Effect of Pulp Quality on Printability (II)

Abstract

Production of coated paper has been increased since it was invented. Bitoko grade is one of the staple commodities of coated paper and the characteristic is the paper containing mechanical pulp. Because bitoko grade paper is mostly printed by rotary offset press with heat-set ink, it is necessary to withstand printing problems like heat-set roughening, blistering and so on. Heat-set roughening is roughening at solid area of printed matter due to rising of fibers. Paper absorbs fountain solution during printing and the fibers are released from out-of-plane stress. Then the shape of the fibers changes from collapsed state to tubular at drying process of the press, and the fibers rise. Mainly, the long fibers of mechanical pulp, especially which cell wall is thick, cause this problem. The effect of pulp is greater than coating conditions such as pre-calendering, coating weight and so forth. Therefore it is quite important to control pulp quality for the better printability.