Chemical crosslinking formaldehyde-free color fixing agent for leather as well as preparation method and application of chemical crosslinking formaldehyde-free color fixing agent

Abstract

The invention provides a chemical crosslinking formaldehyde-free color fixing agent for leather as well as a preparation method and application of the chemical crosslinking formaldehyde-free color fixing agent, and belongs to the technical field of leather chemical industry. The chemical crosslinking formaldehyde-free color fixing agent for leather provided by the invention not only completely avoids the introduction of formaldehyde and international limited substances, meets the strict environmental protection and export requirements, but also can remarkably improve the comprehensive color fastness of the dyed leather, so that the leather has excellent dry rubbing resistance, wet rubbing resistance and perspiration resistance, meanwhile, the yellowing resistance of the dyed leather is effectively improved, and the color fastness of the dyed leather is improved. Therefore, the appearance quality, the durability and the market competitiveness of the leather product are greatly improved.

Description

Technical Field

[0001] This invention relates to the field of leather chemical technology, and in particular to a chemical crosslinking formaldehyde-free fixing agent for leather, its preparation method, and its application. Background Technology

[0002] Leather dyeing is a crucial process for giving leather its color and appearance. Reactive dyes are widely used in leather dyeing due to their complete color spectrum and vibrant colors. However, the bond between reactive dyes and leather fibers is not entirely secure. Under external influences such as moisture, heat, friction, or perspiration, some dyes may desorb, detach, or migrate from the fibers, leading to color fading, staining, or discoloration. This phenomenon is collectively referred to as poor colorfastness. To improve colorfastness, color fixing treatment has become an indispensable and critical subsequent step in leather dyeing and finishing.

[0003] Fixing agents are functional leather chemical auxiliaries whose core function is to enhance the binding force between dyes and fibers through physical or chemical means, thus more firmly "locking" the dyes onto the fibers. Traditional fixing agents widely used formaldehyde or its derivatives as cross-linking components. While these methods offered significant color-fixing effects, they could release free formaldehyde during product storage or use, posing a threat to human health and the environment, and have been gradually restricted and phased out by the market. Subsequent developments of formaldehyde-free fixing agents, such as polyamine-epoxychloropropane condensates, avoided the formaldehyde problem, but their synthesis process may produce byproducts like dichloropropanol, which are strictly regulated by environmental regulations, thus facing export barriers. Currently, most mainstream environmentally friendly formaldehyde-free fixing agents are polycationic, which bind to anionic dyes through cationic charges, making them environmentally friendly. However, when applied to leather products requiring extremely high performance in terms of wet rubbing resistance and yellowing resistance, their overall color-fixing effect still has room for improvement. Therefore, developing a new type of formaldehyde-free color-fixing agent that can meet strict environmental standards and comprehensively improve the various fastness properties of leather dyeing is of great significance for promoting the green and high-quality development of the leather industry. Summary of the Invention

[0004] The purpose of this invention is to provide a chemical crosslinking formaldehyde-free fixing agent for leather, its preparation method and application, which solves the technical problem that existing leather fixing agents are difficult to balance with environmental protection (such as formaldehyde or restricted by-products) and fixing performance (especially wet rubbing resistance and yellowing resistance).

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for preparing a chemically crosslinked formaldehyde-free fixing agent for leather, comprising the following steps: To prepare amine prepolymers, an organic amine compound, glycidyl ether, and water are mixed and subjected to a first heating reaction under inert gas protection to obtain the amine prepolymers. To prepare the fixing agent, a cationic monomer, acrylate, the amine prepolymer, and water are mixed and heated under inert gas protection. Then, an initiator is added to carry out a polymerization reaction to obtain the chemically crosslinked formaldehyde-free fixing agent for leather.

[0006] Preferably, the temperature of the first heating reaction is 60°C to 70°C; The second heating temperature is 70℃~75℃; The polymerization reaction was carried out at 80℃~85℃.

[0007] Preferably, the initiator is added dropwise; The polymerization reaction lasts for 1 to 4 hours.

[0008] Preferably, the organic amine compound is selected from at least one of ethylenediamine, diethylenetriamine, or triethylenetetramine; The glycidyl ether is selected from at least one of ethylene glycol glycidyl ether or glycerol triglycidyl ether; The cationic monomer is dimethyldiallylammonium chloride.

[0009] Preferably, the dimethyl diallyl ammonium chloride is used in the form of an aqueous solution with a mass fraction of 55% to 70%.

[0010] Preferably, the acrylate is selected from at least one of ethyl acrylate, butyl acrylate, or methyl methacrylate; The initiator is selected from at least one of ammonium persulfate or potassium persulfate.

[0011] Preferably, the raw materials in the step of preparing the amine prepolymer include, by weight, 45-60 parts of organic amine compound, 25-40 parts of glycidyl ether and 5-25 parts of water; The raw materials in the preparation of the fixing agent include, by weight, 45-65 parts of cationic monomer, 55-75 parts of acrylate, 5-25 parts of amine prepolymer, 35-50 parts of water, and 0.3-1.0 parts of initiator.

[0012] The present invention also provides a chemical crosslinking formaldehyde-free fixing agent for leather prepared according to the above preparation method.

[0013] The present invention also provides the application of the above-mentioned chemical crosslinking formaldehyde-free fixing agent for leather in leather color fixing.

[0014] Preferably, the application includes use in the dyeing and fixing process of chrome-tanned leather, vegetable-tanned leather or synthetic tanned leather, or in the post-treatment of leather immersion dyeing or spray dyeing processes, or as a base color fixative before leather finishing.

[0015] The technical effects and advantages of this invention are as follows: The chemical crosslinking formaldehyde-free fixing agent for leather provided by this invention not only completely eliminates the introduction of formaldehyde and internationally restricted substances, meeting stringent environmental protection and export requirements, but also significantly improves the overall color fastness of dyed leather, making it excellent in resistance to dry rubbing, wet rubbing and perspiration stains. At the same time, it effectively improves the yellowing resistance of dyed leather, keeping the color bright and without discoloration, thereby greatly enhancing the appearance quality, durability and market competitiveness of leather products. Detailed Implementation

[0016] The primary objective of this invention is to provide an environmentally friendly and efficient method for preparing a chemically crosslinked formaldehyde-free fixing agent for leather. The core concept of this method is to construct a polymer system with chemical crosslinking capabilities through a two-step reaction: First, an amine prepolymer containing active groups (such as hydroxyl groups, secondary / tertiary amines) is synthesized, which serves as the active component and crosslinking site for subsequent polymerization; second, cationic monomers, acrylate monomers, and the aforementioned amine prepolymer are copolymerized to form a polymeric fixing agent integrating cationic fixing, film-forming coating, and chemical crosslinking functions. The entire process is rationally designed, with mild and controllable reaction conditions, facilitating industrial production.

[0017] The preparation method specifically includes the following steps: (1) Preparation of amine prepolymer: This step involves mixing an organic amine compound, glycidyl ether, and water, and carrying out a first heating reaction under an inert gas atmosphere to obtain the amine prepolymer. The inert gas atmosphere can be nitrogen, argon, etc., to isolate oxygen and prevent oxidation of the raw materials or unnecessary side reactions. The first heating reaction aims to promote the ring-opening addition reaction between the organic amine compound and the glycidyl ether, forming a prepolymer containing hydroxyl and amino groups. The preferred temperature range for the first heating reaction is 60°C to 70°C. Within this temperature range, the reaction rate is suitable, which is beneficial for controlling the molecular weight distribution and prepolymer structure. More preferably, the temperature of the first heating reaction is 62°C to 68°C, for example, 65°C. The reaction time can be adjusted according to the amount of feed and the temperature to ensure a complete reaction, typically 1 to 5 hours, until the system is homogeneous and stable.

[0018] (2) Preparation of fixing agent: This step involves mixing cationic monomers, acrylates, the amine prepolymer obtained in step (1), and water, heating under an inert gas atmosphere, and then adding an initiator to carry out a polymerization reaction, ultimately obtaining the target product—a chemically crosslinked formaldehyde-free fixing agent for leather. The purpose of the second heating is to bring the reaction system to the starting temperature required for initiator decomposition and polymerization. The preferred temperature for the second heating is 70℃~75℃. More preferably, it is 72℃~74℃. The polymerization reaction is the key process for forming the fixing agent polymer, and the reaction temperature is preferably controlled at 80℃~85℃. More preferably, the polymerization reaction temperature is 81℃~84℃, for example, 82℃. The initiator is preferably added dropwise, which is beneficial for controlling the polymerization rate and exothermic reaction, thereby obtaining a product with a more uniform molecular weight distribution. The preferred duration of the polymerization reaction is 1 hour to 4 hours. More preferably, the reaction duration is 1.5 hours to 3 hours, for example, 2 hours, to ensure sufficient monomer conversion.

[0019] (1) Organic amine compounds: In this invention, organic amine compounds refer to aliphatic amine compounds containing two or more primary amine groups (-NH2) in their molecules, which can undergo ring-opening reactions with the epoxy groups of glycidyl ethers to form network-like or branched prepolymers. The organic amine compounds are preferably at least one of ethylenediamine, diethylenetriamine, or triethylenetetramine. Ethylenediamine (H2NCH2CH2NH2) is the simplest straight-chain diamine; diethylenetriamine (H2NCH2CH2NHCH2CH2NH2) and tetraethylenepentamine (H2N(CH2CH2NH)3CH2CH2NH2) belong to the polyethylenepolyamine series, containing more amine groups, providing higher reactivity and more potential crosslinking points. These compounds are all common chemical raw materials and are commercially available.

[0020] (2) Glycidyl ether: Glycidyl ether is a class of ether compounds containing epoxy groups, and its general formula can be represented as RO-CH2-CH-CH2, where R is an organic group. It is a key raw material in this invention for reacting with organic amine compounds to construct the prepolymer skeleton and introduce reactive hydroxyl groups. The glycidyl ether is preferably at least one of ethylene glycol diglycidyl ether or glycerol triglycidyl ether. Ethyl glycol diglycidyl ether contains two epoxy groups and can form linear or slightly branched prepolymers with diamines; glycerol triglycidyl ether contains three epoxy groups and can react with amines to form highly branched or three-dimensional network prepolymers, thereby giving the final fixing agent stronger crosslinking potential. Both of these glycidyl ethers are common epoxy resin reactive diluents or crosslinking agents.

[0021] (3) Cationic monomer: The cationic monomer is preferably dimethyl diallyl ammonium chloride (DADMAC). This is a quaternary ammonium salt cationic monomer containing two allyl groups and one quaternary ammonium cation center in its molecule. In the polymerization reaction, the allyl groups participate in free radical polymerization to form the polymer backbone, while the quaternary ammonium salt groups are permanently attached to the polymer chain as strong cation centers, giving it excellent positive charge and enabling it to firmly bind with anionic dyes through electrostatic interactions. The dimethyl diallyl ammonium chloride is usually used in the form of an aqueous solution, with a mass fraction preferably of 55% to 70%. More preferably, the mass fraction is 58% to 65%, for example, 60% or 63%. This concentration range takes into account the reactivity, system viscosity, and the convenience of subsequent water dilution.

[0022] (4) Acrylates: Acrylate monomers are used to introduce hydrophobic segments and film-forming properties, which helps to form a polymer film on the surface of leather fibers, physically coating the dye. The acrylate is preferably at least one of ethyl acrylate, butyl acrylate, or methyl methacrylate. Ethyl acrylate and butyl acrylate provide flexible polymer segments; methyl methacrylate provides higher hardness and gloss. Their combined use can adjust the glass transition temperature (Tg) and film-forming properties of the final polymer.

[0023] (5) Initiator: The initiator is used to initiate the free radical copolymerization reaction of the cationic monomer and the acrylate. Preferably, it is selected from at least one of ammonium persulfate or potassium persulfate. These are water-soluble free radical initiators that decompose to generate sulfate free radicals under heating conditions, and are suitable for the aqueous polymerization system of the present invention. They have the advantages of high initiation efficiency, low price, and easy availability.

[0024] (6) Water: The water used in each step of this invention can be deionized water, distilled water or pure water that meets the requirements of chemical production. Its function is to act as a reaction medium to dissolve or disperse the reactants and to adjust the solid content and viscosity of the system.

[0025] To achieve better technical results, the raw material ratio has been optimized in this invention.

[0026] In the step of preparing the amine prepolymer, the raw materials preferably include, by weight, 45-60 parts of an organic amine compound, 25-40 parts of glycidyl ether, and 5-25 parts of water. More preferably, the organic amine compound is 48-58 parts, the glycidyl ether is 28-38 parts, and the water is 8-22 parts. For example, a specific ratio is 50-55 parts of organic amine compound, 30-35 parts of glycidyl ether, and 10-20 parts of water. This ratio ensures a suitable molar ratio of amine groups to epoxy groups, complete reaction, and good prepolymer stability.

[0027] In the step of preparing the fixing agent, the raw materials preferably include, by weight: 45-65 parts of cationic monomer (based on its solid content or pure product, or converted if it is a solution), 55-75 parts of acrylate, 5-25 parts of amine prepolymer, 35-50 parts of water, and 0.3-1.0 parts of initiator. More preferably, the cationic monomer (converted to pure product) is 48-62 parts, the acrylate is 58-72 parts, the amine prepolymer is 8-22 parts, the water is 38-48 parts, and the initiator is 0.4-0.9 parts. For example, a more specific ratio range is: 50-60 parts of cationic monomer (60-65% solution), 60-70 parts of acrylate, 10-20 parts of amine prepolymer, 40-45 parts of water, and 0.5-0.8 parts of initiator. This formulation ensures a balance between cationicity, hydrophobic segment content, and crosslinking components, resulting in a final product with excellent colorfastness, rub fastness, and application performance.

[0028] This invention also provides a formaldehyde-free chemical crosslinking color-fixing agent for leather, prepared according to any of the above-described preparation methods. This color-fixing agent is essentially a water-soluble or water-dispersible polymer formed by copolymerization of cationic monomers, acrylate monomers, and specific amine prepolymers. It is free of formaldehyde and harmful substances such as organic halogens restricted by international regulations, making it environmentally friendly and safe. The polymer molecular chain simultaneously contains a high density of quaternary ammonium cationic groups (for electrostatic color fixing), hydrophobic acrylate segments (for film formation and coating), and reactive hydroxyl / amino groups from the amine prepolymer (which can chemically crosslink with leather fibers or itself), thereby achieving a synergistic effect of multiple color-fixing mechanisms and endowing dyed leather products with excellent dry / wet rubbing fastness, perspiration fastness, yellowing resistance, and color vibrancy.

[0029] This invention further provides the application of the aforementioned chemical crosslinking formaldehyde-free fixing agent for leather in leather color fixing. Here, "leather color fixing" broadly refers to any treatment process performed during leather processing to improve the colorfastness of dyes on leather fibers. Specifically, the application may include, but is not limited to, the following scenarios: Applications in leather dyeing and color fixing processes using different tanning methods: For example, in the post-dyeing color fixing treatment of chrome-tanned leather (referring to leather tanned using trivalent chromium salts as the main tanning agent, which is the most common and produced type of leather on the market, with good softness, heat resistance and strength), vegetable-tanned leather (referring to leather tanned using vegetable tanning agents such as tannin, which has a natural color and is environmentally friendly, but is usually more difficult to dye), or synthetic tanned leather (referring to leather tanned using synthetic tanning agents).

[0030] Applications in post-treatment of various dyeing processes: For example, after leather immersion dyeing (immersing leather in dye solution for overall dyeing) or leather spray dyeing (spraying dye solution onto the surface of leather), it is used as a post-treatment fixing agent to fix the dye.

[0031] Applications in pretreatment before finishing: For example, before leather is surface-finished (by applying a finishing agent to change its appearance and properties), it can be applied as a base color fixative to prevent the base color from migrating or bleeding during subsequent finishing processes, ensuring the purity and vibrancy of the finished layer.

[0032] The color-fixing agent of the present invention is applicable to the above-mentioned scenarios, can significantly improve various color fastness indicators of leather products, and does not affect the inherent qualities of leather such as feel and breathability, and has broad application prospects.

[0033] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0034] Example 1 This embodiment provides a method for preparing a chemically crosslinked formaldehyde-free fixing agent for leather, comprising the following steps: Preparation of amine prepolymer: 50 parts of ethylenediamine, 30 parts of ethylene glycol diglycidyl ether, and 20 parts of deionized water were added to a reaction vessel and stirred and heated to 60°C for 3 hours under inert gas protection until no separation was observed, thus obtaining a stable amine prepolymer. Preparation of a formaldehyde-free chemical crosslinking color-fixing agent for leather: 50 parts of dimethyl diallyl ammonium chloride, 20 parts of butyl acrylate, 40 parts of methyl methacrylate, 20 parts of organic amine prepolymer, and 45 parts of deionized water were added to a reactor. Under inert gas protection, the temperature was raised to 75°C and 0.5 parts of ammonium persulfate were slowly added. The temperature inside the reactor rose slowly. When it reached 78°C, the reaction temperature was maintained at around 80°C by controlling the addition of cooling water. After the addition was completed, the temperature inside the reactor was maintained at 80°C and the reaction continued for 2 hours. The reaction was then completed, and the formaldehyde-free chemical crosslinking color-fixing agent for leather was obtained.

[0035] Example 2 This embodiment provides a method for preparing a chemically crosslinked formaldehyde-free fixing agent for leather, comprising the following steps: Preparation of amine prepolymer: 50 parts of diethylenetriamine, 35 parts of ethylene glycol diglycidyl ether, and 15 parts of deionized water were added to a reaction vessel and stirred and heated to 65°C for 3 hours under inert gas protection until no separation was observed, thus obtaining a stable amine prepolymer. Preparation of a formaldehyde-free chemical crosslinking color-fixing agent for leather: 50 parts of dimethyl diallyl ammonium chloride, 25 parts of butyl acrylate, 35 parts of methyl methacrylate, 15 parts of organic amine prepolymer, and 50 parts of deionized water were added to a reactor. Under inert gas protection, the temperature was raised to 75°C and 0.5 parts of ammonium persulfate were slowly added. The temperature inside the reactor slowly rose, and when it reached 78°C, the reaction temperature was maintained at around 80°C by controlling the addition of cooling water. After the addition was completed, the temperature inside the reactor was maintained at 80°C and the reaction continued for 2 hours. The reaction was then completed, and the formaldehyde-free chemical crosslinking color-fixing agent for leather was obtained.

[0036] Example 3 This embodiment provides a method for preparing a chemically crosslinked formaldehyde-free fixing agent for leather, comprising the following steps: Preparation of amine prepolymer: 50 parts of ethylenediamine, 30 parts of glycerol triglycidyl ether, and 20 parts of deionized water were added to a reaction vessel and stirred and heated to 70°C for 3 hours under inert gas protection until no separation was observed, thus obtaining a stable amine prepolymer. Preparation of a formaldehyde-free chemical crosslinking color-fixing agent for leather: 50 parts of dimethyl diallyl ammonium chloride, 35 parts of butyl acrylate, 30 parts of methyl methacrylate, 10 parts of organic amine prepolymer, and 50 parts of deionized water were added to a reactor. Under inert gas protection, the temperature was raised to 75°C and 0.5 parts of ammonium persulfate were slowly added. The temperature inside the reactor rose slowly. When it reached 78°C, the reaction temperature was maintained at around 80°C by controlling the addition of cooling water. After the addition was completed, the temperature inside the reactor was maintained at 80°C and the reaction continued for 2 hours. The reaction was then completed, and the formaldehyde-free chemical crosslinking color-fixing agent for leather was obtained.

[0037] Example 4 This embodiment provides a method for preparing a chemically crosslinked formaldehyde-free fixing agent for leather, comprising the following steps: Preparation of amine prepolymer: 50 parts of diethylenetriamine, 35 parts of glycerol triglycidyl ether, and 15 parts of deionized water were added to a reaction vessel and stirred and heated to 70°C for 3 hours under inert gas protection until no separation was observed, thus obtaining a stable amine prepolymer. Preparation of a formaldehyde-free chemical crosslinking color-fixing agent for leather: 50 parts of dimethyl diallyl ammonium chloride, 30 parts of butyl acrylate, 30 parts of methyl methacrylate, 10 parts of organic amine prepolymer, and 50 parts of deionized water were added to a reactor. Under inert gas protection, the temperature was raised to 75°C and 0.5 parts of ammonium persulfate were slowly added. The temperature inside the reactor rose slowly. When it reached 78°C, the reaction temperature was maintained at around 80°C by controlling the addition of cooling water. After the addition was completed, the temperature inside the reactor was maintained at 80°C and the reaction continued for 2 hours. The reaction was then completed, and the formaldehyde-free chemical crosslinking color-fixing agent for leather was obtained.

[0038] Comparative Example 1 The difference from Example 1 is that the amine functional prepolymer is removed.

[0039] Comparative Example 2 The difference from Example 1 is that only the amine functional prepolymer is retained.

[0040] Comparative Example 3 The difference from Example 1 is that in step (1) when preparing the amine prepolymer, ethylene glycol diglycidyl ether is replaced with an equimolar amount of epichlorohydrin.

[0041] Comparative Example 4 The difference from Example 1 is that in step (2) when preparing the fixing agent, dimethyl diallyl ammonium chloride is replaced with an equimolar amount of acryloyloxyethyl trimethyl ammonium chloride.

[0042] Experimental Example The chemical crosslinking formaldehyde-free fixing agents for leather prepared in Examples 1-4 and Comparative Examples 1-4 were applied to the fixing process of the standard dyeing process for leather. The control samples were fixing agent Y (a commercially available fixing agent) and formaldehyde-free fixing agent Dawei Lato GSA (Dawei Group). The detection methods were all in accordance with the leather testing method. The reference detection methods and standards are as follows: (1) HG / T 3689-2001 Test method for yellowing resistance of leather; (2) GB / T 3922-2013 Test method for color fastness to perspiration; (3) GB / T 3920-2008 Color fastness to reciprocating rubbing of leather; (4) GB / T19941-2019 Determination of formaldehyde content in leather and fur; The experimental results are shown in Figure 1: Table 1 Performance Test Results project Fixing agent Y Fixing agent GSA Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Formaldehyde content in hide (ppm) 151 ND ND ND ND ND ND ND ND ND Limited materials It is (formaldehyde) It is (dichloropropanol) ND ND ND ND ND ND It is (dichloropropanol) ND Leather yellowing resistance test - sunlight Level 2 Level 3-4 Level 4 Level 4-5 Level 4 Level 4 Level 3-4 Level 3 Level 3 Level 3-4 Leather yellowing resistance test - ultraviolet light Level 2-3 Level 3-4 Level 4-5 Level 4-5 Level 4-5 Level 4-5 Level 4 Level 2-3 Level 3 Level 2-3 Dry rubbing performance Level 4-5 Level 3 Level 3-4 Level 3-4 Level 3-4 Level 3-4 Level 3 Level 2-3 Level 3-4 Level 3 wet scrubbing performance Level 3-4 Level 4 Level 4 Level 4 Level 4 Level 4 Level 3-4 Level 3 Level 2-3 Level 2 Sweat resistance Level 4 Level 4 Level 4-5 Level 4-5 Level 4-5 Level 4-5 Level 3-4 Level 3-4 Level 3-4 Level 2 Color (bright red) yellow Yellowish red red red red red Red bias Yellowish Yellowish Note: The rating system is based on 1-6 levels. The higher the number, the higher the level and the better the performance. By comparing Examples 1-4 with Comparative Examples 1-4 and commercially available color-fixing agents, the formaldehyde-free color-fixing agent prepared in this application, when applied to leather color fixing, produces leather with dry and wet rubbing resistance and sweat stain resistance levels no lower than those of existing technologies. Furthermore, its yellowing resistance level is higher than the control sample, and the color-fixed leather exhibits superior vibrancy compared to existing commercial technologies. Moreover, it eliminates the introduction of restricted substances, resulting in better environmental friendliness and application prospects. Therefore, it can be concluded that the chemically cross-linked formaldehyde-free color-fixing agent prepared according to the formulation of this application has higher color-fixing efficiency and better color-fixing effect.

[0043] As can be seen from the above embodiments, the present invention provides a high-performance chemical crosslinking formaldehyde-free fixing agent for leather. Application experimental results show that, compared with mainstream commercially available fixing agents, leather treated with the fixing agent prepared by the method of the present invention is completely formaldehyde-free, exhibits a significant advantage in yellowing resistance, and maintains a more vibrant and stable color. Simultaneously, it achieves excellent levels in dry rubbing, wet rubbing, and perspiration fastness, significantly improving the overall fixing effect and fully verifying the advanced nature and practicality of the technical solution of the present invention.

[0044] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a formaldehyde-free chemical crosslinking color-fixing agent for leather, characterized in that, Includes the following steps: To prepare amine prepolymers, an organic amine compound, glycidyl ether, and water are mixed and subjected to a first heating reaction under inert gas protection to obtain the amine prepolymers. To prepare the fixing agent, a cationic monomer, acrylate, the amine prepolymer, and water are mixed and heated under inert gas protection. Then, an initiator is added to carry out a polymerization reaction to obtain the chemically crosslinked formaldehyde-free fixing agent for leather.

2. The preparation method according to claim 1, characterized in that, The temperature of the first heating reaction is 60℃~70℃; The second heating temperature is 70℃~75℃; The polymerization reaction was carried out at 80℃~85℃.

3. The preparation method according to claim 1, characterized in that, The initiator is added dropwise. The polymerization reaction lasts for 1 to 4 hours.

4. The preparation method according to claim 1, characterized in that, The organic amine compound is selected from at least one of ethylenediamine, diethylenetriamine, or triethylenetetramine; The glycidyl ether is selected from at least one of ethylene glycol glycidyl ether or glycerol triglycidyl ether; The cationic monomer is dimethyldiallylammonium chloride.

5. The preparation method according to claim 4, characterized in that, The dimethyl diallyl ammonium chloride is used in the form of an aqueous solution with a mass fraction of 55% to 70%.

6. The preparation method according to claim 1, characterized in that, The acrylate is selected from at least one of ethyl acrylate, butyl acrylate, or methyl methacrylate; The initiator is selected from at least one of ammonium persulfate or potassium persulfate.

7. The preparation method according to claim 1, characterized in that, The raw materials in the step of preparing amine prepolymer include, by weight, 45-60 parts of organic amine compound, 25-40 parts of glycidyl ether and 5-25 parts of water; The raw materials in the preparation of the fixing agent include, by weight, 45-65 parts of cationic monomer, 55-75 parts of acrylate, 5-25 parts of amine prepolymer, 35-50 parts of water, and 0.3-1.0 parts of initiator.

8. A chemical crosslinking formaldehyde-free fixing agent for leather prepared by any one of claims 1 to 7.

9. The application of the chemical crosslinking formaldehyde-free fixing agent for leather as described in claim 8 in leather color fixing.

10. The application according to claim 9, characterized in that, The applications include use in the dyeing and fixing processes of chrome-tanned, vegetable-tanned, or synthetic tanned leather, or in the post-treatment of leather immersion dyeing or spray dyeing processes, or as a base color fixative before leather finishing.