THE IMPACT OF XYLANASE ON BLEACHING OF KRAFT PULPS

The application of xylanase as one bleaching stage yields better bleachability for both hardwood and softwood kraft pulps. Combinations of oxygen (O), xylanase treatment (X), hydrogen peroxide (P), enhanced alkaline extraction (Ep) and chlorine dioxide (D) have been tested in a variety of sequences. Hardwood kraft pulp bleached in the OXDP sequence reaches a brightness of 87.7% (ISO) with a viscosity of 17.5 mPa.s. If the xylanase treatment is not applied, a brightness of only 85.7% and a viscosity of 15.8 mPa.s. is obtained Softwood kraft pulp bleached in the OXPDP sequence attains a brightness of 88.6% with a viscosity of 16.3 mPa.s. Without the enzyme stage, a brightness of only 84.5% and a viscosity of 14.9 mPa.s. is obtained. The physical properties of our laboratory bleached pulps compare very favorably with those of commercially produced pulps.