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Indigo or slasher dyeing

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Indigo or slasher dyeing

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  1. “PRODUCTION OF DENIM FABRIC BY THE USE OF SLASHER DYEING”

  2. DEPARTMENT OF TEXTILE ENGINEERING Project Report On “PRODUCTION OF DENIM FABRIC BY THE USE OF SLASHER DYEING”

  3. Introduction Introduction

  4. Denim is the oldest, most widely used, most fashionable and most versatile fabric of the world. At present denim is mainly used for producing garments particularly trousers for the young people. The gross production of denim fabric is approximately 3,000 million metres per year. Denims are produced from 4 oz. to 16 oz./ sq. yds in weight. Technically Denim is defined as a 3/1 warp faced twill but also produced from weaves like: Left hand twill, right hand twill, broken twill, cross hatches, cords, dobby's, structures, etc . Denims are made from yarn dyed warp and undyed weft. Traditionally, denim was dyed with various shades of indigo, yarn-dyed, different costs, and over-dyed with various types finishes at fabric as well as garments state. Denims are manufactured different types of after treatments or washes like stone wash, bleach wash, hand wash, acid wash, over dyed, printed denims and even embossed. Denim fabrics are used as jeans trousers both for men and ladies. It is extensively used in the world as casual garments, Shirts, jackets, children wears are also made of denim fabrics. Its versatility, finds applications in furniture upholstery, bed covers, curtains, etc. Denim now-a-days is a very demandable product. To make a denim fabric the required yarn for the definite construction should be dyed then make a weavers beam to go to weaving to make fabric.

  5. TYPE: TYPE OF FABRIC : TYPE OF FABRIC : Normal Fabric Ring Fabric Half Cross Fabric Cross Latch Fabric FABRIC IDENTIFICATION : Normal Fabric = 6 OE * 6 OE / 66 * 35 Ring Fabric = 6, 9, 12 * 7 OE / 66 * 35 Half Cross Fabric = 6 slub * 7 OE / 66 * 35 Cross Latch Fabric = 10 slub * 10 slub / 66 * 35

  6. 'Some typical denim fabric construction: Description Wt oz/yd2 6 Construction: Finished Fabric 89X55/20RsX16R+16R s 77X49/13RX12R Desig n 2/1 RHT 2/1 RHT i2/IRH T 2/1 RHT 100%Cotton indigo Half Cross Denim 1 00%Cotton indigo Ring OE 8 100%Cotton indigo Vertical Slub 100%Cotton light Indigo Slub Lucky 7.25 68X49/1 ORsX20K 6.50 79X49/1 6RX14Rs 98.5%cotton 1 .5%lycra park indigo stretch slub 100% Cotton indigo normal 11.50 65X46/7.5RsX8+70D 3/1 RHT 2/1 RHT 3/1 RHT 3/1 RHT 2/1 RHT 12 10 OE+10 OE*12 OE/69*44 9 Rs+ 9 R * 7Rs + 7R/ 72 *48 8 Rs + 9R* 8Rs (MC) / 68 *50 9 OES+ 9 OE* 10 OE / 75 * 43 100% Cotton indigo 12.10 100% Cotton indigo 11.65 100% Cotton indigo 9.8

  7. FIBRE Most of the denims are produced with 100% cotton and cotton-based blends with Lycra®, Polyester, Tencel®, Bamboo, Jute, Nylon, and Linen etc. An ideal cotton mix for denim should have the following quality parameters. 2.5% span length > 25mm Strength (g/tex) >18 Micronaire > 4.5 to 5.0 Maturity Coefficient >0.75 Uniformity Ratio> 49% Trash> 4.9% In Bangladeshi mills, in most cases substantial quantity of waste yarns are used. This is mainly done to reduce the cost of production. A well established mix for denim yarns are as follows; i. 80% waste, which consists of (i) Dropping-1, (ii) Dropping-2, (iii) Flat strip, (iv) Comber noil. ii. 20% Fresh Cotton

  8. YARN (i) Rotor yams are the best and most widely used yarns in Denim production. Because of their very high speed rotor yams are much cheaper than ring spun yams. Off course rotor can only produce yarns of up to 30Ne. Though cheap rotor yarns are associated with greater imperfections than corresponding ring yarns therefore knit goods are produced from ring yarns. (ii) Count range from 6 to 16 Ne but most widely used range is 7 to 12 Ne. For slub yarn the range is 9 to 20 Ne. (iii) Quality- Counf CV-<1.2, Single yarn strength> 12.8 gm/tex, Elongation> 6.0,U% <9.5. (iv)As huge amount of slub yarns are used today the idea of too much strict U% is not considered. The diameter of slub varies froml.SD to 2.2D (Where D is the normal dia of yarn). The periodicity of slub also varies widely. Test results show mat the distances between two adjacent slubs varies within certain range. Some of the usual range distances between two adjacent slubs are from 6cm to 10cm, 7 cm to 20 cm, 30cm to 60cm. Some more information on yarns are given in weaving section later

  9. Fig: Creel stand with creel

  10. Fig: Unwinding of creel

  11. Fig: Warpers beam The thread from the packages in the creel is wound on to a beam to make warp beam.

  12. PARTICULARS OF A DIRECT WARPING MACHINE Range Set value Setup parameter >• * Warping Length 1 -99,999m Based on quantity yarn count, warping beam, capacity Cone/Cheese no. in the creel ! 325-410 Based on customer fabric construction Machine speed l- 800m/min 650 m/min; Based on yarn count and quality Length correction % 1 156% Stop motion I m- second Supply Pressure Don't need 1-8 bar 5 bar Beaming Pressure 1-160 40psi Press Pressure 1-160 30psi Carrier Pressure 1-160 50/55 psi Hydraulic Pressure 0-40 16Psi

  13. Normally the process of dyeing dictates the technology of denim manufacturing. The following twoDyeing methods are most popular processes for manufacture of denim SLASHER DYEING: Slasher dyeing dyes the yarns in the warp beam form. It is a continuous process which combines dyeing & sizing in a single operation. Dyeing is done by continuously passing warp yarns through several (at least 5) troughs of indigo dye liquor. The dyed yarns are then sized & wound onto a warp beam to be ready for use in the weaving process. Slasher dyeing is usually of inferior quality as compared to rope dyeing shade evenness or side-to-side shade variations. With the slasher dyeing, the penetration of dyestuff is poorer, and it is easily reveals an uneven pick-up along its width with the distortion of the pad-roll.

  14. Fig: Diagram of Slasher Dyeing

  15. FLOWCHART OF DYEING & SIZING: Warper’s Beam ↓ Pretreatment (Scouring) bath ↓ Dryer- wash bath (1, 2, 3) ↓ Color box - 1 ↓ Dryer - 1 ↓ Color box- 2 ↓ Dryer - 2 (Air oxidation is done here) ↓ Color box - 3 ↓ Steam box ↓ Color box - 4 ↓ Yarn pass between a set of guide roller for oxidation ↓ Color box - 5

  16. ↓ Oxidation ↓ Color box - 6 ↓ Guide Roller ↓ Color box - 7 ↓ Oxidation ↓ Color box - 8 ↓ Oxidation ↓ Wash box (1, 2, 3) ↓ Dryer ↓ Sizing box ↓ Dryer ↓ Accumulator ↓ Leasing ↓ Winding ↓ Weaver’s beam Beam creel section: •Type- Sliding creel •Arrangement- Two creels are placed parallel to each others. •Creel capacity-16 warp beams can be placed in each creel. •Electronic motor is available to slide the creel as well as mount the beams.

  17. Fig: Beam creel Sizing BATH: No of dry cylinders used in this bath = 12 Capacity of cooking tank: 1000 Ltr Cooking Temperature: 85º Cooking time: 25-50 mins Pick up: 5-10% Cylinder temperature: 110- 130ºc Squeezing Pressure: By top roller Delivery squeeze pressure: Lowest: 12-17 kN Highest: 15-20 KN Stretch: 0.7-1% Refractro reading: 7-11% Viscosity: 12-30 sec Sizing Temperature: 85-90ºc Sizing parameter:

  18. Fig: Sizing Tank Scouring: Natural fibers contain oil, fats & waxes together with other impurities. During manufacturing oil & adventitious dirt are collected. And these are affected the absorbency of the cloths & leads to uneven dyeing. Oil, fats & waxes are all insoluble in water; they dissolve in organic solvents such as Chloroform, Ether and Petrol etc. Scouring is the process to remove all these impurities to make a more absorbent, hydrophilic & clean fabric. OBJECT: 1. 01. To remove natural & added impurities like oil, wax, gum, fatty material as completely as possible. 2. 02. To get a clean & even fabric surface for the next process. 3. 03. To increase the absorbency of the fabric, i.e. to make the fabric hydrophilic, so that it can absorb dye molecule, water & other processing easily. Scouring Recipe: NaoH= 36-145 gpl or g/l Wetting agent (Lionil EH) = 0.5g/l Temperature=85ºc Water = 1400 liter Squeezing roller pressure = 4-5 bar

  19. FUNCTION OF THE CHEMICALS USED IN SCOURING: 1. Alkali: It converts the oil into water soluble fatty acid & soap. 02. Wetting agent: A soluble or dispersible material that reduces the surface tension between the material & liquid. Detergency effect helps to clean the material. 03. Sequestering agent: It reacts with metallic ions & thus makes the metallic compounds to become a part of complex anion. DYEING: Dyeing is consists of 2 dyes. The indigo blue & Sulphur black is used in the dyeing process of denim. Sometimes brown color is used instead of indigo blue in the factory according to the requirement of buyer. DYEING RECIPE: For leuco preparation here is a ratio which is followed: Indigo : 100 g/l Caustic Soda : 73 g/l Reducing agent : 93 g/l Dispersing agent : 0.5 g/l Sequestering agent : 0.5 g/l Wetting agent : 0.3 g/l

  20. Forblack preparation the following ratio is followed: Black : 35 g/l Caustic Soda : 15 g/l Antioxidant : 15 g/l Sequestering agent : 0.5 g/l Wetting agent : 0.5 g/l Dyeing Process: Dyeing process that is maintained as follows: Pure Indigo- Continuous Indigo Dyeing Bottoming- Sulphur(Bottom) & Indigo(Topping) Topping- Indigo(Bottoming) & Sulphur (Topping) Black Denim-Continuous Sulphur Black Dyeing Color Denim.

  21. LIST OF SOME CHEMICALS ARE USED & AND THEIR FUNCTION: Pimazol ws: Use as pre-wetting agent to reduce the surface tension of the liquor and allow to penetrated in to the fibers. Sodium Hydrosulphite / Hydrose: It is a reducing agent. It converts the insoluble vat dye to soluble leuco form & also to remove dissolved oxygen from water. Na2S2O4 + H2O + [O] = 2NaHSO3 Specification: ISO 9001, ISO 14001, OHSAS 18001 Purity = 90% min Country = China Caustic Soda: It is scouring agent and removes impurities from the fiber. It is used here as pH controlling agent. NaHSO3 is produced in the vatting bath which has the tendency to destroy leuco compound. To remove NaHSO3,alkali is used. NaHSO3 + NaOH = Na2O3 + H2O Specification: “Caustic Soda Flakes’’ NaOH =96%min Country = China

  22. Ladiquest: It is a sequestering agent and use to remove the hardness of water. Specification: Name = 1097 – U liq Country = Thailand Setamol-Ws: It is a dispersing agent. It is used to disperse the dye molecule properly in the dye solution. Specification: Manufacturer = BASF Country = India Persoftal BD (Paste): It is a softener, used to soften the fabric in the finishing process. Antioxidant: It is used to protect oxidation of dye molecule in dye bath. It is used as reducing agent while Sulphur black is used. It is also known as monohydrate glucose. Acetic Acid: It is used to reduce the percentage of pH in dye bath. Specification: Name = Acetic acid Glasiroyal Composition: Acery = 99% Water = 0.7-1 % Acetic anhydride = 0.3%

  23. SIZING Sizing Mills coat yarn with polyvinyl alcohol and starch for strength, and paraffin to make it easier to weave into cloth and handle in sewing. It is a film- forming polymeric materials, which is applied to a warp sheet for the purpose of protecting it during the weaving process. Objects:- •To increase the strength of yarn Up to 20% after the size application. •To improve the hairiness, thick and thin places, Neps knots in the warp yarn. •To protect the warp yarn from breakage during weaving process. Which is subjected to abrasion width varies loom parts such as reed heald shaft Shuttle, Splitting rod. Sizing composition depends on the following factors: •Types of fibers •Types of yarn •Yarn quality •Quality particulars of fabric to be woven •M/c condition & ambient condition of the loom shade •Cost of various ingredients

  24. The Starch & Softener are used in the sizing bath are given below: Emsland E-14 Starch: These are products from grains & tubers. These are mixture of carbohydrate, oil, nitrogenous substances & mineral matter. Carbohydrate is a polymer consisting of 25% amylase and 75% amylopectin. Structurally it is a highly branched glucose polymer. Starches are cheap & easily available & have proved to valuable adhesives over a many years especially for cellulosic yarns. This is manufactured mainly from maize, wheat, rice etc. When starch is boiled with water, the starch granules swell & break up forming a smooth & homogenous gelatinous mass. Starch: Emsland E-55 (Modified starch) Softener: Mutton Tallow Fin Fix Trefin Wax

  25. EMSIZE E-55: Application: is a low add –on starch sizing agent for spun yarns Characteristics: Application: is a low add –on starch sizing agent for spun yarns Characteristics: Kind of product: Potato starch derivatives Appearance: Off white powder Moisture content: < 20% pH value (5% conc): 6-8 Viscosity: Preparation of the solution: The required quantity of product is added to cold water. Under stirring the slurry should be heated up till 95ºc and kept for at least 10 minutes at this temperature. Preparation in an autoclave has to be heated up to 110ºc and kept for at least 10 mins at this temperature.

  26. EMSIZE E-14: Application: Emsize is a starch sizing agent for spun yarns Characteristics: Kind of product: High modified polymer Appearance: Off white granules Moisture content: 9-14% pH value (5% conc): 9.5-11.5 Viscosity: Preparation of the solution: The required quantity of product is added to cold water. Under stirring the slurry should be heated up till 95ºc and kept for at least 20 minutes at this temperature. Preparation in an autoclave has to be heated up to 110ºc and kept for at least 10 mins at this temperature. Both the starch has the following common properties: excellent sizing effect transparent flexible film high adhesion power compatible with other sizing agents washed out quickly without enzymes good biological degradability

  27. Modified starch: It is manufactured from natural starches mainly maize. Advantage: They are water soluble. Can gelatinize easily & quickly They penetrate well into the yarn because of their small particle Size, & pick up percentage increases for this reason Mutton tallow: It is prepared from the sheep & is chemically composed of the glycerides of stearic, oleic & palmitic acids.

  28. After warping, dyeing and sizing a weaver's beam is produced. The weaver's beam, after drawing and denting is then mounted in the loom to produce the fabric. Weaving of denim fabric is not much different from weaving all other fabric except the idea about the warp and weft way shrinkage percent. It is well known that fabric shrinks after relaxation and also after any wet process treatment. In order to accommodate the aspect of both way shrinkages it is necessary to use a very decisive EPI and PPI in the loom state so that after relaxation and wet treatments the fabric will conform to the customers supplied fabric details. It was found that in general that the fabric shrinkage percent in the length direction varies from I2%-15% while in the width direction the shrinkage percent lies around 4.5% to 5.5 %. The higher shrinkage in the warp direction is mainly due to greater warp tension during weaving and also due to the coarser weft yams than that of the warp yarns. In order to comply with the customer's requirements it will be necessary to choose both EPI and PPI very precisely so that the final EPI and PPI of the ultimate fabric conform to the buyer's requirement.

  29. The typical reed and picks of some commonly produced fabric is given below; Construction Finish EPI Loom Finish PPI Loom Finished Cover Factor warp Weft Cover factor State State Cover factor EPI PPI 9Rs+9R*7Rs+7R/ 72*48 72 68 48 44/45 26.59 24 18.14 8Rs+9R*8Rs(MC)/68 *50 68 63 50 50 26.04 23.33 17.68 8Rs*10Rs+10R/76*5 4 9Rs+9OE*12Rs+10+ 70D/ 78*54 8Rs+10R*8Rs+7OE/ 72*50 76 71 54 50 27.56 26.87 17.08 78 64 54 48/49 27.16 26 16.28 72 71 50 47/48 26 24 17.68 9OEs+9OE*10 OE/75*43 10Rs+10OE*6OE+70 D/ 76*50 8Rs+7R+10R*9R/72 *48 75 68 43 37/39 26.47 25 13.6 76 71 50 44/45 26.93 24.03 20.41 72 66 48 41/44 26.69 24.94 16

  30. We know Cover factor, Kc =( K1 + K2 – K1*K2/28 ) Where, warp Cover factor, K1 = EPI/√ count And weft Cover factor, K2 = PPI/√ count Denim fabrics are highly sensitive to the fault incidence. Therefore maximum care is necessary at all levels to avoid fabric faults. Normally the loom stoppages are regarded as a serious matter in accumulating fault level. Loom stoppages in turn depend on a large extent on the yarn quality. A recommendation based on research study has suggested the following yarn breakage norms in the warping and sizing department;

  31. Warping Ring Rotor Dyeing Ring Rotor yarn yarn yarn yam End break per million metres l<08 <0.5 End break per million metres Loss of extension 0.2 0.3 Loss of extension <0.5% <0.4% <1.3 <1.3 Imperfection also plays an important role in the production of a fault free denim fabric. The norms for some of the important indicator of yarn quality for denim are given below. ^ Parameter Count CV Single Yam Strength Elongation U% j Total Imperfection Norms for Rotor Yarns < 1.2% > 12.8gm/tex Norms for Ring Yarn < 1.7% > 14.0gin/tex > 6.0 < 9.5 < 10 (at 280%) > 6% < 10% <35'9(At200%) N:B: N:B: The CV% can not be applicable to the slub yarns.

  32. GSM Calculation Yarn count = Length (cm) X 0.0059 Wt(gm) Yarn weight = Sample weight X 100X100 / Sample Length X SampleWidthX 33.9063 For example, Construction = 71 X 51 Total yarn = 11 Length of fabric = 3.45cm Weight of fabric = 0.03 gm Count =11X3.45X0.0059 / 0.03 =7.46 Weight = 0.4 X 100 X 1OO X 3.45X2.886X33,9063 =11.83 oz / yd2 Crimp % : Warp Length – Actual Warp Length Production / Warp Length * 100

  33. Shrinkage % : Actual Production – Finishing Production / Actual Production * 100 Fig: Front view of a weaving m\c

  34. Fig: weaving m\c (Picanol omni plus 800)

  35. Fig: J Box of a finishing m\c

  36. Fig: Brushing unit of a finishing m\c

  37. Fig: Singing unit of a finishing m\c

  38. Fig: Scew roller of a finishing m\c

  39. Fig: Drying cylinder of a finishing m\c

  40. Fig: Calendering unit of a finishing m\c

  41. Fig: Spreading unit of a finishing m\c

  42. After weaving, the woven denim fabrics undergo for various finishing processes depending on the end uses. This is because denim fabric produced in a loom is somewhat dirty and very stiff and difficult to make garment from them. Apart from this, the technical specification like width and threads per inch cannot always be achieved straightway from the loom. Therefore some physical and chemical treatments are carried out before delivering the fabric to the customer/garment factory. These processes are discussed under finishing section. Finishing of denim is carried out in both fabrics as well as garment state. The fabric finishing is carried out in the weaving factory where the fabric is produced but the garment state finishing is carried out in the garments washing plant.

  43. Finishing section placed along a line: Finishing Line Fabric Finishing The typical flowchart of the denim fabric finishing is as below Loom state fabric ↓ Brushing ↓ Singeing ↓ Brushing ↓ Softening ↓ Correction of skewing ↓ Compressive shrinkage ↓ Palmer (Calendaring cum drying) ↓ Inspection ↓ folding

  44. Description of the processes: Brushing: The purpose of this process is to remove the lint, fluffs and loose impurities. This is achieved by subjecting the fabric to kind of roller beating action. Singeing: The objective of this process is to burn out the protruding fibres from the surface of the fabric. Only blue side singed and it is done twice. The aim of this process is to modify the feel of denim fabric and to facilitate the movement of the threads during skewing and shrinkage process. This is just a softening process where the fabric is passed continuously through a solution containing 5gm/Htre softener. Sometimes softener is used as foam form. Use of foam reduces the quantity of heat required to dry the fabric. Softening:

  45. The 3/1 twill weave is in the classical denim fabric is inherently unstable weave and has a tendency to twist anticlockwise considering blue side as face side to stable configuration when it CORRECTION OF SKEWING: is put in water. Due to this unstable condition the weft yarns lies with warp yarn at an angle different from 90°. This is regarded as skewing and if it is not corrected then there will be deformation and leg twisting in the jeans made out of it. Therefore skewing is corrected in this section where the fabric is basically passed either over a roller or through two sets of rollers. The basic idea of correction the skewing is that warp yarns deliberately pulled at one end so that the weft yarn can lie with warp at 90° .In the former case the fabric is pulled by a pair of squeeze rollers and the correction roller is either pushed up or down. In the later case two sets of rollers are set at the two extreme ends, the rollers are capable of pulling fabric at different speeds. What ever is the method of correcting the skew ness, in all cases attempt is made to compact the fabric sufficiently so that the tendency of skewing is eliminated.

  46. Compressive shrinkage: The lengthwise shrinkage potential of denim fabric varies from 12% to 18% depending on the quality and construction. It is necessary to correct this type of high potential shrinkage before making a garment. Compressive shrinkage is a very widely used finishing process used for shrinking the denim fabrics deliberately. This is basically a mechanical finishing treatment. The basic working principle of this process is that if a strip of elastic rubber is extended and then a fabric strip is held pressed against the extended rubber. If, now the rubber is allowed to relax, it will relax while the fabric strip will also relax as it is held pressed against the rubber. In the real case, an endless rubber sheet is pressed by a large circular cylinder. The fabric is fed between the cylinder and the rubber sheet. By varying the amount of feed it is possible to control the amount of shrinkage. The extent of relaxation of the fabric can be controlled by controlling the amount of feed.

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