Recyclability of Mixed Office Waste Papers Containing Pressure Sensitive Adhesives and Silicone Release Liners, 2001 Pulping Conference Proceedings

J. Hess, R. Sena-Gomes, L. Davie, M. Sikes--Increased use of pressure sensitive adhesives for labels and stamps has introduced another contaminant into the office paper stream: silicone-coated release liners. This study examines methods and conditions for removal of contaminants, including these liners, from a typical batch of discarded office papers. Removal of contaminants contained in the furnish were compared using alkaline and near neutral pH repulping conditions. Residual contaminants were measured by image analysis, and the number and size of the contaminants were compared on handsheets that were prepared from samples collected at stages from pulping through bleaching. Handsheets were also tested for tear and tensile strength. Results showed that unadjusted pH 8.6 was more effective than pH 10.0 for contaminant removal. Flotation was the most effective stage for removal of contaminants. Presence of residual adhesives or silicone did not compromise final paper strength properties to a great extent; pH 10.0 repulping produced only slightly higher tensile and tear properties than did pH 8.6 pulping.