A copolyester material, its preparation and use

Abstract

This invention belongs to the field of polymer materials technology, specifically relating to a copolyester material, its preparation method, and its applications. The invention involves mixing succinic acid, 1,4-butanediol, 1,4-cyclohexanedicarboxylic acid, and an organometallic catalyst, and conducting an esterification reaction under a protective atmosphere to obtain a prepolymer. The prepolymer is then subjected to a polycondensation reaction under vacuum conditions to obtain the copolyester material. The 1,4-cyclohexanedicarboxylic acid is either cis- or trans-1,4-cyclohexanedicarboxylic acid. The molar amount of 1,4-cyclohexanedicarboxylic acid is 5-20% of the total molar amount of succinic acid and 1,4-cyclohexanedicarboxylic acid. The preparation method provided by this invention, by using a single configuration of 1,4-cyclohexanedicarboxylic acid and limiting the amount of 1,4-cyclohexanedicarboxylic acid added, results in a copolyester material with excellent mechanical properties, gas barrier properties, optical transparency, and ultraviolet shielding ability.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials technology, specifically relating to a copolyester material, its preparation method, and its application. Background Technology

[0002] Currently, replacing traditional petroleum-based plastics with sustainable materials, such as bio-based materials and recyclable polymers, has become a mainstream trend in the plastics industry. Among them, polybutylene succinate (PBS) has become a strong candidate to replace traditional plastics such as polypropylene (PP), polystyrene (PS), polyethylene terephthalate (PET), and polylactic acid (PLA) due to its good processing properties, complete biodegradability, and bio-based production potential. However, the mechanical properties and gas barrier properties of PBS are inferior to those of petroleum-based materials such as polypropylene (PP) and polyethylene (PE), and its cost remains significantly higher than that of traditional petroleum-based materials.

[0003] Existing technologies typically employ copolymerization to introduce rigid monomers, such as aromatic or alicyclic diacids, to improve the mechanical and gas barrier properties of PBS. Among these, 1,4-cyclohexanedicarboxylic acid (1,4-cyclohexanedicarboxylic acid) has attracted widespread attention due to its cyclohexane structure, which enhances the rigidity of PBS. However, current research often utilizes mixed configurations of 1,4-cyclohexanedicarboxylic acid, resulting in polyester materials that still exhibit poor mechanical and gas barrier properties. Summary of the Invention

[0004] The purpose of this invention is to provide a copolyester material, its preparation method, and its applications. The copolyester material prepared by the method provided by this invention exhibits excellent mechanical properties and gas barrier properties.

[0005] To achieve the above objectives, the present invention provides the following technical solution: A method for preparing a copolyester material includes the following steps: Succinic acid, 1,4-butanediol, 1,4-cyclohexanedicarboxylic acid and organometallic catalyst were mixed and esterified under a protective atmosphere to obtain a prepolymer. The prepolymer was subjected to a polycondensation reaction under vacuum conditions to obtain a copolyester material. The 1,4-cyclohexanedicarboxylic acid is either cis-1,4-cyclohexanedicarboxylic acid or trans-1,4-cyclohexanedicarboxylic acid; The molar amount of 1,4-cyclohexanedicarboxylic acid is 5 to 20% of the total molar amount of succinic acid and 1,4-cyclohexanedicarboxylic acid.

[0006] Preferably, the total molar amount of succinic acid and 1,4-cyclohexanedicarboxylic acid to 1,4-butanediol is in a molar ratio of 1:1 to 1.2.

[0007] Preferably, the organometallic catalyst comprises tetrabutyl titanate and / or zinc acetate; the mass of the organometallic catalyst is 0.05 to 0.15% of the total mass of succinic acid and 1,4-cyclohexanedicarboxylic acid.

[0008] Preferably, the esterification reaction is carried out at a temperature of 140~180℃ for 2~6h; the heating rate to the esterification reaction temperature is 2~10℃ / min.

[0009] Preferably, the pressure of the vacuum condition is 10~100 Pa.

[0010] Preferably, the polycondensation reaction is carried out at a temperature of 210~230℃ for 4~8 hours.

[0011] Preferably, the polycondensation reaction is followed by sequential cooling, crushing, and granulation.

[0012] The present invention provides a copolyester material prepared by the preparation method described in the above technical solution.

[0013] Preferably, the copolyester material has a tensile strength of 24.4~40.1 MPa, an elongation at break of 431.4~1862.2%, an oxygen permeability coefficient of 0.09~0.22 barrer, and a water vapor permeability coefficient of 0.50×10⁻⁶. -13 ~2.22×10 - 13 g·cm·cm -2 ·s -1 ·Pa -1 The light transmittance is 65-84.5%, and the ultraviolet shielding rate is 65-99%.

[0014] This invention provides the application of the copolyester material described in the above technical solution in packaging and engineering plastics.

[0015] The method for preparing copolyester materials provided by this invention uses cis-1,4-cyclohexanedicarboxylic acid or trans-1,4-cyclohexanedicarboxylic acid as rigid comonomers. Through esterification and polycondensation reactions with succinic acid and 1,4-butanediol, the mechanical and barrier properties of the copolyester materials are improved. The 1,4-cyclohexanedicarboxylic acid used in this invention has a cis-trans spatial configuration. The steric hindrance effect of the single-configuration 1,4-cyclohexanedicarboxylic acid can induce the formation of a high-density amorphous chain entanglement network while inhibiting excessive growth of crystalline regions. This significantly improves the elongation at break of the copolyester material without significantly sacrificing strength, achieving a synergistic improvement in high strength and ultra-high toughness. Furthermore, the dense amorphous entanglement network effectively reduces the free volume of the polymer, significantly improving the barrier properties of the copolyester material against oxygen and water vapor. The copolyester material prepared by this invention has a tensile strength of 24.4~40.1 MPa, an elongation at break of 431.4~1862.2%, an oxygen permeability coefficient of 0.09~0.22 barrer, and a water vapor permeability coefficient of 0.50×10⁻⁶. -13 ~2.22×10 -13 g·cm·cm -2 ·s -1 ·Pa -1 .

[0016] Furthermore, the copolyester material of the present invention has good optical transparency and ultraviolet shielding ability, and also has good long-term stability, with a visible light transmittance of 65~84.5% and an ultraviolet shielding rate of 65~99%.

[0017] Furthermore, this invention further optimizes the overall performance of copolyester materials by limiting the amount of 1,4-cyclohexanedicarboxylic acid (CHDA) with a single configuration. When the single-configuration CHDA accounts for 5-20% of the total molar amount of the diacid, the steric hindrance effect and crystallization inhibition effect reach the optimal balance, effectively inducing the formation of a high-density amorphous entanglement network while avoiding excessive inhibition of the crystalline region. This results in a significant increase in elongation at break (431.4-1862.2%) while maintaining high tensile strength (24.4-40.1 MPa), and a significant improvement in oxygen and water vapor barrier properties. When the molar amount of CHDA is less than 10%, the introduction of rigid units is insufficient, the entanglement network is inadequate, and the performance improvement is limited. When the molar amount of CHDA is greater than 20%, excessive inhibition of the crystalline region leads to a decrease in material rigidity and a reduction in overall performance. Further, when CHDA accounts for 15% of the total molar amount of the diacid, its overall performance is optimal. The copolyester material of this invention can be widely used in the fields of packaging and engineering plastics. Attached Figure Description

[0018] Figure 1 The Fourier transform infrared (FTIR) spectra of the copolyester materials prepared in Examples 1-8 of this invention and the polyester material prepared in Comparative Example 1 are shown. Figure 2 The proton nuclear magnetic resonance spectra of the copolyester materials prepared in embodiments 1, 3, 5, and 7 of this invention and the polyester material prepared in Comparative Example 1 are shown below. 1 H NMR spectrum; Figure 3 The proton nuclear magnetic resonance spectra of the copolyester materials prepared in embodiments 2, 4, 6, and 8 of this invention and the polyester material prepared in Comparative Example 1 are shown below. 1 H NMR spectrum; Figure 4 The X-ray diffraction (XRD) spectra of the copolyester materials prepared in Examples 1-8 of this invention and the polyester material prepared in Comparative Example 1 are shown. Figure 5 Thermogravimetric analysis (TGA) curves of the copolyester materials prepared in Examples 1-8 of the present invention and the polyester material prepared in Comparative Example 1 are shown. Figure 6 Differential thermogravimetric (DTG) curves of the copolyester materials prepared in Examples 1-8 of this invention and the polyester material prepared in Comparative Example 1; Figure 7 The stress-strain curves of the copolyester materials prepared in Examples 1-8 of the present invention and the polyester material prepared in Comparative Example 1 are shown. Figure 8 The ultraviolet-visible transmission spectra of the copolyester materials prepared in Examples 1-8 of this invention and the polyester material prepared in Comparative Example 1 are shown. Figure 9 The bar chart shows the oxygen permeability coefficients of the copolyester materials prepared in Examples 1-8 of this invention and the polyester material prepared in Comparative Example 1. Figure 10 The bar chart shows the water vapor permeability coefficients of the copolyester materials prepared in Examples 1-8 of this invention and the polyester material prepared in Comparative Example 1. Figure 11 The bar chart shows the weight retention rate of the copolyester material prepared in Example 7 of this invention after being soaked in different solvents for 7 days. Detailed Implementation

[0019] This invention provides a method for preparing a copolyester material, comprising the following steps: Succinic acid, 1,4-butanediol, 1,4-cyclohexanedicarboxylic acid and organometallic catalyst were mixed and esterified under a protective atmosphere to obtain a prepolymer. The prepolymer was subjected to a polycondensation reaction under vacuum conditions to obtain a copolyester material. The 1,4-cyclohexanedicarboxylic acid is either cis-1,4-cyclohexanedicarboxylic acid or trans-1,4-cyclohexanedicarboxylic acid; The molar amount of 1,4-cyclohexanedicarboxylic acid is 5 to 20% of the total molar amount of succinic acid and 1,4-cyclohexanedicarboxylic acid.

[0020] In this invention, unless otherwise specified, all raw materials / components used in the preparation are commercially available products well known to those skilled in the art.

[0021] This invention involves mixing succinic acid, 1,4-butanediol, 1,4-cyclohexanedicarboxylic acid, and an organometallic catalyst, and then performing an esterification reaction under a protective atmosphere to obtain a prepolymer. The 1,4-cyclohexanedicarboxylic acid is either cis-1,4-cyclohexanedicarboxylic acid (cis-CHDA) or trans-1,4-cyclohexanedicarboxylic acid (trans-CHDA), and the molar amount of the 1,4-cyclohexanedicarboxylic acid is 5-20% of the total molar amount of succinic acid and 1,4-cyclohexanedicarboxylic acid, specifically 5%, 10%, 15%, or 20%.

[0022] In one embodiment of the present invention, the total molar amount of succinic acid (SA) and 1,4-cyclohexanedicarboxylic acid (CHDA) to 1,4-butanediol (BDO) is in a molar ratio of 1:1 to 1.2, specifically 1:1, 1:1.1 or 1:1.2.

[0023] In one embodiment of the present invention, the organometallic catalyst comprises tetrabutyl titanate (TBT) and / or zinc acetate; the mass of the organometallic catalyst is 0.05~0.15% of the total mass of succinic acid and 1,4-cyclohexanedicarboxylic acid, specifically 0.05%, 0.10% or 0.15%.

[0024] In one embodiment of the present invention, the protective atmosphere includes a nitrogen atmosphere, the esterification reaction is carried out under normal pressure and stirring conditions, the temperature of the esterification reaction is 140~180℃, specifically 160℃, and the time is 2~6h, specifically 4h; the heating rate to the esterification reaction temperature is 2~10℃ / min, specifically 2℃ / min, 4℃ / min, 6℃ / min, 8℃ / min or 10℃ / min; after the esterification reaction, a prepolymer and by-product water are obtained, and the by-product water is collected and removed by a water separator.

[0025] After obtaining the prepolymer, the present invention performs a polycondensation reaction on the prepolymer under vacuum conditions to obtain a copolyester material. In one embodiment of the present invention, the pressure of the vacuum condition is 10~100 Pa, the temperature of the polycondensation reaction is 210~230℃, specifically 210℃, 220℃, or 230℃, and the time is 4~8 hours, specifically 6 hours; the heating rate from the esterification reaction temperature to the polycondensation reaction temperature is 10℃ / min.

[0026] In one embodiment of the present invention, the polycondensation reaction is further followed by cooling, crushing and granulation in sequence; after the polycondensation reaction, a molten polyester material is obtained, the molten polyester material is cooled to room temperature, the particle size is crushed to 5-10 mm, or more specifically 5-8 mm, and the granulation yields a cylindrical copolyester material with a diameter of 3-5 mm and a length of 4-6 mm.

[0027] This invention provides a copolyester material prepared by the preparation method described in the above technical solution. As one embodiment of this invention, the copolyester material has a tensile strength of 24.4~40.1 MPa, an elongation at break of 431.4~1862.2%, an oxygen permeability coefficient of 0.09~0.22 barrer, and a water vapor permeability coefficient of 0.50×10⁻⁶. -13 ~2.22×10 -13 g·cm·cm -2 ·s -1 ·Pa -1 The light transmittance is 65-84.5%, and the ultraviolet shielding rate is 65-99%.

[0028] This invention provides the application of the copolyester material described in the above technical solution in packaging and engineering plastics.

[0029] To further illustrate the present invention, the technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments thereof. Obviously, the described embodiments are merely some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0030] Example 1 Under nitrogen protection, succinic acid (0.95 mol, 112.2 g), 1,4-butanediol (1.2 mol, 108.1 g), and cis-1,4-cyclohexanedicarboxylic acid (0.05 mol, 8.6 g) were added to a 500 mL three-necked flask. The molar amount of cis-1,4-cyclohexanedicarboxylic acid was 5% of the total molar amount of succinic acid and cis-1,4-cyclohexanedicarboxylic acid. 0.06 g of tetrabutyl titanate was added to the reaction system, the mass of which was 0.06 g of the total mass of succinic acid and cis-1,4-cyclohexanedicarboxylic acid. 0.05%; The temperature was increased from room temperature to 160°C at a rate of 10°C / min, and esterification was carried out for 4 hours under normal pressure and mechanical stirring. Water was removed as a byproduct through a water separator to obtain a prepolymer. The temperature was increased from 160°C to 210°C at a rate of 10°C / min, and a vacuum was applied to a pressure below 100 Pa. The prepolymer was then subjected to a polycondensation reaction for 6 hours to obtain a molten polyester material. The molten polyester material was cooled to room temperature, pulverized, and granulated to obtain a cylindrical copolyester material with a diameter of 3 mm and a length of 4 mm, denoted as PBSC. 5-c .

[0031] Example 2 The process is essentially the same as in Example 1, except that cis-1,4-cyclohexanedicarboxylic acid (0.05 mol, 8.6 g) is replaced with trans-1,4-cyclohexanedicarboxylic acid (0.05 mol, 8.6 g). The resulting copolyester material is designated PBSC. 5-t .

[0032] Example 3 The process is essentially the same as in Example 1, except that the amount of cis-1,4-cyclohexanedicarboxylic acid (0.05 mol, 8.6 g) added is changed to cis-1,4-cyclohexanedicarboxylic acid (0.10 mol, 17.2 g), and the amount of succinic acid (0.95 mol, 112.2 g) added is changed to succinic acid (0.90 mol, 106.3 g). The resulting copolyester material is designated PBSC. 10-c .

[0033] Example 4 (PBSC10-t) The process is essentially the same as in Example 1, except that cis-1,4-cyclohexanedicarboxylic acid (0.05 mol, 8.6 g) is replaced with trans-1,4-cyclohexanedicarboxylic acid (0.10 mol, 17.2 g), and the amount of succinic acid (0.95 mol, 112.2 g) is replaced with succinic acid (0.90 mol, 106.3 g). The resulting copolyester material is designated PBSC. 10-t .

[0034] Example 5 The process is essentially the same as in Example 1, except that the amount of cis-1,4-cyclohexanedicarboxylic acid (0.05 mol, 8.6 g) added is changed to cis-1,4-cyclohexanedicarboxylic acid (0.15 mol, 25.8 g), and the amount of succinic acid (0.95 mol, 112.2 g) added is changed to succinic acid (0.85 mol, 100.4 g). The resulting copolyester material is designated PBSC. 15-c .

[0035] Example 6 The process is essentially the same as in Example 1, except that cis-1,4-cyclohexanedicarboxylic acid (0.05 mol, 8.6 g) is replaced with trans-1,4-cyclohexanedicarboxylic acid (0.15 mol, 25.8 g), and the amount of succinic acid (0.95 mol, 112.2 g) is replaced with succinic acid (0.85 mol, 100.4 g). The resulting copolyester material is designated PBSC. 15-t .

[0036] Example 7 The process is essentially the same as in Example 1, except that the amount of cis-1,4-cyclohexanedicarboxylic acid (0.05 mol, 8.6 g) added is changed to cis-1,4-cyclohexanedicarboxylic acid (0.20 mol, 34.4 g), and the amount of succinic acid (0.95 mol, 112.2 g) added is changed to succinic acid (0.80 mol, 94.5 g). The resulting copolyester material is designated PBSC. 20-c .

[0037] Example 8 The process is essentially the same as in Example 1, except that cis-1,4-cyclohexanedicarboxylic acid (0.05 mol, 8.6 g) is replaced with trans-1,4-cyclohexanedicarboxylic acid (0.20 mol, 34.4 g), and the amount of succinic acid (0.95 mol, 112.2 g) is replaced with succinic acid (0.80 mol, 94.5 g). The resulting copolyester material is designated PBSC. 20-t .

[0038] Comparative Example 1: 1,4-Cyclohexanedicarboxylic acid (CHDA) omitted. Under nitrogen protection, succinic acid (1.0 mol, 118.1 g) and 1,4-butanediol (1.2 mol, 108.1 g) were added to a 500 mL three-necked flask, without adding cis-1,4-cyclohexanedicarboxylic acid. 0.06 g of tetrabutyl titanate was added to the reaction system, the mass of which was 0.05% of the mass of succinic acid. The temperature was increased from room temperature to 160 °C at a rate of 10 °C / min, and the esterification reaction was carried out for 4 h under normal pressure and mechanical stirring. The byproduct water was collected to obtain a prepolymer. The temperature was increased from 160 °C to 210 °C at a rate of 10 °C / min, and a vacuum was applied to a pressure below 100 Pa. The prepolymer was then subjected to a polycondensation reaction for 6 h to obtain a molten polyester material. The molten polyester material was cooled to room temperature, pulverized, and granulated to obtain a cylindrical polyester material with a diameter of 3 mm and a length of 4 mm, denoted as PBS.

[0039] Test Example 1: Fourier Transform Infrared Spectroscopy (FTIR) Test The chemical structures of the copolyester materials prepared in Examples 1-8 and the polyester material prepared in Comparative Example 1 were characterized using a Thermo Scientific Nicolet iS50 Fourier transform infrared spectrometer. The wavenumber range for testing was 4000–400 cm⁻¹. -1 The number of scans was 32, and the resolution was 4cm. -1 All samples were vacuum-dried at 60℃ for 24 hours before testing. Results are as follows: Figure 1 As shown.

[0040] Figure 1 The images show the Fourier transform infrared (FTIR) spectra of the copolyester materials prepared in Examples 1-8 and the polyester material prepared in Comparative Example 1. Figure 1 It can be seen that all samples are at approximately 1715cm. -1 A strong absorption peak appears at 2950-2850 cm⁻¹, attributed to the stretching vibration of the ester carbonyl group (C=O); [further absorption occurs in the 2950–2850 cm⁻¹ range.] -1 Aliphatic CH stretching vibration peaks appeared within the range; at 1150 cm⁻¹ -1 A stretching vibration peak of COC appeared nearby. Compared with Comparative Example 1, no new characteristic absorption peaks appeared in the copolyester materials of Examples 1-8, indicating that the CHDA unit had been successfully embedded into the polymer backbone through ester bonds. Furthermore, in the 2500-3500 cm⁻¹ range... -1 No broad peaks of free carboxyl groups were observed within the range, indicating a high conversion rate in the esterification reaction.

[0041] Test Example 2: Proton NMR Spectroscopy (NMR) 1 H NMR test The copolyester materials prepared in Examples 1-8 and the polyester material prepared in Comparative Example 1 were structurally characterized using a Bruker AVANCE III HD-400 nuclear magnetic resonance spectrometer (400 MHz). Using deuterated chloroform (CDCl3) as solvent and tetramethylsilane (TMS) as an internal standard, the actual CHDA embedding ratio in the copolymers was calculated by integrating the characteristic peak areas. The results are as follows: Figure 2 and Figure 3 As shown.

[0042] Figure 2 The proton nuclear magnetic resonance spectra of the copolyester materials prepared in embodiments 1, 3, 5, and 7 of this invention and the polyester material prepared in Comparative Example 1 are shown below. 1 H NMR spectrum; Figure 3 The proton nuclear magnetic resonance spectra of the copolyester materials prepared in embodiments 2, 4, 6, and 8 of this invention and the polyester material prepared in Comparative Example 1 are shown below. 1 H NMR spectrum. Figure 2 and Figure 3 It can be seen that the multiplet at chemical shift δ=4.14ppm belongs to the methylene proton attached to the ester oxygen in the BDO unit; the singlet at δ=2.65ppm belongs to the methylene proton adjacent to the carbonyl group in the SA unit; and the signal in the range of δ=2.28~2.52ppm represents the methine proton directly attached to the carboxyl group on the CHDA ring. Integral calculations show that the actual molar ratio of CHDA insertion is highly consistent with the feed ratio, indicating that no significant CHDA decomposition or selectivity loss occurred during polymerization. Furthermore, no characteristic signal of cis-to-trans isomerization was detected, proving that the configuration was well maintained.

[0043] Test Example 3: X-ray Diffraction (XRD) Test The crystal structures of the copolyester materials prepared in Examples 1-8 and the polyester material prepared in Comparative Example 1 were characterized using a Rigaku SmartLab SE X-ray diffractometer. Test conditions: Cu-Kα radiation (λ=1.541Å), tube voltage 40 kV, tube current 40 mA, scanning range 2θ=5°~60°, scanning rate 2° / min. The crystallinity (Xc) of the samples was calculated using the peak fractionation method. The results are as follows... Figure 4 As shown.

[0044] Figure 4 The images show the X-ray diffraction (XRD) spectra of the copolyester materials prepared in Examples 1-8 and the polyester material prepared in Comparative Example 1. Figure 4It can be seen that PBS exhibits three characteristic diffraction peaks at 2θ = 19.6°, 22.1°, and 24.5°, corresponding to the (020), (110), and (111) crystal planes of the α-crystal form. The diffraction peak positions of the copolyester materials in Examples 1-8 are basically consistent with those of PBS in Comparative Example 1, indicating that the introduction of CHDA did not change the crystal form of PBS. However, the diffraction peak intensities decreased significantly, and the crystallinity decreased from 45.6% of PBS to PBSC. 20-t 22.7% and PBSC 20-c The 20.7% figure indicates that the rigid ring structure and steric hindrance effect of CHDA effectively suppress the regular arrangement of polymer chains and crystallization ability.

[0045] Test Example 4: Thermogravimetric Analysis (TGA) Test The thermal stability of the copolyester materials prepared in Examples 1-8 and the polyester material prepared in Comparative Example 1 was tested using a Netzsch STA 449 F3 thermogravimetric analyzer. Test conditions: nitrogen atmosphere, flow rate 40 mL / min, heating rate 10 °C / min, temperature range 30–800 °C. The 5% thermogravimetric temperature (T5%) and the maximum decomposition temperature (Tmax) were recorded. Results are as follows: Figure 5 and Figure 6 As shown.

[0046] Figure 5 Thermogravimetric analysis (TGA) curves of the copolyester materials prepared in Examples 1-8 of the present invention and the polyester material prepared in Comparative Example 1 are shown. Figure 6 The differential thermogravimetric (DTG) curves are shown for the copolyester materials prepared in Examples 1-8 of this invention and the polyester material prepared in Comparative Example 1. According to... Figure 5 and Figure 6 It was found that none of the samples showed significant mass loss below 300℃, demonstrating good thermal stability. Compared with PBS, the 5% thermogravimetric temperature and maximum decomposition temperature of the copolyester materials after the introduction of CHDA were both increased, and the values ​​increased with increasing CHDA content. Among them, the cis-CHDA modified copolyester materials exhibited higher thermal decomposition temperatures than the trans-CHDA modified copolyester materials, indicating that the rigid cyclic structure and steric hindrance effectively suppressed the movement of molecular chains at high temperatures, enabling the copolyester materials to maintain structural stability over a wide temperature range, making them suitable for high-temperature processing and long-term use.

[0047] Test Example 5: Mechanical Property Test The tensile properties of the copolyester materials prepared in Examples 1-8 and the polyester material prepared in Comparative Example 1 were tested using an Instron 3366 universal testing machine according to GB / T 1040.4-2006 standard. The samples were injection-molded 2A dumbbell-shaped strips. The test temperature was room temperature, and the tensile rate was 50 mm / min. At least five parallel samples were tested for each sample, and the average value was recorded. The tensile strength and elongation at break were recorded. The results are as follows: Figure 7 As shown.

[0048] Figure 7 The stress-strain curves are shown for the copolyester materials prepared in Examples 1-8 and the polyester material prepared in Comparative Example 1. Figure 7 It can be seen that PBS (Comparative Example 1) exhibits typical characteristics of a semi-crystalline polymer: tensile strength 28.1 ± 1.0 MPa, elongation at break 339.0 ± 33.2%; with the increase of CHDA content, the elongation at break of the copolyester material significantly increases. Among them, PBSC 15-c The tensile strength reached 40.1±0.2MPa, and the elongation at break reached 1834.1±28.7%, PBSC 15-t The tensile strength reached 36.6±0.7 MPa, and the elongation at break reached 1822.2±41.9%, slightly lower than that of the cis sample. When the CHDA content increased to 20%, PBSC... 20-c and PBSC 20-t The decrease in elongation at break indicates that a CHDA content of 15% is the optimal ratio.

[0049] Test Example 6: Ultraviolet-Visible Light Transmittance and Ultraviolet Shielding Performance Test The optical properties of polyester films prepared from the copolyester materials in Examples 1-8 and the polyester material in Comparative Example 1 were tested using a Shimadzu UV-2600 UV-Vis spectrophotometer. The film thickness was 0.1 mm, the scanning wavelength range was 200–800 nm, and measurements were taken at room temperature. The average transmittance in the visible region (400–760 nm) and the blocking rates in the UVB band (280–315 nm) and UVA band (315–400 nm) were recorded. The results are as follows: Figure 8 As shown.

[0050] Figure 8 The images show the UV-Vis transmission spectra of the copolyester materials prepared in Examples 1-8 and the polyester material prepared in Comparative Example 1. Figure 8 It can be seen that all thin film samples have high transmittance (65%~84.5%) in the visible light region (400~760nm); in the ultraviolet B band (280~315nm), PBS has a lower blocking rate, while PBSC... 5-cThe blocking rate is close to complete (>99%); in the UV A band (315~400nm), PBSC 5-c The barrier properties reached over 65%. This indicates that the introduction of CHDA enhanced the intermolecular electronic coupling through a dense amorphous network, giving the copolyester material excellent UV shielding capabilities while maintaining good transparency.

[0051] Test Example 7: Oxygen Barrier Performance Test The oxygen permeability coefficients of polyester films (2 mm thick) prepared from the copolyester materials in Examples 1-8 and the polyester material in Comparative Example 1 were determined using a Labthink OX2 / 231 oxygen permeability tester according to GB / T 1038 standard. Test conditions: temperature 23℃, relative humidity 0%, pressure difference method. Oxygen permeability coefficient (PO2) is expressed in barrers (1 barrer = 10⁻⁶). -10 cm 3 (STP)·cm·cm -2 ·s -1 ·cmHg -1 The result is as follows: Figure 9 As shown.

[0052] Figure 9 The bar chart shows the oxygen permeability of the copolyester materials prepared in Examples 1-8 and the polyester material prepared in Comparative Example 1. According to... Figure 9 It can be seen that the oxygen permeability coefficient of PBS is 0.25 barrer, and the oxygen permeability coefficient gradually decreases with the increase of CHDA content; PBSC 20-c and PBSC 20-t The oxygen permeability coefficients decreased to 0.09 barrer and 0.11 barrer, respectively. At the same CHDA content, the cis sample showed better barrier performance than the trans sample. This is because the stronger steric hindrance effect of cis CHDA induces the formation of a denser amorphous entangled network, reducing the free volume and thus effectively hindering the diffusion of oxygen molecules.

[0053] Test Example 8: Water Vapor Barrier Performance Test The water vapor transmission coefficient of polyester films (2 mm thick) prepared from the copolyester materials in Examples 1-8 and the polyester material in Comparative Example 1 was determined using a Labthink VAC-V2 water vapor transmission rate tester according to GB / T 1037 standard (cup method). Test conditions: temperature 38℃, relative humidity 90%, water vapor transmission coefficient (PH2O) unit is g·cm·cm. -2 ·s -1 ·Pa -1 The result is as follows Figure 10 As shown.

[0054] Figure 10 The bar chart shows the water vapor transmission coefficients of the copolyester materials prepared in Examples 1-8 and the polyester material prepared in Comparative Example 1. According to... Figure 10 It can be seen that the water vapor permeability coefficient of PBS is 3.10 × 10⁻⁶. -13 g·cm·cm -2 ·s -1 ·Pa -1 PBSC 20-c and PBSC 20-t The water vapor permeability coefficient decreased to 0.50×10⁻⁶. -13 g·cm·cm -2 ·s -1 ·Pa -1 and 0.51×10 -13 g·cm·cm -2 ·s -1 ·Pa -1 This indicates that the dense amorphous network and smoother surface morphology effectively inhibit the adsorption and diffusion of water molecules.

[0055] Test Example 9: Solvent Resistance Test Polyester films (20 mg, 2 mm thick) prepared from the copolyester materials in Examples 1-8 and the polyester material in Comparative Example 1 were respectively immersed in 1 M solutions of HCl, N,N-dimethylformamide (DMF), ethanol (EtOH), toluene (TOL), and acetone (ACE) at room temperature for 7 days. After immersion, the polyester film samples were removed, rinsed with fresh solvent, vacuum dried at 60 °C for 24 h, and weighed. The weight retention rate was calculated using the following formula: Where M1 is the initial mass and M2 is the mass after soaking and drying. The results are as follows: Figure 11 As shown.

[0056] Figure 11 This is a bar chart showing the weight retention rate of the copolyester material prepared in Example 7 of the present invention after immersion in different solvents for 7 days. According to... Figure 11 It can be seen that after immersion in representative corrosive solvents such as 1M HCl (strong acid), DMF (polar aprotic solvent), EtOH (alcohol), TOL (aromatic solvent), and ACE (ketone), PBSC 20-c The film showed no visible damage or corrosion, with a mass loss of less than 1.7%. This excellent chemical stability stems from the dense entangled network and the reduction in free volume caused by steric hindrance, which effectively inhibits solvent penetration and diffusion.

[0057] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A method for preparing a copolyester material, comprising the following steps: Succinic acid, 1,4-butanediol, 1,4-cyclohexanedicarboxylic acid and organometallic catalyst were mixed and esterified under a protective atmosphere to obtain a prepolymer. The prepolymer was subjected to a polycondensation reaction under vacuum conditions to obtain a copolyester material. The 1,4-cyclohexanedicarboxylic acid is either cis-1,4-cyclohexanedicarboxylic acid or trans-1,4-cyclohexanedicarboxylic acid; The molar amount of 1,4-cyclohexanedicarboxylic acid is 5 to 20% of the total molar amount of succinic acid and 1,4-cyclohexanedicarboxylic acid.

2. The preparation method according to claim 1, characterized in that, The total molar amount of succinic acid and 1,4-cyclohexanedicarboxylic acid is in a molar ratio of 1:1 to 1.2 to 1,4-butanediol.

3. The preparation method according to claim 1, characterized in that, The organometallic catalyst comprises tetrabutyl titanate and / or zinc acetate; the mass of the organometallic catalyst is 0.05 to 0.15% of the total mass of succinic acid and 1,4-cyclohexanedicarboxylic acid.

4. The preparation method according to claim 1, characterized in that, The esterification reaction is carried out at a temperature of 140~180℃ for 2~6h; the heating rate to the esterification reaction temperature is 2~10℃ / min.

5. The preparation method according to claim 1, characterized in that, The pressure under the vacuum condition is 10~100 Pa.

6. The preparation method according to claim 1, characterized in that, The polycondensation reaction is carried out at a temperature of 210~230℃ for 4~8 hours.

7. The preparation method according to claim 1, characterized in that, The polycondensation reaction is followed by sequential cooling, crushing, and granulation.

8. The copolyester material prepared by the preparation method according to any one of claims 1 to 7.

9. The copolyester material according to claim 8, characterized in that, The copolyester material has a tensile strength of 24.4~40.1 MPa, an elongation at break of 431.4~1862.2%, an oxygen permeability coefficient of 0.09~0.22 barrer, and a water vapor permeability coefficient of 0.50×10⁻⁶. -13 ~2.22×10 -13 g·cm·cm -2 ·s -1 ·Pa -1 The light transmittance is 65-84.5%, and the ultraviolet shielding rate is 65-99%.

10. The use of the copolyester material according to claim 8 or 9 in packaging and engineering plastics.

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