A polyester special film and a method for preparing the same

Abstract

This invention relates to the field of specialty films, specifically to a polyester specialty film and its preparation method. Calculated by weight, it comprises the following components: 95.0-98.8 parts modified PET resin, 0.2-1.2 parts nucleating agent, 0.1-0.9 parts lubricant, 0.3-1.5 parts anti-blocking agent, 0.1-1.2 parts composite antioxidant, and 0.1-0.8 parts hydrolytic stabilizer. This invention, through the modification and optimization of the base resin and the synergistic effect of functional additives, enables the film to possess both high strength and high flexibility, exhibiting excellent tensile, bending, and impact resistance; simultaneously, it possesses dense resistance to media corrosion, effectively resisting the erosion of highly corrosive media such as lithium battery electrolytes. In long-term electrolyte immersion environments, it maintains excellent mechanical properties, significantly improving the long-term reliability and service life of the film in scenarios such as new energy soft-pack lithium battery packaging.

Description

Technical Field

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

[0002] Polyethylene terephthalate (PET)-based polyester film, with its excellent mechanical strength, optical transparency, dimensional stability, chemical resistance, and temperature resistance, has become one of the most widely used substrates in fields such as electronics, printing and packaging, new energy, and precision adhesives. As downstream industries rapidly upgrade towards lightweight, precision, and high reliability, end-use applications are placing higher demands on the performance of polyester films, especially in ultra-thin applications. Achieving high water and oxygen barrier properties, solvent resistance, surface smoothness, and mechanical stability simultaneously has become a core research and development direction in the high-end polyester film field.

[0003] Polyethylene terephthalate (PET) polyester film, with its excellent mechanical strength, optical transparency, dimensional stability, chemical corrosion resistance, and temperature resistance, is widely used in food packaging, electronic information, and new energy fields. With the rapid upgrading of the new energy soft-pack lithium battery and high-frequency electronic component industries, end-user applications are placing more stringent and multi-faceted performance requirements on packaging substrates: not only must they possess excellent water and oxygen barrier properties, but they must also have excellent resistance to electrolyte corrosion, low dielectric constant and low dielectric loss, and high dimensional stability. Simultaneously, they must meet requirements such as a single-layer homogeneous structure, easy recyclability, and strong process adaptability.

[0004] Currently, the mainstream packaging substrate for new energy soft-pack lithium batteries is aluminum-plastic composite film, which mostly adopts a multi-layer composite structure of nylon layer / aluminum foil layer / cast polypropylene layer. Although it can achieve high barrier properties, it has inherent defects that cannot be avoided: poor adhesion between the multi-layer heterogeneous structure, which easily leads to delamination and aluminum foil breakage during battery assembly bending and long-term use, resulting in electrolyte leakage, water and oxygen intrusion, and causing battery bulging and failure; the aluminum foil layer has the risk of puncture and short circuit, and insufficient insulation protection performance; the multi-layer heterogeneous structure is extremely difficult to recycle, has poor environmental performance, and has a long production process and high cost.

[0005] In summary, existing polyester film technology cannot simultaneously achieve a balance of comprehensive performance characteristics, including a single-layer homogeneous structure, resistance to electrolyte corrosion, low dielectric constant, high water and oxygen barrier properties, high mechanical properties, and high dimensional stability. This severely restricts the application and development of polyester films in the high-end packaging field. Summary of the Invention

[0006] To address the problems existing in the prior art, the purpose of this invention is to provide a polyester specialty film and its preparation method.

[0007] The objective of this invention is achieved through the following technical solution: In a first aspect, the present invention provides a polyester specialty film, comprising the following components by weight: 95.0-98.8 parts modified PET resin, 0.2-1.2 parts nucleating agent, 0.1-0.9 parts lubricant, 0.3-1.5 parts anti-blocking agent, 0.1-1.2 parts composite antioxidant, and 0.1-0.8 parts hydrolysis stabilizer; wherein the modified PET resin is prepared by melt blending PET resin chips and multifunctional modifier, and the mass ratio of PET resin chips to multifunctional modifier is 100:2-8.

[0008] Preferably, the PET resin chips are fiber-grade PET chips with an intrinsic viscosity of 0.68-0.72 dL / g and a melt flow index of 18-30 g / 10 min (260℃, 2.16 kg).

[0009] Preferably, the preparation method of the multifunctional modifier includes the following steps: S1. Weigh 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO), 1,4-dioxane, and triethylamine and add them to the reaction apparatus. Use nitrogen as a protective gas, heat to 80-90℃, start stirring, and add 3-(perfluorobutane)-1,2-epoxypropane dropwise. After the addition is complete, keep the reaction at the temperature for 4-8 hours. Post-process to obtain fluorinated DOPO modifier. S2. Isophorone diisocyanate and ethyl acetate are added to the reaction apparatus. Under nitrogen protection, the temperature is raised to 35-45℃, fluorine-containing DOPO modifier is added, then the catalyst is added, the temperature is raised to 50-60℃, and the reaction is maintained for 3-4 hours. The reaction is terminated, and the solvent is removed by vacuum distillation to obtain the terminal-NCO prepolymer. S3. Add octaaminoisobutyl cage-type silsesquioxane and solvent to the reaction apparatus, and stir evenly at room temperature under nitrogen protection; add terminal-NCO prepolymer, with the addition time controlled at 3-5h; after the addition is complete, react at room temperature for 1-3h, then raise the temperature to 40-60℃, add hexahydrobisphenol A diglycidyl ether, and keep the reaction at this temperature for 2-4h. Post-treatment yields a white powdery multifunctional modifier.

[0010] Preferably, in S1, the mass ratio of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and 3-(perfluorobutane)-1,2-epoxypropane is 1:1.76-1.98.

[0011] More preferably, in S1, the mass ratio of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and 3-(perfluorobutane)-1,2-epoxypropane is 1:1.83.

[0012] Preferably, in S1, the amount of triethylamine added is 0.3%-0.8% of the mass of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide.

[0013] Preferably, in S2, the mass ratio of isophorone diisocyanate to fluorinated DOPO modifier is 0.42-0.45:1.

[0014] More preferably, in S2, the mass ratio of isophorone diisocyanate to fluorinated DOPO modifier is 0.43:1.

[0015] Preferably, in S2, the catalyst is zinc isooctanoate, and the amount added is 0.2%-0.3% of the mass of the fluorinated DOPO modifier.

[0016] Preferably, in S3, the mass ratio of octaaminoisobutyl cage-type silsesquioxane, terminal-NCO prepolymer, and hexahydrobisphenol A diglycidyl ether is 1:3.8-4.7:0.7-1.0.

[0017] More preferably, in S3, the mass ratio of octaaminoisobutyl cage-type silsesquioxane, terminal-NCO prepolymer, and hexahydrobisphenol A diglycidyl ether is 1:4.25:0.85.

[0018] Preferably, the nucleating agent is a mixture of nano-talc powder and sodium phenylphosphinate in a mass ratio of 2-4:1, with a particle size of 200-600 nm.

[0019] Preferably, the lubricant is a mixture of silicone powder and polyethylene wax in a mass ratio of 1-3:1.

[0020] Preferably, the anti-blocking agent is polymethyl methacrylate microspheres with a particle size of 1-2 μm.

[0021] Preferably, the composite antioxidant is a mixture of antioxidant 1010, antioxidant 168 and antioxidant 626 in a mass ratio of 2-3:1-2:1.

[0022] Preferably, the hydrolysis stabilizer is polycarbodiimide.

[0023] Preferably, the method for preparing the modified PET resin includes the following steps: (1) Dry PET resin chips in vacuum at 130-150℃ for 10-15h, add them to a high-speed mixer with multifunctional modifier according to the ratio, and mix at 3000-4000rpm for 5-10min at room temperature to obtain a uniformly dispersed mixture. (2) Add the mixture to the twin-screw extruder, with a screw speed of 200-300 rpm and a material residence time of 4-5 min. Set the temperature of each section of the extruder as follows: Zone 1 230-240℃, Zone 2 245-250℃, Zone 3 250-255℃, Zone 4 255-260℃, Zone 5 250-255℃, and Die head 250-255℃. (3) The extruded strips are cooled with water, air-dried and granulated to obtain modified PET resin.

[0024] Secondly, the present invention provides a method for preparing a polyester special film, comprising the following steps: Step 1: After vacuum drying the modified PET resin, nucleating agent, lubricant, anti-blocking agent, composite antioxidant, and hydrolytic stabilizer at 120-140℃ for 6-10 hours, add them to a high-speed mixer according to the preset weight parts and mix at 3000-4000 rpm at room temperature for 4-8 minutes to obtain a uniformly dispersed premixed material. Step 2: Add the premixed material to a twin-screw extruder for melt blending. After the melt is stabilized by a melt pump and filtered by a high-precision filter, it is uniformly extruded from a slit die to obtain molten resin sheets. The screw speed for melt blending is 200-300 rpm, the material residence time is 3-8 min, and the extrusion temperature is the same as that for the preparation of modified PET resin. Step 3: Quickly bond the molten resin sheet onto the chrome-plated cooling roller, control the surface temperature of the cooling roller at 18-22℃, and the cooling time at 3-5s to rapidly cool the sheet to below the glass transition temperature of PET, forming a cooled cast sheet. Step 4: The cooled casting is fed into a synchronous biaxial stretching device and stretched longitudinally and transversely at 105-115℃, with a stretching ratio of 3.5-4.0 times. Step 5: The biaxially stretched film is sent into a heat-setting oven for segmented heat setting: first, it is set at 200-210℃ for 5-10 seconds, then at 220-230℃ for 10-15 seconds, and then cooled to 30-40℃. The film is then wound at a uniform speed with a tension of 3-5 N / cm2 by traction rollers to obtain a special single-layer polyester film with low dielectric and high barrier properties resistant to electrolyte.

[0025] Thirdly, the present invention provides the application of the above-mentioned polyester special film in the fields of new energy soft-pack lithium battery packaging, high-frequency electronic component packaging, and food packaging resistant to steaming and boiling.

[0026] The beneficial effects of this invention are as follows: 1. This invention, through the modification and optimization of the matrix resin and the synergistic effect of functional additives, enables the film to possess both high strength and high flexibility, with excellent tensile, bending and impact resistance properties. Even in ultra-thin sizes, it can maintain stable mechanical load-bearing capacity. At the same time, it has dense resistance to media corrosion, which can effectively resist the erosion of strong corrosive media such as lithium battery electrolytes. In long-term electrolyte immersion environments, the mechanical properties are well retained, which greatly improves the long-term service reliability and service life of the film in new energy soft-pack lithium battery packaging and other scenarios.

[0027] 2. While maintaining the inherent properties of the polyester matrix, this invention also has excellent low dielectric loss performance, which can effectively reduce the loss during signal transmission and meet the needs of high-frequency electronic component packaging. At the same time, by controlling the film matrix, a highly efficient molecular penetration barrier is constructed, which significantly extends the penetration path of water and oxygen molecules and has excellent water and oxygen barrier performance. It can not only isolate the external water vapor and oxygen from the corrosion of the packaged device, but also prevent the leakage of internal media, thus taking into account the dual requirements of high-frequency transmission performance and long-term protection performance.

[0028] 3. The preparation process of the multifunctional modifier of the present invention includes: the pH active bond of DOPO undergoes a ring-opening reaction with the epoxy group of 3-(perfluorobutane)-1,2-epoxypropane under the catalysis of triethylamine base to obtain a monohydroxy fluorinated DOPO modifier; the hydroxyl group of the monohydroxy fluorinated DOPO undergoes an addition reaction with one of the NCO groups of isophorone diisocyanate to form a terminal-NCO prepolymer; then, the octaamino POSS first undergoes a ureation reaction with the terminal-NCO prepolymer, and the remaining amino group reacts with the diepoxy group of hexahydrobisphenol A diglycidyl ether to finally obtain a multifunctional modifier with POSS as the core, containing DOPO group, fluorinated alkyl group, urea bond and other groups, and possessing flame retardancy, hydrophobicity, heat resistance and reactivity.

[0029] 4. The multifunctional modifier of this invention features a synergistic design of rigid heterocyclic structures and flexible connecting segments. Specifically, the perfluoroalkyl hydrophobic structure enhances the surface hydrophobicity and resistance to media penetration of the film; the rigid heterocyclic structure of DOPO improves the chemical corrosion resistance of the molecular chains; and the three-dimensional rigid structure of the cage-like POSS constructs a dense permeation barrier within the matrix. This synergistic effect not only reduces the overall dielectric constant of the system but also prevents the intrusion and diffusion of electrolytes, water molecules, and oxygen. Detailed Implementation

[0030] 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.

[0031] The present invention will be further described below with reference to the following embodiments. Example 1

[0032] A special polyester film, comprising the following components by weight: The mixture comprises 97.5 parts modified PET resin, 0.8 parts nucleating agent, 0.5 parts lubricant, 0.7 parts anti-blocking agent, 0.3 parts composite antioxidant, and 0.2 parts hydrolytic stabilizer; wherein the modified PET resin is prepared by melt blending PET resin chips and multifunctional modifier, and the mass ratio of PET resin chips to multifunctional modifier is 100:5.

[0033] The PET resin chips are fiber grade, with an intrinsic viscosity of 0.70 dL / g and a melt index of 22 g / 10 min (260℃, 2.16 kg). The nucleating agent is nano-talc powder and sodium phenylphosphinate in a mass ratio of 3:1, with a particle size of 300 nm. The lubricant is silicone powder and polyethylene wax in a mass ratio of 2:1. The anti-blocking agent is polymethyl methacrylate (PMMA) microspheres with a molecular weight of 30 W and a particle size of 1.5 μm. The composite antioxidant is antioxidant 1010: antioxidant 168: antioxidant 626 in a mass ratio of 2:1:1. The hydrolytic stabilizer is polycarbodiimide.

[0034] The preparation method of the multifunctional modifier includes the following steps: S1. Weigh 100g DOPO, 500mL 1,4-dioxane, and 0.5g triethylamine and add them to the reaction apparatus. Under nitrogen protection, heat to 85℃ with stirring at 200rpm, and add 183g 3-(perfluorobutane)-1,2-epoxypropane dropwise at a constant rate over 2 hours. After the addition is complete, maintain the temperature for 6 hours. Terminate the reaction, remove the solvent by vacuum distillation, recrystallize twice with anhydrous methanol, and dry under vacuum at 80℃ for 12 hours to obtain the fluorinated DOPO modifier. S2. Add 43g of IPDI and 200mL of ethyl acetate to the reaction apparatus, heat to 40℃ under nitrogen protection, add 100g of the above-mentioned fluorinated DOPO modifier at a uniform rate over 2.5h; then add 0.25g of zinc isooctanoate catalyst, heat to 55℃, and maintain the temperature for 3.5h; terminate the reaction, remove the solvent by vacuum distillation to obtain the terminal-NCO prepolymer; S3. Add 10g of octaaminoPOSS and 100ml of LDMF to the reaction apparatus, under nitrogen protection, and stir at room temperature until completely dissolved; add 42.5g of the above-mentioned terminal-NCO prepolymer at a uniform rate over 4 hours, and react at room temperature for 2 hours after the addition is complete to obtain an amino-terminated POSS grafting intermediate; then raise the temperature to 55℃ and add 8.5g of hexahydrobisphenol A diglycidyl ether at a uniform rate over 1 hour, and keep the reaction at the temperature for 4 hours after the addition is complete; terminate the reaction, add the reaction solution to excess anhydrous methanol to precipitate the product, filter, wash three times with anhydrous methanol, vacuum dry at 85℃ for 12 hours, and pulverize by air jet milling to control the particle size to 2-3μm to obtain a white powdery multifunctional modifier.

[0035] The preparation method of modified PET resin includes the following steps: (1) 1000g of PET resin chips were vacuum dried at 140℃ for 12h, and 50g of the above multifunctional modifier were added to a high-speed mixer and mixed at 3500rpm for 8min at room temperature to obtain a uniformly dispersed mixture. (2) Add the mixture to the twin-screw extruder, with a screw speed of 250 rpm and a material residence time of 4.5 min. Set the temperature of each section of the extruder as follows: Zone 1 235℃, Zone 2 248℃, Zone 3 252℃, Zone 4 258℃, Zone 5 253℃, and Die head 252℃. (3) The extruded strips are cooled with water, air-dried and granulated to obtain modified PET resin.

[0036] The method for preparing the above-mentioned polyester specialty film includes the following steps: Step 1: After vacuum drying at 130℃ for 8 hours, 975g of the above modified PET resin, 8g of nucleating agent, 5g of lubricant, 7g of anti-blocking agent, 3g of composite antioxidant and 2g of hydrolytic stabilizer are added to a high-speed mixer and mixed at 3500rpm for 6 minutes at room temperature to obtain a uniformly dispersed premixed material. Step 2: Add the premixed material to a twin-screw extruder for melt blending. After the melt is stabilized by a melt pump and filtered by a high-precision filter, it is uniformly extruded from a slit die to obtain molten resin sheets. The melt blending parameters are the same as the above-mentioned modified PET resin extrusion parameters. Step 3: Quickly bond the molten resin sheet onto the chrome-plated cooling roller, control the surface temperature of the cooling roller at 20°C, and the cooling time at 4 seconds to rapidly cool the sheet to below the glass transition temperature of PET, forming a cooled cast sheet. Step 4: The cooled casting is fed into a synchronous biaxial stretching device and stretched simultaneously in the longitudinal and transverse directions at 110°C, with a stretching ratio of 3.8 times for both. Step 5: The biaxially stretched film is sent into a heat setting oven for segmented heat setting: first set at 205℃ for 8s, then set at 225℃ for 12s, and then cooled to 35℃. The film is then wound at a uniform speed with a tension of 4N / cm2 by traction rollers to obtain a 25μm thick single-layer polyester special film. Example 2

[0037] A special polyester film, comprising the following components by weight: 95.0 parts modified PET resin, 0.2 parts nucleating agent, 0.1 parts lubricant, 0.3 parts anti-blocking agent, 0.1 parts composite antioxidant, and 0.1 parts hydrolytic stabilizer; wherein the modified PET resin is prepared by melt blending PET resin chips and multifunctional modifier, and the mass ratio of PET resin chips to multifunctional modifier is 100:2.

[0038] The PET resin chips are fiber grade, with an intrinsic viscosity of 0.70 dL / g and a melt index of 22 g / 10 min (260℃, 2.16 kg). The nucleating agent is nano-talc powder and sodium phenylphosphinate in a mass ratio of 2:1 with a particle size of 300 nm. The lubricant is silicone powder and polyethylene wax in a mass ratio of 1:1. The anti-blocking agent is polymethyl methacrylate (PMMA) microspheres with a molecular weight of 30 W and a particle size of 1 μm. The composite antioxidant is antioxidant 1010: antioxidant 168: antioxidant 626 in a mass ratio of 2:1:1. The hydrolytic stabilizer is polycarbodiimide.

[0039] The preparation method of the multifunctional modifier is the same as that in Example 1; the preparation method of the modified PET resin is the same as that in Example 1. Example 3

[0040] A special polyester film, comprising the following components by weight: The mixture comprises 98.8 parts modified PET resin, 1.2 parts nucleating agent, 0.9 parts lubricant, 1.5 parts anti-blocking agent, 1.2 parts composite antioxidant, and 0.8 parts hydrolytic stabilizer; wherein the modified PET resin is prepared by melt blending PET resin chips and multifunctional modifier, and the mass ratio of PET resin chips to multifunctional modifier is 100:8.

[0041] The PET resin chips are fiber grade, with an intrinsic viscosity of 0.70 dL / g and a melt index of 22 g / 10 min (260℃, 2.16 kg). The nucleating agent is nano-talc powder and sodium phenylphosphinate in a mass ratio of 4:1, with a particle size of 300 nm. The lubricant is silicone powder and polyethylene wax in a mass ratio of 3:1. The anti-blocking agent is polymethyl methacrylate (PMMA) microspheres with a molecular weight of 30 W and a particle size of 1 μm. The composite antioxidant is antioxidant 1010: antioxidant 168: antioxidant 626 in a mass ratio of 3:2:1. The hydrolytic stabilizer is polycarbodiimide.

[0042] The preparation method of the multifunctional modifier is the same as that in Example 1; the preparation method of the modified PET resin is the same as that in Example 1.

[0043] Comparative Example 1 A special polyester film, which differs from Example 1 in that it uses PET resin chips and does not contain a multifunctional modifier.

[0044] Calculated by weight, it includes the following ingredients: 97.5 parts PET resin chips, 0.8 parts nucleating agent, 0.5 parts lubricant, 0.7 parts anti-blocking agent, 0.3 parts composite antioxidant, and 0.2 parts hydrolysis stabilizer.

[0045] The remaining mixing, extrusion, stretching, heat setting, and winding processes are completely consistent with those in Example 1, resulting in a 25μm thick single-layer PET film.

[0046] Comparative Example 2 A special polyester film differs from Example 1 in that the preparation method of the multifunctional modifier is different, and the modifier lacks a fluorinated alkyl structure.

[0047] The preparation method of the multifunctional modifier includes the following steps: S1. 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) is directly used as the core raw material for subsequent reactions without fluorine modification. It is then vacuum dried at 80℃ for 12 hours for later use. S2. Add 43g of isophorone diisocyanate (IPDI) and 200mL of ethyl acetate to the reaction apparatus. Under nitrogen protection, heat to 40°C and add 100g of the above-mentioned dried DOPO at a uniform rate over 2.5h. Then add 0.25g of zinc isooctanoate catalyst, heat to 55°C, and maintain the temperature for 3.5h. Terminate the reaction, remove the solvent by vacuum distillation, and obtain the terminal-NCO prepolymer. S3. 10g of octaaminoisobutyl cage-type silsesquioxane (octaaminoPOSS, molecular weight 873.56g / mol) and 100mL LDMMF were added to the reaction apparatus under nitrogen protection and stirred at room temperature until homogeneous. 42.5g of the above-mentioned terminal-NCO prepolymer was added at a uniform rate over a period of 4 hours. After the addition was complete, the reaction was carried out at room temperature for 2 hours to obtain an amino-terminated POSS grafting intermediate. Subsequently, the temperature was raised to 55℃, and 8.5g of hexahydrobisphenol A diglycidyl ether was added dropwise at a uniform rate over a period of 1 hour. After the addition was complete, the reaction was maintained at this temperature for 3 hours. The reaction was terminated, and the reaction solution was slowly added dropwise to excess anhydrous methanol to precipitate the product. After filtration and washing three times with anhydrous methanol, the product was dried under vacuum at 85℃ for 12 hours. The particle size was controlled to be 2-3μm by air jet milling to obtain a multifunctional modifier without fluorinated alkyl groups.

[0048] Comparative Example 3 A special polyester film differs from Example 1 in that the preparation method of the multifunctional modifier is different, and the modifier lacks the octaaminoPOSS structure.

[0049] The preparation method of the multifunctional modifier includes the following steps: S1. Weigh 100g of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO), 500mL of 1,4-dioxane, and 0.5g of triethylamine and add them to the reaction apparatus. Under nitrogen protection, start stirring (200rpm), heat to 85℃, and add 183g of 3-(perfluorobutane)-1,2-epoxypropane dropwise at a constant rate over 2 hours. After the addition is complete, maintain the temperature for 6 hours. Terminate the reaction, remove the solvent by vacuum distillation, recrystallize twice with anhydrous methanol, and dry under vacuum at 80℃ for 12 hours to obtain the fluorinated DOPO modifier. S2. Add 43g of isophorone diisocyanate (IPDI) and 200mL of ethyl acetate to the reaction apparatus. Under nitrogen protection, heat to 40℃ and add 100g of the above-mentioned fluorinated DOPO modifier at a uniform rate over 2.5h. Then add 0.25g of zinc isooctanoate catalyst, heat to 55℃, and maintain the temperature for 3.5h. Terminate the reaction, remove the solvent by vacuum distillation, and obtain the terminal-NCO prepolymer. S3. Add 0.69g of ethylenediamine (with the same total amino equivalent as 10g of octaamino POSS in Example 2) and 100mL LDM to the reaction apparatus, under nitrogen protection, and stir at room temperature until homogeneous; add 42.5g of the above-mentioned terminal-NCO prepolymer at a uniform rate over a period of 4 hours, and react at room temperature for 2 hours after the addition is complete; then raise the temperature to 55°C and add 8.5g of hexahydrobisphenol A diglycidyl ether dropwise at a uniform rate over a period of 1 hour, and maintain the temperature for 3 hours after the addition is complete; terminate the reaction, slowly add the reaction solution to excess anhydrous methanol to precipitate the product, filter, wash three times with anhydrous methanol, vacuum dry at 85°C for 12 hours, and then pulverize by air jet milling to control the particle size to 2-3μm to obtain a multifunctional modifier without cage-like POSS structure.

[0050] Comparative Example 4 A special polyester film differs from Example 1 in that the preparation method of the multifunctional modifier is different, and the modifier lacks the hexahydrobisphenol A diglycidyl ether structure.

[0051] The preparation method of the multifunctional modifier includes the following steps: S1. Weigh 100g of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO), 500mL of 1,4-dioxane, and 0.5g of triethylamine and add them to the reaction apparatus. Under nitrogen protection, start stirring (200rpm), heat to 85℃, and add 183g of 3-(perfluorobutane)-1,2-epoxypropane dropwise at a constant rate over 2 hours. After the addition is complete, maintain the temperature for 6 hours. Terminate the reaction, remove the solvent by vacuum distillation, recrystallize twice with anhydrous methanol, and dry under vacuum at 80℃ for 12 hours to obtain the fluorinated DOPO modifier. S2. Add 43g of isophorone diisocyanate (IPDI) and 200mL of ethyl acetate to the reaction apparatus. Under nitrogen protection, heat to 40℃ and add 100g of the above-mentioned fluorinated DOPO modifier at a uniform rate over 2.5h. Then add 0.25g of zinc isooctanoate catalyst, heat to 55℃, and maintain the temperature for 3.5h. Terminate the reaction, remove the solvent by vacuum distillation, and obtain the terminal-NCO prepolymer. S3. Add 10g of octaaminoisobutyl cage-type silsesquioxane (octaaminoPOSS, molecular weight 873.56g / mol) and 100mL LDM to the reaction apparatus, under nitrogen protection, and stir at room temperature until homogeneous; add 42.5g of the above-mentioned terminal-NCO prepolymer at a uniform rate, controlling the addition time to 4h, and react at room temperature for 2h after the addition is complete, then raise the temperature to 55℃ and keep the reaction at that temperature for 3h; terminate the reaction, slowly drop the reaction solution into excess anhydrous methanol to precipitate the product, filter, wash 3 times with anhydrous methanol, vacuum dry at 85℃ for 12h, and control the particle size to 2-3μm by air jet milling to obtain a multifunctional modifier without hexahydrobisphenol A diglycidyl ether structure.

[0052] The polyester films prepared in the examples and comparative examples were tested respectively, and the test standards and methods included: Mechanical properties: Refer to GB / T 1040.3-2006, tensile speed 50 mm / min, test longitudinal (MD) tensile strength and elongation at break; Dielectric properties: Refer to GB / T 1409-2006, test frequency 1MHz, 23℃, 50%RH, record dielectric loss tanδ; Barrier performance: Water vapor transmission rate (WVTR) refers to GB / T 26253-2010, 38℃, 90%RH; Oxygen transmission rate (OTR) refers to GB / T 19789-2005, 23℃, 0%RH.

[0053] Electrolyte resistance: The sample was immersed in 1 mol / L LiPF6 in EC / EMC / DMC (1:1:1) electrolyte and sealed at 85℃ for 7 days. The tensile strength before and after immersion was tested.

[0054] Dimensional stability: Refer to GB / T 12027-2004, place at 150℃ for 30 min, and test the longitudinal (MD) heat shrinkage rate.

[0055] Limiting Oxygen Index (LOI): Refer to GB / T 2406.2-2009, tested at room temperature.

[0056] The test results are shown in Table 1: Table 1. Overall performance test results of the thin films in Example 1 and the comparative example. As can be seen from Table 1, the single-layer special film structure of Example 1 of the present invention has high mechanical strength (tensile strength 233 MPa), ultra-low dielectric loss (tanδ=0.0042), high water and oxygen barrier properties, excellent resistance to electrolyte corrosion (strength retention rate 96.8%), excellent low-temperature heat-sealing properties, high dimensional stability (heat shrinkage rate <0.85% at 150℃), and high oxygen index. Comparative Example 1 (without modifier) ​​showed significantly inferior core performance compared to the examples; Comparative Example 2 (lacking the fluorinated alkyl structure) exhibited a significant decrease in electrolyte resistance and water and oxygen barrier properties; Comparative Example 3 (lacking the POSS structure) showed a significant deterioration in mechanical properties, dimensional stability, dielectric properties, and barrier properties; Comparative Example 4 (lacking the epoxy end-capping component) showed a significant increase in processing yellowing index and a decrease in electrolyte resistance and mechanical properties.

[0057] In summary, it can be demonstrated that the thin film prepared in Example 1 of the present invention can simultaneously achieve a comprehensive balance of properties, including a single-layer homogeneous structure, resistance to electrolyte corrosion, low dielectric, high water and oxygen barrier, high mechanical properties, and high dimensional stability.

[0058] 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.

[0059] 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 specialty film, characterized in that, Calculated by weight, it includes the following ingredients: 95.0-98.8 parts modified PET resin, 0.2-1.2 parts nucleating agent, 0.1-0.9 parts lubricant, 0.3-1.5 parts anti-blocking agent, 0.1-1.2 parts composite antioxidant, and 0.1-0.8 parts hydrolysis stabilizer; wherein the modified PET resin is prepared by melt blending PET resin chips and multifunctional modifier, and the mass ratio of PET resin chips to multifunctional modifier is 100:2-8.

2. The polyester specialty film according to claim 1, characterized in that, The PET resin chips are fiber-grade PET chips with an intrinsic viscosity of 0.68-0.72 dL / g and a melt index of 18-30 g / 10 min at 260℃ and 2.16 kg.

3. The polyester specialty film according to claim 1, characterized in that, The preparation method of the multifunctional modifier includes the following steps: S1. Weigh 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 1,4-dioxane, and triethylamine and add them to the reaction apparatus. Use nitrogen as a protective gas, heat to 80-90℃, start stirring, and add 3-(perfluorobutane)-1,2-epoxypropane dropwise. After the addition is complete, keep the reaction at the temperature for 4-8 hours. Post-process to obtain fluorinated DOPO modifier. S2. Isophorone diisocyanate and ethyl acetate are added to the reaction apparatus. Under nitrogen protection, the temperature is raised to 35-45℃, fluorine-containing DOPO modifier is added, then the catalyst is added, the temperature is raised to 50-60℃, and the reaction is maintained for 3-4 hours. The reaction is terminated, and the solvent is removed by vacuum distillation to obtain the terminal-NCO prepolymer. S3. Add octaaminoisobutyl cage-type silsesquioxane and solvent to the reaction apparatus, and stir evenly at room temperature under nitrogen protection; add terminal-NCO prepolymer, with the addition time controlled at 3-5h; after the addition is complete, react at room temperature for 1-3h, then raise the temperature to 40-60℃, add hexahydrobisphenol A diglycidyl ether, and keep the reaction at this temperature for 2-4h. Post-treatment yields a white powdery multifunctional modifier.

4. A polyester specialty film according to claim 3, characterized in that, In S1, the mass ratio of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and 3-(perfluorobutane)-1,2-epoxypropane is 1:1.76-1.98; in S2, the mass ratio of isophorone diisocyanate and fluorinated DOPO modifier is 0.42-0.45:1; the mass ratio of octaaminoisobutyl cage-type silsesquioxane, terminal-NCO prepolymer and hexahydrobisphenol A diglycidyl ether is 1:3.8-4.7:0.7-1.

0.

5. A polyester specialty film according to claim 1, characterized in that, The nucleating agent is a mixture of nano-talc powder and sodium phenylphosphinate in a mass ratio of 2-4:1, with a particle size of 200-600nm; the lubricant is a mixture of silicone powder and polyethylene wax in a mass ratio of 1-3:

1.

6. A polyester specialty film according to claim 1, characterized in that, The anti-blocking agent is polymethyl methacrylate microspheres with a particle size of 1-2 μm; the hydrolytic stabilizer is polycarbodiimide.

7. A polyester specialty film according to claim 1, characterized in that, The composite antioxidant is a mixture of antioxidant 1010, antioxidant 168 and antioxidant 626 in a mass ratio of 2-3:1-2:

1.

8. A polyester specialty film according to claim 1, characterized in that, The preparation method of the modified PET resin includes the following steps: (1) Dry PET resin chips in vacuum at 130-150℃ for 10-15h, add them to a high-speed mixer with multifunctional modifier according to the ratio, and mix at 3000-4000rpm for 5-10min at room temperature to obtain a uniformly dispersed mixture. (2) Add the mixture to the twin-screw extruder, with a screw speed of 200-300 rpm and a material residence time of 4-5 min. Set the temperature of each section of the extruder as follows: Zone 1 230-240℃, Zone 2 245-250℃, Zone 3 250-255℃, Zone 4 255-260℃, Zone 5 250-255℃, and Die head 250-255℃. (3) The extruded strips are cooled with water, air-dried and granulated to obtain modified PET resin.

9. A method for preparing the polyester special film according to claim 1, characterized in that, Includes the following steps: Step 1: After drying, the modified PET resin, nucleating agent, lubricant, anti-blocking agent, composite antioxidant, and hydrolysis stabilizer are mixed evenly to obtain a premixed material. Step 2: Add the premixed material to a twin-screw extruder for melt blending to obtain molten resin sheets; Step 3: Quickly bond the molten resin sheet onto the chrome-plated cooling roller to rapidly cool the sheet to below the glass transition temperature of PET, forming a cooled cast sheet; Step 4: The cooled casting is fed into a synchronous biaxial stretching device for longitudinal and transverse stretching. Step 5: The biaxially stretched film is sent into a heat-setting oven for segmented heat setting, followed by cooling, traction, and winding to obtain a polyester special film.

10. The application of the polyester special film according to claim 1 in the fields of soft-pack lithium battery packaging, electronic component packaging, and food packaging resistant to cooking.

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