Influência das xilanas na produção e nas propriedades de polpas de eucalipto para papéis

• Ano de defesa: 2009
• Autor(a) principal: Pedrazzi, Cristiane
• Orientador(a): Colodette, Jorge Luiz
• Banca de defesa: Costa, Marcelo Moreira da , Eiras, Kátia Maria Morais
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Viçosa
• Programa de Pós-Graduação: Doutorado em Ciência Florestal
• Departamento: Manejo Florestal; Meio Ambiente e Conservação da Natureza; Silvicultura; Tecnologia e Utilização de
• País: BR
• Palavras-chave em Português: Eucalipto; Polpa Kraft; Xilanas; Propriedades; Rendimento
• Palavras-chave em Inglês: Eucalyptus; Kraft pulp; Xylans; Properties; Yields
• Área do conhecimento CNPq: CNPQ::CIENCIAS AGRARIAS::RECURSOS FLORESTAIS E ENGENHARIA FLORESTAL::TECNOLOGIA E UTILIZACAO DE PRODUTOS FLORESTAIS
• Link de acesso: http://locus.ufv.br/handle/123456789/533

The xylans plays important role in cooking and bleaching processes of cellulosics pulps and in paper properties. To change the xylans contents permit to lose or to gain yields of production and differentiate the properties of pulps and paper produced. The objective of this study was to produce brown and bleached kraft pulps from Eucalyptus grandis and Eucalyptus grandis x Eucalyptus urophylla ("Eucalyptus urograndis") of distinct morphologic characteristics differentiated and chemical composition, mainly in refers to its xylans contents, for the manufacture of tissue and printing and writing (P&W) paper grades. Brown pulps of kappa number 17-18 and xylans contents varying of 6-21% and yields in the range of 40-62% had been produced under different cooking protocols: 1) conventional kraft; 2) pre-hydrolysis kraft; 3) high alkalinity kraft; and 4) kraf of high yield, which had been bleached up to 90% ISO of brightness by bleaching sequences: AD-(EO)-D, O-A/D-(PO)-D and CCE-O-A/D-(PO)-D, resulting in samples with xylans contents 4.2-20.3%. The highest pulp yields and hexenuronic acids were achieved with the Eucalyptus grandis wood under protocol (4), with the inverse being observed for protocol (2). No correlation between pulping yield and pulp viscosity was observed, with the highest pulp viscosity reached under cooking protocol (2). The xylans content of pulps influenced its bleachability negative, increasing the consumption of chemical reagents. On the other hand, the operation of bleaching caused reduction of the xylans content of pulps. The brown and bleached pulps of Eucalyptus urograndis wood and the protocol (4) had resulted in fibers with high coarseness and of the protocol (3) presented greater number of fibers per gram and fines content with regard to other pulps. The xylans content influenced in the amount of water retention value (WRV) of fibers, being that the brown and bleached pulps with high xylans contents had resulted in the biggest values of WRV and the lesser values of hornification. The refinability and resistance properties of brown and bleached pulps had been better for pulps contend higher xylans contents. The pulps of cookings protocols (2) and (3), with low xylans contents, had revealed interesting in the manufacture of tissue papers, for presenting high bulk.The bleached pulps of protocols (1) and (4), with high xylans contents, had been presented technically viable and with resistance characteristics adjusted for the manufacture of P&W papers.