Canadian Oilseed flax in traditional pulping: 2. Bleaching characteristics

Flax fiber from Canadian oilseed flax straw proved to be a valuable additive to traditional hardwood kraft pulping. The advantages of the flax fiber addition are a lower Kappa number and improved strength properties after the kraft cook. The flax containing pulps show very favorable bleaching behaviors, resulting in significantly lower chlorine dioxide consumption. Bleached hardwood pulp samples produced with addition of up to 35 % flax fiber in the digester were beaten in a valley beater and strength properties compared to a bleached hardwood control and a bleached hardwood/softwood sample (ratio 50/50). The advantage in tear strength through addition of flax fiber carries through the bleaching process. Tensile and bust strength of the bleached samples are comparable to the hardwood control.