The Effect Of Pigment And Base Paper On The Rheology Of The Coat Material And The Coverage Of Coating Layer

Paper is coated to obtain a good printing surface. So it is important and necessary to improve the coverage of the coating layer. Coverage is one of the key factors that affecting surface properties of paper. And the surface properties has an important relationship to the printing properties. The base paper and pigments have an important influence on the coverage of the coating layer. The rheology is the important property of the coating material. The aid of this study is to find out the relationship of the base paper the pigments and the coverage of the coated paper.1. Design of Experiments(DOE),which can screen out the most important factor in an experiment, was used in this study. Four-factors-two-levels'experiments, with the mixed pulp, fillings, the dosage of AKD and the dosage of CS as the main factors were designed and studied. The result shows that fillings is the most important factor in this study.2. Cationic starch, oxidation starch and enzymatic starch were used to surface sizing agents . The effect of them on the base paper and coated paper were discussed. Cationic starch as the surface sizing agent can high improve the base paper strength than oxidation starch and enzymatic starch. The starch sizing agent with 0.7% PVA can cause lower coverage of the coating layer than 100% starch ,because PVA penetrates easily into the paper .It can form a compact glue layer on the surface of coated paper and reduce air permeability. The print mottle can reduce and the coverage of coating layer can increase after paper is sized with starch. Compared with other starches, cationic starch or it with 0.7% PVA can high improve the scott bond of paper and the coverage of coating layer, reduce the printing mottle.3. And in this study, we found that the rheology of the coating material has an important influence on the coverage of the coating layer. we have studied the mixture of different coating pigments affected the rheology of coating material and the coverage of coating layer. This study used three pigments: calcium carbonate 65, calcium carbonate 95 and clay. And this study shows us that put the calcium carbonate into the coating material can improve the strength of the coated paper surface.4. Precipitated calcium carbonate(PCC) was used to put in the stock for improving the optical and printing properties of base paper. The research focused on the effects on the rheology of coating colors and the properties of coated paper for aragonite PCC. It shows that the low shear viscosity of coating color reduces and the high shear viscosity increases with PCC increasing. The water retention of coating color became bad and it is disadvantageous to the high slurry solid and the runability of the coating machine. But PCC can increase the L* and a* and reduces b* of coated paper. It can enhance CIE whiteness and opacity of paper and decreases the dosage of fluorescent whitening agents. PCC can provide better the surface strength of coated paper and reduce the latex dosage compared with clay.