The saturated solubility of the purified disperse dye is quite low even at high temperatures. The solubility of more than 40 disperse dyes measured at 25°C is only in the range of 0.1 m/l to 32 m/l. When the leveling agent is added, its saturation solubility in water will increase sharply. In recent years, a series of dispersion leveling agents such as Tohosalt uf-350, Sun Salt 700, and Sun salt RZ-8F have appeared in foreign countries. The main component of this type of dispersion leveling agent is a non-ionic surfactant mixture with a relatively large molecular weight, and an anionic surfactant is added, which can prevent the aggregation of the dye and improve the dispersibility and leveling property during dyeing. Some of the most notable new levelling agents are dyeing performances also at high temperatures, Levegal MHT (Mobay), Palegal SF (ASF), Fanapal WHL (Tanatex) and others. Application studies have shown that this dispersion leveler can not only promote dye migration but also increase dye uptake rate and can be used for rapid dyeing. But so far, systematic studies on the mechanism of action of these auxiliaries in the dyeing process have not been reported.
Using the thin film permeation balance method, the authors studied the solubilizing effect of the new additives Polegal SF and Dilation EN, Toho Salt uF-350 and the carrier B (Palanil Carder B) on disperse dyes. A large number of experimental facts have shown that different structures of the dispersion leveling agent are different for dye solubilization, and its structure determines the difference in the solubilization mechanism. So as to study the sF and other additives on the disperse dye solubilization effect and the actual dyeing performance provides a reliable basis. This method is superior to previous pressure filtration methods that study the solubility of disperse dyes.
1.1 Materials and Instruments
Dye: Foron Brill Red E-RLN.
Auxiliaries: Palegal SF (BASF), Dilatin EN (Sandoz), Palanil Carrier B, Toho Salt uF.350.
Material: Polypropylene film (33, mn thick) (Tianjin 17th Plastic Factory).
Reagents: dimethylformamide (DMF) (Analytical Pure), acetone (Analytical Pure).
Instrument: Hong Kong Ericsson high temperature dyeing machine, UW-VIS-NIR spectrophotometer.
1.2 Experimental Methods
First, the polypropylene film was welded into a small bag, and four different levels of the dispersion leveling agent (2 g/L) and a blank solution (distilled water) were injected into the dyeing bath. The concentration of dyes inside and outside the film was reached. After equilibration, the pouch was removed and the dye remaining on the outer wall was washed away with cold acetone and weighed (V1). Then, the dye in the pouch was washed with cold DMF into a volumetric flask, diluted to a certain volume (v) of the colorimetric liquid to be measured, and the dried pouch was weighed (V2). The measurement temperatures were 100°C, 110°C, 120°C, 130°C, and 135°C.
1.3 Experimental Principle
Based on the principle of thin film permeation balance. There is a gradient of dye concentration inside and outside the film pouch inside the dye bath. The chemical position of the dye solution outside the pouch is higher than that inside the pouch, forming a pressure for the dissolved dye to penetrate into the pouch until the chemical level of the dye solution inside and outside the pouch is equal. The diffusion of the dye reaches a dynamic equilibrium. At this point, the solubility of the dye in the bag is measured to compare the solubilization of the auxiliary. The test instrument is a UV-VIS-NIR spectrophotometer.
2 Results and Discussion
The test results of the influence of various additives on the solubility of the disperse dye Fomn Brill Red E.RLN are listed in the following table:
From the solubility-temperature (S~T) diagram, various additives have significant solubilizing effects on disperse dyes. They can increase the solubility of the dye by several times. In addition to uF-350 in the S~T curve, it is basically In the form of an index, the solubilization effects of dyes with different compositional auxiliaries are different.
In the polyester dyeing process, a leveling agent having little foaming, good solubility, and a good balance between dispersibility and dye migration properties is mostly a mixture of nonionic and anionic surfactants. The leveling agents EN, uF-350, and SF selected for this experiment are of this type. Non-ionic surfactants have a strong solubilizing ability for disperse dyes because non-ionic surfactants have lower CIVIC values. Anionic surfactants have the ability to promote dye migration, increase the level of dye penetration, and increase the cloud point. Therefore, the higher the proportion of non-ionic surfactant, the greater the solubility of the disperse dye. The order of the solubility curves in the figure confirms this.
The solubilization of dyes by different dispersing and leveling agents is influenced by temperature. With the increase of temperature, the solubility of the dyestuff is greatly improved. This is due to the non-ionic surfactant with polyoxyethylene group in the leveling agent. When the temperature increases, the hydration of the polyoxyethylene group proceeds.
With less, micelles are easier to form. In particular, when the temperature rises close to the cloud point of the surfactant, the number of micelle aggregates increases dramatically, so the dye solubilization ability increases. It is noteworthy that there is a turning point in the solubility curve of the fat-based dispersion leveling agent. That is, the solubilization curve of the SF adjuvant does not show significant solubilization at temperatures below 110°C, but increases more than 110°C. It can be seen that sF is not suitable for low-temperature dyeing but a leveler for high-temperature conditions. Carrier B also shows a similar phenomenon.
3.1 The thin film permeation balance method was used to study the solubilization effect of additives on disperse dyes. The results obtained were close to the results obtained by the pressure filtration method. This method provides a simple, easy-to-use and effective method for the study of solubilization effects of different auxiliaries under dyeing conditions and their effects on dyeing performance.
3.2 The solubility of disperse dyes is an important parameter that affects the dyeing performance and dyeing quality. Surfactant leveling agents have solubilizing and dispersing effects, which are controlled by the composition of the leveling agent and the temperature of the system, and promote the dye migration and leveling permeation during the dyeing process.