Introduction

A long-term aim of dye research has been to combine the brightness and fastness properties of anthraquinone dyes with the strength and economy of azo dyes. This aim is now being realized with heterocyclic azo dyes, which fall into two main groups: those derived from heterocyclic coupling components and those derived from heterocyclic diazo components. All the heterocyclic coupling components that provide commercially important azo dyes contain only nitrogen as the heteroatom. They are indoles, pyrazolones, and especially pyridones, providing yellow to orange dyes for various substrates. In contrast to the heterocyclic coupling component, all the heterocyclic diazo components that provide commercially important azo dyes contain sulfur either alone or in combination with nitrogen.

These dyes offer bright, strong shades ranging from red through blue to green, complementing the yellow/orange colors of the nitrogen heterocyclic coupling components (Hunger, 2003). In continuation of our interest in the synthesis of condensed arylazopyrazoles as new dyestuffs (Elgemeie et al., 1987, 1989, 1991, 1994, 2003a, b, 2004; Helal, 2004).

Disperse dyes are used for printing synthetic fabrics in general using all techniques. Specially designed disperse dyes with specific molecular weight and sublimation properties are designed for use in the transfer printing technique.

The sublimation transfer printing process involves the transfer of disperse dye from paper to fabric and is particularly popular for printing 100 percent polyester (EL-Kashoutie et al., 2000). It has been reported that the most suitable disperse dyes for transfer printing are those with molecular weights varying between 240 and 340 mole/g. and it is important to work with those dyes which have similar sublimation temperature properties. The molecular weight cannot be taken as too rigid an indicator of the suitability of a dye, since a dye of high molecular weight with a less polar structure may sublime more rapidly than one with a lower molecular weight (El-Molla et al., 1998; Vellins, 1973). Thus, it is clear that for adequate sublimation, it is generally accepted that a dye should have a molecular weight below 350 mole/g. and should not contain an excessive number of non-ionic polar groups (NO2, CN, and SO2R, etc.). In particular, no ionized grouping should be present (Griffiths and Jones, 1977).