Lee Kyong Ho, Youn Hye Jung, Lee Hak Lae
Hankuk Paper Manufacturing Company Ltd., Ulsan 45010, South Korea.
Department of Forest Sciences, College of Agriculture & Life Sciences, and Research Institute of Agriculture and Life Sciences, Seoul National University, Seoul 08826, South Korea.
ACS Omega. 2020 Jun 18;5(25):15529-15536. doi: 10.1021/acsomega.0c01673. eCollection 2020 Jun 30.
Defect spots degrade paper quality and often cause sheet breaks and other problems in the subsequent coating process. We encountered sporadic surges of defect spots on paper from a paper machine producing printing and writing grades of paper. We found that white or light-colored filler spots and waxy, translucent, elliptical spots accounted for 27.3 and 34.4% of these defects, respectively, and that both types of defect contained unhydrolyzed AKD as a major component. Paper machine's wet-end deposits, however, did not contain unhydrolyzed AKD as a deposit component. We hypothesized that the colloidal stability of AKD was the main factor causing the increase in spot defects, and we verified this by deposit testing experiments. Among the papermaking additives tested, bentonite caused the most significant increase in AKD deposition during testing, which was attributed to its causing the electrostatic coagulation of cationically charged AKD emulsion particles. In contrast, anionically charged AKD emulsions showed improved stability and less deposit formation in the presence of bentonite.
缺陷斑点会降低纸张质量，并常常在后续的涂布过程中导致纸张断裂及其他问题。我们在一台生产印刷书写纸的造纸机生产的纸张上遇到了缺陷斑点的零星激增情况。我们发现，白色或浅色填料斑点以及蜡质、半透明的椭圆形斑点分别占这些缺陷的27.3%和34.4%，并且这两种类型的缺陷均含有未水解的AKD作为主要成分。然而，造纸机的湿部沉积物中并不含有未水解的AKD作为沉积物成分。我们推测AKD的胶体稳定性是导致斑点缺陷增加的主要因素，并通过沉积物测试实验对此进行了验证。在所测试的造纸添加剂中，膨润土在测试期间导致AKD沉积量增加最为显著，这归因于其致使带阳离子电荷的AKD乳液颗粒发生静电凝聚。相比之下，带阴离子电荷的AKD乳液在有膨润土存在的情况下表现出更高的稳定性且沉积物形成较少。
