Polyester knitted fabrics are dyed at high temperature and high pressure, and problems such as color spots, stains, uneven dyeing, recrystallization, agglomeration and coking often occur. That is, oligomers, dye aggregation, etc. are generated in the fiber during the dyeing process. The specific measures to prevent color spots and stains are analyzed from each process and pointed out to reduce quality problems in production.
Polyester knitted fabrics include polyester cover cotton and polyester-cotton blended knitted fabrics. In actual production, they often encounter problems such as color spots and stains on the cloth surface after high temperature and high pressure dyeing with disperse dyes. Minor ones can be repaired by stripping and re-dying, and serious ones cannot be repaired. They can only be picked up and cut later, causing great losses.
The raw material of polyester fiber is a hydrophobic synthetic fiber. On the one hand, the molecular structure of polyester lacks active groups such as cellulose fiber or protein fiber that can be combined with dyes; on the other hand, the polyester molecules are arranged relatively tightly, and there are only small ones in the fiber. When the temperature is low, the molecular thermal motion changes its position to a small extent. Under humid conditions, polyester fiber will not increase the gap through violent swelling like cotton fiber, and it is difficult for dye molecules to penetrate into the fiber. .