Reductive Discharge Ink-Jet Printing of Pre-Dyed Textile Fabrics

Abstract

Bleached cotton fabrics have been dyed with Remazol (sulphatoethylsulphone (Dystar)), Procion MX (dichloro-s-triazine (Dystar)) and Procion HE (bis-monochloro-s-triazine (Dystar)) reactive dyes to yield suitable coloured backgrounds for subsequent reductive discharge inkjet printing. Silk fabric has also been dyed with an acid dye to provide an alternative substrate for subsequent discharge printing. Suitable white discharge inks have been formulated using either Decrolin (zinc sulphoxylate formaldehyde (BASF)) or Rongalit C (sodium sulphoxylate formaldehyde (BASF)), whilst coloured illuminating inks have been formulated using either vat or solubilised vat dyes. Inks containing both a discharging agent and an illuminating colour have also been developed. A process has been developed in which the free aromatic amine groups present in the discharged areas of white prints are diazotised and coupled to a suitable aromatic amine, phenol or naphthol derivative to provide an illuminated print. Introduction Discharge printing is a technique that is widely used in the textile industry and involves the local discharge of dye on a ground shade using a suitable chemical in a print paste [1]. Such discharge agents include oxidants, such as per-acids, or reductants, such as sodium or zinc sulphoxylate formaldehyde, the latter being more usually used. Coloured prints are also desired and so illuminated discharge pastes that contain a discharge agent and either an oxidation or reduction-resistant dye, such as a vat or sulphur dye, are extremely important. This study concerns the ink-jet printing of reductive discharge styles on coloured backgrounds dyed with azo dyes, using inks formulated with either Decrolin or Rongalit C: