Dyeing polyester with disperse dyes is generally carried out under acidic conditions.
So, what are the advantages and disadvantages of dyeing with disperse dyes under alkaline conditions? Please look down.
When dyeing conventional polyester with disperse dyes, the dyeing bath is generally controlled to be acidic (pH 5-6). Because dyeing under acidic conditions, most disperse dyes have the purest shade and higher dye uptake. However, the polyester simulated silk fabric must be treated with alkali reduction to produce cavities on the surface of the fiber, which can make the hand feel soft, gloss, drape, etc. to be further improved, but the fabric after alkali reduction has been neutralized and washed with water. It is still unavoidable to be alkaline, so the disperse dye alkaline dyeing method appeared. The disperse dyes that can be dyed in the alkaline bath are called disperse dyes for alkaline dyeing.
The alkaline dyeing method has the advantages of effectively removing oligomers, shortening the dyeing time, stabilizing the color and saving energy and so on.
Because there are more oils on synthetic fibers, it is difficult to completely remove residual oils, slurries, etc. with the existing scouring method, so it is easy to cause uneven dyeing and even color flowers, and the dye bath is alkaline during alkaline dyeing. At the same time, add alkaline leveling agent, which has the effect of degreasing and desizing, can effectively improve the problem of insufficient washing in the pre-treatment process, and is beneficial to the rationality and simplification of the dyeing process.
For synthetic fiber fabrics to obtain a soft feel and high quality, it is an ideal method to use intermittent alkali weight reduction, but its decomposition products and caustic soda are difficult to be completely cleaned, resulting in an increasing concentration of dispersion residues in the working fluid The higher is, if dyeing in an acid bath, the residue of the dispersion will easily re-stain and cause color stains, and when dyeing in an alkaline bath, the residue of the decomposition product can be dissolved in the dyeing bath, thereby preventing alkali reduction of the dispersion residue Reattach.
There are some cyclic linear oligomers in polyester. During dyeing, these oligomers transfer to the surface of the fiber, fall off into the dye bath, and are easy to agglomerate and adhere to the fabric or cylinder body; while in the alkaline dye bath, due to low The polymer is soluble in alkaline solution and will not cause dyeing quality problems.
When dyeing under acidic conditions, the surface of polyester fabric has a rough feel, while under alkaline conditions it has a sense of lubricity. Therefore, when dyeing in an alkaline bath, it can reduce the wrinkles that are easy to appear in the acid dye bath. Problems such as scratches, scratches, etc., and can also give the dyed fabric a soft touch, thereby improving the quality of the dyed product. At the same time, the application of alkaline leveling agent has an excellent buffering capacity for the pH value in the dye bath, so that the dyeing before dyeing After the pH value is basically the same, it is helpful to reduce the tank difference and improve the reproducibility of dyeing.
Since the structure of conventional disperse dyes contains ester groups, amido groups, cyano groups, etc., the dyes are easily hydrolyzed under neutral or alkaline conditions, resulting in changes in the color of the dyed material and loss of dye strength. Therefore, dyeing in alkaline conditions needs to be screened.