Tensile tire sidewall rubber with high cutting resistance and impact resistance and preparation method thereof

Abstract

The invention relates to the field of rubber formulas and manufacturing processes, and provides high-cutting-resistance and impact-resistance side wall rubber of a tensile tire and a preparation method of the high-cutting-resistance and impact-resistance side wall rubber. The sidewall rubber is prepared from components in parts by weight as follows: 60-80 parts of natural rubber, 10-20 parts of emulsion polymerized styrene-butadiene rubber, 10-20 parts of butadiene rubber, 30-40 parts of carbon black, 10-25 parts of white carbon black, 1-5 parts of carbon nanotubes, 1-3 parts of a silane coupling agent, 1-3 parts of tear-resistant resin, 1.5-2 parts of stearic acid, 2-3 parts of zinc oxide, 2-5 parts of an anti-aging agent, 1-2 parts of protective wax, 1-2 parts of an accelerant and 1-2 parts of sulfur. According to the invention, a ternary polymer matrix of natural rubber / emulsion polymerized styrene-butadiene rubber / butadiene rubber is adopted to balance strength, rigidity and toughness, a ternary composite reinforcing system taking carbon black as a main body, a small amount of white carbon black as an auxiliary and carbon nanotubes as a key reinforcing phase is constructed, and the problem of dispersion of the carbon nanotubes is effectively solved by utilizing a multi-section mixing process.

Description

Technical Field

[0001] This invention relates to the field of rubber formulation and manufacturing process, specifically to a high-cut-resistant and impact-resistant rally tire sidewall rubber and its preparation method. Background Technology

[0002] The sidewall of a rally tire is its weakest point. On tracks full of sharp gravel and broken logs, the sidewall faces the dual deadly threats of cutting (long, narrow wounds caused by lateral shear force) and impact (holes caused by vertical punctures). Once the sidewall is punctured, the tire will quickly lose pressure, causing the car to retire from the race.

[0003] Traditional tire sidewall rubber has a long service life. To achieve better flexural resistance, a blend of natural rubber (NR) and high-cis-butadiene rubber (BR) is typically used. NR provides high strength and tear resistance, while BR offers excellent elasticity and low heat generation. However, this system has inherent drawbacks: BR has low strength, and NR softens easily at high temperatures. When subjected to high-speed impacts from sharp objects, the rubber compound is insufficient to resist penetration, and puncture holes tend to enlarge rapidly due to stress concentration.

[0004] Emulsion styrene-butadiene rubber (ESBR, such as 1502) has high tensile strength, tensile stress and hardness, which can effectively improve the "rigidity" of the rubber compound and thus resist the intrusion of foreign objects. However, it has high heat generation and poor elasticity. Simply adding ESBR will damage the fatigue resistance of the tire sidewall.

[0005] Carbon nanotubes (CNTs), as one-dimensional nanomaterials, theoretically possess a strength approximately 100 times that of steel, while also exhibiting extremely high toughness and aspect ratio. Theoretically, applying them to tire sidewall rubber could reinforce the rubber matrix like "steel bars." However, CNTs are highly prone to aggregation and are difficult to disperse within the rubber matrix. Uneven dispersion can create stress concentration points, leading to performance degradation. Therefore, the scientific microstructural design of CNTs in conjunction with ESBR, NR, and BR for effective application in tire sidewall rubber, synergistic effects with other components (such as carbon black and silica), and the achievement of perfect application through advanced processing techniques, remains a significant technological challenge.

[0006] Furthermore, there is a lack of mature solutions in the current technology for successfully applying carbon nanotubes to tire sidewalls and effectively solving their cut resistance and impact resistance problems. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a rally tire sidewall compound with high cut resistance and impact resistance, as well as its preparation method. To address the technical challenge of rally tire sidewalls being easily cut or impacted by sharp stones under extreme road conditions, leading to instantaneous pressure loss or bulging, this invention employs a ternary polymer matrix of natural rubber / latex styrene-butadiene rubber / cis-butadiene rubber to balance strength, rigidity, and toughness. It constructs a ternary composite reinforcement system with carbon black as the main component, a small amount of silica as an auxiliary component, and carbon nanotubes as the key reinforcing phase. In this system, the high amount of carbon black provides solid basic strength and modulus; the fibrous carbon nanotubes, through their large aspect ratio, bridge the carbon black aggregates, forming a through-hole three-dimensional reinforcing network, much like adding "nano-steel bars" to concrete. Through efficient stress transfer, crack bridging, and fiber pull-out mechanisms, the tear strength of the material is significantly improved; the small amount of silica further optimizes the filler network density. The multi-stage mixing process provided by this invention effectively solves the problem of carbon nanotube dispersion. This tire sidewall rubber has achieved a breakthrough in cut resistance and impact resistance, fully meeting the demanding requirements of top-level rally racing.

[0008] To achieve the above technical objectives, the technical solution adopted in the embodiments of the present invention is as follows: In a first aspect, embodiments of the present invention provide a high-cut-resistant and impact-resistant rally tire sidewall compound, comprising the following components by weight: 60-80 parts natural rubber, 10-20 parts latex styrene-butadiene rubber, 10-20 parts butadiene rubber, 30-40 parts carbon black, 10-25 parts silica, 1-5 parts carbon nanotubes, 1-3 parts silane coupling agent, 1-3 parts tear-resistant resin, 1.5-2 parts stearic acid, 2-3 parts zinc oxide, 1-2.5 parts antioxidant 4020, 1-2.5 parts antioxidant RD, 1-2 parts protective wax, 1-2 parts accelerator, and 1-2 parts sulfur, wherein the total number of parts of natural rubber, latex styrene-butadiene rubber, and butadiene rubber is 100 parts.

[0009] Furthermore, the butadiene rubber is selected from one of BR9000, BR9106, CB22, CB24 and BR40.

[0010] Furthermore, the carbon nanotubes are multi-walled carbon nanotubes with a length of 3-12 μm, a diameter of 10-15 nm, and a specific surface area of ​​240-290 m² / g.

[0011] Furthermore, the silica is selected from 165MP, 175MP and 195MP, and the tear-resistant resin is a DCPD resin; The silane coupling agent is selected from Si69 and Si75; The accelerator is selected from at least one of sulfenamides, thiazoles, thiurams, and guanidines.

[0012] Secondly, embodiments of the present invention provide a method for preparing the high cut-resistant and impact-resistant rally tire sidewall rubber described in the first aspect, comprising the following steps by weight: Step S1, First stage mixing: Put carbon nanotube masterbatch, the remaining 30%-50% natural rubber, emulsion styrene-butadiene rubber and cis-butadiene rubber into the internal mixer, press the top plug, hold and then raise the top plug, add all carbon black and silica, press the top plug, hold and then raise the top plug, then add silane coupling agent, tear-resistant resin, antioxidant, protective wax and stearic acid, press the top plug, raise the top plug after reaching a certain temperature, hold and then press the top plug to maintain the constant temperature for a period of time before discharging the rubber to obtain the first stage masterbatch; Step S2, two-stage mixing: After the first stage masterbatch has been left to stand for 4-24 hours, put it back into the internal mixer, add zinc oxide, press the top plug, hold, then raise the top plug, press the top plug, hold, then raise the top plug, press the top plug, hold until a certain temperature is reached, then discharge the rubber to obtain the second stage masterbatch. In order to avoid the influence of zinc oxide on the silanization reaction, zinc oxide is added in the second stage. Step S3, three-stage mixing: After the two-stage compound has been left to stand for 4-24 hours, it is added to the internal mixer for further mixing to obtain the three-stage compound, which further promotes the dispersion of the reinforcing agent and reduces the Mooney viscosity. Step S4, Final Mixing: After the three-stage masterbatch has been left to stand for 4-24 hours, put it into an internal mixer, add accelerator and sulfur, mix to a certain temperature and then discharge the rubber to obtain the final rubber of the rally tire sidewall with high cut resistance and impact resistance.

[0013] Further, in step S1, the carbon nanotube masterbatch is prepared as follows: Plasticize 50%-70% of the total natural rubber in an internal mixer, then add all the carbon nanotubes, press the top plug and mix the rubber compound at a speed of 50-60 rpm, a top plug pressure of 0.5-0.6 MPa, and a plug mixing time of 20-30 seconds. After three press plugs, the discharge temperature is 155-165℃, and a well-dispersed carbon nanotube masterbatch is obtained.

[0014] Further, in step S1, the parameters for the first bolt lifting and repressing mixing are: rotation speed of 50-55 rpm, repressing mixing time of 20-25 seconds, and top bolt pressure of 0.5-0.6 MPa; the parameters for the second bolt lifting and repressing mixing are: rotation speed of 45-50 rpm, repressing mixing time of 15-25 seconds, and top bolt pressure of 0.5-0.6 MPa; the parameters for the third bolt lifting and repressing mixing are: rotation speed of 40-45 rpm, top bolt pressure of 0.5-0.6 MPa, and bolt lifting temperature of 150-155℃; the parameters for the fourth bolt lifting and repressing mixing are: rotation speed of 20-25 rpm, top bolt pressure of 0.2-0.3 MPa, and constant temperature mixing time of 150-155℃ for 30-50 seconds.

[0015] Furthermore, in step S2, the parameters for secondary mixing are: rotation speed of 40-45 rpm, top bolt pressure of 0.5-0.6 MPa, press the top bolt and hold for 20-30 seconds, increase the pressure of the top bolt and hold for 20-30 seconds, increase the pressure of the top bolt, and discharge the glue after the temperature rises to 150-155℃.

[0016] Furthermore, in step S3, the parameters for the three-stage mixing are: rotation speed of 35-40 rpm, top bolt pressure of 0.5-0.6 MPa, press the top bolt and hold for 20-30 seconds, increase the pressure of the top bolt, and discharge the glue after the temperature rises to 150-155℃.

[0017] Furthermore, in step S4, the final mixing parameters are: rotation speed of 22-26 rpm, top bolt pressure of 0.3-0.5 MPa, three pressure boosting bolts, mixing time of 20-25 seconds for each step, and discharge temperature of 100-105℃.

[0018] The beneficial effects of the technical solution provided by the embodiments of the present invention are as follows: (1) Through the synergistic effect of the ternary rubber system and the three-dimensional composite reinforcement system, especially the three-dimensional bridging network formed by carbon nanotubes, the sidewall rubber achieves a breakthrough improvement in tear strength, tensile stress and cut resistance while maintaining good flexural fatigue resistance.

[0019] (2) Constructing a three-dimensional reinforcing network: Carbon nanotubes and silica / carbon black form a “point-line-surface” composite reinforcing structure. The fibrous carbon nanotubes bridge and penetrate between silica aggregates to form a more stable reinforcing network, which greatly improves tensile stress, tear strength and impact resistance.

[0020] (3) Excellent damage resistance: The tear-resistant resin and carbon nanotube network jointly construct a multi-level damage resistance mechanism. The carbon nanotube network, as the physical framework, strongly inhibits the macroscopic propagation of cracks; the tear-resistant resin, as the energy dissipation unit, effectively passivates the crack tip. The two complement each other and jointly improve the impact and tear resistance of the material.

[0021] (4) Good durability: The good thermal conductivity of carbon nanotubes helps to reduce the heat generation of the rubber compound under dynamic deformation and delay thermal aging. At the same time, its excellent fatigue properties further extend the service life of the tire sidewall.

[0022] (5) Process innovation ensures performance: By pre-preparing the "carbon nanotube masterbatch", the carbon nanotube aggregates are opened first under high shear force, which lays a solid foundation for the uniform mixing with carbon black and silica in the future, and ensures the stability of the final product performance. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0024] Example 1 A high-cut-resistant and impact-resistant rally tire sidewall compound, comprising, by weight, the following components: 60 parts natural rubber, 20 parts latex styrene-butadiene rubber, 20 parts butadiene rubber BR9000, 40 parts N234 carbon black, 15 parts silica 175MP, 1.5 parts carbon nanotubes GT-300, 2.4 parts silane coupling agent SI69, 2 parts tear-resistant resin SL6903, 2 parts stearic acid, 3 parts zinc oxide, 1.5 parts antioxidant 4020, 1.5 parts antioxidant RD, 1.5 parts protective wax HG72, 1.3 parts accelerator CZ, and 1.1 parts sulfur.

[0025] The preparation method of the above-mentioned high cut-resistant and impact-resistant rally tire sidewall rubber includes the following steps by weight: Step S1, Preparation of carbon nanotube masterbatch: Plasticize 60% of the total natural rubber (36 parts) in an internal mixer, then add all the carbon nanotubes, press the top plug and mix the rubber compound at a speed of 55 rpm, a top plug pressure of 0.6 MPa, and a plug mixing time of 30 s. Then, press the top plug twice, each time for 20 s, and then perform a final press plug mixing. The discharge temperature is 160℃. Step S2, First stage mixing: Add carbon nanotube masterbatch, the remaining 40% of natural rubber (24 parts), emulsion styrene-butadiene rubber and cis-butadiene rubber to the internal mixer, press the top plug, the pressure of the top plug is 0.6 MPa, the speed is 50 rpm, press the plug and mix for 20 seconds, then raise the top plug, add all carbon black and silica, press the top plug, the pressure of the top plug is 0.6 MPa, the speed is 50 rpm, press the plug and mix for 20 seconds, then raise the top plug, add silane coupling agent, tear-resistant resin, antioxidant, protective wax and stearic acid, press the top plug, the pressure of the top plug is 0.6 MPa, the speed is 45 rpm, when the mixing temperature reaches 150℃, raise the top plug, hold for 5 seconds, then press the top plug, the pressure of the top plug is 0.3 MPa, the speed is 22 rpm, mix at a constant temperature of 150℃ for 35 seconds, then discharge the rubber to obtain the first stage masterbatch; Step S3, Second-stage mixing: Put the first-stage masterbatch back into the internal mixer after it has been left to stand, add zinc oxide, press the top plug, the pressure of the top plug is 0.6MPa, the speed is 45 rpm, press the top plug and mix for 30 seconds, then raise the top plug and press the top plug, press the top plug and mix for 25 seconds, then raise the top plug and press the top plug, press the top plug and mix until it reaches 150℃, then discharge the rubber to obtain the second-stage masterbatch; Step S4, three-stage mixing: Add the two-stage compound to the internal mixer, with the top jack pressure at 0.6 MPa and the speed at 35 rpm. Press the top jack down and mix for 30 seconds. Then raise the top jack down and press the top jack down again. After mixing at 150°C, discharge the compound to obtain the three-stage masterbatch. Step S5, Final Mixing: Put the three sections of masterbatch after resting into the internal mixer, add accelerator and sulfur, set the top plug pressure to 0.4 MPa, the speed to 25 rpm, and press the plug three times. The mixing time for the first two presses is 25 seconds. When mixing at 105℃ for the last press, discharge the rubber to obtain a high cut resistance and impact resistance rally tire sidewall final mix.

[0026] Example 2 A high-cut-resistant and impact-resistant rally tire sidewall compound, by weight, comprises the following components: 65 parts natural rubber, 15 parts latex styrene-butadiene rubber, 20 parts butadiene rubber BR9000, 40 parts N234 carbon black, 15 parts silica 175MP, 1.5 parts carbon nanotubes GT-300, 2.4 parts silane coupling agent SI69, 2 parts tear-resistant resin SL6903, 2 parts stearic acid, 3 parts zinc oxide, 1.5 parts antioxidant 4020, 1.5 parts antioxidant RD, 1.5 parts protective wax HG72, 1.3 parts accelerator CZ, and 1.1 parts sulfur.

[0027] The preparation method of the above-mentioned high cut-resistant and impact-resistant rally tire sidewall rubber includes the following steps by weight: Step S1, Preparation of carbon nanotube masterbatch: Plasticize 60% of the total natural rubber (39 parts) in an internal mixer, then add all the carbon nanotubes, press the top plug and mix the rubber compound at a speed of 55 rpm, a top plug pressure of 0.6 MPa, and a plug mixing time of 30 s. Then, press the top plug twice, each time for 20 s, and then perform a final press plug mixing. The discharge temperature is 160℃. Step S2, First stage mixing: Add carbon nanotube masterbatch, the remaining 40% of natural rubber (26 parts), emulsion styrene-butadiene rubber and cis-butadiene rubber to the internal mixer, press the top plug, the pressure of the top plug is 0.6 MPa, the speed is 50 rpm, press the plug and mix for 25 seconds, then raise the top plug, add all carbon black and silica, press the top plug, the pressure of the top plug is 0.6 MPa, the speed is 50 rpm, press the plug and mix for 25 seconds, then raise the top plug, add silane coupling agent, tear-resistant resin, antioxidant, protective wax and stearic acid, press the top plug, the pressure of the top plug is 0.6 MPa, the speed is 45 rpm, when the mixing temperature reaches 150℃, raise the top plug, hold for 5 seconds, then press the top plug, the speed is 22 rpm, the pressure of the top plug is 0.3 MPa, mix at a constant temperature of 150℃ for 35 seconds, then discharge the rubber to obtain the first stage masterbatch; Step S3, Second-stage mixing: Put the first-stage masterbatch back into the internal mixer after it has been left to stand, add zinc oxide, press the top plug, the pressure of the top plug is 0.6MPa, the speed is 45 rpm, press the top plug and mix for 30 seconds, then raise the top plug and press the top plug, press the top plug and mix for 25 seconds, then raise the top plug and press the top plug, press the top plug and mix until it reaches 150℃, then discharge the rubber to obtain the second-stage masterbatch; Step S4, three-stage mixing: Add the two-stage compound to the internal mixer, with the top jack pressure at 0.6 MPa and the speed at 35 rpm. Press the top jack down and mix for 30 seconds. Then raise the top jack down and press the top jack down again. After mixing at 150°C, discharge the compound to obtain the three-stage masterbatch. Step S5, Final Mixing: Put the three sections of masterbatch after resting into the internal mixer, add accelerator and sulfur, set the top plug pressure to 0.4 MPa, the speed to 25 rpm, and press the plug three times. The mixing time for the first two presses is 25 seconds. When mixing at 105℃ for the last press, discharge the rubber to obtain a high cut resistance and impact resistance rally tire sidewall final mix.

[0028] Example 3 A high-cut-resistant and impact-resistant rally tire sidewall compound, by weight, comprises the following components: 70 parts natural rubber, 15 parts latex styrene-butadiene rubber, 15 parts butadiene rubber BR9000, 40 parts N234 carbon black, 15 parts silica 175MP, 2.5 parts carbon nanotubes GT-300, 2.4 parts silane coupling agent SI69, 2 parts tear-resistant resin SL6903, 2 parts stearic acid, 3 parts zinc oxide, 1.5 parts antioxidant 4020, 1.5 parts antioxidant RD, 1.5 parts protective wax HG72, 1.3 parts accelerator CZ, and 1.1 parts sulfur.

[0029] The preparation method of the above-mentioned high cut-resistant and impact-resistant rally tire sidewall rubber includes the following steps by weight: Step S1, Preparation of carbon nanotube masterbatch: Plasticize 60% of the total natural rubber (42 parts) in an internal mixer, then add all the carbon nanotubes, press the top plug and mix the rubber compound at a speed of 55 rpm, a top plug pressure of 0.6 MPa, and a plug mixing time of 30 s. Then, press the top plug twice, each time for 20 s, and then perform a final press plug mixing. The discharge temperature is 160℃. Step S2, First stage mixing: Add carbon nanotube masterbatch, the remaining 40% of natural rubber (28 parts), emulsion styrene-butadiene rubber and cis-butadiene rubber to the internal mixer, press the top plug, the pressure of the top plug is 0.6 MPa, the speed is 50 rpm, press the plug and mix for 25 seconds, then raise the top plug, add all carbon black and silica, press the top plug, the pressure of the top plug is 0.6 MPa, the speed is 50 rpm, press the plug and mix for 20 seconds, then raise the top plug, add silane coupling agent, tear-resistant resin, antioxidant, protective wax and stearic acid, press the top plug, the pressure of the top plug is 0.6 MPa, the speed is 45 rpm, when the mixing temperature reaches 150℃, raise the top plug, hold for 5 seconds, then press the top plug, the speed is 22 rpm, the pressure of the top plug is 0.3 MPa, mix at a constant temperature of 150℃ for 40 seconds, then discharge the rubber to obtain the first stage masterbatch; Step S3, Second-stage mixing: Put the first-stage masterbatch back into the internal mixer after it has been left to stand, add zinc oxide, press the top plug, the pressure of the top plug is 0.6MPa, the speed is 45 rpm, press the top plug and mix for 30 seconds, then raise the top plug and press the top plug, press the top plug and mix for 25 seconds, then raise the top plug and press the top plug, press the top plug and mix until it reaches 150℃, then discharge the rubber to obtain the second-stage masterbatch; Step S4, three-stage mixing: Add the two-stage compound to the internal mixer, with the top jack pressure at 0.6 MPa and the speed at 35 rpm. Press the top jack down and mix for 30 seconds. Then raise the top jack down and press the top jack down again. After mixing at 150°C, discharge the compound to obtain the three-stage masterbatch. Step S5, Final Mixing: Put the three sections of masterbatch after resting into the internal mixer, add accelerator and sulfur, set the top plug pressure to 0.4 MPa, the speed to 25 rpm, and press the plug three times. The mixing time for the first two presses is 25 seconds. When mixing at 105℃ for the last press, discharge the rubber to obtain a high cut resistance and impact resistance rally tire sidewall final mix.

[0030] Comparative Example 1 A conventional tire sidewall rubber comprises the following components in parts by weight: 50 parts natural rubber, 50 parts butadiene rubber BR9000, 48 parts N326 carbon black, 7 parts environmentally friendly oil, 1 part stearic acid, 3 parts zinc oxide, 3 parts antioxidant 4020, 1 part antioxidant RD, 1.5 parts protective wax, 0.9 parts accelerator CZ, and 2 parts sulfur.

[0031] The above-mentioned conventional tire sidewall rubber preparation method, by weight, includes the following steps: Step S1, First stage mixing: Natural rubber, butadiene rubber, carbon black, stearic acid, zinc oxide, antioxidant, and protective wax are put into an internal mixer. The top plug is pressed down, with a pressure of 0.6 MPa and a speed of 50 rpm. After mixing for 25 seconds, the top plug is raised. Environmentally friendly oil is added, and the top plug is pressed down again, with a pressure of 0.6 MPa and a speed of 50 rpm. After mixing for 25 seconds, the top plug is raised again, and the top plug is pressed down again, with a pressure of 0.6 MPa and a speed of 45 rpm. After mixing for 15 seconds, the top plug is raised again. When the mixing temperature reaches 150℃, the rubber is discharged to obtain the first stage masterbatch. Step S2, two-stage mixing: Add the first-stage compound to the internal mixer, with the top jack pressure at 0.6 MPa and the speed at 45 rpm. Press the top jack and mix for 30 seconds. Then raise the top jack, press the top jack, and mix until 150°C. Discharge the compound to obtain the second-stage masterbatch. Step S3, Final Mixing: The rested second-stage masterbatch is put into an internal mixer, accelerator and sulfur are added, the pressure of the top plug is 0.4MPa, the speed is 25 rpm, the pressure is increased three times, the mixing time of the first two pressure plugs is 30s, and the rubber is discharged when the mixing reaches 105℃ after the last pressure plug, to obtain a conventional tire sidewall final compound.

[0032] Comparative Example 2 A rally tire sidewall compound, comprising, by weight, the following components: 60 parts natural rubber, 20 parts latex styrene-butadiene rubber, 20 parts butadiene rubber BR9000, 40 parts N234 carbon black, 15 parts silica 175MP, 4 parts silane coupling agent SI692, 2 parts tear-resistant resin SL6903, 2 parts stearic acid, 3 parts zinc oxide, 1.5 parts antioxidant 4020, 1.5 parts antioxidant RD, 1.5 parts protective wax HG72, 1.3 parts accelerator CZ, and 1.1 parts sulfur.

[0033] The above-mentioned method for preparing rally tire sidewall rubber includes the following steps, by weight: Step S1, First stage mixing: Natural rubber, latex styrene-butadiene rubber, and butadiene rubber are put into an internal mixer, the top plug is pressed down, the pressure of the top plug is 0.6 MPa, the speed is 50 rpm, and after mixing for 20 seconds, the top plug is raised, all carbon black and silica are added, the top plug is pressed down, the pressure of the top plug is 0.6 MPa, the speed is 50 rpm, and after mixing for 20 seconds, the top plug is raised, then silane coupling agent, tear-resistant resin, antioxidant, protective wax, and stearic acid are added, the top plug is pressed down, the pressure of the top plug is 0.6 MPa, the speed is 45 rpm, and when the mixing temperature reaches 150℃, the top plug is raised, held for 5 seconds, and then the top plug is pressed down, the pressure of the top plug is 0.3 MPa, the speed is 22 rpm, and after mixing at a constant temperature of 150℃ for 35 seconds, the rubber is discharged to obtain the first stage masterbatch; Step S2, Second-stage mixing: Put the first-stage masterbatch back into the internal mixer after it has been left to stand, add zinc oxide, press the top plug, the pressure of the top plug is 0.6MPa, the speed is 45 rpm, press the plug and mix for 30 seconds, then raise the top plug, press the top plug and mix for 25 seconds, then raise the top plug and press the top plug, press the plug and mix until it reaches 150℃, then discharge the rubber to obtain the second-stage masterbatch; Step S3, Three-stage mixing: Add the two-stage compound to the internal mixer, with the top jack pressure at 0.6 MPa and the speed at 35 rpm. Press the top jack and mix for 30 seconds. Then raise the top jack, press the top jack again, and mix until the temperature reaches 150°C before discharging the compound to obtain the three-stage masterbatch.

[0034] Step S4, Final Mixing: The three sections of masterbatch after resting are put into an internal mixer, accelerator and sulfur are added, the pressure of the top plug is 0.4MPa, the speed is 25 rpm, the pressure is increased three times, the mixing time of the first two pressure plugs is 25s, and the rubber is discharged when the mixing reaches 105℃ after the last pressure plug, to obtain a high cut resistance and impact resistance rally tire sidewall final compound.

[0035] The sidewall rubbers prepared in Examples 1-3 and Comparative Examples 1-2 of this invention were subjected to performance tests, with vulcanization conditions of 150℃ for 40 minutes. There is currently a lack of unified testing methods and standards in China for evaluating the dynamic cut resistance of rubber materials. The cut resistance evaluation described in this patent was conducted according to the company's internal testing methods. The equipment used was a rubber dynamic cut resistance testing machine manufactured by Beijing Wanhui Yifang Technology Development Co., Ltd. Under a certain load (static load 475g), a cutting blade of specified sharpness (cutting blade tip angle of 60°) was used to repeatedly impact a rotating rubber wheel (rubber wheel speed 720rpm) at a certain frequency (impact speed 120 times / min) within a specified time (20 minutes). This simulates the rubber impacting a sharp object with considerable force, resulting in surface penetration or cutting. The volume loss before and after the test (obtained by dividing the weight difference by the specific gravity of the rubber compound) was compared to characterize the cut and impact resistance of the rubber compound. Hardness was tested according to GB / T531.1-2008, tensile strength according to GB / T528-2009, tear strength according to GB / T529-2008, density according to GB / T533-2008, and flexural cracking and crack growth according to GB / T13934-2006.

[0036] Table 1. Performance comparison of tire sidewall rubbers in Examples 1-3 and Comparative Examples 1-2

[0037] As can be seen from the above data, the high cut-resistant and impact-resistant rally tire sidewall rubbers prepared in Examples 1-3 of this invention exhibit increased hardness and significantly improved tear and cut resistance compared to the conventional tire sidewall rubber of Comparative Example 1, providing better cut resistance and impact resistance. In particular, compared to Comparative Example 2 (without carbon nanotubes), with the rubber system being exactly the same, Example 1 shows approximately 21% higher tear strength and approximately 34% improved cut resistance. This fully demonstrates that carbon nanotubes play a decisive role in the composite reinforcing system of this invention, rather than simply being a superposition of components.

[0038] Analysis of the data from Examples 1-3 and Comparative Example 1 shows that the hardness of the Examples is increased by approximately 12 values ​​compared to the Comparative Example, the tensile strength is increased by more than 49%, the elongation at break is similar, the tear strength is increased by approximately 190%, the cut resistance is increased by approximately 48%, and the flexural resistance can reach 300,000 cycles without cracking (rally tires have a short service life, and 300,000 cycles can meet the usage requirements), and heat generation is reduced. Compared with Comparative Example 2, the core tear and cut resistance properties have also achieved a qualitative leap. Although the tensile strength decreases after aging, the Examples are still significantly better than the Comparative Example.

[0039] Traditional tire sidewalls use a combination of NR and BR. This invention, however, employs a ternary system of NR / ESBR / BR. NR provides high strength and toughness, ESBR provides high modulus and rigidity, serving as the first line of defense against foreign object intrusion; BR ensures the fatigue resistance and low heat generation of the rubber compound under large deformations, balancing the disadvantages of ESBR.

[0040] Traditional tire sidewall rubber uses a pure carbon black system, while this invention employs a composite reinforcement system combining carbon black, silica, and carbon nanotubes. Carbon black serves as both the "main component" and the "matrix" of the reinforcement system. A high dosage of carbon black constructs a robust, high-modulus basic reinforcement network, providing extremely high tensile stress, tensile strength, and hardness. This directly increases the "intrusion threshold" of the sidewall rubber, forcing sharp objects to require greater force to penetrate. The addition of a small amount of silica further fills the gaps between the carbon black networks, making the filler network denser and contributing to improved wet grip and dynamic heat generation of the compound.

[0041] The core role of carbon nanotubes lies in constructing a three-dimensional network bridge. Fibrous carbon nanotubes can span and penetrate multiple carbon black aggregates, "pinning" and "weaving" the carbon black network, which was originally mainly connected by van der Waals forces, into a more complete and robust three-dimensional continuous network. This "carbon black-carbon nanotube" network has a much higher integrity and modulus than a simple carbon black network. When a crack occurs, the "bridging effect" of carbon nanotubes becomes crucial. It strongly holds the two sides of the crack, and due to its extremely high strength, the crack cannot easily break it. For the crack to propagate, the carbon nanotubes must be "pulled out" of the matrix, a process that consumes a huge amount of energy, macroscopically manifested as a sharp increase in tear strength. High tear strength means that the material has an extremely strong ability to resist crack propagation, which directly translates into excellent performance in that the cut is not easily propagated when cut and the hole is not easily torn and enlarged when punctured. In addition, stress diffusion and passivation mechanisms allow the carbon nanotube network to disperse the concentrated stress at the puncture point to a wider area, avoiding rapid failure caused by excessive local stress.

[0042] Therefore, this invention, by constructing a composite reinforcing system using a ternary rubber system as the matrix and incorporating carbon black, silica, and carbon nanotubes, successfully and significantly improved the tear strength of the tire sidewall rubber, directly resulting in a leapfrog improvement in cut resistance and impact resistance. All embodiments are significantly superior to traditional formulations, and a comparison with Comparative Example 2 clearly demonstrates that carbon nanotubes are the key element in achieving this breakthrough, thus achieving the purpose of the invention.

[0043] Finally, it should be noted that the above specific embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A sidewall rubber compound for rally tires with high cut resistance and impact resistance, characterized in that, By weight, it comprises the following components: 60-80 parts natural rubber, 10-20 parts emulsion styrene-butadiene rubber, 10-20 parts butadiene rubber, 30-40 parts carbon black, 10-25 parts silica, 1-5 parts carbon nanotubes, 1-3 parts silane coupling agent, 1-3 parts tear-resistant resin, 1.5-2 parts stearic acid, 2-3 parts zinc oxide, 1-2.5 parts antioxidant 4020, 1-2.5 parts antioxidant RD, 1-2 parts protective wax, 1-2 parts accelerator, and 1-2 parts sulfur, wherein the total number of parts of natural rubber, emulsion styrene-butadiene rubber, and butadiene rubber is 100 parts.

2. The high cut-resistant and impact-resistant rally tire sidewall rubber according to claim 1, characterized in that, The butadiene rubber is selected from one of BR9000, BR9106, CB22, CB24 and BR40.

3. The high cut-resistant and impact-resistant rally tire sidewall rubber according to claim 1, characterized in that, The carbon nanotubes are multi-walled carbon nanotubes with a length of 3-12 μm, a diameter of 10-15 nm, and a specific surface area of ​​240-290 m² / g.

4. The high cut-resistant and impact-resistant rally tire sidewall rubber according to claim 1, characterized in that, The silica is selected from 165MP, 175MP and 195MP, and the tear-resistant resin is dicyclopentadiene resin. The silane coupling agent is selected from Si69 and Si75; The accelerator is selected from at least one of sulfenamides, thiazoles, thiurams, and guanidines.

5. The method for preparing the high cut-resistant and impact-resistant rally tire sidewall rubber according to any one of claims 1-4, characterized in that, By weight, the following steps are included: Step S1, First stage mixing: Put carbon nanotube masterbatch, the remaining 30%-50% natural rubber, emulsion styrene-butadiene rubber and cis-butadiene rubber into the internal mixer, press the top plug, hold and then raise the top plug, add all carbon black and silica, press the top plug, hold and then raise the top plug, then add silane coupling agent, tear-resistant resin, antioxidant, protective wax and stearic acid, press the top plug, raise the top plug after reaching a certain temperature, hold and then press the top plug to maintain the constant temperature for a period of time before discharging the rubber to obtain the first stage masterbatch; Step S2, two-stage mixing: After the first stage masterbatch has been left to stand for 4-24 hours, put it back into the internal mixer, add zinc oxide, press the top plug, hold, then raise the top plug, press the top plug, hold, then raise the top plug, press the top plug, hold until a certain temperature is reached, then discharge the rubber to obtain the second stage masterbatch. Step S3, three-stage mixing: After the two-stage compound has been left to stand for 4-24 hours, it is added to the internal mixer for further mixing to obtain the three-stage compound. Step S4, Final Mixing: After the three-stage masterbatch has been left to stand for 4-24 hours, put it into an internal mixer, add accelerator and sulfur, mix to a certain temperature and then discharge the rubber to obtain the final rubber of the rally tire sidewall with high cut resistance and impact resistance.

6. The method for preparing the high cut-resistant and impact-resistant rally tire sidewall rubber according to claim 5, characterized in that, In step S1, the carbon nanotube masterbatch is prepared as follows: Plasticize 50%-70% of the total natural rubber in an internal mixer, then add all the carbon nanotubes, press the top plug and mix the rubber compound at a speed of 50-60 rpm, a top plug pressure of 0.5-0.6 MPa, and a plug mixing time of 20-30 seconds. After three press plugs, the discharge temperature is 155-165℃, and a well-dispersed carbon nanotube masterbatch is obtained.

7. The method for preparing the high cut-resistant and impact-resistant rally tire sidewall rubber according to claim 5, characterized in that, In step S1, the parameters for the first bolt lifting and re-pressing mixing are: rotation speed of 50-55 rpm, pressing time of 20-25 seconds, and top bolt pressure of 0.5-0.6 MPa; the parameters for the second bolt lifting and re-pressing mixing are: rotation speed of 45-50 rpm, pressing time of 15-25 seconds, and top bolt pressure of 0.5-0.6 MPa; the parameters for the third bolt lifting and re-pressing mixing are: rotation speed of 40-45 rpm, top bolt pressure of 0.5-0.6 MPa, and bolt lifting temperature of 150-155℃; the parameters for the fourth bolt lifting and re-pressing mixing are: rotation speed of 20-25 rpm, top bolt pressure of 0.2-0.3 MPa, and constant temperature mixing time of 150-155℃ for 30-50 seconds.

8. The method for preparing the high cut-resistant and impact-resistant rally tire sidewall rubber according to claim 5, characterized in that, The parameters for the secondary mixing in step S2 are as follows: rotation speed is 40-45 rpm, top bolt pressure is 0.5-0.6 MPa, press the top bolt and hold for 20-30 seconds, increase the pressure of the top bolt and hold for 20-30 seconds, increase the pressure of the top bolt, and discharge the glue after the temperature rises to 150-155℃.

9. The method for preparing the high cut-resistant and impact-resistant rally tire sidewall rubber according to claim 5, characterized in that, The parameters for the three mixing steps in step S3 are as follows: rotation speed is 35-40 rpm, top bolt pressure is 0.5-0.6 MPa, press the top bolt and hold for 20-30 seconds, increase the pressure of the top bolt, and discharge the glue after the temperature rises to 150-155℃.

10. The method for preparing the high cut-resistant and impact-resistant rally tire sidewall rubber according to claim 5, characterized in that, The parameters for the final mixing in step S4 are: rotation speed of 22-26 rpm, top pressure of 0.3-0.5 MPa, three pressure boosting plugs, mixing time of 20-25 seconds for each step, and discharge temperature of 100-105℃.

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