A method for preparing furandicarboxylic acid polyester based on transesterification route

Abstract

The application discloses a furandicarboxylic acid polyester preparation method based on an ester exchange route, and comprises the following steps: taking dihydric alcohol and furandicarboxylic acid diester as monomer raw materials, and obtaining a prepolymer with an end ester group content of 50 mmol / kg or less through ester exchange and melt polycondensation reaction under the action of a zinc-based catalyst; the alcohol-ester ratio in the ester exchange is 1.6-3.0; the prepolymer particle is dried and pre-crystallized, and then the furandicarboxylic acid polyester is obtained through solid-phase tackification; and the solid-phase tackification speed can be significantly accelerated by adding a solid-phase promoter into the prepolymer melt. In the application, the zinc-based catalyst is adopted to inhibit discoloration, a higher alcohol-ester ratio is adopted to prepare a prepolymer with a low end methyl ester group content, and the solid-phase tackification is promoted by combining the solid-phase promoter, so that the intrinsic viscosity is significantly improved in a shorter time, and the furandicarboxylic acid polyester with light color, high intrinsic viscosity and high toughness is obtained.

Description

Technical Field

[0001] This invention relates to the field of polyester synthesis technology, and specifically to a method for preparing furanyl dicarboxylic acid polyester based on the transesterification route. Background Technology

[0002] The synthesis of furanyl dicarboxylic acid polyesters from the bio-based monomer furanyl dicarboxylic acid (FDCA) or its diester and diol is one of the main research and development hotspots in bio-based polymers. Taking polyethylene furanyl dicarboxylate (PEF) as an example, compared with petroleum-based polyester—polyethylene terephthalate (PET)—which is widely used in bottles, films, fibers, and other fields, it not only has superior physical properties such as heat resistance, tensile strength, modulus, and gas barrier properties, but also has the advantages of sustainable development such as resource renewability, low carbon emissions, and low processing energy consumption. However, due to the inevitable presence of a small amount of easily discoloring impurities in FDCA and its diester monomers, the poor thermal stability of monomers and PEF leading to easy side reactions at high temperatures, and the lack of highly active and selective catalysts, it is often difficult to directly obtain PEF with both light color and high intrinsic viscosity through melt polycondensation. The synthesized high intrinsic viscosity PEF often has a dark color, thus failing to meet the application requirements for manufacturing high-quality polyester bottles, films, and fibers. Other furan dicarboxylic acid polyesters such as polypropylene furan dicarboxylate (PPF or PTF), polybutylene furan dicarboxylate (PBF), neopentylene furan dicarboxylate (PNF), and polycyclohexanediol furan dicarboxylate (PCF) also have similar performance advantages and similar problems.

[0003] Melt-solid phase polycondensation is a common technique where a semi-crystalline product (also known as a prepolymer) is first obtained through melt polycondensation. After granulation and pre-crystallization, it undergoes further polycondensation in solid form at a lower temperature (below the melting point) to further increase the intrinsic viscosity (solid phase polycondensation, also known as solid phase thickening). Because melt polycondensation time is relatively short and solid phase thickening temperature is low, solid phase thickening can better avoid side reactions such as discoloration. There are many reports on the synthesis of furanyl dicarboxylic acid polyesters using melt-solid phase thickening. In 2007, Canon's patent WO2007052847 first mentioned a method to increase the molecular weight of PEF through solid phase thickening. PEF synthesized using a tin / titanium composite catalyst, after long-term solid phase thickening, achieved a number-average molecular weight of 22900 g / mol, but the product still had a very dark color. In most subsequent reports on PEF solid phase thickening, a relatively long reaction time is required to obtain polyesters with high intrinsic viscosity. For example, in patent WO2010077133, it is necessary to solid-phase thickening for 60 hours to increase the molecular weight of PEF to 34000 g / mol. In the existing technology, in order to achieve a higher molecular weight, the solid-phase thickening process usually requires a time longer than 24 hours. Such a long reaction time makes it difficult to truly realize industrial production.

[0004] Patent CN116262819A describes a method for increasing the intrinsic viscosity of PEF from 0.5-0.6 dL / g to 0.8-0.9 dL / g through solid-phase thickening for 3-4 hours. While the solid-phase thickening rate is relatively fast, the PEF particle size used is small, ranging from 0.2-0.8 mm. Polymers (2018, 10: 471-491) reported the results of secondary solid-phase thickening of PEF: using tetrabutyl titanate as a catalyst, furanyl dicarboxylic acid and ethylene glycol were melt-polymerized to obtain a PEF prepolymer with an intrinsic viscosity of 0.38 dL / g. After pulverization, sieving (particle size 0.16-0.40 mm), and crystallization, solid-phase thickening was performed at 205°C for 6 hours, increasing the intrinsic viscosity to 0.60 dL / g. After remelting and crystallization, and further solid-phase thickening, the intrinsic viscosity increased to 1.02 dL / g after a reaction at 205°C for 5 hours. Although this method can rapidly increase the intrinsic viscosity of PEF, the secondary solid-phase thickening process is cumbersome, energy-intensive, and has low industrialization value. Other furanyl dicarboxylic acid polyesters also suffer from similar problems of slow solid-phase thickening and excessively long reaction times.

[0005] It is evident that how to rapidly synthesize light-colored, high-intrinsic-viscosity furanyl dicarboxylic acid polyesters through melt-solid phase thickening remains a pressing technical problem. On the other hand, although furanyl dicarboxylic acid polyesters such as PEF and PPF have superior mechanical strength and rigidity compared to their corresponding terephthalic acid polyesters, they often exhibit brittle fracture or failure under external forces. Therefore, how to directly synthesize tough PEF without post-polymerization modification is also worth exploring. Summary of the Invention

[0006] This invention addresses the problems of slow solid-phase thickening reaction, long time, dark color, and poor toughness of furan dicarboxylic acid polyester. It provides a method for preparing furan dicarboxylic acid polyester with light color, high intrinsic viscosity, and high toughness by first synthesizing a prepolymer with low methyl ester content and then performing solid-phase thickening. The solid-phase thickening time is shorter and the product has excellent performance.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A method for preparing furanyl dicarboxylic acid polyester based on transesterification includes the following steps: Step 1: Using diol and furan dicarboxylate as monomer raw materials, a prepolymer melt is obtained through transesterification and melt polycondensation under the action of a zinc-based catalyst. The melt is then pelletized to obtain prepolymer pellets with an end ester group content of less than 50 mmol / kg. Step 2: The prepolymer granules are dried and pre-crystallized to obtain pre-crystallized granules; then, solid-phase thickening is performed to obtain the furan dicarboxylic acid polyester. The alcohol-ester ratio in the transesterification is 1.6-3.0; the zinc-based catalyst is one or more of zinc oxide, zinc carbonate, zinc compounds containing carboxyl groups, and zinc complexes.

[0008] In this invention, a furanyl dicarboxylic acid polyester prepolymer with low methyl ester content is first prepared via transesterification and polycondensation using a relatively high alcohol-ester ratio. The higher alcohol-ester ratio facilitates a higher transesterification rate, resulting in a transesterification product with low ester content, thereby increasing the melt polycondensation rate and shortening the melt polycondensation time, ultimately yielding a prepolymer with low ester content. The prepolymer is further solidified with or without a solid-phase promoter, and the zinc-based catalyst helps prevent discoloration of the polyester during polymerization, resulting in a light-colored furanyl dicarboxylic acid polyester with high intrinsic viscosity.

[0009] Preferably, the zinc element in the zinc-based catalyst accounts for 30-500 ppm of the mass of the obtained furanyl dicarboxylic acid polyester; Preferably, a solid phase accelerator or a masterbatch containing a solid phase accelerator is added to the prepolymer melt obtained in step 1, wherein the amount of the solid phase accelerator is 0.01-0.6 mol of furanyl dicarboxylate.

[0010] In this invention, solid-phase thickening can be performed in the absence of a solid-phase accelerator or in the presence of a solid-phase accelerator. In the presence of a solid-phase accelerator, the solid-phase thickening process can increase the intrinsic viscosity more rapidly. Preferably, the solid-phase accelerator includes one or more of triacid anhydride, tetraacid dianhydride, dioxazoline, and diepoxide.

[0011] The furanyl dicarboxylic acid polyester used to prepare masterbatch containing solid phase accelerator has the same chemical structure as the prepolymer and is selected from furanyl dicarboxylic acid polyester prepolymer, furanyl dicarboxylic acid polyester product, furanyl dicarboxylic acid polyester commodity, or powdered furanyl dicarboxylic acid polyester recycled material generated from solid phase reaction process.

[0012] The triacid anhydride includes trimellitic anhydride and 1,2,4-cyclohexanetriic anhydride, and the tetraacid dianhydride is selected from one or more of 1,2,3,4-cyclobutanetetracarboxylic anhydride, 1,2,4,5-cyclohexanetetracarboxylic anhydride, pyromellitic anhydride, 3,3',4,4'-biphenyltetracarboxylic anhydride, biphenyl ether dianhydride, bisphenol A type diether dianhydride, 3,3',4,4'-benzophenonetetracarboxylic anhydride, diphenyl sulfonetetracarboxylic anhydride, 1,4,5,8-naphthalenetetracarboxylic anhydride, dicyclohexyl-3,4,3',4'-tetracarboxylic anhydride, 2,3,6,7-anthracitetetracarboxylic anhydride, and ethylene glycol bis(triphenyltrimethylene) anhydride. The dioxazoline includes one or more of 2,2'-(1,3-phenylene)-dioxazoline, 2,2'-(1,4-phenylene)-dioxazoline, 2,2'-bis(2-oxazoline), and 2,2'-(ethylene)-dioxazoline; The diepoxide includes one or more of diglycidyl ether, diglycidyl ester, and diglycidylamine.

[0013] The diol comprises 80-100 mol% diol A and 0-20 mol% diol B; The diol A includes one or more of ethylene glycol, 1,3-propanediol, 1,4-butanediol, neopentyl glycol, or cyclohexanediol, and the diol B includes straight-chain or branched aliphatic diols with C≥2 or alicyclic diols with C≥6, and the diol B is different from the diol A. The furanyl dicarboxylate includes dimethyl furanyl dicarboxylate and / or diethyl furanyl dicarboxylate.

[0014] The zinc compounds containing carboxyl groups include one or more of the following: zinc acetate, zinc propionate, zinc lactate, zinc butyrate, zinc isobutyrate, zinc valerate, zinc pivalate, zinc hexanoate, zinc octanoate, zinc isooctanoate, zinc nonanoate, zinc decanoate, zinc neodecanoate, zinc laurate, zinc stearate, zinc malate, zinc citrate, zinc oxalate, zinc succinate, zinc glutarate, zinc adipic acid, zinc octanoate, zinc azelaate, zinc sebacate, zinc dodecanoate, zinc tetradecanoate, and zinc hexadecanoate. The zinc complex includes zinc acetylacetone.

[0015] The reaction in step 1 may also include an auxiliary catalyst, which may include one or more of titanium-based catalysts, antimony-based catalysts, germanium-based catalysts, or tin-based catalysts; the mass ratio of the auxiliary catalyst to the zinc-based catalyst is 0-30:70-100; the auxiliary catalyst and the zinc-based catalyst are added to the reactor together in the transesterification stage; The titanium-based catalysts include one or more of tetrabutyl titanate, tetraisopropyl titanate, tetraethyl titanate, titanium glycolate, titanium acetylacetonate, and diisopropyl di(acetylacetonate)titanate; the amount used is 5-200 ppm; the amount of catalyst used is based on the mass ratio of the metal element to the polyester, and the following descriptions all refer to this definition.

[0016] The antimony-based catalyst includes one or more of antimony trioxide, antimony acetate, and antimony glycol; its dosage is 20-400 ppm; The germanium-based catalyst includes one or more of germanium dioxide and germanium salts; its dosage is 20-400 ppm; The tin-based catalyst includes one or more of stannous oxalate, stannous octanoate, dibutyltin dilaurate, dibutyltin oxide, and butylstannic acid; the amount used is 20-2500 ppm.

[0017] In this invention, antioxidants and heat stabilizers may also be added during the transesterification or melt polycondensation stage.

[0018] The transesterification was carried out at a temperature of 140-240℃ and an absolute pressure of 50kPa-1atm for 1.5-6 hours. The melt polycondensation is carried out at 200-300℃ and absolute pressure < 200Pa for 1.5-6 hours; Between transesterification and melt polycondensation, there is also a pre-polycondensation process, which lasts for 0.5-1 hour. This process involves slow heating and slow increase in vacuum, transitioning from transesterification to melt polycondensation.

[0019] The intrinsic viscosity of the prepolymer is 0.35-0.70 dL / g, preferably 0.40-0.60 dL / g. A higher intrinsic viscosity of the prepolymer is beneficial for rapidly increasing the intrinsic viscosity during solid-phase thickening, but obtaining an excessively high intrinsic viscosity requires a longer melt polycondensation time or a higher melt polycondensation temperature, which is not conducive to suppressing the discoloration of furanyl dicarboxylic acid polyester.

[0020] Preferably, the content of terminal ester groups in the prepolymer is below 30 mmol / kg, more preferably below 20 mmol / kg, and even more preferably below 10 mmol / kg. The low content of terminal ester groups in the prepolymer is beneficial to improving the solid-phase thickening rate and shortening the solid-phase thickening time, thereby facilitating the rapid increase of intrinsic viscosity during the solid-phase thickening process.

[0021] Preferably, the prepolymer particles are controlled at 0.1-5 mm, more preferably 1-4 mm, and even more preferably 2-4 mm. Smaller particle size is more conducive to improving the intrinsic viscosity of the product.

[0022] Before solid-phase thickening, the prepolymer granules are dried at 110-120℃ for 0.5-2 hours; then pre-crystallized at 140-240℃ for 1-4 hours.

[0023] The solid-phase thickening is carried out at a temperature 2-30°C lower than the melting point of the prepolymer granules, a pressure of 10-300 Pa, or under inert gas protection for 4-15 hours. More preferably, it is carried out at a temperature 5-25°C lower than the melting point of the prepolymer granules, a pressure of 10-200 Pa, or under an inert atmosphere, for a reaction time of 4-15 hours.

[0024] The intrinsic viscosity of the furanyl dicarboxylic acid polyester obtained by the present invention is above 0.7 dL / g, preferably above 0.8 dL / g, and more preferably above 0.9 dL / g; the b* value of the furanyl dicarboxylic acid polyester is below 13, preferably below 10, and more preferably below 7.

[0025] PEF typically exhibits brittle tensile behavior and is considered a brittle polymer. This invention unexpectedly discovered that the prepared PEF polyester, when its tensile specimen has an IV > 0.60 dL / g, exhibits ductile fracture behavior in tensile tests, with an elongation at break reaching 40-100%, demonstrating high tensile toughness.

[0026] Compared with the prior art, the present invention has the following beneficial effects: This invention utilizes a transesterification-melt polycondensation-solid-phase thickening technology route, employing a zinc-based catalyst to significantly suppress discoloration of furanyl dicarboxylic acid polyester during polymerization. A higher alcohol-ester ratio yields prepolymers with low methyl ester content. Combined with a solid-phase accelerator, the solid-phase thickening rate is significantly increased, resulting in a substantial increase in intrinsic viscosity within a short time, producing a light-colored furanyl dicarboxylic acid polyester with high intrinsic viscosity. The resulting PEF polyester also exhibits high tensile toughness, avoiding the brittleness inherent in PEF. The zinc-based catalyst, solid-phase accelerator, and polymerization process used are environmentally friendly and harmless, facilitating industrial-scale implementation. Attached Figure Description

[0027] Figure 1 The PEF prepolymer pellets prepared in Example 28 ( Figure 1 a) and PEF final product ( Figure 1 (b)

[0028] Figure 2 The PEF prepolymer pellets prepared in Example 29 ( Figure 2 a) and PEF final product ( Figure 2 (b) Actual picture.

[0029] Figure 3 The tensile curves of PEF prepared in Examples 6, 7, 12, 25, 29 and Comparative Examples 3 and 4 are shown. The tensile curves of Comparative Examples 3 and 4 are obscured by other curves and are not labeled. For details, please refer to [reference needed]. Figure 4 .

[0030] Figure 4 The image shows enlarged views of the tensile curves of PEF prepared in Examples 6, 7, 12, 25, 29 and Comparative Examples 3 and 4.

[0031] Figure 5 Comparison of the tensile properties of PEF obtained in Examples 6, 7, 12, 25, 29 and Comparative Examples 3 and 4. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Modifications or equivalent substitutions made by those skilled in the art based on their understanding of the technical solutions of this invention, without departing from the spirit and scope of the invention, should be covered within the protection scope of this invention.

[0033] All raw materials used in the following specific embodiments were purchased from the market. In the embodiments, the raw materials used, the obtained furan dicarboxylic acid polyester, and their abbreviations are shown below.

[0034] Monomers: Dimethyl 2,5-furandicarboxylate (DMFD), ethylene glycol (EG), 1,3-propanediol (PDO), and cyclohexanediol (CHDM).

[0035] Catalysts: Zinc oxide (ZnO), zinc carbonate (ZnC), zinc acetate dihydrate (ZA), zinc lactate (ZL), zinc isooctanoate (ZEH), zinc laurate (ZLA), zinc adipic acid (ZAA), zinc dodecanoate (ZDA), zinc phthalate (ZPA), zinc acetylacetonate (Zacac), titanium glycolate (TG), and antimony glycolate (SbEG).

[0036] Solid phase promoters: trimellitic anhydride (TMA), pyromellitic dianhydride (PMDA), 2,2'-(1,3-phenylene)-dioxazoline (PBO).

[0037] In the examples, the synthesized furanyl dicarboxylic acid polyesters are abbreviated as follows: polyethylene furanyl dicarboxylate (PEF), 1,3-propanediol polyfuranyl dicarboxylate (PPF), and cyclohexanediol-co-ethylene dicarboxylate (PCEF).

[0038] In this invention, intrinsic viscosity is used to indirectly represent the molecular weight of furanyl dicarboxylic acid polyester. The higher the intrinsic viscosity, the higher the molecular weight.

[0039] In this invention, the amount of catalyst used is expressed as the mass ratio (in ppm) of the metal element in the catalyst to the obtained furan dicarboxylic acid polyester.

[0040] In this invention, the amount of solid phase accelerator is expressed as the molar percentage of solid phase accelerator in furan dicarboxylate.

[0041] The analytical and testing methods used in this invention are as follows: The content of terminal methyl ester groups in the prepolymer was calculated using 1H NMR spectroscopy results.

[0042] Intrinsic viscosity IV: Tested using an IVS300 semi-automatic viscometer (Hangzhou Zhongwang Company) and an Ubbelohde viscometer with a capillary inner diameter of 0.88 mm at a constant temperature of 25℃. The solvent was a phenol / tetrachloroethane mixed solution (mass ratio 3 / 2) with a concentration of 0.5 g / dL. The Billmeyer equation IV = (3ln(...) was used according to GB / T 17931-2018. t / t 0)+ t / t 0-1)) / 4 c Calculate the intrinsic viscosity, where c This is the solution concentration, expressed in g / dL. t and t0 represents the flow time of the solution and the pure solvent, respectively, in seconds.

[0043] chromaticity value L *、 b *: CIELAB colorimetric values ​​of polymer granules were measured using a Hangzhou Caipu CS-821N desktop spectrophotometer. L *、 b * represents brightness and the degree of blue (-) / yellow (+), respectively.

[0044] Tensile properties: Polyester samples were subjected to tensile testing at 70°C. o Vacuum dried at 260°C for 24 hours, then injected at 260°C using a Haake MiniJet II micro injection molding machine. o C. Mold temperature 90 o Dumbbell-shaped specimens (2 mm thick, 4 mm wide) were prepared under temperature C and allowed to stand at room temperature for at least 48 hours before tensile property testing. Tensile testing was conducted according to GB / T 1040-2006 standard using a Zwick / Roell Z020 universal testing machine from Zwick GmbH, Germany, at room temperature. The tensile rate was 10 mm / min, and the preload was 1 N. Five specimens were tested for each sample, and the average value was taken.

[0045] Comparative Example 1: PEF, ZA+TG, R1.35, MEG142, IV 10 0.51 a) Preparation of prepolymer granules: Under nitrogen protection, 73.6 g DMFD, 33.5 g EG (ethanol-ester ratio 1.35), 0.024 g ZA, and 0.0081 g TG were added to a 250 mL glass reactor. The reaction was carried out at 180 °C for 1 h, then at 190 °C for 1 h, and then at 200 °C until no more methanol distilled off. Subsequently, the temperature was raised to 230 °C, and the pressure was gradually reduced to below 50 Pa over 30 min, and the melt polycondensation reaction was carried out for 3 h to obtain PEF prepolymer. The pressure was restored to normal, and the prepolymer was removed. After cooling, it was pulverized and sieved to obtain PEF prepolymer granules with a particle size of 0.2-0.8 mm. The intrinsic viscosity of the prepolymer was measured to be 0.33 dL / g, and the content of terminal methyl ester groups was 142 mmol / kg.

[0046] b) Drying and pre-crystallization: The prepolymer granules are then placed in a solid-phase thickening reactor and dried at 110°C and <150Pa for 1.5 hours. The temperature is then raised to 140°C for 1 hour to pre-crystallize the pre-crystallized PEF prepolymer granules.

[0047] c) Solid-phase thickening: The temperature of the solid-phase thickening reactor was gradually increased to 210℃ at a rate of 1℃ / min, and the pressure was gradually decreased to < 50Pa. Solid-phase thickening was carried out at this temperature and pressure for 10h to obtain PEF with an intrinsic viscosity of 0.51dL / g. The specific reaction conditions and results are shown in Table 1.

[0048] Comparative Example 2: PEF, ZA+TG, R1.45, MEG99.9, IV 10 0.76 The other conditions were the same as in Comparative Example 1, except that the amount of ethylene glycol used was 36.0 g (ethanol-ester ratio 1.45), the intrinsic viscosity of the resulting prepolymer was 0.43 dL / g, the content of terminal methyl ester groups was 99.9 mmol / kg, and the intrinsic viscosity of the PEF obtained after 10 h of solid-phase thickening was 0.76 dL / g. Specific reaction conditions and results are shown in Table 1.

[0049] Comparative Example 3: PEF, ZA+TG, R2.0, MEG82.7, IV 10 0.58 a) Preparation of prepolymer granules: Under nitrogen protection, 736g DMFD, 496g EG, 0.24g ZA, and 0.081g TG were added to a 2.5L stainless steel reactor and reacted at 180℃ for about 3 hours. The temperature was then raised to 230℃, and the pressure was gradually reduced to below 50Pa over 30 minutes, allowing for melt polycondensation for 3 hours. Nitrogen gas was introduced to restore atmospheric pressure, and the mixture was stretched, granulated, and pulverized to obtain PEF prepolymer granules with a particle size of 0.2-0.8mm. Due to abnormal temperature control during the transesterification process, the intrinsic viscosity of the obtained prepolymer was low, only 0.38 dL / g, while the content of terminal methyl ester groups was high, at 82.7 mmol / kg.

[0050] b) Drying and pre-crystallization: The prepolymer granules were placed in a solid-phase thickening reactor and dried at 110°C and <150Pa for 1.5 h. Then the temperature was raised to 140°C for pre-crystallization for 1 h to obtain pre-crystallized PEF prepolymer granules.

[0051] c) Solid-phase thickening: The temperature in the solid-phase thickening reactor was gradually increased to 210℃ at a rate of 1℃ / min, and the pressure was gradually decreased to < 50Pa. Solid-phase thickening was carried out under these temperature and pressure conditions for 10 hours, and the intrinsic viscosity only increased to 0.58 dL / g. The specific reaction conditions and results are shown in Table 1.

[0052] Comparative Example 4: PEF (antimony glycolate 200), R1.5, IV 10 0.86 a) Preparation of prepolymer granules: Under nitrogen protection, 624g FDCA, 496g EG, and 0.253g antimony glycolate were added to a 2.5L stainless steel reactor and reacted at 190℃-200℃ for about 4 hours. Subsequently, the temperature was raised to 230℃, and the pressure was gradually reduced to below 50Pa within 30 minutes, and the melt polycondensation reaction was carried out for 3 hours. Nitrogen gas was introduced to restore normal pressure, and the mixture was stretched, granulated, and crushed to obtain PEF prepolymer granules with a particle size of 0.2-0.8mm and an intrinsic viscosity of 0.52dL / g.

[0053] b) Drying and pre-crystallization: The prepolymer granules were placed in a solid-phase thickening reactor and dried at 110 °C. ℃ The material was dried under a pressure of <150Pa for 1.5 hours, and then the temperature was raised to 140℃ for pre-crystallization for 1 hour to obtain pre-crystallized PEF prepolymer granules.

[0054] c) Solid-phase thickening: The temperature in the solid-phase thickening reactor was gradually increased to 210℃ at a rate of 1℃ / min, and the pressure was gradually decreased to < 50Pa. Solid-phase thickening was carried out under these temperature and pressure conditions for 10 hours, and the intrinsic viscosity only increased to 0.86 dL / g. The specific reaction conditions and results are shown in Table 1.

[0055] Example 1: PEF, ZA+TG, R1.7, MEG44.3, IV 10 1.13 Synthesis of the prepolymer: 73.6 g DMFD, 42.2 g EG (ethanol-ester ratio 1.7), 0.024 g ZA and 0.0081 g TG were added to a 250 mL glass reactor under nitrogen protection. The temperature was raised to 180 °C for transesterification reaction for 1 h, then raised to 190 °C for 1 h; then raised to 200 °C until no more methanol distilled off; then the temperature was raised to 230 °C over 30 min, and the pressure was gradually reduced to below 50 Pa for melt polycondensation reaction for 3 h; the pressure was restored to normal under nitrogen protection, the material was discharged, cooled, crushed and sieved to obtain prepolymer granules with a particle size of 0.2-0.8 mm, an intrinsic viscosity (IV0) of 0.47 dL / g, and a MEG content of 44.3 mmol / kg.

[0056] The prepolymer granules were placed in a solid-phase thickening reactor and dried at 110℃ and < 150Pa pressure for 1.5h. Then the temperature was raised to 140℃ for pre-crystallization for 1h to obtain pre-crystallized PEF granules. Then, the temperature of the solid-phase thickening reactor was gradually increased to 210℃ at a rate of 1℃ / min, and the pressure was gradually decreased to <50Pa. Solid-phase thickening was carried out at this temperature and pressure for 10 hours to obtain PEF polyester with an intrinsic viscosity IV. 10The concentration was 1.13 dL / g. Specific reaction conditions and results are shown in Table 1.

[0057] Example 2: PEF, ZA+TG, R2.0, MEG10.8, IV 10 1.25 Other conditions were the same as in Example 1, except that the amount of ethylene glycol was changed from 42.2 g in Example 2 to 49.6 g, the alcohol-ester ratio was increased from 1.7 to 2.0, the intrinsic viscosity of the resulting prepolymer was 0.50 dL / g, the content of terminal methyl ester groups was 10.8 mmol / kg, and the intrinsic viscosity of the PEF product obtained after 10 hours of solid-phase thickening was 1.25 dL / g. Specific reaction conditions and results are shown in Table 1.

[0058] Example 3: PEF, ZA+TG, R2.5, MEG3.9, IV 10 1.43 Other conditions were the same as in Example 1, except that the amount of ethylene glycol was changed from 42.2 g in Example 2 to 62.1 g, the alcohol-ester ratio was increased from 1.7 to 2.5, the intrinsic viscosity of the resulting prepolymer was 0.58 dL / g, the content of terminal methyl ester groups was 3.9 mmol / kg, and the intrinsic viscosity of the PEF product obtained after 10 hours of solid-phase thickening was 1.43 dL / g. Specific reaction conditions and results are shown in Table 1.

[0059] Example 4: PEF, ZA+TG, R3.0, MEG0.7, IV 10 1.66 Other conditions were the same as in Example 1, except that the amount of ethylene glycol was changed from 42.2 g in Example 2 to 74.5 g, the alcohol-ester ratio was increased from 1.7 to 3.0, the intrinsic viscosity of the resulting prepolymer was 0.63 dL / g, the content of terminal methyl ester groups was 0.7 mmol / kg, and the intrinsic viscosity of the PEF product obtained after 10 hours of solid-phase thickening was 1.66 dL / g. Specific reaction conditions and results are shown in Table 1.

[0060] Example 5* PEF, ZA+TG, R2.0, MEG43.6, IV 10 0.78 Other conditions were the same as in Comparative Example 3, except that the transesterification and melt polycondensation conditions were controlled more normally. The intrinsic viscosity of the obtained prepolymer was 0.40 dL / g, the content of terminal methyl ester groups was 43.6 mmol / kg, and the intrinsic viscosity of the PEF product obtained after 10 hours of solid-phase thickening was 0.78 dL / g. Specific reaction conditions and results are shown in Table 1.

[0061] Example 6: PEF, zinc acetate 100ppm, R2.0, MEG 8.9, IV 10 0.72 Other conditions were the same as in Example 2, except that the 100ppm zinc acetate + 32ppm titanium glycol composite catalyst in Example 2 was replaced with a single 100ppm zinc acetate catalyst. The intrinsic viscosity of the resulting prepolymer was 0.46 dL / g, the content of terminal methyl ester groups was 8.9 mmol / kg, and the intrinsic viscosity of the PEF product obtained after 10 hours of solid-phase thickening was 0.72 dL / g. Specific reaction conditions and results are shown in Table 1.

[0062] Example 7: PEF zinc acetate 300ppm, R2.0, MEG 3.5, IV 10 0.81 Other conditions were the same as in Example 6, except that the amount of zinc acetate catalyst was increased from 100 ppm in Example 6 to 300 ppm. The intrinsic viscosity of the resulting prepolymer was 0.50 dL / g, the content of terminal methyl ester groups was 3.5 mmol / kg, and the intrinsic viscosity of the PEF product obtained after 10 hours of solid-phase thickening was 0.81 dL / g. Specific reaction conditions and results are shown in Table 1.

[0063] Example 8: PEF zinc acetate 300ppm, R3.0, MEG 0, IV 10 1.10 Other conditions were the same as in Example 7, except that the alcohol-ester ratio was increased from 2.0 in Example 7 to 3.0. The intrinsic viscosity of the resulting prepolymer was 0.61 dL / g, and the content of terminal methyl ester groups was 0 (meaning it was not detected by the instrument, the same below). The intrinsic viscosity of the PEF product obtained after 10 hours of solid-phase thickening was 1.10 dL / g. Specific reaction conditions and results are shown in Table 1.

[0064] Example 9: PEF zinc acetate 300ppm, R3.0, MEG 0, IV 10 1.15 The reaction conditions were exactly the same as in Example 8, and the experiment was repeated. The specific reaction conditions and results are shown in Table 1.

[0065] Example 10: PEF zinc oxide 300ppm, R2.0, MEG 5.4, IV 10 0.70 Other conditions were the same as in Example 7, except that the catalyst was changed from 300 ppm zinc acetate in Example 7 to 300 ppm zinc oxide. The intrinsic viscosity of the resulting prepolymer was 0.36 dL / g, the content of terminal methyl ester groups was 5.4 mmol / kg, and the intrinsic viscosity of the PEF product obtained after 10 hours of solid-phase thickening was 0.70 dL / g. Specific reaction conditions and results are shown in Table 1.

[0066] Example 11: PEF zinc carbonate 300ppm, R2.0, MEG 6.8, IV 10 0.79 Other conditions were the same as in Example 7, except that the catalyst was changed from 300 ppm zinc acetate in Example 7 to 300 ppm zinc carbonate. The intrinsic viscosity of the resulting prepolymer was 0.47 dL / g, the content of terminal methyl ester groups was 6.8 mmol / kg, and the intrinsic viscosity of the PEF product obtained after 10 hours of solid-phase thickening was 0.79 dL / g. Specific reaction conditions and results are shown in Table 1.

[0067] Example 12: PEF zinc lactate 300ppm, R2.0, MEG 7.5, IV 10 0.86 Other conditions were the same as in Example 7, except that the catalyst was changed from 300 ppm zinc acetate in Example 7 to 300 ppm zinc lactate. The intrinsic viscosity of the resulting prepolymer was 0.53 dL / g, the content of terminal methyl ester groups was 7.5 mmol / kg, and the intrinsic viscosity of the PEF product obtained after 10 hours of solid-phase thickening was 0.86 dL / g. Specific reaction conditions and results are shown in Table 1.

[0068] Example 13: PEF zinc adipic acid 300ppm, R2.0, MEG 7.7, IV 10 0.76 Other conditions were the same as in Example 7, except that the catalyst was changed from 300 ppm zinc acetate in Example 7 to 300 ppm zinc adipate. The intrinsic viscosity of the resulting prepolymer was 0.45 dL / g, the content of terminal methyl ester groups was 7.7 mmol / kg, and the intrinsic viscosity of the PEF product obtained after 10 hours of solid-phase thickening was 0.76 dL / g. Specific reaction conditions and results are shown in Table 1.

[0069] Example 14: PEF zinc dodecanoate 300ppm, R2.0, MEG 6.4, IV 10 0.85 Other conditions were the same as in Example 7, except that the catalyst was changed from 300 ppm zinc acetate in Example 7 to 300 ppm zinc dodecanoate. The intrinsic viscosity of the resulting prepolymer was 0.52 dL / g, the content of terminal methyl ester groups was 6.4 mmol / kg, and the intrinsic viscosity of the PEF product obtained after 10 hours of solid-phase thickening was 0.85 dL / g. Specific reaction conditions and results are shown in Table 1.

[0070] Example 15: PEF zinc phthalate 300ppm, R2.0, MEG 8.5, IV 10 0.77 Other conditions were the same as in Example 7, except that the catalyst was changed from 300 ppm zinc acetate in Example 7 to 300 ppm zinc phthalate. The intrinsic viscosity of the resulting prepolymer was 0.44 dL / g, the content of terminal methyl ester groups was 8.5 mmol / kg, and the intrinsic viscosity of the PEF product obtained after 10 hours of solid-phase thickening was 0.77 dL / g. Specific reaction conditions and results are shown in Table 1.

[0071] Example 16: PEF 2-Zinc 2-ethylhexanoate 300ppm, R3.0, MEG 0, IV 10 0.81 Other conditions were the same as in Example 7, except that the catalyst was changed from 300 ppm zinc acetate in Example 7 to 300 ppm zinc 2-ethylhexanoate, and the alcohol-ester ratio was changed from 2.0 in Example 7 to 3.0. The intrinsic viscosity of the resulting prepolymer was 0.41 dL / g, the content of terminal methyl ester groups was 0, and the intrinsic viscosity of the PEF product obtained after 10 hours of solid-phase thickening was 0.81 dL / g. Specific reaction conditions and results are shown in Table 1.

[0072] Example 17 PEF Zinc Laurate 300ppm, R3.0, MEG 0, IV 10 0.83 Other conditions were the same as in Example 7, except that the catalyst was changed from 300 ppm zinc acetate in Example 7 to 300 ppm zinc laurate, and the alcohol-ester ratio was changed from 2.0 in Example 7 to 3.0. The intrinsic viscosity of the resulting prepolymer was 0.44 dL / g, the content of terminal methyl ester groups was 0, and the intrinsic viscosity of the PEF product obtained after 10 hours of solid-phase thickening was 0.83 dL / g. Specific reaction conditions and results are shown in Table 1.

[0073] Example 18 PEF Zinc Acetylacetone 300ppm, R3.0, MEG 0, IV 10 0.85 Other conditions were the same as in Example 7, except that the catalyst was changed from 300 ppm zinc acetate in Example 7 to 300 ppm zinc acetylacetonate, and the alcohol-ester ratio was changed from 2.0 in Example 7 to 3.0. The intrinsic viscosity of the resulting prepolymer was 0.47 dL / g, the content of terminal methyl ester groups was 0, and the intrinsic viscosity of the PEF product obtained after 10 hours of solid-phase thickening was 0.85 dL / g. Specific reaction conditions and results are shown in Table 1.

[0074] Example 19: PEF zinc acetate 300ppm, R3.0, MEG 0, PMDA 0.1, IV 10 0.1.49 Other conditions were the same as in Example 8, except that the intrinsic viscosity of the obtained prepolymer was 0.54 dL / g. After melt polycondensation, the pressure was restored to normal under nitrogen protection, and 0.1 mol% PMDA solid phase promoter was added to the prepolymer melt. The melt polycondensation temperature was maintained, and the mixture was stirred for 15 minutes. The intrinsic viscosity of the PEF product obtained after 10 hours of solid phase thickening was 1.49 dL / g. Specific reaction conditions and results are shown in Table 1.

[0075] Example 20: PEF zinc acetate 300ppm, R2.5, MEG 0, PMDA 0.1, IV 10 1.32 Other conditions were the same as in Example 19, except that the alcohol-ester ratio was changed from 3.0 in Example 19 to 2.5. The intrinsic viscosity of the resulting prepolymer was 0.56 dL / g. Furthermore, 0.1 mol% of PBO solid-phase accelerator was added to the prepolymer melt, and the intrinsic viscosity of the PEF product obtained after 10 hours of solid-phase thickening was 1.32 dL / g. Specific reaction conditions and results are shown in Table 1.

[0076] Example 21: PEF zinc dodecanoate 300ppm, R2.0, MEG 0, PMDA 0.1, IV 10 1.29 Other conditions were the same as in Example 19, except that the catalyst was changed from 300 ppm zinc acetate in Example 19 to 300 ppm zinc dodecanoate, and the alcohol-ester ratio was changed from 3.0 in Example 19 to 2.0. The intrinsic viscosity of the resulting prepolymer was 0.51 dL / g, the content of terminal methyl ester groups was 0, and 0.1 mol% PMDA solid phase promoter was added to the prepolymer melt. After 10 hours of solid phase thickening, the intrinsic viscosity of the PEF product was 1.29 dL / g. Specific reaction conditions and results are shown in Table 1.

[0077] Example 22: PPF ZA+TG, R2.0, MEG 6.7, PMDA 0.1, IV 10 1.42 Other conditions were the same as in Example 2, except that 49.6g of ethylene glycol in Example 2 was replaced with 60.9g of 1,3-propanediol. The intrinsic viscosity of the resulting prepolymer was 0.55 dL / g, the content of terminal methyl ester groups was 6.7 mmol / kg, and 0.1 mol% PMDA solid-phase promoter was added to the prepolymer. The melt polycondensation temperature was maintained, and the mixture was stirred for 15 minutes. The intrinsic viscosity of the PEF product obtained after 10 hours of solid-phase thickening was 1.42 dL / g. Specific reaction conditions and results are shown in Table 1.

[0078] Example 23 PC 80EF ZA+TG, R2.0, MEG 7.4, PMDA 0.1, IV 10 1.26 Other conditions were the same as in Example 8, except that the 49.6 g ethylene glycol in Example 2 was replaced with 92.3 g cyclohexanediol and 9.93 g ethylene glycol. The intrinsic viscosity of the resulting prepolymer was 0.50 dL / g, and the content of terminal methyl ester groups was 7.4 mmol / kg. 0.1 mol% PMDA solid-phase promoter was added to the prepolymer, and the melt polycondensation temperature was maintained while stirring and mixing for 15 minutes. After 10 hours of solid-phase thickening, the intrinsic viscosity of the PEF product was 1.26 dL / g. Specific reaction conditions and results are shown in Table 1.

[0079] Example 24: PEF ZA+TG R2.0, MEC 3.7, PMDA 0.1 2-4mm IV 10 1.38 a) Preparation of prepolymer granules: Under nitrogen protection, 736g DMFD, 496g ethylene glycol, 0.24g ZA, and 0.081g TG were added to a 2.5L stainless steel reactor. The reaction was carried out at 180℃ for 1 hour, then at 190℃ for 1 hour, and then at 200℃ until no more methanol distilled off. Subsequently, the temperature was raised to 230℃ over 30 minutes, and the pressure was gradually reduced to below 50Pa for melt polycondensation for 6 hours to obtain PEF prepolymer with an intrinsic viscosity of 0.53 dL / g and a terminal methyl ester group content of 3.7 mmol / kg. The pressure was restored to normal, and 0.10 mol% PMDA (based on DMFD) was added to the reaction system. The mixture was stirred and dispersed at 230℃ for 15 minutes. The mixture was then stretched and pelletized to obtain PMDA-containing PEF prepolymer granules with a particle size of 2-4 mm.

[0080] b) Drying and pre-crystallization: The prepolymer granules were placed in a solid-phase thickening reactor and dried at 110 °C. ℃ The material was dried under a pressure of <150Pa for 1.5 hours, and then the temperature was raised to 140℃ for pre-crystallization for 1 hour to obtain pre-crystallized PEF prepolymer granules.

[0081] c) Solid-phase thickening: The temperature in the solid-phase thickening reactor was gradually increased to 210℃ at a rate of 1℃ / min, and the pressure was gradually decreased to < 50Pa. Solid-phase thickening was carried out under these temperature and pressure conditions for 10 hours. The intrinsic viscosity of the obtained PEF product was 1.38 dL / g. The reaction conditions and results are shown in Table 1.

[0082] Example 25: PEF ZA+TG R2.0, MEC 3.7, PBO 0.1 2-4mm IV 10 0.91 The process was the same as in Example 24, except that the intrinsic viscosity of the prepolymer was 0.46 dL / g, the content of terminal methyl ester groups was 7.9 mmol / kg, and the solid-phase accelerator was changed from 0.1 mol% PMDA in Example 24 to 0.1 mol% PBO. After solid-phase thickening for 10 h, the intrinsic viscosity of the PEF obtained was 0.91 dL / g. The reaction conditions and results are shown in Table 1.

[0083] Example 26: PEF ZA+TG R2.0, MEC 3.7, TMA 0.1 2-4mm IV 10 0.95 The process was the same as in Example 24, except that the intrinsic viscosity of the prepolymer was 0.51 dL / g, the content of terminal methyl ester groups was 8.3 mmol / kg, and the solid-phase accelerator was changed from 0.1 mol% PMDA in Example 24 to 0.13 mol% TMA. After solid-phase thickening for 10 h, the intrinsic viscosity of the PEF obtained was 0.95 dL / g. The reaction conditions and results are shown in Table 1.

[0084] Example 27: PEF ZA300 R2.0, MEC 6.7, PMDA 0.1 2-4mm IV 10 0.89 The process was the same as in Example 24, except that the zinc acetate + titanium glycol catalyst in Example 24 was replaced with a 300 ppm zinc acetate catalyst. The intrinsic viscosity of the prepolymer was 0.51 dL / g, the content of terminal methyl ester groups was 6.7 mmol / kg, and the particle size of the prepolymer granulated by stranding was 1-2 mm. After solid-phase thickening for 10 h, PEF was obtained with an intrinsic viscosity of 0.89 dL / g. The specific reaction conditions and results are shown in Table 1.

[0085] Example 28: PEF ZA+TG R2.0, MEC 3.7, PMDA 0.1 2-4mm nitrogen solid phase viscosity enhancement, IV 10 1.33 The process was the same as in Example 24, except that a tubular fixed-bed reactor was used as the solid-phase thickening reactor. The prepolymer granules obtained in Example 24 were added to the reactor and dried at 110°C for 1.5 h under a dry nitrogen atmosphere of 8 L / min. Then, the temperature was raised to 140°C for pre-crystallization for 1 h to obtain pre-crystallized PEF prepolymer granules. While maintaining a constant nitrogen flow rate, the reactor temperature was gradually increased from 140°C to 210°C at a rate of 1°C / min, and solid-phase thickening was performed at this temperature for 10 h to obtain PEF with an intrinsic viscosity of 1.33 dL / g. The conditions and results are shown in Table 1.

[0086] The PEF prepolymer pellets obtained in Example 28 ( Figure 1a) and PEF final product ( Figure 1 (b) See the actual appearance of the product. Figure 1 .

[0087] Example 29 PEF ZA300 R2.0, MEC 9.1, PMDA 0.1 1-2mm Nitrogen Solid Phase Viscosity Enhancement IV 10 0.88 The process was the same as in Example 27, except that a tubular fixed-bed reactor was used as the solid-phase thickening reactor. The prepolymer granules obtained in Example 27 were added to the reactor and dried at 110°C for 1.5 h under a dry nitrogen atmosphere of 8 L / min. Then, the temperature was raised to 140°C for pre-crystallization for 1 h to obtain pre-crystallized PEF prepolymer granules. While maintaining a constant nitrogen flow rate, the reactor temperature was gradually increased from 140°C to 210°C at a rate of 1°C / min, and solid-phase thickening was performed at this temperature for 10 h to obtain PEF with an intrinsic viscosity of 0.88 dL / g. The conditions and results are shown in Table 1.

[0088] The PEF prepolymer pellets obtained in Example 29 ( Figure 2 a) and PEF final product ( Figure 2 (b) See the actual appearance of the product. Figure 2 .

[0089] Table 1 Summary of conditions and results for the examples and comparative examples

[0090] Table 1 a alcohol-ester molar ratio; b Prepolymer intrinsic viscosity; c Prepolymer end methyl ester group content; d The intrinsic viscosity of the product after 10 hours of solid-phase viscosity enhancement; e The color value L* of solid-phase viscosity-enhancing products represents brightness; f The color value b* of the solid-phase viscosity-enhancing product indicates yellow ( )-blue( )degree; g ZA 100ppm + TG 32ppm; * The transesterification / melt polycondensation was carried out in a 2.5 L stainless steel reactor; ** It was synthesized using the esterification-melt polycondensation-solid-phase polycondensation method.

[0091] Comparative Examples 1 and 2 used a zinc (100 ppm)-titanium (32 ppm) composite catalyst with alcohol-ester ratios of 1.35 and 1.45, respectively. Transesterification-melt polycondensation was carried out in a 250 mL glass reactor. The melt polycondensation rate was slow, and the IV0 of the resulting PEF prepolymers was only 0.33 dL / g and 0.43 dL / g, respectively. The prepolymers had very high terminal methyl ester group content, at 142 mmol / kg and 99.9 mmol / kg, respectively, leading to a slow solid-phase thickening rate. After 10 hours of reaction, the IV0... 10 They increased to 0.51 dL / g and 0.76 dL / g, respectively.

[0092] Compared to Comparative Examples 1-2, Examples 1-4 increased the alcohol-ester ratio to 1.7-3.0 while keeping other conditions the same. Melt polycondensation significantly increased, resulting in a significant increase in the IV0 of the obtained PEF prepolymers, reaching 0.47 dL / g, 0.50 dL / g, 0.58 dL / g, and 0.63 dL / g, respectively. The content of terminal methyl ester groups significantly decreased, reaching 44.3 mmol / kg, 10.8 mmol / kg, 3.9 mmol / kg, and 0.7 mmol / kg, respectively. This led to a significantly faster solid-phase thickening rate. After 10 hours of reaction, the IV0... 10 The viscosity increased to 1.13 dL / g, 1.25 dL / g, 1.43 dL / g, and 1.66 dL / g, respectively. This indicates that appropriately increasing the alcohol-ester ratio can significantly accelerate the melt polycondensation rate and reduce the content of terminal methyl ester groups in the prepolymer. The reduction in the content of terminal methyl ester groups in the prepolymer can further increase the solid-phase viscosity rate, significantly increasing the intrinsic viscosity of the PEF product obtained after 10 hours of solid-phase viscosity enhancement. The obtained PEF is light in color, a pale yellow.

[0093] Comparative Example 3 underwent transesterification-melt polycondensation in a 2.5 L stainless steel reactor under the same conditions as Example 2. Due to improper operation, the melt polycondensation rate was slow, and the IV0 of the obtained PEF prepolymer was only 0.38 dL / g. The content of terminal methyl ester groups in the prepolymer was high, reaching 82.7 mmol / kg, resulting in a slow solid-phase thickening rate. After 10 hours of reaction, the IV0 was... 10 It only increased to 0.58 dL / g.

[0094] In Example 5, the conditions were the same as in Comparative Example 3. The resulting prepolymer had an intrinsic viscosity (IV0) of 0.40 dL / g, which was not significantly different from Comparative Example 3. However, the content of terminal methyl ester groups was significantly lower, at 43.6 mmol / kg. The solid-phase viscosity increase rate was significantly faster than that of Comparative Example 3, and the intrinsic viscosity increased to 0.78 dL / g after 10 hours of reaction. This further demonstrates that reducing the content of terminal methyl ester groups in the prepolymer is beneficial for increasing the solid-phase polycondensation rate.

[0095] Example 6 uses 100 ppm zinc acetate as a single catalyst, and the rest is the same as in Example 2. It can produce PEF with a lighter color, but the intrinsic viscosity is lower than that in Example 2. This indicates that zinc acetate is beneficial to suppress PEF discoloration, but its catalytic activity is relatively lower than that of titanium-based catalysts.

[0096] Examples 7 and 8 used 300 ppm zinc acetate as a single catalyst, with alcohol-ester ratios of 2 and 3, respectively. Compared to Examples 2 and 4, the melt polycondensation rates were comparable, and the intrinsic viscosity and terminal methyl ester group content of the resulting prepolymers were essentially the same. However, the solid-phase viscosity increase rate was relatively slow; after 10 hours of reaction, the intrinsic viscosity increased to 0.81 dL / g and 1.10 dL / g, respectively. On the other hand, compared to Examples 2 and 4, the PEF obtained in Examples 7 and 8 was significantly lighter in color, approaching white. This also indicates that zinc acetate is beneficial in suppressing PEF discoloration, but its catalytic activity is relatively lower than that of titanium-based catalysts.

[0097] Example 9 is a repeat of Example 8, and the results are basically the same as those of Example 8, indicating that the experiment has good repeatability.

[0098] Examples 10-15 used zinc oxide, zinc carbonate, zinc lactate, zinc adipate, zinc dodecanoate, zinc phthalate, and other zinc-based catalysts as single catalysts, respectively. Other conditions were the same as in Example 2. All of them yielded prepolymers with light color and terminal methyl ester group content <10 mmol / kg. After vacuum solid-phase thickening, PEF with intrinsic viscosity of 0.70-0.85 dL / g and very light color was obtained.

[0099] Examples 16-18 used zinc ethylhexanoate, zinc laurate, and zinc acetylacetonate as single catalysts, with an alcohol-ester ratio of 3.0. The resulting prepolymers had very low terminal methyl ester groups, exceeding the instrument's measurement range, and were represented as 0. After solid-state thickening for 10 hours, PEF with an intrinsic viscosity of 0.81-0.85 dL / g was obtained.

[0100] Example 19 used zinc acetate as a single catalyst and added 0.1 mol% of the solid-phase accelerator PDMA to the prepolymer melt. Other steps were the same as in Examples 8 and 9. The intrinsic viscosity of the PEF product obtained after solid-phase thickening reached 1.49 dL / g, significantly higher than the 1.10 dL / g and 1.15 dL / g of Examples 8 and 9, respectively. This indicates that the solid-phase accelerator PMDA significantly promoted the increase of intrinsic viscosity during solid-phase thickening. Example 20 used 0.1 mol% of the solid-phase accelerator PBO and achieved similar results.

[0101] Example 21 used zinc dodecanoate as a single catalyst and added 0.1 mol% of solid phase promoter PDMA to the prepolymer melt. The rest was the same as in Example 14. The intrinsic viscosity of the PEF product obtained by solid phase thickening reached 1.29 dL / g, which was significantly higher than 0.85 dL / g in Example 14.

[0102] Examples 22-23 use zinc acetate and titanium glycol as zinc-titanium composite catalysts to synthesize 1,3-propanediol polyfurandicarboxylate (PPF) and cyclohexanediol-co-ethylene glycol polyfurandicarboxylate (PC). 80 In addition to zinc-based catalysts, 0.1 mol% PDMA was added to the prepolymer melt as a solid-phase promoter, resulting in solid-phase thickening and an increase in intrinsic viscosity to 1.42 dL / g and 1.26 dL / g. This indicates that the synthesis strategy of using zinc-based catalysts, controlling the content of low-end ester groups in the prepolymer, and adding solid-phase promoters can be used not only for the synthesis of light-colored, high intrinsic viscosity PEFs, but also for the synthesis of other crystalline furanyl dicarboxylic acid polyesters.

[0103] Examples 24-26 all used zinc acetate + titanium glycol as a composite catalyst to synthesize PEF prepolymers in a 2.5 L stainless steel reactor. The melt polycondensation time was extended to 6 hours, and PMDA, PBO, and TMA were added to the prepolymer melt as solid-phase promoters, respectively. This yielded large-particle-size prepolymer particles with a particle size of 2-4 mm and low end-methyl ester group content for solid-phase thickening, producing PEF with intrinsic viscosities of 1.38 dL / g, 0.91 dL / g, and 0.95 dL / g, respectively. It is evident that even with a large reactor size and a large prepolymer particle size, resulting in significantly diffusion-controlled reaction, the technical solution of this invention can still produce PEF with high viscosity and a light color.

[0104] Example 27 used zinc acetate as a single catalyst. The prepolymer granules had a particle size of 1-2 mm. Other aspects were the same as in Example 24. After 10 hours of solid-phase thickening, the intrinsic viscosity increased to 0.89 dL / g, which was lower than in Example 24, but the color was significantly lighter. Compared with Example 7, although the particle size was larger, PEF with a higher intrinsic viscosity (0.89 vs. 0.81 dL / g) was still obtained due to the effect of the solid-phase promoter PMDA.

[0105] Examples 28 and 29 were performed under a nitrogen atmosphere for solid-phase thickening, with other conditions being the same as in Examples 24 and 27, respectively, yielding results essentially the same as those in Examples 24 and 27. This indicates that the technical solution of the present invention does not limit the environment for solid-phase thickening, and solid-phase thickening under nitrogen conditions can also achieve excellent effects similar to vacuum solid-phase thickening.

[0106] The tensile curves of the PEF prepared in Examples 6, 7, 12, 25, 29 and Comparative Examples 3 and 4 are shown in the figure. Figure 3 (Note: The stretching curves in comparative examples 3 and 4 are covered by other curves and are therefore not marked. Please refer to the enlarged view for details.) Figure 4 ), Figure 4 Enlarged views of the tensile curves of PEF prepared in Examples 6, 7, 12, 25, 29 and Comparative Examples 3 and 4. The corresponding tensile modulus (E), maximum tensile stress (yield strength σ when yielding is present on the tensile curve), and other parameters are also shown. m ) and elongation at break ε b Summary Figure 5 It can be seen that the PEF prepared by the method of the present invention exhibits brittle fracture with an elongation at break of only 3.4% when its intravitreal index (IV) is too low (Comparative Example 3, IV 0.58 dL / g, which decreased to 0.48 dL / g after processing into specimens); when its IV is sufficiently high (Examples 6, 7, 12, 25, 29), it exhibits brittle fracture with an elongation at break of only 3.4%. When the tensile strength (IV) was 0.72 dL / g, 0.81 dL / g, 0.86 dL / g, 0.91 dL / g, and 0.88 dL / g, respectively, and after processing into specimens, the IV decreased to 0.64 dL / g, 0.69 dL / g, 0.71 dL / g, 0.69 dL / g, and 0.73 dL / g, respectively, all exhibited ductile tensile behavior and yielding, with elongation at break reaching 74%, 82%, 82%, 49%, and 94%, respectively, while maintaining excellent rigidity (tensile modulus 2.6-2.9 gPa) and strength (85-91 MPa).

[0107] This demonstrates that PEF synthesized according to the method of the present invention exhibits ductile tensile behavior as long as its tensile specimen has an intratensile volume (IV) of approximately 0.60 dL / g or higher. In contrast, PEF synthesized under similar conditions using an esterification-melt polycondensation-solid-phase thickening method (Comparative Example 4, IV 0.86 dL / g, which decreased to 0.73 dL / g after specimen preparation), even with an IV comparable to that of Examples 12, 25, and 29, exhibited brittle fracture behavior. Although its tensile modulus and strength remained high at 2.7 GPa and 76 MPa, respectively, its elongation at break was very low, at only 3.2%. This further illustrates the unexpected effectiveness of the method of the present invention in synthesizing ductile PEF.

Claims

1. A method for preparing furanyl dicarboxylic acid polyester based on the transesterification route, characterized in that, Including the following steps: Step 1: Using diol and furan dicarboxylate as monomer raw materials, a prepolymer melt is obtained through transesterification and melt polycondensation under the action of a zinc-based catalyst. The melt is then pelletized to obtain prepolymer pellets with an end ester group content of less than 50 mmol / kg. Step 2: The prepolymer granules are dried and pre-crystallized to obtain pre-crystallized granules; then, solid-phase thickening is performed to obtain the furan dicarboxylic acid polyester. The alcohol-ester ratio in the transesterification is 1.6-3.0; the zinc-based catalyst is one or more of zinc oxide, zinc carbonate, zinc compounds containing carboxyl groups, and zinc complexes.

2. The method for preparing furanyl dicarboxylic acid polyester based on the transesterification route according to claim 1, characterized in that, A solid phase accelerator or a masterbatch containing a solid phase accelerator is added to the prepolymer melt obtained in step 1, wherein the amount of the solid phase accelerator is 0.01-0.6 mol of furan dicarboxylate.

3. The method for preparing furanyl dicarboxylic acid polyester based on the transesterification route according to claim 2, characterized in that, The solid phase accelerator includes one or more of triacid anhydride, tetraacid dianhydride, dioxazoline, and diepoxide.

4. The method for preparing furanyl dicarboxylic acid polyester based on the transesterification route according to claim 3, characterized in that, The triacid anhydride includes trimellitic anhydride and 1,2,4-cyclohexanetriic anhydride, and the tetraacid dianhydride is selected from one or more of 1,2,3,4-cyclobutanetetracarboxylic anhydride, 1,2,4,5-cyclohexanetetracarboxylic anhydride, pyromellitic anhydride, 3,3',4,4'-biphenyltetracarboxylic anhydride, biphenyl ether dianhydride, bisphenol A type diether dianhydride, 3,3',4,4'-benzophenonetetracarboxylic anhydride, diphenyl sulfonetetracarboxylic anhydride, 1,4,5,8-naphthalenetetracarboxylic anhydride, dicyclohexyl-3,4,3',4'-tetracarboxylic anhydride, 2,3,6,7-anthracitetetracarboxylic anhydride, and ethylene glycol bis(triphenyltrimethylene) anhydride. The dioxazoline includes one or more of 2,2'-(1,3-phenylene)-dioxazoline, 2,2'-(1,4-phenylene)-dioxazoline, 2,2'-bis(2-oxazoline), and 2,2'-(ethylene)-dioxazoline; The diepoxide includes one or more of diglycidyl ether, diglycidyl ester, and diglycidylamine.

5. The method for preparing furanyl dicarboxylic acid polyester based on the transesterification route according to claim 1, characterized in that, The diol comprises 80-100 mol% diol A and 0-20 mol% diol B; The diol A includes one or more of ethylene glycol, 1,3-propanediol, 1,4-butanediol, neopentyl glycol, or cyclohexanediol, and the diol B includes straight-chain or branched aliphatic diols with C≥2 or alicyclic diols with C≥6, and the diol B is different from the diol A. The furanyl dicarboxylate includes dimethyl furanyl dicarboxylate and / or diethyl furanyl dicarboxylate.

6. The method for preparing furanyl dicarboxylic acid polyester based on the transesterification route according to claim 1, characterized in that, The zinc compounds containing carboxyl groups include one or more of the following: zinc acetate, zinc propionate, zinc lactate, zinc butyrate, zinc isobutyrate, zinc valerate, zinc pivalate, zinc hexanoate, zinc octanoate, zinc isooctanoate, zinc nonanoate, zinc decanoate, zinc neodecanoate, zinc laurate, zinc stearate, zinc malate, zinc citrate, zinc oxalate, zinc succinate, zinc glutarate, zinc adipic acid, zinc octanoate, zinc azelaate, zinc sebacate, zinc dodecanoate, zinc tetradecanoate, and zinc hexadecanoate. The zinc complex includes zinc acetylacetone.

7. The method for preparing furanyl dicarboxylic acid polyester based on the transesterification route according to claim 1, characterized in that, The transesterification was carried out at a temperature of 140-240℃ and an absolute pressure of 50kPa-1atm for 1.5-6 hours. The melt polycondensation is carried out at 200-300℃ and absolute pressure < 200Pa for 1.5-6 hours.

8. The method for preparing furanyl dicarboxylic acid polyester based on the transesterification route according to claim 1, characterized in that, The solid-phase thickening process is carried out for 4-15 hours at a temperature 2-30°C lower than the melting point of the prepolymer granules and at a pressure of 10-300Pa or under inert gas protection.

9. The method for preparing furanyl dicarboxylic acid polyester based on the transesterification route according to claim 1, characterized in that, The intrinsic viscosity of the prepolymer granules is 0.35-0.70 dL / g, and the content of terminal ester groups is below 30 mmol / kg.

10. The method for preparing furanyl dicarboxylic acid polyester based on the transesterification route according to claim 1, characterized in that, The furan dicarboxylic acid polyester has a b* value ≤ 13, intrinsic viscosity ≥ 0.70 dL / g, exhibits toughness fracture in tensile tests, and has an elongation at break ≥ 20%.

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