introduction

Disperse dyes began to be produced by the German Baden aniline soda company in 1922, mainly for the dyeing of 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 has developed rapidly and become a major product in the dye industry.

1. What is dispersion dye? For which fibers?

Disperse dyes are a class of highly dispersible non-ionic dyes with low solubility in water.

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

Disperse dyes are suitable for: acetate fiber, polyester, nylon, spandex, PTT fiber, DLA fiber dyeing, but also can be used for PVC, polypropylene pulp coloring and plastic coloring.

2. How about the classification and performance of dispersed dyes?

By chemical structure:

There are mainly azo type and anthraquinone type two categories, as well as nitrostyrene, benzimidazole and other heterocyclic structure.

According to the application performance and dyeing fastness is usually divided into:

(1), low temperature type (E type) is suitable for high temperature and high pressure dyeing and carrier dyeing, the dye has poor sublimation fastness and good evenness.

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

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

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

A, carrier dyeing

B, high temperature and high pressure dyeing

C, hot melt pad dyeing

4. Try to describe the dyeing mechanism of disperse dyes

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

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

5. What is carrier dyeing?

Polyester can be dyed with organic acids, alcohols, lipids, benzene compounds and other chemical agents as carriers in disperse dye solution under normal pressure boiling dyeing conditions, the carrier plays the role of expanding fiber and carrying dye, so it is called carrier dyeing method.

6. What are the commonly used carriers?

When the carrier is used for dyeing, the carrier should be selected which is non-toxic, no serious irritating taste, has excellent evenness and good fastness to sun and soap, and has the maximum expansion and dyeing ability for polyester fiber.

Commonly used carriers are methyl salicylate (Holly oil), sodium o-phenylphenol, methylnaphthalene and so on.

7, what is high temperature and high pressure dyeing?

The relationship between the dispersion of disperse dyes and temperature is very close, the higher the temperature, the greater the kinetic energy of dye molecules, that is, the faster the dye diffusion rate, for polyester fibers: High temperature can make the fiber "thermal expansion", thereby increasing the vibration frequency of the fiber molecules, so that the fiber amorphous area increases, the gap increases, the structure is relaxed, so the dyeing rate increases, is conducive to the dye diffusion, and into the fiber interior, so high temperature and high pressure dyeing is a common process of polyester fiber dyeing. The dyeing temperature is 130℃, and the holding time is 15-60 minutes.

8. What is hot melt pad dyeing?

Hot melt pad dyeing process should be used for continuous dyeing of polyester/cotton mixed fabrics, the dyeing principle is also a kind of high temperature dyeing, and the difference between high temperature and high pressure is that the melting color temperature is high (180℃-220℃), and the time is short (90 seconds).

9. Test the performance of disperse dyes in high temperature and high pressure dyeing

(1) Physical properties of disperse dyes:

Wettability, dispersibility, particle fineness, stability of dispersion, etc., these properties will affect the preparation of dye solution, and are the main factors to form color spots.

(2) High temperature dispersion stability of disperse dyes:

It represents the dispersion condensation or decomposition state of dyes during high temperature and high pressure dyeing, and is the main trapping element in the formation of dyeing spots, surface floating color and cylinder stain.

(3) High temperature dyeing:

i, covering: polyester fiber in the manufacturing process has undergone a variety of heat treatment, resulting in the fiber crystallinity, distribution and molecular orientation of the physical structure is uneven, resulting in dyeing rate differences, resulting in the so-called strip flower, warp strip shadow. (Covering this dye property caused by uneven fiber structure is called covering.)

ii, dye transfer: refers to the dye dyed on the fiber, due to increasing the temperature or adding additives, the dye between the fiber and the migration phenomenon. The dyes with good transferability are easier to obtain even dyeing, so the important factors of the transferability are good and bad. Generally, the transferability of E disperse dyes is good, and the transferability of S disperse dyes is poor.

iii. Dyeing rate:

The dyeing process of disperse dyes on polyester fibers is divided into three stages:

A. Disperse dyes are diffused to the fiber surface in a dispersed or micromolten state or dissolved state.

b, disperse dye adsorbed on the surface of polyester fiber.

c. Disperse dye diffuses inside polyester fiber.

Therefore; The high temperature dyeing speed of disperse dyes has a complex relationship with the solubility, adsorption and dispersion of dyes. In order to obtain a good leveling effect, dyes with high dyeing rate and small relationship between dyeing speed and temperature rise should be selected. Dyes with similar dyeing speed (that is, good compatibility) should be selected when mixing colors.

iv, lift rate:

When dyeing dark color, dyes with high lifting rate should be selected, otherwise the utilization rate of dyes is not high.

(4) Adaptability to process factors:

I. Selection of dyeing auxiliaries: In order to improve the dyeing performance of the dye during the dyeing process, dyeing auxiliaries are usually added. The auxiliaries use anionic and non-anionic combination levelling agent, the dosage is 0.5g/ L-1.0g /l, and the high temperature dispersibility decreases when the dosage is too high.

ii, the choice of dyeing solubility ratio: in high temperature and high pressure dyeing, the change of solubility ratio will affect the dyeing rate, especially the coverage. Dyes with good dye transfer, large solubility and large affinity for water have large dependence on the solubility ratio and should be strictly controlled to prevent batch difference.

iii, the choice of dyeing solution PH value: dyeing water, additives, fabric pretreatment residual alkali agent and additives added during dye manufacturing, have a certain impact on the PH value, too high PH value will cause the hydrolysis of some disperse dyes molecular structure and cause color change, the general PH control between 4.5-5.5.

iv. Choice of dyeing water:

If hard water is used or metal ions Ca++, Fe+++, Fe++ are mixed into the dyeing solution, the color of the dye is darkened, so the hardness of the dyeing water is controlled within 100PPM.

(5), high temperature and high pressure dyeing temperature selection:

When disperse dyes are dyed at high temperature and high pressure, the temperature is generally controlled at 130℃. For dyes with low temperature sensitivity, such as E type or SE type, although the temperature changes greatly, their dyeing rate changes are small, so not only can they obtain better dyeing reproducibility, but also have better leveling effect. In addition to the heating process and insulation should be strictly controlled, dyeing temperature should also pay attention to the cooling process, otherwise it will easily cause batch difference. To this end, dyes with more consistent temperature sensitivity should be selected when matching colors, especially when matching colors of different types of dyes.

10. What is the fastness of disperse dyes?

The dyeing fastness of disperse dyes is mainly the fastness of sun exposure, sublimation, friction and washing. Particularly important are the fastness to sun exposure and the fastness to sublimation during post-processing. Others such as water washing fastness and friction fastness can be solved by the method of reduction cleaning after dyeing.

11, why do disperse dyes reduce cleaning?

Due to the tight internal structure of polyester fiber and the surface charge relationship, anion reducing agent can not penetrate into the fiber interior, so through reduction cleaning, only can remove the floating color of the fiber surface, will not affect the dye molecules that have penetrated into the fiber interior, reduction cleaning generally choose 30Beo caustic soda 2-4ml/l, insurance powder 1-2g/l, detergent 1g/l, etc. Temperature 70℃ for ten minutes.

12. How to control the temperature of disperse dyes?

Disperse dyes should be less than 40℃ warm water compound, but from the practice process 40℃ temperature is difficult to control, so advocate normal temperature compound, the temperature is too high will cause dye condensation caused by color spots.

13. What is the effect of polyester oligomer on dyeing?

Oligomers, also known as oligomers, are low molecular polymers caused by synthetic fibers in the spinning process, generally containing about 1-3% of oligomers in polyester fibers. When dyeing, the oligomer migrates from the inside of the fiber to the outside of the fiber under heating condition. Because the oligomer is slightly soluble at high temperature, when the dyeing temperature decreases, the oligomer precipitates out with crystallization, resulting in a "white frost" phenomenon on the yarn surface. The greater the amount of dye and the darker the color, the more serious the influence of the oligomer.

14. Describe dispersion dye hot melt dyeing process:

Pretreatment --> Dipping --> Intermediate drying --> Hot melt --> Reduction cleaning --> Water washing

15, try to disperse dye polyester cotton fabric direct printing process:

Printing → drying → high temperature steaming (180 ~ 185℃, 7 ~ 8 minutes) → plain washing → drying → finishing.