Improving the Optical Properties and Filler Content of White Top Testliners by Using a Size Press

This study aims to investigate the impact of coating with ground calcium carbonate (GCC) on the optical properties and filler content of white top testliner (WTT) papers. The paper properties investigated include brightness, whiteness, opacity, color coordinates, and yellowness. The results showed that the amount of filler mineral used in the coating process significantly affected the optical properties of the paper. The use of 15% total solids of GCC in the coating suspension resulted in the highest level of whiteness and improved the brightness value by 6.8%. The use of 7% total solids of starch and 15% total solids of GCC reduced the yellowness index by 85%. However, the use of only 7 and 10% total solids of starch had an adverse effect on the yellowness values. The surface treatment led to a significant increase in the filler content of the papers, with a maximum of 23.8% achieved using a coating suspension with 10% total solids of starch solution, 15% total solids of GCC suspension, and 1% dispersant. The starch and GCC in the coating suspension were found to have a direct impact on the filler content of the WTT papers. The addition of a dispersant improved the uniform distribution of the filler minerals and increased the filler content of the WTT. The water resistance of WTT papers increases due to the use of GCC, while their surface strength remains at an acceptable level. The study demonstrates the potential benefits of the surface treatment in terms of cost savings and provides valuable information on the impact of the treatment on the properties of WTT papers.