Why do color stains always appear when cotton reactive dyeing in light colors?

Therefore, color difference is closely related to the performance of dyes and the compatibility between dyes, as well as to the quality of the fabric before dyeing and the rationality of the process conditions.

01.Pre processing
The purpose of pre-treatment is to improve the wool effect and whiteness of fabrics, in order to facilitate the uniform and rapid dyeing of fibers with dyes. By designing the feeding sequence, time, feeding method, and washing process reasonably, uniform capillary effect, whiteness, pH value, etc. can be obtained.

Due to the fact that most two or three color combinations are prone to color differences, analyzing the compatibility between dyes is of great significance in reducing color differences. Dyes can be preliminarily screened through the infiltration circle experiment method, and dyes with similar lifting power can be selected. In addition, whether the dye uptake curves of the blended dyes are similar or not also has a certain impact on color difference. Dyes with similar uptake curves have better compatibility.

03.Feeding and heating curve
The dyeing process of reactive dyes is divided into three stages: adsorption, diffusion, and fixation.
A reasonable dyeing process should have the following characteristics:
① Can slow down the initial dyeing rate of reactive dyes.
② Capable of achieving complete effects in different dyeing stages, without the phenomenon of two processes balancing each other
③ The changes in dyeing and bathing conditions are mild, gradual, and relatively not severe
In actual production, a comparison was made between the following two processes, and the results showed that the improved dyeing process two can improve the dyeing effect of the fabric surface and reduce color difference. By appropriately extending the feeding time, adding alkali in batches, and increasing the gradient of the addition amount, the generation of color difference can be reduced to a certain extent.

04.Dyeing equipment
Most pure cotton knitted fabrics are dyed using overflow jet rope dyeing machines. The main pump flow rate and nozzle pressure of most dyeing machines are adjustable, and the fabric speed of each tube can be independently controlled. Therefore, the flow rate, pressure, and fabric speed can be adjusted according to the structural characteristics of different fabrics (such as thin and thick, tight and sparse, and the length and short of each tube of fabric) to form the best dyeing conditions.
Due to the fact that the circulation speed of dye solution in the dyeing machine determines the contact frequency between dye molecules and cotton fibers, a higher contact frequency is more conducive to even dyeing. Therefore, accelerating the circulation speed of fabric in the dyeing machine, increasing the flow rate of the main pump, and increasing the nozzle pressure can to some extent reduce the generation of color difference. However, these process parameters cannot be infinitely increased and will to some extent damage the strength of the fabric. It is necessary to explore the best binding point in practice in order to obtain a suitable process.

05.Dyeing aids
1. Leveling agent
When dyeing light colors, a certain amount of leveling agent needs to be used to achieve uniform dyeing; When dyeing dark colors, there is no need to add a leveling agent. In production, three color matching often uses one dye as the base color (accounting for 80% to 90% of the total dye amount), and the other two dyes as auxiliary colors (accounting for 10% to 20% of the total dye amount).
If the primary color is removed, the other two dyes are actually light colored, so in some cases
The use of a certain proportion of leveling agent in colors with color differences can help reduce color differences. (The leveling agent here refers to traditional polyoxyethylene ether structured surfactants, which have affinity for reactive dyes and have certain permeability, slow dyeing, and leveling properties.)
2. Dispersant
Dispersants are mainly used to evenly disperse the dye molecules in the dyeing solution, in order to form a balanced dyeing bath. Liquid reactive dye leveling agents are mostly a combination of leveling agents and dispersants, and attention should be paid to their leveling and dispersing effects during use.
3. Cosolvent
Some reactive dyes with relatively high molecular weight, such as Cuilan, are difficult to dissolve and dye. Therefore, an appropriate amount of co solvent (such as urea) needs to be added during the dyeing process. In this way, the dye molecules can be better dissolved in the dyeing bath and the fibers can swell, facilitating the penetration of dye molecules into the interior of the fibers and achieving the goal of even dyeing.
4. Anti wrinkle agents and fiber protectants
Due to the characteristic of rope like dyeing of knitted fabrics, some wrinkles are inevitably formed during the pre-treatment and dyeing process. Adding anti wrinkle agents or fiber protectors can improve the texture and appearance of the fabric.

Quick Links:

Reactive dyes products:https://skygroupchem.com/product/skyzol-reactive-dyes/
Products Series of Auxiliaries:https://skygroupchem.com/products/textile-auxiliaries-products/
Dyes Products:https://skygroupchem.com/products/dyes-products/
Agent Proudcts:https://skygroupchem.com/products/textile-auxiliaries-products/
Textile solutions:https://skygroupchem.com/solutions/
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