Views: 1000 Author: Site Editor Publish Time: 2021-05-13 Origin: Site
The pre-dyeing treatment for natural fibers is mainly to remove their symbiotics. For synthetic fibers such as polyester, the artificial “impurities” are removed, including oils added in the spinning or weaving process, and contaminated grease, dust, pigments, etc. Among them, the most notable is the oil agent.
The oil contains lubricants, emulsifiers, antistatic agents and so on. The application of oil is necessary for spinning and weaving of synthetic fibers such as polyester. However, the oil must be washed off during the dyeing and finishing process. If it is not washed before dyeing and dyed with these oils, the oil will form a "dye barrier film" on the surface of the polyester, preventing the dye from evenly spreading and penetrating into the fiber. . As a result, it is easy to cause uneven coloring and produce stains, stains and other dye defects. Moreover, it will increase the floating color and affect the color fastness. If the pre-dyeing process is not in place and the oil on the fiber is unevenly removed, cloud-like colored flowers may be produced; if the dye in the dyeing solution has poor dispersion stability and agglomeration occurs during the dyeing process, these oils will interact with each other. The aggregates of the dyes combine and adhere to the dyed material to produce stains.
Response measures: strengthen pre-dyeing purification treatment
Before dyeing, treat the dyed polyester in a light lye (if necessary, add an appropriate amount of high-temperature resistant, non-foaming surfactant) at 85℃ for 20 min (note that the alkali concentration should not be too high to avoid hydrolysis of the polyester ). Wash once after draining, neutralize with acid if necessary, and then dye.
There are two purposes:
1. Extract most of the oligomers in the fiber and discharge them out of the machine in a dissolved state, which can significantly reduce the content of oligomers in the dye bath.
2. Remove the oily agent applied to the fiber or fabric during the spinning or weaving process, as well as the contaminated grease, dust, pigments, flower clothes, etc.