.When dyeing polyester fabrics with high-temperature and high-pressure dyeing machines, color spots and stains are caused by oligomers produced in the fibers. Is there any way to avoid and overcome them?
Answer: Oligomer, also known as oligomer, is a low-molecular substance with the same chemical structure as polyester that exists inside polyester. It is a by-product of the polyester spinning process. Generally, polyester contains 1% to 3% oligomers, which are mainly composed of cyclic trimers and linear oligomers. Linear oligomers are partially soluble in water; cyclic trimers are insoluble in water and can only be measured in the fiber itself and dye aggregation. When the temperature exceeds 120°C, it can precipitate from the fiber and combine with the agglomerated dye. , after coloring, it can cause stains, color spots and other defects. Someone has analyzed this dyeing defect and found that its main components are: 50% oligomers, 30% dye dispersant, and 20% fiber impurities. It can be seen that oligomers account for 50% of the stains. Remove stains and spots caused by oligomers and how to overcome them are as follows.
① Control the coloring temperature below 120℃) and adopt appropriate carrier coloring method to reduce the generation of oligomers and obtain the same color depth.
②After coloring, the dye liquor is quickly discharged from the machine at high temperature. The drainage time is 5 minutes longer. Because oligomers are evenly distributed in the dye liquor at a temperature of 100q~120°C and tend to accumulate when the temperature is below 100°C. Precipitate on the colored material.
③Add dispersing protective colloid additives, such as Uniperol PE, when coloring, which can not only produce an even gathering effect, but also prevent oligomers from settling on the fabric.
④After coloring, clean with reducing agent: 32.5% (38°Bé) NaOH 3～5mL/L, insurance powder 3～4g/L, Uniperol PE 0.5～1g/L, treat at 70℃ for 30min, then cold wash , hot wash, cold wash, neutralize with acetic acid.
⑤Pre-dyeing treatment. Before dyeing, natural cotton cloth is treated with 100% NaOH 3% (based on cloth weight) and 1% surfactant cleaning agent (based on cloth weight) at 130°C for 60 minutes, with a liquor ratio of 1: (10-15). The pre-dyeing treatment method has a certain corrosive effect on polyester, but is extremely beneficial to the removal of oligomers. For polyester filament fabrics, it can reduce “extreme finish”, and for medium and short fibers, it can improve the pilling phenomenon.
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