High-temperature-resistant antistatic multilayer copolyester film as well as preparation method and application thereof

Abstract

The invention relates to the technical field of multi-layer copolyester films, and discloses a high-temperature-resistant antistatic multi-layer copolyester film and a preparation method and application thereof, and the multi-layer copolyester film comprises an ABA three-layer structure obtained through melt co-extrusion; the layer A is prepared from the following raw materials in percentage by mass: 5 to 30 percent of anti-blocking agent master batch and the balance of modified copolyester; the raw material of the layer B is modified copolyester; the modified copolyester is prepared from a binary acid mixture, a dihydric alcohol mixture and a catalyst through an esterification reaction and a condensation polymerization reaction; the binary acid mixture comprises furandicarboxylic acid and 2, 2 '-bifuran-5, 5'-dicarboxylic acid, and the dihydric alcohol mixture comprises ethylene glycol, 2, 2, 4, 4-tetramethyl-1, 3-cyclobutanediol and 1, 4-cyclohexanedimethanol. According to the invention, the modified copolyester is used as a main raw material, and the film is endowed with good temperature resistance in a copolymerization modification manner, and has stable and lasting antistatic performance.

Description

Technical Field

[0001] The present invention relates to the technical field of multilayer copolyester films, in particular to a high-temperature-resistant and antistatic multilayer copolyester film and a preparation method and application thereof. Background Art

[0002] Polyester film is made from polyethylene terephthalate (PET) through melt extrusion and biaxial stretching. Due to its excellent mechanical, thermal, and optical properties, it has been widely used in electrical, insulation, packaging, transfer printing, display, and window film applications. 2,5-Furandicarboxylic acid (FDCA) has a similar structure to terephthalic acid (PTA). FDCA is the only bio-based platform compound with a planar, rigid aromatic ring structure. It is primarily used to replace the benzene ring series of compounds in the eight petroleum-based platform compounds (triphenyltriene, acetylene, and naphthalene). FDCA and its derivatives can be obtained from biomass feedstocks through biofermentation and can be used as renewable raw materials to replace petroleum-based PTA in the preparation of aromatic polyester materials, offering advantages in barrier properties and other aspects.

[0003] However, polyester film is an insulating material with a surface resistance of 10 14 Ω, which easily accumulates static charge during production or use due to friction between itself or other materials. This static charge causes polyester film to easily absorb dust, affecting product properties such as light transmittance and haze. It can also lead to a series of problems such as reduced adhesion and poor bonding of subsequent functional layers. Therefore, imparting antistatic properties to polyester film is extremely important. To address this issue, existing antistatic technologies primarily involve adding antistatic agents or surface coatings to polyester films. For example, patent application number CN101318393A discloses an antistatic thick polyester film with an ABA three-layer structure, where the polyester substrate is modified for conductivity. By weight, the core film comprises 97-99.5% polyester chips and 0.5-3% antistatic agent, while the surface film layer comprises 90-96% polyester chips and 4-10% antistatic agent. However, significant limitations remain, such as affecting the transparency and mechanical properties of the polyester film. The antistatic agent must migrate to the surface of the polyester film to achieve antistatic properties, resulting in unstable surface resistance and easy failure due to environmental influences.

[0004] Furthermore, during reprocessing processes such as coating, ordinary polyester film has poor heat resistance and can deform when heated, resulting in uneven longitudinal lines at the oven exit, affecting product quality. Current existing solutions to this problem primarily involve adding nano- or micro-sized inorganic or organic particles to the core layer of polyester film to act as nucleating agents, increasing the film's crystallinity. However, nucleating agents can aggregate to form crystal points, affecting the film's optical properties and appearance. Summary of the Invention

[0005] In order to solve the above technical problems, the present invention provides a high-temperature-resistant and antistatic multilayer copolyester film and its preparation method and application. The modified copolyester is used as the main raw material, and the film is given good heat resistance through copolymerization modification. The film also has stable and long-lasting antistatic properties, fundamentally solving the problems of migration failure caused by the addition of antistatic agents and incompatibility, optical properties, and reduced temperature resistance caused by nucleating agents.

[0006] The purpose of the present invention is achieved through the following technical solutions: In a first aspect, the present invention provides a high-temperature-resistant and antistatic multilayer copolyester film, which includes an ABA three-layer structure obtained by melt coextrusion; in terms of mass percentage, the raw materials of layer A are 5-30% of an antiblocking agent masterbatch and the balance of a modified copolyester; the raw materials of layer B are modified copolyester; the modified copolyester is prepared by esterification and polycondensation of a dibasic acid mixture, a diol mixture and a catalyst; in terms of molar percentage, the dibasic acid mixture includes 50-70% of furandicarboxylic acid and 30-50% of 2,2'-bifuran-5,5'-dicarboxylic acid, and the diol mixture includes 20-30% of ethylene glycol, 30-40% of 2,2,4,4-tetramethyl-1,3-cyclobutanediol and 30-40% of 1,4-cyclohexanedimethanol.

[0007] The film of this invention uses a modified copolyester as its primary raw material, which imparts heat resistance and antistatic properties through copolymerization. Specifically, the dibasic acids in the modified copolyester include furandicarboxylic acid (FDCA) and 2,2'-bifuran-5,5'-dicarboxylic acid (BFDCA). The ether oxygen bond on the furan ring carries a lone pair of electrons and has the ability to accept protons. This internal proton transfer allows for static dissipation, effectively reducing the surface resistance of the copolyester film. FDCA is compounded with the functionalized furan derivative BFDCA, surpassing the performance limitations of FDCA alone. The bifuran structure of BFDCA strengthens the conjugated system, further reducing surface resistance. However, if the proportion of BFDCA is too high, the molecular weight distribution of the copolyester becomes broad, affecting the film's heat resistance.

[0008] The diols in the modified copolyester include ethylene glycol, 2,2,4,4-tetramethyl-1,3-cyclobutanediol (CBDO), and 1,4-cyclohexanedimethanol (CHDM). The four-membered ring in CBDO exhibits significant rigidity, which improves the heat resistance of the polyester film. When used in the synthesis of copolyester, CHDM accelerates molecular chain growth, narrows the molecular weight distribution, and improves the heat resistance of the polyester film. Furthermore, the non-planar structure of the six-membered ring in CHDM further enhances the toughness of the polyester film. Furthermore, the introduction of ethylene glycol as a flexible structural unit improves the film's processing stability during biaxial stretching. Maintaining the molar ratio of FDCA, BFDCA, CBDO, and CHDM within a reasonable range synergistically improves the antistatic properties and heat resistance of the polyester film, resulting in the production of a high-temperature-resistant, antistatic copolyester film with excellent overall performance.

[0009] Preferably, the molar ratio of the diol mixture to the dibasic acid mixture is 1.05-1.2:1.

[0010] Preferably, the molar ratio of the catalyst to the dibasic acid mixture is 1-10:1000.

[0011] Preferably, the catalyst includes one or more of tetrabutyl titanate, isopropyl titanate, titanium acetate, titanium tetrachloride, stannous octoate, stannous oxalate, stannous chloride, stannous oxide, antimony glycolate, antimony trioxide and antimony acetate.

[0012] Preferably, the temperature of the esterification reaction is 210-230° C., the pressure is 0.30-0.40 MPa, and the reaction enters the polycondensation reaction stage when the water output reaches 98% or above.

[0013] Preferably, the temperature of the polycondensation reaction is 250-260° C., the vacuum degree is 20-60 Pa, and the reaction time is 3-4 h.

[0014] Preferably, the intrinsic viscosity of the modified copolyester is 0.6-0.7 dL / g.

[0015] Preferably, the raw materials of the opener masterbatch include PET and opener particles, and the intrinsic viscosity is 0.6-0.7 dl / g.

[0016] Preferably, the content of the opening agent particles is 3000-10000 ppm of the mass of the opening agent masterbatch, and the particle size is 1-4 μm; the opening agent particles are inorganic particles, more preferably silicon dioxide particles.

[0017] During and after the roll is rolled, a vacuum forms between the layers of plastic film without an anti-blocking agent, making it difficult to open. Adhesion can easily occur when heated or pressurized, affecting subsequent use and processing. Anti-blocking agents create micro-protrusions on the film surface, reducing adhesion between films and between the film and the equipment, making it easier to separate the stuck plastic films. Therefore, anti-blocking agent masterbatch is only added to the surface layer.

[0018] If too little anti-blocking agent masterbatch is added, the anti-blocking effect will be insignificant. If too much is added, the optical properties will be affected due to the inorganic particles of the anti-blocking agent. The thicker the A layer, the more anti-blocking agent is needed to achieve a good anti-blocking effect. The total number of inorganic particles in the system increases, but too much will lead to a significant increase in the haze of the film and a decrease in light transmittance. Therefore, the amount of anti-blocking agent masterbatch added to the A layer needs to match the thickness of the A layer to obtain better overall performance and expand its application range.

[0019] Preferably, the thickness of the multi-layer copolyester film is 25-150 μm; the thickness ratio of the ABA three-layer structure is 10-15%:70-80%:10-15%.

[0020] In the second aspect, the present invention provides a method for preparing a high-temperature-resistant and antistatic multilayer copolyester film, comprising the following steps: adding the raw materials of layer A and layer B into an extruder, melting the three layers, co-extruding, and casting to form a cast sheet; longitudinally stretching, transversely stretching, shaping, and cooling the cast sheet in sequence to obtain a multilayer copolyester film.

[0021] Preferably, the co-extrusion temperature is 265-285°C.

[0022] Preferably, the casting is carried out on a casting roller, and the temperature of the casting roller is 15-30°C.

[0023] Preferably, the temperature of the longitudinal stretching is 75-110° C., and the stretching ratio is 2.8-4.0 times; the temperature of the transverse stretching is 95-145° C., and the stretching ratio is 3.0-4.5 times.

[0024] Preferably, the setting temperature is 220-240°C.

[0025] Preferably, the cooling temperature is 45-100°C.

[0026] In a third aspect, the present invention provides an application of a high-temperature-resistant and antistatic multilayer copolyester film in a release film.

[0027] The copolyester film product with excellent temperature resistance and antistatic properties prepared by the present invention can be widely used in high-end protection / release films (such as MLCC release films), window films and other fields.

[0028] Compared with the prior art, the present invention has the following beneficial effects: (1) The prior art treats antistatic and temperature resistance as independent issues. The present invention replaces physical blending by copolymer molecular design, fundamentally solving the problems of migration failure caused by the addition of antistatic agents and incompatibility, optical performance, and temperature resistance degradation caused by nucleating agents; (2) The antistatic properties of the film are regulated by copolymerization modification, which avoids the problem of the antistatic coating falling off in some specific environments and failing to play the antistatic role, so that the film has stable and long-lasting antistatic properties; (3) Using bio-based furandicarboxylic acid and its derivatives as copolymer monomers can reduce the consumption of petroleum resources, avoid impurity contamination during material recycling, and improve the recycling rate, which is in line with the trend of green manufacturing. DETAILED DESCRIPTION

[0029] The technical solutions of the present invention are described below with specific embodiments, but the protection scope of the present invention is not limited thereto.

[0030] 1. Modified copolyester The dibasic acid mixture comprises furandicarboxylic acid (FDCA) and 2,2'-bifuran-5,5'-dicarboxylic acid (BFDCA) in molar percentages of 50-70%: 30-50%, and the diol mixture comprises ethylene glycol (EG), 2,2,4,4-tetramethyl-1,3-cyclobutanediol (CBDO), and 1,4-cyclohexanedimethanol (CHDM) in molar percentages of 20-30%: 30-40%: 30-40%. The catalyst comprises one or more of tetrabutyl titanate, isopropyl titanate, titanium acetate, titanium tetrachloride, stannous octoate, stannous oxalate, stannous chloride, stannous oxide, antimony glycolate, antimony trioxide, and antimony acetate.

[0031] The dibasic acid mixture and the diol mixture are subjected to an esterification reaction in the presence of a catalyst at 210-230°C and 0.30-0.40 MPa. The molar ratio of the diol mixture to the dibasic acid mixture is 1.05-1.2:1, and the molar ratio of the catalyst to the dibasic acid mixture is 1-10:1000. The reaction proceeds until the water yield reaches 98% or above, at which point the polycondensation reaction begins. The polycondensation reaction temperature is 250-260°C, the vacuum degree is 20-60 Pa, and the reaction time is 3-4 hours. After completion of the reaction, a modified copolyester is produced with an intrinsic viscosity of 0.6-0.7 dL / g.

[0032] 2. Multilayer copolyester film The raw materials for layer A are 5-30% by mass of an anti-blocking agent masterbatch and the remainder of a modified copolyester. The anti-blocking agent masterbatch is made by mixing and melting PET and anti-blocking agent particles (particle size 1-4 μm) and then pelletizing them. The content of the anti-blocking agent particles is 3,000-10,000 ppm by mass of the anti-blocking agent masterbatch, and the intrinsic viscosity of the anti-blocking agent masterbatch is 0.6-0.7 dl / g. The raw material for layer B is a modified copolyester.

[0033] The raw materials of layer A and layer B are added into an extruder, melted and co-extruded in three layers at an extrusion temperature of 265-285° C., and cast onto a casting roll at a temperature of 15-30° C. after extrusion from a die head to form a cast sheet; the cast sheet is longitudinally stretched at a temperature of 75-110° C. and a stretching ratio of 2.8-4.0 times; and then transversely stretched at a temperature of 95-145° C. and a stretching ratio of 3.0-4.5 times; the stretched film is shaped at 220-240° C., and then cooled at 45-100° C., and then towed and wound to obtain a multi-layer copolyester film.

[0034] The high temperature resistant antistatic copolyester film has an ABA three-layer structure with a thickness of 25-150μm. The thickness ratio of A layer, B layer and A layer is 10-15%:70-80%:10-15%.

[0035] Example 1 1. Modified copolyester The dibasic acid mixture is composed of FDCA and BFDCA at a molar ratio of 50%:50%, and the diol mixture is composed of EG, CBDO, and CHDM at a molar ratio of 30%:30%:40%. The catalyst is ethylene glycol antimony.

[0036] The dibasic acid mixture, diol mixture, and catalyst were mixed and added to a reactor. The esterification reaction was carried out at 215°C and 0.33 MPa. The molar ratio of the diol mixture to the dibasic acid mixture was 1.1:1, and the molar ratio of the catalyst to the dibasic acid mixture was 5:1000. The reaction was continued until the water output reached 98% or above, and then the polycondensation reaction stage was entered. The polycondensation reaction temperature was 260°C, the vacuum degree was 40 Pa, and the reaction time was 3 hours. After the reaction was completed, the modified copolyester was produced.

[0037] 2. Multilayer copolyester film By mass percentage, the raw materials for layer A are 20% anti-blocking agent masterbatch and 80% modified copolyester. The anti-blocking agent masterbatch is made by mixing and melting PET and anti-blocking agent particles (average particle size 2.5μm) and then pelletizing them. The content of anti-blocking agent particles is 6000ppm by mass of the anti-blocking agent masterbatch, and the intrinsic viscosity of the anti-blocking agent masterbatch is 0.642dl / g. The raw material for layer B is modified copolyester.

[0038] The raw materials of layer A and layer B are added into an extruder, melted and co-extruded in three layers at an extrusion temperature of 270°C, and cast onto a casting roller at a temperature of 22°C after extrusion from a die head to form a cast sheet; the cast sheet is longitudinally stretched at a temperature of 95°C and a stretching ratio of 3.0 times; and then transversely stretched at a temperature of 125°C and a stretching ratio of 3.5 times; the stretched film is shaped at 220°C, cooled at 60°C, and pulled and wound to obtain a multi-layer copolyester film.

[0039] The multilayer copolyester film has an ABA three-layer structure with a thickness of 100 μm, and the thickness ratio of the A layer, the B layer, and the A layer is 10%:80%:10%.

[0040] Example 2 The difference from Example 1 is that during the preparation of the modified copolyester, FDCA and BFDCA with a molar percentage of 60%:40% are used as a dibasic acid mixture.

[0041] 1. Modified copolyester The dibasic acid mixture is composed of FDCA and BFDCA at a molar ratio of 60%:40%, and the diol mixture is composed of EG, CBDO, and CHDM at a molar ratio of 30%:30%:40%. The catalyst is ethylene glycol antimony.

[0042] The dibasic acid mixture, diol mixture, and catalyst were mixed and added to a reactor. The esterification reaction was carried out at 215°C and 0.33 MPa. The molar ratio of the diol mixture to the dibasic acid mixture was 1.1:1, and the molar ratio of the catalyst to the dibasic acid mixture was 5:1000. The reaction was continued until the water output reached 98% or above, and then the polycondensation reaction stage was entered. The polycondensation reaction temperature was 260°C, the vacuum degree was 40 Pa, and the reaction time was 3 hours. After the reaction was completed, the modified copolyester was produced.

[0043] 2. Multilayer copolyester film By mass percentage, the raw materials for layer A are 20% anti-blocking agent masterbatch and 80% modified copolyester. The anti-blocking agent masterbatch is made by mixing and melting PET and anti-blocking agent particles (average particle size 2.5μm) and then pelletizing them. The content of anti-blocking agent particles is 6000ppm by mass of the anti-blocking agent masterbatch, and the intrinsic viscosity of the anti-blocking agent masterbatch is 0.642dl / g. The raw material for layer B is modified copolyester.

[0044] The raw materials of layer A and layer B are added into an extruder, melted and co-extruded in three layers at an extrusion temperature of 270°C, and cast onto a casting roller at a temperature of 22°C after extrusion from a die head to form a cast sheet; the cast sheet is longitudinally stretched at a temperature of 90°C and a stretching ratio of 2.8 times; and then transversely stretched at a temperature of 120°C and a stretching ratio of 3.3 times; the stretched film is shaped at 220°C, cooled at 60°C, and pulled and wound to obtain a multi-layer copolyester film.

[0045] The multilayer copolyester film has an ABA three-layer structure with a thickness of 100 μm, and the thickness ratio of the A layer, the B layer, and the A layer is 10%:80%:10%.

[0046] Example 3 The difference from Example 1 is that during the preparation of the modified copolyester, EG, CBDO and CHDM with a molar percentage of 25%:40%:35% are used as a diol mixture.

[0047] 1. Modified copolyester The dibasic acid mixture is composed of FDCA and BFDCA at a molar ratio of 50%:50%, and the diol mixture is composed of EG, CBDO, and CHDM at a molar ratio of 25%:40%:35%. The catalyst is ethylene glycol antimony.

[0048] The dibasic acid mixture, diol mixture, and catalyst were mixed and added to a reactor. The esterification reaction was carried out at 215°C and 0.33 MPa. The molar ratio of the diol mixture to the dibasic acid mixture was 1.1:1, and the molar ratio of the catalyst to the dibasic acid mixture was 5:1000. The reaction was continued until the water output reached 98% or above, and then the polycondensation reaction stage was entered. The polycondensation reaction temperature was 260°C, the vacuum degree was 40 Pa, and the reaction time was 3 hours. After the reaction was completed, the modified copolyester was produced.

[0049] 2. Multilayer copolyester film By mass percentage, the raw materials for layer A are 20% anti-blocking agent masterbatch and 80% modified copolyester. The anti-blocking agent masterbatch is made by mixing and melting PET and anti-blocking agent particles (average particle size 2.5μm) and then pelletizing them. The content of anti-blocking agent particles is 6000ppm by mass of the anti-blocking agent masterbatch, and the intrinsic viscosity of the anti-blocking agent masterbatch is 0.642dl / g. The raw material for layer B is modified copolyester.

[0050] The raw materials of layer A and layer B are added into an extruder, melted and co-extruded into three layers at an extrusion temperature of 270°C, and cast onto a casting roller at a temperature of 22°C after extrusion from a die head to form a cast sheet; the cast sheet is longitudinally stretched at a temperature of 100°C and a stretching ratio of 3.0 times; and then transversely stretched at a temperature of 135°C and a stretching ratio of 3.6 times; the stretched film is shaped at 220°C, cooled at 60°C, and pulled and wound to obtain a multi-layer copolyester film.

[0051] The multilayer copolyester film has an ABA three-layer structure with a thickness of 100 μm, and the thickness ratio of the A layer, the B layer, and the A layer is 10%:80%:10%.

[0052] Example 4 The difference from Example 1 is that during the preparation of the copolyester film, the raw materials of layer A are 30% of the antiblocking agent masterbatch and 70% of the modified copolyester by mass percentage; the thickness of the copolyester film is 150 μm.

[0053] By mass percentage, the raw materials for layer A are 30% anti-blocking agent masterbatch and 70% modified copolyester. The anti-blocking agent masterbatch is made by mixing and melting PET and anti-blocking agent particles (average particle size 2.5μm) and then pelletizing them. The content of anti-blocking agent particles is 6000ppm by mass of the anti-blocking agent masterbatch, and the intrinsic viscosity of the anti-blocking agent masterbatch is 0.642dl / g. The raw material for layer B is modified copolyester.

[0054] The raw materials of layer A and layer B are added into an extruder, melted and co-extruded in three layers at an extrusion temperature of 270°C, and cast onto a casting roller at a temperature of 22°C after extrusion from a die head to form a cast sheet; the cast sheet is longitudinally stretched at a temperature of 95°C and a stretching ratio of 3.0 times; and then transversely stretched at a temperature of 125°C and a stretching ratio of 3.5 times; the stretched film is shaped at 220°C, cooled at 60°C, and pulled and wound to obtain a multi-layer copolyester film.

[0055] The multilayer copolyester film has an ABA three-layer structure with a thickness of 150 μm, and the thickness ratio of the A layer, the B layer, and the A layer is 10%:80%:10%.

[0056] Example 5 The difference from Example 1 is that during the preparation of the copolyester film, the raw materials of layer A are 5% of the antiblocking agent masterbatch and 95% of the modified copolyester by mass percentage; and the thickness of the copolyester film is 50 μm.

[0057] By mass percentage, the raw materials for layer A are 5% anti-blocking agent masterbatch and 95% modified copolyester. The anti-blocking agent masterbatch is made by mixing and melting PET and anti-blocking agent particles (average particle size 2.5μm) and then pelletizing them. The content of anti-blocking agent particles is 6000ppm by mass of the anti-blocking agent masterbatch, and the intrinsic viscosity of the anti-blocking agent masterbatch is 0.642dl / g. The raw material for layer B is modified copolyester.

[0058] The raw materials of layer A and layer B are added into an extruder, melted and co-extruded in three layers at an extrusion temperature of 270°C, and cast onto a casting roller at a temperature of 22°C after extrusion from a die head to form a cast sheet; the cast sheet is longitudinally stretched at a temperature of 95°C and a stretching ratio of 3.0 times; and then transversely stretched at a temperature of 125°C and a stretching ratio of 3.5 times; the stretched film is shaped at 220°C, cooled at 60°C, and pulled and wound to obtain a multi-layer copolyester film.

[0059] The multilayer copolyester film has an ABA three-layer structure with a thickness of 50 μm, and the thickness ratio of the A layer, the B layer, and the A layer is 10%:80%:10%.

[0060] Comparative Example 1 The difference from Example 1 is that the modified copolyester is replaced by PET chips (with an intrinsic viscosity of 0.664 dl / g) to prepare the copolyester film.

[0061] By mass percentage, the raw materials for layer A are 20% anti-blocking agent masterbatch and 80% PET chips. The anti-blocking agent masterbatch is made by mixing and melting PET and anti-blocking agent particles (average particle size 2.5μm) and then pelletizing them. The anti-blocking agent particle content is 6000ppm by mass of the anti-blocking agent masterbatch, and the intrinsic viscosity of the anti-blocking agent masterbatch is 0.642dl / g. The raw material for layer B is PET chips.

[0062] The raw materials of layer A and layer B are added into an extruder, melted and co-extruded in three layers at an extrusion temperature of 270°C, and cast onto a casting roller at a temperature of 22°C after extrusion from a die head to form a cast sheet; the cast sheet is longitudinally stretched at a temperature of 90°C and a stretching ratio of 2.6 times; and then transversely stretched at a temperature of 115°C and a stretching ratio of 3.3 times; the stretched film is shaped at 220°C, cooled at 60°C, and pulled and wound to obtain a multi-layer copolyester film.

[0063] The multilayer copolyester film has an ABA three-layer structure with a thickness of 100 μm, and the thickness ratio of the A layer, the B layer, and the A layer is 10%:80%:10%.

[0064] Comparative Example 2 The difference from Example 1 is that during the preparation of the modified copolyester, only FDCA is used as the dibasic acid.

[0065] 1. Modified copolyester FDCA was used as the dibasic acid, and the diol mixture consisted of EG, CBDO, and CHDM in a molar ratio of 30%:30%:40%. The catalyst was ethylene glycol antimony.

[0066] After mixing the dibasic acid, diol mixture, and catalyst, the mixture was added to a reactor and subjected to an esterification reaction at 215°C and 0.33 MPa. The molar ratio of the diol mixture to the dibasic acid was 1.1:1, and the molar ratio of the catalyst to the dibasic acid was 5:1000. The reaction continued until the water yield reached 98% or above, at which point the polycondensation reaction began. The polycondensation reaction temperature was 260°C, the vacuum was 40 Pa, and the reaction time was 3 hours. After completion of the reaction, the modified copolyester was obtained.

[0067] 2. Multilayer copolyester film By mass percentage, the raw materials for layer A are 20% anti-blocking agent masterbatch and 80% modified copolyester. The anti-blocking agent masterbatch is made by mixing and melting PET and anti-blocking agent particles (average particle size 2.5μm) and then pelletizing them. The content of anti-blocking agent particles is 6000ppm by mass of the anti-blocking agent masterbatch, and the intrinsic viscosity of the anti-blocking agent masterbatch is 0.642dl / g. The raw material for layer B is modified copolyester.

[0068] The raw materials of layer A and layer B are added into an extruder, melted and co-extruded in three layers at an extrusion temperature of 270°C, and cast onto a casting roller at a temperature of 22°C after extrusion from a die head to form a cast sheet; the cast sheet is longitudinally stretched at a temperature of 85°C and a stretching ratio of 3.1 times; and then transversely stretched at a temperature of 125°C and a stretching ratio of 3.7 times; the stretched film is shaped at 220°C, cooled at 60°C, and pulled and wound to obtain a multi-layer copolyester film.

[0069] The multilayer copolyester film has an ABA three-layer structure with a thickness of 100 μm, and the thickness ratio of the A layer, the B layer, and the A layer is 10%:80%:10%.

[0070] Comparative Example 3 The difference from Example 1 is that during the preparation of the modified copolyester, FDCA and BFDCA with a molar percentage of 40%:60% are used as the dibasic acid mixture.

[0071] 1. Modified copolyester The dibasic acid mixture is composed of FDCA and BFDCA at a molar ratio of 50%:50%, and the diol mixture is composed of EG, CBDO, and CHDM at a molar ratio of 30%:30%:40%. The catalyst is ethylene glycol antimony.

[0072] The dibasic acid mixture, diol mixture, and catalyst were mixed and added to a reactor. The esterification reaction was carried out at 215°C and 0.33 MPa. The molar ratio of the diol mixture to the dibasic acid mixture was 1.1:1, and the molar ratio of the catalyst to the dibasic acid mixture was 5:1000. The reaction was continued until the water output reached 98% or above, and then the polycondensation reaction stage was entered. The polycondensation reaction temperature was 260°C, the vacuum degree was 40 Pa, and the reaction time was 3 hours. After the reaction was completed, the modified copolyester was produced.

[0073] 2. Multilayer copolyester film By mass percentage, the raw materials for layer A are 20% anti-blocking agent masterbatch and 80% modified copolyester. The anti-blocking agent masterbatch is made by mixing and melting PET and anti-blocking agent particles (average particle size 2.5μm) and then pelletizing them. The content of anti-blocking agent particles is 6000ppm by mass of the anti-blocking agent masterbatch, and the intrinsic viscosity of the anti-blocking agent masterbatch is 0.642dl / g. The raw material for layer B is modified copolyester.

[0074] The raw materials of layer A and layer B are added into an extruder, melted and co-extruded in three layers at an extrusion temperature of 270°C, and cast onto a casting roller at a temperature of 22°C after extrusion from a die head to form a cast sheet; the cast sheet is longitudinally stretched at a temperature of 105°C and a stretching ratio of 3.0 times; and then transversely stretched at a temperature of 140°C and a stretching ratio of 3.4 times; the stretched film is shaped at 220°C, cooled at 60°C, and pulled and wound to obtain a multi-layer copolyester film.

[0075] The multilayer copolyester film has an ABA three-layer structure with a thickness of 100 μm, and the thickness ratio of the A layer, the B layer, and the A layer is 10%:80%:10%.

[0076] Comparative Example 4 The difference from Example 1 is that during the preparation of the modified copolyester, EG and CBDO with a molar percentage of 30%:70% are used as a diol mixture.

[0077] 1. Modified copolyester The dibasic acid mixture is composed of FDCA and BFDCA at a molar ratio of 50%:50%, and the diol mixture is composed of EG and CBDO at a molar ratio of 30%:70%. The catalyst is ethylene glycol antimony.

[0078] The dibasic acid mixture, diol mixture, and catalyst were mixed and added to a reactor. The esterification reaction was carried out at 215°C and 0.33 MPa. The molar ratio of the diol mixture to the dibasic acid mixture was 1.1:1, and the molar ratio of the catalyst to the dibasic acid mixture was 5:1000. The reaction was continued until the water output reached 98% or above, and then the polycondensation reaction stage was entered. The polycondensation reaction temperature was 260°C, the vacuum degree was 40 Pa, and the reaction time was 3 hours. After the reaction was completed, the modified copolyester was produced.

[0079] 2. Multilayer copolyester film By mass percentage, the raw materials for layer A are 20% anti-blocking agent masterbatch and 80% modified copolyester. The anti-blocking agent masterbatch is made by mixing and melting PET and anti-blocking agent particles (average particle size 2.5μm) and then pelletizing them. The content of anti-blocking agent particles is 6000ppm by mass of the anti-blocking agent masterbatch, and the intrinsic viscosity of the anti-blocking agent masterbatch is 0.642dl / g. The raw material for layer B is modified copolyester.

[0080] The raw materials of layer A and layer B are added into an extruder, melted and co-extruded in three layers at an extrusion temperature of 270°C, and cast onto a casting roller at a temperature of 22°C after extrusion from a die head to form a cast sheet; the cast sheet is longitudinally stretched at a temperature of 105°C and a stretching ratio of 2.8 times; and then transversely stretched at a temperature of 135°C and a stretching ratio of 3.8 times; the stretched film is shaped at 220°C, cooled at 60°C, and pulled and wound to obtain a multi-layer copolyester film.

[0081] The multilayer copolyester film has an ABA three-layer structure with a thickness of 100 μm, and the thickness ratio of the A layer, the B layer, and the A layer is 10%:80%:10%.

[0082] Comparative Example 5 The difference from Example 1 is that during the preparation of the modified copolyester, EG, CBDO and CHDM with a molar percentage of 30%:20%:50% are used as a diol mixture.

[0083] 1. Modified copolyester The dibasic acid mixture is composed of FDCA and BFDCA at a molar ratio of 50%:50%, and the diol mixture is composed of EG, CBDO, and CHDM at a molar ratio of 30%:20%:50%. The catalyst is ethylene glycol antimony.

[0084] The dibasic acid mixture, diol mixture, and catalyst were mixed and added to a reactor. The esterification reaction was carried out at 215°C and 0.33 MPa. The molar ratio of the diol mixture to the dibasic acid mixture was 1.1:1, and the molar ratio of the catalyst to the dibasic acid mixture was 5:1000. The reaction was continued until the water output reached 98% or above, and then the polycondensation reaction stage was entered. The polycondensation reaction temperature was 260°C, the vacuum degree was 40 Pa, and the reaction time was 3 hours. After the reaction was completed, the modified copolyester was produced.

[0085] 2. Multilayer copolyester film By mass percentage, the raw materials for layer A are 20% anti-blocking agent masterbatch and 80% modified copolyester. The anti-blocking agent masterbatch is made by mixing and melting PET and anti-blocking agent particles (average particle size 2.5μm) and then pelletizing them. The content of anti-blocking agent particles is 6000ppm by mass of the anti-blocking agent masterbatch, and the intrinsic viscosity of the anti-blocking agent masterbatch is 0.642dl / g. The raw material for layer B is modified copolyester.

[0086] The raw materials of layer A and layer B are added into an extruder, melted and co-extruded in three layers at an extrusion temperature of 270°C, and cast onto a casting roller at a temperature of 22°C after extrusion from a die head to form a cast sheet; the cast sheet is longitudinally stretched at a temperature of 95°C and a stretching ratio of 3.3 times; and then transversely stretched at a temperature of 125°C and a stretching ratio of 4.1 times; the stretched film is shaped at 220°C, cooled at 60°C, and pulled and wound to obtain a multi-layer copolyester film.

[0087] The multilayer copolyester film has an ABA three-layer structure with a thickness of 100 μm, and the thickness ratio of the A layer, the B layer, and the A layer is 10%:80%:10%.

[0088] Performance testing: (1) Thickness test: GB / T 33399-2016; (2) Glass transition temperature: GB / T 19466.2-2004; (3) Surface resistance test: GB / T 33398-2016; (4) Surface resistance test after aging: After the sample is kept at a constant temperature and humidity of 60°C and 90% for 200 hours, the surface resistance is tested; (5) Temperature resistance test: A 1000mm wide copolyester film roll sample was passed through a 32m long oven at a speed of 40m / min under a pulling tension of 15N / m and an ambient temperature of 160℃. The surface flatness of the film was observed. The higher the flatness, the better the temperature resistance of the copolyester film. "○" indicates excellent temperature resistance; "△" indicates good temperature resistance; "×" indicates poor temperature resistance.

[0089] Table 1 Performance test data of Examples 1-5 and Comparative Examples 1-5

[0090] As shown in Table 1, the films of the present invention utilize modified copolyesters as their primary raw material. This modified copolyester, through copolymerization and modification, imparts excellent heat resistance and antistatic properties to the films. These properties are retained even after aging, addressing the aging and flaking issues associated with conventional antistatic coatings. The copolyester films produced in Examples 1-5 using the methods of the present invention exhibit significantly superior heat resistance and antistatic properties compared to the film produced using conventional polyester in Comparative Example 1.

[0091] Comparative Example 2, in which only FDCA was used as the dibasic acid during the preparation of the modified copolyester, achieved a certain antistatic effect compared to Comparative Example 1. However, the modified copolyester obtained after the reaction of FDCA with the diol mixture was likely affected by the molecular chain structure of the resulting polyester, which limited the internal proton transfer efficiency and the resulting antistatic effect. In Comparative Example 3, the addition of too high a molar ratio of BFDCA resulted in a broad molecular weight distribution of the copolyester, with a higher proportion of low molecular weight chains. Furthermore, the modified copolyester had a lower glass transition temperature, which affected the film's temperature resistance.

[0092] Comparative Example 4, in which CHDM was not added during the preparation of the modified copolyester, also resulted in a wide molecular weight distribution and a low glass transition temperature of the copolyester, leading to poor film temperature resistance. In Comparative Example 5, the molar ratio of CBDO added was too low. The CBDO four-membered ring has significant rigidity, which improves the temperature resistance of the polyester film. Adding too little resulted in poor temperature resistance.

[0093] The above are only preferred embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the description of the present invention, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A high-temperature-resistant antistatic multilayer copolyester film, characterized in that: The multi-layer copolyester film includes an ABA three-layer structure obtained by melt coextrusion; in terms of mass percentage, the raw materials of layer A are 5-30% of antiblocking agent masterbatch and the balance of modified copolyester; the raw material of layer B is modified copolyester; the modified copolyester is prepared by esterification reaction and polycondensation reaction of a dibasic acid mixture, a diol mixture and a catalyst; in terms of molar percentage, the dibasic acid mixture includes 50-70% of furandicarboxylic acid and 30-50% of 2,2'-bifuran-5,5'-dicarboxylic acid, and the diol mixture includes 20-30% of ethylene glycol, 30-40% of 2,2,4,4-tetramethyl-1,3-cyclobutanediol and 30-40% of 1,4-cyclohexanedimethanol.

2. The high-temperature-resistant and antistatic multilayer copolyester film according to claim 1, characterized in that: The molar ratio of the diol mixture to the dibasic acid mixture is 1.05-1.2:

1.

3. The high-temperature-resistant and antistatic multilayer copolyester film according to claim 1 or 2, characterized in that: The molar ratio of the catalyst to the dibasic acid mixture is 1-10:1000.

4. The high-temperature-resistant and antistatic multilayer copolyester film according to claim 1, characterized in that: The temperature of the esterification reaction is 210-230° C., and the pressure is 0.30-0.40 MPa. When the water output reaches 98% or above, the polycondensation reaction stage is entered.

5. The high-temperature-resistant and antistatic multilayer copolyester film according to claim 1 or 4, characterized in that: The temperature of the polycondensation reaction is 250-260° C., the vacuum degree is 20-60 Pa, and the reaction time is 3-4 hours.

6. The high-temperature-resistant and antistatic multilayer copolyester film according to claim 1, characterized in that: The raw materials of the opener masterbatch include PET and opener particles, and the intrinsic viscosity is 0.6-0.7 dl / g; the content of the opener particles is 3000-10000ppm of the mass of the opener masterbatch, and the particle size is 1-4 μm.

7. The high-temperature-resistant and antistatic multilayer copolyester film according to claim 1 or 6, characterized in that: The thickness of the multi-layer copolyester film is 25-150 μm; the thickness ratio of the ABA three-layer structure is 10-15%:70-80%:10-15%.

8. A method for preparing the high-temperature-resistant antistatic multilayer copolyester film according to any one of claims 1 to 7, characterized in that: The method comprises the following steps: adding raw materials of layer A and layer B into an extruder, melting three layers, co-extruding and casting to form a cast sheet; and sequentially longitudinally stretching, transversely stretching, shaping and cooling the cast sheet to obtain a multi-layer copolyester film.

9. The preparation method according to claim 8, characterized in that: The temperature of the longitudinal stretching is 75-110° C., and the stretching ratio is 2.8-4.0 times; the temperature of the transverse stretching is 95-145° C., and the stretching ratio is 3.0-4.5 times.

10. Use of the high-temperature-resistant antistatic multilayer copolyester film according to any one of claims 1 to 7 or the high-temperature-resistant antistatic multilayer copolyester film prepared by the preparation method according to any one of claims 8 to 9 in a release film.

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