Polyester film and preparation method thereof

Abstract

The invention belongs to the field of polyester films, and relates to a polyester film and a preparation method thereof, the polyester film is formed by laminating three polyester resin layers, and the three polyester resin layers are a first surface layer, a core layer and a second surface layer; wherein the first surface layer is also named as a layer A; the core layer is also named as a layer B, and the second surface layer is also named as a layer C; and the layer A consists of 0.5 to 30 weight percent of functional master batch M and 70 to 99.5 weight percent of polyethylene glycol terephthalate resin relative to the weight of the layer A. The polyester film has the performance characteristics of super smoothness (Sa < 5nm), flawless appearance, excellent dynamic thermal performance and the like.

Description

Technical Field

[0001] This invention belongs to the field of polyester film, and relates to a high-performance polyester film with an A / B / C three-layer structure and ultra-smooth function, particularly a polyester film and its preparation method. Background Technology

[0002] BOPET film, short for biaxially oriented polyester film, is a high-performance plastic film produced through a biaxial stretching process. It possesses excellent impact resistance, tear resistance, water and oxygen barrier properties, solvent resistance, and high dielectric strength, and is widely used in various fields such as electronics, magnetic recording, optics, packaging, and industry.

[0003] Electronic products are closely related to people's daily lives, making life more convenient and of higher quality. As the application of traditional electronic products becomes increasingly widespread, the demand for electronic products from emerging industries is also growing. These emerging industries include new energy vehicles, new displays, and supercomputing models. These new applications place higher demands on the stability, small size, and high capacity of electronic products. Multilayer ceramic capacitors (MLCCs), as core components of electronic products, are often referred to as the "rice" of the electronics industry, their most essential function being the storage of electrical charge. The widespread adoption of 5G smartphones is a major driving force. 5G phones need to support more frequency bands (Sub-6GHz, mmWave), increasing the number of internal radio frequency front-end modules (FEMs), resulting in a 20% to 40% higher demand for MLCCs compared to 4G phones. A high-end smartphone may use more than 1500 MLCCs. The "three-electric system" (battery, motor, and electronic control) of new energy vehicles is a major user of MLCCs. In particular, inverters (which convert DC power from the battery to AC power from the motor) require a large number of high-voltage, high-reliability MLCCs. A pure electric vehicle uses approximately 3 to 5 times more MLCCs than a traditional gasoline-powered vehicle. ADAS (Advanced Driver Assistance Systems) sensors (cameras, radar, lidar) and infotainment systems in smart cockpits also require a large number of high-specification MLCCs. Cloud computing and AI servers have extremely high requirements for power management and signal integrity, driving the demand for high-performance MLCCs; a single new energy vehicle may use more than 10,000 MLCCs. As the cornerstone of electronic circuits, the market not only pursues increased "quantity" of MLCCs but also places higher demands on their "quality" (miniaturization, high capacity, high reliability, and high-frequency characteristics). This makes the MLCC industry a dynamic and technologically challenging field.

[0004] The improvement of MLCC "quality" (miniaturization, high capacity, high reliability, and high-frequency characteristics) requires the support of key raw materials in the front-end manufacturing process. Among them, the most crucial is the MLCC release film, the "carrier" for casting ceramic paste. This carrier needs extremely low surface roughness and no defects (scratches, crystal points, etc.). Since a single release layer does not significantly affect surface roughness, the aforementioned high requirements are placed on the BOPET film substrate. Ultra-smooth (Sa < 5nm) MLCC release substrates are still monopolized by foreign companies. Although domestic film manufacturers have made numerous explorations, substantial breakthroughs are still difficult to achieve. Regarding the requirements of MLCC "quality" (miniaturization, high capacity, high reliability, and high-frequency characteristics), the existing technical solutions in the polyester film field include: 1. Adding nanoscale organic or inorganic particles, such as PS, PMMA, silica, calcium carbonate, and kaolin, to the surface layer during polyester film production to obtain low surface roughness and achieve ultra-smooth surfaces. 2. During the downstream release layer processing, multiple release layers are applied to the surface of the BOPET film substrate. Through continuous coverage by the release layers, an ultra-smooth film surface is achieved.

[0005] Although technicians have conducted extensive research on polyester film, current technical solutions for addressing polyester film issues still have many shortcomings: 1. During polyester film production, adding nano-sized organic or inorganic particles to the surface can achieve a low surface roughness. However, we know that the smaller the particle size, the higher the surface energy. When added to polyester film, it is prone to agglomeration, forming crystal points and resulting in uneven surface roughness. Low surface roughness also makes polyester film more susceptible to scratches during production, which can lead to unstable capacitance during MLCC processing and affect product quality. Using slightly larger particles can prevent agglomeration and scratches, but it is difficult to achieve ideal surface roughness. 2. Using multiple release coatings can cover the unevenness of the polyester film surface, achieving a smoother surface. However, applying multiple release layers affects the release force of the release layer, causing unstable adhesion of the outermost release layer surface. At the same time, each coat of release layer means that the polyester film needs to pass through various guide rollers and ovens on the production line, which can easily lead to scratches, impurities, etc., making it more difficult to control the appearance of the polyester film surface, affecting the processing of downstream MLCC products. The multi-layer release process is cumbersome and costly. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a polyester film and its preparation method. The polyester film has the characteristics of ultra-smoothness (Sa < 5nm), no apparent defects, and excellent dynamic thermal properties.

[0007] To achieve the above-mentioned technical objectives, the technical solution adopted in this application is a polyester film, wherein the polyester film is composed of three layers of polyester resin laminated together, the three layers of polyester resin being a first surface layer, a core layer, and a second surface layer; wherein, the first surface layer is also known as layer A; the core layer is also known as layer B; and the second surface layer is also known as layer C. Wherein, layer A is composed of 0.5 wt% to 30 wt% functional masterbatch M and 70 wt% to 99.5 wt% polyethylene terephthalate resin relative to the weight of layer A; The B layer is composed of 10% to 50% modified polyester Y and 50% to 90% polyethylene terephthalate resin relative to the weight of the B layer. The C layer is composed of 50% to 90% by weight of modified polyester Y and 10% to 50% by weight of polyethylene terephthalate resin relative to the weight of the C layer. The functional masterbatch M is composed of 0.5 wt% to 15 wt% inorganic particles K and 85 wt% to 99.5 wt% modified polyester Y; The preparation of the modified polyester Y includes the following steps: Step 1: Add the specified amounts of dicarboxylic acid, ethylene glycol, catalyst, and stabilizer sequentially to the polyester reactor, slurry for 15 minutes, and purge with nitrogen for protection. Esterify for 2-4 hours at 235℃-260℃ and 260KPa. The molar ratio of dicarboxylic acid to ethylene glycol is 1:1.18 to 1:1.43. Step 2: Determine the esterification endpoint based on the water output. After complete esterification, turn on the vacuum and perform polycondensation reaction at 265℃~280℃ and 20Pa~80Pa for 2.5h~4h. After fiber formation, cooling, pelletizing and drying, the modified polyester Y described in this invention is obtained. The intrinsic viscosity of the modified polyester Y is 0.65dl / g~0.69dl / g. In addition to terephthalic acid, the dicarboxylic acid also contains a third component; the third component is selected from bis(3,4-dicarboxyphenyl)dimethylsilane, 2,2,3,3-tetrafluorosuccinic acid and 3,5-bis(p-carboxyphenyl)benzoic acid; the total content of the third component in the dicarboxylic acid is 5 mol% to 15 mol%; the content of terephthalic acid in the dicarboxylic acid is 85 mol% to 95 mol%; the molar ratio of bis(3,4-dicarboxyphenyl)dimethylsilane, 2,2,3,3-tetrafluorosuccinic acid and 3,5-bis(p-carboxyphenyl)benzoic acid is 2 to 5: 1 to 3: 3 to 8. The catalyst is selected from antimony-based, iron-based, aluminum-based, germanium-based, or titanium-based catalysts, and the addition amount is 60ppm~250ppm; The amount of stabilizer added is 30ppm~150ppm.

[0008] As an improved technical solution of this application, the inorganic particles K have a particle size (d) of 0.03μm≤d≤1μm, a volume shape factor (e) of 0.5≤e≤0.9, a Mohs hardness of 3, and are made of calcium carbonate.

[0009] As an improved technical solution of this application, the stabilizer is selected from one or more of the following in any weight ratio: trimethyl phosphate, triphenyl phosphate, tetrabutyl titanate, tetraethyl titanate, etc.

[0010] As an improved technical solution of this application, the surface roughness Sa of the C layer is <5nm.

[0011] As an improved technical solution of this application, the thickness of the polyester film is 8μm~50μm.

[0012] The thickness of layer A in the polyester film accounts for 2% to 15% of the total thickness.

[0013] As an improved technical solution of this application, the thickness of the C layer in the polyester film accounts for 2% to 29% of the total thickness, and the thickness of the A layer and the C layer can be the same or different.

[0014] As an improved technical solution of this application, the intrinsic viscosity of the modified polyester Y is 0.65 dl / g ≤ η ≤ 0.69 dl / g.

[0015] Another object of this application is to provide a method for preparing a polyester film, comprising the following steps: Step 1: Mix the functional masterbatch M, modified polyester Y and polyethylene terephthalate resin in the corresponding proportions for each layer in advance, and then send them into the corresponding melt extrusion system for extrusion and co-extrusion into the three-layer die. Step 2: High-performance polyester film is obtained through casting, longitudinal stretching, transverse stretching, shaping, cooling, traction, and winding; Step 3: The temperature of the melt extrusion is 265℃~285℃.

[0016] As an improved technical solution of this application, the longitudinal stretching ratio of the longitudinal stretching process is 2.8 to 4.0, and the transverse stretching ratio of the transverse stretching process is 3.5 to 5.5.

[0017] As an improved technical solution of this application, the heat setting temperature of the setting process is 220℃~240℃.

[0018] Beneficial effects 1. By selecting a third component to modify the polyester, the functions of each monomer are imparted to the modified polyester, achieving high performance. This component is embedded in the polymer chain in a block form, enabling new functions without altering the polyester's fundamental properties or affecting subsequent processing.

[0019] 2. The functional masterbatch used in this invention is made by modifying polyester and limiting inorganic particles, achieving effects that conventional functional masterbatches cannot achieve.

[0020] 3. By coordinating the formulations of layer A and layer C, ultra-smoothness (Sa < 5nm) is achieved while ensuring the appearance and dynamic thermal properties of the thin film.

[0021] 4. The high-performance polyester film of this invention can be produced in one process, which is simple, low-cost, and has stable performance. Detailed Implementation

[0022] To facilitate understanding of the present invention, a more comprehensive description will be given below with reference to specific embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of the present invention.

[0023] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0024] A polyester film is composed of three layers of polyester resin laminated together, wherein the three layers of polyester resin are a first surface layer (layer A), a core layer (layer B), and a second surface layer (layer C).

[0025] Layer A consists of 0.5% to 30% by weight of functional masterbatch M and 70% to 99.5% by weight of polyethylene terephthalate resin, relative to the weight of Layer A. When the content of functional masterbatch M in Layer A is less than 0.5% by weight, the slip-forming particles are too few, making it difficult to guarantee a slip-forming effect; when the content of functional masterbatch M in Layer A is greater than 30% by weight, the slip-forming particles are too many, which can easily cause slippage between the film surface and the roller surface, and between film surfaces themselves.

[0026] Layer B consists of 10% to 50% by weight of modified polyester Y and 50% to 90% by weight of polyethylene terephthalate resin relative to the weight of Layer B. When the content of modified polyester Y in Layer B is less than 10% by weight, Layer B, as a support layer of the polyester film, has too little modified polyester Y, making it difficult to effectively improve the dynamic thermal properties of the polyester film; when the content of modified polyester Y in Layer B is greater than 50% by weight, the excessive amount of modified polyester may lead to overperformance and increased costs.

[0027] The C-layer is composed of 50% to 90% by weight of modified polyester Y and 10% to 50% by weight of polyethylene terephthalate resin, with a surface roughness Sa < 5 nm. When the content of modified polyester Y in the C-layer is less than 50% by weight, it is difficult to guarantee good machine passability on this surface; when the content of modified polyester Y in the C-layer is greater than 90% by weight, the content of certain monomer components in the modified polyester is too high, which can easily affect the film surface energy and is not conducive to subsequent processing. When the surface roughness Sa of the C-layer is greater than 5 nm, the requirements for miniaturization, high capacity, high reliability, and high frequency characteristics of MLCCs cannot be met.

[0028] Polyethylene terephthalate is typically made from polyester resin with an intrinsic viscosity of 0.67 dl / g.

[0029] The functional masterbatch M consists of 0.5% to 15% inorganic particles K and 85% to 99.5% modified polyester Y.

[0030] The preparation of the modified polyester Y includes the following steps: Step 1: Add the specified amounts of dicarboxylic acid, ethylene glycol, catalyst, and stabilizer sequentially to the polyester reactor, slurry for 15 minutes, and purge with nitrogen for protection. Esterify for 2-4 hours at 235℃-260℃ and 260KPa. The molar ratio of dicarboxylic acid to ethylene glycol is 1:1.18 to 1:1.43. Step 2: Determine the esterification endpoint based on the water output. After complete esterification, turn on the vacuum and perform polycondensation reaction at 265℃~280℃ and 20Pa~80Pa for 2.5h~4h. After fiber formation, cooling, pelletizing and drying, the modified polyester Y described in this invention is obtained. The intrinsic viscosity of the modified polyester Y is 0.65dl / g~0.69dl / g. In addition to terephthalic acid, the dicarboxylic acid also contains a third component; the third component is selected from bis(3,4-dicarboxyphenyl)dimethylsilane, 2,2,3,3-tetrafluorosuccinic acid, and 3,5-bis(p-carboxyphenyl)benzoic acid. The total content of the third component in the dicarboxylic acid is 5 mol% to 15 mol%; the molar ratio of bis(3,4-dicarboxyphenyl)dimethylsilane, 2,2,3,3-tetrafluorosuccinic acid, and 3,5-bis(p-carboxyphenyl)benzoic acid is 2~5:1~3:3~8; and the molar content of terephthalic acid in the dicarboxylic acid is 85 mol% to 95 mol%.

[0031] The catalyst is selected from antimony-based, iron-based, aluminum-based, germanium-based, or titanium-based catalysts, and the addition amount is 60ppm~250ppm.

[0032] The stabilizer is selected from one or any combination of trimethyl phosphate, triphenyl phosphate, tetrabutyl titanate, tetraethyl titanate, etc., with trimethyl phosphate and triphenyl phosphate being preferred, and trimethyl phosphate being the most preferred. The addition amount is 30ppm to 150ppm.

[0033] The modified polyester Y is prepared using the molar ratio designed in this invention, and the functions of each monomer are imparted to the modified polyester, thereby achieving the optimal performance of the modified polyester.

[0034] To achieve the ultra-smooth performance of the polyester film, this invention selects an ultra-smooth surface without adding organic or inorganic particles. Although particles are added to the other side to ensure partial machine passability, the ultra-smooth surface still needs to pass through some rollers during production, and its machine passability still has certain requirements. The third component, bis(3,4-dicarboxyphenyl)dimethylsilane, contains dimethylsilyl groups, which have extremely low surface energy. In polyester, the dimethylsilyl portion tends to migrate to the film surface, like a very thin layer of "silicone oil" on the film surface, greatly reducing the coefficient of friction of the film surface. At the same time, this soft silicone surface layer can act as a buffer barrier. When the film surface is subjected to external forces (such as scratching or friction), this lubricating layer can effectively disperse stress and prevent hard objects from directly contacting and scratching the polyester body, thereby greatly improving the machine passability and scratch resistance of the ultra-smooth surface. The tetrafluoroalkyl group in 2,2,3,3-tetrafluorosuccinic acid has extremely low fluorine-carbon bond energy. Similar to silanes, the fluorinated segments migrate strongly to the film surface, exhibiting excellent lubricity. This minimizes the film's coefficient of friction and enhances the machine passability of the ultra-smooth surface. It forms a double-protection mechanism with the dimethylsilyl group in bis(3,4-dicarboxyphenyl)dimethylsilane, providing a slip-resistant effect without protruding on the film surface and affecting surface roughness. The side phenyl group in 3,5-bis(p-carboxyphenyl)benzoic acid has high steric hindrance, preventing relative movement between polymer chains and ensuring the polyester film does not deform under heat. Hydrogen bonds can form between the formic acid group in the side group, the hydroxyl hydrogen atom (-OH) on the carboxyl group, and the oxygen atom (C=O) on the carbonyl group of the ester group. These hydrogen bonds are stronger than van der Waals forces, ensuring no slippage between polyester polymer chains. Used as an interlayer in polyester films, this effectively improves the dynamic thermal properties of the polyester film. Through the molar fraction design of this invention, the synergistic effect among the acid monomers can optimize the performance of the modified polyester Y. Although the modified polyester Y in this invention has excellent passing performance, it still requires the cooperation of the A layer formulation to achieve ultra-smoothness, excellent dynamic thermal properties, and ensure the appearance of the polyester film surface.

[0035] The functional masterbatch M of this invention is composed of 0.5 wt% to 15 wt% inorganic particles K and 85 wt% to 99.5 wt% modified polyester Y. When the content of inorganic particles K in the functional masterbatch M is less than 0.5 wt%, the content of inorganic particles in the masterbatch is low, which is not conducive to high-concentration addition; when the content of inorganic particles K in the functional masterbatch M is greater than 15 wt%, the content of inorganic particles in the masterbatch is too high. Since the bulk density of the masterbatch and the polyester differs greatly, when added to the film, it is easy to cause delamination, resulting in unstable film performance.

[0036] The inorganic particles K have a particle size (d) of 0.03 μm ≤ d ≤ 1 μm, a volumetric shape factor (e) of 0.5 ≤ e ≤ 0.9, a Mohs hardness of 3, and are made of calcium carbonate. When the particle size d < 0.03 μm, the small particle size results in high surface energy and easy aggregation, forming crystal points within the film. When the particle size d > 1 μm, the large particle size leads to greater surface roughness and a rougher film surface, which can easily affect the surface roughness of the ultra-smooth surface during winding. When the volumetric shape factor e < 0.5, the irregularity is high, which is not conducive to ensuring the smoothness of the film surface. When the volumetric shape factor e > 0.9, the shape is close to spherical, providing excellent smoothness, but the manufacturing cost is high, resulting in a relatively low cost-effectiveness.

[0037] The thickness of the high-performance polyester film described in this invention is 8μm~50μm.

[0038] The thickness of layer A in the high-performance polyester film described in this invention accounts for 2% to 15% of the total thickness.

[0039] The high-performance polyester film of this invention has a C-layer thickness of 2% to 29% of the total thickness, and the A-layer thickness can be the same as or different from the C-layer thickness. When the A-layer thickness is less than 2% of the total thickness, the slip particles (which are calcium carbonate particles in the functional masterbatch M of the A-layer, serving a slipping function) tend to protrude excessively on the film surface, resulting in a large surface roughness. During face-to-face winding, this affects the surface roughness of the other side, making it easy for the roller surface and film surface to slip and cause scratches. When the A-layer thickness is greater than 2% of the total thickness, the surface layer is too thick, making it difficult for the slip particles to protrude, resulting in poor machine passability. When the C-layer thickness is less than 2% of the total thickness, the surface layer is thin, and the content of modified polyester per unit volume is low, affecting the function of modified polyester. When the C-layer thickness is greater than 29% of the total thickness, it is easy to cause performance overkill. When the content of modified polyester per unit volume is too high, the slip properties are too good, which also easily causes slippage.

[0040] The modified polyester Y and functional masterbatch M described in this invention can be prepared using the following methods: The preparation method of modified polyester Y is as follows: Step 1: Add the required dicarboxylic acid, ethylene glycol, catalyst, and stabilizer to the polyester reactor in sequence, slurry for 15 minutes, and purge with nitrogen for protection. Esterify for 2 to 4 hours at 235℃~260℃ and 260KPa.

[0041] Step 2: Determine the esterification endpoint based on the water output. After complete esterification, turn on the vacuum and perform polycondensation reaction at 265℃~280℃ and 20Pa~80Pa for 2.5h~4h. After fiber formation, cooling, pelletizing and drying, the modified polyester Y described in this invention is obtained. The intrinsic viscosity of the modified polyester Y is 0.65dl / g~0.69dl / g.

[0042] The preparation method of functional masterbatch M is as follows: The modified polyester Y with an intrinsic viscosity of 0.65 dl / g to 0.69 dl / g prepared above was selected as the base material; Then, 0.5%~15% by weight of inorganic particles K with 0.03μm≤d≤1μm, 0.5≤e≤0.9, Mohs hardness of 3 and material of calcium carbonate, and 85%~99.5% by weight of modified polyester Y are mixed evenly and fed into a twin-screw extruder. Vacuuming is initiated, and the product is processed through fiber formation, cooling, pelletizing, and drying to obtain the functional masterbatch M described in this invention. The intrinsic viscosity of functional masterbatch M is 0.60 dl / g to 0.66 dl / g.

[0043] The functional masterbatch M of this invention is prepared by twin-screw granulation instead of synthesis. The main reason is that during synthesis, the prolonged high temperature of esterification and polycondensation processes may damage the functional groups in the modified monomers, affecting their effectiveness.

[0044] The specific preparation method of the high-performance polyester film of the present invention is as follows: 1. The functional masterbatch M, modified polyester Y and polyethylene terephthalate resin of each layer are mixed separately in advance and sent to the corresponding melt extrusion system for extrusion, and then co-extruded through a three-layer die at a temperature of 265℃~285℃, and then cast into sheets.

[0045] 2. The casting is stretched longitudinally, with a longitudinal stretching ratio of 2.8 to 4.0.

[0046] 3. Stretch the longitudinal stretching sheet laterally, with a lateral stretching ratio of 3.5 to 5.5.

[0047] 4. Heat set the stretched film at a temperature of 220℃~240℃.

[0048] 5. Then proceed with cooling, traction, and winding.

[0049] The present invention will be further described below with reference to the embodiments, but the implementation and protection scope of the present invention are not limited to these embodiments.

[0050] Example 1 Preparation of modified polyester Y: According to the molar ratio of dicarboxylic acid to ethylene glycol of 1:1.18, the amount of antimony added to ethylene glycol is 60 ppm, and the amount of trimethyl phosphate and triphenyl phosphate combined added is 30 ppm. The dicarboxylic acid contains 5 mol% of a third component. In the third component, the molar ratio of bis(3,4-dicarboxyphenyl)dimethylsilane to 2,2,3,3-tetrafluorosuccinic acid to 3,5-bis(p-carboxyphenyl)benzoic acid is 2:1:3, and the molar percentage of terephthalic acid is 95 mol.

[0051] After the above mixture is evenly mixed, it is added to the polyester synthesis reactor and pulped for 15 minutes. Nitrogen gas is introduced for protection, and esterification is carried out for 2 hours at 235℃~260℃ and 260KPa. After esterification, vacuum is turned on, and polycondensation reaction is carried out for 4 hours at 265℃~280℃ and 20Pa. After fiber forming, cooling, pelletizing and drying, modified polyester Y with an intrinsic viscosity of 0.69dl / g is obtained.

[0052] Preparation of functional masterbatch M: 99.5% by weight of the modified polyester Y with an intrinsic viscosity of 0.69 dl / g prepared above and 0.5% by weight of inorganic particles K with a particle size of d=0.03μm, a volume shape factor of e=0.5, a Mohs hardness of 3, and a material of calcium carbonate were mixed evenly and fed into a twin-screw extruder. Vacuum was applied, and the mixture was filamentized, cooled, pelletized, and dried to obtain a functional masterbatch M with an intrinsic viscosity of 0.66 dl / g.

[0053] Preparation of high-performance polyester films: 30 wt% of functional masterbatch M with an intrinsic viscosity of 0.66 dl / g, 70 wt% of polyethylene terephthalate resin with an intrinsic viscosity of 0.67 dl / g (layer A), 50 wt% of modified polyester Y with an intrinsic viscosity of 0.69 dl / g, 50 wt% of polyethylene terephthalate resin with an intrinsic viscosity of 0.67 dl / g (layer B), 90 wt% of modified polyester Y with an intrinsic viscosity of 0.69 dl / g, and 10 wt% of polyethylene terephthalate resin with an intrinsic viscosity of 0.67 dl / g (layer C) were pre-mixed and treated before being fed into the phase... The corresponding melt extrusion system, at a temperature of 265℃, enters a three-layer die for co-extrusion, and is cast onto a casting roll to form an A / B / C structure extruded casting. The casting is then longitudinally stretched at a temperature of 68℃~87℃ with a longitudinal stretch ratio of 4.0. The longitudinally stretched film is then transversely stretched at a temperature of 100℃~123℃ with a transverse stretch ratio of 5.5. The stretched film is then shaped at a temperature of 220℃. Finally, the film is cooled, drawn, and wound to obtain a polyester film with a thickness of 8μm, wherein the A layer accounts for 15% of the total thickness and the C layer accounts for 15% of the total thickness.

[0054] Example 2 Preparation of modified polyester Y: The mixture was prepared with a dicarboxylic acid to ethylene glycol molar ratio of 1:1.23, ethylene glycol antimony added at 70 ppm, and trimethyl phosphate added at 50 ppm. The dicarboxylic acid contained 7 mol% of a third component, in which the molar ratio of bis(3,4-dicarboxyphenyl)dimethylsilane to 2,2,3,3-tetrafluorosuccinic acid to 3,5-bis(p-carboxyphenyl)benzoic acid was 3:1:4, and the molar percentage of terephthalic acid was 93 mol%. After thorough mixing, the mixture was added to a polyester synthesis reactor and pulped for 15 minutes under nitrogen protection. Esterification was carried out for 2.5 h at 235℃~260℃ and 260 kPa. After esterification, vacuum was applied, and polycondensation was carried out for 3.5 h at 265℃~280℃ and 30 Pa. After fiber formation, cooling, pelletizing, and drying, modified polyester Y with an intrinsic viscosity of 0.68 dl / g was obtained.

[0055] Preparation of functional masterbatch M: 99% by weight of the modified polyester Y with an intrinsic viscosity of 0.68 dl / g prepared above and 1% by weight of inorganic particles K with a particle size of d=0.05μm, a volume shape factor of e=0.5, a Mohs hardness of 3, and a material of calcium carbonate were mixed evenly and fed into a twin-screw extruder. Vacuum was applied, and the mixture was filamentized, cooled, pelletized, and dried to obtain a functional masterbatch M with an intrinsic viscosity of 0.65 dl / g.

[0056] Preparation of high-performance polyester films: 25 wt% of functional masterbatch M with an intrinsic viscosity of 0.65 dl / g, 75 wt% of polyethylene terephthalate resin with an intrinsic viscosity of 0.67 dl / g (layer A), 45 wt% of modified polyester Y with an intrinsic viscosity of 0.68 dl / g, 55 wt% of polyethylene terephthalate resin with an intrinsic viscosity of 0.67 dl / g (layer B), 80 wt% of modified polyester Y with an intrinsic viscosity of 0.68 dl / g, and 20 wt% of polyethylene terephthalate resin with an intrinsic viscosity of 0.67 dl / g (layer C) were pre-mixed and treated before being fed into the appropriate... The melt extrusion system, at a temperature of 270℃, enters a three-layer die co-extrusion process and is cast onto a casting roll to form an A / B / C structure extruded casting. The casting is then longitudinally stretched at a temperature of 68℃~87℃ with a longitudinal stretch ratio of 3.8. The longitudinally stretched film is then transversely stretched at a temperature of 100℃~123℃ with a transverse stretch ratio of 5.2. The stretched film is then shaped at a temperature of 225℃. Finally, the film is cooled, drawn, and wound to obtain a 12μm thick polyester film, in which the A layer accounts for 13% of the total thickness and the C layer accounts for 18% of the total thickness.

[0057] Example 3 Preparation of modified polyester Y: The mixture was prepared with a dicarboxylic acid to ethylene glycol molar ratio of 1:1.35, ethylene glycol antimony added at 130 ppm, and trimethyl phosphate added at 70 ppm. The dicarboxylic acid contained a 10 mol% third component, in which the molar ratio of bis(3,4-dicarboxyphenyl)dimethylsilane to 2,2,3,3-tetrafluorosuccinic acid to 3,5-bis(p-carboxyphenyl)benzoic acid was 3:2:5, and the molar percentage of terephthalic acid was 90 mol%. After thorough mixing, the mixture was added to a polyester synthesis reactor and pulped for 15 minutes under nitrogen protection. Esterification was carried out for 2.5 h at 235℃~260℃ and 260 kPa. After esterification, vacuum was applied, and polycondensation was carried out for 3 h at 265℃~280℃ and 35 Pa. After fiber formation, cooling, pelletizing, and drying, modified polyester Y with an intrinsic viscosity of 0.68 dl / g was obtained.

[0058] Preparation of functional masterbatch M: 97% by weight of the modified polyester Y with an intrinsic viscosity of 0.68 dl / g prepared above and 3% by weight of inorganic particles K with a particle size of d=0.1μm, a volume shape factor of e=0.6, a Mohs hardness of 3, and a material of calcium carbonate were mixed evenly and fed into a twin-screw extruder. Vacuum was applied, and the mixture was filamentized, cooled, pelletized, and dried to obtain a functional masterbatch M with an intrinsic viscosity of 0.63 dl / g.

[0059] Preparation of high-performance polyester films: 20 wt% of functional masterbatch M with an intrinsic viscosity of 0.63 dl / g, 80 wt% of polyethylene terephthalate resin with an intrinsic viscosity of 0.67 dl / g (layer A), 40 wt% of modified polyester Y with an intrinsic viscosity of 0.68 dl / g, 60 wt% of polyethylene terephthalate resin with an intrinsic viscosity of 0.67 dl / g (layer B), 75 wt% of modified polyester Y with an intrinsic viscosity of 0.68 dl / g, and 25 wt% of polyethylene terephthalate resin with an intrinsic viscosity of 0.67 dl / g (layer C) were pre-mixed and treated before being fed into the appropriate... The melt extrusion system, at a temperature of 275°C, enters a three-layer die for co-extrusion, and is cast onto a casting roll to form an A / B / C structure extruded casting. The casting is then longitudinally stretched at a temperature of 68°C to 87°C with a longitudinal stretch ratio of 3.8. The longitudinally stretched film is then transversely stretched at a temperature of 100°C to 123°C with a transverse stretch ratio of 5.0. The stretched film is then shaped at a temperature of 230°C. Finally, the film is cooled, drawn, and wound to obtain a 15μm thick polyester film, in which the A layer accounts for 10% of the total thickness and the C layer accounts for 18% of the total thickness.

[0060] Example 4 Preparation of modified polyester Y: The mixture was prepared according to a dicarboxylic acid to ethylene glycol molar ratio of 1:1.35, with ethylene glycol antimony added at 130 ppm and trimethyl phosphate added at 70 ppm. The dicarboxylic acid contained a 10 mol% third component, in which the molar ratio of bis(3,4-dicarboxyphenyl)dimethylsilane to 2,2,3,3-tetrafluorosuccinic acid to 3,5-bis(p-carboxyphenyl)benzoic acid was 3:3:4, and the molar percentage of terephthalic acid was 90 mol%. After thorough mixing, the mixture was added to a polyester synthesis reactor and pulped for 15 minutes under nitrogen protection. Esterification was carried out for 3 hours at 235℃~260℃ and 260KPa. After esterification, vacuum was applied, and polycondensation was carried out for 3 hours at 265℃~280℃ and 50Pa. After fiber formation, cooling, pelletizing, and drying, modified polyester Y with an intrinsic viscosity of 0.67 dl / g was obtained.

[0061] Preparation of functional masterbatch M: 95% by weight of the modified polyester Y with an intrinsic viscosity of 0.67 dl / g prepared above and 5% by weight of inorganic particles K with a particle size of d=0.3μm, a volume shape factor of e=0.65, a Mohs hardness of 3, and made of calcium carbonate were mixed evenly and fed into a twin-screw extruder. Vacuum was applied, and the mixture was filamentized, cooled, pelletized, and dried to obtain a functional masterbatch M with an intrinsic viscosity of 0.62 dl / g.

[0062] Preparation of high-performance polyester films: 15 wt% of functional masterbatch M with an intrinsic viscosity of 0.62 dl / g, 85 wt% of polyethylene terephthalate resin with an intrinsic viscosity of 0.67 dl / g (layer A), 35 wt% of modified polyester Y with an intrinsic viscosity of 0.67 dl / g, 65 wt% of polyethylene terephthalate resin with an intrinsic viscosity of 0.67 dl / g (layer B), 60 wt% of modified polyester Y with an intrinsic viscosity of 0.67 dl / g, and 40 wt% of polyethylene terephthalate resin with an intrinsic viscosity of 0.67 dl / g (layer C) were pre-mixed and treated before being fed into the appropriate... The melt extrusion system, at a temperature of 275°C, enters a three-layer die for co-extrusion, and is cast onto a casting roll to form an A / B / C structure extruded casting. The casting is then longitudinally stretched at a temperature of 68°C to 87°C with a longitudinal stretch ratio of 3.6. The longitudinally stretched film is then transversely stretched at a temperature of 100°C to 123°C with a transverse stretch ratio of 4.6. The stretched film is then shaped at a temperature of 235°C. Finally, the film is cooled, drawn, and wound to obtain a 19μm thick polyester film, in which the A layer accounts for 10% of the total thickness and the C layer accounts for 29% of the total thickness.

[0063] Example 5 Preparation of modified polyester Y: The mixture was prepared according to a dicarboxylic acid to ethylene glycol molar ratio of 1:1.38, with ethylene glycol antimony added at 180 ppm and trimethyl phosphate added at 85 ppm. The dicarboxylic acid contained a 10 mol% third component, in which the molar ratio of bis(3,4-dicarboxyphenyl)dimethylsilane to 2,2,3,3-tetrafluorosuccinic acid to 3,5-bis(p-carboxyphenyl)benzoic acid was 5:2:6, and the molar percentage of terephthalic acid was 90 mol%. After thorough mixing, the mixture was added to a polyester synthesis reactor and pulped for 15 minutes under nitrogen protection. Esterification was carried out for 3 hours at 235℃~260℃ and 260KPa. After esterification, vacuum was applied, and polycondensation was carried out for 3 hours at 265℃~280℃ and 60Pa. After fiber formation, cooling, pelletizing, and drying, modified polyester Y with an intrinsic viscosity of 0.66 dl / g was obtained.

[0064] Preparation of functional masterbatch M: 90% by weight of the modified polyester Y with an intrinsic viscosity of 0.66 dl / g prepared above and 10% by weight of inorganic particles K with a particle size of d=0.6μm, a volume shape factor of e=0.7, a Mohs hardness of 3, and a material of calcium carbonate were mixed evenly and fed into a twin-screw extruder. Vacuum was applied, and the mixture was filamentized, cooled, pelletized, and dried to obtain a functional masterbatch M with an intrinsic viscosity of 0.62 dl / g.

[0065] Preparation of high-performance polyester films: 10 wt% of functional masterbatch M with an intrinsic viscosity of 0.62 dl / g, 90 wt% of polyethylene terephthalate resin with an intrinsic viscosity of 0.67 dl / g (layer A), 30 wt% of modified polyester Y with an intrinsic viscosity of 0.66 dl / g, 70 wt% of polyethylene terephthalate resin with an intrinsic viscosity of 0.67 dl / g (layer B), 55 wt% of modified polyester Y with an intrinsic viscosity of 0.66 dl / g, and 45 wt% of polyethylene terephthalate resin with an intrinsic viscosity of 0.67 dl / g (layer C) were pre-mixed and treated before being fed into the phase... The corresponding melt extrusion system, at a temperature of 280℃, enters a three-layer die for co-extrusion, and is cast onto a casting roll to form an A / B / C structure extruded casting. The casting is then longitudinally stretched at a temperature of 68℃~87℃ with a longitudinal stretch ratio of 3.5. The longitudinally stretched film is then transversely stretched at a temperature of 100℃~123℃ with a transverse stretch ratio of 4.3. The stretched film is then shaped at a temperature of 235℃. Finally, the film is cooled, drawn, and wound to obtain a 25μm thick polyester film, in which the A layer accounts for 8% of the total thickness and the C layer accounts for 22% of the total thickness.

[0066] Example 6 Preparation of modified polyester Y: The mixture was prepared with a dicarboxylic acid to ethylene glycol molar ratio of 1:1.43, ethylene glycol antimony added at 250 ppm, and trimethyl phosphate added at 150 ppm. The dicarboxylic acid contained 15 mol% of a third component, in which the molar ratio of bis(3,4-dicarboxyphenyl)dimethylsilane to 2,2,3,3-tetrafluorosuccinic acid to 3,5-bis(p-carboxyphenyl)benzoic acid was 5:2:6, and the molar percentage of terephthalic acid was 85 mol%. After thorough mixing, the mixture was added to a polyester synthesis reactor and pulped for 15 minutes under nitrogen protection. Esterification was carried out for 4 hours at 235℃~260℃ and 260KPa. After esterification, vacuum was applied, and polycondensation was carried out for 2.5 hours at 265℃~280℃ and 80Pa. After fiber formation, cooling, pelletizing, and drying, modified polyester Y with an intrinsic viscosity of 0.65 dl / g was obtained.

[0067] Preparation of functional masterbatch M: 85% by weight of the modified polyester Y with an intrinsic viscosity of 0.65 dl / g prepared above and 15% by weight of inorganic particles K with a particle size of d=1.0μm, a volume shape factor of e=0.9, a Mohs hardness of 3, and a material of calcium carbonate were mixed evenly and fed into a twin-screw extruder. Vacuum was turned on, and the mixture was filamentized, cooled, pelletized, and dried to obtain a functional masterbatch M with an intrinsic viscosity of 0.60 dl / g.

[0068] Preparation of high-performance polyester films: 0.5 wt% of functional masterbatch M with an intrinsic viscosity of 0.60 dl / g, 99.5 wt% of polyethylene terephthalate resin with an intrinsic viscosity of 0.67 dl / g (layer A), 10 wt% of modified polyester Y with an intrinsic viscosity of 0.65 dl / g, 90 wt% of polyethylene terephthalate resin with an intrinsic viscosity of 0.67 dl / g (layer B), 50 wt% of modified polyester Y with an intrinsic viscosity of 0.65 dl / g, and 50 wt% of polyethylene terephthalate resin with an intrinsic viscosity of 0.67 dl / g (layer C) were pre-mixed and treated before being fed into… The corresponding melt extrusion system, at a temperature of 285℃, enters a three-layer die co-extrusion process, casting onto a casting roll to form an A / B / C structure extruded casting. The casting is then longitudinally stretched at a temperature of 68℃~87℃ with a longitudinal stretch ratio of 2.8. The longitudinally stretched film is then transversely stretched at a temperature of 100℃~123℃ with a transverse stretch ratio of 3.5. The stretched film is then shaped at a temperature of 240℃. Finally, the film is cooled, drawn, and wound to obtain a 30μm thick polyester film, in which the A layer accounts for 8% of the total thickness and the C layer accounts for 20% of the total thickness.

[0069] Example 7 Preparation of modified polyester Y: The mixture was prepared according to a dicarboxylic acid to ethylene glycol molar ratio of 1:1.40, with 200 ppm of antimony glycolate and 110 ppm of trimethyl phosphate. The dicarboxylic acid contained 11 mol% of a third component, in which the molar ratio of bis(3,4-dicarboxyphenyl)dimethylsilane to 2,2,3,3-tetrafluorosuccinic acid to 3,5-bis(p-carboxyphenyl)benzoic acid was 3:3:8, and the molar percentage of terephthalic acid was 89 mol%. After thorough mixing, the mixture was added to a polyester synthesis reactor and pulped for 15 minutes under nitrogen protection. Esterification was carried out for 4 hours at 235℃~260℃ and 260KPa. After esterification, vacuum was applied, and polycondensation was carried out for 3 hours at 265℃~280℃ and 60Pa. After fiber formation, cooling, pelletizing, and drying, modified polyester Y with an intrinsic viscosity of 0.66 dl / g was obtained.

[0070] Preparation of functional masterbatch M: 87% by weight of the modified polyester Y with an intrinsic viscosity of 0.66 dl / g prepared above and 13% by weight of inorganic particles K with a particle size of d=0.8 μm, a volume shape factor of e=0.8, a Mohs hardness of 3, and a material of calcium carbonate were mixed evenly and fed into a twin-screw extruder. Vacuum was applied, and the mixture was filamentized, cooled, pelletized, and dried to obtain a functional masterbatch M with an intrinsic viscosity of 0.61 dl / g.

[0071] Preparation of high-performance polyester films: 5% by weight of functional masterbatch M with an intrinsic viscosity of 0.61 dl / g, 95% by weight of polyethylene terephthalate resin with an intrinsic viscosity of 0.67 dl / g (layer A), 25% by weight of modified polyester Y with an intrinsic viscosity of 0.66 dl / g, 75% by weight of polyethylene terephthalate resin with an intrinsic viscosity of 0.67 dl / g (layer B), 65% by weight of modified polyester Y with an intrinsic viscosity of 0.66 dl / g, and 35% by weight of polyethylene terephthalate resin with an intrinsic viscosity of 0.67 dl / g (layer C) were pre-mixed and treated before being fed into the appropriate... The melt extrusion system, at a temperature of 280℃, enters a three-layer die co-extrusion process and is cast onto a casting roll to form an A / B / C structure extruded sheet. The casting sheet is then longitudinally stretched at a temperature of 68℃~87℃ with a longitudinal stretch ratio of 3.3. The longitudinally stretched sheet is then transversely stretched at a temperature of 100℃~123℃ with a transverse stretch ratio of 4.1. The stretched film is then shaped at a temperature of 235℃. Finally, the film is cooled, drawn, and wound to obtain a 31μm thick polyester film, in which the A layer accounts for 6% of the total thickness and the C layer accounts for 16% of the total thickness.

[0072] Example 8 Preparation of modified polyester Y: The mixture was prepared according to a dicarboxylic acid to ethylene glycol molar ratio of 1:1.41, with ethylene glycol antimony added at 180 ppm and trimethyl phosphate added at 130 ppm. The dicarboxylic acid contained a 13 mol% third component, in which the molar ratio of bis(3,4-dicarboxyphenyl)dimethylsilane to 2,2,3,3-tetrafluorosuccinic acid to 3,5-bis(p-carboxyphenyl)benzoic acid was 5:3:3, and the molar percentage of terephthalic acid was 87 mol%. After thorough mixing, the mixture was added to a polyester synthesis reactor and pulped for 15 minutes under nitrogen protection. Esterification was carried out for 3 hours at 235℃~260℃ and 260KPa. After esterification, vacuum was applied, and polycondensation was carried out for 3 hours at 265℃~280℃ and 50Pa. The resulting product was then filamentized, cooled, pelletized, and dried to obtain modified polyester Y with an intrinsic viscosity of 0.66 dl / g.

[0073] Preparation of functional masterbatch M: 92% by weight of the modified polyester Y with an intrinsic viscosity of 0.66 dl / g prepared above and 8% by weight of inorganic particles K with a particle size of d=0.9μm, a volume shape factor of e=0.8, a Mohs hardness of 3, and a material of calcium carbonate were mixed evenly and fed into a twin-screw extruder. Vacuum was applied, and the mixture was filamentized, cooled, pelletized, and dried to obtain a functional masterbatch M with an intrinsic viscosity of 0.62 dl / g.

[0074] Preparation of high-performance polyester films: 8 wt% of functional masterbatch M with an intrinsic viscosity of 0.62 dl / g, 92 wt% of polyethylene terephthalate resin with an intrinsic viscosity of 0.67 dl / g (layer A), 20 wt% of modified polyester Y with an intrinsic viscosity of 0.66 dl / g, 80 wt% of polyethylene terephthalate resin with an intrinsic viscosity of 0.67 dl / g (layer B), 75 wt% of modified polyester Y with an intrinsic viscosity of 0.66 dl / g, and 25 wt% of polyethylene terephthalate resin with an intrinsic viscosity of 0.67 dl / g (layer C) were pre-mixed and treated before being fed into the appropriate... The melt extrusion system, at a temperature of 280℃, enters a three-layer die for co-extrusion, and is cast onto a casting roll to form an A / B / C structure extruded casting. The casting is then longitudinally stretched at a temperature of 68℃~87℃ with a longitudinal stretch ratio of 3.4. The longitudinally stretched film is then transversely stretched at a temperature of 100℃~123℃ with a transverse stretch ratio of 3.9. The stretched film is then shaped at a temperature of 240℃. Finally, the film is cooled, drawn, and wound to obtain a polyester film with a thickness of 38μm, wherein the A layer accounts for 5% of the total thickness and the C layer accounts for 10% of the total thickness.

[0075] Example 9 Preparation of modified polyester Y: The mixture was prepared with a dicarboxylic acid to ethylene glycol molar ratio of 1:1.43, ethylene glycol antimony added at 180 ppm, and trimethyl phosphate added at 150 ppm. The dicarboxylic acid contained 13 mol% of a third component, in which the molar ratio of bis(3,4-dicarboxyphenyl)dimethylsilane to 2,2,3,3-tetrafluorosuccinic acid to 3,5-bis(p-carboxyphenyl)benzoic acid was 4:1:4, and the molar percentage of terephthalic acid was 87 mol%. After thorough mixing, the mixture was added to a polyester synthesis reactor and pulped for 15 minutes under nitrogen protection. Esterification was carried out for 4 hours at 235℃~260℃ and 260KPa. After esterification, vacuum was applied, and polycondensation was carried out for 3.5 hours at 265℃~280℃ and 35Pa. After fiber formation, cooling, pelletizing, and drying, modified polyester Y with an intrinsic viscosity of 0.68 dl / g was obtained.

[0076] Preparation of functional masterbatch M: 98.5% by weight of the modified polyester Y with an intrinsic viscosity of 0.66 dl / g prepared above and 1.5% by weight of inorganic particles K with a particle size d=1.0μm, a volume shape factor e=0.9, a Mohs hardness of 3, and a material of calcium carbonate were mixed evenly and fed into a twin-screw extruder. Vacuum was applied, and the mixture was filamentized, cooled, pelletized, and dried to obtain a functional masterbatch M with an intrinsic viscosity of 0.65 dl / g.

[0077] Preparation of high-performance polyester films: 6 wt% of functional masterbatch M with an intrinsic viscosity of 0.68 dl / g, 94 wt% of polyethylene terephthalate resin with an intrinsic viscosity of 0.67 dl / g (layer A), 15 wt% of modified polyester Y with an intrinsic viscosity of 0.68 dl / g, 85 wt% of polyethylene terephthalate resin with an intrinsic viscosity of 0.67 dl / g (layer B), 80 wt% of modified polyester Y with an intrinsic viscosity of 0.68 dl / g, and 20 wt% of polyethylene terephthalate resin with an intrinsic viscosity of 0.67 dl / g (layer C) were pre-mixed and treated before being fed into the phase... The corresponding melt extrusion system, at a temperature of 275℃, enters a three-layer die for co-extrusion, and is cast onto a casting roll to form an A / B / C structure extruded casting. The casting is then longitudinally stretched at a temperature of 68℃~87℃ with a longitudinal stretch ratio of 3.3. The longitudinally stretched film is then transversely stretched at a temperature of 100℃~123℃ with a transverse stretch ratio of 3.6. The stretched film is then shaped at a temperature of 235℃. Finally, the film is cooled, drawn, and wound to obtain a polyester film with a thickness of 43μm, wherein the A layer accounts for 3% of the total thickness and the C layer accounts for 6% of the total thickness.

[0078] Example 10 Preparation of modified polyester Y: The mixture was prepared according to a dicarboxylic acid to ethylene glycol molar ratio of 1:1.41, with ethylene glycol antimony added at 150 ppm and trimethyl phosphate added at 110 ppm. The dicarboxylic acid contained a 10 mol% third component, in which the molar ratio of bis(3,4-dicarboxyphenyl)dimethylsilane to 2,2,3,3-tetrafluorosuccinic acid to 3,5-bis(p-carboxyphenyl)benzoic acid was 5:2:6, and the molar percentage of terephthalic acid was 90 mol%. After thorough mixing, the mixture was added to a polyester synthesis reactor and pulped for 15 minutes under nitrogen protection. Esterification was carried out for 3 hours at 235℃~260℃ and 260KPa. After esterification, vacuum was applied, and polycondensation was carried out for 3 hours at 265℃~280℃ and 50Pa. After fiber formation, cooling, pelletizing, and drying, modified polyester Y with an intrinsic viscosity of 0.67 dl / g was obtained.

[0079] Preparation of functional masterbatch M: 99% by weight of the modified polyester Y with an intrinsic viscosity of 0.67 dl / g prepared above and 1% by weight of inorganic particles K with a particle size d=1.0 μm, a volume shape factor e=0.9, a Mohs hardness of 3, and a material of calcium carbonate were mixed evenly and fed into a twin-screw extruder. Vacuum was applied, and the mixture was filamentized, cooled, pelletized, and dried to obtain a functional masterbatch M with an intrinsic viscosity of 0.65 dl / g.

[0080] Preparation of high-performance polyester films: 5% by weight of functional masterbatch M with an intrinsic viscosity of 0.65 dl / g, 95% by weight of polyethylene terephthalate resin with an intrinsic viscosity of 0.67 dl / g (layer A), 10% by weight of modified polyester Y with an intrinsic viscosity of 0.67 dl / g, 90% by weight of polyethylene terephthalate resin with an intrinsic viscosity of 0.67 dl / g (layer B), 85% by weight of modified polyester Y with an intrinsic viscosity of 0.67 dl / g, and 20% by weight of polyethylene terephthalate resin with an intrinsic viscosity of 0.67 dl / g (layer C) were pre-mixed and treated before being fed into the phase... The corresponding melt extrusion system, at a temperature of 275℃, enters a three-layer die for co-extrusion, and is cast onto a casting roll to form an A / B / C structure extruded casting. The casting is then longitudinally stretched at a temperature of 68℃~87℃ with a longitudinal stretch ratio of 3.3. The longitudinally stretched film is then transversely stretched at a temperature of 100℃~123℃ with a transverse stretch ratio of 4.1. The stretched film is then shaped at a temperature of 235℃. Finally, the film is cooled, drawn, and wound to obtain a 50μm thick polyester film, in which the A layer accounts for 2% of the total thickness and the C layer accounts for 2% of the total thickness.

[0081] Comparative Example 1 25% by weight of a conventional polyester masterbatch with a particle size of 0.05 μm, a concentration of 1%, and an intrinsic viscosity of 0.65 dl / g, and 75% by weight of polyethylene terephthalate (PET) base material (layer A) with an intrinsic viscosity of 0.67 dl / g, 100% by weight of PET base material (layer B) with an intrinsic viscosity of 0.67 dl / g, and 100% by weight of PET base material (layer C) with an intrinsic viscosity of 0.67 dl / g, were pre-mixed and treated before being fed into the corresponding melt extrusion system. At 70℃, the film is co-extruded through a three-layer die and cast onto a casting roll to form an A / B / C structure extruded film. The film is then longitudinally stretched at a temperature of 68℃~87℃ with a longitudinal stretch ratio of 3.8. The longitudinally stretched film is then transversely stretched at a temperature of 100℃~123℃ with a transverse stretch ratio of 5.2. The stretched film is then shaped at a temperature of 225℃. Finally, the film is cooled, drawn, and wound to obtain a 12μm thick polyester film, in which the A layer accounts for 13% of the total thickness and the C layer accounts for 18% of the total thickness.

[0082] Comparative Example 2 0.5 wt% of a conventional polyester masterbatch with a particle size of 1.0 μm, a concentration of 15%, and an intrinsic viscosity of 0.60 dl / g, and 99.5 wt% of a polyethylene terephthalate (PET) base material with an intrinsic viscosity of 0.67 dl / g (layer A), 100 wt% of a PET base material with an intrinsic viscosity of 0.67 dl / g (layer B), and 100 wt% of a PET base material with an intrinsic viscosity of 0.67 dl / g (layer C) are pre-mixed and treated before being fed into the corresponding melt extrusion system. At 285℃, the film is co-extruded through a three-layer die and cast onto a casting roll to form an A / B / C structure extruded film. The film is then longitudinally stretched at a temperature of 68℃~87℃ with a longitudinal stretch ratio of 2.8. The longitudinally stretched film is then transversely stretched at a temperature of 100℃~123℃ with a transverse stretch ratio of 3.5. The stretched film is then shaped at a temperature of 240℃. Finally, the film is cooled, drawn, and wound to obtain a 30μm thick polyester film, in which the A layer accounts for 8% of the total thickness and the C layer accounts for 20% of the total thickness.

[0083] Comparative Example 3 The mixture consists of 5% by weight of a conventional polyester masterbatch with a particle size of 1.0 μm, a concentration of 1%, and an intrinsic viscosity of 0.65 dl / g, and 99.5% by weight of a polyethylene terephthalate (PET) base material with an intrinsic viscosity of 0.67 dl / g (layer A), 100% by weight of a PET base material with an intrinsic viscosity of 0.67 dl / g (layer B), and 10% by weight of a conventional polyester masterbatch with a particle size of 1.0 μm, a concentration of 1%, and an intrinsic viscosity of 0.65 dl / g and 90% by weight of a PET base material with an intrinsic viscosity of 0.67 dl / g (layer C). The mixture is pre-mixed and treated before being fed into the corresponding melt extrusion system. At a temperature of 275°C, it is co-extruded through a three-layer die and cast onto a casting roller to form an A / B / C structure extruded sheet. The casting sheet is then longitudinally stretched at a temperature of 68°C to 87°C with a longitudinal stretch ratio of 3.3. The longitudinally stretched sheet is then transversely stretched at a temperature of 100°C to 123°C with a transverse stretch ratio of 4.1. The stretched film is then shaped at a temperature of 235°C. Finally, the film is cooled, drawn, and wound to obtain a 50μm thick polyester film, in which the A layer accounts for 2% of the total thickness and the C layer accounts for 2% of the total thickness. Implementation effect

[0084] The test results are shown in Table 1:

[0085] Note: Surface roughness (Sa) and apparent properties refer to the C-layer properties of polyester film (processed by downstream customers).

[0086] Thickness test method: GB / T 33399-2016.

[0087] Surface roughness (Sa): ISO 25178.

[0088] Dynamic thermal performance: A small shaft sample, 1300 mm wide and 500 m long, was passed through the machine to evaluate its dynamic thermal performance. Machine conditions: winding tension 160 N / m, oven temperatures 80℃ / 100℃ / 130℃ / 150℃ / 135℃ / 115℃ / 100℃ / 80℃, oven section length 4 m, machine speed 60 m / min. Two horizontal guide rollers were placed 3 m from the oven exit, with a vertical distance of 1.5 m between them. During the passing through the machine, the inspector's line of sight formed a 45° angle with the film surface, and a strong flashlight (model: RJW7102A / LT, Ocean King Lighting Technology Co., Ltd.) was used to carefully observe the film by moving it left and right. Simultaneously, a 1 m long sample of the small shaft after passing through the machine was placed on a horizontal marble platform, with the inspector's line of sight forming a 0° angle with the film surface, and a strong flashlight (model: RJW7102A / LT, Ocean King Lighting Technology Co., Ltd.) was used to carefully observe the film by moving it left and right. If the film surface is free of longitudinal striations or other unevenness during the machine process, and the sample on the marble platform is completely in contact with the marble surface without any undulations or unevenness, it indicates excellent thermal performance, and is marked with "◎". If n (number) > 1 longitudinal striations appear during the machine process, or if n (number) > 1 undulations appear between the sample on the marble platform and the marble surface, it indicates poor thermal performance, and is marked with "×".

[0089] Appearance: Cut a piece of polyester film, 1 meter wide and 1 meter long, and carefully observe its appearance using a high-intensity flashlight (model: RJW7102A / LT, Ocean King Lighting Technology Co., Ltd.). If there are no scratches / abrasions, mark "◎"; if a very slight scratch / abrasion is faintly visible but uncertain, mark "○"; if obvious scratches / abrasions are visible, and n (number) ≤ 5, mark "△"; if obvious scratches / abrasions are visible across the entire surface, mark "×".

[0090] By comparing Example 2 with Comparative Example 1 and Example 6 with Comparative Example 2, it can be seen that under the same conditions of polyester film thickness and film-making process, the surface roughness (Sa), dynamic thermal properties, and appearance of the high-performance polyester film of this technology have significant advantages over ordinary polyester film. By comparing Example 10 with Comparative Example 3, it can be seen that under the same conditions of polyester film thickness and film-making process, although the appearance of Comparative Example 3 is similar to that of Example 10, its surface roughness (Sa) and dynamic thermal properties are significantly worse than those of the high-performance polyester film of this invention.

[0091] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A polyester film, characterized in that, The polyester film is composed of three layers of polyester resin laminated together, namely a first surface layer, a core layer, and a second surface layer; wherein, the first surface layer is also known as layer A; the core layer is also known as layer B; and the second surface layer is also known as layer C. Wherein, layer A is composed of 0.5 wt% to 30 wt% functional masterbatch M and 70 wt% to 99.5 wt% polyethylene terephthalate resin relative to the weight of layer A; The B layer is composed of 10% to 50% modified polyester Y and 50% to 90% polyethylene terephthalate resin relative to the weight of the B layer. The C layer is composed of 50% to 90% by weight of modified polyester Y and 10% to 50% by weight of polyethylene terephthalate resin relative to the weight of the C layer. The functional masterbatch M is composed of 0.5 wt% to 15 wt% inorganic particles K and 85 wt% to 99.5 wt% modified polyester Y; The preparation of the modified polyester Y includes the following steps: Step 1: Add the specified amounts of dicarboxylic acid, ethylene glycol, catalyst, and stabilizer sequentially to the polyester reactor, slurry for 15 minutes, and purge with nitrogen for protection. Esterify for 2-4 hours at 235℃-260℃ and 260KPa. The molar ratio of dicarboxylic acid to ethylene glycol is 1:1.18 to 1:1.

43. Step 2: Determine the esterification endpoint based on the water output. After complete esterification, turn on the vacuum and perform polycondensation reaction at 265℃~280℃ and 20Pa~80Pa for 2.5h~4h. After fiber formation, cooling, pelletizing and drying, the modified polyester Y described in this invention is obtained. The intrinsic viscosity of the modified polyester Y is 0.65dl / g~0.69dl / g. In addition to terephthalic acid, the dicarboxylic acid also contains a third component; the third component is selected from bis(3,4-dicarboxyphenyl)dimethylsilane, 2,2,3,3-tetrafluorosuccinic acid and 3,5-bis(p-carboxyphenyl)benzoic acid; the total content of the third component in the dicarboxylic acid is 5 mol% to 15 mol%; the content of terephthalic acid in the dicarboxylic acid is 85 mol% to 95 mol%; the molar ratio of bis(3,4-dicarboxyphenyl)dimethylsilane, 2,2,3,3-tetrafluorosuccinic acid and 3,5-bis(p-carboxyphenyl)benzoic acid is 2 to 5: 1 to 3: 3 to 8. The catalyst is selected from antimony-based, iron-based, aluminum-based, germanium-based, or titanium-based catalysts, and the addition amount is 60ppm~250ppm; The amount of stabilizer added is 30ppm~150ppm.

2. The polyester film according to claim 1, characterized in that, The inorganic particles K have a particle size (d) of 0.03μm≤d≤1μm, a volume shape factor (e) of 0.5≤e≤0.9, a Mohs hardness of 3, and are made of calcium carbonate.

3. The polyester film according to claim 1, characterized in that, The stabilizer is selected from one or more of the following in any weight ratio: trimethyl phosphate, triphenyl phosphate, tetrabutyl titanate, tetraethyl titanate, etc.

4. A polyester film according to claim 1, characterized in that, The surface roughness Sa of the C layer is less than 5 nm.

5. A polyester film according to claim 1, characterized in that, The thickness of the polyester film is 8μm to 50μm.

6. A polyester film according to claim 1, characterized in that, The thickness of layer A in the polyester film accounts for 2% to 15% of the total thickness.

7. A polyester film according to claim 1, characterized in that, In the polyester film, the thickness of layer C accounts for 2% to 29% of the total thickness, and the thickness of layer A can be the same as or different from that of layer C.

8. A polyester film according to claim 1, characterized in that, The intrinsic viscosity of the modified polyester Y is 0.65 dl / g ≤ η ≤ 0.69 dl / g.

9. A method for preparing a polyester film as described in any one of claims 1-7, characterized in that, Includes the following steps: Step 1: Mix the functional masterbatch M, modified polyester Y and polyethylene terephthalate resin in the corresponding proportions for each layer in advance, and then send them into the corresponding melt extrusion system for extrusion and co-extrusion into the three-layer die. Step 2: High-performance polyester film is obtained through casting, longitudinal stretching, transverse stretching, shaping, cooling, traction, and winding; Step 3: The temperature of the melt extrusion is 265℃~285℃.

10. A method for preparing a polyester film according to claim 8, characterized in that, The longitudinal stretching ratio of the longitudinal stretching process is 2.8 to 4.0, and the transverse stretching ratio of the transverse stretching process is 3.5 to 5.

5.

11. The method for preparing a polyester film according to claim 8, characterized in that, The heat setting temperature of the setting process is 220℃~240℃.

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