PAPERmaking! g FROM THE PUBLISHERS OF PAPER TECHNOLOGY Volume 2, Number 1, 2016
Fig. 5. Bulk (left) and breaking length (right) of handsheets made from recycled and virgin pulp (W/L = white ledger)
Fig. 6. Burst strength (left) and compressive strength (right) of handsheets made from recycled and virgin pulp (W/L = white ledger) Evaluation of First-Pass Retention and the Physical Properties of Handsheets Made from White Ledger Figure 7 shows the first-pass retention of white ledger stock using different dosages and types of C-PAMs. C-PAMs have different molecular weights and charge densities; therefore, the first-pass retention values were products of the varying dosages and types of C-PAMs. The majority of the C-PAMs led to increases in the first-pass retention of the white ledger stock. C-PAM C showed the highest first-pass retention, while B and F displayed the second highest first-pass retention values among the C-PAMs. A, D, and E did not produce noticeable increases in first-pass retention compared with the other C- PAMs. C-PAMs C and F had molecular weights that were similar to the molecular weight of C-PAM A, but their charge densities were higher than that of C-PAM A. Moreover, C- PAM B had the highest charge density among the C-PAMs. Because white ledger contains many fillers and pigments, a C-PAM must have a high charge density to gather anionic fillers and pigments (Gess 1998; Im et al. 2015). Charge density is an important property of C-PAMs for the improvement of the first-pass retention of white ledger. As mentioned previously, the retention aid should improve the paper strength. In the current study, the strength of white ledger was lower than the strength of BKP. In this study, three C-PAMs (B, C, and F) that had the highest first-pass retention were selected for further study. Handsheets from white ledger stock with C-PAMs B, C, and F were evaluated for the ability of these C-PAMs to improve paper strength. Paper strength is affected by ash content (Xu et al. 2005; Jung et al. 2015). Therefore, the effect of C-PAMs on paper strength was analysed as a function of ash content. Figures 8 through 10 show the breaking length, burst strength, and compressive strength of the handsheets. B and F were similar in strength because of their ash content. C had the lowest paper strength,
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Article 1 – Improving Retention and Strength
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