What are the disperse dyes for printing?

Direct printing on polyester fabrics requires high-temperature steaming after printing to avoid mutual penetration of patterns and colors. Dyes with high sublimation fastness must be selected. To prevent the patterns from fading after exposure to the sun, sunlight fastness is also crucial. In order to reduce the concentration of dyes with dark patterns in the printing paste, dyes with high lifting rates must be selected. The above three basic requirements are particularly important for polyester microfibers. At the same time, dyes affected by carcinogenic aromatic amines and sensitizing dyes should be prohibited.

The sublimation fastness of disperse dyes is related to the molecular structure of the dyes, steam fixation humidity and printing depth. The sublimation fastness is related to the intramolecular coincidence of disperse dyes and the large molecular size. The molecular size is more important. Dyes with high sublimation fastness are suitable for high-temperature fixation. Since they are mainly transferred directly to the fibers and the molecules are large, they are prone to poor leveling. Therefore, dye factories should try to use dyes with similar sublimation fastness.

The sunlight fastness of disperse dyes mainly depends on the molecular structure. Generally speaking, the light fastness of anthraquinone disperse dyes is higher than that of azo disperse dyes. The light fastness of anthraquinone disperse dyes is a very complicated issue. In the presence of oxygen, the first and most important stage of light fastness of aminoanthraquinone is to generate hydroxylamine compounds, and then continue to oxidize to destroy the chromophore. The higher the electron cloud density of the amine group, that is, the stronger the alkalinity, the easier it is to oxidize to hydroxylamine, and the lower the light fastness of the dye. However, both the amino group and the hydroxyl group at the a position can form stable intramolecular hydrogen bonds with the oxygen atom of the carbonyl group on the anthraquinone ring. The singlet states of the different energy levels of the dye molecule excited by sunlight quickly transfer energy through intramolecular hydrogen bonds and lose activity, resulting in a shortening of the excited state and reducing the probability of photochemical reaction. If an electron-withdrawing substituent is introduced at the B position, the amino group alkalinity decreases and the light fastness will increase. Anthraquinone disperse dyes with high light fastness all have the above molecular structure.

The enhancement rate of disperse dyes is also closely related to the molecular structure. It is generally believed that the color intensity of azo disperse dyes is higher than that of anthraquinone disperse dyes. For example: the molar extinction system number of red anthraquinone disperse dyes is 1.0-1.4×104 [lumens/mol·cm]. The molar extinction system number of azo type can reach 3.0-4.0×104 [lumens/mol·cm], the molar extinction system number of blue anthraquinone disperse dyes is 2.0-2.5×104 [lumens/mol·cm], and the molar extinction system number of azo type is 3.2-4.5×104 [lumens/mol·cm]. The diazo component of blue azo disperse dyes is at the 2nd or 2.6th position. After the introduction of cyano group, the molar extinction coefficient reaches 7.0-7.2×104 [lumens/mol·cm]. At the same time, the dark effect (red shift of absorption wavelength) and the rich color effect (improved lifting power) of the dyes are improved. Their sublimation fastness and light fastness are greatly improved. Generally, the sublimation fastness can reach 4-5 levels, and the light fastness can reach 7 levels.

Domestic and foreign dye companies use the principle of compounding and synergizing to launch compound disperse dyes, change their melting point and vapor pressure to improve the sublimation fastness, heat transfer performance, dyeing saturation value and lifting power of disperse dyes. The molecular structure of disperse dyes for printing that meet high sublimation fastness (grade 4-5), high light fastness (grade 6-7) and high lifting power is roughly as follows:

1. Quinolinephthalone

Its absorption intensity is very high, about 1.5 times that of pyrazolone commonly used in general yellow disperse dyes. The introduction of hydroxyl at the 3rd position of quinolinephthalone can improve sublimation fastness and light fastness, because hydrogen bonds are formed inside the molecule.

Introducing substituents on the quinolinephthalone ring or on the phthalic anhydride ring can further improve the sublimation fastness of the dye, such as C.I Disperse Yellow 64

2. Pyridones

The yellow disperse dyes synthesized by pyridone derivatives as coupling components have a very high absorption intensity, which is about 1.5 times that of pyrazolones, such as: C.I Disperse Yellow 119, with a sunlight fastness of 6 to 7 and a sublimation fastness of 5.

3. Styrene

Styrene disperse dyes are a type of bright green-yellow dyes with a sunlight fastness of 6 to 7 and a sublimation fastness of 4 to 5. For example, the following disperse dyes can be used for polyester printing. C.I. Disperse Yellow 49, C.I. Disperse Yellow 93

4. Benzoimidazole of naphthalenetetracarboxylic acid imide

This type of disperse dye is a reddish brilliant yellow with bright fluorescence, with a light fastness of 6 to 7 and a sublimation fastness of 4 to 5, for example: C.I. Disperse Yellow 58, C.I. Disperse Yellow 63, C.I. Disperse Yellow 32

5. Anthraquinones

Anthraquinone structures are a large group of red and blue disperse dyes. They have good light fastness. Although the improvement rate is low, due to the difference between printing and dyeing, the dye penetration is low, and the apparent color depth of the fabric is not very serious. Of course, its sublimation fastness is not as good as that of the pyrolytic type disperse dyes. If the molecular weight of the anthraquinone disperse dyes is increased, especially the molecular weight of the B position, the sublimation fastness can be improved. For example: C.I. Disperse Red 92, sublimation level 4 to 5. C.I. Disperse Blue 60, sublimation level 4 to 5. C.I. Disperse Blue 73 sublimation level 4 to 5.

6. Azo type

Azo type disperse dyes are distributed in all color spectrums and are mainly used for dark printing such as red and blue. The main excellent varieties are cyano and heterocyclic, and direct printing disperse dyes with cyano introduced at the 2nd and 2.6th positions of the diazo composition, such as:

C.I. Disperse Red 165, C.I. Disperse Blue 183, C.I. Disperse Blue 316, C.I. Disperse Blue 337

The brightness, light fastness and molar extinction coefficient of heterocyclic disperse dyes are better than those of aromatic amine azo type disperse dyes, so they are the focus of the development of new varieties of disperse dyes in recent years.

Red heterocyclic disperse dyes such as C.I. Disperse Red 338, 339, and 340 are disperse dyes with 1,3,4-thiadiazole as the diazo component. They all have the advantages of brightness, high color intensity, and good light fastness, and the molar extinction coefficient is 5.5×104 [lumens/mol·cm].

C.I. Disperse Red 338C.I. Disperse Red 339C.I. Disperse Red 340

Old varieties of red heterocyclic disperse dyes such as C.I. Disperse Red 145 use nitrobenzthiazole as the diazo component, with excellent color performance, high strength, light resistance and sublimation fastness.

Blue heterocyclic disperse dyes include thiophene, thiazole, isothiazole and tetrazole as diazo components, which can obtain bright colors, high molar extinction coefficients and good fastness. For example: C.I. Disperse Blue 295, sun exposure 6-7 level sublimation 5 level, C.I. Disperse Blue 356 sun exposure 5-6 level, sublimation 5 level, C.I. Disperse Blue 361 sun exposure 7 level sublimation 4 level, C.I. Disperse Blue 367 sun exposure 7 level sublimation 5 level. The disperse dyes used for printing of polyester microfiber are different from those used for dyeing. Since the problem of uniform dyeing in printing is not big, the dye penetration is low, there is no problem of deep dyeing, there is a relatively good color fixation condition, and there is no problem of wet fastness after reduction cleaning, so the dyes are used first to focus on the sublimation fastness that is similar and higher, and the sun fastness is also higher. Tiankun high water washing products have very good sublimation fastness. There are three series TXF/SWF/KXF to meet the high water washing needs of various fabrics.

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