High-filling-white-carbon-black and low-rolling-resistance all-steel-wire radial tire sidewall composition as well as preparation method and application thereof

Abstract

The invention discloses an all-steel-wire radial tire sidewall composition with high filling white carbon black and low rolling resistance as well as a preparation method and application of the all-steel-wire radial tire sidewall composition. The composition comprises the following components in parts by weight: 50-70 parts of natural rubber, 30-50 parts of butadiene rubber, 8-50 parts of carbon black, 5-35 parts of white carbon black, 2-8 parts of oil, 1-7 parts of a coupling agent, 0-3 parts of resin, 0.5-2 parts of stearic acid, 2-5 parts of zinc oxide, 0-2 parts of a dispersing agent, 3-8 parts of an anti-aging agent, 1.5-3 parts of sulfur, 0.5-2 parts of an accelerant and 0-0.3 part of a scorch retarder. According to the invention, the carbon black and the white carbon black are compounded for reinforcement, and the rolling resistance of the sidewall formula is obviously reduced by reducing the parts of the carbon black, increasing the parts of the white carbon black and reducing the parts of the process oil and the resin. According to the mixing process provided by the invention, the dispersity of filler carbon black and white carbon black is improved, and meanwhile, the problems of unsmooth surface and broken edge when a high-content white carbon black sizing material is extruded into a semi-finished product are solved.

Description

Technical Field

[0001] This invention belongs to the field of tire manufacturing technology, specifically relating to a sidewall composition for all-steel radial tires with high filler silica and low rolling resistance, as well as its preparation method and application. Background Technology

[0002] The statements herein provide only background information in relation to this invention and do not necessarily constitute prior art.

[0003] Rolling resistance is a key indicator of tire performance, directly impacting vehicle energy efficiency, environmental friendliness, safety, and economy. Studies show that a 10% reduction in tire rolling resistance reduces passenger car fuel consumption by 1%-2%; electric vehicle range is even more sensitive to rolling resistance, with a 10% reduction increasing range by 3%-5%. For commercial vehicles, a 1kg / t reduction in rolling resistance reduces CO2 emissions by 1.5g / km; low rolling resistance technology can reduce the vehicle's carbon footprint throughout its entire lifecycle. Tire rolling resistance is primarily driven by energy loss due to material deformation, accounting for 90%-95%. The specific contributions of each component are as follows: Tire crown (tread): Approximately 50%. Repeated deformation during contact with the ground causes frictional heat generation from rubber molecules (primarily internal friction loss). The tread compound and tread pattern design significantly influence rolling resistance. Sidewall: Approximately 15-20%. Sidewall bending deformation leads to additional friction. Internal structure such as belt layers / ply layers: Approximately 15-20%. Pressure deformation of the steel wire or nylon ply layers results in energy loss due to friction between internal structural components.

[0004] Currently, tire manufacturers primarily focus on tread compound and pattern design when addressing rolling resistance reduction. The belt / ply layers are the core supporting system for the mechanical performance of all-steel radial tires; the former enhances handling and durability through circumferential tightening, while the latter ensures structural stability and load capacity through radial load bearing. Therefore, solutions for reducing rolling resistance generally do not alter these key components. However, there are no good solutions for optimizing the sidewall compound.

[0005] In terms of formulation, the sidewalls of all-steel radial tires need to balance flexural strength, fatigue resistance, and crack propagation resistance. The choice of reinforcing carbon black directly affects the overall performance of the rubber compound. Currently, carbon blacks such as N375, N326, N550, and N660 are generally selected, along with a small amount of silica (less than 10 parts) for reinforcement. The compound is generally a mixture of natural rubber and butadiene rubber, with a ratio typically ranging from 70:30 to 50:50. Hydrocarbon resins are added to the compounding agents to increase the dispersion of the rubber phase, and process oils are used to increase plasticity. Although carbon black has better reinforcing properties than silica, it generates more heat and has higher rolling resistance. The high content of small molecules such as process oils, resins, and dispersants also negatively impacts rolling resistance. Based on the above formulation components, the difference in rolling resistance between the sidewall formulations is not significant, making it impossible to achieve a substantial reduction in rolling resistance.

[0006] In terms of the compounding process for the high-precision silica system tire sidewall formulation, conventional rubber compounding processes result in rubber compounds with rough surfaces and edge breakage due to small particles during extrusion of semi-finished products. Qualitative analysis of the small particle samples indicates that this is caused by undispersed and agglomerated silica. Existing formulations, due to their high butadiene rubber content, result in weak shear force during compounding; silica itself is highly polar and difficult to disperse, leading to slow absorption of the colloid and reinforcing agent; and the addition of oil to the formulation further complicates subsequent dispersion. Summary of the Invention

[0007] To overcome the shortcomings of the prior art, the present invention provides a sidewall composition for all-steel radial tires with high filler silica and low rolling resistance, as well as its preparation method and application.

[0008] As a first aspect of the present invention, a sidewall composition for an all-steel radial tire with high-filled silica and low rolling resistance is provided, comprising the following components in parts by weight: 50-70 parts natural rubber, 30-50 parts butadiene rubber, 8-50 parts carbon black, 5-35 parts silica, 2-8 parts oil, 1-7 parts coupling agent, 0-3 parts resin, 0.5-2 parts stearic acid, 2-5 parts zinc oxide, 0-2 parts dispersant, 3-8 parts antioxidant, 1.5-3 parts sulfur, 0.5-2 parts accelerator, and 0-0.3 parts scorching inhibitor.

[0009] With the advent of green tires, silica has been widely used in tire treads. However, due to the polarity difference between silica and the rubber surface, the bonding between silica and the elastomer interface is insufficient. Silica surfaces have numerous highly polar silanol groups, which enhance inter-filler interactions, making it difficult to disperse silica well in non-polar rubber and achieve sufficient interfacial compatibility. To mitigate these negative effects, a certain proportion of silane coupling agents is typically added to improve dispersibility and crosslinking density. However, using silica as the sole reinforcing agent increases production costs and reduces tire abrasion resistance and electrostatic properties. Therefore, the tire industry often blends silica and carbon black (CB) fillers to reinforce rubber for optimal performance and cost-effectiveness.

[0010] Furthermore, in the embodiments provided by the present invention, the amount of silica is higher than the amount of carbon black.

[0011] Preferably, the natural rubber used is one or both of SVR3L composite and STR20 composite. The cis-butadiene rubber used is Nd-based cis-butadiene rubber with cis-1,4 content ≥96.0%, acetone extract ≤1.0%, volatile matter ≤0.75%, and Mooney viscosity ML (100℃, 1+4) of 38-48. The carbon black used is one or more of N375, N326, and N550; The silica used is one or more of SILICA HD175MP, TL-175MP, VN3GR, and rice husk silica, used in combination. The oil used is one of the following: TDAE oil, TUDALEN 5244 environmentally friendly aromatic oil, or MES mineral oil. The resin used is one or more of the following: p-tert-octylphenol formaldehyde resin SL-1801 / SP1068 and tackifying resin SL-1410; the present invention eliminates the use of conventional hydrocarbon resins.

[0012] Hydrocarbon resins are petroleum-based resins that are miscible with rubbers of different polarities. In systems using multiple rubbers (natural rubber and butadiene rubber), their addition can promote better mixing and dispersion of compounding agents and rubber. However, due to the composition of hydrocarbon resins, they contain a large amount of small molecules, which can lead to a decrease in the rolling resistance of the compound.

[0013] The coupling agent used is silane coupling agent TESPT 50% (Si-69 50%); The antioxidants used are two or more of antioxidants RD, antioxidant 4020, antioxidant DTPD, and microcrystalline wax; The accelerators used are one or more of the following: accelerator NS, accelerator CZ, accelerator DZ, accelerator DM, and accelerator DPG80, used in combination. The sulfur used is one of the following: insoluble OT20 or other sulfur powders.

[0014] To reduce the rolling resistance of the tire sidewall, this invention selects carbon black and silica as a compound for reinforcement. By reducing the amount of carbon black, increasing the amount of silica, and reducing the amount of process oil and resin, the rolling resistance of the tire sidewall rubber material is significantly reduced.

[0015] Because the increased amount of silica leads to dispersion difficulties and slow absorption of colloids and reinforcing agents, and because the use of dispersants leads to a decrease in heat generation performance, in order to overcome the contradiction between material dispersibility and heat generation performance, the formulation of this invention does not add dispersants, but adopts a new mixing process to solve this problem.

[0016] Specifically, the present invention ensures the dispersion of compounding agents and carbon black in rubber by employing a three-stage mixing process.

[0017] As a second aspect of the present invention, a method for preparing a sidewall composition of an all-steel radial tire with high-filled silica and low rolling resistance is provided. This method utilizes the fact that silica is easier to disperse in natural rubber than butadiene rubber and optimizes the dispersion of silica by taking advantage of the high shear properties of natural rubber during compounding after plasticizing. The preparation method includes the following steps: Stage 1: In the internal mixer, the added colloids and reinforcing agents are natural rubber plasticized rubber and silica, respectively. Some compounding agents are added in Stage 1, and the mixture is mixed to obtain Stage 1 masterbatch. Stage 2: In the internal mixer, the added colloids and reinforcing agents are Stage 1 masterbatch, butadiene rubber, silica, and some compounding agents, respectively, and the mixture is mixed to obtain Stage 2 masterbatch. Stage 3: Stage 2 masterbatch is added to the internal mixer and remixed to further improve the dispersion of each component, resulting in Stage 3 masterbatch. In the final mixing, Stage 3 masterbatch, sulfur, accelerator, and anti-scorching agent are added, and the mixture is mixed to obtain a high-filled silica, low rolling resistance all-steel radial tire sidewall compound.

[0018] Furthermore, before the mixing step, a plasticized natural rubber compound is prepared. The plasticizing method for natural rubber is as follows: natural rubber is added to a mixer and mixed to obtain the plasticized compound, which is then left to stand for 4-10 hours for later use. Plasticizing the natural rubber results in better dispersion of silica.

[0019] The compounding agents added to one stage include stearic acid, resin, and half the amount of antioxidant.

[0020] The compounding agents added in the second stage include the remaining amount of antioxidant, as well as zinc oxide and oil.

[0021] As is generally accepted in the industry, in rubber compound formulations where silica is the main filler, adding zinc oxide and silica together can interfere with the dispersion and silanization of silica, negatively impacting the compound's performance. It is generally believed that adding zinc oxide during the final compounding stage can improve compound performance. To overcome the negative impact of zinc oxide on silica dispersion, this invention proposes adding it in the second stage.

[0022] This invention utilizes the reduced viscosity of natural rubber after plasticizing, increasing its fluidity and making it easier to wet silica, thus reducing its tendency to agglomerate. Simultaneously, the high shear force during the initial mixing stage further facilitates the breakdown of silica aggregates. Therefore, plasticizing natural rubber improves the dispersion of silica, solving the dispersion problem caused by high silica content.

[0023] As a third aspect of the invention, it provides the application of a high-filling silica, low rolling resistance all-steel radial tire sidewall composition in the preparation of tire sidewalls.

[0024] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention provides the components and proportions of a sidewall composition for an all-steel radial tire with high-filled silica and low rolling resistance. This invention selects carbon black and silica for reinforcement, and by reducing the amount of carbon black, increasing the amount of silica, and reducing the amount of process oil and resin, the rolling resistance of the sidewall formulation is significantly reduced; this helps to reduce the overall rolling resistance of the tire.

[0025] 2. This invention provides a new mixing process for the sidewall composition of all-steel radial tires, which improves the dispersion of silica and carbon black. Even if the silica content in the composition provided by this invention is higher than the conventional amount, this process reduces rolling resistance and overcomes the problems of uneven surface and edge breakage caused by small particles that occur when extruding semi-finished products using conventional mixing processes for high silica content rubber compounds.

[0026] 3. The composition provided by the present invention eliminates the use of dispersants, reducing the impact on heat generation performance; and improves the material dispersion performance by improving the mixing process. Attached Figure Description

[0027] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0028] Figure 1 The remaining sample after high-temperature burning of the product in Example 5 was white granules.

[0029] Figure 2 Infrared spectral scanning was performed on the white particles after burning of the product in Example 5.

[0030] Figure 3 The white granular sample of Example 5 was completely dissolved in hydrofluoric acid.

[0031] Figure 4 The results of the carbon black / silica filler dispersion test for Examples 5 and 1 are shown, where a is the dispersion of Example 5 and b is the dispersion of Example 1.

[0032] Figure 5 This shows the performance of the rubber compound in Example 5 during actual calendering and extrusion of semi-finished products.

[0033] Figure 6 This is the performance of the rubber compound in Example 1 during actual calendering and extrusion of semi-finished products.

[0034] Figure 7 The rolling resistance performance of the products in the comparative examples and embodiments is characterized by RPA Tanδ (60°C). Detailed Implementation

[0035] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0036] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0037] Terminology Explanation: Rubber compound: A rubber compound made by mixing raw rubber or plasticized rubber with reinforcing agents and compounding agents according to the formulation components using a rubber mixing mill. Rubber compound is the raw material for manufacturing rubber products. It is then processed into semi-finished products with specific dimensions and shapes using calenders, extruders, and other related equipment. Therefore, the uniformity of dispersion of the components in the rubber compound directly affects the quality of the finished product, and also influences the processing performance of the rubber compound and its subsequent processing capabilities, such as molding, extrusion, calendering, and pressing.

[0038] Semi-finished products: In the manufacturing process of all-steel radial tires, the semi-finished products required for forming include belt layer, sidewall, inner liner, bead wrapping, tread, etc.; after the semi-finished products are produced in the extrusion process, they are wound and formed.

[0039] Rolling resistance refers to the force that hinders movement caused by material deformation, friction, and energy loss during tire rolling. Essentially, it is the continuous conversion of mechanical energy (the kinetic energy driving the wheels) into heat energy. It is the third largest source of energy loss in vehicle operation, after air resistance and transmission losses.

[0040] "Powder absorption" is a crucial stage in the rubber mixing process, referring to the process of uniformly mixing powdered fillers such as carbon black and silica into the rubber through mechanical shearing in an internal mixer. Essentially, the filler particles are encapsulated by rubber molecules, forming a preliminary dispersed mixture that lays the foundation for subsequent dispersion and homogenization.

[0041] Common rubber compounding agents include reinforcing fillers, vulcanizing agents, plasticizers, antioxidants, and accelerators. Generally speaking, the production process of rubber products includes two main parts: compounding and molding / vulcanization. In addition to the mixing process of the rubber matrix and processing aids, the most important aspect of rubber compounding technology is the selection of various compounding agents.

[0042] In the current technology, tire manufacturers mainly focus on the design of tread compound and tread pattern to reduce rolling resistance. The performance requirements of the tread and the sidewall are different, and their compositions are also different.

[0043] Since the tread is in direct contact with the ground and is the most easily worn part of the tire, its compound needs to meet the following core performance requirements: 1. Abrasion resistance and mileage life; 2. Resistance to wet skids and traction; 3. Cut and puncture resistance; 4. Low rolling resistance and fuel efficiency. Butadiene rubber (BR) has poor tear resistance, wet traction, and aging performance due to its molecular structure; therefore, the amount of BR used in tread compounds generally does not exceed 30 parts.

[0044] The sidewall primarily bears flexural stress and protects the tire carcass. Its formulation needs to meet the following core properties: 1. Resistance to flexural cracking; 2. Ozone / aging resistance; 3. Resistance to mechanical damage; 4. Low heat generation. Based on these requirements, the sidewall formulation's raw rubber system needs to incorporate a higher amount of BR (Brassic Rubber), typically between 30-55 parts. The antioxidant dosage is above 5.5%, higher than in the tread formulation.

[0045] To address the issues of high rolling resistance and poor product strength in tire sidewalls prepared using existing technologies, this invention provides a high-filling silica, low rolling resistance all-steel radial tire sidewall composition, its preparation method, and its application.

[0046] In one or more embodiments of the present invention, a sidewall composition for an all-steel radial tire with high-filled silica and low rolling resistance is provided, comprising the following components in parts by weight: 50-70 parts natural rubber, 30-50 parts butadiene rubber, 8-50 parts carbon black, 5-35 parts silica, 2-8 parts oil, 1-7 parts coupling agent, 0-3 parts resin, 0.5-2 parts stearic acid, 2-5 parts zinc oxide, 0-2 parts dispersant, 3-8 parts antioxidant, 1.5-3 parts sulfur, 0.5-2 parts accelerator, and 0-0.3 parts scorching inhibitor.

[0047] Furthermore, the composition does not contain a dispersant and comprises the following components in parts by weight: 50-70 parts natural rubber, 30-50 parts butadiene rubber, 8-50 parts carbon black, 5-35 parts silica, 2-8 parts oil, 1-7 parts coupling agent, 0-3 parts resin, 0.5-2 parts stearic acid, 2-5 parts zinc oxide, 3-8 parts antioxidant, 1.5-3 parts sulfur, 0.5-2 parts accelerator, and 0-0.3 parts scorch inhibitor.

[0048] Furthermore, the composition comprises the following components in parts by weight: 50-70 parts natural rubber, 30-50 parts butadiene rubber, 8-25 parts carbon black, 25-28 parts silica, 2-8 parts oil, 1-7 parts coupling agent, 0-3 parts resin, 0.5-2 parts stearic acid, 2-5 parts zinc oxide, 3-8 parts antioxidant, 1.5-3 parts sulfur, 0.5-2 parts accelerator, and 0-0.3 parts scorching inhibitor.

[0049] Furthermore, in the technical solution provided by this invention, the amount of silica is higher than the amount of carbon black.

[0050] Furthermore, the composition comprises the following components in parts by weight: 60 parts natural rubber, 40 parts butadiene rubber, 12 parts carbon black, 28 parts silica, 3.8 parts oil, 5.6 parts coupling agent, 1.5 parts resin, 1 part stearic acid, 3.2 parts zinc oxide, 6 parts antioxidant, 2.3 parts sulfur, 1.7 parts accelerator, and 0.2 parts scorching inhibitor.

[0051] In one or more embodiments of the present invention, the natural rubber used is one or both of SVR3L composite rubber and STR20 composite rubber.

[0052] In one or more embodiments of the present invention, the cis-butadiene rubber used is Nd-based cis-butadiene rubber with a cis-1,4 content ≥96.0%, acetone extract ≤1.0%, volatile matter ≤0.75%, and Mooney viscosity ML (100℃, 1+4) of 38-48.

[0053] In one or more embodiments of the present invention, the carbon black used is one or more of N375, N326, and N550 used in combination.

[0054] In one or more embodiments of the present invention, the silica used is one or more of SILICA HD175MP, TL-175MP, VN3GR, and rice husk ash silica.

[0055] In one or more embodiments of the present invention, the oil used is one of TDAE oil, TUDALEN5244 and other environmentally friendly aromatic oils, or MES (sodium methyl ester sulfonate) mineral oil.

[0056] In one or more embodiments of the present invention, the resin used is one or more of p-tert-octylphenol formaldehyde resin SL-1801 / SP1068 and tackifying resin SL-1410, and the use of conventional hydrocarbon resins is eliminated in the composition components.

[0057] In one or more embodiments of the present invention, the coupling agent used is silane coupling agent TESPT 50% (Si-69 50%).

[0058] In one or more embodiments of the present invention, the antioxidant used is two or more of antioxidant RD, antioxidant 4020, antioxidant DTPD, and microcrystalline wax.

[0059] In one or more embodiments of the present invention, the accelerator used is one or more of the following: sulfenamide accelerator NS, accelerator CZ, accelerator DZ, thiazole accelerator DM, and guanidine accelerator DPG80.

[0060] In one or more embodiments of the present invention, the sulfur used is one of different sulfur powders such as OT20.

[0061] However, the study found that when the content of silica is high, the silica cannot be fully dispersed into the rubber using conventional mixing processes. This limits the increase in the amount of silica added, resulting in the inability to guarantee the rolling resistance and physical properties of the product.

[0062] To address the aforementioned problems arising from increasing the content of silica, this invention also provides a mixing preparation method. In one or more embodiments of the present invention, the preparation method includes the following steps: S1, Natural Rubber Plasticizing: Set the internal mixer rotor speed to 42-47 rpm, the three-zone water temperature (mixing chamber, rotor, discharge gate) to 35±5℃, and the top bolt pressure to 5.4Mpa±0.3Mpa. Add natural rubber to the internal mixer and mix for 35 seconds. Then raise the bolt, the rotor speed to 35-45 rpm, press the bolt down for 30-40 seconds, raise the bolt again, the rotor speed to 35-45 rpm, press the bolt down again, mix for 15-35 seconds, and discharge the rubber at 150-160℃ to obtain plasticized rubber. Let it stand for 4-10 hours for later use.

[0063] S2, First stage mixing: Set the internal mixer rotor speed to 45-50 rpm, the three-zone water temperature (internal mixing chamber, rotor, discharge gate) to 35±5℃, and the top bolt pressure to 5.4Mpa±0.3Mpa. Add the plasticized rubber obtained in step S1, as well as silica and silane coupling agent, to the internal mixer and mix for 45-60 seconds until the temperature reaches 120-130℃. Then raise the bolt and rotate the rotor speed to 43-48 rpm. Add the oil and compounding agents (stearic acid, resin, antioxidant) to the internal mixer and mix until the temperature reaches 145-153℃. Raise the bolt and rotate the rotor speed to 35-45 rpm for 15-25 seconds. Then press the bolt again and mix until the temperature reaches 158-163℃ before discharging the rubber to obtain the first stage masterbatch. Let it stand for 4-10 hours for later use.

[0064] S3, Two-stage mixing: Set the internal mixer rotor speed to 38-43 rpm, the three-zone water temperature (mixing chamber, rotor, discharge gate) to 35±5℃, and the top bolt pressure to 5.4Mpa±0.3Mpa. Add the first-stage masterbatch rubber, butadiene rubber, carbon black, and compounding agents (antioxidant, zinc oxide, oil) obtained in step S2 to the internal mixer and mix for 30-40 seconds. Then raise the bolt, set the rotor speed to 33-38 rpm, add the oil to the internal mixer, and press the bolt to mix to 138-142℃. Raise the bolt, set the rotor speed to 20-30 rpm, and press the bolt to 155-160℃ to discharge the rubber, obtaining the second-stage masterbatch rubber. Let it stand for 4-10 hours for later use.

[0065] S4, Three-stage mixing: Set the internal mixer rotor speed to 38-43 rpm, the water temperature in the three zones (internal mixing chamber, rotor, and discharge gate) to 35±5℃, and the pressure of the top bolt to 5.4Mpa±0.3Mpa. Add the two-stage masterbatch obtained in step S3 to the internal mixer and mix for 30-40 seconds. Then raise the bolt, the rotor speed to 33-38 rpm, press the bolt down for 30-40 seconds, raise the bolt again, the rotor speed to 33-38 rpm, press the bolt down again, and mix for 15-35 seconds. Mix until the temperature reaches 148-153℃ and discharge the rubber to obtain the three-stage masterbatch. Let it stand for 4-10 hours for later use.

[0066] S5, Final mixing: Set the internal mixer rotor speed to 20-35 rpm, the three-zone water temperature (mixing chamber, rotor, discharge gate) to 30±5℃, and the top bolt pressure to 4.5Mpa±0.3Mpa. Add the three-stage masterbatch rubber, sulfur, accelerator, and anti-scorching agent obtained in step S4 to the internal mixer, mix for 25-35 seconds, raise the bolt and lower the bolt, mix for 25-35 seconds, raise the bolt, set the rotor speed to 15-25 rpm, lower the bolt, and mix until 95-110℃ before discharging the rubber to obtain a tire sidewall rubber compound.

[0067] Example 1: Formulation Components and Material Requirements S1, Natural Rubber Plasticizing: Rotor speed 45 rpm, three-zone water temperature (mixing chamber, rotor, discharge gate) 35±5℃, top bolt pressure 5.5Mpa, add the above natural rubber into the mixing mill and mix for 35 seconds, then raise the bolt, rotor speed 35-45 rpm, press the bolt for 35 seconds, raise the bolt, rotor speed 35 rpm, press the bolt again, mix for 15-35 seconds, mix to 150-160℃ and discharge the rubber to obtain plasticized rubber, let it stand for 4-10 hours for later use.

[0068] S2, First stage mixing: Rotor speed 45-50 rpm, three-zone water temperature (mixing chamber, rotor, discharge gate) 35±5℃, top bolt pressure 5.5Mpa, add the above plasticized rubber, fumed silica, and silane coupling agent to the mixing mill and mix for 45-60 seconds until the temperature reaches 120-130℃, then raise the bolt and rotate the rotor at 43-48 rpm. Add 2 parts of oil and compounding agents (stearic acid, resin, and 3 parts of antioxidant) to the mixing mill and mix until the temperature reaches 145-153℃. Raise the bolt and rotate the rotor at 40 rpm for 20 seconds, then press the bolt again and mix until the temperature reaches 160℃ to discharge the rubber, obtaining the first stage masterbatch. Let it stand for 4-10 hours for later use.

[0069] S3, two-stage mixing, rotor speed 40 rpm, three-zone water temperature (mixing chamber, rotor, discharge door) 35±5℃, top bolt pressure 5.5Mpa, add the above first-stage masterbatch, butadiene rubber, carbon black, compounding agents (3 parts antioxidant, zinc oxide, oil) into the internal mixer and mix for 35 seconds, then raise the bolt, rotor speed 35 rpm, add 1.8 parts oil into the internal mixer, press the bolt and mix to 140℃, raise the bolt, rotor speed 25 rpm, press the bolt to 155-160℃ and discharge the rubber to obtain the second-stage masterbatch, let it stand for 4-10 hours for later use.

[0070] S4, three-stage mixing: rotor speed 35 rpm, water temperature in three zones (mixing chamber, rotor, discharge gate) 35±5℃, top bolt pressure 5.5Mpa, add the above two-stage masterbatch into the mixer and mix for 35 seconds, then raise the bolt, rotor speed 35 rpm, press the bolt for 35 seconds, raise the bolt, rotor speed 35 rpm, press the bolt again, mix for 15-35 seconds, mix to 150℃ and discharge the rubber to obtain the three-stage masterbatch, let it stand for 4-10 hours for later use.

[0071] S5, final mixing: rotor speed 20-35 rpm, three-zone water temperature (mixing chamber, rotor, discharge gate) 30±5℃, top bolt pressure 4.5Mpa, add the above three-stage masterbatch, sulfur, accelerator, and anti-scorching agent to the internal mixer, mix for 25-35 seconds, raise and lower the bolt, mix for 25-35 seconds, raise the bolt, rotor speed 15-25 rpm, lower the bolt, mix to 95-110℃ and discharge the rubber to obtain a tire sidewall rubber compound.

[0072] Comparative Example 1, the conventional compounding preparation steps are as follows: First stage of mixing: Rotor speed 45-50 rpm, water temperature in three zones (mixing chamber, rotor, discharge gate) 35±5℃, top jack pressure 5.5Mpa. Add natural rubber, butadiene rubber, silica, carbon black, and compounding agents (except sulfur, accelerator, and anti-scorching agent) to the mixing mill and mix for 35 seconds. Then raise the jack and rotate the rotor at 40-45 rpm. Add oil to the mixing mill and mix for 30-35 rpm. Raise the jack and rotate the rotor at 35 rpm. Mix until 160-163℃ and discharge the rubber to obtain the first stage of masterbatch. Let it stand for 4-10 hours for later use.

[0073] Two-stage mixing: Rotor speed 35 rpm, three-zone water temperature (mixing chamber, rotor, discharge gate) 35±5℃, top bolt pressure 5.5Mpa, add the above-mentioned first-stage masterbatch into the mixer and mix for 35 seconds, then raise the bolt, rotor speed 35 rpm, press the bolt for 35 seconds, raise the bolt, rotor speed 35 rpm, press the bolt again, mix for 15-35 seconds, mix to 150℃ and discharge the rubber to obtain the second-stage masterbatch, let it stand for 4-10 hours for later use.

[0074] Final mixing: Rotor speed 20-35 rpm, three-zone water temperature (mixing chamber, rotor, discharge gate) 30±5℃, top bolt pressure 4.5Mpa, add the above three-stage masterbatch, sulfur, accelerator, and anti-scorching agent to the internal mixer, mix for 25-35 seconds, raise and lower the bolt, mix for 25-35 seconds, raise the bolt, rotor speed 15-25 rpm, lower the bolt, mix to 95-110℃ and discharge the rubber to obtain a tire sidewall rubber compound.

[0075] Using the component ratios shown in Table 1, compound rubber products were prepared according to the preparation method provided in the embodiments of the present invention and conventional mixing methods, respectively. It should be noted that Comparative Example 1 and Examples 3-5 all used conventional mixing methods to obtain compound rubber, while Examples 1-2 used the mixing steps and methods mentioned in the embodiments of the present invention to obtain compound rubber.

[0076] Table 1. Material proportions for comparative and example cases

[0077] As is a consensus in the industry, the use of dispersants leads to a decrease in heat generation performance; therefore, no dispersant was used in Examples 1 and 5.

[0078] The natural rubber used is a combination of SVR3L composite and STR20 composite in a 1:1 ratio; The cis-butadiene rubber used is Nd-based cis-butadiene rubber with cis-1,4 content ≥96.0%, acetone extract ≤1.0%, volatile matter ≤0.75%, and Mooney viscosity ML (100℃, 1+4) of 38-48. The carbon black used was N375; The silica used was SILICA HD175MP. The oil used is environmentally friendly aromatic oil TUDALEN 5244; The resin used is a mixture of two types: p-tert-octylphenol formaldehyde resin SL-1801 / SP1068 and tackifying resin SL-1410, in a ratio of 1:1. The coupling agent used is silane coupling agent TESPT 50% (Si-69 50%); the ratio of its addition amount to the addition amount of silica is conventionally 1:5. The antioxidants used are antioxidant RD, antioxidant 4020, and microcrystalline wax, and the conventional dosage in this field is sufficient. The accelerator used is accelerator NS; The sulfur used is one of the following: insoluble OT20 or other sulfur powders.

[0079] The amounts of oil, resin, stearic acid, sulfur, accelerator, and anti-scorching agent added are adjusted according to the amount of filler to ensure that the T90 vulcanization performance is between 14.03% and 5%.

[0080] Experimental Example 1: The qualitative analysis of extruded small particles was performed by taking the tire sidewall rubber compound prepared in Example 5 with high silica content and conventional mixing process and conducting the following tests: 1, such as Figure 1 As shown, the remaining sample after high-temperature burning (600℃) is white granules.

[0081] 2. Perform infrared spectral scanning on the white sample, such as... Figure 2 As shown, the main component of the white particles is silica.

[0082] 3. White samples were verified by dissolving them in hydrofluoric acid, such as... Figure 3 As shown, the white granular sample was completely dissolved in hydrofluoric acid.

[0083] It is evident that conventional mixing processes cannot guarantee that silica is fully dispersed in the rubber compound.

[0084] Experimental Example 2: This invention measures the properties of the rubber compounds prepared in the comparative examples and embodiments described above. The tests include evaluation of mechanical properties, heat generation properties, and fatigue properties. The evaluation methods are as follows: 1. Mechanical property evaluation: The tensile stress and tensile properties were tested according to GB / T528-2009, and the tear properties were tested according to GB / T528-2008. The higher the value, the better the relevant properties.

[0085] 2. Evaluation of rolling resistance / heat generation performance: Evaluation was performed using a rubber processing analyzer (RPA). The specific method involved setting the temperature to 151℃, the strain to 7%, and the frequency to 1.67Hz, allowing the conditions to stabilize for 2 minutes. The test specimen was then vulcanized for 30 minutes. The temperature was then lowered to 60℃, the frequency to 10Hz, and the strain to 7% for further testing. The loss factor tanδ was selected as the evaluation index. A larger tanδ value indicates poorer rolling resistance.

[0086] 3. Evaluation of bending fatigue performance: Tests were conducted according to GB / T1687.1-2016 and GB / T1687.3-2016 methods. The number of cycles required for the sample to reach crack grade 1 was used as the evaluation criterion; the higher the value, the better the fatigue performance.

[0087] 4. Evaluation of vulcanization performance: The rubber vulcanizing tester MDR2000 was used according to the GB / T 16584 method, with test conditions of 150℃ × 60 min. T90 was selected as the evaluation index. The larger the T90 value, the slower the vulcanization speed.

[0088] 5. Mixing process / dispersion evaluation: For Examples 5 and 1, the dispersibility of carbon black / white carbon black was evaluated using a carbon black dispersibility tester (model: 91001SR) according to the method of GB / T 6030-2006. The larger the X value and Y value, the better the dispersion state of the filler.

[0089] The test results are shown in Table 2 and Figure 7 As shown.

[0090] Table 2, Summary of Detection Data in Comparative Examples and Examples

[0091] The performance data of the rubber compounds in Comparative Example 1 and Examples 1-5 show that increasing the content of silica can significantly reduce rolling resistance in Examples 1 and 5, even with a 7% decrease in tensile product and a 12% decrease in flexural fatigue performance. The rolling resistance performance is improved by about 45%.

[0092] As described in the background section, the rolling resistance performance of the sidewall components contributes approximately 15%-20% to the tire's overall performance. A 45% increase in sidewall rolling resistance results in an approximately 7%-9% increase in tire rolling resistance and a roughly 2.1%-4.5% increase in vehicle range. Improved sidewall rolling resistance also helps mitigate heat accumulation during tire movement, thus positively impacting tire performance.

[0093] Table 3 compares the carbon black dispersion test data of the rubber compounds produced in Examples 1 and 5. Figure 4 As shown: Table 3. Carbon black dispersion test data of the rubber compounds produced in Examples 1 and 5

[0094] It should be noted that the carbon black dispersibility tester evaluates dispersibility by observing the distribution of particles in vulcanized rubber chips and is applicable to both carbon black and silica. Because the silica content in the tire sidewall formulation provided by this invention is much higher than that of carbon black, the test data obtained using the carbon black dispersibility tester is primarily dominated by silica.

[0095] The data above shows that the rubber compound produced using the mixing process of this scheme in Example 1 has high dispersion of silica and carbon black, and... Figure 5 and Figure 6 As can be seen from the comparison, the surface edge breakage phenomenon of the high-white carbon black-filled tire sidewall compound produced by the mixing process of this scheme is significantly improved during the actual calendering and extrusion of semi-finished products.

[0096] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A sidewall composition for an all-steel radial tire with high silica filling and low rolling resistance, characterized in that, It includes the following components in parts by weight: 50-70 parts natural rubber, 30-50 parts butadiene rubber, 8-50 parts carbon black, 5-35 parts silica, 2-8 parts oil, 1-7 parts coupling agent, 0-3 parts resin, 0.5-2 parts stearic acid, 2-5 parts zinc oxide, 0-2 parts dispersant, 3-8 parts antioxidant, 1.5-3 parts sulfur, 0.5-2 parts accelerator, and 0-0.3 parts scorching inhibitor.

2. The sidewall composition of a high-filled silica, low-rolling-resistance all-steel radial tire according to claim 1, characterized in that, The composition does not contain a dispersant and comprises the following components in parts by weight: 50-70 parts natural rubber, 30-50 parts butadiene rubber, 8-50 parts carbon black, 5-35 parts silica, 2-8 parts oil, 1-7 parts coupling agent, 0-3 parts resin, 0.5-2 parts stearic acid, 2-5 parts zinc oxide, 3-8 parts antioxidant, 1.5-3 parts sulfur, 0.5-2 parts accelerator, and 0-0.3 parts scorch inhibitor.

3. The sidewall composition of a high-filled silica, low-rolling-resistance all-steel radial tire according to claim 1, characterized in that, The composition comprises the following components in parts by weight: 60-70 parts natural rubber, 30-40 parts butadiene rubber, 8-20 parts carbon black, 25-28 parts silica, 2-8 parts oil, 1-7 parts coupling agent, 0-3 parts resin, 0.5-2 parts stearic acid, 2-5 parts zinc oxide, 3-8 parts antioxidant, 1.5-3 parts sulfur, 0.5-2 parts accelerator, and 0-0.3 parts scorching inhibitor.

4. The sidewall composition of a high-filled silica, low-rolling-resistance all-steel radial tire according to claim 1, characterized in that, The amount of silica is higher than the amount of carbon black.

5. The sidewall composition of a high-filled silica, low-rolling-resistance all-steel radial tire according to claim 1, characterized in that, The natural rubber used is one or both of SVR3L composite and STR20 composite.

6. The sidewall composition of a high-filled silica, low-rolling-resistance all-steel radial tire according to claim 1, characterized in that, The carbon black used is one or more of N375, N326, and N550; The silica used is one or more of SILICA HD175MP, TL-175MP, VN3GR, and rice husk ash silica, used in combination.

7. A method for preparing a sidewall composition for all-steel radial tires with high-filled silica and low rolling resistance, characterized in that, Includes the following steps: First stage mixing: In the internal mixer, the added colloids and reinforcing agents are natural rubber plasticized rubber and silica, respectively. Some compounding agents are added in the first stage, and the mixture is mixed to obtain the first stage masterbatch. Two-stage mixing: In the internal mixer, the added colloids and reinforcing agents are the first-stage masterbatch, butadiene rubber, carbon black and some compounding agents, which are mixed to obtain the second-stage masterbatch; Three-stage mixing: The second-stage masterbatch is added to the internal mixing rubber and then mixed to obtain the third-stage masterbatch; Final mixing: Add the three-stage masterbatch rubber, sulfur, accelerator and anti-scorching agent, and mix to obtain a compound rubber compound of high-filled silica and low rolling resistance for the sidewall of all-steel radial tires.

8. The method for preparing the sidewall composition of a high-filled silica, low rolling resistance all-steel radial tire according to claim 7, characterized in that, Before the mixing step, prepare natural rubber plasticizer. The natural rubber plasticizer is prepared by adding natural rubber into an internal mixer and mixing to obtain plasticizer, which is then left to stand for 4-10 hours for later use.

9. The method for preparing the sidewall composition of a high-filled silica, low rolling resistance all-steel radial tire according to claim 7, characterized in that, The compounding agents added in the first stage include stearic acid, resin, and half of the antioxidant; the compounding agents added in the second stage include the remaining antioxidant, as well as zinc oxide and oil.

10. The use of the high-filled silica, low rolling resistance all-steel radial tire sidewall composition of claim 1 in the preparation of tire sidewalls.

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