THE INVESTIGATION OF USING ZIRCONIUM OXIDE MICROSPHERES IN PAPER COATING

Paper and cardboard are the raw materials frequently used in the printing industry. Pulp structure in papermaking process, surface roughness, and strength of electricity, moisture, thickness, thermal conductivity and optical properties are important parameter that influences printing quality. The surface structure of paper and cardboard needs to be improved for the quality prints. Among the methods of reducing paper surface roughness, sizing, coating and calendering processes can be counted. In the surface coating process, fillers are added to the formulations differently from sizing. While these fillers increase absorption, they also affect colour, opacity, gloss, surface roughness, contact angle etc. Materials containing zirconium oxide; due to the increase of strength, unaffected by chemical agents, high opacity and whiteness, it finds different usage area. In this study sizing and surface coating processes have been carried out in order to improve the surface properties of the paper, to improve the gloss, yellowness, whiteness, absorbency and contact angle of the paper. For this purpose, cationic starch and zirconium oxide coating formulations were prepared and applied onto paper with a paper coating tester under laboratory conditions. In addition, surface sizing with cationic starch has been done as a reference. Coated, sized and standard office type base papers were printed with IGT C1 offset printing test with magenta ink. The colour and gloss values of all printed and unprinted samples were measured. Printed samples, coated papers, surface sized papers and base papers were subjected to lightfastness test according to BS4321 and colour and gloss changes were examined with blue wool scale. The contact angle, absorbency and surface energies of all the obtained surfaces were determined. As a result, it has been found that zirconium oxide-added paper coatings have less glossy but lower contact angle and higher absorbency than surface sizing. It has been determined that the coated paper have worst yellowness and gloss changes with light aging. As a result, the addition of zirconium oxide to the coating improves printability.