Aperfeiçoamento de processos de produção de polpas de eucalipto para dissolução e papel tissue

• Ano de defesa: 2011
• Autor(a) principal: Gomes, Valéria Juste
• Orientador(a): Colodette, Jorge Luiz
• Banca de defesa: Magaton, Andréia da Silva , Maltha, Célia Regina álvares
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Viçosa
• Programa de Pós-Graduação: Mestrado em Agroquímica
• Departamento: Agroquímica analítica; Agroquímica inorgânica e Físico-química; Agroquímica orgânica
• País: BR
• Palavras-chave em Português: Polpa; Dissolução; Papel tissue; Eucalipto
• Palavras-chave em Inglês: Pulp; Dissolving; Tissue paper; Eucalyptus
• Área do conhecimento CNPq: CNPQ::CIENCIAS EXATAS E DA TERRA::QUIMICA::QUIMICA ORGANICA
• Link de acesso: http://locus.ufv.br/handle/123456789/2123

Besides the extensive use of the pulp of eucalyptus in the manufacture of hygienic paper (tissue) and the use for printing and writing, they are also used to obtain dissolving pulps. One of the components of wood that has aroused great interest from researchers and cellulose manufacturers is the hemicellulose. However, the desirable amount of hemicellulose which must be present in the pulp used to manufacture tissue paper is still a mystery because they have the advantage of, for instance, of increasing the tensile property and the disadvantage of reducing the drainability of the pulp in the paper machine. In the manufacture of dissolving pulps, the presence of hemicelluloses is totally undesirable, since this type of pulp requires very high levels of pure cellulose (alpha-cellulose). The objectives of this study were: (1) to establish the optimum conditions of alkali charge and temperature using a treatment of cold caustic extraction (CCE), in order to remove as much hemicellulose as possible from eucalyptus dissolving pulp, produced by process pre-hydrolysis kraf, (2) to develop techniques to obtain pulps with varying content of xylans from an unbleached kraft pulp from eucalyptus, aiming to understand the influence of the xylans in the properties of tissue papers. The obtained results in meeting the goals (1) and (2) are presented in chapters 1 and 2 of this thesis, respectively. In relation to objective (1), it was observed by the analysis of the content of xylans and the S10 and S18 solubilities of the pulp that the higher efficiency for removal of hemicellulose from the pre-hydrolysis kraft pulp with pure NaOH or white kraft liquor occurs at a temperature of 20°C in the range of 20-40oC, and concentrations of pure NaOH of 91 g/L (pure NaOH) and 105 g/L (white kraft liquor) in the range 74 to 91 g/L and 75 to 105 g/L, respectively. Concerning the objective (2), in which were investigated techniques of acid hydrolysis, solvent dissolution, alkaline hydrolysis and enzymatic hydrolysis of unbleached kraft pulp in order to obtain pulps with different amounts of xylan, the technique of alkaline hydrolysis was more effective than the others. The increase in the concentration of alkali in the alkaline hydrolysis has a positive effect in the redution of the kappa, without significant losses in the yield of the treatment. The pulps treated with different dosages of NaOH (10, 30, 50 and 70 g/L) showed levels of xylans ranging from 5.9 to 15.6%. As a result of the alkali treatment, the resulting pulp showed a high bleachability, whereas the use of chlorine dioxide decreased from 3.24% (reference pulp) to 1.36% (alkali-treated pulp to a concentration of 5.9% of xylans). The alkali treatment of pulp with 70 g/L of NaOH reduced its content of hexenuronic acids from 61.8 to 22.8 mmol/kg pulp. The bleached pulps containing 5.9% of xylans showed higher values of opacity, bulk, thickness, Klemm capillarity, water absorption capacity, and lower values of tensile index, tear index, specific elasticity modulus and tensile energy absorption in relation to the reference pulp. The refining of the pulps indicated higher energy consumption for the pulps with lower levels of xylans.