Celulose kraft produzida a partir das madeiras de bracatinga (Mimosa scabrella) e eucalipto (Eucalyptus saligna) misturadas em diferentes proporções

• Ano de defesa: 2004
• Autor(a) principal: Araujo, Rafael Hardt
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Santa Maria; Brasil; Recursos Florestais e Engenharia Florestal; UFSM; Programa de Pós-Graduação em Engenharia Florestal; Centro de Ciências Rurais
• Palavras-chave em Português: Engenharia florestal; Celulose Kraft; Bracatinga; Eucalipto; Deslignificação; Branqueamento; CNPQ::CIENCIAS AGRARIAS::RECURSOS FLORESTAIS E ENGENHARIA FLORESTAL
• Link de acesso: http://repositorio.ufsm.br/handle/1/26832

This study had as main objective to evaluate the use of bracatinga (Mimosa scabrella Benth) wood as fibrous source for papermaking. Kraft pulping of bracatinga and eucalyptus (Eucalyptus saligna Smith) wood chip blends were analyzed. Other objectives were: to evaluate characteristics of the trees; wood chemical composition (dichlormethane extractives, alcohol toluene extractives, lignin content and ash content) and anatomical dimensions and population of fibers and vessel elements in the pulps. Twenty kraft cooking were performed, comprising the comparison of 5 treatments with 4 replication for treatment (different wood chip blends based on oven dried wood weight: 100% bracatinga, 5% bracatinga, 10% bracatinga, 20%bracatinga e 100% eucalyptus). Kraft cooking conditions were similar to all treatments, except for 100% bracatinga wood chips, which required 23% active alkali instead of 20% corresponding to the other treatments (active alkali expressed as NaOH). Sulfidity was kept constant as 20%. Other kraft pulping conditions: liquor to wood ratio = 4/1; maximum temperature = 170ºC; time to 170ºC = 90 minutes; time at 170ºC = 60 minutes. Unbleached pulps were analyzed for pulp yield, kappa number, 5% caustic soda solubility, intrinsic viscosity and brightness. Target kappa number was 16 ± 1. After cooking, the unbleached pulps were deslignified by oxygen in alkaline condition followed by an ECF bleaching sequence (D1 Eo D2 SO2 ). Bleached pulps were beaten in a PFI mill and the strength and optical properties compared at unbeaten and 30º SR levels. Lignin content and extractives were similar in both woods( eucalyptus and bracatinga). However, eucalyptus wood had higher ash content and lower wood basic density. Bracatinga and eucalyptus fibers were similar in term of fiber length, but bracatinga fibers were wider and thicker-walled. Bracatinga wood chips led to better pulp yields. Oxygen delignifications provided good results in all treatments. Pulp bleaching started to show losses in brightness when bracatinga wood content in the blend was 20% and over. The same trend for reverted brightness. Higher the bracatinga wood content over 10%, worse the strength properties (tensile, tear, burst and stretch) and pulp opacity. However, the use of bracatinga wood up to 10% based on dry weight did not harm the pulp quality. High bracatinga fiber content in pulp gives pulps more suitable to tissue papers manufacturing and less recommended to printing and writing papers índice.