Metal free phthalocyanine is most commonly prepared by the demetallization of sodium or calcium phthalocyanine. The I.G.Farbenindustries has produced metal free phthalocyanine by the demetallization of the calcium phthalocyanine with boiling 10% hydrochloric acid. Calcium phthalocyanine can be manufactured by reacting phthalonitrile with calcium oxide in the presence of formamide.

Metal-free phthalocyanine can also be obtained by eliminating metal from phthalocyanine complex with labile metals such as magnesium or calcium by reaction with a strong acid, or even more easily by treatment or disodium phthalocyanine with cold methanol. The pigmentary properties of metal-free phthalocyanine may be developed by acid pasting or acid slurrying methods. Metal free phthalocyanine exists in polymorphic modifications.

Modifications of metal free phthalocyanine obtained by treating the gamma from in dilute sulfuric acid for 16 hours at 20°C.

Metal free phthalocyanine is a brighter greenish blue pigment. It has slight inferior light fastness than copper phthalocyanine.

Properties Phthalocyanines

The phthalocyanines have since their discovery increased steadily in importance with the result that they are today the most important organic pigments.

The phthalocyanine pigment are now employed in a wide variety of industries and their applications are increasing continuously. As a consequence increasing demands are made with regard to the quality of the pigment and their outstanding fastness properties alone are not sufficient for many applications. Special characteristics such as good rheological properties and resistance to flocculation are also of importance today and the phthalocyanine range is being continually extended by new products which meet such special requirements.

Copper phthalocyanine have excellent stability to light in both mass tone, and tint, excellent resistance to acid and alkalies, and no bleed in solvent. But they have undesirable properties such as crystallization and flocculation. Phthalocyanine pigment (metal free) crystallizing type finds use due to its electrical properties and the non crystallizing type is used in certain kind of automotive coatings.

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