Ultrathin heat-resistant polyester film and preparation method thereof

Abstract

The invention discloses an ultrathin heat-resistant polyester film and a preparation method thereof, raw materials comprise a polyester matrix, an antioxidant, a lubricant and the like, the polyester matrix is formed by compounding PET, PEN, polyester liquid crystals and hydroxyl-terminated hyperbranched polyester, and a nanofiller is an aluminum oxide, zirconium oxide and boron nitride compounded system and is matched with calix [4] pyrrole, polyhedral oligomeric silsesquioxane and other components. The preparation method comprises the steps of mixing, twin-screw extrusion and filtration, die head extrusion and cooling, two-way stretching, corona treatment and rolling, and extrusion, stretching and shaping process parameters are controlled. The thickness of the thin film is 5-8 microns, the thin film has excellent tensile strength, low thermal shrinkage rate and high-low temperature cycle resistance, the synergistic effect of the components is remarkable, and the thin film is suitable for high-end ultrathin heat-resistant scenes.

Description

Technical Field

[0001] This invention relates to the field of polymer film materials technology, and in particular to an ultrathin heat-resistant polyester film and its preparation method. Background Technology

[0002] With the miniaturization and integration of electronic components, and the rapid advancements in precision manufacturing and flexible displays, the market demand for high-performance ultra-thin tapes is increasing. As the core substrate of tapes, ultra-thin polyester film must simultaneously meet stringent requirements such as thinness, high heat resistance, low heat shrinkage, smooth surface, and excellent mechanical properties to ensure that the tape does not deform after being coated with adhesive and achieves high bonding precision.

[0003] Traditional polyester films, when thin, suffer from insufficient molecular chain orientation, leading to a significantly increased thermal shrinkage rate. This makes them prone to irreversible deformation at high temperatures, failing to meet the requirements of applications such as automotive engine compartments and high-temperature curing of electronic components. To improve heat resistance, the industry often uses copolymerization of PET and polyethylene naphthalate (PEN) or adds inorganic particles (such as silica). However, the introduction of PEN reduces film toughness, increases processing difficulty, and can cause tensile breakage and uneven thickness in ultra-thin applications. The addition of inorganic particles increases film surface roughness, affecting tape adhesion uniformity; furthermore, compatibility issues impact mechanical properties and performance stability, leading to easy damage to the tape substrate and decreased adhesive adhesion.

[0004] Therefore, developing an ultrathin heat-resistant polyester film with breakthrough heat resistance, low heat shrinkage, and a balance between mechanical and processability has become an urgent need in the high-end application field of ultrathin tapes. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide an ultra-thin heat-resistant polyester film with ultra-thin characteristics, excellent heat resistance, mechanical properties and good dimensional stability, as well as a method for preparing the same.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: an ultra-thin heat-resistant polyester film, the raw material composition by mass is as follows: 100 parts polyester matrix, 0.5-0.8 parts antioxidant, 0.3-0.5 parts lubricant, 1-3 parts coupling agent, 5-8 parts nanofiller, 3-5 parts glass fiber, 0.3-0.5 parts methacryloyloxypropyl cage-type polysilsesquioxane, 0.01-0.03 parts 2,5-dimethyl-2,5-di(tert-butylperoxide)hexane, 0.1-0.3 parts Meso-tetramethyl-meso-tetra-p-aminophenylcalix[4]pyrrole, and 0.08-0.12 parts ultraviolet absorber.

[0007] Preferably, the polyester matrix is ​​a compound of PET resin, PEN resin, polyester liquid crystal, and hydroxyl-terminated hyperbranched polyester in a mass ratio of 1:(0.8-1.2):(0.3-0.5):0.8.

[0008] Preferably, the PET resin is PET / PT7450 manufactured by DuPont, USA; and the PEN resin is PEN TN8100 manufactured by Teijin, Japan.

[0009] Preferably, the polyester liquid crystal is prepared according to the preparation method of polyester liquid crystal in Example 1 of Chinese Patent Document CN103965663B.

[0010] Preferably, the hydroxyl-terminated hyperbranched polyester is hydroxyl-terminated hyperbranched polyester HyPer H2O4.

[0011] Preferably, the antioxidant is at least one of antioxidant 1010 and antioxidant 168.

[0012] Preferably, the lubricant is erucamide.

[0013] Preferably, the coupling agent is at least one of silane coupling agent KH550, silane coupling agent KH560, and silane coupling agent KH570.

[0014] Preferably, the nanofiller is a mixture of nano-alumina, nano-zirconia, and nano-boron nitride in a mass ratio of (1-3):1:(0.8-1.2).

[0015] Preferably, the average particle size of the nanofiller is 10-80 nm.

[0016] Preferably, the glass fiber is alkali-free glass fiber with an average diameter of 0.1-0.3µm and an aspect ratio of (10-15):1.

[0017] Preferably, the methacryloyloxypropyl cage-type polysilsesquioxane is methacryloyloxypropyl cage-type polysilsesquioxane Ecotion®POSS102.

[0018] Preferably, the preparation method of the Meso-tetramethyl-meso-tetraaminophenylcalix[4]pyrrole is described in: Guo Yong, Shao Shijun, He Lijun, et al. Synthesis and characterization of Meso-tetramethyl-meso-tetraaminophenylcalix[4]pyrrole [J]. Chemical Reagents, 2002(6):344-345.

[0019] Preferably, the ultraviolet absorber is a mixture of light stabilizer UV-944 and ultraviolet absorber UV-327 in a mass ratio of 1:(1-3).

[0020] Another objective of this invention is to provide a method for preparing the ultrathin heat-resistant polyester film, comprising the following steps: mixing the raw materials evenly according to their weight proportions to obtain a mixture; then adding the mixture to a twin-screw extruder; filtering the melt through a two-stage disc filter with a coarse filtration pore size of 20 μm and a fine filtration pore size of 10 μm; extruding the filtered melt through a die into a cooling drum with a die lip opening of 1.2-1.3 mm, a pre-stretch ratio of 6-10, a cooling drum linear speed of 70-75 m / min, and a cooling drum temperature of 25-30 °C; using a steel wire electrostatic electrode for adsorption to ensure that the film is tightly attached to the cooling drum; after biaxial stretching, corona treatment is performed, and then the film is wound up at a temperature of 23±2 °C and a relative humidity of 50-60% at a winding speed of 200-250 m / min to obtain an ultrathin heat-resistant polyester film with a thickness of 5-8 μm.

[0021] Preferably, the extrusion temperature of the twin-screw extruder is controlled in segments as follows: feeding section 240-250℃, compression section 265-275℃, homogenization section 275-285℃, die temperature 280-285℃, and screw speed 250-300 r / min.

[0022] Preferably, the biaxial stretching includes longitudinal stretching and transverse stretching. The longitudinal stretching adopts high-temperature two-point small-gap stretching, with a preheating section temperature of 90-100℃, a stretching section temperature of 105-115℃, a stretching ratio of 4.2-5.0, a cooling section temperature of 25-30℃, and a cooling roller diameter of 250mm. The transverse stretching has a preheating section temperature of 95-105℃, a stretching section temperature of 100-110℃, a stretching ratio of 4.0-4.8, a heat setting section temperature of 230-245℃, a holding time of 4-6s, and a cooling section temperature of 50-60℃.

[0023] Due to the application of the above technical solution, the present invention has the following beneficial effects: (1) The ultra-thin heat-resistant polyester film disclosed in this invention breaks through the inherent contradiction between heat resistance, toughness and processability in the prior art through the synergy of quaternary compounding of polyester matrix and multi-component modification system, and achieves performance balance. The prior art uses PET and PEN copolymerization, which easily leads to the decrease of film toughness and easy breakage in ultra-thin processing. Simply adding inorganic particles will cause problems such as poor compatibility and rough surface. However, this solution combines PET, PEN, polyester liquid crystal and hydroxyl-terminated hyperbranched polyester in a specific ratio, and combines it with the synergistic modification of Meso-tetramethyl-meso-tetra-p-aminophenylcalix[4]pyrrole and methacryloyloxypropyl cage-type polysilsesquioxane. This not only significantly improves the heat resistance of the film and greatly reduces the risk of irreversible deformation under high temperature environment, but also avoids the processing defects caused by PEN by means of the compatibility adjustment effect of hyperbranched polyester. It can still maintain excellent toughness in ultra-thin specifications, solves the technical bottleneck of "choosing one thing and losing another" in the existing modification scheme, and achieves simultaneous optimization of heat resistance, processability and mechanical properties.

[0024] (2) The ultrathin heat-resistant polyester film disclosed in this invention achieves a dual breakthrough in dimensional stability and surface performance through precise proportioning and interface control of nanofillers and glass fibers, exceeding the expected effects of conventional modification. In the prior art, the addition of inorganic particles easily leads to increased surface roughness and fluctuations in mechanical properties. This solution uses a specific ratio of nano-alumina, zirconium oxide, and boron nitride composite fillers, combined with alkali-free glass fibers of suitable specifications, and interface modification with silane coupling agents. This not only improves the mechanical strength of the film through the synergistic reinforcement effect of the fillers, but also reduces the thermal shrinkage rate of the film, while avoiding the generation of surface defects and ensuring the uniformity of adhesion during tape coating. This simultaneous realization of "reinforcement-heat resistance-surface smoothness" breaks through the conventional understanding that "performance improvement and surface quality are contradictory" in inorganic particle modification.

[0025] (3) The ultrathin heat-resistant polyester film disclosed in this invention achieves stable mass production and maximizes performance of ultrathin specifications through precise matching of the preparation process and formulation system, solving the pain point of difficult processing of ultrathin films in the prior art. In the preparation of 5-8μm ultrathin polyester films, the prior art is prone to problems such as tensile breakage and uneven thickness. This solution achieves stable production of ultrathin films by using twin-screw extrusion with segmented temperature control, two-stage precise filtration, high-temperature two-point small-gap bidirectional stretching, and synergistic control of specific heat setting parameters. Combined with electrostatic adsorption of steel wire to ensure that the film is tightly attached to the cooling drum, this solution not only achieves stable production of ultrathin films, but also further optimizes the molecular chain orientation by matching process parameters and raw material system, so that the film still has excellent dimensional stability and mechanical properties at ultrathin thickness. Compared with the existing process, this solution can achieve a dual improvement in performance and mass production efficiency without the need for additional complex equipment.

[0026] (4) The ultra-thin heat-resistant polyester film disclosed in this invention, through the synergistic effect of its multiple functional components, endows the film with comprehensive performance advantages and expands its high-end application scenarios. In this solution, the synergistic combination of antioxidants, ultraviolet absorbers, and core modifying components not only improves the heat resistance, durability, and anti-aging properties of the film, but also further optimizes the molecular chain structure through the regulation of 2,5-dimethyl-2,5-di(tert-butylperoxide)hexane, making the film suitable for harsh scenarios such as automotive engine compartments and high-temperature curing of electronic components. Compared with the existing technologies that only focus on improving a single heat resistance performance, this technology achieves comprehensive compliance with the standards of "ultra-thin, heat-resistant, mechanical, stable, and anti-aging", filling the market gap for high-end ultra-thin tape substrates.

[0027] (5) The ultrathin heat-resistant polyester film disclosed in this invention has the following raw material composition by weight: 100 parts polyester matrix, 0.5-0.8 parts antioxidant, 0.3-0.5 parts lubricant, 1-3 parts coupling agent, 5-8 parts nanofiller, 3-5 parts glass fiber, 0.3-0.5 parts methacryloyloxypropyl cage-type polysilsesquioxane, 0.01-0.03 parts 2,5-dimethyl-2,5-di(tert-butylperoxide)hexane, 0.1-0.3 parts Meso-tetramethyl-meso-tetra-p-aminophenylcalix[4]pyrrole, and 0.08-0.12 parts ultraviolet absorber. Through the synergistic effect of the various raw materials, the film produced has ultrathin characteristics, excellent heat resistance, mechanical properties and good dimensional stability. Detailed Implementation

[0028] The following description is intended to disclose the invention and enable those skilled in the art to implement it. The preferred embodiments described below are merely examples, and other obvious variations will occur to those skilled in the art.

[0029] Example 1 An ultra-thin heat-resistant polyester film, by weight, has the following raw material composition: 100 parts polyester matrix, 0.5 parts antioxidant, 0.3 parts lubricant, 1 part coupling agent, 5 parts nanofiller, 3 parts glass fiber, 0.3 parts methacryloyloxypropyl cage-type polysilsesquioxane, 0.01 parts 2,5-dimethyl-2,5-di(tert-butylperoxide)hexane, 0.1 parts Meso-tetramethyl-meso-tetra-p-aminophenylcalix[4]pyrrole, and 0.08 parts ultraviolet absorber.

[0030] The polyester matrix is ​​a compound of PET resin, PEN resin, polyester liquid crystal, and hydroxyl-terminated hyperbranched polyester in a mass ratio of 1:0.8:0.3:0.8; the PET resin is PET / PT7450 manufactured by DuPont, USA; the PEN resin is PEN TN8100 manufactured by Teijin, Japan; the polyester liquid crystal is prepared according to the preparation method of polyester liquid crystal in Example 1 of invention patent document CN103965663B; the hydroxyl-terminated hyperbranched polyester is hydroxyl-terminated hyperbranched polyester HyPer H2O4; the antioxidant is antioxidant 1010; the lubricant is erucamide; the coupling agent is silane coupling agent KH550; the nanofiller is a mixture of nano-alumina, nano-zirconia, and nano-boron nitride in a mass ratio of 1:1:0.8; the average particle size of the nanofiller is 10 nm; the glass fiber is alkali-free glass fiber with an average diameter of 0.1 µm and an aspect ratio of 10:1; the methacryloyloxypropyl cage-type polysilsesquioxane is methacryloyloxypropyl cage-type polysilsesquioxane. Siloxane Ecotion®POSS102; the preparation method of the Meso-tetramethyl-meso-tetraaminophenylcalix[4]pyrrole is described in: Guo Yong, Shao Shijun, He Lijun, et al. Synthesis and characterization of Meso-tetramethyl-meso-tetraaminophenylcalix[4]pyrrole [J]. Chemical Reagents, 2002(6):344-345; the ultraviolet absorber is composed of light stabilizer UV-944 and ultraviolet absorber UV-327 in a mass ratio of 1:1.

[0031] A method for preparing the ultrathin heat-resistant polyester film includes the following steps: mixing the raw materials evenly according to their weight proportions to obtain a mixture; then adding the mixture to a twin-screw extruder; filtering the melt through a two-stage disc filter with a coarse filtration pore size of 20 μm and a fine filtration pore size of 10 μm; extruding the filtered melt through a die into a cooling drum with a die lip opening of 1.2 mm, a pre-stretch ratio of 6, a cooling drum linear speed of 70 m / min, and a cooling drum temperature of 25 °C; using a steel wire electrostatic electrode for adsorption to ensure the film adheres tightly to the cooling drum; after biaxial stretching, undergoing corona treatment; and then winding at a temperature of 23 °C and a relative humidity of 50% at a winding speed of 200 m / min. An ultra-thin heat-resistant polyester film with a thickness of 5 μm was obtained. The extrusion temperature of the twin-screw extruder was controlled in segments as follows: feeding section 240℃, compression section 265℃, homogenization section 275℃, die temperature 280℃, and screw speed 250 r / min. The biaxial stretching included longitudinal stretching and transverse stretching. The longitudinal stretching adopted high-temperature two-point small-gap stretching, with a preheating section temperature of 90℃, a stretching section temperature of 105℃, a stretching ratio of 4.2, a cooling section temperature of 25℃, and a cooling roller diameter of 250 mm. The transverse stretching had a preheating section temperature of 95℃, a stretching section temperature of 100℃, a stretching ratio of 4.0, a heat setting section temperature of 230℃, a holding time of 4 s, and a cooling section temperature of 50℃.

[0032] Example 2 An ultra-thin heat-resistant polyester film, by weight, has the following raw material composition: 100 parts polyester matrix, 0.6 parts antioxidant, 0.35 parts lubricant, 1.5 parts coupling agent, 6 parts nanofiller, 3.5 parts glass fiber, 0.35 parts methacryloyloxypropyl cage-type polysilsesquioxane, 0.015 parts 2,5-dimethyl-2,5-di(tert-butylperoxide)hexane, 0.15 parts Meso-tetramethyl-meso-tetra-p-aminophenylcalix[4]pyrrole, and 0.09 parts ultraviolet absorber.

[0033] The polyester matrix is ​​a compound of PET resin, PEN resin, polyester liquid crystal, and hydroxyl-terminated hyperbranched polyester in a mass ratio of 1:0.9:0.35:0.8; the PET resin is PET / PT7450 manufactured by DuPont, USA; the PEN resin is PEN TN8100 manufactured by Teijin, Japan; the polyester liquid crystal is prepared according to the preparation method of polyester liquid crystal in Example 1 of invention patent document CN103965663B; the hydroxyl-terminated hyperbranched polyester is hydroxyl-terminated hyperbranched polyester HyPer H2O4; the antioxidant is antioxidant 168; the lubricant is erucamide; the coupling agent is silane coupling agent KH560; the nanofiller is nano alumina, nano zirconium oxide and nano boron nitride compounded in a mass ratio of 1.5:1:0.9; the average particle size of the nanofiller is 30nm; the glass fiber is alkali-free glass fiber with an average diameter of 0.15µm and an aspect ratio of 12:1; the methacryloyloxypropyl cage polysilsesquioxane is methacryloyloxypropyl cage polysilsesquioxane Ecotion®POSS102; the preparation method of the Meso-tetramethyl-meso-tetraaminophenylcalix[4]pyrrole can be found in: Guo Yong, Shao Shijun, He Lijun, et al. Synthesis and characterization of al. Meso-tetramethyl-meso-tetraaminophenylcalix[4]pyrrole[J]. Chemical Reagents, 2002(6):344-345; The ultraviolet absorber is composed of light stabilizer UV-944 and ultraviolet absorber UV-327 in a mass ratio of 1:1.5.

[0034] A method for preparing the ultrathin heat-resistant polyester film includes the following steps: mixing the raw materials evenly according to their weight proportions to obtain a mixture; then adding the mixture to a twin-screw extruder; filtering the melt through a two-stage disc filter with a coarse filtration pore size of 20 μm and a fine filtration pore size of 10 μm; extruding the filtered melt through a die into a cooling drum with a die lip opening of 1.2 mm, a pre-stretch ratio of 6, a cooling drum linear speed of 72 m / min, and a cooling drum temperature of 27 °C; using a steel wire electrostatic electrode for adsorption to ensure the film adheres tightly to the cooling drum; after biaxial stretching, undergoing corona treatment, and then winding at a temperature of 22 °C and a relative humidity of 53% at a winding speed of 220 m / min. An ultrathin heat-resistant polyester film with a thickness of 5 μm was obtained. The extrusion temperature of the twin-screw extruder was controlled in segments as follows: feeding section 243℃, compression section 268℃, homogenization section 278℃, die temperature 282℃, and screw speed 260 r / min. The biaxial stretching included longitudinal stretching and transverse stretching. The longitudinal stretching adopted high-temperature two-point small-gap stretching, with a preheating section temperature of 93℃, a stretching section temperature of 108℃, a stretching ratio of 4.4, a cooling section temperature of 26℃, and a cooling roller diameter of 250 mm. The transverse stretching had a preheating section temperature of 98℃, a stretching section temperature of 103℃, a stretching ratio of 4.3, a heat setting section temperature of 235℃, a holding time of 4.5 s, and a cooling section temperature of 53℃.

[0035] Example 3 An ultra-thin heat-resistant polyester film, by weight, has the following raw material composition: 100 parts polyester matrix, 0.65 parts antioxidant, 0.4 parts lubricant, 2 parts coupling agent, 6.5 parts nanofiller, 4 parts glass fiber, 0.4 parts methacryloyloxypropyl cage-type polysilsesquioxane, 0.02 parts 2,5-dimethyl-2,5-di(tert-butylperoxide)hexane, 0.2 parts Meso-tetramethyl-meso-tetra-p-aminophenylcalix[4]pyrrole, and 0.1 parts ultraviolet absorber.

[0036] The polyester matrix is ​​a compound of PET resin, PEN resin, polyester liquid crystal, and hydroxyl-terminated hyperbranched polyester in a mass ratio of 1:1:0.4:0.8; the PET resin is PET / PT7450 manufactured by DuPont, USA; the PEN resin is PEN TN8100 manufactured by Teijin, Japan; the polyester liquid crystal is prepared according to the preparation method of polyester liquid crystal in Example 1 of Chinese Patent Document CN103965663B; the hydroxyl-terminated hyperbranched polyester is hydroxyl-terminated hyperbranched polyester HyPer H2O4; the antioxidant is antioxidant 1010; the lubricant is erucamide; the coupling agent is silane coupling agent KH570; the nanofiller is a mixture of nano-alumina, nano-zirconia, and nano-boron nitride in a mass ratio of 2:1:1; the average particle size of the nanofiller is 40 nm; the glass fiber is alkali-free glass fiber with an average diameter of 0.2 µm and an aspect ratio of 13:1; the methacryloyloxypropyl cage-type polysilsesquioxane is methacryloyloxypropyl cage-type polysilsesquioxane. Ecotion®POSS102; The preparation method of the Meso-tetramethyl-meso-tetraaminophenylcalix[4]pyrrole is described in: Guo Yong, Shao Shijun, He Lijun, et al. Synthesis and characterization of Meso-tetramethyl-meso-tetraaminophenylcalix[4]pyrrole [J]. Chemical Reagents, 2002(6):344-345; The ultraviolet absorber is composed of light stabilizer UV-944 and ultraviolet absorber UV-327 in a mass ratio of 1:2.

[0037] A method for preparing the ultrathin heat-resistant polyester film includes the following steps: mixing the raw materials evenly according to their weight proportions to obtain a mixture; then adding the mixture to a twin-screw extruder; filtering the melt through a two-stage disc filter with a coarse filtration pore size of 20 μm and a fine filtration pore size of 10 μm; extruding the filtered melt through a die into a cooling drum with a die lip opening of 1.2 mm, a pre-stretch ratio of 6, a cooling drum linear speed of 73 m / min, and a cooling drum temperature of 28 °C; using a steel wire electrostatic electrode for adsorption to ensure the film adheres tightly to the cooling drum; after biaxial stretching, undergoing corona treatment; and then winding at a temperature of 24 °C and a relative humidity of 55% at a winding speed of 230 m / min. An ultrathin heat-resistant polyester film with a thickness of 5 μm was obtained. The extrusion temperature of the twin-screw extruder was controlled in segments as follows: feeding section 245℃, compression section 270℃, homogenization section 280℃, die temperature 283℃, and screw speed 280 r / min. The biaxial stretching included longitudinal stretching and transverse stretching. The longitudinal stretching adopted high-temperature two-point small-gap stretching, with a preheating section temperature of 95℃, a stretching section temperature of 110℃, a stretching ratio of 4.6, a cooling section temperature of 28℃, and a cooling roller diameter of 250 mm. The transverse stretching had a preheating section temperature of 100℃, a stretching section temperature of 105℃, a stretching ratio of 4.4, a heat setting section temperature of 238℃, a holding time of 5s, and a cooling section temperature of 55℃.

[0038] Example 4 An ultrathin heat-resistant polyester film, by weight, has the following raw material composition: 100 parts polyester matrix, 0.75 parts antioxidant, 0.45 parts lubricant, 2.5 parts coupling agent, 7.5 parts nanofiller, 4.5 parts glass fiber, 0.45 parts methacryloyloxypropyl cage-type polysilsesquioxane, 0.025 parts 2,5-dimethyl-2,5-di(tert-butylperoxide)hexane, 0.25 parts Meso-tetramethyl-meso-tetra-p-aminophenylcalix[4]pyrrole, and 0.11 parts ultraviolet absorber.

[0039] The polyester matrix is ​​a compound of PET resin, PEN resin, polyester liquid crystal, and hydroxyl-terminated hyperbranched polyester in a mass ratio of 1:1.1:0.45:0.8; the PET resin is PET / PT7450 manufactured by DuPont, USA; the PEN resin is PEN TN8100 manufactured by Teijin, Japan; the polyester liquid crystal is prepared according to the preparation method of polyester liquid crystal in Example 1 of Chinese Patent Document CN103965663B; the hydroxyl-terminated hyperbranched polyester is hydroxyl-terminated hyperbranched polyester HyPer H2O4; the antioxidant is composed of antioxidant 1010 and antioxidant 168 in a mass ratio of 1:2; the lubricant is erucamide; the coupling agent is composed of silane coupling agent KH550, silane coupling agent KH560 and silane coupling agent KH570 in a mass ratio of 1:2:3; the nanofiller is composed of nano alumina, nano zirconium oxide and nano boron nitride in a mass ratio of 2.5:1:1.1; the average particle size of the nanofiller is 70nm; the glass fiber is alkali-free glass fiber with an average diameter of 0.25µm and an aspect ratio of 14:1; the methacryloyloxypropyl cage-type polysilsesquioxane is methacryloyloxypropyl cage-type polysilsesquioxane Ecotion®POSS102; the preparation method of the Meso-tetramethyl-meso-tetraaminophenylcalix[4]pyrrole can be found in: Guo Yong, Shao Shijun, He Lijun, et al. Synthesis and characterization of al. Meso-tetramethyl-meso-tetraaminophenylcalix[4]pyrrole[J]. Chemical Reagents, 2002(6):344-345; The ultraviolet absorber is composed of light stabilizer UV-944 and ultraviolet absorber UV-327 in a mass ratio of 1:(1-3).

[0040] A method for preparing the ultrathin heat-resistant polyester film includes the following steps: mixing the raw materials evenly according to their weight proportions to obtain a mixture; then adding the mixture to a twin-screw extruder; filtering the melt through a two-stage disc filter with a coarse filtration pore size of 20 μm and a fine filtration pore size of 10 μm; extruding the filtered melt through a die into a cooling drum with a die lip opening of 1.2 mm, a pre-stretch ratio of 6, a cooling drum linear speed of 74 m / min, and a cooling drum temperature of 29 °C; using a steel wire electrostatic electrode for adsorption to ensure the film adheres tightly to the cooling drum; after biaxial stretching, undergoing corona treatment, and then winding at a temperature of 25 °C and a relative humidity of 58% at a winding speed of 240 m / min to obtain... To produce an ultra-thin heat-resistant polyester film with a thickness of 5μm; the extrusion temperature of the twin-screw extruder is controlled in segments as follows: feeding section 248℃, compression section 273℃, homogenization section 283℃, die temperature 284℃, screw speed 290r / min; the biaxial stretching includes longitudinal stretching and transverse stretching. The longitudinal stretching adopts high-temperature two-point small-gap stretching, with a preheating section temperature of 98℃, a stretching section temperature of 113℃, a stretching ratio of 4.8, a cooling section temperature of 29℃, and a cooling roller diameter of 250mm; the transverse stretching has a preheating section temperature of 103℃, a stretching section temperature of 108℃, a stretching ratio of 4.6, a heat setting section temperature of 243℃, a holding time of 5.5s, and a cooling section temperature of 58℃.

[0041] Example 5 An ultra-thin heat-resistant polyester film, by weight, has the following raw material composition: 100 parts polyester matrix, 0.8 parts antioxidant, 0.5 parts lubricant, 3 parts coupling agent, 8 parts nanofiller, 5 parts glass fiber, 0.5 parts methacryloyloxypropyl cage-type polysilsesquioxane, 0.03 parts 2,5-dimethyl-2,5-di(tert-butylperoxide)hexane, 0.3 parts Meso-tetramethyl-meso-tetra-p-aminophenylcalix[4]pyrrole, and 0.12 parts ultraviolet absorber.

[0042] The polyester matrix is ​​a compound of PET resin, PEN resin, polyester liquid crystal, and hydroxyl-terminated hyperbranched polyester in a mass ratio of 1:1.2:0.5:0.8; the PET resin is PET / PT7450 manufactured by DuPont, USA; the PEN resin is PEN TN8100 manufactured by Teijin, Japan; the polyester liquid crystal is prepared according to the preparation method of polyester liquid crystal in Example 1 of Chinese Patent Document CN103965663B; the hydroxyl-terminated hyperbranched polyester is hydroxyl-terminated hyperbranched polyester HyPer H2O4; the antioxidant is antioxidant 1010; the lubricant is erucamide; the coupling agent is silane coupling agent KH560; the nanofiller is a mixture of nano-alumina, nano-zirconia, and nano-boron nitride in a mass ratio of 3:1:1.2; the average particle size of the nanofiller is 80 nm; the glass fiber is alkali-free glass fiber with an average diameter of 0.3 µm and an aspect ratio of 15:1; the methacryloyloxypropyl cage-type polysilsesquioxane is methacryloyloxypropyl cage-type polysilsesquioxane. Ecotion®POSS102; The preparation method of the Meso-tetramethyl-meso-tetraaminophenylcalix[4]pyrrole is described in: Guo Yong, Shao Shijun, He Lijun, et al. Synthesis and characterization of Meso-tetramethyl-meso-tetraaminophenylcalix[4]pyrrole [J]. Chemical Reagents, 2002(6):344-345; The ultraviolet absorber is composed of light stabilizer UV-944 and ultraviolet absorber UV-327 in a mass ratio of 1:2.5.

[0043] A method for preparing the ultrathin heat-resistant polyester film includes the following steps: mixing the raw materials evenly according to their weight proportions to obtain a mixture; then adding the mixture to a twin-screw extruder; filtering the melt through a two-stage disc filter with a coarse filtration pore size of 20 μm and a fine filtration pore size of 10 μm; extruding the filtered melt through a die into a cooling drum with a die lip opening of 1.2 mm, a pre-stretch ratio of 6, a cooling drum linear speed of 75 m / min, and a cooling drum temperature of 30 °C; using a steel wire electrostatic electrode for adsorption to ensure the film adheres tightly to the cooling drum; after biaxial stretching, undergoing corona treatment, and then winding at 25 °C and 60% relative humidity at a winding speed of 250 m / min. An ultra-thin heat-resistant polyester film with a thickness of 5 μm was obtained. The extrusion temperature of the twin-screw extruder was controlled in segments as follows: feeding section 250℃, compression section 275℃, homogenization section 285℃, die temperature 285℃, and screw speed 300 r / min. The biaxial stretching included longitudinal stretching and transverse stretching. The longitudinal stretching adopted high-temperature two-point small-gap stretching, with a preheating section temperature of 100℃, a stretching section temperature of 115℃, a stretching ratio of 5.0, a cooling section temperature of 30℃, and a cooling roller diameter of 250 mm. The transverse stretching had a preheating section temperature of 105℃, a stretching section temperature of 110℃, a stretching ratio of 4.8, a heat setting section temperature of 245℃, a holding time of 6s, and a cooling section temperature of 60℃.

[0044] Comparative Example 1 An ultrathin heat-resistant polyester film and its preparation method are basically the same as those in Example 5, except that an equal amount of PEN resin is used instead of polyester liquid crystal.

[0045] Comparative Example 2 An ultrathin heat-resistant polyester film and its preparation method are basically the same as those in Example 5, except that an equal amount of polyester liquid crystal is used instead of PEN resin.

[0046] Comparative Example 3 An ultrathin heat-resistant polyester film and its preparation method are basically the same as those in Example 5, except that an equal amount of PET resin is used instead of the terminal hydroxyl hyperbranched polyester.

[0047] Comparative Example 4 An ultrathin heat-resistant polyester film and its preparation method are basically the same as those in Example 5, except that Meso-tetramethyl-meso-tetraaminophenylcalix[4]pyrrole is not added.

[0048] Comparative Example 5 An ultrathin heat-resistant polyester film and its preparation method are basically the same as those in Example 5, except that an equal amount of nano-alumina is used instead of nano-boron nitride.

[0049] Comparative Example 6 An ultrathin heat-resistant polyester film and its preparation method are basically the same as those in Example 5, except that an equal amount of nano boron nitride is used instead of nano aluminum oxide.

[0050] Comparative Example 7 An ultrathin heat-resistant polyester film and its preparation method are basically the same as those in Example 5, except that an equal amount of nano-zirconia is used instead of nano-alumina.

[0051] Comparative Example 8 An ultrathin heat-resistant polyester film and its preparation method are basically the same as those in Example 5, except that an equal amount of nano-alumina is used instead of nano-zirconia.

[0052] To further illustrate the beneficial technical effects of the various embodiments of the present invention, relevant performance tests were conducted on the ultra-thin heat-resistant polyester films prepared in Example 5 and Comparative Examples 1-8. The test results are shown in Table 1, and the test methods are as follows: (1) Tensile properties: The test was conducted in accordance with GB / T1040.3-2006 "Determination of tensile properties of plastics - Part 3: Test conditions for films and sheets", with a tensile speed of 50 mm / min, and the longitudinal (MD) and transverse (TD) tensile strength were tested.

[0053] (2) Heat shrinkage rate: The test was conducted in accordance with GB / T 34848-2017. The oven heating method was adopted, the temperature was set at 150℃, the sample was placed in the oven and baked at a constant temperature for 30 minutes, and after being taken out and cooled to room temperature, the longitudinal and transverse dimensional changes were measured respectively, and the longitudinal and transverse heat shrinkage rates were calculated. The sample preparation met the standard requirements, the dimensional deviation was ≤ ±0.1mm, and each group of tests had no less than 3 samples, and the average value was taken.

[0054] (3) High and low temperature cycling performance: The sample was placed under high and low temperature cycling conditions, which were -40℃ (hold for 2h) → room temperature (hold for 0.5h) → 180℃ (hold for 2h) → room temperature (hold for 0.5h), and repeated for 50 cycles. The tensile strength retention rate was calculated. The larger the value, the better the high and low temperature cycling performance.

[0055] Table 1 Performance test results of ultra-thin heat-resistant polyester film As shown in Table 1, the ultra-thin heat-resistant polyester film of Example 5 of the present invention has the best comprehensive performance. Its longitudinal and transverse tensile strengths are 292 MPa and 285 MPa, respectively, and the longitudinal and transverse thermal shrinkage rates are both ≤0.12%. The retention rate of tensile strength under high and low temperature cycles is 97.8%. However, Comparative Examples 1-3 (replacement of key matrix components), Comparative Example 4 (removal of cup [4] pyrrole), and Comparative Examples 5-8 (single nanofiller) all showed a decrease in tensile strength, an increase in thermal shrinkage rate, and a decrease in retention rate under high and low temperature cycles due to the loss of component synergistic effect. Among them, Comparative Example 4, which removed cup [4] pyrrole, showed the largest performance decline, which fully verified the key role of matrix compounding, cup [4] pyrrole and nanofiller compounding in the excellent performance of the film.

[0056] The above embodiments are only for illustrating the technical concept and features of the present invention. Their purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be used to limit the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. An ultrathin heat-resistant polyester film, characterized in that, The raw materials are composed of the following components by weight: 100 parts polyester matrix, 0.5-0.8 parts antioxidant, 0.3-0.5 parts lubricant, 1-3 parts coupling agent, 5-8 parts nanofiller, 3-5 parts glass fiber, 0.3-0.5 parts methacryloyloxypropyl cage-type polysilsesquioxane, 0.01-0.03 parts 2,5-dimethyl-2,5-di(tert-butylperoxide)hexane, 0.1-0.3 parts Meso-tetramethyl-meso-tetra-p-aminophenylcalix[4]pyrrole, and 0.08-0.12 parts ultraviolet absorber.

2. The ultra-thin heat-resistant polyester film according to claim 1, characterized in that, The polyester matrix is ​​a compound of PET resin, PEN resin, polyester liquid crystal, and hydroxyl-terminated hyperbranched polyester in a mass ratio of 1:(0.8-1.2):(0.3-0.5):0.

8.

3. The ultra-thin heat-resistant polyester film according to claim 2, characterized in that, The PET resin is PET / PT7450; the PEN resin is PEN TN8100.

4. The ultra-thin heat-resistant polyester film according to claim 2, characterized in that, The hydroxyl-terminated hyperbranched polyester is HyPer H2O4.

5. The ultrathin heat-resistant polyester film according to claim 1, characterized in that, The antioxidant is at least one of antioxidant 1010 and antioxidant 168; the lubricant is erucamide.

6. The ultra-thin heat-resistant polyester film according to claim 1, characterized in that, The coupling agent is at least one of silane coupling agent KH550, silane coupling agent KH560, and silane coupling agent KH570; the nanofiller is a compound of nano alumina, nano zirconium oxide, and nano boron nitride in a mass ratio of (1-3):1:(0.8-1.2); the average particle size of the nanofiller is 10-80 nm.

7. The ultra-thin heat-resistant polyester film according to claim 1, characterized in that, The glass fiber is alkali-free glass fiber with an average diameter of 0.1-0.3µm and an aspect ratio of (10-15):1; the methacryloyloxypropyl cage-type polysilsesquioxane is methacryloyloxypropyl cage-type polysilsesquioxane Ecotion®POSS102; the ultraviolet absorber is a mixture of light stabilizer UV-944 and ultraviolet absorber UV-327 in a mass ratio of 1:(1-3).

8. A method for preparing an ultrathin heat-resistant polyester film according to any one of claims 1-7, characterized in that, The process includes the following steps: The raw materials are mixed evenly according to their weight proportions to obtain a mixture. This mixture is then added to a twin-screw extruder. The melt is filtered through a two-stage disc filter with a coarse filtration aperture of 20 μm and a fine filtration aperture of 10 μm. The filtered melt is extruded through a die into a cooling drum with a die lip opening of 1.2-1.3 mm, a pre-stretch ratio of 6-10, a cooling drum linear speed of 70-75 m / min, and a cooling drum temperature of 25-30℃. Steel wire electrostatic electrodes are used to ensure the film adheres tightly to the cooling drum. After biaxial stretching, the film undergoes corona treatment and is then wound up at a temperature of 23±2℃ and a relative humidity of 50-60% at a winding speed of 200-250 m / min to obtain an ultra-thin heat-resistant polyester film with a thickness of 5-8 μm.

9. The method for preparing the ultrathin heat-resistant polyester film according to claim 8, characterized in that, The extrusion temperature of the twin-screw extruder is controlled in segments as follows: feeding section 240-250℃, compression section 265-275℃, homogenization section 275-285℃, die temperature 280-285℃, and screw speed 250-300 r / min.

10. The method for preparing the ultrathin heat-resistant polyester film according to claim 8, characterized in that, The bidirectional stretching includes longitudinal stretching and transverse stretching. The longitudinal stretching adopts high-temperature two-point small-gap stretching, with a preheating section temperature of 90-100℃, a stretching section temperature of 105-115℃, a stretching ratio of 4.2-5.0, a cooling section temperature of 25-30℃, and a cooling roller diameter of 250mm. The transverse stretching has a preheating section temperature of 95-105℃, a stretching section temperature of 100-110℃, a stretching ratio of 4.0-4.8, a heat setting section temperature of 230-245℃, a holding time of 4-6s, and a cooling section temperature of 50-60℃.

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