In the textile printing and dyeing process, polyamide, silk, wool and blended textiles are generally dyed with acid dyes. Acid dyes have the advantages of complete chromatography, excellent levelling performance and convenient use. However, the dyeing fastness is generally poor, and it is difficult to meet the requirements of customers and exports, and acid dye fixing agents must be used to improve it [1]. There are many kinds of acid dye fixing agents, which can be roughly divided into:

(1) The color fixation mechanism of natural tannins, such as tannin-tartar, is to form a composite association film on the surface of the fiber, block the void, reduce dye diffusion, and thus improve the color fastness [2]. Although the color fixing effect with natural tannin is good, the color fixing process is two-bath method, which is more complicated to use, and the fabric becomes rough and hard after the color fixing treatment, affecting the style.

(2) Synthetic tannins, for example, various phenolic sulfonate formaldehyde reactants [3], the color fixing process is a one-bath method, the use is relatively simple, the effect is also better than natural tannins, and does not affect the fabric style, and has been widely used.

The color fixation mechanism is that the Yin charged synthetic tannins form hydrogen bonds with the amino group on the fiber, and the macromolecules are adsorbed by van der Waals force to form multilayer adsorption on the fiber. At the same time, there is a repulsive force between tannin anion and acid dye anion, which prevents the diffusion of acid dye to the dye bath, thus improving the color fastness [4]. For example, LANXess EP5993, Huntsman Erional EFR-01, Germany's WFK Conc, Bayer NBS powder, etc., although the product performance is good, but expensive.

At present, although the domestic independent research and development of acid dye fixing agent is low in cost, but in the sulfonation process, it is useful to sulfuric acid and acetic anhydride, and these two raw materials are strictly controlled by the public security department, although there are a small number of small factories through illegal channels to obtain raw materials, but the sulfonation process in the production process still has safety risks. Therefore, it is very necessary to develop a new acid color fixing agent which is easy to obtain and safe to pro.

To solve this problem, a new acid color fixing agent KX-206S, which is easy to produce, is developed in this paper, and its color fixing effect is studied.