Reactive dyes have good color fastness, complete chromatography, and bright colors. They are widely used in dyeing pure cotton knitted fabrics. In production, the probability of color difference in dark colors (black, dark gray, navy blue, coffee, etc.) is greater than that of light colors; the probability of color difference in three-color combinations is greater than that of two-color combinations or single colors.
Therefore, color difference is closely related to the performance of dyes and the compatibility between dyes. It is also related to the quality of the fabric before dyeing and the rationality of the process conditions.
1 Pre-treatment
The purpose of pre-treatment is to improve the fabric The wool effect and whiteness are favorable for dyeing the fiber evenly and quickly. Through reasonable design of cloth feeding sequence, time, feeding method and washing process, uniform wool effect, whiteness, PH value, etc. can be obtained.
2 dyes
Since most of the two or three colors are Color difference is easy to occur, so analyzing the compatibility between dyes is of great significance to reducing color difference. The dyes can be initially screened through the percolation circle test method and dyes with similar lifting power can be selected. In addition, whether the dye uptake curves of the dyes are similar or not will also have a certain impact on the color difference. Dyes with similar dye uptake curves have better compatibility.
3 Feeding and heating curve
The reactive dye dyeing process is divided into three stages: adsorption, diffusion, and fixation.
4 Dyeing equipment
Most pure cotton knitted fabrics are dyed using Overflow jet rope dyeing machine. The main pump flow rate and nozzle pressure of most dyeing machines are adjustable, and the cloth speed of each tube can be controlled independently. Therefore, according to the structural characteristics of different fabrics (such as thin and thick, tight and sparse, the length and short of each tube of cloth), Adjust the flow rate, pressure and fabric speed to form optimal dyeing conditions.
Since the circulation speed of the dye liquor in the dyeing machine determines the contact frequency between the dye molecules and the cotton fibers, the higher the contact frequency, the more conducive to leveling dyeing. Therefore, the speed of the fabric in the dyeing machine must be accelerated. The speed of internal circulation, increasing the flow rate of the main pump, and increasing the nozzle pressure can all reduce the occurrence of color difference to a certain extent. However, these process parameters cannot be improved indefinitely, and will damage the strength of the fabric to a certain extent. It is necessary to find an optimal combination point in practice to obtain a suitable process.
5 Dyeing auxiliaries
1. Leveling agent
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When dyeing light colors, you need to use a certain leveling agent to achieve uniform dyeing; when dyeing dark colors, you do not need to add leveling agents. In production, three-color combinations often use one dye as the base color (accounting for 80% to 90% of the total dye amount), and the other two dyes are auxiliary colors (accounting for 10% to 20% of the total dye amount).
If the base color is removed, the other two dyes are actually used in light colors. Therefore, in some colors that are prone to color difference, a certain proportion of leveling agent is used to reduce color difference. is helpful. (The leveling agent here refers to the traditional polyoxyethylene ether structural surfactant, which has affinity for reactive dyes and has certain permeability, slow dyeing, and leveling properties)
2. Dispersant
The dispersant mainly disperses the dye molecules in the dye solution evenly to facilitate the formation of A balanced dye bath. Liquid reactive dye leveling agents are mostly a combination of leveling agent and dispersing agent. During use, attention should be paid to the leveling and dispersing effects.
3. Co-solvent
Some relative molecular masses of Cuilan and others Larger reactive dyes are more difficult to dissolve and dye. An appropriate amount of co-solvent (such as urea) must be added during the dyeing process. In this way, the dye molecules can be better dissolved in the dye bath and the fiber can be swelled to facilitate the penetration of the dye molecules into the interior of the fiber to achieve leveling dyeing.
4. Anti-wrinkle agent and fiber protective agent
Due to knitting Due to the characteristics of rope-like dyeing, the fabric will inevitably form some wrinkles during the pre-treatment and dyeing process. Adding anti-wrinkle agent or fiber protective agent can improve the feel and appearance of the cloth. </p
