Manufacture of high bulk paper using alkali swollen kraft pulp

Abstract Effects of alkali swelling of kraft pulp fibers and the order of alkali swelling and beating treatments on paper bulk and paper strength were evaluated in terms of NaOH concentration in order to produce high bulk sheet (i. e., high porous and low density sheet). Effects of replacement of part of furnish with the alkali swollen pulp on paper properties were also investigated. It was found that alkali swelling of pulp fiber can increase the bulk of handsheet. NaOH concentration and beating treatment influenced paper bulk and paper strength. Alkali swollen pulp without beating showed the highest handsheet bulk. The paper bulk of alkali swollen pulp with pre-beating was higher than that with post-beating. Paper strength decreased with increasing the bulk of handsheet. In addition, replacement of part of furnish with alkali swollen pulps increased paper bulk, adversely decreasing paper strength. The highest improvement in paper bulk was achieved with the addition of alkali swollen SwBKP without beating.