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What is Disperse Dyes for Printing

Views: 1     Author: Site Editor     Publish Time: 2022-06-10      Origin: Site Inquire

Direct printing on polyester fabrics requires high temperature steaming after printing to avoid interpenetration of patterns and colors. Dyes with high sublimation fastness must be selected. In order to prevent patterns from fading under sunlight, light fastness is also very important. In order to reduce the concentration of dyes with dark patterns in the printing paste, it is necessary to select dyes with a high rate of increase. 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 banned.

 

The sublimation fastness of disperse dyes is related to the molecular structure of the dye, the humidity of steaming and the printing depth. The sublimation fastness is related to the intramolecular coupling and molecular size of disperse dyes. The size of the molecule is more important. High sublimation fastness dyes are suitable for In high temperature fixing, because it is mainly transferred to the fiber by direct transfer, and the molecule is large, it is easy to cause poor levelness, so the dye factory should try to use the dye matching with the same sublimation firmness.

 

The light fastness of disperse dyes mainly depends on the molecular structure. Generally speaking, the light fastness of anthraquinone type disperse dyes is higher than that of azo type disperse dyes. The light leg color of anthraquinone type disperse dyes is a very complicated problem. The first and most important stage of coloration is the generation of hydroxylamine compounds, which continue to oxidize to destroy the chromophore. The higher the density of the amine electron cloud, 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 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 different energy levels of the excited state of dye molecules by sunlight rapidly lose their activity through energy transfer through intramolecular hydrogen bonds, resulting in the shortening of the excited state and reducing the probability of photochemical reactions. The light fastness will be improved, and the anthraquinone type disperse dyes with high light fastness have the above molecular structure.

 

The promotion rate of disperse dyes is also closely related to the molecular structure. It is generally believed that the color strength of azo disperse dyes is higher than that of anthraquinone disperse dyes. For example: the molar extinction system number of red anthraquinone type disperse dyes is 1.0~1.4×104[lumens/mol·cm]. The 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 azo type is 3.2 ~4.5×104 [lumens/mol·cm]. The diazo component of blue azo disperse dyes is 2 or 2.6. 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 color effect (red shift of absorption wavelength) and the dark color effect (increase of lifting force) of dyes are improved, and their sublimation fastness and light fastness are greatly improved. Generally, the sublimation fastness can reach 4 to 5 grades. , The light fastness can reach 7 grades.

 

Domestic and foreign dyestuff companies use the principle of compounding and synergy to launch compounded disperse dyes, changing their melting point and vapor pressure to improve the sublimation fastness, heat transfer performance, dyeing saturation value and lifting force of disperse dyes.


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