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Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal.

Surfactants are largely present in papermaking/recycling processes. They are added intentionally or come with raw materials or process/functional additives. Once they have reached the process, they build-up in the circuits and, depending on their surface activity and concentration, they can have adverse effects on deinking and on the whole papermaking process, such as excessive frothing, depression of ink floatability, and paper sizing/retention difficulties. In this paper, the removal of apparent surface active chemicals (ASAASAASAC) is first evaluated in different flotation deinking mills through mass balances using surface tension measurements and a specific methodology. Mill data show that, in two-stage deinking lines, ASAASAASAC are slightly concentrated in the second stage, contributing to an increase in pulp frothing behavior, in flotation loss, and in some cases to a low ink removal efficiency. Trends observed in deinking mills are then interpreted using experimental data obtained at the laboratory scale in the presence of a model surfactant, and by process simulation. The effect of ASAASAASAC concentration on the efficiency of the flotation deinking process is explained in terms of their effect on particle and water transport sub processes, namely, flotation, entrainment, frothing, and drainage.

This work was aimed at investigating the potential use of ozone flotation for recovered papers deinking. The mixing characteristics and the bubble size of a Venturi aerated laboratory flotation column were studied in the presence of simplified model systems and of an industrial pulp slurry. Experimental results showed that surfactants dissolved in the pulp slurry stabilized air bubbles while cellulose fibers promoted coalescence. Moreover, bubble buoyancy was sufficient to fluidize the fiber suspension generating perfect mixing. The gas–liquid transfer coefficient of ozone (kLa) estimated from gas hold-up, air bubble size and kLa measured in water was high enough (0.84 1/s) for the complete transfer of ozone in the pulp slurry and the generation of ozone-free gas effluent. With O3 dosage of 0.8 mg O3/mg COD, ozone flotation allowed increasing chemical oxygen demand removal from 41 to 63% with no effect on the ink flotation efficiency, which remained close to that obtained with air flotation, i.e. ∼92%.

Biofilms based on waxy maize and cassava starches (cereal and tuber starch, respectively), plasticized with glycerol were characterized through their crystallinity, dynamic-mechanical behavior (DMA), thermal degradation (TGA), moisture content and water vapor permeability (WVP). X-ray diffraction experiments show that both materials were mainly amorphous, with the waxy starch presenting a discreetly A-type X-ray pattern. Microscopic investigation of the cryo-fractured surfaces supported this observation. The glass transition of the glycerol-rich phase (measured by DMA) occurs at higher temperatures for cassava than for waxy maize starch, suggesting that the dispersion level of glycerol is higher in the former. TGA showed that maize starch has a slightly higher thermal stability than cassava starch, while glycerol interacts more strongly with the last one. The WVP was 18% higher in the case of the cassava starch film.

Steady-state fluorescence emission spectra of various celluloses were measured at an excitation wavelength of 320 nm. Various spectra recorded in the solid state were compared: (1) ECF bleached papers made of hardwood, the anhydroglucose units of which were chemically modified at C1 and C6 or C2 and C3 positions with carboxylic groups; (2) microcrystalline cellulose; (3) cotton linters; and (4) delignified sisal fibers (mercerized or not). Fluorescence emission was quite independent of the carboxylic acid content and average molecular weight (determined by viscosimetry) of the cellulose polymers. Microcrystalline cellulose (Avicel), cotton linters, and mercerized delignified sisal cellulose were acetylated in homogeneous medium (DMAc/LiCl as solvent system) to obtain soluble polymers in dichloromethane for comparison of spectra recorded in the solid and liquid states. Fluorescence of cellulose acetates in solution (CH2Cl2) and in the solid state was compared under similar experimental conditions to non-esterified celluloses in the solid state. The importance of the solid state for fluorescence emission could be demonstrated. Fluorophores are present in minute amounts in the polymer and their favorable energy transfer for excitation in the solid state likely enhances fluorescence emission. Among numerous fluorophores, dityrosine appeared to be a good candidate for fluorescence because it displayed emission in the fluorescence range of cellulose. Dityrosine is an amino acid involved in the lignification of non-woody plants. Mercerized sisal impregnated with tyrosine in the presence of peroxidase and hydrogen peroxide did not show enhanced emission, in contrast to para-hydroxycinnamic acid (coumaric acid), which is also involved in the lignification process at least for non-woody plants. The origin of cellulose fluorescence remains uncertain and appears to have several origins. This study clearly underlines the importance of the solid state for enhancing fluorophore emission.

Model equations and transport coefficients recently used to describe particle and water transport phenomena in a laboratory flotation deinking column were applied to industrial flotation cells and used to simulate multistage flotation systems. The deinking selectivity obtained for a two-stage pre-flotation system was in agreement with data collected in a deinking mill running in similar conditions and process yield, floated pulp composition and ink load in the floated pulp were predicted with good accuracy. Multistage flotation systems with different configurations were simulated, however, only a not conventional three-stage flotation system gave a relevant increase in the ink removal selectivity. Indeed, the addition of a third stage to a conventional two-stage flotation system gave ∼50% decrease in the pulp stock loss and only 10% decrease in ink removal which was recovered by the addition of a flotation cell in the first stage without affecting yield. In general, it was observed that the addition of second and third stages favours the selective removal of particles with the highest flotation rate constant (inks). Indeed, floatable particles, i.e. ink, fillers and fines are mainly removed in the first stage, ink and fillers in the second and ink in the third stage.

This work is a contribution to the characterization of the papermaking potential of wood pulps. Prevision of this potential developed during the drying process is the scope of this study. The VARIDIM© apparatus allows to measure shrinkage for different loads applied on the paper strip samples with constant air-drying conditions. The dried papers are then tested in an extensometer to determine mechanical properties. The main originality of this study lies in the possibility of classifying pulps by the maximum specific energy they are able to develop during drying shrinkage.

In libraries and archives some of the time-acidified items are so brittle that they cannot be handled without risking loss of material. Currently used deacidification processes do not impart improved mechanical properties to the paper. The use of alcoholic solutions of three different types of aminoalkylalkoxysilanes was studied for the deacidification of paper-based items. It was shown that in addition to deacidifying and improving the stability of papers by providing an alkaline buffer the treatment also significantly improved their mechanical resistance, as measured by the folding endurance and tensile breaking resistance. Essential for the appraisal of the deacidification process, the behaviour upon ageing of the materials treated was investigated. Accelerated ageing methods involving heat/humidity and nitrogen dioxide atmosphere were used separately. It was shown that the reinforcement effect of the three aminosilane compounds tested persisted throughout the ageing, and in one case the mechanical properties even improved after ageing. Two of the aminosilanes tested were studied for their impact at the macromolecular level, on the molar masses of cellulose, using size-exclusion chromatography with multiangle light scattering detection. Their effectiveness in protecting paper from acid hydrolysis occurring during ageing was found significant.

Aqueous dispersions of nanometric clay platelets (Laponite) have been dewatered through different techniques: centrifugation, mechanical compression, and osmotic stress (dialysis against a polymer solution). The positional and orientational correlations of the particles have been determined through small-angle neutron scattering. Uniaxial compression experiments produce concentrated dispersions (volume fraction > 0.03) in which the platelets have strong orientational and positional correlations. The orientational correlations cause the platelets to align with their normal along a common axis, which is the axis of compression. The positional correlations cause the platelets to be regularly spaced along this direction, with a spacing that matches the average volume per particle in the dispersion. The swelling law (volume fraction versus separation distance) is one-dimensional, as in a layered system. Changes in the applied osmotic pressure cause the water content of the dispersion to either rise or decrease, with time scales that are controlled by interparticle friction forces and by hydrodynamic drag. At long times, the dispersions approach osmotic equilibrium, which can be defined as the common limit of swelling and deswelling processes. The variation of the equilibrium water content with the applied osmotic pressure has been determined over 1 decade in volume fractions (0.03 < < 0.3) and 3 decades in pressures. This equation of state matches the predictions made from the knowledge of the forces and thermal agitation for all components in the dispersion (particles, ions, and water).

Linters cellulose was subjected to different treatments (mercerization and ionized air) before acetylation with acetic anhydride, in homogeneous medium, using DMAc/LiCl as solvent system. Before derivatization, the treated fibres were characterized by Scanning Electron Microscopy, X-ray diffraction, alpha-cellulose content, Inverse Gas Chromatography and viscosimetry. It was shown that except a decrease in the dispersive surface energy, the treatments induced small changes in the cellulose. The degree of acetylation of these fibers was found to follow a linear behavior with the stoichiometry between acetic anhydride and glucose unit, but this linearity obeyed high rate up to a DS of 2.0. The order of reactivity observed for all samples, C6>>C2>C3, confirms the higher reactivity of OH in C6 position, because this group is the least sterically hindered of the anhydroglucose unity.

Acrylated soybean oil was irradiated in the near UV in the presence of free radical photoinitiators. Given the high substitution density of acrylic moieties, these oils responded very rapidly to the photopolymerization giving high yields of crosslinked materials within a few seconds. The activity of three photoinitiators was compared and the ensuing networks were characterized in terms of crosslink density through swelling measurements. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 99: 3218–3221, 2006

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The chlorine dioxide reaction with residual lignin of chemical pulp during delignification stage was simulated using phenolic and non-phenolic lignin model compounds applying various amounts of chlorine dioxide. Based on the reaction of model compounds and measurement of inorganic chlorinated species, three reaction phases were established for degradation of lignin model compounds. It was found that after the degradation of free phenolic units, the reaction of primary oxidized products by ClO2 competed with the oxidation of non-phenolic aromatic structure. The results obtained by lignin model compounds were compared with the pulp delignification results. This comparison indicated two special phases for the reduction of the kappa number. The initial phase corresponded to the oxidation of phenolic units without secondary reactions. The second phase corresponded to the oxidation of the non-phenolic units in competing with secondary reactions. The results of this confirmed the over consumption of chlorine dio...

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Nanocomposites of cassava starch reinforced with waxy starch nanocrystals were prepared. They showed a 380% increase of the rubbery storage modulus (at 50 °C) and a 40% decrease in the water vapor permeability. X-ray spectra show that the composite was more amorphous than the neat matrix, which was attributed to higher equilibrium water content in the composites. TGA confirmed this result and its thermal derivative suggested the formation of hydrogen bonding between glycerol and the nanocrystals. The reinforcing effect of starch nanocrystals was attributed to strong filler/matrix interactions due to the hydrogen bonding. The decrease of the permeability suggests that the nanocrystals were well dispersed, with few filler/filler interactions. Fil: Garcia, Nancy Lis. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de San Martín; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Física. Laboratorio de Polímeros y Materiales Compuestos; Argentina Fil: Ribba, Laura Gabriela. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Física. Laboratorio de Polímeros y Materiales Compuestos; Argentina Fil: Dufresne, Alain. Grenoble Institute of Technology; Francia Fil: Aranguren, Mirta Ines. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; Argentina Fil: Goyanes, Silvia Nair. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Física. Laboratorio de Polímeros y Materiales Compuestos; Argentina

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In this work, the contribution of flotation deinking banks design on ink removal efficiency, selectivity, and specific energy consumption was simulated using a semiempirical approach. Single-stage with mixed tank/ column cells, two-stage, and three-stage configurations were evaluated, and the total number of flotation units in each stage and their interconnection were used as main variables. Explicit correlations between ink removal efficiency, selectivity, energy consumption, and line design were developed for each configuration. When considering a conventional two-stage configuration as reference, a decrease in the specific energy consumption for constant ink removal efficiency and selectivity was obtained with the single-stage bank with a stack of flotation columns at the front of the line, whereas an increase in ink removal selectivity for constant ink removal efficiency and specific energy consumption was obtained with the three-stage bank. The present results show that the performance of conventional flotation deinking banks can be improved by optimizing process design and implementing mixed tank/column technologies in the same deinking line.

The present investigation focuses on the adsorption of cationic photoluminescent polymer nanoparticles on negatively charged bleached softwood cellulose fibres. The synthesis of the copolyfluorene–fluorenone and its miniemulsification with tetradecyltrimethylammonium bromide (TTAB) as surfactant has been optimized to obtain highly charged cationic nanoparticles. Cellulose pulp beating was performed as mechanical treatment to increase fibres hydration and specific surface area. Although beating promoted nanoparticles adsorption, photoluminescence of handsheets prepared with beaten fibres was less intense comparing to those obtained with untreated fibres. The photoluminescence drop was attributed to the loss of a large fraction of cellulosic fine elements present in the beaten pulp during handsheets preparation. Cationic nanoparticles adsorption kinetics on cellulose fibres and the resulting photoluminescence efficiency was monitored in two cases: with or without the stabilization of nanoparticles in the pulp slurry by TTAB. Pulps preconditioning with TTAB avoided nanoparticles flocculation and led to a homogeneous coverage of the fibres surface giving more efficient photoluminescent papers. However, the formation of a continuous layer on the fibre surface induced a drop in the mechanical resistance of the paper which was ascribed to a decrease of interfibre hydrogen bonding.

Transport coefficients and correlations recently used to describe surfactant contribution to particle and water transport in a laboratory flotation column were used to simulate the impact of surfactant contamination on the flotation selectivity of industrial two-stage deinking lines. Simulation results showed that surfactants are slightly removed in the first flotation stage and are concentrated in the second one, where they induce a drop in ink flotation and in fibre entrainment. Subsequently, flotation units in the second stage displayed lower ink removal than in the first stage. In the presence of a constant water reject flow, the increase in surfactant contamination in the pulp stock gave a general decrease in the removal of suspended solids. Surfactant removal increased from 5 to 50%, however, this increase was not sufficient to prevent surfactant accumulation in the deinking line. Simulation results were compared with data collected in an industrial deinking line and particle/surfactant removal efficiencies obtained with low surfactant contamination were in line with experimental data.

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Two cellulosic substrates (microcrystalline cellulose, MCC, and bleached kraft softwood pulps, BSK) were grafted by polycaprolactone (PCL) chains with different molecular weights, following a three-step procedure using non-swelling conditions in order to limit the reaction to their surface. First, one of the two OH PCL ends was blocked by phenyl isocyanate and the reaction product (adduct 1) was subsequently reacted with 2,4-toluene diisocyanate (adduct 2) to provide it with an NCO function, capable of reacting with cellulose. The ensuing PCL-grafted cellulosic materials were characterized by weight gain, elemental analysis, contact angle measurements, attenuated total reflexion–Fourier transform infrared (ATR–FTIR), X-ray photoelectron spectroscopy (XPS) and biodegradation tests. The modification was proven to occur by the presence of nitrogen atoms in the elemental analysis tests and XPS spectra of modified and soxhlet-extracted cellulose. The contact angle measurements have also shown that the surface became as hydrophobic as PCL itself. The polar component of the surface energy of cellulosic substrates before treatment was found to be about 32 and 10 mJ m −2 , for MCC and BSK, respectively. This value vanished to practically zero after grafting with different PCLs. The strategy proposed in the present work is original since, to the best of our knowledge, this paper reports for the first time the chemical “grafting onto” of the cellulose surface by PCL macromolecular structures, with the aim of obtaining fibre–matrix co-continuous fully sustainable and biodegradable composite materials.

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A general procedure to increase the amount of photoreactive chromophore groups per oligoether chain is presented. In this work, a photoreactive macromonomer with four functionalities was synthesized by a four-step synthetic pathway with high yield. The photochemical behavior of this compound was studied with a view to obtaining polymeric networks. The significant advantage in this strategy is that the preparation of this material has as last operation, the obtaining and processing of polymer as thin film. In this way, the synthetic strategy based on assembling: (i) the polyether chains, (ii) a film forming backbone, and (iii) a photoactive moiety to be used for cross-linking, seems a viable solution to the problem of the continuous processing of materials. Fil: Froimowicz, Pablo. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Departamento de Química Orgánica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Tecnología En Polimeros y Nanotecnología. Universidad de Buenos Aires. Facultad de Ingeniería. Instituto de Tecnología En Polimeros y Nanotecnología; Argentina Fil: Belgacem, Naceur. Grenoble Institute Of Technology; Francia Fil: Gandini, Alessandro. Grenoble Institute Of Technology; Francia Fil: Strumia, Miriam Cristina. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Departamento de Química Orgánica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; Argentina

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