Easily dispersible formulations of pigments and their use in tinting base media
Formulations of easily dispersible (ED) pigments comprising a combination of a carboxylic acid polymer and a non-ionic alkoxylated surfactant are disclosed. The combination is used in the formulation of a plurality of pigments. The formulations are suitable for mixing with a base medium at the point-of-sale (PoS) or by the end user.
1. A method of preparing a flowable particulate formulation for use in the tinting of base media comprising the step of spray drying an aqueous dispersion of a mixture with a total solids content of 45 to 75% (w/w) comprising a plurality of pigments, a polycarboxylic acid and a non-ionic alkoxylated surfactant where the ratio by weight (w/w) of formulant to total pigment is in the range 1.4 to 11.3% polycarboxylic acid and 4.5 to 37.7% non-ionic alkoxylated surfactant.
2. The method of claim 1 where the non-ionic alkoxylated surfactant is an ethylene oxide-propylene oxide diblock copolymer.
3. The method of claim 2 where the polycarboxylic acid is an acrylic acid polymer.
4. The method of claim 3 where the aqueous dispersion additionally comprises a hydroxylated amine.
5. The method of claim 4 where the aqueous dispersion consists essentially of a plurality of pigments, a polycarboxylic acid, a non-ionic alkoxylated surfactant and a hydroxylated amine.
6. The method of claim 5 where the ratio by weight (w/w) of hydroxylated amine to total pigment is in the range 0.5 to 3.8%.
7. The method of claim 6 where the hydroxylated amine is 2-amino-2-methyl-1-propanol.
8. The method of claim 7 where the step of spray drying the aqueous dispersion is at an inlet temperature in the range 180 to 240° C. and the outlet temperature is in the range 80 to 120° C.
9. The method of claim 8 where the step of spray drying the aqueous dispersion is at an inlet temperature in the range 190 to 235° C. and the outlet temperature is in the range 90 to 110° C.