A method for continuously preparing a biodegradable copolyester PBST

Abstract

This invention discloses a method for the continuous preparation of biodegradable copolyester PBST. The method includes: (1) esterifying terephthalic acid and 1,4-butanediol in a stirred vertical esterification reactor; (2) introducing the product of step (1), succinic anhydride, and 1,4-butanediol into the stirred vertical esterification reactor for further esterification; (3) introducing the product of step (2) into a pre-polymerization reactor for pre-polymerization; (4) introducing the product from the pre-polymerization reactor into a final polymerization reactor for final polymerization; and (5) introducing the product from the final polymerization reactor into a melt thickening reactor for melt thickening, so that the melt index of the reaction product reaches 1-20. According to the scheme of this invention, not only can high molecular weight aliphatic aromatic copolyesters be continuously prepared, but the tensile mechanical properties of the prepared PBST are also significantly better.

Description

Technical Field

[0001] This invention relates to the field of polymer material preparation, and specifically to a method for the continuous preparation of biodegradable copolyester PBST. Background Technology

[0002] Polymer materials have been widely used in our daily lives, becoming indispensable. However, with the widespread use of single-use plastic products, large quantities of difficult-to-recycle plastics are directly discarded into the environment, creating alarming phenomena such as white pollution and microplastics, harming the living environment and attracting widespread attention worldwide. There are two main approaches to solving this problem: one is to recycle and reuse these polymer materials, and the other is to use biodegradable materials to replace non-degradable single-use plastic products. Currently, the commercially available biodegradable materials used as packaging film and bag materials are mainly fatty aromatic copolyesters (butylene terephthalate-adipate-glycol) (PBAT), with BASF's... The main production process of this product is "esterification-polymerization-chain extension". Because the organic titanium catalyst used in the PBAT preparation process is difficult to produce high molecular weight products, if it is used as a membrane bag material, it is necessary to add organic compounds such as isocyanates for chain extension to achieve the effect of melt thickening and increase the molecular weight to a certain extent to meet the processing performance requirements. However, the organic compounds such as isocyanates used as chain extenders have certain toxicity, which limits the application of PBAT.

[0003] Biodegradable copolyester poly(terephthalic acid-succinic acid-butanediol) (PBST), prepared from succinic acid, terephthalic acid, and 1,4-butanediol, can overcome the performance deficiencies of PBAT in terms of strength, heat resistance, and water resistance. Its applications can cover all areas of PBAT use, and it has the potential to develop more unique applications in biomedicine, electronic packaging, food preservation films, and heat shrink films. Preparing PBST using succinic anhydride as a monomer overcomes the limitations of high raw material costs and large esterification wastewater discharge associated with using succinic acid as a monomer. This method achieves low cost, low energy consumption, and low emissions, making it an excellent process route. Summary of the Invention

[0004] This invention provides a method for the continuous preparation of biodegradable copolyester PBST, which adopts a process route of "diesterization at atmospheric pressure esterification-pre-condensation-final condensation-liquid phase thickening" to prepare high molecular weight aliphatic aromatic copolyester.

[0005] Specifically, this invention provides a method for the continuous preparation of biodegradable copolyester PBST, the method comprising the following steps:

[0006] (1) In the presence of a first catalyst and / or a second catalyst, terephthalic acid and 1,4-butanediol are subjected to an esterification reaction in a first esterification reactor, which is a vertical esterification reactor with stirring. When the esterification rate in the first esterification reactor reaches 90-95%, the next reaction step is introduced.

[0007] (2) The product of the first esterification vessel, the first catalyst and / or the second catalyst, succinic anhydride and optional 1,4-butanediol are introduced into the second esterification vessel for esterification reaction. The second esterification vessel is a vertical esterification reactor with stirring. When the esterification rate in the second esterification vessel reaches 90-95%, the next reaction step is introduced.

[0008] (3) In the presence of a third catalyst, the product of the second esterification vessel is introduced into a prepolymerization vessel for prepolymerization. The prepolymerization vessel is a vertical stirred vessel. When the degree of polymerization reaches 20-30, the product is introduced into the next reaction step.

[0009] (4) The product of the prepolymerization reactor is introduced into the final polymerization reactor for final polymerization. The final polymerization reactor is a horizontal cage-type film-forming final polymerization reactor. When the degree of polymerization reaches 100-150, the product is introduced into the next reaction step.

[0010] (5) The product from the final polycondensation reactor is introduced into a thickening reactor for melt thickening, so that the melt index of the reaction product reaches 1-20. The thickening reactor is a biaxial horizontal liquid phase thickening reactor.

[0011] Wherein, the first catalyst is an oxide selected from M, M(OR1) n and M(-OOCR2) n At least one compound or a mixture thereof, wherein M is titanium, antimony or zinc, n is the valence state of M, and R1 is C1-C2. 10 Alkyl group, R2 is C1-C 30 Alkyl groups;

[0012] The second catalyst is at least one organotin compound;

[0013] The third catalyst is at least one compound with the chemical formula RE(R3)3, wherein RE is a rare earth metal element, R3 is at least one selected from halogen, alkoxy, aryloxy, acetylacetonyl, and R4COO- group, and R4 is a C1-C2 group. 30 Alkyl groups.

[0014] In the continuous preparation method of aliphatic aromatic copolyesters described in this invention, the esterification reactions in steps (1) and (2) are carried out in a vertical esterification reactor with stirring, and the pre-condensation in step (3) is carried out in a vertical stirred tank to facilitate better and more uniform mixing of materials, more thorough esterification, and reduced mist entrainment. The final condensation in step (4) is carried out in a horizontal cage-type film-forming final condensation reactor, and the melt thickening in step (5) is carried out in a biaxial horizontal liquid-phase thickening reactor to facilitate the full devolatilization of high-viscosity materials and prepare a high-viscosity, low-melt-index resin product. Therefore, the continuous preparation method of biodegradable copolyester PBST according to this invention can achieve continuous preparation of high molecular weight aliphatic aromatic copolyesters with good product stability. In particular, when the catalyst used in steps (1) and (2) is tetraisopropyl titanate, and the catalyst used in step (3) is lanthanum stearate, the performance of the prepared aliphatic aromatic copolyester is even better.

[0015] The method for continuous preparation of aliphatic aromatic copolyesters described in this invention not only breaks the monopoly of foreign technology, but also yields high-molecular-weight, low-toxicity, and widely applicable high-quality biodegradable engineering plastics. This product has excellent performance and can be widely used in engineering plastics, fibers, resins, films and other fields. Detailed Implementation

[0016] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0017] 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.

[0018] The method for continuous preparation of biodegradable copolyester PBST according to the present invention includes the following steps:

[0019] (1) In the presence of a first catalyst and / or a second catalyst, terephthalic acid and 1,4-butanediol are subjected to an esterification reaction in a first esterification reactor, which is a vertical esterification reactor with stirring. When the esterification rate in the first esterification reactor reaches 90-95%, the next reaction step is introduced.

[0020] (2) The product of the first esterification vessel, the first catalyst and / or the second catalyst, succinic anhydride and optional 1,4-butanediol are introduced into the second esterification vessel for esterification reaction. The second esterification vessel is a vertical esterification reactor with stirring. When the esterification rate in the second esterification vessel reaches 90-95%, the next reaction step is introduced.

[0021] (3) In the presence of a third catalyst, the product of the second esterification vessel is introduced into a prepolymerization vessel for prepolymerization. The prepolymerization vessel is a vertical stirred vessel. When the degree of polymerization reaches 20-30, the product is introduced into the next reaction step.

[0022] (4) The product of the prepolymerization reactor is introduced into the final polymerization reactor for final polymerization. The final polymerization reactor is a horizontal cage-type film-forming final polymerization reactor. When the degree of polymerization reaches 100-150, the product is introduced into the next reaction step.

[0023] (5) The product from the final polycondensation reactor is introduced into a thickening reactor for melt thickening, so that the melt index of the reaction product reaches 1-20. The thickening reactor is a biaxial horizontal liquid phase thickening reactor.

[0024] In this invention, both the first and second esterification reactors are vertical esterification reactors equipped with stirring. Their structural feature is that the reactor is divided into inner and outer chambers, allowing for thorough mixing of reactants, resulting in more complete esterification and preventing mist entrainment. The vertical esterification reactor with stirring can be a commercially available product, such as the patented product ZL201920053188.4 manufactured by Yangzhou Huitong Chemical Technology Co., Ltd., or the patented product ZL201420697931.7 manufactured by Wuxi Xingsheng New Material Technology Co., Ltd.

[0025] In this invention, the prepolymerization reactor is a vertical stirred tank, characterized by a multi-zone structure. The vertical stirred tank can be a commercially available product, such as the reaction apparatus of the patented product ZL201220466771.1 manufactured by China Kunlun Engineering Corporation.

[0026] In this invention, the final polycondensation reactor is a horizontal cage-type film-forming final polycondensation reactor, characterized by a disc agitator that increases the devolatilization area. The horizontal cage-type film-forming final polycondensation reactor can be a commercially available product, such as the reaction apparatus of the patented product ZL202021066179.8 from China Petroleum & Chemical Corporation.

[0027] In this invention, the thickening reactor is a biaxial horizontal liquid-phase thickening reactor, characterized by its shaftless design, self-cleaning function, larger reaction area, and smoother melt flow. The biaxial horizontal liquid-phase thickening reactor can be a commercially available product, such as the LSPLINE model manufactured by Yangzhou Huite Technology Co., Ltd.TM The reaction apparatus.

[0028] In step (1), when the esterification rate in the first esterification vessel reaches 90-95%, the next reaction step is introduced. In this invention, the "esterification rate" is detected by acid-base titration. Here, "next reaction step" refers to the esterification reaction in step (2).

[0029] In step (2), when the esterification rate in the second esterification vessel reaches 90-95%, the next reaction step is introduced. Here, "next reaction step" refers to the esterification reaction in step (3).

[0030] In step (3), when the degree of polymerization reaches 20-30, the next reaction step is initiated. In this invention, the method for detecting the "degree of polymerization" is nuclear magnetic resonance hydrogen spectroscopy (NMR spectroscopy). 1 (HNMR). Here, "next reaction step" refers to the final condensation reaction in step (4).

[0031] In step (4), when the degree of polymerization reaches 100-150, the next reaction step is introduced. Here, "next reaction step" refers to the melt thickening reaction in step (5).

[0032] In step (5), the melt thickening process causes the melt index of the reaction product to reach 1-20. Here, "melt index" refers to the melt mass flow rate per 10 minutes at 190°C and 2.16 kg load pressure.

[0033] In this invention, the first catalyst is an oxide selected from M, M(OR1). n and M(-OOCR2) n At least one compound or a mixture thereof, wherein M is titanium, antimony or zinc, n is the valence state of M, and R1 is C1-C2. 10 Alkyl group, R2 is C1-C 30 The alkyl group. To achieve a high molecular weight and improve the tensile mechanical properties of the final prepared aliphatic aromatic copolyester, the first catalyst is preferably at least one selected from alkoxytitanium, antimony acetate, zinc acetate, zinc oxide, antimony oxide, and titanium oxide. Most preferably, the first catalyst is tetraisopropyl titanate.

[0034] In this invention, the second catalyst is at least one organotin compound. To ensure that the final prepared aliphatic aromatic copolyester has a high molecular weight and improves its tensile mechanical properties, the second catalyst is preferably selected from at least one of tin laurylate, dibutyltin oxide, methylphenyltin oxide, tetraethyltin, hexaethyltin oxide, hexacyclohexylditin oxide, di(dodecyl)tin oxide, triethylhydroxytin, triphenylhydroxytin, triisobutyltin acetate, dibutyltin diacetate, diphenyltin dilaurate, monobutyltin trichloride, tributyltin chloride, dibutyltin chloride, dibutyltin sulfide, butyltin hydroxyoxide, methylstannic acid, ethylstannic acid, and butylstannic acid. Most preferably, the second catalyst is selected from tin laurylate.

[0035] In this invention, the third catalyst is at least one compound with the chemical formula RE(R3)3, wherein RE is a rare earth metal element, R3 is at least one selected from halogen, alkoxy, aryloxy, acetylacetonyl, and R4COO- group, and R4 is a C1-C2 group. 30 Alkyl groups. To achieve a high molecular weight in the final prepared aliphatic aromatic copolyester and improve its tensile mechanical properties, preferably, in the third catalyst, RE is selected from yttrium, lanthanum, cerium, praseodymium, neodymium, terbium, ytterbium, dysprosium, samarium, or scandium; the halogen is chlorine or bromine; the alkoxy group is a C3-C6 alkoxy group; the aryloxy group is an aryloxy group comprising at least one benzene ring and / or a naphthalene ring; and R4 in the R4COO- group is a C1-C6 alkoxy group. 20 Alkyl groups. In the most preferred case, the third catalyst is lanthanum stearate.

[0036] According to a preferred embodiment of the present invention, the catalyst used in steps (1) and (2) is tetraisopropyl titanate, and the third catalyst used in step (3) is lanthanum stearate. The fatty aromatic copolyester prepared according to this preferred embodiment has a high molecular weight and good tensile mechanical properties.

[0037] According to the method provided by the present invention, in step (1), preferably, the esterification reaction in the first esterification vessel is carried out under normal pressure or slightly negative pressure, and the reaction temperature is 180-250°C.

[0038] According to the method provided by the present invention, in step (1), preferably, the molar ratio of terephthalic acid to 1,4-butanediol is 1:0.8-3, more preferably 1:1-2.5, and even more preferably 1:1.2-2.5.

[0039] According to the method provided by the present invention, in step (2), preferably, the esterification reaction in the second esterification vessel is carried out under normal pressure or slightly negative pressure, and the reaction temperature is 180-250°C.

[0040] According to the method provided by the present invention, preferably, the molar ratio of the amount of terephthalic acid added in step (1) and succinic anhydride added in step (2) is 1:0.01-100, more preferably 1:0.3-3, and even more preferably 1:0.5-2.

[0041] According to the method provided by the present invention, in steps (1) and (2), the molar ratio of the total amount of terephthalic acid and succinic anhydride to the total amount of 1,4-butanediol is 1:0.8-6, more preferably 1:1-5, and even more preferably 1:1.2-4.

[0042] According to the method provided by the present invention, in step (3), preferably, the pre-polymerization is carried out under an absolute pressure of 600-1000 Pa and the reaction temperature is 190-250 °C.

[0043] According to the method provided by the present invention, in step (4), preferably, the final polycondensation is carried out at 200-300°C and a vacuum degree ≤300Pa (e.g., 50-300Pa). In the present invention, the vacuum degree refers to absolute pressure.

[0044] According to the method provided by the present invention, in step (5), preferably, the melt thickening is carried out at 200-250°C and a vacuum degree of 50-200Pa.

[0045] In this invention, the method for continuous preparation of fatty aromatic copolyesters may further include: sequentially underwater pelletizing, drying, and packaging the product from the thickening reactor.

[0046] The present invention will be further described below through embodiments, but the scope of protection of the present invention is not limited thereto.

[0047] The reaction apparatus in the following embodiments includes a first esterification reactor, a second esterification reactor, a third esterification reactor, a prepolymerization reactor, a final polymerization reactor, and a thickening reactor. The first esterification reactor, the second esterification reactor, and the third esterification reactor are all vertical esterification reactors with stirring. The prepolymerization reactor is a vertical stirred reactor. The final polymerization reactor is a horizontal cage-type film-forming final polymerization reactor. The thickening reactor is a biaxial horizontal liquid-phase thickening reactor.

[0048] Example 1

[0049] This embodiment is used in the method for continuous preparation of aliphatic aromatic copolyesters described in this invention.

[0050] (1) Prepare a PTA slurry by mixing 350 kg / h terephthalic acid and 285 kg / h 1,4-butanediol, and continuously feed it into the first esterification reactor. Add 0.1 kg / h tetraisopropyl titanate and carry out the esterification reaction at atmospheric pressure and temperature of 220°C until the esterification rate reaches 95%.

[0051] (2) The product from the first esterification reactor is introduced into the second esterification reactor. At the same time, 254 kg / h of succinic anhydride and 350 kg / h of 1,4-butanediol are mixed into a slurry and continuously fed into the second esterification reactor. 0.1 kg / h of tetraisopropyl titanate is added, and the esterification reaction is carried out at atmospheric pressure and a temperature of 220°C until the esterification rate reaches 95%.

[0052] (3) The product from the second esterification vessel is introduced into the prepolymerization vessel, and 0.5 g / h of lanthanum stearate is injected at the same time. The product is prepolymerized for 2 h at an absolute pressure of 1 kPa and a temperature of 235 °C, and the degree of polymerization of the product reaches 25.

[0053] (4) The product from the prepolymerization reactor is introduced into the final polymerization reactor and subjected to final polymerization for 5 hours at an absolute pressure of 150 Pa and a temperature of 235 °C. The degree of polymerization of the product reaches 120.

[0054] (5) The product from the final polycondensation reactor was introduced into the thickening reactor and the melt thickening reaction was carried out at an absolute pressure of 100 Pa and a temperature of 225 °C for 1.5 h. The resulting poly(butylene terephthalate) ester (PBST) was melt cooled and granulated. The melt index of the polymer product (190 °C, 2.16 kg) was 2.8 g / 10 min.

[0055] Example 2

[0056] This embodiment is used in the method for continuous preparation of aliphatic aromatic copolyesters described in this invention.

[0057] (1) Prepare a PTA slurry by mixing 350 kg / h terephthalic acid and 285 kg / h 1,4-butanediol, and continuously feed it into the first esterification reactor. Add 0.1 kg / h tetraisopropyl titanate and carry out the esterification reaction at atmospheric pressure and temperature of 220°C until the esterification rate reaches 95%.

[0058] (2) The product from the first esterification vessel is introduced into the second esterification vessel. At the same time, 228 kg / h of succinic anhydride and 350 kg / h of 1,4-butanediol are mixed to form a slurry, which is continuously fed into the second esterification vessel. 0.1 kg / h of tetraisopropyl titanate is added, and the esterification reaction is carried out at atmospheric pressure and a temperature of 220°C until the esterification rate reaches 95%.

[0059] (3) The product from the second esterification vessel was introduced into the prepolymerization vessel, and 0.5 g / h of lanthanum stearate was injected at the same time. The product was prepolymerized for 2 h at an absolute pressure of 1 kPa and a temperature of 235 °C, and the degree of polymerization of the product reached 22.

[0060] (4) The prepolymerization product is introduced into the final polymerization kettle and subjected to final polymerization for 5 hours at an absolute pressure of 150 Pa and a temperature of 235 °C. The degree of polymerization of the product reaches 110.

[0061] (5) The product from the final polycondensation reactor was introduced into the thickening reactor and the melt thickening reaction was carried out at an absolute pressure of 100 Pa and a temperature of 225 °C for 1.5 h. The resulting poly(butylene terephthalate) ester (PBST) was subjected to melt cooling and granulation. The melt index of the polymer product (190 °C, 2.16 kg) was 3.0 g / 10 min.

[0062] Example 3

[0063] This embodiment is used in the method for continuous preparation of aliphatic aromatic copolyesters described in this invention.

[0064] (1) Prepare a PTA slurry by mixing 350 kg / h terephthalic acid and 285 kg / h 1,4-butanediol, and continuously feed it into the first esterification reactor. Add 0.1 kg / h tetraisopropyl titanate and carry out the esterification reaction at atmospheric pressure and temperature of 220°C until the esterification rate reaches 95%.

[0065] (2) The product from the first esterification vessel is introduced into the second esterification vessel. At the same time, 316 kg / h of succinic anhydride and 350 kg / h of 1,4-butanediol are mixed into a slurry and continuously fed into the second esterification vessel. 0.1 kg / h of tetraisopropyl titanate is added, and the esterification reaction is carried out at atmospheric pressure and a temperature of 220°C until the esterification rate reaches 95%.

[0066] (3) The product from the second esterification vessel was introduced into the prepolymerization vessel, and 0.5 g / h of lanthanum stearate was injected at the same time. The product was prepolymerized for 2 h at an absolute pressure of 1 kPa and a temperature of 235 °C, and the degree of polymerization of the product reached 28.

[0067] (4) The prepolymerization product is introduced into the final polymerization reactor and subjected to final polymerization for 5 hours at an absolute pressure of 150 Pa and a temperature of 235 °C. The degree of polymerization of the product reaches 140.

[0068] (5) The product from the final polycondensation reactor was introduced into the thickening reactor and the melt thickening reaction was carried out at an absolute pressure of 100 Pa and a temperature of 225 °C for 1.5 h. The resulting poly(butylene terephthalate) ester (PBST) was subjected to melt cooling and granulation. The melt index of the polymer product (190 °C, 2.16 kg) was 2.9 g / 10 min.

[0069] Example 4

[0070] PBST was prepared according to the method of Example 1, except that in steps (1) and (2), tetrabutyl titanate was used instead of tetraisopropyl titanate in the same molar amount, and the melt index of the polymer product (190°C, 2.16 kg) was 3.1 g / 10 min.

[0071] Comparative Example 1

[0072] PBST was prepared according to the method in Example 1, except that both the final polycondensation reactor and the thickening reactor were vertical stirred tanks, and the melt index of the obtained polymer product (190°C, 2.16 kg) was 14.5 g / 10 min.

[0073] Test case

[0074] The weight-average molecular weight of the polymers prepared in Examples 1-4 and Comparative Example 1 was determined by gel permeation chromatography (GPC) using tetrahydrofuran (THF) as solvent on a Waters-208 instrument (equipped with a Waters 2410RI detector, flow rate of 1.5 ml / min, 30 °C). The weight-average molecular weight was calibrated with styrene standard.

[0075] The tensile mechanical properties, such as elongation at break and tensile strength at break, of the polymers prepared in Examples 1-4 and Comparative Example 1 were tested according to the method of ASTM D638-03.

[0076] Table 1

[0077]

[0078]

[0079] As can be seen from the results in Table 1, the method for continuous preparation of aliphatic aromatic copolyesters according to the present invention not only achieves continuous preparation of aliphatic aromatic copolyesters with a simple process and low energy consumption, but also produces aliphatic aromatic copolyesters with high molecular weight and significantly better tensile mechanical properties.

[0080] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for continuous preparation of biodegradable copolyester PBST, characterized in that, The method includes the following steps: (1) In the presence of a first catalyst, terephthalic acid and 1,4-butanediol are subjected to an esterification reaction in a first esterification reactor, which is a vertical esterification reactor with stirring. When the esterification rate in the first esterification reactor reaches 90-95%, the next reaction step is introduced. (2) The product of the first esterification vessel, the second catalyst, succinic anhydride and optional 1,4-butanediol are introduced into the second esterification vessel for esterification reaction. The second esterification vessel is a vertical esterification reactor with stirring. When the esterification rate in the second esterification vessel reaches 90-95%, the next reaction step is introduced. (3) In the presence of a third catalyst, the product of the second esterification vessel is introduced into a prepolymerization vessel for prepolymerization. The prepolymerization vessel is a vertical stirred vessel. When the degree of polymerization reaches 20-30, the product is introduced into the next reaction step. (4) The product of the prepolymerization reactor is introduced into the final polymerization reactor for final polymerization. The final polymerization reactor is a horizontal cage-type film-forming final polymerization reactor. When the degree of polymerization reaches 100-150, the product is introduced into the next reaction step. (5) The product from the final polycondensation reactor is introduced into the thickening reactor for melt thickening, so that the melt index of the reaction product reaches 1-20 g / 10 min. The test conditions are 190℃ and 2.16 kg. The thickening reactor is a reaction device of model LSPLINE™. The first catalyst is tetraisopropyl titanate; The second catalyst is tetraisopropyl titanate; The third catalyst is lanthanum stearate.

2. The method according to claim 1, characterized in that, In step (1), the esterification reaction in the first esterification vessel is carried out under normal pressure and the reaction temperature is 180-250℃.

3. The method according to claim 1, characterized in that, In step (1), the molar ratio of terephthalic acid to 1,4-butanediol is 1:0.8-3.

4. The method according to claim 1, characterized in that, In step (2), the esterification reaction in the second esterification vessel is carried out under normal pressure and the reaction temperature is 180-250℃.

5. The method according to claim 1, characterized in that, The molar ratio of terephthalic acid in step (1) to succinic anhydride in step (2) is 1:0.01-100.

6. The method according to claim 1, characterized in that, In steps (1) and (2), the molar ratio of the total amount of terephthalic acid and succinic anhydride to the total amount of 1,4-butanediol is 1:0.8-6.

7. The method according to claim 1, characterized in that, In step (3), the prepolymerization is carried out under an absolute pressure of 600-1000 Pa and a reaction temperature of 190-250 °C.

8. The method according to claim 1, characterized in that, In step (4), the final polycondensation is carried out at 200-300°C and a vacuum degree ≤300Pa.

9. The method according to claim 1, characterized in that, In step (5), the melt thickening is carried out at 200-250°C and a vacuum of 50-200Pa.

Images