Removal of Optical Brighteners

Removal of Optical Brighteners - the best method for batch process

A simple OBA stripping technique given below can be adopted in jiggers very efficiently and you can strip off almost 98% of OBA.

Recipe and method of process flow given below may be used as new hint..

a) Wetting the fabric:Soap - 1 gm/liter, Soda ash 1 gm/liter - treat the fabric at 70°C for 30 minutes.

b) Oxidative Bleaching:Potassium Permanganate (KMnO4) - 0.5% wof at cold for 30 minutes - to the same bath add Hydrochloric acid (35% conc.), 3 times the quantity of KMnO4 continue run for another 30 minutes. Then raise the temperature to 50°C and run for 30 minutes.

Drain the bath - cold wash - 30 minutes.

c) Reductive Bleaching:Run 10 minutes with Caustic soda 5 gms/liter and then add 5 gms/liter of Hydros (Sodium Hydro Sulphite) at room temperature and run for 10 minutes. Then slowly raise the temperature to 60°C. During this process the brown coloration you have got would be converted to light beige like shade. Now do one thorough cold wash.

d) Oxalic Acid Treatment:Treat with 2 gms/liter of Oxalic acid at room temperature for 30 minutes or 2 ends followed by a cold wash.

 e) Soda ash Neutralization:Treat with 2 gms/liter of soda ash at room temperature for 30 minutes and again do a cold wash.

 f) Acetic acid Neutralization:Treat the fabric with 1 gm/liter of acetic acid for 10 minutes at cold. Check the pH and let it be 6.

Now you will wonder to see thorough removal of OBA.

Application of Vat Dyes in Knitted Fabrics

Procedure of Vat Dyes

Stock Solution Preparation/Dyes Solution Method:

L: R= 1:10

Dyes = Required %

Caustic = 3.6 g/L          60°C x 15´

Hydrose= 2.5g/L         

Procedure:

Vat dyes- x% from stock solution

NaOH    -6g/L

Hydrose - 4 g/L                                                60°C x 60´

PCLF     - 0.5 g/L

 

Rinse

 

Hydrogen peroxide- 2 g/L at 40°C x 15´

 

Rinse

 

Soda ASH-2g/L

                                                            PCLF     - 2 g/L        95°C x 10´

 

Hot Wash   80°C x10´

 

Acid-1 g/L at room temperature* 10´

 

Fixer (3 g/L) + Softener

[Note: Cut sample at every stage]