Polyester composite special film and preparation method thereof

Abstract

The application relates to the field of special films, in particular to a polyester composite special film and a preparation method thereof.The polyester composite special film comprises, in terms of weight parts, 100 parts of PET base resin, 4-10 parts of a multifunctional reinforcing agent, 1-3 parts of a nucleating agent, 0.6-1.5 parts of a composite antioxidant, 0.3-0.9 parts of a lubricant, 0.08-0.25 parts of an opening agent and 0.2-0.8 parts of a hydrolysis stabilizer.The PET base resin is subjected to multi-component composite modification, and multifunctional reinforcing agents, modified nano montmorillonite nucleating agents, composite antioxidants and hydrolysis stabilizers and other auxiliaries are synergistically utilized, so that the polyester composite special film prepared in the application is obviously improved in mechanical strength, heat resistance, dimensional stability, anti-aging performance and hydrolysis resistance, and can meet the strict requirements of special films in high-end fields such as electronic appliances, new energy and industrial insulation.

Description

Technical Field

[0001] This invention relates to the field of special films, specifically to a polyester composite special film and its preparation method. Background Technology

[0002] Polyethylene terephthalate (PET) polyester film, with its excellent mechanical strength, optical transparency, electrical insulation, temperature resistance, and processability, has become one of the most widely used polymer film materials in packaging, electronics, new energy, and automotive industries. With the rapid iteration of downstream high-end industries, applications such as aluminum-plastic films for new energy soft-pack batteries, flexible foldable high-frequency circuits, and outdoor photovoltaic backsheets place stringent multi-dimensional demands on the performance of PET film: it not only needs to possess high toughness, resistance to bending fatigue, and low-temperature impact resistance, but also needs to simultaneously meet excellent resistance to electrolyte corrosion, high dimensional stability under humid heat, and processing stability for ultra-thin fabrication.

[0003] There are still many unresolved problems with existing PET film modification technologies, making it difficult to meet the comprehensive performance requirements of high-end scenarios. Specifically: (1) Existing toughening modification technologies are mostly copolymer modification or blending toughening. Copolymer modification improves toughness by introducing flexible monomers to disrupt the regularity of PET molecular chains, but it will significantly reduce the heat resistance, crystallinity and thermal dimensional stability of the film; Elastomer blending toughening (such as POE, EVA, TPU, etc.) has the problem of large polarity difference with PET matrix and poor compatibility, which easily leads to phase separation and additive migration and precipitation, resulting in a significant decrease in film transparency and mechanical strength. (2) Existing modification technologies cannot achieve a synergistic balance of multiple properties. Most modification schemes can only achieve a single room temperature toughness improvement, and cannot simultaneously take into account high tensile strength, low temperature impact resistance, electrolyte corrosion resistance and high dimensional stability. For example, in the scenario of new energy soft pack batteries, after long-term contact with electrolyte, existing PET films are prone to toughening agent dissolution, sudden drop in mechanical properties and dimensional deformation, which eventually leads to encapsulation failure. (3) The synergy between existing nucleating modification and toughening modification is seriously insufficient. There is no interfacial interaction between existing nucleating agents and toughening agents, which easily leads to their own aggregation and the formation of stress concentration points inside the film. This not only fails to synergistically improve toughness, but also causes defects such as crystal points and fish eyes in the film, reducing the electrical insulation and aging resistance of the film. In the preparation of ultrathin films, the film breakage problem caused by defects is particularly prominent.

[0004] To address the aforementioned deficiencies in existing technologies, the present invention aims to provide a polyester composite special film and its preparation method. Without sacrificing the original properties of PET film, it achieves a synergistic improvement in multiple properties, including high toughness, resistance to bending fatigue, resistance to electrolyte corrosion, and high dimensional stability. At the same time, the preparation process is compatible with existing industrial production lines, and the yield rate of ultra-thin preparation is high, which can meet the stringent application requirements of high-end scenarios such as new energy and flexible electronics. Summary of the Invention

[0005] To address the problems existing in the prior art, the purpose of this invention is to provide a polyester composite special film and its preparation method.

[0006] The objective of this invention is achieved through the following technical solution: A polyester composite special film, comprising, by weight parts: 100 parts PET matrix resin, 4-10 parts multifunctional reinforcing agent, 1-3 parts nucleating agent, 0.6-1.5 parts composite antioxidant, 0.3-0.9 parts lubricant, 0.08-0.25 parts opening agent, and 0.2-0.8 parts hydrolysis stabilizer.

[0007] Preferably, the PET matrix resin is polyethylene terephthalate, with a density of 1.33-1.34 g / cm³ at 25°C. 3 At 250℃ and 2.16kg, the melt index is 12-20g / 10min and the intrinsic viscosity is 0.68-0.78dL / g.

[0008] Preferably, the nucleating agent is nano-montmorillonite modified with a silane coupling agent.

[0009] Preferably, the method for preparing the nucleating agent includes: Add 10g of 20-30nm nano-montmorillonite and 2-3g of silane coupling agent KH-570 to 100mL of 70wt% ethanol solution. After thorough mixing, reflux and stir at 70-80℃ for 5-6h. After cooling, filter, wash and dry to obtain the nucleating agent.

[0010] Preferably, the composite antioxidant is a mixture of a primary antioxidant and a secondary antioxidant in a mass ratio of 1:1-2; wherein the primary antioxidant is one or a combination of two of antioxidant 1010 and antioxidant 3114, and the secondary antioxidant is one or a combination of two of antioxidant 618 and antioxidant DLTP.

[0011] Preferably, the lubricant is one or a combination of two of pentaerythritol stearate and polyethylene wax.

[0012] Preferably, the opening agent is nano-silica with a particle size of 80-120 nm.

[0013] Preferably, the hydrolysis stabilizer is polycarbodiimide with a number average molecular weight of 3000-6000, a functionality of ≥2, and a nitrogen content of ≥10%.

[0014] Preferably, the preparation method of the multifunctional reinforcing agent includes: S1. Under nitrogen protection, allylamine was mixed in dichloromethane and stirred evenly in an ice-water bath; then p-toluenesulfonyl chloride and triethylamine, an acid-binding agent, were added simultaneously; the ice-water bath was removed and the reaction was stirred at room temperature for 4-6 hours. After the reaction was completed, the mixture was filtered, washed, dried, and the solvent was removed by rotary evaporation to obtain the functional intermediate. S2. Under nitrogen protection, tetrahydrofuran, functional intermediate, and 2-mercaptobenzimidazole are mixed evenly; a photoinitiator is added, and after stirring evenly, the mixture is placed in an ultraviolet light reactor and irradiated at room temperature for 1-2 hours with stirring. After the reaction is completed, the solvent is removed by rotary evaporation to obtain the crude product; after recrystallization, filtration, and drying, the multifunctional reinforcing agent is obtained.

[0015] Preferably, in S1, the mass ratio of p-toluenesulfonyl chloride, allylamine, and triethylamine is 10.0-15.0:3.1-4.9:5.57-9.56.

[0016] More preferably, in S1, the mass ratio of p-toluenesulfonyl chloride, allylamine, and triethylamine is 12.0:3.77:7.01.

[0017] Preferably, in S2, the mass ratio of the functional intermediate and 2-mercaptobenzimidazole is 10.0-16.0:7.0-12.0.

[0018] More preferably, in S2, the mass ratio of the functional intermediate to 2-mercaptobenzimidazole is 13.0:9.24.

[0019] Preferably, in step S2, the photoinitiator is benzoin dimethyl ether or benzoin n-butyl ether, and the amount added is 1.2%-2.4% of the mass of the functional intermediate.

[0020] Secondly, the present invention provides a method for preparing a polyester composite special film, comprising the following steps: Step 1: Add the dried PET, multifunctional reinforcing agent, nucleating agent, composite antioxidant, lubricant, opening agent, and hydrolysis stabilizer to a high-speed mixer and mix at room temperature for 8-10 minutes until the material is uniform. Step 2: Melt blending is performed using a twin-screw extruder. The parameters of the twin-screw extruder include: Zone 1 245℃, Zone 2 260℃, Zone 3 270℃, Zone 4 275℃, Zone 5 275℃, Zone 6 270℃, Die head 265℃, and main extruder speed 300-350 rpm. The molten material is cooled in a water bath, pelletized, and vacuum dried to obtain a polyester composite blend. Step 3: Add the dried blend to a single-screw extruder at a melt temperature of 265-275℃, extrude through a T-die, and rapidly cool on a cooling drum to form a cast sheet; then stretch the cast sheet longitudinally and transversely: longitudinal stretching temperature: 85-95℃, longitudinal stretching ratio: 3.0-3.3 times; transverse stretching temperature: 100-110℃, transverse stretching ratio: 3.0-3.5 times. Step 4: Heat set the stretched composite film: heat set temperature 210-230℃, heat set time 10-30s; after heat set, cool the film to room temperature, control the tension at 5-8N / m, trim the edges and roll it up to obtain a polyester composite special film.

[0021] The beneficial effects of this invention are as follows: 1. This invention modifies PET matrix resin through multi-component composite modification and synergistically utilizes multifunctional reinforcing agents, modified nano-montmorillonite nucleating agents, composite antioxidants, and hydrolysis stabilizers to prepare polyester composite special films. These films exhibit significant improvements in mechanical strength, heat resistance, dimensional stability, anti-aging properties, and hydrolysis resistance, meeting the stringent requirements for special films in high-end fields such as electronics, electrical engineering, new energy, and industrial insulation.

[0022] 2. This invention synthesizes a multifunctional reinforcing agent by introducing a functional structure containing a benzimidazole group into the N-allyl-p-toluenesulfonamide backbone through a UV-induced mercapto-olefin click chemistry reaction. This reinforcing agent molecule contains a benzimidazole group, a sulfonamide group, and a thioether structure, enabling it to simultaneously exert multiple functions in the PET matrix, including reinforcement, UV aging resistance, and thermo-oxidative stability. This achieves multifunctionality from a single additive, avoids interference between multiple additives, and ensures the long-term stability of the film.

[0023] 3. This invention uses silane coupling agent KH-570 to modify nano-montmorillonite, which effectively improves the interfacial compatibility between inorganic nucleating agent and PET matrix resin, promotes the uniform dispersion of nano-montmorillonite in the matrix, significantly improves nucleation efficiency, and induces the PET matrix to form a fine and uniform grain structure, thereby greatly improving the crystallization rate, crystallinity and mechanical properties of the film.

[0024] 4. The present invention uses a compounded antioxidant system and selected lubricants and opening agents to effectively inhibit the thermal oxidative degradation of PET during high-temperature processing, improve the fluidity of the melt and the processing demolding properties, so that the blending modification and subsequent melt extrusion and biaxial stretching processes are stable and controllable, and the resulting film has high surface flatness, uniform thickness and good opening properties, which is easy for industrial continuous production.

[0025] 5. The preparation method provided by this invention has a reasonable process flow design, clear parameters for each step, readily available raw materials, and simple operation. It can achieve large-scale production using conventional melt blending and biaxial stretching equipment, and has good economic benefits and market promotion prospects. Detailed Implementation

[0026] The technical solution of the present invention is illustrated below through specific examples. It should be understood that the one or more method steps mentioned in the present invention do not preclude the existence of other method steps before or after the combined steps, or the insertion of other method steps between these explicitly mentioned steps; it should also be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the present invention. Furthermore, unless otherwise stated, the numbering of each method step is merely a convenient tool for identifying each method step, and not for limiting the order of the method steps or defining the scope of the present invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the present invention.

[0027] To better understand the above technical solutions, exemplary embodiments of the present invention are described in more detail below. While exemplary embodiments of the present invention are shown, it should be understood that the present invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the present invention and to fully convey the scope of the invention to those skilled in the art.

[0028] The present invention will be further described below with reference to the following embodiments. Example 1

[0029] A polyester composite special film, comprising, by weight parts: 100 parts PET matrix resin, 7 parts multifunctional reinforcing agent, 2 parts nucleating agent, 1.0 part composite antioxidant, 0.6 parts lubricant, 0.15 parts opening agent, and 0.5 parts hydrolysis stabilizer; The PET matrix resin is polyethylene terephthalate, industrial grade, with a density of 1.335 g / cm³ at 25°C. 3 The melt index is 15g / 10min at 250℃ and 2.16kg load, and the intrinsic viscosity is 0.72dL / g. It should be vacuum dried at 140℃ for 12h before use. The composite antioxidant is a mixture of antioxidant 1010 and antioxidant 618 in a mass ratio of 1:1.5. The lubricant is pentaerythritol stearate. The opening agent is nano-silica with an average particle size of 100nm. The hydrolytic stabilizer is polycarbodiimide with a number average molecular weight of 4500, a functionality of ≥2, and a nitrogen content of 12%.

[0030] The nucleating agent is silane coupling agent modified nano-montmorillonite, and the preparation method is as follows: 10g of dried montmorillonite nanoparticles with an average particle size of 25nm and 2.5g of silane coupling agent KH-570 were added to 100mL of 70% ethanol aqueous solution and stirred at high speed for 30min to mix thoroughly. The mixture was then placed in an oil bath at 75℃ and refluxed for 5.5h. After the reaction was completed, the mixture was allowed to cool naturally to room temperature, filtered to separate the solid product, washed three times with anhydrous ethanol, and dried under vacuum at 60℃ for 12h to obtain the modified montmorillonite nanoparticle nucleating agent.

[0031] The preparation method of the multifunctional reinforcing agent is as follows: S1. Preparation of the functional intermediate N-allyl-p-toluenesulfonamide Under nitrogen protection, 200 mL of dry dichloromethane and 3.77 g of dry allylamine were added to a dry 500 mL three-necked flask and mechanically stirred in an ice-water bath at 0-5 °C until homogeneous. 12.0 g of p-toluenesulfonyl chloride was dissolved in 80 mL of dry dichloromethane and slowly added dropwise to the flask simultaneously with 7.01 g of triethylamine over 1.8 h. After the addition was complete, the ice-water bath was removed, and the reaction was stirred at room temperature for 5 h. After the reaction was complete, the triethylamine hydrochloride was removed by filtration. The filtrate was washed three times with deionized water, dried over anhydrous sodium sulfate for 12 h, filtered, and then the solvent was removed by rotary evaporation to obtain a white solid functional intermediate, N-allyl-p-toluenesulfonamide, with a yield of 97.8%. S2, Preparation of Multifunctional Enhancers Under nitrogen protection, 150 mL of dry tetrahydrofuran, 13.0 g of the above-mentioned functional intermediate, and 9.24 g of 2-mercaptobenzimidazole were added to a dry 250 mL three-necked flask and stirred at room temperature until completely dissolved. 0.234 g of photoinitiator benzoin dimethyl ether was added and stirred for 10 min until homogeneous. The flask was placed in a 365 nm ultraviolet light reactor and irradiated at room temperature with stirring for 1.5 h. After the reaction was completed, the solvent was removed by rotary evaporation to obtain the crude product. The crude product was recrystallized twice with a 1:3 volume ratio of anhydrous ethanol and n-hexane mixture, filtered, and dried under vacuum at 40 °C for 24 h to obtain a white powdery multifunctional reinforcing agent with a yield of 93.6%.

[0032] The method for preparing the above-mentioned polyester composite special film includes the following steps: Step 1: Raw material premixing: Add the dried PET matrix resin, multifunctional reinforcing agent, nucleating agent, composite antioxidant, lubricant, opening agent, and hydrolytic stabilizer to a high-speed mixer according to the formula ratio. Mix at 1200 rpm for 9 minutes at room temperature until the materials are evenly dispersed to obtain the premix. Step 2, Melt Blending and Granulation: The premixed material is added to a twin-screw extruder for melt blending. Temperature parameters are set as follows: Zone 1 245℃, Zone 2 260℃, Zone 3 270℃, Zone 4 275℃, Zone 5 275℃, Zone 6 270℃, Die Head 265℃, Main Extruder Speed ​​320 rpm, Feeding Speed ​​30 rpm. After the molten material is cooled in a water bath and granulated, it is vacuum dried at 140℃ for 12 hours to obtain a polyester composite blend. Step 3, Casting and Biaxial Stretching: The dried blend is added to a single-screw extruder at a melt extrusion temperature of 270°C. The melt is extruded through a T-die and rapidly cooled on a 25°C cooling drum to obtain an amorphous cast sheet with a thickness of approximately 50 μm. The cast sheet is then fed into a biaxial stretching device for longitudinal stretching at a temperature of 90°C and a stretching ratio of 3.2 times. Transverse stretching is then performed at a temperature of 105°C and a stretching ratio of 3.3 times to obtain the stretched composite film. Step 4, Heat setting and winding: The stretched film is sent into a heat setting oven at 220℃ for 20s. After heat setting, it is cooled to room temperature online while maintaining a running tension of 6N / m. After trimming the edges, it is wound up to obtain a polyester composite special film with a thickness of 5.0μm. Example 2

[0033] A polyester composite special film, comprising, by weight parts: 100 parts of PET matrix resin, 4 parts of the multifunctional reinforcing agent prepared in Example 1, 1 part of the nucleating agent prepared in Example 1, 0.6 parts of composite antioxidant, 0.3 parts of lubricant, 0.08 parts of opening agent, and 0.2 parts of hydrolysis stabilizer; The composite antioxidant is a mixture of antioxidant 1010 and antioxidant 618 in a mass ratio of 1:1; the lubricant is polyethylene wax; and the specifications of the other raw materials are the same as in Example 1.

[0034] The preparation methods for the nucleating agent and the multifunctional enhancer are the same as those in Example 1.

[0035] The method for preparing the above-mentioned polyester composite special film includes the following steps: Step 1: Raw material premixing: Add each raw material to a high-speed mixer according to the formula ratio and mix at 1200 rpm for 8 minutes at room temperature to obtain a uniform premix. Step 2, melt blending and granulation: The temperature parameters of the twin-screw extruder are the same as in Example 1, the main extruder speed is 300 rpm, and the feed speed is 28 rpm; the molten material is cooled, granulated, and dried to obtain polyester composite blend. Step 3, casting and biaxial stretching: melt extrusion temperature 265℃, longitudinal stretching temperature 85℃, stretching ratio 3.0; transverse stretching temperature 100℃, stretching ratio 3.0; Step 4, heat setting and winding: heat setting temperature 210℃, heat setting time 10s; after cooling, control the running tension to 5N / m, trim the edges and wind up to obtain polyester composite special film. Example 3

[0036] A polyester composite special film, comprising, by weight parts: 100 parts of PET matrix resin, 4 parts of the multifunctional reinforcing agent prepared in Example 1, 1 part of the nucleating agent prepared in Example 1, 0.6 parts of composite antioxidant, 0.3 parts of lubricant, 0.08 parts of opening agent, and 0.2 parts of hydrolysis stabilizer; The composite antioxidant is a mixture of antioxidant 1010 and antioxidant 618 in a mass ratio of 1:1; the specifications of the other raw materials are the same as in Example 1.

[0037] The method for preparing the above-mentioned polyester composite special film includes the following steps: Step 1: Raw material premixing: Add each raw material to a high-speed mixer according to the formula ratio and mix at 1200 rpm for 8 minutes at room temperature to obtain a uniform premix. Step 2, melt blending and granulation: The temperature parameters of the twin-screw extruder are the same as in Example 1, the main extruder speed is 300 rpm, and the feed speed is 28 rpm; the molten material is cooled, granulated, and dried to obtain polyester composite blend. Step 3, casting and biaxial stretching: melt extrusion temperature 265℃, longitudinal stretching temperature 85℃, stretching ratio 3.0; transverse stretching temperature 100℃, stretching ratio 3.0; Step 4, heat setting and winding: heat setting temperature 210℃, heat setting time 10s; after cooling, control the running tension to 5N / m, trim the edges and wind up to obtain polyester composite special film.

[0038] Comparative Example 1 The comparative formulation contains no multifunctional reinforcing agent, and the types, weight proportions, and specifications of the other raw materials are completely consistent with those in Example 1. All process parameters and operating steps of the preparation method are completely consistent with those in Example 1, and a polyester film with a thickness of 5.0 μm is finally obtained.

[0039] Comparative Example 2 The comparative formulation uses an equal mass of 2-mercaptobenzimidazole to replace the multifunctional reinforcing agent in Example 1. The other raw materials, weight parts, and specifications are completely consistent with those in Example 1. All process parameters and operating steps of the preparation method are completely consistent with those in Example 1. Finally, a polyester film with a thickness of 4.9 μm is obtained.

[0040] Comparative Example 3 The comparative formulation uses an equal mass of the functional intermediate (N-allyl-toluenesulfonamide) obtained in S1 of Example 1 to replace the multifunctional reinforcing agent in Example 1. The types, weight parts, and specifications of the other raw materials are completely consistent with those in Example 1. All process parameters and operating steps of the preparation method are completely consistent with those in Example 1. Finally, a polyester film with a thickness of 5.1 μm is obtained.

[0041] Test Standards All tests were conducted under standard conditions of 23℃ and 50% relative humidity. Five parallel samples were used in each test group, and the average value of the results was taken. (1) Thickness: GB / T6672-2001 Mechanical Measurement Method for Determination of Thickness of Plastic Films and Sheets; (2) Tensile strength and elongation at break: GB / T1040.3-2006 Determination of tensile properties of plastics - Part 3: Films and sheets, specimen type 2, tensile rate 50 mm / min, test longitudinal (MD) tensile properties; (3) Impact strength of cantilever beam: GB / T1843-2008 "Determination of impact strength of plastic cantilever beam", unnotched specimen; (4) Bending fatigue resistance: GB / T457-2008 "Determination of folding endurance of paper and paperboard", MIT folding endurance tester, tension 4.9N, bending angle 135°, record the number of bends at the time of breakage; (5) Electrolyte corrosion resistance: The sample was immersed in 1 mol / L LiPF6 EC / EMC / DMC (volume ratio 1:1:1) electrolyte, sealed at 85℃ for 72 h, and then removed, cleaned and dried before testing the longitudinal tensile strength and calculating the strength retention rate. (6) Thermal dimensional stability: GB / T12027-2004 "Test method for dimensional change rate of plastic film and sheet under heating", constant temperature at 150℃ for 30min, calculate the longitudinal thermal shrinkage rate.

[0042] The test results are shown in Table 1: Table 1 Performance characteristics of different special films As shown in Table 1, at an ultrathin thickness of 5 μm, the special film of Example 1 achieves a synergistic improvement in multiple properties, including high strength, high toughness, resistance to bending fatigue, resistance to electrolyte corrosion, and high dimensional stability. Compared to Comparative Example 1, Example 1 not only improves mechanical strength but also enhances film toughness and impact resistance, solving the problem of conventional PET films struggling to balance rigidity and toughness. Example 1 exhibits significantly better resistance to electrolyte corrosion than the control groups, maintaining its mechanical properties well even under the harsh immersion environment of high-temperature electrolytes, greatly improving the long-term stability and service reliability of the film in electrolyte media. Example 1 demonstrates significantly better high-temperature dimensional stability than the control groups, significantly reducing the degree of thermal deformation of the film under high-temperature conditions, maintaining stable dimensional accuracy under high-temperature operating conditions, and effectively avoiding service failure caused by thermal shrinkage and deformation.

[0043] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. The illustrative expressions of the above terms in this specification should not be construed as necessarily referring to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. In addition, those skilled in the art can combine and integrate the different embodiments or examples described in this specification.

[0044] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A polyester composite special film, characterized in that, Calculated by weight, including: 100 parts PET matrix resin, 4-10 parts multifunctional reinforcing agent, 1-3 parts nucleating agent, 0.6-1.5 parts composite antioxidant, 0.3-0.9 parts lubricant, 0.08-0.25 parts opening agent, and 0.2-0.8 parts hydrolysis stabilizer.

2. The polyester composite special film according to claim 1, characterized in that, The PET matrix resin is polyethylene terephthalate, with a density of 1.33-1.34 g / cm³ at 25°C. 3 At 250℃ and 2.16kg, the melt index is 12-20g / 10min and the intrinsic viscosity is 0.68-0.78dL / g.

3. The polyester composite special film according to claim 1, characterized in that, The nucleating agent is nano-montmorillonite modified with a silane coupling agent.

4. The polyester composite special film according to claim 1, characterized in that, The composite antioxidant is a mixture of a primary antioxidant and a secondary antioxidant in a mass ratio of 1:1-2; wherein the primary antioxidant is one or a combination of two of antioxidant 1010 and antioxidant 3114, and the secondary antioxidant is one or a combination of two of antioxidant 618 and antioxidant DLTP.

5. A polyester composite special film according to claim 1, characterized in that, The lubricant is one or a combination of two of pentaerythritol stearate and polyethylene wax.

6. The polyester composite special film according to claim 1, characterized in that, The opening agent is nano-silica with a particle size of 80-120nm.

7. A polyester composite special film according to claim 1, characterized in that, The hydrolysis stabilizer is polycarbodiimide with a number average molecular weight of 3000-6000, a functionality of ≥2, and a nitrogen content of ≥10%.

8. A polyester composite special film according to claim 1, characterized in that, The preparation method of the multifunctional reinforcing agent includes: S1. Under nitrogen protection, allylamine was mixed in dichloromethane and stirred evenly in an ice-water bath; then p-toluenesulfonyl chloride and triethylamine, an acid-binding agent, were added simultaneously; the ice-water bath was removed and the reaction was stirred at room temperature for 4-6 hours. After the reaction was completed, the mixture was filtered, washed, dried, and the solvent was removed by rotary evaporation to obtain the functional intermediate. S2. Under nitrogen protection, tetrahydrofuran, functional intermediate, and 2-mercaptobenzimidazole are mixed evenly; a photoinitiator is added, and after stirring evenly, the mixture is placed in an ultraviolet light reactor and irradiated at room temperature for 1-2 hours with stirring. After the reaction is completed, the solvent is removed by rotary evaporation to obtain the crude product; after recrystallization, filtration, and drying, the multifunctional reinforcing agent is obtained.

9. A polyester composite special film according to claim 8, characterized in that, In S1, the mass ratio of p-toluenesulfonyl chloride, allylamine, and triethylamine is 10.0-15.0:3.1-4.9:5.57-9.56; in S2, the mass ratio of the functional intermediate and 2-mercaptobenzimidazole is 10.0-16.0:7.0-12.

0.

10. A method for preparing the polyester composite special film according to claim 1, characterized in that, Includes the following steps: Step 1: Add the dried PET, multifunctional reinforcing agent, nucleating agent, composite antioxidant, lubricant, opening agent, and hydrolysis stabilizer to a high-speed mixer and mix evenly at room temperature; Step 2: Melt blending is performed using a twin-screw extruder. The molten material is cooled in a water bath, pelletized, and vacuum dried to obtain a polyester composite blend. Step 3: Add the dried blend to a single-screw extruder, extrude it through a T-die, and rapidly cool it on a cooling drum to form a cast sheet; then stretch the cast sheet longitudinally and laterally. Step 4: Heat set the stretched composite film. After heat setting, cool the film to room temperature, trim the edges, and roll it up to obtain a polyester composite special film.

Images