1. Foam

Foaming is the most common problem with HPHT jet flood dyeing. In high temperature and high pressure jet overflow dyeing machines, foaming occurs as a result of high energy turbulence caused by the high speed of the fabric and the circulation of the liquid.

The main factors affecting foam formation are the properties and quantities of dyes and auxiliaries. Pre-refining with low-foaming additives or solvent method can eliminate the foam caused by possible contamination on the fibers; when selecting dyes, their foaming properties should be considered, and dyes with low foaming properties should be selected as much as possible. Defoamers are best avoided as they can stain fabrics.

2. Wrinkles (wrinkle strips)

The wrinkles of polyester fabrics dyed on the high temperature and high pressure jet overflow dyeing machine are often in the shape of chicken feet, which is due to the fact that the fabrics are folded and stacked in the stacking area for too long. Permanent creasing is most likely to occur if the fabric is folded and the fibers are cooled past the secondary glass transition temperature.

Prevention method:

The machine should not be overloaded, it will not cause entanglement problems, and the entire stacking area should be fully utilized; the turnover speed and moving speed of the fabric in the stacking area should be quite high (generally, the maximum turnover time that can be recognized is 2-3min); heating and cooling rates Don't go too fast, the latter of the two factors is more important; during dyeing, the fabric is first relaxed and refined, and then the fabric is pre-shaped. At the end of the dyeing cycle, do not pass through the venturi at the beginning, and introduce cold water to cool it. Such treatment will cause considerable impact on the fabric; the fabric should be out of the machine at room temperature; unless there is special need, do not dewater the fabric by centrifugation, vacuum dewatering can be used; lower the maximum dyeing temperature; agent.

3. Uneven color

Causes and prevention methods: If the temperature rises too fast, the heating time should be reasonably determined; if the holding time is too short, the holding time should be reasonably determined; if the circulation speed of the cloth is too slow, the nozzle pressure should be re-adjusted, and the nozzle slit and conical tube should be re-selected to increase the Cloth speed; dye adsorption is not uniform, dyeing materials should be selected reasonably. If disperse dyes with a large difference in dyeing rate are selected when color matching, the amount of dispersant or dye should be appropriately increased; the cloth capacity far exceeds the standard capacity. The capacity should be moderate.

4. Oligomers

①The generation and harm of oligomers

Oligomers are low molecular weight polycondensates produced during polymerization. In polyester products, most of the oligomers are cyclic compounds formed by three ethyl terephthalates. Oligomers can dissolve in the dyebath and crystallize out of solution at high temperatures, and deposit on mechanical or fabric surfaces when cooled, especially in low flow areas. The deposition of oligomers on the exchanger can constrain the flow and reduce the efficiency of heat exchange. The oligomers are deposited on the surface of the fibers, forming white specks or hoarfrosts.

② Elimination of oligomers

Solvent refining the fabric prior to dyeing can greatly reduce the production of oligomers. Oligomer control agents can also be added during dyeing, which can increase the solubility of oligomers in the dyebath or produce a stable oligomer dispersion. Cleaning with certain auxiliaries in post-treatment can also help remove deposited grease and dyes.

5. Coagulation of disperse dyes

The agglomeration of dyes can produce color spots on the fabric, reduce the dye uptake rate, and make the rubbing fastness worse. Causes and prevention methods:

There are too many electrolytes in the dye bath, and the electrolyte in the dye bath should be minimized; improper selection of auxiliaries can cause the precipitation of both auxiliaries and dyes. For dyeing, the auxiliaries with good compatibility should be selected; if the dyeing time is too long, the dyeing time should be shortened; if the dyeing rate is too fast, the dyeing rate should be controlled not to be too fast; Inspection and analysis of the factory; the concentration of dye is too high (dye is easy to agglomerate at high concentration, but in high concentration commercial dyes, the amount of dispersant can be increased to overcome the agglomeration), the amount of dispersant should be increased; the dye bath is contaminated , The fabric should be fully washed before dyeing, and the cleaning and maintenance of the equipment should be strengthened at the same time.

6. Tangle

Knotted tufts can cause downtime, especially with full-fill equipment and when dyeing light fabrics. Some fully-filled units are equipped with back injection and control valves to control the stacking of the fabric, but because it is impossible to see how the fabric is stacked, entanglement is still possible. The only way to reduce tangles is to rely on the experience and responsibility of the operator.

7. Spots and spots

Causes: Dye coagulation; oligomers are produced in the dye bath.

Prevention method: see the relevant content of dye agglomeration and oligomer control.

8. Fluff and Scratches

Causes and prevention methods: the diameter of the nozzle is too small, so that the nozzle pressure is too large, the nozzle of the appropriate diameter should be selected according to the weight of the dye, so that the injection pressure is moderate, not too large; the ratio of the cloth speed and the rotation speed of the cloth guide wheel is out of balance , the two should be commensurate; the grey cloth or semi-finished product is scratched due to impact when handling the grey cloth or semi-finished product, and it should be handled with care to prevent impact and scratches; if it is scratched during opening, manual opening should be used.

9. Elongation

Causes and prevention methods: The cloth capacity is too low, which makes the conveying distance of the cloth longer, and the tension increases, so a moderate cloth capacity should be controlled; the liquid level of the dye liquor is set too high, thus increasing the friction between the water and the cloth. Resistance should be kept as low as possible.

Good factory such coopertailor could solve above issue.