Introduction
Polyester microfiber has excellent strength, dimensional stability, washable and wearable, full hand feel, softness, elegant and other unique styles, which are incomparable to ordinary polyester fibers. However, compared with ordinary polyester fiber, ultra-fine polyester fiber has smaller single filament fineness, larger specific surface area, and higher amorphous zone content. Therefore, it absorbs dye quickly, diffuses slowly, and has poor level dyeing properties, which can easily cause uneven dyeing, especially for deep colors. The color variety is particularly prominent, and its cross-sectional diameter is small and the reflection coefficient of light is large, which weakens the color brightness of the fabric. The dyed color is lighter than that of conventional polyester fiber. To obtain the same depth of color, the amount of dye generally needs to be increased. More than 30%.
In view of the above problems in dyeing ultra-fine polyester fiber, comprehensive measures should be taken during dyeing, that is, dyeing equipment, dye selection, auxiliary selection, dyeing process operation, etc. should be considered. The above issues are briefly summarized as follows for reference only:
1. Equipment selection
Ultra-fine polyester fiber generally comes in loose fibers and yarns. Whether you use a cylindrical high-temperature and high-pressure dyeing machine or a high-temperature and high-pressure jet dyeing machine, you must choose one with a warranty. For certified and qualified products, the pump design, flow rate, head, pressure, etc. must be designed in accordance with specified requirements.
2. Selection of dyes
Ultra-fine polyester fiber dyeing should be dyed with high affinity and Special disperse dyes with good lift and strong color development ability can be used to increase the dye uptake rate. Some compound disperse dyes can also be used to increase the dye uptake and lift rate to obtain darker colors. From the perspective of dye structure, it is generally believed that the color development intensity of azo disperse dyes is higher than that of anthraquinone disperse dyes. From the molecular structure analysis of special disperse dyes recommended abroad, most of the diazo groups in the diazo component of azo dyes and the coupling component substituted amino groups contain cyano groups. The use of disperse dyes with a cyano-containing monoazo structure is beneficial to improving dye depth and dye fastness. Multi-component compound disperse dyes are to select two or more dyes with similar structures to have a certain additivity to the dye saturation value of polyester fibers. Mixing them together for dyeing can increase the dye uptake rate and can Dyeing darker colors
3. Selection of auxiliaries
Superfine polyester fiber , due to differences in single filament fineness and fiber morphology, the dyeing speed is fast and uneven. In addition, the differences in fiber cross-section, fineness, and shrinkage during dyeing result in different shades of light, resulting in chromatic aberration. For this reason, the selection of leveling agents is very important. The selection of leveling agents for high-temperature and high-pressure dyeing of ultra-fine polyester fibers is more demanding than the dyeing of conventional polyester fibers. Its main properties are: it can effectively slow down the initial dyeing rate, reduce the initial adsorption rate, has good mobility, good high-temperature desorption and high-temperature dispersion, low foaming, etc. Generally, it can be used with dispersion, leveling, chelating, etc. Functional non/anionic compound surfactant. Nonionic surfactants can generally form hydrogen bonds with dye molecules through ester-type polyoxyethylene ethers to achieve dye-affinity slow dyeing effects. Anionic surfactants improve the dye migration effect of nonionic surfactants and assist in the dispersion ability. There is also information that the leveling agent used for dyeing ultra-fine polyester fibers requires polyoxyethylene ether sulfonate macromolecular compounds with larger molecular weight and lower sulfonation degree. Most domestic leveling agents have unsatisfactory effects. Among them, the leveling agent 802 launched by Donghua University and the leveling agent TF-215 of Zhejiang Chuanhua Company have better performance. Leveling agent TF-215 is not only suitable for special disperse dyes, but also enables ordinary disperse dyes to achieve leveling effects when used for dyeing microfibers.
4. Control of heating rate
The surface area of ultra-fine polyester fiber is larger than that of ordinary polyester fiber Much faster, the dye adsorption speed is also much faster. The dyeing speed increases as the fineness of the single filament becomes thinner. The cross-section of ultra-fine polyester fiber is not round, the surface is uneven, the surface area is larger, and the adsorption rate is faster. The large surface area is firstly reflected in the high initial dyeing rate, which is not conducive to leveling dyeing. For this reason, the starting temperature of dyeing must be changed. Generally, dyeing can be started at 20°C and the heating rate can be controlled at 0.5°C/min to 110°C. The heating rate is controlled to 1.0°C/min. The temperature can be raised to 130°C and kept for 40 to 60 minutes, and then heated to 1.5°C/min. min, cool down to 80 ℃ and drain the liquid. Hot wash at 80℃ for 20 min, water wash at 50℃ for 10 min, reduction wash at 70~80℃ for 20 min, and water wash.
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