A one-step process for the preparation of high molecular weight polyethylene furanoate

Abstract

The application discloses a one-step method for preparing high-molecular-weight polyethylene furandicarboxylate, and belongs to the technical field of bio-based polyester materials.The method comprises the following steps: weighing raw materials, i.e., 2,5-furandicarboxylic acid, ethylene glycol, an end-group regulator, a protective agent, a decarboxylation inhibitor and a catalyst, mixing and adding the raw materials into a reaction container, introducing nitrogen, maintaining the nitrogen pressure in the reaction container at 50-150 kPa, performing esterification, increasing the temperature after the esterification is completed, and performing vacuumization to less than or equal to 50 Pa to perform polycondensation, obtaining a high-molecular-weight polyethylene furandicarboxylate melt, extruding, drying and obtaining the high-molecular-weight polyethylene furandicarboxylate.The conversion rate of FDCA is greater than or equal to 98%, the number-average molecular weight of the obtained product is greater than or equal to 32 kg / mol, there is no heavy metal residue, and the method is suitable for large-scale production of high-end bio-based packaging materials.

Description

Technical Field

[0001] This invention belongs to the field of bio-based polyester materials technology, and particularly relates to a one-step method for preparing high molecular weight polyethylene furanate (PEF), which is specifically applied to high-barrier bio-based packaging materials, functional films and other fields. Background Technology

[0002] While polyethylene terephthalate (PET) is the most widely used thermoplastic polyester, easy to process, and widely used in food packaging and other fields, it has performance shortcomings. Its core monomer, PTA, is entirely dependent on petroleum, resulting in insufficient gas barrier properties and mechanical stability. Therefore, developing polyester alternatives with superior performance and higher environmental compatibility is urgently needed. Polyethylene furandicarboxylate (PEF), as a new generation of bio-based alternative to PET, has become a focus of industry attention due to the bioconversion of its monomer, 2,5-furandicarboxylic acid (FDCA), and the bio-production of ethylene glycol (EG). Furthermore, its furan ring structure endows it with superior oxygen barrier properties and mechanical stability compared to PET, meeting the demands of high-end packaging.

[0003] However, existing PEF preparation technologies face core challenges, making it difficult to obtain high molecular weight pure PEF in a one-step process. These challenges mainly manifest in: (1) FDCA is prone to decarboxylation at high temperatures, leading to increased side reactions; (2) High temperatures accelerate the degradation and oxidation of the furan ring, resulting in a darker product color; (3) EG molecules undergo etherification at high temperatures, affecting PEF product indicators. At high temperatures, EG molecules undergo intermolecular dehydration to generate diethylene glycol, and intramolecular dehydration to generate acetaldehyde. For example, the research progress on the modification of bio-based polyethylene 2,5-furandicarboxylate reported that FDCA undergoes decarboxylation under high-temperature reaction conditions, and FDCA and EG undergo etherification, generating small molecule impurities such as furanoic acid and furan. These side reactions lead to a decrease in FDCA monomer utilization and introduce chain-terminating impurities, hindering chain growth and ultimately affecting the final product. M nMost are below 28 kg / mol. The patent "An Antibacterial, Heat-Resistant, and High-Barrier Copolyester Containing a Furan Ring and Its Preparation Method" proposes a polymerization system of FDCA and cyclic diols, using a four-stage stepwise polymerization method. The pre-esterification temperature is controlled at 160-180℃ to avoid FDCA decarboxylation. However, low temperatures lead to reduced esterification efficiency and prolonged polymerization time, failing to solve the FDCA decarboxylation problem. The patent "A Synthesis Method of Poly(ethylene Glycol Furan Dicarboxylate)" proposes using ethylene glycol diacetate, followed by a "deacetic acid" transesterification method to obtain the PEF product. However, the corrosive effects of acetic acid on equipment are unsuitable for existing production technologies. Existing technologies also use FDCA dimethyl ester for polymerization, but this method controls the methanol produced during esterification, which is generally unsuitable for industrialization. Methanol is not water-green, and this method requires an alcohol-acid ratio of generally 2:1, introducing more diethylene glycol, resulting in a low molecular weight and poor performance of the final product.

[0004] In summary, existing technologies largely rely on multi-stage polymerization processes, which struggle to meet the demands for efficient PEF preparation. Furthermore, they lack strategies to suppress FDCA decarboxylation and EG glycol side reactions, hindering optimization to overcome molecular weight bottlenecks and failing to resolve the technical difficulties of one-step high-molecular-weight PEF preparation. Therefore, it is crucial to develop a high-molecular-weight PEF preparation technology that overcomes the technical challenges of FDCA decarboxylation and EG side reactions, achieving melt polymerization of PEF. M n The synthetic route with a concentration of ≥32 kg / mol and an FDCA conversion rate of ≥98% is of great significance for the transformation of bio-based polyester industry from R&D to mass production and for enhancing my country's technological competitiveness in this field. Summary of the Invention

[0005] To address the shortcomings of the existing technologies and to solve the problems of low monomer utilization due to high-temperature decarboxylation of FDCA, accelerated degradation and oxidation of furan rings at high temperatures leading to darker product color, low reactivity of FDCA carboxyl groups, etherification side reaction of EG at high temperatures, and the complex and difficult-to-industrialize multi-step process for preparing high molecular weight PEF requiring solid-phase thickening, this invention aims to design and provide a one-step method for preparing high molecular weight polyethylene furanate (PEF), achieving the goals of FDCA conversion rate ≥98%, product Mn ≥32 kg / mol, product b value ≤4, and diethylene glycol content ≤1%.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] On one hand, the present invention provides a one-step method for preparing high molecular weight polyethylene furanate, comprising the following steps:

[0008] Weigh out the raw materials 2,5-furandicarboxylic acid (FDCA), ethylene glycol (EG), end-group regulator, protective agent, decarboxylation inhibitor, and catalyst, mix them and add them to a reaction vessel. Purge with nitrogen gas and maintain the nitrogen pressure in the reaction vessel at 50-150 kPa to carry out the esterification reaction (so that the free FDCA residue is ≤5%, and the end-group regulator reacts with the residual carboxyl group to form active aromatic ester end groups). After completion, raise the temperature and evacuate to ≤50 Pa to carry out the polycondensation reaction to obtain high molecular weight polyethylene furandicarboxylate melt. Extrude and dry to obtain high molecular weight polyethylene furandicarboxylate.

[0009] Optionally, after obtaining high molecular weight polyethylene furanate, post-processing auxiliaries can be recovered. Specifically, the mixture of ester by-products and auxiliaries is separated and recovered by distillation, and the recovery rate of end-group regulators, protective agents, and decarboxylation inhibitors is ≥95%, which are then recycled for PEF preparation.

[0010] The method for preparing high molecular weight polyethylene furanate in one step, wherein the molar ratio of 2,5-furandicarboxylic acid to ethylene glycol is 1:(1.2-1.7).

[0011] The method for preparing high molecular weight polyethylene furanate (PEF) in a one-step process, wherein the end-group regulator is at least one of p-propylphenol, m-ethylphenol, or p-butylphenol. This invention utilizes one of p-propylphenol, m-ethylphenol, or p-butylphenol, with a boiling point of 210-260℃, which is highly compatible with the polycondensation temperature of PEF, thus avoiding premature volatilization and inactivation at high temperatures. The end-group regulator reacts with residual carboxyl groups to form active aromatic ester end groups, enhancing the end-group reactivity while avoiding excessive end-group regulator residue that could negatively impact product performance.

[0012] Preferably, the end-group regulator is p-propylphenol, and the amount added is 1.2%-2.0% of the mass of FDCA. p-propylphenol has a boiling point of 232°C, which is highly compatible with the polycondensation temperature of PEF, thus avoiding premature volatilization and inactivation of low-boiling-point aromatic alcohols.

[0013] The protective agent is a mixture of 1,2-propanediol and xylitol. This invention utilizes a compound of 1,2-propanediol and xylitol to form a reversible multi-point hydrogen bond network, achieving a mechanism where hydrogen bonds reversibly break at high temperatures, allowing EG to participate in the reaction, and hydrogen bond recombination at low temperatures inhibits EG side reactions. This mechanism serves as a protective agent for the preparation of high molecular weight PEF.

[0014] Preferably, the hydrogen bond network formed by the compounding of 1,2-propanediol and xylitol in a 4:1 ratio can stably control the EG volatility at 5-8% at this dosage.

[0015] The decarboxylation inhibitor is a bio-based polyhydroxy compound.

[0016] The method for preparing high molecular weight polyethylene furanate (PEG) in a one-step process, wherein the decarboxylation inhibitor is at least one of erythritol, sorbitan anhydride, or maltitol. This invention utilizes the fact that the hydroxyl groups of one of erythritol, sorbitan anhydride, or maltitol can form strong hydrogen bonds with the carboxyl groups of FDCA, reducing the decarboxylation activity of the carboxyl groups above 190°C, thereby achieving a FDCA decarboxylation rate ≤0.5% and reducing the generation of chain-terminating impurities.

[0017] The method for preparing high molecular weight polyethylene furanate in one step, wherein the amount of end-group regulator added is 0.8-3.0% of the mass of 2,5-furandicarboxylic acid.

[0018] The amount of the protective agent added is 2.5-5.0% of the mass of 2,5-furandicarboxylic acid;

[0019] The amount of the decarboxylation inhibitor added is 0.3-1.0% of the mass of 2,5-furandicarboxylic acid.

[0020] Preferably, in the one-step method for preparing high molecular weight polyethylene furanyl dicarboxylate, the amount of end-group regulator added is 1.2-2.0% of the mass of 2,5-furanyl dicarboxylic acid.

[0021] Preferably, the amount of the protective agent added is 3.0-4.5% of the mass of 2,5-furandicarboxylic acid.

[0022] Preferably, the amount of the decarboxylation inhibitor added is 0.5%-0.8% of the mass of 2,5-furandicarboxylic acid.

[0023] The present invention discloses a one-step method for preparing high molecular weight polyethylene furanate, wherein the catalyst comprises tetrabutyl titanate and zinc acetate. This invention selects a combination of these two catalysts, resulting in a synergistic effect. Existing technologies often use single titanium-based catalysts, leading to excessively rapid catalytic rates, numerous side reactions, and difficulty in forming high molecular weight products. This invention employs a combined catalyst that both catalyzes the reaction and promotes the formation of high molecular weight products.

[0024] Preferably, the mass ratio of tetrabutyl titanate to zinc acetate is (1-2):1.

[0025] The catalyst is added at a rate of 0.1-0.3% of the mass of 2,5-furandicarboxylic acid.

[0026] The method for preparing high molecular weight polyethylene furanate in one step further includes an antioxidant in the raw materials.

[0027] The antioxidant is at least one of antioxidant 1010, antioxidant 330, or triphenyl phosphite.

[0028] The amount of antioxidant added is 0.1-0.3% of the mass of 2,5-furandicarboxylic acid.

[0029] Preferably, the amount of antioxidant added is 0.15-0.25% of the mass of 2,5-furandicarboxylic acid.

[0030] Preferably, the catalyst is added in an amount of 0.15-0.25% of the mass of 2,5-furandicarboxylic acid.

[0031] The method for preparing high molecular weight polyethylene furanate in one step, wherein the esterification reaction conditions are: temperature 180-210℃, time 2.5-3.5h.

[0032] The conditions for the polycondensation reaction are: temperature 220-250℃, time 3-4 h.

[0033] A high molecular weight polyethylene furanate prepared by any one of the methods described herein, wherein the high molecular weight polyethylene furanate has an intrinsic viscosity of 0.65-0.85 dL / g and a number-average molecular weight (M). n ≥32 kg / mol, FDCA conversion rate ≥98%, product b value ≤4, diethylene glycol content ≤1%.

[0034] The principle of this invention: This invention is based on selective control technology of monomer reaction, and uses functional auxiliaries to optimize the preparation process of polymers. Unexpected results are obtained through the design and combination of end-group regulators, protectants and decarboxylation inhibitors.

[0035] (1) First, the present invention selects p-propylphenol / m-ethylphenol / p-butylphenol with boiling point of 210-260℃ as end group regulators, which are highly matched with the polycondensation temperature of PEF; and, by regulating the end group, the carboxyl group reacts first, so that the phenomenon of high-temperature decarboxylation will not occur, thus realizing the protection of the end group and solving the defect of high-temperature decarboxylation side reaction of FDCA monomer.

[0036] (2) Secondly, this invention innovatively proposes a protective agent (such as a mixture of 1,2-propanediol and xylitol in a mass ratio of 4:1) to form a reversible multi-point hydrogen bond network. In this system, multiple hydroxyl groups of xylitol can form hydrogen bonds with the hydroxyl groups (-OH) of different EG molecules, the carboxyl groups (-COOH) of FDCA, or the ester groups (-COO-) of PEF oligomers, respectively. The bond energy of hydrogen bonds is relatively low (10-40 kJ / mol) and is sensitive to temperature. At high temperatures, the thermal energy exceeds the hydrogen bond energy, and the intermolecular or intramolecular hydrogen bonds in the network break reversibly, releasing the active hydroxyl sites of EG, allowing them to participate normally in the esterification-condensation reaction without hindering the main reaction. At low temperatures, the end groups are protected, reducing the etherification side reaction of EG molecules at high temperatures.

[0037] (3) Thirdly, this invention innovatively proposes a decarboxylation inhibitor, which selects bio-based polyhydroxy compounds such as erythritol / sorbitan / maltitol. Its hydroxyl groups can form strong hydrogen bonds with the carboxyl groups of FDCA, thereby increasing the decarboxylation temperature of FDCA (expected to be increased from 190℃ to above 220℃), reducing the decarboxylation rate, and reducing the generation of chain termination impurities.

[0038] Compared with the prior art, the present invention has the following beneficial effects:

[0039] 1. This invention, through the innovative design of functional additives, uses end-group regulators, protectants, and decarboxylation inhibitors to achieve synergistic effects, realizing the industrial-scale scale-up and adaptation of integrated process parameters in a single reactor, supporting large-scale continuous production, and can be directly used for blow molding of high-end food packaging bottles, meeting the development and promotion of PEF products.

[0040] 2. All additives in this invention are bio-based or low-toxicity, with an additive recovery rate ≥94%, providing a superior product performance for the efficient preparation and high-end packaging application of high molecular weight PEF. M n A solution with ≥32 kg / mol, product b-value ≤4, diethylene glycol content ≤1%, no heavy metal residue, stronger process stability, and higher environmental compatibility. The recovered additives can be directly recycled for PEF preparation, reducing raw material loss by 30%.

[0041] 3. This invention employs a one-step method. All additives used in this invention are bio-based or low-toxicity, with an additive recovery rate ≥94%. This provides a superior product performance (M...) for the efficient preparation of high molecular weight PEF and its application in high-end packaging. n A solution with ≥32 kg / mol, product b-value ≤4, diethylene glycol content ≤1%, no heavy metal residue, stronger process stability, and higher environmental compatibility. The recovered additives can be directly recycled for PEF preparation, reducing raw material loss by 30%, and offering simplicity, energy saving, process simplification, and reduced energy consumption. Detailed Implementation

[0042] The present invention will be further described below with reference to specific embodiments. It should be noted that, unless otherwise specified, the technical means used in the following examples are conventional means well known to those skilled in the art, and the raw materials used are all commercially available conventional products. 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 modifications or alterations to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0043] The following are the test methods for the relevant performance indicators in each embodiment and comparative example:

[0044] FDCA conversion rate: The actual conversion amount of FDCA was analyzed by Fourier transform infrared spectroscopy (FTIR), and a standard curve of "peak intensity ratio - FDCA content" was established, with a peak intensity of 1720 cm⁻¹ as the threshold. -1 The conversion rate is calculated based on peak intensity data.

[0045] Product number average molecular weight: The molecular weight of polyester was determined by gel permeation chromatography using a 1260 Infinity II (Agilent Technologies) column at 35°C. The mobile phase was a mixture of sodium trifluoroacetate and hexafluoroisopropanol, and the flow rate was 1 ml / min. -1 The molecular weight was calculated using polystyrene standards.

[0046] Product characteristic viscosity: The test was conducted in accordance with standard GB / T14190-2017. 0.125±0.005g of sample was weighed and dissolved in 25mL of a mixed solution of phenol and 1,1,2,2-tetrachloroethane (mass ratio 3 / 2). The viscosity of the solvent and the dissolved solution was then tested and calculated using a Ubbelohde viscometer at 25℃.

[0047] Additive recovery rate: The fraction collected after distillation is filtered with a 0.22μm organic phase filter membrane to remove insoluble impurities such as PEF oligomers. The additive recovery rate is calculated by the ratio of the total recovered mass to the initial input mass.

[0048] Product b-value: The colorimetry of the polymer was characterized using a colorimeter (TLS-802N, Tianjin Trus Technology Co., Ltd.). A certain amount of polymer was placed in a glass container, and the b-value was obtained using the colorimeter.

[0049] Determination of diethylene glycol content: The test was conducted in accordance with the standard GB / T17931-2018, using the methanol transesterification method and liquid chromatography to determine the diethylene glycol content in the product.

[0050] Example 1:

[0051] (1) Weigh out 2,5-furandicarboxylic acid and ethylene glycol in a molar ratio of 1:1.2 and add them to the polymerization reactor. Then add the catalyst, antioxidant, protective agent, and decarboxylation inhibitor and mix. The catalyst is tetrabutyl titanate and zinc acetate, accounting for 0.25% of the total mass of the diacid, and the molar ratio of tetrabutyl titanate to zinc acetate is 2:1. The antioxidant is antioxidant 330 and triphenyl phosphite, accounting for 0.2% of the total mass of the diacid. The end-group regulator is p-propylphenol, accounting for 1.2% of the total mass of the diacid. The protective agent is a mixture of 1,2-propanediol and xylitol in a mass ratio of 4:1, accounting for 3.0% of the total mass of the diacid. The decarboxylation inhibitor is erythritol, accounting for 0.3% of the total mass of the diacid. Nitrogen gas was introduced to maintain the nitrogen pressure in the reaction vessel at 50 kPa. The esterification reaction was carried out at 210 °C under a nitrogen atmosphere for 2.5 h with stirring until the water yield reached more than 85% of the theoretical value, thus obtaining PEF esterified product.

[0052] (2) Subsequently, the polymerization reactor was heated to 220°C, and the vacuum was gradually evacuated to ≤50Pa. The reaction was maintained at this temperature for 4.0h. The product was then dried under high vacuum at 100°C for 11h, finally yielding a PEF polymer with an intrinsic viscosity of 0.7dL / g. Based on the above-mentioned end-group protection, the side reactions are reduced, resulting in an increase in intrinsic viscosity.

[0053] (3) Polyethylene furanate was prepared by melt extrusion of the above polymer masterbatch, and its number average molecular weight (M) was [not specified]. n The concentration of the active ingredient was 38 kg / mol, the FDCA conversion rate was 98.2%, the auxiliary agent recovery rate was 94.5%, the product b value was 3.8, and the diethylene glycol content was 1%.

[0054] Example 2:

[0055] (1) Weigh 2,5-furandicarboxylic acid and ethylene glycol into a polymerization reactor at a molar ratio of 1:1.4, and then add catalyst, antioxidant, protective agent, and decarboxylation inhibitor. The catalyst is tetrabutyl titanate and zinc acetate, accounting for 0.1% of the total mass of the diacid, with a molar ratio of 2:1 between tetrabutyl titanate and zinc acetate; the antioxidant is antioxidant 1010, accounting for 0.25% of the total mass of the diacid; the end-group regulator is m-ethylphenol, accounting for 0.8% of the total mass of the diacid; the protective agent is a mixture of 1,2-propanediol and xylitol at a mass ratio of 4:1, accounting for 2.5% of the total mass of the diacid; and the decarboxylation inhibitor is maltitol, accounting for 0.8% of the total mass of the diacid. Nitrogen gas is introduced to maintain the nitrogen pressure in the reaction vessel at 100 kPa. The esterification reaction is carried out at 190 °C under a nitrogen atmosphere for 3 hours with stirring until the water yield reaches more than 85% of the theoretical value, thus obtaining PEF esterified product.

[0056] (2) Subsequently, the polymerization reactor was heated to 230°C, and the vacuum was gradually evacuated to ≤50Pa. The reaction was maintained at this temperature for 3.5 hours. The product was then dried under high vacuum at 95°C for 10 hours, finally yielding a PEF polymer with an intrinsic viscosity of 0.65 dL / g. Based on the above-mentioned end-group protection, the side reactions are reduced, resulting in an increase in intrinsic viscosity.

[0057] (3) Polyethylene furanate was prepared by melt extrusion of the above polymer masterbatch, and its number average molecular weight (M) was [not specified]. n The concentration of the active ingredient was 32 kg / mol, the FDCA conversion rate was 98.0%, the auxiliary agent recovery rate was 94%, the product b value was 3.5, and the diethylene glycol content was 0.7%.

[0058] Example 3:

[0059] (1) Weigh out 2,5-furandicarboxylic acid and ethylene glycol in a molar ratio of 1:1.6 and add them to the polymerization reactor. Then add the catalyst, antioxidant, protective agent, and decarboxylation inhibitor and mix. The catalyst is tetrabutyl titanate and zinc acetate, accounting for 0.2% of the total mass of the diacid, and the molar ratio of tetrabutyl titanate to zinc acetate is 2:1. The antioxidant is antioxidant 1010 and triphenyl phosphite, accounting for 0.3% of the total mass of the diacid. The end-group regulator is m-ethylphenol, accounting for 3.0% of the total mass of the diacid. The protective agent is a mixture of 1,2-propanediol and xylitol in a mass ratio of 4:1, accounting for 4.0% of the total mass of the diacid. The decarboxylation inhibitor is sorbitan anhydride, accounting for 0.5% of the total mass of the diacid. Nitrogen gas was introduced to maintain the nitrogen pressure in the reaction vessel at 150 kPa. The esterification reaction was carried out at 180 °C under a nitrogen atmosphere for 3.5 h with stirring until the water yield reached more than 85% of the theoretical value, thus obtaining PEF esterified product.

[0060] (2) Subsequently, the polymerization reactor was heated to 250°C, and the vacuum was gradually evacuated to ≤50Pa. The reaction was maintained at this temperature for 3.0h. The product was then dried under high vacuum at 100°C for 12h, finally yielding a PEF polymer with an intrinsic viscosity of 0.85dL / g. Based on the above-mentioned end-group protection, the side reactions are reduced, resulting in an increase in intrinsic viscosity.

[0061] (3) Polyethylene furanate was prepared by melt extrusion of the above polymer masterbatch, and its number average molecular weight (M) was [not specified]. n The concentration of the active ingredient was 46 kg / mol, the FDCA conversion rate was 99.0%, the auxiliary agent recovery rate was 96%, the product b value was 4, and the diethylene glycol content was 0.5%.

[0062] Example 4:

[0063] (1) Weigh 2,5-furandicarboxylic acid and ethylene glycol in a molar ratio of 1:1.3 and add them to the polymerization reactor. Then add the catalyst, antioxidant, protective agent, and decarboxylation inhibitor and mix. The catalyst is tetrabutyl titanate and zinc acetate, accounting for 0.3% of the total mass of the diacid, and the molar ratio of tetrabutyl titanate to zinc acetate is 2:1; the antioxidant is triphenyl phosphite, accounting for 0.2% of the total mass of the diacid; the end-group regulator is p-butylphenol, accounting for 2.0% of the total mass of the diacid; the protective agent is a mixture of 1,2-propanediol and xylitol in a mass ratio of 4:1, accounting for 5.0% of the total mass of the diacid; and the decarboxylation inhibitor is sorbitan anhydride, accounting for 0.8% of the total mass of the diacid. Nitrogen gas is introduced to maintain the nitrogen pressure in the reaction vessel at 100 kPa. The esterification reaction is carried out at 185 °C under a nitrogen atmosphere for 3.5 h with stirring until the water yield reaches more than 85% of the theoretical value, and PEF esterification is obtained.

[0064] (2) Subsequently, the polymerization reactor was heated to 245°C, and the vacuum was gradually evacuated to ≤50Pa. The reaction was maintained at this temperature for 3.5 hours. The product was then dried under high vacuum at 110°C for 14 hours, finally yielding a PEF polymer with an intrinsic viscosity of 0.8 dL / g. Based on the above-mentioned end-group protection, the side reactions are reduced, resulting in an increase in intrinsic viscosity.

[0065] (3) Polyethylene furanate was prepared by melt extrusion of the above polymer masterbatch, and its number average molecular weight (M) was [not specified]. n The concentration of the active ingredient was 43 kg / mol, the FDCA conversion rate was 98.7%, the auxiliary agent recovery rate was 95.5%, the product b value was 3.6, and the diethylene glycol content was 0.8%.

[0066] Example 5:

[0067] (1) Weigh out 2,5-furandicarboxylic acid and ethylene glycol in a molar ratio of 1:1.5 and add them to the polymerization reactor. Then add the catalyst, antioxidant, protective agent, and decarboxylation inhibitor and mix. The catalyst is tetrabutyl titanate and zinc acetate, accounting for 0.15% of the total mass of the diacid, and the molar ratio of tetrabutyl titanate to zinc acetate is 2:1. The antioxidant is antioxidant 330 and triphenyl phosphite, accounting for 0.15% of the total mass of the diacid. The end-group regulator is p-butylphenol, accounting for 1.7% of the total mass of the diacid. The protective agent is a mixture of 1,2-propanediol and xylitol in a mass ratio of 4:1, accounting for 4.5% of the total mass of the diacid. The decarboxylation inhibitor is maltitol, accounting for 0.5% of the total mass of the diacid. Nitrogen gas was introduced to maintain the nitrogen pressure in the reaction vessel at 100 kPa. The esterification reaction was carried out at 200 °C under a nitrogen atmosphere with stirring for 2.5 h until the water yield reached more than 85% of the theoretical value, thus obtaining PEF esterified product.

[0068] (2) Subsequently, the polymerization reactor was heated to 240°C, and the vacuum was gradually evacuated to ≤50Pa. The reaction was maintained at this temperature for 3.0h. The product was then dried under high vacuum at 105°C for 13h, finally yielding a PEF polymer with an intrinsic viscosity of 0.75dL / g. Based on the above-mentioned end-group protection, the side reactions are reduced, resulting in an increase in intrinsic viscosity.

[0069] (3) Polyethylene furanate was prepared by melt extrusion of the above polymer masterbatch, and its number average molecular weight (M) was [not specified]. n The concentration of the active ingredient was 40 kg / mol, the FDCA conversion rate was 98.5%, the auxiliary agent recovery rate was 95%, the product b value was 3, and the diethylene glycol content was 0.6%.

[0070] Example 6:

[0071] (1) Weigh 2,5-furandicarboxylic acid and ethylene glycol in a molar ratio of 1:1.4 and add them to the polymerization reactor. Then add the catalyst, antioxidant, protective agent, and decarboxylation inhibitor and mix. The catalyst is tetrabutyl titanate and zinc acetate, accounting for 0.2% of the total mass of the diacid, and the molar ratio of tetrabutyl titanate to zinc acetate is 2:1; the antioxidant is antioxidant 330, accounting for 0.1% of the total mass of the diacid; the end-group regulator is p-propylphenol, accounting for 2.5% of the total mass of the diacid; the protective agent is a mixture of 1,2-propanediol and xylitol in a mass ratio of 4:1, accounting for 3.0% of the total mass of the diacid; and the decarboxylation inhibitor is erythritol, accounting for 1.0% of the total mass of the diacid. Nitrogen gas is introduced to maintain the nitrogen pressure in the reaction vessel at 100 kPa. The esterification reaction is carried out at 190 °C under a nitrogen atmosphere for 3.0 h with stirring until the water yield reaches more than 85% of the theoretical value, and PEF esterification is obtained.

[0072] (2) Subsequently, the polymerization reactor was heated to 240°C, and the vacuum was gradually evacuated to ≤50Pa. The reaction was maintained at this temperature for 3.0h. The product was then dried under high vacuum at 100°C for 10h, finally yielding a PEF polymer with an intrinsic viscosity of 0.75dL / g. Based on the above-mentioned end-group protection, the side reactions are reduced, resulting in an increase in intrinsic viscosity.

[0073] (3) Polyethylene furanate was prepared by melt extrusion of the above polymer masterbatch, and its number average molecular weight (M) was [not specified]. n The concentration of the active ingredient was 40 kg / mol, the FDCA conversion rate was 98.5%, the auxiliary agent recovery rate was 95%, the product b value was 3.5, and the diethylene glycol content was 0.8%.

[0074] Comparative Example 1:

[0075] The preparation of polyethylene furanyl dicarboxylate is the same as the specific method protected in this invention, except that end-group regulators, protecting agents, and decarboxylation inhibitors are not added. Specifically, as follows:

[0076] (1) Weigh 2,5-furandicarboxylic acid and ethylene glycol in a molar ratio of 1:1.4 and add them to the polymerization reactor. Then add tetrabutyl titanate as catalyst and triphenyl phosphite as heat stabilizer, accounting for 0.2% of the total mass of the dicarboxylic acid. Stir and react at 190℃ under a nitrogen atmosphere for 4 hours until the water content reaches more than 85% of the theoretical value to obtain PEF esterification. Then heat the polymerization reactor to 230℃, gradually evacuate to a vacuum degree <50Pa, and keep it at the temperature for 4.0 hours to obtain PEF polymer with intrinsic viscosity of 0.53dL / g.

[0077] (2) Polyethylene furanate was prepared by melt extrusion of the above polymer masterbatch, and its number average molecular weight (M) was [not specified]. n The concentration was stable at 24 kg / mol, the FDCA conversion rate was 85%, the product b value was 9, and the diethylene glycol content was 3%.

[0078] In summary, the experimental methods and data results above demonstrate that the end-group regulator, protectant, and decarboxylation inhibitor employed in this invention have a synergistic effect, resulting in an FDCA conversion rate ≥98%, a number-average molecular weight of the product ≥32 kg / mol, a product b-value ≤4, a diethylene glycol content ≤1%, and an auxiliary agent recovery rate ≥94%, demonstrating excellent and significant effects.

Claims

1. A one-step method for preparing high molecular weight polyethylene furanate, characterized in that, Includes the following steps: Weigh out the raw materials 2,5-furandicarboxylic acid, ethylene glycol, end-group regulator, protective agent, decarboxylation inhibitor and catalyst, mix them and add them to the reaction vessel. Purge with nitrogen and maintain the nitrogen pressure in the reaction vessel at 50-150 kPa to carry out the esterification reaction. After completion, heat up and evacuate to ≤50 Pa to carry out the polycondensation reaction to obtain high molecular weight polyethylene furandicarboxylate melt. Extrude and dry to obtain high molecular weight polyethylene furandicarboxylate. The protective agent is a mixed reagent formed by compounding 1,2-propanediol and xylitol in a mass ratio of 4:

1. The catalyst is tetrabutyl titanate and zinc acetate in a molar ratio of 2:1; The end-group regulator is at least one of p-propylphenol, m-ethylphenol, or p-butylphenol; The decarboxylation inhibitor is at least one of erythritol, sorbitol anhydride, or maltitol.

2. The method for preparing high molecular weight polyethylene furanate in one step as described in claim 1, characterized in that, The molar ratio of 2,5-furandicarboxylic acid to ethylene glycol is 1:(1.2-1.7).

3. The method for preparing high molecular weight polyethylene furanate in one step as described in claim 1, characterized in that, The amount of the end-group regulator added is 0.8-3.0% of the mass of 2,5-furandicarboxylic acid; The amount of the protective agent added is 2.5-5.0% of the mass of 2,5-furandicarboxylic acid; The amount of the decarboxylation inhibitor added is 0.3-1.0% of the mass of 2,5-furandicarboxylic acid.

4. The method for preparing high molecular weight polyethylene furanate in one step as described in claim 1, characterized in that, The amount of the end-group regulator added is 1.2-2.0% of the mass of 2,5-furandicarboxylic acid; The amount of the protective agent added is 3.0-4.5% of the mass of ethylene glycol; The amount of the decarboxylation inhibitor added is 0.5%-1.0% of the mass of 2,5-furandicarboxylic acid.

5. The method for preparing high molecular weight polyethylene furanate in one step as described in claim 1, characterized in that, The catalyst is added at a rate of 0.1-0.3% of the mass of 2,5-furandicarboxylic acid.

6. The method for preparing high molecular weight polyethylene furanate in one step as described in claim 1, characterized in that, The raw materials also contain antioxidants; The antioxidant is at least one of antioxidant 1010, antioxidant 330, or triphenyl phosphite; The amount of antioxidant added is 0.1-0.3% of the mass of 2,5-furandicarboxylic acid.

7. The method for preparing high molecular weight polyethylene furanate in one step as described in claim 1, characterized in that, The conditions for the esterification reaction are: temperature 180-210℃, time 2.5-3.5h; The conditions for the polycondensation reaction are: temperature 220-250℃, time 3-4 h.