The principle and role of fixing agent

The fixation mechanism of non-reactive fixing agents for improving the fastness to wet processing is generally two kinds of water-soluble blocking groups and film forming on the surface of fibers. The main types can be divided into cationic fixing agents and resin fixing agents.

(1) Cationic Fixing Agents: Cationic fixing agents mainly form ionic bonds with cation groups in the dye molecules to block water-soluble groups and improve the fastness to wet processing. This kind of fixing agent can be divided into two types of surfactant fixing agent and no surface activating fixing agent according to its surface activity.

1 Cationic Surfactants: In cationic surfactants, most of them can improve the wet fastness of direct dyes and acid dyes to varying degrees. The degree of improvement depends mainly on the solubility of lakes produced by anionic dyes and the relative dyes. The molecular mass, the number of sulfonic acid groups or carboxylic acid groups, and the like. This type of fixing agent is cetyl chloride pyridine and SaparoJn type cationic surfactant, which is an earlier used fixing agent. Since fixing agents of this type have improved the hot water (water immersion) fastness, the improvement in the soaping fastness is not obvious, and there is a drawback that the light fastness is lowered. Therefore, it is not used now.

2 No surface active quaternary ammonium salt: This is a kind of fixing agent which is not resin and has no surface activity. Although it has a cationic group (quaternary ammonium group), it has no surface activity. In the early stages of development, most of them are polyethenylene polyamine derivatives, and there are also highly cross-linked, multi-quaternary ammonium group-containing dye fixing agents produced by reacting polyamines with polyhalogenated compounds, such as with cyanuric chloride. Polymer condensate. This kind of fixing agent can improve the fastness to washing of direct dyes, and has less effect on shade and light fastness. The use of such fixing agents in combination with copper salts can significantly improve the light fastness of acid-land dyes and reactive dyes, and has better cross-linking fastness, but it has a certain influence on fabric strength. This type of fixing agent is less widely used in China.

(2) Resin-type fixing agent: Resin-based fixing agent is a type of fixing agent used in the 1980s and 1990s in China, accounting for 70%-80% of the total amount of fixing agent. Color agent Y. Fixing agent Y has been replaced by other resin-type fixing agents due to the presence of formaldehyde.

1 Dicyandiamide and formaldehyde primary shrinkage: The initial aqueous solution of dicyandiamide and formaldehyde is dye fixing agent Y. It is cationic, capable of forming water-insoluble lakes with anionic dyes such as direct dyes, acid dyes, etc. The film is formed on the surface of the fiber to achieve the purpose of fixation. It can not be mixed with anionic surfactants (such as detergents, powders, etc.) and can be used together with nonionic and cationic surfactants. The amount of fixing agent varies with the chemical structure of the dye, the depth of color, the process of fixation, the type of fabric, and other factors. The fixing agent M can be regarded as a complex product of the fixing agent Y and the copper salt, its main performance is basically the same as the fixing agent Y, and has the effect of improving the light fastness. Sulfur dyed fabrics can also have good soap fastness.

Since these two kinds of fixing agents contain free formaldehyde and the N-methylol groups present in the molecular structure release formaldehyde, the residual formaldehyde content of the dyed material to be processed exceeds the regulations, causing a great impact on the human body and the environment. The use of less and less. In particular, since China issued the GB 18401-2001 Mandatory Standard for Limits on Formaldehyde Content in Textiles, the use of fixing agent Y (or M) has not only been restricted in the production of textiles for export, but also the production of textiles for domestic sales. restricted. Therefore, it has begun to slowly withdraw from the market and is replaced by an aldehyde-free or low-aldehyde fixing agent that meets the environmental protection requirements.

(2 Polyamine Condensers: This type of fixing agent consists of polyamines such as polyamines, dicyandiamides, and other polyamines or polycondensates with other compounds. It is cationic and has a network structure. It can form macromolecular compounds with anionic dyes, can improve the wet processing fastness of dyed fabrics, and can also improve the wet ironing fastness of reactive dyes. The amount and fixing conditions are basically the same with fixing agent Y. Because of its affinity with fibers It is large and therefore has a high exhaustion rate when it is used in impregnation methods.This kind of fixing agent is also one of the fast-growing varieties in China.It is mainly used for the fixation of reactive dyes and direct dyes.However, in the synthesis of such fixing agents, The proportion of dicyandiamide should be controlled, because the high dicyandiamide ratio causes discoloration.

3 Quaternary ammonium salt polymer: This type of fixing agent is a polymer made from the polymerization of olefins with quaternary ammonium groups such as monoallyldimethylammonium chloride and diallyldimethylammonium chloride. , homopolymers, or copolymers with other monomers. With the help of the film forming property of the polymer resin and the cationic groups on the polymer chain, the purpose of fixation is achieved. This kind of fixing agent is water-soluble, especially suitable for reactive dyes, treated fabrics with bright shades, good chlorine fastness, good light fastness, perspiration fastness, and can protect reactive dyes from the acidic atmosphere, However, higher temperature washing fastness is poor.

(3) Sol-gel fixing agent: This is a new type of fixing agent, still in the scientific research stage. The fixation mechanism is due to the fact that the nanosol is easily chemically or physically modified, and after padding or dipping treatment and dried, a thin and transparent metal or nonmetal oxide film is formed on the surface of the textile, and the dye on the fabric is formed. The role of anchorage, thereby improving the color fastness of dyes.