No abstract

Optical property improvements for ONP (old newspaper) and OMG (old magazine) were attempted by application of in-situ CaCO 3 formation process on recycled fiber surfaces. Washing treatment of ONP and OMG resulted in 35~40% yield loss for around 6% brightness improvement. Washing plus bleaching process with H 2 O 2 and FAS (formamidine sulfinic acid) improved brightness and ERIC values a little more with the same amount of yield loss as washing treatment. In-situ CaCO 3 formation method improved those optical properties much better than the washing plus bleaching method without loss of yield, and better than the case of adding high brightness PCC up to the same ash level. It can be said that the in-situ CaCO 3 formation method may be used as an effective alternative for upgrading optical properties of recycled fibers.

Three alkaline mixtures (NaOH/thiourea, NaOH/urea/thiourea, NaOH/urea/ZnO) and sulfuric acid were used at low temperatures as cellulose solvents, and their cellulose solubility and films’ physical properties for bleached chemical wood pulps and cotton linter were compared. Their degree of polymerization (DP) was controlled to 600–800 before dissolution. Among the alkaline solvents, NaOH/urea/ZnO gave the film the highest tensile strength and stretch. When compared to sulfuric acid, NaOH/urea/ZnO gave lower strength properties but higher crystallinity indices in the films. While alkaline solvents could not dissolve the high DP cellulose (DP ~ 2000), sulfuric acid could dissolve the high DP cellulose at below zero Celsius temperature, and the strength properties of the films were not much different from that of the low DP one. It appeared that the low-temperature sulfuric acid treatment did away with the cellulose’s DP controlling stage; it decreased cellulose DP very quickly for the high-DP cellulose at the initial stage, and as soon as the cellulose DP reached a DP low enough for dissolution, it began to dissolve the cellulose to result in stable cellulose solution.

For the manufacture of linerboard with 100% KOCC, we tried to increase the solid content of wet web by employing GCC (grounded calcium carbonate) in the fiber furnish to save drying energy. Three different diameters of GCC, namely, 5, 10, and 35 ㎛, were used. To complement the strength loss by the addition of GCC, cationic starch and refining treatment were tried. It was found that the addition of 10-35 ㎛ dia. GCC to KOCC for 180 g/m 2 basis weight sheets increased the solid content of the furnish about 1-1.5% with better bulk and drainage properties. The loss of strength properties were compensated by the application of cationic starch and/or refining process to the KOCC furnish. The dia. of GCC of 35 ㎛ was, however, too large to make smooth surface of the sample sheet. So, the optimization process was required before implementing the results to the mill by selecting proper diameter and shape of the calcium carbonate.

Printing papers published in between 1950's and 1990's were treated with three methods such as distilled water washing, CaCO 3 solution washing and methyl cellulose solution coating for improving their conservational properties. Accelerated aging with 80 o C and 80% RH for 14 days was applied to the testing papers. Results showed that distilled water and CaCO 3 washing kept increased pH even after accelerated aging, but did not improve folding endurances for 1950's-60's papers. Methyl cellulose treatment did not increased pH of the old papers, but increased folding endurances remarkably for 1950's-60's papers even after accelerated aging. It suggests that methyl cellulose treatment after CaCO 3 washing should give improvements both in pH and folding endurance.