US 6,949,139 : Process for forming cocrystals containing chlorine-free titanyl phthalocyanines and low concentration of titanyl fluorophthalocyanine using organic milling aid
Sorriero, Louis J. (Rochester, NY, US)
In a process for forming an amorphous pigment mixture consisting essentially of TiOPc and TiOFPc and containing more than about 75 weight percent of TiOPc, a mixture of crude crystalline TiOPc and TiOFPc pigments in a weight ratio of at least 75:25 TiOPc:TiOFPc is combined with at least about 5 wt. %, based on the total weight of TiOPc and TiOFPc, of an organic milling aid. The mixture is treated under conditions effective to form a substantially amorphous pigment mixture of TiOPc and TiOFPc. The organic milling aid can be separated from the substantially amorphous pigment mixture, which can be converted to a nanoparticulate cocrystalline TiOPc/TiOFPc composition.