Printing and dyeing auxiliaries are auxiliaries used in the process of fabric printing and dyeing, which can improve the effect of printing and dyeing, including printing auxiliaries and dyeing auxiliaries, printing auxiliaries include thickeners, adhesives, crosslinking agents, emulsifiers, dispersants and other printing auxiliaries.

  Printing auxiliaries can be divided into printing auxiliaries and dyeing auxiliaries.Printing auxiliates include adhesives, thickeners, crosslinking agents, emulsifiers, softeners, diffusers and defoaming agents, etc. Dyeing auxiliates include levelling agents, fixing agents, dispersing agents, fluorescent brightening agents and softening agents, etc.

  Usually although some dyes can be dyed more bright color, and direct dyes, acid dyes and other anionic water-soluble dyes chromatography complete, but because of the dyes with water-soluble groups, the wet treatment fastness is not good, fading and staining phenomenon is serious.Not only make the appearance of the textile itself old, at the same time, the dye falling off will stain the fiber that has been dyed into other colors, resulting in the phenomenon of staining and matching colors.In addition, although the covalent bond formed by the inclusion dye and the fiber is strong, in practice, the dye reactants and hydrolysates cannot be completely washed from the dye, and this part of the dye will fade, while the covalent bond on the dye will hydrolyze and break the bond.In order to improve the colour fastness of the fabric, fixing treatment can be carried out.These auxiliaries which can improve the fastness of various dyes are called fixatives.

　　1. Fixing mechanism of fixing agent

　　Dye dyeing on different fibers, its dyeing mechanism and color fastness is different, so the fixing agent mechanism and application are not the same.

　　(1) Reduce the water solubility of dyes, use fixing agent and dye to generate insoluble lake, so as to improve the wet treatment fastness.For example, direct dyes, acid dyes and reactive dyes contain hydrophilic groups, and cationic compounds are used for fixing color. It can combine with dyes to form insoluble salts, and reduce their water solubility to improve color fastness.(2) Cross-linking was carried out on the dye by using the reactivity of the l1 molecule of solid color, so as to reduce the water solubility of the dye and improve the wet treatment fastness of the dye.By cross-linking between dyes or between dyes and fibers, the broken dye is no longer transferred from the dye to the fabric.(3) The use of fixing agent on the dye to form a film to increase the solubility of the dye, improve its dyeing fastness.And the test results show that: general film - forming good fixing agent, its dyeing effect is better.The polymer made of olefin polymerization, even if it does not contain reactive groups or cationic groups, forms a film on the dye, so that the dissolution of dye is reduced, and the color fastness of polyamine fixing agent can also be improved after improving its molecular weight.If reactive or cationic groups are added to the film forming material, the color fastness can be improved.

　　2. Type of fixing agent

　　2.1 Reactive fixing agent

　　Reactive fixing agent is usually introduced in the fixing agent molecule reactive group, commonly used is epoxy group, this kind of fixing agent can form covalent bond with some groups in the fiber dye molecules, to improve the dyeing fastness more favorable.Common reactive fixing agent has the following categories.(1) reactive cationic resin type fixing agent, usually is the diethylene I amine and dicyandiamide polycondensation and epichlorohydrin (introduced epoxy group) reaction and obtained.It can greatly improve the color fastness of direct dyes and acid dyes without affecting the change of color light.(2) polyether reaction fixing agent, is the reaction of polyether and epichlorohydrin to get non-ionic polyether fixing agent.This fixing agent has a certain solubility in water, and can crosslink itself into macromolecular network structure, and form macromolecular compounds with the dye, so that the dye and fiber are firmly combined, and then improve the wet treatment fastness.(3) Quaternary ammonium reactive fixing agent, trimethylamine, diethylenetriamine and epichlorohydrin condensation, is currently commonly used fixing agent, but the color fastness is not very good.But because it has cationic group, and can cross link with the fiber, can make the cellulose fiber modification, is to achieve no salt or low salt dyeing, improve the dye dye rate effective method.

　　2.2 Non-reactive fixing agent

　　Its color fixing mechanism is mainly in the fiber surface film forming and sealing water-soluble groups, its main types are cationic color fixing agent and resin type color fixing agent.

　　(1) Cationic fixing agent is mainly through the formation of ionic bonds between cations and anionic groups in the dye molecules to seal the water-soluble group, so as to improve the wet treatment fastness, and it is mainly divided into: ① Positive ion surface active color fixing agent, most cationic surfactants have different degrees of color fixing effect, this kind of color fixing agent has cetyl pyridine chloride and Sapamin type cationic surfactants, but its soap fastness and sun fastness is not good, so it has been less used.Its typical structure is as follows:

　　② No surface activity of quaternary ammonium salt, is a kind of fixing agent does not belong to resin and no surface activity, it generally contains two or more than two quaternary ammonium group, belongs to polyvinyl polyamine derivatives.This kind of fixing agent such as: a N+(CH3)2 a CH2CH2 a N+(CH3)2 a, and poly amine and poly cyanogen polymer condensation.This kind of fixing agent can improve the color fastness to washing of direct dyes, and has little effect on the color light and sun fastness, but has a certain effect on the strength of the fabric, which is seldom used in China.

　　(2) resin type fixing agent, this kind of fixing agent is water-soluble resin with three-dimensional structure, and is currently used Z large fixing agent type, accounting for about 70% to 80% of the total fixing agent, and its representative product is fixing agent Y.

　　(1) Dichloramine and formaldehyde initial condensates, their aqueous solution, namely, fixing agent Y, have positive dissociation, and direct dyes, acid dyes and other anionic dyes to generate insoluble ten water lake, film on the fiber surface to achieve the purpose of fixing color.But because it will affect the sun fastness, adding metal salts (such as copper salts) to the fixing agent can improve the sun fastness, such as fixing agent M is a copper salt complex of resin fixing agent.But because copper salt can be perspiring solution from the fiber peeling off, easy to lead to the heavy metal content on the fabric exceeds the standard, another disadvantage is that there is free formaldehyde released by fixing agent on the fabric, and its amount often cannot be reduced to the allowable range.Therefore, now more in line with environmental protection requirements of no aldehyde or low aldehyde fixing agent.(2) polyamine condensation polymer, is by the guanidine classes and polyene polyamine compounds react with hydrochloric acid, urea with helium off of water soluble resin, generally do not contain free formaldehyde, cationic, with mesh structure and generates macromolecular compound with anionic dye, can improve the fastness to wet processing, basic with dosage and the conditions of solid color fixing agent Y.This kind of fixing agent is also one of the varieties of rapid development in China, mainly used in the fixing of reactive dyes and direct dyes.③ Quaternary ammonium polymer is a polymer, homopolymer or copolymer formed by polymerization of olefin with quaternary amino group.This kind of fixing agent is to achieve the purpose of fixing color with the help of polymer resin film forming and polymer chain cationic groups, and is water-soluble, especially suitable for reactive dyes.The treated fabric has bright color, good fastness to sun and perspiration, and can protect reactive dyes from acidic atmosphere, but poor fastness to washing at higher temperatures.

　　2.3 Some new color fixing agents

　　With the progress of social science and technology, people's environmental awareness and quality of raw materials have been greatly improved than before, and the requirements for textiles are becoming higher and higher. This dyeing agent also requires green environmental protection and high efficiency and energy saving. No aldehyde or low aldehyde fixing agent has been applied, and some new fixing agents have emerged in recent years.

　　Sol-gel fixing agent, is still in the stage of scientific research, its fixing mechanism is because nano sol is easy to carry out chemical or physical modification, through dipping or impregnating treatment and after drying, metal or non-metal oxide film is formed on the surface of the textile, anchoring the dye, so as to improve the color fastness of the dye.

　　In recent years, polychlorinated ester production technology has developed vigorously in the field of water-based, green and environmental protection, providing opportunities for the synthesis of high-performance color fixing agents.Water-based polychlorides can improve the color, stain resistance and wear resistance of dyed fabrics, so that the water-based polychlorides with amines can get good color fixing effect by acting with anionic water-soluble dyes such as direct dyes, acid dyes or reactive dyes.

　　3 · conclusion

　　In view of the problem of dyeing fastness in dyeing and finishing, it is necessary to develop a series of aldehyde-free color fixing agents in order to form a convenient dyeing and finishing process, achieve high utilization rate of dyes, excellent fastness and environmental friendliness.Based on the advantages and disadvantages of existing color fixing agent, as a good color fixing agent development trend :(1) good directness, high reactivity, good stability, mild application conditions, strong color fixing force, good general performance.(2) Low cost, low toxicity, even non-toxic, environmentally friendly application.(3) significantly improve the dye fixation rate on the fiber, will not cause color changes.(4) Significantly improve the fabric wet treatment fastness, resistance to friction fastness, improve dyeing performance, at the same time both finishing effect.(5) does not affect the feel of the fabric, does not cause the decline of the strength of the fabric, does not affect the use of other additives.

　　If excellent fixing agent can be widely used, it can further promote the development of China's textile printing and dyeing industry, economic and social benefits are obvious.