Air-tight TPU / EVOH composite material and preparation method thereof

Abstract

The invention relates to the technical field of high polymer materials, in particular to an air-tight TPU / EVOH composite material and a preparation method thereof. The air-tight TPU / EVOH composite material comprises a TPU inner layer, an EVOH air blocking layer and a TPU self-repairing outer layer which are sequentially compounded. The TPU / EVOH composite material disclosed by the invention has the advantages of self-repairing capability, high air tightness and high mechanical property, is suitable for being used as a material for life jackets and water supplies, and can achieve the purpose of no air leakage after being used for a long time.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, and in particular to an airtight TPU / EVOH composite material and its preparation method. Background Technology

[0002] Personal water safety equipment such as life jackets, inflatable buoyancy vests, and water rescue airbags rely on the long-term airtightness and structural integrity of the materials in the inflated state for their core functionality. In recent years, thermoplastic polyurethane (TPU) has gradually replaced traditional polyvinyl chloride (PVC) and rubber materials as the preferred substrate for high-end water products due to its excellent elasticity, abrasion resistance, hydrolysis resistance, and heat-sealing properties. Typically, TPU is produced in film form by dry lamination, hot-melt bonding, or co-extrusion processes with high-strength polyester or nylon fabrics to create multilayer composite materials for inflatable airbags.

[0003] However, water activities are often accompanied by external forces such as friction, scratching, and puncture. Once the surface of the TPU composite material is punctured by a sharp object, even if the pore size is small (such as pinhole level), it will cause rapid pressure loss. Traditional TPU materials lack active repair capabilities and cannot prevent the continuous escape of gas.

[0004] Currently, the industry generally attempts to improve airtightness by increasing film thickness, multi-layer barrier structures, or coating with silicone / fluorocarbon coatings. However, these methods often sacrifice material flexibility, increase weight, or raise costs, and cannot fundamentally solve the critical safety hazard of irreversible air leakage after puncture. Summary of the Invention

[0005] This invention provides an airtight TPU / EVOH composite material and its preparation method, solving the technical problem that existing TPU materials cannot actively repair themselves.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: An airtight TPU / EVOH composite material, comprising a TPU inner layer, an EVOH air barrier layer, and a TPU self-healing outer layer sequentially laminated together.

[0007] In some embodiments, the TPU self-healing outer layer comprises the following parts by weight of raw materials: 80-100 parts of polyurethane elastomer 50-60 parts of EVOH resin 50-70 parts of repair agent 1-3 parts crosslinking agent 1-5 parts of coupling agent 1-10 parts of wear-resistant additive; The repair agent comprises a dicyclopentadiene core, a polyurethane intermediate layer encapsulating the surface of the dicyclopentadiene core, and catalyst particles distributed on the surface of the polyurethane intermediate layer.

[0008] In some embodiments, the polyurethane elastomer is a polyether-type thermoplastic polyurethane elastomer from BASF, Germany, specifically the Elastollan product. ® SP 9630.

[0009] In some embodiments, the crosslinking agent includes at least one of dicumyl oxide, hexamethylene diisocyanate trimer, isophorone diisocyanate trimer, and 1,4-butanediol diglycidyl ether.

[0010] In some embodiments, the coupling agent includes at least one of γ-aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, isopropyltris(dioctylpyrophosphate)titanate, and distearate aluminate.

[0011] In some embodiments, the wear-resistant additive includes at least one of alumina fiber, silica fiber, alumina particles, and silica particles.

[0012] In some embodiments, the repair agent is prepared as follows: Step 1: By weight, mix 100 parts of dicyclopentadiene with 2-5 parts of oil-soluble emulsifier and stir until homogeneous to form an oil phase; Step 2: Add 3-8 parts by weight of water-based emulsifier to 300-600 parts of deionized water, heat to 50-70℃ and stir evenly to form an aqueous phase; Step 3: Slowly add the oil phase prepared in Step 1 to the aqueous phase prepared in Step 2, and emulsify under ultrasonic conditions to form an emulsion; Step 4: Add 10-30 parts by weight of polyisocyanate monomer and 8-25 parts by weight of polyol to the emulsion, control the reaction temperature at 40-60℃, react for 2-6 hours, cool to room temperature, and filter to obtain a repair agent intermediate with dicyclopentadiene as the core and polyurethane shell on the surface. Step 5: Disperse the repair agent intermediate prepared in step 4 in an inert solvent, add 1-10 parts by weight of catalyst particles, stir evenly, filter, and obtain the above-mentioned repair agent.

[0013] In some embodiments, in step one, the oil-soluble emulsifier includes at least one of Span 80 and Span 60.

[0014] In some embodiments, the aqueous emulsifier includes at least one of polyvinyl alcohol, sodium dodecyl sulfate, and hydroxyethyl cellulose.

[0015] In some embodiments, the polyisocyanate monomer includes at least one of TDI and MDI.

[0016] In some embodiments, the polyol includes at least one of polyethylene glycol and polycaprolactone diol.

[0017] In some embodiments, the catalyst includes a Grubbs catalyst.

[0018] In some embodiments, the EVOH barrier layer comprises the following raw materials in parts by weight: 100 parts of EVOH resin PA6 5–15 servings 5–15 parts compatibilizer Antioxidant 0.5–2 parts Lubricant 0.5–3 parts.

[0019] In some embodiments, the compatibilizer includes maleic anhydride-grafted compatibilizers.

[0020] In some embodiments, the antioxidant includes at least one of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], tris(2,4-di-tert-butylphenyl)phosphite, and dilauryl thiodipropionate.

[0021] In some embodiments, the lubricant includes at least one of erucamide, oleamide, polyethylene wax, and glyceryl monostearate.

[0022] The present invention also provides a method for preparing the above-mentioned airtight TPU / EVOH composite material, which includes the following preparation steps: Step 1: Preparation of EVOH gas barrier masterbatch: By weight, 100 parts of EVOH resin, 5-15 parts of PA6, 5-15 parts of compatibilizer, 0.5-2 parts of antioxidant, and 0.5-3 parts of lubricant are melt-granulated in a twin-screw extruder to obtain EVOH gas barrier masterbatch; Step 2: Preparation of TPU self-healing masterbatch: By weight, add 80-100 parts of polyurethane elastomer, 50-60 parts of EVOH resin, 50-70 parts of repair agent, 1-3 parts of crosslinking agent, 1-5 parts of coupling agent, and 1-10 parts of wear-resistant additive to a twin-screw extruder for melt granulation to obtain TPU self-healing masterbatch. Step 3: Using a three-layer co-extrusion casting process, the TPU inner layer raw material, EVOH gas barrier masterbatch, and TPU self-healing masterbatch are added to three independent extrusion channels of the casting equipment. Inside the die, the three melts flow in parallel at high temperature and are bonded layer by layer. After being cooled and shaped by the casting roller, a three-layer structure film composed of the TPU inner layer, the EVOH gas barrier layer, and the TPU self-healing outer layer is formed, resulting in an airtight TPU / EVOH composite material.

[0023] In some embodiments, the preparation method of TPU self-healing masterbatch is as follows: S1. Dry the polyurethane elastomer and EVOH resin at 70-90℃ for 6-12 hours; S2. Mix EVOH resin with 80-100 parts by weight of polyurethane elastomer evenly, then add 1-3 parts by weight of crosslinking agent, 1-5 parts by weight of coupling agent, and 1-10 parts by weight of wear-resistant additive, stir and mix evenly to obtain a mixture. S3. Add the above mixture and 50-70 parts by weight of the repair agent to a twin-screw extruder for melt granulation to obtain TPU self-healing masterbatch.

[0024] In some embodiments, the stirring speed in step S2 is 800-1200 rpm, and the stirring time is 1-2 hours; the stirring speed in step S3 is 1500-1800 rpm, and the stirring time is 1-1.5 hours.

[0025] In some embodiments, in step S3, the extrusion temperature of the twin-screw extruder is 160-200°C and the rotation speed is 100-200 rpm.

[0026] The beneficial effects of this invention are: This invention utilizes a TPU composite material comprising a sequentially composited TPU inner layer, an EVOH gas barrier layer, and a TPU self-healing outer layer. This TPU composite material possesses excellent mechanical properties, gas barrier properties, and self-healing properties, making it suitable as a material for life jackets and water sports equipment, and enabling long-term use without leakage. Detailed Implementation

[0027] To make the objectives, technical solutions, and technical effects of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely. The embodiments described below are some embodiments of the present invention, but not all embodiments. All other embodiments obtained by those skilled in the art in conjunction with the embodiments of the present invention without creative effort are within the scope of protection of the present invention. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed; where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0028] In the description of this invention, the term "and / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0029] In the description of this invention, "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can each be single or multiple.

[0030] It should be understood that the weights of the relevant components mentioned in the embodiments of this invention can refer not only to the specific content of each component, but also to the proportional relationship between the weights of the components. Therefore, any scaling up or down of the content of the relevant components according to the embodiments of this invention is within the scope of this invention. Specifically, the weights mentioned in the embodiments of this invention can be well-known units of mass in the chemical industry, such as μg, mg, g, and kg.

[0031] Furthermore, unless the context explicitly uses it otherwise, the singular form of a word should be understood as including the plural form of that word. The terms "comprising" or "having" are intended to specify the presence of a feature, quantity, step, operation, element, part, or combination thereof, but are not intended to exclude the presence or possible addition of one or more other features, quantities, steps, operations, elements, parts, or combinations thereof.

[0032] The present invention provides an airtight TPU / EVOH composite material, which includes a TPU inner layer, an EVOH gas barrier layer and a TPU self-healing outer layer sequentially laminated together.

[0033] This invention utilizes a TPU composite material comprising a sequentially composited TPU inner layer, an EVOH gas barrier layer, and a TPU self-healing outer layer. This TPU composite material possesses excellent mechanical properties, gas barrier properties, and self-healing properties, making it suitable as a material for life jackets and water sports equipment, and enabling long-term use without leakage.

[0034] In some embodiments, the TPU self-healing outer layer comprises the following parts by weight of raw materials: 80-100 parts of polyurethane elastomer 50-60 parts of EVOH resin 50-70 parts of repair agent 1-3 parts crosslinking agent 1-5 parts of coupling agent 1-10 parts of wear-resistant additive; The repair agent comprises a dicyclopentadiene core, a polyurethane intermediate layer encapsulating the surface of the dicyclopentadiene core, and catalyst particles distributed on the surface of the polyurethane intermediate layer.

[0035] This invention introduces a repair agent with a specific structure into a composite material, namely, a dicyclopentadiene core, a polyurethane intermediate layer, and catalyst particles loaded on the surface. When the material is punctured by a sharp object and forms micropores, the repair agent core breaks down and releases dicyclopentadiene monomers. After contacting air or moisture, these monomers come into contact with the surface catalyst, triggering a ring-opening metasomatic polymerization (ROMP) reaction. This rapidly generates a high-molecular polymer to block the puncture, thereby achieving active, in-situ, and rapid sealing of pinhole-level puncture damage and effectively preventing the continuous escape of gas.

[0036] The formulation of this invention synergistically introduces ethylene-vinyl alcohol copolymer (EVOH) barrier components, which significantly improves the gas barrier capability of the material body; at the same time, the polyurethane elastomer (TPU) as the matrix ensures good flexibility and elasticity, maintains good mechanical properties and flexibility, and improves the gas barrier performance of the composite material, so that the composite material does not leak gas during long-term use.

[0037] In this invention, the addition of crosslinking agents and coupling agents enhances the interfacial bonding force between the components and improves the long-term stability of the material in complex water environments such as humid heat and salt spray; the wear-resistant additives further enhance the surface's scratch resistance, reduce the probability of initial damage, and extend the service life.

[0038] In some embodiments, the polyurethane elastomer is a polyether-type thermoplastic polyurethane elastomer from BASF, Germany, specifically the Elastollan product. ® SP 9630.

[0039] In some embodiments, the crosslinking agent includes at least one of dicumyl oxide, hexamethylene diisocyanate trimer, isophorone diisocyanate trimer, and 1,4-butanediol diglycidyl ether.

[0040] In some embodiments, the coupling agent includes at least one of γ-aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, isopropyltris(dioctylpyrophosphate)titanate, and distearate aluminate.

[0041] In some embodiments, the wear-resistant additive includes at least one of alumina fiber, silica fiber, alumina particles, and silica particles.

[0042] In some embodiments, the repair agent is prepared as follows: Step 1: By weight, mix 100 parts of dicyclopentadiene with 2-5 parts of oil-soluble emulsifier and stir until homogeneous to form an oil phase; Step 2: Add 3-8 parts by weight of water-based emulsifier to 300-600 parts of deionized water, heat to 50-70℃ and stir evenly to form an aqueous phase; Step 3: Slowly add the oil phase prepared in Step 1 to the aqueous phase prepared in Step 2, and emulsify under ultrasonic conditions to form an emulsion; Step 4: Add 10-30 parts by weight of polyisocyanate monomer and 8-25 parts by weight of polyol to the emulsion, control the reaction temperature at 40-60℃, react for 2-6 hours, cool to room temperature, and filter to obtain a repair agent intermediate with dicyclopentadiene as the core and polyurethane shell on the surface. Step 5: Disperse the repair agent intermediate prepared in step 4 in an inert solvent, add 1-10 parts by weight of catalyst particles, stir evenly, filter, and obtain the above-mentioned repair agent.

[0043] This invention encapsulates dicyclopentadiene (DCPD) within a polyurethane shell using an emulsion method, and loads catalyst particles onto the shell surface, forming an integrated microcapsule structure with a core storing the monomer, an intermediate layer providing controlled-release protection, and an outer surface catalyzing polymerization. This structure effectively isolates the highly active monomer from the catalyst, preventing premature polymerization during processing or storage and ensuring the stability of the repair agent in an undamaged state. If the material is punctured, the microcapsule ruptures, the DCPD monomer flows out and comes into contact with the exposed catalyst, rapidly initiating ring-opening metathesis polymerization (ROMP) to quickly seal the breach.

[0044] This invention employs an oil / water two-phase emulsification combined with in-situ interfacial polymerization to generate a polyurethane shell on the surface of DCPD droplets in situ. This not only enhances the mechanical strength of the microcapsules, but also significantly improves the interfacial compatibility and uniform dispersion of the repair agent in the composite material due to the similarity between the shell composition and the chemical structure of the TPU matrix. This avoids agglomeration or sedimentation, thereby ensuring that the self-healing performance is uniformly distributed throughout the material.

[0045] In some embodiments, in step one, the oil-soluble emulsifier includes at least one of Span 80 and Span 60.

[0046] Span 80 (sorbitan monooleate) and Span 60 (sorbitan monostearate) are nonionic, oil-soluble emulsifiers with good lipophilicity and interfacial activity. Their use in the dicyclopentadiene (DCPD) oil phase effectively reduces the oil / water interfacial tension, making DCPD droplets easier to disperse in the aqueous phase and forming a stable emulsion with uniform particle size and narrow distribution. This facilitates the uniform encapsulation of the subsequent polyurethane shell, thereby improving the structural consistency and integrity of the repair agent microcapsules.

[0047] The Span series emulsifiers contain long-chain fatty acid groups in their molecular structure, which can interact with the subsequently added polyisocyanates and polyols to a certain extent, helping to form a denser and more continuous polyurethane shell on the oil droplet surface. This not only improves the heat resistance and crack resistance of the microcapsules during TPU composite material processing (such as high-temperature extrusion and casting), but also effectively prevents premature leakage of DCPD during storage, ensuring the long-term stability of the repair agent.

[0048] Span 80 and Span 60 are chemically stable, non-toxic, and have excellent compatibility with polyurethane systems. They are less likely to cause side reactions during emulsification and subsequent polymerization, and will not leave behind impurities (such as metal ions or highly polar substances) that affect catalyst activity. This ensures that the catalyst maintains high activity on the surface of the microcapsule, providing a guarantee for efficient triggering of self-healing reactions after puncture.

[0049] In summary, by selecting specific Span-type oil-soluble emulsifiers, this invention optimizes the emulsification-encapsulation process of the repair agent microcapsules, significantly improving their structural stability, dispersion uniformity, and functional reliability, and enhancing the gas barrier properties of the composite material.

[0050] In some embodiments, the aqueous emulsifier includes at least one of polyvinyl alcohol, sodium dodecyl sulfate, and hydroxyethyl cellulose.

[0051] All of the aforementioned aqueous emulsifiers possess excellent water solubility and interfacial activity. Polyvinyl alcohol (PVA) can form a polymeric protective layer in the aqueous phase, preventing oil droplet aggregation through steric hindrance. Sodium dodecyl sulfate (SDS), as an anionic surfactant, can significantly reduce interfacial tension and promote the refinement of DCPD oil droplets. Hydroxyethyl cellulose (HEC) increases the viscosity of the aqueous phase through thickening, inhibiting oil droplet sedimentation or floating. Used alone or in combination, these three agents can effectively stabilize oil-in-water (O / W) emulsion systems, ensuring uniform dispersion and controllable particle size of dicyclopentadiene droplets during the emulsification stage, which is beneficial for the subsequent formation of microcapsules with regular structures and uniform sizes.

[0052] In particular, high molecular weight emulsifiers such as polyvinyl alcohol and hydroxyethyl cellulose can partially participate in or guide the in-situ deposition of polyurethane shells at the emulsion interface, which helps to form a denser and more continuous coating layer, reduce shell defects, thereby improving the sealing performance and mechanical strength of microcapsules and preventing leakage of repair monomers (DCPDs) during material processing or storage.

[0053] The selected aqueous emulsifiers are all non-metallic and non-polar substances, and do not contain functional groups that may deactivate the catalyst (such as sulfur, phosphorus, amines, etc.). They will not interfere with the catalytic active center in the subsequent catalyst loading step, ensuring the efficient triggering of the self-repair reaction after puncture.

[0054] In some embodiments, the polyisocyanate monomer includes at least one of TDI and MDI.

[0055] Both TDI and MDI are aromatic polyisocyanates with high reactivity. The polyurethane formed by their reaction with polyols has a high hard segment content and rigid molecular chains. The resulting polyurethane shell is dense, strong, and heat-resistant, effectively encapsulating the dicyclopentadiene (DCPD) core. This ensures structural integrity during the subsequent high-temperature melt extrusion and casting process of the TPU composite material, preventing premature leakage or deactivation of the repair agent.

[0056] The polyurethane shell constructed from TDI and MDI is highly similar to the polyurethane elastomer in chemical structure, which significantly improves the interfacial compatibility and dispersion uniformity of the repair agent microcapsules in the TPU melt, avoids agglomeration or stress concentration caused by phase separation, and thus maintains the overall mechanical properties and flexibility of the composite material.

[0057] The functionality and reaction rate of TDI and MDI are controllable. By adjusting their dosage and reaction conditions (such as temperature and time), the degree of crosslinking and density of the polyurethane shell can be precisely controlled. It can effectively block DCPD exudation under normal conditions and reliably rupture due to local stress concentration during puncture, releasing monomers to trigger a self-healing reaction, thus achieving synergistic optimization of "stable storage" and "rapid response".

[0058] In some embodiments, the polyol includes at least one of polyethylene glycol and polycaprolactone diol.

[0059] Polyethylene glycol (PEG) possesses excellent hydrophilicity and segmental flexibility, endowing the polyurethane shell with a certain degree of elasticity and hydrophilic microdomains. This facilitates controlled rupture due to localized stress concentration at the moment of puncture, allowing for the timely release of dicyclopentadiene (DCPD) monomers. Polycaprolactone diol (PCL) combines biodegradability with excellent low-temperature toughness. The polyurethane soft segments formed by PCL maintain mechanical strength while exhibiting a moderate "weakness point" characteristic, making them more prone to cracking under micro-puncture, thereby enhancing the sensitivity and reliability of self-healing triggering. Using either alone or in combination, a balance can be achieved between shell rigidity and responsiveness, avoiding the problems of an overly brittle shell (prone to premature rupture) or an overly tough shell (failure to rupture after puncture).

[0060] PEG and PCL glycol are both commonly used soft segment raw materials for synthesizing TPU, and their structures are highly similar to those of the polyurethane elastomer matrix. The polyurethane shell constructed in this way has excellent chemical compatibility with the TPU matrix, significantly reducing interfacial tension and allowing the repair agent microcapsules to be uniformly dispersed during melt blending, avoiding agglomeration or phase separation, thereby ensuring the consistency of the overall mechanical properties and self-healing function of the composite material.

[0061] PCL glycol has high thermal stability (decomposition temperature >250℃), and PEG also has a good thermal processing window. The polyurethane shell formed by the two can withstand the twin-screw extrusion temperature, ensuring that the repair agent does not undergo significant degradation or DCPD leakage during high-temperature processing, and maintaining long-term storage stability.

[0062] In some embodiments, the catalyst includes a Grubbs catalyst.

[0063] Grubbs catalysts are a class of ruthenium-based carbene complexes that exhibit extremely high catalytic activity and selectivity for DCPD. When TPU composite materials are punctured and microcapsules rupture, the released DCPD monomers come into contact with the exposed Grubbs catalyst, rapidly initiating a ROMP reaction at room temperature or even in humid environments. Within seconds to minutes, a highly cross-linked polydicyclopentadiene (PDCPD) network is generated in situ, effectively sealing micropores and preventing gas leakage.

[0064] Compared to traditional metal catalysts (such as tungsten and molybdenum-based catalysts), Grubbs catalysts have a certain degree of tolerance to air and moisture. They can maintain high activity in water equipment such as life jackets that may be exposed to high humidity and salt spray environments for a long time, ensuring that the self-healing function is stable and reliable in actual use scenarios.

[0065] The Grubbs catalyst is loaded onto the outer surface of the polyurethane shell, while the DCPD monomer is encapsulated in the core. The two are physically isolated in an undamaged state to prevent premature polymerization during storage or processing; they only come into contact and initiate the reaction when the microcapsule is ruptured due to puncture.

[0066] Grubbs catalysts are essentially inert to the polyurethane backbone, EVOH and other functional components, and will not cause unnecessary degradation or cross-linking side reactions during the preparation of composite materials, thereby maintaining the overall mechanical properties, airtightness and service life of the material.

[0067] In some embodiments, the EVOH barrier layer comprises the following raw materials in parts by weight: 100 parts of EVOH resin PA6 5–15 servings 5–15 parts compatibilizer Antioxidant 0.5–2 parts Lubricant 0.5–3 parts.

[0068] EVOH resin has extremely low permeability to small molecule gases such as oxygen, nitrogen, and water vapor, making it a high-performance barrier material. The introduction of PA6 can form a partial co-crystallization or hydrogen bond network with EVOH, further extending the permeation path of gas molecules. In humid environments, it can also partially compensate for the decrease in barrier performance of EVOH due to moisture absorption, thereby achieving more stable and durable airtightness.

[0069] Pure EVOH film is brittle and has poor tear and puncture resistance. PA6, as a rigid engineering plastic, has high strength, high modulus and good wear resistance. Its addition effectively improves the tensile strength, puncture resistance and dimensional stability of the gas barrier layer. When it encounters friction, scratching or micro-puncture during water activities, the composite layer is not easy to break, providing a more reliable barrier support for the inner TPU layer.

[0070] This invention adds a compatibilizer to the EVOH barrier layer to form a "molecular bridge" at the interface between EVOH and PA6, promoting uniform dispersion of the two phases and inhibiting the formation of micropores or interface defects. At the same time, this compatibilized system also enhances the bonding strength between the EVOH barrier layer and the upper and lower TPU inner layers / self-healing outer layers, preventing delamination, bubbling or detachment of the multilayer structure during inflation or folding.

[0071] Antioxidants can effectively inhibit the thermal oxidative degradation of EVOH and PA6 during high-temperature melt extrusion, preventing molecular chain breakage, yellowing, or viscosity fluctuations; lubricants improve melt flowability, reduce extrusion torque, reduce the risk of melt fracture, ensure stable operation of the three-layer co-extrusion casting process, and obtain a film with a smooth surface and uniform thickness; comprehensively improve the service life of materials under harsh environments such as long-term storage, repeated inflation and deflation, and exposure to sunlight and humidity.

[0072] In some embodiments, the compatibilizer includes maleic anhydride-grafted compatibilizers.

[0073] In some embodiments, the antioxidant includes at least one of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], tris(2,4-di-tert-butylphenyl)phosphite, and dilauryl thiodipropionate.

[0074] In some embodiments, the lubricant includes at least one of erucamide, oleamide, polyethylene wax, and glyceryl monostearate. The present invention also provides a method for preparing the above-mentioned airtight TPU / EVOH composite material, which includes the following preparation steps: Step 1: Preparation of EVOH gas barrier masterbatch: By weight, 100 parts of EVOH resin, 5-15 parts of PA6, 5-15 parts of compatibilizer, 0.5-2 parts of antioxidant, and 0.5-3 parts of lubricant are melt-granulated in a twin-screw extruder to obtain EVOH gas barrier masterbatch; Step 2: Preparation of TPU self-healing masterbatch: By weight, add 80-100 parts of polyurethane elastomer, 50-60 parts of EVOH resin, 50-70 parts of repair agent, 1-3 parts of crosslinking agent, 1-5 parts of coupling agent, and 1-10 parts of wear-resistant additive to a twin-screw extruder for melt granulation to obtain TPU self-healing masterbatch. Step 3: Using a three-layer co-extrusion casting process, the TPU inner layer raw material, EVOH gas barrier masterbatch, and TPU self-healing masterbatch are added to three independent extrusion channels of the casting equipment. Inside the die, the three melts flow in parallel at high temperature and are bonded layer by layer. After being cooled and shaped by the casting roller, a three-layer structure film composed of the TPU inner layer, the EVOH gas barrier layer, and the TPU self-healing outer layer is formed, resulting in an airtight TPU / EVOH composite material.

[0075] In some embodiments, the preparation method of TPU self-healing masterbatch is as follows: S1. Dry the polyurethane elastomer and EVOH resin at 70-90℃ for 6-12 hours; S2. Mix EVOH resin with 80-100 parts by weight of polyurethane elastomer evenly, then add 1-3 parts by weight of crosslinking agent, 1-5 parts by weight of coupling agent, and 1-10 parts by weight of wear-resistant additive, stir and mix evenly to obtain a mixture. S3. Add the above mixture and 50-70 parts by weight of the repair agent to a twin-screw extruder for melt granulation to obtain TPU self-healing masterbatch.

[0076] In some embodiments, the stirring speed in step S2 is 800-1200 rpm, and the stirring time is 1-2 hours; the stirring speed in step S3 is 1500-1800 rpm, and the stirring time is 1-1.5 hours.

[0077] In some embodiments, in step S3, the extrusion temperature of the twin-screw extruder is 160-200°C and the rotation speed is 100-200 rpm.

[0078] The twin-screw extrusion temperature is set at 160-200℃, which ensures melt flowability for good plasticization and mixing while remaining below the significant deactivation temperature of Grubbs catalyst and the violent volatilization temperature of DCPD, effectively balancing processing feasibility and the retention of remedial agent activity. The rotational speed range of 100-200 rpm balances material conveying efficiency and shear strength; too low a speed will lead to uneven mixing, while too high a speed may damage the microcapsule structure. This parameter range ensures that the remedial agent microcapsules are uniformly dispersed in the melt without rupture, while also preventing TPU thermo-oxidative degradation.

[0079] The film produced by the casting process has a smooth surface and small thickness tolerance, which is beneficial for subsequent bonding with fabrics (such as for life jacket airbags), and is free of defects such as pinholes and fisheyes, further improving the initial airtightness from a structural level.

[0080] To enable those skilled in the art to clearly understand the above-described implementation details and operations of the present invention, and to demonstrate the significant advancements in the performance of the embodiments of the present invention, the following examples illustrate the above technical solutions.

[0081] Example 1 An airtight TPU / EVOH composite material, comprising a TPU inner layer, an EVOH air barrier layer, and a TPU self-healing outer layer sequentially laminated together.

[0082] The TPU self-healing outer layer comprises the following raw materials in parts by weight: 90 parts of polyurethane elastomer 55 parts of ethylene-vinyl alcohol copolymer 60 parts of repair agent 2 parts of dicumyl oxide crosslinking agent 3 parts of KH-550 coupling agent 5 parts of alumina fiber wear-resistant additive; The repair agent comprises a dicyclopentadiene core, a polyurethane intermediate layer encapsulating the surface of the dicyclopentadiene core, and catalyst particles distributed on the surface of the polyurethane intermediate layer.

[0083] The polyurethane elastomer is a polyether-type thermoplastic polyurethane elastomer from BASF, Germany, model number Elastollan. ® SP 9630; the ethylene-vinyl alcohol copolymer is Kuraray EVOH.

[0084] The preparation method of the above-mentioned repair agent is as follows: Step 1: By weight, mix 100 parts of dicyclopentadiene with 3.5 parts of oil-soluble emulsifier Span 80 and stir until homogeneous. Stir at 600 rpm for 0.5 hours to form an oil phase. Step 2: By weight, add 5.5 parts of water-based emulsifier polyvinyl alcohol to 450 parts of deionized water, heat to 60°C and stir evenly at a stirring speed of 300 rpm for 20 minutes to form an aqueous phase. Step 3: Slowly add the oil phase prepared in Step 1 to the aqueous phase in Step 2, and emulsify under ultrasonic conditions to form an emulsion; wherein the dropping rate is 1 mL / min, the ultrasonic power is 600 W, and the emulsification temperature is 60℃. Step 4: Add 20 parts by weight of polyisocyanate monomer and 16 parts by weight of polyol to the emulsion, control the reaction temperature at 50°C, react for 4 hours, cool to room temperature, and filter to obtain a repair agent intermediate with dicyclopentadiene as the core and polyurethane shell on the surface. Step 5: Disperse the repair agent intermediate prepared in step 4 in toluene inert solvent, add 5 parts by weight of Grubbs catalyst particles, stir evenly at 300 rpm for 0.5 h, filter, and obtain the above-mentioned repair agent.

[0085] The polyisocyanate monomer is composed of TDI and MDI mixed in a mass ratio of 1:1; the polyol is composed of polyethylene glycol and polycaprolactone diol mixed in a mass ratio of 1:1.5.

[0086] The EVOH barrier layer comprises the following raw materials in parts by weight: 100 parts of EVOH resin PA6 10 servings 10 parts compatibilizer 1 part antioxidant 1.5 parts lubricant.

[0087] The compatibilizer is maleic anhydride-grafted ethylene-octene copolymer, supplied by ExxonMobil; the antioxidant is tris(2,4-di-tert-butylphenyl) phosphite; and the lubricant is glyceryl monostearate.

[0088] The preparation method of the above-mentioned airtight TPU / EVOH composite material includes the following preparation steps: Step 1: Preparation of EVOH gas barrier masterbatch: By weight, 100 parts of EVOH resin, 10 parts of PA6, 10 parts of compatibilizer, 1 part of antioxidant, and 1.5 parts of lubricant are melt-granulated in a twin-screw extruder to obtain EVOH gas barrier masterbatch. Step 2: Preparation of TPU self-healing masterbatch: S1. Dry the polyurethane elastomer and ethylene-vinyl alcohol copolymer at 80℃ for 9 hours; S2. Mix 55 parts by weight of ethylene-vinyl alcohol copolymer with 90 parts by weight of polyurethane elastomer evenly, then add 2 parts by weight of crosslinking agent, 3 parts by weight of coupling agent and 5.5 parts by weight of wear-resistant additive, stir and mix evenly at a stirring speed of 1600 rpm for 1.2 h to obtain the mixture. S3. Add the above mixture and 60 parts by weight of repair agent to a twin-screw extruder for melt granulation. The extrusion temperature of the twin-screw extruder is 180°C and the rotation speed is 150 rpm to obtain TPU self-healing masterbatch. Step 3: Using a three-layer co-extrusion casting process, the TPU inner layer material, EVOH gas barrier masterbatch, and TPU self-healing masterbatch are added to three independent extrusion channels of the casting equipment. Inside the die, the three melts flow in parallel at high temperature and are bonded layer by layer. After cooling and shaping by the casting rollers, a three-layer film structure is formed, consisting of a TPU inner layer, an EVOH gas barrier layer, and a TPU self-healing outer layer, resulting in an airtight TPU / EVOH composite material with a thickness of 0.25 mm. The TPU inner layer material is a polyether-type thermoplastic polyurethane elastomer from BASF, Germany, specifically the Elastollan model. ® SP 9630.

[0089] Example 2 An airtight TPU / EVOH composite material, comprising a TPU inner layer, an EVOH air barrier layer, and a TPU self-healing outer layer sequentially laminated together.

[0090] The TPU self-healing outer layer comprises the following raw materials in parts by weight: 80 parts of polyurethane elastomer 50 parts of ethylene-vinyl alcohol copolymer 50 parts of repair agent 1 part of dicumyl oxide crosslinking agent 1 part of KH-550 coupling agent 1 part alumina fiber wear-resistant additive; The repair agent comprises a dicyclopentadiene core, a polyurethane intermediate layer encapsulating the surface of the dicyclopentadiene core, and catalyst particles distributed on the surface of the polyurethane intermediate layer.

[0091] The polyurethane elastomer is a polyether-type thermoplastic polyurethane elastomer from BASF, Germany, model number Elastollan. ® SP 9630; the ethylene-vinyl alcohol copolymer is Kuraray EVOH.

[0092] The preparation method of the above-mentioned repair agent is as follows: Step 1: By weight, mix 100 parts of dicyclopentadiene with 2 parts of oil-soluble emulsifier Span 60 and stir until homogeneous. Stir at 600 rpm for 0.5 hours to form an oil phase. Step 2: Add 3 parts by weight of sodium dodecyl sulfate, an aqueous emulsifier, to 300 parts of deionized water, heat to 50°C and stir until homogeneous at 300 rpm for 20 minutes to form an aqueous phase. Step 3: Slowly add the oil phase prepared in Step 1 to the aqueous phase in Step 2, and emulsify under ultrasonic conditions to form an emulsion; wherein the dropping rate is 1 mL / min, the ultrasonic power is 600 W, and the emulsification temperature is 60℃. Step 4: Add 10 parts by weight of polyisocyanate monomer TDI and 8 parts by weight of polycaprolactone diol to the emulsion, control the reaction temperature at 40°C, react for 2 hours, cool to room temperature, and filter to obtain a repair agent intermediate with dicyclopentadiene as the core and polyurethane shell on the surface. Step 5: Disperse the repair agent intermediate prepared in step 4 in toluene inert solvent, add 1 part by weight of Grubbs catalyst particles, stir evenly at a stirring speed of 300 rpm for 0.5 h, filter, and obtain the above-mentioned repair agent.

[0093] The EVOH barrier layer comprises the following raw materials in parts by weight: 100 parts of EVOH resin PA6 5 portions 5 parts compatibilizer 0.5 parts antioxidant 0.5 parts of lubricant.

[0094] The compatibilizer is maleic anhydride-grafted ethylene-octene copolymer, supplied by ExxonMobil; the antioxidant is tris(2,4-di-tert-butylphenyl) phosphite; and the lubricant is glyceryl monostearate.

[0095] The preparation method of the above-mentioned airtight TPU / EVOH composite material includes the following preparation steps: Step 1: Preparation of EVOH gas barrier masterbatch: By weight, 100 parts of EVOH resin, 10 parts of PA6, 10 parts of compatibilizer, 1 part of antioxidant, and 1.5 parts of lubricant are melt-granulated in a twin-screw extruder to obtain EVOH gas barrier masterbatch; Step 2: Preparation of TPU self-healing masterbatch: S1. Dry the polyurethane elastomer and ethylene-vinyl alcohol copolymer at 70°C for 12 hours; S2. By weight, 50 parts of ethylene-vinyl alcohol copolymer and 80 parts of polyurethane elastomer are mixed evenly, then 1 part of crosslinking agent, 1 part of coupling agent and 1 part of wear-resistant additive are added, and the mixture is stirred evenly at a stirring speed of 1500 rpm for 1.5 hours to obtain the mixture. S3. Add the above mixture and 50 parts by weight of repair agent to a twin-screw extruder for melt granulation. The extrusion temperature of the twin-screw extruder is 160℃ and the speed is 200rpm to obtain TPU self-healing masterbatch. Step 3: Using a three-layer co-extrusion casting process, the TPU inner layer material, EVOH gas barrier masterbatch, and TPU self-healing masterbatch are added to three independent extrusion channels of the casting equipment. Inside the die, the three melts flow in parallel at high temperature and are bonded layer by layer. After cooling and shaping by the casting rollers, a three-layer film structure is formed, consisting of a TPU inner layer, an EVOH gas barrier layer, and a TPU self-healing outer layer, resulting in an airtight TPU / EVOH composite material with a thickness of 0.25 mm. The TPU inner layer material is a polyether-type thermoplastic polyurethane elastomer from BASF, Germany, specifically the Elastollan model. ® SP 9630.

[0096] Example 3 An airtight TPU / EVOH composite material, comprising a TPU inner layer, an EVOH air barrier layer, and a TPU self-healing outer layer sequentially laminated together.

[0097] The TPU self-healing outer layer comprises the following raw materials in parts by weight: 100 parts of polyurethane elastomer 60 parts of ethylene-vinyl alcohol copolymer 70 parts of repair agent 3 parts of dicumyl oxide crosslinking agent 5 parts of KH-550 coupling agent 10 parts of alumina fiber wear-resistant additive; The repair agent comprises a dicyclopentadiene core, a polyurethane intermediate layer encapsulating the surface of the dicyclopentadiene core, and catalyst particles distributed on the surface of the polyurethane intermediate layer.

[0098] The polyurethane elastomer is a polyether-type thermoplastic polyurethane elastomer from BASF, Germany, model number Elastollan. ® SP 9630; the ethylene-vinyl alcohol copolymer is Kuraray EVOH.

[0099] The preparation method of the above-mentioned repair agent is as follows: Step 1: By weight, mix 100 parts of dicyclopentadiene with 5 parts of oil-soluble emulsifier Span 80 and stir until homogeneous. Stir at 600 rpm for 0.5 hours to form an oil phase. Step 2: By weight, add 8 parts of water-based emulsifier hydroxyethyl cellulose to 600 parts of deionized water, heat to 70°C and stir evenly at a stirring speed of 300 rpm for 20 minutes to form an aqueous phase. Step 3: Slowly add the oil phase prepared in Step 1 to the aqueous phase in Step 2, and emulsify under ultrasonic conditions to form an emulsion; wherein the dropping rate is 1 mL / min, the ultrasonic power is 600 W, and the emulsification temperature is 60℃. Step 4: Add 30 parts by weight of polyisocyanate monomer MDI and 25 parts by weight of polyol polyethylene glycol to the emulsion, control the reaction temperature at 60°C, react for 6 hours, cool to room temperature, and filter to obtain a repair agent intermediate with dicyclopentadiene as the core and polyurethane shell on the surface. Step 5: Disperse the repair agent intermediate prepared in step 4 in toluene inert solvent, add 10 parts by weight of Grubbs catalyst particles, stir evenly at 300 rpm for 0.5 h, filter, and obtain the above-mentioned repair agent.

[0100] The EVOH barrier layer comprises the following raw materials in parts by weight: 100 parts of EVOH resin PA6 15 servings 15 parts compatibilizer 2 parts antioxidant 3 parts lubricant.

[0101] The compatibilizer is maleic anhydride-grafted ethylene-octene copolymer, supplied by ExxonMobil; the antioxidant is tris(2,4-di-tert-butylphenyl) phosphite; and the lubricant is glyceryl monostearate.

[0102] The preparation method of the above-mentioned airtight TPU / EVOH composite material includes the following preparation steps: Step 1: Preparation of EVOH gas barrier masterbatch: By weight, 100 parts of EVOH resin, 10 parts of PA6, 10 parts of compatibilizer, 1 part of antioxidant, and 1.5 parts of lubricant are melt-granulated in a twin-screw extruder to obtain EVOH gas barrier masterbatch. Step 2: Preparation of TPU self-healing masterbatch: S1. Dry the polyurethane elastomer and ethylene-vinyl alcohol copolymer at 90°C for 6 hours; S2. By weight, 60 parts of ethylene-vinyl alcohol copolymer and 100 parts of polyurethane elastomer are mixed evenly, then 3 parts of crosslinking agent, 5 parts of coupling agent and 10 parts of wear-resistant additive are added, and the mixture is stirred evenly at a stirring speed of 1800 rpm for 1 hour to obtain the mixture. S3. Add the above mixture and 70 parts by weight of repair agent to a twin-screw extruder for melt granulation. The extrusion temperature of the twin-screw extruder is 200℃ and the rotation speed is 100rpm to obtain TPU composite masterbatch. Step 3: Using a three-layer co-extrusion casting process, the TPU inner layer material, EVOH gas barrier masterbatch, and TPU self-healing masterbatch are added to three independent extrusion channels of the casting equipment. Inside the die, the three melts flow in parallel at high temperature and are bonded layer by layer. After cooling and shaping by the casting rollers, a three-layer film structure is formed, consisting of a TPU inner layer, an EVOH gas barrier layer, and a TPU self-healing outer layer, resulting in an airtight TPU / EVOH composite material with a thickness of 0.25 mm. The TPU inner layer material is a polyether-type thermoplastic polyurethane elastomer from BASF, Germany, specifically the Elastollan model. ® SP 9630.

[0103] Comparative Example 1 The difference between Comparative Example 1 and Example 1 lies in the TPU self-healing outer layer. The TPU self-healing outer layer of Comparative Example 1 comprises the following parts by weight of raw materials: 90 parts of polyurethane elastomer 55 parts of ethylene-vinyl alcohol copolymer 60 parts of repair agent 2 parts of dicumyl oxide crosslinking agent 3 parts of KH-550 coupling agent 5 parts of alumina fiber wear-resistant additive 5 parts of Grubbs catalyst particles; The repair agent comprises a dicyclopentadiene core and a polyurethane layer encapsulating the surface of the dicyclopentadiene core.

[0104] Compared with the preparation method of the repair agent in Example 1, the preparation method of the repair agent in Comparative Example 1 does not include step five. The other steps are the same as those in Example 1 and will not be described in detail here.

[0105] The preparation method of the TPU self-healing masterbatch in Comparative Example 1 is as follows: S1. Dry the polyurethane elastomer and ethylene-vinyl alcohol copolymer at 80℃ for 9 hours; S2. By weight, 55 parts of ethylene-vinyl alcohol copolymer and 90 parts of polyurethane elastomer are mixed evenly, then 2 parts of crosslinking agent, 3 parts of coupling agent and 5.5 parts of wear-resistant additive are added, and the mixture is stirred evenly at a stirring speed of 1600 rpm for 1.2 hours to obtain the mixture. S4. Add the above mixture, 60 parts by weight of repair agent, and 5 parts by weight of catalyst to a twin-screw extruder for melt granulation. The extrusion temperature of the twin-screw extruder is 180°C and the rotation speed is 150 rpm to obtain TPU self-healing masterbatch. The other preparation steps and process conditions of Comparative Example 1 are the same as those of Example 1, and will not be repeated here.

[0106] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that the TPU self-healing outer layer of Comparative Example 2 does not contain ethylene-vinyl alcohol copolymer, while other process conditions are the same as those of Example 1.

[0107] Comparative Example 3 The difference between Comparative Example 3 and Example 1 is that no crosslinking agent is added to the TPU self-healing outer layer of Comparative Example 3, while the rest is the same as Example 1.

[0108] Comparative Example 4 The difference between Comparative Example 4 and Example 1 is that no repair agent is added to the TPU self-healing outer layer in Comparative Example 4.

[0109] Performance testing The properties of the TPU composite materials prepared in the above embodiments and comparative examples were tested using the following methods: Tensile strength and elongation at break: tested according to the method of GB / T 528-2009; Oxygen permeability: tested according to the method of GB / T 1038-2000; Puncture resistance: Tested according to GB / T10004-2008, the force required to puncture the TPU composite film is determined under the conditions of a needle diameter of 1 mm and an advance speed of 50 mm / min; Self-healing performance: The TPU composite material was heat-sealed into a 10cm×10cm closed airbag with an inflation port. The PU layer was the inner layer and the self-healing layer was the outer layer. Air was filled in to a gauge pressure of 0.15 bar. The airbag was then completely immersed in 30℃ fresh water. After puncturing with a needle, it was observed whether there were continuous bubbles escaping and the time when the bubbles stopped was recorded.

[0110] Test Results Table:

[0111] The test results show that the TPU composite material prepared in Example 1 has good mechanical properties and puncture resistance, better gas leakage prevention or gas barrier properties, and can quickly achieve self-repair after puncture.

[0112] A comparison of Comparative Example 1 and Example 1 shows that the repair agent structure of the present invention is more conducive to improving the self-healing efficiency of TPU composite materials.

[0113] Comparing Comparative Example 2 with Example 1, it can be seen that the addition of ethylene-vinyl alcohol copolymer in this invention is more beneficial to improving the mechanical properties, puncture resistance and gas barrier properties of TPU composite materials.

[0114] Comparing Comparative Example 3 with Example 1, it can be seen that the addition of the crosslinking agent of the present invention can effectively improve the mechanical properties, puncture resistance and gas barrier properties of TPU composite materials.

[0115] A comparison of Comparative Example 4 and Example 1 shows that the addition of the repair agent of the present invention can achieve self-repair of TPU composite materials.

[0116] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. An airtight TPU / EVOH composite material, characterized in that, It consists of a TPU inner layer, an EVOH barrier layer, and a TPU self-healing outer layer, which are sequentially laminated.

2. The airtight TPU / EVOH composite material according to claim 1, characterized in that, The TPU self-healing outer layer comprises the following raw materials in parts by weight: 80-100 parts of polyurethane elastomer 50-60 parts of EVOH resin 50-70 parts of repair agent 1-3 parts crosslinking agent 1-5 parts of coupling agent 1-10 parts of wear-resistant additive; The repair agent comprises a dicyclopentadiene core, a polyurethane intermediate layer encapsulating the surface of the dicyclopentadiene core, and catalyst particles distributed on the surface of the polyurethane intermediate layer.

3. The airtight TPU / EVOH composite material according to claim 2, characterized in that, The polyurethane elastomer is a polyether-type thermoplastic polyurethane elastomer from BASF, Germany, model Elastollan. ® SP 9630.

4. The airtight TPU / EVOH composite material according to claim 2, characterized in that, The crosslinking agent includes at least one of dicumyl oxide, hexamethylene diisocyanate trimer, isophorone diisocyanate trimer, and 1,4-butanediol diglycidyl ether; and / or, the coupling agent includes at least one of γ-aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, isopropyltris(dioctylpyrophosphate)titanate, and distearate aluminate.

5. The airtight TPU / EVOH composite material according to claim 2, characterized in that, The wear-resistant additive includes at least one of alumina fiber, silica fiber, alumina particles, and silica particles.

6. The airtight TPU / EVOH composite material according to claim 1, characterized in that, The EVOH barrier layer comprises the following raw materials in parts by weight: 100 parts of EVOH resin PA6 5–15 servings 5–15 parts compatibilizer Antioxidant 0.5–2 parts Lubricant 0.5–3 parts.

7. The airtight TPU / EVOH composite material according to claim 6, characterized in that, The compatibilizer includes maleic anhydride grafted compatibilizers.

8. The airtight TPU / EVOH composite material according to claim 6, characterized in that, The antioxidant includes at least one of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], tris(2,4-di-tert-butylphenyl)phosphite, and dilauryl thiodipropionate.

9. The airtight TPU / EVOH composite material according to claim 6, characterized in that, The lubricant includes at least one of erucamide, oleamide, polyethylene wax, and glyceryl monostearate.

10. A method for preparing the airtight TPU / EVOH composite material according to any one of claims 1-9, characterized in that, The preparation steps include the following: Step 1: Preparation of EVOH gas barrier masterbatch: By weight, 100 parts of EVOH resin, 5-15 parts of PA6, 5-15 parts of compatibilizer, 0.5-2 parts of antioxidant, and 0.5-3 parts of lubricant are melt-granulated in a twin-screw extruder to obtain EVOH gas barrier masterbatch; Step 2: Preparation of TPU self-healing masterbatch: By weight, add 80-100 parts of polyurethane elastomer, 50-60 parts of EVOH resin, 50-70 parts of repair agent, 1-3 parts of crosslinking agent, 1-5 parts of coupling agent, and 1-10 parts of wear-resistant additive to a twin-screw extruder for melt granulation to obtain TPU self-healing masterbatch. Step 3: Using a three-layer co-extrusion casting process, the TPU inner layer raw material, EVOH gas barrier masterbatch, and TPU self-healing masterbatch are added to three independent extrusion channels of the casting equipment. Inside the die, the three melts flow in parallel at high temperature and are bonded layer by layer. After being cooled and shaped by the casting roller, a three-layer structure film composed of the TPU inner layer, the EVOH gas barrier layer, and the TPU self-healing outer layer is formed, resulting in an airtight TPU / EVOH composite material.

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