Preparation process of low-temperature-resistant and anti-aging high-strength flexible PVC foam

Abstract

The application discloses a kind of low-temperature-resistant and anti-aging preparation process of high-strength flexible PVC foam body.In the application, by the synergistic effect of carboxyl nitrile rubber and plasticizer, the PVC foam body is endowed with excellent low-temperature flexibility while ensuring high strength; the pre-dispersed nano filler constructs a dense reinforcing network, effectively improving the tear resistance and impact resistance of the material; the anti-aging compound system delays the thermal oxidation and ultraviolet aging process from the root, and the mechanical properties and appearance state can still be maintained after long-term use; the pre-dispersed treatment makes the nano filler uniformly distributed in the matrix, which can not only improve the tensile strength and tear resistance of the material, but also effectively block the invasion of oxygen and ultraviolet light, fully exert the synergistic effect of each component, endow the PVC foam body with excellent low-temperature-resistant and anti-aging properties and high-strength flexibility, and further strengthen the resistance of the material to light and oxygen aging, prolong the service life of the product.

Description

Technical Field

[0001] This invention belongs to the field of foaming material technology, specifically a low-temperature resistant and anti-aging preparation process for high-strength flexible PVC foam. Background Technology

[0002] PVC foam is a lightweight polymer material made primarily from polyvinyl chloride (PVC) through physical or chemical foaming processes, with the addition of foaming agents, stabilizers, and other processing aids. Its internal structure is characterized by a large number of uniformly distributed micro-cells, giving it excellent mechanical properties such as high toughness, high rigidity, good sound and heat insulation, and superior flame retardancy and water resistance. Depending on the application, PVC foam can be divided into rigid foam boards (commonly known as PVC foam board) and flexible foam materials. The former is widely used in advertising signage, architectural decoration, furniture making, and industrial model processing, and is easy to cut, carve, and print on; the latter is commonly used in shoe sole materials, sealing gaskets, and shockproof packaging. With its comprehensive advantages of light weight, high strength, corrosion resistance, and moderate cost, PVC foam has become an important environmentally friendly material to replace wood and some metals, playing a crucial role in many industrial sectors.

[0003] However, PVC foams prepared using existing technologies generally suffer from insufficient low-temperature resistance, easily becoming brittle and exhibiting reduced flexibility at low temperatures. They also have weak anti-aging properties, leading to discoloration and mechanical property degradation after prolonged use. Furthermore, some processes suffer from imperfect mixing procedures, resulting in uneven dispersion of nanofillers and subsequent deformation and dimensional instability. Summary of the Invention

[0004] The purpose of this invention is to provide a low-temperature resistant and anti-aging preparation process for high-strength flexible PVC foam in order to solve the problems mentioned above.

[0005] The technical solution adopted in this invention is as follows: a low-temperature resistant and anti-aging preparation process for a high-strength flexible PVC foam, wherein the low-temperature resistant and anti-aging high-strength flexible PVC foam comprises: 100 parts by weight of PVC resin, 32-38 parts by weight of diisooctyl sebacate, 8-12 parts by weight of epoxidized soybean oil, 10-15 parts by weight of carboxylated nitrile rubber, 3-5 parts by weight of calcium-zinc composite stabilizer, 0.8-1.2 parts by weight of antioxidant 1010 and antioxidant 168 compound, 0.6-1.0 parts by weight of ultraviolet absorber UV-327, 5-7 parts by weight of AC foaming agent, 1.5-2.5 parts by weight of zinc oxide, 12-18 parts by weight of modified nano-calcium carbonate, 0.2-0.4 parts by weight of graphene nanosheets, 2-4 parts by weight of acrylate processing aid, and 1.2-1.8 parts by weight of stearic acid and polyethylene wax compound; The preparation process includes the following steps: S1: Add graphene nanosheets and modified nano-calcium carbonate to a high-speed mixer and premix at 1200 rpm for 3 minutes to obtain a pre-dispersed powder for later use; place PVC resin, carboxylated nitrile rubber, calcium-zinc composite stabilizer, antioxidant 1010 and antioxidant 168 compound, ultraviolet absorber UV-327, AC foaming agent, zinc oxide, acrylate processing aid, stearic acid and polyethylene wax compound in an 80℃ oven and dry for 2 hours to remove moisture.

[0006] S2: Add the dried PVC resin to a high-speed mixer, then add diisooctyl sebacate and epoxidized soybean oil in sequence. After heating to 90°C, add the dried carboxylated nitrile rubber and continue mixing for 2 minutes.

[0007] S3: Add the dried calcium-zinc composite stabilizer, antioxidant 1010 and antioxidant 168 compound, and ultraviolet absorber UV-327 to the mixer. After heating to 110°C, add the pre-dispersed powder, dried acrylate processing aid, and stearic acid and polyethylene wax compound. Mix at high speed for 5 minutes, then cool to 40°C and discharge to obtain the mixture.

[0008] S4: Add the mixture to the internal mixer, set the mixing temperature to 165℃, and the mixing time to 4 minutes. Discharge the material after it is completely plasticized to obtain the plasticized material.

[0009] S5: Take the dried AC foaming agent and zinc oxide, and premix them at a speed of 100 rpm for 1 minute to obtain a foaming premix; add the plasticizer to a single screw extruder, set the temperature of each section of the barrel to 145℃, 155℃, 165℃ and 170℃ respectively, set the die temperature to 175℃, add the foaming premix, control the screw speed to 30 rpm during the extrusion process, and the material will naturally foam after being extruded through the die.

[0010] S6: The extruded foam is shaped by a cooling water tank, with the cooling water temperature controlled at 25℃ and the cooling time being 3 minutes.

[0011] S7: Place the shaped foam in a 60℃ oven for 24 hours to cure internal stress and obtain a low-temperature resistant, anti-aging, high-strength flexible PVC foam.

[0012] In a preferred embodiment, in step S1, graphene nanosheets and modified nano-calcium carbonate are first added to a high-speed mixer, with the machine speed set to 1200 rpm, and mixed continuously for 3 minutes. The high-speed shear force ensures sufficient contact and initial dispersion of the two powder materials, preventing agglomeration during subsequent mixing. The resulting pre-dispersed powder is then removed, sealed, and stored for later use. Simultaneously, PVC resin, carboxylated nitrile rubber, calcium-zinc composite stabilizer, antioxidant 1010 and antioxidant 168 compound, UV absorber UV327, AC foaming agent, zinc oxide, acrylate processing aid, and stearic acid and polyethylene wax compound are all placed in a forced-air drying oven set at 80 degrees Celsius and kept at a constant temperature for 2 hours to thoroughly remove trace amounts of moisture from the raw materials, preventing uneven bubble formation and surface defects in the foam during subsequent processing due to moisture content.

[0013] In a preferred embodiment, in step S2, the dried PVC resin is added to a high-speed mixer. The equipment is started and stirred at a low speed of 800 revolutions per minute. Diisooctyl sebacate is slowly added. After the plasticizer evenly covers the resin particles, epoxidized soybean oil is added, and stirring at a low speed is continued for 1 minute.

[0014] In a preferred embodiment, in step S2, the mixer is heated to 90 degrees Celsius, and the dried carboxylated nitrile rubber is added while maintaining this temperature. The stirring speed is increased to 1000 revolutions per minute, and the mixture is continuously mixed for 2 minutes. The high-temperature environment promotes the rubber particles to fully swell under the action of the plasticizer, forming a preliminary blended structure with the PVC resin particles, laying the foundation for the formation of a uniform polymer alloy in the subsequent plasticizing process.

[0015] In a preferred embodiment, in step S3, dried calcium-zinc composite stabilizer, antioxidant 1010 and antioxidant 168 compound, and ultraviolet absorber UV327 are sequentially added to the mixer. The equipment speed is maintained at 1000 rpm, and the mixture is stirred for 1 minute to ensure uniform dispersion of the additives. Subsequently, the mixer is heated to 110 degrees Celsius, and pre-prepared pre-dispersed powder, dried acrylate processing aid, stearic acid and polyethylene wax compound are added. The speed is increased to 1200 rpm, and high-speed mixing is performed for 5 minutes. The high temperature and high shear force ensure that all raw materials are fully integrated to form a homogeneous mixture.

[0016] In a preferred embodiment, in step S3, after mixing is completed, the cooling system of the mixer is started to reduce the material temperature to below 40 degrees Celsius before discharge, so as to avoid premature decomposition of the foaming agent or migration of the additives due to high temperature, and to ensure that the material remains stable before subsequent processing.

[0017] In a preferred embodiment, in step S4, all the mixture obtained in step S3 is fed into an internal mixer. The temperature of the mixing chamber is set to 165 degrees Celsius, and the rotor speed is adjusted to 60 revolutions per minute. The mixing is continued for 4 minutes. Under high temperature and strong shear, the PVC resin particles gradually melt, the plasticizer fully enters between the resin molecular chains, and the carboxylated nitrile rubber and PVC form an interpenetrating network structure. Various additives are uniformly dispersed in the polymer matrix until the material becomes a homogeneous plasticized material without obvious particles. At this point, the mixing is stopped, and the plasticized material is discharged from the outlet of the internal mixer and quickly transferred to subsequent processing equipment to avoid material cooling and agglomeration due to temperature drop.

[0018] In a preferred embodiment, in step S5, the dried AC foaming agent and zinc oxide are first placed in a small mixer and mixed for 1 minute at a speed of 100 rpm to obtain a uniform foamed premix for later use. The plasticized material obtained in step S4 is added to the feed hopper of a single-screw extruder. The temperatures of each section of the barrel are set to 145°C, 155°C, 165°C, and 170°C from the feed port to the die, respectively, with the die temperature set at 175°C. The screw speed is adjusted to 30 rpm to ensure that the material gradually heats up and melts within the barrel. When the material enters the middle of the barrel, the foamed premix is ​​added through a side feeding device, causing the foaming agent to slowly decompose at high temperature and release gas. When the material reaches the die, the pressure suddenly drops, and the gas rapidly expands to form bubbles, eventually being extruded from the die to form a continuous foamed preform.

[0019] In a preferred embodiment, in step S6, the foamed preform extruded from the extruder die is immediately introduced into a cooling water tank. The water temperature in the tank is controlled at 25 degrees Celsius. By adjusting the traction speed, the foam is kept in the tank for 3 minutes. The low-temperature water quickly removes the heat from the inside of the foam, causing the polymer matrix to solidify rapidly, fixing the shape and size of the cells, and preventing the foam from affecting the dimensional accuracy and appearance quality of the final product due to subsequent shrinkage or deformation. During the cooling process, the water flow in the tank is kept stable to avoid water flow impact causing defects such as bending or surface depressions in the foam.

[0020] In a preferred embodiment, in step S7, the cooled and shaped foam is removed from the water tank, its surface is wiped dry with a clean cotton cloth, and then placed in a forced-air drying oven set at 60 degrees Celsius for 24 hours of constant-temperature curing. During the curing process, the residual stress inside the foam is gradually released, the polymer molecular chains are further aligned, and the additives achieve uniform migration and dispersion in the matrix. Simultaneously, the incompletely decomposed foaming agent continues to react slowly, making the cell structure more stable. After curing, the foam is removed and allowed to cool naturally to room temperature, yielding the final low-temperature resistant, anti-aging, high-strength flexible PVC foam. At this point, the product's mechanical properties, low-temperature resistance, and anti-aging properties are all at their optimal levels.

[0021] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are: 1. In this invention, the synergistic effect of carboxylated nitrile rubber and plasticizers ensures the high strength of PVC foam while endowing it with excellent low-temperature flexibility; the pre-dispersed nanofillers construct a dense reinforcing network, effectively improving the material's tear resistance and impact resistance; the anti-aging compound system delays the thermo-oxidative and ultraviolet aging process from the source, maintaining stable mechanical properties and appearance even after long-term use; the precisely proportioned foaming system forms a uniform and fine cell structure, achieving a perfect balance between lightweight characteristics and mechanical strength, ultimately producing a high-performance PVC foam that combines low-temperature resistance, anti-aging properties, high strength, and flexibility.

[0022] 2. In this invention, through precise raw material pretreatment and a multi-stage mixing process, the synergistic effect of each component is fully utilized, endowing the PVC foam with excellent low-temperature resistance, anti-aging properties, and high strength and flexibility. Pre-dispersion treatment allows the nanofillers to be uniformly distributed in the matrix, constructing a dense reinforcing network that not only improves the tensile strength and tear resistance of the material but also effectively blocks the intrusion of oxygen and ultraviolet rays, delaying the aging and degradation of the polymer molecular chains. High-temperature blending of the plasticizer system and the rubber component allows for reasonable control of the intermolecular forces, ensuring that the material maintains good flexibility and resilience even at low temperatures, preventing brittleness. The uniform dispersion of the anti-aging additives further enhances the material's resistance to photo-oxidative aging, extending the product's service life. Attached Figure Description

[0023] Figure 1 This is a schematic diagram illustrating the process principle of the present invention; Figure 2 This is a schematic diagram comparing the basic physical properties and cell structure of the present invention; Figure 3 This is a schematic diagram showing the relationship between mechanical properties and low-temperature resistance in this invention; Figure 4 This is a schematic diagram comparing the anti-aging performance of the present invention; Figure 5 This is a schematic diagram illustrating the long-term performance simulation comparison in this invention. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0025] Example: Refer to Figure 1-5A low-temperature resistant and anti-aging preparation process for a high-strength flexible PVC foam, comprising: 100 parts by weight of PVC resin, 32-38 parts by weight of diisooctyl sebate, 8-12 parts by weight of epoxidized soybean oil, 10-15 parts by weight of carboxylated nitrile rubber, 3-5 parts by weight of calcium-zinc composite stabilizer, 0.8-1.2 parts by weight of a compound of antioxidant 1010 and antioxidant 168, 0.6-1.0 parts by weight of ultraviolet absorber UV-327, 5-7 parts by weight of AC foaming agent, 1.5-2.5 parts by weight of zinc oxide, 12-18 parts by weight of modified nano-calcium carbonate, 0.2-0.4 parts by weight of graphene nanosheets, 2-4 parts by weight of acrylate processing aid, and 1.2-1.8 parts by weight of a compound of stearic acid and polyethylene wax; The preparation process includes the following steps: S1: Add graphene nanosheets and modified nano-calcium carbonate to a high-speed mixer and premix at 1200 rpm for 3 minutes to obtain a pre-dispersed powder for later use; place PVC resin, carboxylated nitrile rubber, calcium-zinc composite stabilizer, antioxidant 1010 and antioxidant 168 compound, ultraviolet absorber UV-327, AC foaming agent, zinc oxide, acrylate processing aid, stearic acid and polyethylene wax compound in an 80℃ oven and dry for 2 hours to remove moisture.

[0026] S2: Add the dried PVC resin to a high-speed mixer, then add diisooctyl sebacate and epoxidized soybean oil in sequence. After heating to 90°C, add the dried carboxylated nitrile rubber and continue mixing for 2 minutes.

[0027] S3: Add the dried calcium-zinc composite stabilizer, antioxidant 1010 and antioxidant 168 compound, and ultraviolet absorber UV-327 to the mixer. After heating to 110°C, add the pre-dispersed powder, dried acrylate processing aid, and stearic acid and polyethylene wax compound. Mix at high speed for 5 minutes, then cool to 40°C and discharge to obtain the mixture.

[0028] S4: Add the mixture to the internal mixer, set the mixing temperature to 165℃, and the mixing time to 4 minutes. Discharge the material after it is completely plasticized to obtain the plasticized material.

[0029] S5: Take the dried AC foaming agent and zinc oxide, and premix them at a speed of 100 rpm for 1 minute to obtain a foaming premix; add the plasticizer to a single screw extruder, set the temperature of each section of the barrel to 145℃, 155℃, 165℃ and 170℃ respectively, set the die temperature to 175℃, add the foaming premix, control the screw speed to 30 rpm during the extrusion process, and the material will naturally foam after being extruded through the die.

[0030] S6: The extruded foam is shaped by a cooling water tank, with the cooling water temperature controlled at 25℃ and the cooling time being 3 minutes.

[0031] S7: Place the shaped foam in a 60℃ oven for 24 hours to cure internal stress and obtain a low-temperature resistant, anti-aging, high-strength flexible PVC foam.

[0032] In step S1, graphene nanosheets and modified nano-calcium carbonate are first added to a high-speed mixer. The mixer speed is set to 1200 rpm, and the mixture is continuously mixed for 3 minutes. The high-speed shear force ensures that the two powder materials come into full contact and achieve initial dispersion, preventing agglomeration during subsequent mixing. The pre-dispersed powder is then removed, sealed, and stored for later use. Simultaneously, PVC resin, carboxylated nitrile rubber, calcium-zinc composite stabilizer, antioxidant 1010 and antioxidant 168 compound, UV absorber UV327, AC foaming agent, zinc oxide, acrylate processing aid, stearic acid, and polyethylene wax compound are all placed in a forced-air drying oven set at 80 degrees Celsius and kept at a constant temperature for 2 hours to thoroughly remove trace amounts of moisture from the raw materials. This prevents uneven bubble formation and surface defects in the foam due to moisture during subsequent processing.

[0033] In step S2, the dried PVC resin is added to a high-speed mixer. The equipment is started and stirred at a low speed of 800 revolutions per minute. Diisooctyl sebacate is slowly added. After the plasticizer evenly covers the resin particles, epoxidized soybean oil is added and stirring is continued at a low speed for 1 minute.

[0034] In step S2, the mixer is heated to 90 degrees Celsius, and the dried carboxylated nitrile rubber is added while maintaining this temperature. The stirring speed is increased to 1000 revolutions per minute, and the mixture is continuously mixed for 2 minutes. The high-temperature environment promotes the rubber particles to fully swell under the action of the plasticizer, forming a preliminary blended structure with the PVC resin particles, laying the foundation for the formation of a uniform polymer alloy in the subsequent plasticizing process.

[0035] In step S3, the dried calcium-zinc composite stabilizer, the antioxidant 1010 and antioxidant 168 compound, and the ultraviolet absorber UV327 are added sequentially to the mixer. The equipment speed is maintained at 1000 rpm, and the mixture is stirred for 1 minute to ensure uniform dispersion of the additives. Subsequently, the mixer is heated to 110 degrees Celsius, and the pre-prepared pre-dispersed powder, as well as the dried acrylate processing aid, stearic acid and polyethylene wax compound, are added. The speed is increased to 1200 rpm, and the mixture is stirred at high speed for 5 minutes. The high temperature and high shear force ensure that all raw materials are fully integrated to form a homogeneous mixture.

[0036] In step S3, after mixing is completed, the cooling system of the mixer is started to reduce the material temperature to below 40 degrees Celsius before discharge, so as to avoid premature decomposition of the foaming agent or migration of the additives due to high temperature, and to ensure that the material remains stable before subsequent processing.

[0037] In step S4, all the mixture obtained in step S3 is fed into an internal mixer. The mixing chamber temperature is set to 165 degrees Celsius, and the rotor speed is adjusted to 60 revolutions per minute. The mixing continues for 4 minutes. Under high temperature and strong shear, the PVC resin particles gradually melt, the plasticizer fully enters between the resin molecular chains, and the carboxylated nitrile rubber and PVC form an interpenetrating network structure. Various additives are evenly dispersed in the polymer matrix until the material becomes a homogeneous plasticized material without obvious particles. At this point, the mixing is stopped, and the plasticized material is discharged from the outlet of the internal mixer and quickly transferred to subsequent processing equipment to avoid material cooling and agglomeration due to temperature drop.

[0038] In step S5, the dried AC foaming agent and zinc oxide are first placed in a small mixer and mixed for 1 minute at 100 rpm to obtain a uniform foamed premix for later use. The plasticized material obtained in step S4 is added to the feed hopper of a single-screw extruder. The temperatures of each section of the barrel are set to 145°C, 155°C, 165°C, and 170°C from the feed port to the die, respectively. The die temperature is set to 175°C, and the screw speed is adjusted to 30 rpm to ensure that the material gradually heats up and melts in the barrel. When the material enters the middle of the barrel, the foamed premix is ​​added through the side feeding device, causing the foaming agent to slowly decompose at high temperature and release gas. When the material reaches the die, the pressure suddenly drops, and the gas rapidly expands to form bubbles, which are finally extruded from the die to form a continuous foamed preform.

[0039] In step S6, the foam preform extruded from the extruder die is immediately introduced into a cooling water tank. The water temperature in the tank is controlled at 25 degrees Celsius. By adjusting the traction speed, the foam remains in the tank for 3 minutes. The low-temperature water quickly removes the heat from the inside of the foam, causing the polymer matrix to solidify rapidly, fixing the shape and size of the cells, and preventing the foam from affecting the dimensional accuracy and appearance quality of the final product due to subsequent shrinkage or deformation. During the cooling process, the water flow in the tank is kept stable to avoid water flow impact that could cause defects such as bending or surface depressions in the foam.

[0040] In step S7, the cooled and shaped foam is removed from the water tank, and any residual moisture on the surface is wiped off with a clean cotton cloth. It is then placed in a forced-air drying oven set at 60 degrees Celsius and cured at a constant temperature for 24 hours. During the curing process, residual stress inside the foam is gradually released, the polymer molecular chains become more regularly aligned, and the additives migrate and disperse evenly in the matrix. Simultaneously, the incompletely decomposed foaming agent continues to react slowly, making the cell structure more stable. After curing, the foam is removed and allowed to cool naturally to room temperature, yielding the final low-temperature resistant, anti-aging, high-strength flexible PVC foam. At this point, the product's mechanical properties, low-temperature resistance, and anti-aging properties are all at their optimal levels.

[0041] Comparative Example 1 (without nanofiller pre-dispersion treatment): Specific implementation methods: S1 Raw Material Drying: Place all the following materials into a forced-air drying oven set at 80℃: polyvinyl chloride (PVC) resin, carboxylated nitrile rubber (NBR), calcium-zinc composite stabilizer, antioxidant 1010 and antioxidant 168 compound, ultraviolet absorber UV-327, azodicarbonamide (AC) foaming agent, zinc oxide (ZnO), modified nano-calcium carbonate (CaCO3), graphene nanosheets, acrylate processing aid (ACR), stearic acid (SA) and polyethylene wax (PE) compound. Dry at this constant temperature for 2 hours to completely remove any trace moisture from the raw materials. After drying, remove and seal for later use.

[0042] S2 matrix resin and plasticizer premixing: Add the dried PVC resin to a 50L high-speed mixer, start the equipment and stir at a low speed of 800 rpm, slowly add diisooctyl sebacate (DOS), and after the plasticizer evenly covers the resin particles, add epoxidized soybean oil (ESBO) and continue stirring at low speed for 1 minute. Then raise the mixer temperature to 90℃, maintain this temperature and add the dried carboxylated nitrile rubber, increase the stirring speed to 1000 rpm, and continue mixing for 2 minutes to complete the premixing of the matrix resin and plasticizer.

[0043] S3 High-Speed ​​Mixing of All Components: Based on step S2, add the dried calcium-zinc composite stabilizer, antioxidant 1010 and antioxidant 168 compound, and ultraviolet absorber UV-327 sequentially to the mixer. Maintain a stirring speed of 1000 rpm for 1 minute. Then, raise the mixer temperature to 110°C and directly add the dried modified nano-calcium carbonate, graphene nanosheets, acrylate processing aid, and stearic acid and polyethylene wax compound. Increase the speed to 1200 rpm and mix at high speed for 5 minutes. After mixing, start the cooling system to lower the material temperature to below 40°C before discharging to obtain the mixed material.

[0044] S4 Internal Mixing and Plasticizing: Put all the mixture obtained from S3 into the internal mixer, set the mixing chamber temperature to 165℃, the rotor speed to 60 rpm, and continue mixing for 4 minutes until the material becomes a uniform plasticized material without obvious particles, and then discharge the material.

[0045] S5 Extrusion Foaming Molding: The dried AC foaming agent and zinc oxide are placed in a small mixer and mixed at 100 rpm for 1 minute to obtain a foamed premix. The plasticized material of S4 is added to the feed hopper of a single-screw extruder. The temperatures of each section of the barrel are set from the feed port to the die as 145℃, 155℃, 165℃, and 170℃ respectively, the die temperature is 175℃, and the screw speed is 30 rpm. When the material enters the middle of the barrel, the foamed premix is ​​added through the side feeding device, and finally the foamed preform is extruded from the die.

[0046] S6 Cooling and Shaping: Immediately introduce the extruded foam blank into a cooling water tank with a water temperature of 25℃, adjust the traction speed to keep the foam in the water tank for 3 minutes, and remove it after cooling and shaping.

[0047] S7 curing treatment: Wipe the surface moisture of the cooled foam with a cotton cloth, place it in a 60℃ forced-air oven for constant temperature curing for 24 hours, remove it and let it cool naturally to room temperature to obtain the final product.

[0048] Comparative Example 2 (without added anti-aging compound system): Specific implementation methods: S1 Raw Material Pretreatment: Graphene nanosheets and modified nano-calcium carbonate were added to a high-speed mixer at 1200 rpm and mixed continuously for 3 minutes to obtain a pre-dispersed powder. The powder was then removed, sealed, and set aside for later use. Simultaneously, PVC resin, carboxylated nitrile rubber, calcium-zinc composite stabilizer, AC foaming agent, zinc oxide, acrylate processing aid, stearic acid, and polyethylene wax compound were placed in an 80℃ forced-air drying oven and dried at a constant temperature for 2 hours to remove trace amounts of moisture. The dried powder was then set aside for later use.

[0049] S2 matrix resin and plasticizer premixing: Add the dried PVC resin to a 50L high-speed mixer and stir at a low speed of 800 rpm. Slowly add diisooctyl sebacate. After the plasticizer covers the resin particles, add epoxidized soybean oil and continue stirring at low speed for 1 minute. After heating to 90℃, add the dried carboxylated nitrile rubber and increase the speed to 1000 rpm. Mix for 2 minutes to complete the premixing.

[0050] S3 Full-Component High-Speed ​​Mixing: Add the dried calcium-zinc composite stabilizer to the mixer and stir at 1000 rpm for 1 minute. Then, raise the temperature to 110°C, add the pre-prepared pre-dispersed powder, dried acrylate processing aid, and stearic acid and polyethylene wax compound, and increase the speed to 1200 rpm for high-speed mixing for 5 minutes. After mixing, cool to below 40°C and discharge to obtain the mixture.

[0051] S4 Internal Mixing and Plasticizing: Put the mixture into the internal mixer, set the mixing chamber temperature to 165℃, the rotor speed to 60 rpm, and mix for 4 minutes until the material is completely plasticized. Then discharge the plasticized material.

[0052] S5 Extrusion Foaming Molding: The dried AC foaming agent and zinc oxide are mixed at 100 rpm for 1 minute to obtain a foamed premix. The plasticizer is added to a single-screw extruder, with the barrel temperatures set to 145℃, 155℃, 165℃, and 170℃, the die temperature set to 175℃, and the screw speed set to 30 rpm. The foamed premix is ​​added when the material enters the middle of the barrel, and the foamed preform is extruded.

[0053] S6 Cooling and Shaping: The foamed blank is introduced into a 25℃ cooling water bath and held for 3 minutes to complete the cooling and shaping.

[0054] S7 curing treatment: After wiping off the surface moisture, place it in a 60℃ forced-air oven and cure at a constant temperature for 24 hours. Remove and cool to room temperature to obtain the final product.

[0055] A comparison of basic physical properties and cell structure can be found in [link to relevant documentation]. Figure 2 A comparison of mechanical properties and low-temperature resistance is shown in [link to relevant documentation]. Figure 3 For a comparison of anti-aging properties, see [link to relevant documentation]. Figure 4 For long-term performance simulation comparisons, see [link to performance simulation]. Figure 5 ; From the above, we can conclude that: Based on fundamental physical and mechanical property data, the PVC foam prepared by the original process exhibits significant advantages in cell structure and mechanical strength: its average cell diameter is only 85 μm with the highest level of uniformity, which is denser than the 150 μm large cell structure of Comparative Example 1 (without pre-dispersed filler), achieving a density of 0.42 g / cm³. 3 Its lightweight properties, tensile strength of 18.2 MPa, and tensile strength of 8.6 kJ / m 2 The high strength and low-temperature resistance are balanced by impact toughness at -40℃. Comparative Example 1 shows that due to uneven cell collapse caused by nanofiller agglomeration, the tensile strength and low-temperature impact toughness decreased to 14.5 MPa and 5.2 kJ / m, respectively. 2Although the cell structure of Comparative Example 2 (without anti-aging system) was better than that of Comparative Example 1, the number of low-temperature bending cycles was only 780, which is significantly lower than the 1200 cycles of the original process, highlighting the key role of filler pre-dispersion treatment in the mechanical properties of the material.

[0056] Anti-aging and long-term performance data further validated the technical advantages of the original process: the original process maintained a tensile strength retention rate of 92.5% after thermal aging, with a color difference of only 1.8 after UV aging, and retained 86.7% of the tensile strength after 2000 hours of artificial climate aging. In contrast, Comparative Example 2, lacking an anti-aging compound system, experienced a tensile strength retention rate of only 81.2% after thermal aging, a color difference as high as 4.2 after UV aging, and a long-term dynamic fatigue life of only 90,000 cycles, a 40% decrease compared to the original process's 150,000 cycles. Although Comparative Example 1 added anti-aging components, uneven filler dispersion led to internal stress concentration, resulting in a thermal weight loss rate of 1.2%, four times that of the original process, and a long-term dimensional stability deviation of ±2.5%, further demonstrating the importance of the synergistic effect of nanofiller pre-dispersion and the anti-aging system on the long-term performance of the material.

[0057] It should be noted that, in this document, relational terms such as "first" and "second" are used merely 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 term "comprising" or any other variations thereof is 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 the element.

[0058] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A low-temperature resistant and anti-aging preparation process for high-strength flexible PVC foam, characterized in that: The low-temperature resistant, anti-aging, high-strength, flexible PVC foam comprises: 100 parts by weight of PVC resin, 32-38 parts by weight of diisooctyl sebate, 8-12 parts by weight of epoxidized soybean oil, 10-15 parts by weight of carboxylated nitrile rubber, 3-5 parts by weight of calcium-zinc composite stabilizer, 0.8-1.2 parts by weight of antioxidant 1010 and antioxidant 168 compound, 0.6-1.0 parts by weight of ultraviolet absorber UV-327, 5-7 parts by weight of AC foaming agent, 1.5-2.5 parts by weight of zinc oxide, 12-18 parts by weight of modified nano-calcium carbonate, 0.2-0.4 parts by weight of graphene nanosheets, 2-4 parts by weight of acrylate processing aid, and 1.2-1.8 parts by weight of stearic acid and polyethylene wax compound. The preparation process includes the following steps: S1: Add graphene nanosheets and modified nano-calcium carbonate to a high-speed mixer and premix at 1200 rpm for 3 minutes to obtain a pre-dispersed powder for later use; place PVC resin, carboxylated nitrile rubber, calcium-zinc composite stabilizer, antioxidant 1010 and antioxidant 168 compound, ultraviolet absorber UV-327, AC foaming agent, zinc oxide, acrylate processing aid, stearic acid and polyethylene wax compound in an 80℃ oven and dry for 2 hours to remove moisture; S2: Add the dried PVC resin to a high-speed mixer, then add diisooctyl sebacate and epoxidized soybean oil in sequence. After heating to 90°C, add the dried carboxylated acrylonitrile rubber and continue mixing for 2 minutes. S3: Add the dried calcium-zinc composite stabilizer, antioxidant 1010 and antioxidant 168 compound, and ultraviolet absorber UV-327 to the mixer. After heating to 110°C, add the pre-dispersed powder, dried acrylate processing aid, and stearic acid and polyethylene wax compound. Mix at high speed for 5 minutes, then cool to 40°C and discharge to obtain the mixture. S4: Add the mixture to the internal mixer, set the mixing temperature to 165℃, and the mixing time to 4 minutes. Discharge the material after it is completely plasticized to obtain the plasticized material. S5: Take the dried AC foaming agent and zinc oxide, and premix them at a speed of 100 rpm for 1 minute to obtain a foaming premix; add the plasticizer to a single screw extruder, set the temperature of each section of the barrel to 145℃, 155℃, 165℃ and 170℃ respectively, set the die temperature to 175℃, add the foaming premix, control the screw speed to 30 rpm during the extrusion process, and the material will naturally foam after being extruded through the die; S6: The extruded foam is shaped by a cooling water tank, with the cooling water temperature controlled at 25℃ and the cooling time being 3 minutes; S7: Place the shaped foam in a 60℃ oven for 24 hours to cure internal stress and obtain a low-temperature resistant, anti-aging, high-strength flexible PVC foam.

2. The low-temperature resistant and anti-aging preparation process of a high-strength flexible PVC foam as described in claim 1, characterized in that: In step S1, graphene nanosheets and modified nano-calcium carbonate are first put into a high-speed mixer, the machine speed is set to 1200 revolutions per minute, and the mixture is continuously mixed for 3 minutes. The high-speed shear force makes the two powder materials come into full contact and achieves preliminary dispersion, avoiding agglomeration in the subsequent mixing process. After obtaining the pre-dispersed powder, it is taken out and sealed for later use. At the same time, PVC resin, carboxylated nitrile rubber, calcium-zinc composite stabilizer, antioxidant 1010 and antioxidant 168 compound, ultraviolet absorber UV327, AC foaming agent, zinc oxide, acrylate processing aid, stearic acid and polyethylene wax compound are all put into a forced-air drying oven set at 80 degrees Celsius and kept at a constant temperature for 2 hours.

3. The low-temperature resistant and anti-aging preparation process of a high-strength flexible PVC foam as described in claim 1, characterized in that: In step S2, the dried PVC resin is added to a high-speed mixer. The equipment is started and stirred at a low speed of 800 revolutions per minute. Diisooctyl sebacate is slowly added. After the plasticizer evenly covers the resin particles, epoxidized soybean oil is added, and stirring at a low speed is continued for 1 minute.

4. The low-temperature resistant and anti-aging preparation process of a high-strength flexible PVC foam as described in claim 1, characterized in that: In step S2, the mixer is heated to 90 degrees Celsius, and the dried carboxylated nitrile rubber is added while maintaining this temperature. The stirring speed is increased to 1000 revolutions per minute, and the mixture is continuously mixed for 2 minutes.

5. The low-temperature resistant and anti-aging preparation process of a high-strength flexible PVC foam as described in claim 1, characterized in that: In step S3, the dried calcium-zinc composite stabilizer, antioxidant 1010 and antioxidant 168 compound, and ultraviolet absorber UV327 are added sequentially to the mixer. The equipment speed is maintained at 1000 revolutions per minute, and the mixture is stirred for 1 minute to ensure uniform dispersion of the additives. Then, the mixer is heated to 110 degrees Celsius, and the pre-prepared pre-dispersed powder, as well as the dried acrylate processing aid, stearic acid and polyethylene wax compound, are added. The speed is increased to 1200 revolutions per minute, and the mixture is high-speed mixed for 5 minutes.

6. The low-temperature resistant and anti-aging preparation process of a high-strength flexible PVC foam as described in claim 1, characterized in that: In step S3, after mixing is completed, the cooling system of the mixer is started to reduce the material temperature to below 40 degrees Celsius before discharging.

7. The low-temperature resistant and anti-aging preparation process of a high-strength flexible PVC foam as described in claim 1, characterized in that: In step S4, all the mixture obtained in step S3 is put into the internal mixer, the temperature of the mixing chamber is set to 165 degrees Celsius, the rotor speed is adjusted to 60 revolutions per minute, and the mixing is continued for 4 minutes.

8. The low-temperature resistant and anti-aging preparation process of a high-strength flexible PVC foam as described in claim 1, characterized in that: In step S5, the dried AC foaming agent and zinc oxide are first placed into a small mixer and mixed for 1 minute at a speed of 100 revolutions per minute to obtain a uniform foamed premix for later use. The plasticized material obtained in step S4 is added to the feed hopper of a single-screw extruder. The temperatures of each section of the barrel are set to 145 degrees Celsius, 155 degrees Celsius, 165 degrees Celsius, and 170 degrees Celsius from the feed port to the die head, respectively. The die head temperature is set to 175 degrees Celsius, and the screw speed is adjusted to 30 revolutions per minute.

9. The low-temperature resistant and anti-aging preparation process of a high-strength flexible PVC foam as described in claim 1, characterized in that: In step S6, the foamed material extruded from the extruder die is immediately introduced into a cooling water tank. The water temperature in the tank is controlled at 25 degrees Celsius. The foamed material is kept in the tank for 3 minutes by adjusting the traction speed.

10. The low-temperature resistant and anti-aging preparation process of a high-strength flexible PVC foam as described in claim 1, characterized in that: In step S7, the cooled and shaped foam is taken out of the water tank, the surface moisture is wiped off with a clean cotton cloth, and then placed in a forced-air drying oven with the temperature set at 60 degrees Celsius to maintain a constant temperature for 24 hours.

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