A polyester film and a method for producing the same

Abstract

The present application relates to the technical field of thin film, especially to a polyester film and a preparation method thereof, containing modified polyester; the modified polyester is formed by esterification and polycondensation of binary acid and binary alcohol according to a molar ratio of 1:(1.2-1.5); the binary acid includes the following substances: terephthalic acid, a molar number M1, alpha, beta-bis(2-chlorophenoxy)ethane-4,4'-dicarboxylic acid, a molar number M 21 , 5-tert-butyl-1,3-benzenedicarboxylic acid, a molar number M 22 , 5-nitrophthalic acid, a molar number M 23 , a molar number M2, M2=M 21 +M 22 +M 23 , wherein 1.5≤M1 / M2≤9. The polyester film has excellent dynamic thermal performance, optical performance, mechanical performance, flatness, and good apparent quality, and can be widely used in the fields of liquid crystal display, protection, and separation.

Description

Technical Field

[0001] The present invention relates to the technical field of films, in particular to a polyester film and a preparation method thereof, in particular to a polyester film with excellent dynamic thermal properties and a preparation method thereof. Background Art

[0002] Polyethylene terephthalate (PET), as a key synthetic material, plays a crucial role in our daily lives. Polyester film, a specialized form of polyester, exists independently. Due to its high mechanical strength, excellent cold and heat resistance, stable shrinkage, and excellent electrical insulation properties, polyester film is widely used in packaging, industry, electronics, electrical engineering, magnetics, and photosensitive applications.

[0003] As one of the world's important polyester film production and consumption bases, China plays a vital role in the field of polyester film. After decades of development, the polyester film industry in mainland China and Taiwan has shown a booming trend, and various BOPET film production lines have sprung up everywhere. In 2021, the total production capacity of China's BOPET industry reached 4.6 million tons. Even at an average operating rate of 75%, the output of polyester film reached 3.45 million tons. The large output can be imagined. Taking the fields of liquid crystal display, protection, and release (ordinary protection and release have no special quality requirements and are excluded) that have high requirements for the quality of polyester film as an example, they have something in common: polyester film is used as a carrier, and then deep processing is carried out on it. Therefore, the quality of the polyester film base film directly affects the quality of the finished product to a large extent. At present, there are two main problems in the production of polyester film and downstream deep processing: 1. When the film is just produced, the sample is placed on a marble platform to observe the unevenness of the film surface, or on the small shaft body, the unevenness is clearly visible to the naked eye. 2. During downstream deep processing, the polyester film will have longitudinal uneven lines at the outlet of the hot oven, which seriously affects the product quality and causes direct economic losses.

[0004] Such problems hinder the polyester film industry from moving towards higher-end development and have become a "bottleneck" technical problem in the industry. These problems can be collectively referred to as poor dynamic thermal performance of the film (mainly referring to the thermal performance of the polyester film when it is in a temperature field or when it passes through a temperature field and is subjected to external forces). Technical personnel easily confuse the concepts of dynamic thermal performance with static thermal performance (mainly referring to the thermal performance of the polyester film when the external force is zero in the temperature field, with thermal shrinkage being a typical representative). They often judge the thermal performance of polyester film by its thermal shrinkage value, which is actually not the case and can easily mislead technical personnel.

[0005] The existing technical solutions to the above problems are as follows: 1. During the melt extrusion process of polyester film, nanometer / micrometer-sized inorganic or organic particles are added to the core layer to increase the crystallinity of the polyester film, improve its thermal performance, and resist film deformation after heating. 2. Increasing the temperature of the heat setting zone to make the crystal growth more complete, reduce the creep of the crystal molecular chain in the subsequent heating process, and ensure flatness. 3. When using polyester film in downstream processing, reduce the production speed and reduce the winding tension, so that the polyester film is subjected to less force after leaving the oven and the relative deformation of the film is small.

[0006] Despite extensive research into improving the stiffness of polyester film, existing technologies for enhancing the dynamic thermal properties of polyester film still face numerous challenges: 1. While inorganic or organic particles in the polyester film core layer act as nucleating agents, while they can effectively increase the crystallinity and thermal performance of polyester film, these nucleating agents do not meet the dynamic thermal properties required for downstream processing. Furthermore, nucleating agents typically have a large surface area and high surface energy, which can lead to microscopic aggregation and formation of crystal points, compromising film quality. Macroscopic aggregation can also lead to uneven crystallization across the film surface, exacerbating surface unevenness upon heating. 2. Technologists consider crystal growth solely to correlate crystal perfection with crystallization temperature, but ignore the reversible relationship between molecular chain orientation and deorientation. As temperatures rise, the reverse reaction also occurs, resulting in counterproductive results. This confuses dynamic thermal properties with static thermal properties. While perfect crystals may reduce film thermal shrinkage, dynamic thermal properties may also deteriorate. 3. Reducing winding tension can improve poor dynamic thermal properties to some extent, but this results in lost productivity and increased production costs. Summary of the Invention

[0007] The present invention aims to overcome the deficiencies of the prior art and provide a polyester film and a method for preparing the same. The polyester film has excellent dynamic thermal performance, optical properties, mechanical properties, flatness, and good surface quality, and can be widely used in liquid crystal display, protection, release, and other fields.

[0008] To overcome the deficiencies in the prior art, the present invention adopts the following technical solution: a polyester film comprising a modified polyester; the modified polyester is prepared by esterification and polycondensation of a dibasic acid and a diol at a molar ratio of 1: (1.2-1.5);

[0009] Dibasic acids include the following:

[0010] Terephthalic acid, mole number M1,

[0011] α,β-Bis(2-chlorophenoxy)ethane-4,4′-dicarboxylic acid, molar number M 21 ,

[0012] 5-tert-Butyl-1,3-benzenedicarboxylic acid, molar number M 22,

[0013] 5-nitrophthalic acid, moles M 23 ,

[0014] Mole number M2, M2 = M 21 +M 22 +M 23 ,

[0015] Among them, 1.5≤M1 / M2≤9.

[0016] As the improved technical solution of this application, 0.6≤M 21 / M 22 ≤5, 0.2≤M 22 / M 23 ≤3, 0.4≤M 21 / M 23 ≤5.

[0017] As an improved technical solution of the present application, the thickness of the polyester film is 23 μm to 250 μm.

[0018] As an improved technical solution of the present application, the structure of the polyester film is a single-layer structure A, a double-layer structure A / B, or a three-layer structure A / B / A, and the A layer and / or the B layer contain the modified polyester.

[0019] As an improved technical solution of this application, the polyester film adopts a double-layer structure A / B, and the thickness of the A layer is H a The thickness of the B layer H b The relationship between them is 2.5≤H b / H a ≤12.

[0020] As an improved technical solution of the present application, the polyester film adopts a three-layer structure A / B / A, and the thickness of the A layer (H a ) and the thickness of the B layer (H b ) is 5≤H b / H a ≤22.

[0021] As an improved technical solution of the present application, the preparation of the modified polyester comprises the following steps:

[0022] Add the required dibasic acid, diol, catalyst and stabilizer into the polyester reactor in sequence, beat for 15 minutes, and introduce nitrogen protection, and esterify at 230℃~260℃ and 265KPa for 2.5h~4h;

[0023] The esterification end point is determined according to the water output. After the esterification is complete, vacuum is applied and the polycondensation reaction is carried out at 260° C. to 278° C. and 20 Pa to 70 Pa for 2 h to 4 h. The modified polyester is obtained by spinning, cooling, pelletizing and drying.

[0024] The amount of the catalyst used is 80ppm to 300ppm, and the amount of the stabilizer used is 20ppm to 150ppm.

[0025] As an improved technical solution of the present application, the intrinsic viscosity of the modified polyester is 0.60 dl / g to 0.72 dl / g.

[0026] Another object of the present application is to provide a method for preparing a polyester film, comprising the following steps:

[0027] A number of modified polyester chips, functional masterbatch and pure polyester chips are mixed in advance, sent to the corresponding melt extrusion system, extruded at a temperature of 260℃~285℃, and entered into the die for co-extrusion;

[0028] Then, the polyester film is produced through casting, longitudinal stretching, transverse stretching, shaping, cooling, pulling and winding.

[0029] As an improved technical solution of the present application, the longitudinal stretching ratio of the longitudinal stretching process is 2.5 to 3.5.

[0030] As an improved technical solution of the present application, the transverse stretching ratio of the transverse stretching process is 3.5 to 5.0.

[0031] As an improved technical solution of the present application, the heat setting temperature of the setting process is 225°C to 240°C.

[0032] In the present invention, the molar numbers M1, M2, M 21 、M 22 、M 23 Named to distinguish different acid dosages, H a 、H b The name is used to distinguish the thickness of different layers of polyester film. The letters themselves have no meaning.

[0033] The beneficial effects of the present invention are:

[0034] 1. Starting from the microstructure, the molecular structure is designed, and groups such as chlorophenoxy are introduced into the main chain of the molecule, and tert-butyl and nitro groups are introduced into the side chain for acid modification. This gives ordinary polyethylene terephthalate properties that cannot be achieved, solving technical problems in the industry.

[0035] 2. The molecular structure design modification completely avoids the incompatibility problem caused by doping modification, making the surface performance of polyester film more uniform and stable.

[0036] 3、The application greatly improves the dynamic thermal performance of the polyester film, improves the stability of the downstream deep processing of the polyester film, reduces the cost, and ensures the yield of semi-finished products and finished products. DETAILED DESCRIPTION

[0037] In order to facilitate the understanding of the present application, the present application will be described more fully below with reference to specific embodiments. However, the present application can be realized in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present application more thorough and comprehensive.

[0038] 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 the present application belongs. The terms used in the specification of the present application herein are only for the purpose of describing specific embodiments and are not intended to limit the present application.

[0039] The polyester film of the present application contains a modified polyester; the modified polyester is prepared by esterification and polycondensation of a dibasic acid and a dibasic alcohol at a molar ratio of 1:(1.2-1.5);

[0040] The dibasic acid includes the following substances:

[0041] terephthalic acid, molar number M1,

[0042] α, β-bis (2-chlorophenoxy) ethane-4, 4'-dicarboxylic acid, molar number M 21 ,

[0043] 5-tert-butyl-1, 3-benzenedicarboxylic acid, molar number M 22 ,

[0044] 5-nitrophthalic acid, molar number M 23 ,

[0045] Molar number M2, M2=M 21 +M 22 +M 23 ,

[0046] Wherein, 1.5≤M1 / M2≤9, 0.6≤M 21 / M 22 ≤5, 0.2≤M 22 / M 23 ≤3, 0.4≤M 21 / M 23 ≤5.

[0047] Polyethylene terephthalate (PET) is a semi-crystalline polymer that undergoes nucleation, growth, and finalization during the polyester film manufacturing process. In fact, the finished polyester film is not simply composed of a "crystalline phase" and an "amorphous phase," but rather a "crystalline phase," an "amorphous phase," and an "interphase." These three components together constitute the "long cycle" of the polyester film. The "interphase" plays a crucial role in post-processing, acting as a "buffer" to effectively offset post-deformation. Polyester melt casting undergoes asynchronous stretching, through longitudinal and transverse stretching, and finalization into film. The transverse stretching process typically disrupts the molecular chain orientation formed during longitudinal stretching, and finalization occurs after transverse stretching. Consequently, in the transverse direction, the number of chemical bonds per cross-section of the covalently bonded molecular chains increases significantly. In the longitudinal direction, the weaker van der Waals forces between the molecular chains predominate. Consequently, polyester film exhibits distinct anisotropy in different directions across the film surface, a property that must be fully considered in formulation design and downstream processing. In this invention, the polyester molecular structure is redesigned by introducing monomers such as α,β-bis(2-chlorophenoxy)ethane-4,4′-dicarboxylic acid, 5-tert-butyl-1,3-benzenedicarboxylic acid, and 5-nitrophthalic acid, thereby altering the polymer's aggregated structure. The addition of α,β-bis(2-chlorophenoxy)ethane-4,4′-dicarboxylic acid effectively increases the polyester polymer's long period, prolongs the mesophase transition, and effectively improves the polyester film's resistance to post-deformation, thereby addressing the poor dynamic thermal properties of conventional polyester films. The addition of 5-tert-butyl-1,3-benzenedicarboxylic acid and 5-nitrophthalic acid allows for the formation of hydrogen bonds between the tert-butyl group and the nitro and phenoxy groups, which are stronger than van der Waals forces, thereby reducing the impact of the initial anisotropic properties of the polyester film. At the same time, the steric hindrance of chlorine atoms, benzene rings, and nitrogen atoms is much greater than that of ordinary carbon atoms. The three methyl groups in the tert-butyl group can also increase the steric hindrance to a certain extent. The presence of large steric hindrance can effectively offset the increase in the trans conformation in the amorphous region of the polyester film after heating, or the transformation of the Pond's conformation to the trans conformation. Because the trans conformation has high energy and is unstable, it can easily lead to poor dynamic thermal properties of the polyester film. In the present invention, several monomers interact and coordinate with each other, and none of them can be missing. At the same time, the appropriate proportions of terephthalic acid, α,β-bis(2-chlorophenoxy)ethane-4,4'-dicarboxylic acid, 5-tert-butyl-1,3-benzenedicarboxylic acid, and 5-nitrophthalic acid are designed in the present invention to achieve the best technical effect.

[0048] 1. Modified polyester

[0049] Specifically, the dibasic acid and the diol are esterified and polycondensed in a molar ratio of 1: (1.2-1.5) under the joint action of a catalyst and a stabilizer.

[0050] 1) Dibasic acid:

[0051] The dibasic acid is one or a combination of terephthalic acid, phthalic acid, isophthalic acid, naphthalene dicarboxylic acid, anthracene dicarboxylic acid, α,β-bis(2-chlorophenoxy)ethane-4,4'-dicarboxylic acid, 5-tert-butyl-1,3-benzenedicarboxylic acid, and 5-nitrophthalic acid.

[0052] The most preferred is a combination of terephthalic acid, naphthalene dicarboxylic acid, α,β-bis(2-chlorophenoxy)ethane-4,4′-dicarboxylic acid, 5-tert-butyl-1,3-benzenedicarboxylic acid, and 5-nitrophthalic acid.

[0053] The best is a combination of terephthalic acid, α,β-bis(2-chlorophenoxy)ethane-4,4′-dicarboxylic acid, 5-tert-butyl-1,3-benzenedicarboxylic acid, and 5-nitrophthalic acid.

[0054] At this time, the dibasic acid includes the following substances:

[0055] Terephthalic acid, mole number M1,

[0056] α,β-Bis(2-chlorophenoxy)ethane-4,4′-dicarboxylic acid, molar number M 21 ,

[0057] 5-tert-Butyl-1,3-benzenedicarboxylic acid, molar number M 22 ,

[0058] 5-nitrophthalic acid, moles M 23 ,

[0059] Mole number M2, M2 = M 21 +M 22 +M 23 ,

[0060] Wherein, 1.5≤M1 / M2≤9; preferably, 0.6≤M 21 / M 22 ≤5, 0.2≤M 22 / M 23 ≤3, 0.4≤M 21 / M 23 ≤5. Several monomers interact and coordinate with each other, and none of them can be missing. At the same time, the appropriate proportions of terephthalic acid, α,β-bis(2-chlorophenoxy)ethane-4,4'-dicarboxylic acid, 5-tert-butyl-1,3-benzenedicarboxylic acid, and 5-nitrophthalic acid are designed in the present invention to achieve the best technical effect. Terephthalic acid is used as the basic monomer. Acid modification usually refers to replacing part of the terephthalic acid with other dibasic acids. If terephthalic acid is absent, then it is not PET, but a different substance.

[0061] 2) Diols

[0062] The diol is one or a combination of ethylene glycol, propylene glycol, butanediol, and 1,4-cyclohexanedimethanol. The ideal diol is a combination of ethylene glycol and 1,4-cyclohexanedimethanol, and the best diol is ethylene glycol.

[0063] 3) Catalyst

[0064] The catalyst can be one of antimony, aluminum, germanium, or titanium, or a combination of any number in any weight ratio. Antimony is ideal, with ethylene glycol antimony being the best. Ethylene glycol antimony is the most commonly used catalyst in the polyester industry. Germanium and aluminum catalysts react quickly, are difficult to control, and are costly. Polyester produced using titanium catalysts tends to have a high b-value and a yellowish tint.

[0065] 4) Stabilizer

[0066] The stabilizer is one or a combination of trimethyl phosphate, triphenyl phosphate, tetrabutyl titanate, tetraethyl titanate, etc. in any weight ratio. The ideal one is a combination of trimethyl phosphate and triphenyl phosphate, and the best one is triphenyl phosphate. Triphenyl phosphate contains a benzene ring and has better compatibility with polyesters containing the same benzene ring.

[0067] 5) Preparation method of modified polyester

[0068] The preparation of the modified polyester comprises the following steps:

[0069] Add the required dibasic acid, diol, catalyst and stabilizer into the polyester reactor in sequence, beat for 15 minutes, and introduce nitrogen protection, and esterify at 230℃~260℃ and 265KPa for 2.5h~4h;

[0070] The esterification end point is determined according to the water output. After the esterification is complete, vacuum is applied and the polycondensation reaction is carried out at 260° C. to 278° C. and 20 Pa to 70 Pa for 2 h to 4 h. The modified polyester is obtained through silk making, cooling, pelletizing and drying.

[0071] Finally, a modified polyester with an intrinsic viscosity of 0.60 dl / g to 0.72 dl / g was obtained.

[0072] 2. Polyester film

[0073] Another object is to provide a method for preparing a polyester film, comprising the steps of:

[0074] Several modified polyester chips, functional masterbatches, and pure polyester chips are pre-mixed and fed into the corresponding melt extrusion system. In the film industry, to improve the winding and slitting performance of polyester film, a functional masterbatch containing inorganic silica particles with a particle size of 1μm to 4μm, a concentration of 1%, and an intrinsic viscosity of 0.62dl / g is added to the A layer. This results in an overall concentration of inorganic silica particles in the polyester film of 300ppm to 3000ppm, and an intrinsic viscosity of 0.65dl / g for the pure high-gloss polyester chips. Extrusion is performed at a temperature of 260℃ to 285℃ and then enters the die for co-extrusion.

[0075] Then, the polyester film is produced through casting, longitudinal stretching, transverse stretching, shaping, cooling, pulling and winding.

[0076] The longitudinal stretching ratio of the longitudinal stretching process is 2.5 to 3.5; the transverse stretching ratio of the transverse stretching process is 3.5 to 5.0; and the heat setting temperature of the setting process is 225° C. to 240° C.

[0077] It should be noted that, without affecting the technical effects of the present invention, the polyester film of the present invention can be subjected to corona pretreatment on one or both sides, or a primer pretreatment with a thickness of 0.01 μm to 0.20 μm, and then supplied to downstream for further processing.

[0078] 3. Structure of polyester film

[0079] The polyester film has a thickness of 23 μm to 250 μm. The polyester film of this application is designed to have a single-layer structure A, a double-layer structure A / B, or a triple-layer structure A / B / A, wherein the A layer and / or the B layer contain the modified polyester. That is, regardless of whether the polyester film has a single-layer structure A, a double-layer structure A / B, or a triple-layer structure A / B / A, the thickness of the polyester film is always 23 μm to 250 μm.

[0080] Wherein, when the polyester film adopts a double-layer structure A / B, the thickness of the A layer H a The thickness of the B layer H b The relationship between them is 2.5≤H b / H a ≤12.

[0081] When the polyester film adopts a three-layer structure A / B / A, the thickness of the A layer (H a ) and the thickness of the B layer (H b ) is 5≤H b / H a ≤22. The purpose is: the A layer is mainly used as a functional layer, adding functional masterbatch, modified materials, etc. to give the film relevant properties. Taking the slip masterbatch as an example, if the A layer is too thin, the particles protrude too much, which easily leads to particle shedding. If the A layer is too thick, the particles are buried in the polyester and have no slippery effect.

[0082] The present invention will be further described below with reference to the following examples, but the implementation and protection scope of the present invention are not limited to these examples.

[0083] Example 1

[0084] Preparation of modified polyester

[0085] According to the molar ratio of dibasic acid to ethylene glycol of 1:1.35, the addition amount of ethylene glycol antimony is 100ppm, and the addition amount of triphenyl phosphate is 50ppm. Among them, the relationship between the molar number of terephthalic acid in the dibasic acid (M1) and the molar number of the mixture of α,β-bis(2-chlorophenoxy)ethane-4,4'-dicarboxylic acid, 5-tert-butyl-1,3-benzenedicarboxylic acid and 5-nitrophthalic acid (M2) is M1 / M2=2, M2=M 21 +M 22 +M 23 , the number of moles of α,β-bis(2-chlorophenoxy)ethane-4,4′-dicarboxylic acid (M 21 ) and the number of moles of 5-tert-butyl-1,3-benzenedicarboxylic acid (M 22 ) is M 21 / M 22 =1.1, the number of moles of 5-tert-butyl-1,3-benzenedicarboxylic acid (M 22 ) and the number of moles of 5-nitrophthalic acid (M 23 ) is M 22 / M 23 =0.4, the number of moles of α,β-bis(2-chlorophenoxy)ethane-4,4′-dicarboxylic acid (M 21 ) and the number of moles of 5-nitrophthalic acid (M 23 ) is M 21 / M 23 =0.8. After being uniformly mixed, the above mixture was added to a polyester synthesis reactor and beaten for 15 minutes. Esterification was carried out at 230°C to 260°C and 265 kPa under nitrogen protection for 3 hours. After the esterification was completed, vacuum was turned on and polycondensation was carried out at 260°C to 278°C and 35 Pa for 2.5 hours. After spinning, cooling, pelletizing, and drying, a modified polyester with an intrinsic viscosity of 0.66 dl / g was obtained.

[0086] The modified polyester of the present invention and a functional masterbatch (for providing lubricity) containing inorganic silica particles with a particle size of 2.5 μm, a concentration of 1%, and an intrinsic viscosity of 0.62 dl / g, wherein the overall content of inorganic silica particles with a particle size of 2.5 μm in the polyester film is 1500 ppm, are added to a corresponding melt extrusion system, extruded into a die at a temperature of 265°C, and cast onto a casting roller to form a single-layer A extruded casting sheet. The casting sheet is longitudinally stretched at a longitudinal stretching temperature of 50°C to 85°C and a longitudinal stretching ratio of 3.3; the longitudinally stretched sheet is transversely stretched at a transverse stretching temperature of 93°C to 125°C and a transverse stretching ratio of 5.0; the stretched film is shaped at a shaping temperature of 230°C; the film is then cooled, pulled, and wound to obtain a polyester film with a thickness of 23 μm.

[0087] Example 2

[0088] Preparation of modified polyester

[0089] According to the molar ratio of dibasic acid to ethylene glycol of 1:1.2, the amount of ethylene glycol antimony added is 80ppm, and the amount of triphenyl phosphate added is 20ppm. Among them, the relationship between the molar number of terephthalic acid in the dibasic acid (M1) and the molar number of the mixture of α,β-bis(2-chlorophenoxy)ethane-4,4'-dicarboxylic acid, 5-tert-butyl-1,3-benzenedicarboxylic acid and 5-nitrophthalic acid (M2) is M1 / M2=1.5, M2=M 21 +M 22 +M 23 , the number of moles of α,β-bis(2-chlorophenoxy)ethane-4,4′-dicarboxylic acid (M 21 ) and the number of moles of 5-tert-butyl-1,3-benzenedicarboxylic acid (M 22 ) is M 21 / M 22 =0.6, the number of moles of 5-tert-butyl-1,3-benzenedicarboxylic acid (M 22 ) and the number of moles of 5-nitrophthalic acid (M 23 ) is M 22 / M 23 =0.2, the number of moles of α,β-bis(2-chlorophenoxy)ethane-4,4′-dicarboxylic acid (M 21 ) and the number of moles of 5-nitrophthalic acid (M 23 ) is M 21 / M 23=0.4. After uniform mixing, the above mixture was added to a polyester synthesis reactor and beaten for 15 minutes. Under nitrogen protection, esterification was carried out at 230°C to 260°C and 265 kPa for 2.5 hours. After the esterification was completed, vacuum was turned on and polycondensation was carried out at 260°C to 278°C and 20 Pa for 2 hours. After spinning, cooling, pelletizing, and drying, a modified polyester with an intrinsic viscosity of 0.60 dl / g was obtained.

[0090] The modified polyester of the present invention and the functional masterbatch (for providing lubrication) containing inorganic silica particles with a particle size of 1 μm, a concentration of 1%, and an intrinsic viscosity of 0.62 dl / g, wherein the total content of the inorganic silica particles with a particle size of 1 μm in the polyester film is 3000 ppm (A layer), and the intrinsic viscosity is 0.65 dl / g. Pure large glossy polyester chips and the functional masterbatch (for providing lubrication) containing inorganic silica particles with a particle size of 1 μm, a concentration of 1%, and an intrinsic viscosity of 0.62 dl / g, wherein the inorganic silica particles with a particle size of 1 μm in the polyester film are 3000 ppm (A layer), and the intrinsic viscosity is 0.65 dl / g. The overall content of the polyester is 1500ppm (B layer), added to the corresponding melt extrusion system, extruded into the die at a temperature of 260°C, cast onto a casting roll to form an A / B structure co-extruded cast sheet, the cast sheet is longitudinally stretched at a longitudinal stretching temperature of 50°C to 85°C, and a longitudinal stretching ratio of 3.3; the longitudinally stretched sheet is transversely stretched at a transverse stretching temperature of 93°C to 125°C, and a transverse stretching ratio of 4.3; the stretched film is shaped at a shaping temperature of 240°C; the film is then cooled, pulled, and wound to obtain a polyester film with a thickness of 23μm, wherein the thickness of the A layer (H a ) and the thickness of the B layer (H b ) is related to H b / H a =12.

[0091] Example 3

[0092] Preparation of modified polyester

[0093] According to the molar ratio of dibasic acid to ethylene glycol of 1:1.23, the addition amount of ethylene glycol antimony is 100ppm, and the addition amount of triphenyl phosphate is 35ppm. Among them, the relationship between the molar number of terephthalic acid in the dibasic acid (M1) and the molar number of the mixture of α,β-bis(2-chlorophenoxy)ethane-4,4'-dicarboxylic acid, 5-tert-butyl-1,3-benzenedicarboxylic acid and 5-nitrophthalic acid (M2) is M1 / M2=4, M2=M 21 +M 22 +M 23 , the number of moles of α,β-bis(2-chlorophenoxy)ethane-4,4′-dicarboxylic acid (M 21 ) and the number of moles of 5-tert-butyl-1,3-benzenedicarboxylic acid (M 22) is M 21 / M 22 =1.1, the number of moles of 5-tert-butyl-1,3-benzenedicarboxylic acid (M 22 ) and the number of moles of 5-nitrophthalic acid (M 23 ) is M 22 / M 23 =0.9, the number of moles of α,β-bis(2-chlorophenoxy)ethane-4,4′-dicarboxylic acid (M 21 ) and the number of moles of 5-nitrophthalic acid (M 23 ) is M 21 / M 23 =0.4. After being uniformly mixed, the above mixture was added to a polyester synthesis reactor and beaten for 15 minutes. Esterification was carried out at 230°C to 260°C and 265 kPa under nitrogen protection for 2.5 hours. After the esterification was completed, vacuum was turned on and polycondensation was carried out at 260°C to 278°C and 20 Pa for 2.5 hours. After spinning, cooling, pelletizing, and drying, a modified polyester with an intrinsic viscosity of 0.63 dl / g was obtained.

[0094] The modified polyester of the present invention and a functional masterbatch (for providing lubrication) containing inorganic silica particles with a particle size of 1.8 μm, a concentration of 1%, and an intrinsic viscosity of 0.62 dl / g, wherein the total content of the inorganic silica particles with a particle size of 1.8 μm in the polyester film is 2500 ppm (layer A), and the intrinsic viscosity is 0.65 dl / g. Pure large glossy polyester chips and a functional masterbatch (for providing lubrication) containing inorganic silica particles with a particle size of 1.8 μm, a concentration of 1%, and an intrinsic viscosity of 0.62 dl / g, wherein the inorganic silica particles with a particle size of 1.8 μm are in The overall content of the polyester film is 1000ppm (B layer), which is added to the corresponding melt extrusion system, extruded into the die at a temperature of 260°C, and cast onto a casting roll to form an A / B structure co-extruded cast sheet. The cast sheet is longitudinally stretched at a longitudinal stretching temperature of 50°C to 85°C and a longitudinal stretching ratio of 3.5; the longitudinally stretched sheet is transversely stretched at a transverse stretching temperature of 93°C to 125°C and a transverse stretching ratio of 4.1; the stretched film is shaped at a shaping temperature of 240°C; the film is then cooled, pulled, and rolled to obtain a polyester film with a thickness of 30μm, wherein the thickness of the A layer (H a ) and the thickness of the B layer (H b ) is related to H b / H a =7.

[0095] Example 4

[0096] Preparation of modified polyester

[0097] According to the molar ratio of dibasic acid to ethylene glycol of 1:1.4, the amount of ethylene glycol antimony added is 130ppm, and the amount of triphenyl phosphate added is 98ppm. Among them, the relationship between the molar number of terephthalic acid in the dibasic acid (M1) and the molar number of the mixture of α,β-bis(2-chlorophenoxy)ethane-4,4'-dicarboxylic acid, 5-tert-butyl-1,3-benzenedicarboxylic acid and 5-nitrophthalic acid (M2) is M1 / M2=3.5, M2=M 21 +M 22 +M 23 , the number of moles of α,β-bis(2-chlorophenoxy)ethane-4,4′-dicarboxylic acid (M 21 ) and the number of moles of 5-tert-butyl-1,3-benzenedicarboxylic acid (M 22 ) is M 21 / M 22 = number of moles of 3,5-tert-butyl-1,3-benzenedicarboxylic acid (M 22 ) and the number of moles of 5-nitrophthalic acid (M 23 ) is M 22 / M 23 =0.2, the number of moles of α,β-bis(2-chlorophenoxy)ethane-4,4′-dicarboxylic acid (M 21 ) and the number of moles of 5-nitrophthalic acid (M 23 ) is M 21 / M 23 =1.9. After being uniformly mixed, the above mixture was added to a polyester synthesis reactor and beaten for 15 minutes. Esterification was carried out at 230°C to 260°C and 265 kPa for 3 hours under nitrogen protection. After the esterification was completed, vacuum was applied and polycondensation was carried out at 260°C to 278°C and 50 Pa for 3 hours. After spinning, cooling, pelletizing, and drying, a modified polyester with an intrinsic viscosity of 0.65 dl / g was obtained.

[0098] The modified polyester of the present invention and the functional masterbatch (for providing lubrication) containing inorganic silica particles with a particle size of 2.8 μm, a concentration of 1%, and an intrinsic viscosity of 0.62 dl / g, wherein the total content of the inorganic silica particles with a particle size of 2.8 μm in the polyester film is 1800 ppm (layer A), and the intrinsic viscosity is 0.65 dl / g. Pure large glossy polyester chips and the functional masterbatch (for providing lubrication) containing inorganic silica particles with a particle size of 2.8 μm, a concentration of 1%, and an intrinsic viscosity of 0.62 dl / g, wherein the inorganic silica particles with a particle size of 2.8 μm are The overall content in the polyester film is 900ppm (B layer), which is added to the corresponding melt extrusion system, extruded into the die at a temperature of 270°C, and cast onto a casting roll to form an A / B structure co-extruded cast sheet. The cast sheet is longitudinally stretched at a longitudinal stretching temperature of 50°C to 85°C and a longitudinal stretching ratio of 3.5; the longitudinally stretched sheet is transversely stretched at a transverse stretching temperature of 93°C to 125°C and a transverse stretching ratio of 3.9; the stretched film is shaped at a shaping temperature of 225°C; the film is then cooled, pulled, and rolled to obtain a polyester film with a thickness of 30μm, wherein the thickness of the A layer (H a ) and the thickness of the B layer (H b ) is related to H b / H a =2.5.

[0099] Example 5

[0100] Preparation of modified polyester

[0101] According to the molar ratio of dibasic acid to ethylene glycol of 1:1.3, the amount of ethylene glycol antimony added is 150ppm, and the amount of triphenyl phosphate added is 80ppm. Among them, the relationship between the molar number of terephthalic acid in the dibasic acid (M1) and the molar number of the mixture of α,β-bis(2-chlorophenoxy)ethane-4,4'-dicarboxylic acid, 5-tert-butyl-1,3-benzenedicarboxylic acid and 5-nitrophthalic acid (M2) is M1 / M2=3.5, M2=M 21 +M 22 +M 23 , the number of moles of α,β-bis(2-chlorophenoxy)ethane-4,4′-dicarboxylic acid (M 21 ) and the number of moles of 5-tert-butyl-1,3-benzenedicarboxylic acid (M 22 ) is M 21 / M 22 = 2.2, the number of moles of 5-tert-butyl-1,3-benzenedicarboxylic acid (M 22 ) and the number of moles of 5-nitrophthalic acid (M 23 ) is M 22 / M 23=0.9, the number of moles of α,β-bis(2-chlorophenoxy)ethane-4,4′-dicarboxylic acid (M 21 ) and the number of moles of 5-nitrophthalic acid (M 23 ) is M 21 / M 23 =1.3. After uniform mixing, the above mixture was added to a polyester synthesis reactor and beaten for 15 minutes. Under nitrogen protection, esterification was carried out at 230°C to 260°C and 265 kPa for 3 hours. After the esterification was completed, vacuum was turned on and polycondensation was carried out at 260°C to 278°C and 70 Pa for 3.5 hours. After spinning, cooling, pelletizing, and drying, a modified polyester with an intrinsic viscosity of 0.67 dl / g was obtained.

[0102] The modified polyester of the present invention and a functional masterbatch (for providing lubricity) containing inorganic silica particles with a particle size of 4 μm, a concentration of 1%, and an intrinsic viscosity of 0.62 dl / g, wherein the total content of inorganic silica particles with a particle size of 4 μm in the polyester film is 1500 ppm (layer A), and a pure high-gloss polyester chip with an intrinsic viscosity of 0.65 dl / g (layer B) are added to a corresponding melt extrusion system, extruded into a die at a temperature of 280° C., and cast onto a casting roll to form an A / B / A structure co-extruded cast sheet, which is longitudinally stretched at a longitudinal stretching temperature of 50° C. to 85° C. and a longitudinal stretching ratio of 3.3; the longitudinally stretched sheet is transversely stretched at a transverse stretching temperature of 93° C. to 125° C. and a transverse stretching ratio of 4.4; the stretched film is shaped at a shaping temperature of 235° C.; the film is then cooled, pulled, and rolled to obtain a polyester film with a thickness of 30 μm, wherein the thickness of layer A (H a ) and the thickness of the B layer (H b ) is related to H b / H a =5.

[0103] Example 6

[0104] Preparation of modified polyester

[0105] According to the molar ratio of dibasic acid to ethylene glycol of 1:1.43, the addition amount of ethylene glycol antimony is 200ppm, and the addition amount of triphenyl phosphate is 100ppm. Among them, the relationship between the molar number of terephthalic acid in the dibasic acid (M1) and the molar number of the mixture of α,β-bis(2-chlorophenoxy)ethane-4,4'-dicarboxylic acid, 5-tert-butyl-1,3-benzenedicarboxylic acid and 5-nitrophthalic acid (M2) is M1 / M2=4, M2=M 21 +M 22 +M 23 , the number of moles of α,β-bis(2-chlorophenoxy)ethane-4,4′-dicarboxylic acid (M 21) and the number of moles of 5-tert-butyl-1,3-benzenedicarboxylic acid (M 22 ) is M 21 / M 22 = number of moles of 3,5-tert-butyl-1,3-benzenedicarboxylic acid (M 22 ) and the number of moles of 5-nitrophthalic acid (M 23 ) is M 22 / M 23 =1.3, the number of moles of α,β-bis(2-chlorophenoxy)ethane-4,4′-dicarboxylic acid (M 21 ) and the number of moles of 5-nitrophthalic acid (M 23 ) is M 21 / M 23 =1.9. After uniform mixing, the above mixture was added to a polyester synthesis reactor and beaten for 15 minutes. Under nitrogen protection, esterification was carried out at 230°C to 260°C and 265 kPa for 2.5 hours. After the esterification was completed, vacuum was turned on and polycondensation was carried out at 260°C to 278°C and 55 kPa for 3.5 hours. After spinning, cooling, pelletizing, and drying, a modified polyester with an intrinsic viscosity of 0.65 dl / g was obtained.

[0106] The modified polyester of the present invention and a functional masterbatch (for providing lubricity) containing inorganic silica particles with a particle size of 3 μm, a concentration of 1%, and an intrinsic viscosity of 0.62 dl / g, wherein the total content of inorganic silica particles with a particle size of 3 μm in the polyester film is 1300 ppm (layer A), and a pure high-gloss polyester chip with an intrinsic viscosity of 0.65 dl / g (layer B) are added to a corresponding melt extrusion system, extruded into a die at a temperature of 270° C., and cast onto a casting roll to form an A / B / A structure co-extruded cast sheet, which is longitudinally stretched at a longitudinal stretching temperature of 50° C. to 85° C. and a longitudinal stretching ratio of 3.4; the longitudinally stretched sheet is transversely stretched at a transverse stretching temperature of 93° C. to 125° C. and a transverse stretching ratio of 3.9; the stretched film is shaped at a shaping temperature of 230° C.; the film is then cooled, pulled, and rolled to obtain a polyester film with a thickness of 50 μm, wherein the thickness of layer A (H a ) and the thickness of the B layer (H b ) is related to H b / H a =8.

[0107] Example 7

[0108] Preparation of modified polyester

[0109] According to the molar ratio of dibasic acid to ethylene glycol of 1:1.3, the amount of ethylene glycol antimony added is 220ppm, and the amount of triphenyl phosphate added is 80ppm. Among them, the relationship between the molar number of terephthalic acid in the dibasic acid (M1) and the molar number of the mixture of α,β-bis(2-chlorophenoxy)ethane-4,4'-dicarboxylic acid, 5-tert-butyl-1,3-benzenedicarboxylic acid and 5-nitrophthalic acid (M2) is M1 / M2=4.3, M2=M 21 +M 22 +M 23 , the number of moles of α,β-bis(2-chlorophenoxy)ethane-4,4′-dicarboxylic acid (M 21 ) and the number of moles of 5-tert-butyl-1,3-benzenedicarboxylic acid (M 22 ) is M 21 / M 22 =3.2, the number of moles of 5-tert-butyl-1,3-benzenedicarboxylic acid (M 22 ) and the number of moles of 5-nitrophthalic acid (M 23 ) is M 22 / M 23 =1.7, the number of moles of α,β-bis(2-chlorophenoxy)ethane-4,4′-dicarboxylic acid (M 21 ) and the number of moles of 5-nitrophthalic acid (M 23 ) is M 21 / M 23 =1.5. After uniform mixing, the above mixture was added to a polyester synthesis reactor and beaten for 15 minutes. Under nitrogen protection, esterification was carried out at 230°C to 260°C and 265 kPa for 3 hours. After the esterification was completed, vacuum was turned on and polycondensation was carried out at 260°C to 278°C and 50 Pa for 2.5 hours. After spinning, cooling, pelletizing, and drying, a modified polyester with an intrinsic viscosity of 0.66 dl / g was obtained.

[0110] The modified polyester of the present invention and a functional masterbatch (for providing smoothness) containing inorganic silica particles with a particle size of 3.2 μm, a concentration of 1%, and an intrinsic viscosity of 0.62 dl / g, wherein the total content of the inorganic silica particles with a particle size of 3.2 μm in the polyester film is 1400 pm (layer A), and the modified polyester chips with an intrinsic viscosity of 0.66 dl / g (layer B) are added to a corresponding melt extrusion system, extruded into a die at a temperature of 275° C., and cast onto a casting roll to form an A / B / A structure co-extruded cast sheet, which is longitudinally stretched at a longitudinal stretching temperature of 50° C. to 85° C. and a longitudinal stretching ratio of 3.3; the longitudinally stretched sheet is transversely stretched at a transverse stretching temperature of 93° C. to 125° C. and a transverse stretching ratio of 4; the stretched film is shaped at a shaping temperature of 235° C.; the film is then cooled, pulled, and rolled to obtain a polyester film with a thickness of 50 μm, wherein the thickness of layer A (Ha ) and the thickness (H b ) of the B layer is H b / H a = 9.

[0111] Example 8

[0112] Preparation of the modified polyester

[0113] According to the binary acid and ethylene glycol molar ratio 1:1.5, the addition amount of ethylene glycol antimony is 300 ppm, the addition amount of triphenyl phosphate is 150 ppm, wherein the relationship between the number of moles (M1) of terephthalic acid and the number of moles (M2) of the mixture of α, β-bis (2-chlorophenoxy) ethane-4, 4'-dicarboxylic acid, 5-tert-butyl-1, 3-benzenedicarboxylic acid and 5-nitro phthalic acid in the binary acid is M1 / M2=5, M2=M 21 +M 22 +M 23 , the relationship between the number of moles (M 21 ) of α, β-bis (2-chlorophenoxy) ethane-4, 4'-dicarboxylic acid and the number of moles (M 22 ) of 5-tert-butyl-1, 3-benzenedicarboxylic acid is M 21 / M 22 = 3.5, the relationship between the number of moles (M 22 ) of 5-tert-butyl-1, 3-benzenedicarboxylic acid and the number of moles (M 23 ) of 5-nitro phthalic acid is M 22 / M 23 = 1.8, the relationship between the number of moles (M 21 ) of α, β-bis (2-chlorophenoxy) ethane-4, 4'-dicarboxylic acid and the number of moles (M 23 ) of 5-nitro phthalic acid is M 21 / M 23 = 2.5. After mixing uniformly, it is added to the polyester synthesis reactor, and the pulp is beaten for 15 minutes, and nitrogen protection is carried out, and esterification is carried out at 230-260℃, 265KPa for 4h; after esterification, vacuum is opened, and polycondensation reaction is carried out at 260-278℃, 65Pa for 4h, and the modified polyester with an intrinsic viscosity of 0.72dl / g is prepared by spinning, cooling, pelletizing and drying.

[0114] The modified polyester of the present invention and a functional masterbatch (for providing lubricity) containing inorganic silica particles with a particle size of 2.5 μm, a concentration of 1%, and an intrinsic viscosity of 0.62 dl / g, wherein the total content of the inorganic silica particles with a particle size of 2.5 μm in the polyester film is 1000 ppm (layer A), and a pure high-gloss polyester chip with an intrinsic viscosity of 0.65 dl / g (layer B) are added to a corresponding melt extrusion system, extruded into a die at a temperature of 285° C., and cast onto a casting roll to form an A / B / A structure co-extruded cast sheet, which is longitudinally stretched at a longitudinal stretching temperature of 50° C. to 85° C. and a longitudinal stretching ratio of 3.3; the longitudinally stretched sheet is transversely stretched at a transverse stretching temperature of 93° C. to 125° C. and a transverse stretching ratio of 4.1; the stretched film is shaped at a shaping temperature of 235° C.; the film is then cooled, pulled, and rolled to obtain a polyester film with a thickness of 75 μm, wherein the thickness of layer A (H a ) and the thickness of the B layer (H b ) is related to H b / H a =10.5.

[0115] Example 9

[0116] Preparation of modified polyester

[0117] According to the molar ratio of dibasic acid to ethylene glycol of 1:1.25, the amount of ethylene glycol antimony added is 250ppm, and the amount of triphenyl phosphate added is 100ppm. Among them, the relationship between the molar number of terephthalic acid in the dibasic acid (M1) and the molar number of the mixture of α,β-bis(2-chlorophenoxy)ethane-4,4'-dicarboxylic acid, 5-tert-butyl-1,3-benzenedicarboxylic acid and 5-nitrophthalic acid (M2) is M1 / M2=6.5, M2=M 21 +M 22 +M 23 , the number of moles of α,β-bis(2-chlorophenoxy)ethane-4,4′-dicarboxylic acid (M 21 ) and the number of moles of 5-tert-butyl-1,3-benzenedicarboxylic acid (M 22 ) is M 21 / M 22 =0.8, the number of moles of 5-tert-butyl-1,3-benzenedicarboxylic acid (M 22 ) and the number of moles of 5-nitrophthalic acid (M 23 ) is M 22 / M 23 = 2.2, the number of moles of α,β-bis(2-chlorophenoxy)ethane-4,4′-dicarboxylic acid (M 21 ) and the number of moles of 5-nitrophthalic acid (M 23 ) is M 21 / M 23=3. After the above mixture is uniformly mixed, it is added to a polyester synthesis reactor and beaten for 15 minutes. Under nitrogen protection, esterification is carried out at 230°C to 260°C and 265 kPa for 3 hours. After the esterification is completed, vacuum is turned on and polycondensation is carried out at 260°C to 278°C and 68 Pa for 4 hours. After spinning, cooling, pelletizing, and drying, a modified polyester with an intrinsic viscosity of 0.69 dl / g is obtained.

[0118] The modified polyester of the present invention and a functional masterbatch (for providing lubricity) containing inorganic silica particles with a particle size of 3.5 μm, a concentration of 1%, and an intrinsic viscosity of 0.62 dl / g, wherein the total content of the inorganic silica particles with a particle size of 3.5 μm in the polyester film is 300 ppm (layer A), and a pure high-gloss polyester chip with an intrinsic viscosity of 0.65 dl / g (layer B) are added to a corresponding melt extrusion system, extruded into a die at a temperature of 285° C., and cast onto a casting roll to form an A / B / A structure co-extruded cast sheet, which is longitudinally stretched at a longitudinal stretching temperature of 50° C. to 85° C. and a longitudinal stretching ratio of 3.1; the longitudinally stretched sheet is transversely stretched at a transverse stretching temperature of 93° C. to 125° C. and a transverse stretching ratio of 3.5; the stretched film is shaped at a shaping temperature of 230° C.; the film is then cooled, pulled, and rolled to obtain a polyester film with a thickness of 100 μm, wherein the thickness of layer A (H a ) and the thickness of the B layer (H b ) is related to H b / H a =12.

[0119] Example 10

[0120] Preparation of modified polyester

[0121] According to the molar ratio of dibasic acid to ethylene glycol of 1:1.35, the amount of ethylene glycol antimony added is 150ppm, and the amount of triphenyl phosphate added is 125ppm. Among them, the relationship between the molar number of terephthalic acid in the dibasic acid (M1) and the molar number of the mixture of α,β-bis(2-chlorophenoxy)ethane-4,4'-dicarboxylic acid, 5-tert-butyl-1,3-benzenedicarboxylic acid and 5-nitrophthalic acid (M2) is M1 / M2=7.5, M2=M 21 +M 22 +M 23 , the number of moles of α,β-bis(2-chlorophenoxy)ethane-4,4′-dicarboxylic acid (M 21 ) and the number of moles of 5-tert-butyl-1,3-benzenedicarboxylic acid (M 22 ) is M 21 / M 22 =3.9, the number of moles of 5-tert-butyl-1,3-benzenedicarboxylic acid (M 22) and the number of moles of 5-nitrophthalic acid (M 23 ) is M 22 / M 23 = 2.5, the number of moles of α,β-bis(2-chlorophenoxy)ethane-4,4′-dicarboxylic acid (M 21 ) and the number of moles of 5-nitrophthalic acid (M 23 ) is M 21 / M 23 =3.4. After uniform mixing, the above mixture was added to a polyester synthesis reactor and beaten for 15 minutes under nitrogen protection. Esterification was carried out at 230°C to 260°C and 265 kPa for 3 hours. After the esterification was completed, vacuum was turned on and polycondensation was carried out at 260°C to 278°C and 25 Pa for 2.5 hours. After spinning, cooling, pelletizing, and drying, a modified polyester with an intrinsic viscosity of 0.62 dl / g was obtained.

[0122] The modified polyester of the present invention and a functional masterbatch (for providing lubricity) containing inorganic silica particles with a particle size of 2 μm, a concentration of 1%, and an intrinsic viscosity of 0.62 dl / g, wherein the total content of inorganic silica particles with a particle size of 2 μm in the polyester film is 800 ppm (layer A), and a pure high-gloss polyester chip with an intrinsic viscosity of 0.65 dl / g (layer B) are added to a corresponding melt extrusion system, extruded into a die at a temperature of 275° C., and cast onto a casting roll to form an A / B / A structure co-extruded cast sheet, which is longitudinally stretched at a longitudinal stretching temperature of 50° C. to 85° C. and a longitudinal stretching ratio of 3; the longitudinally stretched sheet is transversely stretched at a transverse stretching temperature of 93° C. to 125° C. and a transverse stretching ratio of 3.8; the stretched film is shaped at a shaping temperature of 235° C.; the film is then cooled, pulled, and rolled to obtain a polyester film with a thickness of 125 μm, wherein the thickness of layer A (H a ) and the thickness of the B layer (H b ) is H b / H a =16.5.

[0123] Example 11

[0124] Preparation of modified polyester

[0125] According to the molar ratio of dibasic acid to ethylene glycol of 1:1.28, the amount of ethylene glycol antimony added is 130ppm, and the amount of triphenyl phosphate added is 40ppm. Among them, the relationship between the molar number of terephthalic acid in the dibasic acid (M1) and the molar number of the mixture of α,β-bis(2-chlorophenoxy)ethane-4,4'-dicarboxylic acid, 5-tert-butyl-1,3-benzenedicarboxylic acid and 5-nitrophthalic acid (M2) is M1 / M2=8, M2=M 21 +M 22 +M23 , the number of moles of α,β-bis(2-chlorophenoxy)ethane-4,4′-dicarboxylic acid (M 21 ) and the number of moles of 5-tert-butyl-1,3-benzenedicarboxylic acid (M 22 ) is M 21 / M 22 =4.3, the number of moles of 5-tert-butyl-1,3-benzenedicarboxylic acid (M 22 ) and the number of moles of 5-nitrophthalic acid (M 23 ) is M 22 / M 23 = 2.8, the number of moles of α,β-bis(2-chlorophenoxy)ethane-4,4′-dicarboxylic acid (M 21 ) and the number of moles of 5-nitrophthalic acid (M 23 ) is M 21 / M 23 =4.3. After being uniformly mixed, the above mixture was added to a polyester synthesis reactor and beaten for 15 minutes under nitrogen protection. Esterification was carried out at 230°C to 260°C and 265 kPa for 3.2 hours. After the esterification was completed, vacuum was turned on and polycondensation was carried out at 260°C to 278°C and 50 Pa for 2 hours. After spinning, cooling, pelletizing, and drying, a modified polyester with an intrinsic viscosity of 0.60 dl / g was obtained.

[0126] The modified polyester of the present invention and a functional masterbatch (for providing lubricity) containing inorganic silica particles with a particle size of 1.8 μm, a concentration of 1%, and an intrinsic viscosity of 0.62 dl / g, wherein the total content of the inorganic silica particles with a particle size of 1.8 μm in the polyester film is 990 ppm (layer A), and a pure high-gloss polyester chip with an intrinsic viscosity of 0.65 dl / g (layer B) are added to a corresponding melt extrusion system, extruded into a die at a temperature of 270° C., and cast onto a casting roll to form an A / B / A structure co-extruded cast sheet, which is longitudinally stretched at a longitudinal stretching temperature of 50° C. to 85° C. and a longitudinal stretching ratio of 2.8; the longitudinally stretched sheet is transversely stretched at a transverse stretching temperature of 93° C. to 125° C. and a transverse stretching ratio of 3.8; the stretched film is shaped at a shaping temperature of 230° C.; the film is then cooled, pulled, and wound to obtain a polyester film with a thickness of 188 μm, wherein the thickness of layer A (H a ) and the thickness of the B layer (H b ) is H b / H a =18.

[0127] Example 12

[0128] Preparation of modified polyester

[0129] According to the molar ratio of dibasic acid to ethylene glycol of 1:1.28, the amount of ethylene glycol antimony added is 200ppm, and the amount of triphenyl phosphate added is 65ppm. Among them, the relationship between the molar number of terephthalic acid in the dibasic acid (M1) and the molar number of the mixture of α,β-bis(2-chlorophenoxy)ethane-4,4'-dicarboxylic acid, 5-tert-butyl-1,3-benzenedicarboxylic acid and 5-nitrophthalic acid (M2) is M1 / M2=9, M2=M 21 +M 22 +M 23 , the number of moles of α,β-bis(2-chlorophenoxy)ethane-4,4′-dicarboxylic acid (M 21 ) and the number of moles of 5-tert-butyl-1,3-benzenedicarboxylic acid (M 22 ) is M 21 / M 22 = the number of moles of 5,5-tert-butyl-1,3-benzenedicarboxylic acid (M 22 ) and the number of moles of 5-nitrophthalic acid (M 23 ) is M 22 / M 23 =3, α,β-bis(2-chlorophenoxy)ethane-4,4′-dicarboxylic acid moles (M 21 ) and the number of moles of 5-nitrophthalic acid (M 23 ) is M 21 / M 23 = 5. After uniform mixing, the above mixture was added to a polyester synthesis reactor and beaten for 15 minutes. Nitrogen was introduced for protection and esterification was carried out at 230°C to 260°C and 265 kPa for 3 hours. After the esterification was completed, vacuum was turned on and polycondensation was carried out at 260°C to 278°C and 60 Pa for 3.5 hours. After spinning, cooling, pelletizing, and drying, a modified polyester with an intrinsic viscosity of 0.68 dl / g was obtained.

[0130] The modified polyester of the present invention and a functional masterbatch (for providing smoothness) containing inorganic silica particles with a particle size of 2 μm, a concentration of 1%, and an intrinsic viscosity of 0.62 dl / g, wherein the total content of the inorganic silica particles with a particle size of 2 μm in the polyester film is 800 pm (layer A), and the modified polyester chips with an intrinsic viscosity of 0.68 dl / g (layer B) are added to a corresponding melt extrusion system, extruded into a die at a temperature of 265° C., and cast onto a casting roll to form an A / B / A structure co-extruded cast sheet, which is longitudinally stretched at a longitudinal stretching temperature of 50° C. to 85° C. and a longitudinal stretching ratio of 2.5; the longitudinally stretched sheet is transversely stretched at a transverse stretching temperature of 93° C. to 125° C. and a transverse stretching ratio of 3.5; the stretched film is shaped at a shaping temperature of 235° C.; the film is then cooled, pulled, and rolled to obtain a polyester film with a thickness of 250 μm, wherein the thickness of layer A (H a) and the thickness of the B layer (H b ) is H b / H a =22.

[0131] Comparative Example 1

[0132] Add pure high-gloss polyester with an intrinsic viscosity of 0.67 dl / g and a functional masterbatch (for lubrication) containing inorganic silica particles with a particle size of 4 μm and a concentration of 1% and an intrinsic viscosity of 0.62 dl / g, wherein the total content of inorganic silica particles with a particle size of 4 μm in the polyester film is 1500 ppm (layer A) and pure high-gloss polyester chips with an intrinsic viscosity of 0.65 dl / g (layer B) are added to the corresponding melt extrusion system and heated at 280°C. The film is extruded into a die head at a temperature of 50°C to 85°C and cast onto a casting roll to form an A / B / A structure co-extruded casting sheet. The casting sheet is longitudinally stretched at a temperature of 50°C to 85°C and a longitudinal stretch ratio of 3.3. The longitudinally stretched sheet is transversely stretched at a temperature of 93°C to 125°C and a transverse stretch ratio of 4.4. The stretched film is shaped at a temperature of 235°C. The film is then cooled, pulled, and wound to obtain a polyester film with a thickness of 30 μm. The thickness of the A layer (H a ) and the thickness of the B layer (H b ) is H b / H a =5.

[0133] Comparative Example 2

[0134] Add pure high-gloss polyester with an intrinsic viscosity of 0.65 dl / g and a functional masterbatch (for lubrication) containing inorganic silica particles with a particle size of 3 μm and a concentration of 1% and an intrinsic viscosity of 0.62 dl / g, wherein the total content of inorganic silica particles with a particle size of 3 μm in the polyester film is 1300 ppm (layer A) and pure high-gloss polyester chips with an intrinsic viscosity of 0.65 dl / g (layer B) are added to the corresponding melt extrusion system and heated at 270°C. The film is extruded into a die head at a temperature of 50°C to 85°C and cast onto a casting roll to form an A / B / A structure co-extruded casting sheet. The casting sheet is longitudinally stretched at a temperature of 50°C to 85°C and a longitudinal stretch ratio of 3.4. The longitudinally stretched sheet is transversely stretched at a temperature of 93°C to 125°C and a transverse stretch ratio of 3.9. The stretched film is shaped at a temperature of 230°C. The film is then cooled, pulled, and wound to obtain a polyester film with a thickness of 50 μm. The thickness of the A layer (H a ) and the thickness of the B layer (H b ) is H b / H a =8.

[0135] Comparative Example 3

[0136] Add pure high-gloss polyester with an intrinsic viscosity of 0.68 dl / g and a functional masterbatch (for lubrication) containing inorganic silica particles with a particle size of 2 μm and a concentration of 1% and an intrinsic viscosity of 0.62 dl / g, wherein the total content of inorganic silica particles with a particle size of 2 μm in the polyester film is 800 pm (layer A) and pure high-gloss polyester chips with an intrinsic viscosity of 0.68 dl / g (layer B) are added to the corresponding melt extrusion system and heated at a temperature of 265°C. The film is then extruded into a die and cast onto a casting roll to form an A / B / A structure co-extruded cast sheet. The cast sheet is longitudinally stretched at a temperature of 50°C to 85°C and a longitudinal stretch ratio of 2.5. The longitudinally stretched sheet is transversely stretched at a temperature of 93°C to 125°C and a transverse stretch ratio of 3.5. The stretched film is shaped at a temperature of 235°C. The film is then cooled, pulled, and wound to obtain a polyester film with a thickness of 250 μm. The thickness of the A layer (H a ) and the thickness of the B layer (H b ) is H b / H a =22.

[0137] Specific implementation effects

[0138] The test results are shown in Table 1:

[0139] Table 1 Performance data

[0140]

[0141] Thickness test method: GB / T 33399-2016.

[0142] Thermal shrinkage test method: ASTM D1204 (150°C, 30 min).

[0143] Dynamic thermal performance: take the small shaft sample, width 1300, length 500 m, and run through the machine to evaluate the dynamic thermal performance. Machine running conditions: set the winding tension to 150 N / m, oven temperature to 80℃ / 100℃ / 125℃ / 140℃ / 130℃ / 115℃ / 100℃ / 80℃, each oven length to 4 m, and the running speed to 50 m / min. At 3 m from the oven outlet, set 2 horizontal guide rollers with a vertical distance of 1.5 m. During the machine running, the inspector's line of sight forms a 45° angle with the film surface, and a strong light flashlight (model: RJW7102A / LT, Haoyang Lighting Technology Co., Ltd.) is used to carefully observe the left and right sides. At the same time, take a 1 m long sample after the machine running, place it on a horizontal marble platform, and the inspector's line of sight forms a 0° angle with the film surface. A strong light flashlight (model: RJW7102A / LT, Haoyang Lighting Technology Co., Ltd.) is used to carefully observe the left and right sides. If there is no longitudinal striation or other unevenness on the film surface during the machine running, and the sample on the marble platform completely adheres to the marble surface without unevenness, it indicates that the dynamic thermal performance is excellent, and is marked as "◎". If there is one longitudinal striation or one place of unevenness on the marble platform, but it is not certain, it indicates that the dynamic thermal performance is good, and is marked as "○". If there are n (number) of longitudinal striations or n (number) of places of unevenness on the marble platform, it indicates that the dynamic thermal performance is poor, and is marked as "×".

[0144] It can be seen from the comparison of Example 5 and Comparative Example 1 that under the same conditions of polyester film thickness, film making process, etc., and the same thermal shrinkage rate, the dynamic thermal performance of the polyester film of the application is obviously better than that of the ordinary polyester film. It can be seen from the comparison of Example 6 and Comparative Example 2, and Example 12 and Comparative Example 3 that under the same conditions of polyester film thickness, film making process, etc., although the thermal shrinkage rate in the comparative examples is smaller than that in the examples, the dynamic thermal performance of the polyester film of the application is still obviously better than that of the ordinary polyester film.

[0145] Although the embodiments of the application 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 therein without departing from the principles and spirit of the application, and the scope of the application is defined by the appended claims and their equivalents.

Claims

1. A polyester film, characterized in that Contains modified polyester; the modified polyester is prepared by esterification and polycondensation of dibasic acid and diol at a molar ratio of 1: (1.2-1.5); Dibasic acids include the following: Terephthalic acid, mole number M1, α,β-Bis(2-chlorophenoxy)ethane-4,4′-dicarboxylic acid, molar number M 21 , 5-tert-Butyl-1,3-benzenedicarboxylic acid, molar number M 22 , 5-nitrophthalic acid, molar number M 23 , Mole number M2, M2= M 21 +M 22 +M 23 , Among them, 1.5≤M1 / M2≤9, 0.6≤M 21 / M 22 ≤5,0.2≤M 22 / M 23 ≤3,0.4≤M 21 / M 23 ≤5。 2. A polyester film according to claim 1, characterized in that: The polyester film has a thickness of 23 μm to 250 μm.

3. A polyester film according to claim 1, characterized in that: The structure of the polyester film is a single-layer structure A, a double-layer structure A / B, or a three-layer structure A / B / A, and the A layer and / or the B layer contain the modified polyester.

4. A polyester film according to claim 1, characterized in that: The polyester film adopts a double-layer structure A / B, the thickness of the A layer (H a ) and the thickness of the B layer (H b ) is 2.5≤H b / H a ≤12.

5. The polyester film according to claim 1, characterized in that: The polyester film adopts a three-layer structure A / B / A, and the thickness of the A layer (H a ) and the thickness of the B layer (H b ) is 5≤H b / H a ≤22.

6. A polyester film according to any one of claim 1, characterized in that: The preparation of the modified polyester comprises the following steps: Add the required dibasic acid, diol, catalyst and stabilizer into the polyester reactor in sequence, beat for 15 minutes, and introduce nitrogen protection, and esterify at 230℃~260℃ and 265KPa for 2.5h~4h; The esterification end point is determined according to the water output. After the esterification is complete, vacuum is applied and the polycondensation reaction is carried out at 260° C. to 278° C. and 20 Pa to 70 Pa for 2 h to 4 h. The modified polyester is obtained by spinning, cooling, pelletizing and drying. The amount of the catalyst used is 80ppm to 300ppm, and the amount of the stabilizer used is 20ppm to 150ppm.

7. A polyester film according to claim 6, characterized in that: The intrinsic viscosity of the modified polyester is 0.60 dl / g to 0.72 dl / g.

8. A method for preparing the polyester film according to claim 1, characterized in that: The steps include: A number of modified polyester chips, functional masterbatch and pure polyester chips are mixed in advance, sent to the corresponding melt extrusion system for extrusion, and then enter the die head for co-extrusion; Then, the polyester film is produced through casting, longitudinal stretching, transverse stretching, shaping, cooling, pulling and winding.

9. The method for preparing the polyester film according to claim 8, wherein: The longitudinal stretching ratio in the longitudinal stretching process is 2.5 to 3.

5.

10. The method for preparing the polyester film according to claim 8, wherein: The transverse stretching ratio in the transverse stretching process is 3.5 to 5.

0.

11. The method for preparing the polyester film according to claim 8, wherein: The heat setting temperature of the setting process is 225°C to 240°C.

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