Date of Award


Degree Name

Bachelor of Science


Pulp and Paper Technology


The main objective of this research project was the investigation of the most feasible method for the bleaching of a soft-cooked unbleached neutral sulphite semichemical aspen pulp cooked to a 70 percent yield. Furthermore, treatment of unbleached, laboratory bleached and commercially bleached neutral sulphite semichemical pulp with a new chemical, sodium borohydride, was also carried out.

The results of our experimental work showed that, the best bleaching procedure was when 15 percent chlorine as hypochlorite was used in the first stage, followed by a hydrochloric acid soaking stage with a final treatment of 2.6 percent hydrogen peroxide. With the above procedure brightness values over 80 percent were obtained with the yields in the 90 percent range based on the weight of the pulp. Sodium borohydride treatment of the three pulps showed that, with regards to ultra-violet light and heat stability the chemical, sodium borohydride, had no effect on the unbleached and the bleached lignin-containing pulps. Treatment of the commercially bleached, lignin-free, pulp however showed that the chemical had a marked effect in improving the heat and light stability of the pulp. It was noted that with all three types of pulp the chemical sodium borohydride did procedure a bleaching effect.