A fully bio-based 2,5-furandicarboxylic acid copolyester, its preparation method, applications, and closed-loop recycling method.

Abstract

This invention discloses a fully bio-based 2,5-furandicarboxylic acid copolyester, its preparation method, applications, and closed-loop recycling method, belonging to the field of materials synthesis technology. Using bio-based dimethyl 2,5-dimethylfurandicarboxylate (DMFD), 1,4-butanediol (BDO), and (1R,3S)-1,2,2-trimethylcyclopentane-1,3-diethanol (TCDM) as raw materials, a high-performance 2,5-furandicarboxylic acid copolyester suitable for closed-loop chemical recycling was synthesized. This invention utilizes the aforementioned fully bio-based 2,5-furandicarboxylic acid copolyester, its preparation method, applications, and closed-loop recycling method. The addition of the (1R,3S)-1,2,2-trimethylcyclopentane-1,3-diethanol unit enhances the thermal and mechanical properties of the 2,5-furandicarboxylic acid copolyester, while also exhibiting excellent UV shielding and solvent resistance. It can be gently depolymerized and recycled with minimal loss of repolymerization performance, achieving a balance between high performance and recyclability.

Description

Technical Field

[0001] This invention relates to the field of materials synthesis technology, and in particular to a fully bio-based 2,5-furandicarboxylic acid copolyester, its preparation method, application, and closed-loop recovery method. Background Technology

[0002] The overconsumption of petroleum-based polymers has exacerbated energy shortages and environmental pollution, making the development of sustainable polymer alternatives a research hotspot. Among a range of candidate monomers for polymer preparation, biomass monomers have emerged as alternatives to petroleum monomers due to their abundance and renewability. 2,5-furandicarboxylic acid (2,5-Furfural), synthesized from bio-based carbohydrates through hydrolysis and oxidation, has attracted widespread attention and is one of the 12 high-value biomass-derived platform chemicals identified by the U.S. Department of Energy. Compared to existing bio-based aliphatic polymers such as polylactic acid (PLA) and polybutylene succinate (PBS), the unique structural features of the furan ring, including its conformational rigidity, intrinsic polarity, and strong intermolecular interactions, endow 2,5-furandicarboxylic acid-based polyesters with excellent thermal, mechanical, and barrier properties. In recent years, a series of polyesters or copolyesters derived from 2,5-furandicarboxylic acid have been extensively studied. Nevertheless, achieving a high glass transition temperature (Tg) through precise molecular structure tuning remains a challenge. g 2,5-furandicarboxylic acid copolyesters, in terms of strength and toughness, remain one of the major challenges.

[0003] Introducing monomers with different structures into the main chain of 2,5-furandicarboxylic acid polyesters allows for the regulation of their structure and properties. In particular, the ability of cyclic bio-based monomers to modulate the structure and enhance the properties of copolyesters has attracted widespread attention. For example, 2,5-hydroxymethyltetrahydrofuran (THFDM), isosorbide (IS), 2,3:4,5-di-o-methylenemannitol (Glux), 2,4:3,5-di-o-methylenemannitol (Manx), spirodiol (SPG), and N,N'-trans-1,4-cyclohexane-bis(pyrrolidone-4-carboxylate) (CBPC) can inhibit chain mobility through copolymerization, thereby improving the TT of the copolyester. g And improve mechanical properties.

[0004] Natural camphor, extracted from camphor trees, is widely used as a chiral precursor for the synthesis of enantiomeric compounds due to its low cost and easy availability. (1R,3S)-1,2,2-trimethylcyclopentane-1,3-diethanol, a camphor-derived diol, is a promising structural unit for bio-based polyesters, primarily due to its heteroatom-free, fully alicyclic skeleton, which imparts superior thermal stability compared to glycocyclic monomers, while the two primary hydroxyl groups ensure reactivity in polycondensation reactions.

[0005] In addition to meeting the high-performance requirements of 2,5-furandicarboxylic acid copolyester materials in advanced applications, their post-waste management must also be considered. Similar to petroleum-based aromatic polyesters, 2,5-furandicarboxylic acid polyesters are hydrolyzable and do not readily decompose. The accumulation of these persistent wastes poses a significant threat to ecosystems and human health. To ensure that bio-based polyester packaging complies with green chemistry principles, efficient recycling strategies are now imperative. Summary of the Invention

[0006] The purpose of this invention is to provide a fully bio-based 2,5-furandicarboxylic acid copolyester, its preparation method, applications, and closed-loop recovery method. The addition of the (1R,3S)-1,2,2-trimethylcyclopentane-1,3-diethanol unit improves the Tg of the 2,5-furandicarboxylic acid copolyester. g This process enhances the strength and toughness of the 2,5-furandicarboxylic acid copolyester; the 2,5-furandicarboxylic acid copolyester exhibits excellent UV shielding and solvent resistance. Furthermore, this 2,5-furandicarboxylic acid copolyester can be rapidly depolymerized under mild conditions in a mixture of sodium hydroxide, tetrahydrofuran, and 1,4-butanediol to produce high-purity monomer feedstock. Compared to the original polymer, the repolymerized 2,5-furandicarboxylic acid copolyester shows almost no reduction in thermal and mechanical properties, enabling the 2,5-furandicarboxylic acid-based copolyester of this invention to simultaneously achieve high performance and chemical recyclability. This provides guidance for the future design of recyclable, high-performance bio-based polyesters.

[0007] To achieve the above objectives, the present invention provides a fully bio-based 2,5-furandicarboxylic acid copolyester, wherein the molecular structural formula of the fully bio-based 2,5-furandicarboxylic acid copolyester is as follows:

[0008] .

[0009] This invention also provides a method for preparing a fully bio-based 2,5-furandicarboxylic acid copolyester, comprising the following steps:

[0010] S1. 1,4-Butanediol, (1R,3S)-1,2,2-trimethylcyclopentane-1,3-diethanol and dimethyl 2,5-furandicarboxylate are added to a reaction flask, and a catalyst is added to carry out the transesterification reaction.

[0011] S2. After the transesterification reaction, the temperature is raised to carry out a polycondensation reaction to obtain a fully bio-based 2,5-furandicarboxylic acid copolyester, denoted as PBTCF. x , x This indicates the molar percentage of (1R,3S)-1,2,2-trimethylcyclopentane-1,3-diethanol units in the 2,5-furandicarboxylic acid copolyester.

[0012] Preferably, the molar ratio of the mixture of 1,4-butanediol, (1R,3S)-1,2,2-trimethylcyclopentane-1,3-diethanol to dimethyl 2,5-dimethylfurandicarboxylate is (1.5-2.2):1, and the molar amount of (1R,3S)-1,2,2-trimethylcyclopentane-1,3-diethanol accounts for 0.1-99 mol of the mixture of 1,4-butanediol and (1R,3S)-1,2,2-trimethylcyclopentane-1,3-diethanol.

[0013] Preferably, in S1, the catalyst is titanium isopropoxide or tetrabutyl titanate, and the amount of catalyst used is 0.1-0.8 mol of dimethyl 2,5-dimethylfuran dicarboxylate.

[0014] Preferably, in S1, the temperature of the transesterification reaction is 160-180℃, the time of the transesterification reaction is 4-6h, and the transesterification reaction is carried out under a nitrogen atmosphere.

[0015] Preferably, in step S2, the pressure in the reaction flask is reduced to 10-90 Pa to carry out the polycondensation reaction, and the reaction temperature is 190-240℃. The reaction time is 2-8 hours.

[0016] This invention also provides an application of a fully bio-based 2,5-furandicarboxylic acid copolyester, which applies the aforementioned fully bio-based 2,5-furandicarboxylic acid copolyester to high-performance environmentally friendly plastic packaging.

[0017] This invention also provides a closed-loop recovery method for a fully bio-based 2,5-furandicarboxylic acid copolyester as described above, comprising the following steps:

[0018] T1. Add a mixture of fully bio-based 2,5-furandicarboxylic acid copolyester, sodium hydroxide, tetrahydrofuran and 1,4-butanediol into a flask, heat and stir to carry out the reaction.

[0019] T2. The product after the reaction is filtered to obtain a precipitate and a filtrate. The precipitate is redissolved in deionized water, and concentrated hydrochloric acid is added for acidification and further filtration to obtain the recovered 2,5-furandicarboxylic acid. The filtrate is distilled under normal pressure and then under reduced pressure to obtain the recovered 1,4-butanediol.

[0020] T3. Add the recovered 2,5-furandicarboxylic acid obtained in T2 to the flask, and reflux in a methanol solution containing sulfuric acid. Filter to obtain a precipitate, wash and dry the precipitate to obtain the recovered dimethyl 2,5-furandicarboxylic acid.

[0021] Preferably, in T1, the mass ratio of fully bio-based 2,5-furandicarboxylic acid copolyester, sodium hydroxide, tetrahydrofuran and 1,4-butanediol is 1:(0.6-2):(8-15):(6-8), the stirring temperature is 50-70℃, and the stirring time is 2-5h;

[0022] In T2, the mass fraction of concentrated hydrochloric acid is ≥30%, and the solution is acidified to pH 2-2.5. The filtrate is then distilled at 75-85℃ for 0.3-0.5h to remove tetrahydrofuran. The vacuum distillation temperature is 130-150℃ and the distillation time is 1.5-3h.

[0023] In T3, the methanol solution containing sulfuric acid has a volume ratio of methanol to sulfuric acid of 300:1, a sulfuric acid mass fraction of ≥90%, a reflux temperature of 90-100℃, a reflux time of 4-5h, is washed with distilled water, and is dried for 6-12h at a drying temperature of 60-70℃.

[0024] Therefore, the present invention, employing the above-mentioned fully bio-based 2,5-furandicarboxylic acid copolyester, its preparation method, application, and closed-loop recovery method, has the following beneficial effects:

[0025] (1) The addition of (1R,3S)-1,2,2-trimethylcyclopentane-1,3-diethanol unit improved the T of 2,5-furandicarboxylic acid copolyester. g This also enhances the strength and toughness of the copolyester;

[0026] (2) 2,5-furandicarboxylic acid copolyester exhibits excellent UV shielding and solvent resistance properties;

[0027] (3) 2,5-furandicarboxylic acid copolyester can be rapidly depolymerized under mild conditions in a mixture of sodium hydroxide, tetrahydrofuran and 1,4-butanediol to produce high-purity monomer raw materials;

[0028] (4) The mechanical and thermal properties of the 2,5-furandicarboxylic acid copolyester obtained by repolymerization are almost not reduced compared with the original polymer, which makes the 2,5-furandicarboxylic acid copolyester both high performance and chemical recyclability.

[0029] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the synthesis and closed-loop recovery process of 2,5-furandicarboxylic acid copolyester in this invention;

[0031] Figure 2 This is a schematic diagram illustrating the preparation and structure of (1R,3S)-1,2,2-trimethylcyclopentane-1,3-diethanol in this invention.

[0032] Figure 3 It is (1R,3S)-1,2,2-trimethylcyclopentane-1,3-diethanol in this invention. 1 H-NMR and 13 C-NMR spectrum, in which Figure 3 (a) in the middle is 1 H-NMR spectrum, Figure 3 (b) in the middle is 13 C-NMR spectrum;

[0033] Figure 4 These are Examples 1-6 and Comparative Example 1 of this invention. 1 H-NMR spectrum;

[0034] Figure 5 These are Examples 1-6 and Comparative Example 1 of this invention. 13 C-NMR spectrum;

[0035] Figure 6 These are the DSC curves of Examples 1-6 and Comparative Example 1 in this invention, wherein... Figure 6 (a) in the figure is the single-stage heating curve. Figure 6 (b) in the figure is the secondary heating curve;

[0036] Figure 7 These are the optical properties and ultraviolet shielding performance diagrams of the thin films in Examples 1, 2, 3, 6 and Example 1 of this invention;

[0037] Figure 8 These are the stress-strain curves of Examples 1-6 and Comparative Example 1 in this invention;

[0038] Figure 9 The 2,5-furandicarboxylic acid recovered by depolymerization in Example 1 of this invention is compared with the original 2,5-furandicarboxylic acid. 1 H-NMR, 13 C-NMR and liquid chromatogram, among which Figure 9 (a) in the middle is 1 H-NMR spectrum, Figure 9 (b) in the middle is 13 C-NMR spectrum, Figure 9 (c) in the figure is a liquid chromatogram;

[0039] Figure 10 This invention relates to the depolymerization and recovery of dimethyl 2,5-furandicarboxylate obtained in Example 1 and the original 2,5-furandicarboxylic acid. 1 H-NMR, 13 C-NMR and liquid chromatogram, among which Figure 10 (a) in the middle is 1 H-NMR spectrum, Figure 10 (b) in the middle is 13 C-NMR spectrum, Figure 10 (c) in the figure is a liquid chromatogram;

[0040] Figure 11 This refers to the 1,4-butanediol obtained from the depolymerization and recovery in Example 1 of this invention, and the original 1,4-butanediol. 13 C-NMR and liquid chromatogram, among which Figure 11 (a) in the middle is 13 C-NMR spectrum, Figure 11 (b) in the figure is a liquid chromatogram;

[0041] Figure 12 This invention refers to the repolymerization of monomers obtained from the depolymerization and recovery of Example 1, which is the recovered product of Example 1 and the original Example 1. 1 H-NMR spectrum, DSC and stress-strain curves, among which Figure 12 (a) in the middle is 1 H-NMR spectrum, Figure 12 (b) in the figure is the DSC curve. Figure 12 (c) in the figure is the stress-strain curve. Detailed Implementation

[0042] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0043] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0044] This invention provides a fully bio-based 2,5-furandicarboxylic acid copolyester, prepared by the following method: Figure 1 As shown, its molecular structural formula is:

[0045] .

[0046] The preparation and structural schematic diagram of (1R,3S)-1,2,2-trimethylcyclopentane-1,3-diethanol are shown below. Figure 2 As shown, the detailed synthesis process is as follows:

[0047] A mixed solution of lithium aluminum hydride (1.70 g, 45.0 mmol) and tetrahydrofuran (125 mL) was cooled to 0 °C, and a solution of (1R,3S)-(+)-camphoric acid (2.80 g, 14.0 mmol) in tetrahydrofuran (20 mL) was added dropwise. The resulting suspension was gradually heated to room temperature and stirred for 8 hours, then heated under reflux for 4 hours and cooled to 0 °C. Subsequently, water (2.0 mL), sodium hydroxide (15% w / v, 5.0 mL), and water (10.0 mL) were added dropwise. The mixture was extracted with dichloromethane, dried over sodium sulfate, and concentrated under vacuum to give a crude product, which was recrystallized from dichloromethane / n-hexane (v / v = 1:1) to give a white solid of (1R,3S)-1,2,2-trimethylcyclopentane-1,3-diethanol. 1 H-NMR and 13 C-NMR spectrum as shown Figure 3 As shown.

[0048] In this invention, unless otherwise specified, all other test materials and instruments are conventional test materials in the field and can be purchased through commercial channels.

[0049] Example 1

[0050] Synthesis of PBTCF3: S1. Dimethyl 2,5-furandicarboxylate (DMFD, 80 mmol, 14.73 g), 1,4-butanediol (136.8 mmol, 12.33 g), (1R,3S)-1,2,2-trimethylcyclopentane-1,3-diethanol (7.2 mmol, 1.24 g), and titanium isopropoxide catalyst (0.3 mol% DMFD, 0.068 g) were added to a reaction flask. Nitrogen gas was introduced into the reaction system, the temperature was raised to 180 °C, and maintained for 5 h. The reaction continued until all byproducts were distilled off, completing the transesterification reaction.

[0051] S3. During the polycondensation reaction, the system pressure is reduced to below 60 Pa, the reaction temperature is raised to 200 °C and maintained for 4 h until the Weissenberg effect occurs, and the product PBTCF3 is obtained.

[0052] Example 2

[0053] Synthesis of PBTCF6: S1. Dimethyl 2,5-furandicarboxylate (DMFD, 80 mmol, 14.73 g), 1,4-butanediol (108 mmol, 9.73 g), (1R,3S)-1,2,2-trimethylcyclopentane-1,3-diethanol (12 mmol, 2.07 g), and tetrabutyl titanate catalyst (0.5 mol% DMFD, 0.136 g) were added to a reaction flask. Nitrogen gas was introduced into the reaction system, the temperature was raised to 170 °C, and maintained for 6 h. The reaction continued until all byproducts were distilled off, completing the transesterification reaction.

[0054] S3. During the polycondensation reaction, the system pressure is reduced to 80 Pa, the reaction temperature is increased to 220 °C and maintained for 6 h until the Weissenberg effect occurs, and the product PBTCF6 is obtained.

[0055] Example 3

[0056] Synthesis of PBTCF10: S1. Dimethyl 2,5-furandicarboxylate (DMFD, 80 mmol, 14.73 g), 1,4-butanediol (136 mmol, 12.25 g), (1R,3S)-1,2,2-trimethylcyclopentane-1,3-diethanol (24 mmol, 4.13 g), and tetrabutyl titanate catalyst (0.6 mol% DMFD, 0.204 g) were added to a reaction flask. Nitrogen gas was introduced into the reaction system, the temperature was raised to 180 °C, and maintained for 5 h. The reaction continued until all byproducts were distilled off, completing the transesterification reaction.

[0057] S3. During the polycondensation reaction, the system pressure is reduced to 40 Pa, the reaction temperature is increased to 230 °C and maintained for 7 h until the Weissenberg effect occurs, and the product PBTCF10 is obtained.

[0058] Example 4

[0059] Synthesis of PBTCF15: S1. Dimethyl 2,5-furandicarboxylate (DMFD, 80 mmol, 14.73 g), 1,4-butanediol (115.2 mmol, 10.38 g), (1R,3S)-1,2,2-trimethylcyclopentane-1,3-diethanol (28.8 mmol, 4.96 g), and titanium isopropoxide catalyst (0.5 mol% DMFD, 0.114 g) were added to a reaction flask. Nitrogen gas was introduced into the reaction system, the temperature was raised to 180 °C, and maintained for 5 h. The reaction continued until all byproducts were distilled off, completing the transesterification reaction.

[0060] S3. During the polycondensation reaction, the system pressure is reduced to 30 Pa, the reaction temperature is increased to 220 °C and maintained for 5 h until the Weissenberg effect occurs, and the product PBTCF15 is obtained.

[0061] Example 5

[0062] Synthesis of PBTCF21: S1. Dimethyl 2,5-furandicarboxylate (DMFD, 80 mmol, 14.73 g), 1,4-butanediol (100.8 mmol, 9.08 g), (1R,3S)-1,2,2-trimethylcyclopentane-1,3-diethanol (43.2 mmol, 7.44 g), and titanium isopropoxide catalyst (0.8 mol% DMFD, 0.182 g) were added to a reaction flask. Nitrogen gas was introduced into the reaction system, the temperature was raised to 180 °C and maintained at 5.5 °C, and the reaction was carried out until all byproducts were distilled off, completing the transesterification reaction.

[0063] S3. During the polycondensation reaction, the system pressure is reduced to 70 Pa, the reaction temperature is increased to 230 °C and maintained for 7 h until the Weissenberg effect occurs, and the product PBTCF21 is obtained.

[0064] Example 6

[0065] Synthesis of PBTCF27: S1. Dimethyl 2,5-furandicarboxylate (DMFD, 80 mmol, 14.73 g), 1,4-butanediol (86.4 mmol, 7.79 g), (1R,3S)-1,2,2-trimethylcyclopentane-1,3-diethanol (57.6 mmol, 9.92 g), and titanium isopropoxide catalyst (0.3 mol% DMFD, 0.068 g) were added to a reaction flask. Nitrogen gas was introduced into the reaction system, the temperature was raised to 170 °C, and maintained for 5 h. The reaction continued until all byproducts were distilled off, completing the transesterification reaction.

[0066] S3. During the polycondensation reaction, the system pressure is reduced to 40 Pa, the reaction temperature is increased to 200 °C and maintained for 5 h until the Weissenberg effect occurs, and the product PBTCF27 is obtained.

[0067] Comparative Example 1

[0068] Synthesis of PBF: S1. Dimethyl 2,5-furandicarboxylate (DMFD, 80 mmol, 14.73 g), 1,4-butanediol (160 mmol, 14.42 g), and titanium isopropoxide catalyst (0.3 mol% DMFD, 0.068 g) were added to a reaction flask. Nitrogen gas was introduced into the reaction system, the temperature was raised to 170 °C, and maintained for 4 h. The reaction continued until all byproducts were distilled off, completing the transesterification reaction.

[0069] S3. During the polycondensation reaction, the system pressure is reduced to 70 Pa, the reaction temperature is increased to 200 °C and maintained for 6 h until the Weissenberg effect occurs, and the product PBF is obtained.

[0070] The products obtained in Examples 1-6 and Comparative Example 1 were characterized in terms of performance.

[0071] I. Structural Characterization:

[0072] 1 H-NMR verified the structures of Examples 1-6 and Comparative Example 1. Figure 4 In the spectrum of Comparative Example 1 (PBF), the -OCH2- (9) and -CH2- (10) signals of 1,4-butanediol appeared at 4.48 and 1.84 ppm, respectively, and the peak at 7.45 ppm was the signal peak of the -CH- group (11) in the furan ring. For Examples 1-6, the peaks 4, 5, and 6 of the methyl group in the (1R,3S)-1,2,2-trimethylcyclopentane-1,3-diethanol unit were observed at 1.12-1.28 and 0.86 ppm, respectively. The protons at 2.45, 2.08, 1.84, and 1.55 ppm in the camphor ring were attributed to the hydrogen atoms at 1, 2, 2', and 3 / 3'. The -OCH2- (7 and 8) peaks in the (1R,3S)-1,2,2-trimethylcyclopentane-1,3-diethanol structure were located between 4.34 and 4.41 ppm. Figure 5 Examples 1-6 and Comparative Example 1 13 The C-NMR spectrum shows that each resonance peak is clearly assigned to carbon atoms in different chemical environments. This confirms the successful synthesis of the products from Examples 1-6 and Comparative Example 1.

[0073] II. Viscosity Test:

[0074] The intrinsic viscosity [η] of Examples 1-6 and Comparative Example 1 was determined using an Ubbelohde viscometer (model B-013205, capillary inner diameter 0.7-0.8 mm). The test medium was a 1,1,2,2-tetrachloroethane / phenol mixed solvent (mass ratio 2:3), and the tests were conducted at a constant temperature of 25°C. The specific logarithmic viscosity and viscosity-average molecular weight of the 2,5-furandicarboxylic acid copolyester were calculated using the following formulas:

[0075] (1);

[0076] (2);

[0077] (3);

[0078] int 0 represents the solvent outflow time. t 1 represents the solution effluent time, and c represents the solution concentration (5 g / L). K and α are the characteristic constants of the test system (K = 2.11 × 10⁻⁶). -5 (α = 1.02).

[0079] Table 1 shows that the intrinsic viscosity [η] of Examples 1-6 and Comparative Example 1 ranged from 1.02 to 1.15 dL / g, and the viscosity-average molecular weight ( ) was 1.02–1.15 dL / g. M η The concentration fluctuated between 39.0 and 43.8 kg / mol.

[0080] Table 1. Intrinsic viscosity and viscosity-average molecular weight of Examples 1-6 and Comparative Example 1 (%) M η )

[0081]

[0082] III. Thermal performance characterization:

[0083] DSC was used to evaluate the thermal behavior of Examples 1-6 and Comparative Example 1. Table 2 lists the melting temperatures (T). m ), molten heat function (ΔH) m ) and glass transition temperature (T g The corresponding DSC curve is as follows: Figure 6 As shown. Melting temperature (T) of Comparative Example 1 (PBF) m The temperature was 172.3℃. The introduction of the (1R,3S)-1,2,2-trimethylcyclopentane-1,3-diethanol unit significantly reduced the thermal transition parameters of the resulting 2,5-furandicarboxylic acid copolyester. m and ΔH m The content of (1R,3S)-1,2,2-trimethylcyclopentane-1,3-diethanol decreased with increasing content until it showed melting and disappearance.

[0084] In contrast to the melting temperature, T in Examples 1-6 g The temperature increased with increasing (1R,3S)-1,2,2-trimethylcyclopentane-1,3-diethanol unit content, rising from 38.4℃ in Comparative Example 1 to 64.3℃ (Table 2). This occurs because the (1R,3S)-1,2,2-trimethylcyclopentane-1,3-diethanol unit replaces the more flexible butene segment, thereby limiting the fluidity of the 2,5-furandicarboxylic acid copolyester chain.

[0085] Table 2 Thermal performance parameters of Examples 1-6 and Comparative Example 1

[0086]

[0087] IV. Transparency, UV shielding, and solvent resistance:

[0088] The optical properties of the films from Examples 1, 2, 3, 6, and Comparative Example 1 were investigated using UV-Vis spectroscopy to evaluate the potential of 2,5-furandicarboxylic acid copolyester as a food packaging material. Figure 7 As shown in Table 3, the 2,5-furandicarboxylic acid copolyester film exhibits high transparency in the visible light range (400-760 nm). With increasing concentration of (1R,3S)-1,2,2-trimethylcyclopentane-1,3-diethanol units, compared to Comparative Example 1, the transmittance at 760 nm in Examples 1, 2, 3, and 6 of this invention increased from 12.4% to 87.5%, while the haze decreased from 74.8% to 15.6%. Furthermore, as... Figure 7 As shown, the 2,5-furandicarboxylic acid copolyester films of Examples 1, 2, 3 and 6 of this invention also provide the required ultraviolet shielding, completely blocking UVC (200-280nm) and UVB (280-320nm) radiation, thereby reducing food discoloration, nutrient degradation and oxidative damage caused by free radicals.

[0089] Table 3. Transmittance and haze of Examples 1-3, Example 6, and Comparative Example 1

[0090]

[0091] Solvent resistance was evaluated by testing the solubility of 10 mg of Examples 1-6 and Comparative Example 1 in 1 mL of various organic solvents. As shown in Table 4, Examples 1-6 exhibited partial solubility upon heating in chloroform, tetrahydrofuran, and N,N-dimethylformamide, while remaining substantially insoluble in methanol, ethanol, acetone, and toluene. This broad solvent resistance suggests that the 2,5-furandicarboxylic acid copolyester of this invention is a promising candidate for food packaging applications requiring resistance to corrosive chemicals.

[0092] Table 4. Solubility of Examples 1-6 and Comparative Example 1 in different organic solvents

[0093]

[0094] V. Mechanical property testing:

[0095] According to ASTM D638 standard, the tests were conducted at 25°C using a universal testing machine (CMT6104, MITES Industrial Systems (China) Co., Ltd.). The crosshead speed was 5 mm / min. Dumbbell-shaped specimens (2 mm wide, 5 mm thick) were prepared using a miniature injection molding machine (SZS-15, Wuhan Ruiming Experimental Instrument Co., Ltd.).

[0096] The stress-strain curves of Examples 1-6 and Comparative Example 1 are as follows: Figure 8 As shown, the corresponding data, including Young's modulus, yield strength, tensile strength, and elongation at break, are summarized in Table 5. Figure 8 It can be seen that Examples 1-6 and Comparative Example 1 all exhibit typical thermoplastic behavior. With the addition of the minimum amount of (1R,3S)-1,2,2-trimethylcyclopentane-1,3-diethanol unit, tensile strength and elongation at break increase. Examples 1 and 2 show significantly improved tensile strength (from 32 MPa to 39 MPa), yield strength, and Young's modulus compared to Comparative Example 1. Furthermore, Example 1 exhibits a higher elongation at break (500%) compared to Comparative Example 1. With further increases in the content of rigid (1R,3S)-1,2,2-trimethylcyclopentane-1,3-diethanol unit, the tensile strength and elongation at break of Examples 3-6 gradually decrease, but the yield strength and Young's modulus are higher than those of Comparative Example 1.

[0097] Table 5 Mechanical properties of Examples 1-6 and Comparative Example 1

[0098]

[0099] To further evaluate the properties of the 2,5-furandicarboxylic acid copolyester synthesized in this invention, the basic parameters of Examples 1 and 2 were compared with those of commercial polyesters such as petroleum-based polybutylene terephthalate (PBT, Macromolecules 2012, 45, 8257) and biodegradable polybutylene adipate terephthalate (PBAT, Journal of Hazardous Materials 2024, 465, 133475), and polybutylene succinate (PBS, Polymer 2024, 313, 127672), including the glass transition temperature (T0). g ), tensile strength, elongation at break, Young's modulus, and 5% temperature of weight loss (T). d,5% The comparison results are shown in Table 6. Example 2's T g The tensile strength reached 46.0°C, exceeding that of Comparative Example 1 and several commercial plastics such as PBT, PBAT, and PBS. The addition of the rigid ring-structured (1R,3S)-1,2,2-trimethylcyclopentane-1,3-diethanol unit significantly increased the tensile strength of Example 2 to 39 MPa and the Young's modulus to 1230 MPa. The fully bio-based 2,5-furandicarboxylic acid copolyester of this invention is environmentally friendly and sustainable, reducing dependence on petroleum. Furthermore, its superior performance makes it a viable alternative to petroleum-based plastics.

[0100] Table 6. Performance comparison of Examples 1-2 with Comparative Example 1 and currently commercially available plastics PBT, PBAT, and PBS.

[0101]

[0102] VI. Chemical closed-loop recycling:

[0103] In this invention, the chemical recovery of 2,5-furandicarboxylic acid copolyester is achieved under mild conditions in a sodium hydroxide / tetrahydrofuran / 1,4-butanediol ternary system.

[0104] Taking the recycling in Example 1 as an example, the process includes the following steps:

[0105] A mixture of T1, PBTCF3 (6.0 g), sodium hydroxide (5 g), tetrahydrofuran (60 g) and 1,4-butanediol (40 g) was stirred in a 250 mL flask at 60 °C for 3 h.

[0106] T2. The reaction product was filtered to obtain a precipitate of sodium 2,5-furandicarboxylate and a filtrate. The sodium 2,5-furandicarboxylate precipitate was redissolved in deionized water, and the pH was adjusted to 2 using concentrated hydrochloric acid (>30%) to produce recovered 2,5-furandicarboxylic acid, which was collected by filtration. The filtrate obtained after the reaction was distilled at 80°C for 2 hours to remove tetrahydrofuran, and then distilled under reduced pressure at 140°C for 2 hours to obtain recovered 1,4-butanediol.

[0107] T3. Preparation of dimethyl 2,5-furandicarboxylate from recovered 2,5-furandicarboxylic acid:

[0108] 10 g of the recovered 2,5-furandicarboxylic acid was dissolved in a methanol solution containing sulfuric acid (150 mL of methanol containing 0.5 mL of sulfuric acid with a mass fraction ≥90%) in a reaction flask and refluxed at 90 °C for 5 hours. The resulting precipitate was filtered, washed with distilled water, and dried to obtain the recovered dimethyl 2,5-furandicarboxylic acid.

[0109] Figure 9 The recovered 2,5-furandicarboxylic acid and the original 2,5-furandicarboxylic acid 1 H-NMR, 13 C-NMR and liquid chromatograms were obtained. The figures show that the recovered 2,5-furandicarboxylic acid has the same structure as the original 2,5-furandicarboxylic acid. Furthermore, the purity of the recovered 2,5-furandicarboxylic acid was 99.1%, and the calculated yield was 85%.

[0110] Figure 10 For dimethyl 2,5-furandicarboxylate before and after recovery 1 H-NMR, 13C-NMR and liquid chromatograms were obtained. The figures show that the recovered dimethyl 2,5-furandicarboxylate has the same structure as the original dimethyl 2,5-furandicarboxylate. Furthermore, the purity of the recovered dimethyl 2,5-furandicarboxylate was 98.8%, and the calculated yield was 89.5%.

[0111] Figure 11 For the recovery of 1,4-butanediol 1 H-NMR, 13 C-NMR and gas chromatograms were also obtained. The figures show that the recovered 1,4-butanediol has the same structure as the original 1,4-butanediol. Furthermore, the purity of the recovered 1,4-butanediol is 97.8%.

[0112] A new recycled Example 1 was synthesized using recovered dimethyl 2,5-furandicarboxylate, recovered 1,4-butanediol, and (1R,3S)-1,2,2-trimethylcyclopentane-1,3-diethanol under the same conditions as in Example 1.

[0113] The chemical structure of the recovered Example 1 was obtained through 1 Verification was performed using H-NMR spectra, and thermal and mechanical properties were analyzed using DSC and stress-strain curves, respectively. Figure 12 As shown, the recycled Example 1 retained thermal properties (T0) comparable to those of the original Example 1. m =157.8℃, T g =41.3℃), and the recovery example 1 exhibited almost the same mechanical properties as example 1, which verifies the feasibility of the closed-loop recovery of the 2,5-furandicarboxylic acid copolyester designed and prepared in this invention.

[0114] Therefore, this invention employs the above-mentioned fully bio-based 2,5-furandicarboxylic acid copolyester, its preparation method, application, and closed-loop recovery method. The addition of the (1R,3S)-1,2,2-trimethylcyclopentane-1,3-diethanol unit improves T g This process enhances the strength and toughness of the copolyester; the copolyester exhibits excellent UV shielding and solvent resistance; the copolyester can be rapidly depolymerized under mild conditions in a sodium hydroxide-tetrahydrofuran-1,4-butanediol system to produce high-purity monomer raw materials; compared with the original polymer, the mechanical and thermal properties of the repolymerized copolyester are almost not reduced, making the 2,5-furandicarboxylic acid-based copolyester an ideal combination of chemical recyclability and high performance.

[0115] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A fully bio-based 2,5-furandicarboxylic acid copolyester, characterized in that: The molecular structural formula of the fully bio-based 2,5-furandicarboxylic acid copolyester is as follows: 。 2. The method for preparing a fully bio-based 2,5-furandicarboxylic acid copolyester as described in claim 1, characterized in that: Includes the following steps: S1. 1,4-Butanediol, (1R,3S)-1,2,2-trimethylcyclopentane-1,3-diethanol and dimethyl 2,5-furandicarboxylate are added to a reaction flask, and a catalyst is added to carry out the transesterification reaction. S2. After the transesterification reaction, the temperature is raised to carry out a polycondensation reaction to obtain a fully bio-based 2,5-furandicarboxylic acid copolyester, denoted as PBTCF. x , x This indicates the molar percentage of (1R,3S)-1,2,2-trimethylcyclopentane-1,3-diethanol units in the 2,5-furandicarboxylic acid copolyester.

3. The method for preparing a fully bio-based 2,5-furandicarboxylic acid copolyester according to claim 2, characterized in that: The molar ratio of the mixture of 1,4-butanediol, (1R,3S)-1,2,2-trimethylcyclopentane-1,3-diethanol to dimethyl 2,5-furandicarboxylate is (1.5-2.2):1, and the molar amount of (1R,3S)-1,2,2-trimethylcyclopentane-1,3-diethanol is 0.1-99 mol of the mixture of 1,4-butanediol and (1R,3S)-1,2,2-trimethylcyclopentane-1,3-diethanol.

4. The method for preparing a fully bio-based 2,5-furandicarboxylic acid copolyester according to claim 2, characterized in that: In S1, the catalyst is titanium isopropoxide or tetrabutyl titanate, and the amount of catalyst used is 0.1-0.8 mol of dimethyl 2,5-furandicarboxylate.

5. The method for preparing a fully bio-based 2,5-furandicarboxylic acid copolyester according to claim 2, characterized in that: In S1, the transesterification reaction is carried out at a temperature of 160-180℃ for 4-6 hours under a nitrogen atmosphere.

6. The method for preparing a fully bio-based 2,5-furandicarboxylic acid copolyester according to claim 2, characterized in that: In S2, the pressure in the reaction flask is reduced to 10-90 Pa to carry out the polycondensation reaction, the reaction temperature is 190-240℃, and the reaction time is 2-8 hours.

7. An application of a fully bio-based 2,5-furandicarboxylic acid copolyester, characterized in that: The fully bio-based 2,5-furandicarboxylic acid copolyester of claim 1 is applied to high-performance environmentally friendly plastic packaging.

8. The closed-loop recovery method for a fully bio-based 2,5-furandicarboxylic acid copolyester as described in claim 1, characterized in that: Includes the following steps: T1. Add a mixture of fully bio-based 2,5-furandicarboxylic acid copolyester, sodium hydroxide, tetrahydrofuran and 1,4-butanediol into a flask, heat and stir to carry out the reaction. T2. The product after the reaction is filtered to obtain a precipitate and a filtrate. The precipitate is redissolved in deionized water, and concentrated hydrochloric acid is added for acidification and further filtration to obtain the recovered 2,5-furandicarboxylic acid. The filtrate is distilled under normal pressure and then under reduced pressure to obtain the recovered 1,4-butanediol. T3. Add the recovered 2,5-furandicarboxylic acid obtained in T2 to the flask, and reflux in a methanol solution containing sulfuric acid. Filter to obtain a precipitate, wash and dry the precipitate to obtain the recovered dimethyl 2,5-furandicarboxylic acid.

9. The closed-loop recovery method for a fully bio-based 2,5-furandicarboxylic acid copolyester according to claim 8, characterized in that: In T1, the mass ratio of fully bio-based 2,5-furandicarboxylic acid copolyester, sodium hydroxide, tetrahydrofuran and 1,4-butanediol is 1:(0.6-2):(8-15):(6-8), the stirring temperature is 50-70℃, and the stirring time is 2-5h. In T2, the mass fraction of concentrated hydrochloric acid is ≥30%, and the solution is acidified to pH 2-2.

5. The filtrate is then distilled at 75-85℃ for 0.3-0.5h to remove tetrahydrofuran. The vacuum distillation temperature is 130-150℃ and the distillation time is 1.5-3h. In T3, the methanol solution containing sulfuric acid has a volume ratio of methanol to sulfuric acid of 300:1, a sulfuric acid mass fraction of ≥90%, a reflux temperature of 90-100℃, a reflux time of 4-5h, is washed with distilled water, and is dried for 6-12h at a drying temperature of 60-70℃.

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