Molecular markers could aid recycling.One of the most fundamental recycling problems--the sorting of mixed plastics into pure waste steams--will soon have two new chemical solutions. Both Eastman Chemical Corp. of Kingsport, Tenn., and Germany's Bayer AG Bayer AG German chemical and pharmaceutical company. Founded in 1863 by Friedrich Bayer (1825–1880), it now operates plants in more than 30 countries. Bayer has originated scores of pharmaceuticals, chemicals, and synthetic materials; it was the first developer and each have developed identification technology that allows sorting based on "marker" chemicals that are readily detectable and do not affect the resin's properties. PVC PVC: see polyvinyl chloride. PVC in full polyvinyl chloride Synthetic resin, an organic polymer made by treating vinyl chloride monomers with a peroxide. , for example, already has a built-in marker--the chlorine atom, which fluoresces in response to x-rays. PET and polyolefins normally have no such "tag." Now Eastman has applied for a patent on a molecular marker Molecular marker is a term with a number of uses. It is any kind of molecule indicating the existence of a chemical or physical process. In particular, in the fields of geology and astrobiology, biomarkers (also known as biosignatures) are sometimes understood as molecules that would be built onto PET's polymer backbone during resin manufacture. The company envisions other markers that would be added to polyolefins during color compounding. "We realized a couple of years ago that it was of great importance to be able to make a very positive, inexpensive identification of plastic materials," explains David Cornell, manager of plastic recycling Plastic recycling is the process of recovering scrap or waste plastics and reprocessing the material into useful products, sometimes completely different from their original state. technology. Cornell says the marker detection method is unsophisticated and inexpensive, though he declines to elaborate for now. Eastman tentatively plans to run the first demonstration within the year. The marker technology's effectiveness will hinge on Verb 1. hinge on - be contingent on; "The outcomes rides on the results of the election"; "Your grade will depends on your homework" depend on, depend upon, devolve on, hinge upon, turn on, ride total acceptance by competing resin suppliers and recyclers. "In order for the technology to work, the markers have to be added by common consent," Cornell says. But in keeping with the notion that "everyone has to use it," Eastman's PET marker would likely add less than l|cent~/lb to the resin's price. And only minuscule minuscule Lowercase letters in calligraphy, in contrast to majuscule, or uppercase letters. Unlike majuscules, minuscules are not fully contained between two real or hypothetical lines; their stems can go above or below the line. amounts would be needed--5 ppm or less. Cornell expects any licensing fees to be nominal as well. DYEING FOR RECOGNITION A related concept comes from Bayer AG (German parent of Miles Inc. in Pittsburgh), which introduced its own marking method at the K'92 exhibition in Dusseldorf. Bayer proposed that fluorescent dyes would provide the means for differentiating resins. A calibrated cal·i·brate tr.v. cal·i·brat·ed, cal·i·brat·ing, cal·i·brates 1. To check, adjust, or determine by comparison with a standard (the graduations of a quantitative measuring instrument): sensor would pick up the individual spectral pattern for each unique resin/dye combination. Because of high detection sensitivity, no more than 5 grams of dye per metric ton (5 ppm) would be required. |
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