Recent development in denim manufacturing

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Prepared by RAJIB CHANDRA GOSH

IntroductionTraditionally the denim fabric is made of 100 per cent cotton indigo dyed warp and white weft yarn of coarser counts. Comfort and fit are very important aspects of denim garments. So, a lot of research has being done to make stretch denims. elastane fibers are incorporated into the fabric. Lycra and Spandex are used in weft yarn. Ring and open-end core spun yarns are also used in denim to provide stretch property. To impart fancy effect, different kinds of fancy yarns are being used. The examples of such yarn

are slub yarn and multi-count yarn Other synthetic fibers such as polyester and polypropylene fibers are also used.

For making softer denim fabrics especially for women wear, blend of Modal, Promodal, Tancel, and Rayon are being used. Bamboo fibers, hemp fibers and their blends are being used to make denim fabrics.Now the scenario is different.

Denim fabrics has gained immense popularity and accepted by all irrespective of gender, age-groups and profession. So, there is tremendous challenge on the part of denim product manufactures to innovate and develop products to suit requirements of different consumers. It is attempted to put latest developments in the field of denim fabrics.

Spinning sectionBlow room Yarn spinning starts with the transfer of the cotton bales from warehouse chosen by a special software to the blowing room feeder as a initial step of yarn spinning process. From this point onwards, cotton undergoes preparation processes like cleaning, opening and blending with the content of other bales. During this process, the fibers which are too short are extracted.Carding machineThe cotton fibers are then subjected to a carding operation that ensures that the fibers are parallel to each other. The function of carding machine- Opening of the fiber bundles to separate Removal of extraneous and dust Elimination of short fibers Removal of neps Obtaining fiber evenness Blending properly Producing sliver from cotton fibers

Spinning sectionDraw Frames In draw-frames, slivers from different carding machines are brought together to form a homogenous blend and parallelism of the fibers is further enhanced. The fiber hook-ends that are a part of the fiber nature are flattened and fibers are further elongated.

Roving Frames In order to monitor the weight per unit length of the Sliver under control highly developed electronic regulation systems are utlilized. The Sliver from the drawing frame operation with uniform mass per unit length are further drawn out by the roving frame operation.

Spinning – Ring Frames After this operation ,the Rovings are subjected to a further drawing out operation on the ring machines and are further thinned out to the required yarn thickness. The yarn produced through Ring Frame is more soft and has more strength and character as compared to those produced by the Open End machines.

Winding sectionThe last phase of the yarn production is the Winding Process. Here the cops produced by the ring machines are joined together and transformed into the bobbin format of specific length . The joining process is very important from the point of view of productivity of the subsequent phases where bobbins will be used and final appearance of the fabric. During the winding process , the yarns are monitored for every mm of the way by high technology sensors on the bobbin machines and the faulty areas that may affect the texture of the fabric are eliminated. Any yarn defects (unevenness, yarn count, thin & thick places etc.) are detected and removed during winding. Yarn spinning is completed by winding process.

warping section

Two methods of warping are practiced. These are ball warping and direct warping. Ball Warping –from the point of view of color quality and authentic appearance is the preliminary preparation for the Rope Dyeing System- which is the preferred system of denim production. The yarns that will be used in the warping of the fabric are stacked in the ball warping machines Creel section and all brought to the front of the machine to be transformed into Rope . The Rope thus produced and Cones are warped as ropes at ball warping and prepared for Indigo rope dyeing process.

Dyeing sectionIn the clothing sector, denim is an indigo blue “evergreen”. Denim fabric is normally is produced by processing undyed weft yarns with ring-dyed warp yarns. Ring dyeing is a characteristic feature of denim production. In the conventional process, the yarns are either processed as a hank (rope) or spread out next to each other (slasher) and only the sheath is dyed. The dye is applied in several treatment stages.Comparison between slasher dyeing and rope dyeing process:

Slasher dyeing Rope dyeingContinuous process Discontinuous process

Color depth 4.5% Color depth 5.5%

Immersion length 5m Immersion length 9m

Stage production process from the back beam to the weaving beam

Stages up to production of the weaving beam ( dyeing , long chain beamer, sizing)

Production capacity 9-11 million metres Production capacity 22 million metres

New technology of dyeing (KARL MAYER’s IOM-Double technology)

• A characteristic feature of denim production is that it is still carried out using traditional methods, but this can now be done using highly innovative technical systems. The result of this modernisation is that production can be carried out more efficiently, using fewer resources and more accurately, i.e. with better reproducibility.

• KARL MAYER is the leader in producing the processing machine.KARL MAYER’s IOM-Double technology is based on the processing sequences of SLASHER-DYEING but has the productivity advantages of ROPE-DYEING. This innovative machine concept has been used successfully in Turkey in particular for some years. Textile companies benefit from KARL MAYER’s IOM-Double technology.

Advantages of KARL MAYER’s IOM-Double technology

maximum production capacities of up to 22 million dyed metres, i.e. the production

equivalent of 24 rope dyeing machines the energy required for steaming and drying is reduced considerably. improved heat transfer and reduced energy losses. The interaction between optimum yarn loading, excellent flow-through patterns

and a high dye affinity, together with the specific working width in the dyeing section, also results in an excellent product quality.

The process guarantees homogeneous dyeing properties as a function of time uniform dyeing across the working width (on the right, in the centre and on the

left). The yarns are also transported and wound without becoming entangled. immersion lengths of 1.5 m to 11.5 m dye depths of up to 5.5%

Weaving section Nowadays, different functions and processing steps are integrated into the weaving preparatory processes to increase quality, flexibility and economic viability. Denim fabrics are mostly woven on high speed air-jet looms. Various loom manufacturers are offering a number of modifications to weave fault free high quality fabric. Main parts of weaving machine: Warp beam Harness Heddles Reed Shuttle Drop pin Fabric beam Yarn carrier

Development of Weaving machine here sheds the light on how the weaving machine manufacturers and woven fabric producers might strengthen the weaving industry by further advanced the rapier technology with the help of electro-mechanics, electronics, microprocessors, information technology and their application to the production of woven fabrics.Development in Filling Insertion• Versatility in Colour Insertion by Electronic Insertion• Picking Speed• Secure Filling Transfer• Versatility of Rapier Gripper• Prewinder Switch-off Monitoring• Light and Small Rapier Head• Electronic Filling Tension Controller• Filling Detection at the End of Insertion and Rapier Cleaning Device

Developments in Shedding Mechanism• Versatility- upto 10 healds; positive cams, maximum 8 harness frames, 12 mm pitch• Controllable Shed Geometry• Electronic Setting of Shed Crossing• Variable Shed Geometry• Shortest Drive Path

Development of Weaving machine

Development in Let-off Mechanism The electronic motor driven let-off supplies the loom with necessary wrap yarn, maintaining the yarn tension constant from full beam to empty beam. Let-off speed is automatically calculated in context with loom speed, weft density, wrap beam diameter & close loop tension control.Developments in Take-Up Mechanism The take-up motion is also electronically controlled and synchronized with let-off motion. Inside the machine the cloth is wound on to a 600 mm diameter cloth beam. External cloth beam on to batching motion upto 1800 mm cloth roll diameter is also available. The required pick density can be programmed on the microprocessor keyboard or the jacquard control unit. The accuracy of the setting ensures easy to adjust of the pick density of the fabric for optimum fabric weight and minimum yarn consumption.

Finishing section

Finishing section is consists of :DesizingMercerizing StenteringShrinkage controllingFunctional finishes : Functional finishes such as antibacterial

finishes, UV- protection finishes are applied on denim fabrics to improve functional performances of denim fabrics. The use of nano-clay is also reported to impart old look, soft handle, flame retardant and antibacterial properties to denim fabrics.

Finishing method

Discontinuous finishing method for weft- elastic denim

The semi-continuous finishing method for weft- elastic denim

The fully continuous finishing method for weft- elastic denim

The latest fully continuous finishing method for weft- elastic denim

Development of finishing section- (Monforts - possibilities for finishing denim)

Monforts offers a wide variety of processes and ranges for the

finishing of denim. For the finishing of grey denim fabric after

cleaning and singeing, for example (e.g), padders, foam

applicators, minimum-liquor applicators, numerous versions of

stretching- and skewing-units, dryers and compressive shrinkage

ranges. Processes and ranges are offered for desizing,

mercerising, bleaching, stripping, continuous dyeing, washing,

drying and coating in order to create special effects.

Comparison between conventional and Monforts finishing method

significantly lower stretching forces, less fabric tension, better ‘look and feel’ with higher production speed and simpler residual moisture control.

The fabric width, skew and number of filling threads is monitored by a special camera and the measured values are converted into corresponding control pulses for the range control.

The following stenter with upline Matex ECO-Applicator and a coating range is then used either for finishing, drying of the coating or surface stabilisation (fixing), depending on the article.

The machine settings depend on the process to be employed. The fabric arrives at the range for the compressive shrinking process with a controlled residual moisture content or with moisture application using the Matex ECO-Applicator.

Two rubber calenders and two felt calenders ensure a high production speed with gentle use of the rubber blanket and effective energy consumption.

Two rubber calenders and two felt calenders are required to produce, for example, denim of 14.5oz/yd² with 1-2% residual shrinkage with at least 7m/min.

Low-tension guidance of the fabric during rolling is important for the end of the process.

Washing

Washing of denim garments is one of the most important processes. This process adds a lot of value to the final garment. In the washing process, fading effect is imparted to the denim products. There are many methods to impart faded effects. The traditionally washing is done using any of the methods or combinations such as stone washing, washing with strong bleaching agents such as sodium hypochlorite, potassium per magnet. There are two types of denim washing :• Wet process • Dry process

WET PROCESS Rinse wash Enzyme wash Enzyme bleaching wash Softeners wash Acid wash Rubber ball wash Resin wash Garments wash Heavy enzyme and stone wash Sand wash Silicon wash Tie wash Pigment wash

Dry process Hand sand Sand blast Whisker Laser whisker Destroy Pp spray Tagging Grinding Crinkle 3-D Crinkle PP rubbing Resin spray Heat pressing Pocket marking Seam marking Center crease

Development in washing of denim fabrics

These processes are not environment friendly. Alternative methods have been developed. Cellulases enzymes are used in place of pumice stone to impart

abraded effect. Laccase based bleaching technique is developed. This enzyme only attacks indigo dyed yarn bit does affect nature of white weft yarn. It can also be used to bleach fabrics containing elastane filaments without losing stretch property.

Laser based techniques are used to give faded effect. Further this technique can also be used to create motifs on the denim fabrics.

Ozone base denim washing treatments have been developed. In this process, ozone gas is used as bleaching agent, which attacks indigo dyes and destroy to create faded look.

World Denim Market

The world denim market is likely to grow continuously for the next few years. However, supply is growing at a faster pace.• World Jeans Market- 51.6$ Billion in 2007 and 56.2$ billion in

2014• Expected to become 61.4$ billion by 2021• Global demand growing at 7%, supply at 10%• Global Denim fabric production in 2015- 4.1 billion mtrs.• Over 50 percent of denim production is based in Asia with

China, India, Turkey, Pakistan and Bangladesh.• Between EU, US and China, 75% of world jeans consumption.

Estimated Share of Jeans Purchase By Region

North America : 39%Western Europe : 20%Japan & Korea : 10%Rest of the world : 31%

No. Of Denim Mills Worldwide

Region No. Of Denim MillsAsia(China) 297

Asia(Other countries) 104

North America 9

Europe 41

Latin America 46

Africa 15

Australia 3

Total Denim Mills (World) 515

Conclusion

In conclusion, it is well accepted that denim is an evergreen fashion and liked by all irrespective of gender, age and profession. A lot of innovation and research are to be done on continuous basis to fulfill requirements of diverse consumers keeping in mind its impact on society and environment.