Cationic hyperbranched antibacterial chrome-free tanning agent as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of leather tanning, and relates to a cationic hyperbranched antibacterial chrome-free tanning agent and a preparation method and application thereof.The method comprises the steps that amino of 6-hydroxy-2, 4, 5-triaminopyrimidine sulfate and epoxy of triglycidyl isocyanurate are subjected to a chemical cross-linking reaction under the catalysis of triethylamine, and the cationic hyperbranched antibacterial chrome-free tanning agent is obtained; and purifying to obtain the hyperbranched antibacterial chrome-free tanning agent. The antibacterial property, the thickening property, the shrinkage temperature, the mechanical strength, the washing resistance and other properties of the chrome-free tanning agent are improved, and the chrome-free tanning agent has a good application prospect in the field of clean sustainable tanning.

Description

Technical Field

[0001] This invention belongs to the field of leather tanning technology, specifically relating to a cationic hyperbranched antibacterial chromium-free tanning agent, its preparation method, and its application. Background Technology

[0002] Currently, the use of traditional chrome tanning agents is being gradually restricted due to a series of problems, including heavy metal pollution, high wastewater treatment costs, and low tanning agent utilization. Chromium-free tanning agents still present significant challenges in terms of antibacterial properties and environmental friendliness. Regarding antibacterial properties, while natural tanning agents such as vegetable tanning agents contain antibacterial components like tannins, their antibacterial stability in practical applications is insufficient due to limitations such as long tanning cycles (requiring several weeks) and the sensitivity of antibacterial effects to pH and temperature. Synthetic tanning agents, such as aldehydes (glutaraldehyde), while possessing strong antibacterial properties, can easily cause skin allergies due to residual formaldehyde and may release harmful gases under high temperatures, posing health risks. Metal salt tanning agents (such as aluminum and zirconium tanning agents) have weaker antibacterial properties than chrome tanning agents, requiring the addition of antibacterial agents such as nano-silver to compensate. This not only increases production costs but also limits large-scale application due to the complexity of the process. In terms of environmental friendliness, some chrome-free tanning agents pose new pollution risks: phosphorus-containing synthetic tanning agents may lead to eutrophication of water bodies, while organophosphorus tanning agents may release toxic byproducts.

[0003] 6-Hydroxy-2,4,5-triaminopyrimidine sulfate (HATAS) has broad-spectrum antibacterial and cationic properties, but its cross-linking density is low when used alone; triglycidyl isocyanurate (TGIC) has highly reactive epoxy groups, but its cross-linked products have limited functionality and no antibacterial function. Summary of the Invention

[0004] To address the problems in the prior art, this invention constructs a hyperbranched polymer network by combining the amino groups of HATAS and the epoxy groups of TGIC, forming a cationic chromium-free tanning agent that combines antibacterial properties, high cross-linking density, and multiple functions. It can strongly bind to collagen fibers without acid soaking, while also improving the absorption rate of subsequent wet finishing materials.

[0005] This invention aims to provide a method for preparing and applying a cationic hyperbranched antibacterial chromium-free tanning agent. The invention involves covalently bonding the amino functional group of 6-hydroxy-2,4,5-triaminopyrimidine sulfate (HATAS) with the epoxy group of triglycidyl isocyanate (TGIC) to synthesize a crude antibacterial chromium-free tanning agent with a hyperbranched structure. This crude product is then subjected to solid-liquid separation, purification, and drying to obtain a solid powder form of the chromium-free tanning agent. This invention creatively combines the excellent antibacterial and bactericidal properties of HATAS with the highly efficient chemical reactivity of TGIC. Hyperbranched polymerization technology is used to construct a cross-linked network, significantly enhancing the interfacial bonding strength between the tanning agent molecules and leather collagen fibers. The composite functional material prepared using this technology can simultaneously impart excellent antibacterial properties, increased thickness, high-temperature dimensional stability (shrinkage temperature), mechanical strength, and durable wash resistance to leather during the leather-making process, thereby achieving the goal of multifunctional synergistic antibacterial leather manufacturing in a single process step.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution: A method for preparing a cationic hyperbranched antibacterial chromium-free tanning agent includes the following steps: (1) Dissolve 6-hydroxy-2,4,5-triaminopyrimidine sulfate (HATAS) in water, add triglycidyl isocyanate (TGIC) and heat to 25-60°C, add triethylamine (TEA) dropwise, stir and keep warm to react, and monitor the disappearance of the epoxy group characteristic peak by FTIR to complete the reaction. (2) After the reaction solution is cooled to room temperature, it is precipitated with anhydrous ethanol, filtered, washed and dried. The results of nuclear magnetic resonance characterization and grafting degree calculation show that a hyperbranched polymer antibacterial chromium-free tanning agent is obtained.

[0007] Preferably, in step (1), the molar ratio of HATAS to TGIC is 1:0 to 1:1.8.

[0008] Preferably, in step (1), the amount of triethylamine used is 2% to 8% of the mass of HATAS, and the triethylamine dropping rate is 1 to 2 mL / min.

[0009] Preferably, in step (1), the reaction time is 1~3h.

[0010] Preferably, in step (2), the rate of adding anhydrous ethanol is 5~10 mL / min, and the stirring rate is 200~300 rpm.

[0011] Preferably, in step (2), the precipitate is washed with a mixture of ethanol and water and dried in an oven at 45~60℃ for 12~24h.

[0012] The cationic hyperbranched antibacterial chromium-free tanning agent prepared by the above method.

[0013] The application of the above-mentioned hyperbranched polymer antibacterial chromium-free tanning agent in tanning includes the following steps: First, the softened animal hide is added to a drum, along with water equal to 200% of the hide's weight. Then, the hyperbranched polymer antibacterial chromium-free tanning agent is dissolved in water at a dosage of 3-12% of the hide's weight to obtain a chromium-free tanning agent solution, which is then added to the drum. Next, the pH of the system is adjusted to 7.0-8.5 with baking soda, and the drum temperature is controlled at 30-40°C. The drum is rotated at 15-40 RPM for 4-10 hours to complete the tanning process, yielding the tanned leather.

[0014] Compared with the prior art, the present invention can achieve the following technical effects: (1) The entire process is chromium-free and free of toxic solvents. Traditional chromium tanning agents contain heavy metals, which are carcinogenic and environmentally toxic, and their use has been strictly restricted. This invention uses HATAS and TGIC to prepare chromium-free tanning agents, which can eliminate chromium emissions from the source and meet the standards for eco-friendly leather manufacturing. The reaction medium is water, and the solvent can be recycled. The catalyst triethylamine is used in small amounts and is non-toxic. Ethanol precipitation is easy to recover, and the entire process is environmentally friendly and controllable.

[0015] (2) The binding ability of the tanning agent to collagen fiber is characterized by X-ray photoelectron spectroscopy (XPS). The N element content is increased by 20%~30%, which in turn increases the antibacterial properties of the finished leather.

[0016] (3) Relying on the broad-spectrum antibacterial properties of 6-hydroxy-2,4,5-triaminopyrimidine sulfate (HATAS) (antibacterial rate of ≥98% against Escherichia coli and Staphylococcus aureus), it far surpasses traditional chromium-free tanning agents (antibacterial rate ≤60%). The hyperbranched polymer structure (branching degree ≥80%) significantly enhances the binding capacity of collagen fibers, with a shrinkage temperature ≥88℃ (close to 95℃ of traditional chromium tanning agents), a thickness increase of ≥12% (traditional chromium-free tanning agents only 5%-8%), and an increase in the absorption rate of wet finishing materials by 30%~50%. Mechanical properties such as tensile strength and tear strength are significantly improved (the examples show a maximum improvement of 50%). There is no shrinkage after boiling in water for 30 minutes, solving the core pain point of poor water resistance of traditional chromium-free tanning agents.

[0017] (4) Mild reaction conditions: The reaction temperature is low and the time is short, making it suitable for industrial production. Flexible raw material adaptation: The molar ratio of HATAS to TGIC and the amount of catalyst can be adjusted, making it suitable for different types of leather (cowhide, sheepskin, pigskin, etc.). Simple post-processing: The ethanol precipitation method has high purification efficiency, and the purity of the product after drying reaches more than 90%, making it easy to prepare on a large scale.

[0018] (5) Both raw materials HATAS and TGIC are commercial products with mild reaction conditions and reduced energy consumption. They also meet diverse needs such as antibacterial properties, environmental protection, and high performance, which are in line with the global trend of green transformation in the leather industry. They can replace traditional chrome tanning agents and inefficient chrome-free products. Detailed Implementation

[0019] The present invention will be further described below with reference to specific embodiments, and the advantages and features of the present invention will become clearer with the description. However, the embodiments are merely exemplary and do not constitute any limitation on the scope of the present invention. Those skilled in the art should understand that modifications or substitutions can be made to the details and form of the technical solutions of the present invention without departing from the spirit and scope of the present invention, but all such modifications and substitutions fall within the protection scope of the present invention.

[0020] Example 1 A method for preparing a hyperbranched polymer antibacterial chromium-free tanning agent includes the following steps: (1) Dissolve 12.5 g HATAS in 5.75 g water and stir until completely dissolved. Add 16.2 g TGIC and heat to 40 °C. Add 0.625 g TEA dropwise at a TEA dropping rate of 1 mL / min. Keep the mixture at 600 rpm for 2 hours. Monitor the characteristic peak of the epoxy group (910 cm⁻¹) by FTIR. -1 The reaction has disappeared, confirming its completion.

[0021] (2) After the reaction solution has cooled to room temperature, slowly add 2 times the liquid volume of anhydrous ethanol, let stand for 1 hour, and filter after the product has completely precipitated. After filtration, wash the precipitate 3 times with a mixture of ethanol and water (volume ratio 4:1) to remove unreacted TGIC and catalyst TEA.

[0022] (3) Dry the filter cake in a vacuum drying oven at 55°C for 12 hours. After it is completely dried, crush it and pass it through a 200-mesh sieve to obtain a hyperbranched polymer antibacterial chromium-free tanning agent.

[0023] First, the softened animal hide is added to the drum, along with 200% water by weight of the animal hide. Then, tanning agent powder is dissolved in water at a concentration of 10% of the animal hide's weight to prepare a 10% chromium-free tanning agent solution, which is then added to the drum. Next, baking soda is used to adjust the pH of the system to 7.5.

[0024] Control the drum temperature at 30°C and rotate it at 15 RPM for 5 hours.

[0025] Tanned cowhide (12% of leather weight), shrinkage temperature 84.5℃, thickening rate 40%, antibacterial rate 99% (Staphylococcus aureus), fatliquoring agent absorption rate increased by 40%, and has water resistance (no shrinkage after boiling in water for 30 minutes).

[0026] Example 2 A method for preparing a hyperbranched polymer antibacterial chromium-free tanning agent includes the following steps: (1) Dissolve 12.5 g HATAS in 5.2 g water and stir until completely dissolved. Add 13.5 g TGIC and heat to 25 °C. Add 1.0 g TEA dropwise at a TEA dropping rate of 1.5 mL / min. Keep the mixture at 600 rpm for 3 hours and monitor the epoxy group characteristic peak (910 cm⁻¹) by FTIR. -1 The reaction has disappeared, confirming its completion.

[0027] (2) After the reaction solution has cooled to room temperature, slowly add 3 times the liquid volume of anhydrous ethanol, let stand for 1 hour, and filter after the product has completely precipitated. After filtration, wash the precipitate 3 times with a mixture of ethanol and water (volume ratio 4:1) to remove unreacted TGIC and catalyst TEA.

[0028] (3) Dry the filter cake in a vacuum drying oven at 50°C for 18 hours. After it is completely dried, crush it and pass it through a 200-mesh sieve to obtain a hyperbranched polymer antibacterial chromium-free tanning agent.

[0029] First, the softened animal hide is added to the drum, along with water equal to 200% of the animal hide's weight. Then, tanning agent powder is dissolved in water at a dosage of 3% of the animal hide's weight to prepare a 12% chromium-free tanning agent solution, which is then added to the drum. Next, the pH of the system is adjusted to 7.5 using baking soda.

[0030] Control the drum temperature at 30°C and rotate it at 15 RPM for 4 hours.

[0031] Tanned sheep leather (10% dosage), shrinkage temperature 85℃, thickness increase 35%, antibacterial rate reaches 98%, fatliquoring agent absorption rate increased by 35%.

[0032] Example 3 A method for preparing a hyperbranched polymer antibacterial chromium-free tanning agent includes the following steps: (1) Dissolve 12.5 g HATAS in 6.55 g water and stir until completely dissolved. Add 20.25 g TGIC and heat to 55 °C. Add 0.25 g TEA dropwise at a TEA dropping rate of 2 mL / min. Keep the mixture at 600 rpm for 1 hour and monitor the epoxy group characteristic peak (910 cm⁻¹) by FTIR.- ¹) Disappears, confirming the reaction is complete.

[0033] (2) After the reaction solution has cooled to room temperature, slowly add 2 times the liquid volume of anhydrous ethanol, let stand for 1 hour, and filter after the product has completely precipitated. After filtration, wash the precipitate 3 times with a mixture of ethanol and water (volume ratio 4:1) to remove unreacted TGIC and catalyst TEA.

[0034] (3) Dry the filter cake in a vacuum drying oven at 60°C for 24 hours. After it is completely dried, crush it and pass it through a 200-mesh sieve to obtain a hyperbranched polymer antibacterial chromium-free tanning agent.

[0035] First, the softened animal hide is added to the drum, along with 200% water by weight of the animal hide. Then, tanning agent powder is dissolved in water at a concentration of 6% of the animal hide to prepare a 15% chromium-free tanning agent solution, which is then added to the drum. Next, the pH of the system is adjusted to 7.5 using baking soda.

[0036] Control the drum temperature at 30°C and rotate it at 15 RPM for 6 hours.

[0037] Tanned pig leather (10% dosage): shrinkage temperature 84.8℃, thickness increase 50%, wet finishing material absorption rate increased by 50%, antibacterial rate 99%, leather surface zeta potential +28 mV.

[0038] Table 1. Tanning results of the tanning agents used in the examples and conventional tanning agents.

Claims

1. A method for preparing a cationic hyperbranched antibacterial chromium-free tanning agent, characterized in that, Includes the following steps: (1) Dissolve 6-hydroxy-2,4,5-triaminopyrimidine sulfate (HATAS) in water, add triglycidyl isocyanate (TGIC) and heat to 25-60°C, add triethylamine (TEA) dropwise, stir and keep warm to react, and monitor the disappearance of the epoxy group characteristic peak by FTIR to complete the reaction. (2) After the reaction solution is cooled to room temperature, it is precipitated with anhydrous ethanol, filtered, washed and dried to obtain the cationic hyperbranched antibacterial chromium-free tanning agent.

2. The preparation method of the cationic hyperbranched antibacterial chromium-free tanning agent according to claim 1, characterized in that, In step (1), the molar ratio of HATAS to TGIC is 1:0 to 1:1.

8.

3. The preparation method of the cationic hyperbranched antibacterial chromium-free tanning agent according to claim 1, characterized in that, Step (1), the reaction time is 1~3h.

4. The method for preparing the cationic hyperbranched antibacterial chromium-free tanning agent according to claim 1, characterized in that, Step (1): The amount of triethylamine used is 2% to 8% of the mass of HATAS.

5. The method for preparing the cationic hyperbranched antibacterial chromium-free tanning agent according to claim 1, characterized in that, Step (2): Wash the precipitate with a mixture of ethanol and water at a volume ratio of 4:1, and dry it in an oven at 45~60℃ for 12~24h.

6. A cationic hyperbranched antibacterial chromium-free tanning agent prepared by the preparation method according to any one of claims 1 to 5.

7. The application of the cationic hyperbranched antibacterial chromium-free tanning agent according to claim 6, characterized in that, For tanning animal hides, the application method includes the following steps: First, the softened animal hide is added to the drum, along with water equal to 200% of the hide's weight. Then, the hyperbranched polymer antibacterial chromium-free tanning agent is dissolved in water at a dosage of 3-12% of the leather's weight to obtain a chromium-free tanning agent solution, which is then added to the drum. Next, the pH of the system is adjusted to 7.0-8.5 with baking soda, and the drum temperature is controlled at 30-40°C. The drum is then rotated at a speed of 15-40 RPM for 4-10 hours to complete the tanning process.

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