Magnetic deinking of waste papers

Abstract

An improved process is disclosed for deinking waste paper which contains laser, electrostatic, and other non-impact printing toners/inks to produce high quality (high brightness, little to no dirt content) pulp with little or no fiber loss. The process involves attachment of ink particles in the waste paper pulp to a magnetic carrier material with the help of an agglomeration agent followed by removal of the attached ink particles by magnetic separation. The magnetic treatment preferably is conducted at ambient or greater temperature, at neutral to alkaline pH, and at a low pulp consistency. Agglomeration and magnetite addition, followed by exposure of the repulped waste paper to a magnetic field provides near complete ink removal over exposure to the magnetic field without such pretreatment. Also, the process may be employed as an additional step in a conventional process for removing inks from reprographic printed papers, such as ink removal by screening, flotation, centrifugal cleaning, washing, and sedimentation with or without decantation.

Dependencies are inferred from the claim text.