Rope dyeing consists of twisting the yarns into a rope that is then quickly dipped into indigo baths. This dyeing is considered a superior dyeing technology where the dyeing uniformity achieved is better than other Indigo Dyeing technologies like Slasher Dyeing. However, Rope Dyeing is also a more difficult dying technology. A flow chart of rope dyeing is given below.
Flow Chart of Rope Dyeing
Importance of Rope dyeing
Rope dyeing consists of twisting the yarns into a rope that is then quickly dipped into indigo baths. It is considered the best method for dyeing denim as the short dyeing time does not allow the indigo to fully penetrate the fibers. Thus creating ring-dyed yarn that fades better and faster than fully dyed yarn.
The denim industry has been playing an important role in the textile sector with approximately 636,000 tons per annum production. Pakistan is the second-largest exporter of denim fabric with 40 major production units producing around 50 million square meters of finished denim fabrics per month. Traditionally denim fabric is produced by dyeing cotton yarn with naturally occurring indigo dye but nowadays due to the enormous consumption of denim fabrics and articles, a larger percentage of synthetic indigo dyes are also used for dyeing.
There are a number of techniques used for indigo dyeing. But rope dyeing is one of the most suitable indigo dyeing processes in terms of uniformity of dyeing yarns. Indigo is a water-insoluble vat dye and cannot mobilize itself towards cotton fiber until it is converted into a water-soluble form known as “leuco” through the process of reduction. Sodium dithionite aka sodium hydrosulfite or hydro is one of the most commonly used reducing agents in the indigo dyeing process.
Author of this Article: Rana Sohel Executive Engineer Sunman Textile Mills Ltd. Chittagong Cell: +8801912-420118 Email: [email protected]