Foamed polyphenyl ether bead and preparation method thereof

Abstract

The invention discloses a foamed polyphenyl ether bead and a preparation method thereof. The material is prepared by compounding polyphenyl ether, a styrene polymer, a three-dimensional fiber microsphere reinforcement, a CNTs coated SiO2 core-shell nucleating agent, modified resin, a flame retardant and an antioxidant according to a specific ratio. The innovation of the invention lies in that a three-dimensional reinforcement with glass beads as a core and carbon fibers as a network and a composite foaming agent with silicon dioxide coated with carbon nanotubes are introduced to synergistically improve the cellular structure and mechanical properties. The preparation process comprises the key steps of component drying, melt blending granulation, carbon dioxide physical foaming under an autoclave aqueous dispersion system and the like. Through component design and surface modification, the foamed bead has the advantages of light weight, high strength, flame retardance and uniform foam structure, and is suitable for the fields of high-end heat insulation and bearing.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, specifically to a foamed polyphenylene ether bead and its preparation method. Background Technology

[0002] Polyphenylene oxide (PPE or PPO, hereinafter referred to as PPE) resin is a high-performance engineering plastic with excellent heat resistance, dimensional stability, flame retardancy, and electrical insulation properties. Its foamed products have broad application prospects in lightweighting, heat insulation, sound insulation, and high load-bearing applications. However, pure PPE resin has high melt strength and viscosity, and its foaming window is narrow, making it difficult to obtain high-ratio foamed beads with uniform and fine cells. To improve its processing and foaming properties, a common approach is to blend it with styrene-based polymers (such as high-impact polystyrene HIPS). However, this method often sacrifices some of the material's heat resistance and mechanical strength while improving processability.

[0003] In existing technologies, researchers have explored various approaches to improve the performance of PPE-based foamed materials: First, chemical modification (such as bromination and grafting) introduces active groups to improve the compatibility of PPE with other components; second, the addition of inorganic fillers or fibers (such as glass fiber and carbon fiber) enhances mechanical properties, but this often leads to deterioration of melt flowability, affecting foaming; third, a combination of physical or chemical foaming agents with nucleating agents (such as talc and nano-calcium carbonate) is used to regulate the cell structure. However, these methods often struggle to simultaneously achieve high melt strength (to support cell growth), efficient heterogeneous nucleation (to obtain uniform and fine cells), and significant structural reinforcement (to maintain high mechanical properties). In particular, traditional reinforcing fillers tend to cause cell coarsening or merging during the foaming process, while conventional nucleating agents have limited efficiency.

[0004] Therefore, developing an innovative composite material system that can synergistically address the balance issues of processability, cell structure uniformity, mechanical strength, and functionality (such as flame retardancy) in polyphenylene ether foam materials has significant technological and application value. This invention is proposed against this backdrop.

[0005] Polyphenylene oxide (PPE) resin is a high-performance engineering plastic with excellent heat resistance, dimensional stability, flame retardancy, and electrical insulation properties. Its foamed products have broad application prospects in lightweighting, thermal insulation, sound insulation, and high load-bearing applications. However, the inherent high melt strength and high melt viscosity of pure PPE result in an extremely narrow foaming window, making it difficult to achieve stable and uniform expansion. The conventional method of blending with styrene-based resins to improve processing flowability reduces processing difficulty but often significantly sacrifices the intrinsic heat resistance and mechanical strength of the material, failing to meet the comprehensive performance requirements of high-end applications. Traditional fiber or particulate reinforcements (such as chopped glass fibers and mineral fillers) introduced to improve mechanical properties severely hinder melt flow during processing and act as defect points, inducing cell coarsening, merging, or rupture, making it difficult to obtain foams with both high mechanical properties and a fine, uniform cell structure. Commonly used inorganic nucleating agents (such as talc and calcium carbonate) have limited dispersibility in polymer melts and low heterogeneous nucleation efficiency, resulting in low cell density and wide size distribution. Current technologies lack advanced nucleating agent designs that can efficiently induce heterogeneous nucleation without impairing melt rheological properties. Adding conventional flame retardants (especially high-filling-content inorganic hydroxides) severely deteriorates the processing flowability and mechanical properties of materials, while some brominated flame retardants pose risks related to thermal stability and environmental compliance. Minimizing the negative impact on the foaming process and the physical properties of the final product while ensuring flame retardant efficacy remains a long-standing challenge. Summary of the Invention

[0006] Technical problem to be solved: The purpose of this invention is to solve the technical difficulties of existing polyphenylene ether foam materials in terms of high strength and fine and uniform pores.

[0007] Technical solution: A type of foamed polyphenylene ether beads, comprising, by weight, the following raw materials: 70-80 parts polyphenylene ether, 20-30 parts styrene-based polymer (filler-like), 5-8 parts three-dimensional fiber microsphere reinforcement, 1.5-2 parts inorganic nucleating foaming agent, 5-10 parts modified resin, 1-10 parts flame retardant, 0.1-0.5 parts antioxidant 1010; 0.01-0.05 parts sodium dodecylbenzenesulfonate, 0.01-0.05 parts dispersant, and 0.5-0.8 parts dispersant. Wherein, the filler-like styrene polymer is at least one of GPPS, ABS, SBS, MBS, ASA, and SPS; The three-dimensional fiber microsphere reinforcement is a core-shell network structure with a particle size of 1-3 mm, consisting of solid glass microspheres as the core, short-cut carbon fibers as the network, and polyethylene as the binder. The inorganic nucleating foaming agent is a CNTs@SiO2 core-shell structured composite material; The modified resin is a low molecular weight polyphenylene ether or a styrene-maleic anhydride copolymer. The flame retardant is decabromodiphenyl ethane or surface-modified magnesium hydroxide.

[0008] The above-mentioned method for preparing foamed polyphenylene ether beads includes the following steps: S1. Drying and Blending Granulation: Polyphenylene ether, modified resin, antioxidant 1010, styrene-based filler, inorganic nucleating foaming agent, and flame retardant are dried separately, and then fed into a twin-screw extruder according to the formula. The feed rate is 4-5 kg / h, the screw speed is 250-300 r / min, and the temperature is 180-270℃. The mixture is then blended and granulated to obtain a length of 1-3 mm and a diameter of 0.5-1.5 mm. Finally, the granules are dried by forced air at 60-80℃ for 4-6 h and by vacuum drying at 100-120℃ for 4-6 h. S2. Preparation of foamed beads: Mix 90-100 parts of the above-mentioned dried granules, 300-350 parts of deionized water, 0.01-0.05 parts of sodium dodecylbenzenesulfonate, and 0.5-0.8 parts of dispersant in an autoclave. Heat the autoclave to 180°C at a heating rate of 2°C / min and hold for 8 min. Add carbon dioxide to the autoclave to make the internal pressure 8 MPa. Then open the valve at the bottom of the autoclave to discharge the dispersion into the air. At the same time as discharging, carbon dioxide gas should be injected to maintain the pressure inside the autoclave at 8 MPa to obtain foamed beads.

[0009] Preferably, the method for preparing the polyphenylene ether includes the following steps: S11. Under N2 protection, PPE is dissolved in chlorobenzene solvent, NBS is added as a brominating agent, and benzoyl peroxide is used as an initiator. The mixture is stirred and reacted at 70-90℃ for 4-5 hours. S12. Pour the reaction solution into anhydrous ethanol to obtain an orange-yellow flocculent precipitate; after standing for 20-24 hours, filter, wash with anhydrous ethanol and deionized water in sequence, and dry in a vacuum oven at 40-60℃ for 48 hours to obtain brominated polyphenylene ether.

[0010] Preferably, the preparation steps of the three-dimensional fiber microsphere reinforcement include: drying solid glass microspheres at 80-100℃ for 1-2 hours, mixing solid glass microspheres, chopped carbon fibers, and polyethylene adhesive in a weight ratio of 100:(10-20):5, adding the mixture to a high-speed mixer and heating it to 130-150℃ to melt the adhesive, stirring to make the fibers entangle and adhere to the surface of the glass microspheres; cooling and solidifying the mixture and sieving it to take particles with a diameter of 1-3 mm, which are then sealed for later use.

[0011] Preferably, the preparation steps of the inorganic nucleating foaming agent CNTs@SiO2 include: S21. Add carbon nanotubes to concentrated nitric acid with a mass fraction of 65%-68%, reflux at 80-90℃ for 4-6 hours, wash repeatedly with deionized water until the pH of the filtrate is 6.5-7.0, and then vacuum dry at 80-100℃ for 8-12 hours to obtain acidified carbon nanotubes. S22. Mix acidified carbon nanotubes with 0.5%-1% CTAB solution at a solid-liquid ratio of 1:50-1:80, and ultrasonically disperse at 200-300W for 30-60 min; then add ammonia water at 5-8 times the mass of carbon nanotubes, stir for 10-15 min, and then add tetraethyl orthosilicate at 10-15 times the mass of carbon nanotubes dropwise. Stir at a constant temperature of 25-30℃ for 4-6 h to obtain the reaction solution. S23. Centrifuge the reaction solution at 8000-10000 r / min for 10-15 min, collect the precipitate and wash it until neutral. After vacuum drying at 80-100℃ for 12-24 h, place it in a muffle furnace and calcine at 500-600℃ for 2-3 h to obtain the CNTs@SiO2 core-shell structure.

[0012] Preferably, the dispersant in step S2 is any one or more of calcium carbonate, kaolin, or talc with a particle size of 10-80 mesh.

[0013] Preferably, the stirring speed in step S2 is 200-300 r / min.

[0014] Preferably, the three-dimensional fiber microsphere reinforcement is soaked in a silane coupling agent KH550 ethanol solution for 1-2 hours and then vacuum dried.

[0015] Preferably, the flame retardant is magnesium hydroxide surface-modified by silane coupling with KH550, with a particle size of 100-500 mesh.

[0016] Beneficial Effects: This invention introduces a three-dimensional fiber microsphere reinforcement and a CNTs@SiO2 core-shell nucleating agent, and combines it with a matrix resin of a specific composition, resulting in a significant synergistic effect and thus achieving the following comprehensive beneficial effects: 1. As a highly efficient heterogeneous nucleating agent, the SiO2 core-shell structure greatly increases the nucleation density of the foam cells, effectively refines and homogenizes the foam cell size, thereby improving the uniformity of the material's thermal insulation, sound insulation and mechanical properties.

[0017] 2. The unique three-dimensional fiber microsphere reinforcement forms a multi-level reinforcement network in the matrix, which can significantly improve the compressive strength, modulus and impact resistance of foamed beads with extremely low addition amount. At the same time, due to its low density characteristics, it achieves high specific strength of the material.

[0018] 3. CNTs@SiO2 core-shell structure, as a highly efficient heterogeneous nucleating agent, greatly increases the cell nucleation density, effectively refines and homogenizes the cell size, thereby improving the uniformity of the material's thermal insulation, sound insulation and mechanical properties.

[0019] 4. By optimizing the flame retardant and surface modification, and ensuring its good compatibility with the matrix and reinforcement, the material can be endowed with excellent flame retardant properties (such as high flame retardant rating, low smoke and non-toxicity) at a low addition amount, while minimizing the negative impact on mechanical properties and foam structure.

[0020] 5. The melt blending and autoclave physical foaming processes adopted are mature and controllable. Key additives such as specific dispersants can be recycled and reused. The three-dimensional reinforcement can avoid the traditional long fiber processing problems. The overall solution has good potential for large-scale production and cost-effectiveness. Detailed Implementation

[0021] The present invention will be further described below with reference to embodiments. These embodiments are illustrative of the present invention, but the present invention is not limited to these embodiments: This invention provides foamed polyphenylene ether beads, comprising 70-80 parts by weight of polyphenylene ether, 20-30 fillers (styrene-based polymers), a uniformly dispersed three-dimensional fiber microsphere reinforcement structure, and an inorganic nucleating foaming agent to regulate the cell structure. The polyphenylene ether matrix exhibits high temperature resistance and high strength. Combined with GPPS and other fillers (styrene-based polymers), the complementary properties improve processing fluidity and toughness, solving the problems of difficult processing and high brittleness of traditional polyphenylene ether. 5-8 parts of the three-dimensional fiber microsphere reinforcement (1-3mm core-shell network structure: glass microsphere core, carbon fiber mesh, polyethylene binder) provide a rigid core and stress transfer. The mesh enhances compressive strength and provides uniform and stable reinforcement; 1.5-2 parts of CNTs@SiO2 core-shell nucleating foaming agent provide nucleation sites, while SiO2 regulates the rate and improves compatibility, forming uniform cells and preventing collapse; 5-10 parts of modified resin (low molecular weight polyphenylene ether or styrene-maleic anhydride copolymer) optimize flowability and interfacial bonding; 1-10 parts of decabromodiphenyl ethane or modified magnesium hydroxide enhance the flame retardant rating; 0.1-0.5 parts of antioxidant 1010 delay oxidative aging and inhibit the oxidative degradation of beads during processing and use, extending product lifespan.

[0022] The above-mentioned method for preparing foamed polyphenylene ether beads includes the following steps: S1. Drying and Blending Granulation: Polyphenylene ether, modified resin, antioxidant 1010, styrene-based filler, inorganic nucleating foaming agent, and flame retardant are dried separately, and then fed into a twin-screw extruder according to the formula. The feed rate is 4-5 kg / h, the screw speed is 250-300 r / min, and the temperature is 180-270℃. The mixture is then blended and granulated to obtain a length of 1-3 mm and a diameter of 0.5-1.5 mm. Finally, the granules are dried by forced air at 60-80℃ for 4-6 h and by vacuum drying at 100-120℃ for 4-6 h. S2. Preparation of foamed beads: Mix 90-100 parts of the above-mentioned dried granules, 300-350 parts of deionized water, 0.01-0.05 parts of sodium dodecylbenzenesulfonate, and 0.5-0.8 parts of dispersant in an autoclave. Heat the autoclave to 180°C at a heating rate of 2°C / min and hold for 8 min. Add carbon dioxide to the autoclave to make the internal pressure 8 MPa. Then open the valve at the bottom of the autoclave to discharge the dispersion into the air. At the same time as discharging, carbon dioxide gas should be injected to maintain the pressure inside the autoclave at 8 MPa to obtain foamed beads.

[0023] In step S1 above, the drying, blending, and granulation are differentiated by group because different components have different hygroscopicity and heat resistance (e.g., polyphenylene ether requires a higher drying temperature to remove water), to avoid bubbles or degradation during processing. The twin-screw blending and granulation ensures uniform dispersion of the three-dimensional fiber microsphere reinforcement, nucleating foaming agent, etc., by precisely controlling the speed and temperature. The secondary drying after granulation further removes water, laying a uniform substrate foundation for subsequent foaming. In step S2 above, the foaming preparation involves adding water, dispersant, and sodium dodecylbenzenesulfonate to the autoclave to ensure uniform suspension of the granules and prevent agglomeration. Slowly raising the temperature and maintaining it allows the granules to soften fully, facilitating CO2 penetration. Maintaining a high pressure of 8 MPa and adding CO2 during unloading ensures that CO2 forms uniform bubble nuclei within the granules and grows stably, preventing sudden pressure drops that could cause cell collapse, ultimately resulting in foamed beads with uniform performance.

[0024] In one embodiment, the method for preparing the polyphenylene ether includes the following steps: S11. Under N2 protection, PPE is dissolved in chlorobenzene solvent, NBS is added as a brominating agent, and benzoyl peroxide is used as an initiator. The mixture is stirred and reacted at 70-90℃ for 4-5 hours. S12. Pour the reaction solution into anhydrous ethanol to obtain an orange-yellow flocculent precipitate; after standing for 20-24 hours, filter, wash with anhydrous ethanol and deionized water in sequence, and dry in a vacuum oven at 40-60℃ for 48 hours to obtain brominated polyphenylene ether.

[0025] The N2 protection in step S11 isolates PPE from air, preventing oxidation during the heating reaction and also preventing the initiator benzoyl peroxide from decomposing prematurely upon contact with oxygen, thus ensuring a controllable reaction. Chlorobenzene, as a solvent, effectively dissolves PPE, providing a homogeneous environment for sufficient contact between the brominating reagent NBS and PPE molecules, ensuring a uniform bromination reaction. NBS is a mild brominating reagent that can precisely introduce bromine atoms into the PPE molecular chain, avoiding over-bromination that could lead to chain breakage. Benzoyl peroxide effectively initiates the bromination reaction. Anhydrous ethanol in step S12 is a poor solvent for PPE. Pouring the reaction solution into anhydrous ethanol can cause the brominated polyphenylene ether to precipitate rapidly and form a flocculent precipitate, thus separating the product from the solvent and unreacted reagents. Letting it stand for 20-24 hours can allow the precipitate to fully aggregate, which is convenient for subsequent filtration operations.

[0026] In one embodiment, the preparation steps of the three-dimensional fiber microsphere reinforcement include: drying solid glass microspheres at 80-100℃ for 1-2 hours; mixing solid glass microspheres, chopped carbon fibers, and polyethylene adhesive in a weight ratio of 100:(10-20):5; adding the mixture to a high-speed mixer and heating it to 130-150℃ to melt the adhesive; stirring to cause the fibers to entangle and adhere to the surface of the glass microspheres; cooling and solidifying, then sieving to obtain particles with a diameter of 1-3 mm, which are then sealed for later use. The above-mentioned drying process removes water and impurities, preventing voids during bonding and ensuring rigidity. The microspheres provide a rigid core, 10-20 parts of carbon fiber form a stress network, and 5 parts of adhesive balance bonding strength and network effect. Cooling and sieving ensure uniformity; sieving to 1-3 mm ensures uniformity; and sealing prevents moisture absorption and contamination.

[0027] In one embodiment, the preparation steps of the inorganic nucleating foaming agent CNTs@SiO2 include: S21. Add carbon nanotubes to concentrated nitric acid with a mass fraction of 65%-68%, reflux at 80-90℃ for 4-6 hours, wash repeatedly with deionized water until the pH of the filtrate is 6.5-7.0, and then vacuum dry at 80-100℃ for 8-12 hours to obtain acidified carbon nanotubes. S22. Mix acidified carbon nanotubes with 0.5%-1% CTAB solution at a solid-liquid ratio of 1:50-1:80, and ultrasonically disperse at 200-300W for 30-60 min; then add ammonia water at 5-8 times the mass of carbon nanotubes, stir for 10-15 min, and then add tetraethyl orthosilicate at 10-15 times the mass of carbon nanotubes dropwise. Stir at a constant temperature of 25-30℃ for 4-6 h to obtain the reaction solution. S23. Centrifuge the reaction solution at 8000-10000 r / min for 10-15 min, collect the precipitate and wash it until neutral. After vacuum drying at 80-100℃ for 12-24 h, place it in a muffle furnace and calcine at 500-600℃ for 2-3 h to obtain the CNTs@SiO2 core-shell structure.

[0028] In step S21, the reflux of concentrated nitric acid is a strong oxidation treatment that removes amorphous carbon and metallic catalyst impurities from the surface of CNTs, and destroys the end caps and sidewall defects of CNTs, generating a large number of carboxyl and hydroxyl groups on the surface. In S22, CTAB is a cationic surfactant. Its hydrophilic, positively charged quaternary ammonium salt head group is firmly adsorbed onto the negatively charged acidified CNT surface through electrostatic interaction. In S23, at a high temperature of 500-600℃, the CTAB used as a template in step y is completely decomposed, carbonized, and finally oxidized into CO2 and other gases that evaporate. Calcination further condenses the amorphous SiO2 shell, forming a strong ceramic shell.

[0029] In one embodiment, the dispersant in step S2 is calcium carbonate, kaolin, or talc with a particle size of 10-80 mesh. It can be recycled and reused after foaming. In the high shear field of melt blending, these inorganic particles with high hardness and large particle size are like countless tiny "grinding balls" and "isolation blocks". They can break up the agglomerates of CNTs@SiO2. At the same time, they occupy space themselves to prevent the broken CNTs@SiO2 particles from approaching each other and agglomerating again, thereby forcing their uniform distribution through physical means.

[0030] Example 1

[0031] The preparation method of inorganic nucleating foaming agent CNTs@SiO2 includes the following steps: S21. Carbon nanotubes were added to concentrated nitric acid with a mass fraction of 65%, refluxed at 80°C for 4 hours, washed repeatedly with deionized water until the pH of the filtrate was 7.0, and then vacuum dried at 80°C for 8 hours to obtain acidified carbon nanotubes. S22. Mix acidified carbon nanotubes with 0.5% CTAB solution at a solid-liquid ratio of 1:50 and disperse by ultrasonication at 200W for 30 min; then add ammonia water at 5 times the mass of carbon nanotubes, stir for 10 min, and then add tetraethyl orthosilicate at 10 times the mass of carbon nanotubes dropwise. Stir and react at 25℃ for 4 h to obtain the reaction solution. S23. Centrifuge the reaction solution at 8000 r / min for 10 min, collect the precipitate and wash it until neutral. After vacuum drying at 80℃ for 12 h, place it in a muffle furnace and calcine at 500℃ for 2 h to obtain the CNTs@SiO2 core-shell structure.

[0032] Example 2

[0033] The preparation method of polyphenylene ether includes the following steps: S11. Under N2 protection, PPE was dissolved in chlorobenzene solvent, NBS was added as a brominating agent, and benzoyl peroxide was used as an initiator. The mixture was stirred and reacted at 80°C for 4 hours. S12. Pour the reaction solution into anhydrous ethanol to obtain an orange-yellow flocculent precipitate; after standing for 20 h, filter, wash with anhydrous ethanol and deionized water in sequence, and dry in a vacuum oven at 60 °C for 48 h to obtain brominated polyphenylene ether.

[0034] Example 3

[0035] The preparation steps of the three-dimensional fiber microsphere reinforcement include: drying solid glass microspheres at 100℃ for 2 hours, mixing solid glass microspheres, chopped carbon fibers (treated with concentrated nitric acid reflux to introduce carboxyl groups on the surface), and polyethylene adhesive in a weight ratio of 100:20:5, heating to 130℃ in a high-speed mixer to melt the adhesive, stirring to make the fibers entangle and adhere to the surface of the glass microspheres; after cooling and solidification, sieving, taking 3mm particle size particles, sealing for later use, and then soaking the three-dimensional fiber microsphere reinforcement in a silane coupling agent KH550 ethanol solution for 2 hours and then vacuum drying.

[0036] Example 4

[0037] A type of foamed polyphenylene ether beads, by weight, comprises the following raw materials: 80 parts polyphenylene ether, 20 parts styrene-based polymer (filler-like), 5 parts three-dimensional fiber microsphere reinforcement, 2 parts inorganic nucleating foaming agent, 5 parts modified resin, 5 parts flame retardant, and 0.5 parts antioxidant 1010. Wherein, the filler-like styrene polymer is GPPS; the modified resin is 25000g / mol polyphenylene ether; and the flame retardant is decabromodiphenyl ethane.

[0038] The above-mentioned method for preparing foamed polyphenylene ether beads includes the following steps: S1. Drying and Blending Granulation: Polyphenylene ether, modified resin, and antioxidant 1010 are dried at 120℃ for 4 hours; styrene-based polymer (filler), inorganic nucleating foaming agent, and flame retardant are dried at 80℃ for 3 hours; the mixture is fed into a twin-screw extruder at a feed rate of 4 kg / h, screw speed of 300 r / min, and temperature of 220℃ to obtain granules with a length of 3 mm and a diameter of 1.0 mm; the granules are then dried by forced air drying at 80℃ for 4 hours and vacuum drying at 100℃ for 4 hours. S2. Preparation of foamed beads: 100 parts of the above granules, 350 parts of deionized water, 0.05 parts of sodium dodecylbenzenesulfonate, and 0.5 parts of kaolin are mixed in an autoclave at 250 r / min and stirred. The autoclave is heated to 180°C at a heating rate of 2°C / min and held at that temperature for 8 min. Carbon dioxide is added to the autoclave to make the internal pressure 8 MPa. Then, the valve at the bottom of the autoclave is opened to discharge the dispersion into the air. At the same time as discharging, carbon dioxide gas is injected to maintain the pressure inside the autoclave at 8 MPa, thus obtaining foamed beads.

[0039] Example 5

[0040] A type of foamed polyphenylene ether beads, by weight, comprises the following raw materials: 70 parts polyphenylene ether, 30 parts styrene-based polymer (filler-like), 8 parts three-dimensional fiber microsphere reinforcement, 1.5 parts inorganic nucleating foaming agent, 8 parts modified resin, 5 parts flame retardant, and 0.5 parts antioxidant 1010; Wherein, the filler-like styrene polymer is ABS; the modified resin is 25000 g / mol polyphenylene ether; and the flame retardant is magnesium hydroxide with a particle size of 300 mesh, which is surface modified by silane coupling with KH550.

[0041] The above-mentioned method for preparing foamed polyphenylene ether beads includes the following steps: S1. Drying and Blending Granulation: Polyphenylene ether, modified resin, and antioxidant 1010 are dried at 120℃ for 4 hours; styrene-based filler, inorganic nucleating foaming agent, and flame retardant are dried at 80℃ for 3 hours; the mixture is fed into a twin-screw extruder at a feed rate of 4 kg / h, screw speed of 300 r / min, and temperature of 220℃ to obtain granules with a length of 3 mm and a diameter of 1.0 mm; the granules are then dried by forced air drying at 80℃ for 4 hours and vacuum drying at 100℃ for 4 hours. S2. Preparation of foamed beads: 90 parts of the above granules, 300 parts of deionized water, 0.05 parts of sodium dodecylbenzenesulfonate, and 0.5 parts of calcium carbonate are mixed in an autoclave at 250 r / min and stirred. The autoclave is heated to 180°C at a heating rate of 2°C / min and held at that temperature for 8 min. Carbon dioxide is added to the autoclave to make the internal pressure 8 MPa. Then, the valve at the bottom of the autoclave is opened to discharge the dispersion into the air. At the same time as discharging, carbon dioxide gas is injected to maintain the pressure inside the autoclave at 8 MPa to obtain foamed beads.

[0042] Example 6

[0043] A type of foamed polyphenylene ether beads, by weight, comprises the following raw materials: 75 parts polyphenylene ether, 25 parts styrene-based polymer (filler-like), 8 parts three-dimensional fiber microsphere reinforcement, 1.5 parts inorganic nucleating foaming agent, 8 parts modified resin, 5 parts flame retardant, and 0.5 parts antioxidant 1010. Wherein, the filler-like styrene polymer is SPS; the modified resin is 25000 g / mol polyphenylene ether; and the flame retardant is magnesium hydroxide with a particle size of 300 mesh, which is surface-modified by silane coupling with KH550.

[0044] The above-mentioned method for preparing foamed polyphenylene ether beads includes the following steps: S1. Drying and Blending Granulation: Polyphenylene ether, modified resin, and antioxidant 1010 are dried at 100℃ for 4 hours; styrene-based filler, inorganic nucleating foaming agent, and flame retardant are dried at 60℃ for 4 hours; the mixture is fed into a twin-screw extruder at a feed rate of 4 kg / h, screw speed of 300 r / min, and temperature of 220℃ to obtain granules with a length of 2 mm and a diameter of 1.0 mm; the granules are then dried by forced air drying at 80℃ for 4 hours and vacuum drying at 100℃ for 4 hours. S2. Preparation of foamed beads: 100 parts of the above granules, 300 parts of deionized water, 0.05 parts of sodium dodecylbenzenesulfonate, and 0.5 parts of kaolin are mixed in an autoclave at 250 r / min and stirred. The autoclave is heated to 180°C at a heating rate of 2°C / min and held at that temperature for 8 min. Carbon dioxide is added to the autoclave to make the internal pressure 8 MPa. Then, the valve at the bottom of the autoclave is opened to discharge the dispersion into the air. At the same time as discharging, carbon dioxide gas is injected to maintain the pressure inside the autoclave at 8 MPa to obtain foamed beads.

[0045] Comparative Example 1 The difference between Comparative Example 1 and Example 4 is that no inorganic nucleating foaming agent CNTs@SiO2 is added.

[0046] Comparative Example 2 The difference between Comparative Example 2 and Example 4 is that the polyphenylene ether is not brominated, and a polyphenylene ether with a molecular weight of 30,000 g / mol is selected.

[0047] Comparative Example 3 The difference between Comparative Example 3 and Example 4 is that no three-dimensional fiber microsphere reinforcement is added.

[0048] Comparative Example 4 The difference between Comparative Example 4 and Example 4 is that: a foamed polyphenylene ether bead, by weight, comprises the following raw materials: 60 parts polyphenylene ether, 40 parts styrene-based polymer with filler-like structure, 10 parts three-dimensional fiber microsphere reinforcement, 5 parts inorganic nucleating foaming agent, 10 parts modified resin, 1 part flame retardant, and 0.5 parts antioxidant 1010. Comparative Example 5 The difference between Comparative Example 5 and Example 4 is that in step S1, the drying and blending granulation involves drying polyphenylene ether, modified resin, antioxidant 1010 h, filler-like styrene polymer, inorganic nucleating foaming agent, and flame retardant at 100°C for 3 h; feeding the mixture into a twin-screw extruder at a feed rate of 4 kg / h, screw speed of 300 r / min, and temperature of 220°C to obtain granules with a length of 3 mm and a diameter of 1.0 mm; the granules are then dried by forced air drying at 80°C for 4 h and vacuum drying at 100°C for 4 h.

[0049] Comparative Example 6 The difference between Comparative Example 6 and Example 4 is that no dispersant or surfactant is added. The preparation of foamed beads in step S2 is as follows: 100 parts of the above-mentioned granules and 350 parts of deionized water are mixed in an autoclave at 250 r / min and stirred. The autoclave is heated to 180°C at a heating rate of 2°C / min and kept at that temperature for 8 min. Carbon dioxide is added to the autoclave to make its internal pressure 8 MPa. Then the valve at the bottom of the autoclave is opened to discharge the dispersion into the air to obtain foamed beads. Carbon dioxide gas is injected at the same time as the discharge to maintain the pressure inside the autoclave at 8 MPa.

[0050] Comparative Example 7 The difference between Comparative Example 7 and Example 4 is that in the S2 foaming step, the discharge pressure is not controlled, that is, no CO2 is added during discharge, and the pressure inside the reactor naturally decreases. The remaining process parameters are the same as in Example 4.

[0051] Comparative Example 8 The difference between Comparative Example 8 and Example 4 is that the inorganic nucleating foaming agent is CNTs.

[0052] Comparative Example 9 The difference between Comparative Example 9 and Example 4 is that the microsphere reinforcement is experimental glass microspheres.

[0053] Performance testing: Test Example 1 Foaming rate: The apparent density (ρ) of the foamed beads was measured using the water displacement method. f ), and the theoretical density (ρ) of the substrate particles. p Compare and calculate the foaming rate:

[0054] Where, ρ p The measured density of the unfoamed blended granules (approximately 1.05 g / cm³) was taken. 3 ).

[0055] Test Example 2 Porosity and cell structure uniformity: Scanning electron microscopy was used to observe the cross-section of the foamed beads, count the number of cells per unit area, and calculate the average cell diameter and diameter distribution variance to assess pore density and uniformity. Porosity was qualitatively described as "high," "medium," and "low," and was comprehensively evaluated in conjunction with the average cell diameter (μm) and distribution uniformity.

[0056] Test Example 3 Compressive strength: The foamed beads were molded into standard specimens (size: 50mm×50mm×25mm), and compressed to 50% deformation using a universal testing machine at a rate of 2mm / min. The compressive strength (MPa) was recorded.

[0057] Test Example 4 Thermal conductivity: The thermal conductivity (W / (m·K)) of the molded product is measured using a heat flow thermal conductivity meter to evaluate its thermal insulation performance.

[0058] Table 1 Group Foaming ratio Average cell diameter (μm) Bubble diameter variance Hole uniformity Compressive strength (MPa) Thermal conductivity (W / (m·K)) Example 4 15.6 85.6 12.3 high 8.7 0.038 Example 5 13.3 88.2 13.1 high 9.1 0.039 Example 6 12.1 86.9 11.8 high 8.9 0.037 Comparative Example 1 9.4 142.5 45.6 Low 6.2 0.048 Comparative Example 2 9.7 155.3 52.1 Low 5.8 0.051 Comparative Example 3 8.2 92.4 18.7 middle 5.1 0.042 Comparative Example 4 6.6 168.9 61.3 Low 4.3 0.056 Comparative Example 5 6.8 136.8 38.4 middle 7.1 0.046 Comparative Example 6 4.3 158.2 55.7 Low 6.8 0.049 Comparative Example 7 7.5 138.4 42.6 middle 6.5 0.047 Comparative Example 8 8.1 140.9 43.7 Low 5.9 0.043 Comparative Example 9 10.7 105.7 37.6 middle 5.3 0.049 As can be seen from the table above, the foaming rate of Comparative Example 7 without pressure replenishment during unloading is significantly lower than that of Example 4, and the average cell diameter is larger and the diameter distribution variance is higher. This indicates that the pressure drop during unloading leads to unstable cell growth, with some cells merging or collapsing, resulting in a decrease in cell uniformity. The compressive strength and thermal conductivity of Comparative Example 7 are both worse than those of Example 4, further proving that the non-uniformity of the cell structure reduces the material's load-bearing capacity and thermal insulation effect. Maintaining constant pressure during unloading (as described in Example 4) plays a key role in maintaining a stable cell growth environment and obtaining a highly uniform cell structure, which is one of the important process advantages of this foaming method.

[0059] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A type of foamed polyphenylene ether beads, characterized in that, By weight, the raw material composition includes: 70-80 parts polyphenylene ether, 20-30 parts styrene-based polymer (filler-like), 5-8 parts three-dimensional fiber microsphere reinforcement, 1.5-2 parts inorganic nucleating foaming agent, 5-10 parts modified resin, 1-10 parts flame retardant, 0.1-0.5 parts antioxidant 1010; 0.01-0.05 parts sodium dodecylbenzenesulfonate, 0.01-0.05 parts dispersant, and 0.5-0.8 parts dispersant. Wherein, the filler-like styrene polymer is at least one of GPPS, ABS, SBS, MBS, ASA, and SPS; The three-dimensional fiber microsphere reinforcement is a core-shell network structure with a particle size of 1-3 mm, consisting of solid glass microspheres as the core, short-cut carbon fibers as the network, and polyethylene as the binder. The inorganic nucleating foaming agent is a CNTs@SiO2 core-shell structured composite material; The modified resin is a low molecular weight polyphenylene ether or a styrene-maleic anhydride copolymer. The flame retardant is decabromodiphenyl ethane or surface-modified magnesium hydroxide.

2. The method for preparing foamed polyphenylene ether beads according to claim 1, characterized in that, Includes the following steps: S1. Drying and Blending Granulation: Polyphenylene ether, modified resin, antioxidant 1010, styrene-based filler, inorganic nucleating foaming agent, and flame retardant are dried separately, and then fed into a twin-screw extruder according to the formula. The feed rate is 4-5 kg / h, the screw speed is 250-300 r / min, and the temperature is 180-270℃. The mixture is then blended and granulated to obtain a length of 1-3 mm and a diameter of 0.5-1.5 mm. Finally, the granules are dried by forced air at 60-80℃ for 4-6 h and by vacuum drying at 100-120℃ for 4-6 h. S2. Preparation of foamed beads: Mix 90-100 parts of the above-mentioned dried granules, 300-350 parts of deionized water, 0.01-0.05 parts of sodium dodecylbenzenesulfonate, and 0.5-0.8 parts of dispersant in an autoclave. Heat the autoclave to 180°C at a heating rate of 2°C / min and hold for 8 min. Add carbon dioxide to the autoclave to make the internal pressure 8 MPa. Then open the valve at the bottom of the autoclave to discharge the dispersion into the air. At the same time as discharging, carbon dioxide gas should be injected to maintain the pressure inside the autoclave at 8 MPa to obtain foamed beads.

3. The foamed polyphenylene ether beads according to claim 1, characterized in that, The preparation method of the polyphenylene ether includes the following steps: S11. Under N2 protection, PPE is dissolved in chlorobenzene solvent, NBS is added as a brominating agent, and benzoyl peroxide is used as an initiator. The mixture is stirred and reacted at 70-90℃ for 4-5 hours. S12. Pour the reaction solution into anhydrous ethanol to obtain an orange-yellow flocculent precipitate; after standing for 20-24 hours, filter, wash with anhydrous ethanol and deionized water in sequence, and dry in a vacuum oven at 40-60℃ for 48 hours to obtain brominated polyphenylene ether.

4. The foamed polyphenylene ether beads according to claim 1, characterized in that, The preparation steps of the three-dimensional fiber microsphere reinforcement include: drying solid glass microspheres at 80-100℃ for 1-2 hours, mixing solid glass microspheres, chopped carbon fibers, and polyethylene adhesive in a weight ratio of 100:(10-20):5, adding the mixture to a high-speed mixer and heating it to 130-150℃ to melt the adhesive, stirring to make the fibers entwine and adhere to the surface of the glass microspheres; after cooling and solidification, sieving and taking particles with a diameter of 1-3 mm, sealing and storing for later use.

5. The foamed polyphenylene ether beads according to claim 1, characterized in that, The preparation steps of the inorganic nucleating foaming agent CNTs@SiO2 include: S21. Add carbon nanotubes to concentrated nitric acid with a mass fraction of 65%-68%, reflux at 80-90℃ for 4-6 hours, wash repeatedly with deionized water until the pH of the filtrate is 6.5-7.0, and then vacuum dry at 80-100℃ for 8-12 hours to obtain acidified carbon nanotubes. S22. Mix acidified carbon nanotubes with 0.5%-1% CTAB solution at a solid-liquid ratio of 1:50-1:80, and ultrasonically disperse at 200-300W for 30-60 min; then add ammonia water at 5-8 times the mass of carbon nanotubes, stir for 10-15 min, and then add tetraethyl orthosilicate at 10-15 times the mass of carbon nanotubes dropwise. Stir at a constant temperature of 25-30℃ for 4-6 h to obtain the reaction solution. S23. Centrifuge the reaction solution at 8000-10000 r / min for 10-15 min, collect the precipitate and wash it until neutral. After vacuum drying at 80-100℃ for 12-24 h, place it in a muffle furnace and calcine at 500-600℃ for 2-3 h to obtain the CNTs@SiO2 core-shell structure.

6. The method for preparing foamed polyphenylene ether beads according to claim 2, characterized in that, The dispersant mentioned in step S2 is any one or more of calcium carbonate, kaolin, or talc with a particle size of 10-80 mesh.

7. The method for preparing foamed polyphenylene ether beads according to claim 2, characterized in that, The stirring speed in step S2 is 200-300 r / min.

8. The foamed polyphenylene ether beads according to claim 1, characterized in that... The three-dimensional fiber microsphere reinforcement was soaked in silane coupling agent KH550 ethanol solution for 1-2 hours and then vacuum dried.

9. The foamed polyphenylene ether beads according to claim 1, characterized in that, The flame retardant is magnesium hydroxide with a particle size of 100-500 mesh, which is surface-modified by silane coupling with KH550.

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