A powder with the deepest hue of blue possessing a structure reminiscent to that of an airborne drone, phthalocyanine is a pigment distinguished from the rest. Deriving its name from the Greek name for 'naphtha' and 'blue', the compound was first discovered in 1933 by British chemist Sir Patrick Linstead with multiple reports of its accidental discovery in 1907. In recent times, phthalocyanine has been the subject of much study within academic circles and has seen much industrial use. The derivative phthalocyanine blue consists of the phthalocyanine complex with a copper ion in its center. It is widely used as a blue pigment in the paint industry for paints and inks. This article will aim to expound on the properties, production processes and main applications of phthalocyanine blue within the paint industry with the goal of enlightening readers on the beauty of this organic pigment.
It is necessary to first elaborate on the unsubstituted compound. Phthalocyanine, an intensely blue-green aromatic macrocyclic compound and commonly abbreviated as H2Pc, is normally synthesized by the associative heating of several phthalic acid derivatives containing nitrogen functional groups. The vacant center of the compound is surrounded by 4 nitrogen atoms, allowing it to donate a total of 4 lone pairs of electrons to a metal ion. Phthalocyanine is thus well known for its ability to form a variety of coordination complexes with charged metal ions such as copper and lead. Combined with variations in its molecular structure e.g. chlorination of the benzene rings in its structure, phthalocyanine forms a range of compounds with varying shades and colours which are subsequently widely used as dyes or pigments for paints and inks.
Phthalocyanine blue, a subset of Copper Phthalocyanine (CPC), is a pigment that has dominated the colorant industry since its inception in 1935. Possessing an exceptionally brilliant shade, high tinting strength, low cost and good fastness properties, phthalocyanine blue has remained as a key blue pigment for paints, surpassing predecessors Ultramarine Blue and Prussian Blue. Its structure, the phthalocyanine system, bears much resemblance to the porphine system of haemoglobin, the iron complex and chlorophyll, the magnesium complex. The below figures illustrate the structures of phthalocyanine blue, haemoglobin and chlorophyll.
Phthalocyanine blue is produced commercially by two main methods. The first method is based on the use of phthalonitrile which yields a purer product and provides the possibility for formation of chloro-phthalocyanines when the right amounts of copper salts are utilized. The second method involves reaction with phthalic anhydride, urea, copper/copper salt and ammonium molybdate in a high boiling solvent. The product is then further purified and distilled to obtain a pure end product.
Moreover, phthalocyanine blue is a pigment with a strong upward trend with regards to demand and supply. According to Zauba.com, primary importers of phthalocyanine blue from India include the United States, Japan, South Korea, Netherlands and Thailand with a net total export volume worth USD$376 million. Prices vary slightly around the range of USD$4.60 over FY2014-2015 and continue to remain steady in the current financial year of 2016.
However, this valued pigment is not without its flaws as phthalocyanine blue is classified as a mildly toxic blue pigment for paints. Exposure to phthalocyanine blue and other derivatives has been reported to cause birth defects in developing embryos. Upon ingestion, the pigment is also known to cause abdominal pain and severe nausea. Although there have been no reported incidents of fatal bodily reactions when in contact with the compound, one should adhere to safety procedures when using paints, inks and dyes containing phthalocyanine blue.
Phthalocyanine blue is a pigment that has stood the test of time and triumphed over more toxic pigments such as Ultramarine and Prussian blue. With these desirable properties, it is no surprise that phthalocyanine blue continues to be utilized in various types of paints, inks and colourants. Until research and development confers new and improved products upon the industry, we can be sure that phthalocyanine blue is a pigment that we will be seeing on the ingredient label of both water-based and solvent-based paints alike.
Phthalocyanine blue and a variety of other organic and inorganic pigments can be found on http://www.paint-chemicals.com. If interested, please email firstname.lastname@example.org for further information and details.
Written by Jonathan Quah