A high-strength carbon dioxide-epoxide copolymer foam material

Abstract

A high-strength carbon dioxide-epoxide copolymer foam material belongs to the field of polymer materials technology. This foam material is composed of 100 parts of a self-toughening carbon dioxide-epoxide copolymer, 0-30 parts of polylactic acid, 0-15 parts of polyglycolic acid, and 5-30 parts of additives. The copolymer is obtained by catalytic copolymerization of carbon dioxide, alicyclic epoxides, propylene oxide, and aliphatic or alicyclic acid anhydrides. Self-toughening is achieved by embedding flexible anhydride segments in the molecular backbone, eliminating the need for external toughening agents such as PBAT. In preparation, the copolymer is first melt-blended and granulated with PLA and PGA, then extruded with additives using a twin-screw / single-screw extruder for foaming, followed by curing and compression molding. The resulting foam material has a foaming ratio of 60-70 times and a notched impact strength of 7.8-8.9 kJ / m². 2 It has a heat distortion temperature of 61~69℃, a biodegradability rate of over 92%, and combines high toughness, high heat resistance, and high foaming ratio.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, specifically to a high-strength carbon dioxide-epoxide copolymer foam material. Background Technology

[0002] The preparation of biodegradable polycarbonate materials through copolymerization of carbon dioxide and epoxides is an important direction for the resource utilization of greenhouse gases and the development of green chemistry. These materials, due to their environmental friendliness and potential degradability, show promise in areas such as disposable packaging and cushioning insulation materials. However, traditional CO2 copolymers, represented by polypropylene carbonate, generally suffer from insufficient mechanical properties, particularly poor toughness, low heat distortion temperature, and weak melt strength. This results in the impact resistance and dimensional stability of their directly foamed products failing to meet practical application requirements, thus limiting their commercialization.

[0003] To overcome the aforementioned shortcomings, existing technologies typically employ physical blending modification methods. For example, Chinese invention patent application CN116496542A discloses a method for preparing a carbon dioxide-based biodegradable foam material. This prior art uses a specific polypropylene carbonate-co-cyclohexyl propyl carbonate (PPCCP) as the main resin, modifies it by adding polylactic acid (PLA), and explicitly states that polybutylene adipate / terephthalate (PBAT) or polycaprolactone (PCL) must be added as toughening agents to obtain a foam material with excellent dimensional stability and toughness. Although this technical solution improves the material performance to some extent through composite modification, its core technical path has inherent limitations: a mandatory dependence on the externally added petroleum-based or chemically synthesized toughening agents (PBAT / PCL). This technical approach presents at least the following challenges: First, the added toughening agent and the matrix resins such as PPCCP and PLA are physically blended. Due to differences in molecular structure, there may be a risk of poor interfacial compatibility, affecting the homogeneity of the blend system and leading to fluctuations in material properties or the presence of weak points. Second, while introducing flexible toughening agents improves toughness, it often results in a decrease in properties such as rigidity, modulus, and heat distortion temperature. Achieving a balance in overall performance requires complex formulation adjustments. Third, toughening agents such as PBAT are expensive, and the environmental impact of their production and final degradation products still needs comprehensive evaluation. Moreover, multi-component blending increases the complexity of ingredient formulation, premixing, and processing, placing higher demands on the homogenization control of the production process.

[0004] Therefore, developing a novel material that, through molecular structure design, enables CO2-based copolymers to possess excellent toughness, thereby eliminating the reliance on external toughening agents in the preparation of high-performance foam materials, is of significant technical and economic importance for simplifying formulations, reducing costs, improving the uniformity and inherent environmental friendliness of material performance, and promoting the application of CO2-based polymers in the field of high-end foam packaging. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a high-strength carbon dioxide-epoxide copolymer foam material with high toughness, good heat resistance and high foaming ratio.

[0006] The technical solution adopted by this invention to solve its technical problem is: a high-strength carbon dioxide-epoxide copolymer foam material, prepared from raw materials comprising the following parts by weight: 100 parts of carbon dioxide-epoxide copolymer; 0-30 parts of polylactic acid (PLA); 0-15 parts of polyglycolic acid (PGA); and 5-30 parts of additives; wherein the carbon dioxide-epoxide copolymer is obtained by catalytic copolymerization of monomers comprising carbon dioxide, alicyclic epoxides, propylene oxide, and acid anhydride compounds, wherein the alicyclic epoxide is at least one of cyclopentane oxide and cyclohexane oxide, and the acid anhydride compound is at least one of aliphatic diacid anhydride or alicyclic anhydride.

[0007] The core of this invention lies in the use of a high-strength copolymer with an innovative molecular structure as the foaming matrix. By selecting alicyclic epoxides (epoxycyclopentane, epoxycyclohexane) and flexible alicyclic / alicyclic acid anhydrides for copolymerization, rigid and flexible segments are successfully "built into" the main chain of the copolymer molecule. The alicyclic epoxides provide a rigid cyclic structure, ensuring the material's basic strength, heat resistance, and gas barrier properties; while the introduction of flexible acid anhydrides acts as intramolecular toughening units, effectively absorbing and dispersing impact energy. This "rigid-flexible" structure designed from the molecular level gives the copolymer itself excellent toughness, thus eliminating the need for physically blended toughening agents such as PBAT and PCL, which are required in traditional formulations, when preparing the final foamed material. This not only simplifies the formulation system and reduces raw material costs and supply chain complexity, but more importantly, it avoids problems such as phase separation, uneven performance, or decreased long-term stability caused by poor compatibility between added toughening agents and the matrix, fundamentally improving the uniformity and overall reliability of the foamed material. Using this self-toughening copolymer as the matrix, and with adjustable PLA, PGA and additives, high-performance foamed materials with high toughness, good heat resistance, high foaming ratio and complete biodegradability can be flexibly designed.

[0008] Preferably, the aliphatic dicarboxylic anhydride is at least one of adipic anhydride, sebacic anhydride, or dodecanoic anhydride; and / or, the alicyclic anhydride is at least one of tetrahydrophthalic anhydride or hexahydrophthalic anhydride.

[0009] Specific selection of anhydride compounds aims to optimize monomers with the best toughening effect and reactivity. Aliphatic dicarboxylic anhydrides such as adipic anhydride, sebacic anhydride, and dodecanoic anhydride, with their straight-chain alkane molecular chains, exhibit excellent flexibility. Introducing them into the main chain significantly reduces the chain segment movement barrier, imparting excellent low-temperature toughness and high ductility to the material. Alicyclic anhydrides such as tetrahydrophthalic anhydride and hexahydrophthalic anhydride, on the other hand, possess both cyclic rigidity and aliphatic chain flexibility. While their toughening effect is slightly less than that of long-chain aliphatic anhydrides, they cause less loss of overall copolymer stiffness, contributing to a better balance between toughness and modulus. These specific anhydrides are preferred because they exhibit good reaction rates and controllability in multi-component copolymerization reactions with cyclohexane / cyclopentane oxide, propylene oxide, and CO2, are easily integrated into the polymer chain, and their degradation products are environmentally friendly. By selecting anhydrides with different carbon chain lengths or ring / chain structures, precise control can be achieved over the glass transition temperature, crystallization behavior, and mechanical properties of the final foamed material.

[0010] More preferably, the anhydride compound is a mixture of adipic anhydride and tetrahydrophthalic anhydride in a mass ratio of 1 to 3:1, more preferably 1.5:1. Using specific types and proportions of anhydride mixtures allows for finer control over the molecular chain structure of the copolymer. Optimizing the ratio of the two compounds can achieve a synergistic effect, resulting in a more ideal "rigid-flexible synergy" distribution in the molecular chain of the synthesized self-toughening copolymer. This ratio ensures that the total amount of flexible units meets the self-toughening requirements, while the introduction of alicyclic anhydrides can moderately constrain excessive softening caused by overly long aliphatic chains, allowing the copolymer to maintain high modulus and heat distortion temperature while achieving outstanding toughness.

[0011] Preferably, the molar ratio of each monomer in the preparation of the carbon dioxide-epoxide copolymer is: propylene oxide: alicyclic epoxide: acid anhydride compound = 10:3~12:2~8.

[0012] Propylene oxide is set as the primary chain growth unit and cost adjustment unit, serving as the baseline. The proportion of alicyclic epoxides provides the necessary rigid framework and heat distortion temperature; too low a proportion results in insufficient material rigidity, while too high a proportion leads to decreased toughness and processing difficulties. The proportion of anhydride compounds directly determines the content of built-in flexible segments and is the core of achieving self-toughening; too low a proportion results in insignificant toughening effect, while too high a proportion excessively sacrifices the material's stiffness, strength, and melt strength, which is detrimental to the stability of the foaming process. Within this preferred proportion range, it is possible to ensure that the synthesized copolymer has suitable molecular chain rigidity, sufficient flexible unit density, and good melt elasticity, thus enabling it to not only serve as a foaming matrix to withstand the stretching and expansion during the foaming process but also exhibit excellent impact and tear resistance in the final product, truly achieving the goal of eliminating the need for external toughening agents. More preferably, the ratio of PO: alicyclic epoxide: anhydride compound = 10:5~10:3~6.

[0013] Preferably, the polylactic acid (PLA) content is 5-20 parts. Limiting the PLA content to 5-20 parts is based on a comprehensive consideration of performance synergy and processability. Below 5 parts, its effect on improving rigidity and heat resistance is limited; above 20 parts, the compatibility challenges between PLA and the self-toughened PPCCP matrix during melt blending may lead to a weak phase interface, reducing the material's toughness and even affecting melt homogeneity and cell quality during foaming. Within this preferred range, PLA can be uniformly dispersed as a reinforcing phase, forming a good complementarity with the self-toughened matrix, resulting in an increased heat distortion temperature of the final foamed material without a significant decrease in impact strength.

[0014] Preferably, the content of polyglycolic acid (PGA) is 1-8 parts. Controlling its content within this range is based on a balance between degradation rate regulation and material properties. Adding 1-3 parts of PGA can act as an effective degradation rate regulator, guiding the material to begin degradation more uniformly under composting conditions. Adding 5-8 parts can further accelerate the overall degradation rate without significantly impairing the material's toughness, and may also contribute additionally to the material's heat distortion temperature due to its higher crystallinity. However, excessively high PGA content can lead to compatibility issues due to the polarity difference between PGA and the matrix resin, and PGA itself is relatively brittle, increasing the brittleness of the foamed material. Therefore, this preferred range ensures that good mechanical and processing properties of the foamed material are maintained while achieving the desired degradation performance.

[0015] Preferably, the additives include compatibilizers, crosslinking agents, nucleating agents, and physical foaming agents. The scientific formulation of the additive system is also a key guarantee for the successful preparation of this high-performance foamed material. Compatibilizers are used to improve the interfacial compatibility between the self-toughening matrix and the added PLA / PGA, promote the uniform dispersion of each component during melt blending, prevent phase separation, and ensure the uniformity and stability of material properties. Crosslinking agents can induce the matrix resin to form a suitable crosslinking network during processing. This is a core means to improve melt strength and prevent cell merging or rupture during foaming, directly determining whether a high-ratio, uniformly fine-celled foam can be obtained. Nucleating agents provide a large number of nucleation sites for heterogeneous nucleation of bubbles, significantly increasing cell density, making the cell structure more uniform and smaller in size, thereby improving the compression resilience and cushioning performance of the foamed material. Physical foaming agents provide the foaming motive force. These four additives work synergistically and are indispensable, jointly ensuring the successful transformation from resin to high-quality foamed products.

[0016] Specifically, the compatibilizer is a composite of succinic anhydride and polytrimethylene carbonate; the crosslinking agent is benzoyl peroxide or dicumyl peroxide; the nucleating agent is at least one of talc, silica, titanium dioxide or magnesium oxide; and the physical foaming agent is carbon dioxide or azodicarbonamide.

[0017] Specific optimization of various additives aims to match the chemical properties and processing requirements of the self-toughened polycarbonate matrix. A composite of succinic anhydride and polytrimethylene carbonate is used as a compatibilizer; its anhydride functional groups can react with the terminal hydroxyl or ester groups of PLA / PGA, while the polytrimethylene carbonate segments have good compatibility with the matrix of this invention, thus efficiently "bridging" different components at the interface. Benzoyl peroxide or dicumyl peroxide is chosen as a crosslinking agent because its decomposition temperature matches well with the processing temperature window of the blend system, enabling controllable crosslinking and avoiding excessive crosslinking that could lead to material embrittlement or processing difficulties. Talc and silica are classic and efficient nucleating agents; their flake or granular morphology and surface properties facilitate dispersion in the polymer melt, providing numerous stable bubble nucleation sites. Carbon dioxide or azodicarbonamide is chosen as a physical foaming agent primarily for environmental and process considerations: CO2 is clean and non-toxic, leaving no residue after foaming; azodicarbonamide has a controllable decomposition temperature and a large gas generation rate. The combination of these specific additives, through optimized formulation, can maximize synergistic effects, ensuring the stability of the foaming process and the excellent performance of the products.

[0018] Preferably, the catalytic system used in the preparation of the carbon dioxide-epoxide copolymer includes triethylboron and quaternary ammonium salt.

[0019] A catalytic system composed of triethylboron (TEB) and a quaternary ammonium salt is a highly efficient formulation suitable for the copolymerization of carbon dioxide, epoxides, and acid anhydrides. Triethylboron, as a Lewis acid, activates the carbonyl groups in epoxides and acid anhydrides; the quaternary ammonium salt, acting as a nucleophile or co-catalyst, provides active species for initiation and propagation. This catalytic system offers advantages such as high activity, relative insensitivity to water and oxygen, and a good balance between the copolymerization rates of each monomer.

[0020] The quaternary ammonium salt is preferably at least one of tetrabutylammonium bromide, tetrabutylammonium chloride, methyltrioctylammonium chloride, or bis(triphenylphosphine)ammonium chloride. More preferably, the molar ratio of triethylboron to the quaternary ammonium salt in the catalytic system is 1:0.5~2, and even more preferably 1:1. Controlling the molar ratio of triethylboron to the quaternary ammonium salt at 1:0.5~2, especially 1:1, achieves optimal synergistic catalytic balance, ensuring sufficient initiation and chain growth rates while maintaining the stability of the catalytic system and the controllability of the copolymerization reaction. This results in a self-toughening copolymer with a moderate molecular weight distribution and a sequence structure that meets design expectations, providing an ideal matrix resin for subsequent foaming processing.

[0021] Preferably, the preparation method of the foamed material includes the following steps:

[0022] (1) The carbon dioxide-epoxide copolymer is melt-blended and granulated with optional polylactic acid and polyglycolic acid to obtain the foaming main material;

[0023] (2) After mixing the foaming main material with the additive, the foaming is carried out by extrusion foaming using a twin-screw extruder and a single-screw extruder connected in series to obtain foamed beads;

[0024] (3) After the foamed beads are cured, they are molded in the mold to obtain the biodegradable foamed material.

[0025] The preparation method is scientifically designed with clear steps, taking into account both the feasibility of industrial production and the optimization of product performance. The melt blending granulation in step (1) ensures that the self-toughened PPCCP matrix and modified resins such as PLA and PGA are fully pre-dispersed and compatible, forming a uniform and stable foaming masterbatch, which lays the foundation for subsequent stable foaming. Step (2) adopts a twin-screw and single-screw series extrusion foaming technology: the twin-screw extruder has a strong shearing and mixing effect, which can ensure that various additives such as foaming agents, crosslinking agents, and nucleating agents are efficiently and uniformly mixed and initially plasticized with the molten resin; the series single-screw extruder mainly plays the role of homogenization, pressure stabilization and metering conveying. Its relatively gentle shear and stable pressure field are conducive to the dissolution, diffusion and formation of uniform foam nuclei of supercritical CO2 or decomposed foaming gas in the melt. Finally, controllable expansion is achieved by pressure release at the die, resulting in foamed beads with excellent cell structure. Step (3) of curing and in-mold molding is the final shaping stage: curing balances the internal air pressure of the foamed beads with the external environment, resulting in a stable pre-foamed structure; in-mold molding using steam heating causes the beads to expand a second time and fuse together to form a complex-shaped final foamed product. This process is mature, controllable, and easy to implement for large-scale continuous production.

[0026] Preferably, in step (2), the screw length-to-diameter ratio of the twin-screw extruder is 30~40:1, and the processing temperature range is 135℃~160℃; the screw length-to-diameter ratio of the single-screw extruder is 30~35:1, and the processing temperature range is 140℃~160℃.

[0027] The length-to-diameter ratio of a twin-screw extruder provides a sufficiently long residence time and mixing zone to ensure that the resin is fully melted, the additives are uniformly dispersed, and the necessary initial reactions are completed. Processing temperature is a crucial control window: if the temperature is too low, the resin melt viscosity is high, resulting in uneven mixing and potentially incomplete decomposition of the crosslinking agent; if the temperature is too high, the melt strength decreases too rapidly, easily causing cell rupture and merging during foaming, making it difficult to form a closed-cell structure, and may also lead to resin thermal degradation.

[0028] The length-to-diameter ratio of a single-screw extruder enables the establishment of stable and sufficient die pressure in the homogenization section, preventing premature gas escape and ensuring that the gas in the melt reaches a supersaturated state. Its processing temperature is slightly higher than or equal to the end temperature of a twin-screw extruder, aiming to maintain good melt flowability. At the same time, precise temperature control regulates the viscoelasticity of the melt, ensuring that it is in the most suitable foaming state at the die exit.

[0029] Compared with existing technologies, this invention has the following advantages: Through molecular structure design, this invention introduces flexible anhydride units into the copolymer backbone, achieving self-toughening and high strength of the material itself. This completely eliminates the reliance on external toughening agents such as PBAT and PCL when preparing high-performance foamed materials. This not only solves the problems of poor compatibility, uneven performance, and increased cost caused by physical blending toughening, but also simplifies the formulation and process. The resulting foamed material maintains a high biodegradability rate while possessing excellent toughness, good heat resistance, and a high foaming ratio, achieving an ideal balance between mechanical properties, thermal properties, and biodegradability. It has significant advantages in reducing costs, improving performance, and promoting green packaging applications. Detailed Implementation

[0030] The present invention will be further described below with reference to specific embodiments, wherein Embodiment 1 is the best embodiment, and the process conditions in other embodiments not explicitly described are all in accordance with Embodiment 1.

[0031] Example 1

[0032] Synthesis of carbon dioxide-epoxide copolymer

[0033] In a nitrogen-filled glove box, 0.80 g (2.48 mmol) of tetrabutylammonium bromide catalyst and 2.48 mL of triethylboron (1.0 mol / L n-hexane solution) were added sequentially to a pre-dried 500 mL high-pressure reactor, with a molar ratio of triethylboron to tetrabutylammonium bromide of 1:1. Subsequently, 58.1 g (1.0 mol) of propylene oxide and 98.2 g (1.0 mol) of cyclohexane oxide were added, followed by an anhydride compound composed of 20.5 g of adipic anhydride and 13.7 g of tetrahydrophthalic anhydride. The molar ratio of each monomer was propylene oxide:cyclohexane oxide:anhydride compound = 10:10:4. The reactor was sealed, and the air inside was purged three times with high-purity carbon dioxide gas, then carbon dioxide was introduced to an initial pressure of 5.0 MPa. Stirring was started and the reaction system temperature was raised to 70℃. The reaction was carried out under these conditions for 8 hours, with the pressure maintained between 4.5 MPa and 5.5 MPa during the reaction using a back pressure valve. After the reaction was complete, the reactor was cooled to room temperature, and residual gas was slowly released. The reactor was opened, and the resulting viscous polymer product was dissolved in approximately 500 mL of chloroform. This solution was then added dropwise to a 1:1 mixture of ethanol and methanol under vigorous stirring to induce precipitation. The white flocculent solid was collected by filtration and washed three times with fresh ethanol. Finally, the solid product was dried in a vacuum drying oven at 50℃ for 48 hours to constant weight, yielding a white self-toughened PPCCP-1 polymer with a calculated yield of 92%.

[0034] Step 2: Preparation of toughening agent-free foamed materials

[0035] First, prepare the materials according to the following mass ratio: 100 parts of the self-made PPCCP-1 polymer, 15 parts of polylactic acid (brand name 4032D), and 3 parts of polyglycolic acid. The total amount of the auxiliary agent system is 15 parts, specifically including: 4 parts of compatibilizer (a complex of succinic anhydride and polytrimethylene carbonate, mass ratio 3:5), 0.5 parts of crosslinking agent dicumyl peroxide, 1.5 parts of talc nucleating agent with an average particle size of 3μm, and liquid carbon dioxide, which will be injected during the extrusion process, as the physical foaming agent.

[0036] The preparation process consists of three stages:

[0037] (1) Granulation of foaming master materials: PPCCP-1, polylactic acid and polyglycolic acid were melt-blended and granulated in a twin-screw extruder. The length-to-diameter ratio of the extruder screw was 40:1, and the processing temperature from the feeding section to the die head was set to 155℃, 160℃, 165℃ and 160℃, and the screw speed was 200 rpm. The extruded strip was cooled with water and then granulated to obtain uniform foaming masterbatch.

[0038] (2) Tandem Extrusion Foaming: The foaming masterbatch is premixed with compatibilizer, crosslinking agent, and nucleating agent until homogeneous. Foaming is performed using a tandem extrusion system consisting of a twin-screw and a single-screw. The premix is ​​fed into the main feed port of a twin-screw extruder with a screw length-to-diameter ratio of 36:1. The temperatures of each section are set as follows: Zone 1 135℃, Zone 2 145℃, Zone 3 150℃, Zone 4 155℃, and Die Head 155℃. In the melting section of the twin-screw, liquid carbon dioxide is injected as a physical foaming agent through a high-pressure metering pump. After thorough mixing and plasticization by the twin-screw, the melt enters a tandem single-screw extruder with a screw length-to-diameter ratio of 32:1 for homogenization, cooling, and pressurization. The temperatures are set at 140℃, 145℃, and 150℃ at the die head. The melt is finally extruded through a slit die maintained at 155°C, and the pressure is released instantly to achieve foaming. After being drawn and cooled, it is cut into cylindrical foam beads with a diameter of 3mm to 5mm.

[0039] (3) Curing and molding: The obtained foamed beads are cured at room temperature for 48 hours to balance the internal and external pressure. Then the cured beads are filled into a flat mold and heated with saturated steam at 120℃ and 1.3MPa for 5 minutes in the molding machine to make the beads expand and fuse into one piece. After pressure holding and cooling, the beads are demolded to obtain a foamed board with a thickness of about 20mm.

[0040] The performance of the foamed board prepared in Example 1 was tested, and the results are as follows: the apparent density of the material is 0.031 g / cm³. 3Its foaming ratio is calculated to be approximately 65 times; its heat distortion temperature is 66℃ under a load of 0.45MPa; according to standard controlled composting methods, the biodegradation rate reaches 92.8% after 56 days; the compressive strength at 10% deformation is 172kP; and the notched impact strength of the cantilever beam is 8.6kJ / m. 2 .

[0041] Example 2

[0042] In a nitrogen-filled glove box, a catalytic system consisting of triethylboron and tetrabutylammonium bromide in a molar ratio of 1:1 was added to a dry 500 mL high-pressure reactor. Subsequently, 58.1 g (1.0 mol) of propylene oxide, 29.5 g (0.3 mol) of cyclohexane oxide, and 20.4 g (0.2 mol) of adipic anhydride were added sequentially, with a monomer molar ratio of propylene oxide:cyclohexane oxide:adipic anhydride = 10:3:2. After replacing the air with carbon dioxide, the reaction was carried out at an initial pressure of 5.0 MPa and 70 °C for 8 h. The post-treatment was the same as in Example 1, yielding the self-toughening copolymer PPCCHP-2. Using 100 parts of the copolymer as the main material, 5 parts of polylactic acid, 1 part of polyglycolic acid, and an additive consisting of 4 parts compatibilizer, 0.5 parts dicumyl peroxide, and 1.5 parts talc (the physical foaming agent is injected CO2) were added. Following the two-step extrusion process described in Example 1, with a twin-screw temperature of 135℃~155℃ and a single-screw temperature of 140℃~150℃, foamed beads were prepared and molded. The resulting foamed material had a foaming ratio of 60 times, a heat distortion temperature of 61℃, and a notched impact strength of 7.8 kJ / m². 2 .

[0043] Example 3

[0044] In the polymerization reaction, the monomer molar ratio was propylene oxide:cyclohexane oxide:dodecanoic anhydride = 10:12:8, and the catalytic system and reaction conditions were the same as in Example 2. The resulting copolymer was designated PPCCP-3. Using 100 parts of this copolymer as the main material, 20 parts of polylactic acid, 8 parts of polyglycolic acid, and the same additive system as in Example 2 were added. Due to the high content of flexible units, the processing temperature was appropriately reduced in the extrusion foaming process to maintain sufficient melt strength: the temperatures of each section of the twin-screw extruder were set to 135℃, 140℃, 145℃, and 150℃, and the temperatures of the single-screw extruder were set to 140℃, 145℃, and 148℃. The resulting foamed material had a foaming ratio of 58 times, a heat distortion temperature of 69℃, and a notched impact strength of 8.9 kJ / m². 2 .

[0045] Example 4

[0046] Following the polymerization formulation and process of Example 1, a self-toughening copolymer PPCCHP-4 was synthesized. Without adding polylactic acid or polyglycolic acid, 100 parts of PPCCP-4 were directly mixed with 3 parts compatibilizer, 0.8 parts dicumyl peroxide, and 2 parts talc. The mixture was then foamed using the tandem extrusion foaming process of Example 1 (twin-screw extruder temperature 140-160℃, single-screw extruder temperature 145-160℃). The resulting foamed material exhibited a foaming ratio as high as 70 times, a heat distortion temperature of 58℃, and a notched impact strength of 8.0 kJ / m². 2 The biodegradation rate is 94.5% after 56 days.

[0047] Example 5

[0048] In the copolymer synthesis, the catalytic system used triethylboron and tetrabutylammonium chloride, with their molar ratio controlled at 1:0.5. The monomer feed ratio was optimized: propylene oxide:cyclohexane oxide:compound anhydride (adipic anhydride / tetrahydrophthalic anhydride mass ratio 1.5:1) = 10:7:4.5. The reaction was carried out at 5.5 MPa and 75°C for 10 h to obtain copolymer PPCCP-5. This polymerization reaction had a slightly longer induction period, but the later reaction was stable, and the polymer molecular weight distribution was relatively narrow. 100 parts of this copolymer were mixed with 10 parts polylactic acid, 3 parts polyglycolic acid, and standard additives, and foamed according to the process in Example 1. The resulting material exhibited balanced properties, a foaming ratio of 63 times, a heat distortion temperature of 64°C, and a notched impact strength of 8.3 kJ / m². 2 .

[0049] Example 6

[0050] The polymerization reaction used propylene oxide, cyclopentane oxide, and a compound anhydride (adipic anhydride / tetrahydrophthalic anhydride mass ratio of 3:1) as monomers, with a molar ratio of 10:8:5. The catalytic system was the same as in Example 1. Due to the difference in steric hindrance and reactivity between cyclopentane oxide and cyclohexane oxide, the reaction temperature was increased to 80°C to ensure reaction efficiency, yielding copolymer PPCCP-6. 100 parts of this copolymer were then foamed with 8 parts of polylactic acid, 5 parts of polyglycolic acid, and standard additives.

[0051] The resulting foamed material has very uniform and fine pores, a foaming ratio of 62 times, a heat distortion temperature of 63℃, and a notched impact strength of 8.5 kJ / m. 2 .

[0052] Example 7

[0053] In the polymerization stage, a catalytic system with a 1:1 molar ratio of triethylboron to tetrabutylammonium bromide was used, and the monomer feed molar ratio was propylene oxide:cyclohexane oxide:anhydride compound = 10:7.5:4.5. The anhydride compound was composed of sebacic anhydride and hexahydrophthalic anhydride in a 2:1 mass ratio. The reaction was carried out at an initial pressure of 5.2 MPa and a temperature of 72 degrees Celsius for 9 hours, followed by post-treatment to obtain the self-toughening copolymer PPCCP-7. Using 100 parts of this copolymer as the main material, 12 parts of polylactic acid, 4 parts of polyglycolic acid, and an additive consisting of 4.5 parts of succinic anhydride compatibilizer, 0.6 parts of benzoyl peroxide, and 1.5 parts of silica nucleating agent were added. CO2 was used as the physical foaming agent. The extrusion foaming process strictly follows the optimized parameters: the twin-screw extruder has an L / D ratio of 35:1 and the temperature gradually increases from 135℃ to 158℃; the single-screw extruder has an L / D ratio of 32:1 and the temperature range is 142℃~155℃.

[0054] The resulting foamed material has a foaming ratio of 66 times, a heat distortion temperature of 65℃, and a notched impact strength of 8.4 kJ / m². 2 The biodegradation rate is 93.0% after 56 days.

[0055] Example 8

[0056] The copolymer used 100 parts of the base resin PPCCP-1 obtained in Example 1, 20 parts of polylactic acid, and no polyglycolic acid was added. The additive system was the same as in Example 7. The upper limit of the processing temperature of the twin-screw extruder was slightly increased to 168°C to ensure that the PLA was completely melted and thoroughly blended with the matrix. During the extrusion foaming stage, to prevent thermal degradation of PLA, the upper limit of the processing temperature of both the twin-screw and single-screw extruders was controlled at 158°C.

[0057] The resulting foamed material has a foaming ratio of 61 times and a heat distortion temperature of 68℃, while its notched impact strength remains at 7.9 kJ / m. 2 .

[0058] Example 9

[0059] In the polymerization reaction, the catalytic system used triethylboron and methyltrioctylammonium chloride in a molar ratio of 1:2. The preferred monomer feed ratio was propylene oxide:cyclohexane oxide:(adipic anhydride / tetrahydrophthalic anhydride compound at a mass ratio of 1.5:1) = 10:6:3.5. The reaction was carried out at 5.0 MPa and 70°C for 7 hours to obtain copolymer PPCCP-8. Using 100 parts of PPCCP-8 as the main material, 8 parts of polylactic acid, 2 parts of polyglycolic acid, and the additives from Example 1 were added, and the copolymer was prepared using a general extrusion foaming process. The resulting foamed material had a fine and uniform cell structure, a foaming ratio of 64 times, a heat distortion temperature of 63°C, and a notched impact strength of 8.7 kJ / m². 2 .

[0060] Example 10

[0061] The copolymer used was PPCCP-1 obtained in Example 1. In the preparation of the foamed material, 0.8 parts of azodicarbonamide were used as the blowing agent component, premixed with the compatibilizer, 0.5 parts of dicumyl peroxide (crosslinking agent), and 1.0 part of titanium dioxide (nucleating agent) from Example 1. The main foaming material formulation was 100 parts of PPCCP-1, 10 parts of PLA, and 2 parts of PGA. Because the decomposition temperature of azodicarbonamide matches the system processing temperature, the extrusion foaming process required precise temperature control: the twin-screw extruder temperature was set to 140℃~165℃ to ensure complete decomposition of the blowing agent in the melt homogenization section; the single-screw temperature was set to 145℃~162℃ to maintain melt strength. Under these conditions, the foaming process was stable, and the resulting foamed material had a foaming ratio of 59 times, a heat distortion temperature of 64℃, and a notched impact strength of 8.1 kJ / m². 2 .

[0062] Comparative Example 1

[0063] Except for the acid anhydride compound, other conditions were consistent with those in Example 1 of this invention: the catalytic system was the same, the monomers were carbon dioxide, propylene oxide, and cyclohexane oxide, and no adipic anhydride or tetrahydrophthalic anhydride was added; the molar ratio of propylene oxide to cyclohexane oxide was 10:10. The reaction was carried out at the same pressure and temperature as in Example 1 for 8 hours to obtain the copolymer Ref-PPCCH. 100 parts of this copolymer were used as the matrix, and polylactic acid, polyglycolic acid, and additives were added in the same proportions as in Example 1 for foaming. Due to the poor toughness and low melt strength of this copolymer, it was extremely difficult to control a stable cell structure during extrusion foaming, resulting in uneven foam beads. The notched impact strength of the molded sheet was only 4.5 kJ / m². 2 Furthermore, the foaming ratio is only 45 times. Lacking the flexible anhydride segments designed in this invention, the copolymer itself cannot provide sufficient toughness, making it difficult to produce high-performance foamed materials.

[0064] Comparative Example 2

[0065] The same monomer types, proportions, and catalytic system as in Example 1 were used. However, the polymerization process was changed: all monomers and catalysts were added to the reactor at once, and then reacted for 8 hours under a single condition of 5.0 MPa and 70°C to obtain the random copolymer Random-PPCCP. Using 100 parts of this as the matrix, and formulated with the same PLA, PGA, and additives as in Example 1, foaming was performed using the same process. The resulting material properties were: a foaming ratio of 62 times, a heat distortion temperature of 64°C, and a notched cantilever beam impact strength of 7.5 kJ / m². 2 The decrease in toughness indicates that even with the use of flexible anhydrides, the random structure formed will have limited effect on improving toughness if the chain segment sequence cannot be optimized and controlled through specific polymerization processes.

[0066] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A high-strength carbon dioxide-epoxide copolymer foam material, characterized in that, It is prepared from raw materials comprising the following parts by weight: 100 parts of carbon dioxide-epoxide copolymer; 0-30 parts of polylactic acid; 0-15 parts of polyglycolic acid; and 5-30 parts of additives; The carbon dioxide-epoxide copolymer is prepared by catalytic copolymerization of monomers including carbon dioxide, alicyclic epoxides, propylene oxide and acid anhydride compounds. The alicyclic epoxide is at least one of cyclopentane oxide and cyclohexane oxide, and the acid anhydride compound is at least one of aliphatic dicarboxylic acid anhydride or alicyclic acid anhydride.

2. The high-strength carbon dioxide-epoxide copolymer foam material according to claim 1, characterized in that, The aliphatic dicarboxylic acid anhydride is at least one selected from adipic anhydride, sebacic anhydride, or dodecanoic anhydride; and / or... The alicyclic anhydride is at least one of tetrahydrophthalic anhydride or hexahydrophthalic anhydride.

3. The high-strength carbon dioxide-epoxide copolymer foam material according to claim 1, characterized in that, The molar ratio of each monomer used to prepare the carbon dioxide-epoxide copolymer is: propylene oxide: alicyclic epoxide: acid anhydride compound = 10:3~12:2~8.

4. The high-strength carbon dioxide-epoxide copolymer foam material according to claim 1, characterized in that, The content of polylactic acid is 5 to 20 parts.

5. The high-strength carbon dioxide-epoxide copolymer foam material according to claim 1, characterized in that, The content of polyglycolic acid is 1 to 8 parts.

6. The high-strength carbon dioxide-epoxide copolymer foam material according to claim 1, characterized in that, The additives include compatibilizers, crosslinking agents, nucleating agents, and physical foaming agents.

7. The high-strength carbon dioxide-epoxide copolymer foam material according to claim 6, characterized in that, The compatibilizer is a complex of succinic anhydride and polytrimethylene carbonate; The crosslinking agent is benzoyl peroxide or dicumyl peroxide; The nucleating agent is at least one of talc, silicon dioxide, titanium dioxide, or magnesium oxide; The physical foaming agent is carbon dioxide or azodicarbonamide.

8. A high-strength carbon dioxide-epoxide copolymer foam material according to any one of claims 1 to 7, characterized in that, In the preparation of the carbon dioxide-epoxide copolymer, the catalytic system used includes triethylboron and quaternary ammonium salt.

9. A high-strength carbon dioxide-epoxide copolymer foam material according to any one of claims 1 to 7, characterized in that, The preparation method includes the following steps: (1) The carbon dioxide-epoxide copolymer is melt-blended and granulated with optional polylactic acid and polyglycolic acid to obtain the foaming main material; (2) After mixing the foaming main material with the additive, the foaming is carried out by extrusion foaming using a twin-screw extruder and a single-screw extruder connected in series to obtain foamed beads; (3) After the foamed beads are cured, they are molded in the mold to obtain the biodegradable foamed material.

10. A high-strength carbon dioxide-epoxide copolymer foam material according to claim 9, characterized in that, In step (2), the twin-screw extruder has a screw length-to-diameter ratio of 30~40:1 and a processing temperature range of 135℃~160℃; the single-screw extruder has a screw length-to-diameter ratio of 30~35:1 and a processing temperature range of 140℃~160℃.