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Strategies for improving kraftliner pulp properties
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
2008 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

A large part of the world paper manufacturing consists of production of corrugated board components, kraftliner and fluting, that are used in many different types of corrugated boxes. Because these boxes are stored and transported, they are often subjected to changes in relative humidity. These changes together with mechanical loads will increase the deformation of the boxes compared to the case where the same loads are applied in a static environment. This enlarged creep due to the changes in relative humidity is called mechano-sorptive or accelerated creep. Mechano-sorptive creep forces producers to use high safety factors when designing boxes, and therefore, this is one of the key properties of kraftliner boards.

 

Different strategies to decrease mechano-sorptive creep, and to simultaneously gain more knowledge about the causes for this phenomenon in paper, are the aim of this work. Derivatised and underivatised black liquor lignins, a by-product produced in pulp mills in large quantities, have been used together with biomimetic methods, to modify the properties of kraftliner pulp. Furthermore, the properties of kraftliner pulp have been compared to other pulps in order to evaluate the influence of fibre morphological factors, such as fibre width and shape factor, on the mechano-sorptive creep. In addition the influence of the chemical composition of the kraftliner pulp has been evaluated both by means of treating a kraftliner pulp with chlorite and xylanase and by producing pulps with different chemical composition.

 

By using lignin and biomimetic methods, to create radical coupling reactions, it has been shown that it is possible to increase the wet strength of kraftliner pulp sheets. This method of treating the pulp showed, however, no significant effects on the mechano-sorptive creep. The addition of an apolar suberin-like lignin derivative, which has been shown to be possible to produce from natural resources, did show a positive effect on mechano-sorptive creep properties, but at the expense of stiffness properties in constant climate. Different pulps were compared with a kraftliner pulp and it was observed that the ratio between tensile stiffness and hygroexpansion can be used to estimate the mechano-sorptive creep properties. The hardwood kraft pulps investigated had lower hygroexpansion, probably due to more slender and straighter fibres, and higher tensile stiffness, probably due to lower lignin content. As the lignin content was varied by different methods in kraft pulps, it was observed that increased lignin content gives an increased hygroexpansion and decreased tensile stiffness as well as an increased mechano-sorptive creep. There were also indications of increased mechano-sorptive creep due to higher xylan content.

 

 

Abstract [sv]

En stor del av världens papperstillverkning utgörs av produktion av wellpappkomponenter, kraftliner och fluting, som används i en uppsjö av olika wellpapplådor. När dessa lådor lagras och transporteras utsätts de ofta för förändringar i relativa luftfuktigheten. Dessa förändringar tillsammans med mekanisk belastning ökar lådornas deformation jämfört med om samma belastning skulle ha applicerats vid ett statiskt klimat. Denna förhöjda krypning på grund av förändringarna i relativ luftfuktighet kallas mekanosorptiv- eller accelererad krypning. Mekanosorptiv krypning tvingar producenterna att ha höga säkerhetsmarginaler vid dimensioneringar av lådor och är därför en av nyckelegenskaperna för kraftliner.

 

Olika strategier för att minska denna effekt, och på samma gång erövra mer kunskap om orsakerna till detta fenomen, har varit syftet med arbetet. Derivatiserade och oderivatiserade svartlutslignin, en biprodukt möjlig att få ut i stora kvantiteter från massabruk, har används tillsammans med biomimetriska metoder, för att modifiera kraftlinermassas egenskaper. Dessutom har kraftlinermassans egenskaper jämförts med andra massors egenskaper för att utvärdera inverkan av fibermorfologiska faktorer, såsom fiberbredd och fibreform på det mekanosorptiva krypet. Också inverkan av den kemiska sammansättningen av kraftliner massan har undersökts både genom behandling med klorit och xylanas och genom att producera massor med olika kemiska sammansättningar.

 

Genom att använda lignin och biomimetriska metoder för att skapa radikal-kopplingsreaktioner har det visats på möjligheten att öka våtstyrkan i massa-ark. Det här sättet att behandla massa visade dessvärre inga signifikanta effekter på det mekanosorptiva krypet. Tillsatts av ett apolärt suberin-liknande ligninderivat, som visats möjligt att producera ur naturliga råmaterial, visade en positiv effekt på det mekanosorptiva krypegenskaperna även om det var på bekostnad av styvheten vid konstant klimat. Olika massor jämfördes med en kraftlinermassa och det observerades att relationen mellan dragstyvhet och hygroexpansion kan användas för att uppskatta de mekanosorptiva krypegenskaperna. Lövvedssulfatmassorna som undersöktes hade lägre hygroexpansion, antagligen beroende på smalare och rakare fibrer, och högre dragstyvhet, troligen beroende på en lägre ligninhalt. När ligninhalten varierades i sulfatmassor med olika metoder observerades att ökad ligninhalt ger en ökad hygroexpansion och minskad dragstyvhet liksom en ökad mekanosorptiv krypning. Dessutom fanns indikationer på en ökad mekanosorptiv krypning till följd av högre xylaninnehåll.

Place, publisher, year, edition, pages
Stockholm: KTH , 2008. , 43 p.
Series
Trita-CHE-Report, ISSN 1654-1081 ; 2008:70
Keyword [en]
lignin, xylan, kraftliner pulp, mechano-sorptive creep, hygroexpansion, stiffness, fibre shape, fibre width
Keyword [sv]
lignin, xylan, kraftlinermassa, mekanosorptivt kryp, hygroexpansion, styvhet, fiberform, fiberbredd
National Category
Paper, Pulp and Fiber Technology
Identifiers
URN: urn:nbn:se:kth:diva-9718ISBN: 978-91-7415-175-6 (print)OAI: oai:DiVA.org:kth-9718DiVA: diva2:127121
Public defence
2008-12-19, E2, KTH, Lindstedtsvägen 3, Stockholm, 14:00 (Swedish)
Opponent
Supervisors
Note
QC 20100629Available from: 2008-12-08 Created: 2008-12-01 Last updated: 2010-06-30Bibliographically approved
List of papers
1. Low Mw-lignin fractions together with vegetable oils as available oligomers for novel paper-coating applications as hydrophobic barrier
Open this publication in new window or tab >>Low Mw-lignin fractions together with vegetable oils as available oligomers for novel paper-coating applications as hydrophobic barrier
2008 (English)In: Industrial crops and products (Print), ISSN 0926-6690, E-ISSN 1872-633X, Vol. 27, no 1, 98-103 p.Article in journal (Refereed) Published
Abstract [en]

Lignin residues are available in large amounts as kraft lignin from chemical pulping processes. This lignin is mainly incinerated in recovery boilers. The recovery boilers are often the bottle-necks in the overall pulping process when pulp production increases are desired. Through cross-flow nano-filtration of the black liquor from kraft pulping, a low-molecular weight lignin fraction can be removed thus decreasing the organic load on the recovery boilers. The low-molecular weight lignin fraction furthermore exhibit different characteristics compared to other commercial kraft lignins and represents a new raw material source in novel applications.

The low-molecular weight lignin was used together with a vegetable oil to produce a new hydrophobic lignin derivative similar to suberin. The lignin and the lignin derivative was analysed with FT-IR, UV-vis and SEC. The ability of the product to make paper surfaces hydrophobic was also evaluated.

The results demonstrate the possibility to make a suberin-like lignin derivative that is potentially of interest in paper-coating applications due to its capability to interact well with wood fibres and make paper hydrophobic.

Keyword
lignin; black liquor; nano-filtration; hydrophobization; linseed oil; suberin
National Category
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-9708 (URN)10.1016/j.indcrop.2007.08.006 (DOI)000252909500016 ()2-s2.0-36448982818 (Scopus ID)
Note
QC 20100622Available from: 2008-12-01 Created: 2008-12-01 Last updated: 2017-12-14Bibliographically approved
2. Laccase-initiated cross-linking of lignocellulose fibres using a ultra-filtered lignin isolated from kraft black liquor
Open this publication in new window or tab >>Laccase-initiated cross-linking of lignocellulose fibres using a ultra-filtered lignin isolated from kraft black liquor
Show others...
2007 (English)In: Applied Microbiology and Biotechnology, ISSN 0175-7598, E-ISSN 1432-0614, Vol. 77, no 4, 809-817 p.Article in journal (Refereed) Published
Abstract [en]

In this work, the effect of Trametes pubescens laccase (TpL) used in combination with a low-molecular-weight ultra-filtered lignin (UFL) to improve mechanical properties of kraft liner pulp and chemi-thermo-mechanical pulp was studied. UFL was isolated by ultra-filtration from the kraft cooking black liquor obtained from softwood pulping. This by-product from the pulp industry contains an oligomeric lignin with almost twice the amount of free phenolic moieties than residual kraft pulp lignin. The reactivity of TpL on UFL and kraft pulp was studied by nuclear magnetic resonance spectroscopy and size exclusion chromatography. Laccase was shown to polymerise UFL and residual kraft pulp lignin in the fibres, seen by the increase in their average molecular weight and in the case of UFL as a decrease in the amount of phenolic hydroxyls. The laccase initiated cross-linking of lignin, mediated by UFL, which gives rise to more than a twofold increase in wet strength of kraft liner pulp handsheets without loosing other critical mechanical properties. Hence, this could be an interesting path to decrease mechano-sorptive creep that has been reported to lessen in extent as wet strength is given to papers. The laccase/2,2'azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) mediator system showed a greater increase in wet tensile strength of the resulting pulp sheets than the laccase/UFL system. However, other mechanical properties such as dry tensile strength, compression strength and Scott Bond internal strength were negatively affected by the laccase/ABTS system.

Keyword
laccase; oxidation; ultra-filtered lignin; mediator; wet strength; biorefinery; kraft pulp; fibre bonding; MEDIATOR SYSTEM; PULP FIBERS; OXIDATION; PAPER; BIODEGRADATION; DEGRADATION; MECHANISMS; ACIDS
National Category
Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:kth:diva-9709 (URN)10.1007/s00253-007-1203-6 (DOI)000251090900008 ()2-s2.0-36348971163 (Scopus ID)
Note
QC 20100629Available from: 2008-12-01 Created: 2008-12-01 Last updated: 2017-12-14Bibliographically approved
3. Adding lignin derivatives to decrease the effect of mechano-sorptive creep in linerboard
Open this publication in new window or tab >>Adding lignin derivatives to decrease the effect of mechano-sorptive creep in linerboard
2008 (English)In: Appita journal, ISSN 1038-6807, Vol. 61, no 6, 468-471 p.Article in journal (Refereed) Published
Abstract [en]

When load is applied to any type of paper while varying the relative humidity, the paper will creep more than if the same load is applied at constant humidity. This behaviour is called mechano-sorptive creep or accelerated creep, and the reasons for its occurrence in paper are still not fully understood. However, wet strength and the addition of apolar (hydrophobic) compounds to sheets have previously been suggested as factors improving the mechano-sorptive creep performance.

This work evaluates a method for improving wet strength and tests the addition of a hydrophobic compound, with particular reference to mechano-sorptive creep stiffness. Wet strength was improved by subjecting kraft liner pulp to low-molecular-weight lignin, obtained by cross-flow filtration, and to the radical initiator manganese(III). The hydrophobic compound added was a suberin-like lignin derivative. Adding the suberin-like lignin derivative significantly increased the mechano-sorptive creep stiffness, even though the stiffness at 90% rh decreased in the tested samples. This was probably because of the decrease in hygroexpansion caused by this hydrophobic additive.

Even though it is possible significantly to increase the wet strength of kraft liner pulp by adding manganese(III) and cross-flow-filtered lignin, doing so has no significant effect on mechano-sorptive creep stiffness.

Keyword
lignin derivatives; mechano-sorptive creep; wet strength; kraft liner; hygroexpansion; oxidative coupling; CROSS-LINKING; BLACK LIQUOR; PAPER
National Category
Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:kth:diva-9710 (URN)000261303200021 ()2-s2.0-56649114226 (Scopus ID)
Note
Uppdaterad från manuskript till artikel: 20101103. QC 20100629Available from: 2008-12-01 Created: 2008-12-01 Last updated: 2017-12-14Bibliographically approved
4. Comparison of the physical properties between hardwood and softwood pulps
Open this publication in new window or tab >>Comparison of the physical properties between hardwood and softwood pulps
2009 (English)In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 24, no 4, 409-414 p.Article in journal (Refereed) Published
Abstract [en]

High mechano-sorptive creep resistance, i.e., good creep resistance in environments with changing relative humidity, is one of the key requirements for linerboards. The aim of this study was to investigate the influence of pulp types and pulp properties on the mechano-sorptive creep of kraftliner. A high-yield softwood, kraftliner pulp, and four different hardwood pulps were investigated. The physical properties of laboratory sheets were evaluated, with emphasis on the mechano-sorptive creep properties.

The results showed that the density increase due to increased beating significantly improved the tensile stiffness of all pulps, while its effect on the isocyclic creep stiffness was less pronounced. The hardwood pulps showed higher tensile stiffness, better mechano-sorptive creep properties, and lower hygroexpansion than the softwood pulp at a given density. However, the softwood pulp did exhibit better tensile strength and fracture toughness properties than the hardwood pulps.

The results imply that hardwood pulps can be competitive with softwood pulps in kraftliners, provided that their tensile strength and fracture toughness properties can be improved by, for example, chemical means. Furthermore, the isocyclic creep stiffness correlates with the ratio of tensile stiffness to hygroexpansion, indicating that this ratio can be used for engineering estimates of the mechano-sorptive creep performance of paper materials.

Keyword
Birch, Dimensional stability, Eucalypt, Fracture toughness, Hygroexpansion, Linerboard, Mechano-sorptive creep, Softwood, Stiffness
National Category
Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:kth:diva-9712 (URN)10.3183/NPPRJ-2009-24-04-p409-414 (DOI)000273724200006 ()2-s2.0-76349105687 (Scopus ID)
Note

QC 20100629

Available from: 2008-12-01 Created: 2008-12-01 Last updated: 2017-12-14Bibliographically approved
5. The relationship between hygroexpansion, tensile stiffness, and mechano–sorptive creep in bleached hardwood kraft pulps
Open this publication in new window or tab >>The relationship between hygroexpansion, tensile stiffness, and mechano–sorptive creep in bleached hardwood kraft pulps
Show others...
2010 (English)In: Appita journal, ISSN 1038-6807, Vol. 63, no 1, 231- p.Article in journal (Refereed) Published
Abstract [en]

Hygroexpansion coefficient and tensile stiffness are important parameters in many paper applications. This study compares several bleached industrial hardwood kraft pulps, comprising five eucalypt pulps from South America, Europe, and Africa as well as an acacia pulp from Asia and a birch pulp from Scandinavia. Refined and unrefined pulps are compared. The results indicate significant differences in hygroexpansion but smaller differences in tensile stiffness index at comparable densities. No single factor offering a reasonable explanation of these differences in hygroexpansion coefficient, such as carbohydrate composition, fibre dimensions, or fibre form, was found. However, correlation between hygroexpansion coefficient and the mechano-sorptive creep stiffness was observed. We suggest that the hygroexpansion coefficient at a given tensile stiffness level can be used to rank pulps in terms of their mechano-sorptive creep properties.

Keyword
Mechano–sorptive creep, hygroexpansion, dimensional stability, eucalypt, birch, acacia
National Category
Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:kth:diva-11719 (URN)000279222500012 ()2-s2.0-77956655760 (Scopus ID)
Note

QC 20100629

Available from: 2009-12-08 Created: 2009-12-08 Last updated: 2017-12-12Bibliographically approved
6. The influence of lignin and xylan on some kraftliner pulp properties
Open this publication in new window or tab >>The influence of lignin and xylan on some kraftliner pulp properties
2009 (English)In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 24, no 4, 403-408 p.Article in journal (Refereed) Published
Abstract [en]

This study investigates the influence of lignin and hemicellulose content on the mechanical and physical properties of softwood kraft liner pulp. Tensile properties, hygroexpansion, and mechano-sorptive creep properties were measured. The lignin and hemicellulose contents were modified by chlorite delignification and xylanase treatment.

After treatment, the chemical composition of the pulps was 3-14% Klason lignin, 69-77% cellulose, 16-21% hemicellulose, and 4-7% xylan. In the tested pulps, low lignin content tended to decrease hygroexpansion as well as increase tensile stiffness and mechano-sorptive creep stiffness. Xylan contributed less to the pulp sheet properties, but at equal lignin contents, higher xylan content tended to give increased hygroexpansion and worse mechano-sorptive creep properties.

Keyword
Xylan; Lignin; Tensile stiffness; Hygroexpansion; Mechano-sorptive creep; Kraftliner pulp; Softwood; EDGEWISE COMPRESSION CREEP; ELASTIC-MODULUS; MECHANOSORPTIVE CREEP; ALDITOL ACETATES; FIBERS; PAPER; STRENGTH; COOKING
National Category
Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:kth:diva-9714 (URN)000273724200005 ()2-s2.0-76349089739 (Scopus ID)
Note
QC 20100629Available from: 2008-12-01 Created: 2008-12-01 Last updated: 2017-12-14Bibliographically approved
7. Applying a novel cooking technique to produce high kappa number pulps: the effects on physical properties
Open this publication in new window or tab >>Applying a novel cooking technique to produce high kappa number pulps: the effects on physical properties
2009 (English)In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 24, no 4, 415-420 p.Article in journal (Refereed) Published
Abstract [en]

A recently developed kraft cooking technique, with a longer impregnation time at lower temperatures to facilitate diffusion over consumption of active cooking chemicals, makes it possible to produce kraftliner pulp without inline refining. This technique was applied to prepare two pulps with different lignin contents, which were compared with two industrial pulps from conventional kraft cooks in order to evaluate the physical properties of the pulps.

It was demonstrated that pulps with lower lignin content can increase tensile stiffness, decrease hygroexpansion, and decrease the mechano-sorptive creep of handsheets. However, no difference in SCT and tensile energy absorption values due to different lignin contents was observed. It was further demonstrated that pulps made with Extended Impregnation Cooking (EIC) results in straighter pulp fibres with higher cellulose content. These pulps tended to have lower mechano-sorptive creep than conventional pulps. A higher brightness of the pulp sheets can also be obtained by choosing a higher alkali profile.

Keyword
High kappa number pulp, Extended impregnation, Softwood, Mechano-sorptive creep, Hygroexpansion, Tensile properties
National Category
Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:kth:diva-11718 (URN)000273724200007 ()2-s2.0-76349088958 (Scopus ID)
Note
QC 20100629Available from: 2009-12-08 Created: 2009-12-08 Last updated: 2017-12-12Bibliographically approved

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