Process for preparing stable aqueous pigment dispersions

Claim 1

PROCESS FOR THE MANUFACTURE OF STABLE AQUEOUS PIGMENT DISPERSIONS, WHICH COMPRISES MIXING AN AQUEOUS PIGMENT FILTER CAKE OF AN ORGANIC ALKALI-RESISTANT PIGMENT WITH A NON-IONIC DISPERSANT WHICH IS SOLUBLE IN AN ACID TO WEAKLY ALKALINE MEDIUM BUT INSOLUBLE IN CONCENTRATED AQUEOUS ALKALIS, ADDING TO THE MIXTURE CONTAINING THE SAID DISPERSANT IN AQUEOUS SOLUTION AN AMOUNT OF ALKALI METAL HYDROXIDE SUFFICIENT TO CAUSE THE DISPERSANT TO SEPARATE FROM THE AQUEOUS SOLUTION WHICH AND TO FORM A SEPARATE PHASE, WORKING THE PIGMENT INTO THE DISPERSANT PHASE, REMOVING THE BULK OF THE RESULTING PIGMENT-FREE AQUEOUS ALKALINE SOLUTION, AND CONVERTING THE NON-IONIC DISPERSANT BY NEUTRALIZING THE RESIDUAL ALKALI AND BY ADDING WATER INTO AN AQUEOUS SOLUTION WHICH CONTAINS THE PIGMENT IN A FINELY DISPERSED STATE, THE SAID NON-IONIC DISPERSANT BEING A REACTION PRODUCT OF 5 TO 150 MOLS OF ETHYLENE OXIDE WITH ONE MOL OF A WATER-INSOLUBLE ORGANIC COMPOUND, OF THE FORMULA RR-X-H, WHEREIN R REPRESENTS A HYDROCARBON RADICAL HAVING FROM 8 TO 24 CARBON ATOMS AND X IS SELECTED FROM THE GROUP CONSISTING OF -COO-, -CO-NH-, -O-, -S- AND -NH-, AND THE RATIO OF PIGMENT TO SAID NON-IONIC DISPERSANT BEING 1:0.5 TO 1:2.