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Interfacial Adhesion Failure: Impact on print-coating surface defects
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The aim of this work was to develop a solid knowledge on formulation effects controlling offset ink-paper coating adhesion and to identify key factors of the coating and printing process affecting it. Focus lay on comprehending the impact of pigment dispersant on ink-paper coating adhesion and ultimately on the print quality of offset prints.

The work covers laboratory studies, a pilot coating trial designed to produce coated material with a span in surface chemistry and structure, and an industrial offset printing trial.

The lab scale studies quantified ink-paper coating adhesion failure during ink setting with a developed laboratory procedure based on the Ink-Surface Interaction Tester (ISIT) and image analysis. Additional polyacrylate dispersant resulted in slower ink setting and reduced ink-paper coating adhesion, with a dependence on its state of salt neutralisation and cation exchange, mainly in the presence of moisture/liquid water.

The industrial printing trial on pilot coated papers was designed to study how these laboratory findings affected full scale offset print quality. These trials confirmed the dispersant-sensitive effect on ink-paper coating adhesion, especially at high water feeds. Evaluation of prints from the printing trial resulted in two fundamentally different types of ink adhesion failure being identified. The first type being traditional ink refusal, and the second type being a novel mechanism referred to as ink-lift-off adhesion failure. Ink-lift-off adhesion failure occurs when ink is initially deposited on the paper but then lifted off in a subsequent print unit. In this work, ink adhesion failure by this ink-lift-off mechanism was observed to occur more often than failure due to ink refusal.

Print quality evaluation of the industrial prints suggested that water induced mottle was caused by a combination of ink-surface adhesion failure, creating white spots on the print, together with variation in ink layer thickness due to emulsified ink.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2016. , 102 p.
Series
TRITA-CHE-Report, ISSN 1654-1081 ; 2016:35
Keyword [en]
Ink-paper coating adhesion, offset printing, calcium carbonate pigments, polyacrylate, dispersant, print mottle, surface chemistry, hygroscopy of surfaces, coating structure, print quality, water interference mottle
National Category
Chemical Engineering
Research subject
Fibre and Polymer Science
Identifiers
URN: urn:nbn:se:kth:diva-194166ISBN: 978-91-7729-136-7OAI: oai:DiVA.org:kth-194166DiVA: diva2:1038638
Public defence
2016-11-18, F3, Lindstedtsvägen 26, Stockholm, 09:00 (English)
Opponent
Supervisors
Note

QC 20161019

Available from: 2016-10-19 Created: 2016-10-18 Last updated: 2016-10-26Bibliographically approved
List of papers
1. Characterization of ink-paper coating adhesion failure: Effect of Pre-dampening of Carbonate Containing Coatings
Open this publication in new window or tab >>Characterization of ink-paper coating adhesion failure: Effect of Pre-dampening of Carbonate Containing Coatings
2010 (English)In: Journal of Adhesion Science and Technology, ISSN 0169-4243, E-ISSN 1568-5616, Vol. 24, no 3, 449-469 p.Article in journal (Refereed) Published
Abstract [en]

To attain an improved knowledge about ink-paper coating adhesion during offset printing, we have developed a laboratory procedure to measure adhesion failure between ink and coated paper during ink setting. This paper describes the technique and a special case where two ground calcium carbonate (GCC)-based coatings have been printed, one normal coating containing the delivered amount of dispersing agent already present in a typical GCC slurry and another coating made from the same GCC slurry but with excess additional free dispersant in the form of sodium polyacrylate. The areas where the ink-paper coating adhesion had failed at the pull-off points after tack testing were characterized by determining white spots in the retained print using image analysis. The white spots represent areas where ink has detached from the coating after contact with a rubber coated cylinder. This area is referred to as ink-paper coating adhesion failure area (IPCAFA). A minimum in IPCAFA at the point of maximum in tack force was found for both coatings where the print was applied onto dry coating. When the coatings, however, were pre-damped, IPCAFA increased on the normal coating over a short time period, independent of the dampening level. For the coating with excess dispersant, on the other hand, the higher dampening level strongly increased the IPCAFA. The strong impact of excess dispersing agent in this work may be explained by a number of related effects, including increased polarity of the coating surfiated moisture layer and an effective reduction of fine pores due to water-swelling polyacrylate that blocks these pores.

Keyword
ink-paper coating adhesion, ink-water interference, offset printing, ink tack, coating dispersant, print mottle, ink piling, print rub
National Category
Chemical Engineering
Research subject
Fibre and Polymer Science
Identifiers
urn:nbn:se:kth:diva-194161 (URN)10.1163/016942409X12561252292341 (DOI)000275981400003 ()2-s2.0-77949582742 (ScopusID)
Note

QC 20161019

Available from: 2016-10-18 Created: 2016-10-18 Last updated: 2016-10-19Bibliographically approved
2. Effect of excess dispersant on surface properties and liquid interactions on calcium carbonate containing coatings
Open this publication in new window or tab >>Effect of excess dispersant on surface properties and liquid interactions on calcium carbonate containing coatings
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2010 (English)In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 25, no 1, 82-92 p.Article in journal (Refereed) Published
Abstract [en]

The aim of this work was to identify what effects excess amount of sodium polyacrylate, a commonly used dispersant, has on the coating properties and the interaction between ink and the paper coating in offset printing. Since polyacrylate strongly interacts with calcium ions, soluble calcium salt was added to some coating colours to illustrate the impact of charge neutralization by calcium ions. It was found that the coating structure was only slightly affected by the extra addition of polyacrylate, showing some weak flocculation, whereas the surface chemistry was strongly influenced. The coatings became more polar and interacted more strongly with water. This resulted in slower ink setting and reduced ink-paper coating adhesion, especially in the presence of applied water/dampening solution, which are identified as contributory factors in ink piling and print mottle.

Keyword
Coating, Sodium polyacrylate, Hygroscopy, Offset, Ink-paper coating interaction, Coating structure, Surface energy, Ink adhesion
National Category
Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:kth:diva-27570 (URN)10.3183/NPPRJ-2010-25-01-p082-092 (DOI)000278043500011 ()2-s2.0-78650715032 (ScopusID)
Note

QC 20101215

Available from: 2010-12-15 Created: 2010-12-13 Last updated: 2016-10-19Bibliographically approved
3. Temperature and moisture effects on wetting of calcite surfaces by offset ink constituents
Open this publication in new window or tab >>Temperature and moisture effects on wetting of calcite surfaces by offset ink constituents
2011 (English)In: Colloids and Surfaces A: Physicochemical and Engineering Aspects, ISSN 0927-7757, E-ISSN 1873-4359, Vol. 390, 105-111 p.Article in journal (Refereed) Published
Abstract [en]

Offset printability is influenced by interactions between ink constituents: linseed oil, mineral oil and water (fountain solution), with the mineral surfaces of paper coatings. To exclude complications of the porous structure effects, the influence of temperature and moisture on wetting by offset ink model liquids were studied on cleaved optical calcite surfaces with and without sodium polyacrylate dispersant. Contact angle measurement was chosen as the method of analysis. The results show that a moderate temperature increase from 25 °C to 60 °C, which might occur in the process, does not affect the wetting of these surfaces by mineral oil. Water and linseed oil are affected by the transport of moisture at the surfaces as an indirect consequence of temperature increase. The linseed oil behavior was found to be sensitive to polarity changes of the surfaces.

Place, publisher, year, edition, pages
Elsevier, 2011
Keyword
offset ink constituents, surface wetting, temperature, calcite, sodium polyacrylate, polarity
National Category
Chemical Engineering
Research subject
Fibre and Polymer Science
Identifiers
urn:nbn:se:kth:diva-194162 (URN)10.1016/j.colsurfa.2011.09.012 (DOI)000297960400013 ()2-s2.0-80855132653 (ScopusID)
Note

QC 20161019

Available from: 2016-10-18 Created: 2016-10-18 Last updated: 2016-10-19Bibliographically approved
4. Moisture sorption by thin layers of sodium and calcium neutralized polyacrylate
Open this publication in new window or tab >>Moisture sorption by thin layers of sodium and calcium neutralized polyacrylate
2012 (English)In: The 8th International paper and Coating Chemistry Symposium, 2012, 71-73 p.Conference paper, Abstract (Refereed)
Keyword
polyacrylate, sodium polyacrylate, dispersing agent, calcium, GCC, moisture sorption
National Category
Chemical Engineering
Research subject
Fibre and Polymer Science
Identifiers
urn:nbn:se:kth:diva-194163 (URN)
Conference
Presented at the 8th International paper and Coating Chemistry Symposium, Stockholm, June 2012
Note

QC 20161019

Available from: 2016-10-18 Created: 2016-10-18 Last updated: 2016-10-19Bibliographically approved
5. Ink-lift-off during offset printing: a novel mechanism behind ink-paper coating adhesion failure
Open this publication in new window or tab >>Ink-lift-off during offset printing: a novel mechanism behind ink-paper coating adhesion failure
2014 (English)In: Journal of Adhesion Science and Technology, ISSN 0169-4243, E-ISSN 1568-5616, Vol. 29, no 5, 370-391 p.Article in journal (Refereed) Published
Place, publisher, year, edition, pages
Taylor & Francis, 2014
Keyword
ink adhesion, adhesion failure, uncovered area, offset, GCC-based coating, print mottle
National Category
Chemical Engineering
Research subject
Fibre and Polymer Science
Identifiers
urn:nbn:se:kth:diva-194164 (URN)10.1080/01694243.2014.989650 (DOI)000346851300003 ()2-s2.0-84920177011 (ScopusID)
Note

QC 20161019

Available from: 2016-10-18 Created: 2016-10-18 Last updated: 2016-10-19Bibliographically approved
6. Ink adhesion failure during full scale offset printing: causes and impact on print quality
Open this publication in new window or tab >>Ink adhesion failure during full scale offset printing: causes and impact on print quality
Show others...
2015 (English)In: Journal of Print and Media Technology Research, ISSN 2223-8905, Vol. 4, no 4, 257-278 p.Article in journal (Refereed) Published
Place, publisher, year, edition, pages
International Association of Research Organizations for the Information, Media and Graphic Arts Industrie (IARIGAI), 2015
Keyword
coated paper, coating permeability, offset print quality, water induced print mottle, uncovered area, polyacrylic dispersant
National Category
Chemical Engineering
Research subject
Fibre and Polymer Science
Identifiers
urn:nbn:se:kth:diva-194165 (URN)
Note

QC 20161019

Available from: 2016-10-18 Created: 2016-10-18 Last updated: 2016-10-19Bibliographically approved

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