Preparation method of modified polyester and catalyst

Abstract

The preparation method comprises the following steps: sequentially carrying out esterification reaction and polycondensation reaction on terephthalic acid, ethylene glycol, equol or a derivative thereof in the presence of the catalyst to generate the modified polyester, wherein the catalyst is prepared by enabling antimony trioxide, stannous octoate, tetrabutyl titanate and triphenyl phosphite to react in a solvent at the temperature of 100 DEG C or above; the modified polyester prepared by the method has relatively high intrinsic viscosity and fracture tensile strength, can meet the application requirements of special high polymer materials, and solves the problem that the application of semi-biomass PET copolyester in the field of special high polymer materials is limited in the prior art.

Description

Technical Field

[0001] This invention relates to the field of biomass polymer material synthesis technology, and particularly to a multi-metal synergistic catalyst and a method for preparing semi-biomass polyethylene terephthalate-co-estradiol terephthalate using the catalyst, specifically to a method for preparing a modified polyester and a catalyst. Background Technology

[0002] Polyethylene terephthalate (PET) is a crystalline saturated polyester with excellent mechanical, barrier, acid, alkali, and weather resistance properties, and is widely used in textile fibers, automotive lightweighting, and packaging materials. Given the unsustainability of petrochemical resources and environmental concerns, replacing traditional petrochemical resources with biomass resources in the field of polymer materials is one approach. Currently, biomass monomers that can be used to prepare biomass PET copolyesters include 2,5-furandicarboxylic acid, 2,5-furandiethanol, 2,5-tetrahydrofurandicarboxylic acid, 2,5-tetrahydrofurandiethanol, isosorbide, itaconic acid, vanillic acid, lactic acid, 1,3-propanediol, and 1,10-sebacic acid. However, practical experience shows that the mechanical properties of these semi-biomass PET copolyesters do not meet the requirements for the use of special polymer materials.

[0003] It should be noted that the information disclosed in the background section above is only for understanding the background of this application. Therefore, the background section of this invention may include background information about the problems or environment of this invention, and is not necessarily a description of the prior art. Thus, the content included in the background section does not constitute an admission of the prior art by the applicant. Summary of the Invention

[0004] The purpose of this invention is to overcome one or more shortcomings in the prior art and provide a new method for preparing modified polyester. The modified polyester prepared by this method can have both high intrinsic viscosity and tensile strength at break, which can meet the application requirements of special polymer materials and solve the problem that the application of semi-biomass PET copolyester in the field of special polymer materials is limited in the prior art.

[0005] The present invention also provides a catalyst that can be used to prepare the above-mentioned modified polyester.

[0006] To achieve the above objectives, the present invention employs the following technical solution: A method for preparing a modified polyester, the method comprising: subjecting terephthalic acid, ethylene glycol, and the compound shown in formula (I) to an esterification reaction and a polycondensation reaction in the presence of a catalyst to generate a modified polyester; The catalyst is prepared by reacting antimony trioxide, stannous octoate, tetrabutyl titanate and triphenyl phosphite in a solvent at a temperature above 100°C. In equation (Ⅰ), R1 and R2 are independently selected from H and C. 1-6 Alkyl group =, a is selected from 1, 2 or 3, b is selected from 1, 2, 3 or 4.

[0007] In some embodiments of the present invention, R1 and R2 are independently selected from H, methyl, ethyl, n-propyl, and isopropyl.

[0008] According to one specific aspect of the present invention, the compound represented by formula (I) is 7-hydroxy-3-(4-hydroxyphenyl)-benzodihydropyran, also known as equadol, with the molecular formula Ci. 14 H 15 O3 is a heterocyclic structure containing two active hydroxyl groups and a relatively inert oxygen in its central pyran ring. It can be prepared by chemical synthesis (Bioorganic & Medicinal Chemistry, 2004, 12(6): 1559-1567.), microbial preparation (Journal of Food Processing and Preservation, 2019, 43(11): e14205.), and biosynthesis (Applied and Environmental Microbiology, 2013, 79(11): 3494-3502.).

[0009] The structural formula of equadol is as follows: .

[0010] Using equadol as the compound represented by formula (I) to prepare the modified polyester of the present invention, the structure of the prepared modified polyester is exemplarily shown below: .

[0011] In this invention, the catalyst is based on a multi-metal synergistic catalytic mechanism. Under the gradient catalysis of multiple components, it can significantly reduce the reaction activation energy, improve catalytic efficiency, and significantly enhance the intrinsic viscosity and mechanical strength of the final product. In addition, by introducing biomass equol as a third rigid monomer into the PET main chain structure, the mechanical strength of the product can be significantly improved while reducing the use of petroleum-based resources, thereby meeting the application needs of the field of special polymer materials and expanding the high-end application scenarios of PET.

[0012] In some embodiments of the present invention, the molar ratio of ethylene glycol to the compound shown in formula (I) is 1:0.01-99, and the ratio of the total molar amount of ethylene glycol and the compound shown in formula (I) to the molar amount of terephthalic acid is 1.0-2.2:1.

[0013] Furthermore, the molar ratio of the ethylene glycol to the compound shown in formula (I) is 1:0.1-60, even more so 1:0.2-40, and still more so 1:0.3-25.

[0014] According to some preferred and specific aspects of the invention, the molar ratio of the ethylene glycol to the compound represented by formula (I) is 1:0.5-15.

[0015] According to some preferred and specific aspects of the invention, the ratio of the total molar amount of the ethylene glycol and the compound represented by formula (I) to the molar amount of the terephthalic acid is 1.0-1.5:1.

[0016] In some embodiments of the present invention, the amount of catalyst added is 0.005 wt.% to 0.5 wt.% of the weight of the reaction system (all raw materials, including terephthalic acid, ethylene glycol, the compound shown in formula (I), and the catalyst). Further, the amount of catalyst added is 0.008 wt.% to 0.4 wt.% of the weight of the reaction system. Even further, the amount of catalyst added is 0.009 wt.% to 0.3 wt.% of the weight of the reaction system. Still further, the amount of catalyst added is 0.009 wt.% to 0.25 wt.% of the weight of the reaction system.

[0017] In some embodiments of the present invention, the reaction temperature of the esterification reaction is controlled to be 220-240°C.

[0018] In some embodiments of the present invention, the reaction temperature of the polycondensation reaction is controlled to be 240-280°C.

[0019] In some embodiments of the present invention, the esterification reaction is carried out in a protective atmosphere. Further, the protective atmosphere is formed by introducing nitrogen and / or an inert gas, which may include, but is not limited to, argon, helium, etc.

[0020] In some embodiments of the present invention, the method for preparing the modified polyester includes: (1) Esterification reaction: Under the protection of protective gas, terephthalic acid, ethylene glycol, the compound shown in formula (Ⅰ) and catalyst are added to the reaction vessel, and the reaction temperature is controlled at 220-240℃. (2) Pre-condensation reaction: The temperature inside the reaction vessel is raised to 240-260℃, and the vacuum degree is gradually reduced to below 1000Pa, and the reaction proceeds. (3) Final polycondensation reaction: The temperature inside the reaction vessel is raised to 260-280℃ and the vacuum is reduced to below 50Pa. The reaction is carried out to generate modified polyester.

[0021] In some embodiments of the present invention, the temperature rise rate inside the reaction vessel is controlled at 1-10°C / min, and more specifically at 2-8°C / min.

[0022] In some embodiments of the present invention, in step (1), the reaction time of the esterification reaction is controlled to be 3-8 hours.

[0023] In some embodiments of the present invention, in step (2), the reaction is carried out under vacuum of 7000-9000 Pa, 4000-6000 Pa, and 500-1000 Pa, respectively. Further, in step (2), the reaction is carried out under vacuum of 7500-8500 Pa, 4500-5500 Pa, and 800-1000 Pa, respectively.

[0024] In some embodiments of the present invention, in step (2), the reaction temperature of the pre-condensation reaction is 240-250°C.

[0025] In some embodiments of the present invention, in step (2), the reaction time of the pre-condensation reaction is not less than 1 hour, for example, it can be 1-24 hours, or 1-16 hours, or 1-12 hours, etc.

[0026] In some embodiments of the present invention, in step (3), the reaction temperature of the final polycondensation reaction is 270-280°C.

[0027] In some embodiments of the present invention, in step (3), the reaction time of the final polycondensation reaction is controlled to be 2-6 hours.

[0028] In some embodiments of the present invention, in step (3), after the final polycondensation is completed, the product is cooled by water, granulated, and dried to obtain a modified polyester (also known as polyethylene terephthalate-co-estradiol terephthalate).

[0029] Further, in step (3), after the final polycondensation is completed, the pressure in the reaction system is increased to 0.1~0.3MPa using nitrogen or inert gas. The product melt is then water-cooled and cut into particles. The particles are then placed in a vacuum oven to dry, thus obtaining polyethylene terephthalate-co-estradiol terephthalate.

[0030] According to some preferred aspects of the present invention, the mass ratio of the antimony trioxide, the stannous octoate, the tetrabutyl titanate, and the triphenyl phosphite is 1:1-10:1-15:1-5.

[0031] Furthermore, the mass ratio of the antimony trioxide, the stannous octoate, the tetrabutyl titanate, and the triphenyl phosphite is 1:1-8:1-12:1-5.

[0032] Furthermore, the mass ratio of the antimony trioxide, the stannous octoate, the tetrabutyl titanate, and the triphenyl phosphite is 1:1-6:1-10:1-5.

[0033] In some preferred embodiments of the present invention, the mass ratio of the antimony trioxide, the stannous octoate, the tetrabutyl titanate and the triphenyl phosphite is 1:1-5:2-10:1.5-5.

[0034] According to some specific aspects of the present invention, the mass ratio of the antimony trioxide, the stannous octoate, the tetrabutyl titanate, and the triphenyl phosphite is 1:1-3:2-5:2-4.

[0035] In some preferred embodiments of the present invention, during the preparation of the catalyst, the reaction temperature is controlled at 120-180°C, for example, 125°C, 130°C, 135°C, 140°C, 145°C, 150°C, 155°C, 160°C, 165°C, 170°C, or 175°C. Furthermore, during the preparation of the catalyst, the reaction time is controlled at 10-24 hours.

[0036] In some embodiments of the present invention, the method for preparing the catalyst includes: Step 1: Antimony trioxide, stannous octoate, tetrabutyl titanate and triphenyl phosphite are mixed and added to the solvent, and reacted at 120-180℃ for 10-24 hours. Step 2: After cooling the reactants to room temperature, filter them, wash and dry them to obtain a white solid, which is the catalyst (also known as a multi-metal synergistic catalyst).

[0037] In some embodiments of the present invention, the solvent used in the preparation of the catalyst is petroleum ether; further, the mass ratio of antimony trioxide to the solvent is 1:50-150, and even more specifically 1:80-100.

[0038] In some embodiments of the present invention, the reaction time is controlled to be 16-20 h during the preparation of the catalyst.

[0039] Another technical solution provided by the present invention is a catalyst (also known as a multi-metal synergistic catalyst), which is prepared by reacting antimony trioxide, stannous octoate, tetrabutyl titanate and triphenyl phosphite in a solvent at a temperature above 100°C.

[0040] Another technical solution provided by the present invention: a modified polyester, wherein the modified polyester is generated by sequentially subjecting terephthalic acid, ethylene glycol, and the compound shown in formula (I) to an esterification reaction and a polycondensation reaction in the presence of the above catalyst; In equation (Ⅰ), R1 and R2 are independently selected from H and C. 1-6 Alkyl group, where a is selected from 1, 2 or 3, and b is selected from 1, 2, 3 or 4.

[0041] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art: The mechanical properties of existing semi-biomass PET copolyesters are insufficient to meet the requirements of special polymer materials, such as relatively low tensile strength at break. This invention innovatively provides a modified polyester resin. This modified polyester resin, under the gradient catalysis of a specific multi-metal synergistic catalyst (different catalysts play different roles at different stages, especially since the components are pre-mixed and reacted, organically combining them through coordination and other mechanisms; specifically, antimony trioxide and triphenyl phosphite can provide active sites for the reaction system through a metal-ligand synergistic mechanism, accelerating the esterification reaction; simultaneously, triphenyl phosphite can also promote Sb-Sn-T through bridging). i. Forming polynuclear complexes, inhibiting metal aggregation, stabilizing multi-metal centers, and regulating the electronic and spatial environment, thereby promoting the formation of active intermediates between the catalyst and the reaction substrate, enhancing carbonyl polarization, lowering the reaction energy barrier, shifting the equilibrium towards polymerization, and improving reaction efficiency. Compared with simple physical mixing, the catalyst prepared by the pre-high-temperature reaction of this invention can achieve better catalytic effects. Using melt polycondensation, compounds shown in formula (I), such as biomass estrol monomer, are introduced into the PET main chain structure to obtain high-strength semi-biomass PET copolyester (intrinsic viscosity can reach 0.95~1.2 dL / g, tensile strength at break can reach 80~100 MPa), which can meet the application requirements of special polymer materials. Using the multi-metal synergistic catalyst of this invention, the rapid preparation of high-viscosity, high-strength polyethylene terephthalate-co-estrol terephthalate can be achieved. Attached Figure Description

[0042] Figure 1 A photograph of the catalyst prepared in Example 1-1 of this invention; Figure 2 The image shows the XRD pattern of the catalyst prepared in Example 1-1 of this invention. Detailed Implementation

[0043] The above-mentioned solution will be further described below with reference to specific embodiments; it should be understood that these embodiments are used to illustrate the basic principles, main features and advantages of the present invention, and the present invention is not limited to the scope of the following embodiments; the implementation conditions used in the embodiments can be further adjusted according to specific requirements, and the implementation conditions not specified are usually the conditions in conventional experiments.

[0044] Unless otherwise specified in the following examples, all raw materials were commercially available or prepared using conventional methods in the art. XRD testing method in the examples: The sample was uniformly laid on a backgroundless sample stage, and XRD was performed using a Bruker D8-Advance XRD system equipped with a Ni filter and a wavelength of 0.154 nm, producing Cu / Kα rays. Specifically, the XRD pattern was recorded at room temperature (25°C) within the range of 5.0–80.0° at a rate of 0.025° / s. Catalyst preparation Example 1-1:

[0045] This example provides a catalyst prepared by the following method: Antimony trioxide (2.92 g, 0.01 mol), stannous octoate (4.05 g, 0.01 mol), tetrabutyl titanate (6.81 g, 0.02 mol), and triphenyl phosphite (3.10 g, 0.01 mol) are mixed evenly and placed in a hydrothermal reactor containing petroleum ether (292 g). The mixture is reacted at 140°C for 18 h. After the reaction system is allowed to cool naturally to room temperature, it is filtered, washed, and dried to obtain a white solid, which is the catalyst (i.e., a multi-metal synergistic catalyst) C1. Figure 1 This is a photograph of the catalyst; it can be seen that it is a white powder. Figure 2 The image shows the XRD pattern of the catalyst. As can be seen from the image, the main diffraction peaks of the obtained catalyst are located at 11.8°, 26.9°, 31.0°, 45.8°, and 52.2°. Compared with the simple complex, there is an anisotropic shift, which indicates the formation of a polynuclear complex. Examples 1-2:

[0046] This example provides a catalyst prepared by the following method: Antimony trioxide (2.92 g, 0.01 mol), stannous octoate (8.10 g, 0.02 mol), tetrabutyl titanate (6.81 g, 0.02 mol), and triphenyl phosphite (9.31 g, 0.03 mol) are mixed evenly and placed in a hydrothermal reactor containing petroleum ether (292 g). The mixture is reacted at 150 °C for 20 h. After the reaction system is cooled to room temperature naturally, it is filtered, washed, and dried to obtain a white solid, which is the catalyst (i.e., a multi-metal synergistic catalyst) C2. Preparation of modified polyester (polyethylene terephthalate-co-estroxy terephthalate) Example 2-1:

[0047] This example provides a method for preparing a modified polyester and the modified polyester produced therefrom. The method for preparing the modified polyester includes: (1) Esterification reaction: Under the protection of nitrogen atmosphere, 830.7g terephthalic acid, 155.2g ethylene glycol, 605.7g estrol and 0.32g polymetallic synergistic catalyst C1 were added to the reactor. The temperature inside the reactor was raised to 230℃ at a rate of 5℃ / min and kept at the temperature for 5h. The esterification reaction was then completed. (2) Pre-condensation reaction: Turn off the esterification device, turn on the condensation device, raise the temperature inside the reactor to 250°C at a rate of 3°C / min, and slowly reduce the vacuum degree. React for 20 min at 8000 Pa, 5000 Pa and 1000 Pa respectively. The pre-condensation reaction is over. (3) Final polycondensation reaction: The temperature inside the reactor is raised to 270°C at a rate of 5°C / min. The gas inlet valve is completely closed, and the vacuum degree of the reaction system is reduced to below 50Pa. The reaction is maintained under the above conditions for 5 hours. After water cooling, granulation and drying, the modified polyester, namely polyethylene terephthalate-co-estradiol terephthalate, is obtained. Example 2-2:

[0048] This example provides a method for preparing a modified polyester and the modified polyester produced therefrom. The method for preparing the modified polyester includes: (1) Esterification reaction: Under the protection of nitrogen atmosphere, 830.7g terephthalic acid, 93.1g ethylene glycol, 847.9g estrol and 0.17g multi-metal synergistic catalyst C2 were added to the reactor. The temperature inside the reactor was raised to 240℃ at a rate of 5℃ / min and kept at the temperature for 6h. The esterification reaction was then completed. (2) Pre-condensation reaction: Turn off the esterification device, turn on the condensation device, raise the temperature inside the reactor to 250°C at a rate of 3°C / min, and slowly reduce the vacuum degree. React for 20 min at 8000 Pa, 5000 Pa and 1000 Pa respectively. The pre-condensation reaction is over. (3) Final polycondensation reaction: The temperature inside the reactor is raised to 270°C at a rate of 5°C / min. The gas inlet valve is completely closed, and the vacuum degree of the reaction system is reduced to below 50Pa. The reaction is maintained under the above conditions for 5 hours. After water cooling, granulation and drying, the modified polyester, namely polyethylene terephthalate-co-estradiol terephthalate, is obtained. Examples 2-3:

[0049] This example provides a method for preparing a modified polyester and the modified polyester produced therefrom. The method for preparing the modified polyester includes: (1) Esterification reaction: Under the protection of nitrogen atmosphere, 830.7g terephthalic acid, 31.0g ethylene glycol, 1090.2g estrol and 0.39g polymetallic synergistic catalyst C1 were added to the reactor. The temperature inside the reactor was raised to 240℃ at a rate of 5℃ / min and kept at the temperature for 6h. The esterification reaction was then completed. (2) Pre-condensation reaction: Turn off the esterification device, turn on the condensation device, raise the temperature inside the reactor to 250°C at a rate of 3°C / min, and slowly reduce the vacuum degree. React for 20 min at 8000 Pa, 5000 Pa and 1000 Pa respectively. The pre-condensation reaction is over. (3) Final polycondensation reaction: The temperature inside the reactor is raised to 280°C at a rate of 5°C / min. The gas inlet valve is completely closed, and the vacuum degree of the reaction system is reduced to below 50Pa. The reaction is maintained under the above conditions for 5 hours. After water cooling, granulation and drying, the modified polyester, namely polyethylene terephthalate-co-estradiol terephthalate, is obtained. Comparative Example 1:

[0050] This example provides a method for preparing a modified polyester and the modified polyester produced therefrom, which is basically the same as in Example 2-1, except that the multi-metal synergistic catalyst C1 is replaced with an equal mass of antimony trioxide. Comparative Example 2:

[0051] This example provides a method for preparing a modified polyester and the modified polyester produced therefrom, which is basically the same as in Example 2-1, except that the multi-metal synergistic catalyst C1 is replaced with an equal mass of stannous octoate. Comparative Example 3:

[0052] This example provides a method for preparing a modified polyester and the modified polyester produced therefrom, which is basically the same as in Example 2-1, except that the multi-metal synergistic catalyst C1 is replaced with an equal mass of tetrabutyl titanate. Comparative Example 4:

[0053] This example provides a method for preparing a modified polyester and the modified polyester produced therefrom, which is basically the same as in Example 2-1, except that the multi-metal synergistic catalyst C1 is replaced with an equal mass of triphenyl phosphite. Comparative Example 5:

[0054] This example provides a method for preparing a modified polyester and the modified polyester produced therefrom. The method for preparing the modified polyester includes: (1) Preparation of catalyst: Antimony trioxide (2.92g, 0.01mol) and tetrabutyl titanate (6.81g, 0.02mol) were mixed evenly and placed in a hydrothermal reactor containing petroleum ether (292g). After treatment at 140℃ for 18h, the system was cooled to room temperature naturally and then filtered. After washing and drying, catalyst C3 was obtained. (2) Esterification reaction: Under the protection of nitrogen atmosphere, 830.7g terephthalic acid, 155.2g ethylene glycol, 605.7g estrol and 0.32g catalyst C3 were added to the reactor. The temperature inside the reactor was raised to 230℃ at a rate of 5℃ / min and kept at that temperature for 5h. The esterification reaction was then completed. (3) Pre-condensation reaction: Turn off the esterification device, turn on the condensation device, raise the temperature inside the reactor to 250°C at a rate of 3°C / min, and slowly reduce the vacuum degree. React for 20 min at 8000 Pa, 5000 Pa and 1000 Pa respectively. The pre-condensation reaction ends. (4) Final polycondensation reaction: The temperature inside the reactor is raised to 270°C at a rate of 5°C / min. The gas inlet valve is completely closed, and the vacuum degree of the reaction system is reduced to below 50Pa. The reaction is maintained under the above conditions for 5 hours. After water cooling, granulation and drying, the modified polyester, namely polyethylene terephthalate-co-estradiol terephthalate, is obtained. Comparative Example 6:

[0055] This example provides a method for preparing a modified polyester and the modified polyester produced therefrom. The method for preparing the modified polyester includes: (1) Preparation of catalyst: Stannous octoate (4.05g, 0.01mol) and tetrabutyl titanate (6.81g, 0.02mol) were mixed evenly and placed in a hydrothermal reactor containing petroleum ether (292g). After treatment at 140℃ for 18h, the system was cooled to room temperature naturally and then filtered. After washing and drying, catalyst C4 was obtained.

[0056] (2) Esterification reaction: Under the protection of nitrogen atmosphere, 830.7g terephthalic acid, 155.2g ethylene glycol, 605.7g estrol and 0.32g catalyst C4 were added to the reactor. The temperature inside the reactor was raised to 230℃ at a rate of 5℃ / min and kept at that temperature for 5h. The esterification reaction was then completed. (3) Pre-condensation reaction: Turn off the esterification device, turn on the condensation device, raise the temperature inside the reactor to 250°C at a rate of 3°C / min, and slowly reduce the vacuum degree. React for 20 min at 8000 Pa, 5000 Pa and 1000 Pa respectively. The pre-condensation reaction ends. (4) Final polycondensation reaction: The temperature inside the reactor is raised to 270°C at a rate of 5°C / min. The gas inlet valve is completely closed, and the vacuum degree of the reaction system is reduced to below 50Pa. The reaction is maintained under the above conditions for 5 hours. After water cooling, granulation and drying, the modified polyester, namely polyethylene terephthalate-co-estradiol terephthalate, is obtained. Comparative Example 7:

[0057] This example provides a method for preparing a modified polyester and the modified polyester produced therefrom. The method for preparing the modified polyester includes: (1) Preparation of catalyst: Stannous octoate (4.05g, 0.01mol), tetrabutyl titanate (6.81g, 0.02mol), and triphenyl phosphite (3.10g, 0.01mol) were mixed evenly and placed in a hydrothermal reactor containing petroleum ether (292g). After treatment at 140℃ for 18h, the system was cooled to room temperature naturally and then filtered. After washing and drying, catalyst C5 was obtained.

[0058] (2) Esterification reaction: Under the protection of nitrogen atmosphere, 830.7g terephthalic acid, 155.2g ethylene glycol, 605.7g estrol and 0.32g catalyst C5 were added to the reactor. The temperature inside the reactor was raised to 230℃ at a rate of 5℃ / min and kept at that temperature for 5h. The esterification reaction was then completed. (3) Pre-condensation reaction: Turn off the esterification device, turn on the condensation device, raise the temperature inside the reactor to 250°C at a rate of 3°C / min, and slowly reduce the vacuum degree. React for 20 min at 8000 Pa, 5000 Pa and 1000 Pa respectively. The pre-condensation reaction ends. (4) Final polycondensation reaction: The temperature inside the reactor is raised to 270°C at a rate of 5°C / min. The gas inlet valve is completely closed, and the vacuum degree of the reaction system is reduced to below 50Pa. The reaction is maintained under the above conditions for 5 hours. After water cooling, granulation and drying, the modified polyester, namely polyethylene terephthalate-co-estradiol terephthalate, is obtained. Comparative Example 8:

[0059] This example provides a method for preparing a modified polyester and the modified polyester produced therefrom. The method for preparing the modified polyester includes: (1) Preparation of catalyst: Stannous octoate (4.05 g, 0.01 mol), cesium oxide (Cs2O, 5.64 g, 0.02 mol), and triphenyl phosphite (3.10 g, 0.01 mol) were mixed evenly and placed in a hydrothermal reactor containing petroleum ether (292 g). After treatment at 140 °C for 18 h, the system was cooled to room temperature naturally and then filtered. After washing and drying, catalyst C6 was obtained.

[0060] (2) Esterification reaction: Under the protection of nitrogen atmosphere, 830.7g terephthalic acid, 155.2g ethylene glycol, 605.7g estrol and 0.32g catalyst C6 were added to the reactor. The temperature inside the reactor was raised to 230℃ at a rate of 5℃ / min and kept at that temperature for 5h. The esterification reaction was then completed. (3) Pre-condensation reaction: Turn off the esterification device, turn on the condensation device, raise the temperature inside the reactor to 250°C at a rate of 3°C / min, and slowly reduce the vacuum degree. React for 20 min at 8000 Pa, 5000 Pa and 1000 Pa respectively. The pre-condensation reaction ends. (4) Final polycondensation reaction: The temperature inside the reactor is raised to 270°C at a rate of 5°C / min. The gas inlet valve is completely closed, and the vacuum degree of the reaction system is reduced to below 50Pa. The reaction is maintained under the above conditions for 5 hours. After water cooling, granulation and drying, the modified polyester, namely polyethylene terephthalate-co-estradiol terephthalate, is obtained. Comparative Example 9:

[0061] This example provides a method for preparing a modified polyester and the modified polyester produced therefrom. The method for preparing the modified polyester includes: (1) Esterification reaction: Under nitrogen atmosphere protection, 830.7g terephthalic acid, 155.2g ethylene glycol, 605.7g estrol, 0.05g antimony trioxide, 0.08g stannous octoate, 0.13g tetrabutyl titanate and 0.06g triphenyl phosphite were added to the reaction vessel. The temperature inside the vessel was raised to 230℃ at a rate of 5℃ / min and kept at that temperature for 5h. The esterification reaction was then completed. (2) Pre-condensation reaction: Turn off the esterification device, turn on the condensation device, raise the temperature inside the reactor to 250°C at a rate of 3°C / min, and slowly reduce the vacuum degree. React for 20 min at 8000 Pa, 5000 Pa and 1000 Pa respectively. The pre-condensation reaction is over. (3) Final polycondensation reaction: The temperature inside the reactor is raised to 270°C at a rate of 5°C / min. The gas inlet valve is completely closed, and the vacuum degree of the reaction system is reduced to below 50Pa. The reaction is maintained under the above conditions for 5 hours. After water cooling, granulation and drying, the modified polyester, namely polyethylene terephthalate-co-estradiol terephthalate, is obtained. Comparative Example 10:

[0062] This example provides a method for preparing a modified polyester and the modified polyester produced therefrom. The method for preparing the modified polyester includes: (1) Esterification reaction: Under the protection of nitrogen atmosphere, 780.5g of 2,5-furandicarboxylic acid, 403.5g of ethylene glycol and 0.24g of C1 multi-metal synergistic catalyst were added to the reactor. The temperature inside the reactor was raised to 200℃ at a rate of 5℃ / min and kept at that temperature for 5h. The esterification reaction was then completed. (2) Pre-condensation reaction: Turn off the esterification device, turn on the condensation device, raise the temperature inside the reactor to 250°C at a rate of 3°C / min, and slowly reduce the vacuum degree. React for 20 min at 8000 Pa, 5000 Pa and 1000 Pa respectively. The pre-condensation reaction is over. (3) Final polycondensation reaction: The temperature inside the reactor is raised to 270°C at a rate of 5°C / min. The gas inlet valve is completely closed, and the vacuum degree of the reaction system is reduced to below 50Pa. The reaction is maintained under the above conditions for 5 hours. After water cooling, granulation and drying, the modified polyester, namely polyethylene furanate, is obtained. Performance testing:

[0063] The polyethylene terephthalate-co-estradiol terephthalate obtained in Examples 2-1 to 2-3, Comparative Examples 1-9, and polyethylene furanate obtained in Comparative Example 10 were subjected to the following performance tests, and the specific results are shown in Table 1.

[0064] The test method for intrinsic viscosity is as specified in section 5.1.1 of GB / T 14190-2008.

[0065] Intrinsic viscosity: 0.2 g of polyethylene terephthalate-co-estradiol terephthalate was dissolved in 20 mL of a phenol-1,1,2,2-tetrachloroethane mixed solution (mass ratio 1:1). The intrinsic viscosity was measured using a single-point method in a 25°C water bath. The formula for calculating intrinsic viscosity is:

[0066] in: Relative viscosity Increase specific viscosity, Solvent outflow time : Polymer solution outflow time : Concentration of polymer solution.

[0067] The test method for tensile strength at break shall be in accordance with ISO 527-2019.

[0068]

[0069] The test results in Table 1 show that: In the reaction system of this invention, the selection of catalyst is crucial. If a single raw material component in the catalyst of this invention is used, the effect is relatively poor, with all intrinsic viscosities below 0.62 dL / g and all tensile strengths at break below 65 MPa. Meanwhile, even when two or three components of the catalyst of this invention were pre-mixed, the effect was still not ideal. Among them, Comparative Example 7 had a relatively better effect, but its intrinsic viscosity decreased by 39.7% and its tensile strength at break decreased by 14.1% compared with Example 1. Comparative Example 9 used all the raw material components of the catalyst of this invention, but did not carry out the coordination reaction in high temperature and solvent beforehand. Instead, it was directly added to the reaction raw material substrate of polyester. Practice showed that this method not only had low catalytic efficiency, but also did not even achieve the catalytic effect of Comparative Example 7. It can be seen that, under the reaction system of this invention, the catalyst obtained by pretreating antimony trioxide, stannous octoate, tetrabutyl titanate and triphenyl phosphite in high temperature and solvent can make full use of the synergistic effect between the components and achieve unexpected catalytic effect.

[0070] Comparative Example 10 verified the conventional polyester preparation using the catalyst of the present invention. As shown in Table 1, the present invention introduces the biomass monomer equol into the PET main chain structure, and the resulting polyethylene terephthalate-co-equol terephthalate has a significantly better tensile strength at break than biomass polyfuran dicarboxylate.

[0071] As used throughout the specification and claims, the term "comprising" is an open-ended term and should be interpreted as "comprising but not limited to." "Substantially" means that within an acceptable margin of error, those skilled in the art can solve the technical problem and substantially achieve the technical effect. It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a product or system comprising a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a product or system. Without further limitations, an element defined by the phrase "comprising one" does not exclude the presence of other identical elements in the product or system comprising said element.

[0072] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting 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.

[0073] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

Claims

1. A method for preparing a modified polyester, characterized in that, The preparation method includes: subjecting terephthalic acid, ethylene glycol, and the compound shown in formula (I) to esterification and polycondensation reactions in sequence in the presence of a catalyst to generate a modified polyester; The catalyst is prepared by reacting antimony trioxide, stannous octoate, tetrabutyl titanate and triphenyl phosphite in a solvent at a temperature above 100°C. In equation (Ⅰ), R1 and R2 are independently selected from H and C. 1-6 Alkyl group, where a is selected from 1, 2 or 3, and b is selected from 1, 2, 3 or 4.

2. The method for preparing the modified polyester according to claim 1, characterized in that, R1 and R2 are independently selected from H, methyl, ethyl, n-propyl, and isopropyl.

3. The method for preparing the modified polyester according to claim 1, characterized in that, The compound represented by formula (I) is 7-hydroxy-3-(4-hydroxyphenyl)-benzodihydropyran; and / or, the molar ratio of the ethylene glycol to the compound represented by formula (I) is 1:0.01-99, and the ratio of the total molar amount of the ethylene glycol and the compound represented by formula (I) to the molar amount of the terephthalic acid is 1.0-2.2:

1.

4. The method for preparing the modified polyester according to claim 1, characterized in that, The molar ratio of ethylene glycol to the compound shown in formula (I) is 1:0.5-15, and the ratio of the total molar amount of ethylene glycol and the compound shown in formula (I) to the molar amount of terephthalic acid is 1.0-1.5:1; and / or, the amount of catalyst added is 0.005wt.%-0.5wt.% of the weight of the reaction system.

5. The method for preparing the modified polyester according to claim 1, characterized in that, The reaction temperature of the esterification reaction is controlled at 220-240°C; and / or the reaction temperature of the polycondensation reaction is controlled at 240-280°C; and / or the esterification reaction is carried out in a protective atmosphere.

6. The method for preparing the modified polyester according to claim 1, characterized in that, The method for preparing the modified polyester includes: (1) Esterification reaction: Under the protection of protective gas, terephthalic acid, ethylene glycol, the compound shown in formula (Ⅰ) and catalyst are added to the reaction vessel, and the reaction temperature is controlled at 220-240℃. (2) Pre-condensation reaction: The temperature inside the reaction vessel is raised to 240-260℃, and the vacuum degree is gradually reduced to below 1000Pa, and the reaction proceeds. (3) Final polycondensation reaction: The temperature inside the reaction vessel is raised to 260-280℃ and the vacuum is reduced to below 50Pa. The reaction is carried out to generate modified polyester.

7. The method for preparing the modified polyester according to claim 6, characterized in that, In step (2), the reaction is carried out under vacuum of 7000-9000 Pa, 4000-6000 Pa and 500-1000 Pa respectively; and / or, in step (2), the reaction temperature of the pre-condensation reaction is 240-250℃; and / or, in step (3), the reaction temperature of the final condensation reaction is 270-280℃.

8. The method for preparing the modified polyester according to claim 1, characterized in that, The mass ratio of antimony trioxide, stannous octoate, tetrabutyl titanate, and triphenyl phosphite is 1:1-10:1-15:1-5; and / or, during the preparation of the catalyst, the reaction temperature is controlled at 120-180℃.

9. The method for preparing the modified polyester according to claim 1, characterized in that, The mass ratio of antimony trioxide, stannous octoate, tetrabutyl titanate, and triphenyl phosphite is 1:1-5:2-10:1.5-5; and / or, in the preparation of the catalyst, the solvent is petroleum ether, and the mass ratio of antimony trioxide to the solvent is 1:50-150.

10. A catalyst, characterized in that, The catalyst is prepared by reacting antimony trioxide, stannous octoate, tetrabutyl titanate, and triphenyl phosphite in a solvent at a temperature above 100°C.

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