Common defects and solutions for nylon dyeing

Nylon is the trade name of synthetic polyamide fiber, whose basic component is aliphatic polyamide connected by amide bond - NHC0. Nylon commonly used in textile fabrics include nylon 6 and nylon 66. nylon macromolecule mainly consists of three parts, namely, hydrophobic methylene part, hydrophilic amide group and amino and carboxyl groups at the end of the chain. Although the amino content of nylon is low, its molecular chain has a large number of methylene groups that can form van der Waals forces and hydrogen bonds with dyes, so nylon can be colored by strong van der Waals forces in addition to bonding with anionic dyes through ionic bonds. Although there are some small differences between nylon 6 and nylon 66 in terms of molecular structure and dyeing properties, their dyeing and finishing processes are the same.

Because of its good strength, excellent abrasion resistance, moisture absorption than polyester fiber, taking comfort than polyester clothing, nylon fiber has been widely used in clothing fabrics, high-grade underwear, sportswear and hiking clothing. Due to the development of the market and the progress of spinning technology, most of the nylon fabrics have increased the elastic fiber (spandex) to enhance the abrasion resistance and resilience of nylon fabrics, which increases the difficulty of dyeing and finishing nylon fabrics.

·Transverse bar

Cause Analysis：

Differences in the chemical or physical characteristics of nylon fibers on fabrics.

Solutions：

(1) Strengthen the detection of the blank fabric, and select for light color, native white or whitening if there are differences.

(2) Select dyestuff with good coverage and evenness. Disperse dyes have better coverage and evenness than acid dyes, so you can choose to add some disperse dyes.

·Paintstain of leather caused by the dip dye

 Cause Analysis:

The content of terminal amine in nylon is low and the saturation value is low, so when two or more dyes are dyed together, competition for dyeing position will occur, which is called the competition dyeing phenomenon. If the selected dyestuff has a large difference in dyeing rate and affinity, the dyed color of the fiber will be very different in different dyeing time, resulting in poor color difference and reproducibility of the size sample.

Solutions：

Select dyeing materials with similar dyeing curves and affinity, good compatibility, and suitable for the production machine. When choosing dyeing materials, we should consider the dyeing rate, dyeing curve, leveling property, color fastness property, and sensitivity to temperature and leveling agent, etc.

·Paintstain of leather caused by process conditions

Nylon dyeing is extremely demanding in terms of process. Process conditions are important factors that affect the color and evenness of the dyed products, such as temperature and pH value, etc. They affect the quality of the products.

1、Control the starting dyeing temperature and temperature rise rate.

2、Control the pH value.

3、Pay attention to the selection and dosage of Homogenizing stain.

Final thoughts

In summary, the dyeing effect of nylon fiber is affected by many factors, therefore, in actual operation, we have to choose suitable dyestuff, auxiliaries, predetermined type process and the best pH, temperature, time and other dyeing conditions according to the specific dyeing requirements, only when these factors are taken into account, we can get good even dyeing effect.