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Presentations 2015, 2016

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iarigai, VIGC, IS&T at drupa 2016

iarigai VIGC, Brussels
Evolutions in food packaging printing

You are here: Conferences & Events * 2008 Valencia * Abstracts * 2. Printing and printing materials

2. Printing and printing materials

2.04. A new test method to measure dynamic contact in a printing nip for rotogravure papers

Janet Preston(1), Roger Bollström(2), Kenneth Nylander(2), Martti Toivakka(2), Jouko Peltonen(2)

(1) Imerys Minerals Limited, Par, Cornwall, UK, PL24 2SQ
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(2) Laboratory of Paper Coating and Converting, Åbo Akademi University, Turku, Finland

In rotogravure printing a common problem is the non-transfer of ink from cells to the paper, resulting in "missing dots". This is often because of rough or incompressible papers, which do not make good enough contact with the printing cylinder. A novel method for studying dynamic contact between the paper and the print cylinder whilst in the printing nip was developed. In the method, a blue carbon paper is contacted with the test papers and passed through a printing nip at different pressures. The resultant setoff pattern on the test paper was captured using a scanner and then analysed using image analysis software. A Fast Fourier Transform (FFT) was applied to the set-off pattern to quantify the degree of variation occurring at different length scales. A range of different common coating pigments were assessed, which had been coated onto a ULWC basepaper at three different solids concentrations. When compared to the percent missing dots on the laboratory printed coatings a significant correlation between degree of contact variation and the missing dots was found.

Keywords: Compressibility, printing nip, rotogravure printing, topography, test method


2.05. Influence of plasma activation on absorption of ink components and dampening water in sheet-fed offset printing

Maiju Pykönen(1), Hanna Silvaani(1), Janet Preston(2), Pedro Fardim(3), Martti Toivakka(1)

(1) Laboratory of Paper Coating and Converting and Center for Functional Materials
Åbo Akademi University. Porthaninkatu 3, FI-20500 Turku, Finland
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(2) Imerys Minerals Ltd., Par Moor Centre
Par Moor Rd, Par, Cornwall, United Kingdom. PL 24 2SQ

(3) Laboratory of Fibre and Cellulose Technology
Åbo Akademi University, Porthaninkatu 3, FI-20500 Turku, Finland

The influence of plasma activation on offset printability was investigated. Four different model pigment coated papers were treated with corona, experimental pilot scale argon plasma, and laboratory scale nitrogen plasma. Surface characterization was made by contact angle measurements, X-ray Photoelectron Spectroscopy (XPS) and Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS). Five different model inks with different portions of linseed and mineral oils, and one commercial ink were used in ink setting evaluation with Ink Surface Interaction Tester (ISIT) and laboratory scale printing. In addition, samples were printed in a pilot scale sheet-fed printing press using the same commercial ink as in laboratory scale. According to results, plasma activation increased surface wettability and polarity due to oxidation of high molecular weight dispersion chemicals of pigment and latex particles. Therefore, the dispersion system of different pigments seemed to influence the effectiveness of the plasma treatment: Talc containing paper had the greatest change in O/C ratio determined by XPS, whereas ground calcium carbonate (GCC) containing paper had the smallest. Plasma treatment had a clear impact on ink setting with all the papers, but the response depended on the ink composition. The ink setting rate decreased with linseed oil dominating inks, probably due to increased acid-base interaction between ink oil and polar plasma treated coating. With mineral oils ink setting accelerated. Pilot scale plasma treatments did not have an impact on print density and gloss, but the laboratory scale plasma treatment led to a significant print density variation. Ga focused ion beam (FIB) and optical microscope images, showed that micro-picking was occurring in the surface layers of the coating, leading to a decrease in the print density with laboratory plasma treated samples.

Keywords: Dampening water, ink components, pigment coated paper, plasma treatment, sheet-fed offset printing, surface chemistry

2.06. Flexographic print quality of pilot coated paperboard

Robert Olsson(1.2), Li Yang(2,3), Magnus Lestelius(2)

(1) Holmen Paper AB, Hallsta Paper Mill
SE-763 81 Hallstavik, Sweden
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(2) Karlstad University, Department of Chemical Engineering, SE-651 88 Karlstad, Sweden

(3) Holmen Paper AB, Holmen Paper Development Center, SE-601 88, Norrköping, Sweden

The study addresses how paperboard coating structures and ink properties (waterbased) affect print quality in flexography, from an ink setting perspective. Pilot coated paperboards with different pigment blends and lattices in the coating were printed with a pilot flexographic printing press. The inks used are one solution polymer binder based (SPB) ink and one emulsion polymer binder based (EPB) ink. The study showed that the type of ink affects all of the measured print-quality parameters: print density, print gloss, and dot gain, and is of the greatest importance to achieve the best print-quality. The portion of clay pigment in the coating has great influence on the dot gain. Increasing the clay content in the coating leads to a higher dot gain. Changing coating binders from soft to hard latex results in increased paper gloss and print density.

Keywords: Coated paperboard, clay pigment, binders, print quality

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