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.