scholarly journals Alkali Extraction of Kraft Pulp Fibers: Influence on Fiber and Fluff Pulp Properties

2012 ◽  
Vol 7 (2) ◽  
pp. 155892501200700 ◽  
Author(s):  
Kristoffer Lund ◽  
Karin Sjöström ◽  
Harald Brelid
Keyword(s):  
Kraft Pulp ◽  
Pulp Fibers ◽  
Fiber Network ◽  
Alkali Extraction ◽  
Flexible Fiber ◽  
Softwood Pulp ◽  
Softwood Kraft Pulp ◽  
Patent Literature ◽  
Network Strength ◽  
Birch Kraft Pulp

The importance of hemicelluloses for the papermaking properties of pulp fibers is well documented. In the patent literature, it can be seen that there is also an interest in this type of modification of pulp fibers for use in absorption products. In this study, a Scandinavian softwood kraft pulp and a birch kraft pulp were alkali extracted at 3 different concentrations of NaOH (2%, 4% and 8% NaOH in the suspension). The alkali extraction removed a large part of the hemicelluloses from the pulp fibers and decreased the content of the charged groups. After extraction, the pulps were dried in the form of sheets (approx. 600 g/m2). The alkali extracted pulp fibers exhibited a greater decrease in swelling when re-wetted than untreated pulp. A significant increase in the curl index after extraction with 4% and 8% NaOH was also noted. The tensile strength index of the formed sheets increased at the lowest concentration of NaOH and, at the higher concentrations, a decrease was observed. The pulp sheets were dry defibrated at different defibration intensities and the performance of the resulting pulps in fluff pulp applications was studied. The air-laid fiber networks of softwood pulp fibers showed higher network strength than the networks of birch pulps. The birch pulp extracted at the highest alkali level tended to give the highest network strength. The results from the network strength tests also indicated that the increased curl of the fibers from the softwood pulp extracted at the highest alkali level rendered a more flexible fiber network. In water absorption tests, the alkali treated softwood fibers tended to give networks with a somewhat enhanced water holding capacity under pressure.

scholarly journals The relationship between shrinkage and elongation of bleached softwood kraft pulp sheets

2018 ◽  
Vol 33 (3) ◽  
pp. 522-533 ◽  
Author(s):  
Jarmo Kouko ◽  
Elias Retulainen
Keyword(s):  
Kraft Pulp ◽  
Drying Shrinkage ◽  
Total Elongation ◽  
Reference Points ◽  
Pulp Fibers ◽  
Fiber Network ◽  
Softwood Kraft Pulp ◽  
The Difference ◽  
Novel Concept ◽  
The Relationship

AbstractThe relationship between shrinkage and elongation of hand sheets was examined. The results show that the same dimensional contraction brought about by shrinkage can be strained out in tensile testing. However, percentage-wise the elongation is greater than the shrinkage due to different reference points, and the difference increases strongly at higher shrinkage levels. Elongation of paper can be explained mainly by two factors: the shrinkage and the net elongation of paper. Here shrinkage refers to all kinds of in-plane contraction of the fiber network (drying shrinkage, in-plane-compaction and creping). The novel concept ‘net elongation’ was proposed in order to separate the effect of shrinkage from the total elongation of paper. Net elongation is the elongation of corresponding unshrunken paper dried under restraint. Sheets with high elongation were prepared from bleached softwood kraft pulp and the effects of shrinkage on elongation, strength and stiffness of the paper were investigated. Mechanical treatment methods of pulp fibers and chemical strength additives were applied in order to maximize the strength and elongation. In-plane compaction and creping were used to further boost shrinkage of the high basis weight (100 g/m2) sheets up to 160 percent. Experimental elongation data confirmed the proposed theoretical relationships.

scholarly journals 1,2,3,4-Butanetetracarboxylic Acid Cross-Linked Softwood Kraft Pulp Fibers for Use in Fluff Pulp Applications

2014 ◽  
Vol 9 (3) ◽  
pp. 155892501400900
Author(s):  
Kristoffer Lund ◽  
Harald Brelid
Keyword(s):  
Kraft Pulp ◽  
Cross Linking ◽  
Hydroxyl Groups ◽  
Pulp Fibers ◽  
Fiber Networks ◽  
Polycarboxylic Acids ◽  
Fiber Wall ◽  
Softwood Kraft Pulp ◽  
Cross Linker ◽  
Butanetetracarboxylic Acid

Cross-linked fluff pulp fibers for use in, for example, acquisition layers in absorption products can be found in the patent literature. Cross-linking improves properties such as the wet resilience of fluff pulp fiber networks. Among the more commonly seen cross-linkers are polycarboxylic acids, such as 1,2,3,4-butanetetracarboxylic acid (BTCA). These acids form ester bonds with the hydroxyl groups in the fiber wall. In this study, softwood kraft pulp fibers were cross-linked with BTCA. The swelling behavior of the fibers and properties related to acquisition in absorption products were studied. It was found that the water retention value (WRV) decreased as a consequence of the introduced cross-linker. After deprotonization of a large part of the introduced carboxylic acids, the WRV increased, but the cross-linker was still able to limit significant swelling of the fiber wall. The wet bulk under load of fiber networks, composed of cross-linked fibers, generally increased with a decrease in WRV. Furthermore, it was found that the property development obtained after a cross-linking reaction with BTCA may be predicted by introducing a relative reaction intensity, RIrel, that takes into account both time and temperature in the curing step. This shows that the time and temperature in the curing step are interchangeable.

Impact of dissolved organic matter in D0- and AD0-stages in bleaching of birch kraft pulp

2019 ◽  
Vol 34 (4) ◽  
pp. 433-441
Author(s):  
Caroline Wilke ◽  
Niclas Andersson ◽  
Ulf Germgård
Keyword(s):  
Organic Matter ◽  
Dissolved Organic Matter ◽  
Kraft Pulp ◽  
Pulp Mill ◽  
Good Control ◽  
Process Conditions ◽  
Dissolved Matter ◽  
Softwood Kraft Pulp ◽  
Polluting Emissions ◽  
Birch Kraft Pulp

Abstract To be able to charge a correct amount of chlorine dioxide in the D0-stage, a pulp mill needs good control of the bleaching process and good sensors to keep the variability of the bleaching result on an acceptable level. It is also important to include the bleaching agent demand from the dissolved matter in the pulp slurry. If this is done correctly, over- or undercharging of bleaching agents can be reduced, which lead to lower bleaching chemical cost, lower polluting emissions and higher pulp quality. Our previous research has shown that the dissolved organic carryover from the O2-stage varies significantly when bleaching softwood kraft pulp. The present study investigated the corresponding impact in the case of bleaching of birch pulp. Different mill configurations and process conditions have been simulated in laboratory trials, including proceeding A-stage treatment, different degrees of washing before and between the stages, and a comparison of the effects of recycled and non-recycled wash filtrates. The results have confirmed the significant impact of the dissolved organic matter, and the knowledge which have been generated can be used to understand how measurement and control concepts can be developed to improve the pulp quality control and to decrease production cost.

scholarly journals Potential of bleached eucalyptus kraft pulp for applications in nonwoven fibrous fabrics

2020 ◽  
Vol 15 ◽  
pp. 155892502098014
Author(s):  
Sofia M Rebola ◽  
Joana Ferreira ◽  
Dmitry V Evtuguin
Keyword(s):  
Kraft Pulp ◽  
Pilot Scale ◽  
Absorption Capacity ◽  
Raw Material ◽  
Process Conditions ◽  
Fiber Morphology ◽  
Pulp Bleaching ◽  
Fiber Network ◽  
Eucalyptus Kraft Pulp ◽  
Network Strength

A series of six industrial bleached hardwood kraft pulps produced from Eucalyptus globulus (BEKPs) under variable process conditions were dry-defiberized on a pilot scale hammermill at 3500 rpm and the nonwoven air-laid fabrics evaluated for their specific volume, absorption capacity/absorption rate and fiber network strength. The effect of non-defiberized fiber aggregates (knots) on the former properties was evaluated. Processual variations in pulping and bleaching conditions revealed variability within 15% in the absorption capacity of fluff pulps and within 25% in the network strength of the air-laid formulations. These variations were attributed to changes in the chemical composition of BEKPs and fiber morphology. The importance of pulp bleaching sequence on the quality of BEKPs for fluff applications was highlighted. BEKPs, having a high residual xylan content with a greater amount of uronic/hexenuronic moieties and coarser/deformed fibers, revealed the best performance in fluff applications. The coarseness was considered a critical morphological parameter of the fibers, strongly affecting the porosity of air-laid formulations, which determined the absorption capacity and the network strength. The absorption capacity of fluffed BEKP was comparable of commercial bleached softwood kraft pulp (BSKP), although the latter showed almost triple the network strength of air-laid formulations produced with BEKP. BSKP proved to be much more vulnerable to dry defiberization conditions than BEKP and suffered a pronounced cut of fibers, producing larger amounts of fines (dust) and stronger undesirable peeling and straightening of fibers. BEKPs can be considered a promising raw material for fluff applications, whose basic properties can be adjusted according to the needs by varying conditions in the pulping and bleaching process steps.

scholarly journals Synthesis of Nanofibrillated Cellulose by Combined Ammonium Persulphate Treatment with Ultrasound and Mechanical Processing

Nanomaterials ◽  
2018 ◽  
Vol 8 (9) ◽  
pp. 640 ◽  
Author(s):  
Inese Filipova ◽  
Velta Fridrihsone ◽  
Ugis Cabulis ◽  
Agris Berzins
Keyword(s):  
Zeta Potential ◽  
Mechanical Treatment ◽  
Kraft Pulp ◽  
Cellulose Nanofibrils ◽  
Crystallinity Index ◽  
Nanofibrillated Cellulose ◽  
Ammonium Persulfate ◽  
Pulp Fibers ◽  
Persulfate Oxidation ◽  
Birch Kraft Pulp

Ammonium persulfate has been known as an agent for obtaining nanocellulose in recent years, however most research has focused on producing cellulose nanocrystals. A lack of research about combined ammonium persulfate oxidation and common mechanical treatment in order to obtain cellulose nanofibrils has been identified. The objective of this research was to obtain and investigate carboxylated cellulose nanofibrils produced by ammonium persulfate oxidation combined with ultrasonic and mechanical treatment. Light microscopy, atomic force microscopy (AFM), powder X-Ray diffraction (PXRD), Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and Zeta potential measurements were applied during this research. The carboxylated cellulose suspension of different fractions including nanofibrils, microfibrils and bundles were produced from bleached birch Kraft pulp fibers using chemical pretreatment with ammonium persulfate solution and further defibrillation using consequent mechanical treatment in a high shear laboratory mixer and ultrasonication. The characteristics of the obtained nanofibrils were: diameter 20–300 nm, crystallinity index 74.3%, Zeta potential −26.9 ± 1.8 mV, clear FTIR peak at 1740 cm−1 indicating the C=O stretching vibrations, and lower thermostability in comparison to the Kraft pulp was observed. The proposed method can be used to produce cellulose nanofibrils with defined crystallinity.

Application of a Catalyst in Peroxide Bleaching of Eucalyptus Kraft Pulp

Holzforschung ◽  
2000 ◽  
Vol 54 (4) ◽  
pp. 407-412 ◽  
Author(s):  
L. Kühne ◽  
J. Odermatt ◽  
T. Wachter
Keyword(s):  
Hydrogen Peroxide ◽  
Kraft Pulp ◽  
Pulp Bleaching ◽  
Selective Catalyst ◽  
Peroxide Bleaching ◽  
Softwood Pulp ◽  
Kraft Pulp Bleaching ◽  
Eucalyptus Kraft Pulp ◽  
Softwood Kraft Pulp

Summary A binuclear [Mn(III)Mn(IV)(μ-O)2(μ-CH3COO)L](ClO4−)2 complex with L = 1,2 Bis-(4,7-dimethyl-1,4,7-triazacyclonon-1-yl)-ethane, described as a selective catalyst in hydrogen peroxide bleaching of softwood pulps, was tested in hardwood kraft pulp bleaching. The catalyst application gave rise to a higher consumption of peroxide which resulted in higher pulp brightness. The delignification improvement caused by the catalyst was shown to be much lower compared to catalysed peroxide bleaching of softwood kraft pulp. In contrast to the results of softwood pulp bleaching no selectivity improvements could be found when using the catalyst in bleaching of eucalyptus kraft pulp.

Understanding extensibility of paper: Role of fiber elongation and fiber bonding

TAPPI Journal ◽  
2020 ◽  
Vol 19 (3) ◽  
pp. 125-135
Author(s):  
JARMO KOUKO ◽  
TUOMAS TURPEINEN ◽  
ARTEM KULACHENKO ◽  
ULRICH HIRN ◽  
ELIAS RETULAINEN
Keyword(s):  
Strain Curve ◽  
Tensile Tests ◽  
Pulp Fibers ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Fiber Network ◽  
Fiber Networks ◽  
Strain Behavior ◽  
Softwood Kraft Pulp ◽  
Random Fiber Networks

The tensile tests of individual bleached softwood kraft pulp fibers and sheets, as well as the micro-mechanical simulation of the fiber network, suggest that only a part of the elongation potential of individual fibers is utilized in the elongation of the sheet. The stress-strain curves of two actual individual pulp fibers and one mimicked classic stress-strain behavior of fiber were applied to a micromechanical simulation of random fiber networks. Both the experimental results and the micromechanical simulations indicated that fiber bonding has an important role not only in determining the strength but also the elongation of fiber networks. Additionally, the results indicate that the shape of the stress-strain curve of individual pulp fibers may have a significant influence on the shape of the stress-strain curve of a paper sheet. A large increase in elongation and strength of paper can be reached only by strength-ening fiber-fiber bonding, as demonstrated by the experimental handsheets containing starch and cellulose microfi-brils and by the micromechanical simulations. The key conclusion related to this investigation was that simulated uniform inter-fiber bond strength does not influence the shape of the stress-strain curve of the fiber network until the bonds fail, whereas the number of bonds has an influence on the activation of the fiber network and on the shape of the whole stress-strain curve.

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