scholarly journals Softwood kraft pulp fines: application and impact on specific refining energy and strength properties

Cellulose ◽  
2020 ◽  
Vol 27 (17) ◽  
pp. 10359-10367
Author(s):  
Daniel Mandlez ◽  
Lukas Zangl-Jagiello ◽  
Rene Eckhart ◽  
Wolfgang Bauer
Keyword(s):  
Tensile Strength ◽  
Linear Relationship ◽  
Apparent Density ◽  
Kraft Pulp ◽  
Strength Properties ◽  
Air Permeability ◽  
Research Interest ◽  
Paper Properties ◽  
Softwood Kraft Pulp ◽  
Breaking Length

AbstractAlong with the emergence of micro and nanofibrillated celluloses and their application in papermaking, the influence of the so called fines fraction of pulps on both process and product properties has received increasing research interest in recent years. Several researchers have experimented with primary and/or secondary pulp fines to assess their effects on paper properties with not always consistent results. Our work focuses on the targeted application of the primary fines fraction of an unbleached softwood kraft pulp. The primary fines are separated from the pulp to be subsequently added to achieve blends of $$5\%, 9\%$$ 5 % , 9 % and $$12\%$$ 12 % primary fines content. These blends were then refined in a PFI mill to evaluate the effect of the primary fines on refining as well as on paper properties of hand sheets prepared from these pulps. It is shown that the addition of primary fines enhances tensile strength in the unrefined and slightly refined state, while the maximum tensile strength of the highly refined reference pulp is not increased. A slightly increased dewatering resistance (Schopper Riegler) at comparable air permeability (Gurley) for a given tensile strength was also observed. The linear relationship between tensile index and apparent sheet density seems to be affected in the unrefined and slightly refined state where the breaking length of the fines enriched samples is higher for a given apparent density.

Effect of machine speed on formation and strength efficiency in twin-wire roll forming of never-dried unbleached softwood kraft pulp

2018 ◽  
Vol 33 (2) ◽  
pp. 271-278
Author(s):  
Bengt Nordström ◽  
Lennart Hermansson
Keyword(s):  
Tensile Strength ◽  
Kraft Pulp ◽  
Roll Forming ◽  
Favorable Effect ◽  
Paper Properties ◽  
Difference Curve ◽  
Insignificant Effect ◽  
Wide Range ◽  
Softwood Kraft Pulp ◽  
Machine Speed

Abstract There is a constant drive to increase machine speed in the production of kraftliner and most other major paper grades, but the separate effect of the machine speed on the paper properties has been unclear. The effect of machine speed in twin-wire roll forming of never-dried unbleached softwood kraft pulp was evaluated here in a pilot machine investigation by examining three machine speed levels (500, 750, and 1000 m/min) over a series of jet-to-wire speed differences. Similar headbox consistency and draw from wire section to winding were employed at the different machine speed levels. An increase in the machine speed had a favorable effect on formation and Z-strength efficiency over a wide range of jet-to-wire speed differences, whereas the machine speed had an insignificant effect on tensile strength efficiency and tensile stiffness efficiency. For all properties, the overall shape of the jet-to-wire speed difference curve remained similar when changing the machine speed.

Fibre characteristics and paper properties of formic acid / peroxyformic acid birch pulps

1997 ◽  
Vol 12 (4) ◽  
pp. 237-243 ◽  
Author(s):  
Anu Seisto ◽  
Krisriina Poppius-Levlin
Keyword(s):  
Tensile Strength ◽  
Formic Acid ◽  
Kraft Pulp ◽  
Strength Properties ◽  
Kappa Number ◽  
Strength Development ◽  
Paper Properties ◽  
Fibre Breakage ◽  
High Degree ◽  
Peroxyformic Acid

Abstract The fibre and paper properties of nine unbleached formic acid / peroxyformic acid (MILOX) pulps with kappa number 6-20 were studied and compared with a kraft pulp with kappa number 20. The degree of deformation was greater in the MILOX fibres, affecting the paper properties of the MILOX pulps. The large number of curl and kinks in the MILOX fibres were probably caused mechanically. The MILOX fibres showed greater conformability, resulting in higher paper density. The defects in the MILOX fibres were apparently so severe as to cause fibre breakage during PFI beating of the pulps. As a result of both fibre deformation and breakage, the tensile strengths of the MILOX pulps were lower than that of the reference kraft pulp, and tensile strength development during beating was slower. The tear strength of the best MILOX pulp was lower than that of the kraft pulp when compared at the same tensile index. Fibre deformation in both MILOX and the kraft pulp increased during bleaching. The kinks in the fibres were possibly set into position, giving the bleached MILOX pulps poorer bonding ability and lower paper density. A high degree of fibre defo~mation had the same effect on the tensile strength development of the bleached MILOX pulps as it did in the unbleached state. The light scattering properties of the MlLOX pulps were better than those of the kraft pulp, possibly due to the higher fines content of the MILOX pulps. The results indicate that more attention should be given to mechanical treatments during MILOX pulping in order to bring the strength properties closer to those of kraft pulp.

Reinforcing potential of wood pulp-derived microfibres in a PVA matrix

Holzforschung ◽  
2006 ◽  
Vol 60 (1) ◽  
pp. 53-58 ◽  
Author(s):  
Ayan Chakraborty ◽  
Mohin Sain ◽  
Mark Kortschot
Keyword(s):  
Tensile Strength ◽  
Aspect Ratio ◽  
Polyvinyl Alcohol ◽  
Microcrystalline Cellulose ◽  
Comparative Studies ◽  
Kraft Pulp ◽  
Fold Increase ◽  
Minimum Length ◽  
Reinforcing Agent ◽  
Softwood Kraft Pulp

Abstract In this study, the reinforcing potential of cellulose “microfibres” obtained from bleached softwood kraft pulp was demonstrated in a matrix of polyvinyl alcohol (PVA). Microfibres are defined as fibres of cellulose of 0.1–1 μm in diameter, with a corresponding minimum length of 5–50 μm. Films cast with these microfibres in PVA showed a doubling of tensile strength and a 2.5-fold increase in stiffness with 5% microfibre loading. The theoretical stiffness of a microfibre was calculated as 69 GPa. The study also demonstrated that the strength of the composite was greater at 5% microfibre loading compared to 10% loading. Comparative studies with microcrystalline cellulose showed that the minimum aspect ratio of the reinforcing agent is more criticalthan its crystallinity in providing reinforcement in the composite.

scholarly journals Use of fines-enriched chemical pulp to increase CTMP strength

TAPPI Journal ◽  
2021 ◽  
Vol 20 (4) ◽  
pp. 255-263
Author(s):  
ELISABETH BJORK ◽  
MIKAEL BOUVENG ◽  
HANNES VOMHOFF ◽  
PER ENGSTRAND
Keyword(s):  
Kraft Pulp ◽  
Fine Fraction ◽  
Strength Properties ◽  
Strength Increase ◽  
Fines Content ◽  
Chemical Pulp ◽  
Softwood Kraft Pulp

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.

scholarly journals Hydrogen peroxide bleaching of hardwood kraft pulp with adsorbed birch xylan and its effect on paper properties

BioResources ◽  
2011 ◽  
Vol 6 (1) ◽  
pp. 721-736
Author(s):  
Lizi Li ◽  
Sanghoon Lee ◽  
Hak Lae Lee ◽  
Hye Jung Youn
Keyword(s):  
Hydrogen Peroxide ◽  
Optical Properties ◽  
Kraft Pulp ◽  
Strength Properties ◽  
Pulp Fibers ◽  
Paper Properties ◽  
Peroxide Bleaching ◽  
Initial Ph ◽  
The Relationship ◽  
Temperature Time

The adsorption of xylan on pulp fibers improves the strength properties of paper. However, the optical properties are decreased significantly. The objective of our research was to bleach hardwood kraft pulp with adsorbed birch xylan by hydrogen peroxide and study the effect of bleaching parameters on paper properties. The bleaching parameters studied included bleaching temperature, time, initial pH as well as MgSO4 dosage. The optical properties (whiteness, brightness, opacity) and physical properties (tensile index, tearing index, bulk) of handsheets made from the pulp bleached with different process variables were measured. The results showed that better optical properties were obtained with higher bleaching temperature, longer bleaching time, and more MgSO4 dosage. Bleaching from an initial pH of 11 provided the highest brightness value. On the other hand, strength properties were improved with decreasing of the bleaching temperature, and increasing the initial pH and MgSO4 dosage. The relationship between strength properties and bleaching time varied depending on bleaching temperature. According to the results, both good mechanical properties and optical properties could be achieved when the operating parameters were controlled properly. Therefore hydrogen peroxide bleaching was proved to be a suitable method for bleaching hardwood kraft pulp with adsorption of birch xylan.

Using cationic polyvinyl alcohol (C-PVA) to improve the strength of wood-free papers containing high-yield pulp (HYP)

Holzforschung ◽  
2010 ◽  
Vol 64 (5) ◽  
Author(s):  
Xin Liu ◽  
Pedram Fatehi ◽  
Yonghao Ni ◽  
Huining Xiao
Keyword(s):  
Polyvinyl Alcohol ◽  
Apparent Density ◽  
Fiber Surface ◽  
Strength Properties ◽  
High Yield ◽  
Kraft Pulps ◽  
Paper Properties ◽  
Atomic Force ◽  
Tear Index ◽  
Afm Analysis

AbstractHigh-yield pulp (HYP) is gaining increasing interest in wood-free papers, because it can improve the bulk, formation, and opacity of papers. However, one of the challenges for the papermakers is the strength of papers when a large amount of HYP is replaced with hardwood kraft pulp. In this work, we explored the potential of using cationic-modified polyvinyl alcohol (C-PVA) in increasing the strength properties of HYP. Also, C-PVA was applied to the paper-sheets made of softwood/hardwood bleached kraft pulps (SBKP/HBKP) and HYP under various conditions, and the corresponding paper properties were evaluated. It was observed that C-PVA increased the strength properties of these paper-sheets, and the results obtained from using C-PVA were only slightly less effective than those obtained from using cationic starch (C-starch). Furthermore, the addition of C-PVA to HYP, and subsequently mixing with the blend of SBKP/HBKP (option no. 1) improved the tensile and burst indices, light scattering coefficient and apparent density of paper-sheets more significantly than did the addition of C-PVA directly to the mixed furnish of SBKP/HBKP/HYP (option no. 2). Additionally, atomic force microscope (AFM) analysis showed that the attraction force, developed between the AFM-tip and the fiber surface, was changed by the C-PVA modification. The tensile and burst indices of paper-sheets were improved by adding 10 mg g-1C-PVA and substituting 30% of HYP for HBKP, whereas the tear index, apparent density, PPS-roughness, and brightness decreased.

The Importance of Xylan for the Strength Properties of Spruce Kraft Pulp Fibres

Holzforschung ◽  
2001 ◽  
Vol 55 (6) ◽  
pp. 639-644 ◽  
Author(s):  
C. Schönberg ◽  
T. Oksanen ◽  
A. Suurnäkki ◽  
H. Kettunen ◽  
J. Buchert
Keyword(s):  
Tensile Strength ◽  
Chemical Composition ◽  
Fracture Energy ◽  
Kraft Pulp ◽  
Fibre Length ◽  
Strength Properties ◽  
Total Charge ◽  
Pulp Fibres ◽  
Considerable Impact

Summary In this work the role of xylan in spruce kraft pulp fibres was investigated by selectively removing the pulp fibre xylan and also by sorbing xylan onto the pulp fibres. The effects of xylan removal and sorption on fibre properties were measured and the chemical composition of the fibres and also that of the selectively removed xylans was analyzed. According to the results the xylanase could act on both sorbed and native xylan located on accessible fibre surfaces. Xylan was found to affect the strength properties of handsheets. The location and the charge of xylan had a considerable impact on the formation of interfibre bonds. Scott Bond-values correlated with the amount of surface xylan on fibre surfaces, whereas tensile strength was affected by the total amount of xylan and particularly by the total charge of the fibres. The fracture energy was determined by the combined effect of interfibre bonding ability and effective fibre length.

scholarly journals A comparative study of the effect of cellulose-based deep coating and pulp refining on the structural and mechanical properties of paper

BioResources ◽  
2021 ◽  
Vol 16 (3) ◽  
pp. 5376-5389
Author(s):  
Marta Krysztof ◽  
Konrad Olejnik ◽  
Piotr Kulpiński ◽  
Aleksandra Erdman ◽  
Elżbieta Sąsiadek
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Strength Properties ◽  
Air Permeability ◽  
Refining Process ◽  
Deep Penetration ◽  
Coating Process ◽  
Cellulosic Fibers ◽  
Coating Method ◽  
Paper Structure

A new coating method was developed, based on cellulose regenerated from an N-methylmorpholine N-oxide (NMMO) solution applied to paper. In particular, the purpose of this study was to compare the effectiveness of the “deep coating” method using cellulose regenerated from NMMO solution and the classic pulp refining process as methods to improve paper mechanical properties and overall quality. The “deep coating” name comes from the fact that the coating process is combined with subsequent heating of the coating before its final solidification. As a result of this operation, deep penetration of the cellulosic solution into the paper structure occurs. This increases the contact surface of the solution with the cellulosic fibers, which increases the strength properties of the paper structure. It was found that the cellulosic coating increased the apparent density of the paper, the tensile strength, the elongation, the resistance to bursting, and the double fold number. However, the coating also decreased the air permeability and the tear resistance of the paper samples. Despite some technological difficulties, this method could be an attractive solution in the case of a need for additional functionalization of a paper structure.

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