DBL GroupTraining Report

View With Charts And Images

Mymun Textiles Ltd


From Fabric to Garments, the DBL GROUP is a truly integrated undertaking. The Textile Division has the capability to offer a complete product range for the export and domestic textile markets. The goal of the Textile Division is to become the preferred partner for sourcing high quality fabrics and clothing from Bangladesh. With highly advanced technology and an emphasis on developing local human resources, the Textile Division has the potential to make an important contribution to the nation’s growing readymade garments export sector.

General Information about the Mill

Name of the factory: Mymun Textiles Ltd.

Owner of the mill: Mr. A .WAHED

Authorized capital: 50 Croere Taka .

Business Line: Manufacturing and marketing of high quality Dyed fabrics & garments.

Location: Mymun Textile Mills Ltd. is situated in the Nayapara, Kashimpur, Gazipur. It is about 60 km from Dhaka.

Lay out plan of knit dyeing & finishing Departments & evacuation plan about the mill

The lay out of the knit dyeing & finishing department & evacuation plan is given in the next page

Organizational Structure

Given in the next page

Total Manpower and section-wise manpower:

Total manpower: 478 persons. Section wise manpower (month of December) :


Day Shift —————— 56

Night Shift —————— 44


Day Shift —————— 09

Night Shift —————— 06


Day Shift —————— 86

Night Shift —————— 64


Day Shift —————— 04

Night Shift —————— 02


Day Shift —————— 07

Night Shift —————— 05


Day Shift —————— 31

Night Shift ——————28


Day Shift —————— 04

Night Shift ——————02


Day Shift ——————17

Night Shift ——————07


Day Shift ——————05

Night Shift ——————-05


Day Shift ——————27

Night Shift ——————01







Capacity: Knit dyeing —21 tons per day

Actual : Average 16 tons /day.

Costing of Dyeing

Products Dyeing Charge

White ————————— 30-35 Tk/Kg

Average Colors —————— 85 Tk/Kg

Reactive Black —————– 110 Tk/Kg

Royal blue ———————- 110 Tk/Kg

Polyester ———————— 65 Tk/Kg

Wash ————————– 15-20 Tk/Kg

P C ————————– 130 Tk/Kg

Utilities + Overall cost : 30-35 Tk/Kg

Dyes & Chemicals cost : 30 Tk/Kg

Total Turnover:

Total turnover in 2003-2004 financial years was million Taka.


Building a true marketing led enterprise with motivated workforce, innovative vision, strong revenue based product portfolio, customer satisfaction and understanding of global market.


Each of our activities must benefit and add value to the common wealth of our society. We firmly believe that, in the final analysis we are accountable to each of the constituents with whom we interact; namely, our employees, our customers, our business associates, our fellow, citizens .

Product Mix and Their Sequence of Operation

Product mix in knit dyeing

Name of Product mix :

  • Single Jersey
    • Double Jersey or Heavy Jersey
    • Plain Interlock
    • Needle Top Interlock
    • 1×1 Rib
    • 2×1 Rib
    • 2×2 Rib
    • Lycra Rib
    • Very Rib
    • Loop Back
    • Fleece Fabric
    • Fleece Terry
    • Lycra Single Jersey
    • Polo PK
    • CVC (Cheap Valued Cotton) [% of Cotton is more in Blend]
    • PC/TC(The more % of polyester in the cotton part ) [Such as 65% Polyester + 35% Cotton]
    • Plated fabric


Millange is a blended knitted fabric generally blending Cotton with Polyester & Viscose . 100% Millange means the blending of Cotton & viscose . The one part dyeing of CVC/PC then we can get millange effect .

Ecru Millange / Silver Millange(Cotton 95% + Viscose 5%)

[If the millange is dyed with white recipe then it’s Silver

Millange & Ecro Millange generally dyed with Cream color]

Grey Millange [Cotton 85% + Viscose (15% )]

Anthra Millange ( >50% Viscose)

Theory of Pretreatmen

The term “pretreatment” covers all operations of preparing textile material for subsequent dyeing and finishing processes.

a. Objective:

The preparation of goods for dyeing and printing is a far important process than the production of white goods. Textile material to be dyed or printed must have the following properties:

· High and uniform dye uptake and absorptivity.

· Completely free from husks.

· High degree of polymerization of the cellulose.

· Adequate degree of whiteness to permit faultless dyeing of pale shades.

b. Degree of whiteness:

In the past, it was customary to regard the degree of whiteness as the most reliable criterion for judging the quality of the pretreatment. But now there are other factors governing the results obtained in subsequent operations. Today, therefore, the object of pretreatment is not a full bleach, but only a partial bleach as necessary to ensure good purity and brilliance of shade in subsequent dyeing or printing.

c. Hydrophilic properties:

High and uniform absorbtivity of the goods is essential. It is the hydrophilic properties that govern the evenness of uptake of the dyes and chemicals, particularly in cases where these are applied continuously.

d. Swelling State:

Swelling changes the inner surface of the cotton fibre and consequently its sorption behavior. Maximum, uniform swelling of the cellulose is therefore, essential for complete and level uptake of dye. This can be ensured by:

  • Removing the hydrophobic impurities from the fibre.
  • Treatment with alkali in scouring, bleaching, mercerizing etc.
  • Full width, tight-strand passage of the goods during the swelling process.

e. Solubilizing and washing- out of the impurities:

The purer the cellulosic fibre, the greater the assurance that the desired quality and uniformity of the pretreatment effect will be obtained. When the impurities of the cotton fibre have been solubilized, only the chemical problem has been solved. The next step is to remove by washing large amount of various substances in as short a time as possible.

Theory of Scouring:

Scouring is almost invariably the first wet process applied to textile materials. The object is to remove oils, fats, waxes, soluble impurities and any particulate or solid dirt adhering to the fibers. The process consists essentially of treatment with a detergent with, or without, the addition of an alkali. When soap is used a good supply of soft water is essential but this is of less importance with the synthetic detergents, which, now occupy such a prominent position.

After the cloth still contains fats and waxes (both natural and added), due to the presence of which the cloth becomes non-absorbent. These are removed from the cloth by scouring, also called kiering, kier-boiling, boiling out etc.

Objective of scouring

· To remove the natural as well as added impurities as completely as possible to from textile material.

· To produce hydrolytic characteristics.

· To produce a clean material by adding alkali.

· To make the fabric suitable for the next process.

· To leave the materials in a highly absorptive condition without undergoing physical and chemical damage.

The main purpose of scouring cotton fabrics is to remove natural as well as added chemicals of essentially hydrophobic character as completely a possible and leave the fabric in a high absorptive condition without undergoing chemical or physical damage significantly and also to make the goods suitable for removing the natural coloring matter of the cotton during the subsequent process.

The main processes occurring during scouring are ——-

1. Saponification of fats into water-soluble soap and water-miscible glycerin under alkaline conditions,

2. Hydrolysis of proteins into water-soluble degradation products,

3. Dissolution of hydrolysis to ammonia of simpler amino compounds,

4. Conversion of pectose and pectin into their soluble salts,

5. Dissolution of mineral matter,

6. Emulsification of unsaponifiable oils and waxes, and

7. Removal of dirt particles from the kier liquor by the detergent present therein.

The chief aim of scouring textile materials is to remove the natural and added impurities, thus rendering the material cleaner and more absorbent. Both this properties are highly desirable in view of the subsequent bleaching, dyeing operations. Scouring can be carried out in a number of ways. The selection of a particular scouring process is governed by the needs of the production, i.e. the degree of purification required for subsequent operations to be carried out.

The scouring or boiling off process permits the removal of certain impurities with which the fiber is associated. In fact, one of the main advantages of cotton lies in its resistance to alkali solutions; this property enables the cleansing of the raw material in a manner that is not possible with wool or silk. The scouring process, while purifying the ?-cellulose, imparts the hydrophilic character and permeability necessary for the subsequent process.

It may be said that good scouring is the foundation of successful finishing. In fact, scouring is a purifying treatment of cotton ?-cellulose, which contains impurities such as waxes, pectin’s, hemi-cellulose and mineral salts. Cotton goods also contain certain proportion of lignified substances, consisting of residues seeds, husks and leaves, which have not been completely removed mechanically during yarn manufacture. In fact, scouring is the only industrial method capable of removing cotton impurities almost totally.

The chemical most commonly used for scouring cotton textiles is caustic soda in combination with other supporting alkaline substance like soda ash, sodium silicate and tri-sodium phosphate. Sodium silicate is used to assist the detergent action of the kier liquor and its deflocculating action reduces the danger of kier stains. Both the silicates and phosphates cause the soaps formed to function better in hard water.

During the caustic soda boil, all the impurities, with the exception of coloring matter and wax, are converted into soluble substances, which are washed away when the fabric is rinsed. The oils and fats are converted into soaps and these in turn emulsify the waxes. The proteins are broken down into the sodium salts of simple amino acids and the adventitious dirt fats away when the oil are removed and is held in suspension by the soap.

The reaction of caustic soda with the impurities is governed by the following factors —

1. Quantity of alkali used.

2. Concentration of the alkali in solution.

3. Temperature of the reaction.

4. Time allowed for the reaction.

When fabrics have been desized, they are normally scoured using an array of chemicals chosen for particular purposes. A typical mixture of chemicals useful for cleaning fabrics is shown in Table.

Chemical Use
Caustic (NaOH) Neutralize acidic materials, saponify glycerides (Waxes and Oils), and solubilize silicate.
Sodium Silicate Penetrate and break down lignins in motes.
Surfactant Reduces surface tension and minimize interfacial tensions.
Detergent Emulsify oils, fats, and waxes; remove oil – borne stains; suspend materials after they have been removed.
Chelating (Sequestering) agent Deactivate metal ions.
Builder (Salt) Cause detergents to become increasingly effective.
Solvent Assist emulsification by dissolving oily materials.

Table: chemicals and their purposes

When cleaning soiled surfaces, five variables become involved that interact during scouring and they are as follows:

1. The nature of the surface to be cleaned,

2. The nature of the dirt or soil,

3. The chemicals to be used,

4. The nature of the water or solvent, and

5. The nature of the detergent or soap.

Changes occurring in alkaline treatments

The changes brought by boiling with alkali are summarized in a somewhat over – simplified manner as follows:

1. Saponifiable oils and free fatty acids are converted into soap.

2. Pectin’s and pectoses are converted to soluble salts of pectic acid.

3. Proteins are degraded to simple soluble amino acids or to ammonia.

4. Mineral matter is dissolved.

5. Unsaponifiable oils are emulsified by the soaps formed during the hydrolysis of the saponifiable matter.

6. Adventitious dirt is removed and retained in suspension by the soap.

7. Dressing and sizing materials are broken down into soluble products.

It is clear that most of the impurities are removed because of their solubility in the alkaline liquor, but with the wax, the position is more complex. On contact with alkali, the free fatty acids in the wax will be dissolved to form soaps and some of the wax itself will be saponified to give free alcohols and some soap. The soaps so formed will then be capable of removing the wax and alcohols by detergent action, the wax mixture being molten at the scouring temperature. The extent to which hydrolysis of the wax is important is not known for certain.

Reaction with cellulose

Alkaline solutions may attack cellulose in two distinct ways. In the absence of oxygen, the reducing ends of the cellulose chains may transform by the degradation process, in which a terminal metasaccharinic acid residue is formed. This residue is stable to alkali so that, once it has been formed, degradation causes. This reaction is of considerable importance when cellulose is treated with alkali and offers an explanation of the fact that, in general, scouring losses exceed the total amount of impurity present.

In the presence of oxygen, degradation can be very severe. Unfortunately, however, the reaction of oxygen with cellulose in the presence of alkali has not thoroughly been worked out, mainly due to the complex number of possible reactions, which may occur.

Scouring process

1. Batch or Discontinuous process

E.g. Kier boiling process

2. Continuous process

E.g. Scouring in J – box

3. Semi – continuous process

E.g. pad – roller process.

Scouring processes are basically similar but vary within limits because of plant equipment and the fabric constructions produced by individual mills. The first line of demarcation is the variation caused by continuous versus batch equipment. Both of these can be used to produce goods using either rope or open width methods, but the equipment dictates whether or not the possibility exists. A plant may be equipped to continuously process fabrics only in rope form. When this situation exists, and fabrics must be handled in an open configuration, Either Jigs or other open width equipment must be found or the order rejected.

The main purpose of scouring textile material is to remove natural as well as added impurities of essentially hydrophobic character as completely as possible and leave the material in a highly absorptive condition without undergoing chemical or physical damage significantly and also to make the goods suitable for removing the natural coloring matter of the cotton during the subsequent bleaching process.


1. To remove natural as well as added impurities.

2. To produce hydrophilic characteristics.

3. To make goods cleaner.

4. To leave the material in a highly absorptive condition without undergoing chemical or physical damage.

Basic principle:

The scouring process of cotton consists of an alkali treatment in the presence of wetting and sequestering agents, in order to convert the impurities, other than natural colouring matter, into products which can be removed by aqueous washing.

The processes occurring during the scouring are:

1. Saponifiable oils and free fatty acids are converted into soap.

2. Pectins and pectoses are converted to soluble salts of pectic acid.

3. Proteins are degraded to simple soluble amino acids or to ammonia.

4. Mineral matter is dissolved.

5. Unsaponifiable oils are emulsified by the soaps formed during the shydrolysis of the saponifiable matter.

6. Adventitious dirt is removed and retained in suspension by the soap.

7. Dressings and sizing materials are broken down into soluble products.

Factors involved in scouring:

When cleaning soiled surfaces, five variables become involved that interact during scouring and they are as follows:

1. The nature of the surfaces to be cleaned.

2. The nature of the dirt or soil.

3. The chemicals to be used.

4. The nature of the water or solvent.

5. The nature of the detergent or soap

Theory of Bleaching:

Bleaching is a process, which is designed to produce white fabrics and must be accomplished with a minimum of damage to the cotton being bleached. Bleaching is not a cleaning process in the sense of scouring; bleaching does not remove dirt. Bleaching is an oxidation process whereby coloring matter is destroyed (not removed) and cotton invariably is degraded. Production personnel must be aware that degradation is part of the process and must be regulated in a way so that satisfactory whiteness is obtained while fabric properties are maintained within customer specifications.

The removal of cotton wax, natural fats and added fatty matter (of the size) and others components from the desized fabric during the scouring process carried out in a kier leaves the material in a more absorbent condition than the grey fabric. But the natural coloring matter of the cotton is still present in the cloth. In order to obtain white cloth (so that pure or pale shades are produced on it either by dyeing or printing), the normal is to decolorize the natural coloring matter present in the cloth. Bleaching in different ways does this.

An effective bleaching process must ensure pure and permanent white level dyeing properties (over-bleaching and under-bleaching adversely affect the dye absorption properties of the fabric) and the fabric too should not undergo chemical damage or degradation during bleaching. A control over the concentration of the bleaching agent, the pH, and temperature of the solution, the duration of bleaching, the presence of catalysts like rust etc. on the cloth during bleaching should be kept in order to minimize or prevent any chemical damage of the cloth being bleached or wastage of the bleaching agent by self-decomposition.

The properly scoured cotton cloth goes for bleaching after a thorough washing treatment. The fabric must be approximately in a neutral condition at this stage. When it comes out of the kier, it contains alkali and this has to be completely removed; otherwise the residual alkali increases the pH of the bleaching solution (sodium hypochlorite or bleaching powder), which is usually kept at pH 10 to 11. Hypochlorite solutions at higher pH values are usually less active at room temperature. Further, the cloth leaving the washing machine is in a wet condition and the water accompanying the cloth dilutes the bleaching solutions with which the cloth is impregnated. In order to reduce this tendency, the washed cloth should be thoroughly squeezed to remove as much water as possible before saturating with bleaching solutions.

Bleaching process

Cotton can be bleached in fiber, yarn and fabric states. Some processes used are the following:

Fiber: Raw stock

Yarn: Package machine

Skein machine

Beam machine

Fabric: Kier

Continuous rope

Continuous open width

Jig, Kettle or beck

Types of bleaching agents

There are different types of bleaching agents are used:

(A) Reducing bleaching agents

1. Sulphur dioxide.

2. Sodium dithionite

3. Sulphoxylates

(B) Oxidizing bleaching agents

1. Sodium hypochlorite

2. Hydrogen peroxide.

3. Sodium peroxide.

4. Sodium perborate.

5. Sodium percarbonate

6. Peracetic acid.

7. Sodium chlorite.

These processes may be used whether bleaching continuously or discontinuously (Batch) and in staged combinations with each other. The term “ staged combinations” infers that two or three methods for bleaching can be used in sequence but not as a mixture in one application. A common two – stage sequence is to first bleach using hypochlorite, rinse and re-bleach with hydrogen peroxide.

Bleaching of cotton with hydrogen peroxide

Hydrogen peroxide is virtually the only bleaching agent available for protein fibers and it is also used very extensively for the cellulosic fibers. Hydrogen peroxide is a colorless liquid soluble in water in all proportions. It is reasonably stable when the pH is below 7, but tends to become unstable as the alkalinity increases. Commercial hydrogen peroxide, therefore, is made slightly acid so that it will not lose strength during storage. Solutions of hydrogen peroxide of more than 20 volumes cause intense irritation when they come into contact with skin and should be washed away immediately.

Cotton is usually bleached in 1-volume liquor at the boil. The most important factor in bleaching is to achieve the right degree of stability in the bleach liquor. If the pH were too low no per hydroxyl ions are set free and bleaching does not take place; when the liquor is too unstable the whole of the oxygen is liberated and escapes into the atmosphere before it has had time to act upon the cotton.

The bleaching liquor must be made alkaline, otherwise it would be too stable, but it is virtually impossible to adjust to the optimum pH with alkali alone and there is a marked tendency for the liquor to is too unstable, however carefully it has made alkaline. It is, therefore, necessary to add a stabilizer, and of all the substances, which have been, tried sodium silicate is the most effective.

Hydrogen peroxide is a stable chemical under acidic conditions and needs the addition of an alkali for activating it. Above pH 10, it is extremely unstable when it gets decomposed under water and oxygen.

2H2O2 2H2O + O2

This liberated oxygen, however, has no bleaching action and the catalysts are therefore a cause of loss of bleaching power. In fact, hydrogen peroxide is used bleaching under alkaline conditions (pH 10) after stabilizing at this pH by adding sodium silicate, borax, phosphate etc. Generally bleaching is done at 80ºC to 85ºC temperature.

Hydrogen peroxide solution at any concentration can be stable or unstable depending upon the several factors listed below.

1. pH: Stable in acidic solution and unstable in alkaline baths.

2. Temperature: As temperature increases the solution becomes increasingly unstable.

3. Buffers: Silicates, Phosphates, Borax, Proteins and others tend to stabilize peroxide.

4. Metals: (a) Ca and Mg in the presence of silicates tend to stabilize baths; (b) other metals, i.e., Cu, Fu, etc. tend to unstabilize bleach solutions.

5. Hard water: Depending upon the hardness of water and the metals making it hard, peroxide is unstabilize.

It was at one time believed that the bleaching action of hydrogen peroxide was due to the liberation of nascent oxygen but this explanation is no longer tenable. It is known that under certain conditions, particularly with regard to pH, hydrogen peroxide will liberate hydrogen and per hydroxyl ions in the following manner:

H2O2 H+ + HO2

Hydrogen peroxide is a universal bleaching agent and is used extensively for the bleaching of cotton materials. The advantages in its use are:

1. It can be employed for bleaching fibers like wool, silk and jute also.

2. It requires less manipulation of fabric and hence less labor.

3. The loss in weight in bleaching is less than that with hypochlorite bleaching

4. Less water is required with peroxide bleaching and there is no need for souring after bleaching.

5. Peroxide bleached goods are more absorbent than hypochlorite bleached goods.

6. After – yellowing of white goods bleached with peroxide or less than with hypochlorite bleached goods.

7. Peroxide bleaching is safer in regard to chemical degradation and

8. Continuous scouring and bleaching in one operation is possible by employing peroxide.

Application methods

(1) Batch or Discontinuous process

e.g. Kier, Jigger, Winch.

(2) Continuous process.

e.g. J – box, Vaporloc

(3) Semi – continuous process

e.g. pad – roll.

In the bleaching process the coloured material is destroyed and thus to confer a pure white appearance to the fabric. Bleaching should also decolourise or remove any residual impurities left by scouring. An efficient bleaching process must ensure:

· A pure and permanent white.

· Level dyeing properties (over-bleaching or under-bleaching adversely affects the dye absorption properties of the fabric).

· The fabric does not undergo tendering (chemical damage or degradation, which results in loss in tensile strength and hence the durability is affected) during bleaching.


Bleaching of cotton is carried out with two objects in view:

  • To achieve a high degree of whiteness, for goods that are to remain white or to be dyed in pastel shades; for goods to be dyed in dark shades, bleaching improves the brilliance.
  • To improve the even appearance of the goods by removing the husks.

Basic principle:

The oxidizing agent most commonly used today in bleaching is hydrogen peroxide. Owing to its dissociation constant of 1.5 X 10-12 at 20oC, hydrogen peroxide is a very weak acid. In alkaline solution, there is a certain amount of hydrogen peroxide anions above the equilibrium (1), and these anions are the source of the active oxygen that has the bleaching effect (2). In a secondary reaction (3) there is always a certain formation of molecular oxygen, which develops no efficiency for bleaching.

  • H2O2 + OH ¯ H2O + HO2¯
  • HO2¯ OH¯ + O
  • 2H2O2 2H2O +O2

A higher concentration of OH¯ ions has an activating effect; with increasing amount of hydrogen peroxide anions available in the liquor, the bleaching effect increases.

The advantages of bleaching with hydrogen peroxide are:

  1. No need for severe pre cleaning processes.
  2. No need for exotic materials of construction, but iron and copper must not be used.
  3. Environmentally acceptable; no AOX even in the presence of salt.
  4. Decomposition products are oxygen and water.
  5. Excellent storage stability.
  6. Compatible with most dyes and FBAs.
  7. Gives versatile processing (batch/continuous, hot/cold, rapid/long dwell, most fibre types).
  8. Produces a stable white fibre with good absorbency.
  9. Allows route shortening by combining stages (desize with scour, scour with bleach and desize with scour and bleach).

The disadvantages of bleaching with peroxide are:

  1. Some water is always transported.
  2. Sensitivity to metallic transported.
  3. Multichemical baths which need control.
  4. Comparatively expensive.

Chemical used and their functions:

1. Caustic Soda:

The vegetable oil, which is immiscible with water, is a glyceride of fatty acids like oleic, stearic, palmitic, ricinoleic acids. When such an oil is heated with a solution of sodium hydroxide in water, the oil is split up into its constituents, fatty acid and glycerine, of which the latter is freely miscible with water. The fatty acid reacts with sodium hydroxide present in the solution forming its sodium salt, i.e. soap, which is also soluble in water. The reaction is called saponification. As a result of saponification, the insoluble and water immiscible oil is converted into water-soluble products.

2. Soda ash:

Soda ash is used as alkali in addition with caustic soda. For scouring pH 11 should be maintained. But if only caustic soda is used to maintain the alkalinity then it would hamper the fabric quality. When the amount of caustic soda increases, the swelling of the fabric will also be increased and which leads to shrinkage. Thus the fabric dimension will also be changed. To avoid this problem, soda ash is added. Soda ash has superior cleansing action. Moreover it is used to increase the efficiency of Kieralon-OL.

3. Hydrogen peroxide:

Hydrogen peroxide is a colourless liquid which is used, in the textile industry, as a 35 or 50% solution with specific gravity of 1.131 or 1.195 respectively, it is the most widely used bleaching agent.

Hydrogen peroxide is an extremely versatile bleaching agent applicable over a very wide range of bleaching temperatures (ambient to 130oC) and times (minutes to days) on a wide range of machinery. Bleaching is usually carried out under alkaline conditions and this allows combination with other processes, such as scouring.

Hydrogen peroxide has achieved its dominant position as a bleaching agent because of three factors:

  • It is environmentally innocuous (potentially it can decompose into oxygen and water).
  • It is versatile (it can be used hot or cold, in rapid or long-dwell processes, batch wise or continuously).
  • A variety of activation routes are available.

4. Organic stabilizer:

High pH and temperature lead to the decomposition of peroxide bleaching liquor and degradation of the cellulose, which are catalyzed by transition metal ions. The role of the stabilizer is simply to control or regulate these effects by a multiplicity of functions. For example, they act as buffers, sequestrates and dispersants as well as, in special cases, enhancing performance of the surfactants used in the bleach bath. The sequestering action inactivates metallic impurities which cause catalytic decomposition of hydrogen peroxide or precipitation of hydroxides or carbonates. These impurities, the most common being calcium and iron, are brought into the bleaching system by the fabric, water supply or the other chemicals. Many chemical compounds are suitable as stabilizers. The cheapest method of stabilizing is with sodium silicate and magnesium ions. This combination has, however, significant disadvantages; the sparingly soluble magnesium silicate deposits in the machines and causes fiber incrustations, which cannot be removed by rinsing and are therefore liable to impair the handle.

Organic stabilizers are blends of organic materials with or without magnesium salts, are mainly of five chemical types:

  • Organic sequestering agents.
  • Protein degradation products.
  • Certain surfactants.
  • Polymeric materials.

· Mixtures of any of the above.

Theory of Reactive Dyeing

The dyeing of textiles is usually understood to mean giving them a colour which is of comparative permanence. This implies that it should not be possible to wash the colour out easily in laundering, nor should it fade rapidly when exposed to light.

There are three steps in the reactive dyeing procedure comprising adsorption of dye on the fiber, diffusion into the fibre and the covalent reaction with the particular nucleophilic groups present in the substrate. The reaction of dye occurs with the ionized hydroxyl of cellulose via the nucleophilic substitution or addition mechanism. Alkaline conditions are required to generate the cellulosate ion. The presence of OH- throughout the reaction is the cause for the hydrolysis of dye, because of the reaction of dye with hydroxyl anion. Hydrolysis is the same type of reaction as that employed during fixation to the functional groups of fibres and as a result of hydrolysis the dye become unreactive towards the textile substrate. Hydrolysis of the dye causes problems associated with highly coloured exhausted dye baths.

The reactions of fixation and hydrolysis are in competition with each other although the dye-fibre fixation reaction is more likely than hydrolysis, due to absorption of dye by cellulose under neutral conditions. The usage of electrolytes in the reactive dyeing is much higher than for any other class of dye. Addition of electrolyte promotes the dye uptake (exhaustion), rate of reaction and efficiency of the dyeing process.

Mechanism of dyeing:

The cellulose anion is a nucleophile, which can take part in addition and substitution reaction.

Nucleophilic substitution reaction:

Triazinyl reactive dyes undergo reaction with cellulose substrates via this mechanism. The hydroxyl anion of cellulose attacks at the electron deficient carbons of the heterocyclic ring.

Scheme: Substitution mechanism for a dichloro-s-triazine dye

Nucleophilic addition mechanism:

Reactive dyes based on B-sulphatoethylsulphone undergo eliminate to the vinylsulphone form with then react via an addition mechanism.

Scheme: Hydrolysis and fixation reaction of vinylsulphone dyes

The carbon-carbon double bond is polarized by the powerfully electron attracting sulphone group. The polarizing effect results in a positive charge to the end carbon atom and allowing nucleophilic addition of ionized cellulose to occur. The electron deficient Sq2 group activates the ethylenic carbon atom and acts as a bridge between the dye chromophore and the reactive group.

Factors governing reactive dye uptake:

All conventional reactive dyes for cellulose, irrespective of whether they react by nucleophilic addition, substitution, or both mechanism, rely on the reactivity of the cellulosate anion as the nucleophilic reagent and hence hydrolysis of the dye by reaction with hydroxide ions from water will always compete with the desired fixation reaction. Reaction between the dye and cellulose can occur only when the dye has been absorbed into the cellulose phase. Thus the kinetics of the dye- cellulose reaction are strongly influenced by the rate of absorption of dye. The ratio of the rate constants for reaction of the dye with the fibre and with water is a constant for a given dye over a wide range alkaline pH values. The efficiency of fixation is a function of:

  1. The reactivity ratio, the ratio of rate constants for the fixation reaction and hydrolysis.
  2. The substantivity ratio, the relative concentrations of dye absorbed into the substrate and remaining in the dyebath.
  3. The diffusion coefficient of the dye in the substrate.
  4. The liquor ratio.
  5. The surface area of the substrate available for absorption of dye.

An increase of dyeing temperature lowers the substantivity ratio and accelerates the rate of hydrolysis of the dye; both of these effects reduce the fixation efficiency. The rates of diffusion into and reaction with the fibre are also accelerated, however, and these factors both favour fixation of the dye. An increase in electrolyte concentration always enhances substantivity without impairing reactivity providing the dye remains completely dissolved.

Basic principle:

The conventional dyeing process entails three stages:

  1. Exhaustion from an aqueous bath containing electrolyte, normally under neutral conditions.
  2. Addition of alkali to promote further uptake and chemical reaction of absorbed dye with the fibre at optimum pH and temperature.
  3. Washing of the dyed material to remove electrolyte, alkali and unfixed dye.

Chemical used and their functions:

Salt: Electrolyte (sodium chloride or sulfate) increases the substantivity of the dyes toward the cellulose fibre, by suppressing dye-fibre repulsion and by increasing the activity of the anionic dyes in solution, thereby increasing of the dye exhaustion, rate of reaction, and efficiency of the dyeing process.

Alkali: Anhydrous sodium carbonate is the mostly widely used alkali; sodium bicarbonate and sodium hydroxide are also employed, enabling pH range of 8-12 to be achieved. The fixation of the dye occurs only on alkaline condition. The optimum pH should be maintained for better yield.

Anti migrating agent: Anti-migrating agent is used to prevent the migration of dyes on the fabric surface.

Wetting agent: Wetting agent is used to increase the wet ability of the fabric so that the dyes can penetrate easily.

Sequestering agent: These are the compounds, which react with metallic ions in such a way that they become part of a complex anion. The most commonly used sequestering agent is the sodiumhexametaphosphate (Na6P6O18). It is also known as Calgon T. They are used to soften process water and so avoid precipitation of alkaline earth metal salts during dye fixation and their deposition on the dyed material. An excess of inorganic sequestering agent can, however, lead to reduced color yield. The use of organic sequestering agents such as EDTA (ethylenediaminetetraacetic acid) is avoided, since they decopperize metal-complex reactive dyes to the detriment of light fastness and shade

Theory of Disperse dyeing

A disperse dye is defined as a substantially water insoluble dye having substantivity for one or more hydrophobic fibers and usually applied from aqueous dispersion.

Characteristically, disperse dyes are small molecular size compounds which contain no ionic groups but do carry polar substituents such as –OH, -CH2OH. As a consequence of their low size, they possess a small but nevertheless important solubility in water. The dyes are volatile due to their relative lack of cohesive energy in the solid state, and may therefore be applied via the vapor phase in heat-fixation processes such as thermofixation.

Basic principle:

The dyeing of hydrophobic fibers with disperse dyes may be considered as a process of dye transfer from a liquid (water) to a solid organic ‘solvent’ (fiber) and the dyeing is considered to take place in the following stages:

1. Dispersion of the dye in the solid phase into water by breaking up into molecules (dissolution in water).

2. Adsorption of the dissolved dye from the solution onto the fiber surface.

3. Diffusion of the dye molecules from the fiber surface into the interior of the fiber substance towards the center.

Chemical used:

Urea: Urea is a substance which is soluble in water and has dye solvent and hygroscopic properties. Urea assists in getting more complete fixation of the dyes so that a deeper shade is produced.

Dispersing agent: The dispersing agent performs many functions in dyeing. It assists the process of particle size reduction of the dye. It also enables the dye to be formed in the powder formed. When the powder is added to the dye bath it facilitates the reconversion of the powder into dispersion in a fine form in the dye bath through out the dyeing process, in which it is assisted by an additional dispersing agent, which is normally added to the dye bath.

It is seen that the dispersing agent considerably increases the solubility of the dye in water and that different dispersing agents affect the solubility to different extents. Thus, maximum solubilising effect can be conferred on a disperse dye by a particular dispersing agent, which varies with the dye.

Chemical used in Mymun Textiles ltd are as bellow :


Tinovetin TC Anionic Detergent , Wetting agent Pretreatment
Invadine LUN Nonionic Wetting Agent Pretreatment
Invadine DP Leveling Agent, Dispersing Agent PES Dyeing
Invatex CRA Sequestering Agent & Wetting Agent Pretreatment
Tinoclarite CBB Stabilizer Pretreatment
Ciba Flow JET Antifoaming Agent Pretreatment, Dyeing
Primasol JET Anticreasing Agent Pretreatment, Dyeing
Caustic Soda Alkali / To improve fibre cross-section Pretreatment
Hydrogen Peroxide Bleaching /Oxidizing Agent Pretreatment
Invatex PC Hydrogen peroxide Killer Pretreatment
Invatex CS Sequestering Pretreatment
Tinozyme 44L Enzyme Bio polishing
Cibacell DBC Leveling Agent, Wash off (Dye bath conditioner) Dyeing (Cotton)
Irgasol CO-NEW Leveling Agent Dyeing (Cotton)
Lyoprint RG-Gran Mild Oxidizing Agent Dyeing(Cotton)
Uvitex 2B Optical Brightener White Dyeing(Cotton)
Uvitex BHV Optical Brightener White Dyeing(Cotton)
Sapamine FPG Nonionic Softener / To improve handle property After treatment
Tinofix FRD Fixing Agent (Formaldehyde Free) After treatment
Alcamine CWS Anionic Softener After treatment
Cibatex AB-45 Buffer solution / pH control PES Dyeing
Glauber’s Salt Exhausting Agent Dyeing (Cotton)
Soda Ash Alkali / Fixing Agent Dyeing(Cotton), Partial Stripping
Acetic Acid Neutralization of Alkali (For pH control) Pretreatment/Dyeing /After treatment
Dekol SN Mild Sequestering , Washing off, Dye bath leveling After treatment
Cibafix ECO Fixing Agent After treatment
Bleaching Powder Oxidizing Agent Bleaching
Hydrose Reducing Agent Stripping of cotton, Reduction clearing of PES
Carrier MN Carrier PES Dyeing / Partial stripping of PES
Palegal FA-6 Dispersing Agent PES Dyeing
Fulysin FA-S Buffer solution / pH control PES Dyeing
Eriopron OS Washing off PES Dyeing

Uvitex EBF Optical Brightener PES Dyeing

Flow chart diagram of each operation

Process Flow Chart for 100% Cotton:

This is a typical process for 100% cotton fabric dyed to a Bluish pink shade (bleaching , dyeing & rinsing).

Batch No : 284888 Machine No : 04

Batch Date: 09.12.04 Water : 4200 Lit

Order No : 494930 # 8616 Fabric Wt : 508.00 kg

Customer : H & M GSM : 220

Color : Bluish pink Nature Of Fabric : 2×2 rib

Product Coad SI . No. Pre-treatment item G.L % Quantity in Kg
TC 0.3 1 kg 600 gm
LUN 0.2 1 kg 100 gm
CRA 0.5 2 kg 600 gm
CBB 0.2 1 kg 100 gm
Jet 0.1 420 gm
P. Jrt 0.5 2 kg 600 gm
Caustic 2.5 10 kg 500 gm
H2O2 2.5 10kg 500 gm
PC 0.8 3kg 400 gm
A.Acid 1.2 5kg 100 gm
44L 0.7 3kg 600 gm
CRA 0.5 2kg 100 gm
DBC 1.0 4kg 200 gm
Jet 0.1 420 gm
P.Jet 0.5 2kg 100 gm
CO New 0.5 2kg 100 gm
RG 0.2 900 gm
DR Yellow -K2R 0.0044% 25 gm 115 mg
DR Red -K7B 0.215% 1 kg 158 gm
DR Violet -K2R 0.138% 743 gm 102 mg
Salt 25 105 kg
Soda 5.0 21 kg
Acid 1.0 4 kg 200gm
SN 0.5 2 kg 100 gm
A.Acid 0.2 840 gm


At first fabric is loaded to machine and water is fed to maintain. The auxiliaries are transfer at temperature 500 C. And within 3 minutes temp. increased 600 C and add caustic soda. Next 10 minutes temp. raised 850C and add H202 by dozing system. After that temperature raised 1100 C and process run for 25 minutes. Then within 7 min. temperature lowered to 940 C and wash with hot water keep the temperature 900 C. At this stage peroxide killer is added and run for 8 min.

Then washing is done, add acetic acid, keep the temp. 580 C and pH at 4.5. After that add enzyme and treat the material for 40 min. Then temp. raised at 900 C, run for 10 min. with Invatex CRA ( Sequestring Agent ).

At last wash is done and maintained temp. 600, pH 5.7 to make ready the material for dyeing.

Fig : Scheme


At temp 600 C added leveling agent and run 10-15 min. then added high by dozing system for 20 min. After that add salt by dozing progress-1 for 20 min. and the process run for 15 min. Add soda ash by dozing progress-3 for 45 min. and run for 10 min. At this stage sample is taken every 10 min. interval and check the shade. In our process shade was lighter. So added extra dye about 30% overall and again taken sample for shade matching. After being the shade ok the material is washed to remove hydrolyzed dye for 20 min. Then acid wash done to neutralized alkali and to improve shade. Then Dekol SN ( for washing off ) is added according to shade. Finally wash add 450 C and use soften

Fig: Dyeing scheme Process

Flow Chart for white dyeing :

Batch No : 28677 Machine No : 02

Batch Date : 12.12.04 Water : 5600 Lit

Order No : 221153 Fabric Wt : 7000.00 kg

Customer : H & M GSM : 240

Color : White 10-100 Nature Of Fabric: P/I

Product Coad SI . No. Pre-treatment item G.L % Quantity in Kg
A.Acid 0.9 5 kg 40 gm
LUN 0.5 2 kg 800 gm
44L 0.5 3 kg 500 gm
Acid 0.6 3kg 400 gm
TC 0.4 2kg 300 gm
44L 1.0 7kg
TC 0.4 2kg 300 gm