Istrazivanja i projektovanja za privreduJournal of Applied Engineering Science


DOI: 10.5937/jaes10-2526
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Volume 10 article 240 pages: 209 - 220

Dimic-Misic Katarina 
Aalto University, Lampomiehenkuja 2, 02150 Espoo, Helsinki, Finland

Paltakari Jouni 
Aalto University, Lampomiehenkuja 2, 02150 Espoo, Helsinki, Finland

The micro-fibrillated cellulose (MFC) is a potential material which will at least partly substitute the syn­thetic co- binders, such as carboxymethyl cellulose (CMC), in paper coating color formulations. Co-bind­ers play an important role in controlling both the flow properties and the dewatering rate of coating colors during the application process as well as during the subsequent film immobilization [25, 19, 02]. In this study, MFC fibers are used to substitute standard, synthetic co-binder material, CMC, affecting both dewatering and rheological properties of coating colors. This study was partly attempting to establish standard measurement procedures that can give overall picture of complex rheological behavior of MFC coating colors. Elastic effects of coating color in low shear rate influence both the flow and blade load [23]. By influencing leveling, elasticity, substitution of CMC with MFC influences coating color application and immobilization process, as well as the uniformity and optical properties of the coating film [06]. It has been demonstrated that coating colors which contained MFC fibers as a co-binder had pronounced shear-thinning characteristics which is a desirable property for paper coatings. However, a complete substitution of CMC with MFC fibers in paper coatings induced low retention properties, longer shear- recovery time and fast immobilization of coating colors, which can have a negative influence on leveling and final coating layer uniformity.Coating suspension rheology of the coating influences the coating per­formance at high speeds. The quality of the coated and printed papers is also affected by the rheology of the suspension [06,26]. Co-binders play an important role in controlling both the flow properties and the dewatering rate of coating colors during the application process as well as during the subsequent film immobilization [23,06]. The micro fibrillated cellulose (MFC) is a potential material which will at least partly substitute the synthetic co- binders, such as carboxymethyl cellulose (CMC), in paper coating color formulations [08,22]. It was expected that the introduction of the MFC material into the coating formulation affects the coating color rheology since the MFC fibers are highly flocculated and have reactive groups on their surface [08].Micro-fibrillated cellulose matenal (MFC), can beproduced through several pre-treat­ment and refining routes, each giving products with very differentmorphological and chemical properties [18].It is expected that refining and treatment route of MFC influence traditional coating layer properties as those designed for special purposes [18]. The observation that MFC could be used in paper coating formulations, as a co-binder, since it is biodegradable and has good shear thinning properties, raises a question about the processability of MFC coatings in a high speed coating process(above 1000m/min) [12]. This work focuses on determining general rheological and dewatering behavior of coating colors that contain MFC fibers used as co-binders. A thickener is added to prevent an excessive loss of water from coating color into the base paper and to adjust the rheological properties of the color, a thickener is usually added [03,28]. The physical and chemical properties of the thickeners differ, and they can be roughly divided into synthetic and natural polymers [01]. Water retention and immobilization are the key properties for successful paper coating formulations [21,05]. The task of research is to evaluate how the replacement of CMC co-binder with MFC material influences the viscoelastic and dewatering properties of the coating color [07]. Correlation of the data matrix obtained from dewatering, low-shear viscoelastic and immobilization time measurements show that there is a pattern providing general un­derstanding of the MFC fiber performance in coating suspensions. It is important to understand what the typical behavioral pattern of all MFC coatings would be once they are in the coating process. A key characteristic of the response of a viscoelastic material, as are coating colors, to its deformation during dynamic process, is its ability to recover after cessation of the force which causes deformation [13,04], Pigment reactivity with binders and co binders has an important effect in viscoelastic behavior of coating color.It has been proved through many previous research papers that more elastic structures of clay coat­ings yield larger elastic moduli than the carbonate coatings [05,14].

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This data is from Author's Licentiate thesis " In­fluence of fibrillar cellulose on pigment coating formulation's rheology”, supervising professor PaltakariJouni,published at Aalto University, Hel­sinki, 2012.

Adams P. D andKuszewskiJ., Crystallogra­phy and NMR system: a new software suite for macromolecular structure determination, ActaCrystallogr, 1988, p. 18

Akerholm J., Berg C. and Kirstila V., An ex­perimental evaluation of the governing mois ture movement phenomena in the paper coating process, Part II, AboAkademi Uni­versity, Finland

BackfolkK., Methods for controlling surface contact area of a paper or board structure, Doc­toral Thesis, AbO Academy, Finland, 2002

BarnessH. A., Hutton J. F., WaltersK., An In­troduction to Rheology, Coating Conference proceedings, Amsterdam, 1998

BourneP. andWeissigH., Structural bioinfor­matics A John Wiley & Sons Publication, Fig­ures. 15, 18, 34, 2003

BruunS-E., Pigment Coating and Surface siz­ing of Paper, Totally updated version, Paltakari J. ed., Ch. 14, PaperijaPuuOy, Finland, 2009

BruunS-E., Pigment Coating and Surface siz­ing of Paper, Totally updated version, Paltakari J. ed., Ch. 6, PaperijaPuuOy, Finland, 2009

DreiffenbergI., Lohmander S., Effects of the air content on the rheological properties of coating colors, Advanced Coating Funda­mentals Symposium, 1999

Eklund D, Grankvist T., Salahetdin R., Thein- fluence of viscosity and water retention on blade forces, PTS Coating Symposium, 21stpaper, Munich, Germany

EngstromD. and Ridahl, On the transition from linear to non-linear viscoelastic behavior of CMC /Latex coating colors, Nordic Pulp Paper, 1991

EngstromD. and Ridahl, The effect of some polymer dispersions on the rheological prop­erties of coating colors, Tappi press, 1989

GrovesR., Ruggles C., Paper Coating Struc­ture - The Role of Latex, PITACoating Con­ference Proceedings, 1993

Jader J. and JarnstromL., Calculation of filter cake thickness under conditions of dewatering under shear, Annual transactions of the Nordic Rheological Society, vol. 9, p. 113-117, 2001

Jader J., Engstrom G, and Jarnstrom L., Ex- tensional Viscosity of paper coating Suspen­sions studies by converging Channel-flow and filament stretching, Annual transactions of the Nordic Rheology Society, vol. 12, 2004

JaderJ., Consolidation and Rheology at High Solid Content, Dissertation; Karlstad Univer­sity Studies, 2004

Kugge C., Consolidation and structure of pa­per coating and fiber systems, Doctoral dis­sertation, Stockholm, 2003

Kugge C., DaicicJ. and Furo, Compressional rheology of model paper coatings, funda­mental research paper symposium, Pira in­ternational, Oxford, 2001

Leino M., VeikkolaT., A New Board Coating Meth­od, TappiCoating Conference Proceedings, 1998

Lepoutre P., Coating structure and surface coverage, Symposium on Surface Cover­age, Helsinki, Finland, 1999

Lepoutre P., Substrate Absorbency and Coat­ing StructureTappi Journal, 61[5], 1978

Li J., Tanguy P., Carreau J., Moan M., Effect of thickener structure on paper-coating color properties, Colloid Polymer Sci. 2001

Paltakari J., Puu-21. 3060 Pigment Coating Technology, Aalto University, Finland

Pigment Coating and Surface sizing of Pa­per, Totally updated version, Paltakari J. ed., Ch. 5, PaperijaPuuOy, Finland, 2009

Triantafillopoulos N., Paper coating Visco­elasticity, Tappi press, 1996

Watanabe J. andLepoutre P., A Mechanism for the Consolidation of the Structure of Clay- latex Coatings Appl. Polym. Sci., 1982

Willenbacher N., Wagner H., High Shear Rhe­ology of Paper Coating colors-More than just viscosity , Chem. Eng. Technol. 20, 1997

Young T, Fu E., Associative behavior of cel­lulose thickeners and its implementation on coating structure and rheology, Coating Con­ference Proceedings Tappi press

Zeyringer E. and EichingerR., A new method to determine the water retention of coating colours and its impact on mottling of coated paperTappi Advanced Coating Symposium, October, 2010