Environment-friendly tire side rubber composition and preparation method thereof, and engineering machinery tire

Abstract

The present application belongs to the technical field of rubber, and particularly relates to an environment-friendly tire side rubber composition, a preparation method thereof and an engineering machinery tire. According to mass parts, the composition comprises the following components: 100 parts of diene rubber, 0.1-1.5 parts of tear resistance modifier, 2-8 parts of antioxidant, 20-100 parts of reinforcing filler, 5-15 parts of plasticizer, 2-3 parts of vulcanization aid, 1-3 parts of microcrystalline wax and 4-7 parts of vulcanization activator; the present application avoids the generation of carcinogen 6PPD quinone from the source by adopting a non-6PPD type antioxidant compound system with a specific structure and a pyrazolone type tear resistance modifier. While significantly reducing the environmental and ecological toxicity, the present application endows the tire side rubber with excellent tear resistance, cutting resistance, fatigue resistance and heat-oxygen aging resistance, and the tensile strength and elongation at break retention rate are high, and the present application is particularly suitable for engineering machinery tires in scenes such as mining areas and ecological protection areas with strict environmental protection requirements.

Description

Technical Field

[0001] This invention belongs to the field of rubber technology, specifically relating to an environmentally friendly tire sidewall rubber composition and its preparation method, and engineering machinery tires. Background Technology

[0002] In recent years, with the rapid development of infrastructure construction, energy, and mining in my country, a large number of construction machinery are operating in ecologically fragile mining areas such as deserts, grasslands, Gobi, and deep mountains. This poses a dual challenge to the tires used in construction machinery: on the one hand, the tires must possess excellent stability, durability, cut resistance, tear resistance, and fatigue resistance to cope with heavy-load, long-term, and harsh road conditions; on the other hand, the tire materials must have good green and environmentally friendly properties to meet increasingly stringent ecological and environmental regulations and mining area usage requirements.

[0003] Currently, the most widely used rubber antioxidant in the global tire industry is 6PPD (N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine). Although 6PPD itself has low toxicity, it reacts with ozone during use to produce a highly toxic conversion product—6PPD quinone. Studies have shown that 6PPD quinone is extremely toxic to aquatic organisms (such as coho salmon) and poses a potential carcinogenic risk to human health. In 2023, the California Department of Toxic Substances Control added tires containing 6PPD to its priority product list and is urging the industry to find safe and environmentally friendly alternatives.

[0004] Traditional construction machinery tires rely heavily on 6PPD (6-part powder) in their sidewall rubber compound to achieve ozone aging resistance and fatigue resistance. Simply removing 6PPD would lead to rapid cracking of the sidewall rubber and a sharp decline in performance. Existing alternative technologies are either insufficient in performance or too expensive, making it difficult to achieve a balance between "environmentally friendly and non-toxic" and "high tear resistance, fatigue resistance, and aging resistance."

[0005] Therefore, developing a green and environmentally friendly sidewall rubber composition that can completely replace 6PPD while significantly improving tear resistance, cut resistance, fatigue resistance, and heat and oxygen aging resistance is a technical challenge that urgently needs to be solved in this field. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of existing technologies and provide an environmentally friendly sidewall rubber composition and its preparation method, as well as an engineering machinery tire. The sidewall rubber composition of this invention completely eliminates the use of the antioxidant 6PPD, thus avoiding the formation of the toxic product 6PPD quinone from the source. Simultaneously, through the synergistic effect of a non-6PPD antioxidant compound system with pyrazolone-based modifiers, the tear resistance, cut resistance, fatigue resistance, and aging resistance of the sidewall rubber are significantly improved.

[0007] 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 an environmentally friendly tire sidewall rubber composition, comprising the following components by weight: 100 parts of diene rubber, 0.1-1.5 parts of tear modifier, 2-8 parts of antioxidant, 20-100 parts of reinforcing filler, 5-15 parts of plasticizer, 2-3 parts of vulcanization aid, 1-3 parts of microcrystalline wax, and 4-7 parts of vulcanization activator; The tear-resistant modifier is a pyrazolone compound with the structural formula shown in (1) or (2): (1) (2) R1, R2, R3, and R4 may be the same or different, representing hydrogen atoms, alkyl, aralkyl, aryl, or heterocyclic groups; R3 and R4 are connected to form an alkylene group, or any two of R2, R3, and R4 are connected together to form an alkylene group; R5, R7, and R8 may be the same or different, representing one or more of hydrogen atoms, alkyl, aralkyl, aryl, and heterocyclic groups; R6 represents one of alkyl, aralkyl, aryl, and heterocyclic groups. Furthermore, R1, R2, R3, R4, R5, R6, R7, and R8 have one or more substituents.

[0008] Furthermore, the antioxidant comprises 0.5-3 parts of a first antioxidant, 0.5-3 parts of a second antioxidant, and 1-2 parts of a third antioxidant; The first antioxidant is 4,4'-bis(α,α-dimethylbenzyl)diphenylamine, the second antioxidant is Anti901, and the third antioxidant is antioxidant RD.

[0009] The primary and secondary antioxidants form a complementary antioxidant / ozone-resistant network in the rubber. The primary antioxidant mainly provides chain-terminating antioxidant capabilities, while the secondary antioxidant provides long-lasting thermal and oxygen protection and ozone protection.

[0010] The heterocyclic groups (pyrazolone compounds) in tear-resistant modifiers can form non-covalent network structures with double bonds on rubber molecular chains and in rubber compounds, significantly improving the cohesive energy and crack propagation resistance of the rubber matrix. The synergistic effect of these three components not only completely replaces 6PPD but also achieves a significant leap in overall performance.

[0011] Furthermore, the tear-resistant modifier comprises at least one of pyrazolone compounds; The pyrazolone compound is one or a combination of 3-methyl-5-pyrazolone, 3-phenyl-5-pyrazolone, 3-ethyl-5-pyrazolone, 3-propyl-5-pyrazolone, and 3-butyl-5-pyrazolone. Preferably, the pyrazolone compound is present in an amount of 0.3-1.2 parts by weight.

[0012] Furthermore, the diene rubber is one or more of the following: natural rubber, polyisoprene rubber, polybutadiene rubber, and styrene-butadiene copolymer rubber.

[0013] Furthermore, the diene rubber includes 30-70 parts by weight of natural rubber or polyisoprene rubber and 30-70 parts by weight of polybutadiene rubber.

[0014] Preferably, the diene rubber comprises 40-60 parts by weight of natural rubber and 40-60 parts by weight of polybutadiene rubber. Natural rubber provides excellent strength and tear resistance, while polybutadiene rubber provides good fatigue resistance.

[0015] Furthermore, the reinforcing filler is carbon black, and the nitrogen adsorption specific surface area of ​​the carbon black is 20-160 m². 2 / g; Preferably, the nitrogen adsorption specific surface area of ​​the carbon black is 20-150 m². 2 / g, DBP absorption value 80-150cm 3 / 100g, carbon black is 30-80 parts.

[0016] The plasticizer is one or more of environmentally friendly aromatic oils, naphthenic oils, and petroleum hydrocarbon resins, or a combination thereof.

[0017] Furthermore, the sulfidation activator is a combination of zinc oxide and stearic acid; The vulcanization aids include vulcanization accelerators and vulcanizing agents.

[0018] Secondly, embodiments of the present invention provide a method for preparing the environmentally friendly tire sidewall rubber composition described in the first aspect, comprising the following steps: Step S1: Add diene rubber, reinforcing filler, antioxidant, microcrystalline wax, vulcanization activator, and tear-resistant modifier into an internal mixer and mix until 100-130°C. Add plasticizer and continue mixing until 140-170°C. Discharge the rubber, cool, and obtain masterbatch. Step S2: Mix the masterbatch obtained in step S1 with the vulcanizing agent at a temperature below 120°C, discharge the rubber, and obtain the finished rubber composition.

[0019] Furthermore, the glue removal temperature in step S1 is 150-165℃; the glue removal temperature in step S2 is 100-115℃.

[0020] Thirdly, embodiments of the present invention provide an engineering machinery tire, comprising the rubber composition described in the first aspect, wherein the rubber composition is used at least in the sidewall portion of the tire.

[0021] The beneficial effects of the technical solution provided by the embodiments of the present invention are as follows: 1. Environmentally friendly and non-toxic: It completely replaces the toxic antioxidant 6PPD, eliminating the formation of 6PPD quinone from the source. It is non-toxic and harmless to humans and aquatic organisms, meeting the most stringent environmental protection requirements for ecological mining areas.

[0022] 2. Significant improvement in tear and cut resistance: By combining a non-6PPD antioxidant compound system with pyrazolone tear modifiers, the tear strength before and after aging is increased by 17%-18%, the cut resistance is increased by 3%-6%, and the crack growth rate is reduced by 22%-31%, giving the tire sidewall rubber an excellent ability to resist mechanical damage from harsh road conditions.

[0023] 3. Significantly enhanced resistance to heat and oxygen aging and fatigue: The retention rate of tensile strength and tear strength after aging is 17-18% higher than that of the traditional 6PPD system, the flexural fatigue life is extended, and the tire performance remains stable under heavy load, long-term and high temperature conditions.

[0024] 4. Balanced overall performance: While improving resistance to damage and aging, it maintains good dynamic heat generation characteristics, perfectly matching the comprehensive performance requirements of engineering machinery tires.

[0025] 5. Strong industrial applicability: All raw materials used are commercially available industrial products, and the preparation method is compatible with existing tire mixing processes. No equipment modification is required, making it easy to achieve large-scale industrial production and widespread application. Detailed Implementation

[0026] 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.

[0027] The raw material information in Table 1 is as follows: Natural rubber: TSR20, Sinochem International (Holdings) Co., Ltd.; Butadiene rubber: BR9000, Sinopec Qilu Petrochemical Company; Carbon black: N330, Cabot Corporation; Aromatic oil: VIVATEC 500, H&R GmbH, Germany; First antioxidant: 4,4'-bis(α,α-dimethylbenzyl)diphenylamine, Dainei New Chemicals; Second antioxidant: Anti901, Qingdao Chuangzhi Hengye New Materials Co., Ltd.

[0028] Anti-aging agent: 6PPD, Sheng'ao Chemical; Tear-resistant modifier: 3-methyl-5-pyrazolone, THICA (Shanghai) Chemical Industry Development Co., Ltd.

[0029] Others: zinc oxide, stearic acid, microcrystalline wax, third antioxidant RD, sulfur, accelerator NS.

[0030] Table 1 below lists the formulations of Comparative Examples 1-2 and Examples 1-2 of the present invention.

[0031] Table 1. Formulations (parts by weight) of Examples 1-2 and Comparative Examples 1-2 Preparation method Comparative Example 1: A conventional two-stage mixing process was adopted, specifically including the following steps: First stage mixing: Add natural rubber, butadiene rubber, carbon black N330, zinc oxide, stearic acid, antioxidant 6PPD, third antioxidant RD and microcrystalline wax to the internal mixer and mix until the rubber compound temperature reaches 115℃. Then, lift the top plug to add environmentally friendly aromatic oil and mix until the temperature reaches 150-160℃ before discharging and sheeting. Second stage mixing: Add the first stage masterbatch, sulfur and accelerator to the internal mixer. The rotor speed is 25rpm and the mixture is mixed until the temperature is below 110℃ before discharging and sheeting.

[0032] Examples 1-2 employ the two-stage mixing process of the present invention, specifically including the following steps: Step S1, First stage mixing: Natural rubber, butadiene rubber, carbon black N330, zinc oxide, stearic acid, third antioxidant, microcrystalline wax, tear modifier, first antioxidant 4,4'-bis(α,α-dimethylbenzyl)diphenylamine and second antioxidant Anti901 are added to an internal mixer. The rotor speed is 50 rpm. When the rubber compound temperature reaches 120℃, the top plug is raised to add environmentally friendly aromatic oil. Mixing continues until 155℃, the rubber is discharged and sheeted. After cooling at room temperature for 8 hours, the first stage masterbatch is obtained.

[0033] Step S2, final mixing: Add a section of masterbatch, sulfur, and accelerator NS to an internal mixer, rotate the rotor at 30 rpm, mix until the rubber compound temperature reaches 110℃, discharge the rubber into sheets, and cool to obtain the tire sidewall rubber composition.

[0034] The preparation method of Comparative Example 2 is the same as that of Examples 1-2, and it is prepared according to the formula.

[0035] Vulcanization conditions: 150℃×30min.

[0036] Performance testing methods and standards The methods and standards for the corresponding performance tests in Table 3-4 are shown in Table 2.

[0037] Table 2 The performance of Examples 1-2 and Comparative Examples 1-2 was tested using the test methods and standards in Table 2, and the results are shown in Table 3.

[0038] Table 3 Performance comparison between Examples 1-2 and Comparative Examples 1-2 Note: TS stands for Tensile Strength in the table; EB stands for Elongation at Break.

[0039] As can be seen from the data in Table 3: Compared with Comparative Example 1, Comparative Example 2 only replaced the environmentally friendly antioxidant without adding a modifier. Although it is environmentally friendly, its other properties are basically not improved.

[0040] In Example 1, a tear-resistant modifier was added. Compared with Comparative Example 1, the cutting resistance, tear resistance, and crack growth resistance before and after aging were significantly improved, and the flexural fatigue after aging was also greatly improved (240%).

[0041] Compared with Example 1, Example 2 optimized the proportion of tear-resistant modifier, reduced the hardness to 56.2 degrees, and made the elongation modulus closer to the original formula (Comparative Example 1). It limited the increase in dynamic heat generation (2%), and maintained and improved the tear resistance, cut resistance and other properties (compared to Comparative Example 1). It achieved a perfect combination of high resistance to damage without a significant increase in heat generation.

[0042] Results analysis: 1. Environmental friendliness: Example 2 contains no 6PPD at all, thus avoiding the generation of toxic 6PPD quinone from the source, and its environmental safety is significantly better than the control example.

[0043] 2. Mechanical Properties: Compared with Comparative Example 1, the tensile strength, elongation at break, and tear strength of Example 2 of the present invention are significantly improved. This indicates that the compound system of tear modifier and antioxidant effectively enhances the interaction between rubber molecular chains.

[0044] 3. Fatigue Resistance and Crack Growth Resistance: The reduced crack growth rate in Example 2 indicates a significant slowdown in crack propagation, which is crucial for the tire sidewall's resistance to repeated flexing. At 2 million flexural fatigue cycles, Example 2 exhibited the same crack grade as Comparative Example 1, demonstrating that the fatigue resistance and crack resistance of the rubber composition in Example 2 of this invention have not decreased.

[0045] 4. Aging resistance: After harsh thermo-oxidative aging at 100℃ for 72h, the performance of Comparative Example 1 decreased significantly, while the retention rate of key indicators such as tensile strength, tear strength, tensile volume, and elongation at break of Example 2 was much higher than that of Comparative Example 1. When the flexural fatigue reached 500,000 cycles, the crack level of Example 2 was significantly better than that of Comparative Example 1. All of the above show excellent long-term aging resistance.

[0046] 5. Dynamic heat generation: The dynamic loss factor at 60℃ in Example 2 is basically the same as that in the comparative example before and after aging, indicating that while improving tear resistance and fatigue resistance, rolling resistance or heat generation performance is not sacrificed, thus meeting the requirements of long-term heavy-load operation of engineering machinery tires.

[0047] Factory raw material formulation and tire road test data To further verify the practical application effect of the present invention, the formulation of Example 2 was scaled up and mass-produced in a tire factory to make engineering machinery tires (specification 505 / 95 / R29). A tire of the same specification using a traditional 6PPD formulation (Comparative Example 1) was used as a control tire. The results are shown in Table 4.

[0048] Table 4 Factory Raw Material Formula Data As shown in Table 4, the basic physical properties (such as cut resistance, 100% tensile stress, and Demercia flexural fatigue crack grade) of the two formulations before aging are highly similar, and the numerical deviation of Shore A hardness is strictly controlled within ±2%, which is within the allowable error range for rubber material testing. This result fully demonstrates that the compound component of Example 2 has excellent compatibility with the NR / BR blended rubber system, does not damage the original basic mechanical properties of the rubber compound, and fully meets the physical property access standards for OTR tire sidewall rubber compounds. At the same time, the tensile strength, elongation at break, heat generation (dynamic loss factor at 60℃), tear strength, and crack growth rate of the compound component of Example 2 are all superior to the 6PPD formulation of Comparative Example 1.

[0049] From the perspective of the changes in physical properties after aging, both formulations exhibited typical rubber aging characteristics after thermo-oxidative aging, including increased hardness and tensile stress, decreased strength and elongation, and increased abrasion. However, the degradation of physical properties in the formulation of Example 2 was significantly lower than that of the 6PPD formulation in Comparative Example 1. Overall, the compounded anti-aging system can achieve basic physical properties equivalent to 6PPD. In addition, it is superior to the 6PPD formulation in Comparative Example 1 in terms of heat generation, tear resistance, fatigue resistance, and crack growth resistance. Furthermore, it exhibits better physical property stability after thermo-oxidative aging, providing a good basis for substitution.

[0050] Table 5. Results of Tire Machine Tool Durability Test As shown in Table 5, under completely identical test conditions, the tires made with the rubber composition formulation of Comparative Example 1 had a durability failure time of 85.6 hours, and typical fatigue aging failure problems such as tread groove cracking appeared at the end of the test. In contrast, the tires made with the rubber composition formulation of Example 2 had a durability time of 94.7 hours, which is 9.1 hours longer than that of Comparative Example 1, and the durability performance improvement rate reached 10.5%, showing a significant performance improvement effect.

[0051] Real-vehicle road tests were conducted on typical mining area roads. Meanwhile, tires of the same specifications were manufactured using the same formulation as a comparison.

[0052] Road test conditions: The test vehicle is a 150-ton mining dump truck, the road surface is a gravel road, and the test is conducted for 1500 hours.

[0053] Evaluation method: Three experienced tire engineers subjectively evaluate and score the condition of the tire sidewall (0-5 points, with 5 points being the best, indicating no damage), and record the ozone crack level of the tire sidewall (ASTM D1149, 0-3, with 0 being no cracks).

[0054] Table 6. Tire Road Test Results (Subjective Evaluation and Ozone Crack Level) Road test conclusion: During a rigorous 1500-hour road test in a mining area, the tires made with the rubber composition formulation of Example 2 of this invention exhibited sidewall cut resistance, tear resistance, and ozone aging resistance that were no less than those made with the rubber composition formulation of Comparative Example 1. Subjective evaluation scores consistently remained above 5 points. Regarding ozone cracking resistance, the tires of Example 2 showed no cracks throughout the entire test. This fully demonstrates the superior performance and environmental value of the rubber composition of this invention in practical applications of engineering machinery tires.

[0055] 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. An environmentally friendly tire sidewall rubber composition, characterized in that, The product comprises the following components by weight: 100 parts diene rubber, 0.1-1.5 parts tear modifier, 2-8 parts antioxidant, 20-100 parts reinforcing filler, 5-15 parts plasticizer, 2-3 parts vulcanization aid, 1-3 parts microcrystalline wax, and 4-7 parts vulcanization activator. The tear-resistant modifier is a pyrazolone compound with the structural formula shown in (1) or (2): （1） （2） R1, R2, R3, and R4 may be the same or different, representing hydrogen atoms, alkyl, aralkyl, aryl, or heterocyclic groups; R3 and R4 are connected to form an alkylene group, or any two of R2, R3, and R4 are connected together to form an alkylene group; R5, R7, and R8 may be the same or different, representing one or more of hydrogen atoms, alkyl, aralkyl, aryl, and heterocyclic groups; R6 represents one of alkyl, aralkyl, aryl, and heterocyclic groups. Furthermore, R1, R2, R3, R4, R5, R6, R7, and R8 have one or more substituents.

2. The environmentally friendly tire sidewall rubber composition according to claim 1, characterized in that, The antioxidant comprises 0.5-3 parts of a first antioxidant, 0.5-3 parts of a second antioxidant, and 1-2 parts of a third antioxidant; The first antioxidant is 4,4'-bis(α,α-dimethylbenzyl)diphenylamine, the second antioxidant is Anti901, and the third antioxidant is antioxidant RD.

3. The environmentally friendly tire sidewall rubber composition according to claim 1, characterized in that, The tear-resistant modifier contains at least one of pyrazolone compounds; The pyrazolone compounds are one or more combinations of 3-methyl-5-pyrazolone, 3-phenyl-5-pyrazolone, 3-ethyl-5-pyrazolone, 3-propyl-5-pyrazolone, and 3-butyl-5-pyrazolone.

4. The environmentally friendly tire sidewall rubber composition according to claim 1, characterized in that, The diene rubber is one or more of natural rubber, polyisoprene rubber, polybutadiene rubber, and styrene-butadiene rubber.

5. The environmentally friendly tire sidewall rubber composition according to claim 1 or 4, characterized in that, The diene rubber includes 30-70 parts by weight of natural rubber or polyisoprene rubber and 30-70 parts by weight of polybutadiene rubber or styrene-butadiene rubber.

6. The environmentally friendly tire sidewall rubber composition according to claim 1, characterized in that, The reinforcing filler is carbon black, and the nitrogen adsorption specific surface area of ​​the carbon black is 20-160 m². 2 / g; The plasticizer is one or more of environmentally friendly aromatic oils, naphthenic oils, and petroleum hydrocarbon resins, or a combination thereof.

7. The environmentally friendly tire sidewall rubber composition according to claim 1, characterized in that, The sulfidation activator is a combination of zinc oxide and stearic acid; The vulcanization aids include vulcanization accelerators and vulcanizing agents.

8. A method for preparing the environmentally friendly tire sidewall rubber composition according to any one of claims 1-7, characterized in that, Includes the following steps: Step S1: Add diene rubber, reinforcing filler, antioxidant, microcrystalline wax, vulcanization activator, and tear-resistant modifier into an internal mixer and mix until 100-130°C. Add plasticizer and continue mixing until 140-170°C. Discharge the rubber, cool, and obtain masterbatch. Step S2: Mix the masterbatch obtained in step S1 with the vulcanizing agent at a temperature below 120°C, discharge the rubber, and obtain the finished rubber composition.

9. The method for preparing the environmentally friendly tire sidewall rubber composition according to claim 8, characterized in that, The glue discharge temperature in step (1) is 150-165℃; the glue discharge temperature in step (2) is 100-115℃.

10. A tire for engineering machinery, characterized in that, The rubber composition includes any one of claims 1-7, wherein the rubber composition is used at least in the sidewall portion of the tire.

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