Since the advent of polyester fabrics, the dispersion dyeing process under weakly acidic conditions has been used. However, with the development of high-speed spinning of polyester fabrics and the development of new synthetic fibers and the application of high-speed weaving technology, the fiber oil agent and sizing agent are renewed, and the factory adopts a warp sizing agent with higher quality than the past, which increases the difficulty of pretreatment. The alkali reduction treatment often used in polyester fabrics makes the fibers have strong alkalinity and is not easy to remove; the weak acid high temperature dyeing and the oligomers precipitated from the fibers in the pretreatment have affinity for the dyes, thereby producing The oligomer is the core of the dye secondary aggregation, blocking the mesh and coke, reducing the function of the dyeing machine, staining the fabric and equipment, and affecting the smoothness of the fabric. The above oil agents, slurries, oligomers and the like have extremely low solubility under acidic conditions, and exhibit good solubility under alkaline conditions.
During the dyeing process, the effect of polyester fabric oligomers on dyeing is mainly manifested in: deposition on fabric or equipment surface; poor reproducibility of dyeing; poor leveling; causing waste of energy, chemicals, water and time. Due to the speed of spinning and the fact that the oligomers of new synthetic fibers are more than before, this problem has received more and more attention.
In the process of dyeing and finishing of polyester fabrics, most of the processes are usually carried out in alkali. Only the dyeing is carried out under acidic conditions. If the polyester fabric can be dyed under alkaline conditions, the process is simple and can be dissolved. We do not need spinning oils, slurries and oligomers.
Polyester fabric alkaline dyeing characteristics Polyester fabric disperse dye alkaline dyeing has the following characteristics:
Improve the quality of dyed fabrics in polyester fabrics. Scanning electron microscopy showed that the alkaline condition dyeing had less oligomeric surface on the surface of the polyester fabric than the acid dyeing. This is due to the fact that there is a certain amount of oligomer in the fiber. Under the action of the heat of the dyeing process, these oligomers will precipitate from the polyester fabric to the surface, similar to the thermal migration of the disperse dye, because the oligomer and the disperse dye have very Similar physical properties, so some people call the oligomer a colorless disperse dye. In the acid dyebath, oligomers are easily crystallized and deposited on polyester fabric fibers and machines due to their low solubility; however, under alkaline conditions, oligomers are easily hydrolyzed into monomers. However, the condition is high temperature, and the pH value is above 11 (for the oligomers in which the single molecule is dissolved in the dye bath, the pH is urged to have no affinity with the polyester fabric, and it is not crystallized after cooling, and is easy to remove, thus maintaining the oligomer in It will not deposit in the dye bath. The polyester fabric will be removed and dissolved. In addition, alkaline dyeing can effectively remove residual propylene slurry, wax and oil, reduce and prevent fabric scratches and dyes, The residual slurry, lint, and the like adhere to the cylinder.
Since the alkaline dyeing has the above characteristics, the dyeing quality is remarkably improved.
This process can also be illustrated by testing the amount of oligomer dissolved in the dyebath and the amount of fiber deposited. The deposited oligomer was obtained by analyzing the three-molecular ring on the polyester fabric yarn, and the dissolved oligomer was known by analyzing the sodium terephthalate salt in the dyebath. In contrast to several dye baths, the o dye stabilizer JPH95 reduces the amount of acid dyed oligomer deposition by half, while the amount of oligomer deposition on the foot is only one-fifth that of acid dyeing.
Dyed fabrics have good reproducibility. Generally, polyester fabrics need to be processed by scouring or alkali reduction before dyeing. This has the possibility that some alkali remains on the polyester fabric fibers, thus affecting the shade. The presence of residual alkali is a key factor when high color reproducibility is required, but in alkaline dyeing, the color change is small due to the buffering effect of the dye stabilizer.
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