Precautions for High-temperature Dyeing

High - temperature and high - pressure dyeing machines often produce defects such as color streaks, color stains, and color spots due to improper process operations and poor handling. Therefore, the following precautions should be taken during dyeing:

    1. Preparation of the dye liquorWhen preparing the dye liquor, firstmix the dye into a paste with a small amount of cold water, and then dilute it with room temperature water. It should be noted that the temperatureof the water for dilution should not be too high. If it is higher than 60 degrees Celsius, the disperse dyes will be damaged and agglomerate. In addition to the above method of preparation, the dye can also be prepared by the powder - sprinkling method. That is, slowly sprinkle the dye into cold water while stirring at a high speed. After the dye bath is prepared, it is not advisable to leave it standing for a long time. Meanwhile, use a stirrer to stir slowly to prevent the formation of precipitates.  
2. Selection of dyesWhen dyeing, try to choose varieties with good diffusivity and leveling property. When matching colors, dyes with similar dyeing properties should be selected.

3. Reductive cleaningReductive cleaning is an important step to remove the floating color. After reductive cleaning, the color becomes slightly lighter. At the same time, the rubbing fastness and light fastness are improved.

4. Prevention of tar spotsThe so - called tar spots are the viscous substances formed in the dye liquor. The main components are dye dispersants and polyester oligomers. During the polycondensation of polyester, polyester oligomers will exude from the fibers and flow into the dye liquor and adhere to the fiber surface during the high - temperature and long - time dyeing process. The measures to prevent tar spots are as follows:
       （1）Strengthen the pretreatment of the fabric.

（2） Increase the dyeing bath ratio.

（3）Apply high - temperature and high - pressure dispersants.

（4 ）Adopt high - temperature drainage to avoid the crystallization and precipitation of dyes after cooling.5. Shorten the equipment cleaning cycle.