Preparation and characterization of PVOH/kaolin and PVOH/talc coating dispersion by one-step process

The poor barrier of cellulosic paper against water vapor and oil limits its wide application as a packaging material. Lamination, extrusion, and dispersion coating are applied on paper surface to improve barrier properties. Dispersion coating can be applied to paper surface on line during paper preparation using rod coater. In the present study, an attempt has been made to increase the process speed of coating preparation by single-step process at varying pigment concentration. Coating dispersion was applied on kraft paper using laboratory rod coated and dried in hot air oven at 80°C for 5 min. Furthermore, thermal stability, water vapor barrier properties, and grease resistance of PVOH/kaolin and PVOH/talc-coated paper were studied. Additionally, the effect of single layer and bilayer coating on paper properties was also studied. Permeability model was used to predict the orientation of pigments to the surface of paper. Viscosity of both kaolin and talc-based dispersion increased with the increase in pigment concentration. Thermal studies showed that at 600°C residual mass (%) of PVOH film increased from 0.6 to 9.89% and 15% with the addition of 25% (by weight) kaolin and talc pigment. At high pigment concentration (40–50%, by weight), the highest reduction in WVTR was observed for both the pigments. Excellent coverage of paper surface and high grease resistance was observed for all coating formulations. Our study showed that talc provides better thermal and barrier properties to coated paper than kaolin.