Sidewall rubber composition as well as preparation method and application thereof

Abstract

The invention relates to a sidewall rubber composition as well as a preparation method and application thereof. The sidewall rubber composition comprises the following components in parts by weight: 40-48 parts of natural rubber, 55-75 parts of butadiene rubber, 10-30 parts of regenerated rubber, 2-3 parts of a lignin modified anti-aging agent, 3-5.5 parts of an active agent, 4-8 parts of a homogenizing agent, 1-4 parts of octyl phenolic resin, 0.5-1.8 parts of an accelerant, 45-65 parts of carbon black, 2-10 parts of operating oil and 0.4-3 parts of sulfur. The sidewall rubber composition provided by the invention has good aging resistance, flex cracking resistance and mechanical properties, and is not easy to cause blooming and discoloration problems.

Description

Technical Field

[0001] This invention relates to the field of rubber technology, and in particular to a tire sidewall rubber composition, its preparation method, and its application. Background Technology

[0002] The tire sidewall is a crucial component of the tire structure, primarily protecting the tire carcass cords from damage. Therefore, the rubber compound in the sidewall requires excellent flexural strength, ozone resistance, weather resistance, and good adhesion. Currently, most antioxidants used in China are p-phenylenediamine-based, with N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD) being the most commonly used. This is because it effectively addresses sidewall aging issues—dynamic ozone cracking and flexural weakness. It is typically combined with quinoline antioxidants (TMQ, providing long-lasting antioxidant protection) and paraffin wax (providing a physical barrier) to form a synergistic antioxidant system. The main advantages of this system are its superior dynamic protection performance and mature reliability. Disadvantages include the risk of blooming, discoloration, and environmental pressures faced by the core component, 6PPD.

[0003] Therefore, it is necessary to develop a sidewall rubber composition with good anti-aging properties, dynamic protection properties, and that is not prone to blooming and discoloration. Summary of the Invention

[0004] To solve the above-mentioned technical problems, the present invention provides a sidewall rubber composition, its preparation method and application, wherein the sidewall rubber composition has good anti-aging properties, flexural crack resistance and mechanical properties, and is not prone to blooming and discoloration problems.

[0005] To achieve this objective, the present invention adopts the following technical solution: In a first aspect, the present invention provides a sidewall rubber composition comprising, by weight, the following components: 40-48 parts of natural rubber (e.g., 43, 44, 45, 46, or 47 parts, etc.), 55-75 parts of butadiene rubber (e.g., 58, 61, 64, 67, 70, or 73 parts, etc.), 10-30 parts of reclaimed rubber (e.g., 12, 14, 16, 18, 20, 22, 24, 26, or 28 parts, etc.), 2-3 parts of lignin-modified antioxidant (e.g., 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, or 2.9 parts, etc.), and 3-5.5 parts of activator (e.g., 3.3, 3.6, 3.9, 4.2, 4.5, 4. 8 parts, 5.1 parts, or 5.4 parts, etc.), homogenizer 4-8 parts (e.g., 4.5 parts, 5 parts, 5.5 parts, 6 parts, 6.5 parts, 7 parts, or 7.5 parts, etc.), octylphenol resin 1-4 parts (e.g., 1.5 parts, 2 parts, 2.5 parts, 3 parts, or 3.5 parts, etc.), accelerator 0.5-1.8 parts (0.7 parts, 0.9 parts, 1.1 parts, 1.3 parts, 1.5 parts, or 1.7 parts, etc.) 45-65 parts carbon black (e.g., 47, 49, 51, 53, 55, 57, 59, 61 or 63 parts, etc.), 2-10 parts processing oil (e.g., 3, 4, 5, 6, 7, 8 or 9 parts, etc.), and 0.4-3 parts sulfur (e.g., 0.7, 1, 1.3, 1.6, 1.9, 2.2, 2.5 or 2.8 parts, etc.).

[0006] In this invention, a lignin-modified antioxidant is used instead of a traditional antioxidant to improve the problem of discoloration in the sidewall rubber composition. The lignin molecule contains abundant phenolic hydroxyl groups (-OH) and ether functional groups. In particular, catechol endows lignin with a strong free radical scavenging ability, which can quench free radicals and chelate metal ions. Simultaneously, the lignin molecule contains a large number of aromatic rings and other conjugated systems, which are natural ultraviolet light absorbing groups. It can effectively absorb ultraviolet light in the UV-B (wavelength 280~315nm) and UC-A (wavelength 315~400nm) wavelength ranges and convert the light energy into low-energy heat energy. Furthermore, as a high-molecular-weight three-dimensional network polymer, lignin molecules can be well dispersed in the rubber matrix, forming a certain physical barrier to prevent the diffusion and penetration of oxygen and ozone in the rubber matrix. The hydrogen bonding of hydroxyl functional groups in lignin can interact with rubber; therefore, the addition of a lignin-modified antioxidant to the sidewall rubber composition can improve tensile strength. Lignin itself is dark brown or even black. Lignin-modified antioxidants can better color rubber in tires, improving the problems of blooming and discoloration in traditional antioxidant systems. Furthermore, lignin-modified antioxidants are bio-based modified materials, possessing environmentally friendly and sustainable characteristics. However, lignin itself has high polarity, resulting in poor compatibility with rubber molecules. This invention uses a homogenizing agent and increases its proportion, which significantly improves the compatibility between the lignin-modified antioxidant and rubber molecules, achieving excellent mechanical properties.

[0007] In this invention, the octylphenol resin serves as a tackifier and vulcanizer.

[0008] Preferably, the activator includes zinc oxide and stearic acid.

[0009] Preferably, the mass ratio of zinc oxide to stearic acid is (0.6~7):1, for example, 1:1, 2:1, 3:1, 4:1, 5:1 or 6:1.

[0010] Preferably, the natural rubber includes SMR20 type natural rubber.

[0011] Preferably, the butadiene rubber includes BR9000 type butadiene rubber.

[0012] Preferably, the recycled rubber includes Wuxi Wanfeng high-strength recycled rubber.

[0013] Preferably, the lignin-modified antioxidant includes Kobot antioxidant HS-L501.

[0014] Preferably, the carbon black includes N330 type carbon black.

[0015] Preferably, the homogenizer comprises a 40MS type homogenizer.

[0016] Preferably, the accelerator comprises dibenzothiazole disulfide (accelerator DM).

[0017] Preferably, the operating oil comprises aromatic oil.

[0018] In a second aspect, the present invention provides a method for preparing the sidewall rubber composition as described in the first aspect, the method comprising the following steps: mixing natural rubber, butadiene rubber, reclaimed rubber, lignin-modified antioxidant, activator, homogenizer, octylphenol resin, accelerator, carbon black, processing oil and sulfur to obtain the sidewall rubber composition.

[0019] Preferably, the preparation method includes the following steps: (1) mixing natural rubber, butadiene rubber, reclaimed rubber, lignin-modified antioxidant, zinc oxide, stearic acid, homogenizer, octylphenol resin, carbon black and processing oil to obtain a masterbatch; (2) mixing the masterbatch obtained in step (1), accelerator and sulfur to obtain the sidewall rubber composition.

[0020] Preferably, the mixing in step (1) includes internal mixing.

[0021] Preferably, the mixing in step (2) includes sequential internal mixing and open mixing.

[0022] Thirdly, the present invention provides the application of the sidewall rubber composition as described in the second aspect in an all-steel radial tire.

[0023] Compared with the prior art, the present invention has at least the following beneficial effects: The sidewall rubber composition of this invention incorporates a lignin-modified antioxidant to replace the traditional antioxidant system. While ensuring anti-aging performance meets tire usage requirements, it exhibits better environmental characteristics, superior mechanical properties, and effectively improves the discoloration problem that easily occurs in traditional antioxidant systems. The sidewall rubber composition has an aging coefficient ≥0.512; tensile strength before aging ≥15.9 MPa; and tear strength before aging ≥73.2 kN / m. Preferably, the aging coefficient of the sidewall rubber composition is ≥0.574. Attached Figure Description

[0024] Figure 1 Physical images of the sidewall rubber compositions provided in Examples 1, 2, 1, and 2; Figure 2 The images show the tire sidewall rubber compositions provided in Examples 1, 2, 1, and 2 after being sun-dried outdoors for one day. Figure 3 The images show the tire sidewall rubber compositions provided in Examples 1, 2, Comparative Example 1, and Comparative Example 2 after being sun-dried outdoors for 2 days. Figure 4 The images show the sidewall rubber compositions provided in Examples 1, 2, 1, and 2 after being sun-dried outdoors for 7 days. Detailed Implementation

[0025] To facilitate understanding of the present invention, the following embodiments are provided. Those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as limiting the scope of the invention.

[0026] Unless otherwise specified, the materials and equipment involved in the following detailed embodiments are all conventional materials and equipment in the art and will not affect the technical effects of the present invention.

[0027] Example 1 This embodiment provides a sidewall rubber composition and its preparation method. The sidewall rubber composition comprises the following components by weight: 40 parts of natural rubber (model SMR20), 60 parts of butadiene rubber (model BR9000), 29 parts of reclaimed rubber (Wuxi Wanfeng high-strength reclaimed rubber with a strength of 14 MPa), 2 parts of lignin-modified antioxidant (Kobot antioxidant HS-L501), 3 parts of activator (zinc oxide and stearic acid in a mass ratio of 2:1), 7 parts of homogenizer (model 40MS), 3 parts of octylphenol resin (model SL-7015, manufactured by Huachi (China) Chemical Co., Ltd.), 0.8 parts of accelerator (accelerator DM), 52 parts of carbon black (model N330), 3 parts of processing oil (aromatic oil, model SQ-20, manufactured by Anhui Shuangqiao Chemical Co., Ltd.), and 2 parts of sulfur.

[0028] The preparation method includes the following steps: (1) Natural rubber, butadiene rubber, reclaimed rubber, lignin-modified antioxidant, zinc oxide, stearic acid, homogenizer, octylphenol resin, processing oil, and a portion of carbon black are fed into a mixing chamber. The total mass of carbon black is 100%, and the aforementioned portion of carbon black accounts for 50% of the total mass. The initial temperature of the mixing chamber is set to 80℃, the rotor speed to 26 rpm, and the pressure of the top plug to 5.0 N / cm. 2 After pressing for 20 seconds, the remaining carbon black is added by lifting the plug. After pressing for 40 seconds, the plug is lifted and held for 10 seconds. Then the plug is pressed again until the rubber temperature reaches 120°C and the rubber is discharged. The discharged rubber is then pressed into sheets by an extruder and cooled to below 45°C before the sheets are collected to obtain the masterbatch.

[0029] (2) After the masterbatch obtained in step (1) is left to dry for 4 hours, it is fed into an internal mixer along with the accelerator and sulfur. The speed of the internal mixer is set to 26 rpm, and the pressure of the top plug is 5.0 N / cm. 2Press the rubber to 45 seconds, lift the plug and let it stand for 5 seconds, then press it to 108°C and discharge the rubber. The discharged rubber is then re-milled on an open mill and sheeted out. After cooling to below 45°C, the sheets are collected and stacked to obtain the tire sidewall rubber composition.

[0030] Example 2 This embodiment provides a tire sidewall rubber composition and its preparation method. The difference between this embodiment and Example 1 is that the weight of the lignin-modified antioxidant (Cobot antioxidant HS-L501) is adjusted to 3 parts, while other conditions are the same as in Example 1.

[0031] Example 3 This embodiment provides a sidewall rubber composition and its preparation method. The sidewall rubber composition comprises the following components by weight: 45 parts of natural rubber (model SMR20), 55 parts of butadiene rubber (model BR9000), 30 parts of reclaimed rubber (Wuxi Wanfeng high-strength reclaimed rubber with a strength of 14 MPa), 3 parts of lignin-modified antioxidant (Kobot antioxidant HS-L501), 4 parts of activator (zinc oxide and stearic acid in a mass ratio of 1:1), 5 parts of homogenizer (model 40MS), 4 parts of octylphenol resin (model SL-7015, manufactured by Huachi (China) Chemical Co., Ltd.), 0.8 parts of accelerator (accelerator DM), 65 parts of carbon black (model N330), 5 parts of processing oil (aromatic oil, model SQ-20, manufactured by Anhui Shuangqiao Chemical Co., Ltd.), and 2 parts of sulfur.

[0032] The preparation method includes the following steps: (1) Natural rubber, butadiene rubber, reclaimed rubber, lignin-modified antioxidant, zinc oxide, stearic acid, homogenizer, octylphenol resin, processing oil, and a portion of carbon black are fed into a mixing chamber. The total mass of carbon black is 100%, and the aforementioned portion of carbon black accounts for 50% of the total mass. The initial temperature of the mixing chamber is set to 80℃, the rotor speed to 26 rpm, and the pressure of the top plug to 5.0 N / cm. 2 After pressing for 20 seconds, lift the plug and add the remaining carbon black. After pressing for 40 seconds, lift the plug and let it stand for 10 seconds. Then press the plug again until the rubber temperature is 120℃ and discharge the rubber. The discharged rubber is then pressed into sheets by an extruder and cooled to below 45℃. The sheets are then collected to obtain the masterbatch. (2) After the masterbatch obtained in step (1) is left to dry for 4 hours, it is fed into an internal mixer along with the accelerator and sulfur. The speed of the internal mixer is set to 26 rpm, and the pressure of the top plug is 5.0 N / cm. 2 Press the rubber to 45 seconds, lift the plug and let it stand for 5 seconds, then press it to 108°C and discharge the rubber. The discharged rubber is then re-milled on an open mill and sheeted out. After cooling to below 45°C, the sheets are collected and stacked to obtain the tire sidewall rubber composition.

[0033] Example 4 This embodiment provides a sidewall rubber composition and its preparation method. The sidewall rubber composition comprises the following components by weight: 48 parts of natural rubber (model SMR20), 75 parts of butadiene rubber (model BR9000), 10 parts of reclaimed rubber (Wuxi Wanfeng high-strength reclaimed rubber with a strength of 14 MPa), 3 parts of lignin-modified antioxidant (Kobot antioxidant HS-L501), 4.5 parts of activator (zinc oxide and stearic acid in a mass ratio of 5:1), 8 parts of homogenizer (model 40MS), 2 parts of octylphenol resin (model SL-7015, manufactured by Huachi (China) Chemical Co., Ltd.), 0.8 parts of accelerator (accelerator DM), 45 parts of carbon black (model N330), 6 parts of processing oil (aromatic oil, model SQ-20, manufactured by Anhui Shuangqiao Chemical Co., Ltd.), and 2 parts of sulfur.

[0034] The preparation method includes the following steps: (1) Natural rubber, butadiene rubber, reclaimed rubber, lignin-modified antioxidant, zinc oxide, stearic acid, homogenizer, octylphenol resin, processing oil, and a portion of carbon black are fed into a mixing chamber. The total mass of carbon black is 100%, and the aforementioned portion of carbon black accounts for 50% of the total mass. The initial temperature of the mixing chamber is set to 80℃, the rotor speed to 26 rpm, and the pressure of the top plug to 5.0 N / cm. 2 After pressing for 20 seconds, the remaining carbon black is added by lifting the plug. After pressing for 40 seconds, the plug is lifted and held for 10 seconds. Then the plug is pressed again until the rubber temperature reaches 120°C and the rubber is discharged. The discharged rubber is then pressed into sheets by an extruder and cooled to below 45°C before the sheets are collected to obtain the masterbatch.

[0035] (2) After the masterbatch obtained in step (1) is left to dry for 4 hours, it is fed into an internal mixer along with the accelerator and sulfur. The speed of the internal mixer is set to 26 rpm, and the pressure of the top plug is 5.0 N / cm. 2 Press the rubber to 45 seconds, lift the plug and let it stand for 5 seconds, then press it to 108°C and discharge the rubber. The discharged rubber is then re-milled on an open mill and sheeted out. After cooling to below 45°C, the sheets are collected and stacked to obtain the tire sidewall rubber composition.

[0036] Comparative Example 1 This comparative example provides a tire sidewall rubber composition and its preparation method. The difference between this example and Example 1 is that the weight of the lignin-modified antioxidant (Cobot antioxidant HS-L501) is adjusted to 1 part, while other conditions are the same as in Example 1.

[0037] Comparative Example 2 This comparative example provides a tire sidewall rubber composition and its preparation method. The difference between this composition and Example 1 is that no lignin-modified antioxidant (Cobot antioxidant HS-L501) is added, while other conditions are the same as in Example 1.

[0038] Comparative Example 3 This comparative example provides a tire sidewall rubber composition and its preparation method. The difference between this example and Example 1 is that the weight of the homogenizer (model 40MS) is adjusted to 3 parts, while other conditions are the same as in Example 1.

[0039] Comparative Example 4 This comparative example provides a tire sidewall rubber composition and its preparation method. The difference between this example and Example 1 is that the weight of the homogenizer (model 40MS) is adjusted to 9 parts, while other conditions are the same as in Example 1.

[0040] The following properties of the sidewall rubber compositions provided in Examples 1-4 and Comparative Examples 1-4 were tested before and after aging. The aging conditions were: placed at 100°C for 48 h. The test results are shown in Table 1.

[0041] (1) 300% constant elongation stress: Tested in accordance with GB / T 528-2009.

[0042] (2) Tensile strength and elongation at break: tested in accordance with GB / T 528-2009.

[0043] (3) Tear strength: Tested in accordance with GB / T 529-2008.

[0044] (4) Hardness: The Shore A hardness at 52℃ was tested according to GB / T 531.1-2008.

[0045] (5) Flexural cracking grade: Tested in accordance with GB / T 13934-2006.

[0046] Aging coefficient: Calculated according to the following formula: Aging coefficient = (Tensile strength after aging × Elongation at break after aging) / (Tensile strength before aging × Elongation at break before aging).

[0047] The sidewall rubber compositions provided in Examples 1-4 and Comparative Examples 1-4 were subjected to the following performance tests, and the test results are shown in Table 1.

[0048] (1) Mooney viscosity: tested according to GB / T1232.1-2000.

[0049] (2) Mooney scorch time: Tested according to GB / T 1233-2008.

[0050] (3) Vulcanization characteristics: Tested using an RPA2000 rubber processing analyzer in accordance with ASTM D5289.

[0051] (4) Viscoelasticity: According to ASTM D5289, the test was conducted using an RPA2000 rubber processing analyzer; test conditions: the rheological test was conducted at 150℃ for 30 min, recorded as 150℃×30'; the frequency was 60 cpm and the angle was 0.5 deg.

[0052] Table 1 According to the test results in Table 1, the sidewall rubber compositions provided in Examples 1-4 have superior mechanical properties, aging resistance, and flexural crack resistance, with an aging coefficient ≥0.512; tensile strength before aging ≥15.9 MPa; and tear strength before aging ≥73.2 kN / m.

[0053] Figure 1 The images show the physical samples of the sidewall rubber compositions provided in Examples 1, 2, Comparative Examples 1 and 2 as of May 27, 2025; and the physical samples taken on May 28, 2025, after being dried in the sun outdoors for one day. Figure 2 As shown; the actual product photo taken on May 29, 2025, after being dried outdoors in the sun for 2 days. Figure 3 As shown; the actual product, photographed on June 3, 2025, after being dried outdoors in the sun for 7 days. Figure 4 As shown, the sidewall rubber composition provided in Comparative Example 2 exhibited significant discoloration on its surface. Compared to Comparative Examples 1-2, Example 2 demonstrated superior overall performance, with a marked improvement in discoloration, excellent aging resistance, and the best results.

[0054] Compared with Example 1, if the weight of the lignin-modified antioxidant is too small (Comparative Example 1) or no lignin-modified antioxidant is added (Comparative Example 2), the mechanical properties such as tensile strength, aging resistance, and flexural crack resistance of the prepared sidewall rubber composition will decrease.

[0055] Compared with Example 1, if the weight fraction of the homogenizer is too small (Comparative Example 3), the components in the sidewall rubber composition are prone to uneven dispersion due to differences in polarity and viscosity, resulting in a decrease in mechanical properties such as tensile strength and tear strength, and a lower elongation at break.

[0056] Compared with Example 1, if the homogenizer is used in too many parts by weight (Comparative Example 4), it will interfere with the interaction between rubber molecules and lead to a decrease in the physical properties of the rubber material, mainly affecting tensile strength, tear strength and elongation at break; at the same time, it will increase the processing difficulty and change the flowability of the sidewall rubber composition.

[0057] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A tire sidewall rubber composition, characterized in that, The sidewall rubber composition comprises the following components by weight: 40-48 parts natural rubber, 55-75 parts butadiene rubber, 10-30 parts reclaimed rubber, 2-3 parts lignin-modified antioxidant, 3-5.5 parts activator, 4-8 parts homogenizer, 1-4 parts octylphenol resin, 0.5-1.8 parts accelerator, 45-65 parts carbon black, 2-10 parts processing oil, and 0.4-3 parts sulfur.

2. The sidewall rubber composition according to claim 1, characterized in that, The activators include zinc oxide and stearic acid.

3. The sidewall rubber composition according to claim 2, characterized in that, The mass ratio of zinc oxide to stearic acid is (0.6~7):

1.

4. The sidewall rubber composition according to any one of claims 1 to 3, characterized in that, The accelerator includes dibenzothiazole disulfide.

5. The sidewall rubber composition according to any one of claims 1 to 4, characterized in that, The operating oil includes aromatic oil.

6. A method for preparing a tire sidewall rubber composition according to any one of claims 1 to 5, characterized in that, The preparation method includes the following steps: mixing natural rubber, butadiene rubber, reclaimed rubber, lignin-modified antioxidant, activator, homogenizer, octylphenol resin, accelerator, carbon black, processing oil and sulfur to obtain the sidewall rubber composition.

7. The preparation method according to claim 6, characterized in that, The preparation method includes the following steps: (1) Natural rubber, butadiene rubber, reclaimed rubber, lignin-modified antioxidant, zinc oxide, stearic acid, homogenizer, octylphenol resin, carbon black and processing oil are mixed to obtain masterbatch; (2) The masterbatch, accelerator and sulfur obtained in step (1) are mixed to obtain the sidewall rubber composition.

8. The preparation method according to claim 7, characterized in that, The mixing process in step (1) includes internal mixing.

9. The preparation method according to claim 7 or 8, characterized in that, The mixing process in step (2) includes sequential internal mixing and open mixing.

10. The use of a sidewall rubber composition as described in any one of claims 1 to 5 in an all-steel radial tire.

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