Preparation method of anti-aging regenerated plastic particles

Abstract

The invention discloses a preparation method of anti-aging regenerated plastic particles, and relates to the technical field of plastics. According to the invention, the regenerated plastic is used as a raw material and is firstly melt-blended with the layered composite nanoparticles, so that contact sites are increased, free radicals are removed, and the anti-aging performance is enhanced; then the plastic particles are immersed in a polymethyl methacrylate thermal coating solution mixed with hydroxylated graphene, and graphene in the solution permeates into the plastic particles, so that the compatibility between the plastic particles and the regenerated plastic is improved, and the overall mechanical strength is enhanced; a layer-by-layer assembly structure is formed after cooling, so that the anti-aging performance is improved. The layered composite nanoparticles are prepared by coprecipitating cobalt chloride and magnesium sulfate to generate layered hydroxide and then modifying 3-(benzyl dimethyl ammonium) propane sulfonic acid, sulfonate radicals are intercalated into layered hydroxide particles, magnesium hydroxide and cobalt hydroxide are assisted, the flame-retardant and smoke-suppression effects are achieved, the dispersity is improved along with the intercalation reaction, and the flame-retardant and smoke-suppression effects are achieved. And the anti-aging agent is in better contact with free radicals in the plastic, so that the aging is effectively inhibited.

Description

Technical Field

[0001] The invention relates to the technical field of plastics, in particular to a method for preparing aging-resistant recycled plastic particles. Background Art

[0002] Recycled plastics refer to plastic products obtained through a series of processing steps, including recycling, sorting, cleaning, crushing, and melting and remaking waste plastics. Compared to virgin plastics, recycled plastics offer significant advantages in terms of resource utilization, environmental protection, and economic benefits. Waste plastic recycling methods include sanitary landfill, incineration for heat generation, and resource-based recycling. Landfill and incineration are prone to waste resources and secondary pollution. However, modified recycled products can achieve certain mechanical properties that match or exceed those of virgin resin products, offering high added value and representing a promising future for the resource-based recycling of waste plastics. However, directly recycled products experience a significant decline in mechanical properties, and are also subject to issues such as inability to resist aging and flammability.

[0003] Currently, flame retardant modification of recycled plastics primarily involves physical blending of flame retardants and coating surface treatment. Physical blending of flame retardants is widely used in flame retardant modification of recycled plastics due to their ease of processing and low cost. However, existing flame retardant modification of recycled plastics often focuses solely on their flame retardant properties, while ignoring the impact of flame retardant properties on aging resistance. Aging of recycled plastics can lead to breakage of the main molecular chain, making them more flammable and reducing the durability of their flame retardant properties. Therefore, it is crucial to develop recycled plastic particles that exhibit excellent aging resistance, flame retardancy, and high strength. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for preparing aging-resistant recycled plastic particles to solve the problems existing in the prior art.

[0005] In order to solve the above technical problems, the present invention provides the following technical solution: a method for preparing aging-resistant recycled plastic particles, comprising the following preparation steps:

[0006] (1) 10-20 parts of magnesium sulfate heptahydrate, 6-14 parts of cobalt chloride hexahydrate, and 60-100 parts of deionized water were mixed uniformly, heated to 50-70°C, and stirred at 120 rpm. The pH value was adjusted to 9-11 with a 2 mol / L sodium hydroxide aqueous solution. The mixture was reacted for 16-24 hours. The solid was filtered and washed three times with deionized water. The solid was dried in an oven at 35-45°C for 12-24 hours, and ground into a powder with a particle size of 20-70 nm to obtain layered nanoparticles.

[0007] (2) 5 to 11 parts of layered nanoparticles were dispersed in 30 to 50 parts of ethanol-water solution, 8 to 18 parts of 3-(benzyldimethylammonio)propanesulfonic acid-ethanol solution were added dropwise at a rate of 3 mL / min, and ultrasonic stirring was performed at 40 kHz and 100 rpm for 2 to 6 hours. The solid was filtered and washed twice with deionized water and ethanol alternately, and dried in an oven at 30 to 40 ° C for 12 to 24 hours to obtain layered composite nanoparticles;

[0008] (3) 85 to 95 parts of recycled plastic with a molecular weight of 70,000 to 100,000, 4 to 8 parts of layered composite nanoparticles, and 1 to 3 parts of a plasticizer are uniformly mixed, and the mixture is extruded and pelletized through an extruder to obtain recycled plastic particles;

[0009] (4) Immersing the recycled plastic particles in the hot coating solution for 2 to 4 minutes, taking them out, cooling them, and drying them at 45 to 55° C. for 24 to 36 hours to obtain aging-resistant recycled plastic particles.

[0010] Furthermore, the volume ratio of ethanol to water in the ethanol-water solution in step (2) is 2:3.

[0011] Furthermore, the content of 3-(benzyldimethylammonio)propane sulfonic acid in the 3-(benzyldimethylammonio)propane sulfonic acid-ethanol solution in step (2) is 15 wt%.

[0012] Furthermore, the recycled plastic in step (3) is polyethylene terephthalate.

[0013] Furthermore, the plasticizer in step (3) is a mixture of any one or more of dioctyl phthalate, sodium sulfonate, n-butyl alkyl benzoate, and epoxy soybean oil.

[0014] Furthermore, the parameters of the extruder in step (3) are head temperature 250-270°C, screw speed 190-210 r / min, extrusion pressure 6-18 MPa, shear rate 200-300 s -1 .

[0015] Furthermore, the preparation step of the thermal coating solution in step (4) is: mixing 10 to 20 parts of polymethyl methacrylate, 0.5 to 1.5 parts of hydroxylated graphene, and 50 to 120 parts of toluene under ultrasonic stirring at 60 to 80° C., 40 kHz, and 150 rpm for 2 to 6 hours to prepare a thermal coating solution.

[0016] Furthermore, the molecular weight of the polymethyl methacrylate is 60,000 to 90,000.

[0017] Furthermore, the preparation steps of the hydroxylated graphene are: 0.1 to 0.3 parts of graphene are uniformly dispersed in 80 to 120 parts of water, after adjusting the pH to 3 with hydrochloric acid, 0.96 parts of ferrous chloride tetrahydrate are added, 20 vol% hydrogen peroxide solution is added dropwise at a rate of 50 mL / min for 8 to 30 minutes, stirred at 80 rpm for 1 to 3 hours, filtered, washed with deionized water 3 times, and placed in an oven at 40 to 50 ° C. and dried for 12 to 18 hours to obtain hydroxylated graphene.

[0018] Furthermore, the cooling conditions in step (4) are: cooling air temperature 20-30° C., wind speed 0.9-1.3 m / s, wind pressure 500-650 Pa, and cooling time 5-15 min.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] The present invention uses recycled plastic as raw material, which is first melt-blended with layered composite nanoparticles. During heat treatment, polymer chains continuously move, inserting and exfoliating the layered composite nanoparticles, thereby reducing the particle size and thickness and generating a large number of defects, thereby increasing contact sites, removing free radicals, and enhancing anti-aging performance. At the same time, due to the conversion and dissipation of thermal energy, the aging process of the polymer itself is inhibited, the growth of its carbonyl value is slowed down, and the anti-aging effect is further enhanced; the plastic particles are then immersed in a polymethyl methacrylate thermal coating solution mixed with hydroxylated graphene, the molecular chain segments of the plastic particles move more rapidly in the thermal solution, the gaps between molecules are increased, which is conducive to the diffusion and bonding of the thermal coating solution, improves the compatibility between the coating and the recycled plastic, modifies the surface defects of the plastic particles, and improves the overall mechanical strength; finally, cooling forms a double-layer structure, increases the reflection and absorption times of ultraviolet rays, and gradually weakens the ultraviolet rays in the process of layer-by-layer blocking and absorption, thereby indirectly improving the anti-aging performance.

[0021] Secondly, the layered composite nanoparticles are prepared by coprecipitating cobalt chloride and magnesium sulfate to form layered hydroxides, which are then modified with 3-(benzyldimethylammonium)propane sulfonic acid. 3-(benzyldimethylammonium)propane sulfonic acid is intercalated into the layered hydroxide particles through sulfonate groups. The presence of sulfonate groups can decompose when heated to form non-combustible products such as sulfonates and sulfonate esters, thereby achieving a flame retardant effect. It assists magnesium and cobalt hydroxides and has a lower decomposition temperature. When combustion occurs, the decomposition absorbs a large amount of heat to produce water and carbon dioxide gas, which inhibits the spread of smoke and blocks oxygen, thereby achieving the effect of flame retardancy and smoke suppression. On this basis, as the intercalation reaction proceeds, the interlayer spacing is expanded, the dispersibility is improved, and thus it helps to better contact with the free radicals in the plastic, and a quenching effect occurs with the free radicals in the plastic to generate large molecular free radicals, thereby reducing the attack of free radicals on plastic particles and effectively inhibiting the occurrence of aging. DETAILED DESCRIPTION

[0022] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0023] In order to more clearly illustrate the method provided by the present invention, the following examples are used to describe in detail the various index testing methods of the aging-resistant recycled plastic particles prepared in the following examples.

[0024] Tensile strength: The same mass of plastic particles of the embodiment and the comparative example were made into 0.3 mm films and tested in accordance with GB / T13022.

[0025] Tensile strength after aging: The same mass of plastic particles of the embodiment and comparative example was made into a 0.3 mm film, irradiated with a 6 kW xenon lamp and sprayed with water at a pressure of 0.12 to 0.15 MPa. The film was irradiated with ultraviolet light in a cycle of 120 minutes, with 18 minutes of simultaneous water spraying and light exposure and the remaining 120 minutes of light exposure alone, for a total exposure time of 2000 hours. The sample was then placed at room temperature for 20 hours and tested in accordance with GB / T 13022.

[0026] Oxygen index and flame retardancy: The same mass of plastic particles of the embodiment and the comparative example were made into 0.3 mm films and tested in accordance with ANSI / UL-94-1985.

[0027] Example 1: (1) 10 parts of magnesium sulfate heptahydrate, 6 parts of cobalt chloride hexahydrate, and 60 parts of deionized water were mixed uniformly, heated to 50°C, and stirred at 120 rpm. The pH value was adjusted to 9 with a 2 mol / L sodium hydroxide aqueous solution. The mixture was reacted for 16 h, and the solid was filtered, washed three times with deionized water, dried in an oven at 35°C for 12 h, and ground into a powder with a particle size of 20 nm to obtain layered nanoparticles.

[0028] (2) 5 parts of layered nanoparticles were dispersed in a mixture of 30 parts of ethanol and water in a volume ratio of 2:3, and 8 parts of a 3-(benzyldimethylammonio)propanesulfonic acid-ethanol solution containing 15 wt% of 3-(benzyldimethylammonio)propanesulfonic acid was added dropwise at a rate of 3 mL / min. The mixture was ultrasonically stirred at 40 kHz and 100 rpm for 2 h. The solid was filtered and washed twice with deionized water and ethanol alternately. The solid was dried in an oven at 30°C for 12 h to obtain layered composite nanoparticles.

[0029] (3) 85 parts of polyethylene terephthalate with a molecular weight of 70,000, 4 parts of layered composite nanoparticles, and 1 part of dioctyl phthalate were mixed uniformly and extruded into pellets using an extruder with a head temperature of 250°C, a screw speed of 190 r / min, an extrusion pressure of 6 MPa, and a shear rate of 200 s -1 , to obtain recycled plastic particles;

[0030] (4) 0.1 parts of graphene were uniformly dispersed in 80 parts of water, and after adjusting the pH to 3 with hydrochloric acid, 0.96 parts of ferrous chloride tetrahydrate were added, and a 20 vol% hydrogen peroxide solution was added dropwise at a rate of 50 mL / min for 8 minutes. The mixture was stirred at 80 rpm for 1 hour, filtered, washed with deionized water 3 times, and dried in an oven at 40 °C for 12 hours to obtain hydroxylated graphene.

[0031] (5) 10 parts of polymethyl methacrylate (MW 60,000), 0.5 parts of hydroxylated graphene, and 50 parts of toluene were mixed under ultrasonic stirring at 60°C, 40 kHz, and 150 rpm for 2 h to prepare a thermal coating solution;

[0032] (6) The recycled plastic particles were immersed in the hot coating solution for 2 minutes, taken out, cooled for 5 minutes at a cooling air temperature of 20°C, a wind speed of 0.9 m / s, and a wind pressure of 500 Pa, and dried at 45°C for 24 hours to obtain aging-resistant recycled plastic particles.

[0033] Example 2: (1) 15 parts of magnesium sulfate heptahydrate, 10 parts of cobalt chloride hexahydrate, and 80 parts of deionized water were mixed uniformly, heated to 60°C, and stirred at 120 rpm. The pH value was adjusted to 10 with a 2 mol / L sodium hydroxide aqueous solution. The mixture was reacted for 20 h, and the solid was filtered, washed three times with deionized water, dried in an oven at 40°C for 18 h, and ground into a powder with a particle size of 45 nm to obtain layered nanoparticles.

[0034] (2) 8 parts of layered nanoparticles were dispersed in a mixture of 40 parts of ethanol and water in a volume ratio of 2:3, and 13 parts of a 3-(benzyldimethylammonio)propanesulfonic acid-ethanol solution containing 15 wt% of 3-(benzyldimethylammonio)propanesulfonic acid was added dropwise at a rate of 3 mL / min. The mixture was ultrasonically stirred at 40 kHz and 100 rpm for 4 h. The solid was filtered and washed twice with deionized water and ethanol alternately. The solid was dried in an oven at 35°C for 18 h to obtain layered composite nanoparticles.

[0035] (3) 90 parts of polyethylene terephthalate with a molecular weight of 85,000, 6 parts of layered composite nanoparticles, and 2 parts of sodium sulfonate were mixed uniformly and extruded into pellets using an extruder with a head temperature of 260°C, a screw speed of 200 r / min, an extrusion pressure of 12 MPa, and a shear rate of 250 s -1 , to obtain recycled plastic particles;

[0036] (4) 0.2 parts of graphene were uniformly dispersed in 100 parts of water, and after adjusting the pH to 3 with hydrochloric acid, 0.96 parts of ferrous chloride tetrahydrate were added, and a 20 vol% hydrogen peroxide solution was added dropwise at a rate of 50 mL / min for 19 minutes. The mixture was stirred at 80 rpm for 2 hours, filtered, washed with deionized water three times, and dried in an oven at 45°C for 15 hours to obtain hydroxylated graphene.

[0037] (5) 15 parts of polymethyl methacrylate (MW 75,000), 1.0 part of hydroxylated graphene, and 85 parts of toluene were mixed under ultrasonic stirring at 70°C, 40 kHz, and 150 rpm for 4 h to prepare a thermal coating solution;

[0038] (6) The recycled plastic particles were immersed in the hot coating solution for 3 minutes, taken out, cooled for 10 minutes at a cooling air temperature of 25°C, a wind speed of 1.1 m / s, and a wind pressure of 575 Pa, and dried at 50°C for 30 hours to obtain aging-resistant recycled plastic particles.

[0039] Example 3: (1) 20 parts of magnesium sulfate heptahydrate, 14 parts of cobalt chloride hexahydrate, and 100 parts of deionized water were mixed uniformly, heated to 70°C, and stirred at 120 rpm. The pH value was adjusted to 11 with a 2 mol / L sodium hydroxide aqueous solution. The mixture was reacted for 24 h. The solid was filtered, washed three times with deionized water, dried in an oven at 45°C for 24 h, and ground into a powder with a particle size of 70 nm to obtain layered nanoparticles.

[0040] (2) 11 parts of layered nanoparticles were dispersed in a mixture of 50 parts of ethanol and water in a volume ratio of 2:3, and 18 parts of a 3-(benzyldimethylammonio)propanesulfonic acid-ethanol solution containing 15 wt% of 3-(benzyldimethylammonio)propanesulfonic acid was added dropwise at a rate of 3 mL / min. The mixture was ultrasonically stirred at 40 kHz and 100 rpm for 6 h. The solid was filtered and washed twice with deionized water and ethanol alternately. The solid was dried in an oven at 40°C for 24 h to obtain layered composite nanoparticles.

[0041] (3) 95 parts of polyethylene terephthalate with a molecular weight of 100,000, 8 parts of layered composite nanoparticles, and 3 parts of n-butyl alkyl benzoate were mixed uniformly and extruded into pellets using an extruder with a head temperature of 270°C, a screw speed of 210 r / min, an extrusion pressure of 18 MPa, and a shear rate of 300 s -1 , to obtain recycled plastic particles;

[0042] (4) 0.3 parts of graphene were uniformly dispersed in 120 parts of water, and after adjusting the pH to 3 with hydrochloric acid, 0.96 parts of ferrous chloride tetrahydrate were added, and a 20 vol% hydrogen peroxide solution was added dropwise at a rate of 50 mL / min for 30 minutes. The mixture was stirred at 80 rpm for 3 hours, filtered, washed with deionized water 3 times, and dried in an oven at 50°C for 18 hours to obtain hydroxylated graphene.

[0043] (5) 20 parts of polymethyl methacrylate (MW 90,000), 1.5 parts of hydroxylated graphene, and 120 parts of toluene were mixed under ultrasonic stirring at 80°C, 40 kHz, and 150 rpm for 6 h to prepare a thermal coating solution;

[0044] (6) The recycled plastic particles were immersed in the hot coating solution for 4 minutes, taken out, cooled for 15 minutes at a cooling air temperature of 30°C, a wind speed of 1.3 m / s, and a wind pressure of 650 Pa, and dried at 55°C for 36 hours to obtain aging-resistant recycled plastic particles.

[0045] Comparative Example 1: The difference between Comparative Example 1 and Example 2 lies in the differences in steps (3) and (5). Step (3) is changed to: 90 parts of polyethylene terephthalate with a molecular weight of 85,000, 6 parts of layered composite nanoparticles, 2 parts of sodium sulfonate, and 1 part of hydroxylated graphene are uniformly mixed and extruded and pelletized in an extruder at a head temperature of 260°C, a screw speed of 200 r / min, an extrusion pressure of 12 MPa, and a shear rate of 250 s-1 to obtain recycled plastic particles; Step (5) is changed to: 15 parts of polymethyl methacrylate with a molecular weight of 75,000 and 85 parts of toluene are mixed under ultrasonic stirring at 70°C, 40 kHz, and 150 rpm for 4 hours to obtain a thermal coating solution. The remaining steps are the same as in Example 2.

[0046] Comparative Example 2: The difference between Comparative Example 2 and Example 2 lies in step (5), which is modified to: 15 parts of polymethyl methacrylate (MW 75,000) and 85 parts of toluene were mixed under ultrasonic stirring at 70°C, 40 kHz, and 150 rpm for 4 hours to prepare a thermal coating solution. The remaining steps were the same as in Example 2.

[0047] Comparative Example 3: Comparative Example 3 differs from Example 2 in that steps (1) and (2) are omitted, and step (3) is modified to: 90 parts of polyethylene terephthalate having a molecular weight of 85,000, 6 parts of 3-(benzyldimethylammonio)propane sulfonic acid, and 2 parts of sodium sulfonate are uniformly mixed, and pelletized by extrusion using an extruder at a feed temperature of 260° C., a screw speed of 200 r / min, an extrusion pressure of 12 MPa, and a shear rate of 250 s⁻¹ to produce recycled plastic pellets. The remaining steps are the same as those of Example 2.

[0048] Comparative Example 4: Comparative Example 4 differs from Example 2 in that step (2) is omitted and step (3) is modified to: 90 parts of polyethylene terephthalate (PET) with a molecular weight of 85,000, 6 parts of layered nanoparticles, and 2 parts of sodium sulfonate are uniformly mixed and pelletized by extrusion in an extruder at a feed temperature of 260° C., a screw speed of 200 r / min, an extrusion pressure of 12 MPa, and a shear rate of 250 s⁻¹ to produce recycled plastic pellets. The remaining steps are the same as in Example 2.

[0049] Comparative Example 5: The difference between Comparative Example 5 and Example 2 is that there are no steps (4), (5), and (6). The remaining steps are the same as Example 2.

[0050] Table 1 below shows the performance analysis results of the aging-resistant recycled plastic particles of Examples 1 to 3 of the present invention and Comparative Examples 1 to 5.

[0051] Table 1

[0052]

[0053] From the comparison of the experimental data of Examples 1, 2, and 3 with those of Comparative Examples 1, 2, and 5, it can be found that in the process of melt blending of the layered composite nanoparticles with the recycled plastic, the polymer chains will continue to move, intercalate and peel the layered composite nanoparticles, so that the particle size and thickness are reduced, a large number of defects are generated, contact sites are increased, free radicals are scavenged, and the anti-aging performance is enhanced. Moreover, due to the conversion and dissipation of thermal energy, the aging process of the polymer itself is inhibited, and the growth of its carbonyl value is slowed down, further enhancing the anti-aging effect. At the same time, the movement of the molecular chain segments of the plastic particles in the hot solution is intensified, and the gap between molecules is increased, which is conducive to the diffusion and bonding of the hot coating solution, improves the compatibility between the coating and the recycled plastic, modifies the internal defects of the plastic particles, improves the overall mechanical strength, and cooperates with the layered assembly structure formed after the coating is cooled to increase the reflection and absorption times of ultraviolet rays, so that the ultraviolet rays are gradually weakened in the process of layer-by-layer blocking and absorption, thereby improving the anti-aging performance. Comparison of the experimental data of Examples 1, 2, and 3 with Comparative Examples 3 and 4 shows that cobalt chloride and magnesium sulfate are coprecipitated to form a layered hydroxide, which is modified with 3-(benzyldimethylammonium)propane sulfonic acid. 3-(benzyldimethylammonium)propane sulfonic acid is intercalated into the layered hydroxide particles through sulfonate groups. The presence of sulfonate groups can decompose when heated to form non-combustible products such as sulfonates and sulfonate esters, assisting magnesium and cobalt hydroxides, and having a lower decomposition temperature. When combustion occurs, the decomposition absorbs a large amount of heat to produce water and carbon dioxide gas, which inhibits the spread of smoke and blocks oxygen, thereby achieving the effect of improving the limiting oxygen index. At the same time, as the intercalation reaction proceeds, the interlayer spacing of the layered hydroxide continues to expand, improving dispersibility, contributing to better contact with free radicals in the plastic, and generating a quenching effect with free radicals in the plastic to generate macromolecular free radicals, reduce the attack of free radicals on plastic particles, and effectively inhibit the occurrence of aging.

[0054] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the invention is defined by the appended claims, not the foregoing description, and all variations within the meaning and range of equivalents of the claims are intended to be encompassed therein. Any reference in a claim should not be construed as limiting the claim to which it relates.

Claims

1. A method for preparing aging-resistant recycled plastic particles, characterized in that: The method comprises the following preparation steps: (1) 10-20 parts of magnesium sulfate heptahydrate, 6-14 parts of cobalt chloride hexahydrate, and 60-100 parts of deionized water were mixed uniformly, heated to 50-70°C, and stirred at 120 rpm. The pH value was adjusted to 9-11 with a 2 mol / L sodium hydroxide aqueous solution. The mixture was reacted for 16-24 hours. The solid was filtered and washed three times with deionized water. The solid was dried in an oven at 35-45°C for 12-24 hours, and ground into a powder with a particle size of 20-70 nm to obtain layered nanoparticles. (2) 5 to 11 parts of layered nanoparticles were dispersed in 30 to 50 parts of ethanol-water solution, 8 to 18 parts of 3-(benzyldimethylammonio)propanesulfonic acid-ethanol solution were added dropwise at a rate of 3 mL / min, and ultrasonic stirring was performed at 40 kHz and 100 rpm for 2 to 6 hours. The solid was filtered and washed twice with deionized water and ethanol alternately, and dried in an oven at 30 to 40 ° C for 12 to 24 hours to obtain layered composite nanoparticles; (3) 85 to 95 parts of recycled plastic with a molecular weight of 70,000 to 100,000, 4 to 8 parts of layered composite nanoparticles, and 1 to 3 parts of a plasticizer are uniformly mixed, and the mixture is extruded and pelletized through an extruder to obtain recycled plastic particles; (4) Immersing the recycled plastic particles in the hot coating solution for 2 to 4 minutes, taking them out, cooling them, and drying them at 45 to 55° C. for 24 to 36 hours to obtain aging-resistant recycled plastic particles.

2. The method for preparing aging-resistant recycled plastic particles according to claim 1, characterized in that: The volume ratio of ethanol to water in the ethanol-water solution of step (2) is 2:

3.

3. The method for preparing aging-resistant recycled plastic particles according to claim 1, characterized in that: The content of 3-(benzyldimethylammonio)propanesulfonic acid in the 3-(benzyldimethylammonio)propanesulfonic acid-ethanol solution in step (2) is 15 wt %.

4. The method for preparing aging-resistant recycled plastic particles according to claim 1, characterized in that: The recycled plastic in step (3) is polyethylene terephthalate.

5. The method for preparing aging-resistant recycled plastic particles according to claim 1, characterized in that: The plasticizer in step (3) is a mixture of any one or more of dioctyl phthalate, sodium sulfonate, n-butyl alkyl benzoate, and epoxy soybean oil.

6. The method for preparing aging-resistant recycled plastic particles according to claim 1, characterized in that: The parameters of the extruder in step (3) are head temperature 250-270°C, screw speed 190-210 r / min, extrusion pressure 6-18 MPa, shear rate 200-300 s -1 .

7. The method for preparing aging-resistant recycled plastic particles according to claim 1, characterized in that: The preparation step of the thermal coating solution in step (4) is as follows: 10 to 20 parts of polymethyl methacrylate, 0.5 to 1.5 parts of hydroxylated graphene, and 50 to 120 parts of toluene are mixed under ultrasonic stirring at 60 to 80° C., 40 kHz, and 150 rpm for 2 to 6 hours to prepare a thermal coating solution.

8. The method for preparing aging-resistant recycled plastic particles according to claim 7, characterized in that: The molecular weight of the polymethyl methacrylate is 60,000 to 90,000.

9. The method for preparing aging-resistant recycled plastic particles according to claim 7, characterized in that: The preparation steps of the hydroxylated graphene are as follows: 0.1 to 0.3 parts of graphene are uniformly dispersed in 80 to 120 parts of water, after adjusting the pH to 3 with hydrochloric acid, 0.96 parts of ferrous chloride tetrahydrate are added, 20 vol% hydrogen peroxide solution is added dropwise at a rate of 50 mL / min for 8 to 30 minutes, stirred at 80 rpm for 1 to 3 hours, filtered, washed with deionized water three times, and dried in an oven at 40 to 50° C. for 12 to 18 hours to obtain the hydroxylated graphene.

10. The method for preparing aging-resistant recycled plastic particles according to claim 1, characterized in that: The cooling conditions in step (4) are: cooling air temperature 20-30° C., wind speed 0.9-1.3 m / s, wind pressure 500-650 Pa, and cooling time 5-15 min.

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