denim washing

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Preface

All praise is to Allah, Lord of the Worlds, the most Beneficent, the most Merciful and every grace of Allah is on His Prophet Muhammad (P.B.U.H), who is always a source of knowledge and guidance for humanity as a whole.

It is a matter of great satisfaction and pleasure for us to present this project. This project report is a part of our Degree program which is done during fourth year of our studies. We chose Denim sector of Textile field as it is a Shinning, growing and challenging field. The entire contents of this report are based on our project in US DENIM. Our major emphasis has been on process, machine and product with the calculations involved. We have included in this project report the technical as well as the Mechanical aspects. We moved department wise covering various aspects. These days of Industrial training enhanced our spirit, courage and confidence. We also improved our presentation and technical skills.

Even though every precaution has been taken, it may be possible that any mistake(s) is found. We will feel grateful, if it is intimate.

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PRESTON UNIVERSITY

ACKNOWLEDGEMENTS

First of all we thank Almighty Allah who brought this moment in our life when we came in US DENIM for the project. It has been a great experience to work with all of you and we are feeling proud that we can say we have worked in US DENIM which is not only one of the best DENIM manufacturer & Exporters in Pakistan but also all over the world and where the management and the workers have demonstrated a very good performance in all areas of the business.

US DENIM is a dynamic organization with professionals loving and professionals making setup. As it is said “Time Spent in Training is time Well-spent”. The golden time, which we spend here and the practical, conceptual and industry- related knowledge, which we gained here will be a milestone in our professional carrier.

We would like to thanks

US DENIM MANAGEMENT Mr. Asif (HR Manager US Denim) Mr. Haroon (Admin)

Mr. Bilal Tariq (Production Manager) Mr. Faisal (MT)

US APPAREL MANAGEMENT

Mr. khurram (HR Manager US Apparel) Mr. Hanif Khan

We are grateful to our class advisor Mr. KASHIF MUNIR for arranging this project.

We always remember the hospitality we received during our stay at the US DENIM. We are privileged to work with experienced personnel, who are the master of their skill and field. Their ever supporting behavior, kind advice, and professional approach taught us how to perform tough and critical tasks with utmost ease.

We have very much enjoyed being amongst wonderful people. We wish each and every one everlasting progress, success and of course wish US DENIM a very prosperous future.

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Contents _________________________________________________________________________________________ U S Denim Introduction . . . .. . . ..….. . .…………..….. .. ... . . . . . . .5 History Of Denim. . . .. . ………… . . . ………….. .. . . . . ………... . .6 Types Of Denim……….10 Introduction of Cotton………..………... . . ………….…….13 Yarn Manufacturing………..………..…. . . ………...14 Warping………..………..…….. . . ………....16 Warping in U S Denim………...19 Warping Plan………...22 Dyeing……….………..…….…. . . …………...24 Sulphur Dye……….25 Vat Dye………..…….………...……...30 Denim Dyeing………..…….………...….……...33 Rope Dyeing………..………….………...………...38 Dyeing in U S Denim………..44 Rebeaming………...………. . . …….………...46 Sizing……….…………. . . ………….…...47 Weaver’s Beam………...………. . . ……….……...48 Weaving……….………...……….……. . . ….………..49 Air-Jet Weaving………..……….…. . . …….…..…...51 Weaving in U S Denim………..………. . . ……..…..…...54 Finishing……….…….………..………….…. . . ………...56 Singeing………..…….…...….……...58 Mercerizing………..…………...………….….………..62 Stenter………..………..…...64 Sanforizing………...65 Inspection Department………..………. . . …….…...68 Packing………..……….……. . . ……..…...70 Faults……….……….…………. .. . . ……....71

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PRESTON UNIVERSITY Contents ______________________________________________________________________________________________ U S Apparel Introduction……….……….……73 Store Room……….……….……..75 Cutting Department……….………..76 Embroidery Department……….………..79 Stitching Department……….………...80 Types of Stitch……….…….………83 Hems………..………90 Wet processing……….….……….93 Chemicals On Denim……….98 Denim Washing. . . .. . . .. . . .. . . . ……110 Mechanical Washes. . . .. . ... . . . .. . . . ………….111 Chemical Washes. . . .. . . …………. ………. . . .. . ….... ……...…119

New Development in Denim Washes. ……….... . . .... . . . . . . …….129

Trimming………..……….132 Buttoning………..……….133 Pressing………..………..136 Finishing………..………..137 Packing………..………138 Glossary Of Denim………..139

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PRESTON UNIVERSITY WEAVING

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US Denim Mills is an upstart denim manufacturing company. We see ourselves as the foremost source of innovative textile products for today's apparel world and are committed to delivering value to our customers in terms of product development, on-time delivery and high quality. We are responsible to our shareholders for a good return on investment. As corporate citizens we work towards achieving the best environmental and ethical practices.

No of Employees more than 500 Established in 2005

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HISTROY OF DENIM:

In fashion history, jeans and denim history continues to baffle. No one truly knows the perfect answer to where jeans began. As so often happens fashions often emerge together in various parts of the world and are the result of the sudden availability of a new fabric, cloth, dye or technique.

But we do know that the phrase denim jeans are thought to derive from several sources. No one is totally certain where the words come from. A majority of source books suggest that denim derives from the English translation of the South of France French phrase 'serge de Nîmes'. Denim fashion history is thus associated with Serge de Nimes.

It may well be that the fabric which was made in France also had a version made locally in England and was called by the same name of denim in the same way that Cheddar cheese is called cheddar all over the world. The Serge de Nîmes was originally a wool silk mix, twill weave. Certainly by the 19th_{century in England denim had a white warp and}

a navy woof (weft). Denim was considered a hard wearing sturdy fabric, ideal for heavy laboring.

When talking about denim the name Levi´ s is one of the first to be mentioned. Levi´ s which stands for Levi Strauss is normally called the forefather of jeans.

When tracing back the history of these trousers to its origins it is true that Levi Strauss played an important role concerning their development and distribution but he had also other inventive business partners. Now the question is: who has sewn the first jeans and where does the history of this „blue phenomenon” begin?

Levi Strauss in the year 1860 In 1847, at the age of 17 Levi Strauss left his Frankonian native country in Germany and emigrated to New York together with his family. The members of the Strauss family were capable and skilful businessmen and ran a pedlary at that time. So Levi and his brother followed their parents´ footsteps and also became peddlers. When his great gold rush began in 1850, however, he decided to take part and sent over to San Francisco

in California. He took with him a spade, a pick hammer and a bale of fabric out of brown sail cloth which was meant to put up a tent. This did not happen, however: Levi found out that the gold diggers´ hard work in the mines made their clothes get worn out very quickly and he produced stout working trousers out of the sail cloth he had taken with him which

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he called „half overalls“. When he continued producing these trousers he used cheap cotton fabrics coming from Genova. At that time Genova was a flourishing place where cotton was exported all over the world. The name of the town of Genova was modified into „jeans” in the American slang. At the end of the sixties of the 19th century he replaced

the brown sail cloth by an indigo-dyed, wear resistant cotton fabric coming from France. The name of this fabric was „Serge de Nimes“. Serge is the French Expression for combined twill and Nimes is the French town where the fabric comes from. The fabric´s name Serge de Nimes was quickly turned into „Denim“in American colloquial language. By applying this indigo-dyed combined twill the first jeans out of Denim was almost born - or better sewn. The only thing missing were the famous metallic vets. The application of metal rivets for jeans is due to the Polish emigrant Jacob W. Davis, also called Jacob Youphes. Although the working trousers out of Denim were stout they had a tendency to get worn out where the pockets were. Jacob Youphes mended the trousers with a needle and thread. One day a customer inspired him to repair the torn off pockets with the help of rivets. From then on Jacob Youphes made a lot of money out of repairing trousers. Since he was worried that his invention might be stolen he wanted to apply for a patent.

For doing so, however, he needed a financially strong partner. For that reason he addressed the manufacturer of the trousers that he mended, Mr. Levi Strauss. Levi Strauss agreed and together they applied for a patent to strengthen the pockets of the trousers and Levi Strauss acquired a share of 50%. This patent was written down in 1873 and can thus be called the true year of birth. Under the management of Levi Strauss the jeans were now produced in series. Since the trousers were so stout not only the gold diggers liked them but which is not surprising in America?

The cowboys appreciated them very much, too. When the trousers were applied as working trousers for cowboys, however they got worn out at the crotch tip. This was no problem for Levi Strauss and Co. since they reinforced the trousers again with metal rivets at the crossing point of the four seams at the crotch tip. The metal rivet at the crotch had to be removed quickly since the way of living of the cowboys had not been taken into consideration. The cowboys used to repair their meals at the campfire and then they spent the rest of the evening sitting round the campfire. When the cowboy approached the fire too much at night, however he quickly learned the difference between the physical conductivity of cotton and metal.

Those wearing these trousers were then suddenly startled out of their sleep. By knowing very well the need for such a stout garment and thanks to the good cooperation with Jacob Youphes as well as his very good instinct for marketing Levi Strauss is still an important brand name in today’s textile industry. About 1947 denim made a break-away from work clothing image, chiefly in the area of sportswear and rainwear and an occasional appearance in high fashion collections as a "different-looking" evening dress. Jeans fashion history was truly made in the 1950s when film stars wore it in movies that the teenagers of the day followed with avid interest. For many years jeans were only used as work wear clothes, but by the 1940s they were considered leisure wear in America.

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western world. 1970 American youth adopted denim as their favorite fabric. Part of a "back to nature" movement that emphasized ecology and the natural denim being a fabric created from a natural fiber was a primary factor. Since 1960 the jeans business has undergone an explosive transformation, from a source of tough, cheap clothing for cowboys, blue-collar workers and penniless youth into a fashion conscious market for a widening mass of people of almost all ages.

Substantial growth in overseas sales of American jeans and denim. Exports of American-made blue jeans grew. Overseas manufacturers of jeans also grew. Production of indigo dyed denim started in Europe on an industrial level in 1972. Spreading of jeans fashions in the 1970’s and doubling of denim capacity in U.S.led to the onslaught of imports. From 1976 to 1979 U.S. imports of denim into Europe enjoyed penetration levels between 33% and 42%. European textile industry saw in denim, an opportunity to restructure itself into a more capital intensive high technology industry, thus becoming more competitive against imports from lower-cost countries. From 1972 to 1976 capacities grew from approximately 20 million square meters to 130 million. All mills were basically running at capacity. It was a period of worldwide shortage of denim when demand was substantially greater than capacity. The 1976/7 fashion element subsided in Europe and U.S. Return to specialist jean manufacturer producing basic jeans, with relative little fashion styling. The introduction of "baggy" jeans – originated in Italy where previous shortage led to youth wearing any size jeans available. Since 1978 specialized denim manufacturers re established positions mainly in terms of quality.

Indigo denim first produced at Yarraville during 1965 on a narrow width Slasher dyeing machine designed and built on the area. This dyeing method has now been entirely replaced by the commissioning of the Morrison Rope Dyeing Machine on July 4th, 1980.

Dyeing capacity 15 to 16,000,000 square meters of denim per annum are possible on this new Morrison dyeing Machine. By the 1980s ripped, frayed and torn jeans were a normal sight. Colored jeans from white through to pastels were also popular as were stonewashed blue jeans. In the 80s, designer jeans with names like Gloria Vanderbilt, Calvin Klein and Armani among so many fashion designers became the designer label jeans to be seen in. Stone washed jeans became a must.

By the 1990s black jeans were very popular for a while and jeans in general were seen a lot in the early 1990s. But shades of blue are always loved and sometimes the darkest shade is high fashion and sometimes the most washed out faded pairs become the hottest. Colored jeans of all shades made an appearance.

In 2000 designers were crystal beading and silver or gold spraying jeans amid tears, frayed slashes, and fur and feather decoration. Denim was hot yet again and used to make everything from footwear, jackets, bags, basque corsets to jeweled cuffs.

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TYPES OF DENIM

While the original denim was a 100% cotton serge material, you can now get it in a variety of materials, including blends that give you the same wonderful look of 100% cotton denim with some great additional features. Denim’s unique look comes from the rich indigo blue in one shade or another woven together with white threads to give the “depth” that people associate with denim. Today, some denims no longer have indigo, but other colors with the white opposing threads, producing denims in a rainbow of shades.

DRY DENIM

Dry or raw denim, as opposed to washed denim, is a denim fabric that is not washed after being dyed during its production. Most denim is washed after being crafted into an article of clothing in order to make it softer and to eliminate any shrinkage which could cause an item to not fit after the owner washes it. In addition to being washed, non-dry denim is sometimes artificially "distressed" to achieve a worn-in look. Much of the appeal of dry denim lies in the fact that with time the fabric will fade in a manner similar to factory distressed denim. With dry denim, however, such fading is affected by the body of the person who wears the jeans and the activities of their daily life. This creates what many enthusiasts feel to be a more natural, unique look than pre-distressed denim. To facilitate the natural distressing process, some wearers of dry denim will often abstain from washing their jeans for more than six months,[3]

though it is not a necessity for fading. Predominantly found in premium denim lines, dry denim represents a small niche in the overall market.

Dry denim can be identified by its lack of a wash, or "fade". It typically starts out as the dark blue color pictured here.

SELVAGE DENIM

Selvage denim (also called selvedge denim) is a type of denim which forms a clean natural edge that does not unravel. It is commonly presented in the unwashed or raw state. Typically, the selvage edges will be located along the outseam of the pants, making it visible when cuffs are worn. Although selvage denim is not completely synonymous with unwashed denim, the presence of selvage typically implies that the denim used is a higher quality. The word "selvage" comes from the phrase "self-edge" and denotes denim made on old-style shuttle looms. These looms weave fabric with one continuous cross

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separate wefts which leave an open edge that must be stitched. Shuttle looming is a more time-consuming weaving process that produces denim of a tighter weave resulting in a heavier weight fabric that lasts. Shuttle looms weave a more narrow piece of fabric, and thus a longer piece of fabric is required to make a pair of jeans (approximately 3 yards). To maximize yield, traditional jean makers use the fabric all the way to the selvage edge. When the cuff is turned up the two selvage edges, where the denim is sewn together, can be seen. The selvage edge is usually stiched with colored thread: green, white, brown, yellow, and red (red is the most common). Fabric mills used these colors to differentiate between fabrics.

Most selvage jeans today are dyed with synthetic indigo, but natural indigo dye is available in smaller niche denim labels. Loop dying machines feed a rope of cotton yarn through vats of indigo dye and then back out. The dye is allowed to oxidize before the next dip. Multiple dips create a deep dark indigo blue. In response to increased demand for jeans in the 1950's, American denim manufacturers replaced the old shuttle style looms with modern projectile looms. The new looms produced fabric faster and wider (60-inches or wider), yet lighter and less durable. Synthetic dyeing techniques along with post-dye treatments were introduced to control shrink and twist. Raw selvage is material that has not been washed once undergoing the dying process. It is especially desirable because the material will fade in the creases and folds of the jeans. This process is known as whiskering.

Here are some of the newer types of denim on the market:

STRETCH DENIM is usually about 98% cotton and 2% Spandex for a bit of that forgiving

stretch we all love. This blend gives you wonderful ease of movement and at the same time some support for those “trouble spots” you aren’t so fond of around the hips or thighs. Stretch denim jeans are one of the fastest growing segments of the women’s market for jeans manufacturers.

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POLY DENIM blends appeal to those who like the look of denim but prefer polyester

blends that wash and dry quickly and are lighter weight and a bit dressier. These usually appeal to a slightly older market, but are also finding favor for pantsuits, etc. when the look is meant to be “dressy but casual.”

RAMIE COTTON DENIM blends are found in a variety of combinations, with a wide price

variance. Ramie is a plant fiber usually added because it reduces wrinkling and adds a silky luster to the fabric. It isn’t as strong as cotton, however, so it has to be blended with this stronger material in order to stand up as a denim material.

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COTTON

The botanical name of cotton is Gossypium.

COTTON PROPERTIES

Length & Uniformity Upper Half Mean Length

Below 0.99 Short 0.99-1.10 Medium

1.11-1.26 Long

Above 1.26 Extra Long

Uniformity Index

Below 77 Very Low

77-79 Low

80-82 Low

83-85 High

Above 85 Very High

Fiber Fineness

Fineness (millitex) Description

Below 135 Very Fine

135-175 Fine

175-200 Average

200-230 Coarse

Above 230 Very Coarse

Fiber Strength

(1/8 in. gauge strength in grams/tex) 20 and Below Very Weak

21-25 Weak

26-29 Base

30-32 Strong

32 and above Very Strong

Fiber Elongation (%)

Below 5.0 Very Low

5.0-5.8 Low

5.9-6.7 Average

6.8-7.6 High

Above 7.6 Very High

Fiber Maturity

Maturity Ration Description

Below 0.7 Uncommon

0.7-0.8 Immature

0.8-1.0 Mature

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YARN MANUFACTURING

The initial stage of denim production is Opening and Blending. Opening begins with baled cotton fiber being separated into small tufts. A blend of cotton fibers is made on each opening line. These bales are selected using USDA High Volume Instrument (HVI) data, and PCCA's unique computer blending software produces optimal yarn strength. Cotton is delivered by air suction from the Opening and Blending lines, through additional cleaning and blending machines, to the Cards. The major functions of Carding are to remove foreign matter and short fibers, form the cotton into a web and convert the web into a rope-like form known as a sliver.

The drawing process produces a single, uniform sliver from six card slivers. The additional blending, paralleling of fibers and cleaning in this process produces a sliver for Open End and Ring Spinning. For Ring Spinning, however, the sliver must pass through an additional process called Roving.

Cotton Fibers are formed into a yarn by centrifugal action in Open- End Spinning. Individual fibers are laid down in the groove of a fast spinning rotor and twisted into yarn. After the cotton fibers are spun into yarn, the yarn is wound into a large package.

The Open End Spinning Machines have robots on each side which automatically pieces up (repairs broken ends). On a different track, they have another robot that automatically doffs (removes full packages) and starts up a new package. The size and quality of each yarn end are monitored by the Barco Profile System to ensure uniformity.

In Ring Spinning, the spinning frames receive Roving via a transit system from the roving machine. Yarn is formed from cotton fibers that are twisted together after being drafted by passing between three steel rolls and three rubber rolls. The yarn then is wrapped on a bobbin as it spins on a spindle by use of a traveler. The relationship between roll speeds, traveler speeds and spindle speeds controls the amount of twist in the yarn. Ends down levels and production information are gathered by the Uster Ring

Expert System. The spinning frames automatically doff bobbins full of yarn and send them to package winding.

ACG also has the capacity to produce Amsler Open-End yarn, also known as Faux Ring Spun yarn. This technology enables ACG to impart various slub patterns into an Open-End yarn. Denim made from this type of yarn has yarn character and surface interest that

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BALANCING OF A SPINNING LINE FOR DENIM MANUFACTURING

Count 6 7

Production Required per day (kg) 8763 14235 Auto Coro Average Speed 70000 75000 TM 5 4.8 TPI 12.25 12.7 % Installed Efficiency 90 90 % waste 0.2 0.2 Prod/rotor/day 18.515 16.401 prod/day required 8763 14235 rotors 473 868 machines 1.97 3.62 rotors/mc. 240 240

production /month in tonnes 263 427

DrawFrame

Installed n% 70 70

Production /day 3788 3788

Hank Delivered 0 0

Production Required per day 8789 14292

Passages 1 1

% waste 0.6 0.6

m/c required 2.32 3.77

Cards 6 7

Doffer dia/ inch 27 27

Doffer rpm 51 51 installed effe. 85% 85% % waste 5% 5% hank delivered 0.1 0.1 tension draft 2 2 production/hr in kg 43 43 produc daykg 1036 1036 production required 8842 14378 Machines required 8.53 13.87 Blowroom Lines 6 7 efficiency 90 90 Production/day 10800 10800 prod required/day 9308 9308 lines required 0.86 1.4 Count 6 7 Speed/mt/min 700 700

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WARPING

In general terms, warping is transferring many yarns from a creel of single-end packages forming a parallel sheet of yarns wound onto a beam or a section beam. The warp beam that is installed on weaving machine is called the weaver’s beam. A weaver’s beam can contain several thousand ends and for different reasons it is rarely produced in one operation.

There are four types of warping, which are as follows 1. Direct Warping

2. Indirect or Sectional Warping 3. Ball Warping

4. Draw Warping

DIRECT WARPING

In direct warping, the yarns are withdrawn from the single-end yarn packages on the creel and directly wound on a beam.

Direct warping is used in two ways:

a) It can be used to directly produce the weaver’s beam in a single operation. This is suitable for strong yarns that do not require sizing and when the number of warps on the warp beam is relatively small. This is also called direct beaming.

b) It can also be used to make smaller, intermediate beams called warper’s beams. These smaller beams are combined later at the slashing stage to produce the weaver’s beam. This process is called beaming.

INDIRECT OR SECTIONAL WARPING

In Indirect warping, a section beam is produce first. It is also called band warping or drum warping. The section beam is tapered at one end. Warp yarn is wound on the beam in sections, starting with the tapered end of the beam. Each section has multiple ends that are traversed together slowly during winding along the length of the section to form the angle. Due to the geometry of the yarn sections, the last section on the beam will have a tapered end that will make the whole yarn on the beam stable. It is important that each layer on the beam contain the same number of yarns. The same length of yarn is wound on each section.

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After all the sections on the beam are wound completely, then the yarn on the beam is wound on to a regular beam with flanges, before slashing. This process is called rebeaming.

BALL WARPING

Ball Warping is mainly used in manufacturing of denim fabrics. The warp yarns are wound on a ball beam in the form of a tow for indigo dyeing. After the dyeing process, the tow is separated and wound on a beam. This stage is also called long chain beaming or re-beaming.

DRAW WARPING

Draw Warping is combining the drawing of filament yarns with heat setting and warping processes to achieve uniform stretching and heating for improved dye uniformity, end to end. It is used for weaving of thermoplastic yarns.

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WARPING IN US DENIM:

In US Denim ball warping is used. There are three creel machines of GRIFFIN. Two creels have capacity of 420 cones each weather one creel has a capacity of 540 cones. The department is connected with dyeing section directly and working 24 hrs. R &D department inspects the cones which is converted in beams of required length and forwarded to dyeing section.

COMPONENTS OF MACHINE • CREEL • LEASING STAND • TURN-AROUND ROLL • TURN-AROUND STAND • BALL WARPER

• Dual MOTOR DRIVE

CREEL:

Custom designed to meet package dimensions, end count requirements and available space. Electromagnetic Tension Control with individual post adjustment, 0-75 GPE tension range, with individual post-post calibration. Integrated Motion Sensor with 25

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millisecond response time, end break indicator, end count confirmation, and recurring break indication for same package.

LEASING STAND: Semi-Automatic lease insertion at programmable intervals with ertical

oscillation to reduce wear.

TURN-AROUND ROLL: Provides additional length to the yarn path (in sheet form) to

allow for recovery of lost or broken ends and reduces rolling in the trumpet at the end of the traverse stroke.

TURN-AROUND STAND: Constructed of heavy duty steel with an aluminum flanged

300mm diameter x 125mm wide guide wheel. The guide wheel has a pneumatic disk brake for controlled stops.

BALL WARPER: The Ball Warper is capable of producing a 1220mm width ball with

diameters up to 1524mm (60”) and safe operating speeds up to 500 mpm.

DUAL MOTOR DRIVE: utilizes the latest drive technologies, including AC vector

drive/motors, high strength polyurethane timing belts and heavy duty beveled gearboxes. The trumpet carrier; which has no bearings, is machined from thermoplastic to reduce weight and improve durability thus eliminating routine maintenance. Drive Rolls are rubber covered for maximum durability and are coupled to Dual Caliper Disc Brakes for quick stopping. The hold down arms provide programmable hold down pressure and are

used in loading and doffing the beam.

The Griffin Director is a PC based drive and control system that completely automates the operation of the machine. Operator interface is by 380mm Touchscreen. Customer support is provided through modem communication 24/7 by Griffin technicians.

OPTIONAL EQUIPMENT: Automatic Traveling Cleaner, Inside loading/outside running

creel design, Manual Post/Disc Tensions, Drop Wire Stopmotion System, Sheet Vacuum System (SVS).

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COMPARISON OF H AND V CREEL

H-CREEL V-CREEL

Parallel warping is used for sectional warping as well as for direct warping.

V-creel is used for only in direct warping. Suitable for comparatively low speed

warping.

Suitable for high speed yarn warping.

Needs proper yarn guides. No need of yarn guide

Provide low tension on wholebeam. Provide uniform yarn tension across the

whole beam. No free yarn from creel to the warping

machine because proper yarn guides are required.

Free yarn run from creel to the warping machine.

More time consumable because oflow speed.

Less time consumable.

More space is consumed. Less space is consumed.

In indirect warping, a constant speed drive is generally required to provide approximately uniform yarn speed on the surface of the beam.

Surface friction drive and variable speed drive is commonly used to attain the uniform yarn speed.

H-creel has a wide range of package change system. Example: with reversible package, with unrolling draw off, with fixed package frames, with package trucks, with swiveling package frames.

V-creel has a low range of package change. Example: reversible frames, reversible frames with automatic knotter, and with traveling package.

PROCEDURE OF WARPING:

The creel stand has maximum capacity of five cones per stand. The yarn from the cones is unwounded and passes from rod by cross wound, holed by a catcher guided to the tensioning zone when cone rotates anticlockwise. There are three types of tension in warping i.e. catcher tension, rod tension, and sacker tension. Magnetic tensioner is used for yarn tension. Then the yarn comes to the winding zone or headstock. Combs straighten the yarns towards pressure drum, which supports beam, and yarns in an alignment so that each and every yarn end can wound separately. Static charges due to friction of yarns on metal surface cause static charges, which are removed through an anti static device. Then the yarn is wounded on beam in this way for a required length if beam is changed after one filling of beam then knotting of yarns is made. Similarly if cones are finished on one frame side then trolley system of cone changing is used in this way chains rotates the whole frame of empty side and new filled side of frame is forwarded again knotting is done between the new cones yarn and already winded yarn. Extra yarn is then removed through cutting. Sensors sense any type of yarn breakage and in case of yarn breakage knotting is done.

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WARPING PLAN

The warper gets the required no of ends and the number of beams from the weaving department and then he made the warping plan that how to complete that task whether on one creel or on more no. of creels.

Some examples are given below to show the concept of warping plans using one creel and two creels.

For example;

If,

No. of ends = 1080 No. of beam = 4 Count = 10/s

No. of cones in one bag = 16

No. of warper's beams with no. of ends on each = ? Length per beam = ?

No. of Bags of 100 lbs = ?

Plan for one Creel

Then,

The total no. of ends on the weavers beam = 1080 x 4 = 4320 ends

Cone wt. = bag wt. / no. of cones in bag

Cone wt = 100 / 16 = 6.25 lbs

Length of yarn on one cone = cone wt. In lbs x count x 768.1

Length of yarn on one cone = 6.25 x 10 x 768.1 = 48006 m

lessen the length up to 1 % because of variation in yarn length among different cones

length of yarn on one cone = 47600 m

no. of ends x no. of beams = total no. of ends 617 x 6 = 3702

618 x 1 = 618

4320 ends

so, 7 warper's beams

i.e. 6 beams of 617 ends and

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Bags required = No. of ends on warper beam / no. of cones in one bag

Bags required = 618 / 16 = 39 bags approx. For example;

If,

No. of ends = 1140 No. of beams = 4 Count = 10/s

No. of cones in one bag = 24

No. of warper's beams with no. of ends on each = ? Length per beam = ?

No. of Bags of 100 lbs = ?

Plan for two Creel

The total no. of ends on the weavers beam = 1140 x 4 = 4560 ends

Cone wt. = bag wt. / no. of cones in bag

Cone wt = 100 / 24 = 4.16 lbs

Length of yarn on one cone = cone wt. In lbs x count x 768.1

Length of yarn on one cone = 4.16x 10 x 768.1 = 31952 m

lessen the length up to 1 % because of variation in yarn length among different cones length of yarn on one cone = 51600 m

no. of ends x no. of beams = total no. of ends

570 x 8 = 4560 ends

so, 8 warper’s beams 0f 570 ends each

No. of beams per creel = no. of warper’s beam / no. of creels No. of beams per creel = 8 / 2 = 4

Length / Beam = length of yarn on one cone / no. of beams per creel Length / Beam = 31600 / 4 = 7950 m / beam

Bags required = No. of ends on warper beam X no. of creels / no. of cones in one bag Bags required = 570 X 2 / 24 = 48 bags approx.

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DYEING

Dyeing is a process in which we impart colour to the fabric. All commercial textile dyeing processes take place by the application of a solution or a dispersion of the dyes to the textile material followed by some type of fixation process. The dye solution or dispersion is almost always in an aqueous medium.

A major objective of the fixation step is normally to ensure that the coloured textile exhibits satisfactory fastness to subsequent treatment in aqueous wash liquors.

Dyeing is mainly depends on the type of fabric, structure of fabric and the properties of dyes.

Dyes use for Denim

• Sulphur Dyes • Vat Dyes

SULPHUR DYES:

Sulphur dyes are widely used on cotton mainly because they are economical to use. They have good to excellent wash fastness and good light fastness in dark shades. Light fastness of pale shades is poor. Sulphur dyes are usually dull in shade since the molecular structures are complex. As a class, the sulphur dyes are not resistant to chlorine containing bleaches.

Chemical nature of sulphur dyes

Partial chemical structures involved in dyeing with sulphur dyes

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CHARACTERISTICS OF SULPHUR AND LEUCO SULPHUR DYES ON COTTON:

Sulphur dyes have the dullest range of colours of all dye classes but are relatively inexpensive. They are used to dye medium to deep, dull shades on cellulosic materials. There are several excellent blacks giving dyeings with good wet fastness properties. In fact, when black, and deep brown, blue and dull olive green shades are needed, with good washing and satisfactory light fastness at reasonable cost, sulphur dyes are irreplaceable. There are few green sulphur dyes and no true reds.

There are, however, an abundance of blacks, blues, yellows and browns. On a world basis, sulphur dyes constitute one of the major dye classes. Sulphur dyes are used in cotton dyeing for woven goods using jig dyeing machines and also in continuous dyeing. They are commonly used for the continuous dyeing of corduroy. They are now being used more widely in jet machines. Sulphur dyes are also used for dyeing denim olive, brown and maroon, rather than the traditional Indigo blue, as well as to ‘bottom’ or ‘top’ Indigo dyed cotton warps. To ‘bottom’ or ‘top’ means that a sulphur dye is applied either before or after the Indigo. The fastness to wet processes and to crocking can be varied almost as required to satisfy the demand for the faded look so popular for denim. This is achieved by allowing premature oxidation of the leuco dye during dyeing, by using short dyeing times so that there is inadequate time for dye penetration into the fibres, and by poor rinsing and soaping after dyeing. The dyeings can then be subsequently treated to produce the faded worn look by removing the surface colour.

Although cellulosic goods dyed with sulphur dyes usually have good washing fastness, it can be further improved by resin finishing. The light fastness varies from moderate to good in heavy shades. A major characteristic of sulphur dyes is the poor fastness to chlorine, which distinguishes them from most quinone vat dyes. Dyeings with sulphur dyes cannot be bleached with hypochlorite. In fact, these dyes are readily distinguished from other cotton dyes by their dark, dull colours and the bleaching that occurs when a dyeing is spotted with hypochlorite and allowed to dry.

Cotton dyed with some sulphur blacks becomes tendered on storing under warm humid conditions. This is a consequence of the formation of sulphuric acid from oxidation of the sulphur dye in the fibres. It can be minimised by thorough washing after dyeing before the oxidation of the leuco dye, by a final alkaline rinsing with soda ash solution, and by resin finishing. Such tendering is avoided by dichromate oxidation of the leuco dye.

DYEING METHOD:

Initially the goods are wet out in the bath. Since the dyeing liquor contains appreciable amounts of sulphide, copper fittings must be avoided. If wetting or penetrating agents are used these should be of the anionic type since ionic surfactants form stable, non-substantive complexes with the leuco thiols. An anionic product such as phosphated 2-ethylhexanol is suitable. The bath may then be set at 40 °C with some sodium polysulphide . Polysulphides in the leuco dyebath prevent premature oxidation of the dye and reduce the tendency to bronziness of deep dyeings of blues, navies and blacks. An addition of a sequestrant such as EDTA avoids precipitation of the leuco thiolate by calcium and magnesium ions. The leuco dye is then added slowly and, since the leuco dyes only have low to moderate substantivity for cellulose, some salt may be added

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Sulphur dyes usually have acceptable substantivity, particularly in the presence of salts, so that stripping in a fresh reducing bath is not easy. Dyeing is often conducted at the boil but this decreases the degree of exhaustion. Sulphur dyes require less salt than reactive dyes and usually have reasonable exhaustion. Low sulphide leuco dyes require more salt and no polysulphide. They do not give good exhaustion in heavy shades and the use of a low liquor ratio is recommended. For popular shades such as black, it has long been common practice to use a standing bath. This is a dye bath that is re-used for subsequent dyeings after addition of more reduced dye. Any free sulphur that tends to accumulate is dissolved by addition of sodium sulphite to give thiosulphate. This prevents it sticking to the goods. The actual dyeing temperature can vary. At higher temperatures around the boil, the bath exhaustion is less but penetration of the leuco dye into the fibres is better than at lower temperatures.

POST-DYEING TREATMENTS:

After dyeing, good rinsing before oxidation helps reduce bronziness and poor rubbing fastness by removing loosely adhering surface leuco dye solution before oxidation precipitates the insoluble pigment. Once the rinsing is completed, the leuco dye in the fibres is oxidised to the insoluble pigment. Some leuco dyes can be oxidised in air, others need chemical oxidation. Sodium dichromate, hydrogen peroxide, or sodium percarbonate or perborate are used in warm, weakly alkaline solution. The peroxy compounds used for vat dyes can be used for sulphur dyes, but some leuco dyes (red-browns) are not oxidised by these agents. Some blues are over-oxidised, probably by oxidation of the disulphide links between the heteroaromatic units to form ionic sulphinate and sulphonate groups. This increases the water solubility, decreases the wet fastness and results in staining of other goods during washing. Even sulphur blacks oxidised with peroxides tend to be bluer, lighter and somewhat less fast to washing. The best washing fastness is obtained by oxidation of the leuco dye with sodium dichromate and acetic acid. Sodium bromate (NaBrO3) is now more widely used as an oxidant, particularly in North America. It requires a small amount of metavanadate ion (VO3 –) as catalyst.

Some dyeings are treated with copper sulphate, or with this and sodium dichromate, to improve the light fastness, and in some cases the wet fastness. Fabrics for use inside rubber articles should not be copper treated. Some yellowbrown dyes are treated with copper sulphate to improve light fastness but theeffect is lost on washing. The use of chromium salts is now declining because of their adverse environmental impact.

Because of their dull colours, dyeings with sulphur dyes are often topped with the much brighter basic dyes. The sulphur dye pigment acts as a mordant for the cationic dyes. Dyeings with sulphur dyes may also be shaded with some sulphide stable direct dyes, but this tends to lower the washing fastness.

DYEING WITH SOLUBLE SULPHUR DYES:

Large amounts of such dyes are sold in liquid form. They are of two types –1.

Water-soluble reduced leuco dyes, and-2. solubilised sulphur dyes – the former being far more important. The water soluble leuco dyes are completely in solution and contain far less insoluble matter than a sulphur dye powder. This is beneficial in package dyeing. They often still require a small addition of sodium sulphide or another reducing agent. These liquids contain the stabilised leuco dye, sodium sulphoxyate-formaldehyde or sulphide and sodium carbonate. The solubilised sulphur dyes are thiosulphate esters prepared from the leuco thiols with sodium sulphite . They usually have low substantivity for

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cellulose and are useful for package, padding and pad–jig applications. Reduction is necessary before or during dyeing and the usual aftertreatments are needed.

CONTINUOUS DYEING WITH SULPHUR DYES:

Sulphur dyes are used for continuous dyeing of cotton goods using a pad–steam– wash process, with three groups of wash boxes for rinsing, oxidising and soaping. Padding may take place at up to 80 °C to reduce the substantivity of the leuco dye for the cotton fibres. This reduces the problems of selective absorption and the resulting initial colour tailing that it causes. As for other vat dyes, steaming is carried out in air-free saturated steam. Then the dyeing is rinsed at 40–60 °C and oxidised with sodium bromate plus metavanadate catalyst at pH 4 in the presence of acetic acid. In the remaining wash boxes, the best possible soaping and rinsing is done. For black dyes tending to produce sulphuric acid by oxidation on storage, a final soda ash rinse may be added. In some instances better appearances result using a two-pad method. This involves padding with the sulphur dye suspension or solution, followed by intermediate drying, padding with sodium sulphide solution, steaming, and the usual aftertreatment sequence.

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VAT DYES:

Vat dyes are mainly applied on cellulosic fibres, but some can be applied to protein fibres. They usually have outstanding colour-fastness properties. Vat dyes are more expensive and difficult to apply than other classes for cellulose such as directs, sulphurs, and reactive. Indigo is a special case in the vat dye class. Indigo is attractive for its pleasing blue colour and for the unique fading characteristics of garment dyed with it. Vat dyes are characterized by the presence of a keto group. Vat dyes in keto form are water insoluble pigments.

CHEMICAL CONSTITUTION OF QUINONE VAT DYES

CI Vat Red 42 (1); leuco compound formed by reduction (2); vat acid formed by protonation of the anionic leuco derivative (3); CI Vat Blue 4 (4)

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Reducing vat dyes with hydros

THE SUBSTANTIVITY AND DYEING CHARACTERISTICS OF VAT DYES FOR CELLULOSIC FIBRES

BASIC STEPS IN THE DYEING PROCESS:

The dyeing of cellulosic materials with quinone vat dyes follows a four-step sequence: (1) Preparation of the vat containing the leuco forms of the dyes;

(2) Dyeing of the material, in which the fibres absorb the water-soluble leuco compound; (3) Oxidation of the absorbed leuco compound back to the parent pigment inside the fibres;

(4) Soaping of the dyed material to remove pigment loosely adhering to the fibre surfaces and to develop the true shade and fastness properties.

DYEING WITH INDIGO AND INDIGOID VAT DYES:

Natural Indigo was rapidly displaced from the market once the synthetic product became available. The quality of natural Indigo was quite variable because of the presence of other coloured impurities. The fastness properties of Indigo dyeings are not up to the standards expected from the vat dye class as a whole. It is, however, the appearance of faded Indigo in denim that is so fashionable today. After dyeing, various wet processes, such as stone washing, deliberately enhance this faded effect. Indigo builds up primarily on the cotton fibre surface. This is one reason for the somewhat inferior fastness properties of Indigo compared to quinone vat dyes.

APPLICATION OF INDIGO TO COTTON:

Dyeing cotton yarn for blue jeans is an important use of Indigo. In a typical batch operation, concentrated reduced Indigo is added to a dyebath from which oxygen has been removed with little alkaline hydros. The goods are entered and fully immersed to avoid oxidation. After about 15 min at 20–25 °C, the goods are removed and well squeezed before air oxidation. Indigo does not exhaust well because of its limited substantivity for cotton, not surprising considering its small molecular size . Deep shades must be built up by repeated dipping in the dyebath after each oxidation. The use of too concentrated a dyebath is not effective for deep shades as it results in poor rubbing fastness. Some salt may be added to aid exhaustion. After dyeing, the goods are well soaped. The final dyed material may be aftertreated to produce a faded, worn look.

Continuous methods are used for dyeing ball warps, warp beams and piece goods with Indigo. This is usually carried out in a series of 4–6 wash boxes with upper and lower rollers and nips at the exits. The goods are threaded through each box and may be skyed at the mid-point. The first box is used to wet out the material. In subsequent boxes, the goods are immersed in the leuco Indigo solution for 10–30 s at a linear speed of about 25 m min–1, squeezed and skyed for 2 min to oxidize the leuco dye to Indigo. The boxes are

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fed with a stock vat of leuco Indigo and the liquor in the boxes is circulated to maintain constant dyeing conditions. This process of several dips and oxidations is then repeated in a second series of boxes, and so on. Several rinsing and washing boxes complete the process.

INDIGOID VAT DYES:

Besides Indigo itself, there are a number of other important indigo and thioindigo derivatives used for dyeing cellulosic fibres. These include chlorinated and brominated indigo and thioindigo dyes in which the nitrogen atoms of Indigo are partially or totally replaced by sulphur atoms. Compared to the anthraquinone type vat dyes, Indigoid vat dyes give much paler yellow to brown leuco compound solutions. The vatting process is also slower and requires less alkali.

SOLUBILISED VAT DYES:

The solubilised vat dyes provided a means of avoiding the difficult vatting process required for quinone and indigoid vat dyes. The preparation of a solution of a leuco vat dye requires care and time, and protection of the solution from excessive exposure to air. The solubilised vat dyes avoid these problems. These dyes are preprepared sulphate esters of the leuco vat acid. The first product of this type was that derived from Indigo . Later solubilised leuco dyes derived from quinone vat dyes were marketed.

Cotton absorbs these dyes directly from a neutral or slightly alkaline solution but they are not very substantive even in the presence of added salt. Although a leuco sulphate ester has the same negative charge as the normal leuco dye, its charge is localised in the sulphate groups whereas that of the phenolate ion is delocalised. Cotton therefore repels a leuco sulphate ester molecule more strongly than the normal leuco compound. Because of their limited substantivity, solubilised vat dyes are generally only suitable for pale shades. After dyeing, the goods are rinsed or hydroextracted to remove superficial dye solution, and the vat dye pigment is developed in the fibre by oxidation with sodium persulphate or acidified sodium nitrite solution. After neutralising with dilute soda ash solution, the goods are soaped as in the case of normal vat dyeing. The dyeing has the same fastness properties as one prepared from the original vatted pigment.

The low substantivity of the leuco sulphate esters avoids the problems of the high strike of leuco vat dyes. Since they can be used in solutions close to neutrality, they can also be used for wool dyeing. Unfortunately, the dyeing and oxidation conditions for each dye

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DENIM DYEING:-

The classical jeans was produced out of indigo-dyed Denim fabric. The special character of this fabric – only the warp thread is dyed – makes it necessary to carry out dyeing in yarn form. The yarns applied for Denim were exclusively produced on ring spinning machines in former times. The development of OE(open end) yarns – by applying smaller rotors with a spinning speed of up to 200 m/min – has led to the application of OE rotor yarns both for warp and weft. The yarns applied for weaving must be of high quality: a high fiber for strength, regularity as well as a small part of short-stapled cotton fibers belong to the basic features of the denim yarn. For regular jeans qualities the warp yarns are spun in a fineness of 50 to 90 tex, for the weft yarn the fineness ranges are mainly 75 to 120 tex. If Denim is made out of Tencel or Modal especially for jeans shirts the finenesses are up to 25 tex. Indigo, sulphur and indanthrene are mainly used in the dyeing process. Two methods are applicable for continuous dyeing with indanthrene dyes: rapid dyeing and vat dyeing. While processing the basic colored denim, reactive dyes are used and fixed with hot caustic soda solution. The dyeing process is mainly influenced by the dyestuff characteristics, dyeing temperature and necessary chemicals used in the process. Indigo dye is the most popular choice as it has good depth of shade and suitable rubbing and washing fastness. When cotton yarn is dyed with indigo, it leaves a ring-dyeing effect, because of which the outer layer of warp yarn is coated with indigo, and the core of the yarn remains undyed. This gives the denim garment a unique ‘faded look’ and a rich blue shade after repeated use and wash. Originally, the warp yarns or ends were put through the dye bath side by side to form a sheet of yarn, which passed continuously through several dye baths, squeeze rollers or airing sequences.

However, if there were breaks in the yarn (and there would be, as each yarn had to take the tension of being pulled through these processes virtually on its own), the dyeing process had to be stopped. The yarns would be then mended, or else it would lead to very bad tangling. These stoppages would in turn cause large shade variations, and the yarn breaks would show up as bad faults in the fabric. Now, an infinitely more efficient system has been introduced.

Special attention shall be paid here to Indigo, the „king of dyestuffs“since it plays an important role in obtaining the jeans effect. Indigo belongs to the category of water-insoluble dyestuffs. It was first mentioned in a book 13 BC; at that time the name Indian blue indicated the country the color came from. It is said to have been used for dyeing in India and China 2000 years BC already.

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The Indigo plant is used for preparing Indigo

(Indigo tinctoria L.)

This plant came to Europe in the 16th century via India and gradually replaced the

woad which was one of the most important dyeing plants up to this time. Only the leaves were used for good qualities whereas the leaves together with the stalks were applied for normal qualities. In a vat filled with water and partially with human fermented urine as alkali donor stems and leaves were exposed to a putrefactive process. During this putrefactive process hydrogen was created by means of micro-organisms which, as a reduction agent, transformed the dyestuff contained in the Indigo plant into a water-soluble form.

When this process was over the whole mass was filled into a liquid where the fermented mass was stirred with poles. The reason for doing so was to transform the Indigo into its water insoluble form again by air oxidation. In a last step the water-insoluble dyestuff particles could then deposit on the bottom of a stationary vat.

Then the liquid standing above was drained and what was left was a thin mash which was dried in the open air and was put on the market in pressed or in powder form

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As shown in figure trading form of Indigo at that time, approx. 9 cm length of edges and 163 g in weight. When looking at these methods one can easily imagine that the reduction of Indigo was considered to be an evil-smelling trade. In 1880 Adolf von Baeyer succeeded in carrying out the first synthetic production of Indigo. In the year 1897 the “Badische Anilin- und Sodafabrik“in Ludwigshafen -hich is nowadays called BASF - was able to carry out an industrial-scale production of the Indigo dyestuff for the first time. A few years later this synthetic dyestuff replaced the indigo coming from British-India almost completely. As was already mentioned Indigo is a dyestuff insoluble in water. In order to be able to apply it on cotton it must be transformed into a water-soluble form. Similar to the former production of Indigo this is done by reducing the dyestuff (ill. 4). In practice this is nowadays carried out with sodium dithionite or hydroxiacetone in the alkaline range.

INDIGO REDUCTION

C16H10O2N2 + Na2S2O4 + 4NaOH

.

C16H10O2N2Na2 + 2Na2SO3 + 2H2O

OXIDATION REACTION

Na2S2O4 + O2 + 2NaOH

.

Na2SO4 + Na2SO3 + H2O + C16H10O2N2Na2 + ½ O2 + H2O +

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Fiber cross-section of a yarn dyed with Indigo

This is Fiber cross-section of a yarn dyed with Indigo simplified description of the reduction/oxidation of Indigo In former times dyeing with Indigo was carried out in wood or metal vats, normally in rope form.

Indigo sample dyer as very clearly visible on the above picture, at the bottom side of the rope the water-soluble Leuco form of the indigo is yellowish and on the side of the rope oxidized with air the indigo blue can be seen again. Nowadays, yarn dyeing with indigo is done continuously. Here the various dyeing processes with different concentrations of chemicals as well as the subsequent yarn sizing exert an influence on the quality and the appearance of the ready fabric.

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HOW TO MAKE INDIGO SOLUTION

In a tank of 1000 liters:

a. take 400 litres of water (soft)

b. add setamol ws--> 4 g/l (stirring) ( dispersing solution)

c. Add 100 kg of Indigo ( at 1.8 % shade -see the indigo calculations- stirring) d. add caustic soda --> stirring ( for solubilising and pH)

e. allow to cool it for 2/3 hours

f. Add hydrosulphide ( As reducing agent) g. Make the solution to 1000 l by adding water.

If pH is fluctuating, if it is > 11.7 then hydro is added (2-3 kg), if (<11.2) then caustic is added.

For 100 kg of Indigo, Caustic Required= 90 kg Hydro Required= 80 kg

INDIGO CALCULATIONS

For 12 ropes, at 24 m/min, of 344 ends of 14000 m length of 7s count. wt of yarn = (12*344*14000*100*453.6)/(7*840*36*2.54*1000) kg= 5000 kg at 24 m/min, a lot of 14000 m will be completed in 14000/24 = 583.3 min at 1.8% shade

100 kg of yarn needs--> 1.8 kg of Indigo 5000 kg of yarn needs --> 90 kg of dye at 100 gpl

100 gms of dye = 1 lit of solution 90 kg of dye = 900 litres

900 litres should be completed in 583.3 min

1 litre would be completed in = 583.3/900= 38.8 seconds so flow rate will be 38.8 seconds / litre

Similarly flow rate of caustic and hydro can be determined Hydro is taken around 100 gpl

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There are three processes in the practice for continuous dyeing: 1) Rope Dyeing

2) Slasher Or Sheet Dyeing 3) Loop Dyeing

ROPE DYEING:

Indigo Rope Dyeing When dyeing according to the rope dyeing or cable dyeing method.350 - 400 warp threads are bound on the ball warper to very thick cables of 10000 - 15 000 m length. On the continuous dyeing installation, 12 to 36 cables are led side by side, wetted, dyed and dried after the dyeing process on cylinders and put into cans. Then the cables are dissolved to warps on the long chain beamer. The warps are added to the sizing machine, sized and then led together to warp depending on the total numbers of threads.

In practice, this method has proven to be very good through obtaining an optimum indigo dyeing. However it is important that the cables have a constant tension in order to avoid warp stripes. The disadvantage compared to other methods is that yarn breakages do occur more often. Size of the dyeing unit is between 60 - 80 m. normally, 6 dyeing vats are in use. There are nevertheless variations with 3 to 8 dyeing vats.

The dyeing methods described here do not allow a total penetration of the dyestuff during the short dyeing time and give the desired and necessary ring dyeing important for the jeans effect.

The sizing process follows the dyeing process of the yarn; this is already visible by the machine sequences and is necessary to stabilize the warp thread against the high mechanical stress while the weft thread is being fed. For sizing the warp, PVA, CMC and acrylate sizes are used besides starch-containing products.

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DYEING AIR TIMING

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PROCESS CONTROL OF ROPE DYEING FOR DENIM

1. Concentration of Hydrosulphite

It is measured by vatometer. It should be from 1.5 gpl to 2.5gpl , or by redox potential of dye bath which should be from -730 mV to -860 mV.

2. Caustic Soda or pH value

Should be from 11.5-12.5

3. Dye concentration in Dye bath

it is measured by spectrophotometer. It should be in g/l

Guidelines

High Indigo Concentration --> Shade is greener and lighter Low Indigo Concentration --> Shade is dull and Red. High pH or Caustic Concentration --> Redder and lighter Low pH or caustic concentration --> greener and darker

Dipping Time

Longer the dipping time, better will be the penetration and lesser will be the ring dyeing effect. It varies from 15-22 seconds.

Squeeze Pressure

High pressure will lead to lower wet pick up and result in lesser color and better penetration. At rope dyeing, squeeze pressure is 5-10 tonnes, ie. wet pick up is as low as 60%. Hardness of squeeze roller is about 70-75 deg. shores. It sqeeze rolls are too hard then there are chances of slippage and uneven yarn tension.. If

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Airing Time

it should be 60-75 seconds. Longer airing time results in high tension on the yarn and subsequent processes will become difficult.

Drying

Insufficient or unevenly dried yarns will result in poor rebeaming

Calculation of Replenishing Dye feed/min

Conc. of stock vat is g/l= 90 range speed in yards/min=25 count = 7s

totoal ends = 4100

Wt of yarn dyed /min= (4100*25*1000)/(7*840*202)= 7924 gms shade desired = 2%

Amount of dye to be replenished/min= 158.5 gms

Effect of pH

At pH of 10.5 to 11.5, there will be formation of more monophenolate ions, which lead to higher color yield, as strike rate of the dye to the yarn bundle is very high, and wash down activities will be very good.

At pH higher than this, dye penetration will be less and wash down characteristics are also poor.

Testing

1. Alkalanity in Dye Bath Liquor

Pipet 10.0 ml of vat liquor into 100ml of distilled water in a 150 ml beaker. place under continuous agitation and insert the electrodes of a pH meter caliberated at pH 7.0 with standard buffer solution.

Titrate with tenth normal HCl ( 0.1 HCl) to pH 7.0 (ml = A) calculate

g/l of NaOH = A *0.40

2. Hydro in Dye bath Liquor

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25% glacial acetic acid solution prepared by diluting 1 part acid with 3 parts water. Add 2 ml of starch/KI indicator. Add ml of water. Titrate with 0.046 N ( prepared by diluting 460 ml of 0.1 N Iodine to one liter ) solution until the color changes from emarald green to bluish purple.

G/l of hydro= mo fo 0.046N of Iodine

Importance of High Concentration of Free Hydrosulphite

The clearest shades with minimum reddish streaks are observed at by relatively high conc. of hydrosulphite. On the other side, with lack of hydrosulphite, the leuco indigo is less dissolved and thereby adheres to a greater extent to the fibres. With lack of

hydrosulphite furthermore, the amount of unreduced dyestuff by oxidation at the upper level of the liquor and through activiation of unfixed dyestuff, gets separated from the fibrous material would constantly rise as the reducing agent for creating leucoform would be missing. Under these circumstances a reddish bronze like shade results due to dispersion of not reduced dyestuff in the yarn. The min. proportion of hydrosulphite should be around 1.3 to 1.5 gpl in case of rope dyeing and 3-4 gpl in case of sheet dyeing. Also to avoid the lack of hydrosulphite or Indigo at certain places in the immersion, vat, the whole quantity of the liquor should be circulated 2-3 times every hour.

Reaction Time

At very short reaction time, an adequate liquor exchange ( i.e. the amount of

chemicals consumed and replaced by fresh addition of reduced indigo) is not assured. This has a negative influence on dyeing and depth of dye penetration. In addition to this the time available for diffusion of dyestuff until oxidation commences is too short. To ensure an even and good depth of dye penetration by dyeing in several passages, the reaction time should be 20-30 sec. for each vat (eg. at a speed of 20m/min for a reaciton time of 10 seconds, the immersion path should be maximum 3.3 meters). A reaction time exceeding 60 seconds should be avoided as the amount of dyestuff again get reduced and released may again supersede that of additionally take up dye stuff, resulting in higher shades.

Softening Agent: 8 g/lit

Drying: Rest humidity should be 30% and then sized.

Addition of chemicals

1. Red Tinge: reduce addition of NaOH, increase slightly Na2S2O3 2. Darkish Red: increase Hydro