STUDY OF SALT FREE REACTIVE DYEING ON COTTON

(CATIONIZED) KNIT FABRIC

BY

MD. IBRAHIM HOSSAIN

SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENT FOR THE DEGREE OF

B. SC IN TEXTILE ENGINEERING

AHSANULLAH UNIVERSITY OF SCIENCE AND TECHNOLOGY

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[PROJECT TITLE: STUDY OF SALT FREE REACTIVE DYEING ON COTTON

(CATIONIZED) KNIT FABRIC]

SUPERVISED BY: MOHAMMAD MAHBUBUL ALAM

Assistant Professor Department of Textile Technology Ahsanullah University of science and technology

Submitted by:

NIAZ MOHAMMED RAJIB 06.01.06.053

GOLAM KIBRIA 06.01.06.062

MD. RAKIBUL HASAN 06.01.06.064

MD. JAHIRUL ISLAM 06.01.06.068

MD. TAWFIQ SAEED 06.01.06.069

MD. ASHADUZZAMAN 06.01.06.071

MD. IBRAHIM HOSSAIN 06.01.06.076

AHSANULLAH UNIVERSITY OF SCIENCE AND TECHNOLOGY

DEPARTMENT OF TEXTILE TECHNOLOGY

COURSE NO: TEX- 400 COURSE TITLE: PROJECT WORK

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Acknowledgements:

First of all, we like to thank the almighty ALLAH for enabling us to complete the project work successfully. We express our heartiest thanks to our project supervisor and honorable teacher Mohammad Mahbubul Alam, Assistant Professor for his logical guidelines, constant inspirations, necessary instructions and proper supervision. A special thanks to Professor Dr. Mustafizur Rahman, Head, Department of Textile Technology of Ahsanullah University of Science and Technology, for his continuous encouragement and valuable suggestions. Finally we thank all of our respected teachers of the Department of Textile Technology for their insights, advice, and suggestions.

Broad Objective: Elimination of the use of salt in reactive dyeing and comparative analysis with conventional dyeing process.

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Introduction:

The problem of dyeing cotton with direct dyes in washing fastness was overcome by introducing reactive dyes. In this type of 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 cotton and other cellulose blends. They represent about 45% of colorants used for coloring cellulose fibers because of its flexible application method, wide range of shades, improved fastness properties and cost efficiency. Conventional reactive dyeing of cotton involves the use of huge amount of electrolytes such as common salt or glauber’s salt with causes environmental problem due to discharge of effluent having high salt concentration. Chemical modification of cotton for improving dyeability without using large amount of salts has been developed by pre treating cellulose with cationic fixing agents can eliminate the amount of electrolyte required. In our final project, we dyed cotton by reactive dyes without salt, using Cyclanon fix as cationic fixer and compared dyeing effects with conventional cotton dyeing using salts. We found differences in color values through spectrophotometer and also variation in fastness properties which are illustrated in our project.

Objectives:

To compare the color appearance of cotton fabrics dyed using salt and with fabrics pretreated using Cyclanon fix (Cationic fixing agent).

To determine CMC L*a*b* values of both type of dyeing and to measure color difference (dE) by using spectrophotometer.

To compare different fastness properties e.g. washing fastness, rubbing fastness between both types of dyeing.

To achieve a clear concept about both type of cotton dyeing using reactive dyes.

Pretreatment

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A coloration process consists of three stages namely pretreatment, dyeing/printing and finishing. Among these pretreatment is said to be the heart of wet processing. This stage brings the grey fabric into a dyeable condition. Before dyeing of cotton fabric, it undergoes the following pretreatment.

Scouring: Natural fibers contain oils, fats and waxes together with other impurities. Garments, fabrics, or yarns may contain oil and adventitious dirt collected during manufacturing. Scouring process is applied for the removal of these impurities. Fat and related substances can be removed from textiles by three methods.

By saponification when the fabric is not damaged by alkalis in the case of cotton.

By emulsification with soap or some other surface active compounds; and

By extraction with an organic solvent. The actual scouring process is often referred to as kier boiling. Kiers may be either low pressure or, which are open to the atmosphere or high pressure, which are sealed and can operate at temperature well above 100°c. During the caustic soda boil, all the impurities except the coloring matter and wax are converted into soluble substances which are washed away when rinsing takes place. The oils and fats are converted soaps which in turn emulsify the waxes. The proteins are broken up into the sodium salts of simple amino acids and the adventitious darts fall away when the oils are removed and are held in suspension by the soap. It is necessary to use soft water during kier boiling to avoid troubles due to the precipitation of calcium and magnesium salts. Some assistance is recommended to improve penetration or keep insoluble matters in suspension. An addition of sodium metasilicate to the kier liquor improves the scouring effect as silicates have a greater power of holding dart in suspension but they should be rinsed out thoroughly to avoid harsh handle produced by silica. The removal of impurities is accompanied with a corresponding loss of weight. Properly alkali boiled cotton will loss weight between 4 and 8 percent. Weight loss below and beyond this limit is not commercially acceptable.

Bleaching: Scouring generally removes all impurities except the natural coloring matters which have to be broken down by bleaching, either with an oxidizing agent or a reducing agent. Almost invariably the oxidizing agent gives a permanent white. The traditional oxidizing bleaching agent for cellulose fibers was bleaching

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powder. For all practical purposes now it is replaced by sodium hypochlorite. Hydrogen peroxide which is a strong bleaching agent has replaced hypochlorite. When bleaching with hypochlorite the basic factor should be borne in mind that the pH should be controlled properly. The effect of pH is as follows:-

At pH greater than 10 the hypochlorite is present as NaOCl or Ca(OCl)2 Between pH 5and 8.5 the solution consists predominantly of

hypochlorous acid. As the pH falls below 5 the liberation of chlorine begins to take place,

and when the pH falls below 3 the whole of the hypochlorous acid has been converted into chlorine.

Hydrogen peroxide is virtually the only bleaching agent available for protein fibers and is also very extensively used for the cellulose fibers. Bleaching is more rapid in alkaline solution than acidic solution. This may be because of the hydroxyl groups present in the alkaline liquor neutralize the hydrogen ions promoting the liberation of perhydroxyl ions.

Combined scouring and bleaching:

Combined scouring and bleaching involves the use of 3-4% sodium hydroxide and 2-4% hydrogen peroxide at the same bath. The fabric is first impregnated in the bath containing NaOH and hydrogen peroxide and then the temperature is raised at 98◦C for processing. The processing time is maintained for 60 minutes. The processing time is shortened by this process and hence the productivity is very high.

Dyeing: The objective of dyeing is the uniform coloration of the mass of fiber constituting the materials, usually to match a pre specified color. Coloration of textile materials is achieved in a number of different ways.

Direct dyeing, in which the dye in the aqueous solution in contact with the fiber is gradually absorbed by the fiber because of its inherent substantivity.

Dyeing with a soluble precursor of the dye which forms an insoluble pigment deep within the fibers on treatment after dyeing.

Direct dyeing followed by chemical reaction of the dye with appropriate groups in the fiber.

Adhesion of the dye or pigment to the surface of the fibers using an appropriate binder.

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Dyeing is either a batch exhaustion process, or a continuous impregnation and fixation process. In the exhaust technique, the entire textile is in repeated contact with the dye liquor during dyeing and the fibers gradually absorb the dyes. Careful control of the dyeing temperature, time, and pH and auxiliaries concentration is often necessary. In continuous impregnation and fixation method, the fiber passes through a small bath containing the dye solution and then two rubber covered roller squeeze out the solution. This process is called padding. After padding the dyes must diffuse into the fibers. After dyeing the material is rinsed to remove the Adhering solution.

Dyes: Dyes are the chemical substances which are applied and fixed on substrates for coloration. The structure of dye molecules are complex in comparison with other organic compounds. Most dye molecules contain a number of aromatic rings such as those of benzene and naphthalene, linked in a fully conjugated system. At least five or six conjugated double bonds are required in the molecular structure for a compound to be colored.

There are lots of dyes including natural and synthetic are commercially available. Dyes are manufactured depending on the nature of fiber. Amongst the commercially available dyes, basic dyes are cationic, disperse dyes are non ionic and the most of the rest are anionic. So specific dyes have affinity towards specific fibers. As for example, cellulosic fibers have affinity for direct, reactive and sulphur dyes. Protein fibers have affinity for acid dyes. Hydrophobic fibers are dyeable with disperse dyes.

Dyes are held into fibers through several mechanisms such as Vander walls forces, hydrogen bonds, covalent bonds, mechanically trapping, thermal diffusion etc. Each type of dyes has its specific dyeing temperature, pressure, pH, time and required auxiliary concentration. Dyeing properties also vary from dyes to dyes.

Reactive dyes: 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

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with reactive groups originated in the early 1900s. Reactive dyes are water soluble anionic dyes. They react with the fiber to form covalent bonds. They posses a reactive group in their dye molecules which reacts with the hydroxyl groups present in the cellulose to form a stable chemical linkage. Thus the dyestuff becomes a part of the fiber substrate. In 1955, Ratte and Stephen developed a procedure for dyeing cotton with reactive dyes containing dichlorotriazine groups.

Simple representation of reactive dyes:

Where, S is the Solubilizing group

C is the Choromophoric group or the color bearing part{ Example

B is the bridging group X is the halogen containing reactive group

Nature of Reactive Dyes: The molecules of reactive dyes are smaller than those of direct dyes, and their smaller size is accompanied by a correspondingly lower substantivity. The molecules of direct dyes are larger so as to build up the physical attraction between the fiber and dyes, thus making them more substantive. Much smaller molecules are suitable for the use as reactive dyes because one covalent bond is thirty times stronger than one Vander walls bond. As the size of dye molecules become larger, the color imparts become duller. Reactive dye molecules therefore confer very bright colors to dyeing.

Basic principle of Reactive Dyeing: Three basic steps are for dyeing of cellulose fibers with reactive dyes are as follows:- Exhaustion of the dye from an aqueous bath containing common salts or

Glauber’s salt in neutral condition.

S C B X

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Addition of alkali to influence the chemical reaction of absorbed dye with the fiber.

Dyed materials are then rinsed, soaped and neutralized to remove

electrolytes, alkali and unfixed dyes.

Types of Reactive dyes:

Types Exhaust Dyeing Temperature (oc)

Alkali recommended

High reactivity (Cold Brand)

25-40 Weak Alkali(NaHCO3)

Medium reactivity (Warm Brand)

40-60 Mild Alkali (Na2CO3)

Low reactivity(Hot Brand)

60-80 Strong Alkali (NaOH)

Properties of major types of reactive dyes:

Reactive group Reactivity Exhaust dyeing temperature(°c)

DCT High 25-40

DFCP Moderate to low 30-50

VS Moderate 40-60

MFT Moderate 40-60

MCT Low 70-85

TCP Low 70-95

DCQ Low 50-70

NT Moderate to high 100-130

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In our project we used three types of reactive dyes. These are:

i. Hot brand, ii. Bi functional and

iii. Vinyl sulphone reactive dyes.

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 80°-90°c. Theses type of dyes also requires strong alkaline medium and NaOH is used to bring the PH at 10.5-11. Examples include:

Monochlorotriazine (MCT), Dichloroquinaxoline (DCQ) and Trichloro pyrimidine reactive dyes.

For dyeing with MCT 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 40 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.

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Vinyl Sulphone Reactive Dyes: Vinyl sulphone dyestuffs are reactive dyes possessing vinyl sulphone as the reactive group. In presence of alkali, these dyes chemically react with the hydroxyl group of cellulose and form covalent linkage. These dyes are versatile enough to suit different dyeing methods. Results are excellent and shade come clean and brilliant with no variation in the dyeing. These dyes are the sulphates ester of hydroxyethylsulphonyl dyes which on treatment with mild alkali, generates the vinyl sulphone group, which in turn reacts with ionized cellulose to form the dye fiber bond.

The vinyl sulphone group is not normally present in commercial dyes since it is more convenient to use a less reactive precursor such as the β- sulphatoethylsulphonyl group obtained from the corresponding β- hydroxyethylsulphonyl compounds.

Dye-SO2-CH2CH2OSO3Na + NaOH Dye-SO2-CH=CH2

β- Sulphatoethyl sulphonyl vinyl sulphone

The main features of vinyl sulphone dyes are

Possess excellent brightness and good wet fastness. They are dischargeable. Suitable for exhaust and different pad dyeing methods and

discharge printing. Ease of washing off unfixed dyestuff i.e. minimum staining of

the white ground in printing. They are applicable at a temperature ranging between 40-

60°c.

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Bi functional Reactive dyes: A deficiency of using reactive dyes is that their dyeing efficiency is significantly less than 100% and may be near 70%. Recent development has been made by introducing more than one reactive group into the dye molecules so that even though one group may hydrolyze, there is another group remaining for reaction with cellulose. Dyes with suitable diffusion and substantivity properties, but carrying two reactive groups have to be selected carefully. Bi functional dyes with two reactive groups of different reactivity towards the cotton, which have different optimal fixation condition and give a more uniform degree of fixation. These types of reactive dyes give quite high fixation and thus less color in dye house effluent. Important types of Bi functional reactive dyes include:-

MFT-VS, MCT-VS and Bi functional reactive dyes having two NT groups in each dye molecule.

MCT-VS dyes gives 1.3-2.3 times higher degree of fixation over the dyes containing either MCT or VS reactive groups. There are two types of bi functional reactive dyes. One type is Homo functional which have two reactive groups of similar type in nature. Another type is Hetero functional which have two reactive groups dissimilar in nature. The use of Bi functional reactive dyes gives:-

Excellent leveling property, Better reproducibility in dyeing, High exhaustion and fixation efficiency, Good all round fastness property and

Hydrolyzed dyes can be washed off easily.

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Recent classification of Reactive Dyes:

Alkali controllable dyes:

These are of relatively high reactivity and moderate substantivity. They are applied at relatively low temperature and level dyeing requires controlled addition of the alkali. Examples include:-

DCT, DFCP and VS reactive dyes.

Salt controllable dyes: These dyes are relatively low reactive towards cotton under alkaline conditions and therefore dyeing temperature will be as high as 80◦ C. Level dyeing requires careful addition of salt to promote exhaustion. Examples include:-

TCP, MCT, and MFT reactive dyes.

Temperature controllable dyes These dyes undergo fixation at high temperatures even under neutral condition. NT dyes fall in this class.

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Role of Salts in Reactive Dyeing process :

When a fiber is immersed in water, a negative electrostatic charge

develops on its surface. The charge repels any dye anions present in the solution. So the degree of exhaustion is low. If the dyebath contains an electrolyte such as sodium chloride or sodium sulphate, a diffuse layer of positive sodium ions form on the surface which neutralizes the negative charges. The dye ions are then able to approach closely to the fiber for the inherent attractive forces between the dye and the fiber.

In the absence of salt, the reactive dyes show very little substantivity. The addition of common salt or Glauber’s salt is necessary as it increases the exhaustion of the dye bath and a salt concentration of 30-50 g/l is adequate for cool reactive dyeing. The quantity of salt to be used depends on the dye concentration and liquor ratio. For deeper dyeing, the electrolyte concentration must be higher, where as if liquor ratio is reduced the electrolytes required is also less.

Amount of Salts & Alkali required for different shade%:

Shade% Salt (g/l) Na2CO3 (g/l) NaOH (g/l)

< 0.5 10-15 2-5 0

0.5-1 15-30 5-10 0

1-3 30-60 10-15 0

3-5 60-80 15-20 1-5

> 5 80 and above 20 and above 1-5

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Types of reactive groups present and their reaction:

Nucleophilic substitution:

Those that react by neucleophilic substitution mechanism based on presence of halogen substituents in a heteroatomic system e.g. among the principle reactive system of the type are halogensubstituted triazine, pyrimidine, pyrozine, quinoxaline.

Dye-X- + Cell-OH

- Dye-O-Cell + HX

Addition reaction:

Those that reacting with cellulose by neucleophilic addition to a carbon-carbon double bond, usually activated by an adjacent electron –attracting sulphone group.

Dye-SO2-CH=CH2 + Cell-OH Dye-SO2-CH2-CH2-O-Cell Normal dyeing procedure that is most commonly used:

The relatively simple procedure for batch dyeing of cotton materials with reactive dyes, developed by Rattee and Stephen, is still used for all types of reactive dyes irrespective of their particular reactive group. Dyeing is commenced in neutral solution, often in the presence of salt to promote exhaustion of the dye onto the cotton. During this period, the dye does not react with the fibre and migrate from fibre to fibre is possible. Then an appropriate alkali is used to the dyebath to increase its pH. This initiates the desired dye fibre reaction. The hydroxyl group in cellulose are weakly acidic and absorption of hydroxide ions causes some dissociation, forming cellulose ions. It is these that react with the dye by

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neucleophilic addition or substitution (scheme: Nucleophilic substitution reaction and Scheme: Addition Reaction) In addition the reactivity of the reactive groups of the dye towards the alkaline cellulose, the higher the final dyeing temperature and the final pH of the dyebath.

The three steps exhaust dyeing process:

1. The initial exhaust phase: Dyeing is started in neutral solution so that there is little likelihood of the dye reacting with the cellulose. During that stage of dyeing, some reactive dyes will be absorbed by the fibres, the amount depending upon its substantivity. This dye is capable of migration to promote level dyeing. Sodium chloride or sulphate will often be present initially or be added gradually to the dyebath during this phase to promote exhaustion. The temperature of the dyebath may also be increased for the penetration of dye into the fibre and to assist migration.

2. The fixation phase: After the initial exhaustion phase, the pH of the dyebath is increased by complete or gradual addition of the appropriate type and amount of alkali. This causes dissociation of some of the hydroxyl groups in the cellulose and the nucleophilic cellulose ions begin to react with the dye. The fixation process then results in additional dye absorption, to re-establish the dyeing equilibrium. Dye absorption from solution and reaction with the fibre then progress until no further dye is taken up.

3. The post-dyeing washing: The rinsed dyeing content dye bonded to the cellulose, absorbed but unreacted dye as well as hysrolysed dye. There will also be residual alkali and salt. The latter are relatively easy to remove by successive rinsing in cold and then warm water. As much unfixed dye as possible must be washed out of the dyeing. If this is not done, desorption of this dye during washing by the consumer can cause staining of other materials in the wash. Some unfixed dye is eliminated during the initial rinsing that removes salt and alkali. Through washing of the dyeing using a boiling detergent solution (soaping) eliminates the reminder. The dyeing is then finally rinsed in warm water. Soaping must often be repeated for deep dyeing or the residual unfixed dye must be complexed with a cationic agent.

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Salt free Reactive dyeing of cotton:

Cellulosic fibers when come in contact with water produce slightly negative charge due to ionization of hydroxyl groups, whereas most of the dye classes suitable for cotton are anionic in solution. The slightly negative charge on the fiber causes the repulsion of anionic dyestuffs. Therefore in dyeing of cotton with anionic dyes, a huge amount of electrolyte is required in order to reduce the repulsion.

Modifying the ionic nature of cotton the dyeability of cotton can be improved without using a large amount of salt. Pre treating the cellulosic fibers with reactive cationic agents will eliminate the use of electrolyte required. Chemical modification of cotton is generally performed in hydroxyl groups present in the cotton. By introducing amino groups, the cellulosic fiber will be cationized giving high substantivity for anionic dyes. This cationized cotton can be dyed with reactive dyes under neutral condition in the absence of electrolytes. Reactive dyes can be exhausted almost entirely onto the treated cellulose fibers.

Dyeing on the treated cotton gives better color strength than dyeing in the conventional method. The color fastness of these dyeing is equal or superior to that of the some dyes on untreated cotton. The type of reactive groups of reactive dyes has no influences on the dyeing properties of the cationized cotton fabric.

Chemical review and modification: Chemical modification of cotton in order to improve its dye ability without the large amount of salt has been considered for a long time. Pre-treating the cellulose fibers with reactive cationic agent could diminish or eliminate the amount of electrolyte required. Chemical modification of cotton is generally performed by reaction with the functional groups (hydroxyl groups) already present in the fiber. Many studies devoted to improving the dyeability of cotton fibers have used quaternary cationic agents having various reactive groups (e.g. epoxy and chlorotriazine).

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The most common approach is via reaction of various types of fiber- reactive substituted amino compounds. By introducing amino groups, the cellulose fiber will be cationized giving high substantivity for anionic dyes due to columbic attraction between the positive charge on the fiber and the negative charge on the anionic dyes.

This cationized cotton could be dyeable with reactive dyes under mild acidic conditions in the absence of electrolyte in the dye bath. It is also known that cotton treated with modified poly carboxylic acid can be dyed with different anionic dyes such as acid, direct and reactive dyes under specific dyeing condition.

Figure: Chemical structure of cotton (cellobiose, the basic unit of cotton)

Cotton fabric treated with quaternary compound will posse’s positive charge and this is illustrated here in the following scheme reacted with quaternary compound.

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Untreated cotton Treated cotton

Figure: figure showing the changes in surface charges.

Very little research has been conducted and published on the dyeing of cationic cotton. This has been a major focus at Cotton Incorporated though virtually all the research has been on exhaust dyeing. Initial trials at Cotton Incorporated have shown fiber reactive and direct dyes to be better candidates for dyeing cationic pretreated cotton than vat and acid dyes.

Materials and Methods Materials: Plain cotton knitted fabric. Cationizing agent: Cyclanon Fix (BASF). Method: The material is first cationized using cyclanon fix, before, during and after combined scouring and bleaching with caustic soda and hydrogen peroxide. Then the fabric is ready for dyeing.

Cycalnon® Fix: Nature : Aqueous solution of polyquaternary compound. Cationic &,

formaldehyde free,

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Physical form: yellowish to yellow liquid. Storage : When it is stored in the original, sealed containers at temperature of

between 5°c and 40°c Cycalnon® Fix has a life of at least 12 months. When container has been opened the contents should be used up as quickly as possible.

Properties: Solubility : Miscible with water Density : 1.05 g/cm3

Compatibility : Compatible with cationic and nonionic product. By using cyclanon fix the wash fastness improve substantially by the following

mechanism.

But it can be used as cationic agent before dyeing cotton fabric with reactive dye. As they are quaternary compounds. The chemical structure after cationization of cotton will be as follows:

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Scheme: Cationized cotton

Application method:

Application in long liquor:

Reactive dye

Cyclanon Fix 0.5-1.5% (owf) Liquor ratio 5:1-20:1

Addition of required amount of diluted Cyclanon Fix to the fresh bath and set the pH at around 7. Heat up from 25°c to 40°-50°c in 15 minutes. Treat at 40°-50°c for 20 minutes.

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Dyeing Process:

We have used: 1. Bi- functional dyes 2. Vinyl Sulphone dyes and 3. Monochloro triazine dyes For every class of dyes we have used: 1. Light shade (0.5%) 2. Medium shade (1.5%) and 3. Deep shade (4%)

After the dyeing process we measured different fastness characteristics of the treated dyed fabric about which we have discussed later.

For conventional dyeing process with salt:

Recipe:

Dye = 0.5/1.5/4.0 % Salt (Na2So4) = 7 / 15 / 30 g/L Soda Ash (Na2CO3) = 5 / 10 / 15 g/L Wetting Agent = 1 g/L Sequestering Agent = 1 g/L Temperature = 60 C Time = 45 min M: L = 1: 30

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Dyeing Process without salt:

1. Treating the fabric with cationic fixing agent Before Scouring &

Bleaching and then dye the fabric without salt:

Treatment of fabric with cationic fixing agent

↓ One bath scouring and bleaching of treated fabric

↓ Dyeing of bleached fabric

2. Treatment of the fabric with cationic fixing agent during scouring & bleaching and then dye the fabric without salt:

Treatment of the fabric with cationic fixing agent during scouring &

bleaching

↓ Dyeing of the treated fabric

3. Treatment of the fabric with cationic fixing agent After scouring &

bleaching and then dye the fabric without salt:

Conventional scouring and bleaching

↓ Treatment with cationic fixing agent

↓ Dyeing of treated fabric

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Recipe & Dyeing process of salt free dyeing:

Treatment with cationic fixing agent before scouring & bleaching

Treatment with cationic fixing agent during scouring & bleaching

Treatment with cationic fixing agent after scouring & bleaching

Cationization recipe : Cyclanon Fix : 1.0 % (owf) Liquor ratio : 1 : 30 Temperature : 25°c - 40°c Time : 15 – 20 minutes

Scouring & bleaching recipe:

Caustic soda : 5 g/L Hydrogen peroxide : 3 g/L Wetting agent : 1% Sodium silicate : 1 g/l

Temperature : 98°c Time : 90 min M:L : 1: 40

Dyeing Recipe: Dye : 0.5 / 1.5 / 4.0 % Soda Ash(Na2CO3) : 5 / 10 / 15 g/L

Wetting Agent : 1 g/L Sequestering Agent : 1 g/L Temperature : 60 C Time : 45 min M:L :1 : 30

Scouring, bleaching & cationization recipe : Cyclanon Fix : 1.0 % (owf) Caustic soda : 5 % Hydrogen peroxide : 3 % Wetting agent : 1% Sodium silicate : 1% Temperature : 98°c Time : 90 minutes M:L : 1: 40 Dyeing Recipe: Dye : 0.5%/1.5%/ 4.0% Soda Ash(Na2CO3) : 5 / 10 / 15 g/L Wetting Agent : 1 g/L Sequestering Agent : 1 g/L Temperature : 60 C Time : 45 min M:L : 1 : 30

Scouring & bleaching recipe : Caustic soda : 5 % Hydrogen peroxide : 3 % Wetting agent : 1%

Sodium silicate : 1% Temperature : 98°c Time : 90 minutes M:L : 1 : 40

Treatment with cationic fixing agent : Cyclanon Fix : 1.0 % (owf) Liquor ratio : 1 : 30 Temperature : 25°c - 40° Time : 15 – 20 minutes

Dyeing recipe :

Dye : 0.5 / 1.5 / 4.0 % Soda Ash(Na2CO3) : 5 / 10 / 15 g/L Wetting Agent : 1 g/L Sequestering Agent: 1 g/L Temperature : 60 C Time : 45 min M:L : 1 : 30

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Dyed fabric samples:

For 0.5% shade

Dye class With salt Without salt

Vinyl sulphones

Hot brand

Bi functional

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Dyed fabric samples:

For 1.5% shade

Dye class With salt Without salt

Vinyl sulphones

Hot brand

Bi functional

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Dyed fabric samples:

For 4.0% shade

Dye class With salt Without salt

Vinyl sulphones

Hot brand

Bi functional

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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. The specific tests used were ISO 105 C01:1989, color fastness to washing; ISO 105-X12:1993, color fastness to rubbing. Color change was rated according to the appropriate gray scale.

Relative Fastness comparison of the samples: Fastness to washing:

Shade % Dyes

0.5 % 1.5 % 4 %

With salt Without salt

With salt Without salt

With salt Without salt

V.S 4/5 5 4 4/5 4/5 5

B.F 4 5 4 4 4 3/4

H.B 4/5 4/5 4/5 4/5 4/5 4/5

Comment:

From experimental data we can see that the wash fastness of the dyed sample without salt for Vinyl Sulphone is better than that of with salt. In the case of Bi functional dye the wash fastness of the dyed sample without salt is better than that of with salt.

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In the case of Hot Brand dye there is no significant difference between salt and salt free reactive dyeing.

Fastness to rubbing:

Shade% Dyes

0.5 % 1.5 %

4.0 %

Grey scale Staining scale Grey scale Staining scale Grey scale Staining scale

With salt

Without salt

With salt

Without salt

With salt

Without salt

With salt

Without salt

With salt

Without salt

With salt

Without salt

V.S

Dry 4/5 4/5 5 4/5 4/5 4 4/5 4 5 4/5 5 4/5

Wet 4 3 4 2 4 3 4 2 4/5 3 4/5 2

B.F

Dry 5 4/5 5 5 4/5 4 4/5 4 4/5 4/5 5 4/5

wet 2/3 5 2 5 3 5 3/4 5 4/5 3/4 4/5 2

H.B

Dry 5 4 5 4 5 4 5 4/5 4/5 4 4 4

Wet 4/5 2/3 4/5 2 4/5 4 4 3 4 3 3/4 3

Comment:

From the above result it is observed that the rubbing fastness of the dyed sample with salt is better than the sample dyed without salt. In case of Vinyl sulphone the dry and wet rubbing fastness with salt is quite good than in case of rubbing fastness of samples dyed without salt. For Bi functional reactive dyes both dry and wet rubbing fastness is better in case of dyeing with salt from dyeing without salt. For Hot brand reactive dyes both dry and wet rubbing fastness is also better in case of dyeing with salt from dyeing without salt.

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Limitation: Unfortunately Under the alkaline conditions necessary for the dye-fibre reaction, Hydroxide ions also react with the reactive of the dye in much the same manner as the cellulose ions. This produces the hydrolysed dye, which is incapable of reaction with the fibre. Hydrolysis of the dye is slower the than the reaction with the alkaline cotton bur it is significant and reduces the efficiency of the fixation process. After dyeing, any unreacted and hydrolsed dye present in the cotton must be removed by through washing.

Reflectance data comparison of the sample dyed measured with spectrophotometer:

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Comparison of conventional dyeing process & salt free dyeing process for 1 kg fabric:

Fabric wt. = 1 kg

Conventional dyeing process ( with salt )

Dyes & Chemicals Percentage used of dyes & chemicals

(Tk/kg.) Cost/kg

Pretreatment SPL 0.5 g/L 150 0.6

Sequestering agent 0.1 g/L 200 0.16

Anti-creasing agent 0.5 g/L 220 0.88

Enzyme 0.7 % 400 2.8

Acetic acid 0.5 g/L 120 0.48

Caustic soda 1 g/L 42 0.168

Soda ash 1.5 g/L 23 0.138

H2O2 3 % 46 1.38

H2O2 Killer 36

Dyeing

K.B RED ME6BL 4 % 440 17.6

Glauber’s salt 40 g/L 44 14.08

Soda ash 25 g/L 23 4.6

After treatment

Softener 1 % 250 2.5

Silicon 0.1 g/L 200 0.16

Total 45.546

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Salt free dyeing process ( without salt ) Dyes & Chemicals Percentage used of

dyes & chemicals Rate (Tk/kg) Cost/kg

Pretreatment

SPL 0.5 g/L 150 0.6

Sequestering agent 0.1 g/L 200 0.16

Anti-creasing agent 0.5 g/L 220 0.88

Enzyme 0.7 % 400 2.8

Acetic acid 0.5 g/L 120 0.48

Caustic soda 1 g/L 42 0.168

Soda ash 1.5 g/L 23 0.138

H2O2 3 % 46 1.38

H2O2 Killer 36

Dyeing

K.B RED ME6BL 4 % 440 17.6

Cyclanon fix 1 % 280 2.8

Soda ash 25 g/L 23 4.6

After treatment

Softener 1 % 250 2.5

Silicon 0.1 g/L 200 0.16

Total cost 34.3

N: B: Costing information collected from Adorsho chemical house, Kutubail,

Narayanganj.

Comments: Cost for processing and dyeing 1kg of the cotton fabric without salt is less than that of with salt. Salt free dyeing process (without salt) 34.3 Tk/ 1kg fabric processing

35

Conventional dyeing process (with salt) 45.546 Tk/ 1kg fabric processing

Conclusion: The cotton fabric treated with cationic fixing agent provides cationic sites which can be dyed with reactive dyes without electrolytes to give excellent results. Reactive dyes can be exhausted almost entirely onto the treated cellulose fibers. Dyeing on the treated cotton gave better color strength than the comparable dyeing on untreated cotton by the conventional method. The color fastness of these dyeing is equal or superior to that of the some dyes on untreated cotton. The results on the different reactive groups indicated that the type of reactive groups of reactive dyes had no influences on the dyeing properties of the cationized cotton fabrics.

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