woven dyeing process

SOUTHEAST UNIVERSITYSchool of Science & Engineering

DEPARTMENT OF TEXTILE ENGINEERING

Course Code: Tex-3021Course Title: Wet Processing Technology-IIAssignment on: Details study on Woven Dyeing Process.

SUBMITTED TO

Md. Shahidul IslamLecturer

Dept. of Textile Engineering

SUBMITTED BY:Md. Tanvir AhammedID: 201200040003819th Batch, Section-1

Submitted On: 20-08-2014

INTRODUCTION TO DYEING

Day by day dyeing technology is changing for providing more coloration facility, more dyeing machine productivity, more upgraded dyed product, better safety, lower wet processing time, higher quality of textiles, more consistency of dyes in the textile fabric & finally for human comfort. In textile wet processing and synthetic dyeing there are various types of machinery are used from dyeing pretreatment to finishing which vary with dye brand to brand according to their dyeing technology.

Over the years for textile fabric processing we saw a lot of development through which we can provide a wide range of textile product with different coloration appearance & which are used for different purpose. With the aid of textile machine now most delicate fabrics with different finish is provided which could not think at past.

Usually there are three types of fabric.

I. Woven fabric

ii. Knitted fabric

iii. Non-woven fabric

All of the above fabric categories have different derivatives. Among them Woven fabric has a great versatility. That can be used in home textile as well as fashion. New technology machinery provides versatility not only by varying the structure of woven fabric manufacturing but also varying in processing such as in coloration & by different finishes.

FLOWCHART OF WOVEN FABRIC DYEING

Inspection of grey cloth↓

Stitching↓

Cropping↓

Brushing↓

Singeing↓

Desizing↓

Scouring↓

Bleaching↓

Souring↓

Washing↓

Drying↓

Mercerizing

↓Dyeing

↓Aftertreatment

↓Finishing

↓Inspection

↓Packing

↓Baling

Methods of woven dyeing

Color is applied to fabric by different methods of dyeing for different types of fiber and at different stages of the textile production process. Dyeing can be done during any stage in the textile manufacturing process. Textiles may be dyed as fibre, as yarn, as fabric, as garments, depending upon the type of the fabric or garment being produced.

These methods include direct dyeing; Stock dyeing; top dyeing; Yarn dyeing; Piece dyeing; Solution is pigmenting or dope dyeing; Garment dyeing etc. Of these Direct dyeing and Yarn Dyeing methods are the most popular ones.

Direct Dyeing

When a dye is applied directly to the fabric without the aid of an affixing agent, it is called direct dyeing. In this method the dyestuff is either fermented (for natural dye) or chemically reduced (for synthetic vat and sulfur dyes) before being applied. The direct dyes, which are largely used for dyeing cotton, are water soluble and can be applied directly to the fiber from an aqueous solution. Most other classes of synthetic dye, other than vat and sulfur dyes, are also applied in this way.

Stock Dyeing

Stock dyeing refers to the dyeing of the fibers, or stock, before it is spun in to yarn. It is done by putting loose, unspun fibres in to large vats containing the dye bath, which is then heated to the appropriate temperature required for the dye application and dyeing process.

Stock dyeing is usually suitable for woolen materials when heather like color effects are desired. Wool fibre dyed black, for example, might be blended and spun with un-dyed (white) wool fibre to produce soft heather like shade of grey yarn. Weed fabrics with heather like color effects such as Harris Tweed are examples of stock dyed material. Other examples include heather like colours in covert and woolen cheviot.

Top Dyeing

Top dyeing is also the dyeing of the fibre before it is spun in to yarn and serves the same purpose as stock dyeing – that is, to produce soft, heather like color effects. The term top

refers to the fibres of wool from which the short fibres have been removed. Top is thus selecting long fibres that are used to spin worsted yarn. The top in the form of sliver is dyed and then blended with other colors of dyed top to produce desired heather shades.

BRIEF DESCRIPTION OF EACH STEP OF DYEING

SINGEING

Singeing is the first step of dyeing. Singeing is important for a fabric to provide a smooth finish. Woven fabric goods usually contain protruding fibers from textile yarns. Singing process is used to remove those protruding fibres from the surface of the fabric. The fabric is passed in to a flame and these protruding fibers are burned out. Sometime copper plate is used remove the fibre. For printing, singing is most essential to improve the surface smoothness by eliminating the pilling and fibres.

DESIZING

Desizing is an important dyeing preparation step. During weaving sizing material is used to increase the strength of warp yarn. The sizing material is hydrophobic in nature. That’s why it must be removed before dyeing. Desizing is the process to remove the size material from the fibre. There are many chemical to remove the size material. Enzymes are the most popular material to use in sizing process.

SCOURING

Scouring is one of the most important processes of textile fabric dyeing. All of the natural fibre contains natural oil and wax. Before dyeing, those oil and wax must be clean for smooth and proper dyeing. The Scouring is a cleaning procedure that used to eliminate those oil, wax from fibers, yarns, or fabric by soaping. For scouring process alkaline solutions are typically used; however, Solvent solution may be used in some case. The parameter of scouring procedures like temperature, chemicals, and time vary with the type of fabric and fibre types. Impurities are including natural materials, dirt lubricants and other. Residual tints antistatic agents, water-soluble sizes, used for yarn verification.

BLEACHING

Bleaching is a complex process. The most common bleaching agents include sodium chlorite, hydrogen peroxide, sulfur dioxide gas and sodium hypochlorite. All the natural fibre contains a natural color which is harmful for dyeing shade matching. For example the cotton has natural yellowish shade. So it is important to remove the natural color from the fibre. Bleaching is a used to eliminate the natural color from the fibre and prepare the fabric for further process. According to the types of fibre the bleaching chemical is selected. Hydrogen peroxide is most popularly used bleaching agent for cotton and cotton blends.

MERCERIZING

Mercerization is used to increase appearance, luster and dye ability of textile fibre. Mercerizing is a semi-continuous or continuous chemical process used for cotton and cotton/polyester goods.Room temperature must be maintain during this process, causes the twisted ribbon-like cotton or cotton

polyester blend fabric to swell into a round shape and to contract in length. This causes the fiber to become more lustrous than the increase in strength original fiber, by as much as 20 percent, and increase its affinity for dyes during dyeing

DYEING

Dyeing is proper way to coloration of textile material (fibre, yarn, woven fabric, knitted fabric, non-woven fabric). Suitable dyestuff, dyeing machine and dyes chemical is required for achiving proper dyeing shade.

There are four types of dyeing,

1. Fiber Dyeing

2. Yarn Dyeing

3. Fabric Dyeing

4. Garment Dyeing

BASIC REQUIRMENT OF DYEING MACHINE

. Dyeing machine shall provide sufficient movement for the dyeing and dyes chemical liquor to penetrate uniformly into every part of the goods (fibre, yarn, fabric or cloth garments)

. The dyeing liquor movement inside the dyeing machine shouldn't be so vigorous that it damages the finer textile materials

. Dyeing Machine must be constructed of a material which will withstand prolonged boiling with acid or alkaline solutions from the dye bath.

. Heating arrangement inside the dyeing machine should be such that uniform temperature could be maintained.

. There should be some means of adding the concentrated dyestuff solution in such a way that it becomes well diluted before it comes into contact with the goods

Some Woven Dyeing Machine:

Jet Dyeing Machine

It was found that in using Winch machines, there were some inherent problems. So the Jet dyeing machines when they came up in the 1970’s were specifically designed to overcome those shortcomings.In the Jet dyeing machine the reel is completely eliminated. A closed tubular system exists where the fabric is placed. For transporting the fabric through the tube a jet of dye liquor is supplied through a venturi. The Jet creates turbulence. This helps in dye penetration along with preventing the fabric from touching the walls of the tube. As the fabric is often exposed to comparatively higher concentrations of liquor within the transport tube, so little dye bath is needed in the bottom of the vessel. This is just enough for the smooth movement from rear to

front. Aqueous jet dyeing machines generally employs a driven winch reel along with a jet nozzle.The following diagram explains the functioning of a Jet dyeing machine:

Fig: Jet dyeing machineTypes of Jet Dyeing Machine

In deciding the type of dyeing machine the following features are generally taken into consideration for differentiating. They are the following. Shape of the area where the fabric is stored i.e. long shaped machine or J-box compact machine. Type of the nozzle along with its specific positioning i.e. above or below the bath level. Depending more or less in these criteria for differentiation following types of Jet Machines can be said to be as developments of the conventional jet dyeing machine.

A. Overflow Dyeing MachineB. Soft-flow Dyeing MachineC. Airflow Dyeing Machine

Advantages of Jet Dyeing Machine

The Jet Dyeing Machine offers the following striking advantages that make them suitable for fabrics like polyesters.

Low consumption of water Short dyeing time Can be easily operated at high temperatures and pressure Comparatively low liquor ratios, typically ranges between 1:4 and 1:20 Fabrics are handled carefully and gently.

A. Overflow Dyeing Machine

Overflows Dyeing Machines are designed for use in delicate knitted and woven fabrics that are made up of natural as well as synthetic fibers. They are also extensively used in the production of carpets. The main difference between jet and overflows machines is that in jet machines the fabric gets transported by a bath that flows at high speed through the nozzle, while in Overflow Dyeing Machine it is the gravitational force of the liquor overflow that is responsible for fabric transportation.

Functioning of an Overflow Dyeing Machine

A typical Overflow Dyeing Machine works like this. A winch that is not motor driven usually is located in the top side of the machine where the fabric is hanged. A longer length of textile is made to hang from the exit side of the winch as compared to the inlet side. By applying the force of gravitation the longer length of textile is pulled downward more strongly than the shorter one. Consequently the fabric is soaked in the bath without any sort of tension. The following diagram well illustrates the working process.

Advantages of Overflow Dyeing Machine

No evaporative losses- As the dyeing vessel is closed, there is no evaporative losses stemming from the dye bath. Further, depending on the situation the temperature may be raised to more than 1000oC.

No buildup of steam condensate in the dye bath- The latest technology implies that the dye bath gets heated by a heat transducer which is steam driven. This technology apart from being very efficient ensures that there is no buildup of steam condensate in the dye bath.

Low liquor ratios- Dyeing is conducted at relatively low liquor ratios, e.g. 10:1 and may be lesser resulting in substantial savings in water and energy.

Excellent dye liquor contact- Excellent dye liquor contact with the fabric rope results in better and more improved level dyeing.

Computer control- The machines are operated by computer and hence, operator error is eliminated.

B. Airflow Dyeing MachineThis is another development of the very popular jet dyeing machines. The main difference between the Air Flow Machine and Jet Dyeing machine is that the airflow machine utilizes an air jet instead of the water jet for keeping the fabric in circulation. Typically the fabric is allowed to pass into the storage area that has a very small amount of free liquor. This results in a reduction in consumption of water, energy and chemicals.The figure below shows how in an Airflow Machine the bath level is always under the level of the processed textile. Here the fabric does not remain in touch with the liquor (the bath used is below the basket that holds the fabric in circulation). This invariably means that the bath conditions can be altered without having any impact on the process phase of the substrate.

Advantages of Airflow Machine

Completely Separated circuit for liquor circulation without getting in touch with the textile

Bath less Dyeing operation Rinsing process offers all the added benefits of continuous processing as it is no

longer a batch operation Extremely low liquor ratio Virtually nonstop process Comparatively lesser energy requirement due to faster heating/cooling and optimum

heat recovery from the hot exhausted dye liquors Reduction in consumption of the chemicals (e.g. salt) dosage of which is based on the

amount of dye bath Lesser water consumption savings up to 50% from the conventional Jet dyeing

machines

Sensitivity towards ecology Economical operation More safety while dyeing.

Jigger dyeing machine

Based on experience and developments in industry and controller technology, the This-Jigger is developed. Suitable for processing fabric at atmospheric temperatures of up to 98°C and in HT execution up to 143°C, this Jigger is especially recommended for the treatment of crease sensitive, permeable and non-permeable articles in open width form, offering optimum flexibility for the finishing of all modern fibres and blends. Incorporating innovations in step less tension and material speed control and with an economical dye trough designed for uniform dyeing in short liquor ratio conditions.

An industrial PC, proven in the exhaust dyeing industry, including PLC and a fabric rope monitoring system is used for the complete machine control, ensuring the maintenance of optimum processing conditions.

Significant innovations in the process technology ensure modern utilization1. Direct drive of the main rollers via frequency controlled three-phase motors with

brake drive current return (energy saving)2. A dye trough design ensuring minimum possible liquor ratio3. Fabric rope monitoring control system for precise calculation and control of the fabric

speed and tension4. Uniform dyeing conditions in the dye trough, independent of the batch size5. Water meter for controlled rinsing6. Dosing of dyes and chemicals dependent on the fabric length passing through the dye

bath7. Addition pressure pump for shading corrections and dosing8. On the HT-Jigger dosing under pressure possible9. External pump and heat exchanger ensure uniform liquor heating and circulation10. Sidewise displacement of the main batch roller11. Analogue level for dyeing kier12. Floor level track system*13. Easy maintenance

Fig: Schematic diagram of Jigger dyeing machine

High-temperature High-pressure Auto jigger dyeing Machine

This machine is for the jig dyeing at high temperature and high pressure conditions of all types of thick, thin fabrics, Terylene, chemical fiber and real silk fabrics. Under normal temperature and pressure conditions, it can replace common jigs to dye all types of natural silk, rayon and polyamide fiber. The machine is reasonably structured, with good safety and capacity, easy to maintain.

Major Technical Parameters

Roller diameter 219mm Max. Rolling width 1800mm Max. Rolling diameter 680mm Working speed 40-110m/min Max. Pressure 0.28MPa Max. Temperature 140

Limitations of Jigger Dyeing

1. Jigs exert considerable lengthwise tension on the fabric and are more suitable for the dyeing of woven than knitted fabrics.

2. In textile preparation due to the swelling and dissolution of size, this makes the fabric slippery and unstable in roll form.

3. The low liquor ratio makes washing-off difficult.

4. There is little mechanical action in a jig machine and it is less suitable where vigorous scouring is required before dying.

5. Moir effects or water marks may arise on some acetate and nylon fabrics because of pressure flattening the structure of the rolled fabric.

Winch Dyeing Machine

Winch dyeing machines comes with the lucrative options of low cost design, simplicity in operation and maintenance yet uncompromising features when it comes to versatility.Mostly woolen fabrics are dyed by using Winch Dyeing machine. The dyeing machine derives its name "Winch" as the fabric rope gets circulated in the machine by way of a mechanical action of a horizontal rotor or reel, called as a winch or sometimes winces. The cross-section of the winch rotor may be circular or elliptical.As shown in the diagram below, the winch dyeing machine has a front compartment; a perforated partition separates it from the main dyeing chamber. It is this front compartment where dyestuff and dyeing auxiliary additions are made. Gradually they move to main dyeing vessel from there. The process works like this first a series of fabric ropes are immersed in the dye bath. This fabric ropes must be of equal lengths. A part of each rope is then taken over two reels or over the winch itself. In the subsequent course of dyeing operation a rope of fabric is circulated through the dye bath and the winch. The dyestuff and auxiliaries are dosed manually or automatically according to the recipe method.

Features: - Width the wide soft nozzle. It plans a soft the hazard which gets a soft process wide and soft nozzle system especially.Air parts system (the selective evening sunlight): It is tied with the system which pours an air in the knit fabric which has not become dog width, the back which is entangled it prevents and also the quality improves.The work characteristic which excels: The mechanical structure is simplicity the excellent work and irrigation to be easy and the American expert the work is possible.Width wide application : Reel [li] and other it will come, Oh, the wool, the cotton and the pulley Oh America [tu], the acryl, the viscose and the pulley nose the product back which sprouts dyeing, bleaching and washing the product which is various are possible with the bell.Performance Mechanism: Wide and soft nozzle. The special designed wide

soft flow nozzle system with high liquor flow to achieve the soft and smoothprocess.

Air ballooning system (Option): Air ballooning device which are to be shootair in the tubular type knitted fabrics so that fabric can be dye at anycondition.Excellent Workability: The compact structure of machine provides easyoperation and maintenance and even the unskilled.Wide Application: The machine provides multi-purpose of dyeing and bleachingand washing for terry towel, velour, wool, cotton, polyamide, acrylic andviscose and poly/cotton brand and so on.

Technical Characteristics: Capacity (kg): 400 ~ 450Electric power: 18kwMax temp: 98 °CNumber of nozzle: 4

Beam Dyeing Machine

The beam dyeing machine operates with the same principle as that of package dyeing machine. It can be effectively used to dye yarn or fabric. The process works like this, fabric or yarn in open width is rolled on to a perforated beam. The beam then subsequently slid into a vessel that is closed and pressurized. The color impregnates the fabric as the dye liquor is allowed to go on circulating through the perforations in the beam. Usually the beam machines are designed in such a manner so as to hold a single beam or multiple beams in a batch.

Features of Beam dyeing Machine Able to adjust water level in accordance to fabric volume. Even dyeing and superior dyeing quality. Optimized circulation system along with high performance pumps.

Advantages of a Beam Dyeing Machine

The fabric is put under controlled tension, and is wound on to a perforated beam. This results in elimination of creases from the fabric. It also ensures total control of dimensions of the roll of fabric.

The fabric is not allowed to do any movement during the process of dyeing. This actually means that there is no application of mechanical action on to the fabric.

Fig. Beam Dyeing Machine

Technical Specification of the featured modelLoading Cap: 100 kgElectric wattage: 22KwMaximum Operating Pressure: 5kgf/cm2g Maximum Operating Temperature: 158°C

DYEING PROCESS OF COTTON FABRIC WITH REACTIVE DYES

Dyeing process is the process of giving of colour at textile material equally (uniformly).

In principle mechanism of dyeing process consists of 3 steps:

1. Migration dyestuff towards fibre.

2. Adsorption molecule dyestuff at surface of fibre.

3. Diffusion dyestuff from surface of fibre to fibre interior.

To get good result hence there are 6 important thing which must be taken care of :

1. Hardness of water

2. Chemicals balance (dyes, auxiliaries, salt, alkali)

3. Liquor Ratio (comparison of water with fabric weight)

4. pH dye solution (beginning of process and phase process of fixation )

5. Dyeing temperature

6. Dyeing time

100% cotton fabric can be dyed with following types of dyes:

- Reactive Dyes

- Direct Dyes

- Sulphuric Dyes

- Vat Dyes

- Pigment Dyes

Among some of the above dyes, reactive dye is most applied at 100% cotton fabric good in the form of knitted fabric or woven fabric.

Reactive dye is applied for following reasons:

1. Simple dyeing process.

2. Choice of more colours available

3. Good colour resilience

Based on its reactivity, reactive dyes are divided into 2 types, that is:

1. Hot reactive dyes

Reactive dyes which have low reactivity

2. Cool reactive dyes

Reactive dyes which have high reactivity

Reactive Dyes are applied to for following reasons:

- Good dye condensation

- Good colour resilience

- Dyeing at hot temperature so that penetrating of dye into fibre is better

- Have good levelness of dyeing result

- Have choice of complete colour

- Easier process control

- Very suited for mercerized cotton cloth

- Generally resistant to process “ post bleach ”

Principle

In principle process of dyeing 100% cotton knitted fabric with reactive dye is with circulation material textile with dye solution and some auxiliaries, with certain concentration, certain time and certain temperature applies of dyeing machine.

PROCESS OF DYEING WITH HE TYPE REACTIVE DYES WITH EXHAUST DYEING SYSTEM

1. METHOD SALT ADDITION STEP BY STEP: This method is suited for all dyeing colours and for machine in which dyeing solution do not have circulation, for example Winch machine.

2. METHOD ADDITION SALT IN THE BEGINNING OF PROCESS (SALT-AT-START): This method is more compatibly applied for dyeing colour from medium to depth colour and for machine with dyeing solution circulation and it’s the textile material, the example jet dyeing machine, jet flow machine.

Example of dyeing recipe for red colour:

- Reactive Orange HER 2.0 %

- Reactive Red HE-7B 1.5 %

- Glauber salt 70 g/l

- Soda Ash 20 g/l

- Dispersing-sequestering agent 1 – 2 g/l

- Anti crease mark agent 1 – 2 g/l

- Anti foam agent 1 g/l

Liquor Ratio 1: 10

Temperature 80 0C

The time 60 minute

Jet dyeing machine

Auxiliaries and its function

1. SALT (GLAUBER SALT / SULPHATE SODIUM / Na2SO4)

Function to increase absorption of reactive dye into fibre

2. ASH SODA (CARBONATE SODIUM / Na2CO3)P: Function to react dye with fibre (fixation)

3. DISPERSING-SEQUESTERING

Functions to tie metal ion (iron, calcium, copper, magnesium and other) which is in the dyeing solution be so that got by colour better dyeing result. Besides functioning to increase reactive dye solution in high rate electrolyte.

4. ANTI CREASE MARK AGENT

Functions to prevent incidence of crease-mark / rope mark ( piebald of fold ) during process of dyeing takes running.

5. ANTIFOAM AGENT

Functions to eliminate foam arising during dyeing process because it can cause piebald dyeing colour and colour scraggly. Foam arises from water circulation and material which quickly by, also from auxiliaries which can generate foam. Too much foam can result in machine stuck.

WASHING PROCESS

There are 4 phase process of wash which is done after dyeing process :

1. Hot rinsing before soaping process

- Eliminate or drop concentration of salt and alkali as many as possible

- Avoid from the happening of precipitation of reactive dye

- Eliminate the happening of wrinkling line at fabric as result of degradation

of dyeing temperature solution which would throw.

2. Soaping: Eliminate reactive dye pickings which is hydrolysis by nit and is not

Fixation / reacts with fibre

- Increase power reactive dye diffusion to exit from surface of fibre

3. Hot rinsing after soaping.

- Help to prevents reactive dye pickings to return to surface of fabric ( back staining )

Phase of washing process for light colour fabric, medium colour and deep of colour

A. LIGHT COLOUR (dyes < 1%, concentration of salt < 30 g/l )

- Hot rinsing (70 0C, 10 minutes)

- Soaping (95 0C, 10 minutes)


- Cold rinsing (30 0C, 10 minutes), overflow

B. MEDIUM COLOUR (dyes 1 – 4 %, concentration of salt 30 – 60 g/l )







C. DEEP OF COLOUR (dyes > 4%, concentration of salt > 70 g/l)







- Fixing process

FIXING PROCESS: For medium colour and deep colour the process fixing by using of fixing agent. Fixing agent functions for :

1. Strengthen strong tying dye with fabric fibre.

2. Increase resilience cleans fabric.

Process of workmanship with fixing agent:

- Fixing agent 1 – 2 % (medium colour) or 2 – 3 % (deep colour)

- pH 5

- Temperature 50 – 60 0C

- Time 20 minutes

After completing in cold rinsing then dried.

Reference:

http://www.fibre2fashion.com/industry-article/49/4898/dyeing-process-of-jigger-dyeing-machine2.asp

http://www.slideshare.com/wovendyeing

http://blog.adplcolors.com/?p=10

http://textilelearner.blogspot.com/2011/12/methods-of-dyeing-different-dyeing.html

http://www.slideshare.com/wovendyeing

woven dyeing process

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