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Disperse Dyes

Updated: Oct 16



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

[1] https://www.chemicalbook.com/ProductCatalog_EN/161113-2.htm


Hope you learned something new!

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