The effect of polysulphide pre-treatment and cooking parameters on the chemical properties and TCF bleachability of alkaline pulps

The effect of pre-treating softwood chips with polysulphide on the chemical properties of the resulting pulp has been investigated. During subsequent pulping after such pre-treatment, high alkali content is maintained in the cooking liquor and, consequently, an unbleached pulp with a decreased amoun t of hexenuronic acid is obtained. As compared to other kraft pulps in this study, a polysulphide pre-treatment gives high cooking field, a high visco sity and brightness for the unbleached pulp and a pulp of good bleachabilit y.