In case of VS Turquoise Blue G, Soda Ash is used as an alkali and dyeing is carried out at 80^oC common salt should not be used.

 

Padding process

Any conventional padding equipment could be used for dyeing with this method. It is preferable to have the size of the troughs as small as possible.

(I) One bath pad batch using Sodium Silicate

Sodium silicate and caustic soda required are as follows:

 

Padding:

The well-prepared fabric is padded at 60-70% expression for cotton and 80-90% expression for staple viscose fabric at 20-25^oC. The lower temperature is preferred on grounds of dye liquor stability.

Fixation:

After the padding is complete the batch is covered with polythene film to avoid localized evaporation of water and allowed to dwell for 24 hours.

(II) One batch pad-dry steam process

The process is carried out on machines consisting of a padder with drying unit attached, and also a continuous steamer as normally used in printing.

The pad liquor consists of :
 

The material is padded at room temperature in the above liquor at a nip expression of 60-70%, dried at 60^oC-80^oC and then fixed by steaming in the normal continuous steamer for 7-10 minutes at 100^oC-130^oC

(III) Two Bath pad-dry steam process

Pad the material through dyestuff solution at 25-35^oC & dry. After intermediate drying the goods are padded at room temperature using:             

          250-300 g/l    common salt and
                  20 cc/l    caustic soda 71^oCTw

The dyestuff is fixed by steaming at 103-105^oC for 20-30 seconds. When longer steaming time of 90-120 seconds is given then amount of caustic soda solution should be reduced to 10 cc/liter. When working without intermediate drying the chemical padding should have 25% higher expression than dyestuff padding and chemical liquor should contain:
 

Steaming is carried out for 20-30 seconds at 103-105^oC. for longer steaming time of 100 seconds the amount of caustic soda is reduced to 20 cc/l (71^oCTw)

(IV) Pad-Dry thermofix process

In this process a padding machine with attached hot flue and curing unit that allows treatment for 5 minutes are required.

The pad liquor consists of: (parts/1000)

For inferior varieties of cloth and on the drying equipments where fear of dyestuff migration is there, an addition of 5 to 10 g/l of sodium alginate paste thickening to the padding liquor is necessary.

Fixation:

After treatment:

To obtain optimum fastness properties, irrespective of any dyeing temperature, alkali or dyestuff used, unfixed dyestuff must be washed out from the fibre.

This can be carried out on any suitable equipment such as jigger, winch or open width soaper.

The material is rinsed in cold water, then in cold water containing 2cc/l acetic acid. This is followed by a rinse in hot water & finally soaped at boil in a bath containing 2g/l anionic soap followed by hot & cold rinse.

Printing:

VS dyes produce prints with excellent brightness as compared to those with other classes of dyestuffs. It is possible to get a variety of shades, as the colors are available in all hues.

There are two methods of direct printing of cellulosic fibers

(1) One phase printing (2) Two phase printing

In one phase printing method the alkali is added to the printing paste while in two phase printing paste is made without alkali and the prints are fixed by padding to dipping the printed fabric in an alkaline fixation liquor.

The prints can then be fixed various steaming conditions.
 

Fixation:

(1) One Phase Printing:
The printed and dried fabric is steamed with saturated steam at 103 deg c for 10 to 15 minutes in a star ager or 5 to 7 minutes in continuous steamer.

(2) Two Phase Printing:
The printed and dried fabric is passed through a hot fixation bath, which is maintained at 95 - 100 deg. C., preferably with indirect heating arrangement to avoid dilution of the liquor.

The Fixation bath consist of the following:
 

Washing procedure

In order to obtain maximum wet-fastness properties, brightness and purity of shades with consistent dyeing results, which is essential to give a thorough `Soaping' to clear off unreacted hydrolysed dye from the dyed fabric.

The dyed fabric is rinsed repeatedly in cold water to remove most of the alkali, salt and unfixed dye present and rinse again in warm water not higher than 60 deg. C. Then run in a bath containing :

Anionic detergent - 1 -2 gms/liter for 15 minutes at the boil. Then rinse in warm water (upto 60 deg. C )and finally in cold water. The most satisfactory results in Washing-off, particularly for piece goods, are obtained by employing an Open soaper or perforated Beam-washing machine. If such equipments are not available, conventional ones like Jig or Winch may be used. For yarn is the Hank form open - vat is employed and for yarn in packaged form the package dyeing machine itself used.