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Sjöberg, Jessica
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Publications (10 of 10) Show all publications
Sjöberg, J. C., Häggquist, M., Wikström, M., Lindström, T. & Höglund, H. (2008). Effects of pressurised high consistency refining on sheet density. Nordic Pulp & Paper Research Journal, 23(1), 39-45
Open this publication in new window or tab >>Effects of pressurised high consistency refining on sheet density
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2008 (English)In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 23, no 1, p. 39-45Article in journal (Refereed) Published
Abstract [en]

This study investigates the possibility of decreasing the sheet density of paper made from unbleached kraft pulp for the middle layer in board production. The objective was to evaluate how treatments in a compressive screw equipment pressure expansion (PREX) plug screw feeder, atmospheric (HCatm) and pressurised high-consistency refining (HCpress refining) affect both fibre and paper properties and, in particular, how fibre curl affects sheet density.The plug screw pre-treatments and HC refining were performed under atmospheric and steam-pressurised conditions at 100 degrees C, 125 degrees C and 175 degrees C. Even though fibre curl increased considerably during plug screw treatment and HCatm and HCpress refining, the density of the paper sheets did not decrease, as had been expected. A possible explanation for this result may be that the fibres become more flexible during curl treatment, resulting in increased sheet density.In order to obtain fibres that were both very curly and stiff, three ways of improving the fibre stiffness were tested: 1) lowering the pH during refining, 2) drying the fibres (hornification) and 3) treating the fibres with 1,2,3,4-ButaneTetraCarboxylic Acid (BTCA). If the fibres are dried (hornified), there is a lowering effect on sheet density. However, fibre curl does not have any lowering effect on sheet density. If the pH is decreased during plug screw treatment, the sheet density may be reduced but, again, the fibre curl does not have any positive effect on sheet density. Fibres treated with BTCA had a marked lowering effect on sheet density. With this treatment, the fibre curl does have a positive effect on sheet density. The BTCA-treated fibres were also used to lower sheet density. A mixture of 15% by weight BTCA- treated fibres resulted in an approximately 9% density reduction.

National Category
Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:miun:diva-7509 (URN)10.3183/NPPRJ-2008-23-01-p039-045 (DOI)000255491400007 ()2-s2.0-50949089275 (Scopus ID)
Available from: 2008-12-09 Created: 2008-12-09 Last updated: 2017-12-14Bibliographically approved
Sjöberg, J. C. (2007). High Consistency Mechanical Treatment of Kraft Pulps under Steam Pressurised Conditions - Effects on Fibre and Sheet Properties. (Doctoral dissertation). Sundsvall: Mittuniversitetet
Open this publication in new window or tab >>High Consistency Mechanical Treatment of Kraft Pulps under Steam Pressurised Conditions - Effects on Fibre and Sheet Properties
2007 (English)Doctoral thesis, comprehensive summary (Other academic)
Place, publisher, year, edition, pages
Sundsvall: Mittuniversitetet, 2007. p. 67
Series
Mid Sweden University doctoral thesis, ISSN 1652-893X ; 29
National Category
Chemical Engineering
Identifiers
urn:nbn:se:miun:diva-8891 (URN)978-91-85317-60-8 (ISBN)
Public defence
(English)
Available from: 2009-05-06 Created: 2009-05-06 Last updated: 2009-07-16Bibliographically approved
Sjöberg, J. & Höglund, H. (2007). High consistency refining of kraft pulp for reinforcing paper based on TMP furnishes. In: International Mechanical Pulping Conference 2007, TAPPI: . Paper presented at International Mechanical Pulping Conference 2007, TAPPI; Minneapolis, MN; United States; 6 May 2007 through 9 May 2007; Code 73991 (pp. 943-953). , 2
Open this publication in new window or tab >>High consistency refining of kraft pulp for reinforcing paper based on TMP furnishes
2007 (English)In: International Mechanical Pulping Conference 2007, TAPPI, 2007, Vol. 2, p. 943-953Conference paper, Published paper (Refereed)
Abstract [en]

This study evaluated whether the reinforcement effect of bleached softwood kraft pulp fibres added to a thermomechanical pulp (TMP) -based furnish for light weight coated (LWC) paper could be improved by high consistency. (HC) refining. The reinforcement pulp was HC refined under various temperature and steam-pressure conditions. Fibre and sheet properties, such as fibre length, fibre curl, tensile strength, strain at break and tensile energy absorptioh, of both isotropic handsheets and orthotropic paper were studied. The reinforcement effect was estimated by fracture-mechanics for a larger web containing a small crack. The critical force and critical elongation were calculated based on material parameters measured on laboratory made orthotropic papers. The study revealed that HC refining did not significantly increase the final level of fibre curl of bleached softwood kraft fibres after a combination of high- and low-consistency refining. Despite this, testing of laboratory sheets indicated that the highest levels of tensile energy absorption and strain at break were achieved as a result of HC refining. The highest level being achieved with fibres refined in the pressurised refiner at high temperature. Testing of orthotropic sheets indicated that it is possible to increase the strain at break, tensile energy absorption index, critical' deformation and critical load of sheets made of a TMP furnish reinforced with HC refined kraft pulp (70% TMP and 30% kraft pulp), the disadvantage of such reinforcement is a decline in tensile index. The best combination of critical load and critical elongation was achieved with reinforcement pulp HC refined in a steampressurised system at 125°C. Both undried and dried kraft pulps were investigated: the dried pulp generally displayed similar or better performance, regardless of whether or not it was pre-treated in a HC refiner before the low consistency (LC) refining stage or not. Pore size and pore size distribution in the fibre wall were determined by studying the relaxation behavior of 2H in 2H2O-saturated fibres using NMR spectroscopy. This was done in order to analyse the effect of high consistency refining on the fibre wall ultrastructure. The result indicated that the pore size decreases in fibres subject to HC refining, higher temperatures during HC refining resulting in smaller pores. HC refining thus produces effects resembling hornification in the fibres.

National Category
Chemical Engineering
Identifiers
urn:nbn:se:miun:diva-9395 (URN)2-s2.0-55949098198 (Scopus ID)978-160560293-6 (ISBN)
Conference
International Mechanical Pulping Conference 2007, TAPPI; Minneapolis, MN; United States; 6 May 2007 through 9 May 2007; Code 73991
Available from: 2009-07-16 Created: 2009-07-16 Last updated: 2016-09-23Bibliographically approved
Pettersson, G., Sjöberg, J., Wågberg, L., Höglund, H. & Averheim, A. (2007). Increased joint-forming ability of ductile kraft pulp fibres by polyelectrolyte multilayer treatment-Influence of refining and drying strategies. Nordic Pulp & Paper Research Journal, 22(2), 228-235
Open this publication in new window or tab >>Increased joint-forming ability of ductile kraft pulp fibres by polyelectrolyte multilayer treatment-Influence of refining and drying strategies
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2007 (English)In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 22, no 2, p. 228-235Article in journal (Refereed) Published
Abstract [en]

In this study a sack paper furnish was used. It consisted of a high-consistency kraft pulp refined in either an atmospheric pressure or a pressurized system. The pulps were subsequently low-consistency refined in an Escher-Wyss laboratory refiner to 17.5-20.5 SR. Ordinary ISO sheets and freely dried sheets were manufactured from these pulp samples to serve as reference sheets. The laboratory sheets made of pulp from the pressurized system had a higher strain at break and tensile energy adsorption index but a lower tensile index than sheets made of pulp from a conventional atmospheric highconsistency refiner. These sheets were subject to a polyelectrolyte multilayer treatment to increase the interaction between the fibres, thus enhancing the paper strength properties. The polyelectrolyte multilayers (PEM) were applied by sequentially treating fibres from an unbleached kraft pulp for sack paper production with cationic starch and anionic carboxymethyl cellulose. The multilayer treatment was only applied to 50% of the stock and both ordinary ISO sheets and freely dried sheets were prepared with one and three layers of polyelectrolyte. Evaluation of the strength properties of the sheets showed that the addition of only one layer of starch increased strain at break, tensile index, tensile energy adsorption index, and out-of-plane properties measured as Scott-bond values. Using the multilayer technique created large increases in Scott-bond, a measure of the internal bonding of the sheets. The achieved effects were significantly larger than those usually achieved by applying starch alone to enhance the out-of plane strength properties. Also, the density increased considerably when the third layer was applied, for both ISO and freely dried sheets, though the tensile strength was enhanced significantly only in the freely dried sheets.

Keywords
adsorption, interaction, mechanical properties, multilayer
National Category
Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:miun:diva-4169 (URN)10.3183/NPPRJ-2007-22-02-p228-235 (DOI)000248057800012 ()2-s2.0-34547365094 (Scopus ID)4864 (Local ID)4864 (Archive number)4864 (OAI)
Available from: 2008-09-30 Created: 2009-06-08 Last updated: 2017-12-12Bibliographically approved
Sjöberg, J. & Höglund, H. (2007). Refining systems for sack paper, Part II: Plug screw and Bivis treatment under pressurised conditions and subsequent LC refining. Nordic Pulp & Paper Research Journal, 22(1), 61-71
Open this publication in new window or tab >>Refining systems for sack paper, Part II: Plug screw and Bivis treatment under pressurised conditions and subsequent LC refining
2007 (English)In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 22, no 1, p. 61-71Article in journal (Refereed) Published
Abstract [en]

Unbleached kraft pulp for making sack paper is usually first refined in a high consistency process followed by low consistency refining in order to achieve desired paper properties, such as high strain at break and high tensile energy absorption at low airflow resistance. Conventional atmospheric high consistency refining is compared to treatments using two types of compressive screw equipment, Bivis equipment and the pressure expansion (PREX) plug screw feeder, commonly used in thermo mechanical pulp (TMP) plants. The plug screw pretreatments were performed under atmospheric and steam-pressurised conditions at 120°C and 130°C. Treatment in the Bivis equipment was performed under different compressive and shear conditions. After the Bivis and plug screw treatments, the pulp samples were refined in a low consistency process using the Escher-Wyss refiner. Paper properties were evaluated on freely dried sheets which were produced in order to simulate paper made under industrial sack paper drying conditions. The highest levels of the tensile energy absorption index and strain at break were achieved from curled and kinked fibres, pre-treated under the most compressive and highest shear stress conditions before low consistency refining. These results were obtained at very low airflow resistance, which is advantageous for sack paper, and with very low energy consumption during pre-treatment with the plug screw. The pulp samples pre-treated at high consistency in a plug screw feeder under steam-pressurised conditions or in the Bivis equipment showed, after low consistency refining, increased shrinking ability compared to the pulp samples pre-treated in high consistency refining under atmospheric conditions.

Keywords
Airflow resistance, Bivis equipment, Fibre length, LC refining, Plug screw, Pressurised HC refining, Sack paper, Shape factor
National Category
Chemical Engineering
Identifiers
urn:nbn:se:miun:diva-4581 (URN)10.3183/NPPRJ-2007-22-01-p061-071 (DOI)000248528700009 ()2-s2.0-34247200586 (Scopus ID)4865 (Local ID)4865 (Archive number)4865 (OAI)
Available from: 2008-09-30 Created: 2009-06-08 Last updated: 2017-12-12Bibliographically approved
Sjöberg, J. & Höglund, H. (2005). Refining system for sack paper pulp: Part I HC refining under pressurised conditions and subsequent LC refining. Nordic Pulp & Paper Research Journal, 20(3), 320-328
Open this publication in new window or tab >>Refining system for sack paper pulp: Part I HC refining under pressurised conditions and subsequent LC refining
2005 (English)In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 20, no 3, p. 320-328Article in journal (Refereed) Published
Abstract [en]

Unbleached kraft pulp for sack paper is usually refined in a high consistency process followed by low consistency refining in order to achieve the desired paper properties, such as a high strain at break and high tensile energy absorption at low airflow resistance. In this study, conventional atmospheric high consistency refining is compared to pressurised high consistency refining after preheating to 125C and 175C. After high the consistency refining stage, the pulp samples were refined in a low consistency process in a laboratory Escher-Wyss refiner. The results show that the highest levels of tensile energy absorption and strain at break were achieved with curled and kinked fibres refined in a pressurised refiner at 175C at a relatively low refining energy input, before the low consistency refining stage. These results were obtained at low airflow resistance, which is advantageous for sack paper. The disadvantage of the pressurised high consistency refining process is a loss in tensile strength. Paper properties were evaluated on freely dried as well as ISO sheets.

Keywords
Airflow resistanse, fibre length, LC refining, pressurised HC refining, sack paper, shape factor, strain at break, tensile energy absorption
National Category
Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:miun:diva-3390 (URN)10.3183/NPPRJ-2005-20-03-p320-328 (DOI)000235257900010 ()3389 (Local ID)3389 (Archive number)3389 (OAI)
Available from: 2008-09-30 Created: 2009-06-08 Last updated: 2017-12-12Bibliographically approved
Sjöberg, J. & Höglund, H. (2004). Highly extensible kraft pulp fibres: The 2004 Progress in Paper Physics Seminar. In: : .
Open this publication in new window or tab >>Highly extensible kraft pulp fibres: The 2004 Progress in Paper Physics Seminar
2004 (English)Conference paper, Published paper (Other academic)
Keywords
Pressurised HC refining, strain at break
National Category
Chemical Engineering
Identifiers
urn:nbn:se:miun:diva-1504 (URN)2508 (Local ID)2508 (Archive number)2508 (OAI)
Available from: 2008-09-30 Created: 2009-06-08Bibliographically approved
Sjöberg, J., Höglund, H. & Andreasson, B. (2003). Highly Extensible Kraft Pulp Fibres. In: 5th International Paper and Coating Chemistry Symposium 2003: Montreal,Canada,June 16-19 2003.
Open this publication in new window or tab >>Highly Extensible Kraft Pulp Fibres
2003 (English)In: 5th International Paper and Coating Chemistry Symposium 2003: Montreal,Canada,June 16-19 2003, 2003Conference paper, Published paper (Other academic)
Abstract [en]

Objective To improve paper properties for sack paper such as high strength to failure and tensile energy absorption at low air resistance. Experimental The conventional HC refining is compared to pressurized HC refining regarding how the final paper properties are affected. After HC refining the pulp have also been beaten in a LC refining stage in a laboratory EscherWyss refiner.

Keywords
HC refining, Pressurised HC refining, strength to failure, tensile energy absorption, air resistance
National Category
Chemical Engineering
Identifiers
urn:nbn:se:miun:diva-2224 (URN)1331 (Local ID)1331 (Archive number)1331 (OAI)
Available from: 2008-09-30 Created: 2009-06-08Bibliographically approved
Sjöberg, J. & Höglund, H. Ductile reinforcement Kraft pulp in TMP-based furnishes.
Open this publication in new window or tab >>Ductile reinforcement Kraft pulp in TMP-based furnishes
(English)Manuscript (Other academic)
Keywords
Kraft pulp
National Category
Chemical Engineering
Identifiers
urn:nbn:se:miun:diva-6436 (URN)4872 (Local ID)4872 (Archive number)4872 (OAI)
Available from: 2009-01-28 Created: 2009-01-28 Last updated: 2010-01-14Bibliographically approved
Sjöberg, J. & Höglund, H. Effects on paper bulk from pressurised high consistency refining.
Open this publication in new window or tab >>Effects on paper bulk from pressurised high consistency refining
(English)Manuscript (preprint) (Other (popular science, discussion, etc.))
Keywords
Bulk
National Category
Chemical Engineering
Identifiers
urn:nbn:se:miun:diva-6437 (URN)4873 (Local ID)4873 (Archive number)4873 (OAI)
Available from: 2009-02-24 Created: 2009-02-24 Last updated: 2010-01-14Bibliographically approved
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