The impact of the summer effect on ink detachment and removal

The goal of this study was to understand how the thermal aging of inks during the summer season impacts ink detachment, fragmentation, and removal. To achieve this goal, the author investigated the summer effect at deinking operations across North America, combined with a laboratory study to identify the different parameters for improving or maintaining ink removal performance under summer conditions. The information on mill performance was collected as part of Free Ink '98 and includes 27 newsprint deinking lines across North America. Experimental design parameters in the lab study included alkaline charge, ratio of sodium silicate to caustic, pulping time, pulping temperature, deinking agent, and the dosage of deinking chemicals. The experimental work also examined the role of ink type (mineral and vegetable).The combination of mill data and experimental data shows that the summer effect increased ink content and ink attachment. The best response is to employ shorter pulping times, increase pulping temperature, increase the alkali charge, and increase the dosage of deinking agent.