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  • 251.
    Nelsson, Erik
    et al.
    SLU.
    Sandberg, Christer
    Hildén, Lars
    Daniel, Geoffrey
    SLU.
    Pressurised compressive chip pre-treatment of Norway spruce with a mill scale Impressafiner2012Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, ISSN 0283-2631, Vol. 27, nr 1, s. 056-062Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Mill scale trials were performed to evaluate pressurised compressive chip pre-treatment with the Impressafiner installed in one of the thermomechanical pulp lines at Braviken paper mill (Holmen Paper AB). The aim of the study was to determine if earlier reported effects of the Impressafiner pre-treatment on spruce chips from pilot scale trials (i.e. energy reduction and extractives removal) could also be attained with the mill scale Impressafiner.The mill scale Impressafiner pre-treatment resulted in partial disintegration of chips into a material consisting of fragmented chips with cracks running along the longitudinal fibre axis. Splits or evidence for weaknesses were observed between the primary and secondary fibre walls of pre-treated chips. An increase in water uptake for pre-treated chips was also observed. The extractive content was reduced by up to 24% for pulps produced with pre-treated chips compared to pulps from untreated chips. Pulp produced from pre-treated chips had higher tensile- and tear indices, elongation and light scattering and lower freeness compared to pulps from untreated chips produced with the same total specific energy consumption. The total specific energy needed to reach a tensile index of 47 Nm/g was reduced by 120 kWh/bone dry ton (6%) with Impressafiner pre-treatment. A smaller refiner plate gap was needed to reach the same specific energy consumption for pre-treated chips compared to untreated chips.

  • 252.
    Nelsson, Erik
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Sandberg, Christer
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Svensson-Rundlöf, E
    Muhic, D
    Engberg, Birgitta A.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Engstrand, Per
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Substantially improved energy efficiency in mechanical pulping by new feeding segment design and low dosage sulfonation in mill scaleArtikkel i tidsskrift (Fagfellevurdert)
  • 253.
    Nelsson, Erik
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Sandberg, Christer
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Svensson-Rundlöf, Eva
    Holmen Paper AB, S-60188 Norrkoping, Sweden.
    Engstrand, Per
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Fernando, Dinesh
    Swedish Univ Agr Sci, Dept Forest Prod Wood Sci, S-75007 Uppsala, Sweden.
    Daniel, Geoffrey
    Swedish Univ Agr Sci, Dept Forest Prod Wood Sci, S-75007 Uppsala, Sweden.
    Low dosage sulfite pretreatment in a modern TMP-line2015Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 30, nr 4, s. 591-598Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The effects of low dosage sulfite pretreatment combined with modern high consistency double disc refining were evaluated for production of thermomechanical pulp in a mill scale trial using Norway spruce wood at the Braviken paper mill (Holmen Paper AB, Sweden). Spruce wood chips were mechanically pretreated in an Impressafiner before impregnation with different dosages (0-1.2%) of sodium sulfite (Na2SO3) at pH 9. Approximately 23% of the added sulfite was converted to sulfonate groups in pulp, resulting in a sulfonate content of 0-0.28% (as Na2SO3). The low dosage sulfite addition increased tensile index, elongation, density, brightness and decreased shive content, light scattering and light absorption coefficients when compared at equal specific energy consumption (SEC). The increase in tensile index was proportional to dosage of sulfite. Further analyses showed that low dosage sulfite addition did not affect the distribution of the Bauer-McNett fractions nor the fibre length for pulps refined with equal SEC. However, the low dosage sulfite addition increased fibre delamination/internal fibrillation (D/IF). With the addition of 1.2% Na2SO3, it was possible to produce pulp with a tensile index of 47 Nm/g using ~320 kWh/bdt (~15%) lower refining energy, compared with pulps produced without sulfite addition.

  • 254.
    Nelsson, Erik
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Sandberg, Christer
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Svensson-Rundlöf, Eva
    Muhic, Dino
    Valmet AB.
    Rohdén, Lennart
    A. Engberg, Birgitta
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Engstrand, Per
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Improved energy efficiency in thermomechanical pulping through co-optimixation of intensity by segment design and wood softening by sulfonation2014Inngår i: International mechanical pulping conference IMPC 2014, 2014Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    A mill scale trial was performed where chips were mechanically pretreated and impregnated with sodium sulfite (<7.2 g/kg). Pretreated chips were refined in two parallel double disc refiners (RGP68DD) using two different conditions: Turbine™ segment at higher production rate (higher intensity) and Low Shive™ segment at normal production rate (lower intensity). By combining the Turbine segments with chip pretreatment using a sodium sulphite charge of 3.6 g/kg it was possible to reduce the specific energy consumption by 15%, while maintaining pulp properties, compared with the lower intensity refining without pretreatment.

  • 255.
    Niga, Petru
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Örtegren, Jonas
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Klaman, Marianne
    Innventia.
    Blohm, Erik
    Innventia.
    Lofthus, Jon
    Innventia.
    Hybrid package printing. Assessment of the influence of paper media parameters for inkjet printing on flexographic printed paper.2014Inngår i: Narrow WebTech, ISSN 1617-206X, nr 1, s. 16-22Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Hybrid printing combining inkjet technology with flexography can be used to add customer specific information in the production of packaging and print. However, in order to improve print quality a comprehensive understanding of the mechanisms governing print quality is required. In this work, inkjet printing using three aqueous inkjet inks was performed on top of flexographic printouts on four paper substrates. The flexographic film contained tone values ranging from 0 to 100% ink coverage. Line quality and print density of the inkjet print were evaluated in order to estimate the influence of paper parameters on the print quality. Specifically, it was found that for the system studied, the flexographic film essentially dictates the surface energy while keeping the porosity and the surface roughness of the paper unaltered. These findings are further supported by micrograph images.

  • 256.
    Nilsson, Boel
    et al.
    SCA Graphic research, McGill University.
    Wågberg, Lars
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Gray, Derek
    Paprican, McGill University.
    Conformability of wet pulp fibres at small length scales2000Rapport (Annet vitenskapelig)
  • 257.
    Niskanen, Kaarlo
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Lagra kol i form av trämaterial2014Annet (Annet (populærvitenskap, debatt, mm))
  • 258.
    Nordin, Lisa
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Measurement and prediction of dewatering characteristics for mechanical pulpsusing optical fibre analysis2009Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    On‐line measurement of relevant fibre and pulp characteristics is necessary in order to increase

    productivity and to maintain uniform quality. The drainage properties within the wire and the press

    section are important factors since they affect the dry content after the press section. The higher the

    dry content, the less the steam consumption and thus less energy is consumed. In some cases the

    drier section has a limiting capacity and thus decreased web dryness will reduce the production. The

    runnability in the paper machine is also affected by the dry content after the press section, because

    web breaks might occur in the drier section or in the calendar.

    The long term aim of this work was to obtain an on‐line measurement of dewatering behaviour in

    paper machines based on optically measured fibre and fines characteristics. However, due to the

    difficulty in obtaining pulps with sufficient distribution in dewatering properties and the difficulty in

    varying the pulps characteristics on one single paper machine, a comparative study between four

    different laboratory dewatering methods were conducted as a first step. Optical measured fibre

    characteristics were used to attempt to predict the dewatering behaviour of the different laboratory

    equipments for different mechanical pulps. In addition, a designed experiment was conducted in

    order to further evaluate the quality of the optical fibre and fines measurement.

    The results showed that there are rough correlations between the dewatering equipments; however

    they rank the pulps differently depending on the wood raw material used and whether the refining

    conditions are gentle or harsh. The prediction models formulated for the dewatering equipments

    based on optically measured fibre characteristics showed rather good correlation between the

    measured versus the calculated values; however, not sufficiently good for use in on‐line applications.

    It was also found that the same measured fines amounts show different dewatering behaviour,

    depending on the quality of the fines used. The difference in fines quality was, however, not

    reflected in the optical measurement and it was thus concluded that there is a need for higher

    resolution of the measurement equipments in order to make it possible to measure the shape and

    the exact amount of the fines.

    The results obtained from this work have provided an increase in both knowledge and understanding

    and can hopefully be utilized in characterizing paper machine dewatering with on‐line measurements

    of fibre properties in the future.

  • 259.
    Norgren, Magnus
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    FSCN sommarskola 2002: Sommarskoleelever år 2002 Mitthögskolan Projektredovisningar2002Collection/Antologi (Annet (populærvitenskap, debatt, mm))
    Abstract [sv]

    FSCN SOMMARSKOLA 2002Vid institutionen för Naturvetenskap och miljö vid Mitthögskolans campus i Sundsvall erbjöds denna sommar elever i årskurserna 2 och 3 på gymnasieskolans naturvetenskapliga program i Hudiksvall, Härnösand, Sundsvall, Timrå och Östersund plats vid en Sommarskola med skogsindustriella förtecken. Totalt inkom 67 ansökningar till de 16 platserna. På Sommarskolan varvades föreläsningar i bl.a. träkemi, massa- och pappersteknik med laborationer, studiebesök/exkursioner och projektarbeten under 5 sommarveckor.Förutom att vara ett nytt grepp i den långsiktiga rekryteringen av studenter till Mitthögskolans tekniska och naturvetenskapliga utbildningar, syftade projektet Sommarskolan till att stärka samarbetet med de regionala företagen. I år ställde sig Metso, M-real och SCA positiva till detta samarbete. Företagen fick ge förslag på projekt, anordna program för studiebesök samt sponsra elevlönerna. Doktorander inom Skogsindustriell fiberförädling på FSCN (Fibre Science and Communication Network) svarade för skapande och handledning av 7 av de 8 projektarbetena. Som avslutning fick eleverna till uppgift att redovisa sina projekt muntligt för företagsrepresentanter, men även skriftligt vilket nu redovisas i denna rapport.Sammanfattningsvis så har det övergripande målet för Sommarskolan varit att förmedla en bild av naturvetenskap och teknik som en användbar helhet i yrkeslivet snarare som en anhopning av abstrakta ämnen i skolan. Under Sommarskolans gång har deltagande eleverna erbjudits insikt i skogsbruket och träfiberprodukters vikt för dagens samhälle, informerats om olika typer av arbeten inom det skogsindustriella området och naturligtvis fått erfarenhet av hur det är att studera och forska vid Institutionen för naturvetenskap och miljö och FSCN.Magnus Norgrenprojektledare Sommarskolan, FSCN Mitthögskolan

  • 260.
    Norgren, Magnus
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    FSCN sommarskola 20032003Rapport (Annet vitenskapelig)
  • 261.
    Norgren, Magnus
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Fundamental physical aspects on lignin dissolution2002Rapport (Annet vitenskapelig)
  • 262.
    Norgren, Magnus
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för tillämpad naturvetenskap och design.
    Höga värden finns i det termomekaniska massabrukets processvatten. Men vem tar hem vinsten?2012Inngår i: Nordisk papper & massa, ISSN 1651-2995, nr 2, s. 41-41Artikkel i tidsskrift (Annet (populærvitenskap, debatt, mm))
  • 263.
    Norgren, Magnus
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Self-aggregation of kraft lignin in aqueous solutions.2005Inngår i: Proceedings. International Workshop of Wood-Based Adhesives, Latvian State Institute of Wood Chemistry, Riga, Latvia, 2005, s. 23-30Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    Self-aggregation of kraft lignin in aqueous solution at various conditions was studied by light scattering. The tendency for kraft lignin to self-aggregate was found to increase either when the acidity, the ionic strength or the temperature was increased. From cryo-TEM analysis it was shown that the particle clusters formed exhibits fractal structures. By studying the kinetics of aggregation it was possible to distinguish between two different modes of aggregation from the fractal dimensions of the kraft lignin particles formed. The reaction limited cluster-colloid aggregation (RLCA) process creates denser particles whereas the diffusion limited cluster-colloid aggregation (DLCA) gives particles of looser shapes. Regarding the sensibility towards self-aggregation and precipitation by various monovalent electrolytes, the Hofmeister series for cations was found to be valid for kraft lignin. For anions, however, kraft lignin showed a reversed order of sensibility towards self-aggregation and precipitation compared with the Hofmeister series. The stability against self-aggregation was seen to increase dramatically when small amounts of bile acid salts were added to kraft lignin solutions. The outcome of these studies shows that in order to understand the solution behaviour of kraft lignin, sometimes kraft lignin should be treated as a macromolecule and sometimes as a colloid.

  • 264.
    Norgren, Magnus
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för tillämpad naturvetenskap och design.
    Andersson, Kerstin
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för tillämpad naturvetenskap och design.
    Eriksson, Marie
    SCA R&D Centre, Sundsvall, Sweden.
    Lignin Removal by Adsorption to Fly Ash in Wastewater Generated by Mechanical Pulping2012Inngår i: Industrial & Engineering Chemistry Research, ISSN 0888-5885, E-ISSN 1520-5045, Vol. 51, nr 8, s. 3444-3451Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Stringent discharge requirements call for advanced methods of wastewater treatment to take on where biological treatment fails to succeed. Here, the adsorption potential of fly ash, an on-site available and cheap material, was tested in batch and continuous flow fixed bed experiments using bleaching effluent from an integrated mill producing mechanical pulp. Various models were fitted to the experimental data to find the best description of the adsorption system and to obtain important model parameters: the Freundlich model yielded the highest correlation and indicated that the process was favorable. The bed depth service time model suggested that the adsorption in the column setup involved more than one rate limiting step, and the Thomas and Clark models generated similar curves which satisfactorily described adsorption at short bed depth. The fly ash showed good adsorptive properties of wood derived substances: both lignin and extractives were effectively separated from the effluent.

  • 265.
    Norgren, Magnus
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Bergfors, E
    Sorption of kraft lignin from spent liquors on fibres. 2004Inngår i: Eighth European Workshop on lignocellulosics and pulp : utilization of lignocellulosics and by-products of pulping ; August 22-25,2004 ; proceedings: Workshop on Lignocellulosics and Pulp (EWLP) ; 8 (Riga) : 2004.08.22-25, Riga: Institute of Wood Chemistry , 2004, s. 562-Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    In this investigation sorption of kraft lignin (KL) from spent liquors, membrane filtrated and model KL liquors onto fully bleached TCF softwood kraft pulp fibres was studied. The time, temperature and alkalinity during the sorption experiments were chosen to reflect black liquor impregnation of chips before the cooking operation. The amount sorbed KL was estimated by brightness and kappa number measurements. 1H PFG NMR self-diffusion measurements were applied in situ on the industrial spent liquors to determine differences in molecular mass distributions of KL between the membrane filtrated and feed liquors. The influences of KL concentration, metal ion profile and KL molecular weight distribution in black liquor impregnation as well as conventional kraft cooking are discussed.

  • 266.
    Norgren, Magnus
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Bergfors, E.
    Sorption of kraft lignin from spent liquors on pulp fibres2005Inngår i: Wood Science and Technology, ISSN 0043-7719, E-ISSN 1432-5225, Vol. 39, nr 6, s. 512-520Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this investigation, the sorption of kraft lignin (KL) from spent liquors, membrane filtrated and model KL liquors on fully bleached softwood kraft pulp fibres, was studied. The time, temperature and alkalinity during the sorption experiments were chosen to reflect the conditions of black liquor impregnation of chips before the cooking operation. The amount of sorbed KL was estimated by brightness and kappa number measurements. A linear correlation between the k value and the kappa number was found. Among the parameters investigated, the concentration of metal non-process elements was found the most crucial for the sorption of KL on pulp fibres under black liquor impregnation. The influences of KL concentration, metal ion profile and KL molecular weight distribution on the KL sorption behaviour under black liquor impregnation are discussed.

  • 267.
    Norgren, Magnus
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Edlund, Håkan
    Ion specific differences in salt induced precipitation of kraft lignin2002Rapport (Annet vitenskapelig)
  • 268.
    Norgren, Magnus
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Edlund, Håkan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Stabilisation of Kraft Lignin Solutions by Surfactant Additions2001Inngår i: Colloids and Surfaces A, ISSN 0927-7757, Vol. 194, nr 1-3, s. 239-248Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The colloidal stability of kraft lignin (KL) and some various KL-surfactant mixtures in aqueous alkaline solutions, pH 10.0-11.50, was tuned and investigated at high ionic strengths, 0.5-1.1 M, and elevated temperatures, 70 and 150°C. The main techniques used were Quasi-Elastic Light-Scattering (QELS) and turbidity measurements, together with sample inspection by the naked eye. Samples without surfactant additions and samples containing various alkyl sulfonates showed a comparably low colloidal stability, whereas in mixtures containing sodium salts of bile acids, the stability was found greatly improved. The efficiency of different bile salts was investigated and it was found that the overall best solution stability is obtained in mixtures of KL and sodium taurodeoxycholate (STDC). STDC showed a relatively good stabilising effect also at very high temperatures (150°C). Furthermore, in already aggregated KL solutions, additions of STDC were found to cause 'de-aggregation' and the number of formed aggregates was dramatically decreased. From the outcome of the investigation, it can be concluded that by introducing surfactants, and maybe other designed additives too, new possibilities in controlling the colloidal stability of KL at rough solution conditions are given.

  • 269.
    Norgren, Magnus
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Edlund, Håkan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Nilvebrant, Nils-Olof
    Physiochemical differences between dissolved and precipitated Kraft lignin fragments as determined by PFG NMR, CZE and quantitative UV spectrophotometry2001Inngår i: Journal of Pulp and Paper Science (JPPS), ISSN 0826-6220, Vol. 27, nr 11, s. 359-363Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A combination of analytical techniques, specifically capillary zone electrophoresis, H-1 pulsed-field gradient nuclear magnetic resonance se (diffusion measurements and quantitative UV spectrophotometric measurements, was used to investigate physicochemical differences between dissolved and precipitated kraft lignin (KL)fragments, obtained from the same sample. Precipitation was induced by heating alkaline (pOH4)Indulin AT solutions, containing various concentrations of NaCl (0.20-1.0 mol/L), at 75 degreesC. Depending on the salt concentration in the samples, different amounts of KL were precipitated. The KL precipitated at the lowest NaCl concentrations was found to consist of the largest lignin fragments whereas, at high NaCl concentrations, the KL fragments in the supernatants were found to be of comparably lower mean molecular weights. From the outcome of the investigation, it was found that the combination of analytical techniques used provides the possibility of collecting important information about physicochemical characteristics related to the solution behaviour of industrial lignins.

  • 270.
    Norgren, Magnus
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Edlund, Håkan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Wågberg, Lars
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Aggregation of Lignin Derivatives under Alkaline Conditions. Kinetics and Aggregate Structure2002Inngår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 18, nr 7, s. 2859-2865Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The kinetics of kraft lignin (KL) aggregation at alkaline conditions was studied by quasi-elastic light scattering (QELS) and turbidity measurements. Stability ratios (W) for KL were obtained at 70 °C and various concentrations of sodium chloride. By analyzing the early-time evolution data of aggregate growth obtained from QELS, fractal dimensions of flocs formed in both reaction-limited cluster-cluster aggregation regimes and diffusion-limited cluster-cluster aggregation regimes were determined. Correlations between the fractal dimension and the W-ratio were found in accordance to recent studies of a system containing monodisperse polystyrene colloids. By cryogenic transmission electron microscopy, the fractality of KL aggregate structures in the system was also shown. It was seen from stability studies of KL solutions that the effects of specific co- and counterions follow the Hofmeister series. From the outcome of the investigation, different modes of aggregation occurring in a KL system are proposed. Starting from the macromolecular state of KL and evolving through larger aggregates, the KL clusters finally exhibit a supramolecular structure similar to what earlier has been proposed for native softwood lignin.

  • 271.
    Norgren, Magnus
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Edlund, Håkan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Wågberg, Lars
    Annergren, Göran
    Fundamental Physical Aspects on Lignin Dissolution2002Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 17, nr 4, s. 370-373Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The aggregation of diluted kraft lignin (KL) solutions was studied by turbidity measurements at elevated temperatures, various sodium chloride and sodium hydroxide concentrations. Since adsorptive processes usually precede self-aggregation in macromolecular systems as the solution conditions get worse, the interaction between KL and pulp fibres was also investigated. When treating samples of fully bleached softwood pulp fibres in KL solutions under various solution conditions, the light-absorption coefficient increased and the brightness was found to decrease rapidly above pOH 1, as the temperature was elevated. At pOH 2 and 175°C, the adsorption of KL was up to about 6 mg g-1. The results are also discussed theoretically in terms of lignin solubility and lignin coagulation.

  • 272.
    Norgren, Magnus
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Edlund, Håkan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Wågberg, Lars
    Lindström, Birger
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Annergren, Göran
    Aggregation of Kraft Lignin Derivatives under Conditions Relevant to the Process. Part I. Phase Behaviour2001Inngår i: Colloids and Surfaces A: Physicochemical and Engineering Aspects, ISSN 0927-7757, E-ISSN 1873-4359, Vol. 194, nr 1-3, s. 85-96Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Aggregation of a commercial, polydisperse softwood kraft lignin (Indulin AT) in diluted aqueous alkaline solutions was investigated experimentally, by means of turbidity measurements. The influence of temperature, salt concentration and pOH and the role of a divalent counterion on the aggregation behaviour were studied. When the temperature was increased, an increased tendency of aggregation in samples containing high concentrations of sodium chloride was found. Phase separation could be detected even at pOH=2 at 175°C and the effect was pronounced when the concentration of hydroxide ions decreased. The phase transition from soluble to precipitated lignin was found to be irreversible concerning temperature change. Small amounts of calcium ions were seen to induce dramatic effects on the system stability, even at relatively high hydroxide concentrations (pOH 1-2). At a given temperature and pOH, the coagulation was found to appear at a certain critical coagulation concentration (CCC) of the added electrolyte. Furthermore, calculations were carried out to compare with the outcome of the experimental observations. A theoretical model, based on the DLVO theory, was found to predict the kraft lignin solution behaviour well.

  • 273.
    Norgren, Magnus
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Gärdlund, Linda
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Notley, S. M.
    Australian National University, Canberra, Australia.
    Htun, Myat
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Wågberg, Lars
    Royal Institute of Technology, Stockholm.
    Smooth model surfaces from lignin derivatives: II. Adsorption of polyelectrolytes and PECs monitored by QCM-D2007Inngår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 23, nr 7, s. 3737-3743Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    For the first time, well-defined and stable lignin model surfaces have been utilised as substrates in polyelectrolyte adsorption studies. The adsorption of polyallylamine (PAH), polyacrylic acid (PAA), and polyelectrolyte complexes (PECs) was monitored using quartz crystal microgravimetry with dissipation (QCM-D). The PECs were prepared by mixing PAH and PAA at different ratios and sequences, creating both cationic and anionic PECs with various charge levels. The adsorption experiments were performed in 1 and 10 mM sodium chloride solutions at pH 5 and 7.5. The highest adsorption of PAH and cationic PECs was found at pH 7.5, where the slightly negative charged nature of the lignin substrate is more pronounced, governing electrostatic attraction of oppositely charged polymeric substances. An increase in the adsorption was further found when the electrolyte concentration was increased. In comparison, both PAA and the anionic PEC showed remarkably high adsorption to the lignin model film. The adsorption of PAA was further studied on silica and was found to be relatively low even at high electrolyte concentrations. This indicated that the high PAA adsorption on the lignin films was not induced by a decreased solubility of the anionic polyelectrolyte. The high levels of adsorption on lignin model surfaces found both for PAA and the anionic PAA-PAH polyelectrolyte complex, points to the presence of strong non-ionic interactions in these systems.

  • 274.
    Norgren, Magnus
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Lindström, Birger
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Dissociation of Phenolic Groups in Kraft Lignin at Elevated Temperatures.2000Inngår i: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 54, nr 5, s. 519-527Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The dissociation of the phenolic groups in a polydisperse, low molecular weight kraft lignin (Indulin AT) was studied in alkaline aqueous solutions in the temperature interval 21-70°C, using a UV-spectrophotometric method. It was found that at a constant concentration of hydroxide ions, the degree of dissociation was decreasing when the temperature was elevated. Dissociation curves and apparent pK0 values were also calculated for the polydisperse sample at the same conditions, using the van't Hoff and the Poisson-Boltzmann equations. At degrees of dissociation exceeding α ≈ 0.4, the outcome of the theoretical approach showed to be in good agreement with the experimentally obtained results. Furthermore, calculations were performed for different molecular weights of kraft lignin and from this it was found that the apparent pK0 is shifted to higher values by increasing molecular weight, due to an increased electrostatic attraction of the hydrogen ions, which is arising from a less curved surface. Predictions of the dissociation behavior at temperatures reached in the kraft process were performed and under these conditions, higher molecular weight lignin fragments seem never to reach the point of complete dissociation. It was also found that an increase in temperature results in phase separation in kraft lignin solutions with high ionic strengths and pH values close to the pKa of the phenolic groups.

  • 275.
    Norgren, Magnus
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Lindström, Birger
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Physico-Chemical Characterization of a Fractionated Kraft Lignin2000Inngår i: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 54, nr 5, s. 528-534Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A kraft lignin was leached from a softwood pulp and fractionated by ultrafiltration. The fractions were characterized in respect to phenolic group content, molecular weight distributions and self-diffusion coefficients. The 1H-Pulsed Field Gradient (PFG) NMR self-diffusion measurements and the High-Pressure Size Exclusion Chromatography (HPSEC) analysis of the fractions, were seen to correlate fairly well. From the self-diffusion measurements, the mass-weighted median hydrodynamic radii of the diffusants in the fractions, were calculated assuming spherical fragments. Furthermore, the content of phenolic groups in the fractions, was found to decrease by increasing hydrodynamic radius and molecular weight, but the calculated median surface charge densities of the macromolecules, were determined to be constant in the range of oligomers up to at least 65 structural units.

  • 276.
    Norgren, Magnus
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Lindström, Birger
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Physicochemical characterization of fractionated kraft lignins: Pre-symposium to the 9th ISWPC1997Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    Kraft lignins are known to associate and form large clusters in aqueous solutions at pH values close to pKa. Some physicochemical properties related to association, such as the amount of free phenolic groups and hydrodynamic radius, have been determined in ultrafiltrated fractions of leached softwood kraft lignins and Indulin AT. Average diffusion coefficients were measured by the 1H PFG-NMR method in 2 % w/w lignin solutionsof 0.1 M LiOH/D2O. The hydrodynamic radius were calculated using the Stoke-Einstein expression. Conductometric titrations were used to determine the average amount of free phenolic groups in the fractions. The repulsive electrostatic potential, F0, originating from the phenolic charges, was calculated at different pH values for one of the fractions, using the Poisson-Boltzmann cell model.

  • 277.
    Norgren, Magnus
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    Mackin, S
    Sulfate and Surfactants as Precipitation Boosters in Kraft Lignin Separation2009Inngår i: Industrial & Engineering Chemistry Research, ISSN 0888-5885, E-ISSN 1520-5045, Vol. 48, nr 10, s. 5098-5104Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In the spirit of the biorefinery concept, an increasing interest in further utilization of technical lignins outside the pulp mills has arisen. In this context optimization of the precipitation process to increase the yield of the lignin recovered is of great importance. The objectives of this investigation have been to study how specific salts and surfactants affect kraft lignin yield during precipitation and washing. From the results it was seen that additions of sodium sulfate increased the yield of precipitation at elevated temperatures at much lower concentrations than sodium chloride. Earlier studies of the effect of monovalent salts on kraft lignin stability have shown that specific ions either increase or decrease the fort-nation of precipitates during kraft lignin aggregation. Thus, the presented results in this study further strengthen this dependency concerning divalent anions. Regarding the role of surfactants as precipitation enhancers, cationic surfactants gave rise to fast aggregation and relatively high yields. This was found mainly due to attractive electrostatic interactions between the cationic surfactant headgroup and the oppositely charged groups on the kraft lignin macromolecules, introducing an increased degree of hydrophobicity of the lignin and thus a decreased stability. The nonionic surfactants tested affected the system very differently. In some cases the aggregation was fast and the aggregates became relatively large before settling, whereas some surfactants induced the formation of relatively dense precipitates that settled rapidly. Concerning kraft lignin precipitate washing, calcium chloride at concentrations in the millimolar region decreased the lignin losses dramatically.

  • 278.
    Norgren, Magnus
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Mackin, S
    Edlund, Håkan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Different aggregations processes during kraft lignin aggregation.2004Inngår i: Eighth European Workshop on lignocellulosics and pulp : utilization of lignocellulosics and by-products of pulping ; August 22-25,2004 ; proceedings.: Workshop on Lignocellulosics and Pulp (EWLP) ; 8 (Riga) : 2004.08.22-25, Riga: Institute of Wood Chemistry , 2004, s. 562-Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This study is focused on the aggregation behaviour of kraft lignin (KL) in presence of different types of surfactants at elevated temperatures. Especially the initial part of the aggregation process, the nucleation and onset, is of interest. KL aggregation is induced either by adding surfactants or salt. The KL-surfactant interactions are found to be different depending on the type of surfactant. Starting with KL as a negatively charged polymeric fragment and adding a positively charged surfactant, the aggregation behaviour is significantly influenced. However, adding non-ionic surfactants without obvious head group interactions to the KL solutions, or surfactants with negatively charged head groups, completely different aggregation processes and particle structures are observed.

  • 279.
    Norgren, Magnus
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Notley, S. M
    Physical properties of kraft lignin and interactions at lignin interfaces. 2007Inngår i: Proceedings. The 8th ILI Forum, Rome, Italy, 10-12 May, 2007, Lausanne: International Lignin Institute , 2007, s. 13-16Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper deals with some of the underlying physical properties of kraft lignin during its transformation from dissolved to solid state. The interactions at lignin interfaces are further focused. Fundamental approaches to increase the overall physical knowledge of lignin derivatives by combining relatively simple methods like turbidity with more advanced experimental techniques such as cryogenic transmission electron microscopy, scanning electron microscopy and atomic force microscopy, are treated. The overall message in this report is that many issues related to the isolation, use and development of technical lignins into new products can be successfully addressed through the utilisation of model systems.

  • 280.
    Norgren, Magnus
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Notley, S. M.
    Department of Applied Mathematics, Research School of Physical Sciences and Engineering, Australian National University, Canberra, Australia.
    Majtnerova, A.
    Department of Fiber and Polymer Technology, Royal Institute of Technology, Stockholm.
    Gellerstedt, G.
    Department of Fiber and Polymer Technology, Royal Institute of Technology, Stockholm.
    Smooth model surfaces from lignin derivatives: I. Preparation and characterization2006Inngår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 22, nr 3, s. 1209-1214Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Lignin model surfaces were prepared from aqueous alkaline solutions by spin-coating on silica wafers. Films of thicknesses between 20 and 140 nm were easily made by variations in the spinning rate or in the lignin concentration. The roughnesses of the lignin surfaces were relatively low, approximately 1.1 nm (rms) on an area of 25 μm2, as determined by atomic force microscopy imaging. The stability of the lignin films in aqueous solutions was found to be excellent. No changes in the thickness of model surfaces immersed in slightly alkaline solutions (pH 9.2) could be detected even after 5 h soaking. A 10 percent reduction in the thickness of the lignin film was observed after 5 h of exposure to a solution containing 0. M NaCl. This novel preparation method opens great possibilities for further fundamental studies, where interactions between lignin and other substances are of interest to investigate.

  • 281.
    Norgren, Magnus
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för tillämpad naturvetenskap och design.
    Notley, Shannon M
    Department of Applied Mathematics, ANU, Australia.
    Study of thin films of kraft lignin and two DHPs by means of single-molecule force spectroscopy (SMFS)2012Inngår i: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 66, nr 5, s. 615-622Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The adhesion of single and associated lignin chains to a substrate has been studied by means of single-molecule force spectroscopy (SMFS). Softwood kraft lignin (KL) and two lignin polymer models (dehydrogenation polymers, DHPs) based on coniferyl alcohol (DHPc.alc.)and coniferaldehyde (DHPc.ald.) were in focus. The desorption force from the "silicon nitride SMFS tip" for the KL was significantly greater than that of the DHPs. The higher desorption force was interpreted as being due to the interaction of carboxyl groups through hydrogen bonding with the tip as well as to the less compact polymeric layer at the interface. The distribution of the extended chain lengths was determined, and self-association of lignin chains was observed. For both KL and the DHPc.ald., chains were extended significantly beyond the limit that would be expected for polymers with the corresponding degree of polymerization. The alpha-carbon on the DHPc.alc. has a strong intramolecular hydrogen bonding interaction with the adjacent aryl ether, which inhibits the possibility of the ether to participate in intermolecular hydrogen bonding with nearby lignin chains. Thus, the self-association for KL and DHPc.ald. was found to be dominated by intermolecular hydrogen bonding with carboxylic groups and aryl ether functionalities.

  • 282.
    Norgren, Sven
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    Höglund, Hans
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    Consolidation of fibre-fibre bonds in TMP and CTMP based papers2011Inngår i: PROCEEDING OF INTERNATIONAL MECHANICAL PULPING CONFERENCE 2011, 2011, s. 448-453Konferansepaper (Fagfellevurdert)
    Abstract [en]

    TMP and CTMP fibres are viscoelastic materials, which behave very differently at different temperatures and loading rates, which should to be considered also in papermaking. The positive effects of increased web temperature on dewatering and web consolidation (sheet strength) in pressing and drying of TMP/CTMP based papers are well known since a long time. However, the effects of dry content during such conditions are less closely investigated. In this paper the effect of dry content on fibre-fibre bonds in consolidation of paper webs during press drying at high temperature is discussed. It is shown that the final paper strength is especially positively affected when a Z-directional pressure is applied in the dryness range 50%similar to 75 %.

  • 283.
    Norgren, Sven
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Höglund, Hans
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Irreversible long fibre collapse at high temperature reject refining in a TMP system: Effects on fibre and surface properties2005Inngår i: Proceedings International Mechanical Pulping Conference Oslo 2005, 2005, s. 163-168Konferansepaper (Annet vitenskapelig)
  • 284.
    Norgren, Sven
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Höglund, Hans
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Moisture-Induced Surface Roughness in TMP Sheets.2007Inngår i: International Mechanical Pulping Conference 2007, TAPPI, TAPPI Press, 2007, Vol. 2, s. 718-729Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    Favourable surface properties can be attained in softwood thermomechanical pulp (TMP)-based sheets, if most of the thick-walled long fibres are collapsed. Provided this can be done, a large amount of TMP can be used in highquality wood-containing papers, i.e., LWC or SC grades, without serious printability problems. It is known that the degree of fibre collapse during refining under standard TMP conditions is strongly related to the fibre wall thickness. However, the thickness of the thickest fibre walls cannot easily be changed by peeling actions in refining under standard TMP conditions in the CSF range of interest for news and magazine grades. Therefore, refining conditions obviously must be changed to enable the proper collapse of these fibres. Earlier studies (Norgren and Höglund, IMPC 2003 and 2005) have demonstrated that thick-walled fibres are more easily collapsed by reject refining after preheating to temperatures well above the softening temperature of lignin, i.e., high temperature conditions, than under standard conditions. If water is applied to the surface of a TMP-based paper during coating or printing, some fibres "decollapse", i.e., revert to their original shape. Earlier studies have demonstrated that decollapse is affected by both fibre wall thickness and fibre circumference (Norman and Höglund, IMPC 2003 and Norgren and Höglund, IMPC 2003). The present study evaluates the effects of moisture on sheets made of different Bauer-McNett (BMN) fractions, both individually and in combination. The pulps investigated are spruce TMP reject pulp made under reference and hightemperature conditions. The smoothness of laboratory sheets made of the BMN fractions were measured with PPS and with an optical scanning instrument, after moistening the sheets in environments of different relative humidities, i.e., 50-98%, to a sheet moisture content (MC) in approximately the 5-25% range. This was done to gain a better fundamental understanding of the conditions resulting in irreversible fibre collapse and of how combinations of types of fibres with different bonding abilities influenced the surface roughness. It is well known that the coarse, stiff, long fibres from the BMN >16 fractions cause surface roughness in dry sheets. However, this study indicates that the shapes of these fibres remain relatively unchanged when moisture diffuses into the sheet structure, i.e., the degree of decollapse is low. It also indicates that sheets including both coarse fibres and fibres from the middle fractions display the highest surface roughness values at a high MC. The fibres from the middle fraction rise easily, causing the greatest change in surface roughness when moisture is added to the sheet. The trials also indicate that fines contribute somewhat to increased surface roughness; when the degree of bonding in the sheet structure is increased, there is a risk that the whole structure or fibre flocks, instead of the individual fibres, may swell.

  • 285.
    Norgren, Sven
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Höglund, Hans
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Bäck, R
    Irreversible long fibre collapse at high temperature TMP reject refining - initial studies2004Inngår i: Pulp & paper Canada, ISSN 0316-4004, Vol. 105, nr 7, s. 47-51Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Effects of preheating temperature on energy consumption,fibre collapse and pulp quality in refining of spruce TMP reject material were studied. At preheating to temperatures well above the softening temperature of lignin thick-walled fibres were collapsed to a higher degree. Shives and fibres in the BMN +10 fraction were efficiently reduced. An increase in sheet density was obtained. Energy consumption was reduced, at a certain freeness level. This study indicates that an improved surface smoothness can be achieved as result of high temperature reject refining.

  • 286.
    Norgren, Sven
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Pettersson, Gunilla
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Höglund, Hans
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    High strength papers from high yield pulps2014Inngår i: International Mechanical Pulping Conference, IMPC 2014, 2014Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The positive effects changing the present standard conditions regarding temperature and moisture content during pressing and drying in papermaking of high yield pulp furnishes, such as those from TMP and CTMP, has previously been reported in a series of studies at Mid Sweden University. In the current study, the effects of fibre surface modification by starch/CMC at press-drying conditions have been investigated. It is shown how the strength properties of sheets from HTCTMP, manufactured at very low electric energy consumption (approximately 600 kWh/ton), can be radically improved by several hundred percent at optimum papermaking conditions.

  • 287.
    Norgren, Sven
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Pettersson, Gunilla
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Höglund, Hans
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Strong paper from spruce CTMP - Part II: Effect of pressing at nip press temperatures above the lignin softening temperature2018Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 33, nr 1, s. 142-149Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The main objective of the current study was to demonstrate that it is possible to enhance strength properties of sheets from spruce HT-CTMP and CTMP furnishes up to the same level as is common on sheets from softwood kraft pulps by changing conditions in papermaking. To achieve that, sheets of spruce HT-CTMP and CTMP were consolidated at densities close to that of the reference bleach kraft pulp by pressing at press nip temperatures well above the tack and softening temperatures of lignin. On sheets from spruce CTMP (CSF 420 ml), where the fibers were surface treated with cationic starch, it was possible to reach tensile index at the same level as on sheets from the untreated reference kraft pulp. The compression strength (SCT) of CTMP and HT-CTMP sheets, which were achieved at the highest press nip temperature (200 °C) in the study, was equal to or higher than that of the reference kraft pulp sheets. The results show that there is a great yet unexploited potential in papermaking from spruce HT-CTMP and CTMP furnishes, which could be utilized in manufacturing of products where very high requirements upon strength is demanded. 

  • 288. Norman, Fredrik
    et al.
    Höglund, Hans
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Moisture-induced surface roughness in TMP-based paper - The influence of fiber cross-section dimensions: IMPC 20032003Konferansepaper (Annet vitenskapelig)
  • 289. Notley, S M
    et al.
    Norgren, Magnus
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Polyelectrolyte adsorption to model lignin films.2007Inngår i: 14th ISWFPC, 2007Konferansepaper (Annet vitenskapelig)
  • 290.
    Notley, Shannon
    et al.
    Australian National University, Canberra, Australia.
    Norgren, Magnus
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Measurement of interaction forces between lignin and cellulose as a function of aqueous electrolyte solution conditions.2006Inngår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 22, nr 26, s. 11199-11204Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The interaction between a lignin film and cellulose sphere has been measured using the colloidal probe force technique as a function of aqueous electrolyte solution conditions. The lignin film was first studied for its roughness and stability using atomic force microscopy imaging and quartz crystal microbalance measurements respectively. The film was found to be smooth and stable in the pH range of 3.5 to 9 and in ionic strengths up to and including 0.01 M. This range of ionic strength and pH was hence used to measure the surface forces profiles between lignin and cellulose. Under these solution conditions, the measured forces behaved according to DLVO theory. The force-distance curves could be fitted between the limits of constant charge and constant potential and the surface potential of the lignin films was determined as a function of pH. At pH greater than 9.5, a short range steric repulsion was observed indicating that the film was swelling to a large extent but did not dissolve. Thus, lignin films prepared in this manner are suitable for a range of surface forces studies.

  • 291. Notley, SM
    et al.
    Norgren, Magnus
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    Adsorption of a strong polyelectrolyte to model lignin surfaces2008Inngår i: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 9, nr 7, s. 2081-2086Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The adsorption of a strong, highly charged cationic polyelectrolyte to a kraft lignin thin film was investigated as a function of the adsorbing solution conditions using the quartz crystal microbalance. The polyelectrolyte, PDADMAC, with a molecular weight of 100 kDa and one cationic charge group per monomer, was adsorbed to the anionically charged lignin film in the pH range 3.5-9.5 in electrolyte solution of 0.1 to 100 mM NaCl. At low pH, the adsorbed amount of PDADMAC was minimal, however, this increased as a function of increasing pH. Indeed, the surface excess increased significantly at about pH 8.5, where ionization of the phenolic groups on the lignin macromolecule may be expected. Furthermore, at this elevated pH, the adsorbed amount of PDADMAC decreased as the ionic strength of the solution increased above I mM. This is due to the competitive adsorption of counterions to the lignin surface and indicates that the adsorption of PDADMAC to lignin is of a pure electrosorption nature.

  • 292. Nygren, Olle
    et al.
    Höglund, Hans
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Roland, Bäck
    On characterization of mechanical and chemimechanical pulps2003Inngår i: International Mechanical Pulping conference, Quebec, Que, Canada, 2-5 June 2003,, Montreal: Pulp and Paper Technical Association of Canada , 2003, s. 486-Konferansepaper (Fagfellevurdert)
  • 293.
    Nyström, Jonas
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Gradin, Per
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Thörnberg, Benny
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för elektronikkonstruktion.
    An experimental study of the chipping process with focus on energy consumption and chipping angles2018Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 33, nr 3, s. 460-467Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A series of chipping experiments were performed under both dynamic and quasi-static conditions in a laboratory wood chipper (dynamic) and in a MTS-servohydraulic testing machine (quasi-static). One aim with the experiments was to investigate the rate dependency of the energy consumption during chipping. Another aim was to try to determine the load per unit knife edge length required to initiate cutting. The experiments were carried out using different combinations of spout and edge angles. It was found that for large edge angles (keeping the spout angle constant at 30 °30^\circ ) there was a slight rate dependency such that the energy consumption was larger at higher cutting rates which is quite in opposite of what is expected if wood is assumed to be a viscoelastic material. It was also found that to determine the force at initiation of cutting, is not a trivial task. Both Acoustic Emission monitoring and visual inspection was used to this end. The wood species used in this study was pine (Pinus silvestris). 

  • 294.
    Osong, Sinke H.
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    Engstrand, Per
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    Norgren, Sven
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    A New Concept to Produce Nano-ligno-cellulose Materials by Means of High Pressure Homogenization2012Konferansepaper (Fagfellevurdert)
  • 295.
    Osong, Sinke H.
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Engstrand, Per
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Norgren, Sven
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Mechanical Properties of high-yield pulp handsheets, as affected by blends of Nano-ligno-cellulose2013Konferansepaper (Fagfellevurdert)
  • 296.
    Osong, Sinke H.
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Engstrand, Per
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Norgren, Sven
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    New Products based on Mechanical Pulps: Nano-ligno-cellulose (NLC)2013Konferansepaper (Fagfellevurdert)
  • 297.
    Osong, Sinke H.
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Norgren, Sven
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Engstrand, Per
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Nano-ligno-cellulose as strength enhancer in handsheets2013Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    In recent years, there has been tremendous work in the research field of nanocellulose or microfibrillated cellulose but, very few scholars have envisioned the use of the low quality fibre fraction of mechanical pulps for the production of mechanical pulp based nanocellulose, referred to as nano-ligno-cellulose (NLC) in this paper. Today, it has been noticed by many that there has been an economic downturn in the pulp and paper industry and that this adverse situation could be somewhat alleviated by possibly searching for better products or by improving the material quality of existing products (papers and paperboards). This paper presents results related to paper strength properties based on testing of handsheets of pulp fibres blended with nanocellulose. The results indicate that the addition of nano-ligno-cellulose (NLC) to chemi-thermomechanical pulp (CTMP) fibres improved the z-strength property of laboratory sheets with only a slight effect in relation to the sheet density. Also the crill characterisation method was used to evaluate fibre size distribution. The measurement of crill is based on optical response of a suspension at two wavelengths of light; UV and IR. The UV light contains information on both the total fibres and the crill, while IR only contains information on fibres. Results showed that the crill value of NLC of CTMP correlated (linearly) fairly well with the homogenisation time.

  • 298.
    Osong, Sinke H.
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Norgren, Sven
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Engstrand, Per
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Nano-ligno-cellulose from mechanical pulp fines2013Konferansepaper (Fagfellevurdert)
  • 299.
    Osong, Sinke H.
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Norgren, Sven
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Engstrand, Per
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Recent developments in nano-ligno-cellulose production and the crill characterization technique2014Inngår i: TAPPI International Conference on Nanotechnology for Renewable Materials 2014, TAPPI Press, 2014, s. 193-205Konferansepaper (Fagfellevurdert)
  • 300.
    Osong, Sinke H.
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Norgren, Sven
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Pettersson, Gunilla
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Engstrand, Per
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Còrdova, Armando
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Afewerki, Samson
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Alimohammadzadeh, Rana
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Processing of nanocellulose and applications relating to CTMP-based paperboard and foams2016Inngår i: International Mechanical Pulping Conference 2016, IMPC 2016, TAPPI Press, 2016, s. 87-93Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Although remarkable success has been made in the production of nanocellulose through several processing methods, it still remain a challenge to reduce the overall energy consumption, to use green chemistry and sustainable approach in order to make it feasible for industrial production of this novel nanomaterial. Herein, we have developed a new eco-friendly and sustainable approach to produce nanocellulose using organic acid combined with high-shear homogenisation, made hydrophobisation of nanocellulose and cross-linked the modified nanocellulosic material. Also, TEMPO-mediated oxidised nanocellulose was produced in order to compare the processing route with that of mild organic acid hydrolysis. Freeze-dried 3D structure of TEMPO-derived nanocellulose foam materials made fi-om bleached sulphite pulp and CTMP, respectively. Further, there is growing interest in using nanocellulose or microfibrillated cellulose (MFC) as an alternative paper sfrength additive in papermaking, and in using chemi-thermomechanical pulp (CTMP) with high freeness in producing CTMP-based paperboard with high bulk properties. To achieve greater strength improvement results, particularly for packaging paperboards, different proportions of cationic starch (CS) or MFC can be used to significantly improve the z-strength, with only a slight increase in sheet density. Research in this area is exploring CS or MFC as potential strength additives in CTMP-based paperboard, which is interesting from an industrial perspective. The mean grammage of the CTMP handsheets produced was approximately 150 g m~, and it was found that blending CTMP with CS or MFC yielded handsheets with significantly improved z-strength, tensile index, burst index and other strength properties at similar sheet densities.

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