Effect of Grade and Mixing Ratio of Pulps on the Physical Properties and Drying Efficiency of Multi-ply Thin Paper

In this study, we attempted to measure the drying efficiency and physical properties of multi-layer thin paper using softwood bleached kraft pulp (SwBKP), hardwood bleached pulp (HwBKP), recycled steel interleaf and recycled LCD interleaf used in a thin paper mill.Using virgin and recycled pulps, which were confirmed to have excellent drying efficiency and strength in previous studies, two-layer thin papers were prepared in a laboratory, and the minimum drying time until the oven-dried state of a sheet and drying energy reduction were analyzed.After measuring drying efficiency, their tensile strength, light scattering coefficient, and opacity were measured.The mixing ratio of SwBKP and HwBKP was set to 60:40, 40:60, and 20:80 on the top layer, and the bottom layer was made of recycled pulps to prepare two-layer thin papers.As the mixing ratio of HwBKP increased in the top layer and recycled LCD interleaf in the bottom layer was used, the minimum drying time decreased, and drying energy reduction increased.As a result of measuring the physical properties of two-layer thin papers, the tensile strength decreased and opacity increased as the light scattering coefficient increased when the mixing ratio of HwBKP increased and recycled LCD paper was used in the bottom layer.Therefore, if the mixing ratio of SwBKP increases for the top layer and the bottom layer is produced using recycled LCD interleaf, it is possible to manufacture multi-ply thin paper with high drying efficiency and opacity while minimizing the decrease in strength.In conclusion, the drying energy of a multi-ply thin paper was expected to be reduced effectively by controlling the grade and mixing ratio of the pulps while minimizing changes in its physical properties rather than single-ply thin paper.