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Academic literature on the topic 'Softwood kraft pulp'

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Published: 4 June 2021

Last updated: 2 February 2022

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Journal articles on the topic "Softwood kraft pulp"

GUSTAFSON, RICHARD, GAURAV RAYAL, MING QIAO, and JINGLIANG MAO. "The Nature of Single Fiber Kappa Distributions." March 2009 8, no. 3 (April 1, 2009): 26–31. http://dx.doi.org/10.32964/tj8.3.26.

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We examined the uniformity of a variety of kraft pulps with the University of Washington’s single fiber kappa analyzer (FKA). Some consistent patterns and trends with regard to pulp uniformity have emerged. This paper provides a synthesis of the significant observations we made in examining the kappa uniformity of kraft pulps. Hardwood pulps are generally more uniform than pulps from softwoods, but all the single fiber kappa distributions are broad. Virtually all softwood pulps have high kappa tails, whereas hardwood pulps have a high kappa tail only if the pulping is extremely non-uniform. Hardwood pulp kappa distributions appear to be Gaussian. Softwood pulps from commercial digesters are generally much less uniform than those made in the laboratory. The differences in uniformity in hardwood pulps from laboratory and commercial digesters are less dramatic than for softwood pulps. Hardwoods that we have examined appear to be much easier to pulp with uniformity than softwoods.

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Kühne, L., J. Odermatt, and T. Wachter. "Application of a Catalyst in Peroxide Bleaching of Eucalyptus Kraft Pulp." Holzforschung 54, no. 4 (July 4, 2000): 407–12. http://dx.doi.org/10.1515/hf.2000.068.

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Summary A binuclear [Mn(III)Mn(IV)(μ-O)2(μ-CH3COO)L](ClO4−)2 complex with L = 1,2 Bis-(4,7-dimethyl-1,4,7-triazacyclonon-1-yl)-ethane, described as a selective catalyst in hydrogen peroxide bleaching of softwood pulps, was tested in hardwood kraft pulp bleaching. The catalyst application gave rise to a higher consumption of peroxide which resulted in higher pulp brightness. The delignification improvement caused by the catalyst was shown to be much lower compared to catalysed peroxide bleaching of softwood kraft pulp. In contrast to the results of softwood pulp bleaching no selectivity improvements could be found when using the catalyst in bleaching of eucalyptus kraft pulp.

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POTUCEK, FRANTIŠEK, MOSTAFIZUR RAHMAN, and JOZEF MIKLÍK. "DISPLACEMENT WASHING OF KRAFT PULP WITH VARIOUS CONSISTENCY." Cellulose Chemistry and Technology 54, no. 9-10 (November 11, 2020): 943–52. http://dx.doi.org/10.35812/cellulosechemtechnol.2020.54.91.

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The paper deals with the displacement washing of kraft softwood and hardwood pulps with various consistency of the pulp fibre bed. The results obtained revealed differences between the two types of kraft pulp with various morphological properties of fibres. The washing efficiency decreased with decreasing Péclet number for both kraft pulps, but, due to lower longitudinal dispersion of the wash liquid, greater washing efficiency was achieved for the short-fibred hardwood pulp. On the other hand, the long-fibred softwood pulp exhibited lower hydraulic resistance of the pulp fibre bed. The change in pulp consistency and, similarly, the volumetric mass transfer coefficient, characterising the rate of leaching of alkali lignin from pulp fibres, did not have a significant effect on the washing efficiency. However, the mass transfer coefficient decreased with increasing specific resistance of the pulp bed. With increasing bed consistency of both softwood and hardwood pulps, as the amount of black liquor in the inter-fibre pores decreased, the difference between the space time, characterising the holding time of wash liquid, and the mean residence time of alkali lignin increased.

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Yanagisawa, Masahiro, and Akira Isogai. "Size exclusion chromatographic and UV-VIS absorption analyses of unbleached and bleached softwood kraft pulps using LiCl/1,3-dimethyl-2-imidazolidinone as a solvent." Holzforschung 61, no. 3 (May 1, 2007): 236–41. http://dx.doi.org/10.1515/hf.2007.046.

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Abstract Unbleached and bleached kraft pulps and holocellulose prepared from softwood were totally soluble in 8% LiCl/1,3-dimethyl-2-imidazolidinone (LiCl/DMI). The solutions were analyzed by size exclusion chromatography with photodiode array and multi-angle laser light scattering detection (SEC-PDA-MALLS). The mobile phase consisted of 1% LiCl/DMI. The degree of polymerization (DP) and DP distribution of the softwood kraft pulps were determined, as well as the DP distribution of residual lignins based on their UV-VIS absorption patterns. Changes in DP for kraft pulps after a conventional bleaching sequence were evaluated, and the residual lignins were analyzed in the same way. Approximately half of the residual lignin in unbleached and bleached kraft pulps was present in polysaccharide fractions with high DP, which represented approximately 90% of the total yield. Some characteristic differences in the UV-VIS absorption pattern were observed between kraft pulps bleached with oxygen and chlorine. DP, DP distribution of polysaccharides, and distribution of residual lignin were clearly different for unbleached kraft pulp, unbleached sulfite pulp, and holocellulose. An unbleached kraft pulp prepared from hardwood showed different properties to the corresponding softwood preparation. The UV-VIS absorption patterns due to residual lignins were also very characteristic for the various pulps and holocellulose.

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Janzon, Ron, Jürgen Puls, and Bodo Saake. "Upgrading of paper-grade pulps to dissolving pulps by nitren extraction: Optimisation of extraction parameters and application to different pulps." Holzforschung 60, no. 4 (July 1, 2006): 347–54. http://dx.doi.org/10.1515/hf.2006.055.

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Abstract Xylans were selectively removed from paper-grade pulps by nitren extraction to produce dissolving pulps. Extraction parameters were optimised for a birch kraft pulp regarding time, temperature, liquor/pulp ratio, and total nitren charge. Furthermore, the applicability of the method was investigated for two other kraft pulps obtained from eucalyptus and mixed softwood, and for one beech sulfite pulp. Extracted pulps were characterised regarding their carbohydrate content and Cuen viscosity. The nitren charge was a decisive factor for xylan removal and pulp purity. The combination of a high nitren concentration and low liquor/pulp ratio was most effective for xylan removal. However, a high liquor/pulp ratio with a lower nitren concentration proved to be more selective and minimised cellulose degradation as well. Glucomannans were almost insoluble under the extraction conditions investigated. Therefore, softwood pulps were not suitable for the upgrading of chemical pulps to dissolving pulps by nitren extraction. On the other hand, hardwood pulps obtained by kraft and sulfite processes contained 96–97% cellulose after nitren extraction.

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Aksenov, Andrey S., Irina V. Tyshkunova, Daria N. Poshina, Anastasia A. Guryanova, Dmitry G. Chukhchin, Igor G. Sinelnikov, Konstantin Y. Terentyev, Yury A. Skorik, Evgeniy V. Novozhilov, and Arkady P. Synitsyn. "Biocatalysis of Industrial Kraft Pulps: Similarities and Differences between Hardwood and Softwood Pulps in Hydrolysis by Enzyme Complex of Penicillium verruculosum." Catalysts 10, no. 5 (May 13, 2020): 536. http://dx.doi.org/10.3390/catal10050536.

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Kraft pulp enzymatic hydrolysis is a promising method of woody biomass bioconversion. The influence of composition and structure of kraft fibers on their hydrolysis efficiency was evaluated while using four substrates, unbleached hardwood pulp (UHP), unbleached softwood pulp (USP), bleached hardwood pulp (BHP), and bleached softwood pulp (BSP). Hydrolysis was carried out with Penicillium verruculosum enzyme complex at a dosage of 10 filter paper units (FPU)/g pulp. The changes in fiber morphology and structure were visualized while using optical and electron microscopy. Fiber cutting and swelling and quick xylan destruction were the main processes at the beginning of hydrolysis. The negative effect of lignin content was more pronounced for USP. Drying decreased the sugar yield of dissolved hydrolysis products for all kraft pulps. Fiber morphology, different xylan and mannan content, and hemicelluloses localization in kraft fibers deeply affected the hydrolyzability of bleached pulps. The introduction of additional xylobiase, mannanase, and cellobiohydrolase activities to enzyme mixture will further improve the hydrolysis of bleached pulps. A high efficiency of never-dried bleached pulp bioconversion was shown. At 10% substrate concentration, hydrolysates with more than 50 g/L sugar concentration were obtained. The bioconversion of never-dried BHP and BSP could be integrated into working kraft pulp mills.

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Chen, Zhiwen, Thomas Q. Hu, Ho Fan Jang, and Edward Grant. "Multivariate Analysis of Hemicelluloses in Bleached Kraft Pulp Using Infrared Spectroscopy." Applied Spectroscopy 70, no. 12 (October 28, 2016): 1981–93. http://dx.doi.org/10.1177/0003702816675363.

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The hemicellulose composition of a pulp significantly affects its chemical and physical properties and thus represents an important process control variable. However, complicated steps of sample preparation make standard methods for the carbohydrate analysis of pulp samples, such as high performance liquid chromatography (HPLC), expensive and time-consuming. In contrast, pulp analysis by attenuated total internal reflection Fourier transform infrared spectroscopy (ATR FT-IR) requires little sample preparation. Here we show that ATR FT-IR with discrete wavelet transform (DWT) and standard normal variate (SNV) spectral preprocessing offers a convenient means for the qualitative and quantitative analysis of hemicelluloses in bleached kraft pulp and alkaline treated kraft pulp. The pulp samples investigated include bleached softwood kraft pulps, bleached hardwood kraft pulps, and their mixtures, as obtained from Canadian industry mills or blended in a lab, and bleached kraft pulp samples treated with 0–6% NaOH solutions. In the principal component analysis (PCA) of these spectra, we find the potential both to differentiate all pulps on the basis of hemicellulose compositions and to distinguish bleached hardwood pulps by species. Partial least squares (PLS) multivariate analysis gives a 0.442 wt% root mean square errors of prediction (RMSEP) for the prediction of xylan content and 0.233 wt% RMSEP for the prediction of mannan content. These data all support the idea that ATR FT-IR has a great potential to rapidly and accurately predict the content of xylan and mannan for bleached kraft pulps (softwood, hardwood, and their mixtures) in industry. However, the prediction of xylan and mannan concentrations presented a difficulty for pulp samples with modified cellulose crystalline structure.

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Lund, Kristoffer, Karin Sjöström, and Harald Brelid. "Alkali Extraction of Kraft Pulp Fibers: Influence on Fiber and Fluff Pulp Properties." Journal of Engineered Fibers and Fabrics 7, no. 2 (June 2012): 155892501200700. http://dx.doi.org/10.1177/155892501200700206.

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The importance of hemicelluloses for the papermaking properties of pulp fibers is well documented. In the patent literature, it can be seen that there is also an interest in this type of modification of pulp fibers for use in absorption products. In this study, a Scandinavian softwood kraft pulp and a birch kraft pulp were alkali extracted at 3 different concentrations of NaOH (2%, 4% and 8% NaOH in the suspension). The alkali extraction removed a large part of the hemicelluloses from the pulp fibers and decreased the content of the charged groups. After extraction, the pulps were dried in the form of sheets (approx. 600 g/m2). The alkali extracted pulp fibers exhibited a greater decrease in swelling when re-wetted than untreated pulp. A significant increase in the curl index after extraction with 4% and 8% NaOH was also noted. The tensile strength index of the formed sheets increased at the lowest concentration of NaOH and, at the higher concentrations, a decrease was observed. The pulp sheets were dry defibrated at different defibration intensities and the performance of the resulting pulps in fluff pulp applications was studied. The air-laid fiber networks of softwood pulp fibers showed higher network strength than the networks of birch pulps. The birch pulp extracted at the highest alkali level tended to give the highest network strength. The results from the network strength tests also indicated that the increased curl of the fibers from the softwood pulp extracted at the highest alkali level rendered a more flexible fiber network. In water absorption tests, the alkali treated softwood fibers tended to give networks with a somewhat enhanced water holding capacity under pressure.

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Brelid, Harald, Tornrny Friberg, and Rune Sirnonson. "TCF bleaching of softwood kraft pulp." Nordic Pulp & Paper Research Journal 10, no. 4 (December 1, 1995): 222–26. http://dx.doi.org/10.3183/npprj-1995-10-04-p222-226.

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Brelid, Harald, Tommy Friberg, and Rune Simonson. "TCF bleaching of softwood kraft pulp." Nordic Pulp & Paper Research Journal 11, no. 2 (May 1, 1996): 105–8. http://dx.doi.org/10.3183/npprj-1996-11-02-p105-108.

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Dissertations / Theses on the topic "Softwood kraft pulp"

Yuan, Zhirun. "Peracetic acid brightening of softwood kraft pulp." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp02/NQ29474.pdf.

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Toven, Kai. "Ozone based ECF bleaching of softwood kraft pulp." Doctoral thesis, Norwegian University of Science and Technology, Department of Chemical Engineering, 2000. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-457.

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The objective of this work was to explore fundamental aspects of utilizing (DZ) and (ZD) bleaching stages in the prebleaching of oxygen delignified Scandinavian softwood kraft pulp, and compare paper properties of fully bleached pulps with a DEoD₁ED₂ bleached EDF reference pulp. According to the literature, the use of chlorine dioxide and ozone in combination in (DZ) and (ZD) bleaching stages seems advantageous from both environmental and economical points of view. A significant reduction in the formation of chloro-organic compounds and efficient delignification relative to chemical consumption is obtained.

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Sillanpää, M. (Mervi). "Studies on washing in kraft pulp bleaching." Doctoral thesis, Oulun yliopisto, 2005. http://urn.fi/urn:isbn:9514278771.

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Abstract Washing during kraft pulping can be divided into two separate areas each with its own distinct features: namely brownstock washing and washing in bleaching. Research interest has so far concentrated mostly on investigating brownstock washing and factors affecting its efficiency. Pulp washing in bleaching, however, has been practically neglected. The basic phenomena are the same as in brownstock washing, but there are differences which have not been taken into consideration to a sufficient extent. This less explored area is the focus of this research. In this thesis, it is shown that brownstock washing and pulp washing between bleaching stages are distinct areas with their own specific features. They differ for example in terms of the composition and molecular size of the impurities in the pulp suspension. Various process conditions, pH, temperature and so on cause further differences between washing in bleaching and brownstock washing. The removal of specific compounds can be clearly affected by the appropriate selection of wash liquor. It is shown that the dynamic behaviour during washing is different for different compounds and depends on the properties of the wash water. The key element is to find the most harmful compounds in specific positions in bleaching and on the basis of that finding, to determine the most suitable wash liquor system. Chemical oxygen demand (COD) is a widely used method for evaluating the washing result, but as a collective measurement variable it does not describe the actual compounds that cause the "loss" of bleaching chemicals. Studies have shown that many compounds contribute to COD load but ultimately most of them have no real effect on the bleaching result. A suggestion for more precise definition of wash loss is offered than COD.

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Karlsson, Hanna. "Strength Properties of Paper produced from Softwood Kraft Pulp : Pulp Mixture, Reinforcement and Sheet Stratification." Doctoral thesis, Karlstads universitet, Avdelningen för kemiteknik, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-5612.

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For paper producers, an understanding of the development of strength properties in the paper is of uttermost importance. Strong papers are important operators both in the traditional paper industry as well as in new fields of application, such as fibre-based packaging, furniture and light-weight building material. In the work reported in this thesis, three approaches to increasing paper strength were addressed: mixing different pulps, multilayering and reinforcement with man-made fibres. In specific: The effects of mixing Swedish softwood kraft pulp with southern pine or with abaca (Musa Textilis) were investigated. Handsheets of a softwood kraft pulp with the addition of abaca fibres were made in a conventional sheet former. It was seen that the addition of abaca fibres increased the tearing resistance, fracture toughness, folding endurance and air permeance. Tensile strength, tensile stiffness and tensile energy absorption, however, decreased somewhat. Still it was possible to add up to about 60% abaca without any great loss in tensile strength. As an example, with the addition of 30% abaca, the tear index was increased by 36%, while the tensile index was decreased by 8%. To study the effect of stratification, a handsheet former for the production of stratified sheets, the LB Multilayer Handsheet Former was evaluated. The advantage of this sheet former is that it forms a stratified sheet at low consistency giving a good ply bond. It was shown to produce sheets with good formation and the uniformity, evaluated as the variation of paper properties, is retained at a fairly constant level when the number of layers in the stratified sheets is increased. The uniformity of the sheets produced in the LB Multilayer Handsheet Former is generally at the same level as of those produced in conventional sheet formers. The effects of placing southern pine and abaca in separate layers, rather than mixing them homogeneously with softwood pulp were studied. Homogeneous and stratified sheets composed of softwood and southern pine or softwood and abaca were produced in the LB Multilayer Handsheet Former. It was found that by stratifying a sheet, so that a pulp with a high tear index and a pulp with a high tensile index are placed in separate layers, it was possible to increase the tear index by approximately 25%, while the tensile index was decreased by 10-20%. Further, by mixing a pulp with less conformable fibres and no fines with a pulp with more flexible fibres and fines, a synergy in tensile strength (greater strength than that predicted by linear mass fraction additivity) was obtained. The effects of stratifying sheets composed of softwood and abaca were compared to the effects of refining the softwood pulp. Homogeneous and stratified sheets composed of softwood with three different dewatering resistances and abaca were also produced in the LB Multilayer Handsheet Former. It was found that by stratifying the sheets the tear index was retained while the tensile index was increased by the refining. The effects of reinforcing softwood pulp of different dewatering resistances with man-made fibres with low bonding ability were also investigated. Man-made fibres (i.e. regenerated cellulose, polyester and glass fibres) were added in the amounts 1, 3, or 5 wt% to softwood pulp of three different dewatering resistances. It was found that with refining of a softwood pulp and subsequent addition of long fibres with low bonding ability the tensile-tear relationship can be shifted towards higher strength values. The bonding ability of the man-made fibres was evaluated by pull-out tests and the results indicated that, in relation to the fibre strength, regenerated cellulose (lyocell) was most firmly attached to the softwood network while the glass fibres were most loosely attached.

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Mackinnon, John 1963. "Dynamic simulation of the first two stages of a kraft softwood bleach process." Thesis, McGill University, 1987. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=66188.

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Svedinger, Andersson Maria. "The Effect of Different Xylan Contents on the Strength Properties of Softwood Kraft pulp." Thesis, Karlstads universitet, Fakulteten för teknik- och naturvetenskap, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-28850.

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The aim of this Master thesis was to investigate if the xylan content had any influence on the physical properties of softwood kraft pulps. To achieve pulps with different xylan content different kraft cooking conditions were used; two different temperatures and two different effective alkali levels. The cooking conditions used were 160°C with 30% effective alkali (EA) referred to as reference cook and 145°C with 17% effective alkali (EA) referred to as the mild cook. The first step in this study was to determine the cooking time needed for reaching a certain kappa number, i.e.30. It was also determined whether the difference in xylan content between the pulp samples was sufficient when these cooking conditions were used. When the correct cooking time and cooking conditions had been found new cooks were made using these conditions. All cooks were made at a liqour to wood ratio of 4:1. The difference in xylan content between the corresponding pulp samples was found to be 3%. The physical testing showed no significant difference in the tensile strength between the two pulps after beating. There was a difference in tear index however and the pulp with the highest content of xylan had the lowest tear index. Zero-span index was the same for the two pulps when unbeaten. After beating the zero-span index decreased for the pulp with highest xylan content but stayed unchanged for the pulp with the lower amount of xylan. These results can be explained by the results from the fibre analysis which showed that the fibres with high xylan content were longer, thicker and had a higher coarseness. Thicker fibres are probably stiffer than thinner fibres which gives the paper fewer bonding points and a lower strength. The result from the zero-span test indicated that the fibres with higher xylan content are affected more by beating than fibres with the lower xylan content.
Målet med examensarbetet var att undersöka om och hur mycket xylaneti pappersmassan påverkar fiberns och därmed papperets fysikaliska egenskaper. Egenskaperna som undersöktes var drag- och rivstyrka samt zero-spanstyrka. Xylaninnehållet skulle varieras genom att kokförhållandena förändrades dels genom olika koktemperaturer dels olika satsningar av effektivt alkali vid given sulfiditet. Dessa var 160ºC med 30% effektivt alkali(EA) hädanefter benämnd referenskoket och 145ºC med 17% effektivt alkali(EA) som benämns det milda koket i fortsättningen.En bestämning av koktiden gjordes för att nå 30 i kappatal och två provkok, ett vid varje temperatur behövde göras.Skillnaden i xylanhalt mellan de slutliga massaproverna låg på c:a 3% enheter. Styrkeproverna gav inga entydiga svar på om skillnaden i xylanhalt gav någon effekt på massastyrkan. Dragproverna visade att för omald massa var massan från referenskoket starkast men att massan från det mildare koket reagerade kraftigare på malningen. Redan vid 1000 varv hade den i princip samma dragindex som referensmassan vid samma malgrad. Zero-span mätningarna visade att fibrerna hade samma styrka när de var omalda. Resultaten från fiberanalysenverifierade resultaten från styrketesterna eftersom en tjockare fiber bör ge en styvare fiber och därmed erhålls färre bindningspunkter. Färre bindningspunkter ger en lägre dragstyrka och det krävs mindre energi för att bryta bindningarna. Efter malningen kan man se att zero-span styrkan har minskat betydligt för massan med högre xylanhalt medan referensmassan behöll styrkan. Dessutom har dragstyrkan ökat för båda massorna men mest för massan med högre xylanhalt. Det kan förklaras med att malningen ger små fibriller på ytan av fibern och en mjukare och böjligare fiber. Därmed ökar bindningsstyrkan då bindningsarean ökar och fibern blir mjukare och böjligare. Den ökade bindningsgraden samt den minskade fiberstyrkan kan förklara varför rivindex fortfarande var lägre för massan med högre xylanhalt trots att dragindex ökade med ökad malning.En annan förklaring kan vara att vid ett långt kok med låg temperatur är det troligt att lignin adsorberas på fibrerna.Ligninet på ytan ger en sämre bindningsförmåga vilket leder till att de är lättare att dra ur nätverket med lägre energiåtgång som följd.

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Rahman, Hafizur. "Modifying kraft pulping to produce a softwood pulp requiring less energy in tissue paper production." Licentiate thesis, Mittuniversitetet, Avdelningen för kemiteknik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:miun:diva-32833.

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Modification of softwood kraft pulp by the addition of either polysulfide (PS) or sodium borohydride (NaBH4) has been shown to increase the pulp yield due to a higher retention of glucomannan. The pulps with higher yield gave a paper with higher tensile index than reference pulp, especially at lower degrees of refining. The higher yield pulps also showed a greater porosity of the fibre wall, indicating an increase in the swelling potential of the fibres. This can lead to increased fibre flexibility and increased joint strength between the fibres and to the higher handsheet tensile index. However, the swelling increase associated with the higher hemicellulose content could also make dewatering more challenging because of the higher water retention of the pulp. The results of this study show however that the positive influence of the increase in yield (fewer fibres and a more open sheet structure) dominates over the negative influence of the higher hemicellulose content on the dewatering properties, especially at lower refining energy levels. Studies simulating full-scale tissue machine dewatering conditions showed that pulps with a higher yield and a higher hemicellulose content had a higher tensile index at the same dryness. Moreover, the same dryness level was achieved in a shorter dwell-time. A given tensile index was also achieved with less refining energy. Increasing the yield and hemicellulose content by the addition of either an oxidizing or a reducing agent in the softwood kraft pulping process thus has a potential for giving high quality fibres for tissue paper production with less refining energy and lower drying energy costs.

Vid tidpunkten för framläggningen av avhandlingen var följande delarbeten opublicerade: delarbete 2 inskickat.

At the time of the defence the following papers were unpublished: paper 2 submitted.

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Sugiharto, Andoyo. "The effect of chemical and xylanese pretreatment on the quality of softwood kraft pulp bleached with CED sequence." Thesis, Georgia Institute of Technology, 1993. http://hdl.handle.net/1853/25316.

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Melander, Erik. "The effect of charged groups on the beatability of pulp fibres." Thesis, KTH, Skolan för kemivetenskap (CHE), 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-35226.

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The purpose of this bachelor thesis was to investigate how charged groups within the pulp fibre affect the beatability and the strength of the papers. To obtain different levels of charges on the pulp it was carboxymethylated. The different pulp samples were beaten to different degrees to investigate how charges interact with the beating. A PFI-mill was used for the beating because of the relatively homogenous effect on the fibres and the low demand for pulp fibres for each beating. The influence of the amount of charged groups on the surface and bulk swelling, as a result of the beating process, was evaluated. The fibres were then analysed in a Fibre tester and using a microscope to see what had happened to the fibre structure. The results showed that the PFI-mill mainly affects the surface of the fibres. The beatability, defined as the swelling obtain for a specific energy input, was greatly increased by the introduction of charges. It was also shown that there is a possibility to replace some of the energy input in the mill with the introduction of charges to obtain the same swelling and strength. Paper sheets were formed from the different samples and some mechanical properties were analyzed. It was shown that the strength was initially improved by the introduction of charges but the improvement was partially lost during the beating. At the highest rate of beating the difference in strength between the samples had disappeared. This can be explained by the fact that the fibres, from the sample with highest number of charges, were destroyed. Microscopic images showed that the fibre was delaminated and at some sites there were extreme balloon-like swellings
Syftet med detta examensarbete var att undersöka hur laddade grupper hos massafibrer påverkar malbarheten och styrkan hos de papper som tillverkats av dessa fibrer. För att skapa olika laddningsnivåer karboxymetylerades viss del av massan för att introducera laddade grupper, två delar av ursprungsmassan karboxymetylerades och en del användes som referensmassa. De olika massaproverna maldes i olika nivåer för att undersöka hur laddningarna och malningen interagerade. En PFI-kvarn användes för att mala fibrerna då det endast krävs små mängder fibrer och denna typ av kvarn påverkar fibrerna relativt homogent. Fibrerna analyserades sedan i en Fibre tester och med ett mikroskop för att se vad som hade hänt med fiberstrukturen. Resultaten visade att en PFI-kvarn till största delen påverkar fibrernas yta. Malbarheten, som definierades som den svällning som åstadkoms vid en viss energiinsats i form av malvarv i kvarnen, ökades markant då ytterligare laddningar fanns närvarande i fibrerna. Det visades också att det går att ersätta en del av malningen med introduktion av laddningar till fibrerna för att uppnå samma svällning och styrka. Pappersark tillverkades därefter av de olika massatyperna och några mekaniska egenskaper testades. Det visades att styrkan ökades initialt av introduktionen av laddningar men denna förbättring minskade vid malningen. Vid den högsta malgraden hade skillnaden mellan de olika massorna försvunnit. Det kan förklaras av att fibrerna, från den massatyp med mest laddningar, hade förstörts. På vissa ställen hade fibern helt delaminerats och extrema ballonglika svällningar fanns.

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Clayton, John Morris. "Incorporation of environmental, economic and product quality criteria in multiobjective engineering design of Cl₂/ClO₂ softwood kraft pulp bleaching processes." Diss., Georgia Institute of Technology, 2003. http://hdl.handle.net/1853/21481.

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Books on the topic "Softwood kraft pulp"

Marcoccia, Bruno Sisto. Photo-enhanced oxygen delignification of softwood kraft pulp. 1992.

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Earl, Paul Francis. The chlorination of softwood kraft pulp in a high-intensity laboratory mixer. 1990.

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Book chapters on the topic "Softwood kraft pulp"

van Heiningen, Adriaan R. P., Yun Ji, and Vahid Jafari. "Recent Progress on Oxygen Delignification of Softwood Kraft Pulp." In Cellulose Science and Technology, 67–97. Hoboken, NJ, USA: John Wiley & Sons, Inc., 2018. http://dx.doi.org/10.1002/9781119217619.ch4.

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Wong, Ken K. Y., Patricia Clarke, and Sandra L. Nelson. "Possible Roles of Xylan-Derived Chromophores in Xylanase Prebleaching of Softwood Kraft Pulp." In ACS Symposium Series, 352–62. Washington, DC: American Chemical Society, 1996. http://dx.doi.org/10.1021/bk-1995-0618.ch023.

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Mansfield, Shawn D., Neil R. Gilkes, R. Antony J. Warren, and Douglas G. Kilburn. "The Effects of Recombinant Cellulomonas fimi β-1,4-glycanases on Softwood Kraft Pulp Fibre and Paper Properties." In Progress in Biotechnology, 301–10. Elsevier, 2002. http://dx.doi.org/10.1016/s0921-0423(02)80033-8.

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Reports on the topic "Softwood kraft pulp"

Simo Sarkanen. Producing a True Lignin Depolymerase for Biobleaching Softwood Kraft Pulp. Office of Scientific and Technical Information (OSTI), February 2002. http://dx.doi.org/10.2172/792705.

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