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High consistency refining of kraft pulp for reinforcing paper based on TMP furnishes
Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
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.

Place, publisher, year, edition, pages
2007. Vol. 2, p. 943-953
National Category
Chemical Engineering
Identifiers
URN: urn:nbn:se:miun:diva-9395Scopus ID: 2-s2.0-55949098198ISBN: 978-160560293-6 (print)OAI: oai:DiVA.org:miun-9395DiVA, id: diva2:227699
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
In thesis
1. High Consistency Mechanical Treatment of Kraft Pulps under Steam Pressurised Conditions - Effects on Fibre and Sheet Properties
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

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Sjöberg, JessicaHöglund, Hans

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