Vat dye

Vat dye:

The vat dyes are found amongst the oldest natural coloring matters used for textile. The vat dyes are  naturally obtained coloring matter from the ancient time and kept into wooden vat and make solubilised in vat by the process of fermentation, so it is called vat dyes. They water insoluble color compounds. They can’t be directly applied on cotton or other fibres as direct dyes are dyed. They have to be converted into their water soluble forms. During dyeinghey are soluble form of the dyes that are applied on cotton, followed be reconverted of the soluble form into the original insoluble form.They are excellent wash fastness and  treatment.

Properties of vat dyes:

         i.            Vat dyes are insoluble in water

       ii.            Mainly use for cellulose fibre but protein fibre dyeing p^H should be controlled.

      iii.            Very costly

     iv.            Poor rubbing fastness

       v.            Good wash fastness

     vi.            Difficult to dyeing

Trade name of vat dyes:

Trade Name	Manufacturer	Country
Cibanone	Ciba-geigy A.G.	Switzerland
Sandothrene	Sandoz Ltd	Switzerland
Caledon	I.C.I.	U.K.
Artex vat	Rainbow Texdyes Corp.	India
Solanthrene	Francolor	France

Cotton dyeng with vat dyes:

During  dyeing process the chemical and other specimen:

1)      Dyestuff

2)      Caustic soda

3)      T.R. oil

4)      Sodium hydro sulfite

5)      Vetting temperature-70°C

6)      Water

Dung Oxidation:

1)      Hydrogen peroxide

or

2)      Sodium peroxide

or

3)      Sodium perborate

or

4)      Hydroze

During Soaping:

1)      Detergent

2)      Soda ash

3)      Water

4)      Temoerature 95-100°C

Working procedure:

Ø  This dye is insoluble in water. Ti is Dissolving in water and converted into leuco compound. If vat dye is in liquid form, can directly be converted but if it obtain powder form, then Y.R. oil is required and hot water are mixed.  Then the solution should be stirred gently and forms a paste.

Ø  The dye bath is set at 40°C  at required water level with auxiliaries.

Ø  Then sodium hydrosulfite and soda are added and leuco compound will be formed and vat dye dissolves in water.

Ø   In the bath rest of water is mixed with the solution perfectly and closed the dye bath.

Ø  Temperature raised 60°C and run time 10-15 minutes

Ø  Temperature raised 70°C and run time 40-50 minutes

Ø  Then dye bath drain and rinse

Oxidation:-

After dyeing the exhausted dyes are then oxidized to convert it to insoluble form into the fibre.

The oxidation process can be done in contact of air or other oxidizing agent

Soaping:

The dyed material is tt in a bath by detergent, soda ash.

Then rinse with cold water.

Then perform hot wash.

Again cold wash

Then acetic acid applied for neutralization

Then cold wash and dried.