Study On Coating Consolidation Mechanism Of Coated Paper

Coating consolidation is a complicated process, in which the liquid coating sample applied on substrate transforms into an immobilized (dry) coating layer. And it has significant effect on the coating surface properties such as porosity and optical properties, and printability. Therefore, it is always a very important research subject to clarify consolidation mechanism of coating layer, so as to advance coating structure, optimize coating formula and further promote surface property. Based on Lepoutre’s classic coating consolidation theory, Croll’s latex film mechanism was introduced into consolidation study of coating layer. The drying processes of model clay coatings are monitored to investigate consolidation mechanism. Both surface gloss development and evaporation rate of coating layer were measured to characterize consolidation process. A new consolidation mechanism of filter cake was used to describing consolidation process. Moreover, all the data is recorded by cameras so as to improve synchrony between time and data and minimize systematical error. The critical time of evaporation development of coating layer could be found by the conception of correlation coefficient.By studying influence of coating layer weight, initial solid content, latex content and pigment content on coating consolidation process, some results could be gained:the evaporation development during coating layer consolidation could be described by new consolidation mechanism, and separated into there stages, i.e. constant, drop, slow. And the critical point at constant phase that begin to drop sharply is at LCC. The time when coating layer gets FCC is independent of coating weight, but FCC increases with increasing coating weight. The solid content at FCC, SCC and LCC increase with increasing initial solid content of coating layer, but all the critical time become short. With increasing latex content of coating layer, the solid content at both FCC and LCC keep invariable, but the solid content of SCC increases.In addition, the influence of coating weight, initial solid content, latex content and pigment content on properties and structure of coating layer was investigated. And the results show that with increasing the coating weight, initial solid content, latex content and GCC content, the coating porosity decreases and the roughness keep constant. And the whiteness increases with increasing the coating weight, initial solid content and GCC content, but it also keep invariable with increasing latex content.All the data indicated that the new consolidation mechanism can be a successful model for describing the drying process of pigment model coatings. It established the firm foundations for further investigation of coated paper. In this paper, the critical value as a function of different factors was confirmed, and a new consolidation model of water-based coating layer was built. It was further to improve the reorganization of consolidation process of coating layer and mass and heat transfer (such as binder migration). It contributed to the development of new energy-saving coating formula, new highly efficient binder and additives.