Define Scouring Machine
The process to remove the fats, oil, and waxy substance and added other impurities by certain percent of alkali and which increases the absorbency power of the textile goods is called scouring machine . Scouring machine is used for removing the natural as well as added impurities as completely as possible. To provide a clean material by adding alkali, To leave the material to a highly absorptive condition without undergoing any physical & chemical damage and To make fabric suitable for next process etc.
The main changes soccurring during scouring:
- Saponifiable oils & fatty acid are converted in to soap & peptic acid.
- Pectin & pectoses are converted into soluble salt & peptic acid.
iii. Proteins are degraded into simple soluble amino acid.
- Mineral matters are dissolved
- Dirt is removed.
- Sizing materials are broken down into soluble product.
Chemical used in scouring
- Caustic (Na0H)
- Wetting agent.za
The process of bleaching machine by which the natural color of a fibre can be removed and make the textile materials pure white and bright is called bleaching. Objective of bleaching machine is to provide permanent whiteness, To increase absorbency of fabric, To prepare fabric ready for next process.
Example of some bleaching agent
- Oxidizing –agent reducing agent
- H202 –zinc dust
- Na0Cl –carbon (c)
- NaCl02 –hydrogen (H)
- Ca (0Cl) –2S02
- Bleaching powder –NaHS04
Bleaching with hydrogen peroxide (H2O2)
- H2O2 is a colorless clear liquid
- It should stored away from light
- In presence of heavy metal it decompose with the liberation of oxygen.
- The material is irritant for skin.
- M/C name: scouring machine and bleaching machine
- Origin: Germany.
- Capacity: 70-80 thousands meter/ day.
- Speed: 50-60 m/min
- Pressure(bar): Air- 50 bar
- Steam- 7 bar
- Washing temperature: W 1+2 =98’c, W 3= 70’c, W 4 -7= 98’c, W 8= 90’c
- Steamer temperature: Steamer
- Steamer 3 = 103’cSteamer timing: For White Fabrics- 26 mins, Yarn dyed- 24 mins, Vat dyed- 12-14 mins, Only for scouring- 18 mins
- Padded Pressure: 2.5 – 3 bar
- But in washing chamber, W-3 and W-8 = 2.5 and W-1, W-2, W-4, W-5, W-6, W-7 = 3
- Drying r/r temperature: 130 -140’c
- Cooling dryer temperature: 25-30C
- Fabric condition: whiteness – above 78% yellowness – 1 or below 1, But incase of OBA, whiteness – 100%, yellowness – (-22%), Standard- 15%
Flow chart of Scouring Process
Fabric inlet section
Washing chamber 1 2 3
Vacuum suction unit
Chemical mixing Unit
Washing Chamber 4 5 6 7
Scouring Machine and Bleaching Machine Scouring Process:
In continuous scouring & bleaching the following steps are followed.
Fabric inlet of Scouring Machine and Bleaching Machine: After rotation of batcher it is feed into the inlet of scouring & bleaching range. Where the fabric is passed over some free roller, parpet roller & platter. Here there is a compensator to control fabric open width entry.
Washing chamber of Scouring Machine and Bleaching Machine 🙁 1 2 3) Fabric comes in open width & entered in washing zone. Here there are three chambers for removing water soluble decomposed starch. Here temperature is maintained is around 1st & 2nd 98’C and 3rd chamber 70’c. Then fabric is passed in chemical chamber after squeezing where pressure is maintained approximately 2.5-3 bar.
In every washing chamber, there are two pressure bars-
- one for compressor roller
- other for padded roller
Vacuum suction unit of Scouring Machine and Bleaching Machine : With washing unit 1&2 a vacuum suction unit is connected. In this unit through air suction the inferior particles are collected & moved out through duct.
Chemical Chamber of Scouring Machine and Bleaching Machine: In chemical Chamber both scouring & bleaching is occurred. Recipe is setted according to its requirement. In chemical bath temperature remains as bath like room temperature. Here a Doctor blade is used to add chemicals in fabrics evenly. A typical recipe is given below:
Steamer of Scouring Machine and Bleaching Machine: After chemical padding the fabric is directly goes through the steamer. Here temperature is 104’C approximately. Here fabric stays for 12 to 26 minute. This depends on type of fabric & operational speed as well as quality required.
Chemical feeding of Scouring Machine and Bleaching Machine: beside chemical bath there is a chemical mixing tank. Chemical comes from individual storage according to setting and add with water finally agitated and pumped into chemical tank.
Washing chamber (4 5 6 7 8) of Scouring Machine and Bleaching Machine : After steaming in steamer fabric pass through the washing chamber once again. Here temperature is maintained is around 4 to 7 is 98’c and 8 no. chamber is 80’c After every washing bath there is a squeezer having pressure approximately 2 to 2.5 bar.
Neutralizing chamber: After washing there is a option of neutralizing. Here neutralizing is done by acetic acid. But those fabric which will be mercerized need not to neutralized. That will be done at mercerizing stage.
Cylinder dryer of Scouring Machine and Bleaching Machine: scoured & bleached fabric is finally passed through the drying unit. It passes through two stage cylinder dryer.
Cooling roller of Scouring Machine and Bleaching Machine: Dried fabric is passed over two cooling roller. It is cooled by cold water passing through roller by contact of which fabric become cool.
Batching: finally the fabric is rolled in batcher. Then it is feed as a raw material of mercerizing machine.
For all color-
- Sequestering agent: – 2g/L
- NaOH : 40g/L
iii. H2O2 : 45g/L
- Stabilizer : 8g/L (catalyst)
- Wetting agent: 8g/L
For pocketing fabric
- Sequestering agent: KEB- 2g/L
- NaOH : 20g/L
iii. H2O2 : 30g/L
- Stabilizer : GAL 8g/L (catalyst)
- Wetting agent: RGN-8g/L
- Dearting agent: ASN- 2g/L
- Timing of chemical chamber: 20-30 mins
- Timing of steamer: 30mins
- ph: Washing chamber 1-3=7.5-8
Washing chamber 4=11
Washing chamber 5=10
Washing chamber 6=9
Washing chamber 7=8
Washing chamber 8=7.5
Strength of chemicals: NaOH: 30-40 baume
Pick up%: L= 110.3
Caustic specific gravity: 1.2
Clibration: Calibration is done according to timing.
Amount of chemical/ min=Fabric G.L.M× Recipe%×Speed/1000
Effect of ph:
Ph<10 – active as bleach
Ph 10.2- 10.7 – is optimum for controlled bleaching.
Ph 11.b – bleaching is out of control.
Scouring & bleaching in same bath:
In Auto Textile bleaching and scouring are done in combine process which called solomity process.
In Auto Textile the Scouring & bleaching can be occurred in the same bath. It will reduce time as well as provide same quality. For that procedure as additional chemical stabilizer should be used.
Bleach Chemical Formula
It is the process used for identifying the amount of chemicals present in the solution. In solemnity process titration is done for caustic & hydrogen peroxide.
Titration process of NaOH:
- Key Accessories:- Burette, Pipette, Beaker etc
- Standard solution:- 0.1N HCl
- Reagent:- Phenolpthelene indicator (1%)
- 1ml mixer solution or chemical solution is taken from the mother tank in a chemical flask.
- 20ml water is added with the solution and stirred for a few seconds.
- 2-3 drods phenopthelene indicator is taken.
- To do titration 0.1 N HCl is used.
- The number of drops of 0.1 N HCl is used to calculate the amount of NaOH present in the mixing tank.
Amount of NaOH = Reading X 4
Titration process of H2O2:
1) Key Accessories:- Burette, Pipette, Beaker etc
2) Standard solution:- H2SO4
3) Reagent:- 0.1N K2MnO4
- 2ml mixer solution or chemical solution is taken.
- Adding 10ml H2SO4(25%)
- Taking 0.1 N K2MnO4in a burette
- The number of drops of 0.1N K2MnO4is use to calculate the readings until the solution turns in to light pink color.
H2O2 (% or gm/l) = 3.4 X reading
Baum Test (OBe):
A scale used for measurement of the relative density (RD) of liquids by hygrometry.
Bleach Chemical Formula
To make a specific strength of a chemical i.e. Caustic soda we can formulate as like —
OBe x 10
Strength (OBe) of NaOH = ————- x 100
But this formula is used for 100% pure NaOH. But in case of impurities (5-10%) tolerance is kept.So the conversion of strength measure of caustic soda solution–
|Strength (OBe)||Slid caustic soda content (g/l)|
PH find out test:
1) Drop method:-
- Chemical name: Universal indicator solution
- Color scale: Integrator scale.
- pH range of scale: 4-11
More Bleach Chemical Formula Procedure: a single drop of indicator solution is fall down in to the fabric and given 5 seconds for measuring. Then the color of round shape is matched with the color scale.
2) Core test:- Core test is done to find out pH.
- 8m fabric
- 200ml water
- pH meter
- At first 8gm fabric is cut in every small piece.
- Taking 200 ml water in a vessel & boiled for 10min
- After 10min 8gm fabrics are added to the boiled water & boiled for 10min.
- Then kept for conditioning at room temp. (4 hour)
- After 4 hrs pH meter is used for measuring the pH value.
Here saturated kCl solution is used to immerse the electrode & distilled water wash it & for calibration pH 4, pH 7, pH 10, are used. It is an one type Dyeing Machine
Prof. Dr. Morisas, Head of Wet Processing Dept, University of Textile And Apparel, UK