Novel bio-based copolyester material and preparation method thereof

Abstract

The invention discloses a preparation method of a novel bio-based copolyester material, and belongs to the field of green high polymer materials. According to the method, a furan carboxylic acid source, a pentanediol source and glutaric acid are used as raw materials, and the poly (neopentyl glycol glutarate-co-neopentyl glycol furandicarboxylate) series random copolyester is synthesized through ester exchange and condensation polymerization. The method comprises the following operation steps: mixing a furan carboxylic acid source, a pentanediol source and glutaric acid according to a molar ratio, adding a catalyst, sequentially carrying out heating reaction in an inert gas atmosphere, carrying out vacuum polycondensation, dissolving and precipitating, and drying to obtain a target product. The obtained copolyester material is controllable in composition and stable in structure, and has good thermal stability (Tdmaxgt; the glass transition temperature (4-64 DEG C) is adjustable, the mechanical property is excellent, the highest elongation at break can reach 917%, and the Young modulus can reach 1963 MPa. The material performance can be continuously regulated and controlled along with the monomer feeding ratio, and the material has wide application prospects in the aspects of elastomers, high-barrier thermoplastic materials and the like. The method is simple in process, raw materials are easy to obtain, and the method is suitable for sustainable development of the high-performance full-bio-based plastic.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, specifically to a method for preparing a novel bio-based copolyester material synthesized from furan carboxylic acid source, pentanediol source, and glutaric acid as raw materials. This material possesses both excellent thermodynamic properties and adjustable mechanical properties, and is suitable for various fields such as biodegradable plastics and thermoplastic elastomers. Background Technology

[0002] With the depletion of petroleum resources and increasing environmental pressure, the development of renewable and biodegradable materials has become a hot topic in materials research. Polyfuran dicarboxylate (such as PEF and PNF), as FDCA-derived materials, possess excellent thermal stability and mechanical properties, and are considered ideal alternatives to polyterephthalate (such as PET and PBT). For example, patent CN202411933145.7 polymerizes furan dicarboxylic acid (FDCA), butanediol, catalyst, and heat stabilizer to obtain polybutylene furan dicarboxylate, which not only has good mechanical properties but also excellent barrier and antibacterial properties. However, the inherent brittleness (elongation at break <5%) of currently synthesized neopentylene furan dicarboxylate limits its application. Existing bio-based polyesters such as polylactic acid (PLA) and polybutylene adipate terephthalate (PBAT) also suffer from insufficient mechanical properties or dependence on petroleum-based monomers.

[0003] In existing technologies, the shortcomings of polylactic acid (PNF) have not been effectively addressed through copolymerization modification. For example, in patent CN202411342411.9, furanyl dicarboxylic acid, neopentyl glycol (NPG), and polylactic acid are polymerized, and the beneficial effect of the resulting block copolymer is only that its toughness exceeds that of pure polylactic acid and that it is biodegradable. Therefore, developing a copolyester with high bio-based content, adjustable mechanical properties, and excellent thermal stability is of great significance. Summary of the Invention

[0004] The purpose of this section is to outline some aspects of embodiments of the present invention and to briefly describe some preferred embodiments. Simplifications or omissions may be made in this section, as well as in the abstract and title of this application, to avoid obscuring the purpose of these documents; however, such simplifications or omissions should not be construed as limiting the scope of the invention.

[0005] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a novel bio-based polyester material with excellent thermal stability, adjustable glass transition temperature, and mechanical properties, solving problems such as poor toughness and large crystallinity differences in existing PNF-based polyesters. This invention provides the following technical solution:

[0006] Furan carboxylic acid source, pentanediol source and glutaric acid are added to the reaction flask in a specific molar ratio, and a catalyst is added at the same time;

[0007] Under nitrogen protection, the transesterification reaction was carried out by heating: 160℃ for 0.5 hours, followed by heating to 180℃, 190℃ and 200℃, with each stage lasting 1 hour;

[0008] After the water generated in the reaction reaches the theoretical value, the polycondensation reaction continues at 220°C under a vacuum of 0.1 mmHg for 3 hours.

[0009] The obtained polyester was dissolved in fluorinated alcohol (HFIP), precipitated with cold methanol, filtered, and then vacuum dried to obtain the target polyester material.

[0010] In a preferred embodiment of the preparation method described in this invention, the furan carboxylic acid source includes one or more of the following: furanyl dicarboxylic acid, dimethyl furanyl dicarboxylate, diethyl furanyl dicarboxylate, dipropyl furanyl dicarboxylate, dibutyl furanyl dicarboxylate, dipentyl furanyl dicarboxylate, monomethyl furanyl dicarboxylate, monoethyl furanyl dicarboxylate, monopropyl furanyl dicarboxylate, monobutyl furanyl dicarboxylate, and monopentyl furanyl dicarboxylate.

[0011] As a preferred embodiment of the preparation method described in this invention, the pentylene glycol source includes one or more of neopentylene glycol, neopentylene glycol diacetate, neopentylene glycol dipropionate, neopentylene glycol dibutyrate, and neopentylene glycol dibenzoate.

[0012] As a preferred embodiment of the preparation method described in this invention, the catalyst comprises p-toluenesulfonic acid, titanium citrate, titanium isopropoxide, tetrabutyl titanate, tetraethyl titanate, dibutyltin dilaurate, tri-n-butylmethoxytin, stannous octoate, and stannous benzoate.

[0013] Beneficial effects of this invention:

[0014] (1) High performance adjustability: By adjusting the ratio of FDCA and GA, the glass transition temperature (T) can be continuously adjusted from 4℃ to 64℃, the elongation at break can be adjusted from 9% to 916%, and the Young's modulus can be adjusted from 0.6MPa to 1963MPa.

[0015] (2) Good thermal stability: The thermal decomposition temperature (T) of the obtained copolyester material is... dmax All temperatures are above 400℃, exhibiting good thermal stability;

[0016] (3) Controllable crystallization behavior: The crystallinity of doped GA units can be adjusted to form new crystal phases, thus expanding their structural diversity;

[0017] (4) Renewability: The raw materials can be synthesized from renewable biomass, which has the potential to be green, environmentally friendly and sustainable.

[0018] (5) Excellent mechanical properties: The samples in the PNGF30-40 range have a combination of rigidity and flexibility, making them suitable for packaging materials, elastomers and structural materials. Attached Figure Description

[0020] Figure 1 It is PNGF polyester in various proportions. 1 H NMR spectrum;

[0021] Figure 2 The images show the DSC curves of (a) the first heating, (b) cooling, and (c) the second heating of PNGF polyesters in various proportions, and the XRD pattern of the PNGF polyesters.

[0022] Figure 3 These are the (a) TGA curves and (b) DTG curves of PNGF polyesters at various proportions;

[0023] Figure 4 (a) Stress-strain curves and (b) Mechanical property data obtained by stress-strain measurements for PNGF polyesters of various proportions;

[0024] Table 1 is a schematic diagram of the molecular composition of PNGF polyester at various proportions calculated by proton NMR.

[0025] Table 2 shows the thermal performance data of PNGF polyesters at various ratios obtained by DSC and TGA.

[0026] Table 3 shows the tensile properties of PNGF polyester at various proportions. Detailed Implementation

[0027] The technical solution of the present invention will be further explained below with reference to the accompanying drawings.

[0028] Example 1: 2,5-Furandicarboxylic acid, neopentyl glycol, and glutaric acid were added to a two-necked flask equipped with a mechanical stirrer, nitrogen vent, and condenser at a molar ratio of FDCA:GA:NPG of 20:30:100. Tetrabutyl titanate was added as a catalyst. The reaction system was evacuated to 0.1 mmHg and purged with nitrogen three times before starting the reaction. The reaction was then carried out according to the following temperature program:

[0029] -160℃, reaction time 0.5 hours;

[0030] - Raise the temperature to 180°C and react for 1 hour;

[0031] - Raise the temperature to 190°C and react for 1 hour;

[0032] - Raise the temperature to 200°C and react for 1 hour.

[0033] Approximately 1.8 mL of water generated during the reaction was collected, and the polycondensation reaction was continued at 220°C under a vacuum of 0.1 mmHg for 3 hours. After the reaction was completed, the product was cooled to room temperature, dissolved in fluorinated isopropanol, precipitated with cold methanol, filtered, and dried in a vacuum oven at 60°C for 24 hours to obtain a light yellow solid polyester material, named PNGF20.

[0034] Example 2: Repeat the steps of Example 1, except that the molar ratio of FDCA, GA and NPG is adjusted to 25:25:100, and the resulting polyester is named PNGF25.

[0035] Example 3: Repeat the steps of Example 1, except that the molar ratio of FDCA, GA and NPG is adjusted to 30:20:100, and the resulting polyester is named PNGF30.

[0036] Example 4: Repeat the steps of Example 1, except that the molar ratio of FDCA, GA and NPG is adjusted to 40:10:100, and the resulting polyester is named PNGF40.

[0037] Example 5: Repeat the steps of Example 1, except that the molar ratio of FDCA, GA and NPG is adjusted to 45:5:100, and the resulting polyester is named PNGF45.

[0038] Example 6: Repeat the steps of Example 1, except that the molar ratio of FDCA, GA and NPG is adjusted to 50:0:100, and the resulting polyester is named PNF.

[0039] Combination Figure 1 The study clearly shows the characteristic peaks of FDCA, GA and NPG units in the PNGF copolyester. The typical peaks of PNF are located at δ = 7.86 (1), 4.85 (2) and 1.68 (3) ppm, which are respectively attributed to CH in the furan ring, methylene CH2 and methyl CH3 of NPG; the newly added peaks of δ = 3.04 (4) and 2.54 (5) ppm in PNGF can be attributed to the GA unit; when NPG is connected to the glutaric acid unit, the chemical shifts of CH2 and CH3 move to 4.61 (6) and 1.52 (7) ppm, respectively, indicating that the reaction product is successfully copolymerized and the structure is significantly affected by the monomer composition.

[0040] As shown in Table 1, the GA content in the final polyester increases synchronously with the increase of the GA molar fraction in the feed. Although there is a slight deviation (the maximum is about 8%), which may be caused by the partial sublimation of GA during polycondensation, the copolymerization reaction of the system is controllable and the composition can be adjusted by the feed ratio. This provides a basis for the subsequent systematic comparison of thermal and mechanical properties.

[0041] Table 1. Schematic diagram of PNGF polyester molecular composition

[0042]

[0043] Combination Figure 2 As shown in Table 2, with increasing GA content, the glass transition temperature of polyester decreased from 64.2℃ to 4.1℃, and the melting point and crystallization temperature also decreased simultaneously, indicating a trend of increased chain flexibility and weakened crystallinity. PNGF20-30 showed no obvious melting and crystallization peaks, indicating that it was mainly an amorphous structure, while PNGF40 and above still retained a certain degree of crystallinity. Enthalpy changes further confirmed that crystallinity decreased with increasing GA content; the melting enthalpy of PNF was 51.3 J / g, while that of PNGF40 decreased to 21.6 J / g. Despite the weakened thermophysical properties, the thermal stability of all samples remained at a high level, with maximum thermal degradation temperatures exceeding 400℃, demonstrating good resistance to thermal degradation. XRD results also showed that PNGF20-40 produced a new crystal structure different from PNF, confirming that GA copolymerization not only affected crystallinity but also changed the crystal phase type. In summary, the addition of GA units modulated the thermodynamic properties of PNGF, enabling it to smoothly transition from a highly crystalline rigid material to a flexible polyester while maintaining high thermal stability.

[0044] Combination Figure 3 As shown in Table 2, the analysis indicates that all PNGF polyesters exhibit good thermal stability, T dmax All exceeded 400℃. d5 The fluctuation in GA content indicates that a small proportion of GA will temporarily reduce thermal stability, but overall it still has good processing and use safety under high temperature environment. The DTG curves of some PNGF samples showed multiple degradation peaks, suggesting that its degradation mechanism has changed from a single mode to a multiphase process.

[0045] Table 2. Thermal performance data of PNGF polyester obtained by DSC and TGA.

[0046]

[0047] Combination Figure 4 Table 3 shows that the transition of PNGF from the rubbery to the glassy state mainly occurs in the PNGF30-40 range, with the modulus jumping from 13.3 MPa to 527 MPa, while the elongation drops sharply to below 10%, indicating a clear brittle-ductile transition window. PNGF20-30 exhibits extremely high elongation at break (up to 917%), suitable for flexible material applications; PNGF40-45 displays high strength and high modulus, making it more suitable for rigid structural applications. This characterization further confirms that by adjusting the GA content, mechanical properties can be finely tuned to suit different application scenarios.

[0048] Table 3 Tensile Properties of PNGF Polyester

[0049]

Claims

1. A method for preparing a bio-based polyester material, characterized in that, Includes the following steps: ① Add furan carboxylic acid raw material, pentanediol raw material and glutaric acid (GA) to the reaction flask in a specific molar ratio, and add a catalyst; ② Inert gas is introduced, and the temperature is increased in a stepwise manner to carry out ester exchange; ③ Polycondensation is carried out under high temperature and vacuum conditions; ④ The obtained polyester was dissolved in fluorinated alcohol and precipitated with cold methanol, then filtered and dried to obtain the product.

2. The method according to claim 1, characterized in that, The furan carboxylic acid raw materials include one or more of the following: furandicarboxylic acid, dimethyl furanate, diethyl furanate, dipropyl furanate, dibutyl furanate, dipentyl furanate, monomethyl furanate, monoethyl furanate, monopropyl furanate, monobutyl furanate, and monopentyl furanate.

3. The method according to claim 1, characterized in that, The pentylene glycol raw material includes one or more of neopentylene glycol, neopentylene glycol diacetate, neopentylene glycol dipropionate, neopentylene glycol dibutyrate, and neopentylene glycol dibenzoate.

4. The method according to claim 1, characterized in that, The catalyst is one of the following: titanium citrate p-toluenesulfonate, titanium isopropoxide, tetrabutyl titanate, tetraethyl titanate, dibutyltin dilaurate, tri-n-butylmethoxytin, stannous octoate, and stannous benzoate.

5. The method according to claim 1, characterized in that, The molar ratio of furan carboxylic acid source to glutaric acid is 50:0 to 20:30, corresponding to an actual doping amount of glutaric acid unit in the copolyester of 0% to 53.44%.

6. The polyester material prepared by the method according to claim 1, characterized in that... Mechanical properties, crystallization behavior, and thermal stability can be controlled by the furan carboxylic acid / glutaric acid ratio.

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