Mordant dyes click here
Trade names of mordant dyes click here
Properties of mordant dyes click here
Classification of mordant dyes click here
Method of application of mordant dyes click here
Dyeing of cotton with mordant dye(alizarin dye) click here
Mordant dyes:
The dyes which have no affinity towards textile fibres and
are attached with the fibre with the help of mordants are known as mordant
dyes.
Mordant dyes may be organic or inorganic substances. The
most commonly used mordant is inorganic chromium. So sometimes these dyes are
called chrome dyes.
These dye molecules have some mordant attracting groups
which have some influence on secondary valency bonds due to a particular
configuration with metal ions so that insoluble color takes are produced.
Mainly neighbouring –OH groups or –COOH groups appear in neighbouring position
in azo dyes. A metal equivalent takes the place of hydrogen in the –OH group
or -COOH group each time.
The mordants have affinity both for fibre and dye. So those
dyes which do not have any affinity to fibres can be applied by using a
suitable mordant ( as dyes have mordant attracting groups)
Trade names of mordant dyes:
|
Trade Name
|
Manufacturer
|
Country of origin
|
|
Diacromo
|
ACNA
|
Italy
|
|
Chrome
|
Ciba
|
Switzerland
|
|
Alizarin
|
Bayer
|
Germany
|
|
Omega chrome
|
Sandoz
|
Switzerland
|
|
Basolan chrome
|
B.A.S.F.
|
Germany
|
Properties of mordant dyes:
i.
Mordant dyes have no affinity for textile
fibres.
ii.
They are attached to the fibres with the help of
mordants. these mordant have affinity both for the dye abd fibre.
iii.
Mordant dyes are capable of combining with
metallic oxides to form insoluble color lakes.
iv.
Mordant dyes may be natural or synthetic.
v.
Mordant dyes are mostly applied on natural
protein fibres, nylon and acrylic fibres.
vi.
Good light fastness rating about 4-5
vii.
Most mordant dye are soluble in cold water.
viii.
The main feature of the molecule is that, there
remains a metal ion as a central atom which is bonded to neighbouring –OH,
-COOH or azo group.
ix.
Wide range of hues can be produced from mordant
dyes. t no good blue, green ang violet are available for wool. Largely used for
black shades.
Classification of mordant dyes:
On the basis of origin, there are 2 types of mordant dyes:
1. Natural
mordant dyes
2. Synthetic
mordant dyes
Now they are described below:
1 ) Natural Mordant Dyes:
Very few natural dyes are color fast with fibres. So
mordants are used to fix a dye with the fibre. These dyes as derived from
natural source e.g. plants, are natural mordant dyes.
Among the naturally occurring dyes alizarin(1,2-dihydroxy
anthraquinine) is extracted from the roots of madder. Alizarin produces red,
pink, brown and yellowish brown color when treated with compounds of Al, Sn, Fe
and Cu respectively.
Dyeing with natural mordant dyes is a time consuming
process. So they are used in lesser extent. In all these dyes chromium or other
metals combine chemically with certain groups present in dye and further
bounded by other force.
2 ) Synthetic Mordant Dyes:
As all synthetic mordant dyes are obtain from acid dyes,
they are called acid chrome dyes. That is to say,
Acid color + Cr -----àAcid
chrome
These dyes can co-ordinate easily with chromium. They can be
dyed as acid dyes and mordanted by after treatment with K2Cr2O7
or Na2Cr2O7
.
These acid chrome dyes are extensively used for wool and
polyamide fibres dyeing. They have good wet fastness and most of them possess
satisfactory light fastness.
The commonest method of application is to dye in an acid dye
bath and when exhaustion is complete, add appropriate amount of dichromate to
the liquor. Then boil it for 30 minutes
Example of some synthetic mordant dyes are as below:
|
Dye
|
C.I> Number
|
|
Chrome Fast Orange R
|
Mordant Orange 10
|
|
Solochrome Red B
|
Mordant Red 9
|
|
Eriochrome Black T
|
Mordant Black 11
|
Method of application of mordant dyes:
There are three general method of application of mordant
dyes as mentioned below:
1. Chrome
mordant process
2. After-chrome
mordant process
3. Meta
chrome or chromate mordant process
Now they are shortly described below:
1 ) Chrome mordant
process:
This is a two bath process. In this process at first
material is impregnated with an insoluble chromium hydrate and then dyeing is
done a separate bath.
2
) After-chrome mordant process:
This is the oldest and the most common mordant dyeing
process. Here the material is first dyed with an acid dye and then mordanting
with chromium is carried out in a separate bath. Or mordanting can be done in
the same bath after exhaustion of the dye has been completed.
3 ) Meta chrome/chromate mordant process:
In mete chrome process, dyeing and mordanting are carried
out simultaneously in the same bath. Here the mordant is present in the form of
chromate which does not form the lake with the dye and which is generally
converted into dichromate. The pH of the bath is kept around 6-7.This method
has the advantage of facilitating shading and requires less time, then the
after-chrome process. It gives highly level of residual chromium in the
effluent. This method is now almost obsolete.
Dyeing of cotton with mordant dye(alizarin dye):
The dyeing procedure of cotton with mordant dye(alizarin
dye) is describe below:
i.
At first cotton fabric is boiled in the solution
of
Ø
1 part TR Oil &
Ø
10 part water for 12 hours.
ii.
Then the fabric is dried at 40-60°C
iii.
Treated again with al-acetate at 60°C for 2 hours.
iv.
Then dry at 40-60°C.
v.
Again treated with 2 parts Na-phosphate and 10
parts water at 40-40°C
for 40 min.
vi.
1-1.5% dye ( on the weight of fabric) is added
in the solution with ca-acetate at room temperature for 30 minutes.
vii.
Then fabric is hot rinsed (at 70°C) for 30 minutes.
viii.
Finally the fabric is washed with soap solution
and water and then dried.