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The present work investigates the creation of water-resistant and antifungal papers by using biobased compounds. Two approaches were developed: A surface modification by coating or a cellulose fibre modification. For the coating approach, two formulations were studied. The first one, consisting in chitosan and modified precipitated calcium carbonate (PCC) was mainly used to limit the development of molds while improving paper water resistance. The formulation incorporating 20 % of modified PCC showed a significant increase of the lag phase of the target fungal strain. The second coating formulation, especially designed to improve papers water resistance by a coating layer of prevulcanized natural rubber latex, showed very positive results, leading to 95 % reduction of liquid water absorption but with a negative impact on the material opacity after water penetration. As a consequence, physico-chemical modification of cellulose fibre was investigated in a second approach. An hybridization process was used, leading to stearic acid adsorption on in situ PCC synthesized at the surface of cellulosic fibres. A compromise between fillers retention, water resistance and mechanical properties was found. After determination of optimal conditions carried out to an industrial scale up, an industrial pilot was performed and gave promising results., Ce travail de thèse a été conduit dans le but d’élaborer des papiers résistants à l’eau liquide et ayant des propriétés antifongiques, ce par utilisation de composés biosourcés. Deux approches ont été proposées : soit une modification en surface par enduction, soit une modification des fibres de cellulose. Dans le cas de la modification en surface, deux formulations d’enductions ont été étudiées. La première, composée de chitosane et de carbonate de calcium précipité (PCC) modifié, a été utilisée pour limiter le développement de moisissures et améliorer la résistance des papiers à l’eau. La formulation incorporant 20 % de PCC modifié a montré un retard de croissance significatif de la souche fongique sélectionnée en tant que souche cible. La seconde formulation, destinée à améliorer la résistance à l’eau des papiers, par enduction d'un latex prévulcanisé d’hévéa, a montré de très bons résultats, conduisant à une réduction de près de 95 % de l’absorption d’eau liquide. Toutefois, une perte d’opacité des papiers a été observée après pénétration de l’eau dans le matériau. Par conséquent, une seconde approche a été proposée, basée sur la modification physico-chimique des fibres de cellulose. Un procédé d’hybridation a été utilisé, permettant l’adsorption d’acide stéarique sur le PCC synthétisé in situ à la surface des fibres de cellulose. Un compromis entre la rétention des charges, la résistance à l’eau et les propriétés mécaniques a pu être proposé. Après détermination des conditions optimales de mise à l’échelle industrielle du procédé d’hybridation, un essai industriel a pu être réalisé et a conduit à des résultats prometteurs.

A study on oxygen-plasma treatment of ink-jet paper is presented. Paper was exposed to a weakly ionized, highly dissociated oxygen plasma with an electron temperature of 5?eV, a positive-ion density of 8 ? 1015?m?3 and a density of neutral oxygen atoms of 5 ? 1021?m?3. Optical emission spectroscopy (OES) was applied as a method for detection of the reaction products during the plasma treatment of the paper. OES spectra between 250 and 1000?nm were measured continuously during the plasma treatment. The wettability of the samples before and after the plasma treatment was determined by measuring the contact angle of a water drop. The appearance of the surface-functional groups was determined by using high-resolution x-ray photoelectron spectroscopy (XPS), while changes in the surface morphology were monitored with scanning electron microscopy (SEM). Already after 1?s of the plasma treatment the surface, which was originally hydrophobic, changed to hydrophilic, as indicated by a high absorption rate of a water drop into the paper. The OES showed a rapid increase of the CO and OH bands for the first few seconds of the plasma treatment, followed by a slow decrease during the next 40?s. The intensity of the O atom line showed reversed behaviour. The XPS analyses showed a gradual increase of oxygen-rich functional groups on the surface, while SEM analyses did not show significant modification of the morphology during the first 10?s of the plasma treatment. The results were explained by degradation of the alkyl ketene dimer sizing agent during the first few seconds of the oxygen-plasma treatment.

Conselho Nacional de Desenvolvimento Científico e Tecnológico The objective of this study was to evaluate the behavior of alkaline size of ECF and TCF pulps, as well as develop a procedure for alkaline size in laboratory and the development o a methodology for the quantification of AKD alkaline size agent which is retained in the paper. The studies carried out in the evaluation of the behavior of the alkaline size were: variation in the furnish consistency (0,2%, 0,3% and 0,4%), variation in the paper formation consistency (0,016%, 0,033%, 0,066% and 0,3%), variation in the dosage of the AKD agent (0,15%, 0,30%, 0,45%, 0,60% and 0,75% based on pulp), photochemical aging of papers, water activity on papers and protection of pulp functional groups. The pulps showed significant differences in morphological characteristics, such as lumen diameter (φ) and fiber wall thickness, while no difference in fiber length were noticed. The physical characteristic, such as average length of the fibrous material, number of fibers per gram and fines content did not show significant differences among the pulps studied. On the other hand, characteristics such as coarseness and water retention value (WRV) showed significant differences. Both pulps (ECF and TCF) do not differ significantly as far as the chemical characteristics of α, β e γ - cellulose is concerned. The TCF pulp showed higher content of carboxylic groups. The methodology adjusted for the quantification of the AKD coating agent retained in the paper through gas chromatography, showed to be efficient with good results. Then consistency of furnish preparation of 0,4 % showed negative effects in the retention of mineral charge of mineral fillers and in the alkaline size development (Cobb test). The retention of mineral fillers is reduced as the formation consistency is increased but with tendency to stabilize, while the alkaline size development is significantly affected at furnishes consistencies below 0,1%. At laboratory level, the retention of the AKD alkaline size agent (retention chemical plus physical) did not surpass 36% and papers produced with TCF pulp presenting higher retention. On the other hand, statistical analysis demonstrated those papers from ECF and TCF pulps, within the same dosage level of AKD agent, showed the same development gain of hydrophobicity to the cellulose fiber. Also, at laboratory level, the ECF and TCF pulps did not show alkaline size development with dosages below 0,3% (based on pulp). ECF and TCF papers with internal sizing did not suffer influence by the length of exposure to UV-light. Among the papers with internal sizing, those of ECF pulp showed water activity, both for aged and non-aged papers. However, in the papers without internal sizing, the TCF paper showed higher water activity. Among the mathematical models, which were tested, the one that was adjusted to the experimentally observed data was the so-called G.A.B (Guggenheim-Anderson de Boer). The effect of hydroxyl groups in the pulp was less impressive in the retention of the AKD agent than the carboxylic groups. The effect of protection of carboxylic groups the TCF pulp showed a strong reduction in the retention of mineral charge. O objetivo deste estudo foi avaliar o comportamento da colagem alcalina nas polpas ECF e TCF, bem como desenvolver a técnica de colagem alcalina em laboratório e uma metodologia para a quantificação do agente de colagem AKD retido no papel. Os estudos realizados na avaliação do comportamento da colagem alcalina foram: variação na consistência de preparo da massa (0,2%, 0,3% e 0,4%); variação na consistência de formação do papel (0,016%, 0,033%, 0,066% e 0,3%); variação no nível de dosagem do agente de colagem AKD (0,15%, 0,30%, 0,45%, 0,60% e 0,75% base polpa); envelhecimento fotoquímico dos papéis; atividade de água dos papéis e proteção dos grupos funcionais das polpas celulósicas. As polpas apresentaram características morfológicas de largura, φ do lúmen e espessura de parede da fibra celulósica, com diferenças significativas, enquanto o comprimento da fibra celulósica não apresentou. As características físicas como comprimento médio do material fibroso, número de fibras por grama e teor de finos não mostraram diferenças significativas entre as polpas. Já as características físicas coarseness e o índice de retenção de água (WRV) apresentaram-se diferenciados. As duas polpas, estatisticamente, não diferiram entre si para as características químicas α, β e γ - celulose. A polpa TCF apresentou maiores teores de grupos carboxílicos. A metodologia ajustada para a quantificação do agente de colagem AKD retido no papel via cromatografia gasosa demonstrou ser eficaz e gerou resultados confiantes. A consistência de preparo de massa 0,4% apresentou efeitos negativos na retenção da carga mineral e no desenvolvimento de colagem (teste de cobb60). A retenção da carga mineral é reduzida à medida que a consistência de formação é elevada, mas com tendências à estabilização, enquanto o desenvolvimento da colagem é afetado significativamente em consistências inferiores a 0,1%. Em nível de laboratório, a retenção do agente de colagem AKD (retenção química + retenção física) não ultrapassou 36% e os papéis produzidos a partir da polpa TCF apresentaram retenção superior. As análises estatísticas, porém, demonstraram que os papéis das polpas ECF e TCF, dentro de um mesmo nível de dosagem do agente AKD, apresentaram o mesmo ganho de desenvolvimento de hidrofobicidade à fibra celulósica. Em laboratório, as polpas ECF e TCF não apresentaram desenvolvimento de colagem em dosagens abaixo de 0,3% base polpa. Os papéis ECF e TCF com colagem interna não sofreram influência do tempo exposto à luz ultravioleta. Dentre os papéis com colagem interna, os da polpa ECF apresentaram atividade de água superior, tanto os envelhecidos quanto os não-envelhecidos. Entretanto, nos papéis sem colagem interna, o TCF apresentou maior atividade de água. Dentre os modelos matemáticos testados, o que melhor se ajustou aos dados observados experimentalmente foi o modelo G.A.B (Guggenheim- Anderson-de Boer). O efeito de proteção dos grupos hidroxílicos nas polpas foi menos expressivo na retenção química do agente AKD que os grupos carboxílicos. O efeito de proteção dos grupos carboxílicos na polpa TCF provocou forte decréscimo da retenção da carga mineral.