|Du Pont acid dissolves problems|
In 1940s, Du Pont developed a process to make ethylene glycol, or antifreeze, from hydroxyacetic (glycolic) acid. Over the next 30 years, the company developed other markets for glycolic acid, and in the mid-1970s, when more cost-effective methods of producing antifreeze had been discovered, the company opted to continue making the product for its growing list of new applications.
Today, glycolic acid is marketed as a mild organic acid for use in a variety of industries, including applications in everything from medicine to metal processing.
Du Pont's Mean Green Solution
Du Pont supplies glycolic acid as 70% technical aqueous solution (in this form it is a clear, light amber liquid with a mild odor resembling burnt sugar), as 70% high purity aqueous solution, and as 99% high purity crystal.
Aqueous solutions of glycolic acid contain both free and soluble polyacids in equilibrium; the ratio is determined by solution concentration. Since the polyacids hydrolyze readily on dilution, their presence can be ignored for most uses, and total glycolic acid concentration can be considered as free acid.
This organic acid is very soluble in acetic acid, acetone, ethanol, ethyl acetate, methanol and, most importantly, water. It is slightly soluble in ethyl ether, but only sparingly soluble in hydrocarbon solvents.
Glycolic acid can function as both an acid and an alcohol. This dual functionality leads to a variety of chemical reactions and valuable physical properties for metal cleaning, metal complexing, electroplating, as well as many other uses.
Since it exhibits complexing power and oxide solubility for many metals, glycolic acid is a logical candidate for inclusion in metal cleaning formulations. It has a low corrosion rate on nonferrous metals and is effective is dissolving such deposits as smut and/or aluminum. Cleaning compounds that contain this acid have excellent rinsibility and reduce the spotting caused by trace metal residues. These properties are important in a variety of applications, including cleaning of airplane, train, and truck bodies, and are especially important in metal plating operations.
Glycolic acid effectively removes hard water scale from all types of heat exchange equipment. It should be considered for pH adjustment of cooling waters to prevent scale build-up.
For metal processing, glycolic acid can be used to replace volatile organic acids in special pickling operations. Its nonvolatile characteristic prevents losses due to elevated temperatures and reduces the ventilation requirements. It can usually be used to replace any organic acid in pickling formulations.
There are numerous applications for the acid in the electroplating industry. The sodium and potassium salts of the acid are excellent substitutes for Rochelle salts used as bath additives. Because glycolic acid forms complexes with virtually all multivalent metals, its salts are used in many electroplating baths, such as those for chrome, lead, cobalt, tin, and nickel.
Other applications for the acid in metal processing include etching, electropolishing, and copper brightening. Glycolic acid's properties also make it well suited for cleaning hard surfaces, boiler and process equipment, water wells, dairy and food processing equipment, and masonry.
In the piping sections of Du Pont Belle's glycolic acid production facility, velocity erosion reduced the lifetime of silver-lined tubes to a few years. In the past, the plant experienced blowouts of this high-pressure piping caused by interior corrosion. Here, the silver lining failed, exposing the carbon steel tube to the process chemical, sulfuric acid, which ate through it rapidly.
High quality monomers and polymers of glycolic acid and lactic acid are used to manufacture bioabsorbable surgical sutures, staples, and clips; sustained-release drug delivery systems; and implantable prosthetic devices. The Food and Drug Administration (FDA) has approved specific applications using this family of polymers.
Polymers of glycolic acid are water degradable and water insoluble. This allows them to be used in the controlled release of chemicals in an aqueous environment. These polymers are currently being used in the acidification of oil wells. The polymer is finely ground and forced down the well out into the surrounding formation where it fills in the porous formation. This contains the well and avoids the excessive use of strong cleaning agents. After the cleaning is performed, the acid degrades naturally into glycolic acid, which is then easily flushed from the well.
Bill Weber, Business Manager for the acid, says glycolic is attractive because it provides a lot of active performance given its weight. Its combination of being an acidulant, a chelating agent, and also easily water soluble makes it very user-friendly.
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