Class Scouring

5/27/2018 Class Scouring

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Preparatory processes

All the processes of this stream are carried out inan aqueous state or aqueous medium. The

main processes of this section include :

singeing

Desizing

Scouring

Bleaching

Mercerizing


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Singeing:

The verb singe literally means to burnsuperficially. Technically, singeing refers to the

burning-off of. Loose fibers not firmly bound into

the yarn and/or fabric structure. Singeing is an

important part of pretreatment. This is theburning off of protruding fiber ends from the

surface of the fabric.


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Singeing:

Singeing is the process is removing the hairs offabrics or fibers. In singeing process, we use

three technique to applied it. Such as, gas

flame technique. At the end of this process, we

will find, that the fabrics is smoother than beforeand the fabrics wet ability is increase.


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Technique of singeing:


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Singeing Process is as follows:

To produce a smooth surface finish on fabrics made fromstaple fibers first the fabric surfaces are brushed lightly to

raise the unwanted fiber ends.

Then the fabric is singed with or passed over heated

copper plates or open gas flames. The fiber ends burn

off.

The fabric is moved very rapidly, and only the fiber ends

are destroyed.

As soon as the fabric leaves the singeing area, it enters a

water bath or Desizing bath. This stops any singeingafterglow or sparks that might damage the cloth.


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Figure of singeing M/C:


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All the processes of this stream are carried out inan aqueous state or aqueous medium. The

main processes of this section include :

singeing

Desizing

Scouring

Bleaching

Mercerizing


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Singeing:

The verb singe literally means to burnsuperficially. Technically, singeing refers to the

burning-off of. Loose fibers not firmly bound into

the yarn and/or fabric structure. Singeing is an

important part of pretreatment. This is theburning off of protruding fiber ends from the

surface of the fabric.


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Singeing

Singeing is the process is removing the hairs offabrics or fibers. In singeing process, we use

three technique to applied it. Such as, gas

flame technique. At the end of this process, we

will find, that the fabrics is smoother than beforeand the fabrics wet ability is increase.


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Technique of singeing:


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Singeing Process is as follows:

To produce a smooth surface finish on fabrics made fromstaple fibers first the fabric surfaces are brushed lightly to

raise the unwanted fiber ends.

Then the fabric is singed with or passed over heated

copper plates or open gas flames. The fiber ends burn

off.

The fabric is moved very rapidly, and only the fiber ends

are destroyed.

As soon as the fabric leaves the singeing area, it enters a

water bath or Desizing bath. This stops any singeingafterglow or sparks that might damage the cloth.


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Figure of singeing M/C:


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Scouring:

Scouring is the process by which all natural and

additive impurities such as oil, wax, fat, handdust etc. are removed to produce hydrophilic

and clean textile material. It is one of the vital

processes of wet processing.


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Objects of Scouring:

To make the fabric highly hydrophilic.

To remove impurities such as oils, waxes, gum,

husks as nearly as possible.

To increase absorbency of fabric or textilematerials without physical and chemical

damage.

To produce a clean material by adding alkali.

To make the fabric ready for next process. Toremove non-cellulosic substance in case of

cotton.


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Scouring process depends on:

The type of Yarn. The color of Yarn.

The cleanliness of Yarn.

The twist and count of the yarn.

The construction of the fabric. The shade % and type of shade of finished

product.


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Scouring Mechanism

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 glycerine. Glycerine is misciblewith 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 areimmiscible in water. Normal washing soap is used as a emulsifying agent

which makes emulsion of them.


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Mechanism

The changes occurring of cotton fibers during scouring:

Saponifiable oils and free fatty acids are converted into soaps.

Pectins and pectoses are converted into soluble salts of pectic acid.

Proteins are degraded to simple soluble amino acids or ammonia.

Mineral matters are mostly dissolved.

Non-saponifiable oils are emulsified by the soluble soaps generated from the

saponifiable oils.

Additive dirts are removed.

Residual sizing materials are broken down into soluble products.

Ch i l d i i


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Chemicals used in scouringprocess:

Main chemicals UseCaustic soda Neutralize acidic materials, saponify

glycerides (waxes and oil),solubilise

silicatesSurfactants Reduce surface tension & minimize

interfacial tension.Detergents Emulsify oil, fats, waxes and remove oil-

borne stains.Chelating agent Deactivate metal ions.Sodium silicate Penetrate & break drown lignin's.Soda ash Maintain pH.Solvent Assist emulsification by dissolving oily

materials.


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Form of Scouring:

Yarn scouring: Hank form

Package form

Continuous sheet warp form.

Fabric scouring:

Open width form :

Jigger

Pad batch

Progressive jig

Rope form

Kier

Washer.


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Scouring process:

Batch process. Semi continuous process.

Discontinuous process.

Modern process.


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Scouring methods of Cotton:Generally, there are two principle methods of

cotton scouring.

Discontinuous (Kier boiling process or winch

dyeing machine) Continuous (Scouring in J or L box)


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Kier Boiling

Kier boiler process/ Scouring of cotton fabric inBatch process/ discontinuous process:

In this process of cotton scouring, the fabric is

scoured in rope form, by alkali liquor.

Kier means specially constructed large cylindrical ironvessel. The kier boiler may be-

a. horizontal(yarn scouring)

b. vertical(fabric scouring).

Kier boiler capacity: maximum 5ton, but in industrially2-3 ton kier boiler is very popular.


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Kier Boiling

Standard Recipe:The amount of different chemicals used ina kier boiler may vary according to

Hardness of water.

Quality / Quantity of cotton.

Fabric construction/ texture, yarn twist etc.

But in generally, the following amounts of the chemical areused.

Caustic Soda (Strong) 2-5% owf

Soda ash (mild) 0.3-0.5%

Sequestering agent0.05-0.5%

Wetting agent 0.25-1.0%

M:L1:4 to1:5

Temp100C-120C

Time12hrs - 4hrs


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Kier Boiling

The fabric is loaded in the m/c and kept in rope form. The hot liquor is pumped and sprayed by circular

tube on to the fabric

The liquor passes slowly over the packed cloth and

collects at the false bottom of the kier. The liquor again pumped into the heater by a

centrifugal pump and this cycle is repeated

After scouring ,the fabric is washed with 800C water

to remove impurities on the fabric


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Kier Boiling


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Scouring- J Box

Process:The working process in J-box can be dividedinto four units. There are

Impragnaion box

Pre heater.

J box.

Washing unit.


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Continuous scouring

Process:The working process in J-box can be dividedinto four units. There are

Impragnaion box

Pre heater.

J box.

Washing unit.

Impragnaion box:The fabric is passed through the

guide roller and immersed into the solution at

temperature 70C 80C for about 40-90 sec

Pre heater:Material is passed into the thermostaticcontrolling system at temperature 90C 100C for 30

sec

J-box: In j-box, fabric is stored in this solution of NaOH

for about 1-4 hrs at a temperature of 102C.


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Continuous scouring

Continuous scouring process of cotton (Scouring in J- box)The

scouring vessel is looks like the English letter J hence, this process is

called j box process. In the process, desizing, scouring and bleaching

can be performed at a time.

Standard recipe

Alkali (NaOH) 4-5gm/L

Wetting agent +Detergent 4-5gm/L

M:L 1:3

Pick up 90-100%

Impregnation Temp 70-800C

Impregnation Time 45-90sec

Storing time in J-box 2-4hr

Temperature in J-box 102-105oC


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Continuous Process


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Assessment of scouring:/Absorbency test: 1. Drop /Spo t test:

In a pipette a solution of 0.1% direct red or Congo red

is taken and droplet of solution put on the different

places of the fabric. Then the absorption time of the

fabric is observed. The standard time for the absorption of one drop of

solution is 0.5-0.8 sec up to 1 sec.


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Souring

Souring: The treatment/the process by which the fabric, after

processing with alkali or scouring, is treated with Acetic

Acid, Hydrochloric acid or dilute H2SO4for removing

alkali or neutralization of alkali is souring


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Good scouring

Uniform scouring

Uneven scouring

Documents

Class Scouring