At one point in time, about three years ago, it was completely permissible to dispose of non-hazardous water-wash paint residue in approved landfills. That changed in 1993 with what were called the "Landban" regulations. Its effect, simply put, rests in a redefinition of what a liquid is: If droplets of a presumed substance will exude through a standard conical paper filter within a prescribed period, then it's deemed a liquid and, as such, is banned from landfill disposal. Period.
Solutions. This sent Caterpillar chemists—primarily John Spangler at the East Peoria, Illinois, works scrambling for solutions. The first—and pretty much an industry standard response—was to switch to electrostatic spray equipment in the paint booths to increase spray transfer efficiency and decrease overspray. But because of the large diversity and variety of part geometries, this alternative limited overall efficiency improvement by only 10% and still resulted in a lot of waste material—just at a lower rate.
The next thought was to "dewater" the paint sludge material. The idea was to take enough water out, on a continuous basis, without interrupting the paint process, to pass the paint/liquid filter test. And while this approach seemed to bear merit, it had to be abandoned because one attempt after another failed to produce significant yields of dewatered sludge. The main obstacle was not a chemical one, but an equipment one: the spray booths themselves were not designed so that overspray sludge could be continuously collected and processed.
Chemistry. Next, chemist Spangler became convinced that as spray booth design was unlikely to change anytime soon, the chemistry of the paint and overspray material might be changed to produce a recyclable, useful paint product. Over a period of time, the chemists worked with various forms of "detackification" (methods to alter the dirty, sticky physical state of water-wash paint sludge so that it could more easily be worked with and could be "inexpensively" made recyclable). And they finally hit upon a unique particle encapsulation phenomena called "hyrdophobic fumed silica," which Caterpillar now holds a patent on. The process encapsulates paint particles with an inert, extremely thin layer of a hydrophobic product that is routinely used in other paint formulations, which opened the door to detackifying overspray paint sludge without detrimentally altering its chemistry as a recyclable feedstock for new paint. In other words, the true recycling of paint.
Not So Fast. While efforts to decrease the variation of detackified sludge material to meet Caterpillar performance and durability characteristics continued, Moline Paint Manufacturing Company (a major paint product supplier for Caterpillar) began a long-term recycling research program with Caterpillar. Both companies knew going in the skepticism other recycling programs had met with and suffered through—specifically plastics and paper products. So both companies agreed that if paint recycling were to become a reality, it could only happen with demonstrated, repeated success, ideally with Caterpillar as the customer.
Together they developed a strategy to develop a workable series of processing steps that could transform raw, detackified paint sludge into a dry, pulverized quality paint raw material. Then, pressing the new product introductions only as far as the processing improvements would allow—thus solidifying support for paint recycling by creating an internal and external network of satisfied customers.
Early Results. By the early 1990s, the first recycled coating was brought into the Peoria plant as safety yellow-line-marking. Next, the interior and exterior walls of the plant's new materials technology laboratory, completed last May, were coated with quality paints using the Caterpillar recycling process. Other players now involved included the Sherwin-Williams Company, Moline Paint/Guardsman, and the Valspar Corporation—all developing products targeted at appropriate applications they already had in Caterpillar.
One of the most striking results, however, has been the discovery that the presence of reclaimed pigment not only has no negative effect on products in which it is used, but in some cases the presence of reclaimed materials can significantly increase performance characteristics.
Closing the Loop. When asked if this is truly a "closed-loop" solution, Spangler observes that as far as industrial recycling, it's the only one he's aware of. Not only is the overspray, turned into sludge, turned into dry, pulverized pigment, turned back into paint, applied to Caterpillar products rolling off the line (very soon), ad infinitum, truly closed-loop, but even the water used in to reclaim the overspray is recycled, 100%.
Plating Plastic W/Out VOCs?
David Crosley, president of Challenge, Inc. (Indianapolis, IN), says that his company is working on a process that, when fully developed, should have a positive effect on the environmental concerns of those companies that chrome plate plastics. Currently, chrome plating of plastic, a technology which, incidentally, hasn't changed much since the 1930s, usually involves a solvent-based lacquer, employing a variety of different resins, all of which result in very high VOCs6 to 7 pounds per gallon, typically. Challenge is working on a water-based replacement technology, employing a new resin, which will lower the resulting VOCs to 1.9 to 2 pounds per gallona 75% reduction.RYB