate the impact of any new regulations. Two years ago, the group evaluated NMP in personal care products and suggested that manufacturers of such products consult NMP makers before using the solvent. The group did so because it anticipated a ban on NMP in cosmetics in the European Union. WORLD PRODUCTION capacity for NMP was 226 million lb per year in 2006, according to Sean Davis, an analyst at SRI Consulting, publisher of the Chemical Economics Handbook. Accounting for about 20% of all uses for NMP, the coatings market, which includes waterborne polyurethanes, is the largest one affected by regulatory concerns, Davis notes. However, the coatings category includes uses where workers are not exposed to NMP, such as the application of electric motor wire enamels, an industry source says. Davis says worker exposure to NMP cannot always be easily controlled in applications such as paint stripping (8%) and agriculture (5%), where NMP is used as a solvent in the formulation of insecticides, fungicides, and herbicides. Additional applications for NMP include recovery of hydrocarbons in petrochemical processing and cleaning of microelectronic components. Alternatives to NMP for agricultural use include dimethylamide, an oleochemical solvent made by Cognis, Davis adds. Potential substitutes for paint stripping, he suggests, include ethyl lactate and benzyl alcohol. NMP makers may yet come up with a drop-in replacement for the polyurethane coatings market. Even if they don’t, users still have options ranging from the less-than-perfect substitutes to process modifications that do not require NMP at all. But one thing that’s clear is that regulators are gunning for NMP, and users will have to adjust their strategies accordingly.—MARC REISCH
