Views: 0 Author: Site Editor Publish Time: 2024-01-19 Origin: Site
The hot-melt pad dyeing process is suitable for continuous dyeing of polyester/cotton blended fabrics. Its dyeing principle is also a type of high-temperature dyeing. The difference from high-temperature and high-pressure dyeing is that the melting temperature is high (180℃-220℃) and the time is short. (90 seconds).
1. Physical properties of disperse dyes:
Wettability, dispersion, particle fineness, dispersion stability, etc. These properties will affect the quality of dye solution preparation and are the main factors in forming dyeing color spots.
2. High temperature dispersion stability of disperse dyes:
Represents the dispersion, aggregation or decomposition state of dyes during high-temperature and high-pressure dyeing, and is the main factor that causes dyeing stains, surface floating colors, and cylinder contamination.
3. High temperature dyeability:
(1) Hiding: Polyester fiber has undergone various heat treatments during the manufacturing process, resulting in uneven physical structures such as crystallinity, distribution and molecular orientation of the fiber, resulting in differences in dyeing rates, resulting in so-called stripes, warps, etc. Toward the shadow. (The property of the dye that covers the dye flowers caused by uneven fiber structure is called hiding property.)
(2) Dye migration: refers to the phenomenon of dye migration between fibers due to raising the temperature or adding additives after the dye is dyed onto the fiber. Dyes with good dye migration properties are easier to obtain level dyeing, so whether the dye migration properties are good or bad is an important factor in level dyeing. Generally, E-type disperse dyes have good dyeing properties, while S-type disperse dyes have poor dyeing properties.
(3) Dyeing rate:
The dyeing process of disperse dyes on polyester fiber is divided into three stages:
a. Disperse dyes diffuse to the fiber surface in a dispersed state or a slightly molten state or a dissolved state.
b. Disperse dyes are adsorbed on the surface of polyester fibers.
c. Disperse dyes diffuse into the polyester fiber.
Therefore, the high-temperature dyeing speed of disperse dyes has a complex relationship with the solubility, adsorption and diffusivity of the dye. In order to obtain good leveling effect, dyes with high dye uptake rates should be selected with high dyeing speed and small relationship between dyeing speed and temperature rise. When choosing dyes, you should choose dyes with similar dyeing speeds (that is, good compatibility).
(4) Promotion rate:
When dyeing dark colors, dyes with high lifting rates should be used, otherwise the dye utilization rate will not be high.
4. Adaptability to process factors:
(1) Selection of dyeing auxiliaries: In order to improve the dyeing performance of dyes during the dyeing process, dyeing auxiliaries are usually added. The auxiliaries use anionic and non-anionic compound leveling agents, and the dosage is 0.5g/l-1.0 g/l, excessive dosage will cause a decrease in high temperature dispersibility.
(2) Selection of dyeing solution ratio: In high-temperature and high-pressure dyeing, changes in the solution ratio will affect the dyeing rate, especially the coverage. Dyes with good dye migration, high solubility, and high affinity for water are highly dependent on the solvent ratio and should be strictly controlled to prevent batch differences.
(3) Selection of pH value of dye solution: Dyeing water, auxiliaries, residual alkali agents from fabric pre-treatment and auxiliaries added during dye manufacturing all have a certain impact on the pH value. Too high a pH value will cause some dispersion. The hydrolysis of the dye molecular structure causes color change. Generally, the pH is controlled between 4.5-5.5.
(4) Selection of dyeing water:
If hard water is used or metal ions Ca++, Fe+++, Fe++, etc. are mixed into the dyeing solution, the color of the dyed material will become dull, so the hardness of the dyeing water should be controlled within 100PPM.
5. Temperature selection during high temperature and high pressure dyeing:
When high-temperature and high-pressure dyeing with disperse dyes, the temperature is generally controlled at 130°C. Dyes that are less sensitive to temperature, such as type E or type SE, have small changes in dye uptake despite large temperature changes. Therefore, not only can they obtain better dyeing reproducibility, but also have better level dyeing. Effect. The dyeing temperature should be strictly controlled in addition to the heating process and heat preservation. Attention should also be paid to the cooling process, otherwise batch differences will easily occur. For this reason, dyes with relatively consistent temperature sensitivity should be selected when color matching, especially when color matching different types of dyes.
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