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Prevention of high temperature and high pressure dyed color of ordinary polyester fabric
- Jan 04, 2019 -

Polyester fabric is widely used in various textiles and apparel fabrics due to its high strength, good elasticity, excellent wear resistance, good dimensional stability and good crease resistance. However, since it has a compact structure, is highly hydrophobic, and does not contain a hydrophilic group such as -SO3- or -COO- in the molecule, it is difficult to dye with a hydrophilic dye at normal temperature. Dispersed material has small molecular weight, does not contain hydrophilic groups, and is slightly soluble in water. It is an ideal dye for polyester fabrics. It is usually dyed with disperse dyes, and has three methods: hot melt dyeing, high temperature and high pressure dyeing, and carrier dyeing. We are now using high-quality high-temperature dyeing method with good quality. In order to prevent coloring and color spots in the dyeing process, we must pay attention to the following aspects:


Dye selection

Disperse dyes are difficult to dye polyester fibers at low or normal temperatures, and dyes are quickly dyed only when the glass transition temperature of polyester is exceeded. If the initial dyeing speeds of the selected color matching dyes are too different, it is easy to form a local competitive dyeing at this time to cause coloring. Therefore, when selecting a dye, the initial dyeing rate of several color-matching dyes should be similar, and if the dye has a high initial dyeing rate, it is easy to cause coloring. In general, when dyeing polyester with dispersing materials, dyes with initial dyeing rates close to each other, initial dyeing rate, good quality, and similar color matching properties should be selected. For example, the light color uses the E type, the medium color uses the SE type, the dark color uses the XF, and the SF type can basically dye the deep medium and light color of the polyester, and the effect is good.


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Auxiliary choice

The dispersant has a great influence on the high temperature and high pressure dyeing of polyester. Because of different HBL values of different dispersants, the dispersing ability is also different. Since the dyeing temperature of the disperse dye to the polyester is 80-100 ° C, the dispersing agent is required to have a high dispersing ability, that is, the HBL value is high, and the cloud point is preferably 100 ° C or more. The practice of major dyeing plants proves that anionic dispersants and non-anionic dispersants have higher cloud point and are ideal dispersants.


Heating rate control

The heating rate is also an important factor in the generation of color flower. After reaching the glass transition temperature of polyester, the temperature rises too fast, and the dye will quickly dye the fiber to form a partial dyeing to cause color flower and color block. If the dye is initially dyed. High, the color flower is more serious. Therefore, in the dyeing and heating process, it can be controlled in three stages with different heating rates. The first stage is to raise the temperature to 75 °C at normal temperature. At this stage, the disperse dye will hardly dye the fiber. The faster heating rate can be 2-3 °C, and the second stage is 75-110 °C. This temperature zone is dye. In the fastest stage of dyeing, it is necessary to adopt a slow temperature rise, and the control is preferably at 0.8-1 °C, and the third stage is 110-130 ° C. At this stage, the dye dyeing is exhausted, and the heating rate of 1.5-2 ° C can be used.


Other factors

For example, the chemical material, the capacity, the bath ratio, the PH value, whether the fabric is clean, the flow speed is appropriate, the speed of the fabric, etc. also have a certain influence on the production of color flowers. The dispersion material is generally heated with 40 ° C, stirring. Evenly, it can be injected into the dyeing tank; the dosage should not exceed the maximum capacity of the dyeing tank; the bath ratio is more suitable for 1:8-12; the pH should be controlled at 4-4.5; the cloth surface is clean and PH value is required for dyeing. Neutral; in addition, the flow rate and the speed of the fabric in the cylinder should be adjusted reasonably.

Finally, if a slight color flower is found after the dyeing is finished, a certain amount of repairing agent may be added to perform color correction by means of transfer dyeing.