Impacto da qualidade da madeira na deslignificação, no branqueamento e nas propriedades físico-mecânicas da polpa kraft de eucalipto

• Autor(a) principal: Silva, Deusanilde de Jesus
• Data de Publicação: 1996
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/3131
• topic: Eucalipto; Polpa kraft; Deslignificação; Eucalyptus; Kraft pulp; Delignification; CNPQ::CIENCIAS AGRARIAS::RECURSOS FLORESTAIS E ENGENHARIA FLORESTAL::TECNOLOGIA E UTILIZACAO DE PRODUTOS FLORESTAIS

Pulp production from the wood of two clones of a Eucalyptus urophylla x Eucalyptus grandis hybrid was studied at two delignilication levels with subsequent bleaching by either ECF or TCF sequences. Wood basic density, chemical composition, and fiber dimensions were detemiined previously to experiments. The wood most easily delignified during cooking (MI) consumed less chemicals and produced higher screen yields. Higher efficiency and selectivity of oxygen delignification were obtained for the wood showing harder delignification (MII). However, for higher kappa numbers, the selectivity tended to be the same for both MI and MII. TCF sequence greatly reduced pulp viscosity. Such intense reduction, not observed for ECF, was attributed to the bleaching sequence rather than to wood quality. Unrefined MII-derived pulp showed higher values for resistance properties, optical characteristics, and water retention (WRV). A trend towards lesser energy consumption during processing was Observed for MII-derived pulps alter retining. Also, the values for the optical characteristics of MII-derived pulps were higher than those of MI-derived ones, being little affected by the levels of delignification and the bleaching sequences. The physical and mechanical properties of the pulps showed less variation after refining than did the optical characteristics. MI-derived pulp opacity was more , sensitive to refining. Although wood basic density and chemical composition were similar, excluding the content of extractives in ethanol-toluene, MI and MII behavior during the processing steps greatly differed from each other, which demonstrates that wood density and chemical composition data are not sufficient for wood selection. The number of fibers per grain of pulp affected the opacity and the resistance of the pulps and, therefore, should be considered an important factor for tree selection. Considering MI wood, the lowest kappa number, and the ECF sequence, values for physical, mechanical and optical properties showed differences in the order of 47%, 19% and 34% for unrefined pulp. and of 35%, 18% and 47% for refined pulp that were attributed to wood quality, delignification level and bleaching sequence, respectively.