How to identify the quality of disperse dyes

Diffusion test: Accurately weigh 1g of dye, add 100mL of 30°C water, stir evenly with a glass rod, drop 4-5 drops of the dye suspension on the filter paper with a pipette, observe its natural seepage circle, good diffusivity the larger its area.

Some dye solutions have 1~2 layers of fuzzy seepage circles appearing, the area is not large, and the outside of the dye solution seepage circle is an aqueous solution. It is best to add 20% to 30% of the dyestuff when stirring the dye. , or add 2g/L disperse dye repair agent to improve the dye diffusion and improve the dye migration. Diffuser N must not be used for very warm dyeing as it is not resistant to high temperatures.

Dispersion test: Heat the remaining dye solution above to 70℃~72℃ on a constant temperature electric furnace, leave the heat source, stir with a glass rod, and observe whether the dye on the beaker wall and glass rod is viscous.

If the fluidity of the dye solution is good, and there is almost no contamination on the glassware, it means that the dye has good dispersibility and can be dyed at 100°C or under high temperature and high pressure conditions.

High temperature dispersion stability test: still pour the above dye solution into the glass dyeing cup, put it in the dyeing machine, and treat it at 130 ℃ and 0.18MPa for 30 minutes. After taking it out, observe whether the solution thickens, and slowly pour it on the filter paper ( The filter paper can generally be placed on a 50mL beaker), and the shorter the filtration time, the better. If it is observed that the dye solution becomes thick after heating and feels pasty when touched with fingers, it indicates that the high temperature dispersion stability of the dye is poor.

The dye should also take measures to supplement the amount of 20% to 30% of the diffusing agent MF of the dye when it is used. If the hardness of the water used in production is too high, the addition of disperse dyes to the dyebath will cause secondary agglomeration. To prevent this situation, first, the pH value of the dye bath should be stabilized with ammonium sulfate; secondly, 1~2g/L dispersing agent can be added to improve it.

Do not add sodium hexametaphosphate as a water softener, because sodium hexametaphosphate will lose the ability to complex calcium and magnesium ions under high temperature and high pressure conditions, and to a certain extent, it can also increase the pH value of the dye bath and destroy the dye bath. stability. In light cases, the floating color on the fiber surface increases, the color fastness decreases, and in severe cases, dark color discoloration occurs.

In actual production, once the above phenomenon occurs, the color clarity can be improved by reducing and cleaning, or adding a dispersing chelating agent in the reducing bath is more effective.

Tar content detection: Most of the diffusing agents produced now use crude methyl naphthalene, 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 and dried, if the filter paper has small and irregular black spots, it can be regarded as impurities such as tar.

If the impurity content is low, it is only necessary to add some leveling agents with good dispersing and emulsifying ability to the prescription, and it is not a problem to dye medium or dark colors. If the tar content is high, the surface of the dye solution will also appear as an oil flower-like golden layer.

2g/L dispersant WA can be added during dyeing, and a small amount of foam suppressor can be added before the dye is added. Practice has proved that this identification method of "multiple uses in one liquid" is very suitable for printing and dyeing enterprises and is easy to operate.

Thermal migration detection: After polyester products are dyed with disperse dyes, during heat treatment such as heat setting and ironing, the dyes inside the fibers migrate out of the fibers and stain on other fibers. It is different from sublimation fastness, but can be simulated by using the test method of sublimation/ironing fastness.

That is, a piece of dyed polyester is used, and a piece of nylon and acetate fabric is attached to each side. After hot pressing at 180 ° C for 30 seconds, the degree of thermal migration performance is judged by the color obtained on the attached fabric. Generally, it is better to use gray card level 3 or above, and vice versa. Dyes with poor thermal migration cannot be used for products with high color fastness requirements or for yarn-dyed products.