High silica-alumina-coated TiO₂ pigment with improved dry hiding for flat paints

High silica-alumina coated TiO₂ pigment with enhanced dry hiding was prepared by the precipitation method under varying treatment conditions. XRF, TEM, FTIR spectra as well as particle size and surface area analyses were used to characterize the prepared TiO₂ samples. The pigmentary properties and performance of the TiO₂ samples were evaluated. The hiding power of TiO₂ particle surface modified with silica throughout in the moderate acidic range has been found to be significantly increased. At moderate acidic pH range, sodium silicate precursor hydrolyzes to form large number of void-bearing siliceous micelles which anchor on the surface of TiO₂ pigment to obtain porous coating layers. It is inferred that this voluminous coating containing network of air voids has contributed to the enhanced dry hiding by promoting spatial relationship among the TiO₂ particles. This will reduce the amount of TiO₂ pigment required without any change in hiding power of low-gloss, flat coatings formulated at high pigment volume concentration. The inventive TiO₂ pigment makes a good dry hide grade quality pigment with good optical properties and ink-stain resistance.