Estudo de tratamentos alternativos no processo de branqueamento de pastas kraft de eucalipto - caracterização da superfície das folhas por técnicas não convencionais

FERREIRA, P.J.; CARVALHO, M.G..; BARBEIROS, N.,; FELISSIA, F.E.; AREA, M.C

Tomar, Portugal

Congreso; XX Encontro Nacional da Tecnicelpa; 2007

TECNICELPA

This work aims at characterizing the surface of handsheets produced with kraft pulps of Eucalyptus grandis obtained from several treatments in the OQOpP bleaching sequence. The effect of chelation on pulps previously submitted to washing with a Na+ or Ca2+ counter-ion exchange was evaluated. The resulting pulps were delignifi ed with oxygen in two stages, with or without a chelation step between them and with the addition of hydrogen peroxide in the second stage. The infl uence of a chelating agent in the Op stage and in the subsequent hydrogen peroxide stage was also analysed. All pulps were characterized in terms of the most common papermaking properties and also with regard to some unconventional parameters like skeletal and true density, porosity, fi bre specifi c surface, contact angle (with water) and cristallinity index. The latter has continuously increased along the consecutive treatments while the true density, porosity and fi bre specifi c surface did not varied very signifi cantly from the fi rst oxygen stage to the peroxide stage. However, true density and fi bre specifi c surface were higher after the washing process with Na+ or Ca2+ and porosity was mainly affected by the oxygen stage to higher values. For each experimental step, Ca2+ based pulps always exhibited higher value of porosity than Na+ based. Besides, this property had systematically lower values after O or P stages with chelant addition, and decreased when the total amount of chelant was distributed along the two oxygen steps instead of being applied in an isolated reactor. Water absorption, was higher for the Ca2+ based pulps than for the Na+ based pulps.