Common Problems in Dyeing and Their Remedies

Common Problems in Dyeing and Their Remedies

Dyeing is a process of coloring fibers, yarns, or fabrics with either natural or synthetic dyes. Many known-unknown faults occur during dyeing operation.

Dyeing Faults
Major dyeing faults which occur during are mentioned below:

1.    Uneven Dyeing

2.    Batch to Batch Shade variation

3.    Patchy dyeing effect

4.    Roll to roll variation or Meter to Meter variation

5.    Crease mark

6.    Dye spot

7.    Wrinkle mark

8.    Softener Mark

Uneven Dyeing:

Causes:

• Uneven pretreatment (uneven scouring & bleaching).
• Improper color dosing.
• Using dyes of high fixation property.
• Uneven heat-setting in case of synthetic fibers.
• Lack of control on dyeing m/c

Remedies:

• By ensuring even pretreatment.
• By ensuring even heat-setting in case of synthetic fibers.
• Proper dosing of dyes and chemicals.
• Proper controlling of dyeing m/c

Batch to Batch Shade Variation:

Causes:

• Fluctuation of Temperature.
• Improper dosing time of dyes & chemicals.
• Batch to batch weight variation of dyes and chemicals.
• Dyes lot variation.
• Improper reel speed, pump speed, liquor ratio.
• Improper pretreatment.

Remedies:

• 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.

Patchy Dyeing Effect:

Causes:

• Entanglement of fabric.
• Faulty injection of alkali.
• Improper addition of color.
• Due to hardness of water.
• Due to improper salt addition.
• Dye migration during intermediate dyeing.
• Uneven heat in the machine, etc.

Remedies:

• By ensuring proper pretreatment.
• Proper dosing of dyes and chemicals.
• Heat should be same throughout the dye liquor.
• Proper salt addition.

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 & pump 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.

Wrinkle Mark:

Causes:

• Poor opening of the fabric rope
• Shock cooling of synthetic material
• High temperature entanglement of the fabric

Remedies:

• Maintaining proper reel sped & pump speed.
• Lower rate rising and cooling the temperature
• Higher liquor ratio

         

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 & pump speed.
• Proper Mixing of the softener before addition.
• Prevent the entanglement of the fabric during application of softener

Advantages of the Reactive Dyes

Advantages of the Reactive Dyes :

·       Permanency of the colour :

Fibre Reactive Dyes can be easily said to be the most permanent of all dye types. This is because of an unique quality, unlike other dyes, it can actually form a covalent bond with the substrate (cellulose or protein molecule). After the formation of the bond, there is only one molecule, as the molecule of the is now part of the cellulose fiber molecule.

·       Easy washing :

The fibres that are dyed with reactive dyes can be safely dyed even with white garments without the danger of colouring it.

·       Chemical Binding :

The chemical bonds as explained above significantly improves the product’s colour stability and washability. Thus, no doubt reactive dyeing of cotton is presently the most popular textile dyeing process in the world. 

Factors considered for selection of dyes

Factors considered for selection of dyes :

 Dye selection depends upon the following factors :

1.    Selection of dyeing method :

§  Batch wise / Discontinuous / Exhaustion method

§  Semi-continuous method, i.e.

ü Pad batch method

ü Pad roll method

ü Pad jig method

§  Continuous method, i.e.

ü Pad steam method

ü Pad dry method

ü Pad thermofix method

2.    Brand selection :

§  Hot brand    : Less reactive dye (temp 72°c-93°c)

§  Medium brand       : Medium reactive dye (temp 60°c-71°c)

§  Cold brand   : Most reactive dye (temp 32°c-60°c)

3.    Economy of production.

4.    Availability of dyes.

5.    Storage facilities.

6.    Bond stability i.e. kind of bonding.

7.    Fastness of the dye i.e. wash, light, rubbing fastness.

·       Dye Terminology :

v Exhaustion

v Proportion of dye taken up by the fiber at any stage of the process relative to the amount originally available.

v Fixation

v Proportion of dye remaining on the fiber at the end of the process relative to the amount originally available

v Fastness

v Resistance to fading due to washing, light, etc.