| 1. |
- Björk, Elisabeth, et al.
(författare)
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Fibre-based strength aids for increased board stiffness
- 2019
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Ingår i: PaperCon 2019. - : TAPPI Press.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- A pilot scale study has been made of the concept of adding fibre-based strength agents (fines enriched (FE)-pulp or highly refined (HR)-pulp) in a board middle ply containing chemithermomechanical bleached pulp (CTMP) in order to increase bending stiffness of the board while maintaining Z-strength. It has been demonstrated that the bending stiffness of a sheet consisting of a top ply and a CTMP based middle ply could be improved by increasing the CTMP fraction and preventing Z-strength loss via addition of a fibre based strength agent. Compared with the reference pulp, both Z-strength and bulk increased for three of the compositions, namely 65% CTMP with 5% strength agent of either FE or HR type and 85% CTMP with 10% HR-pulp. FE-pulp was found to be more efficient than HR-pulp concerning bending stiffness improvement. While the highly-refined fibres of the strength agents had a negative effect on the drainage resistance and press dryness, an increased share of CTMP increased the press dryness linearly. FE-pulp and HR-pulp had the same impact on press dryness. Press solids could be improved by approximately 2% without significantly reducing the bulk by increasing press loads.
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| 2. |
- Björk, Elisabeth, et al.
(författare)
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Fines-enriched pulp as a strength agent in a CTMP middle ply
- 2018
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Ingår i: PaperCon 2018. - : TAPPI. - 9781595102683 ; , s. 741-760
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Konferensbidrag (refereegranskat)abstract
- The objective of this pilot scale trial, was to evaluate fines-enriched pulp (FE-pulp) as a strength agent in amiddle ply of a board product.A typical CTMP-based middle ply was produced on the FEX pilot paper machine. The stock consisted of CTMP,refined hardwood and softwood pulp, and filler. FE-pulp as strength agent was compared with glue pulp, ahighly refined chemical pulp. FEX sheets and hand sheets made of pulp mixtures were evaluated. Also, thedewatering and pressing conditions on the paper machine were compared.The results confirmed the results of earlier experiments with handsheets; FE-pulp used as strength agent showedto be twice as efficient as glue pulp regarding strength properties without impairing the bulk. Further, thedewatering conditions and press dryness's on the paper machine was comparable at these additions. Thus, allthese results imply that addition of FE-pulp can replace the double amount of glue pulp as a strength agent.
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| 3. |
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| 4. |
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| 5. |
- Björk, Elisabeth, et al.
(författare)
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Production of a fine fraction using micro-perforated screens
- 2020
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Ingår i: Nordic Pulp & Paper Research Journal. - : Walter de Gruyter GmbH. - 0283-2631 .- 2000-0669. ; 35:4, s. 611-620
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Tidskriftsartikel (refereegranskat)abstract
- The objective for this work was to investigate the possibility to use a pressure screen equipped with a micro-perforated screen basket to produce a fine fraction from bleached chemical pulp. Trials were performed with unrefined bleached chemical hardwood pulp, and with unrefined and refined bleached chemical softwood pulp. The effect of feed concentration, feed flow, and volumetric fine fraction flow was evaluated. The difference between the fine fraction (i. e. the particles passing the screen) and the feed was analysed by studying the fibre morphology. The results showed that high feed concentration was positive for both the fine fraction concentration and the separation efficiency. A higher fine fraction concentration was also obtained when using hardwood pulp, which was explained by the shorter fibre length. Refining of the pulp prior to the fractionation proved beneficial, as a larger share of the refined pulp passed the screen, resulting in a twice as high concentration of the fine fraction when compared to unrefined pulp.
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| 6. |
- Björk, Elisabeth, et al.
(författare)
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Production of pulps with an extremely high fines content for use as strength agent
- 2018
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Ingår i: PaperCon 2018. - : TAPPI. - 9781595102683
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Konferensbidrag (refereegranskat)abstract
- The objective was to optimize the production of fines-enriched pulp (FE-pulp) from chemical pulp.The first trial was a continuous production of FE-pulp with unbleached and bleached never-dried softwood. Thepulp was refined using a JC00 equipped with SF filling, and screened with a micro-perforated screen basket with250 μm diameter holes, but the produced FE-pulp got low concentration, below 3 g/l.The second trial aimed at optimised conditions, using dried bleached softwood. Three fillings, microbar, AA andFF were evaluated in a JC01 refiner, where microbar was most energy efficient. Microbar and AA reachedtargeted FE-pulp concentration, 10 g/l. The refined pulps were screened with different hole diameters, where, asexpected, larger hole diameters resulted in higher concentration but also lower fines content in the FE-pulps.The last trial, the microbar filling was evaluated for never-dried softwood pulp, unbleached and bleached. Now,the refining of unbleached softwood gave 3 times more fines per kWh/ton compared with first trial.These trials demonstrated the importance of the right refining conditions regarding effect of refiner and type offilling to achieve glue-pulp with high enough fines content. With the right conditions, it was possible to produceFE-pulp with high concentration at moderate energy consumption.
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| 7. |
- Björk, Elisabeth, et al.
(författare)
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Usage of Fines-enriched pulp to increase strength in CTMP
- 2017
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Ingår i: Paper Conference and Trade Show, PaperCon 2017. - : TAPPI Press. - 9781510847286 ; , s. 1607-1631
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Fines-enriched pulp (FE-pulp) was benchmarked against glue pulp as strength agent in eucalypt CTMP. FE-pulp was produced by combining high intensity multiple-pass refining with a fractionation in a microperforated screen basket. The fraction passing through the holes of the screen is the FE-pulp. The FE-pulp comprises of secondary fines, created in the refiner, and flexible, fibrillated highly-refined fibres or fibre fragments. Glue pulp is highly refined kraft pulp, commonly added as a strength agent in middle plies of board products, or between plies to increase the plybond. Equal amounts of FE-pulp and glue pulp were added to the original CTMP as well as to washed CTMP, where most of the CTMP-fines had been removed. The effects of the strength agents were evaluated using laboratory sheets. Both glue pulp and FE-pulp increased the strength of the CTMP sheets. The bulk of the sheets decreased however. When 5 % FE-pulp was added, the tensile index increased by more than 50 %, and the tensile energy absorption and z-strength increased by more than 100 %. FE-pulp proved to be twice as effective as glue pulp. The addition of 5 % FE-pulp resulted in the same relative strength increase as an addition of 10 % glue pulp. The washed CTMP lost all strength when the CTMP-fines content was reduced from 17 % to 3% through washing. The addition of 5 % FE-pulp restored the strength values, and at a higher bulk. The drainability in terms of CSF of that stock was much higher when compared to the original pulp.
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| 8. |
- Björk, Elisabeth, et al.
(författare)
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Use of fines-enriched chemical pulp to increase CTMP strength
- 2021
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Ingår i: TAPPI Journal. - : TAPPI Press. - 0734-1415. ; 20:4, s. 255-263
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Tidskriftsartikel (refereegranskat)abstract
- In this study, fines-enriched pulp (FE-pulp)-the fine fraction of highly-refined kraft pulp-was benchmarked against highly-refined kraft pulp (HRK-pulp) as a strength agent in eucalyptus chemithermomechanical pulp (CTMP). Both the FE-pulp and the HRK-pulp were produced from unbleached softwood kraft pulp, and equal amounts of those strength agents were added to the original CTMP, as well as to washed CTMP, where most of the fines had been removed. The effects of the added strength agents were evaluated with laboratory handsheets. The FE-pulp proved to be twice as effective as HRK-pulp. Both HRK-pulp and FE-pulp increased the strength of the CTMP handsheets. The bulk of the handsheets decreased, however, as well as the drainability. The addition of 5% FE-pulp resulted in the same strength increase as an addition of 10% HRK-pulp, as well as the same decrease in bulk and CSF. For the handsheets of washed CTMP, the strengths were not measurable; the CTMP lost the sheet strength when the CTMP-fines content was reduced through washing. The reduced strength properties were compensated for by the addition of chemical pulp fines that proved to be an efficient strength agent. The addition of 5% FE-pulp restored the strength values, and at a higher bulk and higher drainability. Application: In this study, we show how the strength of a CTMP sheet can be improved by adding fine material from kraft pulp.
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| 9. |
- Chinga-Carrasco, Gary, et al.
(författare)
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Structural effects on print-through and set-off
- 2012
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Ingår i: Nordic Pulp & Paper Research Journal. - 0283-2631 .- 2000-0669. ; 27:3, s. 596-603
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Tidskriftsartikel (refereegranskat)abstract
- In this study the effect of paper structure on ink transfer and cold-set print quality was assessed. A factorial experiment involving 5 factors with two levels was designed. Several sheet structures were constructed. The sheets were made from three basic pulps, thermomechanical pulp (TMP), de-inked pulp (DIP) and stone groundwood (SGW). The designed structures were homogeneous and layered to verify the effect of sheet structure and fines content on print quality. A comprehensive multiscale characterisation of the sheet structures was performed. The analyses comprised scanning electron microscopy (SEM) and mercury porosimetry for bulk structure assessment. Parker Print Surf (PPS), laser profilometry and field-emission scanning electron microscopy (FE-SEM) were applied for giving a detailed description of the surface structure affecting ink transfer. The study revealed that the surface structure affects the ink demand and set-off. Increasing the micro-roughness leads to an increment of ink demand in order to achieve a given print density. The bulk pore structure affects the light scattering coefficients. Small pores are positive for increasing the light scattering and thus for reducing the print-through level. This was confirmed by SEM and mercury porosimetry measurements.
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| 10. |
- Vomhoff, Hannes, et al.
(författare)
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Evaluation of the compressibility of kitchen towel
- 2016
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Ingår i: Tappi Tissue 360 Forum.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The out-of-plane compressibility of kitchen towels is a very important product property in order to achieve a high absorption capacity. A method for the measurement of the compressibility was therefore developed. It allows the compression of a tissue sample by a defined pressure in the range between 0 and 30 kPa. The thickness of the sample is measured. Both single-ply base paper samples and fully converted multi-ply products can be evaluated. The measurement can be performed on both dry or wet samples. Multiple compressions of the samples can also be performed in order to evaluate the difference in plastic deformation as a result of consecutive compressions. Under normal conditions, the applied pressure is gradually increased from 0 to 30 kPa and then decreased back to 0 kPa. This procedure can then be repeated. The compressibility of the sample was evaluated in terms of a bulk versus applied pressure.The compressibility of different tissue grades was evaluated and compared. A clear difference in compressibility between standard DCT and structured tissue samples was observed. The first compression cycle lead to a considerable irreversible, plastic deformation of the sample. The plastic deformation decreased then considerably during the consecutive compression cycles. Wetting the samples lead to a considerable decrease in compressibility. The results allow interesting conclusions in terms of the influence of base sheet production process and the converting processes on the absorption properties.
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