The document discusses the scouring process used to clean fabrics prior to dyeing or finishing. Scouring removes natural and mechanical impurities through processes like saponification, solubilization, and emulsification. Saponification converts oils and fats to soap and glycerin. Solubilization and emulsification remove other impurities like pectins, proteins, waxes, and minerals by making them water soluble or dispersing them. Selection of scouring agents depends on fiber type, fabric properties, and impurity level. Effectiveness is tested through measures like absorbency, weight loss, and residual wax content.

2.  Grey fabric contains mainly three type of
impurities:
◦ Waxes, proteins, pectic substances and mineral
matters
◦ Mechanically held impurities e.g. motes, leaves
◦ Spin oils, waxes, grease
◦ Machine oils, tars, greases, dirt, dust

3.  Cellulose 85-96%
 Oil and Wax 0.5 -1%
 Proteins, Pectoses 3-5%
and colouring Matter
 Mineral Matter 0.5-1%
 Moisture 7-8%

4. • Natural fibers contain oils, fats, waxes,
minerals, leafy matter and motes as
impurities that interfere with dyeing and
finishing.
• Synthetic fibers contain producer spin
finishes, coning oils and/or knitting oils.
• Mill grease used to lubricate processing
equipment mill dirt, temporary fabric
markings and the like may contaminate
fabrics as they are being produced.

5.  Scouring is a purifying treatment of textiles.
 Also known as kiering, kier boiling or boiling
out.
 The objective of scouring is to reduce the
amount of impurities sufficiently to obtain
level and reproducible results in dyeing and
finishing operations.

7.  Selection of Scouring Agents depends on:
◦ Kind of fiber
 Wool and silk are dissolved by alkali
 Acetate and triacetate are converted to cellulose
 Cotton absorbs it
◦ Fabric type i.e. woven or knitted
◦ Fabric density i.e. thick or thin
◦ Texturised or non-texturised
◦ Extent of impurities present in the fiber

8.  Scouring mechanism involves the following
processes:
(for vegetable oils, animal fats,
mineral oils)
(for pectins, minerals, heavy metals,
amino acid, proteins)
(for mineral oils, waxes)
(for dirt, dust, china clay)

9.  Sponification
◦ The name given to the chemical reaction that
occurs when a vegetable oil, animal fat and mineral
oils (not soluble in water) are mixed with a strong
alkali. The products of the reaction are two: soap
and glycerin
◦ Fats, oils and waxes (glycerides of fatty acids)
◦ Soap formed enhances scouring
◦ Quantity of residual waxes in particular decide the
absorbency of fabric

10.  Oil + Caustic Soda Glycerine + Soap

11.  Solublisation
◦ NaOH swells the impurities & makes them water
soluble
 For Pectins, protiens and motes
◦ Minerals and heavy metals are converted to soluble
salts by use of acids
◦ Amino acids and protiens are removed by formation
of their sodium salts

12.  Emulsification
◦ An emulsion is a mixture of two or
more liquids that are normally immiscible
◦ Non-sponifiable mineral oils and waxes which are
esters of higher fatty alcohols and fatty acids
(natural and added) can be removed by emulsifying
them with a surfactant (emulsifying agent)
◦ Ordinary soap (washing soap) is a good emulsifying
agent

13. Emulsification
 An emulsion consists of a base liquid, with
the other liquid contained and spread within
the base liquid in tiny droplets.
 The base liquid is called the ‘continuous
phase’ and the contained liquid is called the
‘dispersed phase.’

14.  In order to keep the liquids uniformly distributed and
stable, an agent used is called emulsifying agent.
 These agents have both a hydrophilic and a lipophilic
part in their chemical structure.
 They concentrate at and are adsorbed onto the
oil:water interface to provide a protective barrier
around the dispersed droplets.
 They also reduce the interfacial tension of the system.
 Some agents enhance stability by imparting a charge
on the droplet surface.
 In scouring it is a soap formed already.

15.  The remaining constituent of size and other
dust and dirt particles, stains, are removed by
detergency.
 Detergency is closely bound up with surface
tension.

16.  When a piece of greige fabric is placed on the surface
of water in a beaker, the piece does not sink but floats
on its surface.
 This is because every molecule of water is attracted by
every other molecule of water.
 The molecules inside the water counterbalance the
forces from all sides and cancel out the overall effect
on them.
 While the surface molecules are only pulled sideways
and downward, due to which they form and interface
between liquid and solid.

17.  Generally, surface tension between textile fibres, and water
is high, and hence wetting of the fibre surface does not
take place thoroughly and quickly.
 A surfactant is a substance which, when applied in low
concentration, markedly reduces the surface tension of a
solution.
 A good surfactant, for example, will reduce the surface
tension of water from 72 dynes/cm to 30 dynes/ cm at a
concentration of less than 0.1%.
 The concentration at which no further reduction in surface
tension occurs is known as 'critical micelle concentration'.

18.  When a surfactant (soap) is dissolved
in water the hydrocarbon chain
(hydrophobic part tail, ==) tries to
get away from the water medium due
to its hydrophobicity and concentrate
at the surface.
 The hydrophilic grouping (carboxyl
head, O) just dip in the water at the
surface and the sodium cation is in
the vicinity of negatively charged
carboxyl head.
 Thus this compound, sodium
stearate (soap), distort the structure
of water and decrease the free
energy of the system.

19. ◦ The reason for reddish shade after bleaching with peroxide is
the high content of manganese.
◦ The contents of Fe, Mn, Ca and Mg varies depending upon the
origin of cotton
◦ Can be done by complexion and consequent solublization
using an acid or alkali
◦ Usually done by sequestering action.
◦ They form complexes with metal ions and keep them away
from fabric.
 Generally good pre-treated materials should have 100-
300 p.p.m, of Ca and Mg and 4-8 p.p.m, iron.

20. ◦ Advantages
 Better Levelness and more Brilliance in textile dyeing
 lower peroxide consumption in bleaching
 Increase in degree of Whiteness
 regular decomposition of peroxide and No catalytic
damage

21.  Absorbency: Drop Test
◦ Min 3 Sec and max 10 sec
 Weight loss is also checked
 Residual Wax Content
◦ Wax is dissolved in a solvent
◦ Solvent is distilled off
◦ The sample is reweighed

22.  Dyeing and Chemical Technology of Textile
Fibers, By: E.R. Trotman
 Chemical Technology in the pretreatment
processes of Textiles, By: S.R. Karmakar.

23.  Absorbency:
◦ Drop Test
 Less than 5 sec
◦ Other tests
 Wicking Height
 Sinking Test
 Weight loss is also checked
 Residual Wax Content
◦ Wax is dissolved in a solvent
◦ Solvent is distilled off
◦ The sample is reweighed
 Removal of Motes
◦ Observed visually and given a rating of 1-5