ARTICLE

Scott Heitzman
scott.heitzman@na.sunchem.com

Organic Blue for Plastics

Organic Blues
Copper Phthalocyanine Blue C. I. Pigment Blue 15:x

Cincinnati, Ohio - Peter A. Lewis -- The most important and most widely used blue throughout all applications of the plastics industry is copper phthalocyanine blue, Pigment Blue 15, C.I. Number 74160, Fig. 1.

First described in 1928 by chemists working for the Scottish Dye Works, this pigment has steadily increased in importance to become a product with worldwide significance. The only metal derivative of significant commercial use is that of copper, derivatives of other metals having been shown by research to have less desirable shade or fastness characteristics. Metal-free phthalocyanine, Pigment Blue 16, C.I. Number 74100, once found an outlet as a green shade blue. However, this pigment's inferior heat stability and poorer chemical resistance, coupled with a price almost three times that of the copper containing salt, has resulted in a rapid decline in its consumption for all but very special applications.

Copper phthalocyanine is commercially available in three crystal forms, alpha, beta and epsilon. However, only the first two crystal morphs have any real commercial significance within the plastics industry. The alpha crystal, using the Colour Index nomenclature, is described as Pigment Blue 15, 15:1 and 15:2 and is a clean, bright red shade blue. The beta crystal, described as Pigment Blue 15:3 and 15:4 is a clean green shade blue. Because of the way color is perceived by our eyes the red shade, alpha crystal, appears to be a cleaner, stronger color when incorporated into a plastic, especially if white is also included in the blend.