Optimum Conditions in Mechanical Pulp Bleaching with Regard to Optical Properties

摘要

When bleaching mechanical pulps to high brightness levels both, opacity and light scattering coefficient drop considerably, which is not wanted in the production of high quality printing papers. A bleaching study carried out with a TMP pulp showed that it is possible to maintain the optical properties at a high level if bleaching conditions are adjusted accordingly. The use of less NaOH led to better opacity and light scattering coefficient at slightly increased bleaching costs. Post-bleaching with dithionite also helped to keep the optical properties at a higher level compared to the results obtained with only peroxide bleached pulps.