Electrochemical dyeing process from DyStar: first pilot plant for dyeing cheeses with Indigo

Citation

(2004), "Electrochemical dyeing process from DyStar: first pilot plant for dyeing cheeses with Indigo", Pigment & Resin Technology, Vol. 33 No. 3. https://doi.org/10.1108/prt.2004.12933cab.003

Electrochemical dyeing process from DyStar: first pilot plant for dyeing cheeses with Indigo

Electrochemical dyeing process from DyStar: first pilot plant for dyeing cheeses with Indigo

Keywords: Dyes, Electrochemistry, Textiles

In December 2003, the textile processing company Orta Anadolu of Kayseri, Turkey, signed a cooperation agreement on the installation of the first pilot plant for electrochemical dyeing of cheeses with Indigo dyes. This new technology, which is patented by DyStar, is the result of a research alliance between DyStar Textilfarben GmbH and Co. Deutschland KG, Germany, the Institute for Textile Chemistry and Textile Physics of Innsbruck University, Austria, and the machinery manufacturer Thies GmbH and Co. KG, Coesfeld, Germany. Orta Andolu will be installing the pilot plant in 2004.

Orta Anadolu currently dyes Indigo on conventional yarn dyeing ranges which produce the ring-dyed yarns required for classic denim articles. However, these units are not suitable for fine yarns or for full penetration dyeings. Electrochemical dyeing of cheeses will therefore give Orta Anadolu access to new article segments such as shirting fabrics and wash-fast jeans in various deniers.

Although there are conventional processes for dyeing Indigo on cheeses, they are rarely used because they tend to result in unlevelled dyeings and other quality problems. Moreover, only a small proportion of the Indigo is taken up by the fibre and the non-regenerable reducing agents pollute production effluent.

By contrast, electrochemical dyeing with DyStar's pre-reduced Indigo Vat 40 per cent solution ensures good levelness. Electrons from an electric current are used instead of hydrosulphite as the reducing agent. These are applied to the dye via a regenerable mediator and the dyebath can be reused.

This minimises both the amount of process chemicals required and the contamination of production effluent.

DyStar and Thies presented the new technology at the ITMA textile machinery exhibition in Birmingham, UK, and are anticipating high demand for this environment-friendly innovation.

Electrochemical dyeing

The electrochemical dyeing process has technical, ecological and economic benefits: shorter and more reliable dyeing processes, improved reproducibility, lower effluent costs and better quality. This process, which is patented by DyStar, was developed in collaboration with the Institute for Textile Chemistry and Textile Physics of Innsbruck University in Dornbirn, Austria and the textile machinery manufacturer Thies in Coesfeld, Germany. It is suitable for Indanthren vat dyes, Indigo and Cassulfon sulphur dyes. Unlike conventional dyeing processes, which use non-regenerable reducing agents, the new electrochemical process uses electric current to reduce the dyes with the aid of a regenerable Fe²⁺/Fe³⁺ redox system (mediator).

By measuring the redox potential of the dye liquor it is possible to control the dyeing process and minimise process chemicals.