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  • 1.
    Engberg, Birgitta
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Logenius, Louise
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Engstrand, Per
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Mechanical properties of sulphonated wood in relation to wing refiner properties2014In: International Mechanical Pulping Conference, IMPC 2014, Espoo: Paper Engineers' Association (PI) , 2014Conference paper (Other academic)
    Abstract [en]

    To reach maximum effect of different pretreatments we need to know how wood properties can be changed and how this can be related to both refining conditions and pulp characteristics. To understand how the material properties were affected, sulphonated wood samples were tested using several new testing techniques. The data was correlated to pulp properties of batch refined chips to learn more how the initial defibration mechanisms and pulp properties were affected by the pretreatments.

  • 2.
    Fjellström, Helena
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Engstrand, Per
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Granfeldt, T.
    Metso Paper Sundsvall AB, SE-851 94, Sundsvall, Sweden.
    Logenius, Louise
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Predicting CTMP bleachability using wood shavings2011In: 16th International Symposium on Wood, Fiber and Pulping Chemistry - Proceedings, ISWFPC, 2011, Vol. 1, p. 613-616Conference paper (Refereed)
    Abstract [en]

    To predict the brightness reduction in a chemithermomechanical process as well as the bleachability of pulps produced from different species of wood raw materials there are, at present, no shortcuts available. Pulps have to be manufactured in pilot or mill scale and bleached; evaluating and predicting the bleachability has consequently been very resource consuming and thus expensive - until now! Due to this, we have used a laboratory method based on 60 × 60 mm wood shavings making it possible to predict the bleachability of primarily chemithermomechanical pulps but also other mechanical pulps. Our experiments showed that retention time and impregnation temperature appears to have no impact on the final brightness of birch shavings. When being subjected to a simulated chemithermomechanical pulp process, eucalyptus exhibited an increase in chromophore content before the bleaching stage. In addition, eucalyptus suffered from severe alkaline darkening. After the bleaching stage, the alkaline darkening diminished. A higher retention temperature resulted in lower brightness of the eucalyptus shavings compared to when using a lower retention temperature. Birch reached the highest final brightness levels and had a higher overall yield too.

  • 3.
    Friman, Linda
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Logenius, Louise
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Agnemo, Roland
    Högberg, Hans-Erik
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Comparison of metal profiles in thermomechanical pulping processes in which either hydrogen peroxide or dithionite bleaching is used2003In: Paperi ja Puu/Paper and timber, ISSN 0031-1243, Vol. 85, no 6, p. 334-339Article in journal (Refereed)
  • 4.
    Logenius, Louise
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    The influence of high temperature on the discoloration and degradation of carbohydrates and on hydrogen peroxide bleaching of spruce TMP2008Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    When processing wood to obtain pulp, the fibers are subjected to high temperatureat moisture levels and to the influence of metal ions. Many process developmentshave resulted in utilization of higher temperatures that induce chemical reactionsin the wood fibers. This thesis deals with some aspects of using high temperaturesin pulping processes. The first part of this work concerns how carbohydrates areaffected, in terms of discoloration and degradation, by high temperature, moisture,and the presence of metal ions. The next part deals with the metal ion profiles inthermomechanical pulp (TMP) processes and the effects of the high temperaturetreatment of native wood under TMP processing conditions. The third sectionconcerns processing conditions present in the high‐temperature hydrogenperoxide bleaching of TMP.In experiments using cotton linter sheets impregnated with glucuronic acid anddifferent metal ions, increased 5‐(hydroxymethyl)furfural and 2‐furaldehydeconcentrations were accompanied by decreased viscosity and increaseddiscoloration when Mg2+ ions and, to some extent, Ca2+ ions were present. Thisindicates that under certain conditions, in this case, dry heat‐induced ageing underslightly acidic conditions and with access to oxygen, the presence of alkaline earthmetals can cause substantial degradation and discoloration of cellulose. Thisindicates that Mg2+ ions can promote the Lewis‐acid‐catalyzed degradation ofcellulose. When glucuronic acid was added to the cotton linter sheets, the presenceof Ca2+ or Mg2+ ions decreased the discoloration caused by the dry heat‐inducedageing of glucuronic acid and also led to a smaller decrease in viscosity comparedto that in cotton linter sheets containing only Ca2+ or Mg2+ ions. This may explainwhy the negative effect of Ca2+ or Mg2+ ions on viscosity is less pronounced incertain pulps.

    In mechanical pulping processes, the addition of sodium silicate and kaolin clayand re‐circulation of water from the paper machines increased the levels of ironand aluminum ions. In a mill using dithionite bleaching, the levels of iron andaluminum ions in the final pulp were approximately ten times higher than in a millusing hydrogen peroxide bleaching. This was probably due to extraction of moreiron and aluminum ions from the clay to the water due to low pH and to thecorrosion of process equipment induced by thiosulfate ions derived fromdecomposed dithionite. In laboratory trials, it was impossible to completelyremove iron from these pulps using diethylenetriaminepentaacetic acid orextraction with hydrochloric acid. This was probably due to the strong binding ofiron to the wood fiber or its presence as oxide/hydroxide clusters. The mostimportant issue is to avoid contaminating the pulp with iron ions; process waterand process chemicals with low iron contents should therefore be used. Especiallyin the dithionite bleaching process, iron contamination increases thedecomposition of the dithionite, causing corrosion of the process equipment andadding further iron to the pulp.The shavings method is a straightforward method for studying the formation andelimination of chromophores in wood. Light absorption coefficients, lightscattering coefficients, and brightness can easily be obtained using this method.The method was used for studying how temperature in the absence of mechanicalenergy affects wood brightness. This provided useful information about the effectof process conditions in mechanical pulping and its relationship to chromophoreformation. An advantage of using thin shavings is the rapid penetration ofchemicals into the fibers. The shavings method was therefore also used in studyingthe kinetics of hydrogen peroxide bleaching at high temperature.The high‐temperature (HT) hydrogen peroxide bleaching of a thermomechanicalpulp was carried out in a pressurized laboratory‐scale wing defibrator. Theexperiments demonstrate two ways to obtain high brightness under HT conditions.One way is two‐stage peroxide bleaching with a low total alkali/peroxide ratio inthe first stage to avoid alkaline darkening. The second way is to pre‐impregnatethe pulp with hydrogen peroxide before adding alkali in two stages. Themaximum brightness was reached after only 2.5 minutes at low alkali charge.Thus, the bleaching time can be short and the total alkali charge low under hightemperatureperoxide bleaching conditions. To achieve very high brightness usingHT hydrogen peroxide bleaching, other measures than increasing the alkali chargeand prolonging the bleaching time are necessary.

  • 5.
    Logenius, Louise
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Agnemo, Roland
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Höglund, Hans
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    A study of the formation and elimination of chromophores in wood under mechanical pulping conditions using spectroscopy2010In: Paperi ja puu - Paper and timber, ISSN 0031-1243, Vol. 92, no 5, p. 35-39Article in journal (Refereed)
    Abstract [en]

    Thin sections of wood, i.e., shavings, were used in spectroscopic measurements studying the formation and elimination of chromophores under mechanical pulping conditions. Light absorption coefficients, light scattering coefficients, and brightness were monitored.The method was applied to study how temperature in the absence of mechanical energy affects wood brightness. An increase in absorption coefficient at 420 nm indicates formation of ortho-quinone structures. By applying mechanical pulp processing conditions, the light absorption coefficient increased in the 400-500-nm wavelength region, probably due to the formation of chromophores in the lignin. Comparison of heat treated wood shavings with mechanical pulps indicated that additional chromophores were created during the mechanical pulping processes.The method was also used in studying how high-temperature hydrogen peroxide bleaching of the wood shavings affects the light absorption coefficients. The light absorption spectra reveal information about chromophore elimination in wood chemical components during hydrogen peroxide bleaching at slightly pressurized conditions. This is relevant to processes, such as the alkaline peroxide mechanical pulp process, in which the wood chips are impregnated with bleaching chemicals before refining. The easy penetration of chemicals into the wood shavings ensures rapid and even distribution of the treatment chemicals. A change in light absorption coefficient at shorter wavelengths (400-500 nm) was observed.

  • 6.
    Logenius, Louise
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Agnemo, Roland
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Höglund, Hans
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    High temperature bleaching of mechanical pulps from spruce2005In: Proceedings, International Mechanical Pulping Conference, 7-9 June, 2005, Oslo, Norway, 2005, p. 80-84Conference paper (Other academic)
    Abstract [en]

    A laboratory method was developed, which facilitates to investigate how the temperature profile during a TMP-process including a bleaching stage influences pulp brightness. Thin shavings are prepared by slicing a fresh and frozen block of wood with a microtome. The shavings are rapidly dried in an air-stream at room temperature and the optical properties are measured in an Elrepho instrument. After that the shavings are placed in a stainless steel container that can be pressurized with steam, where the temperature profile in a TMP-process or a bleach plant can be simulated. Addition of bleaching chemicals can be done during the simulation. The optical properties are measured and can be compared to those of the same shaving before treatments. The temperature profile in a TMP-process has a large impact on the optical properties of the pulp. Many studies have been done to show how brightness is affected, when temperature/pressure in TMP processes are varied. However, pilot-scale or full scale-trials can often be performed only under certain limitations. With this new method it is easy to simulate different processing conditions and measure the kinetics of the brightness change on a shaving sample before and after treatments. To get as high final brightness as possible it is necessary to limit the brightness reduction as much as possible in manufacturing of the unbleached pulp.

  • 7.
    Logenius, Louise
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Agnemo, Roland
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Höglund, Hans
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    High-Temperature Bleaching of Mechanical Pulps from SpruceManuscript (Other academic)
    Abstract [en]

    High-temperature (HT)-peroxide bleaching of a thermomechanical pulp made of Norwegian spruce was investigated; to that end, one-stage reference bleaching at 70°C and one- and two-stage bleaching at 105°C at different total alkali charges (TAs) using a wing defibrator as a mixer were performed. Two-stage HT peroxide bleaching produces a brighter pulp than one-stage HT peroxide bleaching does. The TA should be kept low (10�15 kg/t) and the total alkali/peroxide ratio should be low in the first stage to minimize the COD load and obtain higher residual peroxide. Increased TA does not improve brightness. The bleaching time in HT bleaching at 105°C can be short, since the maximum brightness is reached after only 2.5 min.Preimpregnation of the pulp with hydrogen peroxide before a two-stage alkali addition can produce a pulp with a brightness and residual peroxide comparable to those obtained in conventional one-stage peroxide bleaching at the same hydrogen peroxide charge and at a low TA. The COD load was, however, higher than in conventional bleaching

  • 8.
    Logenius, Louise
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Agnemo, Roland
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Höglund, Hans
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    High-Temperature Bleaching of Mechanical Pulps from Spruce2007In: Proceedings. Internationl mechanical pulping conference 6-9 May, 2007, Minneapolis, MN, USA, TAPPI Press, 2007, Vol. 2, p. 580-587Conference paper (Refereed)
    Abstract [en]

    High-temperature (HT)-peroxide bleaching of a thermomechanical pulp made of Norwegian spruce was investigated; to that end, one-stage reference bleaching at 70°C and one- and two-stage bleaching at 105°C at different total alkali charges (TAs) using a wing defibrator as a mixer were performed. Two-stage HT peroxide bleaching produces a brighter pulp than one-stage HT peroxide bleaching does. The TA should be kept low (10�15 kg/t) and the total alkali/peroxide ratio should be low in the first stage to minimize the COD load and obtain higher residual peroxide. Increased TA does not improve brightness. The bleaching time in HT bleaching at 105°C can be short, since the maximum brightness is reached after only 2.5 min. Preimpregnation of the pulp with hydrogen peroxide before a two-stage alkali addition can produce a pulp with a brightness and residual peroxide comparable to those obtained in conventional one-stage peroxide bleaching at the same hydrogen peroxide charge and at a low TA. The COD load was, however, higher than in conventional bleaching.

  • 9.
    Logenius, Louise
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Angemo, Roland
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Höglund, Hans
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    High temperature Peroxide Bleaching of TMP from Spruce2006In: 5th Fundamental Mechanical Pulping Reasearch Seminar, 31 May- 1 June, 2006, Trondheim, Norway, 2006Conference paper (Other academic)
  • 10.
    Logenius, Louise
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Engberg, Birgitta A.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Fjellström, Helena
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Engstrand, Per
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Mechanical Properties of Sulphonated Spruce Wood2013Conference paper (Other academic)
    Abstract [en]

    The chip-refining stage in the production of high yield pulps as TMP and CTMP determines a large part of the optical and mechanical characteristics of the pulp. Softening of the raw material influences where the fiber walls fracture sites will be located.

    In the thermomechanical pulping (TMP) processes, refining is performed at temperatures close to the lignin softening temperature, which normally leads to fractures located in the in the primary wall and outer parts of the secondary wall. When wood material is chemically treated before chip-refining the position of the fracture is altered due to that the softening and swelling properties of the fiber walls are changed. In the chemi-thermomechanical (CTMP) process most of the fractures are, therefore, located in the middle lamella or in the primary wall due to introduction of charged groups in the lignin which facilitates the fiber separation. At alkaline pH phenolic lignin structures are sulphonated, at lower pH non-phenolic structures in the lignin are also sulphonated. In the mechanical pulping processes the wood material is subjected to both low strain rates (e.g. plug screw treatment) and high strain rates (refining). Since wood is a viscoelastic material it behaves differently at different strain rates.

    In this study, sulphonation has been carried out using different sulphite concentrations and pH-levels and we have thereby influenced the sulphonation degree as well as where in the lignin the sulphonation takes place.

    We used a hydraulic testing machine for low strain-rate testing and a Split-Hopkinson pressure bar device for high strain-rate testing to categorize pretreatments according to their material softening effect and the energy needed for fiber separation. This gives us increased fundamental knowledge of how the mechanical properties of wood are affected by the sulphonation in order to develop new/improved pretreatments.

  • 11.
    Logenius, Louise
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Engberg, Birgitta A.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Nelsson, Erik
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering. Holmen Paper.
    Engstrand, Per
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Mechanical testing methods for evaluation of the mechanical properties of sulphonated wood2013Conference paper (Other academic)
  • 12.
    Logenius, Louise
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Engstrand, Per
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Karlström, A.
    Chalmers Industriteknik, SE-41288 Gothenburg, Sweden.
    Paulsson, Magnus
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Improved hydrogen peroxide bleaching of mechanical pulps using carbon dioxide in combination with sodium and magnesium based alkali sources2011In: 16th International Symposium on Wood, Fiber and Pulping Chemistry - Proceedings, ISWFPC, 2011, Vol. 1, p. 741-745Conference paper (Refereed)
    Abstract [en]

    The pH-profile in the hydrogen peroxide bleaching stage of a Norway spruce thermomechanical pulp was levelled out by using carbon dioxide in combination with sodium or magnesium based alkali sources. Addition of carbon dioxide when magnesium hydroxide was used as the alkali source increased the pulp brightness with up to 1.5 brightness units when the bleaching was performed at 70 °C. When the temperature was increased from 70°C to 90 °C the brightness was increased with about two brightness units, addition of carbon dioxide increased it further. The residual hydrogen peroxide and the chemical oxygen demand (COD) levels were not affected as a consequence of the carbon dioxide addition. In the experiments where sodium hydroxide was used as the alkali source, addition of carbon dioxide lowered the pH that resulted in a decreased COD level, a slightly lower brightness level and, to some extent, an increased residual hydrogen peroxide level.

  • 13.
    Logenius, Louise
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Fjellström, Helena
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Engstrand, Per
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    A sustainable analysis of sulphonic acid content in CTMP pulps2014In: International Mechanical Pulping Conference, IMPC 2014, part of PulPaper 2014 Conference, Espoo: Paper Engineers' Association (PI) , 2014Conference paper (Other academic)
    Abstract [en]

    Sulphonic acid analyses were performed on wing refiner chemithermomechanical pulps, low sulphite charge pulps, thermomechanical pulps and on wood samples using a new method referred to as the niacin method. This method gives sulphonic acid content comparable to those estimated with the quinoline method or the Schoniger method. The method gives low interference with carboxylic acids and dissolved substances in the pulp if the pH is kept sufficiently low and the pulp is well washed.

  • 14.
    Logenius, Louise
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Friman, Linda
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Agnemo, Roland
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    The influence of high temperature on the ageing of cellulose impregnated with metal chlorides under dry and moist conditions.2005In: Proceedings, 13th International Symposium on Wood, Fibre and Pulping Chemistry, 16-19 May, Auckland, New Zealand, 2005, p. 243-249Conference paper (Other academic)
    Abstract [en]

    Cellulose sheets impregnated with metal chlorides were treated at high temperatures in either a dry or a humid environment. The influence of Mg2+, Ca2+ and Fe3+ on the heat-induced discolouration and on the viscosity of cellulose was investigated. Addition of metal ions to cellulose sheets did not significantly influence the colour of the un-aged sheets. At 120 and 150C there are only small increases in the discolouration during heat-ageing. The samples with iron are somewhat more discoloured than the others. After 3,5 hours at 150C Mg2+ also showed an increased discolouration. When the sheets are aged at 180C for short time no large difference between the cellulose reference and the metal impregnated cellulose can be observed. After longer time there is a significant discolouration caused by Ca2+ and Mg2+. Samples with Ca2+ and Mg2+ are 4 and 10 times, respectively, more discoloured than cellulose reference and cellulose impregnated with Fe3+. Under humid conditions at 180C and after 30 minutes Ca2+ and Mg2+ impregnated cellulose are more discoloured than the cellulose reference and the Fe3+ impregnated cellulose. Moisture more than doubles the effect of temperature. pH has no large influence on the discolouration of the cellulose but acid in combination with Mg2+ increases the discolouration 20 times compared to the un-aged reference. The k-values are related to the amount of chromophore formed during ageing. The largest increase in k-values was observed at 285 nm, which was due to the formation of 5-hydroxymethyl-2-furaldehyde (HMF) from wood hexoses formed during hydrolysis of cellulose. Mg2+ and Ca2+ caused a large decrease in DP and increased formation of HMF, compared to the cellulose reference with subsequent formation of chromophores upon heating.

  • 15.
    Logenius, Louise
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Friman, Linda
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Agnemo, Roland
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    The influence of temperature and moisture on the optical properties of cellulose in the presence of metal chlorides and glucuronic acid2008In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 23, no 1, p. 72-80Article in journal (Refereed)
    Abstract [en]

    The influence of Mg2+, Ca2+, Fe3+ ions and glucuronic acid on the dry and humid heat-induced (120180C) discoloration of cotton linter sheets was investigated. The quantity of the added metal ions was similar to that of metal ions found in wood and pulp. Heat-induced ageing (120150C, pH 5) under dry conditions caused only slight discoloration of the reference sheets and of the sheets impregnated with the metal ions. However, during ageing at 180C, the presence of Mg2+ ions accelerated the discoloration. An initial pH in the range of 38 had no great influence on the discoloration of the reference sheets, but a low pH in combination with Mg2+ ions increased the discoloration drastically. Under humid ageing conditions at 180C (<30 min), the sheets discolored approximately twice as much as under dry conditions; the difference in discoloration caused by the metal ions was less than in dry ageing. Adding glucuronic acid to the sheets caused extensive discoloration under dry ageing conditions (120180°C), while Ca2+ and Mg2+ ions decreased the glucuronic acid induced discoloration. Under humid conditions (180°C), however, Mg2+ and Ca2+ ions did not prevent the discoloration caused by glucuronic acid. An increase in the absorption coefficient was observed at 285 nm, most likely due to the formation of 5-hydroxy-2-methyl-furaldehyde (HMF) and 2-furaldehyde (furfural). GC-MS analysis reveals increased formation of HMF in the sheets impregnated with Mg2+ ions. Degradation of the cellulose in which the alkaline earth metals act as Lewis acids is proposed.

  • 16.
    Logenius, Louise
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Friman, Linda
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Agnemo, Roland
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    The influence of temperature and moisture on the physical properties of cellulose in the presence of metal chlorides and glucuronic acid2008In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 23, no 1, p. 81-86Article in journal (Refereed)
    Abstract [en]

    We investigated the influence of Mg2+, Ca2+, and Fe3+ ions and glucuronic acid on the viscosity, after dry or humid ageing, of two different cellulosic materials, cotton linters and dissolving pulp. The quantity of added metal ions was similar to that found in pulp. In the cotton linters sheets, especially in those containing Mg2+, increased 5-hydroxy-2-methyl furfural (HMF) and 2-furaldehyde (furfural) concentrations were accompanied by decreased viscosity under dry conditions at 180C (pH 5). This indicates that Mg2+ ions can promote the Lewis-acidcatalyzed degradation of cellulose. For cotton linters and dissolving pulp sheets, adding Ca2+ and Mg2+ ions is detrimental when ageing at 180C under dry conditions (pH 5). Adding glucuronic acid increases the viscosity of cotton linters sheets, especially when Ca2+ and Mg2+ ions are present. Due to formation of complexes between the Ca2+ and Mg2+ ions and glucuronic acid, these ions reduce pulp viscosity to a smaller degree.

  • 17.
    Logenius, Louise
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Höglund, Hans
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Agnemo, Roland
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Impact of temperature profile on the brightness of spruce wood2004In: 4th Fundamental Mechanical Pulping Research Seminar, 7-8 June, 2004, Stockholm, Sweden, 2004Conference paper (Other academic)
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