Sunday, May 27, 2018

Yarn Dyeing in Textile | Hank Dyeing | Package Dyeing

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Textile Yarn Dyeing in Wet Processing:
Yarn dyed in hank form (i.e. endless bundle of specified length) or in the form of package, namely cones, chees or bobbins. The first patent was issued to Obermaier for package dyeing around 1882, whereas hank dyeing has a much longer history and probably dates back to antiquity when yarn was simply suspended on wooden poles and turned by hand. It is still preferred in the cottage sector as dyeing (wet processing) may be carried out manually in an earthen pot or cemented tank. Hank form is very convenient to handle and to transport.
Textile yarn dyeing process
Fig: Textile yarn dyeing process
May spinners are still equipped with hank-reeling machines as the last operation in the spinning process. It is often claimed that with certain products, a better quality is obtained by the hank route. The products, normally hank dyed, are cotton doubled-yarn, hand-knitting yarns in wool, nylon, acrylic and their blends, carpet yarns and acrylic yarn for machine knitting.

Features of Hank Dyeing in Textile Wet Processing:
The characteristic features of hank dyeing are pointed in the below:
  1. Hank dyed yarn has a fuller bulk and softer handle.
  2. Yarn entanglement may occur.
  3. Levelness may be inferior to package-dyed yarn.
  4. Hank reeling and back-winding is costly and may generate waste.
  5. Dyeing cost is less.

Advantages of Package Dyeing Over Hank Dyeing in Textile:
The advantages claimed for package dyeing over hank dyeing include in the following:

  1. Elimination of hank reeling.
  2. Waste is less.
  3. Less number of labor.
  4. More controlled dyeing with better levelness and fastness.
  5. Lower liquor ratio causing savings in water, effluent, energy, dyes and chemicals.
  6. Back winding is faster.
  7. Larger control on the process makes automation easier.
  8. Lesser floor space.
  9. High temperature dyeing and rapid dyeing possible.

Criticisms against package dyeing are increased cost of plant and the fear that less bulk yarn may result. The latter fear can be minimized by modification of the process or by changing the yarn specification. Currently, yarns of many fiber types for a large range of end uses can be package dyed namely:
  • Texturized yarns for both weaving and knitting.
  • Sewing thread.
  • Single cotton yarn.
  • Continuous filament yarn.
  • Wool or acrylic yarn for apparel and furnishing.

Features of Package Dyeing in Textile:
The key characteristic features of package dyeing are listed in the below:
  1. Learner yarn, but the yarn gives better fabric definition.
  2. Savings in space, energy, water, chemicals etc.
  3. Faster back-winding and lesser waste.
  4. Higher levelness and reproducibility.
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