1. The document discusses sulphur dyes, including their properties, dyeing process, advantages, defects and remedies. 2. Sulphur dyes contain sulphur linkages and are converted to water-soluble forms using reducing agents before dyeing cellulosic fabrics. 3. The dyeing process involves a reducing step to dissolve the dyes followed by an oxidizing step to convert them back to insoluble forms for good fastness.

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Midterm Based On Assignment
SULPHUR DYE
Course Code: TE-321
Course Title: Textile wet processing-II
Submitted To
Sumon Mozumder
Assistant Professor, Department of Textile Engineering
Submitted By
Name : Md. Toukir Ahmed Srabon
ID: 152-23-4325
Daffodil International University
Date Of Submission:10-04-2020

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INDEX
Name Of The Topic Page No
Significance of the study 03
Sulphur dye O4
Properties of sulphur dye 05
Advantage of sulphur dye 06
Chemistry of dyeing with sulphur dye 07
Reducing step of sulphur dye 08
Oxidant step of sulphur dye 09
Defects of sulphur dye 10
Remedies of sulphur dye 11
Stripping of sulphur dye 12
Uses & Limits of sulpher dye 13
Conclusion 14
References 15

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Significance of the study
1.To know about sulphur dye.
2.To know about the properties of sulphur dye.
3.To know about the advantage of sulphuir dye.
4.To know about the chemistry of dyeing with
sulphur dyes.
5.To know about the reducing step of sulphur
dyes.
6.To know about the oxidant step of sulphur dyes.
7.To know about defescts of sulphur dyes.
8.To know about remedies of sulphur dyes.
9.To know about the stripping of sulphur dyes.
10.To know about uses of sulphur dyes.
11.To about limitation of sulphur dyes.

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Description of the study
Sulphur Dye:
Sulphur dyes are highly coloured, water insoluble
compounds and have to be converted into water soluble
substantive forms (leuco forms) before application to the
textile materials. This conversion is carried out by a
treatment with a reducing agent like dilute aqueous Na 2 S.
Since this leuco form of sulphur dye is substantive to
cellulosic materials, these are absorbed on the fibre surface.
Then, these are converted into original water insoluble form
by the oxidation. This oxidation is carried out by “airing”
(exposure to air) or by using an oxidizing agent like Na-
dichromate (Na 2 Cr 2 O 7 ).
The dyes are so called as they contain sulphur linkage within
their molecules but dissolved in a solution of sulphide which
acts as a reducing agent, breaking the Sulphur linkage and
converting the molecules into simpler components which are
soluble in water and substantive towards cellulose.

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Properties Of Sulphur Dye:
Sulphur dyes have Sulphur linkage within their molecules.
Sulphur dyes are highly colored water insoluble
dyesSome dyes are partially soluble in water.
They have no direct affinity towards cellulosic fibres. To
make them substantive they are to be converted in to soluble
leuco form by treating them with reducing agent.
Sulphur dyes have good light fastness with rating about 4.
This light fastness may be improved by an after treatment
with metallic salt.
These dyes have excellent wash fastness with rating about
3-4. This good wash fastness is due to its larger molecular
size & insolubility in water.
They are not applicable to wool due to strong alkaline
condition.

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Advantage Of Sulphur Dye:
1. Low Cost
2. Fair to good light fastness
3. High wash
4. Easy to wash
5. Low energy required
6. Chemical resistance is moderate to good
7. Wet fastness is good
8. Chlorine fastness good

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Chemistry With Dyeing:
The Sulphur dyes contain Sulphur linkage within their molecules. They are
insoluble in water but can be made
soluble in water by treating them with reducing agents. This also makes them
substantive towards cellulosic
fibres. Na 2 S acts as reducing agent that breaks the Sulphur linkage and break
down the longer molecules in to
simple components which can penetrate the material (fiber/fabric) surface easily.
Reducing Agent
Dye-S-S_Dye+2[H]------------------------------------------Dye-SH+HS-Dye
This things containing the –SH groups are readily oxidized by the action of
atmospheric O 2 or any other
oxidizing agents. This reconverts the water soluble leuco form of Sulphur dye
into previous water insoluble
form which has a very good wash fastness property.
Oxidant Agent
Dye-SH+Hs-Dye+[O]-------------------------------------------Dye-S-S-Dye+H2O
Sulphur dyes are negatively ionized. Addition of salt improves efficiency of
dyeing by increasing physical force.

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Reducing Step Of Sulphur Dye:
Reducing step is the most important in the application of sulphur dyes. Unless the
dyes are converted into the completely soluble form, the full colour value cannot be
achieved. The solubility of reduced sulphur dyes varies appreciably from dye to
dyes. The reducing agents used for sulphur dyes are:
1) Na-Sulphide
2) Na-Hydro Sulphide
3) Thioglycolic Acid
But, Na Sulphide is the most widely used reducing agent for dissolving sulphur
dyes. These may be replaced by Na-Hydrosulphide in some cases. Again, over
reducing of the dye may take place, leading to a product having lower affinity for
cellulosic fibres. Hence lower colour yields are obtained along with wastage of
dyestuff. In some cases lower wash fastness results if Na-Hydrosulphide is used. It
also decreases the life time of the vessel.

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Oxidant Step Of Sulphur Dye:
After dyeing the reduced water soluble form of the dyes have to be
converted in to the original water insoluble form by oxidation. The
commonly used oxidizing agents are-
1) Potassium dichromate
2) Na-Perborate
3) Na-per carbonate
4) Na-peroxide
The method of oxidizing agent selection plays an important role in
the development of correct shades & their optimum fastness
properties. Using of different oxidizing agents may give the
following results-
1) Use of perborate or per carbonate in presence of acetic acid
gives brighter shade.
2) Treating dyed material with dichromate without rinsing reduces
color losses and causes dull shade.

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Defects Of Sulphur Dyes:
A) Bronziness or Dullness of shades:
Causes:
1) Excessive delay between lifting of the material from the dye
bath and washing off.
2) Exposure of goods to air while dyeing.
3) Too much use of common salts as exhausting agents.
4) Insufficient Na 2 S (i.e. reducing agent) in dye bath.
5) Strong dye liquor in the dye bath.
B) Sulphur black Tendering:
Causes:
1) Gradual oxidation of Sulphur to H 2 SO 4 on storage.
2) After treatment with copper salts causes rapid tendering.
3) Presence of iron as an impurity causes rapid tendering.
4) The method of oxidation for the recon version to insoluble
form influence tendering.

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Remedies Of Sulphur Dye:
A) Bronziness or Dullness of shades:
1) Good washing and dilute solution of Na 2 S (0.1%) at 30 0 C.
2) A treatment with boiling soap solution or a strong Na 2 S
solution .
3) A treatment with a solution containing 10% saponified palm oil
at 60 0 C.
B) Sulphur black Tendering:
1) Treatment of dyed material with 1-3% of K 2 Cr 2 O 7 and 1-
3% of CH 3 COOH at 60 o C temperature for 30 minutes followed
by through rinsing.
2) Treatment with a little CH 3 COOH so that H 2 SO 4 may be
converted in to harmless acetic acid.
3) Using 5 gm/litre soda ash after dyeing followed by drying
without rinsing.

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Stripping Of Sulphur Dye:
Unevenly Dyed shades on cellulosic materials with sulphur dyes
may be corrected by a treatment with a warm solution of Na 2 S
in the presence of polyvinyl pyrolodine. If this method is found
to be ineffective then the uneven dyed material may be treated
with a solution of a NaOCl or bleaching powder (2-3 gm/litre of
available chlorine). In some cases bleaching with KMnO 4
solution may be effectively carried out. In other cases the dyed
material may be treated with warm NaOCl solution in the
presence of NaOH. The uneven dyeing of material causes due to
the following reasons:
1) The oxidation of dye during dyeing when the material comes
in contact with air.
2) Presence of gummy material on the fabric.
3) Defective Dye.

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Uses & Limits Of Sulphur Dye:
Uses Of Sulphur Dye:
1) To dye Umbrella cloth with sulphur black.
2) To dye cotton fabric
3) To dye rubber material hence after treatment by CuSO 4 is
necessary.
Limits of Sulphur Dye:
● Inadequate tinctorial ability limits the production of light
shades
● Limited hue range -true rate, orange and yellow can not be
produced
● Shade lack brightness
● Improved by topping with basic dyes
● Bronzing due to heavy dyeing
● Tendering of cotton on stage in a humid atmosphere
● Not applicable on swimming costume for fear of discoloration
● Not applicable to protein fiber due to the high alkalinity of the
bath

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Conclusion:
By doing this assignment we know about sulpher dye and it’s
dyeing mechanism steps and also many chemical functions which
will helps us a lot in future in textile industry.It is almost
impossible to thinking of dyeing without sulphur dyes in textile
industry.So it is very helpful for us.

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References:
(1) Sumon Mozumder, Assistant Professor, Department of Textile
Engineering
(2) www.textiletoday.com.bd
(3) www.danti.it
(4) www.textileschool.com
(5) www.encyclopedia.com

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THE END