All About Disperse Dye | Introduction, Properties and Classification - 1
Introduction:
Dyes are coloured, unsaturated organic chemical compounds capable of giving colour to a substrate (a textile), i.e. colouring or dyeing it.
The term “disperse dye” have been applied to the organic colouring substances which are free from ionizing groups, are of low water solubility and are suitable for dyeing hydrophobic fibres. Disperse dyes have substantivity for one or more hydrophobic fibres e.g. cellulose acetate, nylon, polyester, acrylic and other synthetic fibres.
The negative charge on the surface of hydrophobic fibres like polyester can not be reduced by any means, so non-ionic dyes like disperse dyes are used which are not influenced by that surface charge.
The term “disperse dye” have been applied to the organic colouring substances which are free from ionizing groups, are of low water solubility and are suitable for dyeing hydrophobic fibres. Disperse dyes have substantivity for one or more hydrophobic fibres e.g. cellulose acetate, nylon, polyester, acrylic and other synthetic fibres.
The negative charge on the surface of hydrophobic fibres like polyester can not be reduced by any means, so non-ionic dyes like disperse dyes are used which are not influenced by that surface charge.
History of Disperse dyes:
In 1922, Green and Saunders made one type of coloured azo compound, in which a solubilizing group (for example- methyl sulphate, -CH2-SO3H) is attached to amino group. In dye bath, they are slowly hydrolyzed and produce azo compound and formaldehyde bi sulphate. This free azo compound was capable of dyeing cellulose acetate fibres. This dye was named “ionamine”. But this ion amine did not give satisfactory result in dyeing.
Later in 1924, Baddiley and Ellis produced sulpho ricinoleic acid (SRA) for dyeing acetate fibres. This SRA was used as dispersing agent. Later it was seen that SRA was capable of dyeing Nylon, polyester, acrylic etc. In 1953 this dye was named as “Disperse Dye”.
Later in 1924, Baddiley and Ellis produced sulpho ricinoleic acid (SRA) for dyeing acetate fibres. This SRA was used as dispersing agent. Later it was seen that SRA was capable of dyeing Nylon, polyester, acrylic etc. In 1953 this dye was named as “Disperse Dye”.
Properties of Disperse Dyes:
- Disperse dyes are nonionic dyes. So they are free from ionizing group.
- They are ready made dyes and are insoluble in water or have very low water solubility.
- They are organic colouring substances which are suitable for dyeing hydrophobic fibres.
- Disperse dyes are used for dyeing man made cellulose ester and synthetic fibres specially acetate and polyester fibres and sometimes nylon and acrylic fibres.
- Carrier or dispersing agents are required for dyeing with disperse dyes.
- Disperse dyes have fair to good light fastness with rating about 4-5.
Classification of Disperse Dyes:
According to Chemical Structure:
- Nitro Dyes
- Amino Ketone dyes
- Anthraquinonoid dyes
- Mono azo dyes
- Di- azo dyes
Application Methods of Disperse Dyes:
- Method N: Normal dyeing method. Dyeing temperature is 80-100°C.
- Normal NC method: Method of dyeing at normal temperature with carriers. Dyeing temperature 80-100°C.
- Method HT: High temperature dyeing method. Dyeing temperature 105-140°C.
- Method T: Thermasol dyeing method. Dyeing temperature 180-220°C, continuous method of dyeing.
- Pad roll method: Semi continuous dyeing method.
- Pad steam method: Continuous dyeing method.
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