Elastic anti-aging plastic particle and preparation method thereof

Abstract

The invention discloses elastic anti-aging plastic particles and a preparation method thereof, and relates to the technical field of plastics. The preparation method comprises the following steps: performing in-situ synthesis of cerium dioxide on the surface of a hydroxylated multi-walled carbon nanotube, performing freeze drying treatment to enhance the dispersibility of the multi-walled carbon nanotube, performing carboxyl activation, grafting ethylenediamine on the surface of a carrier, and polymerizing the carrier with polyurethane through an in-situ polymerization method to obtain the polyurethane-modified multi-walled carbon nanotube composite material. The multiwalled carbon nanotubes not only play a role of a physical filler, but also react with a soft segment and a hard segment in polyurethane through hydroxyl groups on the surfaces of the multiwalled carbon nanotubes, so that the elastomer achieves high-temperature aging resistance and ultraviolet aging resistance, ethylenediamine in the multiwalled carbon nanotubes can generate ureido with isocyanate, the interface bonding capacity of inorganic matter and a matrix is enhanced, and the mechanical property of the elastomer is improved. And the cohesive energy of the ureido is relatively large, so that the polyurethane hard segment is easy to react and gather, and the heat resistance and ultraviolet aging resistance of the matrix are further enhanced.

Description

Technical Field

[0001] The present invention relates to the technical field of plastics, and particularly to an elastic and aging-resistant plastic particle and a preparation method thereof. Background Art

[0002] The modulus of polyurethane elastomer is between that of rubber and plastic, and it has the characteristics of both plastic and rubber, and is known as the "fifth largest plastic". The performance range of polyurethane elastomer is relatively wide, and it has the advantages of high strength, tear resistance, impact resistance, good flexural performance, oil resistance, wear resistance and good biocompatibility, etc., and is widely used in various fields, including printing and packaging, textiles, aerospace, navigation, automobiles, military industry, electromechanics and construction, etc.; and the use environments of many products are outdoor environments, and they will be irradiated by sunlight for a long time during application; long-term ultraviolet irradiation will cause serious aging of TPU, resulting in irreversible chemical structure changes, affecting the apparent appearance, such as loss of luster, yellowing, blistering, cracking, peeling, etc., and mechanical strength, such as strength reduction, embrittlement, etc.

[0003] At the same time, polyurethane elastomer also has the disadvantage of poor thermal stability and is easy to soften and decompose at high temperatures. At higher temperatures, the appearance size and mechanical properties of polyurethane elastomer will change. It is reported that the long-term use temperature of polyurethane should not exceed 80 °C, and the short-term use temperature should not exceed 120 °C, which to a certain extent limits the application of polyurethane elastomer in the fields of high-temperature processing or high-temperature use. Summary of the Invention

[0004] The purpose of the present invention is to provide an elastic and aging-resistant plastic particle and a preparation method thereof to solve the problems existing in the prior art.

[0005] To solve the above technical problems, the present invention provides the following technical solution: A preparation method of an elastic and aging-resistant plastic particle, comprising the following steps:

[0006] (1) Mix cerium nitrate hexahydrate and deionized water, stir at 60 - 150 rpm for 20 min, add hydroxylated multi-walled carbon nanotubes, heat up to 60 - 90 °C, stir at 300 - 600 rpm for 1 h, add 40 wt% sodium hydroxide aqueous solution and continue to react for 4 h, cool to room temperature, continue to stir for 24 h, then centrifuge at a rate of 8000 rpm for 4 - 8 min, take the solid, wash with deionized water until the pH of the washing solution is 7, and dry at 60 - 90 °C for 8 - 15 h to obtain a carrier;

[0007] (2) Mix the carrier and tert-butanol, ultrasonically treat at 28 kHz for 2 - 5 h, perform freeze-drying treatment, and then place it in toluene and ultrasonically treat for 30 min to obtain a carrier suspension;

[0008] (3) Mix diethylene glycol and polyacrylic acid, heat to 100 - 120 °C under a nitrogen atmosphere, stir at 100 rpm for 20 - 50 min, add the negative carrier suspension, react for 1 h, then heat to 200 - 300 °C and react for 1 - 4 h. Then cool to room temperature, add ethanol for precipitation, and centrifuge at a rate of 8000 rpm for 4 - 8 min to obtain intermediate A;

[0009] (4) Activate the carboxyl group of intermediate A to obtain intermediate B;

[0010] (5) Disperse intermediate B in dichloromethane, add ethylenediamine, react for 10 - 16 h, centrifuge and take the solid, then disperse it in tetrahydrofuran and ultrasonicate at 22 kHz for 20 min to obtain the prepolymer;

[0011] (6) Mix diphenylmethane diisocyanate and polycaprolactone diol 1000, add tetrahydrofuran under a nitrogen atmosphere, heat to 60 - 80 °C and react for 30 min, then heat to 70 - 85 °C and react for 1.5 h. Add diethyltoluenediamine and the prepolymer, continue to react for 1.5 h, then let it stand at room temperature for 24 h and at 50 - 100 °C for 24 h. Finally, perform extrusion granulation at a temperature of 150 - 250 °C to obtain the elastic anti - aging plastic particles.

[0012] Further, the preparation method of the hydroxylated multi - walled carbon nanotubes in step (1): Mix multi - walled carbon nanotubes and 40 wt% sodium hydroxide aqueous solution at a mass ratio of 0.5:200, ultrasonicate at 21 kHz for 30 min, stir at 300 - 600 rpm for 8 - 15 h, add 30 wt% hydrogen peroxide aqueous solution which is 3 - 5 times the mass of the multi - walled carbon nanotubes at a rate of 1 - 5 mL / min, continue to stir for 2 - 6 h, then centrifuge at a rate of 8000 rpm for 4 - 8 min, take the solid, wash it with deionized water until the pH of the washing solution is 7, and dry it at 60 - 90 °C for 8 - 15 h to obtain the product.

[0013] Further, the mass ratio of cerium(IV) nitrate hexahydrate, deionized water, hydroxylated multi - walled carbon nanotubes, and 40 wt% sodium hydroxide aqueous solution in step (1) is 0.1 - 1:100:0.1:500.

[0014] Further, the specific steps of the freeze - drying treatment in step (2) are: rapidly freeze in liquid nitrogen, and then dry at a vacuum degree of 0.2 - 1 kPa and - 30 - 50 °C for 25 h.

[0015] Further, the mass ratio of the negative carrier, tert - butyl alcohol, and toluene in step (2) is 0.1:50:2.

[0016] Further, the mass ratio of diethylene glycol, polyacrylic acid, the negative carrier suspension, and ethanol in step (3) is 100:1-2:8-12:100.

[0017] Further, the specific steps of the carboxyl activation treatment in step (4) are as follows: Disperse intermediate A in dichloromethane, perform ultrasonic treatment at 22 kHz for 30 min, add 2-(7-azabenzotriazol-1-yl)-N,N,N',N'-tetramethyluronium hexafluorophosphate and N,N'-diisopropylethylamine, react for 20 min, and take the solid after centrifugation.

[0018] Further, the mass ratio of intermediate A, dichloromethane, 2-(7-azabenzotriazol-1-yl)-N,N,N',N'-tetramethyluronium hexafluorophosphate, and N,N'-diisopropylethylamine in the step is 1:100:0.02-0.3:0.01-0.1.

[0019] Further, the mass ratio of intermediate B, dichloromethane, ethylenediamine, and tetrahydrofuran in step (5) is 1:100:15-35:10-50.

[0020] Further, the mass ratio of diphenylmethane diisocyanate, polycaprolactone diol 1000, tetrahydrofuran, diethyltoluenediamine, and the prepolymer in step (6) is 14:5:35:0.6:0.1-0.4.

[0021] Compared with the prior art, the beneficial effects achieved by the present invention are as follows: The present invention utilizes hydroxylated multi-walled carbon nanotubes to in-situ synthesize cerium dioxide on the surface of the multi-walled carbon nanotubes through their hydroxyl groups to form a negative carrier, and then performs vacuum freeze-drying treatment. During the pre-freezing process, the dispersion medium heterogeneously nucleates on the surface of the multi-walled carbon nanotubes and undergoes vitrification transformation, which is beneficial to fixing the dispersed state of the multi-walled carbon nanotubes and obtaining fine tube walls, thereby enhancing the absorption capacity of ultraviolet light and improving the ultraviolet aging resistance of the matrix. At the same time, the firmness of the nano-cerium dioxide inside the tube is enhanced. Then, after carboxyl activation, ethylenediamine is grafted onto the surface of the negative carrier and mixed with polyurethane by in-situ polymerization. Among them, cerium oxide can be dispersed in the matrix to absorb ultraviolet light and consume the absorbed ultraviolet light energy in the form of heat energy or electromagnetic waves to protect the surrounding polymer matrix and play a role in shielding ultraviolet light, or eliminate the free radicals generated by the fracture of the molecular chain during the aging of polyurethane during the transformation between trivalent cerium ions and tetravalent cerium ions, inhibiting the further fracture of the molecular chain. When ultraviolet light irradiates the multi-walled carbon nanotubes, electrons will undergo transitions when excited by light and absorb photons with corresponding energies, thereby showing strong ultraviolet absorption capacity and greatly improving the ultraviolet aging resistance of the matrix. During the polymerization process, the multi-walled carbon nanotubes not only act as physical fillers to improve the thermal decomposability of the polymer, but also react with isocyanate groups through the hydroxyl groups on their surfaces, and then bond with the polyurethane molecular chain in a covalent bond manner to increase the crosslinking density of the polymer network structure and improve the heat aging resistance of the elastomer. At the same time, the hydroxyl groups also form hydrogen bond interactions with the ether groups in the soft segment phase, hindering the movement of the molecular chain segments of the polyurethane soft segment, resulting in fewer molecular chains showing relaxation phenomena, and inducing the polyurethane soft segment phase and hard segment phase to be regularly arranged around the carbon nanotubes, which is beneficial to the crystallization of polyurethane. And these interactions also promote the aggregation of carbon nanotubes and form a nanocomposite material in the polyurethane matrix, further enhancing the thermal stability of the matrix. Among them, ethylenediamine can react with the isocyanate-terminated prepolymer to generate urea groups, enhancing the interfacial bonding ability between the inorganic substance and the matrix, and the cohesive energy of the urea groups is relatively large, which is easy to cause the reaction and aggregation of the polyurethane hard segment, thereby further enhancing the heat resistance and ultraviolet aging resistance of the matrix. Detailed implementation mode

[0022] The following will combine the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present invention.

[0023] In order to more clearly illustrate the method provided by the present invention, the following embodiments are used for detailed description. The test methods for each index of the elastic anti-aging plastic particles prepared in the following embodiments are as follows:

[0024] Resistant to ultraviolet aging and high-temperature aging: Take dumbbell-shaped specimens of the same size prepared from the examples and comparative examples according to the GB / T 1040.1 standard. Use an electronic universal testing machine to test their tensile strength. Place the dumbbell-shaped specimens in a UV weathering test chamber model HD-E802-4 to test their tensile strength after UV aging. The UV aging conditions are: temperature 50°C, light intensity 1 W / m 2 , time 30 d; Place the dumbbell-shaped specimens in a hot air aging oven to test their tensile strength after high-temperature aging. The high-temperature aging conditions are: temperature 100°C, time 30 d.

[0025] Example 1; (1) Mix multi-walled carbon nanotubes and 40 wt% aqueous sodium hydroxide solution at a mass ratio of 0.5:200, ultrasonicate for 30 min at 21 kHz, stir at 300 rpm for 8 h, add 30 wt% aqueous hydrogen peroxide solution three times the mass of the multi-walled carbon nanotubes at a rate of 1 mL / min, continue stirring for 2 h, then centrifuge at a rate of 8000 rpm for 4 min. Take the solid, wash it with deionized water until the pH of the washing solution is 7, and dry it at 60°C for 8 h to obtain hydroxylated multi-walled carbon nanotubes; Mix cerium(III) nitrate hexahydrate and deionized water, stir at 60 rpm for 20 min, add the hydroxylated multi-walled carbon nanotubes, heat up to 60°C, stir at 300 rpm for 1 h, add 40 wt% aqueous sodium hydroxide solution and continue to react for 4 h, cool to room temperature, continue stirring for 24 h, then centrifuge at a rate of 8000 rpm for 4 min. Take the solid, wash it with deionized water until the pH of the washing solution is 7, and dry it at 60°C for 8 h to obtain the carrier; The mass ratio of cerium(III) nitrate hexahydrate, deionized water, hydroxylated multi-walled carbon nanotubes, and 40 wt% aqueous sodium hydroxide solution is 0.1:100:0.1:500;

[0026] (2) Mix the carrier and tert-butanol, ultrasonicate at 28 kHz for 2 h, perform freeze-drying treatment, rapidly freeze it in liquid nitrogen, then dry it at a vacuum of 0.2 kPa and -30°C for 25 h, and then place it in toluene and ultrasonicate for 30 min to obtain a carrier suspension; The mass ratio of the carrier, tert-butanol, and toluene is 0.1:50:2;

[0027] (3) Mix diethylene glycol and polyacrylic acid, heat up to 100°C under a nitrogen atmosphere, stir at 100 rpm for 20 min, add the carrier suspension, react for 1 h, heat up to 200°C, react for 1 h, then cool to room temperature, add ethanol for precipitation, centrifuge at a rate of 8000 rpm for 4 min to obtain intermediate A; The mass ratio of diethylene glycol, polyacrylic acid, carrier suspension, and ethanol is 100:1:8:100;

[0028] (4) The intermediate A is subjected to carboxyl activation treatment. First, it is dispersed in dichloromethane, sonicated at 22 kHz for 30 min, 2-(7-azabenzotriazol-1-yl)-N,N,N',N'-tetramethyluronium hexafluorophosphate and N,N'-diisopropylethylamine are added, and the reaction is carried out for 20 min. After centrifugation, the solid is taken to obtain intermediate B; the mass ratio of the intermediate A, dichloromethane, 2-(7-azabenzotriazol-1-yl)-N,N,N',N'-tetramethyluronium hexafluorophosphate, and N,N'-diisopropylethylamine is 1:100:0.02:0.01;

[0029] (5) The intermediate B is dispersed in dichloromethane, ethylenediamine is added, and the reaction is carried out for 10 h. After centrifugation, the solid is taken and then dispersed in tetrahydrofuran, sonicated at 22 kHz for 20 min to obtain a prepolymer; the mass ratio of the intermediate B, dichloromethane, ethylenediamine, and tetrahydrofuran is 1:100:15:10;

[0030] (6) Diphenylmethane diisocyanate and polycaprolactone diol 1000 are mixed. Under a nitrogen atmosphere, tetrahydrofuran is added, the temperature is raised to 60 °C, and the reaction is carried out for 30 min. Then the temperature is raised to 70 °C, and the reaction is carried out for 1.5 h. Diethyltoluenediamine and the prepolymer are added, and the reaction is continued for 1.5 h. Then it is left standing at room temperature for 24 h and at 50 °C for 24 h. Finally, it is extruded and granulated at a temperature of 150 °C to obtain elastic anti-aging plastic particles; the mass ratio of diphenylmethane diisocyanate, polycaprolactone diol 1000, tetrahydrofuran, diethyltoluenediamine, and the prepolymer is 14:5:35:0.6:0.1.

[0031] Example 2; (1) Multi-walled carbon nanotubes and 40 wt% aqueous sodium hydroxide solution are mixed at a mass ratio of 0.5:200, sonicated at 21 kHz for 30 min, stirred at 450 rpm for 11 h, 30 wt% aqueous hydrogen peroxide solution 4 times the mass of the multi-walled carbon nanotubes is added at a rate of 3 mL / min, and stirring is continued for 4 h. Then it is centrifuged at a rate of 8000 rpm for 6 min, the solid is taken, washed with deionized water until the pH of the washing solution is 7, and dried at 75 °C for 12 h to obtain hydroxylated multi-walled carbon nanotubes; Cerium(III) nitrate hexahydrate and deionized water are mixed, stirred at 120 rpm for 20 min, hydroxylated multi-walled carbon nanotubes are added, the temperature is raised to 75 °C, stirred at 450 rpm for 1 h, 40 wt% aqueous sodium hydroxide solution is added and the reaction is continued for 4 h, cooled to room temperature, and stirring is continued for 24 h. Then it is centrifuged at a rate of 8000 rpm for 6 min, the solid is taken, washed with deionized water until the pH of the washing solution is 7, and dried at 75 °C for 12 h to obtain a carrier; the mass ratio of cerium(III) nitrate hexahydrate, deionized water, hydroxylated multi-walled carbon nanotubes, and 40 wt% aqueous sodium hydroxide solution is 0.6:100:0.1:500;

[0032] (2) Mix the carrier and tert-butanol, ultrasonicate at 28 kHz for 3.5 h, perform freeze-drying treatment, rapidly freeze in liquid nitrogen, then dry at a vacuum of 0.4 kPa and -40 °C for 25 h, and then place in toluene and ultrasonicate for 30 min to obtain a carrier suspension; the mass ratio of the carrier, tert-butanol, and toluene is 0.1:50:2;

[0033] (3) Mix diethylene glycol and polyacrylic acid, heat to 110 °C under a nitrogen atmosphere, stir at 100 rpm for 35 min, add the carrier suspension, react for 1 h, heat to 250 °C, react for 2.5 h, then cool to room temperature, add ethanol for precipitation, and centrifuge at a rate of 8000 rpm for 6 min to obtain intermediate A; the mass ratio of diethylene glycol, polyacrylic acid, carrier suspension, and ethanol is 100:1.5:10:100;

[0034] (4) Activate the carboxyl group of intermediate A. First, disperse it in dichloromethane, ultrasonicate at 22 kHz for 30 min, add 2-(7-azabenzotriazol-1-yl)-N,N,N',N'-tetramethyluronium hexafluorophosphate and N,N'-diisopropylethylamine, react for 20 min, centrifuge and take the solid to obtain intermediate B; the mass ratio of intermediate A, dichloromethane, 2-(7-azabenzotriazol-1-yl)-N,N,N',N'-tetramethyluronium hexafluorophosphate, and N,N'-diisopropylethylamine is 1:100:0.16:0.06;

[0035] (5) Disperse intermediate B in dichloromethane, add ethylenediamine, react for 13 h, centrifuge and take the solid, then disperse it in tetrahydrofuran and ultrasonicate at 22 kHz for 20 min to obtain a prepolymer; the mass ratio of intermediate B, dichloromethane, ethylenediamine, and tetrahydrofuran is 1:100:25:35;

[0036] (6) Mix diphenylmethane diisocyanate and polycaprolactone diol 1000, add tetrahydrofuran under a nitrogen atmosphere, heat to 70 °C, react for 30 min, heat to 77 °C, react for 1.5 h, add diethyltoluenediamine and the prepolymer, continue to react for 1.5 h, then let stand at room temperature for 24 h and at 80 °C for 24 h, and finally extrude and pelletize at a temperature of 200 °C to obtain elastic anti-aging plastic particles; the mass ratio of diphenylmethane diisocyanate, polycaprolactone diol 1000, tetrahydrofuran, diethyltoluenediamine, and prepolymer is 14:5:35:0.6:0.25.

[0037] Example 3; (1) Mix multi-walled carbon nanotubes and 40 wt% sodium hydroxide aqueous solution at a mass ratio of 0.5:200, ultrasonicate for 30 min at 21 kHz, stir at 600 rpm for 15 h, add 30 wt% hydrogen peroxide aqueous solution which is 5 times the mass of the multi-walled carbon nanotubes at a rate of 5 mL / min, continue stirring for 6 h, then centrifuge at a rate of 8000 rpm for 8 min, take the solid, wash with deionized water until the pH of the washing liquid is 7, and dry at 90 °C for 15 h to obtain hydroxylated multi-walled carbon nanotubes; Mix cerium(III) nitrate hexahydrate and deionized water, stir at 150 rpm for 20 min, add the hydroxylated multi-walled carbon nanotubes, heat up to 90 °C, stir at 600 rpm for 1 h, add 40 wt% sodium hydroxide aqueous solution and continue to react for 4 h, cool to room temperature, continue stirring for 24 h, then centrifuge at a rate of 8000 rpm for 8 min, take the solid, wash with deionized water until the pH of the washing liquid is 7, and dry at 90 °C for 15 h to obtain the carrier; The mass ratio of cerium(III) nitrate hexahydrate, deionized water, hydroxylated multi-walled carbon nanotubes, and 40 wt% sodium hydroxide aqueous solution is 1:100:0.1:500;

[0038] (2) Mix the carrier and tert-butanol, ultrasonicate at 28 kHz for 5 h, perform freeze-drying treatment, rapidly freeze in liquid nitrogen, and then dry at a vacuum of 1 kPa and -50 °C for 25 h, and then place in toluene and ultrasonicate for 30 min to obtain a carrier suspension; The mass ratio of the carrier, tert-butanol, and toluene is 0.1:50:2;

[0039] (3) Mix diethylene glycol and polyacrylic acid, heat up to 120 °C under a nitrogen atmosphere, stir at 100 rpm for 50 min, add the carrier suspension, react for 1 h, heat up to 300 °C, react for 4 h, then cool to room temperature, add ethanol for precipitation, and centrifuge at a rate of 8000 rpm for 8 min to obtain intermediate A; The mass ratio of diethylene glycol, polyacrylic acid, carrier suspension, and ethanol is 100:2:12:100;

[0040] (4) Activate the carboxyl group of intermediate A. First, disperse it in dichloromethane, ultrasonicate at 22 kHz for 30 min, add 2-(7-azabenzotriazol-1-yl)-N,N,N',N'-tetramethyluronium hexafluorophosphate and N,N'-diisopropylethylamine, react for 20 min, centrifuge and take the solid to obtain intermediate B; The mass ratio of intermediate A, dichloromethane, 2-(7-azabenzotriazol-1-yl)-N,N,N',N'-tetramethyluronium hexafluorophosphate, and N,N'-diisopropylethylamine is 1:100:0.3:0.1;

[0041] (5) Disperse intermediate B in dichloromethane, add ethylenediamine, and react for 16 h. After centrifugation, take the solid and redisperse it in tetrahydrofuran, and ultrasonicate at 22 kHz for 20 min to obtain a prepolymer; the mass ratio of intermediate B, dichloromethane, ethylenediamine, and tetrahydrofuran is 1:100:35:50;

[0042] (6) Mix diphenylmethane diisocyanate and polycaprolactone diol 1000. Under a nitrogen atmosphere, add tetrahydrofuran, heat up to 80 °C, and react for 30 min. Then heat up to 85 °C and react for 1.5 h. Add diethyltoluenediamine and the prepolymer, and continue to react for 1.5 h. Then let it stand at room temperature for 24 h and at 100 °C for 24 h. Finally, perform extrusion granulation at a temperature of 250 °C to obtain elastic anti-aging plastic particles; the mass ratio of diphenylmethane diisocyanate, polycaprolactone diol 1000, tetrahydrofuran, diethyltoluenediamine, and the prepolymer is 14:5:35:0.6:0.4.

[0043] Comparative Example 1; The difference between Comparative Example 1 and Example 2 is that step (1) is absent, and step (2) is modified as follows: Mix multi-walled carbon nanotubes and 40 wt% aqueous sodium hydroxide solution at a mass ratio of 0.5:200, ultrasonicate at 21 kHz for 30 min, stir at 450 rpm for 11 h, add 30 wt% aqueous hydrogen peroxide solution four times the mass of the multi-walled carbon nanotubes at a rate of 3 mL / min, continue to stir for 4 h, then centrifuge at a rate of 8000 rpm for 6 min, take the solid, wash it with deionized water until the pH of the washing liquid is 7, and dry it at 75 °C for 12 h to obtain hydroxylated multi-walled carbon nanotubes; Mix the hydroxylated multi-walled carbon nanotubes and tert-butanol, ultrasonicate at 28 kHz for 3.5 h, perform freeze-drying treatment, rapidly freeze it in liquid nitrogen, then dry it at a vacuum of 0.4 kPa and -40 °C for 25 h, and then place it in toluene and ultrasonicate for 30 min to obtain a carrier suspension; the mass ratio of the carrier, tert-butanol, and toluene is 0.1:50:2; the remaining steps are the same as in Example 2.

[0044] Comparative Example 2; The difference between Comparative Example 2 and Example 2 is that step (2) is different. Step (2) is modified as follows: Mix the carrier and toluene, ultrasonicate at 28 kHz for 30 min to obtain a carrier suspension; the mass ratio of the carrier and toluene is 0.1:2; the remaining steps are the same as in Example 2.

[0045] Comparative Example 3; The difference between Comparative Example 3 and Example 2 is that steps (3), (4), and (5) are absent. Step (2) is modified as follows: Mix the carrier and tert-butanol, ultrasonicate at 28 kHz for 3.5 h, perform freeze-drying treatment, rapidly freeze it in liquid nitrogen, then dry it at a vacuum of 0.4 kPa and -40 °C for 25 h, and then place it in tetrahydrofuran and ultrasonicate for 30 min to obtain a prepolymer; the mass ratio of the carrier, tert-butanol, and tetrahydrofuran is 0.1:50:2; the remaining steps are the same as in Example 2.

[0046] Comparative Example 4; The difference between Comparative Example 4 and Example 2 is that steps (1) and (2) are absent, and step (3) is changed to: Mix nano-ceria and toluene at a mass ratio of 0.1:2, and perform ultrasonic treatment at 28 kHz for 30 min to obtain a ceria dispersion; Mix diethylene glycol and polyacrylic acid, heat to 110°C under a nitrogen atmosphere, stir at 100 rpm for 35 min, add the ceria dispersion, react for 1 h, heat to 250°C, react for 2.5 h, then cool to room temperature, add ethanol for precipitation, and centrifuge at a rate of 8000 rpm for 6 min to obtain intermediate A; The mass ratio of the diethylene glycol, polyacrylic acid, ceria dispersion, and ethanol is 100:1.5:10:100; The remaining steps are the same as those in Example 2.

[0047] Effect Example

[0048] The following Table 1 gives the performance analysis results of the elastic anti-aging plastic particles of Examples 1 to 3 and Comparative Examples 1 to 4 of the present invention.

[0049] Table 1

[0050] Tensile strength (MPa) Resistance to UV aging (MPa) Resistance to high-temperature aging (MPa) Example 1 74.7 71.3 70.0 Example 2 75.2 72.8 71.3 Example 3 74.9 71.6 70.4 Comparative Example 1 71.5 60.2 63.9 Comparative Example 2 71.7 64.4 63.8 Comparative Example 3 71.8 64.7 61.2 Comparative Example 4 63.1 52.5 47.6

[0051] From the comparison of the experimental data of the examples and the comparative examples in Table 1, it can be found that the present invention uses hydroxylated multi-walled carbon nanotubes to in-situ synthesize cerium dioxide on the surface of the multi-walled carbon nanotubes through their hydroxyl groups to form a negative carrier, and then vacuum freeze-drying treatment is carried out. During the pre-freezing process, the dispersion medium heterogeneously nucleates on the surface of the multi-walled carbon nanotubes and a glass transition occurs, which is conducive to fixing the dispersion state of the multi-walled carbon nanotubes and obtaining fine tube walls, thereby enhancing the absorption ability of ultraviolet light, improving the ultraviolet aging resistance of the matrix, and at the same time enhancing the firmness of the nano-cerium dioxide in the tubes. Then, after carboxyl activation, ethylenediamine is grafted on the surface of the negative carrier and mixed with polyurethane by in-situ polymerization. Among them, cerium oxide can be dispersed in the matrix to absorb ultraviolet light and consume the absorbed ultraviolet light energy in the form of heat energy or electromagnetic waves to protect the surrounding polymer matrix and play a role in shielding ultraviolet light, or eliminate the free radicals generated by the molecular chain breakage of polyurethane during aging during the transformation process between trivalent cerium ions and tetravalent cerium ions, inhibiting the further breakage of the molecular chain. When ultraviolet light irradiates the multi-walled carbon nanotubes, electrons will transition when excited by light and absorb photons with corresponding energies, thereby showing strong ultraviolet absorption ability and greatly improving the ultraviolet aging resistance of the matrix. During the polymerization process, the multi-walled carbon nanotubes not only act as physical fillers to improve the thermal decomposition of the polymer, but also bond with the polyurethane molecular chains through the hydroxyl groups on their surfaces to increase the crosslinking density of the polymer network structure, enhance the heat aging resistance of the elastomer, and induce the soft segment phase and hard segment phase of polyurethane to be regularly arranged centered on the carbon nanotubes, which is conducive to the crystallization of polyurethane and further enhances the thermal stability of the matrix. The ethylenediamine therein can react with the isocyanate-terminated prepolymer to form urea groups, and the cohesive energy of the urea groups is relatively large, which easily causes the reaction and aggregation of the polyurethane hard segments, thereby further enhancing the heat resistance and ultraviolet aging resistance of the matrix.

[0052] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present invention. Any reference signs in the claims should not be construed as limiting the claimed claim.

Claims

1. A method for preparing elastic aging-resistant plastic particles, characterized in that: The following steps are involved: (1) Cerium nitrate hexahydrate and deionized water were mixed, stirred at 60-150 rpm for 20 min, hydroxylated multi-walled carbon nanotubes were added, the temperature was raised to 60-90° C., stirred at 300-600 rpm for 1 h, 40 wt % sodium hydroxide aqueous solution was added and the reaction was continued for 4 h, the temperature was cooled to room temperature, and the stirring was continued for 24 h, and then centrifuged at 8000 rpm for 4-8 min, the solid was taken, washed with deionized water until the pH of the washing solution was 7, and dried at 60-90° C. for 8-15 h to obtain a support; (2) The support and tert-butyl alcohol are mixed, ultrasonicated at 28 kHz for 2 to 5 hours, freeze-dried, and then placed in toluene and ultrasonicated for 30 minutes to obtain a suspension of the support; (3) Diethylene glycol and polyacrylic acid were mixed, heated to 100-120° C. in a nitrogen atmosphere, stirred at 100 rpm for 20-50 min, added with the support suspension, reacted for 1 h, heated to 200-300° C., reacted for 1-4 h, then cooled to room temperature, added with ethanol for precipitation, and centrifuged at 8000 rpm for 4-8 min to obtain intermediate A; (4) Activating the intermediate A by carboxyl group to obtain intermediate B; (5) Disperse the intermediate B in dichloromethane, add ethylenediamine, react for 10 to 16 hours, centrifuge and take out the solid, disperse it in tetrahydrofuran, and ultrasonicate it at 22 kHz for 20 minutes to obtain a prepolymer; (6) Diphenylmethane diisocyanate and polycaprolactone diol 1000 are mixed, tetrahydrofuran is added under a nitrogen atmosphere, the temperature is raised to 60-80°C, the reaction is carried out for 30 minutes, the temperature is raised to 70-85°C, the reaction is carried out for 1.5 hours, diethyltoluenediamine and prepolymer are added, the reaction is continued for 1.5 hours, and then the mixture is allowed to stand at room temperature for 24 hours and at 50-100°C for 24 hours, and finally extruded and granulated at a temperature of 150-250°C to obtain elastic and aging-resistant plastic particles.

2. The method for preparing elastic aging-resistant plastic particles according to claim 1, characterized in that: The preparation method of the hydroxylated multi-walled carbon nanotubes in step (1) is as follows: multi-walled carbon nanotubes and 40wt% sodium hydroxide aqueous solution are mixed in a mass ratio of 0.5:200, ultrasonicated at 21kHz for 30min, stirred at 300-600rpm for 8-15h, 30wt% hydrogen peroxide aqueous solution of 3-5 times the mass of the multi-walled carbon nanotubes is added at 1-5mL / min, stirring is continued for 2-6h, and then centrifuged at a speed of 8000rpm for 4-8min, the solid is taken, washed with deionized water until the pH of the washing liquid is 7, and dried at 60-90°C for 8-15h.

3. The method for preparing elastic aging-resistant plastic particles according to claim 1, characterized in that: The mass ratio of the cerium nitrate hexahydrate, deionized water, hydroxylated multi-walled carbon nanotubes, and 40 wt % sodium hydroxide aqueous solution in step (1) is 0.1-1:100:0.1:

500.

4. The method for preparing elastic anti-aging plastic particles according to claim 1, characterized in that: The specific steps of the freeze-drying treatment in step (2) are: rapid freezing in liquid nitrogen, and then drying for 25 hours at a vacuum degree of 0.2 to 1 kPa and -30 to -50°C.

5. The method for preparing elastic anti-aging plastic particles according to claim 1, characterized in that: In step (2), the support, tert-butyl alcohol and toluene are in a mass ratio of 0.1:50:

2.

6. The method for preparing elastic anti-aging plastic particles according to claim 1, characterized in that: The mass ratio of diethylene glycol, polyacrylic acid, support suspension and ethanol in step (3) is 100:1-2:8-12:

100.

7. The method for preparing elastic anti-aging plastic particles according to claim 1, characterized in that: The specific steps of the carboxyl activation treatment in step (4) are as follows: dispersing intermediate A in dichloromethane, ultrasonicating at 22kHz for 30min, adding 2-(7-azabenzotriazole)-N,N,N',N'-tetramethyluronium hexafluorophosphate and N,N'-diisopropylethylamine, reacting for 20min, and collecting the solid after centrifugation.

8. The method for preparing elastic anti-aging plastic particles according to claim 7, characterized in that: The mass ratio of the intermediate A, dichloromethane, 2-(7-azabenzotriazole)-N,N,N',N'-tetramethyluronium hexafluorophosphate, and N,N'-diisopropylethylamine is 1:100:0.02-0.3:0.01-0.

1.

9. The method for preparing elastic anti-aging plastic particles according to claim 1, characterized in that: The mass ratio of the intermediate B, dichloromethane, ethylenediamine and tetrahydrofuran in step (5) is 1:100:15-35:10-50.

10. The method for preparing elastic anti-aging plastic particles according to claim 1, characterized in that: The mass ratio of diphenylmethane diisocyanate, polycaprolactone diol 1000, tetrahydrofuran, diethyltoluenediamine and prepolymer in step (6) is 14:5:35:0.6:0.1-0.4.