Application of enzyme to the kraft pulp bleaching was investigated to reduce the amount of AOX generated during bleaching.
The pulp which had been pretreated with xylanase was bleached using several sequences and the qualities of the resultant pulps were compared with one another.
As a result, it was found that the pretreatment with xylanase enabled to reduce the amount of chlorine or chlorine dioxide at the first stage by 20 to 25% without any adverse influence on the pulp quality.
The reason why the brightness was improved owing to the treatment with xylanase is considered to result not only the reduction of the kappa number of (D/C) E pulp, but also the improvement in the bleachability in a subsequent stage.
Reference is also made to a non-chlorine bleaching trial on the mill scale using the xylanase.