Novel Nanopigment Derived from Vat dyes for Printing Cotton Fabrics

Abstract

WATER insoluble organic pigments presented by vat dyes were …… converted to the soluble leuco form through reduction using different reducing agents. The latter include Glucose, β-Cyclodextrin, sodium sulfoxylate formaldehyde (Rongalite C), and Redoxal Z reducing agent based on zinc sulfoxylate. The leuco form was then submitted to sudden oxidation using sodium perborate in presence of acetic acid under sonication. The obtained nano-sized pigment particles were used for printing cotton fabrics , and the color strength (K/S) of the prints were monitored. Results disclose that the K/S values for nanopigment prepared under Cyclodextrin reduction are nearly the same, if not higher than those obtained using sulfer-based reducing agents (Rongalate and Redoxal), while Glucose brings about the lowest K/S values. Four vat dyes have been used in the current work, and results of concern verify that the size of nanopigment obtained and the colour strength values (K/S) are manifestation of nature of the dye including molecular size and structure and molecular configuration. Regardless of the type of reducing agent used and/or the method of fixation, the highest K/S values are obtained with nanopigment dispersion prepared using 125g/L reducing agent at pH 7. Under these conditions, a homogeneous morphology with quite uniform particle size distribution in the range of 6-16 nm could be achieved vis-á-via 160-280nm for the blank Cibanon Golden Yellow RK vat dye.

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