Process for de-inking recycled paper pulp with a reducing agent
AssigneeMorton International, Inc.
InventorsMaurice Hache, Sheri Prosperi
Life of this patent
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Abstract
Recycled paper pulp is de-inked by pulping it at neutral or alkaline pH with an aqueous deinking composition comprising one or more reducing agents. The preferred reducing agents are sodium bisulfite and sodium borohydride. Sodium hydroxide is preferably used to give the desired pH.
Claims9
A process for reductive de-inking wood-containing recycled paper consisting essentially of pulping the recycled paper in an open pulper in the presence of an aqueous de-inking composition consisting essentially of an alkali metal hydroxide, flotation agent, and a reducing agent selected from the group consisting of sodium hydrosulfite and mixtures of sodium borohydride and sodium bisulfite, wherein said de-inking composition is added immediately upon the onset of pulping at a pH of from 7 to about 8.5, and immediately and with no hold time after pulping the dislodged inks are removed by screening, flotation and/or washing stages, and then optionally subjecting the de-inked pulp to a bleaching step.
Dependencies are inferred from the claim text.