Prepared By : Mazadul Hasan sheshir
Batch (session 2009-2013)
Department : Wet Processing Technology
Blog : www. Textilelab.blogspot.com (visit)
Department Of Textile Engineering
I/A 251,252 Tejgaon Dhaka Bangladesh
Prepared By :
Today, the textile industry, which uses on an average six hundred dyes
and chemicals for the production of consumer textiles, is considered
With the kind of awareness and restrictions coming in to ecology of
textiles world over, the first thing every textile processor need to
know prior to processing any materials are the nature of end use of
the textile being processed and the country which being exported.
Because each end use, e.g. baby wear, clothing in direct contact with
skin, furnishing fabrics etc. will have different specifications just as
each country will have different legislation.
We are polluting our environment as well as destroying
our world by using non eco dyes and chemical
Because it create different problem:
• Health Problems
• Clothing dyes can cause the following health problems:
• skin rashes
• trouble concentrating
• muscle and joint pain
• breathing difficulties
• irregular heart beat
•Furthermore, children can experience the following:
•red cheeks and ears
•dark circles under the eyes
Because clothing is in constant contact with your skin, the chemicals are
absorbed into your skin through your pores. They can then enter your
liver, kidney, bones, heart and brain.
Most people have some sort of chemical sensitivity. Some are more
sensitive to chemicals than others. Those who are more sensitive will
notice the impact of clothing dyes more than others. Those of us who
aren’t as sensitive, may still experience some symptoms but just not
A Dyeing process that is most suitable
and within the norms of Eco labels
standards is called Eco Dyeing.
Some of the useful tips all may consider are:
• Select dyestuff that does not contain Chlorinated benzene and toluene.
• Avoid using Carcinogenic dyestuffs in your combinations.
• Avoid using Allergic dyestuffs (some selected disperse dyes are allergic).
• Do not use chelating agents that contain phosphates.
• Use APEO and NPEO free surfactants as dispersing agents.
• Ascertain that your surfactant do not contain any ethoxylated products.
• Use Formic acid for neutralization purposes rather than Acetic acid.
• Do not use formaldehyde containing dye fixing agents after reactive/direct
• Use Natural dyes can be used and that does not have heavy metals etc,
give the first preference.
• Most important is to control and limit the use of water for
• If reactive dyeing is carried out, where ever possible go for
low salt and no salt dyeing/trials.
• Avoid reprocessing, save energy, money and water.
• Try and establish a system of Right First Time practice in
• In reactive dyeing, where ever possible you may try cold
dyeing to save energy. Preconditioning method is one such
• In disperse dyeing avoid using phenolic carriers. Select
• In wool and silk dyeing metal complex dyes' selection
should be optimistic.
• In all cases of wet processing, establish a suitable system of
water recycling either with an R.O.system or Nano System.
Government Eco-Labels Commercial Eco-Labels
Eco mark – Japan Oeko Tex 100 – Germany/
Green Seal – USA Tox Proof – TUV, Germany
Flower – EU GuT – Carpets, Germany
Different country maintain different Eco-Labels
No Eco parameter Permissible limits
01 Presence of banned amine <30 ppm
02 Presence of pentachlorophenol(PCP) <0.5 ppm (Baby wear : <0.05 ppm)
03 Presence of formaldehyde <300 ppm - material not in direct skin
<75 ppm – material in direct skin contact,
<20 ppm – baby wear.
04 Presence of heavy metals*
05 Residual pesticides <1.0 ppm (Baby wear 0.5 ppm)
06 Allergenic dyes Not to be used
07 Carcinogenic dyes Not to be used
08 Chlorinated benzene & Toluene <1.0 ppm
09 Presence of Phthalate <0.01 ppm
10 Organic Tin Compounds <1.0 ppm
value of Aqueous Extract Should be nearly neutral (pH
-4.5 to 7.5)
12 Color fastness As per specification
Typical eco-parameters under the Eco-labels for finished textiles are,
CRITERIA FOR ECO-LABELS
• Oeko—Tex standard,
• EU Eco Label
• Made In Green
• Made By
Pertains to the limits of harmful chemicals which vary with the
intended use of textiles.
• Group 1
Baby wear, the limits are the lowest (stringent) for the cloths and
textiles for babies below age 3.
• Group 2
Material in direct skin contact, worn next to skin, for example –
underwear, bed sheets and night dresses etc.
• Group 3
Materials are not in direct skin contact. Textile worn as second layer
dresses, coats, articles with linings.
• Group 4
Furnishings articles and accessories for decorative purpose. e.g.
table wear, upholstery, curtains, textiles flooring and mattresses.
• These are recommendations for processes to be avoided such as
• Bleaching with hypochlorite.
• Use of chlorinated organic compounds as carriers in dyeing of polyester
• Optimum use of water and energy.
• Dyestuffs when exhausted on fiber are fixed only to the extent of 50-
90%, the un-exhausted dye with chemical impurities contaminate the
effluent, hence there is a need to ensure that dyestuff and dye additives
that go in to the dyeing process are eco friendly.
• Ecological norms for the dye are considered assuming it’s concentration
up to 10% on textile and 2% dye diluted to 1:2500 in effluent.
• Fastness properties (washing and rubbing dry/wet) of dyes on finished
textiles also form part of eco norms considering their possible transfer
on the skin.
Any of a class of colored, water soluble
compounds that have an affinity for fiber and
are taken up directly, such as the benzidine
derivatives. Direct dyes are usually cheap and
easily applied, and they can yield bright colors.
Wash fastness is poor but may be improved
by after treatment. Most packaged dyes sold
for home use are direct dyes.
Direct dyes are also called substantive dyes because of their
excellent substantively for cellulosic textile materials like
cotton and viscose rayon. This class of dyes derives its name
from its property of having direct affinity for cellulosic fibres,
when applied from an aqueous solution.
• Solubility in water.
• Affinity to cellulosic fiber.
• Easy penetration
• Washing fastness are not good enough
• It is applied in neutral as alkali medium
• This dye does not react with fiber. But create H-bond
R N H-----------O cellulose
• Chemically, direct dyes are sodium salts of aromatic sulphonic acids and
most of them contain an azo group as the main chromophore. They are in
general duller than the fiber reactive dyes, and exhibit poor wash
fastness. Goods dyed with direct dyes unless; given a proper after
treatment tend to bleed with every wash. The direct dyes in many cases
exhibit a better light fastness as compared to the reactive dyes.
Properties of Direct Dyes:
Vat dyes are an ancient class of dye, based on the
original natural dye, Indigo, which is now
produced synthetically. Both cotton and wool, as
well as other fibers, can be dyed with vat dyes.
Not all vat dyeing is done with vat dyes! "Vat
dyeing" means dyeing in a bucket or vat. It can be
done whenever a solid even shade, the same
color over the entire garment, is wanted, using
almost any dye, including fiber reactive dye,
direct dye, acid dye, etc. The opposite of vat
dyeing is direct dye application, such as, for
example, tie dyeing.
Most vat dyes are less suitable than, say, fiber
reactive dyes, for the home dyer, as they are difficult
to work with; they require a reducing agent to
solubilize them. The dye is soluble only in its reduced
(oxygen-free) form. The fiber is immersed repeatedly
in this oxygen-free dye bath, and then exposed to
the air, whereupon the water-soluble reduced form
changes color as oxygen turns it to the water-
insoluble form. Indigo is an example of this dye class;
it changes from yellow, in the dye bath, to green and
then blue as the air hits it.
• Vat dye, being insoluble in water, cannot be directly applied to
textile materials. They have to be converted into their water soluble
form, having affinity for textile fibre such as cellulosic fibres. This
conversion is usually brought about in two steps,
• Reduction of the dye into the weakly acidic leuco vat form and
• Salt formation by neutralizing these acidic leuco vat dyes by sodium
hydroxide to give a water soluble product.
• Since the second step result in the formation of water soluble
sodium salt of the leuco vat dye it may be called the solubilising
step. Reduction followed by solubilising is called vatting of the dye.
For this purpose sodium hydrosulphite Na2S2O4( usually called
hydros) is used as the reducing agent and sodium hydroxide as the
solubilising (neutralizing ) agent.
Properties of vat dye:
They tend to be fairly hydrophobic (though this depends on the structure of R1 and R2), but not
as much as, say, a long hydrocarbon would be, since the -COOC- groups cause some polarity.
The polymer chains in a sample of polyester are highly crystalline (for a polymer) and quite
tightly packed together. The result of this is that polyesters have very little affinity for large
ionic dyes- the dyes simply cannot either distribute between the chains, or form satisfactory
intermolecular interactions. Therefore, acid and direct dye classes are useless for this
polymer. Disperse dyes have low solubility in water, but they can interact with the polyester
chains by forming dispersed particles. Their main use is the dyeing of polyesters, and they
find minor use dyeing cellulose acetates and polyamides. The general structure of disperse
dyes is small, planar and non-ionic, with attached polar functional groups like -NO2 and -CN.
The shape makes it easier for the dye to slide between the tightly-packed polymer chains, and
the polar groups improve the water solubility, improve the dipolar bonding between dye and
polymer and affect the color of the dye. However, their small size means that disperse dyes
are quite volatile, and tend to sublime out of the polymer at sufficiently high temperatures.
The dye is generally applied under pressure, at temperatures of about 130o
C. At this
temperature, thermal agitation causes the polymer's structure to become looser and less
crystalline, opening gaps for the dye molecules to enter. The interactions between dye and
polymer are thought to be Van-der-Waals and dipole forces. The volatility of the dye can
cause loss of color density, and staining of other materials at high temperatures. This can be
counteracted by using larger molecules or making the dye more polar (or both). This has a
drawback, however, in that this new larger, more polar molecule will need more extreme
forcing conditions to dye the polymer.
• Non soluble
• Non ionic
• Molecularly disperse
• Used for manmade fibre dyeing ex-polyester, polyamide fibre.
• Hydrophobic textile material dyeing.
• Fair to good light fastness (4-5)
• Color fastness, wash fastness (3-4)
Properties of disperse dye:
Unlike other dyes, reactive dye actually forms a covalent bond with the cellulose or
protein molecule. Once the bond is formed, the dye molecule has become an actual
part of the cellulose fiber molecule. No wonder you can safely wash a garment that
has been dyed in bright fiber reactive colors with white clothing, a hundred times,
without endangering the whites in the least - even if it is all different bright colors, or
even solid black! The official definition of a "fiber reactive dye" is provided by Rys
and Zollinger in chapter VII of their book, The Theory of Coloration of Textiles
(1975) from the Dyers Company Publications Trust, England. A fiber reactive dye "is
a colored compound which has a suitable group capable of forming a covalent bond
between a carbon atom of the dye ion or molecule and an oxygen, nitrogen, or
sulphur atom of a hydroxy, an amino or a mercapto group respectively of the
substrate." They point out that the definition excludes mordant dyes and 1: 1
chromium azo dye complexes which, in dyeing protein fibers may form covalent
bonds between metal ion and nucleophilic groups of the fiber. What all this means is
that a fiber reactive dye reacts to form a true bond (not just a plus or minus charge
attraction or an entrapment in the fiber) with the fiber involved. In the case of
cellulose the bond is with the hydroxyl (-OH) groups present in vast numbers on the
cellulose molecule and in the case of protein fibers with the amino (-NH3 ) group
present on the protein molecule.
• Reactive dyes are highly soluble in water.
• Dye creates on covalent bond with fiber.
• Reactive dye can be used for dyeing cellulosic cotton, wool nylon.
• Fixation occurred in alkaline solution.
• Reactive dye can produce all types of shades.
• Dyeing method is easy for reactive dye.
• Light fastness is very good; rating 6 out of 8.
• Wash fastness is also good (rating: 4-5).
• Fixation occurred in alkaline solution.
Properties of reactive dye
The dyeing principle is based on fiber reactivity and involves the reaction of a functional group of the
dyestuff with a site on the fiber to form a covalent link between the dye molecule and the
The Four structural feature of typical reactive dyes molecule are:
• 1. The chromophoric grouping, contributing the color
• 2. The reactive system, enabling the dye to react with hydroxy group in cellulose.
• 3. A bridging group that links the reactive system to the chromophore.
• 4. One or more solublising group, usually sulphuric acid substituent attached to the chromophoric
group for their color, although the azo chromophore –N=N- is by itself the most important.
All the reactive dyes contain sodium sulphonate group for solubility and dissolve in water to
give colored sulphonate anions and sodium cations. Most reactive dyes have one to four of these
sulphonate group, General form of reactive dye is as follows:
Where, S = Water solubility group
R = Chromophore
X = Reactive System
B = Bond between reactive system and Chromophore
Mechanism of Dyeing
Natural Indigo Madder Lac Catechu
Pomegranate Kamala Mayrabolan Himalayan Rubrub
Natural dye Extract From This plant
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