Bangalore
Sulphur Dyeing Process in the Lab
Master the lab-scale sulphur dyeing process. Learn key steps, chemical ratios, and best practices for flawless, wash-fast results.
SohaniSharma
Sequestering agent: A sequestering agent is a substance that suppresses as property or reaction of metal ions without the removal of that metal from the system.
Leveling agent: Levelling agent tends to slow down the dye uptake on the fibers, helping to produce a more uniform color in the textile fiber.
Reducing agent: The chemical compound which losses electrons during the chemical reaction. It reduces other substrates chemically.
Common salt: Salt is used as an electrolyte. This electrolyte neutralizes the negative charge formed in the fiber surface and puts extra energy to increase dye absorption.
Soda ash: Soda ash creates proper pH in the dye bath and works as the dye-fixing agent. It helps in forming a strong covalent bond between the dye with the fabric.
Oxidizing agent: An oxidizing agent is a substance that has the ability to oxidize other substances. It undergoes a chemical reaction in which it gains or accepts one or more electrons.
Acetic acid: Its function is to control pH in the process.
Detergent: For emulsifying fats, oils, and waxes. Removes the unfixed dyes from the surface of the fabric.
Theory
Sulphur dye is a water-insoluble dye. It needs to be water-soluble before a reducing agent is used to make it soluble for dyeing. In the final stage, the fabric needs to be insoluble again through the chemical oxidation process. Generally, potassium or sodium dichromate is used for oxidation. Then the fabric is washed off with detergent to remove the unfixed dyes.
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Recipe
Functions of the Chemicals Required
Wetting agent: It accelerates the wettability of material in solution, thus helping to ease the penetration of chemicals into the substrate. It reduces the surface tension of water to allow it to spread drops on a surface, increasing the spreading abilities of a liquid.
Sequestering agent: A sequestering agent is a substance that suppresses as property or reaction of metal ions without the removal of that metal from the system.
Leveling agent: Levelling agent tends to slow down the dye uptake on the fibers, helping to produce a more uniform color in the textile fiber.
Reducing agent: The chemical compound which losses electrons during the chemical reaction. It reduces other substrates chemically.
Common salt: Salt is used as an electrolyte. This electrolyte neutralizes the negative charge formed in the fiber surface and puts extra energy to increase dye absorption.
Soda ash: Soda ash creates proper pH in the dye bath and works as the dye-fixing agent. It helps in forming a strong covalent bond between the dye with the fabric.
Oxidizing agent: An oxidizing agent is a substance that has the ability to oxidize other substances. It undergoes a chemical reaction in which it gains or accepts one or more electrons.
Acetic acid: Its function is to control pH in the process.
Detergent: For emulsifying fats, oils, and waxes. Removes the unfixed dyes from the surface of the fabric.
Recipe Calculation
Here, M: L= 1:40
Sample weight: 10 gm
Total liquor: (10✕40)= 400 ml
Chemicals= (g/L ✕ Total liquor)/1000
Na2S= (8✕400)/1000= 3.2 gm
Soda ash= (3✕400)/1000= 1.2 gm
Glauber salt= (10✕400)/1000= 4 gm
Wetting agent= (1✕400)/1000= 0.4 ml
Leveling agent= 0.4 ml
Sequestering agent= 0.4 gm
Total= (0.4+0.4)= 0.8 ml
Shade Attachment
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| Sulphur Dyed Cotton Sample |
Dyeing Curve
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| Sulphur Dyeing Curve |
Conclusion
Sulphur dyes are inexpensive, generally have good wash-fastness, and are easy to apply. They are predominantly black, brown, and dark. Recent advances in dyeing technologies have allowed the substitution of toxic sulfide-reducing agents. Future developments in the field of reducing dye levels by means of electrochemical processes are promising.
Ahmedabad
