20287842-Project-of-Denim-Dyeing

Preface

In line with recent trends toward high-quality production and diversification in the textile processing , much efforts is being exerted to improve the performance of mixed fabrics of natural and synthetic fibres and to introduce the new product with new values. This technical information presents a detailed description of the standard working procedure adopted under normal practice for continous dyeing of polyester/cellulosic blended fabrics,a and series of important suggestions over the selection of dye sftuff. As continous dyeing polyester /cellulosic blended fabrics involves a large variety of fibre substrates, processing methods and recommendable dye stuffs, in this information two possible dye stuffs are described—one is disperse vat combination and second is disperse reactive combination .

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Acknowledgment All thanks are due to Almighty “ALLAH” most beneficial and merciful who enable us to complete this project.

The completion of this project is perceived as the fruitful result of and incredible effort, devotion and hardwork. It can be stated without any hesitation that this subject is the outcome of the joint effort of all concerned by successfully negotiating the various tedious problems and hurdles.

We are particularly thankful of S.M Qutab ,our project advisor for the guidance and valuable cooperation render by him at any stage regarding this project. He full indulged himself to facilitate our job whenever approached him to seek guidance regarding this study.

Finally we acknowledge a debt of gratitude to our parents and other encouragement, who led us to complete this project work.

Authors

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HISTROY OF DENIM Denim is more than a cotton fabric; it inspires strong opinions from historians, designers, teenagers, movie stars, reporters and writers. In 1969 a writer for American Fabrics magazine declared, "Denim is one of the world's oldest fabrics, yet it remains eternally young." If continuous use of and interest in an item makes it "eternally young," then denim certainly qualifies. Legend and fact are also interwoven when scholars discuss the origin of the name denim. Most reference books say that denim is an English corruption of the French phrase "serge de Nimes;" a serge fabric from the town of Nimes in France. However, some scholars have begun to question this explanation. ORIGINS IN EUROPE: There are a few schools of thought on the derivation of the word "denim." The serge de Nimes fabric traces back to France prior to the 17th century. At the same time, there was also a fabric known in France as "nim." Both fabrics were composed partly of wool. Serge de Nimes was also known in England before the end of the 17th century. The question then arises: was this fabric imported from France or was it an English fabric bearing the same name? Fabrics which were named for a certain geographic location were often also made elsewhere; the name was used to lend a certain cachet to the fabric when it was offered for sale. Therefore a "serge de Nimes" purchased in England was very likely also made in England, and not in Nimes, France. There still remains the question of how the word "denim" is thought to have descended from the word "serge de Nimes." Serge de Nimes was made of silk and wool, but denim has always been made of cotton. Again, this relation between fabrics is in name only, though both fabrics are twill weave. Is the real origin of the word denim "serge de nim," meaning a fabric that resembled the part-wool fabric called nim? Was serge de Nimes more well-known than serge de nim and mistranslated when it crossed the English Channel? It's likely we will never really know.

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To confuse things even more, another fabric known as "jean" also existed at this same time. Research on this textile indicates that it was a fustian - a cotton, linen and/or wool blend - and that fustian from Genoa, Italy was called jean. This is evidence of a fabric being named for a place of origin. It was apparently quite popular and imported into England in large quantities during the 16th century. By the end of this period, jean was being produced in Lancashire. By the 18th century, jean cloth was made completely of cotton and used to make men's clothing, valued especially for its property of durability even after many types of washing. Denim's popularity was also on the rise. It was stronger and more expensive than jean, and though the two fabrics were very similar in some ways, they did have one major difference: denim was made of one colored thread and one white thread; jean was woven of two threads of the same color. DENIM COMES TO AMERICA: As denim moved across the Atlantic in the late 18th century, American textile mills started to produce their own denim fabric on a small scale, mostly as a way to become independent from foreign producers (mainly the English). From the very beginning, cotton fabrics were an important component of American mills' product line. A factory in the state of Massachusetts wove both denim and jean. American President George Washington toured this mill in 1789 and was shown the machinery that wove denim. That same year, one of the first printed references to the word "denim" in the United States appeared: a Rhode Island newspaper reported on the local production of denim among other fabrics. The book "The Weavers Draft Book and Clothiers Assistant," published in 1792, contains technical sketches of the weaving methods for a variety of denims. In 1864, an East Coast wholesale house advertised that it carried 10 different kinds of denim, including "New Creek Blues" and "Madison River Browns," terms that still sound contemporary today. Webster's Dictionary from the same year contained the word "denim," referring to it as "a coarse cotton drilling used for overalls, etc." Research shows that jean and denim were two very different fabrics in 19th century America. They also differed in how they were used. In 1849, a New York clothing

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manufacturer advertised topcoats, vests or short jackets in chestnut, olive, black, white and blue jean. Fine trousers were offered in blue jean; overalls and trousers made for work were offered in blue and fancy denim. Other American advertisements show working men wearing clothing that illustrates this difference in jean and denim usage. Mechanics and painters wore overalls made of blue denim. Working men in general, including those not engaged in manual labor, wore more tailored trousers made of jean. Denim, then, seems to have been reserved for work clothes, when both durability and comfort were needed. Jean was a sturdy fabric, but it did not offer the added benefits of denim, such as durability and comfort. THE FIRST BLUE JEANS: In 1962, the magazine American Fabrics ran an article that stated, "If we were to use a human term to describe a textile we might say that denim is an honest fabric - substantial, forthright, and unpretentious." So how did this utilitarian and unpretentious fabric become the stuff of legends that it is today? And how did pants made out of denim come to be called jeans, when they were not made out of the fabric called jean? One very important reason can be found in the life and work of a Bavarian-born businessman who made his way to Gold Rush San Francisco nearly 150 years ago. Levi's® jeans, of course, are named for the founder of the company that invented them: Levi Strauss, born as "Loeb" Strauss in Bavaria in 1829. He, his mother and two sisters left Germany in 1847 and sailed to New York, where Loeb's half-brothers ran a wholesale dry-goods business (selling bolts of cloth, linens, clothing, etc.). For a few years, young Loeb worked for his brothers, and by 1850 had changed his name to Levi. In 1853, he obtained his American citizenship and decided to make a new start and undertake the hazardous journey to San Francisco, a city enjoying the benefits of the recent Gold Rush. His mission was to open the West Coast branch of his brothers' wholesale dry- goods business, which he started as soon as he got off the boat. He sold common dry-goods products to small stores all over the West. These products included pillows, blankets, underwear and clothing whose manufacturers

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are no longer in business. Levi worked hard, and acquired a reputation for quality products over the next two decades. In 1872, he got a letter from Jacob Davis, a Reno, Nevada tailor, who had come up with a great idea. To improve the strength of the pants he made for his customers, he added metal rivets, which proved to be a big success. He wanted to patent the idea, but didn't have the money he needed to file the papers. So he wrote to Levi, saying that if he would pay for the application, the two men could make riveted clothing and, as Davis put it in his letter, "make a very large amount of money." Levi knew a good business opportunity when he saw one, and in 1873 he and Davis received a patent for an "Improvement in Fastening Pocket-Openings." Levi brought Jacob Davis to San Francisco to oversee the first manufacture of their copper riveted "waist overalls," the old name for jeans. These pants were made from brown cotton duck and blue denim. Knowing that the riveted pants were going to be perfect for work wear, Levi and Jacob decided to make them out of denim rather than jean because denim was a very sturdy fabric appropriate for workwear. Levi Strauss died in 1902, at the age of 73. He left his thriving manufacturing and dry goods business to his four nephews — Jacob, Louis, Abraham and Sigmund Stern — who helped rebuild the company after the big earthquake and fire of 1906. The following year, Jacob Davis sold back his share of the company. The oldest surviving catalog in our company archives, which was published after the earthquake, shows a variety of denim products for sale. DENIM MEETS THE 21ST CENTURY: American Fabrics magazine predicted back in 1969 that denim would become a fashion statement for many occasions when it said, "What has happened to denim in the last decade is really a capsule of what happened to America. It has climbed the ladder of taste." Today, millions of people wear jeans to work, where the suit once ruled. Looking back, we know that the very first people to wear Levi's® jeans worked with pick and shovel. Though our tools are now pencils, paper and computer keyboard, we have been moved to wear the same thing: denim jeans.

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Born in Europe, denim's function and adaptable form found a perfect home in untamed 19th century America with the invention of jeans. Denim gives us a little bit of history every time we put it on.

DYES WHICH ARE BEING USED FOR THE DENIM DYEING

Background Indigo, or indigotin, is a dyestuff originally extracted from the varieties of the indigo and woad plants. Indigo was known throughout the ancient world for its ability to color fabrics a deep blue. Egyptian artifacts suggest that indigo was employed as early as 1600 B.C. and it has been found in Africa, India, Indonesia, and China. The dye imparts a brilliant blue hue to fabric. In the dying process, cotton and linen threads are usually soaked and dried 15-20 times. By comparison, silk threads must be died over 40 times. After dying, the yarn may be sun dried to deepen the color. Indigo is unique in its ability to impart surface color while only partially penetrating fibers. When yarn died with indigo is untwisted, it can be seen that the inner layers remain uncolored. The dye also fades to give a characteristic wom look and for this reason it is commonly used to color denim. Originally extracted from plants, today indigo is synthetically produced on an industrial scale. It is most commonly sold as either a 100% powder or as a 20% solution. Through the early 1990s, indigo prices ranged near $44/lb ($20/kg). History The name indigo comes from the Roman term indicum, which means a product of India. This is somewhat of a misnomer since the plant is grown in many areas of the world, including Asia, Java, Japan, and Central America. Another ancient term for the dye is nil from which the Arabic term for blue, al-nil, is derived. The English word aniline comes from the same source. The dye can be extracted from several plants, but historically the indigo plant was the most commonly used because it is was more widely available. It belongs to the

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legume family and over three hundred species have been identified. Indigo tinctoria and I. suifruticosa are the most common. In ancient times, indigo was a precious commodity because plant leaves contain only about small amount of the dye (about 2-4%). Therefore, a large number of plants are required to produce a significant quantity of dye. Indigo plantations were founded in many parts of the world to ensure a controlled supply. Demand for indigo dramatically increased during the industrial revolution, in part due to the popularity of Levi Strauss's blue denim jeans. The natural extraction process was expensive and could not produce the mass quantities required for the burgeoning garment industry. So chemists began searching for synthetic methods of producing the dye. In 1883 Adolf von Baeyer (of Baeyer aspirin fame) researched indigo's chemical structure. He found that he could treat omega-bromoacetanilide with an alkali (a substance that is high in pH) to produce oxindole. Later, based on this observation, K. Heumann identified a synthesis pathway to produce indigo. Within 14 years their work resulted in the first commercial production of the synthetic dye. In 1905 Baeyer was awarded the Nobel Prize for his discovery. At the end of the 1990s, the German based company BASF AG was the world's leading producer, accounting for nearly 50% of all indigo dyestuffs sold. In recent years, the synthetic process used to produce indigo has come under scrutiny because of the harsh chemicals involved. New, more environmentally responsible methods are being sought by manufacturers. Raw Materials The raw materials used in the natural production of indigo are leaves from a variety of plant species including indigo, woad, and polygonum. Only the leaves are used since they contain the greatest concentration of dye molecules. In the synthetic process, a number of chemicals are employed as described below. SOURCES AND USES: A variety of plants, including woad, have provided indigo throughout history, but most natural indigo is obtained from those in the genus Indigofera, which are native to the tropics. In temperate climates indigo can also be obtained from woad (Isatis tinctoria) and dyer's knotweed (Polygonum tinctorum), although the Indigofera

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species yield more dye. The primary commercial indigo species in Asia was true indigo (Indigofera tinctoria, also known as Indigofera sumatrana). In Central and South America the two species Indigofera suffructicosa and Indigofera arrecta (Natal indigo) were the most important. Natural indigo was the only source of the dye until about 1900. Within a short time, however, synthetic indigo had almost completely superseded natural indigo, and today nearly all indigo produced is synthetic. In the United States, the primary use for indigo is as a dye for cotton work clothes and blue jeans. Over one billion pairs of jeans around the world are dyed blue with indigo. For many years indigo was used to produce deep navy blue colors on wool. Indigo does not bond strongly to the fiber, and wear and repeated washing may slowly remove the dye. Indigo is also used as a food coloring, and is listed as FD&C Blue No. 2. The specification for FD&C Blue No. 2 includes three substances, of which the major one is the sodium salt of Indigotindisulfonate. Indigotinesulfonate is also used as a dye in renal function testing, as a reagent for the detection of nitrates and chlorates and in the testing of milk.

INDIGO MOLECULE

CHEMICAL PROPERTIES: Indigo is a dark blue crystalline powder that melts at 390°–392°C. It is insoluble in water, alcohol, or ether but soluble in chloroform, nitrobenzene, or concentrated sulfuric acid. The chemical structure of indigo corresponds to the formula C16H10N2O2.

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The naturally occurring substance is indican, which is colorless and soluble in water. Indican can easily be hydrolyzed to glucose and indoxyl. Mild oxidation, such as by exposure to air, converts indoxyl to indigo. The manufacturing process developed in the late 1800s is still in use throughout the world. In this process, indoxyl is synthesized by the fusion of sodium phenylglycinate in a mixture of sodium hydroxide and sodamide. Several simpler compounds can be produced by decomposing indigo; these compounds include aniline and picric acid. The only chemical reaction of practical importance is its reduction by urea to indigo white. The indigo white is reoxidized to indigo after it has been applied to the fabric. Indigo treated with sulfuric acid produces a blue-green color. It became available in the mid-1700s. Sulfonated indigo is also referred to as Saxon blue or indigo carmine. Tyrian purple was a valuable purple dye in antiquity. It was made from excretions of a common Mediterranean Sea snail. In 1909 its structure was shown to be 6,6′dibromoindigo. It has never been produced synthetically on a commercial basis.

INDIGO CARMINE

HOW THE DYE WAS PRODUCED IN INDIA The cut plant is tied into bundles, which are then packed into the fermenting vats and covered with clear fresh water. The vats, which are usually made of brick lined with cement, have an area of about 400 square feet and are 3 feet deep, are arranged in two rows, the tops of the bottom or "beating vats" being generally on a

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level with the bottoms of the fermenting vats. The indigo plant is allowed to steep till the rapid fermentation, which quickly sets in, has almost ceased, the time required being from 10-15 hours. The liquor, which varies from a pale straw colour to a golden-yellow, is then run into the beaters, where it is agitated either by men entering the vats and beating with oars, or by machinery. The colour of the liquid becomes green, then blue, and, finally, the indigo separates out as flakes, and is precipitated to the bottom of the vats. The indigo is allowed to thoroughly settle, when the supernatant liquid is drawn off. The pulpy mass of indigo is then boiled with water for some hours to remove impurities, filtered through thick woollen or coarse canvas bags, then pressed to remove as much of the moisture as possible, after which it is cut into cubes and finally air-dried Nature 1 November 1900 INDIGO DYEING: Indigo dye is an important dyestuff with a distinctive blue color (see indigo). The natural dye comes from several species of plant, but nearly all indigo produced today is synthetic. Among other uses, it is used in the production of denim cloth for blue jeans. The form of indigo used in food is called "indigotine", and is listed as FD&C Blue No. 2.

PHYTOCHEMISTRY OF INDIGO Now just a bit of chemistry about how the compounds in plants are converted into indigo...

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In Indigofera species, the precursor of indigo is indican (left), indoxyl-β-D-glucopyranoside, While in woad it is mainly isatan A (right)

INDUSTRIAL SYNTHESIS OF INDIGO Current world production of indigo is 17,000 tons/year, mostly (40%) produced by BASF in Ludwigshafen. That is where things started in July 1897, using a process developed by von Heumann. It started with naphthalene...

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VAT DYES Vat dyes are used in the dyeing and printing of all types of cellulose fibres, and also of blends of cotton with polyester. In their coloured form they are insoluble pigments, so their applications depend on reversible reduction-oxidation (redox) reaction. In dye bath the pigment is converted into a water-soluble form using a strongly alkaline solution of a powerful reducing agent. This form the sodium “leuco” compound of the dye, which is soluble in water but often different in colour from the original in pigment. It is then allowed to dye the cellulose in this water-soluble from once exhaustion is completed the leuco compound is oxidized. REDOX REACTIONS Oxidation-reduction reactions (redox reaction) are important in textile colouration because they are an essential part of the process of the application of vat and sulphur dyes. In rather oversimplified terms, when a compound id oxidized it gain oxygen when something is reduced it loses oxygen. Reduction of a substance can also be thought of as gaining oxygen atoms, and oxidation as losing hydrogen atoms. For example when hydrogen reacts with oxygen to form water the hydrogen to become oxidized and the oxygen is reduced. In a redox reaction there is always a compound acting a reducing agent (hydrogen in this example). The reducing agents become oxidized the reaction by the compound that is being reduced, which is acting as an oxidizing agent. (In this case oxygen) NaOH Sodium Hydroxide

Na+ + OHSodium

Hydroxide

ion

ion

In the water molecule each hydrogen atom shares the only electron it possesses by pairing with one of the six electron of the oxygen atom, to form a covalent bond. Thus the hydrogen atom has lost one electron to become oxidized and the oxygen atom is reduced by gaining electrons. This is a more general way of expressing the phenomena of oxidation and reduction. Oxidation = entails the loss of electrons by the oxidized compound Reduction = entails the net gain of electrons by the reduced compound

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vat dyes such as indigo and compounds derived from anthrequinone are applied after the temporary reduction of two carboxyl group in a conjugated chain, this convert the dye in to a colorless water insoluble form. The conversion is carried out using a strong reducing agent and in this reaction the two oxygen atom becomes reduced –O – and the two hydrogen atoms are oxidized to H+. The reduced form is called the leuco vat acid, and is applied from an alkaline. Once on the fibre it can be re -oxidized back to the insoluble carbonyl form by air or by the use of an oxidizing agent. Sulphur dyes are also applied using a redox reaction mechanism, in which sodium sulphide is used as the reducing agent, CHEMICAL NATURE OF VAT DYES A large majority of vat dyes are based on the anthraquinonoid or the indigo (or thioindigo) chromophores; indigo, one of the oldest dyes still in use, remains popular through the wide use of indigo-dyed anthrequinone dyes are complex polycyclic quinines (Appendix 1), and they all possess two carbonyl groups (C = O) linked by alternate single and double bonds in a conjugated chain. The molecular arrangement is responsible for the easily reversible redox reactions on which the application of vat dyes depends. In earlier countries, when all textile colorants where obtained from natural sources, indigo plant is steeped in a large vat. It is forming this ancient vatting process that the term fermentation vat dyes are derived. Fermentation converts one of the plant constituents into the soluble leuco dye, which diffuses out of the plant. The replacement of the natural by synthetic indigo at the end of the nineteenth century gave the imputes to research on other syntheses vat dyes have since followed. Synthetic vat dyes are costly because they are difficult to prepare, so their use is usually directed to the higher quality fabrics. Nevertheless, they are widely used and noted for their high fastness to light, in the dyeing of fabric for uses such as awning, curtains, upholstery, military and naval uniforms and high quality gabardines.

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High fastness to bleaching is another strong point of the anthraquinonoid group. This is exploited in the production of patterned fabric from vat-dyed yarn in which the white areas of the can be safely bleached out after weaving. Anthraquinonoid vat dyes are widely used in the manufacturer of for example good quality, shirting’s, table cloths, towels, sportswear, high quality over all, fabrics of women and children clothing and tropical suiting, and yarns and effect threads where repeated washing will be required. With careful dye solution, the use of vat dyes allows is that the range lacks scarlet, maroon and wide shades. APPLICATION OF VAT DYES Both the extent of reduction and the rate at which equilibrium between the reduced and oxidized from is achieved are of practical significance. Vat dyes vary in the speed with which they go undergo reduction (Na2S2O4), which is capable of completely reducing even the most stable of vat dyes. As a result any difficulties in vatting can be over come by raising the vatting temperature, increasing the concentration of reducing agent or prolonging the vatting time. The vatted dyes must be kept in a strongly alkaline solution, because its leuco from is an insoluble acid. If instead of being formed as its water soluble salt, it will not readily oxidize to the coloured form. There are still some application methods in which reduction and adsorption in the fibre take place rapidly and almost simultaneously. Under those conditions the rate and extent of reduction can be decisive factors in the dye stuff choice for example, in textile printing. Premature oxidation of the leuco compound in his print paste must also be avoided during both storage and steaming. This condition is usually met by using as the reducing agent sodium formaldehyde sulphoxylate (Formosul) a compound that is fairly stable in air at room temperature and develops the necessary action during steaming. Variables such as pigment practical size and crystalline from can affect the rate of reduction but these are controlled by the dye manufacturing. Consequently the colourist needs to concentrate only on the temperature and the concentration of reducing agent.

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Leuco compounds can be applied by batch wise methods similar to those used for other dye classes, but there are difficulties in obtaining leveling dyeing. The necessary high concentration of sodium hydroxide and reducing agent affect the exhaustion. The difference is that the option of reducing the concentration of the addition is not available, because they are needed to form the leuco compound. Serious leveling problems can be lessened by raising the temperature of dyeing and then cooling to obtain satisfactory exhaustion, or by using a dye bath auxiliary that restrains the rate of exhaustion. A different approach is to use specially formulated to stable dispersion of the pigment, in which form they are evenly distributed on the fabric by padding (pigment padding), followed by working the padded fabric through a of caustic soda and sodium dithionite on a jig. Pre-pigmentation can be carried out using package, jig, winch or beam dyeing machines provided specially formulated vat dyes are used. Once the pigmentation is completed, sodium hydroxide and sodium dithionite are added to the dye bath to reduce the pigment and allow the leuco day salt to diffuse into the fibre. Oxidation in air or in solution is then used to regenerate the pigment. A soaping treatment is given to the fabric at the end of the dyeing process this is essential, both for cleaning the dyed fabric and for developing the final shade. In some cases a change in the crystalline form of dye accompanies the change in shade. SOLUBILISED VAT DYES The need to reduce vet dyes before use makes their application a cumbersome process. Although it is possible to isolate the reduced form of the dye. It is too readily oxidized in air for the manufacturer to provide the dyer with the leuco compounds. it is possible however to convert the leuco acid into the leuco ester, a derivative that has greater resistance to oxidation and grater solubility in water. Such ester can be formed by the reaction of a hydroxyl group of a leuco acid with sulphuric acid forming a sulphuric ester. The sodium salt of such esters are stable and can be stored until required for use. Since the ester group is only weakly attached to the rest of the dye molecule, it is easily removed by the action of sodium nitrate in dilute sulphuric acid. The regenerated leuco compound may then be oxidized back to the pigment form.

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Solubilised vat dyes are less rapidly taken up than are the more conventional vat dyes and are mainly used for the production of pale shade. As with ordinary vat dyes application under alkaline condition is essential, thus eliminating wool from the list of possible substrates because alkaline condition modifies the wool fibres. The low up take and higher cost of solubilised vat dyes make them uneconomical for deep shade however and for theses normal vat dyes alternative have to be used. A interesting property of solubilised vat yes is their sensitivity to light in the solubilised state. This is used to produce “photographic” print on fabric. R - OH + H2S2O4 Leuco vat Dyes

sulphuric

R - OH + H2S2O4 + H2O sulphuric ester

acid

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SULPHUR DYES Deposition of insoluble pigments inside fibres may achieve more cheaply using sulphur dyes. But with these the shade gamut is restricted to back, mauves, olives, Bordeaux and reddish-browns. One of the earliest and best known sulphur dyes is Cl sulphur black 1, which is popular black with good fastness properties still in use today. Like vat dyes, sulphur dyes are reduced and applied as soluble leuco compounds that need to be kept under alkaline condition, but sulphur dyes need only sodium sulphide to act as both alkaline and reducing agent. A simplified the version of the reaction is represented in following equation. The structure of the chromophores of sulphur dyes is complex and unknown. Again like vat dyes, these dyes can not be applied to wool without damage to the fibres due to the action of sodium sulphide on the cystine cross links. After exhausting the dye bath for approximately 1 hour at 6090Co the fabric is thoroughly rinsed and exposed to the atmosphere, where oxidation generates the mechanically entrapped insoluble pigment. One disadvantages of certain sulphur dyes (although, strangely, this problems appears to arise with the black shade only) is that dyed material stored under condition of high humidity and temperature can lose its nature strength. This is because inadequate washing-off after dyeing can lead to the slow generation of sulphuric acid in the fibre, arising from the presence of sulphur. Sulphur dyes are used mainly in the dyeing of cellulose fabrics and in blend of cellulose with polyester, nylon and acrylic fibres. Typical application is for heavy drill fabrics. Corduroys, overalls, denim, awning and canvas. Limited quantities are also consumed in the colouration of silk, paper and more widely, leather. Ar’ – S – S- Ar’

Reduction with Na2S Ar’ – S – S- Ar’

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LATEST DYEING METHODS Now processing and dyeing methods for indigo warps were introduced from 19781987 to obtain a higher productivity and savings in dyeing or to achieve the required darker shades (hard rock washing, super blue, soft denim), or softness of the yarn for final finishing. The following table gives you a comparison of the possible processing stages such as: 1- Indigo rope dyeing process 2- Indigo one sheet dye slashing 3- Indigo double sheet dyeing 4- Loop dye 1 for 6 (continuous dye slashing) 5- Loop dye 1for 6 with dyemer (continuous mercerization dyeing and sizing). For the five major Indigo dyeing methods for the basic denim, super blue denim, soft denim, stone wash denim, we also must take into consideration that a certain appearance of the garments is only achieved after a certain washing method. (Chemical washing, stone washing, hard rock washing), use of certain sizing agents (soft denim) or irregular appearance in warp or weft direction by using a yarn with slubs and neps (antic denim). The final finishing methods have influence on fabric construction and dyeing methods. CHEMICAL WASHED DENIM The father of snow wash denim or of f-side denim is Edwin Co. Limited Japan. These chemical washed types of ready made garments show less tensile strength and a harder hand. STONE WASHING With soft stones it takes 20 – 30 min. to achieve the desire surface appearance. DRY BLEACH Soft rock are socked with chloride and the garment treated in washing machines.

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HARD STONE WASHING Treatment takes approx. 3 – 4 hours. A very soft hand the garments is achieved. Due to the extended time of treatment in washing with hard rocks the strength of fabric is influenced. This treatment requires improved yarn quality and deeper dyed shades. Hard stone washing fades out partly at hems and stitched lines. SUPER BLUE Deepness shade is achieved by dyeing in 8 – 12 dye boxes with rope dyeing methods. With mercerized yarn where the colour stays at the surface of the yarn (ring dyeing) with continuous loop dye range with integrated mercerizing and dyeing unit (dyemer). BLACK DENIM Sulfur dyed, padazoic dyed etc. on continuous dyeing sizing machines or loop dye ranges. INDIGO, DYESTUFF AND HIS DENIM CHARATERISTICS

Indigo has despite many other blue dyestuffs kept his popularity. This by no doubt is achieved by the fact that Indigo has a number of properties which have in this combination not yet been achieved by other single dyestuffs. The main properties are: •

Pleasant colour shade.

•

Possibility to achieve by simple repeated dipping, deep marine blue shade.

•

Possibility to dye cotton in cold dye bath.

•

Competitive in price.

•

Possibility to achieve an acceptable colour fastness and the exceptional advantage by repeated washing of fading colour, to keep the colour shade that always a clear, pleasant blue shade result.

The following drawing shows the symbolic the built-up of dye stuff of the yarn according to the multi-deep process.

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The sketch shows how Indigo layers one after the other is placed on the surface of the yarn then again scraped off, similar tot knife. Through force or tension or by washing.

An Indigo has only a very low affinity the depth of colour of the fibre is achieved by repeated dipping / oxidation. Each dipping cycle occur in a certain balanced manner as dye stuff is observed by the fibre at the same time and part of the already oxidized dye stuff is reduced and migrates from the fibres.

With increasing dipping operations. The balance of absorption / migration moves towards migration. A very important factor for the reduction of migration is the squeezing effect and the oxidation which follows. A high squeezing effect promotes a quick and through oxidation and reduces the migration and reduction in the following bye bath. With the low squeezing effect, that means with high liquid absorption, the purely visual impression of a good oxidation can be deceptive as the outer colour skin looks blue. In the core of the thread however more or less vat dye stuff may be deposited

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Let us have a close look at the different dyeing systems. CONVENTIONAL CLASSICAL CONTINUOUS INDIGO ROPE DYEING The classical rope dyeing system is very labour intensive and consists of: •

Ball warping

•

Indigo dyeing

•

Rebeaming on long- chain-beamer

•

Sizing

Yarn from the ring spinning machine is wound on automatic winding machines on to a suitable package either cylindrical or 5057 cone. The winders are directly linked to the ring spinning frames and the cops joint by splicing. OE yarns are directly creeled up on the Ball warper. The requires No. of ends (usually 380 – 420 ends) are assembled into a rope. These ends are wound onto a core. The rope is guided similar as a cross wound package and wound into a ball, length of ball approx. 12 – 15.000 meters. A lease is inserted at the start and end of the rope. The facilitate Rebeaming every 1000

meters

an additional

lease

is inserted.

Usually 18

–

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ropes

are

simultaneously process on the rope dyeing machine. Prior to dyeing, the ropes are boiled out and treated with caustic-soda and wetting agent to remove from the cotton oil, impurities which could influence the fastness for the dye. To dye with indigo, the ropes are immersed into the dye-bath. To dye in rope 30 – 60 seconds immersion (20 meters yarn) and 60 - 180 seconds are required for the oxidation of the Indigo dyestuff to ensure that also ends in the centre of the rope are equally dyed. Please note that squeezing pressure is important 5 tons as fastness of colour and shade depends on even squeezing pressure. The comparatively long immersion and oxidation time requires a comparatively expensive equipment of machinery. In order to obtain the required deep shade of blue colour the ropes are 5 – 6 times immersed in a sequence of dye boxes with an oxidation range then so called skying after each dye box. (Indigo belongs to the group of the vat dyes which is watersoluble in reduced solution and becomes an insoluble pigment when oxidized.

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Having passed the dyeing and oxidation rage the ropes are guided through 2 or 3 washing boxes to wash off excessive loss pigments in the last box softener are added to ease the opening of the ropes. They are dried in series of cans. The dried ropes which contain 380 – 420 ends are then deposited into large coilers Rebeaming with 300 – 380 ends per rope is easer. These coilers are placed behind the long chain beamer where the Rebeaming and opening of the ropes takes place. In order to guarantee even yarn tension through Rebeaming on to a back beam ready for sizing the ropes are guided over a tension device which is placed approx. in 10 -11 meters distance from the long chain beamer. Broken ends which very really happen process of the rope are repaired at this process stage. Initially these machines were supplied without yarn stop motion but are available now a days on special request. This is of major importance as lost ends, fluff, 3 – tail ends and yarn remnants can cause inferior performance in weaving. The so prepared beck beams are now sized in a sizing machine preferably with 2 size boxes. The size pick up varies between 8 – 10%. In Europe mainly modified starches with binders are used, whilst in USA certain low % of PVA is applied sin combination with starches by some companies. Depending on the final finishing process (washed denim) with no filler also CMC gives excellent performance in weaving. Special size mixes for soft denim will be discussed separately. We recommend however not to use

24

PVA for sizing of denim as a surface of denim may show a leather skinned appearance. CONTINUOUS SLASHER DYEING Contrary to the Indigo rope dyeing system, for the continuous slasher dyeing and sizing back beams are used. That means that the total No of ends required for a weavers beam are dyed, dried, sized and dried simultaneously. The back beam contains similar to rope 380 – 420 ends but distributed evenly over the width of 140 or 160 cm between the flanges so the end lay parallel to each other, warp length 12 – 15.000 meters, similar to the rope dyeing system the full No of ends are pretreated (washed) dyed in 4 dye boxes and oxidized, no softener are used in the last wash box. CONTINUOUS INDIGO DYEING AND SIZING PROCESS

We must however consider that the squeezing effect is lower and therefore the danger streakiness and shade variation from centre to out side is also higher. Consequently it would be better to deduce the warping width rather to 140 cm instead of using warper beams with 160 – 180 cm warping width.

25

The immersion time in the dye boxes is approx. 10 – 15 seconds and time for oxidation 30 – 60 second. The final result is a weaver’s beam. This system allows the installation of less expensive dye rage and less additional preparatory machinery. One of the disadvantages in previous year when warp preparation (knots, weak, thick places) was not kept at a very high level was that ends sown in the dyeing range could cause major colour variation through machine stops. DOUBLE SHEET CONTINUOUS DYEING Patents applied for double shade dyeing by E. Godau date back as 1976. With the system dyeing sizing is done in 2 operations. The main reason for dyeing of 2 sheet simultaneously is achieved a more even dyed sheet, that means 8000 – 8200 end are dyed, oxidized, dried and the full length of the warper beam 12.000 – 15.000 meters flange diameter. These beams are transported with the aid of air cushions to the sizing machine and the yarn sheet sized in double size boxes. Immersion time and oxidation time is the same as with continuous slasher dyeing. Indigo full-width warping process

With double sheet dyeing the linear warp thread density is doubled. Therefore: Squeezing effect is increased,

26

An even squeezing over the whole width is achieved, Condensation and concentration of ends at one spot show compared to single sheet dyeing no colour strips formation, streakiness or shading in the finished fabric. The production out put of the dyeing is increased by 75%. Dyeing of 3 layers of yarn simultaneously is possible but very difficult to control the beaming on 3 big warp batches. Unfortunately the double sheet dyeing machine as well as the rope dyeing range cannot be linked with a sizing machine which must be regarded as disadvantage as the processes of dyeing and sizing must be carried out separately. Loop dye system 1 for 6 Similar to the sheet dyeing systems 10 – 16 warper beams with the total number of ends required for the weaver beams are used. The warper beams are placed in a moveable warp creel which can be loaded whilst one set is in potation.

The yarn sheet is guided to the soaking bath through a feed-in system with tension compensation rollers. The soaking bath has the task to prepare the yarn for the following dyeing operation. The yarn sheet after having been immersed into a single indigo dye bath runs into a long loop where oxidation takes place. As you can see from the slide the back beams are inside the yarn sheet passes through the dye box as often as necessary to obtain the required deepness of shade. One of the advantages is:

27

Ideal, utilization of Hydrosulphite through squeezing 4 – 6 layers simultaneously and oxidation of yarn in a comparatively long oxidation loop. After the oxidation the yarn sheet is guided through 2 washing boxes into a yarn accumulator and finally on to a series of drying cans, dried up to 25 – 30% final moisture content prior being immersed into size boxes, dried and wound onto a weavers beam.

The molecules are controlled DC drive to maintain warp tensions. Temperatures are automatically controlled as well as the PH value in the dye box. The automatic control unit of the PH value supplies automatically hydrosulfite and caustic soda to stabilize the present value from the start to end of a dye set. All rollers are contact with the dyed sheet are fluted, they keep the sheet in position and reduce deposit of dye and build-up of other deposit (fluff). In addition to width is controlled by guides to ensure even distribution of the yarn layer over the whole width of the dyed sheet. All accumulators placed between washing boxes and drying cans guarantees a continuous production of the dye range when a weaver beam has to be exchanged at the head stock. The creels can be loaded with back beam with 1200 mm diameter which allows to warp approx. 36.800 meters of yarn, count No 7, 5 (tex 78) or 50.000 m count No 10 (tex 60). This means that depending on the count normally one cyl-spool is used in warping to fill a warper beam. WARPING SPEED PRODUCTION Speed varies between 1000 m/min, 35 m/min. No 5, 5 (tex 107) and 42 m/min. No 10 (tex 60) MACHINE STOPS DURING SIZING For 36800 m, 4 recorded on expansion comb.

28

WASTE OF MATERIAL Approx. 15-20 kg per set. TIME REQUIRED FOR CHANGE OF SET 2 hour Linear warp densities in the squeeze. The linear density in the nip is calculated in the same manner as for sizing. Q= linear thread density F= ends in cm -1 D= diameter of yarn D= 0,921 mm = Nm

0,921

= 0, 29125

10 = 3.1622

Q= F x D As already mentioned previously the warp density has an influence on colour fastness. A higher squeezing effect is achieved due to the over laying of the watp ends this also gives more side to side squeezing, therefore reduce strips formation. The high squeezing effect results also in better, quicker and proper oxidation and better colour fastness. It must be mentioned that recommended dip and oxidation times on warp dyeing ranges are of little use if not the squeezing effect is taken into consideration. Under a given squeeze pressure, for instance 500 kg the squeezing effect of the mentioned 4dyeing systems can be compared. We can see that similar squeezing effect can be achieved with the loop dyeing system 1 for 6 (75%) as with rope dyeing 70 – 110%. Double dyeing with 2 layers width with 150 cm gives approx. 80% squeezing effect, whilst single sheet slasher dyeing varies depending on count between 100 – 130%. Loop dye 1 for 6

Rope-dyeing

Slasher-dyeing

29

As only one short indigo dye bath is deeded only one feeding tanks, no separate feeding of chemicals is necessary. Dye liquor is use in 1500 1 instead of 6-4500 1, therefore less chemicals in use at same time. •

Lowe power consumption.

•

Fine counts can be dyed as well (No 30)

•

For dark shades, black shades or other shades needed by fashion, other indanthrene dye stuff can be directly added into the indigo dye bath (indanthrene yellow or orange).

LOOP DYE 1 FOR 6 COMBINED WITH DYEMER The demand for dark shades specially dark marine blue for super blue denims also led to new ideas in indigo dyeing ranges have been increased between 8-15 dye boxes with corresponding oxidation ranges.

In some cases Hydroxyaceton has been specially treated with high frequency. Besides achieving a darker shaded with the desire greenish touch it is very suitable for biological treatment. In order to achieving ring dyeing, mercerized yarn has also been used. A mercerizing prevents penetration of dye stuff into the inner code it is suitable for this purpose to obtain an optical blue effect and superior colour fastness and behavior in washing. Mercerizing is very costly, therefore new ways is continuous mercerizing and indigo dyeing was found.

30

DYEMER The dyemer range is integrated. For impregnation padder for hot caustic solution is placed after the heating system. The yarn is guided over could cylinders and with an adjustable roller the tension of the yarn sheet can be adjusted according to the required tension prior to the scouring in 2 more boxes. After having passed this, the yarn sheet is immersed into the dye box and the same process as with the loop dye method is repeated. CONTINUOUS DYEING AND SIZING ON THE DYEMER RANGE If fashion needs other colours than indigo blue it is comparatively simply to dye and size on this range.

31

INDIGO ROPE DYEING SLASHER (INDIGOFLOW) DYEING

Indigoflow We can explain the indigo flow dyeing tech as, every phase included the of the yarn with the Leuco solution, in

ALKALINE

IMPREGNATION

bath and at temperature relatively low

to oxidation it follows, after squeezing a pressure a passage in air to allow the leuco to oxidation and to become blue and therefore insoluble. Oxidation The oxidation is very important in the dyeing process; the purpose of the oxidation is to get the permanent dye on the yarn and to eliminate the insolubility of the dye stuff in the water. According to the practical experience the average time for a perfect oxidation is about 60 seconds, this means that after the first dyeing/squeezing the yarn has to remain exposed in the air for about 60 seconds before being dipped again in the second dyeing vat and so on for all the following dyeing. The dyeing mean time can be calculated in about 30/35 meters of yarn per minutes therefore keeping as base the machine with eight dye vats. The total yarn in the oxidized can be calculated as m 35 x 8 = 280 meters. But indigo flow with their special device Rapidsky only eight meters per dye vat of yarn remain in the Rapidsky device. That means the total saving of yarn with Rapidsky is m 24 x 8 = 216 meters. FLEXIBILITY IN USE The high degree of evolution that can be reached by completing the basic machine with the mercerizing and an intermediate drying can group, a steamer and a special double circuit system for bath circulation system, enabling separation of vats and that allows the maximum flexibility in use. In addition to the classical indigo blue it thus possible to dye the modern mercerized to dye the modern mercerized indigo

32

blue and black, the new indigo supper blue the per-dyed indigo, as well as the large range of colour denim with sulphurs, indanthrene, naftoles, direct, relatives and pigments dyes. CIRCULATION SYSTEM OF DYE STUFF This system has a ingenious and perfect dye bath circulation system. Through a variable flow pump, the dye bath is sent from the circulation vat to the first dyeing vat, and from this by means of an overflow system with special conveyors/mixers, to the next vat and so on until it falls back into the circulation vat, where it is filtered its temperature is adjusted and colour Hydrosulphite and soda are automatically added. This system is very simple and dose not required maintenance. Dye bath circulation vat, stainless steel made, complete with interchangeable bucket filters, automatic level adjustment, temperature control and dosing of colours, Hydrosulphite and soda. ACCUMULATORS This system have to Gravity accumulators for automatic storage of the dye yarn when the slasher machines stops for beam change complete with finned stainless steel rollers for synchronization and safety devices. MERCERIZATION Mercerization causes morphological and mechanical changes in the yarn thus increasing its resistance and dye affinity (dye stuff) saving, mercerized warp makes it possible to obtain a better texture handle and look as well as particular chromatic effect on the ready made cloth. MERCERIZED PROCESS Mercerizing group consisting of soda process vat with circulation pump and filter, timing cans neutralizing and washing vats with 10 tons squeezing foulards, automatic feeding and electronic yarn tension regulation devices.

33

TECHNICAL CHARACTERISTICS 1. Reduced capacity dye vat with semicircular bottoms and with only 2-3 large diameter immersed rollers, to avoid the yarn breaking and tangling and to reduce the bath quantity. 2. Squeezing foulards with special rollers enabling a uniform squeeze effect over the entire width under all pressure conditions. 3. In order to eliminate the cleaning operations and to help the colour oxidation this system has special finning on the surface on the rollers of the oxidizers and accumulators. 4. Compactness, thus being accessible and easy to handle.

Ropes are stronger and less subjective to broken ends that, if they do occur, will tend to pass through the machine. Ropes are braided from let-off creels to provide continuous operation. Therefore there is no yarn waste from beam set splicing stops or shade tailing from dye class changes. Standards pretreatment consists of counter flow scour/boxes. Optional mercerizing section adds a caustic box plus skying rolls to provide proper reaction time before washing. This adds important properties such as improved dye affinity, fabric luster and strength as well as popular faction effects. Rope dyeing is economical and well suited for processing chambrays, dark shades, over dye and fashion colours. These would include sulfur, reactive and vat dyes. Multiple dips of indigo and proper oxidation time and in the skying section achieve depth of shade. Basic range consists of eight box/sky sections. High production and/or deep fashion blue ay require more sections. Dyestuff preparation circulation and custom designed chemical and system allow full flexibility for variation dyestuff application. Morrison’s color kitchen for caustic, Hydrosulphite and indigo is supplied with filters and stand by pumps to allow uninterrupted operation. Large diameter feed and return lines assure content level in the each dye box

34

After dyeing the ropes enter multiple wash boxes for rinsing and chemical application. Ropes are than carefully dried to 6% moisture or steam heated drying cylinders. Coilers lay the individual ropes into drums in a pattern to facilitate the subsequent Rebeaming operation. The 350 plus ends per rope are blended during the Rebeaming (post dye) stage, and then further randomized when the twelve beams set are sized prior to weaving. Virtually guaranteeing side/side colour uniformity.

Following are the major features of the rope dyeing systems which results in a uniformly dyed quality denim to meets the strict quality standards of the BIG BRANDS NAMES. •

Dye boxes with maximum yarn contents for highest production speed.

•

Kept the surface area to a minimum.

•

Reducing the risk of dye-stuff oxidation.

Two different working position of bottom rolls feature maximum flexibility in operating speeds. This system has HV nip which permits the removal of bottom nip rolls without dismantling the top rolls. Those nips are used on all dyes and wash boxes throughout the range. Large diameter direction rolls in the skying section insure the optimum guarding of yarn ropes, a major contribution to a more efficient Rebeaming process. Optimal sulfur black, top or bottom, can easily be achieved with slight modifications of entire system. The indigo dyes ranges can be built to give you the flexibility to switch from bottom to top application or use indigo dye stuff only, based on customers choice and market requirement. The use of sulfur black has for some time been a popular tool to the denim manufacturer to achieve the dark shades economically by reducing the use of

35

expenses indigo dye stuff without violating the high quality standards of “genuine denim” The dry cans are other factors in making the rope dyeing range efficient and reliable. Teflon coating are available upon costumer request. The dye stuff circulation system is an extremely important part of an indigo dye range. Constant circulation at high rates guarantees of dye-stuff, caustic and Hydrosulphite. Standby pumps ensure the uninterrupted operation of the range

36

SLASHER DYEING VS ROPE DYEING

SLASHER DYEING Required lesser floor

CRITICAL POINTS Building Area

Space

ROPE DYEING floor space required more than indigo flow

Is a continuous process

It is not a continues

or beam, beam process

process. Including

including.

Ball warping

a) Pre-washing

indigo dyeing (6-8)

b) Mercerizing

boxes

c) Dyeing with (6 -8 boxes)

Rebeaming critical

d) Washing e) Sizing f) Drying The mercerizing process

Mercerizing

Is easy and simple

in rope dyeing mercerizing is difficult. Due to Rebeaming (critical)

Required lesser

Manpower

manpower

required more man-power due to extra steps

i.e

Ball

warping

&

Rebeaming The capacity of one dye

Dye bath

the dye bath are in requ-

Bath is 100 lits to make

ire shape. The capacity

more effective and to

of dye stuff is 2.500 lits.

save the expensive indigo

the dye bath have five

dye stuff. The dye bath

rollers of same size

have three rollers one is

37

bigger than the other two this system have the

Yarn

this major allows to use

option to use the yarn

the yarn from Ne 1-16

from Ne 1-30 count on

count without any major

the same system with

change

out ant major change this system have the

Flexibility

this system allows to pro-

flexibility to produce

duce denim only in two

the denim in different

colours i.e blue and black

colours. Reason is requ-

reason is difficult to chan-

ired short time to change

ge colours quality as in

colours.

Slasher dyeing

we can produce the any

Limitation

type of denim on this range

this system is only allows to produce the classic Denim

With this system we can

Market share

The market share of class-

entire denim market. Or

ic denim in 70 & in internat-

we can meet the all demands

ional denim market. It is

of the international denim.

very difficult to fulfill the require of major buyers.

The piece of the denim

Price

we can get the premium

Produce with its tech-

price of the classic denim

nology in comparatively

with this technology i.e

low than the denim pro-

approx. $ 2.85 per meter

duced on rope dyeing

in international market

technology.

38

COST COMPARISON A study made recently to compare the 3 main systems in use in indigo dyeing, rope dyeing, slasher single sheet dyeing and loop dye system 1 for 6 for a given production are summarized in the following the comparison. The dye systems with 12 ropes has been taken as basis of comparison. The percentage figures in brackets refer to the quantities required for an equivalent production. QUALITY OF DYEING AND COLOUR FASTNESS Shading of fabric from center to selvedge has always been critical. To test colour evenness, fabric have been sewn together from center and out side to compare the colour after weaving and sanforizing, With the trends towards mill washed denims and garment washed denim with the systems mentioned earlier (stone wash, hard rock, chemical treatment with chloride of super blue and normal basic denim) where the fabric is exposed to washing treatment varying from 30 min to 4 hour and more, the quality of dyeing becomes a very critical aspects in the choice of the dyeing process. If we remember the squeezing effect of the rope dyeing system and the loop dye system 1 for 6 give very similar good results. Single slasher dyed denim fabrics however will experience more problems to match specification for colour shade. Despite the fact that yarns in rope dyeing are expose to varying squeezing effect in the rope slightly different colour take-up is equalized in Rebeaming and use of 10 – 12 back beam in sizing. Despite the fact we have learnt from one of our customers who operate his loop dye system between 35-42 m/min, depending on the yarn count used, we feel that a comparison the operating speed of 30 m/min. is still justified. The comparison does not claim to complete in all respects but should give an objectives bases to interested listeners.

39

CONSTRUCTIONS FOR DENIM FABRICS STANDARD DENIM As a rule denim fabric for woven as twill 3/1 Z or broken twill 3/1 or 2/2. Depending on the final used. The weight of the finished fabrics vary between 3,5 and 16,15 ounces sq/yd. depending on the weight, the fabrics are used for different garments. 3 ½ - 12

ounces, ideal for blouses, tops, shirts, sweet shirts, sweat shirts and jogging suits.

11 - 16 ½

ounces, trousers and jackets

The classical construction of a 14/ ½ ounce denim is 24,6 ends/cm, 16,5 picks/cm, tex 100 warp/tex 100 weft. But there are many other possibilities to in constructions a cloth to (size and stiffening). It also gives us the possibility to show a more pronounced twill-line, weft appearance and to achieve the desired tearing strength in warp direction by using open-end yarns or ring spun yarns. (See table 3.1.1. and 3.1.2.) A fashion continuously creates new ideas the cloth manufacturers have to follow the demands, of the marketing teams and market leaders. Checks in fabrics for jackets and trousers were very popular in USA 1975-1978, herringbone weaves, bed fords card, crinkle cloth, combinations of twill 3/1 and 1/3 or twill 2/1 and plain weave popular just recently. There is no limitation for a designer to turn a apparently simple fabric into a highly sophisticated fashion fabric. Last year jacquard designer and diamond weaves were the runner on the fashion market. Let me show you a few examples what can be achieved by rearranging the drafting plan and the lifting frequencies of the heddles. Some fabric cam be woven with tappet motion whilst other will require dobbys reversals, diamond blocks) four colour machines or second beam in high position. DENIM CLOTH CONSTRUCTIONS

40

Some typical denim grey fabric constructions Weave: twill 3/1 Z No. of ends per cm yarn count Warp weft

warp tex

weft

tex

weave

24

16

7

84

6

98

3/1

25

16

7

84

6

98

24

16

7

84

5.5

107

20.8

15.5

7.4

80

6

98

27

19

7.5

78

6.7

88

24

17

7

84

6

98

23

15

11.8

50

11.8

50

23

16.5

7

84

7

84

24.6

16.5

6

98

7

84

30

18

8.6

71

7

84

25

26

7

84

5.5

107

26

21

11.8

50

11.8

50

22.8

16.5

6.7

88

6.7

88

25

18

7

84

7

84

27

18

7

84

5.5

107

CHAMBRAY FABRICS Weave: plain or twill 2/1 24

20

24

25

24

25

1/1

27

16

24

25

24

25

1/1

21

12

12

49

12

49

1/1

23

16

12

49

14

42

1/1

25

15

9

66

7

84

1/2

23.3

16

16

37

12

50

1/2

25

16

16

37

16

37

1/2

25

15

9

66

12

50

1/1

23

19

20

30

20

30

1/1

41

Denim with strips: combination twill 3/1, plain 1/1 whipcord. Possibilities to achieve different fabric appearance.

Stripps twill 2/1 + ½

Whipcord narrow strips

Stripps twill 2/1 + plain

whipcord weave strips

42

Fancy fabric woven on dobby (fig. 14 + 16 woven on tappets) by inserting Lurex or count. Viscose filament in weft good cloth.

Fig. 12

Fig. 14 Reversal drafting

Fig. 13

Fig. 14 Fancy drafting

43

Fig. 14 Broken drafting

Fig. 17

Effects are achieved with multicolor WM and warp beam in high pos.

44

Elastic Denim For many years, warp elastic and bi-elastic corduroy was highly in demand in Europe. Consequently efforts were made to compete with elastic corduroy. As mentioned earlier denim, flats and corduroy share the market for leisure wear. The denim ranges in USA consists nearly 100% of rope dyeing units. With this dyeing system it is practically impossible to warp and dye and rebeam yarns with an elastomeric core. Warp dyeing systems were warper beams are used are very well suitable for a continuous open width dyeing and sizing operation. Because of these facts only weft elastic denims are used in USA for leisure wear. In Europe however because of the different dyeing technologies byproducts of the classical denim warp elastic denim is produced. The fabrics are not only pleasant to wear they also help to improve the appearance of the fashion conscious individuals. ELASTIC FABRICS WEFT ELASTIC Ends per cm Warp

25.6

counts

stretch% reed width

weft

warp

cm

Ne

tex

Ne

tex

17.3

84

70/20/20

7.8/30/30

192

twisted 25.6

17.3

84

6.5 91

15.6/91 24

192

WARP ELASTIC Ends per finished

counts

45

Warp

weft

warp

weft

Ne

tex

Ne

tex

26.7

18

finished 13*2+15.6

24.7

14

grey

23.5

14

reed

23.5

18

finished 18.5*2+15.6

21.5

15.5

grey

20.8

15.5

reed

45*2+15.6 6.5 91

32*2+15.6 6 98.5

Metallic Thread Used In Weft In fancy metallic threads are very suitable to achieve a bright luster when used in weft faced weave. PRINTED DENIM A special surface appearance can be achieved on denim fabrics with multicolour print, filigree prints or acid prints. Cashmere designs in different colours as well as check over prints have been in demand for some time. In consequence of this trend jacquard designs in indigo warps with different colours in weft came for a short time on the market. Some are shown in fig. 25

46

Fig. 24 Cockling appearance of fabric by combining weave and different twisted yarn types.

47

Fig. 25 jacquard design of denim.

Fig. 26 printed denim with cashmere.

Fig. 27 coloured printed denim.

48

WARP PREPARATION SPINNING The base of a good fabric and weaving operation is already laid down with the purchase of the cotton fiber. Although the count range suitable for denim fabrics is rather towards coarse counts, we require perfect spun yarn. Warp – and Weft preparation plays a major part. Main problems in denim production in previous years were uneven weft, knots on surface of denim fabrics and weft bars. With the aid of weft mixers or 4 colour mixing uneven yarn appearance or irregular yarn blending can be more or less avoided. But most of the problems can already be solved in spinning through:



Good blending



Correct drafting ratio on draw frames



Speed frames



Ring frames



OE – spinning.

RING YARN: With the possibility to link the ring spinning frame with an automatic winder ring yarn has become of interest again for denim production. The superiority of spliced joins over knots is felt not only when weaving outerwear fabrics but also for technical cloth. It contributes substantially towards improved yarn performance in weaving not only for course, but also find counts. As a rough figure we can say that end breaks in weaving are reduced by 30 – 40% in some case for example dense fabrics and fine count up to 50%. OPEN END YARNS:

49

Due to the lower tensile strength of OE – spun yarn it took quite some time before they were accepted by the garment manufacturers . Many problems existing with ring yarns such as thick, thin places, twist variation tube base top of ring tube and therefore tendency to barriness in weft were eliminated. The slightly higher hairiness and different colour Take-up, deeper colour, good colour fastness were of advantage but some of the garment finishing techniques reduce the tensile strength of OE – yarns that a switch to ring yarn is necessary. In a few tables I would like to compare standards in spinning under similar conditions (Ne 6) for ring and OE – yarns. Nov. 1979 / 1080 and standards from 1986 where especially thick thin places and neps are reduced by 50 %. It must be mentioned that in order to meet higher standards 2 draw frame passage give better results, dust content max. 0.15 %. Jets on OE spinning machines

80.000 trs. / Min 4 groves 60.000 trs. / Min 6 groves

Stop value standards: tex 84, Ne 7, 17

stops per 1000 rotor hours.

tex 30, Ne 20,15 stops per 1000 rotor hours. Check for: •

Perfect yarn joins

•

Thick, thin place

•

1st yarn layers must be wound tight on spool cores.

•

Tails must be perfect.

50

WARPING Indigo dyeing required even tension over the whole width of the yarn sheet irrespective whether the yarn is rope dyed or in full width. But uneven tension from front to rear rows of a creel may show up more on a single sheet slasher dyeing machine than in rope dyeing. TYPE OF CREEL: The selection of a creel which provides more or less even tension from front to back rows is important irrespective whether •

A parallel creel with trucks , with or without automatic knotter

•

Magazine creel (to run from nose to tail )

•

V – creel

•

V - creel with trucks

is used. Depending on the advanced transport and automatic in spinning a truck creel where trucks can be loaded automatically by robots in the spinning may be more suitable than a magazine creel. But all creels should have one thing in common: the tension must be adjustable. We must remember that each supported guiding eyelet in addition to distance to the head stock, difference in spool diameter, warping speed adds to increase tension during the warping process. We have measured on different occasion’s tension and found a tension increase from front to back row of 80 – 100 %. Machine supplier offer today electronic tension control devices. These units not only help to reduce tension variation caused by warper acceleration, deceleration, or when a warper stopped to keep a certain tension to avoid snarling or sagging of the yarn.

51

The adjustment of the tension in 3 – 6 zones to compensate for different in length is a first start. (Reed Chatwood) Other possibilities are offered by adopting a pre-tensioner in V- creels. Despite the fact that tension variations are far less pronounced in a V- creel Benninger now offers an automatic pre-tensioner, which can be used as creel length compensating unit as well as automatic pre-tensioner for the 3 main positions. •

Stop:

tensioner is open to allow free access to spools.

•

Acceleration:

yarn is diverted to eliminate snarls.

•

Running speed:

tensioner open to allow optimal warping tension.

These controls are important for both warping systems, ball-warping as well as full width warping, but will bring certainly more benefits for high speed full width warping at 1000 – 1200 m/min.

Automatic pre-tensioner with creel

scheme: automatic pre-tensioner in

length compensating unit.

three working position.

ELECTRIC STOP MOTIONS:Especially on ball warpers very often faller bar stop devices are fitted. Even at low warping speeds of 350 – 450 m/min they are sometimes not fast enough to stop a yarn break prior the yarn has been condensed into the rope. To find the end is time consuming and the danger exists that the end is tied whilst still twisted with one or more ends. Electronic yarn stop motion sensor at the exit of each spool should be standard equipment for a denim warp producer, especially when magazine creels are used, a

52

dependable thread monitoring is necessary if faultless ropes or beams are to be warped without lost ends or wrapped threads.

THREAD TENSIONERS The yarn is controlled by 2 or 3 post- and disc- tension system. It consists of mechanical pivot levers, ceramic posts, chromeplated tension discs and varying weight washers. I have been realized that uniform thread tension is important: •

From full to empty package

•

Between front and rear packages.

Fibre abrasion (fluff, fly) causes problems resulting in: •

Uncontrolled thread tension

•

Or deflecting pins cut- in

•

Missing loading discs

•

Uneven distributed loading discs.

V- Creels equipped with electronic tension control and broken end detectors, or adjustable roller tensioner performs better, even at high beaming speeds of 1000 – 1200 meters.

Tension level remains content across

tension level remains nearly content

entire yarn sheet

throughout yarn package.

53

SOME HINTS FOR WARPING Mistakes made in ball warping and direct beaming can no longer be corrected in downstream operations. It is therefore, vital to: BALL WARPER WITH MAGAZINE CREEL That •

all bobbins are properly wound

•

transfer tail are perfect (no 2 tails )

•

Spools without transfer tail not to be used as in many cases they lead to lost ends or it is difficult to find ends.

•

Joins to be made by weaver knots.

•

thread monitoring devices must work perfect

•

tension units to be checked regularly

•

Leases to be inserted at 1000 meter intervals.

FULL WIDTH WARPING •

The back beam flanges are in perfect condition with no sign of damage.

•

Threads do not built up at beam flanges. Make sure that the last end at the flange drops. This will prevent that the last ends in the size box separate from the dye or sizing sheet or become slack.

•

Loose ends in the selvedge zone may lead to breaks in the dry split zone or taped ends and badly twisted selvedge ends.

•

Lost ends lead to wrapped ends on back beams, running out or missing ends on the loom beam.

•

Beaming speed to be adapted to the yarn material to be warped.

•

One source of trouble frequently encountered are loose ends on back beams due to poor machine maintenance.

54

•

Broken ends should be joined in such a manner that the thread is warped under tension upon restarting, and not wound slack onto the beam.

•

Unsuitable package types lead to layers sloughing off from the cone and can cause multiple end breakages at the expanding comb on the sizing machine.

•

End breaks must be recorded regularly. Specifying the causes and where they occur.

•

Spinning faults.

•

Winding faults.

•

Inadequate maintenance, packages running out etc.

•

Packages with metered length can be worked off, down ta a few meters of waste on each spool. They help to improve warping standards, because no creel remnants have to be rewound.

The danger of faults at change over

does not exist. Less knots in all other processing stages.

In most cases

rewinding is more expensive because the remnants entail less costs if they are reeled off as waste. LONG CHAIN BEAMER The ropes are opened at the long chain beamer and warpers beams made. In order to obtain the required thread tension to separate the rope into single ends the rope has to be tensioned by a tow tensioning system which consists of 2 belt connected cylinders designed open ended for rapid threading.

A shake-out rolls

system with a square rather than round design. An expansion comb separates and distributes the threads over the width of the warper beam. The shake reed is a useful tool to separate entangled ends, to prevent end breaks prior passing the expansion comb.

A machine mounted accumulator

microprocessor- coordinated with the beam reverse function is of advantage to find lost ends quick in rebeaming. All broken ends caused mainly through the separation process must be repaired with weavers knots. (No dog knots) The leases made at the ball warper in certain intervals (1000 – 2000m) are used to check the position of

55

the threads in the rope in relation to the comb to prevent that broken ends are twisted with other ends. Depending on the quality of the ropes and yarn preparation rebeaming speeds up to 340 m/min can be achieved. Some hints: •

The distance of the shake out roll system to the beamer should be 11 – 14 meters.

•

It is of advantage to equip the long chain beamer with suction devices at the comb in combination with beamer mounted fans.

•

As in most cases beamers are operated without broken thread monitoring devices, a perfect training in repairing ends, handling machines and warp built-up control is of vital importance.

Assessing End Stop Rates At Ball Warpers, And Full Width Warpers. Ball warper

Full width warper

400 m/min

1000 m/min

Ring yarn knotted

5

7

Ring yarn spliced

3

5

Rotor yarns

2

4

Rebeamer

240 m/min

Ring yarn knotted

40 – 70

Ring yarn spliced

16 – 40

OE- yarn

10 – 30

56

STANDARDS

57

BALL WARPER

FULL WIDTH WARPER

STANDARDS

58

REBEAMER

SIZING OF INDIGO WARPS The main purpose of sizing is to surround the warp ends with a protective coating, to prevent fibre abrasion due to shedding in subsequent processing on the weaving machine. It can be performed in various ways. But there is one thing we have to bear in mind. Oversized warps which optically appear to be perfect as there are no protruding fibres at all may cause tremendous problems in weaving. In order to obtain the required weft density a very high warp tension is needed. This can lead to over tensioning of warp ends and high warp end stop frequency. It is therefore the task of the sizes to apply just as much size which is needed to avoid beading of the dyed yarn during weaving. For many years native starches or slightly modified starches with corresponding binders were sometimes regarded as the most economical way to size Indigo warps. The change in garment washed denims led to new sizing recipes. The final size pick-up is not only influenced by the applied size mix but also, squeezing pressure and type of size box, 1 or 2 boxes, 1 or 2 nip. SIZE BOX If we look at the different possible size box combinations only 2 size boxes with normal squeeze pressure 1200 kg but 2 squeeze rolls or 1 size box with 2 squeeze and immersion rolls and squeeze pressure 2500 – 3000 kg will give good results in sizing. Besides this, shore hardness of the squeeze rolls is important. With normal pressure we have With high pressure

70 – 75 shore top

90 – 95 shore

Bottom

95 – 100 shore

59

SIZE PREPARATION Under the just mentioned conditions, size concentration and viscosity of size is different for normal squeeze pressure and high squeeze pressure (2500 – 3000 kg). We must make sure that size concentration and size viscosity remain uniform through the sizing operation. Apart from the moisture content of the size products the accuracy of weighing-in also effects the viscosity and concentration. Particularly prone to errors are sizing recipes quoting the required quantities in bags. This may seem a simple way of establishing recipes, but is may bring serious disadvantages such as weights indicated on the bags differ from actual weights (moisture content). The viscosity and concentration should therefore be monitored and checked continuously (at least twice per cooking) with refractometer and Ford cup. Modern size preparation can be accomplished in different ways: a) Automatic metering from silos or large containers through duct system and weigh scales (size, wetting agent, lubricants). b) The size is dissolved in turbo-cookers or other open cookers with high-speed agitators, and pumped into the stock tanks after reaching the right viscosity. c) Production of a stock size for dilution as required. This is equally possible with synthetic as natural or modified starch products.

This method of size

preparation gives high flexibility in use and reduces the size losses in sizing when batches and recipes are changed. The concentration may be raised or lowered again in simple fashion. SIZING PRODUCTS FOR NORMAL DENIM. In many cases sizing products used are governed by:

60

a)

Product availability

b)

Material and yarn to be sized

c)

Finishing

loom state denim sanforized denim

SIZING FORMULAS With the following examples I would like to give a few figures from industrial practice. The sizing recipes depend of course on the type of size box, squeeze roll pressure, sizing speed, and yarn whether ring- or OE- yarns are used. We have to consider in addition, rope dye, sheet dye or loop dye. •

Size mix

•

Size pick-up

•

Stretch of warp during sizing (loss of elongation) as low as possible.

•

Residual moisture content of yarn (7 – 8.5%)

In order to achieve good weaving performance: •

Elongation of yarn should remain 6%, residual moisture content 7 – 8.5%

All recipes are based on 100 L of water. Depending on the type of cooker a finished solution of size of 120 – 130 L is achieved.

ROPE DYED YARN Noredux M 20

10.0 kg

Noredux 20/50

6.0 kg

U – size

6.1 kg

Fibrosint M 85

2.0 kg

Fat

0.8 kg

Olinor NW 81

0.3 kg

Belsoft 200

0.2 kg

Refractometer

9 – 9.3%

7.8 - 8%

Viscosity Ford cup

16 sec

12 sec.

Size pick-up

12%

9%

61

Perfectamyle 35

9.0 kg

Wax (Softner)

0.5 kg

Refractometer

8%

Viscosity

14 sec.

Size pick-up

11 % LOOP DYE SYSTEM OR SINGLE SHEET DYEING.

Kollotex 1250

7.0 kg

Extramyle WS 60

14.0 kg

Carbocil CMC

1.0 kg

Plastifil M

1.4 kg

Leomin WG

0.2 kg

Cerapol

0.8 kg

Glissofil

0.5 kg

Fixot N5

2.2 kg

Refractometer

8 – 8.3%

12 – 12.3%

Size pick-up

9%

12%

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SOFT DENIM: •

Horsil HV 55

3.5 kg

Alkazet 2069

5.0 kg

•

Olinor NW 81

0.2 kg

Viskosil PSN

0.5 kg

•

Belsoft

0.2 kg

Digoral PV

0.5 kg

•

Refractometer

3.5 %

4 – 4.3 %

•

Size pick-up

6%

7 %

•

Viscosity Ford cup

200

Carbocol CMC

4.0 kg

Refractometer

4 %

Size pick-up

6%

12.5 sec.

WITH HIGH PRESSURE SIZE BOX (2700 – 3000 KG): Perfect amyl 35

8.0 kg

Glissofil

0.3 kg

Refectometer

7 – 7.5 %

Viscosity ford cup

9 sec

Size pick-up

10 %

For soft denim it is important to know whether the material will be mill washed prior to garment make-up or the fabric is used loom state or Sanforized. Size mixes with CMC have also shone excellent results on gray fabric which which are printed or dyed black after weaving. As salt-free CMC is water soluble in warm water, desizing for modified starch printing is not necessary. The mentioned products have an ideal viscosity and good binding properties in normal and high pressure sizing. High elasticity which can improve weaving properties, hand of fabric and

63

shows better twill line as a higher crimp can be achieved as far less tension is required to weave with same recoil of fell as with normal viscose sizes. It also reduces dust in weaving which will allow to produces certain gray, less critical qualities side by side with denim. Besides modified starches pure CMC products are since many years in use in Corduroy Manufacturing with excellent results. AFTER WAXING: In cases where a higher percentage of size pick-up with starches is reached after waxing with 0.5 – 0.8 % will help to obtain more flexible warp ends without danger of beading. Will in addition reduce dusting-off during weaving. Further important points in sizing: As we can assume that at the moment very few companies have computerized sizing machines installed , which automatically control and adjust let-off tension , intake tension , wet split tension , dry split tension , winding tension , pressure roller , pressure at head stock , size pick-up which is very important . Let me just point a few things out which always need attention irrespective whether size and dye or just size the indigo back beams. CREEL FOR BACK BEAMS: One requirement for proper sizing, especially in the edge zones, is perfect alignment of the back beams with their flanges. Crowded threads due to inaccurately aligned back beam flanges may lead to inadequate size take-up in the affected zones. Odd ends may be undersized, roughened or slack. LET-OFF TENSION (3% OF WARP BREAKING STRENGTH): Modern back beam stands are designed so that the thread tension in the drawing-in section is regulated automatically to a preset level , thus ensuring more or less constant tension on the individual threads in beaming may be corrected a little by raising

the take-in tension, in many cases this leads to undesirable threads loading

and loss of elongation.

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With the breaking system normally today, with braking belt and weight, the draw-off direction and weighting must be taken into account. Whether the weighting is applied by spring, suspended weight or breaking piston actuated by compressed air, It must act against the direction of the yarn draw-off. If the weighting is applied in the same direction as the yarn run-off, this will raise the tension in the drawing-in section. More recent run-off systems operate with disk brake and roller bearings. This allows much more accurate braking via tension rolls than band or rope brakes. If shafts with bushes are used, check for wear very often only certain ends breaks in weaving they might be caused by worn-out bushes on one side only. WET SPLIT SECTION TENSION (2.5% OF WARP BREAKING STRENGTH): Attention must be given to proper elongation while the yarn is exposed to the size, Especially in the wet split section between size box and first drying cylinder. Cotton fabrics increase slightly in strength in the wet state if properly stretched. If however the tension in the wet split section is too high, the thread elongation will diminish. Now the highest possible elongation is important in downstream weaving operations. It must under no circumstances be reduced or eliminated by using excessive tension in the wet split section. The tension to be adjusted here depends on the weight of the thread sheet: •

Light/medium-weight articles

20 – 30 kg

•

Heavy articles

30 – 50 kg

•

Very heavy articles

over 50 kg

These figures may be calculated approx. from the yarn count and kind of yarn. They should then be recorded in the sizing instruction sheet for future warps of the same article. WET SPLITTING THE WARPS True wet splitting, even if two size boxes are already being used, brings benefits especially when sizing cotton/polyester blends. The warp ends are separated from a thicker layer in the wet state and predried on drying cylinders. The threads thus lie

65

spaced well apart on the drying cylinder. Protruding fibres are less likely to cling together, and splitting in the dry split section is simpler. The warp ends are smoother and have fewer fibers protruding. There are various possibilities for single or multiple warp splitting in the wet state: •

Single box

single split - quadruple splitting

•

Double box

double split - sextuple splitting

DRY SPLIT SECTION (10% OF WARP BREAKING STRENGTH) This is calculated from the number of ends and the yarn count. In the dry spilt section the uniformity of this squeeze roll pressure can be ascertained in sample faction. The split wedge before the first split rode must show evenly over the full width of the warp (about 3 – 5 cm). if there are groves in the squeeze roll or the squeezing action is uneven across the width of the bath, this will be apparent at ounce on the first split roll. Very often different tension of a yarn sheet visible when sizing is done in 2 boxes and the drying cans are paced in 2 rows only. The reason for this is that the moisture from the bottom row of cans is absorbed by the top row as the drying temperature on both rows is the same; the top sheet has higher moisture content when it leaves the final drying cans. End breaks in the dry split section usually lead to double thread and ends running out. To prevent this, the split rods should be put in a fresh after more than 2 breaks. This should be done also when changes beams if end breaks occurred during sizing, otherwise there is no guarantee that the warp will run of satisfactorily. Special attention must be given to the warp ends in the edge zones. This can be watched best in the dry split section. Taped threads cause trouble with the stop motions droppers. Double ends taped are already apparent in the dry split section. WINDING TENSION (12% OF WARP BREAKING STRENGTH)

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The winding tension should be equal to the split section tension, but at any rate not more that 10% higher. Set the winding tension just high enough to ensure proper warp beam winding. PRESSING Formula: Damage to the thread layers may result from excessive pressing. Often small burrs form on the press rolls if these are handled inexpertly, due to impacts. Before every fresh run the press rolls should be inspected for possible dents and polished with emery paper if necessary. The pieces of pressing material at the ends of the press rolls must correspond to the press roll diameter. Roughness on the end pieces may lead to damage warp beam flanges and roughened warp thread, and ultimately to end breaks. TOTAL ELONGATION ON THE SIZING MACHINE It is important that the necessary the warp tension is properly selected and maintains. Warps with little elongation may lead to higher end break rates on densely woven fabric. The aim must therefore be to retain the inherent elongation of the threads. As a rule, this elongation is. •

Cotton yarns

1.2 – 1.5%

•

Blended yarns

1.5 – 2.0%

•

Rayon

2.0 – 3.0%

The total elongation is determined between the entry tension before the size box and the entry roll trio on the beaming machine. WARP WAXING For denim warps however the main aim is to achieve a soft thread, less friction and dusting-off during weaving. EXPENDING COMB

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When guiding warps through the sizing machine, make sure that the thread layers are as parallel as possible. Leasing in to a fixed comb brings advantages with grey and also with coloured yarn warps. If good results are to be obtained, parallel warps ends are indispensable. The demands of weaving are diametrically opposed to those of sizing. High sizing speed call for coarser combs. Good parallelism of the warp ends calls for finer combs, to prevent the warp ends rolling. With high number of warp ends, as in poplin, warp satin and down proof fabrics with 40 – 60 threads per cm, it is advise able to lease the end into the expending comb. It must however be realized that finer expending combs are not unattended by risks: •

Work must be done more carefully

•

There is a danger of several threads breaking out if breaks are not noticed at ounce

The expending comb should be traversed as little as possible; otherwise thread tangles may increase, especially with high warp densities. •

Normal

6 – 14 ends per dent

•

Fine comb about

6 – 8 ends per dent

Important is that as few correction as possible are made on the expending comb ounce it is leased. Switching threads in the comb means crossed ends. TAPING-OFF THE WARPS Warps are taped-off with adhesive taped on both sides for tying-on in weaving. RATIO BETWEEN WARPING AND BEAMING WIDTHS Warps with warping width identical with beaming width are ideal strictly speaking. A relatively short dry split section can be adopted. Experience gathered by sizing machine makers indicates that a widening of the warp by up to 70 per side

68

(equivalent to 25 cm per meter dry split section length) is quite acceptable. As already mentioned, wider back beam feeds yield benefits in sizing because there are then fewer end in the size box, so that sizing is better. With the sheet dyeing process the width of back beams should be as narrow as possible (140 cm) to obtain even dye pressure and colour shade over the width. This is exactly opposite to what we need in sizing. RESIDUAL YARN MOISTURE Yarn should have their normal residual moisture content if possible. Often yarns are over dried after sizing. Which not only affects the elasticity of the sized coating but also increases the hairiness, and as a result the thread-to-threads friction. Nor can yarns reabsorbed the missing moisture during storage in air-conditioned rooms. The point must be given attention. For denim warps moisture contents 7 – 8.5% should be attained.

SIZE BOX YARN LOADING IN THE SIZE BOX Continuous filament yarns without twist can be sized successfully only on a singleend sizing machine. Followed by a assembling the sectional beam into the warp beam (single size box without dipping roll). Up to now, trials with multiple splitting using revolving split rods have been successful only with textured and air-tangled yarns. However tangling techniques have recently undergone big changes, so that in feature it may be possible to omit sizing for various material. With spun yarns especially, through also with polyester/cotton and polyester/rayon blends yarns and 100% polyester, sizing the warp in a double in double box brings advantages if the thread loading exceeds 50 – 70% The thread loading is calculated as follows: Loading% = yarn diameter x total no of ends x 10 Back beam width in cm

69

For example: metric 17s (English 10s), 4200 ends, back beam width 1600 mm 0.303 x 4200 x 10 = 79.53% 160 Thread loading guide lines: Cotton

(metric 10 – 34s) over 70 % (sizing with double)

Cotton

(metric 40 – 120s) over 70 % (box is advisable)

Yarn blends

(metric 10 – 100s) over 50 %

Coarse to medium yarn are sized to advantage in size boxes equipped with 2 dipping and squeezing unit. MAINTENANCE OF SQUEEZING ROLLS To ensure optimal sizing results the squeezing pressure must be checked regularly over the entire roll width using blue paper. This will enable faults due to worn squeeze rolls or defect bearings to be a identified in good time. The squeezing action at crawl speed and in normal running should also be checked regularly. Irrequalities in the squeezing pressure are already visible on the first rode in the dry split section. The squeezing rolls should be checked regularly for true running, and the surface grinded-off according to the instruction of the roll makers. The shore hardness of the rubber or daico rolls must also be checked. Shore hardness recommendations: Normal pressure

70 – 75 shore

High pressure

90 – 95 top squeeze roll 95 – 100 bottom squeeze roll

OTHER CHECKS ON THE SIZE BOX •

Automatic temperature control function

•

Function of the feed valves for automatic size level control.

70

•

Viscosity metering by ford cup or other viscometer Haake, Brookfield.

•

Concentration control by Refractometer

GENERAL CHECKS •

Sizing speed

•

Temperature of sizing cylinder.

•

Yarn elongation on the sizing machine

•

Prescribe values in the sizing instructions with actual values.

•

Breaking strength, breaking extension and residual moisture percentage of the yarn

•

Size uptake on the yarn.

•

Abrasion with “Ruti-Reutlingen Webtester”.

RECOGNATION OF PROBLEMS Possible causes: Size dust-off

warp overdried Poor unsuitable sizing agents

Waft density can be attained

warp oversized

only with difficulty

incorrect shaft adjustment, whip roller covering, shed closure wrong.

Crossed threads

Expanding comb too coarse threads lifted out of expending comb. Thread sheet not taped off with double tape. Poor knotting in weaving mills.

Hairy yarn

Not

enough fibres

in the yarn cross

section. Too many ends in the size box. High warp end break rate

Yarn over stretched, over dried, damage during dyeing.

Ends cut by projectiles

insufficient size uptake. Shaft setting too high. Shed closure too late. Whip roller too high.

Lint balls in healds and reed

warp under sized. Too many ends in the

71

roughened selvedge threads.

size

box,

size

concentration

too

low.

Incorrect cooking. Neighbouring ends broken.

Knot ends too long. Warp over sized.

TYPICAL CALCULATION FOR COTTON YARNS Given data: a) Number of warp ends

4000

b) Yarn count

metric 50s

c) Yarn breaking strength (length)

12 km

d) Warp tension and adjustment according to table Warp weight = number of ends = 4000 = 80 grams per running meter Metric count

50

Thread breaking load = breaking length = 12 = 0.240 kp per end Metric count

50

Warp breaking load = 0.240 x 4000 = 960 kp Run-off tension (3% of warp breaking load) = 960 x 3 = 29 kp 100 Entry tension (1.5% of warp breaking load) = 960 x 1.5 = 15 kp 100 Wet tension (2.5%% of warp breaking load) = 960 x 2.5 = 24 kp 100 Dry tension (10% of warp breaking load) = 960 x 10 = 95 kp 100 Winding tension (12% of warp breaking load) = 960 x 12 = 115 kp 100

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Pressing (for warp weight 80 g/running meter, factor 2) = 80 x 1000 x 2 = 160kp 1000 For rayon the calculation procedure is the same. The values for rayon must be taken from the table.

73

WEFT PREPARATION FOR HIGH PERFORMANCE WEAVING MACHINES Different limits are set depending on the machine used in spinning and weaving operation. Thus, from a new rotor spinning machine better values are expected than those yielded by machines supplied 5 years ago. (Typically 50% - 25% range user statistics). From the weavers point of view the regularity of a yarn is of prime importance, more important than breaking strength. This has been demonstrated beyond all doubt, since rotor yarns for example give much lower thread stoppage frequencies in weaving than knotted ring yarns, in the 20 - 250 tex range, regarded as suitable now a days despite lower breaking strength, even when spun from 100% comber waste of 36 - 100 tex. Quite apart from the fact that a comber waste assortment with average staple length 11 - 12 mm can not be spun on ring frame anyhow. Important for weaving are:

•

Yarn regularity

•

Elongation

•

Breaking strength

•

Thick places

•

Thin places

•

Neps

YARN CLEARING Spun yarn contains faults which may be caused by various shortcoming in spinning such as bad manual sliver piecings, fly, foreign fibres (jute, polypropylene fibres), malfunctioning of stop motions.

74

NEW SPINNING TECHNOLOGIES With latest equipment in the market for automatic flyer bobbin doffing (Howa) and auto matic splicing, single motor driven ring spinning machine, automatic sliver stop, these faults should be prevented. with the aid of automatic piecing at the spinning machine (Fill-A-mat Zinser), with the integrated controls for thickness of splicers show by different companies at the ITMA in Paris with their links with spinning machines, autospinnconer, Murata No 7 - 11, links coner for ring spun yarns as well as rotor spun yarns. New electronic clearers have been developed which allow single spindle data collection, "Uster Polyguard" in rotor spinning "Uster Polymatic" in winding which automatically record and allow to stop individual spindles or spinning units if the preset values of count, thick, thin places are not within these values. in addition automatic transfer-tail winding at spool core and full bobbin and start-up is performed. ADJUSTING CLEARERS Suppliers of yarn clearers recommend certain sensitivities and reference length for the different yarn types. The degree of clearing depends not only on the reference values named, but also on the winding speed. Excessive clearing should be avoided, because it only leads to more knots, which in downstream processing cause thread breaks and especially on high speed weaving machines may cause neighboring threads to break also. if coarse ring yarn are used without splicers or spinning links. The cops should hold 120 - 150 grams of yarn, fine combed yarn about 80 grams. The number knots per kg yarn will increase or decrease accordingly. With coarse yarn (metric 10 – 34 s) 10 to 12 knots per kg yarn are expected, with combed yarns (metric 10 – 160s) 20 to 40 knots per 100 000 m yarns (35 to 90 per 100 000 m length). KNOTS AND OTHER YARNS JOINS SIMPLE WEAVER KNOTS

75

This knot is still used on a large scale with cotton yarns, through it has certain disadvantages owing to its inferior strength under the alternating stresses of weaving.

DOUBLE WEAVER KNOT With smooth yarn especially, this gives added strength. FISHERMAN KNOT Pure rayon yarns, wool worsted and also cotton/polyester blends are very smooth. This knot has found increasing favor in recent years in order to prevent knots coming undone in the downstream operation section warping, direct beaming, sizing and weaving. It brings considerable disadvantages in the finished cloth; however especially in outerwear fabrics on account of the time taken it opening it or pushing it through to the outer side. New techniques like splicing like from much better here. SPLICING The advantages of splicing over knotting are felt with all yarn types and counts. There are now only few yarns (smooth filament, acrylic OE-yarns and monofils) demanding a knot or some other join, such as welding or latexing. Splicing contributes significantly toward improved running performance in weaving, both in warp and weft. For certain fabric categories a surface as smooth as possible is even minatory (emery twill, coated fabric for artificial leather, outerwear). A separate lecture is being giving on splicing. ROTOR YARN

76

Some new spinning techniques, like rotor spinning, have already integrated continuous yarn regularity monitoring and knotless joining by splicer in the spinning operation. CHECKING In many cases we still have to deal with machines installed a few years ago and we have to assure good quality of yarn by continuous checks such as •

Knotters (functional checks at least once every shift.)

•

splicers

This involves to take 5 – 10 knots from a knotters, warp them on a black board and check for strength. The same applies also for spliced joins. In addition evenness of length of the knot tail is to be checked. Maximum length of tail of coarse to medium counts (100 – 36 Tex) is approx. 7 mm, finer accounts approx. 5 mm. Possible faults due to poor maintenance: •

Slack layers in the knotting zone 9thread tension).

•

3 legged knots

•

thread remnants wound in (suction, nozzle distance)

•

fly

•

soft packages

•

rings on packages

(suction) (pressure of spool cradle)

WINDING DESTINY FOR CROSSWOUND PACKAGES RANDOM WINDING Cross wound packages must be wound hard enough for the draw off speed in direct beaming 800 to 1200 m/min, up to 1500 m/min, to be expected in the future. There is practically no longer any difference between warp and weft packages. Only dye packages require random winding with less density. Precision –wound packages may be used for dyeing to with normal winding hardness. The deal winding density is influenced by 3 factors

77

•

Winding speed, thread tensioners

•

Package cradle pressure on the drum

•

Winding angle. The angle should be between 25 – 28o

As we know from Monofils-weaving a bobbin with flanges and exactly parallel wound layers side by side could give the lowest packages are random or precision wound packages. A thread guiding drum with symmetrical guiding groves gives uniform winding hardness over the whole width of a spool. For direct weft insertion up to 800 m/min or via weft accumulators this winding system has advantages. The winding angle of approx. 25 – 28o corresponds to drum traverses of:

•

83 mm 1.5 pitches, thread length per double traverse 835 mm

•

125 mm 2.5 pitch, thread length per double traverse 1150 mm

•

150 mm 2.5 pitch, thread length per double traverse 1450 mm

OPTIMUM WINDING DENSITY PER DM3 For yarns to be used in warp or weft winding densities are as follows: Ring yarn Coarse counts

400 g/dm3

Fine counts

450 g/dm3

OPEN END YARN Count metric

Nm 40/1 (tex 25) = 380 – 420 g/dm3 Nm 20/1 (tex 50) = 390 – 430 g/dm3 Nm 10/1 (tex 100) = 400 – 440 PATTERING AND CROSS WOUND PACKAGES

Pattering appears on every cross wound package driven by a grooved drum.

78

Pattering is always pronounced when the package and drum diameters are in a whole-number ratio such as 1:1, 1:2 etc. (drum diameter 90 mm spool diameter 180 mm) less marked pattering results with ration 1:1.5, 1:2.5, etc. the pattering may cause problems if it coincides with the knotting zone and cause layers sloughing-off or entanglements on spools.

ANTI PATTERING DEVICES Attempts are made to achieve a certain slippage between drum and package by varying the drum speed, causing a rhythmic change in the winding angle. Anti pattering drives yield better results than regularly lifting the packages off from the winding drum surface. With increasing outside diameter of the spools (warp and weft packages) anti pattering gains more and more importance. The aim therefore is to produce random wound packages without patterns What are the differences of the 4 systems? •

Random winding

•

Precision winding

•

Step precision winding (digital winding) pattern free random winding

•

Pattern free random winding

RANDOM WINDING The crossing angle is constant from small to big diameter. The winding ratio becomes smaller with increasing spool diameter. Random winding Precision winding Step precision winding (Digital winding)

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Pattern free random winding

PRECISION WINDING With precision winding we have constant wind ratio. The winding angle varies from small to large package diameter in accordance with the wind ratio selected. For instance 20 and 14o corresponds to a winding angle between 20 and 40o. The wind ratio is selected to suit the yarn geometry, and differs for fine and coarse yarns as well as types. With appropriate choice of wind ration and reversing point displacement, ideal winding is obtained. The distribution of the thread layers prevents patterning and assures uniform wining density. Open precision diamond winding for all continuous filament yarns and dye packages. Closed precision diamond winding for coarse yarns. DIGITAL WINDING (SCHWEITER) With digital winding the wind ration alerts with growing package diameter. By employing microprocessors the winding angle is allowed to change within narrow, closely definable limits during the package build from small to final diameter. Advantages are uniform density, precisely controlled thread laying and hence no pattering. PATTERN FREE RANDOM WINDING With this winding technique 2 layers of yarn with different winding angles are used. With the aid of a second displacement frequencies the main patterns and intermediate patterns are over jumped. PACKAGE CORES Surface If the thread layers are to be worked off completely from the package tube, as it is the case when using magazine creels in direct beaming and by weft insertion and shuttle- less weaving machines, the tube must be slightly rough. Thus roughness

80

may be obtained by brushing the tubes or cones with high-speed wire brushes, sandblasting or flocking the surface. Brushing is the most common method used today, through it should be borne in mind that 10 mm at the front of the tube is to be left smooth. This treatment ensures that the last thread layers do not slough-off. The smooth part at the front end of the core prevents that the last layers get caught by roughness at the edge f the tube. PACKAGE FROM CORE DIAMETER For weft insertion on the SRWM-P following package sizes are recommended: Cylindrical; tube, ideal 100-105 mm outside diameter Minimum 60 mm Cones: 2o, 3o30, 4o20, 5o57 EQUIPMENT NEED FOR THE WEAVING MACHINE WEFT ACCUMULATORS OR WEFT FEEDERS PU-WEAVING MACHINES Here accumulators must be employed with cones of 2o, 3o30, 4o20, 5o57, at weft insertion rates exceeding 800 m/min For weft insertion rates above 1000 m/min, accumulators are always needed. PACKAGE TRAVERSE In the design of winding machine as well as rotor spinning machines there is a clear trend to travels widths around 150 mm, for coarse yarns even 200 to 300 mm. ROTOR YARN (PACKAGE TRAVERSE 150 MM) Rotor yarns are now being spun in the 250 tex count range (metric 4 to 50s) DREF YARNS (FRICTION SPUN)

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Metric count range 1.2 to 10s (833 – 10 tex) Normally cylindrical cheeses, through also cones up 3o30, to are possible, mostly precision -wound. JET SPINNING (MURATA) Yarns are taken up on cylindrical cheeses of 100 mm diameter and 128 mm traverse, metric count range 55 to 14s (18 – 72 tex). As a rule yarns up to metric 40x (25 tex) may be inserted from a package of this format via accumulators. FACTORS NECESSITATING REDUCED PACKAGE TRAVERSE For finer yarns from metric 50s the package traverse must be reduced to 3 inches, or a cone of 2 to 5o57, employed, using as accumulators or storage motion in any case. Reason for this are: Fine yarns from a small balloon, causing to thread to drag over the package surface. With cylindrical package surface, with cylindrical packages this may lead to trapped triangles in the pattern zone or catching on the front edge of the package, and inevitably to end breaks. Entangled threads are however directly connected with the winding direction on the package and yarn twist. A distinction is made between P and Q winding. Drawing-off a yarn over the end of the package reduces the twist or increases it, depending on the direction of the yarn twist and the winding direction. Fibres projecting slightly from the package surface sometime twisted is so strongly by the thread dragging on the surface that the thread gets caught. Remedies:

User cones from 2o to 5o50

Reduce the package traverse to 80 mm possibly S – P = twist reducing

S – Q = twist increasing

Z – Q = twist reducing

Z – P = twist reducing

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MAXIMUM PACKAGE DIAMETER Various winding machines and also spinning machines are now capable of producing packages up to 300 mm diameter. •

For multi-colour machines maximum package diameter is 240 mm

•

For single-colour and weft mixing machines, 300 mm diameter.

TRANSFER TAILS To ensure smooth transfer from the package running out to the next one, a transfer tail 50 to 70 cm long is needed. More recent winding and rotor spinning machines allow transfer trails to be produced automatically (autoconer, autocore, ingoldstadt). Repairing a thread break before the accumulator takes an average of 1.20 minutes, compared with 0.55 to 0.70 minutes tails are therefore especially important. LENGTH MEASUREMENT Uniform thread length on the cross wound packages does not affect weft run-off. On the other hand length measurement is very important for reducing waste in warping. Results are secured in the neighborhood of 0.2% constancy. Length metering is an integral feature on all winding and rotor spinning machines. PERSONNEL SUPERVISION •

The way the personnel do its work must be verified regularly.

•

Cleanliness and tidiness at the work place are indispensable

•

Damages package centers must be rejected. Damaged tubes cause not only more stoppages but more waste s well.

•

Routine maintenance and check on machinery and equipment must be performed regularly.

PACKAGE STORAGE

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Cross wound package intended for weft insertion should be woven as soon as possible. Prolonged storage is to be avoided, because where small-diameter package core are employees, depending on the material the yarn layers contract, causing more and less severe “cauliflower” deformation. This may be aggravated further by distorted thread laying on cylindrical cheeses. These may give trouble during unwinding, leading to thread tangling due to lateral sloughing or soft layers pressed out close to the package core. Careful handling, packing and storage on transport and storage tracks specially made for the purpose, will help to prevent damage to weft packages. Long storage periods are detrimental to good weft insertion in the pattern zones and sloughing-off. Cotton approx. 15-20 days. CALCULATION FOR DENIM FABRICS Figures given for the weight for denims are usually for the finished fabric in ounces and square yards. CALCULATION FOR REED WIDTH For the construction of a fabric the following values are closely related with each other: a) Total No of ends b) Reed density (No. of dents/cm) c) Reed density (No. of dents per dent) d) Reed width If we want to make a calculation we need to know at least 2 of the mentioned values. We assume that the following values are known to us: Finished width of fabric

150.0 cm

Warp ends/cm in finished fabric

26.7

Picks/cm in finished fabric

18.75 cm

Yarn count warp

Ne

6.5 Nm 11, Tex 91

Yarn count weft

Ne

6.5 Nm 11, Tex 91

Warp crimp

12%

84

Weft contraction

4%

Contraction in finishing f.e sanforizing Warp

14

Weft

3

Size and colour pick-up

CALCULATION Reed width/cm

Grey width/cm

finished width X 100

150 X 100

Crimp + sanfor %i.H.

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finished width X 100

150 X 100

Contraction in sanfor %i.H.

97

Total No. of ends

150 X 26.7

= 4005

ends

Total No. of dents

4005: 4

= 1001

dents

No of dents/cm

1001: 161.3 = 6.205

6.2

Total dents of reed

161.3 X 6.20 = 1000

dents

Total No of ends/width

1000 X 4

ends

Yarn weight kg: For 1 m cloth Or

= 4000

total No. ends X crimp X tex

161.3

154.6

=

kg/m

=

kg/m

=

407.68 kg/m

1000 X 1000 No of ends X warp crimp Nm. X 1000

4000 X 1.12 X 91 1000 Size pick-up 8%

+ 32.61 g

Total weight

= 440.29 g

Yarn weight

= reed width/cm X pick/cm X 100 X Tex

=

kg

1000 X 1000

85

Weft kg for I m cloth 161.3 X 1605 X 100 X 91

=

242.19 g/m

1000 X 100 Total weight

682.48 g/m

Weight increase by sanforizing 14%

+ 95.02 g/m

Total weight finished

Weight 1 m2

778.02 g/m

778.02 X 100

=

518.68 g/ m2

=

433.68 g/yd2

=

15.29 ounce/yd2

150 Weight 1 sq/yd

518058 X 8361.3 10.000

Weight in ounce

433.68 28.35

WEIGHT AND MEASURES USED 1 ounce

=

28.35 g

1 yard

=

91.44 cm

1 square yard

=

8361.3 cm2

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CALCULATION OF WEFT DENSITY FOR WARP STRENGTH DENIM We have to produce warp stretch denim with 26% warp elasticity (warp stretch) Construction of finished fabric:

26.7 / 18.0 ends / cm

Yarn count warp

Tex 45 X 2 + 15.6 Elastan

Yarn count weft

Tex 91

Warp crimp (weave take-up):

6%

Sheath fibre shrinkage:

2%

Cloth elasticity fabric elongation

26%

Required No. of picks in fabric:

fabric under tension on weaving machine

Picks/cm X (1-warp crimp)X1-fibre sheath shrinkage

=

picks/cm

1 + cloth elasticity 18 X 0.94 X 0.98

= 13.16 picks/cm on weaving machine

1.26 The pick density increase in relaxed condition of machine. Considering 6% weave take-up (warp crimp) the weft density is as follows: 18 X 0.98

= 14.0 picks/cm of weaving machine

1.26 The cloth is now boiled off for 10 minutes and the actual weft density counted elongation and relaxed fabric length measured. In order to do this, a distance of, for example 20 cm, is marked on the fabric in warp direction. The cloth is stretched and measured again, boiled off, as after washing is finishing it develops its final expected elasticity; but loses some contractive power during dyeing and finishing due it extended heat exposure. Final cloth elongation

stretched length-relaxed length X 100

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Relaxed length = (25.2 – 20) X 100 = 26% 20 In case the check shows higher elongation than required we add picks, with lower elongation we reduce picks.. Weft stretch fabrics Finished cloth construction Warp:

26.7 ends/cm

Weft:

16.5 picks/cm

Yarn count warp:

tex 91

Yarn count waft:

tex 91 core spun (with 15.6 tex Elastan)

Warp crimp:

12%

Sheath fibre shrinkage:

1%

Weft elongation

22%

Finished width

150.0 cm

Weft contraction:

4%

Setting ends in the reed: = 26.7 X 0.96 X 0.99

= 20.79 ends/cm

1.22 With weft stretch fabrics the No. of ends have to be dented more open to allow the elastic weft to contract. Reed with cm

150 X 26.7

= 192.64 cm

20.79 To determine the weft elongation and relaxed with, the same procedure is used as for warp stretch fabrics. According to the final elongation the reed width is changed. The elasticity is governed by the count of the elastomeric (44, 78 or 156 d Tex) BI-ELASTIC FABRICS In order to determine elongation and relaxed state with bielastic fabrics the procedure is used to determine reed width and required weft density.

88

WIDTH SETTING FOR WEFT ELASTIC DENIM Denim 3/1 twill Warp: cotton tex 91 Weft: tex 91 core spun (with 15.6 tex Elasthan +22.0% Stretch width 2X183 cm -2.3% Boil-off width 2X146 cm 100%

Finished width 2X150 cm +24.0%

Grey width 2X186 cm +28.4% Reed width 2X192.6 cm

P 7100

390

89

FINISHING PROCESS FINISHING PROCEDURE The fabric already inspected in the weaving shed where all faults are recorded and minor faults required at the batching motions with the aid of an integrated inspection table and cloth accumulator is transported direct to the finishing range. From the batch roll the fabric is guided into an inlet scray or accumulator which contains 60 – 70 meters to ensure continuous finishing. Depending on the final use on the fabric. Denim can be processed differently, in-line, continuously or discontinuously. We recommend to apply the continuous process as skewing of the fabric is easier and the skew can be controlled easier. In case of mill washed denim or bleached denim a discontinuous process can be applied too. The following lay-out shows a version of a continuous finishing process MILL WASHED

DENIM NORMAL

FOAM FINISHING

BIG BATCH BRUSHING SINGING RIGHT SIDE DUST EXHAUSTION WASHING

PADDING ON FOULARD

FOAM APPLICATOR

STRETCH METER

STRETCH METER

STRETCH METER

ANTI TWISTER

ANTI TWISTER

ANTI TWISTER

90

DRYING

DRYING

SANFORIZING

SANFORIZING

SANFORIZING

Continuous finishing range for denim

STRETCHING, SKEWING After the fabric has been brushed, double singed on the face of the fabric it is impregnated on a padder (Foulard) to guarantee moisture absorption. After leaving the padder, the fabric passes the squeeze roller and if necessary is stretched on a stretch meter to achieve the required fabric width. An integrated ani-twisted serves to de-twist the fabric to avoid twisting of the trouser legs in the finished garment. SKEWING Denim basically twill 3/1 Z (right and twill) is usually skewed 6 – 10% during the finishing process. Broken twill, as well as chambray is finished without skew.

91

IDEAL SCEW

A=

First selvedge thread in fabric

B=

Last selvedge thread in fabric

TOLERANCES

A=

First selvedge thread in fabric

B=

Last selvedge thread in fabric

No stretch between A and B: max. tolerance 20 cm No stretch between A and B: max. tolerance 20 cm NOT TOLERATED The piece is not accepted if the distances A-B and C-D are greater than 20 cm and the stretch runs in direction opposite to the twill.

92

A=

First selvedge thread in fabric

B=

Last selvedge thread in fabric

SANFORIZING If the fabric is finished in line it leaves the drying cans with approx. 15 – 20% residual moisture content. The finished range works with continuous speed to achieve the desired sanfor standard. It is therefore not possible to slow down the line. Moisture measure and control units installed after the drying cans influences the steam pressure ¼ of the installed cans and influenced cabs and thus influence the residual moisture of the fabric. COMPRESSIVE SHRINKAGE The shrinkage of the fabric takes place between rubber belt and shrinkage drum. The pressure roller with precision setting controls and scale compresses the rubber belt by an amount corresponding to the specified shrinkage and so the rubber belt stretches and lengthens its surface. The fabric guided in close content with the belt is forced to follow the subsequent shortening of the belt when the pressure is relaxed and again is automatically shrunk in the process.

The basic rubber belt shrinkage installation consists of a water spraying system (damping) of fabric, steaming drum, straightening roller, clip chain, rubber belt shrinkage unit, felt calendar, felt drying drum, cloth scray to allow the fabric to cool out prior it is plaited or wound on a big batch roll.

93

RUBBER BELT SHRINKAGE INSTALLATION

1. High cloth inlet for working from the stack with powered draw in roller 2. Water spraying (damping) system 3. Steaming drum 4. Straightening roller to remove bias stretch 5. Clip-chain, full-width expanded track 1400 mm long 6. Rubber-belt shrinkage unit compl with rubber belt. 7. Felt calendar, 1500 mm diameter, with felt control and tension system 8. Felt drying drum, 1000 mm diameter 9. Cloth plaiter Despite the fact, that sanfor standard specifies: Maximum residual shrinkage + 1% as tested to fixed rules, very often denim is finished –2 to -2.5% (3 washings) Under normal circumstances the finished fabric contains approx 8% filler. The warp shrinkage of 14 ¾ ounce denim is approx. 14-15%, weft contraction 3-4%

94

LIQUID –AMMONIA PROCESS In some mills denims are Sanforized by liquid-ammonia process. The fabric is treated in liquid-ammonia. Where a dimensional control is necessary as the fabric would otherwise shrinkage several times more than the normal shrink during washing. As soon as a fabric is submerged in liquid ammonia, the swelling of fibre starts instantaneously, and the whole swelling effects is visible in 1 – 2 seconds. The fabric shrinkage take place slower as the shrinkage demands a mechanical reorientation. Approx, 80 % shrinkage is reached in 5 – 6 seconds. The extent of shrinkage is controlled by observing the duration over which the fabric is immersed in liquid ammonia before drying. In this way the weft and warp shrinkage of denim is treated with liquid ammonia is treated. In addition the warp shrinkage can be limited by tensioning the warp while the fabric is treated in liquid ammonia. In weft direction the fabric may shrink to such an extent that when it leaces the machine it posses approx. 12 % shrinkage after washing. In warp direction the fabric shows a 5 – 6 % shrinkage after washing. Subsequently the fabric is compressed shrunk. Before the fabric enters the treatment camber, it is passed over a tension regulating device and several drying cylinders to let it have minimum humidity. A cooling device placed after the steam heated drying cylinders reduce the temperature of the fabric. Before it submerges in liquid ammonia.

95

The fabric enters the machine through a sluice and is submerged in a bath containing water free liquid ammonia, which is evenly spread over in the cloth by squeezing rollers. A special reaction compartment after the squeezing roller allows regulation of reaction time. In this way the required effect is achieved. Subsequently the ammonia is taken away from the fabric under the action of dry heat from belt calendar.

FOAM FINISHING In addition to the already mentioned finishing possibilities some companies see in foam finishing advantages •

The fabric has only 20 % moisture and therefore no staining of the white weft.

•

No drying process needed therefore lower cost.

•

Less water pollution

1- Cloth scray

4- Anti twisted

96

6-Shrinkage range

11-Foam applicator

3- Stretching unit

Moanforts vacu-foam 1- Cloth 2- Knife 3- Bottom roller 4- Air tight for runner 5- Runner control unit, 6- Vacuum drums 7- Foam 8- Washing and brushing unit

97

TINTING OF DENIM FABRIC The achieve certain colour variations, fabric can be tinted. To grey weft takes up the desired color shade and can lead to very interesting colour combinations, such as blue / yellow, blue/ green, blue / red. FINAL FABRIC CONTROL In our final cloth inspection remaining cloth faults as wall as colour variations centre / selvedge get special attention. From each piece prepared for the garment manufacturer a small 10 cm wide cutting over the whole width of the inspection table and fastened in clamps. With this system colour variations or shading of the fabric can immediately been seen. If the colour shade varies, the piece is cut and the control strips is kept for the allotment of the different pieces in the corresponding colour class. Further test stripes are taken to check skewing, weight, tensile strength, tearing strength, washing shrinkage and colour fastness prior the pieces are packed and prepared for delivery. STANDARDS OF DENIM FINAL CLOTH INSPECTION (LEVIS – STANDARD) The standards are layed down by the market leaders and specify weight and tolerance. •

Breaking strength

•

Tear strength

•

Abrasion

•

Shrinkage

98

•

Colour fastness

As well as quality standards for the finished fabric the standard layed down in 1975 by Levis Strauss consists of 12 pages.

FINISH GOODS QUALITY STANDARDS A piece shall not have more than 12 demerit points for 100m2 to be recognized for first grade. The demerit points are assigned as follows: •

Weft bars/ starting marks

4 points

•

Dropped picks

4 points

•

Oil spots

5 mm o up to 10 mm

1 points 2 points

•

Oil sports above

100 mm

4 points

•

Slub yarn

70 – 150 mm

2 points

•

Slub yarn exceeding

•

Fly – woven-in

22 mm

4 points 1 points

Piece with the following continuous faults are regarded as second grade fabric. •

Double end

•

Temple marks

•

Slack picks

•

Stitches

•

Dyeing and sizing marks (stripes)

In addition skew and hand is checked and must meet the requirements.

99

Specification for Raw Material Evaluation

100

FIRST AND II GRADE Weaving basic denim : Weaving soft denim Total

0.5% - 1.5%

: max

0.5%

1. grade:

97% - 98% inclusive finishing

Second:

2% - 3%

inclusive finishing

LIGHTING IN WEAVE ROOM The ideal lighting for a denim-installation is 800 – 1000 lux. The tube should run parallel to the warp and be as possible without interruption. A twin flamed tube line should be placed at distance of 3m from whip rollers and be without shades so that the roof is also illuminated. AIR CIRCULATIONS / OVER HEAD CLEANER In indigo dyeing blue particles adhere to the fibres, and the dust development during weaving is quite considerable. Existing A/C plants have to be improved in most cases. To minimize the fibre and colour dust in the weave room, a minimum of 26 air changes per hour should be considers as the lower limit. 32 air changes are would be ideal. Over head cleaner should be installed in addition so that the dust and fly deposited on the fabric. As well as machine elements are continuously removed. The advantages of over head cleaner are best utilized if the weave room floor has returned air pockets CENTRAL / MOBILE VACUUM CLEANER PLANT For a denim installation a central or a vacuum cleaning unit can be strongly recommended. For a small to medium sized plant a mobile unit is better suited as it requires less investment.

101

The central vacuum cleaning unit is more suitable for bigger installations. It should be observed that for a least every four SRWM one connection is available.

TEMPERATURE / RELATIVE AIR HUMIDITY IN WEAVE ROOM Ideal temperature and relative air humidity values are:

•

Temperature:

22 – 24oC

•

Humidity:

70 – 75%

Sulzer will be to assist you in your planning, air conditioning as well as suitable vacuum systems. ECONOMICAL ASPECTS For some years my experience with denim was based on Rope dyeing double sheet dyeing installations. The fist installation for single sheet. Dyeing 1 saw in 1986. EXPERIENCE IN MILL During ITMA 1983 I paid a visit to (Italdenim) with operated for some time already the first 1 for 6 loop dye installation knowing that I had loop-dye installation No. worldwide, I was mush interested in the plant. How the operate spinning, weaving and finishing. The most striking example was hoe one operator could handle the finishing of denim supplied by 96 rapier machines, (2 widths, 170 and 200 picks/min); one weaver looked after 12 machines. 1983

1987

•

Over looker

2

2

•

Assistant over looker

2

3

•

Knotter

2

2

•

Cleaner

2

2

•

Weaver

8

6

•

Assistant weaver

3

1

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Total:

19

16

After more then 4 years I had now the opportunity to visit the mill again. The computer print-out which I received shows 91.9% weaver efficiency for the step by step installed 84 PU-153, WME 10, averages machine speed 276 picks/min. Why do I mention this? By installing new weaving machines as well as spinning and warping machines the production with only 84 weaving machines has been increased by more than 33% with a total of 107 workers including the technical and sales department

SOME DETAILS: Quality standard:

for 14 ¾, 14, 14, 12, 6, 41/2 ounce denim and chambrai.

Weaving:

0.5% seconds

Dyeing and finishing:

1.5%

Colour variations

Max. 3 shade variation per shade

Waste:

At beam change 15- 20 kg.

Warping speed:

1000 m/min. Hacoba warper with roller tension.

Sizing:

220 000m 5 days (42 m/min. Ne 7.5) (35 m/min. Ne 5.5)

Production weaving:

Approx. 12 million m/year

WEAVING COST CALCULATION Details of achievable stoppage standard have already been given. You may asked yourself are these just figures which have very little to do with your own results because you have far fewer breaks in your mill or they exceed these. Lets remember perfect yarn preparation, good preventive maintenance, good organization, effective warp changes, influence our costs. With the increasing machine speed, reduced down time at warp change become even more important.

103

The tendency to larger warper beam diameters of 1016 mm in denim plants is single to increase the running time of a warp and increase productivity. The 6 denim qualities have been taken in the same proportion to be produced simultaneously in the mill consisting of 96 weaving machines Type 360 N 1-1 EPR. Weaving Cost Structure

104

DENIM WASHING INTRODUCTION:Denim fabric can be define as a warp faced twill fabric made from 100% cotton containing havey weight indigo dyed warp yarn and undyed weft yarn the coun of yarn used varied between 6’s to 12’s. In today’s fasion a special place is occupied by the denim, fasions. The spread of denim culture all over the world brought with it a trend of a fast changing fashions the finish of this denim in the key perameter. The main part of the globle production of denim garment-that is aroud 800 million pairs of jeans on a yearly bases is passing through finishing laundries all over the world where they are givien the desire fashionable look. Denim garments have also formed a significant part of the apparel export basket from India. The stone wash effect is most popular abrasion effect on the garments obtained by the locally removing the surface bound indigo dye. This reveals the white interior of the yarn. One after an other several washes where introduce such as stone wash, acid wash, moon wash, monkey wash, show wash, white wash, mud wash etc. over the last 6-8 years India has a probably since the most domestic and the exciting changes in the washing of denim washing. Garments washing place important role to provide fashion and the functionality elements. In garment washing the seams, waist bands, pockets, cuffs etc can be given different effect. The processors however face the several problems and hence the need to use the right chemical in denim garments processing is very essential.

105

106

DESIZING:Traditional desizing is performed by using detergent and sodha or hydrochloric acid are axidative desizing agents which is associated with many drawbacks and limitations. Due to uncontrolled and non-specific reactions, the cellulose material gets damage and losses strength. With the introduction of enzyme based desizing process, the limitations and drawback of treditionals desizing process can be overcome. The enzymatic desizing process is performed by the alpha amylase enzyme. ADVANTAGES OF ENZYMATIC DESIZING OVER TRADITIONAL DESIZING:•

Due to very specific reactions of enzyme, there is no adverse effect on cellulose, there for batter strength retention.

•

Process time of desizing can be reduce.

•

Neutralization is not required because same processing conditions are required in next process there for zero salt formation in ETP.

•

Saving of energy as desizing takes place at moderate temperature.

•

Feel of fabric is much softer and less hairiness on the fabric.

RECIPE AND CONDITIONS:Strip SAL 4 (thrmo stable alpha amylase):0.5-1%(on weight of garments)lub pro vx (creas inbitor ):0.5-1gm/ltr. Treat at 80-85C and ph -6.5for 30min. STONE WASH:Still the most famous of all washings. The jeans are washed with oval or round pumice stones which should all have roughly the same format. The pumice stones are very light with a rough surface. Sometimes,

107

when the final quality inspectors at the jeans factory forget to clean the pockets, you may even find some residue of these stones in the pockets of your new jeans. During the washing process these stones will scrap off a thin layer of the denim does showing some of the white threads from the part of the cloth where the indigo dyeing stuff was not able to penetrate. It also creates and effect called brilliance. You may also encounter words like deep stone or super stonewash, which are an indication of how long the jeans have been stonewashed. Ergo: The longer the wash, the lighter the jeans. In traditional washing process volcanic rocks are pumice stones are added to the garments during washing as abradant. Due to rings dyeing and heavy abrasions, fading is more apparent but less uniform. The degree of colour fading depends on the garments to stone ratio, washing time, size of stone, material to liquor ration and load of garments. Normally after desizing, stone wash process start with the pumice stones addition in rotary drum type garment washer. Gernally 12 kg stone is used for 1 kg of garment. The process time varies from 60-12minutes. They are many limitations and drawbacks associated with stone washing process, which can be over come by using anzymes base washing technology.

Enzyme washing:The cellulose anzymes are used in washing. They act on the cotton yarn and there by facilitate the abrasions of the indigo dyeing from the yarn surface. The cellulose hydrolyses cellulose, yelding sloble produce sach as a short-chain polysaccharibes and glucose. The action loosens the indigo lyer, which is then more easily to remove by the chemical abrasions. Use of cellulose overcome must of the disadvantages of stone while yelding the desire softening and “worn” look. They are two cetagories of the enzyme, acid cellulose and nature cellulose. The nature anzyme gives less back staining. The latter property is responsible for a more reproducible finish from different wash. CLASSIFICATION OF CELLULOSE ANZYME:1: Acid cellulose (cellulose 450 AP)

108

It works best in the Ph range of 4.5-5.5 and exhibite optimine activity 50oC 2: Natural cellulose (cellucom 110 OM) It works best at Ph 6 however its activity is not adversely affected in the range of Ph 6-8 and show maximum activity at 550Oc. RECIPE AND CONDITIONS:1: FOR ACID CELLULASE ANZYME:Cellucos 450 AP: 0.5-1%(on weight of garment) Lube pro vx (creases inhibitor) : 0.5-1gm/ltr White MRC (anti-redepositing agent) : 1-2gm/ltr Treat at 50 Oc and Ph 5 for 30-45 min 2: FOR NATURAL CELLULASE ANZYME:Cellucom 110 OM : 0.5-1% (on weight of garment) Lube PRO VX (crease inhibitor) : 0.5-1%gm/ltr White MRC (anti-redepositing agent) : 1-2gm/ltr Treat at 550 Oc and Ph 6-8 for 30-60 min ADVANTAGES OF ANZYME WASHING:1: Soft handle and attractive clean appearance is obtained without severe damage to the surface of the yarn. 2: Inexpensive, low-grade fabric quality can be finish to a top quality product by the removal of the hairiness fluff and pills etc. 3: Simple process handling and minimum effluent problem. 4: Batter feel to touch and increases bellows and luster. 5: More re-productible effect can be obtained.

ENZYME AND STONE WASHING:-

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The cellulose anzyme can also be combine with the pumice stone. This is recommendable for heavy stone wash finish. The same result can be reach in a shorter time. Around 0.5kg pumice stone is used for 1kg garment and 50% of the normal doze age to the enzyme is used. BLEACHING:In this process, as a stone oxidative bleaching agent such as sodium hydrochlorite or KMNO4 is added during the washing with or without stone addition. This colouration is usually more apparent depending on the strength of the bleach liquor, quantity, temperature and treatment time. RECIPE AND CONDITIONS:Sodium hypochlorite “1-3kg/ltr” available chlorine Lube PRO VX (crease inhibitor) : 0.5-1%gm/ltr Adjust Ph 9.5-10 and treated for 10-30 min depending upon the fading

LIMITATION:1: Process is difficult to control i.e. difficult to reach the same level of bleaching in repeated runs. When desire level to bleaching reach the time span available to stop the bleaching is very narrow. 2: Due to the harshness of chemical, it may case damage to the cellulose resulting in sever strength losses and / or breaks or pinhole at the seam, pocket, etc. 3: Required antichlor treatment. 4: Problem of yellowing is very frequent due to residual chlorine.

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