Parallel to the bleaching effect th

Parallel to the bleaching effect there is also an attack on the carbohydrates which can be seen
by the simultaneous decrease in pulp viscosity, Figure 10.4. However, for the carbohydrates the
initial part of the bleaching reaction is very selective with a limited attack on the cellulose but
with increasing bleaching the attack on the carbohydrates increases. It can therefore be concluded
that in the initial part of the bleaching stage the bleaching chemicals charged to the stage are
especially consumed in lignin degradation reactions and the selectivity i.e. the lignin degrada
part of the reaction rate vs. the carbohydrate degradation rate, is therefore high. The selectivity decreases with
increasing bleaching which means that it is recommended of pulp quality reasons to avoid too
intense bleaching stages.