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Polyelectrolyte multilayers of cationic and anionic starch and their use for improving the strength of papers made from mechanical pulps
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
2009 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Graphic paper is experiencing severe competition from other materials and, most of all, from other media. This means there is a great need to improve paper quality while reducing raw material and production costs. Polyelectrolyte multilayer (PEM) treatment (i.e., consecutively adding cationic and anionic polyelectrolytes to the charged surface of wood fibres and fines, to form layers of these polyelectrolytes on the fibres/fines) has in recent years been found to offer great potential both to introduce new properties and to improve the mechanical properties of papers made of the treated fibres.

The main objective of this thesis was to develop a strategy for the PEM treatment of cationic and anionic starch to improve the mechanical properties of paper made of thermomechanical pulp (TMP), since PEM treatment of fibres has displayed great potential to improve the mechanical properties of sheets made of chemical pulp. Mechanical pulp, however, has a large fine material content. Since the fine material is highly charged, polyelectrolyte consumption would be unacceptably high if the entire pulp were PEM treated, so we applied PEM treatment only to a fibre fraction of the pulps in most trials in the present work. The polyelectrolytes used for PEMs have so far mostly been well-defined, expensive ones unsuitable for use in standard paper grades; to develop a more economically realistic alternative, we used cationic and anionic starches.

PEM formation on SiO2 surfaces from three differently charged cationic and anionic starches was first evaluated at three different salt levels using quartz crystal microbalance with dissipation (QCM-D) and stagnation point adsorption reflectometry (SPAR). The starch combinations displaying the highest potential for stable PEM formation at higher salt concentrations were then evaluated on an entire TMP pulp, as well as on a fraction of the pulp to reduce the amount of starch needed for PEM formation.

The results indicate that it is possible to form PEMs from cationic and anionic starch on a SiO2 surface. The charge density, salt concentration, and combination of starches all influenced PEM formation. PEM formation on mechanical fibres produced large improvements in the mechanical properties of the sheets made of the treated fibres, and the tensile index, stretch-at-break, Z-strength, and Scott bond values all increased. Fractionating the pulp and PEM treating only a fraction of the pulp, the long fibre and middle fraction, produced large decreases in the amount of starch needed and large improvements in the mechanical properties of the sheets when no fine material was subsequently added. As untreated fine material was subsequently added, the improvement in mechanical properties decreased. PEM formation produced almost no reduction in formation and only a slight increase in sheet density.

Abstract [sv]

Grafiskt papper är under hård konkurrens från andra material och, framför allt, andra media.  På grund av detta finns det ett stort behov av att förbättra papperskvalitén samtidigt som råmaterial- och produktionskostnader sänks. Polyelektrolyt-multiskikt (multiskikt) på massa (dvs. växelvis adsorption av katjoniska och anjoniska polyelektrolyter till träfibrer och finmaterial) har på senare år visat sig ha bra potential både för att ge nya egenskaper och för att förbättra de mekaniska egenskaperna hos papper gjorda av behandlad fiber.

Huvudsyftet med denna avhandling var att utveckla en strategi för multiskiktsbehandling med katjonisk och anjonisk stärkelse för att förbättra de mekaniska egenskaperna hos papper gjort av behandlad termomekanisk massa (TMP). Multiskiktsbehandling av fiber har visat stor potential för att ge förbättrade mekaniska egenskaper till ark gjorda av behandlad kemisk massa. Mekanisk massa innehåller dock en stor andel högladdat finmaterial som kan öka mängden polyelektrolyt som krävs för multiskiktsbehandling, därför multiskiktsbehandlas bara en fraktion av massan i de flesta experiment i detta arbete. De polyelektrolyter som använts för multiskikt har hittills mest varit väldefinierade och dyra, och därmed opassande för användning i vanliga papperskvalitéer. För att utveckla ett mer realistiskt alternativ så användes katjonisk och anjonisk stärkelse i detta arbete.

Multiskiktsuppbyggnad på SiO2-ytor av tre katjoniska och tre anjoniska stärkelser med olika laddningsdensitet utvärderades först vid tre olika saltnivåer genom att använda kvartskristal‑mikrogravimetri (QCM-D) och reflektometri (SPAR). Stärkelsekombinationerna som uppvisade störst potential för en stabil multiskiktsuppbyggnad på högre saltkoncentrationer blev sedan utvärderade på en hel TMP-massa, men även på en fraktion av massan för att minska mängden stärkelse som krävdes för multiskiktsuppbyggnad.

Resultaten visar på att det är möjligt att bygga upp multiskikt av katjonisk och anjonisk stärkelse på en SiO2-yta. Laddningsdensiteten, saltkoncentrationen och kombinationen av stärkelser var faktorer som påverkade multiskiktsuppbyggnaden. Multiskiktsuppbyggnad på mekaniska fibrer gav stora förbättringar av de mekaniska egenskaperna hos ark gjorda av behandlad fiber, och dragindex, töjning, Z-styrka och Scott bond-värde ökade. Fraktionering av massan och multiskiktsbehandling av endast en del av massan, långfiber- och mellanfraktion, innebar att mycket mindre stärkelse behövdes och gav stora förbättringar av de mekaniska egenskaperna hos arken om inget obehandlat finmaterial tillsattes efteråt. Då obehandlat finmaterial tillsattes så blev förbättringarna hos de mekaniska egenskaperna mindre. Multiskitsuppbyggnad gav nästan ingen reduktion av formationen och endast en liten ökning i arkdensitet.

Place, publisher, year, edition, pages
Stockholm: KTH , 2009. , 57 p.
Series
Trita-CHE-Report, ISSN 1654-1081 ; 2009:16
National Category
Paper, Pulp and Fiber Technology
Identifiers
URN: urn:nbn:se:kth:diva-10537ISBN: 978-91-7415-294-4 (print)OAI: oai:DiVA.org:kth-10537DiVA: diva2:218908
Presentation
2009-05-26, STFI-salen, STFI-Packforsk, KTH, Drottning Kristinas väg 61, Stockholm, 10:00 (Swedish)
Opponent
Supervisors
Available from: 2009-05-25 Created: 2009-05-25 Last updated: 2010-10-27Bibliographically approved
List of papers
1. Adsorption Behavior and Adhesive Properties of Biopolyelectrolyte Multilayers formed from Cationic and Anionic Starch
Open this publication in new window or tab >>Adsorption Behavior and Adhesive Properties of Biopolyelectrolyte Multilayers formed from Cationic and Anionic Starch
2009 (English)In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 10, no 7, 1768-1776 p.Article in journal (Refereed) Published
Abstract [en]

Cationic starch (D.S. 0.065) and anionic starch (D.S. 0.037) were used to form biopolyelectrolyte multilayers. The influence of the solution concentration of NaCl on the adsorption of starch onto silicon oxide substrates and on the formation of multilayers was investigated using stagnation point adsorption reflectometry (SPAR) and quartz crystal microbalance with dissipation (QCM-D). The wet adhesive properties of the starch multilayers were examined by measuring pull-off forces with the AFM colloidal probe technique. It was shown that polyelectrolyte multilayers (PEM) can be successfully constructed from cationic starch and anionic starch at electrolyte concentrations of 1 mM NaCl and 10 mM NaCl. The water content of the PEMs was approximately 80% at both electrolyte concentrations. However, the thickness of the PEMs formed at 10 mM NaCl was approximately twice the thickness formed at I mM NaCl. The viscoelastic properties of the starch PEMs, modeled as Voigt elements, were dependent on the polyelectrolyte that was adsorbed in the outermost layer. The PEMs appeared to be more rigid when capped by anionic starch than when capped by cationic starch. The wet adhesive pull-off forces increased with layer number and were also dependent oil the polyelectrolyte adsorbed in the outermost layer. Thus, starch PEM treatment has a large potential for increasing the adhesive interaction between solid substrates to levels higher than can be reached by a single layer of cationic starch.

Keyword
Adhesive interaction; Adhesive properties; Adsorption behavior; AFM; Anionic starch; Cationic starches; Colloidal probe techniques; Electrolyte concentration; Layer number; Polyelectrolyte multilayer; Pull-off forces; Quartz crystal microbalance with dissipation; Silicon oxide substrates; Single layer; Solid substrates; Solution concentration; Stagnation point adsorption reflectometry; Viscoelastic properties; Voigt elements; Wet adhesives
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-9461 (URN)10.1021/bm900191s (DOI)000268139300013 ()2-s2.0-67650497882 (Scopus ID)
Note
QC 20100826. Uppdaterad från manuskript till artikel (20100826)Available from: 2008-11-05 Created: 2008-11-05 Last updated: 2017-12-14Bibliographically approved
2. Polyelectrolyte Multilayers from Cationic and Anionic Starch: Influence of Charge Density and Salt Concentration on the Properties of the Adsorbed Layers
Open this publication in new window or tab >>Polyelectrolyte Multilayers from Cationic and Anionic Starch: Influence of Charge Density and Salt Concentration on the Properties of the Adsorbed Layers
2010 (English)In: Starke (Weinheim), ISSN 0038-9056, E-ISSN 1521-379X, Vol. 62, no 2, 102-114 p.Article in journal (Refereed) Published
Abstract [en]

The purpose of the present work was for identify limits for the formation of stable polyelectrolyte multilayers (PEMs) from cationic and anionic starches (with degrees of substitution of 0.04-0.09) on SiO2 surfaces, taking account of the effect of the charge density of the starches and the salt concentration in the surrounding water phase. The experiments were performed at a pH of 6.3 using stagnation point adsorption reflectometry (SPAR) and quartz crystal microbalance with dissipation (QCM-D). From these experiments it was concluded that it is possible to form PEMs by the adsorption of oppositely charged starches on SiO2 surfaces; it was also found that adsorption of the first layer is controlled both by electrostatic, non-ionic interactions and by pure steric restrictions, Le, geometrical restrictions, at the surface. The results also indicate that the charge density of the starch must exceed a certain value to allow multilayer formation and that this critical charge density increases with increasing salt concentration. The combination of charge densities of the cationic/anionic starches was also found to influence the adsorption behaviour, and the formed polyelectrolyte multilayers had a high water content of 69-92%.

Keyword
Model surfaces, Polyelectrolyte multilayer, Stagnation point adsorption, reflectometry, Starch, Quartz crystal microbalance, paper strength properties, wood fibers, adhesive properties, ionic-strength, adsorption, size, flow
National Category
Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:kth:diva-19287 (URN)10.1002/star.200900176 (DOI)000275242000005 ()2-s2.0-77249173310 (Scopus ID)
Note
QC 20100525, QC 20110930.Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2017-12-12Bibliographically approved
3. The adsorption of polyelectrolyte multilayers (PEM) of starch on mechanical pulps for improved mechanical paper properties
Open this publication in new window or tab >>The adsorption of polyelectrolyte multilayers (PEM) of starch on mechanical pulps for improved mechanical paper properties
Show others...
2009 (English)In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 24, no 4, 459-468 p.Article in journal (Refereed) Published
Abstract [en]

In the present work, the long fibre and middle fibre fraction of a thermomechanical pulp (TMP) was treated with polyelectrolyte multilayers (PEMs) of cationic and anionic starch and sheets were made from both the treated and untreated fractions. In separate experiments, different amounts of untreated fines were added to the PEM-treated fraction before sheets were prepared, and the results were also compared with PEM treatment of the entire pulp containing 17% fines before sheet preparation. The PEMs were made of two different combinations of starch, two cationic potato starches with DS values of 0.06 and 0.09, both in combination with an anionic potato starch with a DS of 0.04, at 0.010 M NaCl and pH 6.3. Sheets were formed using the Rapid Kothen sheet former and the resulting mechanical and optical sheet properties were evaluated. Four-layer PEM treatment of the long fibre and middle fraction resulted in significant improvements in in-plane and out-of-plane mechanical properties. However, a subsequent fines addition reduced the effect of the PEMs, and this is explained by a blocking of the necessary PEM interaction with the treated TMP long fibre and middle fraction by the subsequently added fines. PEM treatment of the entire pulp increased the amount of starch needed for PEM treatment, but improved the in-plane and out-of-plane mechanical properties compared with those of sheets prepared from a PEM-treated long fibre and middle fraction with a subsequent addition of fine material. The increase in the tensile index for sheets made from a PEM-treated long fibre and the middle fraction without a subsequent fines addition, however, was much larger.

Keyword
Polyelectrolyte multilayer, Mechanical pulp, Starch, Adsorption, Mechanical properties, enhance strength properties, cationic starch, wood fibers, part i
National Category
Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:kth:diva-19119 (URN)10.3183/NPPRJ-2009-24-04-p459-468 (DOI)000273724200013 ()2-s2.0-76349120582 (Scopus ID)
Note
QC 20100525Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2017-12-12Bibliographically approved

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