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PEER-REVIEWED ARTICLE
Preparation of handsheets To test the effect of sizing treatment on ink absorption, handsheets of 70 g/m 2 were prepared by putting the required softwood pulp (1%), AKD (0.1%) and water into the disintegrator and using the Rapid Kothen Sheet Former machine (RK-3A, Austria). The paper was vacuum-heated and dried at 95 q C for 10 min. Without special explanation, sizing agent was not present in other samples. Before testing, all the samples were treated at 23 °C and 65% relative humidity for 24 h. Determination of ink absorption The ink droplets between the printing plate and the paper strip in the sector of the IGT printing applicator (GST-1, IGT Testing Systems, Almere, Netherlands) were 5.8 mg ± 0.3 mg and spread out. The ink mark length was measured as an indicator of absorption capacity; the ink mark length increases as the absorbability of the paper decreases. Determination of overprint accuracy The handsheets were affixed on A4 paper, and adjacent color patches were printed twice on the handsheets using a Bizhub PRESS C6000 electrostatic printer (Konica Minolta, Tokyo, Japan). The whitening, or overprinting, distance between the colors patches was measured, which was the overprint accuracy. Beating is an important step in papermaking. Beating resulted in swelling, fibrillation, removal of primary layer and outer secondary layer. Correspondingly, the adsorption ability to ink was facilitated. On the other hand, beating could promote the binding of cellulose and further hinder the osmosis of ink. Table 1 shows the size distributions of pulp fibers, as measured by the fiber quality analyzer (FQA). The fiber length decreased from 1.221 mm to 1.116 mm when the beating degree was increased from 15 °SR to 40 °SR. Moreover, the width correspondingly decreased from 28.2 μ m to 26.9 μ m. During the beating process, the raw fibers were separated into several fibrillated fibers, which increased the surface area of the fibers and the number of hydroxyl groups. The hydrogen bonding among hydroxyl groups enhanced the bonding forces among the fibers. Table 1. Effect of Beating Degree on Fiber Morphology RESULTS AND DISCUSSION Effect of Beating on the Ink Absorption
Fiber Mean Length (mm)
Fines Content (%)
Beating Revoluti ons (r)
Beating Degree (°SR)
Width (μm)
Length- weighted Length
Weight- weighted Length
Arithmetic Length
Arithmetic Length
Length- weighted
5000 10000 12500 15000
15 26 33 40
1.221 1.165 1.313 1.116
2.085 1.894 1.875 1.846
2.665 2.624 2.609 2.589
28.2 27.6 27.3 26.9
41.3 43.2 43.8 44.5
10.4
9.7 9.4 9.1
1399
Dong et al . (2020 ). “Ink absorption and overprint,” B io R esources 15(1), 1397-1406.
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