Strength Improvement of the Coloring Paper for Fruit Bag by Using Non-woody Bamboo Kraft Pulp

In this study, we evaluated the effect of bamboo bleached kraft pulp (BKP) on the strength of the coloring paper used for pear paper bags. The characteristics of bamboo BKP were measured to compare them with those of softwood BKP and hardwood BKP. Handsheets from bamboo and hardwood BKPs were prepared at various mixing ratios, and their strengths were then analyzed. After that, a mill trial was performed to produce a prototype of coloring paper with bamboo BKP, and the effect of bamboo BKP on the strength of the coloring paper was finally determined. The initial freeness and fiber shape of bamboo BKP were similar to those of hardwood BKP, although the average fiber length and curl of bamboo BKP were higher than those of hardwood. As the mixing ratio of bamboo BKP increased, the strength of the handsheets increased, indicating the enhancing effect of bamboo BKP on the strength of coloring paper. As a result of the mill trial of coloring paper in the specialty paper mill, it was found that the tensile strength increased by 27.8% and burst strength by 20.0% when bamboo chemical pulp replaced 20% of the hardwood chemical pulp. Therefore, it was concluded that bamboo chemical pulp can replace and improve the strength of hardwood chemical pulp for manufacturing coloring paper.