Safe as milk

Ethyl lactate, an ecologically benign chemical, is all set to replace dangerous solvents

Last Updated: Saturday 04 July 2015

-- a simple substitute made from ingredients found in a glass of wine and a milk bottle could have easily replaced the hazardous organic chemicals used in everything from paint thinners to solvents years ago, say scientists. But this substitute, till now, was far too expensive to be an economically-feasible alternative to the solvents available in the market.

Not any more. Engineers in Illinois, usa , have figured out a way to cut the cost of manufacturing ethyl lactate -- the above-mentioned magic substitute -- by almost half, making it as cheap as the solvents it will soon replace. The chemical is produced from ethyl alcohol and lactic acid, the main ingredient in milk. The chemicals benignity is can be judged by the fact that it is also a legitimate food additive. Lactate esters occur naturally and are biodegradable by-products of fermentation. "You get them in soy sauce and some wines," says Eugene Bergmann, president of ntec, a Chicago-based chemicals company.

Ethyl lactate could replace a formidable percentage of the 2.5 million tonnes of regular solvents produced annually for use in paints, glues, inks and dyes. It also has the potential to replace up to 80 per cent of the halocarbons -- many of which severely damage the ozone layer -- used by the electronics industry to clean circuit boards. One of them, called trichloroethylene, frequently turns up in groundwater reserves, is a known carcinogen, and leads to congenital deformities.

With ntec funding, Jim Frank and his team at the Argone National Laboratory have found a way to make the solvent substitute practical by dramatically reducing its manufacturing costs. The traditional method is to ferment corn starch to produce lactic acid and ethyl alcohol. More ethyl alcohol is added and the mixture is heated to 100 c so that the acid and the alcohol combine, and the magic substitute -- chemically an ester -- is ready.

However, this reaction also produces water, which eventually halts the reaction so that the yield of the ester never crosses 60 per cent. In an expensive second stage, the water is removed by distillation. This also removes the alcohol, which must be recaptured, dried and returned to the reactor vessel.

In the new process, the brew passes over a membrane that allows only the smallest molecules, including water, to pass. The hot water then evaporates from the other side of the membrane. The efficient removal of water leads to a complete reaction, and the resultant ethyl lactate is more or less pure. Bergmann speculates that this new membrane method will allow his company to produce the ester for about us $2 per kg, almost as cheap as the conventional solvents. Unlike the conventional solvents, ethyl lactate is highly biodegradable. "In a fifty-fifty mix with water, it starts to break down in just five days," says Bergmann. The breakdown products are carbon dioxide and water.

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