The effect of paper coatings containing biopolymer binder and different natural pigments on printability

Paper is an environmentally friendly, recyclable material whose main material is cellulose, which can be obtained from all kinds of trees and plants, used as writing, printing and packaging material. Due to its structural properties, papers are not resistant to temperature and humidity, as well as problems with ink transfer with its porous structure and experienced negative printability properties. In recent years, especially the growth of the packaging industry has increased the demand for papers with improved printability properties. In order to obtain better printability properties from papers, some processes can be performed in paper production, as well as some surface treatments after production. These processes are paper coating, sizing and calendering. Paper coatings are generally water-dispersed coating solutions with one or more pigments, binders and certain additives to improve the desired properties. With these processes, by filling the gaps between the pores of the paper, a shapely and smooth surface is obtained and good printability is obtained together with the optical and physical properties of the papers. In this study, the interactions and printability properties of different types of pigments with xanthan gum binder were investigated by preparing paper coating formulations using calcium carbonate, barite and talc pigments and xanthan gum as binder. As a result, xanthan is a good coating binder and CaCO 3 {\mathrm{CaCO}_{3}} from the compared pigments is the most suitable compared to the other 2 pigments, considering all the studied areas.

CRACKING PHENOMENA OF COATINGS ON LABEL PAPERS

"The phenomenon of paper coating cracking when folded was studied. Coating mixtures were compared according to their composition, applied on different base paper, to find which combinations of the constituents of the base paper and the paper coating results in a lower tendency towards fold cracking of the coating layer. It was shown that the appropriate selection of pigments (calcium carbonate, kaolin) and binders (starch, latex), whose elastic behavior extensively influences the deformation of paper under physical and mechanical stress, is of central importance. The choice of the base paper plays a significant role as well, it should have the longest and the most numerous cellulose fibers possible in order to avoid fiber breaks and inter- and intra-fiber connections. The content of inorganic substances has the greatest negative effect on deteriorating the physical-mechanical properties of the studied label papers, leading to the deposition of inorganic substances at the joints between the cellulose fibers and reducing their bonding."