Environment-friendly amphoteric acrylic retanning agent and preparation method thereof

Abstract

The present application relates to the technical field of leather chemical materials, and particularly relates to an environment-friendly amphoteric acrylic re-tanning agent and a preparation method thereof. The amphoteric acrylic re-tanning agent is prepared by mixing a mixed solution obtained by mixing raw materials of acrylamide, acrylic acid, acrylonitrile, ethyl acrylate and hydroxyethyl acrylate, an initiator solution, a reaction aid and beta-cyclodextrin. The crude leather treated by the re-tanning agent has excellent mechanical properties, the thickening rate is improved, the resilience is excellent, and the grain surface is fine, which indicates that the prepared re-tanning agent has excellent comprehensive performance.

Description

Technical Field

[0001] This invention relates to the field of leather chemical materials technology, specifically to an environmentally friendly amphoteric acrylic retanning agent and its preparation method. Background Technology

[0002] In leather production, the retanning process is a crucial step determining the performance and quality of leather. Retanning agents, as the core chemical materials in this process, directly affect the fullness, elasticity, softness, dyeing uniformity, and chemical stability of the leather. Currently, a large portion of the retanning agents used in leather manufacturing are acrylic resin tanning agents, which are homopolymers of (meth)acrylic acid (esters) or copolymers of acrylic monomers with other vinyl monomers. It is an important class of leather chemical materials, not only imparting excellent chemical and physical properties to leather but also offering a highly competitive cost-performance ratio. Due to their chemical stability and environmental friendliness during application, and more importantly, their high absorption capacity for mineral-tanned leather, especially chrome-tanned leather, acrylic resin tanning agents occupy an important position in the retanning of chrome-tanned leather.

[0003] Chinese patent CN119101191B discloses an emulsion-type acrylic retanning agent and its preparation method. An intermediate is obtained by reacting a nonionic surfactant with maleic anhydride, and then copolymerizing it with ethylene monomers in the presence of a reaction medium, emulsifier and initiator to obtain the emulsion-type acrylic retanning agent. The finished product is stable and does not separate. It is simple to produce and has low cost. The processed leather is full and soft and has good filling properties. Chinese Patent CN115181216B discloses a retanning agent and its preparation method. The method involves mixing N,N-dihydroxyethyl maleamic acid self-reactive ester, an emulsifier, a first water-based initiator, and water to obtain a first monomer solution. Trimethylolpropane trimethacrylate and an oil-soluble initiator are then mixed to obtain a second monomer solution. The second monomer solution is added to the first monomer solution to conduct a first polymerization reaction, resulting in a prepolymer system. Acrylic acid and a second water-soluble initiator are added to the prepolymer system to conduct a second polymerization reaction, yielding the retanning agent. After use, the resulting leather exhibits strong tear resistance, fine grain, and good resilience after embossing.

[0004] However, traditional acrylic retanning agents are mostly single anionic or cationic structures, which have performance limitations, poor filling effect on soft parts of leather tissue, and the monomers or auxiliaries used in the preparation process are volatile and toxic. Therefore, there is an urgent need to develop an acrylic retanning agent that has both excellent performance and environmental protection characteristics. Summary of the Invention

[0005] To address at least one of the above problems, this invention provides a method for preparing an environmentally friendly amphoteric acrylic retanning agent, comprising the following steps: S100 uses acrylamide, acrylic acid, acrylonitrile, ethyl acrylate, and hydroxyethyl acrylate as raw materials. After mixing, nitrogen-containing heterocyclic monomers, phosphorus-containing monomers, and quaternary ammonium salt cationic monomers are added to obtain a mixed solution. S200, using potassium persulfate and sodium sulfite as raw materials, an initiator solution is prepared; epoxidized polyamide-amine dendritic macromolecules are mixed evenly with solvent to obtain a reaction aid; S300. Add the mixture and initiator solution to the reaction vessel. After the addition is complete, add the reaction aid, adjust the pH of the system, add β-cyclodextrin, and the reaction is completed to obtain the amphoteric acrylic retanning agent.

[0006] Further, step S100 specifically involves: dissolving acrylamide in deionized water, adjusting the pH of the solution to 4.5-5.5 with dilute hydrochloric acid, then sequentially adding acrylic acid, acrylonitrile, ethyl acrylate, and hydroxyethyl acrylate, stirring for 20-30 minutes, and then adding a nitrogen-containing heterocyclic monomer, a phosphorus-containing monomer, and a quaternary ammonium salt cationic monomer, and continuing to stir for 15-25 minutes to obtain a mixed solution.

[0007] Further, the nitrogen-containing heterocyclic monomer is one or more of 4-vinylpyridine, 4-methyl-2-vinylpyridine, N-vinylpyrrolidone, and 2-vinylquinoline; the phosphorus-containing monomer is one or more of 2-methyl-2-acrylate-2-hydroxyethyl phosphate, dimethyl vinyl phosphate, and 1,2-vinyl diphosphonic acid; and the quaternary ammonium salt cationic monomer is one or more of methacryloyloxyethyltrimethylammonium chloride, dimethyl diallyl ammonium chloride, and methacryloyloxyethyldimethylbenzyl ammonium chloride.

[0008] Furthermore, step S200 specifically includes: S210. Dissolve potassium persulfate in deionized water, stir until dissolved, add sodium sulfite, and continue stirring until completely dissolved to obtain the initiator solution. S220. Add epoxidized polyamide-amine dendritic macromolecules to deionized water and ultrasonically disperse for 10-20 minutes to obtain a uniform dispersion, which is the reaction aid.

[0009] Further, the preparation method of the epoxidized polyamide-amine dendritic macromolecule is as follows: the polyamide-amine dendritic macromolecule is dissolved in anhydrous ethanol, a catalyst is added, and after stirring evenly, epichlorohydrin is added to it at 30-40℃. After the addition is completed, the temperature is raised to 50-60℃ and the reaction is maintained for 4-6 hours. After the reaction is completed, the epoxidized polyamide-amine dendritic macromolecule is obtained by vacuum distillation.

[0010] Furthermore, epichlorohydrin was added dropwise at a rate of 1-2 mL / min.

[0011] Further, step S300 specifically involves: raising the temperature of the reactor to 50-60°C, starting the stirrer, adding the mixture and initiator solution dropwise, raising the temperature to 70-80°C after the addition is complete, maintaining the temperature for 1-3 hours, lowering the temperature to 40-50°C, adding the reaction aid, and stirring the reaction for 30-40 minutes; then adding sodium hydroxide solution to the reactor to adjust the pH of the system to 6.0-7.0, lowering it to room temperature, adding β-cyclodextrin, stirring for 1-2 hours to obtain the mixture, and filtering to obtain the amphoteric acrylic retanning agent.

[0012] Furthermore, the dropping rate of the initiator solution in the mixture is 1-3 mL / min.

[0013] The present invention also provides an environmentally friendly amphoteric acrylic retanning agent, which is prepared by the preparation method of an environmentally friendly amphoteric acrylic retanning agent as described in any of the above technical solutions.

[0014] The present invention has the following beneficial effects: This invention uses acrylamide, acrylic acid, acrylonitrile, ethyl acrylate, and hydroxyethyl acrylate as raw materials, and introduces various functional monomers. These are mixed to obtain a mixture, which is then reacted with an initiator solution, reaction aids, and β-cyclodextrin to obtain the amphoteric acrylic retanning agent. The addition of nitrogen-containing heterocyclic monomers can interact with metal ions in leather collagen fibers, improving leather properties. The addition of phosphorus-containing monomers can combine with hydroxyl groups on collagen fibers, enhancing the flame retardancy of the retanning agent; the strong polarity of their phosphate groups can improve the dispersion stability of the retanning agent. The addition of quaternary ammonium salt cationic monomers introduces a cationic charge, which synergistically forms an amphoteric retanning agent with the anionic charge of acrylic acid, enhancing the softness and evenness of the leather and avoiding uneven dyeing caused by a single charge. The reaction aid is an epoxidized polyamide-amine dendritic macromolecule, whose highly branched structure provides a large number of active sites for the copolymer, enhancing the binding ability of the retanning agent to the leather fiber; the unique hollow structure of the β-cyclodextrin molecule, its hydrophobic cavity forms an inclusion effect with the hydrophobic groups on the copolymer chain, and at the same time, the hydroxyl groups on its outer surface can form hydrogen bonds with the groups on the surface of the leather fiber, further enhancing the binding ability of the retanning agent to the leather. Detailed Implementation

[0015] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the embodiments of this application. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0016] Retanning agents are a key step in leather production, and their performance directly determines core indicators such as the softness and fullness of the finished leather. They are one of the most critical leather chemical materials in leather processing. Acrylic retanning agents are widely used in leather processing due to their advantages such as chemical stability, high cost-effectiveness, and good filling properties. However, their solubility and permeability need to be optimized because their molecules tend to aggregate. This invention provides a method for preparing an environmentally friendly amphoteric acrylic retanning agent, comprising the following steps: S100 uses acrylamide, acrylic acid, acrylonitrile, ethyl acrylate, and hydroxyethyl acrylate as raw materials. After mixing, nitrogen-containing heterocyclic monomers, phosphorus-containing monomers, and quaternary ammonium salt cationic monomers are added to obtain a mixed solution. S200, using potassium persulfate and sodium sulfite as raw materials, an initiator solution is prepared; epoxidized polyamide-amine dendritic macromolecules are mixed evenly with solvent to obtain a reaction aid; S300. Add the mixture and initiator solution to the reaction vessel. After the addition is complete, add the reaction aid, adjust the pH of the system, add β-cyclodextrin, and the reaction is completed to obtain the amphoteric acrylic retanning agent.

[0017] Specifically, step S100 involves adding acrylamide to deionized water and stirring at room temperature until completely dissolved. The pH of the solution is adjusted to 4.5-5.5 with dilute hydrochloric acid. Acrylic acid, acrylonitrile, ethyl acrylate, and hydroxyethyl acrylate are added sequentially. The mixture is stirred at 200-300 r / min for 20-30 min, followed by the addition of nitrogen-containing heterocyclic monomers, phosphorus-containing monomers, and quaternary ammonium salt cationic monomers. The mixture is stirred for another 15-25 min to obtain the final mixture.

[0018] The nitrogen-containing heterocyclic monomer is one or more of 4-vinylpyridine, 4-methyl-2-vinylpyridine, N-vinylpyrrolidone, and 2-vinylquinoline, preferably 4-vinylpyridine, whose pyridine ring can interact with metal ions in leather collagen fibers to improve leather properties; the phosphorus-containing monomer is one or more of 2-methyl-2-acrylate-2-hydroxyethyl phosphate, dimethyl vinyl phosphate, and 1,2-vinyl diphosphonic acid, preferably 2-methyl-2-acrylate-2-hydroxyethyl phosphate. It can combine with the hydroxyl groups on collagen fibers to enhance the flame retardancy of retanning agents. The strong polarity of the phosphate ester group can improve the dispersion stability of retanning agents. The quaternary ammonium salt cationic monomer is one or more of methacryloyloxyethyltrimethylammonium chloride, dimethyl diallyl ammonium chloride, and methacryloyloxyethyldimethylbenzyl ammonium chloride, preferably methacryloyloxyethyltrimethylammonium chloride. It introduces a cationic charge, which synergistically forms an amphoteric retanning agent with the anionic charge of acrylic acid. This can enhance the softness and evenness of leather and avoid uneven dyeing caused by a single charge. The mass ratio of acrylamide, acrylic acid, acrylonitrile, ethyl acrylate, hydroxyethyl acrylate, nitrogen-containing heterocyclic monomer, phosphorus-containing monomer, quaternary ammonium salt cationic monomer, and deionized water is 12-18:10-14:6-9:8-12:6-10:5-8:4-7:5-9:35-55; the mass fraction of dilute hydrochloric acid is 5%-20%.

[0019] In this step, acrylamide, as a monomer containing amide groups, can form hydrogen bonds with the carboxyl groups of leather fibers, thereby enhancing the binding strength of the retanning agent; acrylic acid provides anionic carboxyl groups, which is the core monomer for realizing the anionic properties of the retanning agent; acrylonitrile can improve the chemical stability of the retanning agent; ethyl acrylate, as a flexible monomer, can improve the softness of the retanning agent; hydroxyethyl acrylate can introduce hydroxyl active sites, undergo cross-linking reactions with other monomers, improve the cross-linking density and filling properties of the retanning agent, and synergistically improve the fullness of the leather.

[0020] Specifically, step S200 is as follows: S210. Dissolve potassium persulfate in deionized water, stir at 150-200 r / min until dissolved, then add sodium sulfite and continue stirring until completely dissolved to obtain the initiator solution. S220. Add epoxidized polyamide-amine dendritic macromolecules to deionized water and ultrasonically disperse them at a power of 200-300W for 10-20 minutes to obtain a uniform dispersion, which is the reaction aid.

[0021] In step S210, the mass ratio of potassium persulfate, sodium sulfite, and deionized water is 1-3:0.5-1.5:10-20. Potassium persulfate acts as an oxidant, and sodium sulfite acts as a reducing agent, forming a redox system. In the aqueous solution, persulfate ions and sulfite ions undergo a redox reaction to generate sulfate free radicals and sulfite free radicals, initiating subsequent free radical copolymerization reactions. In step S220, the mass ratio of epoxidized polyamide-amine dendritic macromolecules to deionized water is 4-7:10-20. Epoxidized polyamide-amine dendritic macromolecules act as a reaction aid, enhancing the binding ability of retanning agents to leather fibers. Ultrasonic dispersion ensures that the epoxidized polyamide-amine dendritic macromolecules form a uniform dispersion in water, preventing uneven improvement due to aggregation.

[0022] The preparation method of the epoxidized polyamide-amine dendritic macromolecule is as follows: the polyamide-amine dendritic macromolecule (Qiyue Biotechnology Co., Ltd., G5.0 PAMAM-NH2) is dissolved in anhydrous ethanol, a catalyst is added, and after stirring evenly, epichlorohydrin is added at 30-40℃. After the addition is completed, the temperature is raised to 50-60℃ and the reaction is maintained for 4-6 hours. After the reaction is completed, the epoxidized polyamide-amine dendritic macromolecule is obtained by vacuum distillation at 0.06-0.09MPa and 60-70℃.

[0023] The mass ratio of polyamide-amine dendritic macromolecules, catalyst, epichlorohydrin, and anhydrous ethanol is 5-10:0.25-0.5:3-8:20-40; the catalyst is triethylamine; and the dropping rate of epichlorohydrin is 1-2 mL / min. In this process, the polyamide-amine dendritic macromolecule contains a large number of amino groups. Under the action of a catalyst, the amino groups react with the epoxy groups in the epichlorohydrin molecule to undergo an epoxy ring-opening reaction, introducing epoxy groups onto the surface of the polyamide-amine dendritic macromolecule to form an epoxidized polyamide-amine dendritic macromolecule.

[0024] Specifically, step S300 involves: raising the temperature of the reactor to 50-60°C, starting the stirrer, adding the mixture and initiator solution dropwise, raising the temperature to 70-80°C after the addition is complete, maintaining the temperature for 1-3 hours, lowering the temperature to 40-50°C, adding the reaction aid, and stirring the reaction for 30-40 minutes; then adding sodium hydroxide solution to the reactor to adjust the pH of the system to 6.0-7.0, lowering the temperature to room temperature, adding β-cyclodextrin, stirring for 1-2 hours to obtain the mixture, and filtering to obtain the amphoteric acrylic retanning agent.

[0025] The mass ratio of the mixture, initiator solution, reaction aid, and β-cyclodextrin is 60-85:12-20:13-22:2.5-4.5. The dropping rate of the initiator solution in the mixture is 1-3 mL / min. Slow dropping allows the monomer and initiator to come into uniform contact, avoiding excessively high local free radical concentrations that could lead to a violent reaction. The mass fraction of sodium hydroxide is 10%-20%.

[0026] In this process, sulfate and sulfite radicals in the initiator solution first attack the carbon-carbon double bonds in the monomer molecules, opening them and initiating a free radical copolymerization reaction. Then, the epoxy groups in the epoxidized polyamide-amine dendritic macromolecule undergo an epoxy ring-opening reaction with the hydroxyl and amide groups in the system, grafting the dendritic macromolecule onto the copolymer chain. The highly branched structure of the dendritic macromolecule provides numerous active sites for the copolymer, enhancing the binding ability of the retanning agent to leather fibers. The unique hollow structure of the β-cyclodextrin molecule, with its hydrophobic cavity forming an inclusion complex with the hydrophobic groups on the copolymer chain, and the hydroxyl groups on its outer surface forming hydrogen bonds with groups on the leather fiber surface, further enhances the binding ability of the retanning agent to leather.

[0027] Preparation Example 1 The preparation method of epoxidized polyamide-amine dendritic macromolecule is as follows: 5 parts by weight of polyamide-amine dendritic macromolecule are dissolved in 20 parts by weight of anhydrous ethanol and stirred at 200 r / min until completely dissolved. Then, 0.25 parts by weight of triethylamine are added and stirred for another 10 min until homogeneous. Then, 3 parts by weight of epichlorohydrin are slowly added to the mixture at 30℃ with a dropping rate of 1 mL / min. After the addition is complete, the temperature is raised to 50℃ and the reaction is maintained for 4 h. After the reaction is complete, the mixture is placed in a rotary evaporator and distilled under reduced pressure at 0.06 MPa and 60℃ to obtain epoxidized polyamide-amine dendritic macromolecule.

[0028] Preparation Example 2 This preparation example differs from Preparation Example 1 in the following ways: The preparation method of epoxidized polyamide-amine dendritic macromolecule is as follows: 8 parts by weight of polyamide-amine dendritic macromolecule are dissolved in 32 parts by weight of anhydrous ethanol, 0.35 parts by weight of triethylamine are added, and then 6 parts by weight of epichlorohydrin are slowly added to it at 35°C at a dropping rate of 1.5 mL / min. After the addition is completed, the temperature is raised to 55°C and the reaction is maintained for 5 hours. After the reaction is completed, the mixture is distilled under reduced pressure at 65°C with a vacuum degree of 0.08 MPa.

[0029] Preparation Example 3 This preparation example differs from Preparation Example 1 in the following ways: The preparation method of epoxidized polyamide-amine dendritic macromolecule is as follows: 10 parts by weight of polyamide-amine dendritic macromolecule are dissolved in 40 parts by weight of anhydrous ethanol, 0.5 parts by weight of triethylamine are added, and then 8 parts by weight of epichlorohydrin are slowly added to it at 40℃ with a dropping rate of 2 mL / min. After the addition is completed, the temperature is raised to 60℃ and the reaction is maintained for 6 hours. After the reaction is completed, the mixture is distilled under reduced pressure at 70℃ with a vacuum degree of 0.089 MPa.

[0030] Example 1 A method for preparing an environmentally friendly amphoteric acrylic retanning agent includes the following steps: S1. Add 12 parts by weight of acrylamide to 35 parts by weight of deionized water and stir at room temperature until completely dissolved. Adjust the pH of the solution to 4.5 with 5% (w / w) dilute hydrochloric acid. Add 10 parts by weight of acrylic acid, 6 parts by weight of acrylonitrile, 8 parts by weight of ethyl acrylate and 6 parts by weight of hydroxyethyl acrylate in sequence. Stir at 200 r / min for 20 min. Then add 5 parts by weight of 4-vinylpyridine, 4 parts by weight of 2-methyl-2-acrylate-2-hydroxyethyl phosphate and 5 parts by weight of methacryloyloxyethyltrimethylammonium chloride. Continue stirring for 15 min to obtain a mixed solution. S2. Dissolve 1 part by weight of potassium persulfate in 10 parts by weight of deionized water, stir at 150 r / min until dissolved, then add 0.5 parts by weight of sodium sulfite, and continue stirring until completely dissolved to obtain an initiator solution; add 4 parts by weight of the epoxidized polyamide-amine dendritic macromolecules prepared in Preparation Example 2 to 10 parts by weight of deionized water, and ultrasonically disperse at 200 W for 10 min to obtain a uniform dispersion, which is the reaction aid; S3. Raise the temperature of the reactor to 50°C, start stirring, and add 60 parts by weight of the mixed solution and 12 parts by weight of the initiator solution dropwise at a speed of 250 r / min. After the addition is complete, raise the temperature to 70°C, keep it at this temperature for 1 hour, and then lower the temperature to 40°C. Add 13 parts by weight of the reaction aid and stir for 30 minutes. Then add 10% sodium hydroxide solution to the reactor to adjust the pH of the system to 6.0. After cooling to room temperature, add 2.5 parts by weight of β-cyclodextrin and stir for 1 hour to obtain a mixture. After filtration, obtain the amphoteric acrylic retanning agent.

[0031] Example 2 This embodiment differs from Embodiment 1 in the following ways: In step S1, 14 parts by weight of acrylamide are added to 45 parts by weight of deionized water, and the pH of the solution is adjusted to 5.0 with 5% hydrochloric acid. Then, 11.5 parts by weight of acrylic acid, 7.5 parts by weight of acrylonitrile, 10 parts by weight of ethyl acrylate and 8 parts by weight of hydroxyethyl acrylate are added sequentially. After stirring at 250 r / min for 25 min, 6.5 parts by weight of 4-vinylpyridine, 5.5 parts by weight of 2-methyl-2-acrylate-2-hydroxyethyl ester phosphate and 7 parts by weight of methacryloyloxyethyltrimethylammonium chloride are added. After stirring for another 20 min, a mixture is obtained.

[0032] In step S2, 1.5 parts by weight of potassium persulfate were dissolved in 14 parts by weight of deionized water. After stirring at 150 r / min, 0.8 parts by weight of sodium sulfite were added and stirring was continued until completely dissolved to obtain an initiator solution. 5.5 parts by weight of the epoxidized polyamide-amine dendritic macromolecules prepared in Preparation Example 2 were added to 14 parts by weight of deionized water and ultrasonically dispersed at 250 W for 15 min to obtain a uniform dispersion, which is the reaction aid.

[0033] In step S3, the temperature of the reactor is raised to 55°C, stirring is started, and 75 parts by weight of the mixed solution and 15 parts by weight of the initiator solution are added dropwise at a speed of 250 r / min. After the addition is completed, the temperature is raised to 75°C and kept at this temperature for 2 hours. Then, the temperature is lowered to 45°C, and 16 parts by weight of the reaction aid is added. The mixture is stirred for 35 minutes. Then, 10% sodium hydroxide solution is added to the reactor to adjust the pH of the system to 6.5. After cooling to room temperature, 3.2 parts by weight of β-cyclodextrin is added. After stirring for 1.5 hours, a mixture is obtained. The mixture is then filtered to obtain the amphoteric acrylic retanning agent.

[0034] Example 3 This embodiment differs from Embodiment 1 in the following ways: In step S1, 16 parts by weight of acrylamide are added to 55 parts by weight of deionized water, and the pH of the solution is adjusted to 5.0 with 5% hydrochloric acid. Then, 13 parts by weight of acrylic acid, 8.5 parts by weight of acrylonitrile, 11 parts by weight of ethyl acrylate and 9 parts by weight of hydroxyethyl acrylate are added sequentially. After stirring at 250 r / min for 20 min, 7 parts by weight of 4-vinylpyridine, 6 parts by weight of 2-methyl-2-acrylate-2-hydroxyethyl ester phosphate and 8 parts by weight of methacryloyloxyethyltrimethylammonium chloride are added, and stirring is continued for 15 min to obtain a mixture. In step S2, 2.5 parts by weight of potassium persulfate were dissolved in 18 parts by weight of deionized water. After dissolving by stirring at 200 r / min, 1.2 parts by weight of sodium sulfite were added and stirring was continued until completely dissolved to obtain an initiator solution. 6.5 parts by weight of the epoxidized polyamide-amine dendritic macromolecules prepared in Preparation Example 2 were added to 18 parts by weight of deionized water and ultrasonically dispersed at 250 W for 20 min to obtain a uniform dispersion, which is the reaction aid.

[0035] In step S3, the temperature of the reactor is raised to 55°C, stirring is started, and 80 parts by weight of the mixed solution and 18 parts by weight of the initiator solution are added dropwise at a speed of 250 r / min. After the addition is completed, the temperature is raised to 75°C and kept at this temperature for 2 hours. Then, the temperature is lowered to 45°C, and 20 parts by weight of the reaction aid is added. The mixture is stirred for 35 minutes. Then, 10% sodium hydroxide solution is added to the reactor to adjust the pH of the system to 6.5. After cooling to room temperature, 4 parts by weight of β-cyclodextrin are added. After stirring for 2 hours, a mixture is obtained. The mixture is then filtered to obtain the amphoteric acrylic retanning agent.

[0036] Example 4 This embodiment differs from Embodiment 1 in the following ways: In step S1, 18 parts by weight of acrylamide are added to 55 parts by weight of deionized water and stirred at room temperature until completely dissolved. The pH of the solution is adjusted to 5.5 with 5% hydrochloric acid. Then, 14 parts by weight of acrylic acid, 9 parts by weight of acrylonitrile, 12 parts by weight of ethyl acrylate and 10 parts by weight of hydroxyethyl acrylate are added sequentially. After stirring at 300 r / min for 30 min, 8 parts by weight of 4-vinylpyridine, 7 parts by weight of 2-methyl-2-acrylate-2-hydroxyethyl ester phosphate and 9 parts by weight of methacryloyloxyethyltrimethylammonium chloride are added. After stirring for another 55 min, a mixture is obtained.

[0037] In step S2, 3 parts by weight of potassium persulfate were dissolved in 20 parts by weight of deionized water. After stirring at 200 r / min, 1.5 parts by weight of sodium sulfite were added and stirring was continued until completely dissolved to obtain an initiator solution. 7 parts by weight of the epoxidized polyamide-amine dendritic macromolecules prepared in Preparation Example 2 were added to 20 parts by weight of deionized water and ultrasonically dispersed at 300 W for 20 min to obtain a uniform dispersion, which is the reaction aid.

[0038] In step S3, the temperature of the reactor is raised to 60°C, stirring is started, and 85 parts by weight of the mixed solution and 20 parts by weight of the initiator solution are added dropwise at a speed of 250 r / min. After the addition is completed, the temperature is raised to 80°C and kept at this temperature for 3 hours. Then the temperature is lowered to 50°C, and 22 parts by weight of the reaction aid are added. The mixture is stirred for 40 minutes. Then, 10% sodium hydroxide solution is added to the reactor to adjust the pH of the system to 7.0. After cooling to room temperature, 4.5 parts by weight of β-cyclodextrin are added. After stirring for 2 hours, a mixture is obtained. The mixture is then filtered to obtain the amphoteric acrylic retanning agent.

[0039] Comparative Example 1 Compared with Example 1, this comparative example does not add nitrogen-containing heterocyclic monomers during the preparation process; all other aspects are the same as in Example 1. Specifically: In step S1, 12 parts by weight of acrylamide are added to 35 parts by weight of deionized water and stirred at room temperature until completely dissolved. The pH of the solution is adjusted to 4.5 with 5% hydrochloric acid. Then, 10 parts by weight of acrylic acid, 6 parts by weight of acrylonitrile, 8 parts by weight of ethyl acrylate and 6 parts by weight of hydroxyethyl acrylate are added sequentially. After stirring at 200 r / min for 20 min, 4 parts by weight of 2-methyl-2-acrylate-2-hydroxyethyl phosphate and 5 parts by weight of methacryloyloxyethyltrimethylammonium chloride are added. After stirring for another 15 min, a mixture is obtained.

[0040] Comparative Example 2 Compared with Example 1, this comparative example does not add phosphorus-containing monomers during the preparation process, but otherwise follows the same procedure as Example 1. Specifically: In step S1, 12 parts by weight of acrylamide are added to 35 parts by weight of deionized water and stirred at room temperature until completely dissolved. The pH of the solution is adjusted to 4.5 with 5% hydrochloric acid. Then, 10 parts by weight of acrylic acid, 6 parts by weight of acrylonitrile, 8 parts by weight of ethyl acrylate and 6 parts by weight of hydroxyethyl acrylate are added sequentially. The mixture is stirred at 200 r / min for 20 min, and then 5 parts by weight of 4-vinylpyridine and 5 parts by weight of methacryloyloxyethyltrimethylammonium chloride are added. The mixture is stirred for another 15 min to obtain a mixed solution.

[0041] Comparative Example 3 Compared with Example 1, this comparative example does not add quaternary ammonium salt-type cationic monomers during the preparation process; the rest is the same as in Example 1. Specifically: In step S1, 12 parts by weight of acrylamide are added to 35 parts by weight of deionized water and stirred at room temperature until completely dissolved. The pH of the solution is adjusted to 4.5 with 5% by weight of dilute hydrochloric acid. Then, 10 parts by weight of acrylic acid, 6 parts by weight of acrylonitrile, 8 parts by weight of ethyl acrylate and 6 parts by weight of hydroxyethyl acrylate are added sequentially. The mixture is stirred at 200 r / min for 20 min, and then 5 parts by weight of 4-vinylpyridine and 4 parts by weight of 2-methyl-2-acrylate-2-hydroxyethyl phosphate are added. The mixture is stirred for another 15 min to obtain a mixed solution.

[0042] Comparative Example 4 Compared with Example 1, the epoxidized polyamide-amine dendritic macromolecule in this comparative example was replaced with a polyamide-amine dendritic macromolecule during the preparation process; the rest was the same as in Example 1. Specifically: In step S2, 1 part by weight of potassium persulfate is dissolved in 10 parts by weight of deionized water. After stirring at 150 r / min, 0.5 parts by weight of sodium sulfite is added and stirring is continued until completely dissolved to obtain an initiator solution. 4 parts by weight of polyamide-amine dendritic macromolecules are added to 10 parts by weight of deionized water and ultrasonically dispersed at 200 W for 10 min to obtain a uniform dispersion, which is the reaction aid.

[0043] Comparative Example 5 Compared with Example 1, this comparative example does not add epoxidized polyamide-amine dendritic macromolecules during the preparation process; the rest is the same as in Example 1. Specifically: In step S2, 1 part by weight of potassium persulfate is dissolved in 10 parts by weight of deionized water. After stirring at 150 r / min to dissolve, 0.5 parts by weight of sodium sulfite is added, and stirring is continued until completely dissolved to obtain the initiator solution.

[0044] In step S3, the temperature of the reactor is raised to 50°C, stirring is started, and 60 parts by weight of the mixed solution and 12 parts by weight of the initiator solution are added dropwise at a speed of 250 r / min. After the addition is completed, the temperature is raised to 70°C, kept at this temperature for 1 hour, and then the temperature is lowered to 40°C. Then, 10% sodium hydroxide solution is added to the reactor to adjust the pH of the system to 6.0. After cooling to room temperature, 2.5 parts by weight of β-cyclodextrin are added, and the mixture is stirred for 1 hour to obtain a mixture. After filtration, the amphoteric acrylic retanning agent is obtained.

[0045] Comparative Example 6 Compared with Example 1, this comparative example does not add β-cyclodextrin during the preparation process, but otherwise follows the same procedure as Example 1. Specifically: In step S3, the temperature of the reactor is raised to 50°C, stirring is started, and 60 parts by weight of the mixed solution and 12 parts by weight of the initiator solution are added dropwise at a speed of 250 r / min. After the addition is completed, the temperature is raised to 70°C and kept at this temperature for 1 hour. Then, the temperature is lowered to 40°C, and 13 parts by weight of the reaction aid are added. The mixture is stirred for 30 minutes. Then, a 10% sodium hydroxide solution is added to the reactor to adjust the pH of the system to 6.0. After cooling to room temperature, the mixture is stirred for 1 hour to obtain a mixture. The mixture is then filtered to obtain the amphoteric acrylic retanning agent.

[0046] Related tests: Using wet blue leather as raw material, the experiment was conducted in a GBS-type pump-heated stainless steel temperature-controlled test drum (manufactured by Jiangsu Wuxi Xinda Light Industry Machinery Co., Ltd.). The softening, chrome retanning, and neutralization processes were carried out according to conventional procedures. During the retanning process, the retanning agents prepared in each example and comparative example were added at 15% of the wet blue leather weight. The leather was treated in the drum for 1.5 hours at 35°C. After drainage, it entered the fatliquoring process, where the general-purpose fatliquoring agent BUXOM SS (Qihe Lihou Chemical Co., Ltd.) was added. The leather was treated in the drum for 1 hour at 50°C. Then, formic acid at 1.2% of the wet blue leather weight was added for fixation. This formic acid was diluted with three times the amount of water and added in three portions, each 10 minutes apart. Finally, the leather was washed with water and then vacuum dried.

[0047] Thickness gain: The thickness was measured using a GJ9BI leather thickness gauge manufactured by Zhejiang Yuyao Light Industry Machinery Factory, according to the relevant standards in QB / T2009-2005. The calculation formula is as follows: Thickness increase rate = (L1-L0) / L0×100%, where L1 is the thickness of the raw leather after treatment, mm; L0 is the thickness of the raw leather before treatment, mm.

[0048] Tensile strength: The tensile strength was determined using an XWN-20 micro-controlled electronic universal testing machine in accordance with the relevant standard QB / T 2710-2005.

[0049] Tear strength: Tested using an XWN-20 micro-controlled electronic universal testing machine, according to the relevant standards in garment leather standard QB 1872-93.

[0050] Resilience and grain fineness are subjectively evaluated by relevant testers.

[0051] The test results are shown in Table 1.

[0052] Table 1 Relevant Test Results The test results above show that the retanning agents prepared in Examples 1 to 4 of this invention have excellent mechanical properties for raw leather, and the thickening rate after treatment is also improved. The resilience is excellent and the grain is fine, indicating that the retanning agents have excellent comprehensive performance.

[0053] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0054] Although embodiments of this application have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of this application, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing an environmentally friendly amphoteric acrylic retanning agent, characterized in that, Includes the following steps: S100 uses acrylamide, acrylic acid, acrylonitrile, ethyl acrylate, and hydroxyethyl acrylate as raw materials. After mixing, nitrogen-containing heterocyclic monomers, phosphorus-containing monomers, and quaternary ammonium salt cationic monomers are added to obtain a mixed solution. S200. Dissolve potassium persulfate in deionized water, stir until dissolved, then add sodium sulfite and continue stirring until completely dissolved to obtain an initiator solution. The mass ratio of potassium persulfate, sodium sulfite, and deionized water is 1-3:0.5-1.5:10-20. Add epoxidized polyamide-amine dendritic macromolecules to deionized water and ultrasonically disperse for 10-20 minutes to obtain a uniform dispersion, which is the reaction aid. The mass ratio of epoxidized polyamide-amine dendritic macromolecules to deionized water is 4-7:10-20. S300. Raise the temperature of the reactor to 50-60℃, start stirring, and add the mixture and initiator solution dropwise. After the addition is complete, raise the temperature to 70-80℃, keep it at this temperature for 1-3 hours, and then lower the temperature to 40-50℃. Add the reaction aid, stir and react for 30-40 minutes, then add sodium hydroxide solution to the reactor to adjust the pH of the system to 6.0-7.

0. After cooling to room temperature, add β-cyclodextrin, stir for 1-2 hours to obtain a mixture, and filter to obtain the amphoteric acrylic retanning agent. The mass ratio of the mixture, initiator solution, reaction aid, and β-cyclodextrin is 60-85:12-20:13-22:2.5-4.

5.

2. The preparation method of the environmentally friendly amphoteric acrylic retanning agent according to claim 1, characterized in that, Step S100 is as follows: After fully dissolving acrylamide in deionized water, adjust the pH of the solution to 4.5-5.5 with dilute hydrochloric acid, then add acrylic acid, acrylonitrile, ethyl acrylate and hydroxyethyl acrylate in sequence, stir for 20-30 minutes, then add nitrogen-containing heterocyclic monomer, phosphorus-containing monomer and quaternary ammonium salt cationic monomer, and continue stirring for 15-25 minutes to obtain a mixed solution.

3. The preparation method of the environmentally friendly amphoteric acrylic retanning agent according to claim 1, characterized in that, The nitrogen-containing heterocyclic monomer is one or more of 4-vinylpyridine, 4-methyl-2-vinylpyridine, N-vinylpyrrolidone, and 2-vinylquinoline; the phosphorus-containing monomer is one or more of 2-methyl-2-acrylate-2-hydroxyethyl phosphate, dimethyl vinyl phosphate, and 1,2-vinyl diphosphonic acid; the quaternary ammonium salt cationic monomer is one or more of methacryloyloxyethyltrimethylammonium chloride, dimethyl diallyl ammonium chloride, and methacryloyloxyethyldimethylbenzyl ammonium chloride.

4. The preparation method of the environmentally friendly amphoteric acrylic retanning agent according to claim 1, characterized in that, The preparation method of the epoxidized polyamide-amine dendritic macromolecule is as follows: the polyamide-amine dendritic macromolecule is dissolved in anhydrous ethanol, a catalyst is added, and after stirring evenly, epichlorohydrin is added to it at 30-40℃. After the addition is completed, the temperature is raised to 50-60℃ and the reaction is maintained for 4-6 hours. After the reaction is completed, the epoxidized polyamide-amine dendritic macromolecule is obtained by vacuum distillation.

5. The preparation method of an environmentally friendly amphoteric acrylic retanning agent according to claim 4, characterized in that, Epichlorohydrin was added dropwise at a rate of 1-2 mL / min.

6. The preparation method of an environmentally friendly amphoteric acrylic retanning agent according to claim 1, characterized in that, The dropping rate of the initiator solution in the mixture is 1-3 mL / min.

7. An environmentally friendly amphoteric acrylic retanning agent, characterized in that, It is prepared by the method described in any one of claims 1-6 for an environmentally friendly amphoteric acrylic retanning agent.

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