Vat dyes are made from naturally not synthetically. these dyes are windly used for coloration  of cellulose materials such as cotton.

this dyes is also used as a indigo dye for colouration of jince or denim materials. this dyes are given good overall fastness property. its application process is near similar as Sulphur dyes.

if you want to know about vat dye, dyeing of cotton with vat dye, vat dyeing process and more then hold your seat and be with the end of guide.

I have made this guide to help you out.

Lets get started,

Read MoreSulphur dyeing Process, dyeing of cotton with sulphur dye?

What is vat dye in textile?

Vat   dye   is  used  for  coloration on textile materials, such as cotton materials. vat dye are  made  from  naturally,  so  vat  dye  is called indigo dye. it is  natural  Colouring materials. Vat dye are insoluble in  water  but  with  the  help  of  vatting process vat dye is easily  soluble  in  water. then  dyeing  is done. i mean to say that vatting is required for before dyeing.

Vat dye

• Vat dye are not properly soluble in water.

.• Vat dyeing is also called indiagosole.

• this dye is the oldest base dye. This dye are made from natural plants.

• This dye are normally made from naturally not synthetically.

• Vat dye is more suitable for cellulosic fiber for best overall fastness properties.

• This dye is also be called indigo dye which is windly use for dyeing of denim fabric.

• Vat dye is the one of the most important or  popular dye in the world in present time.
• Vatting process is must be necessary before dyeing.
• It can be converted insoluble to soluble form with the help of vatting process.
• This is the reasons, that vatting process is very important before dyeing.
• This dyes have good affinity for cellulose materials.
• In case of vat dyeing, vatting process is necessary to required before dyeing.
• In case of vatting process, converting insoluble vat dye by strong reducing agent.
• Vat dye displays no substantivity towards cellulose but with the help of suitable reducing agent and alkali convert the insoluble vat dye to its soluble leuco form results in change of colour. 
•They are substantively for cotton. Reducing agent is used in vat dyeing.
• most commonly (Na2S2O4) it’s helps to convert easily in leuco form.
• This vat dyeing process is used from very long time in textile industry for dyeing of cellulose materials.
• vat dyeing process is used for production of denim, jeance products.
• Vat dyeing process is very complex compared with other dyeing methods such as reactive dyes,basic dyes.

Vat dyes properties

Vat dyes have lots of Properties which are must be required to know before the vat dyeing process.

the main properties of Vat dyes is as follows;

1. Vat dye are insoluble in water.
2. The particle size of vat dye is very small.
3. Vat dye are applied in alkaline condition PH 12-14.
4. vat dye mostly belong to indigoid, and Anthraquinone class.
5. vat dyes can’t be directly applied on cotton material for dyeing.
6. In vat dyeing process, first need vatting process.
7. First vatting process is done then it can apply on textile materials for dyeing purpose.

8. After dyeing it gives different shade.

9. wet fastness is very good but rubbing fastness is not good.

10. wet fastness is very good around 4-5.

11. rubbing fastness is very poor.

12. Vat dye are also apply on wool and silk material for dyeing and printing purpose.
13. After dyeing, dye are entrapped inside the fiber and it is not easy to come out during any process and any treatment.
14.  dye is more costly.
16. this dye are not cheap process compared with the direct dye, because vat is more expensive compare with other dyes. 

Classification of vat dyes

Classification of vat dye is divided in three different groups.

• IN group

• IW group

• IK group

IN group  – In case of IN group of dyes required Different stages

(a) required concentrated NaoH

(b) vatting is required with high temperature at 60C.

(c) dyeing temperature required 60C.

(d) Salt is not required to added in dyeing solution.

 IW group – In case of IW group of dyes, its required also Different stages such as,

(a) in case of dyes its required medium amount of NaoH

(b) low vatting is required

(c) dyeing temperature is also be low (50C)

(d) salt is necessary to required during dyeing.

(c) Normal Substantivity for cotton.

IK group – In this case of dyes, some important stage is required, such as

(a) in this case of dyes, need low concentration of NaoH.

(b) low vatting is required.

(c) dyeing temperature also should be low (20C).

(d) low substantivity for cotton.

(e) considerable salt is required during dyeing.

• Chemical Classification

Vat dyes are divided Different types of group and it’s depend upon Chemical nature.

(a)  Indigo

|

natural and synthetic

(b) Thio- Indigo

|

Containing Sulphur

(c) Indigo derivatives

|

Brom indigo

(d) Anthraquinone derivatives

|

Alog dyes, Indanthrene

(e)  Carbazol derivatives

|

Hydro bluvat

Read More Basic Dyeing Process, Dyeing of Acrylic, Acrylic/Cotton, Acrylic/Wool, with basic dye? 

Vat dyes examples

• vat dyes most important dyes for cotton or cellulose materials.

• Indigo is an example of vat dyes.

• These dyes are windly use for dyeing of denim materials with old times.

• Indigo dyes are the best examples of vat dyes.

• Alizarin are also best examples of vat dyes.

• These are two best examples of vat dyes, such as indigo and alizarin.

Vat dyes are Windly used for

1. Toweling
2. denim
3. shirting
4. furnishing
5. uniforms

Dyeing Of Cotton with vat dye 

(Vat dyeing process)

Vat dyes are water insoluble pigment.
vat dyes are solubilized by vatting process.
In this case, first required vatting for making it solubilized form.
After this dyeing process is done.
After dyeing, re-oxidation is required.
then after treatment required for even dyeing.
these are the 4 basic step are must required for vat dyeing.
 

Vatting process

Vat dye are insoluble in water but it become soluble by vatting.
It converting insoluble vat dyes into soluble form is known as vatting.
It is given more solubility in water.
they are reduced to soluble leuco compound.
this process is called vatting process.
vat dye are more difficult to reduced then sulphur dye.
vat dye displays no substantivity towards cellulose but with the help of suitable reducing agent and alkali convert the insoluble vat dye to its soluble leuco form results in change of colour. 
Sodium dithionite (work as a reducing agent) they are windly use in vatting.
Sodium dithiouite are more popular reducing agent are mostly used in case of vatting process.
Dihydropyrane, Na2S2O4.2H2O and hydrose are mostly used in case of vat dyeing.

Dyeing Process

• Vat dyeing process is one of the best or profitable methods for cellulose materials.

• This vat dyeing process is gives satisfactory results especially on cellulose materials.

• This vat dyeing process is complex compared with other dye process.

• This dye is not proper soluble in water this is the reason, can not be used directly for dyeing.

• in case of vat dyeing, vatting process is necessary to required before dyeing.

• In case of vatting process, converting insoluble vat dye by strong reducing agent.

Recipe

vat dye                   – 1 %
wetting agent         – 1.5 g/L
sequestering agent – 0.75 g/L
caustic                   – 4%
hydrose                 – 3%
salt                        – 20 g/L
M:L                        – 1:10
Temp                     – 60-100C
The vatted dye are substantive to the cellulose material.
Vat Dyeing is carried out at lower temp for proper exhaustion.
on electrolyte is added to the dye liquor.
temp should be 20-60°C and agitated for 15 mint.
the cellulose materials are total immersed to prevent premature oxidation.

3. Re-oxidation treatment

• In this case dye in its soluble leuco form is converted to the original pigment by oxidation.
• This process is carried out in the source of wet treatment With the help of addition of oxidants such as hydrogen peroxide.

4. After Treatment

• In this process, after dyeing some pigment particles is present on the surface of materials.
this is carryout with the help of detergent at boiling temp.
• But removing pigment particles is necessary with the surface of the fabric because these treatment gives final or proper shade.
• Soaping are required for removing pigment particles with the surface of the fabric.
• Which gives the material final shade and improved the fastness properties typical of vat dye.
It gives different type of shade.

Advantage of vat dyes

• Excellent light fastness.

• Vat dyes have good stability for cotton dyeing and printing.

• High reproducibility.

• produce full range colours.

• vat dyes are produce better shade for blend materials.

• vat dyes are produced excellent wet fastness.

Disadvantage of vat dyes

• Poor rubbing fastness.

• costly process

• In this process, first vatting is required before dyeing.

Frequently Asked Question

1. What is diffrence between Vat dyes and solubilised vat dyes? 

Vat dyes

• Water insoluble

• More affinity for cell-OH in form of sod salt of leuco vat. 

• No affinity for protein fibre. 

• Chemically it is sod salt of leuco vat dye. 

Solubilised vat dyes

• Solubilised vat dyes are properly soluble in water. 
 
• Low affinity  for cell-OH (cellulosic materials).
• Good affinity for protein fibre or materials. 
• Chemically it is sod salt of sulphuric ester of leuco vat dye
• Solubilised vat dyes is gives pale shade and light shade.
• this dyes is not able to dye protein materials such as wool and silk materials. 

2. What is oxidation dyeing vat?

oxidation dyeing vat, in this process wet treatment (washing) is carried out after dye absorption by the fibre.
In case of wet treatment ( washing is carried out with hydrogen peroxide).
In this case vat leuco form is converted to pigment by oxidation.

3. What is indigo dyes?

Indigo dye is an organic compound.
Indigo dyes   are   made  from  naturally.
In other words, indigo   dyes   are   made   from extracted of leaves of certain plants.
Colour of indigo dyes is light blue.
This dyes is also called natural indigo dyes.
This dyes are using vary old time for dyeing purpose in textile industry.
Indigo dyes are used for dyeing of denim materials.
It gives good results on denim materials.

4. What is Anthraquinone vat dyes?

Anthraquinone dyes are insoluble in water.
Anthraquinone vat dyes have good quality to   produce   brilliant   colours  and  good washing fastness.
Anthraquinone dyes are insoluble in water.
In other words, the solubility  ability  of Anthraquinone dyes is not good in water.
Some important treatment is required for improving solubility in water.
All medium hydro sulphite is used as a reducing agent for improving solubility in water.
If treatment is   done    properly then the dye is easy to penetrate into the fabric.
It is given even dyeing.

5. What is dyes and classification?

Dyes are colorful organic compound that are used to impart color on Different materials such as leather, hair, cosmetics, plastic and textile materials.

dye is used in solutions form on textile materials and dye have able to fixed to a fabric.

6. How are vat dye applied to cotton?

Vat dye are insoluble in water.
It become soluble with the help of vatting process.
This process is done with the help of strong reducing agent.
They make water soluble pigment is called leco form.
Vat dye are more sensitive to cotton.
vat dye are more suitable for dyeing of cellulose materials.

7. What is the difference between vat dye and reactive dye?

Vat dye – vat dye are insoluble in water and its required solubilized form for dyeing purpose and then oxidation is done after adsorption. these are the process of vat dye.
Reactive dye – reactive dye are soluble in water so this dye is easy to make a covalent bond with the hydroxyl group of cellulose. then dyeing is done. these are the process of reactive dye.
                                                                                                   


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