This invention relates to a new process for finishing phthalocyanine coloring matters in a finely divided, solid state, exhibiting high tinctorial strength and excellent pigmentary properties in’general. More particularly, this invention relates to an improved process for finishing copper-phthalocyanine,zenith grinding mill metal-free phthalocyanine and chlorinated derivatives of either, in a finely divided, pigmentary state.Phthalocyanine coloring matters are a well known class of compounds enjoying wide use as colored pigments because of their brilliance of shade, high tinctorial strength, and remarkable stability under a wide variety of conditions of use. The commercial forms are generallyblues and greens, and for the most part they are derivatives of copper-phthalocyanine.

It is well recognized in the art that crude copper-phthalocyanine, i. e. the product obtained directly in the synthesis thereof, has relatively little value as a pigment. It is generally composed of large particles, in the order of 25 to 50 microns in length, and consequently exhibits very low tinctorial strength, and is quite dull in shade. The same is true of other phthalocyanine compounds and of at least some of the methods of producing metal-free phthalocyanine.Two methods have been proposed heretofore for converting the large-particle size,crushing equipment crude phthalocyanine compounds to a pigmentary state of very fine sub-division exhibiting high tinctorial strength and brilliance of shade. The most widely described method of accomplishing this purpose is the so-called acid-pasting process. This process involves dissolving the phthalocyanine coloring matter in concentrated sulfuric acid and then precipitating the pigment by very rapid dilution of the sulfuric acid solution with water.

Most commercial phthalocyanine pigments heretofore have been made by this method, but the method suifers from certain inherent disadvantages, resulting from the required use of large quantities ,of sulfuric acid, such as high cost of the acid and the problem of disposal of the acid waste. The method also imparts certain disadvantageous properties to the resulting pigment. For instance, if the pigment is dried without further treatment, it almost invariably becomes hard in texture and is very difficult to incorporate in the usual vehicles of coating compositions or printing inks. A second disadvantage resides in a pronounced tendency of the acid-pasted pigment to fiocculate in enamels, lacquers, and similar compositions.