High-activity dealuminated zeolite-based nano tanning agent as well as preparation method and application thereof

Abstract

The invention discloses a high-activity dealumination zeolite-based nano tanning agent as well as a preparation method and application thereof, and belongs to the technical field of leather tanning agents. The preparation method comprises the following steps: dissolving A-type artificial zeolite in an acidic solution with the pH value of 1.0-2.5, and then carrying out dealumination treatment; after the dealumination treatment is finished, alkali is added to adjust the pH value to 3.5-4.0, and a dealuminated nano zeolite suspension is obtained; mixing the dealuminated nano zeolite turbid liquid with organic hydroxyl carboxylate to obtain a modified nano zeolite solution; and the modified nano zeolite solution is subjected to spray drying, and the high-activity dealumination zeolite-based nano tanning agent is obtained. The method is easy to operate, process parameters are easy to control, raw materials are easy to obtain, the cost is moderate, and the prepared dealuminated zeolite-based nano tanning agent has good stability and biocompatibility, can effectively adsorb protein and improve the stability of the protein, has high antibacterial performance and can meet the use requirements of leather products.

Description

Technical Field

[0001] This invention relates to the field of leather tanning agent technology, and more specifically, to a highly active dealuluminated zeolite-based nano-tanning agent, its preparation method, and its application. Background Technology

[0002] Leather is an important material widely used in shoes, clothing, bags, and furniture. While traditional chrome tanning methods can impart excellent thermal stability, a comfortable feel, and superior leather-making properties to leather, they also generate large amounts of chromium-containing wastewater, chromium-containing solid waste, and chromium-containing waste leather products, leading to environmental pollution and severely hindering the sustainable and healthy development of the leather industry.

[0003] To address the environmental pollution caused by chrome tanning, developing clean, environmentally friendly, and ecological chrome-free tanning agents and methods has become an inevitable trend in the leather industry. Currently, chrome-free tanning agents include chrome-free metallic tanning agents and organic tanning agents, among which aluminosilicate-based synthetic zeolite materials have attracted widespread attention due to their unique structure and properties. Because aluminosilicates have in-situ polymerization properties, aluminum silicate can achieve a Ts ≥ 70℃ for raw hides, making it suitable as a tanning agent for producing wet white leather and for molding and machining.

[0004] However, there is a contradiction between the dealumination of zeolite tanning agents, which improves activity and storage stability, and it is difficult to achieve both simultaneously.

[0005] In view of this, the present invention is proposed. Summary of the Invention

[0006] The purpose of this invention is to provide a highly active dealuminolite-based nanotanning agent, its preparation method, and its application, so as to solve or improve the above-mentioned technical problems.

[0007] This invention can be implemented as follows: In a first aspect, the present invention provides a method for stabilizing and preparing a highly active dealuated zeolite-based nano-tanning agent, comprising the following steps: dissolving type A synthetic zeolite in an acidic solution with a pH of 1.0 to 2.5, followed by dealuated treatment; after the dealuated treatment is completed, adding alkali to adjust the pH to 3.5 to 4.0 to obtain a dealuated nano-zeolite suspension; A modified nano-zeolite solution was obtained by mixing a dealuminolite nano-zeolite suspension with an organic hydroxycarboxylate; the modified nano-zeolite solution was then spray-dried to obtain a highly active dealuminolite-based nano-tanning agent.

[0008] In an optional embodiment, the acidic solution comprises water and an inorganic acid; the weight ratio of type A synthetic zeolite, water, and inorganic acid is 20:(30~70):(10~20).

[0009] In an optional embodiment, type A synthetic zeolite includes at least one of type 3A, type 4A, and type 5A synthetic zeolite prepared from silicates and alumina.

[0010] In an optional embodiment, the molar ratio of Si atoms to Al atoms in the type A synthetic zeolite is 1:1.

[0011] In an optional embodiment, the inorganic acid includes at least one of hydrochloric acid and sulfuric acid.

[0012] In an optional embodiment, the dealuminization process is carried out at 50°C to 70°C for 4 to 10 hours.

[0013] In an optional implementation, during the dealumination process, an inorganic acid is used to adjust the pH to 1-2.5.

[0014] In an optional embodiment, the molar ratio of Si atoms to Al atoms in the dealuminol nanozeolite suspension is 20:1 to 40:1. And / or, in the dealuminol nanozeolite suspension, the particle size of the dealuminol nanozeolite is 300nm~800nm.

[0015] In an optional embodiment, the organic hydroxycarboxylate salt is 5% to 10% of the mass of the dealuminated nanozeolite suspension.

[0016] In an optional embodiment, the organic hydroxycarboxylic acid salt comprises 70wt% to 90wt% sodium hydroxymalonate and 10wt% to 30wt% sodium dihydroxysuccinate.

[0017] In an optional embodiment, the dealuminated nanozeolite suspension is mixed with an organic hydroxycarboxylate and stirred at 50°C to 70°C for 20 to 30 minutes to obtain a modified nanozeolite solution.

[0018] In an optional embodiment, spray drying includes at least one of the following features: Feature 1: Spray drying is performed using a centrifugal rotary atomizing spray dryer; Feature 2: The inlet temperature of the spray dryer is at least 60°C higher than the outlet temperature; Feature 3: The material flow rate is 2 mL / min to 3 mL / min.

[0019] In an optional embodiment, the inlet temperature of the spray dryer is 160°C to 190°C.

[0020] In an optional embodiment, the outlet temperature of the spray dryer is 85°C to 110°C.

[0021] Secondly, the present invention provides a highly active dealuated zeolite-based nanotanning agent, which is prepared by any of the preparation methods described in the foregoing embodiments.

[0022] In an optional embodiment, the average particle size of the highly active dealuated zeolite-based nanotanning agent is 125 μm to 190 μm.

[0023] Thirdly, the present invention provides a leather in which the leather is tanned using the highly active dealuated zeolite-based nano-tanning agent described in the foregoing embodiments.

[0024] In an optional implementation, the shrinkage temperature of the leather is not lower than 80°C.

[0025] The beneficial effects of this invention include: The method provided by this invention involves acid dissolution and dealuminization of synthetic type A zeolite, followed by the use of hydroxycarboxylic acid groups to react with Al on the zeolite surface. 3+ Chelating and sealing highly active sites stabilizes the structure and improves storage stability, resulting in ideal modified nano-zeolite. Further, spray drying and flash evaporation fix the structure and prevent recrystallization from increasing the size, thereby effectively improving tanning penetration and obtaining dealuminolite-based nano-tanning agents with both high activity and high storage stability.

[0026] This dealuated zeolite-based nano-tanning agent exhibits good stability and biocompatibility, effectively adsorbing proteins and improving their stability. It also possesses strong antibacterial properties, meeting the requirements for use in leather products. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0028] The following provides a detailed description of the highly active dealuminolite-based nanotanning agent, its preparation method, and its application provided by this invention.

[0029] This invention provides a method for stabilizing and preparing a highly active dealuated zeolite-based nano-tanning agent, comprising the following steps: dissolving type A synthetic zeolite in an acidic solution with a pH of 1.0 to 2.5, followed by dealumination treatment; after the dealumination treatment is completed, adding alkali to adjust the pH to 3.5 to 4.0 to obtain a dealuated nano-zeolite suspension; A modified nano-zeolite solution was obtained by mixing a dealuminolite nano-zeolite suspension with an organic hydroxycarboxylate; the modified nano-zeolite solution was then spray-dried to obtain a highly active dealuminolite-based nano-tanning agent.

[0030] The above method involves acid dissolution and dealuminization of synthetic type A zeolite, followed by the use of hydroxycarboxylic acid groups to react with Al on the zeolite surface. 3+ Chelating and sealing highly active sites stabilizes the structure and improves storage stability, resulting in ideal modified nano-zeolite. Further, spray drying and flash evaporation fix the structure and prevent recrystallization from increasing the size, thereby effectively improving tanning penetration and obtaining dealuminolite-based nano-tanning agents with both high activity and high storage stability.

[0031] In some alternative embodiments, type A synthetic zeolite includes at least one of type 3A, type 4A, and type 5A synthetic zeolite prepared from silicates and alumina. The molar ratio of Si atoms to Al atoms (abbreviated as "Si / Al") in type A synthetic zeolite can be 1:1.

[0032] In some alternative embodiments, the acidic solution comprises water and an inorganic acid, wherein the inorganic acid may include at least one of hydrochloric acid and sulfuric acid.

[0033] In some optional embodiments, the weight ratio of type A synthetic zeolite, water, and inorganic acid can be 20:(30~70):(10~20). Specifically, the weight ratio of type A synthetic zeolite to water can be 20:30, 20:35, 20:40, 20:45, 20:50, 20:55, 20:60, 20:65, or 20:70, or other values ​​within the range of 20:(30~70). The weight ratio of type A synthetic zeolite to inorganic acid can be 20:10, 20:15, 20:16, 20:17, 20:18, 20:19, or 20:20, or other values ​​within the range of 20:(15~20). For example, each 100 parts may contain 20 parts type A synthetic zeolite, 30 to 70 parts water, and 10 to 20 parts inorganic acid.

[0034] In some alternative embodiments, type A synthetic zeolite can be dissolved in an acidic solution at 25°C to 35°C. The pH value of the acidic solution can be 1, 1.5, 2, or 2.5, or other values ​​within the range of 1 to 2.5.

[0035] In some optional embodiments, the dealumination treatment can be carried out at 50°C to 70°C (e.g., 50°C, 55°C, 60°C, 65°C, or 70°C) for 4 to 10 hours (e.g., 4 hours, 6 hours, 8 hours, or 10 hours). In some optional embodiments, during the dealumination treatment, an inorganic acid is used to adjust the pH value to 1 to 2.5, such as 1, 1.5, 2, or 2.5, or other values ​​within the range of 1 to 2.5.

[0036] In some alternative implementations, the pH value after adding alkali can be adjusted to 3.5, 3.6, 3.7, 3.8, 3.9 or 4, or other values ​​in the range of 3.5 to 4.

[0037] By subjecting type A synthetic zeolite to acid-controlled gradient dealumination (including acid dissolution at 25℃~35℃ and dealumination at 50℃~70℃), the crystal volume of the zeolite is significantly reduced, and the surface porosity is increased, forming a high-density, high-potential electrophilic function. This enhances the zeolite's affinity for proteins and significantly strengthens the tanning effect, raising the shrinkage temperature of leather from ≤65℃ (before modification) to ≥80℃. Furthermore, acid dissolution at low temperatures effectively protects the skeletal structure, while dealumination at high temperatures accelerates aluminum dissolution. In addition, segmented pH control avoids excessive acid corrosion.

[0038] In some alternative embodiments, the molar ratio of Si atoms to Al atoms in the dealuminolite nanozeolite suspension is 20:1 to 40:1, such as 20:1, 25:1, 30:1, 35:1 or 40:1, or other values ​​in the range of 20:1 to 40:1.

[0039] In the above suspension, after the Si / Al ratio of the dealuminolite nano-zeolite is increased from 1 to 20-40, the crystal volume decreases and a large number of hydroxyl vacancies appear on the surface, forming a high-position surface. This surface has a high affinity for nucleophilic groups, which is conducive to increasing the binding energy with collagen proteins, thereby increasing the skin contraction temperature to 78°C or above after the treatment.

[0040] In some alternative embodiments, the dealuminol nanozeolite suspension has a particle size of 300 nm to 800 nm.

[0041] In some alternative embodiments, the organic hydroxycarboxylate salt is 5% to 10% of the dealuminol nanozeolite suspension, such as 5%, 6%, 7%, 8%, 9% or 10%, or other values ​​within the range of 5% to 10%.

[0042] In some alternative embodiments, the organic hydroxycarboxylate includes 70wt% to 90wt% (e.g., 70wt%, 75wt%, 80wt%, 85wt%, or 90wt%) of sodium hydroxymalonate and 10wt% to 30wt% (e.g., 10wt%, 15wt%, 20wt%, 25wt%, or 30wt%) of sodium dihydroxysuccinate.

[0043] In some alternative embodiments, the dealuminated nanozeolite suspension is mixed with an organic hydroxycarboxylate and stirred at 50°C to 70°C (e.g., 50°C, 55°C, 60°C, 65°C, or 70°C) for 20 to 30 minutes (e.g., 20 minutes, 25 minutes, or 30 minutes) to obtain a modified nanozeolite solution.

[0044] By stabilizing the structure of dealubilized nano-zeolite using organic hydroxycarboxylate, the hydroxycarboxylate reacts with the Al on the zeolite surface. 3+ Chelation, by blocking highly active sites, can improve storage stability and effectively solve the problem of poor stability of zeolite tanning agents in existing technologies. In some alternative implementations, a centrifugal rotary atomizing spray dryer is used for spray drying.

[0045] The inlet temperature of the spray dryer is at least 60°C higher than the outlet temperature. In some alternative embodiments, the inlet temperature of the spray dryer can be 160°C to 190°C, such as 160°C, 165°C, 170°C, 175°C, 180°C, 185°C, or 190°C, or other values ​​within the range of 160°C to 190°C. The outlet temperature of the spray dryer can be 85°C to 110°C, such as 85°C, 90°C, 95°C, 100°C, 105°C, or 110°C, or other values ​​within the range of 85°C to 110°C.

[0046] In some alternative implementations, the size of the adjustable pump nozzle can be, for example, 10 mm × 24 mm (length × width).

[0047] In some alternative implementations, the material flow rate can be 2 mL / min to 3 mL / min, such as 2.5 mL / min.

[0048] By employing two-phase fluid physicochemical spray drying and ensuring a temperature difference of >70℃ between the inlet and outlet temperatures of the spray dryer, a powdered high-activity dealuated zeolite-based nano-tanning agent was prepared. This high-activity dealuated zeolite-based nano-tanning agent exhibits relatively uniform particle size and distribution, thereby improving product purity and performance stability.

[0049] In conclusion, the preparation method provided by this invention is simple to operate, the process parameters are easy to control, the raw materials are readily available, the cost is moderate, and it has good prospects for industrial application.

[0050] Accordingly, the present invention also provides a highly active dealuminolite-based nanotanning agent, which is prepared by the above preparation method.

[0051] In some alternative embodiments, the average particle size of the highly active dealuated zeolite-based nanotanning agent is 125 μm to 190 μm.

[0052] The highly active dealuated zeolite-based nano-tanning agent prepared by this method has good biocompatibility, can effectively adsorb proteins and improve protein stability, and also has strong antibacterial properties, which can meet the requirements for use in leather products.

[0053] In addition, the present invention also provides a leather, which is tanned using the above-mentioned highly active dealuminolite-based nano-tanning agent during its preparation.

[0054] In some alternative embodiments, the shrinkage temperature of the prepared leather is not lower than 80°C.

[0055] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0056] Example 1 This embodiment provides a highly active dealuminolite-based nanotanning agent, the preparation method of which includes: Step 1: Add 20 parts of type 5A synthetic zeolite (Si / Al=1) to an acid-resistant, stirred container, followed by 60 parts of water and 20 parts of an acidic solution (37% hydrochloric acid) with a pH of 2.2. Stir at 35°C for 0.8 hours to completely dissolve the type 5A synthetic zeolite. Continue to heat the solution to 60°C and perform a dealumination treatment for 8 hours with stirring. During the dealumination treatment, stabilize the pH at 2.2 with 37% hydrochloric acid. Then adjust the pH to 4.0 with soda ash to form a dealuated nano-zeolite suspension. The dealuated nano-zeolite in this suspension has a Si / Al ratio of 30 and a particle size distribution of 450nm~550nm.

[0057] Step 2: At 50℃, 8wt% of an organic hydroxycarboxylate (a mixture of 70% sodium hydroxymalonate and 30% sodium dihydroxysuccinate) was added to the dealuminol nano-zeolite suspension obtained in Step 1 for structural stabilization. The mixture was stirred at 50℃ for 30 min to obtain a modified nano-zeolite solution. The modified nano-zeolite solution was poured into a supply tank and pumped into a spray dryer. The inlet temperature of the spray dryer was 170℃, the outlet temperature was 110℃, the pump nozzle size was adjusted to 10mm × 24mm (length × width), and the flow rate was 2.5mL / min. This yielded a powdered, highly active dealuminolite-based nano-tanning agent with an average particle size of 150μm, which was then packaged in a moisture-proof plastic seal.

[0058] Example 2 This embodiment provides a highly active dealuminolite-based nanotanning agent, the preparation method of which includes: Step 1: Add 20 parts of type 3A synthetic zeolite (Si / Al=1) to an acid-resistant, stirred container, followed by 62 parts of water and 18 parts of an acidic solution (30% sulfuric acid) with a pH of 1.8. Stir at 25°C for 0.5 hours to completely dissolve the type 3A synthetic zeolite. Continue to heat the solution to 65°C and perform a dealumination treatment for 6 hours with stirring. During the dealumination treatment, stabilize the pH at 1.8 with 30% sulfuric acid. Then adjust the pH to 3.8 with soda ash to form a dealuated nano-zeolite suspension. The dealuated nano-zeolite in this suspension has a Si / Al ratio of 25 and a particle size distribution of 400nm~500nm.

[0059] Step 2: At 60℃, 6wt% of an organic hydroxycarboxylate (a mixture of 90% sodium hydroxymalonate and 10% sodium dihydroxysuccinate) was added to the dealuminol nano-zeolite suspension obtained in Step 1 for structural stabilization. The mixture was stirred at 60℃ for 20 min to obtain a modified nano-zeolite solution. The modified nano-zeolite solution was poured into a supply tank and pumped into a spray dryer. The inlet temperature of the spray dryer was 165℃, the outlet temperature was 100℃, the pump nozzle size was adjusted to 10mm × 24mm (length × width), and the flow rate was 2.5mL / min. This yielded a powdered, highly active dealuminolite-based nano-tanning agent with an average particle size of 170μm, which was then packaged in a moisture-proof plastic seal.

[0060] Example 3 This embodiment provides a highly active dealuminolite-based nanotanning agent, the preparation method of which includes: Step 1: Add 20 parts of type 4A synthetic zeolite (Si / Al=1) to an acid-resistant, stirred container, followed by 60 parts of water and 20 parts of an acidic solution (30% sulfuric acid) with a pH of 1.2. Stir at 35°C for 0.5 hours to completely dissolve the type 4A synthetic zeolite. Continue to heat the solution to 70°C and perform a dealumination treatment for 10 hours with stirring. During the dealumination treatment, stabilize the pH at 1.2 with 30% sulfuric acid. Then adjust the pH to 3.5 with soda ash to form a dealuated nano-zeolite suspension. The dealuated nano-zeolite in this suspension has a Si / Al ratio of 38 and a particle size distribution of 320nm~420nm.

[0061] Step 2: At 70℃, 7wt% of an organic hydroxycarboxylate (a mixture of 80% sodium hydroxymalonate and 20% sodium dihydroxysuccinate) was added to the dealuminol nano-zeolite suspension obtained in Step 1 for structural stabilization. The mixture was stirred at 70℃ for 25 min to obtain a modified nano-zeolite solution. The modified nano-zeolite solution was poured into a supply tank and pumped into a spray dryer. The inlet temperature of the spray dryer was 185℃, and the outlet temperature was 105℃. The pump nozzle size was adjusted to 10mm × 24mm (length × width), and the flow rate was 2.5mL / min. This yielded a powdered, highly active dealuminolite-based nano-tanning agent with an average particle size of 125μm, which was then packaged in a moisture-proof plastic seal.

[0062] Example 4 This embodiment provides a highly active dealuminolite-based nanotanning agent, the preparation method of which includes: Step 1: Add 20 parts of type 5A synthetic zeolite (Si / Al=1) to an acid-resistant, stirred container, followed by 65 parts of water and 15 parts of an acidic solution (37% hydrochloric acid) with a pH of 2.5. Stir for 1 hour at 30°C to completely dissolve the type 5A synthetic zeolite. Continue to heat the solution to 50°C and perform a dealumination treatment for 4 hours with stirring. During the dealumination treatment, stabilize the pH at 2.5 with 37% hydrochloric acid. Then adjust the pH to 4.0 with soda ash to form a dealuated nano-zeolite suspension. The dealuated nano-zeolite in this suspension has a Si / Al ratio of 20 and a particle size distribution of 650nm~750nm.

[0063] Step 2: At 70℃, 9wt% of an organic hydroxycarboxylate (a mixture of 75% sodium hydroxymalonate and 25% sodium dihydroxysuccinate) was added to the dealuminol nano-zeolite suspension obtained in Step 1 for structural stabilization. The mixture was stirred at 70℃ for 30 min to obtain a modified nano-zeolite solution. The modified nano-zeolite solution was poured into a supply tank and pumped into a spray dryer. The inlet temperature of the spray dryer was 175℃, and the outlet temperature was 95℃. The pump nozzle size was adjusted to 10mm × 24mm (length × width), and the flow rate was 2mL / min. A powdered, highly active dealuminolite-based nano-tanning agent with an average particle size of 190μm was obtained, and then packaged in a moisture-proof plastic seal.

[0064] Example 5 This embodiment provides a highly active dealuminolite-based nanotanning agent, the preparation method of which includes: Step 1: Add 20 parts of type 4A synthetic zeolite (Si / Al=1) to an acid-resistant, stirred container, followed by 70 parts of water and 10 parts of an acidic solution with a pH of 1.8 (a mixture of 37% hydrochloric acid and 30% sulfuric acid at a mass ratio of 2:1). Stir at 25°C for 0.5 hours to completely dissolve the type 4A synthetic zeolite. Continue to heat the solution to 60°C and perform a dealumination treatment for 7 hours with stirring. During the dealumination treatment, stabilize the pH at 1.8 with 30% sulfuric acid. Then adjust the pH to 4.0 with soda ash to form a dealuated nano-zeolite suspension. The dealuated nano-zeolite in this suspension has a Si / Al ratio of 23 and a particle size distribution of 400nm~500nm.

[0065] Step 2: At 50℃, 10wt% of an organic hydroxycarboxylate (a mixture of 85% sodium hydroxymalonate and 15% sodium dihydroxysuccinate) was added to the dealuminol nano-zeolite suspension obtained in Step 1 for structural stabilization. The mixture was stirred at 50℃ for 30 min to obtain a modified nano-zeolite solution. The modified nano-zeolite solution was poured into a supply tank and pumped into a spray dryer. The inlet temperature of the spray dryer was 160℃, the outlet temperature was 85℃, the pump nozzle size was adjusted to 10mm × 24mm (length × width), and the flow rate was 3mL / min. This yielded a powdered, highly active dealuminolite-based nano-tanning agent with an average particle size of 185μm, which was then packaged in a moisture-proof plastic seal.

[0066] Comparative Example 1 The difference between this comparative example and Example 3 is that type A synthetic zeolite was directly dissolved in an acidic solution at 70°C and pH 1.2 for dealumination treatment.

[0067] Comparative Example 2 The difference between this comparative example and Example 3 is that no alkali was added to adjust the pH value after the dealumination treatment.

[0068] Comparative Example 3 The difference between this comparative example and Example 3 is that the pH value corresponding to the acid dissolution and dealumination treatment is 0.5.

[0069] Comparative Example 4 The difference between this comparative example and Example 3 is that the pH value corresponding to the acid dissolution and dealumination treatment is 3.

[0070] Comparative Example 5 The difference between this comparative example and Example 3 is that the dealuminol nanozeolite suspension was not stabilized using organic hydroxycarboxylate.

[0071] Comparative Example 6 The difference between this comparative example and Example 3 is that the mass of the organic hydroxycarboxylate is 2% of the dealuminated nano-zeolite suspension.

[0072] Comparative Example 7 The difference between this comparative example and Example 3 is that the mass of the organic hydroxycarboxylate is 15% of the mass of the dealuminated nano-zeolite suspension.

[0073] Comparative Example 8 The difference between this comparative example and Example 3 is that spray drying is replaced by ordinary drying.

[0074] Application and Implementation Methods A Stabilized Preparation and Leather Application of a Highly Active Dealuated Aluminate Zeolite-Based Nanotanning Agent: Acid-treated cowhide with a pH of 2.8–3.0 and a thickness of 1.4 mm was placed in a constant-temperature rotary drum. The acid treatment solution was replenished by 50%, maintaining the drum temperature at 25 °C. The prepared 5% powdered modified synthetic zeolite tanning agent was added, and the drum was rotated for 4 hours. The pH of the bath solution was gradually increased using a 10% sodium bicarbonate solution (divided into 5 applications, each approximately 0.5% of the leather weight), reaching a pH of 4.5–4.8. Then, 100% water was added, and the temperature was raised to 35 °C. Rotation was maintained for 2 hours, followed by rotation for 55 minutes per hour and a 5-minute pause, repeated 10 times. The solution was drained, and 5% oxalic acid was added. The hide was rinsed with 150% water for 10 minutes before being removed from the drum.

[0075] Application examples The leather is tanned using the various tanning agents as follows.

[0076] Tanning process: Acid-treated cowhide with a pH of 2.8-3.0 and a thickness of 1.4 mm is divided into two halves and placed in a constant-temperature drum. The acid treatment solution is replenished by 50%, maintaining the drum temperature at 25°C. 5 wt% of powdered unmodified synthetic zeolite tanning agent or the highly active dealuminolite-based nano-tanning agent from Example 3 is added. The drum is rotated for 4 hours. The pH of the bath solution is gradually increased using a 10% sodium bicarbonate solution (divided into 5 applications, each approximately 0.5% of the leather weight). Once the pH reaches 4.5-4.8, 100% water is added, the temperature is raised to 3°C, and the drum is maintained for 2 hours. Then, the drum is rotated for 55 minutes per hour, paused for 5 minutes, and repeated 10 times. The solution is drained, 5% oxalic acid is added, and the leather is rinsed with 150% water for 10 minutes before being removed from the drum. Squeeze out water, cut evenly to 1.15~1.2mm, weigh, rinse back in the drum, neutralize to pH=5.2, fatliquoring with 12% fatliquoring agent at 48℃, fix with formic acid to pH=3.6, exit the drum and collect the waste liquid.

[0077] Finishing process: Dewatering and stretching → Vacuum drying (45℃) → Hanging to cool and dry → Rehydration → Vibration and softening → Grinding (300# sandpaper) → Trimming → Softening by tumbling (40 min) → Light stretching → Obtaining sample.

[0078] Sample analysis: Sampling and testing were carried out in accordance with the requirements of QB / T 1873-2010 "Leather for Footwear Uppers", and the results are shown in Table 1.

[0079] Table 1 Test Results

[0080] In addition, the tannins of other examples and comparative examples 1 to 8 were tested using the same method as described above, and the results are shown in Tables 2 to 4.

[0081] Table 2 Test Results

[0082] Table 3 Test Results

[0083] Table 4 Test Results

[0084] The results in Tables 1 to 4 show that the dealuated zeolite-based nano tanning agent prepared in this invention can make leather smooth and firm after tanning, with high tear strength, crack height and crack strength, and high heat shrinkage temperature.

[0085] In summary, the preparation method provided by this invention is simple to operate, the process parameters are easy to control, the raw materials are readily available, and the cost is moderate. The prepared dealuminolite-based nano-tanning agent has good stability and biocompatibility, can effectively adsorb proteins and improve protein stability, and also has strong antibacterial properties, which can meet the requirements for use in leather products.

[0086] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for stabilizing and preparing a highly active dealuminolite-based nano-tanning agent, characterized in that, Includes the following steps: Type A synthetic zeolite was dissolved in an acidic solution with a pH of 1.0 to 2.5, followed by a dealumination process. After the dealumination treatment is completed, alkali is added to adjust the pH value to 3.5~4.0 to obtain a dealuminated nano-zeolite suspension; The dealuminol nano-zeolite suspension was mixed with an organic hydroxycarboxylate to obtain a modified nano-zeolite solution; the modified nano-zeolite solution was spray-dried to obtain a highly active dealuminolol-based nano-tanning agent.

2. The stabilization preparation method according to claim 1, characterized in that, The acidic solution comprises water and an inorganic acid; the weight ratio of the type A synthetic zeolite, water, and the inorganic acid is 20:(30~70):(10~20); Preferably, the type A synthetic zeolite includes at least one of type 3A, type 4A, and type 5A synthetic zeolite prepared from silicates and alumina; Preferably, the molar ratio of Si atoms to Al atoms in the type A synthetic zeolite is 1:1; Preferably, the inorganic acid includes at least one of hydrochloric acid and sulfuric acid.

3. The stabilization preparation method according to claim 1, characterized in that, The dealuminization process is carried out at 50℃~70℃ for 4h~10h; Preferably, during the dealumination process, an inorganic acid is used to adjust the pH value to 1~2.

5.

4. The stabilization preparation method according to claim 1, characterized in that, In the dealuminol nanozeolite suspension, the molar ratio of Si atoms to Al atoms is 20:1 to 40:1; And / or, in the dealuminol nanozeolite suspension, the particle size of the dealuminol nanozeolite is 300nm~800nm.

5. The stabilization preparation method according to claim 1, characterized in that, The mass of the organic hydroxycarboxylic acid salt is 5% to 10% of the dealuminol nanozeolite suspension.

6. The stabilization preparation method according to claim 5, characterized in that, The organic hydroxycarboxylic acid salt comprises 70wt%~90wt% sodium hydroxymalonate and 10wt%~30wt% sodium dihydroxysuccinate.

7. The stabilization preparation method according to claim 1, characterized in that, The dealuminol nanozeolite suspension is mixed with the organic hydroxycarboxylate and stirred at 50°C to 70°C for 20 to 30 minutes to obtain the modified nanozeolite solution.

8. The stabilization preparation method according to claim 1, characterized in that, Spray drying includes at least one of the following characteristics: Feature 1: Spray drying is performed using a centrifugal rotary atomizing spray dryer; Feature 2: The inlet temperature of the spray dryer is at least 60°C higher than the outlet temperature; Feature 3: Material flow rate is 2 mL / min to 3 mL / min; Preferably, the inlet temperature of the spray dryer is 160℃~190℃; Preferably, the outlet temperature of the spray dryer is 85℃~110℃.

9. A highly active dealuminolite-based nanotanning agent, characterized in that, Prepared by the preparation method according to any one of claims 1 to 8; Preferably, the average particle size of the highly active dealuminolite-based nanotanning agent is 125 μm to 190 μm.

10. A type of leather, characterized in that, The leather is tanned using the highly active dealuminolite-based nano-tanning agent as described in claim 9 during the preparation process. Preferably, the shrinkage temperature of the leather is not lower than 80°C.

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