Preparation method and application of sulfur-containing high-molecular-weight polyester PES capable of being naturally degraded
By using 2,5-thiophene dicarboxylic acid and 4,4'-dithiobisbenzoic acid and dihydroxy compounds as raw materials, high molecular weight polyesters were synthesized by melt polymerization, which solved the problems of low molecular weight and poor natural degradation performance of existing polyesters, and realized the preparation of high-strength membrane materials and rapid environmental degradation.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- WUHAN UNIV OF SCI & TECH
- Filing Date
- 2024-11-04
- Publication Date
- 2026-05-08
AI Technical Summary
Existing polyesters have low molecular weight, low melting point, poor mechanical and processing properties, require large amounts of catalysts with low efficiency, resulting in dark-colored polymer products with poor light transmittance, making them difficult to process into food-grade packaging bags and high-strength ultra-thin films. Furthermore, they have poor natural degradation properties, causing environmental pollution.
High molecular weight polyesters were synthesized by melt polymerization using 2,5-thiophene dicarboxylic acid, 4,4'-dithiobisbenzoic acid, and dihydroxy compounds as raw materials. Using catalysts such as tri(ethylenediamine)ruthenium chloride, biodegradable high molecular weight polyesters with CS bonds were prepared.
It improves the molecular weight, melting point, and thermal stability of polyester, enhances its mechanical and tensile properties, and can be processed into polyester film materials with a thickness of 13μm to 23μm, which are rapidly degraded by microorganisms in soil.
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Abstract
Description
Technical fields:
[0001] This invention belongs to the field of synthetic technology of biodegradable polymer materials, specifically relating to a method for preparing sulfur-containing biodegradable high molecular weight polyesters. Using two sulfur-containing organic diacids and a dihydroxy compound as raw materials, a series of novel biodegradable high molecular weight polyesters are synthesized by melt polymerization. These polyesters are used in the preparation of packaging film materials for food packaging, express delivery packaging, and fast-moving consumer goods packaging, meeting the requirements for high plasticity and degradation capability. Background technology:
[0002] With the development of the plastics industry, synthetic polymer materials play an extremely important role in various fields of industrial and agricultural production and daily life. Meanwhile, environmentally friendly and sustainable materials have always been important goals of academic and industrial research. Researching next-generation sustainable materials as competitive alternatives to petroleum-based plastics has always been a challenge, and for these new materials to match the performance and cost-effectiveness of commonly used petroleum plastics, the key is to achieve this. Due to the accumulation of plastic waste in recent decades, it has had adverse effects on the surrounding environment and human health. Unlike small-molecule organic waste, plastics can take decades to hundreds of years to degrade in nature. If no action is taken, by 2050, there will be more plastic than fish in the ocean.
[0003] Petroleum-based polyesters are a general term for polymers obtained by the condensation polymerization of polyols and polyacids derived from petroleum. They primarily refer to polyethylene terephthalate (PET), but also conventionally include linear thermoplastic resins such as polybutylene terephthalate (PBT) and polyarylates. They possess excellent physical properties and chemical stability, making them a class of high-performance, widely used engineering plastics. They can also be made into fibers and films. Currently, global demand for petroleum-based polyesters continues to grow. [1] Its main application areas include films, fibers, communications, construction, and packaging materials. The polyester industry currently faces several challenges and difficulties that need to be addressed. Firstly, there is the issue of resource supply, as petroleum, as the primary source material, is not a renewable resource. The large-scale use of polyester products inevitably exacerbates global energy shortages and resource depletion. Secondly, there is the issue of environmental impact; polyester waste is difficult to degrade, leading to long-term environmental pollution. [2-4] With rising living standards and advancements in production technology, people are placing increasingly stringent requirements on the main performance characteristics of polyester. Against the backdrop of growing environmental awareness, biodegradable polyesters have gradually gained attention and are being widely applied. [5，6] . [1] Cui Y, Deng C, Fan L, et al. Progress in the biosynthesis of bio-based PET and PEF polyester monomers[J]. Green Chemistry, 2023, 25: 5836 - 5837 [2] Jambeck J R, Geyer R, Wilcox C, et al. Plastic waste inputs from land into the ocean[J]. Science, 2015, 347(6223): 768 - 771. [3] Pellis A, Malinconico M, Guarneri A, et al. Renewable polymers and plastics: Performance beyond the green[J]. New Biotechnology, 2021, 60: 146 - 158. [4] Ma Y, Ji Y, Zhang J, et al. Research advances in vegetable - oil - based pressure - sensitive adhesives[J]. Green Materials. 2023(11): 147 - 161. [5] Sharma V, Sehgal R, Gupta R. Polyhydroxyalkanoate(PHA): properties and modifications[J]. Polymer, 2021, 212: 123161 - 123191. [6] Zhang Q, Song M, Xu Y, et al. Bio - based polyesters: Recent progress and future prospects[J]. Progress in Polymer Science, 2021, 120: 101 - 430. Summary of the invention:
[0004] Existing polyesters suffer from low molecular weight, low melting point, poor mechanical properties, and poor processing performance. Furthermore, the high catalyst dosage and low catalytic polymerization efficiency of the polymerization system result in dark-colored polymers with poor light transmittance. The resulting polyesters typically have molecular weights of only 0.5 to 20,000, and their mechanical properties, particularly tensile strength and ductility, are low, leading to poor tensile or film-forming properties. This makes them unsuitable for processing into food-grade packaging bags or for producing high-strength, ultra-thin polyester films, thus limiting their effective application in film production. In addition, existing polyesters generally have poor biodegradability, causing environmental impact when discarded into the natural environment. To address these problems, the main objective of this invention is to provide a method for preparing high molecular weight biodegradable polyesters and their applications. Specifically, this method uses 2,5-thiophene dicarboxylic acid (TDCA), 4,4'-dithiobisbenzoic acid (DDBA), and dihydroxy compounds as raw materials, employing a melt polymerization method to obtain a series of biodegradable high molecular weight polyesters. Compared with polyesters reported in existing literature, this high molecular weight polyester has an ultra-high molecular weight, a high melting point, good thermal stability, strong mechanical properties, high viscosity, and good tensile and film-forming properties.
[0005] To achieve the above objectives and solve the problems described in the background section, the following technical solution is proposed:
[0006] 1. A method for preparing sulfur-containing biodegradable high molecular weight polyester (PES), characterized in that the synthesized sulfur-containing biodegradable high molecular weight polyester (PES) has the following molecular structure: PES1: PES2: Where m and r are positive integers between 20 and 30, and n and s are positive integers between 30 and 50.
[0007] 2. A method for preparing sulfur-containing biodegradable high molecular weight polyester PES, comprising the following two main steps: 1) Using 2,5-thiophene dicarboxylic acid (CAS 1155-51-7), 4,4'-dithiobisbenzoic acid, and a dihydroxy compound as raw materials, under nitrogen protection, the three raw materials were stirred and reacted at 160-185℃ for 4.0-5.0h under normal pressure and with the action of a catalyst to complete the esterification reaction. Then, the temperature was raised to 200-220℃ and the reaction was continued for 2.0-3.5h under a pressure of 5-15KPa to obtain crude polyester. 2) After cooling the crude polyester, add a certain amount of chloroform, shake to promote dissolution, filter, and add low-carbon alcohols such as ethanol or propanol to the filtrate until the precipitate no longer increases. Wash the filter residue with cold ethanol to further remove impurities, and then vacuum dry at 40-60℃ for 1.0-2.0h to obtain the desired sulfur-containing biodegradable high molecular weight polyester PES.
[0008] 3. The method for preparing sulfur-containing biodegradable high molecular weight polyester PES described above is characterized in that, in step 1) of claim 2, the dihydroxy compound is one of the following diols: diol a, with the structural formula [insert structural formula here]. Diol b, with the structural formula as follows
[0009] 4. The method for preparing sulfur-containing biodegradable high molecular weight polyester PES described above is characterized in that the molar ratio of 2,5-thiophene dicarboxylic acid, 4,4'-dithiobisbenzoic acid and dihydroxy compound is 1:1:1.5 to 1:1:1.2.5.
[0010] 5. The method for preparing sulfur-containing biodegradable high molecular weight polyester PES as described above, characterized in that the catalyst in claim 2 is one of tri(ethylenediamine)ruthenium chloride or 1,2-diphenylethylenediamineruthenium; the amount of the catalyst is 0.01%-0.09% of the total amount of reactants.
[0011] 6. The purpose of the sulfur-containing biodegradable high molecular weight polyester PES prepared by the above preparation method is to be used as a raw material for functional films. The characteristic is that the following components are thoroughly mixed in a mass ratio of 100:(3-4) for the sulfur-containing biodegradable high molecular weight polyester PES to the toughening agent. After mixing, the polyester film material with a film thickness of 13μm-23μm is obtained through extrusion blow molding, extrusion casting, and extrusion stretching. Compared with existing polyesters, it has good mechanical properties and is used in various packaging and covering applications requiring high elasticity, such as food packaging, functional greenhouse films, express delivery packaging, and fast-moving consumer goods packaging. The toughening agent is one of polyvinyl acetate, polyvinyl alcohol, and polyvinyl butyral.
[0012] 7. The polyester prepared by the sulfur-containing biodegradable high molecular weight polyester PES as described above is characterized by the following: the biodegradability of the prepared polyester material reaches more than 8% when the detection period is 6 months, which has good degradation performance compared with existing synthetic polyesters.
[0013] The polymer prepared in this patent possesses excellent physical and mechanical properties and is easily processed into materials with the required film thickness. Existing polyesters are generally only used for polyester fibers or polyester bottles, and their mechanical properties do not meet the requirements for preparing polyester film materials with a thickness of 13μm to 23μm. Compared with other film-forming polymers such as PE, PP, and PVC, the polyester film material made from sulfur-containing biodegradable high molecular weight polyester prepared in this patent exhibits superior degradation performance. Beneficial effects
[0014] 1. Currently developed polyester products mainly include polyethylene terephthalate (PET), polylactic acid (PLA), polycaprolactone (PCL), polybutylene succinate (PBS), polyhydroxyalkanoates (PHA), polypropylene carbonate, polyvinyl alcohol, and polyethylene carbonate (PEC). These materials often have shortcomings that limit their widespread adoption. Using bio-based renewable 2,5-thiophene dicarboxylic acid and 4,4'-dithiobisbenzoic acid (CAS 1155-51-7) as diacid sources, and ruthenium tri(ethylenediamine)chloride and ruthenium 1,2-diphenylethylenediamine as catalysts, a partially biomass-derived ultra-high molecular weight polyester was prepared through a well-matched reaction with selected dihydroxy compounds. This effectively solves the problems of poor thermal and mechanical properties, difficulty in natural degradation, and inability to meet the current market's dual requirements for polyester products to possess both good mechanical properties and degradability.
[0015] 2. By introducing 2,5-thiophene dicarboxylic acid and 4,4'-dithiobisbenzoic acid (CAS 1155-51-7) as diacid monomers in polyester synthesis, the CS bonds in the polyester molecular chain are increased, thereby effectively improving the natural degradation performance of current aromatic polyesters. At the same time, the natural environment contains relatively abundant bacteria such as thiobacilli and other microbial environments, which can partially engulf and digest the sulfur-containing polyesters abandoned in the natural soil environment. The natural degradation rate is much faster than that of existing plastics.
[0016] 3. Comparison of the data in Table 1 (see specific implementation methods and examples) shows that the tensile strength of polyethylene terephthalate (PET) is 115 MPa, while the tensile strength of polyesters PES1 and PES2 synthesized in this invention using 2,5-thiophene dicarboxylic acid, 4,4'-dithiobisbenzoic acid, and dihydroxy compounds as raw materials is 6-49.4 MPa higher than that of PET; the elongation at break of PET is 145, while the elongation at break of polyesters PES1 and PES2 synthesized in this invention is 15.1-33.9% higher than that of PET; the number-average molecular weight reduction of sulfur-containing polyesters PES1 and PES2 abandoned in the natural soil environment after one year reaches 33,800-38,000 g / mol; the biodegradation rate of the obtained polyester reaches more than 8% after a detection period of 6 months, which shows good degradation performance compared with existing synthetic polyesters. The thermal decomposition temperature of PET is 420℃. The thermal decomposition temperatures of PES1 and PES2 synthesized in this invention using 2,5-thiophene dicarboxylic acid, 4,4'-dithiobisbenzoic acid and dihydroxy compounds are 19-63℃ higher than that of PET.
[0017] The above facts and data demonstrate that, using 2,5-thiophene dicarboxylic acid, 4,4'-dithiobisbenzoic acid, and dihydroxy compounds as raw materials, and one of tri(ethylenediamine)ruthenium chloride, 1,2-diphenylethylenediamineruthenium, tantalum pentachloride, dodecacarbonyltriruthenium, or tetracarbonyldirhodium chloride as a catalyst, and through a well-matched reaction with the selected diacid and diol monomers, a partially biomass-derived ultra-high molecular weight polyester was prepared. The polyester prepared by this invention exhibits significantly improved molecular weight, thermal properties, and mechanical properties compared to existing polyesters. Moreover, and remarkably, the sulfur-containing polyester abandoned in the natural soil environment can be partially consumed and decomposed by bacteria and microorganisms in the soil, resulting in a significantly faster natural degradation rate compared to existing plastics. Detailed implementation method:
[0018] The present invention will be further illustrated by the following embodiments, but the present invention is not limited to the embodiments. All raw materials used in the present invention are commercially available. To determine the structure, molecular weight, and thermal properties of the polyesters prepared in this embodiment, the polyesters PES1-PES5 prepared in Examples 1-5 were characterized and tested using a Bruker Avance DMX600 nuclear magnetic resonance spectrometer (BRU), a BRUK VERTEX70 Fourier transform infrared spectrometer (BRU), a Waters-Breeze gel electrophoresis system (Water Systems, Inc.), and a Netzsch STA449 F3 Jupite thermogravimetric analyzer (Netzsch, Inc.). Yield = 100% × Actual amount of target product produced / Theoretical amount of target product produced. The biodegradability of polyester was determined according to the standard GB / T 19277.1-2011. The testing period for the biodegradability test was 6 months. Vermiculite method was selected for composting to test the biodegradability. Thin-layer chromatography grade cellulose was used as the reference material. A 180-day compost biodegradation experiment was conducted under the conditions of pH 7.0-9.0 and temperature 58±2℃.
[0019] Example 1: In a 150 mL Shlenk flask, 11.3 mmol of 2,5-thiophene dicarboxylic acid, 11.3 mmol of 4,4'-dithiobisbenzoic acid, 22.6 mmol of diol a, and 0.015 mmol of tris(ethylenediamine)ruthenium chloride were added sequentially. The reaction mixture consisting of the three raw materials and the ruthenium catalyst was reacted at 165 °C for 4.0 h under nitrogen protection. Then, the temperature was increased to 210 °C and the reaction was carried out at a pressure of 15 kPa for 3.0 h to obtain a crude polymer product. After cooling the crude polymer product, a certain amount of chloroform was added, and the mixture was shaken to promote dissolution. After centrifugation and precipitation, the product was filtered, and isopropanol was added to the filtrate until the precipitation no longer increased. The product was centrifuged and filtered again, and the filter residue was washed with cold ethanol and then dried under vacuum at 60 °C for 3.0 h to obtain sulfur-containing polyester PES1 with a number average molecular weight of 85,500 Da, a molecular weight distribution (PDI) of 1.96, and a yield of 89.92%. To determine the structure, molecular weight, and thermal properties of the sulfur-containing polyester PES1 prepared in this embodiment, a Bruker Avance DMX600 nuclear magnetic resonance spectrometer, a Waters-Breeze gel electrophoresis analyzer, and a Netzsch STA449 F3 Jupiter thermogravimetric analyzer were used to characterize and test the sulfur-containing polyester PES1 prepared in Example 1. The structure of PES1 is shown in the following formula:
[0020] The sulfur-containing biodegradable high molecular weight polyester (PES) prepared by the above-described preparation method is used as a raw material for functional films. Its characteristics include: thorough mixing of the following components in a mass ratio of 100:3 (sulfur-containing biodegradable high molecular weight polyester PES : polyvinyl alcohol with a molecular weight of 100,000); after mixing, extrusion blow molding, extrusion casting, and extrusion stretching to obtain a polyester film material with a film thickness of 13 μm. Compared with existing polyesters, it has good mechanical properties and is used in various packaging and covering applications requiring high stretchability, such as food packaging, functional greenhouse films, express delivery packaging, and fast-moving consumer goods packaging; the polyvinyl alcohol with a molecular weight of 100,000 is used as a toughening agent.
[0021] The polyester PES1 film material prepared by the sulfur-containing biodegradable high molecular weight polyester PES preparation method described above, after being buried in natural soil environment after 1 year of use, showed that the number average molecular weight at the end of the second year was reduced by 33,800 compared with the previous year. A 180-day composting biodegradation experiment showed that its biodegradation rate was 8.3%, which has good degradation performance compared with existing polyesters.
[0022] Example 2: In a 150 mL Shlenk flask, 13.1 mmol of 2,5-thiophene dicarboxylic acid, 13.1 mmol of 4,4'-dithiobisbenzoic acid, 26.2 mmol of diol b, and 0.011 mmol of 1,2-diphenylethylenediamine ruthenium were added sequentially. The reaction mixture consisting of the three raw materials and the ruthenium catalyst was reacted at 160 °C for 3.5 h under nitrogen protection. Then, the temperature was increased to 215 °C and the reaction was carried out at a pressure of 13 kPa for 3.0 h to obtain a crude polymer product. After cooling the crude polymer product, a certain amount of chloroform was added, and the mixture was shaken to promote dissolution. After centrifugation and precipitation, the product was filtered, and propanol was added to the filtrate until the precipitation no longer increased. The product was centrifuged and filtered again, and the filter residue was washed with cold ethanol and then vacuum dried at 60 °C for 3.0 h to obtain sulfur-containing polyester PES2 with a number average molecular weight of 79,500 Da, a molecular weight distribution of 1.93, and a yield of 90.20%. The structure of PES2 is shown in the following formula:
[0023] The sulfur-containing biodegradable high molecular weight polyester PES2 prepared by the above-described preparation method is used as a raw material for functional films. Its characteristics include: thorough mixing of the following components in a mass ratio of 100:4 (sulfur-containing biodegradable high molecular weight polyester PES : polyvinyl acetate with a molecular weight of 220 million). After mixing, the film material with a thickness of 23 μm is obtained through extrusion blow molding, extrusion casting, and extrusion stretching. Compared with existing polyesters, it has good mechanical properties and is used in various packaging and covering applications requiring high elasticity, such as food packaging, functional greenhouse films, express delivery packaging, and fast-moving consumer goods packaging. The polyvinyl acetate with a molecular weight of 220 million is used as a toughening agent.
[0024] The polyester PES1 film material prepared by the sulfur-containing biodegradable high molecular weight polyester PES preparation method described above, when buried in natural soil environment after one year of use, showed a decrease in number-average molecular weight of 38,000 compared to the previous year, and a biodegradation rate of over 10%. Compared with existing polyesters, it has good degradation performance.
[0025] Table 1. Comparison of mechanical and degradation properties of polyester samples with PET in the examples.
[0026] Mechanical property tests in the example: tensile property test and elongation at break test were performed according to GB / T 1040.2—2006 standard; the results were taken as the average value of 5 test samples for each. M1 refers to the number average molecular weight of the synthesized polyester at the beginning of the first year, and M2 refers to the number average molecular weight of the synthesized polyester at the end of the second year after it was buried in the natural soil environment after 1 year of use.
[0027] As shown in Table 1, the tensile strength of commercially available polyester PET is 115 MPa, while the tensile strengths of the polyesters PES1 and PES2 synthesized in this invention, using 2,5-thiophene dicarboxylic acid, 4,4'-dithiobisbenzoic acid, and dihydroxy compounds as raw materials, are 164.5 MPa and 150.6 MPa, respectively, which are 35.6–49.5 MPa higher than the tensile strength of PET. The elongation at break of commercially available polyester PET is 145, while the elongation at break of the polyester synthesized in this invention, using 2,5-thiophene dicarboxylic acid, 4,4'-dithiobisbenzoic acid, and dihydroxy compounds as raw materials, is significantly higher. The polyesters PES1 and PES2 synthesized from 4'-dithiobisbenzoic acid and dihydroxy compounds have an elongation at break that is 16.3-33.9% higher than that of PET. The polyesters PES1 and PES2 prepared in this invention, when buried in natural soil environment after one year of use, show a molecular weight reduction of 33,800 to 38,000. The thermal decomposition temperature of PET is 420℃, while the thermal decomposition temperature of the synthesized polyesters PES1 and PES2 is 19-63℃ higher than that of PET. A one-to-one comparison of the data of the sulfur-containing polyesters PES1 and PES2 obtained by the method of this invention with those of commercial polyester PET shows that: the sulfur-containing polyester PES1 obtained by the method of this invention has a molecular weight of approximately 85,500 Da, a PDI of 1.96, a tensile strength of 164.5 MPa, and a decomposition temperature of 483°C. After one year of use, the sulfur-containing polyester was buried in a natural soil environment, and its molecular weight decreased to 51,700 Da; the sulfur-containing polyester PES2 obtained by the method of this invention has a molecular weight of approximately 79,500 Da, a PDI of 1.93, a tensile strength of 150.6 MPa, and a decomposition temperature of 461°C. After one year of use, the sulfur-containing polyester PES2 was buried in a natural soil environment, and its molecular weight decreased to 41,500 Da.
[0028] Commercially available polyester PET has a tensile strength of 115 MPa, a PDI of 1.65, a decomposition temperature of 420°C, and a molecular weight of approximately 50,000 Da. After one year of use, it was buried in natural soil. After another year, its molecular weight was 49,600 Da, showing almost no decrease. This indicates that commercially available polyester PET has very poor degradation performance.
[0029] As can be seen from the above data, the polyesters PES1 and PES2 synthesized by this invention using 2,5-thiophene dicarboxylic acid, 4,4'-dithiobisbenzoic acid and dihydroxy compounds as raw materials have significantly improved molecular weight, thermal properties, and mechanical properties compared with existing PET. This greatly improves the mechanical properties of polyester, enhances its thermal properties, and also significantly improves its degradation performance.
[0030] Existing literature reports that polyester synthesis requires relatively large amounts of catalysts, resulting in low catalytic efficiency, darker colors, and lower molecular weights. This leads to insufficient strength, poor mechanical and processing properties, making it difficult to meet the diverse performance requirements of practical applications. Addressing these issues in existing technologies, including the low molecular weight, poor mechanical and processing properties of current polyesters, the large catalyst dosage in the polymerization system, low catalytic polymerization efficiency leading to dark-colored polymers and poor light transmittance, and especially the fact that existing polyesters typically have molecular weights of only 0.5–20,000, their mechanical properties, particularly tensile strength and ductility, are low, resulting in poor tensile and film-forming properties. This makes them unsuitable for processing into food-grade packaging bags or producing high-strength, ultra-thin polyester films, thus limiting their effective application in film production. Furthermore, the generally poor biodegradability of existing polyesters leads to environmental impacts when discarded into the environment. To address the aforementioned problems, the main objective of this invention is to provide a method for preparing high molecular weight biodegradable polyesters and their applications. Using 2,5-thiophene dicarboxylic acid (TDCA), 4,4'-dithiobisbenzoic acid (DDBA), and dihydroxy compounds as raw materials, a series of biodegradable high molecular weight polyesters are prepared via melt polymerization. Compared with polyesters reported in existing literature, this sulfur-containing polyester exhibits extremely high molecular weight, good thermal stability, and excellent mechanical properties.
[0031] In summary, this invention uses 2,5-thiophene dicarboxylic acid, 4,4'-dithiobisbenzoic acid, and dihydroxy compounds as raw materials, and tri(ethylenediamine)ruthenium chloride and 1,2-diphenylethylenediamineruthenium as catalysts. Through a well-matched reaction with the selected diacid and diol monomers, a partially biomass-derived ultra-high molecular weight polyester is prepared. The sulfur-containing polyester prepared by this invention exhibits significantly improved molecular weight, thermal properties, and mechanical properties compared to existing polyester PET. Therefore, it can be processed into polyester film materials with excellent tensile and film-forming properties. Moreover, and remarkably, it is suitable for use in natural soil environments where biomass has been abandoned. Sulfur-containing polyester PES can be partially consumed and digested by bacteria and microorganisms in the soil. In particular, the introduction of 2,5-thiophene dicarboxylic acid and 4,4'-dithiobisbenzoic acid (CAS 1155-51-7) as diacid monomers in polyester synthesis increases the CS bonds in the polyester molecular chain, thereby effectively improving the natural degradation performance of current aromatic polyesters. At the same time, the natural environment contains abundant bacteria such as thiobacilli and other microorganisms, which can partially consume and digest sulfur-containing polyesters abandoned in the natural soil environment. The natural degradation rate is much faster than that of existing plastics.
[0032] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention. Clearly, those skilled in the art can make various alterations and modifications to the invention without departing from its spirit and scope. Thus, if these modifications and modifications of the invention fall within the scope of the claims and their equivalents, the invention is also intended to include these modifications and modifications.
Claims
1. A method for preparing sulfur-containing biodegradable high molecular weight polyester PES, characterized in that... The prepared sulfur-containing biodegradable high molecular weight polyester PES has the following molecular structure: PES1: PES2: Where m and r are positive integers between 20 and 30, and n and s are positive integers between 30 and 50.
2. A method for preparing sulfur-containing biodegradable high molecular weight polyester PES, comprising the following two main steps: 1) Using 2,5-thiophene dicarboxylic acid (CAS 1155-51-7), 4,4'-dithiobisbenzoic acid, and a dihydroxy compound as raw materials, under nitrogen protection, the three raw materials were stirred and reacted at 160-185℃ for 4.0-5.0h under normal pressure and with the action of a catalyst to complete the esterification reaction. Then, the temperature was raised to 200-220℃ and the reaction was continued for 2.0-3.5h under a pressure of 5-15KPa to obtain crude polyester. 2) After cooling the crude polyester, add a certain amount of chloroform, shake to promote dissolution, filter, and add ethanol or propanol to the filtrate until the precipitate no longer increases; wash the filter residue with cold ethanol to remove impurities, and then vacuum dry at 40-60℃ for 1.0-2.0h to obtain the desired sulfur-containing biodegradable high molecular weight polyester PES.
3. The method for preparing a sulfur-containing biodegradable high molecular weight polyester PES according to claim 2, characterized in that... In step 1) of claim 2, the dihydroxy compound is one of the following diols: diol 3a, with the structural formula [insert structural formula here]. Diol 3b, structural formula is 4. The method for preparing sulfur-containing biodegradable high molecular weight polyester PES according to claim 2, characterized in that... The molar ratio of 2,5-thiophene dicarboxylic acid, 4,4'-dithiobisbenzoic acid, and the dihydroxy compound is from 1:1:1.5 to 1:1:2.
5.
5. The method for preparing a sulfur-containing biodegradable high molecular weight polyester PES according to claim 2, characterized in that... The catalyst in claim 2 is ruthenium tri(ethylenediamine)chloride, ruthenium 1,2-diphenylethylenediamine; the amount of the catalyst is 0.01%-0.09% of the total amount of reactants.
6. The use of a sulfur-containing biodegradable high molecular weight polyester PES prepared by the preparation method according to any one of claims 1-5, characterized in that it is used as a main raw material for functional films. The following components are thoroughly mixed in a mass ratio of sulfur-containing biodegradable high molecular weight polyester PES to toughening agent of 100:(3-4). After mixing, a polyester film material with a film thickness of 13μm to 30μm is obtained by extrusion blow molding, extrusion casting, and extrusion stretching. Compared with existing polyesters, it has good mechanical properties and can be used in various packaging and covering applications with high tensile requirements, such as food packaging, functional greenhouse films, express packaging, and fast-moving consumer goods packaging. The toughening agent is one of polyvinyl acetate, polyvinyl alcohol, and polyvinyl butyral.
7. The use of the polyester obtained by the method for preparing sulfur-containing biodegradable high molecular weight polyester PES as described in claim 6, characterized in that: The obtained polyester material achieved a biodegradability rate of over 8% during a 6-month testing period. Its number-average molecular weight at the end of the second year after being buried in natural soil was lower than that at the beginning of the first year, demonstrating good degradation performance compared to existing synthetic polyesters.