Heat-resistant regenerated rubber and preparation method thereof

Abstract

The invention relates to the technical field of regenerated rubber production, in particular to heat-resistant regenerated rubber. The composite material is prepared from the following components in parts by weight: 60-80 parts of waste rubber powder, 15-30 parts of ethylene propylene diene monomer, 5-10 parts of silane modified graphene / nano silicon dioxide composite filler, 3-8 parts of N-phenylmaleimide-glycidyl methacrylate copolymer heat-resistant agent, 5-12 parts of polyphosphazene elastomer, 1-3 parts of vulcanizing agent, 0.5-2 parts of accelerant, 1-3 parts of active agent and 1-3 parts of anti-aging agent. The waste rubber powder is subjected to ozone-microwave synergistic treatment, and the composite filler is modified through a silane coupling agent; the vulcanizing agent is a ternary compound of dicumyl peroxide, sulfur and 2-mercaptobenzothiazole, and the anti-aging agent is a compound of 4010NA, RD and 2, 6-butylated hydroxytoluene. Through multi-component collaborative design and process optimization, the mechanical property, heat resistance, heat conductivity and aging resistance of the material are improved, the problems that traditional regenerated rubber is unbalanced in rigidity and toughness, poor in heat resistance and the like are solved, and the comprehensive performance is excellent.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of regenerated rubber production, in particular to a heat-resistant regenerated rubber and a preparation method thereof. BACKGROUND

[0002] As a core product of waste rubber resource utilization, regenerated rubber has important significance in resource saving and pollution reduction, and is widely used in tire, sealing, shock absorbing products and other fields. However, traditional regenerated rubber has poor heat resistance and insufficient mechanical properties, which seriously limits its application in high-end fields. At present, the regenerated rubber on the market is mostly treated by single devulcanization process of waste rubber powder. The structure is damaged due to the rupture of rubber molecular chain during the devulcanization process, which greatly reduces the mechanical properties such as tensile strength and tear strength of the regenerated rubber. Especially in the environment above 100℃, the thermal oxidation aging speed is accelerated, and the material is prone to hardening and cracking, thus the service life is significantly shortened.

[0003] In the prior art, the methods for improving the performance of regenerated rubber mainly focus on adding a single elastomer or filler for blending modification. For example, by adding ethylene-propylene-diene rubber to improve weather resistance, but the compatibility of ethylene-propylene-diene rubber with waste rubber powder is poor, and the interfacial bonding force is weak, which limits the improvement of material toughness. When using inorganic fillers such as nano-silica for reinforcement, the surface of the filler is highly polar and easy to agglomerate, which not only cannot play a reinforcing role, but also becomes a stress concentration point, reducing the processing performance and use performance of the material. In addition, the traditional vulcanization system mostly uses sulfur or peroxide as a single vulcanizing agent, which has low vulcanization efficiency and uneven cross-linking structure, resulting in insufficient heat resistance and fatigue resistance of the material.

[0004] In terms of anti-aging, the existing technology mostly uses a single anti-aging agent, which is difficult to resist multiple aging factors such as thermal oxidation aging and ultraviolet aging at the same time, and the material performance decays significantly after long-term use. At the same time, the preparation process of regenerated rubber has many defects: high energy consumption and low efficiency in the devulcanization process, easy to cause secondary pollution; unreasonable design of mixing process parameters leads to uneven dispersion of components; lack of precise control in the vulcanization process, resulting in large fluctuations in product performance. These problems make it difficult for traditional regenerated rubber to meet the demand for heat-resistant, high-toughness and long-life materials in high-end fields such as automobile industry and rail transportation, restricting the high-quality development of waste rubber resource utilization. Therefore, developing a regenerated rubber with excellent heat resistance, mechanical properties and processing performance and its efficient preparation process has become a key problem to be solved in the industry. SUMMARY

[0005] (I) Technical problems solved

[0006] In view of the deficiencies of the prior art, the present application provides a heat-resistant regenerated rubber and a preparation method thereof.

[0007] (ii) Technical Solution

[0008] A heat-resistant reclaimed rubber, comprising, by weight fraction: waste rubber powder 60-80 parts, ethylene-propylene-diene rubber 15-30 parts, silane-modified graphene / nano-silica composite filler 5-10 parts, N-phenyl maleimide-glycidyl methacrylate copolymer heat-resistant agent 3-8 parts, polyphosphazene elastomer 5-12 parts, vulcanizing agent 1-3 parts, accelerator 0.5-2 parts, active agent 1-3 parts, antioxidant 1-3 parts; the composite filler is prepared by the following reaction: first, graphene is reacted with silane coupling agent KH-570 in toluene solution at 80°C for 6 hours to form intermediate G-570, then ultrasonic dispersion with nano-silica in ethanol solution for 2 hours, and then reaction at 120°C for 12 hours to obtain the modified composite filler; the heat-resistant agent is prepared by solution polymerization method, the molar ratio of N-phenyl maleimide to glycidyl methacrylate is 3:1, the amount of initiator BPO is 1.5% of the total mass of monomers, the reaction is carried out at 80°C for 4 hours, and the grafting rate is 2.5-5wt%; the polyphosphazene elastomer main chain is -(NP(OPh)2)n- structure, the number average molecular weight is 30000-50000, and the glass transition temperature is -60°C to -50°C.

[0009] Preferably, the carbon nanotubes are multi-walled carbon nanotubes with a diameter of 10-20 nm and a length of 5-10 μm, which are modified by the following steps: refluxing in mixed acid at 80°C for 3 hours, carboxylating the surface to a content of 0.8-1.5 mmol / g, reacting with silane coupling agent KH-550 in toluene at 110°C for 8 hours with a grafting rate of 2.0-3.5wt%, and mixing with the modified graphene / nano-silica composite filler at a mass ratio of 1:5-1:3 in a high-speed stirrer at 2000 rpm for 15 minutes to form a three-dimensional heat conduction network through π-π interaction, with a network node density of 0.8-1.2 / μm 2 .

[0010] Preferably, the toughening agent is prepared by emulsion polymerization: taking polybutadiene as the core, using potassium persulfate as the initiator, and polymerizing at 60°C for 12 hours to form a latex with an average particle size of 200-500 nm; grafting copolymerization is carried out by adding γ-aminopropyl triethoxysilane as the shell monomer, with a grafting rate of 1.2-2.0wt% and a grafting density of 0.3-0.6 segments / nm 2 ; the powder-like toughening agent is obtained by coagulation method, and in the mixing process, the toughening agent is dispersed in the matrix through "island-in-the-sea structure", and when the material is impacted by external force, the core layer absorbs energy through elastic deformation, and the shell layer forms chemical bonding with the matrix to transfer stress.

[0011] Preferably, the waste rubber powder is tire rubber powder with a particle size of 60-120 mesh, which is treated by ozone-microwave synergy: the rubber powder is treated in a sealed container with an ozone concentration of 8-12 mg / L for 15 minutes to oxidize the double bonds on the surface of the rubber powder into carbonyl and carboxyl groups, and the surface energy is increased to 40-50 mJ / m 2 ; immediately transferred to a microwave reactor and treated at a power of 300-500 W for 10 minutes at a microwave frequency of 2450 MHz to generate local high temperature on the rubber molecular chain and promote the breaking of crosslinking bonds.

[0012] Preferably, the ethylene content of the ethylene-propylene-diene rubber is 50-65 wt%, the ethylidene norbornene content is 5-8 wt%, and the Mooney viscosity is 30-50; the mass ratio of the ethylene-propylene-diene rubber to the polyphosphazene elastomer is 3:1-2:1, and a continuous phase network is formed by the following method: pre-mixing in an internal mixer at 150°C for 5 minutes to preliminarily disperse the two elastomers; adding 0.5-1 part of bis-tetrasulfide as a compatibilizer and continuing to mix at 160°C for 8 minutes, the compatibilizer reacts with the double bonds of the ethylene-propylene-diene rubber through vulcanization, and at the same time forms hydrogen bonds with the phenoxy groups of the polyphosphazene elastomer, the thickness of the interfacial layer reaches 50-100 nm; the network structure formed exhibits a single glass transition temperature in a dynamic mechanical analyzer.

[0013] Preferably, the vulcanizing agent is a ternary compound of dicumyl peroxide, sulfur, and 2-mercaptobenzothiazole with a mass ratio of 3:1:0.5; the vulcanizing agent forms three types of crosslinking structures during vulcanization: dicumyl peroxide forms C-C crosslinking bonds, accounting for 60-70% of the total crosslinking bonds, with a bond energy of 347 kJ / mol; sulfur forms polysulfide bonds and monosulfide bonds, accounting for 20-30% and 10-20%, respectively, with bond energies of 272 kJ / mol and 351 kJ / mol, respectively; 2-mercaptobenzothiazole promotes uniform distribution of crosslinking bonds, resulting in a crosslinking density gradient of ≤10%.

[0014] Preferably, the antioxidant is a compound of antioxidant 4010NA, antioxidant RD, and 2,6-di-tert-butyl-p-cresol with a mass ratio of 2:2:1; the antioxidant resists aging through the following synergistic mechanisms: antioxidant 4010NA captures free radicals generated by rubber oxidation to form stable amine radicals, inhibiting chain oxidation reactions, with a reaction rate constant k1 = 1.2 x 10 6 L / (mol·s); antioxidant RD decomposes hydroperoxides to form stable alcohol compounds with a decomposition efficiency of 85-90%; 2,6-di-tert-butyl-p-cresol protects the rubber molecular chain through steric hindrance.

[0015] Preferably, a method for preparing a heat-resistant regenerated rubber comprises the following steps:

[0016] S1: Pretreatment of waste rubber powder: Place the waste rubber powder in a high-pressure devulcanization kettle, and introduce nitrogen to a pressure of 0.8-1.2 MPa. Increase the temperature to 130-145°C at a rate of 5°C / min, and add 0.5-1.5 parts of the devulcanizing agent dibenzoylmethane. React for 30-35 minutes at a stirring rate of 30-50 rpm. The devulcanizing agent decomposes to generate free radicals, which attack the C-S and S-S bonds in the cross-linking bonds of the rubber, reducing the gel content to 50-60%. After the reaction is complete, naturally cool to room temperature to obtain devulcanized rubber powder with a Mooney viscosity of 40-60.

[0017] S2: Pre-mixing of composite filler and heat-resistant agent: Add the modified graphene / nano-silicon dioxide composite filler and heat-resistant agent in a mass ratio of 1:1 to a high-speed mixer and pre-mix for 5-8 minutes at a speed of 1000-1500 rpm to form composite particles through physical adsorption and hydrogen bonding. Then add the devulcanized rubber powder obtained in step S1 to a Banbury mixer and mix at 140-155°C and a rotor speed of 50-60 rpm for 6-8 minutes. The composite particles are uniformly dispersed in the rubber matrix, and the interfacial bonding strength reaches 1.5-2.5 MPa.

[0018] S3: Mixing of main body material: Add the ethylene-propylene-diene rubber, polyphosphazene elastomer, and active agent to the Banbury mixer, heat to 145-160°C, and adjust the rotor speed to 50-70 rpm. Mix for 10-12 minutes. The active agent forms zinc fatty acid complexes at this temperature, promoting subsequent vulcanization. The ethylene-propylene-diene rubber and polyphosphazene elastomer form a continuous phase network with an average pore size of 1-3 μm and a porosity of 5-10%.

[0019] S4: Mixing of vulcanization system: Reduce the temperature of the Banbury mixer to 85-95°C, and add the vulcanizing agent, accelerator, and core-shell structure toughener. Continue mixing for 4-5 minutes. The vulcanizing agent is in a stable state at this temperature, avoiding early vulcanization. The accelerator is uniformly dispersed, reducing the activation energy of the vulcanization reaction to 80-100 kJ / mol. After mixing is complete, discharge the rubber compound and allow it to stand for 8-12 hours to allow the components to fully diffuse and balance.

[0020] S5: Shaping and vulcanization: Thin pass the rubber compound 8-10 times on an open mill to a thickness of 2-3 mm to eliminate internal stress. Then vulcanize in a flat plate vulcanizing machine at 160-170°C and a pressure of 10-15 MPa for 15-20 minutes. The pressure fills the mold cavity with the rubber compound, and the temperature promotes the decomposition of the vulcanizing agent to generate free radicals, initiating cross-linking reactions. After vulcanization is complete, cool to room temperature and remove the mold to obtain heat-resistant recycled rubber products with a Shore hardness of 75-85A, a tensile strength of ≥18 MPa, and an elongation at break of ≥350%.

[0021] Preferably, the composite filler in S2 is pretreated: the modified graphene / nano-silica composite filler is dispersed in anhydrous ethanol to form a 5-10wt% suspension, and is treated in an ultrasonic instrument with a power of 600W and a frequency of 25kHz for 20-30 minutes to make the filler aggregate depolymerize and the average particle size decrease to 50-100nm; then the suspension is transferred to a rotary evaporator, and the ethanol is evaporated at 80°C and-0.09MPa to obtain loose powder; and then the powder is placed in a vacuum drying oven at 110-130°C for 4-6 hours to control the water content of the filler to be less than or equal to 0.05%.

[0022] Preferably, the vulcanization in S5 adopts a segmented temperature rising procedure: first, heat preservation at 120°C for 5 minutes, the pressure is 10MPa, so that the glue flows fully, and internal air and volatile components are removed, and the volatile component removal amount is 0.3-0.5wt%; then heat preservation at 150°C for 5 minutes, the pressure is increased to 12MPa, to promote the preliminary decomposition of the vulcanizing agent, and about 30-40% of crosslinked structures are formed; finally, heat preservation at 170°C for 10 minutes, the pressure is maintained at 15MPa, to complete the remaining crosslinking reaction, and the crosslinking density reaches the peak value.

[0023] (III) Beneficial effects

[0024] Compared with the existing technology, the beneficial effects of the present application are:

[0025] 1. In terms of heat resistance, by introducing N-phenyl maleimide-glycidyl methacrylate copolymer heat-resistant agent and polyphosphazene elastomer, a heat-resistant network structure is synergistically constructed, which effectively delays the thermal oxidative aging of the material in a high-temperature environment, solves the problem of insufficient heat resistance of traditional reclaimed rubber, and widens the application range of the material in high-temperature working conditions.

[0026] 2. In terms of mechanical property balance, the synergistic effect of the core-shell structure toughening agent and the carbon nanotube-graphene composite filler not only absorbs impact energy through the elastic deformation of the toughening agent to improve the toughness of the material, but also enhances the rigidity by means of the three-dimensional network structure of the composite filler, achieving a good balance between strength and toughness of the material, and overcoming the technical bottleneck of “toughening at the expense of rigidity” in traditional modification.

[0027] 3. In terms of interface compatibility, the surface activity of the waste rubber powder treated by ozone-microwave synergistic treatment is improved, a stable continuous phase network is formed with the ethylene-propylene-diene rubber and the polyphosphazene elastomer, and the interface bonding force is significantly enhanced with the filler modified by the silane coupling agent, avoiding the phase separation phenomenon.

[0028] 4. In terms of process optimization, the adoption of segmented desulfurization, precise temperature control mixing and step vulcanization process ensures uniform dispersion of each component, stable vulcanization crosslinking structure, reduces energy consumption and pollution, and improves the stability and consistency of product performance. The heat-resistant reclaimed rubber of the present application has excellent comprehensive performance, efficient and environmentally friendly preparation process, and provides a new idea for the high-value utilization of waste rubber. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 is a heat-resistant reclaimed rubber preparation flow chart proposed by the present application;

[0030] Figure 2 is a mechanical property comparison column chart of examples and comparative examples;

[0031] Figure 3 is a heat-resistant performance line chart of examples and comparative examples;

[0032] Figure 4 is a heat conduction and compression performance column chart of examples and comparative examples;

[0033] Figure 5 is a line chart of the influence of the amount of composite filler on the performance of examples and comparative examples;

[0034] Figure 6 is a column chart of the influence of vulcanization temperature on compression deformation of examples and comparative examples. DETAILED DESCRIPTION

[0035] According to Figures 1 to 6 , the specific embodiments of the present application are as follows:

[0036] The application discloses a heat-resistant reclaimed rubber, which comprises the following components in parts by weight: waste rubber powder 60-80 parts, ethylene-propylene-diene rubber 15-30 parts, silane modified graphene / nano-silica composite filler 5-10 parts, N-phenyl maleimide-glycidyl methacrylate copolymer heat-resistant agent 3-8 parts, polyphosphazene elastomer 5-12 parts, vulcanizing agent 1-3 parts, accelerator 0.5-2 parts, active agent 1-3 parts and anti-aging agent 1-3 parts; the composite filler is prepared by the following reaction: graphene is reacted with silane coupling agent KH-570 in a toluene solution at 80 DEG C for 6 hours to generate an intermediate G-570, the reaction formula is as follows: G-OH+CH2=C(CH3)COOC3H6Si(OCH3)3→G-OOC(CH3)C=CH2+C3H6Si(OCH3)3, then the intermediate is ultrasonically dispersed in an ethanol solution for 2 hours, and the modified composite filler is obtained by reacting at 120 DEG C for 12 hours; the heat-resistant agent is prepared by a solution polymerization method, the molar ratio of N-phenyl maleimide to glycidyl methacrylate is 3:1, the amount of initiator BPO is 1.5% of the total mass of monomers, and the reaction is carried out at 80 DEG C for 4 hours, with a grafting rate of 2.5-5 wt%; the polyphosphazene elastomer has a main chain of -(NP(OPh)2)n- structure, a number average molecular weight of 30000-50000, and a glass transition temperature of -60 DEG C to -50 DEG C, and further comprises 0.5-2 parts of carbon nanotubes, the carbon nanotubes are multi-walled carbon nanotubes, have a diameter of 10-20 nm and a length of 5-10 microns, and are modified by the following steps: ①carboxylation treatment at 80 DEG C for 3 hours in mixed acid (concentrated sulfuric acid: concentrated nitric acid = 3:1 in volume ratio), with a surface carboxyl content of 0.8-1.5 mmol / g; ②reaction with silane coupling agent KH-550 in toluene at 110 DEG C for 8 hours, with a grafting rate of 2.0-3.5 wt%; and ③mixing with the modified graphene / nano-silica composite filler at a mass ratio of 1:5-1:3 in a high-speed stirrer at 2000 rpm for 15 minutes, so that a three-dimensional heat conduction network is formed through π-π interaction, and the network node density is 0.8-1.2 per micrometer 2 The thermal conductivity of the material is improved to 0.35-0.45 W / (m*K), and the thermal conductivity retention rate is greater than or equal to 90% after heat aging at 150 DEG C for 72 hours.

[0037] In the application, 1-4 parts of a core-shell structure toughening agent is further included, and the toughening agent is prepared by emulsion polymerization: ①polybutadiene is used as the core, and potassium persulfate is used as an initiator to polymerize at 60 DEG C for 12 hours to form latex with an average particle size of 200-500 nm; ②methyl methacrylate is used as a shell monomer, and γ-aminopropyl triethoxysilane (accounting for 3% of the mass of the shell monomer) is added for graft copolymerization, with a grafting rate of 1.2-2.0 wt% and a grafting density of 0.3-0.6 segments / nm 2; ③ the toughening agent in powder form is obtained by coacervation method, and in the mixing process, the toughening agent is dispersed in the matrix through the "island-in-sea structure", when the material is impacted by external force, the core layer absorbs energy through elastic deformation, the shell layer forms chemical bonding with the matrix to transfer stress, so that the elongation at break of the material is increased to 350-450%, and the elongation at break retention rate is ≥80% after heat aging at 150 DEG C.

[0038] In the application, the waste rubber powder is tire rubber powder with a particle size of 60-120 mesh, which is treated by ozone-microwave cooperation: ① the surface double bond of the rubber powder is oxidized to generate carbonyl and carboxyl in an airtight container with an ozone concentration of 8-12 mg / L for 15 minutes, so that the surface energy is increased to 40-50 mJ / m 2 ; ② immediately transferred into a microwave reactor, treated at a power of 300-500 W for 10 minutes, and microwave frequency is 2450 MHz, so that local high temperature is generated on the rubber molecular chain to promote the breaking of crosslinking bonds, and the desulfurization efficiency is increased by 15-20%; ③ the content of hydroxyl on the surface of the treated rubber powder is increased to 1.2-2.0 mmol / g, the gel content is reduced to 60-70%, and the interfacial shear strength with the matrix in the subsequent mixing process reaches 2.5-3.5 MPa, which is increased by 50-80% compared with the untreated rubber powder.

[0039] In the application, the ethylene content of the ethylene-propylene-diene rubber is 50-65 wt%, the ethylidene norbornene content is 5-8 wt%, and the Mooney viscosity (ML1+4, 125 DEG C) is 30-50; the mass ratio of the ethylene-propylene-diene rubber to the polyphosphazene elastomer is 3:1-2:1, and the following methods are used to form a continuous phase network: ① preliminary dispersion of the two elastomers in a mixer at 150 DEG C for 5 minutes; ② adding 0.5-1 part of bis(gamma-triethoxysilylpropyl) tetrasulfide as a compatibilizer, and continuing to mix at 160 DEG C for 8 minutes, the compatibilizer is vulcanized with the double bond of the ethylene-propylene-diene rubber, and at the same time, hydrogen bonds are formed with the phenoxy group of the polyphosphazene elastomer, and the thickness of the interfacial layer reaches 50-100 nm; ③ the network structure formed exhibits a single glass transition temperature (-45 DEG C to -50 DEG C) in a dynamic mechanical analyzer, and the peak value of the loss factor is reduced by 15-20%, so that the upper limit of the material use temperature is increased to 160-180 DEG C, and the tensile strength retention rate is ≥70% after heat aging at 180 DEG C for 24 hours.

[0040] In the application, the vulcanizing agent is a ternary compound of dicumyl peroxide, sulfur and 2-mercaptobenzothiazole, with a mass ratio of 3:1:0.5; the vulcanizing agent forms three cross-linking structures during the vulcanization process: ① dicumyl peroxide forms C-C cross-linking bonds, accounting for 60-70% of the total cross-linking bonds, with a bond energy of 347 kJ / mol; ② sulfur forms polysulfide bonds and monosulfide bonds, accounting for 20-30% and 10-20%, respectively, with bond energies of 272 kJ / mol and 351 kJ / mol, respectively; and ③ 2-mercaptobenzothiazole promotes uniform distribution of cross-linking bonds, so that the cross-linking density gradient is ≤10%; the vulcanization efficiency of the vulcanization system at 160°C is 0.8-1.2 min -1 , the vulcanization time is shortened to 8-12 minutes, and the cross-linking density of the vulcanized rubber reaches 8-12 × 10 -5 mol / cm 3 , the cross-linking bond distribution index (polysulfide bond / monosulfide bond) is 1.5-2.5, so that the compression set of the material at 150°C is ≤25%, which is 15-25% better than that of the traditional binary vulcanization system.

[0041] In the application, the antioxidant is a compound of antioxidant 4010NA, antioxidant RD and 2,6-di-tert-butyl-p-cresol, with a mass ratio of 2:2:1; the antioxidant resists aging through the following synergistic mechanisms: ① antioxidant 4010NA (N-isopropyl-N'-phenyl-p-phenylenediamine) captures free radicals generated by rubber oxidation to form stable amine radicals, inhibiting chain oxidation reactions, with a reaction rate constant k1 = 1.2 × 10 6 L / (mol·s); ② antioxidant RD (2,2,4-trimethyl-1,2-dihydroquinoline polymer) decomposes hydroperoxides to form stable alcohol compounds, with a decomposition efficiency of 85-90%; and ③ 2,6-di-tert-butyl-p-cresol protects rubber molecular chains through steric hindrance effects to prevent oxidative attack; after 72 hours of hot air aging at 150°C, the material has a tensile strength retention rate ≥85% and an elongation at break retention rate ≥75%, which is 15-25% better than that of a single antioxidant system; after 1000 hours of ultraviolet aging test, the surface color difference ΔE is ≤5, which is better than the national standard (ΔE ≤10).

[0042] A method for preparing heat-resistant reclaimed rubber, comprising the following steps:

[0043] S1: Pretreatment of waste rubber powder: Put the waste rubber powder into a high-pressure devulcanization kettle, and introduce nitrogen to a pressure of 0.8-1.2 MPa. Increase the temperature to 130-145°C at a rate of 5°C / min, and add 0.5-1.5 parts of devulcanizing agent dibenzoylmethane (melting point 108-112°C, decomposition temperature 150°C). React for 30-35 minutes at a stirring rate of 30-50 rpm. The decomposition of the devulcanizing agent generates free radicals, which attack the C-S and S-S bonds in the cross-linking bonds of the rubber (bond energies are 272 kJ / mol and 226 kJ / mol, respectively), reducing the gel content to 50-60%. After the reaction is complete, naturally cool to room temperature to obtain devulcanized rubber powder with a Mooney viscosity (ML1+4, 100°C) of 40-60.

[0044] S2: Pre-mixing of composite filler and heat-resistant agent: Add the modified graphene / nano-silicon dioxide composite filler and the heat-resistant agent in a mass ratio of 1:1 into a high-speed mixer and pre-mix for 5-8 minutes at a speed of 1000-1500 rpm to form composite particles through physical adsorption and hydrogen bonding. Then add the devulcanized rubber powder obtained in step S1 into an internal mixer and mix for 6-8 minutes at a temperature of 140-155°C and a rotor speed of 50-60 rpm. The composite particles are uniformly dispersed in the rubber matrix, and the interfacial bonding strength reaches 1.5-2.5 MPa.

[0045] S3: Mixing of main body material: Add the ethylene-propylene-diene rubber, polyphosphazene elastomer, and active agent (zinc oxide and stearic acid in a mass ratio of 8:1) into an internal mixer, heat to 145-160°C, adjust the rotor speed to 50-70 rpm, and mix for 10-12 minutes. The active agent forms a zinc stearate complex at this temperature, promoting the subsequent vulcanization reaction. The ethylene-propylene-diene rubber and polyphosphazene elastomer form a continuous phase network with an average pore size of 1-3 μm and a porosity of 5-10%, keeping the storage modulus of the material at 5-10 MPa at 100°C. S4: Mixing of vulcanization system: Reduce the temperature of the internal mixer to 85-95°C, and add the vulcanizing agent, accelerator, and core-shell structure toughener, and continue mixing for 4-5 minutes. The vulcanizing agent is in a stable state at this temperature, avoiding early vulcanization (scorching). The accelerator (TMTD and CZ in a mass ratio of 1:2) is uniformly dispersed, reducing the activation energy of the vulcanization reaction to 80-100 kJ / mol. After mixing is complete, discharge the rubber compound and allow it to stand for 8-12 hours to allow the components to fully diffuse and balance.

[0046] S5: molding vulcanization: the rubber compound is thin passed 8-10 times on the open mill (the roll gap is 0.5-1 mm), the sheet thickness is 2-3 mm, so as to eliminate internal stress; then vulcanized in a flat plate vulcanizing machine at 160-170 DEG C, the pressure is 10-15 MPa, and the vulcanization time is 15-20 minutes; during the vulcanization process, the pressure makes the rubber compound fill the mold cavity, and the temperature promotes the decomposition of the vulcanizing agent to generate free radicals, so as to initiate crosslinking reaction; after the vulcanization is completed, the product is cooled to room temperature, and then demolded to obtain the heat-resistant reclaimed rubber product, wherein the Shore hardness of the product is 75-85 A, the tensile strength is greater than or equal to 18 MPa, and the elongation at break is greater than or equal to 350%.

[0047] In the present application, in step S2, the modified graphene / nano-silicon dioxide composite filler is dispersed in anhydrous ethanol (concentration ≥ 99.5%) to form a 5-10 wt% suspension, and the suspension is treated in an ultrasonic instrument with a power of 600 W and a frequency of 25 kHz for 20-30 minutes to depolymerize the filler agglomerates and reduce the average particle size to 50-100 nm; then the suspension is transferred to a rotary evaporator, and the ethanol is evaporated at 80 DEG C and -0.09 MPa to obtain loose powder; then the powder is dried in a vacuum drying oven at 110-130 DEG C for 4-6 hours (vacuum degree -0.08 to -0.1 MPa), and the water content of the filler is controlled to be less than or equal to 0.05%; the BET specific surface area of the pretreated filler is 150-200 m 2 / g, and the dispersion degree in the rubber matrix is greater than or equal to 95% (statistically determined by transmission electron microscopy).

[0048] In the present application, in step S5, the vulcanization adopts a segmented temperature rising procedure: first, heat preservation at 120 DEG C for 5 minutes, the pressure is 10 MPa, so that the rubber compound flows fully, and the internal air and volatile components (such as residual ethanol and low molecular vulcanizing agent) are removed, and the amount of volatile components removed is 0.3-0.5 wt%; then heat preservation at 150 DEG C for 5 minutes, the pressure is increased to 12 MPa, so as to promote the preliminary decomposition of the vulcanizing agent and form about 30-40% of crosslinking structure; finally, heat preservation at 170 DEG C for 10 minutes, the pressure is maintained at 15 MPa, so as to complete the remaining crosslinking reaction and reach the peak value of crosslinking density; this procedure improves the uniformity of crosslinking density distribution of the vulcanized rubber by 10-15%, and the fluctuation range of mechanical properties is controlled within ± 5%; the product has a pore rate of less than or equal to 1%, a surface roughness Ra of less than or equal to 3 μm, and a dimensional accuracy of ± 0.1 mm.

[0049] Example 1:

[0050] The raw materials are accurately weighed by weight fraction: 70 parts of waste rubber powder: 80 mesh tire rubber powder is selected, and ozone-microwave synergistic treatment is carried out (ozone concentration 10 mg / L in a sealed environment for 15 minutes, immediately transferred into a 2450 MHz microwave reactor, 400 W power for continuous treatment for 10 minutes), the surface hydroxyl content is 1.6 mmol / g, the surface energy is 45 mJ / m 2 , and the gel content is 65%.

[0051] EPDM 20: ethylene monomer content 55 wt%, ethylidene norbornene content 6 wt%, Mooney viscosity (ML 1+4, 125°C) 40, density 0.86 g / cm 3 .

[0052] Silane-modified graphene / nano-silica composite filler 7: graphene and nano-silica mixed at a mass ratio of 1:5, modified by silane coupling agent KH-570, particle size 20 nm measured by transmission electron microscopy, BET specific surface area 180 m 2 / g, laboratory-made.

[0053] Heat-resistant agent 5: N-phenylmaleimide and glycidyl methacrylate were polymerized at a molar ratio of 3:1, 1.5 wt% benzoyl peroxide (BPO) as initiator, 80°C solution for 4 hours, and the grafting rate was 3.5 wt% measured by titration.

[0054] Polyphosphazene elastomer 8: main chain is -(NP(OPh)2)n- structure, number average molecular weight 40000 measured by gel permeation chromatography, glass transition temperature -55°C measured by differential scanning calorimetry.

[0055] Carbon nanotube 1: multi-walled carbon nanotube, diameter 15 nm, length 8 μm, carboxylated by refluxing in 55 wt% nitric acid solution at 85°C for 2.5 hours, surface carboxyl content 1.2 mmol / g measured by potentiometric titration.

[0056] Core-shell structure toughening agent 2: polybutadiene as core, polymethyl methacrylate as shell, core-shell mass ratio 3:1, particle size 300 nm measured by dynamic light scattering instrument, surface grafted and modified by γ-aminopropyl triethoxysilane, grafting rate 1.6 wt%.

[0057] Vulcanizing agent 2: compound of dicumyl peroxide, sulfur and 2-mercaptobenzothiazole at a mass ratio of 3:1:0.5, purity 98%.

[0058] Accelerator 1: compound of accelerator TMTD and accelerator CZ at a mass ratio of 1:2, effective ingredient content 98%.

[0059] Active agent 2: compound of 50 nm particle size zinc oxide and stearic acid at a mass ratio of 8:1, stearic acid melting point 120°C, purity 99%.

[0060] Antioxidant 2: compound of antioxidant 4010NA, antioxidant RD and 2,6-di-tert-butyl-p-cresol at a mass ratio of 2:2:1, total effective ingredient content 99%.

[0061] Preparation steps

[0062] S1: Put the waste rubber powder into a high-pressure devulcanization kettle, introduce nitrogen to a pressure of 1.0 MPa, heat to 135℃ at a rate of 5℃ / min, add 1 part of the devulcanizing agent dibenzoylmethane, maintain a stirring rate of 30 rpm for 32 minutes of devulcanization, and after the reaction is completed, naturally cool to room temperature to obtain devulcanized rubber powder, which has a Mooney viscosity (ML1+4, 100℃) of 50.

[0063] S2: Put the silane-modified graphene / nano-silicon dioxide composite filler and heat-resistant agent into a 10L high-speed mixer, pre-mix for 6 minutes at a speed of 1200 rpm, add the devulcanized rubber powder obtained in step S1, and transfer to an internal mixer, mix at 145℃ and a rotor speed of 55 rpm for 7 minutes until the material is uniformly dispersed.

[0064] S3: Add the ethylene-propylene-diene rubber, polyphosphazene elastomer, and active agent to the internal mixer, heat to 150℃, adjust the rotor speed to 60 rpm, and continue mixing for 11 minutes until the material forms a uniform continuous phase network.

[0065] S4: Reduce the temperature of the internal mixer to 90℃, add the vulcanizing agent, accelerator, and core-shell structure toughening agent, and continue mixing for 4.5 minutes. After discharging the rubber compound, let it stand at room temperature for 10 hours.

[0066] S5: Thin pass the rubber compound 9 times on an open mill (roll gap 0.8 mm), control the thickness of the discharged sheet to 3 mm, then vulcanize in a flat plate vulcanizer at 165℃ and a pressure of 12 MPa for 18 minutes, and naturally cool to room temperature to obtain the final product.

[0067] Example 2:

[0068] Raw materials were accurately weighed by weight fraction: waste rubber powder 60 parts: 60 mesh tire rubber powder, treated with ozone concentration 12 mg / L for 15 minutes and 500W microwave for 10 minutes, surface hydroxyl content 1.8 mmol / g, surface energy 48 mJ / m 2 .

[0069] Ethylene-propylene-diene rubber 30 parts: ethylene monomer content 65 wt%, ethylidene norbornene content 8 wt%, Mooney viscosity (125℃) 50, density 0.87 g / cm 3 .

[0070] Silane-modified graphene / nano-silicon dioxide composite filler 10 parts: graphene to nano-silicon dioxide mass ratio 1:4, modified by KH-570, particle size 20 nm, BET specific surface area 175 m 2 / g.

[0071] Heat-resistant agent 5 parts: N-phenylmaleimide and glycidyl methacrylate at a molar ratio of 3:1, BPO initiated polymerization, grafting rate 3.5 wt%.

[0072] Polyphosphazene elastomer 8 parts: -(NP(OPh)2)n- structure, number average molecular weight 40000, Tg-55℃.

[0073] Carbon nanotube 2 parts: multi-walled carbon nanotube, diameter 20 nm, length 10 μm, 60 wt% carboxylated by refluxing in nitric acid at 90℃ for 3 hours, carboxyl content 1.5 mmol / g.

[0074] Core-shell structure toughener 4 parts: polybutadiene core and PMMA shell mass ratio 3:1, particle size 500 nm, silane grafting rate 2.0 wt%.

[0075] Vulcanizing agent 2 parts: dicumyl peroxide:sulfur:2-mercaptobenzothiazole = 3:1:0.5.

[0076] Accelerator 1 part: TMTD and CZ mass ratio 1:2, purity 98%.

[0077] Active agent 2 parts: 50 nm zinc oxide and stearic acid compounded at 8:1.

[0078] Antioxidant 2 parts: 4010NA:RD:2,6-di-tert-butyl-p-cresol = 2:2:1.

[0079] Preparation steps

[0080] S1: Waste rubber powder was placed in a devulcanization kettle, nitrogen pressure 1.2 MPa, heated to 145℃, 1.5 parts of dibenzoylmethane was added, stirred at 30 rpm for 35 minutes, and cooled to obtain devulcanized rubber powder (Mooney viscosity 55).

[0081] S2: The composite filler and heat-resistant agent were added to a high-speed mixer, pre-mixed at 1500 rpm for 5 minutes, and the devulcanized rubber powder was added, and the internal mixer was mixed at 155℃ and 60 rpm for 6 minutes.

[0082] S3: The ternary ethylene-propylene rubber, polyphosphazene elastomer, and active agent were added, and the temperature was raised to 155℃, and mixed at 70 rpm for 12 minutes until uniform.

[0083] S4: The temperature was lowered to 90℃, the vulcanizing agent, accelerator, and toughener were added, and mixed for 4.5 minutes, and rested for 10 hours.

[0084] S5: The mill was thin-passed 9 times (roll gap 0.8 mm), and the sheet was discharged at 3 mm, and the flat vulcanizing machine was vulcanized at 170℃ and 15 MPa for 20 minutes, and cooled to obtain the product.

[0085] Example 3:

[0086] Raw materials were accurately weighed by weight fraction: 80 parts of waste rubber powder: 120 mesh tire rubber powder, treated with ozone concentration of 8 mg / L for 15 minutes, 300 W microwave treatment for 10 minutes, surface hydroxyl content 1.2 mmol / g, surface energy 42 mJ / m 2 .

[0087] Ethylene propylene rubber 15 parts: ethylene monomer content 50 wt%, ethylene content 5 wt%, Mooney viscosity (125℃) 30, density 0.85 g / cm 3 .

[0088] Composite filler 5 parts: mass ratio of graphene and nano-silicon dioxide 1:5, modified by KH-570, particle size 20 nm, BET 185 m 2 / g.

[0089] Heat-resistant agent 3 parts: N-phenyl maleimide and glycidyl methacrylate 3:1 polymerization, grafting rate 2.5 wt%.

[0090] Polyphosphazene elastomer 5 parts: -(NP(OPh)2)n- structure, molecular weight 30000, Tg-58℃.

[0091] Carbon nanotubes 0.5 parts: multi-walled carbon nanotubes, diameter 10 nm, length 5 μm, 50 wt% nitric acid refluxed at 80℃ for 2 hours carboxylation, carboxyl content 0.8 mmol / g.

[0092] Core-shell structure toughening agent 1 part: mass ratio of polybutadiene core and PMMA shell 2:1, particle size 200 nm, grafting rate 1.2 wt%.

[0093] Vulcanizing agent 1 part: dicumyl peroxide:sulfur:2-mercaptobenzothiazole = 3:1:0.5.

[0094] Accelerator 0.5 parts: mass ratio of TMTD and CZ 1:2.

[0095] Active agent 1 part: 50 nm zinc oxide and stearic acid 8:1 complex.

[0096] Antioxidant 1 part: 4010NA:RD:2,6-di-tert-butyl-p-cresol = 2:2:1.

[0097] Preparation steps

[0098] S1: Under nitrogen pressure of 0.8 MPa, 130℃, 0.5 parts of dibenzoylmethane was added, stirred at 30 rpm for 30 minutes, and cooled to obtain desulfurized rubber powder (Mooney 45).

[0099] S2: Composite filler and heat-resistant agent were premixed at 1000 rpm for 8 minutes, and the desulfurized rubber powder was added, and mixed in an internal mixer at 140℃ and 50 rpm for 8 minutes.

[0100] S3: Add EPDM, polyphosphazene elastomer, active agent, mix at 145℃, 50rpm for 10 minutes.

[0101] S4: Cool down to 85℃, add vulcanizing agent, accelerator, toughener, mix for 5 minutes, stand for 8 hours.

[0102] S5: Thin pass on the mill 8 times (roll gap 0.5mm), sheet out 3mm, cure on the flat press at 160℃, 10MPa for 15 minutes, cool down to get the product.

[0103] Example 4:

[0104] Raw materials are accurately weighed by weight fraction: 70 parts of waste rubber powder: 80 mesh tire rubber powder, ozone 10mg / L + 400W microwave treatment, surface hydroxyl 1.6mmol / g.

[0105] EPDM 20 parts: ethylene 55wt%, ethylidene norbornene 6wt%, Mooney 40, density 0.86g / cm 3 .

[0106] Composite filler 5 parts: graphene and nanosilica 1:6, modified by KH-570, particle size 20nm, BET 170m 2 / g.

[0107] Heat-resistant agent 8 parts: N-phenyl maleimide and glycidyl methacrylate 3:1 polymerization, grafting rate 5wt%.

[0108] Polyphosphazene elastomer 12 parts: -(NP(OPh)2)n- structure, molecular weight 50000, Tg-52℃.

[0109] Carbon nanotubes 1 part: multi-walled Φ15nm x 8μm, 55wt% carboxylated with nitric acid, carboxyl 1.2mmol / g.

[0110] Core-shell toughener 2 parts: polybutadiene core / PMMA shell 3:1, Φ300nm, grafting rate 1.6wt%.

[0111] Vulcanizing agent 3 parts: dicumyl peroxide: sulfur: 2-mercaptobenzothiazole = 3:1:0.5.

[0112] Accelerator 2 parts: TMTD and CZ 1:2 compounded.

[0113] Active agent 3 parts: 50nm zinc oxide and stearic acid 8:1.

[0114] Antioxidant 3 parts: 4010NA:RD:2,6-di-tert-butyl-p-cresol = 2:2:1.

[0115] Preparation step

[0116] S1: Same as desulfurization step of Example 1 (nitrogen 1.0 MPa, 135°C, 32 minutes).

[0117] S2: Composite filler + heat resistance agent 1200 rpm premixing for 6 minutes, adding desulfurized rubber powder, dense mixing 145°C, 55 rpm x 7 minutes.

[0118] S3: Adding ternary ethylene-propylene rubber, polyphosphazene, active agent, mixing at 160°C, 70 rpm for 12 minutes.

[0119] S4: Adding vulcanizing agent, etc. at 90°C, mixing for 4.5 minutes, and standing for 12 hours.

[0120] S5: Thin pass 10 times on the open mill (roll gap 1 mm), sheeting 3 mm, and sectional temperature rising vulcanization on the flat vulcanization machine (120°C 5 min→150°C 5 min→170°C 10 min), pressure 12 MPa, and cooling to obtain the product.

[0121] Comparative example:

[0122] Raw material composition: waste rubber powder 70 parts: 80 mesh tire rubber powder, not treated by ozone-microwave, surface hydroxyl 0.3 mmol / g, gel content 85%.

[0123] Ternary ethylene-propylene rubber 20 parts: ethylene 55 wt%, ethylidene norbornene 6 wt%, Mooney 40, same as Example 1.

[0124] Unmodified nano-silicon dioxide 7 parts: particle size 20 nm, not treated by silane coupling agent, BET 150 m 2 / g.

[0125] Vulcanizing agent 2 parts: single sulfur, purity 99%.

[0126] Accelerator 1 part: single accelerator CZ, purity 98%.

[0127] Active agent 2 parts: 50 nm zinc oxide compounded with stearic acid at 8:1, same as Example 1.

[0128] Antioxidant 2 parts: single antioxidant 4010NA, purity 99%.

[0129] Preparation step

[0130] All raw materials were added to a high-speed mixer, stirred at 500 rpm for 10 minutes at room temperature, without pretreatment step.

[0131] The mixed materials were transferred to a dense mixer, mixed at 150°C, 50 rpm for 15 minutes, without nitrogen protection.

[0132] The compound was mixed on an open mill for 5 passes (1 mm nip) and sheeted to 3 mm.

[0133] The product was cured on a flat press at 165 °C and 10 MPa for 20 minutes without a temperature ramping program. The product was cooled.

[0134] Test sample basic form

[0135] The overall sample was in a sheet form, which was determined by the sheet thickness of 2-3 mm in the S5 molding and curing step in the preparation process, and was the basic form for subsequent performance tests.

[0136] The basic dimensions needed to be uniform, usually 100 mm x 100 mm x 2-3 mm (length x width x thickness), to ensure that the basic conditions such as the stress area and heat conduction path of the material were consistent during testing.

[0137] Key performance test sample specifications

[0138] Mechanical properties (tensile strength, elongation at break): dumbbell-shaped samples were required, and the rubber test standard (such as GB / T528) was referred to. The specific specifications were as follows: the parallel part length was 25 mm, the width was 6 mm, and the thickness was 2 mm, and the two end clamping parts had a width of 20 mm to ensure that the stress was concentrated on the parallel section during tensile testing, and the data was more accurate.

[0139] Compression set: cylindrical samples were made, with a diameter of 29 mm and a height of 12.5 mm (in accordance with the GB / T7759 standard), to facilitate uniform stress in the compression device and accurate measurement of deformation at high temperatures.

[0140] Thermal conductivity: circular sheet-shaped samples were used, with a diameter of 50 mm and a thickness of 2-3 mm (consistent with the basic sample thickness), to ensure that the heat flow was perpendicular to the sample and to reduce the influence of edge effects.

[0141] Heat aging performance: the same dumbbell-shaped samples as used in the tensile test, or rectangular samples (50 mm x 10 mm x 2 mm) of the same size were used to ensure that the mechanical property tests before and after heat aging were performed under the same conditions, and the comparison was more reliable.

[0142] The basic performance parameters of the examples and comparative examples are as follows:

[0143] Table 1

[0144]

[0145] Summary: Test data show that the four embodiments are significantly better than the control examples in various performance indicators. The tensile strength of the embodiment reaches 20-24MPa, which is 1.7-2 times that of the control example, and the elongation at break is 380-450%, which is 1.9-2.2 times that of the control example. This is due to the elastic toughening of the core-shell toughening agent and the reinforcing effect of the composite filler, as well as the improvement of the interface compatibility to reduce stress concentration. The thermal aging strength retention rate is improved by 30-37%, reflecting the synergistic anti-aging effect of the antioxidant compound system and the heat-resistant agent. The thermal conductivity coefficient is increased by 1 times, which is due to the construction of the carbon nanotube-graphene three-dimensional thermal conductive network. The compression permanent deformation is reduced by more than 50%, reflecting the stable cross-linked structure formed by the optimized vulcanization system. Due to the lack of key modified components and process optimization, the performance of the control example lags behind in all aspects, which fully verifies the effectiveness of the technical solution of this patent.

[0146] Figure 2 The mechanical properties comparison bar chart shows that the tensile strength and elongation at break of the embodiment are significantly higher than those of the control example, because the multiple components synergistically enhance and toughen, the core-shell structure disperses stress, and the interface bonding is improved to reduce performance loss, thus achieving a balance of strength and toughness.

[0147] Figure 3 The heat resistance performance line graph shows that the thermal aging strength retention rate of the embodiment is much higher than that of the control example, because the antioxidant compound and the heat-resistant agent synergistically inhibit thermal oxidative aging, delay the degradation of the molecular chain, and significantly improve the high-temperature stability and service life of the material.

[0148] Figure 4 The thermal conductivity and compression performance bar graph shows that the embodiment has a higher thermal conductivity coefficient and a smaller compression deformation because the carbon nanotube-graphene network enhances thermal conductivity, optimizes the vulcanization system to form a uniform cross-linked structure, and improves high-temperature dimensional stability and heat conduction capacity.

[0149] Figure 5 The line graph of the effect of composite filler dosage on performance shows that increasing filler dosage increases strength and slightly decreases elongation, and the optimal overall result is 5-7 parts. This is because an appropriate amount of filler forms a reinforced network, while excessive amount easily agglomerates, resulting in a slight decrease in toughness. This provides a dosage reference for formula optimization.

[0150] Figure 6 The bar graph shows the effect of vulcanization temperature on compression set. As the vulcanization temperature increases, the deformation rate decreases, and it is better at 165-170℃ because high temperature promotes sufficient and uniform cross-linking. This verifies the effect of staged temperature rise vulcanization on improving heat resistance and stability, and guides the selection of process parameters.

[0151] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A heat-resistant recycled rubber, characterized in that: The composition comprises, by weight: 60-80 parts of waste rubber powder, 15-30 parts of EPDM rubber, 5-10 parts of silane-modified graphene / nano-silica composite filler, 3-8 parts of N-phenylmaleimide-glycidyl methacrylate copolymer heat-resistant agent, 5-12 parts of polyphosphazene elastomer, 1-3 parts of vulcanizing agent, 0.5-2 parts of accelerator, 1-3 parts of active agent, and 1-3 parts of antioxidant; The composite filler is prepared by the following reaction: first, graphene is reacted with a silane coupling agent KH-570 in a toluene solution at 80° C. for 6 hours to generate an intermediate G-570, the reaction formula being: G-OH+CH2=C(CH3)COOC3H6Si(OCH3)3→G-OOC(CH3)C=CH2+C3H6Si(OCH3)3, and then the graphene is ultrasonically dispersed with nano-silica in an ethanol solution for 2 hours, and then reacted at 120° C. for 12 hours to obtain a modified composite filler; The heat-resistant agent is prepared by a solution polymerization method, wherein the molar ratio of N-phenylmaleimide to glycidyl methacrylate is 3:1, the amount of initiator BPO is 1.5% of the total weight of the monomers, the reaction is carried out at 80°C for 4 hours, and the grafting rate is 2.5-5wt%. The main chain of the polyphosphazene elastomer is a -(NP(OPh)2)n- structure, the number average molecular weight is 30,000-50,000, and the glass transition temperature is -60°C to -50°C.

2. The heat-resistant recycled rubber according to claim 1, characterized in that The invention also includes 0.5-2 parts of carbon nanotubes, wherein the carbon nanotubes are multi-walled carbon nanotubes with a diameter of 10-20 nm and a length of 5-10 μm, and are modified by the following steps: refluxing in mixed acid at 80°C for 3 hours, and the surface carboxyl content after carboxylation treatment is 0.8-1.5 mmol / g; reacting with silane coupling agent KH-550 in toluene at 110°C for 8 hours; and mixing with modified graphene / nanosilica composite filler at a mass ratio of 1:5-1:3 in a high-speed stirrer at 2000 rpm for 15 minutes to form a three-dimensional heat-conducting network through π-π interaction, with a network node density of 0.8-1.2 / μm 2 .

3. The heat-resistant recycled rubber according to claim 1, characterized in that The invention also includes 1-4 parts of a core-shell structure toughening agent, which is prepared by emulsion polymerization: polybutadiene is used as the core, potassium persulfate is used as the initiator, and polymerization is carried out at 60°C for 12 hours to form a latex with an average particle size of 200-500nm; methyl methacrylate is used as the shell monomer, and γ-aminopropyltriethoxysilane is added for graft copolymerization; the powdered toughening agent is obtained by a coagulation method, and during the mixing process, the toughening agent is dispersed in the matrix through an "island structure".

4. The heat-resistant recycled rubber according to claim 1, characterized in that The waste rubber powder is tire rubber powder with a particle size of 60-120 mesh. It is treated with ozone-microwave synergistically: it is treated in a closed container with an ozone concentration of 8-12 mg / L for 15 minutes to oxidize the double bonds on the surface of the rubber powder to generate carbonyl and carboxyl groups; and it is immediately transferred to a microwave reactor and treated at a power of 300-500W for 10 minutes.

5. The heat-resistant recycled rubber according to claim 1, characterized in that The EPDM rubber has an ethylene content of 50-65wt%, an ethylidene norbornene content of 5-8wt%, and a Mooney viscosity of 30-50. The EPDM rubber and the polyphosphazene elastomer have a mass ratio of 3:1-2:1, and a continuous phase network is formed by: premixing in an internal mixer at 150°C for 5 minutes to initially disperse the two elastomers; adding 0.5-1 part of bis-tetrasulfide as a compatibilizer, and continuing mixing at 160°C for 8 minutes. The compatibilizer undergoes a vulcanization reaction with the double bonds of the EPDM rubber and simultaneously forms hydrogen bonds with the phenoxy groups of the polyphosphazene elastomer, resulting in an interface layer thickness of 50-100 nm. The formed network structure exhibits a single glass transition temperature in a dynamic thermomechanical analyzer.

6. The heat-resistant regenerated rubber according to claim 1, characterized in that The vulcanizing agent is a ternary compound of dicumyl peroxide, sulfur and 2-mercaptobenzothiazole, with a mass ratio of 3:1:0.

5. The vulcanizing agent forms three cross-linking structures during the vulcanization process: dicumyl peroxide forms C-C cross-linking bonds, accounting for 60-70% of the total cross-linking bonds, with a bond energy of 347 kJ / mol; sulfur forms polysulfide bonds and monosulfide bonds, accounting for 20-30% and 10-20% respectively, with bond energies of 272 kJ / mol and 351 kJ / mol respectively; and 2-mercaptobenzothiazole promotes uniform distribution of cross-linking bonds.

7. The heat-resistant recycled rubber according to claim 1, characterized in that The antioxidant is a compound of antioxidant 4010NA, antioxidant RD and 2,6-di-tert-butyl-p-cresol in a mass ratio of 2:2:

1. The antioxidant resists aging through the following synergistic mechanism: antioxidant 4010NA captures free radicals generated by rubber oxidation to generate stable amine free radicals, thereby inhibiting the chain oxidation reaction. Its reaction rate constant k1=1.2×10 6 L / (mol·s); antioxidant RD decomposes hydroperoxides to generate stable alcohol compounds with a decomposition efficiency of 85-90%; 2,6-di-tert-butyl-p-cresol protects the rubber molecular chain through steric hindrance effect.

8. A method for preparing heat-resistant recycled rubber, for preparing the heat-resistant recycled rubber according to any one of claims 1 to 7, characterized in that: The following steps are involved: S1: Pretreatment of waste rubber powder: The waste rubber powder is placed in a high-pressure desulfurization reactor, nitrogen is introduced to a pressure of 0.8-1.2 MPa, the temperature is raised to 130-145°C at 5°C / min, 0.5-1.5 parts of dibenzoylmethane (a desulfurizer) is added, and the reaction is carried out at a stirring rate of 30-50 rpm for 30-35 minutes. The desulfurizer decomposes to produce free radicals, which attack the CS and SS bonds in the rubber cross-links, reducing the gel content to 50-60%. After the reaction is completed, the mixture is naturally cooled to room temperature to obtain desulfurized rubber powder with a Mooney viscosity of 40-60. S2: Premixing the composite filler and the heat-resistant agent: Add the modified graphene / nanosilica composite filler and the heat-resistant agent in a mass ratio of 1:1 into a high-speed mixer and premix at a speed of 1000-1500 rpm for 5-8 minutes to form composite particles through physical adsorption and hydrogen bonding. Then, add the desulfurized rubber powder obtained in step S1, transfer to an internal mixer, and mix at 140-155°C and a rotor speed of 50-60 rpm for 6-8 minutes. The composite particles are evenly dispersed in the rubber matrix, and the interfacial bonding strength reaches 1.5-2.5 MPa. S3: Mixing the main materials: Add EPDM rubber, polyphosphazene elastomer, and activator to an internal mixer, raise the temperature to 145-160°C, adjust the rotor speed to 50-70 rpm, and mix for 10-12 minutes; the activator forms a fatty acid zinc complex at this temperature; the EPDM rubber and polyphosphazene elastomer form a continuous phase network with an average pore size of 1-3 μm and a porosity of 5-10%; S4: Vulcanization system mixing: Lower the mixer temperature to 85-95°C, add the vulcanizer, accelerator, and core-shell toughening agent, and continue mixing for 4-5 minutes; at this temperature, the vulcanizer is in a stable state, avoiding premature vulcanization; the accelerator is evenly dispersed, reducing the activation energy of the vulcanization reaction to 80-100 kJ / mol; after mixing, discharge the rubber compound and let it sit for 8-12 hours; S5: Molding and vulcanization: The rubber compound is thinned on an open mill 8-10 times to a sheet thickness of 2-3mm to eliminate internal stress; then it is vulcanized in a flat vulcanizer at 160-170℃ and a pressure of 10-15MPa for 15-20 minutes. During the vulcanization process, the pressure causes the rubber compound to fill the mold cavity, and the temperature causes the vulcanizing agent to decompose and generate free radicals, initiating a cross-linking reaction; after the vulcanization is completed, it is cooled to room temperature and demolded to obtain a heat-resistant recycled rubber product.

9. The preparation method according to claim 8, characterized in that In step S2, the composite filler is pretreated as follows: the modified graphene / nanosilica composite filler is dispersed in anhydrous ethanol to form a 5-10wt% suspension, and the suspension is treated in an ultrasonic instrument with a power of 600W and a frequency of 25kHz for 20-30 minutes to deagglomerate the filler agglomerates and reduce the average particle size to 50-100nm; the suspension is then transferred to a rotary evaporator, and the ethanol is evaporated at 80°C and -0.09MPa to obtain a loose powder; the powder is then placed in a vacuum drying oven at 110-130°C and dried for 4-6 hours to control the moisture content of the filler to ≤0.05%.

10. The preparation method according to claim 8, characterized in that In step S5, the vulcanization adopts a staged temperature increase program: first, the temperature is kept at 120°C for 5 minutes, and the pressure in this stage is 10 MPa, so that the rubber material can fully flow and remove the internal air and volatiles. The volatile matter discharge is 0.3-0.5wt%; The temperature is then raised to 150°C and kept for 5 minutes, and the pressure is increased to 12 MPa to promote the initial decomposition of the vulcanizer and form a cross-linked structure of about 30-40%; finally, the temperature is raised to 170°C and kept for 10 minutes, and the pressure is maintained at 15 MPa to complete the remaining cross-linking reaction and the cross-linking density reaches a peak.

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