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Wednesday, September 9, 2015

Working Flowchart of Knit Dyeing

The main object of dyeing process is to give woven or knitted fabric its intended color, crucial to its ultimate use. The process can be carried out at different stages of fibre processing, i.e. in different forms: staple, yarn, fabric (rope or open-width), and piece. It is done in a special type of solution containing dyes and other required chemicals. As a result of dyeing, dye molecules make uncut chemical bond with fibre molecules.

Winch Dyeing Machine
The Process Flowchart of Knit dyeing is as follows:
Tank filling with water
Fabric loading
Addition of Anti-creasing + Sequestering agent (600 c, inject)
Detergent (inject)
Soda + Caustic (dosing 10')
H2O2 (700c, inject)
Temperature rise (1100c for 60 minutes)
Temperature is decreased for sample check
Hot wash
P.K.K (980c for 10 minutes)
Rinse & Drain
Acid (550c for 10 minutes, PH check-4.5)
Enzyme (600c for 60 minutes and then sample checked)
Rinse & Drain
Tank again filled with water
Temperature raised to 600c and PH checked 5.5)
Leveling agent (inject, run time 5min)
Salt 1/3 (run time 10 minutes)
Dye (dosing, 600c for 30 minutes)
Salt 2/3 (run time 15 minutes)
Steam down (600c, sample check)
Soda (dosing, 600c for 60 minutes)
Hot wash (900c for 10 minutes)
Rinse (3 times)
Acid (400c for 10 minutes, sample check)
Rinse (1 time)
Softener (450c for 10 minutes, sample check)
Cold wash
Unload fabric

Monday, August 24, 2015

Precautions to be taken before Garments Dyeing

At first garments dyeing technology applied on woolen and silk garments but now it is applied on polyester, acrylic, nylon and also extensively on cotton garments. Its popularity is increasing all over the world. There are many advantages of garments dyeing which are the reasons of its popularity increase.

garments dyeing machine

Before garments dyeing some precautions are needed to avoid dyeing problems that may occur during garments dyeing. The precautions are discussed below:
  • We have to design the garments and the design should be made from engineering point of view.
  • There will be fewer problems if garment is made after desizing, scouring and bleaching of grey fabrics and then dyed in garments form.
  • Grey fabrics lot and source should be same.
  • Irregular dye penetration may be resulted due to too tight or too looseness of seams especially in the areas containing elastic like waistband, cuff etc.
  • After garments dyeing seam pucker may develop if the knit fabric is not pre-shrunken when the garments are made from woven and knitted fabric combination.
  • If the garment fabric is made from blended fibres, dye selection should be done very carefully during garments dyeing. Otherwise, irregular dyeing may be resulted.
  • The accessories metal should be of good qualities. If we use poor metal, it may be damaged during dyeing by the action of salt and alkali. It is better to use the metals made from nickel or its alloy.
  • Color difference may occur between garments fabric and sewing thread if the sewing thread fibre is not same as garments fabric.
  • Buttons selection should be done very carefully. Because, casin, cellulose and nylon buttons may be damaged during garments dyeing. In this case, it is safe to use buttons made from polyester.
  • Sometimes we have to use elastic in garments. If the elastic is made from natural rubber or polyurethane fibre like lycra may create great problem during garments dyeing. So dye should be selected properly to avoid such problem. The dye should be copper free.
  • Interlining is a necessary part of a garment. We should use only those interlinings in the garments are recommended for garments dyeing. If not then the performance of the interlining will be destroyed.
  • Problem of irregular dye penetration may occur if the garment made from compacted woven cotton fabric is not dyed with hot brand reactive dyes.
  • If we use some specific dyes for some specific colors, then the dyeing cost will be lower. As for example, sulpher dyes produce navy-blue and black color at lower cost.
  • Presence of mineral impurities in the cotton fibres may vary which may impede the stability of peroxide liquor during bleaching with hydrogen peroxide, even; insoluble compounds may form during hydrogen peroxide bleaching. Those insoluble compounds may redeposit on the garments fabric resulting spots on the fabric, special chemicals are available to avoid such problem.
  • During dyeing of cotton garments crease marks may develop. Special chemicals like ‘Imacol brand’ may be used to avoid such problem.

Sunday, June 21, 2015

Skein (Hank), Package, Warp-beam and Piece Dyeing

Textiles may be dyed at any stage of their development from fibre into fabric or certain garments.
Skein (hank) Dyeing
Yarn may be prepared in skein or hank form and then dyed. The loose arrangement of the yarn allows for excellent dye penetration. The skeins are hung over a rung and immersed in a dye bath in a large container. Skein dyeing is the most costly method of yarn dyeing, but the color penetration is best and the yarns retain a softer, loftier hand. Skein-dyed yarn is used to a considerable extent for suiting and dress goods.

Hank Dyeing
Package Dyeing
Yarn wound on spools, cones, or similar units and then dyed is referred to as package-dyed yarn. The packages of yarn are stacked on perforated rods in a rack and then immersed in a tank wherein the dye is forced outward from the rods under pressure through the spools and then back through the packages toward the center to penetrate the entire yarn as thoroughly as possible. Most carded and combed cotton that is used for knitted outerwear is package-dyed.

Package Dyeing
Warp-beam Dyeing
This method is similar to package dyeing but is more economical. Yarn is wound onto a perforated warp beam, immersed in a tank, and dyed under pressure. It is used when fabrics are to be woven with dyed warp yarns.

Warp-beam Dyeing
Piece Dyeing
The great bulk of dyed fabric on the market is dyed in the piece. This method gives manufacturers maximum flexibility for their inventories to meet large or small demands for a given color as fashion requires. Where yardage warrants it, fabrics are dyed in continuous range machines. Small lots of fabrics of all fibres are dyed in batches. Piece dyeing is thoroughly satisfactory as regards levelness, penetration, and overall fastness, as summing that the proper dyes have been used.

Piece Dyeing
Fabric may be piece-dyed whether it is composed of only one kind of fibre or yarn or of blends of different fibres or combinations of different yarns. When the fabric is made of one kind of fibre or yarn, then dyeing is relatively uncomplicated because the one appropriate dye is used. However, when the fabric contains a blend of fibres or combination of different yarns, then special procedures are required which employ different dyes that are each specific for the particular fibres used. These procedures are called union dyeing and cross-dyeing.

Friday, June 19, 2015

Stock, Top and Yarn Dyeing

Textiles may be dyed at any stage of their development from fibre into fabric or certain garments. Stock dyeing is done in the fibre stage, Top dyeing in the combed wool sliver stage and Yarn dyeing is done after the fibre has been spun into yarn.
Definition of Stock Dyeing
Stock dyeing refers to dyeing a staple fibre before it is spun. There are two methods. The older and widely practiced procedure is that of removing the packed fibre from the bales and then packing the stock in large vats and circulating dye liquor through the mass of fibre at elevated temperatures.

Stock dyeing

The newer method, bale dyeing, which is applicable to wool and all types of manmade fibres, is that of splitting the bale covering on all six sides, placing the entire bale in a specially designed machine (covering and straps need not be removed), and then forcing the dye liquor through the bale of fibre. This latter method obviously saves time and labor costs.
Although the dye liquor is pumped through the fibre in large quantities, there may be areas where the dye does not penetrate completely. However, in subsequent blending and spinning operations, these areas are so mixed with the thoroughly dyed fibre that an overall even color is obtained. In stock dyeing, which is the most effective and expensive method of dyeing, the color is well penetrated into the fibres and does not crock readily. Stock-dyed fibre does not spin as readily as undyed fibre because it loses some of its flexibility, but lubricants add in the final rinsing overcome most of this difficulty.
Definition of Top Dyeing
One step nearer to the finished yarn than stock dyeing is what is called top dyeing in the worsted industry. Top is wool that has been combed to take out the short fibres, then delivered from the combs in a ropelike form about 1.25” the top is wound on perforated spools and the dye liquor is circulated through it. Very even dyeing is possible with this method.

Top Dyeing

Definition of Yarn dyeing
When dyeing is done after the fibre has been spun into yarn, it is described as yarn dyeing. There are several methods of yarn dyeing. The purpose is to have the dyestuff penetrate to the fibres in the core of the yarn; this is similar to the penetration of the fibres in stock dyeing. Cloths made of dyed yarns are called yarn-dyed.

Yarn dyeing

Yarn-dyed fabrics are usually deeper and richer in color. These fabrics intended for laundering must be quite colorfast, or bleeding could occur. The primary reason for dyeing in the yarn form is to create interesting checks, stripes, and plaids with different-colored yarns in the weaving process. Chambrays, for example are usually woven with a colored warp and white filling. Other combinations of different-colored yarns are checked gingham, shepherds check, plaid, seersucker, and heater mixtures.

Tuesday, May 19, 2015

Working Principle of Sancowad Foam Dyeing Machine

The machine was originally developed for solvent dyeing. The goods are placed in a rotating drum (D), which is rotated by a motor (M). The dye liquor is made up in the mixing tank (T). The drum is set in motion. The dye liquor is pumped via valve (V) and pump (P) and is sprayed onto the rotating load with the help of a sprayer (S) to give a pick-up of about 100% on wt of dry goods. The dye liquor contains:
1.     x% of dye
2.     20 to 40 g/l of foaming agent
3.     Other assistance required for the specific dye-class
4.     Required amount of water to have a M : L ratio of 1 : 1.5 to 1
The consumption of the foaming agent is not revealed, but sodium salt of lauryl sulphuric ester of an ethylene oxide condensate and nonylphenyl pentadecaglycol ether are quoted as possible foaming agents. In addition a foam stabilizer is required.

Foam Dyeing Machine
When the whole of the liquor has been discharged through the spray into the drum, the rotation is continued at cold for 15 minutes during which the foam bearing the dye is distributed uniformly throughout the charge. After 15 minutes, the temperature is raised to 1000C or at the temperature required for the particular dye-class, either with steam or hot air or both, and the machine is allowed to run at the temp. for 30-45 minutes during which fixation takes place.
The cycle may be programmed to carry out any desired sequence of operations such as dyeing, rinsing, finishing, centrifuging and drying. As the necessary amount of water is significantly lower is conventional process, the Sancowad technique resulted in substantial savings, in both water consumption and the energy required for heating.
The Sancowad foam-dyeing principle has been extended from batch wise to continuous dyeing systems and thus approaches to the saving of water and energy has been proved appropriate for the dyeing of pole fabrics and carpets.

Tuesday, April 7, 2015

Difference between Dyeing and Printing

Dyeing is the process by which a textile material is changed physically and chemically and finally looks like colored materials.
Printing means partial or localized dyeing. It can be described as the controlled placing of defined areas of color onto a substrate.

Difference between Dyeing and Printing method

It means full dyeing of fabric.
It means partial dyeing of the fabric.
Fabrics, yarns and fibres are generally dyed.
Only fabric is printed.
Dyed both side of the fabric.
One side is printed.
Here, any specific design is not necessary.
Here, specific design is necessary.
Generally one color is used.
One or more color is used.
Color is applied in solution form.
Color is applied in thick paste form.
Thickener is not used.
Thickener is used.
Large amount of water is used.
Less amount of water is used.
Steaming or curing is not necessary.
Steaming or curing is necessary for fixation.
Not expensive.
Dyed fabric is relatively soft.
Printed fabric is relatively harsh.
Liquor ratio is high.
Liquor ratio is less.
Dye solution concentration is less in dye bath.
Printing paste concentration is higher in printing.

Sunday, March 29, 2015

Dyeing of PC blended fabric with Disperse dye to produce Resist effect

Blended fabric is a collection of many artists work mixture of styles and a celebration of talent. Blends are any textile materials from fibres through yarn to fabric which are deliberate combinations of chemically or physically fibrous polymer.
Under this definition, blends can range from bi-component fibres, mixture of different filament core spun yarn, uniformly blended staple fibre throughout fabric and everything which falls between.

Resist or Reserve dyeing with blends
At least one of the components of the blend remains essentially un-dyed i.e. almost white. Example: milens fabric, here in resists dyeing – cotton part remain un-dyed.
Resist effect of PC fabric

Fibre and Fabric
Fibre: Cotton and Polyester
Fabric: Knitted

Any class of disperse dye. Slightly water soluble. They are made soluble with the help of some dispersing agent. Colorfastness of this dye is excellent. It gives a variety of shade.

Instruments and glass wares
  • Beaker
  • Glass rod
  • Measuring rod
  • Bowl
  • Electronic balance
  • Scissor
  • Sample dyeing machine
  • Pipette
  • Conical flask etc.
Dyeing of polyester part
  • Disperse red: 2%
  • Dispersing agent: 1g/l
  • Acetic acid: 1g/l
  • Sample: 1 : 20
  • Total liquor: 100
  • PH : 4 – 4.5
Chemicals and auxiliaries
  • Acid
  • Dispersing agent
  • Leveling agent
  • Buffer solution
Necessary calculation
We know required dye in CC = (Sample wt. X shade %)/( Stock solution %)
Disperse red: 1% stock solution = (5 X 2%)/1% = 10CC
Required chemical in CC = (gm/l X Total liquor)/(stock solution%)
Dispersing agent: 1% stock solution = (1 X 100 X 100)/1000 = 10CC

Dye bath is set at 50-600C with buffering solution for maintaining PH 4 - 4.5. dispersing agents are applied in two stages. First half with dye solution. Rest half in the dye bath with fabric. Then the temperature is raised to 85 – 95% by 3 gradients. PH is checked here if there is any fluctuation then it is adjusted by buffer solution. Now raise the temperature to 1300C by 1.5 – 2 0C/min. Keep the entire bath running at 1300C for 30 – 60 minute depending upon the required depth of shade. Temperature is down by cooling 800C.

Acetic acid: 1gm/l
         A.    Acid: 1% stock solution = (1 X 100X 100)/(1000 X 1) = 10CC
Water required = (1000 -10)CC = 90CC
Neutralization is done to remove alkali from the fabric. 1gm/l acetic acid is used. Then treat the sample at 400C for 10 minutes.

Resist effect of PC fabric with disperse dye

  • Stock solution should be prepared carefully.
  • Time and temperature should be properly maintained.
  • Neutralization should be done properly.