If you are looking for direct dyes which are economic and cheaper, yet yield bright colours get in touch with one of the leading direct dyes manufacturers India. Direct dyes are water soluble compounds with colour pigments which can be used to colour coat cotton, linen, rayon, wool, pure silk, leather and also paper. Not only for colouring purposes, but also direct dyes are used a pH indicators and biological stains. The process of direct dyeing is processed in neutral or slight alkaline dyebath at or nearly boiling point. Even though direct dyes bring forth bright colours but they have a poor wet fastness. So in order to improve the wet fastness an after treatment, like that of dye fixing is necessary in most direct dyeing items. There is more that you need to know if you are about to finalise direct dyes for your requirement. Check from one of the leading and experienced direct dyes manufacturers India so that you get all the desirable properties and also make sure that they are quality tested so that they can stand the test of time. Below are some quick facts that you need to know before you finalise them for your next big project.
Chemical Composition of Direct Dyes – The direct dyes are actually salts of complex sulfonic acids which means by chemical structure about 75% or more are of all direct dyes are non-metallised azo structures while others are disazo or polyazo types. They are anionic in nature and are water soluble. The direct dyes have a strong affinity for fibers such as cotton, viscose, silk jute,linen etc. However they do not form any kind of permanent chemical bond with the cellulosic fibers but are still connected via a weak hydrogen bonding along with van-der-waals forces. It is their shape and length which allows them to lie beside the cellulose as well as maximise the van-der-waals, improve the dipole and hydrogen bonds.
Types of Direct Dyes – The different types of direct dyes can be classified as below:
- Class A – dyes which are self-levelling in nature
- Class B – dyes that are not self-levelling, Thee can be tamed by addition of salt to give the desired results and are described as salt-controllable.
- Class C – dyes that are not self-levelling and highly sensitive to salt, these cannot be tamed by addition of salt only. They need to be controlled by temperature as well and are described as temperature-controllable.
Method of Direct Dyeing–First, the colour pigment is added and boiled in water for about half an hour to 45 minutes to make a lump free solution. Salt is added during the boiling process, however note that for lighter shades negligible or no salt is required. The boiling can be then started to cool at about 80 degree Celsius and then again add salt and stir the mixture well. Allow it to cool.
After Treatment– It is important to go for an after treatment of the dyed material to improve the wet fastness. You can opt for any of the below after treatments:
- Diazotisation and development
- Metal salt treatments
- Cationic fixing agents
- Formaldehyde treatment
- Cross linking agents and resin treatments
Consult one of the leading direct dyes manufacturers India to obtain the best and quality tested direct dyes!