The reason for the uneven dyeing of high temperature and high pressure dyeing machine is that the water temperature is too high when disperse dyes are dissolved. Some even use high temperature hydration material to agglomerate disperse dyes. It may also be low temperature chemicals, but too little dispersant is used when dissolving dyes, which makes disperse dyes agglomerate and can not be evenly distributed in water. In addition, when dyeing, the temperature rises too fast, the holding time is too short, the cloth circulation speed is too slow, so that the dye has not diffused and penetrated into the fiber interior, dyeing has occurred, resulting in uneven dyeing.

To prevent uneven dyeing, the heating time and holding time should be reasonably determined, and the nozzle pressure should be readjusted to increase the cloth speed. Reasonable selection of dyes and chemicals, if the disperse dyes with different dyeing rates are selected in color matching, the dispersant or dyes should be increased appropriately, and the cloth capacity should be moderate.

When uneven dyeing occurs, light uneven dyed fabrics are usually re-dyed by the migration of dyes. This migration phenomenon is beneficial to production, that is, to leveling. In practice, this phenomenon can not only improve the uniformity of dyeing, but also make use of it to achieve so-called fast dyeing. The disperse dyes suitable for fast dyeing mainly have strong interfacial migration motion to achieve fast dyeing and uniformity. The dyeing temperature should be raised to 135 ~140 C if the dyes with poor migration are used, but the premise is that the mechanical properties are allowed and the texture feel is not affected. The dyeing of disperse dyes is strongly influenced by temperature. Therefore, in the temperature region of absorbing dyes, increasing the number of cycles of fabric and dye solution can make the dyes and temperature distribution uniform in the dyeing room, which is beneficial to fabric leveling.

When dyeing is seriously unevenness, it is not possible to use dye migration to repair, and must be Decolorated and dyed again. Such as light or medium color, can be darkly dyed dark or very deep color. The decolorization methods include oxidation decolorization and reductive decolorization. Reduction and decolorization may damage the fabric handle and avoid it.

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