Expandable polystyrene particles with high expansion ratio, a material for preparation and a method for preparation

Abstract

The application relates to the technical field of expandable polystyrene, and discloses expandable polystyrene particles with high foaming ratio, a preparation material and a preparation method, the preparation method comprising the following steps: prepolymerization, demonomerization and volatilization, mixed extrusion, underwater pelletization, screening and drying and foaming treatment; in the application, through the adoption of nanometer grinding and reaction extrusion polymerization technology, a rubber phase is uniformly dispersed in a polystyrene matrix in a nanometer scale and forms a stable chemical crosslinking network, the compatibility of the matrix material is improved, a polymer matrix with uniform structure and high strength is constructed for a subsequent foaming process, the problems of coarse cells and collapse are avoided, high ratio and uniform and fine cell structures of the foaming material are ensured, and the impact toughness and the dimensional stability of the material are improved.

Description

Technical Field

[0001] This invention relates to the field of expandable polystyrene technology, specifically to expandable polystyrene particles with high expansion ratio, preparation materials, and preparation methods. Background Technology

[0002] Expandable polystyrene is a polystyrene product with added foaming agent. It appears as colorless, transparent, bead-like granules. Due to its excellent and long-lasting thermal insulation properties, unique cushioning and shock resistance, anti-aging properties, and waterproof properties, expandable polystyrene has been widely used in daily life, agriculture, transportation, military industry, and aerospace industry. It is especially favored in the fields of construction, packaging, electronic and electrical products, shipbuilding, vehicle and aircraft manufacturing.

[0003] Currently, in the field of expandable polystyrene materials, existing technologies for preparing high-expansion polystyrene materials often face several technical bottlenecks. During the foaming process, poor compatibility between the base resin and the foaming agent and additives easily leads to large, unevenly distributed, or even collapsing and merging of the cell structure. This not only directly limits the final foaming ratio of the material but also severely weakens its impact strength and dimensional stability, making the material prone to deformation and damage when subjected to loads and changes in ambient temperature. Secondly, conventional production processes lack sufficient control over cell morphology and size, making it difficult to form a uniform and dense closed-cell structure, resulting in moisture loss from the material. Poor barrier properties and high water absorption rate severely affect its long-term performance and insulation reliability in humid environments. Furthermore, existing materials have limited functionality and generally lack antistatic capabilities. When used for packaging precision electronic products, static electricity accumulation can easily damage the devices. At the same time, the material's inherent toughness is insufficient to meet the protection requirements under conditions of repeated drops or long-term vibration. In addition, traditional foaming processes are ineffective in controlling volatile organic compounds, posing environmental risks. Moreover, the stability and efficiency of the production process need to be improved, making it difficult to achieve a balance between mechanical properties, functionality, and environmental friendliness while ensuring a high foaming ratio.

[0004] Therefore, this paper proposes expandable polystyrene particles with high foaming ratio, preparation materials, and preparation methods to solve the above problems. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides expandable polystyrene particles with high expansion ratio, preparation materials, and preparation methods, solving the problems mentioned in the background technology, such as the materials being prone to deformation and damage when subjected to loads and changes in ambient temperature, and the difficulty in achieving a balance between mechanical properties, functionality, and environmental friendliness while ensuring a high expansion ratio.

[0006] To achieve the above objectives, the present invention provides the following technical solution: expandable polystyrene particles with high foaming ratio, preparation materials, and preparation method, wherein the preparation method includes the following steps: Step 1: Prepolymerization. Styrene monomer, rubber nanoparticles, initiator and stabilizer are added to the reactor and stirred for 1-2 hours at a temperature of 60-80℃ and a pressure of 0.1-0.5MPa to obtain the prepolymer. Step 2: Remove monomers and volatiles. Transfer the prepolymer to a devolatilization device and remove unreacted monomers and volatiles under a vacuum of 0.01-0.05 MPa and a temperature of 100-120°C for 0.5-1 hour. Step 3: Mixed extrusion. The devolatilized prepolymer, antistatic agent, dispersant, and lubricant are added to a twin-screw extruder at a weight ratio of 100:5-10:1-3:0.5-2. Reactive extrusion bulk polymerization is carried out at a screw speed of 200-500 r / min and a barrel temperature of 150-200℃ to obtain a melt copolymer. Step 4: Underwater pelletizing. The molten copolymer is extruded through a die into a high-pressure underwater cutting device. Under a water pressure of 5-10 MPa and a cutting speed of 100-200 m / min, it is cut into particles with a diameter of 1-3 mm. Step 5: Screening and drying. The granulated particles are screened through a vibrating screen to remove unqualified products, and then dried in a hot air dryer at 80-100℃ for 1-2 hours to obtain expandable polystyrene particles. Step 6: Foaming treatment. Place the dried granules in a supercritical carbon dioxide foaming device, introduce carbon dioxide gas, control the pressure at 10-20 MPa and the temperature at 100-150℃, maintain the pressure and temperature for 1-2 hours to make the carbon dioxide reach the supercritical state, then quickly release the pressure to normal pressure, cool and solidify to obtain expandable polystyrene foam material with high foaming ratio. The rubber nanoparticles are obtained by processing rubber using nano-grinding technology, with a particle size of 50-100 nm. The initiator is benzoyl peroxide or azobisisobutyronitrile, and its dosage is 0.1-0.5% of the styrene monomer. The stabilizer is calcium stearate or epoxidized soybean oil, and its dosage is 0.5-1% of the styrene monomer.

[0007] Preferably, in step one, the prepolymerization reactor is a batch reactor, the stirring speed is 100-300 r / min, the reaction temperature is controlled at 65-75℃, the pressure is controlled at 0.2-0.4 MPa, and the reaction time is 1.5 hours; the preparation method of the rubber nanoparticles includes: after the rubber is embrittled in a liquid nitrogen environment, it is placed in a nano-grinding mill, using zirconia balls as the grinding medium, the ball-to-material ratio is 10:1, the grinding speed is 1000-2000 r / min, and the grinding time is 2-4 hours, to obtain rubber nanoparticles with a particle size of 50-100 nm.

[0008] Preferably, in step three, the twin-screw extruder is a co-rotating twin-screw extruder with a screw length-to-diameter ratio of 40:1. The barrel temperature is controlled in zones: zone 1 150-160℃, zone 2 160-170℃, zone 3 170-180℃, zone 4 180-190℃, and die zone 190-200℃. The reaction extrusion bulk polymerization pressure is 5-10 MPa, and the residence time is 2-5 minutes. The antistatic agent, dispersant, and lubricant are premixed before being added. The premixing is carried out in a high-speed mixer at 500-1000 r / min for 10-20 minutes.

[0009] Preferably, in step four, the water pressure of the high-pressure underwater cutting device is 8-10 MPa, the cutting speed is 150-200 m / min, the die head diameter is 1-2 mm, and the cutting blade rotation speed is 1000-1500 r / min; the granules after cutting are dehydrated by a centrifugal dewatering machine at a dewatering speed of 2000-3000 r / min for 5-10 minutes.

[0010] Preferably, in step six, the depressurization rate of the supercritical carbon dioxide foaming device is 1-5 MPa / s, the cooling method is water cooling, the cooling temperature is 20-30℃, and the cooling time is 10-30 minutes; the density of the foamed material is 20-50 kg / m³, and the closed-cell rate is ≥90%.

[0011] Preferably, the preparation method further includes step seven: surface treatment, in which the foamed particles are immersed in a waterproof coating liquid, wherein the waterproof coating liquid is composed of an organosilicon waterproofing agent and ethanol in a mass ratio of 1:9, the immersion time is 1-2 minutes, and after removal, it is dried at 80°C for 30 minutes to form a waterproof coating with a thickness of 1-5 μm; the concentration of the organosilicon waterproofing agent in the waterproof coating liquid is 10-20%, and methylsilane or ethylsilane is used.

[0012] Preferably, the pore structure of the particles is formed by supercritical carbon dioxide foaming process, wherein the pore morphology is a closed-cell structure with a pore diameter ranging from 50 to 200 micrometers. In the foamable polystyrene / rubber copolymer matrix, the polystyrene segments and rubber segments are cross-linked by chemical bonds formed by reactive extrusion bulk polymerization, with a cross-linking degree of 5-15%. The rubber nanoparticles are uniformly dispersed in the polystyrene continuous phase at a particle size of 50-100 nanometers. The particles are composed of an expandable polystyrene / rubber copolymer matrix, an antistatic agent, a dispersant, and a lubricant. Based on 100 parts by weight of the expandable polystyrene / rubber copolymer matrix, the content of the antistatic agent is 3-8 parts by weight, the content of the dispersant is 1-3 parts by weight, and the content of the lubricant is 0.5-2 parts by weight.

[0013] Preferably, the antistatic agent is conductive carbon black or a quaternary ammonium salt, forming a three-dimensional continuous conductive network in the polymer matrix. The particle surface is coated with a dense coating formed by an organosilicon waterproofing agent through an impregnation and drying process, with a coating thickness of 1-5 micrometers. The spherical or ellipsoidal geometry of the particles is directly formed by a high-pressure underwater cutting process with a water pressure of 8-12 MPa, and its sphericity is not less than 0.9.

[0014] Preferably, the preparation material is composed of the following raw materials in parts by weight: Styrene monomer 60-80 parts, rubber nanoparticles 10-20 parts, initiator 0.1-0.5 parts, stabilizer 0.5-1 parts, antistatic agent 5-10 parts, dispersant 1-3 parts, lubricant 0.5-2 parts, foaming agent 5-15 parts; The rubber nanoparticles have a BET specific surface area greater than 50 m² / g, and the styrene monomer has a purity of not less than 99.8%.

[0015] Preferably, the rubber nanoparticles are prepared by wet grinding using nano-grinding technology, wherein the grinding solvent is ethanol or water, the mass ratio of solvent to rubber is 5:1, and the rubber nanoparticles are obtained by centrifugation and vacuum drying after grinding. The centrifugation speed is 3000-5000 r / min, the separation time is 10-30 minutes, the vacuum drying temperature is 60-80℃, the vacuum degree is maintained at -0.09 to -0.10 MPa, and the drying time is 2-4 hours. The foaming agent is supercritical carbon dioxide with a purity of not less than 99.9%, and the injection amount is 10% to 20% of the reactor volume.

[0016] Compared with the prior art, the present invention provides expandable polystyrene particles with high foaming ratio, preparation materials and preparation methods, which have the following beneficial effects: 1. In this invention, by employing nano-grinding and reactive extrusion polymerization technology, the rubber phase is uniformly dispersed in the polystyrene matrix at the nanoscale and forms a stable chemical cross-linking network, which improves the compatibility of the matrix material and constructs a polymer matrix with uniform structure and high strength for the subsequent foaming process. This avoids the problems of large cell size and collapse, ensures that the foamed material obtains a high-ratio and uniform and fine cell structure, and at the same time improves the impact toughness and dimensional stability of the material.

[0017] 2. In this invention, the synergistic effect of supercritical carbon dioxide foaming process and the chemically cross-linked copolymer matrix formed by reactive extrusion bulk polymerization creates a uniform pore morphology with high closed-cell rate inside the material, blocking the penetration path of water vapor. At the same time, the waterproof coating formed by the introduced surface treatment technology further constructs a dense hydrophobic barrier on the material surface. This dual protection mechanism from the inside out works synergistically to enhance the water-blocking performance of the material, enabling it to maintain stable performance in humid environments.

[0018] 3. In this invention, by constructing a three-dimensional continuous conductive network in the polymer matrix and combining it with a high-pressure underwater cutting molding process, the material can maintain its lightweight and high-strength characteristics while also possessing a durable antistatic function. The synergistic effect of multiple modification technologies integrates high foaming ratio, excellent buffering performance, good dimensional stability, and reliable antistatic function into one, achieving a comprehensive improvement in the overall performance of the material. Detailed Implementation

[0019] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0020] Example 1: Expandable polystyrene particles with high foaming ratio, preparation materials and preparation method. The preparation method includes the following steps: Step 1: Prepolymerization. Styrene monomer, rubber nanoparticles, initiator and stabilizer are added to the reactor and stirred for 1 hour at a temperature of 60℃ and a pressure of 0.1MPa to obtain the prepolymer. Step 2: Remove monomers and volatiles. Transfer the prepolymer to a devolatilization device and remove unreacted monomers and volatiles under a vacuum of 0.01 MPa and a temperature of 100°C for 0.5 hours. Step 3: Mixed extrusion. The devolatilized prepolymer, antistatic agent, dispersant, and lubricant are added to a twin-screw extruder at a weight ratio of 100:5:1:0.5. Reactive extrusion bulk polymerization is carried out at a screw speed of 200 r / min and a barrel temperature of 150℃ to obtain a melt copolymer. Step 4: Underwater pelletizing. The molten copolymer is extruded through a die into a high-pressure underwater cutting device and cut into 1mm particles at a water pressure of 5MPa and a cutting speed of 100m / min. Step 5: Screening and drying. The granulated particles are screened through a vibrating screen to remove unqualified products, and then dried in a hot air dryer at 80°C for 1 hour to obtain expandable polystyrene particles. Step 6: Foaming treatment. Place the dried granules in a supercritical carbon dioxide foaming device, introduce carbon dioxide gas, control the pressure at 10MPa and the temperature at 100℃, maintain the pressure and temperature for 1 hour to make the carbon dioxide reach the supercritical state, then quickly release the pressure to normal pressure, cool and solidify to obtain expandable polystyrene foam material with high foaming ratio. Among them, the rubber nanoparticles are obtained by processing rubber through nano-grinding technology, with a particle size of 50nm. The initiator is benzoyl peroxide or azobisisobutyronitrile, and the amount used is 0.1% of the styrene monomer. The stabilizer is calcium stearate or epoxidized soybean oil, and the amount used is 0.5% of the styrene monomer.

[0021] In step one, the prepolymerization reactor is a batch reactor with a stirring speed of 100 r / min, a reaction temperature controlled at 65℃, a pressure controlled at 0.2 MPa, and a reaction time of 1.5 hours. The preparation method of rubber nanoparticles includes: after the rubber is embrittled in a liquid nitrogen environment, it is placed in a nano-grinding mill, using zirconia balls as the grinding medium, with a ball-to-material ratio of 10:1, a grinding speed of 1000 r / min, and a grinding time of 2 hours, to obtain rubber nanoparticles with a particle size of 50 nm.

[0022] In step three, the twin-screw extruder is a co-rotating twin-screw extruder with a screw length-to-diameter ratio of 40:1. The barrel temperature is controlled in zones: zone 1 150℃, zone 2 160℃, zone 3 170℃, zone 4 180℃, and die zone 190℃. The reaction extrusion bulk polymerization pressure is 5MPa, and the residence time is 2 minutes. The antistatic agent, dispersant, and lubricant are premixed before being added. The premixing is carried out in a high-speed mixer at 500r / min for 10 minutes.

[0023] In step four, the water pressure of the high-pressure underwater cutting device is 8MPa, the cutting speed is 150m / min, the die head diameter is 1mm, and the cutting blade speed is 1000r / min; the granules after cutting are dehydrated by a centrifugal dewatering machine at a speed of 2000r / min for 5 minutes.

[0024] In step six, the depressurization rate of the supercritical carbon dioxide foaming device is 1 MPa / s, the cooling method is water cooling, the cooling temperature is 20℃, and the cooling time is 10 minutes; the density of the foamed material is 20 kg / m³, and the closed-cell rate is ≥90%.

[0025] The preparation method also includes step seven: surface treatment, in which the foamed particles are immersed in a waterproof coating liquid, which is composed of organosilicon waterproofing agent and ethanol in a mass ratio of 1:9, the immersion time is 1 minute, and after removal, they are dried at 80℃ for 30 minutes to form a waterproof coating with a thickness of 1μm; the concentration of organosilicon waterproofing agent in the waterproof coating liquid is 10%, and methylsilane or ethylsilane is used.

[0026] The pore structure of the particles is formed by supercritical carbon dioxide foaming process, wherein the pore morphology is a closed pore structure with a pore diameter of 50 micrometers. In the foamable polystyrene / rubber copolymer matrix, the polystyrene segments and rubber segments are cross-linked by chemical bonds formed by reactive extrusion bulk polymerization, with a cross-linking degree of 5%. The rubber nanoparticles are uniformly dispersed in the polystyrene continuous phase at a particle size of 50 nanometers. The granules are composed of expandable polystyrene / rubber copolymer matrix, antistatic agent, dispersant and lubricant. Based on 100 parts by weight of expandable polystyrene / rubber copolymer matrix, the content of antistatic agent is 3 parts by weight, the content of dispersant is 1 part by weight and the content of lubricant is 0.5 parts by weight.

[0027] The antistatic agent is conductive carbon black or quaternary ammonium salt, forming a three-dimensional continuous conductive network in the polymer matrix. The particle surface is coated with a dense coating formed by an organosilicon waterproofing agent through an impregnation and drying process. The coating thickness is 1 micrometer, and the spherical or ellipsoidal geometry of the particles is directly formed by a high-pressure underwater cutting process with a water pressure of 8 MPa, and its sphericity is not less than 0.9.

[0028] The preparation material is composed of the following raw materials in parts by weight: 60 parts styrene monomer, 10 parts rubber nanoparticles, 0.1 parts initiator, 0.5 parts stabilizer, 5 parts antistatic agent, 1 part dispersant, 0.5 parts lubricant, and 5 parts foaming agent; Among them, the BET specific surface area of ​​the rubber nanoparticles is greater than 50 m² / g, and the purity of the styrene monomer is not less than 99.8%.

[0029] The preparation of rubber nanoparticles specifically involves wet grinding using nano-grinding technology. The grinding solvent is ethanol or water, and the mass ratio of solvent to rubber is 5:1. After grinding, the rubber nanoparticles are obtained by centrifugation and vacuum drying. The centrifugation speed is 3000 r / min, the separation time is 10 minutes, the vacuum drying temperature is 60℃, the vacuum degree is maintained at -0.09 MPa, and the drying time is 2 hours. The foaming agent used is supercritical carbon dioxide with a purity of not less than 99.9%, and the injection amount is 10% to 20% of the reactor volume.

[0030] Example 2: Expandable polystyrene particles with high foaming ratio, preparation materials and preparation method. The preparation method includes the following steps: Step 1: Prepolymerization. Styrene monomer, rubber nanoparticles, initiator and stabilizer are added to the reactor and stirred for 1.5 hours at a temperature of 70℃ and a pressure of 0.3MPa to obtain the prepolymer. Step 2: Remove monomers and volatiles. Transfer the prepolymer to a devolatilization device and remove unreacted monomers and volatiles under a vacuum of 0.03 MPa and a temperature of 110°C for 0.7 hours. Step 3: Mixed extrusion. The devolatilized prepolymer, antistatic agent, dispersant, and lubricant are added to a twin-screw extruder at a weight ratio of 100:7:2:1. Reactive extrusion bulk polymerization is carried out at a screw speed of 350 r / min and a barrel temperature of 170℃ to obtain a melt copolymer. Step 4: Underwater pelletizing. The molten copolymer is extruded through a die into a high-pressure underwater cutting device and cut into pellets with a diameter of 2 mm at a water pressure of 7 MPa and a cutting speed of 150 m / min. Step 5: Screening and drying. The granulated particles are screened through a vibrating screen to remove unqualified products, and then dried in a hot air dryer at 90°C for 1.5 hours to obtain expandable polystyrene particles. Step 6: Foaming treatment. Place the dried granules in a supercritical carbon dioxide foaming device, introduce carbon dioxide gas, control the pressure at 15MPa and the temperature at 120℃, maintain the pressure and temperature for 1.5 hours to make the carbon dioxide reach the supercritical state, then quickly release the pressure to normal pressure, cool and solidify to obtain expandable polystyrene foam material with high foaming ratio. Among them, the rubber nanoparticles are obtained by processing rubber through nano-grinding technology, with a particle size of 70nm. The initiator is benzoyl peroxide or azobisisobutyronitrile, with an amount of 0.3% of the styrene monomer. The stabilizer is calcium stearate or epoxidized soybean oil, with an amount of 0.8% of the styrene monomer.

[0031] In step one, the prepolymerization reactor is a batch reactor with a stirring speed of 200 r / min, a reaction temperature controlled at 70℃, a pressure controlled at 0.3 MPa, and a reaction time of 1.5 hours. The preparation method of rubber nanoparticles includes: after the rubber is embrittled in a liquid nitrogen environment, it is placed in a nano-grinding mill, using zirconia balls as the grinding medium, with a ball-to-material ratio of 10:1, a grinding speed of 1500 r / min, and a grinding time of 3 hours, to obtain rubber nanoparticles with a particle size of 70 nm.

[0032] In step three, the twin-screw extruder is a co-rotating twin-screw extruder with a screw length-to-diameter ratio of 40:1. The barrel temperature is controlled in zones: zone 1 155℃, zone 2 165℃, zone 3 175℃, zone 4 185℃, and die zone 195℃. The reaction extrusion bulk polymerization pressure is 7MPa, and the residence time is 3 minutes. The antistatic agent, dispersant, and lubricant are premixed before being added. The premixing is carried out in a high-speed mixer at 700r / min for 15 minutes.

[0033] In step four, the water pressure of the high-pressure underwater cutting device is 9MPa, the cutting speed is 170m / min, the die head diameter is 1.5mm, and the cutting blade speed is 1200r / min; the granules after cutting are dehydrated by a centrifugal dewatering machine at a speed of 2500r / min for 7 minutes.

[0034] In step six, the depressurization rate of the supercritical carbon dioxide foaming device is 3 MPa / s, the cooling method is water cooling, the cooling temperature is 25℃, and the cooling time is 20 minutes; the density of the foamed material is 35 kg / m³, and the closed-cell rate is ≥90%.

[0035] The preparation method also includes step seven: surface treatment, in which the foamed particles are immersed in a waterproof coating liquid, which is composed of organosilicon waterproofing agent and ethanol in a mass ratio of 1:9, and the immersion time is 1.5 minutes. After removal, the particles are dried at 80°C for 30 minutes to form a waterproof coating with a thickness of 3 μm. The concentration of organosilicon waterproofing agent in the waterproof coating liquid is 15%, and methylsilane or ethylsilane is used.

[0036] The pore structure of the particles is formed by supercritical carbon dioxide foaming process, wherein the pore morphology is a closed pore structure with a pore diameter of 100 micrometers. In the foamable polystyrene / rubber copolymer matrix, the polystyrene segments and rubber segments are cross-linked by chemical bonds formed by reactive extrusion bulk polymerization, with a cross-linking degree of 10%. The rubber nanoparticles are uniformly dispersed in the polystyrene continuous phase at a particle size of 70 nanometers. The granules are composed of expandable polystyrene / rubber copolymer matrix, antistatic agent, dispersant and lubricant. Based on 100 parts by weight of expandable polystyrene / rubber copolymer matrix, the content of antistatic agent is 5 parts by weight, the content of dispersant is 2 parts by weight and the content of lubricant is 1 part by weight.

[0037] The antistatic agent is conductive carbon black or quaternary ammonium salt, forming a three-dimensional continuous conductive network in the polymer matrix. The particle surface is coated with a dense coating formed by an organosilicon waterproofing agent through an impregnation and drying process. The coating thickness is 3 micrometers, and the spherical or ellipsoidal geometry of the particles is directly formed by a high-pressure underwater cutting process with a water pressure of 10 MPa, and its sphericity is not less than 0.9.

[0038] The preparation material is composed of the following raw materials in parts by weight: 70 parts styrene monomer, 15 parts rubber nanoparticles, 0.3 parts initiator, 0.7 parts stabilizer, 7 parts antistatic agent, 2 parts dispersant, 1 part lubricant, and 10 parts foaming agent; Among them, the BET specific surface area of ​​the rubber nanoparticles is greater than 50 m² / g, and the purity of the styrene monomer is not less than 99.8%.

[0039] The preparation of rubber nanoparticles specifically involves wet grinding using nano-grinding technology. The grinding solvent is ethanol or water, and the mass ratio of solvent to rubber is 5:1. After grinding, the rubber nanoparticles are obtained by centrifugation and vacuum drying. The centrifugation speed is 4000 r / min, the separation time is 20 minutes, the vacuum drying temperature is 70℃, the vacuum degree is maintained at -0.095 MPa, and the drying time is 3 hours. The foaming agent used is supercritical carbon dioxide with a purity of not less than 99.9%, and the injection amount is 15% of the reactor volume.

[0040] Example 3: Expandable polystyrene particles with high foaming ratio, preparation materials and preparation method. The preparation method includes the following steps: Step 1: Prepolymerization. Styrene monomer, rubber nanoparticles, initiator and stabilizer are added to the reactor and stirred for 2 hours at a temperature of 80℃ and a pressure of 0.5MPa to obtain the prepolymer. Step 2: Remove monomers and volatiles. Transfer the prepolymer to a devolatilization device and remove unreacted monomers and volatiles under a vacuum of 0.05 MPa and a temperature of 120°C for 1 hour. Step 3: Mixed extrusion. The devolatilized prepolymer, antistatic agent, dispersant, and lubricant are added to a twin-screw extruder at a weight ratio of 100:10:3:2. Reactive extrusion bulk polymerization is carried out at a screw speed of 500 r / min and a barrel temperature of 200℃ to obtain a melt copolymer. Step 4: Underwater pelletizing. The molten copolymer is extruded through a die into a high-pressure underwater cutting device. Under a water pressure of 10 MPa and a cutting speed of 200 m / min, it is cut into pellets with a diameter of 3 mm. Step 5: Screening and drying. The granulated particles are screened through a vibrating screen to remove unqualified products, and then dried in a hot air dryer at 100°C for 2 hours to obtain expandable polystyrene particles. Step 6: Foaming treatment. Place the dried granules in a supercritical carbon dioxide foaming device, introduce carbon dioxide gas, control the pressure at 20MPa and the temperature at 150℃, maintain the pressure and temperature for 2 hours to make the carbon dioxide reach the supercritical state, then quickly release the pressure to normal pressure, cool and solidify to obtain expandable polystyrene foam material with high foaming ratio. Among them, the rubber nanoparticles are obtained by processing rubber through nano-grinding technology, with a particle size of 100nm. The initiator is benzoyl peroxide or azobisisobutyronitrile, with an amount of 0.5% of the styrene monomer. The stabilizer is calcium stearate or epoxidized soybean oil, with an amount of 1% of the styrene monomer.

[0041] In step one, the prepolymerization reactor is a batch reactor with a stirring speed of 300 r / min, a reaction temperature of 75℃, a pressure of 0.4 MPa, and a reaction time of 1.5 hours. The preparation method of rubber nanoparticles includes: embrittlement of rubber in liquid nitrogen environment, placing it in a nano-grinding mill, using zirconia balls as the grinding medium, a ball-to-material ratio of 10:1, a grinding speed of 2000 r / min, and a grinding time of 4 hours to obtain rubber nanoparticles with a particle size of 100 nm.

[0042] In step three, the twin-screw extruder is a co-rotating twin-screw extruder with a screw length-to-diameter ratio of 40:1. The barrel temperature is controlled in zones: zone 1 160℃, zone 2 170℃, zone 3 180℃, zone 4 190℃, and die zone 200℃. The reaction extrusion bulk polymerization pressure is 10MPa, and the residence time is 5 minutes. The antistatic agent, dispersant, and lubricant are premixed before being added. The premixing is carried out in a high-speed mixer at 1000r / min for 20 minutes.

[0043] In step four, the water pressure of the high-pressure underwater cutting device is 10MPa, the cutting speed is 200m / min, the die head diameter is 2mm, and the cutting blade speed is 1500r / min; the granules after cutting are dehydrated by a centrifugal dewatering machine at a speed of 3000r / min for 10 minutes.

[0044] In step six, the depressurization rate of the supercritical carbon dioxide foaming device is 5 MPa / s, the cooling method is water cooling, the cooling temperature is 30℃, and the cooling time is 30 minutes; the density of the foamed material is 50 kg / m³, and the closed-cell rate is ≥90%.

[0045] The preparation method also includes step seven: surface treatment, in which the foamed particles are immersed in a waterproof coating liquid, which is composed of organosilicon waterproofing agent and ethanol in a mass ratio of 1:9, the immersion time is 2 minutes, and after removal, they are dried at 80℃ for 30 minutes to form a waterproof coating with a thickness of 5μm; the concentration of organosilicon waterproofing agent in the waterproof coating liquid is 20%, and methylsilane or ethylsilane is used.

[0046] The pore structure of the particles is formed by supercritical carbon dioxide foaming process, wherein the pore morphology is a closed pore structure with a pore diameter of 200 micrometers. In the foamable polystyrene / rubber copolymer matrix, the polystyrene segments and rubber segments are cross-linked by chemical bonds formed by reactive extrusion bulk polymerization, with a cross-linking degree of 15%. The rubber nanoparticles are uniformly dispersed in the polystyrene continuous phase at a particle size of 100 nanometers. The granules are composed of expandable polystyrene / rubber copolymer matrix, antistatic agent, dispersant and lubricant. Based on 100 parts by weight of expandable polystyrene / rubber copolymer matrix, the content of antistatic agent is 8 parts by weight, the content of dispersant is 3 parts by weight and the content of lubricant is 2 parts by weight.

[0047] The antistatic agent is conductive carbon black or quaternary ammonium salt, forming a three-dimensional continuous conductive network in the polymer matrix. The particle surface is coated with a dense coating formed by an organosilicon waterproofing agent through an impregnation and drying process. The coating thickness is 5 micrometers, and the spherical or ellipsoidal geometry of the particles is directly formed by a high-pressure underwater cutting process with a water pressure of 12MPa, and its sphericity is not less than 0.9.

[0048] The preparation material is composed of the following raw materials in parts by weight: 80 parts styrene monomer, 20 parts rubber nanoparticles, 0.5 parts initiator, 1 part stabilizer, 10 parts antistatic agent, 3 parts dispersant, 2 parts lubricant, and 15 parts foaming agent; Among them, the BET specific surface area of ​​the rubber nanoparticles is greater than 50 m² / g, and the purity of the styrene monomer is not less than 99.8%.

[0049] The preparation of rubber nanoparticles specifically involves wet grinding using nano-grinding technology. The grinding solvent is ethanol or water, and the mass ratio of solvent to rubber is 5:1. After grinding, the rubber nanoparticles are obtained by centrifugation and vacuum drying. The centrifugation speed is 5000 r / min, the separation time is 30 minutes, the vacuum drying temperature is 80℃, the vacuum degree is maintained at -0.10 MPa, and the drying time is 4 hours. The foaming agent used is supercritical carbon dioxide with a purity of not less than 99.9%, and the injection amount is 10% to 20% of the reactor volume.

[0050] Comparative Example 1: The difference between this comparative example and Example 1 is that no rubber nanoparticles were added when preparing the prepolymer in this comparative example.

[0051] Comparative Example 2 differs from Example 1 in that the comparative example did not undergo surface waterproofing treatment after the granules were formed.

[0052] Comparative Example 3 differs from Example 1 in that supercritical carbon dioxide was not used as a foaming agent during the foaming process in this comparative example.

[0053] Comparative Example 4 differs from Example 1 in that no antistatic agent was added during the mixing and extrusion process in this comparative example.

[0054] The performance of the expandable polystyrene particles with high foaming ratio prepared in Examples 1-3 and Comparative Examples 1-4 was tested. The test items and test methods are as follows: The expansion ratio test involves placing a certain mass of expandable polystyrene granules in a sealed container, introducing saturated water vapor, and foaming at 100°C and normal pressure for 20 minutes. After cooling to room temperature, the volume change before and after foaming is measured and the expansion ratio is calculated. For the water absorption test, the foamed sample was completely immersed in distilled water and soaked at a constant temperature of 25°C for 24 hours. After the sample was removed and the surface moisture was absorbed with filter paper, it was weighed and the mass increase per unit volume was calculated. For the compressive strength test, a universal testing machine is used. The foamed sample is placed at the center of the pressure plate, and the deformation of 25% of the sample thickness is taken as the endpoint. The maximum compressive load is recorded and the compressive strength is calculated. Surface resistivity testing was conducted using a ring electrode to measure the surface resistance of the foamed material under a standard environment of 23°C and 50% relative humidity. The surface resistivity was calculated after the readings were stabilized.

[0055] The test data of the high foaming ratio expandable polystyrene particles prepared in Examples 1-3 and Comparative Examples 1-4 are recorded in the table below: By comparing and analyzing the data in the table, it can be seen that the expandable polystyrene particles with high expansion ratio prepared by the process in Examples 1-3 have significantly better performance than the expandable polystyrene particles prepared by the process in Comparative Examples 1-4. This indicates that by using nano-grinding and reactive extrusion polymerization technology, the rubber phase is uniformly dispersed in the polystyrene matrix at the nanoscale and forms a stable chemical cross-linking network, which improves the compatibility of the matrix material and constructs a polymer matrix with uniform structure and high strength for the subsequent foaming process. This avoids the problems of large cell size and collapse, ensures that the foamed material obtains a high expansion ratio and uniform and dense cell structure, and at the same time improves the impact toughness and dimensional stability of the material. Through the synergistic effect of supercritical carbon dioxide foaming technology and the chemically cross-linked copolymer matrix formed by reactive extrusion bulk polymerization, a uniform pore morphology with high closed-cell ratio is formed inside the material, blocking the penetration path of water vapor. Simultaneously, the waterproof coating formed by the introduced surface treatment technology further constructs a dense hydrophobic barrier on the material surface. This dual protection mechanism from the inside out enhances the material's water-blocking performance, enabling it to maintain stable performance even in humid environments. By constructing a three-dimensional continuous conductive network in the polymer matrix and combining it with a high-pressure underwater cutting molding process, the material maintains its lightweight and high-strength characteristics while also possessing durable antistatic properties. The synergistic effect of multiple modification technologies integrates high foaming ratio, excellent cushioning performance, good dimensional stability, and reliable antistatic function into one, achieving a comprehensive improvement in the material's overall performance.

[0056] By comparing and analyzing the relevant data in the table, it can be seen that the high-expansion-ratio expandable polystyrene granules prepared by the molding process of this invention not only have a high expansion ratio, low water absorption, good compressive strength, and stable antistatic properties, but also demonstrate that the expandable polystyrene granule preparation process provided by this invention has superior overall performance.

[0057] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0058] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing expandable polystyrene granules with high expansion ratio, characterized in that: The preparation method includes the following steps: Step 1: Prepolymerization. Styrene monomer, rubber nanoparticles, initiator and stabilizer are added to the reactor and stirred for 1-2 hours at a temperature of 60-80℃ and a pressure of 0.1-0.5MPa to obtain the prepolymer. Step 2: Remove monomers and volatiles. Transfer the prepolymer to a devolatilization device and remove unreacted monomers and volatiles under a vacuum of 0.01-0.05 MPa and a temperature of 100-120°C for 0.5-1 hour. Step 3: Mixed extrusion. The devolatilized prepolymer, antistatic agent, dispersant, and lubricant are added to a twin-screw extruder at a weight ratio of 100:5-10:1-3:0.5-2. Reactive extrusion bulk polymerization is carried out at a screw speed of 200-500 r / min and a barrel temperature of 150-200℃ to obtain a melt copolymer. Step 4: Underwater pelletizing. The molten copolymer is extruded through a die into a high-pressure underwater cutting device. Under a water pressure of 5-10 MPa and a cutting speed of 100-200 m / min, it is cut into particles with a diameter of 1-3 mm. Step 5: Screening and drying. The granulated particles are screened through a vibrating screen to remove unqualified products, and then dried in a hot air dryer at 80-100℃ for 1-2 hours to obtain expandable polystyrene particles. Step 6: Foaming treatment. Place the dried granules in a supercritical carbon dioxide foaming device, introduce carbon dioxide gas, control the pressure at 10-20 MPa and the temperature at 100-150℃, maintain the pressure and temperature for 1-2 hours to make the carbon dioxide reach the supercritical state, then quickly release the pressure to normal pressure, cool and solidify to obtain expandable polystyrene foam material with high foaming ratio. The rubber nanoparticles are obtained by processing rubber using nano-grinding technology, with a particle size of 50-100 nm. The initiator is benzoyl peroxide or azobisisobutyronitrile, and its dosage is 0.1-0.5% of the styrene monomer. The stabilizer is calcium stearate or epoxidized soybean oil, and its dosage is 0.5-1% of the styrene monomer.

2. The method for preparing expandable polystyrene particles with high foaming ratio according to claim 1, characterized in that: In step one, the prepolymerization reactor is a batch reactor with a stirring speed of 100-300 r / min, a reaction temperature controlled at 65-75℃, a pressure controlled at 0.2-0.4 MPa, and a reaction time of 1.5 hours. The method for preparing the rubber nanoparticles includes: embrittlement of rubber in a liquid nitrogen environment, placing it in a nano-grinding mill, using zirconia balls as the grinding medium, a ball-to-material ratio of 10:1, a grinding speed of 1000-2000 r / min, and a grinding time of 2-4 hours to obtain rubber nanoparticles with a particle size of 50-100 nm.

3. The method for preparing expandable polystyrene granules with high foaming ratio according to claim 1, characterized in that: In step three, the twin-screw extruder is a co-rotating twin-screw extruder with a screw length-to-diameter ratio of 40:

1. The barrel temperature is controlled in zones: zone one 150-160℃, zone two 160-170℃, zone three 170-180℃, zone four 180-190℃, and die zone 190-200℃. The reaction extrusion bulk polymerization pressure is 5-10MPa, and the residence time is 2-5 minutes. The antistatic agent, dispersant, and lubricant are premixed before being added. The premixing is carried out in a high-speed mixer at 500-1000r / min for 10-20 minutes.

4. The method for preparing expandable polystyrene particles with high foaming ratio according to claim 1, characterized in that: In step four, the water pressure of the high-pressure underwater cutting device is 8-10 MPa, the cutting speed is 150-200 m / min, the die head diameter is 1-2 mm, and the cutting blade rotation speed is 1000-1500 r / min; the granules after cutting are dehydrated by a centrifugal dewatering machine at a dewatering speed of 2000-3000 r / min for 5-10 minutes.

5. The method for preparing expandable polystyrene particles with high foaming ratio according to claim 1, characterized in that: In step six, the depressurization rate of the supercritical carbon dioxide foaming device is 1-5 MPa / s, the cooling method is water cooling, the cooling temperature is 20-30℃, and the cooling time is 10-30 minutes; the density of the foamed material is 20-50 kg / m³, and the closed-cell rate is ≥90%.

6. The method for preparing expandable polystyrene granules with high foaming ratio according to claim 1, characterized in that: The preparation method further includes step seven: surface treatment, in which the foamed particles are immersed in a waterproof coating liquid, wherein the waterproof coating liquid is composed of an organosilicon waterproofing agent and ethanol in a mass ratio of 1:9, the immersion time is 1-2 minutes, and after removal, it is dried at 80°C for 30 minutes to form a waterproof coating with a thickness of 1-5 μm; the concentration of the organosilicon waterproofing agent in the waterproof coating liquid is 10-20%, and methylsilane or ethylsilane is used.

7. Expandable polystyrene granules with high expansion ratio, prepared by the method for preparing expandable polystyrene granules with high expansion ratio according to any one of claims 1-6, characterized in that: The pore structure of the particles is formed by supercritical carbon dioxide foaming process, wherein the pore morphology is a closed pore structure with a pore diameter ranging from 50 to 200 micrometers. In the foamable polystyrene / rubber copolymer matrix, the polystyrene segments and rubber segments are cross-linked by chemical bonds formed by reactive extrusion bulk polymerization, with a cross-linking degree of 5-15%. The rubber nanoparticles are uniformly dispersed in the polystyrene continuous phase at a particle size of 50-100 nanometers. The particles are composed of an expandable polystyrene / rubber copolymer matrix, an antistatic agent, a dispersant, and a lubricant. Based on 100 parts by weight of the expandable polystyrene / rubber copolymer matrix, the content of the antistatic agent is 3-8 parts by weight, the content of the dispersant is 1-3 parts by weight, and the content of the lubricant is 0.5-2 parts by weight.

8. The expandable polystyrene granules with high foaming ratio according to claim 7, characterized in that: The antistatic agent is conductive carbon black or quaternary ammonium salt, and forms a three-dimensional continuous conductive network in the polymer matrix. The surface of the particles is coated with a dense coating formed by an organosilicon waterproofing agent through an impregnation and drying process, with a coating thickness of 1-5 micrometers. The spherical or ellipsoidal geometry of the particles is directly formed by a high-pressure underwater cutting process with a water pressure of 8-12 MPa, and its sphericity is not less than 0.

9.

9. A material for preparing expandable polystyrene particles with a high expansion ratio, characterized in that, The preparation material is composed of the following raw materials in parts by weight: Styrene monomer 60-80 parts, rubber nanoparticles 10-20 parts, initiator 0.1-0.5 parts, stabilizer 0.5-1 parts, antistatic agent 5-10 parts, dispersant 1-3 parts, lubricant 0.5-2 parts, foaming agent 5-15 parts; The rubber nanoparticles have a BET specific surface area greater than 50 m² / g, and the styrene monomer has a purity of not less than 99.8%.

10. The preparation material of expandable polystyrene particles with high foaming ratio according to claim 9, characterized in that: The rubber nanoparticles are prepared by wet grinding using nano-grinding technology, with ethanol or water as the grinding solvent and a solvent-to-rubber mass ratio of 5:

1. After grinding, the rubber nanoparticles are obtained by centrifugation and vacuum drying. The centrifugation speed is 3000-5000 r / min, the separation time is 10-30 minutes, the vacuum drying temperature is 60-80℃, the vacuum degree is maintained at -0.09 to -0.10 MPa, and the drying time is 2-4 hours. The foaming agent is supercritical carbon dioxide with a purity of not less than 99.9%, and the injection amount is 10% to 20% of the reactor volume.

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