Westvaco Corporation

Nipun Marwah

G Frederick Hutter

Allen A Gold

An improved process is disclosed for removing nonimpact inks and stickies contaminants from waste paper containing same by repulping the waste paper to form a slurry, adding a densifying agent and an agglomeration agent to the slurry, and subjecting the slurry to treatment with a conical cleaner to remove the inks/stickies. The densifying agent and agglomeration agent addition may be simultaneous or the densifying agent addition may precede agglomeration agent addition and, preferably, is conducted at ambient or greater temperature, at neutral to alkaline pH, and at a pulp consistency (below 18%). Densifying agent addition and agglomeration, followed by passing the repulped waste paper through a conical cleaner, provides improved ink removal over passing the slurry through a conical cleaner without such pre-treatment or with treatment only with densifying agent or only with agglomeration agent. 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. When the densifying agent is magnetite, the process may be employed with magnetic removal as an additional step.

Decontamination of waste papers

An improved process is disclosed for deinking waste paper which contains nonimpact printed papers printed with xerographic and laser inks by repulping the waste paper to form a slurry in the presence of an agglomeration agent and magnetite and subjecting the slurry to a magnetic field to remove the agglomerated ink particles, whereby the improvement comprises replacement of a portion of the agglomeration agent with a copolymer of styrene and acrylic monomers which copolymer is further characterized by having a Ring and Ball softening point of 70.degree.-105.degree. C. and an number average molecular weight of 2,000 to 10,000. The magnetic treatment preferably is conducted at ambient or greater temperature, at neutral to alkaline pH, and at a low pulp consistency. 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.

Magnetic deinking of waste papers

An improved process is disclosed for removing 'stickies' from waste paper which contains hot-melt and pressure-sensitive adhesives and lattices to produce high quality (high brightness, little to no dirt content) pulp with little or no fiber loss. The process involves attachment of sticky particles in the waste paper pulp to a magnetic carrier material with the help of an agglomeration agent followed by removal of the attached sticky 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 sticky removal over exposure to the magnetic field without such pre-treatment.

Magnetic removal of 'stickies' from waste papers

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.

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Mt. Pleasant, SC, United States of America

Nipun Marwah