Introduction
Akik Vat Dyes are particularly suitable for the dyeing of cellulosic fibres. They are employed for dyeing Cellulosic fibres wherever shades of the highest fastness properties are required. This shade-card deals with their application on cotton, but they can be applied equally well to other fibres such as Viscose, Polynosic, Jute and Linen with certain modifications in the dyeing process.
Primary Classification
They are primarily classified on basis of their chemical structure:
- 1. Indigo - Which are less coloured.
- 2. Thio-indigo - Which are medium coloured.
- 3. Anthraquinone - Which are highly coloured.
Commercial Forms
Akik Vat Dyes are supplied in various forms to suit the various modes of dyeing applications. They differ in strength and fineness of dispersion.
- 1. Ultra conc., Highly conc., Acra conc., Powder Brands: These brands do not possess high fineness of dispersion & are suitable for leuco vat dyeing only.
- 2. Powder Fine Brands: These brands possess uniform particle fineness and are suitable for pigmentation dyeing. They can also be used in leuco vat dyeing.
- 3. Micro Dispersed Brands: These are a further improvement over powder fine brands and are suitable for high speed and continuous dyeing on account of their fast rate of reduction. They are also suitable for leuco vat dyeing.
General Dyeing Procedure
Akik Vat Dyes are insoluble in water however they can be dissolved by converting them to their leuco compounds using Sodium Hydrosulphite (Hydro) in the presence of Caustic Soda Flakes. This reduced leuco compound has a high substantivity towards cellulosic fibre and can therefore be dyed easily in this leuco form.
Method of Application
Akik Vat Dyes are applied by the following methods:
- A/Q, Hot Method: Dyestuffs belonging to this method require large quantities of Caustic Soda Flakes and Sodium Hydrosulphite and are readily exhausted at 50-60°C.
- A/Q, SpL Method: Dyestuffs belonging to this method require high concentration of Caustic Soda Flakes and Sodium Hydrosulphite and are dyed at 70-80°C.
- A/C, Medium Method: Dyestuffs belonging to this method require moderate amounts of Caustic Soda Flakes and Sodium Hydrosulphite and are dyed at 45-50°C. They also require additional Glauber's Salt to exhaust light, medium and dark shades.
- A/O, Method: Dyestuffs belonging to this method require the least amount of Caustic Soda Flakes and Sodium Hydrosulphite and are normally dyed at 25-30°C. These colours require a larger amount of Glauber's Salt or Common Salt compared to the A/Q, Method for proper exhaustion.
Note:
Dyeing Vessels:
Vessels made of Stainless Steel, Enamelled Metal and Wood are generally used.
Stock Vat Preparation:
Method: The Ultra conc., Acra conc., and Powder brands are pasted with Turkey Red Oil and warm water is added. The Powder Blue and Micro dispersed brands are sprinkled with warm/hot water. Hot water is added to bring the bath to the recommended vatting temperature. Then the requisite quantity of the pre-dissolved Caustic Soda Flakes is added while stirring. Then the required quantity of Sodium Hydrosulphite is added and stirred. The luster solution is seen immediately. The vatting is completed when the desired depth of shade is produced. The bath is maintained at the vatting temperature for 15-20 minutes with occasional stirring. The reduced dye solution is then added to the dye bath containing the requisite amount of Caustic Soda Flakes and Sodium Hydrosulphite at the recommended temperature through a filter cloth.
| Stock Vat Method | Unit | A | B | Indigoid |
|---|---|---|---|---|
| Akik Vat Dyes | Kgs. | 1 | 1 | 1 |
| Water | Litres | 50 | 50 | 50 |
| Turkey Red Oil | Kgs. | 0.1 | 0.1 | 0.1 |
| Caustic Soda Flakes | Kgs. | 1.0 | 1.0 | 2.0 |
| Sodium Hydrosulphite | Kgs. | 0.5 | 0.5 | 0.8 |
| Temperature | °C | 50 | 60 | 80 |
| Time | Mins. | 15 | 15 | 15 |
Full Volume Vatting in Dyebath:
In the case of the following dyes:
- Akik Vat Blue RSN
- Akik Vat Blue RSN Reddish Spl.
- Akik Vat Blue RSN Ultra Reddish Spl.
- Akik Vat Blue BC
- Akik Vat Blue BCL
- Akik Vat Blue GCDN
A dyebath is prepared by using the full volume of water required for the dye bath and the total quantity of Caustic Soda Flakes is added at the beginning. Recommended full quantity of Sodium Hydrosulphite is split and vatting is carried out for 15-20 minutes as mentioned above.
Specific Methods:
A modernized earlier Akik Vat dyes are applied by different methods of dyeing named as; A/Q, A/Q Spl., A/Q modern.
The quantities of various chemicals like Sodium Hydrosulphite and Caustic Soda Flakes required to keep the dyeing result as per recommended shade are given based on the depth of shade. Salt is required to increase the depth of the shade. The bath is different for each depth of shade.
The dyeing temperature may vary depending on the dyeing qualities of dyes. The quantities of chemicals used differ depending on the Material to Liquor Ratios (MLR) as required for different depths of shade.
Note:
Table illustrates the total quantities of the chemicals required based on the quantities used to prepare the stock vat should be deducted from it."Specific methods, chemicals, and quantities vary depending on the depth of shade and dyeing method used."
Table I - A/Q Method
| Chemical | Depth of Shade | Material to Liquor Ratio | |||
|---|---|---|---|---|---|
| 1:4 | 1:10 | 1:20 | 1:30 | ||
| Caustic Soda Flakes g/l | Pale | 10-12 | 6-8 | 4-6 | 4-4.5 |
| Medium | 12-16 | 8-10 | 5-6 | 4.5-5.5 | |
| Deep | 16-20 | 10-12 | 6-7 | 5.5-6.5 | |
| Sodium Hydrosulphite g/l | Pale | 9-12 | 5-7 | 2.5-3.5 | 2-3 |
| Medium | 12-17 | 7-9 | 3.5-5 | 3-4.5 | |
| Deep | 15-20 | 9-11 | 5-7 | 4.5-6 | |
Table I - A/Q, Spl. Method
| Chemical | Depth of Shade | Material to Liquor Ratio | |||
|---|---|---|---|---|---|
| 1:4 | 1:10 | 1:20 | 1:30 | ||
| Caustic Soda Flakes g/l | Pale | 16-20 | 10-12 | 8-10 | 6-8 |
| Medium | 20-25 | 12-15 | 10-13 | 8-11 | |
| Deep | 25-30 | 15-18 | 13-15 | 11-13 | |
| Sodium Hydrosulphite g/l | Pale | 7-10 | 6-8 | 5-6 | 5-6 |
| Medium | 10-15 | 8-10 | 6.7-7.5 | 6-7 | |
| Deep | 15-18 | 10-12 | 7.5-9 | 7-9 | |
Table I - A/Q Method (Alternative)
| Chemical | Depth of Shade | Material to Liquor Ratio | |||
|---|---|---|---|---|---|
| 1:4 | 1:10 | 1:20 | 1:30 | ||
| Caustic Soda Flakes g/l | Pale | 6-7 | 3.5-4.5 | 2.2-2.5 | 1.8-2.2 |
| Medium | 7-10 | 4-5 | 2.5-3 | 2-3 | |
| Deep | 10-12 | 5.5-7 | 3.5-4.5 | 3-4 | |
| Sodium Hydrosulphite g/l | Pale | 6-8 | 2.5-4 | 1.8-2.4 | 1.8-2 |
| Medium | 8-11 | 4-6 | 3-4.5 | 2.5-4 | |
| Deep | 11-13 | 6-7 | 4.5-5 | 3.5-4.5 | |
| Glauber's Salt or Common Salt g/l | Pale | 8-10 | 5-7 | 5-10 | 5-10 |
| Medium | 10-15 | 10-12 | 10-15 | 10-15 | |
| Deep | 15-20 | 12-14 | 15-20 | 15-20 | |
A/Q Method
| Chemical | Depth of Shade | Material to Liquor Ratio | |||
|---|---|---|---|---|---|
| 1:4 | 1:10 | 1:20 | 1:30 | ||
| Caustic Soda Flakes g/l | Pale | 4-5.5 | 3-3.5 | 1.8-2 | 1.5-1.8 |
| Medium | 5-7 | 3.5-4.5 | 2.5-3 | 2-2.5 | |
| Deep | 7-10 | 5.5-7 | 3.5-4.5 | 3-4 | |
| Sodium Hydrosulphite g/l | Pale | 5-7 | 2.5-4 | 1.8-2.4 | 1.8-2 |
| Medium | 7-9 | 4-5 | 3-4 | 2-3 | |
| Deep | 11-13 | 6-7 | 4.5-5.5 | 2.5-4 | |
| Glauber's Salt or Common Salt g/l | Pale | 15-20 | 10-15 | 10-15 | 10-15 |
| Medium | 15-20 | 12-14 | 15-20 | 15-20 | |
| Deep | 20-30 | 20-30 | 20-30 | 20-30 | |
| Dyeing Temperature: 25-30°C | |||||
Indigoid Method
This dye requires an addition of 0.5 cc/l T.R. Oil in the dye bath over and above the quantities used for stock vat.
| Chemical | Depth of Shade | Material to Liquor Ratio | |||
|---|---|---|---|---|---|
| 1:4 | 1:10 | 1:20 | 1:30 | ||
| Caustic Soda Flakes g/l | Pale | 6-10 | 4-6 | 2.5-4 | 2-3 |
| Medium | 10-14 | 6-8 | 4-5 | 3-4 | |
| Deep | 14-20 | 10-13 | 6-10 | 5-7 | |
| Sodium Hydrosulphite g/l | Pale | 6-9 | 2.5-4 | 2-3 | 1.8-2.4 |
| Medium | 9-12 | 3-5 | 3-5 | 2-3 | |
| Deep | 9-12 | 3-5 | 3-5 | 2-3 | |
| Dyeing Temperature: 70-80°C | |||||
Dyeing of Yarn:
Priming:
The scoured and bleached material is worked in a solution containing 3 g/l of Caustic Soda Flakes and 3 g/l Sodium Hydrosulphite prior to dyeing to remove oxidized matter that may cause quick exhaustion of the Sodium Hydrosulphite rendering the dye insoluble during the dyeing process.
Hank Dyeing:
Hanks are dyed in open becks of MLR 1:20 or 1:30 as desired. These could also be dyed in machines. The dye bath is prepared by stock vat or full volume method with chemicals as mentioned in Table I. Well scoured yarn is introduced into the dye bath and worked for 45-60 mins at the recommended dyeing temperature. The agitation should be brisk in the beginning and decreases as the dyeing proceeds. Glauber’s Salt, if required, is added 25 minutes after the commencement of dyeing.
Standing Baths:
Owing to the fact that complete exhaustion of the dye bath is not always obtained, this method is used for medium and deep shades particularly in Blacks, as there is a considerable saving of dyes and chemicals. The method is generally used for self-shades; practice perfects this process.
| Chemical | Replenishment Amount |
|---|---|
| Akik Vat Dyes | 4/5 of original quantity |
| Caustic Soda Flakes | 1/4 to 1/2 of original quantity |
| Sodium Hydrosulphite | 3/4 of original quantity |
| Glauber's Salt | 1/10 of original quantity |
