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:
- Poor opening of the fabric rope.
- Shock cooling of synthetic material.
- Incorrect process procedure.
- Higher fabric speed.
Remedies:
- Pre-Heat setting.
- Lower rate rising and cooling the temperature.
- Reducing the m/c load.
- Higher liquor ratio.
- Running at a slightly higher nozzle pressure.
Fabric Distortion and Increase in Width
Causes:
- Too high material speed.
- Low liquor ratio.
Remedies:
- By decreasing both nozzle pressure & winch speed.
- By using high liquor ratio.
Pilling
Causes:
- Too high mechanical stress on the surface of the fabric.
- Excess speed during processing.
- Excess foam formation in the dye bath.
Remedies:
- By using of a suitable chemical lubricant.
- By using antifoaming agent.
- 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:
- Uneven pretreatment (uneven scouring, bleaching & mercerizing).
- Uneven heat-setting in case of synthetic fibers.
- Quick addition of dyes and chemicals.
- Lack of control of dyeing machine.
Remedies:
- By ensuring even pretreatment.
- By ensuring even heat-setting in case of synthetic fibers.
- By slow addition of dyes and chemicals.
- 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-
- Use standard dyes and chemicals.
- Maintain the same liquor ratio.
- Follow the standard pretreatment procedure.
- Maintain the same dyeing cycle.
- Identical dyeing procedure should be followed for the same depth of the shade.
- Make sure that the operators add the right bulk chemicals at the same time and temperature in the process.
- 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:
- Uneven heat in the machine.
- Improper impregnation of dye liquor due to the low wetting property of the fabric.
- Dye migration during intermediate dyeing.
Remedies:
- By proper pretreatment.
- By adding extra wetting agent.
- Heat should be same throughout the dye liquor.
Specky Dyeing
Causes:
- Excessive foam in the dye bath.
- Fall of water droplets on fabric surface before or after dyeing.
- In sufficient after treatment.
Remedies:
- By using antifoaming agent.
- Sufficient after treatment.
- By using a good wetting agent in the dye bath.
Roll to Roll Variation or Meter to Meter Variation
Causes:
- Poor migration property of dyes.
- Improper dyes solubility.
- Hardness of water.
- Faulty m/c speed, etc
Remedies:
- Use standard dyes and chemicals.
- Proper m/c speed.
- Use of soft water.
Crease Mark
Causes:
- Poor opening of the fabric rope.
- Shock cooling of synthetic material.
- If pump pressure & reel speed is not equal
- Due to high speed m/c running.
Remedies:
- Maintaining proper reel sped & pumps speed.
- Lower rate rising and cooling the temperature.
- Reducing the m/c load.
- Higher liquor ratio.
Dye Spot
Causes:
- Improper Dissolving of dye particle in bath.
- Improper Dissolving of caustic soda particle in bath.
Remedies:
- By proper dissolving of dyes & chemicals.
- By passing the dissolved dyestuff through a fine stainless steel mesh strainer, so that the large un-dissolved particles are removed.
Softener Mark
Causes:
- Improper mixing of the Softener.
- Improper running time of the fabric during application of softener.
- Entanglement of the fabric during application of softener.
Remedies:
- Maintaining proper reel sped & pumps speed.
- Proper Mixing of the softener before addition.
- 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.
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