A high-barrier PEF composite material and its preparation method

Abstract

This invention belongs to the field of polymer materials technology, and specifically relates to a high-barrier PEF composite material and its preparation method. The composite material comprises the following components by weight fraction: 80-95 parts of PEF resin, 3-15 parts of barrier filler, 0.5-1.5 parts of epoxy chain extender, and 0.2-1 parts of antioxidant. The high-barrier PEF composite material of this invention achieves a comprehensive improvement in barrier properties, mechanical properties, and thermal stability through the composite of a high-purity PEF matrix and montmorillonite.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials technology, and specifically relates to a high-barrier PEF composite material and its preparation method. Background Technology

[0002] Polyethylene terephthalate (PET), a traditional petroleum-based polyester material, is widely used in food packaging, fibers, and engineering plastics. However, with the increasing depletion of global oil resources and the intensification of environmental problems, the development of renewable and biodegradable bio-based polymer materials has become a research hotspot in the field of polymer science. Polyethylene 2,5-furandicarboxylate (PEF) is a novel bio-based polyester synthesized from biomass-derived 2,5-furandicarboxylic acid (FDCA) and ethylene glycol. Its rigid furan ring in its molecular structure endows the material with excellent gas barrier properties, a high glass transition temperature, and mechanical strength, making it considered one of the ideal alternatives to PET. It shows broad application prospects in high-end food packaging, pharmaceutical packaging, and electronic device encapsulation.

[0003] Despite its numerous advantages, pure PEF resin still faces the following technical bottlenecks in practical applications: First, the rigidity of PEF molecular chains leads to high brittleness and low elongation at break, making it difficult to meet the toughness requirements of flexible packaging and engineering plastics. Second, PEF is prone to thermal and oxidative degradation during high-temperature processing, resulting in a decrease in molecular weight, deterioration of mechanical properties, and yellowing, which seriously affects the appearance and performance stability of the products. Third, although PEF has better gas barrier properties than PET, its barrier performance still needs further improvement for applications with high barrier requirements (such as carbonated beverage bottles and pesticide packaging).

[0004] Therefore, developing a PEF composite material that combines high barrier properties, excellent mechanical properties, and processing stability has become an urgent problem to be solved. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides a high-barrier PEF composite material and its preparation method. The high-barrier PEF composite material of this invention achieves a comprehensive improvement in barrier properties, mechanical properties, and thermal stability through the combination of a high-purity PEF matrix and montmorillonite.

[0006] The technical solution of the present invention to solve the above problems is as follows: A high-barrier PEF composite material comprises the following components by weight fraction: 80-95 parts of PEF resin, 3-15 parts of barrier filler, 0.5-1.5 parts of epoxy chain extender, and 0.2-1 parts of antioxidant; The preparation method of the PEF resin is as follows: Step a: Mix FDCA (2,5-furandicarboxylic acid) with methanol, add an acidic catalyst, stir and react at 65-70℃ for 3-6 hours. After the reaction is completed, recover methanol by vacuum distillation, and then perform two recrystallizations to purify and obtain dimethyl 2,5-furandicarboxylic acid. Step b: Mix the dimethyl 2,5-furandicarboxylate, ethylene glycol, and titanium-phosphorus composite catalytic system obtained in step a, and perform transesterification reaction at 180-200℃ for 2-3 hours under a nitrogen atmosphere. Then, raise the temperature to 220-240℃ and perform pre-condensation reaction at 1-5 kPa for 1-2 hours. Finally, perform vacuum condensation reaction at 250-265℃ and below 100 Pa for 3-5 hours to obtain PEF resin.

[0007] Preferably, in step a, the mass ratio of FDCA (2,5-furandicarboxylic acid), methanol, and concentrated sulfuric acid as an acidic catalyst is 100:200-400:0.5-1.

[0008] Preferably, in step b, the mass ratio of ethylene glycol to 2,5-furandicarboxylic acid and the titanium-phosphorus composite catalytic system in step a is 1.1-1.3:1:0.0003-0.0005, and the titanium-phosphorus composite catalytic system is a mixture of tetrabutyl titanate and triphenyl phosphite in a mass ratio of 1:0.5-1.0.

[0009] Preferably, the barrier filler is modified montmorillonite, and the preparation method of the modified montmorillonite is as follows: Step 1: Sodium-based montmorillonite is mixed with deionized water to prepare a homogeneous slurry. Hexadecyltrimethylammonium bromide is mixed with 1-hexadecyl-3-methylimidazolium chloride to prepare a composite aqueous solution. The pH is adjusted to 6.5-7.5 with acetic acid. The composite aqueous solution is added dropwise to the montmorillonite slurry. After the addition is complete, the temperature is raised to 75-85℃, and the reaction is stirred for 4-6 hours. After purification, synergistically modified montmorillonite is obtained. Step 2: Disperse the synergistically modified montmorillonite obtained in Step 1 in ethanol to obtain a dispersion, and then sonicate it at 250-300W for 20-40 minutes. Dissolve the silane coupling agent KH-550 in a mixed solvent of anhydrous ethanol and water, adjust the pH to 4.5-5.5 with acetic acid, and perform pre-hydrolysis by stirring at 30-40℃ for 30-45 minutes. Add the pre-hydrolyzed KH-550 solution dropwise to the dispersion at 30-40℃, and reflux the mixture at 75-80℃ for 5-6 hours. After post-treatment, the desired product is obtained.

[0010] Preferably, in step 1, the total mass ratio of sodium montmorillonite, deionized water, hexadecyltrimethylammonium bromide, and 1-hexadecyl-3-methylimidazole chloride is 1:15-25:0.15-0.22, the mass ratio of hexadecyltrimethylammonium bromide to 1-hexadecyl-3-methylimidazole chloride is 1.5-3:1, and the total concentration of hexadecyltrimethylammonium bromide and 1-hexadecyl-3-methylimidazole chloride in the composite aqueous solution is 8-12%.

[0011] Preferably, in step 2, the mass ratio of the synergistically modified montmorillonite and ethanol obtained in step 1 in the dispersion is 100:800-1200, the mass ratio of the synergistically modified montmorillonite and silane coupling agent KH-550 is 100:3-6, and during the pre-hydrolysis of the silane coupling agent, the mass ratio of silane coupling agent KH-550, ethanol and water is 1:4-6:0.8-1.2.

[0012] Preferably, the antioxidant is antioxidant 1010 and antioxidant 168 in a mass ratio of 1:0.5-1.

[0013] The preparation method of the above-mentioned high-barrier PEF composite material is as follows: Dry PEF resin, barrier filler, epoxy chain extender, and antioxidant are mixed. The mixture is then extruded using a twin-screw extruder. The temperatures are as follows: Zone 1 (feeding section): 190-200℃; Zone 2 (melting section): 220-230℃; Zone 3 (mixing section): 235-245℃; Zone 4 (homogenization section): 235-245℃; Zone 5 (die head): 230-240℃; and the screw speed is 250-300 rpm. The melt-blended material is then extruded, cooled, dried, and pelletized to obtain the final product.

[0014] The present invention has the following beneficial effects: This invention provides a high-performance composite material based on bio-based polyethylene 2,5-furandicarboxylate (PEF), which possesses excellent gas barrier properties, good mechanical properties, and processing stability. In the PEF preparation process, step a involves a two-stage recrystallization process with strict control of the cooling rate and washing conditions, significantly improving the purity and chemical homogeneity of the key monomer, dimethyl 2,5-furandicarboxylate. The first recrystallization uses a high ethanol / water ratio of 80-90:10-20, effectively removing polar impurities using the principle of "like dissolves like." The second recrystallization is adjusted to 70-75:25-30, increasing the crystallization yield by reducing solubility and further purifying the material. Slow cooling to 50°C at 0.5°C / min, followed by rapid cooling in an ice-water bath, yields crystals with complete crystalline structure and higher purity, avoiding impurity inclusion. This lays a solid foundation for subsequent polycondensation reactions to obtain high-molecular-weight, high-quality PEF resin, avoiding side reactions and molecular chain defects caused by impurities. Step b employs a stepwise melt polycondensation process combined with a titanium-phosphorus composite catalytic system. The composite catalyst (tetrabutyl titanate / triphenyl phosphite) combines high catalytic activity with the inhibition of side reactions (such as ether bond formation and thermal degradation). A mass ratio of 1:0.5-1.0 achieves the optimal balance between activity and stability. Simultaneously, the purification of dimethyl 2,5-furandicarboxylate and the introduction of a phosphorus-based stabilizer effectively suppress yellowing during PEF thermal processing, broadening its application in the transparent packaging field.

[0015] The modification of montmorillonite involves two steps: First, the synergistic effect of hexadecyltrimethylammonium bromide (CTAB) and 1-hexadecyl-3-methylimidazolium chloride effectively widens the interlayer spacing of montmorillonite (more effectively than a single intercalating agent, creating space for subsequent polymer intercalation and exfoliation), and improves its wettability and dispersibility in PEF melt. Imidazole-based ionic liquids have higher thermal decomposition temperatures, enabling the modified montmorillonite to withstand the high temperatures of 235-245℃ during PEF processing, preventing lamination collapse caused by intercalating agent decomposition. Second, surface grafting introduces organic functional groups onto the surface of the montmorillonite sheets using the silane coupling agent KH-550, creating "molecular bridges" between the inorganic filler and organic resin, significantly enhancing interfacial adhesion. Silane modification reduces the surface energy of montmorillonite, improves wettability with the PEF polyester matrix, reduces filler agglomeration, achieves nanoscale dispersion, and inhibits nanosheet agglomeration. Modified montmorillonite, with its uniformly dispersed nanosheets, can form "zigzag paths" within the PEF matrix, significantly increasing resistance to gas diffusion and dramatically improving the material's barrier properties. Excellent interfacial bonding effectively transfers stress, enabling montmorillonite to act as a "nano-reinforcement," enhancing the material's tensile strength, modulus, and dimensional stability. Modified montmorillonite itself possesses high thermal stability; its layered structure acts as a physical barrier, delaying heat transfer to the polymer interior and improving the composite material's thermal decomposition temperature and dimensional stability.

[0016] Modified montmorillonite forms a two-dimensional nanobarrier within the PEF matrix, forcing gas molecules to bypass it and extending the permeation path. The interaction between modified montmorillonite and the PEF molecular chains restricts the movement of polyester chain segments, reducing the gas diffusion coefficient. The chemical interface established by the silane coupling agent effectively transfers external loads from the PEF matrix to the rigid montmorillonite sheets, increasing the elastic modulus. The montmorillonite sheets can deflect or inhibit crack propagation, improving material toughness and overcoming the brittleness of pure PEF. The filler also reduces the molding shrinkage and coefficient of thermal expansion of PEF, improving the dimensional accuracy of the finished product. The thermal stability of modified montmorillonite, synergistically with phosphorus-based stabilizers, effectively protects the molecular chain integrity of PEF during high-temperature processing.

[0017] In summary, the high-barrier PEF composite material of the present invention achieves a comprehensive improvement in barrier properties, mechanical properties, and thermal stability through the combination of a high-purity PEF matrix and montmorillonite. Attached Figure Description

[0018] Figure 1 The oxygen permeability test results of the composite materials obtained in Examples 1-3 and Comparative Examples 1-3 are shown. Figure 2 The composite materials obtained in Examples 1-3 and Comparative Examples 1-3 are the results of water vapor transmission rate tests; Figure 3The composite materials obtained in Examples 1-3 and Comparative Examples 1-3 are the results of tensile strength tests; Figure 4 The composite materials obtained in Examples 1-3 and Comparative Examples 1-3 are the results of the elongation at break test. Detailed Implementation

[0019] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0020] All of the following raw materials are commercially available.

[0021] Epoxy chain extender, model 4468, active ingredient content 98%, brand BASF; acid catalyst is 98% concentrated sulfuric acid; sodium montmorillonite, white in color, density 2.6 g / cm³, Lingshou Yongzhuo New Material Technology Co., Ltd.; acetic acid is 8% (v / v) acetic acid solution.

[0022] Example 1 A high-barrier PEF composite material comprises the following components by weight: 90 parts PEF resin, 8 parts barrier filler, 1 part epoxy chain extender, and 0.6 parts antioxidant. The preparation method of the PEF resin is as follows: Step a: Mix FDCA (2,5-furandicarboxylic acid) with methanol, add concentrated sulfuric acid as an acidic catalyst, and stir at 68°C for 4 hours. After the reaction is complete, recover methanol by vacuum distillation, and then perform two recrystallizations. Specifically: Add the obtained crude product to a mixed solvent of ethanol and water in a mass ratio of 85:15 (6 times its mass), set up a reflux condenser, introduce cooling water, maintain a water bath temperature of 80°C, and stir under reflux until the solid is completely dissolved. Filter the above hot solution through a preheated Buchner funnel to remove insoluble impurities. The resulting clear hot filtrate is then treated with 0... The temperature was lowered to 50℃ at a rate of 0.5℃ / min, and then cooled in an ice-water bath at 3℃ to allow dimethyl 2,5-furandicarboxylate to crystallize out. The crystals were filtered and washed with ice water at 0-5℃ and an 8% ethanol aqueous solution at 0-5℃ until the filtrate was colorless. Then, the crystals were vacuum dried at 55℃ for 9 hours. The dried material was then added back into a mixed solvent of 6 times the volume of ethanol and water at a mass ratio of 75:25, and the above process of dissolution, filtration, cooling, recrystallization, filtration, washing, and drying (i.e., secondary recrystallization) was repeated to obtain dimethyl 2,5-furandicarboxylate. In step a, the mass ratio of FDCA (2,5-furandicarboxylic acid), methanol, and concentrated sulfuric acid as an acidic catalyst is 100:300:0.8.

[0023] Step b involves mixing dimethyl 2,5-furandicarboxylate, ethylene glycol, and the titanium-phosphorus composite catalytic system obtained in step a. Under a nitrogen atmosphere, the mixture undergoes an ester exchange reaction at 190°C for 2.5 hours. The temperature is then raised to 230°C, and a pre-condensation reaction is carried out at 3 kPa for 1.5 hours. Finally, a vacuum condensation reaction is performed at 255°C and below 100 Pa for 4 hours. The mixture is then slowly pressurized to atmospheric pressure using nitrogen, and the molten polymer is extruded, cooled in a water bath, dried, and then pelletized to obtain PEF resin. In step b, the mass ratio of ethylene glycol to the 2,5-furandicarboxylate and titanium-phosphorus composite catalytic system in step a is 1.2:1:0.0004. The titanium-phosphorus composite catalytic system is a mixture of tetrabutyl titanate and triphenyl phosphite in a mass ratio of 1:0.8.

[0024] The barrier filler is modified montmorillonite, and the preparation method of the modified montmorillonite is as follows: Step 1: Sodium montmorillonite was mixed with deionized water and stirred at 70°C and 700 rpm for 2.5 hours to obtain a homogeneous slurry. Hexadecyltrimethylammonium bromide and 1-hexadecyl-3-methylimidazolium chloride were mixed to prepare a composite aqueous solution. The pH was adjusted to 6.5-7.5 with acetic acid. The composite aqueous solution was added dropwise to the montmorillonite slurry at a rate of 2.5 mL / min. After the addition was complete, the temperature was raised to 80°C, and the reaction was stirred for 5 hours. After the reaction was completed, the mixture was hot-filtered and washed with 65°C hot deionized water until the filtrate was 0.1 mol / L. No precipitate was detected by AgNO3 solution. The filter cake was vacuum dried at 80℃ for 11 hours to obtain synergistically modified montmorillonite. In step 1, the total mass ratio of sodium-based montmorillonite, deionized water, hexadecyltrimethylammonium bromide, and 1-hexadecyl-3-methylimidazole chloride was 1:20:0.2, the mass ratio of hexadecyltrimethylammonium bromide to 1-hexadecyl-3-methylimidazole chloride was 2:1, and the total concentration of hexadecyltrimethylammonium bromide and 1-hexadecyl-3-methylimidazole chloride in the composite aqueous solution was 10%. Step 2: Disperse the synergistically modified montmorillonite obtained in Step 1 in ethanol to obtain a dispersion, and then sonicate it at 280W for 30 min. Dissolve the silane coupling agent KH-550 in a mixed solvent of anhydrous ethanol and water, adjust the pH to 4.5-5.5 with acetic acid, and stir at 35℃ for 40 min for pre-hydrolysis (use within 5-10 minutes after pre-hydrolysis). At 35℃, add the pre-hydrolyzed KH-550 solution dropwise to the dispersion at 1.5 mL / min, and stir at 78℃. The reaction was carried out for 5.5 hours; cooled to room temperature, filtered, washed 4 times with anhydrous ethanol, dried under vacuum at 68°C for 14 hours, ground and sieved (200 mesh) to obtain the product; in step 2, the mass ratio of the synergistic modified montmorillonite and ethanol obtained in step 1 in the dispersion is 100:1000, the mass ratio of the synergistic modified montmorillonite and silane coupling agent KH-550 is 100:4, and in the pre-hydrolysis process of the silane coupling agent, the mass ratio of silane coupling agent KH-550, ethanol and water is 1:5:1.

[0025] The preparation method of the above-mentioned high-barrier PEF composite material is as follows: Dry PEF resin, barrier filler, epoxy chain extender, and antioxidant are mixed and extruded using a twin-screw extruder. The temperatures are as follows: Zone 1 (feeding section): 195℃; Zone 2 (melting section): 225℃; Zone 3 (mixing section): 240℃; Zone 4 (homogenization section): 245℃; Zone 5 (die head): 235℃; and the screw speed is 280 rpm. The melt-blended material is then extruded, cooled, dried, and pelletized to obtain the final product.

[0026] Example 2 A high-barrier PEF composite material comprises the following components by weight fraction: 80 parts PEF resin, 15 parts barrier filler, 0.5 parts epoxy chain extender, and 1 part antioxidant. The preparation method of the PEF resin is as follows: Step a: FDCA (2,5-furandicarboxylic acid) is mixed with methanol, and concentrated sulfuric acid, an acidic catalyst, is added. The mixture is stirred at 65°C for 6 hours. After the reaction is completed, methanol is recovered by vacuum distillation, and then recrystallization is performed twice (specifically as in Example 1) to obtain dimethyl 2,5-furandicarboxylic acid. In step a, the mass ratio of FDCA (2,5-furandicarboxylic acid), methanol, and concentrated sulfuric acid, an acidic catalyst, is 100:200:1. Step b involves mixing dimethyl 2,5-furandicarboxylate, ethylene glycol, and the titanium-phosphorus composite catalytic system obtained in step a. Under a nitrogen atmosphere and at 200°C, a transesterification reaction is carried out for 2 hours. The temperature is then raised to 240°C, and a pre-condensation reaction is performed at 1 kPa for 2 hours. Following this, a vacuum condensation reaction is carried out at 250°C and below 100 Pa for 5 hours. The mixture is then slowly pressurized to atmospheric pressure using nitrogen, and the molten polymer is extruded, cooled in a water bath, dried, and then pelletized in a pelletizer to obtain PEF resin. In step b, the mass ratio of ethylene glycol to the 2,5-furandicarboxylate and titanium-phosphorus composite catalytic system in step a is 1.1:1:0.0005. The titanium-phosphorus composite catalytic system is a mixture of tetrabutyl titanate and triphenyl phosphite in a mass ratio of 1:0.5.

[0027] The barrier filler is modified montmorillonite, and the preparation method of the modified montmorillonite is as follows: Step 1: Sodium-based montmorillonite is mixed with deionized water and stirred at 65°C and 800 rpm for 2 hours to obtain a homogeneous slurry. Hexadecyltrimethylammonium bromide and 1-hexadecyl-3-methylimidazolium chloride are mixed to prepare a composite aqueous solution. The pH is adjusted to 6.5-7.5 with acetic acid. The composite aqueous solution is added dropwise to the montmorillonite slurry at a rate of 3 mL / min. After the addition is complete, the temperature is raised to 75°C, and the reaction is stirred for 6 hours. After the reaction is complete, the mixture is hot-filtered and washed with 60°C hot deionized water until the filtrate has a concentration of 0.1 mol / L. No precipitate was detected by AgNO3 solution. The filter cake was vacuum dried at 85℃ for 10 hours to obtain synergistically modified montmorillonite. In step 1, the total mass ratio of sodium-based montmorillonite, deionized water, hexadecyltrimethylammonium bromide, and 1-hexadecyl-3-methylimidazole chloride was 1:15:0.22, the mass ratio of hexadecyltrimethylammonium bromide to 1-hexadecyl-3-methylimidazole chloride was 1.5:1, and the total concentration of hexadecyltrimethylammonium bromide and 1-hexadecyl-3-methylimidazole chloride in the composite aqueous solution was 12%. Step 2: Disperse the synergistically modified montmorillonite obtained in Step 1 in ethanol to obtain a dispersion, and then sonicate it at 250W for 40 min. Dissolve the silane coupling agent KH-550 in a mixed solvent of anhydrous ethanol and water, adjust the pH to 4.5-5.5 with acetic acid, and pre-hydrolyze it by stirring at 30℃ for 45 min (use within 5-10 minutes after pre-hydrolysis). At 30℃, add the pre-hydrolyzed KH-550 solution dropwise to the dispersion at 1 mL / min, and reflux at 80℃. The reaction was carried out for 6 hours; cooled to room temperature, filtered, washed 3 times with anhydrous ethanol, dried under vacuum at 75°C for 12 hours, ground and sieved (200 mesh) to obtain the product; in step 2, the mass ratio of the synergistic modified montmorillonite and ethanol obtained in step 1 in the dispersion was 100:1200, the mass ratio of the synergistic modified montmorillonite and silane coupling agent KH-550 was 100:6, and during the pre-hydrolysis of the silane coupling agent, the mass ratio of silane coupling agent KH-550, ethanol and water was 1:6:0.8.

[0028] The preparation method of the above-mentioned high-barrier PEF composite material is the same as that in Example 1.

[0029] Example 3 A high-barrier PEF composite material comprises the following components by weight: 95 parts PEF resin, 3 parts barrier filler, 1.5 parts epoxy chain extender, and 0.2 parts antioxidant; The preparation method of the PEF resin is as follows: Step a: FDCA (2,5-furandicarboxylic acid) is mixed with methanol, and concentrated sulfuric acid, an acidic catalyst, is added. The mixture is stirred at 70°C for 3 hours. After the reaction is complete, methanol is recovered by vacuum distillation, and then recrystallization is performed twice (specifically as in Example 1) to obtain dimethyl 2,5-furandicarboxylic acid. In step a, the mass ratio of FDCA (2,5-furandicarboxylic acid), methanol, and concentrated sulfuric acid, an acidic catalyst, is 100:400:0.5. Step b involves mixing dimethyl 2,5-furandicarboxylate, ethylene glycol, and the titanium-phosphorus composite catalytic system obtained in step a. Under a nitrogen atmosphere, the mixture undergoes an ester exchange reaction at 180°C for 3 hours. The temperature is then raised to 220°C, and a pre-condensation reaction is carried out at 5 kPa for 1 hour. Following this, a vacuum condensation reaction is performed at 265°C and below 100 Pa for 3 hours. The mixture is then slowly pressurized to atmospheric pressure using nitrogen, and the molten polymer is extruded, cooled in a water bath, dried, and then pelletized in a pelletizer to obtain PEF resin. In step b, the mass ratio of ethylene glycol to the 2,5-furandicarboxylate and titanium-phosphorus composite catalytic system in step a is 1.3:1:0.0003. The titanium-phosphorus composite catalytic system is a mixture of tetrabutyl titanate and triphenyl phosphite in a mass ratio of 1:1.0.

[0030] The barrier filler is modified montmorillonite, and the preparation method of the modified montmorillonite is as follows: Step 1: Sodium-based montmorillonite is mixed with deionized water and stirred at 75°C and 600 rpm for 3 hours to obtain a homogeneous slurry. Hexadecyltrimethylammonium bromide and 1-hexadecyl-3-methylimidazolium chloride are mixed to prepare a composite aqueous solution. The pH is adjusted to 6.5-7.5 with acetic acid. The composite aqueous solution is added dropwise to the montmorillonite slurry at a rate of 2 mL / min. After the addition is complete, the temperature is raised to 85°C, and the reaction is stirred for 4 hours. After the reaction is complete, the mixture is hot-filtered and washed with 70°C hot deionized water until the filtrate has a concentration of 0.1 mol / L. No precipitate was detected by AgNO3 solution. The filter cake was vacuum dried at 75℃ for 12 hours to obtain synergistically modified montmorillonite. In step 1, the total mass ratio of sodium-based montmorillonite, deionized water, hexadecyltrimethylammonium bromide, and 1-hexadecyl-3-methylimidazole chloride was 1:25:0.15, the mass ratio of hexadecyltrimethylammonium bromide to 1-hexadecyl-3-methylimidazole chloride was 3:1, and the total concentration of hexadecyltrimethylammonium bromide and 1-hexadecyl-3-methylimidazole chloride in the composite aqueous solution was 8%. Step 2: Disperse the synergistically modified montmorillonite obtained in Step 1 in ethanol to obtain a dispersion, and then sonicate it at 300W for 20 min. Dissolve the silane coupling agent KH-550 in a mixed solvent of anhydrous ethanol and water, adjust the pH to 4.5-5.5 with acetic acid, and pre-hydrolyze it by stirring at 40℃ for 30 min (use within 5-10 minutes after pre-hydrolysis). At 40℃, add the pre-hydrolyzed KH-550 solution dropwise to the dispersion at 2 mL / min, and reflux at 75℃. The reaction was carried out for 5 hours; cooled to room temperature, filtered, washed 5 times with anhydrous ethanol, dried under vacuum at 60°C for 16 hours, ground and sieved (200 mesh) to obtain the product; in step 2, the mass ratio of the synergistic modified montmorillonite and ethanol obtained in step 1 in the dispersion was 100:800, the mass ratio of the synergistic modified montmorillonite and silane coupling agent KH-550 was 100:3, and during the pre-hydrolysis of the silane coupling agent, the mass ratio of silane coupling agent KH-550, ethanol and water was 1:4:1.2.

[0031] The preparation method of the above-mentioned high-barrier PEF composite material is the same as that in Example 1.

[0032] Comparative Example 1 A high-barrier PEF composite material, wherein the PEF resin is prepared by the following method: Step a: Mix FDCA (2,5-furandicarboxylic acid) with methanol, add concentrated sulfuric acid as an acidic catalyst, and stir at 68°C for 4 hours. After the reaction is complete, recover methanol by vacuum distillation, and then perform a recrystallization. Specifically, add the crude product to a mixed solvent of ethanol and water in a mass ratio of 85:15 (6 times the mass of the original product). Set up a reflux condenser, introduce cooling water, and maintain a water bath temperature of 80°C. Stir under reflux until the solid is completely dissolved. Filter the hot solution through a preheated Buchner funnel to remove insoluble impurities. Cool the clear hot filtrate to 50°C at a rate of 0.5°C / min, and then cool it in an ice-water bath at 3°C ​​to allow dimethyl 2,5-furandicarboxylic acid (2,5-furandicarboxylic acid dimethyl ester) to crystallize out. Filter the crystals and wash them with ice water at 0-5°C and an 8% ethanol aqueous solution at 0-5°C until the filtrate is colorless. Then, dry the crystals under vacuum at 55°C for 9 hours to obtain dimethyl 2,5-furandicarboxylic acid. The rest is the same as in Example 1.

[0033] Comparative Example 2 A high-barrier PEF composite material, wherein in the preparation of PEF resin, in step b, only tetrabutyl titanate is used as a catalyst, the amount of which is 0.03% of the mass of FDCA, and triphenyl phosphite is not added, the rest is the same as in Example 1.

[0034] Comparative Example 3 A high-barrier PEF composite material, wherein the filler is modified montmorillonite, and the modified montmorillonite is prepared by mixing sodium-based montmorillonite with deionized water and stirring at 70°C and 700 rpm for 2.5 hours to obtain a uniform slurry. Hexadecyltrimethylammonium bromide aqueous solution is adjusted to pH 6.5-7.5 with acetic acid and added dropwise to the montmorillonite slurry at a rate of 2.5 mL / min. After the addition is complete, the temperature is raised to 80°C and the reaction is stirred for 5 hours. After the reaction is complete, the mixture is hot-filtered and washed with hot deionized water at 65°C until no precipitate is detected by 0.1 mol / L AgNO3 solution. The filter cake is vacuum-dried at 80°C for 11 hours to obtain modified montmorillonite. The mass ratio of sodium-based montmorillonite, deionized water, and hexadecyltrimethylammonium bromide is 1:20:0.2, and the concentration of the hexadecyltrimethylammonium bromide aqueous solution is 10%.

[0035] The rest is the same as in Example 1.

[0036] Performance testing: The high-barrier PEF composite particles obtained in Examples 1-3 and Comparative Examples 1-3 were vacuum dried at 80°C for 6 hours until the moisture content was <0.02%, and then cast into a film. The process parameters were: feeding section 195°C, compression section 225°C, metering section 240°C, die head 245°C, cooling roller temperature 45°C, and traction speed 6 m / min, resulting in a transparent film with a thickness of 0.20 ± 0.02 mm. The obtained film was then subjected to performance tests. Oxygen permeability was analyzed and tested according to the method of GB / T1038-2000 "Gas Permeability Test Method for Plastic Films and Sheets - Differential Pressure Method"; water vapor permeability was analyzed and tested according to the method of GB / T1037-2021 "Determination of Water Vapor Permeability of Plastic Films and Sheets - Cup Weight Gain and Loss Method". Tensile properties were determined according to GB / T 1040.3-2006 "Determination of Tensile Properties of Plastics - Part 3: Test Conditions for Films and Sheets".

[0037] Table 1. Test Results From Table 1, Figures 1-4 As can be seen, the composite materials obtained in Examples 1-3 of this invention exhibit excellent and balanced performance, with improved barrier properties and mechanical properties. While enhancing barrier properties, these composite materials maintain excellent tensile strength and elongation at break, overcoming the common "high strength, low toughness" defect of highly filled composite materials, achieving a balance between rigidity and toughness, and greatly expanding their application potential. The oxygen permeability and water vapor permeability of the examples are both at extremely low levels, indicating that the material has excellent barrier properties. This is mainly due to the modified montmorillonite filler used, which, through double intercalation modification and silane coupling agent surface treatment, achieves nanoscale dispersion, forming an effective "maze effect" in the PEF matrix, significantly extending the gas permeation path. Furthermore, the synergistic modification of ionic liquid and silane coupling agent in the modified montmorillonite filler not only significantly improves the dispersibility and compatibility of the nanofiller in the polymer matrix, forming a highly efficient and stable nanocomposite structure, but also greatly enhances the barrier properties. The tensile strength of the examples is at a high level, which is due to the double recrystallization and titanium-phosphorus composite catalytic system used in the synthesis of PEF resin in this invention, which significantly improves the purity and molecular weight of the resin matrix, laying the foundation for the excellent mechanical properties and good processability of the material. The modified montmorillonite has a good interface with the PEF matrix, which can effectively transfer stress and improve mechanical properties. In contrast, the tensile strength and elongation at break of the comparative examples are significantly reduced, especially the comparative example using a single titanium catalyst, which shows obvious brittleness due to the decrease in molecular weight caused by thermal degradation. The barrier properties of the three comparative examples are significantly worse than those of the examples, with the comparative examples using single recrystallization and a single catalyst showing the worst barrier properties, demonstrating the key role of raw material purity and catalytic system in polymer densification.

[0038] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0039] Although embodiments of this application have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of this application, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A high-barrier PEF composite material, characterized in that, The composition by weight fraction includes the following components: 80-95 parts PEF resin, 3-15 parts barrier filler, 0.5-1.5 parts epoxy chain extender, and 0.2-1 parts antioxidant. The preparation method of the PEF resin is as follows: Step a: Mix FDCA with methanol, add an acidic catalyst, stir and react at 65-70℃ for 3-6 hours. After the reaction is complete, recover methanol by vacuum distillation, then recrystallize twice and purify to obtain dimethyl 2,5-furandicarboxylate. Step b: Mix the dimethyl 2,5-furandicarboxylate, ethylene glycol, and titanium-phosphorus composite catalytic system obtained in step a, and perform transesterification reaction at 180-200℃ for 2-3 hours under a nitrogen atmosphere. Then, raise the temperature to 220-240℃ and perform pre-condensation reaction at 1-5 kPa for 1-2 hours. Finally, perform vacuum condensation reaction at 250-265℃ and below 100 Pa for 3-5 hours to obtain PEF resin.

2. The high-barrier PEF composite material according to claim 1, characterized in that, In step a, the mass ratio of FDCA, methanol, and acid catalyst is 100:200-400:0.5-1.

3. The high-barrier PEF composite material according to claim 1, characterized in that, In step b, the mass ratio of ethylene glycol to 2,5-furandicarboxylic acid and the titanium-phosphorus composite catalytic system in step a is 1.1-1.3:1:0.0003-0.0005. The titanium-phosphorus composite catalytic system is a mixture of tetrabutyl titanate and triphenyl phosphite in a mass ratio of 1:0.5-1.

0.

4. The high-barrier PEF composite material according to claim 1, characterized in that, The barrier filler is modified montmorillonite, and the preparation method of the modified montmorillonite is as follows: Step 1: Sodium-based montmorillonite is mixed with deionized water to prepare a homogeneous slurry. Hexadecyltrimethylammonium bromide is mixed with 1-hexadecyl-3-methylimidazolium chloride to prepare a composite aqueous solution. The pH is adjusted to 6.5-7.5 with acetic acid. The composite aqueous solution is added dropwise to the montmorillonite slurry. After the addition is complete, the temperature is raised to 75-85℃, and the reaction is stirred for 4-6 hours. After purification, synergistically modified montmorillonite is obtained. Step 2: Disperse the synergistically modified montmorillonite obtained in Step 1 in ethanol to obtain a dispersion, and then sonicate it at 250-300W for 20-40 minutes. Dissolve the silane coupling agent KH-550 in a mixed solvent of anhydrous ethanol and water, adjust the pH to 4.5-5.5 with acetic acid, and perform pre-hydrolysis by stirring at 30-40℃ for 30-45 minutes. Add the pre-hydrolyzed KH-550 solution dropwise to the dispersion at 30-40℃, and reflux the mixture at 75-80℃ for 5-6 hours. After post-treatment, the desired product is obtained.

5. The high-barrier PEF composite material according to claim 4, characterized in that, In step 1, the total mass ratio of sodium montmorillonite, deionized water, hexadecyltrimethylammonium bromide, and 1-hexadecyl-3-methylimidazole chloride is 1:15-25:0.15-0.22, the mass ratio of hexadecyltrimethylammonium bromide to 1-hexadecyl-3-methylimidazole chloride is 1.5-3:1, and the total concentration of hexadecyltrimethylammonium bromide and 1-hexadecyl-3-methylimidazole chloride in the composite aqueous solution is 8-12%.

6. The high-barrier PEF composite material according to claim 4, characterized in that, In step 2, the mass ratio of the synergistic modified montmorillonite and ethanol obtained in step 1 in the dispersion is 100:800-1200, the mass ratio of the synergistic modified montmorillonite and silane coupling agent KH-550 is 100:3-6, and during the pre-hydrolysis of the silane coupling agent, the mass ratio of silane coupling agent KH-550, ethanol and water is 1:4-6:0.8-1.

2.

7. The high-barrier PEF composite material according to claim 1, characterized in that, The antioxidants are antioxidant 1010 and antioxidant 168 in a mass ratio of 1:0.5-1.

8. The method for preparing the high-barrier PEF composite material according to any one of claims 1-7, characterized in that, Specifically: Dry PEF resin, barrier filler, epoxy chain extender, and antioxidant are mixed. The mixture is then extruded using a twin-screw extruder. The temperatures are as follows: feeding section: 190-200℃, melting section: 220-230℃, mixing section: 235-245℃, homogenization section: 235-245℃, die head: 230-240℃, screw speed: 250-300 rpm. The melt-blended material is then extruded, cooled, dried, and pelletized to obtain the final product.

Images