High-strength composite film with multiple barrier structure and preparation process thereof

Abstract

This invention discloses a high-strength composite membrane with a multi-barrier structure and its preparation process, belonging to the field of composite membrane preparation technology. It addresses the technical problem that the barrier and tensile properties of existing composite membranes need further improvement. Specifically, it includes the following steps: uniformly coating a carboxyl-rich polysaccharide graft copolymer solution onto the surface of a release PET film, drying it to a moisture content of 15-20% to obtain a matrix layer. This invention sequentially coats carboxyl-rich polysaccharides to construct a highly active matrix, sprays zirconium phytate sol at the interface to induce coordination crosslinking, then coats dopamine-modified MXene and uses fluid shear force to achieve highly parallel orientation of nanosheets. Finally, it removes micropores through segmented vacuum hot pressing and deeply cures the membrane. This integrates interfacial chemical anchoring, forced shear orientation, and thermal coupling densification, constructing a dense three-dimensional interpenetrating barrier network in situ, synergistically improving the tensile strength and gas-liquid shielding performance of the composite membrane.

Description

Technical Field

[0001] This invention relates to the field of composite membrane preparation technology, specifically to a high-strength composite membrane with multiple barrier structures and its preparation process. Background Technology

[0002] With the rapid development of food packaging, pharmaceutical packaging, flexible electronic device encapsulation, and chemical protection, the market has placed higher demands on the comprehensive performance of film materials. These materials not only need to have excellent gas and water vapor barrier properties to reduce the impact of external media on the contents or device performance, but also need to have high mechanical strength, dimensional stability, and environmental adaptability to meet the requirements of long-term use under complex working conditions. In recent years, composite film materials have gradually shifted from optimizing a single performance to synergistically improving multiple performances. However, in practical applications, it is still difficult to achieve a good balance between barrier performance, mechanical properties, and service stability.

[0003] Currently, the commonly used organic matrices for composite membranes mainly include polyvinyl alcohol, ethylene-vinyl alcohol copolymer, polylactic acid, cellulose derivatives, chitosan, and other hydrophilic polymers. Commonly used inorganic barrier phases include montmorillonite, kaolin, graphene oxide, and inorganic nanofibers. For the above material systems, various methods are used to improve the structural uniformity and comprehensive performance of the membrane, such as coupling agent surface treatment, surfactant dispersion, solution blending, melt blending, electrostatic layer-by-layer self-assembly, stretching orientation, heat treatment crystallization enhancement, and single crosslinking agent curing. Although these technical routes can improve the dispersion state of fillers or enhance the local barrier effect to a certain extent, they generally still have the disadvantages of limited interfacial bonding levels and insufficient control of the orientation of the reinforcing phase.

[0004] In existing technologies, the interfacial interactions between inorganic phases and organic matrices are relatively simple, usually consisting of physical adsorption and surface coating. The interfacial bonding stability and stress transfer efficiency still need to be improved. Under stress or moisture conditions, local debonding and defect propagation are prone to occur. Furthermore, the distribution and arrangement of barrier components during film formation lack effective control, making it difficult to form continuous, regular, and highly tortuous mass transfer barrier paths. This results in gas and water molecules still migrating along local defect areas. At the same time, some matrix materials still suffer from insufficient chain segment stacking and difficulty in effectively eliminating local micropores during film formation, which in turn affects the barrier stability and mechanical reliability of the film.

[0005] To address this technical deficiency, a solution is proposed. Summary of the Invention

[0006] The purpose of this invention is to provide a high-strength composite membrane with multiple barrier structures and its preparation process, in order to solve the technical problem that the barrier performance and tensile properties of composite membranes in the prior art need to be further improved.

[0007] The objective of this invention can be achieved through the following technical solution: a process for preparing a high-strength composite membrane with a multi-barrier structure, comprising the following steps: S1. The carboxyl-rich polysaccharide graft copolymer solution is uniformly coated on the surface of the release PET film and dried to a moisture content of 15-20% to obtain the matrix layer. S2. Spray phytate zirconium-based hybrid crosslinking sol onto the surface of the substrate layer. When the water content of the phytate zirconium-based hybrid crosslinking sol is 10-15%, apply dopa-modified titanium carbide liquid. Use the shear force generated by the doctor blade coating to induce the dopa-modified titanium carbide nanosheets in the dopa-modified titanium carbide liquid to be parallel oriented in the film surface direction to obtain an interface barrier composite layer. S3. Place the interface barrier composite layer in a vacuum hot press and hold it at 85-90℃ and 0.4-0.6MPa for 8-12 minutes, then hold it at 120-130℃ and 7-9MPa for 35-45 minutes. After cooling to room temperature, peel off the high-strength composite film.

[0008] Furthermore, in step S1, the wet film thickness is 300-500 μm, and the drying temperature is 40-50℃; in step S2, the spraying rate of the zirconium phytate-based hybrid crosslinked sol is 5-15 mL / m. 2 When applying dopa-modified titanium carbide liquid, the gap between the scraper and the substrate surface is 100-150μm, and the coating speed is 10-20mm / s.

[0009] Furthermore, the zirconium phytate-based hybrid crosslinked sol is prepared by the following steps: A1. Place zirconium oxychloride and methanol in a reaction vessel and stir. Add acetylacetone and stir at room temperature for 15-30 min. Add hydrochloric acid aqueous solution to adjust the pH to 4.5-5.5 and react at room temperature for 1-2 h. Post-process to obtain acetylacetone chelated zirconium precursor. A2. Place the acetylacetone-chelated zirconium precursor, phytic acid aqueous solution, ethanol and deionized water in a reaction vessel and stir. Add hydrochloric acid aqueous solution to adjust the pH to 3.0±0.1. Stir evenly at room temperature to obtain phytic acid zirconium-based hybrid crosslinked sol.

[0010] Further, in step A1, the ratio of zirconium oxychloride, methanol, and acetylacetone is 2-4g:70-90mL:3.5-5.5g, and the concentration of the hydrochloric acid aqueous solution is 0.1-0.2mol / L. The post-processing steps include: after the reaction is completed, the reaction system is cooled to room temperature, filtered, the filter cake is washed 2-4 times with deionized water, and then transferred to an oven at 50-60℃ to dry for 4-6 hours to obtain the acetylacetone chelated zirconium precursor.

[0011] Furthermore, in step A2, the ratio of the amount of the acetylacetone chelated zirconium precursor, phytic acid aqueous solution, ethanol and deionized water is 2-4g:2-4mL:15-25mL:15-25mL, the concentration of the phytic acid aqueous solution is 50wt%, and the concentration of the hydrochloric acid aqueous solution is 0.1-0.2mol / L.

[0012] Furthermore, the carboxyl-rich polysaccharide graft copolymer solution is prepared by the following steps: B1. Place itaconic anhydride, glacial acetic acid and acetic anhydride in a reaction vessel and stir. Keep the reaction vessel in an ice bath at 0-5°C. Slowly add β-alanine and keep stirring in the ice bath for 1-2 hours. Heat the reaction vessel to 110-120°C and keep it at that temperature for 6-8 hours. Post-treatment yields carboxylated itaconic imide. The reaction formula for the preparation of carboxylated itconimide is as follows: The mass spectrometry data of carboxylated itaconitumide were: m / z: 169.07 (100.0%), 170.07 (7.8%), 171.07 (1.1%).

[0013] B2. Place pullulan polysaccharide and deionized water in a reaction vessel under nitrogen atmosphere and stir. Heat the reaction vessel to 70-80℃, add ammonium persulfate, keep warm and stir for 15-25 min, add carboxylated itconimide acetone solution, keep warm and react for 4-6 h, and then post-process to obtain a 6wt% carboxylated polysaccharide graft copolymer solution.

[0014] Further, in step B1, the ratio of itaconic anhydride, glacial acetic acid, acetic anhydride and β-alanine is 10-12g:140-160mL:1-2g:8-10g. The post-processing steps include: after the reaction is completed, heating the reaction vessel to 115-125℃, removing glacial acetic acid by vacuum distillation, recrystallizing the concentrated solution with deionized water, filtering, washing the filter cake with deionized water 1-3 times, transferring it to an oven at 45-55℃, and drying it to constant weight to obtain carboxylated itaconic imide.

[0015] Further, in step B2, the ratio of pullulan polysaccharide, deionized water, ammonium persulfate, and carboxylated itconimide acetone solution is 9-11g:80-100mL:0.1-0.3g:8-10mL. The carboxylated itconimide acetone solution is composed of carboxylated itconimide and acetone mixed evenly at a ratio of 2g:10mL. The post-treatment step includes: after the reaction is completed, after the reaction system cools to room temperature, ethanol is added to the reaction solution to precipitate, the mixture is filtered, the filter cake is washed with ethanol 1-3 times, transferred to an oven at 50-60℃, dried to constant weight, and then added to deionized water to prepare a 6-8wt% carboxylated polysaccharide graft copolymer solution.

[0016] Furthermore, the dopa-modified titanium carbide liquid is prepared by the following steps: C1. Melamine chloride and acetone are placed in a reaction vessel and stirred. The reaction vessel is kept in an ice bath at 0-5°C. Then, levodopa ethanol solution is added and the reaction is kept at this temperature for 2-4 hours. After post-treatment, dichlorotriazine dopamine is obtained. C2. Place MXene and deionized water in a reaction vessel and stir. Add dichlorotriazine dopamine. Heat the reaction vessel to 35-45℃ and stir for 25-35 minutes. Post-treatment yields 2wt% dopamine-modified titanium carbide solution.

[0017] Further, in step C1, the ratio of melamine chloride, acetone, and levodopa ethanol solution is 1-2g:50-70mL:80-100mL. The levodopa ethanol solution is composed of levodopa and ethanol mixed evenly at a ratio of 3-5g:100mL. The post-treatment steps include: after the reaction is completed, the reaction system is heated to room temperature, the pH of the system is adjusted to neutral with a 1mol / L hydrochloric acid aqueous solution, filtered, the filter cake is washed 2-4 times with deionized water, transferred to a freeze dryer at -60℃, and freeze-dried for 6-8 hours to obtain dichlorotriazine tridopa.

[0018] Further, in step C2, the ratio of MXene, deionized water and dichlorotriazine dopamine is 1-2g:50-70mL:0.4-0.6g. The post-treatment steps include: after the reaction is completed, the reaction system is cooled to room temperature, filtered, the filter cake is washed 2-4 times with deionized water, transferred to an oven at 50-60℃ and dried for 4-6 hours, and dispersed in deionized water to prepare a 2wt% dopamine-modified titanium carbide solution.

[0019] The present invention also proposes a high-strength composite membrane with multiple barrier structures, which is prepared by the above-mentioned preparation process of a high-strength composite membrane with multiple barrier structures.

[0020] The present invention has the following beneficial effects: 1. This invention utilizes dichlorotriazine-dopa to surface-functionalize MXene, synergistically combining the high-density active sites of carboxyl-rich polysaccharide graft copolymers with the introduction of zirconium phytate-based hybrid crosslinked sol to construct a highly dense covalent-coordination dual crosslinked network in situ at the interface between the organic matrix and the inorganic phase. This structure leverages the chemical bridging effect of the triazine ring and the strong chelating properties of the catechol structure to achieve molecular-level anchoring of the inorganic nanophase on the organic framework, effectively improving the interfacial bonding force of traditional composite materials. Furthermore, the chemical synergistic gain between the components significantly enhances the interfacial adhesion work and compatibility, enabling the composite film to synergistically improve tensile strength and toughness under external forces through efficient load transfer and energy dissipation mechanisms between interfaces, thus ensuring the structural stability of the material under complex stress environments.

[0021] 2. This invention also utilizes the highly parallel orientation of dopa-modified MXene nanosheets induced by shear force field, combined with the deep filling of micropores by a zirconium phytate hybrid network, to construct a biomimetic layered multi-dimensional spatial barrier system. This structure significantly increases the geometric tortuosity factor by utilizing the high aspect ratio of two-dimensional nanosheets, causing permeating molecules to diffuse along extremely circuitous paths. At the same time, the zirconium phytate-based hybrid sol achieves the unity of physical barrier and chemical interception through interfacial permeation and coordination crosslinking with the polysaccharide matrix. This regular and dense internal configuration synergistically induces a decrease in the diffusion coefficient of the permeating medium, thereby further reducing the oxygen permeation rate and water vapor permeability of the composite membrane.

[0022] 3. This invention also promotes deep relaxation and cross-linking densification of the polymer network through a segmented hot-pressing process, effectively eliminating residual micropores inside the system. This highly densified three-dimensional interfacial cross-linked network not only enhances the reinforcing efficiency of the rigid two-dimensional skeleton, but also further improves the tensile properties of the membrane material due to the high-density hydrogen bond network and covalent cross-linking points. The modified inorganic nanophase and the functionalized polysaccharide matrix exhibit extremely strong interfacial bonding energy. This synergistic enhancement effect ensures that the composite membrane can maintain excellent mechanical retention under harsh environments such as high humidity. Detailed Implementation

[0023] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] The release PET film used in this invention was purchased from Shenzhen Rongmaoda Electronic Materials Co., Ltd., with a thickness of 0.05mm, a substrate of PET, and a release force of 70-90g; The pullulan used in this invention was purchased from Anhui Zhonghong Bioengineering Co., Ltd., with CAS number 9057-02-7, product name pullulan, and molecular weight of 100-500kDa. The MXene used in this invention was purchased from Ningbo Beigaer New Materials Co., Ltd., with an average lateral dimension of 1.5-3.5μm and a sheet thickness of 1.0-1.5nm.

[0025] Example 1 This embodiment provides a process for preparing dopa-modified titanium carbide liquid, including the following steps: Step I: Preparation of dichlorotriazine methyldopa Mix levodopa and ethanol at a ratio of 30g:1000mL to obtain a levodopa ethanol solution for later use. Weigh 10g of cyanuric chloride and 500mL of acetone and place them in a reaction vessel and stir. Heat the reaction vessel to 0℃ in an ice bath, add 800mL of levodopa ethanol solution, and keep the reaction at this temperature for 2h. After the reaction is complete, wait for the reaction system to heat to room temperature, adjust the pH of the system to neutral with a 1mol / L hydrochloric acid aqueous solution, filter, wash the filter cake twice with deionized water, transfer it to a freeze dryer at -60℃, and freeze dry for 6h to obtain dichlorotriazine tridopa.

[0026] Step II: Preparation of DOPA-modified titanium carbide liquid Weigh 10g of MXene and 500mL of deionized water and place them in a reaction vessel and stir. Add 4g of dichlorotriazine dopamine. Heat the reaction vessel to 35℃ and keep it at that temperature for 25min. After the reaction is complete, wait for the reaction system to cool to room temperature, filter it, wash the filter cake twice with deionized water, transfer it to an oven at 50℃ and dry it for 4h. Disperse it in deionized water to prepare a 2wt% dopamine-modified titanium carbide solution.

[0027] Under the low-temperature conditions of an ice bath, cyanuric chloride undergoes a controlled monosubstituted nucleophilic reaction, where an active chlorine atom on its triazine ring condenses with the amino group of levodopa to generate dichlorotriazine dopa, which retains the dichloro activity. Subsequently, under heating conditions, the dichlorotriazine dopa utilizes the remaining active chlorine atom on the triazine ring to undergo a further nucleophilic substitution reaction with the active hydroxyl end group on the MXene surface to construct a covalent bond. In conjunction with the catechol structure in the dopa fragment and the hydrogen bonding and coordination chelation on the MXene surface, the dopa group is grafted and anchored onto the MXene nanosheet surface, thereby achieving surface functionalization modification of titanium carbide and preparing a dopa-modified titanium carbide solution.

[0028] Selective monosubstituted L-DOPA amino groups were achieved through the temperature gradient activity of cyanochlorohydrin, and a highly reactive heteromorphic bifunctional intermediate, dichlorotriazine-dopa, was constructed while retaining the catechol functional building blocks. Subsequently, MXene surface functionalization was achieved through covalent grafting and multiple non-covalent synergistic effects, which significantly enhanced the interfacial shear strength and compatibility between the inorganic nanophase and the polymer matrix. By optimizing the highly oriented distribution of functionalized nanosheets in the membrane layer, a biomimetic layered multi-dimensional spatial barrier configuration was constructed, which increased the diffusion tortuosity of permeating molecules, induced a decrease in the oxygen permeation rate and water vapor permeation rate of the membrane material, and improved the gas barrier efficiency. At the same time, the dense three-dimensional interfacial cross-linked network strictly limited the micro-relaxation and free volume expansion of polymer chain segments, effectively reducing the diffusion coefficient of the permeating medium. Furthermore, the efficient load transfer mechanism of the rigid two-dimensional skeleton and the interfacial energy dissipation effect synergistically improved the tensile strength of the composite membrane, enabling it to exhibit excellent impact fracture resistance while maintaining high flexibility.

[0029] Example 2 This embodiment provides a process for preparing dopa-modified titanium carbide liquid, including the following steps: Step I: Preparation of dichlorotriazine jidopa Mix levodopa and ethanol at a ratio of 40g:1000mL to obtain a levodopa ethanol solution for later use. Weigh 15g of cyanuric chloride and 600mL of acetone and place them in a reaction vessel and stir. Heat the reaction vessel to 3°C in an ice bath. Add 900mL of levodopa ethanol solution and keep the reaction at this temperature for 3 hours. After the reaction is complete, wait for the reaction system to heat to room temperature and adjust the pH of the system to neutral with a 1mol / L hydrochloric acid aqueous solution. Filter the system and wash the filter cake three times with deionized water. Transfer the filter cake to a freeze dryer at -60°C and freeze dry for 7 hours to obtain dichlorotriazine tridopa.

[0030] Step II: Preparation of DOPA-modified titanium carbide liquid Weigh 15g of MXene and 600mL of deionized water and place them in a reaction vessel and stir. Add 5g of dichlorotriazine dopamine. Heat the reaction vessel to 40℃ and stir for 30min. After the reaction is complete, wait for the reaction system to cool to room temperature, filter, wash the filter cake three times with deionized water, transfer it to an oven at 55℃ and dry for 5h. Disperse it in deionized water to prepare a 2wt% dopamine-modified titanium carbide solution.

[0031] Example 3 This embodiment provides a process for preparing dopa-modified titanium carbide liquid, including the following steps: Step I: Preparation of dichlorotriazine jidopa Mix levodopa and ethanol at a ratio of 50g:1000mL to obtain a levodopa ethanol solution for later use. Weigh 20g of cyanuric chloride and 700mL of acetone and place them in a reaction vessel and stir. Heat the reaction vessel to 5°C in an ice bath. Add 1000mL of levodopa ethanol solution and keep the reaction at this temperature for 4 hours. After the reaction is complete, wait for the reaction system to heat to room temperature and adjust the pH of the system to neutral with a 1mol / L hydrochloric acid aqueous solution. Filter the system and wash the filter cake four times with deionized water. Transfer the filter cake to a freeze dryer at -60°C and freeze dry for 8 hours to obtain dichlorotriazine tridopa.

[0032] Step II: Preparation of DOPA-modified titanium carbide liquid Weigh 20g of MXene and 700mL of deionized water and place them in a reaction vessel and stir. Add 6g of dichlorotriazine dopamine. Heat the reaction vessel to 45℃ and stir for 35min. After the reaction is complete, wait for the reaction system to cool to room temperature, filter, wash the filter cake 4 times with deionized water, transfer it to an oven at 60℃ and dry for 6h. Disperse it in deionized water to prepare a 2wt% dopamine-modified titanium carbide solution.

[0033] Example 4 This embodiment provides a process for preparing a carboxyl-rich polysaccharide graft copolymer solution, including the following steps: Step ①: Preparation of carboxylated itconimide Weigh out 100g of itaconic anhydride, 1400mL of glacial acetic acid, and 10g of acetic anhydride and place them in a reaction vessel. Stir the reaction vessel and heat it to 0°C in an ice bath. Slowly add 80g of β-alanine and stir while maintaining the ice bath for 1 hour. Heat the reaction vessel to 110°C and keep it at that temperature for 6 hours. After the reaction is complete, heat the reaction vessel to 115°C and remove the glacial acetic acid by vacuum distillation. Recrystallize the concentrated solution with deionized water, filter it, wash the filter cake once with deionized water, transfer it to an oven at 45°C, and dry it to constant weight to obtain carboxylated itaconic imide.

[0034] Step ②: Prepare carboxyl-rich polysaccharide graft copolymer solution Carboxylated itconimide and acetone were mixed evenly at a ratio of 20g:100mL to obtain a carboxylated itconimide-acetone solution for later use. Weigh 90g pullulan polysaccharide and 800mL deionized water and place them in a reaction vessel under nitrogen atmosphere protection. Stir the mixture and heat the reaction vessel to 70℃. Add 1g ammonium persulfate and stir for 15min. Add 80mL of carboxylated itconimide acetone solution and keep the mixture at this temperature for 4h. After the reaction is complete, wait for the reaction system to cool to room temperature. Add ethanol to the reaction solution to precipitate the product. Filter the product and wash the filter cake once with ethanol. Transfer the cake to an oven at 50℃ and dry it to constant weight. Add deionized water to prepare a 6wt% carboxylated polysaccharide graft copolymer solution.

[0035] Under ice bath conditions, the amino group of β-alanine undergoes nucleophilic ring-opening addition to itaconic anhydride, followed by intramolecular ring-closing imidization under heating and dehydration of acetic anhydride, synthesizing carboxylated itaconic animide monomers that retain free carboxyl groups and active carbon-carbon double bonds. Under heating and a nitrogen atmosphere, the free radicals generated by the thermal decomposition of ammonium persulfate abstract hydrogen atoms from the pullulan polysaccharide backbone to form macromolecular free radicals, which in turn initiate free radical graft copolymerization of the unsaturated double bonds in the above monomers, covalently attaching the carboxyl-rich polymer side chains to the polysaccharide backbone, and finally obtaining carboxyl-rich polysaccharide graft copolymers.

[0036] By constructing a carboxylated itconimide heteromorphic unit with both polymerization activity and polar functional groups through intramolecular dehydration cyclization, and then using free radical initiation grafting technology to build high-density side chain carboxyl functional domains on the pullulan polysaccharide backbone, the transformation of biomacromolecules from a single structure to a highly reactive multifunctional template was achieved. Through chemical anchoring, the interfacial binding energy and reactive site abundance of the matrix phase were significantly improved, laying the molecular foundation for establishing strong interaction forces with the modified inorganic nanophase and constructing a highly dense three-dimensional cross-linked network. The high-density side chain carboxyl groups effectively compressed the local free volume of polymer chain segments by strengthening the hydrogen bond network and covalent cross-linking between interfaces, inducing a decrease in the oxygen permeability and water vapor permeability of the composite membrane compared to the pure membrane. At the same time, the intermolecular entanglement effect and interfacial energy dissipation mechanism constructed by the grafted chain segments significantly improved the tensile stress of the composite membrane and ensured that the material could maintain extremely high structural mechanical properties under high humidity environments.

[0037] Example 5 This embodiment provides a process for preparing a carboxyl-rich polysaccharide graft copolymer solution, including the following steps: Step ①: Preparation of carboxylated itconimide Weigh out 110g of itaconic anhydride, 1500mL of glacial acetic acid, and 15g of acetic anhydride and place them in a reaction vessel. Stir the reaction vessel and heat it to 3°C in an ice bath. Slowly add 90g of β-alanine and stir while maintaining the reaction in an ice bath for 1.5 hours. Then heat the reaction vessel to 115°C and keep it at that temperature for 7 hours. After the reaction is complete, heat the reaction vessel to 120°C and remove the glacial acetic acid by vacuum distillation. Recrystallize the concentrated solution with deionized water, filter it, wash the filter cake twice with deionized water, transfer it to an oven at 50°C, and dry it to constant weight to obtain carboxylated itaconic imide.

[0038] Step ②: Prepare carboxyl-rich polysaccharide graft copolymer solution Carboxylated itconimide and acetone were mixed evenly at a ratio of 20g:100mL to obtain a carboxylated itconimide-acetone solution for later use. Weigh 100g pullulan polysaccharide and 900mL deionized water and place them in a nitrogen-protected reactor. Stir the reactor and heat it to 75℃. Add 2g ammonium persulfate and stir for 20min. Add 90mL of carboxylated itconimide acetone solution and keep the reaction at this temperature for 5h. After the reaction is complete, let the reaction system cool to room temperature. Add ethanol to the reaction solution to precipitate the product. Filter the product and wash the filter cake twice with ethanol. Transfer the cake to an oven at 55℃ and dry it to constant weight. Add deionized water to prepare a 6wt% carboxylated polysaccharide graft copolymer solution.

[0039] Example 6 This embodiment provides a process for preparing a carboxyl-rich polysaccharide graft copolymer solution, including the following steps: Step ①: Preparation of carboxylated itconimide Weigh out 120g of itaconic anhydride, 1600mL of glacial acetic acid, and 20g of acetic anhydride and place them in a reaction vessel. Stir the reaction vessel and heat it to 5°C in an ice bath. Slowly add 100g of β-alanine and stir the reaction while maintaining the ice bath for 2 hours. Then heat the reaction vessel to 120°C and keep it at that temperature for 8 hours. After the reaction is complete, heat the reaction vessel to 125°C and remove the glacial acetic acid by vacuum distillation. Recrystallize the concentrated solution with deionized water, filter it, wash the filter cake three times with deionized water, transfer it to an oven at 55°C, and dry it to constant weight to obtain carboxylated itaconic imide.

[0040] Step ②: Prepare carboxyl-rich polysaccharide graft copolymer solution Carboxylated itconimide and acetone were mixed evenly at a ratio of 20g:100mL to obtain a carboxylated itconimide-acetone solution for later use. Weigh 110g pullulan polysaccharide and 1000mL deionized water and place them in a nitrogen-protected reactor. Stir the reactor and heat it to 80℃. Add 3g ammonium persulfate and stir for 25min. Add 100mL of carboxylated itconimide acetone solution and keep the reaction at this temperature for 6h. After the reaction is complete, let the reaction system cool to room temperature. Add ethanol to the reaction solution to precipitate the product. Filter the product and wash the filter cake three times with ethanol. Transfer the cake to an oven at 60℃ and dry it to constant weight. Add deionized water to prepare a 6wt% carboxyl-rich polysaccharide graft copolymer solution.

[0041] Example 7 This embodiment provides a preparation process for a zirconium phytate-based hybrid crosslinked sol, including the following steps: Step 1: Preparation of acetylacetone-chelated zirconium precursor Weigh 20g of zirconium oxychloride and 700mL of methanol and place them in a reaction vessel and stir. Add 35g of acetylacetone and stir at room temperature for 15min. Add 0.1mol / L hydrochloric acid aqueous solution to adjust the pH to 4.5 and react at room temperature for 1h. After the reaction is complete, wait for the reaction system to cool to room temperature, filter, wash the filter cake twice with deionized water, and transfer it to an oven at 50℃ to dry for 4h to obtain the acetylacetone chelated zirconium precursor.

[0042] Step 2: Preparation of phytate zirconium-based hybrid crosslinked sol Weigh out 20g of acetylacetone chelated zirconium precursor, 20mL of 50wt% phytic acid aqueous solution, 150mL of ethanol and 150mL of deionized water and place them in a reaction vessel and stir. Add 0.1mol / L hydrochloric acid aqueous solution to adjust the pH to 2.9 and stir evenly at room temperature to obtain phytic acid zirconium-based hybrid crosslinked sol.

[0043] A zirconium-based chelate precursor was constructed by coordinating and chelating acetylacetone with zirconium oxychloride in a weakly acidic alcoholic solution to achieve effective control over the reactivity of the zirconium center. Subsequently, ligand exchange and synergistic complexation between the chelated zirconium precursor and the polyphosphate functional group of phytic acid were carried out. In an acidic aqueous alcoholic medium, a phytic acid zirconium-based hybrid crosslinked sol with a highly spatially branched structure was constructed through controlled hydrolysis and crosslinking reactions.

[0044] The chelation coordination of acetylacetone to zirconium centers effectively regulated the hydrolysis kinetics and chemical activity of metal ions, ensuring the molecular-level dispersion and structural stability of the precursor in the liquid system. Subsequently, phytic acid functional groups with multidentate coordination capabilities were introduced to drive the in-situ construction of a highly branched zirconium-phosphorus hybrid network through ligand exchange, which greatly improved the crosslinking density and interfacial film quality of the system. This process induced the formation of a highly dense three-dimensional spatial barrier and rigid mechanical framework inside the composite membrane, synergistically strengthening the composite membrane's resistance to tortuous diffusion of the permeating medium and the efficiency of interfacial load transfer during the stress process, thereby improving the barrier performance and mechanical strength of the composite membrane.

[0045] Example 8 This embodiment provides a preparation process for a zirconium phytate-based hybrid crosslinked sol, including the following steps: Step 1: Preparation of acetylacetone-chelated zirconium precursor Weigh 30g of zirconium oxychloride and 800mL of methanol and place them in a reaction vessel and stir. Add 45g of acetylacetone and stir at room temperature for 22min. Add 0.15mol / L hydrochloric acid aqueous solution to adjust the pH to 5.0 and react at room temperature for 1.5h. After the reaction is complete, wait for the reaction system to cool to room temperature, filter, wash the filter cake three times with deionized water, and transfer it to an oven at 55℃ to dry for 5h to obtain the acetylacetone chelated zirconium precursor.

[0046] Step 2: Preparation of phytate zirconium-based hybrid crosslinked sol Weigh out 30g of acetylacetone chelated zirconium precursor, 30mL of 50wt% phytic acid aqueous solution, 200mL of ethanol and 200mL of deionized water and place them in a reaction vessel and stir. Add 0.15mol / L hydrochloric acid aqueous solution to adjust the pH to 3.0 and stir evenly at room temperature to obtain phytic acid zirconium-based hybrid crosslinked sol.

[0047] Example 9 This embodiment provides a preparation process for a zirconium phytate-based hybrid crosslinked sol, including the following steps: Step 1: Preparation of acetylacetone-chelated zirconium precursor Weigh 40g of zirconium oxychloride and 900mL of methanol and place them in a reaction vessel and stir. Add 55g of acetylacetone and stir at room temperature for 30min. Add 0.2mol / L hydrochloric acid aqueous solution to adjust the pH to 5.5 and react at room temperature for 2h. After the reaction is complete, wait for the reaction system to cool to room temperature, filter, wash the filter cake 4 times with deionized water, and transfer it to an oven at 60℃ to dry for 6h to obtain the acetylacetone chelated zirconium precursor.

[0048] Step 2: Preparation of phytate zirconium-based hybrid crosslinked sol Weigh out 40g of acetylacetone chelated zirconium precursor, 40mL of 50wt% phytic acid aqueous solution, 250mL of ethanol and 250mL of deionized water and place them in a reaction vessel and stir. Add 0.2mol / L hydrochloric acid aqueous solution to adjust the pH to 3.1 and stir evenly at room temperature to obtain phytic acid zirconium-based hybrid crosslinked sol.

[0049] Example 10 This embodiment provides a process for preparing a high-strength composite membrane with multiple barrier structures, including the following steps: Step 1: Preparation of the substrate layer The 6 wt% carboxyl-rich polysaccharide graft copolymer solution prepared in Example 4 was uniformly coated onto the surface of a release PET film using an automatic coating machine. The wet film thickness of the doctor blade coating was set to 300 μm. The coated film was then placed in an oven at 40°C for temperature-controlled drying. When the moisture content dropped to 15%, it was removed to obtain the substrate layer.

[0050] Step 2: Preparation of the interfacial barrier composite layer The phytate-zirconium-based hybrid crosslinked sol prepared in Example 7 was uniformly sprayed onto the substrate surface using a fine atomizing sprayer, with the spray volume controlled at 5 mL / m. 2When the sol layer penetrates into the substrate surface and the surface moisture content is maintained at 15%, the dopa-modified titanium carbide liquid prepared in Example 1 is coated on its surface a second time. The gap between the scraper and the substrate surface is set to 100 μm, and the coating is performed at a coating speed of 10 mm / s. The stable shear force field generated during the scraper coating process induces the dopa-modified titanium carbide nanosheets in the dopa-modified titanium carbide liquid to undergo forced parallel orientation in the film surface direction, thus obtaining an interface barrier composite layer.

[0051] Step 3: Preparation of high-strength composite membrane The interface barrier composite layer was placed in a vacuum hot press and held at 85℃ and 0.4MPa for 8 minutes, then at 120℃ and 7MPa for 35 minutes. After cooling to room temperature, a high-strength composite film was obtained.

[0052] Solvent evaporation film formation based on carboxyl-rich polysaccharide matrix layer, using the permeation and diffusion of zirconium phytate sol at the interface to drive the coordination and chelation of multivalent metal centers with carboxyl / phosphate groups, combined with shear force field to induce the directional horizontal regularization of dopa-modified MXene nanosheets at the composite interface, and finally accelerating the chemical bonding, physical entanglement and structural densification between the interfaces through a segmented vacuum hot pressing process, constructing an organic-inorganic three-dimensional interpenetrating network system with highly oriented inorganic phases, thus obtaining an interface barrier composite layer.

[0053] By pre-forming a film using carboxyl-rich polysaccharide materials, a continuous flexible framework with numerous active reaction sites was constructed. Subsequently, through the infiltration and coordination crosslinking of zirconium phytate sol at the interface, a strong and tough chemical transition layer was generated in situ between the organic matrix and the inorganic phase. This not only effectively filled the microscopic interface pores but also significantly improved the interfacial adhesion and prevented phase separation. Next, during the coating process, fluid shear force guided the two-dimensional MXene nanosheets to achieve a highly parallel and regular arrangement along the film plane. This highly ordered layered structure provides an efficient channel for load transfer under stress, enhancing mechanical strength, and significantly lengthens the physical diffusion path of the permeating medium, constructing an extremely strong barrier. Finally, a segmented vacuum hot-pressing process was used to further eliminate residual pores within the system, promoting deep crosslinking and densification of the polymer network, firmly locking the aforementioned multi-level regular structure, and ultimately achieving a synergistic improvement in the tensile strength and gas-liquid barrier performance of the composite membrane.

[0054] Example 11 This embodiment provides a process for preparing a high-strength composite membrane with multiple barrier structures, including the following steps: Step 1: Preparation of the substrate layer The 6 wt% carboxyl-rich polysaccharide graft copolymer solution prepared in Example 5 was uniformly coated onto the surface of a release PET film using an automatic coating machine. The wet film thickness of the doctor blade coating was set to 400 μm. The coated film was then placed in an oven at 45°C for temperature-controlled drying. When the moisture content dropped to 17.5%, it was removed to obtain the substrate layer.

[0055] Step 2: Preparation of the interfacial barrier composite layer The phytate-zirconium-based hybrid crosslinked sol prepared in Example 8 was uniformly sprayed onto the substrate surface using a fine atomizing sprayer, with the spray volume controlled at 10 mL / m. 2 When the sol layer penetrates into the substrate surface and the surface moisture content is maintained at 12.5%, the dopamine-modified titanium carbide liquid prepared in Example 2 is coated on its surface a second time. The gap between the scraper and the substrate surface is set to 1250 μm, and the coating is performed at a coating speed of 15 mm / s. The stable shear force field generated during the scraper coating process induces the dopamine-modified titanium carbide nanosheets in the dopamine-modified titanium carbide liquid to undergo forced parallel orientation in the film surface direction, thus obtaining an interface barrier composite layer.

[0056] Step 3: Preparation of high-strength composite membrane The interface barrier composite layer was placed in a vacuum hot press and held at 87°C and 0.5MPa for 10 minutes, then at 125°C and 8MPa for 40 minutes. After cooling to room temperature, a high-strength composite film was obtained.

[0057] Example 12 This embodiment provides a process for preparing a high-strength composite membrane with multiple barrier structures, including the following steps: Step 1: Preparation of the substrate layer The 6 wt% carboxyl-rich polysaccharide graft copolymer solution prepared in Example 6 was uniformly coated onto the surface of a release PET film using an automatic coating machine. The wet film thickness of the doctor blade coating was set to 500 μm. The coated film was then placed in an oven at 50°C for temperature-controlled drying. When the moisture content dropped to 20%, it was removed to obtain the substrate layer.

[0058] Step 2: Preparation of the interfacial barrier composite layer The phytate-zirconium-based hybrid crosslinked sol prepared in Example 9 was uniformly sprayed onto the substrate surface using a fine atomizing sprayer, with the spray volume controlled at 15 mL / m. 2When the sol layer penetrates into the substrate surface and the surface moisture content is maintained at 10%, the dopamine-modified titanium carbide liquid prepared in Example 3 is coated on its surface a second time. The gap between the scraper and the substrate surface is set to 150 μm, and the coating is performed at a coating speed of 20 mm / s. The stable shear force field generated during the scraper coating process induces the dopamine-modified titanium carbide nanosheets in the dopamine-modified titanium carbide liquid to undergo forced parallel orientation in the film surface direction, thus obtaining an interface barrier composite layer.

[0059] Step 3: Preparation of high-strength composite membrane The interface barrier composite layer was placed in a vacuum hot press and held at 90℃ and 0.6MPa for 12 minutes, then at 130℃ and 9MPa for 45 minutes. After cooling to room temperature, a high-strength composite film was obtained.

[0060] Comparative Example 1 The difference between this comparative example and Example 12 is that dichlorotriazine tridopa was omitted when preparing the dopa-modified titanium carbide liquid in step II.

[0061] Comparative Example 2 The difference between this comparative example and Example 12 is that the zirconium phytate-based hybrid crosslinked sol was omitted when preparing the interface barrier composite layer in step two.

[0062] Comparative Example 3 The difference between this comparative example and Example 12 is that the carboxylated itconimide acetone solution was omitted in step ② when preparing the carboxylated polysaccharide graft copolymer solution.

[0063] Performance testing: The oxygen permeability and water vapor permeability of the high-strength composite films prepared in Examples 10-12 and Comparative Examples 1-3 were determined in accordance with the standard GB / T 40266-2021 "General Rules for Quality of Oxide Barrier Transparent Plastic Composite Films and Bags for Food Packaging". The tensile strength and elongation at break of the high-strength composite films prepared in Examples 10-12 and Comparative Examples 1-3 were tested in accordance with the standard GB / T 528-2009 "Determination of tensile stress-strain properties of vulcanized rubber or thermoplastic rubber". The specific data are shown in Table 1.

[0064] Table 1 - Performance Test Data for Each Sample Data Analysis: A comparative analysis of the data in the table above shows that the oxygen permeability of the high-strength composite membrane prepared by this invention is 0.61 cm⁻¹. 3 ·(m 2 ·24h·0.1MPa) -1 The water vapor permeability is 0.93 g·(m³).2 ·24h) -1 The tensile strength was 44.5 MPa and the elongation at break was 48.9%, all of which were better than the comparative example.

[0065] This invention involves sequentially coating a carboxyl-rich polysaccharide to construct a highly active matrix, spraying zirconium phytate sol at the interface to induce coordination crosslinking, then coating with dopamine-modified MXene and using fluid shear force to achieve highly parallel orientation of the nanosheets. Finally, the micropores are eliminated and the nanosheets are deeply cured by segmented vacuum hot pressing. This process integrates interfacial chemical anchoring, forced shear orientation, and thermal coupling densification to construct a dense three-dimensional interpenetrating barrier network in situ, thereby synergistically improving the tensile strength and gas-liquid shielding performance of the composite membrane.

[0066] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to specific implementations. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A process for preparing a high-strength composite membrane with a multi-barrier structure, characterized in that, Includes the following steps: S1. The carboxyl-rich polysaccharide graft copolymer solution is uniformly coated on the surface of the release PET film and dried to a moisture content of 15-20% to obtain the matrix layer. The carboxyl-rich polysaccharide graft copolymer solution is prepared by reacting itaconic anhydride with β-alanine to synthesize a carboxylated itaconicimide functional monomer, which is then grafted onto pullulan polysaccharide molecular chains under the action of an initiator. S2. Spray phytate-zirconium hybrid crosslinked sol onto the surface of the substrate layer. When the water content of the phytate-zirconium hybrid crosslinked sol is 10-15%, apply dopa-modified titanium carbide liquid to obtain an interface barrier composite layer. The phytate-zirconium hybrid crosslinked sol is a hybrid crosslinked sol system constructed by acetylacetone chelated zirconium precursor and phytic acid molecules through dynamic coordination of phosphate groups with zirconium ions in an acidic alcohol-water medium. S3. Place the interface barrier composite layer in a vacuum hot press and hold it at 85-90℃ and 0.4-0.6MPa for 8-12 minutes, then hold it at 120-130℃ and 7-9MPa for 35-45 minutes. After cooling to room temperature, peel off the high-strength composite film.

2. The preparation process of a high-strength composite membrane with a multi-barrier structure according to claim 1, characterized in that, In step S1, the wet film thickness is 300-500 μm, and the drying temperature is 40-50℃; in step S2, the spraying rate of the zirconium phytate-based hybrid crosslinked sol is 5-15 mL / m. 2 When applying dopa-modified titanium carbide liquid, the gap between the scraper and the substrate surface is 100-150μm, and the coating speed is 10-20mm / s.

3. The preparation process of a high-strength composite membrane with a multi-barrier structure according to claim 1, characterized in that, The phytate-zirconium-based hybrid crosslinked sol was prepared by the following steps: A1. Place zirconium oxychloride and methanol in a reaction vessel and stir. Add acetylacetone and stir at room temperature for 15-30 min. Add hydrochloric acid aqueous solution to adjust the pH to 4.5-5.5 and react at room temperature for 1-2 h. Post-process to obtain acetylacetone chelated zirconium precursor. A2. Place the acetylacetone-chelated zirconium precursor, phytic acid aqueous solution, ethanol and deionized water in a reaction vessel and stir. Add hydrochloric acid aqueous solution to adjust the pH to 3.0±0.

1. Stir evenly at room temperature to obtain phytic acid zirconium-based hybrid crosslinked sol.

4. The preparation process of a high-strength composite membrane with a multi-barrier structure according to claim 3, characterized in that, In step A1, the ratio of zirconium oxychloride, methanol, and acetylacetone is 2-4g:70-90mL:3.5-5.5g, and the concentration of the hydrochloric acid aqueous solution is 0.1-0.2mol / L; in step A2, the ratio of the acetylacetone-chelated zirconium precursor, phytic acid aqueous solution, ethanol, and deionized water is 2-4g:2-4mL:15-25mL:15-25mL, the concentration of the phytic acid aqueous solution is 50wt%, and the concentration of the hydrochloric acid aqueous solution is 0.1-0.2mol / L.

5. The preparation process of a high-strength composite membrane with a multi-barrier structure according to claim 1, characterized in that, The carboxyl-rich polysaccharide graft copolymer solution was prepared by the following steps: B1. Place itaconic anhydride, glacial acetic acid and acetic anhydride in a reaction vessel and stir. Keep the reaction vessel in an ice bath at 0-5°C. Slowly add β-alanine and keep stirring in the ice bath for 1-2 hours. Heat the reaction vessel to 110-120°C and keep it at that temperature for 6-8 hours. Post-treatment yields carboxylated itaconic imide. B2. Place pullulan polysaccharide and deionized water in a reaction vessel under nitrogen atmosphere and stir. Heat the reaction vessel to 70-80℃, add ammonium persulfate, keep warm and stir for 15-25 min, add carboxylated itconimide acetone solution, keep warm and react for 4-6 h, and then post-process to obtain a 6wt% carboxylated polysaccharide graft copolymer solution.

6. The preparation process of a high-strength composite membrane with a multi-barrier structure according to claim 5, characterized in that, In step B1, the ratio of itaconic anhydride, glacial acetic acid, acetic anhydride, and β-alanine is 10-12g:140-160mL:1-2g:8-10g; in step B2, the ratio of pullulan, deionized water, ammonium persulfate, and carboxylated itaconicimide acetone solution is 9-11g:80-100mL:0.1-0.3g:8-10mL, and the carboxylated itaconicimide acetone solution is composed of 2g:10mL of homogeneous mixture.

7. The preparation process of a high-strength composite membrane with a multi-barrier structure according to claim 1, characterized in that, The dopa-modified titanium carbide liquid was prepared by the following steps: C1. Melamine chloride and acetone are placed in a reaction vessel and stirred. The reaction vessel is kept in an ice bath at 0-5°C. Then, levodopa ethanol solution is added and the reaction is kept at this temperature for 2-4 hours. After post-treatment, dichlorotriazine dopamine is obtained. C2. Place MXene and deionized water in a reaction vessel and stir. Add dichlorotriazine dopamine. Heat the reaction vessel to 35-45℃ and stir for 25-35 minutes. Post-treatment yields 2wt% dopamine-modified titanium carbide solution.

8. The preparation process of a high-strength composite membrane with a multi-barrier structure according to claim 7, characterized in that, In step C1, the ratio of melamine chloride, acetone, and levodopa ethanol solution is 1-2g:50-70mL:80-100mL, and the levodopa ethanol solution is composed of levodopa and ethanol mixed evenly at a ratio of 3-5g:100mL; in step C2, the ratio of MXene, deionized water, and dichlorotriazine dopamine is 1-2g:50-70mL:0.4-0.6g.

9. A high-strength composite membrane with a multi-barrier structure, characterized in that, The high-strength composite membrane with multiple barrier structures is prepared using the preparation process of a high-strength composite membrane with multiple barrier structures as described in any one of claims 1-8.

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