Environmentally Benign Usps Stamps: Baseline Pilot Recycling Results

Stickies continue to represent the most challenging contaminant to remove from recycled secondary fiber. Current projections suggest that pressure sensitive adhesive (PSA) markets will continue to grow rapidly, increasing the concentration of these contaminants in common office-pack wastepaper. PSA’s reformulated to exhibit higher removal efficiencies within standard secondary fiber processing equipment are expected to prove effective in alleviating cleanliness demands for the recycling industry. The US Postal Service, in their program to develop postage stamp adhesives that do not adversely affect the environment, have focused considerable efforts on developing a benign PSA stamp product for recycled fine paper operations. This program has encompassed both laboratory and pilot plant recycling studies to quantify the removability of such adhesives and high removal efficiencies have recently been reported. In order to translate pilot removal efficiencies to commercial full scale recycling operations, a baseline wastepaper recycling study using conventional stickie and dirt contaminants was run at the Forest Products Laboratory pilot facility. Contaminant removal efficiencies of 50% across fine slotted pressure screens were observed for these conventional contaminants, and were significantly lower than the reported removal efficiencies for reformulated stamp adhesive materials: Likewise, final product dirt levels were 23 times greater for the conventional contaminants, when compared to the reformulated adhesive, despite comparable initial contaminant levels. The relatively low yields observed in the pilot facilities may have impacted overall removal efficiencies and are being addressed through protocol modifications.