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Views: 26 Author: Site Editor Publish Time: 2024-05-30 Origin: Site
The cationic group in the fixative molecule is used to form an ionic bond with the anionic group of the dye to form an insoluble lake on the fabric, blocking the soluble group of the dye, making it difficult for the dye on the fabric to dissolve and fall off when exposed to water, thereby improving the moisture content of the fabric. The purpose of processing fastness. The stronger the cationic property of the color-fixing agent, the better the color fastness. Direct dyes, acid dyes and unbonded reactive dyes contain hydrophilic groups, which reduce the affinity between the dye and fiber when exposed to water. Cationic compounds are used for color fixation, which can combine with dyes to form insoluble salts. Water-soluble dyes can also be regarded as an anionic active colloidal electrolyte, which dissociates when exposed to water to generate polymer anions. It can perform ion exchange with cationic surfactants on the fiber to generate slightly soluble or insoluble in water of salts.
The reactive groups in the fixative molecules are used to react with the reactive groups on the dye molecules and the hydroxyl groups on the cellulose molecules to form a highly diversified cross-linking system, making the dyes and fibers more closely and firmly linked together. , prevent the dye from falling off the fiber and thereby improve the color fastness of the dye, thus improving the wet processing fastness. At present, the main method is to introduce active groups such as epoxy groups on the color-fixing agent.
Utilizing the film-forming properties of the fixative, a network-like film is formed on the surface of the fiber to coat the dye on the surface of the fiber to prevent the dye from falling off and improve the wet processing fastness. Any color-fixing agent with good film-forming properties will have better color-fixing effects. Polymers polymerized from olefins can improve dye fastness even if they do not contain reactive groups or cationic groups. This is because the polymer forms a film on the dye, which reduces dye dissolution; polyamines After the molecular weight of the dye fixing agent is increased, the dye fastness can also be improved. If reactive groups or cationic groups are introduced into the film-forming material, the dye fastness can be improved.
The molecular attraction between the fixing agent and the fiber is used to increase the fixing strength of the dye, thereby improving the washing fastness of the dyed fabric. The molecular attraction mentioned here is mainly the hydrogen bond attraction.
The buffering ability of the color-fixing agent is used to neutralize the acidic substances in the sweat and prevent the covalent bond between the dye and the fiber from breaking, thereby improving the sweat fastness. Reactive dyes are not resistant to acid attack. In an acidic environment, the covalent bonds between reactive dyes and fibers will be hydrolyzed and broken, resulting in a reduction in perspiration fastness. Sweat contains acidic substances. To improve the fastness of sweat stains, the molecular structure of the color-fixing agent must have a strong acid-absorbing ability, that is, it must have good buffering capacity. This is the reason why most color-fixing agents containing nitrogen in their molecular structure have good acid resistance. The polyhydric alcohol amine condensate used as a color-fixing agent has better perspiration fastness than the color-fixing agent made of polybasic acid or naphthalene diphenol condensate. After dyeing, anti-shrinkage fibers are treated with a fixing agent prepared by reacting formaldehyde with urea, thiourea, dicyandiamide or melamine, which can improve the wet treatment fastness and perspiration fastness, especially for complex dyes.
Use the smoothing effect of the fixing agent to reduce the friction coefficient on the fiber surface: use the fixing agent to react with the fiber and the dye to make the dye and fiber more tightly and firmly combined to prevent the dye from falling off the fiber; use the fixing agent to react with the fiber and the dye. The dye is combined into a water-insoluble salt to make it difficult to dissolve in water to improve the wet processing fastness; the dye-fixing agent can form a three-dimensional network-like, water-insoluble protective film on the fiber surface to block the dye (reaction and unreactive) contact with water and other media, increase the smoothness of the cloth surface, reduce the friction coefficient, thereby further preventing dye swelling, hydrolysis and shedding during the rubbing process, and improving dry and wet rubbing fastness.
Utilize the chlorine resistance or chlorine absorption properties of some substances to prevent active chlorine from attacking dyes, thereby improving the chlorine immersion fastness and chlorine bleaching fastness of dyes.
