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Editors Dr. Monica Ek Professor em.
- Pulp and Paper Chemistry and Technology Volume 2 Pulping Chemistry and Technology Edited ...
- Pulp and Paper. Chemistry and Chemical Technology, Volume 3. Edition No. 3
- Cellulose Pulp from Wood
- Pulp and Paper: Chemistry and Chemical Technology, Volume 3
Edited by Casey, James P. Edited by James P. McGinnis and F. Lignin W. Pulpwood W.
Pulp and Paper Chemistry and Technology Volume 2 Pulping Chemistry and Technology Edited ...
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Start by pressing the button below! Monica Ek Professor em. KG, Berlin. All rights reserved, including those of translation into foreign languages. No part of this book may be reproduced or transmitted in any form or by any means, electronic or mechanic, including photocopy, recording, or any information storage retrieval system, without permission in writing from the publisher.
Printed in Germany. Cover design: Martin Zech, Bremen, Germany. Foreword The production of pulp and paper is of major importance in Sweden and the forestry industry has a profound influence on the economy of the country. The technical development of the industry and its ability to compete globally is closely connected with the combination of high-class education, research and development that has taken place at universities, institutes and industry over many years.
In many cases, Swedish companies have been regarded as the initiator of new technology which has started here and successively found a general world-wide acceptance.
This leadership in knowledge and technology must continue and be developed around the globe in order for the pulp and paper industry to compete with high value-added forestry products adopted to a modern sustainable society. The production of forestry products is based on a complex chain of knowledge in which the biological material wood with all its natural variability is converted into a variety of fibre-based products, each one with its detailed and specific quality requirements.
In order to make such products, knowledge about the starting material, as well as the processes and products including the market demands must constitute an integrated base. The possibilities of satisfying the demand of knowledge requirements from the industry are intimately associated with the ability of the universities to attract students and to provide them with a modern and progressive education of high quality.
A major share of the grant was devoted to the development of a series of modern books covering the whole knowledge-chain from tree to paper and converted products. This challenge has been accomplished as a national four-year project involving a total of 30 authors from universities, Innventia and industry and resulting in a four volume set covering wood chemistry and biotechnology, pulping and paper chemistry and paper physics.
For the benefit of pulp and paper engineers and other people with an interest in this fascinating industry, we hope that the availability of this material as printed books will provide an understanding of all the fundamentals involved in pulp and paper-making. The water in the cell wall is usually divided into water in a gel phase and water in voids in the fibre wall.
However, some authors also claim that the concept of the fibre wall as a gel is an unnecessary exercise, since most of the effects achieved by changing the chemical environment around the fibres can be explained by a swollen surface layer of the fibres, see e.
Pelton Without entering this debate, it is a fact that the discussion about how the water is accommodated in the fibre wall is very dependent on the structure of the wall and how this fibre wall is changed by different process conditions.
Therefore it is necessary to start by discussing the current understanding of the structure of the fibre wall and then go on to discuss how recent developments have changed our understanding of the structure of the fibre wall and how it is changed upon for example lignin and hemicellulose removal. In an early paper, Stone and Scallan a introduced the concept of the multilamellar structure of the fibre wall with the lamellae arranged concentrically with the cell wall axis.
The number of lamellae was dependent on the degree of swelling and upon drying the lamellae join together. This latter technique results in an unnatural swelling of the fibre wall and the results can at best be used for qualitative discussions. The nitrogen gas adsorption, how- 2 ever, is very accurate and these results also showed that the saturation point of the cell wall was 0. The basis behind the nitrogen adsorption method is an adsorption isotherm of nitrogen onto the fibres Haselton The fibres are exposed to an increasing concentration, i.
Up to a monolayer coverage of nitrogen on the fibres the adsorption can be described by the BET equation, i. Stone and Scallan b also introduced a pulp preparation technique, where the wood chips could be delignified under extremely well controlled conditions and the first results with this technique were virtually the same as the earlier published results regarding the multilamellar structure of the fibre wall.
They were also able to show that the specific surface area and the volume of voids in the fibre wall, from nitrogen gas adsorption, increased as the degree of delignification increased. The surface area increased from Corresponding figures for the void volume in the fibre wall were 0.
By applying the same technique for delignification, Stone and Scallan prepared a number of kraft pulps with different yields and they then characterised these pulps with N2 adsorption, pressure plate analysis and a method where they determined the non-solvent water in the fibre wall.
In this latter technique, macromolecules with a molecular mass too high to allow for penetration into the fibre wall were used and by knowing the total amount of water in the system and the concentration of the macromolecules in the water phase, it was possible to determine the volume of the fibre wall inaccessible to the polymer. In the pressure plate technique, a water-saturated sample is subjected to an increasing air pressure and the volume of liquid remaining in the sample is measured at different pressures.
From this it is then possible to estimate a total void volume of the fibre wall. The results of this comparison are summarised in Table 1. This term was then called the fibre saturation point FSP since it included water in the gel phase of the fibre wall and in the void volume of the fibre wall.
Assuming a density of the components in the fibre wall they were also able to calculate how the solid material decreased with decreasing yield. They also made a further division of the pores in the fibre wall into macro-pores, i. A representation of this is given in Figure 1. The different volumetric changes in the fibre wall occurring when the degree of delignification is increased. The graph shows the volumetric changes from one gram of wood, i. The macro-pore water is defined as the volume of N2 adsorption and the micro-pore water is defined as the difference between the FSP-value and the macro-pore volume.
From Stone and Scallan and the data are collected from experiments with a kraft pulp. In a continuation of this series of papers Stone and Scallan the authors used the solute exclusion technique to determine how the size of the pores of the fibre wall changes as the yield of the pulp decreases. By using macromolecules with known dimensions and measuring how the volume of non-solvent water changed with the molecular mass, it was possible to estimate the size distribution of the pores of the fibre wall.
It can nevertheless be concluded that Stone and Scallan showed that the size of the pores, i. This was definitely a large step in our understanding of the structure of the fibre wall and this picture is still very dominating. It should however be stressed that these figures must be taken as relative.
Recent experimental evidence van de Ven , Li et. Based on these results and on electron micrographs, Scallan introduced the now very well known picture of how the internal fibrillation takes place with increasing swelling of the fibre wall. This figure is shown in Figure 1. Schematic view of how the fibrillation of the fibre wall takes place when the swelling is increased. From Scallan There is also a need for a considerable mechanical action on the fibre wall in order to make this fibrillation occur.
In the models presented by Stone and Scallan the arrangement of different chemical components in the fibre wall is not discussed, even though some comments were made regarding the arrangement of pores around the cellulosic microfibrils Stone and Scallan In order to fill this gap in knowledge, Kerr and Goring conducted work in which they studied ultra-thin microtome sections of permanganate-stained fibres from black spruce with transmission electron microscope.
They showed that cellulose was not stained by the permanganate and that only a minor part of the hemicellulose was stained, which means that it was possible to see the distribution of the lignin in the fibre wall. From cross-sections both along the fibres and across the fibres, they concluded that the ultrastructural arrangement of the different components of the fibre wall could be represented by the picture shown in Figure 1.
Schematic representation of the ultrastructural arrangement of cellulose, lignin and hemicellulose in the fibre wall of black spruce tracheids. From Kerr and Goring When the authors started to compare the amounts of the different components in the fibre wall, they found literature values corresponding to 0.
This means that a fraction of the hemicellulose had been stained by the permanganate and might therefore be assumed to be associated with the lignin.
The rest of the hemicellulose was assumed to be associated with the cellulose microfibrils. First of all the use of new techniques for determination of fibre structure via cryofixation and deep etching of the fibres followed by Field Emission Scanning Electron Microscopy FESEM should be mentioned Duchesne This technique has revealed a new very open structure of the fibre wall, for most commercial chemical pulps in their never dried form, where the fibrils are clearly separated.
The openings between the fibrils are of the order of 10—50 nm, naturally depending on the degree of delignification, and the lateral dimension of fibril aggregates are shown to be of the order 10—20 nm. This is demonstrated in Figure 1. In Figure 1. It should be stressed that the scale in the figures is the same and the size of the bar is nm in both diagrams. Figure 1. High resolution Cryo-FE-SEM micrograph showing the surface structure of a frozen hydrated kraft pulp fibre from spruce.
The bar in the figure corresponds to nm. Duchesne From these two figures it is clear that the openings in the fibre wall are larger then the pore size as estimated with the solute exclusion technique but this might not be so unexpected since this method is known not to be able to determine the correct pore size distribution of the fibres eventhough it is excellent for a determination of the Fibre Saturation Point FSP as defined earlier.
It is also clear from these figures that drying in air lads to a collapse of the pores in the fibre wall most likely caused by the capillary forces between the fibrils during drying. Despite the elegance of these types of micrographs it is very difficult to quantify the pore size and pore size distribution from these figure based on single fibre evaluations.
Methods based on some type of average property is the fibres is therefore of very large interest and Li et al used 2 H and 1H NMR relaxation measurements to determine the pore size distribution within pulp fibres. With this technique the relaxation of water molecules within the fibres are 8 determined from NMR spin lattice relaxation profiles using D2O and H2O as probe liquids.
The principal behind the method is schematically shown in Figure 1. FE-SEM micrograph of an air dried kraft pulp fibre from spruce. The bar in the figure corresponds to nm Duchesne Schematic representation of the principal behind the NMR relaxation method.
It is assumed that two types of water exist in the fibre wall, bound water and free water. As indicated in the figure the method is based on a number of assumptions. First of all it is assumed that two types of water molecules exists within the fibre wall, bound water that will be affected by the surface of the fibres and free water with the same properties as bulk water.
This means that the method will determine a surface to volume ratio of the water inside the fibre wall. In order to calculate and average pore radius of the fibre wall it is also assumed that the pores within the fibre wall has a cylindrical arrangement, similar to that shown in Figure 1. In mathematical terms this can be summarised by equation 1.
However, as can be seen in this set of equations it is possible to calculate a pore size distribution from NMR relaxation measurements after some assumptions about the geometry of the fibre wall. Andreasson et al conducted an investigation similar to the investigation by Stone and Scallan b where a set a kraft pulps from carefully selected chips were carefully delignified and then subjected to NMR relaxtion measurements and a typical result from these measurements are shown in Figure 1.
Pore size distribution of pores within the fibre for a set of kraft pulps from spruce, delignified to different yield, as determined with NMR relaxation measurements Data from Andreasson As can be seen from this figure the average pore radius increases from 10 nm to around 23 nm as the kappa number is changed from to 35 and then again decreases to around 17 nm as further lignin and hemicellulose is removed to a kappa number of Simultaneous measurements of the total volume of liquid held by the fibre wall, for the different fibres shown in Figure 1.
This also supports the hypothesis that as material is removed from the fibre during kraft pulping empty spaces are created within the fibre wall but that the total volume of the fibre wall is fairly constant.
Pulp and Paper. Chemistry and Chemical Technology, Volume 3. Edition No. 3
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Get this from a library! Pulp and paper chemistry and technology. Volume 1, Wood chemistry and wood biotechnology. [Monica Ek; Göran Gellerstedt; Gunnar.
Cellulose Pulp from Wood
This four volume set covers the entire spectrum of pulp and paper chemistry and technology from starting material to processes and products including market demands. This work is essential for all students of wood science and a useful reference for those working in the pulp and paper industry or on the chemistry of renewable resources. Volume 3 provides an overview of paper production and the ways in which the chemistry of starting materials and processes influence its quality and properties. EN English Deutsch.
An in-depth look at the chemistry and chemical technology involved in the manufacture of pulp and paper, the properties of paper, and the uses for paper. This new edition contains contributions by forty recognized authorities in the field. Emphasizes the underlying science and technology and reviews, in detail, chemical and engineering principles.
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