When Acid Dyes Are Dyed With Cotton Fiber, What Are The Problems And How To Solve Them?

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Cause analysis: there are differences in chemical or physical characteristics of nylon fibers on fabrics.

1. The physical differences of yarn include the number of yarns, the number of fibers in the yarn or the fiber size. The difference between the ends of a single fiber in the yarn or the crimp of the ends of the fibers is different.

2, chemical differences originate from the difference in amino content of fibers. This difference may be caused by spinneret process, hot drawing process or filaments.

For example, the heterogeneity of the supramolecular structure produced during the processing of nylon fibers, such as the crystallinity and orientation difference of fibers, or the heterogeneity of core structure.

Terms of settlement:

1, strengthen the detection of grey cloth, and make different choices for light, white or white.

2. Choose dye with good coverage and levelling.

Disperse dyes have better coverage and levelling properties than acid dyes, and some disperse dyes can be selected.

Two. The color flowers caused by competition.

Cause analysis: the content of terminal amino group in nylon is low and the saturation value is low. When two or more than two dyestuffs are dyed together, the competition of dyeing position will happen.

If the dye has a great difference in dye uptake and affinity, the color of the fiber will vary greatly during different dyeing time, resulting in poor color difference and repeatability.

The solution is to select the dye dyeing curve with similar affinity, good compatibility and suitable series of dyes.

To master the dyeing properties of all kinds of dyes, the dye uptake, dye uptake, levelling, color fastness, and sensitivity to temperature and levelling agents should be considered comprehensively.

1, give full consideration to compatibility of dyes.

When using several dyes to dye, it is necessary to select suitable dyes and control the amount of dyes.

In general, the same series of dyes from the same company should be chosen as far as possible. Even if the dyes of different companies have to be selected, the dye should be similar to the dye, similar to the initial dye temperature, and the dye that is sensitive to temperature and levelling agent.

2, pay attention to the difference between dye size and sample dyeing.

Some dyestuffs do not compete in small sample dyeing, but they are completely exposed in large production.

For example, when producing lake green and peacock blue, there is a similar problem if acid blue and acid yellow are used.

This is due to the large molecular structure of acid turquoise blue, which is quite different from that of the acid yellow dye.

If we use acid green basket and acid green with yellow light, we will basically solve the competition dyeing problem.

Three. Coloured flowers and so on caused by process conditions.

Nylon dyeing is highly demanding.

Process conditions are important factors affecting the shade and levelness of dyed products, such as temperature and pH.

Unreasonable technology can easily produce defects such as poor leveling, color flowers, willow, color difference and poor fastness.

1, control the initial dyeing temperature and heating rate.

The influence of temperature is that nylon is a thermoplastic fiber.

Therefore, the dyeing rate of fiber has a great relationship with temperature, and the dyeing temperature must be higher than that of glass fiber (35~50 degree C).

Polyamide fibers begin to adsorb dyes at 40. With the increase of temperature, the dyeing rate is accelerated. The dyeing process can basically be finished at 100C, although the dyeing can be basically finished when the temperature is 100C. However, the continuous heating will help the dye migration and improve levelling.

However, if the heating rate is not well controlled, it is easy to cause uneven dyeing.

The influence of temperature on dyeing rate and dyeing rate is also different because of different dyes. The dyeing rate of levelling dyes increases with the increase of temperature. The dye uptake rate of cashmere dyes begins to increase rapidly with the increase of temperature after dyeing bath temperature is higher than 60 degrees C.

Especially in the temperature range of 65~85 C, controlling the heating rate is the key to the success or failure of nylon dyeing. If the control is not proper, it will cause rapid color change, poor migration and easy to repair.

If polyamide fiber is used to dye nylon, the initial dyeing temperature should be room temperature. In the temperature range of 65~85 C, strictly control the heating rate of 1C/min, add levelling agent, adopt step heating method, and then heat up to 95~98C, heat preservation 45~60min.

In addition, the dyeing properties of the fiber also changed with the heat treatment conditions before dyeing, and the dyeing rate of the fibers after dry heat setting decreased significantly.

2. Control pH value.

When dyeing nylon fiber, when the pH value of dye solution is relatively high, dyes are rarely dye up; when the pH value of dye solution reaches a certain value, dyes begin to dye up, and quickly reach saturation, and continue to reduce pH value at night. The dye uptake has not increased significantly. However, when pH is further reduced to 3, the dye uptake has increased dramatically, and super equivalent adsorption has occurred.

Polyamide fiber will also be hydrolyzed when it is dyed at very low pH value. Especially after super equivalent adsorption, the pH value of the fiber is lower than that in the solution, the hydrolysis speed is accelerated, more amino is generated after hydrolysis, the accessibility of the fiber increases, and more dyes can be adsorbed, thus making the dyeing irregularity easier.

Therefore, according to the actual situation, the pH value can be adjusted by light to reduce the phenomenon of colored flowers.

When weak acid dyes are used to dye nylon, the pH value of dyed light color is generally controlled at 6~7 (commonly used as ammonium acetate), and the amount of levelling agent is increased to enhance levelling and avoid dyeing. But pH value can not be too high, otherwise the color will be darkly darkened. The dyed dark color pH value is 4~6 (commonly used acetic acid and ammonium acetate), and add proper amount of acetic acid in the process of heat preservation to reduce pH value and promote dye dyeing.

3. Pay attention to the selection and dosage of levelling agents.

In view of the poor levelling property and poor coverage of nylon dyeing, a small amount of anionic or non-ionic levelling agents should be added to the dye bath, of which anionic surfactants are the main ones.

It can be used in dyeing with dyestuffs in the same bath or levelling agent.

The anionic levelling agent dissociates into negative ions in the dye bath, enters the fiber, first occupies the limited dye holder on the nylon fiber, and then gradually becomes replaced by the dye in the dyeing process with the increase of temperature, reducing the binding speed between the dye and the fiber and achieving the purpose of leveling dyeing. The non-ionic levelling agent combines with the dye in the dye bath to form hydrogen bonds, and then gradually decomposes and releases the dye in the dyeing process, and is adsorbed by the fiber.

The addition of levelling agent can obviously improve the levelling and dyeing ability, but with the increase of the concentration of auxiliaries, the dyeing rate decreases, and the exhaustion rate decreases, so the amount of levelling agent can not be too much.

Because leveling agent has a levelling effect in dyeing process, and also has a blocking effect.

Too much amount of levelling agent will reduce the dye uptake and increase the concentration of dyeing residue, resulting in poor color difference and repeatability.

In general, the amount of levelling agent used in light coloured dyeing is larger; when dyed dark, the amount of levelling agent is less.

Four. Yellowing

The slight yellowing phenomenon often occurs in the process of storage and pportation of nylon light colored fabric, which affects the appearance and quality of the plant.

Cause analysis: pollutants on plastic bags and BHT (Ding Ji hydroxy anisole) react with nylon, resulting in color variation, resulting in yellowing.

Solution: use anti phenol yellow agent to dip or dip.

Five, conclusion

In summary, the dyeing effect of polyamide fiber is affected by many factors. Therefore, in actual operation, the dyeing conditions should be selected according to the specific dyeing requirements, suitable dyes, auxiliaries, predefined technology and the optimum pH, temperature and time. Only these factors can be synthesized, and good leveling effect can be obtained.