Phase- and Flocculation-Stabilized Copper Phthalocyanine Blue Pigments

4 Phase- and Flocculation-Stabilized Copper Phthalocyanine Blue Pigments 

There are various methods of stabilizing a pigment in order to prevent conversion to a different phase, i.e., change of modification, and flocculation during pigment application. The two following techniques have been found to be most effective  

Only a minor amount of chlorinated copper phthalocyanine, for instance, especially in the 4-position of the copper phthalocyanine molecule, prevents a change of modification from a to (3. Approximately 3 to 4% chlorine is commonly used, which corresponds to the formula CuPc-Cl0.5, also referred to as semi-chloro-CuPc . The phthalic anhydride/urea synthesis, for instance, affords a partially chlorinated product if 4-chlorophthalic anhydride is added to the reaction mixture. Copper chlorides in the phthalonitrile process have the same effect. 

Partial sulfonation or sulfamide formation may stabilize a pigment toward flocculation. Combining partial sulfonation and chlorination will further improve the effect of each individual type of modification. Similar results are observed if carboxylic acid groups are introduced into the pigment molecule. 

There is an interesting technique which makes it possible to introduce carboxylic acid groups into a copper phthalocyanine structure by an economical route. Carrying out the phthalic anhydride/urea process in the presence of a small amount of trimellitic acid or another benzene polycarboxylic acid will afford a car-boxylated pigment. 

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