Properties of Bleachable Alkaline Sulfite Pulp from Old Corrugated Container

Alkaline sulfite pulping of old corrugated container to produce bleachable pulp was investigated. Pulping variables including active alkali of 14, 16, and 18% (based on oven-dry weight of OCC and Na2O); sodium sulfite to sodium hydroxide ratios of 50:50 and 30:70; pulping temperatures of 125,145,165 and 175ºC and pulping time of 60 and 120 minutes were examined. After preliminary pulping and evaluation of the strength of the pulps with the lowest kappa number, pulp with kappa number of 18.3 and brightness of 50.17% which was produced applying 18% active alkali, sodium sulfite to sodium hydroxide ratio of 30:70 and pulping time and temperature of 120 minutes and 175ºC respectively with 64% yield (based on oven dry weight of washed OCC) and 72.7% yield (based on original weight of the OCC) was selected for totally chlorine free bleaching trials. Brightness, opacity, tensile and tear strength indices of this pulp were measured as 50.17%, 81.36%, 27.7 N.m/g and 12.35mN.m2/g, respectively. Bleaching this pulp applying 3% H2O2 and 2.25% NaOH generated bleached pulp with brightness and opacity as 57.14% and 78.24%, respectively. The bleaching yield was measured as 92%. Tensile and tear strength indices of this pulp were measured as 27 N.m/g and 12.45 mN.m2, respectively.