Field of the invention
The present invention relates dyeing of textile fibres. More particularly, invention
relates to novel composition for use as mordant for the dyeing of wool fabric.
Background of the invention
Dyeing is one of the oldest techniques of human civilization. People have dyed
the textile materials since thousands of years and most of the times the dyes
have come from nature. People used these dyes in cosmetics, food, leather, and
also in medicine. The use of natural dyes has increased after the development of
weaving technique. The use of synthetic dyes has become faster acceptability in
the field of food, cosmetics and more importantly in the field of textile industries
after the invention of synthetic dyes by William Henry Perkin in 1856. The
manufacturers preferred the synthetic dyes because of easy dyeing process,
variation of shades and color fastness properties as compared to natural dyes.
But, the synthetic dyes cause some serious health hazards like allergic reactions,
carcinogenicity, and skin diseases, though they are widely and commercially
popular. They also pose threat towards eco-friendliness, as most of the dyes
contain azo groups of aromatic amines that may be harmful to human health and
environment. As a result, recently a ban has been imposed all over the world
including European Economic Community (EEC), Germany, USA and India on
the use of some synthetic dyes. Due to environmental awareness and harmful
effects of either toxicity or non-biodegradable nature of synthetic dyes, the use of
the dyes is gradually decreasing during the last few decades.
Potassium chromate is a yellow crystalline solid. It is soluble in water. The
primary hazard is the threat to the environment from six oxidation state of
chromium present in this compound. Immediate steps should be taken to limit its
spread to the environment. It is used in chemical analysis, in making pigments for
paints and inks, as a fungicide, and to make other chromium compounds.
Potassium chromate enjoys a wide variety of industrial uses. In the textile
industry, manufacturers use potassium chromate to tan leather and dye clothing
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items and fabrics. In science, potassium chromate is often used as an indicator,
meaning that it can identify the presence, location and quantity of certain
elements such as iron. Beyond these applications, potassium chromate also
functions as an oxidizing agent in manufacturing and scientific experiments.
Thus, in view of the foregoing, there arises a need to develop a mordant which is
capable of dyeing wool fabric without damaging the fabric.
Summary of Invention:
According to an aspect of the invention, there is provided a composition for
dyeing fabrics, said composition comprising ascorbic acid and potassium
chromate.
Yet according to another aspect of the invention, there is provided a composition
wherein the amount of ascorbic acid and potassium chromate ranges from 0.5:1,
1:0.5, and1:1mole/litre respectively.
Yet according to another aspect of the invention, there is provided a composition
wherein the ascorbic acid has a concentration of 1 mole/litre, and potassium
chromate has a concentration is 1 mole/litre.
Yet according to another aspect of invention there is provided a process for the
production of the mordant (CR-AA), wherein the reactants potassium chromate
and ascorbic acid are made to react on shaker at room temperature for 24 hour
and cool dried in lypholyser.
Yet according to another aspect of the invention, there is provided a novel
mordant composition wherein the fabric is wool.
Detailed description of drawings:
Figure 1 shows colored sample mordanted with compound CR-AA and dyed with
turmeric.
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Figure 2 shows colored sample mordanted with only potassium chromate and
dyed with turmeric.
Figure 3 shows colored non-mordanted samples dyed with turmeric.
Detailed Description
Present invention provides a composition for use as mordant for dyeing of
textiles. Dyeing of wool requires mild mordants which allows retention of dye
color without spoiling the fabric. The materials and methods for dyeing of fabrics
of present invention are mentioned herein.
Materials and method used
All the chemicals were AR grade, and double distilled water was used to
dissolve various chemicals. Reaction procedure involved the formation of 1
mole/litre (194.19 g/litre) potassium chromate solution and each aliquot of
potassium chromate solution reacted with 1 mole/litre (176.13 g/litre) strength of
ascorbic acid. The reaction mixture solution was kept for 24 h on shaker for
complete reaction. Then the solution was kept in lypholyser for getting anhydrous
reacted salt. The salt was labeled as CR-AA. The CR-AA was used as a mordant
on the 100% of wool fabric and after this the wool fabric was dyed with natural
turmeric dye.
Dyeing of wool was carried out on pre-mordanted samples. The mordanting was
carried out using synthesized compound (CR-AA) as mordant. For experimental
comparisons, dyeing of wool with potassium chromate was also carried out. For
another experimental comparison, dyeing of wool without mordanting was also
carried out.
Mordant used
Potassium Chromate and its compound CR-AA.
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Dyes
Turmeric natural dyes (from Botanical garden, Guru Nanak Dev University,
Amritsar)
Chemicals used for dyeing
 Non Ionic Detergent,
 Standard Soap Without Optical Brightening Agent (SDC Enterprises
Limited), Grade 3 Water
Instruments and Equipment used in dyeing
 Water Bath,
 UV Spectrophotometer,
 Glass Rod,
 Stainless Steel Vessels
Methods used for dyeing
 Pre- Mordanting with K2CrO4, CR-AA.
 Dyeing with Turmeric dye
Fabric and mordants
Scoured and bleached wool twill (2/2) fabric with the following
characteristics was purchased locally. Multifibre stripe (SDC Enterprises limited)
was used to check the washing fastness of treated samples.
Preparation of the fabric
The fabric was treated with a solution containing 5 g/litre standard soap
(SDC, Bradford) at 50°C for 30 min. The material to liquor ratio was taken as
1:40. After washing, the fabric was thoroughly rinsed in cold water and air dried
at room temperature.
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Mordanting
Pre-mordanting treatment was conducted using metal salts such as
K2CrO4, CR-AA compounds. Wool was treated with a solution 5.0% on the
weight of fabric of an appropriate mordant at material to liquor ratio of 1:30, for 30
min. Mordanting was conducted at 80°C. After mordanting the samples were
rinsed in cold water to remove the excess of mordant and used in the respective
dye baths as described below.
Dyeing
Dyeing with 1% on the weight of fabric of the pre-mordanted samples was
performed for 1 h at 100°C in an open bath beaker dyeing machine at 30:1 liquor
to material ratio. The dyed samples were rinsed in cold water and dried in open
air.
Fastness testing and colorimetric evaluation
Color fastness to washing was evaluated using standard ISO C06 C2S
test. ECE reference detergent 4g/litre and sodium perborate 1g/litre at pH 10.5
and steel balls (25) were employed in the test. A 10 x 4 cm dyed fabric strip
stitched through the short end to SDC’s multifibre test fabric was washed on a
Washtec (RBE) at 60°C for 30 min, the samples was rinsed with cold water air
dried and analyzed for the color change and staining.
The colorimetric properties of the dyeings (D65 illumination, 10° observer)
were determined using a Spectraflash 600 colorimeter (Datacolor International).
Figure 1 shows colored sample mordanted with compound CR-AA and dyed with
turmeric.
Figure 2 shows colored sample mordanted with only potassium chromate and
dyed with turmeric.
Figure 3 shows colored non-mordanted samples dyed with turmeric.
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Samples treated with synthesized compound (CR-AA) have good shades
on the wool fabric after dyeing with turmeric dye.
Potassium chromate (K2CrO4) has also given good results but not as good
as its derived compound after reaction with ascorbic acid, that is CR-AA.
Washing fastness properties of CR-AA mordanted dyed wool are
extremely good.
Grey scale readings (Staining on different fibres)
Sample Secondary
Acetate
Cotton Nylon Polyester Acrylic Wool
CR-AA 5 5 5 4/5 5 4/5
Potassium
Chromate
4/5 5 4 5 5 5
With
Turmeric
only
4/5 4 2/3 4/5 5 4/5
Grey Scale Reading (Change in colour)
S.No. Sample Readings
1 CR-AA 3
2 Potassium chromate 2/3
3 With Turmeric only 2

CLAIMS:
We Claim-
1. A composition for dyeing fabrics, said composition comprising ascorbic
acid and potassium chromate.
2. The composition as claimed in claim 1, wherein the ratio of concentration
in moles/litre of ascorbic acid and potassium chromate ranges from 0.5:1
to 1:0.5.
3. The composition as claimed in claim 1, wherein the ratio of concentration
in moles/litre of ascorbic acid and potassium chromate is 1:1.
4. The composition as claimed in claim 1, wherein the fabric is wool.
5. A process for preparation of composition comprising ascorbic acid and
potassium chromate, for use as mordant, said process comprises reacting
of potassium chromate and ascorbic acid while shaking at room
temperature for 24 hour and cool dried in lypholyser.