Pre-treatment Process of Woven Fabric

Pre-treatment process:

Pre-treatment is the processes that are used to remove impurities from fibres or fabric to make it dyeable or printable. Natural fibres and synthetic fibres contain primary impurities that are contained naturally and secondary impurities that are added during spinning, knitting and weaving processes. Textile pre-treatment is a series of cleaning operations. All impurities, which causes adverse effect during dyeing and printing, are removed in the pre-treatment process.

The Pre-treatment process of woven fabric follows the following steps:

1. Singeing and Desizing
2. Scouring and Bleaching
3. Mercerizing
4. Washing

1. Singeing and Desizing:

Singeing is done to remove the protruding fibres from the fabrics and to make the fabric smoother.

Machine Parameter:

• Machine name: OSTHOFF
• Made: GERMANY
• No of gas burner: Two
• Process: Gas singeing
• Source of flame: L.P.G.
• Pressure of L.P.G.: 1.5 bar
• Flame height: 6” approximately
• Temperature of flame: 1100 ?C
• Speed of fabrics: 100 m/min
• Colour of flame: blue
• Flame intensity: depends upon the G.L.M. of fabrics

Table of GLM and Flame Intensity:

Filaments are not singed in order to avoid bead formation on the surface of the fibre.

Desizing:

Desizing is done to remove the size materials that applied on weaving to improve weave ability. Here enzyme is used as desizing agent.

Machine Parameter:

• Nip pressure: 0.8 bar
• Capacity of trough: 750 lit.

Chemical Recipe:

• Enzyme: 5 g/l
• Wetting agent: 4 g/l
• Complexer: 1 to 1.5 g/l
• Temperature: 85 ?C
• pH : 6 to 9.5
• Speed: 80 to 100 m/min
• Enzyme used: Palkozyme Plus.

Process Sequence:

Pre-brushing unit

↓

Singeing

↓

Dancer Roll

↓

Post brushing

↓

Padding with desize (85 ?C)

↓

Batch Formation

↓

Keep the batch in rotation for 8 to 12 hours

Cold Bleach:

Sometimes cold bleach is also done in the OSTHOFF machine. Cold bleach is the process of removing dirt, dust, husk, leaf and other impurities from the fabric and transfer the fabric into permanent white by chemical treatment in cold condition.

2. Scouring and Bleaching:

Scouring is the process of removing the impurities such as oil, fat, wax dust and dirt from the textile material to make it hydrophilic. Bleaching is the chemical treatment for removal of natural colouring matter from the fabric. The source of natural colour is organic compounds with conjugated double bonds, by doing chemical bleaching the discolouration takes place by breaking chromophore. The material appears whiter after the bleaching.

Machine Specification:

• M/C name: Scouring and Bleaching machine
• Origin: Germany.
• Capacity: 70-80 thousand meters/ 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

↓

Chemical chamber

↓

Steamer

↓

Washing Chamber 4 5 6 7

↓

Drying Unit

↓

Batching Unit

Recipe:

For all colour

1. Sequestering agent: – 2g/L
2. NaOH: 40g/L
3. H2O2: 45g/L
4. Stabilizer : 8g/L (catalyst)
5. Wetting agent: 8g/L

For pocketing fabric

1. Sequestering agent: KEB- 2g/L
2. NaOH: 20g/L
3. H2O2: 30g/L
4. Stabilizer: GAL 8g/L (catalyst)
5. Wetting agent: RGN-8g/L
6. Deaerating agent: ASN- 2g/L
7. Timing of chemical chamber: 20-30 mins
8. Timing of steamer: 30mins
9. 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

C=112.42

R=111.56

Caustic specific gravity: 1.2

Calibration: Calibration is done according to timing.

Amount of chemical/ min=Fabric G.L.M× Recipe%×Speed/1000

3. Mercerizing:

Mercerization is a chemical treatment applied to cotton fibres or fabrics to permanently impart a greater affinity for dyes and various chemical finishes. Mercerizing also gives cotton cloth increased tensile strength, greater absorptive properties, and, usually, a high degree of lustre, depending on the method used.

Mercerizing Machine

Mercerization is a process for increasing absorbency, strength, and lustier of the fabric by physio-chemical treatment. And this chemical treatment is occurred in two IMP-1 and IMP-2 bath by passing the fabric into an airing zone. John Mercer, a person was the first chemist in the world who found this phenomenon in 1844. Therefore the process of this type of wet processing was called Mercerizing.

Objectives of Mercerizing Machine

To make the goods more lustre because raw cotton fibres are ribbon-like. After this process, the fibres change to a cylindrical shape, resulting in more evenness reflected light from the goods.

 Reflectance Before Mercerization               and             Reflectance After Mercerization

To improve dye ability of the goods by about 5-10%.

Specification of Mercerizing Machine

• Machine name: Mercerize Machine
• Brand: Goller
• Origin: Germany
• Speed: 60 m/min
• Capacity: 1 lac m/day
• Expander roller: Remove dirtness and keep the fabrics in level Padder Upperb padder: made by rubber Check hardness: 80-90%, Lower padder: made by AUTO Check hardness: 100%
• Dancing roller: Tension keeps proper before going on the dryer.
• Caustic temperature: 35-55’C
• Vacuum pump(air): Remove water
• Padder pressure: 3bar-washing, IMP-1 & IMP-2—3.5bar
• IMP-1: Strong lime with 30’ Baume Solid caustic + 28’ Baume mercerize oil.
• IMP-2: Here shrinkage is controlled by using caustic and mercerizing oil. Airing zone: In airing zone = 11 air roller/8 air roller airing zone, fabrics are dried by air and chemical is added with fabrics.
• Gear+chain: Maintain width, control shrinkage in weft And caustic is utilized in every fibre equally.

Tanki: No. of tanks-5 These keeps water hot and creates a ?weak line (8baume)

• Washing chamber (1-3): Hot wash 90’c
• Washing chamber 4: Wash at room temperature
• Cylinder dryer temperature: 110=-130’c
• Cooling dryer temperature: 25-40’c
• Exact roller: Maintain fabrics that, selvedge does not remain straight.Using acid according to fabric GLM -1. 300+GLM thick- 100% acid, 2.     140-274 thickness- 50% acid + 50% water
• Types of mercerizer: (1) Cool mercerizer – 18’ Baume. But for cool mercerizer good chillers are needed. (2) Hot mercerizer- 28-30’ Baume
• Recipe: Sodium Hydroxide (NaOH) – (28±2)o Be (Baume′) 267 gm/l (see note) Steam, water â€“   As required, Green acid / Nurta acid (32%) – 3-4 % of total water, Wetting agent- 1-1.5 gm/l,
• Compressed air -: As required
• Mercerizing Oil (Mercirol QW2F) : 3-4 gm/l
• Tests: 1. Barium activity test, 2. PH, 3. Absorbency, 4. Size chemical Suitable For All cotton fabric, TC/CVC fabric, Twill Fabric

Flow chart of Mercerization

Fabric inlet

↓

J-Box

↓

Impregnation-1(IMP)

↓

Airing Zone

↓

Impregnation-2(IMP)

↓

Gripping Chain

↓

Stabilizing Compartment

↓

Washing Chamber 1 2 3

↓

Neutralizing chamber

↓

Drying unit

↓

J-Box

↓

Batching

4. Washing:

Washing is a process by which various types of impurities are removed through water treatment. Water treatment helps in removing dust and hydrolysis product of sizing materials. Washing plays a vital role in removing size chemicals, eliminating stains and increasing absorbency.

Machine used: Washing machine

Recipe:

Hot water

Detergent = 2-3 gram per kg of fabric

Acitic Acid = 2-3 g/l

Machine parameters:

Fabric speed = 40-50 m/min

Temperature for washing = (90-95)?c

Pressure for squeezer = 1-2 bar

Compensator pressure = 2.5-3 bar

Fabric position = Face/Back

Water level = Always full