Color Stripping of Mixed Office Waste Papers, 1995 Pulping Conference Proceedings

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G. Rangamannar

Beloit Corporation R&D

Colored papers present in a mixed office waste furnish (MOW) can be detrimental to the final brightness of the deinked pulps. Color and the color stripping process of these pulps significantly influence the maximum achievable brightness in a deinking plant. Stripping of color components by a non-chlorine bleaching process depends upon the color and nature of color components and the types of pulps present in the furnish. This study was undertaken to gather scientific information about color of various types of papers present in a ledger furnish and their impact on brightness of deinked pulp during a bleaching process. Color values of various types of papers such as carbon, Carbonless paper, mechanical, direct dye and marbled papers are analyzed. These pulps are bleached by both oxidative (peroxide) and reductive (formamidine sulfunic acid) bleaching processes. The color removal process is evaluated by comparing color values of the pulps against color numbers of a standard white paper. In the case of Carbonless paper, mechanical and carbon paper brightness of the pulps correlates well with the darkness values (‘L’ value). Direct dye and marbled papers showed color reversion phenomena during peroxide bleaching. Color stripping by an oxidative and a reductive bleaching process depends upon the color content, color intensity, nature of color components and the types of pulps present in a MOW furnish.