A method for synthesizing polyethylene furanate dicarboxylate

Abstract

This invention discloses a method for synthesizing polyethylene furanate (PEF). Using furanate and ethylene glycol diacetate as polymerization raw materials, PEF is prepared through transesterification melt polycondensation. This PEF polymerization method is a novel polymerization route using different polymerizing raw materials, resulting in a polymer with a weight-average molecular weight exceeding 17,000. The material prepared by this method exhibits excellent thermal stability, with a thermal decomposition temperature exceeding 300°C. This method provides a new route and approach for PEF synthesis and can be widely applied.

Description

Technical Field

[0001] This invention relates to a method for synthesizing polyethylene furanate, belonging to the field of polymer chemistry. Background Technology

[0002] Polyethylene 2,5-furandicarboxylate (PEF) is a high-strength, high-modulus thermoplastic polyester with many excellent mechanical properties. It is also resistant to chemical corrosion and has a lower permeability to oxygen and water than common plastics. Therefore, it is widely used in various containers, food packaging materials, textile industry and civil construction.

[0003] Currently, most domestic and international manufacturers of PEF use furan dicarboxylic acid or dimethyl furan dicarboxylic acid to directly esterify and melt polycondensate with ethylene glycol or transesterification and melt polycondensate.

[0004]

[0005] Gruter et al. from Vantium used DMF and EG as raw materials and tetraisopropyl titanate as a catalyst. The transesterification stage was carried out at 160℃, 170℃, and 180℃ for 1 h, 1 h, and 2 h respectively, followed by a polycondensation stage at 230℃ for 2 h. The resulting polyester PEF had an absorbance of only 0.07, good color, and a number-average molecular weight of 13 kg / mol. DNBikiaris et al. from Aristotle University reported using DMF and EG as raw materials and n-butyl titanate as a catalyst. The transesterification stage was carried out at 160℃, 170℃, and 180-190℃ for 2 h, 2 h, and 1 h respectively, followed by a polycondensation stage at 220℃ and 250℃ for 2 h respectively. The product had an intrinsic viscosity of only 0.45 dL / g and a number-average molecular weight of 11.2 kg / mol. Rosenboom et al. successfully and rapidly synthesized bottle-grade PEF from cyclic PEF oligomers within minutes, thus avoiding degradation and discoloration. The melting point of this cyclic oligomer mixture is about 370°C, which is much higher than the degradation temperature of PEF (~329°C).

[0006] The direct esterification method has two main drawbacks: 1. It requires high purity of the raw material furanyl dicarboxylic acid (FDCA), and under high temperature conditions, FDCA is prone to decarboxylation and other side reactions, resulting in a darker color of the prepared PEF. 2. Under acidic conditions, ethylene glycol molecules are prone to intramolecular dehydration to form acetaldehyde.

[0007] In China, Xu Yutao et al. from Zhejiang University used an ester exchange-melt polycondensation method for synthesis. In the ester exchange stage, stannous oxalate was used as a catalyst, reacting at 170-200℃ for 2-3 hours. The ester exchange product was then purified and the catalyst deactivated using trifluoroacetic acid. Subsequently, antimony glycolate was used as a catalyst for polycondensation, reacting at 240-250℃ for 4-6 hours, resulting in a final intrinsic viscosity of 0.757 dL / g for PEF. However, this process involved purification and deactivation, using large amounts of strongly acidic solvents, making the operation relatively cumbersome. Li Zhibo et al. from Qingdao University of Science and Technology proposed a novel melt polycondensation strategy. Using asymmetric monomethyl 2,5-furan dicarboxylate monomers containing terminal hydroxyl and methyl ester groups, they prepared a series of colorless polyesters with long alkyl chains at low cold polymerization temperatures, including poly(POF), poly(2,5-furan diester) (PNF), poly(xylene 2,5-furan dimethyl carboxylate), and poly(dodecylene 2,5-furan diester) (PdodF). Volatile methanol, rather than high-boiling-point diols, was removed as a byproduct. Finally, they obtained a colorless polyester with an intrinsic viscosity as high as 0.86 dL / g and a narrow molecular weight distribution.

[0008] The transesterification melt polycondensation method has the following main disadvantages: 1. Small molecule methanol is generated during the transesterification stage. Compared with water, methanol is toxic and volatile; 2. Intermolecular dehydration occurs during the transesterification melt polycondensation stage, producing diethylene glycol (ether bond) fragments. The presence of these fragments lowers the melting point of the polyester and reduces the regularity of the polyester macromolecular chain. Summary of the Invention

[0009] To address the problems existing in the prior art, this invention provides a method for synthesizing polyethylene furanate, which uses furanate and ethylene glycol diacetate as polymerization raw materials and polymerizes them through a "deacetic acid" transesterification method under the action of a catalyst to obtain polyethylene furanate.

[0010] The present invention discloses a method for synthesizing polyethylene furanate, which uses furanate dicarboxylic acid (FDCA) and ethylene glycol diacetate (EGDA) as polymerization raw materials to obtain polyethylene furanate through a polycondensation reaction.

[0011] The synthetic route for preparing PEF using transesterification melt polycondensation in this invention is shown below:

[0012]

[0013] The specific steps include: adding furan dicarboxylic acid and ethylene glycol diacetate into a 1L titanium polyester reactor, replacing the air in the reactor with an inert gas and maintaining a certain pressure, and then starting to heat up. The first stage of transesterification occurs at 220-240℃, and the pressure is always controlled at 2-3 bar. The progress of the transesterification reaction is evaluated by the amount of acetic acid received as a byproduct. The second stage of polycondensation reaction involves grinding the product collected in the first stage and mixing it evenly with the catalyst. The reaction is carried out at 240-250℃ and under a high vacuum of less than 500 Pa for 4-8 hours. The progress of the polycondensation reaction is judged by the degree of stirring up the stir bar.

[0014] The molar ratio of furanyl dicarboxylic acid to ethylene glycol diacetate is 1:1.0 to 1:1.7.

[0015] The catalyst is selected from one or a combination of several of antimony trioxide, antimony acetate, antimony glycol, tetrabutyl titanate, titanium dioxide, zinc acetate dihydrate, and germanium oxide.

[0016] The mass ratio of the catalyst to the oligomer is from 1:100000 to 1:100.

[0017] During the first stage of the transesterification reaction, the pressure inside the reactor was controlled at 2-3 bar, and the reaction temperature was 220-240℃.

[0018] During the first stage of the transesterification reaction, the inert gas is selected from nitrogen or argon, with nitrogen being preferred for inert gas protection.

[0019] During the second stage of polycondensation reaction, the reactor temperature is 240-260℃ and the vacuum degree is less than 500Pa.

[0020] During the second stage of polycondensation reaction, the mechanical stirring speed is between 400 rpm and 1500 rpm.

[0021] Mechanical mixing methods include one or more of the following: propeller mixers, turbine mixers, paddle mixers, anchor mixers, and ribbon mixers.

[0022] In the method of this invention, the catalyst content and type that mainly affect the material properties are those in the second stage of melt polycondensation.

[0023] This invention presents a novel PEF polymerization method using different polymerizing raw materials (furan dicarboxylic acid and ethylene glycol diacetate), resulting in a polymer with a weight-average molecular weight exceeding 17,000. This method avoids undesirable condensation processes (such as the formation of diethylene glycol fragments) that could affect polymer properties. Theoretically, diethylene glycol fragments in polyester chips are formed by the side reaction—etherification—of free hydroxyl groups. However, this invention's method does not involve free hydroxyl groups, theoretically preventing the formation of diethylene glycol fragments. Furthermore, according to method 5.2.1A (methanol transesterification) of diethylene glycol in the national standard GB / T 14190-2017, the product of this invention showed no diethylene glycol-related peaks under the corresponding gas-phase testing conditions, thus proving the absence of diethylene glycol fragments in the product.

[0024] Furthermore, because EG is not used, the reaction exhibits greater tolerance to oxygen. The raw material EGDA can be derived from waste plastics obtained through acetic acid depolymerization, representing a reuse of waste resources and achieving recycling. The first-stage transesterification product is easy to prepare with high yield and no catalyst residue. No intramolecular dehydration to acetaldehyde side reaction occurs during the transesterification stage. The material prepared by this method exhibits excellent thermal stability, with a thermal decomposition temperature exceeding 300℃. This method provides a new route and approach for the synthesis of PEF and can be widely applied. Attached Figure Description

[0025] Figure 1 This is a physical image of the first-stage transesterification intermediate.

[0026] Figure 2 This is the 1H NMR spectrum (¹H NMR) of the first-stage transesterification intermediate in deuterated chloroform.

[0027] Figure 3 The image shows the 1H NMR spectrum of the polymerization product of Example 3 in deuterated trifluoroacetic acid.

[0028] Figure 4 This is a thermogravimetric analysis diagram of the polymerization product of Example 3. Detailed Implementation

[0029] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0030] This invention provides a novel synthetic route for polyethylene furanate dicarboxylate. The core technology lies in the transesterification melt polycondensation of furanate dicarboxylic acid and ethylene glycol diacetate, which is one of the polymerization principles of polyethylene furanate dicarboxylate. The transesterification intermediates during the polymerization process and the final melt polycondensation product are characterized by nuclear magnetic resonance (NMR), and the molecular weight of the polymer is determined by gel permeation chromatography (GPC). For macroscopic properties, thermogravimetric analysis (TGA) was performed using a NETZSCH TG209F1Libra thermogravimetric analyzer to further analyze the thermodynamic properties of the material.

[0031] Example 1:

[0032] Furan dicarboxylic acid (156g) and ethylene glycol diacetate (190g, 1.3 eq) were mixed in a 1L titanium polyester reactor. The air inside the reactor was then purged with nitrogen three times, maintaining a final pressure of 3 atm. The transesterification reaction occurred at 220–240℃, with the pressure controlled at approximately 3 atm. The progress of the reaction was evaluated by the yield of the byproduct acetic acid. After approximately 6 hours, about 110g of acetic acid was collected, indicating the completion of the transesterification reaction, and the transesterification intermediate was collected. 13.0g of the transesterification intermediate and 13.0mg of tetrabutyl titanate (1‰wt) were added to a 250mL three-necked flask, and the mixture was heated under vacuum. The polycondensation reaction began at 250℃ and a high vacuum of less than 300Pa, with the stirrer activated. The polycondensation reaction lasted for 5 hours, yielding the desired polymer. The number-average molecular weight of the obtained polymer was 8438, the weight-average molecular weight was 18395, and the polydispersity index was 2.2.

[0033] Example 2:

[0034] Furan dicarboxylic acid (156g) and ethylene glycol diacetate (190g, 1.3 eq) were mixed in a 1L titanium polyester reactor. The air inside the reactor was then purged with nitrogen three times, maintaining a final pressure of 3 atm. The transesterification reaction occurred at 220–240℃, with the pressure controlled at approximately 2 atm. The progress of the reaction was evaluated by the yield of the byproduct acetic acid. After approximately 5.5 hours, about 110g of acetic acid was collected, indicating the completion of the transesterification reaction, and the transesterification intermediate was collected. 13.0g of the transesterification intermediate and 65.0mg of antimony trioxide (5‰wt) were added to a 250ml three-necked flask, and the mixture was heated under vacuum. The polycondensation reaction began at 250℃ and a high vacuum of less than 300Pa, with the stirrer activated. The polycondensation reaction lasted for 6 hours, yielding the desired polymer. The number-average molecular weight of the obtained polymer was 7820, the weight-average molecular weight was 17986, and the polydispersity index was 2.3.

[0035] Example 3:

[0036] Furan dicarboxylic acid (156g) and ethylene glycol diacetate (190g, 1.3 eq) were mixed in a 1L titanium polyester reactor. The air in the reactor was then purged with nitrogen four times, maintaining a final pressure of 2 atm. The transesterification reaction occurred at 220–240℃, with the pressure controlled at approximately 2 atm. The progress of the reaction was evaluated by the yield of the byproduct acetic acid. After approximately 6 hours, about 115g of acetic acid was collected, indicating the completion of the transesterification reaction, and the transesterification intermediate was collected. 13.0g of the transesterification intermediate and 65mg of tetrabutyl titanate (5‰wt) were added to a 250ml three-necked flask, and the mixture was heated under vacuum. The polycondensation reaction began at 250℃ and a high vacuum of less than 300Pa, with the stirrer activated. The polycondensation reaction lasted for 6 hours, yielding the desired polymer. The number-average molecular weight of the obtained polymer was 9674, the weight-average molecular weight was 17509, and the polydispersity index was 1.8. Figure 4 In this embodiment, thermogravimetric analysis showed that the decomposition rate was slow at 305.5℃, but began to decompose rapidly around 345℃. Therefore, the poly(ethylene furanate) prepared by this invention has excellent thermal stability, with a thermal decomposition temperature of approximately 300℃, which meets application requirements.

Claims

1. A method for synthesizing poly(ethylene furandicarboxylate), characterized in that: poly(ethylene furandicarboxylate) is prepared by transesterification melt polycondensation using furandicarboxylic acid and ethylene glycol diacetate as polymerization raw materials, comprising the following steps: furandicarboxylic acid and ethylene glycol diacetate are added to a titanium reaction kettle, the air in the reaction kettle is replaced with an inert gas, and a certain pressure is maintained, then the temperature is raised, the first stage is an ester exchange reaction, the progress of the ester exchange reaction is evaluated by the amount of byproduct acetic acid received, and the ester exchange product is collected; the second stage is to grind the product collected in the first stage, mix it uniformly with a catalyst, and then start the mechanical stirring and heating for polycondensation, and finally obtain poly(ethylene furandicarboxylate); In the first stage ester exchange reaction, the pressure in the reaction kettle is controlled to be 2-3 bar, and the reaction temperature is 220-240℃; In the second stage polycondensation reaction, the reaction temperature is 240-260℃, and the system vacuum degree is less than 500 Pa; The catalyst is selected from one or a combination of several of antimony trioxide, antimony acetate, ethylene glycol antimony, tetrabutyl titanate, titanium dioxide, zinc acetate dihydrate, and germanium oxide.

2. The method according to claim 1, characterized in that: the molar ratio of raw materials furandicarboxylic acid and ethylene glycol diacetate is 1:1.0 to 1:1.

7.

3. The method according to claim 1, characterized in that: the mass ratio of the catalyst to the ester exchange product is 1:100000 to 1:

100.

4. The method according to claim 1, characterized in that: in the first stage ester exchange reaction, the inert gas is selected from nitrogen or argon.

5. The method according to claim 1, characterized in that: in the second stage polycondensation reaction, the mechanical stirring speed is between 400 rpm and 1500 rpm.

6. The mechanical stirring according to claim 5, characterized in that: the mechanical stirring method includes one or more of a propeller stirrer, a turbine stirrer, a paddle stirrer, an anchor stirrer, and a screw belt stirrer. ​ ​ ​ ​ ​ ​ ​

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