Polyethylene succinate and its preparation method and application

Abstract

The present invention relates to the technical field of polyethylene succinate production, specifically polyethylene succinate, its preparation method, and application. The method comprises the following steps: adding succinic acid and ethylene glycol to a reactor to cause an esterification reaction to generate oligomers containing terminal carboxyl groups and terminal hydroxyl groups; adding treated nano-silica sol in batches under stirring; at the start of the polycondensation reaction, dispersing organic montmorillonite in toluene to form a suspension, adding the suspension to the reaction system, and continuing the polycondensation reaction; after the polycondensation reaction is completed, removing the product from the reactor, cooling it to room temperature, and blending and extruding the cooled product with surface-treated chopped glass fibers in a twin-screw extruder to obtain polyethylene succinate. The method accelerates the reaction and reduces the generation of by-products by enhancing catalytic activity. Furthermore, the method has a stable structure, a strong load, and good reusability, thereby reducing production costs.

Description

Technical Field

[0001] The present invention relates to the technical field of polyethylene succinate production, in particular to polyethylene succinate and a preparation method and application thereof. Background Art

[0002] Polyethylene succinate (PES), a biodegradable polyester material, has garnered widespread attention in numerous fields in recent years. However, it has inherent performance limitations that restrict its application in certain scenarios. Pure PES has a relatively low thermal decomposition temperature. Under high-temperature conditions, the molecular chains are susceptible to breakage and degradation, leading to material performance degradation. In terms of mechanical strength, its tensile strength, flexural strength, and impact toughness are limited. This makes products made from it susceptible to deformation and rupture when subjected to significant external forces, making it difficult to meet the demands of applications requiring high mechanical properties. Furthermore, its barrier effect against gases and liquids is unsatisfactory.

[0003] These performance deficiencies exacerbate the problems faced by polyethylene succinate in water quality monitoring buoys, which are exposed to the harsh natural environment outdoors, subject to high temperatures, strong UV radiation, wind and wave impacts, and collisions with various underwater objects.

[0004] Furthermore, while polyolefin plastics such as polyethylene (PE) and polypropylene (PP), commonly used in traditional water quality monitoring buoys, offer certain advantages, they also suffer from poor thermal stability, insufficient mechanical strength, poor barrier properties, and difficulty in degradation, leading to microplastic pollution. While polyethylene succinate offers the advantage of being biodegradable, these performance limitations prevent it from fully meeting practical requirements for use in water quality monitoring buoys.

[0005] To sum up, there are currently many problems with both the performance of polyethylene succinate itself and the traditional water quality monitoring buoy materials, which urgently need to be solved through new material formulas and preparation processes to improve the performance of water quality monitoring buoys, ensure the efficient implementation of water quality monitoring work, and reduce pollution to the water environment. Summary of the Invention

[0006] In view of the above shortcomings of the prior art, the present invention aims to provide a polyethylene succinate that accelerates the reaction and reduces by-product production by enhancing catalytic activity. Furthermore, it has a stable structure, a strong load, and good reusability, thereby reducing production costs.

[0007] Another object of the present invention is to provide a method for preparing polyethylene succinate, which improves the thermal stability, mechanical properties, barrier properties and degradation properties of polyethylene succinate by adding organic montmorillonite, glass fiber and nano-silica.

[0008] The third purpose of the present invention is to provide an application of polyethylene succinate. The water quality monitoring buoy prepared with polyethylene succinate as the main material has a strong ability to adapt to complex outdoor environments, is both environmentally friendly and durable, and also has antibacterial and good electrical properties to ensure the normal operation of the monitoring equipment.

[0009] The present invention is achieved by adopting the following technical solutions:

[0010] The preparation method of the polyethylene succinate comprises the following steps:

[0011] (1) Add succinic acid and ethylene glycol to a reactor, add a catalyst accounting for 0.1-0.5% of the total mass of the raw materials, control the reaction temperature at 160-180°C, the pressure at 0.1-0.3 MPa, and the stirring speed at 100-300 rpm, react for 2-4 hours, and esterification reaction occurs to generate oligomers containing terminal carboxyl groups and terminal hydroxyl groups; then reduce the temperature to 120-150°C, add nano-silica sol in batches under stirring conditions, increase the stirring speed to 300-500 rpm, and stir for 1-2 hours;

[0012] (2) After the treatment in step (1) is completed, the reaction temperature is raised to 220-260°C, and the reaction system is evacuated to a vacuum with a pressure lower than 100 Pa. At the beginning of the polycondensation reaction, the organic montmorillonite is dispersed in toluene to form a suspension, which is added to the reaction system to continue the polycondensation reaction for 3-8 hours.

[0013] (3) After the polycondensation reaction is completed, the product is taken out from the reactor and cooled to room temperature. The cooled product is blended and extruded with short-cut glass fibers in a twin-screw extruder to obtain polyethylene succinate.

[0014] The molar ratio of succinic acid to ethylene glycol is 1:(1.2-1.5); the added amount of organic montmorillonite is 2-5% of the theoretical output mass of polyethylene succinate; the added amount of glass fiber is 10-25% of the theoretical output mass of polyethylene succinate; and the added amount of nano-silica is 3-8% of the theoretical output mass of polyethylene succinate.

[0015] The nano-silica sol must be pretreated before addition. The pretreatment process involves dispersing the nano-silica in anhydrous ethanol, adding a silane coupling agent, and stirring at 70-80°C for 2-3 hours to graft organic groups onto the nano-silica surface, forming a stable sol. The chopped glass fibers must also be pretreated before addition. The pretreatment process involves soaking the chopped glass fibers in a solution of vinyltrimethoxysilane for 1-2 hours, removing them, and drying them. The silane coupling agent is γ-aminopropyltriethoxysilane (KH-550).

[0016] The pretreatment process of organic montmorillonite is as follows: dispersing montmorillonite in toluene, stirring and reacting at 80-100°C for 2-3 hours to allow the organic modifier to be inserted into the interlayer of the montmorillonite, and then filtering, washing, drying and other steps to obtain the organized montmorillonite; dispersing the organized montmorillonite in the inert solvent toluene, and ultrasonically treating the montmorillonite suspension (20-40kHz, 30min) before adding it to the reaction system; and vacuum extraction after adding it to the reaction system to ensure that the solvent residue does not affect the polycondensation reaction.

[0017] Preparation of the nanosilica sol: Select nanosilica powder with a particle size of 20-50 nm and a purity of at least 99%. Prepare γ-aminopropyltriethoxysilane (KH-550) and anhydrous ethanol (water content less than 0.1%) to prevent moisture from interfering with the reaction. Slowly add the nanosilica powder to the anhydrous ethanol, maintaining a mass ratio of 1:10-20. During the addition, stir the mixture using a high-speed stirrer at 800-1200 rpm for 30-60 minutes to initially disperse the nanosilica in the ethanol and form a uniform suspension. Weigh KH-550 to 3-5% of the mass of the nanosilica. Slowly add it dropwise to the nanosilica suspension, maintaining stirring throughout the addition at a rate of 3-5 drops per minute. After the addition is complete, continue stirring for 30 minutes to ensure uniform dispersion of the coupling agent. The reaction temperature is raised to 70-80°C and the reaction is carried out at this temperature for 2-3 hours. Stirring is continued during the reaction, and the stirring speed is adjusted to 400-600 rpm to allow KH-550 to fully react with nano-silica and promote the grafting of organic groups on the surface of nano-silica. After the reaction is completed, the reaction system is cooled to room temperature. Then, an ultrasonic disperser is used to ultrasonically treat the reacted sol, with the ultrasonic power set to 300-500W and the ultrasonic time being 15-20 minutes. Ultrasonic treatment further refines the dispersion state of the nano-silica particles, improves the stability of the sol, and ultimately forms a stable nano-silica sol.

[0018] Treatment of chopped glass fibers: Prepare a dilute coupling agent solution with a concentration of 2-5% by mass using vinyltrimethoxysilane and anhydrous ethanol. Stir thoroughly to ensure the coupling agent is completely dissolved in the ethanol. Soak chopped glass fibers (3-6 mm in length) in the dilute coupling agent solution, ensuring they are completely immersed. Soak for 1-2 hours to allow the coupling agent molecules sufficient time to chemically react with the glass fiber surface. After soaking, remove the chopped glass fibers from the coupling agent solution and gently blot any excess solution with filter paper. Next, dry the glass fibers in an oven at 80-100°C for 2-3 hours. This drying process removes the solvent from the glass fiber surface and allows the coupling agent to form stable chemical bonds on the glass fiber surface, thereby creating reactive groups on the glass fiber surface that effectively bind to polyethylene succinate.

[0019] Organic montmorillonite has a layered structure that forms a good interfacial bond with the polyethylene succinate (PES) matrix, enhancing its strength and toughness. Glass fiber, a reinforcing material, is evenly dispersed within the matrix, significantly improving the material's mechanical properties, such as tensile and flexural strength. Nanosilica fills the material, improving its microstructure and further enhancing its overall strength. The addition of organic montmorillonite and nanosilica improves the material's thermal stability. They form a barrier layer when heated, slowing heat transfer and inhibiting thermal degradation of the polymer matrix, allowing PES to maintain better performance in high-temperature environments. The lamellar structure of organic montmorillonite and the nanoscale effect of nanosilica create tortuous pathways within the material, hindering the diffusion of gas and liquid molecules. This enhances the barrier properties of PES, making it superior in terms of water resistance and gas permeation resistance.

[0020] The preparation method of the catalyst comprises the following steps:

[0021] a. Add mesoporous silica to an anhydrous ethanol solution containing a silane coupling agent, the amount of the silane coupling agent being 1-3% of the mass of the mesoporous silica, and stir the reaction at 60-80°C for 2-4h;

[0022] b. In a dry glove box, tetrabutyl titanate was added to anhydrous ethanol to prepare a 0.1 mol / L tetrabutyl titanate ethanol solution; lanthanum acetate was added to anhydrous ethanol to prepare a 0.05 mol / L lanthanum acetate ethanol solution; zinc oxide nanoparticles and boric acid were taken, added to anhydrous ethanol, and ultrasonically dispersed for 30-60 min;

[0023] c. The prepared tetrabutyl titanate ethanol solution and lanthanum acetate ethanol solution were mixed in a molar ratio of titanium: lanthanum = 3:1, stirred continuously during the mixing process, and polyvinyl pyrrolidone was added as a dispersant and stirred for 1-2h to obtain a main catalyst solution; the mixed solution containing zinc oxide nanoparticles and boric acid was then added to the main catalyst solution and stirred for 30-60min;

[0024] d. The mesoporous silica obtained in step a is added to the solution obtained in step c to load the catalyst into the pores of the mesoporous silica, stirred at room temperature for 2-4h, and then heated and stirred at 60-80°C for 4-8h;

[0025] e. The product obtained in step d is filtered and washed, then transferred to a vacuum drying oven and dried at 60-80°C for 12-24 hours; after drying, the mixture is placed in a muffle furnace and calcined at 250-300°C for 2-3 hours while passing nitrogen protection for activation treatment to remove organic matter and impurities on the surface to obtain a catalyst; the catalyst specific surface area BET ≥ 200 m² / g.

[0026] The silane coupling agent is used in an amount of 1-3% of the mass of the mesoporous silica, the zinc oxide nanoparticles in an amount of 5-10% of the total mass of the main catalyst, and the boric acid in an amount of 2-5% of the total mass of the main catalyst. The polyvinyl pyrrolidone is used in an amount of 0.5-1% of the mass of the tetrabutyl titanate ethanol solution, and the catalyst loading is 20-40%. The silane coupling agent is γ-aminopropyltriethoxysilane (KH-550). The loading is the percentage of the total mass of the active components to the mass of the mesoporous silica support.

[0027] The combination of tetrabutyl titanate and lanthanum acetate unleashes the synergistic effect of the two catalysts, providing more active sites, accelerating the rates of esterification and polycondensation reactions, shortening reaction time, and improving production efficiency. The addition of zinc oxide nanoparticles and boric acid as co-catalysts stabilizes the catalyst's active structure, maintaining high catalytic activity during the reaction, reducing the loss and deactivation of active components, and ensuring stable reaction progress. Mesoporous silica, with its high specific surface area and rich pore structure, serves as a carrier, effectively loading active components, preventing their aggregation, and improving the catalyst's stability and reusability. Furthermore, by controlling the loading amount and calcination conditions, the catalyst's structure is optimized, ensuring its catalytic performance.

[0028] The polyethylene succinate is prepared by the above method for preparing polyethylene succinate.

[0029] The poly(ethylene glycol succinate) is used to prepare a water quality monitoring buoy.

[0030] The method for preparing the water quality monitoring buoy comprises the following steps:

[0031] Ⅰ. In a high-speed mixer, first add polyethylene succinate particles, then add hindered amine light stabilizer, maleic anhydride grafted polyethylene succinate, and stir at 50-80 ° C for 5-10 minutes; then add nano-silver antibacterial agent, continue stirring, then add nano-calcium carbonate and graphene dispersion, and continue stirring for 10-20 minutes;

[0032] Ⅱ. Add the material obtained in step Ⅰ to a twin-screw extruder for melt blending and extrusion. At the same time, during the extrusion process, add the carbon nanotube suspension to the twin-screw extruder and mix it with other materials. Control the screw speed at 100-300 rpm. Then extrude it into the shape of a water quality monitoring buoy through a mold, and then cool it down by air cooling or water cooling to obtain a water quality monitoring buoy.

[0033] The weight proportions of the raw materials are as follows: polyethylene succinate: 100 parts; carbon nanotubes: 1-3 parts; hindered amine light stabilizer: 0.5-2 parts; nano silver antibacterial agent: 0.3-1 parts; graphene: 0.5-2 parts; maleic anhydride grafted polyethylene succinate: 5-15 parts; and nano calcium carbonate: 5-15 parts.

[0034] The carbon nanotube suspension is prepared by placing carbon nanotubes in a mixed acid solution of concentrated nitric acid and concentrated sulfuric acid, and reflux-treating the mixture at 60-80° C. for 2-4 hours; washing the carbon nanotubes with deionized water until neutral, and drying the mixture to obtain purified carboxylated carbon nanotubes; dissolving polyvinyl alcohol (PVA) in deionized water to prepare a solution having a mass fraction of 1-5%; adding the purified carbon nanotubes to the PVA solution, and ultrasonically treating the mixture (at a power of 200-500 W and a time of 30-60 minutes) to uniformly coat the carbon nanotubes with PVA; centrifuging and drying the mixture to obtain PVA-coated carbon nanotubes; and adding the dried PVA-coated carbon nanotubes to N,N-dimethylformamide (DMF) and ultrasonically dispersing or mechanically stirring the mixture (at a speed of 1000-2000 rpm and a time of 1-2 hours) to form a uniform suspension. The preparation method for the nano-calcium carbonate dispersion comprises: surface-modifying the nano-calcium carbonate with fatty acids and titanate coupling agents, adding a silane coupling agent, and stirring at 80-120°C for 1-2 hours to organicize the surface. The nano-calcium carbonate is co-modified using a combination of titanate coupling agents and silane coupling agents to enhance surface hydrophobicity. The preparation method for the graphene dispersion comprises: preparing a uniform dispersion of graphene in an organic solvent or water by ultrasonic exfoliation. The amount of silane coupling agent added is 1-5% of the mass of the nano-calcium carbonate.

[0035] In the raw material system of water quality monitoring buoys, polyethylene succinate is the basic continuous phase matrix. Granular or fibrous raw materials such as nano-calcium carbonate, carbon nanotubes, and graphene are dispersed in it. They act like fillers and are tightly bound to polyethylene succinate. Nano-calcium carbonate, with its tiny size and large specific surface area, evenly fills the molecular gaps of polyethylene succinate, increasing the material density while also having a physical reinforcement effect, improving the hardness and rigidity of the buoy. Carbon nanotubes and graphene, with their unique microstructures, construct a three-dimensional network structure in the polyethylene succinate matrix, significantly enhancing the mechanical strength, thermal stability, and electrical conductivity of the material. For example, carbon nanotubes, with their excellent mechanical properties, can bear part of the external stress, allowing the buoy to better maintain structural integrity and resist damage when impacted by water currents and waves. Silane coupling agents and maleic anhydride-grafted polyethylene succinate (PES-g-MAH) act as chemical bridges between polyethylene succinate and other raw materials. The siloxy group on one end of the silane coupling agent molecule reacts chemically with the hydroxyl groups on the surface of inorganic raw materials such as nano-calcium carbonate and nano-silicon dioxide, while the organic functional group on the other end physically or chemically reacts with the polyethylene succinate molecule, thereby strengthening the interfacial bonding between the inorganic raw materials and the polyethylene succinate. The maleic anhydride groups in PES-g-MAH react with active groups such as hydroxyl groups on the surfaces of organic montmorillonite and glass fibers. The polyethylene succinate chain segments in PES-g-MAH are also highly compatible with the polyethylene succinate matrix, improving the compatibility of the organic montmorillonite, glass fibers, and the polyethylene succinate matrix, reducing phase separation and ensuring a more stable overall structure for the raw materials within the buoy material system. Functional ingredients such as hindered amine light stabilizers and nanosilver antimicrobial agents work synergistically with polyethylene succinate to impart special properties to the buoy. The hindered amine light stabilizer effectively absorbs ultraviolet light, inhibiting the oxidative degradation of polyethylene succinate under light, thereby extending the buoy's service life in outdoor environments. The nanosilver antimicrobial agent inhibits the growth and reproduction of bacteria, algae, and other microorganisms on the buoy's surface, preventing microbial attachment and corrosion, and keeping the buoy's surface clean. Working together with polyethylene succinate, it enhances the buoy's durability and stability in complex water environments. Furthermore, glass fiber enhances the mechanical strength of polyethylene succinate, enabling it to withstand greater external forces. Together with the other ingredients, this ensures the buoy's proper operation in a variety of harsh natural conditions.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] (1) The catalyst of the present invention uses mesoporous silica as a carrier, loaded with tetrabutyl titanate, lanthanum acetate, etc., and added with zinc oxide nanoparticles and boric acid as catalyst promoters. γ-aminopropyltriethoxysilane (KH-550) is used as a silane coupling agent. The synergistic effect of these components results in high catalyst activity and good selectivity, accelerating the reaction and reducing by-products. It also exhibits excellent thermal and chemical stability, and is stable at high temperatures and in complex environments. Its robust loading and good reusability can reduce production costs.

[0038] (2) Organic montmorillonite, glass fiber, and nano-silica are added to the preparation of polyethylene succinate. Organic montmorillonite strengthens and toughens the material, glass fiber improves mechanical properties, and nano-silica improves the microstructure and overall strength. The three work together to enhance the material's thermal stability and barrier properties, and also improve its degradation properties, facilitating its decomposition in the natural environment.

[0039] (3) The water quality monitoring buoy, made with polyethylene succinate as the main raw material, has excellent comprehensive performance, including good thermal stability and adaptability to high outdoor temperatures; high mechanical strength to withstand external impact; strong barrier properties to protect monitoring equipment; and biodegradable and water-resistant, making it environmentally friendly and durable. The addition of hindered amine light stabilizers and nanosilver antimicrobial agents gives the buoy UV resistance and antibacterial properties, extending its service life and keeping its surface clean. Furthermore, the buoy has good electrical performance, ensuring stable operation of the monitoring equipment and smooth water quality monitoring. DETAILED DESCRIPTION

[0040] In order to make the purpose and technical solution of the present invention more clear, the present invention is further described in detail.

[0041] Test method:

[0042] Catalytic activity test: Succinic acid and ethylene glycol were added as raw materials at a molar ratio of 1:1.3 to a reaction vessel equipped with a stirrer, thermometer, and condenser. The catalyst to be tested was then added (0.3% of the total raw material mass). The esterification reaction was carried out at a set temperature (170°C) and pressure (0.2 MPa). The change in acid value (determined by acid-base titration) was recorded at different reaction times. A faster decrease in acid value indicates a faster esterification rate and higher catalyst activity. After the esterification reaction was completed, the temperature was raised to the polycondensation temperature (240°C), and the pressure was evacuated to below 100 Pa. The reaction was continued, and the progress of the polycondensation reaction was monitored by measuring the intrinsic viscosity of the system (using an Ubbelohde viscometer). A faster increase in intrinsic viscosity indicates a faster polycondensation rate, further demonstrating catalyst activity.

[0043] Selectivity test: The reaction products were analyzed by gas chromatography-mass spectrometry (GC-MS).

[0044] Stability test:

[0045] Thermal stability: Heat treat the catalyst for 5 hours at 300°C (300°C) above the actual reaction temperature. Then, perform the reaction according to the catalytic activity test method described above. Compare the changes in catalytic activity before and after heat treatment. The smaller the decrease in activity, the better the thermal stability.

[0046] Chemical stability: Place the catalyst in a simulated reaction system containing raw materials and products, maintain it at the reaction temperature for a period of time (24 hours), then remove the catalyst and conduct the catalytic activity test again to observe the activity changes and evaluate its chemical stability.

[0047] Load firmness test:

[0048] The supported catalyst sample was placed in an ultrasonic cleaner and ultrasonically treated at a specific power (200 W) and duration (30 minutes). The sample was then centrifuged and the supernatant was measured using atomic absorption spectrometry (AAS) or inductively coupled plasma optical emission spectrometry (ICP-OES) to determine the content of active components (such as titanium and lanthanum). This was used to calculate the shedding rate of the active components. The ultrasonically treated catalyst was then tested for specific surface area and pore size distribution to observe any structural changes. A lower shedding rate indicates less structural change, indicating better loading stability.

[0049] Reusability testing

[0050] The first reaction was conducted according to the catalytic activity test method. After the reaction was completed, the catalyst was recovered through filtration, washing, and drying. The recovered catalyst was then reintroduced into the same reaction system for the next reaction, and this process was repeated five times. After each reaction, the product's intrinsic viscosity, conversion rate, and other indicators were measured. The results of each reaction were compared to assess the catalyst's reusability. If these indicators showed little change with increasing use, the catalyst demonstrated good reusability.

[0051] Thermal stability testing method: Onset decomposition temperature (Tonset) and residual mass percentage at 400°C: Testing is performed using thermogravimetric analysis (TGA). Using a thermogravimetric analyzer, an appropriate amount of sample (8 mg) is placed in a platinum or ceramic crucible. Under an inert gas atmosphere such as nitrogen or argon (gas flow rate controlled at 50 mL / min), the temperature is increased at a constant rate (15°C / min) from room temperature to a temperature above the target test temperature (500°C). During the heating process, the instrument records the change in sample mass with temperature in real time. The onset decomposition temperature (Tonset) is the temperature at which the sample mass begins to significantly decrease, reflecting the point at which thermal decomposition of the material begins. When the temperature reaches 400°C, the residual mass of the sample is recorded and calculated as a percentage of the initial mass. A higher percentage indicates better thermal stability at 400°C and a lower degree of decomposition.

[0052] Tensile strength: tested in accordance with GB / T1040.2 using a universal material testing machine.

[0053] Bending strength: According to GB / T9341 standard, use universal material testing machine.

[0054] Izod notched impact strength: tested in accordance with GB / T1843 standard using an Izod impact testing machine.

[0055] Barrier test method

[0056] Oxygen transmission rate: Testing is performed using an isobaric or differential pressure oxygen transmission rate tester. For the isobaric method, for example, a prepared polyethylene succinate film (0.1mm thick) is sealed in the center of a test chamber, dividing the chamber into two independent chambers. One chamber is filled with oxygen of a known concentration (99.99% purity), while the other is filled with an inert gas such as nitrogen. Under certain temperature (25°C) and relative humidity (50% RH), oxygen diffuses through the film from the high-concentration side to the low-concentration side. A sensor monitors the oxygen concentration in the low-concentration chamber in real time. Based on the test instrument's principles and built-in algorithms, the oxygen transmission rate (OTR) is calculated in cm³ / (m² / 24h / 0.1MPa). A lower OTR indicates a better oxygen barrier performance.

[0057] Degradability test method:

[0058] Mass loss rate after 6 months of soil burial: Tested in a simulated natural soil environment. Prepare a certain amount (8g) of polyethylene succinate sample and record its initial mass. Bury the sample in soil that meets certain standards (e.g., uncontaminated farmland soil that has been screened to remove impurities and ensure uniform soil particles) to a depth of 5cm. Allow the sample to degrade in the soil for 6 months under natural environmental conditions (temperature, humidity, etc. similar to the local natural climate). After 6 months, carefully remove the sample, rinse it with clean water to remove soil particles attached to the surface, and then dry it in an oven (at 70°C) to constant weight. Record the sample mass again. Calculate the mass loss rate after 6 months of soil burial using the formula: Mass loss rate = (initial mass - degraded mass) ÷ initial mass × 100%. The higher the mass loss rate, the better the degradability of the material.

[0059] Shore hardness (Type A): Tested in accordance with GB / T531.1 standard using a Shore A hardness tester.

[0060] Processability test method

[0061] Processing Temperature Range: Polyethylene succinate (PES) is processed in a twin-screw extruder to determine its processing temperature range. PE granules are added to the hopper of the twin-screw extruder. The temperature in different zones of the extruder is set, starting at a low temperature and gradually increasing. Extrusion is performed at a constant screw speed (100 rpm). The material flow and the appearance of the extrudate (e.g., melt fracture, surface roughness, bubbles, etc.) are observed during extrusion. The temperature at which obvious processing defects (e.g., melt fracture, severe surface unevenness, etc.) begin to appear, as well as the temperature range within which smooth extrusion and a good product quality are achieved, is recorded. This constitutes the processing temperature range for the material. The temperature ranges where defects of varying degrees occur are also clearly marked. For example, "175-195 (Increased Processing Defects)" indicates an increase in defects during processing within the 175-195°C temperature range.

[0062] Water resistance test method

[0063] Water absorption: tested according to GB / T1034 standard.

[0064] Weathering test: GB / T16422.2-2014 "Plastics laboratory light source exposure test method Part 2: Xenon arc lamp".

[0065] Antibacterial performance test: GB / T21510-2008 "Test method for antibacterial properties of nano-inorganic materials".

[0066] Electrical performance test: GB / T1410-2006 "Test method for volume resistivity and surface resistivity of solid insulating materials".

[0067] In the following examples, the pretreatment process of the organic montmorillonite, nano-silica sol and chopped glass fibers is as follows:

[0068] The pretreatment process of organic montmorillonite is as follows: montmorillonite is dispersed in toluene, stirred and reacted at 90°C for 3 hours to allow the organic modifier to insert into the interlayer of montmorillonite, and then filtered, washed, dried and other steps to obtain organized montmorillonite; the organized montmorillonite is dispersed in an inert solvent, toluene, and the montmorillonite suspension is ultrasonically treated (30kHz, 30min) before being added to the reaction system; after being added to the reaction system, vacuum extraction is performed to ensure that solvent residue does not affect the polycondensation reaction.

[0069] Preparation of the nanosilica sol: Prepare nanosilica powder with a particle size of 30 nm and a purity of 99%. Prepare γ-aminopropyltriethoxysilane (KH-550) and anhydrous ethanol (water content less than 0.1%) to prevent moisture from interfering with the reaction. Slowly add the nanosilica powder to the anhydrous ethanol, maintaining a mass ratio of 1:15. During the addition, stir the mixture using a high-speed stirrer at 1000 rpm for 50 minutes to initially disperse the nanosilica in the ethanol and form a uniform suspension. Weigh KH-550 to 4% of the mass of the nanosilica. Slowly add it dropwise to the nanosilica suspension, maintaining stirring at a rate of 4 drops per minute. After the addition is complete, continue stirring for 30 minutes to ensure uniform dispersion of the coupling agent. Raise the reaction temperature to 75°C and continue the reaction at this temperature for 3 hours. During the reaction, stirring was continued at a speed of 500 rpm to allow the silane coupling agent to fully react with the nano-silica and promote the grafting of organic groups onto the surface of the nano-silica. After the reaction was completed, the reaction system was cooled to room temperature. The reacted sol was then ultrasonically treated using an ultrasonic disperser with an ultrasonic power of 400 W and a sonication time of 18 minutes. The ultrasonic treatment further refined the dispersion of the nano-silica particles, improved the stability of the sol, and ultimately formed a stable nano-silica sol.

[0070] Treatment of chopped glass fibers: Prepare a 5% by weight dilute coupling agent solution using vinyltrimethoxysilane and anhydrous ethanol as the solvent. Stir thoroughly during preparation to ensure the coupling agent is completely dissolved in the ethanol. Soak chopped glass fibers (4 mm in length) in the dilute coupling agent solution, ensuring they are completely immersed. Soak for 2 hours to allow the coupling agent molecules sufficient time to chemically react with the glass fiber surface. After soaking, remove the chopped glass fibers from the coupling agent solution and gently blot any excess solution with filter paper. The glass fibers are then dried in an oven at 90°C for 3 hours. Drying removes the solvent from the glass fiber surface and allows the coupling agent to form stable chemical bonds on the glass fiber surface, thereby forming reactive groups on the glass fiber surface that bind well to polyethylene succinate.

[0071] Example 1

[0072] The preparation method of polyethylene succinate comprises the following steps:

[0073] (1) Add succinic acid and ethylene glycol to a reactor, add a catalyst accounting for 0.5% of the total weight of the raw materials, control the reaction temperature at 180°C, the pressure at 0.3 MPa, the stirring speed at 300 rpm, and react for 4 hours. Esterification reaction occurs to generate oligomers containing terminal carboxyl groups and terminal hydroxyl groups; then reduce the temperature to 150°C, add the treated nano-silica sol in batches under stirring conditions, increase the stirring speed to 500 rpm, and stir for 2 hours;

[0074] (2) After the treatment in step (1) is completed, the reaction temperature is raised to 260°C, and the reaction system is evacuated to a vacuum pressure of 90 Pa. At the beginning of the polycondensation reaction, the organic montmorillonite is dispersed in toluene to form a suspension, which is added to the reaction system to continue the polycondensation reaction for 8 hours.

[0075] (3) After the polycondensation reaction is completed, the product is taken out from the reactor and cooled to room temperature. The cooled product is blended and extruded with surface-treated short-cut glass fibers in a twin-screw extruder to obtain polyethylene succinate.

[0076] In the above, the molar ratio of succinic acid to ethylene glycol is 1:1.5; the addition amount of organic montmorillonite is 5% of the theoretical output mass of polyethylene succinate; the addition amount of glass fiber is 25% of the theoretical output mass of polyethylene succinate; and the addition amount of nano-silica is 8% of the theoretical output mass of polyethylene succinate.

[0077] The preparation method of the catalyst comprises the following steps:

[0078] a. The mesoporous silica was added to an anhydrous ethanol solution containing KH-550, where the amount of KH-550 was 3% of the mass of the mesoporous silica, and the reaction was stirred at 80°C for 4h;

[0079] b. In a dry glove box, tetrabutyl titanate was added to anhydrous ethanol to prepare a 0.1 mol / L tetrabutyl titanate ethanol solution; lanthanum acetate was added to anhydrous ethanol to prepare a 0.05 mol / L lanthanum acetate ethanol solution; zinc oxide nanoparticles and boric acid were added to anhydrous ethanol and ultrasonically dispersed for 60 min;

[0080] c. The prepared tetrabutyl titanate ethanol solution and lanthanum acetate ethanol solution were mixed in a molar ratio of titanium: lanthanum = 3:1, stirred continuously during the mixing process, and polyvinyl pyrrolidone was added as a dispersant and stirred for 2h to obtain a main catalyst solution; the mixed solution containing zinc oxide nanoparticles and boric acid was then added to the main catalyst solution and stirred for 60min;

[0081] d. The mesoporous silica obtained in step a was added to the solution obtained in step c to load the catalyst into the pores of the mesoporous silica, stirred at room temperature for 4 h, and then heated and stirred at 80 ° C for 8 h;

[0082] e. The product obtained in step d was filtered, washed, transferred to a vacuum drying oven, and dried at 80 ° C for 24 h; after drying, placed in a muffle furnace and calcined at 300 ° C for 3 h while passing nitrogen protection for activation treatment to remove surface organic matter and impurities to obtain a catalyst; the catalyst specific surface area BET was 260 m² / g.

[0083] The dosage of KH-550 is 3% of the mass of mesoporous silica, the dosage of zinc oxide nanoparticles is 10% of the total mass of the main catalyst, the dosage of boric acid is 5% of the total mass of the main catalyst; the dosage of polyvinyl pyrrolidone is 1% of the mass of tetrabutyl titanate ethanol solution; and the catalyst loading is 40%.

[0084] Example 2

[0085] The preparation method of polyethylene succinate comprises the following steps:

[0086] (1) Add succinic acid and ethylene glycol to a reactor, add a catalyst accounting for 0.3% of the total weight of the raw materials, control the reaction temperature at 170°C, the pressure at 0.2 MPa, and the stirring speed at 200 rpm, and react for 3 hours to cause esterification reaction to generate oligomers containing terminal carboxyl groups and terminal hydroxyl groups; then reduce the temperature to 135°C, add the treated nano-silica sol in batches under stirring conditions, increase the stirring speed to 400 rpm, and stir for 2 hours;

[0087] (2) After the treatment in step (1) is completed, the reaction temperature is raised to 240°C, and the reaction system is evacuated to a vacuum pressure of 80 Pa. At the beginning of the polycondensation reaction, the organic montmorillonite is dispersed in toluene to form a suspension, which is added to the reaction system to continue the polycondensation reaction for 5 hours.

[0088] (3) After the polycondensation reaction is completed, the product is taken out from the reactor and cooled to room temperature. The cooled product is blended and extruded with surface-treated short-cut glass fibers in a twin-screw extruder to obtain polyethylene succinate.

[0089] In the above, the molar ratio of succinic acid to ethylene glycol is 1:1.3; the addition amount of organic montmorillonite is 3% of the theoretical output mass of polyethylene succinate; the addition amount of glass fiber is 20% of the theoretical output mass of polyethylene succinate; and the addition amount of nano-silica is 5% of the theoretical output mass of polyethylene succinate.

[0090] The preparation method of the catalyst comprises the following steps:

[0091] a. Add mesoporous silica to an anhydrous ethanol solution containing KH-550, where the amount of KH-550 is 2% of the mass of the mesoporous silica, and stir the reaction at 70°C for 3h;

[0092] b. In a dry glove box, tetrabutyl titanate was added to anhydrous ethanol to prepare a 0.1 mol / L tetrabutyl titanate ethanol solution; lanthanum acetate was added to anhydrous ethanol to prepare a 0.05 mol / L lanthanum acetate ethanol solution; zinc oxide nanoparticles and boric acid were taken, added to anhydrous ethanol, and ultrasonically dispersed for 30-60 min;

[0093] c. The prepared tetrabutyl titanate ethanol solution and lanthanum acetate ethanol solution were mixed in a molar ratio of titanium: lanthanum = 3:1, stirred continuously during the mixing process, and polyvinyl pyrrolidone was added as a dispersant and stirred for 2h to obtain a main catalyst solution; then the mixed solution containing zinc oxide nanoparticles and boric acid was added to the main catalyst solution and stirred for 40min;

[0094] d. The mesoporous silica obtained in step a was added to the solution obtained in step c to load the catalyst into the pores of the mesoporous silica, stirred at room temperature for 3 h, and then heated and stirred at 70 ° C for 6 h;

[0095] e. The product obtained in step d was filtered, washed, transferred to a vacuum drying oven, and dried at 70 ° C for 20 h; after drying, placed in a muffle furnace and calcined at 280 ° C for 3 h while passing nitrogen protection for activation treatment to remove surface organic matter and impurities to obtain a catalyst; the catalyst specific surface area BET was 230 m² / g.

[0096] The dosage of KH-550 is 2% of the mass of mesoporous silica, the dosage of zinc oxide nanoparticles is 8% of the total mass of the main catalyst, the dosage of boric acid is 4% of the total mass of the main catalyst; the dosage of polyvinyl pyrrolidone is 0.8% of the mass of tetrabutyl titanate ethanol solution; and the catalyst loading is 30%.

[0097] Example 3

[0098] The preparation method of polyethylene succinate comprises the following steps:

[0099] (1) Add succinic acid and ethylene glycol to a reactor, add a catalyst accounting for 0.1% of the total weight of the raw materials, control the reaction temperature at 160°C, the pressure at 0.1 MPa, and the stirring speed at 100 rpm, and react for 2 hours to cause esterification reaction to generate oligomers containing terminal carboxyl groups and terminal hydroxyl groups; then reduce the temperature to 120°C, add the treated nano-silica sol in batches under stirring conditions, increase the stirring speed to 300 rpm, and stir for 1 hour;

[0100] (2) After the treatment in step (1) is completed, the reaction temperature is raised to 220°C, and the reaction system is evacuated to a vacuum pressure of 80 Pa. At the beginning of the polycondensation reaction, the organic montmorillonite is dispersed in toluene to form a suspension, which is added to the reaction system to continue the polycondensation reaction for 3 hours.

[0101] (3) After the polycondensation reaction is completed, the product is taken out from the reactor and cooled to room temperature. The cooled product is blended and extruded with surface-treated short-cut glass fibers in a twin-screw extruder to obtain polyethylene succinate.

[0102] In the above, the molar ratio of succinic acid to ethylene glycol is 1:1.2; the addition amount of organic montmorillonite is 2% of the theoretical output mass of polyethylene succinate; the addition amount of glass fiber is 10% of the theoretical output mass of polyethylene succinate; and the addition amount of nano-silica is 3% of the theoretical output mass of polyethylene succinate.

[0103] The preparation method of the catalyst comprises the following steps:

[0104] a. Add mesoporous silica to an anhydrous ethanol solution containing KH-550, where the amount of KH-550 is 1% of the mass of the mesoporous silica, and stir the reaction at 60°C for 2h;

[0105] b. In a dry glove box, tetrabutyl titanate was added to anhydrous ethanol to prepare a 0.1 mol / L tetrabutyl titanate ethanol solution; lanthanum acetate was added to anhydrous ethanol to prepare a 0.05 mol / L lanthanum acetate ethanol solution; zinc oxide nanoparticles and boric acid were added to anhydrous ethanol and ultrasonically dispersed for 30 min;

[0106] c. The prepared tetrabutyl titanate ethanol solution and lanthanum acetate ethanol solution were mixed in a molar ratio of titanium: lanthanum = 3:1, stirred continuously during the mixing process, and polyvinyl pyrrolidone was added as a dispersant and stirred for 1h to obtain a main catalyst solution; then the mixed solution containing zinc oxide nanoparticles and boric acid was added to the main catalyst solution and stirred for 30min;

[0107] d. The mesoporous silica obtained in step a was added to the solution obtained in step c to load the catalyst into the pores of the mesoporous silica, stirred at room temperature for 2 h, and then heated and stirred at 60 ° C for 4 h;

[0108] e. The product obtained in step d was filtered, washed, transferred to a vacuum drying oven, and dried at 60 ° C for 12 h; after drying, placed in a muffle furnace and calcined at 250 ° C for 2 h while passing nitrogen protection for activation treatment to remove surface organic matter and impurities to obtain a catalyst; the catalyst specific surface area BET was 210 m² / g.

[0109] The dosage of KH-550 is 1% of the mass of mesoporous silica, the dosage of zinc oxide nanoparticles is 5% of the total mass of the main catalyst, the dosage of boric acid is 2% of the total mass of the main catalyst; the dosage of polyvinyl pyrrolidone is 0.5% of the mass of tetrabutyl titanate ethanol solution; and the catalyst loading is 20%.

[0110] Comparative Example 1

[0111] Compared with Example 1, KH-550 was not added during the catalyst preparation.

[0112] Comparative Example 2

[0113] Compared with Example 1, no mesoporous silica was added during the catalyst preparation, ie, no loading was performed.

[0114] Comparative Example 3

[0115] Compared with Example 1, no zinc oxide nanoparticles were added during the catalyst preparation.

[0116] Comparative Example 4

[0117] Compared with Example 1, no boric acid was added during the catalyst preparation.

[0118] Comparative Example 5

[0119] Compared with Example 1, no polyvinyl pyrrolidone was added during the catalyst preparation.

[0120] Comparative Example 6

[0121] Compared with Example 1, no nano-silicon dioxide was added.

[0122] Comparative Example 7

[0123] Compared with Example 2, no organic montmorillonite was added.

[0124] Comparative Example 8

[0125] Compared with Example 3, no glass fiber was added.

[0126] The test data of the catalysts prepared in Examples 1-3 and Comparative Examples 1-5 are shown in Table 1.

[0127] The test data of the polyethylene succinate prepared in Examples 1-3 and Comparative Examples 6-8 are shown in Table 2.

[0128] Table 1: Test data of the catalysts prepared in Examples 1-3 and Comparative Examples 1-5

[0129]

[0130]

[0131] Table 1 shows that the catalysts in Examples 1-3 exhibit high activity (short esterification time, rapid acid value decrease, and high polycondensation intrinsic viscosity), good selectivity (byproducts <2%), excellent thermal and chemical stability (activity drop ≤ 14%), robust loading (shedding rate ≤ 4%), and good reusability (intrinsic viscosity change ≤ 9%). At a loading of 30%, the support and active components are more evenly distributed, resulting in the highest catalytic efficiency. Comparative studies show that mesoporous silica supports (Comparative Example 2), KH-550 (Comparative Example 1), and zinc oxide / boric acid (Comparative Examples 3-4) are crucial for improving catalytic performance.

[0132] Table 2: Test data of polyethylene succinate obtained in Examples 1-3 and Comparative Examples 6-8

[0133]

[0134]

[0135] As shown in Table 2, the polyethylene succinates in Examples 1-3 exhibit significantly better thermal stability (onset decomposition temperature ≥ 280°C), mechanical properties (tensile strength ≥ 45 MPa), barrier properties (oxygen transmission rate ≤ 5.0), and biodegradability (mass loss rate ≥ 30%) than Comparative Examples 6-8. The synergistic effect of organic montmorillonite, glass fiber, and nano-silica (performance declined in Comparative Examples 6-8 without these additives) is key, demonstrating that these three ingredients collectively enhance the overall performance of the material.

[0136] Application Example 1

[0137] Polyethylene succinate is used to prepare water quality monitoring buoys.

[0138] The preparation method of the carbon nanotube suspension is as follows: placing the carbon nanotubes in a mixed acid solution of concentrated nitric acid and concentrated sulfuric acid, and reflux treatment at 80°C for 4 hours; washing with deionized water until neutral, and drying to obtain purified carboxylated carbon nanotubes; dissolving polyvinyl alcohol in deionized water to prepare a solution with a mass fraction of 5%; adding the purified carbon nanotubes to the polyvinyl alcohol solution, and ultrasonically treating (power 500W, time 60min) to uniformly coat the surface of the carbon nanotubes with PVA; centrifuging and drying to obtain PVA-coated carbon nanotubes; adding the dried PVA-coated carbon nanotubes to N,N-dimethylformamide (DMF), and ultrasonically dispersing for 1 hour to form a uniform suspension.

[0139] The nano-calcium carbonate dispersion was prepared by surface-modifying the nano-calcium carbonate with fatty acids and titanate coupling agents, then adding KH-550 and stirring at 120°C for 2 hours to organicize the surface. The graphene dispersion was prepared by ultrasonically exfoliating the graphene in water to form a uniform dispersion. The KH-550 was added at 5% of the mass of the nano-calcium carbonate.

[0140] The preparation method of the water quality monitoring buoy comprises the following steps:

[0141] Ⅰ. In a high-speed mixer, first add polyethylene succinate particles, then add hindered amine light stabilizer, maleic anhydride grafted polyethylene succinate, and stir at 80°C for 10 minutes; then add nanosilver antibacterial agent and continue stirring, then add nano-calcium carbonate and graphene dispersion, and continue stirring for 20 minutes;

[0142] Ⅱ. Add the material obtained in step Ⅰ to a twin-screw extruder for melt blending and extrusion. At the same time, during the extrusion process, add the carbon nanotube suspension to the twin-screw extruder and mix it with other materials. Control the screw speed at 300 rpm. Then, extrude it into the shape of a water quality monitoring buoy through a mold, and then cool it down by air cooling or water cooling to obtain a water quality monitoring buoy.

[0143] The mass parts of each raw material are: polyethylene succinate: 100 parts; carbon nanotubes: 3 parts; hindered amine light stabilizer: 2 parts; nano silver antibacterial agent: 1 part; graphene: 2 parts; maleic anhydride grafted polyethylene succinate: 15 parts; nano calcium carbonate: 15 parts.

[0144] Application Example 2

[0145] Polyethylene succinate is used to prepare water quality monitoring buoys.

[0146] The preparation method of the carbon nanotube suspension is as follows: placing the carbon nanotubes in a mixed acid solution of concentrated nitric acid and concentrated sulfuric acid, and reflux treatment at 70°C for 3 hours; washing with deionized water until neutral, and drying to obtain purified carboxylated carbon nanotubes; dissolving PVA in deionized water to prepare a solution with a mass fraction of 3%; adding the purified carbon nanotubes to the PVA solution, and ultrasonically treating (power 300W, time 40min) to uniformly coat the PVA on the surface of the carbon nanotubes; centrifuging and drying to obtain PVA-coated carbon nanotubes; adding the dried PVA-coated carbon nanotubes to N,N-dimethylformamide, and ultrasonically dispersing for 2 hours to form a uniform suspension.

[0147] The nano-calcium carbonate dispersion was prepared by surface-modifying the nano-calcium carbonate with fatty acids and titanate coupling agents, adding KH-550, and stirring at 100°C for 2 hours to organicize the surface. The graphene dispersion was prepared by ultrasonically exfoliating the graphene in anhydrous ethanol to form a uniform dispersion. The KH-550 was added at 3% of the mass of the nano-calcium carbonate.

[0148] The preparation method of the water quality monitoring buoy comprises the following steps:

[0149] Ⅰ. In a high-speed mixer, first add polyethylene succinate particles, then add hindered amine light stabilizer, and then maleic anhydride grafted polyethylene succinate, and stir at 70°C for 8 minutes; then add nanosilver antibacterial agent and continue stirring, then add nano-calcium carbonate and graphene dispersion, and continue stirring for 15 minutes;

[0150] Ⅱ. Add the material obtained in step Ⅰ to a twin-screw extruder for melt blending and extrusion. At the same time, during the extrusion process, add the carbon nanotube suspension to the twin-screw extruder and mix it with other materials. Control the screw speed at 200 rpm. Then, extrude it into the shape of a water quality monitoring buoy through a mold, and then cool it by air cooling or water cooling to obtain a water quality monitoring buoy.

[0151] The mass parts of each raw material are: polyethylene succinate: 100 parts; carbon nanotubes: 2 parts; hindered amine light stabilizer: 1 part; nano silver antibacterial agent: 0.8 parts; graphene: 1 part; maleic anhydride grafted polyethylene succinate: 10 parts; nano calcium carbonate: 10 parts.

[0152] Application Example 3

[0153] Polyethylene succinate is used to prepare water quality monitoring buoys.

[0154] The preparation method of the carbon nanotube suspension is as follows: placing the carbon nanotubes in a mixed acid solution of concentrated nitric acid and concentrated sulfuric acid, and reflux treatment at 60°C for 2 hours; washing with deionized water until neutral, and drying to obtain purified carboxylated carbon nanotubes; dissolving polyvinyl alcohol in deionized water to prepare a solution with a mass fraction of 1%; adding the purified carbon nanotubes to the PVA solution, and ultrasonically treating (power 200W, time 30 minutes) to uniformly coat the PVA on the surface of the carbon nanotubes; centrifuging and drying to obtain PVA-coated carbon nanotubes; adding the dried PVA-coated carbon nanotubes to N,N-dimethylformamide, and mechanically stirring (speed 1000 rpm, time 2 hours) to form a uniform suspension.

[0155] The nano-calcium carbonate dispersion was prepared by surface-modifying the nano-calcium carbonate with fatty acids and titanate coupling agents, then adding KH-550 and stirring at 80°C for 1 hour to organicize the surface. The graphene dispersion was prepared by ultrasonically exfoliating the graphene in anhydrous ethanol to form a uniform dispersion. The KH-550 was added at a concentration of 1% by weight of the nano-calcium carbonate.

[0156] The preparation method of the water quality monitoring buoy comprises the following steps:

[0157] Ⅰ. In a high-speed mixer, first add polyethylene succinate particles, then add hindered amine light stabilizer, maleic anhydride grafted polyethylene succinate, and stir at 50°C for 5 minutes; then add nanosilver antibacterial agent and continue stirring, then add nano-calcium carbonate and graphene dispersion, and continue stirring for 10 minutes;

[0158] Ⅱ. Add the material obtained in step Ⅰ to a twin-screw extruder for melt blending and extrusion. At the same time, during the extrusion process, add the carbon nanotube suspension to the twin-screw extruder and mix it with other materials. Control the screw speed at 100 rpm. Then, extrude it into the shape of a water quality monitoring buoy through a mold, and then cool it down by air cooling or water cooling to obtain a water quality monitoring buoy.

[0159] The mass parts of each raw material are: polyethylene succinate: 100 parts; carbon nanotubes: 1 part; hindered amine light stabilizer: 0.5 parts; nano silver antibacterial agent: 0.3 parts; graphene: 0.5 parts; maleic anhydride grafted polyethylene succinate: 5 parts; nano calcium carbonate: 5 parts.

[0160] Comparative Example 1 was applied, and the polyethylene succinate prepared in Comparative Example 1 was used, and the middle value was taken.

[0161] Compared with Application Example 1, in Application Comparative Example 2, nano-silica and graphene were not added.

[0162] In Comparative Example 3, compared with Example 1, no carbon nanotubes were added, and the amount of nano-calcium carbonate added was the sum of the masses of nano-calcium carbonate and carbon nanotubes in Example 1.

[0163] In Application Comparative Example 4, compared with Application Example 1, no nano-silicon dioxide was added.

[0164] In Comparative Application Example 5, compared with Example 1, no pretreatment was performed on the nanomaterial.

[0165] The test data of Application Examples 1-3 and Application Comparative Examples 1-5 are shown in Table 3.

[0166] Table 3: Test data of application examples 1-3 and application comparative examples 1-5

[0167]

[0168]

[0169] As shown in Table 3, the water quality monitoring buoys using Examples 1-3 demonstrated superior thermal stability (onset decomposition temperature ≥ 305°C), mechanical strength (tensile strength ≥ 60 MPa), antibacterial rate (≥ 94%), and electrical performance (volume resistivity ≥ 1.4×10¹³Ω·m) compared to the comparative examples. The nanomaterial pretreatment (performance degradation in Comparative Example 5) and the synergistic composition (performance degradation in Comparative Examples 2-4 without the addition of key components) demonstrate the essentiality of this formulation design, ensuring the durability and functionality of the buoys in complex environments.

[0170] The present invention significantly improves the thermal stability, mechanical properties and degradability of polyethylene succinate by optimizing the catalyst (high activity and high stability) and material formulation (synergistic reinforcement of organic montmorillonite / glass fiber / nanosilica), and gives the water quality monitoring buoy excellent comprehensive performance (weather resistance, antibacterial, and high barrier), thus possessing significant technical advantages.

Claims

1. A method for preparing polyethylene succinate, characterized in that: The following steps are involved: (1) Add succinic acid and ethylene glycol to a reactor, add a catalyst accounting for 0.1-0.5% of the total mass of the raw materials, control the reaction temperature at 160-180°C, the pressure at 0.1-0.3 MPa, and the stirring speed at 100-300 rpm, react for 2-4 hours, and esterification reaction occurs to generate oligomers containing terminal carboxyl groups and terminal hydroxyl groups; then reduce the temperature to 120-150°C, add nano-silica sol in batches under stirring conditions, increase the stirring speed to 300-500 rpm, and stir for 1-2 hours; (2) After the treatment in step (1) is completed, the reaction temperature is raised to 220-260°C, and the reaction system is evacuated to a vacuum with a pressure lower than 100 Pa. At the beginning of the polycondensation reaction, the organic montmorillonite is dispersed in toluene to form a suspension, which is added to the reaction system to continue the polycondensation reaction for 3-8 hours. (3) After the polycondensation reaction is completed, the product is taken out from the reactor, cooled to room temperature, and the cooled product is blended and extruded with short glass fibers in a twin-screw extruder to obtain polyethylene succinate; The nano-silica sol must be pretreated before being added. The pretreatment process is as follows: dispersing the nano-silica in anhydrous ethanol, adding a silane coupling agent, and stirring at 70-80°C for 2-3 hours to graft organic groups on the surface of the nano-silica to form a stable sol; before adding the chopped glass fibers, the pretreatment process is as follows: soaking the chopped glass fibers in a solution of vinyltrimethoxysilane for 1-2 hours, taking them out, and drying them; The preparation method of the catalyst comprises the following steps: a. Add mesoporous silica to an anhydrous ethanol solution containing a silane coupling agent, the amount of the silane coupling agent being 1-3% of the mass of the mesoporous silica, and stir the reaction at 60-80°C for 2-4h; b. In a dry glove box, tetrabutyl titanate was added to anhydrous ethanol to prepare a 0.1 mol / L tetrabutyl titanate ethanol solution; lanthanum acetate was added to anhydrous ethanol to prepare a 0.05 mol / L lanthanum acetate ethanol solution; zinc oxide nanoparticles and boric acid were taken, added to anhydrous ethanol, and ultrasonically dispersed for 30-60 min; c. The prepared tetrabutyl titanate ethanol solution and lanthanum acetate ethanol solution were mixed in a molar ratio of titanium: lanthanum = 3:1, stirred continuously during the mixing process, and polyvinyl pyrrolidone was added as a dispersant and stirred for 1-2h to obtain a main catalyst solution; the mixed solution containing zinc oxide nanoparticles and boric acid was then added to the main catalyst solution and stirred for 30-60min; d. The mesoporous silica obtained in step a is added to the solution obtained in step c to load the catalyst into the pores of the mesoporous silica, stirred at room temperature for 2-4h, and then heated and stirred at 60-80°C for 4-8h; e. The product obtained in step d was filtered, washed, transferred to a vacuum drying oven, and dried at 60-80 ° C for 12-24 h; after drying, placed in a muffle furnace, calcined at 250-300 ° C for 2-3 h while passing nitrogen protection, and activated to remove organic matter and impurities on the surface to obtain a catalyst; the catalyst specific surface area BET ≥ 200 m² / g; The pretreatment process of organic montmorillonite is as follows: dispersing montmorillonite in toluene, stirring and reacting at 90°C for 3 hours to allow the organic modifier to be inserted into the interlayer of montmorillonite, and then filtering, washing, and drying to obtain organized montmorillonite; dispersing the organized montmorillonite in an inert solvent of toluene, and ultrasonically treating the montmorillonite suspension before adding it to the reaction system; and vacuum extraction after adding it to the reaction system.

2. The method for preparing polyethylene succinate according to claim 1, wherein The molar ratio of succinic acid to ethylene glycol is 1:(1.2-1.5); the added amount of organic montmorillonite is 2-5% of the theoretical output mass of polyethylene succinate; the added amount of glass fiber is 10-25% of the theoretical output mass of polyethylene succinate; and the added amount of nano-silica is 3-8% of the theoretical output mass of polyethylene succinate.

3. The method for preparing polyethylene succinate according to claim 1, wherein The amount of the silane coupling agent is 1-3% of the mass of the mesoporous silica, the amount of the zinc oxide nanoparticles is 5-10% of the total mass of the main catalyst, the amount of boric acid is 2-5% of the total mass of the main catalyst; the amount of polyvinyl pyrrolidone is 0.5-1% of the mass of the tetrabutyl titanate ethanol solution; and the loading amount of the catalyst is 20-40%.

4. A polyethylene succinate, characterized in that The poly(ethylene succinate) is prepared by the preparation method of any one of claims 1 to 3.

5. Use of the polyethylene succinate according to claim 4, characterized in that: Used to prepare water quality monitoring buoys.

6. The use of polyethylene succinate according to claim 5, characterized in that: The method for preparing the water quality monitoring buoy comprises the following steps: Ⅰ. In a high-speed mixer, first add polyethylene succinate particles, then add hindered amine light stabilizer, maleic anhydride grafted polyethylene succinate, and stir at 50-80 ° C for 5-10 minutes; then add nano-silver antibacterial agent, continue stirring, then add nano-calcium carbonate and graphene dispersion, and continue stirring for 10-20 minutes; Ⅱ. The material obtained in step Ⅰ is added to a twin-screw extruder for melt blending and extrusion. At the same time, During the extrusion process, the carbon nanotube suspension is added to a twin-screw extruder and mixed with other materials, and the screw speed is controlled at 100-300 rpm; it is then extruded through a mold into the shape of a water quality monitoring buoy, and then cooled and shaped by air cooling or water cooling to obtain a water quality monitoring buoy.

7. The use of polyethylene succinate according to claim 6, characterized in that: The mass proportions of the raw materials are as follows: polyethylene succinate: 100 parts; carbon nanotubes: 1-3 parts; hindered amine light stabilizer: 0.5-2 parts; nano silver antibacterial agent: 0.3-1 parts; Graphene: 0.5-2 parts; Maleic anhydride grafted polyethylene glycol succinate: 5-15 parts; Nano calcium carbonate: 5-15 parts.

8. The use of polyethylene succinate according to claim 6, characterized in that: The carbon nanotube suspension is prepared by placing carbon nanotubes in a mixed acid solution of concentrated nitric acid and concentrated sulfuric acid, reflux-treating the solution at 60-80°C for 2-4 hours, washing the solution with deionized water until neutral, and drying the solution to obtain carboxylated carbon nanotubes; dissolving polyvinyl alcohol in deionized water to prepare a solution with a mass fraction of 1-5%, adding the carboxylated carbon nanotubes, ultrasonically treating the solution, centrifuging the solution, and drying the solution to obtain polyvinyl alcohol-coated carbon nanotubes; and adding the solution to N,N-dimethylformamide, ultrasonically dispersing the solution or mechanically stirring the solution to form a suspension. The nano-calcium carbonate dispersion is prepared by surface-modifying the nano-calcium carbonate with fatty acid and titanate coupling agent, adding a silane coupling agent, and stirring the solution at 80-120°C for 1-2 hours to organicize the surface. The graphene dispersion is prepared by ultrasonically exfoliating the graphene in an organic solvent or water to prepare a uniform dispersion.

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