A biaxially oriented polyester film

Abstract

The application discloses a biaxial oriented polyester film, which contains A1 / B / A2 three-layer polyester resin layers, wherein the main component of the A1 layer is 10-50 parts by weight of functional masterbatch X and 50-90 parts by weight of pure polyester resin, the main component of the B layer is 5-40 parts by weight of functional masterbatch Y and 60-95 parts by weight of pure polyester resin, the main component of the A2 layer is 5-30 parts by weight of functional masterbatch Z and 70-95 parts by weight of pure polyester resin, and the thickness of the A1 layer and the thickness of the A2 layer can be the same or different. The thickness of the biaxial oriented polyester film is 12-188 mu m. The biaxial oriented polyester film has excellent heat performance, no scratch and no smudge, improves product quality, simplifies production process and reduces production cost. The product can be widely used in many fields such as aluminized film, release film for ceramic capacitor, IMD, plate polishing, high-end release film and satellite thermal control film.

Description

Technical Field

[0001] This invention pertains to a polyester film, specifically a biaxially oriented polyester film. Background Technology

[0002] Polyethylene terephthalate (PET), chemical formula (C 10 H8O4) n PET (Polyethylene terephthalate) is produced by transesterification of dimethyl terephthalate with ethylene glycol or by esterification of terephthalic acid with ethylene glycol to synthesize diethyl terephthalate, followed by polycondensation. It exhibits excellent physical and mechanical properties over a wide temperature range, as well as excellent electrical insulation; even at high temperatures and high frequencies, its electrical properties remain good. It also demonstrates excellent creep resistance, fatigue resistance, abrasion resistance, and dimensional stability. PET materials, processed in various ways, can be used in different fields, such as spinning, engineering plastics, and films. Polyester film, made from polyethylene terephthalate through melt co-extrusion and biaxial stretching, has a wide range of applications due to its good mechanical, thermal, electrical insulation, and optical properties.

[0003] When polyester film is used in fields such as aluminized film, release film for ceramic capacitors, IMD (Integrated Device Modulation), sheet polishing, high-end release films, and satellite thermal control films, extremely high requirements are placed on the film's thermal performance and resistance to scratches / abrasions on the film surface. Taking the well-known release film for ceramic capacitors as an example, the ceramic capacitor manufacturing process generally consists of two steps: first, ceramic slurry casting (the ceramic slurry is poured through the casting machine's inlet and coated onto a winding PET release film, then dried in a conventional hot air zone); second, electrodes are printed on the formed ceramic sheet, then the release film is removed, and finally, high-temperature sintering is performed. Here, the PET release film is for ceramic capacitors, meaning that a release coating process is performed on the film substrate for ceramic slurry casting. The quality of the film substrate directly determines the quality of the ceramic sheet; if the polyester film has poor thermal performance, the film surface will be uneven during machine coating of the release layer, resulting in uneven spread of the release layer and affecting the uniformity of the ceramic slurry thickness. The appearance of the film also affects the uniformity of deep processing. Scratches / abrasions on the film surface will prevent the release layer from spreading at the scratches / abrasions. When casting ceramic slurry downstream, the scratches / abrasions cannot be peeled off, and may even lead to the breakage of the ceramic sheet. Similarly, the thermal properties and appearance of polyester film limit its application in fields such as metallized film, IMD, sheet varnishing, high-end release films, and satellite thermal control films.

[0004] To address the high-performance requirements of various fields, existing technical solutions in the polyester film industry include: 1. During polyester film production, increasing the temperature in the TDO setting zone to improve film crystallinity and thermal properties. 2. Adding larger particles (≥4.0μm) to the surface of the polyester film to increase slip resistance and reduce surface scratches / abrasions. 3. During downstream processing, reducing production speed and tension to improve film surface unevenness caused by the film passing through the machine.

[0005] Although technicians have conducted extensive research on polyester film, current technical solutions for addressing polyester film issues still have many shortcomings: 1. Heating the setting zone can improve film crystallinity to some extent, but high crystallinity makes the film brittle, hindering downstream processing, easily causing scratches, and leading to uneven film crystallization, affecting flatness. 2. Adding larger particles (≥4.0μm) to the surface improves the smoothness of the polyester film, but large particles can create a strong unevenness on the film surface, making it difficult to meet the requirements of applications with high surface gloss (such as IMD and sheet varnishing). 3. Reducing production speed leads to decreased downstream production efficiency and increased production costs. Summary of the Invention

[0006] This invention provides a biaxially oriented polyester film with excellent thermal properties and a scratch-free / abrasion-free surface, improving product quality, simplifying the production process, and reducing production costs. The product can be widely used in many fields such as aluminized film, release film for ceramic capacitors, IMD (Integrated Device Modulation), sheet coating, high-end release films, and satellite thermal control films.

[0007] To overcome the shortcomings of the prior art, the technical solution adopted by the present invention is as follows:

[0008] A biaxially oriented polyester film comprising three polyester resin layers, A1 / B / A2; the A1 layer comprises the following substances in parts by weight:

[0009] Functional masterbatch x 10 parts by weight to 50 parts by weight

[0010] 50 to 90 parts by weight of pure polyester resin;

[0011] The functional masterbatch X comprises the following substances in parts by weight:

[0012] Inorganic filler x 0.3 parts by weight to 10 parts by weight

[0013] 90 parts by weight to 99.7 parts by weight of modified polyester.

[0014] Wherein, the inorganic filler x is a crystalline spherical silica particle with amorphous silica coated on its surface, and the average particle size is 0.3μm to 3μm;

[0015] Layer B comprises the following substances in parts by weight:

[0016] Functional Masterbatch Y: 5 parts by weight to 40 parts by weight

[0017] 60 to 95 parts by weight of pure polyester resin;

[0018] The functional masterbatch Y is composed of:

[0019] Inorganic filler y 1 part by weight to 15 parts by weight

[0020] Modified polyester 85 parts by weight to 99 parts by weight,

[0021] The inorganic filler y is a crystalline spherical silica particle with an average particle size of 0.03 μm to 1 μm.

[0022] Layer A2 comprises the following substances in parts by weight:

[0023] Functional Masterbatch Z: 5 parts by weight to 30 parts by weight

[0024] 70 to 95 parts by weight of pure polyester resin;

[0025] The functional masterbatch Z has the same composition as the functional masterbatch X;

[0026] The modified polyester uses 4-(3,5-dicarboxyphenoxy)phthalic acid, 4,4-propanediyldioxydibenzoic acid, 3,5-bis(p-carboxyphenyl)benzoic acid, and terephthalic acid.

[0027] definition:

[0028] X1 represents the percentage of 4-(3,5-dicarboxyphenoxy)phthalic acid in the modified polyester relative to the total dicarboxylic acid content.

[0029] X2 represents the content of 4,4-propanediyldioxybenzoic acid relative to the total dicarboxylic acid content;

[0030] X3 represents the percentage of 3,5-bis(p-carboxyphenyl)benzoic acid relative to the total dicarboxylic acid content;

[0031] X4 represents the percentage of terephthalic acid relative to the total dicarboxylic acid content;

[0032] X1, X2, X3, and X4 satisfy the following relationship:

[0033] 5 mol% ≤ X1 ≤ 15 mol%

[0034] 2 mol% ≤ X2 ≤ 10 mol%

[0035] 3 mol% ≤ X3 ≤ 25 mol%

[0036] 50 mol% ≤ X4 ≤ 90 mol%

[0037] X1 + X2 + X3 + X4 = 100 moles.

[0038] As an improved technical solution of this application, the thickness of the biaxially oriented polyester film is 12μm to 188μm.

[0039] As an improved technical solution of this application, the biaxially oriented polyester film contains three polyester resin layers, A1 / B / A2, wherein the A1 layer accounts for 3% to 29% of the total thickness and the A2 layer accounts for 3% to 29% of the total thickness.

[0040] As an improved technical solution of this application, the pure polyester resin is polyethylene terephthalate resin with an intrinsic viscosity of 0.62 dl / g to 0.68 dl / g.

[0041] As an improved technical solution of this application, the method for preparing the biaxially oriented polyester film is as follows: the functional masterbatch X, the functional masterbatch Y, the functional masterbatch Z and the pure polyester resin are mixed in advance and fed into the corresponding melt extrusion system for extrusion. The mixture enters a three-layer co-extrusion die and is then cast, stretched longitudinally, stretched laterally, heat-set, cooled, drawn and wound to obtain the film.

[0042] As an improved technical solution of this application, the melt extrusion temperature is 260℃~280℃.

[0043] As an improved technical solution of this application, the longitudinal stretch ratio is 2.7 to 3.8.

[0044] As an improved technical solution of this application, the transverse stretch ratio is 3.3 to 5.6.

[0045] As an improved technical solution of this application, the heat setting temperature is 220℃~243℃.

[0046] The functional masterbatch X, functional masterbatch Y, and functional masterbatch Z mentioned in this invention are named to distinguish different functional masterbatches. The inorganic filler x and inorganic filler y are named to distinguish different types of silica. The dicarboxylic acid content X1, X2, X3, and X4 used for modification are named to distinguish the different amounts of materials used in each step. The letters themselves have no meaning.

[0047] The beneficial effects achieved by this invention are reflected in:

[0048] 1. Using modified polyester in functional masterbatch can achieve the integration of modified polyester and inorganic particle functions. If modified polyester is not used in functional masterbatch, then the functional masterbatch will not have the properties of modified polyester. This invention designs polyester polymer from the microscopic perspective of polymer chain segments, endowing polyester polymer materials with new properties and improving the thermal properties and appearance of the product.

[0049] 2. This invention focuses on theoretical mechanism research, and uses a clever combination of crystalline spherical silica particles and crystalline spherical silica particles with amorphous silica coating on the surface, which not only improves the thermal performance of polyester film, but also ensures the appearance of film, with no scratches / abrasions on the surface.

[0050] 3. This invention uses a combination design of modified polyester and functional masterbatch to directly melt-extrude and stretch into film, which is simple and low-cost. Detailed Implementation

[0051] 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.

[0052] 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.

[0053] Definition: All dicarboxylic acids used in this article are dicarboxylic acids.

[0054] The present invention provides a biaxially oriented polyester film containing three polyester resin layers of A1 / B / A2.

[0055] The main components of layer A1 are 10 to 50 parts by weight of functional masterbatch X and 50 to 90 parts by weight of pure polyester resin; the main components of layer B are 5 to 40 parts by weight of functional masterbatch Y and 60 to 95 parts by weight of pure polyester resin; and the main components of layer A2 are 5 to 30 parts by weight of functional masterbatch Z and 70 to 95 parts by weight of pure polyester resin.

[0056] When the amount of functional masterbatch X in layer A1 is less than 10 parts by weight, the insufficient addition of inorganic particles makes it difficult to achieve its slip-resistant and anti-scratch-prevention effects during winding, and also reduces the effectiveness of the modified polyester. When the amount of functional masterbatch X in layer A1 is greater than 50 parts by weight, the excessive addition of inorganic particles leads to excessive slip-resistant properties, which can easily cause the film to slip and scratch when passing through the rollers. When the amount of functional masterbatch Y in layer B is less than 5 parts by weight, the insufficient addition of inorganic particles and modified polyester makes it difficult to act as a nucleating agent, and also makes it difficult to achieve the effect of modified polyester in improving the thermal properties of the film. When the amount of functional masterbatch Y in layer B is greater than 40 parts by weight, it can easily cause the film to become brittle, affecting its performance in machine processing and further processing, and also results in excessive performance and waste of functional masterbatch. When the amount of functional masterbatch Z added to the A2 layer is less than 5 parts by weight, the insufficient addition of inorganic particles in the masterbatch makes it difficult to exert its functions of smoothing and preventing scratches during winding, and also reduces the effectiveness of the modified polyester. When the amount of functional masterbatch Z added to the A2 layer is greater than 30 parts by weight, the excessive addition of inorganic particles leads to excessive smoothing properties, which can easily cause the film to slip when passing through the rollers, resulting in scratches. Due to the different number and materials of rollers that the A1 and A2 sides pass through during polyester film production, or due to the selection of downstream deep processing surfaces, the amount of functional masterbatch added to the A1 and A2 layers may differ.

[0057] The functional masterbatch X is composed of 0.3 to 10 parts by weight of inorganic filler x and 90 to 99.7 parts by weight of modified polyester. The inorganic filler x is crystalline spherical silica particles with amorphous silica coated on the surface. The main manufacturer is Fuji Silicon Chemical Co., Ltd., and the average particle size is 0.3 μm to 3 μm. The functional masterbatch Z has the same composition as the functional masterbatch X.

[0058] When the amount of inorganic filler x added is less than 0.3 parts by weight, the concentration is too low. To achieve the same effect, a larger proportion of functional masterbatch needs to be added, which can easily cause a large difference in viscosity between the surface layer and the core layer, which is not conducive to overall performance stability and also increases costs. When the amount of inorganic filler x added is greater than 10 parts by weight, the addition of more inorganic particles can easily reduce the viscosity of the masterbatch system. At the same time, the masterbatch concentration is too high, which is not conducive to small-proportion addition. It is easy to cause delamination between the masterbatch and pure polyester resin, making it difficult to ensure the uniformity of film surface properties. When the average particle size of inorganic filler x is less than 0.3 μm, the particle size is too small, and it is difficult to achieve a smoothing effect when added to the surface layer, resulting in scratches on the film surface. When the average particle size of inorganic filler x is greater than 3 μm, the film surface is too rough, making it difficult to meet the requirements of IMD, sheet varnishing and other fields with high requirements for surface smoothness.

[0059] The functional masterbatch Y is composed of 1 to 15 parts by weight of inorganic filler y and 85 to 99 parts by weight of modified polyester. The inorganic filler y is crystalline spherical silica particles with an average particle size of 0.03 μm to 1 μm.

[0060] When the amount of inorganic filler y added is less than 1 part by weight, the concentration is too low, reducing the efficiency of masterbatch manufacturing and increasing production costs. When the amount of inorganic filler y added is greater than 15 parts by weight, the addition of too many inorganic particles can easily lead to a decrease in the viscosity of the masterbatch system. At the same time, the masterbatch concentration is too high, which is not conducive to small-proportion addition and makes it difficult to ensure uniform addition. When the average particle size of inorganic filler y is less than 0.03 μm, the smaller the particle size, the higher the surface energy, and the easier it is for inorganic particles to agglomerate and generate crystal points, increasing the difficulty of functional masterbatch manufacturing. When the average particle size of inorganic filler y is greater than 1 μm, the particle size of inorganic particles is too large, and the number of nucleation sites provided per unit weight is small, which is not conducive to the formation of crystal nuclei.

[0061] Functional masterbatch Y is used in the B layer of polyester film, employing crystalline spherical silica particles, primarily manufactured by Fuji Silicon Chemical Co., Ltd. This is mainly because the morphology of a substance determines its properties. Crystalline spherical silica particles, due to their crystallization, possess a dense internal structure. When used as a nucleating agent in the nucleation and crystallization process, compared to ordinary spherical silica particles, they do not cause crystal system destruction or film deformation due to the cracking of the spherical silica particle nuclei during downstream processing and heating. The crystal system formed by crystalline spherical silica particles as a nucleating agent is more stable and temperature-resistant.

[0062] When designing formulations to improve the performance of a three-layer polyester film, engineers often overlook the influence of the surface layer. However, as the outermost layer, it is more susceptible to and the first to be affected by external environmental factors, whether under heat or stress. Only by improving the performance of each layer can the overall product performance be improved. This invention takes this into consideration, and therefore also uses crystalline spherical silica particles as nucleating agents to enhance the surface heat resistance. However, due to the crystallization of these particles, they have a dense internal structure and high surface hardness, which can easily cause scratches between layers during polyester film winding, affecting the product's appearance. Furthermore, prolonged operation can also cause wear on the surface of the equipment's mirror rollers. Therefore, this invention cleverly designs a surface coated with amorphous silica crystalline spherical silica particles. The relatively soft texture of amorphous silica ensures improved surface thermal performance while avoiding scratches between film layers and wear on the surface of the equipment's mirror rollers.

[0063] The modified polyester uses 4-(3,5-dicarboxyphenoxy)phthalic acid, 4,4-propanediyldioxydibenzoic acid, 3,5-bis(p-carboxyphenyl)benzoic acid, and terephthalic acid.

[0064] Among them, the content of 4-(3,5-dicarboxyphenoxy)phthalic acid in the modified polyester relative to the total dicarboxylic acid content is X1, the content of 4,4-propanediyldioxybenzoic acid relative to the total dicarboxylic acid content is X2, the content of 3,5-bis(p-carboxyphenyl)benzoic acid relative to the total dicarboxylic acid content is X3, and the content of terephthalic acid relative to the total dicarboxylic acid content is X4.

[0065] X1, X2, X3, and X4 satisfy the following relationship:

[0066] 5 mol% ≤ X1 ≤ 15 mol%

[0067] 2 mol% ≤ X2 ≤ 10 mol%

[0068] 3 mol% ≤ X3 ≤ 25 mol%

[0069] 50 mol% ≤ X4 ≤ 90 mol%

[0070] X1 + X2 + X3 + X4 = 100 moles.

[0071] Among them, 4-(3,5-dicarboxyphenoxy)phthalic acid has a tetracarboxyl group and two benzene rings. When the carboxyl groups on the two benzene rings participate in the reaction, the two benzene rings directly participate in the formation of the polymer chain segment, improving the rigidity of the polymer chain segment. When the carboxyl group on the same benzene ring participates in the reaction, one benzene ring is located in the side chain, increasing the steric hindrance of the polymer chain segment, which is beneficial to maintaining the stability of the chain segment. Similarly, 4,4-propanediyldioxybenzoic acid and 3,5-bis(p-carboxyphenyl)benzoic acid also have two benzene rings participating in the formation of the polymer chain segment, improving the overall rigidity of the polymer chain segment. Furthermore, in 3,5-bis(p-carboxyphenyl)benzoic acid, while the two benzene rings participate in the reaction, another benzene ring is located in the side chain, increasing the steric hindrance of the polymer chain segment and maintaining the stability of the chain segment. In the direction of the polymer chain segment, they are connected by chemical bonds, which are relatively stable. Perpendicular to the direction of the polymer chain, strong hydrogen bonds can form between the carboxyl groups and phenoxy groups, which play a role in fixing the molecular chains and ensuring that the film does not deform during subsequent heating. Meanwhile, when the phenoxy group is located in the polymer chain, its special structure can provide a buffer for the movement of the polymer chain, which is beneficial to improving the micro-deformation in subsequent processing.

[0072] The inclusion of 4-(3,5-dicarboxyphenoxy)phthalic acid, 4,4-propanediyldioxybenzoic acid, 3,5-bis(p-carboxyphenyl)benzoic acid, and terephthalic acid, through the appropriate total dicarboxylic acid content design in this invention, allows the technical effects of this invention to be optimized. When modified polyester is used as a surface layer, it also improves the scratch resistance of the polyester film surface. Since inorganic particles have limited effect on improving the thermal properties of the film, the combination design of modified polyester and inorganic particles in this invention allows the relevant properties of the functional masterbatch to be more fully utilized.

[0073] The modified polyester, functional masterbatch X, and functional masterbatch Y described in this invention can be prepared using the following methods:

[0074] The modified polyester is prepared by:

[0075] 1. Add the required dibasic acid, diol, catalyst, and stabilizer to the polyester reactor in sequence, pulverize for 15 minutes, and purge with nitrogen for protection. Esterify for 2 to 3.5 hours at 235℃~260℃ and 260KPa. The dicarboxylic acids are selected from 4-(3,5-dicarboxyphenoxy)phthalic acid, 4,4-propanediyldioxybenzoic acid, 3,5-bis(p-carboxyphenyl)benzoic acid, and terephthalic acid. Specifically, the content of 4-(3,5-dicarboxyphenoxy)phthalic acid in the modified polyester relative to the total dicarboxylic acid content is 5 mol% ≤ X1 ≤ 15 mol%; the content of 4,4-propanediyldioxybenzoic acid relative to the total dicarboxylic acid content is 2 mol% ≤ X2 ≤ 10 mol%; the content of 3,5-bis(p-carboxyphenyl)benzoic acid relative to the total dicarboxylic acid content is 3 mol% ≤ X3 ≤ 25 mol%; and the content of terephthalic acid relative to the total dicarboxylic acid content is 50 mol% ≤ X4 ≤ 90 mol%, where X1 + X2 + X3 + X4 = 100 mol.

[0076] The diol is selected from ethylene glycol, propylene glycol, butanediol, 1,4-cyclohexanediol, hexanediol, polyethylene oxide glycol, etc., with ethylene glycol being preferred; the molar ratio of diacid to diol is 1:1.23 to 1:1.43; the catalyst is selected from antimony-based, iron-based, aluminum-based, germanium-based, titanium-based, etc., with antimony glycolide being preferred, and the addition amount is 80ppm to 300ppm; the stabilizer is selected from trimethyl phosphate, triethyl phosphate, triphenyl phosphate, tri-n-butyl phosphate, tetrabutyl titanate, tetraethyl titanate, etc., with triphenyl phosphate being preferred, and the addition amount is 30ppm to 100ppm.

[0077] 2. Determine the esterification endpoint based on the amount of water discharged. After complete esterification, turn on the vacuum and carry out the polycondensation reaction for 3 to 5 hours at 262℃~280℃ and 20Pa~65Pa. After fiber formation, cooling, pelletizing and drying, the modified polyester described in this invention is obtained. The intrinsic viscosity of the modified polyester is 0.60dl / g~0.69dl / g.

[0078] The preparation method of functional masterbatch Y is as follows:

[0079] Modified polyester with an intrinsic viscosity of 0.60 dl / g to 0.69 dl / g, prepared above, was selected as the base material. Then, 85 to 99 parts by weight of the modified polyester and 1 to 15 parts by weight of crystalline spherical silica particles (inorganic filler y) with an average particle size of 0.03 μm to 1 μm were mixed evenly and fed into a twin-screw extruder. Vacuum was applied, and the mixture was filamentized, cooled, granulated, and dried to obtain the functional masterbatch Y described in this invention. The intrinsic viscosity of functional masterbatch Y is 0.56 dl / g to 0.66 dl / g. This invention uses a twin-screw extrusion method instead of a synthesis method, mainly because the prolonged high temperature during esterification and polycondensation processes in synthesis may damage the surface coating structure of the inorganic particles, affecting their effectiveness. Functional masterbatch X / Z with intrinsic viscosities of 0.58 dl / g to 0.68 dl / g can be prepared using the same method as functional masterbatch Y.

[0080] The thickness of the biaxially oriented polyester film is 12 μm to 188 μm.

[0081] The biaxially oriented polyester film contains three polyester resin layers, A1 / B / A2, wherein the A1 layer accounts for 3% to 29% of the total thickness and the A2 layer accounts for 3% to 29% of the total thickness.

[0082] The biaxially oriented polyester film contains three polyester resin layers, A1 / B / A2, and the thickness of the A1 layer and the thickness of the A2 layer can be the same or different.

[0083] The pure polyester resin is polyethylene terephthalate resin with an intrinsic viscosity of 0.62 dl / g to 0.68 dl / g.

[0084] The biaxially oriented polyester film of the present invention can be prepared by the following method:

[0085] 1. The functional masterbatch X, functional masterbatch Y, functional masterbatch Z and pure polyester resin in corresponding weight proportions are mixed and treated in advance, and then fed into the corresponding melt extrusion system for extrusion.

[0086] 2. The melt is co-extruded through the die head and cast onto the casting roller to form a three-layer co-extruded sheet.

[0087] 3. The casting is stretched longitudinally, with a longitudinal stretching ratio of 2.7 to 3.8.

[0088] 4. Stretch the longitudinal stretching sheet laterally, with a lateral stretching ratio of 3.3 to 5.6.

[0089] 5. Heat set the stretched film at a temperature of 220℃~243℃.

[0090] 6. Then proceed with cooling, traction, and winding.

[0091] It should be noted that, without affecting the technical effect of the present invention, the polyester film of the present invention can be pretreated with corona discharge on one or both sides, or pretreated with a base coating with a thickness of 0.01μm to 0.20μm, and then supplied to downstream for further processing.

[0092] 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.

[0093] Example 1

[0094] Preparation of modified polyester:

[0095] Based on a dicarboxylic acid to ethylene glycol molar ratio of 1:1.23, the antimony glycolate addition was 80 ppm and the triphenyl phosphate addition was 30 ppm. The dicarboxylic acids, including 4-(3,5-dicarboxyphenoxy)phthalic acid, 4,4-propanediyldioxybenzoic acid, 3,5-bis(p-carboxyphenyl)benzoic acid, and terephthalic acid, had the following percentages relative to the total dicarboxylic acid content: X1 = 5 mol%, X2 = 2 mol%, X3 = 1 mol%, X4 = 1 mol%, X5 = 1 mol%, X6 = 1 mol%, X7 = 1 mol%, X8 = 1 mol%, X9 = 1 mol%, X1 = 1 mol%, X1 = 1 mol%, X1 = 1 mol%, X9 ... =3 mol%, X4 = 90 mol%, after being mixed evenly, are added to a polyester synthesis reactor, pulped for 15 minutes, and protected with nitrogen gas. Esterification is carried out for 2 hours at 236℃~262℃ and 265KPa. After esterification, vacuum is turned on, and polycondensation reaction is carried out for 3 hours at 265℃~282℃ and 20Pa. After fiber formation, cooling, pelletizing and drying, modified polyester with an intrinsic viscosity of 0.60dl / g is obtained.

[0096] Preparation of functional masterbatch Y:

[0097] 85 parts by weight of the modified polyester with an intrinsic viscosity of 0.60 dl / g prepared above and 15 parts by weight of crystalline spherical silica particles (inorganic filler y) with an average particle size of 0.03 μm 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 functional masterbatch Y with an intrinsic viscosity of 0.56 dl / g.

[0098] Preparation of functional masterbatch X / functional masterbatch Z:

[0099] 90 parts by weight of the modified polyester with an intrinsic viscosity of 0.60 dl / g prepared above and 10 parts by weight of crystalline spherical silica particles (inorganic filler x) with an average particle size of 0.3 μm and amorphous silica coating are mixed evenly; the mixture is fed into a twin-screw extruder, vacuum is applied, and the mixture is filamentized, cooled, pelletized, and dried to obtain functional masterbatch X with an intrinsic viscosity of 0.58 dl / g. Functional masterbatch Z has the same composition as functional masterbatch X.

[0100] Ten parts by weight of functional masterbatch X with an intrinsic viscosity of 0.58 dl / g and 90 parts by weight of pure polyester resin with an intrinsic viscosity of 0.62 dl / g (A1 layer), five parts by weight of functional masterbatch Y with an intrinsic viscosity of 0.56 dl / g and 95 parts by weight of pure polyester resin with an intrinsic viscosity of 0.62 dl / g (B layer), five parts by weight of functional masterbatch Z with an intrinsic viscosity of 0.58 dl / g and 95 parts by weight of pure polyester resin with an intrinsic viscosity of 0.62 dl / g (A2 layer) were pre-mixed and treated; then fed into the corresponding melt extrusion system and extruded at 260°C. The film is melt-extruded and co-extruded through a three-layer die, then cast onto a casting roll to form an A1 / B / A2 structure extruded sheet. The sheet is then longitudinally stretched at a temperature of 75℃~87℃ with a longitudinal stretch ratio of 3.8. The longitudinally stretched sheet is then transversely stretched at a temperature of 108℃~130℃ with a transverse stretch ratio of 5.6. The stretched film is then shaped and cooled at a shaped temperature of 220℃. Finally, the film is cooled, drawn, and wound to obtain a 12μm thick biaxially oriented polyester film, in which the A1 layer accounts for 29% of the total thickness and the A2 layer accounts for 29% of the total thickness.

[0101] Example 2

[0102] Preparation of modified polyester:

[0103] Based on a dicarboxylic acid to ethylene glycol molar ratio of 1:1.3, the antimony glycolate addition was 90 ppm and the triphenyl phosphate addition was 35 ppm. The dicarboxylic acids, including 4-(3,5-dicarboxyphenoxy)phthalic acid, 4,4-propanediyldioxybenzoic acid, 3,5-bis(p-carboxyphenyl)benzoic acid, and terephthalic acid, had the following percentages relative to the total dicarboxylic acid content: X1 = 5 mol%, X2 = 3 mol%, X3 = 1 mol%, X4 = 1 mol%, X5 = 1 mol%, X6 = 1 mol%, X7 = 1 mol%, X8 = 1 mol%, X9 = 1 mol%, X1 = 1 mol%, X1 = 1 mol%, X1 = 1 mol%, X9 = 1 mol%, X1 = 1 mol%, X1 = 1 =5 mol%, X4 = 87 mol%, after being mixed evenly, are added to a polyester synthesis reactor, pulped for 15 minutes, and protected with nitrogen gas. Esterification is carried out for 2 hours at 236℃~262℃ and 265KPa. After esterification, vacuum is turned on, and polycondensation reaction is carried out for 3 hours at 265℃~282℃ and 30Pa. After fiber forming, cooling, pelletizing and drying, modified polyester with an intrinsic viscosity of 0.61dl / g is obtained.

[0104] Preparation of functional masterbatch Y:

[0105] 87 parts by weight of the modified polyester with an intrinsic viscosity of 0.61 dl / g prepared above and 13 parts by weight of crystalline spherical silica particles (inorganic filler y) with an average particle size of 0.03 μm 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 functional masterbatch Y with an intrinsic viscosity of 0.58 dl / g.

[0106] Preparation of functional masterbatch X / functional masterbatch Z:

[0107] 93 parts by weight of the modified polyester with an intrinsic viscosity of 0.61 dl / g prepared above and 7 parts by weight of crystalline spherical silica particles (inorganic filler x) with an average particle size of 0.5 μm and amorphous silica coating 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 functional masterbatch X with an intrinsic viscosity of 0.59 dl / g. Functional masterbatch Z has the same composition as functional masterbatch X.

[0108] 15 parts by weight of functional masterbatch X with an intrinsic viscosity of 0.59 dl / g and 85 parts by weight of pure polyester resin with an intrinsic viscosity of 0.63 dl / g (A1 layer), 8 parts by weight of functional masterbatch Y with an intrinsic viscosity of 0.58 dl / g and 92 parts by weight of pure polyester resin with an intrinsic viscosity of 0.63 dl / g (B layer), 10 parts by weight of functional masterbatch Z with an intrinsic viscosity of 0.59 dl / g and 90 parts by weight of pure polyester resin with an intrinsic viscosity of 0.63 dl / g (A2 layer) were pre-mixed and treated, then fed into the corresponding melt extrusion system and extruded at 265°C. The film undergoes melt extrusion, enters a three-layer die for co-extrusion, and is cast onto a casting roll to form an A1 / B / A2 structure extruded sheet. The casting sheet is then longitudinally stretched at a temperature of 75℃~87℃ with a longitudinal stretch ratio of 3.6. The longitudinally stretched sheet is then transversely stretched at a temperature of 108℃~130℃ with a transverse stretch ratio of 5.5. The stretched film is then shaped and cooled at a shaped temperature of 225℃. Finally, the film is cooled, drawn, and wound to obtain a 19μm thick biaxially oriented polyester film, in which the A1 layer accounts for 27% of the total thickness and the A2 layer accounts for 27% of the total thickness.

[0109] Example 3

[0110] Preparation of modified polyester:

[0111] Based on a dicarboxylic acid to ethylene glycol molar ratio of 1:1.28, the antimony glycolate addition amount is 150 ppm and the triphenyl phosphate addition amount is 60 ppm. The content of each of the dicarboxylic acid components—4-(3,5-dicarboxyphenoxy)phthalic acid, 4,4-propanediyldioxybenzoic acid, 3,5-bis(p-carboxyphenyl)benzoic acid, and terephthalic acid—relative to the total dicarboxylic acid content are as follows: X1 = 7 mol%, X2 = 5 mol%, X3 = 8 mol% and X4 = 80 mol% were mixed evenly and then added to a polyester synthesis reactor. The mixture was pulped for 15 minutes and protected with nitrogen. Esterification was carried out for 2.5 hours at 236℃~262℃ and 265KPa. After esterification, vacuum was applied and polycondensation was carried out for 3.5 hours at 265℃~282℃ and 30Pa. The resulting product was filamentized, cooled, pelletized, and dried to obtain a modified polyester with an intrinsic viscosity of 0.63dl / g.

[0112] Preparation of functional masterbatch Y:

[0113] 90 parts by weight of the modified polyester with an intrinsic viscosity of 0.63 dl / g prepared above and 10 parts by weight of crystalline spherical silica particles (inorganic filler y) with an average particle size of 0.05 μm 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 functional masterbatch Y with an intrinsic viscosity of 0.60 dl / g.

[0114] Preparation of functional masterbatch X / functional masterbatch Z:

[0115] 95 parts by weight of the modified polyester with an intrinsic viscosity of 0.63 dl / g prepared above and 5 parts by weight of crystalline spherical silica particles (inorganic filler x) with an average particle size of 0.5 μm and amorphous silica coating are mixed evenly and fed into a twin-screw extruder. Vacuum is turned on, and the mixture is filamentized, cooled, pelletized, and dried to obtain functional masterbatch X with an intrinsic viscosity of 0.60 dl / g. Functional masterbatch Z has the same composition as functional masterbatch X.

[0116] 18 parts by weight of functional masterbatch X with an intrinsic viscosity of 0.60 dl / g and 82 parts by weight of pure polyester resin with an intrinsic viscosity of 0.63 dl / g (A1 layer), 10 parts by weight of functional masterbatch Y with an intrinsic viscosity of 0.60 dl / g and 90 parts by weight of pure polyester resin with an intrinsic viscosity of 0.63 dl / g (B layer), and 18 parts by weight of functional masterbatch Z with an intrinsic viscosity of 0.60 dl / g and 82 parts by weight of pure polyester resin with an intrinsic viscosity of 0.63 dl / g (A2 layer) were pre-mixed and treated, then fed into the corresponding melt extrusion system and extruded at 270°C. The film undergoes melt extrusion, enters a three-layer die for co-extrusion, and is cast onto a casting roll to form an A1 / B / A2 structure extruded sheet. The casting sheet is then longitudinally stretched at a temperature of 75℃~87℃ with a longitudinal stretch ratio of 3.5. The longitudinally stretched sheet is then transversely stretched at a temperature of 108℃~130℃ with a transverse stretch ratio of 5.1. The stretched film is then shaped and cooled at a shaped temperature of 230℃. Finally, the film is cooled, drawn, and wound to obtain a 23μm thick biaxially oriented polyester film, in which the A1 layer accounts for 25% of the total thickness and the A2 layer accounts for 20% of the total thickness.

[0117] Example 4

[0118] Preparation of modified polyester:

[0119] Based on a dicarboxylic acid to ethylene glycol molar ratio of 1:1.33, the antimony glycolate addition was 180 ppm and the triphenyl phosphate addition was 70 ppm. The dicarboxylic acid components, 4-(3,5-dicarboxyphenoxy)phthalic acid, 4,4-propanediyldioxybenzoic acid, 3,5-bis(p-carboxyphenyl)benzoic acid, and terephthalic acid, had the following percentages relative to the total dicarboxylic acid content: X1 = 10 mol%, X2 = 7 mol%, X3 = 10 mol%, X4 = 7 mol%, X5 = 10 mol%, X6 = 10 mol%, X7 = 10 mol%, X8 = 10 mol%, X9 = 10 mol%, X1 ... =12 mol%, X4=71 mol%, after being mixed evenly, are added to a polyester synthesis reactor, pulped for 15 minutes, and protected with nitrogen gas. Esterification is carried out for 3 hours at 236℃~262℃ and 265KPa. After esterification, vacuum is turned on, and polycondensation reaction is carried out for 3.5 hours at 265℃~282℃ and 35Pa. After fiber forming, cooling, pelletizing and drying, modified polyester with an intrinsic viscosity of 0.65dl / g is obtained.

[0120] Preparation of functional masterbatch Y:

[0121] 92 parts by weight of the modified polyester with an intrinsic viscosity of 0.65 dl / g prepared above and 8 parts by weight of crystalline spherical silica particles (inorganic filler y) with an average particle size of 0.1 μm 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 functional masterbatch Y with an intrinsic viscosity of 0.62 dl / g.

[0122] Preparation of functional masterbatch X / functional masterbatch Z:

[0123] 94 parts by weight of the modified polyester with an intrinsic viscosity of 0.65 dl / g prepared above and 6 parts by weight of crystalline spherical silica particles (inorganic filler x) with an average particle size of 1 μm and amorphous silica coating are mixed evenly and fed into a twin-screw extruder. Vacuum is turned on and the mixture is filamentized, cooled, pelletized and dried to obtain functional masterbatch X with an intrinsic viscosity of 0.63 dl / g. Functional masterbatch Z has the same composition as functional masterbatch X.

[0124] 20 parts by weight of functional masterbatch X with an intrinsic viscosity of 0.63 dl / g and 80 parts by weight of pure polyester resin with an intrinsic viscosity of 0.64 dl / g (A1 layer), 15 parts by weight of functional masterbatch Y with an intrinsic viscosity of 0.62 dl / g and 85 parts by weight of pure polyester resin with an intrinsic viscosity of 0.64 dl / g (B layer), 18 parts by weight of functional masterbatch Z with an intrinsic viscosity of 0.63 dl / g and 82 parts by weight of pure polyester resin with an intrinsic viscosity of 0.64 dl / g (A2 layer) were pre-mixed and treated, then fed into the corresponding melt extrusion system and extruded at 270°C. The film undergoes melt extrusion, enters a three-layer die for co-extrusion, and is cast onto a casting roll to form an A1 / B / A2 structure extruded sheet. The casting sheet is then longitudinally stretched at a temperature of 75℃~87℃ with a longitudinal stretch ratio of 3.4. The longitudinally stretched sheet is then transversely stretched at a temperature of 108℃~130℃ with a transverse stretch ratio of 4.9. The stretched film is then shaped and cooled at a shaped temperature of 230℃. Finally, the film is cooled, drawn, and wound to obtain a 30μm thick biaxially oriented polyester film, in which the A1 layer accounts for 18% of the total thickness and the A2 layer accounts for 18% of the total thickness.

[0125] Example 5

[0126] Preparation of modified polyester:

[0127] Based on a dicarboxylic acid to ethylene glycol molar ratio of 1:1.35, the antimony glycolate addition was 180 ppm and the triphenyl phosphate addition was 80 ppm. The content of each of the dicarboxylic acid components—4-(3,5-dicarboxyphenoxy)phthalic acid, 4,4-propanediyldioxybenzoic acid, 3,5-bis(p-carboxyphenyl)benzoic acid, and terephthalic acid—relative to the total dicarboxylic acid content were as follows: X1 = 9 mol%, X2 = 6 mol%, X3 = 9 mol%, X4 = 6 mol%, X5 = 9 mol%, X6 = 9 mol%, X7 = 9 mol%, X8 = 9 mol%, X9 ... =20 mol%, X4 = 65 mol%, after being mixed evenly, are added to a polyester synthesis reactor, pulped for 15 minutes, and protected with nitrogen gas. Esterification is carried out for 3 hours at 236℃~262℃ and 265KPa. After esterification, vacuum is turned on, and polycondensation reaction is carried out for 4 hours at 265℃~282℃ and 40Pa. After fiber formation, cooling, pelletizing and drying, modified polyester with an intrinsic viscosity of 0.65dl / g is obtained.

[0128] Preparation of functional masterbatch Y:

[0129] 93 parts by weight of the modified polyester with an intrinsic viscosity of 0.65 dl / g prepared above and 7 parts by weight of crystalline spherical silica particles (inorganic filler y) with an average particle size of 0.3 μm 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 functional masterbatch Y with an intrinsic viscosity of 0.62 dl / g.

[0130] Preparation of functional masterbatch X / functional masterbatch Z:

[0131] 96.5 parts by weight of the modified polyester with an intrinsic viscosity of 0.65 dl / g prepared above and 3.5 parts by weight of crystalline spherical silica particles (inorganic filler x) with an average particle size of 1.5 μm and amorphous silica coating are mixed evenly and fed into a twin-screw extruder. Vacuum is applied, and the mixture is filamentized, cooled, pelletized, and dried to obtain functional masterbatch X with an intrinsic viscosity of 0.64 dl / g. Functional masterbatch Z has the same composition as functional masterbatch X.

[0132] 25 parts by weight of functional masterbatch X with an intrinsic viscosity of 0.64 dl / g and 75 parts by weight of pure polyester resin with an intrinsic viscosity of 0.65 dl / g (A1 layer), 20 parts by weight of functional masterbatch Y with an intrinsic viscosity of 0.62 dl / g and 80 parts by weight of pure polyester resin with an intrinsic viscosity of 0.65 dl / g (B layer), 15 parts by weight of functional masterbatch Z with an intrinsic viscosity of 0.64 dl / g and 85 parts by weight of pure polyester resin with an intrinsic viscosity of 0.65 dl / g (A2 layer) were pre-mixed and treated, then fed into the corresponding melt extrusion system and extruded at 275°C. The film undergoes melt extrusion, enters a three-layer die for co-extrusion, and is cast onto a casting roll to form an A1 / B / A2 structure extruded sheet. The casting sheet is then longitudinally stretched at a temperature of 75℃~87℃ with a longitudinal stretch ratio of 3.3. The longitudinally stretched sheet is then transversely stretched at a temperature of 108℃~130℃ with a transverse stretch ratio of 4.8. The stretched film is then shaped and cooled at a shaped temperature of 230℃. Finally, the film is cooled, drawn, and wound to obtain a 50μm thick biaxially oriented polyester film, in which the A1 layer accounts for 16% of the total thickness and the A2 layer accounts for 16% of the total thickness.

[0133] Example 6

[0134] Preparation of modified polyester:

[0135] Based on a dicarboxylic acid to ethylene glycol molar ratio of 1:1.4, the antimony glycolate addition was 200 ppm and the triphenyl phosphate addition was 80 ppm. The content of each of the dicarboxylic acid components—4-(3,5-dicarboxyphenoxy)phthalic acid, 4,4-propanediyldioxybenzoic acid, 3,5-bis(p-carboxyphenyl)benzoic acid, and terephthalic acid—relative to the total dicarboxylic acid content were as follows: X1 = 12 mol%, X2 = 8 mol%, X3 = 18 mol% and X4 = 62 mol% were mixed evenly and then added to a polyester synthesis reactor. The mixture was pulped for 15 minutes and protected with nitrogen. Esterification was carried out for 2.5 hours at 236℃~262℃ and 265KPa. After esterification, vacuum was applied and polycondensation was carried out for 4 hours at 265℃~282℃ and 40Pa. After fiber formation, cooling, pelletizing and drying, a modified polyester with an intrinsic viscosity of 0.65dl / g was obtained.

[0136] Preparation of functional masterbatch Y:

[0137] 95 parts by weight of the modified polyester with an intrinsic viscosity of 0.65 dl / g prepared above and 5 parts by weight of crystalline spherical silica particles (inorganic filler y) with an average particle size of 0.5 μm 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 functional masterbatch Y with an intrinsic viscosity of 0.63 dl / g.

[0138] Preparation of functional masterbatch X / functional masterbatch Z:

[0139] 97 parts by weight of the modified polyester with an intrinsic viscosity of 0.65 dl / g prepared above and 3 parts by weight of crystalline spherical silica particles (inorganic filler x) with an average particle size of 1.8 μm and amorphous silica coating 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 functional masterbatch X with an intrinsic viscosity of 0.63 dl / g. Functional masterbatch Z has the same composition as functional masterbatch X.

[0140] 27 parts by weight of functional masterbatch X with an intrinsic viscosity of 0.63 dl / g and 73 parts by weight of pure polyester resin with an intrinsic viscosity of 0.65 dl / g (A1 layer), 22 parts by weight of functional masterbatch Y with an intrinsic viscosity of 0.63 dl / g and 78 parts by weight of pure polyester resin with an intrinsic viscosity of 0.65 dl / g (B layer), 18 parts by weight of functional masterbatch Z with an intrinsic viscosity of 0.63 dl / g and 82 parts by weight of pure polyester resin with an intrinsic viscosity of 0.65 dl / g (A2 layer) were pre-mixed and treated, then fed into the corresponding melt extrusion system and extruded at 275°C. The film undergoes melt extrusion, enters a three-layer die for co-extrusion, and is cast onto a casting roll to form an A1 / B / A2 structure extruded sheet. The casting sheet is then longitudinally stretched at a temperature of 75℃~87℃ with a longitudinal stretch ratio of 3.3. The longitudinally stretched sheet is then transversely stretched at a temperature of 108℃~130℃ with a transverse stretch ratio of 4.8. The stretched film is then shaped and cooled at a shaped temperature of 230℃. Finally, the film is cooled, drawn, and wound to obtain a 75μm thick biaxially oriented polyester film, in which the A1 layer accounts for 16% of the total thickness and the A2 layer accounts for 16% of the total thickness.

[0141] Example 7

[0142] Preparation of modified polyester:

[0143] Based on a dicarboxylic acid to ethylene glycol molar ratio of 1:1.4, the antimony glycolate addition amount is 250 ppm and the triphenyl phosphate addition amount is 90 ppm. The dicarboxylic acids, specifically 4-(3,5-dicarboxyphenoxy)phthalic acid, 4,4-propanediyldioxybenzoic acid, 3,5-bis(p-carboxyphenyl)benzoic acid, and terephthalic acid, have the following percentages relative to the total dicarboxylic acid content: X1 = 13 mol%, X2 = 8 mol%, X3 = 13 mol%, X4 = 8 mol%, X5 = 13 mol%, X6 = 13 mol%, X7 = 13 mol%, X8 = 13 mol%, X9 = 13 mol%, X1 = 13 mol%, X1 = 13 mol%, X1 = 13 mol%, X2 = 13 mol%, X1 = 13 mol%, X1 = 13 mol%, X2 = 13 mol%, X1 = 13 mol%, X1 = 13 mol%, X2 = 13 mol%, X1 = 13 mol%, X2 = 13 mol%, X3 ...2 = 13 mol%, X3 = 13 mol%, X2 = 13 mol%, X2 = 13 mol%, X2 = 13 mol%, X2 = 13 mol%, X2 = =20 mol%, X4=59 mol%, after being mixed evenly, are added to a polyester synthesis reactor, pulped for 15 minutes, and protected with nitrogen gas. Esterification is carried out for 3 hours at 236℃~262℃ and 265KPa. After esterification, vacuum is turned on, and polycondensation reaction is carried out for 4 hours at 265℃~282℃ and 50Pa. After fiber formation, cooling, pelletizing and drying, modified polyester with an intrinsic viscosity of 0.66dl / g is obtained.

[0144] Preparation of functional masterbatch Y:

[0145] 96 parts by weight of the modified polyester with an intrinsic viscosity of 0.66 dl / g prepared above and 4 parts by weight of crystalline spherical silica particles (inorganic filler y) with an average particle size of 0.8 μm 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 functional masterbatch Y with an intrinsic viscosity of 0.64 dl / g.

[0146] Preparation of functional masterbatch X / functional masterbatch Z:

[0147] 96 parts by weight of the modified polyester with an intrinsic viscosity of 0.66 dl / g prepared above and 4 parts by weight of crystalline spherical silica particles (inorganic filler x) with an average particle size of 2 μm and amorphous silica coating are mixed evenly and fed into a twin-screw extruder. Vacuum is turned on, and the mixture is filamentized, cooled, pelletized, and dried to obtain functional masterbatch X with an intrinsic viscosity of 0.64 dl / g. Functional masterbatch Z has the same composition as functional masterbatch X.

[0148] 30 parts by weight of functional masterbatch X with an intrinsic viscosity of 0.64 dl / g and 70 parts by weight of pure polyester resin with an intrinsic viscosity of 0.66 dl / g (A1 layer), 25 parts by weight of functional masterbatch Y with an intrinsic viscosity of 0.64 dl / g and 75 parts by weight of pure polyester resin with an intrinsic viscosity of 0.66 dl / g (B layer), 20 parts by weight of functional masterbatch Z with an intrinsic viscosity of 0.64 dl / g and 80 parts by weight of pure polyester resin with an intrinsic viscosity of 0.66 dl / g (A2 layer) were pre-mixed and treated, then fed into the corresponding melt extrusion system and extruded at 275°C. The film undergoes melt extrusion, enters a three-layer die for co-extrusion, and is cast onto a casting roll to form an A1 / B / A2 structure extruded sheet. The casting sheet is then longitudinally stretched at a temperature of 75℃~87℃ with a longitudinal stretch ratio of 3.2. The longitudinally stretched sheet is then transversely stretched at a temperature of 108℃~130℃ with a transverse stretch ratio of 4.6. The stretched film is then shaped and cooled at a shaped temperature of 235℃. Finally, the film is cooled, drawn, and wound to obtain a 100μm thick biaxially oriented polyester film, in which the A1 layer accounts for 15% of the total thickness and the A2 layer accounts for 15% of the total thickness.

[0149] Example 8

[0150] Preparation of modified polyester:

[0151] Based on a dicarboxylic acid to ethylene glycol molar ratio of 1:1.43, the antimony glycolate addition was 300 ppm and the triphenyl phosphate addition was 100 ppm. The dicarboxylic acids, including 4-(3,5-dicarboxyphenoxy)phthalic acid, 4,4-propanediyldioxybenzoic acid, 3,5-bis(p-carboxyphenyl)benzoic acid, and terephthalic acid, had the following percentages relative to the total dicarboxylic acid content: X1 = 15 mol%, X2 = 10 mol%, X... 3 = 25 mol%, X4 = 50 mol%, and after being mixed evenly, the mixture is added to a polyester synthesis reactor and pulped for 15 minutes. Nitrogen gas is introduced for protection, and esterification is carried out for 3.5 hours at 236℃~262℃ and 265KPa. After esterification, vacuum is applied, and polycondensation reaction is carried out for 5 hours at 265℃~282℃ and 65Pa. After fiber formation, cooling, pelletizing, and drying, modified polyester with an intrinsic viscosity of 0.69dl / g is obtained.

[0152] Preparation of functional masterbatch Y:

[0153] 99 parts by weight of the modified polyester with an intrinsic viscosity of 0.69 dl / g prepared above and 1 part by weight of crystalline spherical silica particles (inorganic filler y) with an average particle size of 1 μm 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 functional masterbatch Y with an intrinsic viscosity of 0.66 dl / g.

[0154] Preparation of functional masterbatch X / functional masterbatch Z:

[0155] 99.7 parts by weight of the modified polyester with an intrinsic viscosity of 0.69 dl / g prepared above and 0.3 parts by weight of crystalline spherical silica particles (inorganic filler x) with an average particle size of 3 μm and amorphous silica coating are mixed evenly and fed into a twin-screw extruder. Vacuum is applied, and the mixture is filamentized, cooled, pelletized, and dried to obtain functional masterbatch X with an intrinsic viscosity of 0.68 dl / g. Functional masterbatch Z has the same composition as functional masterbatch X.

[0156] 50 parts by weight of functional masterbatch X with an intrinsic viscosity of 0.68 dl / g and 50 parts by weight of pure polyester resin with an intrinsic viscosity of 0.68 dl / g (A1 layer), 40 parts by weight of functional masterbatch Y with an intrinsic viscosity of 0.66 dl / g and 60 parts by weight of pure polyester resin with an intrinsic viscosity of 0.68 dl / g (B layer), 30 parts by weight of functional masterbatch Z with an intrinsic viscosity of 0.68 dl / g and 70 parts by weight of pure polyester resin with an intrinsic viscosity of 0.68 dl / g (A2 layer) were pre-mixed and treated, then fed into the corresponding melt extrusion system and extruded at 280°C. The film undergoes melt extrusion, enters a three-layer die for co-extrusion, and is cast onto a casting roll to form an A1 / B / A2 structure extruded sheet. The casting sheet is then longitudinally stretched at a temperature of 75℃~87℃ with a longitudinal stretch ratio of 3.2. The longitudinally stretched sheet is then transversely stretched at a temperature of 108℃~130℃ with a transverse stretch ratio of 4.4. The stretched film is then shaped and cooled at a shaped temperature of 235℃. Finally, the film is cooled, drawn, and wound to obtain a 125μm thick biaxially oriented polyester film, in which the A1 layer accounts for 10% of the total thickness and the A2 layer accounts for 10% of the total thickness.

[0157] Example 9

[0158] Preparation of modified polyester:

[0159] Based on a dicarboxylic acid to ethylene glycol molar ratio of 1:1.38, the antimony glycolate addition amount is 200 ppm and the triphenyl phosphate addition amount is 90 ppm. The dicarboxylic acid components, 4-(3,5-dicarboxyphenoxy)phthalic acid, 4,4-propanediyldioxybenzoic acid, 3,5-bis(p-carboxyphenyl)benzoic acid, and terephthalic acid, have the following percentages relative to the total dicarboxylic acid content: X1 = 15 mol%, X2 = 9 mol%, X3 = 15 mol%, X4 = 9 mol%, X5 = 9 mol%, X6 = 9 mol%, X7 = 9 mol%, X8 = 9 mol%, X9 ... =15 mol%, X4=61 mol%, after being mixed evenly, are added to a polyester synthesis reactor, pulped for 15 minutes, and protected with nitrogen gas. Esterification is carried out for 2.5 hours at 236℃~262℃ and 265KPa. After esterification, vacuum is turned on, and polycondensation reaction is carried out for 4 hours at 265℃~282℃ and 50Pa. After fiber forming, cooling, pelletizing and drying, modified polyester with an intrinsic viscosity of 0.66dl / g is obtained.

[0160] Preparation of functional masterbatch Y:

[0161] 98.5 parts by weight of the modified polyester with an intrinsic viscosity of 0.66 dl / g prepared above and 1.5 parts by weight of crystalline spherical silica particles (inorganic filler y) with an average particle size of 0.6 μm 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 functional masterbatch Y with an intrinsic viscosity of 0.62 dl / g.

[0162] Preparation of functional masterbatch X / functional masterbatch Z:

[0163] 99 parts by weight of the modified polyester with an intrinsic viscosity of 0.66 dl / g prepared above and 1 part by weight of crystalline spherical silica particles (inorganic filler x) with an average particle size of 2.5 μm and amorphous silica coating are mixed evenly and fed into a twin-screw extruder. Vacuum is turned on and the mixture is filamentized, cooled, pelletized and dried to obtain functional masterbatch X with an intrinsic viscosity of 0.65 dl / g. Functional masterbatch Z has the same composition as functional masterbatch X.

[0164] 35 parts by weight of functional masterbatch X with an intrinsic viscosity of 0.65 dl / g and 65 parts by weight of pure polyester resin with an intrinsic viscosity of 0.67 dl / g (A1 layer), 28 parts by weight of functional masterbatch Y with an intrinsic viscosity of 0.62 dl / g and 72 parts by weight of pure polyester resin with an intrinsic viscosity of 0.67 dl / g (B layer), 22 parts by weight of functional masterbatch Z with an intrinsic viscosity of 0.65 dl / g and 78 parts by weight of pure polyester resin with an intrinsic viscosity of 0.67 dl / g (A2 layer) were pre-mixed and treated, then fed into the corresponding melt extrusion system and extruded at 275°C. The film is melt-extruded and co-extruded through a three-layer die, then cast onto a casting roll to form an A1 / B / A2 structure extruded sheet. The sheet is then longitudinally stretched at a temperature of 75℃~87℃ with a longitudinal stretch ratio of 2.9. The longitudinally stretched sheet is then transversely stretched at a temperature of 108℃~130℃ with a transverse stretch ratio of 3.5. The stretched film is then shaped and cooled at a temperature of 240℃. Finally, the film is cooled, drawn, and wound to obtain a 175μm thick biaxially oriented polyester film, in which the A1 layer accounts for 8% of the total thickness and the A2 layer accounts for 8% of the total thickness.

[0165] Example 10

[0166] Preparation of modified polyester:

[0167] Based on a dicarboxylic acid to ethylene glycol molar ratio of 1:1.3, the antimony glycolate addition was 180 ppm and the triphenyl phosphate addition was 80 ppm. The dicarboxylic acids, including 4-(3,5-dicarboxyphenoxy)phthalic acid, 4,4-propanediyldioxybenzoic acid, 3,5-bis(p-carboxyphenyl)benzoic acid, and terephthalic acid, had the following percentages relative to the total dicarboxylic acid content: X1 = 12 mol%, X2 = 8 mol%, X3 = 12 mol%, X4 = 8 mol%, X5 = 12 mol%, X6 = 12 mol%, X7 = 12 mol%, X8 = 12 mol%, X9 = 12 mol%, X1 ... =20 mol%, X4 = 60 mol%, after being mixed evenly, are added to a polyester synthesis reactor, pulped for 15 minutes, and protected with nitrogen gas. Esterification is carried out for 3 hours at 236℃~262℃ and 265KPa. After esterification, vacuum is turned on, and polycondensation reaction is carried out for 5 hours at 265℃~282℃ and 30Pa. After fiber formation, cooling, pelletizing and drying, modified polyester with an intrinsic viscosity of 0.69dl / g is obtained.

[0168] Preparation of functional masterbatch Y:

[0169] 99 parts by weight of the modified polyester with an intrinsic viscosity of 0.69 dl / g prepared above and 1 part by weight of crystalline spherical silica particles (inorganic filler y) with an average particle size of 0.8 μm 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 functional masterbatch Y with an intrinsic viscosity of 0.66 dl / g.

[0170] Preparation of functional masterbatch X / functional masterbatch Z:

[0171] 99.4 parts by weight of the modified polyester with an intrinsic viscosity of 0.69 dl / g prepared above and 0.6 parts by weight of crystalline spherical silica particles (inorganic filler x) with an average particle size of 2.8 μm and amorphous silica coating 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 functional masterbatch X with an intrinsic viscosity of 0.67 dl / g. Functional masterbatch Z has the same composition as functional masterbatch X.

[0172] 38 parts by weight of functional masterbatch X with an intrinsic viscosity of 0.67 dl / g and 62 parts by weight of pure polyester resin with an intrinsic viscosity of 0.67 dl / g (A1 layer), 35 parts by weight of functional masterbatch Y with an intrinsic viscosity of 0.66 dl / g and 65 parts by weight of pure polyester resin with an intrinsic viscosity of 0.67 dl / g (B layer), 25 parts by weight of functional masterbatch Z with an intrinsic viscosity of 0.67 dl / g and 75 parts by weight of pure polyester resin with an intrinsic viscosity of 0.67 dl / g (A2 layer) were pre-mixed and treated, then fed into the corresponding melt extrusion system and extruded at 280°C. The film is melt-extruded and co-extruded through a three-layer die, then cast onto a casting roll to form an A1 / B / A2 structure extruded sheet. The sheet is then longitudinally stretched at a temperature of 75℃~87℃ with a longitudinal stretch ratio of 2.7. The longitudinally stretched sheet is then transversely stretched at a temperature of 108℃~130℃ with a transverse stretch ratio of 3.3. The stretched film is then shaped and cooled at a shaped temperature of 243℃. Finally, the film is cooled, drawn, and wound to obtain a 188μm thick biaxially oriented polyester film, in which the A1 layer accounts for 3% of the total thickness and the A2 layer accounts for 3% of the total thickness.

[0173] Comparative Example 1

[0174] 10 parts by weight of ordinary silica polyester masterbatch with an intrinsic viscosity of 0.58 dl / g, an average particle size of 0.3 μm, and a concentration of 10%, and 90 parts by weight of pure polyester resin with an intrinsic viscosity of 0.62 dl / g (A1 layer), 5 parts by weight of ordinary silica polyester masterbatch with an intrinsic viscosity of 0.56 dl / g, an average particle size of 0.03 μm, and a concentration of 15%, and 95 parts by weight of pure polyester resin with an intrinsic viscosity of 0.62 dl / g (B layer), 5 parts by weight of ordinary silica polyester masterbatch with an intrinsic viscosity of 0.58 dl / g, an average particle size of 0.3 μm, and a concentration of 10%, and 95 parts by weight of pure polyester resin with an intrinsic viscosity of 0.62 dl / g The resin (A2 layer) is pre-mixed and treated; it is fed into the corresponding melt extrusion system and melt-extruded at 260°C, then co-extruded through a three-layer die and cast onto a casting roller to form an A1 / B / A2 structure extruded sheet; the casting sheet is longitudinally stretched at a temperature of 75°C to 87°C with a longitudinal stretch ratio of 3.8; the longitudinally stretched sheet is then transversely stretched at a temperature of 108°C to 130°C with a transverse stretch ratio of 5.6; the stretched film is then shaped and cooled at a shaped temperature of 220°C; finally, the film is cooled, drawn, and wound to obtain a 12μm thick biaxially oriented polyester film, in which the A1 layer accounts for 29% of the total thickness and the A2 layer accounts for 29% of the total thickness.

[0175] Comparative Example 2

[0176] 25 parts by weight of ordinary silica polyester masterbatch with an intrinsic viscosity of 0.64 dl / g, an average particle size of 1.5 μm, and a concentration of 3.5%, and 75 parts by weight of pure polyester resin with an intrinsic viscosity of 0.65 dl / g (A1 layer), 20 parts by weight of ordinary silica polyester masterbatch with an intrinsic viscosity of 0.62 dl / g, an average particle size of 0.3 μm, and a concentration of 7%, and 80 parts by weight of pure polyester resin with an intrinsic viscosity of 0.65 dl / g (B layer), and 15 parts by weight of ordinary silica polyester masterbatch with an intrinsic viscosity of 0.64 dl / g, an average particle size of 1.5 μm, and a concentration of 3.5%, and 85 parts by weight of pure silica polyester resin with an intrinsic viscosity of 0.65 dl / g... Ester resin (A2 layer), after pre-mixing and other treatments, is fed into a corresponding melt extrusion system and melt-extruded at 275°C. It then enters a three-layer die for co-extrusion and is cast onto a casting roller to form an A1 / B / A2 structure extruded sheet. The casting sheet is longitudinally stretched at a temperature of 75°C–87°C with a longitudinal stretch ratio of 3.3. The longitudinally stretched sheet is then transversely stretched at a temperature of 108°C–130°C with a transverse stretch ratio of 4.8. The stretched film is then shaped and cooled at a temperature of 230°C. Finally, the film is cooled, drawn, and wound to obtain a 50μm thick biaxially oriented polyester film, in which the A1 layer accounts for 16% of the total thickness and the A2 layer accounts for 16% of the total thickness.

[0177] Comparative Example 3

[0178] 30 parts by weight of a common silica polyester masterbatch with an intrinsic viscosity of 0.64 dl / g, an average particle size of 2 μm, and a concentration of 4%, and 70 parts by weight of a pure polyester resin with an intrinsic viscosity of 0.66 dl / g (A1 layer), 25 parts by weight of a common silica polyester masterbatch with an intrinsic viscosity of 0.64 dl / g, an average particle size of 0.8 μm, and a concentration of 4%, and 75 parts by weight of a pure polyester resin with an intrinsic viscosity of 0.66 dl / g (B layer), 20 parts by weight of a common silica polyester masterbatch with an intrinsic viscosity of 0.64 dl / g, an average particle size of 2 μm, and a concentration of 4%, and 80 parts by weight of a pure polyester resin with an intrinsic viscosity of 0.66 dl / g (A1 layer) were mixed. The film is pre-mixed and treated (2 layers); it is fed into the corresponding melt extrusion system and melt-extruded at 275℃, then co-extruded through a three-layer die and cast onto a casting roller to form an A1 / B / A2 structure extruded sheet; the casting sheet is longitudinally stretched at a temperature of 75℃~87℃ with a longitudinal stretching ratio of 3.2; the longitudinally stretched sheet is then transversely stretched at a temperature of 108℃~130℃ with a transverse stretching ratio of 4.6; the stretched film is then shaped and cooled at a temperature of 235℃; finally, the film is cooled, drawn, and wound to obtain a 100μm thick biaxially oriented polyester film, in which the A1 layer accounts for 15% of the total thickness and the A2 layer accounts for 15% of the total thickness.

[0179] Table 1 Specific Implementation Results

[0180]

[0181]

[0182] Thickness test method: GB / T 33399-2016.

[0183] Thermal Performance: A small shaft sample, 1300 mm wide and 500 m long, was tested by passing it through the machine to evaluate its dynamic thermal performance. Testing conditions: Winding tension was set at 160 N / m; oven temperatures were 80℃ / 100℃ / 130℃ / 150℃ / 135℃ / 115℃ / 100℃ / 80℃; each oven section was 4 m long; the machine speed was 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 testing process, the inspector's line of sight formed a 45° angle with the film surface, and a high-intensity 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 testing was placed on a horizontal marble platform, with the inspector's line of sight forming a 0° angle with the film surface, and a high-intensity 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 "×".

[0184] Scratches / Abrasions: Take a sample sheet approximately 1m long from the entire film. Use a three-wavelength lamp or a high-intensity lamp, with the angle between the light and the film surface at approximately 45°. The inspector's line of sight should be approximately 30cm from the light spot on the film. Visually inspect the film surface for scratches / abrasions using both transmitted and reflected light methods. Record the results. If there are no scratches / abrasions on the film surface, record "Δ". If any scratch / abrasion is present, record "×".

[0185] By comparing Example 1 with Comparative Example 1, Example 5 with Comparative Example 2, and Example 7 with Comparative Example 3, it can be seen that under the same conditions of polyester film thickness, film-making process, inorganic particle size, and additive concentration, the biaxially oriented polyester film of the present invention has significantly better thermal performance and scratch / abrasion resistance than ordinary polyester film.

[0186] 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.

[0187] While the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the invention. Those skilled in the art can make various modifications and refinements without departing from the spirit and scope of the invention. Therefore, the scope of protection of the present invention shall be determined by the claims.

Claims

1. A biaxially oriented polyester film comprising A1 / B / A2 three-layered polyester resin layers, characterized in that, The A1 layer comprises the following substances in the following weight parts: functional masterbatch X 10-50 parts by weight pure polyester resin 50-90 parts by weight; The functional masterbatch X comprises the following substances in the following weight parts: inorganic filler x 0.3-10 parts by weight modified polyester 90-99.7 parts by weight, wherein the inorganic filler x is crystalline spherical silica particles coated with amorphous silica on the surface, with an average particle size of 0.3-3 μm; The B layer comprises the following substances in the following weight parts: functional masterbatch Y 5-40 parts by weight pure polyester resin 60-95 parts by weight; The functional masterbatch Y is composed of: inorganic filler y 1-15 parts by weight modified polyester 85-99 parts by weight, wherein the inorganic filler y is crystalline spherical silica particles, with an average particle size of 0.03-1 μm; The A2 layer comprises the following substances in the following weight parts: functional masterbatch Z 5-30 parts by weight pure polyester resin 70-95 parts by weight; The functional masterbatch Z has the same composition as the functional masterbatch X; The modified polyester uses the following acids: 4-(3,5-dicarboxyphenoxy)phthalic acid, 4,4-propanediyl dioxy dibenzoic acid, 3,5-di-(p-carboxyphenyl)benzoic acid, terephthalic acid; Definitions: X1 is the content rate of 4-(3,5-dicarboxyphenoxy)phthalic acid component in the total dicarboxylic acid component in the modified polyester; X2 is the content rate of 4,4-propanediyl dioxy dibenzoic acid component in the total dicarboxylic acid component; X3 is the content rate of 3,5-di-(p-carboxyphenyl)benzoic acid component in the total dicarboxylic acid component; X4 is the content rate of terephthalic acid component in the total dicarboxylic acid component; X1, X2, X3, X4 satisfy the following relationship: 5 mole%≤X1≤15 mole% 2 mole%≤X2≤10 mole% 3 mole%≤X3≤25 mole% 50 mole%≤X4≤90 mole% X1+X2+X3+X4=100 mole%.

2. The biaxially oriented polyester film according to claim 1, characterized in that, The thickness of the biaxially oriented polyester film is 12-188 μm.

3. The biaxially oriented polyester film according to claim 2, characterized in that, The biaxially oriented polyester film contains A1 / B / A2 three-layer polyester resin layers, wherein the A1 layer accounts for 3-29% of the total thickness, and the A2 layer accounts for 3-29% of the total thickness; the thickness of the A1 layer is the same as or different from the thickness of the A2 layer.

4. The biaxially oriented polyester film according to claim 1, characterized in that, The pure polyester resin is polyethylene terephthalate resin with an intrinsic viscosity of 0.62-0.68 dl / g.

5. The biaxially oriented polyester film according to claim 1, characterized in that, The biaxially oriented polyester film is prepared by mixing the functional masterbatch X, the functional masterbatch Y, the functional masterbatch Z and the pure polyester resin in advance, feeding them into a corresponding melt extrusion system for extrusion, entering a three-layer co-extrusion die, and then being subjected to casting, longitudinal stretching, transverse stretching, heat setting, cooling, traction and winding.

6. The biaxially oriented polyester film according to claim 5, characterized in that, The melt extrusion temperature is 260-280 °C.

7. The biaxially oriented polyester film according to claim 5, characterized in that, The longitudinal stretching ratio is 2.7-3.

8.

8. The biaxially oriented polyester film according to claim 5, characterized in that, The transverse stretching ratio is 3.3-5.

6.

9. The biaxially oriented polyester film according to claim 5, characterized in that, The heat setting temperature is 220-243 °C.

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