Modal fiber is a new generation of regenerated cellulose fiber with high wet modulus made by spinning pulp from European beech. It has good moisture absorption and the production process is clean and non-toxic, with good environmental performance. In recent years, the dyeing and finishing of Modal knitted fabrics in China has gradually increased. However, technical problems such as color flowers, color spots, creases, holes, and easy pilling on the surface of Modal knitted fabrics during dyeing and finishing have seriously affected the quality of the fabric and reduced the grade of knitted garments. The following are effective measures to solve these problems.
Boiling and Bleaching
If Modal knitted fabrics are used for dyeing dark colors, only boiling is needed during pretreatment to remove the oil and wax from spinning and weaving process. If used for dyeing bright colors, high whiteness is required, and the boiling and bleaching process can be used by adding hydrogen peroxide to the boiling bath. Modal fiber is prone to creases and holes, so the boiling and bleaching process conditions should be milder than cotton knitted fabrics, usually using weak alkali pure alkali. In order to achieve better results, anti-wrinkle agent LBH and anti-pilling agent should be added to the boiling and bleaching bath, and the temperature should be raised slowly. After the boiling and bleaching is completed, it should be naturally cooled to 70℃ before washing.
Modal knitted fabrics are generally dyed with reactive dyes, which are prone to color flowers and color spots. Three measures can be taken to solve the above problems. Firstly, add an appropriate amount of refined salt or sodium carbonate to the dyeing vat, and then fully turn the fabric in a neutral salt bath before slowly adding the dye in portions, so that the cellulose slowly contacts the dye in the neutral salt bath to maintain a mild and balanced dyeing rate, avoiding color flowers and color spots. Secondly, select dyes with good reproducibility, compatibility, and even dyeing, and with moderate directness to Modal fiber. Taking into account factors such as cost-effectiveness, the EF type dye from Shanghai Dyestuff Chemical Factory can be selected, which greatly reduces the repair rate of Modal knitted fabrics and solves the problem of difficult repairs to some extent. Thirdly, use the overflow jet dyeing machine from Lisheng Company in Hong Kong for dyeing to ensure the quality of the dyed fabric.
The level of softening technology and the choice of softener directly affect the hand feel, good drape and luster of the fabric. After using amino silicone oil finishing agent, the hand feel is smoother and fuller.
The hot air stenter machine is used for sizing. The optimal sizing temperature for Modal knitted fabrics is 150-155℃, and for Modal knitted fabrics containing spandex, the optimal sizing temperature is 175-180℃, with a machine speed of 15-20r/min and an overfeed of 10-20%. The sized Modal knitted fabric is dimensionally stable and has a better hand feel.