Pigment continuous chemical precipitation and controlled - crystal growth in agitated conditions

摘要

The reagents for the precipitation of the pigment are introduced continuously into a first agitated reactor vessel, where they react together, then fed through a separate continuous agitated reactor vessel, where the residence time enables a close control and uniform grain growth of the pigment. The uniform growth of the pigment cannot be achieved in conventional batch precipitation processes,where the nucleation and the growth of the pigment crystals take place in the same location with relatively long filling times and emptying times, normally in relatively large vessels in which it is difficult to achieve an adequate degree of turbulence to ensure complete uniformity of concentration, and initially formed nuclei promote further growth of crystals before precipitation is complete. The initial precipitation is complete. The initial precipitation and crystal growth may take place in different compartments in the same reactor vessel.