In contrast to the prior art acid-pasted phthal ocyanine, this product required no special treatment prior to drying out, in order to be usable as a pigment. When incorporated in a coatin composition it exhibited a tinctorial strength at least as good as the best acid-pasted product, coal mining equipment manufacturers and it was as much as to stronger than many such prior art commercial products. It was substantially equal to such pigments in both hue and brilliance of shade, and had the pronounced advantage of a very much reduced tendency to fiocculate in enamels and lacquer vehicles. The particles were so small in size as to be extremely difficult to resolve even by means of an electron microscope, but the best possible measurement was less than .1 micron. Measurement of the surface area of the particles by the Emmet gas-absorption technique, indicated a surface area of approximately 90 square meters per gram of pigment, as contrasted to an average of about 75 square meters per gram for normal acidpasted samples.
Example 2 One hundred and eighty grams of the same partially chlorinated copper-phthalocyanine pigment as used in Example 1, together with 1500 cc. of 91 isopropanol were charged into a stainless steel ball mill with a capacity of about 6800 cc. and containing 13,000 grams of steel shot. The mill was rotated at about 70% of the critical speed about four days, whereupon the charge was diluted with water and strained from the balls. After removal of the isopropanol by distillation, tantalite mining equipment the aqueous slurry was extracted with 2-3% sulfuric acid, filtered, washed sulfate free, reslurried and again extracted with dilute ammonia. It was then filtered, washed alkali-free and dried in an oven at about 60 C. The bright blue powder was a highly desirable phthalocyanine pigment with substantially the same properties as the product of Example 1.
Example 3 pounds of crystalline sodium chromate were charged into a ball mill of approximately 1000 gallons capacity, containing a nominal 40% load of A, steel balls. The mill was rotated at about 70% of the critical speed for about 24 hours and, after some dilution with additional acetone, the fluid mass was discharged from the mill. The acetone was removed by distillation and the resulting aqueous slurry was extracted first with dilute sodium hydroxide and, after filtering, washing, and reslurrying, was further extracted with 2% sulfuric acid to which has been added a small amount of sodium chromate. The pigment was then isolated by filtration, washing free of acid, and drying at about C. The resulting bright green pigment exhibited a tinctorial strength at least as good as the best prior art pigment finished by acid-pasting and from 10-15% above that of many corresponding commercial products.