Color light control technology in dyeing
1. Causes of color light deviation
1. Different batches of pre-processed semi-finished fabrics have differences in fiber properties, whiteness, wool effect, etc., which will cause color and light deviations in dyed fabrics.
2. There are differences between dyeing materials from different manufacturers or different batches of the same manufacturer, causing color differences.
3. Improper selection of color matching dyes, failure to follow the principles of same color matching, near color matching, and less color matching, leads to poor dyeing synchronization, which reduces color reproducibility and causes dyeing shade deviation.
4. Improper control of dyeing process conditions is the main cause of color deviation.
① Dyeing temperature is a key factor that affects the color light. For example, reactive dyes are very sensitive to dyeing temperature. If the dyeing temperature is high, the balance of X-GN and X-BR will be affected. Compared with other dyes, the dyeing percentage is relatively increased, while X-3B and X-2B are relatively reduced, resulting in a deviation in the color light.
② Fluctuations in the pH value of the dye bath mainly affect the fixation rate of reactive dyes, and the color light of some disperse dyes containing ester groups, amide groups, cyano groups, etc. when dyed at high temperatures.
③The fluctuation of liquor ratio in dip dyeing affects the reproducibility of color light. Reactive dye dyeing is more obvious. Generally, the smaller the liquor ratio, the higher the color yield.
④Influence of post-dyeing treatment: Peracid oxidation, soaping, whitening, resin finishing and other processes after fabric dyeing have an impact on the shade of dyed fabrics.
In addition, dyeing materials and auxiliaries may be stored for too long or be affected by water vapor, acidity, alkalinity, oxidizing and reducing gases in the air, which may lead to dyeing color differences. Measurement errors, dyeing equipment, poor pipe cleaning, etc. can also cause certain color differences.
2. Shade repair techniques and methods
When dyeing fabrics When the color light does not meet the requirements, the color light needs to be repaired to improve product quality and reduce production costs. There are two main categories of shade restoration methods: non-dye shade restoration and dye overlay restoration.
1. Non-dye color light repair:
This method is easy to operate, low cost and good quality.
① Wash with water. This method is suitable for repairing the color of dyed fabrics that are slightly darker, have more floating colors, and have poor water and soap washing fastness. It is the simplest method for repair. Floating colors can be removed by washing with water to achieve the purpose of correcting the seemingly light color. Whether this method can be applied, generally before color correction, you should check whether the soaping fastness in the physical test and the color change after soaping are consistent with the color correction direction. If they are consistent, this method can be used. In addition, master the color change characteristics of individual dyes during washing and soaping, which can be used in color correction. For example: when reactive yellow and blue dyes are mixed with green dyes, in view of the characteristics of reactive emerald blue KNG and reactive emerald blue KGL that are easy to fade when washed and soaped, the color light deviation after green dyeing can be improved by water washing to improve the yellow light of the dyed finished fabric. The purpose of color correction can be achieved.
②Alkaline washing. This method is suitable for color repair of alkali-sensitive dyes. Many reactive dyes can be used. For example, if the color of dyed cloth using reactive black KN-B is bluish, it can be flat-washed by rolling an appropriate amount of caustic soda. This method can achieve the purpose of removing blue light and making it lighter.
Not all stains can be repaired using this method. For those dyed fabrics that are dark in color, dull in color or still do not meet the standard after being lightened, they can only be repaired by over-dying, stripping and re-dying, or changing to a darker color.
2. Dye registration, back-dyeing and repair
When applying this method for repair, you should try to choose a process that is easy to operate, low-cost and of good quality.
① When the dyed cloth sample is much lighter in color, but the hue is basically the same, the original prescription can be used and the dosage of the prescription can be determined according to the number of shades. And use the original process for color registration.
② There are fewer light shades, and the direct dye process can be used for color registration.
③When the color depth is close but the hue is wrong, use the principle of matching what is missing.
④ If the color is darker, but within the color correction range, the color should be stripped first and then overdyed and repaired.
Examples of common stripping processes and techniques are as follows:
Sulfur dye dyeing fabrics can achieve satisfactory results through the sodium hypochlorite method, and reactive dyes Dyeing fabrics can be stripped using the insurance value method or the sodium chlorate method, but the insurance powder method is not very satisfactory for stripping phthalocyanine structural dyes such as emerald blue KN-G. If you use the two methods one after another, you can achieve satisfactory results. The two methods are as follows:
① Insurance powder method: insurance powder 5g/L, caustic soda (360Cbe’) 15Ml/L, liquor ratio 1:20~30, temperature T=40 ~900C, time=40min.
② Sodium hypochlorite method: effective chlorine 5g/L, pH value 11, liquor ratio 1:20~30, temperature T = room temperature, time = 30min, and then washed twice – —Pickling (acetic acid) dechlorination.
③If the color is dark and cannot be repaired, it can only be changed to a darker color.
3. Precautions for color light repair
1. When using direct dyes for repair, the dosage should generally be controlled below 1g/L to avoid affecting the dye fastness of the finished fabric after repair.
2. When repairing the color, you should not only consider that the color conforms to the standard sample, but also pay attention to the strength, width, brightness of the color and dye fastness of the fabric after repair, which must all meet the standards. </p
