Group MembersM Usman Azeem 3609Syed Qutaiba Bin Tariq 3605M Saqlain Chishti 3577Jahangir Khan Bazai 3617Jaleel Ahmed Arif Hussain

Title Study of pretreatment & Dyeing recipies and role of axillaries used in these processes

Project Supervisor

Miss Lubna Syed

Study program

Section

BS(Textile)

Fall-06

Balochistan University of Information Technology, Engineering and Management Sciences

DEDICATION

We dedicate our project to our grate parents.

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ACKNOWLEDGEMENT

Our first experience of project has been successfully, thanks to the support staff of many friends & colleagues with gratitude. We wish to acknowledge all of them. However, we wish to make special mention of the following:First of all, we thankful to almighty ALLAH for the successful completion of this project. Who gave us strength and power to attain our target. After that we are thankful to our project supervisor Ms. Lubna Syed under whose guideline we were able to complete this project. We are wholeheartedly thankful to her for giving us her value able time & attention & for providing us a systematic way for completing our project in time.We are thankful to H.O.D Dr. Fahim Udin and Chairman Mr. Ali Asgher and all other staff for providing their assistance and guidance at different stages during this project. We are also thankful to the Sapphire Mills ltd. who allow us in their unit to perform our project experiments.We are also very thankful to our vice chancellor Engr. Farooq Ahmed Bazai who gave us an opportunity to present this project.

All Group Members

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Table of contents

Summary of Project

Chapter no 1

Introduction to fibers

Cotton

Types of cotton fibers

Characteristics of cotton

Properties of cotton

Physical properties of cotton

Chemical properties of cotton

Molecular structure

Polyester

Types of polyester

Characteristics of polyester

Cotton polyester blend

Spandex

Spandex Fiber Characteristics

Cotton lycra blend

Chapter no 2

Greige department

Fabric receiving

Report receiving and storage

Inspection

Inspection of faults

Department mechanicals

Winding pporcess

Chapter no 3

Pretreatment department

Singeing

Objectives of singeing

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Methods of singeing

Gas singeing mechanism

Parameters of gas singeing process

Perble Sando Iron works Japan

Osth-off Singeing Machine

Desizing

Oxidative desizing

Role of process axillaries

Enzymatic desizing

Role of process axillaries

Differentiate of process and chemicals

Scouring

Surfactants

Classification of surfactants

Detergents

Emulsifying Agents

Sapphire Mills ltd. Scouring Process

Machine Lay out: Perble Sando Scouring

Bleaching

Sodium Chlorite Bleaching

Sodium Chlorite Bleaching

Mercerization

Chain mercerization

Sapphire mills ltd Mercerization Machine

Mercerizing Fiber Blends

Chapter no 4

Dyeing

Types of dyeing

Reactive dyes

Chemical structure of Reactive dyes

Methods of dyeing of reactive dyes

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Disperse dyes

Application of disperse dyes

Properties of disperse dye

Chemical characteristics and general application conditions

Auxiliaries

Classes of disperse dye

Disperse and Reactive dyes in one bath

Advantages of Disperse dyes

Vat dyes

Chemical structure of vat dyes

Dyeing structure of vat dyes

Machines for continuous dyeing

Machine details of Sapphire Mills ltd. pad-thermosol

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Summary of Project:

The following fibers were studied during our project:

Cotton Polyester and cotton blend Cotton and lycra blend

All experiments and observations were taken on the fabrics used these fibers.

The following processes are discussed

Singeing Desizing Scouring Bleaching Mercerization Dyeing

All fibers mentioned above are tested at different processes with varying the standard conditions and the results are discussed in this booklet.

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Chapter no 1

Introduction to fibers

Cotton

It is a soft, fluffy staple fiber that grows in a boll around the seeds of the cotton plant. Cotton the purest form of cellulose found in nature is the seed hair plants of genus gossypium. The fiber most often is spun into yarn or thread and used to make a soft, breathable textile, which is the most widely, used natural-fiber cloth in clothing today. Many species are grown commercially but there are mainly three types of cotton:

o Type 1 having staple length from about 26-60 mm e.g. Egyptiano Type 2 having staple length from about 13-33 mm e.g. Americano Type 3 having staple length from about 9-25 mm e.g. Asian

Major producers of cotton in world are USA, China, India, Pakistan and other central Asian countries. Mature cotton forms a flat ribbon varying in width from 13-20. Number of convolutions vary from 4-6 per millimeter, reversing in direction per millimeter or so along the fiber.

The normal lot of cotton contains three types of fibers

Mature fiber

Which swell to rod like structure in sodium hydroxide solution with continuous lumens and no well defined convolutions.

Immature fibers

These are the fibers which have not been given time to develop there secondary wall, so some of the proteins remain in the fibers which give lot shade during dyeing.

Dead fibers

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In dead fibers the after swell width is less than one fifth of the maximum ribbon width. They are usually found on mid way b/w two convolutions.

Characteristics of cotton

Cotton, as a natural cellulose fiber, has a lot of characteristics, such as;

Comfortable Soft hand Good absorbency Color retention Prints well Machine-washable Dry-cleanable Good strength Drapes well Easy to handle and sew

Properties of cotton

There are two types of properties that should be described here.

Physical properties of cotton

Fiber length

Fiber length is described as "the average length of the longer one-half of the fibers (upper half mean length)" This measure is taken by scanning a "beard” of parallel fibers through a sensing region. The beard is formed from the fibers taken from the sample, clasped in a holding clamp and combed to align the fibers. Typical lengths of Upland cottons might range from 0.79 to 1.36in. This experiment was done by us during 6th semester, course advisor: Mr. Ahmer Shah.

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Cottons come from the cotton plant; the longer strand types such as Pima or Sea Island produce the finest types of cotton fabrics.

 

Length uniformity

Fiber strength is measured in grams per denier. It is determined as the force necessary to break the beard of fibers, clamped in two sets of jaws, (1/8 inch apart). Typical tensile levels are illustrated. The breaking strength of cotton is about 3.0~4.9 g/denier, and the breaking elongation is about 8~10%.

Color

The color of cotton samples is determined from two parameters: degree of reflectance and yellowness. Degree of reflectance shows the brightness of the sample and yellowness depicts the degree of cotton pigmentation. The color of the fibers is affected by climatic conditions, impact of insects and fungi, type of soil, storage conditions etc. There are five recognized groups of color: white, gray, spotted, tinged, and yellow stained. As the color of cotton deteriorates the process ability of the fibers decreases.

Chemical properties of cotton

Cotton swells in a high humidity environment, in water and in concentrated solutions of certain acids, salts and bases. The swelling effect is usually attributed to the sorption of highly hydrated ions. The moisture regain for cotton is about 7.1~8.5% and the moisture absorption is 7~8%.

Cotton is attacked by hot dilute or cold concentrated acid solutions. Acid hydrolysis of cellulose produces hydro-celluloses. Cold weak acids do not affect it. The fibers show excellent resistance to alkalis. There are a few other solvents that will dissolve cotton completely. One of them is a copper complex of cupramonium hydroxide and cupriethylene diamine.

Cotton degradation is usually attributed to oxidation, hydrolysis or both. Oxidation of cellulose can lead to two types of so-called oxy-cellulose, depending on the environment, in which the oxidation takes place.

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Also, cotton can degrade by exposure to visible and ultraviolet light, especially in the presence of high temperatures around 250~397° C and humidity. Cotton fibers are extremely susceptible to any biological degradation (microorganisms, fungi etc.)

Molecular structure

Cotton is natural fiber. It structure can be described as 1,4 beta–D-glucan i.e. a condensation polymer of beta –D-glucopyranose with 1,4 glycosodic bonds.

The degree of polymerization of cellulose varies with the conditions and depends upon

the nature of soil. It contains the characteristics of both an alcohol and aldehyde under

appropriate conditions as shown below:

Cotton sample

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Sample place here

Polyester

Polyester is a term often defined as “long-chain polymers chemically composed of at least 85% by weight of an ester and a dihydric alcohol and a terephthalic acid”. In other words, it means the linking of several esters within the fibers. Reaction of alcohol with carboxylic acid results in the formation of esters. Polyester fibers, the synthetic fibers, are long chain polymers derived from coal, air, water, and petroleum. They are formed through chemical reaction between an acid and alcohol.

Types of Polyester

The polyester fibers are generally available in two varieties

PET (polyethylene terephthalate) and PCDT (poly-1, 4-cyclohexylene-dimethylene terephthalate).

PET Polyester

For manufacturing PET Polyester, the main raw material is ethylene derived from petroleum. It is oxidized to produce a glycol monomer dihydric alcohol which is further combined with another monomer, terephthalic acid at a high temperature in a vacuum. Polymerization, the chemical process that produces the finished polyester, is done with the help of catalysts. The colorless molten polyester then flows from a slot in a vessel on to a casting wheel and takes shape of a ribbon as it cools to hardness. The polymer thus

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produced is then cut into very small chips, dried to remove all moisture and blended to make it uniform for getting it ready for spinning into yarn.

PCDT Polyester

This variation of polyester is made by condensing terephthalic acid with 1,4-cyclohexane-dimethanol to form poly-1, 4-cyclohexylene-dimethylene terephthalate or the PCDT Polyester. As for PET Polyester, PCDT is processed for melt spinning.

Characteristics of polyester Polyester fabrics and fibers are extremely strong. Polyester is very durable: resistant to most chemicals, stretching and shrinking,

wrinkle resistant, mildew and abrasion resistant.

Polyester is hydrophobic in nature and quick drying. It can be used for insulation by manufacturing hollow fibers.

Polyester retains its shape and hence is good for making outdoor clothing for harsh climates.

It is easily washed and dried.

Cotton Polyester Blend

Cotton polyester blend is a very useful blend in textile industry because it has high rating of desired properties. This blend is mostly used for wearing.

Cotton polyester blend ratio test

Cotton polyester blend ratio can be calculated by dipping the fabric in concentrated or dilute H2SO4 solution.

The sample of the test is positioned below:

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Detection of cotton polyester blend

Cotton polyester blend can be detected by using the reflection of the ultra violet light as polyester refractive index is higher than cotton.

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Sample place

Sample place

Spandex

Spandex, Lycra or elastane is a synthetic fiber known for its exceptional elasticity. Spandex is a lightweight soft, strong and very stretchable. In fact, spandex fiber was developed as an alternative to rubber but has a better quality than it. The name Lycra has also come to be a synonymous of spandex. However, Lycra is the trademark brand but it has become so popular that all the varieties of spandex are popularly referred to as Lycra. It is used to make stretchable clothing such as sportswear. It is used to make stretchable clothing such as sportswear. It is made up of a long chain polymer called polyurethane, which is produced by reacting polyester with a diisocyanate (-NCO) group on both ends. The polymer is converted into a fiber using a dry spinning technique.

Spandex Fiber Characteristics

Can be stretched repeatedly and still recover to very near its original length and shape

Generally, can be stretched more than 500% without breaking Stronger, more durable and higher retractive force than rubber Lightweight, soft, smooth, supple In garments, provides a combination of comfort and fit, prevents bagging

and sagging Heat-settable — facilitates transforming puckered fabrics into flat fabrics,

or flat fabrics into permanent rounded shapes Dye able Resistant to deterioration by body oils, perspiration, lotions or detergents Abrasion resistant When fabrics containing spandex are sewn, the needle causes little or no

damage from “needle cutting” compared to the older types of elastic materials

Available in fiber diameters ranging from 10 denier to 2500 denier Available in clear and opaque luster

Cotton lycra blend sample

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Sample place here

Greige Department

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The fabric comes from the weaving unit in this department. In the gray department the fabric are coming in two forms namely roller form and bale form the packing list are attached with the fabric and with piece detailing. There are two type fabric coming in greige, own fabric and commercial fabric. The main purpose of grey department is inspection of the fabric.

The other purposes of grey fabric are:

1. Fabric receiving2. Report receiving and storage report3. Inspection4. Issuance

Fabric Receiving:

First of all the fabric comes from the weaving mills through transportation. The weaving mill handover the all documents to finishing unit by means of transportation incharge. In these documents all specification of fabric are presented e.g.

1. Quality;2. Bale No; 3. Construction;4. Blend;5. Roll No;6. Selvedge;7. Weight etc.

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1. Report receiving and storage

The collector reports the received fabric to the greige department incharge. The documentation is saved as for record. After that the fabric is forward to storage or for directly inspection.

2. Inspection

The fabric is inspected to find the ratio of errors occur during manufacturing of fabric. In the gray department we have to inspect 10 percent of fabric. These defects are classified into three types:

1. Avoidable and unavoidable

2. Major and minor

3. Mendable and unmendable

While most of the faults in the fabric are avoidable some are unavoidable such as certain floats/smashes. Faults such as weft crack is considered to be a minor if it is within 1-2 cm while the same faults is major when it is more than 2cm. Certain defects such as isolated snarls could be mended while the others such as big cracks are un-mendable.

The most common or general faults are mentioned below:

i. Contamination : Presence of the any other fibers along with the original fibers in the fabric is called contamination. Mainly polypropylene, hair, jute etc. are some common contaminations.

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ii. Cockled yarn : Fluff or any material pressed by machine in warp or end is called cockled yarn. It forms hard surface.

iii. Color variation : At some places color is found different then the actual one.

iv. Oily weft : When weft or pick yarn is oily then it is called oily weft.

v. Black end : When end or warp is black may be due to oil is called black end.

vi. Count variation : In this case warp or weft may be thick or thin then the count shown in the construction. In this case cloudy like appearance occurs.

vii. Courses pick: One thick pick or weft is called course pick.

Some mechanical faults are given below:

i. Short miss pick : If pick or weft is missing at any point than it is called short miss pick.

ii. Short double pick : In this case two yarns in pick are found for short distance.

iii. Short end : Any warp or end may be missing.

iv. Double end : In this case double yarn is found in warp direction rather than the single one.

v. Miss pick : A pick or weft yarn is missing.

vi. Double pick : Double weft yarn is inserted by loom in a single stroke.

vii. Starting mark : When loom starts after a short stoppage it produces a pattern on fabric in weft direction called starting mark.

viii. Wrapping marks : It is just like starting mark but here the surface become very hard on weft side,

ix. Oil stains : It is the spot of oil dropped on the fabric from any machine part.

x. Loose ends : Warp yarn or end comes out of fabric and not properly interlaced, it does not remain straight and goes in zigzag way.

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xi. Sizing stains : It is like oily stain but more opaque then oily stain.

Some important mending faults are mentioned below:

i. Hanging thread : Any thread hanging in the fabric is called hanging thread.

ii. Mending : If slub is taken out or kink is pulled out then a space appears in fabric and called mending fault.

There are some faults may occur in selvedges also, these are given below:

i. Curled selvedge : caused due to incorrect balance of cloth structure between body and selvedge.

ii. Cut/torn or burst selvage : it is due to selvedge sticking to emery roller or damages caused by temple roller.

iii. Loopy selvedge : when the selvedge or cut the race board felt at the reed and the weft is caught on this groove when the slay beats up.

iv. Rugged or ragged selvedge : when the variations in tension of the selvedge ends.

v. Slacked selvedge: caused due the incorrect balance of cloth structure between the body and the selvedge.

vi. Tight selvedge: caused due to incorrect balance of structure between body and selvedge, selvedge yarns woven at high tension.

vii. Uneven selvedge : when variation in weft tension, lack of control on number of selvedge ends uneven selvedge is produced.

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Analysis Of Faults

The methods employed for analysis of fabric defects are

1. First piece inspection

2. Grey inspection

3. Point rate system

1. First piece inspection

The first piece of the newly gated loom is taken to the grey folding departments and is inspected fir design verifications. The report is immediately sent to the weaving department and if there is any defect the necessary changes are made.

2. Grey inspection

Fabrics are tested in grey state after weaving. In the grey inspection the fabric faults are identified and mended if they are mendable.

3. Point rate system

It is an American system. Two most commonly used point rate systems are

4-point rate system

10-point rate system.

4-point system

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Given by American standard ASTM, the test method describes a procedure to establish a numerical designation for grading of fabrics from a visual inspection. This system does not establish a quality level for a given product, but rather provides a means of defining defects according to their severity by assigning demerit point values.

Length of defect Points

3 inches or less 1

3 - 6 inches 2

6 - 9 inches 3

9 inches 4

Points to be remembered while using 4-point system are:

1. No running yard shall be penalized more than 4 points for warp and weft faults.

2. For Fabric width exceeding 64"-66",Maximum penalty points can be increased above 4 per linear yard in proportion to the

width.

3. Defects appearing within one inch of either edge shall be disregarded.

4. Any hole other than a pin hole shall be considered a major defect and assigned 4 points for penalty.

Issuance:

According to production planning and control department the production planning card is send to greige department according to this card the fabric is unroll and send to pretreatment department.

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Department mechanicals:

INSPECTION FRAMES

No of machines : 3

Company : AL-HADDID (PAKISTAN)

ROLLING & UN-ROLLING MACHINES

No o machines : 2

Company : HSING CHENG (TAIWAN)

Winding process:

In this process the fabric are wind on batch’s because they are suitable for further process. The winding is achieved through the winding machine because the fabric are in roll or bale form they are difficult to process therefore we are done winding and suitable for further process. And forward to pretreatment department.

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Inspection frame Al-HADID

Singeing

This is usually the first stage in pre-treatment; consist of destroying by burning all the tufts, fibers and hairs protruding form the surface of the material (yarn and fabric). There by giving it smooth and cleaning face. Singeing is generally done o grey goods before any other treatment. The fabric is singed on one or both sides by passing either over plates or heated cylinder or by gas flame.

Objectives of singeing:

Surface hair traps air in the fabric when it is immerged in water. This means that it takes longer time for water to enter the fabric, singeing therefore indirectly helps to increase the fabric wet ability.

To prominent the woven structure of the fabric. To create smooth surface for printing. To prevent firstly or cloudy after dyeing.

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To prevent or minimize the tending of landed fabrics composed of cellulose and synthetic fiber (mainly polyester) the form pills after abrasion during usage.

Methods of singeing:

Usually three types of singeing can be carried out:

i. Plate Singeing Machine.ii. Rotary Singing Machine.

iii. Gas Singeing Machine.

In Sapphire only Gas singing process is done so it is discussed below

Gas singeing machine:

Gas Singeing is intended for single and double face singeing of fabric with passes through the guide roller. Then in brushing zone which rotate in the sense opposite to fabric to be singed. The brushes are placed in a special chamber from which dust and fluff removed form the fabric, which are further exhausted by a fan.

Then the fabric passes over gas burner with ceramics nozzles where singing is covered out. Coming out of the gas singeing machine a box containing water. This bath may also contain desizing agent. In this way after singeing we can desize and batched the fabric.

In Sapphire mills ltd. Single action machine, singe only, is installed. Machine specifications are given below:

Parameters of gas singeing process

The parameters which are belong the singeing is following

1. Flame height2. Flame Intensity3. Flame Distance4. Flame angle

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1. Flame height

The height is of flame is same to every fabric so its should be common and height is 6 inches

2. Flame Intensity

The are three position of flame intensity in machine which are differ from fibers the position are following

Position1 Position2 Position3

I. Position1

Position1 is not use in machine due to draw backs. These draw backs are:

In this position the flame is directly in contact with fabric and metal roller due to which fabric damages and the roller heats up.

It has fewer angles between flame and fabric and has no medium for flame to cross the fabric surface.

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II. Position2

Position2 is used for polyesters blends with lycra and all type of cotton blends. In this position the flame is in angle with the roller about 45-60’ and reflect its surface which burns only cotton hairiness.

III. Position3

Position3 only use for cotton in this positions the flame crosses the fabric surface and then burn the hairiness.

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Sapphire mills ltd’s OSTH-OFF machine position 3 is shown below:

3. Flame Distance

The distance of flame and fabric is same for all type of fabrics the distance is 25 – 30mm

4. Flame angle

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The angle is differ by type of fiber its should be minimum 20 and maximum 30

For cotton (Heavy Quality):

The 20° is used for pure cotton

For cotton (Fine Quality):

25° angle is used for the fine quality cotton.

For polyester + Lycra:

30° angle is used for polyester and lycra blend.

Types of Machines

There are two types of singeing machines are installed in sapphire

Perble Sando Iron works Japan

Osth-Off 423260 Wuppertal Germany

Perble Sando Iron works Japan

It is a continuous type pretreatment machine. Singeing is also done on this machine. In this machine firstly the fabric is dried through steam rollers for maintaining fabric moisture. If fabric has more moisture in its surface then singeing objectives can’t be achieved and if the fabric is more dried then there are possibilities of burning of fabric. After the steam rollers, there are six brushing rollers. These rollers remove the protruding fibers which are loosely held on the fabric surface and which fibers, these rollers can’t remove because they have strong relation with fabric surface, only emboss

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those protruding fibers which are burnt in further processings singeing.In Sapphire Mills ltd. gas singeing is in process. Gas flames are used to singe the fabric. Details of singeing process are mentioned above. After singeing in Perble Sando, after singeing, the fabric is washed with simple water.

Perble Sando Singe machine

Parameters

These are following parameters

Machine Speed 50-150m/min Chamber temp 40°-42°C Flame Pressure 23mbar Flame tube temp is controlled by water circulation Flame intensity 30-60Hz Flame ratio 80% Air – 20% Natural gas

Different internal parts of Perble Sando singe machine are shown below in figures:

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Flames positions can easily be seen in this diagram.

Brushing rollers

Osth-off Singeing Machine

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It is a semi continuous machine. It is an advanced machine in which singeing, desizing and bleaching process can be done. In this machine singeing is done by gas flame. Single and double sided singe can be done.

Here in OSTH-OFF machine, singeing is done in any of three positions, mentioned above. Selection of flame position and angle depends upon the fabric quality which has to be processed. Physical diagram of Sapphire Mills Ltd is shown below:

After singeing, the fabric can also be desized. Enzymatic desizing is done on this machine. For the application, the fabric is dipped in a bath containing enzymes at specific temperature. For the proper reaction and complete removal of sizing agent, the fabric is wound on a batch and is rotated for about 8-10 hours

Parameters

These are following parameters

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Machine Speed 50-150m/min Chamber Temp 40°-42°C Flame Pressure 23mbar Flame tube temp is controlled by water circulation

Advancement of this machine is that it can process singeing, Desizing as well as cold Bleaching

Recipe no 1

Machine OSTHOFF

Quality 16*12/120*60

Blend 100% Cotton

Process Singe + Desize

Speed/min 80 m/min

Flame 23 mbar

Position 3

PP-1 (bar/ton) 2 bar/ton

Temp (‘C) S-1 85

PP-2 (bar/ton) 1.2 bar/ton

Temp (‘C) S-2 85

pH S-2 5.5-6.5

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Explanation:

Recipe for every quality or every different fabric is different. Recipe depends upon the weight per unit of fabric. Here for the given quality machine speed should be maintained at 80 m/min. if this optimized speed is varies from the given fabric, it can cause a lot of damages i.e. if speed is decreased from the limit, the fabric may burn and if the speed increases, it might result in irregular singeing. Now if selection of flame position is discussed, it is also depends upon the fabric quality as discussed earlier. Generally in case of 100% cotton position 3 is preferred. In OSTH-OFF singeing machine, enzymatic desizing is done. For this purpose, the desizing material is applied to the fabric and left for enzyme reaction for about eight hours in batch form. This batch with desizing material (enzymes) is rotated continually for eight hours as for better and uniform application. So this is important to note that how much enzymes are applied on which quality, heavy or light quality. So pad pressures are also very important to be maintained in the whole application process. For the given quality pad pressures are optimized at 2bar/ton and 1.2bar/ton.

Recipe no 2:

Machine OSTHOFF

Quality 16*162/88*52

Blend 100% cotton

Process Singe + Desize

Speed/min 80 m/min

Flame 23 mbar

Position 3

PP-1 (bar/ton) 2 bar/ton

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PP-2 (bar/ton) 1.2 bar/ton

Temp (‘C) S-1 85

Temp (‘C) S-2 80

pH S-2 6-7

Recipe no 3:

Machine OSTHOFF

Quality 32/2 comb*24/2comb/92*41

Blend 100% cotton

Speed/min 70 m/min

Flame 23 mbar

Position 3

PP-1 (bar/ton) -

PP-2 (bar/ton) -

Temp (‘C) S-1 -

Temp (‘C) S-2 -

pH S-2 -

Explanation:

Here in this process, only singeing process is being done on OSTH-OFF machine. That’s why there are no pad pressures, temperatures and power of hydrogen mentioned.

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Recipe no 4:

Machine OSTHOFF

Quality 14*14 82*50

Blend 65% polyester, 35% cotton

Process Dry singe

Speed/min 130 m/min

Flame 23 m bar

Position 3

PP-1 (bar/ton) -

PP-2 (bar/ton) -

Temp (‘C) S-1 -

Temp (‘C) S-2 -

Remarks

Recipe no 5:

Machine OSTHOFF

Quality 10*6/64*48

Blend 100% cotton

Process Dry singe

Speed/min 80 m/min

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Flame 23m bar

Position 3

PP-1 (bar/ton) -

PP-2 (bar/ton) -

Temp (‘C) S-1 -

Temp (‘C) S-2 -

pH S-2 -

Recipe no 6:

Machine OSTH-OFF

Quality 16*12/120*60

Process Singe + Desize

Speed/min 80 m/min

Flame 23 mbar

Position 3

PP-1 (bar/ton) 2 bar/ton

PP-2 (bar/ton) 1 bar/ton

Temp (‘C) S-1 85

Temp (‘C) S-2 85

pH S-2 5.5-6.5

Rotation time (min.) 8 hrs

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DESIZING

The process which removes the sizing material in the grey fabric is called the Desizng process. When fabric is woven before the warp end is coated with the material (starch) it give the strength in the end which bear the looms forces and reduction in the broken of threads during weaving process. Then this material should be removed if it not removed yet it’s present on the fabric and make problems in dyeing. The desizing process is depending upon the sizing material which used before the weaving knows the properties of sizing material we set the desizing agents and process. In sizing material there is always glucose and cellulose is used. There is three types of desizing is present in textile sector.

Acid Desizing Oxidative Desizing Enzymatic Desizing

1. Oxidative Desizing

It’s also the one of the good technique in textile sector to remove the sizing material. In this technique used the oxidative chemicals like sodiumpersulphate (Na2S2O8) sodium hypochlorite, sodiumhypobromite. This chemical takes part of reaction solublizing group (ONa+). Which impact the sizing material and remove the sizing material by help of water. In oxidative desizing there is only heavy quality will be treated because it’s high oxidative agent and damage the light quality and remarks is pin hole in it. The reaction open the hydro glucose rings at 2,3 hydroxyls converting into carboxylic acid. Which is soluble in water and starch is removed from fabric. We done practice on the oxidative agents the agents which we are used is the sodiumpersulphate. The oxidative desizing mostly done on the perbale sando machine which is continous machine and desizing chamber is placed after the singeing. after singeing the fabric is proceeding to saturators. There are four hot washes for the better application. The basic purpose of hot saturators is to increase the fabric temperature, as the desizer is more likely to react in high temperature conditions. Temperature for these hot wash is 90°-95°C. After hot washes the chemical is applied by means of a trough. In trough, sodium persulphate, Felosan NKB, acetic acid, Heptol B-95 or VL is used. These chemicals have their own application.

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After it there is 3 cold washer which removed the soluble material and the process is done

For 100% cotton 16*16/58*12:

Chemicals g/l Temp/PH

Sodiumpersulphate 1 90’C/4.5-5.5

NKB 1

Acetic Acid 0.4

B-95 2

ROLE OF PROCESS AUXILARIES:

i. ACETIC ACID:

Acetic acid is a weak acid. pH is controlled by this acid during process. The chemical formula of acetic acid is the CH3COOH. The PH of acetic acid is the 5-6 which is very useful to the oxidative agents. The Titration is placed after each compellation of Liquor because its good to make precipitate in the water.

ii. Felosan NKB:

It is a soaping agent. It’s manufacture by the CHT chemical company. It’s give the soaping properties during the process which remove the starch cleanly in the farbric. Synergetic mixture of modified fatty alcohol alkoxlyates. pH-value 7.0 – 8.0. ALKAPOL NKB has a good stability in usual concentrations toacids, alkalis, metal salts as well as oxidation agents, reduction agents and hardening agents of the water.

ALKAPOL NKB is also compatible with non ionic, anionic and cationic products. The product is not sensitive to frost.

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iii. Heptol B-95/VL:

It is a cleaning agent. It is used to clean the scattering from the rollers, caused by the fabric passage form these rollers. If this chemical not use in the process the pasing of fabric is must be difficult on rollers.

2. Enzymatic Desizing

Enzymes are the bacteria which are not be lived or dead but work in suitable condition and temperature. There is two types of enzymes

Hot Cold

Hot enzymes are those who works only in hot condition and temp like the 90-95’c thy only activate on this temperature.

Cold enzymes are those whose works only in 25-30’c and it activate and suitable for working in this conditions.

Enzymatic desizing is the process in which enzymes are used in it and the starch is removed by the help of this. This technique is very suitable in textile sector and mostly used in the industry. It’s very fast process and also not toxic to environment. In Enzymes the main unit which degrade the cellulose is the amalyse because the sizing agent is used is amaloyse. There is three sources to get the amalyse

Malt Pancreatic Bacterial

Bacterial are form the sources but it only works in condition it’s very useful for desizing process and mostly alpha amalyse is present in it.

Enzyme has property it eat the starch by giving its time and no toxic is produce in it. We done our practice on the enzymatic desizing there is JRL is used in it. Osthoff singe machine done the desizing process because it is batchwise process. In this machine there is two tanks is presnt which capacity are the 500 ml in each tank and after it there is making of batch and it give the time of 8hr that removed the all starch in it when it give time the batch should be revolve it because all the starch is removed in it. When we used

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the enzymatic desizing there should be carefull the following parameters which are desizing chemical is based on it. : after singeing the fabric is proceed to saturated portion. There are two saturators. In which the temperature is 40°-42° C. If Osth-Off machine is used of oxidative desizing, cold bleaching should be done with this process. Saturator capacity is 500 liters/saturator. Stock tank at normal condition is 1000 litters but max. capacity is 2000 litters. Machine speed is 50-150m/min. Dancer rollers are used for proper tensioning. There are two nipping points in Osth-Off machine. Fabric is dipped in each saturator for 8 times for better chemical application. Treated fabric is wound on batcher

PH TEMP Type of Enzyme

For 100% cotton 20*20/100*20

Chemicals g/l Temp/PH

JRL 2 100’C/ 4-5.5

NKB 1

Acetic Acid/ Formic Acid

0.6

B-95 2

After the time there is should be wash in hot water at temp of 90’c If there is presence of any sizng material which removed by the hot water Time should be 10min

ROLE OF PROCESS AUXILARIES:

I. Formic Acid:

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It’s optional acid in the process but its uses is more than the acetic acid because it give accurate PH value for enzyme. PH is very important factor in enzyme cases if PH is not stable the enzyme is also not activated properly. Due to the accuracy in PH the process its give te better result. The PH is 5 - 5.5. The chemical formula is the CHCOOH and manufacture company is the calariant.

II. Felosan NKB:

It is a soaping agent. It’s manufacture by the CHT chemical company. It’s give the soaping properties during the process which remove the starch cleanly in the farbric. Synergetic mixture of modified fatty alcohol alkoxlyates. pH-value 7.0 – 8.0. ALKAPOL NKB has a good stability in usual concentrations toacids, alkalis, metal salts as well as oxidation agents, reduction agents and hardening agents of the water.

ALKAPOL NKB is also compatible with non ionic, anionic and cationic products.The product is not sensitive to frost.

III. Heptol B-95/VL:

It is a cleaning agent. It is used to clean the scattering from the rollers, caused by the fabric passage form these rollers. If this chemical not use in the process the pasing of fabric is must be difficult on rollers.

Differentiate of process and chemicals:

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45

PROCESS ENZYAMTIC OXIDATIVE

CHEMICALS JRL SPS

AUXILLARIES FELSON NKB FELSON NKB

ACID FORMIC ACID ACETIC ACID

OTHER AUXILLARIES

B - 95 B- 95

PH 5 – 5.5 5 – 6.5

REMARKS SEMI CONTINOUS CONTINOUS

PROBLEMS PH MAINTAINANCE PARTICIPATES

DIFFERENCE TAKE 8 HRS, BATCH MADE

CONTINOUS, OTHER PROCESS DONE LIKE SCOURING

EXPERINCE & OPINION

COMPLETE DESIZING

SCOURING

Scouring is a process in which we remove the foreign material of any kind on the fabric surface and as well as from the interior structure of it.Natural fibers contain oils, fats, waxes, minerals, leafy matter and motes as impurities that interfere with dyeing and finishing. Synthetic fibers contain producer spin finishes, coning oils and/or knitting oils. Mill grease used to lubricate processing equipment mill dirt, temporary fabric markings and the like may contaminate fabrics as they are being produced. The process of removing these impurities is called Scouring. Even though these impurities are not soluble in water, they can be removed by Extraction, dissolving the impurities in organic solvents,

Scouring plant of Sapphire Mills ltd.

Two main processes of scouring to achieve its objectives:

Emulsification:

Forming stable suspensions of the impurities in water and

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Soaponification:

Converting contaminates into water soluble components.

SURFACTANTS

The word Surfactant is coined from the expression "surface active agent".As the phrase implies, a surfactant molecule possesses surface activity, a property associated with the chemical structure of the molecule. The characteristic feature of a surfactant molecule is its two ends attached by a covalent bond. The two ends have diametrically opposed polarities. The non-polar end is lyophilic (strongly attracted to organic molecules) while the strongly polar end is lyophobic (having little attraction for organic molecules) yet strongly hydrophilic (water loving). Duality of polarity causes the molecule to align itself with respect to the polar nature of the surfaces it contacts.

Physical Chemistry of Surfactant Solutions

When soap (sodium oleate) molecules are added to pure water one molecule at a time, the first few molecules align at the air/water interface and the hydrocarbon tails orient toward air. The driving force for this alignment is the non-polar tail seeking to associate them with the most non-polar interface it can find, in this case air. As additional molecules are added, they too will align at the water/air interface until all of the surface area is completely packed. As more molecules are added, they are forced into the bulk of the water, floating about as individual a molecule until a saturation level is reached. At this point, called the Critical Micelle Concentration, soap molecules agglomerate into water soluble clumps (Micelles), where the lyophobic tails are associated with themselves and the hydrophilic heads are surrounded by water molecules. The first beaker represents close packing of surfactant molecules at the surface. The second beaker represents the condition before micelle formation. The third beaker shows the formation of micelles.

Classification of surfactants

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Surfactants are classified according to use, to ionic charge and to chemical Structure. By Use Wetting Agents: The ability of a liquid to spread on a smooth solid surface is dependent on the polar nature of the solid and the surface tension of the liquid. A non-polar solid surface such as paraffin wax or Teflon will cause a drop of pure water to bead-up and not spread. Water containing surfactants on the other hand will easily spread on paraffin surfaces and have lower contact angles on Teflon. Surfactants used this way are called wetting agents, or penetrating agents when used to wet out repellent fabrics. Penetration of fabrics is a function of surface wetting, however fabric assemblies have a volume of air entrapped in the void formed spaces. Before a liquid can move in, the air must move out. Penetrates facilitate this process.

Detergents

These are surfactants that help remove soils from solid surfaces. Over and above reducing water's surface tension, detergents must adsorb onto the soils surface to aid in spontaneous release. Detergents must also keep the soil suspended to prevent redeposit ion.

Emulsifying Agents:

These are surfactants that convert water-insoluble oils into stable, aqueous suspensions. The lyophobic part of the surfactant molecule is absorbed by the oil droplet and the lyophobic head is oriented outward, surrounding the droplet with a hydrophilic sheath. Ionic surfactants add another dimension to the stability of emulsions; they set up a charge-charge repulsion field which adds to keeping the droplets separated.

By Ionic Charge

Anionic: Those that develop a negative charge on the water solubilizing end.

Cationic: Those that develop a positive charge on the water solubilizing end.

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Non-Ionic: Those that develop no ionic charge on the water solubilizing end.

Amphoteric: Those that have both a positive and negative charged group on the molecule

Sapphire Mills ltd. Scouring Process:

In sapphire there is caustic soda is used for scouring, with scouring sometimes the oxidative desizing agent is present in it. If there is enzymatic desizing the scouring is done individually and alone caustic soda, Heptol B-95, NKB is present in the tough. During scouring, the titration is of the solution is done at the intervals of approx 10min. There is concept that more titration more it is advantageous and the process comes reliable. The concept of titration is that it controls the precipitate formation in the tough and water keeps good for the process. For titration there is the KMNO4, dil H2SO4 used. Both are strong acid and base. In sapphire the scouring is done on the perble sando machine where is parameters is checked and the machine description is given below. In sapphire the scouring is done by means of a J-Box. For this purpose, first of all the fabric is passed to saturators. In these washes the temperature is about 95°C as the fabric is preparing for chemical treatment. Now chemical is applied on the fabric by means of a trough.In j-box there is time needed for the further operation but this time varies by changing in fabric quality even by changing the fiber type but the time is about 23-28 min it means that the fabric is placed in the j-box and treated with steam at temperature, approx 100’C and fabric is under treatment of steam. This steam energizes the ions of scouring chemicals and chemical action is ready to take control.

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J-Box and saturators of sapphire

Machine Lay out: Perble Sando Scouring

Scouring machine parts;Cold wash;Scouring chemical bath;Steamer (J-box);Washers;

4 hot washers

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Internal part of J-box

Fabric passage from the inner side of J-box

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Inner part of J-box

Inner part of J-box

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Recipe no1:

Quality 16*162/88*52Blend 100% cottonMachine & process

Perble, Singe+Desize (osth-off) Machine Conditions

Titration NaOH

Recipe Saturator Chamber saturator ChamberCaustic (NaOH) 80 g/l 150 kg Chamber

time30 min 84-86

g/lSodium persulphate

- 35 kg Boil box temp

99’C

Felosan NKB 2 g/l 20 kg Top part temp

98’C

Heptol B-95 1 g/l 10 kg Pad pressure 7-1Level 4 (ton)

Recipe no 2:

Quality 16*12/120*60Blend 100% cottonMachine&Process Perble, Singe+Desize

(osth-off) Machine ConditionsTitration NaOH

Recipe Saturator Chamber saturator ChamberCaustic (NaOH) 80 g/l 150 kg Chamber

time29 min 84-86

g/lSodium persulphate

5% 35 kg Boil box temp

99’C

Felosan NKB 2 g/l 20 kg Top part temp

98’C

53

Heptol B-95 1 g/l 10 kg Pad pressure

7-1

Level 4 (ton)

Recipe no 3:

Quality 20*20/100*50Blend 100% cottonMachine&Process Perble, Singe+Desize

(osth-off) Machine ConditionsTitration NaOH

Recipe Saturator Chamber saturator ChamberCaustic (NaOH) 80 g/l 150 kg Chamber

time30 min 84-86

g/lSodium persulphate

- 35 kg Boil box temp

99’C

Felosan NKB 2 g/l 20 kg Top part temp

98’C

Heptol B-95 1 g/l 10 kg Pad pressure

7-1

Level 4 (ton)

Recipe no 4:

Quality 20*12(70D)/104*48

Blend 98%cotton 2%LycraMachine&Process

Perble, Singe+Desize (osth-off)Machine Conditions

Titration NaOH

Recipe Saturator Chamber saturator ChamberCaustic (NaOH) 80 g/l 150 kg Chamber

time30 min

73-74 g/l

Sodium persulphate

- 35 kg Boil box temp

99’C

Felosan NKB 2 g/l 20 kg Top part temp

98’C

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Heptol B-95 1 g/l 10 kg Pad pressure

7-1

Level 4 (ton)

Recipe no 5:

Quality 20*12(70D)/104*48

Blend 98%cotton 2%LycraMachine&Process

Perble, Singe + DesizeMachine Conditions

Titration NaOH

Recipe Saturator Chamber saturator ChamberCaustic (NaOH) 80 g/l 150 kg Chamber

time30 min

73-74 g/l

Sodium persulphate

20 g/l 35 kg Boil box temp

99’C

Felosan NKB 2 g/l 20 kg Top part temp

98’C

Heptol B-95 1 g/l 10 kg Pad pressure

7-1

Level 4 (ton)

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BLEACHING

Scouring generally removes all impurities from the cotton except colouring matters therefore bleaching is done after scouring. This is the process in which natural and other colouring matters are discoloured either with reducing or oxidising agents. Almost invariably oxidising agents give a more permanent white.If cloth is to be finished white or is to be given surface ornamentation, all natural colours must be removed by bleaching. This is also necessary if discoloration or stains have occurred during the previous manufacturing process. Bleaching can be done in yarn stage as well as in the constructed fabric. When cloth has been bleached for finishing it is called bleached goods. All bleaching processes reduce the strength of the fibre. If durability is more important then appearance; the consumer should select greige goods rather than bleached material. With continued laundering, greige goods will gradually whiten.There are some commonly used bleaching agents.

Reducing bleaching agents

SO2, NaHSO3, Na2S2O4

Oxidizing bleaching agents

KMnO4 Cl2 and ClO2 Na2O2 NaOCl and NaClO2 (Sapphire)

BaO2 Ca(OCl)2 H2O2 (Sapphire)

Sodium Chlorite Bleaching:

Sodium chlorite was actually introduced for bleaching of synthetic fibres but now it is found that it can be used for bleaching cotton goods.Bleaching activity of sodium chlorite is highly dependent on pH, Generation of different degradation products and rate of decomposition may vary with the change in pH.Bleaching occurs most rapidly below pH 1-2, rapidly at pH 2-3, and the rate decreases as the pH increases.

General Recipe:

NaC1O2 10 g/l

Sodium chlorite, bleaching agent.HOOCH 2g/lFormic aid, to maintain pH at 2.2-3.5CH3 OH 1g/lMethyl alcohol, buffer to maintain pH

Chamber time 22minBoil Box Temp. 95-99Top Part Temp. 95-98Pad Pressure 7…..1Saturator Temp. 40

Saturator:

At the back of the Perble tanks are given for the chemical preparation. Recipe chemicals are fed to these tanks and pipe lines connect these tanks to the metering pumps, filters and to the saturator.Fabric to be bleached is impregnated with the sodium chlorite solution and squeezed by a padder to remove the excess liquor and to ensure the even pickup. After impregnation fabric goes to the chlorite chamber

Chamber:

Chlorite chamber is slightly different from scouring chamber. It is completely closed chamber having no drainage for chemicals, no recycling of liquor due to the highly toxic nature of chlorine dioxide, capacity of this chamber less then scouring chamber. Chlorite chamber is coated from inside with titanium to prevent any damage by the corrosive nature of chlorine compounds, Excess of chlorine gas is produced in this chamber which is collected and shifted away from the working area through ducts, where it is processed. Chlorite chamber has no plate for pilling the fabric but it has wings which control the movement of fabric. After completion of required dwell time fabric goes to washing baths for washing.Specifications are as given Fabric Capacity 2800 meter Dwell time 20-25 min

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Temperature 97-100 °C Under liquor level 3.5-4.0 ton

De-chlorination Chamber:

Treatment of liberated chlorine gas is necessary to minimize any health hazards. De-chlorination chamber is used for this treatment. Treatment is done by showering of hydrogen peroxide and sodium hydroxide to the chlorine gas. Reaction is given as under,

For chlorine dioxide

ClO2 + H2 O2 ———> HCl + H2ONaOH + HCl ———> NaCl + H2O

For chlorine

Cl2 + H2 O2 + 2 NaOH ———> NaCl + H2O+ O2

Washing Baths:

After chlorite chamber fabric enters into washing baths. In first washing bath an anti chlor treatment is given to the fabric with HT enzyme, which removes chlorine from the fabric. After anti chlor treatment fabric goes to next washers where it is washed with hot water at temperature of 80-90 ºC

Bleaching with H2O2:

In case of heavy quality fabric or fabric having lycra blend, bleaching is carried out with hydrogen peroxide. In most organic and inorganic compounds which contain oxygen (e.g. water, metal oxides, alcohols, carbonates) the oxygen atom is bounded to other type of atoms. The oxygen in these atoms can not easily be split off. On the other hand oxygen in all the peroxides and per salts is bonded such that two oxygen atoms are bonded to each other. This linkage in these compounds can be much easily broken librating one atom as active oxygen. Hydrogen peroxide is used as bleaching agent on natural cellulose (cotton, linen, jute) as well as the protein fibers (wool, silk) etc. it is also effective on blended fibers as pc.

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Bleaching Action:

It is generally agreed that the first stage is an ionization to form per hydroxyl ion (HOO-)H2O2 ——> HOO- + H+

The formation of per hydroxyl ions is favored by alkaline conditions and so most H2O2

bleaching is carried out under this condition.A number of reactions can also occur, particularly in presence of metallic catalysts, to convert it into water and molecular oxygen.2H2O2 ——> 2H2O + O2

+

This break down is more rapid in highly alkaline solution. The molecular oxygen escapes from the bleach solution reducing the bleaching effect and intermediates in its formation are very active and can cause fiber damage. Selection of alkali to be used in peroxide bleaching is dependent on the fibers or blend being bleached. Sodium hydroxide (caustic soda) and sodium carbonate (soda ash) will be used generally on cellulose fibers.

General Recipe:

H2 O2 18 – 38 g/lBleaching agentFelosan 1.5 – 2 g/lWetting agent Heptol B-95 1 – 3 g/lSequestering agentNaOH 3 – 10 g/lActivatorStabilizer SIFA 2 – 8 g/l

Machine parameters:

Chamber Time 20-25 minBoil Box Temp. 95-99

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Top Part Temp. 95-98Pad Pressure 7 m-barSaturator Temp. 40-45

Saturator:

After passing from cold washer the fabric enters into hydrogen peroxide saturator, which contains the following chemicals.

1. H2 O2 (bleaching agent)2. Felosan NKB (wetting agent) 3. Heptol B-95 (sequestering agent) to remove iron particles4. NaOH (caustic)5. Stabilizer SIFA

Chamber:From saturator, saturated fabric enters into peroxide bleaching chamber and here bleaching of fabric occurs. This chamber is similar to the chlorite chamber capacity wise and process wise but the chemicals are different. Here we use hydrogen peroxide as bleaching agent.

Washing Baths:After coming-out from peroxide bleaching chamber, we pass the fabric from four hot washers and then finally pass to last chamber, which has neutralizing agent.Temp of 1st,2nd & 3rd Washers are 98 C and 4th is 60 C.Pad Pressure is 1.6 Ton.

Drying:3 columns of drying cylinders are used.12 cylinders per column.Temp or pressure of total 36 cylinders is 0.3 MPa each.

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Mercerization

The process, in which we improve absorbency of the fabric, the dimensional stability and control its shrinkage. This is done by the help of strong alkali (NAOH). In Sapphire the NaOH is main chemical for mercerization.

Sando mercerization machine line

This process gives the strength, dimensional stability and smoothness to fabric. In process NAOH, salt, caustic, soap is used.Mercerizing require cotton to be treated with concentrated solutions of sodium hydroxide (caustic soda). Mercerization requires higher concentrations of caustic soda (19 to 26 % solutions). The procedure is effective in completing the removal of motes that may have escaped the scouring and bleaching steps. Caustic soda solution swells cotton fibers breaking hydrogen bonds and weak van der Waal forces between cellulose chains. The expanded, freed chains rearrange and re-orient and when the caustic soda is removed, the chains form new bonds in the reorganized state. When done tensionless, the cotton fiber swells, the cross section becomes thicker and the length is shortened. Because of fiber thickening, the fabric becomes denser, stronger and more elastic. Held under tension, the coiled shape of the fiber is straightened and the characteristic lumen almost disappears. The fibers become permanently round and rod like in cross section and the fiber surface is smoother. Decrease in surface area reduces light scattering, adding to fiber luster. Tension increases alignment of cellulose chains which results in

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more uniform reflection of light. The strength of the fiber is increased about 35 %. The fiber also becomes more absorbent.The cellulose crystal unit cell changes from cellulose I to cellulose II and the amorphous area become more open, therefore more accessible to water, dyes and chemicals. Mercerized cotton will absorb more dye than un-mercerized cotton and in addition, yields an increase in color value a given quantity of dye.The amount of fiber shrinkage is a measure of the effectiveness of caustic soda's ability to swell cotton.

Types of mercerization

Chain Chain less

Chain Mercerizing

Chain mercerizing is done on a range equipped with tenter chains for tension control. The range consists of a pad mangle followed by a set of timing cans and then a clip tenter frame. Fresh water cascades onto the fabric to remove the caustic soda as it is held tensioned in the tenter frame, . The length of the frame must match the range speed and assure that the caustic level is reduced below 3% before tensions are released. The tenter frame is followed by a series of open-width wash boxes which further reduces the caustic level. Acetic acid is in one of the last boxes to complete the neutralization of caustic.

Procedure

1. Apply 22 to 25 % (48 - 54" Tw) caustic at the pad mangle at 100 wet pickup.2. Pass fabric over timing cans. The number of cans must correspond to the range speed and provide at least one minute dwell time. 3. Clip fabric onto tenter chains and stretch filling-wise while maintaining warp tension. 4. Run fabric under cascade washers to remove caustic. Keep under tension until caustic level is less than 3% otherwise fabric will shrink in filling direction. This width loss is impossible to recover later. 5. Release tension and continue washing in open-width wash boxes, to further reduce the caustic. 6.

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Neutralize with acetic acid in the next to last wash box and rinse with fresh water in the last.

Sapphire mills ltd Mercerization Machine

In sapphire mercerization set up was install by SANDO IRON WORKS WAKAYAMA, Nichimen corporation. Two machine lines are installed one line was cotton and polyester blends and other is for pure cotton the difference between both machine is number of trough. One have two troughs and the other have three. The two troughs are 22 be calibration is used and the three troughs using 28 Be caustic soda.

Mercerization Trough

Mechanically, in mercerization, the fabric is passed through a stanter. The purpose of this stanter is to maintain the width of the fabric. Before the process the width of the chain is adjusted as required. Before chain, the fabric is treated with caustic soda. Caustic soda is applied in a trough. There are three chemical troughs in both mercerizing machines. Use of three chemical troughs is because of better application. All troughs are one dip one nip. In all troughs, 28 Be NaOH is applied. After trough the fabric is given some time about 11-15 sec. There are 14 timing rollers for 1st trough. 11 timing rollers for 2nd trough and given 7-8 sec. after 3rd trough, the fabric is transferred to chain. At chain, NaOH is showered on the fabric when it is being passing through the chain. This showering is because the fabric has lost some of its amount during passing through chain. So showering recovers the leaked amount of caustic soda.

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Points of Concern and Control

For best results, goods should be dry entering the liquid caustic impregnation unit. Need to get uniform and even caustic pick-up through out the fabric. Wet pickup must be at least 100 %. A certain amount of liquid caustic must surround each fiber to provide proper lubrication so that the fibers can be deformed. For piece goods, a caustic concentration between 48 - 540 Tw should be maintained. Caustic stronger than 540 Tw does not add to Mercerized properties whereas below 480 Tw, the Mercerized fabric will have poor luster and appearance. Caustic solution and impregnated fabric temperatures should be controlled between 70 - 1000 F. Above 1100 F, there is a noticeable decrease in luster of the Mercerized goods. Below 700 F, there is no noticeable improvement. Proper framing during the washing step is crucial.The goods must be maintained at greige width to one inch over greige for maximum luster. The tensioned width must be maintained through out the caustic removal operations otherwise the fabric shrinks and luster is lost. If optimum washing is obtained. there will be only a slight loss in width as the goods come off the tenterclips.

Caustic Concentration Units

Caustic concentrations, expressed as percentages, are ratios calculated as weight caustic/weight solution. However the specific gravity or density of the solution (weight/volume) is directly related to the concentration. Calibrated hydrometers are used to determine specific gravity. The calibration scales most often used on caustic solutions are Twaddle (“Tw) and Baume’ (“Be’). The relationships between concentration and hydrometer readings are:The relationship between the Baume’ scale and concentration is not linear, the values get closer at higher concentrations. The reader is referred to various handbooks and manuals that have conversion tables.

Barium Number

AATCC Test Method 89 is a common test used for quantifying the degree of Mercerization. It is based on the fabric‘s ability to absorb barium hydroxide. A two gram swatch of fabric is placed in a flask containing 30 ml of a standardized 0.25 N barium hydroxide solution. The fabric is stirred for two hours (to allow the barium hydroxide to

64

be absorbed by the fabric). A 10 ml aliquot is withdrawn and titrated with 0.1N hydrochloric acid to a phenolphthalein end point. The difference between the starting concentration and the remaining concentration of barium hydroxide is the amount absorbed by the fabric. The procedure is carried out on the fabric both before and after Mercerizing and the barium number is calculated as shown below.Unmercerized fabric will give a barium number of 100 to 105. Completely mercerized fabric will give a barium number of 150. Commercially treated fabrics fall in a range between 115 to 130. Mercerizing Fiber Blends

Color yield, ease of dyeing and uniformity of dyed fabric will offset cost of Mercerizing. This holds true even for yarn blends with low levels of cotton. The temptation to Mercerize must temper with thoughts about how caustic affects the blending fiber. The following section discusses these issues.

Polyester/Cotton

These can be handled under the same conditions as 100 % cotton. Even though polyester fibers are sensitive to caustic, the temperature and time the fibers are in contact with mercerizing strength caustic are insufficient to cause fiber damage. One problem with polyester/cotton blends it that they may not be as absorbent as 100 % cotton fabrics coming to the caustic saturator. This is because they have not been given the same thorough scouring and bleaching as 100 % cotton. In this case, special penetrating agents are needed to help the caustic solution wet out the fabric.

Quality 16*16/2 88*52

Blend 100% CottonMachine ConditionsChain width 65

Required full width 59 – 60

Width After 61 full

Speed 60

65

NaOH (Be)o 28

showers 5

Name Pad P. Temp. pH Fabric resultsW. mangle PP 7 normal Tegwa 7-81st saturator 6 pH 5-62nd saturator 8 Absorbency okFeed mangle 1.5 whiteness 75-76After chain 1.5Washer no 1 1/0.2 80 11-12Washer no 2 1/0.2 90 11-12Washer no 3 1/0.2 95 10-11Washer no 4 1/0.2 60 10Washer no 5 1/0.2 normal 2Washer no 6 1/0.2 normal 2Washer no 7 1/0.2 60 2Washer no 8 1/0.2 80 3-4Washer no 9 1/0.2 90 5-6Washer no10 1/0.2 90 6-7

Washerno11/ B4Drye PP

7 normal 4

Quality 16*12/120*60Blend 100% CottonMachine ConditionsChain width 63Required full width 58Width after 59.5Speed 55NaOH (Beo) 28

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showers 5Name Pad P. Temp. pH Fabric resultsW. mangle PP 7 normal Tegwa 7-81st saturator 6 pH 5-62nd saturator 8 Absorbency okFeed mangle 1.5 whiteness 67-68After chain 1.5Washer no 1 1/0.2 80 11-12Washer no 2 1/0.2 90 11-12Washer no 3 1/0.2 95 10-11Washer no 4 1/0.2 60 10Washer no 5 1/0.2 normal 2Washer no 6 1/0.2 normal 2Washer no 7 1/0.2 60 2Washer no 8 1/0.2 80 3-4Washer no 9 1/0.2 90 5-6Washer no 10 1/0.2 90 6-7Washer no 11/ B4 Dryer PP

7 normal 4

Dyeing

The process of imparting color to any colorless or colored material is called dyeing. Dyeing of textile materials (fibers) is called textile dyeing. Textile dyeing is a very ancient process….The color materials used in dyeing are called dyes. Dyes are forced to make bonds or strong interactions with fibers. The interaction of dye and dyed material is important for better results. This means that dyeing is not only the process of imparting the dye into the fiber but it also include the good and strong chemical attachments between both, dye and fiber. This chemical bonding is responsible for good wash fastness properties, light properties etc.

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Dyeing is done in aqueous medium. As dyes are in different forms like powder or liquid, so it is better to use aqueous medium. Different liquid ratios are used according to dyeing method. The solution includes the fibers (to be dyed), the dye and the auxiliaries.The purpose of these auxiliaries is to improve efficiency of dyeing in other words they help to make strong and lasting connections between dye and fibers. These auxiliaries for dyeing vary according to the dyeing material and condition in which the dyeing is being done. These auxiliaries include the retardants, levelers, wetting agents, detergents etc.

Types of dyeing

There are different types of dyeing processes according to the condition these conditions include the type of fiber, type of dyeing material and temperature conditions etc. there are three main types of dyeing process:Continuous dyeing;Semi continuous dyeing;Batch-wise dyeing.

Types of dyes

There are different types of textile dyes. These are different in chemical formula, chemical nature, physical and chemical properties, and their behavior with different fibers.Some dyes are cationic, some anionic and some are neutral and etc. Dyes are classified into different classes according to their nature. Some are given below:Reactive dyes;Disperse dyes;Vat dyes;Acid dyes;Mordant dyes;Sulpher dyes;Cationic dyes, etc.We process only reactive, disperse and vat dye due to Sapphire mills limitations, so only these dyes are discussed here.

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Reactive dyes

Among the different classes of dyes for the cellulosic fibres the reactive dyes are the only ones that attach themselves to the fibres by covalent bonds and get their name for the same reason. Reactive dyes have certain groups in their molecules that are capable of forming of covalent linkages between carbon atom of the dye ion and oxygen, nitrogen or sulpher atom of a hydroxyl, an amino or a mercapto group respectively of the fibrous substrates. At this stage it is relevant to consider the basic mechanisms of the dye fibre attachments that can be of three types:

Physical adsorption Mechanical retention and Chemical reaction

Chemical structure of Reactive dyes

After the success of procion dyes in 1953, all the major dyestuff manufacturers begin investigating to find new reactive groups. In 1958 after going through their wool dyes ranges, introduced Remazol dyes that formed the covalent bond by “nucleophilic addition” reaction as indicated below:

(-HCl)D-SO2CH2-CH2Cl = [D-SO2CH=CH2] + HO-Cell = D-SO2CH2-CH2OCell These developments made the colour chemists think seriously, perhaps for the first time, about the chemical structures of fibres especially of cellulosic fibres and their role in dyeing mechanisms. In subsequent years all the major dye manufacturers many new reactive groups. It is known that about 250 reactive groups have been patent but only 20-30 have actually been marketed for both cellulosic and protein fibres by cold as well as hot dyeing process.The four distinct structural features of mono-functional reactive dye are chromogen, the the reactive system, the bridging link and one or more solubilising groups. The structure can be represented as:

W-D-Q-RG-XWhere D is the chromogen, W is the water-solubilising groups, Q the bridging link, RG the reactive group and X the leaving group.Some reactive groups are shown below:

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Reactive group Trade name manufacturer

D-SO2CH2-CH2-NR2 REMAZOL(HOECHST)DYESTAR

D-NHCOCH2CH2OSO3H +D-NHCOCH = CH2Cl

PRIMAZINE(BASE)DYESTAR

The reactive dyes are the brightest dyes available for the cellulosic fibres and have a full range of shades with very good wash and fairly high fastness properties. These dyes offer a great flexibility in application methods with a wide choice of effeuipment and process sequences and so have become very popular. As a class, the reactive dyes are stable to peroxide bleaching and so are used for dyeing cotton and viscose yarns to be employed as effect threads. Strong reducing agents and chlorine however destroy the chromogens.

Methods of dyeing of reactive dyes

In the absence of alkalis, the reactive dyes behave like levelling class of direct dyes but being of relatively smaller molecular size, are exhausted with higher consentrations of electrolytes. Even then exhaustion of the dye is low and varies between 50-75% in most classes. Reactive dyes can be applied by various methods but choice of dyeing process depends on factors such as availability of equipment, depth of shade, length of fabric and how much production is required.

Here in Sapphire mills limited, dyeing process is limited to full continuous method due to the limitations of equipment as well as it is the production requirement.

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Disperse Dye

Disperse dye is originally developed for the dyeing of cellulose acetate. They are substantially water insoluble. The dyes are finely ground in the presence of a dispersing agent then sold as a paste or spray dried and sold as a powder. They can also be used to dye nylon, triacetate, polyester and acrylic fibers. In some cases a dyeing temperature of 130 deg C is required and a pressurized dye bath is used. The very fine particle size gives a large surface area that aids dissolution to allow uptake by the fiber. The dyeing rate can be significantly influenced by the choice of dispersing agent used during the grinding.

Disperse dyes have low solubility in water, but they can interact with the polyester chains by forming dispersed particles. Their main use is the dyeing of polyesters, and they find minor use dyeing cellulose acetates and polyamides. The general structure of disperse dyes is small, planar and non-ionic, with attached polar functional groups like -NO2 and -CN. The shape makes it easier for the dye to slide between the tightly-packed polymer chains, and the polar groups improve the water solubility, improve the dipolar bonding between dye and polymer and affect the color of the dye. However, their small size means that disperse dyes are quite volatile, and tend to sublime out of the polymer at sufficiently high temperatures.The dye is generally applied under pressure, at temperatures of about 130oC. At this temperature, thermal agitation causes the polymer's structure to become looser and less crystalline, opening gaps for the dye molecules to enter. The interactions between dye and polymer are thought to be Van-der-Waals and dipole forces.The volatility of the dye can cause loss of color density, and staining of other materials at high temperatures. This can be counteracted by using larger molecules or making the dye more polar (or both). This has a drawback, however, in that this new larger, more polar molecule will need more extreme forcing conditions to dye the polymer2.

The most important class is the azo class. This class of azo disperse dyes may be further sub-divided into four groups, the most numerous of which is the aminoazobenzene class. This class of dye can be altered as mentioned before, to produce bathochromic shifts. A range of heterocyclic aminoazobenzene dyes are also available. These give bright dyes, and are bathochromically shifted to give blues. The third class of disperse dye is based on heterocyclic coupling components, which produce bright yellow dyes. The fourth classes

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are disazo dyes. These tend to be quite simple in structure. Other than these, there are disperse dyes of the carbonyl class, and a few from the nitro and polymethine classes.

Application of disperse dyes:

Dyeing Polyester with Disperse Dyes

Polyester requires the use of disperse dyes. Other types of dyes leave the color of polyester almost entirely unchanged. While novices happily charge into dyeing with acid dyes (for wool or nylon) and fiber reactive dyes (for cotton and rayon), often with excellent results, the immersion dyeing of polyester is a different story. However, disperse dye can be used by even young children to make designs on paper, which can then be transferred to polyester fabric, or other synthetics, with a hot iron. The possibilities are endless, using fabric crayons, rubber stamps, painting, and even screen printing.

Properties of disperse dye:

Fastness to light is generally quite good, while fastness to washing is highly dependent on the fiber. In particular, in polyamides and acrylics they are used mostly for pastel shades because in dark shades they have limited build-up properties and poor wash fastness.

Chemical characteristics and general application conditions

Disperse dyes are characterized by the absence of solublizing groups and low molecular weight. From a chemical point of view more than 50 % of disperse dyes are simple azo compounds, about 25 % are anthraquinones and the rest are methine, nitro and naphthoquinone dyes.The dye-fiber affinity is the result of different types of interactions:· Hydrogen bonds· Dipole-dipole interactions· Van der Waals forces.

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Disperse dyes have hydrogen atoms in their molecule, which are capable of forming hydrogen bonds with oxygen and nitrogen atoms on the fiber.Dipole-dipole interactions result from the asymmetrical structure of the dye molecules, which makes possible electrostatic interactions between dipoles on the dye molecules and polarized bonds on the fiber.Van der Waals forces take effect when the molecules of the fiber and colorant are aligned and close to each other. These forces are very important in polyester fibers because they can take effect between the aromatic groups of the fiber and those of the colorant.Disperse dyes are supplied as powder and liquid products. Powder dyes contain 40 - 60 % of dispersing agents, while in liquid formulations the content of these substances is in the range of 10 - 30 %. Formaldehyde condensation products and ligninsulphonates are widely used for this purpose.

Dyeing with disperse dyes may require the use of the following chemicals and

auxiliaries:

· Dispersing agents: although all disperse dyes already have a high content of dispersing agents, they are further added to the dyeing liquor and in the final washing step· Carriers: for some fibers, dyeing with disperse dyes at temperatures below 100 °C requires the use of carriers. This is the case with polyester, which needs the assistance of carriers to enable an even penetration of disperse dyes below boiling temperature. Because of environmental problems associated with the use of these substances, polyester is preferably dyed under pressure at temperature >100 °C without carriers. However, carrier dyeing is still important for polyester-wool blends, as wool must not be submitted to wet treatment at temperatures significantly above 100 °C · Thickeners: polyacrylates or alginates are usually added to the dye liquor in padding processes. Their function is to prevent migration of the dye liquor on the surface during drying· Reducing agents (mainly sodium hydrosulphite): they are added in solution with alkali in the final washing step.Disperse dyes are widely used not only for dyeing, but also for printing synthetic fibers.

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Classes of disperse dye:

Azo Disperse Dye:

The most important class of disperse dye is the azo class.  This class of azo disperse dyes may be further sub-divided into four groups, the most numerous of which is the aminoazobenzene class.  This class of dye can be altered as mentioned before, to produce bathochromic shifts.  A range of heterocyclic aminoazobenzene dyes are also available.  These give bright dyes, and are bathochromically shifted to give blues.  The third class of disperse dye is based on heterocyclic coupling components, which produce bright yellow dyes.  The fourth class is disazo dyes.  These tend to be quite simple in structure.  Other than these, there are disperse dyes of the carbonyl class, and a few from the nitro and polymethine classes.  Below is an example of a disperse dye

Anthraquinone Disperse Dye:

Anthraquinone disperse dyes lack the water-solubilizing groups of the acid dyes, but they are adsorbed by hydrophobic fibres such as nylon or acetate rayon with the aid of soap or other agents that keep the dye suspended in the application bath.In the synthetic dye field, many hundreds of individual products are manufactured. Of these, a small number become established as market leaders in their particular area of utility. Factors influencing the attainment of this status by a particular dye include hue, brightness, ease of manufacture, dyeing properties and fastness properties. One dye that has reached this position for the production of blue shades on polyester fibers is CI Disperse Blue 56 which has a simple anthraquinone structure and is easily applied giving bright blue colorations of high fastness.

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Dyes of the anthraquinone series are noted for their brilliance of hue, especially in the blue region, and also for their excellent fastness properties, especially fastness to light. Unfortunately, they have relatively low tinctorial strength compared with all other major classes of dye and they are costly to manufacture. The replacement of anthraquinone dyes by other chromophores, because of their low cost-effectiveness, has been described by Renfrew (Rev.Prog.Coloration, 15, 1985, 15) as "a commercially attractive but technically difficult objective for dye manufacturers".

Thiocyanomethyl substituted anthraquinone disperse dyes

The present invention relates to disperse dyestuffs of the anthraquinone series which contain at least one group of formula --Y--CH2 (SCN) where Y is a mono- or binuclear aryl group, which dyestuffs are useful for dyeing or printing textile substrates consisting of or comprising synthetic or semi-synthetic, hydrophobic high molecular weight organic materials.

Light fastness:

The photofading behaviors of anthraquinone disperse dyes on polylactide fabrics were investigated. The fabrics which had been dyed with 13 commercial dyes were exposed to a carbon arc light source. The polylactide fabrics dyed with Disperse Red 127 or Violet 26, which has phenoxy substituents, showed the light fastness higher than 4 grades.

Disperse and Reactive dyes in one bath:

If we want to dye polyester/cotton blend in one bath(i.e. both the reactive and disperse

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in the same bath instead of two bath) then the parameters we need to consider besides

what must be the properties of both the dyes to withstand in one bath giving good results

and fastnesses from pastal shades to darker shades.

The temperature and chemical requirements for the dye reaction of fiber reactive dyes, versus the dye deposition of disperse dye, are so different that the idea of combining both in one step seems bizarre. Disperse dye is applied at a boil, using a chemical to reduce the temperature needed for dye transfer, while reactive dyes, unlike direct dyes, are generally applied at considerably lower temperatures, and may actually degrade quickly when boiled.

Advantages of Disperse dyes

The disperse dyes used for the dyeing hydrophobic advantageous from the dyes used for cotton and wool fibers in the following respects:

Essentially low molecular weight azo, anthraquinone and diphenylamine derivates.

Carry no charge groups but contain polar sites like –OH, -NH2, -CH2-CH2-OH etc. Crystalline solids with low molecular weight that melt under pressure at 200-

250’C and sublime without decomposition. Low substantivity that increases with rise in temperature and by addition of a

dispersing agent. The solubility ranges from 0.2 to 100 mg/l at 80’C but completely dissolve at 130’C.

Relatively high saturation value ranging from 30-200 mg/gm of hydrophobic fibres.

Particle size of marketed dye is low (about one micron) so as to accelerate the rate of dyeing.

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Vat dyes

Vat dyes form a very important class of dyes for the cellulosic fibers because the dyeing produced with these have the highest overall fastness properties. All of these dyes have good fastness against wet treatments and crocking and most have light fastness in the region of 6-7. the vat dyes can also with stand oxizing agents like hydrogen peroxide, sodium chlorite and hypo chlorites, and extensively used for dyeing yarn that is to be woven along with the grey yarn. This cloth can undergo the pretreatment process like alkali boiling, bleaching and mercerizing without any damage to the dyed yarn. It may however be mentioned that after the introduction of hydrogen peroxide tolerant reactive dyes, a good proportion of the yarn dyeing has been taken over by the reactive dyes. This is because the reactive dyes are relatively less expensive ang are also easier to apply. In spite of the great in roads made by the reactive dyes for dyeing cotton woven and knit fabrics, vat dyes are still popular on account of the all round high fastness properties. Vat dyes are commonly used for superior quality shirting materials, military uniforms, furnishings, curtains, toweling etc. There are about 60 vat dyes in the market that cover the entire gamut of shades except the deep red colors. Vat dyes are essentially insoluble polycyclic aromatic compounds containing two or more pairs of quinone groups. It may be interesting to remember that indigo and tyrian purple, the earliest non natural dyes, also belong to this family. In order to apply to the cellulosic fibers, vat pigments are made water soluble by reducing to hydro-quinone forms in an alkaline media. The process is known as vatting, a term referring to a historical link with the vegetable indigo dye that used to be reduced in wooden vats with natural reducing agents like sugars. The present day vatting chemicals are sodium hydroxide and a strong reducing agents (one with high reduction potential) sodium dithionite (Na2S2O4) commonly termed in industry as sodium hydrosulphite or simply hydros. Sodium dithionite reduces the keto group of the dyes into the enol form and sodium hydroxide forms sodium salt of the enol to make the dyes water soluble. Caustic soda also neutralizes the acidic decomposition products of the reducing agent dithionite that are produced during vatting and dyeing. Quantity of the reducing chemicals depends upon the no of the keto groups present in the dyeing molecules to the extent of exposure of the dye bath to air. The reduction process may be represented as shown below:

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Reduction is accompanied by a change in color that is due to alteration in the conjugation of the double bonds. The reduced indigo has a pale shade and so it was called the leuco (white) dye. This term is still used although the leucos of many vat dyes are deeply colored.

Chemical structure of vat dyes

Vat dyes were developed soon after synthesis of indigo but the earlier dyes were either halogen derivatives or sulpher substituted indigo as shown below:

CI Vat Yellow 4 CI Vat Orange 1

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The vat dyes are often classified as indigoid, thio-indigoid and anthraquinonoid but majority of these belongs to the anthraquinonoid group. The thio-indigoid class also includes the hydrone blues that are type of hybrids of sulpher and vat dyes are often used as substitute of indigo. The indigoid and thio-indigoid group of vat dyes have low substantives for cellulose but the anthrax-quinone derivatives, on account of having more complex structures, posses high affinity. These also have better all-round fastness properties then the other two groups.

Dyeing structure of vat dyes

The vat dyes are divided into three main classes for application processes and this division is based on the substanitivity characteristics of their leuco derivatives. Due of the class one are IN (where I stands for indanthrene and N for normal) in their leuco forms have a high substanitivity further cellulosic fibers. These made high alkalinity for the dissolution and are dyed at about 75’C. the class two ( or IW i.e. warm) dyes have moderate substanitivity, require edium alkalinity, are dyed at temperature between 45-75”C and need electrolytes for complete exhaustion of the dyes. The class three (or IK i.e. kalt/cold) dyes have low substanitivity, need moderate alkalinity, or dyed at low temperatures between 20-30”C and required electrolytes in higher a concentration then that needed for the class two.

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Machines for continuous dyeing

The basic equipment required for the continuous dyeing of fabric of cotton and its blends with man-made fibers are dye padder, infra-red, predryer, cylinder or hot air dryer, chemical/development padder, steamer or thermo-fixation, heater, washing range and cylinder dryer. These machines are in the process of continuous improvement but the basic function of the equipment remains essentially the same. A brief description of the important features of these machines is discussed below:

Padder:

The padder is the padding mangles are meant to apply dye liquor in an even manner to the entire width and the length to a batch of fabric. The padding operation consists of two parts:

Immersion of the fabric in dye liquor in a trough. Passing the fabric between two rollers to force the dye liquor into the fabric and

also to squeeze the excess liquor back to the trough.Padder is the most sensitive component of the continuous dyeing system as any fault develop at the padding stage will not be corrected later. Padders usually have two rollers although the three roller types with two dip troughs where also marketed but these are used mainly for applying finishes to the heavy weight fabrics. Diagram…

The padder roll has a steel mandrel that is covered with hard rubber, toped by 15 mm of soft rubber that has the hardness of 60-70’ shore. Both the rollers should have exactly the same hardness other wise there will be a color difference in the face and back side of the fabric. The material of the rubber should be chemically resistant to dye liquors and auxiliary products. The bottom roller is coupled with a variable speed motor so that the fabric may is run at the linear speed ranging fro 30-90 m/min. the usual liquor pickup in a modern padder for different fiber is as under.Cotton: 60-70% p/c: (50:50) 45-50%

Padding trough:

The padding trough that was once considered to be just a container for the dye liquor without realizing its importance in obtaining a uniform shade and dye economy, has now, like padders, undergone vast modifications in recent years. The trough is placed

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below and in front of the padder and consist of the U shaped box with one or more free running guide rollers of about 10cm diameter each, as shown in figure below:

. An expander roller is fitted before the nip of the roles to eliminate any creases that may develop during passage of fabric through the trough. The dye liquor is fed in through a perforated pipe running across the entire light of the tank with perforations pointing towards the wall of the trough and away from the fabric so as to avoid spraying of the dye liquor on fabric

Ideally a trough should contain the minimum quantity of the dye liquor consistent with adequate pickup so as it reduce the wastage of the unused dye at the end of the process and more importantly to have a high liquor replacement value. In continuous dyeing, dye should have no or minimum possible affinity with the fibers so that the dye liquor squeezed out of the fabric during padding and returning to the trough should have the same concentration as the freshly fed dye solution. In case the dye has a slightly affinity, the trough should have as low of volume as possible so that the liquor is replaced rapidly and concentration of the dye solution in the trough remain constant and there is negligible or small tailing effect. To reduce the volume of the dye liquor, or displacer is fitted above the single roller trough. In oil roller troughs the displacer becomes unnecessary while time of contact of fabric with dye liquor increases. The troughs are double weld so that hat or cold water could be circulated through the jacket to maintain, usually automatically, the dye liquor at constant and optimum temperature. To ensure constancy of the fabric immersion time through out its funning in the trough, level of the dye liquor is kept constant by automatic controls.

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Drying the dye padded fabric:

To get even and uniform results specially for medium and deep shades, the dye padded fabric is required to be dried before the dye is made to diffuse into the fibers by steam or thermofixation. A no of drying machines such as cylinders, hot flue, infra red, stanter, suction dryers etc. are available but their choice depends upon important consideration of uniformity of drying, capital cost and thermal efficiency as well as some special requirements. We have studied infra red dryers in Supphire mills limited.

Infra red dryers:

…………………………………..

Continuous steamer:

In continuous roller steamer is used for the diffusion of the reactive, vat and sulpher dyes into cotton fibers in an atmosphere of heat and moisture that is created by saturated steam injected into the steamer. The fabric is moved in open width around rollers in top and bottom horizontal banks in a heat insulated steel chamber like that of a hot flue dryer. The top rollers are driven by chains or preferably by a series of motors. Capacity of the steamers varies between 30-60m and the time of steaming ranges between 20-60sec depending on class of dye used and depth of its shade. The steam coil heats ceiling of the machine to avoid condensation of steam and subsequent dripping of water on the dye padded cloth. Temperature of the steamer is maintained 102-104’c for getting the optimum results. The fabric enters the steamer through a narrow and heated slot so as to prevent entry of air into it and to eliminate condensation of steam on the fabric. It is essential to have a minimum of air in the steamer so that there Is no premature oxidation of sulpher and wet dyes and also to avoid lowering of evaporation temperature of the steam. The elimination is air is done before entry the fabric by blowing steam and forcing air out of steamer through an outlet in the roof. In some steamer air is rewove through a duct near the floor of the machine and is claimed give better extraction because air is heavier than steam.

When leaving the steamer, the fabric passes through a cold water seal so that steam doesn’t escape from the exit. The water in the seal should be kept cool by

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continuous running of fresh cool water in it especially when steaming the wet dyed fabrics as other vise the seal would become a reducing dye bath. After steaming the fabric is fed into a continuous washing range for removal of the unfixed dye and chemicals.In Kusters, steam is generated by boiling water at atmospheric pressure at 100’c inside the steamer itself.

Thermofixation of dyes:

In the thermofixation (also incorrectly called thermosol) process of dyeing the synthetic fibers, the disperse dyes diffuse into the polyester fibers on bringing the dye padded fabrics to a temperature of 200-220’c for a contact time of 60-30 sec. the machines commonly used for such dye fixation are mainly hot flue, stanter and suction drums. The hot flue machines are basically similar to the hot air dryers except that temperature of the hot air is maintained at 200-220’c with heated oil. The stanter, which was originally used as a finishing machine to stretch cloth to a constant and specified width, has now been extensively modified and technically upgraded for the thermofixation and heat setting purposes.

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Machine details of Sapphire Mills ltd. pad-thermosol:

Pad-thermosol consists of following parts that dye and guide the fabric during dyeing:

Batcher Guide rollers Screy Cooling drum Trough Squeezing rollers Padder VTG rollers IR-dryers Drying chambers Radiator Heat exchanger Curing chamber Piller

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