Study On The Interaction Between Lignin And Optical Brightening Agents

The cost of high-yield pulp (HYP) is low because of its high yield, less raw materials and chemicals consumption, and the discharge waste pollution of the BOD5, CODCr, and AOX of the production process is less than chemical pulp. The reasons for high yield pulp to product the fine paper are that good quality, low cost, and high yield. Therefore, more and more HYP will be used to product the fine paper.Optical properties are of great importance for coated and uncoated paper, especially the brightness and whiteness, which are the key parameters to determine the value of the final products in these years, Optical Brightening Agents (OBAs) are widely used in the production of uncoated and coated paper grades to increase the brightness. HYP has been increasingly used in the manufacture of various paper grades. HYP contains much of the lignin originated from wood, which can decrease the OBA brightening efficiency. Therefore, further study of effect of interactions between lignin and OBA is necessary for improving the OBA efficiency to theoretical value.The effect of blending ratio of lignin and OBA on UV spectrum and the optical properties were investigated. A modified Kubelka-Munk equation was developed to predict/model the brightness and whiteness response of different lignin types and OBA. It was found that paper present to yellowness for lignin color system. After joining the OBA, it can compensation the yellowness caused by lignin. So the paper would be look at more white. At the same time, it also found that lignin will compete with OBA to absorb ultraviolet light, so it would reduce the OBA efficiency. Because of different kinds of OBA has different structures, they would have the different effect on the optical performance. Along with the increase of the content of this three kinds of OBA, the optical properties of the paper could be improved, especially when the content of OBA between 0% and 0.2%, these were improved very obvious.In this research, it would detecte the UV spectrum of the different blending ratio of lignin and OBA. Injecte the different concentrations of lignin and OBA into the paper surface, then study the effect of the interactions between lignin and optical brightening agents on paper optical properties.In this study, a modified Kubelka-Munk equation was developed to predict the brightness and whiteness response of different lignin types and OBA. This formula can predict briteness and whiteness of the OBA-containing paper. In addition, in order to meet the need of brightness and whiteness index, we can reverse this formula model to determine the content of the OBA.