The characteristics of reactive dyes, S, E, R and F of dyes, the reaction mechanism of salt and alkali resistance of dyes with cellulose fiber and water. The main reasons of producing color spot and color flower were analyzed. The method to solve the problem of color spot and color flower in dyeing was put forward.
Reactive dyes play an important role in the dyeing of cellulose fibers. They are widely used in dip dyeing, pad dyeing, overflow dyeing and cold pad batch dyeing. They have bright color, good color fastness and simple process. They meet the environmental protection requirements of European Union oeko-text100. They are favored by the majority of dyeing workers, especially reactive brilliant blue and turquoise blue. However, the two dyes often appear in the dyeing process, so that when they are used, some dyeing workers have a lingering fear. In fact, as long as we recognize the structural characteristics of these two dyes, formulate the process reasonably, and operate strictly according to the process, we can completely avoid the color spot.
1.Alkali resistance test
So far, there is no unified standard for salt and alkali resistance test of reactive dyes in the industry. Different customers have different requirements on dye concentration, alkali agent type, alkali agent concentration, salt content in the test and the required stable time, which are difficult to unify and keep each other confidential. Therefore, the alkali resistance test requires different customers to formulate various enterprise standards. During the test, reactive brilliant blue KN-R and reactive turquoise blue KN-G were dissolved in the specified volume of nas0 aqueous solution under stirring according to the enterprise standard, 5olna: CO solution was added under 50%, and then heated and stirred to the specified time to evaluate the residual spots of filter paper. The less residue, the less likely it is to color. Salt tolerance test can also be used as one of the detection methods for selecting dyes.
2.The process of forming color dots
“D” is the dye matrix. In the process of alkali resistance stability test, according to the observation of the residual spots on the filter paper, it can be judged that: when alkali agent is added, the dye molecules react about 5 minutes, and the solubility decreases a lot. If external factors (electrolyte, poor water quality, some additives, etc.) are encountered, it is very easy to form color spots in the dye solution, and the phenomenon of color spots and flowers will appear on the fabric; Reactive turquoise blue KN-G, copper phthalocyanine structure, the whole molecular structure coplanarity is good. Under normal circumstances, the dyes in the state of “aggregation” exist in the dye solution, and it is difficult for these dyes to penetrate into the fiber, because the amorphous region of cotton fiber only allows the penetration and diffusion of single molecule dyes, so there are fewer dye molecules in the upper dyed fabric, and a large number of dyes exist in the dye solution. In case of external factors (high hardness of water, some additives, etc.), it is easy to get more and more aggregated, In the fabric will be very easy to appear on the color dot color.
Post time: May-12-2021