Heat-resistant bio-based degradable polyester material and preparation method thereof

Abstract

The invention discloses a heat-resistant bio-based degradable polyester material and a preparation method of the heat-resistant bio-based degradable polyester material, and belongs to the field of bio-based high polymer materials. Two brand-new bio-based modified compounds are introduced, wherein one compound is diol with a bicyclic structure prepared by reacting bio-based vanillin with epichlorohydrin and carrying out hydroboration-oxidation, and the other compound is binary acid with an imidazole ring generated by hydrogenating bio-based itaconic acid and condensing the hydrogenated bio-based itaconic acid with ethylenediamine. The preparation method comprises the following steps: melting and mixing 1, 4-butanediol, adipic acid and two modified compounds, adding a catalyst and a nucleating agent, carrying out condensation polymerization under a high-temperature vacuum condition, and drying to obtain the polyester material. According to the material, the heat resistance is synergistically improved through the rigidity of a double-ring structure and the polarity of an imidazole ring, and the material is clear in bio-based source, can be completely biodegraded and is suitable for the fields of high-temperature packaging, degradable meal boxes and the like.

Description

Technical Field

[0001] This invention relates to the field of bio-based polymer materials technology, specifically to a heat-resistant bio-based biodegradable polyester material and its preparation method. Background Technology

[0002] The large-scale use of petroleum-based plastics has severely impacted the global ecological environment. Of the hundreds of millions of tons of plastic waste generated annually, only about 10% can be effectively recycled; the rest either accumulates on land, forming "white deserts," or flows into the ocean, threatening marine life. Because of their stable chemical structure, these plastics take hundreds of years to degrade in the natural environment, creating a sharp contradiction between their non-degradability and the demands of sustainable development. Against this backdrop, bio-based biodegradable polyester plastics, with their advantages of renewable raw materials and degradation into water and carbon dioxide, have become a core direction for replacing petroleum-based plastics. These materials use diols and diacids as basic raw materials, forming a polyester structure with a main chain containing numerous hydrolyzable ester bonds through a condensation reaction. This retains the high molecular weight and mechanical properties of traditional polyesters while possessing biodegradability, making them widely used in packaging, disposable daily necessities, and 3D printing consumables. However, the generally insufficient heat resistance of existing bio-based polyester plastics has become a key bottleneck restricting their further promotion.

[0003] Existing bio-based polyester plastics mainly include polylactic acid (PLA), polybutylene succinate (PBS), and polybutylene adipate (PSA). While PLA has garnered attention due to its widely available raw materials, its low glass transition temperature makes it prone to softening and deformation at high temperatures, failing to meet the needs of hot beverage packaging and summer daily necessities. PBS has an even lower glass transition temperature and is primarily used in room-temperature packaging. Although copolymerization has improved some properties of PSA, it remains a semi-crystalline polyester, exhibiting significant softness and plasticity at low temperatures, and exhibiting even weaker heat resistance. The heat resistance deficiencies of these materials stem from the limitations of their molecular chain structure: an excessively high proportion of flexible aliphatic segments in the main chain, low rotational resistance within the molecular chain, and active chain segment movement, leading to softening at relatively low temperatures. To improve heat resistance, existing technologies have explored various modification methods: First, aromatic monomers are introduced to suppress molecular chain movement through rigid aromatic rings. However, these monomers are mostly petroleum-based and do not meet the definition of bio-based. Second, heterocyclic monomers are used to improve heat resistance by utilizing the rigidity of the heterocyclic structure. However, heterocyclic monomers rely on petroleum-based raw materials, and the heterocycles have poor compatibility with the polyester backbone, easily leading to cyclization and dehydration side reactions during polycondensation, resulting in lower molecular weight and decreased mechanical properties. Third, nanofillers are added to improve thermal stability through reinforcement. However, the interfacial bonding between the filler and the polyester matrix is ​​weak, requiring additional surface modification treatment, which is complex and prone to interfacial defects, thus reducing the material's biodegradability. None of these methods achieve an effective balance between bio-based sourcing, improved heat resistance, and biodegradability, making it difficult to meet the market demand for high-performance bio-based polyester plastics.

[0004] To address the aforementioned technical challenges, there is an urgent need to develop a novel bio-based modification scheme that can significantly improve the heat resistance of polyester plastics while maintaining high bio-based content and biodegradability. This invention proposes to solve this problem through the synergistic effect of two novel bio-based modifying monomers: one is a bio-based diol with a rigid bicyclic structure, whose bicyclic skeleton can effectively inhibit intramolecular chain rotation and increase the glass transition temperature of the material; the other is a bio-based dicarboxylic acid with a polar imidazole ring, whose polar groups can enhance intermolecular hydrogen bonding and improve the melting point and thermal stability of the material. Both of these modifying monomers are derived from biomass raw materials, ensuring the bio-based properties of the material; simultaneously, the modified monomers retain a large number of hydrolyzable ester bonds, ensuring that the material can still be gradually degraded into water and carbon dioxide by esterases secreted by microorganisms under composting conditions. Through the structural design and copolymerization of these two monomers, it is expected to overcome the bottleneck of insufficient heat resistance in existing bio-based polyester plastics, expanding their applications in high-temperature packaging, biodegradable food containers, and other scenarios, possessing significant environmental and economic value. Summary of the Invention

[0005] The purpose of this invention is to provide a heat-resistant bio-based biodegradable polyester material and its preparation method, which solves the technical problem of insufficient heat resistance caused by excessive flexible segments in the main chain of existing bio-based polyester materials.

[0006] The present invention achieves the above objectives through the following technical solutions:

[0007] A heat-resistant, biodegradable polyester material comprising the following raw materials in parts by weight:

[0008] 1,4-Butanediol: 100-150 parts by weight;

[0009] Adipic acid: 80-120 parts by weight;

[0010] Bio-based bicyclic [2.2.2]oct-2-en-1,4-diol: 10-20 parts by weight;

[0011] 3-(1-Imidazolyl)-5-methyl adipic acid: 5-15 parts by weight;

[0012] Tetrabutyl titanate: 0.1-0.5 parts by weight;

[0013] Talc: 0.5-2 parts by weight;

[0014] The preparation method of the bio-based bicyclic [2.2.2]oct-2-en-1,4-diol includes: A1, dissolving bio-based vanillin in anhydrous ethanol, adding formaldehyde solution, and reacting at 60-64℃; filtering to separate the intermediate, adding bio-based epichlorohydrin and sodium hydroxide, and reacting at 80-84℃; A2, adding sodium borohydride and methanol, reducing at room temperature, and then acidifying with dilute hydrochloric acid to pH=4.8-5.2 to precipitate the crude product; purifying the crude product by column chromatography.

[0015] In this invention, the preparation mechanism of bio-based bicyclic [2.2.2]oct-2-en-1,4-diol originates from the multi-step functional group transformation and structural reconstruction of bio-based vanillin. First, the phenolic hydroxyl group in the bio-based vanillin molecule undergoes a nucleophilic addition reaction with formaldehyde in the polar solvent anhydrous ethanol. The carbonyl carbon of formaldehyde is attacked by the oxygen atom of the phenolic hydroxyl group, forming a cyclic condensation intermediate containing a methylene bridge. This process constructs a preliminary cyclic framework structure through multiple condensation-cyclization reactions. Subsequently, the intermediate undergoes a ring-opening reaction with bio-based epichlorohydrin under alkaline conditions (sodium hydroxide): the tricyclic epoxy ring of epichlorohydrin is polarized under the influence of the alkaline environment, and the hydroxyl group in the intermediate acts as a nucleophile to attack a carbon atom of the epoxy ring, causing the ring to cleave and form a new ether bond. At the same time, a chloroalkyl side chain is introduced. This ring-opening process transforms the original linear intermediate into an intermediate product with a bicyclic rudimentary structure. Next, sodium borohydride, acting as a selective reducing agent, reduces unsaturated bonds (such as double bonds or epoxy residues) in the intermediate product at room temperature, converting the less polar unsaturated bonds into saturated structures and enhancing molecular stability. Subsequently, the pH of the system is adjusted to weakly acidic by acidification with dilute hydrochloric acid to neutralize excess alkaline substances in the reaction system, while simultaneously promoting the precipitation of the hydroxyl-containing crude product from the organic phase. Finally, column chromatography is used for separation and purification to remove unreacted raw materials and byproducts, ultimately yielding a bio-based bicyclic diol with a rigid bicyclic skeleton and hydrophilic hydroxyl groups. The entire process, through multiple steps including condensation, ring-opening, reduction, and acidification, achieves the structural transformation from aromatic aldehydes to rigid bicyclic diols, endowing the monomer with excellent rigidity characteristics.

[0016] According to a preferred embodiment of the present invention, the 1,4-butanediol was purchased from Xinjiang Meike Chemical Co., Ltd. (model: MBDO-01, industrial grade, high purity).

[0017] According to a preferred embodiment of the present invention, the adipic acid was purchased from Sinopec Baling Petrochemical Co., Ltd. (model: BA-02, superior grade).

[0018] According to a preferred embodiment of the present invention, the bio-based vanillin was purchased from Meihua Biotechnology Group Co., Ltd. (model: LX-001, produced by bio-fermentation, purity ≥99.5%).

[0019] According to a preferred embodiment of the present invention, the anhydrous ethanol was purchased from Anhui Huayi Industrial Development Co., Ltd. (model: WH-99.9, analytical grade).

[0020] According to a preferred embodiment of the present invention, the formaldehyde was purchased from Hebei Wen'an Xingyuan Formaldehyde Co., Ltd. (model: WAN-37, industrial grade 37% aqueous solution).

[0021] According to a preferred embodiment of the present invention, the bio-based epichlorohydrin was purchased from Shandong Binhua Binyang Petrochemical Co., Ltd. (model: BH-01, refined from biodiesel by-product, purity ≥99%).

[0022] According to a preferred embodiment of the present invention, the sodium hydroxide was purchased from Shandong Haihua Co., Ltd. (model: HAI-99, industrial grade caustic soda flakes, purity ≥99%).

[0023] According to a preferred embodiment of the present invention, the sodium borohydride was purchased from Liaoning Aoke Chemical Co., Ltd. (model: AK-01, reagent grade).

[0024] According to a preferred embodiment of the present invention, the methanol was purchased from Shaanxi Yulin Energy Group Co., Ltd. (model: YL-99.9, industrial grade superior product).

[0025] According to a preferred embodiment of the present invention, the dilute hydrochloric acid was purchased from Shandong Hualu Hengsheng Chemical Co., Ltd. (model: HNS-36, industrial grade 36% aqueous solution).

[0026] According to a preferred embodiment of the present invention, the tetrabutyl titanate was purchased from Jiangsu Hehai Nanotechnology Co., Ltd. (model: HT-01, reagent grade, purity ≥98%).

[0027] According to a preferred embodiment of the present invention, the talc powder was purchased from Liaoning Aihai Talc Co., Ltd. (model: AH-325, industrial grade 325 mesh, purity ≥98%).

[0028] According to a preferred embodiment of the present invention, in step A1, the reaction time is 2-4 hours at 60-64°C; and the ring-opening reaction time is 4-6 hours at 80-84°C.

[0029] According to a preferred embodiment of the present invention, in step A2, the reduction time at room temperature is 4-6 hours.

[0030] According to a preferred embodiment of the present invention, the preparation method of 3-(1-imidazolyl)-5-methyladipic acid includes: B1, adding bio-based itaconic acid to a mixture of palladium on carbon catalyst and ethanol, and hydrogenating it at 50-52°C and hydrogen pressure of 1-1.2 MPa; filtering and distilling under reduced pressure to obtain methylbutenedioic acid; B2, reacting methylbutenedioic acid with bio-based ethylenediamine in toluene under reflux at 120-125°C, followed by rotary evaporation; adding potassium permanganate and sulfuric acid aqueous solution, oxidizing it at 80-84°C, filtering, and washing with water until neutral.

[0031] In this invention, the preparation mechanism of 3-imidazolium adipic acid involves the transformation of unsaturated bonds and the construction of heterocyclic structures in bio-based itaconic acid. First, the carbon-carbon double bond in the bio-based itaconic acid molecule undergoes catalytic hydrogenation under the synergistic effect of a palladium-on-carbon catalyst and hydrogen gas: hydrogen molecules dissociate into active hydrogen atoms on the palladium-on-carbon surface, attacking the itaconic acid double bond and undergoing addition, converting the unsaturated carbon-carbon double bond into a saturated single bond structure, generating the intermediate methylbutenedioic acid. After filtration to remove the catalyst, the low-boiling-point solvent (ethanol) and reaction byproducts are removed by vacuum distillation to obtain the purified methylbutenedioic acid intermediate. Subsequently, methylbutenedioic acid undergoes a condensation reaction with bio-based ethylenediamine in toluene solvent: the amino group (-NH2) in the ethylenediamine molecule acts as a nucleophile, attacking the carboxyl group (-COOH) of methylbutenedioic acid, removing one molecule of water to form an amide bond (-CONH-), while the other end of the ethylenediamine continues to react with the adjacent carboxyl group, constructing an intermediate containing the characteristic structure of an imidazolium ring through intermolecular condensation. To further enhance the polarity and reactivity of the molecule, the intermediate undergoes an oxidation reaction in an acidic aqueous solution of potassium permanganate. Potassium permanganate acts as a strong oxidizing agent, oxidizing unsaturated bonds (such as double bonds or aldehyde groups) in the side chain to carboxylic acid groups (-COOH). Toluene acts as an inert solvent to avoid side reactions during the oxidation process. After the reaction is complete, the oxidizing agent residue is removed by filtration, and the mixture is washed with water until neutral to obtain 3-imidazolium adipic acid containing a polar imidazole ring and a long-chain alkyl group. This process, through hydrogenation saturation, condensation ring formation, and functional group transformation, converts an aliphatic diacid into a modified diacid containing a polar heterocycle, providing strong intermolecular interaction sites for the polyester backbone.

[0032] According to a preferred embodiment of the present invention, the bio-based itaconic acid was purchased from Shandong Longli Biotechnology Co., Ltd. (model: LK-YN-01, produced by bio-fermentation, purity ≥99.0%).

[0033] According to a preferred embodiment of the present invention, the palladium-on-carbon catalyst was purchased from Jiangsu Hehai Nanotechnology Co., Ltd. (model: HH-PdC-01, palladium content 5%, industrial-grade hydrogenation catalyst).

[0034] According to a preferred embodiment of the present invention, the ethanol was purchased from Anhui Huayi Industrial Development Co., Ltd. (model: WH-95, industrial grade ethanol, purity ≥95%).

[0035] According to a preferred embodiment of the present invention, the bio-based ethylenediamine was purchased from Shandong Lukang Pharmaceutical Co., Ltd. (model: LKE-Diamine-01, produced by bio-fermentation, purity ≥99.0%).

[0036] According to a preferred embodiment of the present invention, the toluene was purchased from China Petrochemical Corporation Jinling Petrochemical Co., Ltd. (model: JL-Toluene-01, industrial grade toluene, purity ≥99.5%).

[0037] According to a preferred embodiment of the present invention, the potassium permanganate was purchased from Tianjin Dagu Chemical Co., Ltd. (model: DG-KMnO4-01, industrial grade potassium permanganate, purity ≥99.3%).

[0038] According to a preferred embodiment of the present invention, the sulfuric acid was purchased from Shaanxi Yulin Energy Group Co., Ltd. (model: YL-H2SO4-98, industrial grade concentrated sulfuric acid, purity ≥98%).

[0039] According to a preferred embodiment of the present invention, the reactor was purchased from Weihai Chemical Machinery Co., Ltd. (model: WH-5000L, stainless steel, design pressure 0.6MPa).

[0040] According to a preferred embodiment of the present invention, the nitrogen gas is purchased from Yingde Gases (Shanghai) Co., Ltd. (model: YD-N2-99.999%, industrial grade high-purity nitrogen gas).

[0041] According to a preferred embodiment of the present invention, in step B1, the hydrogenation reaction takes 3-4 hours.

[0042] According to a preferred embodiment of the present invention, in step B2, the reflux reaction time at 120-125°C is 5-6 hours; the oxidation time at 80-84°C is 3-4 hours.

[0043] The present invention also provides a method for preparing the heat-resistant bio-based biodegradable polyester material, comprising the following steps:

[0044] S1. Add 1,4-butanediol, adipic acid, bio-based bicyclo[2.2.2]oct-2-en-1,4-diol, and 3-(1-imidazolyl)-5-methyl adipic acid to the reaction vessel, purge the air with nitrogen, and stir at 118-122℃ to melt and mix.

[0045] S2. Add tetrabutyl titanate and talc, heat to 230-260℃, and gradually reduce the system pressure to below 50Pa to react.

[0046] S3. Dry the product at 100-104℃ and 10Pa vacuum.

[0047] In this invention, the preparation mechanism of the heat-resistant bio-based biodegradable polyester material is a synergistic polymerization process of bio-based diols, diacids, and two modified monomers. First, 1,4-butanediol (containing two hydroxyl groups) and adipic acid (containing two carboxyl groups) are used as basic raw materials and melt-mixed at 118-122°C under nitrogen protection: nitrogen replaces the air in the reaction system to prevent oxidation and deterioration of the raw materials at high temperatures; in the molten state, the hydroxyl and carboxyl groups initially associate through hydrogen bonding, forming a homogeneous prepolymer melt. Subsequently, two modified monomers, a bio-based bicyclic diol and 3-imidazolium adipic acid, are added, and stirring continues to ensure thorough dispersion of the components. The bicyclic structure and imidazolium ring of the modified monomers are embedded in the prepolymer melt through van der Waals forces and hydrogen bonding, forming a multi-component homogeneous system. In the second step, tetrabutyl titanate acts as a catalyst for the polycondensation reaction, activating the esterification reaction of hydroxyl and carboxyl groups at a high temperature of 230-260℃. The titanium-oxygen bond of tetrabutyl titanate coordinates with the oxygen atom of the hydroxyl group, lowering the activation energy of the esterification reaction and promoting the dehydration of carboxyl and hydroxyl groups to form ester bonds (-COO-). Simultaneously, the system pressure is gradually reduced to below 50 Pa, and water molecules generated in the reaction are removed through a vacuum environment, driving the polycondensation reaction towards higher molecular weight. The molecular chains continuously grow and intertwine, forming a polyester matrix with a three-dimensional network structure. Talc acts as a nucleating agent, dispersing in the melt to form microcrystalline nuclei, promoting the orderly arrangement and crystallization of polyester molecular chains, and improving the crystallinity and thermal stability of the material. Finally, the reaction product is dried at 100-104℃ and a vacuum of 10 Pa to remove residual trace moisture and low molecular weight byproducts, yielding a heat-resistant biodegradable polyester material with uniform molecular weight distribution and regular structure. This material forms a main chain through esterification and polycondensation of basic raw materials. The bicyclic structure of the modified monomer inhibits intramolecular rotation (increasing the glass transition temperature), and the polar groups of the imidazole ring enhance intermolecular hydrogen bonding (increasing the melting point). At the same time, a large number of hydrolyzable ester bonds are retained (ensuring biodegradability), ultimately achieving a synergistic improvement in heat resistance and biodegradability.

[0048] According to a preferred embodiment of the present invention, in step S1, nitrogen is introduced to replace air 3-4 times; the stirring time is 30-40 minutes.

[0049] According to a preferred embodiment of the present invention, in step S2, the reaction time is 5-8 hours.

[0050] According to a preferred embodiment of the present invention, in step S3, the drying time is 2-4 hours.

[0051] The beneficial effects of this invention are as follows:

[0052] This invention demonstrates significant advantages in terms of heat resistance, bio-based origin, and biodegradability through the synergistic design and copolymerization of two novel bio-based modified monomers.

[0053] Regarding improved heat resistance, traditional bio-based polyesters suffer from softening at relatively low temperatures due to the high proportion of flexible aliphatic segments in the main chain, resulting in low rotational resistance and active chain segment movement. This invention introduces a bio-based diol with a rigid bicyclic structure. Its stable bicyclic skeleton effectively restricts the internal rotational freedom of the molecular chain, significantly increasing the resistance to chain segment movement and thus substantially raising the glass transition temperature. Simultaneously, the bio-based dicarboxylic acid containing a polar imidazole ring forms strong hydrogen bonds with adjacent molecular chains through polar groups, enhancing intermolecular bonding and further improving the melting point and thermal stability. The synergistic effect of these two modified monomers enables the material to maintain good shape stability even at high temperatures, effectively solving the problem of insufficient heat resistance in traditional bio-based polyesters. This makes it suitable for applications requiring high-temperature performance, such as hot beverage packaging and summer daily necessities.

[0054] Regarding the sustainability of bio-based sources, all key raw materials in this invention are derived from biomass resources, ensuring the high bio-based properties of the materials. Specifically, the bicyclic diol is prepared from bio-based vanillin and bio-based epichlorohydrin through a multi-step green chemical reaction; the polar imidazole cyclic dicarboxylic acid is prepared from bio-based itaconic acid and bio-based ethylenediamine as core raw materials through hydrogenation, condensation, and oxidation processes. The main chain base raw materials, 1,4-butanediol and adipic acid, are also derived from renewable biomass, ensuring strong traceability of the entire raw material chain. The bio-based content is significantly higher than that of traditional petroleum-based modified polyesters, providing a feasible path to reduce the plastics industry's dependence on petroleum resources.

[0055] Regarding biodegradability, this invention retains the core advantage of bio-based polyesters: complete biodegradability. The main chain of the material retains a large number of hydrolyzable ester bonds, which is the key structural basis for the biodegradability of polyester materials. Under composting conditions, esterases secreted by microorganisms can gradually break these ester bonds, causing the large molecules of the material to degrade into small oligomers, ultimately converting into water and carbon dioxide. No harmful substances are released during the entire degradation process. It is worth noting that the modified bicyclic structure and the imidazole ring are both oxygen-containing heterocycles. While chemically stable, they can be recognized and decomposed by enzymes secreted by microorganisms, without hindering the degradation process. Conversely, the moderate rigidity of the heterocyclic structure can adjust the molecular chain packing density, avoiding the problem of decreased degradation rate due to excessive crystallization. Detailed Implementation

[0056] The following detailed embodiments are only used to further illustrate this application and should not be construed as limiting the scope of protection of this application. Those skilled in the art can make some non-essential improvements and adjustments to this application based on the above application content.

[0057] Example 1

[0058] 100g of bio-based vanillin was dissolved in 500g of anhydrous ethanol by stirring. Then, 30g of formaldehyde solution was added, and the mixture was reacted in a 60°C water bath for 2 hours, stirring every 30 minutes to ensure homogeneous mixing. After the reaction, the intermediate solid was obtained by filtration. The intermediate was transferred to a reaction vessel, and 80g of bio-based epichlorohydrin and 10g of sodium hydroxide were added. The ring-opening reaction was continued at 80°C for 4 hours, with gentle stirring to promote contact between reactants. After the reaction, unreacted epoxy was removed by hot filtration. Chloropropane; Add 5g sodium borohydride and 200g methanol to the filtrate, stir and reduce at room temperature for 4 hours. During the reduction process, control the temperature not to exceed 30℃ to avoid side reactions. After the reduction is completed, slowly add dilute hydrochloric acid to adjust the pH of the system to 5. At this time, a large amount of crude product precipitates out. Filter and collect the crude product. Dissolve the crude product in an appropriate amount of methanol and then perform column chromatography purification. Use ethyl acetate and petroleum ether in a volume ratio of 1:3 as the mobile phase. Collect the target fraction and concentrate under reduced pressure to finally obtain bio-based bicyclic [2.2.2]oct-2-en-1,4-diol.

[0059] Next, 3-(1-imidazolyl)-5-methyladipic acid was prepared: 120g of bio-based itaconic acid was added to a three-necked flask containing 5g of palladium-on-carbon catalyst (5% by mass) and 600g of ethanol. A hydrogen inlet device was installed and the airtightness was checked. Hydrogen gas was introduced until the system pressure reached 1MPa, and the reaction was carried out with stirring at 50°C for 3 hours. During the reaction, a reflux condenser was used to prevent ethanol evaporation. After the reaction was completed, the hydrogen gas was turned off, the palladium-on-carbon catalyst was removed by filtration, and the filtrate was distilled under reduced pressure to recover ethanol, yielding 110g of solid methylbutenedioic acid. The methylbutenedioic acid was transferred to a round-bottom flask, and 60g of bio-based itaconic acid was added. Ethylenediamine and 300g of toluene were refluxed and heated to 120°C for 5 hours. During the reaction, samples were taken periodically to monitor the progress. After the reaction was completed, the toluene solvent was removed by rotary evaporation to obtain a viscous intermediate. 20g of potassium permanganate and 10% sulfuric acid aqueous solution (sulfuric acid to water volume ratio 1:9) were added to the intermediate. The mixture was heated to 80°C and stirred for 3 hours to oxidize. During the oxidation process, the pH of the system was maintained by adding sodium hydroxide solution dropwise. After the reaction was completed, the manganese dioxide precipitate was removed by filtration. The filtrate was repeatedly washed with deionized water until neutral and dried to obtain 3-(1-imidazolyl)-5-methylhexanoic acid.

[0060] Finally, heat-resistant bio-based biodegradable polyester material was prepared by mixing 120g of 1,4-butanediol, 100g of adipic acid, 15g of the bio-based bicyclo[2.2.2]oct-2-en-1,4-diol prepared above, and 10g of... 3-(1-Imidazolyl)-5-methyladipic acid was sequentially added to a reactor equipped with a stirrer, thermometer, and water separator. Nitrogen gas was introduced to purge the air from the reactor three times (each purging lasted 10 minutes at a pressure of 0.1 MPa). After purging, the nitrogen valve was closed, and the stirrer was turned on and stirred at 200 rpm. The mixture was continuously melted and mixed at 120°C for 30 minutes to ensure that the raw materials were fully and uniformly dispersed. 0.3 g of tetrabutyl titanate and 1 g of talc were added to the reactor, and stirring was continued for 10 minutes to ensure that the catalyst and nucleating agent were evenly dispersed. The temperature was then gradually increased to 240°C, while the vacuum pump was turned on to slowly reduce the system pressure to below 30 Pa. This condition was maintained for 6 hours. During the reaction, the water generated was collected through the water separator and removed promptly. After the reaction, the product was transferred to a vacuum drying oven and dried at 100°C and a vacuum of 10 Pa for 2 hours to remove residual moisture and low molecular weight byproducts, finally yielding a heat-resistant biodegradable polyester material.

[0061] Example 2

[0062] The specific implementation method is the same as in Example 1, except that the preparation of bio-based bicyclic [2.2.2]oct-2-en-1,4-diol (BDOX) is as follows: 100g of bio-based vanillin is dissolved in 500g of anhydrous ethanol, 30g of formaldehyde solution is added, and the reaction is carried out at 60°C for 3 hours. The intermediate is obtained by filtration and separation. 80g of bio-based epichlorohydrin and 10g of sodium hydroxide are added to the intermediate, and the ring-opening reaction is carried out at 80°C for 5 hours. 5g of sodium borohydride and 200g of methanol are added, and the reaction is carried out at room temperature for 5 hours. The mixture is then acidified with dilute hydrochloric acid to pH=5, and the crude product is precipitated. The crude product is purified by column chromatography to obtain bio-based bicyclic [2.2.2]oct-2-en-1,4-diol. Preparation of 3-(1-Imidazolyl)-5-methylhexanoic acid (IMDA): 120 g of bio-based itaconic acid was added to a mixture of 5 g of palladium on carbon catalyst (5% by mass) and 600 g of ethanol. The mixture was hydrogenated at 50 °C and 1.2 MPa for 4 hours. The catalyst was removed by filtration, and 110 g of methylbutenedioic acid was obtained by vacuum distillation. 110 g of methylbutenedioic acid was then reacted with 60 g of bio-based ethylenediamine in 300 g of toluene under reflux at 120 °C for 6 hours. The solvent was removed by rotary evaporation. 20 g of potassium permanganate and 10% sulfuric acid aqueous solution were added, and the mixture was oxidized at 80 °C for 4 hours. The mixture was then filtered and washed with water until neutral to obtain 3-(1-Imidazolyl)-5-methylhexanoic acid. Preparation of heat-resistant bio-based biodegradable polyester material: 140g of 1,4-butanediol, 80g of adipic acid, 20g of bio-based bicyclo[2.2.2]oct-2-en-1,4-diol, and 5g of 3-(1-imidazolyl)-5-methyl adipic acid were added to a reaction vessel, and nitrogen gas was introduced to replace the air 4 times. The mixture was stirred at 120℃ for 40 minutes to melt mix. 0.5g of tetrabutyl titanate and 2g of talc were added, and the temperature was raised to 250℃. The system pressure was gradually reduced to below 20Pa and the reaction was carried out for 8 hours. The product was dried at 100℃ and a vacuum of 10Pa for 4 hours to obtain the heat-resistant bio-based biodegradable polyester material.

[0063] Example 3

[0064] The specific implementation method is the same as in Example 1, except that the preparation of bio-based bicyclic [2.2.2]oct-2-en-1,4-diol (BDOX) is as follows: 100g of bio-based vanillin is dissolved in 500g of anhydrous ethanol, 30g of formaldehyde solution is added, and the reaction is carried out at 60°C for 2.5 hours. The intermediate is obtained by filtration and separation. 80g of bio-based epichlorohydrin and 10g of sodium hydroxide are added to the intermediate, and the ring-opening reaction is carried out at 80°C for 4.5 hours. 5g of sodium borohydride and 200g of methanol are added, and the reaction is carried out at room temperature for 4.5 hours. The mixture is then acidified with dilute hydrochloric acid to pH=5, and the crude product is precipitated. The crude product is purified by column chromatography to obtain bio-based bicyclic [2.2.2]oct-2-en-1,4-diol. Preparation of 3-(1-Imidazolyl)-5-methylhexanoic acid (IMDA): 120 g of bio-based itaconic acid was added to a mixture of 5 g of palladium on carbon catalyst (5% by mass) and 600 g of ethanol. The mixture was hydrogenated at 50 °C and 1.1 MPa for 3.5 hours. The catalyst was removed by filtration, and 110 g of methylbutenedioic acid was obtained by vacuum distillation. 110 g of methylbutenedioic acid was then reacted with 60 g of bio-based ethylenediamine in 300 g of toluene under reflux at 120 °C for 5.5 hours. The solvent was removed by rotary evaporation. 20 g of potassium permanganate and 10% sulfuric acid aqueous solution were added, and the mixture was oxidized at 80 °C for 3.5 hours. The mixture was then filtered and washed with water until neutral to obtain 3-(1-Imidazolyl)-5-methylhexanoic acid. Preparation of heat-resistant bio-based biodegradable polyester material: 130g of 1,4-butanediol, 90g of adipic acid, 18g of bio-based bicyclo[2.2.2]oct-2-en-1,4-diol, and 8g of 3-(1-imidazolyl)-5-methyl adipic acid were added to a reaction vessel, and nitrogen gas was introduced to replace the air three times. The mixture was stirred at 120℃ for 35 minutes to achieve melt mixing. 0.4g of tetrabutyl titanate and 1.5g of talc were added, and the temperature was raised to 245℃. The system pressure was gradually reduced to below 25Pa and the reaction was carried out for 7 hours. The product was dried at 100℃ and a vacuum of 10Pa for 3 hours to obtain the heat-resistant bio-based biodegradable polyester material.

[0065] Comparative Example 1

[0066] The specific implementation method is the same as in Example 1, except that the heat-resistant biodegradable polyester material (pure PBS) is prepared as follows: 140g of 1,4-butanediol and 100g of adipic acid are added to the reaction vessel, nitrogen is introduced to replace the air three times, and the mixture is stirred at 120°C for 30 minutes to melt and mix; 0.3g of tetrabutyl titanate and 1g of talc are added, the temperature is raised to 240°C, and the system pressure is gradually reduced to below 30Pa to react for 6 hours; the product is dried at 100°C and a vacuum of 10Pa for 2 hours to obtain the polyester material.

[0067] Comparative Example 2

[0068] The specific implementation method is the same as in Example 1, except that only the polyester material containing bio-based bicyclic [2.2.2]oct-2-ene-1,4-diol is prepared: 120g of 1,4-butanediol, 100g of adipic acid, and 15g of bio-based bicyclic [2.2.2]oct-2-ene-1,4-diol are added to a reaction vessel, nitrogen is introduced to replace the air three times, and the mixture is stirred at 120°C for 30 minutes to melt mix; 0.3g of tetrabutyl titanate and 1g of talc are added, the temperature is raised to 240°C, and the system pressure is gradually reduced to below 30Pa to react for 6 hours; the product is dried at 100°C and a vacuum of 10Pa for 2 hours to obtain the polyester material.

[0069] Comparative Example 3

[0070] The specific implementation method is the same as in Example 1, except that the polyester material containing only 3-(1-imidazolyl)-5-methyl adipic acid is prepared as follows: 120g of 1,4-butanediol, 100g of adipic acid, and 10g of 3-(1-imidazolyl)-5-methyl adipic acid are added to a reaction vessel, and nitrogen is introduced to replace the air three times. The mixture is stirred at 120°C for 30 minutes to melt mix. 0.3g of tetrabutyl titanate and 1g of talc are added, the temperature is raised to 240°C, and the system pressure is gradually reduced to below 30Pa to react for 6 hours. The product is dried at 100°C and a vacuum of 10Pa for 2 hours to obtain the polyester material.

[0071] Performance testing

[0072] The heat-resistant bio-based biodegradable polyester materials prepared in Examples 1-3 and Comparative Examples 1-3 were subjected to performance tests according to the following methods:

[0073] 1. The heat resistance test adopts differential scanning calorimetry (DSC): 5-10 mg of the sample to be tested is placed in an aluminum crucible, sealed and placed in the sample chamber of the DSC instrument. Under a nitrogen atmosphere (flow rate 50 mL / min), the temperature is increased from 25℃ to 200℃ at a heating rate of 10℃ / min. The instrument automatically records the heat flow curve. The glass transition temperature (Tg, midpoint temperature) is determined by analyzing the baseline shift of the curve, and the melting point (Tm) corresponding to the endothermic peak is identified.

[0074] 2. Mechanical property testing was performed using a universal testing machine: The sample was cut into dumbbell-shaped specimens (gauge length 25 mm, thickness 2 mm, width 4 mm) and placed in an environment of 25℃ and 50% relative humidity for 24 hours to achieve condition conditioning; during testing, an axial tensile force was applied to the specimen at a tensile rate of 50 mm / min until the specimen broke. The instrument automatically recorded the maximum tensile force (used to calculate tensile strength, unit MPa) and the gauge length change rate at break (used to calculate elongation at break, unit %).

[0075] 3. Biodegradability test adopts composting degradation method: The sample is cut into 2mm×2mm particles and mixed with compost substrate (made of straw, sawdust and animal manure in a mass ratio of 3:3:4, with moisture content adjusted to 60% and initial pH=7.0) in a mass ratio of 1:10. The mixture is placed in a 58℃ constant temperature composting box and turned over every 7 days to ensure uniform fermentation. The test period is 180 days. The remaining sample mass is weighed every 7 days and the degradation rate is calculated (degradation rate = (initial mass - remaining mass) / initial mass × 100%).

[0076] 4. Thermal stability testing is conducted using thermogravimetric analysis (TGA): 10-15 mg of the sample to be tested is placed in a ceramic crucible and then placed in the sample chamber of the TGA instrument. Under a nitrogen atmosphere (flow rate 100 mL / min), the temperature is increased from 25 °C to 600 °C at a heating rate of 20 °C / min. The instrument automatically records the mass change curve with temperature. The initial descent phase of the curve is used to determine the 5% mass loss temperature (T5%, i.e., the temperature at which the sample mass decreases by 5%), and the temperature corresponding to the maximum weight loss rate (Tmax, i.e., the temperature at which the slope of the curve is the largest) is identified.

[0077] 5. Performance test results:

[0078] Table 1: Performance test results of each embodiment and comparative example

[0079]

[0080] As can be seen from Table 1, the performance comparison results between Examples 1-3 and Comparative Examples 1-3 show that by introducing two modified monomers, bio-based bicyclic [2.2.2]oct-2-ene-1,4-diol (BDOX) and 3-(1-imidazolyl)-5-methyl adipic acid (IMDA), the problem of insufficient heat resistance caused by excessive flexible segments in the main chain of existing bio-based polyester materials is effectively solved.

[0081] From the perspective of core heat resistance indicators, Comparative Example 1 (pure PBS) has a glass transition temperature (Tg) of only 45℃ and a melting point (Tm) of 110℃. The proportion of flexible aliphatic segments (butanediol, adipic acid) in the main chain is too high, resulting in low rotational resistance within the molecular chain and active chain segment movement, causing the material to soften at relatively low temperatures. Examples 1-3 show Tg increases to 88-92℃ and Tm increases to 152-158℃, significantly higher than Comparative Example 1. This improvement stems from the inhibitory effect of the rigid bicyclic [2.2.2]octane structure of BDOX on rotation within the molecular chain (increasing resistance to chain segment movement), and the enhancing effect of the polar imidazole ring of IMDA on intermolecular hydrogen bonds (increasing intermolecular binding force). The synergistic effect of these two factors effectively inhibits the movement of flexible segments in the main chain, thereby significantly improving heat resistance.

[0082] Regarding thermal stability, Comparative Example 1 showed a 5% mass loss temperature (T5%) of 280℃ and a maximum weight loss rate temperature (Tmax) of 340℃, indicating its easy decomposition at high temperatures. Examples 1-3 showed T5% increased to 320-325℃ and Tmax increased to 380-385℃, demonstrating a significant enhancement in the stability of the modified polyester main chain. This is because the bicyclic structure of BDOX reduces the flexibility of the main chain, decreasing chain segment movement at high temperatures; the imidazole ring structure of IMDA exhibits strong thermal stability, inhibiting main chain breakage at high temperatures. The combined effect of these two factors improves the material's thermal stability.

[0083] In terms of mechanical properties, the tensile strength of Comparative Example 1 was only 40 MPa, and the elongation at break was 65%, while the tensile strength of Examples 1-3 increased to 58-60 MPa, and the elongation at break increased to 82-85%. This improvement stems from the synergistic effect of the modified monomers: the bicyclic structure of BDOX enhances the rigidity of the molecular chain, and the imidazole ring of IMDA enhances the intermolecular bonding force through hydrogen bonding, enabling the material to achieve higher mechanical strength while maintaining high flexibility, thus avoiding the brittleness problem caused by excessive rigidity in traditional modification methods.

[0084] Regarding biodegradability, the 180-day compost degradation rate of Comparative Example 1 was 85%, while the degradation rates of Examples 1-3 increased to 93-94%. This is because the hydrolyzable ester bonds of the polyester backbone (derived from basic raw materials such as diacid and butanediol) were retained during the modification process. Furthermore, both the bicyclic structure of BDOX and the imidazole ring of IMDA are oxygen-containing heterocycles, which can be gradually recognized and decomposed by esterases secreted by microorganisms, without hindering the degradation process. In contrast, the degradation rates of Comparative Example 2 (containing only BDOX) and Comparative Example 3 (containing only IMDA) were 88% and 86%, respectively, showing limited improvement. This indicates that the effect of a single modified monomer is relatively weak, while the synergistic effect of two modified monomers is more conducive to maintaining degradability.

[0085] In summary, Examples 1-3 effectively solve the problem of insufficient heat resistance caused by excessive flexible segments in the main chain of existing bio-based polyesters through the synergistic effect of the rigid bicyclic structure of BDOX and the polar imidazole ring of IMDA, while maintaining good mechanical properties and biodegradability, providing a feasible solution for the application of high-performance bio-based polyester materials.

[0086] The embodiments described above are merely examples of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. A heat resistant bio-based degradable polyester material, characterized in that, The raw materials include the following weight parts: 1,4-butanediol: 100-150 parts by weight; adipic acid: 80-120 parts by weight; biobased bicyclo[2.2.2]oct-2-ene-1,4-diol: 10-20 parts by weight; 3-(1-imidazolyl)-5-methyl adipic acid: 5-15 parts by weight; tetrabutyl titanate: 0.1-0.5 parts by weight; talc: 0.5-2 parts by weight; The preparation method of the biobased bicyclo[2.2.2]oct-2-ene-1,4-diol includes: A1, dissolving biobased vanillin in anhydrous ethanol, adding formaldehyde solution, and reacting at 60-64 DEG C; filtering and separating the intermediate, adding biobased epichlorohydrin and sodium hydroxide, and ring-opening reaction at 80-84 DEG C; A2, adding sodium borohydride and methanol, reducing at room temperature, and then acidifying with dilute hydrochloric acid to pH = 4.8-5.2 to precipitate the crude product; the crude product is purified by column chromatography.

2. The heat-resistant bio-based degradable polyester material according to claim 1, characterized in that, In step A1, the reaction time at 60-64 DEG C is 2-4 h; the ring-opening reaction time at 80-84 DEG C is 4-6 h.

3. The heat-resistant, bio-based, degradable polyester material according to claim 1, characterized in that, In step A2, the reduction time at room temperature is 4-6 h.

4. The heat-resistant, bio-based, degradable polyester material of claim 1, wherein, The preparation method of the 3-(1-imidazolyl)-5-methyl adipic acid includes: B1, adding biobased itaconic acid to a mixed system of palladium-carbon catalyst and ethanol, hydrogenation reaction at 50-52 DEG C under hydrogen pressure of 1-1.2 MPa; filtering, and distilling under reduced pressure to obtain methyl butenedioic acid; B2, refluxing methyl butenedioic acid with biobased ethylenediamine in toluene at 120-125 DEG C, rotary evaporation; adding potassium permanganate and aqueous sulfuric acid solution, oxidizing at 80-84 DEG C, filtering, and washing with water until neutral.

5. The heat-resistant bio-based degradable polyester material according to claim 4, characterized in that, In step B1, the hydrogenation reaction time is 3-4 h.

6. The heat-resistant, bio-based, degradable polyester material according to claim 4, characterized in that, In step B2, the reflux reaction time at 120-125 DEG C is 5-6 h; the oxidation time at 80-84 DEG C is 3-4 h.

7. A process for the preparation of a heat resistant bio-based degradable polyester material according to any one of claims 1-6, characterized by the steps It includes: S1, adding 1,4-butanediol, adipic acid, biobased bicyclo[2.2.2]oct-2-ene-1,4-diol, and 3-(1-imidazolyl)-5-methyl adipic acid into a reaction kettle, replacing air with nitrogen, stirring at 118-122 DEG C, and melting and mixing; S2, adding tetrabutyl titanate and talc, heating to 230-260 DEG C, and gradually reducing the system pressure to below 50 Pa for reaction; S3, drying the product at 100-104 DEG C under a vacuum degree of 10 Pa.

8. The preparation method according to claim 7, characterized in that, In step S1, the number of times of replacing air with nitrogen is 3-4 times; the stirring time is 30-40 min.

9. The preparation method according to claim 7, characterized in that, In step S2, the reaction time is 5-8 h.

10. The preparation method according to claim 7, characterized in that, In step S3, the drying time is 2-4 h.

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