BLEACH ACTIVATION OF THERMOMECHANICAL PULP

Under mild alkaline condition the bleaching activator tetraacetyl ethy lenediamine (TAED) forms peroxyacetic acid with sodium perborate and i mproves the brightness of thermomechanical pulp. The activator makes i t possible to bleach the pulp efficiently even without addition of sod ium hydroxide at any temperature in the range 40 to 70 degrees C. A ma thematical model has been proposed to allow estimation of the total pe roxy acid consumption during activated bleaching process. Using this m odel it is possible to calculate the extent of peroxy acid decompositi on by predetermining the rate constant and activation energy. The effe ct of bleach activation was found to be maximum at temperatures below 60 degrees C. The influences of bleaching time, pH, consistency, tempe rature and TAED charge on the bleach activation has been evaluated. Th e activator is effective enough to improve the brightness of sodium pe rborate bleached pulp at an average charge of about 50 mass% of sodium perborate. Apparently, high consistency dispersive bleaching without free alkali is a technological and economic advantage of the process.