PAPER making! FROM THE PUBLISHERS OF PAPER TECHNOLOGY INTERNATIONAL ® Volume 8, Number 1, 2022
COATING “ Effect of coating pigment type on paper printability with water-based inks ”, Arif Ozcan, Sinan Sonmez & Dogan Tutak, Journal of Coatings Technology and Research, (2022) online . Nowadays, the need for papers and cardboards with improved surface properties is increasing with the development of the packaging industry. The improvements made are not only limited to the paper and paper surface, but also environmentalist approaches are exhibited in printing ink. For this purpose, the use of water-based ink tends to become widespread, especially in food packaging. In this study, five different paper coating formulations were prepared using different proportions of precipitated calcium carbonate (PCC) and kaolin pigments. Latex (Acronal S360D) was used as a binder. All prepared coating mixes were applied onto the base paper surface. All coated papers were also subjected to the calendering process. In addition, three different dyestuffs (14, 17, 20%) concentrations of water-based printing inks were prepared. Prints were made by the silk screen printing technique on the calendered-coated papers. The optical and physical properties (roughness, air permeance, paper gloss and printing gloss, contact angle and surface energy) of all papers were measured according to the standards. Paper gloss, print gloss, ΔE00 color differences, contact angles and surface energy measurements were made, and the effects of dye ratio on printing and gloss in water-based inks and coating type suitable for printability were investigated. As a result, papers can be coated and even calendered to achieve better paper surface properties and printability. In the case of printing with water-based inks, better printability properties are obtained by choosing PCC pigmented coated papers. “ Effect of filler additions on pilot-scale extrusion coating of paperboard with PLA- based blends ”, Karoliina Helanto, Riku Talja, Sai Li & Orlando J. Rojas, Nordic Pulp & Paper Research Journal , (2022) online. We study the incorporation of minerals (talc, kaolin and surface-treated calcium carbonate) in paperboard coatings based on PLA to improve their performance, often limited by the low crystallinity and moderate gas barrier of the polymer. Masterbatches of PLA-based blends mixed with the mineral fillers were melt-blended in a twin-screw extruder and applied as a coating on paperboard in a pilot- scale unit operating at velocities up t o 140 m/min. Thermal imaging was used during the extrusion coating and the effect of the fillers was investigated as far as processability and their effect on the mechanical performance. A reduction of neck-in and improved adhesion between the coating and the substrate were achieved at intermediate mineral loadings. Excess filler and low coating weight generated pinholes, leading to a reduction of the integrity and mechanical properties of the coatings. Overall, we define the performance window for continuous, pilot-scale coating of paperboard with a biopolyester filled with mineral particles, opening the opportunity to realize operations in industrial settings. “Failure prediction of waterborne barrier coatings during folding”, Yaping Zhu, Douglas Bousfield & William Gramlich, Journal of Coatings Technology and Research , Vol.18, pp.1117-1129 (2021). Adding pigments into waterborne barrier coatings improves barrier properties and cost-effectiveness but increases the risk of crack formation during folding. Crack formation is affected by pigment shape, aspect ratio, and concentration; however, the exact mechanism for these effects is still not well understood. In this work, a systematic model was used to understand the influence of the paper and coating thickness, the latex and pigment modulus, the pigment shape and aspect ratio, and pigment concentration on the failure of waterborne barrier coatings during folding. A finite element method-based model was solved with a commercial package to simulate the folding process. These simulations were compared to experimental results to verify the key parameters that affect coating failure. High paper and coating thickness, pigment loadings,
Technical Abstracts
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