The Effect Of Base Paper And Coating Formulation On The Properties Of Coated Paper

In the paper coating process, a water based pigmented coating is applied to base paper to enhance the optical and topographical properties of the pigmenting surface. The quality of coated paper is mainly governed by the characteristics of base paper. It generally believed that the base paper properties, coating process, and coating formulation are very important, since these might affect the optical properties of coated paper, as well as the structure and uniformity of coating layer.The variations in formation, absorption, thickness, moisture, and roughness of the base paper have a great influence on the properties of the coating layer and its variations. The uneven coat weight distribution is the most important factor influencing the uneven print image, mottling. Several mechanisms have been proposed to explain the effect of base paper on coated paper quality. Essentially all of these literatures don’t refer to the brightness of coated paper. Very few literatures refer to the relationship of base paper brightness and coated paper brightness. So it’s very important to study the effect of base paper and the relationship of base paper and coating formulation on the brightness of coated paper.The effect of base paper brightness and blending ratio of clay and GCC on the optical properties, mechanical properties and printability of coated paper were investigated. It was found that the brightness of coated paper not only depend on the brightness of base paper but also on the blending ratio of clay and GCC. The brightness of coated paper increased with increasing of brightness of base paper. The effect of differences in pigment properties on the optical properties of a coated paper depends on the brightness of base paper. For low-brightness base paper,100% clay coating layer gave a higher brightness of coated paper than 100%GCC coating layer. The blending ratio of clay and GCC had synergy effect on the brightness of coated paper. While for high-brightness base paper,100% GCC coating layer gave a higher brightness of coated paper than 100% clay coating layer. The gloss, printing surface strength and mechanical properties of coated paper decreased with the increasing of GCC.In this research, OBA was applied in base paper and coating layer to improve the optical of coated paper. The result showed that they all increase the brightness of coated paper, while the efficiency of OBA which is applied in top-layer is highest. Pigments and base paper brightness have great effect on the OBA efficiency. Higher brightness of base paper and the ratio of GCC helped to improve the OBA efficiency. Studying the OBA efficiency of coated paper may helped to improve the brightness of coated paper and decrease the cost of coated paper.