High Weatherability Titania Preparation Techinique And PH Control Method Of Aqueous Suspension

Titanium dioxide (TiO2) is the best white pigment widely used in paint, plastics, rubber, paper and other fields. In order to improve the weatherability of titania pigment, the coating process of hydrous silica and alumina on TiO2 particles has been investigated, which favors to form homogeneous and compact membrane. Thus, the parameters for coating were studied by experiments, including pH, temperature, etc. Samples were taken in the coating process and analyzed by transmission electron microscope(TEM), the weatherabilty was detected by manual aging experiment. The results show the condition for the after-treatment of titanium pigment is fixed, and the test method for weatherabilty is efficient.The pH of an aqueous suspension of titania particles coated with silica and alumina were investigated. TEM images showed that SiO2 and Al2O3 form a film coating on the particle surface, and the film became thicker as the coating amount increased. According to GB/T 1706-2006, the samples were made into aqueous suspension at a concentration of 10% in weight. pH value showed that the suspension of titania particles coated with SiO2 was alkaline, and the pH increased with coating amount till pH 9.7. While the suspension of titania particles coated with Al2O3 was acid, and the pH decreased with coating amount till pH 4.4. The zeta potential was also affected by the surface coating similarly as pH. The suspension's pH can be controlled effectively by a minor coating of alumina on silica coated particles, and a minor coating of silica on alumina coated particles.