Weather-resistant and corrosion-resistant leather and method for preparing the same

Abstract

The application discloses weather-resistant and corrosion-resistant leather and a preparation method thereof, and belongs to the technical field of leather. The weather-resistant and corrosion-resistant leather is obtained by uniformly coating polyurethane finishing agent on the surface of a leather product and performing light curing. The preparation method of the polyurethane finishing agent comprises the following steps: mixing diisocyanate, a catalyst, a cashew phenol grafted mesoporous silica compound and n-hexane, heating, condensing, refluxing and stirring, adding a capping monomer, stirring after temperature reduction, removing n-hexane through rotary evaporation, and obtaining a polyurethane prepolymer; and mixing the polyurethane prepolymer, active monomers, a photoinitiator, an antioxidant, a leveling agent and a defoaming agent, and uniformly stirring to obtain the polyurethane finishing agent. The mesoporous silica compound is mesoporous silica coated lignin-zinc oxide nano powder. The weather-resistant and corrosion-resistant leather improves the weather-resistant and corrosion-resistant performance of the leather product, and improves the service life and stability of the leather product.

Description

Technical Field

[0001] This invention belongs to the field of leather technology, specifically relating to a weather-resistant and corrosion-resistant leather and its preparation method. Background Technology

[0002] The core component of leather (especially genuine leather) is collagen fibers, which have a large number of porous structures. Artificial leather / synthetic leather is mostly made of PVC, PET, or polyurethane resin, and its surface also has microscopic cracks. The peptide bonds in collagen fibers are easily degraded and broken by ultraviolet (UV) radiation, causing the leather fibers to lose their toughness, resulting in hardening, brittleness, cracking, and fading. The porous structure of leather easily absorbs external corrosive media (such as sweat and surfactants in detergents), which can penetrate into the fibers, causing collagen hydrolysis and mold growth. For artificial leather, acidic and alkaline media can damage the cross-linking structure of the base resin, leading to coating peeling and base material powdering. Without weather-resistant and corrosion-resistant surface treatment, leather will rapidly fail due to environmental erosion and cannot meet diverse application requirements. Summary of the Invention

[0003] The purpose of this invention is to provide a weather-resistant and corrosion-resistant leather and its preparation method, which can improve the weather resistance and corrosion resistance of leather products, and improve their service life and stability.

[0004] The objective of this invention can be achieved through the following technical solutions:

[0005] A method for preparing weather-resistant and corrosion-resistant leather includes the following steps: uniformly coating a polyurethane coating agent onto the surface of a leather product, and obtaining the weather-resistant and corrosion-resistant leather after light curing;

[0006] The preparation method of the polyurethane coating agent includes the following steps:

[0007] A1. Mix diisocyanate, catalyst, cashew phenol grafted mesoporous silica complex and n-hexane, heat to 55-65℃ in a nitrogen atmosphere, reflux and stir for 3-4 hours, add end-capping monomer, cool to 50℃, continue stirring for 4-6 hours, and then remove n-hexane by rotary evaporation to obtain polyurethane prepolymer.

[0008] A2. Take the polyurethane prepolymer, active monomer, photoinitiator, antioxidant, leveling agent and defoamer, mix them, and stir evenly to obtain the polyurethane coating agent;

[0009] The mesoporous silica composite is mesoporous silica-coated lignin-zinc oxide nanopowder.

[0010] As a preferred embodiment of the present invention, in step A1, the ratio of diisocyanate, catalyst, cashew phenol grafted mesoporous silica complex, n-hexane, and end-capping monomer is 10-12g: 0.028-0.036g: 18-20g: 40-50mL: 10-12g.

[0011] As a preferred technical solution of the present invention, in step A2, the mass ratio of the polyurethane prepolymer, active monomer, photoinitiator, antioxidant, leveling agent and defoamer is 40-60:18-24:2-4:0.4-0.8:0.25-0.65:0.15-0.35.

[0012] As a preferred embodiment of the present invention, the preparation method of the cashew phenol-grafted mesoporous silica composite includes the following steps:

[0013] S1. Purify the enzymatically hydrolyzed lignin (purchased from Wuhan Jiyesheng Chemical Co., Ltd.): Mix the enzymatically hydrolyzed lignin with deionized water, sonicate for 10-20 min, filter, dry the solid phase, mix the dried enzymatically hydrolyzed lignin with tetrahydrofuran at a mass ratio of 1:30, stir for 30-40 min, centrifuge, and remove the tetrahydrofuran by rotary evaporation of the supernatant to obtain pure enzymatically hydrolyzed lignin.

[0014] S2. Dissolve the purified enzymatically hydrolyzed lignin in tetrahydrofuran, add deionized water while stirring to replace the solvent, then heat and stir continuously at 55-60℃ for 8-10h, and dry at a vacuum of 10-20Pa and a temperature of -40~-20℃ for 20-40h to obtain lignin nanoparticles; the ratio of the enzymatically hydrolyzed lignin, tetrahydrofuran, and deionized water is 4-6mg:4-5mL:15mL;

[0015] S3. Mix zinc nitrate hexahydrate, hexamethylenetetramine, and deionized water evenly, add the lignin nanoparticles, ultrasonically stir for 10-20 min, pack into a 100 mL hydrothermal crystallization vessel, and dry in a 120℃ oven for 4-8 h, then dry at a vacuum of 10-20 Pa and a temperature of -50℃ for 25-35 h to obtain lignin-zinc oxide nanoparticles; the mass ratio of zinc nitrate hexahydrate, hexamethylenetetramine, deionized water, and lignin nanoparticles is 0.1-0.3:0.02-0.05:20-30:0.06-0.08;

[0016] S4. Take the lignin-zinc oxide nanopowder and anhydrous ethanol, mix them, and ultrasonically disperse them for 20-30 min. Adjust the pH to 8-9 with 0.1 mol / L ammonia water, add tetraethyl orthosilicate and continue stirring for 3-4 h. Centrifuge, take the solid phase, wash and dry it to obtain mesoporous silica composite particles; the ratio of lignin-zinc oxide nanopowder, anhydrous ethanol and tetraethyl orthosilicate is 0.3-0.4 g: 50-80 mL: 0.35-0.45 mL;

[0017] S5. Take the mesoporous silica composite particles, deionized water, and anhydrous ethanol, mix them, and ultrasonically disperse them for 10-30 min. Adjust the pH to 4-5 with 0.1 mol / L hydrochloric acid solution, add γ-mercaptopropyltrimethoxysilane, stir at 80℃ for 4-8 h, filter, wash the solid phase, and dry in a vacuum drying oven at 100℃ for 8-12 h to obtain the mercapto-modified mesoporous silica composite particles. The ratio of the mesoporous silica, deionized water, anhydrous ethanol, and γ-mercaptopropyltrimethoxysilane solution is 0.3-0.5 g: 50 mL: 70-80 mL: 1-2 mL.

[0018] S6. Mix cashew phenol (M-[(Z)-8-pentadecanenyl]phenol), mercapto-modified mesoporous silica composite particles, photoinitiator, and ethyl acetate. Stir ultrasonically for 20-30 minutes. Place the mixture at 80℃ with a 375nm UV LED light source and a light intensity of 5-15nW / cm². 2 The reaction was carried out under the following conditions for 8-12 hours, followed by centrifugation, washing and drying of the solid phase to obtain a cashew phenol-grafted mesoporous silica composite. The mass ratio of cashew phenol, mercaptoized mesoporous silica composite particles, photoinitiator and ethyl acetate was 3-5:7-9:0.1-0.2:80-100.

[0019] As a preferred embodiment of the present invention, in step A2, the active monomer is selected from at least one of isobornyl acrylate, tricyclodecanediethanol diacrylate, trimethylolpropane triacrylate, and neopentyl glycol diacrylate.

[0020] As a preferred embodiment of the present invention, in step A2, the photoinitiator is at least one of photoinitiator 184 and photoinitiator 819.

[0021] In a preferred embodiment of the present invention, in step A2, the antioxidant is antioxidant 1010.

[0022] As a preferred embodiment of the present invention, in step A2, the leveling agent is BYK-333.

[0023] In a preferred embodiment of the present invention, in step A2, the defoamer is BYK-022.

[0024] A weather-resistant and corrosion-resistant leather prepared using the above-described method.

[0025] The beneficial effects of this invention are:

[0026] This invention protects leather from ultraviolet rays and corrosive substances by coating the leather surface with a polyurethane coating agent with good weather and corrosion resistance, thereby improving the weather and corrosion resistance of leather products.

[0027] Specifically, the synergistic effect of lignin-zinc oxide nanopowder, through the dual superposition of chemical corrosion inhibition and physical shielding, not only inhibits the direct reaction between the substrate and the corrosive medium but also slows down the penetration rate of the corrosive medium, ultimately achieving a more durable and comprehensive corrosion protection effect than a single component. The porous structure of mesoporous nano-silica refracts some ultraviolet light, improving weather resistance. The mercapto groups of mercapto-modified mesoporous silica undergo a mercapto-olefin click reaction with the carbon-carbon double bonds of cashew nut shells, resulting in uniform dispersion of the mesoporous silica composite particles within the polyurethane matrix. This significantly extends the penetration path of the corrosive medium, making it difficult to reach the leather substrate and improving the leather's corrosion resistance. Furthermore, the phenolic hydroxyl groups of cashew nut shells undergo an addition reaction with the isocyanate groups of diisocyanate to form urethane bonds, which are chemically inert and not easily damaged by acids, alkalis, organic solvents, or ultraviolet light. This significantly improves the crosslinking density and chemical stability of the polyurethane matrix, preventing matrix degradation that could lead to coating cracking and powdering.

[0028] The above-mentioned multi-dimensional synergistic approach improves the weather resistance and corrosion resistance of leather. Detailed Implementation

[0029] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with embodiments, is provided below.

[0030] Example 1

[0031] A method for preparing weather-resistant and corrosion-resistant leather includes the following steps:

[0032] Wipe the surface of the sheepskin clean, then apply a polyurethane finishing agent evenly to the surface of the leather product at a coating amount of 5g / m². 2 The UV curing machine uses a 300W ultraviolet lamp as its light source, with a curing time of 5 seconds and a curing energy of 1200 mJ / cm². 2 The weather-resistant and corrosion-resistant leather is then obtained.

[0033] The preparation method of the polyurethane coating agent includes the following steps:

[0034] S1. Purification of enzymatically hydrolyzed lignin: Mix enzymatically hydrolyzed lignin and deionized water, sonicate for 10 min, filter, dry the solid phase, mix the dried enzymatically hydrolyzed lignin with tetrahydrofuran at a mass ratio of 1:30, stir for 30 min, centrifuge, and remove the tetrahydrofuran by rotary evaporation of the supernatant to obtain pure enzymatically hydrolyzed lignin.

[0035] S2. Dissolve the purified enzymatically hydrolyzed lignin in tetrahydrofuran, add deionized water while stirring to replace the solvent, then heat and stir continuously at 55°C for 8 hours, and dry at a vacuum of 10 Pa and a temperature of -40°C for 20 hours to obtain lignin nanoparticles; the ratio of the enzymatically hydrolyzed lignin, tetrahydrofuran, and deionized water is 4 mg: 4 mL: 15 mL.

[0036] S3. Mix zinc nitrate hexahydrate, hexamethylenetetramine, and deionized water evenly, add the lignin nanoparticles, ultrasonically stir for 10 min, pack into a 100 mL hydrothermal crystallization vessel, and hydrothermally heat in an oven at 120℃ for 4 h, then dry at a vacuum of 10 Pa and a temperature of -50℃ for 25 h to obtain lignin-zinc oxide nanoparticles; the mass ratio of zinc nitrate hexahydrate, hexamethylenetetramine, deionized water, and lignin nanoparticles is 0.1:0.02:20:0.06;

[0037] S4. Take the lignin-zinc oxide nanopowder and anhydrous ethanol, mix them, and ultrasonically disperse them for 20 min. Adjust the pH to 8 with 0.1 mol / L ammonia water, add tetraethyl orthosilicate and continue stirring for 3 h. Centrifuge, take the solid phase, wash and dry it to obtain mesoporous silica composite particles; the ratio of lignin-zinc oxide nanopowder, anhydrous ethanol and tetraethyl orthosilicate is 0.3 g: 50 mL: 0.35 mL.

[0038] S5. Take the mesoporous silica composite particles, deionized water, and anhydrous ethanol, mix them, and ultrasonically disperse them for 10 min. Adjust the pH to 4 with 0.1 mol / L hydrochloric acid solution, add γ-mercaptopropyltrimethoxysilane, stir at 80℃ for 4 h, filter, take the solid phase for washing, and dry in a vacuum drying oven at 100℃ for 8 h to obtain mercapto-modified mesoporous silica composite particles; the ratio of the mesoporous silica, deionized water, anhydrous ethanol, and γ-mercaptopropyltrimethoxysilane solution is 0.3 g: 50 mL: 70 mL: 1 mL;

[0039] S6. Mix cashew phenol, mercapto-modified mesoporous silica composite particles, photoinitiator 184, and ethyl acetate. Stir ultrasonically for 20 minutes. Place the mixture at 80℃ with a 375nm UV LED light source and a light intensity of 5nW / cm². 2The reaction was carried out under the following conditions for 12 hours, followed by centrifugation, washing and drying of the solid phase to obtain a cashew phenol-grafted mesoporous silica composite; the mass ratio of cashew phenol, mercaptoized mesoporous silica composite particles, photoinitiator 184 and ethyl acetate was 3:7:0.1:80.

[0040] S7. Mix isophorone diisocyanate, dibutyltin dilaurate, cashew phenol-grafted mesoporous silica complex, and n-hexane. Heat the mixture to 55°C under a nitrogen atmosphere, reflux and stir for 3 hours. Add hydroxyethyl methacrylate, cool to 50°C, and continue stirring for 4 hours. Remove n-hexane by rotary evaporation to obtain a polyurethane prepolymer. The ratio of isophorone diisocyanate, dibutyltin dilaurate, cashew phenol-grafted mesoporous silica complex, n-hexane, and hydroxyethyl methacrylate is 10g:0.028g:18g:40mL:10g.

[0041] S8. Take the polyurethane prepolymer, trimethylolpropane triacrylate, photoinitiator 184, antioxidant 1010, leveling agent BYK-333, and defoamer BYK-022, mix them, and stir evenly to obtain the polyurethane coating agent; the mass ratio of the polyurethane prepolymer, trimethylolpropane triacrylate, photoinitiator 184, antioxidant 1010, leveling agent BYK-333, and defoamer BYK-022 is 40:18:2:0.4:0.25:0.15.

[0042] Example 2

[0043] A method for preparing weather-resistant and corrosion-resistant leather includes the following steps:

[0044] Wipe the surface of the sheepskin clean, then apply a polyurethane finishing agent evenly to the surface of the leather product at a coating amount of 10g / m². 2 The UV curing machine uses a 300W ultraviolet lamp as its light source, with a curing time of 9 seconds and a curing energy of 1200 mJ / cm². 2 The weather-resistant and corrosion-resistant leather is then obtained.

[0045] The preparation method of the polyurethane coating agent includes the following steps:

[0046] S1. Purification of enzymatically hydrolyzed lignin: Mix enzymatically hydrolyzed lignin and deionized water, sonicate for 15 min, filter, dry the solid phase, mix the dried enzymatically hydrolyzed lignin with tetrahydrofuran at a mass ratio of 1:30, stir for 35 min, centrifuge, and remove the tetrahydrofuran by rotary evaporation of the supernatant to obtain pure enzymatically hydrolyzed lignin.

[0047] S2. Dissolve the purified enzymatically hydrolyzed lignin in tetrahydrofuran, add deionized water while stirring to replace the solvent, then heat and stir continuously at 58°C for 9 hours, and dry at a vacuum of 15 Pa and a temperature of -30°C for 30 hours to obtain lignin nanoparticles; the ratio of the enzymatically hydrolyzed lignin, tetrahydrofuran, and deionized water is 5 mg: 4.5 mL: 15 mL.

[0048] S3. Mix zinc nitrate hexahydrate, hexamethylenetetramine, and deionized water evenly, add the lignin nanoparticles, ultrasonically stir for 15 min, pack into a 100 mL hydrothermal crystallization vessel, and hydrothermally heat in an oven at 120℃ for 6 h, then dry at a vacuum of 15 Pa and a temperature of -50℃ for 30 h to obtain lignin-zinc oxide nanoparticles; the mass ratio of zinc nitrate hexahydrate, hexamethylenetetramine, deionized water, and lignin nanoparticles is 0.2:0.035:25:0.07;

[0049] S4. Take the lignin-zinc oxide nanopowder and anhydrous ethanol, mix them, and ultrasonically disperse them for 25 min. Adjust the pH to 9 with 0.1 mol / L ammonia water, add tetraethyl orthosilicate and continue stirring for 3.5 h. Centrifuge, take the solid phase, wash and dry it to obtain mesoporous silica composite particles; the ratio of lignin-zinc oxide nanopowder, anhydrous ethanol and tetraethyl orthosilicate is 0.35 g: 65 mL: 0.40 mL.

[0050] S5. Take the mesoporous silica composite particles, deionized water, and anhydrous ethanol, mix them, and ultrasonically disperse them for 20 min. Adjust the pH to 5 with 0.1 mol / L hydrochloric acid solution, add γ-mercaptopropyltrimethoxysilane, stir at 80℃ for 6 h, filter, take the solid phase for washing, and dry in a vacuum drying oven at 100℃ for 10 h to obtain mercapto-modified mesoporous silica composite particles; the ratio of the mesoporous silica, deionized water, anhydrous ethanol, and γ-mercaptopropyltrimethoxysilane solution is 0.4 g: 50 mL: 75 mL: 1.5 mL;

[0051] S6. Mix cashew phenol, mercapto-modified mesoporous silica composite particles, photoinitiator 184, and ethyl acetate. Sonicate the mixture for 25 minutes. Place the mixture at 80℃ with a 375nm UV LED light source and a light intensity of 10nW / cm². 2 The reaction was carried out under the following conditions for 10 hours, followed by centrifugation, washing and drying of the solid phase to obtain a cashew phenol-grafted mesoporous silica composite; the mass ratio of cashew phenol, mercapto-modified mesoporous silica composite particles, photoinitiator 184 and ethyl acetate was 4:8:0.15:90.

[0052] S7. Mix isophorone diisocyanate, dibutyltin dilaurate, cashew phenol-grafted mesoporous silica complex, and n-hexane. Heat the mixture to 60°C under a nitrogen atmosphere, reflux and stir for 3.5 h. Add hydroxyethyl methacrylate, cool to 50°C, and continue stirring for 5 h. Remove n-hexane by rotary evaporation to obtain a polyurethane prepolymer. The ratio of isophorone diisocyanate, dibutyltin dilaurate, cashew phenol-grafted mesoporous silica complex, n-hexane, and hydroxyethyl methacrylate is 11 g: 0.032 g: 19 g: 45 mL: 11 g.

[0053] S8. Take the polyurethane prepolymer, neopentyl glycol diacrylate, photoinitiator 184, antioxidant 1010, leveling agent BYK-333, and defoamer BYK-022, mix them, and stir evenly to obtain the polyurethane coating agent; the mass ratio of the polyurethane prepolymer, neopentyl glycol diacrylate, photoinitiator 184, antioxidant 1010, leveling agent BYK-333, and defoamer BYK-022 is 50:21:3:0.6:0.45:0.25.

[0054] Example 3

[0055] A method for preparing weather-resistant and corrosion-resistant leather includes the following steps:

[0056] Wipe the surface of the sheepskin leather clean, then apply a polyurethane finishing agent evenly to the surface of the leather product at a coating amount of 15g / m². 2 The UV curing machine uses a 300W ultraviolet lamp as its light source, with a curing time of 12 seconds and a curing energy of 1200 mJ / cm². 2 The weather-resistant and corrosion-resistant leather is then obtained.

[0057] The preparation method of the polyurethane coating agent includes the following steps:

[0058] S1. Purification of enzymatically hydrolyzed lignin: Mix enzymatically hydrolyzed lignin and deionized water, sonicate for 20 min, filter, dry the solid phase, mix the dried enzymatically hydrolyzed lignin with tetrahydrofuran at a mass ratio of 1:30, stir for 40 min, centrifuge, and remove the tetrahydrofuran by rotary evaporation of the supernatant to obtain pure enzymatically hydrolyzed lignin.

[0059] S2. Dissolve the purified enzymatically hydrolyzed lignin in tetrahydrofuran, add deionized water while stirring to replace the solvent, then heat and stir continuously at 60°C for 10 hours, and dry at a vacuum of 20 Pa and a temperature of -20°C for 40 hours to obtain lignin nanoparticles; the ratio of the enzymatically hydrolyzed lignin, tetrahydrofuran, and deionized water is 6 mg: 5 mL: 15 mL.

[0060] S3. Mix zinc nitrate hexahydrate, hexamethylenetetramine, and deionized water evenly, add the lignin nanoparticles, ultrasonically stir for 20 min, pack into a 100 mL hydrothermal crystallization vessel, and hydrothermally heat in an oven at 120℃ for 8 h, then dry at a vacuum of 20 Pa and a temperature of -50℃ for 35 h to obtain lignin-zinc oxide nanoparticles; the mass ratio of zinc nitrate hexahydrate, hexamethylenetetramine, deionized water, and lignin nanoparticles is 0.3:0.05:30:0.08;

[0061] S4. Take the lignin-zinc oxide nanopowder and anhydrous ethanol, mix them, and ultrasonically disperse them for 30 min. Adjust the pH to 9 with 0.1 mol / L ammonia water, add tetraethyl orthosilicate and continue stirring for 4 h. Centrifuge, take the solid phase, wash and dry it to obtain mesoporous silica composite particles; the ratio of the lignin-zinc oxide nanopowder, anhydrous ethanol and tetraethyl orthosilicate is 0.4 g: 80 mL: 0.45 mL.

[0062] S5. Take the mesoporous silica composite particles, deionized water, and anhydrous ethanol, mix them, and ultrasonically disperse them for 30 min. Adjust the pH to 5 with 0.1 mol / L hydrochloric acid solution, add γ-mercaptopropyltrimethoxysilane, stir at 80℃ for 8 h, filter, take the solid phase for washing, and dry in a vacuum drying oven at 100℃ for 12 h to obtain mercapto-modified mesoporous silica composite particles; the ratio of the mesoporous silica, deionized water, anhydrous ethanol, and γ-mercaptopropyltrimethoxysilane solution is 0.5 g: 50 mL: 80 mL: 2 mL;

[0063] S6. Mix cashew phenol, mercapto-modified mesoporous silica composite particles, photoinitiator 184, and ethyl acetate. Sonicate the mixture for 30 minutes. Place the mixture at 80℃ with a 375nm UV LED light source and a light intensity of 15nW / cm². 2 The reaction was carried out under the following conditions for 8 hours, followed by centrifugation, washing and drying of the solid phase to obtain a cashew phenol-grafted mesoporous silica composite; the mass ratio of cashew phenol, mercapto-modified mesoporous silica composite particles, photoinitiator 184 and ethyl acetate was 5:9:0.2:100.

[0064] S7. Mix isophorone diisocyanate, dibutyltin dilaurate, cashew phenol-grafted mesoporous silica complex, and n-hexane. Heat the mixture to 65°C under a nitrogen atmosphere, reflux and stir for 4 hours. Add hydroxyethyl methacrylate, cool to 50°C, and continue stirring for 6 hours. Remove n-hexane by rotary evaporation to obtain a polyurethane prepolymer. The ratio of isophorone diisocyanate, dibutyltin dilaurate, cashew phenol-grafted mesoporous silica complex, n-hexane, and hydroxyethyl methacrylate is 12g:0.036g:20g:50mL:12g.

[0065] S8. Take the polyurethane prepolymer, isobornyl acrylate, photoinitiator 184, antioxidant 1010, leveling agent BYK-333, and defoamer BYK-022, mix them, and stir evenly to obtain the polyurethane coating agent; the mass ratio of the polyurethane prepolymer, isobornyl acrylate, photoinitiator 184, antioxidant 1010, leveling agent BYK-333, and defoamer BYK-022 is 60:24:4:0.8:0.65:0.35.

[0066] Comparative Example 1

[0067] The difference from Example 2 is that the preparation method of this polyurethane coating agent specifically includes the following steps:

[0068] S1. Mix zinc nitrate hexahydrate, hexamethylenetetramine, and deionized water evenly, ultrasonically stir for 15 min, and put into a 100 mL hydrothermal crystallization vessel. Dry in a 120℃ oven for 6 h, and dry at a vacuum of 15 Pa and a temperature of -50℃ for 30 h to obtain zinc oxide nanopowder; the mass ratio of zinc nitrate hexahydrate, hexamethylenetetramine, and deionized water is 0.2:0.035:25.

[0069] S2. Take the zinc oxide nanopowder and anhydrous ethanol, mix them, and ultrasonically disperse them for 25 min. Adjust the pH to 9 with 0.1 mol / L ammonia water, add tetraethyl orthosilicate and continue stirring for 3.5 h. Centrifuge, take the solid phase, wash and dry it to obtain mesoporous silica composite particles; the ratio of zinc oxide nanopowder, anhydrous ethanol and tetraethyl orthosilicate is 0.35 g: 65 mL: 0.40 mL.

[0070] S3. Take the mesoporous silica composite particles, deionized water, and anhydrous ethanol, mix them, and ultrasonically disperse them for 20 min. Adjust the pH to 5 with 0.1 mol / L hydrochloric acid solution, add γ-mercaptopropyltrimethoxysilane, stir at 80℃ for 6 h, filter, wash the solid phase, and dry in a vacuum drying oven at 100℃ for 10 h to obtain mercapto-modified mesoporous silica composite particles; the ratio of the mesoporous silica, deionized water, anhydrous ethanol, and γ-mercaptopropyltrimethoxysilane solution is 0.4 g: 50 mL: 75 mL: 1.5 mL;

[0071] S4. Mix cashew phenol, mercapto-modified mesoporous silica composite particles, photoinitiator 184, and ethyl acetate. Sonicate the mixture for 25 minutes. Place the mixture at 80℃ with a 375nm UV LED light source and a light intensity of 10nW / cm². 2 The reaction was carried out under the following conditions for 10 hours, followed by centrifugation, washing and drying of the solid phase to obtain a cashew phenol-grafted mesoporous silica composite; the mass ratio of cashew phenol, mercapto-modified mesoporous silica composite particles, photoinitiator 184 and ethyl acetate was 4:8:0.15:90.

[0072] S5. Mix isophorone diisocyanate, dibutyltin dilaurate, cashew phenol-grafted mesoporous silica complex, and n-hexane. Heat the mixture to 60°C under a nitrogen atmosphere, reflux and stir for 3.5 h. Add hydroxyethyl methacrylate, cool to 50°C, and continue stirring for 5 h. Remove n-hexane by rotary evaporation to obtain a polyurethane prepolymer. The ratio of isophorone diisocyanate, dibutyltin dilaurate, cashew phenol-grafted mesoporous silica complex, n-hexane, and hydroxyethyl methacrylate is 11 g: 0.032 g: 19 g: 45 mL: 11 g.

[0073] S6. Take the polyurethane prepolymer, neopentyl glycol diacrylate, photoinitiator 184, antioxidant 1010, leveling agent BYK-333, and defoamer BYK-022, mix them, and stir evenly to obtain the polyurethane coating agent; the mass ratio of the polyurethane prepolymer, neopentyl glycol diacrylate, photoinitiator 184, antioxidant 1010, leveling agent BYK-333, and defoamer BYK-022 is 50:21:3:0.6:0.45:0.25.

[0074] Comparative Example 2

[0075] The difference from Example 2 is that the preparation method of this polyurethane coating agent includes the following steps:

[0076] S1. Purification of enzymatically hydrolyzed lignin: Mix enzymatically hydrolyzed lignin and deionized water, sonicate for 15 min, filter, dry the solid phase, mix the dried enzymatically hydrolyzed lignin with tetrahydrofuran at a mass ratio of 1:30, stir for 35 min, centrifuge, and remove the tetrahydrofuran by rotary evaporation of the supernatant to obtain pure enzymatically hydrolyzed lignin.

[0077] S2. Dissolve the purified enzymatically hydrolyzed lignin in tetrahydrofuran, add deionized water while stirring to replace the solvent, then heat and stir continuously at 58°C for 9 hours, and dry at a vacuum of 15 Pa and a temperature of -30°C for 30 hours to obtain lignin nanoparticles; the ratio of the enzymatically hydrolyzed lignin, tetrahydrofuran, and deionized water is 5 mg: 4.5 mL: 15 mL.

[0078] S3. Take the lignin nanoparticles and anhydrous ethanol, mix them, and ultrasonically disperse them for 25 min. Adjust the pH to 9 with 0.1 mol / L ammonia water, add tetraethyl orthosilicate and continue stirring for 3.5 h. Centrifuge, take the solid phase, wash and dry it to obtain mesoporous silica composite particles; the ratio of lignin nanoparticles, anhydrous ethanol and tetraethyl orthosilicate is 0.35 g: 65 mL: 0.40 mL.

[0079] S4. Take the mesoporous silica composite particles, deionized water, and anhydrous ethanol, mix them, and ultrasonically disperse them for 20 min. Adjust the pH to 5 with 0.1 mol / L hydrochloric acid solution, add γ-mercaptopropyltrimethoxysilane, stir at 80℃ for 6 h, filter, wash the solid phase, and dry in a vacuum drying oven at 100℃ for 10 h to obtain mercapto-modified mesoporous silica composite particles; the ratio of the mesoporous silica, deionized water, anhydrous ethanol, and γ-mercaptopropyltrimethoxysilane solution is 0.4 g: 50 mL: 75 mL: 1.5 mL;

[0080] S5. Take cashew phenol, mercapto-modified mesoporous silica composite particles, photoinitiator 184 and ethyl acetate, mix them, ultrasonically stir for 25 min, and place them in an 80℃, 375nm ultraviolet LED light source with a light intensity of 10nW / cm². 2 The reaction was carried out under the following conditions for 10 hours, followed by centrifugation, washing and drying of the solid phase to obtain a cashew phenol-grafted mesoporous silica composite; the mass ratio of cashew phenol, mercapto-modified mesoporous silica composite particles, photoinitiator 184 and ethyl acetate was 4:8:0.15:90.

[0081] S6. Mix isophorone diisocyanate, dibutyltin dilaurate, cashew phenol-grafted mesoporous silica complex, and n-hexane. Heat the mixture to 60°C under a nitrogen atmosphere, reflux and stir for 3.5 h. Add hydroxyethyl methacrylate, cool to 50°C, and continue stirring for 5 h. Remove n-hexane by rotary evaporation to obtain a polyurethane prepolymer. The ratio of isophorone diisocyanate, dibutyltin dilaurate, cashew phenol-grafted mesoporous silica complex, n-hexane, and hydroxyethyl methacrylate is 11 g: 0.032 g: 19 g: 45 mL: 11 g.

[0082] S7. Take the polyurethane prepolymer, neopentyl glycol diacrylate, photoinitiator 184, antioxidant 1010, leveling agent BYK-333, and defoamer BYK-022, mix them, and stir evenly to obtain the polyurethane coating agent; the mass ratio of the polyurethane prepolymer, neopentyl glycol diacrylate, photoinitiator 184, antioxidant 1010, leveling agent BYK-333, and defoamer BYK-022 is 50:21:3:0.6:0.45:0.25.

[0083] Comparative Example 3

[0084] The difference from Example 2 is that the preparation method of this polyurethane coating agent includes the following steps:

[0085] S1. Purification of enzymatically hydrolyzed lignin: Mix enzymatically hydrolyzed lignin and deionized water, sonicate for 15 min, filter, dry the solid phase, mix the dried enzymatically hydrolyzed lignin with tetrahydrofuran at a mass ratio of 1:30, stir for 35 min, centrifuge, and remove the tetrahydrofuran by rotary evaporation of the supernatant to obtain pure enzymatically hydrolyzed lignin.

[0086] S2. Dissolve the purified enzymatically hydrolyzed lignin in tetrahydrofuran, add deionized water while stirring to replace the solvent, then heat and stir continuously at 58°C for 9 hours, and dry at a vacuum of 15 Pa and a temperature of -30°C for 30 hours to obtain lignin nanoparticles; the ratio of the enzymatically hydrolyzed lignin, tetrahydrofuran, and deionized water is 5 mg: 4.5 mL: 15 mL.

[0087] S3. Mix zinc nitrate hexahydrate, hexamethylenetetramine, and deionized water evenly, add the lignin nanoparticles, ultrasonically stir for 15 min, pack into a 100 mL hydrothermal crystallization vessel, and hydrothermally heat in an oven at 120℃ for 6 h, then dry at a vacuum of 15 Pa and a temperature of -50℃ for 30 h to obtain lignin-zinc oxide nanoparticles; the mass ratio of zinc nitrate hexahydrate, hexamethylenetetramine, deionized water, and lignin nanoparticles is 0.2:0.035:25:0.07;

[0088] S4. Take the lignin-zinc oxide nanopowder and anhydrous ethanol, mix them, and ultrasonically disperse them for 25 min. Adjust the pH to 9 with 0.1 mol / L ammonia water, add tetraethyl orthosilicate and continue stirring for 3.5 h. Centrifuge, take the solid phase, wash and dry it to obtain mesoporous silica composite particles; the ratio of lignin-zinc oxide nanopowder, anhydrous ethanol and tetraethyl orthosilicate is 0.35 g: 65 mL: 0.40 mL.

[0089] S5. Mix isophorone diisocyanate, dibutyltin dilaurate, cashew phenol, and n-hexane. Heat the mixture to 60°C under a nitrogen atmosphere, reflux and stir for 3.5 hours. Add hydroxyethyl methacrylate, cool to 50°C, and continue stirring for 5 hours. Remove n-hexane by rotary evaporation to obtain a polyurethane prepolymer. The ratio of isophorone diisocyanate, dibutyltin dilaurate, cashew phenol, n-hexane, and hydroxyethyl methacrylate is 11g:0.032g:19g:45mL:11g.

[0090] S6. Take the polyurethane prepolymer, neopentyl glycol diacrylate, photoinitiator 184, antioxidant 1010, leveling agent BYK-333, defoamer BYK-022, and mesoporous silica composite particles, mix them, and stir evenly to obtain the polyurethane coating agent; the mass ratio of the polyurethane prepolymer, neopentyl glycol diacrylate, photoinitiator 184, antioxidant 1010, leveling agent BYK-333, defoamer BYK-022, and mesoporous silica composite particles is 50:21:3:0.6:0.45:0.25:5.

[0091] Comparative Example 4

[0092] The difference from Example 2 is that the preparation method of this polyurethane coating agent includes the following steps:

[0093] S1. Mix isophorone diisocyanate, dibutyltin dilaurate, and n-hexane, heat to 50°C in a nitrogen atmosphere, add hydroxyethyl methacrylate, stir for 5 hours, and then remove n-hexane by rotary evaporation to obtain a polyurethane prepolymer; the ratio of isophorone diisocyanate, dibutyltin dilaurate, n-hexane, and hydroxyethyl methacrylate is 11g:0.032g:45mL:30g;

[0094] S2. Take the polyurethane prepolymer, neopentyl glycol diacrylate, photoinitiator 184, antioxidant 1010, leveling agent BYK-333, and defoamer BYK-022, mix them, and stir evenly to obtain the polyurethane coating agent; the mass ratio of the polyurethane prepolymer, neopentyl glycol diacrylate, photoinitiator 184, antioxidant 1010, leveling agent BYK-333, and defoamer BYK-022 is 50:21:3:0.6:0.45:0.25.

[0095] Performance testing

[0096] I. Weather Resistance Test: The leather samples obtained from Examples 1-3 and Comparative Examples 1-4 were subjected to the following performance tests:

[0097] 1. QUV accelerated aging test: 340nm lamp, irradiance 0.71W / m 2 UV exposure at 60℃ for 4 hours (UV stage); condensation at 50℃ and 95% humidity for 4 hours (condensation stage); cycle count: 1000 hours (simulating natural aging for 2-3 years), testing color difference ΔE, yellowing index YI, and tensile strength retention rate.

[0098] 2. Ultraviolet shielding rate test

[0099] UV shielding efficiency (T%): Calculate the blocking efficiency of the coating for 280-320nm (UVB) and 320-400nm (UVA).

[0100] The test results are shown in Table 1 below.

[0101] Table 1

[0102] Color difference ΔE Yellowing Index YI UVB (280-320nm) shielding rate / % UVA (320-400nm) shielding rate / % Tensile strength retention rate / % Example 1 0.79 0.97 97.36 94.36 96.35 Example 2 0.73 0.94 97.84 94.57 96.87 Example 3 0.75 0.95 97.62 94.48 96.53 Comparative Example 1 1.23 1.87 91.35 88.79 91.07 Comparative Example 2 1.14 1.82 91.48 89.06 91.48 Comparative Example 3 1.08 1.54 93.52 91.14 92.66 Comparative Example 4 2.78 3.12 84.36 80.41 85.21

[0103] The test results above show that the leathers prepared in Examples 1-3 of this scheme have better weather resistance than the comparative examples.

[0104] II. Corrosion Resistance Test

[0105] 1. The leather samples prepared in Examples 1-3 and Comparative Examples 1-4 were immersed in a 5% NaCl aqueous solution, and the time of first surface blistering was recorded.

[0106] 2. The leather samples prepared in Examples 1-3 and Comparative Examples 1-4 were immersed in a 5% sodium hypochlorite solution for 72 hours, and the damage to the leather surface was observed and the coating damage rate was calculated.

[0107] The test results are shown in Table 2 below.

[0108] Table 2

[0109] Destruction time / h Coating damage rate / % Example 1 144 1.32 Example 2 152 1.18 Example 3 148 1.26 Comparative Example 1 132 2.14 Comparative Example 2 135 2.08 Comparative Example 3 71 5.36 Comparative Example 4 48 10.28

[0110] The test results above show that the leathers prepared in Examples 1-3 of this scheme have better corrosion resistance than the comparative examples.

[0111] This solution utilizes the conjugated aromatic ring structure of lignin to efficiently absorb ultraviolet light; nano-zinc oxide has both physical shielding and chemical absorption functions, forming a dual anti-ultraviolet effect with lignin, which can effectively scavenge free radicals induced by ultraviolet light, greatly reducing the photodegradation process and indirectly improving the UV resistance of polyurethane; the mesoporous structure of nano-silica has a refractive index difference with the polyurethane matrix, which can refract some ultraviolet light, while the coating structure prevents lignin and zinc oxide from agglomerating, ensuring uniform distribution of anti-ultraviolet components and extending weather resistance; the long-chain alkyl and aromatic ring structure of cashew phenol can enhance the flexibility and crack resistance of the polyurethane coating, preventing the coating from becoming embrittled after ultraviolet aging; the aromatic ring structure itself can also help absorb ultraviolet light, further improving the anti-aging ability; after the polyurethane is cured by light, the crosslinking density increases, reducing the porosity of the coating, reducing the damage of ultraviolet light to the internal structure, and delaying the yellowing and chalking of the coating.

[0112] Mesoporous silica composite particles can be uniformly dispersed in polyurethane coatings, significantly extending the penetration path of corrosive media and making it difficult for them to reach the leather substrate. The high specific surface area of ​​the mesoporous structure can also adsorb some of the corrosive media, reducing their activity. The polyurethane prepolymer is fully cross-linked with modified cashew phenol and active monomers to form a low-porosity coating, optimizing film formation and avoiding defects such as pinholes and cracks in the coating, thus reducing the penetration channels of corrosive media. In addition, the synergistic effect of lignin and zinc oxide inhibits the chemical reaction between the substrate and the corrosive media, further blocking corrosion.

[0113] The thiol groups of mesoporous silica undergo a thiol-olefin click reaction with the carbon-carbon double bonds of cashew nut shells to form stable CSC covalent bonds, which anchor the mesoporous silica to the cashew nut shell molecular chain. This prevents the silica from falling off due to immersion in corrosive media or friction, thus ensuring the long-lasting weather and corrosion resistance.

[0114] The phenolic hydroxyl groups of cashew phenol undergo an addition reaction with the isocyanate groups of diisocyanate to form urethane bonds. This is chemically inert and not easily damaged by acids, alkalis, organic solvents, ultraviolet rays, etc. It can significantly improve the crosslinking density and chemical stability of the polyurethane matrix, and avoid the coating cracking and powdering caused by matrix degradation.

[0115] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for preparing weather-resistant and corrosion-resistant leather, characterized in that, Includes the following steps: The weather-resistant and corrosion-resistant leather is obtained by uniformly applying a polyurethane coating agent to the surface of the leather product and then curing it with light. The preparation method of the polyurethane coating agent includes the following steps: A1. Mix diisocyanate, catalyst, cashew phenol grafted mesoporous silica complex and n-hexane, heat to 55-65℃ in a nitrogen atmosphere, reflux and stir for 3-4 hours, add end-capping monomer, cool to 50℃, continue stirring for 4-6 hours, and then remove n-hexane by rotary evaporation to obtain polyurethane prepolymer. A2. Take the polyurethane prepolymer, active monomer, photoinitiator, antioxidant, leveling agent and defoamer, mix them, and stir evenly to obtain the polyurethane coating agent; The mesoporous silica composite is mesoporous silica-coated lignin-zinc oxide nanopowder.

2. The method for preparing weather-resistant and corrosion-resistant leather according to claim 1, characterized in that, In step A1, the ratio of diisocyanate, catalyst, cashew phenol grafted mesoporous silica complex, n-hexane, and end-capping monomer is 10-12g: 0.028-0.036g: 18-20g: 40-50mL: 10-12g.

3. The method for preparing weather-resistant and corrosion-resistant leather according to claim 1, characterized in that, In step A2, the mass ratio of the polyurethane prepolymer, active monomer, photoinitiator, antioxidant, leveling agent, and defoamer is 40-60:18-24:2-4:0.4-0.8:0.25-0.65:0.15-0.

35.

4. The method for preparing weather-resistant and corrosion-resistant leather according to claim 1, characterized in that, In step A2, the active monomer is selected from at least one of isobornyl acrylate, tricyclodecanediethanol diacrylate, trimethylolpropane triacrylate, and neopentyl glycol diacrylate.

5. The method for preparing weather-resistant and corrosion-resistant leather according to claim 1, characterized in that, In step A2, the photoinitiator is at least one of photoinitiator 184 and photoinitiator 819.

6. The method for preparing weather-resistant and corrosion-resistant leather according to claim 1, characterized in that, In step A2, the antioxidant is antioxidant 1010.

7. The method for preparing weather-resistant and corrosion-resistant leather according to claim 1, characterized in that, In step A2, the leveling agent is BYK-333.

8. The method for preparing weather-resistant and corrosion-resistant leather according to claim 1, characterized in that, In step A2, the defoamer is BYK-022.

9. A weather-resistant and corrosion-resistant leather prepared by the preparation method according to any one of claims 1-8.