Departamento de Ciências e Tecnologias do Papel
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[Departamento extinto em 27 de outubro de 2009]
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- Avaliação da qualidade do papel produzido com fibras de Acacia sppPublication . Santos, António; Anjos, Ofélia; Simões, RogérioCom o presente trabalho pretende-se aprofundar o conhecimento sobre o potencial papeleiro da madeira de Acacia melanoxylon e Acacia dealbata. Para efeitos de posicionamento relativo das matérias primas, utilizaram-se aparas industriais de Eucalyptus globulus. A transformação da madeira em pasta foi realizada através do processo ao sulfato. O comportamento global das três espécies nos processos de cozimento e branqueamento é semelhante. No entanto, face à amostra de Eucalyptus globulus usada, a Acacia melanoxylon exibe um rendimento em pasta ligeiramente superior, o que está de acordo com os teores de lenhina e extractivos das madeiras. Para avaliar o potencial das pastas branqueadas na produção de papel, estas foram submetidas ao processo de refinação, em PFI, tendo-se obtido suspensões de pastas com resistência à drenagem crescentes. Posteriormente, caracterizou-se a suspensão fibrosa e o potencial papeleiro. Para o mesmo nível de refinação, os papéis produzidos com fibras de acácia apresentam valores superiores de lisura, índice de tracção e índice de rebentamento. Por outro lado, as fibras da Eucalyptus globulus apresentam maior resistência intrínseca e têm potencial para produzir papeis mais resistentes, embora à custa de maior consumo de energia na refinação. Para um dado nível de resistência mecânica, as características ópticas dos papéis são semelhantes.
- Behaviour of two main portuguese wood species towards enzymatic hydrolysisPublication . Spiridon, Iuliana; Belgacem, Mohamed Naceur; Duarte, Ana PaulaThis paper presents the influence of cellulolytic and hemicellulolytic enzymes on the papermaking properties of pulps from Eucalyptus globulus and Pinus pinaster wood species from Portugal. It was shown that these enzymes increased the delignification efficiency and degraded the cellulose macromolecules, having effects on the fiber strength. Thus, it was found that these treatments decreased strongly the burst index, but increased significantly the tearing properties. The zero span tensile strength was also affected, especially for Eucalyptus globulus pulps. Finally, these treatments were found to increase the brightness of the treated pulps.
- Characterization of kraft lignin from Pinus pinasterPublication . Duarte, Ana Paula; Batista, Cecilia; Belgacem, Mohamed NaceurThis paper presents the results about the lignin from Pints pinaster, the only softwood used in Portuguese pulp and paper industries. Six samples of lignin were collected and studied. The first three samples were precipitated from kraft black liquors at different H-factors. using conventional batch pulping. The other three corresponded to the lignin obtained from black liquors of flow-through reactor at the same H-factors. The residual sugars from the lignin obtained were hydrolysed according to the trifluoroacetic acid method and quantified by HPLC. The main residual sugars on the lignin samples from both reactors were found to be xylose, galactose and arabinose, which indicates that the lignin-carbohydrate linkages are similar to other common softwoods. The elemental analyses of these samples showed that, in the initial stage of delignification, the HS' anions are strongly involved in the delignification mechanism. It was also shown that the C/H ratio was relatively constant, which indicated the weak participation of condensation reactions. The infrared spectra of these samples evidenced the presence of the main peaks corresponding to different functional groups of softwood lignin structure. They also showed that the content of conjugated carbonyl groups decreased with the reaction time. Finally, the permanganate potassium oxidation of the lignin samples showed the presence of the principal fragments present in softwood lignin. It was also shown that. when the time of delignification increased, the amount of non-condensed units decreased, whereas that corresponding to condensed ones increased.
- Determination of sugar content in Pinus pinaster and its corresponding hollocellulose, cellulose and kraft pulpsPublication . Duarte, Ana Paula; Gaiolas, Carla Sofia Cardona Jorge; Belgacem, Mohamed Naceur; Simões, RogérioThis paper deals with the study of the polysaccharide complex from Portuguese Pinus pinaster, as well as from its main components, i.e., holocellulose, cellulose and pulps obtained using different cooking conditions. Nordic Pinus sylvestris was also studied in order to compare it with Portuguese pine. Two methods were used: one consisted of the hydrolysis of polysaccharides with trifluoroacetic acid (TFA) and quantification of the amount of each sugar using High Performance Liquid Chromatography (HPLC). The latter approach used here consisted of the hydrolysis of the samples under scrutiny by sulphuric acid and converting it into alditols, which were then esterified before injecting to Gas Chromatography coupled with Mass Spectrometry. Myo-inositol was used as an internal standard. The results obtained by the two methods showed that the TFA procedure prevents monosaccharide degradation, comparatively with the sulphuric acid one. In fact, the overall sugar yield was found systematically higher than 93% for TFA hydrolysis, whereas that corresponding to H2SO4 treatment never exceeded 77%. The sugar composition of both pines was found very similar and the sulfidity level (from 10 to 55%) did not affect the pulp sugar composition. The glucose/mannose and xylose/arabinose ratios were found to be around 3.5 for both Portuguese and Nordic pines. Finally, kraft pulping of Pinus pinaster was found to affect drastically galactose, mannose and arabinose.
- Effect of carry-over on the kinetics of chlorine dioxide delignification of an unbleached hardwood kraft pulpPublication . Simões, Rogério; Barroca, Maria J. M. C.; Castro, José Almiro A. M.This work is concerned with the kinetics of the prebleaching stage of a kraft pulp of Eucalyptus globulus with chlorine dioxide. Its main purpose is to discuss the influence of the degree of washing, expressed as the COD of the pulp, on the kinetics and stoichiometry of chlorine dioxide delignification. The effect of the carry-over on the rate of delignification of a Do stage was studied over time for pulps with different initial organic charges (COD). A set of experiments was specially designed to discriminate the individual role of lignin and of COD upon the initial consumption of chlorine dioxide. A modified mathematical model, taking into account the reactions of chlorine dioxide with both lignin and the carry-over, has been developed. In this model, the initial chlorine dioxide consumption (in the fast phase of reaction) is dependent on two factors: the carry-over of the pulp and the temperature of operation. However, the carry-over does not affect the corresponding initial depletion factor for the Kappa number. The role of the dissolved organic material, carried with the pulp, upon the rate of reaction in the slow period is better described in the stoichiometry. The fit of the experimental results obtained for pulps with different COD reveals good prediction capabilities for both Kappa number and chlorine dioxide concentration in a conventional D0 stage.
- Effect of unbleached pulp kappa number on the kinetics of chlorine dioxide delignificationPublication . Simões, Rogério; Barroca, Maria J. M. C.; Castro, José Almiro A. M.Chlorine dioxide delignification of different unbleached kraft pulps from Eucalyptus globulus, having Kappa numbers of 12 to 18, was studied in the temperature range of 285 K to 358 K. The effect of the unbleached pulp Kappa number on the initial fast phase of delignification was investigated with respect to the depletion factors for Kappa number and chlorine dioxide concentration, as proposed by Barroca et al. Furthermore, the behaviour of the floor lignin content of the pulp, or the floor Kappa number, was analysed within this range. The results show that all pulps exhibit a similar pattern, with respect to temperature, in depletion factors for Kappa number and chlorine dioxide concentration. The degree of normalised delignification and chlorine dioxide consumption is very similar and independent of the Kappa number of the unbleached pulps. Moreover, the results reveal that there is a strong correlation between the floor lignin content and the temperature, and that this correlation is applicable to a wide range of unbleached pulp Kappa numbers, since the residual Kappa number is independent of its initial value. The results enable the general application of a kinetic model to kraft pulps with different unbleached Kappa numbers.
- Estudo da interação tinta-papel na impressão inkjetPublication . Sousa, Sónia Cristina Lopes de; Ramos, Ana Maria Matos; Mendes, António de OliveiraAs tintas para impressão inkjet são pouco viscosas e possuem baixa tensão superficial, o que exige ao papel características controladas de absorção e mecanismos de fixação, na superfície, da substância que confere cor, de modo a obter-se uma imagem bem definida e com elevada densidade de impressão. Através dos tratamentos de superfície do papel, é possível modificar características que determinam a interação entre a tinta e o papel, como a energia de superfície, a porosidade e a rugosidade, as quais influenciam a qualidade de impressão. Esta tese tem como principal objetivo determinar os fenómenos de interação tinta/papel que contribuem para a qualidade de impressão inkjet. O conhecimento destes fenómenos permitirá otimizar os tratamentos de superfície, com vista ao melhoramento da qualidade de impressão inkjet em papéis não revestidos. A modificação da superfície do papel foi realizada através da aplicação de formulações preparadas com compostos químicos comerciais. Os papéis modificados foram caraterizados quanto às seguintes propriedades: espessura, porosidade aparente, permeabilidade ao ar, lisura Bekk, parâmetros de rugosidade obtidos por perfilometria ótica, opacidade, brancura, análise de penetração dinâmica de água, energia de superfície e respetivas componentes dispersiva e polar. Foi ainda analisada a composição química da superfície dos papéis através de XPS, permitindo conhecer a quantidade relativa dos elementos presentes na superfície, assim como, as ligações químicas envolvidas no carbono e no azoto detetado. Os resultados obtidos mostraram que as modificações realizadas tiveram um enorme impacto nas propriedades químicas dos papéis, nomeadamente nos parâmetros relativos à energia de superfície e na composição química, enquanto as propriedades estruturais, a topografia de superfície e as propriedades óticas sofreram apenas ligeiras alterações. De modo a avaliar o efeito das modificações realizadas na qualidade de impressão, os papéis foram impressos em duas impressoras que utilizam tintas de cor de natureza distinta, permitindo, assim, estudar o comportamento das tintas base corante e base pigmento. A avaliação da qualidade de impressão compreendeu a medição dos seguintes parâmetros: densidades óticas de impressão do preto, ciano, magenta e amarelo; área gamut; chroma; largura, raggedness e blur da linha preta; inter color bleed; ganho e circularidades dos pontos preto e magenta. Verificou-se que, a retenção da tinta à superfície do papel, resultante do controlo do espalhamento e absorção, proporciona elevada qualidade de impressão. Para tal é necessário que o papel possua uma certa rugosidade, baixa energia de superfície e componente polar significativa. No caso das tintas base corante, a carga catiónica na superfície do papel é preponderante no que concerne às propriedades de cor. É importante conhecer quais os parâmetros que afetam o processo de absorção e espalhamento da tinta, e a forma como estes processos influenciam os parâmetros de avaliação da qualidade de impressão, de modo a controlar estes mecanismos e assim otimizar a qualidade de impressão. Neste trabalho foi avaliada a dinâmica de interação entre gotas de tinta preta e magenta, provenientes dos tinteiros das impressoras usadas nos testes de impressão, e a superfície de alguns dos papéis modificados. Os resultados mostraram que o espalhamento das gotas de tinta preta é principalmente determinado pela energia de superfície dos papéis, enquanto que o espalhamento das gotas de tinta magenta é influenciado pela permeabilidade ao ar. No que diz respeito à absorção da tinta, verifica-se a existência de uma relação inversa entre a permeabilidade ao ar e variação da profundidade de penetração ao longo do tempo. No entanto, dado o coeficiente de correlação moderado, supõe-se que os parâmetros físico-químicos interfiram também no processo de penetração. Observou-se que, os papéis que registam maior área de espalhamento máximo das gotas de tinta preta, tendem a originar pior qualidade de impressão no que concerne aos seguintes parâmetros: largura e raggedness da linha, e ganho do ponto preto. Os resultados obtidos podem ser aplicados pela indústria de papel, e podem também servir de base a futuros estudos de espalhamento e absorção de gotas de tinta.
- Influence of xilanase treatment on Pinus pinaster kraft pulpPublication . Spiridon, Iuliana; Duarte, Ana Paula; Curto, JoanaIn Portugal, pulp and paper industry uses especially two wood species, Eucalyptus globules and Pinus pinaster. The second species gives pulps with low bleachability (compared with other common softwood species, like Pinus silvester), utilised for packaging papers. It is known that treatments with different hydrolytic enzymes could improve the bleaching capacity of softwood pulp. That is why, xylanases were used to improve Pinus pinaster kraft pulp characteristics. The enzymatic hydrolysis improved brightness and some papermaking properties.
- Ozone depolymerization of polysaccharides in different materialsPublication . Simões, Rogério; Castro, José Almiro A. M.The behaviour of polysaccharides contained in different cellulosic materiais is studied with respect to depolymerization by ozone in an aqueous medium. The ejJect of concentration in the liquid phase, temperature and time upon the depolymerization of holocellulose, bleached and unbleached pulps, microcrystalline and native celluloses is investigated. The viscosimetric degree of polymerization and lhe molecular weighl dislribulion are used to monitor the processo The resulls show that, allow values of temperature and pH, which inhibit the produclion ofradicals, the depolymerization rate is moderalefor lignin-free materiais. However, Ihis rale and its maximum exlent increase markedly with temperature. Moreover; the experiments suggest that the reactivity of ozone and the amounl of radicais in the system and its physical accessibility are the key factors to explain the observed depolymerization pro files. Finally, the results for lignin-free materiais are compared with those obtained with similar materiais but containing residuallignin, and this study confirms that lhe presence of lignin in the fibre matrix increases the depolymerization of the carbohydrates.
- A refinabilidade de pastas químicas papeleiras: um contributo para a sua avaliação utilizando o refinador ValleyPublication . Vaz, Álvaro Frederico Campos; Silvy, Jacques; Simões, Rogério Manuel dos SantosThe goal of this thesis is to set up a methodology to establish a relationship between pulp properties, namely morphological and physical, and paper properties, specifically structural, optical and strength, with the operating variables of refining and the physical and chemical properties of the raw material. The goal is to contribute to the analysis of the beatability of chemical pulps for paper production. The beatings took place in a laboratory Valley beater, and the studied variables were the charge on the roll, the rotor speed of rotation and the specific applied energy. For its feasibility, one fitted the following adaptations to the Valley: a rotor speed of rotation variation controller, a sensor to measure the distance between rotor and stator and an electrical power consumption meter. The effects for three different bleached Kraft pulps were studied, one being pine and the others Portuguese eucalyptus and birch. At the fibre level, its morphology was analysed by image analysis, such as the average fibre length and distribution, its width, coarseness, curl, kinks, fibrillation and fines proportion; the intrinsic fibre resistance was evaluated, such as its water retention value and wet flexibility. At the paper level, one measured its density, tensile strength, burst strength, tear strength, brightness, opacity and its scattering and absorption coefficients. One implemented methodologies to evaluate the relative bonded area and the bond strength in the paper structure using optical and mechanical methods. The hydromechanics of the beating was analysed for the three pulps. So the beating effects on the specific edge load was studied, the normal and tangential forces were evaluated, the pulp apparent viscosity evolution during refining was determined, the distance between rotor and stator was measured and also the energetic efficiency was quantified. One obtained relationships between the apparent viscosity and the rotor-stator gap, and another between the first one and the rate of shear. One explored the experimental results in order to develop control relationships for the pulp properties to paper production. One essayed an optimization of the refining conditions for each pulp for specific types of industrial papers, namely in terms of paper properties and the energy consumption in the Valley beater. The pulp suspension presents rheofluidificant behaviour and the apparent viscosity diminishes along the refining. The different pulps reveal different rheological behaviour, which leads to the inference that from the hydrodynamical point of view one should treat pulps with different morphological characteristics separately. The obtained adjustment equations for the different studied properties permit the comparison between the pulps and the study of the effects of the operating conditions. As expected, the pine revealed the best strength performance, the eucalyptus showed the best optical properties, and the birch showed a better mechanical performance relatively to the other hardwood. In what concerns the analysis of the operating conditions, one verified that the rotor speed of rotation has a major influence on the pulp and paper properties. One also inferred that the birch reveals an opposite behaviour comparatively to the pine and the eucalyptus, from the standpoint of the sped of rotation and the specific edge load.