I. Pretreatment
1. Blanching/Bleaching:
Add a lubricant (such as a bleaching agent) to reduce fabric friction and prevent creases, especially important for thin cotton fabrics under 150 grams.
Place the sewn fabric roll into the dyeing vat, adding auxiliaries according to the weight, ensuring even penetration.
2. Washing and Neutralization:
Residual auxiliaries are removed by cooling water washing using CCR.
Residual alkali is neutralized with acetic acid to adjust the pH value.
II. Dyeing Stage
1. Feeding and Heating:
The dye must be thoroughly stirred in the auxiliary vat and completely dissolved before being added to the main vat.
Heating must be strictly controlled: reactive dyes should be maintained at 60℃, and polyester at 125℃ or higher, with a temperature increase of no more than 0.5℃ per minute.
It is recommended to install a camera on the fabric conveyor pipe to monitor fabric uniformity in real time.
2. Circulation and Penetration:
The fabric enters the dye bath in a rope-like form through a guide tube, with approximately 2/3 submerged in the dye liquor. The remaining fabric floats on the surface and circulates, with each settling period lasting 3-4 minutes.
Segmented temperature control is employed. Reactive dyes require low-temperature dyeing at 60℃, while polyester requires high-temperature, high-pressure treatment at 125-130℃.
III. Post-treatment
1. Color Fixing:
Color fixing at 80℃ for 20 minutes improves colorfastness.
Cotton fabric requires two consecutive hot water baths: first neutralization with acetic acid, then boiling twice in 95℃ alkaline water.
2. Washing and Soaping:
Residual liquor is quickly removed using the overflow washing function.
Acid washing and two soaping washes are performed (heated water from the auxiliary tank), followed by a final hot water wash.
IV. Key Control Points
Temperature Gradient: Precise control is required to avoid issues such as uneven color distribution and "chicken claw" marks.
Liquor Ratio: High-temperature, high-pressure type liquor ratio 1:5-1:10; room-temperature type liquor ratio even lower.
Equipment Selection: Pipeline-type high-temperature, high-pressure presses have a 20% higher loading capacity and are suitable for synthetic fiber fabrics; room-temperature types are suitable for natural fibers such as cotton and linen.
V. Common Problems and Solutions
Color Variation: Check if the dye has fully dissolved and if the temperature rise is too rapid.
Chicken Claw Marks: Ensure sufficient lubricant is added to reduce fabric friction.
Straight Stripe Dyeing: Check if the nozzle gap is uniform and if the fabric speed is stable.
