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Copper phthalocyanines

(2006)

Basic structure of copper phthalocyanines

CAS No: see below Physical data: Melting point: Evaporate at 500-600°C instead of melting (sublimate). Boiling point: Evaporate at 500-600°C instead of boiling (sublimate). Vapour pressure: Very low. Water solubility:  Vary from insoluble to highly soluble. Molecular weight: at least 576 gram/mole.

Copper phthalocyanines are solid crystalline substances with different turquoise colours. The water solubility varies largely within this group. They are fairly stable to light and weather conditions. Many are also termostable which partially relates to the metal ion. The sublimating behaviour at 500 till 600°C also reflects the high termostability.

Copper phthalocyanines are synthetic pigments/dyestuffs, which belong to the group metal complex colouring agents. The plane aromatic structure, with a central copper atom, has many similarities with the iron complex in haemoglobin and the magnesium complex in chlorophyll. This structure gives the molecule an exceptional high stability. Phthalocyanines were first synthesized in 1907. The influence of a metal in the molecular structure was observed bycoincidence when blue residues were found in a reaction vessel made of iron. The first molecular variants where synthesized in England 1935 and were used as pigments. The molecule was later modified to be a colouring agent, e.g. by sulfonation. Copper phthalocyanines became quickly popular because turquoise pigments/colouring agents at that time were completely missing. The word turquoise, that occurs only rarely in the literature before this discovery, became thereafter frequently used.

The nuance can be changed by a subsequent halogenation of the molecule. The change in nuance increases with increasing halogenation. Chlorination gives greenish nuances while bromination gives yellow-greenish nuances. A chlorinated molecule contains normally about 15 chlorine atoms.

Also other metals can be used in phthtalocyanines, e.g. cobalt and nickel. There are also metal free phthtalocyanines (e.g. Pigment Blue16) which are used for e.g. in art paints.

The production of copper phthalocyanines can alternatively be made from phthalonitrile which reacts catalytically with copper compounds. Phthalonitrile can be replaced with phthalic acid anhydride + urea. Originally this reaction was performed without a solvent. In course of time the method was developed with the help of different solvents. Choice of solvents has a strong effect on the colour nuance of the produced pigment. It has an influence on both the size and form of the crystals as well as the degree of impurities in the final product. Chlorinated and nitrated aromates was shown to have the best physical properties for this purpose. However, these are toxic and require expensive abatement technique and may also form dangerous impurities such as PCBs. New solvents have been developed to avoid these effects. Phthalonitrile causes fewer impurities but is more expensive than phthalic acid anhydride. The production methods are very sensitive. Therefore, even if a method is repeated it can result in substances with different nuances.

Copper phthalocyanines are used as colouring agents with nuances in blue and green. The most frequent uses in Sweden are as colouring agents or pigments in printing ink, paint, plastic and paper. Copper phthalocyanines are also used for textile colouring. The highly chlorinated ”Pigment Green 16” is very persistent and is used in paints.

Contact person: Margareta Östman,  Tel +468 519 411 62
Swedish Chemicals Agency Box 2 SE-172 13 Sundbyberg, kemi@kemi.se
Tel +468 519 411 00 Fax +468 735 7698