Preparation of ground calcium carbonate-based TiO2 pigment by a two-step coating method

Abstract

A two-step coating method for preparing ground calcium carbonate-based TiO2 pigment (GCTD) was proposed and studied in this paper. The tetraethoxysilane (TEOS, C8H20O4Si) was selected as Si source. Aqueous ammonia was used as precipitant in the first coating step while titanyl sulfate (TiOSO4·2H2O) was used as Ti source in the second step. The Energy dispersive spectrometer (EDS) and X-ray fluorescence (XRF) results prove that SiO2 is coated on the surface of ground calcium carbonate (GCC) particles successfully. The X-ray diffraction (XRD) and transmission electron microscopy (TEM) results demonstrate that the coated SiO2 is in the form of amorphous. The EDS, XRD, TEM and Scanning electron microscope (SEM) results show that TiO2 is coated on the surface of SiO2 coated GCC (SiO2@GCC) and TiO2 particles are composed of mixed crystal of anatase and rutile. The hiding power of obtained GCTD is significantly improved compared with ordinary composite TiO2 pigment (CTD) and close to that of anatase TiO2 (ATD). The whiteness and lightness of this GCTD are just slightly decreased compared to that of CTD and ATD. Nevertheless, its oil absorption value is some higher than that of ATD but lower than that of CTD.