Viscose Filament Skein Dyeing Process Technology

When viscose filament hank dyes, the color difference is easy to occur. The reasons are as follows:

1 The fiber surface has a longitudinal groove or a multi-page gap, so the hygroscopicity is strong. During the entire wet process (pretreatment and dyeing), the yarn morphology is changed, and the self-weight is increased, which directly affects the wet processing effect.

2 Viscose fibers, especially the amorphous and crystalline regions of ordinary viscose rayon are irregular, which are related to raw materials and spinning process;

3 The viscose fiber, especially silk and yarn, has not wide mechanical adaptability to pretreatment dyeing. Practice has proved that the spray-type dyeing machine is ideal.

4 viscose silk is divided into ordinary silk and strong silk, they are all light. Due to the limitation of the application of the filament, in order to facilitate the spinning and improve the fiber performance, a matting agent (TiO2) is added to the spinning and is smooth, soft, moldproof, defoaming, antistatic, antioxidation, etc. Surfactants are used to make no-gloss and semi-glossy threads. Since the gloss of the silk itself is different, there is also a difference in the degree of refraction of the light. Therefore, to overcome the color difference of the hank yarn, first of all, the physical and chemical properties of the viscose rayon must have a certain understanding.

Second, pay attention to the following three points when dyeing:

First, strengthen the pre-treatment to promote the expansion of the fiber and thoroughly remove the additives attached to the surface of the fiber so that the yarn basically meets the dyeing requirements. The following process is recommended:

Prescription (g/L)

NaOH (36°B) 2-5

Na2CO3 2-4

Scouring agent HS-120A (Wuxi) 3-5

Na2S2O4 0.5-1

Process conditions (spray dyeing machine)

Bath ratio 1:10-15

Holding temperature (°C) 95-98

Holding time (min) 60-90

To fully clean. Because NaOH is not easy to clean, after washing, it should be neutralized with 98% acetic acid 2mL/L (room temperature) to keep the fiber neutral and to be dyed. Practice has proved that this works well and has little effect on the strength of the fiber. The scouring agent HS-120A is an anionic/nonionic compound. The anionic part has a good net washing effect, and the nonionic partial emulsification, even dyeing and other properties are good. Since the pretreatment is performed at a relatively high temperature for a long period of time, and each batch of viscose rayon is very different, it must undergo a small test before it is put into production.

Second, choose dyes with better dye transfer and leveling. The initial dyeing rate of viscose fiber is very high, and the dye uptake rate is not high. The color flowers and chromatic aberration produced during the initial dyeing are not easy to correct, even if the dyeing time is prolonged. In terms of dye selection, it is generally preferable to select a water-soluble group (-SO2Na) in the direct and reactive dye molecular structure. The solubility of the dye should be large and the directness should be low. The purpose is to reduce the initial dyeing rate and improve the level dyeing. At the same time, the hardness of the water should not be too high. The dyeing dispersant and the good leveling agent can be added during dyeing. The dyeing agent should be added before adding the dye. After dyeing, the dye should be added after 10-15 minutes. In addition, the dyes should be selected for their close compatibility with the three primary colors.

Third, strictly control the process conditions, especially the heating rate, generally 1 °C/min. In addition, both direct dyes and reactive dyes should be added with an electrolyte (Na2SO4 or NaCl) as an accelerator, and the latter should be fixed with an alkali agent. Both electrolytes and alkalis are diluted and added in 3-4 increments to ensure dye uptake. In general, the dye uptake rate is low at the time of initial dyeing, and the dye uptake rate is not necessarily low at the end of dyeing, and can be achieved by extending the dyeing time. The time for heat preservation and dyeing of viscose (yarn) yarn is about 90 minutes, depending on the depth of dyeing. Because only transmissive, can get the correct color and good color fastness.