Readily dispersible inorganic pulverous compositions and process for their production

Dispersible inorganic pigments contain as a surface-active substance, a diester of orthophosphoric acid of the general formula in which R1 and R2 can be the same or different alkyl, cycloalkyl or aryl radicals, or alkyl, cycloalkyl or aryl radicals substituted by halogen, NO2, OH, COOH, SO3H, NH2, NHR, NR2 (R being alkyl), alkyl, alkoxy and/or polyalkoxy radicals; or polyalkoxy radicals or polyol radicals provided that at least R1 or R2 is alkyl or both R1 and R2 are polyalkoxy or polyol radicals. Pigments exemplified are TiO2, ZnS, Cr2O3 and iron oxides. The diester may be present in amount 0.01-10% based on the weight of the pigment. The coating with the diester may take place before, during or after other surface treatments of the pigment such as coating with the oxides of Ti, Al and Si; various procedures for grinding or mixing the pigment and diester, including treatment of the pigment, e.g. as a suspension with the pure diester or solutions or suspensions thereof, are referred to. missing page 252