Combined process of peroxide bleaching of wood pulps and addition of optical brightening agents

摘要

A process for improving optical properties of high-yield pulp (HYP) for producing paper products with superior brightness. Optical brightening agents (OBAs) can effectively improve the optical properties of high-yield pulp (HYP). The present process involves incorporating the OBAs into the alkaline peroxide bleaching process. By combining peroxide bleaching with an optical brightening agent, one can decrease the bleaching cost to reach the same brightness target. Some key advantages of adding OBA to HYP at the pulp mill over the conventional wet-end addition of OBA include: i) the quenching effect on OBA by the wet-end cationic polymers such as PEI is decreased by fixing OBA on HYP fibers; ii) the negative impact of metal ions in the white water system on the OBA performance is minimized when OBA is pre-adsorbed and fixed on HYP fibers; iii) the photo-yellowing (color reversion) of HYP and HYP-containing paper sheets is decreased when more OBA is on HYP fibers to protect them from harmful UV radiation.