A polyester composite film and a method for manufacturing the same

Abstract

This invention discloses a polyester composite film and its preparation method. The polyester composite film comprises at least, in sequence, a polyester base layer, a high-strength functional layer, and a heat-sealing layer. The base layer and the high-strength functional layer, and the high-strength functional layer and the heat-sealing layer, are bonded together by an adhesive layer. This polyester composite film, by combining a specific polyester base layer, a specially formulated high-strength functional layer, and a universal heat-sealing layer through a dry lamination process, achieves a composite film that maintains good heat-sealing and printability. Furthermore, its core mechanical properties, particularly tensile strength, elastic modulus, and puncture resistance, are significantly improved compared to traditional polyester films or simple blended modified films, better meeting the application requirements of modern packaging fields for high strength, lightweight, and high reliability of materials.

Description

Technical Field

[0001] This invention belongs to the field of composite film materials technology, specifically relating to a polyester composite film and its preparation method. Background Technology

[0002] Polyester film, especially polyethylene terephthalate (PET) film, has become one of the most widely used polymer film materials due to its excellent comprehensive properties, such as high mechanical strength, good chemical stability and heat resistance, excellent electrical insulation, high transparency and gloss. In the packaging field, biaxially oriented polyethylene terephthalate (BOPET) film is often used as a printing layer or composite substrate for packaging products such as food, pharmaceuticals, and daily chemical products. Furthermore, polyester film also plays an indispensable role in the electronics, photographic film, magnetic recording, and photovoltaic industries.

[0003] However, with the rapid development of modern industry and consumer markets, the performance requirements for film materials are becoming increasingly stringent. In applications such as high-end packaging and specialized industries, traditional pure polyester film is gradually revealing its inherent performance bottlenecks. Its main shortcomings are: although its tensile strength is relatively high, its rigidity (Young's modulus), puncture resistance, and tear resistance still need improvement when facing more severe mechanical challenges. For example, in industrial applications used for packaging heavy goods or requiring exposure to complex stress environments, traditional polyester film may break due to insufficient strength, failing to provide reliable protection for the contents. Furthermore, on high-speed automated packaging lines, insufficient film rigidity can also lead to problems such as vibration, wrinkles, or dimensional instability during processing, affecting production efficiency and product yield.

[0004] To overcome the aforementioned shortcomings, those skilled in the art have conducted extensive research and experimentation, primarily through physical blending or the addition of fillers to reinforce and modify polyester films. A common technique involves adding inorganic rigid particles, such as nano-silica, calcium carbonate, or talc, to the polyester matrix to improve the modulus and hardness of the composite material. Another approach is to use melt blending to mix other types of high-performance polymers with polyester to obtain composite materials with complementary properties. These methods have indeed been able to improve certain mechanical properties of polyester films to some extent.

[0005] However, the aforementioned existing technologies still have significant technical drawbacks. When adding inorganic rigid particles, the interfacial compatibility between the conventional inorganic particles (which are typically hydrophilic) and the polyester matrix (which is hydrophobic) is extremely poor. This makes it difficult for the particles to achieve uniform nanoscale dispersion within the polyester matrix, and instead, they easily form micron-sized agglomerates. These agglomerates not only fail to effectively bear and transfer stress, but also become stress concentration points within the material, causing a severe decline in key properties such as toughness and elongation at break of the composite film, even leading to brittleness and a decrease in overall mechanical properties. While melt blending modification can improve certain properties, it is often difficult to achieve a simultaneous and significant improvement in multiple performance indicators. Sometimes, compatibility issues can also lead to material delamination, limiting its application range.

[0006] Therefore, developing a new technology that can significantly and evenly improve the comprehensive mechanical properties of polyester film while maintaining its original advantages, and at the same time ensure material uniformity and processing stability, is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the present invention aims to provide a polyester composite film and its preparation method.

[0008] To achieve the above objectives, the present invention provides the following technical solution: A polyester composite film, comprising at least in sequence: a polyester base layer, a high-strength functional layer, and a heat-sealing layer, wherein the base layer and the high-strength functional layer, and the high-strength functional layer and the heat-sealing layer are bonded together by an adhesive layer.

[0009] Preferably, the polyester substrate layer is a biaxially oriented polyethylene terephthalate film or a polybutylene terephthalate film.

[0010] Preferably, the heat-sealing layer is a cast polypropylene film or a linear low-density polyethylene film; the adhesive is a polyurethane adhesive.

[0011] Preferably, the high-strength functional layer comprises the following raw materials in parts by weight: 80-90 parts of polyethylene terephthalate, 10-20 parts of polyethylene naphthalate, 0.8-1.2 parts of modified graphene oxide, and 0.2-0.3 parts of antioxidant.

[0012] Preferably, the method for preparing the modified graphene oxide includes the following steps: S1. Graphene oxide is dispersed in an alkaline dopamine solution, stirred evenly, and then tetraethyl orthosilicate is added. The reaction is carried out at a constant temperature. After the reaction is completed, the mixture is filtered, washed, and dried to obtain pretreated graphene oxide. S2. Add the pretreated graphene oxide to acetone, then add trimellitic anhydride, and heat to react. After the reaction is complete, filter, wash, and dry to obtain organic graphene oxide. S3. Add organic graphene oxide to toluene, then add 1,2-epoxyoctadecane and triethylamine, stir and react. After the reaction is complete, filter, wash and dry to obtain modified graphene oxide.

[0013] Preferably, in step S1, the mass concentration of the alkaline dopamine solution is 3-5 g / L, the pH is 8-9, the mass ratio of graphene oxide, alkaline dopamine solution, and tetraethyl orthosilicate is 10:800-1000:1-1.5, the temperature of the isothermal reaction is 50-70℃, and the time is 12-20 h.

[0014] In this invention, graphene oxide is used as the substrate. Its single-layer thickness is on the nanoscale, and it possesses the highest known strength and modulus. This extremely high aspect ratio is the physical basis for its use as an ideal reinforcement. However, the strong van der Waals forces between graphene oxide layers make it prone to agglomeration. Agglomerates not only cannot bear stress but also become mechanical defects in the composite material. Therefore, the core objective of step S1 is to achieve effective dispersion of graphene oxide. By adding dopamine and tetraethyl orthosilicate for co-deposition reaction, the physical coating of polydopamine (PDA) and the in-situ generated silica nanoparticles play a dual role of physical isolation and steric hindrance, effectively overcoming the attractive forces between layers and preventing them from agglomerating again in subsequent processing. This not only ensures that the reinforcement can be uniformly distributed in the matrix in the form of single or a few layers, which is a key prerequisite for exerting its excellent mechanical properties and avoiding premature material failure, but also introduces highly active functional groups (such as amine and hydroxyl groups) on the surface of graphene oxide, providing abundant reaction sites for subsequent covalent grafting modification.

[0015] Preferably, in step S2, the mass ratio of pretreated graphene oxide to trimellitic anhydride is 10:4-6.5, the heating reaction temperature is 40-50℃, and the time is 2-4h; in step S3, the mass ratio of organic graphene oxide, 1,2-epoxyoctadecane, and triethylamine is 10:6-9:3-4, the stirring reaction temperature is 70-80℃, and the time is 5-7h.

[0016] In this invention, pretreated graphene oxide is reacted with trimellitic anhydride. The amino groups on the surface of the pretreated graphene oxide react with the anhydride rings in the trimellitic anhydride to form amide bonds, introducing a rigid benzene ring structure on its surface. This structure has a natural π-π interaction with the benzene rings in the polyester matrix, greatly enhancing their chemical affinity. More importantly, the 1,2-epoxyoctadecane grafted in step S3 constructs a large number of flexible long alkyl chains on the surface of the graphene oxide. During melt blending, these long chains can penetrate and entangle into the molecular chain network of the polymer matrix like physical rivets, forming a strong mechanical locking effect. When the composite material is subjected to stress, the external stress is efficiently transferred to the high-strength graphene oxide sheets through this strong interface composed of π-π interactions and physical entanglement, thereby significantly improving the tensile strength, elastic modulus, and tear resistance of the composite film.

[0017] Preferably, the preparation method of the high-strength functional layer is as follows: weigh the raw materials according to the formula, add polyethylene terephthalate, polyethylene naphthalate, modified graphene oxide and antioxidant into a high-speed mixer, mix for 10-15 minutes, then add to a twin-screw extruder, melt extrude and granulate at 240-280℃, and dry to obtain a high-strength functional layer masterbatch; the high-strength functional layer masterbatch is then processed into a high-strength functional layer film by casting or blow molding.

[0018] This invention also protects a method for preparing the polyester composite film as described above, comprising the following steps: An adhesive is coated on one side of the polyester substrate layer, and then dry-laminated with a high-strength functional layer and cured to obtain a double-layer film. Then, an adhesive is coated on one side of the high-strength functional layer of the double-layer film, and then dry-laminated with a heat-sealing layer. After lamination, it is cured to obtain a polyester composite film.

[0019] Preferably, the coating amount of the adhesive is 3-5 g / m². 2 The dry compounding process is carried out at a temperature of 40-60℃ and a pressure of 0.3-0.5MPa, and the curing process is carried out at a temperature of 40-50℃ and a time of 24-72h.

[0020] Compared with the prior art, the present invention has the following beneficial effects: (1) The polyester composite film provided by the present invention combines a specific polyester base layer, a specially made high-strength functional layer and a general heat-sealing layer through a dry composite process. The composite film obtained maintains good heat-sealing and printability, while its core mechanical properties, especially tensile strength, elastic modulus and puncture resistance, are significantly improved compared with traditional polyester films or simple blended modified films. The structure is reasonably designed and the process route is clear, so that the film not only has excellent physical properties, but also ensures the feasibility and stability of industrial production, and can better meet the application requirements of modern packaging field for high strength, lightweight and high reliability of materials.

[0021] (2) The polyester composite film provided by the present invention, wherein the modified graphene oxide added to the high-strength functional layer, firstly, utilizes the self-polymerization of dopamine and the hydrolytic condensation of tetraethyl orthosilicate to construct a PDA / SiO2 hybrid coating on the surface of graphene oxide. This coating fundamentally solves the problem of easy aggregation of graphene oxide sheets through physical isolation and steric hindrance effect, ensuring that it can be uniformly dispersed in the form of single sheets as a nano-reinforcement, avoiding the damage to material properties caused by agglomerates as mechanical defect points; subsequently, through a two-step grafting reaction, two unique functional small molecules—triphenyltrihydric anhydride and 1,2-epoxyoctadecane—are constructed on the surface of graphene oxide; the trimellitic anhydride grafted in step S2 An anhydride was introduced to the surface of graphene oxide, introducing a rigid benzene ring. This benzene ring has a π-π interaction with the benzene / naphthalene ring in the PET / PEN polyester matrix, increasing their chemical affinity. Then, in step S3, 1,2-epoxyoctadecane was grafted to introduce flexible long carbon chains. These long chains can penetrate and entangle deeply into the polymer molecular chain network during melt blending, forming a strong physical-mechanical locking effect. The super-strong interface constructed by the π-π interaction and physical entanglement ensures that stress can be efficiently transferred from the softer polymer matrix to the high-strength graphene oxide sheets, resulting in a significant improvement in the tensile strength, elastic modulus, tear resistance, and puncture resistance of the prepared composite film. Detailed Implementation

[0022] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0023] Unless otherwise specified, all chemical reagents and materials in this invention are purchased from the market or synthesized from raw materials purchased from the market.

[0024] In the following embodiments, the resin grade of the biaxially oriented polyethylene terephthalate film is SKPET BB7755 from South Korea, and the film thickness is 12-15 μm; the grade of the cast polypropylene film is Shanghai Petrochemical FC801, and the thickness is 20-25 μm; the polyurethane adhesive is a two-component solvent-based polyurethane adhesive; the grade of the polyethylene terephthalate is Yuanfang CB-608S; the grade of the polyethylene naphthalate is Teijin TN8050SC; the particle size of the graphene oxide is 0.5-3 μm; and the antioxidant is composed of antioxidant 1010 and antioxidant 168 in a mass ratio of 2:1.

[0025] Example 1 A polyester composite film, comprising at least in sequence: a polyester base layer, a high-strength functional layer, and a heat-sealing layer, wherein the base layer and the high-strength functional layer, and the high-strength functional layer and the heat-sealing layer are bonded together by an adhesive layer.

[0026] The polyester base layer is a biaxially oriented polyethylene terephthalate film; the heat-sealing layer is a cast polypropylene film; and the adhesive is a polyurethane adhesive. By weight, the high-strength functional layer comprises the following raw materials: 85 parts polyethylene terephthalate, 15 parts polyethylene naphthalate, 1 part modified graphene oxide, and 0.25 parts antioxidant.

[0027] The method for preparing the modified graphene oxide includes the following steps: S1. 10 graphene oxide was dispersed in 900 mL of alkaline dopamine solution with a concentration of 4 g / L and a pH of 8.5. After stirring evenly, 1.3 g of tetraethyl orthosilicate was added and reacted at a constant temperature of 60 °C for 16 h. After the reaction was completed, the mixture was filtered, washed and dried to obtain pretreated graphene oxide. S2. Add 10g of pretreated graphene oxide to 900mL of acetone, then add 5.5g of trimellitic anhydride, and react at 45℃ for 3h. After the reaction is complete, filter, wash and dry to obtain organic graphene oxide. S3. Add 10g of organic graphene oxide to 1L of toluene, then add 7.5g of 1,2-epoxyoctadecane and 3.5g of triethylamine. Stir the mixture at 75℃ for 6h. After the reaction is complete, filter, wash and dry to obtain modified graphene oxide.

[0028] The preparation method of the high-strength functional layer is as follows: Weigh the raw materials according to the formula, add polyethylene terephthalate, polyethylene naphthalate, modified graphene oxide and antioxidant into a high-speed mixer, mix for 15 minutes, and then add to a twin-screw extruder. Set the temperature of each zone of the extruder to 240℃-250℃-260℃-265℃-27℃-280℃-270℃, and perform melt extrusion granulation and drying to obtain high-strength functional layer masterbatch. The high-strength functional layer masterbatch is then processed into a high-strength functional layer film with a thickness of 35-40μm by casting or blow molding.

[0029] A method for preparing a polyester composite film includes the following steps: An adhesive is applied to one side of the polyester substrate at a coating weight of 4 g / m². 2 Subsequently, a high-strength functional layer was dry-laminated with the film at 50°C and 0.4 MPa pressure, followed by curing at 45°C for 48 hours to obtain a bilayer film. An adhesive was then coated onto one side of the bilayer film on the high-strength functional layer, with a coating amount of 4 g / m². 2 Then, it is dry-laminated with the heat-sealing layer at 50°C and 0.4MPa pressure. After lamination, it is cured at 45°C for 48 hours to obtain a polyester composite film with an average thickness of 77μm.

[0030] Example 2 A polyester composite film, comprising at least in sequence: a polyester base layer, a high-strength functional layer, and a heat-sealing layer, wherein the base layer and the high-strength functional layer, and the high-strength functional layer and the heat-sealing layer are bonded together by an adhesive layer.

[0031] The polyester base layer is a biaxially oriented polyethylene terephthalate film; the heat-sealing layer is a cast polypropylene film; and the adhesive is a polyurethane adhesive. By weight, the high-strength functional layer comprises the following raw materials: 80 parts polyethylene terephthalate, 20 parts polyethylene naphthalate, 0.8 parts modified graphene oxide, and 0.2 parts antioxidant.

[0032] The method for preparing the modified graphene oxide includes the following steps: S1. 10 graphene oxide was dispersed in 800 mL of an alkaline dopamine solution with a concentration of 3 g / L and a pH of 8. After stirring evenly, 1 g of tetraethyl orthosilicate was added and reacted at a constant temperature of 50 °C for 20 h. After the reaction was completed, the solution was filtered, washed and dried to obtain pretreated graphene oxide. S2. Add 10g of pretreated graphene oxide to 900mL of acetone, then add 4g of trimellitic anhydride, and react at 40℃ for 4h. After the reaction is complete, filter, wash and dry to obtain organic graphene oxide. S3. Add 10g of organic graphene oxide to 1L of toluene, then add 6g of 1,2-epoxyoctadecane and 3g of triethylamine. Stir the mixture at 70℃ for 7h. After the reaction is complete, filter, wash and dry to obtain modified graphene oxide.

[0033] The preparation method of the high-strength functional layer is as follows: Weigh the raw materials according to the formula, add polyethylene terephthalate, polyethylene naphthalate, modified graphene oxide and antioxidant into a high-speed mixer, mix for 10 min, and then add to a twin-screw extruder. Set the temperature of each zone of the extruder to 240℃-250℃-260℃-265℃-27℃-280℃-270℃, and perform melt extrusion granulation and drying to obtain high-strength functional layer masterbatch. The high-strength functional layer masterbatch is then processed into a high-strength functional layer film with a thickness of 35-40 μm by casting or blow molding.

[0034] A method for preparing a polyester composite film includes the following steps: An adhesive is applied to one side of the polyester substrate at a coating weight of 3 g / m². 2 Subsequently, a high-strength functional layer was dry-laminated with the film at 40°C and 0.5 MPa pressure, followed by curing at 50°C for 24 hours to obtain a bilayer film. An adhesive was then coated onto one side of the bilayer film on the high-strength functional layer, with a coating amount of 3 g / m². 2 Then, it is dry-laminated with the heat-sealing layer at 40℃ and 0.5MPa pressure. After lamination, it is cured at 50℃ for 24h to obtain a polyester composite film with an average thickness of 79μm.

[0035] Example 3 A polyester composite film, comprising at least in sequence: a polyester base layer, a high-strength functional layer, and a heat-sealing layer, wherein the base layer and the high-strength functional layer, and the high-strength functional layer and the heat-sealing layer are bonded together by an adhesive layer.

[0036] The polyester base layer is a biaxially oriented polyethylene terephthalate film; the heat-sealing layer is a cast polypropylene film; and the adhesive is a polyurethane adhesive. By weight, the high-strength functional layer comprises the following raw materials: 90 parts polyethylene terephthalate, 10 parts polyethylene naphthalate, 1.2 parts modified graphene oxide, and 0.3 parts antioxidant.

[0037] The method for preparing the modified graphene oxide includes the following steps: S1. 10 graphene oxide was dispersed in 1000 mL of alkaline dopamine solution with a concentration of 5 g / L and a pH of 9. After stirring evenly, 1.5 g of tetraethyl orthosilicate was added and reacted at a constant temperature of 70 °C for 12 h. After the reaction was completed, the mixture was filtered, washed and dried to obtain pretreated graphene oxide. S2. Add 10g of pretreated graphene oxide to 900mL of acetone, then add 6.5g of trimellitic anhydride, and react at 50℃ for 2h. After the reaction is complete, filter, wash and dry to obtain organic graphene oxide. S3. Add 10g of organic graphene oxide to 1L of toluene, then add 9g of 1,2-epoxyoctadecane and 4g of triethylamine. Stir the mixture at 80℃ for 5h. After the reaction is complete, filter, wash and dry to obtain modified graphene oxide.

[0038] The preparation method of the high-strength functional layer is as follows: Weigh the raw materials according to the formula, add polyethylene terephthalate, polyethylene naphthalate, modified graphene oxide and antioxidant into a high-speed mixer, mix for 15 minutes, and then add to a twin-screw extruder. Set the temperature of each zone of the extruder to 240℃-250℃-260℃-265℃-27℃-280℃-270℃, and perform melt extrusion granulation and drying to obtain high-strength functional layer masterbatch. The high-strength functional layer masterbatch is then processed into a high-strength functional layer film with a thickness of 35-40μm by casting or blow molding.

[0039] A method for preparing a polyester composite film includes the following steps: An adhesive is applied to one side of the polyester substrate at a coating weight of 5 g / m². 2 Subsequently, it was dry-laminated with a high-strength functional layer at 60℃ and 0.3MPa pressure, followed by curing at 40℃ for 72 hours to obtain a bilayer film; then, an adhesive was coated onto one side of the high-strength functional layer of the bilayer film at a coating amount of 5g / m². 2 Then, it is dry-laminated with the heat-sealing layer at 60°C and 0.3MPa pressure. After lamination, it is cured at 40°C for 72 hours to obtain a polyester composite film with an average thickness of 78μm.

[0040] Comparative Example 1 A polyester composite film, comprising at least in sequence: a polyester base layer, a high-strength functional layer, and a heat-sealing layer, wherein the base layer and the high-strength functional layer, and the high-strength functional layer and the heat-sealing layer are bonded together by an adhesive layer.

[0041] The polyester base layer is a biaxially oriented polyethylene terephthalate film; the heat-sealing layer is a cast polypropylene film; and the adhesive is a polyurethane adhesive. By weight, the high-strength functional layer comprises the following raw materials: 85 parts polyethylene terephthalate, 15 parts polyethylene naphthalate, 1 part graphene oxide, and 0.25 parts antioxidant.

[0042] The preparation method of the high-strength functional layer is as follows: Weigh the raw materials according to the formula, add polyethylene terephthalate, polyethylene naphthalate, graphene oxide and antioxidant to a high-speed mixer, mix for 15 minutes, and then add to a twin-screw extruder. Set the temperature of each zone of the extruder to 240℃-250℃-260℃-265℃-27℃-280℃-270℃, and perform melt extrusion granulation and drying to obtain high-strength functional layer masterbatch. The high-strength functional layer masterbatch is then processed into a high-strength functional layer film with a thickness of 35-40μm by casting or blow molding.

[0043] A method for preparing a polyester composite film includes the following steps: An adhesive is applied to one side of the polyester substrate at a coating weight of 4 g / m². 2 Subsequently, a high-strength functional layer was dry-laminated with the film at 50°C and 0.4 MPa pressure, followed by curing at 45°C for 48 hours to obtain a bilayer film. An adhesive was then coated onto one side of the bilayer film on the high-strength functional layer, with a coating amount of 4 g / m². 2 Then, it is dry-laminated with the heat-sealing layer at 50°C and 0.4MPa pressure. After lamination, it is cured at 45°C for 48 hours to obtain a polyester composite film with an average thickness of 78μm.

[0044] Compared with Example 1, the graphene oxide in this comparative example was not modified.

[0045] Comparative Example 2 A polyester composite film, comprising at least in sequence: a polyester base layer, a high-strength functional layer, and a heat-sealing layer, wherein the base layer and the high-strength functional layer, and the high-strength functional layer and the heat-sealing layer are bonded together by an adhesive layer.

[0046] The polyester base layer is a biaxially oriented polyethylene terephthalate film; the heat-sealing layer is a cast polypropylene film; and the adhesive is a polyurethane adhesive. By weight, the high-strength functional layer comprises the following raw materials: 85 parts polyethylene terephthalate, 15 parts polyethylene naphthalate, 1 part modified graphene oxide, and 0.25 parts antioxidant.

[0047] The method for preparing the modified graphene oxide includes the following steps: 10 graphene oxide was dispersed in 900 mL of an alkaline dopamine solution with a concentration of 4 g / L and a pH of 8.5. After stirring evenly, 1.3 g of tetraethyl orthosilicate was added, and the mixture was reacted at a constant temperature of 60 °C for 16 h. After the reaction was completed, the mixture was filtered, washed, and dried to obtain modified graphene oxide.

[0048] The preparation method of the high-strength functional layer is as follows: Weigh the raw materials according to the formula, add polyethylene terephthalate, polyethylene naphthalate, modified graphene oxide and antioxidant into a high-speed mixer, mix for 15 minutes, and then add to a twin-screw extruder. Set the temperature of each zone of the extruder to 240℃-250℃-260℃-265℃-27℃-280℃-270℃, and perform melt extrusion granulation and drying to obtain high-strength functional layer masterbatch. The high-strength functional layer masterbatch is then processed into a high-strength functional layer film with a thickness of 35-40μm by casting or blow molding.

[0049] A method for preparing a polyester composite film includes the following steps: An adhesive is applied to one side of the polyester substrate at a coating weight of 4 g / m². 2 Subsequently, a high-strength functional layer was dry-laminated with the film at 50°C and 0.4 MPa pressure, followed by curing at 45°C for 48 hours to obtain a bilayer film. An adhesive was then coated onto one side of the bilayer film on the high-strength functional layer, with a coating amount of 4 g / m². 2 Then, it is dry-laminated with the heat-sealing layer at 50°C and 0.4MPa pressure. After lamination, it is cured at 45°C for 48 hours to obtain a polyester composite film with an average thickness of 76μm.

[0050] Compared to Example 1, the modified graphene in this comparative example did not introduce trimellitic anhydride and 1,2-epoxyoctadecane.

[0051] Comparative Example 3 A polyester composite film, comprising at least in sequence: a polyester base layer, a high-strength functional layer, and a heat-sealing layer, wherein the base layer and the high-strength functional layer, and the high-strength functional layer and the heat-sealing layer are bonded together by an adhesive layer.

[0052] The polyester base layer is a biaxially oriented polyethylene terephthalate film; the heat-sealing layer is a cast polypropylene film; and the adhesive is a polyurethane adhesive. By weight, the high-strength functional layer comprises the following raw materials: 85 parts polyethylene terephthalate, 15 parts polyethylene naphthalate, 1 part modified graphene oxide, and 0.25 parts antioxidant.

[0053] The method for preparing the modified graphene oxide includes the following steps: S1. 10 graphene oxide was dispersed in 900 mL of alkaline dopamine solution with a concentration of 4 g / L and a pH of 8.5. After stirring evenly, 1.3 g of tetraethyl orthosilicate was added and reacted at a constant temperature of 60 °C for 16 h. After the reaction was completed, the mixture was filtered, washed and dried to obtain pretreated graphene oxide. S2. Add 10g of pretreated graphene oxide to 900mL of acetone, then add 5.5g of trimellitic anhydride, and react at 45℃ for 3h. After the reaction is complete, filter, wash and dry to obtain modified graphene oxide.

[0054] The preparation method of the high-strength functional layer is as follows: Weigh the raw materials according to the formula, add polyethylene terephthalate, polyethylene naphthalate, modified graphene oxide and antioxidant into a high-speed mixer, mix for 15 minutes, and then add to a twin-screw extruder. Set the temperature of each zone of the extruder to 240℃-250℃-260℃-265℃-27℃-280℃-270℃, and perform melt extrusion granulation and drying to obtain high-strength functional layer masterbatch. The high-strength functional layer masterbatch is then processed into a high-strength functional layer film with a thickness of 35-40μm by casting or blow molding.

[0055] A method for preparing a polyester composite film includes the following steps: An adhesive is applied to one side of the polyester substrate at a coating weight of 4 g / m². 2 Subsequently, a high-strength functional layer was dry-laminated with the film at 50°C and 0.4 MPa pressure, followed by curing at 45°C for 48 hours to obtain a bilayer film. An adhesive was then coated onto one side of the bilayer film on the high-strength functional layer, with a coating amount of 4 g / m². 2 Then, it is dry-laminated with the heat-sealing layer at 50°C and 0.4MPa pressure. After lamination, it is cured at 45°C for 48 hours to obtain a polyester composite film with an average thickness of 77μm.

[0056] Compared to Example 1, 1,2-epoxyoctadecane was not introduced into the modified graphene of this comparative example.

[0057] The high-barrier composite films prepared in Examples 1-3 and Comparative Examples 1-3 were subjected to performance tests. The tensile strength (longitudinal), elongation at break (longitudinal), and modulus of elasticity were tested according to standard GB / T 1040.3-2006 "Determination of tensile properties of plastics - Part 3: Test conditions for films and sheets"; the puncture resistance was tested according to standard GB / T 37841-2019 "Test method for puncture resistance of plastic films and sheets"; and the interlayer peel strength was tested according to standard GB / T 8808-1988 "Peel test method for flexible composite plastic materials". The test results are shown in Table 1 below.

[0058] Table 1 As can be seen from Table 1 above, the polyester composite film prepared by this invention has excellent tensile strength, elastic modulus and puncture resistance, and has good application prospects.

[0059] The above description is a further detailed explanation of the present invention in conjunction with specific implementation examples. It should not be considered that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, several simple deductions or substitutions can be made without departing from the concept of the present invention, and all such deductions or substitutions should be considered to fall within the protection scope of the present invention.

[0060] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A polyester composite film, characterized in that, The polyester composite film comprises at least the following in sequence: a polyester base layer, a high-strength functional layer, and a heat-sealing layer, wherein the base layer and the high-strength functional layer, and the high-strength functional layer and the heat-sealing layer are bonded together by an adhesive layer.

2. The polyester composite film according to claim 1, characterized in that, The polyester substrate layer is a biaxially oriented polyethylene terephthalate film or a polybutylene terephthalate film.

3. The polyester composite film according to claim 1, characterized in that, The heat-sealing layer is a cast polypropylene film or a linear low-density polyethylene film; the adhesive is a polyurethane adhesive.

4. The polyester composite film according to claim 1, characterized in that, By weight, the high-strength functional layer comprises the following raw materials: 80-90 parts of polyethylene terephthalate, 10-20 parts of polyethylene naphthalate, 0.8-1.2 parts of modified graphene oxide, and 0.2-0.3 parts of antioxidant.

5. The polyester composite film according to claim 1, characterized in that, The method for preparing the modified graphene oxide includes the following steps: S1. Graphene oxide is dispersed in an alkaline dopamine solution, stirred evenly, and then tetraethyl orthosilicate is added. The reaction is carried out at a constant temperature. After the reaction is completed, the mixture is filtered, washed, and dried to obtain pretreated graphene oxide. S2. Add the pretreated graphene oxide to acetone, then add trimellitic anhydride, and heat to react. After the reaction is complete, filter, wash, and dry to obtain organic graphene oxide. S3. Add organic graphene oxide to toluene, then add 1,2-epoxyoctadecane and triethylamine, stir and react. After the reaction is complete, filter, wash and dry to obtain modified graphene oxide.

6. The polyester composite film according to claim 5, characterized in that, In step S1, the alkaline dopamine solution has a mass concentration of 3-5 g / L and a pH of 8-9. The mass ratio of graphene oxide, alkaline dopamine solution, and tetraethyl orthosilicate is 10:800-1000:1-1.

5. The isothermal reaction is carried out at a temperature of 50-70°C for 12-20 hours.

7. The polyester composite film according to claim 5, characterized in that, In step S2, the mass ratio of pretreated graphene oxide to trimellitic anhydride is 10:4-6.5, and the heating reaction temperature is 40-50℃ for 2-4 hours. In step S3, the mass ratio of organic graphene oxide, 1,2-epoxyoctadecane, and triethylamine is 10:6-9:3-4, and the stirring reaction temperature is 70-80℃ for 5-7 hours.

8. The polyester composite film according to claim 5, characterized in that, The preparation method of the high-strength functional layer is as follows: Weigh the raw materials according to the formula, add polyethylene terephthalate, polyethylene naphthalate, modified graphene oxide and antioxidant into a high-speed mixer, mix for 10-15 minutes, then add to a twin-screw extruder, melt extrude and granulate at 240-280℃, and dry to obtain high-strength functional layer masterbatch; High-strength functional layer masterbatch is made into high-strength functional layer film through casting or blow molding processes.

9. A method for preparing a polyester composite film as described in any one of claims 1-8, characterized in that, Includes the following steps: An adhesive is coated on one side of the polyester substrate layer, and then dry-laminated with a high-strength functional layer and cured to obtain a double-layer film. Then, an adhesive is coated on one side of the high-strength functional layer of the double-layer film, and then dry-laminated with a heat-sealing layer. After lamination, it is cured to obtain a polyester composite film.

10. The preparation method according to claim 9, characterized in that, The adhesive is applied at a rate of 3-5 g / m². 2 The dry compounding process is carried out at a temperature of 40-60℃ and a pressure of 0.3-0.5MPa, and the curing process is carried out at a temperature of 40-50℃ and a time of 24-72h.

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