Dyeing process of direct dye cellulose fiber
1. Dyeing method: dip dyeing, jig dyeing, pad dyeing
2. Dip (roll) dyeing process
(1) Process flow
Dip dyeing: chemical material → dip dyeing → washing (→fixing treatment) → dehydration → drying
Jig dyeing: chemical material → jig dyeing → washing (→fixing treatment) → rolling → drying
(2) Process conditions
Dyeing temperature: Category A: 70~80°C; Category B: 80~90°C; Category C: 90~100°C
Dyeing time: 30~60min (or 6~8 passes)
(3) Operation precautions
①When mixing materials, use hot soft water to adjust the slurry, then dilute with hot soft water, and add a wetting agent if necessary;
②Jig dyeing is to prevent head and tail color difference, the dye should be added in batches, the temperature is from high to low;
③In order to ensure uniform dyeing, the dye accelerator should be added after half of the dyeing time;
④ In order to improve the utilization rate of dyestuffs, continuous vat dyeing can be used. During continuous vat dyeing, the amount of dye is generally 75% of the initial vat and the amount of additives is 30% of the initial vat. 3. Pad dyeing process (1) Process flow
Padding liquid → steaming → washing → (fixing treatment) → drying
(2) Craft prescription
Dye 0.2~10 g/L Soda ash (or trisodium phosphate) 0.5~1.0 g/L Wetting agent 2~5g/L
(3) Process conditions padding method: two padding and two rolling;
Rolling liquid temperature: 40~60°C; Rolling liquid rate: 85% Steam temperature: 100~102°C;
Steaming time: 40~60 s
(4) Operation precautions
①The evenness of pad dyeing is poor, and levelling agent needs to be added;
② The cloth surface should be kept neutral (pH: 7~8.5), otherwise the shade will be affected;
③The padding tank should be small to keep the dye liquor fresh;
④ Use salt and a small amount of dye solution as a liquid seal when steaming to prevent the dye from falling off;
⑤At the beginning of driving, the padding tank should be diluted with water to prevent head deepness. The water conversion rate is generally about 25%. Water exchange rate = (water exchange volume / normal dye solution volume) × 100%
