Color stains are those that appear on the dyed fabric with regular, similar shape and size or irregular, irregular shape and size are not fixed, and the color of the dyed fabric is the same color. This kind of problem is difficult to repair once it occurs, which has a great impact on the quality of dyeing products and must be paid attention to.

A. Condensation of dyes. Due to the direct collision of dye molecules, they aggregate into larger dye aggregates (or dye associations). These larger dye aggregates are deposited on the fabric during the dyeing process, causing color stains.

B. Taring of dyes. The so-called tarification of dyes refers to the process in which dye particles and surfactants agglomerate into coal tar-like substances under high temperature conditions. There are usually the following four factors that cause dye tar.

C. Adherence of dye to fabric. In the dyeing process, due to improper operation, foaming of additives, etc., the dye liquor often has lakes on the surface. If these lakes are not treated, they will be brought to the fabric by the dye liquor foam, which will cause sticky color. Stains. For example, when dyeing with Haichang blue sulphur dyes, the dye liquor foams too much during the dyeing process, and the agitation is excessive, the blue foam is drawn into the cloth roll and adheres to the fabric to form stains.

①Strengthen the pretreatment of fabric. The oil or grease contained in the fabric has a greater affinity for the hydrophobic synthetic fibers such as polyester, so it is not suitable to be cleaned. Especially during pre-setting, the oil stains penetrated into the fiber, making washing more difficult. Desizing, scouring, bleaching and other pre-treatments to remove impurities and clean the fabric. For some fabrics containing polyester and other chemical fiber components to take scouring and cleaning process, it is necessary to choose efficient refining detergents and washing equipment. However, after cleaning must clean the additives, otherwise it is easy to form tar with dyes and sticky fabric.

② Strictly prevent dye aggregation. Choose dyes with less cohesiveness under dyeing conditions, and choose leveling agents or dispersants with excellent performance. When disperse dyes are dyed at high temperature, adding an appropriate amount of leveling agent or dispersant can effectively improve the thermal stability of the dye in the water bath and reduce the thermal agglomeration tendency of the dye.

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