Sulfur dye Presentation

Md. Al-Amin Masum
ID: 2015100400011
Batch: 29th
BSc in Textile Engineering
Southeast University
alaminmasum11@gmail.com

Sulfur dye
 Sulfur dyes are inexpensive complex reaction
mixtures of selected aromatic compounds with
sodium polysulfide. The sulfur dyes are chemically
reduced in the presence of base prior to
application to the fiber, and are reoxidized after
dyeing on the fiber by oxygen in the air orby
application of a mild oxidizing agent such as
hydrogen peroxide. Sulfur is a water insoluble
dye. Which have to be converted into water
soluble substantive form (Leuco form).

Leuco
 Leuco is the colorless form of dye, creates as a result
of its insoluble form interacting with alkaline liquor. This
color retunes upon oxidation.
 This conversion is carried out by dilute aqueous
solution of sodium sulfide. This leuco compound has
affinity towards cellulose fiber & they sensitive to
atmospheric oxygen. This reduction form of sulfur dye
absorbed by the fiber substance and dyeing occurred.
After dyeing it finally again reconverted into insoluble
form of dye by chemical oxidizing with Na/K
dichromate.
 Dye – S – S – Dye + 2 [H] Dye – SH + Dye – SH
 2 Dye – SH + [O] Dye – S – S –
Dye + H2O

Properties of sulfur dye
 Anionic dye.
 Water insoluble dye.
 Sulfur dye is used to dye cotton, cellulose, regenerated
cellulose.
 Two stage dyeing.
 Shade ( 8% - 12%)
 Only few dark shade are available. (Navy, black, coffee).
 Wash fastness excellent.
 Rubbing fastness average.
 Light fastness very good. If wash the fabric with metallic salt (
copper sulfate ), its light fastness will be excellent.
 Very cheep dye.
 Sulfur is unhygienic for nature and human body.
 Sea water fastness is poor (because of Cl- anion).

Dyeing of cotton fabric with Sulfur
dye
 Recipe:
 Dye = 8 – 12%
 Reducing agent (Na2S) = 8 g/l
 Alkali (Na2CO3) =10 g/l, NaOH =5g/l
 Salt ( NaCl) =10g/l (increase affinity)
 Wetting agent =1g/l
 Sequestering agent =1g/l
 Leveling agent =1g/l
 Temp =80◦C
 Time =40min

Continue….
 Oxidation and neutralization done simultaneously
because they contain same PH and temperature.
 Oxidation & Neutralization:
 CH3COOH =1g/l
 Na2Cr2O7 =1g/l
 Temp =50◦C
 Time =10min
 Soaping:
 Detergent =1g/l
 Temp =70◦C
 Time =5-10 min

Stripping of Sulfur dye
 Stripping is the process by which to remove the
excess dye for uneven dyeing or shade
matching. In sulfur dyeing stripping is done
with the help of NaOCl.
 NaOCl = 2-3 g/l
 Temp = 70◦C
 Time = 10 – 20 min

Zero sulfur product
 In dyeing of fabric by sulfur dye we required a
reducing agent to make insoluble sulfur dye
soluble. Generally Sodium sulfide (Na2S) is used
as a reducing agent. But sodium sulfide has sulfur
which is very toxic so it harmful for human body.
To eliminated this problem we can used Glucose
(C6H6O6) as reducing, which sulfur free. So that
the product is less toxic and this product is called
zero sulfide products.

Faults of sulfur dyeing
 Tendering.
 Bronziness.
 Tendering: Tendering is a strength loss fault of
sulfur dyeing/ sulfur dyed fabric. Cellulose fabric
may degrade upon long storage. It is causes due
to formation of sulfuric acid. This fault is called
tendering.
S + H2O +O2 H2SO4
 If we wash fabric with 2-3 g/l of buffer solution (
CH3COONa), then this problem will eliminated.

Continue….
 Bronziness: Bronziness is a fault of sulfur dyeing,
where sulfur black or navy color fabric may change
to bronze or reddish shade.
Causes:
 Excessive delay between lifting of the fabric from dye
bath to washing off.
 Use excess amount of salt.
 Use excess amount of dye.
 Insufficient amount of reducing agent.

Continue….
Remedies:
 Use sodium hydro sulfide (NaHS) in conjunetion with
Na2S & NaHO, or use sodium bi-sulfide (NaHSO3) in
conjunction with Na2S & NaOH. Here NaHS &
NaHSO3 keep the dye bath in reduced condition and
prevent premature oxidation which was prime causes
of bronziness.
 Treatment of dyed fabric with oil emulsion.
 Ammonia liquid = 0.125 – 2 g/l
 T.R. oil = 2-3 g/l
 Temp = Room temperature
 Time = 10 min

Continue….
 Treatment with boiling soap solution.
 Soaping chemicals = 1g/l
 Temp =( 95 – 100)◦C
 Time = 10 – 20 min
 Treatment with
 Na2CO3 = 2g/l
 Olive oil =2g/l
 Temp =60◦C
 Time = 20min

After-treatment
 After oxidation and soaping, dyeing are passed
through CH3COONa at a lower liquor ratio, and
are dried to counteract inorganic corrosive acid
formed at the post-dyeing stage.
 S+ O2 → SO2+ H2O → H2SO3 + CH3COONa → CH3COOH + NaHSO3
 However, deposition of salt (NaHSO3 ) makes
dyeing marginally stiffer. To improve light fastness,
dyeing can be treated with metal salts in the
presence of acid. Light fastness may also be
improved by treatment with dye-ﬁxing agents. Dull
shades can be improved to some extent by
topping with basic dye.

Advantages
 The main advantage of using sulphur dye lies in their
cheapness, even when producing deep shades on
cotton with good wash and light fastness, compared
against other classes of cotton dye. Consumption of
costlier indigo in dyeing denim can be reduced by
topping or bottoming with sulphur dye. In topping,
denim dyed with indigo to a lighter shade is re-dyed
with sulphur dye to develop the desired shade. The
bottoming process is just the opposite: denim dyed
with sulphur dye is then re-dyed with indigo, with the
sulphur dye remaining at the bottom of the indigo
layer. The top or bottom can be accomplished by
applying sulphur dye in the pre-wash, ﬁnal indigo
bath, or in the after-treatment section.

Limitation
 Inadequate tinctorial ability limits production of light
shades.
 Limited hue range – true red, orange and yellow
cannot be produced.
 Shades lack brightness (though this can be
manageably .
 Improved by topping with basic dyes.
 Bronzing due to heavy dyeing.
 Tendering of cotton on storage in a humid atmosphere
 Not applicable on swimming costumes for fear of
discolorization.
 Not applicable on protein ﬁbres due to the high
alkalinity of the bath.

Sulfur dye Presentation

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Sulfur dye Presentation