Anti-aging expandable polystyrene particles and preparation process thereof

Abstract

The invention belongs to the technical field of high polymer materials, and particularly relates to anti-aging expandable polystyrene particles and a preparation process thereof. The low-smoke halogen-free flame-retardant styrene resin is prepared from the following components in parts by weight: 100 to 120 parts of styrene, 200 to 300 parts of deionized water, 7 to 10 parts of a composite flame retardant, 0.3 to 0.6 part of an initiator, 1.5 to 3.0 parts of a nucleating agent, 0.7 to 1.2 parts of a composite toughening agent, 6 to 8 parts of a foaming agent, 0.2 to 0.8 part of a dispersing agent and 0.01 to 0.05 part of an emulsifying agent, the composite flame retardant is prepared by mixing modified graphene / boron nitride, ammonium polyphosphate and modified silicon dioxide; by designing the material, the contradiction that the mechanical property is reduced when the flame retardant property of traditional polystyrene is improved is overcome, collaborative optimization of the flame retardant property and the mechanical property is realized, and an organic-inorganic interpenetrating network structure is constructed through multi-component interface engineering. The components are accurately distributed and interacted on the nanoscale, so that the material has excellent flame retardance, ageing resistance, heat-conducting property and mechanical strength at the same time.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials technology, specifically relating to an anti-aging expandable polystyrene particle and its preparation process. Background Technology

[0002] Polystyrene, a general-purpose thermoplastic, is widely used in packaging, construction, and electronics due to its excellent electrical insulation, transparency, processability, and low cost. However, traditional polystyrene materials have significant limitations, including flammability, brittleness, poor heat resistance, and susceptibility to aging, which severely restricts its application in high-end fields. Particularly in building insulation materials and electronic component encapsulation, higher requirements are placed on the material's flame retardancy, mechanical properties, and long-term durability.

[0003] In recent years, domestic and international research on the modification of polystyrene has mainly focused on two aspects: flame retardancy and mechanical reinforcement. Regarding flame retardant modification, traditional halogenated flame retardants, while effective, pose environmental risks. Current research focuses on halogen-free flame retardant systems, such as intumescent flame retardants (IFR), phosphorus-nitrogen flame retardants, and nanofiller compounding techniques. For example, ammonium polyphosphate (APP) combined with melamine derivatives can form a char layer barrier effect, but when used alone, it is prone to migration and has poor compatibility with the matrix. Two-dimensional nanomaterials such as graphene and boron nitride (h-BN), due to their unique layered structure and high thermal stability, can improve both flame retardancy and thermal conductivity; however, the problem of nanoparticle agglomeration has not yet been completely solved.

[0004] In the field of anti-aging modification, ultraviolet radiation and thermo-oxidative aging are the main factors leading to the breakage of polystyrene molecular chains, yellowing, and performance degradation. Conventional antioxidants such as hindered phenols (e.g., BHT) and light stabilizers (e.g., benzotriazole) have some effect, but they suffer from the problem of small molecule migration loss. In recent years, constructing long-term stable systems by modifying nanomaterials with dopamine biomimetic technology has become a new approach. The catechol structure of polydopamine (PDA) can effectively quench free radicals, and its adhesive properties help to enhance interfacial bonding. Mechanical property modification usually employs elastomer toughening (e.g., SEBS) or rigid particle reinforcement, but single toughening methods often lead to a decrease in modulus or limited improvement in toughness. Cellulose nanofibers (CNFs) are considered ideal reinforcements due to their high aspect ratio and biodegradability, but the interfacial compatibility between hydrophilic CNFs and hydrophobic polystyrene remains a technical challenge.

[0005] Current production processes for expandable polystyrene (EPS) mostly employ suspension polymerization. While the addition of the blowing agent n-pentane can create a closed-cell structure, the uniformity and size control of the cells directly affect the compressive strength and thermal insulation performance of the final product. Traditional nucleating agents such as talc, although inexpensive, have limited effect on cell refinement. Polyethylene wax (PE wax), as a novel nucleating agent, can reduce interfacial energy, but its synergistic mechanism with flame-retardant systems remains unclear. Furthermore, dispersion stability during production is crucial for particle morphology. Anionic dispersants such as sodium dodecylbenzenesulfonate (SDBS) are easily affected by electrolytes and need to be used in combination with polymeric dispersants. Although some studies have attempted to combine the above modification methods, the synergistic effects of multiple components have not been fully explored, especially the lack of systematic solutions for multifunctional integrated designs that combine flame retardancy, toughening, and anti-aging. For example, the influence of the mixing ratio of CNF and SEBS, the degree of surface functionalization of modified nanofillers, and polymerization process parameters on the final performance has not yet been quantitatively modeled. Therefore, developing a polystyrene composite material that combines high-efficiency flame retardancy, long-lasting anti-aging properties, excellent mechanical properties, and controllable foaming structure still requires innovation in three dimensions: molecular design, interface engineering, and process optimization. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide an anti-aging expandable polystyrene particle and its preparation process. This material design overcomes the contradiction of decreased mechanical properties when flame retardant properties are improved in traditional polystyrene, achieving synergistic optimization of flame retardancy and mechanical properties. An organic-inorganic interpenetrating network structure is constructed through multi-component interface engineering. The precise distribution and interaction of each component at the nanoscale enable the material to simultaneously possess excellent flame retardant properties, anti-aging properties, thermal conductivity, and mechanical strength.

[0007] The technical solution adopted by the present invention to achieve the above objectives is as follows: An anti-aging expandable polystyrene granule, by weight, comprises the following components: 100-120 parts styrene, 200-300 parts deionized water, 7-10 parts composite flame retardant, 0.3-0.6 parts initiator, 1.5-3.0 parts nucleating agent, 0.7-1.2 parts composite toughening agent, 6-8 parts foaming agent, 0.2-0.8 parts dispersant, and 0.01-0.05 parts emulsifier; wherein the composite flame retardant is prepared by mixing modified graphene / boron nitride, ammonium polyphosphate, and modified silica, and the mass ratio of modified graphene / boron nitride, ammonium polyphosphate, and modified silica is 5:7-9:0.5-1.0; The method for preparing the modified silica is as follows: (1) Disperse silica in anhydrous ethanol by ultrasonication, then add 3-aminopropyltriethoxysilane dropwise under nitrogen atmosphere and stirring, raise the temperature to 75-85℃, react for 20-30h, cool to room temperature, filter, wash and dry to obtain aminated silica; (2) Mix aminated silica, phosphorus oxychloride, tetrahydrofuran and triethylamine evenly, and then add 4,4'-diaminodiphenylmethane after ultrasonic treatment. Stir and react at room temperature for 20-30 hours. After purification and drying, the product is obtained.

[0008] Further, in step (1), the volume ratio of anhydrous ethanol to 3-aminopropyltriethoxysilane is 150:10-20, and the amount of silicon dioxide added in anhydrous ethanol is 0.010-0.013 g / mL; in step (2), the mass ratio of aminated silicon dioxide, phosphorus oxychloride, triethylamine, and 4,4'-diaminodiphenylmethane is 5:2.5-3.5:2-3:6-7, and the mass-volume ratio of aminated silicon dioxide to tetrahydrofuran is 0.010-0.015 g / mL.

[0009] The preparation of the modified silica is divided into two stages. In the first stage, silica is ultrasonically dispersed in anhydrous ethanol, and then 3-aminopropyltriethoxysilane is added dropwise under a nitrogen atmosphere and stirring. During this process, the ethoxy group in the 3-aminopropyltriethoxysilane molecule undergoes a hydrolysis-condensation reaction with the hydroxyl group on the silica surface. Specifically, 3-aminopropyltriethoxysilane is first hydrolyzed in the presence of ethanol and water (possibly from trace amounts of moisture in the environment), and the ethoxy group is replaced by the hydroxyl group to generate a silanol intermediate. Then, the hydroxyl group on the silanol intermediate undergoes a condensation reaction with the hydroxyl group on the silica surface to form a Si-O-Si bond, thereby grafting 3-aminopropyltriethoxysilane onto the silica surface and amening the silica. In the second stage, aminated silica, phosphorus oxychloride, tetrahydrofuran, and triethylamine were mixed uniformly and ultrasonically treated. The chlorine atoms in phosphorus oxychloride exhibit high reactivity; the amino groups on the surface of the aminated silica initiate a nucleophilic attack on the chlorine atoms in phosphorus oxychloride, resulting in a nucleophilic substitution reaction. The chlorine atoms are replaced by amino groups, introducing phosphorus-containing groups. Next, 4,4'-diaminodiphenylmethane is added, and the amino groups in its molecule also undergo a nucleophilic substitution reaction with the intermediate generated in the previous reaction, further introducing nitrogen-containing groups. The entire preparation process first achieves the amination of silica through a hydrolysis-condensation reaction, and then further introduces other functional groups using a nucleophilic substitution reaction, thereby obtaining nitrogen / phosphorus modified silica.

[0010] Furthermore, the preparation method of modified graphene / boron nitride is as follows: Step S1: Disperse boron nitride in an aqueous sodium hydroxide solution and stir at 70-90℃ for 20-30 hours. Cool to room temperature, filter, wash, dry, and grind to obtain hydroxylated boron nitride. Step S2: Disperse hydroxylated boron nitride and graphene in an ethanol aqueous solution, sonicate for 50-70 min, then add 3-aminopropyltriethoxysilane, purge with nitrogen, stir and react at 80-100℃ for 7-11 h, cool to room temperature, filter, wash and dry to obtain silane graphene / boron nitride. Step S3: Disperse silane graphene / boron nitride in an ethanol aqueous solution, sonicate for 0.5-1.5 h, add dopamine hydrochloride, adjust the pH to 8-9, stir at 75-95℃ for 5-7 h, cool to room temperature, filter, wash, dry, and pulverize to obtain the final product.

[0011] Further, in step S1, the mass-to-volume ratio of boron nitride to sodium hydroxide aqueous solution is 1:8-12, and the concentration of sodium hydroxide aqueous solution is 4-6 mol / L; in step S2, the mass ratio of hydroxylated boron nitride, graphene, 3-aminopropyltriethoxysilane, and ethanol aqueous solution is 0.1:0.2-0.3:2.5-3.5:20-25, the mass fraction of ethanol in the ethanol aqueous solution is 85-95%, the ultrasonic power is 100-300W, and the ultrasonic frequency is 20-40kHz; in step S3, the mass ratio of silane graphene / boron nitride, dopamine hydrochloride, and ethanol aqueous solution is 4:0.8-1.2:400-600, the mass fraction of ethanol in the ethanol aqueous solution is 45-55%, the ultrasonic power is 150-250W, and the ultrasonic frequency is 20-30kHz.

[0012] The preparation process of modified graphene / boron nitride involves first reacting boron nitride with sodium hydroxide. Utilizing the strong nucleophilicity of the hydroxide ions in sodium hydroxide, the hydroxyl groups attack the active sites on the boron nitride surface, introducing hydroxyl groups. Then, the ethoxy groups in the silane molecules undergo hydrolysis to generate silanol groups. These silanol groups can condense with the hydroxyl groups on the surface of hydroxylated boron nitride and the active groups on the graphene surface, forming silicon-oxygen bonds. This grafts silane molecules onto the surfaces of hydroxylated boron nitride and graphene, achieving silanization. Finally, the process is carried out in a weakly alkaline environment... Under alkaline conditions, the amino groups in dopamine hydrochloride undergo deprotonation, forming highly reactive amino anions. Simultaneously, the catechol structure in the dopamine molecule is easily oxidized under alkaline conditions, forming a quinone structure. The quinone structure has strong electrophilicity and undergoes nucleophilic addition reactions with the amino groups on the surface of silane-modified graphene / boron nitride, thereby initiating the polymerization of dopamine molecules and forming a polydopamine coating on the surface of silane-modified graphene / boron nitride, ultimately yielding polydopamine-silane dual-modified graphene / boron nitride.

[0013] Further, the initiator is one or more of benzoyl peroxide, dicumyl peroxide, and tert-butyl peroxide; the nucleating agent is polyethylene wax; the foaming agent is isopentane or n-pentane; the dispersant is one or more of activated calcium phosphate, polyvinyl alcohol, sodium dodecylbenzenesulfonate, and hydroxyethyl cellulose; and the emulsifier is calcium dodecylbenzenesulfonate.

[0014] Furthermore, the composite toughening agent is prepared by mixing styrene-ethylene-butene-styrene block copolymer, cellulose nanofibers, and castor oil polyoxyethylene ether, with the mass ratio of styrene-ethylene-butene-styrene block copolymer, cellulose nanofibers, and castor oil polyoxyethylene ether being 2:0.5-1.0:0.5-1.0.

[0015] This invention also provides a preparation process for anti-aging expandable polystyrene particles, comprising the following steps: adding a dispersant to deionized water and stirring for 20-40 minutes; then adding styrene, a composite flame retardant, and an emulsifier in sequence, and continuing to stir for 30-60 minutes; raising the temperature to 45-55°C; then adding a nucleating agent, a composite toughening agent, and an initiator; mixing evenly and continuing to raise the temperature to 88-92°C; stirring for 5-6 hours; adding a foaming agent and continuing to stir; raising the temperature to 120-125°C; reacting for 3.3-5.5 hours; and discharging after cooling to obtain the final product.

[0016] The present invention has the following beneficial effects: In the preparation of anti-aging expandable polystyrene granules, the various raw material components and process conditions work together to improve the overall performance of polystyrene granules from multiple aspects.

[0017] The composite flame retardant employs a multi-component synergistic approach, consisting of modified graphene / boron nitride, ammonium polyphosphate, and modified silica. A multi-scale protective network is constructed through a synergistic flame retardant system of polydopamine-silane dual-modified graphene / boron nitride and organic nitrogen / phosphorus modified silica. The catechol structure of polydopamine is tightly anchored to the graphene surface via π-π stacking and hydrogen bonding, while the hydrolysis and condensation reaction of the silane coupling agent forms a silicon-oxygen bridging structure between the boron nitride layers. This dual modification endows the originally inert two-dimensional material with excellent interfacial compatibility. During combustion, the modified graphene / boron nitride delays heat and mass transfer through a physical barrier effect. Its layered structure effectively hinders the diffusion of volatile decomposition products, while the high thermal conductivity of boron nitride uniformly disperses localized thermal stress, preventing hotspot concentration. Organic nitrogen / phosphorus modified silica functions through a chemical flame-retardant mechanism. Phosphorus generates phosphate compounds at high temperatures, promoting char formation, while nitrogen decomposes to produce non-combustible gases such as NH3, diluting the oxygen concentration. The silica framework enhances the mechanical strength of the char layer. When modified graphene / boron nitride, ammonium polyphosphate, and modified silica are compounded, they form a comprehensive flame-retardant mode of "gas phase-condensed phase-radiation shielding": ammonium polyphosphate decomposes upon heating to generate polyphosphoric acid, which catalyzes dehydration to form char; the modified nanomaterials construct a dense ceramic barrier in the condensed phase, synergistically improving the flame-retardant performance of the composite material.

[0018] The composite toughening agent employs a multi-component synergistic approach, consisting of styrene-ethylene-butene-styrene block copolymer, cellulose nanofibers, and castor oil polyoxyethylene ether. The elastomeric network of the styrene-ethylene-butene-styrene block copolymer (SEBS) can entangle with the polystyrene molecular chains. This entanglement not only promotes stress transfer but also increases the interaction forces between molecular chains, thereby improving the mechanical strength of polystyrene. Cellulose nanofibers (CNF), with their high aspect ratio and surface hydroxyl groups, form hydrogen bonds with the matrix, inducing microcrack deflection and bridging effects under external forces. Castor oil polyoxyethylene ether, acting as an interfacial compatibilizer, inserts its hydrophobic segments into the SEBS phase while its hydrophilic ends connect to the CNF, effectively reducing the interfacial energy between the two phases. This ternary structure—a "soft phase-hard phase-interfacial transition layer"—with the styrene-ethylene-butene-styrene block copolymer as the soft phase, cellulose nanofibers as the hard phase, and castor oil polyoxyethylene ether as the interfacial compatibilizer, allows the material to maintain stable mechanical properties over a wide temperature range. Furthermore, there is a molecular-level synergy between the composite flame retardant and the composite toughening agent: the two-dimensional structure of boron nitride can orient the SEBS molecular chains, improve their crystallinity, and make stress transfer more efficient, while the flexible segments of SEBS can alleviate the increase in brittleness caused by the flame retardant filler, so that the material can have both good flame retardant properties and mechanical properties.

[0019] In terms of anti-aging performance, the unique structure of polydopamine-silane dual-modified graphene / boron nitride plays a crucial role. The catechol structure and amino groups in the polydopamine molecule have excellent free radical scavenging capabilities, which can interrupt the chain reaction during the material aging process. Organic nitrogen / phosphorus modified silica decomposes upon heating to generate phosphorus-containing free radical scavengers, forming a synergistic "double insurance" mechanism with polydopamine for anti-aging. The cellulose nanofibers in the composite toughening agent react with the peroxides generated during aging through their reducing terminal aldehyde groups, further enhancing the stability of the system. In addition, the improvement in thermal conductivity mainly depends on the in-situ construction of a three-dimensional thermally conductive network. Polydopamine modification enables the graphene / boron nitride sheets to be nanoscale dispersed in a styrene matrix, and the hydrolysis products of the silane coupling agent form siloxane crosslinking points between the sheets, thereby constructing a chemically bonded network structure. In composite materials, phonons are one of the main carriers of heat conduction, and this network structure provides a continuous channel for phonon transmission, allowing phonons to propagate more efficiently in the material. The two-dimensional planar structure of boron nitride has an extremely high in-plane thermal conductivity. The sp² hybrid carbon network of modified graphene and boron nitride form conjugate thermal conduction channels through π-π stacking, which allows heat to diffuse rapidly along the two-dimensional plane. Detailed Implementation

[0020] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the embodiments of this application. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0021] Graphene, 2000 mesh, 99% fixed carbon content, purchased from Jinan Yuanhai Chemical Co., Ltd.; Boron nitride, 1μm particle size, >99% purity, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.; Silica, TH-1300, 99.6% effective ingredient content, purchased from Shandong Wanhua Tianhe New Material Co., Ltd.; Polyethylene wax, Q-18PE wax, 99% effective ingredient content, brand Xindongyi; Styrene-ethylene-butene-styrene block copolymer (SEBS), 28-31wt% styrene content, grade 6159, purchased from Dongguan Shenghao Plastic Raw Materials Co., Ltd.; Cellulose nanofibers, 3-10nm particle size, 99.9% purity, purchased from Hubei Shineng Chemical Technology Co., Ltd.; Castor oil polyoxyethylene ether, EL-40, density 1.05g / mL at 20℃, purchased from Shandong Yueyang New Materials Co., Ltd.; activated calcium phosphate, purity ≥92%, purchased from Wuhan Jiyesheng Chemical Co., Ltd.; polyvinyl alcohol, brand 1799, content ≥99%, purchased from Nantong Changchen Chemical Co., Ltd.; hydroxyethyl cellulose, density 0.75g / mL at 25℃ g / mL, pH (20g / L, 25℃): 5.0-8.0, brand Nengju Chemical. All raw materials used in the following examples are commercially available products.

[0022] Example 1

[0023] An anti-aging expandable polystyrene granule comprises, by weight, the following components: 110 parts styrene, 250 parts deionized water, 9 parts composite flame retardant, 0.5 parts initiator, 2.0 parts nucleating agent, 1.0 part composite toughening agent, 7 parts foaming agent, 0.5 parts dispersant, and 0.03 parts emulsifier; the composite flame retardant is prepared by mixing modified graphene / boron nitride, ammonium polyphosphate, and modified silica, with a mass ratio of modified graphene / boron nitride, ammonium polyphosphate, and modified silica of 5:8:0.8; the initiator is peroxide. Benzoyl; the nucleating agent is polyethylene wax; the foaming agent is isopentane; the dispersant is prepared by mixing active calcium phosphate and polyvinyl alcohol, with a mass ratio of active calcium phosphate to polyvinyl alcohol of 1:2; the emulsifier is calcium dodecylbenzenesulfonate; the composite toughening agent is prepared by mixing styrene-ethylene-butene-styrene block copolymer, cellulose nanofibers, and castor oil polyoxyethylene ether, with a mass ratio of styrene-ethylene-butene-styrene block copolymer, cellulose nanofibers, and castor oil polyoxyethylene ether of 2:0.7:0.7; The preparation process of the modified silica is as follows: (1) Silica was ultrasonically dispersed in anhydrous ethanol (ultrasonic power of 200W, frequency of 25kHz, time of 5min), and then 3-aminopropyltriethoxysilane was added dropwise under nitrogen atmosphere and stirring at 160rpm. The addition was completed within 1h. The temperature was raised to 80℃ and the reaction was carried out for 24h. After natural cooling to room temperature, the mixture was filtered under vacuum and washed three times with anhydrous ethanol. Finally, it was dried at 60℃ to constant weight to obtain aminated silica. The volume ratio of anhydrous ethanol to 3-aminopropyltriethoxysilane was 150:15, and the amount of silica added in anhydrous ethanol was 0.011g / mL. (2) Mix aminated silica, phosphorus oxychloride, tetrahydrofuran, and triethylamine evenly, sonicate, and then add 4,4'-diaminodiphenylmethane. Stir and react for 24 hours in the dark and at room temperature. Purify with tetrahydrofuran and deionized water in sequence, dry under reduced pressure at 80°C for 24 hours, pulverize and pass through an 800-mesh sieve to obtain the product. The mass ratio of aminated silica, phosphorus oxychloride, triethylamine, and 4,4'-diaminodiphenylmethane is 5:3:2.5:6.5, the mass-volume ratio of aminated silica to tetrahydrofuran is 0.013 g / mL, the ultrasonic power of the sonication is 200 W, the frequency is 20 kHz, and the time is 1 hour. The preparation process of the modified graphene / boron nitride is as follows: Step S1: Disperse boron nitride in an aqueous sodium hydroxide solution, stir at 80℃ and 160 rpm for 24 h, cool naturally to room temperature, filter, take the filter residue, wash with deionized water until neutral, vacuum dry at 60℃ to constant weight, and grind to a particle size ≤2 μm to obtain hydroxylated boron nitride; wherein, the mass-to-volume ratio of boron nitride to aqueous sodium hydroxide solution is 1:10, and the concentration of aqueous sodium hydroxide solution is 5 mol / L; Step S2: Disperse hydroxylated boron nitride and graphene in an ethanol-water solution, sonicate for 60 min (ultrasound power 200 W, sonic frequency 30 kHz), then add 3-aminopropyltriethoxysilane, purge with nitrogen, and stir under reflux at 90 °C and 180 rpm for 9 h. Allow to cool naturally to room temperature, filter, and take the filter residue. Wash three times with anhydrous ethanol, then three times with deionized water. Separate the solid and liquid, take the solid, and freeze-dry to constant weight to obtain silane-based graphene / boron nitride. The mass ratio of hydroxylated boron nitride, graphene, 3-aminopropyltriethoxysilane, and ethanol-water solution is 0.1:0.25:3:22, and the mass fraction of ethanol in the ethanol-water solution is 90%. Step S3: Disperse silane-based graphene / boron nitride in an ethanol-water solution, sonicate for 1 hour (ultrasonic power 200W, ultrasonic frequency 25kHz), add dopamine hydrochloride, mix thoroughly, adjust pH to 8.5 with Tris salt, stir at 85℃ and 180rpm for 6 hours, allow to cool naturally to room temperature, filter, collect the filter residue, wash three times with deionized water, separate solid and liquid, collect the solid, freeze-dry to constant weight, pulverize and pass through an 800-mesh sieve to obtain the final product; wherein, the mass ratio of silane-based graphene / boron nitride, dopamine hydrochloride, and ethanol-water solution is 4:1:500, and the mass fraction of ethanol in the ethanol-water solution in step S3 is 50%.

[0024] A process for preparing anti-aging expandable polystyrene granules includes the following steps: adding a dispersant to deionized water and stirring for 30 minutes; then adding styrene, a composite flame retardant, and an emulsifier sequentially and stirring for another 50 minutes; raising the temperature to 50°C; then adding a nucleating agent, a composite toughening agent, and an initiator; mixing thoroughly; raising the temperature to 90°C and stirring for 5.5 hours; adding a foaming agent and continuing to stir; raising the temperature to 122°C; reacting at a pressure of 0.55 MPa for 4.5 hours; naturally cooling to 40°C; and obtaining expandable polystyrene granules after washing, dehydration, and drying. The proportion of product particles with a diameter of 0.75 ± 0.15 mm is 80.2%.

[0025] Example 2

[0026] An anti-aging expandable polystyrene particle, by weight, comprises the following components: 110 parts styrene, 250 parts deionized water, 7 parts composite flame retardant, 0.5 parts initiator, 2.0 parts nucleating agent, 0.7 parts composite toughening agent, 7 parts foaming agent, 0.5 parts dispersant, and 0.03 parts emulsifier; the composite flame retardant is prepared by mixing modified graphene / boron nitride, ammonium polyphosphate prepared in Example 1, and modified silica prepared in Example 1. The mass ratio is 5:8:0.5; the initiator is dicumyl peroxide; the nucleating agent is polyethylene wax; the foaming agent is isopentane; the dispersant is sodium dodecylbenzenesulfonate; the emulsifier is calcium dodecylbenzenesulfonate; the composite toughening agent is prepared by mixing styrene-ethylene-butene-styrene block copolymer, cellulose nanofibers, and castor oil polyoxyethylene ether, with a mass ratio of styrene-ethylene-butene-styrene block copolymer, cellulose nanofibers, and castor oil polyoxyethylene ether of 2:0.7:0.7.

[0027] A process for preparing anti-aging expandable polystyrene particles, prepared according to the method described in Example 1, wherein the proportion of particles with a diameter of 0.75±0.15mm is 75.6%.

[0028] Example 3

[0029] An anti-aging expandable polystyrene particle, by weight, comprises the following components: 110 parts styrene, 250 parts deionized water, 10 parts composite flame retardant, 0.5 parts initiator, 2.0 parts nucleating agent, 1.2 parts composite toughening agent, 7 parts foaming agent, 0.5 parts dispersant, and 0.03 parts emulsifier; the composite flame retardant is prepared by mixing modified graphene / boron nitride, ammonium polyphosphate prepared in Example 1, and modified silica prepared in Example 1. The mass ratio of the components is 5:8:0.8; the initiator is tert-butyl peroxide; the nucleating agent is polyethylene wax; the foaming agent is isopentane; the dispersant is hydroxyethyl cellulose; the emulsifier is calcium dodecylbenzenesulfonate; the composite toughening agent is prepared by mixing styrene-ethylene-butene-styrene block copolymer, cellulose nanofibers, and castor oil polyoxyethylene ether, with a mass ratio of styrene-ethylene-butene-styrene block copolymer, cellulose nanofibers, and castor oil polyoxyethylene ether of 2:0.7:0.7.

[0030] A process for preparing anti-aging expandable polystyrene particles, prepared according to the method described in Example 1, wherein the proportion of particles with a diameter of 0.75±0.15mm is 78.4%.

[0031] Example 4

[0032] The preparation process of the modified silica is as follows: (1) Silica was ultrasonically dispersed in anhydrous ethanol (ultrasonic power of 200W, frequency of 25kHz, time of 5min), and then 3-aminopropyltriethoxysilane was added dropwise under nitrogen atmosphere and stirring at 160rpm. The addition was completed within 1h. The temperature was raised to 80℃ and the reaction was carried out for 24h. After natural cooling to room temperature, the mixture was filtered under vacuum and washed three times with anhydrous ethanol. Finally, it was dried at 60℃ to constant weight to obtain aminated silica. The volume ratio of anhydrous ethanol to 3-aminopropyltriethoxysilane was 150:10, and the amount of silica added in anhydrous ethanol was 0.010g / mL. (2) Mix aminated silica, phosphorus oxychloride, tetrahydrofuran, and triethylamine evenly, and then add 4,4'-diaminodiphenylmethane after ultrasonic treatment. Stir and react for 24 hours in the dark and at room temperature. After purification with tetrahydrofuran and deionized water, dry under reduced pressure at 80°C for 24 hours. After pulverization, pass through an 800-mesh sieve to obtain the product. The mass ratio of aminated silica, phosphorus oxychloride, triethylamine, and 4,4'-diaminodiphenylmethane is 5:2.5:2:6, the mass-volume ratio of aminated silica to tetrahydrofuran is 0.013 g / mL, the ultrasonic power of ultrasonic treatment is 200 W, the frequency is 20 kHz, and the time is 1 hour.

[0033] An anti-aging expandable polystyrene particle and its preparation process are disclosed. The particle size of the product is 0.75±0.15mm, accounting for 73.3%.

[0034] Example 5

[0035] The preparation process of the modified graphene / boron nitride is as follows: Step S1: Disperse boron nitride in an aqueous sodium hydroxide solution, stir at 80℃ and 160 rpm for 24 h, cool naturally to room temperature, filter, take the filter residue, wash with deionized water until neutral, vacuum dry at 60℃ to constant weight, and grind to a particle size ≤2 μm to obtain hydroxylated boron nitride; wherein, the mass-to-volume ratio of boron nitride to aqueous sodium hydroxide solution is 1:10, and the concentration of aqueous sodium hydroxide solution is 5 mol / L; Step S2: Disperse hydroxylated boron nitride and graphene in an ethanol-water solution, sonicate for 60 min (ultrasound power 200 W, sonic frequency 30 kHz), then add 3-aminopropyltriethoxysilane, purge with nitrogen, and stir under reflux at 90 °C and 180 rpm for 9 h. Allow to cool naturally to room temperature, filter, and take the filter residue. Wash the residue three times with anhydrous ethanol, then three times with deionized water. Separate the solid and liquid, take the solid, and freeze-dry to constant weight to obtain silane-based graphene / boron nitride. The mass ratio of hydroxylated boron nitride, graphene, 3-aminopropyltriethoxysilane, and ethanol-water solution is 0.1:0.2:2.5:22, and the mass fraction of ethanol in the ethanol-water solution is 90%. Step S3: Disperse silane-based graphene / boron nitride in an ethanol-water solution, sonicate for 1 hour (ultrasonic power 200W, ultrasonic frequency 25kHz), add dopamine hydrochloride, mix thoroughly, adjust pH to 8.5 with Tris salt, stir at 85℃ and 180rpm for 6 hours, allow to cool naturally to room temperature, filter, collect the filter residue, wash three times with deionized water, separate solid and liquid, collect the solid, freeze-dry to constant weight, pulverize and pass through an 800-mesh sieve to obtain the final product; wherein, the mass ratio of silane-based graphene / boron nitride, dopamine hydrochloride, and ethanol-water solution is 4:0.8:500, and the mass fraction of ethanol in the ethanol-water solution in step S3 is 50%.

[0036] An anti-aging expandable polystyrene particle and its preparation process are disclosed. The particle size of the product is 0.75±0.15mm, accounting for 77.0%.

[0037] Comparative Example 1

[0038] An anti-aging expandable polystyrene particle and its preparation process are disclosed. The preparation process is carried out according to the method described in Example 1, except that the composite flame retardant is prepared by mixing modified graphene / boron nitride, ammonium polyphosphate, and silicon dioxide (commonly available in the market), and the mass ratio of modified graphene / boron nitride, ammonium polyphosphate, and silicon dioxide is 5:8:0.8.

[0039] Comparative Example 2

[0040] An anti-aging expandable polystyrene particle and its preparation process are disclosed. The preparation process is carried out according to the method described in Example 1, except that the composite flame retardant is prepared by mixing graphene / boron nitride (obtained by conventional mechanical mixing of commercially available graphene and boron nitride), ammonium polyphosphate, and modified silica prepared in Example 1. The mass ratio of graphene / boron nitride, ammonium polyphosphate, and modified silica is 5:8:0.8.

[0041] Comparative Example 3

[0042] An anti-aging expandable polystyrene particle and its preparation process are disclosed. The preparation process is carried out according to the method described in Example 1, except that the composite flame retardant is prepared by mixing graphene / boron nitride (obtained by conventional mechanical mixing of commercially available graphene and boron nitride), ammonium polyphosphate, and silicon dioxide (commonly available), with a mass ratio of graphene / boron nitride, ammonium polyphosphate, and silicon dioxide of 5:8:0.8.

[0043] In accordance with the provisions of GB / T6594.2-2003 "Plastics - Polystyrene (PS) Molding and Extrusion Materials - Part 2: Specimen Preparation and Performance Determination", the anti-aging expandable polystyrene granule compression molded specimens prepared in Examples 1-5 and Comparative Examples 1-3 were subjected to relevant performance tests. Oxygen index testing was conducted according to GB / T2406.2-2009 "Determination of Combustion Behavior by Oxygen Index Method for Plastics - Part 2: Room Temperature Test"; flammability testing was performed on the samples according to the UL-94 vertical combustion test standard, with a sample length of 125 mm, width of 13 mm, and thickness of 11 mm; foaming tests were conducted on the samples prepared in Examples 1-5 and Comparative Examples 1-3. After foaming, the samples were cooled and dried, and the volumes before and after foaming were measured, and the foaming ratio was calculated using the formula: foaming ratio = V2 / V1, where V1 is the volume of the sample before foaming, and V2 is the volume of the sample after foaming; thermal conductivity testing was conducted according to GB / T10294-2008 "Determination of Steady-State Thermal Resistance and Related Properties of Insulation Materials - Protective Hot Plate Method", with sample dimensions of 250 mm × 90 mm × 60 mm, using a thermal conductivity meter; tensile strength testing was conducted according to GB / T The test was conducted according to 9641-1988 "Tension Properties Test Method for Rigid Foamed Plastics" at a temperature of 25℃. The anti-aging performance test was conducted by aging the sample at 120℃ for 1000 hours and then testing the retention rate of the tensile strength. All tests were repeated three times and the average value was taken. The test results are shown in Table 1.

[0044] As can be seen from the data in Table 1, compared with the comparative examples, the expandable polystyrene prepared in the examples exhibits better flame retardant properties, anti-aging properties, thermal conductivity, and mechanical properties. Although the foaming ratio is slightly lower, it still maintains a high level, with the foaming ratio of the polystyrene prepared in the examples all exceeding 24 times. Data from Example 1 and Comparative Examples 1-3 show that modified graphene / boron nitride and modified silica were prepared through multi-step chemical modification, and further compounded with ammonium polyphosphate to obtain a composite flame retardant. The composite flame retardant and composite toughening agent can synergistically enhance each other, significantly improving the multifaceted properties of polystyrene particles.

[0045] Table 1. Test results of relevant properties of anti-aging expandable polystyrene particles

[0046] Although embodiments of this application have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of this application, the scope of which is defined by the appended claims and their equivalents.

Claims

1. An anti-aging expandable polystyrene particle, characterized in that, The product comprises, by weight, the following components: 100-120 parts styrene, 200-300 parts deionized water, 7-10 parts composite flame retardant, 0.3-0.6 parts initiator, 1.5-3.0 parts nucleating agent, 0.7-1.2 parts composite toughening agent, 6-8 parts foaming agent, 0.2-0.8 parts dispersant, and 0.01-0.05 parts emulsifier; the composite flame retardant is prepared by mixing modified graphene / boron nitride, ammonium polyphosphate, and modified silica, wherein the mass ratio of modified graphene / boron nitride, ammonium polyphosphate, and modified silica is 5:7-9:0.5-1.

0. The method for preparing the modified silica is as follows: (1) Disperse silica in anhydrous ethanol by ultrasonication, then add 3-aminopropyltriethoxysilane dropwise under nitrogen atmosphere and stirring, raise the temperature to 75-85℃, react for 20-30h, cool to room temperature, filter, wash and dry to obtain aminated silica; (2) Mix aminated silica, phosphorus oxychloride, tetrahydrofuran and triethylamine evenly, and then add 4,4'-diaminodiphenylmethane after ultrasonic treatment. Stir and react at room temperature for 20-30 hours. After purification and drying, the product is obtained.

2. The anti-aging expandable polystyrene granules according to claim 1, characterized in that, The volume ratio of anhydrous ethanol to 3-aminopropyltriethoxysilane in step (1) is 150:10-20, and the amount of silicon dioxide added to the anhydrous ethanol is 0.010-0.013 g / mL.

3. The anti-aging expandable polystyrene granules according to claim 1, characterized in that, In step (2), the mass ratio of aminated silica, phosphorus oxychloride, triethylamine, and 4,4'-diaminodiphenylmethane is 5:2.5-3.5:2-3:6-7, and the mass-volume ratio of aminated silica to tetrahydrofuran is 0.010-0.015 g / mL.

4. The anti-aging expandable polystyrene granules according to claim 1, characterized in that, The preparation method of the modified graphene / boron nitride is as follows: Step S1: Disperse boron nitride in an aqueous sodium hydroxide solution and stir at 70-90℃ for 20-30 hours. Cool to room temperature, filter, wash, dry, and grind to obtain hydroxylated boron nitride. Step S2: Disperse hydroxylated boron nitride and graphene in an ethanol aqueous solution, sonicate for 50-70 min, then add 3-aminopropyltriethoxysilane, purge with nitrogen, stir and react at 80-100℃ for 7-11 h, cool to room temperature, filter, wash and dry to obtain silane graphene / boron nitride. Step S3: Disperse silane graphene / boron nitride in an ethanol aqueous solution, sonicate for 0.5-1.5 h, add dopamine hydrochloride, adjust the pH to 8-9, stir at 75-95℃ for 5-7 h, cool to room temperature, filter, wash, dry, and pulverize to obtain the final product.

5. The anti-aging expandable polystyrene granules according to claim 4, characterized in that, In step S1, the mass-to-volume ratio of boron nitride to sodium hydroxide aqueous solution is 1:8-12, and the concentration of sodium hydroxide aqueous solution is 4-6 mol / L.

6. The anti-aging expandable polystyrene particles according to claim 4, characterized in that, In step S2, the mass ratio of hydroxylated boron nitride, graphene, 3-aminopropyltriethoxysilane, and ethanol aqueous solution is 0.1:0.2-0.3:2.5-3.5:20-25, the mass fraction of ethanol in the ethanol aqueous solution is 85-95%, the ultrasonic power is 100-300W, and the ultrasonic frequency is 20-40kHz.

7. The anti-aging expandable polystyrene granules according to claim 4, characterized in that, In step S3, the mass ratio of silane graphene / boron nitride, dopamine hydrochloride, and ethanol aqueous solution is 4:0.8-1.2:400-600, the mass fraction of ethanol in the ethanol aqueous solution is 45-55%, the ultrasonic power is 150-250W, and the ultrasonic frequency is 20-30kHz.

8. The anti-aging expandable polystyrene granules according to claim 1, characterized in that, The initiator is one or more of benzoyl peroxide, dicumyl peroxide, and tert-butyl peroxide; the nucleating agent is polyethylene wax; the foaming agent is isopentane or n-pentane; the dispersant is one or more of active calcium phosphate, polyvinyl alcohol, sodium dodecylbenzenesulfonate, and hydroxyethyl cellulose; and the emulsifier is calcium dodecylbenzenesulfonate.

9. The anti-aging expandable polystyrene particles according to claim 1, characterized in that, The composite toughening agent is prepared by mixing styrene-ethylene-butene-styrene block copolymer, cellulose nanofibers, and castor oil polyoxyethylene ether, with the mass ratio of styrene-ethylene-butene-styrene block copolymer, cellulose nanofibers, and castor oil polyoxyethylene ether being 2:0.5-1.0:0.5-1.

0.

10. The preparation process of anti-aging expandable polystyrene particles according to any one of claims 1-9, characterized in that, Includes the following steps: Add a dispersant to deionized water and stir for 20-40 minutes. Then add styrene, composite flame retardant, and emulsifier in sequence and continue stirring for 30-60 minutes. Raise the temperature to 45-55℃, then add a nucleating agent, composite toughening agent, and initiator. Mix well and continue raising the temperature to 88-92℃ and stirring for 5-6 hours. Add a foaming agent and continue stirring. Raise the temperature to 120-125℃ and react for 3.3-5.5 hours. After cooling, discharge the material to obtain the final product.

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