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How To Identify The Quality Of Disperse Dyes

Date:Jul 16, 2019

From the point of view of dye application, the quality of disperse dyes mainly depends on five aspects: diffusibility, dispersibility, high temperature dispersion stability, tar content and thermal mobility. Practice has shown that the key to these properties is the quality of the fillers, diffusers and lignin, which are mixed into the disperse dye.

    Diffusion detection: Accurately weigh 1g dye, add 100mL water at 30°C, stir evenly with glass rod, drop 4-5 of dye suspension on filter paper with straw, observe its natural osmosis circle, good diffusion Then the area is larger. Some dye solutions have 1 to 2 layers of oozing circles in the dropping place, the area is not large, and the dyeing liquid is outside the water ring. This kind of dye is preferably used to add 20% to 30% of the diffusing agent MF when stirring. Or add 2g/L disperse dye repair agent to improve dye diffusibility and improve dye transferability. Do not apply the diffusing agent N because of very warm dyeing because it is not resistant to high temperatures.

    Dispersion test: The above remaining dye solution was heated to 70 ° C to 72 ° C on a constant temperature electric furnace, left the heat source, and stirred with a glass rod to observe whether the dye on the beaker wall and the glass rod was sticky. If the fluidity of the dye solution is very good, there is almost no stain on the glassware, indicating that the dye has good dispersibility and can be dyed at 100 ° C or high temperature and high pressure.

    High-temperature dispersion stability test: The above dye solution was still poured into a glass dyeing cup, placed in a dyeing machine, and treated at 130 ° C and 0.18 MPa for 30 minutes. After taking out, observe whether the solution became thick and slowly poured on the filter paper ( The filter paper can generally be placed on a 50 mL beaker), and the shorter the filtration time, the better. If it is observed that the dye solution becomes thick after heating, it is sticky with a finger, indicating that the dye has poor high-temperature dispersion stability. The dye should also be used in a manner that supplements the amount of the dye by 20% to 30% of the diffusing agent MF. If the water quality used in the production is too high, secondary dispersing of the disperse dye into the dyebath will occur. To prevent this, first, the pH of the dye bath should be stabilized with ammonium sulfate; secondly, 1-2 g/L dispersing chelating agent can be added to improve. Sodium hexametaphosphate should not be added as a softener, because sodium hexametaphosphate will lose the ability to complex calcium and magnesium ions under high temperature and high pressure conditions, and to some extent, the pH of the dyebath will rise and the dyebath will be destroyed. Stability. When it is light, the surface of the fiber increases in color and the color fastness decreases. In severe cases, dark color changes occur. In actual production, once the above phenomenon occurs, the color definition can be improved by reduction cleaning, or the dispersion chelating agent can be added to the reduction bath to achieve better effect.

    Tar content detection: Most of the diffusing agents currently produced use crude methylnaphthalene, which has a high impurity content, not only tar but also other compounds. Generally, after the above heated and unheated dye solution is poured on the filter paper, if the filter paper has fine irregular black spots, it can be regarded as impurities such as tar. If the amount of impurities is small, it is only necessary to add some leveling agent with good dispersing emulsification ability in the prescription, and the problem of dyeing medium or deep color is not serious. If the tar content is high, a bright color layer such as a scented flower may appear on the surface of the dye solution. 2 g/L of dispersant WA can be added during dyeing, and a small amount of suds suppressor is added before the dye is added. Practice has proved that this "one-liquid multi-purpose" identification method is very suitable for printing and dyeing enterprises, and it is easy to operate.

    Thermal migration test: After the polyester product is dyed by disperse dye, the dye inside the fiber migrates to the outside of the fiber and is contaminated on other fibers during heat treatment such as heat setting and ironing. It is different from sublimation fastness, but can be simulated using the sublimation/ironing fastness test method. A piece of dyed polyester is used, and a piece of nylon and vinegar fiber fabric is attached to both sides. After hot pressing at 180 ° C for 30 seconds, the color migration performance of the attached fabric is judged to be good or bad. Generally, it is better to use the gray card level 3 or higher, and vice versa. For dyes with high color fastness or yarn-dyed products, dyes with poor thermal mobility cannot be used.