ADVANCES IN DENIM PROCESSING

ByDhanraj Desai

Under the guidance ofDr. M D Teli sir

INTRODUCTION• The term "Denim" has originated from the city of Nimmes in France where “Serge de Nimmes" was manufactured.• A fabric made from 100% cotton and having twill construction (diagonal) is called denim.• The classical denim is a heavy fabric made from 100% cotton and woven from coarse indigo dyed warp and grey undyed weft yarn. • The traditional denim is hard-wearing, high density fabrics with a high mass per unit area and a 3/1 or 2/1- twill weave construction.• Denim is made from a vat dye, the Indigo dye, which is applied to cotton fabric in loosely held form in layers.

MANUFACTURING PROCESS OF DENIM

YARN Parameters FOR DENIM production

Parameters Ring Yarn OE YarnTenacity cn/tex 15 – 16 11.5 – 12Elongation % 7.5 8

Uniformity CV% 13.5 14.6Thin places per

1000 m8 5

Thick places per 1000 m

70 20

Neps per 1000 m 60 60

DENIM DYEING• It is of Two types

a) Sheet form dyeing type.b) Rope form dyeing type.

•Dye Useda) Indigob) Sulphur

ROPE DYEING UNIT

ENTERING FEEDING

Cont.….

DYEING AIRING/OXIDATION

CONT….

DRYING DELIVERY

STYLES IN DYEING• SDINDIGO • SDSBIT

• DIBST• LBIT

• LGBIT• SBBIT

Advancements in rope dyeing machine

• Hunter lab installed in the coiler section which measures L , a , b values and is connected to computerized system gives the dyer the power to take correction if the shade is going wrong.• Front-to-front bath circulating system. • Big delivery pumps for higher recycle/hour of the dyeing bath. • Caustic soda and sodium hydrosulphite automatic dosing systems

with special dissolving device. • Oxidisers groups with big diameters rollers, short laps and extreme

ergonomics. • Ground fitted colour kitchen tanks.• Drying rollers groups with side housing and suction hoods for a safe

working environment.

SLASHER DYEING

Advancements in slasher dyeing machine

• Half circular bottom and double flow, on all width (pat.) dyeing vats for an even and total bath rechange, without turbulences and with reduction in hydrosulphite consumption.• Special construction vats for each specific use and/or treatment, to

get the maximum operative quality and flexibility.• Feeding of the reinforce bath to each single vat by compensate

circulation system, guarantee of dyestuff concentration evenness. • Stainless steel/rubber squeezing pads with big diameter

equipressure rollers, for an even squeezing at each working pressure. • Mixing/circulation bath group with ponderal dosing system and

hydrosulphite dissolving and set of n° 5 baskets for total filtering.

CONT……• Mixing/circulation bath group with ponderal dosing system and

hydrosulphite dissolving and set of n° 5 baskets for total filtering.• RapidSky” (pat.) oxidation enhancing devices with differentiated

effect, they reduce even the yarn stress and the wastages at lot change. • Enhanced washing units “EcoWash” (Pat.) with three sections

vats with half circular bottom, with guided circulation and with internal counter flow, for an effective action and sensible water saving. • Benninger advancements.• Innovative Pad Sizing Ox process developed by clariant.

PAD/SIZING-OX PROCESS By Clariant

ADVANTAGES OF PAD/SIZING-OX PROCESS

• DYEING1. Quick shade stabilization & efficient colour shift Easy correction and

adjustment of shades.2. High productivity & reproducibility.3. Suitable for wash-down effects.4. Good level of fastness.• SIZING1. Good adhesive power.2. Good water solubility.3. Stable to alkaline conditions.4. Insensitive to high humidity.5. Excellent size film.6. High performance also on high speed looms.

SLASHER DYEING v/s PAD/SIZING OX PROCESS

DENIM Washing or FINISHING OF DENIM

• In denims, washing is done to produce effects like color fading with or without patchiness, crinkles, seam puckering, hairiness, de-pilling, softened-hand feel, stabilized dimensions etc.• Normally the process of denim washing involves stages like product

evaluation and preparation desizing, braiding, bleaching, anti-chlorine / post scouring, over dyeing (optional), softening, hydro-extracting and tumble drying. Various process effects for special products can be obtained by using combinations of these procedures. Different processing parameters can be set for each stage to enhance and improve the effects.• Since denim constitutes the largest portion of the garments that are

washed, the term 'wash' has come to mean the finishing of denim garments.

STONE Washing• This method is most common and is used to give denim

an 'old-look'. • Pumice stone is one of the most important components

used to abrade the surface of the fabric to obtain a surface pattern effect with color contrast and soft - handle.

Pumice Stones• They are a light weight, highly porous rocky substance which will float on water.• It is a common product as a result of explosive volcanic

eruptions.• The world’s major pumice stone supplying countries are

the U.S.A, Turkey, Italy, Germany, Iceland, New Zealand, Japan, Indonesia and Philippines etc.

Cont.….• In this process, the fibres on the surface of the fabric are broken and removed and the inner white fibres of the warp yarn are gradually exposed. • Natural patterns can be formed as the degree of abrasions varies in various parts of the garment.• The degree of colour fading depends on the washing time, stone ratio, sizes of stones, liquor ratio and garment load.

ENZYME Washing

• This is a bio-catalytic method wherein an ultra-soft handle effect can be produced on denim. The hydrolytic effect of enzymes causes the loss of surface fibre, which improves surface smoothness and softness of the fabric.

Bleach washing•This process is usually done without stones by using an oxidative bleaching agent like hypochlorite. •Sodium hypochlorite is normally used as it is cheap, convenient and quick. •Other agents used are sodium percarbonate and sodium perborate. •A bio-bleaching technique known as "DeniBleach Technology" has recently been introduced by Novo Nordisk.

Cont.…•

Acid or ICE or Snow washing• This is achieved by dry tumbling with pumice stones

soaked with bleaching agents to produce a 'snow' pattern effect on denim. • Stones are used to deposit a chemical on garments to strip off the colour. • This chemical deposit removes colour only from the outer surface of the garments and produces a frosted appearance. • Indigo and selected sulphur dyes are the most popular candidates for this procedure.

NEW DENIM FINISHES

NEW DENIM FINISHESSand blasting• Sand blasting technique is based blasting an abrasive material in granular , powdered form through a nozzle at a very high speed and pressure on to specific areas of the garment surface to be treated to give the desired distressed /abraded /used look.• This process is used to obtain localized abrasion effect. The abrasion force rubs off the indigo-dyed fibres.• Blasting jeans with silica sand produces the desired vintage look.• The abrasive material can be quartz, emery, granite, silicon-carbide, boron-carbide, aluminum-oxide and chilled iron. However in practice, oxides of aluminum and copper with certain auxiliaries are widely used.

CONT….

New denim finishes• Buffies/MoustacheThese are the lighter-colored contours running across the trousers that look like real seat creases. The pair of jeans is treated by hand with fine sandpaper according to the designer’s draft. The sanding of these wear creases is also referred to as scraping.

• SprayingSpraying the jeans with a solution of potassium permanganate produces even traces of wear.

cont.….• PliesTo generate wrinkles, the material is twisted slightly and fixatedwith synthetic yarn. After washing, the strands of yarn are cut and removed. There is significantly more dye in the wrinkles thanin the surrounding material.

• Brush effectTo enhance the bleaching results, the denims are brushed withpotassium permanganate several times.

Cont.….• BakingTo add three-dimensional creases to the optical effect, thejeans are tied together in the desired areas and sprayed witha special synthetic resin. Afterwards, bake the trousers in the oven.

SOME UNCOMMON DENIMPrinted Denim• Denim printed with pattern such as batik or floral pattern

often in contrasting colours mainly meant for adolescents.Crushed Denim• Textured effect achieved through a special fabric construction coupled with wet processing. • Fabric is woven with an over twist weft yarn. • On washing the yarn shrinks, acquiring a goffre look.• The effect can also be improved by bleach and stone wash.

CONT….Marble Denim• It is an another name for acid wash. • Some crushed denims, if strongly bleached, are also called marble.

Petroleum Wash• Developed in 1992 by US brand Williwear. • A left hand denim is enzyme washed until it has lost most of the

colour. • It is then overdyed and put through a silicone wash, which gives

it an oily coating and, in turn a super-soft, butter like hand.

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