Laboratory Recycling of Benign Pressure Sensitive Adhesive Stamp Materials, 1998 Recycling Symposium Proceedings

The United States Postal Service (USPS) has initiated a program to develop environmentally benign pressure sensitive stamp products. The first phase of this program has focused on postage stamps. From the efforts of the pressure sensitive adhesive manufacturers, fourteen adhesives were developed which meet the USPS performance standards. These products are based on synthetic rubber block copolymer, acrylic copolymer or dispersible acrylic formulations. The USPS has developed a laboratory recycling protocol for evaluating recyclability of stamp materials made from these products. Its basic elements are high consistency pulping followed by screening operations. The focus of this work is to determine the performance of these products under both pre- and post-consumer feed conditions and develop a recycling database for these unique products. Similar studies done at the pilot scale level at USDA Forest Products Laboratory will allow comparison of laboratory and pilot scale results. Data is given for the composite of each of the classes of adhesives, as well as the individual adhesives. Both block rubber copolymer and acrylic formulations give good screenability, with over 90% of the adhesive removed. For pre-consumer waste streams, the presence of the silicone release liner can have positive, neutral or negative effect on the removal of the adhesive. As expected, dispersible acrylic formulations show poor removal by the screening operations, and other methods such as flotation and cleaning must be used.