Introduction


The synthesis of pyridone azo compounds has been extensively studied (Schaetzer and Ger. Offen, 1995). Many derivatives of this type were proven to be excellent dyes (Rether and Russ, 1995). In spite of the large number of reports on the use of these compounds in dye industry, according to our knowledge, only few of their corresponding pyridinethione had been reported. In continuation of our interest in synthesis of arylazopyridine-2(1H)-thiones (Elgemeie and Fatty, 1995; Elgemeie and Hussain, 1994; Elgemeie et al., 1990, 1992a, b, 1993, 1995, 1997, 2002). The present paper reports synthesis and printing properties of arylazo pyridine-2(1H)thione.


There are currently two major printing processes for fabrics: silk screen printing and heat transfer printing. Silk screen printing consists of lithographic printing and circular screen printing. Both require the use of a stencil to obtain the desired patterns. In order to fix the ink, the fabrics needs to go through the processes of the steaming, fixation, washing and rinsing. Such printing technique is well-developed. A conventional machine can print up to 60 m/min, but it produces a large amount of wastewater, as every 100m of fabric could use up to 5m3 of water. As far as water consumption is concerned, heat transfer printing, developed in the 1960s, offers an alternative and has found extensive applications in various industrial sectors. Dyestuff is used to colour patterns printed on heat transfer paper, which is then transferred onto the fabric surface to fix the patterns under certain temperature. Such method saves the finishing process and eliminates the problem of wastewater. The downside, however, is an increased consumption of paper, and the method can only apply on synthetic fabrics.


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The authors M.A. El-Kashouti, M.M. El Molla, H.S. Elsayad, K.A. Ahmed are associated with Textile Division, National Research Centre, Cairo, Egypt, and M.H. Helal and G.H. Elgemeie are from Chemistry Department, Faculty of Science, Helwan University, Cairo, Egypt