Pretreatment (Scouring & Bleaching) of Dyeing

1. Presentation on
PRETREATMENT (SCOURING & BLEACHING)

2. PRESENTED
By
Name: Shawan Roy
ID: 11122107023
Intake: 5th
Section: 01
B.Sc. In Textile Engineering, BUBT
To
Md. Mahabub Hasan
Lecturer,
Department of Textile Engineering,
BUBT

3. CHAPTER
• What is pretreatment?
• Types of Pretreatment Process.
• What is Scouring?
• Objective of Scouring.
• Recipe of Scouring.
• Future of Scouring.
• What is Bleaching?
• Objective of Bleaching.
• Recipe of Bleaching.
• Future of Bleaching.
• Conclusion

4. PRETREATMENT
• Pretreatment means treatment
the fabric, yarn or fiber before
dyeing.
• Pretreatment processes include
desizing, scouring, and bleaching
which make subsequent dyeing
and softening processes easy.

5. TYPES OF PRETREATMENT PROCESS
• There are various types of
pretreatment process.
• Singeing
• Desizing
• Scouring
• Bleaching
• Mercerizing etc.

6. SCOURING
• The term scouring applies to the
removal of impurities such as oil,
wax gum, soluble impurities and
solid dirt commonly found in
textile material.
• The process consists essentially of
treatment with alkali, a good
supply of water is essential.

7. OBJECTIVE OF SCOURING
• To remove natural as well as
added impurities of essentially
hydrophobic character as
completely as possible.
• To increase absorbency of textile
materials.
• To leave the fabric in a highly
hydrophilic condition without
undergoing physical or chemical
treatment or damage.

8. RECIPE OF SCOURING
• Sodium Hadroxyde = 4gm/l
• Soda ash = 2gm/l
• Wetting Agent = 1cc/l
• Sequestering Agent = 1cc/l
• Detergent = 1gm/l
• Time = 30min
• Temperature = 95°C
• pH = 10.5 - 11
• M:L = 1:10

9. FUTURE OF SCOURING
• EcoScour or Bio-scouring is
possible in future scouring
process.
• Features:
– No caustic soda
– Neutral pH scouring process
– Combined scouring and bio-finishing
• Benefits
– Up to 31% shorter process
– Softer fabrics
– Enhanced absorbency/dye uptake
– Reduced fabric weight loss

10. BLEACHING
• The process of destroying natural
color from fabric is called
bleaching
• This bleaching done by destroying
the chromophore linkage from
fabric.
• Oxidizing or reducing agent must
be needed to break the
chromophore linkage

11. OBJECTIVE OF BLEACHING
• To produce white fabric by destroying
coloring matter with minimum fiber
degradation.
• Further improvement of whiteness by
treatment with optical whiteness agents.
• Removal of colored impurities.
• Removal of the seed coats.
• Minimum tendering of fiber.
• Technically reliable & simple mode of
operation.
• Low chemical & energy consumption.
• Increasing the degree of whiteness.

12. RECIPE OF BLEACHING
• Hydrogen peroxide = 5gm/l
• Sodium Silicate = 2.5gm/l
• Wetting Agent = 1cc/l
• Sequestering Agent = 1cc/l
• Detergent = 1gm/l
• Time = 30min
• Temperature = 95°C
• pH = 10.5 - 11
• M:L = 1:10

13. FUTURE OF BLEACHING
• Enzymatic bleaching is the advance
type of bleaching which is used in
future.
• Features:
– No Hydrogen peroxide
– Neutral pH bleaching process
– Enzyme should be automatically destroy.
• Benefits
– Up to 25% shorter process
– Enhanced brightness or whiteness of
fabric
– Increase the reflection of whitness.

14. CONCLUSION
• Now a days scouring and bleaching must be done in same
machine with combined recipe.
• Souring and bleaching are must be needed for white fabric.
• For dark shade of dyeing we can reduce our cost by removing
any of this process.
• But in light shade those two process must be needed.
• In future, we can imagine that the all pretreatment section are
must be done in one machine.