Category Archives: Knit Dyeing

Process Flow Chart Of Knit Fabric Dyeing With Reactive Dyes

Knit dyeing is near similar as yarn dyeing process but there is some difference in quality measurement. Generally all types of single jersey, double jersey and their derivatives are dyed by the following way.

Here, I have given a discontinuous dyeing process by hot brand reactive dyes. It is more practical process which is done in the dyeing industry. But the dyeing sequence and chemical brand can be different depending on the choice of the manufacturer. Also, some steps of dyeing can be removed or some steps can be added for better dyeing efficiency. Different dyeing parameter is also important to get better dyeing efficiency.

Fabric received from the batching section

Required amount of water was taken into the machine

The fabric was loaded and run for 5-10 minutes in normal temperature

CK-2, D-600/C, SQ-12UD and PH-100(Scouring Chemicals) were added at a time for 5 minutes

Caustic was added at normal temperature for 5 minutes

Temperature increased at 600 C

Hydrogen per Oxide (H2O2) was added for 5 minutes

Temperature increased at 950C and continues for 1 hrs

Sample check

Cold wash at 400C for 5-10 minutes

Hot wash at 950C for 5-10 minutes

Required amount of water was loaded

Croak-N was added

Acetic acid was added

Temperature increased at 800C for 15-20 minutes

Cold wash at 400C and drain

Water filled and Acetic acid was added

PH check at 4.5

Temperature increased at 550C

Enzyme (Bio-EC) was added and   run for 1hrs at 550C

Shade check

Cold wash at 400C and drain

Water filled/Required amount of water was taken

Temperature increased at 95-990C for 5-10 minutes

Cold wash at 400C and drain

Acetic acid was added

PH check at 4.5

EDX/200B and C/D-600 were added at a time

Salt dosing

Color dosing for 30 min

Run for 10 min

Soda dosing for 40 min

Run for 7 min

Temperature increase at 600C for 5 min

Run for 10 min

Shade check (OK)

Rinsing

Water was filled at required amount

PS-60 was added

Temperature increase at 800 C for 10 min

Hot wash at 900 C for 20 min and shade check in this time (OK)

Rinsing

Water was filled at required amount

Acetic acid was added for neutralization for 10 min

Shade check (ok)

ECO/FRD was added for 10 min

Rinsing

Water was filled at required amount

PH check at 6.5

(C.W.S) softener was added

Final shade checks and run for 20 min

Unload the dyed fabric

Various types of dyeing faults can be occurring due to wrong process. For this reason, quality control department should be aware about the quality of the fabrics.

Hydro Extractor Machine For Dyed Knit Fabric | Functions Of Hydro Extractor

Hydro extractor machine is the first sequence of finishing unit of dyeing and finishing floor. After completion of dyeing process, dyed fabrics are hold for sometimes before hydro extraction. Hydro extractor machine is important one before de-watering process.

Functions of Hydro-extractor: Hydro extractor machine is used for removing excess water from fabric by centrifugal extraction. About 65% water is removed by this process. The extraction time is about 5-10 minutes. After extraction process, we can find out the efficiency of the hydro extractor. I have written about the hydro extraction process of yarn dyeing and calculating system of efficiency of the hydro extractor in one of my blog post.

Working Procedure Of Hydro Extractor Machine: Hydro extractor machine is like a round basket and it is made of steel. There are a lot of holes on the down side of this basket. After putting the wet fabric in the hydro extractor, it moves and water is removed by the centrifugal extraction. Extract water is drained out through the holes.

Various types of hydro extractor are available in the market. Here, I have present a profile of a hydro extractor. The brand name of the hydro extractor is Dilmenler, which is made of Turkey.

So, choose your hydro extractor machine, which is suitable for removing excess water from the wet knit fabric.

Knit Dyeing | Common Knit Dyeing Faults And Their Way Of Remedies

Knit fabric dyeing process is different from yarn dyeing or woven fabric dyeing process. During knit dyeing; some dyeing faults can be occurred due to wrong operating system. But it can be overcome by applying some techniques.

Knit Dyeing Faults and Their Way of Remedies: Common knit fabric dyeing faults and their way of remedies are given below.

Crack, Rope & Crease Marks

Causes:

  1. Poor opening of the fabric rope.
  2. Shock cooling of synthetic material.
  3. Incorrect process procedure.
  4. Higher fabric speed.

Remedies:

  1. Pre-Heat setting.
  2. Lower rate rising and cooling the temperature.
  3. Reducing the m/c load.
  4. Higher liquor ratio.
  5. Running at a slightly higher nozzle pressure.

Fabric Distortion and Increase in Width

Causes:

  1. Too high material speed.
  2. Low liquor ratio.

Remedies:

  1. By decreasing both nozzle pressure & winch speed.
  2. By using high liquor ratio.

Pilling

Causes:

  1. Too high mechanical stress on the surface of the fabric.
  2. Excess speed during processing.
  3. Excess foam formation in the dye bath.

Remedies:

  1. By using of a suitable chemical lubricant.
  2. By using antifoaming agent.
  3. By turn reversing the Fabric before dyeing.

Running Problem

A. Ballooning:

Causes: Seam joining with too densely sewn.

Remedies: By cutting a vertical slit of 10-15 cm in length for escaping the air.

B. Intensive Foaming

Causes: Pumping a mixture of air and water.

Remedies: By using antifoaming agent.

Uneven Dyeing

Causes:

  1. Uneven pretreatment (uneven scouring, bleaching & mercerizing).
  2. Uneven heat-setting in case of synthetic fibers.
  3. Quick addition of dyes and chemicals.
  4. Lack of control of dyeing machine.

Remedies:

  1. By ensuring even pretreatment.
  2. By ensuring even heat-setting in case of synthetic fibers.
  3. By slow addition of dyes and chemicals.
  4. Proper controlling of dyeing machine.

Shade variation (Batch to batch)

Batch to batch shade variation is common in exhaust dyeing which is not completely avoidable. Even though, to ensure a consistent batch to batch production of shade the following matters should be controlled carefully-

  1. Use standard dyes and chemicals.
  2. Maintain the same liquor ratio.
  3. Follow the standard pretreatment procedure.
  4. Maintain the same dyeing cycle.
  5. Identical dyeing procedure should be followed for the same depth of the shade.
  6. Make sure that the operators add the right bulk chemicals at the same time and temperature in the process.
  7. The Ph, hardness and sodium carbonate content of supply water should check daily.

Dye Spot

Causes: Improper mixing of dyestuff in the solution, in right amount of water, at the temperature.

Remedies: We should pass the dissolved dyestuff through a fine stainless steel mesh strainer when adding it to the chemical tank, so that the large un-dissolved particles are removed.

Patchy Dyeing

Causes:

  1. Uneven heat in the machine.
  2. Improper impregnation of dye liquor due to the low wetting property of the fabric.
  3. Dye migration during intermediate dyeing.

Remedies:

  1. By proper pretreatment.
  2. By adding extra wetting agent.
  3. Heat should be same throughout the dye liquor.

Specky Dyeing

Causes:

  1. Excessive foam in the dye bath.
  2. Fall of water droplets on fabric surface before or after dyeing.
  3. In sufficient after treatment.

Remedies:

  1. By using antifoaming agent.
  2. Sufficient after treatment.
  3. By using a good wetting agent in the dye bath.

Roll to Roll Variation or Meter to Meter Variation

Causes:

  1. Poor migration property of dyes.
  2. Improper dyes solubility.
  3. Hardness of water.
  4. Faulty m/c speed, etc

Remedies:

  1. Use standard dyes and chemicals.
  2. Proper m/c speed.
  3. Use of soft water.

Crease Mark

Causes:

  1. Poor opening of the fabric rope.
  2. Shock cooling of synthetic material.
  3. If pump pressure & reel speed is not equal
  4. Due to high speed m/c running.

Remedies:

  1. Maintaining proper reel sped & pumps speed.
  2. Lower rate rising and cooling the temperature.
  3. Reducing the m/c load.
  4. Higher liquor ratio.

Dye Spot

Causes:

  1. Improper Dissolving of dye particle in bath.
  2. Improper Dissolving of caustic soda particle in bath.

 Remedies:

  1. By proper dissolving of dyes & chemicals.
  2. By passing the dissolved dyestuff through a fine stainless steel mesh strainer, so that the large un-dissolved particles are removed.

Softener Mark

Causes:

  1. Improper mixing of the Softener.
  2. Improper running time of the fabric during application of softener.
  3. Entanglement of the fabric during application of softener.

Remedies:

  1. Maintaining proper reel sped & pumps speed.
  2. Proper Mixing of the softener before addition.
  3. Prevent the entanglement of the fabric during application of softener.

So, we should be careful about the knit dyeing faults as well as yarn dyeing faults.