Scouring And Bleaching In Textiles

1. Scouring And Bleaching In
Textiles
Prepared by
Takbir Ahmed
Department of Textile Engineering
Daffodil International University

2. What is scouring and bleaching?
 Scouring: Scouring is a process of removing impurities
such as oil, wax, fats, dust and dirt from textile material
to make it hydrophilic.
 Bleaching: Bleaching is the destruction of natural
coloring(Gray) matters to produce a white material.

3. Importance of scouring in textiles.
 To remove impurities such as oil, wax,
dirt etc.
 To clean the textile material.
 To make the material more hydrophilic
 To increase the absorbency

4. Importance of bleaching in
textiles
1.To impart a permanent white
effect to the fiber.
2. To destroy natural the coloring
matter.

5. Types of Scouring and Bleaching
 Types of Scouring process.
1. Dis-continuous process.
2. Continuous process.
 Types of Bleaching Process.
1.Hydrochlorite Bleaching.
2.Peroxide Bleaching.
3. Sodium Chlorite Bleaching.

6. Mechanism Of Scouring
 Saponification: The vegetable oil, which is immiscible
with water, is glyceride of fatty acids. When such oils are
heated with a solution of sodium hydroxide in water, the
oil splits up into its constituents-fatty acid and glycerin.
Glycerin is miscible with water easily and the fatty acids
reacts with sodium hydroxide present in the solution
forming its sodium salt i.e. soap which is also soluble in
water. Thus oil is removed
 Emulsification: Wax and non saponifiable oils are
removed by emulsification as they are immiscible in
water. Normal washing soap is used as a emulsifying
agent which makes emulsion of them.

7. Mechanism Of Bleaching (Hypochlorite
Bleaching )
 Used Sodium or Calcium Hypochlorite. Produces Metallic Hydroxide and
Hypochlorous acid.
 Ca(OCl)2 + H2O Ca(OH)2 + 2HOCl
NaOCl + H2O NaOH + 2HOCl
 Hypochlorous acid produces Hydrogen ion(H+ )and Hypochlorous ion(OCl- )
HOCl H+ + OCl-
 Hypochlorous ion is responsible for bleaching process.
OCl- + Colored Material White Material.

8. Mechanism Of Bleaching
 Mechanism of peroxide bleaching
 Hydrogen Peroxide Used as Bleaching agent.
 H2O2 produces Hydrogen and perhydroxyl ion.
H2O2 H+ + OH2
-
 This process carried out in alkaline condition PH =11.5.
 perhydroxyl ion is responsible for bleaching action.
OH2
- + Colored Material White material.

9. Machine Used in Scouring And Bleaching
Process.
 Same used both machine is in scouring and
bleaching.
 For continuous process J- Box Machine.
 For discontinuous/batch process kier boiler
machine.

10. J –box Process
 Machine Description:
 Impregnation bath: Padded with caustic soda/Peroxide and wetting agent at
70-80⁰ C for 30-40 sec.
 Pre Heater : Thermostatically control system for 30 sec at temp 90-100⁰ C .
 J-box : Fabric is stored for 1-2 hours at 98-102⁰ C.NaOH/H2O2 solution reacts with
impurities and dissolves them.
 Washing Unit: Fabric firstly hot wash and then cold wash.

11. J –box Process for scouring and bleaching

12. Kier Boiler Process
 Filled with solution about ½ or 1/3 of the kier.
 Filled fabric about 80-85%.
 Steam is passed through the whole kier.
 Remove the pocket air otherwise it will damage the cellulose structure.
 After 1-2 hours kier is closed for 6 hours then scouring or bleaching will be
completed.

13. Kier Boiler Process

14. THANKS TO ALL