A dye is an organic substance which is used to impart colour to materials such that the colouring is not altered by heat, lighting, washing or other factors to which the material is likely to be exposed to. A dye intermediate is the main raw material which is used for making dyes. Various organic compounds like aniline, benzene, phenols are used as intermediates in the production of dyes.
Classification
Dyes are classified as under:
- Natural dyes
Natural dyes are dyes which are extracted from plants, animals and minerals. For e.g. blue is extracted from indigo, yellow is extracted from turmeric, brown is extracted from minerals etc.
- Synthetic dyes
Synthetic dyes are made from chemical processing using various dye intermediates. Synthetic dyes are widely used compared to natural dyes on account of being more colourful, long lasting and being able to be produced in a large scale.
Process of dyeing
The process of dyeing involves closely and evenly associating the specific material to give even colouring with some measure of resistance to moisture, heat and light. The factors involve chemical and physical interaction between the dye and the material/s through various intermediates. Natural gas and petroleum downstream products like naphtha act as intermediates in the dyeing process.
Some of the key dyeing techniques used are:
- Direct dyeing
In this process, dyes are applied to the material from hot aqueous solution of dye.
- Disperse dyeing
The materials are dyed by immersion in an aqueous dispersion of insoluble dyes. They dye then transfers into the fibre and forms a solid solution.
- Reactive dyeing
Reactive dye is a dye which reacts with the material to form a permanent link i.e. it becomes a part of the material itself and cannot be removed by repeated treatment under neutral conditions.
Applications
Dyes have applications in various industries like textiles, paints, plastics, paper and foodstuffs. In our everyday use, we encounter products manufactured by these industries. Synthetic dyes are being used since the 19th century and are here to stay.
DU Organics manufactures Quinaldine, a dye intermediate. To know more about the same, visit our website or contact us today!