The dyeing of polyester with disperse dyes is generally carried out under acidic conditions. However, some selected disperse dyes can be used for dyeing under alkaline conditions, the alkaline dyeing method offers advantages such as effective removal of oligomers, shorter dyeing times, colorfastness, and energy savings.
一,Alkaline dyeing of disperse dyes
When dyeing conventional polyester with disperse dyes, the dye bath is generally controlled in a slightly acidic environment (pH 5-6). This is because most disperse dyes achieve the purest colors and the highest dye uptake under acidic conditions. However, polyester imitation silk fabrics must undergo alkali reduction treatment to create pits on the fiber surface, which further improves the softness, luster, and drape. Although the fabric is neutralized and washed after alkali reduction, it still retains some alkalinity. Therefore, alkaline dyeing methods for disperse dyes have emerged. Disperse dyes that can be dyed in an alkaline bath are called alkaline dyeing disperse dyes.
二,Advantages of alkaline dyeing with disperse dyes
Alkaline staining has advantages such as effectively removing oligomers, shortening staining time, stabilizing color, and saving energy.
三,Disadvantages of alkaline dyeing with disperse dyes
Because conventional disperse dyes contain ester groups, amide groups, cyano groups, etc., they are prone to hydrolysis under neutral or alkaline conditions, leading to changes in the color of the dyed material and a loss of dye strength. Therefore, dye screening is necessary for dyeing under alkaline conditions.
1. Improves scouring effect:
Since synthetic fibers contain a lot of oil, existing scouring methods cannot completely remove residual oil and sizing agents, which can easily lead to uneven dyeing or even color spots. In alkaline dyeing, the dye bath is alkaline, and an alkaline leveling agent is added. This leveling agent also has degreasing and desizing effects, effectively improving the problem of insufficient washing in the pretreatment process, and contributing to the rationality and simplification of the dyeing process.
2.Prevents re-adhesion of alkali reduction dispersion residues:
For synthetic fabrics to achieve a soft hand feel and high quality, intermittent alkali reduction is an ideal method. However, the decomposition products and caustic soda are difficult to completely remove, resulting in an increasingly high concentration of dispersion residues in the working solution. If dyeing is performed in an acidic bath, the dispersion residues are prone to re-adhesion, causing color spots. However, when dyeing in an alkaline bath, the decomposition residues can dissolve in the dye bath, thus preventing the re-adhesion of alkali reduction dispersion residues.
3.Prevents the aggregation of oligomers: Polyester contains some cyclic linear oligomers. During dyeing, these oligomers transfer to the fiber surface, fall into the dye bath, and easily aggregate and adhere to the fabric or dyeing vat. However, in alkaline dyeing baths, since oligomers are soluble in alkaline solutions, they will not cause dyeing quality problems.
4.Improves the quality and reproducibility of dyed products:
When dyeing under acidic conditions, polyester fabrics have a rough feel, while under alkaline conditions they have a smooth feel. Therefore, dyeing in an alkaline bath can reduce problems such as wrinkling, abrasion, and scratches that are prone to occur in acidic dyeing baths. It can also give dyed fabrics a soft hand feel, thereby improving the quality of dyed products. At the same time, the application of alkaline leveling agents has an excellent buffering capacity for the pH value in the dyeing bath, making the pH value before and after dyeing basically consistent, which helps to reduce batch difference and improve dyeing reproducibility.
四,Disperse dyes that can be used for alkaline dyeing
When using the disperse dyes provided by our company, you can choose the alkaline stabilizer JPH95. This stabilizer has good buffering properties, which can keep the pH value of the dye bath at 9.5±0.5 during the dyeing process. It also has excellent chelating and masking properties for metal ions, which can effectively protect the dye from decomposition and dissolve oligomers in polyester.
If you need disperse dyes that can be used for basic staining or want to learn more about related knowledge, you can contact usdirectly by clicking the small window on the right or leaving a message in the message box below.
