A Few Words on the Dyeing & Finishing Process of Linen

Time of issue：2023-08-30 13:05:19

1. Pretreatment

1.1 The Pretreatment and Equipment for Ramee

Process: Singeing→Desizing→Boiling & Bleaching→Mercerizing

Singeing: Strengthen singeing. The double-jetting burner made by Chengdu Keda or the cyclone pre-mixing burner made by Jinan Fist Printing is the best choice for singeing. The flame temperature can reach above 1,350℃ and bring about high singeing quality.

Desizing: Desizing and boiling can be integrated for the thin type; and boiling after desizing is suitable for the thick and heavy type or ramie cotton fabrics. Full-width equipment including full-width steaming machine, R-Box, and double-layer under-surface crawler steaming machine is suitable. And the dosage of soda is generally 15～25g/L.

Bleaching: Chlorine bleaching or peroxide bleaching is applicable; and the whiteness can be promoted with acid rinsing added prior to bleaching.

Mercerizing: Clip mercerizing is generally adopted, and the J box or crawler box is also adopted for slack mercerizing. The small-lot intermittent pretreatment is adopted with time of 5～10 minutes and soda liquor concentration of 160～200g/L. The process of singeing, padding and batching up and soda boiling oxygen-bleaching can be adopted. Mercerizing is not suitable for fabric with light color.

1.2 Pretreatment for Linen Cloth

Process: Singeing (Clipping) →Desizing→Boiling & Bleaching→Mercerizing

Singeing: Singeing is generally carried out after clipping, and a gas singeing machine is adopted.

Desizing: The rope form or full-width processing mode can be adopted according to the purpose of the product. The rope form processing mode is suitable for thick fabric, while the full-width one is suitable for colored cloth. Soda boiling is usually carried out to boil the fabric evenly and thoroughly by equipment like the R-Box, J-Box, double-layer crawler box, and kier.

Bleaching: The chlorine-peroxide bleaching is usually adopted due to high lignin content. The steaming process is usually adopted for peroxide bleaching.

Mercerizing: Dyed cloth or printed cloth needs to be mercerized; and open bleached fabric can be bleached again without mercerizing.

2. Dyeing Process and Equipment

Due to its higher crystallinity, ramie and linen is more difficult to be dyed than cotton and is easier to corrugate with uneven dyeing. Therefore, dye stuff with high level dyeing property and higher dyeing temperature should be adopted.

Neutral and light color dyeing should adopt reactive dye stuff. Deep color dyeing should adopt reductive or liquid curing dye stuff. The applicable reactive dye stuff includes M type, ME type, ProcionH?E type, H?Exl type, SumifixSupra made by Sumitomo, and RH type and RM type made by Shanghai 8th Dye Stuff Plant.

The dyeing process can adopt continuous pad dyeing, jig dyeing or overflow spray. The full width mode is better for it can better prevent friction damage and stripe. Large package jig dyeing also has a bright prospect.

3. Afterfinish Process and Equipment

Special attention should be attached to the afterfinish for it is very import for the hand touch and style of linen.

3.1 Soft Finishing

Soft finishing can be carried out in a chemical or mechanical mode by a great variety of softening agents like amino modified silicone oil including SiliconAm made by Rihua and DC?108 and home-made TS-19 epoxy polyether modified silicone oil including UcarsilEPS，home-made CGF and 204 silicone oil.

The chemical soft finishing equipment can be the hot flue stenter or SST. The cross linking and fixation temperature of the silicone oil is preferred under 140℃.

The mechanical soft finishing equipment can be AIRO-1000 made by BIANCALANI or Tumble made by Ramisch, Germany. The dry or wet mode can be adopted according to varied requirements.

3.2 Pre-Shrinking Treatment

The pre-shrinking treatment capable of reducing the shrinkage of linen and improving hand touch can be carried out by a felt pre-shrinking machine with 20～30% of cloth face humidity and 0.3MPa or above of steam pressure. Foreign manufacturers of the pre-shrinking machine include Monforts, Morrison, etc.

3.3. Bio-Enzyme Treatment

The cellulose is partly hydrolyzed due to the specificity of the bio-enzyme and therefore the soft and lofty hand touch is obtained and the scratchiness of ramie fabric is also partly prevented. The determination data from the style tester verifies the same effect.

The enzymes in current use include CellusoftL made by NOVO, Denmark, and products from Sandoz, Taiwan and domestic manufacturers.

Appropriate Process Conditions:

pH4.5～5.5. Temperature: 45～55℃

Treatment time: 30～60 minutes

5% or below of decrement rate and 20% below of loss in strength

Applicable equipment: Overflow dyeing machine, garment dyeing machine, etc.

3.4 Anti-Crease Finishing

To eliminate linen’s shortcoming of easy crease, loose type preliminary drying resin finishing can be adopted. The finishing agent can be combined 2D resin and polyurethane resin, and the finishing equipment can be the short circle loose type preliminary drying stenter (SST).

4. Future Research Direction

4.1 Abbreviated System of the Linen Dyeing and Finishing Process

4.2 Impact of the Flax Pretreatment Conditions on the Color Fastness and Strength

4.3 Multi-Functional Finishing Technology for Linen, and the Afterfinish Technology of Water and Flame Resistance