Fractionation of recycled pulp obtained from mixed paper

Past investigations of pulp fractionation have been directed toward classification of pulp fibers based on their physical dimensions. The present investigation describes a new method of segregating mixtures of wood pulp fibers into their mechanical and chemical pulp fractions. The technique exploits differences in the surface morphology and wetting characteristics of mechanical and chemical pulps. These differences were enhanced by adsorbing surfactants on the fiber surfaces, thus modifying their behavior in the pulp slurry. Fibers were then selectivity separated into various fractions by flotation.