Dye removal in oxygen color stripping of secondary fibers
AssigneeAir Products and Chemicals, Inc.
InventorsRonald C. Naddeo, Konstantinos Hristofas, Vincent L. Magnotta
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Abstract
Color from dyes is removed from secondary pulps with non-chlorine based bleaching agents in treating sequences using oxygen with combinations of peroxide, ozone, and/or hydrosulfite at controlled pH conditions (less than 8 or greater than 10). Acid treatment prior to bleaching steps improves color removal and protects fibers from damage at more severe bleaching conditions.
Claims16
A method for removing color from a pulp prepared from waste paper material which comprises contacting said pulp in a first step with oxygen gas at pH values of less than 8 or greater than 10, wherein said oxygen reacts with one or more dyes present in said pulp, thereby removing said color therefrom to yield a decolorized pulp suitable for making a recycled paper product.
Dependencies are inferred from the claim text.