What is Coated DenimOne reader has asked about coated denim.

Such jeans have a coating that feels like as if the cotton of the denim is waxed. If black in color, the jeans shines up like leather pants.

The coating is generally done using pigment, acrylic or polyurethane coating. Pigment coating provides the denim a new look and experience after every wash. Acrylic and PU, however, act as a transparent coating. This protects the fading properties. It also gives the fabric a protective breathable layer with stain resistant properties. The luster and feel of the fabric are also improved.

Resin Coating is generally done with the help of wooden handle. A rubber squeezer is used to extract resin under pressure to form leather effect on denim garment. It is a neutral ( pH 7) cream-colored paste that is miscible in cold water and resistant to heat upto 200 degreeCelcius. It is self catalysed and chlorine resistant.

The coating can be applied on the garment by screen, brush or knife edge. Machine coating is also possible.

After applying coating the fabric is dried and cured at 150 degree Celcius of 5 minutes.

Normally the coating are permanent in nature and able to sustain multiple launderings.

Critical Process Parameters- Denim ManufacturingCritical Process Parameters- Denim Manufacturing

Warping: 

Machine Speed m/min= 600+-50Tension on individual thread ( cN) 90+-30Warping breaks ( Avg/10000m/400 ends) < = 0.2 

Dyeing-cum-Sizing 

1. Machine Speed = 30+-2 2. Size Viscosity ( Flow seconds) = 6+-1 3. Size Add on ( %)= 6+-2 4. Breaking Force (gf) sized yarn = >=11005. Tenacity ( cN/tex) ( sized yarn) = >136. Elongation ( %) of sized yarn >= 4.5 

Finishing

Quality 7 x 6 7 x 6 7 x 7 7 x 9 7 x 6Width(cm) 151+-1 149+-1 151+-1 151+-1 151+-1Shrinkage

( %) 15+-1 14.5+-1 15.5+-1 16+-1 14+-1

Skew ( %) 5-11 5-11 5-11 5-11 5-11

Finished Properties of some Common Denim FabricsNew Page 1

Ideal Weight 14.5 Oz/Sq yd 13.75 oz/sq yard 12.5 oz/sq yardWarp Count

(Washed) 6.9 +-0.6 6.9+-0.5 6.9+-0.5

Weft Count (Washed) 6.0+-0.4 6.9+-0.5 9.0+-0.5EPI ( Unwashed) 70+-2 70+-2 70+-2PPI ( Unwashed) 43+-2 43+-2 43+-2Wt ( Oz./ sq.Yd) 14.2 13.4 12.2

Rubbing Fastness ( Dry) 2-3 2-3 2-3

Fastness to Laundering 2 2 2

Hard waste % in denim industry

Hard Waste % in Denim Industry

Warping--> 0.7%Unsized Yarn--> 0.4%Sized Yarn--> 0.6%Fringe--> 1.7%

All these  above are percentage of Hacoba Production

Knotting + Reknotting waste --. 0.7%Extra ends--> 0.7%

All the above are as percentage of loom shed production

Total Hard Waste= 4.8%

shrinkage norms for 14.5 oz. denimLength wise shrinkage--> after 3rd wash---> -1.2% to -2.8%Width wise shrinkage --> after 3rd wash--> -2.5% to -3.5%

Receipes for different shades of DenimReceipes For Different Shades on Denim

A) Black-on-BlackBlack-on-Blue

Recipe

Liquid Sulphast Black= 200 gplSodium Sulphide= 20 gplSandozol HSI = 10 gplSoda Ash= 10 gpl

B) Blue-on- Blue

Receipe

Liquid Sulphar Navy Blue = 100 gplLiquid Sulphast Black= 50 gplSodium Sulphide= 20 gplSandozol HSI= 10 gplSoda Ash= 10 gpl

C) Reactive Series

Receipe

01) Ramazol Turquoise Blue G = 110 gplUrea= 100 gplSwanic 6L= 10 gpl

02) Sodium Silicate= 250 gplCaustic Soda = 10 gpl

Ratio of 01) and 02) = 3:1

D) Ramazol Coffee Brown G

Receipe01) Coffee Brown G = 100gplUrea = 100 gplSwanic 6L= 10 gpl

02) Sodium Silicate = 250 gplCaustic Soda= 10 gpl

Ratio of 01) and 02) = 3:1

E) Ramazol Parrot Green

Receipe01) Ramazol Turquoise Blue G = 90 gplRamazol Yellow FG = 40 gplUrea= 100 gplSwanic 6L= 10 gpl

02) Sodium Silicate = 250 gplCaustic Soda = 10 gpl

Ratio of 01) and 02) = 3:1

F) Ramazol Blue 

Receipe01) Ramazol Black B = 70 gplUrea = 100 gplSwanic 6L = 10 gpl

02) Sodium Silicate = 250 gplCaustic Soda = 10 gpl

Ratio of 01) and 02) = 3:1

Integrated Finishing for Denim- my NotesPreshrinking of Textile Fabrics- or compressive shrinkage

Shrinkage can be- Natural Wash shrinkage- When the fibres swell in the presence of water and tensions induced during Spinning, weaving and processing of fabrics- Compressive or Mechanical Shrinkage

It can be compared to the action of press. The effectiveness of ironing depends upon:Temperature of the pressAmount of Moisture present in the fabricsAmount of Physical Pressure AppliedTime duration of application of press.

In case of pressing, the new memory is set by drying, in compressive shrinking, it is the palmer unit which dries the fabric, thereby setting its new memory

Amount of preshrinkage left in the fabric is adjusted by varying the relative speed of the palmer to that of the rubber belt unit.

Temperature

The temperature affects in the following way the various components of the palmer/ compressive shrinkage unit

- Rubber Belt Cylindero Lower Temperature- Fabric appearance is affected- Sharp creaseo Higher temperature- rubber belt life is shortened- Palmer Cylindero If lower temperature: No dry Stuff; Elongation of preshrunk fabric- also stretching of inspection and rolling operation.o The purpose of palmer cylinder is to dry a fabric to a level of about 4% relative humidity. If there is higher temperature, there is elongation with natural moisture regain.- Temperature of fabric as it enters rubber belt unitIf properly controlled, then high production. Most fabrics will shrink more easily if heated before entering the rubber belt unit.Moisture

- 100% cotton denim may require as much as 14% moisture to permit effective pre shrinkage- Moisture must be uniform thoroughout the length, width, and depth of fabric

How to ensure moisture uniformity- Use of heated cans- Apply needed moisture of fabric vial cooling water applied to rubber belt surface. But it also depends upon the condition of the rubber belt. Freshly grinded rubber belt carry more water à water removal roll of the rubber belt unit

Penetration of moisture applied to the fabric is very important. If insufficient moistureà Innermost dry layers of yarn will act like spring and cause the fabric to elongate.

Pressure

Maximum amount of rubber belt compression should not be greater than 25% of the actual belt thickness.

More heavy the fabric, more potential, more compression will it need

d. Duration

If above three factors are maintained and we have a sufficiently large palmer unit, we can compress durably a fabric to its ‘zero’ potential.

Its important to use cooling cans at the exit of the palmer

Fabric Scray: Use of exit scray allows additional time for fabric cooling as it is impossible to roll fabrics without the use of lengthwise tension.

Guider: The function of the guider is to keep the fabric to its full width.

Skyer: It is a sort of time delay device allowing time for moisture to penetrate into the fabric without the need to increase the machine length.

Heated Can: purpose: it is to drive the surface moisture into the fabric and to preheat the fabric.

Palmer

Function

Dry the fabric and set shrinkageAdjust the shrinkageTo compare incoming and outgoing fabric tension and determine fabric shrinkage

Less dense the felt, greater is the drying capacity

Exit Scary- To relax and cool;- To prevent hot stop marks. It increases the rubber belt life- To facilitate shrink environmentWhy Wet Finishing for Denim

- Moisture doesn’t penetrate in the core- in foam finishing- Its better to shrink fabric with a low moisture content than those which are bone dried

In integrated Machine

Padder- wetting- squeezing the moisture- application of heat

Once it is shrunk the fabric is thoroughly dried by palmer

- Hand can be adjusted in padder use of starch, lubricant- Width can be controlled by adjusting tension between the padder and dry can- Higher speed- Even ness of the moisture content- Residual moisture after leaving palmer should be 4%

Drying depends upon the pressure of the steam, m/c speed, size of palmer , construction of felt

Rubber Belts: 36-40 deg. Shore

Harder- crack and lesser shrinkage capacitySofter- require replacement frequentlyThickness- 67mm

Thicker- more grinding- cracking- more wear and tear to machine parts

- energy consumption

Rubber belt: Inside circumference- 3.962m- Rubber surface width should exceed fabric width by at least 6” and preferably 8”

How to increase the life of the Rubber belt

- Nip pressure used on rubber belt should be optimum- Over tension in the rubber belt should be avoided- Belt should be run with sufficient cooling water in its interior and exterior surface- Belt should be run with lowest possible operating temperature 115 deg- 140deg- Frequency of grinding of the rubber belt should be optimum ie should be enough and at sufficient depth.- Grind when density of belt surface has varied by 10% of its original hardness- Water removal roll pressure adjustment is very important to insure max. belt life. Water acts not only to cool the rubber, but is also a lubricant- Product machine stops or “hot stops” should be avoided to the maximum extent possible. One of the best ways to eliminate is to install scrays at the entrance and exit of the shrinking machine.- Foreign objects should be avoided. Knot size for joining fabrics should be smaller.- Regular cleaning and inspection of rubber belt.- Use correct belt width- Be careful during installation and maintenance of rubber belt, avoid use of chemicals.

Function of Felt Palmer

- It is required to maintain the preshrunk fabrics in intimate uniform contact with the surface of the heated cylinder in order to ensure uniform smooth drying of the fabricà new dimensionally stable memory.- Fabric drying depends upon, palmer cylinder temperature, shrinking machine speed and permeability of the drying felt.

- It helps in precise fabric shrinking adjustment. It acts as a fabric puller to precisely control tension on the fabric- Provides a pressing and calendaring effect on the preshrunk fabric

Making Fancy Denim- Amsler Slub, Multicount and Multitwist YarnMost of the Cross-Hatch Denim is produced on Amsler Slub or multi-count yarn.

Here are some examples:

Amsler is a swiss fancy-yarn machine manufacturing company. The fabrics produced of the yarn are becoming synonymous with the name of the company

What is Amsler Slub

Amsler yarn can be made on open end or on a ring spinning. 

Mostly amsler slub effect in denim is produced on open end. Thus this is an attachment to open end spinning that allows slub and multi-twist effects at less cost than true ring spun yarn.

The basic problems in producing slub yarn can be enumerated as follows ( source):

1. Weak Places in the Yarn: The thick place in the yarn is followed immediately by a thin place, rather than by a simple return to the basic yarn count being spun. This, in turn, creates a weak place in the yarn.  

2. Increase in Basic Yarn twist:

Increased length of the slub leads to the increased twists of the basic yarn. It is necessary to adjust the slub length to avoid basic yarn twist exceeding critical twist.  Twists in every section of the slub yarn are in inversely proportion to the square of the linear density of the corresponding section.

The Principle of Amsler effect goes like this: The Normal yarn is formed from the basic machine speed. There is a microprocessor controlled servomotor that overfeeds with a pre-programmed textile ramp.

In case of ring frame, the servo drive system is connected to the back and middle roller via a special gear box. Only at the time of slub formation the servo motor starts and additional speed is given to the drafting system. Thus the normal yarn formation is not disturbed which results in making a yarn without weak spots. 

In case of open end yarn the principle is the same, ie. excess feed which can be explained with this figure:

Multi-Count Effect

Multi-count yarn, becoming so popular in denim fabrics is produced by a special device. This effect is characterized by having controlled count changes in length ( as short as 2 meters) while maintaining a constant twist level.

Multi-Twist Effect

Multi-twist yarns are those that feature a constant count but have different levels inside yarns. These twist levels create variations in the yarn's dye intake thus creating a special fabric appearance. 

How to Stonewash BetterHow to Stonewash Better

Traditionally Natural pumice stone is used in denim washing process. It has the following disadvantages:

1. Residual pumice is difficult to remove from washed fabric/garment.

2. There is always a danger of damage to the equipment by overload of tumbling stones and material.This can also clog the drains and sewer lines.

Thus enzymes like cellulase are used to achieve the desirable appearance and soft handle for the fabric.

The problem with using enzymatic treatment is that the removed indigo dye can be redposited on the white yarn of the denim fabric. this process is called back staining and it can mar the look of garment.

Industrially cellulase is used along with Pumice stone for stone

washing.

The cellulase can be at ph=7, when it is called the neutrual cellulase or at a pH of 5.5, when it is called the acidic cellulase.

In general the cellulase added is for 60min at 55 deg C as a percentage of the weight of the garment. It can be 3%, 6%, 9% or 12% depending upon the appearance required.

Pumice stone is generally taken as equal in weight that of the garment.

According to  a study , the best stone washing ( as measured by the lightness of the sample is achieved for treatment with Neutral cellulases with pumice stone, acid cellulases with pumice stone, neutral cellulases, acid cellulases and pumice stone, in that order.

In the same order tensile strength of the sample decreases.

However, degree of back staining increases in the order of treatment with pumice stone, acid cellulases, neutral cellulases, acid cellulases with pumice stone and neutral cellulases with pumice.

which means a balance needs to be achieved- and where the effort to increase one desirable leads to increase in another undesirable one.

Manufacturing Process of Denim

Manufacturing of DenimFor manufacturing Denim and Grey Fabric, the process is same up to the level of weaving, but in case of Denim Fabric, dyeing is done at the stage of sizing where as for Grey Fabric it depends upon the finished product. The details of each process are given below:1. Fabric Weavinga. Grey Yarn on ConesNormally yarns received for weaving in cone forms are either from ring spinning or from open end spinning in single or double fold as required. For weaving, yarn used is categorised into:o Warp yarno Weft yarnNormally for Weaving, yarn used as warp should be sufficiently strong to withstand stress and strains exerted during weaving operations. Hence they are having Count Strength Product(CSP) and further sized to increase its strength. The weft yarn is directly used on weaving machines and in some cases, if required, is rewound also so as to enhance its performance in weaving.b. Warping on Sectional/ Direct WarpingThe warp yarn is required to be fed into a sheet form to the weaving machines. At warping, the individual cones are put into the creel (the number of cones depends upon fabric construction)

and yarn from individual cones is pulled together in sheet form, wound on a barrel called warping beams (for Direct warping) or on weaving beams (for Sectional Warping). Normally if warp sheet is with patterns of different coloured yarns it is processed on sectional warping machine.c. Sizing of yarn in Set/ Beam to Beam PositionThe object of Sizing is to improve the strength of yarn by chemically binding the fibres with each other and also improve upon its friction resistance capacity by chemically coating the surface of yarn/fibres. Further, number of threads in warpers beam sheet is very less against number of threads required in whole width of fabric. Hence multiplication of sheets by drawing yarns together from many warp beams and again making one sheet is also performed on sizing machine. On sizing, normally, 8-12 % size material on warp thread is applied. This improvement in strength and frictional resistance characteristic of warp yarn is essential because during weaving, yarn has to undergo severe strain & stress as well as frictional operations.d. Drawing–inWeaving is basically interlacement of two sets i.e. warp and weft threads in desired sequence and pattern. To obtain this interlacement, warp yarn sheet is bifurcated & opened in the form of two layers/ sheet and weft thread is inserted between so opened two warp sheets. This operation is called shedding. to perform shedding the warp yarn needs to be passed through heald eyes of the heald shafts, this operation is called as drawing-in.e. Beam Gaiting or Knotting on LoomThe drawn weavers beams are fixed on weaving machines, threads are tied and heald shafts are coupled. This operation is called Beam Gaiting. If undrawn warp threads are directly knotted to the threads of finished beams, it is called Knotting. These operations are essential because normally weavers beam can carry only certain length of warp sheet on it and when so woven, whole length is converted to the fabric by weaving machine. Further warp length is required to be fed which can be done by knotting or gaiting other beams on weaving machine.f. WeavingAs stated earlier, weaving is interlacing two sets of yarn and

making fabric. One set is called warp thread which is in sheet form, the other one is called weft thread which is inserted between two layers of warp sheet by means of a suitable carrier i.e. Shuttle, Projectile, Rapier, Air current, Water current, etc. Depending upon the type of the weaving machines. The different types of technologies available for weaving machines are briefly explained as below:o Conventional Shuttle Weaving System by Ordinary Looms or Automatic Looms.o Shuttle less Weaving System by Airjet /Waterjet/Rapier/ProjectileShuttle loom is a conventional Technology with much less production on account of slow speed and excessive wear and tear of machinery. This shuttle loom technology has now become obsolete. Denim is woven through Shuttle less Weaving System by using 96 ZAX-e Type Tsodakoma Corporation’s Airjet looms or rapier looms or projectile looms. These looms are distinguished by weft insertion method, which is briefly discussed hereunder.Airjet LoomsThese types of looms adopt the latest development in Weaving Technology where weft insertion is done with the help of compressed air. A very high weft insertion rate up to 1800 metre per minute is achieved. Compared to rapier and projectile looms, these looms are less versatile but are economical and are used in mass textile production unit like denim.Finishing a. Grey FabricThe finally woven fabric or Grey Fabric, as it is popularly called, wound on a cloth roll is taken out from weaving machines at certain intervals and checked on inspection machines for possibilities of any weaving fault. If such faults are seen anywhere in fabric during inspection, certain corrective steps are taken at weaving, warping, sizing, etc so that they can be minimised in subsequent product. This is a quality control exercise.b. Denim FabricDenim Fabrics woven of 100% cotton would be very strong and durable.Traditionally Blue Denim is warp faced cotton fabric with 3 x 1

twill construction with warp being dyed in a solid colour and weft left un-dyed. The look and quality of the Denim Fabric shall improve after dyeing, the process of which differs from plant to plant. Normally the process of dyeing dictates the technology of Denim manufacturing.The dyeing for Denim Fabric happens at the sizing stage. Generally there are two most popular methods of dyeing Denim Fabric. They are:o Rope Dyeingo Sheet DyeingA company can adopt any of the methods. In countries like India Sheet Dyeing Method is commonly used for manufacture of its Denim Fabrics, which has following advantages over Rope Dyeing Method:o The technology is less capital intensive.o The technology is a proven one.o The cost of production is lower.o The process time is lower.o The Sheet Dyeing machines are very easy to operate.The only defect in Sheet dyeing is that their is a problem of center to selvedge shade variation.c. Sheet Dyeing ProcessThis process eliminates a few intermediate processes of the rope dyeing. The yarn sheet is washed with chemicals such as caustic and washing soda and after squeezing the excess water; the yarn sheet is allowed to pass through Dyeing Troughs one time for oxidation and development of dye on yarn. After dyeing, the dyed yarn is washed again with fresh water for two-three times and finalIy squeezed before allowing it to pass through six drying cylinders. The dyed yarn enters the starching device and sizing is done. After sizing, the sized warp beam goes for weaving. After weaving, the woven Denim Fabrics goes for various finishing processes consisting of brushing, singeing, washing, impregnation for dressing and drying. Brushing and singeing should eliminate impurities and help to even the surface of the fabric. Dressing regulates the hand and rigidity of the fabric while compressive shrinking regulates its dimensional stability.Even today Denim Fabric without Indigo Dyeing is not called authentic Denim. Initially when Denim Fabric entered the

fashion market, Denim manufacturers were using Natural Indigo Dye, which was costly and giving a natural finish. Though Synthetic Indigo Dye has gradually replaced Natural Indigo Dye, some unorganised manufacturers still prefer the latter and attract premium after branding them “Natural Dye Used”.d. Making-UpWeaving of fabrics on such multi sizes is not economical, hence a standard width fabrics is then sent to making up. Fabrics are cut into the desired width as per size required on this machine. Denim Fabric and Grey Fabric are thoroughly checked for various types of defects such as:o Weaving Defects· Uneven Dyeingo Bleaching and Dyeing Defecto Oil Staino PatchesHere the final product is categorised quality-wise. The products then found okay are segregated and sent to packaging department whereas defective ones are sent for correction. After inspection, the sets are wrapped with polythene covers and sent for despatch as per buyer’s specifications.DespatchRolls and sets so formed and packed as per buyers’ requirements are then sent for final despatches.

Proposed Inspection Process for Indigo Dyed Denim* A four point system can be adopted, with 9 qualities ( from 9 to 1).

The point distribution is as follows:

upto 3"= 1 point3-6"= 2 point6-9"= 3 points9" and above= 4 points

Any defect across full width = 4 point

All the above defects may be length or width wise.Length wise one course or fine ends/ up to one meter=4Starting mark (across the width)=4Cuttable Defects-moire- continuous slub or slubbing weft- thinck end more than one meter- major shade variation-burnt selvedge- blanket impression-width variation-Jala-jerky-chira-wrong drawn- float-snarls-missing ends- more warp breaks- patti-holes-cuts-sever temple mark- more pick findings in short length, double pick-Slack and tight ends >1m

* From qualities 3-9, only 2 pieces in a single roll are allowed and no piece should be less than 30 meters.

The qualities Criterian can be defineds as follows:

9--> 2 shades allowed, allow 20 points per linear meter which no greater than 2 to 3 4 points defects8--> 3 shades are allowed, allow 36 points per linear meter no greater than 4, 4 point defects7--> same as 8 but here we allow upto 5 shades6--> Allow 72 points per linear meter, upto 3 shades -no greater than 5 to 6 , 4 point defects5--> same as 6, but 5 shades are allowed.4--> points should not be greater than 72, any number of shades, any number of 4 point defects. We do not allow patta ( width wide strips)3--> Same as 4, we can allow patta2--> same as 3, 5 pieces are allowed ( every piece 10-30 meters each)1--> any continuous defect is allowed ( pack the piece less than 1 meter)

Shade gradation can beDark Shade--> D+Normal Shade --> DLight Shade --> D-

Relation between Manual and "l a b" grading systeml, a, b valuesD- = 554,654,655D= 454,555,656D+= 455,456,556

Tolerance for l a b values--> L = +-0.5, a = +/- 0.5, b= +/- 0.5