Application of sericite to LWC coatings

Abstract

Sericite is a mica mineral locally produced from the east coast of Taiwan. It carries high negative charges on its plate surfaces and has a high aspect ratio that might be useful for adjusting water retention values and the viscosity of coating colors. In this study, we partially or totally replaced delaminated clay in a lightweight coating (LWC) formulation with sericite and examined the resulting effects on the optical and printing properties of the coating colors and coated sheets. The water retention value (WRV) of the color decreased with increasing amounts of sericite substitution, reflecting an increase in water retention of the color by about 30%. Low shear viscosities decreased with increasing amounts of sericite substitution, while high shear viscosities showed a V-shaped response, suggesting an increase in the elasticity of the coating color under high shear conditions. Among the coated paper properties, the addition of sericite raised the opacity of the sheet. The brightness of the coated sheets, however, decreased linearly with increasing sericite substitution. When sericite was applied, notable swelling and delamination effects occurred during the preparation of the coating color.