Phthalocyanine pigments are organic pigments built around a copper phthalocyanine molecule. They give the strong, clean blues and greens used in printing inks, paints, plastics and textile printing.
Pigment Blue 15 is copper phthalocyanine itself, with Colour Index constitution number 74160. Pigment Green 7 is the highly chlorinated form, with number 74260. Both are among the most widely used organic pigments because they combine high strength, good light fastness and good heat and chemical resistance.
How they are made
Makers first produce crude copper phthalocyanine, usually from phthalic anhydride, urea and a copper salt. The crude is coarse and has little colour value. It is then finished by acid treatment, milling or solvent treatment to give the particle size, crystal form and surface that the end use needs.
Green is made by chlorinating the crude blue, then finishing it. Pigment Green 36, a brominated version, gives a yellower green.
Gujarat has a strong base in crude blue and finished phthalocyanines, because the same estates make the raw materials and intermediates. Some plants sell crude to other finishers, so ask whether your supplier makes its own crude.
The Pigment Blue 15 family
The number after the colon tells you the crystal form and stabilisation. These forms are not interchangeable:
- Pigment Blue 15 and 15:1 are alpha forms with a redder shade; 15:1 is stabilised so it does not change crystal form in solvents.
- Pigment Blue 15:2 is an alpha form that is also stabilised against flocculation, for paints.
- Pigment Blue 15:3 is the beta form, with a greener shade, and is the standard cyan for printing inks and a common plastics blue.
- Pigment Blue 15:4 is a beta form treated to resist flocculation, used in paints and some inks.
- Pigment Blue 15:6 is the epsilon form, the reddest of the group, used in some inks and paints.
What to check when buying
- Specify the exact Colour Index name, including the number after the colon, and the end use.
- Ask for strength and shade against your own standard, tested in your system, such as your ink vehicle or polymer.
- Ask for dispersion results, since a poorly finished pigment needs more energy to disperse. See how pigment dispersion quality is tested.
- For plastics, ask for heat stability and any warping effect in polyolefin moulding, a known issue with some phthalocyanines.
- Ask for test results for unintentionally formed polychlorinated biphenyls, which can occur as trace by-products in some pigment processes and are restricted in several markets.
- Ask for heavy metal results other than the bound copper, and for free copper if your customer limits it.
Next step
Phthalocyanines are widely available from Gujarat, but finishing quality is what separates suppliers. We find and audit pigment makers, compare their samples in your system and have lots tested before loading. For plastics grades, also read heat stability in pigments for plastics. To start, book a free sourcing review.