Causes of shading during dyeing process

Dye properties

Before fabric dyeing, you must first color-match proofing. There are two basic methods for selecting dyes when proofing: one is to choose a dye that is similar to the color you want to dye, and then add a small amount of other dyes to adjust its color; the other method is to use Three primary color matching, this method can spell out most colors and is one of the main material selection methods for dyeing fabrics. However, too many types of dyes are used, which will affect the color, depth and brightness of the fabric. If the color and light of the fabric changes greatly after dyeing, it will cause the original color difference of the fabric, that is, it will not match the sample.

Some dyes have thermal denaturation, that is, high temperatures will cause discoloration or shading changes in dyed fabrics. Reactive dyes and Shihlin dyes are more obviously denatured by heat, and it takes a long time to return to normal color. Some dyes may even take more than ten hours or longer. For example, general green dyes tend to emit blue light when heated and tend to yellow light when cooled; while Shilinlian IR rays tend to be reddish when heated and blue when cooled. This will cause the color of the dyed fabric to be unstable or difficult to determine the color and contrast, affecting the pattern of the fabric and easily causing color difference.

Dye liquor preparation

The preparation of dye liquor consists of weighing, grinding and chemical mixing. The accuracy of weighing and chemical mixing when preparing dye liquor, as well as the standardization of abrasive and chemical mixing operations, have a very obvious impact on the original color difference and front and back color difference of the fabric. Such as equipment errors, errors in the use of weighing equipment and instruments, operational errors in weighing materials, abrasives, and chemical materials, errors caused by inconsistent moisture regain of dyes, insufficient dye strength, and different production batch numbers of dyes used in the same order. etc., will cause color changes and chromatic aberration of dyed fabrics.

Fluctuations in process parameters

During the padding process of fabrics in the dyeing bath, due to the large differences in the directivity of each dye in the dyeing bath to the fabric, after reaching dynamic equilibrium, the dye concentration in the working solution will be very different from the initial concentration. In actual production, before the fabric is padded with dye, that is, before the initial start-up, the dye liquor is often thickened (the suspended dye liquor is concentrated by 10%) or the dye liquor is diluted with different dilution coefficients according to the dye (aqueous solution). However, in actual production, the color difference of dyed cloth will still be caused due to unstable process parameters.

The fluctuation of the process conditions and parameters of the hot-melt dyeing machine and the color soaping machine directly affects the color difference of the dyed fabric. If the vehicle speed is unstable, the dynamic balance of the dye liquor will be disrupted, causing the color light of the fabric to change after dyeing, resulting in color difference between the front and back. During the padding process of the fabric, the changes and fluctuations of the air pressure and oil pressure of the uniform padding car will cause the left, middle and right padding rates of the dyed fabric to be inconsistent, resulting in color differences between the left, middle and right sides of the dyed fabric, and in severe cases, It causes obvious color difference between the front and back of the dyed fabric. In addition, the temperature and air volume of the infrared and hot air drying chambers are uneven. If the fabric is quickly dried after color rolling, it will cause migration, resulting in left, center and right color differences in the fabric or uneven cloth surface.

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