Cabinet dyeing machine is popular for reactive dyeing of cotton hanks. The main drawback of this technique is high material to liquor ratio (1:15).Due to high material liquor ratio, it requires high amount of salt to transfer the dye from liquor to the yarn. The current study aims at reduction of material to liquor ratio to as low as 1:1 and eliminate salt during dyeing of cotton hanks using ultra low liquor dyeing machine developed by NITRA. A comparison is also made between conventional and newly developed technique. Dyed hanks were also evaluated for colour fastness properties. The dyed samples were found to have high fixation percentage and excellent color fastness properties. The technology thus developed will not only conserve the resources, but also make the process eco friendly fulfilling the needs of small and medium scale dyeing units.
Cotton yarns are traditionally dyed either in the form of packages or hanks by batch process using exhaust method. The biggest drawback of hank dyeing is generation of total dissolved solids (TDS) due to addition of huge amount of salt at rate of 30-80gpl. For this reason the Australian dyeing company (ADC) adopted cleaner production method for yarn dyeing i.e. cold-pad-batch dyeing of reactive dyes (CPB)1. The process has been proven to be more ecologically sound, more cost efficient, and produces better quality product than conventional method. ADC installed the latest developed continuous yarn dyeing equipment for fine counts. This dyeing system works at 1: 0.3 to 0.45 MLR. 100% cotton yarns were dyed without addition of salt using cold pad batch method. Using the cold pad batch dyeing process for yarn and fabric, ADC was able to achieve 45% reduction in water consumption, 48% reduction in steam comparison, 33% saving in electricity and 100% reduction in salt consumption, totally removing salt from the effluent 2. On similar line in the present study a new technique based on semi-continuous principle is developed, which not only eliminates use of salt but also reduces material to liquor ratio from 1:15 (Cabinet dyeing) to 1:1. The present study was carried out in two parts, improvisation of commercial recipe making suitable for the semi-continuous process and consumption of ultra low liquor dyeing processes with that of conventional exhaust dyeing of cotton hank yarn.
The authors are associated with Northern India Textile Research Association, Ghaziabad and Ms. Mona Suri is from the Department of FAS, Lady Irwin College, Delhi University.