Because reactive dyes have the advantages of excellent performance, complete color spectrum and bright shades, they have been widely used in medium and dark colors for many years. Now some light bright colors, light colors, including difficult to dye light colors such as light rice, light gray , Light stone color, etc. are increasingly replacing the traditional reduction and soluble vat dyes in the past. However, for a long time in these light-colored dyeings, many dyeing factories have habitually believed that the dyeing time is based on the color. Depending on the shade, the time for dyeing deep and thick colors should be long, the amount of additives should be large, and the additives should be added in batches. When dyeing light colors, the dyeing time can be short, the amount of additives can be small, and it can be added in batches or at once.
As a result, the phenomenon of color flower, color difference or color light inaccuracy occurs from time to time in dyeing. In fact, the reason for this phenomenon is precisely that it is controlled by this traditional concept, that is, the essential process points that need attention have been ignored. The following is correct This is a brief analysis and discussion for peer reference.
1. Determination of dyeing time
The dyeing time depends on the color depth. The dyeing time for light colors should be short. In fact, this is a misunderstanding. The dyeing time should not be determined by the depth of the dyed color or the amount of dye, but should be based on the performance of the dye itself. The dye uptake rate or absorption rate includes some dyeing characteristic values such as fixation rate and fixation rate. The dye will not increase the dyeing rate or speed up the fixation due to the light color, but according to its own performance, Speed and curve operation, if dyeing is completed in the sensitive time period of dyeing or fixation, it is easy to cause uneven dyeing and color difference. On the contrary, if the dyeing or fixation rate reaches equilibrium or saturation and then keeps stable for a period of time, the uniformity can be obtained. Dyeing, penetrating dyeing and stable shade to avoid the generation of chromatic aberration.
Therefore, the time for dark and light dyeing should be basically the same. According to experience, it can be controlled to add salt and heat for 20-30 minutes followed by dyeing and alkali to fix the color and then keep it for at least 30-40 minutes.
2. How to add auxiliarie
Because the amount of light-colored additives is small, it is not necessary to add them in batches like dark ones, but can be pumped in one time or quickly. In fact, this is a misunderstanding. The time or frequency of adding dyeing auxiliaries should not be determined by the number of auxiliaries, but by the function of the dye and auxiliaries and the rate and performance of the mutual chemical reaction. The lighter the color, the easier it is to discolor. The reason is that the dye is in Under the action of auxiliaries and temperature, the dye uptake speed and the reaction speed with cellulose anions become faster, causing adsorption and fixation on the fiber in a short time, resulting in uneven dyeing or color blur.
If the auxiliaries are still added in batches or multiple times, the dye uptake and the reaction with the fiber will be slower, and there will be no rapid or instantaneous dyeing phenomenon, so as to effectively avoid coloring, such as some special For difficult-to-dye light colors, the salt-alkali can be added in 2-3 batches. That is, 1/6, 2/6, 3/6 or 1/10, 3/10, 6/10, etc., and the interval time should also be controlled at least 10-15 minutes.
3. Other process requirements and points of attention
In the production of some difficult to dye light colors, in addition to the improvement of the above items, temperature, bath ratio and time are the three major elements of dyeing and need to be strictly controlled. It is recommended that the bath ratio should be as large as possible, and the speed should also be higher than that of conventional dyeing. It should be high, and the amount of the tank should not be too large. In addition, the post-treatment at the end of dyeing is also a factor that cannot be ignored that affects the shade and fastness. Of course, these are based on the correct dye selection and good quality of the semi-products.