Closed Loop Pilot Plant Results Recycling an Environmentally Benign PSA Using a Wood-Free Recovered Paper Furnish, 2000 Recycling Symposium Proceedings

Kurt Lorenz, Oliver Heise and Bangji Cao--The US Postal Service, in cooperation with Forest Products Laboratory (FPL), has actively sponsored a research campaign to quantify the impact of PSA (Pressure Sensitive Adhesive) postage stamp adhesives on the recycling industry and, ultimately the consumer. A portion of this research centered upon two recent process system trials at the Voith Sulzer Technology Center. The model system used for the two trials consisted of: High Density Cleaning, Coarse Screening with //0.30mm C-Bar slots, Fine Screening with //0.10mm C-Bar slots, Primary and Secondary ECO Flotation, 60mm Forward Cleaning, Ø75mm Through Flow Cleaning, Washing, Twin Wire Belt Press Thickening, and DAF Water Loop Clarification. The quantification of stickies was carried out in accordance with TAPPI T 277 pm-99 and FPL protocol. The first trial, using a mixture of three types of PSA, showed over 99% of stickies are removed in our representative recycle process with the vast majority (>98%) being removed via slotted screening. The second trial was performed using a single highly tacky PSA. This trial was performed to determine the effect of this PSA material on mill equipment runnability and maintenance. The results show no measurable final product impact beyond what is typically found using present grades of recycle furnish. The same high stickies removal efficiencies were again found in this second system run. No noticeable affinity for deposition on internal piping and equipment was discerned. This PSA material exhibited a higher level of shear and tensile strength as well as a propensity to adhere to itself and create balled stickies over 25mm in diameter. These balled stickies were only noted in the coarse screen (//0.30mm C-Bar) reject stream.