Problems in Garment Dyeing

With today’s exploding clothing markets of leisure , casual wear and sports wear , garment wet processing has emerged as one of the best production routes towards meeting the quick changing fashion markets.

Unlike fabric or yarn as a substrate , a garment is not a uniform in texture ,it is full of thick places like seams , multilayered sites like pockets , cuffs and shoulders. At times certain unevenness like puckered seams lend a distinct style often highly valued but it could result into rejection of goods at other times .

Here we will try to figure out certain key problems associated with garment dyeing and their possible causes, so that a garment can analyze and overcome these problems. 

Garment size control and appearance

• variations in yarn size / twist
• ends per inch
• picks per inch
• courses per inch in the knitted fabrics   

Spirality in Knitted Fabrics 

 

• Twist of the yarn
• Fibre parameters,
• Yarn formation system,
• Yarn geometry,
• Knit structure
• Fabric finishing.            

Poor tear strength of garment

• Degradation of cotton during
• pretreatment,
• dyeing and
• finishing  such as stone /enzyme washing.

Pilling

• Low twisted yarns.
• Use of low staple length, cheaper fibre in manufacture of yarns
• Surface friction of fabrics/garments during wet processing and handling
• Reworking of  goods
• Cylinder rotation is too high.
• Liquor ratio is too low.
• Excessive cycle time

Puckering of seams during dyeing

• Improper selection of stitching thread.
• Due to high twist in sewing thread
• High residual and wet  shrinkage of sewing threads
• High stitching tension and improper stitch length..

Poor Rubbing fastness

• Improper washing and soaping treatment after dyeing.
• Too much unexhausted dye in dyebath.
• Loosely held surface indigo dyes
• Considerable back staining in each step
• Exposure to atmospheric ozone

Poor light fastness  

• Use of reactive dyes which are not light fast
• Use of formaldehyde based dyefixing agents

White, undyed or light seams

• Use of improper thread such as polyester thread on cotton garments.
• Use of mercerized thread on unmercerized garments.
• Mixing of different types of threads such as mercerized and un mercerized .
• High tension stitching .
• Unmatched Shrinkage behavior of  garment and thread .

Dullness around Metallic fittings

• Corrosion and chemical reaction between metallic parts in
• Pretreatment
• Bleaching
• Dyeing
• Finishing

Streakmarks/ Lines / Creases

• Overloading of machine
• Friction between Garments
• Entanglement of garments.

Shade nonuniformity

• Differences in fabric preparation processes like
1. Desizing,
2. Scouring
3. Bleaching.
• Inconsistency in the garment assembly

Poor Dye Yield

•   Garments contain a finish, softener, or an optical brightener.
•    Garments were allowed to dry out after pretreatment stage
•    Liquor ratio is too high.
•         Agitation is too slow.
•         Excessive washing between cycles.
•         Excessive time spent in any cycle.
•         Too much/too little pretreatment.
•    Not pretreated for correct time and/or temperature.

Blotchy or Non-Uniformly Dyed Garments

• Garments contain a finish, softener, or an optical brightener.
•  Liquor ratio is too low (want 20:1). 
•  Excessive bath temperature at beginning of pretreat or dye cycle.
•  Dye bath temperature ramped too quickly .
•  Improper addition or dilution of dyes/chemicals.
•  Live steam injection into bath.
•  Hard water.
•  Garments not scoured properly
•  Garments were allowed to dry out after pretreatment stage 
•  Garments not allowed to wet-out sufficiently before adding pretreatment.
  

           

Patchy dyeing

• Starting temperature too high
• Heating rate too High
• Salt addition at high temperature
• Addition of dyes and chemical at once

Spotting

• Formation of foam
• Improper washing
• Machine not clean.
• Excess pretreat not rinsed from garment before dyeing.
• Dye not properly diluted or stirred before bath addition.
• Incompatibility of auxiliaries.

Harshness

• Insufficient size removal
• Use of high quantities of alkali
• Poor softner application

Smell

• Acetic acid,
• Residual chlorine,
• Cationic softners

Back staining

Improper maintenance of

• pH
• Temperature

Blotchy / unlevel dyeing in pigment dyeing

• Improper preparation
• Higher dosage of cationic reactant
• High rate of rise in temperature during Cationization
• Direct contact of steam with garment
• Too low MLR hence uneven build-up of Cationizer

Batch to batch shade reproducibility in Pigment dyeing

• Change in pH during cationization

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Related topics

1.Fabric spirality

2.Measurement of Fabric spirality

3. ComprehensiveView on Garment Dyeing and Finishing

4.Precaution in Garment Dyeing

5.Garment Washing Techniques for cottonapparels

6. Wrinkle-Resistant Finishing ofCotton Fabrics and Garments 

What is wrinkle free finish

7.Finishing of garments : slideshow

8.FUNCTIONAL FINISHES FORCOTTONPRODUCTS

9. Garment dyeing – Sewing thread and sewing recommendations

10.Garment Dyeing Machines

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Polyester Microfibers:- Dyeing and Wet Processing

Microfiber

A synthetic fiber that is extremely soft, lightweight, breathable, durable and ultrafine. In fact, microfibers are two times finer than silk and one hundred times finer than a human hair. Microfiber is currently manufactured from acrylic, nylon, polyester and rayon.Ultra-microfibers on the market are even finer – some having thickness of just 1/200th the thickness of human hair!

Microfibres refer to staple fibres, or individual filaments within yarns, which have fineness less than 1 decitex ( 1 grams per 10,000 meters) and For any fiber to be classified as microfibre yarn, the weight per 10,000 metres of yarn (dtex) is divided by the number of filaments (f), the result must be below 1.
All about microfibers

Microfibers: Functional Beauty

Properties of Polyester Microfibers

1. Lightweight and flexible
2. 
   
   Good stability and shape retention
3. 
   
   Anti-wrinkle property
4. 
   
   Have a wicking ability that permits perspiration
5. 
   
   Comfortable to wear as they are more spongy
6. 
   
   Doesn't water stain - superior water repellency is available
7. 
   
   Woven or knitted into a very high quality fabric construction
8. 
   
   Formerly commenced as a polyester microfiber, today you can find nylon, rayon and acrylic microfibers too.
9. 
   
   Strong and durable, water repellent and wind resistant -so tightly woven, that the fabric can't be penetrated by wind, rain or cold
10. 
    
    Lightweight, resilient or resist wrinkling, have a comfortable array, preserve shape and resist pilling
11. 
    
    The positively charged microfibers draw dust; the tiny fibers are capable to enter the microscopic surface voids most materials
12. 
    
    Washable, dries quickly and also washable in at the water temperatures up to 200 degrees and their characteristics will remain intact.
13. 
    
    Electrostatic effect - Hair, lint and other dust particles are attracted and grabbed by the microfibers without lifting dust.
14. 
    
    The density of the material allowable it to grip six to eight times its weight in water hence high absorbing power capacity
15. 
    
    The attraction capability of the microfibers is so sound, even absorbs bacteria and germs - hence can be use as germ or bacteria free purpose
16. 
    
    The fabric consists of millions of small tiny conduits that carry oil and grease too.
17. 
    
    Benefits of microfibers
18. 
    
    Comfortable - very soft, texture like silk, lightweight
19. 
    
    Due to its fineness and superior fiber surface area making deep, rich and bright colors achievable
20. 
    
    Less "sweaty" in warm weather than usual synthetics
21. 
    
    Quickly cleanable - clean just with water
22. 
    
    Highly intense and shrink-resistant
23. 
    
    Presents insulation and breathability
24. 
    
    Change without help - to establish lovely drape
25. 
    
    Very fine - finer than the most precise silk
26. 
    
    More reusable for cleaning alternative - compared to other mops more efficient and long life

Dyeing of polyester Microfibers
Due to their fineness, the total surface area of microfibre yarn or fabric is far greater than ordinary fibres. Threfore

1.Due to its special structure ,micro fibers has much larger quantity of size ,oil agents and wax on warp yarns.

2.Since microfibres have very small interstitces, with consequent difficulties of size accessibility and duffusibility, desizing becomes quite difficult and costly.

3.Microfibres have greater absorption area resulting in a dyeing rate four times higher than that of normal, which can cause unlevelness in dyeing.

4.They also require more dyestuff than standard fibres to obtain the same depth of shade.
5.Larger external surface means an increase in number of threads exposed to light which, on destruction of dye, is expressed as lower light fastness rating.
6. Wash fastness and color fastness to rubbing is also poor.
7.Staple microfibres offer difficulty in carding.

The problems in wet processing of microfibers can be overcome by

1.Better knowledge about the size applied and optimum parameters during desizing operation.

To achieve satisfactory dyeing effects ,desizing and refining process must be done before dyeing and after desizing and refining , there should be no impurities left such as electrolyte, antistatic finishing agent , spin finishes and blot.

2.Pre-setting

Suitable pre setting conditions ( time ,temperature and tension) helps not only in stable dimensional stability ,softness but also better dyeing results.

3.Alkali weight reduction

Alkali weight reduction s to treat the fabric with concentrated alkali at high temperature.fber molecule hydrolyse under this condition and lose some weight with change in properties, thus space occurs between crossing points and rubbing resistance relative to slippage among yarns becomes small.Alkali weight reduction makes fabric soft, liveliness, limber and improved absorption.

2.Careful selection of the dyes.

Proper dye selection which are
1.Compatible
2.Having same exhaustion rates
3.Having high wash fastness properties.
4.Good migration and levelling properties
 eliminates problems regarding build-up and fastness properties.
Disperse dyes for polyester microfibers

3.Optimizing the dyebath conditions and dyeing cycle.


Optimised dyeing cycles can be worked out by controlling the temperature to account for the high rate of dyeing and to eliminate the risk of uneven dyeing.Chemicals and dyes to be added at, at least 10-20 deg.C lower temperature than normal polyester fiber dyeing. The additions of dyes must be progressive or devided at least into 4 parts. The heating rate must be slow from 40 deg C to 100 deg C. 10-20 min more holding time required at 130 deg C as compared to normal PES.


4.Proper selection of  Dyeing machinery.

The dyeing machine must have the required automation to fufil the requirements of microfiber dyeing such as microprocessor controlled dosing , proper and accurate heating rate control etc.


5.Proper selection of dyebath additives
such as
Levelling agents :- A strong levelling agent which shall start working at lower temperatures.
Dispersing agents :- Higher quantities of dispersing agents are needed because amount of dyes required are more to produce the desired depth.
Chelating agents:-
Anticreasing agents,Dyebath softners/Lubricants :- Because microfiber textiles are prone to creasing , therefore use off dyebath lubricants is must.

6.Proper aftertreatment of dyed goods.
Soaping :- In order to obtain satisfactory color effect , fabric should be soaped after dyeing .Soaping is the key process to achieve satisfactory dyeing results on polyester especially polyester / nylon microdenier fabric.


Reduction clear :-Good reduction clear process is needed to achieve satisfactory washing , rubbing and light fastness properties.
Washing :-Is required for neutralising and removing alkali after reduction clear treatment.
Softening, anti soil and antistatic treatment :-Because microdenier fiber easily stains and produces static charges, a hydrophilic ,antistatic and antisoil treatment besides softening is highly recommended to ensure fabric softness and comfortability.

Recommended Dyeing Cycle for polyester Microfibers

Dianix PLUS( Dystar) or Longsheng  is a new range of five compatible, level-dyeing dyes for reliable dyeing of medium and heavy shades, especially on microfiber and weight-reduced polyester, whether applied under mild alkaline conditions to control trimer, or under conventional acid conditions.
Dianix E-PLUS" for Pale Shades on Polyester Fabrics
Fashion application of polyester

Application of polyester Microfibres

Microfibers are most commonly found in polyester and nylon. Some rayon and acrylic micros are in production and available to consumers. Micros can be used alone or blended with conventional denier man-made fibers as well as with natural fibers such as cotton, wool, and silk.

In textiles

Microfibers are used in a variety of fabrics, but most commonly in dress and blouse weight garments. Suit jackets and bottom weights are becoming available. Look for micros in lingerie, rainwear, outdoor fleece and wind-resistant sportswear, as well as tents, sleeping bags, track and jogging suits. The strength of microfibers make them particularly adaptable to sueded or sandwashed finishes because of their extensive fiber surface area and the use of strong fibers like polyester and nylon. As a result, many microfibers simulate the appearance of sandwashed silk.

Other Main products for which microfiber are ideally suited:

• Microfiber Glass Cloth

• Duster/Multi-purpose Microfiber Cleaning Cloth

• Microfiber Scrubber

• Microfiber Kitchen Cloth

• Microfiber Optical & CD Cloth

• Microfiber Mops

• Microfiber Cleaning Sponge

• Microfiber Cleaning Cloths – Terry Cloths, Suede Cloths, Waffle-Weave Cloths

Microfiber Makes the Grade
http://www.tex.in/education/nextiles/fib/mic/mic.html
http://ygmfranchise.blogspot.com/2007/07/cleaning-tips-microfiber.html
http://www.microfibergreen.com/is-microfiber-green-product.html
http://www.norwexnow.com/microfiber%20science.html

 

Textile Wet Processing

An Introduction to textile Wet Processing

Fibers ,Yarns , threads ,Woven and knit textiles goods cannot be processed into apparel and other finished textile products until they have passed through several water-intensive wet processing stages. Wet processing enhances the appearance, durability, and serviceability of textiles by converting undyed and unfinished goods, known as gray or greige goods, into finished consumers’goods. Also collectively known as  dyeing and fmishing, wet processing has been broken down into four stages:

1.Fabric or yarn  preparation
To ensure that the textile has the right physical and chemical properties to enable it to be coloured or finished.
EXAMPLE:
Desizing, Singeing, Scouring, Bleaching etc.
2.Coloration or dyeing
To provide the textile with colour either for aesthetic reasons or for some functional purpose determined by the end-use of the product.
EXAMPLE:
Yarn Dyeing ,Fabric Dyeing
3.Printing
Textile printing is the process of applying colour to fabric in definite patterns or designs.
EXAMPLE
Roller printing, cylinder printing, or machine printing ,Stencil printing ,Screen-printing ,Digital textile printing 4.Finishing.
To provide the textile with the properties that the end-use demands and which have not already been provided by any earlier processes.
EXAMPLE:
Crease resistance, dimensional stability, stain resistant ,Water Repellency, Flame Repellency, Antisoiling finish etc.
These stages, involve treating gray goods with chemical baths and often require additional washing,rinsing, and drying steps. Note that some of these steps may be optional or repeated depending on the style-quality- type  of textile items being manufactured.

Read More
Water and textile Wet Processing -1
Historical notes on the wet-processing industry
AATCC Garment Wet Processing Technical Manual
A workbook for pollution prevention by source reduction in textile wet processing
Trainer's Workbook on Cleaner Production in Textile Wet Processing

Automation in Dye House

Automation is a need for todayAutomation today’’s competitive market where quality, cost and availability is playing major role.
In today today’s scenario quality , quantity and service are the most critical requirements for the servival of textile industry . The cost of production is increasings rapidly but the costs such as  labour cost, raw material cost, power cost, etc. are not in our control. The biggest question for a textile dyer today  is to increase the productivity and reduce the production cost.
The options for increasing productivity and reducing cost of production are
􀂾Reduction in Labour cost
􀂾Reducing Utility cost by power saving
􀂾Value enhancement by Quality improvement
􀂾Increasing output Through state of art machinery
􀂾Improving efficiency and service through managemant systems

All these can be possible only by implementing Automation

What is Automation?
Monitoring and controlling of any process with the help of latest technologies like software, ladder and logic controls, Robotics, ERP system and incorporating central computer is called Automation.
 
WHY AUTOMATION

􀂾Achieve more with less.
􀂾Elimination of human error
􀂾Consistency of product
􀂾Minimize Energy consumption
􀂾Easy diagnosis of fault
􀂾Reduction in Resources(Chemicals ,water , energy etc.)
􀂾Reduce manpower.
􀂾Data collection and consolidation.
􀂾Effective application for Complex tasks
􀂾Trending and Report generation.
􀂾Reduction in Effluent
􀂾Improve Safety and Health.
􀂾Reduce breakdowns.
 Dyehouse Management Manual
The very important area for Automation is the dyeing process, because it involves lot of minute parameters which are very  critical. Even in milligrams variation of recipe can change the shade of  the fabric. All the parameters for dyeing like temperature, pressure,water level, water flow, circulation and time of treatment are  most important.
Automation of the dyeing process can improve the producti productivity by controlling the above parameters very accurately.

Automation in textile dyeing and printing means one or more (or all) of the following steps:
a. Programmable process control (by microprocessors) of the machinery;
b. Dissolving and dispensing of the dyes, pigments and chemicals in a central colour kitchen;
c. Computer-controlled weighing of solid material with automatic stock control and the printing of recipe and process cards;
d. Colour measurement, computerized colour matching;
e. Central computer (network), computerized management system

Criteria for selection of  an Automation System

It is very important to identify the need and the feasibility of the system to be automated.The production cost, the complicity of the machines, the utility requirement of the machines, quality parameters of the products are most important factors to consider while planning for Automation.
Select The System which has

1.Flexibility
2.Ease of Programming.
3.Adaptability to change.
4.Expandability
5.Enhanceability of  function.
6.Ruggedness in system.
7.Service Back up.
Learn More
Different types of  automation systems
Seven Steps to Superior Color Control in the Dyehouse
Need of Automation
The Textile Management System

Cotton Processing : Fiber to Fabric

COTTON, cool, soft, comfortable, the principal clothing fiber of the world. Its production is one of the major factors in world prosperity and economic stability.Cotton's popularity stems from the fiber's inherent benefits, such as tactile comfort (that is, a sensation of softness when touching cotton fabric), and an unsurpassed ability to accept and retain color. Cotton is a seasonless fiber--cool in the summer, insulating in the winter. It "breathes" and therefore keeps body moisture away from the skin. It launders beautifully.Its beauty and natural comfort make the world a better place. Can you imagine a world without cotton? It's often the first fiber we touch when we are born into the world… and it stays with us throughout our lives. Consumer demand clearly shows that people want cotton in their lives all year long because the comfort and strength that cotton provides is empowering.There is nothing fake about cotton. Cotton feels wonderful against your skin and we believe it is the healthiest of all fibers. Life can be hard, but cotton makes our lives easier. What would we do without cotton? Since cotton wrinkles, polyester was added to give it wash and wear properties for a busy world. In recent times, the consumer determined that polyester, although easier to care for, took away the cool from cotton and also added a "pilling" effect to cotton/polyester blends. Consumers now often request "100% Cotton".

cotton is known as for its friendly properties with environment and human body. Cotton is a natural fibre and donot have any hazardess effect as comparison to polyester.

Properties of the cotton
1.Cotton is entirely made up of cellulose.
2.It can also withstand high temperatures in water and tumble drying and remarkably can be bent as many as 50,000 times before breaking point.
3.It is soft and comfortable.
4.It absorbs perspiration quickly.
5.It has good colour retention.
6.It is also strong and durable.
7.It is very versatile, stable chemically, resistant to alkalis.
8.It is of moderate cost.
9.It is sunlight resistant. Handle is soft, cool to the touch.
10.Cotton has an incredible ability to absorb moisture up to 27 times its own weight in water.
Processing of Cotton
Textile – Fibre to Fabric Processing
Textile Raw Materials and Their Conversion Into Yarns; (The Study of the Raw Materials and the Technology of the Spinning Process) a Text-Book
1.Cultivation of cotton
How a cotton plant grows
2.Chemistry of cotton

Cotton is cellulose fiber. Cotton consists typically of 88-96% cellulose. A single molecule of cellulose consists of chain of millions of glucose molecules. Cellulose is natural polymer (C6H10O5)n. It is a polysaccharide. Glucose is a chemical compound in which C (carbon), H (hydrogen),and O (oxygen) are bounded together by covalent bonds (chemical bond).

physical and chemical properties of cotton
3.Ginning

The cotton gin is where cotton fiber is separated from the cotton seed.

Ginning and classing

Grades of cotton

Processability of cotton

Ginning process

The first step in the ginning process is when the cotton is vacuumed into tubes that carry it to a dryer to reduce moisture and improve the fiber quality. Then it runs through cleaning equipment to remove leaf trash, sticks and other foreign matter.

Ginning is accomplished by one of two methods. Cotton varieties with shorter staple or fiber length are ginned with saw gins. This process involves the use of circular saws that grip the fibers and pull them through narrow slots.
Cotton ginning Basics
Fiber quality aspects of cotton ginnning
Ginning machinery
Cotton ginning process video 1
cotton ginning video
4.Spinning
Mixing
Practice of Cotton Fibre Selection for Optimum Mixing
Cotton Mixing
Blow room
Process parameters in Blow Room
Carding
The blow room only opens the row material to flock whereas the card opens the flock into individual fibers. During this individualization process, coarse trash particles are removed in the licker-in zone and fine trash particles/ dust sucked away. The sheet of carded fibers is removed through a funnel into a loose rope like strand called a sliver.
PROCESS PARAMETERS IN CARDING
Combing
Combing process serves to improve the row material in production of medium, medium to fine and fine yarns. This in turn reflects into better yarn evenness, strength, cleanliness, smoothness and visual appearance. In the wool system, combed sliver is used to make worsted yarn, while cards sliver is used for woolen yarn. In cotton system, the term combed cotton applies to the yarn mad from combed sliver. The function of comber is:

• To eliminate pre-determine quantity of short fiber.
• To eliminate remaining impurities.
• To eliminate large proportion of naps.
• To form a sliver of maximum possible evenness.
Process parameters in combing
Drawing

The task of drawing process is to improve evenness over short, medium and especially long term level by straightening and paralyzing the fiber. In addition to this it also for blending of different fibers (Blending of Polyester / Cotton, Polyester / Viscose, Polyester / Wool Etc.) The drawing frame contains several pairs of rollers that rotate at successively faster speed. As the slivers pass through, they are further drawn out and lengthened, to the point where they may be five to six times as long as they were originally. In this process 4 to 8 carded or combed slivers are fed to the drafting arrangement.
Process parameters in Drawing
Roving

The main function of the roving is to attenuate the sliver. In this process draw frame sliver is fed to the drafting arrangement, which attenuate the sliver with a draft of between 5-20. The delivered strand is too thin to hold, which is strengthened by imparting twist immediately at the exit form the drafting arrangement. The twisted (rove) is finally wound on the bobbin, so that it is easy to transport to next process, stored and crelled on ring frame.
Process parameters in Speed frame
Ring Spinning
Spinning Machines (Machine Technology)
Air jet spinning
A spinning system in which yarn is made by wrapping fibers around a core stream of fibers using compressed air.
Air Jet Spinning of Cotton Yarns :- Read here
Compact Spinning
Ring spinning technology : Development in drafting system
open end spinning
Rotor spinning technology
PROCESS PARAMETER IN SPINNING
Production Technology and Applications of Nu-Torque™ Singles Ring Yarns
FAQ cotton spinning
5.Weaving
Basics of Weaving-1
Basics of Weaving -2
Basics of weaving-3
Basics of Weaving -4
The Weaving Book: Patterns and Ideas
Learning to Weave
 6.Knitting
A short history of knitting

Introduction to knitting
V-Bed machine technology
Circular machine technology
Warp knitting machine technology
V-Bed machine fabric structure and patterning
Circular knitting fabric structures and patterning
Yarn tension, cam forces and robbing back
Quality control in v-bed knitting
Graphical representation of warp knitted structures
Graphical representation of weft knitted structures
Quality control in circular knitting
Positive feeding on v-bed machines
Weft knitting quality control
Glossary
Advances in Knitting Technology

Knitting Technology: A Comprehensive Handbook and Practical Guide to Modern Day Principles and Practices
7.Dyeing and finishing
The dyeing of cotton in high-temperature dyeing machines (Technical circulars)
8.Applications : applications of cotton
10. All about cotton

Read About Cotton processing
1.Field to Fabric
2.Process of making cotton cloth
3.Process of.making Cotton Textiles step by step in brief
4. Cotton Textile Processing :-Sustainable solutions for a better future
5.Cotton manufacturing :-An article from 1900s
6.Story of cotton :- Step by step from seed to your wardrobe
7.Organic Cotton Manufacturing
8.Growing cotton : History and cultivation
9. Ring spinning Vs Compact spinning
10. Developments in Spinning
Manual: Sizing, Pretreatment, and Dyeing of Cellulosic Fibres
Dyeing of cellulosic fibres and related processesNew Spinning Systems (Manual of Textile Technology)

Pad Dyeing Machines

Padding Mangles


The pad dyeing machines overcome the deficiency of winch and jigger dyeing machines of smaller batch size and discontinuity in dyeing. Padding mangle offer continuous process of the fabric in concerned liquor , such as pretreatment, dyeing or finishing.
Application of dyestuffs is conducted in the pad dyeing machines with single or multiple dipping in solution .During padding, the fabric passes into a solution of chemicals, under a submerged roller and out of the bath. It is then squeezed to remove excess solution .The objective of this process is to mechanically impregnate the fabric with the solution or dispersion of chemicals Pad impregnation is common for the dyeing of fabric and for the application of finishing chemicals.

A Practical Introduction to the Continuous Dyeing of Woven Fabrics

Machine Description

Main parts of a padding mangle

The main frame

The frames are usually fabricated construction , to withstand vibrations and heavy workloads.

Tension elements

While the cloth passes on to the padding machine no slackness should occur in fabric either in weft or warp directions and the weft threads of cloth should remain parallel to the nip at the squeezing point.

The padding mangle bowls

The nip rollers (often called bowls) are the key to successful pad dyeing. In general, two-bowl nips are preferred for lightweight or standard fabrics running at moderate speeds, whereas three-bowl arrangements are intended for heavier or more densely woven qualities that may be more difficult to wet out and thus require a double-dip and double-nip treatment.

Cloth Guiding arrangement

Are provided so that machine should have a universal feeding and delivery system at a uniform tension .

Pressure generation and application

It is either pneumatic or hydraulic.

The dye trough

The pad trough is usually a deep U-shaped vessel with a single roller attached to the base of a displacement block that leaves a narrow passage to accommodate the moving fabric.
A cost study of thermosol and continuous solvent dyeing

Dyeing Method

The padding operation itself consists of two essential steps: thorough impregnation by immersion of the absorbent fabric in a dye solution containing a wetting agent, followed by squeezing of the wet fabric between rollers to expel air and replace it with dye liquor, as well as expressing surplus liquor back down the sloping fabric surface to the pad trough.

The cloth to be padded is taken up by either from the folded form or from the batched condition and fed to the padding machine over a set of guide rollers. The fabric is straighten in warp as well as weft directions .It is necessary to attach and end piece on both the sides of batch.

The fabric to be padded should be padded should be pretreated , free from loose fly ,waste ,oily matter , flat , crease free and with opened-out selvedges.

To obtain consistency of shade it is most important that the fabric running speed and the length of immersion of fabric in the dye liquor remain constant throughout the padding run. The three main types of automatic level control are:

1. Float switches: these are reliable and are unaffected by foam but they are relatively bulky

2. Conductivity probes: these are small and neat but foaming of the pad liquor adversely affects their performance

3. Differential pressure detectors: those with a hollow tube projecting downwards from the liquor surface are difficult to clean and the preferred type is that with a closed diaphragm set in the base of the vessel.

4. The control of pad liquor temperature is highly desirable to achieve consistent results.

Further Readings
 Jet or pad/wet steam dyeing of tublualr knitted cotton fabrics with reactives: Which costs less? : a summary report (Hatra research report)
Pad-batch Dyeing of Plant Fibres (Rural Technology Guide)