Study on hot brand reactive dyes and its application system on cotton goods in exhaust method.
Introduction:
The problem of dyeing cotton with direct dyes in washing fastness is
overcome by introducing reactive dyes. In this reactive dyeing, dyes are held on
substrate by chemical reaction and hence a better resistance to fading or bleeding is
achieved. Reactive dyes are the most important class of dyes for dyeing and printing
for cotton and other cellulose blends. They represent about 45% of colorants used for
coloring cellulose fibres because of its application method, wide range of shades,
improve fastness properties and cost efficiency.
Hot brand reactive dye is one of the types of reactive dyes. These types of
reactive dyes have lower reactivity towards cotton. High dyeing temperature is
required and normally dyeing is carried out at the temperature between 800-850c, these
types of dyes also requires strong alkaline medium and NAOH is used to bring the PH
at 10.5-11.
Moreover, these dyes offer optimum fixation when used with urea in high
thermo fixation temperature or used in a long steaming time. Besides, these dyes hold
a low to medium substantivity and medium to high reactivity, which efficiently avoids
Tailing. Tailing is avoided by selecting dyes of low or medium substantivity, using
small padding troughs. These troughs are fed to constant level and operate at the
highest running speed commensurable with the needs of the rest of the process.
In our final project, we dyed cotton goods by hot brand reactive dyes in
exhaust method. And also found difference in color because of variable temperature
and fastness properties also.
Broad Objectives:
To know about hot brand reactive dyeing and its application system on cotton goods
in exhaust method.
Objectives:
Comparison of the color appearance of cotton fabrics dyed using hot
brand reactive dyes at different temperature.
Describe exhaust dyeing method on cotton goods.
Comparison of different fastness properties e.g. washing fastness,
rubbing fastness between standard temperature and different temperature
of dyeing.
Reactive dyes:
Reactive Dyes are capable of forming chemical covalent bonds with the
Hydroxyl groups of cellulose fibre and therefore, better anchored to the substrate and
not depend on the relatively weak physical forces to give better levels of fastness. All
of the features that are desirable for a reasonably ‘fast to wash’ Direct Cotton dyes are
not essential for Reactive class of dyes (because of the more strong covalent bond),
though cannot be totally discarded as undesirable.
Some of them could be counter productive. For example, Reactive Dyes with
features listed under I and 2 of the direct cotton dyes would exhibit problems of low
migration and or difficulty to wash off the hydrolyzed dye. Certain quantity of
Hydrolyzed dye is inevitable after the fixation stage and non removal of such unfixed
dye would entail bleeding/staining of white during washing. Migration is facilitated
by increase in temperature; but higher temperatures induce hydrolysis of Reactive dye
during the fixation phase and therefore it would be necessary to bring down the
temperature to the most favorable temperature for the reaction between dye stuff and
substrate before alkaline addition can be made.
There fore, in the case of Reactive dyes the following aspects are most
important 1. Degree of Exhaustion of the dye bath on to the fibre (both primary and
secondary) that is directly related to the substantivity should be maximized /optimized
(assisted more by salt addition than by the physical forces). 2. The migration of the
dye within the substrate during the primary exhaustion phase should be maximized. 3.
Efficiency of reaction of the exhausted dye to the fibre should be maximized during
fixation phase. 4.
The kinetics of reactivity has the final influence on the success of dyeing,
irrespective of high levels of success achieved in the exhaustion stages, though
exhaustion is an important (primary and or secondary) pre-requisite... 5.
The above four aspects need to be performed within a reasonable span of time.
6. The corollary here is that the extent of hydrolysis of the dye during exhaustion and
fixation stages needs to be minimized.
Types of reactive dyes:
Types Exhaust dyeing
temperature(0c)
Alkali recommended
High reactivity(cold brand) 25-40 Weak Alkali(NaHCO3)
Medium reactivity(Warm
brand)
40-60 Mild Alkali(Na2CO3)
Low Reactivity(hot brand) 60-95 Strong Alkali(NaOH)
Hot brand reactive dyes:
Hot brand reactive dye is one of the types of reactive dyes. These types of
reactive dyes have lower reactivity towards cotton. High dyeing temperature is
required and normally dyeing is carried out at the temperature between 800-850c, these
types of dyes also requires strong alkaline medium and NAOH is used to bring the PH
at 10.5-11.
Example includes:
Monochlorotriazine(MCT)
Dichloroquinaxoline(DQT) and
Trichloro pyrimidine reactive dyes
Figure of Monochlorotriazine (MCT):
Cl
S unfix Hot Brand Reactive Dyes: (Monochloro Triazine Based)
These are monochlorotriazine reactive dyes having a low reactivity and low
substantivity. Since these dyes have low reactivity, they require more severe
conditions for fixation with cellulosic materials. They are readily soluble by pouring
water of 80-85ºC on powder & stirring well. They are applicable on cellulosic
materials by both dyeing as well as printing methods.
In comparison with cold brand dyes, the `H' brand dyes require either a long
steaming time or a high thermo fixation temperature (with urea) for optimum fixation.
H dyes of low to medium substantivity and medium to high reactivity are most
suitable, dyes of very low substantibity may lead to migration problems in dyeing
prior to fixation.
When low concentration of highly substantive dyes is used, tailing becomes
evident. Tailing is avoided by selecting dyes of low or medium substantivity, using
small padding troughs fed to constant level and operating at the highest running speed
commensurate with the needs of the rest of the process.
In this project we used Sunfix hot brand reactive dyes based on Monochloro Triazine.
Literature Review:
Dyeing of cotton using direct dyes has rather poor washing fastness because
only weak polar forces bind the molecules to the cellulose polymer chains. Direct dye
molecules therefore can easily diffuse out of the cotton during washing. The idea of
immobilizing a dye molecule by covalent bond formation with reactive groups
originated in the early 1900s.
Reactive dyes are the water soluble anionic dyes. They react with the fibre to
form covalent bonds. They posses a reactive group in their dye molecules which
reacts with the hydroxyl groups presents in the cellulose to form a stable chemical
linkage. Thus the dyestuff becomes a part of the fibre substrate. In 1955, Ratte and
Stephen developed a procedure for dyeing cotton with reactive dyes containing
dichlotriazine groups.
The dye is enclosed in microcapsules, tiny (few micrometers in diameter)
drops of liquid ... 24 June 1991; ^ "Generra: Hot Star. Camel yarn dyed by reactive
hot KVIC method (RH-KVIC). 14 ... is not known for it outdates the beginning of
record history.
Material and Method:
Raw Material that are used in this project:
1. Fabric
2. Dye stuff
3. Chemical and auxiliaries
Fabric Types:
100% cotton fabric
Single jersey with lycra(1*1)
Dyes that are used in this project:
Sunfix M Turquoise PGR Reactive Blue 72
Sunfix Blue H3RP / P3R Reactive Blue 49 / 99
Sunfix Red P3BN Reactive Red 29
Method: In this project Exhaust dyeing method is used for dyed of cotton goods by
sunfix hot brand reactive dyes.
Primary Exhaustion Phase
Exhaustion of dye from the dye bath to the cellulose during Primary Exhaustion phase
is governed by the following three physical processes and the phenomenon of
substantivity
Adsorption
Diffusion,
Absorption/ Exhaustion/Migration
Secondary Exhaustion
The observations and inferences in the above deliberations related to primary
exhaustion in a Reactive exhaust dyeing process are incomplete without the final
fixation. When Alkali is added, the cellulose ionizes to form Cell-O- and H+ (Cell O–
Na+) and starts forming covalent bonds with the reactive functional groups of the dye
Chromophore.
When more and more of dye anions are covalently bond, the distribution coefficient
shifts to fiber phase effecting further exhaustion due to deficiency of dye anions in the
cellulose phase and dye bath concentration starts depleting further. The degree of
alkalinity in terms of pH plays a major role in shifting the fixation of dye to its
hydrolysis reacting with water. Any exhaustion during this stage if it is hydrolyzed
dye it would be far more undesirable In a reactive dye system therefore, primary
exhaustion alone does not govern the efficiency of dyeing. The degree of secondary
exhaustion also would influence the efficiency.
During the secondary exhaustion when alkalie is added, there is a second reaction that
also sets in motion in parallel ( i.e. the hydrolysis of the Reactive dye with water) in
competition to the fixation of the dye that is the primary aim. The dye anion is equally
facilitated to react with OH of water to form the hydrolyzed dye in which state the dye
is as good as a direct dye with all its ‘undesirable’ characteristics.
It is the reactive group in the dye, pH and temperature that influence the hydrolysis of
dye in preference to reacting with cellulose. It becomes critical that the hydrolysis is
curbed to maximize efficiency.
The relationship between temperature and reactivity is that higher temperatures
require lower alkalinity; to optimize on hydrolysis. They can be broadly grouped
under ‘High’ ‘Medium’ and ‘Low’ categories requiring 40º C. 60 º C and 80º.C
respectively - levels of pH 12.5 for High (cold dyeing), 11.5 for Medium (Warm) and
10 - 11.0 for Low (Hot Dyeing) for the reaction to proceed more favorably towards
the substrate.
The term more reactive is used in the sense that it requires lesser levels of alkalinity
and lower temperatures (and not the reaction itself. Given the right temperatures,
alkalinity and time the reaction proceeds to completion in all cases.)
Migration phase
Since fiber surface area is a factor in diffusion process, the exhaustion would proceed
to locations where relatively more surface area is presented like in the amorphous
areas and less densely packed crystalline areas in that order in the cellulose and
therefore the dye concentration within the cellulose substrate would not be
uniform/even.
Such a situation would result in uneven build up of the dye both in hue and intensity.
In a trichromatic mixture the situation could be worse.
The process of Migration of the exhausted dye depends on the molecular size of the
dye its spatial profile (Steric) and the solubilizing groups present. The other external
factors would relate to temperature, machinery used and the package profiles and
densities (in case of package dyeings)
Raising the temperature would provide the required thermal energy; but cannot be
increased arbitrarily due to limitations discussed under ‘Temperature’. Both
exhaustion and migrations can be maximized /improved by better mechanical
agitations that would facilitate intimate surface area contact of the cellulose with dye
liquor and by improved flow designs that facilitate better liquor exchange at the fiber
liquor inter-phase.
Migration phase should precede the fixation phase as once the reactive dye forms a
covalent bond with Cell O- it is anchored strongly and cannot be shifted.
Properties of major types of hot brand reactive dyes
Hot Brand Reactive Group Reactivity Exhaust Dyeing
Temperature(0c)
MCT(Sunfix) Low 70-85
TCP Low 70-95
DCQ Low 50-70
Dyeing Process:
We have used:
Sunfix dyes (Reactive Blue 72)of Monochlorotriazine dyes.
For every class of dyes we have used 4 different shades as 0.042, 0.42.
After the dyeing process we measured different fastness characteristics of the dyed
fabric about which we have discussed later.
For Exhaust dyeing system on Cotton:
It has been done at 800c temperature and in our project it is standard.
Recipe:
Dye : 0.042/0.42%
Salt : 12/20 g/l
Soda : 5/10 g/l
Wetting Agent : 1 g/l
Sequestering Agent : 1 g/l
Temperature : 800c
Time : 45 min
M: L : 1:8
Recipe calculation:
Recipe% * Sample Weight
=
Stock%
Sample Weight is 5 gm.
0.042 * 5
Recipe calculation=
o.1
= 2.1
12 * 80 * 100Salt=
1000 * 20
= 4.8
5 * 80 * 100Soda=
1000 * 10
= 4
So,
Additional water : 80-(2.1+4.8+4)
: 69.1
Procedure:
For dyeing with MCT based sunfix (Reactive Blue 72), Hot brand reactive
dyes, first the machine is loaded with water and material. The temperature is adjusted
as appropriate. Dyeing starts at 50°c during the next 45 minutes add the salt required
in three portions of increasing sizes at intervals of 10 minutes. Start to raise the
temperature while adding the second portion. A rate of raise is not greater than
2°c/minute should allow the required temperature 80°c in approximately 20-30
minutes. Allow 15 minutes after the last addition before adding soda ash slowly over
15 minutes and continue dyeing at 80°c for 30-60 minutes.
Dyeing Curve:
800c Shade check
20c min
Drain
10 min 15 min 20 min 40-60 minDyes+auxilaries+sample Salt Salt+salt Soda Dosing
Dyeing curve at 80 0 c temperature
Dyeing process at 940c temperature,
Recipe:
Dye : 0.042/0.42%
Salt : 12/20 g/l
Soda : 5/10 g/l
Wetting Agent : 1 g/l
Sequestering Agent : 1 g/l
Temperature : 940c
500c
Time : 45 min
M: L : 1:8
Dyeing Curve:
940c Shade check
500c 20c/m
Drain 10 min 22 min 20 min 45 min
Dyes+Auxiliaries+Sample Salt+salt Salt Soda
Dyeing curve at 940c temperature
The sample that is dyed at (80 & 94) 0 c temperature and recipe% 0.042 is shown as
follows:
Standard 800c temp.
Recipe%= 0.042
940c temp.
Recipe%= 0.042
The sample that is dyed at (80 & 94) 0 c temperature and recipe% 0.42 is shown as
follows:
Standard
800c temp.
Recipe%= 0.42
940c temp.
Recipe%= 0.42
Relative Comparison of the sample at temperature difference:
Fastness:
The color fastness of a colored textile is defined as it resistance to change
when subjected to particular set condition. Fastness is the ability of a colored material
to withstand the action of different agencies that come to play on it during its
manufacture or use. Fastness is the ability of a colored substrate to retain its
appearance when it is exposed to environment.
The dyed samples were tested according to ISO standard methods.
For wash fastness according to ISO 105 C01:
Fabric specimen : 10*4
Soap : 5gm
Temperature : 400c
Time : 30 min
For rubbing fastness according to ISO 105 c01:
Fabric specimen : 14*5cm
For staining bleached fabric: 5*5
Gray scale rating:
Rating Result5 Excellent4 Good3 Fair2 Poor1 Very poor
Relative Fastness comparison of the sample:
Fastness to washing:
Temperature
Recipe%
800c(Standard) 940c
0.042 0.42 0.042 0.42
Rating 5/5 5/5 5/5 4/5
Comment:
From experimental data we can see that the wash fastness of the dyed
sample at 800c temperature is better than 940c temperature when recipe
% is 0.42.
But in the case of recipe% 0.042 there is no significant difference
between the sample at 800c temperature and 940c temperature.
Fastness to rubbing:
Temperature
Recipe%
800c(Standard) 940c
0.042 0.42 0.042 0.42
Rating Dry rub 5/4 5/4 5/3 4/4
Wet rub 5/4 5/3 5/4 4/3
Comment:
From the above result it is observed that the rubbing fastness of the
dyed sample at 800c temperature is better than the dyed sample at 940c
temperature.
Both dry and wet rubbing fastness is better at 800c temperature than
940c temperature.
Overall comments about shade for dyed sample at temperature difference:
Shade% of Cotton fabric dyeing in exhaust method by hot brand
reactive dye is better at 800c temperature than that of 940c temperature.
Fastness properties to wash and rubbing is better at standard
temperature (800c) than 900c temperature.
Appling this method maximum time we can get our required shade.
Suggestion:
For further research related to this project, combination shade dyeing
as well as using different types of application method and as well as
different temperature.
Conclusion:
The cotton fabric dyed with hot brand reactive dye in exhaust dyeing process
to give a excellent results. Hot brand reactive dyes can be exhausted almost entirely
on to the cellulose fibres. Dyeing on the cotton gave better color strength at 800c
temperature than 940c temperature. The color fastness of these dying at different
temperature is approximately same. The results on the different temperature is
indicate that in case of hot brand reactive dyes perfect temperature is too much
important for matching the shade properly.
Reference:
1. Dyeing and Chemical Technology for Textile Fibres - E.R Trotman.
2. Textile Preparation and Dyeing - Asim Kumar Roy Chowdhury.
3. A Hand Book of Dyeing Technology – Mohammad Mahbubul Alam.
4. Internet.
Dyes:
Dyes are the chemical substances which are applied and fixed on substrates for
coloration.
Dyeing:
The objective of dyeing is the uniform coloration of the mass of fibre
constituting the materials, usually to match a pre specified color.
Reactive dyes:
Reactive Dyes are capable of forming chemical covalent bonds with the
Hydroxyl groups of cellulose fibre and therefore, better anchored to the substrate and
not depend on the relatively weak physical forces to give better levels of fastness. All
of the features that are desirable for a reasonably ‘fast to wash’
Hot brand reactive dyes:
These types of reactive dyes have lower reactivity towards cotton. High
dyeing temperature is required and normally dyeing is carried out at the temperature
between 800-850c, these types of dyes also requires strong alkaline medium and
NAOH is used to bring the PH at 10.5-11.
Fastness:
Fastness is the ability of a colored material to withstand the action of different
agencies that come to play on it during its manufacture or use. Fastness is the ability
of a colored substrate to retain its appearance when it is exposed to environment.
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