In cooperation with the Rockhammar mill of Sweden, Eka Chemicals developed a new method for bleaching chemithermomechanical pulp (CTMP), using hydrogen peroxide in 1975.
The mechanical pulping process is not the ideal one for wood fiber. The lignin in the pulp, which is not removed, results in an increased need for bleaching. Therefore, for mechanical pulp, hydrogen peroxide is the only brightening solution that will provide high brightness gains (>15 brightness points) while preserving yield.
Because of its environmentally friendly properties – decomposed products being oxygen and water – hydrogen peroxide is well suited to the bleaching of mechanical pulps.
Hydrogen peroxide, however, needs to be stabilized when bleaching CTMP. The role of a stabilizer is to reduce the detrimental effects of transition metal ions, such as iron and manganese, which find their way into the mechanical pulping process from wood and water inputs. Transition metals lead to excessive use of peroxide and undermine bleaching efficiency.