1 Fixing mechanism of fixing agent
Dyeing on different fibers has different dyeing mechanism and color fastness. Therefore, the mechanism and application of dye fixing agent are also different.
(1) Reducing the water solubility of the dye, using the fixing agent and the dye to produce an insoluble lake, thereby improving the wet processing fastness. For example, direct dyes, acid dyes, and reactive dyes contain hydrophilic groups, and they are fixed using cationic compounds. They can combine with dyes to form insoluble salts and reduce their water solubility to improve color fastness.
(2) Cross-linking is performed on the dyestuff using the reactivity of the solid color homogenizer l1, thereby reducing the water solubility of the dye and improving the wet-process fastness of the dye. Dyes or dyes and fibers are cross-linked so that the dyestuffs that are bonded off can no longer be transferred from the dye to the fabric.
(3) The use of a fixing agent to form a film on the dye increases the difficulty of dissolving the dye and improves its color fastness. Moreover, the test results prove that all fixing agents with good film-forming properties have better dyeing effects. Polymers derived from the polymerization of olefins, even if they do not contain reactive groups or cationic groups, form a film on the dyed product, reducing the dye dissolution, and the dyeing fastness of the polyamine fixing agent after improving its molecular weight. Can improve with it. If a reactive group or a cationic group is introduced on the film forming material, the color fastness can be more improved.
2 type of fixing agent
2.1 Reactive Fixatives <br style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !im<em></em>portant; word-wrap: Break-word !im<em></em>portant;"> Reactive fixatives usually introduce reactive groups into the molecules of the fixer. Commonly used are epoxy groups. Such fixatives can Some of the groups in the fiber dye molecules form covalent bonds, which is more advantageous for the improvement of the color fastness.
The common reactive fixing agents are the following types:
(1) A reactive cationic resin-type fixing agent is usually obtained by reacting a polycondensate of divinylamine with dicyandiamide with epichlorohydrin (an epoxy group is introduced). It can not only improve the color fastness of direct dyes and acid dyes, but also does not affect the change of color light.
(2) Polyether reaction fixing agents are polyethers and epichlorohydrin reacted to obtain nonionic polyether fixing agents. The fixing agent has certain solubility in water and can be cross-linked into a macromolecular network structure, and forms a macromolecular compound with the dye, so that the dye and the fiber can be combined firmly, thereby improving the wet processing fastness.
(3) Quaternized reactive fixatives, often using a condensate of trimethylamine, diethylenetriamine and epichlorohydrin, are currently used as color fixing agents, but the color fastness is not very good. However, due to its cationic group and its ability to cross-link with fibers, cellulose fibers can be modified, which is an effective way to achieve salt-free or low-salt dyeing and increase dye uptake.
2.2 non-reactive fixing agent <br style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !im<em></em>portant; word-wrap : break-word im <em> </ em> portant; "> fixation mechanism which is mainly formed on the surface of the fiber and the two kinds of closed water soluble group, which is divided into the main types of the cationic fixing agent and a resin-type! Fixative.
(1) Cationic fixing agent, mainly through cations and ionic groups formed in the dye molecules to form an ionic bond to block the water-soluble groups, to improve the fastness to wet processing, and it is mainly divided into:
A: Ionic surfactants, most of the cationic surfactants have different degrees of fixation. This type of fixing agent has cetylpyridinium chloride and Sapamin type cationic surfactant, but its soaping Fastness and light fastness are not good, so it is rarely used at present. Its typical structure is as follows:
B: The non-surface active quaternary ammonium salt is a kind of fixing agent which is not a resin and has no surface activity. It generally contains two or more quaternary ammonium groups and belongs to polyethylene polyamine derivatives. Such fixing agents such as: a N + (CH3) 2 - CH 2 CH 2 - N + (CH 3) 2 a, there are polyamines and cyanuric chloride polymer condensate. This type of fixing agent can improve the fastness of direct dyes to washing, and has little effect on color shade and light fastness, but it has a certain influence on the strength of fabrics, and it has less domestic applications.
(2) Resin type fixing agent, which is a water-soluble resin having a three-dimensional structure, and is the type of fixing agent currently used in the largest amount, accounting for about 70% to 80% of the total amount of the fixing agent. The representative product is Fixing Agent Y.
A: Dichloroamine and formaldehyde primary shrinkage, the aqueous solution is the fixing agent Y, with cationicity, can produce insoluble ten lakes of anionic dyes such as direct dyes, acid dyes, etc., and form a film on the fiber surface to achieve The purpose of fixation. However, because it affects the light fastness, adding a metal salt (such as a copper salt) to the fixing agent can improve the light fastness. For example, the fixing agent M is a copper salt complex of a resin-type fixing agent. However, because copper salts can be stripped from the fibers by the sweat solution, the content of heavy metals on fabrics can easily exceed the standard, and another disadvantage is that the free formaldehyde released by the fixing agent is contained on the fabric, and its amount cannot be reduced to the permissible range. Inside. Therefore, some aldehyde-free or low-aldehyde fixing agents that meet environmental requirements are now used.
B: Amine condensation products, which are water-soluble resins derived from the deodorization reaction of terpenoids and polyene polyamine compounds with hydrochloric acid and urea, generally do not contain free formaldehyde and are cationic, ie have a network structure and can Anionic dyes produce macromolecular compounds that can improve the fastness to wet processing. The amount and fixing conditions are basically the same with the fixing agent Y. This type 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. C: Quaternary ammonium salt polymer, which is a copolymer formed by polymerizing a quaternary amino group-containing olefin polymerized, homopolymer or copolymerized with other monomers. This kind of fixing agent is based on the film forming property of the polymer resin and the cationic group on the polymer chain to achieve the purpose of fixation, and is water-soluble, and is particularly suitable for reactive dyes. Treated fabrics have bright shades, good lightfastness, perspiration resistance, and good fastness, and can protect reactive dyes from the effects of acidic atmospheres, but poor wash fastness at higher temperatures.
2.3 Some new fixing agents
With the advancement of social science and technology, people’s awareness of environmental protection and quality of life have been greatly improved, and the demand for textiles has become higher and higher. For dyeing auxiliaries, it is also required to develop in a green, energy-efficient, and aldehyde-free manner. Fixing agents with low aldehydes have been used, and some new fixatives have appeared in recent years.
The sol-gel fixing agent is still in the scientific research stage. Its fixation mechanism is due to the fact that the nanosol is easily chemically or physically modified. After padding or impregnation treatment and drying, metal or non-metal oxides are formed on the surface of the textile. The film plays an anchoring role on the dye, thereby improving the color fastness of the dye.
In recent years, the development of polychlorinated ester production technology has been booming, and it is also green and environmentally friendly, providing opportunities for the synthesis of high-performance fixing agents. Water-based polychloroesters can improve the color, stain resistance and abrasion resistance of dyed fabrics, making water-based polychlorinated compounds that react with amines react well with anionic water-soluble dyes such as direct dyes, acid dyes, or reactive dyes. Fixing effect.
3. Conclusion
In view of the current problem of color fastness in dyeing and finishing, a series of non-aldehyde fixing agents need to be developed in order to form a convenient dyeing and finishing process, achieving high dye utilization, excellent fastness properties, and achieving environmental friendliness. Based on the advantages and disadvantages of the existing fixing agents, the trend of development as a good fixing agent:
(1) Good directness, high reactivity, good stability, mild application conditions, strong fixing power, and good general performance.
(2) Low cost, low toxicity, even non-toxicity, friendly application environment.
(3) Significantly increase the fixation rate of the dye on the fiber, which will not cause the change of shade.
(4) Significantly improve fabric wetness, fastness to rubbing, improve dyeing performance, and at the same time provide finishing effects.
(5) Does not affect the fabric feel, does not cause the fabric strength to drop, does not affect the use of other additives.
If the good fixing agent can be widely applied, it can further promote the development of China's textile printing and dyeing industry, and the economic and social benefits are obvious.
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