A tanning method for growing nanotannins in situ between collagen fibers

Abstract

The application discloses a tanning method for growing nano-tanning agents in situ between collagen fibers, and belongs to the technical field of leather tanning. The application uses metal salts with tanning properties and anionic small molecule ligands as raw materials, uses the masking effect of the anionic small molecule ligands on the metal salts with tanning properties, promotes the uniform in-situ growth of LDHs in the collagen fibers, and thus improves the moisture and heat stability, chemical medicine resistance, microbial action resistance and physical and mechanical properties of the crude leather. The metal salts and the organic ligands used are widely sourced and have low cost.

Description

Technical Field

[0001] The invention belongs to the technical field of leather tanning, and relates to a tanning method for in-situ growing nano-tanning agents between collagen fibers. Background Art

[0002] Tanning is a key process in leathermaking, transforming raw hides into crust leather. Chrome tanning, which imparts excellent heat and moisture stability, a pleasant feel, and superior physical and mechanical properties, is the most widely used tanning agent in leather. However, in conventional chrome tanning, only 60% to 70% of the chromium is absorbed, with the remainder remaining in the wastewater. Under certain conditions, the chromium in the wastewater can be oxidized to toxic hexavalent chromium, posing serious risks to human health and the environment. Consequently, the development of chrome-free tanning agents has attracted considerable attention.

[0003] Non-chromium metal tanning agents can impart excellent moisture and heat stability and physical and mechanical properties to tanned crust leather, and are metal tanning agents that are expected to replace chrome tanning. However, non-chromium metal tanning agents are not easy to form uniform and stable bonds with collagen fibers. Layered double metal hydroxides (LDHs) are nanomaterials assembled from positively charged main layers and interlayer anions through non-covalent interactions. They have the characteristics of adjustable layer composition and interlayer anions, and controllable size. However, in order to obtain layered double metal hydroxides (LDHs) with more regular morphology, high-temperature synthesis in alkaline solution is required, which increases energy consumption and the possibility of water resource pollution. Summary of the Invention

[0004] The purpose of the present invention is to overcome the problems of energy consumption and environmental pollution caused by the high-temperature synthesis of layered bimetallic composite hydroxide nano-tanning agents in alkaline solutions. The present invention uses the anions in the structure of layered bimetallic composite hydroxides (LDHs) as self-masking agents to promote the penetration of inorganic metal ions, realize the growth of layered bimetallic composite hydroxides (LDHs) between collagen fibers, combine with collagen fibers, and improve the physical and chemical properties of crust leather after tanning.

[0005] On the one hand, the present invention provides a tanning method for in situ growing nano-tanning agents between collagen fibers, comprising: using anions in the structure of a bimetallic composite hydroxide as self-masking agents to promote the penetration of metal ions between leather collagen fibers, so that the bimetallic composite hydroxide nano-tanning agent grows in situ between the leather collagen fibers, and then performing leather tanning.

[0006] Furthermore, the present invention performs a double acid treatment on the acid leather before in-situ growth of the bimetallic composite hydroxide nano-tanning agent between the leather collagen fibers, thereby promoting the penetration of anions and metal ions in the bimetallic composite hydroxide structure.

[0007] Further, the acid solution in the double-dipping acid treatment is any one of formic acid and sulfuric acid.

[0008] Further, the acid solution is used to adjust the pH of the bath to 2.0-3.5.

[0009] Further, the acid solution is 0.5%-2.5% of the reference mass of the acid crust.

[0010] Further, in the process of growing the layered double hydroxide in situ between the collagen fibers of the leather, an organic small molecule ligand is used as the source of anions, and the organic small molecule ligand is any one of sodium citrate, sodium tartrate, and polyethylene glycol.

[0011] Further, the organic small molecule ligand is 3%-5% of the mass of the acid crust.

[0012] Further, in the process of growing the layered double hydroxide in situ between the collagen fibers of the leather, the metal ions include at least one of Mg 2+ , Al 3+ , Zr 4+ , and Fe 3+ .

[0013] Further, the source of the metal ions is the corresponding metal salt, and the mass of the metal salt is 4%-7% of the mass of the acid crust.

[0014] In another aspect, the present application provides a leather prepared by the above method and subjected to scanning electron microscope testing, and the synthesized layered double hydroxide nano-tanning agent is uniformly distributed between the collagen fibers of the leather and tightly adheres to the collagen fibers of the leather.

[0015] Compared with the prior art, the technical solution provided by the present application has at least the following beneficial effects or advantages:

[0016] The application discloses a tanning method for growing nanometer tanning agents in collagen fibers in situ, and has the advantages that the nanometer tanning agent has self-shielding performance, the small-molecule ligand plays a shielding role on the metal ions with tanning performance, the growth of the tanning agent in the collagen fibers is promoted, the wet heat stability and the physical and mechanical properties of the crude leather after tanning are improved, the problems of uneven distribution and poor combination of the conventional metal tanning agent in the crude leather are solved, the metal salt and the small-molecule organic material are widely available, and the cost is low. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 A scanning electron microscope image of the crude leather with the layered double metal composite hydroxide grown in collagen fibers in situ. DETAILED DESCRIPTION

[0018] In the following, the technical solutions of the application are described in combination with examples, but the application is not limited to the following examples. The experimental methods and detection methods described in the examples are conventional methods, and the reagents and materials described are commercially available, unless otherwise specified.

[0019] Example 1

[0020] The example provides a tanning method for growing nanometer tanning agents of layered composite hydroxide in collagen fibers in situ.

[0021] 1. Double-dipping acid

[0022] The mass of the tanning acid skin is taken as the double-dipping acid and the reference mass of the tanning process. First, water and sodium chloride are added to the drum under normal temperature conditions to dissolve completely to obtain a bath solution. The mass of the water is 50% to 150% of the reference mass, and the mass of the sodium chloride is 6% to 10% of the reference mass. Then, the acid skin is placed in the drum, and after rotating for 5 to 30 minutes, a diluted acid solution (formic acid solution or sulfuric acid solution) is added to adjust the pH of the bath solution in the drum to 2.0 to 3.5 to obtain an acid dipping bath solution. The mass ratio of acid to water in the acid solution is 1:10, and the mass of the acid solution is 0.5% to 2.5% of the reference mass. Finally, the acid drum is rotated again for 60 to 180 minutes. The double-dipping acid treatment of the acid skin promotes the penetration of anions and metal ions in the double-metal composite hydroxide structure.

[0023] 2. Tanning

[0024] The organic small molecule ligand required for synthesizing the layered double hydroxide (LDHs) nano-tanning agent is added to the pickling bath, and the mass of the organic small molecule ligand is 3% to 5% of the reference mass, and the drum is rotated for 10 to 20 minutes. Then, the metal salt is added to the bath, and the mass of the metal salt is 4% to 7% of the reference mass, and the drum is rotated for 30 to 180 minutes. Then, the pH of the bath in the drum is adjusted to 4.0 to 6.0 by using a diluted alkaline solution (sodium bicarbonate or sodium carbonate solution), the mass ratio of alkali to water in the alkaline solution is 1:10, and the mass of the alkaline solution is 0.5% to 2.5% of the reference mass. Finally, the temperature of the bath in the drum is increased to 38°C, the drum is rotated for 90 minutes, and then the drum is left to stand for 12 hours, and then the drum is rotated again for 30 to 90 minutes, and then the tanning agent is washed out of the drum, and the tanned crust leather is obtained.

[0025] Example 2

[0026] The present embodiment provides a tanning method for growing a layered composite hydroxide nano-tanning agent in situ between collagen fibers.

[0027] 1. Double pickling

[0028] The mass of the tanning acid skin is weighed as the reference mass for double pickling and the tanning process. First, water and sodium chloride are added to the drum at room temperature to be fully dissolved to obtain a bath. Among them, the mass of water is 80% of the reference mass, and the mass of sodium chloride is 6% of the reference mass. Then, the acid skin is placed in the drum, and after rotating for 30 minutes, a diluted formic acid solution is added to adjust the pH of the bath in the drum to 2.0, and a pickling bath is obtained. Among them, the mass ratio of formic acid to water in the formic acid solution is 1:10, and the mass of the acid solution is 1.5% of the reference mass. Finally, the acid drum is rotated again for 60 minutes.

[0029] 2. Tanning

[0030] Sodium citrate is added to the pickling bath, and the mass of the sodium citrate is 3% of the reference mass, and the drum is rotated for 10 minutes. Then, Mg(NO3)2·6H2O and Al(NO3)3·9H2O are added to the bath, and the mass of Mg(NO3)2·6H2O and Al(NO3)3·9H2O is 5% of the reference mass, and the molar ratio is 2:1, and the drum is rotated for 120 minutes. Then, the pH of the bath in the drum is adjusted to 4.5 by using a diluted sodium bicarbonate solution, the mass ratio of sodium bicarbonate to water in the sodium bicarbonate solution is 1:10, and the mass of the sodium bicarbonate solution is 1.5% of the reference mass. Finally, the temperature of the bath in the drum is increased to 38°C, the drum is rotated for 90 minutes, and then the drum is left to stand for 12 hours, and then the drum is rotated again for 30 minutes, and then the tanning agent is washed out of the drum, and the tanned crust leather is obtained.

[0031] Example 3

[0032] The present embodiment provides a tanning method of growing a layered composite hydroxide nanotanning agent in situ between collagen fibers.

[0033] 1. Double pickling

[0034] The mass of the tanning acid skin is weighed as the reference mass for the double pickling and tanning process. First, water and sodium chloride are added to the rotating drum under normal temperature conditions to be fully dissolved to obtain a bath solution. The mass of the water is 100% of the reference mass, and the mass of the sodium chloride is 7% of the reference mass. Then, the acid skin is placed in the rotating drum, and after rotating for 15 min, a diluted formic acid solution is added to adjust the pH of the bath solution in the rotating drum to 2.5 to obtain a pickling bath solution. The mass ratio of formic acid to water in the formic acid solution is 1:10, and the mass of the formic acid solution is 1.0% of the reference mass. Finally, the acid drum is rotated again for 60 min.

[0035] 2. Tanning

[0036] Sodium tartrate is added to the pickling bath solution, and the mass of the sodium tartrate is 4% of the reference mass, and the drum is rotated for 20 min. Then, Mg(NO3)2·6H2O, Al(NO3)3·9H2O, and Zr(NO3)4·5H2O are added to the bath solution, and the mass of Mg(NO3)2·6H2O, Al(NO3)3·9H2O, and Zr(NO3)4·5H2O is 6% of the reference mass, and the molar ratio is 2:0.7:0.3, and the drum is rotated for 120 min. Then, a diluted sodium bicarbonate solution is used to adjust the pH of the bath solution in the rotating drum to 5.0, and the mass ratio of sodium bicarbonate to water in the sodium bicarbonate solution is 1:10, and the mass of the sodium bicarbonate solution is 1.5% of the reference mass. Finally, the temperature of the bath solution in the rotating drum is raised to 38℃, and after rotating for 90 min, it is left to stand for 12 h, and then rotated again for 30 min, and then washed out of the drum to obtain tanned crust leather.

[0037] Example 4

[0038] The present embodiment provides a tanning method of growing a layered composite hydroxide nanotanning agent in situ between collagen fibers.

[0039] 1. Double pickling

[0040] The mass of the tanning acid skin is weighed as the reference mass for the double pickling and tanning process. First, water and sodium chloride are added to the rotating drum under normal temperature conditions to be fully dissolved to obtain a bath solution. The mass of the water is 120% of the reference mass, and the mass of the sodium chloride is 8% of the reference mass. Then, the acid skin is placed in the rotating drum, and after rotating for 30 min, a diluted formic acid solution is added to adjust the pH of the bath solution in the rotating drum to 2.0-3.5 to obtain a pickling bath solution. The mass ratio of formic acid to water in the formic acid solution is 1:10, and the mass of the formic acid solution is 1.0% of the reference mass. Finally, the acid drum is rotated again for 60 min.

[0041] 2. Tannage

[0042] Polyethylene glycol was added into the pickling bath, the mass of polyethylene glycol was 5% of the reference mass, and the rotation was performed for 10 min. Then, Mg(NO3)2·6H2O and Fe(NO3)3·9H2O were added into the bath, the mass of Mg(NO3)2·6H2O and Fe(NO3)3·9H2O was 7% of the reference mass, the molar ratio was 2:1, and the rotation was performed for 150 min. Then, the pH of the bath in the rotating drum was adjusted to 6.0 by using a diluted sodium bicarbonate solution, the mass ratio of sodium bicarbonate to water in the sodium bicarbonate solution was 1:10, the mass of the sodium bicarbonate solution was 2.5% of the reference mass. Finally, the temperature of the bath in the rotating drum was increased to 38℃, the rotation was performed for 90 min, and then the drum was statically placed for 12 h, the rotation was performed for 90 min again, and then the tannage crust was obtained by washing out of the drum.

[0043] Figure 1 The scanning electron microscope image of the collagen fiber in-situ growth layered double hydroxide crust leather prepared in the embodiment is shown in Fig. 1. Figure 1 As can be seen from Fig. 1, the layered double hydroxide nano-tanning agent synthesized in the embodiment is uniformly distributed between the collagen fibers of the leather, and is tightly adhered to the collagen fibers of the leather.

[0044] The above-described embodiments are only a part of the embodiments of the present application, but not all the embodiments. The detailed description of the embodiments of the present application is not intended to limit the scope of the claimed application, but only represents selected embodiments of the present application. All other embodiments obtained by related deduction and replacement made by those skilled in the art under the condition of the concept of the present application, without making creative labor, belong to the scope of protection of the present application.

Claims

1. A tanning method for in situ growth of nanotannins between collagen fibers, characterized by, The application relates to a tanning method, which comprises the following steps: taking anions in a layered double hydroxide structure as a self-masking agent to promote the penetration of metal ions between leather collagen fibers, growing a layered double hydroxide nano-tanning agent in situ between the leather collagen fibers, and then tanning the leather. The source of the anions is an organic small-molecule ligand. The organic small-molecule ligand is any one of sodium citrate, sodium tartrate and polyethylene glycol. The organic small-molecule ligand accounts for 3-5% of the weight of the acid skin. The source of the metal ions is a corresponding metal salt. The metal ions include at least one of Mg 2+ and Al 3+ , Zr 4+ , Fe 3+ . The metal salt accounts for 4-7% of the weight of the acid skin. The acid skin is subjected to a re-dip acid treatment before the layered double hydroxide nano-tanning agent is grown in situ between the leather collagen fibers.

2. The tanning method according to claim 1, characterized in that, The acid solution in the re-dip acid treatment is any one of formic acid and sulfuric acid.

3. The tanning method according to claim 2, characterized in that, The pH of the bath solution in the re-dip acid treatment is 2.0-3.

5.

4. The tanning method according to claim 2, characterized in that, The acid solution accounts for 0.5-2.5% of the weight of the acid skin.

5. The tanning method according to claim 3, characterized in that, The tanning method is prepared according to any one of claims 1-5.

6. A leather characterized by, ​

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