Acrylic / nylon interlaced stretch knitted fabric dyeing and finishing process

1 Fabric, dyeing and dyeing equipment

1.1 Fabric Specifications and Fiber Content

15.63 tex acrylic and 2.22 tex/7.78tex (20D/70D) nylon spandex knitted fabrics with 81.3% acrylic, 18.7% nylon wrap, 690 mm/100 stitch acrylic, nylon 280 mm/100 stitches. The grey fabric quality is 180 g/m2.

1.2 Dyeing agent additives

Non-ionic scouring agent C-24 (Shanghai Daxiang), non-ionic wrinkle-reducing agent AC (multi-spot), cationic dye Messillon Red SL (Huntsman), reactive dye red K-4BL (Clariant), Yuan Mingfen (Sichuan Meishan), pH regulator NC.1109 (Shanghai Bin), cationic soap lotion A-900 (Shanghai Daxiang), silicone oil softener MEX (more smell).

1.3 Dyeing and finishing equipment

HS-380 twister (Taipei Huangxin), 01090101 sewing machine (Guangdong United), DW-4T2 overflow dyeing machine (Hong Kong Lixin), GS5550 centrifugal dehydrator (Hong Kong Lixin), flat washer, NT- Model 503 Tumble Dryer (Japan Rising Sun), MB2000- 24/20 Twister (Wuxi Tianxu), C-540C Type Calender (Hong Kong Ericsson).

2 route analysis

Acrylic and polyamide fibers are hydrolyzed under hot and humid conditions for a long time. Fibers are damaged and their strength is reduced. In addition, nitrile-knitted stretch fabrics are prone to stretching in the straight direction during processing, and their recovery ability is weak, resulting in poor straight shrinkage. Therefore, it is necessary to use mild processing conditions as far as possible to reduce the tension during the processing of the grey fabric.

Process flow: Blank cloth cloth → joints → pretreatment → dyeing → dehydration → soft → drying → fluffing → light fabrics turning cloth → calendering.

2.1 rough turn cloth joints

The nitrile-knit interlaced elastic fabrics are mechanically affected during the dyeing and finishing process, causing damage to the surface of the grey fabric. Therefore, the fabric is turned over so that the frontal surface of the fabric is protected from fluffing. The design of the fabric must be fluffed without affecting the final quality of the fabric.

The cloth is used to turn the cloth, and the adjacent cloth heads are sewn with a sewing machine. The sewing head must be fastened to prevent breakage. To achieve uniform stitches, do not skip needles, and do not leak needles to prevent air leakage during downstream processing.

2.2 Pre-processing

The pre-treatment of the grey cloth is to remove the oil on the fiber. It must be cleaned, squeegeed thoroughly, and prevented from uneven dyeing.

Process flow: Add auxiliaries at 50 °C to the grey cloth, heat to 1.5 °C/min to 95 °C for 30 min, cool at 1 °C/min to 65 °C, drain and wash twice.

Process prescription:

Non-ionic scouring agent C- 24 1%

Nonionic anti-wrinkle agent AC 8%

Bath ratio 1:15

2.3 Staining

The nitrile-knit interlaced elastic fabrics are prone to color and wrinkles when dyed and severely stretched longitudinally. For this purpose, Lixin Overflow Dyeing Machine was selected for air blowing dyeing. The air is filled into the cloth between the drum and the dye bath, and the dyeing liquid carried on the cloth seals the air in the cloth so that the cloth bulges in a cylindrical shape to eliminate wrinkles. At the same time, the closed air gives the cloth a lateral tension, thereby reducing longitudinal stretching. The dye liquor penetrates evenly onto the cloth and is evenly colored.

Process flow: add additive at room temperature → add dye → cycle for 20 min → heat up to 70 °C at 1.5 °C/min → heat at 0.5 °C/min to 98 °C for 40 min → cool at 1 °C/min to 65 °C → drain → Wash once → Add A-900 (2%, 80 °C, 10 min) → Wash twice.

Process prescription:

Cationic dye Messillon Red SL 0.100%

Reactive Dye Red K-4BL 0.012%

Yuan Mingfen 5%

pH regulator NC.1109 1.5%

(The pH is adjusted to 4.5 to 5.0)

Nonionic anti-wrinkle agent AC 8%

Bath ratio 1:15

In order to shorten the high-temperature processing time and reduce the damage of the fabric, one-step one-bath dyeing was used. Acrylic dyes for acrylic fibers react with anionic dyes and anionic additives to produce precipitated or oily substances. To avoid this phenomenon, nylon is dyed with a K-type reactive dye, and anionic additives cannot be added to the dye bath. Because K-type reactive dyes can bind hydrogen ions in acidic conditions and neutralize their own negative charge, to avoid the formation of precipitation with the combination of cationic dye, so when dyeing, you must first add a pH adjuster to adjust the pH to 4.5~5.0 Then, K type reactive dye is added, and finally cationic dye is added.

The cationic dye-dyed acrylic fibers and the K-type reactive dye-dyed nylon are dyed under acidic conditions, and the color fastness is improved with the decrease of the pH value, but the pH is too low and can damage the nylon. Therefore, pH value of the pH adjuster NC.1109 that does not damage the nylon is used to adjust the pH value to 4.5 to 5.0, so that the fabric has the best color fastness.

Because Yuan Mingfen can be used to slow the dyeing under acidic conditions, it is used as a substitute for leveling agent. The non-ionic wrinkle-reducing agent AC can prevent wrinkles from forming on the grey fabric, and it can also act as a lubricant for the grey fabric so that the fabric can run smoothly during the dyeing process to avoid scratches.

When the temperature does not reach the glass transition temperature of acrylic fiber, the coloration rate is very low. After reaching the glass transition temperature, the coloration rate rapidly increases [2]. Therefore, it is necessary to strictly control the rate of temperature increase and decrease during dyeing to prevent uneven dyeing and wrinkle formation.

2.4 Dehydration soft

The grey cloth was dewatered after centrifugation. The speed of the dehydrator is 500 r/min, the dehydration time is 3 min, and the moisture content of the grey cloth is controlled at about 100%. If the dehydration is excessive, it is easy to produce wrinkles.

Soft treatment in the dyeing machine, easy to break emulsion of silicone oil softener, stained fabric, difficult to repair. Therefore, after the dehydration, put the wet cloth directly into the flat washer and soften it. The grey cloth was passed through the chute and silicone oil softener MEX 80 g/L was added to the trough. The fabrics are carried with softeners and are passed through two rubber rolls to squeeze and dehydrate the fabrics. The fabric is inflated between the rollers and the chute, and the softener carried by the fabric seals the air in the cloth so that the fabric bulges in a cylindrical shape, eliminates wrinkles, recoils straight, expands laterally, and improves the shrinkage of the fabric. During the softening process, care must be taken not to leak gas. When the cloth is fed, it must be over-fed and cannot be stretched. The additional amount of silicone oil softener should be controlled so that the fabric can be soft and uniform.

2.5 Dry fluffing

The soft gray cloth has a moisture content of about 80%, which is put into a tumble dryer and dried. The grey cloth rotates in the drum to straighten the shrinkage and improve the straight shrinkage of the grey fabric. Note that the drying temperature can not exceed 100 °C, otherwise it is easy to form wrinkles, and acrylic is easy to yellow. The soft gray fabric should be dried as soon as possible, and it cannot be stored for a long time, otherwise it may cause wind tracks.

After drying the grey fabric, use a lint raising machine to lift the hair twice, suck the net bristles, and the fabric is soft and plump.

2.6 roll cloth calendering

The cloth that has been finished is turned upside down so that the raising surface is inside, and then calendered.

Although the calendering will cause fluff to fall down, because it is fluffy, it will not affect the appearance of the grey cloth, and the fluff is turned to one side, which makes the hand feel smoother and is suitable for personal wear. Calendering also eliminates creases on the fabric and increases the dimensional stability and gloss of the fabric.

The drum temperature is 120 °C when calendered, overfeed 15%, and the speed is 12 m/min. The amount of steam should be enough to make the fabric fully wet and the grey cloth rolled to the specified width.

3 Conclusion

3.1 Knitted fabrics made of nitrile and jacquard have unique antibacterial properties. After being softened and fuzzed with silicon oil, the fabrics are soft and smooth, warm, breathable and comfortable to wear.

3.2 The processing of knitted fabrics made of nitrile and jacquard stretch should adopt mild conditions, short flow and low tension to prevent damage to the fabric and wrinkle.

3.3 One-step one-bath dyeing improves the quality of the grey fabric and production efficiency, saving energy and reducing consumption. The dyeing process should strictly control the rising and cooling rates to prevent uneven dyeing and wrinkle formation.

3.4 Be sure to blow air when soft and control the amount of silicone oil softener added to make it soft and even.