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Uniformity of liquid absorption by coatings: Technique and impact of coating composition
Innventia AB, Stockholm.
Innventia AB, Stockholm.
Innventia AB, Stockholm.
Innventia AB, Stockholm.
2012 (English)In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, Vol. 27, no 2, 456-465 p.Article in journal (Refereed) Published
Abstract [en]

The interaction between a liquid and a paper surface is important for a number of paper treatment processes, where absorption is of special significance during printing. Many absorption measurement techniques use a large available volume of liquid to characterise absorption, when compared to the volume of the coating. The uniformity of the absorption is also seldom characterised. We have developed a new technique, which is presented in this article, to study the uniformity of absorption of a small amount of liquid. This technique is based on the short-time absorption (tenth of a second) of a coloured liquid, the blotting of excess liquid and a characterisation of the pattern of the stain. This method made it possible to detect differences among coating layers with different compositions. In many cases, the absorption non-uniformity could be linked to variations in the coating thickness and/or wettability. The thinner and thicker areas of the coating layers were interpreted as having different pore structures. Neither the coating thickness nor the wettability could provide a full explanation, which showed the need to develop a method to characterise absorption uniformity instead of only relying on measuring the total absorption potential.

Place, publisher, year, edition, pages
2012. Vol. 27, no 2, 456-465 p.
Keyword [en]
Coated boards, Flexographic printing, Liquid absorption, Test method
National Category
Chemical Engineering
Identifiers
URN: urn:nbn:se:kau:diva-34906DOI: 10.3183/NPPRJ-2012-27-02-p459-465OAI: oai:DiVA.org:kau-34906DiVA: diva2:780742
Available from: 2015-01-15 Created: 2015-01-15 Last updated: 2015-02-12Bibliographically approved
In thesis
1. Absorption non-uniformity characterisation and its impact on flexographic ink distribution of coated packaging boards
Open this publication in new window or tab >>Absorption non-uniformity characterisation and its impact on flexographic ink distribution of coated packaging boards
2015 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

There are high demands on flexographic print quality to be sufficiently high and consistent in order to create a competitive packaging. At the same time the production efficiency need to be high. Printers thus need to achieve the same quality every time and quickly start-up new printing jobs. To accomplish this, one needs to gain a thorough understanding of how the liquid packaging board interacts with the ink and impacts the print quality.

This thesis focuses on water-based ink absorption of liquid packaging boards and particularly on a) how uniformity of ink absorption can be measured and b) to what extent the absorption characteristics contribute to print mottle in flexographic printing.

The work encompasses two parts. First, an absorption non-uniformity test method has been developed using a staining technique. This method is unique as it measures how unevenly an aqueous solution is absorbed, in a short time period and without impact from surface roughness. Moreover, the contributions from white-top mottle and absorption non-uniformity can be quantified simultaneously from one single measurement.

Second, a method to independently study the effects of absorption non-uniformity on print quality has been established. This is achieved by introducing artificial absorption non-uniformities with well-controlled barrier patterns. A barrier pattern may modify local pore structure and/or surface energy, hence lead to lateral absorption variations. By these means, it is possible to produce a substrate property-matrix; encompassing absorption non-uniformity and for example surface roughness. It was demonstrated that non-uniform absorption indeed has a negative impact on print quality, both on smoother and rougher boards. Low absorption made print density decrease and uneven absorption caused print mottle. This was the case when other properties of the samples were kept within a narrow range; otherwise surface roughness appeared to determine print mottle ranking.

Place, publisher, year, edition, pages
Karlstad: Karlstads universitet, 2015. 70 p.
Series
Karlstad University Studies, ISSN 1403-8099 ; 2015:7
Keyword
Liquid absorption, Absorption non-uniformity, Characterisation, Measurement technique, Print Mottle, Flexography, Coated packaging boards
National Category
Chemical Engineering
Research subject
Chemical Engineering
Identifiers
urn:nbn:se:kau:diva-34910 (URN)978-91-7063-618-9 (ISBN)
Presentation
2015-03-05, Nyqvistsalen, Karlstads universitet, Karlstad, 10:00 (English)
Opponent
Supervisors
Available from: 2015-02-12 Created: 2015-01-15 Last updated: 2015-02-12Bibliographically approved

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