Basic knowledge of disperse dyes (1)

Disperse dyes were produced by the Baden Aniline Soda Company in Germany in 1922 and are mainly used for dyeing polyester fibers and acetate fibers. At that time, it was mainly used for dyeing acetate fibers. After the 1950s, with the emergence of polyester fiber, it developed rapidly and became a major product in the dye industry.

1. What are disperse dyes? Which fiber is suitable for dyeing?

Disperse dyes are a class of non-ionic dyes with low solubility in water and high dispersibility.

Disperse dyes are usually mixed with dispersants and are suspended in water.

Disperse dyes are suitable for dyeing acetate fiber, polyester fiber, nylon, spandex, PTT fiber, DLA fiber, and can also be used for the coloring of virgin pulp of polyvinyl chloride and polypropylene and the coloring of plastics.

2. What is the classification of disperse dyes and their performance?

According to chemical structure:

There are mainly two types of azo type and anthraquinone type, as well as nitrostyrene, benzimidazole and other heterocyclic structures.

According to application performance and color fastness, it is usually divided into:

(1) Low temperature type (E type) is suitable for high temperature and high pressure dyeing and carrier dyeing, with poor sublimation fastness and good level dyeing.

(2) The medium temperature type (SE type, M type) is suitable for high temperature, high pressure, hot melt pad dyeing, and can also be used for carrier dyeing, with medium sublimation fastness and medium level dyeing.

(3) High temperature type (S type, H type) is suitable for high temperature and pressure, hot melt pad dyeing, good sublimation fastness, poor level dyeing.

3. What are the common methods for dyeing polyester with disperse dyes?

A. Vector dyeing

B. High temperature and high pressure dyeing

C. Hot melt pad dyeing

4. Describe the dyeing mechanism of disperse dyes

Because disperse dyes are insoluble in water and only use water as a medium, they are directly dissolved in the fiber during dyeing, using the fiber as a solvent, and the dye as a solute dissolution process. Since both the solvent and the solute are solid, they are called "solid solution theory".

Polyester fiber has the characteristics of compact molecular structure, high crystallinity, strong hydrophobicity and high negative potential, and lacks the functional genes combined with ionic dyes. Therefore, to solve the difficult dyeability of polyester fiber and increase the diffusion rate of the dye in the fiber, in addition to the use of disperse dyes with small molecular weight and micromolecules, the above three dyeing methods should be used in the dyeing method.

5. What is carrier dyeing method?

Polyester can be dyed by adding chemical agents such as organic acids, alcohols, lipids and benzene compounds as a carrier to the disperse dye liquor under normal pressure boiling dyeing conditions. The carrier plays the role of puffing fiber and carrying dye, so it is called carrier Dyeing method.

6. What are the commonly used carriers?

When using carrier for dyeing, it should be a carrier that is non-toxic, non-severely irritating, has excellent levelling properties, good fastness to sunlight and soaping, and has the greatest expansion performance and dye-conducting ability for polyester fibers.

Commonly used carriers are: methyl salicylate (wintergreen oil), sodium o-phenylphenol, methyl naphthalene and so on.

7. What is high temperature and high pressure dyeing method?

The diffusibility of disperse dyes is closely related to temperature. The higher the temperature, the greater the kinetic energy of the dye molecules, that is, the faster the diffusion speed of the dye. For polyester fibers: high temperature can make the fiber "thermally expand", thereby increasing The vibration frequency of the fiber molecules increases the amorphous area of the fiber, increases the gap, and relaxes the structure. Therefore, the dyeing rate is increased, which is beneficial to the diffusion of the dye and enters the fiber. Therefore, high temperature and high pressure dyeing is a common process for dyeing polyester fibers. The dyeing temperature is 130℃, and the heat preservation interval is 15-60 minutes.