Dicyandiamide formaldehyde color fixing agent
Dicyandiamide formaldehyde color fixing agent, namely color fixing agent y, was developed in the 1930s. Color fixing agent y is generally used in the fixation of direct dyes and acid dyes, not reactive dyes. When it is used in the fixation of cotton woven fabrics dyed with direct bright red 4BS, the dry rubbing fastness is grade 4 and the wet rubbing fastness is grade 2 ~ 3. Due to its low price, color fixing agent y was once widely used, but later research found that color fixing agent y will release formaldehyde after finishing. Formaldehyde is easy to harden the skin and even local tissue necrosis when touching the skin, resulting in cracks in the contact part and tumors. Therefore, with the gradual enhancement of people’s awareness of environmental protection and the higher and higher requirements for the internationalization of products after China’s entry into WTO, this kind of color fixing agent is gradually replaced by aldehyde free color fixing agent.
Polyamine fixing agent
Polyamine color fixing agent appeared in the 1960s. It is the earliest aldehyde free resin type color fixing agent developed. It is a condensation resin of polyamine (mainly diethylenetriamine) and guanidine and its derivatives (such as dicyandiamide). It is a network cationic structure. The cations in the structure can form a lake with anions in dyes through ionic bond to improve color fastness. It has large molecular weight and strong intermolecular force with fibers, so it has good color fastness, Its overall fixation performance is better than that of fixing agent y. The results show that the color fixing performance can be effectively improved by further introducing reactive groups that can covalently crosslink with the hydroxyl group of cotton fabric in its structure and strengthening the interaction between it and the fiber in the form of covalence.
Except for individual varieties, this kind of color fixing agent generally does not contain free formaldehyde, and its color fixing performance is better than that of color fixing agent y, especially it can improve the washing fastness of reactive dyes. There are many kinds of color fixing agents, which have been greatly developed and applied for a time, such as color fixing agent sh-96, color fixing agent h, color fixing agent dfrf-1, color fixing agent gq-600, etc.
The disadvantage of this kind of color fixing agent is that the structure contains not only cations, but also more primary amines, secondary amines and tertiary amines. It is often easy to be oxidized during post-treatment, resulting in color change. Therefore, with the higher and higher requirements for color fixing agent products, the development of new low color change color fixing agents has gradually become the focus of attention.
Polycationic color fixing agent
Polycationic color fixing agent was developed in the late 1960s. It is mainly used for color fixing of reactive dyes. Generally, it will not cause color change and decline of light fastness. Polycationic color fixing agents mostly have linear structure, which can be divided into primary amine, secondary amine, tertiary amine and quaternary ammonium salt. Because quaternary ammonium salt has the strongest cationic property and the best color fixing effect, it is mainly quaternary ammonium salt in practical development. Quaternary ammonium salt type color fixing agents mainly include the reactants of epichlorohydrin and amines (mainly dimethylamine, trimethylamine and diethylenetriamine) and diallyl quaternary ammonium salt derivatives, such as color fixing agent F, color fixing agent mrt-1, etc. Among them, the reactants of epichlorohydrin and amines are color fixing agents sold in batches in China’s market.
The reaction products of epichlorohydrin and amines can prevent color change and improve the color fastness to light, but the color fastness to soaping and perspiration are reduced; The color fastness of diallyl quaternary ammonium salt polymer to soaping is better than that of epichlorohydrin and amine quaternary ammonium salt polymer, and there will be no color change and reduction of color fastness to light. The fixation principle of this kind of color fixing agent is mainly to form a lake with the dye through its cationic group to reduce the water solubility of the dye, but it still does not solve the problem of low rubbing fastness of the color fixing agent, especially the wet rubbing fastness. The research shows that the introduction of reactive groups that can effectively covalently react with hydroxyl groups in dyes or cotton fibers into the structure of PDMDAAC, so as to strengthen the interaction between PDMDAAC and cotton fibers or dyes in the form of covalence, which can effectively improve its color fastness.
Reactive fixing agent
This kind of color fixing agent was developed in the 1980s. The structure of reactive color fixing agent contains reactive groups that can covalently crosslink with some groups (such as hydroxyl) in cotton fiber or dye structure. Reactive color fixing agents are generally divided into non-ionic reactive color fixing agents and cationic reactive color fixing agents. Non ionic reactive color fixing agents are generally prepared by the reaction of organic compounds such as 1,5-binaphthol and hydroquinone [44,45] with epichlorohydrin. There are active epoxy groups at both ends of its molecular structure, which can covalently react with active groups (hydroxyl groups, etc.) in fabric fibers, significantly improving the wet friction color fastness of acid dyes, direct dyes and sulfide dyes; In addition, non-ionic reactive color fixing agents include polyether reactive color fixing agents (polyether synthesized by condensation of polyethanolamine and polyhydroxynaphthalene), polycarboxylic acid reactive color fixing agents (polyester condensed by condensation of polycarboxylic acid and tetracarboxylic acid methane), etc. In addition to covalent crosslinking between the cationic reactive color fixing agent and the hydroxyl group on the fiber molecule through its reactive group, its cation can also form a salt with the sulfonic acid anion of the dye, that is, a lake, which further improves the color fixing performance of the color fixing agent. Many reactive color fixing agents are modified by polyamine color fixing agents or polycationic color fixing agents. For example, the condensate of polyamine 46 and dicyandiamide reacts with epichlorohydrin to obtain polycondensate.
According to the types of reactive groups, reactive color fixing agents mainly include epoxy chloropropane derived color fixing agents, polyurethane color fixing agents, silicone color fixing agents, etc.
Compound color fixing agent
The compound color fixing agent is composed of two or more kinds of color fixing agents. It can effectively solve the problem of combining reactive groups with cationic structure, has structural advantages, and the preparation process is simple and convenient, and has a wide application prospect.
Dr. Yang juping first synthesized polyamine from monomethylamine and epichlorohydrin, and then mixed it with the copolymer of Dimethyldiallyl Ammonium Chloride and acrylamide (PDA) to prepare a composite color fixing agent fhad. When it was used to treat matte cotton dyed with reactive dyes, the dye uptake was increased by 25% ~ 66%, and its water washing and sweat fastness reached grade 5. Because these color fixing agent components not only contain cationic components that can form salt bonds (lakes) with the anions of dyes, but also contain reactive groups that can covalently crosslink with hydroxyl groups in the structure of cotton fabrics, they can form an effective covering film on the surface of the fabric, so as to further strengthen the role between dyes, fabrics and color fixing agents and make them have ideal color fixing properties.
New color fixing agent
(1) sol-gel type
This kind of color fixing agent is still in the stage of scientific research. Its color fixing mechanism is to hydrolyze metal alkoxide or inorganic salt directly to form sol or to form sol by de coagulation. The small sol particles have great specific surface area and high specific surface energy, which promotes the particles to form a three-dimensional network structure and form a layer of oxide film on the fabric. This film fixes the dye in three dimensions to achieve the purpose of color fixation.
(2) Nano type
Nano color fixing agent made by nanotechnology can not only form a lake with water-soluble dyes, but also form a film with polymer nano silicone to improve the color fastness to friction
