Effect of bleaching sequence on paper ageing

High-yield bagasse pulp was prepared by mechanical treatment after soaking in cold 10% sodium hydroxide. One-, two- and three-stage bleaching of the pulp were investigated by using hydrogen peroxide (P) and/or sodium dithionite (D), in different sequences. Paper sheets were prepared and tested for the strength properties and brightness value. The effect of ageing on paper properties and brightness was investigated. It was found that three-stage bleaching by using two steps with hydrogen peroxide and one step with sodium dithionite provides the optimum bleaching results with regard to the strength properties and the brightness values. Comparable results were also obtained after paper ageing. The best bleaching sequence is PPD followed by DPP and then PDP. (C) 2004 Elsevier Ltd. All rights reserved.