Patent ID: 6824821
Filing Date: 2004-11-30
Classification: B01J,C01P,C04B,C09C

Abstract:
A process for preparing encapsulated pigment granules, comprising the steps of:(1) loading 1000-3000 kg of iron oxide powder, having a grain size of not less than 0.8 microns at a temperature of 15-20 degrees C., into a mixer rotating at a speed of 1-25 rpm; (2) rotating the mixer for approximately 0.5-2.0 hours, with the pigment powder cascading within the mixer so as to result in the formation of compacted pigment granules of approximately 0.30-1.20 mm diameter, with the compacted pigment granules being created solely through the action of rotational compaction and in the absence of a binder or encapsulation solution; (3) spraying, while the mixer is rotated, liquid encapsulation solution onto the cascading compacted pigment granules of approximately 0.30-1.20 mm diameter, where the liquid encapsulation solution is made by mixing 200-850 liters of water with 2.5-15 kg of polyvinyl alcohol encapsulating powder, and where the liquid encapsulation solution is sprayed at a rate of 40-200 liters per hour, for 1-4 hours, whereby the liquid encapsulation solution encapsulates the cascading, previously-formed compacted pigment granules, with the encapsulated compacted pigment granules having a diameter of approximately 0.30-1.2 mm diameter and a moisture content of approximately 10-14%; and (4) directing, while the mixer is rotating, heated air at a temperature of 200-600 degrees C. onto the encapsulated compacted pigment granules, so that the encapsulated compacted pigment granules are dried at a temperature of approximately 50-100 degrees C., and continuing this process for approximately 2-3 hours until the moisture content of the encapsulated compacted pigment granules is reduced to approximately 2% or less whereupon the encapsulated compacted pigment granules are removed from the mixer.