Identification of Purity and Structure of Dyes (1) Thin Layer Analysis: Using cyclohexane/acetone=1/1 and chloroform/acetone=9/1 and acetone/cyclohexane=3/2 and chloroform/acetone=9/1 as developing agents, the purity of the dyes obtained from two column chromatography separations was identified.
(2) The melting point of the separated dye is measured using an X15 micro melting point tester (microcomputer controlled temperature type), and the purity of the dye is determined by its melting range.
(3) The infrared spectroscopy method detects the structure of the purified dye using a Fourier transform infrared spectrometer. Determine whether the synthesized substance matches its designed structure through spectral analysis.
The application performance of synthetic dyes is used for thermal transfer printing experiments on cotton, comparing the changes before and after soap washing. Mix the modified dye with existing yellow and black dyes, and then perform heat transfer soap washing.
Experiments have shown that the first route of modification involves replacing the original - NH2 with - NHCOCH3 and - NHC0CH2C1 groups, and then heat transferring the modified dye onto treated cotton, resulting in an orange yellow color for the fabric sample. This indicates that although the - NH2 group belongs to the same electron withdrawing group as the - NHCOCH3 and - NHCOCH2C1 groups, the difference in electron withdrawing properties among the three groups leads to different degrees of color assistance, resulting in different hues of the dye. In addition, the color of the obtained fabric sample shifts towards the red light direction after soap washing, and the color changes but does not fade after soap washing.
According to the second route modification, the original - NH2 is hydrolyzed through diazotization reaction to -0H. The modified dye is heat transferred onto the treated cotton, and the fabric sample color is orange. It does not change color or fade after soap washing.
The third route improvement method is to replace the original phenoxy group with a substituted phenoxy group. The first two modified dyes were heat transferred onto treated cotton, and the resulting fabric sample had a color closer to magenta compared to C1I1 Disperse Red 60. Both soap washing color change and fading fastness met the standards. Mix it with existing blue and yellow dispersed dyes to create other colors, resulting in purer color and good soap fastness.
From the table, it can be seen that due to the different coloring groups of anthraquinone dyes, there are differences between the modified dye and the original dye. The change of 1-position NH2 causes changes in the color and soap fastness of the dye, while the change of 2-position tail group phenoxy group changes the dyeing performance of the dye. Compared with C1I1 Disperse Red 60, the soap fastness of dyes 604 and 605 is more suitable for heat transfer printing of cotton fabrics.
Conclusion: The influence of color aid groups on the soap washing fastness of dyes is extremely important. Different color aid groups result in significant differences in the soap washing fastness of cotton heat transfer printing. A magenta dye with better performance for pure cotton fabrics was developed by modifying the structure of the existing anthraquinone dye C1I1 dispersed red 60 and introducing new substituents. It can be seen that it is feasible to use anthraquinone based dispersed dyes for thermal transfer printing of pure cotton fabrics through effective structural modification.
Low surface tension can cause leakage and reduce print quality, and the optimal range should be between 115510 centipoise.
The rapid stability testing method for liquid acid dyes is as described earlier. For liquid acid dyes, they must be high-purity dyes without salt and other impurities, so they must be filtered and membrane separated to remove salt and other impurities.
After practical application, the following methods can be used to test the storage stability of liquid acidic dyes: prepare 20g dye and 80ml pure water solution separately; 30g dye+70ml pure water solution; 50g dye+50ml pure water solution.
Three different ratios of dye aqueous solutions were observed after being left for 1 hour (using filter paper to observe the diffusion and precipitation of droplets dropped on it), and after standing for 24 hours, the stability was determined by filtering (funnel diameter 415mm) to observe the passage time and residual impurities.
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