Reversible reaction-based perovskite composite tanning agent as well as preparation method and application thereof

Abstract

The invention discloses a reversible reaction-based perovskite composite tanning agent as well as a preparation method and application thereof, and belongs to the technical field of leather tanning agents. According to the method disclosed by the invention, zirconium halide perovskite with high stability is adopted as a raw material, the stability of the perovskite can be synergistically improved by adding halogen metal salt, zirconium ions provide tanning performance for the material, and meanwhile, when the zirconium halide perovskite is compounded with other zirconium tanning agents for tanning, the concentration of the zirconium ions in tanning bath liquid is improved by introducing the zirconium tanning agents; on the basis of the reversible reaction principle, hydrolysis of the zirconium halide perovskite can be slowed down, the nano structure of the zirconium halide perovskite is further maintained, uniform permeation of zirconium is facilitated, the comprehensive tanning performance of the zirconium tanning agent is improved, and particularly the damp and heat resistance stability and filling performance of tanned crust leather are improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of leather tanning agents, and particularly relates to a perovskite composite tanning agent based on a reversible reaction, a preparation method thereof, and an application thereof. Background Art

[0002] Leather making can convert waste animal skins into leather, which is applied to daily necessities, automotive ornaments, etc. At present, chromium tanning agents are the most mainstream tanning agents in the tanning stage. Chromium tanning endows the green leather with excellent physical and chemical properties such as strong resistance to heat and humidity. However, when using chromium tanning agents for tanning, chromium tanning factories discharge wastewater containing a large amount of trivalent chromium ions, and trivalent chromium will be oxidized to hexavalent chromium under specific conditions. Hexavalent chromium is a highly toxic teratogenic chemical substance, which causes great harm to the ecological environment and biological systems. In addition, with the increasing attention of various countries to environmental problems, the use of chromium has been more and more restricted. Therefore, the research on chromium-free tanning agents is of great significance, and the innovation of green chromium-free tanning agents is extremely important for the green transformation of the leather industry. The heat and humidity resistance of zirconium-tanned leather is similar to that of chromium-tanned leather, and it has good filling properties, tight grain surface, etc. However, the hydrolysis and polymerization of zirconium tanning agents are relatively fast, so that they are deposited on the leather surface and cannot effectively penetrate into the skin collagen, resulting in uneven tanning of zirconium-tanned leather, and the application of zirconium tanning agents is restricted. Perovskite tanning agents, as nano-tanning agents, can better penetrate into collagen fibers, but have disadvantages such as poor water resistance stability and limited tanning performance. Summary of the Invention

[0003] The purpose of the present invention is to provide a perovskite composite tanning agent based on a reversible reaction, a preparation method thereof, and an application thereof, so as to solve the technical problems of surface over-tanning when zirconium tanning agents are applied, poor water resistance stability of perovskite tanning agents, and limited tanning performance.

[0004] In order to achieve the above purpose, the present invention adopts the following technical solutions: The present invention discloses a preparation method of a perovskite composite tanning agent based on a reversible reaction, comprising the following steps: Adding a zirconium-based metal salt to an acidic organic solvent, and then carrying out a heating reaction in an oil bath container to obtain a clear product; Adding a homohalogen metal salt, a cesium-based metal salt, and oleic acid and oleylamine ligands to the clear product, and then continuing to heat. After the reaction is completed, a zirconium halide perovskite precursor solution is obtained; Injecting a halogen reagent into the zirconium halide perovskite precursor solution, and then carrying out a heating reaction again to obtain a reaction product. The reaction product is post-treated to obtain zirconium halide perovskite; Combining the zirconium halide perovskite with a zirconium tanning agent to obtain a perovskite composite tanning agent based on a reversible reaction.

[0005] Further, the zirconium-based metal salt is one of zirconium citrate, zirconium bromide, and zirconium nitrate; the acidic organic solvent is obtained by mixing an organic solvent and an acidic solute; the organic solvent is dodecene or tetradecene, and the acidic solute is one of oxalic acid, phosphoric acid, and nitric acid; The dosage ratio of the zirconium-based metal salt, the organic solvent, and the acidic solute is 1 g : (20 - 60) mL : (1 - 3) mL.

[0006] Further, the temperature for the heating reaction in the oil bath container is 5 - 40 °C, the time is 15 - 30 min, and magnetic stirring is used during the heating reaction.

[0007] Further, the homohalogen-based metal salt is zinc bromide or copper bromide; the cesium-based metal salt is cesium sulfate or cesium carbonate; The mass ratio of the zirconium-based metal salt, the homohalogen-based metal salt, and the cesium-based metal salt is 6 : (1 - 4) : (1 - 4); The dosage ratio of the zirconium-based metal salt, oleic acid, and oleylamine is 2 g : (10 - 20) mL : (1 - 6) mL; The temperature for the continued heating is 40 - 120 °C, and the time is 40 - 90 min.

[0008] Further, the halogen reagent is 1-bromopropane or 1-bromobutane; The dosage ratio of the zirconium-based metal salt and the halogen reagent is 2 g : (3 - 12) mL.

[0009] Further, the temperature for the re-heating reaction is 120 - 240 °C, and the time is 10 - 60 s; The post-treatment includes cooling, centrifugation, washing, and drying processes carried out in sequence; the cooling is ice bath cooling or mechanical stirring cooling, and the stirring rate for mechanical stirring cooling is 30 - 800 r / min; the time for centrifugation is 5 - 20 min; the washing is carried out 4 - 6 times with a non-polar solvent; the non-polar solvent is 1-chloropentane or n-heptane.

[0010] Further, the zirconium tanning agent is one of zirconium nitrate, zirconium citrate, and zirconium bromide; The mass ratio of the zirconium halide perovskite to the zirconium tanning agent is 3 : 1 - 3 : 7; The combination is carried out by the action of a mixer or a ball mill, and the time for the action is 240 - 360 min.

[0011] The present invention also discloses a perovskite composite tanning agent prepared by the above preparation method.

[0012] The present invention also discloses the application of the above perovskite composite tanning agent based on a reversible reaction in chrome-free tanning.

[0013] Furthermore, the application of the above perovskite composite tanning agent based on reversible reaction in chrome-free tanning includes the following steps: Put pickled hides and water into a rotating drum at a mass ratio of 1:1 to 1:3, then add sodium chloride accounting for 6% - 12% of the water mass and an oxalic acid solution with a concentration of 8%, adjust the bath solution to pH 0.5 - 1.5 for the first time, and rotate for 60 min; add the perovskite composite tanning agent based on reversible reaction accounting for 2% - 15% of the mass of the pickled hides to the bath solution, and rotate for 2 - 8 h; then use a sodium bicarbonate solution with a concentration of 15% to adjust the pH of the bath solution to 3.0 - 5.0 for the second time, and rotate for 90 - 180 min; raise the temperature to 35 - 40 °C, rotate for 60 - 120 min, let it stand for 12 h, then rotate for 60 - 120 min, and wash with water.

[0014] Compared with the prior art, the present invention has the following beneficial effects: The present invention discloses a preparation method of a perovskite composite tanning agent based on reversible reaction. Using zirconium halide perovskite with high stability as a raw material, it is a nanomaterial prepared from zirconium salt, cesium salt, halogen metal salt of perovskite, organic ligand, etc. The addition of the halogen metal salt of the same halogen can synergistically improve the stability of perovskite. Zirconium ions provide tanning performance for the material. At the same time, when compounded with other zirconium tanning agents, the introduction of zirconium tanning agent increases the concentration of zirconium ions in the tanning bath solution. Based on the principle of reversible reaction, it can slow down the hydrolysis of zirconium halide perovskite, further maintain the nanostructure of zirconium halide perovskite, facilitate the uniform penetration of zirconium, and improve the comprehensive tanning performance of zirconium tanning agent, especially the wet heat stability and filling property of the tanned leather after tanning.

[0015] Furthermore, the method disclosed in the present invention uses the thermal injection method to prepare a highly stable zirconium halide perovskite nanocomposite tanning agent. The operation is easy to repeat. When applied to leather tanning, it can endow the leather with excellent wet heat stability, good filling property, etc., which is conducive to the green transformation of the leather industry.

[0016] The present invention also discloses a perovskite composite tanning agent based on reversible reaction prepared by the above preparation method. The combined use of the highly stable zirconium halide perovskite tanning agent and zirconium tanning agent in the present invention can achieve the effective penetration of zirconium into the skin collagen fibers; compared with zirconium halide perovskite, the highly stable zirconium halide perovskite can better maintain the nanostructure. At the same time, based on the principle of reversible reaction, the presence of zirconium tanning agent can also slow down the hydrolysis of perovskite, both of which are conducive to the penetration of perovskite and improve the tanning performance of the leather; in addition, the addition of zirconium tanning agent can further enhance the tanning effect and solve the problem of limited tanning performance of perovskite-type tanning agents. Description of the Drawings

[0017] Figure 1For the application of the perovskite composite tanning agent based on reversible reaction in Example 2 to the tanning of sheepskin, it is a comparison chart of the shrinkage temperature and thickening rate of the tanned leather blank and the tanned leather blank after tanning with zirconium sulfate. Detailed implementation mode

[0018] To enable those skilled in the art to understand the features and effects of the present invention, the following is a general description and definition of the terms and phrases mentioned in the specification and claims. Unless otherwise specified, all technical and scientific terms used herein shall have the ordinary meaning understood by those skilled in the art for the present invention. In case of conflict, the definition in this specification shall prevail.

[0019] The theories or mechanisms described and disclosed herein, whether right or wrong, shall not limit the scope of the present invention in any way, that is, the content of the present invention can be implemented without being limited by any specific theory or mechanism.

[0020] In this article, all features defined in the form of numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are only for the sake of simplicity and convenience. Accordingly, the description of numerical ranges or percentage ranges should be regarded as having covered and specifically disclosed all possible sub-ranges and individual numerical values within the range (including integers and fractions).

[0021] In this article, unless otherwise specified, "comprising", "including", "containing", "having" or similar terms cover the meanings of "consisting of" and "mainly consisting of". For example, "A comprises a" covers the meanings of "A comprises a and others" and "A only comprises a".

[0022] In this article, for the sake of concise description, all possible combinations of all technical features in each embodiment or example are not described. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each embodiment or example can be combined arbitrarily, and all possible combinations should be considered as the scope described in this specification.

[0023] The present invention provides a preparation method of a perovskite composite tanning agent based on reversible reaction. By using a highly stable perovskite to improve the water resistance stability of the material, and at the same time introducing a metal salt with the same metal as the perovskite into the tanning bath solution to increase the concentration of metal ions in the bath solution. Based on the principle of reversible reaction, the hydrolysis of the perovskite can be slowed down, which is beneficial to maintaining the nanoscale structure of the perovskite and further improving the water resistance stability of the perovskite. It is beneficial to the penetration of the perovskite into the skin and improves the tanning performance. The specific steps are as follows: Add a zirconium-based metal salt to an acidic organic solvent, and carry out a heating reaction in an oil bath container to obtain a clear product; Add the same halogen-based metal salt, cesium-based metal salt, oleic acid, and oleylamine ligand to the solution, continue heating, and obtain a highly stable zirconium halide perovskite precursor solution after the reaction ends; Inject a halogen reagent into the highly stable zirconium halide perovskite precursor solution, carry out a heating reaction, and then post-treat the obtained product to obtain a highly stable zirconium halide perovskite; Combine the highly stable zirconium halide perovskite with a common zirconium tanning agent to obtain a highly stable zirconium halide perovskite nanocomposite tanning agent.

[0024] Preferably, the zirconium-based metal salt is one of zirconium citrate, zirconium bromide, or zirconium nitrate; the organic solvent is dodecene or tetradecene; the acidic solute is one of oxalic acid, phosphoric acid, or nitric acid; the mass-volume ratio of the zirconium-based metal salt, organic solvent, and acidic solute is 1 g:(20 - 60) mL:(1 - 3) mL.

[0025] Preferably, the temperature for the heating reaction in the oil bath container is 25 - 40 °C, and the time is 15 - 30 min; magnetic stirring is used during the heating reaction in the oil bath container.

[0026] Preferably, the same halogen-based metal salt is zinc bromide or copper bromide; the cesium-based metal salt is cesium sulfate or cesium carbonate; The mass ratio of the zirconium-based metal salt, the same halogen-based metal salt, and the cesium-based metal salt is 6 g:(1 - 4) g:(1 - 4) g; the mass-volume ratio of the zirconium-based metal salt, oleic acid, and oleylamine is 2 g:(10 - 20) mL:(1 - 6) mL; the heating reaction temperature is 40 - 120 °C, and the time is 40 - 90 min.

[0027] Preferably, the halogen reagent is 1-bromopropane or 1-bromobutane; the mass-volume ratio of the zirconium-based metal salt and the halogen reagent is 2 g:(3 - 12) mL; the temperature of the heating reaction is 120 - 240 °C, and the time is 10 - 60 s; The post-treatment includes cooling, centrifugation, washing, and drying; the cooling treatment is ice bath cooling or mechanical stirring cooling, and the stirring rate is 30 - 800 r / min; the time for centrifugation is 5 - 20 min; the washing treatment is to wash 4 - 6 times with a non-polar solvent; the non-polar washing solvent is 1-chloropentane or n-heptane.

[0028] Preferably, the zirconium tanning agent is one of zirconium nitrate, zirconium citrate, or zirconium bromide; the mass ratio of the highly stable zirconium halide perovskite to the zirconium tanning agent is 3:1 - 3:7.

[0029] The combination is carried out by the action of a mixer or a ball mill, and the action time is 240 - 360 min.

[0030] The present invention also discloses a perovskite composite tanning agent based on a reversible reaction prepared by the above preparation method.

[0031] The present invention also discloses the application of the above perovskite composite tanning agent based on a reversible reaction in chrome-free tanning, including the following steps: Put pickled hides and water into a rotating drum at a mass ratio of 1:1 to 1:3, then add sodium chloride accounting for 6% - 12% of the mass of water and an oxalic acid solution with a concentration of 8%, adjust the bath solution to pH 0.5 - 1.5 for the first time, and rotate for 60 min; add a highly stable zirconium halide perovskite nano composite tanning agent accounting for 2% - 15% of the mass of pickled hides to the bath solution, and rotate for 2 - 8 h; then use a sodium bicarbonate solution with a concentration of 15% to adjust the pH of the bath solution to 3.0 - 5.0 for the second time, and rotate for 90 - 180 min; raise the temperature to 35 - 40 °C, rotate for 60 - 120 min, let it stand for 12 h, then rotate for 60 - 120 min, and wash with water.

[0032] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of this application.

[0033] Conventional instrument equipment in the art is used in the following embodiments. For the experimental methods without specific conditions noted in the following embodiments, they are usually carried out under conventional conditions or according to the conditions recommended by the manufacturer. Various raw materials are used in the following embodiments. Unless otherwise stated, commercially available products are used, and their specifications are conventional specifications in the art. In the specification of the present invention and the following embodiments, unless otherwise specified, "%" represents weight percentage, "parts" represents weight parts, and the ratio represents weight ratio.

[0034] Example 1 A preparation method of a perovskite composite tanning agent based on a reversible reaction includes the following steps: Add 1 g of zirconium bromide, 30 mL of tetradecene, and 2 mL of dilute nitric acid into a flask, place the flask in an oil bath container at 35 °C for heating and magnetic stirring. After reacting for 20 min, a clear product is obtained; then add 0.3 g of zinc bromide to the clear product. After complete dissolution, add 0.5 g of cesium carbonate, 9 mL of oleic acid, and 2 mL of oleylamine to the solution. During the reaction process, continue heating. Under the condition that the reaction temperature is 90 °C, after reacting for 60 min, a highly stable zirconium halide perovskite precursor solution is obtained; Inject 2 mL of bromobutane into the zirconium halide perovskite precursor solution. Under the condition that the reaction temperature is 180 °C, stop heating after reacting for 20 s. After the solution cools, centrifuge for 10 min, wash the precipitate 4 times with n-pentane, and finally dry it in an oven at 40 °C to obtain highly stable zirconium halide perovskite; Combine the zirconium halide perovskite with 1 g of zirconium citrate by means of a mixer or ball mill for 240 min to obtain a highly stable perovskite composite tanning agent based on a reversible reaction.

[0035] Example 2 A preparation method of a perovskite composite tanning agent based on a reversible reaction includes the following steps: Add 1.5 g of zirconium bromide, 60 mL of dodecene, and 4.5 mL of phosphoric acid into a flask. Place the flask in a 40 °C oil bath container for heating and magnetic stirring. After reacting for 25 min, a clear product is obtained; then add 0.36 g of zinc bromide to the clear product. After complete dissolution, add 0.75 g of cesium carbonate, 12 mL of oleic acid, and 3 mL of oleylamine to the solution. Continuously heat during the reaction. Under the condition that the reaction temperature is 100 °C, after reacting for 70 min, a highly stable zirconium halide perovskite precursor solution is obtained; Inject 3 mL of bromopropane into the zirconium halide perovskite precursor solution. Under the condition that the reaction temperature is 200 °C, stop heating after reacting for 40 s. After the solution cools, centrifuge for 15 min, wash the precipitate 5 times with n-pentane, and finally dry it in an oven at 45 °C to obtain highly stable zirconium halide perovskite; Combine the zirconium halide perovskite with 0.5 g of zirconium bromide by means of a mixer or ball mill for 300 min to obtain a highly stable perovskite composite tanning agent based on a reversible reaction.

[0036] Example 3 A preparation method of a perovskite composite tanning agent based on a reversible reaction includes the following steps: Add 2 g of zirconium nitrate, 100 mL of tetradecene, and 2 mL of phosphoric acid into a flask. Place the flask in a 40 °C oil bath container for heating and magnetic stirring. After reacting for 30 min, a clear product is obtained; then add 1.2 g of copper bromide to the clear product. After complete dissolution, add 1 g of cesium carbonate, 16 mL of oleic acid, and 6 mL of oleylamine to the solution. Continuously heat during the reaction. Under the condition that the reaction temperature is 110 °C, after reacting for 80 min, a highly stable zirconium halide perovskite precursor solution is obtained; Inject 6 mL of bromobutane into the zirconium halide perovskite precursor solution. Under the condition that the reaction temperature is 220 °C, stop heating after reacting for 60 s. After the solution cools, centrifuge for 15 min, wash the precipitate 6 times with n-heptane, and finally dry it in an oven at 50 °C to obtain highly stable zirconium halide perovskite; After combining zirconium halide perovskite with 2 g of zirconium bromide in a mixer or ball mill for 360 min, a highly stable perovskite composite tanning agent based on a reversible reaction is obtained.

[0037] Application Example 1 Leather tanning is carried out using the highly stable perovskite composite tanning agent based on a reversible reaction prepared in Example 1, including the following steps: Put pickled hides and water into a drum at a mass ratio of 1:2, then add sodium chloride accounting for 7% of the water mass and an oxalic acid solution with a concentration of 8%. Adjust the pH of the bath solution to 1.5 for the first time and rotate for 60 min; add the highly stable zirconium halide perovskite nano composite tanning agent accounting for 7% of the pickled hide mass to the bath solution and rotate for 7 h; then use a sodium bicarbonate solution with a concentration of 15% to adjust the pH of the bath solution to 5.0 for the second time and rotate for 100 min; raise the temperature to 35 °C, rotate for 60 min, let it stand for 12 h, then rotate for 120 min, and wash with water.

[0038] Application Example 2 Leather tanning is carried out using the highly stable perovskite composite tanning agent based on a reversible reaction prepared in Example 2, including the following steps: Put pickled hides and water into a drum at a mass ratio of 1:3, then add sodium chloride accounting for 11% of the water mass and an oxalic acid solution with a concentration of 8%. Adjust the bath solution to pH 1.0 for the first time and rotate for 60 min; add the highly stable zirconium halide perovskite nano composite tanning agent accounting for 9% of the pickled hide mass to the bath solution and rotate for 6 h; then use a sodium bicarbonate solution with a concentration of 15% to adjust the pH of the bath solution to 3.0 for the second time and rotate for 90 min; raise the temperature to 40 °C, rotate for 90 min, let it stand for 12 h, then rotate for 90 min, and wash with water.

[0039] Application Example 3 Leather tanning is carried out using the highly stable perovskite composite tanning agent based on a reversible reaction prepared in Example 3, including the following steps: Put pickled hides and water into a drum at a mass ratio of 1:1, then add sodium chloride accounting for 9% of the water mass and an oxalic acid solution with a concentration of 8%. Adjust the bath solution to pH 1.5 for the first time and rotate for 60 min; add the highly stable zirconium halide perovskite nano composite tanning agent accounting for 11% of the pickled hide mass to the bath solution and rotate for 5 h; then use a sodium bicarbonate solution with a concentration of 15% to adjust the pH of the bath solution to 4.0 for the second time and rotate for 150 min; raise the temperature to 38 °C, rotate for 120 min, let it stand for 12 h, then rotate for 60 min, and wash with water.

[0040] High-stability zirconium halide perovskite has metal ion tunability. Introducing zirconium ions into perovskite endows the perovskite with tanning properties. Adding the same halogen-based metal salt during the preparation process can improve the stability of the halogen-based perovskite. When combined with a zirconium tanning agent, a high-stability zirconium halide perovskite nanocomposite tanning agent can be obtained, and the tanning performance of the perovskite-type tanning agent can be further improved based on the principle of reversible reaction.

[0041] Figure 1 For Example 1, it is a comparison chart of the shrinkage temperature and thickening rate of the leather after tanning with the high-stability perovskite composite tanning agent based on reversible reaction and the leather after tanning with zirconium chloride. It can be seen from the figure that the leather after tanning with the high-stability zirconium halide perovskite nanocomposite tanning agent has the highest shrinkage temperature and good thickening rate, indicating its best resistance to wet heat stability and good filling property.

[0042] The above content is only to illustrate the technical idea of the present invention and cannot limit the protection scope of the present invention. Any modification made on the basis of the technical solution according to the technical idea proposed by the present invention falls within the protection scope of the claims of the present invention.

Claims

1. A preparation method of a perovskite composite tanning agent based on a reversible reaction, characterized in that, It includes the following steps: Add a zirconium-based metal salt to an acidic organic solvent, and then carry out a heating reaction in an oil bath container to obtain a clear product; Add a homohalogen-based metal salt, a cesium-based metal salt, and oleic acid and oleylamine ligands to the clear product, and then continue heating. After the reaction is completed, a zirconium halide perovskite precursor solution is obtained; Inject a halogen reagent into the zirconium halide perovskite precursor solution, carry out a heating reaction again, obtain a reaction product, and carry out post-treatment on the reaction product to obtain zirconium halide perovskite; Combine the zirconium halide perovskite with a zirconium tanning agent to obtain a perovskite composite tanning agent based on a reversible reaction.

2. The preparation method of a perovskite composite tanning agent based on a reversible reaction according to claim 1, characterized in that, The zirconium-based metal salt is one of zirconium citrate, zirconium bromide, and zirconium nitrate; the acidic organic solvent is obtained by mixing an organic solvent and an acidic solute; the organic solvent is dodecene or tetradecene, and the acidic solute is one of oxalic acid, phosphoric acid, and nitric acid; The dosage ratio of the zirconium-based metal salt, the organic solvent, and the acidic solute is 1 g : (20 - 60) mL : (1 - 3) mL.

3. The preparation method of a perovskite composite tanning agent based on a reversible reaction according to claim 1, characterized in that, The temperature of the heating reaction carried out in the oil bath container is 5 - 40 °C, the time is 15 - 30 min, and magnetic stirring is used during the heating reaction.

4. The preparation method of a perovskite composite tanning agent based on a reversible reaction according to claim 1, characterized in that, The homohalogen-based metal salt is zinc bromide or copper bromide; the cesium-based metal salt is cesium sulfate or cesium carbonate; The mass ratio of the zirconium-based metal salt, the homohalogen-based metal salt, and the cesium-based metal salt is 6 : (1 - 4) : (1 - 4); The dosage ratio of the zirconium-based metal salt, oleic acid, and oleylamine is 2 g : (10 - 20) mL : (1 - 6) mL; The temperature of the continued heating is 40 - 120 °C, and the time is 40 - 90 min.

5. The preparation method of a perovskite composite tanning agent based on a reversible reaction according to claim 1, characterized in that, The halogen reagent is 1-bromopropane or 1-bromobutane; The dosage ratio of the zirconium-based metal salt and the halogen reagent is 2 g : (3 - 12) mL.

6. The preparation method of a perovskite composite tanning agent based on a reversible reaction according to claim 1, characterized in that, The temperature of the re-heating reaction is 120 - 240 °C, and the time is 10 - 60 s; The post-treatment includes cooling, centrifugation, washing, and drying processes carried out in sequence; the cooling is ice bath cooling or mechanical stirring cooling, and the stirring rate of the mechanical stirring cooling is 30 - 800 r / min; the time of the centrifugation is 5 - 20 min; the washing is carried out 4 - 6 times with a non-polar solvent; the non-polar solvent is 1-chloropentane or n-heptane.

7. The preparation method of a perovskite composite tanning agent based on a reversible reaction according to claim 1, characterized in that, The zirconium tanning agent is one of zirconium nitrate, zirconium citrate, and zirconium bromide; The mass ratio of the zirconium halide perovskite to the zirconium tanning agent is 3 : 1 - 3 : 7; The combination is carried out by the action of a mixer or a ball mill, and the time of the action is 240 - 360 min.

8. A perovskite composite tanning agent based on a reversible reaction, characterized in that, It is prepared by using the preparation method described in any one of claims 1 - 7.

9. Application of the perovskite composite tanning agent based on a reversible reaction described in claim 8 in chrome-free tanning.

10. Use of a perovskite composite tanning agent based on a reversible reaction in chrome-free tanning according to claim 9, characterized in that, It includes the following steps: Add the pickled hide and water to the rotary drum at a mass ratio of 1:1 to 1:3, then add sodium chloride accounting for 6% - 12% of the mass of water and an oxalic acid solution with a concentration of 8%. Adjust the bath solution to pH 0.5 - 1.5 for the first time and rotate for 60 min; add a perovskite composite tanning agent based on reversible reaction accounting for 2% - 15% of the mass of the pickled hide to the bath solution and rotate for 2 - 8 h; then use a sodium bicarbonate solution with a concentration of 15% to adjust the pH of the bath solution to 3.0 - 5.0 for the second time and rotate for 90 - 180 min; raise the temperature to 35 - 40 °C, rotate for 60 - 120 min, let it stand for 12 h, then rotate for 60 - 120 min and wash with water.

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