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US 5,639,346 AGranted
Magnetic removal of "stickies" from waste papers
AssigneeWestvaco Corporation
InventorsNipun Marwah, Allen A. Gold
Life of this patent
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AssigneeWestvaco Corporation
InventorsNipun Marwah, Allen A. Gold
Estimating the term…
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.
A process for removing stickies from repulped waste paper stocks including stickies-contaminated papers comprising introducing a magnetic carrier material selected from the group consisting of ferromagnetic and paramagnetic materials to the stocks to form attachments between particles of the stickies and the magnetic carrier material, followed by addition of an agglomeration agent prior to magnetic separation of the agglomerated magnetic carrier material and attached stickies from the stocks, wherein the agglomeration agent is selected from surfactants or blends of surfactants characterized by HBL values of 10 or lower and by molecules which exhibit a long hydrophilic "tail" and a cloud point of above 65.degree. C.
Dependencies are inferred from the claim text.