Dark polyester-cotton blended fabric jet dyeing how to break the white point?

When dyeing the same fabric with the same pre-treatment, dark spots, such as dark green, dark blue, and black, tend to produce white spots, especially when the dispersion/activity two-bath dyeing method is used.

There are two possibilities to produce white spots: (1) the slurry is not completely depleted; (2) dead cotton is present on the raw cotton. The so-called "dead cotton", that is, the cotton bolls in the growth process due to incomplete development of the stiff cotton. Strictly speaking, reactive dyes cannot be dyed to death, whereas direct dyes can rely on van der Waals force to partially kill cotton. Therefore, the former is more obvious than the latter. Once this rickets occur, it is difficult to repair, especially after heat setting. To prevent the occurrence of white spots, first strengthen the pre-treatment. Because whether it is to remove the slurry on the fabric, or to remove dead cotton on the raw cotton, there is a very close relationship between the fabric pre-treatment.

The following are pre-treatment prescriptions and processing conditions for polyester-cotton blended fabrics.

Prescription/g·L-1(1)(2)

NaOH (flaky) 10 to 154 to 6

Na2CO3 2～3 2～3

Penetrant T1～2 1～2

H2O2(30%)3~5 3~5

Scouring agent 2~3-

Digestion enzyme 188-3~5

Process conditions:

Prescription (1) Room temperature feeding, heated to 100°C at 1.5°C/min, immersed in heat for 60-90 minutes, fully washed, until dyeing. Bath ratio 1:10 (same below). The prescription (1) is suitable for desizing.

Prescription (2) At room temperature, increase the temperature to 100°C at 1°C/min, incubate for 60 min in the heat, cool to 85°C, wash in warm water, change the bath, and add 0.3 g/L Na2S2O4 for about 15 min. The residual H2O2 was removed from the fabric, and finally, fully washed and allowed to be dyed. The prescription (2) is suitable for removing dead cotton.

After processing with the above two processes, the fabric is dyed with polyester or dispersion/direct bathing.

Practice has proved that through the above pretreatment, the removal rate of 19.4 tex × 19.4 tex 268 roots / 10cm × 268 roots / 10 cm plain and 29 tex × 29 tex 425 / 10 cm × 228 / 10 cm cotton twill fabrics It can reach 11.5%～13.0%, the gross effect can reach 10.5～12 cm/30min, and the whiteness value is about 70, which fully meets the dyeing requirements.

The cotton fabric dyed blue and black on the jigger, and there was basically no white spots. However, the following points need to be noted in production:

(1) H2O2 can remove some of the slurry and dead cotton, but the amount must be appropriate. If too much, combined with the amount of dead cotton on the raw cotton and more uneven, it will often make fabric holes (eyes), and even make the original cotton drop.

(2) The removal of pulp and dead cotton on the fabric mainly depends on the action of alkali agents and surfactants. In order for the agent to fully function in the treatment bath, penetrant T should be added. It not only helps to improve the dyeing caused by dead cotton, but also penetrates quickly, and is particularly suitable for high-strength and high-density fabrics and textiles with inferior quality of raw cotton.

(3) The scouring agent selects anion/nonionic compounding. It can effectively emulsify and disperse the impurities, dirt and oligomers that have been removed from the fibers, and at the same time, can inhibit the re-staining of these substances.

(4) The soda ash must be added to the pretreatment bath to act as a softener and a cleanser.

In the determination of dyeing prescriptions and processes, if the requirement for high color fastness, it is best to use two-bath dyeing of dispersion/reactive dyes. In order to overcome the defect of non-reactive ability of dead cotton and reactive dyes in raw cotton, it is advisable to add an appropriate amount of direct dye of similar shade in the soap boiling process in the dyeing process of reactive dyes because it has a certain degree of dyeing on the treated cotton. Sex. When implementing the process, note that:

(1) The soaping time of reactive dyes should be prolonged by approximately 10 minutes to ensure that the direct dyes added are sufficiently in contact with the unreacted dead cotton to increase the dye uptake.

(2) Due to the addition of direct dyes, the overall color fastness is reduced. Therefore, fabrics that have been thoroughly cleaned must be treated with a cationic fixing agent. In fact, in order to further improve the dyeing fastness of reactive dyes, especially the wet rubbing fastness, all companies are currently using additives such as fixing agents for post-treatment.

(3) If the dyed fabric still needs softener treatment, it is recommended that the fixation and softening are combined into one. Because most of the fixing agents are positively charged, the softeners are either cationic or non-ionic, and their use will not affect their respective effects.