Comparison of Dye Behavior from Aspen HYP: Dyes Added in the HYP Manufacturing Process Versus Dyes Added at the Papermaking Wet End

Abstract

The yellowish color of High Yield Pulp (HYP) gives some psychological obstacles and limits its application in some paper grades. Dyes are widely used in the papermaking process to shade the yellowish color of the paper products. We proposed to add dyes into the HYP manufacturing process to minimize the yellowish hue. In this work, we substituted the dye-added HYP (dyes added in the HYP manufacturing process) for hardwood kraft pulp in the production of fine paper grades, and compared the results from those by adding dyes into the papermaking wet end. A higher dye effectiveness was obtained when we used the dye-added HYP. Also, the dye-added HYP gave more effective performance of Precipitated Calcium Carbonate (PCC) fillers and Optical Brightening Agents (OBA) in terms of CIE whiteness and b*. In addition, the dye-added HYP showed less negative effect on brightness and better compatibility with other dyes. The underlying mechanism for the above experimental observation was proposed.