1. Diffusion detection
Accurately weigh 1g of dye, add 100mL of 30°C water, stir evenly with a glass rod, and drop 4-5 drops of the dye suspension on the filter paper with a pipette. Observe its natural seepage circle. The better the diffusion, the larger the area. big. Some dye solutions have 1~2 layers of fuzzy seepage circles at the place where they are dropped. The area is not large. Outside the dye solution seepage circle is the aqueous solution. For this kind of dye, it is best to add 20% to 30% of the dye dosage as a diffusing agent when stirring, or Add 2g/L disperse dye repair agent to improve dye diffusion and dye migration.
2. Dispersion detection
Place the remaining dye solution above on a constant-temperature electric furnace and heat it to 70°C to 72°C. Remove the heat source, stir with a glass rod, and observe whether the dye on the wall of the beaker and the glass rod is sticky. If the fluidity of the dye solution is very good and there is almost no stain on the glassware, it means that the dye has good dispersion and can be dyed at 100°C or high temperature and high pressure.
3. High temperature dispersion stability testing
Still pour the above dye solution into the glass dyeing cup, place it in the dyeing machine, treat it at 130°C and 0.18MPa for 30 minutes, take it out and observe whether the solution thickens, and slowly pour it on the filter paper (the filter paper can generally be placed in 50mL beaker), the shorter the filtration time, the better. If it is observed that the dye solution thickens after heating and feels mushy when touched with fingers, it indicates that the dye has poor high-temperature dispersion stability. When using this dye, measures should also be taken to supplement the dye dosage with 20% to 30% of the diffusing agent.
If the water hardness used in production is too high, disperse dyes added to the dye bath will cause secondary agglomeration. To prevent this situation, first of all, the pH value of the dye bath should be stabilized with ammonium sulfate; secondly, 1~2g/L dispersing additive can be added to improve it. Do not add sodium hexametaphosphate as a water softener, because sodium hexametaphosphate will lose its 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 mild cases, the floating color on the fiber surface will increase and the color fastness will decrease. In severe cases, dark discoloration will occur. In actual production, once the above phenomenon occurs, the color clarity can be improved through reduction cleaning, or adding a dispersing chelating agent to the reduction bath will achieve better results.
4. Tar content detection
Most of the diffusing agents produced today use crude methylnaphthalene, which contains high impurity content, including not only tar but also other compounds. Generally, after the above-mentioned heated and unheated dye solutions are poured onto filter paper and dried, if there are small irregular black spots on the filter paper, it can be regarded as tar and other impurities. If the impurity content is small, you only need to add some leveling agents with good dispersing and emulsifying capabilities to the prescription, and dyeing medium or dark colors will not be a big problem. If the tar content is high, a bright golden layer like oil flowers will appear on the surface of the dye solution. 2g/L dispersant can be added during dyeing, and a small amount of foam suppressor can be added before adding dye. Practice has proven that this “one liquid, multiple uses” identification method is very suitable for printing and dyeing enterprises and is easy to operate.
5. 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 contaminate other fibers. It is different from sublimation fastness, but the test method of sublimation/iron fastness can be used to conduct simulation tests. That is, a piece of dyed polyester is used, and a piece of nylon and acetate fabric is attached to both sides. After hot pressing at 180°C for 30 seconds, the degree of thermal migration performance is judged based on the color of the attached fabric. Generally speaking, it is better to have a gray card with level 3 or above, and vice versa. For products with high color fastness requirements or yarn-dyed products, dyes with poor thermal migration cannot be used. Extended reading: https://www.china-fire-retardant.com/post/9402.html
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