The influence of pulping and washing conditions on the properties of Eucalyptus grandis unbleached kraft pulps treated with chelants

摘要

The influence of different addition points of a chelating agent and a counter-ion exchange on the properties of Eucalyptus grandis unbleached kraft pulps is studied. Seven pulps were considered: two laboratory kraft pulps with or without the inclusion of the chelant DTPMPA (diethylene triamine penta (methylene phosphonic acid)), a mill kraft pulp and four mill pulps after Ca+2 or Na+ counter-ion exchange followed, or not, by washing with DTPMPA addition. The laboratory pulps required lower beating energy than the industrial pulps for achieving 30SR, and the corresponding handsheets also showed better strength and optical properties, as well as a more homogeneous and smooth surface. The counterion exchange decreases the mechanical resistances and increases brightness. However, the effects of Ca+2 are deeper than those of Na+. DTPMPA added to pulping causes a decrease in calcium content whereas as a washing additive does not have a relevant impact on the mechanical and optical properties.