Keywords: overflow dyeing; defects; causes; measures
High temperature and high pressure jet overflow Flow dyeing machine dyeing is a better dyeing method. During dyeing, the fabric moves smoothly in the dye tank in a relaxed state, so the color absorption is relatively uniform.
During the dyeing process, the dyestuff is immersed in the dyeing liquid most of the time. Coupled with the function of the injector, the dye molecules can penetrate better and avoid dyeing with high-pressure jigger dyeing machines. Defects such as dark and shallow edges that are easy to occur and white spots, shaft flowers and other defects that are easy to occur when dyeing with high-pressure cage dyeing machines. Moreover, the high-temperature and high-pressure jet overflow dyeing machine has a compact structure, small footprint, wide adaptability, easy operation, and high output, so it is widely used.
However, defects may still occur if the operator is slightly careless during the dyeing process of the high-temperature and high-pressure jet overflow dyeing machine.
This article discusses the operating points, causes and prevention methods of common problems in the dyeing processing of polyester filament, mid-length and interwoven wool-like fabrics in high-temperature and high-pressure jet overflow dyeing machines. Summarized as follows.
1. Operational points
1.1 Preparation before entering the machine
Check whether the machine is clean, whether the tools are fully prepared, whether all instruments, electrical appliances and machinery are complete, whether the rubber rings are intact; check whether the gray fabric is consistent with the plan, and whether the process card is consistent with the plan. The cylinder numbers match; when the gray cloth enters the machine, push the cart stacking the gray cloth to the cloth inlet of the machine cylinder, and then discharge water into the machine to the predetermined water level; check whether the machine cylinder mouth, the cloth feeding rack and the edges of the gray cloth cart are smooth and clean , cloth can be fed only when it is confirmed that it meets the requirements.
1.2 Operation when gray cloth enters the machine
Place the gray cloth head with Tie a slip knot on the lead rope in the cylinder, hold the gray cloth with one hand, and press the main pump and lifting motor with the other hand; hold the gray cloth with both hands to prevent it from being stained by mopping the floor; during the cloth feeding process, scan the quality of the cloth surface with both eyes, and if any pre-inspection is found The oil stains, holes and contamination that were missed during the inspection should be recorded on the process card in time; after the cloth is fed, it should be flat, flat, neat and secure, with four needles at both ends and a needle density of 20-30 needles/10cm. Sew the beginning and end of the gray fabric.
1.3 Material chemical operation
Check the preparation according to the prescription list Whether the dyeing materials are accurate. When dispersing dyes are usually mixed with cold water (mixer stirs for about 20~30 minutes), dilute it with 40~45 °C warm water before use. Dissolve the dispersant and ammonium sulfate with warm water and mix well. Dissolve as needed.
In case of difficult-to-chemical dyes such as Disperse Red 3B and Yuhong S-2GFL, use alcohol or diluting powder solution to make a slurry, beat with cold water and stir evenly, and dilute with warm water.
When adding dyes, be sure to filter through a sieve. The small particles remaining in the sieve are dissolved with water and then filtered. The feeding sequence is to add acetic acid at about 40°C, run for a while, adjust the pH value to 5~6, then add dye, run for 10 minutes, and dye according to the predetermined temperature rise curve. If too much foam is found in the machine after feeding, defoaming agent should be added in time to avoid damaging the circulation pump, reducing the lift, or even causing the fabric to float.
1.4 Operations in the dyeing process
During dyeing, when heating Close the machine cover before use, and observe the operation of the gray fabric in the machine through the glass viewing hole at any time, and check whether there are any abnormal sounds and phenomena in various parts of the machine. At 50~60°C, disperse dyes dye slowly or hardly at all. Above 80°C, the dyeing speed accelerates. Therefore, the temperature should not rise too fast between 80 and 130°C.
Generally, graded heating and graded insulation are used to control the heating rate. This should be especially noted for red 3B, ruby S-2GFL, red S-BWGL, etc. that are prone to color stains. . During the cooling stage, the cooling rate should not be too fast to avoid the formation of wrinkle marks, chicken paw marks and other defects. The heating and cooling speed is generally based on the principle that the temperature change does not exceed 1-1.5 °C for each revolution of the fabric (referring to the main heating and cooling sections).
The dyeing bath ratio depends on the equipment model and structure, and is preferably 1:8~20. The principle of controlling the nozzle spray pressure is: when the fabric is put on the machine, the nozzle pressure can be larger, and when the operation is normal, the nozzle pressure can be smaller; the greater the thickness or weight of the fabric, the greater the nozzle pressure, and the larger the nozzle cross-section; Generally, the ratio of the cross-section diameter of the rope-like fabric to the cross-section diameter of the nozzle is 9:10. When cooling down, it is strictly prohibited to inject cold water into the machine to directly force the cooling when the temperature is high.
1.5 Color matching operation
After the fabric is dyed, it should be cooled to 85°c (exhaust the steam. Remove the lid only after exhausting the steam. 70-80°c. Turn off the lifting motor, touch the head with a hook, and cut the sample within 10cm of the seam. The size of the cut sample is 6cm, about 4cm wide. . Wrap the sample cloth with a cloth on the steam pipe and iron it to dry.
Blow steam to make it regain moisture, and check the color under the color matching light box. If you need to add color and correct it, you should immediately Add materials and heat up to 100°C (re-dyeing; if the color and light match, continue to cool down. After dyeing, light colors should only be washed with hot water. Medium and dark colors, especially dark colors, must be strengthened by reduction cleaning to improve the dyeing brightness and fastness of the fabric. degree. The reducing cleaning agent used should be melted and poured in from the feeding barrel, and should not be added directly through the operation window.
1.6 Clean the vat after dyeing
When the dyeing machine dyes dark colors and changes to light colors, brushing is required. Generally, 4-6kg of 98% caustic soda and 1-2kg of detergent are used for scrubbing. The liquid volume is 2000L, the temperature is 130°C, and the time is 60-90°C. When brushing, open all valves in each pipe to make the brush tank fluid flow smoothly. After the insulation is completed, drain the sewage at high temperature. When producing medium-long fiber fabrics, the filter screen should be brushed once per shift. ;Production of polyesterSpots
Dye spots and color spots are caused by dye agglomeration and oligomers in the dye bath.
Prevention methods:
See methods to prevent aggregation and elimination of oligomers.
2.8 Lining and abrasions
Caused by linting and abrasions The reason is that the diameter of the nozzle is too small, the cloth speed and the rotation speed of the cloth guide wheel are out of proportion, the gray cloth or semi-finished products are hit when transporting, and are scratched when opening the width.
Prevention method:
Select a nozzle of appropriate diameter according to the unit weight of the dye, so that the spray pressure is moderate, and the cloth speed should be consistent with the guide. The rotation speed of the cloth wheel is consistent. When transporting gray cloth or semi-finished products, handle it with care and use manual opening.
2.9 Elongation
The reason for elongation is the fabric capacity If it is too low, the transportation distance will be longer and the tension will increase. The liquid level of the dye liquor is set too high, thereby increasing the resistance between the water and the fabric.
Prevention methods:
Control a moderate volume of cloth and keep the liquid level as low as possible.
3. Repair measures for common defects
3.1 Dyeing Severe unevenness
When encountering serious unevenness in dyeing, you cannot use the migration property of the dye to correct it back and forth. You must decolorize before dyeing. If it is a light or medium color, it can be dyed into a dark or extremely dark color. Decolorization methods include oxidative decolorization and reduction decolorization, examples are as follows
(1) Example of oxidative decolorization prescription:
Sodium chlorite 2~5g/L, acetic acid (98%) 2~3g/L, methylnaphthalene or chlorobenzene 3~5g/L, start treatment at 30 °C, and heat up to 93°C, boiling for 60 minutes and washed with water. If necessary, use bleaching powder and acetic acid to bleach at boiling temperature.
(2) Example of reduction decolorization prescription:
Caustic soda ( Flake) (1g/L, insurance powder 5g/L, chlorobenzene 5g/L, nonionic active agent 2g/L, start processing at 30°C, heat to boiling at 30°C, heat preservation treatment for 60min, then wash with cold water and hot water .If the decolorization is not sufficient, process it again, or use the oxidative decolorization method again. Using the above method may damage the fabric’s feel, so try to avoid it.
3.2 Wrinkles and mild uneven dyeing
The wrinkle treatment method is to put the fabric back into the jet dyeing machine and heat it to a specific The original dyeing temperature is slightly higher, and then slowly cooled. For fabrics that are slightly unevenly dyed, the migration property of the dye is generally used for counterdying. The process flow is to start dyeing at 60°C, raise the temperature to 90°C in 15 minutes, and then Raise the temperature to 130°C for 40 minutes, keep it warm for 60 minutes, and then cool. The repair formula is X% disperse dye (confirmed after testing), leveling agent 1-2g/L, and adjust the pH value to 5~6 with a pH regulator. If When using dyes with poor migration properties, the dyeing temperature should be increased to 135~140°C, but this must be done on the premise that the mechanical properties are acceptable and the feel of the fabric is not affected.
3.3 Dyeing oil spots
To remove local oil spots or dead oil spots in small batches, non-ionic detergents and carbon tetrachloride are usually used , gasoline and other organic solvents, use a spray gun to remove it and manually scrub, and then wash the fabric.
To remove large-area oil spots, use degreasers and non-ionic detergents. 2-3g/L, treat at 100°C for 20min, or use 2~3g/L each of degreasing agent and non-ionic detergent, high-temperature dispersant 1-2g/L, treat at 130°C for 20min. It is difficult to remove For oil spots, you can consider dyeing them into colors with better coverage, such as dark royal blue or black. If necessary, you can consider stripping and re-dying.
4 Energy-saving methods
(1) Reduce heat loss, such as using composite silicic acid Use salt insulation material to cover the dyeing machine and insulate it.
(2) Reuse the steam condensate. For example, connect the water trap outlet to the return pipe and lead it back to the boiler’s low water tank. Use. Steam releases heat and condenses. Before being discharged from the steam trap, the temperature of the condensate water is equal to the steam temperature. If the return water pipe is properly insulated, the condensate water flowing back to the low water tank of the boiler can reach more than %/0. The condensate water is clean distilled water. Reuse in the boiler does not require water treatment, eliminating water treatment costs, increasing the boiler inlet water temperature and reducing fuel consumption.</p
