REFINER PRODUCTION OF SODIUM PERBORATE AND HYDROGEN PEROXIDE BLEACHED MECHANICAL PULP: CHARACTERIZATION AND PHYSICOMECHANICAL PROPERTIES

Paper can be manufactured without bleaching, but high quality white paper grades, which require bleaching, are in demand as well. In paper mills, oxidizing or reducing chemicals are utilized to bleach the pulp. In this study, the utilization of sodium perborate, instead of the generally used sodium dithionite, to brighten mechanically produced wood pulp was investigated. Sodium perborate was chosen, as it is an environmentally friendly chemical and is produced in Turkey - from tincal, one of the boron ores in Turkey. The experiments were performed at Milda Aksu Paper Mill, using fresh pulp. The amount of bleaching chemicals was adjusted so that the dry mechanical pulp contained 0.5-2% more active oxygen. These chemicals were used either alone or in combination to see their bleaching effects. It was seen that the use of 2% sodium perborate together with 1.5% hydrogen peroxide gave better ISO brightness values (68%) than that of the dithionite bleached (64%) pulps. Under these conditions, fringing and fiber to fiber bonding was more pronounced than in the case of the paper from dithionite bleached pulp, which shows the advantage of using perborate in the bleaching process. Besides, the physico-mechanical properties of the produced paper sheets increased noticeably.