A pen resin and a method for synthesizing the same

Abstract

The application relates to a PEN resin and a synthesis method thereof, which comprises the following steps: S1, preparing 2,6-naphthalene dicarboxylic acid and ethylene glycol into a slurry, ultrasonic dispersion, and adding into a microchannel reactor; S2, adding a titanium-tantalum composite catalyst into the microchannel reactor, reacting under the protection of inert gas, and obtaining an esterification reactant; S3, collecting the esterification reactant obtained in the step S2 into a polycondensation kettle, heating, reducing pressure, and reacting to obtain a polymer melt; and S4, cooling the polymer melt obtained in the step S3, granulating, and obtaining the PEN resin; the preparation raw materials of the titanium-tantalum composite catalyst in the step S2 include tetrabutyl titanate, titanium isopropoxide and tantalum isopropoxide. The PEN resin synthesized by the method has a characteristic viscosity of 0.5-0.9 dL / g, a molecular weight distribution of 1.15-1.25, a glass transition temperature of 122-126 DEG C and a melting point of greater than or equal to 268 DEG C.

Description

Technical Field

[0001] This application relates to the field of polymer material synthesis technology, and in particular to a PEN resin and its synthesis method. Background Technology

[0002] Polyethylene naphthalate (PEN) is a high-performance polyester material with excellent thermal stability, mechanical properties, chemical stability, barrier properties, and weather resistance. It has broad application prospects in packaging materials, electronics, automotive industry, aerospace and other fields.

[0003] PEN is typically synthesized using 2,6-naphthalenedicarboxylic acid (2,6-NDA) or its esters with ethylene glycol (EG) in a two-step process involving esterification and polycondensation. For PEN synthesis catalysts, antimony trioxide (Sb₂O₃) or antimony acetate are commonly used industrially for polycondensation. While antimony-based catalysts exhibit high catalytic activity, antimony is a heavy metal and is toxic; its residues in PEN products may pose potential hazards to the environment and human health. Furthermore, antimony-based catalysts are prone to volatilization at high temperatures, leading to decreased catalytic efficiency and reactor wall deposition. In terms of synthesis processes, traditional PEN production mainly employs batch reactors, which suffer from low mass and heat transfer efficiency, long reaction times (5-7 hours), and a wide molecular weight distribution of the product (PDI > 1.5).

[0004] To address these issues, researchers have developed titanium-based catalysts (such as tetrabutyl titanate) as an alternative to antimony-based catalysts. However, single titanium-based catalysts may suffer from insufficient catalytic efficiency and a wide molecular weight distribution of products during PEN synthesis.

[0005] Therefore, developing PEN catalysts and synthesis technologies that are suitable for efficient, environmentally friendly, and continuous production remains a pressing technical problem to be solved in this field. Summary of the Invention

[0006] This invention provides a PEN resin and its synthesis method. By using a titanium-tantalum composite catalyst to catalyze the synthesis of PEN resin from 2,6-naphthalenedicarboxylic acid in a microchannel reactor system, the invention solves the problems of insufficient catalytic efficiency and wide molecular weight distribution of products that may exist in the PEN synthesis process with a single titanium catalyst, and is more efficient and energy-saving.

[0007] In a first aspect of this application, a method for synthesizing PEN resin is provided, comprising the following steps: S1, preparing a slurry from 2,6-naphthalenedicarboxylic acid and ethylene glycol, ultrasonically dispersing it, and adding it to a microchannel reactor; S2, adding a titanium-tantalum composite catalyst to the microchannel reactor and reacting it under the protection of an inert gas to obtain an esterification reactant; S3, collecting the esterification reactant obtained in step S2 into a polycondensation reactor, heating and depressurizing it, and reacting it to obtain a polymerization product; S4, cooling, granulating, and drying the polymerization product obtained in step S3 to obtain PEN resin; wherein the raw materials for preparing the titanium-tantalum composite catalyst in step S2 include tetrabutyl titanate, titanium isopropoxide, and tantalum isopropoxide.

[0008] By adopting the above technical solution, this application provides a method for synthesizing PEN resin. The PEN resin synthesized by this method has an intrinsic viscosity of 0.5-0.9 dL / g, a molecular weight distribution of 1.15-1.25, a glass transition temperature of 122-126℃, and a melting point ≥268℃. This is likely because this application introduces tantalum isopropoxide, tetrabutyl titanate, and titanium isopropoxide to form a titanium-tantalum composite catalytic system. In this composite system, tantalum atoms and titanium atoms may form a bimetallic synergistic center through oxygen bridging bonds. On the one hand, this can adjust the electron cloud density of the titanium center and suppress the thermal degradation side reactions caused by the strong Lewis acidity of the titanium catalyst; on the other hand, the composite catalyst exhibits higher resistance to impurity interference in the reaction system, which is beneficial to maintaining catalytic activity. Simultaneously, this application combines the above composite catalyst with a microchannel reactor, utilizing the excellent mass and heat transfer characteristics of the microchannel reactor to shorten the reaction time while reducing local overheating. Therefore, the finally synthesized PEN resin has the characteristics of high intrinsic viscosity, narrow molecular weight distribution, and excellent thermal properties.

[0009] Optionally, in step S2, the mass ratio of tetrabutyl titanate, titanium isopropoxide, and tantalum isopropoxide in the titanium-tantalum composite catalyst is (0.768-0.816):(0.192-0.204):(0.04-0.08).

[0010] By adopting the above technical solution, within this specific mass ratio range, tetrabutyl titanate, titanium isopropoxide, and tantalum isopropoxide can form a suitable synergistic catalytic effect. If the tantalum content is too low, the composite catalyst's ability to resist impurity interference is insufficient, and the catalytic efficiency is easily affected; if the tantalum content is too high, the excessive Lewis acidity of the metal center in the composite catalytic system may trigger branching or cross-linking side reactions of the polymer chain, thereby affecting the resin's melting point and processing performance. Therefore, when the mass ratio of tetrabutyl titanate, titanium isopropoxide, and tantalum isopropoxide is (0.768-0.816):(0.192-0.204):(0.04-0.08), it is beneficial to balance catalytic activity and side reaction inhibition, thereby enabling the PEN resin to have high intrinsic viscosity, narrow molecular weight distribution, and excellent thermal properties.

[0011] Optionally, in step S2, the mass ratio of tetrabutyl titanate to titanium isopropoxide in the titanium-tantalum composite catalyst is (7-27):3.

[0012] By adopting the above technical solution and adjusting the amount of tetrabutyl titanate and titanium isopropoxide according to the above mass ratio, when the mass ratio of tetrabutyl titanate and titanium isopropoxide is (7-27):3, it can be ensured that PEN resin has the characteristics of high intrinsic viscosity, narrow molecular weight distribution and excellent thermal properties.

[0013] Optionally, the preparation method of the titanium-tantalum composite catalyst includes the following steps: The reactor was first evacuated and then replaced with an inert gas. Under the protection of the inert gas, tetrabutyl titanate, titanium isopropoxide, and tantalum isopropoxide were added to the reactor and mixed. Glacial acetic acid was added, and the mixture was stirred at 55-65°C. After cooling, the mixture was sealed and stored to obtain the titanium-tantalum composite catalyst.

[0014] Optionally, in step S1, the mass ratio of 2,6-naphthalenedicarboxylic acid to ethylene glycol is 1:(1-2.3).

[0015] Optionally, in step S1, the flow rate of the slurry in the microchannel reactor is 30-80 mL / min. Optionally, the mass of the titanium-tantalum composite catalyst in step S2 accounts for 0.06-0.3% of the mass of 2,6-naphthalenedicarboxylic acid in step S1.

[0016] Optionally, in step S2, the nitrogen gas flow rate is 5-20 mL / min, the reaction temperature is 200-240℃, and the reaction time is 15-40 min.

[0017] Optionally, in step S3, the reaction temperature is 240-290℃, the reaction time is 30-90min, and the reaction pressure is 10-100Pa.

[0018] In a second aspect of this application, this application provides a PEN resin synthesized by the synthesis method of PEN resin described in the first aspect of this application.

[0019] Optionally, PEN resin is a high-performance polyester material with excellent thermal stability, mechanical properties, chemical stability, barrier properties, and weather resistance, offering broad application prospects in packaging materials, electronics, automotive, and aerospace industries. In packaging, PEN's superior barrier properties and heat resistance make it suitable for high-end food packaging, beer bottles, and pharmaceutical containers. In electronics, its films are used in flexible circuit boards, capacitors, and 5G communication equipment substrates. In the automotive industry, it can be used in tire cords, wire harness insulation, and sensor protective films. In aerospace, it is applied to satellite solar cell substrates, aviation cable insulation, and cabin interior materials. Furthermore, PEN also shows promising development potential in emerging fields such as optical films and solar backsheets.

[0020] In summary, the present invention has at least one of the following beneficial technical effects: 1. This application provides a method for synthesizing PEN resin. The PEN resin synthesized by this method has an intrinsic viscosity of 0.5-0.9 dL / g, a molecular weight distribution of 1.15-1.25, a glass transition temperature of 122-126℃, and a melting point ≥268℃. This application introduces tantalum isopropoxide, tetrabutyl titanate, and titanium isopropoxide to form a titanium-tantalum composite catalytic system. In this composite system, tantalum atoms and titanium atoms may form bimetallic synergistic centers through oxygen bridging bonds. On the one hand, this can adjust the electron cloud density of the titanium centers and suppress thermal degradation side reactions caused by the strong Lewis acidity of the titanium catalyst; on the other hand, the composite catalyst exhibits higher resistance to impurity interference in the reaction system, which is beneficial to maintaining catalytic activity. Simultaneously, this application combines the above-mentioned composite catalyst with a microchannel reactor, utilizing the excellent mass and heat transfer characteristics of the microchannel reactor to shorten the reaction time and reduce local overheating. Therefore, the finally synthesized PEN resin has the characteristics of high intrinsic viscosity, narrow molecular weight distribution, and excellent thermal properties.

[0021] 2. This application utilizes the extremely high mass and heat transfer characteristics of titanium-tantalum composite catalysts in microchannels to significantly shorten the traditional total reaction time of 5-7 hours. This not only significantly reduces production energy consumption but also greatly narrows the molecular weight distribution of the product, thereby improving the thermal properties of PEN resin. Detailed Implementation

[0022] The embodiments of the present invention will be described in detail below with reference to the examples. However, those skilled in the art will understand that the following examples are only for illustrating the present invention and should not be regarded as limiting the scope of the present invention. Specific conditions not specified in the examples shall be carried out according to conventional conditions or conditions recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0023] 2,6-Naphthalenedicarboxylic acid (2,6-naphthalenedicarboxylic acid) was purchased from Shanghai Maclean Biochemical Technology Co., Ltd. (N665791).

[0024] Preparation Example 1 Preparation of titanium-tantalum composite catalysts A three-necked flask equipped with a stirrer was subjected to three cycles of vacuuming and purging with high-purity nitrogen. Under nitrogen protection, 0.8 g of tetrabutyl titanate, 0.2 g of titanium isopropoxide, and 0.06 g of tantalum isopropoxide were added to the reactor via a syringe and mixed. Then, 0.34 g of strictly dehydrated glacial acetic acid was slowly added dropwise as a complexing agent. The mixture was stirred at 60 °C for 30 min, cooled to room temperature, and then sealed for storage to obtain the titanium-tantalum composite catalyst.

[0025] Preparation Example 2 The difference between Preparation Example 2 and Preparation Example 1 is that the total mass of tetrabutyl titanate and titanium isopropoxide remains unchanged at 1.0 g, and the mass ratio of tetrabutyl titanate and titanium isopropoxide is adjusted to 7:3.

[0026] Preparation Example 3 The difference between Preparation Example 3 and Preparation Example 1 is that the total mass of tetrabutyl titanate and titanium isopropoxide remains unchanged at 1.0 g, and the mass ratio of tetrabutyl titanate and titanium isopropoxide is adjusted to 9:1.

[0027] Preparation Example 4 The difference between Preparation Example 4 and Preparation Example 1 is that the total mass of tetrabutyl titanate, titanium isopropoxide and tantalum isopropoxide remains unchanged at 1.06 g, and the mass ratio of tetrabutyl titanate, titanium isopropoxide and tantalum isopropoxide is adjusted to 0.816:0.204:0.04.

[0028] Specifically, a three-necked flask equipped with a stirrer was subjected to three evacuation-purification operations with high-purity nitrogen. Under nitrogen protection, 0.816 g of tetrabutyl titanate, 0.204 g of titanium isopropoxide, and 0.04 g of tantalum isopropoxide were mixed using a syringe. Then, 0.34 g of strictly dehydrated glacial acetic acid was slowly added dropwise as a complexing agent. The mixture was stirred at 60 °C for 30 min, cooled to room temperature, and then sealed for storage to obtain the titanium-tantalum composite catalyst.

[0029] Preparation Example 5 The difference between Preparation Example 5 and Preparation Example 1 is that the total mass of tetrabutyl titanate, titanium isopropoxide and tantalum isopropoxide remains unchanged at 1.06 g, and the mass ratio of tetrabutyl titanate, titanium isopropoxide and tantalum isopropoxide is adjusted to 0.768:0.192:0.08.

[0030] Specifically, a three-necked flask equipped with a stirrer was subjected to three evacuation-purification operations with high-purity nitrogen. Under nitrogen protection, 0.768 g of tetrabutyl titanate, 0.192 g of titanium isopropoxide, and 0.08 g of tantalum isopropoxide were mixed using a syringe. Then, 0.34 g of strictly dehydrated glacial acetic acid was slowly added dropwise as a complexing agent. The mixture was stirred at 60 °C for 30 min, cooled to room temperature, and then sealed for storage to obtain the titanium-tantalum composite catalyst.

[0031] Comparative Preparation Example 1 The difference between Preparation Example 1 and Preparation Example 2 is that titanium isopropoxide was replaced by tetrabutyl titanate.

[0032] Comparative Preparation Example 2 The difference between Preparation Example 2 and Preparation Example 1 is that tetrabutyl titanate was replaced by titanium isopropoxide in equal mass.

[0033] Comparative preparation example 3 The difference between Preparation Example 3 and Preparation Example 1 is that tantalum isopropoxide is not added.

[0034] Specifically, a three-necked flask equipped with a stirrer was subjected to three evacuation-purification operations with high-purity nitrogen. Under nitrogen protection, 0.8 g of tetrabutyl titanate and 0.2 g of titanium isopropoxide were mixed using a syringe, followed by the slow addition of 0.34 g of strictly dehydrated glacial acetic acid as a complexing agent. The mixture was stirred at 60 °C for 30 min, cooled to room temperature, and then sealed for storage to obtain the titanium composite catalyst.

[0035] Comparative preparation example 4 The difference between Preparation Example 4 and Preparation Example 1 is that the mass of tantalum isopropoxide was replaced with zirconium isopropoxide.

[0036] Specifically, a three-necked flask equipped with a stirrer was subjected to three evacuation-purification operations with high-purity nitrogen. Under nitrogen protection, 0.8 g of tetrabutyl titanate, 0.2 g of titanium isopropoxide, and 0.05 g of zirconium isopropoxide were mixed using a syringe. Then, 0.34 g of strictly dehydrated glacial acetic acid was slowly added dropwise as a complexing agent. The mixture was stirred at 60 °C for 30 min, cooled to room temperature, and then sealed for storage to obtain the titanium-zirconium composite catalyst.

[0037] Example 1

[0038] Example 1 provides a method for synthesizing PEN resin, comprising the following preparation steps: S1. Prepare a slurry with a solid content of 40wt% by mixing 1000g of 2,6-naphthalenedicarboxylic acid (2,6-NDA) and 1500g of ethylene glycol (EG). After ultrasonic dispersion, deliver the slurry to a microchannel reactor at a flow rate of 50mL / min using a metering pump. The microchannel has a hydraulic diameter of 200μm, a rectangular cross-section (200μm wide × 200μm deep), and an effective volume of 1500mL. S2. 1g of the titanium-tantalum composite catalyst prepared by the preparation method in Preparation Example 1 was injected into the microchannel reactor through the catalyst feed port. The nitrogen gas was introduced at a rate of 10mL / min, the microchannel reaction temperature was controlled at 220℃, and the average residence time of the material in the microchannel was 30min. The esterification reaction was completed, and the esterification reaction product flowed out. S3. Collect the esterification reaction product flowing out in step S2 continuously into a 5L stainless steel polycondensation reactor equipped with a screw stirrer and a vacuum pump. Raise the temperature inside the reactor to 275°C, gradually reduce the pressure of the reaction system to 50Pa for high-vacuum de-alcoholization, and continue the reaction for 60 minutes to obtain the polymerization product. S4. Cool the polymerization product obtained in step S3, granulate it, and dry it to obtain PEN resin.

[0039] Example 2

[0040] Example 2 provides a method for synthesizing PEN resin, comprising the following preparation steps: S1. Prepare a slurry with a solid content of 30wt% by mixing 1000g of 2,6-NDA and 2333g of ethylene glycol (EG). After ultrasonic dispersion, deliver the slurry to a microchannel reactor at a flow rate of 30mL / min using a metering pump. The microchannel has a hydraulic diameter of 200μm, a rectangular cross-section (200μm wide × 200μm deep), and an effective volume of 1200mL. S2. 0.6 g of the titanium-tantalum composite catalyst prepared by the preparation method in Preparation Example 1 was injected into the microchannel reactor through the catalyst feed port. The nitrogen gas was introduced at a rate of 5 mL / min, the microchannel reaction temperature was controlled at 200 °C, and the average residence time of the material in the microchannel was 40 min to complete the esterification reaction. The esterification reaction product was then discharged. S3. Collect the esterification reaction product flowing out in step S2 continuously into a 5L stainless steel polycondensation reactor equipped with a screw stirrer and a vacuum pump. Raise the temperature inside the reactor to 260°C, gradually reduce the pressure of the reaction system to 10Pa for high-vacuum de-alcoholization, and continue the reaction for 90 minutes to obtain the polymerization product. S4. Cool the polymerization product obtained in step S3, granulate it, and dry it to obtain PEN resin.

[0041] Example 3

[0042] Example 3 provides a method for synthesizing PEN resin, comprising the following preparation steps: S1. Prepare a slurry with a solid content of 50wt% by mixing 1000g of 2,6-NDA and 1000g of ethylene glycol (EG). After ultrasonic dispersion, deliver the slurry to a microchannel reactor at a flow rate of 80mL / min using a metering pump. The microchannel has a hydraulic diameter of 200μm, a rectangular cross-section (200μm wide × 200μm deep), and an effective volume of 1200mL. S2. 3g of the titanium-tantalum composite catalyst prepared by the preparation method in Preparation Example 1 was injected into the microchannel reactor through the catalyst feed port. The nitrogen gas was introduced at a rate of 20mL / min, the microchannel reaction temperature was controlled at 240℃, and the average residence time of the material in the microchannel was 15min. The esterification reaction was completed, and the esterification reaction product flowed out. S3. Collect the esterification reaction product flowing out in step S2 continuously into a 5L stainless steel polycondensation reactor equipped with a screw stirrer and a vacuum pump. Raise the temperature inside the reactor to 290°C, gradually reduce the pressure of the reaction system to 100Pa for high-vacuum de-alcoholization, and continue the reaction for 30 minutes to obtain the polymerization product. S4. Cool the polymerization product obtained in step S3, granulate it, and dry it to obtain PEN resin.

[0043] Example 4

[0044] Example 4 provides a method for synthesizing PEN resin, which differs from Example 1 in that, in step S2, the titanium-tantalum composite catalyst prepared by the preparation method of Example 1 is replaced by the titanium-tantalum composite catalyst prepared by the preparation method of Example 2 in equal mass.

[0045] The other preparation steps are the same as in Example 1.

[0046] Example 5

[0047] Example 5 provides a method for synthesizing PEN resin, which differs from Example 1 in that, in step S2, the titanium-tantalum composite catalyst prepared by the preparation method of Example 1 is replaced by the titanium-tantalum composite catalyst prepared by the preparation method of Example 3 in equal mass.

[0048] The other preparation steps are the same as in Example 1.

[0049] Example 6

[0050] Example 6 provides a method for synthesizing PEN resin, which differs from Example 1 in that, in step S2, the titanium-tantalum composite catalyst prepared by the preparation method of Example 1 is replaced by the titanium-tantalum composite catalyst prepared by the preparation method of Example 4.

[0051] The other preparation steps are the same as in Example 1.

[0052] Example 7

[0053] Example 7 provides a method for synthesizing PEN resin, which differs from Example 1 in that, in step S2, the titanium-tantalum composite catalyst prepared by the preparation method of Example 1 is replaced by the titanium-tantalum composite catalyst prepared by the preparation method of Example 5 in equal mass.

[0054] The other preparation steps are the same as in Example 1.

[0055] Comparative Example 1 Comparative Example 1 provides a method for synthesizing PEN resin. The difference from Example 1 is that in step S2, the titanium-tantalum composite catalyst prepared by the preparation method of Preparation Example 1 is replaced by the titanium-tantalum composite catalyst prepared by the preparation method of Comparative Example 1 in equal mass.

[0056] The other preparation steps are the same as in Example 1.

[0057] Comparative Example 2 Comparative Example 2 provides a method for synthesizing PEN resin, which differs from Example 1 in that, in step S2, the titanium-tantalum composite catalyst prepared by the preparation method of Preparation Example 1 is replaced by the titanium-tantalum composite catalyst prepared by the preparation method of Comparative Example 2 in equal mass.

[0058] The other preparation steps are the same as in Example 1.

[0059] Comparative Example 3 Comparative Example 3 provides a method for synthesizing PEN resin, which differs from Example 1 in that, in step S2, the titanium-tantalum composite catalyst prepared by the preparation method of Preparation Example 1 is replaced by the titanium composite catalyst prepared by the preparation method of Comparative Example 3 in equal mass.

[0060] The other preparation steps are the same as in Example 1.

[0061] Comparative Example 4 Comparative Example 4 provides a method for synthesizing PEN resin, which differs from Example 1 in that, in step S2, the titanium-tantalum composite catalyst prepared by the preparation method of Preparation Example 1 is replaced by the titanium-zirconium composite catalyst prepared by the preparation method of Comparative Example 4 in equal mass.

[0062] The other preparation steps are the same as in Example 1.

[0063] Comparative Example 5 Comparative Example 5 provides a method for synthesizing PEN resin, which differs from Example 1 in that, in step S2, the titanium-tantalum composite catalyst prepared by the preparation method of Example 1 is replaced by an equal mass of tetrabutyl titanate.

[0064] The other preparation steps are the same as in Example 1.

[0065] Comparative Example 6 Comparative Example 6 provides a method for synthesizing PEN resin, which differs from Example 1 in that the microchannel reaction system is replaced with a conventional reactor process.

[0066] Specifically, the preparation steps are as follows: S1. Prepare a slurry with a solid content of 40wt% by mixing 1000g of 2,6-naphthalenedicarboxylic acid (2,6-NDA) with a purity of 99.6% and an acid value of 755mg KOH / g and 1500g of ethylene glycol (EG). After ultrasonic dispersion, the slurry is loaded into a 5L stainless steel polycondensation reactor equipped with a stirring device in one go. S2. Add 1g of the titanium-tantalum composite catalyst prepared by the preparation method of Preparation Example 1 to the polycondensation reactor in step S1, purge with nitrogen for protection, heat to 220℃ and start stirring, react for 3h to complete the esterification reaction and obtain the esterified product. S3. Raise the temperature inside the reactor to 275°C, gradually reduce the pressure of the reaction system to 50Pa and apply vacuum, continue the reaction for 2.5 hours to obtain the polymerization product; S4. Discharge the polymerization product obtained in step S3, cool it, granulate it, and obtain PEN resin.

[0067] Performance testing The PEN resins prepared in Examples 1-7 and Comparative Examples 1-6 were formulated according to GB / T1632.5-2008. The PEN resins were prepared into sample solutions of 0.005 g / mL, with phenol / tetrachloroethane in a mass ratio of 50:50 as the solvent. The outflow time of the sample solution and the pure solvent was measured in a constant temperature water bath at 25°C using an Ubbelohde viscometer. The intrinsic viscosity (unit: dL / g) was calculated using the Billmeyer formula. The results are shown in Table 1. The glass transition temperature and melting point were tested using a differential scanning calorimeter. Under nitrogen protection (flow rate 50 mL / min), 5 mg of PEN resin prepared in Examples 1-7 and Comparative Examples 1-6 were taken respectively, heated to 300 °C at 10 °C / min to eliminate thermal history, and rapidly cooled to room temperature. The glass transition temperature (Tg) and melting peak temperature (Tm, i.e. melting point) were scanned again at 10 °C / min. The results are shown in Table 1. The molecular weight distribution of the PEN resins prepared in Examples 1-7 and Comparative Examples 1-6 was tested using gel permeation chromatography (GPC), and the results are shown in Table 1.

[0068] Table 1

[0069] Conclusion Analysis and Summary As shown in Table 1, when the amount of catalyst used is 0.06-0.3% of the mass of 2,6-naphthalenedicarboxylic acid, the reaction temperature of the transesterification stage is 200-240℃, and the reaction temperature of the polycondensation stage is 260-290℃, the PEN resin prepared has better intrinsic viscosity, molecular weight distribution, and thermal properties.

[0070] As shown in Table 1, Examples 1 and 4-5 show that adjusting the mass ratio of tetrabutyl titanate to titanium isopropoxide in the titanium-tantalum composite catalyst can affect the performance of PEN resin. In Example 1, when the mass ratio of tetrabutyl titanate to titanium isopropoxide is 4:1, the intrinsic viscosity, molecular weight distribution, and thermal properties of the prepared PEN resin are better than those in Examples 4 and 5.

[0071] As shown in Table 1, Examples 1 and 6-7, adjusting the mass ratio of tetrabutyl titanate, titanium isopropoxide, and tantalum isopropoxide in the titanium-tantalum composite catalyst, while keeping the mass ratio of tetrabutyl titanate to titanium isopropoxide constant at 4:1, can affect the performance of PEN resin. In Example 1, when the mass ratio of tetrabutyl titanate, titanium isopropoxide, and tantalum isopropoxide is 0.8:0.2:0.06, the intrinsic viscosity, molecular weight distribution, and thermal properties of the prepared PEN resin are better than those in Examples 6 and 7.

[0072] As shown in Table 1, the performance of the PEN resins prepared in Examples 1-3 all deteriorated significantly. This may be because, in Comparative Example 1, the titanium isopropoxide was replaced with tetrabutyl titanate by an equal mass, resulting in a lack of highly active components in the composite catalyst and a decrease in esterification efficiency; in Comparative Example 2, the titanium isopropoxide was replaced with tetrabutyl titanate by an equal mass, resulting in a lack of long-lasting catalytic components in the composite catalyst and poor polycondensation reaction; and in Comparative Example 3, tantalum isopropoxide was not added, resulting in a lack of a second metal component in the composite catalyst and a reduction in the stability and resistance to impurity interference of the catalytic system. This indicates that the combination of tetrabutyl titanate, titanium isopropoxide, and tantalum isopropoxide helps to form a titanium-tantalum composite catalytic system with superior performance. This results in PEN resins exhibiting high intrinsic viscosity, narrow molecular weight distribution, and excellent thermal properties.

[0073] As shown in Table 1 of Examples 1 and 4, replacing tantalum isopropoxide with zirconium isopropoxide by mass in Comparative Example 4 significantly degraded the performance of the prepared PEN resin. This may be because zirconium and titanium differ in ionic radius, coordination configuration, and Lewis acidity, making it difficult to form a stable bimetallic synergistic catalytic center like the titanium-tantalum system, thus affecting catalytic efficiency and the ability to suppress side reactions. Consequently, this results in a lower intrinsic viscosity, a wider molecular weight distribution, and poorer thermal properties in the final PEN resin.

[0074] As shown in Table 1 of Examples 1 and Comparative Example 5, the performance of PEN resin was significantly reduced when using tetrabutyl titanate as a single catalyst in Comparative Example 5. This may be because tetrabutyl titanate alone cannot provide a sufficient initial reaction rate during the extremely short residence time in the microchannel, and it cannot resist the interference of impurities, resulting in incomplete reaction. Consequently, the intrinsic viscosity of PEN resin declined significantly.

[0075] As can be seen from Table 1 of Examples 1 and Comparative Example 6, in Comparative Example 6, replacing the microchannel reaction process with the traditional reactor process resulted in a longer reaction time, a worse molecular weight distribution of PEN resin, and increased energy consumption.

[0076] The above are all preferred embodiments of this application and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made to the products, methods and principles of this application should be covered within the scope of protection of this application.

Claims

1. A method for synthesizing PEN resin, characterized in that, Includes the following steps: S1. Prepare a slurry by mixing 2,6-naphthalenedicarboxylic acid and ethylene glycol, disperse it ultrasonically, and add it to a microchannel reactor; S2. Add the titanium-tantalum composite catalyst to the microchannel reactor and react under the protection of an inert gas to obtain the esterified reactants; S3. Collect the esterification reactants obtained in step S2 into a polycondensation reactor, heat up, depressurize, and react to obtain the polymerization product. S4. Cool, granulate, and dry the polymerization product obtained in step S3 to obtain PEN resin. The raw materials for preparing the titanium-tantalum composite catalyst in step S2 include tetrabutyl titanate, titanium isopropoxide, and tantalum isopropoxide.

2. The method for synthesizing PEN resin according to claim 1, characterized in that, In step S2, the mass ratio of tetrabutyl titanate, titanium isopropoxide, and tantalum isopropoxide in the titanium-tantalum composite catalyst is (0.768-0.816):(0.192-0.204):(0.04-0.08).

3. The method for synthesizing PEN resin according to claim 1, characterized in that, In step S2, the mass ratio of tetrabutyl titanate to titanium isopropoxide in the titanium-tantalum composite catalyst is (7-27):

3.

4. The method for synthesizing PEN resin according to claim 1, characterized in that, The preparation method of the titanium-tantalum composite catalyst includes the following steps: The reactor was first evacuated and then replaced with an inert gas. Under the protection of the inert gas, tetrabutyl titanate, titanium isopropoxide, and tantalum isopropoxide were added to the reactor and mixed. Glacial acetic acid was added, and the mixture was stirred at 55-65°C. After cooling, the mixture was sealed and stored to obtain the titanium-tantalum composite catalyst.

5. The method for synthesizing PEN resin according to claim 1, characterized in that, In step S1, the mass ratio of 2,6-naphthalenedicarboxylic acid to ethylene glycol is 1:(1-2.3).

6. The method for synthesizing PEN resin according to claim 1, characterized in that, In step S1, the flow rate of the slurry in the microchannel reactor is 30-80 mL / min.

7. The method for synthesizing PEN resin according to claim 1, characterized in that, In step S2, the mass of the titanium-tantalum composite catalyst accounts for 0.06-0.3% of the mass of 2,6-naphthalenedicarboxylic acid in step S1.

8. The method for synthesizing PEN resin according to claim 1, characterized in that, In step S2, the nitrogen gas flow rate is 5-20 mL / min, the reaction temperature is 200-240℃, and the reaction time is 15-40 min.

9. The method for synthesizing PEN resin according to claim 1, characterized in that, In step S3, the reaction temperature is 240-290℃, the reaction time is 30-90min, and the reaction pressure is 10-100Pa.

10. A PEN resin, characterized in that, The PEN resin is prepared by the synthesis method according to any one of claims 1-9.

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