Nano-hydrotalcite aramid fiber / crosslinked copolymer composite leather finishing agent and preparation method thereof

Abstract

The application discloses a nanometer hydrotalcite aramid fiber / crosslinked copolymer composite leather finishing agent and a preparation method thereof, and belongs to the technical field of nanometer composites. N-hydroxymethyl acrylamide is used as a crosslinking agent to increase the crosslinking density of the polymer, thereby improving the strength of the matrix. Meanwhile, the hydroxyl and amide groups contained in the N-hydroxymethyl acrylamide can further be combined with nanometer hydrotalcite and aramid fibers through hydrogen bonds, thereby significantly reducing the stress concentration phenomenon. Sodium styrene sulfonate is used as an emulsifier and can participate in monomer copolymerization, thereby greatly reducing the influence of the use of traditional emulsifiers on the performance of the product. The introduction of rigid benzene rings also improves the mechanical properties of the polymer matrix. Compared with traditional polymer leather finishing agents, the prepared nanometer composite leather finishing agent has better film forming property, wear resistance and mechanical strength, and also has good hydrophobicity, thermal stability, weather resistance and heat preservation property. The introduction of hydrotalcite nanosheets also endows the finished leather with certain flame retardancy.

Description

Technical Field

[0001] This invention belongs to the field of nanocomposite materials, specifically relating to a nano-hydrotalcite@aramid fiber / crosslinked copolymer composite leather coating agent and its preparation method. Background Technology

[0002] Leather finishing is a branch of the coating industry, referring to coatings applied to the surface of leather products. Its main purpose is to enhance the appearance of the leather, improve the performance and durability of leather products. After a series of processing steps and tanning stages, raw hides must pass through the finishing stage to truly become the leather products needed by the market. The different styles of leather products are also mainly achieved through the finishing process, with leather finishing agents playing a crucial role. Currently, traditional polymer leather finishing materials used in industry mainly suffer from poor mechanical properties and abrasion resistance, failing to meet the functional and quality demands of high-end leather and its products. However, the use of nanomaterials and nanotechnology can significantly improve the poor weather resistance, low mechanical strength, and lack of abrasion resistance of traditional polymer finishing materials. In this work, a multi-crosslinked copolymer coating emulsion was first prepared using a soap-free emulsion crosslinking polymerization method. The selected sodium p-styrene sulfonate monomer not only participates in polymerization as a functional monomer, but also plays an emulsifying role, which greatly reduces the adverse effects of general emulsifiers on the emulsion product. The synergistic coating effect of hydrotalcite two-dimensional nanosheets and one-dimensional aramid nanofibers can not only endow the leather coating layer with certain flame retardant, heat preservation and thermal stability properties, but also significantly improve the wear resistance of the polymer coating film. Summary of the Invention

[0003] This invention utilizes nanotechnology and novel nanomaterials to improve traditional leather-making techniques. The aim is to provide a composite leather coating agent of nano-hydrotalcite@aramid fiber / crosslinked copolymer (LDH@NAF / H-PBMSA) and its preparation method. One-dimensional nano-aramid fibers and two-dimensional hydrotalcite nanosheets exert a synergistic coating effect. The interfacial synergy between the two-dimensional hydrotalcite sheets and aramid fibers improves the water dispersibility of the nanocomposite particles. The nano-aramid fibers can form hydrogen bonds between polymer molecules, increasing the physical crosslinking density and forming a multi-crosslinked copolymer, thereby effectively improving the mechanical properties and wear resistance of the coating film.

[0004] To achieve the above objectives, the present invention adopts the following technical solution: A method for preparing a nano-hydrotalcite@aramid fiber / crosslinked copolymer composite leather finishing agent (LDH@NAF / H-PBMSA) includes the following steps: (1) Dissolve N-hydroxymethylacrylamide (HAM), sodium bicarbonate (NaHCO3) and sodium p-styrene sulfonate (SSS) in water, then add butyl acrylate (BA), methyl methacrylate (MMA) and acrylic acid (AA) for pre-emulsification to obtain pre-emulsified monomer I; mix butyl acrylate (BA), methyl methacrylate (MMA), sodium p-styrene sulfonate (SSS), acrylic acid (AA) and water for emulsification to obtain pre-emulsified monomer II; heat pre-emulsified monomer I to 40~50℃ under stirring to obtain reaction solution ①, add initiator aqueous solution to reaction solution ①, then heat to 75~85℃ and react for 0.5~1 h to obtain reaction solution ②, then add pre-emulsified monomer II and the remaining initiator aqueous solution to reaction solution ② and continue the reaction for 4~7 h to obtain the target product crosslinked copolymer, denoted as H-PBMSA emulsion; (2) Under stirring, a mixed aqueous solution of zinc chloride (ZnCl2) and aluminum chloride (AlCl3) and an aqueous solution of sodium hydroxide (NaOH) were simultaneously added dropwise to the dispersion of nano-aramid fiber (NAF). After the addition was completed, the reaction was carried out at 75~85℃ for 2~3h under stirring. Then the mixture was transferred to a hydrothermal reactor and hydrothermally reacted at 110~120℃ for 10~20h. After the reaction was completed, the solid product was centrifuged, washed and dried to obtain the nano-hydrotalcite@aramid fiber composite product, denoted as LDH@NAF, for later use. (3) Disperse LDH@NAF evenly in water to obtain dispersion A. Take H-PBMSA and adjust its pH to 7~8 under stirring. Add dispersion A to H-PBMSA and stir for 1~2h to obtain nano-hydrotalcite@aramid fiber / crosslinked copolymer composite leather coating agent, denoted as LDH@NAF / H-PBMSA.

[0005] Further, the preparation process of the dispersion of nano-aramid fiber (NAF) in step (2) is as follows: Aramid is uniformly dispersed in dimethyl sulfoxide, and then 0.05~0.2g / mL potassium hydroxide aqueous solution is added. The mixture is stirred at 30℃~50℃ for 7~8 days. After the reaction is completed, deionized water is added and stirred for 1~2 h.

[0006] Preferably, each 1 g of aramid needs to be dissolved in 400-600 mL of dimethyl sulfoxide, and each 1 g of aramid needs to be added to 10-15 mL of potassium hydroxide aqueous solution at 0.05-0.2 g / mL and 2000-3000 mL of deionized water.

[0007] Further, in step (1), the molar ratio of each monomer in preemulsified monomer I is: butyl acrylate: methyl methacrylate: sodium p-styrene sulfonate: acrylic acid: N-hydroxymethylacrylamide = (33~34): (33~34): 1: (2~3): (3~4); the molar ratio of each monomer in preemulsified monomer II is: butyl acrylate: methyl methacrylate: sodium p-styrene sulfonate: acrylic acid = (33~34): (33~34): 1: (2~3), and the amount of sodium bicarbonate added is 50~90% of the total molar amount of acrylic acid in preemulsified monomer I and preemulsified monomer II.

[0008] Further, in step (1), the total mass of preemulsified monomer I (the sum of the masses of butyl acrylate, methyl methacrylate, sodium p-styrene sulfonate, acrylic acid, and N-hydroxymethylacrylamide in preemulsified monomer I) accounts for 33-35% of the total mass of the monomers added (the total mass of butyl acrylate, methyl methacrylate, sodium p-styrene sulfonate, acrylic acid, and N-hydroxymethylacrylamide in preemulsified monomer I and the total mass of butyl acrylate, methyl methacrylate, sodium p-styrene sulfonate, and acrylic acid in preemulsified monomer II).

[0009] Further, in step (1), the initiator is ammonium persulfate (APS), the concentration of the initiator aqueous solution is 0.01~0.02 g / mL, and the amount of initiator (APS) added is 1~1.5% of the total mass of butyl acrylate, methyl methacrylate, acrylic monomer, N-hydroxymethylacrylamide and sodium p-styrenesulfonate, wherein the amount of initiator added in pre-emulsified monomer I is 30~40% of the total amount of initiator.

[0010] Further, in step (2), the molar ratio of zinc chloride, aluminum chloride and sodium hydroxide is 3:1:(9~12), the amount of nano-aramid fiber added is 3~4% of the total mass of zinc chloride and aluminum chloride, the concentration of zinc chloride in the mixed aqueous solution of zinc chloride and aluminum chloride is 0.2~0.3 mmol / mL, and the concentration of sodium hydroxide aqueous solution is 0.8~1 mmol / mL.

[0011] Furthermore, in step (3), the amount of LDH@NAF added to the crosslinked copolymer matrix accounts for 0.1~2.5% of the effective mass of the polymer.

[0012] Furthermore, in step (3), ammonia is used to adjust the pH to 7-8, and 0.004g-0.100g of LDH@NAF is dispersed in 5 mL of distilled water.

[0013] The multi-component crosslinked copolymer consists of soft segments and hard segments, with a mass ratio of (3~2):(2~1). The HAM crosslinking agent accounts for 1~4% of the total mass of the polymer monomers. The soft segments are composed of butyl acrylate monomers, while the hard segments are composed of methyl methacrylate, acrylic acid, and sodium p-styrene sulfonate monomers. Properly controlling the ratio of soft to hard segments is essential for achieving good film-forming properties.

[0014] The nano-hydrotalcite@aramid fiber / crosslinked copolymer composite leather coating agent was prepared using the above preparation method.

[0015] This invention uses one-dimensional linear nano-aramid fibers and two-dimensional sheet-like nano-hydrotalcite composite particles as the reinforcing phase, N-hydroxymethylacrylamide as the crosslinking agent, and sodium styrene sulfonate as a reactive emulsifier participating in copolymerization. A soap-free emulsion polymerization method is employed to prepare a nano-hydrotalcite@aramid fiber / crosslinked copolymer composite leather coating agent. This significantly reduces the impact of traditional emulsifiers on product performance. The prepared nano-composite leather coating agent imparts good hydrophobicity, heat insulation, and wear resistance to the coating film. The introduction of LDH@NAF composite nanoparticles not only significantly reduces stress concentration in the product material but also provides the coating film with certain flame-retardant properties. This invention provides a new approach and method for developing environmentally friendly novel nano-composite leather coating agents. Attached Figure Description

[0016] Figure 1 Fourier transform infrared spectra of LDH, H-PBMSA (prepared in Example 1), and LDH@NAF / H-PBMSA (prepared in Example 6); Figure 2 In the image: a) shows the UV-Vis absorption spectra of four coating films at 250-800 nm: H-PBMSA (prepared in Example 1), LDH / H-PBMSA (prepared in Example 2), NAF / H-PBMSA (prepared in Example 3), and LDH@NAF / H-PBMSA (prepared in Example 6). Insets ① to ④ correspond to the film formation images of H-PBMSA, NAF / H-PBMSA, LDH / H-PBMSA, and LDH@NAF / H-PBMSA on glass slides, respectively. b) shows the UV-Vis absorption spectra of LDH@NAF / H-PBMSA coating films prepared with different amounts of LDH@NAF composite nanoparticles at 250-800 nm. Insets correspond to the film formation images of LDH@NAF added at 0-2.5% on glass slides. Figure 3 The images show the appearance of LDH@NAF nano-hydrotalcite (a) and aramid fiber (b) as observed by scanning electron microscopy (SEM), and (c), (d) and (e) as observed by SEM at different magnifications. Figure 4 In the image: a) is the thermogravimetric analysis (TG) curve of four coated films: H-PBMSA (prepared in Example 1), LDH / H-PBMSA (prepared in Example 2), NAF / H-PBMSA (prepared in Example 3), and LDH@NAF / H-PBMSA (prepared in Example 6); b) is the differential scanning calorimetry (DSC) curve of the four coated films: H-PBMSA (prepared in Example 1), LDH / H-PBMSA (prepared in Example 2), NAF / H-PBMSA (prepared in Example 3), and LDH@NAF / H-PBMSA (prepared in Example 6). Figure 5 The contact angles of four coating films with water in air were measured: H-PBMSA (prepared in Example 1), LDH / H-PBMSA (prepared in Example 2), NAF / H-PBMSA (prepared in Example 3), and LDH@NAF / H-PBMSA (prepared in Example 6). Figure 5 a) Comparison of water absorption rate of coating film ( Figure 5 b) Figure 6 To compare the gloss and smoothness of sheepskin surfaces coated with different samples, H-PBMSA prepared in Example 1 was applied to sheepskin at a concentration of 12 mg / cm³. 2 After spraying, the NAF / H-PBMSA coating agent prepared in Example 3 was applied to sheepskin at a concentration of 12 mg / cm³. 2 After spraying, the LDH / H-PBMSA coating agent prepared in Example 2 was applied to sheepskin at a concentration of 12 mg / cm³. 2 After spraying, the LDH@NAF / H-PBMSA coating agent prepared in Example 6 was applied to sheepskin at a concentration of 12 mg / cm³. 2 After spraying, the leather samples were coated with the H-PBMSA prepared in Example 1 and labeled as P / L. The leather samples coated with LDH / H-PBMSA prepared in Example 2 and labeled as LDH / P / L. The leather samples coated with NAF / H-PBMSA prepared in Example 3 and labeled as NAF / P / L. The leather samples coated with LDH@NAF / H-PBMSA prepared in Example 6 and labeled as LDH@NAF / P / L. Figure 7 To characterize the coating adhesion of different sheepskin samples using the cross-cut adhesion test, samples a, b, c, and d were respectively prepared using H-PBMSA obtained in Example 1 at a concentration of 12 mg / cm³ on sheepskin. 2 After spraying, the NAF / H-PBMSA coating agent prepared in Example 3 was applied to sheepskin at a concentration of 12 mg / cm³. 2After spraying, the LDH / H-PBMSA coating agent prepared in Example 2 was applied to sheepskin at a concentration of 12 mg / cm³. 2 After spraying, the LDH@NAF / H-PBMSA coating agent prepared in Example 6 was applied to sheepskin at a concentration of 12 mg / cm³. 2 The amount of coating is sprayed onto the finished leather; a', b', c', and d' correspond to the leather samples after a, b, c, and d are peeled off using special tape, respectively; Figure 8 In the middle: a is the stress-strain curve of H-PBMSA, LDH / H-PBMSA, NAF / H-PBMSA and LDH@NAF / H-PBMSA (prepared in Example 6); b is the stress-strain curve of LDH@NAF / H-PBMSA coating film prepared with different contents of LDH@NAF composite nanoparticles. Figure 9 The diagrams show the states of different coating films before and after 10 seconds of combustion. a~d represent the initial combustion states of H-PBMSA, NAF / H-PBMSA, LDH / H-PBMSA, and LDH@NAF / H-PBMSA (prepared in Example 6), respectively, and a'~d' correspond to the states of a~d after 10 seconds of combustion. Figure 10 The following were applied to uncoated raw hides and sheepskins with H-PBMSA (prepared in Example 1), LDH / H-PBMSA (prepared in Example 2), NAF / H-PBMSA (prepared in Example 3), and LDH@NAF / H-PBMSA (prepared in Example 6) coating agents at a concentration of 12 mg / cm³. 2 The thermal conductivity of the coated leather after spraying was compared and denoted as Leather and P / L, LDH / P / L, NAF / P / L, LDH@NAF / P / L, respectively. Figure 11 The abrasion marks were obtained by spraying sheepskin with four coating agents: H-PBMSA (prepared in Example 1), LDH / H-PBMSA (prepared in Example 2), NAF / H-PBMSA (prepared in Example 3), and LDH@NAF / H-PBMSA (prepared in Example 6). The coating surfaces before and after abrasion were compared under an optical microscope. Detailed Implementation

[0017] The technical solution of the present invention will be further described in detail below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto. In the following embodiments, the initiator aqueous solution was prepared by dissolving 0.280 g APS in 21 mL of distilled water.

[0018] 1. Preparation of nano-aramid fibers Weigh 1 g of aramid fiber (K-1313, provided by Zhengzhou Junshuo Biotechnology Co., Ltd.) and mix it with 500 mL of dimethyl sulfoxide (DMSO). Stir repeatedly with ultrasonication to ensure uniform dispersion. Then, add a 0.1 g / mL potassium hydroxide aqueous solution (1.2 g potassium hydroxide dissolved in 12 mL distilled water). React in a reaction flask at 30–50 °C for 7–8 days with magnetic stirring. After the reaction is complete, add 2500 mL of deionized water and stir for 1–2 hours. Filter to obtain a solid, dry under vacuum at 60 °C, and thoroughly grind to obtain nano-aramid fibers (denoted as NAF). The nano-aramid fibers exhibit good dispersibility in water.

[0019] 2. Preparation of nano-hydrotalcite (LDH) 4.093 g (30 mmol) of zinc chloride (ZnCl2) and 1.352 g (10 mmol) of aluminum chloride (AlCl3) were dissolved in 50 mL of distilled water and sonicated to obtain a mixed salt solution a; 3.623 g (90.6 mmol) of NaOH and 0.52 g (4.9 mmol) of anhydrous Na2CO3 were dissolved in 30 mL of distilled water and sonicated to obtain a mixed alkali solution b; solution b was added dropwise to solution a with continuous stirring to adjust the pH of the mixed solution to between 11 and 13, and then the mixture was sonicated for 3 min, stirred for 5 min, and repeated three times. After that, it was heated to 80 °C in a water bath and refluxed continuously for 2-3 h. Finally, it was transferred to a 100 mL reaction vessel and reacted at 110-120 °C for 12 h. After the reaction was stopped, the mixture was centrifuged (8000 r / min), and the solid product was washed thoroughly with distilled water until neutral. It was then vacuum dried at 60 °C to obtain nano-hydrotalcite, denoted as LDH, for later use. The prepared nano-hydrotalcite exhibits good dispersibility in water.

[0020] 3. Preparation of nano-hydrotalcite@aramid fiber composite (LDH@NAF) Weigh 1 g of aramid (K-1313, provided by Zhengzhou Junshuo Biotechnology Co., Ltd.) and mix it with 500 mL of dimethyl sulfoxide (DMSO). Stir repeatedly with ultrasonication until the mixture is evenly dispersed. Then, add 12 mL of a 0.1 g / mL potassium hydroxide aqueous solution (1.2 g KOH dissolved in 12 mL distilled water) to the mixture. Transfer the solution to a reaction flask and stir magnetically at 30–50 °C for 7–8 days. After the reaction is complete, add 2500 mL of distilled water and continue stirring for 1–2 hours. Take 90 mL of the reaction solution (NAF content approximately 0.030 g) and stir continuously. Simultaneously, add dropwise 20 mL of an aqueous solution containing 0.713 g zinc chloride (ZnCl2, 5.2 mmol) and 0.231 g aluminum chloride (AlCl3, 1.73 mmol) and 20 mL of an aqueous solution containing 0.720 g sodium hydroxide (NaOH, 18 mmol). After the addition is complete, react at 80 °C with stirring for 2–3 hours. h, then transferred to a hydrothermal reactor and continued hydrothermal reaction at 110~120℃ for 12 h, then the reaction was stopped. The solid precipitate was centrifuged at 8000 r / min, the solid product was washed and vacuum dried at 60℃ to obtain nano-hydrotalcite@aramid fiber composite, denoted as LDH@NAF, for later use.

[0021] Example 1: Weigh 0.736 g (7 mmol) HAM, 0.312 g (3.7 mmol) NaHCO3, 0.206 g (1 mmol) SSS, and 30 mL H2O, and sonicate for 3 min until completely dissolved. Add 4.272 g (33.3 mmol) BA, 3.337 g (33.4 mmol) MMA, and 0.164 g (2.3 mmol) AA, and stir until homogeneous. Then emulsify using a Fluocinolite FA25 shear emulsifier at 10000 rpm for 6 min to form pre-emulsified monomer I, for later use. Weigh 0.409 g (2 mmol) SSS and add to 40 mL distilled water, stirring until completely dissolved. Add 8.528 g (66.6 mmol) BA, 6.663 g (66.6 mmol) MMA, and 0.327 g (4.5 mmol) AA, and stir until homogeneous. Then emulsify using a Fluocinolite FA25 shear emulsifier at 10000 rpm for 6 min. Emulsify at rpm for 6 min to form pre-emulsified monomer II, which is set aside. Add pre-emulsified monomer I to a 250 mL three-necked flask equipped with a condenser, mechanical stirrer and thermometer. While stirring vigorously, heat the mixture to 40 °C and slowly add 7 mL of initiator aqueous solution (0.280 g APS dissolved in 21 mL of distilled water, the same below). After the addition is complete, heat the reaction mixture to 80 °C and react for 1 h. Then, slowly add pre-emulsified monomer II and the remaining 14 mL of initiator aqueous solution to the emulsion. The addition is completed in about 1 h. After the addition is complete, continue the reaction for 6 h to obtain a multi-component crosslinked copolymer, denoted as H-PBMSA (solid content 20 wt%), which is set aside.

[0022] Example 2: Weigh 0.736 g HAM, 0.312 g NaHCO3, 0.206 g SSS, and 30 mL H2O, and sonicate for 3 min until completely dissolved. Add 4.272 g BA, 3.337 g MMA, and 0.164 g AA, and stir until homogeneous. Then emulsify using a Fluocinolite FA25 shear emulsifier at 10000 rpm for 6 min to form pre-emulsified monomer I, for later use. Weigh 0.409 g SSS and add to 40 mL distilled water, stirring until completely dissolved. Add 8.528 g BA, 6.663 g MMA, and 0.327 g AA, and stir until homogeneous. Then emulsify using a Fluocinolite FA25 shear emulsifier at 10000 rpm for 6 min to form pre-emulsified monomer II, for later use. Add pre-emulsified monomer I to a 250 mL container equipped with a condenser, mechanical stirrer, and thermometer. In a three-necked flask, under vigorous stirring, the temperature was simultaneously raised to 40°C. Then, 7 mL of an initiator aqueous solution (0.280 g APS dissolved in 21 mL of distilled water, the same below) was slowly added dropwise. After the addition was complete, the reaction temperature was raised to 80°C and reacted for 1 h. Then, pre-emulsified monomer II and 14 mL of initiator aqueous solution were slowly added dropwise to the emulsion. The addition was completed in about 1 h. After the addition was complete, the reaction was continued for 6 h to obtain a multi-component crosslinked copolymer, denoted as H-PBMSA, for later use. Weigh 20 g of H-PBMSA emulsion into a 50 mL beaker, add 2-3 drops of commercially available concentrated ammonia (the same below) to adjust the pH to 7-8, and stir continuously. This is recorded as emulsion ① for later use. Weigh 0.04 g of nano-hydrotalcite and disperse it in 5 mL of distilled water. Stir continuously with ultrasound to ensure uniform dispersion. Then, slowly add the hydrotalcite dispersion to emulsion ① and stir for 1-2 h to ensure uniform dispersion. This yields a nano-hydrotalcite / crosslinked copolymer composite emulsion, recorded as LDH / H-PBMSA, for later use.

[0023] Example 3: Weigh 0.736 g HAM, 0.312 g NaHCO3, 0.206 g SSS, and 30 mL H2O, and sonicate for 3 min until completely dissolved. Add 4.272 g BA, 3.337 g MMA, and 0.164 g AA, and stir until homogeneous. Then emulsify using a Fluocinolite FA25 shear emulsifier at 10000 rpm for 6 min to form pre-emulsified monomer I, for later use. Weigh 0.409 g SSS and add to 40 mL distilled water, stirring until completely dissolved. Add 8.528 g BA, 6.663 g MMA, and 0.327 g AA, and stir until homogeneous. Then emulsify using a Fluocinolite FA25 shear emulsifier at 10000 rpm for 6 min to form pre-emulsified monomer II, for later use. Add pre-emulsified monomer I to a 250 mL container equipped with a condenser, mechanical stirrer, and thermometer. In a three-necked flask, under vigorous stirring, the temperature was simultaneously raised to 40°C. Then, 7 mL of an initiator aqueous solution (0.280 g APS dissolved in 21 mL distilled water, hereinafter the same) was slowly added dropwise. After the addition was complete, the reaction temperature was raised to 80°C and reacted for 1 hour. Then, pre-emulsified monomer II and 14 mL of initiator aqueous solution were slowly added dropwise to the emulsion simultaneously, completing the addition in about 1 hour. After the addition was complete, the reaction continued for 6 hours to obtain a multi-component crosslinked copolymer, denoted as H-PBMSA, for later use. 20 g of the H-PBMSA emulsion was weighed into a 50 mL beaker, and ammonia was added dropwise to adjust the pH to 7-8 while continuously stirring. This was denoted as emulsion ① for later use. 0.04 g of nano-aramid fiber (NAF) was weighed and dispersed in 5 mL of distilled water, and continuously ultrasonically stirred to ensure uniform dispersion. Then, the hydrotalcite dispersion was slowly added dropwise to emulsion ①, and stirred for 1-2 hours to ensure uniform dispersion, resulting in a nano-aramid fiber / crosslinked copolymer composite emulsion, denoted as NAF / H-PBMSA, for later use.

[0024] Example 4: Weigh 0.736 g HAM, 0.312 g NaHCO3, 0.206 g SSS, and 30 mL H2O, and sonicate for 3 min until completely dissolved. Add 4.272 g BA, 3.337 g MMA, and 0.164 g AA, and stir until homogeneous. Then emulsify using a Fluocinolite FA25 shear emulsifier at 10000 rpm for 6 min to form pre-emulsified monomer I, for later use. Weigh 0.409 g SSS and add to 40 mL distilled water, stirring until completely dissolved. Add 8.528 g BA, 6.663 g MMA, and 0.327 g AA, and stir until homogeneous. Then emulsify using a Fluocinolite FA25 shear emulsifier at 10000 rpm for 6 min to form pre-emulsified monomer II, for later use. Add pre-emulsified monomer I to a 250 mL container equipped with a condenser, mechanical stirrer, and thermometer. In a three-necked flask, under vigorous stirring, the temperature was simultaneously raised to 40°C. Then, 7 mL of an initiator aqueous solution (0.280 g APS dissolved in 21 mL distilled water, hereinafter the same) was slowly added dropwise. After the addition was complete, the reaction temperature was raised to 80°C and reacted for 1 hour. Then, pre-emulsified monomer II and 14 mL of initiator aqueous solution were slowly added dropwise to the emulsion simultaneously, completing the addition in about 1 hour. After the addition was complete, the reaction continued for 6 hours to obtain a multi-component crosslinked copolymer, denoted as H-PBMSA, for later use. 20 g of the H-PBMSA emulsion was weighed into a 50 mL beaker, and ammonia was added dropwise to adjust the pH to 7-8 while continuously stirring. This was denoted as emulsion ① for later use. 0.004 g of LDH@NAF was weighed and dispersed in 5 mL of distilled water, and continuously ultrasonically stirred to ensure uniform dispersion. Then, this dispersion was slowly added dropwise to emulsion ①, and stirred for 1-2 hours to ensure uniform dispersion, resulting in a nano-hydrotalcite@aramid fiber / crosslinked copolymer composite emulsion, denoted as 0.1%LDH@NAF / H-PBMSA, for later use.

[0025] Example 5: Weigh 0.736 g HAM, 0.312 g NaHCO3, 0.206 g SSS, and 30 mL H2O, and sonicate for 3 min until completely dissolved. Add 4.272 g BA, 3.337 g MMA, and 0.164 g AA, and stir until homogeneous. Then emulsify using a Fluocinolite FA25 shear emulsifier at 10000 rpm for 6 min to form pre-emulsified monomer I, for later use. Weigh 0.409 g SSS and add to 40 mL distilled water, stirring until completely dissolved. Add 8.528 g BA, 6.663 g MMA, and 0.327 g AA, and stir until homogeneous. Then emulsify using a Fluocinolite FA25 shear emulsifier at 10000 rpm for 6 min to form pre-emulsified monomer II, for later use. Add pre-emulsified monomer I to a 250 mL container equipped with a condenser, mechanical stirrer, and thermometer. In a three-necked flask, under vigorous stirring, the temperature was simultaneously raised to 40°C. Then, 7 mL of an initiator aqueous solution (0.280 g APS dissolved in 21 mL distilled water, hereinafter the same) was slowly added dropwise. After the addition was complete, the reaction temperature was raised to 80°C and reacted for 1 hour. Then, pre-emulsified monomer II and 14 mL of initiator aqueous solution were slowly added dropwise to the emulsion simultaneously, completing the addition in about 1 hour. After the addition was complete, the reaction continued for 6 hours to obtain a multi-component crosslinked copolymer, denoted as H-PBMSA, for later use. 20 g of the H-PBMSA emulsion was weighed into a 50 mL beaker, and ammonia was added dropwise to adjust the pH to 7-8 while continuously stirring. This was denoted as emulsion ① for later use. 0.020 g of LDH@NAF was weighed and dispersed in 5 mL of distilled water, and continuously ultrasonically stirred to ensure uniform dispersion. Then, this dispersion was slowly added dropwise to emulsion ①, and stirred for 1-2 hours to ensure complete uniform dispersion, yielding a nano-hydrotalcite@aramid fiber / crosslinked copolymer composite emulsion, denoted as 0.5%LDH@NAF / H-PBMSA, for later use.

[0026] Example 6: Weigh 0.736 g HAM, 0.312 g NaHCO3, 0.206 g SSS, and 30 mL H2O, and sonicate for 3 min until completely dissolved. Add 4.272 g BA, 3.337 g MMA, and 0.164 g AA, and stir until homogeneous. Then emulsify using a Fluocinolite FA25 shear emulsifier at 10000 rpm for 6 min to form pre-emulsified monomer I, for later use. Weigh 0.409 g SSS and add to 40 mL distilled water, stirring until completely dissolved. Add 8.528 g BA, 6.663 g MMA, and 0.327 g AA, and stir until homogeneous. Then emulsify using a Fluocinolite FA25 shear emulsifier at 10000 rpm for 6 min to form pre-emulsified monomer II, for later use. Add pre-emulsified monomer I to a 250 mL container equipped with a condenser, mechanical stirrer, and thermometer. In a three-necked flask, under vigorous stirring, the temperature was simultaneously raised to 40°C. Then, 7 mL of initiator aqueous solution (0.280 g APS dissolved in 21 mL distilled water, hereinafter the same) was slowly added dropwise. After the addition was complete, the reaction temperature was raised to 80°C and reacted for 1 hour. Then, pre-emulsified monomer II and 14 mL of initiator aqueous solution were slowly added dropwise to the emulsion simultaneously, completing the addition in about 1 hour. After the addition was complete, the reaction continued for 6 hours to obtain a multi-component crosslinked copolymer, denoted as H-PBMSA, for later use. 20 g of H-PBMSA emulsion was weighed into a 50 mL beaker, and ammonia was added dropwise to adjust the pH to 7-8 while continuously stirring. This was denoted as emulsion ① for later use. 0.040 g of LDH@NAF was weighed and dispersed in 5 mL distilled water, and continuously ultrasonically stirred to ensure uniform dispersion. Then, this dispersion was slowly added dropwise to emulsion ①, and stirred for 1-2 hours to ensure complete uniform dispersion, yielding a nano-hydrotalcite@aramid fiber / crosslinked copolymer composite emulsion, denoted as 1%LDH@NAF / H-PBMSA, for later use.

[0027] Example 7: Weigh 0.736 g HAM, 0.312 g NaHCO3, 0.206 g SSS, and 30 mL H2O, and sonicate for 3 min until completely dissolved. Add 4.272 g BA, 3.337 g MMA, and 0.164 g AA, and stir until homogeneous. Then emulsify using a Fluocinolite FA25 shear emulsifier at 10000 rpm for 6 min to form pre-emulsified monomer I, for later use. Weigh 0.409 g SSS and add to 40 mL distilled water, stirring until completely dissolved. Add 8.528 g BA, 6.663 g MMA, and 0.327 g AA, and stir until homogeneous. Then emulsify using a Fluocinolite FA25 shear emulsifier at 10000 rpm for 6 min. For min, pre-emulsified monomer II is formed and set aside. Pre-emulsified monomer I is added to a 250 mL three-necked flask equipped with a condenser, mechanical stirrer and thermometer. Under vigorous stirring, the temperature is raised to 40 °C. Then, 7 mL of initiator aqueous solution (0.280 g APS dissolved in 21 mL of distilled water, the same below) is slowly added dropwise. After the addition is complete, the reaction temperature is raised to 80 °C and reacted for 1 h. Then, pre-emulsified monomer II and 14 mL of initiator aqueous solution are slowly added dropwise to the emulsion. The addition is completed in about 1 h. After the addition is complete, the reaction is continued for 6 h to obtain a multi-component crosslinked copolymer, denoted as H-PBMSA, for use. Weigh 20 g of H-PBMSA emulsion into a 50 mL beaker, add ammonia water to adjust the pH to 7-8 while stirring continuously, and record this as emulsion ① for later use; weigh 0.060 g of LDH@NAF and disperse it in 5 mL of distilled water and stir continuously with ultrasound to ensure uniform dispersion, then slowly add the dispersion to emulsion ① and stir for 1-2 h to ensure complete uniform dispersion, thus obtaining a nano-hydrotalcite@aramid fiber / crosslinked copolymer composite emulsion, recorded as 1.5%LDH@NAF / H-PBMSA, for later use.

[0028] Example 8: Weigh 0.736 g HAM, 0.312 g NaHCO3, 0.206 g SSS, and 30 mL H2O, and sonicate for 3 min until completely dissolved. Add 4.272 g BA, 3.337 g MMA, and 0.164 g AA, and stir until homogeneous. Then emulsify using a Fluocinolite FA25 shear emulsifier at 10000 rpm for 6 min to form pre-emulsified monomer I, for later use. Weigh 0.409 g SSS and add to 40 mL distilled water, stirring until completely dissolved. Add 8.528 g BA, 6.663 g MMA, and 0.327 g AA, and stir until homogeneous. Then emulsify using a Fluocinolite FA25 shear emulsifier at 10000 rpm for 6 min to form pre-emulsified monomer II, for later use. Add pre-emulsified monomer I to a 250 mL container equipped with a condenser, mechanical stirrer, and thermometer. In a three-necked flask, under vigorous stirring, the temperature was simultaneously raised to 40°C. Then, 7 mL of initiator aqueous solution (0.280 g APS dissolved in 21 mL distilled water, hereinafter the same) was slowly added dropwise. After the addition was complete, the reaction temperature was raised to 80°C and reacted for 1 hour. Then, pre-emulsified monomer II and 14 mL of initiator aqueous solution were slowly added dropwise to the emulsion simultaneously, completing the addition in about 1 hour. After the addition was complete, the reaction continued for 6 hours to obtain a multi-component crosslinked copolymer, denoted as H-PBMSA, for later use. 20 g of H-PBMSA emulsion was weighed into a 50 mL beaker, and ammonia was added dropwise to adjust the pH to 7-8 while continuously stirring. This was denoted as emulsion ① for later use. 0.080 g of LDH@NAF was weighed and dispersed in 5 mL distilled water, and continuously ultrasonically stirred to ensure uniform dispersion. Then, this dispersion was slowly added dropwise to emulsion ①, and stirred for 1-2 hours to ensure complete uniform dispersion, yielding a nano-hydrotalcite@aramid fiber / crosslinked copolymer composite emulsion, denoted as 2%LDH@NAF / H-PBMSA, for later use.

[0029] Example 9: Weigh 0.736 g HAM, 0.312 g NaHCO3, 0.206 g SSS, and 30 mL H2O, and sonicate for 3 min until completely dissolved. Add 4.272 g BA, 3.337 g MMA, and 0.164 g AA, and stir until homogeneous. Then emulsify using a Fluocinolite FA25 shear emulsifier at 10000 rpm for 6 min to form pre-emulsified monomer I, for later use. Weigh 0.409 g SSS and add to 40 mL distilled water, stirring until completely dissolved. Add 8.528 g BA, 6.663 g MMA, and 0.327 g AA, and stir until homogeneous. Then emulsify using a Fluocinolite FA25 shear emulsifier at 10000 rpm for 6 min to form pre-emulsified monomer II, for later use. Add pre-emulsified monomer I to a 250 mL container equipped with a condenser, mechanical stirrer, and thermometer. In a three-necked flask, under vigorous stirring, the temperature was simultaneously raised to 40°C. Then, 7 mL of initiator aqueous solution (0.280 g APS dissolved in 21 mL distilled water, hereinafter the same) was slowly added dropwise. After the addition was complete, the reaction temperature was raised to 80°C and reacted for 1 hour. Then, pre-emulsified monomer II and 14 mL of initiator aqueous solution were slowly added dropwise to the emulsion simultaneously, completing the addition in about 1 hour. After the addition was complete, the reaction continued for 6 hours to obtain a multi-component crosslinked copolymer, denoted as H-PBMSA, for later use. 20 g of H-PBMSA emulsion was weighed into a 50 mL beaker, and ammonia was added dropwise to adjust the pH to 7-8 while continuously stirring. This was denoted as emulsion ① for later use. 0.100 g of LDH@NAF was weighed and dispersed in 5 mL distilled water, and continuously ultrasonically stirred to ensure uniform dispersion. Then, this dispersion was slowly added dropwise to emulsion ①, and stirred for 1-2 hours to ensure complete uniform dispersion, yielding a nano-hydrotalcite@aramid fiber / crosslinked copolymer composite emulsion, denoted as 2.5%LDH@NAF / H-PBMSA, for later use.

[0030] The infrared spectra of LDH, the crosslinked copolymer (H-PBMSA) prepared in Example 1, and the LDH@NAF / H-PBMSA nanocomposite prepared in Example 6 were compared. Figure 1 It can be seen that LDH@NAF / H-PBMSA was successfully prepared.

[0031] The UV-Vis absorption spectra of pure cross-linked copolymer coated films and different nanocomposite coated films were measured using a UV-759S ultraviolet spectrophotometer, such as... Figure 2As shown in Figure a, H-PBMSA, LDH / H-PBMSA, NAF / H-PBMSA, and LDH@NAF / PBMSA correspond to the UV-Vis spectra of the coating films prepared in Examples 1, 2, 3, and 6, respectively. Insets ① to ④ correspond to photographs of the coating films prepared in Examples 1, 2, 3, and 6 formed on glass slides using a spin coater. Figure 2 As can be seen from Figure a, the addition of nanofillers enhances the UV shielding performance of the coating film, while having almost no impact on the transparency of the coating film.

[0032] Figure 2 b shows the UV-Vis absorption spectra of LDH@NAF / H-PBMSA coating films prepared with different contents of LDH@NAF composite nanoparticles in the range of 250-800 nm, as well as images of the films formed on glass slides. The contents of 0%, 0.1%, 0.5%, 1%, 1.5%, 2%, and 2.5% were prepared in Examples 1, 4, 5, 6, 7, 8, and 9, respectively. As can be seen from the figure, when the content of LDH@NAF composite nanoparticles exceeds 1%, the transparency of the film is affected, and the LDH@NAF filler at 1% has good UV shielding performance. Figure 8 b. Stress-strain curves of LDH@NAF / H-PBMSA coating films prepared with different contents of LDH@NAF composite nanoparticles. The contents of 0%, 0.1%, 0.5%, 1%, 1.5%, 2%, and 2.5% were obtained from Examples 1, 4, 5, 6, 7, 8, and 9, respectively. The graph shows that when the content of LDH@NAF composite nanoparticles is 1%, the coating film exhibits the highest elongation at break and the best toughness. In conclusion, the LDH@NAF / H-PBMSA coating film shows the best overall performance when the filler content is 1%.

[0033] The morphological images of the prepared nano-hydrotalcite, aramid fibers, and LDH@NAF were observed using a scanning electron microscope (SEM). See attached images for details. Figure 3 ,from Figure 3 It can be seen that the diameter of the nano-hydrotalcite sheets is about 450 nm and the thickness is about 50 nm. After composite formation, the hydrotalcite nanosheets crystallize and grow uniformly on the surface of aramid fibers.

[0034] The thermal properties of different coated film samples were tested using a TGA / DSC 3+ thermogravimetric analyzer and a DSC250 differential scanning calorimeter. Figure 4(Curve H-PBMS corresponds to the product prepared in Example 1, curve LDH / H-PBMSA corresponds to the product prepared in Example 2, curve NAF / H-PBMSA corresponds to the product prepared in Example 3, and curve LDH@NAF / H-PBMSA corresponds to the product prepared in Example 6.) It can be seen that the maximum thermal decomposition temperature (399.5℃) of the NAF / / H-PBMSA coating film is higher than that of other coating films, indicating that the addition of NAF may further improve the thermal stability of the nanocomposite coating film. Figure 4 b shows the DSC curves of different coated films (curve H-PBMS corresponds to the product prepared in Example 1, curve LDH / H-PBMSA corresponds to the product prepared in Example 2, curve NAF / H-PBMSA corresponds to the product prepared in Example 3, and curve LDH@NAF / H-PBMSA corresponds to the product prepared in Example 6) at -60~70℃, further proving the successful preparation of the target product. The glass transition temperature of the LDH@NAF / H-PBMSA coated film (0.22℃) is significantly lower than that of the pure crosslinked polymer H-PBMSA (3.87℃), which broadens the operating temperature range of the coating agent. In comparison, the LDH@NAF / H-PBMSA nanocomposite coating film has better thermal stability and weather resistance.

[0035] The contact angle test results of H-PBMSA coated film and different nanocomposite coated films (all with a thickness of 0.4~0.5 mm) with water in air are shown in the figure. Figure 5 a. It can be seen that the introduction of LDH@NAF can improve the hydrophobicity of the coating film, increasing the water contact angle of the coating film from 90.9° to 102.1°; the water absorption rates of H-PBMSA coating film and different nanocomposite coating films are as follows: Figure 5 As shown in b and Table 1, the interfacial synergistic effect generated by the composite of LDH and NAF reduces the membrane water absorption rate from 33.4% of the pure polymer to 21.6%.

[0036] A comparison of the gloss and smoothness of sheepskin surfaces coated with different samples was conducted. The H-PBMSA coating agent prepared in Example 1, the NAF / H-PBMSA coating agent prepared in Example 3, the LDH / H-PBMSA coating agent prepared in Example 2, and the LDH@NAF / H-PBMSA coating agent prepared in Example 6 were all applied to sheepskin at a concentration of 12 mg / cm³. 2The following leather samples were coated with H-PBMSA (prepared in Example 1) and LDH / H-PBMSA (prepared in Example 2) and NAF / H-PBMSA (prepared in Example 3) respectively. The samples were denoted as P / L, LDH / P / L, NAF / P / L, and LDH@NAF / H-PBMSA (prepared in Example 6) respectively. Figure 6 It is evident from the image that the leather sample coated with LDH@NAF / H-PBMSA composite coating agent has a more lustrous finish.

[0037] The cross-cut adhesion test was used to test the coating adhesion of different coating films. See the results for details. Figure 7 And Table 2, from Figure 7 (In the figure, a, b, c, and d correspond to the H-PBMSA coating agent prepared in Example 1 applied to sheepskin at a concentration of 12 mg / cm³.) 2 The NAF / H-PBMSA coating agent prepared in Example 3 was sprayed onto sheepskin at a concentration of 12 mg / cm³. 2 The LDH / H-PBMSA coating agent prepared in Example 2 was sprayed onto sheepskin at a concentration of 12 mg / cm³. 2 The LDH@NAF / H-PBMSA coating agent prepared in Example 6 was sprayed onto sheepskin at a concentration of 12 mg / cm³. 2 The amount of coating applied to the finished leather is shown in Figure 1. a', b', c', and d' correspond to the leather samples after being peeled off using special adhesive tape, respectively. It can be seen that the adhesion rating of the LDH@NAF / H-PBMSA composite coating agent is 0, significantly better than the pure polymer's rating of 1.

[0038] Take 20 mL of the H-PBMSA pure copolymer emulsion prepared in Example 1, the LDH / H-PBMSA nanocomposite emulsion prepared in Example 2, the NAF / H-PBMSA nanocomposite emulsion prepared in Example 3, and the LDH@NAF / H-PBMSA nanocomposite emulsion prepared in Example 6, and pour them into 5×13 cm glass molds respectively. Allow them to air dry at room temperature for 48 h, then place them in a vacuum drying oven for 24 h (the film thickness after drying is 0.4~0.5 mm). Cut them into dumbbell-shaped specimens according to the national standard GB / T 528-2009 for the tensile stress-strain properties of thermoplastic rubber for later use. Use a TCS-2000 microcomputer-controlled electronic universal testing machine to test the stress-strain characteristics of different coatings at a tensile speed of 500 mm / min. See [link to specific results]. Figure 8 a. As can be seen from the figure, the introduction of LDH@NAF increases the strength of the nanocomposite coating to approximately 11.3 MPa.

[0039] The H-PBMSA coating film prepared in Example 1, the NAF / H-PBMSA coating film prepared in Example 3, the LDH / H-PBMSA coating film prepared in Example 2, and the LDH@NAF / H-PBMSA coating film prepared in Example 6 were each cut into 1cm × 2cm pieces with a thickness of 0.4~0.5mm, and the results were observed after burning for 10 seconds. Figure 9 It can be seen that the combustion rate of the nanocomposite coating film with the addition of LDH and LDH@NAF is significantly reduced, and the LDH@NAF / H-PBMSA composite coating film can slow down the combustion rate.

[0040] The thermal conductivity of copolymer H-PBMSA and different nanocomposite coatings on sheepskin was tested using a TC3000 thermal conductivity meter at 12 mg / cm². 2 The thermal conductivity of the coated leather obtained after spraying with a certain amount of material is shown in the test results. Figure 10 Compared to H-PBMSA coated leather and uncoated leather, the thermal conductivity of LDH@NAF / H-PBMSA coated leather is reduced to 0.073 W / (m·k), and LDH@NAF / H-PBMSA can improve the heat insulation performance of sheepskin.

[0041] The abrasion test first involves spraying the samples (different coatings were applied to sheepskin at a rate of 12 mg / cm²) onto the sheepskin. 2 Leather samples coated with H-PBMSA prepared in Example 1 are denoted as P / L; leather samples coated with LDH / H-PBMSA prepared in Example 2 are denoted as LDH / P / L; leather samples coated with NAF / H-PBMSA prepared in Example 3 are denoted as NAF / P / L; and leather samples coated with LDH@NAF / H-PBMSA prepared in Example 6 are denoted as LDH@NAF / P / L. The samples are placed facing sandpaper, and a 100 g weight is placed on top of the samples. Then, the sample is moved 10 cm in one direction and another 10 cm in the opposite direction. This process is called an abrasion cycle, and the number of cycles is 10. The abrasion resistance of the samples is compared by observing the abrasion marks on the leather surface after coating with pure multi-component crosslinked copolymers and different nanocomposite coatings using an RTS2 micro-fluorescence spectrometer. Figure 11 It can be seen that the leather coated with the pure polymer coating agent without nanoparticles (prepared in Example 1) has obvious scratches, while the leather sample coated with the LDH@NAF / H-PBMSA nanocomposite coating prepared in Example 6 only shows a very small number of scratches after wear, indicating that the synergistic effect of nano-hydrotalcite and aramid fibers can significantly improve the wear resistance of the coated leather.

[0042] The water absorption rate of the sample was tested and calculated as follows: Three pieces of the same sample, each 3×3 cm in size, were taken and weighed. The initial mass of each piece was recorded as M0. The weighed samples were then labeled and placed in petri dishes filled with water. They were left to soak for 24 hours. After soaking, the samples were removed, the surface water was absorbed, and the samples were weighed and recorded as M1. The water absorption rate W of the sample was then calculated using the following formula: The average value of the three test results was taken as the water absorption rate of the sample. The results are detailed in Table 1.

[0043] Table 1 Comparison of water absorption rates of different coating films As can be seen from the data in Table 1, compared with the pure cross-linked copolymer H-PBMSA, the water absorption rate of different nanocomposite coating films is reduced, and the LDH@NAF / H-PBMSA nanocomposite coating film has better water resistance.

[0044] Table 2. Coating adhesion of finished sheepskin according to national standard GB / T9286-88. As can be seen from the data in Table 2, the adhesion of the LDH@NAF / H-PBMSA nanocomposite coating to sheepskin is significantly improved compared to the pure polymer H-PBMSA.

Claims

1. A method for preparing a nano-hydrotalcite@aramid fiber / crosslinked copolymer composite leather coating agent, characterized in that, Includes the following steps: (1) Dissolve N-hydroxymethylacrylamide, sodium bicarbonate and sodium p-styrene sulfonate in water, then add butyl acrylate, methyl methacrylate and acrylic acid, and pre-emulsify to obtain pre-emulsified monomer I; mix butyl acrylate, methyl methacrylate, sodium p-styrene sulfonate and acrylic acid with water and emulsify to obtain pre-emulsified monomer II; heat pre-emulsified monomer I to 40~50℃ under stirring to obtain reaction solution ①, add initiator aqueous solution to reaction solution ①, then heat to 75~85℃ and react for 0.5~1h to obtain reaction solution ②, then add pre-emulsified monomer II and the remaining initiator aqueous solution to reaction solution ② and continue to react for 4~7h to obtain the target product crosslinked copolymer, denoted as H-PBMSA emulsion; (2) While stirring, a mixed aqueous solution of zinc chloride and aluminum chloride and an aqueous solution of sodium hydroxide were added dropwise to the dispersion of nano-aramid fibers. After the addition was completed, the reaction was carried out at 75~85℃ for 2~3 h with stirring. Then the mixture was transferred to a hydrothermal reactor and hydrothermally reacted at 110~120℃ for 10~20 h. After the reaction was completed, the mixture was centrifuged, and the solid product was washed and dried to obtain the nano-hydrotalcite@aramid fiber composite product, denoted as LDH@NAF, for later use. (3) Disperse LDH@NAF evenly in water to obtain dispersion A. Take H-PBMSA emulsion and adjust its pH to 7~8 under stirring. Add dispersion A dropwise into H-PBMSA emulsion and stir for 1~2h to obtain nano-hydrotalcite@aramid fiber / crosslinked copolymer composite leather coating agent, denoted as LDH@NAF / H-PBMSA.

2. The preparation method of the nano-hydrotalcite@aramid fiber / crosslinked copolymer composite leather coating agent according to claim 1, characterized in that, In step (1), the molar ratio of each monomer in preemulsified monomer II is: butyl acrylate: methyl methacrylate: sodium p-styrene sulfonate: acrylic acid = (33~34): (33~34): 1: (2~3), and the amount of sodium bicarbonate added is 50~90% of the total molar amount of acrylic acid in preemulsified monomer I and preemulsified monomer II.

3. The preparation method of the nano-hydrotalcite@aramid fiber / crosslinked copolymer composite leather coating agent according to claim 1, characterized in that, The preparation process of the nano-aramid fiber dispersion in step (2) is as follows: Aramid is uniformly dispersed in dimethyl sulfoxide, followed by the addition of 0.05~0.2g / mL potassium hydroxide aqueous solution, and stirred at 30℃~50℃ for 7~8 days. After the reaction is completed, deionized water is added and stirred for 1~2 h.

4. The preparation method of the nano-hydrotalcite@aramid fiber / crosslinked copolymer composite leather coating agent according to claim 3, characterized in that, Each 1 g of aramid needs to be dissolved in 400-600 mL of dimethyl sulfoxide, and each 1 g of aramid needs to be added to 10-15 mL of potassium hydroxide aqueous solution at a concentration of 0.05-0.2 g / mL.

5. The preparation method of the nano-hydrotalcite@aramid fiber / crosslinked copolymer composite leather coating agent according to claim 1, characterized in that, In step (1), the total mass of pre-emulsified monomer I accounts for 33-35% of the total mass of monomers added.

6. The preparation method of the nano-hydrotalcite@aramid fiber / crosslinked copolymer composite leather coating agent according to claim 1, characterized in that, In step (1), the initiator is ammonium persulfate, the concentration of the initiator aqueous solution is 0.01~0.02g / mL, and the amount of initiator added is 1~1.5% of the total mass of butyl acrylate, methyl methacrylate, acrylic monomer, N-hydroxymethylacrylamide and sodium p-styrenesulfonate. Among them, the amount of initiator added in pre-emulsified monomer I is 30~40% of the total amount of initiator.

7. The preparation method of the nano-hydrotalcite@aramid fiber / crosslinked copolymer composite leather coating agent according to claim 1, characterized in that, In step (2), the molar ratio of zinc chloride, aluminum chloride, and sodium hydroxide is 3:1:(9~12), the amount of nano-aramid fiber added is 3~4% of the total mass of zinc chloride and aluminum chloride, the concentration of zinc chloride in the mixed aqueous solution of zinc chloride and aluminum chloride is 0.2~0.3 mmol / mL, and the concentration of sodium hydroxide aqueous solution is 0.8~1 mmol / mL.

8. The preparation method of the nano-hydrotalcite@aramid fiber / crosslinked copolymer composite leather coating agent according to claim 1, characterized in that, In step (3), the amount of LDH@NAF added to the crosslinked copolymer matrix accounts for 0.1~2.5% of the solid mass of the H-PBMSA emulsion.

9. The preparation method of the nano-hydrotalcite@aramid fiber / crosslinked copolymer composite leather finishing agent according to claim 1, characterized in that, In step (3), ammonia water is used to adjust the pH to 7-8, and 0.004g-0.100g of LDH@NAF is dispersed evenly in 5 mL of distilled water to obtain dispersion A.

10. A nano-hydrotalcite@aramid fiber / crosslinked copolymer composite leather finishing agent prepared by any one of the preparation methods according to claims 1 to 9.

Images