Disperse Dyes
- A+ Tutors Lanka
- Sep 21, 2020
- 2 min read
Updated: Oct 17, 2020
Introduction
- In 1924 Baddiley and Ellis produced the Sulpho Ricinoleic Acid (SRA) to dye acetate fibers.
- In 1953 this dye was categorized as disperse dye.
- Disperse dyes have a very low solubility in water.
- They are organic substances free of ionizing groups.
- Since they have no charge, they can be used to dye hydrophobic fibers like polyester.
- They have the smallest particle size relative to other types of dyes.
- Disperse dyes are economical.
- They have good to excellent fastness properties especially with wet fastness and light fastness.
- Nylon, polyester, acetate, acrylic and other synthetic fabric are dyed using disperse dyes.
- Dispersing agents increase the solubility of disperse dyes in water. They stabilize the dispersed particles causing them to stay dispersed in the medium.
- Disperse dyes with high molecular weights, which give the beat colors, should be applied in the temperature range of 120 oC to 130 oC for best results.
- The dispersing agent works by forming a bond with the hydrophobic section of the disperse dye by forming a micelle. As a result, the more of the disperse dye is now soluble.
- Carrier agents can be used to conduct disperse dyeing at lower temperatures and pressures.
- Carrier agents act as a swelling agent which cause the pores of the fabric to expand and allow more uptake of dye.
Chemical Properties and Structure
- They are derivatives of azo, anthraquinone, nitro and quinine groups.
- 80% of all disperse dyes have mono-azo type structure.
- 15% of all disperse dyes have the anthraquinone type structure.
- All other structures account for only 5%.
- Disperse dyes can be categorized into several categories (1):
o E-Type disperse dyes
o SE-Type disperse dyes
o S-Type disperse dyes
o P-Type disperse dyes
o RD-Type disperse dyes
- E-Type disperse dyes have good leveling properties and are suitable for dip dyeing process.
- SE-Type disperse dyes have general leveling properties and have good color fastness.
- S-Type disperse dyes have high color fastness.
- P-Type disperse dyes are used for the anti-discharge printing of polyester fibers.
- RD-Type disperse dyes are used for rapid dyeing of polyester fibers.
- In the presence of nitrous oxide some shades of disperse dyes will fade.
Application Methods
- There are two application methods:
o High temperature and pressure
o Hot-melt method
- Mechanism:
o At the high temperatures, the polyester fiber expands forming a small hole.
o The dispersing agents form micelles with the dissolved disperse dye molecule.
o The micelle can then drop the dye molecules into the enlarged pores of the fabric.
o Then more dye molecules from the disperse medium are dissolved and form micelles.
o As the temperature is reduced, the fiber contracts and traps the molecules in its structure.
Dye Spotting
- Disperse dyes with larger molecules such as cyanine turquoises experience shear friction with the molecules of the chemical additives
- Such dyes require experimentation to determine the best compatible chemicals
- Silicone defoamers can cause significant spotting if used in excess
- Amount of defoamer used can be reduced by using multifunction products [1]:
o Sora Scour LF-MD
o Sora Sperse T-N Liquid
o Sora Plus LDE
o Sora LEV HTD
References
Hope you learned something new!
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