Acid Dyes

ACID DYES are the selected range of dyestutfs suitable for dyeing on pure wool. The various dyes in the shade card have been grouped mainly according to their exhaustion behaviour, colour fastness and other characteristics on wool. The following are the main groups:

1. ACID LEVELLING & TPM DYESThe levelling dyes of this group require strongly acid dyebaths employing Sulphuric or Formic acids. The pH of the dyebath is around 2.5-3. The dyes are generally bright with good levelling properties but have moderate wet fastness. The fastness to light varies from moderate to excellent.The Milling & TPM dyestuffs are dyed in a weakly acid or neutral bath employing a pH around 4-4.5. Acetic acid or Acid liberating salt such as Ammonium sulphate or Acetate are used. The shades obtained are bright with good all round colour fastness properties.
2. ACID 1:1 METAL COMPLEX DYESThis group comprises premetallised 1:1 Metal Complex Acid Dyes.These dyes have excellent level dyeing properties and all round good colour fastness. In view of their outstanding levelling properties, the dyes are eminently suitable for the production of even very pale shades with good colour fastness.
3. ACID 1:2 METAL COMPLEX DYESThese dyestutfs are dyed in a neutral or slightly acidic bath employing a pH around 5-7. The dyestuffs have a good degree of penetration, therefore, particularly suitable for the dyeing tightly woven goods. Also shades obtained have good all round fastness properties.

DYEING PROCEDURE FOR WOOL

1. 1. Method IThis is recommended for Acid Levelling Dyes:

      X%

      Dye

      5 – 10%

      Glauber’s Salt Calc.

      2 – 5%

      Sulphuric Acid (168oTW) or Formic Acid (85%)

      Enter the material (without dye) at 50oC and run for 5 minutes. Add the dissolved dye and raise the temperature gradually to the boil over 30 minutes and continue dyeing at the boil for 45-60 minutes. Rinse.

   2. Method IIThis is recommended for acid Milling & TPM Dyes:

      X%

      Dye

      5%

      Glauber’s Salt Calc.

      1 – 3%

      Acetic Acid (30%) or Ammonium Sulphate or Ammonium Acetate

      Enter the material (without dye) at 50oC and run for about 5 minutes. Then Add the well dissolved dyestuff and dye for 15 minutes. Raise the temperature gradually to the boil over 30 minutes and continue at the boil for 45-60 minutes. For heavy shades, if exhaustion is not completed, add:

      2 – 4%

      Acetic Acid (30%) or Formic Acid (85%) or

      1 – 2%

      Sulphuric Acid (168oTW)

      and dye for further 15-30 minutes at the boil. Rinse.

   3. Method IIIThis is specifically recommended for acid Navy Blue 2RNS:-

      X%

      Dye

      5%

      Glauber’s Salt Calc.

      1 – 3%

      Acetic Acid (30%) or Ammonium Sulphate

      0.2 – 0.5%

      Sodium or Potassium Dichromate

      Enter the yarn (without dye) at 40oC for about 5 minutes. Then add the dissolved dye and raise the temperature gradually to the boil over 45 minutes and dye further for 60 minutes at the boil. Rinse.

   4. Method IVThis method is recommended for acid 1:1 Metal Complex Dyes.

      X%

      Dye

      5 – 10%

      Glauber’s Salt Calc.

      Enter the material for 10-15 minutes. Add 4% Sulphuric Acid (l68oTw) and raise the temperature gradually to the boil. In case of medium or deep Shades add a further quantity of 2 – 4% Sulphuric Acid (l68oTw) to the dyebath and continue dyeing at the boil. The total time of the boiling period should be at least 90 minutes. Rinse well to free all acid and preferably neutralise all traces of acid on the yarn with 2 cc/litre Ammonia (25%).

      1:1 Metal Complex Black WA repuires a modified method as under:-

      X%

      Dyestuff

      2%

      Sulphuric Acid (168oTW)

      Enter the material at 70oC and raise the temperature to the boil. After boiling for a short time add a further quantity of 3% Sulphuric Acid (l68oTw) to the dyebath and continue dyeing at the boil. The total time of boiling should be atleast 90 minutes. An addition of 0.3% Sodium or Potassium Dichromate, 30 minutes before dyeing is completed, contributes to enhanced depth of shade, producing a fuller black. Finally rinse well and neutralise all traces of acid on the yarn with a little Ammonia as mentioned for other 1:1 Metal Complex dyes.

   5. Method VThis method is recommended for the dyeing of Chrome Dyes:

      X%

      Dyestuff

      4%

      Chromate Mordant (prepared by mixing one part Sodium or Potassium chromate and two parts of Ammonium Sulphate)

      Enter the material at 50oC and raise the temperature to boil within 45 minutes. Then continue further at the boil for 60-90 minutes. When dyeing medium to heavy shades add for exhaustion:

      0.5-1.0%

      Acetic Acid (30%) or

      0.25 – 0.5%

      Formic Acid

   6. Method VIThis method is recommended for the dyeing of acid 1:2 Metal Complex Dyes:
      The dyeing method is similar to method 1 employing,

      2 – 3%

      Ammonium Sulphate or Ammonium Acetete

      No extra addition of Acetic Acid is normally necessary.

Fastness Properties

Light Fastness :

The rating figures are given on the scale 1-8 i.e. 1 (minimum) poor and 8 (maximum) outstanding.

Other Fastness :

The rating figures are given on the scale 1-5 i.e. I (minimum) poor and 5 (maximum) outstanding.