PRODUCTION OF DENIM FABRIC BY THE USE OF SLASHER DYEING
DEPARTMENT OF TEXTILE ENGINEERING Project Report On PRODUCTION OF DENIM FABRIC BY THE USE OF SLASHER DYEING
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.
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 FIBRE
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- 12.8 gm/tex, Elongation> 6.0,U%
PARTICULARS OF A DIRECT WARPING MACHINE Setup parameter > * RangeSet value Warping Length1 - 99,999m Based on quantity yarn count, warping beam, capacity Cone/Cheese no. in the creel ! 325-410 Based on customer fabric construction Machine speedl- 800m/min 650 m/min; Based on yarn count and quality Length correction % 1156% Stop motion I m- second Don't need Supply Pressure1-8 bar5 bar Beaming Pressure1-16040psi Press Pressure1-16030psi Carrier Pressure1-16050/55 psi Hydraulic Pressure0-4016Psi
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.
Fig: Diagram of Slasher Dyeing
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
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 Weavers beam 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. Beam creel section:
Fig: Beam creel Capacity of cooking tank: 1000 Ltr Cooking Temperature: 85 Cooking time: 25-50 mins Pick up: 5-10% Cylinder temperature: 110-130c 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: 85-90c Sizing BATH: No of dry cylinders used in this bath = 12 Sizing parameter:
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=85c Water = 1400 liter Squeezing roller pressure = 4-5 bar
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
For black 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.
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
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%
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
The Starch & Softener are used in the sizing bath are given below: Starch: Emsland E-55 (Modified starch) Emsland E-14 Softener: Mutton Tallow Fin Fix Trefin Wax 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.
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 95c and kept for at least 10 minutes at this temperature. Preparation in an autoclave has to be heated up to 110c and kept for at least 10 mins at this temperature.
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 95c and kept for at least 20 minutes at this temperature. Preparation in an autoclave has to be heated up to 110c 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
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.
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...