• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.33 no.3
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• pp.37-43
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• 2001

The bleach efficiency between PY and YP bleaching of pulps, which were deinked in neutral (cellulase) and alkaline (NaOH, NaOH/${Na_2}{SiO_3}$) ranges, and were treated on kneader, was compared in this study. The brightness of pulps (84.8~88.4% ISO) which were deinked in alkaline or neutral ranges increased up to 88.4%~88.8% ISO after PY or YP bleaching. There was no difference in the brightness between PY and YP bleaching. And the dirt count of bleached pulps was similar each other at the range of 17~38 ppm. The tensile index of bleached pulps was slightly higher in PY bleaching than those in YP bleaching. While with the treatment of kneading, the brightness and dirt count decreased remarkably compared to those of no-kneading. However, the sharp difference in the brightnesses or in dirt count of bleached pulps decreased after bleaching. The brightness of bleached pulps at YP stages was only numberically higher than those at PY stages without regard to the treatment of kneading. Therefore, in the case of the neutral deinkiing process, the conversion of PY bleaching stages to YP bleaching stages was profitable to water loop system, and was harmless in the aspect of the bleach efficiency.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.34 no.3
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• pp.46-52
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• 2002

To produce the raw material used for printing and writing paper or high quality tissue, MOWs that were consisted of white ledger, colored ledger and old newspaper were bleached with EoP and EoPY(FAS) method, the EoP bleaching process gave the improvement in brightness and a high color removal efficiency. Especially, MOW B(initial brightness: 59.1％ ISO) that contained much old newspaper showed the higher bleaching efficiency than those of MOW A(initial brightness: 68.3%). After EoPY(FAS) bleaching, MOW's brightness was increased from 68.3% ISO to 84.3∼84.0% ISO, and from 59.1% ISO to 78.7∼79.2% ISO, respectively. Also the tensile and burst index of bleached pulps decreased by 10∼30%. The tear index slightly decreased or halted at the same range as unbleached pulps.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.33 no.2
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• pp.8-16
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• 2001

To manufacture toilet tissue with ONP (old newspaper), the effect of fractionation fiber (R150, R100, R70 mesh) and bleaching(P, PY), blending (70/30) with MOW(mixed office wastepaper) or WL(white ledger) and the addition of softener on the optical and mechanical properties were studied. Considering the pulp yield, brightness and strengths, fibers of R100 mesh fraction were proper to be produced to toilet paper from ONP. This pulp showed the pulp yield of 76.8%, brightness of 50.2% ISO and tensile index of 21.1 Nm/g. By the bleach with P and PY stages, the brightness of the pulps increased up to 60.3% ISO and 61.8% ISO, respectively. When blended with MOW (57.3% ISO) or WL (76.2% ISO), the brightness of the former increased up to 58.5% ISO, the latter up to 63.6% ISO. The strengths of pulp blended with WL were higher than those of fractionated pulp from 100% ONP, however there was no difference in strengths between fractionated pulp and blended pulp wth MOW. While the addition of softener improved the softness of paper, but it decreased strengths of pulp and extended dispersing time in water.