What should be paid attention to in the pretreatment of nylon?

1. Nylon fabric needs to be washed before setting

Normally dyeing nylon and spandex fabrics requires washing before setting, because the content of spandex is high, and the relative amount of silicone oil contained in it is relatively high (the content of silicone oil in spandex can generally reach more than 8%). If the silicone oil is not removed before setting, Then, when the embryo is at a high temperature, the silicone oil will be cross-linked and adsorbed on the nylon yarn, which will seriously hinder the dyeing of the acidic materials during dyeing, thereby forming dyed flowers.

a. Generally, dry-cleaning machine (perchloroethylene used as extractant) is used for airtight degreasing. This is a better method, and the removal efficiency of silicone oil is high;

b. Second, the open-width washing machine will be used, the number of feeding tanks and washing tanks can be adjusted, degreasing agent and chelating dispersant are added, each tank needs to be overflowed and drained, and the total water consumption is controlled at 1:40-1 ：60. Generally, the degreasing efficiency is only 30%-40%, but it can make the oil content of the cloth more uniform and improve the dyeing. It is important to pay attention to the choice of degreasing agent and dispersant to prevent the silicone oil from demulsification and staining. Leukoplakia is formed when;

c. Third, the beam cylinder or JET cylinder will be used to remove the oil first (including some indefinite embryos, directly drop the tank to remove the oil and dye), the oil removal efficiency will be higher, but it should be noted that the cloth surface is problematic. If there is no pre-shrinking, directly drop the dye tank to remove the oil. After dyeing, creases and chicken claw marks will easily appear on the cloth surface. It is recommended to wash it with open width (phase dye pre-shrink to relieve stress), and then drop the tank to remove the oil;

2. The high temperature pre-determined embryo affects the dyeing

Nylon fabric, under high temperature conditions, the terminal amino group is very easy to be oxidized (acid coloring group), if the nylon high temperature anti-yellowing protective agent 190°C and 193°C are not added, it will greatly absorb the color of subsequent dyeing. As a result, nylon high-temperature anti-yellowing agent (expensive) must be added when setting the embryo, and it is usually recommended to use LANXESS (Bayer) GR 25-40g/l.

A straightforward mention is the issue of yarn splitting after purchase. We have found that often after a batch of yarn comes back, one or two yarns are always colored differently from other yarns, including Korea Hyosung, Asahi Kasei, Toray and DuPont yarns. In the early stage of bulk weaving, it is necessary to test yarns to separate the yellow and white yarns and dark and light yarns. Because of the slight difference in color absorption of these yarns, when the embryo is set at high temperature, it will appear horizontal and straight in the final dyeing like a triode;

Sometimes the storage conditions of the yarn count will also cause the difference in the color absorption of the nylon yarn, so the storage of the nylon yarn is very important.