Pilot Testing and Recycling Evaluation of Newly Developed Environmentally Benign Pressure Sensitive Adhesives, 1998 Recycling Symposium Proceedings

As a result of an initiative by the U.S. Postal Service (USPS), a team is working cooperatively to help solve the problem of pressure sensitive adhesives (PSAs) in recovered paper. The team consists of the USPS; the USDA Forest Service, Forest Products Laboratory (FPL); Springborn Testing and Research (STR); and industry representatives including papermakers, paper recyclers, paper collectors, equipment manufacturers, and adhesive and chemical suppliers The team’s goal is to work with industry to develop new environmentally benign PSAs for postal applications that will fulfill both USPS specifications and be compatible with the USPS environmental strategic plan. Environmentally benign PSA is a form of adhesive that places no significant additional burden on plants that are using recycled fiber.

Based on the criteria set by the paper industry, the adhesive industry is now striving to formulate new PSAs that are mostly removable in the screening step of the recycling process. As a result of these combined efforts, a pilot-scale separation sequence has been developed to assess the removal of adhesives from various feed stocks containing PSA. This pilot-testing protocol simulates a typical recycling operation, including high consistency pulping, coarse and fine pressure screening, forward and reverse cleaning, washing, and flotation deinking. An optical protocol using image analysis was developed to measure residual adhesive. Handsheets made from pulp accept samples taken after each unit operation and on paper samples from the paper machine runs were analyzed by this protocol. The recycling protocol simulates a typical recycling operation and uses both preconsumed, postconsumed, and control stocks and was further refined to reflect optimum operating conditions, such as temperature, consistency, screen size, repulping energy, and chemical additives.

In this paper, the development of the protocol is explained and data analysis is given for control trials and a trial using experimental PSA that was screenable and appears to meet established criteria for recyclability.