Causes and Solutions of Dyeing and Finishing Defects (1)

1. Macula

①.Cause analysis

The usual cause of macula is the use of river water, especially during the rainy season. This is mainly due to the poor quality of the river water. The river water contains organic suspended solids. During the pretreatment process, these organic suspended solids cannot be fully dispersed. During the pretreatment process, they will re-agglomerate and stick to the fabric together with the impurities treated on the fabric, that is, a macular phenomenon occurs. In the post-finishing process, such as whitening, this macular spot will produce whitening spots; if it is dyed, it will produce color spots and so on.

②.Solution

For the macular caused by this reason, a chelating dispersant with better dispersibility should be selected in the pretreatment process. Equivalent to a reactive dispersant, with strong pertinence and better effect.

2. Oil spots

①.Cause analysis

The pre-treatment oil spot is mainly manifested as oily, almost transparent dot-like spots produced during the pre-treatment process.

The general cause is the large amount of chemical fiber oil contained on the fabric and the spandex oil containing dimethyl silicone oil on the spandex fabric. After these oils were washed off in the pretreatment process, they were not sufficiently emulsified and dispersed, resulting in agglomeration and returning to the fabric. Especially low-grade chemical fiber fabrics use inferior chemical fiber oil or increase the amount of oil, which is easy to produce oil spots.

②.Solution

For chemical fiber oil and dimethicone spandex oil, choose an emulsifying degreaser with excellent dispersibility to the oil, and it can be used in combination with degreaser. It can be used alone for fabrics that are not heavy on oil.

3. Plaque

①.Cause analysis

Mainly due to the large amount of chemical sizing on the fabric. Generally, chemical slurries are high-molecular polymers with relatively high degree of polymerization, high viscosity and easy coagulation. After being washed in the pretreatment process, it was not able to obtain sufficient emulsification and dispersion, resulting in agglomeration and returning to the cloth surface. Its shape resembles a cloudy white or yellow patch. Some are similar to sticky substances or yellow jelly-like substances, which form irregular dot-like substances on the fabric.

②.Solution

In view of the above situations, a dispersant or desizing agent with excellent dispersing properties for the slurry should be selected in the desizing process.

Emulsifying refining agent has excellent dispersing effect on slurry, decontamination effect, and emulsifying effect on oil agent. The desizing agent focuses on the desizing effect and has a better dispersion effect on the slurry. All belong to the type of surfactant, which can achieve desizing and anti-sticking through penetration, emulsification and dispersion. It is mostly used in continuous desizing and overflow machines.

In addition, especially PVA (polyvinyl alcohol) pulp, the solubility in water has a certain relationship with temperature. The temperature drops suddenly, and the PVA in the desizing tank will re-agglomerate. This agglomerated particulate matter is stained back on the cloth to produce pulp spots. Therefore, the temperature of the desizing solution cannot be fluctuated. In addition, the desizing solution must be changed regularly. During the desizing process, the concentration of the slurry in the desizing tank will gradually increase. When the saturation point is reached, the slurry will re-agglomerate and re-stick, so the desizing solution should be replaced in time.