Preparation of low-heat-buildup, high-thermal-conductivity and long-life solid tire based on high-strength and high-toughness ball milling–sulfhydryl synergistically modified graphene / natural rubber

Abstract

The present invention relates to the technical field of graphene and functional natural rubber composite materials, and specifically relates to the preparation of a low-heat-buildup, high-thermal-conductivity and long-life solid tire based on high-strength and high-toughness ball milling–sulfhydryl synergistically modified graphene / natural rubber. Graphene is modified by means of a ball milling–sulfhydryl synergistic modification process, high-strength and high-toughness ball milling–sulfhydryl synergistically modified graphene / natural rubber is then prepared by using an aqueous-phase synergistic polymerization process and a mechanical blending method, and thus a low-heat-buildup, high-thermal-conductivity and long-life solid tire thereof is prepared. By means of ball-milling modification of a graphene oxide slurry, the edge carbon defects thereof are increased, and the content of free radicals on the surface thereof is also increased; the edge carbon defects can increase the loading capacity during subsequent sulfhydryl modification; and the free radicals on the surface can remove free radicals generated by molecular chain breakage caused by thermal and oxygen attacks during the initial heat buildup of a tire in a dynamic driving state, thereby reducing the thermal decomposition of the molecular chain of the natural rubber matrix and decreasing the fatigue compression heat buildup value, and therefore the aging speed of the tire is delayed.

Description

Preparation of low heat generation, high thermal conductivity and long life solid tire based on high strength and high toughness ball milling-thiol synergistic modification of graphene / natural rubber

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to Chinese patent application number 202410109428.3 filed with the China Patent Office on January 26, 2024, entitled "Preparation of low heat generation, high thermal conductivity and long life solid tires based on high strength and high toughness ball milling-thiol synergistic modified graphene / natural rubber", the entire contents of which are incorporated by reference into this application. Technical Field

[0003] The present invention relates to the technical field of graphene and functional natural rubber composite materials, and in particular to the preparation of a low-heat-generation, high-thermal-conductivity, and long-life solid tire based on high-strength and high-toughness ball-milling-thiol synergistically modified graphene / natural rubber. Background Art

[0004] Natural rubber (NR) has excellent properties such as high elasticity, high strength, high insulation, wear resistance and tear resistance. As a strategic resource, it plays an important role that cannot be replaced by artificial synthetic rubber. It is widely used in daily life and military defense fields, such as aircraft tires, engineering vehicle tires, and large-scale defense truck tires.

[0005] However, NR lacks the required strength for practical applications, requiring reinforcement to be used in various products. Furthermore, research on elastomer toughening has a long history, primarily focusing on constructing dissipative systems within elastic networks. Based on this concept, numerous strategies have been developed for NR reinforcement and toughening, including the introduction of nanocomposite structures, multiple crosslinking, copolymerization, metal coordination interactions, ionic interactions, and dual network structures.

[0006] Tires are subject to various stresses during driving. While alternating external forces cause complex deformation, some of this energy is converted into heat due to internal friction within the rubber, generating significant heat within the tire and causing a temperature rise. This elevated operating temperature can break the molecular chains within the rubber matrix, generating a large number of free radicals. Prolonged exposure to heat and oxygen accelerates rubber aging, shortening the service life of the finished tire. Therefore, reducing compression fatigue heat generation in rubber tires is crucial. Consequently, current and future tire development is primarily focused on strengthening and toughening tires, reducing heat generation, and thus delaying aging, thereby promoting environmentally friendly tires.

[0007] Heat generation in rubber primarily stems from filler-filler friction, filler-rubber friction, and rubber-rubber friction. Simultaneously, unsaturated double bonds in the NR molecular chain break, creating active sites that combine with oxygen free radicals, further initiating molecular chain breakage and generating a large number of free radicals. Improving the filler's dispersion in the matrix and enhancing filler-matrix interactions can reduce filler-filler and filler-matrix dynamic friction. Therefore, scavenging free radicals and enhancing filler-matrix interfacial interactions are key to achieving low heat generation in rubber tires.

[0008] Ball milling is a green and environmentally friendly method for modifying carbon materials. It involves the continuous collision and grinding of high-speed balls, breaking down some of the chemical bonds on the carbon material's surface and reducing it to smaller particles. Ball milling can result in carbon materials with larger surface areas, richer pore structures, and a wider variety of oxygen-containing functional groups.

[0009] Graphene oxide has sp 2 The densely packed hybrid carbon atoms form a two-dimensional lamellar structure, which offers advantages such as high thermal conductivity, high strength, excellent thermal stability, and a large specific surface area. The numerous oxygen-containing functional groups on the surface provide active sites for modification of organic compounds. Furthermore, the unique lamellar structure enhances edge defects during ball milling, increases the thiol grafting rate, and provides a foundation for scavenging free radicals generated by thermal decomposition.

[0010] Summary of the Invention

[0011] In order to delay the thermal aging rate of rubber tires and extend their service life, the present invention provides a preparation method for low heat generation, high thermal conductivity and long life solid tires based on high-strength and high-toughness ball milling-thiol synergistic modified graphene / natural rubber.

[0012] The present invention is achieved through the following technical solution: the preparation of a low-heat-generation, high-thermal-conductivity, long-life solid tire based on high-strength and high-toughness ball milling-thiol synergistically modified graphene / natural rubber includes the following steps:

[0013] (1) adding graphene oxide slurry into a ball mill, and ball milling for 15-120 min at a ball-to-material ratio of 100:0.5-2 and a rotation speed of 200-500 rpm; obtaining a ball-milled modified graphene oxide slurry with increased graphene oxide edge carbon defects and surface free radical content; the edge carbon defects can increase the loading capacity during subsequent thiol modification, and the surface free radicals can scavenge free radicals generated by the breakage of natural rubber molecular chains caused by heat and oxygen attack;

[0014] (2) adding a mercapto-containing silane coupling agent to an alcohol aqueous solution, hydrolyzing for a certain period of time, adjusting the pH, adding the ball-milled modified graphene oxide slurry obtained in step (1) under ultrasonic dispersion, heating the reaction for a certain period of time, and freeze-drying to obtain ball-milled-thiol synergistically modified graphene oxide;

[0015] (3) preparing a uniform aqueous dispersion of the ball-milled-thiol-synergistically modified graphene oxide obtained in step (2), and then adding it to natural rubber latex, stirring and mixing thoroughly to obtain a uniformly dispersed mixed emulsion, wherein the ball-milled-thiol-synergistically modified graphene oxide forms bound particles with the protein-phospholipid membrane positive ions on the surface of the rubber particles through electrostatic attraction and remains stable; adding a flocculant, since the repulsion between the particles that keeps the emulsion stable is reduced, flocculation occurs, and the rubber particles with the destroyed protective layer and the modified graphene oxide particles are further adsorbed to each other through the interaction force, and the bound particles and rubber particles are orderly aggregated and synergistically precipitated in the aqueous phase; washing the obtained raw rubber with water, dehydrating, and drying to obtain the ball-milled-thiol-synergistically modified graphene / natural rubber masterbatch;

[0016] (4) The ball-milled-thiol synergistically modified graphene / natural rubber masterbatch prepared in step (3) is placed in an internal mixer, mixed at a certain temperature, and rubber additives and reinforcing fillers are added in sequence. After uniform dispersion, the rubber material is discharged and cooled to room temperature; the rubber material is then mixed on an open mixer at a certain temperature, a vulcanizing agent is added, mixed uniformly, and thinned until there are no bubbles in the rubber material. After standing for a certain period of time, the rubber material is placed in a tire mold and vulcanized at a certain temperature and a certain pressure for a certain period of time. The natural rubber reacts with the vulcanizing agent to form a vulcanized cross-linked network structure, and the mercapto-containing silane coupling agent reacts with the rubber through the mercapto end group to form a unique double cross-linked network structure, thereby obtaining a low heat generation, high thermal conductivity, and long life solid tire based on high-strength and high-toughness ball-milled-thiol synergistically modified graphene / natural rubber.

[0017] As a further improvement to the technical solution of the present invention, in step (2), the volume ratio of alcohol to water in the alcohol-water solution is 5-9:1; the hydrolysis time of the mercapto-containing silane coupling agent in the alcohol-water solution is 1-5 hours, and the pH value after hydrolysis is adjusted to 7-13; the mercapto-containing silane coupling agent is selected from at least one of (3-mercaptopropyl)trimethoxysilane coupling agent, γ-mercaptopropyltriethoxysilane coupling agent and bis-[γ-(triethoxysilyl)propyl]tetrasulfide; the mass ratio of the mercapto-containing silane coupling agent to the graphene oxide in the ball-milled modified graphene oxide slurry is 1-4:1; the heating reaction temperature after adding the ball-milled modified graphene oxide slurry is 60-80°C, and the heating reaction time is 5-8 hours.

[0018] As a further improvement to the technical solution of the present invention, in step (3), the concentration of the prepared ball-milled-thiol synergistically modified graphene oxide uniform aqueous dispersion is 0.5-2wt%, and the mass ratio of the ball-milled-thiol synergistically modified graphene oxide to natural rubber is 0.25-1.5:100; and the flocculant is at least one of calcium chloride solution, sodium chloride solution, hydrochloric acid solution and formic acid solution.

[0019] As a further improvement of the technical solution of the present invention, in step (4), the addition amounts of the raw materials are: 100 parts by mass of natural rubber in the ball-milled-thiol synergistically modified graphene-modified natural rubber masterbatch, 30-90 parts by mass of reinforcing filler, and 10-20 parts by mass of rubber additives.

[0020] As a further improvement of the technical solution of the present invention, in step (4), the rubber additives include an antioxidant, an antioxidant, an activator, a softener and a vulcanization accelerator, and the mass ratio of the antioxidant, antioxidant, activator, softener, vulcanization accelerator and vulcanizer is 2:2:5:2:2:2.

[0021] As a further improvement of the technical solution of the present invention, in step (4), the reinforcing filler is carbon black, selected from at least one of models N110, N330 and N660.

[0022] As a further improvement of the technical solution of the present invention, in step (4), the mixing temperature of the ball milling-thiol synergistically modified graphene / natural rubber masterbatch in the internal mixer is 105-120°C, and the mixing time is 12-20 min; the mixing temperature in the open mixer is 50-70°C, and the mixing time is 8-12 min.

[0023] As a further improvement of the technical solution of the present invention, in step (4), the storage time of the rubber mix is ​​18-36 hours; the vulcanization temperature is 135-170° C., the vulcanization pressure is 10-30 MPa, and the vulcanization time is 3-25 minutes.

[0024] The preparation of a low-heat-generation, high-thermal-conductivity, long-life solid tire based on high-strength and high-toughness ball-milled and mercapto-synergistically modified graphene / natural rubber provided by the present invention has the following advantages over the prior art:

[0025] (1) Graphene is modified by ball milling-thiol synergistic modification process, and then a modified graphene reinforced and toughened natural rubber composite material is prepared by aqueous phase synergistic coagulation process and mechanical blending method, thereby preparing a low heat generation and high thermal conductivity tire. By ball milling the graphene oxide slurry, the carbon defects at its edge are increased, and the free radical content on its surface is increased. The edge carbon defects can increase the loading capacity during subsequent thiol modification. The surface free radicals can remove the free radicals generated by the molecular chain breakage caused by heat and oxygen attack at the initial stage of tire dynamic driving heat generation, reduce the thermal decomposition of the NR matrix molecular chain, reduce the fatigue compression heat value, and thus delay the aging rate of the tire.

[0026] (2) The ball-milled modified graphene oxide is modified with thiol groups through the thiol-ene click chemistry reaction. On the one hand, it can increase the loading amount of the thiol-containing coupling agent. On the other hand, the thiol end group can react with the rubber to form a single sulfur bond, which can not only reduce the time required for natural rubber vulcanization and improve the processing performance; but also improve the interfacial interaction between the ball-milled-thiol synergistically modified graphene and the natural rubber matrix. The double network formed with the rubber vulcanization cross-linking network improves the mechanical and thermal conductivity of the final prepared rubber tire, reduces the frictional heat generated between the filler-matrix and the filler-filler, thereby slowing down the thermal aging rate of the rubber tire during dynamic driving and extending the service life of the tire. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0028] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0029] FIG1 is an infrared spectrum of the ball-milled-thiol synergistically modified graphene oxide (BGO-SH) prepared in Example 1 and the GO of Comparative Example 1.

[0030] Figure 2 is the full XPS spectrum of BGO-SH prepared in Example 1 and GO prepared in Comparative Example 1.

[0031] FIG3 is the XPS spectra of C 1s, Si 2p, and S 2p of BGO-SH prepared in Example 1.

[0032] Figure 4 is the TG weight loss curves of BGO-SH prepared in Example 1 and GO prepared in Comparative Example 1.

[0033] Figure 5 shows SEM photos of GO (a), BGO-SH prepared in Example 1 (b), and a low-heat-generation, high-thermal-conductivity, long-life solid tire material based on high-strength and high-toughness ball-milled-thiol synergistically modified graphene / natural rubber (c).

[0034] FIG6 is an EDX spectrum of C, S, and Si of BGO-SH prepared in Example 1.

[0035] The test method of the above-mentioned accompanying drawings is:

[0036] Infrared spectrum: The functional groups of the materials were analyzed using the IS50 Fourier transform infrared spectrometer from Thermo Fisher Scientific, USA, with a test range of 500-4000 cm -1 The material sample and KBr powder were ground at a ratio of 1:100, mixed evenly and pressed into tablets.

[0037] XPS spectra: The analysis was performed using a Thermo Fisher Scientific NEXSA X-ray photoelectron spectroscopy analyzer. The scan mode was CAE mode, with a pass energy of 160 eV for the full spectrum scan and 40 eV for the narrow spectrum scan.

[0038] TG weight loss curve: The weight loss test was carried out using a Q50 thermogravimetric analyzer from TA Company of the United States. The test was carried out from room temperature to 800℃ at a heating rate of 10℃ / min in a N2 atmosphere.

[0039] SEM photos: The particles and brittle fracture surfaces of Example 1 and Comparative Example 1 were tested using a SU8010 scanning electron microscope produced by Hitachi, Japan, at a voltage of 10 kV.

[0040] As shown in Figure 1, for GO, the characteristic peak of carbonyl (-C=O) appears at 1728 cm -1 3442cm -1 、1628cm -1 and 1401cm -1 The peaks at 1236 cm-1 and 1276 cm-2 correspond to hydroxyl (-OH), -C=C and carboxyl (-COOH) respectively. For BGO-SH, in addition to the above characteristic peaks, two new characteristic peaks appear, namely 1236 cm-1 and 1276 cm-2. -1 Si-C at 1114 cm -1 The Si-O stretching vibration peak at 37° indicated that KH580 was successfully grafted onto the surface of ball-milled modified GO (BGO).

[0041] Figure 2 shows that the full spectrum of BGO-SH shows S 2p and Si 2p peaks, indicating the presence of KH580 on the BGO surface. Simultaneously, the O content decreases from 31.04% to 22.26%, demonstrating that the silanols in KH580 react with the -OH groups on the GO surface, resulting in grafting onto the BGO surface via dehydration condensation. Further analysis of the Si 2p, C1s, and S 2p deconvolution patterns, as shown in Figure 3, reveals the presence of distinct Si-O-Si (102.78 eV), C-S (164.24 eV), and -SH (163 eV) bonds, indicating successful grafting of KH580 onto the BGO surface.

[0042] As shown in Figure 4, the thermal weight loss around 100°C is mainly due to the volatilization of water. 150-250°C is mainly due to the thermal decomposition of unstable oxygen functional groups of graphene oxide. In contrast, from room temperature to 800°C, the thermal weight loss of BGO-SH is 50.32wt%. The significant decrease in total weight loss indicates that silicon-containing functional groups such as Si-O-Si are grafted onto the surface of graphene oxide, because they have higher thermal stability than CC and CO. In addition, a new thermal degradation stage appears in the BGO-SH spectrum at 300-400°C, with a weight loss of 14.54wt%, indicating that the thiol group has decomposed, further proving that KH580 is grafted onto the BGO surface.

[0043] As shown in Figure 5, the surface of the unmilled pristine GO (Figure 5a) exhibits a typical wrinkled lamellar structure with larger flake diameters. After ball milling, the morphology of the BGO (Figure 5b) changes significantly, with the flakes being mechanically destroyed by the milling process, resulting in more edge structures and a smaller flake diameter. In the brittle fracture surface of the BGO-SH-modified NR vulcanizate (NR / BGO-SH / CB), the composite particles are well dispersed within the rubber matrix, with no apparent agglomerates.

[0044] As shown in Figure 6, after thiol modification, the surface of BGO-SH contains S and Si elements, which further proves that KH580 is successfully grafted onto the BGO surface. DETAILED DESCRIPTION

[0045] In order to more clearly understand the above-mentioned objectives, features and advantages of the present invention, the scheme of the present invention will be further described below. It should be noted that, in the absence of conflict, the embodiments of the present invention and the features therein can be combined with each other.

[0046] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein; it is obvious that the embodiments in the specification are only part of the embodiments of the present invention, rather than all the embodiments.

[0047] The present invention provides a specific embodiment of the preparation of a low-heat-generation, high-thermal-conductivity, long-life solid tire based on high-strength and high-toughness ball milling-thiol synergistically modified graphene / natural rubber, comprising the following steps:

[0048] (1) adding graphene oxide slurry into a ball mill, and ball milling for 15-120 min at a ball-to-material ratio of 100:0.5-2 and a rotation speed of 200-500 rpm; obtaining a ball-milled modified graphene oxide slurry with increased graphene oxide edge carbon defects and surface free radical content; the edge carbon defects can increase the loading capacity during subsequent thiol modification, and the surface free radicals can scavenge free radicals generated by the breakage of natural rubber molecular chains caused by heat and oxygen attack;

[0049] (2) adding a mercapto-containing silane coupling agent to an alcohol aqueous solution, hydrolyzing for a certain period of time, adjusting the pH, adding the ball-milled modified graphene oxide slurry obtained in step (1) under ultrasonic dispersion, heating the reaction for a certain period of time, and freeze-drying to obtain ball-milled-thiol synergistically modified graphene oxide;

[0050] (3) preparing a uniform aqueous dispersion of the ball-milled-thiol-synergistically modified graphene oxide obtained in step (2), and then adding it to natural rubber latex, stirring and mixing thoroughly to obtain a uniformly dispersed mixed emulsion, wherein the ball-milled-thiol-synergistically modified graphene oxide forms bound particles with the protein-phospholipid membrane positive ions on the surface of the rubber particles through electrostatic attraction and remains stable; adding a flocculant, since the repulsion between the particles that keeps the emulsion stable is reduced, flocculation occurs, and the rubber particles with the destroyed protective layer and the modified graphene oxide particles are further adsorbed to each other through the interaction force, and the bound particles and rubber particles are orderly aggregated and synergistically precipitated in the aqueous phase; washing the obtained raw rubber with water, dehydrating, and drying to obtain the ball-milled-thiol-synergistically modified graphene / natural rubber masterbatch;

[0051] (4) placing the ball-milled-thiol synergistically modified graphene / natural rubber masterbatch prepared in step (3) in an internal mixer, mixing at a certain temperature, adding rubber additives and reinforcing fillers in sequence, discharging the rubber material after uniform dispersion, and cooling to room temperature; then, mixing the rubber material on an open mixer at a certain temperature, adding a vulcanizing agent, mixing evenly, and thinning the rubber material until there are no bubbles in the rubber material. After standing for a certain time, the rubber material is placed in a tire mold, and vulcanized at a certain temperature and a certain pressure for a certain time. The natural rubber reacts with the vulcanizing agent to form a vulcanized cross-linked network structure, and at the same time, the mercapto-containing silane coupling agent reacts with the rubber through the mercapto end group to form a unique double cross-linked network structure, thereby obtaining a natural rubber tire with low heat generation and high thermal conductivity that is reinforced and toughened by ball-milled-thiol synergistically modified graphene.

[0052] Taking γ-mercaptopropyltriethoxysilane coupling agent (KH580) as an example, the mechanism of preparing ball milling-mercapto-synergistic modified graphene oxide and the mechanism of formation of double cross-linked network structure in natural rubber composite materials are explained:

[0053] During the ball milling process, the GO sheets are broken and reorganized under the action of mechanical force, the size gradually decreases, and a large number of irregular broken edge structures are formed; at the same time, the SP 2 The ordered lattice is destroyed and free radicals are formed. Defects, edges and free radicals increase with the increase of ball milling time:

[0054] GO ball milling modified GO (characterized as BGO)

[0055] During the hydrolysis process, the silicon-oxygen bond (Si-O) in the KH580 molecular chain breaks under the action of water to form silanol (Si-OH):

[0056] KH580

[0057] The formed silanol undergoes a dehydration condensation reaction with the oxygen-containing functional groups (such as hydroxyl groups) on the BGO surface and is grafted onto the BGO surface by forming chemical bonds:

[0058] Mechanism of formation of double cross-linked network structure in natural rubber composites:

[0059] During the NR vulcanization process, NR reacts with the vulcanizing agent to form a vulcanized cross-linked network structure. Furthermore, the ethoxy groups in KH580 thermally decompose to form highly active silanols, which, through the thiol (-SH) groups, construct a chemically bonded BGO-S-NR cross-linked network between the GO and NR molecular chains, forming a unique dual-crosslinked network structure. This not only shortens the time required for natural rubber vulcanization and improves processing performance, but also enhances the interfacial interaction between the ball-milled and thiol-modified graphene and the natural rubber matrix. The resulting dual-network structure improves the mechanical and thermal conductivity of the resulting rubber tire, reduces frictional heat generation between the filler-matrix and filler-filler interfaces, and, in conjunction with ball-milling modification, scavenges free radicals on the graphene surface during the initial heat generation process of the tire, which is caused by heat and oxygen attack and leads to molecular chain breakage. This reduces the thermal decomposition of the natural rubber matrix molecular chains, slows the rate of thermal aging during dynamic driving, and extends the tire's service life.

[0060] In one embodiment provided by the present invention, in step (2), the volume ratio of alcohol to water in the alcohol-water solution is 5-9:1; the hydrolysis time of the mercapto-containing silane coupling agent in the alcohol-water solution is 1-5 hours, and the pH value after hydrolysis is adjusted to 7-13; the mercapto-containing silane coupling agent is selected from at least one of (3-mercaptopropyl)trimethoxysilane coupling agent, γ-mercaptopropyltriethoxysilane coupling agent and bis-[γ-(triethoxysilyl)propyl]tetrasulfide; the mass ratio of the mercapto-containing silane coupling agent to the graphene oxide in the ball-milled modified graphene oxide slurry is 1-4:1; the heating reaction temperature after adding the ball-milled modified graphene oxide slurry is 60-80°C, and the heating reaction time is 5-8 hours.

[0061] In another embodiment provided by the present invention, in step (3), the concentration of the prepared ball-milled-thiol synergistically modified graphene oxide uniform aqueous dispersion is 0.5-2wt%, and the mass ratio of the ball-milled-thiol synergistically modified graphene oxide to natural rubber is 0.25-1.5:100; and the flocculant is at least one of calcium chloride solution, sodium chloride solution, hydrochloric acid solution and formic acid solution.

[0062] In one embodiment provided by the present invention, in step (4), the added amounts of the raw materials are: 100 parts by mass of the natural rubber in the ball-milled-thiol synergistically modified graphene-modified natural rubber masterbatch, 30-90 parts by mass of the reinforcing filler, and 10-20 parts by mass of the rubber additive.

[0063] In another embodiment provided by the present invention, in step (4), the rubber additives include an antioxidant, an antioxidant, an activator, a softener and a vulcanization accelerator, and the mass ratio of the antioxidant to the antioxidant, the activator, the softener, the vulcanization accelerator and the vulcanizing agent is 2:2:5:2:2:2.

[0064] In one embodiment provided by the present invention, in step (4), the reinforcing filler is carbon black, selected from at least one of models N110, N330 and N660.

[0065] In another embodiment provided by the present invention, in step (4), the mixing temperature of the ball milling-thiol synergistically modified graphene / natural rubber masterbatch in the internal mixer is 105-120°C, and the mixing time is 12-20 min; the mixing temperature in the open mixer is 50-70°C, and the mixing time is 8-12 min.

[0066] In one embodiment provided by the present invention, in step (4), the storage time of the rubber mix is ​​18-36 hours; the vulcanization temperature is 135-170° C., the vulcanization pressure is 10-30 MPa, and the vulcanization time is 3-25 minutes.

[0067] The specific embodiments of the present invention are described in detail below.

[0068] Example 1

[0069] A preparation method for a low-heat-generation, high-thermal-conductivity, and long-life solid tire based on high-strength and high-toughness ball-milled and mercapto-synergistically modified graphene / natural rubber comprises the following steps:

[0070] (1) adding graphene oxide slurry into a planetary ball mill and ball milling for 60 min at a ball-to-material ratio of 100:1.5 and a rotation speed of 500 rpm; obtaining a ball-milled modified graphene oxide slurry with increased carbon defects at the edge of graphene oxide and increased surface free radical content; (2) adding γ-mercaptopropyltriethoxysilane coupling agent into an alcohol-water solution with a volume ratio of 9:1, hydrolyzing for 2 h and adjusting the pH to 7, and adding the coupling agent to the graphene oxide in the ball-milled modified graphene oxide slurry at an ultrasonic power of 200 W in a mass ratio of 2.5:1 (step ( 1) The obtained ball-milled modified graphene oxide slurry is reacted at 70° C. for 8 hours and then freeze-dried to obtain ball-milled-thiol synergistically modified graphene oxide; (3) A uniform aqueous dispersion of the ball-milled-thiol synergistically modified graphene oxide obtained in step (2) is prepared with a concentration of 1 wt%, and then added to natural rubber latex at a mass ratio of modified graphene oxide to natural rubber of 0.5:100, and after sufficient stirring and mixing, a uniformly dispersed mixed emulsion is obtained, wherein the ball-milled-thiol synergistically modified graphene oxide will react with the protein on the surface of the rubber particles. The positive ions of the phospholipid membrane form bound particles through electrostatic attraction and remain stable; adding a flocculant calcium chloride solution, the repulsion between the particles that keeps the emulsion stable is reduced, so flocculation occurs, and the rubber particles with the destroyed protective layer and the modified graphene oxide particles will further adsorb each other through the interaction force, and the bound particles and rubber particles will gather in order in the aqueous phase and precipitate together; the obtained raw rubber is washed, dehydrated, and dried until the moisture content is less than 1% as measured by an infrared moisture meter to obtain a ball-milled-thiol-synergistically modified graphene / natural rubber masterbatch; (4) the rubber containing 100 The ball-milled-thiol-synergistically modified graphene / natural rubber masterbatch prepared in step (3) of g natural rubber was placed in an internal mixer and mixed at 110° C. and 40 rpm for 4 min. Then, 2 g of an antioxidant 2,2,4-trimethyl-1,2-dihydroquinoline polymer, 2 g of an antioxidant N-(1-methylisopentyl)-N'-phenyl-p-phenylenediamine, and 2 g of a vulcanization accelerator N-(oxydiethylene)-2-benzothiazolesulfonamide were added and mixed for another 4 min. 5 g of an activator ZnO, 2 g of a softener stearic acid (SA), and 30 g of a slurry were added. N330 carbon black was added and the mixing was continued for 4 minutes; then 30g N330 carbon black was added and the mixing was continued for 4 minutes, the rubber was discharged and cooled to room temperature; the rubber was then mixed on an open mill at 60°C, 2g sulfur was added, and the rubber was mixed for 8 minutes to mix evenly, and then the rubber was thinly passed until there were no bubbles in the rubber. After standing for 24 hours, the rubber was placed in a tire mold and vulcanized at a temperature of 150°C, a vulcanization pressure of 15MPa, and a vulcanization time of 9 minutes (Tc90). The natural rubber reacted with sulfur to form a vulcanized cross-linked network structure, and at the same time, the γ-mercaptopropyltriethoxysilane coupling agent reacted with the rubber through the mercapto end group to form a unique double cross-linked network structure, thereby obtaining a ball-milled-mercapto synergistically modified graphene reinforced and toughened natural rubber tire with low heat generation and high thermal conductivity, wherein t c90Measured by Rubber Process Analyzer (RPA).

[0071] Example 2

[0072] A preparation method for a low-heat-generation, high-thermal-conductivity, and long-life solid tire based on high-strength and high-toughness ball-milled and mercapto-synergistically modified graphene / natural rubber comprises the following steps:

[0073] (1) Same as (1) of Example 1;

[0074] (2) adding γ-mercaptopropyltriethoxysilane coupling agent to an alcohol-water solution with a volume ratio of 9:1, hydrolyzing for 2 hours, adjusting the pH to 7, adding the ball-milled modified graphene oxide slurry obtained in step (1) at an ultrasonic power of 200 W according to a mass ratio of coupling agent to graphene oxide in the ball-milled modified graphene oxide slurry of 2:1, continuing the reaction at 70° C. for 8 hours, and freeze-drying to obtain ball-milled-thiol synergistically modified graphene oxide;

[0075] (3) Same as (3) of Example 1;

[0076] (4) Same as (4) of Example 1.

[0077] Comparative Example 1

[0078] A method for preparing a graphene oxide-natural rubber tire comprises the following steps:

[0079] ① Same as (3) of Example 1, except that the ball-milled-thiol-synergistically modified graphene in Example 1 is replaced with graphene oxide;

[0080] ②Same as (4) in Example 1.

[0081] Comparative Example 2

[0082] A method for preparing a ball-milled modified graphene oxide-natural rubber tire comprises the following steps:

[0083] ① Same as (1) in Example 1;

[0084] ② The same as (3) of Example 1, except that the ball-milled-thiol-synergistically modified graphene in Example 1 is replaced by the ball-milled modified graphene oxide in (1);

[0085] ③Same as (4) in Example 1.

[0086] Comparative Example 3

[0087] A method for preparing a mercapto-modified graphene oxide-natural rubber tire comprises the following steps:

[0088] ① Same as (2) of Example 1, except that the ball-milled modified graphene oxide slurry is replaced with graphene oxide;

[0089] ② The same as (3) of Example 1, except that the ball-milled-thiol-synergistically modified graphene in Example 1 is replaced with thiol-modified graphene;

[0090] ③Same as (4) in Example 1.

[0091] Samples were taken from the tires prepared in Examples 1-2 and Comparative Examples 1-3, and the properties of the modified NR composites were tested. Tensile properties were tested according to ISO 37-2005 at a rate of 500 mm / min. Tear properties were tested according to GB / T 529-2008. Compression fatigue heat generation was tested according to GB / T 1687.1-2016. Thermal conductivity was tested according to GB / T 11205-2009.

[0092] Table 1 Properties of prepared tire rubber composites

[0093] As can be seen from Table 1, the tire rubber composite material prepared in the present invention has the characteristics of high thermal conductivity, low compression heat generation, and excellent mechanical properties.

[0094] The above description is merely a specific embodiment of the present invention, which enables those skilled in the art to understand or implement the present invention. Although detailed descriptions have been made with reference to the aforementioned embodiments, those skilled in the art should understand that they may still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents; and such modifications or replacements do not deviate from the essence of the corresponding technical solutions within the scope of the technical solutions of the embodiments, and they should all be included in the scope of protection of the claims.

Claims

1. Preparation of a low heat - generating, high - thermal - conductivity and long - life solid tire based on high - strength and high - toughness ball - milled - mercapto synergistically modified graphene / natural rubber, characterized in that, It includes the following steps: (1) Add the graphene oxide slurry to a ball mill and ball mill it for 15 - 120 min at a ball-to-material ratio of 100:0.5 - 2 and a rotation speed of 200 - 500 rpm to obtain a ball-milled modified graphene oxide slurry with increased carbon defects at the edges of graphene oxide and surface free radical content. The carbon defects at the edges can increase the loading amount during subsequent mercapto modification, and the surface free radicals can scavenge the free radicals generated by the rupture of natural rubber molecular chains caused by heat and oxygen attacks. (2) Add the mercapto-containing silane coupling agent to an alcohol aqueous solution, hydrolyze it for a certain time, adjust the pH, add the ball-milled modified graphene oxide slurry obtained in step (1) under ultrasonic dispersion, heat and react for a certain time, and then freeze-dry to obtain ball-milled-mercapto synergistically modified graphene oxide. (3) Prepare a uniform aqueous dispersion of the ball-milled-mercapto synergistically modified graphene oxide obtained in step (2), then add it to natural rubber latex, stir and mix well to obtain a uniformly dispersed mixed emulsion. Among them, the ball-milled-mercapto synergistically modified graphene oxide will form binding particles with the positive ions of the protein-phospholipid membrane on the surface of rubber particles through electrostatic attraction and remain stable. Add a flocculant. Since the repulsive force between the particles that keeps the emulsion stable decreases, flocculation occurs, and the rubber particles with damaged protective layers and the modified graphene oxide particles will further adsorb each other through the acting force. The binding particles and rubber particles will orderly aggregate and co-precipitate in the aqueous phase. Wash the obtained raw rubber with water, remove water, and dry it to obtain a ball-milled-mercapto synergistically modified graphene / natural rubber masterbatch. (4) Place the ball-milled-mercapto synergistically modified graphene / natural rubber masterbatch prepared in step (3) in an internal mixer, knead it at a certain temperature, sequentially add rubber additives and reinforcing fillers, discharge the rubber compound after uniform dispersion, and cool it to room temperature. Then, open mill the rubber compound at a certain temperature on an open mill, add a vulcanizing agent, mix well, thin pass until there are no bubbles in the rubber compound, let it stand for a certain time, and then place it in a tire mold and vulcanize it at a certain temperature and a certain pressure for a certain time. Then, the natural rubber reacts with the vulcanizing agent to form a vulcanized crosslinked network structure. At the same time, the mercapto-containing silane coupling agent undergoes a vulcanization reaction with the rubber through the mercapto end group to form a unique double crosslinked network structure, and a low heat generation, high thermal conductivity, and long-life solid tire based on high-strength and high-toughness ball-milled-mercapto synergistically modified graphene / natural rubber is obtained.

2. Preparation of a low heat - generating, high - thermal - conductivity, long - life solid tire based on high - strength and high - toughness ball - milling - mercapto synergistically modified graphene / natural rubber according to claim 1, characterized in that, In step (2), the volume ratio of alcohol to water in the alcohol aqueous solution is 5 - 9:1; the hydrolysis time of the mercapto-containing silane coupling agent in the alcohol aqueous solution is 1 - 5 h, and the pH value after hydrolysis is adjusted to 7 - 13; the mercapto-containing silane coupling agent is selected from at least one of (3-mercaptopropyl)trimethoxysilane coupling agent, γ-mercaptopropyltriethoxysilane coupling agent, and bis-[γ-(triethoxysilyl)propyl]tetrasulfide; the mass ratio of the mercapto-containing silane coupling agent to graphene oxide in the ball-milled modified graphene oxide slurry is 1 - 4:1; the heating reaction temperature after adding the ball-milled modified graphene oxide slurry is 60 - 80 °C, and the heating reaction time is 5 - 8 h.

3. Preparation of a low heat - generating, high thermal - conductivity and long - life solid tire based on high - strength and high - toughness ball - milled - mercapto synergistically modified graphene / natural rubber according to claim 1, characterized in that, In step (3), the concentration of the ball-milling-thiol co-modified graphene oxide uniform aqueous dispersion is 0.5-2 wt%, and the mass ratio of the ball-milling-thiol co-modified graphene oxide to natural rubber is 0.25-1.5:100; the flocculant is at least one of calcium chloride solution, sodium chloride solution, hydrochloric acid solution and formic acid solution.

4. Preparation of a low heat - generating, high - thermal - conductivity and long - life solid tire based on high - strength and high - toughness ball - milling - mercapto synergistically modified graphene / natural rubber according to claim 1, characterized in that, In step (4), the addition amounts of the respective raw materials are as follows: 100 parts by mass of natural rubber in the natural rubber masterbatch modified with ball-milling-thiol co-modified graphene, 30-90 parts by mass of reinforcing filler, and 10-20 parts by mass of rubber additives.

5. Preparation of a low heat - generating, high - thermal - conductivity, long - life solid tire based on high - strength and high - toughness ball - milling - mercapto synergistically modified graphene / natural rubber according to claim 1, characterized in that, In step (4), the rubber additives include anti-aging agents, antioxidants, activators, softeners and vulcanization accelerators, and the mass ratio of the anti-aging agent, antioxidant, activator, softener, vulcanization accelerator to the vulcanizing agent is 2:2:5:2:2:

2.

6. Preparation of a low heat - generating, high - thermal - conductivity, long - life solid tire based on high - strength and high - toughness ball - milling - mercapto synergistically modified graphene / natural rubber according to claim 1, characterized in that, In step (4), the reinforcing filler is carbon black, selected from at least one of the types N110, N330 and N660.

7. Preparation of a low heat - generating, high heat - conducting and long - life solid tire based on high - strength and high - toughness ball - milled - mercapto synergistically modified graphene / natural rubber according to claim 1, characterized in that, In step (4), the kneading temperature of the ball-milling-thiol co-modified graphene / natural rubber masterbatch in the internal mixer is 105-120 °C, and the kneading time is 12-20 min; the open-milling temperature in the two-roll mill is 50-70 °C, and the open-milling time is 8-12 min.

8. Preparation of a low heat - generating, high - thermal - conductivity, long - life solid tire based on high - strength and high - toughness ball - milling - mercapto synergistically modified graphene / natural rubber according to claim 1, characterized in that, In step (4), the standing time of the mixed rubber is 18-36 h; the vulcanization temperature is 135-170 °C, the vulcanization pressure is 10-30 MPa, and the vulcanization time is 3-25 min.

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