Dye
A dye is a colored substance that has an affinity to the substrate to which it is being applied. The dye is generally applied in an aqueous solution, and requires a mordant to improve the fastness of the dye on the fiber.
There are mainly two classes of dye, Natural and Man-Made.
Ø Dyes obtained from flowers, nuts, berries and other forms of vegetables and plants as well as from animal and mineral sources are known as Natural dyes.
Ø The other classes of dyes are known as Man-Made or Synthetic dyes. These are based on a particular type of chemical composition. Some of these dyes are- Acid (Anionic) Dyes, Basic (Cationic) Dyes, Pre-Metalized (Neutral) Dyes, Sulfur Dyes, Vat Dyes, Reactive Dyes, Pigment Dyes Etc.
Characteristics of Textile Dyes
Dye Class |
Description |
Method |
Fibers Typically Applied to |
Typical Pollutants Associated with Various Dyes |
|---|---|---|---|---|
Acid |
Water-Soluble Anionic Compounds |
Exhaust/ Beck/ Continuous (Carpet) |
Wool, Nylon |
Color; Organic Acids; Unfixed Dyes |
Basic |
Water-Soluble, Applied In Weakly Acidic Dye Baths; Very Bright Dyes |
Exhaust/ Beck |
Acrylic, Some Polyesters |
N/A |
Direct |
Water-Soluble, Anionic Compounds ;Can Be Applied Directly To Cellulosic Without Mordant (Or Metals Like Chromium And Copper) |
Exhaust/ Beck/Continuous |
Cotton, Rayon, Other Cellulosic |
Color; Salt; Unfixed Dye; Cationic Fixing Agents; Surfactant; Defoamer; Leveling And Retarding Agents; Finish; Diluents |
Disperse |
Not Water-Soluble |
High Temperature Exhaust Continuous |
Polyester, Acetate, Other Synthetics |
Color; Organic Acids; Carriers; Leveling Agents; Phosphates; Defoamers; Lubricants; Dispersants; Delustrants; Diluents |
Reactive |
Water-Soluble, Anionic Compounds; Largest Dye Class |
Exhaust/ Beck Cold Pad Batch/ Continuous |
Cotton, Other Cellulosic, Wool |
Color; Salt; Alkali; Unfixed Dye; Surfactants; Defoamer; Diluents; Finish |
Sulfur |
Organic Compounds Containing Sulfur Or Sodium Sulfide |
Continuous |
Cotton, Other Cellulosics |
Color; Alkali; Oxidizing Agent; Reducing Agent; Unfixed Dye |
Vat |
Oldest Dyes; More Chemically Complex; Water-Insoluble |
Exhaust/Package/ Continuous |
Cotton, Other Cellulosic |
Color; Alkali; Oxidizing Agents; Reducing Agents |