Chemicals Used Textile Wet Processing (Desizing To Finishing) & Their importance.

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Personal Details of Student
Family Name Md. Shahiduzzaman Given Name (s) Shuvo
ID 111-23-2350 Email Shahid23-2350 @diu.edu.bd
Assignment Details
Assignment Title
Importance of Different Chemicals Used In Textile Wet
Processing
Course Code TE-403
Course Title Textile Wet Processing-III with Lab
Submitted To Asst.Professor Sumon Mazumder
Submission Date 16.04.2014
Declaration:
1. This work is substantially my own.
2. The assessment has not been submitted previously for assessment in this or any other unit, or
another institution
3. I have retained a duplicate copy of the assignment.
Md. Shahiduzzaman Shuvo
Daffodil International University
Faculty of Science & Information Technology
Textile Engineering Department

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Introduction:
We know that dyes, chemicals (or auxiliaries) are the main factor for
producing color in yarn, fabric or garments. Different chemicals are
used during textile wet processing. In different stages (Pretreatment,
dyeing, printing, finishing) of dyeing processing, various chemicals are
used. Every chemical have their own characteristics. [1]
http://textilefashionstudy.com/functions-of-chemical-auxiliaries-
used-in-wet-processing-list-of-chemical-auxiliaries/-6.10 Pm- 15, April,
2014
Processing of textile materials involves the use of diverse types of
compounds to perform various functions. These compounds are
variously known as textile auxiliaries, textile chemicals, textile process
chemicals etc. [2] Chemistry of organic textile chemicals by Dr.V.A
Shenai

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Pre-Treatment Stage
Chemicals used in Desizing process & their function:
Desizing is the first wet processing in textile finishing technology
employed to removing the sizing materials from the warp yarn as well
as woven fabric. In desizing impregnation of the fabric with desizing
agent allowing to degrade & solubilize the size material & finally to
wash out the degraded product.
Chemicals used in Desizing process & their function:
(1) Enzyme: We know that Enzymatic Desizing is the classical
desizing process of degrading starch size on cotton fabrics
using enzymes. Amylases are the enzymes that hydrolyze &
reduce the molecular weight amylase & amylopectin molecules
in starch, rendering it water soluble enough to be washed off
the fabric. It also replaces harsh chemicals & biodegradable.
Enzyme types: pancreatic, Malt extract, bacterial, bactasol
(amylase).
(2) Wetting agent: Reduce surface tension.
(3) Glauber salt (𝑁𝑎2 𝑆𝑂4.10𝐻2 𝑂): Neutralizes the electronegativity
of fiber.
Others:

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Mg𝐶𝑙2(𝑈𝑠𝑒𝑑 𝑖𝑛 𝐸𝑛𝑧𝑦𝑚𝑎𝑡𝑖𝑐 𝐷𝑒𝑠𝑖𝑧𝑖𝑛𝑔), Ammonium or Pottassium or Sodium
persulphate (used in Oxidative Desizing process), dilute 𝐻2 𝑆𝑂4 or HCl
(used in Acid Steeping).
[3] Sheet (Desizing-Wet Processing-1) Prepared By Sumon Mazumder,
Asst. Professor, DIU.
𝐻2 𝑂2 (Used as oxidants during oxidative desizing), NaOH (used in Lye
Desizing process & dissolves starch).
Some desizing agents are: Ecolase LT, Finocon-FBOL.
[4] Pdf books about desizing-Abdul Azeem
KI (potassium Iodide) is used for the estimation of the absence of size
materials in the woven fabric.
[5] Sheet (Desizing-Wet Processing-1) Prepared By Sumon Mazumder,
Asst. Professor, DIU.

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Chemicals used in scouring process & their function:
I want to say something about scouring before discussing the topics.
Scouring is the process of removing the impurities such as oil, wax,
fats, dust & dirt from the textile material to make it hydrophilic.
After the Scouring process it becomes possible to get clean material.
To facilitate the objectives some major chemicals plays an important
role in scouring process:
Chemicals Functions
Detergents Emulsify oils, fat & waxes remove oil borne-stains,
suspend materials after the have been removed.
Caustic
(NaOH/Alkali)
Neutralize acidic matters, saponified glycerides
(waxes & oils) & solubilize silicates. Also acts as a
swelling agent.
Sodium silicates
(Na2 𝑆𝑖𝑂3)
Penetrate & break down lignin into motes
Surfactants/Wetting
agent/Surface active
agents
Reduce surface tension & minimize internal
tension
Sequestering agents/
Chelating agents
Deactivate metal ions, reduce water hardness
Builders Cause detergent to become increasingly effect
Solvents Remove un-saponifiable oil, wax etc.
Soda ash (𝑁𝑎2 𝐶𝑂3) To maintain pH (8.0-8.5) during scouring process
[6] Sheet (Scouring-Wet Processing-1) Prepared By Sumon Mazumder,
Asst. Professor, DIU
Other chemicals used:

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1. Also for absorbency test in scouring direct red or Congo red
solution is used (Drop test/Wicking test).
2. After Scouring mtl/fabric is treated with 𝐶𝐻3 𝐶𝑂𝑂𝐻 (𝐴𝑐𝑒𝑡𝑖𝑐 𝑎𝑐𝑖𝑑),
HCl (Hydrochloric acid) or dilute 𝐻2 𝑆𝑂4 (Sulphuric acid) for
removing alkali or neutralization of alkali. [7]
http://www.slideshare.net/-6.22 -15 April
3. Mild oxidizing agents: Used in Kier Boiler machine in order to
prevent the reduction of dye. [8] Chemistry of Organic textile
chemicals-Dr. V.A. Shenai-Page-22
Chemicals used in Bleaching process & their function:
Bleaching is the destruction of natural coloring matters
to produce a white material & must be accomplished with a
minimum damage to the cotton being bleached. Bleaching is
not cleaning process in the sense of scouring as this process
does not remove dusts, dirt’s.
In bleaching process some chemicals or bleaching agents are used:
1. Bleaching agents:
A bleaching agent is a substance that can whiten or decolorize
other substances. The purpose of bleaching agents is to bleach
the natural substances in cotton fibers & cellulosic fibers that
make the fabric yellowish.
Bleaching agents essentially destroy chromophores (thereby
removing the color), via the oxidation or reduction of these
absorbing groups. Bleaching agents also bleach textile colors.
[9] http://dyeingworld1.blogspot.com/2009/12/textile-
bleaching-agents.html-6.23 Pm-14 April

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Suitable bleaching agents:
A. Oxidizing bleaching agent:
Oxidizing bleaching agent are mostly used for permanent bleaching of
natural cellulosic fibers. [10] Textile chemistry-1-Md.Mujibur Rahman
(Page-149)
I. Calcium hypochlorite, Ca(𝑂𝐶𝑙)2
II. Sodium hypochlorite, NaOCl
III. Potassium dichromate, 𝐾2 𝐶𝑟2 𝑂7
IV. Sodium chlorite, NaCl𝑂2
V. Bleaching powder, Ca(OCl)Cl
VI. Potassium permanganate, KMn𝑂4
VII. Ozone, 𝑂3
VIII. Hydrogen peroxide, 𝐻2 𝑂2 – Universal bleaching agent. In
peroxide bleaching, Hydrogen Peroxide is used as
bleaching agent. It is also used in Anti-chlore treatment.
[11] Sheet (Bleaching-Wet Processing-1) Prepared By
Sumon Mazumder, Asst. Professor, DIU.
Any types of fiber can be bleached with Hydrogen
Peroxide. Extensively used for bleaching cotton fiber.
[12] Textile Chemistry-1-Md.Mujibur Rahman (Page-149)
B. Reducing bleaching agent:
I. Zinc Dust, ZnO
II. Stannous chloride, Sn𝐶𝑙2
III. Ferrus sulphate, FeS𝑂4
IV. Sulphur dioxide, S𝑂2

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V. Sodium hydrosulphite, NaHS𝑂3
Hydrozen suphide, 𝐻2 𝑆 [13] Sheet (Bleaching-Wet Processing-1)
Prepared by Sumon Mazumder, Asst. Professor, DIU.
2. Peroxide stabilizer: To control the decomposition of
H2O2.Keeps active 𝐻2 𝑂2. Provide buffering action to control the
pH and to complex with trace metals which catalyze the
degradation of the fibers. Example: Sodium silicate (Most
commonly used and most effective H2O2 bleach stabilizers),
Tri sodium phosphate, Tetra sodium phosphate, Zelatene.
[14]Textile Chemistry-1-Md.Mujibur Rahman (Page-149)
3. Caustic (NaOH): Cleaning agent (EDTA-Ethylene Di-Amine Tetra
Acetic Acid is also used as powerful chelating agents
in𝐻2 𝑂2 𝑏𝑙𝑒𝑎𝑐ℎ𝑖𝑛𝑔 𝑝𝑟𝑜𝑐𝑒𝑠𝑠).
4. Soda ash (𝑁𝑎2 𝐶𝑂3): To maintain proper pH.
5. Sequestering agents/ Chelating agents: Reduce water hardness
6. Wetting agents: Reduce surface tension. To provide wetting and
detergency
7. Anticreasing agent: Preventing crease marks
Others:
Peroxide killers/Peroxide killer enzymes: Removes residual hydrogen
peroxide from fabric & prevents poor batch-to-batch shade
reproducibility as well as uneven dyeing. Also reduce processing time &
water consumption. [15]
http://www.indiamart.com/tridentcolors/peroxide-killer.html-6.24-Pm-
14 April-2014

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Latest Special Chemicals Used In Pre-treatment Range:
I. Cracking agent: Cracking agent generally used for pretreatment
for textiles which is specially recommended for washing or
desizing of synthetic fibers. It is also used for softening process
water in the textile industry, removing encrustations from tanks
& equipment’s, preventing soil redisposition in heavily
contaminated wash liquors.
Now a days Cracking agent is used in the case of Cellulosic fibers &
their blends. In Pad Batch Cold Peroxide Bleach, Pad Batch Cold
Oxidative Cracking, Viscose-Combo-Batch process.
Cracking agent is a multifunctional agent which optimizes the
pretreatment washing processes after alkaline pretreatment
processes such as mercerizing, alkaline cracking & peroxide
bleaching.
Benefits of using cracking agent:
1) Enhances the effect of simultaneously applied detergents &
dispersants.
2) Prevents precipitation particularly in the sub stoichiometric range
& agglomeration. Also retards precipitation of metal hydroxides,
carbonates & silicates on goods & machinery in pretreatment &
washing baths.
3) Generates no foam, is highly stable to alkali, oxidation &
hydrolysis.
4) Removes oily & greasy impurities as well as size & soil particles as
well as size & soil particles, even in grossly contaminated wash
baths.

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5) Enables quick & uniform wetting in dry-on-wet processes
(particularly in case of grey fabrics).
6) Advantageous in storekeeping. Simplifying of recipe & handling.
Prevents deposits on goods & machinery parts. Keeps soil in
suspension in bleaching liquors.
7) Some cracking agent used for their reducing effect
characteristics. Removes residual peroxide from the goods &
prevents partial destruction of direct & reactive dyes. Some
cracking agent carries Multifunctional Product properties for
which reduces the risk of error.
8) Can be added at the end of the washing range without danger of
corrosion in machines such as Stenters.
9) Ideal for automatic pH controlled dosing.
II. Bleach processor: Bleach processor is applied in silicate-free Cold
Pad Batch & Pas Steam Peroxide bleaching processes on cellulosic
fibers & their blends. Bleach processor particularly suitable for
the Pas Steam Mega Bleach process which ensures longer
steaming times (up to 30 minutes) without making necessary the
use of silicates. At the same time the fiber is protected against
chemical attack.
Benefits of using Bleach Processor:
1) Controls the decomposition of 𝐻2 𝑂2 to produce bleaching active
oxygen & to suppress the harmful catalytic reactions. Best use is
made of the bleaching agent which results in high degree of
whiteness (high protection of the fiber).
2) Prevents deposits on goods & machine parts. Promotes soil
suspension in bleaching systems & improves the rinsing process
after bleaching.
3) No danger of Ca-silicate deposits & incrustations.

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4) Does not generate foam & has a high stability in strongly alkaline
liquors.
5) Ensures well balanced formulation which enables the application in
hard or soft water, without further additions.
III. Surfactant (INVADINE LUN): Wetting & de-aerating in wet
processing textile treatments such as scouring/washing, desizing,
alkaline boil-out & bleaching.
Benefits of using Surfactant (INVADINE LUN):
1) High stability to chemicals, very good solubility which ensures
high versatility, simplifying recipes & reducing storekeeping.
2) Very good rewetting properties of treated material. For which
the goods are optimally prepared for subsequent continuous or
semi-continuous wet processing.
3) No troublesome foaming. Can be uses in a wide range of
machinery, even with high turbulence.
4) Ensures a quick & regular pick-up of the chemical bath to
obtain high & reproducible effects.
IV. Penetration accelerant:
 Removing air from all liquors used in textile wet processing.
 Removing air from fiber assemblies & densely packed or tighty
woven materials.
 Preventing foam formation or destroying existing foam even in
machines with vigorous liquor circulation.
 Particularly recommended for circulating-liquor & jet machine
dyeing even in short liquor ratio processes.
 Jet penetration accelerant is specially used for prevention of
foaming or destruction of foam already present even in machines

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with vigorous liquor circulation. Specially recommended for Jet
short liquors & High Temperature dyeing.
 No stoppages & no damages to goods (chafe marks, creases).
1) Promotes fiber & surface levelness in dyeing. [16] Special
Document’s From Salima Sultana Shimo (Lecturer, D.I.U)
Mercerization
In order to impart lusture, increased strength, increased absorbency &
improved dye uptake to cotton fabrics (or yarns), they are mercerised
either in grey state or after bleaching which is carried out by treating
with a strong solution of caustic soda (NaOH-about 24%, 45º-54º
Tw) & washing off the caustic soda after 1-3 minute.
Penetrating & wetting agents: Generally these agents facilitates the
penetration of the caustic soda solution efficiently & quickly so that
uniform mercerising effect is produced. They are also called
mercerising wetting agent.
Sulphuric acid (𝑯 𝟐 𝑺𝑶 𝟒): Are used for removing extra amount of
Caustic Soda from fabric. [17]

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Dyeing Stage
Chemicals used in dyeing process:
Dyeing: Dyeing is a coloration process, by which coloring substance
(dyes or pigments) is transferred from dye bath into fiber either by
physically or chemically, as a result the textile material is colored by
dyeing process.
[18] Class note: Wet Processing-3(Sumon Mazumder- Asst. Professor,
DIU, and 05-02-2014
Common name of different dye & their application:
Name of dyestuff Fiber Solubility
Direct Cotton, Viscose Water soluble
Reactive Wool, Silk, Nylon Water soluble
Disperse Nylon, Polyester,
Acrylic, Triacetate,
Diacetate
Water insoluble
Vat Cotton, Viscose, Silk,
Wool
Water insoluble
Basic Jute, Acrylic Water insoluble
Acid Wool, Silk, Nylon Water soluble
Azoic Water insoluble
Natural Natural protein fibers
(wool,silk,cotton),leather
Sulphur Cotton, Viscose Water insoluble
Pigment Cotton, Manmade fiber
[19] Basic knowledge of wet processing technology-1 By Anowar Hossain

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Direct dyes chemicals:
Direct dyes are anionic dyes having substantivity for all types of
cellulosic fibers which have strong affinity forwards the fiber & don’t
need any assistance. Easily soluble in water, Moderate light & wash
fatness. Most of the direct dye is Sodium salt of sulphonic acid or
Sodium salt of carboxylic acid.
Some commercial name of Direct dyes: Chloruntine fast (Ciba), Sirius,
Sirius light (Bayer), Pont amine (DuPont)
[20] Basic knowledge of wet processing technology-1 By Anowar
Hossain.
Chemicals uses & their importance:
Major chemicals:
(1) Soda ash (𝑁𝑎2 𝐶𝑂3): Removes hardness of water, increase
effectiveness of salt, enhances lusture of fiber, and prevents
acid in dye bath.
(2) Wetting agent (NaCl): Reduce surface tension, helps solution to
enter into the fiber easily.
(3) Salt: Works as electrolyte. Generally used to increase affinity of
the fiber. It also neutralizes the electronegativity of fiber. It also
increases exhaustion rate also control the levelling power (Class-B-Salt
controllable dye & Class-C dye). Generally 𝑁𝑎2 𝑆𝑂4 is used for medium
shade & 𝑁𝑎2 𝑆𝑂4.10𝐻2 𝑂 (Glauber salt) is used for light shade.
Other chemicals:

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(1) Cu-salt (CuS𝑂4) & Ethanoic acid (𝐶𝐻3 𝐶𝑂𝑂𝐻): They are used as
aftertratment chemicals increase light fastness.
(2) Formaldehyde (HCHO): Increase wash fastness.
(3) Na𝑂2 & HCl mixture: is used as diazotizing & coupling agents in
after treatment.
(4) Cationic dye fixing agent: Ensures good wet fastness
(5) NaOCl solution & Sodium hydrosulphite (Reducing agent-
NaHS𝑂3): Helps to stripping.
[21] Dyeing technology By Md. Abdul Kader Bapary (Chapter-Direct
Dye)
Reactive dyes chemicals
Reactive dyes are water soluble anionic dyes which are comparatively
cheap & fixation of reactive dyes occurs in alkaline condition. These
dyes have very good light fastness (with rating 6) & wash fastness
(with rating 4-5). Reactive dyes give brighter shades & have moderate
rubbing fastness & have good perspiration fastness (with rating 4-
5).Dyeing method is easy, less time 7 temp. Are required.
Chemicals uses & their importance:
I. Salt (NaCl or 𝑁𝑎2 𝑆𝑂4): Acts like electrolyte which increase
exhaustion rate. Electrolyte neutralizes the electro negativity of
fiber. Also decreases the hydrolysis of the dye. Electrolyte
increase the absorption.
II. Alkali (Dye fixing agent): Alkali is used to create optimum pH in
the dye bath. It is used as a fixing agent which increases the
fixation rate. No dyeing will be take place without it.

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Strong alkali (NaHC𝑂3) used for (pH 9-11) lower reactive dye,
Medium alkali (𝑁𝑎2 𝐶𝑂3) used for (pH 11-12) medium reactivity &
Weak alkali (NaOH) used for (pH 12-12.5) strong reactive dye.
[22] Sheet (Reactive Dye & its application-Wet Processing-3)
Prepared by Sumon Mazumder, Asst. Professor, and DIU.
III. Sequestering agent: Minimizes water hardness
IV. Anticreasing agent: Prevents creasing of fabric
V. Levelling agent: To achieve uniform dyeing by controlling the rate
of dyeing.
[23] Basic knowledge of Wet Processing technology By Md.
Anowar Hossain.
VI. Defoaming agent/ Anti-foaming agent: Defoamer is a chemical
additive that reduces and hinders the formation
of foam in process liquids. The terms anti-foam agent and
defoamer are often used interchangeably. Commonly used agents
are insoluble oils, polydimethylsiloxanes and other silicones,
certain alcohols, stearates and glycols. The additive is used to
prevent formation of foam or is added to break a foam already
formed.
[24] http://en.wikipedia.org/wiki/Defoamer-6.30 Pm-15 April
Other chemicals:
Sodium hypochlorite (NaOCl) & Sodium hydrosulphite (𝑁𝑎2 𝑆2 𝑂4)/
Hydrose: Sodium hydrosulfite is a very effective bleaching agent which is
used for full Hydrose stripping of reactive dye with Sodium hypochlorite
at room temperature.
Glacial acetic acid & Formic acid: Used for partial stripping.
[25] Basic knowledge of Wet Processing technology By Md. Anowar
Hossain.
Vat dyes chemicals

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The word vat means vessel. The dye takes their generic names from
vatting. Vat dyes are water insoluble which can’t use directly &
requires vatting. Washing fastness is very good but rubbing fastness is
bad. Various shade is found but dyeing process is difficult & costly.
Some commercial name of vat dyes:
1. Indanthrene- Bayer, Hoechst
2. Sandothrene- Sandoz
3. Alizanthrene- ICi
4. Tinon- Geigy
Chemicals uses & their importance:
Reducing agent (𝑁𝑎2 𝑆𝑂4): With reducing agent insoluble vat dyes are
reduced to produce acidic leucoform. NaOH is used as a solubilizing
agent. This process is called vatting.
[26] Basic knowledge of Wet Processing technology By Md. Anowar
Hossain.
i. Wetting agent: Reduce surface tension of water during the
vatting stage.
ii. Exhausting agent: Exhausting agent like Glauber Salt/ Common
salt (NaCl-added in dye bath) is needed during dyeing with 𝐼 𝑘, 𝐼 𝑤
class dyes.
iii. Retarding agent/ levelling agent: Retarding agent like Lignin
Sulphonate is needed during dyeing with 𝐼 𝑁 dyes. When degree of
unevenness is low then ordinary retarding agent is used. [27]
Chemistry of Organic textile chemicals By Dr. V.A. Shenai
Other chemicals:
NaOH & Sodium hydrosulphite (𝑁𝑎2 𝑆2 𝑂4)/ Hydrose: This chemicals are
used for even dyeing presence of certain levelling agent.

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NaN𝑂2 & 𝐻2 𝑆𝑂4: Uses in dye development bath.
[28] Basic knowledge of Wet Processing technology By Md. Anowar
Hossain.
Polyvinyl pyrolidone: Most efficient vat dye stripping agents when used
along caustic soda & sodium hydrosulphite. [29] Chemistry of Organic
textile chemicals By Dr. V.A. Shenai.
Disperse dyes chemicals
Disperse dyes are nonionic water insoluble dyes suitable for
dyeing hydrophobic fibers. Generally man made cellulose esters &
synthetic fibers specially acetate & polyester fibers & sometimes
nylon & acrylic fibers. Wash fastness of these dyes is moderate
to good & have fair to good light fastness.
[30] Sheet (Disperse Dye-Wet Processing-3) Prepared by Sumon
Mazumder, Asst. Professor, and DIU.
Some commercial name of disperse dyes:
1. Terasil-Cibageigy-Switzerland
2. Foron-Sandoz-Switzerland
3. Pelanil-BASF-Germany
4. Resolin-Bayer-Germany
Samaron-Hoechst-Germany [31] Sheet (Disperse Dye-Wet
Processing-3) Prepared by Sumon Mazumder, Asst. Professor, and
DIU.
Chemicals uses & their importance:
i. Dispersing agent: To ensure uniform & trouble free dyeing the
dye should be present in dye bath in a uniform & very fine form
(because Disperse dyes are water insoluble & form aqueous
dispersion in water) & should give a stable dispersion. For this

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special chemical is used in dye bath named dispersing agent. It
enables the dye to stable in hard water, high temp. Effective
under dyeing conditions. Example: Alkali sulphates, alkyl aryl
sulphonates etc.
ii. Carriers/ Swelling agent: For this more dye can be transferred
easily from the dye bath to fiber (polymer system). It increases
the dyeing rate. It swells the polyester fiber & most suitable for
obtaining dark shades. Hydrocarbons, phenols, amino acids,
amides, alcohols, esters, ketones are some example of carriers.
[32] Sheet (Disperse Dye-Wet Processing-3) Prepared by Sumon
M zumder, Asst. Professor, and DIU.
Other chemicals:
Migration inhibitors: Are used in padding liquors to prevent two-sided
effect (defect) in fabric.
Levelling agent: Used to produce level dyeing.
Emulsified carriers: Used to eliminate the toxic effects of the residual
carrier. [33] Chemistry of Organic textile chemicals By Dr. V.A. Shenai
Sulphur dyes chemicals
Sulphur dyes are highly colored water insoluble dyes which contain
Sulphur linkage within their molecules. No direct affinity towards
cellulosic fibers. This dyes have good & excellent light & wash fastness
respectively.
Some trade name of disperse dyes:
1. Calcogene- American cynanid- USA
2. Thional-ICI-UK
3. Sulphosol-James Robinsone-UK

20. Page | 20
Major chemicals:
i. Reducing agent (𝑁𝑎2 𝑆/ 𝑁𝑎𝐻𝑆/ Thioglycolic acid): Water insoluble
Sulphur dye can be make water soluble by treating with reducing
agent. These also makes them substantive towards cellulosic
fibers. Reducing agent breaks the Sulphur linkage & helps the
material (fiber/surface) surface to penetrate easily.
ii. Soda ash (𝑁𝑎2 𝐶𝑂3): Maintaining optimum pH in dye bath. It also
helps to remove Sulphur black tendering faults after dyeing.
iii. Salt: Uses as electrolyte. Increases exhaustion rate.
iv. T.R oil: Used in dye paste with 𝑁𝑎2 𝐶𝑂3. Later it is used with
reducing agent dye paste.
Others:
Oxidizing agents: Are used to convert the reduced water soluble form
of the dyes to the original water insoluble form by oxidation. Plays an
important role to develop the correct shades & getting brighter
shades. 𝐾2 𝐶𝑟2 𝑂7, Na-Perborate, Na-per carbonate & Na-peroxide are
some examples of oxidizing agents.
𝑁𝑎2 𝑆: Dilute solution or strong solution of 𝑁𝑎2 𝑆(0.1%) helps to prevent
the bronziness or dullness of shades.
Boiling soap solution & saponified palm oil: Also helps to minimizing the
bronziness defect.
𝐾2 𝐶𝑟2 𝑂7/𝐶𝐻3 𝐶𝑂𝑂𝐻 : Dyed materials are treated with these chemicals
to remove Sulphur black tendering defect. 𝐶𝐻3 𝐶𝑂𝑂𝐻 Also converts the
harmful 𝐻2 𝑆𝑂4 into harmless acetic acid.
Bleaching powder (NaOCl), KMn𝑂4: Stripping agents.
CuS𝑂4: Used in aftertratment (dye rubber material case).

21. Page | 21
[34] Sheet (Sulphur Dye-Wet Processing-3) Prepared by Sumon
Mazumder, Asst. Professor, and DIU.
Basic dyes chemicals
Basic dye is water insoluble but soluble in alcohol & methylated spirit.
Brilliant shade can be found. Basic reacts with strong alkali. It also
reduced with reducing agent & produce colorless dye base but when
deoxidized by acetic acid again colored component easily. Direct
affinity to jute fiber & acrylic fiber is also reacts with it. No affinity
to cotton fiber (so special treatment called Mordanting is done). Wash
fastness is moderate to poor. [35] Basic knowledge of Wet Processing
technology By Md. Anowar Hossain.
Some trade name of Basic dye:
1. Methylene blue
2. Methyl violet
3. Bismarck brown
4. Magenta [36] Sheet (Basic Dye-Wet Processing-2) Prepared by
Salima Sultana Shimo, Lecturer and DIU.
Major chemicals:
1. Acetic acid (𝐶𝐻3 𝐶𝑂𝑂𝐻): Works as solubilizing agent for Basic dye
(water insoluble). 40% (owf) Acetic acid are taken to form paste.
Acetic acid is also used as after treatment agent. If dyed
materials are treated with 2%𝐶𝐻3 𝐶𝑂𝑂𝐻, the dye stability
increases.

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2. Salt: Increase exhaustion rate. Salt is also used to add extra
energy to push the dye in the fiber that increase the absorption
rate.
3. Tannic acid: Most important chemicals for basic dye. Used as
mordanting agent when basic dyes are dyed with cellulosic cotton
fiber (since basic dyes have no affinity for cellulosic fiber).
Mordant is a special chemical which have affinity both for dye
stuff & fiber. So both dye & cellulose fiber are treated with
tannic acid to form mordanted cellulose.
4. Tartar emetic acid: Works as fixing agent while dyeing with
cellulosic fiber.
5. Alkali: For proper exhaustion sometimes alkali is used in dye bath
as dyeing assistant (when used acid).
6. Soap solution: Sometimes soap solution is used in dye bath
instead of acetic acid (some cases).
7. Cationic retarding agents are used for producing even dyeing
results during the dyeing of acrylic fibers with basic dyes. [37]
Chemistry of Organic Textile Chemicals-Dr.V.A. Shenai
Others: Tartar emetic acid (𝐶4 𝐻6 𝑂6): It is used in after treatment for
stabling dye in solution.
Tannic acid(𝐶14 𝐻10 𝑂7): Dyed material is also treated with tannic acid
for increasing dye stability but lusture bit decreases.
Alcoholic solution: Stripping agent.
Alum: It is used in after treatment. Due to improvement of lusture
dyed sample is treated with 2% alum. [38] Dyeing Technology by Abdul
Kader Bapary

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Azoic dyes chemicals
Cellulose specially cotton, flax, rayon, jute, hemp, & silk, nylon,
polyester, acetate fibers are dyed & printed with azoic dye. Azoic
colors have excellent light fastness (with rating 6-7) & also have very
good wash fastness (with rating 4-5).
Major chemicals:
Napthol (β-napthol): Generally used for naptholation (very important
stage) treatment.
Alkali (NaOH): Alkali is used to convert napthol to soluble Na-
naptholate. Alkali makes napthol substantive to cotton fiber.
Sodium nitrite (NaN𝑂2), HCl: Both are used for diazotization process
(for making Benzene diazonium chloride).
Common salt: Used as an electrolyte to increase substantivity of
napthol to fiber.
Formaldehydes (HCHO): Na-naptholate shows the tendency to be
converted to free napthol by oxidation process. Formaldehyde
prevents that tendency.
[39] Sheet (Azoic Dye-Wet Processing-3) Prepared by Sumon
Mazumder, Asst. Professor, and DIU.
Others:

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Brine solution (NaCl): Brine solution is used to remove excess napthol.
Soap/Detergent: After treatment agent.
Soda ash (𝑁𝑎2 𝐶𝑂3): After treatment agent.
T.R.oil, methylated spirit: Used in hot dissolution method & cold
dissolution method respectively. T.R.oil used as a stable dispersing
agent.
Caustic, Na-Hydrosulphite: Stripping agent.
[40] Dyeing Technology by Abdul Kader Bapary
Acid dyes chemicals
Acid dyes have great affinity towards protein fiber & it is water
soluble.
Chemicals used:
Glauber salt: increases affinity.
T.R.oil: Used as stable dispersing agent. Prevents the precipitation of
the complex dye bath.
Retarding agents: They are necessary to produce even dyeing result
during dyeing of polyamide fiber materials with acid dyes.
𝐻2 𝑆𝑂4, 𝐶𝐻3 𝐶𝑂𝑂𝐻, (𝑁𝐻4)2 𝑆𝑂4: Used as strong acid dyes on woolen
material, weak acid dye on wool & neutral acid dyes on wool
respectively. Acid helps the material to absorb dye easily.
Acetic acid, Formaldehyde, Hydrosulphite: Used during redyeing of
acid dyed mtl. [41] Dyeing Technology by Abdul Kader Bapary

25. Page | 25
Some special dyeing auxiliaries:
1) Afterclearing agent: Soaping reactive dyeing & prints on
cellulosic fibers & their blends.
Importance:
 Promotes solubility of hydrolyzed reactive dyes. Improved wet
fastness properties. Increased effectiveness of the washing-
off process.
 No impairment of light fastness. No effect on the shades of
dyeing & prints. Softening effect on soaping baths. Maximum
fastness properties are achieved.
 No additional foaming when used in Jets.
 No staining of white grounds on prints.
2) Fixatives: After treating dyeing’s produced with reactive &
direct dyes on cellulosic fibers by exhaustion & padding. After
treating prints produced with reactive dyes on cellulosic fibers.

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 Prevents dye migration during dyeing.
 Excellent water severe, perspiration & hot pressing fastness
to washing.
 No impairment of fastness properties after heat treatments.
 Ensures high exhaustion.
 High affinity, low pH dependence. [42] Special Document’s
Provided by Salima Sultana Shimo (Lecturer D.I.U)
Printing Stage
Printing is a coloration process by which coloring substance (dyes or
pigments) are applied on the surface of textile material in localized
(selection/mark) area according to particular design with following
different styles & methods. [43] Class note: Wet Processing-3(Sumon
Mazumder- Asst. Professor, DIU, and 05-02-2014
Essentials ingredients of printing paste:
1) Dye stuff: Most important elements. Without dye stuff printing
will not happen
2) Wetting agents: To obtain smooth paste, to dissolve the
dyestuff in the paste, to wet the fabric as well as dyestuff
wetting agents are used.
3) Solvent, solution aids (hydrotropic substances), dispersing agents
& humectants: To make proper printing paste, for preventing
precipitation, for getting bright design. For completely dissolving
the solubilized dyes (especially on vat dye for getting full color
value) solution aids are necessary.
4) Thickeners: Thickeners are used to give required viscosity to the
printing paste, to hold the ingredients of the paste on the
fabrics, to prevent premature reaction between the chemicals

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contained in the print paste, to hold or adhere the dye particles
in the desired place on the fabric. Example: Starch, modified
starches (oxidized & hydrolyzed), dextrins (British gums), gums
(gum Arabic, gum Tragacanth, gum Guar), CMC, HEC, sodium
alginate.
5) Defoaming agent & antifoaming agents: Prevents frothing during
the continuous agitation of printing paste. Also prevents faults
during roller printing (sprayed into the printing paste) due to use
of wetting agents in the printing paste. It works like a barrier for
creating foam.
6) Oxidizing & reducing agent: Oxidizing agents prevents premature
development of color, reduction of color during steaming. Also
mild oxidizing agents are used to protect ground dye from partial
destruction (producing lighter ground).
Reducing agents are used to destroy color from the ground of
fabric.
7) Catalyst & oxygen carriers: Prevents oxidization at elevated
temperature of steaming & prevents also fiber damage during
steaming. Example: Potassium Ferro cyanide, copper suphide,
vanadium chloride.
Catalyst like diammonium hydrogen phosphate plays an important & vital
role in pigment printing.
8) Acids & alkalis: Both are used to maintain proper pH. Acetic
condition is needed for fixing the colors & binders strongly at
high temperature (pigment printing, solubilized vat dyes).
9) Carriers & swelling agent: When disperse dyes are printed on
polyester fiber materials, the use of a swelling agent (carrier) in
the printing paste produces better color value of the final prints.
10) Hygroscopic substances (NaCl): Easily absorbs water from
surrounding atmosphere.

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11) Discharging & resisting agents: Especially used in discharge style
of printing.
12) Complexing agents: Certain Complexing agents are
incorporated in the discharge printing paste containing the
reducing agent & printed on vat dyed fabric.
13) Urea: Controls moisture.
14) Binding & fixing agents: Used in pigment printing. [44]
Textile Finishing Chemicals
Bleached, dyed & printed fabrics are subjected to certain processes
known as finishing processes in order to later their appearance, feel &
sale value before sending them to market for sale.
Chemicals used in finishing process:
i. Anticreasing agents: To prevent creasing of fabric or garments.
Anticreasing agents is one types of cross-linking agent.
ii. Antipilling agent: It is used to prevent pills formation during
wearing of cloth. [45] Basic knowledge of Wet Processing By Md.
Anowar Hossain
iii. Softening agents: The harsh feel (rough handle) of a fabric can
be modified by the application of softening agents. These are of
three types- anionic, cationic & nonionic softening agents (fatty
alcohol sulphates, fatty acid amide salts & polyethylene glycol
monoesters). [46] Chemistry of organic Textile Chemicals by
Dr.V.A. Shenai
iv. Antistatic agents: Reduce static electricity which may accumulate
on fibers. [47]

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http://textilelearner.blogspot.com/2011/03/description-of-
textile-finishing_1796.html-08 April-9.34 PM
v. Stain/Soil resistance & Soil-Release finishing agents:
A soil/stain-resistant finish, as the name suggests, improves the
ability of the material to resist soiling and staining by preventing
the stain from spreading on the surface.
Soil-release is “a finish for textiles that makes it easier to
remove stain and soil in laundering. Soil-release finishes were
originally developed to enhance the soil-release properties of
hydrophobic and oleophilic fibers such as polyester and
cotton/polyester blends with durable press finish.
Fluorocarbon finishes that are used as water- and stain-
resistant finishes are also effective as soil-release finishes. [48]
http://www.textileprofessor.com/textileprofessor/html/finishin
g_functionalfinishes_maintenance.htm-08 April-9.22 Pm
vi. Water-repellent & water proofing finishing agents: Waterproof
Finishes -Allows no water to penetrate, but tend to be
uncomfortable because they trap moisture next to the body.
Recently, fabrics have been developed that are waterproof, yet
are also breathable. Water-repellent finishes resist wetting.
vii. Flame retarding agents: prevent highly flammable textiles from
bursting into flame.
viii. Mothproofing finishing: Protect protein-containing fibers, such as
wool, from being attacked by moths, carpet beetles and other
insects.
ix. Enzyme finishing agents: Applied to cellulosic textiles that
produces permanent effects by the use of enzymes. Bio-finishing
removes protruding fibers and slubs from fabrics, significantly
reduces pilling, softens fabric hand and provides a smooth fabric
appearance.

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x. Absorbent finishing agents: Increase fibers moisture holding
power.
[49] http://textilelearner.blogspot.com/2011/03/description-of-
textile-finishing_1796.html-9.46 Pm-08 April
xi. Antimildew agents: Prevents textile material from bacterial
infection.
xii. Weight giving agents: Increases textile materials weight.
[50] Dyeing Technology by Abdul Kader Bapary.
xiii. Resin finishing: Resin finishing is the process of bringing out a
special property of crease recovery to cotton. Resins are cross
linking agents. Advantages: Reduces shrinkage of fabric during
laundering, improves crease resistance & recovery property,
improves weight & dimensional stability, smooth resilience, handle
& draping quality. It also improves light & wash fastness of many
dye-stuff. Increase the strength of rayon fiber both in wet &
dry condition. [51] http://www.slideshare.net/mohanpegu/resin-
finishing-11522628-7.06 Pm-15 April,20
xiv. Special Finishing Chemicals:
a) Lubricant (Dyeing Axillaries): In the wet finishing of textiles of
any fiber prone to creasing, wrinkling, crow’s feet & chafe
marking. This special types of lubricating agent is particularly
useful for processing under difficult conditions, such as in short
liquors or on heavily loaded winches & jets, & for processing
heavy, crease-prone goods & materials.
Importance:
No formation of permanent creases during wet finishing. Ropes
open & displace more easily, so improving levelness.
Textiles run better & more dependably in machines, no chafe
marks or streaks. No stiffness of viscose in wet process.

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Higher utilization of jets, winches, paddle & drum-type dyeing
machines. No foam problems in Jet dyeing machines. Excellent
fastness properties.
No impairment of liquor stability, hence no dye agglomeration &
no quality problems with stains & specks. [52] Special documents
provided by Salima Sultana Shimo (Lecturer, D.I.U)
Conclusion:
Wet processing engineering is one of the major streams in textile
engineering refers to textile chemical processing engineering
and applied science. For successful wet processing operation different
dyes, chemicals or chemical auxiliaries (finishing agent, printing agent)
plays an important role. Without these chemicals dyeing operation will
not be satisfactory (like without alkali no dyeing will be taken place,
without salt proper fixation or sometimes better can’t be achieved,
without sequestering agent-EDTA, NTA is mostly used dye bath water
hardness can’t be removed, without levelling agent level dyeing is
impossible, without wetting agent proper wetting of fabric or smooth
printing paste impossible, without proper using of finishing chemicals

32. Page | 32
satisfactory finishing operation will be uncompleted). Like NaOH
(strong alkali- also called caustic soda) which is must needed for
mercerizing chemical finishing operation, also needed in different
dyeing operation (during Reactive dyeing with less reactive dye, for
removing residual amount of detergent & wetting agent after the
operation, also acts as a swelling agent during scouring operation,
during naptholation for making napthol more substantive to cellulosic
fiber) are mostly used (sometimes soda ash, sodium bicarbonate are
also uses).
Importance of salt can be described in words (for proper fixation,
neutralizing ion, for improving fastness-metallic salts). Generally
Glauber salt (𝑁𝑎2 𝑆𝑂4.10𝐻2 𝑂 is mostly used sometimes common salt is
also used.
Levelling agents (which mostly used in dyeing acid dyes on wool or nylon
or vat dyes on cotton, also uses for different stages of dyeing process)
ensures level dyeing. Without dispersing agents & carriers disperse dye
can’t be used for dyeing synthetic hydrophobic fiber or printing
polyester with disperse dyes. Without using oxidizing
(𝐻2 𝑂2 𝑖𝑠 𝑚𝑜𝑠𝑡𝑙𝑦 𝑢𝑠𝑒𝑑 𝑖𝑛 𝑏𝑙𝑒𝑎𝑐ℎ𝑖𝑛𝑔 𝑝𝑟𝑜𝑐𝑒𝑠𝑠, 𝑜𝑥𝑖𝑑𝑎𝑡𝑖𝑜𝑛 𝑠𝑡𝑒𝑝 𝑜𝑓 𝑆𝑢𝑙𝑝ℎ𝑢𝑟 𝑑𝑦𝑒)
& reducing agent (like reduction of Sulphur dyes-Sodium Sulphide most
widely used reducing agent, Hydrose is also used) proper fixation of
dyes & proper solubility & proper stripping can’t be done.
Water-repelling agents, water-proofing agents, crease resisting, flame
retardants, antistatic finishing agents, dye fixing agents, softening
agents, stiffening agents, resin finishing agents binders & fixers (in
the case of pigment printing) are mostly used finishing chemicals.
Thickeners (CMC, HEC mostly used-ensures proper viscosity of printing
paste), defoaming agents (prevents foaming), catalyst & oxygen
carriers (prevents fiber damage & fixes colors), solvents & solution

33. Page | 33
aids (prevents dye aggregation) are essential for successful printing
operation.
So we should use the chemicals according to their scope of use.

34. Page | 34

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