Method and equipment for manufacturing pigment dispersion

An apparatus for manufacturing pigment dispersion, said apparatus comprising:

• a twin screw extruder including a housing having therein a pair of adjacent parallel screws, the ratio of the length of said housing to the inner diameter thereof being at least 25, said extruder including an upstream feed section, a flushing section downstream of said feed section and a dehydrating second downstream of said flushing section, said feed section including a feeding port;
• first feeding means for feeding a hydrophobic liquid organic media at a constant rate to said feeding port, and second means for feeding pigment wet-cake at a constant rate to said feeding port, and thereby supplying said media and said wet-cake into said feed section of said extruder;
• means for rotating said pair of screws in the same direction within said housing and thereby for sequentially transferring said media and said wet-cake from said feed section to said flushing section and therein continuously flushing pigment particles from a water phase to an organic medium phase, thus forming a flushed pigment mixture, and then transferring said mixture from said flushing section to said dehydrating section and therein continuously dehydrating said mixture, thus forming pigment dispersion;
• said dehydrating section having first vent means for removing a majority of water from said mixture;
• and
• said dehydrating section having second vent means, adapted to be connected to a source of vacuum, for removing residual water from said mixture.