Kraft Pulp

Eucalypts are among the most important short-rotation hardwoods, planted worldwide for the pulp and paper industry. Even though the genus comprises over 700 species, only about a dozen species are used for pulping purposes, therefore, showing the potential for diversification. Six-year-old eucalypt trees from 12 species (Eucalyptus botryoides, Eucalyptus camaldulensis, Eucalyptus globulus, Eucalyptus grandis, Corymbia maculata, Eucalyptus ovata, Eucalyptus propinqua, Eucalyptus resinifera, Eucalyptus rudis, Eucalyptus saligna, Eucalyptus sideroxylon, and Eucalyptus viminalis) were analyzed for chemical composition, fiber morphological, pulping and handsheet paper properties to determine their kraft pulping suitability. The 12 species showed substantial differences regarding extractives (6.1-18.9%), lignin (21.6-30.8%) and holocellulose content (55.4-70.1%). The high inter-species variation in chemical composition produced pulps with different yields (between 38.9 and 49.8%) and degree of delignification (kappa number between 11.6 and 24.2). The combination of these results with the morphological and handsheet properties suggests that E. globulus, E. ovata, E. grandis, E. saligna and E. botryoides have the best overall characteristics for kraft pulping.

With increased interest in using high-yield pulps (HYP) in uncoated and coated wood-free paper, there is a need to evaluate the effects of HYP under the conditions similar to commercial paper machine operations. Such tests were carried out by means of a Dynamic Sheet Former (DSF) sheet with white water recirculation, considering the high fines content of HYP and the usually high filler content in fine papers. In this study, we evaluated the use of a DSF that is equipped with a white water recirculation tank for making oriented sheets under various conditions. The effects of different factors such as operational variables, use of retention aids, and recirculation of white water were examined and clarified in terms of retention of fines and fillers as well as their impact on paper properties. The effect of HYP content on filler retention was also examined.

Industrially made kraft pulps obtained by a modified cooking process may contain 60-75 mmol/kg of hexenuronic acids (HexAs), which represents 6-7.5 kappa units. HexAs do not react with oxygen and very little of it is actually removed across the oxygen delignification stage, causing low efficiencies in the range of 25-35%. In this study, an economical evaluation of the ECF bleaching processes was carried out, having none and double-stage oxygen delignification, when applied to eucalyptus pulps of kappa varying in the range of 14-21. The bleaching processes included sequences containing specific stages for HexAs removal (Z, A/D and D HT ). Results indicated that the use of oxygen delignification was not economically attractive, particularly for HexA-rich low-kappa pulps, but processes without oxygen delignification present significant environmental challenges.

Fibrillation of chemical and mechanical pulps with different lignin contents was studied. The pulps were ion exchanged into their sodium form prior to fibrillation and fibrillated with an increasing level of energy using high-shear friction grinding. The fibrillated samples were characterized for their chemical composition, morphology, rheological properties, and water retention capacity. All pulps had a distinct tendency to form fibrillated material under high shear and compression. The lignincontaining kraft pulps fibrillated easily, and the resulting material can be utilized in applications where high viscosity, water retention capacity, and reinforcement are desired. Fibrillation of mechanical pulps resulted in more heterogeneous samples, which included fiber fragments, branched fibrillar structures, and flake-like particles. This material showed relatively low viscosity and water retention capacity when compared to the samples made from kraft pulps. Chemi-thermomechanical pulp (CTMP), when used as the raw material, yielded a more homogeneous organic filler-like material than did thermomechanical pulp (TMP).

In this study, the chemical composition, fiber morphology, pulp, and paper properties of the pomegranate tree (Punica
granatum L.) were determined. Stem and branch wood were analyzed separately. Kraft and kraft- anthraquinone (AQ) methods
were used for the pulping processes. Stem wood showed superiority to branch wood with longer, wider, thicker-walled fibers. The
holocellulose, α-cellulose, and lignin contents of branch and stem wood were 72.98%–73.50%, 38.37%–39.92%, and 21.04%–25.29%,
respectively. In addition, the yield of kraft pulp made from stem wood was higher than that of branch wood. However, branch wood
handsheets had higher strength properties and brightness than those of stem wood handsheets.
Key words: Anthraquinone, branch wood, kraft pulp, Punica granatum L., paper properties, stem wood

In this study, the evaluability of chickpea stalks generated after harvest in chickpea production was investigated in pulp and paper production. Also, paper production was carried out by blending the chickpea stalk fibers with primary and secondary fibers in certain proportions and the effects of chickpea stalk fibers on the paper properties were determined. The modified kraft method was used in the pulping of chickpea stalks and anthraquinone (AQ) was added to the cooking liquor as a catalyst. Some chemical, mechanical and optical properties of the pulps produced with the addition of different AQ charges were compared and the 0.7% AQ added cooking experiment gave the best results. The yield and viscosity values of the chickpea stalk pulps increased by 12.6% and 34.2%, respectively and the kappa number decreased by 46.7% with the addition of 0.7% AQ to cooking liquor. Paper production was carried out by blending the fibers obtained from an optimum cooking condition with primary and secondary fibers at certain rates and the effects of chickpea stalk fibers on the paper properties were examined. Depending on the amount of chickpea stalk fibers, the mechanical properties of the papers produced with secondary fibers and the optical properties of the papers produced with primary fibers improved. The strength losses that occur during the recycling of waste paper could be reduced by blending the chickpea stalk fibers with secondary fibers and it is possible to produce various paper types such as writingprinting paper by blending the short fiber chickpea stalk fibers and long fibers.

With increased interest in using high-yield pulps (HYP) in uncoated and coated wood-free paper, there is a need to evaluate the effects of HYP under the conditions similar to commercial paper machine operations. Such tests were carried out by means of a Dynamic Sheet Former (DSF) sheet with white water recirculation, considering the high fines content of HYP and the usually high filler content in fine papers. In this study, we evaluated the use of a DSF that is equipped with a white water recirculation tank for making oriented sheets under various conditions. The effects of different factors such as operational variables, use of retention aids, and recirculation of white water were examined and clarified in terms of retention of fines and fillers as well as their impact on paper properties. The effect of HYP content on filler retention was also examined.

Three commercial enzymes were used to evaluate the use of xylanase treatment for enhancing the peroxide bleaching of three oxygen delignified kraft pulps derived from the softwoods red cedar, Douglas fir, and western hemlock. Two bleaching sequences were examined, where the enzyme stage was placed before or between the two peroxide stages. The brightness gain achieved was dependent on the enzyme preparation, the origin of the pulp and the position of the enzyme stage in the bleaching sequence. In general, xylanase was found to enhance the pulp brightness achieved with two peroxide stages by l-1.5% ISO. It could directly brighten oxygen delignified pulps before and after the first peroxide stage. Direct brightening of the oxygen delignified pulps, before peroxide bleaching, appeared to be correlated with the amount of UV-absorbing material solubilized during the enzyme stage.

Trametes trogii (BAFC 463), Coriolus versicolor var. antarcticus (BAFC 266) and Trametes villosa (BAFC 2755) are Argentinean white-rot fungi that proved to be efficient ligninolytic enzyme producers in previous studies. The aim of the present work was investigating the ability of their crude extracellular extracts for the biobleaching of loblolly pine Kraft pulp. The production of laccase, manganese peroxidase, endoxylanase and endoglucanase was also evaluated. Out of the three fungi studied, the best biobleaching results were obtained with culture supernatants from T. trogii grown for 21 days in a synthetic medium with glucose and asparagine as carbon and nitrogen sources, respectively, with the addition of 1 mM copper sulfate. Such medium rendered high level of ligninolytic enzymes: 0.25 U ml −1 of manganese peroxidase and 44 U ml −1 of laccase. A strong brightness increase was attained after the enzymatic treatment followed by H 2 O 2 . Bleaching up to 82% ISO brightness (compared with 37% in the peroxide-bleached control) was obtained. Moreover, after the enzymatic treatment, hydrogen peroxide requirements decreased (as reflected by the higher residual peroxide), and the pulp luminance reached a value of 92.5. Addition of known laccase mediators such as HBT, ABTS, and HBA did not improve the process. The supernatant did not significantly lose its bleaching capacity even after successive recovery and reapplication to unbleached pulp. Correspondingly, laccase and manganese peroxidase activities in the recovered supernatant, exhibited near 100% of their initial values.

A wide range of kraft pulps from radiata pine produced by low-temperature kraft pulping in flow-through reactors was assessed for carboxyl and hexenuronic acid (HexA) contents using the conductometric titrations and UV spectrophotometer, respectively. The Kappa number of pulps varied from 20.8 to 84.7 when using a cooking liquor of 1 M effective alkali as Na 2 O, 25% sulfidity, and cooking time of 100-250 min. The experimental results showed that the carboxyl groups (including HexA) and HexA groups dissolved and their residual values in the pulp samples correlate linearly with Kappa number and pulp yield. The dissolving rate of all carboxyl groups is much faster than the loss of HexA. The HexA/lignin ratio decreased non-linearly with Kappa number.

A summary of an EU project concentrating on separation processes for the closed-loop manufacture of bleached kraft pulp is presented. The project includes four separate tasks in which the need and function of specific "kidneys" are studied. In the first task, the reuse of condensates from black liquor evaporation in pulp bleaching has been studied, including a detailed characterization of the condensates. The discharge of accumulating non-process elements (NPEs) from acidic or neutral bleach filtrates was the focus of the second task of the project. Precipitation of NPEs occurs during a separate pre-evaporation of the filtrates to about 20% DS content. Further precipitation may be obtained by pH adjustment to a level where the precipitation and separation properties can be optimized to favour the discharge of some specific NPEs (e.g., silicon). The third task concentrates on the discharge of accumulating compounds from alkaline bleach filtrates by the use of ceramic nanofiltration membranes developed within the project. In the fourth task an overall system analysis of the closed cycle pulp mill is made.

The natural phenolic compounds syringaldehyde and vanillin were compared to the synthetic mediators 1-hydroxybenzotriazole, violuric acid and promazine in terms of boosting efficiency in a laccase-assisted biobleaching of eucalyptus kraft pulp. Violuric acid and 1-hydroxybenzotriazole revealed to be the most effective mediators of the bioprocess. Nevertheless, laccase-syringaldehyde system also improved the final pulp properties (28% delignification and 63.5% ISO brightness) compared to the process without mediator (23% and 61.5% respectively), in addition to insignificant denaturation effect over laccase. The efficiency of the biobleaching process was further related to changes in non-conventionally used optical and chromatic parameters of pulp, such as (L * ), chroma (C * ) and dye removal index (DRI) showing good correlation. Adverse coupling reactions of the natural phenolic mediators on pulp lignin were predicted by electrochemical studies, demonstrating the complexity of the laccase-mediator reaction on pulp.

A new method employing fluorescence microscopy and fluorescence resonance energy transfer (FRET) has been developed to image the surfaces involved in fibre-fibre bonding in situ. Image analysis of fluorescence micrographs indicates that FRET is occurring at the interface of single cellulose fibre crossings. Since FRET occurs over distances of 10-100 angstroms, this technique is capable of investigating fibre-fibre interfaces at the length scale relevant to molecular interactions. The FRET response to wet pressing was examined for single fibre crossings of both never dried white spruce (Picea glauca) and regenerated viscose fibres. Increased wet pressing results in an increased FRET signal for white spruce fibres. The FRET signal for viscose fibre crossings was comparatively low and remained unchanged with increased wet pressing. Nous présentons une théorie en rapport avec l'influence de l'uniformité de la feuille sur plusieurs paramètres structurels du papier et des catégories générales de matières fibreuses stochastiques planaires. La théorie utilise la distribution binomiale négative pour établir la probabilité de la couverture de points par fibres, ce qui permet de dégager des expressions pour les propriétés structurelles des feuilles avec une plus grande variance de la cou-verture que celle observée dans le processus ponctuel de Poisson correspondant.

The pulping potential of the thistle Cynara cardunculus L. was evaluated by studying anatomy and chemical composition of the stalks and Kraft pulp yields and properties. C. cardunculus is a perennial plant, with annual harvests, that can be grown in hot and dry climates with high productivities. The stalk of the plant has a central pith, ca. 45% in volume and 10% in weight, of small parenchyma cells, surrounded by a cortex where numerous fibre vascular bundles are imbedded. The fibres are on average 1.3 mm long, 18.8 mm wide and have a 4.8 mm wall thickness. The whole stalks have 7.7% ash, 14.6% extractives, 17.0% lignin and 53.0% polysaccharides, mainly cellulose and xylans. The pith has more lignin than the depithed stalk (20.3 vs. 13.6%). The Cynara stalks could be cooked by standard Kraft pulping to produce well delignified pulps with high yields (44 -47% with Kappa 11 -15), low rejects and very good strength properties, especially in relation to tensile strength. Depithing of the stalks has a positive impact on pulp yield, chemical consumption and on the pulp strength properties.

This study centred on the analysis of lignin in situ of cloned eucalypt and pine kraft pulps. Trametes versicolor laccase-violuric acid system (LMS) delignifications were performed on a softwood (Pinus pinaster) and a hardwood (Eucalyptus globulus) conventional kraft pulp with an initial kappa number of 34.5 and 15.5, respectively. The LMS treated pulps were then subjected to alkaline extraction stages (E). The kappa number data show that LMS is effective at biodelignifying both softwood and hardwood kraft pulps. However, under the conditions employed in this study, a greater level of biodelignification was obtained with LMS E. globulus (hardwood) than with LMS P. pinaster (softwood), but the amount of lignin removed was higher for the softwood pulp. The original milled wood samples, kraft pulps, biodelignified kraft pulps, and isolated residual lignin and milled wood lignins from the two wood samples have been characterized by pyrolysis-gas chromatography/mass spectrometry. The analysis of the pyrograms indicates that the lignin compositions of the two wood species and corresponding pulps are very different, as expected; however, the knowledge of the chemical mechanisms of delignification is very limited and requires additional work. Analytical pyrolysis is one the few degradative methods for the analysis of biopolymers that has shown a sufficient degree of success. ß

The addition of a phosphonated chelant (DTPMPA) at different points of a TCF bleaching sequence and its effect on pulp properties were studied in this work. An industrial Eucalyptus grandis kraft pulp was submitted to a counter-ion exchange (Ca 2+ or Na + form) and was then bleached using DTPMPA in the washing or in the bleaching stages of two distinct sequences: OOpP and OQOpP (20 pulps). The counter-ion exchange affected fibre length, as well as the handsheets bulk and air permeability (higher for Na + -based pulps) and handsheet tensile strength, brightness, skeletal density, and total porosity based on Hg porosimetry (higher for Ca 2+ -based pulps). The hydrogen peroxide consumption in Op and P stages achieved the lowest values when the chelant was distributed rather than applied in a separate Q stage. The addition of chelant in the P stage provides pulps with higher ISO brightness (>85%). The chelant effects were always more noticeable in Ca 2+ -based pulps.

A synergistic action of xylano-pectinolytic enzymes from the same bacterial isolate Bacillus pumilus was evaluated for the prebleaching of kraft pulp. The enzymatic prebleaching of kraft pulp resulted in 8.5% reduction in kappa number of the pulp, showing remarkable delignification with the enzyme treatment. This approach resulted in 25% reduction in active chlorine consumption in subsequent bleaching stages without any decrease in brightness. Increase in Burst factor (9%), Tear factor (4.6%), Breaking length (4.4%), Double fold number (12.5%), Gurley porosity (4%) and Viscosity (11.8%) of enzyme treated pulp reflected the significant improvement in pulp properties. This is the first report describing the use of xylanase and pectinase produced simultaneously in the same production medium from the same bacterial isolate for effective biobleaching of kraft pulp. Use of this xylano-pectinolytic synergism in paper and pulp industry will ultimately help in making the process not only economically feasible but also ecofriendly.

The pulping potential of the thistle Cynara cardunculus L. was evaluated by studying anatomy and chemical composition of the stalks and Kraft pulp yields and properties. C. cardunculus is a perennial plant, with annual harvests, that can be grown in hot and dry climates with high productivities. The stalk of the plant has a central pith, ca. 45% in volume and 10% in weight, of small parenchyma cells, surrounded by a cortex where numerous fibre vascular bundles are imbedded. The fibres are on average 1.3 mm long, 18.8 mm wide and have a 4.8 mm wall thickness. The whole stalks have 7.7% ash, 14.6% extractives, 17.0% lignin and 53.0% polysaccharides, mainly cellulose and xylans. The pith has more lignin than the depithed stalk (20.3 vs. 13.6%). The Cynara stalks could be cooked by standard Kraft pulping to produce well delignified pulps with high yields (44 -47% with Kappa 11 -15), low rejects and very good strength properties, especially in relation to tensile strength. Depithing of the stalks has a positive impact on pulp yield, chemical consumption and on the pulp strength properties.

This study compares the suitability of using birch kraft pulp or softwood kraft pulp in the preparation of TEMPO-oxidized pulp, MFC and superabsorbent foam. TEMPO oxidation was performed using five different dosages of primary oxidant. The time of disintegration treatment was varied to study its influence on the properties of the produced MFCs and foams. Both the birch and the softwood pulps could be used for producing superabsorbent foams, depending on the process conditions, the absorption capacities were about the same for the two pulps and varied between 25 and 55 g saline solution/g absorbent. The foams based on birch pulp had, however, on average, 30 % higher retention capacity than the foams based on softwood pulp. The maximum retention capacity obtained was 16.6 g saline solution/g absorbent. The greater retention capacity of birch-based foams is not fully understood, but a smaller pore size may be the reason, which in turn would generate greater capillary forces. In addition to this, it was found that birch pulps, contrary to softwood pulps, had a substantial amount of fibers that were relatively unaffected by the disintegration treatment. These oxidized fibers are likely to reinforce the foam, thereby making the foam more resistant to external pressures, which is in accordance with earlier findings.

Eucalypts are among the most important short-rotation hardwoods, planted worldwide for the pulp and paper industry. Even though the genus comprises over 700 species, only about a dozen species are used for pulping purposes, therefore, showing the potential for diversification. Six-year-old eucalypt trees from 12 species (Eucalyptus botryoides, Eucalyptus camaldulensis, Eucalyptus globulus, Eucalyptus grandis, Corymbia maculata, Eucalyptus ovata, Eucalyptus propinqua, Eucalyptus resinifera, Eucalyptus rudis, Eucalyptus saligna, Eucalyptus sideroxylon, and Eucalyptus viminalis) were analyzed for chemical composition, fiber morphological, pulping and handsheet paper properties to determine their kraft pulping suitability. The 12 species showed substantial differences regarding extractives (6.1-18.9%), lignin (21.6-30.8%) and holocellulose content (55.4-70.1%). The high inter-species variation in chemical composition produced pulps with different yields (between 38.9 and 49.8%) and degree of delignification (kappa number between 11.6 and 24.2). The combination of these results with the morphological and handsheet properties suggests that E. globulus, E. ovata, E. grandis, E. saligna and E. botryoides have the best overall characteristics for kraft pulping.

The Policy Research Working Paper Series disseminates the findings of work in progress to encourage the exchange of ideas about development issues. An objective of the series is to get the findings out quickly, even if the presentations are less than fully polished. The papers carry the names of the authors and should be cited accordingly. The findings, interpretations, and conclusions expressed in this paper are entirely those of the authors. They do not necessarily represent the views of the International Bank for Reconstruction and Development/World Bank and its affiliated organizations, or those of the Executive Directors of the World Bank or the governments they represent.

This study centred on the analysis of lignin in situ of cloned eucalypt and pine kraft pulps. Trametes versicolor laccase-violuric acid system (LMS) delignifications were performed on a softwood (Pinus pinaster) and a hardwood (Eucalyptus globulus) conventional kraft pulp with an initial kappa number of 34.5 and 15.5, respectively. The LMS treated pulps were then subjected to alkaline extraction stages (E). The kappa number data show that LMS is effective at biodelignifying both softwood and hardwood kraft pulps. However, under the conditions employed in this study, a greater level of biodelignification was obtained with LMS E. globulus (hardwood) than with LMS P. pinaster (softwood), but the amount of lignin removed was higher for the softwood pulp. The original milled wood samples, kraft pulps, biodelignified kraft pulps, and isolated residual lignin and milled wood lignins from the two wood samples have been characterized by pyrolysis-gas chromatography/mass spectrometry. The analysis of the pyrograms indicates that the lignin compositions of the two wood species and corresponding pulps are very different, as expected; however, the knowledge of the chemical mechanisms of delignification is very limited and requires additional work. Analytical pyrolysis is one the few degradative methods for the analysis of biopolymers that has shown a sufficient degree of success. ß

The study aims to identify the feasibility and the relevance of a genetic selection for enhancing the pulping potential of the Douglas fir wood. At first, wood predictors for TMP potential are identified through the refining of thirty trees 17-year-old, using a specific procedure on a 12" Andritz refiner. The variations of TMP physical properties are linked with those of anatomical parameters, but also with within ring density related traits. The brightness of the unbleached TMP is negatively correlated with the red chromatic component of wood. Lignin, holocellulose and extractives content on one hand, Kraft fibre morphology on the other hand are considered to evaluate roughly the wood potential for the Kraft process. Then 15 clones out of 200 are non destructively selected within a 24-year-old German test to evaluate the range of the genetic variation of the papermaking potential. Chemical analyses give evidence of large variations of the chemical composition ratio between clones (holocellulose/lignin ratio). The clone discrimination of the fibre length is weak, but significant differences of fibre coarseness are observed as a consequence of the large variability of the latewood density levels. The industrial selection gain for pulping is discussed on the basis of TMP pilot plant tests which show large differences of physical and optical TMP properties between average wood assortments of each clone. This leads to practical recommendations for breeders considering the expectations of both the pulping and the wood industry.

Almost all of the kraft pulp bleach plants worldwide are now practicing elemental chlorine-free (ECF) process to comply with environmental regulations in different countries. Usually, these conventional ECF bleaching sequences contain one or two alkaline extraction stages of which the first one is often the principal source of color and chemical oxygen demand (COD) in the resulting effluent. However, the results of this study showed that the ECF sequences which did not include any alkaline extraction stage and contained solely chlorine dioxide decreased both the color and COD loads of the effluent. On the other hand, the ECF sequences containing both chlorine dioxide and hydrogen peroxide but excluding the alkaline extraction stage could lower only the color but not the COD load. It is suggested that the total kappa factor (the ratio of the total active chlorine to the kappa number) affected the COD load and that the content of hexeneuronic acid groups influenced the color of the bl...

The four bacterial strains were isolated on media containing xylan and screened for xylanase activity. The bacterial strains (Ag12, Ag13, Ag20 and Ag32) were characterized based on morphological, biochemical and physiological characters and identified as belonging to the genus Bacillus. The effects of different factors such as pH (7.0-10.0), temperature (25.0-50.0°C) and inexpensive agro-residues (wheat straw, wheat bran and corncob) on xylanase production of strains were studied under shake flask conditions. Maximal enzyme activities were obtained by cultivation in birch-wood xylan, but high enzyme production was also obtained on wheat straw and corncob when cultivated at pH 8.5. Under optimized fermentation conditions, no cellulolytic activity were detected on the crude extracts. The effects of temperature (40.0-80.0°C), pH (6.0-10.0) and salt concentration (1.0, 5.0 and 10.0%) on the xylanases activity were determined. The maximum activity was obtained temperature 60.0°C and pH at 9.0. The enzyme was stable at 60.0°C for more than 60 min, suggesting that the xylanases of Bacillus strains are thermoactive and being of interests for biobleaching processes. The effectiveness of crude xylanases from the strains Ag12, Ag20 and Ag32 on kraft pulp were carried out at pH 9.0 at 60.0°C. Biobleaching studies of kraft pulp with xylanases and its subsequent treatment with 1.0% EDTA (30 min at 50.0°C) and peroxide (80 min at 70.0°C), showed that the enzymes reduced the kappa number by 27.4, 61.7 and 75.3% and enhanced the brightness by 1.0, 1.5 and 3.0% from xylanases produced by strains Ag12, Ag20 and Ag32, respectively. These results suggest that the application of this xylanases to the paper and pulp industry may be very promising.

Industrially made kraft pulps obtained by a modified cooking process may contain 60-75 mmol/kg of hexenuronic acids (HexAs), which represents 6-7.5 kappa units. HexAs do not react with oxygen and very little of it is actually removed across the oxygen delignification stage, causing low efficiencies in the range of 25-35%. In this study, an economical evaluation of the ECF bleaching processes was carried out, having none and double-stage oxygen delignification, when applied to eucalyptus pulps of kappa varying in the range of 14-21. The bleaching processes included sequences containing specific stages for HexAs removal (Z, A/D and D HT). Results indicated that the use of oxygen delignification was not economically attractive, particularly for HexA-rich low-kappa pulps, but processes without oxygen delignification present significant environmental challenges.

Cellulosic fiber interfaces are critical to the material properties of paper. Likewise, the presence of water in a paper sheet is an important property, because paper is a wet-laid structure and the cellulosic fibers that compose it are hygroscopic. This work uses a fluorescence microscopy technique established by the authors to study the development of individual bleached kraft pulp fiber crossings in situ during drying and through a cycle of rewetting and wet pressing. The results indicate that coalescence of the fiber-fiber interface occurs during drying and that the fluorescence resonance energy transfer (FRET) response, which is proportional to the distance between fiber components, increases logarithmically with time. The FRET signal of once-dried fiber crossings increases dramatically after rewetting and wet pressing for a second time. This indicates that fiber bonds are still compliant after a single drying cycle and that the interactions between fiber components are likely reversible at the solids content present in bleached kraft pulp fiber crossings dried at 258C and 50% relative humidity.

In an effort to alter the physical properties of high-yield kraft, fibers were treated at high consistency (20%) with laccase and syringic, vanillic, or 4-hydroxybenzoic acid. Treatment with laccase and 4-hydroxybenzoic acid resulted in a 20-point increase in kappa number and a 100% increase in bulk acid groups. ESCA analysis of the treated and untreated pulp revealed that the laccase-grafted fibers had a twofold enrichment in acid groups, strongly suggesting a laccase-facilitated coupling of 4-hydroxybenzoic acid to the fiber surface. A model system consisting of lignin-coated cellulosic fibers was developed to determine changes to the lignin structure during laccase grafting. 31 P NMR analysis of lignin from the model system revealed an increase in acid groups with a concomitant decrease in phenolic hydroxyl groups.

A wide range of kraft pulps from radiata pine produced by low-temperature kraft pulping in flow-through reactors was assessed for carboxyl and hexenuronic acid (HexA) contents using the conductometric titrations and UV spectrophotometer, respectively. The Kappa number of pulps varied from 20.8 to 84.7 when using a cooking liquor of 1 M effective alkali as Na 2 O, 25% sulfidity, and cooking time of 100-250 min. The experimental results showed that the carboxyl groups (including HexA) and HexA groups dissolved and their residual values in the pulp samples correlate linearly with Kappa number and pulp yield. The dissolving rate of all carboxyl groups is much faster than the loss of HexA. The HexA/lignin ratio decreased non-linearly with Kappa number.

Trametes trogii (BAFC 463), Coriolus versicolor var. antarcticus (BAFC 266) and Trametes villosa (BAFC 2755) are Argentinean white-rot fungi that proved to be efficient ligninolytic enzyme producers in previous studies. The aim of the present work was investigating the ability of their crude ...

The kinetics of enzyme treatment of hardwood kraft pulp with commercial xylanase Cartazyme NS-10 was investigated. The enzyme treatment process was found to follow closely the topochemical modified equation of Prout–Tompkins. The influence of the initial enzyme concentration was studied and the applicability of the power kinetic equation was established for the initial rate of the process. An equation of

The effects of multiple xylanase treatments were assessed during the peroxide bleaching of three pulps: Douglas-fir (kraft); Western hemlock (oxygen delignified kraft); and trembling Aspen (kraft). The addition of a xylanase treatment stage, either before or after the peroxide bleaching stage(s), resulted in the enhanced brightening of all pulps. A higher brightness was achieved using two enzyme treatments, one before and one after the peroxide stage(s). Both bleach boosting and direct brightening seemed to contribute to the enhancement of peroxide bleaching. Compared to xylanase prebleaching, xylanase posttreatment of the peroxide bleached pulps solubilized less lignin and chromophores and made smaller amounts of these materials alkaline soluble. Nevertheless, the final brightness achieved by xylanase posttreatment was similar or superior to that achieved with xylanase prebleaching of the corresponding unbleached pulps.

The addition of a phosphonated chelant (DTPMPA) at different points of a TCF bleaching sequence and its effect on pulp properties were studied in this work. An industrial Eucalyptus grandis kraft pulp was submitted to a counter-ion exchange (Ca 2+ or Na + form) and was then bleached using DTPMPA in the washing or in the bleaching stages of two distinct sequences: OOpP and OQOpP (20 pulps). The counter-ion exchange affected fibre length, as well as the handsheets bulk and air permeability (higher for Na +-based pulps) and handsheet tensile strength, brightness, skeletal density, and total porosity based on Hg porosimetry (higher for Ca 2+-based pulps). The hydrogen peroxide consumption in Op and P stages achieved the lowest values when the chelant was distributed rather than applied in a separate Q stage. The addition of chelant in the P stage provides pulps with higher ISO brightness (>85%). The chelant effects were always more noticeable in Ca 2+-based pulps.

The importance of enzymes as biotechnological catalysts for paper industry is now recognized. In this study, five cellulase formulations were used for fibre modification. The number of PFI revolutions decreased by about 50% while achieving the same freeness value (decrease in CSF by 200 mL) with the enzymatic pretreatment. The physical properties of handsheets were modified after enzymatic pretreatment followed by PFI refining. A slight decrease in tear strength was observed with enzymes C1 and C4 at pH 7 while the most decrease in tear was observed after C2, C3, C5 treatments. C1 and C4 which had xylanase activity improved paper properties, while other enzymes had a negative impact. Therefore, the intricate balance between cellulolytic and hemicellulolytic activity is the key to optimizing biorefining and paper properties. It was also observed that C1 impact was pH dependent, which supports the importance of pH in developing an enzymatic strategy for refining energy reduction.

O objetivo deste estudo foi avaliar a densidade básica, a composição química e as dimensões de fibras de dez amostras de madeira de Eucalyptus spp. e, verificar o impacto desse conjunto de parâmetros e sua combinação no rendimento do processo de polpação kraft e na qualidade da polpa branqueada. A madeira de dez espécies de eucalipto, com densidade básica variando entre 365 a 544 kg/m3 e teores de carboidratos totais variando entre 70,0 a 74,5% foi transformada em polpa Kraft, com número kappa 15,5-16,7 e branqueada a 90% ISO por uma seqüência de quatro estágios (OD(PO)D) composta de deslignificação com oxigênio (O), deslignificação com dióxido de cloro (D),  extração alcalina com peróxido pressurizado (PO) e branqueamento com dióxido de cloro (D). A densidade básica da madeira mostrou melhor correlação com as dimensões da fibra e qualidade da polpa que a sua composição química. Porém o rendimento depurado foi mais influenciado pela composição química da madeira do que pela densidad...

Industrially made kraft pulps obtained by a modified cooking process may contain 60-75 mmol/kg of hexenuronic acids (HexAs), which represents 6-7.5 kappa units. HexAs do not react with oxygen and very little of it is actually removed across the oxygen delignification stage, causing low efficiencies in the range of 25-35%. In this study, an economical evaluation of the ECF bleaching processes was carried out, having none and double-stage oxygen delignification, when applied to eucalyptus pulps of kappa varying in the range of 14-21. The bleaching processes included sequences containing specific stages for HexAs removal (Z, A/D and D HT ). Results indicated that the use of oxygen delignification was not economically attractive, particularly for HexA-rich low-kappa pulps, but processes without oxygen delignification present significant environmental challenges.

The study aims to identify the feasibility and the relevance of a genetic selection for enhancing the pulping potential of the Douglas fir wood. At first, wood predictors for TMP potential are identified through the refining of thirty trees 17-year-old, using a specific procedure on a 12" Andritz refiner. The variations of TMP physical properties are linked with those of anatomical parameters, but also with within ring density related traits. The brightness of the unbleached TMP is negatively correlated with the red chromatic component of wood. Lignin, holocellulose and extractives content on one hand, Kraft fibre morphology on the other hand are considered to evaluate roughly the wood potential for the Kraft process. Then 15 clones out of 200 are non destructively selected within a 24-year-old German test to evaluate the range of the genetic variation of the papermaking potential. Chemical analyses give evidence of large variations of the chemical composition ratio between clones (holocellulose/lignin ratio). The clone discrimination of the fibre length is weak, but significant differences of fibre coarseness are observed as a consequence of the large variability of the latewood density levels. The industrial selection gain for pulping is discussed on the basis of TMP pilot plant tests which show large differences of physical and optical TMP properties between average wood assortments of each clone. This leads to practical recommendations for breeders considering the expectations of both the pulping and the wood industry.

A synergistic action of xylano-pectinolytic enzymes from the same bacterial isolate Bacillus pumilus was evaluated for the prebleaching of kraft pulp. The enzymatic prebleaching of kraft pulp resulted in 8.5% reduction in kappa number of the pulp, showing remarkable delignification with the enzyme treatment. This approach resulted in 25% reduction in active chlorine consumption in subsequent bleaching stages without any decrease in brightness. Increase in Burst factor (9%), Tear factor (4.6%), Breaking length (4.4%), Double fold number (12.5%), Gurley porosity (4%) and Viscosity (11.8%) of enzyme treated pulp reflected the significant improvement in pulp properties. This is the first report describing the use of xylanase and pectinase produced simultaneously in the same production medium from the same bacterial isolate for effective biobleaching of kraft pulp. Use of this xylano-pectinolytic synergism in paper and pulp industry will ultimately help in making the process not only economically feasible but also eco-friendly.

The zeta potential and cationic demand of various kraft pulps-unbleached, bleached and beaten to different wetness levels-were determined in the laboratory. The magnitude of zeta potential of pulp where the final stage was a lignin degrading and dissolving treatment, such as alkaline extraction or hypochlorite, was lower than that of unbleached pulp. The cationic demand of bleached pulp was lower compared to that of unbleached pulp. Beaten pulps showed larger cationic demands than the unbeaten pulps, which can be attributed to the larger specific surface area of pulp components. Fibres become increasingly electronegative when beaten, and therefore, cationic demand of pulps increases with beating. When the zeta potential method is used with pulp furnishes of different wetness, an almost linear relationship is observed between added polyamine and attained zeta potential. However, the slope of the curve is decreased with the increase in wetness of the pulp.

Effects of microwave drying on the mechanical and optical properties of handsheets made from kraft and chemi-thermomechanical pulps were studied experimentally. The quality of paper dried in a microwave field of 2450 MHz is compared with that of paper dried by conventional method under standard conditions. All properties were found to be either enhanced or at the same level as those obtained under standard conditions. Since microwave field allows volumetric heating of moisture, the drying time is much shorter due to reduced resistance to heat and mass transfer within the paper. Furthermore, it is suggested that microwave drying could replace the conventional drying method in the standard testing of pulp and paper samples for quality control purposes.

Grafting natural antibacterial phenols onto lignocellulosic materials is an environmentally friendly way of imparting antibacterial properties to the substrates. In the present investigation, wood veneer and pulp were treated with tannins in the presence or absence of laccase. Treatments with hydrolysable tannins significantly improved the antibacterial resistance of veneers and paper made from tannin-treated pulp against a Gram-positive bacterium (Staphylococcus aureus) while a more modest protective effect was observed against a Gram-negative bacterium (Escherichia coli). Condensed tannin improved the antibacterial resistance against S. aureus, albeit less than hydrolysable tannin, but had little effect on E. coli. A cationic condensed tannin derivative bearing a quaternary amino group provided far better resistance to pulp against S. aureus and E. coli than the corresponding unmodified condensed tannin. These findings agree with the minimal inhibitory concentrations (MICs) of the tannins and their reactivities toward laccase as determined by O 2 consumption measurements. Due to a better retention of tannins via covalent bonding, treatments with laccase usually resulted in greater antibacterial effects than those without laccase. LC-MS investigations with monomeric tannin and lignin model compounds showed that covalent bonding of tannin to lignin via radical coupling occurred in the presence of laccase.