Investigation on Optical and Mechanical Properties of Bagasse Soda Pulp Bleached With Total Chlorine Free (TCF)

About 60,000 tons of printing papers are annually produced in Ahvaz's Haft-Tapeh Pars factory. In this factory, bagasse soda pulp was already bleached with the CEH sequence and is currently bleached with the EH sequence ((alkaline extraction (E) and hypochlorite (H))‎. ‎ The chlorination stage (C) due to dryness of about 3% and the production of‏ large amounts of effluents and absorbable organic X-halid (AOX) of ‎lignin is significantly important in terms of the environmentally.‎ Therefore, in the Pars factory and in universal conventional systems, the chlorinated (C) ‎stage and some of the bleaching sequences are ‎eliminated by chlorine ‎compounds such as hypochlorite (H) and chlorine dioxide (D). On the other hand, oxygen (O), ozone (Z), hydrogen peroxide (P), disodium ‎hydrosulfite (Y) or ‎a combination of them as a system of total chlorine-free (TCF) are used rather than hypochlorite and chlorine dioxide.‎ Therefore, this study was conducted to evaluate the effect of bleaching on optical ‎and ‎mechanical properties of paper from bagasse soda pulp using TCF method.‎

In this research, the amount of the unbleached pulp of bagasse ‎soda (before the bleaching) was randomly selected from the Ahvaz’s Pars factory. In addition, the selected pulp with 1, 2 and 3 step sequences of P, OP, OPY and O(Ep)P were bleached using the oxygen (O), hydrogen peroxide (P), and also alkaline ‎extraction by hydrogen peroxide (PE) and di-sodium hydrosulfite (Y). ‎ Hand-sheets were provided using the pulp made with a basic weight of 70 gr/m2. After that, ‎optical and mechanical properties of the samples were measured according to TAPPI standard test‎ and then the paper properties were compared.

The results showed that some properties such as the brightness, greenness, tear strength, tensile, ‎burst, tear length, and folding ‎strength were increased due to bleaching‎ by total chlorine free (TCF) method. On the other hand, ‎the opacity and factor a* of papers resulting from ‎bagasse soda pulp were ‎decreased.‎ In the current study, hydrogen peroxide as an oxidative bleach had an effective role in improving the greenness, tear strength, tensile, tear length and folding strength. However, no significant effect was observed on improving the made paper’s brightness ‎compared to the control sample (sequences EH Factory). Furthermore, statistical analysis results showed that there are significant differences at 1% level between the averages of the optical and mechanical properties of the modified pulps, as well.

In general, the role of the three-stage bleaching sequences of OPY and also the two-stage bleaching sequences of OP were more effective in bleaching of pulp paper ‎and improve the brightness and strength of the made papers compared to the two-stage ‎sequences of EH (control) and unbleached pulp paper of the factory of bagasse soda.‎ Key words: Bagasse Soda pulp, Bleaching stage, TCF bleaching, Optical and Mechanical properties.