Deinking Toner Containing Furnishes. Part 4. The Role of Microscopic Ink Particles in Deinking Office Paper

In deinking office wastepaper, efforts have focused on the removal of visible ink particles. However, efficient removal of microscopic ink particles is also important in office paper deinking. It is these particles which have the greatest adverse effect on brightness. Reduced brightness due to the presence of residual microscopic ink particles can increase bleaching agent consumption and thus mill operating costs. Two new types of deinking agents have been developed. While being quite efficient at removing visible ink particles, these are also highly effective in removing microscopic ink particles. In the first type of deinking agent, a chemical additive is used in a deinking surfactant formulation. The second method involved use of a specially developed surfactant not previously used as a deinking surfactant. This surfactant has been used alone and in formulated deinking agents. In combination with a deinking surfactant, a proprietary additive provided at least equal visible ink particle removal efficiency compared to a highly effective deinking formulation also known to aggregate toner particles. In addition, deinked sheet brightness was significantly (2-4 points) greater when using the chemical additive in the formulation. Very high ink removal combined with high sheet brightness can also be obtained using more strongly ink dispersing formulations. Pilot plant tests (including a kneading step) and laboratory experiments indicated the specially developed surfactant was highly effective in flotation deinking at lower than conventional usage rates.