Process conditions are important factors affecting the color and levelness of dyed fabric, such as temperature, liquor ratio, PH value etc. Otherwise, it is easy to produce differences in shades of color and poor fastness.
1.    Control the initial dyeing temperature and heating rate
Temperature is an important factor in controlling dyeing. The temperature will affect the fiber expansion, dye properties (solubility, dispersion rate, dyeing rate, shade, etc.) and the auxiliary performance.

Polyamide is a thermoplastic fiber, when the temperature over 50℃, the swelling of fiber increases with increasing temperature. Especially 65-85℃, controlling the heating rate is the key to the polyamide dyeing. If it is not properly controlled, it will cause problems of fast coloring, poor transferability and difficult to re-dye.

2.    Determine the appropriate liquor ratio
Due to the limitations of the fabric dyeing machines, the sample liquor ratio will be larger than the large production, the large liquor ratio will reduce the dyeing rate, make the color difference.

The light weight of the taffeta liquor ratio is generally 1:50 and the heavy weight fabric is 1:20, which based on the fabric can be completely immersed in the dye solution.

3.    Control the PH value
The dyeing rate will increase with the decreasing PH value. 

When dyeing nylon with weak acid dyeing, the PH value of dyed light color is controlled at 6-7 (adjusted by ammonium acetate), and add the leveling agents to enhance the leveling and avoid the different dyeing shades and the PH value should not be too high, or the color light will be dim.

When dye the nylon PH value at 4-6 (adjusted by acetic acid and ammonium acetate) and adding acetic acid during the insulation process to reduce the PH value to promote the dyeing rate.

4.    Controlling the leveling agent selection and the amount.
Because nylon dyeing has poor leveling and coverage, should be added anionic or nonionic leveling agent, which anionic surfactant is the main component.
The anionic leveling agent dissociates into negative ions in the dyeing liquid and enters the fiber. Firstly, the nylon fiber dyeing has the limitation, during the dyeing process, the dyestuff is replaces by the temperature, which reduces the bonding speed between the dyestuff and fiber to achieve the leveling effect.
The non-ionic leveling agent is hydrogen-bonded with the dyestuff and decomposes during the dyeing process and is absorbed by the fiber.