Raisio, Finland
Raisio, Finland

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Tag C.-M.,Forest Pilot Center Oy | Rajala P.,Saimaa University of Applied Sciences | Toiviainen M.,VTT Technical Research Center of Finland | Juuti M.,VTT Technical Research Center of Finland | And 2 more authors.
Applied Thermal Engineering | Year: 2013

The aim of the study was to explain the transportation of liquid (fountain solution) during transfer to coated paper in the heatset offset printing process, together with the subsequent drying of the printed paper, by using statistical and experimental methods. A coating dispersion, applied as a single coating onto a fine paper substrate, was formulated using a narrow fine particle size distribution natural ground calcium carbonate pigment and a styrene acrylic binder. The moisture variation in the paper during printing was monitored by using online multipoint sensors based on near-infrared diffuse reflectance spectroscopy. Based on the results, a simulation model was created to determine the transfer of liquid thin films in the printing units, the evaporation in the printing units, followed by liquid absorption and evaporation in the heatset offset drying process. An accurate simulation depends on precise determination of the different process parameters that influence these factors. The absolute liquid/moisture amount transferred to the paper showed an increased trend as the paper passed through the application nips, though the proportion varied due to limited capillary absorption capacity properties of the paper. The background evaporation in the printing nips was evaluated with the simulation model as well as the drying stages in the dryer including surface and bulk condensation followed by rapid evaporation and cooling. © 2012 Elsevier Ltd. All rights reserved.


Oksman A.,University of Eastern Finland | Kuivalainen K.,University of Eastern Finland | Peiponen K.-E.,Forest Pilot Center Oy | Tag C.-M.,VTT Technical Research Center of Finland | And 5 more authors.
Optical Engineering | Year: 2011

Gloss of a product, such as print gloss, is mainly inspected with conventional white light glossmeters both at laboratory or production facilities. However, problems occur in conventional gloss measurement when the inspected surface is vertically moved in the plane of incidence and reflection or when the measurement area is small or curved. For a partial solution to these problems, we have previously introduced diffractive optical element-based glossmeters (DOGs) for the gloss inspection in laboratories and off-line use. We present a new construction of DOG, termed μDOG 1D, for the one-dimensional on-line print gloss measurement, in the form of the reflectance determination normal to the surface. The function of the glossmeter is demonstrated by laboratory tests and on-line measurements at a heat-set web offset printing machine. It is shown that gloss (i.e., normal reflectance) and minute gloss variation of papers and prints can be measured at the printing line using the glossmeter. This glossmeter is expected to be useful in real-time monitoring of the gloss and surface-specific absorption not only in the printing industry but also in inspection of products in other industrial sectors, such as metal finishing, laminating, paper, and construction materials manufacturing. © 2011 Society of Photo-Optical Instrumentation Engineers (SPIE).


Tag C.-M.,Forest Pilot Center Oy | Tag C.-M.,Åbo Akademi University | Toiviainen M.,VTT Technical Research Center of Finland | Juuti M.,VTT Technical Research Center of Finland | And 2 more authors.
Nordic Pulp and Paper Research Journal | Year: 2012

In the present study, near-infrared sensors are used to investigate moisture variations on paper in the heatset web offset printing process. The moisture content was determined from both non-image and image printed areas at multiple locations along the printing line. The amount of water based liquid (fountain solution) transferred to the two studied areas as well as the internal moisture content of the paper was investigated in terms of near-infrared absorbance response. In order to achieve absolute moisture content estimates,the sensors were calibrated for the respective measurement regions. It was found that the moisture content was higher in the areas with printing ink compared to those without. The heatset drying had a stronger moisture drying effect on the nonimage areas. The tests were performed in both a laboratory and a full-scale heatset offset printing environment.


Tag C.-M.,Åbo Akademi University | Tag C.-M.,Forest Pilot Center Oy | Toiviainen M.,VTT Technical Research Center of Finland | Juuti M.,VTT Technical Research Center of Finland | And 4 more authors.
Transport in Porous Media | Year: 2012

The influence of isopropyl alcohol and non-ionic surfactant solutions on aqueous droplet wetting behaviour on porous coated paper was determined. Paper coatings provide a micro- and nano-porous surface structure, which strictly speaking cannot be described in simple roughness terms as sub-surface lateral absorption directly impacts on the apparent contact angle. It is this very deviation from an idealised system that leads to novel wetting phenomena. Isopropyl alcohol and surfactant-based systems, both of which are commonly used in the printing industry, show differences in wetting behaviour, on both short and long timescales, with changes in the relative composition of the mixtures. Small variations of 0.1 wt% in surfactant concentration have a dramatic influence on the dynamic surface tension, and thus the wetting. It was observed that the wetting kinetics for isopropyl alcohol and surfactant solutions were different in terms of both wetting area and the penetration rate, even in cases where the dynamic surface tension of the solutions was kept the same. Different stages in the wetting and following drying processes could be observed with near infrared spectral imaging. In addition, the surfactant chemistries such as their degrees of hydrophilicity and molecular weights generated comparative differences in the wetting kinetics. The dominating factor affecting the wetting was, as expected, the solid-liquid interfacial energy defined on the practical porous substrate, which differed from the direct comparison with dynamic surface tension, thus exemplifying the deviation from idealised surface roughness behaviour when considering porous materials. An apparent "equivalent" surface roughness value for the porous material was determined, and it was seen that an increase in this equivalent parameter enhanced the rate of wetting behaviour with decreasing solution surface tension, and so also affected the wetting evolution. The wetting was enhanced by cavities in the coating layer, which were enlarged by the penetrating liquids. © 2012 Springer Science+Business Media B.V.


Tag C.-M.,Forest Pilot Center Oy | Juuti M.,VTT Technical Research Center of Finland | Koivunen K.,Aalto University | Gane P.A.C.,Aalto University | Gane P.A.C.,Omya Development AG
Industrial and Engineering Chemistry Research | Year: 2010

The dynamic wetting of, and absorption into, model porous coatings in the form of compressed particulate pigment tablets by monocomponent, dual-component, and multicomponent liquid droplets has been studied by observation of apparent contact angle and near-infrared spectroscopy to identify the liquid water/moisture content. The absorption of the liquids was studied in a corresponding vapor-saturated environment. Liquid evaporation was determined for the tablets at both equilibrium starting pore saturation and under limited volume-filling conditions as evaporation proceeds. The changes in water and moisture content within the coatings as a function of time were also determined gravimetrically to relate the water uptake and evaporation being observed to changes in the near-infrared spectral data. Model and commercial offset printing fountain solutions were compared with respect to both absorption and evaporation. For the solutions containing isopropyl alcohol in water, a nonlinear behavior in the water response in the near-infrared spectra during absorption is observed as a function of time, which can be related to the fast evaporation of the alcohol. The nonlinear region was followed by a decline in water and moisture content as the penetration/evaporation of the water phase proceeded. Comparing the near-infrared water volume dependency in the upper layers of the structure with weight loss during evaporation showed that the mechanism of liquid transport to the surface'air interface reflected the logarithmic volume distribution of pore sizes, as might be expected from capillarity considerations and pore condensation hysteresis. © 2010 American Chemical Society.


Tag C.-M.,Forest Pilot Center Oy | Toiviainen M.,VTT Technical Research Center of Finland | Juuti M.,VTT Technical Research Center of Finland | Ridgway C.,Omya Development AG | And 2 more authors.
Industrial and Engineering Chemistry Research | Year: 2011

Liquid transfer in a heatset printing process to coated papers has been evaluated online. The porous coatings, applied in various combinations of single coating onto a fine paper substrate, together with selective particle size distributions containing calcium carbonate pigments were calendered under different conditions to establish a range of porosities and pore structures while keeping the formulation and hence the surface chemistry constant. The transfer of fountain solution to the papers was analyzed from unprinted areas (nonimage) at six different positions along the printing line, namely, between each printing unit and after the dryer section, using near-infrared absorption reflectometry. In this way, real-time analysis of the amount of fountain solution (defined as water content) transferred to the paper per printing unit as a function of physical paper surface characteristics has been achieved. The role of printing speed and fountain solution dosage level on water uptake by the various coated paper substrates has been investigated. It was concluded that the higher the speed, firstly, there is less compression of the surface roughness and, secondly, less time for the liquid to respond with respect to capillary forces, resulting in less liquid transfer. © 2011 American Chemical Society.


Tag C.-M.,Forest Pilot Center Oy | Toiviainen M.,VTT Technical Research Center of Finland | Juuti M.,VTT Technical Research Center of Finland | Gane P.A.C.,Aalto University | Gane P.A.C.,Omya Development AG
Measurement Science and Technology | Year: 2010

Dynamic analysis of the water transfer onto coated paper, and its permeation and absorption into the porous structure were studied online in a full-scale heatset web offset printing environment. The moisture content of the paper was investigated at five different positions during the printing process. Changes in the moisture content of the paper were studied as a function of the web temperature, printing speed and silicone application in the folding unit positioned after the hot air drying oven. Additionally, the influence of fountain solution composition on the pick-up by the paper was investigated. The water content of the fountain solution transferred to the paper from the printing units was observed as changes in near-infrared absorbance. A calibration data set enabled the subsequent quantification of the dynamic moisture content of the paper at the studied locations. An increase in the printing speed reduced the water transfer to the paper and an increase in web temperature resulted in a reduction in the moisture content. An increase in the dosage level of the water-silicone mixture was observed as a re-moistening effect of the paper. Differences in the drying strategy resulted in different moisture profiles depending on the type of fountain solution used. As a conclusion, the near-infrared signal provides an effective way to characterize the moisture dynamics online at different press units. © 2010 IOP Publishing Ltd.


Tag C.-M.,Forest Pilot Center Oy | Juuti M.,VTT Technical Research Center of Finland | Koivunen K.,Aalto University | Gane P.A.C.,Aalto University | Gane P.A.C.,Omya Development AG
11th Advanced Coating Fundamentals Symposium Proceedings: The Latest Advances in Coating Research and Development | Year: 2010

The dynamic wetting of, and absorption into, model porous coatings in the form of compressed particulate pigment tablets by mono-, dual- and multi-component liquid droplets, has been studied by observation of apparent contact angle and near infra-red spectroscopy to identify the liquid water/moisture content. The absorption of the liquids was studied in a corresponding vapor-saturated environment. Liquid evaporation was determined for the tablets at both equilibrium starting pore saturation and under limited volume-filling conditions as evaporation proceeds. The changes in water and moisture content within the coatings as a function of time were also determined gravimetrically to relate the water uptake and evaporation being observed to changes in the near infra-red spectral data. Model and commercial offset printing fountain solutions were compared in respect to both absorption and evaporation. For the solutions containing isopropyl-alcohol in water, a non-linear behavior in the water response in the near infra-red spectra during absorption is observed as a function of time, which can be related to the fast evaporation of the alcohol. The non-linear region was followed by a decline in water and moisture content as the penetration/evaporation of the water phase proceeded. Comparing the NIR water volume dependency in the upper layers of the structure with weight loss during evaporation showed that the mechanism of liquid transport to the surface-air interface reflected the logarithmic volume distribution of pore sizes, as might be expected from capillarity considerations and pore condensation hysteresis.


Silfsten P.,University of Eastern Finland | Dutta R.,University of Eastern Finland | Paakkonen P.,University of Eastern Finland | Tag C.-M.,Forest Pilot Center Oy | And 3 more authors.
Measurement Science and Technology | Year: 2012

Absolute reflectance data were measured with a spectrophotometer in the visible and near infrared (NIR) spectral range. The specular reflectance data in the NIR were used for the assessment of the surface roughness of magenta, yellow, cyan and black prints on paper. In addition, surface roughness data obtained from the prints with a mechanical diamond stylus, an optical profiling system and the spectrophotometer are compared with each other. The surface roughness obtained with the aid of the spectrophotometer data suggests a smoother surface than when measured with the diamond stylus and the optical profiling system. The gloss of the prints can be obtained from the absolute specular reflectance spectra in the spectral region of visible light. It is shown that specular reflection data at a fixed wavelength in the NIR are useful also in the interpretation of gloss in the visible spectral range, but using an unconventional grazing angle of incidence. © 2012 IOP Publishing Ltd.

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