Pulp bleaching
Initially, wood pulp has a brown or brownish colour. To obtain the brightness required for white papers, it has to be bleached. During this process of bleaching, the remaining lignin is removed as well. In practical terms, bleaching is a continuation of the chemical cooking process, taking place directly after- ward in the pulp mill as an integrated next step of the overall procedure. Bleaching is a complex process, consisting of several chemical process steps, with washing taking place between the various chemical treatments.
The wood pulp can be bleached with chlorine / chlorine compounds, ozone / oxygen in different forms as well as hydrogen peroxide.
Based on the negative impact of some chlorine containing decomposition products, there are, however, environmental objections against the use of chlorine and chlorine products.
For this reason, Sappi has long ago switched to chlorine- free processes.
These processes are referred to as Totally Chlorine Free
(TCF).