It is difficult to repair the regular or irregular colored spots on the fabric, whose shape and size are basically similar or irregular, whose shape and size are not fixed, and whose color is the same as that of the dyed fabric;

The causes are as follows

1. Condensation of dyes

1) The direct collision of dye molecules leads to the aggregation of large dye aggregates;

2) In the process of color development (fixation), the dye molecules produce strong polymerization force, which makes the dye condense;

2. Tarring of dyes: the process of dye particles and surfactants condensing into tar like substances at high temperature;

1) Poor pretreatment, inadequate cleaning, fabric oiling agent, lubricant and oil dirt, brought to the dyeing bath, under high temperature conditions, contact with hydrophobic dye particles, adsorption, and finally form tar like substances;

2) When the surfactant with cloud point lower than the dyeing temperature is used for pretreatment, if the washing is not clean and the dyeing temperature is too high, the non-ionic components will lose their water solubility, and the hydrophobic oil particles will precipitate, and finally the color stains will be formed;

3) When dyeing with non-ionic and anionic high-temperature leveling agent, if the dosage is too high, tarring substance will be formed;

4) When dyeing with some anionic active agents, such as poor dissolution, color stains will also be formed.

3. Contamination of lake on fabric

1) the color of the foam brought to the fabric, resulting in stained stains.

2) When the fabric goes into the color developing solution, the dye it carries flows into the color developing bath, and forms a lake after hydrolysis and oxidation, which also floats on the liquid surface. If the fabric is not careful, it will stain the fabric and form a color stain;

Solutions

1. Strengthen the pretreatment of the fabric, remove the oil substances, and wash the non-ionic components;

2. Measures to prevent condensation of soluble vat dyes:

The main purpose is to increase the oxidation rate of the dye solution, so as not to make the hydrolysate have the chance of condensation;

1) The stronger the acidity of the bath, the faster the hydrolysis and oxidation rate of the dye;

2) The higher the temperature is, the faster the oxidation rate is;

3) Ammonium metavanadate was added to accelerate the oxidation reaction;

3. Measures to overcome the condensation of disperse dyes

1) Choose the dyes with low cohesiveness at high temperature;

2) The leveling agent and dispersant with excellent properties are selected;

3) Correctly grasp the chemical operation;

4. Measures to prevent staining

1) Try to reduce and avoid the formation of lake;

2) Diffusion agent should be added to both dyeing solution and chromogenic solution to effectively eliminate floating color;

3) Before color development, the froth on the liquid surface should be driven to the corner, and the lake should be diffused by stirring;