Dyeing using direct dyes with different fabrics -
(B) Direct dyes on Protein fibres
(C) Direct dyes on Nylon
(A) Direct dyes on Cotton -
The dye is prepared with the required volume of the stock solution of dye,0.5 to fifteen shades and water to form the desired MLR.
The prescribed quantity of common salt is added in an exceedingly good number of instalments at intervals of 10 to fifteen minutes.
The temperature of the dye bath is slowly raised to a boil (or recommended maximum dyeing temperature).
The dyeing is sustained at this temperature for a period of 45 to hr.
The material is then allowed to remain in an exceedingly cooling bath for 15 to twenty minutes for obtaining better exhaustion.
Finally, the goods are far from the dye solution squeezed or hydro extracted and dried. An after-treatment in an exceedingly solution of a dye compound often precedes the drying step.
The well-prepared material (desizing, scouring and Bleached) is entered within the dye bath at 40°C and dyeing is distributed for 15-20 minutes.
Common salt is typically preferred to salt for reasons of economy. (Glauber's salts being Anhydrous required the employment of larger quantities).
The quantities of salt used to depend on the shade being dyed and vary between 5 to twenty on a load of material for light to heavy shades.
A typical recipe for self-levelling or class A type of dye -
Recipe | Quantity |
Dyestuff (direct dyes) | X % (OWF) |
Soda ash | 0.5 to 1%(owf) |
Common salt | Light shade 5%(owf) |
Medium shade 10%(owf) | |
Dark shade 20%(owf) | |
Temperature | Boil |
Time | 45 to 60 minutes |
The process is altered for classes B and C counting on the colour used.
When dyeing cotton products using direct dyes, equipment like winches and jiggers for material and hank machines for yarn are typically employed.
However, thanks to the tailing issue brought on by their high fatigue properties, direct dyes aren't typically employed in cone or cheese dyeing for yarn or padding mangle for cloth.
 |
| Dyed Cotton fabric |
(B) Direct dyes on Protein Fibres-
The direct dyestuffs are pretty suitable for wool giving as rule faster colours than cotton.
They may be utilized in an exceedingly neutral bath in an identical way as for Cotton. but, wool has practically no affinity for these colours at or below temperature.
The affinity becomes marked only at about 85°C. The inclusion of acid within the dye bath helps the wool fibre to exhaust the dye bath more completely but, only an awfully weak acid should be added.
If strong acid-like acid is added because of the affinity becomes so great that uneven dyeing will result.
On the contrary, the presence of Alkali within the dye bath tends to remain the dyestuff off from the fibre.
The goods are usually immersed in the tub at about 60°C.
The bath conditions are added to the dyestuff, about 1 to twenty-eight acetic acid and about 10 to twenty of Glauber's Salts.
The temperature is raised gradually to the boiling point and also the dyeing is sustained within the gently boiling bath for about three hours.
It is better, in many cases to use 5% of ammonium acetate instead of acetic acid, Since this ensures the gradual liberation of carboxylic acid at boiling point.
About 1% ethanoic acid added towards the highest of the operation will assist exhaustion.
Dyestuffs like way but must always be dyed from a neutral or perhaps fainted Alkaline bath. The direct colour dyed wool could even be treated in an identical way to cotton.
(C) Direct dyes on Nylon -
Direct dyes contain acid groups so they'll behave as anionic dyes however, they have high relative molecular mass and size and their fastness properties on nylon don't seem to be good as those of acid dyes.
The wet fastness of direct dyes on nylon is improved by the phenol after treatment.
Nevertheless, selected direct dyes are used for producing deep shades on nylon due to their low cost.
In pale shades, direct dyes give barre dyeing because the large dye molecules show poor migration during the dyeing.
The method of application of direct dyes to nylon is identical to that of acid dyes, except that 5 to 10% sulphate is added to the dye bath for satisfactory exhaustion.
 |
| Dyeing of the nylon yarn |
Question -
- Explain direct dyes used on Cotton material.
- Explain direct dyes used on the Protein fibre material.
- Explain direct dyes used on Nylon material.
References
Chakrabarti, R., & Mehta, N. (2008, November 8). Quick Level Dyeing of Direct Dyes. Fibre2fashion.com; Fibre2Fashion. https://www.fibre2fashion.com/industry-article/3742/quick-and-level-dyeing-of-direct-dyes-dyrite-process
Clark, M. (2011). Handbook of textile and industrial dyeing: Principles, processes and types of dyes (Matthew Clark, Ed.). Woodhead Publishing.
Hasin, S. (2020, July 16). All about direct dyes. Textile Property. https://www.textileproperty.com/direct-dyes/
Sayed, A. (n.d.). Direct dye: An overview [A to Z]. Blogspot.com. from https://textileapex.blogspot.com/2015/01/direct-dye.html
The Editors of Encyclopedia Britannica. (1998). direct dye. In Encyclopedia Britannica.
Trivedi, Y. (2020, November 18). Dyeing of cotton fabric with direct dyes. Textilesphere.com. https://www.textilesphere.com/2020/11/dyeing-of-cotton-with-direct-dyes.html
Further read,
Writer - Rushikesh Patil (Textile Engineer)
