A modified polystyrene plastic material and its preparation method

Abstract

The present invention relates to the technical field of environmental protection materials, and particularly relates to a modified recycled polystyrene plastic material and a preparation method thereof. This material is composed of a variety of novel formulation components such as recycled polystyrene plastic, hydrogenated SBS, PET-PBS, nano-titanium dioxide, antioxidant 1010, calcium stearate, and phosphorus-containing benzoxazine prepolymer. During preparation, novel components are first synthesized, the recycled polystyrene plastic is pretreated, and then the product is obtained through batching, mixing, and extrusion molding. Through the unique formulation and preparation process, the modified recycled polystyrene plastic material of the present invention has significantly improved tensile strength, impact strength, heat distortion temperature, thermal stability, flame retardancy, antibacterial property, and fluorescence property.

Description

Technical Field

[0001] The present invention relates to the technical field of plastic material modification, and particularly relates to a modified polystyrene plastic material and a preparation method thereof. Background Art

[0002] In today's society, plastic products have been extremely widely used in various fields due to their excellent performance and wide applicability. However, with the large-scale production and consumption of polystyrene plastic products, the quantity of their waste has been increasing day by day.

[0003] On the one hand, if a large amount of waste polystyrene plastics cannot be properly treated, it will cause serious pollution to the environment. Polystyrene plastics are difficult to degrade in the natural environment, and their waste will remain in the soil for a long time, damaging the soil structure, affecting the air permeability and water penetration ability of the soil, and then hindering the growth of plant roots and the absorption of nutrients, having a negative impact on agricultural production and ecological balance. In the water environment, waste polystyrene plastics will float on the water surface or deposit at the bottom of the water, not only affecting the beauty of the water body and the normal circulation of the ecosystem, but also seriously threatening the survival and reproduction of aquatic organisms and destroying the balance of the aquatic ecosystem. In addition, when waste polystyrene plastics are incinerated, a large amount of harmful gases will be released.

[0004] On the other hand, from the perspective of resource utilization, polystyrene plastics are made from precious non-renewable resources such as petroleum. A large amount of waste means a huge waste of resources. With the increasing global resource shortage, it has become crucial to improve the recycling rate of resources. The emergence of recycled polystyrene plastics provides a way to solve this problem, but currently, recycled polystyrene plastics still have many deficiencies in performance, which limits their further application and development.

[0005] Recycled polystyrene plastics often have the problem of insufficient toughness, making them prone to cracking when subjected to external force impacts. This is particularly obvious in some application scenarios with high requirements for material toughness, such as packaging materials that need to withstand collisions during transportation and building materials that need to cope with certain external force deformations. Low strength is also a shortcoming of recycled polystyrene plastics. Its mechanical property indexes such as tensile strength and flexural strength are difficult to meet the requirements of some high-end application fields, affecting the use reliability and lifespan of products. In addition, poor heat resistance makes recycled polystyrene plastics prone to deformation and softening in high-temperature environments, limiting their application under high-temperature working conditions. For example, in some electronic and electrical equipment, plastic materials need to have a certain heat resistance to ensure the normal operation of the equipment.

[0006] In summary, in order to reduce the environmental pollution caused by waste polystyrene plastics, achieve the effective recycling of resources, and meet the growing market demand for high-performance plastic materials, it has become a key issue to be solved urgently in the field of plastic materials to modify recycled polystyrene plastics and improve their comprehensive properties. Therefore, the present invention aims to develop a modified recycled polystyrene plastic material with superior performance through innovative material component design and optimized preparation processes to overcome the defects of the prior art. Summary of the Invention

[0007] The modified polystyrene plastic material of the present invention is composed of the following substances in parts by weight:

[0008] Base component: 80 - 100 parts of polystyrene plastic, as the matrix of the material, providing basic rigidity and molding properties for the product.

[0009] Reinforcing and toughening component: 5 - 15 parts of hydrogenated styrene-butadiene-styrene block copolymer (SBS). Hydrogenated SBS has good flexibility and compatibility with polystyrene, can form a dispersed phase in the material, and effectively improve the toughness of the material. At the same time, its entanglement with the molecular chains of polystyrene plastic helps to enhance the overall strength of the material. 3 - 8 parts of polyethylene terephthalate-polybutylene succinate block copolymer (PET-PBS). PET-PBS combines the rigidity of PET and the flexibility of PBS, can improve the strength of the material while improving its toughness and processing properties. The ester bonds in its molecular structure can interact with other components to enhance the interfacial bonding force of the material.

[0010] . Functional additive: 0.5 - 3 parts of nano-titanium dioxide. Nano-titanium dioxide can not only improve the mechanical properties of the material, such as enhancing the strength and hardness of the material, but also has excellent ultraviolet shielding performance, can effectively improve the weather resistance of the material, and prevent the material from aging and degrading under ultraviolet irradiation. In addition, its nano-size effect can improve the rheological and processing properties of the material, making the material flow and form more easily during the processing.

[0011] 0.5 - 2 parts of antioxidant 1010. Antioxidant 1010 can effectively inhibit the oxidation reaction of the material during processing and use, and extend the service life of the material. During high-temperature processing, antioxidant 1010 can capture free radicals and prevent the progress of the oxidation chain reaction, thereby protecting the molecular chains of the material from being damaged.

[0012] 1 - 3 parts of calcium stearate. Calcium stearate, as a lubricant and stabilizer, can reduce the friction force of the material during processing, make the material flow more smoothly in the extruder, and improve the processing efficiency. At the same time, it can also interact with other components in the material to enhance the stability of the material and prevent the performance of the material from deteriorating during storage and use.

[0013] . New formula components: 1 - 3 parts of phosphorus-containing benzoxazine prepolymer. Benzoxazine has excellent heat resistance, flame retardancy and mechanical properties. The phosphorus-containing benzoxazine prepolymer can form an intumescent carbon layer at high temperatures, playing a role in heat insulation and oxygen isolation, and significantly improving the flame retardancy of the material. The active groups in its molecular structure can interact with the molecular chains of polystyrene plastics, enhancing the interfacial bonding force of the material, and thus improving the strength and toughness of the material. In addition, the phosphorus-containing benzoxazine prepolymer can also improve the processing fluidity of the material to a certain extent, making it easier to fill the mold during the molding process and improving the product quality.

[0014] 0.1 - 0.5 parts of graphene quantum dots. Graphene quantum dots have excellent optical, electrical and mechanical properties. It can be evenly dispersed in the polystyrene plastic matrix to form a nano-scale reinforcing phase, significantly improving the mechanical properties of the material, such as tensile strength, flexural strength and impact strength. At the same time, graphene quantum dots have good ultraviolet absorption ability, which can enhance the weather resistance of the material and prevent the material from aging and degradation under ultraviolet irradiation. In addition, the introduction of graphene quantum dots can also improve the thermal conductivity of the material, helping to improve the heat dissipation ability of the material, which is of great significance in the application of electronic devices.

[0015] 2 - 5 parts of hyperbranched polyamide ester. Hyperbranched polyamide ester has a highly branched molecular structure, and the molecular chain ends contain a large number of active functional groups. These active functional groups can undergo chemical reactions or physical entanglements with components such as polystyrene plastics, hydrogenated SBS, and PET-PBS, enhancing the compatibility between components and improving the comprehensive properties of the material. The branched structure of hyperbranched polyamide ester can also effectively prevent the propagation of cracks and improve the toughness of the material. In addition, it has good film-forming properties, forming a protective film on the surface of the material and improving the chemical corrosion resistance of the material.

[0016] . Rare earth complex 0.3 - 1 part. This rare earth complex can coordinate with the molecular chains of polystyrene plastics, enhancing the intermolecular interaction force, thereby improving the strength and heat resistance of the material. At the same time, the presence of europium ions endows the complex with excellent luminescent properties, which can endow the material with certain luminescent characteristics and expand the application fields of the material. For example, it has potential application value in decorative materials, anti-counterfeiting materials, etc. In addition, the rare earth complex also has certain antibacterial properties, which can inhibit the growth of microorganisms on the surface of the material and improve the hygienic performance of the material.

[0017] 1 - 4 parts of organic montmorillonite. Organic montmorillonite is a layered silicate mineral. After organic modification, its layer spacing increases, surface properties are improved, and compatibility with polymers is enhanced. In the polystyrene plastic system, organic montmorillonite can be uniformly dispersed in the form of nanoscale lamellae, forming a "nano - composite effect", significantly improving the strength, modulus, and barrier properties of the material. The lamellar structure of organic montmorillonite can hinder the penetration of gases and liquids, improving the water resistance and chemical corrosion resistance of the material. At the same time, it can also act as a nucleating agent, promoting the crystallization of polystyrene plastic and improving the thermal stability and dimensional stability of the material.

[0018] Furthermore, the preparation method of the novel formulation components is as follows:

[0019] Preparation of the phosphorus - containing benzoxazine prepolymer: Bisphenol A, paraformaldehyde, and diphenyl phosphite - p - aminophenyl are added to a three - necked flask in a molar ratio of 1:2:1. An appropriate amount of toluene is added as a solvent, and a small amount of p - toluenesulfonic acid is added as a catalyst. Under nitrogen protection, the temperature is raised to 110 - 120 °C, and the mixture is stirred and reacted for 6 - 8 hours. During the reaction, bisphenol A, paraformaldehyde, and diphenyl phosphite - p - aminophenyl undergo a polycondensation reaction under the action of the catalyst to form a phosphorus - containing benzoxazine prepolymer. After the reaction is completed, the reaction solution is cooled to room temperature and poured into an excess of petroleum ether for precipitation, causing the prepolymer to precipitate from the solution. After filtration, the obtained solid is washed with ethanol 3 - 4 times to remove residual solvents, catalysts, and unreacted raw materials. Then it is vacuum - dried at 60 - 70 °C for 12 - 15 hours to obtain a pure phosphorus - containing benzoxazine prepolymer.

[0020] Preparation of the graphene quantum dots: Graphene quantum dots are prepared by a hydrothermal method. Graphite powder and potassium nitrate are added to concentrated sulfuric acid in a mass ratio of 1:5, and the mixture is stirred in an ice - bath for 30 - 40 minutes to fully disperse the graphite powder in the concentrated sulfuric acid. Then the mixture is transferred to a reaction kettle and reacted at 180 - 200 °C for 12 - 18 hours. Under the high - temperature and high - pressure hydrothermal environment, the graphite powder is oxidized and exfoliated to form graphene quantum dots. After the reaction is completed, it is naturally cooled to room temperature, the reaction product is diluted with deionized water, and then unreacted impurities are removed by centrifugation. The supernatant is dialyzed for 48 - 72 hours to remove small - molecule impurities, and finally freeze - dried to obtain graphene quantum dots.

[0021] Preparation of the hyperbranched polyamide ester: Using trimethylolpropane, trimellitic anhydride, and octadecylamine as raw materials, they are added to a three-necked flask equipped with a stirrer, a thermometer, and a reflux condenser in a molar ratio of 1:3:2. Under nitrogen protection, the temperature is raised to 180 - 200 °C and the reaction is carried out for 4 - 6 hours. During the reaction process, the reaction progress is monitored by measuring the acid value. When the acid value reaches the set value, it indicates that the reaction has reached the expected degree and the reaction is stopped. The reaction product is cooled to room temperature, dissolved in dichloromethane, and then poured into an excess of methanol for precipitation, causing the hyperbranched polyamide ester to precipitate from the solution. After filtration, the obtained solid is dried in vacuo at 50 - 60 °C for 8 - 10 hours to obtain the hyperbranched polyamide ester.

[0022] Preparation of the rare earth complex : Weigh an appropriate amount of europium nitrate , 1,10-phenanthroline (phen), and terephthalic acid . All the chemical reagents used are of analytical grade. Dissolve europium nitrate in absolute ethanol to prepare a solution with a concentration of 0.1 - 0.5 mol / L, and fully dissolve it under magnetic stirring to obtain solution A. Dissolve 1,10-phenanthroline (phen) in absolute ethanol to prepare a solution with a concentration of 0.2 - 0.6 mol / L to obtain solution B. Dissolve terephthalic acid in absolute ethanol to prepare a solution with a concentration of 0.15 - 0.4 mol / L to obtain solution C. Under stirring, slowly add solution B and solution C dropwise to solution A, control the dropping rate to make the reaction proceed at room temperature, and the dropping process lasts for about 30 - 60 minutes. After the dropping is completed, raise the temperature of the reaction system to 60 - 80 °C and continue stirring and reacting for 4 - 8 hours to make the reaction proceed fully. After the reaction is completed, cool the reaction mixture to room temperature, and then separate the reaction product by filtration or centrifugation to obtain a precipitate. Wash the precipitate with absolute ethanol multiple times to remove unreacted raw materials and by-products. Finally, dry the washed product in a vacuum oven at a temperature of 60 - 80 °C for 12 - 24 hours to obtain a pure rare earth complex .

[0023] Preparation of the organic montmorillonite: Sodium montmorillonite is added to deionized water to prepare a suspension with a mass fraction of 5 - 10%. It is dispersed under high-speed stirring for 30 - 60 minutes to fully disperse the sodium montmorillonite in water. Then, an appropriate amount of cetyltrimethylammonium bromide is added, and the mass ratio of it to montmorillonite is 1:2 - 1:3. Stirring continues for 4 - 6 hours. Cetyltrimethylammonium bromide can be inserted into the interlayers of sodium montmorillonite, increasing its interlayer spacing and improving its surface properties. After the reaction, the suspension is centrifuged, and the obtained solid is washed with deionized water until there are no bromide ions in the washing liquid (tested with silver nitrate solution). Finally, the washed solid is dried at 80 - 100 °C for 12 - 18 hours and ground to obtain the organic montmorillonite.

[0024] Further, the preparation method of the modified polystyrene plastic material:

[0025] Raw material pretreatment: The polystyrene plastic is pretreated by combining physical screening and chemical cleaning to remove metal impurities and organic pollutants therein. Physical screening can remove larger metal particles and impurities through methods such as screening and magnetic separation, and chemical cleaning can use appropriate solvents or cleaning agents to remove organic pollutants. Then, the treated polystyrene plastic is crushed into particles with a particle size less than 2 mm for subsequent processing.

[0026] Preparation of new formula components: Synthesize the phosphorus-containing benzoxazine prepolymer, graphene quantum dots, hyperbranched polyamide ester, and rare earth complex respectively according to the above preparation methods and the organic montmorillonite.

[0027] . Batching: Weigh hydrogenated SBS, PET-PBS copolymer, nano-titanium dioxide, antioxidant 1010, calcium stearate, the prepared phosphorus-containing benzoxazine prepolymer, graphene quantum dots, hyperbranched polyamide ester, rare earth complex , and the organic montmorillonite according to the proportion. If a coupling agent is used, weigh silane coupling agent KH550 according to 0.5 - 2 times the mass of nano-titanium dioxide.

[0028] Mixing: Add the pretreated polystyrene plastic particles and the above components to a high-speed mixer in sequence, and stir at a rotation speed of 800 - 1200 r / min for 10 - 15 min to fully mix them. High-speed stirring can evenly disperse each component in a short time to form a uniform mixture, laying a good foundation for subsequent extrusion molding.

[0029] Extrusion molding: Add the mixed materials into a twin-screw extruder. The temperature of the extruder is set as follows: the first section is 180 - 190 °C, the second section is 190 - 200 °C, and the third section is 200 - 220 °C. The screw speed is 200 - 300 r / min. Then carry out melt blending extrusion, cooling, air drying, pelletizing, homogenization, and packaging. During the extrusion process, the materials are melted at high temperature. Through the rotation and shear force of the screw, the components are further mixed evenly, and physical and chemical changes occur to form a modified polystyrene plastic material with good performance. After cooling and air drying, the material is pelletized for subsequent storage and transportation. The homogenization process can further ensure the stability of product quality, and finally, packaging is carried out.

[0030] Advantageous technical effects of the invention:

[0031] The good compatibility of hydrogenated SBS and recycled polystyrene plastics enables it to be evenly dispersed in the matrix, effectively transfer stress, combine with the rigid chain segment enhancement of PET-PBS, and the nano-enhancement effect of graphene quantum dots. This means that when the material is subjected to external forces, it can better resist tensile and impact forces, reduce the risk of rupture, and can be widely used in packaging, construction and other fields with high requirements for material strength and toughness. The europium ions in the rare earth complex have empty electron orbits and can form coordination bonds with these atoms or groups containing lone pair electrons on the molecular chain of polystyrene plastics. The formation of this coordination bond is like building a bridge between molecular chains, tightly connecting the originally relatively loose molecular chains. When the material is heated, these additional coordination bonds require higher energy to be broken, so that the molecular chains do not easily slide or separate, thus improving the thermal stability of the material, manifested as enhanced heat resistance of the material. In a high-temperature environment, the metal-ligand bonds in its structure can remain stable within a certain temperature range and are not easily broken. When the material is locally heated, the rare earth complex can act as a thermal stability center, absorb and disperse heat, and prevent the rapid transfer and accumulation of heat inside the material. This is like setting up multiple "heat dissipation points" inside the material, avoiding material degradation caused by local overheating. The intumescent carbon layer formed by the phosphorus-containing benzoxazine prepolymer at high temperature, as well as the coordination of the rare earth complex with the molecular chain, greatly enhances the heat resistance and thermal stability of the material. This enables the material to maintain stable performance in a high-temperature environment and is suitable for components of heating equipment such as electronic appliances, avoiding affecting the normal operation of the equipment due to heat deformation. The present invention endows the material with excellent flame retardant properties, effectively preventing the spread of fire, and significantly improving the fire safety in the applications in the construction and electronics fields. The rare earth complex also endows the material with antibacterial properties, which is suitable for scenarios with strict hygiene requirements such as food packaging and medical devices. In addition, the unique fluorescence properties open up new application spaces for the material in the fields of decoration and anti-counterfeiting. The addition of calcium stearate and the phosphorus-containing benzoxazine prepolymer improves the processing fluidity of the material, enabling it to be successfully formed in an extruder. At the same time, the present invention uses waste polystyrene as a raw material to achieve resource recycling and reuse, reduce environmental pollution, and has significant environmental benefits. Detailed implementation mode

[0032] Example 1

[0033] (I) Preparation of phosphorus-containing benzoxazine prepolymer

[0034] In a three-necked flask equipped with a stirrer, a thermometer, and a reflux condenser, bisphenol A, paraformaldehyde, and diphenyl p-aminophenyl phosphate were successively added, and their molar ratio was precisely controlled at 1:2:1. Then, an appropriate amount of toluene was added to the flask as a solvent, and the amount of toluene was such that it could fully dissolve the reactants and facilitate stirring. A small amount of p-toluenesulfonic acid was added as a catalyst, and its amount was about 0.5%-1% of the total mass of the reactants. Under nitrogen protection, the reaction system was slowly heated to 110-120 °C, and the reaction was stirred for 6-8 hours in this temperature range. During the reaction, the changes in the reaction system were closely observed, and the reaction progress was monitored by thin-layer chromatography (TLC). When TLC showed that the reactants were basically completely converted, heating was stopped, and the reaction solution was cooled to room temperature. Subsequently, the reaction solution was poured into an excess of petroleum ether, and the phosphorus-containing benzoxazine prepolymer would precipitate out. The precipitate was collected by filtration, and the obtained solid was washed 3-4 times with ethanol to remove residual toluene, p-toluenesulfonic acid, and unreacted raw materials. Finally, the washed solid was placed in a vacuum drying oven and vacuum dried at 60-70 °C for 12-15 hours to obtain a pure phosphorus-containing benzoxazine prepolymer. The prepared phosphorus-containing benzoxazine prepolymer was characterized by infrared spectroscopy, and absorption peaks corresponding to the functional groups appeared at the characteristic peaks, indicating successful synthesis.

[0035] (II) Preparation of Graphene Quantum Dots

[0036] Graphene quantum dots were prepared by a hydrothermal method. First, graphite powder and potassium nitrate were added to concentrated sulfuric acid at a mass ratio of 1:5, and under ice bath conditions, a powerful stirrer was used to stir for 30-40 minutes to ensure that the graphite powder was fully dispersed in the concentrated sulfuric acid. Then, the mixed solution was transferred to a high-pressure reaction kettle, the reaction kettle was sealed and placed in an oven, and the reaction was carried out at 180-200 °C for 12-18 hours. After the reaction, the reaction kettle was allowed to cool naturally to room temperature. Next, the reaction product was diluted with a large amount of deionized water, and the dilution ratio was about 1:10. It was centrifuged at a speed of 8000-10000 r / min for 15-20 minutes by a high-speed centrifuge to remove unreacted impurities. The supernatant was filled into a dialysis bag and dialyzed in deionized water for 48-72 hours, and the deionized water was changed every 8-12 hours to fully remove small molecule impurities. Finally, the dialyzed solution was freeze-dried to obtain black powdery graphene quantum dots. Observed by transmission electron microscopy (TEM), the particle size of the graphene quantum dots was distributed between 5-10 nm, proving successful preparation.

[0037] (III) Preparation of Hyperbranched Polyamide Ester

[0038] In a three-necked flask equipped with a stirrer, a thermometer and a reflux condenser, trimethylolpropane, trimellitic anhydride and octadecylamine were added in a molar ratio of 1:3:2. Under nitrogen protection, the reaction system was heated to 180 - 200 °C and reacted for 4 - 6 hours. During the reaction, a small amount of sample was taken every 1 hour, and the acid value was measured by acid-base titration to monitor the reaction progress. When the acid value reached the set value (generally the acid value decreased to 10% - 15% of the initial acid value), the reaction was stopped. The reaction product was cooled to room temperature, dissolved in an appropriate amount of dichloromethane, and then slowly poured into an excess of methanol. The hyperbranched polyamide ester would precipitate out. The precipitate was collected by filtration, and the obtained solid was vacuum dried in a vacuum drying oven at 50 - 60 °C for 8 - 10 hours to obtain the hyperbranched polyamide ester. Its molecular weight was determined by gel permeation chromatography (GPC), and the molecular weight distribution was between 5000 and 10000, indicating that the polymerization reaction achieved the expected effect.

[0039] (IV) Rare earth complex Preparation

[0040] Weigh an appropriate amount of europium nitrate , 1,10-phenanthroline (phen) and terephthalic acid . All chemical reagents used were of analytical grade. Dissolve europium nitrate in absolute ethanol to prepare solution A with a concentration of 0.1 - 0.5 mol / L, and stir it thoroughly for 30 - 40 minutes under magnetic stirring to ensure complete dissolution of europium nitrate. Dissolve 1,10-phenanthroline (phen) in absolute ethanol to prepare solution B with a concentration of 0.2 - 0.6 mol / L, and stir it until completely dissolved. Dissolve terephthalic acid in absolute ethanol to prepare solution C with a concentration of 0.15 - 0.4 mol / L. Under stirring, slowly add solution B and solution C dropwise to solution A, control the dropping rate at 1 - 2 drops per second, and carry out the reaction at room temperature. The dropping process lasts for about 30 - 60 minutes. After the dropping is completed, heat the reaction system to 60 - 80 °C and continue stirring and reacting for 4 - 8 hours. After the reaction is completed, cool the reaction mixture to room temperature, and then obtain the precipitate by filtration or centrifugation. Wash the precipitate with absolute ethanol 3 - 5 times to remove unreacted raw materials and by-products. Finally, dry the washed product in a vacuum oven at 60 - 80 °C for 12 - 24 hours to obtain a pure rare earth complex . Its structure was characterized by X-ray single crystal diffraction, and it was determined that its structure was in line with expectations.

[0041] (V) Preparation of organic montmorillonite

[0042] Sodium-based montmorillonite was added to deionized water to prepare a suspension with a mass fraction of 5-10%. It was dispersed for 30-60 minutes at a rotational speed of 3000-5000 r / min using a high-speed stirrer. Then, an appropriate amount of cetyltrimethylammonium bromide was added, and the mass ratio of it to montmorillonite was 1:2-1:3. Stirring continued for 4-6 hours. After the reaction ended, the suspension was centrifuged at a rotational speed of 5000-8000 r / min for 15-20 minutes. The obtained solid was washed with deionized water until there were no bromide ions in the washing liquid (tested with 0.1 mol / L silver nitrate solution until no white precipitate formed after adding the silver nitrate solution). Finally, the washed solid was dried at 80-100 °C for 12-18 hours and ground to obtain organic montmorillonite. Through X-ray diffraction (XRD) analysis, the layer spacing of the organic montmorillonite was significantly increased compared with that of sodium-based montmorillonite, indicating successful modification.

[0043] Example 2

[0044] Material preparation: Weigh 80 parts of polystyrene plastic, 5 parts of hydrogenated SBS, 3 parts of PET-PBS, 0.5 part of nano-titanium dioxide, 0.5 part of antioxidant 1010, 1 part of calcium stearate, 1 part of the prepared phosphorus-containing benzoxazine prepolymer, 0.1 part of graphene quantum dots, 2 parts of hyperbranched polyamide ester, and 0.3 part of rare earth complex , 1 part of organic montmorillonite, and 0.25 part of silane coupling agent KH550 (based on the mass of nano-titanium dioxide).

[0045] . Pretreat the polystyrene plastic. Physically screen to remove larger impurity particles, then soak and wash with an organic solvent (such as acetone) to remove organic pollutants, and then crush it into particles with a particle size less than 2 mm.

[0046] Weigh each component according to the above batching steps.

[0047] Add each component to a high-speed mixer in sequence and stir at a rotational speed of 1000 r / min for 12 min to make them fully mixed.

[0048] Add the mixed material to a twin-screw extruder. The temperature of the extruder is set as follows: the first section is 185 °C, the second section is 195 °C, the third section is 210 °C, and the screw rotational speed is 250 r / min. Carry out melt blending extrusion, cooling, air drying, pelletizing, homogenization, and packaging.

[0049] Performance test: Conduct performance tests on the prepared material. The tensile strength is 50 MPa, the impact strength is 30 kJ / ㎡, the heat distortion temperature is 90 °C, the melt flow rate is 4.5 g / 10 min, the initial decomposition temperature in the TGA test is 360 °C, the limiting oxygen index is 30%, the antibacterial rate reaches 90%, and it can emit red fluorescence under ultraviolet light excitation.

[0050] Example 3

[0051] Material preparation: Weigh 90 parts of polystyrene plastic, 10 parts of hydrogenated SBS, 5 parts of PET-PBS, 1.5 parts of nano-titanium dioxide, 1 part of antioxidant 1010, 2 parts of calcium stearate, 2 parts of the prepared phosphorus-containing benzoxazine prepolymer, 0.3 part of graphene quantum dots, 3 parts of hyperbranched polyamide ester, 0.6 part of rare earth complex , 2 parts of organic montmorillonite, 0.75 part of silane coupling agent KH550.

[0052] Preparation process:

[0053] Repeat the steps of preparing the new formulation components, pre-treating the polystyrene plastic, and batching in Example 1.

[0054] Add each component to a high-speed mixer and stir at a speed of 1100 r / min for 13 min.

[0055] Add the mixed material to a twin-screw extruder. The temperature of the extruder is set as follows: the first section is 188 °C, the second section is 198 °C, the third section is 215 °C, and the screw speed is 260 r / min. Then carry out melt blending extrusion, cooling, air drying, pelletizing, homogenization, and packaging.

[0056] Performance test: Tensile strength is 58 MPa, impact strength is 38 kJ / ㎡, heat distortion temperature is 95 °C, melt flow rate is 4.2 g / 10 min, initial decomposition temperature is 375 °C, limiting oxygen index is 32%, antibacterial rate reaches 95%, and fluorescence intensity is enhanced.

[0057] Example 4

[0058] Material preparation: Weigh 100 parts of polystyrene plastic, 15 parts of hydrogenated SBS, 8 parts of PET-PBS, 3 parts of nano-titanium dioxide, 2 parts of antioxidant 1010, 3 parts of calcium stearate, 3 parts of the prepared phosphorus-containing benzoxazine prepolymer, 0.5 part of graphene quantum dots, 5 parts of hyperbranched polyamide ester, 1 part of rare earth complex , 4 parts of organic montmorillonite, 1.5 part of silane coupling agent KH550.

[0059] Preparation process:

[0060] Same as the relevant steps in Example 1 and Example 2.

[0061] Add each component to a high-speed mixer and stir at a speed of 1200 r / min for 15 min.

[0062] Add the mixed materials to a twin-screw extruder. Set the extruder temperature at 190 °C for the first section, 200 °C for the second section, and 220 °C for the third section. Set the screw speed at 300 r / min and conduct melt blending extrusion, cooling, air drying, pelletizing, homogenization, and packaging.

[0063] Performance testing: Tensile strength is 65 MPa, impact strength is 45 kJ / ㎡, heat distortion temperature is 100 °C, melt flow rate is 3.8 g / 10 min, initial decomposition temperature is 385 °C, limiting oxygen index is 35%, antibacterial rate reaches 98%, and the fluorescence effect is more significant.

[0064] (I) Introduction of comparative products

[0065] Unmodified polystyrene plastic: Commonly available in the market, it is made directly from recycled waste polystyrene without any modification. Its properties are greatly affected by the source of waste polystyrene and the recycling process, and there are generally problems such as low tensile strength, poor impact toughness, and insufficient heat resistance. Generally, the tensile strength is between 25 - 35 MPa, the impact strength is between 10 - 15 kJ / ㎡, the heat distortion temperature is between 60 - 70 °C, and there are no obvious flame retardant, antibacterial, and fluorescence properties.

[0066] Product A: Prepared a polystyrene plastic product using ordinary SBS as a toughening agent (mass ratio of styrene to butadiene is 30:70, molecular weight is 150,000). In addition to ordinary SBS and recycled polystyrene, 2 parts of stearic acid are added as a lubricant, 0.5 part of antioxidant 168, and 0.3 part of ultraviolet absorber UV-531. Tensile strength is 35 MPa, impact strength is 15 kJ / ㎡, heat distortion temperature is 70 °C, melt flow rate is 5.2 g / 10 min, initial decomposition temperature is 320 °C, limiting oxygen index is 20%, antibacterial rate is less than 50%, and there is no fluorescence property.

[0067] Product B: Prepared a polystyrene plastic product using unmodified PET as a reinforcing agent (intrinsic viscosity is 0.65 dL / g). In addition to unmodified PET and recycled polystyrene, 3 parts of calcium carbonate are added as a filler, 0.8 part of zinc stearate as a lubricant, and 0.6 part of antioxidant CA. Tensile strength is 40 MPa, impact strength is 20 kJ / ㎡, heat distortion temperature is 75 °C, melt flow rate is 4.9 g / 10 min, initial decomposition temperature is 330 °C, limiting oxygen index is 22%, antibacterial rate is less than 60%, and there is no fluorescence property.

[0068] Product C: A polystyrene plastic product is prepared by using linear low-density polyethylene (LLDPE) as a modifier (with a density of 0.92 g / cm³ and a melt flow rate of 2 g / 10 min). In addition to LLDPE and recycled polystyrene, 1.5 parts of talc are added as a filler, 0.5 part of stearic acid amide is added as a lubricant, and 0.4 part of antioxidant 1076 is added. The tensile strength is 42 MPa, the impact strength is 22 kJ / ㎡, the heat distortion temperature is 80 °C, the melt flow rate is 5.0 g / 10 min, the initial decomposition temperature is 340 °C, the limiting oxygen index is 23%, the antibacterial rate is less than 65%, and there is no fluorescence property.

[0069] (II) Synergistic effect description

[0070] Tensile strength: The tensile strength of unmodified polystyrene plastic is usually in the range of 25 - 35 MPa, for Product A it is 35 MPa, for Product B it is 40 MPa, and for Product C it is 42 MPa. The tensile strength of Example 1 of the present invention reaches 50 MPa, Example 2 is 58 MPa, and Example 3 is 65 MPa. This is because in the present invention, hydrogenated SBS has good compatibility with polystyrene plastic, and the molecular chains are intertwined with each other, enhancing the integrity of the material; the rigid chain segments of PET-PBS provide additional strength support; graphene quantum dots are evenly dispersed in the matrix, playing a role of nano-reinforcement; the active functional groups of hyperbranched polyamide ester interact with other components, enhancing the interfacial bonding force; the nanosheet structure of organic montmorillonite also makes a positive contribution to the improvement of tensile strength. Due to the synergistic effect of multiple components, the tensile strength of the product of the present invention is greatly improved. Compared with unmodified polystyrene plastic, it is increased by 43% - 100%, compared with Product A it is increased by 43% - 86%, compared with Product B it is increased by 30% - 63%, and compared with Product C it is increased by 24% - 55%.

[0071] Impact strength: The impact strength of unmodified polystyrene plastic is in the range of 10 - 15 kJ / ㎡, for Product A it is 15 kJ / ㎡, for Product B it is 20 kJ / ㎡, and for Product C it is 22 kJ / ㎡. The impact strength of Example 1 of the present invention is 30 kJ / ㎡, Example 2 is 38 kJ / ㎡, and Example 3 is 45 kJ / ㎡. The elastomeric properties of hydrogenated SBS and the highly branched structure of hyperbranched polyamide ester can effectively disperse and absorb energy when the material is impacted, preventing the rapid propagation of cracks, thus significantly improving the impact strength. Compared with unmodified polystyrene plastic, the impact strength of the product of the present invention is increased by 100% - 200%, compared with Product A it is increased by 100% - 200%, compared with Product B it is increased by 90% - 125%, and compared with Product C it is increased by 82% - 105%.

[0072] Heat distortion temperature: The heat distortion temperature of unmodified polystyrene plastics is 60 - 70 °C, that of Product A is 70 °C, that of Product B is 75 °C, and that of Product C is 80 °C. The heat distortion temperature of Example 1 of the present invention is 90 °C, that of Example 2 is 95 °C, and that of Example 3 is 100 °C. The intumescent carbon layer formed by the phosphorus-containing benzoxazine prepolymer at high temperature can play a heat insulation role, and the coordination of the rare earth complex with the molecular chain of polystyrene plastic enhances the intermolecular interaction force, making the material less likely to deform at high temperature. Compared with unmodified polystyrene plastics, the heat distortion temperature of the products of the present invention has increased by 29% - 43%, compared with Product A by 29% - 43%, compared with Product B by 27% - 33%, and compared with Product C by 20% - 25%.

[0073] Thermal stability: By testing the initial decomposition temperature through TGA, the initial decomposition temperature of unmodified polystyrene plastics is relatively low, generally around 300 °C, that of Product A is 320 °C, that of Product B is 330 °C, and that of Product C is 340 °C. The initial decomposition temperature of Example 1 of the present invention is 360 °C, that of Example 2 is 375 °C, and that of Example 3 is 385 °C. Antioxidant 1010 effectively inhibits the oxidative degradation of the material at high temperature, and the presence of the phosphorus-containing benzoxazine prepolymer and rare earth complex enhances the thermal stability of the material. Compared with unmodified polystyrene plastics, the initial decomposition temperature of the products of the present invention has increased by 20% - 28%, compared with Product A by 13% - 20%, compared with Product B by 14% - 17%, and compared with Product C by 13% - 15%. This greatly expands the application range of the modified polystyrene plastics of the present invention in high-temperature environments. For example, in some industrial production environments that need to withstand a certain temperature or in scenarios such as heat dissipation components of electronic products, the products of the present invention can maintain more stable performance.

[0074] Flame retardancy: The limiting oxygen index of unmodified polystyrene plastics is usually lower than 20%, belonging to flammable materials. The limiting oxygen index of Product A is 20%, that of Product B is 22%, and that of Product C is 23%. The limiting oxygen index of Example 1 of the present invention is 30%, that of Example 2 is 32%, and that of Example 3 is 35%. The intumescent carbon layer formed by the decomposition of the phosphorus-containing benzoxazine prepolymer at high temperature can isolate oxygen and heat, effectively prevent the spread of fire, and significantly improve the flame retardancy of the material. Compared with unmodified polystyrene plastics, the limiting oxygen index of the products of the present invention has increased by 50% - 75%, compared with Product A by 50% - 75%, compared with Product B by 45% - 59%, and compared with Product C by 30% - 52%. In fields such as construction and electronics where high fire safety requirements are imposed, the flame retardancy advantage of the products of the present invention makes them a safer and more reliable material choice.

[0075] Antibacterial performance: Unmodified polystyrene plastics basically do not have antibacterial performance. The antibacterial rate of product A is less than 50%, that of product B is less than 60%, and that of product C is less than 65%. The antibacterial rate of example 1 of the present invention reaches 90%, that of example 2 is 95%, and that of example 3 is 98%. Europium ions in rare earth complexes have certain antibacterial activity, which can inhibit the growth and reproduction of bacteria, giving the products of the present invention obvious advantages in application scenarios with high hygiene requirements, such as food packaging, medical devices and other fields. Compared with product A, the antibacterial rate of the products of the present invention has increased by 40 - 48 percentage points, compared with product B by 35 - 38 percentage points, and compared with product C by 33 - 33 percentage points.

[0076] Fluorescent performance: Unmodified polystyrene plastics, as well as products A, B, and C, have no fluorescent performance. Due to the addition of rare earth complexes in the present invention , example 1 can emit red fluorescence under ultraviolet light excitation, the fluorescence intensity of example 2 is enhanced, and the fluorescence effect of example 3 is more significant. This characteristic endows the material with unique optical properties, making it have potential application value in fields such as decorative materials and anti-counterfeiting materials, greatly expanding the application scope of polystyrene plastics, which is an advantage that unmodified and common modified polystyrene plastics do not have.

[0077] Melt flow rate and processing performance: The melt flow rate of unmodified polystyrene plastics fluctuates greatly due to the influence of raw materials and recycling processes, generally between 3 - 6 g / 10min. The melt flow rate of product A is 5.2 g / 10min, that of product B is 4.9 g / 10min, and that of product C is 5.0 g / 10min. The melt flow rate of example 1 of the present invention is 4.5 g / 10min, that of example 2 is 4.2 g / 10min, and that of example 3 is 3.8 g / 10min. Although the melt flow rate of the products of the present invention is slightly lower than that of some comparative products, in the actual processing process, the addition of phosphorus-containing benzoxazine prepolymer and calcium stearate makes the fluidity of the material good in the extruder, and it can smoothly complete processing and forming processes such as injection molding and extrusion. Moreover, a lower melt flow rate means that the material is more likely to maintain its shape during the forming process, reducing the deformation and defects of the products, and improving the forming quality and dimensional accuracy of the products. For example, when injection molding plastic products with complex shapes, the products of the present invention can better fill the mold cavity and ensure the integrity and surface quality of the products.

Claims

1. A modified polystyrene plastic material, characterized in that: The invention is composed of the following materials in parts by weight: 80-100 parts of polystyrene plastic, 5-15 parts of hydrogenated styrene-butadiene-styrene block copolymer, 3-8 parts of polyethylene terephthalate-polybutylene succinate block copolymer, 0.5-3 parts of nano titanium dioxide, and 1010 parts of antioxidant. 0.5-2 parts, 1-3 parts of calcium stearate, 1-3 parts of phosphorus-containing benzoxazine prepolymer, 0.1-0.5 parts of graphene quantum dots, 2-5 parts of hyperbranched polyamide ester, 0.3-1 parts of rare earth complex Eu2(BDC)3(phen)2, and 1-4 parts of organic montmorillonite; the hydrogenation degree of the hydrogenated styrene-butadiene-styrene block copolymer is greater than 90%, the mass ratio of styrene to butadiene is 30:70, and the molecular weight is 150,000; the phosphorus-containing benzoxazine prepolymer is prepared by bisphenol A, paraformaldehyde, and p-aminophenyl diphenyl phosphate in a molar ratio of 1:2:1, in toluene solvent, with p-toluenesulfonic acid as a catalyst, and under nitrogen protection for 11 The invention discloses a novel nanostructured carbon nanotube film, which is prepared by reacting at 0-120°C for 6-8 hours; the graphene quantum dots are prepared by mixing graphite powder and potassium nitrate in concentrated sulfuric acid in an ice bath at a mass ratio of 1:5, reacting at 180-200°C for 12-18 hours, and then diluting, centrifuging, dialyzing, and freeze-drying. The hyperbranched polyamide ester is prepared by using trimethylolpropane, trimellitic anhydride, and octadecylamine as raw materials in a molar ratio of 1:3:2, and reacting at 180-200°C for 4-6 hours under nitrogen protection. The polyethylene terephthalate-polybutylene succinate block copolymer has a molar ratio of polyethylene terephthalate to polybutylene succinate segments of 3:2, and an intrinsic viscosity of 0.75 dL / g.

2. The modified polystyrene plastic material according to claim 1, characterized in that: The nano titanium dioxide is anatase-type, has a particle size of 20-50 nm, and a specific surface area of ​​more than 50 m2 / g.

3. A method for preparing the modified polystyrene plastic material according to any one of claims 1 to 2, characterized in that: The following steps are involved: The polystyrene plastic is pre-treated by combining physical screening and chemical cleaning to remove impurities and crush into particles with a size of less than 2 mm; Phosphorus-containing benzoxazine prepolymer, graphene quantum dots, hyperbranched polyamide ester, rare earth complex Eu2(BDC)3(phen)2 and organic montmorillonite were prepared respectively; Weigh hydrogenated SBS, PET-PBS copolymer, nano titanium dioxide, antioxidant 1010, calcium stearate, prepared phosphorus-containing benzoxazine prepolymer, graphene quantum dots, hyperbranched polyamide ester, rare earth complex Eu2(BDC)3(phen)2, and organic montmorillonite according to the ratio; Add the pretreated polystyrene plastic particles and the above components into a high-speed mixer in sequence, and stir at a speed of 800-1200 r / min for 10-15 minutes to fully mix them; The mixed materials are added into a twin-screw extruder, the extruder temperature is set to 180-190°C for the first section, 190-200°C for the second section, 200-220°C for the third section, the screw speed is 200-300r / min, melt blending extrusion, cooling, air drying, pelletizing, homogenization, and packaging; The preparation method of the organic montmorillonite comprises the following steps: adding sodium montmorillonite to deionized water to prepare a suspension with a mass fraction of 5-10%, dispersing the suspension for 30-60 minutes under high-speed stirring, then adding hexadecyltrimethylammonium bromide with a mass ratio of 1:2-1:3 to montmorillonite, and continuing stirring for 4-6 hours. After the reaction is completed, centrifuging the suspension, washing the obtained solid with deionized water until there is no bromide ion in the washing liquid, and finally drying the washed solid at 80-100° C. for 12-18 hours, and grinding the washed solid to obtain the organic montmorillonite.

4. The preparation method according to claim 3, characterized in that: The preparation method of the rare earth complex Eu2(BDC)3(phen)2 is as follows: dissolving europium nitrate Eu(NO3)3.6H2O in anhydrous ethanol to prepare a solution A with a concentration of 0.1-0.5 mol / L, dissolving o-phenanthroline in anhydrous ethanol to prepare a solution B with a concentration of 0.2-0.6 mol / L, and dissolving terephthalic acid in anhydrous ethanol to prepare a solution C with a concentration of 0.15-0.4 mol / L; slowly dropping solution B and solution C into the solution under stirring. In liquid A, the dropping speed is controlled so that the reaction proceeds at room temperature, and the dropping process lasts for 30-60 minutes; after the dropping is completed, the reaction system is heated to 60-80°C, and the stirring reaction is continued for 4-8 hours; after the reaction is completed, the reaction mixture is cooled to room temperature, and then the reaction product is filtered or centrifuged to obtain a precipitate, the precipitate is washed several times with anhydrous ethanol, and finally dried in a vacuum oven at 60-80°C for 12-24 hours to obtain a rare earth complex Eu2(BDC)3(phen)2.