Nanoclays used to improve surface properties of paper

Iranian researchers used nanoclay and calcium carbonate particles to improve surface properties of paper, including smoothness and printability, as well as optical properties of printing papers. In this research, coating materials, including nanoclay, at two levels of 5 and 10 weight percent were mixed with deposited calcium carbonate at four levels of 20, 30, 40, and 50 weight percent compared to the latex. TAPPI standards were used to measure the roughness of the surface, water adsorption of the paper, gloss, and permeability of paper against air while ISO standard was used to detect paper printability and picking of the paper, and SCAN standard was employed to measure printing density. The surface of the paper coated with nanoclay in this research has relatively appropriate homogeneity and smoothness due to the high specific area of nanoclay and the difference in the shapes of particles. Scanning microscope images showed that the voids and pores were filled with fillers on the surface of the paper. Decrease in roughness, porosity and water adsorption of the coated papers improves the printability of the paper and stabilization of its dimensions during web offset printing. One of the most important challenges in printing papers was their low printability quality. Results of the research showed that the coating of papers resulted in an increase in the gloss and printing density, which is a sign of improvement in printing quality. Moreover, picking tests demonstrated that the coating increased adhesion of the ink and paper and it prevented the picking of the paper on rolls, specially on the roll of blanket offset. Results of the research have been published in details in Bioresources, vol. 8, issue 3, 2013, 3646-3656.