![COMBINED DESIZING SCOURING AND BLEACHING
Purposes
Removal of starch size
Removal of oils, fats, waxes, protein and pectic substances
Removal of natural and added coloring matter
MLR: 1:20
PH = 11
Temperature= 95oc & Time = 90 min
Temperature= 80oc & Time = 30 min [Steaming]
Chemicals used Concentration (%)
H2O2 (35 %) 5
Caustic soda 0.9
Sodium Silicate 2
Non ionic wetting agent 0.1
Sodium dipersulphate 0.3](https://image.slidesharecdn.com/combinedpretreatmentlecture6-210208121756/85/Combined-pretreatment-lecture-6-13-320.jpg)
Combined pretreatment lecture 6
- 1. 1 1 COMBINED PRETREATMENT PROCESS OF COTTON FABRIC LECTURE - 6 By Robel L. Faculty of Textile and Fashion Technology Aksum University 2020 3/10/2020
- 2. COMBINED PREPARATORY PROCESSES OF COTTON
- 3. CONVENTIONAL PRACTICE Advantages Ideal choice of chemicals and process conditions Reproducible and better results Efficient operation In the conventional preparation, desizing, scouring and bleaching processes are carried out separately.
- 4. 3/10/2020 4 Drawbacks Long time of treatment High energy consumption High cost Less productivity Cont.…
- 5. PRESENT PRACTICE In order to minimize energy and material consumption it has become necessary to combine several pretreatment stages by reducing the number of operations. The most common combined process are:- (DESIZING-SCOURING) + BLEACHING DESIZING + (SCOURING-BLEACHING) DESIZING-SCOURING-BLEACHING
- 6. 3/10/2020 6 Advantage Low energy consumption Less time High productivity Cost saving Disadvantage Restricted choice of chemicals Ideal conditions for each operation can not be maintained Compromise on process efficiency. Cont.…
- 7. PRINCIPLE Combination of chemicals suitable for each operation Use of high concentration High temperature Shorter duration of treatment particularly continuous processing
- 8. COMBINED SCOURING AND DESIZING Purposes Removal of starch size Removal of oils, fats, waxes, protein and pectic substances (caustic soda) Starch removal Enzymatic desizing is not suitable because of high pH and temperature required for scouring under which enzymes are not stable. Choice: oxidative desizing
- 9. 3/10/2020 9 Peroxy compounds or hydrogen peroxides under alkaline conditions are widely used. The most commonly used peroxy compound are Sodium persulphate Potassium persulphate Ammonium persulphate. A combination of peroxy compound and caustic soda at elevated temperature are effective for combined desizing and scouring operation. Cont.…
- 10. Typical recipe for batch process The fabric is treated with a solution containing MLR: 1:20 Temperature= 95 - 98oC Time= 2 - 3h Chemicals used Concentration Caustic soda 4% Potassium persulphate 0.5-2g/l Wetting agent 1-3g/l Emulsifying agent 1-3g/l
- 11. The fabric is padded with solution containing 30 g/l caustic soda, 3 g/l sodium persulphate and 2 g/l non-ionic detergent wet pick-up of about 80% The fabric is steamed for 15 min at 102 oC The fabric is then washed thoroughly in an open soapier with a temperature of about 98 oC in the first and second, 80oC in the third and 60 oC and 50 oC in the fourth and fifth compartments respectively. Typical recipe for continuous process
- 12. 3/10/2020 12 COMBINED SCOURING AND BLEACHING Purposes Removal of oils, fats, waxes, protein and pectic substances (caustic soda) Removal of natural and added coloring matter MLR: 1:20 PH = 11 Temperature= 70 -90oc& Time= 2h Chemicals used Concentration (%) Caustic soda 1-2 Hydrogen peroxide (50%) 1-3 Sodium silicate 2 Sodium phosphate 2
- 13. COMBINED DESIZING SCOURING AND BLEACHING Purposes Removal of starch size Removal of oils, fats, waxes, protein and pectic substances Removal of natural and added coloring matter MLR: 1:20 PH = 11 Temperature= 95oc & Time = 90 min Temperature= 80oc & Time = 30 min [Steaming] Chemicals used Concentration (%) H2O2 (35 %) 5 Caustic soda 0.9 Sodium Silicate 2 Non ionic wetting agent 0.1 Sodium dipersulphate 0.3
- 14. 3/10/2020 14 Hydrogen peroxide 30 g/l Sodium persulphate 3 g/l Sodium hydroxide 20 g/l Sodium silicate 8 g/l Stabilizer 8 g/l Wetting agent 2 g/l The desized fabric is impregnated with the above liquor composition Typical recipe for continuous process
- 15. The padded fabric can be treated in different equipment systems under varying conditions PAD-ROLL 1 Grey goods from the loom (cotton or polyester) ; 2 Singeing unit; 3 Impregnation bath at 20-40 oC 4 Padding mangle (80-100% pick-up) ; 6 Pad-roll chamber (60-120 min at 90-95 oC 5 Washing compartments (95, 95, 70, 50, 30 oC
- 16. 1 Grey goods from the loom (cotton or polyester) ; 2 Singeing unit 3 Impregnation bath at 20-40 oC 4 Padding mangle (80-100% pick-up) ; 7 J-Box (20-60 min at 95-100 oC ) 5 Washing compartments (95, 95, 70, 50, 30 oC ) Combined Desizing-Scouring-Bleaching processes J-BOX RANGE
- 17. PAD-STEAM METHOD 1 Grey goods from the loom (cotton or polyester) ; 2 Singeing unit 3 Impregnation bath at 20-40 oC 4 Padding mangle (80-100% pick-up) 8 Steamer (5-20 min at 100-107 oC ) 5 Washing compartments (95, 95, 70, 50, 30 oC )
- 18. 3/10/2020 18 END
- 19. 3/10/2020 19 Section B 1. Jigger machine 2. Low pressure kier 3. Batch or rebatching system 4. Winch machine 5. Open width roll steamer Section A 1. Jet machine 2. J-Box-rope washer 3. Open width roller steamer 4. Chain mercerizing machine 5. Pad – steam – roll system Content to be included 1.Introduction 2.Machine parameters 3.Working principles 4.Application (pretreatment process) Group Assignments (20%) Presentation date April 28, 2020 Soft copy of PowerPoint should be submitted one week before your presentation