High quinacridone pigments

To obtain the necessary fastness properties, high-quality pigments are generally used for security printing. The range of suitable products covers disazo, disazo condensation, benzimidazolone, naphthol AS, isoindolin, perinone, anthanthrone, dioxazine and quinacridone pigments. 

All industrially significant quinacridone pigments are deeply colored products. They cover the spectral range from yellowish red to violet shades. Quinacridone pigments do not melt but decompose at high temperature. 

All the main classes of pigments are used in the printing ink industry, but the high-performance pigments, e.g. quinacridones, which can be thirty times dearer than azo pigments, are reserved for use in the highest quality printing. 

Quinacridone pigments are available in orange, red, and violet. They have good light fastness, excellent bleed and chemical resistance, and adequate heat stability for most plastics. However, they are high in cost. They perform best in polystyrene and acrylic at lower temperatures. They are not recommended for nylon. 

Like many of the high-performance pigments such as quinacridones, DPPs and phthalocyanine pigments, THI pigments can exist in more than one crystal form. So far, three different crystal modifications with different crystal packings have been identified. 

Analytical studies of the PPA reaction processes by real-time infrared spectroscopy [19A] demonstrate that cycUzation to the corresponding quinacridones is very rapid at the typical reaction temperatures and although not confirmed directly, probably proceeds by a two-stage sequential mechanism. Analogous to the thermal process high dilution conditions favor monomolecular reactions and subsequently the quaUty of the ultimate products. The by-products of bimolecular reactions occasionally have been detected in some quinacridone pigments... 

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