Effect of amphiphilic additives on the behavior of water-based acrylic pressure-sensitive adhesives during paper recycling

Pressure-sensitive adhesives (PSAs) in recovered paper reduce efficiency and increase operating costs for paper recycling mills. Increased PSA fragmentation during pulping and the corresponding reduction in screening efficiency are indications that a PSA will likely interfere with paper recycling. Water-based PSAs, which dominate the label market, have complex formulations that include several amphiphilic materials, i.e., emulsifiers, dispersants, and wetting agents. Increasing the amount of these surface-active materials increased adhesive fragmentation during pulping, and thus reduced screening removal efficiencies. Accompanying the reduction in size was a distinct change in morphology of adhesive particles, which assumed a less collapsed structure during repulping. The presence of surface-active materials also appeared to facilitate the removal of fiber from PSA films during repulping, reducing the importance of paper facestock properties in determining fragmentation behavior. The findings presented here combined with results reported previously provide more complete guidelines for the synthesis and formulation of recycling-compatible acrylic water-based PSAs.