Use of mixed rare earth oxides as environmentally benign pigments

A new class of environmentally benign brown rare earth colorants as alternatives to toxic inorganic colorants is presented. These colorants are based on mixed rare earth oxides. Unique feature of these colorants is the utilization of mixed rare earth oxides after the removal of radioactive thorium from monazite sand. The utility of mixed rare earth oxides for general exterior coating applications has been evaluated through mass tone/hiding power evaluations and the product has been fine tuned with respect to particle size, combination with hydrophilic agents, binders etc. to achieve good hydrophobicity and covering on porous surfaces like leather. The pigment was compatible with various auxiliaries employed in leather finishing and meets the current requirements for pigments like upgrading of finished leather through excellent covering of surface and improved levelness, no overloading of grain, excellent physical properties, ageing resistance and miscibility with water.